0001039399-21-000009 | 10-K | XBRL Viewer

Print Document View Excel Document

Cover - USD ($) $ in Millions	12 Months Ended
Cover - USD ($) $ in Millions	Dec. 26, 2020	Feb. 16, 2021	Jun. 26, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 26, 2020
Current Fiscal Year End Date	--12-26
Document Transition Report	false
Entity File Number	000-50307
Entity Registrant Name	FormFactor, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3711155
Entity Address, Address Line One	7005 Southfront Road
Entity Address, City or Town	Livermore
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94551
City Area Code	925
Local Phone Number	290-4000
Title of 12(b) Security	Common stock, $0.001 par value
Trading Symbol	FORM
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,046.0
Entity Common Stock, Shares Outstanding (in shares)		77,749,914
Documents Incorporated by Reference	Portions of the registrant's definitive Proxy Statement for the 2021 Annual Meeting of Stockholders, which will be filed within 120 days of the end of the registrant's fiscal year ended December 26, 2020, are incorporated by reference in Part III hereof. Except with respect to information specifically incorporated by reference in this Annual Report on Form 10-K, the Proxy Statement is not deemed to be filed as a part of this Annual Report on Form 10-K.
Entity Central Index Key	0001039399
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Current assets:
Cash and cash equivalents	$ 187,225	$ 144,545
Marketable securities	67,810	76,327
Accounts receivable, net	107,603	97,868
Inventories, net	99,229	83,258
Restricted cash	1,904	1,981
Prepaid expenses and other current assets	23,303	15,064
Total current assets	487,074	419,043
Restricted cash	1,969	1,411
Operating lease, right-of-use-assets	30,756	31,420
Property, plant and equipment, net	104,103	58,747
Goodwill	212,761	199,196
Intangibles, net	59,147	57,610
Deferred tax assets	66,242	71,252
Other assets	1,165	1,203
Total assets	963,217	839,882
Current liabilities:
Accounts payable	62,045	40,914
Accrued liabilities	55,342	36,439
Current portion of term loans, net of unamortized issuance cost of $5 and $29	9,516	42,846
Deferred revenue	20,964	9,810
Operating lease liabilities	6,704	6,551
Total current liabilities	154,571	136,560
Term loans, less current portion, net of unamortized issuance cost of $70 and $0	24,978	15,639
Deferred tax liabilities	5,346	6,986
Long-term operating lease liabilities	27,996	29,088
Other liabilities	6,242	10,612
Total liabilities	219,133	198,885
Stockholders' equity:
Preferred stock	0	0
Common stock	78	76
Additional paid-in capital	903,838	885,821
Accumulated other comprehensive income (loss)	5,886	(659)
Accumulated deficit	(165,718)	(244,241)
Total stockholders' equity	744,084	640,997
Total liabilities and stockholders' equity	$ 963,217	$ 839,882

CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Statement of Financial Position [Abstract]
Current unamortized debt issuance costs	$ 5	$ 29
Noncurrent unamortized debt issuance costs	$ 70	$ 0
Preferred stock par value (in USD per share)	$ 0.001	$ 0.001
Preferred stock authorized (in shares)	10,000,000	10,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock authorized (in shares)	250,000,000	250,000,000
Common stock issued (in shares)	77,437,997	75,764,990
Common stock outstanding (in shares)	77,437,997	75,764,990

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Income Statement [Abstract]
Revenues	$ 693,616	$ 589,464	$ 529,675
Cost of revenues	405,696	351,968	319,336
Gross profit	287,920	237,496	210,339
Operating expenses:
Research and development	89,034	81,499	74,976
Selling, general and administrative	115,098	106,335	99,254
Total operating expenses	204,132	187,834	174,230
Operating income	83,788	49,662	36,109
Interest income	1,501	2,714	1,356
Interest expense	(864)	(1,915)	(3,314)
Other income (expense), net	750	602	(224)
Income before income taxes	85,175	51,063	33,927
Provision (benefit) for income taxes	6,652	11,717	(70,109)
Net income	$ 78,523	$ 39,346	$ 104,036
Net income per share:
Basic (in USD per share)	$ 1.02	$ 0.52	$ 1.42
Diluted (in USD per share)	$ 0.99	$ 0.51	$ 1.38
Weighted-average number of shares used in per share calculations:
Basic (in shares)	76,681	74,994	73,482
Diluted (in shares)	79,001	77,286	75,182

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 78,523	$ 39,346	$ 104,036
Other comprehensive income (loss), net of tax:
Translation adjustments and other	5,131	(1,028)	(1,902)
Unrealized gains (losses) on available-for-sale marketable securities	226	316	(8)
Unrealized gains (losses) on derivative instruments	1,188	(727)	(331)
Other comprehensive income (loss), net of tax	6,545	(1,439)	(2,241)
Comprehensive income	$ 85,068	$ 37,907	$ 101,795

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669619-108580

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22595-107794

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669625-108580

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22583-107794

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22658-107794

+ Details

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning balances (in shares) at Dec. 30, 2017			72,532,176
Beginning balances at Dec. 30, 2017	$ 458,637	$ (50)	$ 73	$ 843,116	$ 3,021	$ (387,573)	$ (50)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash (in shares)			134,609
Issuance of common stock pursuant to exercise of options for cash	1,158			1,158
Issuance of common stock pursuant to vesting of restricted stock units (in shares)			862,630
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld for tax	(5,791)			(5,791)
Issuance of common stock under the Employee Stock Purchase Plan (in shares)			610,297
Issuance of common stock under the Employee Stock Purchase Plan	6,662		$ 1	6,661
Stock-based compensation	17,753			17,753
Other comprehensive income (loss)	(2,241)				(2,241)
Net income	104,036					104,036
Ending balances (in shares) at Dec. 29, 2018			74,139,712
Ending balances at Dec. 29, 2018	580,164		$ 74	862,897	780	(283,587)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash (in shares)			162,956
Issuance of common stock pursuant to exercise of options for cash	1,176			1,176
Issuance of common stock pursuant to vesting of restricted stock units (in shares)			918,051
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld for tax	(8,025)		$ 1	(8,026)
Issuance of common stock under the Employee Stock Purchase Plan (in shares)			544,271
Issuance of common stock under the Employee Stock Purchase Plan	6,807		$ 1	6,806
Stock-based compensation	22,968			22,968
Other comprehensive income (loss)	(1,439)				(1,439)
Net income	$ 39,346					39,346
Ending balances (in shares) at Dec. 28, 2019	75,764,990		75,764,990
Ending balances at Dec. 28, 2019	$ 640,997		$ 76	885,821	(659)	(244,241)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash (in shares)			255,769
Issuance of common stock pursuant to exercise of options for cash	2,135		$ 1	2,134
Issuance of common stock pursuant to vesting of restricted stock units (in shares)			931,672
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld for tax	(15,450)		$ 1	(15,451)
Issuance of common stock under the Employee Stock Purchase Plan (in shares)			485,566
Issuance of common stock under the Employee Stock Purchase Plan	7,875			7,875
Stock-based compensation	23,459			23,459
Other comprehensive income (loss)	6,545				6,545
Net income	$ 78,523					78,523
Ending balances (in shares) at Dec. 26, 2020	77,437,997		77,437,997
Ending balances at Dec. 26, 2020	$ 744,084		$ 78	$ 903,838	$ 5,886	$ (165,718)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Cash flows from operating activities:
Net income	$ 78,523	$ 39,346	$ 104,036
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	20,694	17,185	14,314
Amortization	27,991	27,672	29,373
Accretion of discount on investments	(2)	(365)	(10)
Reduction in the carrying amount of right-of-use assets	5,955	5,269	0
Stock-based compensation expense	23,830	23,176	17,827
Amortization of debt issuance costs	32	160	390
Deferred income tax provision (benefit)	(562)	4,954	(74,908)
Provision for excess and obsolete inventories	13,117	10,421	10,479
Acquired inventory step-up amortization	838	465	0
Loss on disposal of long-lived assets	451	486	325
Gain on contingent consideration	(2,879)	0	0
Foreign currency transaction losses (gains)	(968)	408	125
Loss on derivative instruments	372	110	0
Changes in assets and liabilities:
Accounts receivable	(3,545)	481	(13,830)
Inventories	(22,191)	(14,295)	(21,298)
Prepaid expenses and other current assets	(6,207)	230	1,204
Other assets	179	(441)	707
Accounts payable	16,788	(27)	3,050
Accrued liabilities	13,892	7,517	(6,219)
Other liabilities	362	166	3,109
Deferred revenues	8,901	3,130	26
Operating lease liabilities	(6,315)	(5,000)	0
Net cash provided by operating activities	169,256	121,048	68,700
Cash flows from investing activities:
Acquisition of property, plant and equipment	(55,865)	(20,847)	(19,869)
Acquisition of business, net of cash acquired	(51,880)	(20,524)	0
Proceeds from sale of subsidiary	82	132	94
Proceeds from sale of property and property, plant and equipment	0	0	23
Purchases of marketable securities	(51,224)	(76,327)	(30,566)
Proceeds from maturities of marketable securities	59,965	51,214	29,023
Net cash used in investing activities	(98,922)	(66,352)	(21,295)
Cash flows from financing activities:
Proceeds from issuances of common stock	10,010	8,093	7,712
Tax withholdings related to net share settlements of equity awards	(15,450)	(8,025)	(5,791)
Proceeds from term loan	18,000	23,354	0
Payments on term loan	(43,417)	(30,000)	(41,250)
Payment of term loan issuance costs	(78)	0	0
Net cash used in financing activities	(30,935)	(6,578)	(39,329)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	3,762	(727)	(256)
Net increase in cash, cash equivalents and restricted cash	43,161	47,391	7,820
Cash, cash equivalents and restricted cash, beginning of year	147,937	100,546	92,726
Cash, cash equivalents and restricted cash, end of year	191,098	147,937	100,546
Supplemental disclosure of non-cash investing and financing activities:
Operating lease, right-of-use assets obtained in exchange for lease obligations	1,912	36,709	0
Contingent consideration payable related to FRT acquisition	0	5,364	0
Change in accounts payable and accrued liabilities related to property, plant and equipment purchases	2,545	866	2,290
Supplemental disclosure of cash flow information:
Income taxes paid, net	9,150	4,324	4,576
Cash paid for interest	867	1,405	3,113
Reconciliation of cash, cash equivalents and restricted cash:
Total cash, cash equivalents and restricted cash	$ 191,098	$ 100,546	$ 92,726

Formation and Nature of Business	12 Months Ended
Formation and Nature of Business	Dec. 26, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation and Nature of Business	Formation and Nature of Business FormFactor, Inc. was incorporated in Delaware on April 15, 1993 and is headquartered in Livermore, California. We are a leading provider of test and measurement technologies. We provide a broad range of high-performance probe cards, analytical probes, probe stations, metrology systems, thermal systems, and cryogenic systems to both semiconductor companies and scientific institutions. Our products provide electrical and physical information from a variety of semiconductor and electro-optical devices and integrated circuits from early research, through development, to high-volume production. Customers use our products and services to lower production costs, improve yields, and enable development of complex next generation products. We believe our technology leadership enables critical roadmap advances for our customers. Design, development and manufacturing operations are located in Livermore, San Jose, Carlsbad, and Baldwin Park, California, Beaverton, Oregon and Boulder, Colorado, United States and Bergisch Gladbach, Munich and Thiendorf, Germany, and sales, service and support operations are located in the United States, Germany, France, South Korea, Japan, Taiwan, China and Singapore. Fiscal Year Our fiscal year ends on the last Saturday in December. The fiscal years ended on December 26, 2020, December 28, 2019 and December 29, 2018, each consisted of 52 weeks, respectively.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 26, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Consolidation and Foreign Currency Translation

The consolidated financial statements include our accounts and those of our wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated.

We completed the acquisitions of FRT GmbH ("FRT") on October 9, 2019, the probe card assets of Advantest Corporation ("Baldwin Park") on July 30, 2020, and High Precision Devises, Inc. ("HPD") on October 19, 2020. Accordingly, our Consolidated Statements of Income include the results of operations of FRT, Baldwin Park, and HPD since those dates. See Note 4, Acquisitions.

The functional currencies of certain of our foreign subsidiaries are the local currencies and, accordingly, all assets and liabilities of these foreign operations are translated to U.S. Dollars at current period-end exchange rates, and revenues and expenses are translated to U.S. Dollars using average exchange rates in effect during the period. The gains and losses from the foreign currency translation of these subsidiaries' financial statements are included as a separate component of stockholders' equity on our Consolidated Balance Sheets under Accumulated other comprehensive income (loss).

Certain other of our foreign subsidiaries use the U.S. Dollar as their functional currency. Accordingly, monetary assets and liabilities in non-functional currencies of these subsidiaries are remeasured using exchange rates in effect at the end of the period. Revenues and costs in local currency are remeasured using average exchange rates for the period, except for costs related to those balance sheet items that are remeasured using historical exchange rates. The resulting remeasurement gains and losses are included in the Consolidated Statements of Income as a component of Other income (expense), net as incurred.

Use of Estimates

The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Estimates may change as new information is obtained. We believe that the estimates, assumptions and judgments involved in revenue recognition, fair value of marketable securities, fair value of derivative financial instruments used to hedge both foreign currency and interest rate exposures, allowance for doubtful accounts, reserves for product warranty, valuation of obsolete and slow moving inventory, assets acquired and liabilities assumed in business combinations, legal contingencies, valuation of goodwill, the assessment of recoverability of long-lived assets, valuation and recognition of stock-based compensation, provision for income taxes and valuation of deferred tax assets have the greatest potential impact on our consolidated financial statements. Actual results could differ from those estimates.

Business Acquisitions

Our consolidated financial statements include the operations of acquired businesses after the completion of their respective acquisitions. We account for acquired businesses using the acquisition method of accounting, which requires, among other things, that assets acquired and liabilities assumed be recognized at their estimated fair values as of the acquisition date, and that the fair value of acquired intangibles be recorded on the balance sheet. Transaction costs are expensed as incurred. Any excess of the purchase price over the assigned fair values of the net assets acquired is recorded as goodwill.

Cash and Cash Equivalents and Marketable Securities

Cash and cash equivalents consist of deposits and financial instruments which are readily convertible into cash and have original maturities of 90 days or less at the time of acquisition. Marketable securities consist primarily of highly liquid investments with maturities of greater than 90 days when purchased. We classify our marketable securities as available-for-sale and, accordingly, report them at fair value with the related unrealized gains and losses included in Accumulated other comprehensive income (loss) in our Consolidated Balance Sheets. Any unrealized losses which are considered to be other-than-temporary are recorded in Other income (expense), net, in the Consolidated Statements of Income. Realized gains and losses on the sale of marketable securities are determined using the specific-identification method and recorded in Other income (expense), net, in the Consolidated Statements of Income.

All of our available-for-sale investments are subject to a periodic impairment review. If an available-for-sale debt security’s fair value is less than its amortized cost basis, then we evaluate whether the decline is the result of a credit loss, in which case an impairment is recorded through an allowance for credit losses. Unrealized gains and losses not attributable to credit losses are included, net of tax, in Accumulated other comprehensive income (loss) in our Consolidated Balance Sheets. We did not record an allowance for credit losses during fiscal 2020.

Foreign Exchange Management

We transact business in various foreign currencies. We enter into forward foreign exchange contracts in an effort to mitigate the risks associated with currency fluctuations on certain foreign currency balance sheet exposures and certain operational costs denominated in local currency impacting our statement of income. For accounting purposes, certain of our foreign currency forward contracts are not designated as hedging instruments and, accordingly, we record the fair value of these contracts as of the end of our reporting period in our Consolidated Balance Sheets with changes in fair value recorded within Other income (expense), net in our Consolidated Statements of Income for both realized and unrealized gains and losses. Certain of our foreign currency forward contracts are designated as cash flow hedges, and, accordingly, we record the fair value of these contracts as of the end of our reporting period in our Consolidated Balance Sheets with changes in fair value recorded as a component of accumulated other comprehensive income (loss) and reclassified into earnings in the same period in which the hedged transaction affects earnings, and in the same line item on the Consolidated Statements of Income as the impact of the hedge transaction. We do not use derivative financial instruments for trading or speculative purposes.

Accounts Receivable and Allowance for Doubtful Accounts

The majority of our accounts receivable are derived from sales to large multinational semiconductor manufacturers throughout the world, are recorded at their invoiced amount and do not bear interest.

In order to monitor potential credit losses, we perform ongoing credit evaluations of our customers' financial condition. An allowance for doubtful accounts is maintained based upon our assessment of the expected collectability of all accounts receivable. The allowance for doubtful accounts is reviewed and assessed for adequacy on a quarterly basis. We take into consideration (1) any circumstances of which we are aware of a customer's inability to meet its financial obligations and (2) our judgments as to prevailing economic conditions in the industry and their impact on our customers. If circumstances change, and the financial condition of our customers is adversely affected and they are unable to meet their financial obligations, we may need to take additional allowances, which would result in an increase in our operating expense.

Activity related to our allowance for doubtful accounts receivable was as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Balance at beginning of year	$	222	$	185	$	200
Charges (reversals) to costs and expenses	26		37		(15)
Balance at end of year	$	248	$	222	$	185

Inventories

We state our inventories at the lower of cost (principally standard cost which approximates actual cost on a first in, first out basis) or net realizable value. We continually assess the value of our inventory and will periodically write down its value for estimated excess inventory and product obsolescence based upon an analysis of existing inventory quantities compared to estimated future consumption. Future consumption is estimated based upon assumptions about how past consumption, recent purchases, backlog and other factors indicate future consumption. On a quarterly basis, we review existing inventory quantities in comparison to our past consumption, recent purchases, backlog and other factors to determine what inventory quantities, if any, may not be sellable. Based on this analysis, we record an adjustment to the cost basis of inventory when evidence exists that the net realizable value of inventory is lower than its cost, which occurs when we have excess and/or obsolete inventory. Once the value is adjusted, the original cost of our inventory, less the related inventory write-down, represents the new cost basis. Reversal of these write downs is recognized only when the related inventory has been scrapped or sold. Shipping and handling costs are classified as a component of Cost of revenues in the Consolidated Statements of Income.

We design, manufacture and sell a custom product into a market that has been subject to cyclicality and significant demand fluctuations. Many of our products are complex, custom to a specific chip design and have to be delivered on short lead-times. Probe cards are manufactured in low volumes, but, for certain materials, the purchases are often subject to minimum order quantities in excess of the actual underlying probe card demand. It is not uncommon for us to acquire production materials and commence production activities based on estimated production yields and forecasted demand prior to, or in excess of, actual demand for our probe cards. These factors result in normal recurring inventory valuation charges to Cost of revenues.

Inventory write downs totaled $13.1 million, $10.4 million and $10.5 million for fiscal 2020, 2019 and 2018, respectively.

Restricted Cash

Restricted cash is comprised primarily of funds held by our foreign subsidiaries for employee obligations, office leases, customer deposits, temporary customs import permits, and environmental remediation.

Property, Plant, and Equipment

Property, plant and equipment is stated at cost less accumulated depreciation and amortization. Depreciation is provided on a straight-line method. Machinery and equipment, computer equipment and software, and furniture and fixtures are depreciated over 1 to 5 years.

Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Construction-in-progress assets are not depreciated until the assets are placed in service. Upon sale or retirement of assets, the cost and related accumulated depreciation or amortization are removed from the Consolidated Balance Sheets and the resulting gain or loss is reflected in Operating income in our Consolidated Statements of Income.

Leases

The Company determines if an arrangement is a lease at its inception. Right-of-use (“ROU”) assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. We uses our estimated incremental borrowing rate in determining the present value of lease payments considering the term of the lease, which is derived from information available at the lease commencement date. The lease term includes renewal options when it is reasonably certain that the option will be exercised and excludes termination options. To the extent that the Company’s agreements have variable lease payments, the Company includes variable lease payments that depend on an index or a rate and excludes those that depend on facts or circumstances occurring after the commencement date, other than the passage of time.

Lease expense for these leases is recognized on a straight-line basis over the lease term. We have elected not to recognize ROU assets and lease liabilities that arise from short-term leases for any class of underlying asset. Operating leases are included in Operating lease, right-of-use-assets, Operating lease liabilities, and Long-term operating lease liabilities in our Consolidated Balance Sheets.

Goodwill

Goodwill represents the excess of the purchase price over the fair value of identifiable assets acquired and liabilities assumed. Goodwill is not amortized, rather assessed, at least annually, for impairment at a reporting unit level. Impairment of goodwill exists when the carrying amount of a reporting unit exceeds its fair value. A goodwill impairment loss is recognized for the amount that the carrying amount of the reporting unit, including goodwill, exceeds its fair value, limited to the total amount of goodwill allocated to that reporting unit. If the fair value of a reporting unit exceeds the carrying amount, goodwill of the reporting unit is not considered impaired.

We evaluate impairment by first assessing qualitative factors to determine whether it is necessary to perform a quantitative impairment test. If we determine, as a result of the qualitative assessment, that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then the quantitative impairment test is required. Otherwise, no further testing is required.

We perform our annual goodwill impairment test in the fourth quarter of each year by assessing qualitative factors, including, but not limited to an assessment of our market capitalization, which was significantly higher than our book value. Based on these tests, we determined that the quantitative impairment test was not required and no impairment charges were recorded in fiscal 2020, 2019 or 2018.

The evaluation of goodwill for impairment requires the exercise of judgment. In the event of future changes in business conditions, we will be required to reassess and update our forecasts and estimates used in future impairment analysis. If the results of these analysis are lower than current estimates, a material impairment charge may result at that time.

See Note 9, Goodwill and Intangible Assets, for additional information.

Intangible Assets

Intangible assets consist of acquisition related intangible assets and intellectual property. The intangible assets are being amortized over periods of 1 to 10 years, which reflect the pattern in which economic benefits of the assets are expected to be realized. We perform a review of intangible assets when facts and circumstances indicate that the useful life is shorter than originally estimated or that the carrying amount of assets may not be recoverable. Such facts and circumstances include significant adverse changes in the business climate or legal factors; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the intangible assets; and current expectation that the intangible assets will more likely than not be sold or disposed of before the end of their estimated useful lives. We assess the recoverability of identified intangible assets by comparing the projected undiscounted net cash flows associated with the related asset or group of assets over their remaining lives against their respective carrying amounts. Impairments, if any, are based on the excess of the carrying amount over the fair value of those assets.

See Note 9, Goodwill and Intangible Assets, for additional information.

Impairment of Long-Lived Assets

We test long-lived assets or asset groups, such as property, plant and equipment and intangible assets, for recoverability when events or changes in circumstances indicate that their carrying amounts may not be recoverable. Circumstances which could trigger a review include, but are not limited to: significant decreases in the market price of the asset; significant adverse changes in the business climate or legal factors; accumulation of costs significantly in excess of the amount originally expected for the acquisition or construction of the asset; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the asset; and current expectation that the asset will more likely than not be sold or disposed of before the end of its estimated useful life.

Recoverability is assessed based on the carrying amounts of the asset or asset group and the sum of the undiscounted cash flows expected to result from the use and the eventual disposal of the asset. An impairment loss is recognized when the carrying amount is not recoverable and exceeds fair value.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash equivalents, marketable securities and accounts receivable. Our cash equivalents and marketable securities are held in safekeeping by large, credit worthy financial institutions. We invest our excess cash primarily in U.S. banks, government and agency bonds, money market funds and corporate obligations. We have established guidelines relative to credit ratings, diversification and maturities that seek to maintain safety and liquidity. Deposits in these banks may exceed the amounts of insurance provided on such deposits. To date, we have not experienced any losses on our deposits of cash and cash equivalents. We market and sell our products to a relatively narrow base of customers and generally do not require collateral.

The following customers represented 10% or more of our revenues:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Intel Corporation	31.5	%	25.3	%	19.0	%
Samsung Electronics., LTD.	*		11.5		*

* Less than 10% of revenues.

At December 26, 2020, two customers accounted for 15.3% and 13.7% of gross accounts receivable, respectively. At December 28, 2019, three customers accounted for 25.7%, 15.1%, and 11.5% of gross accounts receivable, respectively. No other customers accounted for 10% or more of gross accounts receivable for these fiscal period ends.

We are exposed to non-performance risk by counterparties on our derivative instruments used in hedging activities. We seek to minimize risk by diversifying our hedging program across multiple financial institutions. These counterparties are large international financial institutions, and, to date, no such counterparty has failed to meet its financial obligations to us.

Revenue Recognition

Revenue is recognized upon transferring control of products and services, and the amounts recognized reflect the consideration we expect to be entitled to receive in exchange for these products and services. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities. An arrangement may include some or all of the following products and services: probe cards, systems, accessories, installation services, service contracts and extended warranty contracts. We sell our products and services direct to customers and to partners in two distribution channels: global direct sales force and through a combination of manufacturers’ representatives and distributors.

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer. In contracts with multiple performance obligations, we identify each performance obligation and evaluate whether the performance obligation is distinct within the context of the contract at contract inception. Performance obligations that are not distinct at contract inception are combined and accounted for as one unit of account. Generally, the performance obligations in a contract are considered distinct within the context of the contract and are accounted for as separate units of account.

Our products may be customized to our customers’ specifications, however, control of our product is typically transferred to the customer at the point in time the product is either shipped or delivered, depending on the terms of the arrangement, as the criteria for overtime recognition is not met. In limited circumstances, substantive acceptance by the customer exists which results in the deferral of revenue until acceptance is formally received from the customer. Judgment may be required in determining if the acceptance clause is substantive. In certain instances control of products is transferred to the customer over time based on performance and in those instances we utilize an appropriate input or output measure to determine to what extent control has transferred to the customer. Judgment may be required in determining an appropriate measure of performance.

Installation services are routinely provided to customers purchasing our systems. Installation services are a distinct performance obligation apart from the systems and recognized in the period they are performed. Service contracts, which include repair and maintenance service contracts, and extended warranty contracts are also distinct performance obligations and recognized over the contractual service period, which ranges from one to three years. For these service contracts recognized over time, we use an input measure, days elapsed, to measure progress.

A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. In determining the transaction price, we evaluate whether the price is subject to refund or adjustment to determine the net consideration to which we expect to be entitled. We generally do not grant return privileges, except for defective products during the warranty period. Sales incentives and other programs that we may make available to these customers are considered to be a form of variable consideration, which is estimated in determining the contract’s transaction price to be allocated to the performance obligations.

For contracts with multiple performance obligations, we allocate the contract’s transaction price to each performance obligation based on its relative stand-alone selling price. The stand-alone selling prices are determined based on observable prices, which are the prices at which we separately sell these products. For items which do not have observable prices, we use our best estimate of the stand-alone selling prices.

Transaction price allocated to the remaining performance obligations: On December 26, 2020, we had $7.9 million of remaining performance obligations, which were comprised of deferred service contracts and extended warranty contracts and

contracts with overtime revenue recognition that are not yet delivered. We expect to recognize approximately 84.1% of our remaining performance obligations as revenue in fiscal 2021, approximately 9.5% in fiscal 2022, and approximately 6.4% in fiscal 2023 and thereafter. The foregoing excludes the value of remaining performance obligations that have original durations of one year or less, and also excludes information about variable consideration allocated entirely to a wholly unsatisfied performance obligation.

Contract balances: The timing of revenue recognition may differ from the timing of invoicing to customers. Accounts receivable is recorded at the invoiced amount, net of an allowance for doubtful accounts. A receivable is recognized in the period we deliver goods or provide services or when our right to consideration is unconditional. A contract asset is recorded when we have performed under the contract but our right to consideration is conditional on something other than the passage of time. Contract assets as of December 26, 2020 and December 28, 2019 were $3.7 million and $0.9 million, respectively, and are reported on the Consolidated Balance Sheets as a component of Prepaid expenses and other current assets.

Contract liabilities include payments received and payments due in advance of performance under a contract and are satisfied as the associated revenue is recognized. Contract liabilities are reported on the Consolidated Balance Sheets on a contract-by-contract basis at the end of each reporting period as a component of Deferred revenue and Other liabilities. Contract liabilities totaled $22.2 million and $10.8 million at December 26, 2020 and December 28, 2019, respectively. During fiscal 2020, we recognized $9.5 million of revenue that was included in contract liabilities as of December 28, 2019.

Costs to obtain a contract: We generally expense sales commissions when incurred as a component of Selling, general and administrative expense as the amortization period is typically less than one year.

Revenue by Category: Refer to Note 15, Segments and Geographic Information, for further details.

Warranty Obligations

We offer warranties on certain products and record a liability for the estimated future costs associated with warranty claims at the time revenue is recognized. The warranty liability is based upon historical experience and our estimate of the level of future costs. While we engage in product quality programs and processes, our warranty obligation is affected by product failure rates, material usage and service delivery costs incurred in correcting a product failure. We continuously monitor product returns for warranty and maintain a reserve for the related expenses based upon our historical experience and any specifically identified field failures. As we sell new products to our customers, we must exercise considerable judgment in estimating the expected failure rates. This estimating process is based on historical experience of similar products, as well as various other assumptions that we believe to be reasonable under the circumstances.

We provide for the estimated cost of product warranties at the time revenue is recognized. Warranty costs are reflected in the Consolidated Statement of Income as a Cost of revenues.

A reconciliation of the changes in our warranty liability is as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Balance at beginning of year	$	1,942	$	2,102	$	3,662

Accruals	5,727		3,881		3,181
Settlements	(3,751)		(4,041)		(4,741)
Balance at end of year	$	3,918	$	1,942	$	2,102

Research and Development

Research and development expenses include expenses related to product development, engineering and material costs. All research and development costs are expensed as incurred.

Income Taxes

We utilize the asset and liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statement and tax basis of assets and liabilities using tax rates expected to be in effect during the years in which the basis differences reverse and for operating losses and tax credit carryforwards. We estimate our provision for income taxes and amounts ultimately payable or recoverable in numerous tax jurisdictions around the world. Estimates involve interpretations of regulations and are inherently complex. Resolution of income tax treatments in individual jurisdictions may not be known for many years after completion of any fiscal year. We are required to evaluate the realizability

of our deferred tax assets on an ongoing basis to determine whether there is a need for a valuation allowance with respect to such deferred tax assets. A valuation allowance is recorded when it is more likely than not that some or all of the deferred tax assets will not be realized. In evaluating the ability to recover deferred tax assets, we consider all available positive and negative evidence giving greater weight to our recent cumulative income, our historical ability to utilize net operating losses in recent years and our forecast of future taxable income, including the reversal of temporary differences and the implementation of feasible and prudent tax planning strategies.

We recognize and measure uncertain tax positions taken or expected to be taken in a tax return if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized are then measured based on the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement. We report a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return. We adjust these reserves in light of changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will impact the provision for income taxes in the period in which such determination is made. The provision for income taxes includes the impact of reserve provisions and changes to reserves that are considered appropriate, as well as the related net interest. We recognize interest and penalties related to unrecognized tax benefits within the income tax provision. Accrued interest and penalties are included within the related tax liability in the Consolidated Balance Sheets.

We file annual income tax returns in multiple taxing jurisdictions around the world. A number of years may elapse before an uncertain tax position is audited and finally resolved. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, we believe that our related liability reflects the most likely outcome. We adjust the liability, as well as the related interest, in light of changing facts and circumstances. Settlement of any particular position could require the use of cash.

Stock-Based Compensation

We recognize compensation expense for all stock-based awards based on the grant-date estimated fair values. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service periods in our Consolidated Statements of Income. The fair value of stock options is measured using the Black-Scholes option pricing model, while the fair value for restricted stock units ("RSUs") is measured based on the closing market price of our common stock on the date of grant. The fair value of Performance RSUs ("PRSU") is based on certain market performance criteria and is measured using the Monte Carlo simulation pricing model.

See Notes 11, Stockholders' Equity, and 12, Stock-Based Compensation, for additional information.

Net Income Per Share

Basic net income per share is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted net income per share is computed giving effect to all potentially dilutive common stock and common stock equivalents, including stock options, RSUs and common stock subject to repurchase.

The following table reconciles the shares used in calculating basic net income per share and diluted net income per share (in thousands):


	Fiscal Year Ended
	December 26, 2020	December 28, 2019	December 29, 2018



Weighted-average shares used in computing basic net income per share	76,681	74,994	73,482
Add potentially dilutive securities	2,320	2,292	1,700
Weighted-average shares used in computing basic and diluted net income per share	79,001	77,286	75,182

Accumulated Other Comprehensive Income (Loss)

Accumulated other comprehensive income (loss) ("OCI") includes the following items, the impact of which has been excluded from earnings and reflected as components of stockholders' equity as shown below (in thousands):


	December 26, 2020		December 28, 2019
Unrealized losses on available-for-sale marketable securities	$	(126)	$	(352)
Translation adjustments and other	5,184		53
Unrealized gains (losses) on derivative instruments	828		(360)
Accumulated other comprehensive income (loss)	$	5,886	$	(659)

Balance Sheet Components

12 Months Ended

Dec. 26, 2020

Balance Sheet Components [Abstract]

Balance Sheet Components

Marketable Securities

Marketable securities consisted of the following (in thousands):


December 26, 2020	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasuries	$	40,602	$	124	$	—	$	40,726

Corporate bonds	24,156		176		(2)		24,330
Certificate of deposit	2,160		19		—		2,179
Agency securities	575		—		—		575
	$	67,493	$	319	$	(2)	$	67,810


December 28, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasuries	$	10,458	$	11	$	—	$	10,469
Commercial paper	3,914		1		(4)		3,911
Corporate bond	33,867		68		(7)		33,928
Certificate of deposit	3,584		5		—		3,589
Agency securities	24,408		38		(16)		24,430
	$	76,231	$	123	$	(27)	$	76,327

We classify our marketable securities as available-for-sale. All marketable securities represent the investment of funds available for current operations, notwithstanding their contractual maturities. Such marketable securities are recorded at fair value and unrealized gains and losses are recorded in Accumulated other comprehensive income (loss) until realized.

We typically invest in highly-rated securities with low probabilities of default. Our investment policy requires investments to be rated single A or better, limits the types of acceptable investments, concentration as to security holder and duration of the investment. The gross unrealized gains and losses in fiscal 2020 and 2019 were caused primarily by changes in interest rates.

The longer the duration of marketable securities, the more susceptible they are to changes in market interest rates and bond yields. As yields increase, those securities with a lower yield-at-cost show a mark-to-market unrealized loss. We anticipate recovering the full cost of the securities either as market conditions improve, or as the securities mature. Accordingly, we believe that the unrealized losses are not as a result of a credit loss. As of December 26, 2020 and December 28, 2019, gross unrealized losses related to our marketable securities portfolio were not material.

The contractual maturities of marketable securities were as follows (in thousands):


	December 26, 2020				December 28, 2019
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	50,500	$	50,679	$	38,899	$	38,944
Due after one year to five years	16,993		17,131		37,332		37,383
	$	67,493	$	67,810	$	76,231	$	76,327

See also Note 8, Fair Value.

Fair Value

12 Months Ended

Dec. 26, 2020

Fair Value Disclosures [Abstract]

Fair Value

Whenever possible, the fair values of our financial assets and liabilities are determined using quoted market prices of identical securities or quoted market prices of similar securities from active markets. The three levels of inputs that may be used to measure fair value are as follows:

•Level 1 valuations are obtained from real-time quotes for transactions in active exchange markets involving identical securities;

•Level 2 valuations utilize significant observable inputs, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and

•Level 3 valuations utilize unobservable inputs to the valuation methodology and include our own data about assumptions market participants would use in pricing the asset or liability based on the best information available under the circumstances.

We did not have any transfers of assets or liabilities measured at fair value on a recurring basis to or from Level 1, Level 2 or Level 3 during fiscal 2020, 2019 or 2018.

The carrying values of Cash, Accounts receivable, net, Restricted cash, Prepaid expenses and other current assets, Accounts payable, Accrued liabilities, and Current portion of term loans, net of unamortized issuance costs approximate fair value due to their short maturities.

No changes were made to our valuation techniques during fiscal 2020.

Cash Equivalents

The fair value of our cash equivalents is determined based on quoted market prices for similar or identical securities.

Marketable Securities

We classify our marketable securities as available-for-sale and value them utilizing a market approach. Our investments are priced by pricing vendors who provide observable inputs for their pricing without applying significant judgment. Broker pricing is used mainly when a quoted price is not available, the investment is not priced by our pricing vendors or when a broker price is more reflective of fair value. Our broker-priced investments are categorized as Level 2 investments because fair value is based on similar assets without applying significant judgments. In addition, all of our investments have a sufficient level of trading volume to demonstrate that the fair value is appropriate.

Contingent Consideration

Contingent consideration, arising from the acquisition of FRT (see Note 4, Acquisitions), is a cash amount equal to 1.5x EBIT as defined in the purchase agreement, up to a maximum of €10.3 million, payable subject to the performance of the acquired

business in calendar 2020. We originally estimated the fair value of contingent consideration at acquisition using a probability weighted approach. Key assumptions in determining the fair value of contingent consideration included estimating the probability of achieving certain EBIT levels and discounting at an appropriate discount rate. Based on actual results during the earnout period, contingent consideration as of December 26, 2020 was estimated to be $4.0 million, a net decrease of $1.4 million from $5.4 million as of December 28, 2019.

