Effects of graphene nanosheets on interfacial reaction of Sn–Ag–Cu solder joints

Abstract

In this work, varying amount of graphene nanosheets (GNSs) were introduced as reinforcements into Sn–Ag–Cu (SAC) solder to get composite solders. Then, the formation and growth kinetics of the intermetallic compounds (IMC) were investigated during the liquid–solid reactions and solid-state aging. Experimental results demonstrated that the morphologies of the interfacial IMC were transformed from scalloped to platelike after liquid–solid reactions and solid-state aging. The IMC thickness of composite solder joints was thinner than that of the unreinforced solder joints. The calculations revealed that the growth rate constant of composite solder was lower than that of bulk SAC solder. It's worth to mention that the composite solder joints exhibited lower diffusion coefficients (ranging from 0.6 × 10−12 m2/s to 1.07 × 10−12 m2/s) than that of the SAC solder joints (1.81 × 10−12 m2/s) after liquid–solid reactions and the composite solder joints also exhibited lower diffusion coefficients (ranging from 1.42 × 10−12 m2/s to 1.78 × 10−12 m2/s), as compared to that of the monolithic SAC solder joint (2.46 × 10−12 m2/s) after aging studies. It indicates that the addition of GNSs can effectively suppress the growth of the overall IMC layers, which can also hinder the IMC's growth and enhance solder joints' reliability.