Publications Details

Alloy design options for improvement of the thermomechanical fatigue life of solder joints

Frear, D.R.; Jones, W.B.; Morris Jr., J.W.; Mei, Z.

The eutectic Sn-Pb solder alloy is discussed with respect to alloy development options to improve the thermomechanical fatigue behavior of solder joints. Eutectic Sn-Pb solder joints fail through the development of a heterogeneous coarsened band of recrystallized and coarsened Pb- and Sn-rich phases. All imposed deformation concentrates solely into this thin region, accelerating fatigue failures. The development of solder alloys is currently being undertaken to improve the fatigue characteristics of eutectic Sn-Pb solder. New alloys must retain wetting and manufacturability characteristics similar to eutectic Sn-Pb. The options discussed to improve fatigue life include: creating a fine superplastic microstructure, small alloy additions to homogenize the microstructure, carbon reinforced composite solder, dispersed second phase precipitates that break up the solder microstructure, and using different solder alloys to replace eutectic Sn-Pb.