Improving shear strength of Sn-3.0Ag-0.5Cu/Cu joints and suppressing intermetallic compounds layer growth by adding graphene nanosheets

This study investigated the effects of adding 0.1 wt% of graphene nanosheets (GNSs) into Sn-3.0Ag-0.5Cu solder matrix on the growth of intermetallic compounds (IMC) layer with Cu substrates during isothermal aging at temperatures of 100, 125, 150 and 175 °C for up to 7 days. The results indicated that the GNSs could provide huge diffusion barrier for the diffusion of Sn and Cu atoms in solder matrix, and the activation energy for IMC layer growth was calculated as 46.20 and 59.72 kJ/mol for Sn-3.0Ag-0.5Cu solder and Sn-3.0Ag-0.5Cu-0.1GNSs composite solder, respectively. Compared with Sn-3.0Ag-0.5Cu solder joints, the IMC layer morphology transformation from scallop-type to layer-type and the IMC layer growth for composite solder joints were suppressed. After aging 7 days at 175 °C, the shear strength of composite solder joints, whose IMC layer was comparatively thin, was 30% higher than that of Sn-3.0Ag-0.5Cu solder joints.