Study of mechanical properties of Ag nanoparticle-modified graphene/Sn-Ag-Cu solders by nanoindentation

In this study, mechanical mixing and ball milling were used to mix a variety of different mass fractions of Ag nanoparticle-modified graphene nanosheets (Ag-GNSs) and Sn-Ag-Cu solder alloys to form composite solder alloys. We found that the latter was superior to the former, as the ball-milled samples showed better mechanical properties through nanoindentation tests. The mechanical properties of solder alloys reinforced with Ag-GNSs were compared with those reinforced with unmodified GNSs, and we found that Ag-GNSs were more beneficial for reinforcement. When the amount of Ag-GNSs increased, the composite solders showed improved Young's modulus, hardness, and creep resistance with the exception of 0.2 wt%. The indentation morphologies were observed by scanning electron microscope (SEM), while the microstructure of the composite solder alloys were analyzed by transmission electron microscope (TEM) and electron back scattering diffraction (EBSD). Due to grain boundary and dislocation strengthening, the mechanical properties of the composite solder alloys have been improved. A modified constitutive creep model considering microstructural strengthening showed great agreement with the experiment data.