0001140361-20-006743 | 10-K | XBRL Viewer

Assumptions Used to Determine Fair Value of Share Options Granted

The fair value of each option granted to employee is estimated on the grant date using the Black-Scholes valuation model with the following assumptions.

	December 31,
	2019			2018
Fair value of common share(1)	$	13.64-16.81		$	5.31-13.85
Expected term in years(2)		6.25			6.25
Volatility(3)		39.91%-40.35	%		39.14%-43.00	%
Risk-free interest rate(4)		1.69%-2.46	%		2.55%-2.96	%
Expected dividend(5)		0	%		0	%

(1)

Common stock value was the close market value on the grant date.

(2)

Expected term of share options is based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110.

(3)

Volatility is calculated based on the historical volatility of ACM’s comparable companies in the period equal to the expected term of each grant.

(4)

Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant.

(5)

Expected dividend is assumed to be 0% as ACM has no history or expectation of paying a dividend on its common stock.

Employee Share Option [Member]

Summary of Share Option Activities

The following table summarizes the Company’s employee share option activities during the years ended December 31, 2018 and December 31, 2019:

	Number of Option Share			Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighed Average Remaining Contractual Term
Outstanding at December 31, 2017		2,045,616		$	0.66	$	2.46	7.57 years
Granted		745,700			1.52		8.12
Exercised		(151,650	)	$	0.53	$	2.06
Expired		(4,622	)		0.55		3.00
Forfeited		(131,639	)	$	0.97	$	3.87
Outstanding at December 31, 2018		2,503,405			0.91		4.09	7.30 years
Granted		656,000		$	6.29	$	16.21
Exercised		(106,768	)		0.60		2.09
Expired		(2,757	)	$	3.34	$	8.16
Forfeited/cancelled		(55,817	)		2.38		6.23
Outstanding at December 31, 2019		2,994,063		$	2.59	$	6.77	7.05 years
Vested and exercisable at December 31, 2019		1,773,048

Non-Employee Share Option [Member]

Summary of Share Option Activities

The following table summarizes the Company’s non-employee share option activities during the year ended December 31, 2018 and 2019:

	Number of Option Shares			Weighted Average Grant Date Fair Value		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2017		1,326,676		$	0.78		2.52	7.54 years
Granted		-			-		-		-
Exercised		(114,302	)		0.43		1.92		-
Expired		-			-		-		-
Forfeited		-			-		-		-
Outstanding at December 31, 2018		1,212,374			0.78		2.57	6.66 years
Granted		-			-		-		-
Exercised		(88,529	)		0.45		1.06		-
Expired		-			-		-		-
Forfeited/cancelled		(22,232	)		0.55		3.00		-
Outstanding at December 31, 2019		1,101,613			0.82		2.69	5.85 years
Vested and exercisable at December 31, 2019		1,024,017

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2019

INCOME TAXES [Abstract]

Components of Income Tax Benefit (Expense)

The following represent components of the income tax benefit (expense) for the years ended December 31, 2019 and 2018:

	Year Ended December 31,
	2019			2018

Current:
U.S. federal	$	-		$	-
U.S. state		-			-
Foreign		(3,176	)		(1,149	)
Total current tax expense		(3,176	)		(1,149	)
Deferred:
U.S. federal		3,728			-
U.S. state					-
Foreign		(34	)		343
Total deferred tax benefit		3,694			343
Total income tax benefit (expense)	$	518		$	(806	)

Deferred tax Assets

Tax effects of temporary differences that give rise to significant portions of the Company’s deferred tax assets at December 31, 2019 and 2018 are presented below:

	Year Ended December 31,
	2019			2018

Deferred tax assets:
Net operating loss carry forwards (offshore)	$	216		$	16
Net operating loss carry forwards (U.S.) and credit		3,218			4,105
Deferred revenue (offshore)		1,181			558
Accruals (U.S.)		15			11
Reserves and other (offshore)		426			1,080
Stock-based compensation (U.S.)		1,168			1,021
Property and equipment (U.S.)		3			1
Total gross deferred tax assets		6,227			6,792
Less: valuation allowance		(896	)		(5,155	)
Total deferred tax assets		5,331			1,637
Total deferred tax liabilities		-			-
Translation difference		-			-
Deferred tax assets, net	$	5,331		$	1,637

Effective Income Tax Rate

	Year Ended December 31,
	2019			2018

Effective tax rate reconciliation:
Income tax provision at statutory rate		21.00	%		21.00	%
Foreign rate differential		(12.26	)		(20.88	)
Other permanent difference		8.71			15.59
Change in valuation allowance		(20.19	)		(4.78	)
Total income tax expense (benefit)		(2.74	%)		10.93	%

