Effect of TiO2 additions on Sn-0.7Cu-0.05Ni lead-free composite solder

Abstract The effect of TiO 2 addition on the microstructure, melting behavior, microhardness and interfacial reaction between Sn-0.7Cu-0.05Ni and a Cu-substrate were explored. Samples with various TiO 2 percentages (0, 0.25, 0.5, 0.75 and 1.0 wt.%) were prepared using a microwave-assisted sintering powder metallurgy method. Microstructural analysis reveals that TiO 2 was uniformly distributed along the grain boundary of the bulk solder. Differential scanning calorimetry (DSC) results showed a decrease in the undercooling while melting temperature of the solder slightly increase. The thickness of the interfacial intermetallic compounds of the solder joint was reduced with the addition of TiO 2 particles. This thickness reduction indicates that the presence of a small amount of TiO 2 particles is effective in suppressing the growth of the intermetallic compound layer. Small dimples on the fracture surface have revealed that the Sn-Cu-Ni composite solder exhibits typical ductile failure. Overall, the addition of TiO 2 to Sn-0.7Cu-0.05Ni solder dramatically increases its shear strength and hardness and improves its wetting properties and fracture surface.