Morphology, growth and size distribution of Cu/sub 6/Sn/sub 5/ intermetallic compound by flux-driven ripening at SnPb solder and Cu interface

Abstract

The size distribution and growth of scallop-type Cu/sub 6/Sn/sub 5/ intermetallic compound at the interface between molten SnPb solder and Cu was investigated, along with morphological change of Cu/sub 6/Sn/sub 5/ according to SnPb solder composition. Cu/sub 6/Sn/sub 5/ showed round scallop-type morphology when SnPb solder composition was from eutectic (63Sn37Pb) to about 40Sn60Pb. In other compositions, the intermetallic compounds showed faceted morphology. This change of morphology is due to variation of interfacial energy with solder composition. The scallop growth rate is proportional to cube root of time, and size distribution is in good agreement with the flux-driven-ripening (FDR) theory. Comparison with other works showed that intermetallic compound scallops with shape close to hemisphere give better agreement with the FDR theory.