Aggregate Changes in Balance of Gross Unrecognized Tax Benefits

The aggregate changes in the balance of gross unrecognized tax benefits, which excludes interest and penalties, for the years ended December 31, 2019 and 2018, are as follows:

	Year Ended December 31,
	2019		2018

Beginning balance	$	44	$	44
Increase/ (decrease) of unecognized tax benefits taken in prior years		-		-
Increase/ (decrease) of unecognized tax benefits related to current year		-		-
Increase/ (decrease) of unrecognized tax benefits related to settlements		-		-
Reductions to unrecognized tax benefits related to lapsing statute of limitations		-		-
Ending balance	$	44	$	44

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION (Tables)

12 Months Ended

Dec. 31, 2019

PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION [Abstract]

Condensed Balance Sheet

CONDENSED BALANCE SHEET

	December 31,
	2019		2018
Assets	(in thousands)
Current assets:
Cash and cash equivalents	$	27,733	$	13,161
Accounts Receivable		-		983
Inventory		444		720
Due from intercompany		4,542		14,494
Other receivable		5		175
Total current assets		32,724		29,533
Investment in unconsolidated subsidiaries		68,527		26,861
Total assets		101,251		56,394

Liabilities and Stockholders’ Equity
Accounts payable		1,138		2,818
Other payable		589		58
Income taxes payable		3,129		1,193
Total liabilities		4,856		4,069
Total stockholders’ equity		96,395		52,325
Total liabilities and stockholders’ equity	$	101,251	$	56,394

Condensed Statement of Operations

CONDENSED STATEMENT OF OPERATIONS

	Year Ended December 31,
	2019			2018
	(in thousands)
Revenue	$	10,683		$	25,506
Cost of revenue		(10,036	)		(23,927	)
Gross profit		647			1,579
Operating expenses:
Sales and marketing expenses		(490	)		(301	)
General and administrative expenses		(3,639	)		(5,083	)
Research and development expenses		(476	)		(255	)
Loss from operations		(3,958	)		(4,060	)
Equity in earnings of unconsolidated subsidiaries		22,510			10,360
Interest income, net		231			166
Interest expense, net		(67	)		-
Non-operating income (expense), net		178			108
Income before income taxes		18,894			6,574
Income tax expense		-			-
Net income	$	18,894		$	6,574

Condensed Statement of Cash Flows

CONDENSED STATEMENT OF CASH FLOWS

	Year Ended December 31,
	2019			2018
	(in thousands)
Net cash used in operating activities	$	(7,957	)	$	(1,189	)
Net cash provided by investing activities		-			946
Net cash provided by financing activities		23,347			3,510
Net increase in cash and cash equivalents		15,390			3,267
Cash and cash equivalents, beginning of year		13,161			10,874
Effect of exchange rate changes on cash and cash equivalents		(818	)		(980	)
Cash and cash equivalents, end of year	$	27,733		$	13,161

DESCRIPTION OF BUSINESS (Details) ¥ / shares in Units, ¥ in Thousands, $ in Thousands							3 Months Ended	12 Months Ended
	Nov. 29, 2019 USD ($) Investor	Nov. 29, 2019 CNY (¥) Investor ¥ / shares	Jun. 17, 2019	Jun. 12, 2019 USD ($) Investor	Jun. 12, 2019 CNY (¥) Investor	Sep. 13, 2017	Sep. 30, 2019	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2019 CNY (¥)	Dec. 31, 2018	Nov. 08, 2017	Aug. 31, 2017
Class A Common Stock [Member]
Description of Business [Abstract]
Reverse stock split						0.33
Class B Common Stock [Member]
Description of Business [Abstract]
Reverse stock split						0.33
ACM Research (Shanghai), Inc. [Member]
Description of Business [Abstract]
Purchase of equity interest percentage												18.36%	18.77%
Term to complete listing of shares			3 years
Name of subsidiaries								ACM Research (Shanghai), Inc.
Date and place of Incorporation								China, May 2006
Effective interest held as at								91.70%			100.00%
ACM Research (Shanghai), Inc. [Member] \| First Tranche Investors [Member]
Description of Business [Abstract]
Purchase of equity interest percentage								3.80%
Number of investors with agreements entered \| Investor				7	7
Purchase price of stock agreed by investors				$ 27,300	¥ 187,900
Percentage of outstanding shares to be sold to investors				4.20%	4.20%		4.20%
ACM Research (Shanghai), Inc. [Member] \| Second Tranche Investors [Member]
Description of Business [Abstract]
Purchase of equity interest percentage								4.50%
Number of investors with agreements entered \| Investor	8	8
Purchase price of stock agreed by investors	$ 32,400	¥ 228,200
Share price (in RMB per share) \| ¥ / shares		¥ 13
ACM Research (Wuxi), Inc. [Member]
Description of Business [Abstract]
Name of subsidiaries								ACM Research (Wuxi), Inc.
Date and place of Incorporation								China, July 2011
Effective interest held as at								91.70%			100.00%
CleanChip Technologies Limited [Member]
Description of Business [Abstract]
Proceeds from sale of interest in subsidary \| $								$ 3,500
Name of subsidiaries								CleanChip Technologies Limited
Date and place of Incorporation								Hong Kong, June 2017
Effective interest held as at								91.70%			100.00%
ACM Research Korea CO., LTD [Member]
Description of Business [Abstract]
Name of subsidiaries								ACM Research Korea CO., LTD.
Date and place of Incorporation								Korea, December 2017
Effective interest held as at								91.70%			100.00%
Shengwei Research (Shanghai), Inc. [Member]
Description of Business [Abstract]
Purchase of equity interest percentage								91.70%
Registered capital									$ 727	¥ 5,000
Capital injected in subsidiary \| $								$ 142
Name of subsidiaries								Shengwei Research (Shanghai), Inc.
Date and place of Incorporation								China, March 2019
Effective interest held as at								91.70%			100.00%
ACM Research (CA), Inc. [Member]
Description of Business [Abstract]
Name of subsidiaries								ACM Research (CA), Inc.
Date and place of Incorporation								USA, June 2019
Effective interest held as at								91.70%			100.00%