Assets and liabilities Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis were as follows (in thousands):


December 26, 2020	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	43,019	$	—	$	—	$	43,019

Marketable securities:
U.S. Treasuries	40,726		—		—		40,726
Certificates of deposit	—		2,179		—		2,179
Agency securities	—		575		—		575
Corporate bonds	—		24,330		—		24,330

	40,726		27,084		—		67,810
Foreign exchange derivative contracts	—		1,057		—		1,057
Interest rate swap derivative contracts	—		57		—		57
Total assets	$	83,745	$	28,198	$	—	$	111,943
Liabilities:
Foreign exchange derivative contracts	$	—	$	—	$	—	$	—
Interest rate swap derivative contracts	—		(87)		—		(87)
Contingent consideration	—		—		(4,012)		(4,012)
Total liabilities	$	—	$	(87)	$	(4,012)	$	(4,099)


December 28, 2019	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	17,056	$	—	$	—	$	17,056


Marketable securities:
U.S. Treasuries	10,468		—		—		10,468
Certificates of deposit	—		3,590		—		3,590
Agency securities	—		24,430		—		24,430
Corporate bonds	—		33,928		—		33,928
Commercial paper	—		3,911		—		3,911
	10,468		65,859		—		76,327
Foreign exchange derivative contract	—		41		—		41
Interest rate swap derivative contracts	—		26		—		26
Total assets	$	27,524	$	65,926	$	—	$	93,450
Liabilities:
Foreign exchange derivative contracts	$	—	$	(240)	$	—	$	(240)
Contingent consideration	—		—		(5,364)		(5,364)
Total liabilities	$	—	$	(240)	$	(5,364)	$	(5,604)

Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis

We measure and report our non-financial assets such as Property, plant and equipment, Goodwill and Intangible assets at fair value on a non-recurring basis if we determine these assets to be impaired or in the period when we make a business

acquisition. Other than as discussed in Note 4, Acquisitions, there were no assets or liabilities measured at fair value on a nonrecurring basis during fiscal 2020, 2019 or 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Goodwill and Intangible Assets

12 Months Ended

Dec. 26, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

Goodwill

Goodwill by reportable segment was as follows (in thousands):


	Probe Cards		Systems		Total
Goodwill, gross, as of December 30, 2017	$	172,482	$	17,438	$	189,920
Foreign currency translation	—		(706)		(706)
Goodwill, gross, as of December 29, 2018	172,482		16,732		189,214
Addition - FRT acquisition	—		10,148		10,148
Foreign currency translation	—		(166)		(166)
Goodwill, gross, as of December 28, 2019	172,482		26,714		199,196
Addition - FRT acquisition	—		975		975
Addition - Baldwin Park acquisition	5,590		—		5,590
Addition - HPD acquisition	—		4,654		4,654
Foreign currency translation	—		2,346		2,346
Goodwill, gross, as of December 26, 2020	$	178,072	$	34,689	$	212,761

We have not recorded any goodwill impairments as of December 26, 2020.

Intangible Assets

Intangible assets were as follows (in thousands):


	December 26, 2020						December 28, 2019
Other Intangible Assets	Gross		Accumulated Amortization		Net		Gross		Accumulated Amortization		Net
Existing developed technologies	$	176,265	$	137,754	$	38,511	$	154,951	$	116,138	$	38,813
Trade name	8,162		7,363		799		7,816		6,976		840
Customer relationships	52,488		33,378		19,110		44,229		27,057		17,172
Backlog	2,227		1,900		327		1,676		891		785
In-process research and development	400		—		400		—		—		—
	$	239,542	$	180,395	$	59,147	$	208,672	$	151,062	$	57,610

Amortization expense was included in our Consolidated Statements of Income as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Cost of revenues	$	21,609	$	20,036	$	20,530
Selling, general and administrative	6,382		7,636		8,843
	$	27,991	$	27,672	$	29,373

The estimated future amortization of definite-lived intangible assets, excluding in-process research and development, is as follows (in thousands):


Fiscal Year	Amount
2021	$	20,207
2022	10,594
2023	8,364
2024	5,951
2025	4,398
Thereafter	9,233
Total	$	58,747

We did not record any impairment of intangible assets in fiscal 2020, 2019 and 2018.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 26, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases See Note 6, Leases. Environmental Matters We are subject to U.S. federal, state, local, and foreign governmental laws and regulations relating to the protection of the environment, including those governing the discharge of pollutants into the air and water, the management and disposal of hazardous substances and wastes, the clean-up of contaminated sites and the maintenance of a safe workplace. We believe that we comply in all material respects with the environmental laws and regulations that apply to us. We did not receive any notices of violations of environmental laws and regulations in fiscal 2020, 2019 or 2018. In the future, we may receive notices of violations of environmental regulations, or otherwise learn of such violations. Environmental contamination or violations may negatively impact our business. Indemnification Arrangements We have entered, and may from time to time in the ordinary course of our business enter, into contractual arrangements with third parties that include indemnification obligations. Under these contractual arrangements, we have agreed to defend, indemnify and/or hold the third party harmless from and against certain liabilities. These arrangements include indemnities in favor of customers in the event that our products or services infringe a third party's intellectual property or cause property or other indemnities in favor of our lessors in connection with facility leasehold liabilities that we may cause. In addition, we have entered into indemnification agreements with our directors and certain of our officers, and our bylaws contain indemnification obligations in favor of our directors, officers and agents. These indemnity arrangements may limit the type of the claim, the total amount that we can be required to pay in connection with the indemnification obligation and the time within which an indemnification claim can be made. The duration of the indemnification obligation may vary, and for most arrangements, survives the agreement term and is indefinite. We believe that substantially all of our indemnity arrangements provide either for limitations on the maximum potential future payments we could be obligated to make, or for limitations on the types of claims and damages we could be obligated to indemnify, or both. However, it is not possible to determine or reasonably estimate the maximum potential amount of future payments under these indemnification obligations due to the varying terms of such obligations, a lack of history of prior indemnification claims, the unique facts and circumstances involved in each particular contractual arrangement and in each potential future claim for indemnification, and the contingency of any potential liabilities upon the occurrence of events that are not reasonably determinable. We have not had any material requests for indemnification under these arrangements. We have not recorded any liabilities for these indemnification arrangements on our Consolidated Balance Sheets as of December 26, 2020 or December 28, 2019. Legal Matters From time to time, we may be subject to legal proceedings and claims in the ordinary course of business. As of December 26, 2020, and as of the filing of these financial statements, we were not involved in any material legal proceedings. In the future, we may become a party to additional legal proceedings that may require us to spend significant resources. Litigation can be expensive and disruptive to normal business operations. The results of legal proceedings are difficult to predict, and the costs incurred in litigation can be substantial, regardless of outcome.

Stockholders' Equity

12 Months Ended

Dec. 26, 2020

Equity [Abstract]

Stockholders' Equity

Preferred Stock

We have authorized 10,000,000 shares of undesignated preferred stock, $0.001 par value, none of which is issued and outstanding. Our Board of Directors shall determine the rights, preferences, privileges and restrictions of the preferred stock, including dividends rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series.

Common Stock

Each share of common stock has the right to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the Board of Directors, subject to the prior rights of holders, if any, of all classes of stock outstanding having priority rights as to dividends. No dividends have been declared or paid as of December 26, 2020.

Common Stock Repurchase Program

On October 26, 2020, our Board of Directors authorized a program to repurchase up to $50 million of outstanding common stock to offset potential dilution from issuances of common stock under our stock-based incentive plans. The share repurchase program will expire October 28, 2022. This repurchase program replaced the previous repurchase program that expired in February 2020 to purchase up to $25.0 million of outstanding common stock. During fiscal 2020, 2019 and 2018, we did not repurchase any shares.

Equity Incentive Plan

We currently grant equity-based awards under our Equity Incentive Plan, as amended (the "2012 Plan") which was approved by our stockholders. As amended, the 2012 Plan has authorized for issuance a total of 16.8 million shares, 6.0 million of which were available for grant as of December 26, 2020.

RSUs granted under the 2012 Plan generally vest over three years in annual tranches, though we have granted, and will continue to grant, such awards that vest over a shorter term for employee retention purposes.

The 2012 Plan provides that incentive stock options may be granted to our employees and nonqualified stock options, and all awards other than incentive stock options, may be granted to employees, directors and consultants. The exercise price of incentive stock options must be at least equal to the fair market value of our common stock on the date of grant. All restricted stock units and options granted under the 2012 Plan generally vest over three years and expire after seven years, unless otherwise determined by the Compensation Committee of the Board of Directors.

Stock Options

Stock option activity was as follows:


	Outstanding Options
	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value
Outstanding at December 28, 2019	361,769	$	8.35

Options exercised	(255,769)	8.35

Outstanding at December 26, 2020	106,000	$	8.35	2.16	$	3,627,900
Vested and expected to vest at December 26, 2020	106,000	$	8.35	2.16	$	3,627,900
Exercisable at December 26, 2020	106,000	$	8.35	2.16	$	3,627,900

Restricted Stock Units

RSUs, including Performance Restricted Stock Units ("PRSUs") are converted into shares of our common stock upon vesting on a one-for-one basis. The vesting of RSUs is subject to the employee's continuing service. RSU activity was as follows:


	Number of Shares	Weighted Average Grant Date Fair Value
Restricted stock units at December 28, 2019	3,069,000	$	14.30
Granted	1,274,453	25.96
Vested	(1,453,378)	13.72
Canceled	(49,153)	15.70
Restricted stock units at December 26, 2020	2,840,922	19.80

The PRSUs granted in fiscal 2020, 2019 and 2018 listed below vest based on us achieving certain market performance criteria. The performance criteria are based on a metric called Total Shareholder Return ("TSR") for the performance period of three years, relative to the TSR of the companies identified as being part of the S&P Semiconductor Select Industry Index (FormFactor peer companies) as of a specific date.

Of the 333,000 PRSUs granted in fiscal 2017, 78,333 shares were forfeited, resulting in 255,000 shares vesting in fiscal 2020. These shares achieved the maximum 125% TSR performance, which resulted in an additional 63,750 shares issued in fiscal 2020 related to the fiscal 2017 PRSU grant.

PRSU grant activity was as follows:

Fiscal Year Ended

December 26, 2020

December 28, 2019

December 29, 2018

Grant Date

August 27, 2020

June 4, 2019

August 16, 2018

Performance period

July 1, 2020 - June 30, 2023

July 1, 2019 - June 30, 2022

July 1, 2018 - June 30, 2021

Number of shares

258,000

273,000

318,100

TSR as-of date

August 27, 2020

June 4, 2019

August 16, 2018

Stock-based compensation

$6.9 million

$4.4 million

$4.7 million

Employee Stock Purchase Plan

Our 2012 Employee Stock Purchase Plan (the "ESPP"), as amended, allows for the issuance of a total of 7,000,000 shares. The offering periods under the ESPP are 12 months commencing on February 1 of each calendar year and ending on January 31 of the subsequent calendar year, and a six-month fixed offering period commencing on August 1 of each calendar year and ending on January 31 of the subsequent calendar year. The 12-month offering period consists of two six-month purchase periods and the six-month offering period consists of one six-month purchase period. The price of the common stock purchased is 85% of the lesser of the fair market value of the common stock on the first day of the applicable offering period or the last day of each purchase period.

During fiscal 2020, employees purchased 485,566 shares under this program at a weighted average exercise price of $16.47 per share, which represented a weighted average discount of $11.00 per share from the fair value of the stock purchased. As of December 26, 2020, 2,171,656 shares remained available for issuance.

Stock-Based Compensation

12 Months Ended

Dec. 26, 2020

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Stock-Based Compensation Expense

Certain information regarding our stock-based compensation was as follows (in thousands, except per share amounts):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018

Weighted average grant date per share fair value of RSUs granted	$	25.96	$	15.12	$	13.79
Total intrinsic value of stock options exercised	4,688		1,814		631
Fair value of RSUs vested	$	42,597	$	23,450	$	17,541

Pre-tax stock-based compensation expense by financial statement line and related tax benefit in the Consolidated Statements of Income are as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Stock-based compensation expense included in:
Cost of revenues	$	3,951	$	4,055	$	3,525
Research and development	5,824		6,367		5,398
Selling, general and administrative	14,055		12,754		8,904

Total stock-based compensation	$	23,830	$	23,176	$	17,827
Stock-based compensation tax benefit	$	4,962	$	911	$	453

Unrecognized Stock-Based Compensation Expense

Unrecognized stock-based compensation expense at December 26, 2020 consisted of the following (in thousands):


	Unrecognized Expense		Weighted Average Recognition Period (Years)

Restricted stock units	$	32,122	2.2
Performance restricted stock units	9,075		2.1
Employee stock purchase plan	248		0.1
Total unrecognized stock-based compensation expense	$	41,445	2.2

Valuation Assumptions

The following assumptions were used in estimating the fair value of PRSUs:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
PRSUs:
Dividend yield	—	%	—	%	—	%
Expected volatility	52.01	%	47.34	%	45.61	%
Risk-free interest rate	0.18	%	1.83	%	2.67	%
Expected life (in years)	2.8		3.1		2.9

The following assumptions were used in estimating the fair value of shares under the Employee Stock Purchase Plan:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Employee Stock Purchase Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	30.4% - 74.4%		36.6% - 59.5%		44.9% - 48.9%
Risk-free interest rate	0.10% - 1.54%		2.04% - 2.46%		0.83% - 2.22%
Expected life (in years)	0.5 - 1.0		0.5 - 1.0		0.5 - 1.0

Income Taxes

12 Months Ended

Dec. 26, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Components of Income Before Income Taxes

The components of income before income taxes were as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
United States	$	72,950	$	41,115	$	20,877
Foreign	12,225		9,948		13,050
	$	85,175	$	51,063	$	33,927

Provision for Income Taxes

The components of the provision (benefit) for income taxes are as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Current provision:
Federal	$	1,799	$	179	$	79
State	1,194		2,302		388
Foreign	4,278		4,202		4,687
	7,271		6,683		5,154
Deferred provision (benefit):
Federal	1,472		8,128		(72,295)
State	(267)		(1,898)		(2,056)
Foreign	(1,824)		(1,196)		(912)
	(619)		5,034		(75,263)
Total provision (benefit) for income taxes	$	6,652	$	11,717	$	(70,109)

Tax Rate Reconciliation

The following is a reconciliation of the difference between income taxes computed by applying the federal statutory rate of 21% and the provision (benefit) from income taxes (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
U.S. statutory federal tax rate	$	17,887	$	10,723	$	7,125
State taxes, net of federal benefit	663		441		778
Stock-based compensation	(4,962)		(911)		(453)
Research and development credits	(6,576)		(6,436)		(3,213)
Foreign taxes at rates different than the U.S.	415		1,454		1,287
Other permanent differences	400		(148)		152
Global intangible low-taxed income	—		1,369		1,828
Foreign Derived Intangible Income	(3,668)		—		—
Change in valuation allowance	1,862		2,567		(75,803)
Other	631		2,658		(1,810)
Total	$	6,652	$	11,717	$	(70,109)

Deferred Tax Assets and Liabilities

Deferred tax assets and liabilities are recognized for the future tax consequences of differences between the carrying amounts of assets and liabilities and their respective tax basis using enacted tax rates in effect for the year in which the differences are expected to be reversed.

Significant deferred tax assets and liabilities consisted of the following (in thousands):


	As of
	December 26, 2020		December 28, 2019
Tax credits	$	42,927	$	44,696
Inventory reserve	13,401		12,350
Other reserves and accruals	9,470		5,852
Non-statutory stock options	2,794		2,982
Depreciation and amortization	20,961		27,758
Net operating loss carryforwards	18,421		21,410
Gross deferred tax assets	107,974		115,048
Valuation allowance	(38,466)		(36,604)
Total deferred tax assets	69,508		78,444
Acquired intangibles and fixed assets	(8,395)		(13,997)
Unrealized investment gains	(106)		(106)
Tax on undistributed earnings	(110)		(75)
Total deferred tax liabilities	(8,611)		(14,178)
Net deferred tax assets	$	60,897	$	64,266

We are required to evaluate the realizability of our deferred tax assets in both our U.S. and non-U.S. jurisdictions on an ongoing basis to determine whether there is a need for a valuation allowance with respect to such deferred tax assets. From the fourth quarter of fiscal 2009 to the third quarter of fiscal 2018, we maintained a 100% valuation allowance against most of our U.S. deferred tax assets because there was insufficient positive evidence to overcome the existing negative evidence such that it was not more likely than not that the U.S. deferred tax assets were realizable. While we reported U.S. pre-tax income in fiscal 2015 and fiscal 2017, because we reported U.S. pre-tax losses during the previous seven fiscal years, we continued to maintain the 100% valuation allowance through the third quarter of fiscal 2018.

The valuation allowance decreased by $75.8 million in fiscal 2018 as we released the valuation allowance against a significant portion of the U.S. federal deferred tax assets and a portion of the U.S. state deferred tax assets. We determined that the positive

evidence overcame any negative evidence and concluded that it was more likely than not that the U.S. deferred tax assets were realizable after considering the reported positive operating performance in the U.S. for two consecutive fiscal years, the reported cumulative three-year U.S. pre-tax profit, and the expected positive operating performance in the U.S. for 2019.

As of December 26, 2020, we maintained a valuation allowance of $38.5 million, primarily related to California deferred tax assets arising from research credits and foreign tax credit carryovers, due to uncertainty about the future realization of these assets.

Tax Credits and Carryforwards

Tax credits and carryforwards available to us at December 26, 2020 consisted of the following (in thousands):


	Amount		Latest Expiration Date
Federal research and development tax credit	$	36,579	2023-2040
Foreign tax credit carryforwards	1,059		2021-2027
California research credits	42,615		Indefinite
State net operating loss carryforwards	247,990		2022-Indefinite
Singapore net operating loss carryforwards	7,046		Indefinite

Undistributed Earnings

As of December 26, 2020, unremitted earnings of foreign subsidiaries was estimated at $34.4 million. We intend to permanently invest $12.0 million of undistributed earnings indefinitely outside of the U.S. To the extent we repatriate the remaining $22.4 million of undistributed foreign earnings to the U.S., we established a deferred tax liability of $0.1 million for foreign withholding taxes. Our estimates are provisional and subject to further analysis.

Unrecognized Tax Benefits

We recognize the benefits of tax return positions if we determine that the positions are “more-likely-than-not” to be sustained by the taxing authority. Interest and penalties accrued on unrecognized tax benefits are recorded as tax expense in the period incurred.

The following table reflects changes in the unrecognized tax benefits (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Unrecognized tax benefit, beginning balance	$	28,800	$	25,224	$	18,296
Additions based on tax positions related to the current year	3,072		3,679		1,677
Additions based on tax positions from prior years	702		—		5,332
Reductions for tax positions of prior years	—		(5)		(7)
Reductions due to lapse of the applicable statute of limitations	(77)		(98)		(74)
Unrecognized tax benefit, ending balance	$	32,497	$	28,800	$	25,224

Interest and penalties recognized as a component of Provision (benefit) for income taxes	$	50	$	59	$	71
Interest and penalties accrued at period end	204		212		230

Of the unrecognized tax benefits at December 26, 2020, $15.8 million would impact the effective tax rate if recognized.

The amount of income taxes we pay is subject to ongoing audits by federal, state and foreign tax authorities which might result in proposed assessments. Our estimate for the potential outcome for any uncertain tax issue is judgmental in nature. However, we believe we have adequately provided for any reasonably foreseeable outcome related to those matters. Our future results may include favorable or unfavorable adjustments to our estimated tax liabilities in the period the assessments are made or resolved or when statutes of limitation on potential assessments expire. As of December 26, 2020, changes to our uncertain tax positions in the next 12 months that are reasonably possible are not expected to have a significant impact on our financial position or results of operations.

At December 26, 2020, our tax years 2017 through 2020, 2016 through 2020 and 2015 through 2020, remain open for examination in the federal, state and foreign jurisdictions, respectively. However, to the extent allowed by law, the taxing authorities may have the right to examine prior periods where net operating losses and credits were generated and carried forward, and make adjustments up to the net operating loss and credit carryforward amounts.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 26, 2020
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit PlansWe have an employee savings plan that qualifies as a deferred salary arrangement under Section 401(k) of the Internal Revenue Code. The plan is designed to provide employees with an accumulation of funds for retirement on a tax-deferred basis and provide for annual discretionary employer contributions. The total charge to net income under the 401(k) plan for fiscal 2020, 2019 and 2018 aggregated $2.2 million, $2.1 million and $2.0 million, respectively.

