UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Title of Each Class Trading Symbol Name of Each Exchange on which Registered Class A Common Stock, $0.0001 par value ACMR NASDAQ Global Market FORM 10-Q (Mark One) ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _________ to __ ...