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable [Abstract]
Allowance for doubtful accounts	$ 0	$ 0

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Inventory (Details)	12 Months Ended
	Dec. 31, 2019
Inventory [Abstract]
Maximum shipment period of finished goods from warehouse	1 month

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Property, Plant and Equipment, Net (Details)	12 Months Ended
	Dec. 31, 2019
Computer and Office Equipment [Member] \| United States [Member] \| Minimum [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	3 years
Computer and Office Equipment [Member] \| United States [Member] \| Maximum [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	5 years
Manufacturing Equipment [Member] \| PRC [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	5 years
Furniture and Fixtures [Member] \| United States [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	5 years
Furniture and Fixtures [Member] \| PRC [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	5 years
Transportation Equipment [Member] \| PRC [Member] \| Minimum [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	4 years
Transportation Equipment [Member] \| PRC [Member] \| Maximum [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	5 years
Electronic Equipment [Member] \| PRC [Member] \| Minimum [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	3 years
Electronic Equipment [Member] \| PRC [Member] \| Maximum [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	5 years
Leasehold Improvement [Member] \| PRC [Member] \| Minimum [Member]
Property, Plant and Equipment, Net [Abstract]
Useful lives	3 years

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Intangible Assets, Net (Details)	12 Months Ended
	Dec. 31, 2019
Software [Member]
Intangible Assets, Net [Abstract]
Intangible assets amortization period	2 years
Maximum [Member]
Intangible Assets, Net [Abstract]
Intangible assets amortization period, if neither the contract nor local law specifies a beneficial period	10 years

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Shipping and Handling Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Shipping and Handling Costs [Abstract]
Sales and marketing expenses	$ 11,902	$ 9,611
Shipping and Handling [Member]
Shipping and Handling Costs [Abstract]
Sales and marketing expenses	$ 172	$ 146

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Warranty Obligations [Roll Forward]
Balance at beginning of period	$ 1,710	$ 839
Additions	2,105	1,412
Utilized	(1,004)	(541)
Balance at end of period	$ 2,811	$ 1,710
Minimum [Member]
Warranty [Abstract]
Standard product warranty period	12 months
Maximum [Member]
Warranty [Abstract]
Standard product warranty period	36 months

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Government Subsidies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Subsidy	Dec. 31, 2018 USD ($)
Government Subsidies [Abstract]
Number of subsidies awarded \| Subsidy	4
Subsidies recognized as reductions of relevant expenses	$ 3,195	$ 1,486
Subsidies recognized as other income	$ 147	$ 144

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Basic and Diluted Net Income (Loss) per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Numerator [Abstract]
Net income	$ 19,458	$ 6,574
Net income attributable to redeemable non-controlling interest	564	0
Net income available to common stockholders, basic and diluted	$ 18,894	$ 6,574
Weighted average shares outstanding, basic (in shares)	16,800,623	15,788,460
Effect of dilutive securities (in shares)	2,334,874	2,123,645
Weighted average shares outstanding, diluted (in shares)	19,135,497	17,912,105
Net income per common share [Abstract]
Basic (in dollars per share)	$ 1.12	$ 0.42
Diluted (in dollars per share)	$ 0.99	$ 0.37
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,173,486	3,795,779
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,095,676	3,715,779
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)	77,810	80,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Comprehensive Income (Loss) Attributable to the Company (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Comprehensive Income (Loss) Attributable to the Company [Abstract]
Comprehensive income attributable to the Company	$ 18,559	$ 5,595

