A diffusion model and growth kinetics of interfacial intermetallic compounds in Sn-0.3Ag-0.7Cu and Sn-0.3Ag-0.7Cu-0.5CeO2 solder joints

Abstract The growth kinetics of the intermetallic compounds (IMCs) between the low-silver composite solders (Sn–0.3Ag–0.7Cu-xCeO2) and copper substrates during reflow soldering process has been studied in this work. The thickness and grain size of the interfacial IMCs increase with an increase of reflow time. The addition of CeO2 nanoparticles can effectively suppress the growth of the interfacial IMCs. The interfacial reaction between composite solders and copper substrates is a dynamic response to the comprehensive effects of IMC growth at the interface, diffusion rate of copper atoms, and changes in composition at the solder/copper interface. A diffusion-controlled kinetics model is put forward to investigate the comprehensive effects. The modeling results show that, the diffusion rate of copper atoms at the solder/copper interface is related to the interfacial IMC grain size, IMC thickness and reaction time, and the addition of CeO2 nanoparticles can lead to a relatively lower diffusion rate of Cu atoms at the solder/copper interface. The change characteristic of the copper atom diffusion introduced in this model is supported by a good agreement between experimental and theoretical results. The mechanism of CeO2 nano-additive on the diffusion behavior of Cu atoms at the interface and interfacial IMC growth is explained by using the theory of adsorption and heterogeneous nucleation.