Hybrid Solder Joints: Morphology and Mechanical Properties of lead-free Sn-based Solders with nano-sized Fe doped Flux

In this research, the impact of Fe nanoparticles (NPs) addition on the microstructure and mechanical properties of Sn-3.5Ag solder joints was investigated. As opposed to the more pronounced approach of adding NPs directly to the solder paste, varying concentrations of nanoparticles (0.0 – 2.0 wt.%) were mixed with the flux to increase their concentration at the interface and to control the formation and growth of intermetallic compound layers (IMCs) in more effective way. The solder joints were subjected to thermal treatment at different temperatures and durations, and the growth rate of the IMCs in the as-reflowed and aged samples was examined. It was found that the application of Fe-NPs doped flux led to an increase in the shear strength of the solder joints. This improvement could be attributed to the reduction in the growth rate of brittle intermetallic phases as well as refinement of the microstructure.