Improved microstructure and mechanical properties for Sn58Bi0.7Zn solder joint by addition of graphene nanosheets

The effects of graphene nanosheets (GNSs) on the microstructure and mechanical properties of Sn58Bi0.7Zn solder joint were investigated. Experimental results and finite element (FE) simulations showed that the best mechanical properties improvement came from the 0.076 wt.% GNS-doped Sn58Bi0.7Zn sample. It exhibited the highest creep resistant in all the as-prepared solder joints, and the average interphase spacing in solders was reduced by 32.52%, the stress exponent was increased by 13.70%. For the thermal aging samples, the ultimate tensile strength (UTS) of the solder joint was also increased by 2.04%. Moreover, the 0.114 wt.% GNS-doping significantly reduced the time exponent from 0.403 to 0.362 and decreased the thickness of total IMC layers by 56.31%. Based on the theories related to material performance and the restacking behavior of GNSs, the strengthening mechanism of GNSs in composite solder joint was analyzed and an optimum concentration of GNSs in Sn58Bi0.7Zn solder alloy was proposed.