Tensile deformation behavior and melting property of nano-sized ZnO particles reinforced Sn–3.0Ag–0.5Cu lead-free solder

In the present study, nano-sized ZnO particle-reinforced Sn–3.0Ag–0.5Cu (SAC305) composite solder was prepared by mechanically dispersing nano-particles into SAC305 solder at 900°C for 2h. The effects of ZnO addition on microstructure, melting behavior and corresponding mechanical properties of SAC305 solder were explored. Microstructure analysis revealed that the wurtzite ZnO particles were effective in reducing both the β-Sn grain size and spacing between Ag3Sn and Cu6Sn5 particles. The refined microstructure, which resulted in a strong adsorption effect and high surface-free energy of ZnO nanoparticles, could obstruct the dislocation slipping, and thus provides classical dispersion strengthening mechanism. This apparently enhances the yield stress (0.2%YS) and ultimate tensile strength (UTS) of SAC(305)–0.7%ZnO composite solder, whereas its ductility is lower than that of the SAC305 solder. In addition, ZnO particles keep the melting temperature of composite solder nearly at the SAC305 level although the pasty range is decreased. Empirical equations for 0.2% YS, UTS and elastic modulus E with the strain rate have been developed and the predicted tensile parameters for both solders are reasonably close to the present experimental data.