Segments and Geographic Information

12 Months Ended

Dec. 26, 2020

Segment Reporting [Abstract]

Segments and Geographic Information

We operate in two reportable segments consisting of the Probe Cards Segment and the Systems Segment.

Our chief operating decision maker ("CODM") is our Chief Executive Officer, who reviews operating results to make decisions about allocating resources and assessing performance for the entire company.

The following table summarizes the operating results by reportable segment (dollars in thousands):


	Fiscal 2020
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	581,739		$	111,877		$	—		$	693,616
Gross profit	$	263,215		$	51,835		$	(27,130)		$	287,920
Gross margin	45.2		%	46.3		%	—		%	41.5		%


	Fiscal 2019
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	491,363		$	98,101		$	—		$	589,464
Gross profit	$	211,382		$	50,927		$	(24,813)		$	237,496
Gross margin	43.0		%	51.9		%	—		%	40.3		%


	Fiscal 2018
	Probe Cards			Systems		Corporate and Other			Total
Revenues	$	434,269		$	95,406	$	—		$	529,675
Gross profit	$	187,320		$	47,074	$	(24,055)		$	210,339
Gross margin	43.1		%	49.3%		—		%	39.7		%

Operating results provide useful information to our management for assessment of our performance and results of operations. Certain components of our operating results are utilized to determine executive compensation along with other measures.

Corporate and Other includes unallocated expenses relating to amortization of intangible assets, share-based compensation expense, acquisition-related costs, including charges related to inventory stepped up to fair value, and other costs, which are not used in evaluating the results of, or in allocating resources to, our reportable segments. Acquisition-related costs include transaction costs and any costs directly related to the acquisition and integration of acquired businesses.

The following table summarizes revenue, by geographic region, as a percentage of total revenues based upon ship-to location:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
China	25.2	%	18.0	%	14.7	%
Taiwan	21.7		14.7		20.3
United States	18.4		26.3		25.2
South Korea	12.5		19.8		17.2
Europe	9.5		7.0		7.5
Japan	6.3		8.9		9.4
Asia-Pacific (1)	4.8		3.7		4.9
Rest of World	1.6		1.6		0.8
Total Revenues	100.0	%	100.0	%	100.0	%

(1)Asia-Pacific includes all countries in the region except Taiwan, South Korea, China, and Japan, which are disclosed separately.

The following table summarizes revenue by market (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Foundry & Logic	$	446,183	$	318,552	$	258,459
DRAM	109,734		147,257		135,333
Flash	25,822		25,554		40,477
Systems	111,877		98,101		95,406
Total revenues	$	693,616	$	589,464	$	529,675

The following table summarizes revenue by timing of revenue recognition (in thousands):


	Fiscal Year Ended
	December 26, 2020						December 28, 2019						December 29, 2018
	Probe Cards		Systems		Total		Probe Cards		Systems		Total		Probe Cards		Systems		Total
Products transferred at a point in time	$	579,569	$	104,858	$	684,427	$	488,925	$	93,837	$	582,762	$	432,033	$	91,514	$	523,547
Services transferred over time	2,170		7,019		9,189		2,438		4,264		6,702		2,236		3,892		6,128
Total	$	581,739	$	111,877	$	693,616	$	491,363	$	98,101	$	589,464	$	434,269	$	95,406	$	529,675

Long-lived assets, comprised of Operating lease, right-of-use-assets, Property, plant and equipment, net, Goodwill and Intangibles, net, reported based on the location of the asset was as follows (in thousands):


	December 26, 2020		December 28, 2019		December 29, 2018
United States	$	347,654	$	287,600	$	280,405
Europe	51,791		52,309		26,118
Asia-Pacific	7,322		7,064		4,385
Total	$	406,767	$	346,973	$	310,908

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8721-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8657-108599

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8721-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-URI http://asc.fasb.org/topic&trid=2134510

+ Details

New Accounting Pronouncements	12 Months Ended
New Accounting Pronouncements	Dec. 26, 2020
Accounting Policies [Abstract]
New Accounting Pronouncements	New Accounting Pronouncements ASU 2016-13 In June 2016, the Financial Accounting Standard Board ("FASB") issued ASU No. 2016-13, "Measurement of Credit Losses on Financial Instruments (Topic 326)." The provisions of this standard require financial assets measured at amortized cost to be presented at the net amount expected to be collected. An allowance account would be established to present the net carrying value at the amount expected to be collected. ASU 2016-13 also provides that credit losses relating to available-for-sale debt securities should be recorded through an allowance for credit losses. The guidance was amended through various ASU's subsequent to ASU 2016-13, all of which was effective beginning fiscal 2020. We adopted ASU 2016-13 on a prospective basis on December 29, 2019, the first day of fiscal 2020. The adoption did not have a material effect on our financial position, results of operations or cash flows. ASU 2018-15 In August 2018, the FASB issued ASU 2018-15, "Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The new guidance clarifies the accounting for implementation costs in cloud computing arrangements. ASU 2018-15 is effective for fiscal years, including interim periods within those fiscal years, beginning after December 15, 2019. We adopted ASU 2018-15 on a prospective basis on December 29, 2019, the first day of fiscal 2020. The adoption did not have a material effect on our financial position, results of operations or cash flows. ASU 2019-12 In December 2019, the FASB issued ASU 2019-12, “Income Taxes (Topic 740),” which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption of the amendments is permitted, including adoption in any interim period for which financial statements have not yet been issued. Depending on the amendment, adoption may be applied on the retrospective, modified retrospective or prospective basis. We do not expect the adoption of ASU 2019-12 to have a material effect on our financial position, results of operations or cash flows. ASU 2020-04 In March 2020, the FASB issued ASU 2020-04, "Referenced Rate Reform (Topic 848) - Facilitation of the Effects of Reference Rate Reform on Financial Reporting." The amendments in this update apply only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. The expedients and exceptions provided by the amendments do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022. The amendments in this update are elective and are effective upon issuance for all entities. We have not yet evaluated the transition approach for our LIBOR indexed contracts and have not determined whether we will be electing such expedients and exceptions.

- Definition

The entire disclosure for change in accounting principle. Includes, but is not limited to, nature, reason, and method of adopting amendment to accounting standards or other change in accounting principle.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 65
-Paragraph 1
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=113356391&loc=SL49131195-203048

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-URI http://asc.fasb.org/topic&trid=2122394

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 65
-Paragraph 1
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=113356391&loc=SL49131195-203048

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section S99
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=112272810&loc=SL108384541-122693

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 65
-Paragraph 1
-Subparagraph (i)(2)
-URI http://asc.fasb.org/extlink&oid=113356391&loc=SL49131195-203048

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(iii)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(ii)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(i)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 65
-Paragraph 1
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=113356391&loc=SL49131195-203048

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(iv)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
-SubTopic 20
-Section 65
-Paragraph 2
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=120154821&loc=SL120154904-197079

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section S99
-Paragraph 5
-Subparagraph (SAB Topic 11.M.Q2)
-URI http://asc.fasb.org/extlink&oid=112272810&loc=d3e31137-122693

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
-SubTopic 20
-Section 65
-Paragraph 2
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=120154821&loc=SL120154904-197079

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
-SubTopic 20
-Section 65
-Paragraph 2
-Subparagraph (f)(3)
-URI http://asc.fasb.org/extlink&oid=120154821&loc=SL120154904-197079

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (e)(2)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (e)(1)

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (e)(2)

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (e)(3)

+ Details

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 26, 2020
Accounting Policies [Abstract]
Fiscal Year	Fiscal YearOur fiscal year ends on the last Saturday in December.
Basis of Consolidation	Basis of Consolidation and Foreign Currency Translation The consolidated financial statements include our accounts and those of our wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated. We completed the acquisitions of FRT GmbH ("FRT") on October 9, 2019, the probe card assets of Advantest Corporation ("Baldwin Park") on July 30, 2020, and High Precision Devises, Inc. ("HPD") on October 19, 2020. Accordingly, our Consolidated Statements of Income include the results of operations of FRT, Baldwin Park, and HPD since those dates. See Note 4, Acquisitions.
Foreign Currency Translation	The functional currencies of certain of our foreign subsidiaries are the local currencies and, accordingly, all assets and liabilities of these foreign operations are translated to U.S. Dollars at current period-end exchange rates, and revenues and expenses are translated to U.S. Dollars using average exchange rates in effect during the period. The gains and losses from the foreign currency translation of these subsidiaries' financial statements are included as a separate component of stockholders' equity on our Consolidated Balance Sheets under Accumulated other comprehensive income (loss). Certain other of our foreign subsidiaries use the U.S. Dollar as their functional currency. Accordingly, monetary assets and liabilities in non-functional currencies of these subsidiaries are remeasured using exchange rates in effect at the end of the period. Revenues and costs in local currency are remeasured using average exchange rates for the period, except for costs related to those balance sheet items that are remeasured using historical exchange rates. The resulting remeasurement gains and losses are included in the Consolidated Statements of Income as a component of Other income (expense), net as incurred.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Estimates may change as new information is obtained. We believe that the estimates, assumptions and judgments involved in revenue recognition, fair value of marketable securities, fair value of derivative financial instruments used to hedge both foreign currency and interest rate exposures, allowance for doubtful accounts, reserves for product warranty, valuation of obsolete and slow moving inventory, assets acquired and liabilities assumed in business combinations, legal contingencies, valuation of goodwill, the assessment of recoverability of long-lived assets, valuation and recognition of stock-based compensation, provision for income taxes and valuation of deferred tax assets have the greatest potential impact on our consolidated financial statements. Actual results could differ from those estimates.
Business Acquisitions	Business Acquisitions Our consolidated financial statements include the operations of acquired businesses after the completion of their respective acquisitions. We account for acquired businesses using the acquisition method of accounting, which requires, among other things, that assets acquired and liabilities assumed be recognized at their estimated fair values as of the acquisition date, and that the fair value of acquired intangibles be recorded on the balance sheet. Transaction costs are expensed as incurred. Any excess of the purchase price over the assigned fair values of the net assets acquired is recorded as goodwill.
Cash and Cash Equivalents	Cash and Cash Equivalents and Marketable SecuritiesCash and cash equivalents consist of deposits and financial instruments which are readily convertible into cash and have original maturities of 90 days or less at the time of acquisition.
Marketable Securities	Marketable securities consist primarily of highly liquid investments with maturities of greater than 90 days when purchased. We classify our marketable securities as available-for-sale and, accordingly, report them at fair value with the related unrealized gains and losses included in Accumulated other comprehensive income (loss) in our Consolidated Balance Sheets. Any unrealized losses which are considered to be other-than-temporary are recorded in Other income (expense), net, in the Consolidated Statements of Income. Realized gains and losses on the sale of marketable securities are determined using the specific-identification method and recorded in Other income (expense), net, in the Consolidated Statements of Income. All of our available-for-sale investments are subject to a periodic impairment review. If an available-for-sale debt security’s fair value is less than its amortized cost basis, then we evaluate whether the decline is the result of a credit loss, in which case an impairment is recorded through an allowance for credit losses. Unrealized gains and losses not attributable to credit losses are included, net of tax, in Accumulated other comprehensive income (loss) in our Consolidated Balance Sheets.
Foreign Exchange Management	Foreign Exchange Management We transact business in various foreign currencies. We enter into forward foreign exchange contracts in an effort to mitigate the risks associated with currency fluctuations on certain foreign currency balance sheet exposures and certain operational costs denominated in local currency impacting our statement of income. For accounting purposes, certain of our foreign currency forward contracts are not designated as hedging instruments and, accordingly, we record the fair value of these contracts as of the end of our reporting period in our Consolidated Balance Sheets with changes in fair value recorded within Other income (expense), net in our Consolidated Statements of Income for both realized and unrealized gains and losses. Certain of our foreign currency forward contracts are designated as cash flow hedges, and, accordingly, we record the fair value of these contracts as of the end of our reporting period in our Consolidated Balance Sheets with changes in fair value recorded as a component of accumulated other comprehensive income (loss) and reclassified into earnings in the same period in which the hedged transaction affects earnings, and in the same line item on the Consolidated Statements of Income as the impact of the hedge transaction. We do not use derivative financial instruments for trading or speculative purposes.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts The majority of our accounts receivable are derived from sales to large multinational semiconductor manufacturers throughout the world, are recorded at their invoiced amount and do not bear interest. In order to monitor potential credit losses, we perform ongoing credit evaluations of our customers' financial condition. An allowance for doubtful accounts is maintained based upon our assessment of the expected collectability of all accounts receivable. The allowance for doubtful accounts is reviewed and assessed for adequacy on a quarterly basis. We take into consideration (1) any circumstances of which we are aware of a customer's inability to meet its financial obligations and (2) our judgments as to prevailing economic conditions in the industry and their impact on our customers. If circumstances change, and the financial condition of our customers is adversely affected and they are unable to meet their financial obligations, we may need to take additional allowances, which would result in an increase in our operating expense.
Inventories	Inventories We state our inventories at the lower of cost (principally standard cost which approximates actual cost on a first in, first out basis) or net realizable value. We continually assess the value of our inventory and will periodically write down its value for estimated excess inventory and product obsolescence based upon an analysis of existing inventory quantities compared to estimated future consumption. Future consumption is estimated based upon assumptions about how past consumption, recent purchases, backlog and other factors indicate future consumption. On a quarterly basis, we review existing inventory quantities in comparison to our past consumption, recent purchases, backlog and other factors to determine what inventory quantities, if any, may not be sellable. Based on this analysis, we record an adjustment to the cost basis of inventory when evidence exists that the net realizable value of inventory is lower than its cost, which occurs when we have excess and/or obsolete inventory. Once the value is adjusted, the original cost of our inventory, less the related inventory write-down, represents the new cost basis. Reversal of these write downs is recognized only when the related inventory has been scrapped or sold. Shipping and handling costs are classified as a component of Cost of revenues in the Consolidated Statements of Income. We design, manufacture and sell a custom product into a market that has been subject to cyclicality and significant demand fluctuations. Many of our products are complex, custom to a specific chip design and have to be delivered on short lead-times. Probe cards are manufactured in low volumes, but, for certain materials, the purchases are often subject to minimum order quantities in excess of the actual underlying probe card demand. It is not uncommon for us to acquire production materials and commence production activities based on estimated production yields and forecasted demand prior to, or in excess of, actual demand for our probe cards. These factors result in normal recurring inventory valuation charges to Cost of revenues.
Restricted Cash	Restricted CashRestricted cash is comprised primarily of funds held by our foreign subsidiaries for employee obligations, office leases, customer deposits, temporary customs import permits, and environmental remediation.
Property, Plant, and Equipment	Property, Plant, and Equipment Property, plant and equipment is stated at cost less accumulated depreciation and amortization. Depreciation is provided on a straight-line method. Machinery and equipment, computer equipment and software, and furniture and fixtures are depreciated over 1 to 5 years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Construction-in-progress assets are not depreciated until the assets are placed in service. Upon sale or retirement of assets, the cost and related accumulated depreciation or amortization are removed from the Consolidated Balance Sheets and the resulting gain or loss is reflected in Operating income in our Consolidated Statements of Income.
Leases	Leases The Company determines if an arrangement is a lease at its inception. Right-of-use (“ROU”) assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. We uses our estimated incremental borrowing rate in determining the present value of lease payments considering the term of the lease, which is derived from information available at the lease commencement date. The lease term includes renewal options when it is reasonably certain that the option will be exercised and excludes termination options. To the extent that the Company’s agreements have variable lease payments, the Company includes variable lease payments that depend on an index or a rate and excludes those that depend on facts or circumstances occurring after the commencement date, other than the passage of time. Lease expense for these leases is recognized on a straight-line basis over the lease term. We have elected not to recognize ROU assets and lease liabilities that arise from short-term leases for any class of underlying asset. Operating leases are included in Operating lease, right-of-use-assets, Operating lease liabilities, and Long-term operating lease liabilities in our Consolidated Balance Sheets.
Goodwill	Goodwill Goodwill represents the excess of the purchase price over the fair value of identifiable assets acquired and liabilities assumed. Goodwill is not amortized, rather assessed, at least annually, for impairment at a reporting unit level. Impairment of goodwill exists when the carrying amount of a reporting unit exceeds its fair value. A goodwill impairment loss is recognized for the amount that the carrying amount of the reporting unit, including goodwill, exceeds its fair value, limited to the total amount of goodwill allocated to that reporting unit. If the fair value of a reporting unit exceeds the carrying amount, goodwill of the reporting unit is not considered impaired. We evaluate impairment by first assessing qualitative factors to determine whether it is necessary to perform a quantitative impairment test. If we determine, as a result of the qualitative assessment, that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then the quantitative impairment test is required. Otherwise, no further testing is required. We perform our annual goodwill impairment test in the fourth quarter of each year by assessing qualitative factors, including, but not limited to an assessment of our market capitalization, which was significantly higher than our book value. Based on these tests, we determined that the quantitative impairment test was not required and no impairment charges were recorded in fiscal 2020, 2019 or 2018. The evaluation of goodwill for impairment requires the exercise of judgment. In the event of future changes in business conditions, we will be required to reassess and update our forecasts and estimates used in future impairment analysis. If the results of these analysis are lower than current estimates, a material impairment charge may result at that time.
Intangible Assets	Intangible Assets Intangible assets consist of acquisition related intangible assets and intellectual property. The intangible assets are being amortized over periods of 1 to 10 years, which reflect the pattern in which economic benefits of the assets are expected to be realized. We perform a review of intangible assets when facts and circumstances indicate that the useful life is shorter than originally estimated or that the carrying amount of assets may not be recoverable. Such facts and circumstances include significant adverse changes in the business climate or legal factors; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the intangible assets; and current expectation that the intangible assets will more likely than not be sold or disposed of before the end of their estimated useful lives. We assess the recoverability of identified intangible assets by comparing the projected undiscounted net cash flows associated with the related asset or group of assets over their remaining lives against their respective carrying amounts. Impairments, if any, are based on the excess of the carrying amount over the fair value of those assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We test long-lived assets or asset groups, such as property, plant and equipment and intangible assets, for recoverability when events or changes in circumstances indicate that their carrying amounts may not be recoverable. Circumstances which could trigger a review include, but are not limited to: significant decreases in the market price of the asset; significant adverse changes in the business climate or legal factors; accumulation of costs significantly in excess of the amount originally expected for the acquisition or construction of the asset; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the asset; and current expectation that the asset will more likely than not be sold or disposed of before the end of its estimated useful life. Recoverability is assessed based on the carrying amounts of the asset or asset group and the sum of the undiscounted cash flows expected to result from the use and the eventual disposal of the asset. An impairment loss is recognized when the carrying amount is not recoverable and exceeds fair value.
Concentration of Credit Risk and Other Risk and Uncertainties	Concentration of Credit Risk and Other Risks and UncertaintiesFinancial instruments that potentially subject us to concentrations of credit risk consist primarily of cash equivalents, marketable securities and accounts receivable. Our cash equivalents and marketable securities are held in safekeeping by large, credit worthy financial institutions. We invest our excess cash primarily in U.S. banks, government and agency bonds, money market funds and corporate obligations. We have established guidelines relative to credit ratings, diversification and maturities that seek to maintain safety and liquidity. Deposits in these banks may exceed the amounts of insurance provided on such deposits. To date, we have not experienced any losses on our deposits of cash and cash equivalents. We market and sell our products to a relatively narrow base of customers and generally do not require collateral.
Revenue Recognition	Revenue Recognition Revenue is recognized upon transferring control of products and services, and the amounts recognized reflect the consideration we expect to be entitled to receive in exchange for these products and services. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities. An arrangement may include some or all of the following products and services: probe cards, systems, accessories, installation services, service contracts and extended warranty contracts. We sell our products and services direct to customers and to partners in two distribution channels: global direct sales force and through a combination of manufacturers’ representatives and distributors. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer. In contracts with multiple performance obligations, we identify each performance obligation and evaluate whether the performance obligation is distinct within the context of the contract at contract inception. Performance obligations that are not distinct at contract inception are combined and accounted for as one unit of account. Generally, the performance obligations in a contract are considered distinct within the context of the contract and are accounted for as separate units of account. Our products may be customized to our customers’ specifications, however, control of our product is typically transferred to the customer at the point in time the product is either shipped or delivered, depending on the terms of the arrangement, as the criteria for overtime recognition is not met. In limited circumstances, substantive acceptance by the customer exists which results in the deferral of revenue until acceptance is formally received from the customer. Judgment may be required in determining if the acceptance clause is substantive. In certain instances control of products is transferred to the customer over time based on performance and in those instances we utilize an appropriate input or output measure to determine to what extent control has transferred to the customer. Judgment may be required in determining an appropriate measure of performance. Installation services are routinely provided to customers purchasing our systems. Installation services are a distinct performance obligation apart from the systems and recognized in the period they are performed. Service contracts, which include repair and maintenance service contracts, and extended warranty contracts are also distinct performance obligations and recognized over the contractual service period, which ranges from one to three years. For these service contracts recognized over time, we use an input measure, days elapsed, to measure progress. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. In determining the transaction price, we evaluate whether the price is subject to refund or adjustment to determine the net consideration to which we expect to be entitled. We generally do not grant return privileges, except for defective products during the warranty period. Sales incentives and other programs that we may make available to these customers are considered to be a form of variable consideration, which is estimated in determining the contract’s transaction price to be allocated to the performance obligations. For contracts with multiple performance obligations, we allocate the contract’s transaction price to each performance obligation based on its relative stand-alone selling price. The stand-alone selling prices are determined based on observable prices, which are the prices at which we separately sell these products. For items which do not have observable prices, we use our best estimate of the stand-alone selling prices. Transaction price allocated to the remaining performance obligations: On December 26, 2020, we had $7.9 million of remaining performance obligations, which were comprised of deferred service contracts and extended warranty contracts and contracts with overtime revenue recognition that are not yet delivered. We expect to recognize approximately 84.1% of our remaining performance obligations as revenue in fiscal 2021, approximately 9.5% in fiscal 2022, and approximately 6.4% in fiscal 2023 and thereafter. The foregoing excludes the value of remaining performance obligations that have original durations of one year or less, and also excludes information about variable consideration allocated entirely to a wholly unsatisfied performance obligation. Contract balances: The timing of revenue recognition may differ from the timing of invoicing to customers. Accounts receivable is recorded at the invoiced amount, net of an allowance for doubtful accounts. A receivable is recognized in the period we deliver goods or provide services or when our right to consideration is unconditional. A contract asset is recorded when we have performed under the contract but our right to consideration is conditional on something other than the passage of time. Contract assets as of December 26, 2020 and December 28, 2019 were $3.7 million and $0.9 million, respectively, and are reported on the Consolidated Balance Sheets as a component of Prepaid expenses and other current assets. Contract liabilities include payments received and payments due in advance of performance under a contract and are satisfied as the associated revenue is recognized. Contract liabilities are reported on the Consolidated Balance Sheets on a contract-by-contract basis at the end of each reporting period as a component of Deferred revenue and Other liabilities. Contract liabilities totaled $22.2 million and $10.8 million at December 26, 2020 and December 28, 2019, respectively. During fiscal 2020, we recognized $9.5 million of revenue that was included in contract liabilities as of December 28, 2019. Costs to obtain a contract: We generally expense sales commissions when incurred as a component of Selling, general and administrative expense as the amortization period is typically less than one year. Revenue by Category: Refer to Note 15, Segments and Geographic Information, for further details.
Warranty Obligations	Warranty Obligations We offer warranties on certain products and record a liability for the estimated future costs associated with warranty claims at the time revenue is recognized. The warranty liability is based upon historical experience and our estimate of the level of future costs. While we engage in product quality programs and processes, our warranty obligation is affected by product failure rates, material usage and service delivery costs incurred in correcting a product failure. We continuously monitor product returns for warranty and maintain a reserve for the related expenses based upon our historical experience and any specifically identified field failures. As we sell new products to our customers, we must exercise considerable judgment in estimating the expected failure rates. This estimating process is based on historical experience of similar products, as well as various other assumptions that we believe to be reasonable under the circumstances. We provide for the estimated cost of product warranties at the time revenue is recognized. Warranty costs are reflected in the Consolidated Statement of Income as a Cost of revenues.
Research and Development	Research and Development Research and development expenses include expenses related to product development, engineering and material costs. All research and development costs are expensed as incurred.
Income Taxes	Income Taxes We utilize the asset and liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statement and tax basis of assets and liabilities using tax rates expected to be in effect during the years in which the basis differences reverse and for operating losses and tax credit carryforwards. We estimate our provision for income taxes and amounts ultimately payable or recoverable in numerous tax jurisdictions around the world. Estimates involve interpretations of regulations and are inherently complex. Resolution of income tax treatments in individual jurisdictions may not be known for many years after completion of any fiscal year. We are required to evaluate the realizability of our deferred tax assets on an ongoing basis to determine whether there is a need for a valuation allowance with respect to such deferred tax assets. A valuation allowance is recorded when it is more likely than not that some or all of the deferred tax assets will not be realized. In evaluating the ability to recover deferred tax assets, we consider all available positive and negative evidence giving greater weight to our recent cumulative income, our historical ability to utilize net operating losses in recent years and our forecast of future taxable income, including the reversal of temporary differences and the implementation of feasible and prudent tax planning strategies. We recognize and measure uncertain tax positions taken or expected to be taken in a tax return if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized are then measured based on the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement. We report a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return. We adjust these reserves in light of changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will impact the provision for income taxes in the period in which such determination is made. The provision for income taxes includes the impact of reserve provisions and changes to reserves that are considered appropriate, as well as the related net interest. We recognize interest and penalties related to unrecognized tax benefits within the income tax provision. Accrued interest and penalties are included within the related tax liability in the Consolidated Balance Sheets. We file annual income tax returns in multiple taxing jurisdictions around the world. A number of years may elapse before an uncertain tax position is audited and finally resolved. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, we believe that our related liability reflects the most likely outcome. We adjust the liability, as well as the related interest, in light of changing facts and circumstances. Settlement of any particular position could require the use of cash.
Stock-Based Compensation	Stock-Based Compensation We recognize compensation expense for all stock-based awards based on the grant-date estimated fair values. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service periods in our Consolidated Statements of Income. The fair value of stock options is measured using the Black-Scholes option pricing model, while the fair value for restricted stock units ("RSUs") is measured based on the closing market price of our common stock on the date of grant. The fair value of Performance RSUs ("PRSU") is based on certain market performance criteria and is measured using the Monte Carlo simulation pricing model. See Notes 11, Stockholders' Equity, and 12, Stock-Based Compensation, for additional information.
Net Income Per Share	Net Income Per ShareBasic net income per share is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted net income per share is computed giving effect to all potentially dilutive common stock and common stock equivalents, including stock options, RSUs and common stock subject to repurchase.
Fair Value Measurement	Whenever possible, the fair values of our financial assets and liabilities are determined using quoted market prices of identical securities or quoted market prices of similar securities from active markets. The three levels of inputs that may be used to measure fair value are as follows: •Level 1 valuations are obtained from real-time quotes for transactions in active exchange markets involving identical securities; •Level 2 valuations utilize significant observable inputs, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and •Level 3 valuations utilize unobservable inputs to the valuation methodology and include our own data about assumptions market participants would use in pricing the asset or liability based on the best information available under the circumstances. We did not have any transfers of assets or liabilities measured at fair value on a recurring basis to or from Level 1, Level 2 or Level 3 during fiscal 2020, 2019 or 2018. The carrying values of Cash, Accounts receivable, net, Restricted cash, Prepaid expenses and other current assets, Accounts payable, Accrued liabilities, and Current portion of term loans, net of unamortized issuance costs approximate fair value due to their short maturities. No changes were made to our valuation techniques during fiscal 2020. Cash Equivalents The fair value of our cash equivalents is determined based on quoted market prices for similar or identical securities. Marketable Securities We classify our marketable securities as available-for-sale and value them utilizing a market approach. Our investments are priced by pricing vendors who provide observable inputs for their pricing without applying significant judgment. Broker pricing is used mainly when a quoted price is not available, the investment is not priced by our pricing vendors or when a broker price is more reflective of fair value. Our broker-priced investments are categorized as Level 2 investments because fair value is based on similar assets without applying significant judgments. In addition, all of our investments have a sufficient level of trading volume to demonstrate that the fair value is appropriate. Contingent Consideration Contingent consideration, arising from the acquisition of FRT (see Note 4, Acquisitions), is a cash amount equal to 1.5x EBIT as defined in the purchase agreement, up to a maximum of €10.3 million, payable subject to the performance of the acquired business in calendar 2020. We originally estimated the fair value of contingent consideration at acquisition using a probability weighted approach. Key assumptions in determining the fair value of contingent consideration included estimating the probability of achieving certain EBIT levels and discounting at an appropriate discount rate.
New Accounting Pronouncements	ASU 2016-13 In June 2016, the Financial Accounting Standard Board ("FASB") issued ASU No. 2016-13, "Measurement of Credit Losses on Financial Instruments (Topic 326)." The provisions of this standard require financial assets measured at amortized cost to be presented at the net amount expected to be collected. An allowance account would be established to present the net carrying value at the amount expected to be collected. ASU 2016-13 also provides that credit losses relating to available-for-sale debt securities should be recorded through an allowance for credit losses. The guidance was amended through various ASU's subsequent to ASU 2016-13, all of which was effective beginning fiscal 2020. We adopted ASU 2016-13 on a prospective basis on December 29, 2019, the first day of fiscal 2020. The adoption did not have a material effect on our financial position, results of operations or cash flows. ASU 2018-15 In August 2018, the FASB issued ASU 2018-15, "Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The new guidance clarifies the accounting for implementation costs in cloud computing arrangements. ASU 2018-15 is effective for fiscal years, including interim periods within those fiscal years, beginning after December 15, 2019. We adopted ASU 2018-15 on a prospective basis on December 29, 2019, the first day of fiscal 2020. The adoption did not have a material effect on our financial position, results of operations or cash flows. ASU 2019-12 In December 2019, the FASB issued ASU 2019-12, “Income Taxes (Topic 740),” which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The amendments also improve consistent application of and simplify GAAP for other areas of Topic 740 by clarifying and amending existing guidance. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption of the amendments is permitted, including adoption in any interim period for which financial statements have not yet been issued. Depending on the amendment, adoption may be applied on the retrospective, modified retrospective or prospective basis. We do not expect the adoption of ASU 2019-12 to have a material effect on our financial position, results of operations or cash flows. ASU 2020-04 In March 2020, the FASB issued ASU 2020-04, "Referenced Rate Reform (Topic 848) - Facilitation of the Effects of Reference Rate Reform on Financial Reporting." The amendments in this update apply only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. The expedients and exceptions provided by the amendments do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022. The amendments in this update are elective and are effective upon issuance for all entities. We have not yet evaluated the transition approach for our LIBOR indexed contracts and have not determined whether we will be electing such expedients and exceptions.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 26, 2020

