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:
Mar. 26, 1996
Filed:
Oct. 04, 1994
Wah-Sang Wong, Montebello, CA (US);
William D Gray, Redondo Beach, CA (US);
Hughes Aircraft Company, Los Angeles, CA (US);
Abstract
A process is provided for passivating surfaces (12') of III-V microwave monolithic integrated circuit (MMIC) flip chips (40). Essentially, two cured, patterned polyimide layers (10, 28) are applied, one on the chip surface supporting a gold-plated bridge (26) and passivating the surface and the other over the gold-plated bridge to passivate the bridge surface. Further, a silver-titanium composite layer (32) is deposited over a gold-plated bump-post (24), which is then covered by a silver-plated bump (38), in order to prevent scavenging of gold from the bump-post by a subsequent Pb-Sn reflow solder process used to mount the chip to a metallized ceramic substrate. The process of the invention facilitates a more compatible reflow solder silk-screening process with passivated III-V MMIC flip chips, resulting in a more uniform and consistent solder thickness and relieving a tight tolerance requirement on the plated silver bump height uniformity.