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Statutory Reserves (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
ACM Research (Shanghai), Inc. [Member]
Statutory Reserves [Abstract]
Statutory surplus reserve	$ 1,427	$ 0

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Operating and Financial Risks (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($) Customer
Foreign Currency Risk and Translation [Abstract]
Foreign currency translation adjustment \| $	$ (899)	$ (979)
Revenue [Member]
Concentration of Credit Risk [Abstract]
Number of major customers \| Customer	3	3
Customer A [Member] \| Revenue [Member]
Concentration of Credit Risk [Abstract]
Concentration of credit risk	26.46%	24.17%
Customer B [Member] \| Revenue [Member]
Concentration of Credit Risk [Abstract]
Concentration of credit risk	19.84%	23.83%
Customer C [Member] \| Revenue [Member]
Concentration of Credit Risk [Abstract]
Concentration of credit risk	27.50%	39.63%
RMB [Member]
Consolidated balance sheets [Abstract]
Exchange rate	6.9784	6.8634
Consolidated statements of operations and comprehensive income [Abstract]
Exchange rate	6.8966	6.6181
KRW [Member]
Consolidated balance sheets [Abstract]
Exchange rate	1,156.07	1,114.83
Consolidated statements of operations and comprehensive income [Abstract]
Exchange rate	1,165.50	1,100.11

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Recent Accounting Pronouncements [Abstract]
Operating lease right-of-use assets	$ 3,887	$ 0
Lease liabilities	3,887
ASU 2016-02 [Member]
Recent Accounting Pronouncements [Abstract]
Operating lease right-of-use assets	5,109
Lease liabilities	$ 5,109

SIGNIFICANT ACCOUNTING POLICIES, Borrowing Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Capitalized Interest Costs [Abstract]
Capitalized borrowing costs	$ 0	$ 0

ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable [Abstract]
Accounts receivable	$ 31,091	$ 24,608
Less: allowance for doubtful accounts	0	0
Total	31,091	24,608
Accounts receivable pledged as collateral for borrowings	$ 1,433	$ 1,457

INVENTORIES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory [Abstract]
Raw materials	$ 15,105	$ 12,646
Work in process	10,407	9,631
Finished goods	19,284	16,487
Total inventory, gross	44,796	38,764
Inventory reserve	0	0
Total inventory, net	44,796	38,764
Inventory pledged as collateral for borrowings	$ 0	$ 0

PROPERTY, PLANT AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Total cost	$ 6,095	$ 11,778
Less: Total accumulated depreciation	(3,077)	(8,102)
Construction in progress	601	32
Total property, plant and equipment, net	3,619	3,708
Depreciation expense	713	350
Manufacturing equipment retired	5,824
Manufacturing Equipment [Member]
Property, Plant and Equipment [Abstract]
Total cost	3,902	9,703
Office Equipment [Member]
Property, Plant and Equipment [Abstract]
Total cost	627	512
Transportation Equipment [Member]
Property, Plant and Equipment [Abstract]
Total cost	124	184
Leasehold Improvement [Member]
Property, Plant and Equipment [Abstract]
Total cost	$ 1,442	$ 1,379