Accounting Policies [Abstract]

Schedule of Allowance for Doubtful Accounts

Activity related to our allowance for doubtful accounts receivable was as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Balance at beginning of year	$	222	$	185	$	200
Charges (reversals) to costs and expenses	26		37		(15)
Balance at end of year	$	248	$	222	$	185

Schedules of Concentration of Risk, by Customer

The following customers represented 10% or more of our revenues:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Intel Corporation	31.5	%	25.3	%	19.0	%
Samsung Electronics., LTD.	*		11.5		*

* Less than 10% of revenues.

Schedule of Product Warranty Liability Reconciliation

A reconciliation of the changes in our warranty liability is as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Balance at beginning of year	$	1,942	$	2,102	$	3,662

Accruals	5,727		3,881		3,181
Settlements	(3,751)		(4,041)		(4,741)
Balance at end of year	$	3,918	$	1,942	$	2,102

Schedule of Calculation of Numerator and Denominator in Earnings Per Share

The following table reconciles the shares used in calculating basic net income per share and diluted net income per share (in thousands):


	Fiscal Year Ended
	December 26, 2020	December 28, 2019	December 29, 2018



Weighted-average shares used in computing basic net income per share	76,681	74,994	73,482
Add potentially dilutive securities	2,320	2,292	1,700
Weighted-average shares used in computing basic and diluted net income per share	79,001	77,286	75,182

Schedule of Accumulated Other Comprehensive Income (Loss)


	December 26, 2020		December 28, 2019
Unrealized losses on available-for-sale marketable securities	$	(126)	$	(352)
Translation adjustments and other	5,184		53
Unrealized gains (losses) on derivative instruments	828		(360)
Accumulated other comprehensive income (loss)	$	5,886	$	(659)

Balance Sheet Components (Tables)

12 Months Ended

Dec. 26, 2020

Balance Sheet Components [Abstract]

Schedule of Marketable Securities

Marketable securities consisted of the following (in thousands):


December 26, 2020	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasuries	$	40,602	$	124	$	—	$	40,726

Corporate bonds	24,156		176		(2)		24,330
Certificate of deposit	2,160		19		—		2,179
Agency securities	575		—		—		575
	$	67,493	$	319	$	(2)	$	67,810


December 28, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
U.S. Treasuries	$	10,458	$	11	$	—	$	10,469
Commercial paper	3,914		1		(4)		3,911
Corporate bond	33,867		68		(7)		33,928
Certificate of deposit	3,584		5		—		3,589
Agency securities	24,408		38		(16)		24,430
	$	76,231	$	123	$	(27)	$	76,327

Contractual Maturity of Marketable Securities

The contractual maturities of marketable securities were as follows (in thousands):


	December 26, 2020				December 28, 2019
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	50,500	$	50,679	$	38,899	$	38,944
Due after one year to five years	16,993		17,131		37,332		37,383
	$	67,493	$	67,810	$	76,231	$	76,327

Schedule of Net Inventory

Inventories consisted of the following (in thousands):


	December 26, 2020		December 28, 2019
Raw materials	$	48,122	$	38,528
Work-in-progress	30,806		29,720
Finished goods	20,301		15,010
	$	99,229	$	83,258

Schedule of Property, Plant and Equipment

Property, plant and equipment, net consisted of the following (in thousands):


	December 26, 2020		December 28, 2019
Land	$	4,751	$	—
Machinery and equipment	226,185		201,861
Computer equipment and software	36,361		35,192
Furniture and fixtures	6,894		6,756
Leasehold improvements	79,144		76,081
Sub-total	353,335		319,890
Less: Accumulated depreciation and amortization	(294,468)		(273,001)
Net property, plant and equipment	58,867		46,889
Construction-in-progress	45,236		11,858
Total	$	104,103	$	58,747

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):


	December 26, 2020		December 28, 2019
Accrued compensation and benefits	$	33,110	$	21,329
Accrued employee stock purchase plan contributions withheld	4,240		3,331
Accrued warranty	3,918		1,942
Accrued income and other taxes	6,976		6,846
Accrued contingent consideration	4,012		—
Other accrued expenses	3,086		2,991
	$	55,342	$	36,439

Acquisition (Tables)

12 Months Ended

Dec. 26, 2020

Business Combinations [Abstract]

Schedule of Assets Acquired and Liabilities Assumed

The total estimated purchase price allocated to the underlying assets acquired and liabilities assumed based on the provisional amounts are as follows (in thousands):`


	Amount
Cash and cash equivalents	$	1,680
Accounts receivable	1,017
Inventory	3,047
Property, plant and equipment	669
Operating lease, right-of-use-assets	2,554
Prepaid expenses and other assets	599
Tangible assets acquired	9,566
Deferred revenue	(2,393)
Accounts payable and accrued liabilities	(1,268)
Operating lease liabilities	(2,554)
Deferred tax liability	(3,465)
Total net tangible assets acquired and liabilities assumed	(114)
Intangible assets	14,020
Goodwill	4,654
Net assets acquired	$	18,560

The estimated fair value of assets acquired, including goodwill and intangibles, and liabilities assumed for the purchase as follows (in thousands):


	Amount
Accounts receivable	$	4,365
Inventory	2,579
Property, plant and equipment	9,053
Operating lease, right-of-use-assets	519
Prepaid expenses and other assets	56
Tangible assets acquired	16,572
Accounts payable and accrued liabilities	(743)
Operating lease liabilities	(519)
Total net tangible assets acquired and liabilities assumed	15,310
Intangible assets	14,100
Goodwill	5,590
Net assets acquired	$	35,000

We have finalized our allocation of the assets acquired, including goodwill and intangibles, and liabilities assumed for the purchase as follows (in thousands):


	Amount
Cash and cash equivalents	$	1,687
Accounts receivable	3,079
Inventory	2,643
Property, plant and equipment	696
Operating lease, right-of-use-assets	335
Prepaid expenses and other assets	838
Tangible assets acquired	9,278
Customer deposits	(1,933)
Accounts payable and accrued liabilities	(1,182)
Operating lease liabilities	(335)
Deferred tax liabilities	(5,757)

Total net tangible assets acquired and liabilities assumed	71
Intangible assets	17,429
Goodwill	11,123
Net assets acquired	$	28,623

Summary of Finite-Lived Intangible Assets Acquired

The preliminary intangible assets as of the closing date of the acquisition included (in thousands):


	Amount		Weighted Average Useful Life (in years)
Developed technologies	$	8,000	10.0
Customer relationships	5,400		5.0
Order backlog	400		0.5
Trade names	220		5.0
Total intangible assets	$	14,020	7.7

The preliminary intangible assets as of the closing date of the acquisition included (in thousands):


	Amount		Weighted Average Useful Life (in years)
Developed technologies	$	10,400	10.0
Customer relationships	3,300		3.0
In-process research and development	400		N/A
Total intangible assets	$	14,100	8.3

The intangible assets as of the closing date of the acquisition included (in thousands):


	Amount		Weighted Average Useful Life (in years)
Developed technologies	$	12,505	8.0
Customer relationships	3,071		6.0
Order backlog	1,645		0.5
Trade names	208		2.0

Total intangible assets	$	17,429	6.9

Debt (Tables)

12 Months Ended

Dec. 26, 2020

Debt Disclosure [Abstract]

Schedule of Debt

Our debt consisted of the following (in thousands):


	December 26, 2020		December 28, 2019
Term loans	$	34,569	$	58,514
Less unamortized issuance costs	(75)		(29)
Term loans less issuance costs	$	34,494	$	58,485

Schedule of Maturities of Long-term Debt

Future principal and interest payments on our term loans as of December 26, 2020, based on the interest rate in effect at that date were as follows (in thousands):


	Payments Due In Fiscal Year
	2021		2022		2023		2024		2025		2026 and thereafter		Total
Term loans - principal payments	$	9,521	$	9,549	$	1,050	$	1,080	$	1,111	$	12,258	$	34,569
Term loans - interest payments(1)	503		377		290		271		248		1,185		2,874
	$	10,024	$	9,926	$	1,340	$	1,351	$	1,359	$	13,443	$	37,443

(1) Represents our minimum interest payment commitments at 1.24% per annum for the FRT Term Loan and 1.90% per annum for the Building Term Loan.

