Nanoindentation characterization of intermetallic compounds formed between Sn–Cu (–Ni) ball grid arrays and Cu substrates

The formation of intermetallic compounds (IMCs) at the solder–substrate interface is essential in the manufacturing of solder joints. In this study, the effect of Ni addition into Sn–Cu lead-free solders on mechanical properties of the IMCs formed at the interface between solder ball grid arrays (BGAs) and Cu substrates, which experienced multiple reflows, were investigated. The results from nanoindentation tests showed that elastic modulus and hardness of (Cu,Ni)6Sn5 were higher than those of Cu6Sn5. The hardnesses of (Cu,Ni)6Sn5 were more scattered compared to those of Cu6Sn5, which may be attributed to the crystallographic characteristics such as growth texture of the IMCs.