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:
Jul. 03, 2001
Filed:
Jul. 05, 2000
Lars-Anders Olofsson, Järfälla, SE;
Telefonaktiebolaget LM Ericsson, Stockholm, SE;
Abstract
The present invention relates to a method of soldering a semiconductor chip to a substrate, such as to a capsule in an RF-power transistor, for instance. The semiconductor chip is provided with an adhesion layer consisting of a first material composition. A solderable layer consisting of a second material composition is disposed on this adhesion layer. An antioxidation layer consisting of a third material composition is disposed on said solderable layer. The antioxidation layer is coated with a layer of gold-tin solder. The chip is placed on a solderable capsule surface, via said gold-tin solder. The capsule and chip are exposed to an inert environment to which a reducing gas is delivered and the capsule and chip are subjected to a pressure substantially beneath atmospheric pressure whilst the gold-tin solder is heated to a temperature above its melting point. The gas pressure is increased whilst the gold-tin solder is molten and the temperature is lowered when a predetermined gas pressure is exceeded, so that the gold-tin solder will solidify.