Leases (Tables)

12 Months Ended

Dec. 26, 2020

Leases [Abstract]

Components of Lease Expense

The components of lease expense were as follows (in thousands):


	Lease Expense
	December 26, 2020		December 28, 2019
Operating lease expense	$	7,468	$	6,985
Short-term lease expense	136		142
Variable lease expense	1,574		1,286
	$	9,178	$	8,413

Operating lease expense for the year ended December 29, 2018 was $8.4 million.

Schedule of Future Minimum Payments

Future minimum payments under our non-cancelable operating leases were as follows as of December 26, 2020 (in thousands):


Fiscal Year	Amount
2021	$	7,349
2022	6,115
2023	5,254
2024	4,903
2025	4,863
Thereafter	12,531
Total minimum lease payments	41,015
Less: interest	(6,315)
Present value of net minimum lease payments	34,700
Less: current portion	(6,704)
Total long-term operating lease liabilities	$	27,996

Derivative Financial Instruments (Tables)

12 Months Ended

Dec. 26, 2020

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Foreign Currency Forward Contracts Outstanding

The following table provides information about our foreign currency forward contracts outstanding as of December 26, 2020 (in thousands):


Currency	Contract Position	Contract Amount (Local Currency)	Contract Amount (U.S. Dollars)

Euro	Buy	(11,350)	$	(13,019)
Euro	Sell	12,304	15,002
Japanese Yen	Sell	1,707,934	16,479
Korean Won	Sell	2,309,079	2,093
Total USD notional amount of outstanding foreign exchange contracts			$	20,555

The location and amount of gains (losses) related to derivative instruments designated as cash flow hedges on our Consolidated Statements of Income was as follows (in thousands):


	Amount of Gain or (Loss) Recognized in Accumulated OCI on Derivative		Location of Gain or (Loss) Reclassified from Accumulated OCI into Income	Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income
Fiscal 2020	1,142		Cost of revenues	$	89
			Research and development	77
			Selling, general and administrative	25
				$	191

Fiscal 2019	$	93	Cost of revenues	$	(526)
			Research and development	(75)
			Selling, general and administrative	(172)
				(773)

Schedule of Non-designated Derivative Gains (Losses)

The location and amount of gains (losses) related to non-designated derivative instruments in the Consolidated Statements of Income were as follows (in thousands):


	Location of Gain (Loss) Recognized on Derivatives	Fiscal Year Ended
Derivatives Not Designated as Hedging Instruments		December 26, 2020		December 28, 2019		December 29, 2018
Foreign exchange forward contracts	Other income (expense), net	$	(1,437)	$	248	$	906

Schedule of the Impact of Cash Flow Hedges on Consolidated Financial Statements

The impact of the interest rate swaps on the Consolidated Statements of Income was as follows (in thousands):


	Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)		Location of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)
Fiscal 2020	$	(119)	Other income (expense), net	$	(64)
Fiscal 2019	$	(86)	Other income (expense), net	$	548
Fiscal 2018	$	340	Other income (expense), net	$	721

Fair Value (Tables)

12 Months Ended

Dec. 26, 2020

Fair Value Disclosures [Abstract]

Schedule of Fair Values Measured on Recurring Basis


December 26, 2020	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	43,019	$	—	$	—	$	43,019

Marketable securities:
U.S. Treasuries	40,726		—		—		40,726
Certificates of deposit	—		2,179		—		2,179
Agency securities	—		575		—		575
Corporate bonds	—		24,330		—		24,330

	40,726		27,084		—		67,810
Foreign exchange derivative contracts	—		1,057		—		1,057
Interest rate swap derivative contracts	—		57		—		57
Total assets	$	83,745	$	28,198	$	—	$	111,943
Liabilities:
Foreign exchange derivative contracts	$	—	$	—	$	—	$	—
Interest rate swap derivative contracts	—		(87)		—		(87)
Contingent consideration	—		—		(4,012)		(4,012)
Total liabilities	$	—	$	(87)	$	(4,012)	$	(4,099)


December 28, 2019	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	17,056	$	—	$	—	$	17,056


Marketable securities:
U.S. Treasuries	10,468		—		—		10,468
Certificates of deposit	—		3,590		—		3,590
Agency securities	—		24,430		—		24,430
Corporate bonds	—		33,928		—		33,928
Commercial paper	—		3,911		—		3,911
	10,468		65,859		—		76,327
Foreign exchange derivative contract	—		41		—		41
Interest rate swap derivative contracts	—		26		—		26
Total assets	$	27,524	$	65,926	$	—	$	93,450
Liabilities:
Foreign exchange derivative contracts	$	—	$	(240)	$	—	$	(240)
Contingent consideration	—		—		(5,364)		(5,364)
Total liabilities	$	—	$	(240)	$	(5,364)	$	(5,604)

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 26, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

Goodwill by reportable segment was as follows (in thousands):


	Probe Cards		Systems		Total
Goodwill, gross, as of December 30, 2017	$	172,482	$	17,438	$	189,920
Foreign currency translation	—		(706)		(706)
Goodwill, gross, as of December 29, 2018	172,482		16,732		189,214
Addition - FRT acquisition	—		10,148		10,148
Foreign currency translation	—		(166)		(166)
Goodwill, gross, as of December 28, 2019	172,482		26,714		199,196
Addition - FRT acquisition	—		975		975
Addition - Baldwin Park acquisition	5,590		—		5,590
Addition - HPD acquisition	—		4,654		4,654
Foreign currency translation	—		2,346		2,346
Goodwill, gross, as of December 26, 2020	$	178,072	$	34,689	$	212,761

Schedule of Finite-lived Intangible Assets

Intangible assets were as follows (in thousands):


	December 26, 2020						December 28, 2019
Other Intangible Assets	Gross		Accumulated Amortization		Net		Gross		Accumulated Amortization		Net
Existing developed technologies	$	176,265	$	137,754	$	38,511	$	154,951	$	116,138	$	38,813
Trade name	8,162		7,363		799		7,816		6,976		840
Customer relationships	52,488		33,378		19,110		44,229		27,057		17,172
Backlog	2,227		1,900		327		1,676		891		785
In-process research and development	400		—		400		—		—		—
	$	239,542	$	180,395	$	59,147	$	208,672	$	151,062	$	57,610

Schedule of Amortization Expense

Amortization expense was included in our Consolidated Statements of Income as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Cost of revenues	$	21,609	$	20,036	$	20,530
Selling, general and administrative	6,382		7,636		8,843
	$	27,991	$	27,672	$	29,373

Schedule of Remaining Estimated Amortization Expense

The estimated future amortization of definite-lived intangible assets, excluding in-process research and development, is as follows (in thousands):


Fiscal Year	Amount
2021	$	20,207
2022	10,594
2023	8,364
2024	5,951
2025	4,398
Thereafter	9,233
Total	$	58,747

Stockholders' Equity (Tables)

12 Months Ended

Dec. 26, 2020

Equity [Abstract]

Schedule of Stock Option Activity

Stock option activity was as follows:


	Outstanding Options
	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value
Outstanding at December 28, 2019	361,769	$	8.35

Options exercised	(255,769)	8.35

Outstanding at December 26, 2020	106,000	$	8.35	2.16	$	3,627,900
Vested and expected to vest at December 26, 2020	106,000	$	8.35	2.16	$	3,627,900
Exercisable at December 26, 2020	106,000	$	8.35	2.16	$	3,627,900

Schedule of Restricted Stock Unit Activity

RSU activity was as follows:


	Number of Shares	Weighted Average Grant Date Fair Value
Restricted stock units at December 28, 2019	3,069,000	$	14.30
Granted	1,274,453	25.96
Vested	(1,453,378)	13.72
Canceled	(49,153)	15.70
Restricted stock units at December 26, 2020	2,840,922	19.80

Schedule of Performance Restricted Stock Unit Activity

PRSU grant activity was as follows:

Fiscal Year Ended

December 26, 2020

December 28, 2019

December 29, 2018

Grant Date

August 27, 2020

June 4, 2019

August 16, 2018

Performance period

July 1, 2020 - June 30, 2023

July 1, 2019 - June 30, 2022

July 1, 2018 - June 30, 2021

Number of shares

258,000

273,000

318,100

TSR as-of date

August 27, 2020

June 4, 2019

August 16, 2018

Stock-based compensation

$6.9 million

$4.4 million

$4.7 million

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 26, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Additional Information Regarding Stock Based Compensation

Certain information regarding our stock-based compensation was as follows (in thousands, except per share amounts):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018

Weighted average grant date per share fair value of RSUs granted	$	25.96	$	15.12	$	13.79
Total intrinsic value of stock options exercised	4,688		1,814		631
Fair value of RSUs vested	$	42,597	$	23,450	$	17,541

Schedule of Stock-based Compensation Expense

Pre-tax stock-based compensation expense by financial statement line and related tax benefit in the Consolidated Statements of Income are as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Stock-based compensation expense included in:
Cost of revenues	$	3,951	$	4,055	$	3,525
Research and development	5,824		6,367		5,398
Selling, general and administrative	14,055		12,754		8,904

Total stock-based compensation	$	23,830	$	23,176	$	17,827
Stock-based compensation tax benefit	$	4,962	$	911	$	453

Schedule of Unrecognized Compensation Expense

Unrecognized stock-based compensation expense at December 26, 2020 consisted of the following (in thousands):


	Unrecognized Expense		Weighted Average Recognition Period (Years)

Restricted stock units	$	32,122	2.2
Performance restricted stock units	9,075		2.1
Employee stock purchase plan	248		0.1
Total unrecognized stock-based compensation expense	$	41,445	2.2

Schedule of Assumptions, Fair Value of PRSUs

The following assumptions were used in estimating the fair value of PRSUs:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
PRSUs:
Dividend yield	—	%	—	%	—	%
Expected volatility	52.01	%	47.34	%	45.61	%
Risk-free interest rate	0.18	%	1.83	%	2.67	%
Expected life (in years)	2.8		3.1		2.9

Schedule of Assumptions, Fair Value of Employee Purchase Rights

The following assumptions were used in estimating the fair value of shares under the Employee Stock Purchase Plan:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Employee Stock Purchase Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	30.4% - 74.4%		36.6% - 59.5%		44.9% - 48.9%
Risk-free interest rate	0.10% - 1.54%		2.04% - 2.46%		0.83% - 2.22%
Expected life (in years)	0.5 - 1.0		0.5 - 1.0		0.5 - 1.0

Income Taxes (Tables)

12 Months Ended

Dec. 26, 2020

Income Tax Disclosure [Abstract]

Schedule of Components of Income Before Income Taxes

The components of income before income taxes were as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
United States	$	72,950	$	41,115	$	20,877
Foreign	12,225		9,948		13,050
	$	85,175	$	51,063	$	33,927

Schedule of Components of Provision for Income Taxes

The components of the provision (benefit) for income taxes are as follows (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Current provision:
Federal	$	1,799	$	179	$	79
State	1,194		2,302		388
Foreign	4,278		4,202		4,687
	7,271		6,683		5,154
Deferred provision (benefit):
Federal	1,472		8,128		(72,295)
State	(267)		(1,898)		(2,056)
Foreign	(1,824)		(1,196)		(912)
	(619)		5,034		(75,263)
Total provision (benefit) for income taxes	$	6,652	$	11,717	$	(70,109)

Schedule of Effective Income Tax Rate Reconciliation

The following is a reconciliation of the difference between income taxes computed by applying the federal statutory rate of 21% and the provision (benefit) from income taxes (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
U.S. statutory federal tax rate	$	17,887	$	10,723	$	7,125
State taxes, net of federal benefit	663		441		778
Stock-based compensation	(4,962)		(911)		(453)
Research and development credits	(6,576)		(6,436)		(3,213)
Foreign taxes at rates different than the U.S.	415		1,454		1,287
Other permanent differences	400		(148)		152
Global intangible low-taxed income	—		1,369		1,828
Foreign Derived Intangible Income	(3,668)		—		—
Change in valuation allowance	1,862		2,567		(75,803)
Other	631		2,658		(1,810)
Total	$	6,652	$	11,717	$	(70,109)

Schedule of Deferred Tax Assets and Liabilities

Significant deferred tax assets and liabilities consisted of the following (in thousands):


	As of
	December 26, 2020		December 28, 2019
Tax credits	$	42,927	$	44,696
Inventory reserve	13,401		12,350
Other reserves and accruals	9,470		5,852
Non-statutory stock options	2,794		2,982
Depreciation and amortization	20,961		27,758
Net operating loss carryforwards	18,421		21,410
Gross deferred tax assets	107,974		115,048
Valuation allowance	(38,466)		(36,604)
Total deferred tax assets	69,508		78,444
Acquired intangibles and fixed assets	(8,395)		(13,997)
Unrealized investment gains	(106)		(106)
Tax on undistributed earnings	(110)		(75)
Total deferred tax liabilities	(8,611)		(14,178)
Net deferred tax assets	$	60,897	$	64,266

Summary of Tax Credit Carryforwards

Tax credits and carryforwards available to us at December 26, 2020 consisted of the following (in thousands):


	Amount		Latest Expiration Date
Federal research and development tax credit	$	36,579	2023-2040
Foreign tax credit carryforwards	1,059		2021-2027
California research credits	42,615		Indefinite
State net operating loss carryforwards	247,990		2022-Indefinite
Singapore net operating loss carryforwards	7,046		Indefinite

Schedule of Unrecognized Tax Benefits

The following table reflects changes in the unrecognized tax benefits (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Unrecognized tax benefit, beginning balance	$	28,800	$	25,224	$	18,296
Additions based on tax positions related to the current year	3,072		3,679		1,677
Additions based on tax positions from prior years	702		—		5,332
Reductions for tax positions of prior years	—		(5)		(7)
Reductions due to lapse of the applicable statute of limitations	(77)		(98)		(74)
Unrecognized tax benefit, ending balance	$	32,497	$	28,800	$	25,224

Interest and penalties recognized as a component of Provision (benefit) for income taxes	$	50	$	59	$	71
Interest and penalties accrued at period end	204		212		230

Segments and Geographic Information (Tables)

12 Months Ended

Dec. 26, 2020

Segment Reporting [Abstract]

Operating Results by Reportable Segments

The following table summarizes the operating results by reportable segment (dollars in thousands):


	Fiscal 2020
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	581,739		$	111,877		$	—		$	693,616
Gross profit	$	263,215		$	51,835		$	(27,130)		$	287,920
Gross margin	45.2		%	46.3		%	—		%	41.5		%


	Fiscal 2019
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	491,363		$	98,101		$	—		$	589,464
Gross profit	$	211,382		$	50,927		$	(24,813)		$	237,496
Gross margin	43.0		%	51.9		%	—		%	40.3		%


	Fiscal 2018
	Probe Cards			Systems		Corporate and Other			Total
Revenues	$	434,269		$	95,406	$	—		$	529,675
Gross profit	$	187,320		$	47,074	$	(24,055)		$	210,339
Gross margin	43.1		%	49.3%		—		%	39.7		%

Summary of Revenue by Geographic Region

The following table summarizes revenue, by geographic region, as a percentage of total revenues based upon ship-to location:


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
China	25.2	%	18.0	%	14.7	%
Taiwan	21.7		14.7		20.3
United States	18.4		26.3		25.2
South Korea	12.5		19.8		17.2
Europe	9.5		7.0		7.5
Japan	6.3		8.9		9.4
Asia-Pacific (1)	4.8		3.7		4.9
Rest of World	1.6		1.6		0.8
Total Revenues	100.0	%	100.0	%	100.0	%

(1)Asia-Pacific includes all countries in the region except Taiwan, South Korea, China, and Japan, which are disclosed separately.

Summary of Revenue by Market

The following table summarizes revenue by market (in thousands):


	Fiscal Year Ended
	December 26, 2020		December 28, 2019		December 29, 2018
Foundry & Logic	$	446,183	$	318,552	$	258,459
DRAM	109,734		147,257		135,333
Flash	25,822		25,554		40,477
Systems	111,877		98,101		95,406
Total revenues	$	693,616	$	589,464	$	529,675

Summary of Revenue by Timing of Recognition

The following table summarizes revenue by timing of revenue recognition (in thousands):


	Fiscal Year Ended
	December 26, 2020						December 28, 2019						December 29, 2018
	Probe Cards		Systems		Total		Probe Cards		Systems		Total		Probe Cards		Systems		Total
Products transferred at a point in time	$	579,569	$	104,858	$	684,427	$	488,925	$	93,837	$	582,762	$	432,033	$	91,514	$	523,547
Services transferred over time	2,170		7,019		9,189		2,438		4,264		6,702		2,236		3,892		6,128
Total	$	581,739	$	111,877	$	693,616	$	491,363	$	98,101	$	589,464	$	434,269	$	95,406	$	529,675

Long-lived Assets by Location


	December 26, 2020		December 28, 2019		December 29, 2018
United States	$	347,654	$	287,600	$	280,405
Europe	51,791		52,309		26,118
Asia-Pacific	7,322		7,064		4,385
Total	$	406,767	$	346,973	$	310,908

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	$ 222	$ 185	$ 200
Charges (reversals) to costs and expenses	26	37	(15)
Balance at end of year	$ 248	$ 222	$ 185

Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Accounting Policies [Abstract]
Aggregate inventory write downs	$ 13,117	$ 10,421	$ 10,479

Summary of Significant Accounting Policies - Property, Plant, and Equipment (Details)	12 Months Ended
	Dec. 26, 2020
Machinery and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	1 year
Machinery and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	5 years
Computer equipment and software \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	1 year
Computer equipment and software \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	5 years
Furniture and fixtures \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	1 year
Furniture and fixtures \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	5 years

Summary of Significant Accounting Policies - Intangible Assets (Details)	12 Months Ended
	Dec. 26, 2020
Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	1 year
Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	10 years

Summary of Significant Accounting Policies - Concentration of Credit Risk and Other Risks and Uncertainties (Details) - Customer Concentration Risk	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Intel Corporation \| Revenue Benchmark
Concentration Risk [Line Items]
Concentration risk percentage	31.50%	25.30%	19.00%
Samsung Electronics., LTD. \| Revenue Benchmark
Concentration Risk [Line Items]
Concentration risk percentage		11.50%
Major Customer 1 \| Accounts Receivable
Concentration Risk [Line Items]
Concentration risk percentage	15.30%	25.70%
Major Customer 2 \| Accounts Receivable
Concentration Risk [Line Items]
Concentration risk percentage	13.70%	15.10%
Major Customer 3 \| Accounts Receivable
Concentration Risk [Line Items]
Concentration risk percentage		11.50%

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019
Disaggregation of Revenue [Line Items]
Revenue, performance obligation, description of timing	one to three years
Remaining performance obligations	$ 7.9
Contract assets	3.7	$ 0.9
Contract liabilities	22.2	$ 10.8
Revenue recognized on contract liabilities	$ 9.5