SHORT-TERM BORROWINGS (Details) ¥ in Thousands, $ in Thousands		12 Months Ended
	Dec. 13, 2019 CNY (¥)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 CNY (¥)
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 13,753	$ 9,447
Short-term borrowings repaid		14,005	13,131
Interest expense related to short-term borrowings		745	498
Line of Credit Due on April 17, 2019 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 0	3,133
Maximum borrowing capacity \| ¥				¥ 50,000
Annual interest rate		4.99%
Line of credit due date		Apr. 17, 2019
Line of Credit Due on February 14, 2019 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 0	485
Maximum borrowing capacity \| ¥				50,000
Annual interest rate		5.15%
Line of credit due date		Feb. 14, 2019
Line of Credit Due on January 23, 2020 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 5,057	0
Maximum borrowing capacity \| ¥				50,000
Annual interest rate		5.22%
Line of credit due date		Jan. 23, 2020
Short-term borrowings repaid \| ¥	¥ 14,500
Line of Credit Due on June 6, 2019 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 0	2,186
Maximum borrowing capacity \| ¥				30,000
Annual interest rate		5.22%
Line of credit due date		Jun. 06, 2019
Line of Credit Due on June 13, 2019 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 0	2,186
Maximum borrowing capacity \| ¥				30,000
Annual interest rate		5.22%
Line of credit due date		Jun. 13, 2019
Line of Credit Due on January 23, 2019 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 0	1,457
Maximum borrowing capacity \| ¥				10,000
Annual interest rate		5.44%
Line of credit due date		Jan. 23, 2019
Line of Credit Due on February 21, 2020 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 1,433	0
Maximum borrowing capacity \| ¥				20,000
Annual interest rate		5.66%
Line of credit due date		Feb. 21, 2020
Line of Credit Due on January 18, 2020 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 1,433	0
Maximum borrowing capacity \| ¥				20,000
Annual interest rate		5.66%
Line of credit due date		Jan. 18, 2020
Line of Credit Due on January 22, 2020 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 717	0
Maximum borrowing capacity \| ¥				20,000
Annual interest rate		5.66%
Line of credit due date		Jan. 22, 2020
Line of Credit Due on February 14, 2020 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 717	0
Maximum borrowing capacity \| ¥				20,000
Annual interest rate		5.66%
Line of credit due date		Feb. 14, 2020
Line of Credit Due on March 25, 2020 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 3,250	0
Maximum borrowing capacity \| ¥				50,000
Annual interest rate		4.94%
Line of credit due date		Mar. 25, 2020
Line of Credit Due on April 17, 2020 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 1,146	$ 0
Maximum borrowing capacity \| ¥				¥ 50,000
Annual interest rate		5.66%
Line of credit due date		Apr. 17, 2020

OTHER PAYABLE AND ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OTHER PAYABLE AND ACCRUED EXPENSES [Abstract]
Lease expenses and payable for leasehold improvement due to a related party (note 11)	$ 0	$ 53
Accrued commissions	4,082	2,931
Accrued warranty	2,811	1,710	$ 839
Accrued payroll	2,092	626
Accrued professional fees	165	64
Accrued machine testing fees	1,456	3,076
Others	2,268	1,950
Total	$ 12,874	$ 10,410

LEASES (Details) ¥ in Thousands			1 Months Ended	12 Months Ended
LEASES (Details) ¥ in Thousands	Apr. 26, 2018 USD ($)	Apr. 26, 2018 CNY (¥)	Jan. 31, 2018 Squarefeet	Dec. 31, 2019 USD ($) Squarefeet	Apr. 26, 2018 CNY (¥)
Components of lease expense [Abstract]
Operating lease cost				$ 1,432,000
Short-term lease cost				165,000
Lease cost				1,597,000
Cash paid for amounts included in the measurement of lease liabilities [Abstract]
Operating cash outflow from operating leases				1,597,000
Maturities of lease liabilities [Abstract]
2020				1,504,000
2021				1,488,000
2022				1,496,000
2023				53,000
2024				13,000
Total lease payments				4,554,000
Less: Interest				(667,000)
Present value of lease liabilities				$ 3,887,000
Weighted average remaining lease terms and discount rates [Abstract]
Weighted average remaining lease term				3 years 7 days
Weighted average discount rate				5.43%
ACM Shanghai [Member]
Lessee Disclosure [Abstract]
Term of lease agreement				2 years
Area of space for office and warehouse \| Squarefeet			50,000	3,000
Monthly rental fee	$ 55,000	¥ 366		$ 2,000
Increased base rent for April 1, 2019 to March 31, 2020				3,300
Increased base rent for April 1, 2020 to March 31, 2021				3,400
Security deposit amount	$ 163,000				¥ 1,077
ACM Wuxi [Member] \| Maximum [Member]
Lessee Disclosure [Abstract]
Monthly rental fee				$ 1,000
Shanghai Zhangjiang Group Co., Ltd. [Member]
Lessee Disclosure [Abstract]
Area of space for office and warehouse \| Squarefeet				63,510

OTHER LONG-TERM LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Long-term Liabilities [Abstract]
Other long-term liabilities	$ 4,186	$ 4,583
Subsidies to Stress Free Polishing Project, Commenced in 2008 and 2017 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	1,251	1,483
Subsidies to Electro Copper Plating Project, Commenced in 2014 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	2,666	2,860
Subsidies to Polytetrafluoroethylene Project, Commenced in 2018 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	135	178
Other [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	$ 134	$ 62

