Effect of TiO_2 nanoparticle addition and cooling rate on microstructure and mechanical properties of novel Sn1.5Sb0.7Cu solders

摘要

The effects of TiO_2 nanoparticles and cooling rate on the microstructure and mechanical properties of Sn1.5Sb0.7Cu alloy were investigated. A higher cooling rate and TiO_2 nanoparticles refined the primary β-Sn dendrites, Cu_6Sn_5 and SbSn phase. Especially, the microstructure of the Sn1.5Sb0.7Cu composite solders under the rapid-cooled condition exhibited fine dot-like Cu_6Sn_5 in the eutectic regions. The improvement in strength was mostly attributed to (1) refinement of the β-Sn grain size; (2) the Orowan strengthening effect; (3) CTE mismatch between reinforcement second phase particles (Cu_6Sn_5 and TiO_2) and the matrix; and (4) the load-bearing effect. However, the total elongation of the composite solders was observed to decrease because of micro-voids both at and along the Cu_6Sn_5 grain boundary regions. The fracture surfaces of all Sn1.5Sb0.7Cu composite solder were confirmed to exhibit the ductile fracture mode.