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:
Jan. 24, 1995
Filed:
Dec. 10, 1993
Richard E Gegenwarth, Poughkeepsie, NY (US);
Anthony F Arnold, Poughkeepsie, NY (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A method of making integrated circuit chip to substrate connections first deposits a blanket layer of CrCu over a completed wafer which has terminal vias etched in the final insulator. Then PbSn solder is electrolytically plated through a photoresist mask. After the plating is done, the resist is removed and the Cu is etched using the solder dot as a mask, and then the solder dots are melted to form spheroid or ball shapes. Next, a positive photoresist is applied in a manner that distributes the photoresist around the base of the solder balls. The solder balls are then used as a self-aligned exposure mask. Since the photoresist under the balls is not exposed, each ball has a concentric layer of resist at the base after exposure and development. This concentric layer of resist protects the Cu/PbSn interface and is used as the mask for etching excess Cr. The resist is then removed.