Microstructure and reliability of Mo nanoparticle reinforced Sn–58Bi-based lead-free solder joints

Abstract

The effect of Mo nanoparticles on the microstructure, wettability and mechanical properties of Sn–58Bi–xMo (x = 0–2.00) solder joints was investigated. The results showed that the optimal wettability of Sn–58Bi–0.25Mo solder was obtained and the microstructure was refined by adding small amounts of Mo. The intermetallic compounds (IMCs) thickness was increased from Sn–58Bi 2.17 µm to Sn–58Bi–2Mo 2.73 µm. The tensile strength of Sn–58Bi solder joint was improved by adding 0.25 wt-% Mo. The fracture mode of Sn–58Bi solder joint and Sn–58Bi–0.25Mo solder joint was brittle fracture and the mixed mode was ductile failure and brittle fracture, respectively. The microstructure of Sn–58Bi and Sn–58Bi–0.25Mo solder joints was coarsened, IMCs thickness was increased and the mechanical properties were deteriorated with increasing aging time.