Summary of Significant Accounting Policies - Revenue Remaining Performance Obligation (Details)	Dec. 26, 2020
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-12-27
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, percentage	84.10%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-12-26
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, percentage	9.50%
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, percentage	6.40%
Revenue, remaining performance obligation, expected timing of satisfaction, period

Summary of Significant Accounting Policies - Warranty Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of year	$ 1,942	$ 2,102	$ 3,662
Accruals	5,727	3,881	3,181
Settlements	(3,751)	(4,041)	(4,741)
Balance at end of year	$ 3,918	$ 1,942	$ 2,102

Summary of Significant Accounting Policies - Net Income per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Accounting Policies [Abstract]
Weighted-average shares used in computing basic net income (loss) per share (in shares)	76,681	74,994	73,482
Add potentially dilutive securities (in shares)	2,320	2,292	1,700
Weighted-average shares used in computing basic and diluted net income per share (in shares)	79,001	77,286	75,182

Summary of Significant Accounting Policies - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Accounting Policies [Abstract]
Unrealized losses on available-for-sale marketable securities	$ (126)	$ (352)
Translation adjustments and other	5,184	53
Unrealized gains (losses) on derivative instruments	828	(360)
Accumulated other comprehensive income (loss)	$ 5,886	$ (659)

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References + Details

Balance Sheet Components - Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	$ 67,493	$ 76,231
Gross Unrealized Gains	319	123
Gross Unrealized Losses	(2)	(27)
Fair Value	67,810	76,327
Amortized Cost
Due in one year or less	50,500	38,899
Due after one year to five years	16,993	37,332
Amortized Cost	67,493	76,231
Fair Value
Due in one year or less	50,679	38,944
Due after one year to five years	17,131	37,383
Fair Value	67,810	76,327
U.S. Treasuries
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	40,602	10,458
Gross Unrealized Gains	124	11
Gross Unrealized Losses	0	0
Fair Value	40,726	10,469
Amortized Cost
Amortized Cost	40,602	10,458
Fair Value
Fair Value	40,726	10,469
Commercial paper
Debt Securities, Available-for-sale [Abstract]
Amortized Cost		3,914
Gross Unrealized Gains		1
Gross Unrealized Losses		(4)
Fair Value		3,911
Amortized Cost
Amortized Cost		3,914
Fair Value
Fair Value		3,911
Corporate bonds
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	24,156	33,867
Gross Unrealized Gains	176	68
Gross Unrealized Losses	(2)	(7)
Fair Value	24,330	33,928
Amortized Cost
Amortized Cost	24,156	33,867
Fair Value
Fair Value	24,330	33,928
Certificates of deposit
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	2,160	3,584
Gross Unrealized Gains	19	5
Gross Unrealized Losses	0	0
Fair Value	2,179	3,589
Amortized Cost
Amortized Cost	2,160	3,584
Fair Value
Fair Value	2,179	3,589
Agency securities
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	575	24,408
Gross Unrealized Gains	0	38
Gross Unrealized Losses	0	(16)
Fair Value	575	24,430
Amortized Cost
Amortized Cost	575	24,408
Fair Value
Fair Value	$ 575	$ 24,430

Balance Sheet Components - Inventory (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Balance Sheet Components [Abstract]
Raw materials	$ 48,122	$ 38,528
Work-in-progress	30,806	29,720
Finished goods	20,301	15,010
Inventory, net	$ 99,229	$ 83,258

Balance Sheet Components - Property Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 353,335	$ 319,890
Less: Accumulated depreciation and amortization	(294,468)	(273,001)
Net property, plant and equipment	58,867	46,889
Construction-in-progress	45,236	11,858
Property, plant and equipment, net	104,103	58,747
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,751	0
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	226,185	201,861
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	36,361	35,192
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,894	6,756
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 79,144	$ 76,081

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 33,110	$ 21,329
Accrued employee stock purchase plan contributions withheld	4,240	3,331
Accrued warranty	3,918	1,942
Accrued income and other taxes	6,976	6,846
Accrued contingent consideration	4,012	0
Other accrued expenses	3,086	2,991
Total	$ 55,342	$ 36,439

Acquisition - Additional Information (Details)				12 Months Ended
Acquisition - Additional Information (Details)	Oct. 19, 2020 USD ($) millikelvin	Jul. 30, 2020 USD ($)	Oct. 09, 2019 USD ($)	Dec. 26, 2020 USD ($)	Dec. 28, 2019 USD ($)	Dec. 29, 2018 USD ($)	Oct. 25, 2019 USD ($)	Oct. 09, 2019 EUR (€)
Business Acquisition [Line Items]
Fair value of purchase consideration				$ 51,880,000	$ 20,524,000	$ 0
Contingent consideration				$ 4,012,000	$ 5,364,000
FRT Term Loan
Business Acquisition [Line Items]
Debt instrument, face amount							$ 23,400,000
Maximum
Business Acquisition [Line Items]
Contingent consideration \| €								€ 10,300,000
High Precision Devices, Inc.
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%
Total acquisition consideration	$ 16,900,000
Cash acquired in combination	$ 1,680,000
High Precision Devices, Inc. \| Minimum
Business Acquisition [Line Items]
Sensor markets, operating temperature \| millikelvin	30
Baldwin Park
Business Acquisition [Line Items]
Total acquisition consideration		$ 35,000,000.0
FRT
Business Acquisition [Line Items]
Percentage of voting interests acquired			100.00%					100.00%
Total acquisition consideration			$ 26,900,000
Cash acquired in combination			1,687,000
Fair value of purchase consideration			22,200,000
Contingent consideration			$ 6,500,000
Contingent consideration, multiple of EBIT			150.00%
FRT \| Minimum
Business Acquisition [Line Items]
Contingent consideration \| €								€ 0
FRT \| Maximum
Business Acquisition [Line Items]
Contingent consideration \| €								€ 10,300,000

Acquisition - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Oct. 19, 2020	Jul. 30, 2020	Oct. 09, 2019	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Business Acquisition [Line Items]
Goodwill				$ 212,761	$ 199,196	$ 189,214	$ 189,920
High Precision Devices, Inc.
Business Acquisition [Line Items]
Cash and cash equivalents	$ 1,680
Accounts receivable	1,017
Inventory	3,047
Property, plant and equipment	669
Operating lease, right-of-use-assets	2,554
Prepaid expenses and other assets	599
Tangible assets acquired	9,566
Deferred revenue	(2,393)
Accounts payable and accrued liabilities	(1,268)
Operating lease liabilities	(2,554)
Deferred tax liabilities	(3,465)
Total net tangible assets acquired and liabilities assumed	(114)
Intangible assets	14,020		$ 14,020
Goodwill	4,654
Net assets acquired	18,560
Total acquisition consideration	$ 16,900
Baldwin Park
Business Acquisition [Line Items]
Accounts receivable		$ 4,365
Inventory		2,579
Property, plant and equipment		9,053
Operating lease, right-of-use-assets		519
Prepaid expenses and other assets		56
Tangible assets acquired		16,572
Accounts payable and accrued liabilities		(743)
Operating lease liabilities		(519)
Total net tangible assets acquired and liabilities assumed		15,310
Intangible assets		14,100
Goodwill		5,590
Total acquisition consideration		$ 35,000
FRT
Business Acquisition [Line Items]
Cash and cash equivalents			1,687
Accounts receivable			3,079
Inventory			2,643
Property, plant and equipment			696
Operating lease, right-of-use-assets			335
Prepaid expenses and other assets			838
Tangible assets acquired			9,278
Deferred revenue			(1,933)
Accounts payable and accrued liabilities			(1,182)
Operating lease liabilities			(335)
Deferred tax liabilities			(5,757)
Total net tangible assets acquired and liabilities assumed			71
Intangible assets			17,429
Goodwill			11,123
Net assets acquired			28,623
Total acquisition consideration			$ 26,900

Acquisition - Intangible Assets Acquired (Details) - USD ($) $ in Thousands	Jul. 30, 2020	Oct. 09, 2019	Oct. 19, 2020
High Precision Devices, Inc.
Business Acquisition [Line Items]
Intangible assets		$ 14,020	$ 14,020
Weighted Average Useful Life (in years)		7 years 8 months 12 days
FRT
Business Acquisition [Line Items]
Intangible assets		$ 17,429
Weighted Average Useful Life (in years)		6 years 10 months 24 days
Baldwin Park
Business Acquisition [Line Items]
Intangible assets	$ 14,100
Weighted Average Useful Life (in years)	8 years 3 months 18 days
Baldwin Park \| In-process research and development
Business Acquisition [Line Items]
Intangible assets	$ 400
Developed technologies \| High Precision Devices, Inc.
Business Acquisition [Line Items]
Intangible assets		$ 8,000
Weighted Average Useful Life (in years)		10 years
Developed technologies \| FRT
Business Acquisition [Line Items]
Intangible assets		$ 12,505
Weighted Average Useful Life (in years)		8 years
Developed technologies \| Baldwin Park
Business Acquisition [Line Items]
Intangible assets	$ 10,400
Weighted Average Useful Life (in years)	10 years
Customer relationships \| High Precision Devices, Inc.
Business Acquisition [Line Items]
Intangible assets		$ 5,400
Weighted Average Useful Life (in years)		5 years
Customer relationships \| FRT
Business Acquisition [Line Items]
Intangible assets		$ 3,071
Weighted Average Useful Life (in years)		6 years
Customer relationships \| Baldwin Park
Business Acquisition [Line Items]
Intangible assets	$ 3,300
Weighted Average Useful Life (in years)	3 years
Order backlog \| High Precision Devices, Inc.
Business Acquisition [Line Items]
Intangible assets		$ 400
Weighted Average Useful Life (in years)		6 months
Order backlog \| FRT
Business Acquisition [Line Items]
Intangible assets		$ 1,645
Weighted Average Useful Life (in years)		6 months
Trade name \| High Precision Devices, Inc.
Business Acquisition [Line Items]
Intangible assets		$ 220
Weighted Average Useful Life (in years)		5 years
Trade name \| FRT
Business Acquisition [Line Items]
Intangible assets		$ 208
Weighted Average Useful Life (in years)		2 years

Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Debt Disclosure [Abstract]
Term loans	$ 34,569	$ 58,514
Less unamortized issuance costs	(75)	(29)
Term loans less issuance costs	$ 34,494	$ 58,485

Debt - Additional Information (Details) - USD ($)					12 Months Ended
Debt - Additional Information (Details) - USD ($)	Jun. 22, 2020	Mar. 17, 2020	Oct. 25, 2019	Jun. 24, 2016	Dec. 26, 2020	Dec. 28, 2019	Dec. 31, 2016
Debt Instrument [Line Items]
Term loans					$ 34,569,000	$ 58,514,000
Derivative, notional amount							$ 95,600,000
FRT Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount			$ 23,400,000
Line of credit facility, expiration period			3 years
Long-term line of credit, quarterly repayment amount			$ 2,000,000.0
Interest rate at period end					1.24%
Term loans					$ 17,100,000
Building Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount	$ 18,000,000.0
Interest rate at period end					1.90%
Term loans					$ 17,500,000
Debt instrument, term	15 years
Debt instrument, interest payment term	15 years
Debt instrument, interest rate, effective percentage		2.75%
Building Term Loan \| Interest Rate Contract
Debt Instrument [Line Items]
Derivative, notional amount		$ 18,000,000.0			$ 18,000,000.0
Derivative, floor interest rate		0.00%
Derivative, floor interest rate term		1 year			1 year
LIBOR \| Building Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%	1.75%			1.75%
Euro Interbank Offered Rate (EURIBOR) \| FRT Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate			175.00%
Senior Secured Term Loan
Debt Instrument [Line Items]
Derivative, notional amount					$ 17,500,000
Senior Secured Term Loan \| CMI Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount				$ 150,000,000
Interest payment term				5 years
Debt principal payable in current year, percentage				5.00%
Debt principal payable in year two, percentage				10.00%
Debt principal payable in year three, percentage				20.00%
Debt principal payable in year four, percentage				30.00%
Debt principal payable in year five, percentage				35.00%
Senior Secured Term Loan \| LIBOR \| CMI Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate				2.00%
Senior Secured Term Loan \| Base Rate \| CMI Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate				1.00%

Debt - Future Principle and Interest Payments (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Debt Instrument [Line Items]
Principal, 2021	$ 9,521
Principal, 2022	9,549
Principal, 2023	1,050
Principal, 2024	1,080
Principal, 2025	1,111
Principal, 2026 and thereafter	12,258
Principal, total	34,569	$ 58,514
Interest, 2021	503
Interest, 2022	377
Interest, 2023	290
Interest, 2024	271
Interest, 2025	248
Interest, 2026 and thereafter	1,185
Interest, total	2,874
Total payments, 2021	10,024
Total payments, 2022	9,926
Total payments, 2023	1,340
Total payments, 2024	1,351
Total payments, 2025	1,359
Total payments, 2026 and thereafter	13,443
Long-term debt, maturities, total payments due	37,443
FRT Term Loan
Debt Instrument [Line Items]
Principal, total	$ 17,100
Interest rate at period end	1.24%
Building Term Loan
Debt Instrument [Line Items]
Principal, total	$ 17,500
Interest rate at period end	1.90%

Leases - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Leases - Narrative (Details) - USD ($) $ in Millions	Dec. 29, 2018	Dec. 26, 2020
Lessee, Lease, Description [Line Items]
Operating lease, renewal term		20 years
Operating lease, weighted average remaining lease term		6 years 7 months 6 days
Operating lease, weighted average discount rate		4.33%
Rent expense	$ 8.4
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract		1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract		8 years
Automobiles \| Minimum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract		1 year
Automobiles \| Maximum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract		3 years

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019
Leases [Abstract]
Operating lease expense	$ 7,468	$ 6,985
Short-term lease expense	136	142
Variable lease expense	1,574	1,286
Total lease expense	$ 9,178	$ 8,413

Leases - Schedule of Future Minimum Payments Under Leases (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Leases [Abstract]
2021	$ 7,349
2022	6,115
2023	5,254
2024	4,903
2025	4,863
Thereafter	12,531
Total minimum lease payments	41,015
Less: interest	(6,315)
Present value of net minimum lease payments	34,700
Less: current portion	(6,704)	$ (6,551)
Long-term operating lease liabilities	$ 27,996	$ 29,088

Derivative Financial Instruments - Foreign Currency Derivatives (Details) € in Thousands, ₩ in Thousands, ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 26, 2020 USD ($)	Dec. 26, 2020 EUR (€)	Dec. 26, 2020 JPY (¥)	Dec. 26, 2020 KRW (₩)	Dec. 31, 2016 USD ($)
Derivatives, Fair Value [Line Items]
Cash flow hedge amount to be reclassified within twelve months	$ 900
Derivative, notional amount					$ 95,600
Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Derivative, notional amount	20,555
Buy \| Euro \| Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Derivative, notional amount	13,019	€ 11,350
Sell \| Euro \| Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Derivative, notional amount	15,002	€ 12,304
Sell \| Japanese Yen \| Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Derivative, notional amount	16,479		¥ 1,707,934
Sell \| Korean Won \| Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Derivative, notional amount	$ 2,093			₩ 2,309,079

Derivative Financial Instruments - Gains (Losses) Of Cash Flow Hedges (Details) - Foreign Exchange Forward - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Not Designated as Hedging Instrument \| Other income (expense), net
Derivatives, Fair Value [Line Items]
Foreign exchange forward contracts	$ (1,437)	$ 248	$ 906
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)	1,142	93
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	191	(773)
Designated as Hedging Instrument \| Cost of revenues
Derivatives, Fair Value [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	89	(526)
Designated as Hedging Instrument \| Research and development
Derivatives, Fair Value [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	77	(75)
Designated as Hedging Instrument \| Selling, general and administrative
Derivatives, Fair Value [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 25	$ (172)

Derivative Financial Instruments - Interest Rate Swaps (Details) - USD ($) $ in Thousands			12 Months Ended
	Jun. 22, 2020	Mar. 17, 2020	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount						$ 95,600
Building Term Loan
Derivative Instruments, Gain (Loss) [Line Items]
Debt instrument, interest rate, effective percentage		2.75%
Interest Rate Contract \| Building Term Loan
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount		$ 18,000	$ 18,000
Derivative, floor interest rate		0.00%
Derivative, floor interest rate term		1 year	1 year
Interest Rate Swap \| Designated as Hedging Instrument \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)			$ (119)	$ (86)	$ 340
Interest Rate Swap \| Other income (expense), net \| Designated as Hedging Instrument \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)			(64)	$ 548	$ 721
Senior Secured Term Loan
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount			$ 17,500
Fixed interest rate, derivative						2.94%
LIBOR \| Building Term Loan
Derivative Instruments, Gain (Loss) [Line Items]
Basis spread on variable rate	1.75%	1.75%	1.75%
LIBOR \| Senior Secured Term Loan
Derivative Instruments, Gain (Loss) [Line Items]
Derivative variable rate basis spread						2.00%

Fair Value - Narrative (Details) € in Millions		12 Months Ended
Fair Value - Narrative (Details) € in Millions	Oct. 09, 2019 USD ($)	Dec. 26, 2020 USD ($)	Dec. 28, 2019 USD ($)	Oct. 09, 2019 EUR (€)	Dec. 29, 2018 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent consideration		$ 4,012,000	$ 5,364,000
Change in contingent consideration		(1,400,000)
Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets (liabilities), net		$ 0	$ 0		$ 0
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent consideration \| €				€ 10.3
FRT
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent consideration, multiple of EBIT	150.00%
Contingent consideration	$ 6,500,000
FRT \| Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent consideration \| €				€ 10.3

Fair Value - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	$ 67,810	$ 76,327
Total assets	111,943	93,450
Contingent consideration	(4,012)	(5,364)
Liabilities measured at fair value	(4,099)	(5,604)
Foreign exchange derivative contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	1,057	41
Derivative liability	0	(240)
Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	57	26
Derivative liability	(87)
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents:	43,019	17,056
U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	40,726	10,468
Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	2,179	3,590
Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	575	24,430
Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	24,330	33,928
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:		3,911
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	40,726	10,468
Total assets	83,745	27,524
Contingent consideration	0	0
Liabilities measured at fair value	0	0
Level 1 \| Foreign exchange derivative contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	0	0
Derivative liability	0	0
Level 1 \| Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	0	0
Derivative liability	0
Level 1 \| Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents:	43,019	17,056
Level 1 \| U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	40,726	10,468
Level 1 \| Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Level 1 \| Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Level 1 \| Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Level 1 \| Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:		0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	27,084	65,859
Total assets	28,198	65,926
Contingent consideration	0	0
Liabilities measured at fair value	(87)	(240)
Level 2 \| Foreign exchange derivative contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	1,057	41
Derivative liability	0	(240)
Level 2 \| Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	57	26
Derivative liability	(87)
Level 2 \| Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents:	0	0
Level 2 \| U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Level 2 \| Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	2,179	3,590
Level 2 \| Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	575	24,430
Level 2 \| Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	24,330	33,928
Level 2 \| Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:		3,911
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Total assets	0	0
Contingent consideration	(4,012)	(5,364)
Liabilities measured at fair value	(4,012)	(5,364)
Level 3 \| Foreign exchange derivative contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	0	0
Derivative liability	0	0
Level 3 \| Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	0	0
Derivative liability	0
Level 3 \| Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents:	0	0
Level 3 \| U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Level 3 \| Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Level 3 \| Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	0	0
Level 3 \| Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:	$ 0	0
Level 3 \| Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities:		$ 0

