Nanoindentation for measuring individual phase mechanical properties of lead free solder alloy

The elimination of lead from electronics due to its detrimental effects to environment and health is pushing component manufacturers to consider lead free solder alloys as the substitute. Application of such alloys requires a better understanding of their mechanical behavior at small volume size and at elevated temperatures. Such information is still lacking for both solder joints and bulk materials. In this study, nanoindentation technique was used to investigate the mechanical properties, namely the hardness and Young’s modulus, of the constituent phases in a near eutectic ternary SAC387 lead free solder alloy. The indentation-induced piling-up of the soft Sn phase was accounted for in the nanoindentation mechanical property calculations using a semi-ellipse method. The modified results agreed well with previous studies on similar alloys. Also, finite element simulation was used to estimate the effect of the complicated network between the eutectic Sn and the intermetallic phases on the mechanical properties acquired, which showed that the tested modulus of the intermetallic phase in the eutectic area exhibited considerable reduction. Vickers tests were also carried out at elevated temperatures, and the hardness of constituent phases dropped 35% from 25 °C to 85 °C.