LONG-TERM INVESTMENT (Details) $ / shares in Units, ¥ in Thousands, $ in Thousands		12 Months Ended
	Sep. 05, 2019 Investor	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 CNY (¥)	Jun. 27, 2019 USD ($)	Sep. 11, 2017 USD ($) $ / shares shares
Investments [Abstract]
Investment in partnership				$ 4,200	¥ 30,000
Ownership percentage in partnership				10.00%	10.00%
Equity income in net income of affiliates		$ 168	$ 123
Classification of Investments [Abstract]
Investment - equity method		5,827	1,360
Investment - cost method		107	0
Total		$ 5,934	$ 1,360
Ninebell [Member]
Investments [Abstract]
Percentage of ordinary shares issued							20.00%
Purchase price							$ 1,200
Ninebell [Member] \| Class A Common Stock [Member]
Investments [Abstract]
Purchase price							$ 1,000
Shares issued (in shares) \| shares							133,334
Share price (in dollars per share) \| $ / shares							$ 7.50
Shengyi [Member]
Investments [Abstract]
Percentage of ordinary shares issued						15.00%
Classification of Investments [Abstract]
Number of investors with agreements entered \| Investor	6
Investment - cost method						$ 109

RELATED PARTY BALANCES AND TRANSACTIONS (Details) $ / shares in Units, ¥ in Thousands, $ in Thousands							1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 14, 2019 USD ($) $ / shares shares	Apr. 26, 2018 USD ($)	Apr. 26, 2018 CNY (¥)	Mar. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($) shares	Mar. 14, 2017 USD ($) $ / shares shares	Aug. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Apr. 26, 2018 CNY (¥)	Sep. 29, 2017 USD ($)	Aug. 18, 2017 USD ($)	Dec. 09, 2016 USD ($)	Dec. 09, 2016 CNY (¥)
Related Party Transaction [Abstract]
Shares issued value									$ 26,435
Common Class A [Member]
Related Party Transaction [Abstract]
Shares issued (in shares) \| shares							2,053,572
Stock price (in dollars per share) \| $ / shares							$ 14.00
ACM Shanghai [Member]
Related Party Transaction [Abstract]
Amount funded for leasehold improvements												$ 771
Monthly rental fee		$ 55	¥ 366						2
Security deposit amount		$ 163									¥ 1,077
Lease expense under lease agreement									$ 595	$ 620
Repayments of notes							$ 1,161
Ninebell Co., Ltd [Member]
Related Party Transaction [Abstract]
Interest-free loan to related party													$ 946
Loans payable period									180 days
Loans extended period									180 days
Purchased materials amount									$ 8,572	7,785
Accounts payable-related party									727	1,477
Prepaid for material purchases									348	572
Shanghai Zhangjiang Group Co., Ltd. [Member]
Related Party Transaction [Abstract]
Lease expenses and payable for leasehold improvement due to a related party									$ 0	$ 53
Shanghai Zhangjiang Group Co., Ltd. [Member] \| Common Class A [Member]
Related Party Transaction [Abstract]
Shares issued (in shares) \| shares					787,098
Shares issued value					$ 5,903
SMC [Member]
Related Party Transaction [Abstract]
Cash delivered as of the close of business														$ 2,981	¥ 20,124
Stock price (in dollars per share) \| $ / shares								$ 13.195
Investment repayment period									60 days
Repayments of notes								$ 882
Number of shares repurchased/surrender in exchange (in shares) \| shares								154,821
SMC [Member] \| Senior Secured Promissory Note [Member]
Related Party Transaction [Abstract]
Promissory note principal amount				$ 2,981
Interest rate on promissory note				3.01%
Promissory note maturity date									Aug. 17, 2023
SMC [Member] \| Common Class A [Member]
Related Party Transaction [Abstract]
Shares issued (in shares) \| shares						397,502
Shares issued value						$ 2,981
Stock price (in dollars per share) \| $ / shares	$ 13.195					$ 7.50
Exercise of common stock warrant issued (in shares) \| shares				397,502
Number of shares repurchased/surrender in exchange (in shares) \| shares	214,286
Cancellation of options to acquire shares (in shares) \| shares	53,571
Cancellation of options to acquire stock, amount	$ 3,403
Shengyi [Member]
Related Party Transaction [Abstract]
Purchased materials amount									$ 856
Accounts payable-related party									$ 488

