Effect of transient current bonding on interfacial reaction in Ag-coated graphene Sn–Ag–Cu composite solder joints

Abstract To address the problem of floating and aggregation of Ag–GNSs in the molten pool during the traditional reflow soldering process, Cu/SAC/Ag–GNSs/Cu sandwich joints were prepared under an applied current density (1.0×104 A/cm2) for a few hundred milliseconds to produce Ag-coated graphene-reinforced Sn–Ag–Cu (SAC/Ag– GNSs) solder joints. The experimental results showed that Ag–GNSs were homogenously dispersed in the solder joints, providing more Cu6Sn5 grain nucleation sites, which refined these grains and reduced the thickness difference at the anode and cathode. In addition, the Cu6Sn5 morphology changed from rod-like to plate-shaped because of the uniform distribution of Ag–GNSs and constitutional supercooling. The significantly increased shear strength of the transient current bonding and the change in the fracture mechanism were due to the uniformly distributed Ag–GNSs and the microstructural changes.