Design and performance of Ag nanoparticle-modified graphene/SnAgCu lead-free solders

In this study, various weight percentages of Ag-nanoparticle-modified graphene (Ag-GNSs) were incorporated into Pb-free Sn-Ag-Cu (SAC) solder matrices via ball milling and mechanical mixing methods to form composite solders. Up to 0.2 wt% of the Ag-GNSs particles was successfully incorporated into the composite solders, and the microstructures and mechanical properties of the solders were investigated. The experimental results demonstrated that as the Ag-GNSs content increased, the number of intermetallic particles gradually decreased in size. In addition, the uniformity of the interfacial structure increased compared to that of the pure SAC solder. Furthermore, the melting points of the SAC/Ag-GNSs composite solders were unchanged compared to that of the pure SAC solder. The experimental results also revealed that the wettability of the composite solders on Cu substrates was greatly improved. Thermomechanical measurements showed that the thermal stability of the composite solders was also improved. In addition, tensile tests showed that the ultimate tensile strength of the composite solders was enhanced compared to that of the pure SAC solder, but the ductility of the composite solders was reduced. In particular, the tensile strength of the composite solders with low Ag-GNSs contents was increased, but the tensile strength then decreased once a critical Ag-GNSs content was reached. For the ball-milled solders, the reinforcement provided by the addition of Ag-GNSs particles was much better than that provided by unmodified graphene. By comparing the properties of solders fabricated with different preparation methods, it was determined that the ball-milled solders were superior to the mechanically mixed solders.