Influence of ZnO nanoparticle addition on interfacial intermetallic compound evolution in Sn-3.0Ag-0.5Cu solder joints

The effect of ZnO nanoparticles on intermetallic compound (IMC) layer in solder joints was investigated by comparing plain Sn-3.0Ag-0.5Cu (SAC305) and Sn-3.0Ag-0.5Cu+0.5ZnO composite solder during isothermal aging. It was shown that the morphology of the IMC layer in composite solder is flatter and the thickness of the IMC layer solder was thinner than the composite solder. The wettability was better and the melting point was not changed distinctly by adding ZnO nanoparticles into the SAC305 solder. The diffusion coefficients of plain SAC305 and composite solder were calculated and were 0.28 and 0.151 mu m(2)h(-1), respectively. Furthermore, the activation energy of composite solder is higher, and it was indicated that the activation energy dominated the growth of the IMC layer in solder during aging. The emphasis was placed on the mechanism of ZnO nanoparticles, and it was clarified that the ZnO nanoparticles acted as an adsorbate and diffusion obstacle that restrained the diffusion of Sn and Cu atoms. Consequently, the growth of the IMC layer was suppressed on account of insufficient activation energy. (C) 2019 The Japan Society of Applied Physics