Effect of alumina nanoparticles on the microstructure and mechanical durability of meltspun lead-free solders based on tin alloys

As one of the key technologies for high performance electronic devices, composite solders have been recently developed to improve thermal and mechanical properties of solder joints. In this research, melt spinning was employed to fabricate a lead-free based nanocomposite solder for electronic application materials via introducing Ni-coated Al2O3 nanoparticles (0.1 wt%) into a Sn-Ag-Cu ternary eutectic alloy during rapid solidification. These surface-modified nanoparticles were synthesized by an in situ chemical reduction method. The effect of rapid solidification on the distribution of reinforcing nanoparticles, microstructural evolution, and solderability of the tin alloy were studied. Microstructural studies determined that rapid solidification refined brittle and elongated intermetallic compounds (IMCs) into small particles with an average diameter of a few hundred nanometers. The particles were uniformly dispersed into an amorphous/recrystallized fine-grained eutectic morphology of the solder matrix. It was also found that the addition of Ni-coated Al2O3 nanoparticles could effectively suppress the growth of IMC layers, which enhanced the reliability of solder joints. Effects of solid-state ageing phenomenon on the tensile and shear properties of the soldered joints were also evaluated. Higher strength and ductility was measured for joints prepared from the nanocomposite solder as compared with the unreinforced solder. A maximum enhancement of ∼20% in the shear strength was obtained.