Patent Number: 6,255,002

Title: Soldering of a semiconductor chip to a substrate

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.

Inventors: Olofsson; Lars-Anders (Jarfalla, SE)

Assignee: Telefonaktiebolaget LM Ericsson

International Classification: H01L 21/02 (20060101); H01L 21/60 (20060101); H01L 023/48 (); H01L 029/72 (); H01L 023/52 ()

Expiration Date: 07/03/2018