The growth and size distribution of scallop-type Cu6Sn5 intermetallic compound (IMC) at the interface between molten SnPb solder and Cu was investigated, along with a systematic study of morphology change of Cu6Sn5 morphology change as a function of SnPb solder composition. When SnPb solder composition was changed from eutectic (63Sn37Pb) to about 40Sn60Pb, Cu6Sn5 with round scallop-type morphology was found. In other compositions, the Cu6Sn5 scallops showed faceted scallop-type morphology. This morphological change is due to variation of interfacial energy between Cu6Sn5 and solder with a change of solder composition. The growth rate of Cu6Sn5 layer was proportional to cube root of time, and size distribution was in good agreement with the Flux-Driven-Ripening (FDR) theory. The pre-exponent factor k obtained by the measurement was 2.10×10-14 cm3/sec. Based on the k value, the calculated channel width with was about 2 nm, which was in good agreement with experimental observation by transmission electron microscopy.