Influence of TiO2 nanoparticles addition on the microstructural and mechanical properties of Sn0.7Cu nano-composite solder

Composites of SC solder reinforced with 0, 0.25, 0.5 and 1 wt.% of TiO2 nanoparticles were fabricated using a mechanical technique. With increased addition of TiO2 nanoparticles, the SC nano-composite solder was found to have a slightly lower melting temperature. The addition of TiO2 nanoparticles can also effectively refine the microstructure as so β-Sn and Cu6Sn5, and increase the percentage of eutectic area. The mechanical properties (microhardness, 0.2% YS and UTS) increase with the increasing presence of reinforcement, far exceeding the strength of the eutectic SC solder. The yield strength improvement was attributed to (i) the Hall–Petch effect due to β-Sn grain size refinement. (ii) Orowan strengthening, (iii) generation of geometrically necessary dislocations to accommodate CTE mismatch between the matrix and the second phase (Cu6Sn5 and TiO2), and (iv) the load-bearing effects due to the presence of nano-sized reinforcements.