Enhancing creep resistance of SnBi solder alloy with non-reactive nano fillers: A study using nanoindentation

With excellent performance in mechanical strength and hardness, low melting point solder alloys have been identified as a promising lead-free alternative for microelectronic industry. However, the application of such alloys is hindered because of the serious creep deformation when electronic devices are inevitably heated up during operation or even at room temperature. In this study, non-reactive Al2O3 nano particles is explored as an option to enhance the creep resistance of eutectic SnBi alloy that has a melting temperature of 139 °C. Eutectic SnBi was mixed with nano Al2O3 particles for up to 4 wt%. Nanoindentation testing protocol for the creep properties measurement is used in this study. Core diffusion controlled dislocation climb is found to be the creep mechanism for the composite alloy. Other mechanical properties including elastic modulus and hardness are also evaluated and related to the microstructure evolvement of the nanocomposite alloy at various filler loadings. This work also compares the effectiveness of non-reactive fillers with the reactive fillers on enhancing the creep resistance of SnBi alloy. Suitable filler candidates for the best mechanical performance of SnBi composite alloys are recommended.