Effects of the surface roughness on wetting properties and interfacial reactions between SAC305 solder and Cu substrate with Ni–W–P coating

Abstract

The SAC305/Ni–W–P/Cu joint system has been investigated in previous studies, and Ni–W–P barrier was suggested to be efficient to inhibit excessive diffusion of atoms. Thus, much attention was drawn to improve the performance of this diffusion barrier, but there were few studies focusing on exploring the effect of substrate surface roughness on interfacial microstructure evolution in the solder joint with Ni–W–P barrier. In this work, copper substrates with different surface roughness were prepared for establishing SAC305/Ni–W–P/Cu joint systems. Results revealed that as roughness of substrate surface increased, sizes of coating grains became larger and the surface of Ni–W–P coatings tended to be rougher. On the other hand, with the decrease of substrate surface roughness, wetting properties of SAC305 solder were remarkably improved and the growth rate of intermetallic compound (IMC) layer would decrease. It is suggested that the roughness of substrate surface had remarkable influences on microstructure of Ni–W–P coating, and hence affected the microstructure evolution of IMC layer.