COMMON STOCK (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 14, 2019	Mar. 30, 2018	Mar. 14, 2017	Aug. 31, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Abstract]
Net proceeds from issuance of stock						$ 26,434	$ 0
Conversion of class B common shares to Class A common shares (in shares)						35,815
SMC [Member]
Class of Stock [Abstract]
Stock price (in dollars per share)					$ 13.195
Number of shares repurchased (in shares)					154,821
Common Class A [Member]
Class of Stock [Abstract]
Common stock, shares authorized (in shares)						50,000,000	50,000,000
Common stock, par value (in dollars per share)						$ 0.0001	$ 0.0001
Number of votes for each share entitled						1
Number of shares issued (in shares)				2,053,572
Stock price (in dollars per share)				$ 14.00
Net proceeds from issuance of stock				$ 28,750
Underwriting discount and offering expenses				$ 2,287
Common stock, shares issued (in shares)						16,182,151	14,110,315
Common stock, shares outstanding (in shares)						16,182,151	14,110,315
Common Class A [Member] \| SMC [Member]
Class of Stock [Abstract]
Exercise of common stock warrant issued (in shares)		397,502
Number of shares issued (in shares)			397,502
Stock price (in dollars per share)	$ 13.195		$ 7.50
Number of shares repurchased (in shares)	214,286
Common Class B [Member]
Class of Stock [Abstract]
Common stock, shares authorized (in shares)						2,409,738	2,409,738
Common stock, par value (in dollars per share)						$ 0.0001	$ 0.0001
Number of votes for each share entitled						20
Convertible shares in to Class A common stock (in shares)						1
Common stock, shares issued (in shares)						1,862,608	1,898,423
Common stock, shares outstanding (in shares)						1,862,608	1,898,423
Common Stock [Member] \| Common Class A [Member]
Class of Stock [Abstract]
Exercise of common stock warrant issued (in shares)						1,438	397,502
Stock issued upon exercise of stock options (in shares)						195,297	265,952
Number of shares issued (in shares)						2,053,572
Number of shares repurchased (in shares)						214,286
Conversion of class B common shares to Class A common shares (in shares)						35,815	511,315
Common Stock [Member] \| Common Class B [Member]
Class of Stock [Abstract]
Exercise of common stock warrant issued (in shares)						0	0
Stock issued upon exercise of stock options (in shares)						0	0
Number of shares issued (in shares)						0
Conversion of class B common shares to Class A common shares (in shares)						(35,815)	(511,315)

REDEEMABLE NON-CONTROLLING INTERESTS (Details) $ in Thousands		3 Months Ended		12 Months Ended
	Jun. 12, 2019	Dec. 31, 2019 USD ($)	Sep. 30, 2019 Investor	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Change in Redeemable Noncontrolling Interests [Abstract]
Balance				$ 0
Net income attributable to redeemable non-controlling interests				564	$ 0
Effect of foreign currency translation loss attributable to redeemable non-controlling interests				(81)
Balance		$ 60,162		60,162	$ 0
Tranche 1 [Member]
Change in Redeemable Noncontrolling Interests [Abstract]
Increase in redeemable non-controlling interests due to issuance of common stock				27,264
Tranche 2 [Member]
Change in Redeemable Noncontrolling Interests [Abstract]
Increase in redeemable non-controlling interests due to issuance of common stock				$ 32,415
ACM Shanghai [Member]
Redeemable Noncontrolling Interest [Abstract]
Percentage of redeemable non-controlling interest issued		91.70%
ACM Shanghai [Member] \| Tranche 1 [Member]
Redeemable Noncontrolling Interest [Abstract]
Percentage of outstanding shares issued	4.20%		4.20%
Number of investors owned by employees entities \| Investor			2
Percentage of discount on purchase price for employee entities			20.00%
Term of supplemental agreement			3 years
Percentage of redeemable non-controlling interest issued		3.80%
ACM Shanghai [Member] \| Tranche 2 [Member]
Redeemable Noncontrolling Interest [Abstract]
Percentage of redeemable non-controlling interest issued		4.50%

STOCK-BASED COMPENSATION (Details) - USD ($)
$ / shares in Units, $ in Thousands

12 Months Ended

Dec. 28, 2016

Apr. 29, 1998

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2017

Aug. 31, 2019

Class A Common Stock [Member]

Fair value of common share (in dollars per share)

$ 14.00

Employee Share Option [Member]

Outstanding, beginning of period (in shares)

2,503,405

2,045,616

Granted (in shares)

656,000

745,700

Exercised (in shares)

(106,768)

(151,650)

Expired (in shares)

(2,757)

(4,622)

Forfeited/cancelled (in shares)

(55,817)

(131,639)

Outstanding, end of period (in shares)

2,994,063

2,503,405

2,045,616

Vested and exercisable (in shares)

1,773,048

Weighted Average Grant Date Fair Value [Abstract]

Outstanding at beginning of period (in dollars per share)

$ 0.91

$ 0.66

6.29

1.52

0.60

0.53

3.34

0.55

Outstanding at end of period (in dollars per share)

2.38

0.97

2.59

0.91

$ 0.66

Weighted Average Exercise Price [Abstract]

Outstanding, beginning of period (in dollars per share)

4.09

2.46

16.21

8.12

2.09

2.06

8.16

3.00

Outstanding, end of period (in dollars per share)

6.23

3.87

$ 6.77

$ 4.09

$ 2.46

Weighed Average Remaining Contractual Term [Abstract]

