The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 28, 1999
Filed:
Jul. 11, 1997
David A Baker, Hillsboro, OR (US);
Credence Systems Corporation, Fremont, CA (US);
Abstract
A semiconductor tester includes a support frame and a test head assembly mounted to the support frame for vertical movement relative thereto. A counterbalance assembly also is mounted to the support frame for vertical movement relative thereto. A force transmission member interconnects the test head assembly and the counterbalance assembly, whereby upward movement of the test head assembly is accompanied by downward movement of the counterbalance assembly and downward movement of the test head assembly is accompanied by upward movement of the counterbalance assembly. A force sensing transducer which is coupled to the test head assembly develops an output signal dependent on an external effort applied to the test head assembly to cause vertical movement thereof in a selected direction. A force amplifier is responsive to the output signal of the force sensing transducer and has an output member coupled drivingly to at least one of the assemblies for applying a force thereto dependent on and assisting the external effort applied to the test head.