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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 ( Mark One ) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 or TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Delaware ( State or other jurisdiction of Incorporation or organization ) Form 10 - K 000-31311 ( Commission file number ) PDF SOLUTIONS , INC . ( Exact name of registrant as specified in its charter ) 2858 De La Cruz Blvd. Santa Clara , California ( Address of Registrant's principal executive offices ) Title of each class Common Stock , $ 0.00015 par value Securities registered pursuant to Section 12 ( b ) of the Act : ( 408 ) 280-7900 ( Registrant's telephone number , including area code ) Trading Symbol ( s ) PDFS 25-1701361 ( I.R.S. Employer Identification No. ) 95050 ( Zip Code ) Name of each exchange on which registered The Nasdaq Stock Market LLC Securities registered pursuant to Section 12 ( g ) of the Act : None 1 Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes No ✔ No ✔