Effect of Mo Nanoparticles on the Microstructure Evolution and Tensile Strength of Sn58Bi/Cu Solder Joints

A new type of composite lead-free solder was prepared by adding Mo nanoparticles in Sn58Bi solder. The microstructure evolution and tensile strength of the composite solder joints were investigated. The experimental results show that the Mo nanoparticles in the composite solder joints are mainly distributed in the Bi-rich phase. Mo nanoparticles have an inhibiting effect on the growth of the intermetallic compound (IMC) layer during high-temperature aging. The tensile strength of Sn-Bi/Cu lead-free solder joints has been improved. Before aging, the tensile strength of Sn58Bi/Cu, Sn58Bi-0.5%Mo/Cu, and Sn58Bi-1.0%Mo/Cu joints was 124.8 MPa, 129.4Mpa, and 131.4 MPa, respectively. After aging for 360 h at 120°C, the tensile strength of the Sn58Bi/Cu joint decreased by 49.0%, while the tensile strength of the Sn58Bi-1.0%Mo/Cu joint decreased by only 29.4%.