Influence of BaTiO3 Nanoparticle Addition on Microstructure and Mechanical Properties of Sn-58Bi Solder

The effect of BaTiO3 nanoparticles on the microstructure, wettability, and mechanical properties of Sn-58Bi solder has been investigated. The results show that the microstructure of the Sn-58Bi-x wt.%BaTiO3 (x = 0.5, 1, 2, 3) composite solders is refined and homogeneous due to increasing heterogeneous nucleation sites of BaTiO3 nanoparticles in the solder matrix. The best wettability with spreading coefficient of 0.86 was obtained for Sn-Bi-1 wt.%BaTiO3, increased by 10.24% compared with Sn-58Bi solder. High mechanical properties were achieved for Sn-58Bi solder with small addition (0.5 wt.% to 3 wt.%) of BaTiO3. The ultimate tensile strength (UTS) of Sn-58Bi is 44.7 MPa, and that of Sn-Bi-1%BaTiO3 is 59.1 MPa. Fracture surface analysis indicated that the microscopic fracture of Sn-Bi-1%BaTiO3 solder is composed of tearing marks and ductility is improved. Therefore, Sn-Bi-1%BaTiO3 composite solder is one of the candidates for packaging and interconnection applications.