Outstanding weighed average remaining contractual term

7 years 18 days

7 years 3 months 18 days

7 years 6 months 25 days

Unrecognized employee stock-based compensation expense

$ 2,265

$ 712

$ 4,712

$ 2,424

Weighted-average period over which unrecognized compensation is expected to be recognized

1 year 5 months 19 days

1 year 7 months 13 days

Employee Share Option [Member] | Minimum [Member]

Expected term in years

^[1]

6 years 3 months

Expected dividend

^[2]

0.00%

Fair value of common share (in dollars per share)

^[3]

$ 13.64

$ 5.31

Volatility

^[4]

39.91%

39.14%

Risk-free interest rate

^[5]

1.69%

2.55%

Employee Share Option [Member] | Maximum [Member]

Fair value of common share (in dollars per share)

^[3]

$ 16.81

$ 13.85

Volatility

^[4]

40.35%

43.00%

Risk-free interest rate

^[5]

2.46%

2.96%

Employee Share Option [Member] | ACM Shanghai [Member]

Weighed Average Remaining Contractual Term [Abstract]

Percentage of discount on purchase price for employee entities

20.00%

Employee Share Option [Member] | ACM Shanghai [Member] | Cost of Revenue [Member]

$ 949

Weighed Average Remaining Contractual Term [Abstract]

Employee Share Option [Member] | ACM Shanghai [Member] | Sales and Marketing Expenses [Member]

119

Weighed Average Remaining Contractual Term [Abstract]

Employee Share Option [Member] | ACM Shanghai [Member] | Research and Development Expenses [Member]

111

Weighed Average Remaining Contractual Term [Abstract]

Employee Share Option [Member] | ACM Shanghai [Member] | General and Administrative Expenses [Member]

625

Weighed Average Remaining Contractual Term [Abstract]

Non-Employee Share Option [Member]

$ 94

Outstanding, beginning of period (in shares)

1,212,374

1,326,676

Granted (in shares)

Exercised (in shares)

(88,529)

(114,302)

Expired (in shares)

Forfeited/cancelled (in shares)

(22,232)

Outstanding, end of period (in shares)

1,101,613

1,212,374

1,326,676

Vested and exercisable (in shares)

1,024,017

Weighted Average Grant Date Fair Value [Abstract]

Outstanding at beginning of period (in dollars per share)

$ 0.78

0.45

0.43

Outstanding at end of period (in dollars per share)

0.55

0.82

0.78

$ 0.78

Weighted Average Exercise Price [Abstract]

Outstanding, beginning of period (in dollars per share)

2.57

2.52

1.06

1.92

Outstanding, end of period (in dollars per share)

3.00

$ 2.69

$ 2.57

$ 2.52

Weighed Average Remaining Contractual Term [Abstract]

Outstanding weighed average remaining contractual term

5 years 10 months 6 days

6 years 7 months 28 days

7 years 6 months 14 days

Unrecognized employee stock-based compensation expense

$ 1,307

$ 2,651

$ 406

$ 1,713

Weighted-average period over which unrecognized compensation is expected to be recognized

2 months 23 days

1 year 3 months 22 days

Non-Employee Share Option [Member] | Class A Common Stock [Member]

Outstanding, beginning of period (in shares)

3,715,779

Outstanding, end of period (in shares)

4,095,676

3,715,779

Outstanding stock options intrinsic value

$ 52,300

$ 27,100

Options vested (in shares)

2,797,062

2,273,880

Options vested intrinsic value

$ 43,400

$ 20,000

Options unvested (in shares)

1,298,614

1,441,899

Options unvested intrinsic value

$ 8,900

$ 7,100

Non-Employee Share Option [Member] | Class A Common Stock [Member] | Director [Member]

Forfeited/cancelled (in shares)

(22,232)

1998 Stock Option Plan [Member]

Shares of common stock reserved for issuance (in shares)

766,667

1998 Stock Option Plan [Member] | Incentive Stock options [Member] | Maximum [Member]

Option price at the time of grant, fair market value of stock price percentage

100.00%

1998 Stock Option Plan [Member] | Nonstatutory Stock Options [Member] | Maximum [Member]

Option price at the time of grant, fair market value of stock price percentage

85.00%

2016 Omnibus Incentive Plan [Member] | Class A Common Stock [Member]

Shares outstanding immediate preceding year, percentage

4.00%

2016 Omnibus Incentive Plan [Member] | Class A Common Stock [Member] | Maximum [Member]

Shares of common stock reserved for issuance (in shares)

2,333,334

2016 Omnibus Incentive Plan [Member] | Class B Common Stock [Member]

Shares outstanding immediate preceding year, percentage

4.00%

2016 Omnibus Incentive Plan [Member] | Incentive Stock options [Member]