Improved compositions, methods and devices for high temperature lead-free solder

Abstract

A lead-free solder comprises an alloy of silver and bismuth in amounts of about 2 wt% to about 18 wt% and about 98 wt% to about 82 wt%, respectively. Contemplated alloys further comprise at least one of zinc, nickel, germanium or a combination thereof in an amount of up to about 1000 ppm (preferably about 500ppm) and have a solidus of no lower than about 262.5 DEG C and a liquidus of no higher than about 400 DEG C. Contemplated alloys may further comprise a chemical element with an oxygen affinity that is higher than the oxygen affinity of at least one of the constituents of the alloy, and particularly contemplated elements are phosphorus and germanium.

Description

technical field [0001] The field of the invention is lead-free solders and solder materials. Background technique [0002] Several known die attach methods utilize high lead content solder or solder material to attach the semiconductor die within the integrated circuit to the lead frame for mechanical connection and to provide thermal and electrical conductivity between the die and lead frame . The use of lead in die attach and other solders has come under greater scrutiny from an environmental and occupational health perspective, although most high-lead solders are relatively inexpensive and exhibit different desirable physicochemical properties . Accordingly, various approaches have been taken to replace leaded solders with lead-free die attach compositions. [0003] For example, in one method described in U.S. Pat. The core is attached to the substrate. Polymeric adhesives typically cure at temperatures below 200°C in a relatively short period of time and can even re...

AI Technical Summary

Problems solved by technology

However, Alloy J has a solidus of 228 °C and is also adversely affected by relatively poor mechanical properties

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