Influence of graphene nanosheets addition on the microstructure, wettability, and mechanical properties of Sn-0.7Cu solder alloy

In this study, Sn-0.7Cu composite solders with different weight of graphene nanosheets (GNSs) were successfully prepared by mechanical milling and hot-pressing sintering. The effects of GNSs on the microstructure, wettability, and mechanical properties of Sn-0.7Cu solder alloys were investigated. The experimental results indicate that the distribution density of GNSs in the solder matrix became larger as the content of the GNSs increased, and the GNSs basically distributed at the grain boundary. In addition, the grain size of the solder deceased firstly and then increased with increasing GNSs. Furthermore, the melting temperature of Sn-0.7Cu-xGNSs composite solders barely change compared with original Sn-0.7Cu solder. After Sn-0.7Cu-xGNSs, composite solders reflowed on Cu substrate at 250 °C for 20 min, and the experimental results reveal that the spread area and spread rate of composite solders on Cu substrate decreased with increasing content of GNSs. In addition, the mechanical properties of Sn-0.7Cu-xGNSs composite solders were obtained by tensile test. The tensile test results show that the yield strength and the ductility of composite solders both increased firstly and then decreased with addition of GNSs. In summary, the composite solders have best ductility and best yield strength when the content of GNSs is 0.05 wt% and 0.075 wt%, respectively.