Goodwill and Intangible Assets - Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 199,196,000	$ 189,214,000	$ 189,920,000
Foreign currency translation	2,346,000	(166,000)	(706,000)
Goodwill, ending balance	212,761,000	199,196,000	189,214,000
Goodwill impairments	0
FRT GmbH
Goodwill [Roll Forward]
Goodwill, acquired during period	975,000	10,148,000
Baldwin Park
Goodwill [Roll Forward]
Goodwill, acquired during period	5,590,000
High Precision Devices, Inc.
Goodwill [Roll Forward]
Goodwill, acquired during period	4,654,000
Probe Cards
Goodwill [Roll Forward]
Goodwill, beginning balance	172,482,000	172,482,000	172,482,000
Foreign currency translation	0	0	0
Goodwill, ending balance	178,072,000	172,482,000	172,482,000
Probe Cards \| FRT GmbH
Goodwill [Roll Forward]
Goodwill, acquired during period	0	0
Probe Cards \| Baldwin Park
Goodwill [Roll Forward]
Goodwill, acquired during period	5,590,000
Probe Cards \| High Precision Devices, Inc.
Goodwill [Roll Forward]
Goodwill, acquired during period	0
Systems
Goodwill [Roll Forward]
Goodwill, beginning balance	26,714,000	16,732,000	17,438,000
Foreign currency translation	2,346,000	(166,000)	(706,000)
Goodwill, ending balance	34,689,000	26,714,000	$ 16,732,000
Systems \| FRT GmbH
Goodwill [Roll Forward]
Goodwill, acquired during period	975,000	$ 10,148,000
Systems \| Baldwin Park
Goodwill [Roll Forward]
Goodwill, acquired during period	0
Systems \| High Precision Devices, Inc.
Goodwill [Roll Forward]
Goodwill, acquired during period	$ 4,654,000

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Finite-Lived Intangible Assets [Line Items]
Gross	$ 239,542	$ 208,672
Accumulated Amortization	180,395	151,062
Net	59,147	57,610
Existing developed technologies
Finite-Lived Intangible Assets [Line Items]
Gross	176,265	154,951
Accumulated Amortization	137,754	116,138
Net	38,511	38,813
Trade name
Finite-Lived Intangible Assets [Line Items]
Gross	8,162	7,816
Accumulated Amortization	7,363	6,976
Net	799	840
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross	52,488	44,229
Accumulated Amortization	33,378	27,057
Net	19,110	17,172
Backlog
Finite-Lived Intangible Assets [Line Items]
Gross	2,227	1,676
Accumulated Amortization	1,900	891
Net	327	785
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Gross	400	0
Accumulated Amortization	0	0
Net	$ 400	$ 0

Goodwill and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 27,991	$ 27,672	$ 29,373
Finite-Lived Intangible Assets, Net, Amortization Expense, Rolling Maturity [Abstract]
2021	20,207
2022	10,594
2023	8,364
2024	5,951
2025	4,398
Thereafter	9,233
Total	58,747
Cost of revenues
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	21,609	20,036	20,530
Selling, general and administrative
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 6,382	$ 7,636	$ 8,843

Goodwill and Intangible Assets - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Impairment of intangible assets	$ 0	$ 0	$ 0

Stockholders' Equity - Preferred Stock (Details) - $ / shares	Dec. 26, 2020	Dec. 28, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock authorized (in shares)	10,000,000	10,000,000
Preferred stock par value (in USD per share)	$ 0.001	$ 0.001
Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock authorized (in shares)	10,000,000
Preferred stock par value (in USD per share)	$ 0.001

Stockholders' Equity - Common Stock and Repurchase Program (Details) - USD ($)	12 Months Ended
	Dec. 26, 2020	Oct. 26, 2020	Feb. 29, 2020
Class of Stock [Line Items]
Dividends declared and paid	$ 0
Common Stock
Class of Stock [Line Items]
Stock repurchase program authorized amount		$ 50,000,000	$ 25,000,000.0

Stockholders' Equity - Equity Incentive Plans (Details) - 2012 Plan	12 Months Ended
	Dec. 26, 2020 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)	16,800,000
Shares available for grant (in shares)	6,000,000.0
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Term granted	7 years
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Term granted	7 years

Stockholders' Equity - Stock Options Rollforward (Details) - 2012 Plan	12 Months Ended
	Dec. 26, 2020 USD ($) $ / shares shares
Number of Shares
Number of Shares, Outstanding (in shares) \| shares	361,769
Number of Shares, Options exercised (in shares) \| shares	(255,769)
Number of Shares, Outstanding (in shares) \| shares	106,000
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding (in USD per share) \| $ / shares	$ 8.35
Weighted Average Exercise Price, Options exercised (in USD per share) \| $ / shares	8.35
Weighted Average Exercise Price, Outstanding (in USD per share) \| $ / shares	$ 8.35
Vested and Expected to Vest
Number of Shares, Vested and expected to vest (in shares) \| shares	106,000
Weighted Average Exercise Price, Vested and expected to vest (in USD per share) \| $ / shares	$ 8.35
Weighted Average Remaining Contractual Life, Vested and expected to vest	2 years 1 month 28 days
Aggregate Intrinsic Value, Vested and expected to vest \| $	$ 3,627,900
Additional Disclosures
Number of Shares, Exercisable (in shares) \| shares	106,000
Weighted Average Exercise Price, Exercisable (in USD per share) \| $ / shares	$ 8.35
Weighted Average Remaining Contractual Life, Outstanding	2 years 1 month 28 days
Aggregate Intrinsic Value, Outstanding \| $	$ 3,627,900
Weighted Average Remaining Contractual Life, Exercisable	2 years 1 month 28 days
Aggregate Intrinsic Value, Exercisable \| $	$ 3,627,900

Stockholders' Equity - Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended				48 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017	Dec. 26, 2020
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Granted (in USD per share)	$ 25.96	$ 15.12	$ 13.79
Stock-based compensation expense	$ 23,830	$ 23,176	$ 17,827
Performance Restricted Stock Units
Number of Shares
Number of Shares, Granted (in shares)	258,000	273,000	318,100
Weighted Average Grant Date Fair Value
Performance period	3 years
Stock options granted (in shares)	258,000	273,000	318,100
Stock-based compensation expense	$ 6,900	$ 4,400	$ 4,700
2012 Plan
Number of Shares
Number of Shares, Granted (in shares)				333,000
Number of Shares, Vested (in shares)	(255,000)
Number of Shares, Canceled (in shares)					(78,333)
Weighted Average Grant Date Fair Value
Stock options granted (in shares)				333,000
2012 Plan \| Maximum
Weighted Average Grant Date Fair Value
Total shareholder return	125.00%
2012 Plan \| Restricted stock units
Number of Shares
Number of Shares, Restricted stock units, beginning balance (in shares)	3,069,000
Number of Shares, Granted (in shares)	1,274,453
Number of Shares, Vested (in shares)	(1,453,378)
Number of Shares, Canceled (in shares)	(49,153)
Number of Shares, Restricted stock units, ending balance (in shares)	2,840,922	3,069,000			2,840,922
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Restricted stock units, beginning balance (in USD per share)	$ 14.30
Weighted Average Grant Date Fair Value, Granted (in USD per share)	25.96
Weighted Average Grant Date Fair Value, Vested (in USD per share)	13.72
Weighted Average Grant Date Fair Value, Canceled (in USD per share)	15.70
Weighted Average Grant Date Fair Value, Restricted stock units, ending balance (in USD per share)	$ 19.80	$ 14.30			$ 19.80
Stock options granted (in shares)	1,274,453
2012 Plan \| Performance Shares, Total Shareholder Return Grants
Number of Shares
Number of Shares, Granted (in shares)	63,750
Weighted Average Grant Date Fair Value
Stock options granted (in shares)	63,750

Stockholders' Equity - Employee Stock Purchase Plan (Details)	12 Months Ended
	Dec. 26, 2020 purchasePeriod $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount from market price, offering date	85.00%
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)	7,000,000
Issuance of common stock under the Employee Stock Purchase Plan (in shares)	485,566
Weighted average exercise price, exercisable (in USD per share) \| $ / shares	$ 16.47
Weighted average discount (in USD per share) \| $ / shares	$ 11.00
Shares available for grant (in shares)	2,171,656
Employee Stock \| Twelve Month
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering period, duration	12 months
Number of purchase periods \| purchasePeriod	2
Purchase period, duration	6 months
Employee Stock \| Six Month
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering period, duration	6 months
Number of purchase periods \| purchasePeriod	1
Purchase period, duration	6 months

Stock-Based Compensation - Stock-based compensation details (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Share-based Payment Arrangement [Abstract]
Weighted average grant date per share fair value of RSUs granted (in USD per share)	$ 25.96	$ 15.12	$ 13.79
Total intrinsic value of stock options exercised	$ 4,688	$ 1,814	$ 631
Fair value of RSUs vested	$ 42,597	$ 23,450	$ 17,541

Stock-Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	$ 23,830	$ 23,176	$ 17,827
Stock-based compensation tax benefit	4,962	911	453
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	3,951	4,055	3,525
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	5,824	6,367	5,398
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	$ 14,055	$ 12,754	$ 8,904

Stock-Based Compensation - Unrecognized Stock-Based Compensation (Details) $ in Thousands	12 Months Ended
	Dec. 26, 2020 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense	$ 41,445
Weighted Average Recognition Period (Years)	2 years 2 months 12 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense	$ 32,122
Weighted Average Recognition Period (Years)	2 years 2 months 12 days
Performance restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense	$ 9,075
Weighted Average Recognition Period (Years)	2 years 1 month 6 days
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Expense	$ 248
Weighted Average Recognition Period (Years)	1 month 6 days

Stock-Based Compensation - Valuation Assumptions (Details)	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Performance restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	52.01%	47.34%	45.61%
Risk-free interest rate	0.18%	1.83%	2.67%
Expected life (in years)	2 years 9 months 18 days	3 years 1 month 6 days	2 years 10 months 24 days
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Minimum \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	30.40%	36.60%	44.90%
Risk-free interest rate	0.10%	2.04%	0.83%
Expected life (in years)	6 months	6 months	6 months
Maximum \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	74.40%	59.50%	48.90%
Risk-free interest rate	1.54%	2.46%	2.22%
Expected life (in years)	1 year	1 year	1 year

Income Taxes - Components of Income Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
United States	$ 72,950	$ 41,115	$ 20,877
Foreign	12,225	9,948	13,050
Income before income taxes	$ 85,175	$ 51,063	$ 33,927

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Current provision:
Federal	$ 1,799	$ 179	$ 79
State	1,194	2,302	388
Foreign	4,278	4,202	4,687
Total current provision (benefit)	7,271	6,683	5,154
Deferred provision (benefit):
Federal	1,472	8,128	(72,295)
State	(267)	(1,898)	(2,056)
Foreign	(1,824)	(1,196)	(912)
Total deferred provision (benefit)	(619)	5,034	(75,263)
Total provision (benefit) for income taxes	$ 6,652	$ 11,717	$ (70,109)

Income Taxes - Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Income Tax Reconciliation
U.S. statutory federal tax rate	$ 17,887	$ 10,723	$ 7,125
State taxes, net of federal benefit	663	441	778
Stock-based compensation	(4,962)	(911)	(453)
Research and development credits	(6,576)	(6,436)	(3,213)
Foreign taxes at rates different than the U.S.	415	1,454	1,287
Other permanent differences	400	(148)	152
Global intangible low-taxed income	0	1,369	1,828
Foreign Derived Intangible Income	(3,668)	0	0
Change in valuation allowance	1,862	2,567	(75,803)
Other	631	2,658	(1,810)
Total provision (benefit) for income taxes	$ 6,652	$ 11,717	$ (70,109)

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 29, 2018	Dec. 28, 2019
Components of Deferred Tax Assets and Liabilities [Abstract]
Tax credits	$ 42,927		$ 44,696
Inventory reserve	13,401		12,350
Other reserves and accruals	9,470		5,852
Non-statutory stock options	2,794		2,982
Depreciation and amortization	20,961		27,758
Net operating loss carryforwards	18,421		21,410
Gross deferred tax assets	107,974		115,048
Valuation allowance	(38,466)		(36,604)
Total deferred tax assets	69,508		78,444
Acquired intangibles and fixed assets	(8,395)		(13,997)
Unrealized investment gains	(106)		(106)
Tax on undistributed earnings	(110)		(75)
Total deferred tax liabilities	(8,611)		(14,178)
Net deferred tax assets	$ 60,897		$ 64,266
Decrease in valuation allowance		$ 75,800
Consecutive period with positive operating performance	2 years
Cumulative period with U.S. pre-tax profit	3 years

Income Taxes - Tax Credits and Carryforwards (Details) $ in Thousands	Dec. 26, 2020 USD ($)
California
Operating Loss Carryforwards [Line Items]
California research credits	$ 42,615
Singapore
Operating Loss Carryforwards [Line Items]
Singapore net operating loss carryforwards	7,046
Federal
Operating Loss Carryforwards [Line Items]
Federal research and development tax credit	36,579
Foreign tax credit carryforwards	1,059
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 247,990

Income Taxes - Undistributed Earnings (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019
Income Tax Contingency [Line Items]
Repatriation of earnings of foreign subsidiaries	$ 34,400
Deferred tax liabilities on undistributed earnings	110	$ 75
Non-US
Income Tax Contingency [Line Items]
Repatriation of earnings of foreign subsidiaries	12,000
United States
Income Tax Contingency [Line Items]
Repatriation of earnings of foreign subsidiaries	$ 22,400

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit, beginning balance	$ 28,800	$ 25,224	$ 18,296
Additions based on tax positions related to the current year	3,072	3,679	1,677
Additions based on tax positions from prior years	702	0	5,332
Reductions for tax positions of prior years	0	(5)	(7)
Reductions due to lapse of the applicable statute of limitations	(77)	(98)	(74)
Unrecognized tax benefit, ending balance	32,497	28,800	25,224
Interest and penalties recognized as a component of Provision (benefit) for income taxes	50	59	71
Interest and penalties accrued at period end	204	$ 212	$ 230
Tax-effected unrecognized tax benefits	$ 15,800

Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Millions	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Retirement Benefits [Abstract]
Cost recognized under defined contribution plans	$ 2.2	$ 2.1	$ 2.0

Segments and Geographic Information - Operating Results By Segment (Details) $ in Thousands	12 Months Ended
	Dec. 26, 2020 USD ($) segment	Dec. 28, 2019 USD ($)	Dec. 29, 2018 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment	2
Segment Reporting Information [Line Items]
Revenues	$ 693,616	$ 589,464	$ 529,675
Gross profit	$ 287,920	$ 237,496	$ 210,339
Gross margin	41.50%	40.30%	39.70%
Probe Cards
Segment Reporting Information [Line Items]
Revenues	$ 581,739	$ 491,363	$ 434,269
Systems
Segment Reporting Information [Line Items]
Revenues	111,877	98,101	95,406
Operating Segments \| Probe Cards
Segment Reporting Information [Line Items]
Revenues	581,739	491,363	434,269
Gross profit	$ 263,215	$ 211,382	$ 187,320
Gross margin	45.20%	43.00%	43.10%
Operating Segments \| Systems
Segment Reporting Information [Line Items]
Revenues	$ 111,877	$ 98,101	$ 95,406
Gross profit	$ 51,835	$ 50,927	$ 47,074
Gross margin	46.30%	51.90%	49.30%
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	$ 0	$ 0	$ 0
Gross profit	$ (27,130)	$ (24,813)	$ (24,055)
Gross margin	0.00%	0.00%	0.00%

Segments and Geographic Information - Revenue by Country (Details) - Geographic Concentration Risk - Revenue	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Product Information [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%
United States
Product Information [Line Items]
Concentration risk percentage	18.40%	26.30%	25.20%
South Korea
Product Information [Line Items]
Concentration risk percentage	12.50%	19.80%	17.20%
China
Product Information [Line Items]
Concentration risk percentage	25.20%	18.00%	14.70%
Taiwan
Product Information [Line Items]
Concentration risk percentage	21.70%	14.70%	20.30%
Japan
Product Information [Line Items]
Concentration risk percentage	6.30%	8.90%	9.40%
Europe
Product Information [Line Items]
Concentration risk percentage	9.50%	7.00%	7.50%
Asia Pacific
Product Information [Line Items]
Concentration risk percentage	4.80%	3.70%	4.90%
Rest of World
Product Information [Line Items]
Concentration risk percentage	1.60%	1.60%	0.80%

Segments and Geographic Information - Revenue by Market (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Revenue from External Customers [Line Items]
Revenues	$ 693,616	$ 589,464	$ 529,675
Foundry & Logic
Revenue from External Customers [Line Items]
Revenues	446,183	318,552	258,459
DRAM
Revenue from External Customers [Line Items]
Revenues	109,734	147,257	135,333
Flash
Revenue from External Customers [Line Items]
Revenues	25,822	25,554	40,477
Systems
Revenue from External Customers [Line Items]
Revenues	$ 111,877	$ 98,101	$ 95,406

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Segments and Geographic Information - Revenue by Timing of Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	$ 693,616	$ 589,464	$ 529,675
Products transferred at a point in time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	684,427	582,762	523,547
Services transferred over time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	9,189	6,702	6,128
Probe Cards
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	581,739	491,363	434,269
Probe Cards \| Products transferred at a point in time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	579,569	488,925	432,033
Probe Cards \| Services transferred over time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	2,170	2,438	2,236
Systems
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	111,877	98,101	95,406
Systems \| Products transferred at a point in time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	104,858	93,837	91,514
Systems \| Services transferred over time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	$ 7,019	$ 4,264	$ 3,892

- Definition

+ References

+ Details

Segments and Geographic Information - Long-Lived Assets by Geographical Location (Details) - USD ($) $ in Thousands	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Long-Lived Assets [Line Items]
Long-lived assets	$ 406,767	$ 346,973	$ 310,908
United States
Long-Lived Assets [Line Items]
Long-lived assets	347,654	287,600	280,405
Europe
Long-Lived Assets [Line Items]
Long-lived assets	51,791	52,309	26,118
Asia Pacific
Long-Lived Assets [Line Items]
Long-lived assets	$ 7,322	$ 7,064	$ 4,385

Label	Element	Value
Restricted Cash, Noncurrent	us-gaap_RestrictedCashNoncurrent	$ 1,969,000
Restricted Cash, Noncurrent	us-gaap_RestrictedCashNoncurrent	1,411,000
Restricted Cash, Noncurrent	us-gaap_RestrictedCashNoncurrent	1,225,000
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	1,904,000
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	1,981,000
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	$ 849,000
Accounting Standards Update [Extensible List]	us-gaap_AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201712Member

- Definition

Indicates amendment to accounting standards.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(i)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (e)(3)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(iv)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(iii)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 24: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (e)(4)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 65
-Paragraph 15
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 10
-Section 65
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121646688&loc=SL121648383-210437

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(ii)
-URI http://asc.fasb.org/extlink&oid=121370832&loc=SL117420844-207641

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (d)(2)

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 65
-Paragraph 8
-Subparagraph (d)(3)

+ Details