Excellent reliability with high throughput techniques and materials for alloy attachment

An evaluation is presented which comprehensively examines alloys which can be utilized for secondary attachment in microwave modules. After reflow, the evaluation cycle encompassed in 168-h bake operation, thermal cycling, and mechanical vibration and shock. The samples were X-rayed, examined visually for wetting anomalies, and microsectioned to analyze intermetallic formation. All alloys tested were reflowed without flux in a reducing atmosphere reflow furnace, a high-throughput process clearly amenable to high-volume production. although PbIn 50/50 forms intermetallics with time and temperature, the problem can be controlled with control of the Au plating process. In situations where such monitoring would be difficult, alloys are identified which perform reliably under extended conditioning.<>