Phase field simulations of intermetallic compound growth during soldering reactions

Phase field simulations of the microstructural evolution of the intermetallic compound (IMC) layer formed during isothermal soldering reactions between Sn-Cu solder alloys and a Cu substrate are presented. The simulation accounts for the fast grain boundary (GB) diffusion in the IMC layer, the concurrent IMC grain coarsening along with the IMC layer growth, and the dissolution of Cu from the substrate and IMC layer. The simulation results support the previous suggestions that the growth kinetics of the IMC layer during soldering is predominantly governed by the fast GB diffusion and the concurrent coarsening rate of the IMC grains. The IMC grain coarsening is initiated by a competitive growth of the IMC grains at the solder/IMG interface. It is also shown that the dissolution of Cu into an unsaturated solder reduces the coarsening rate of the IMC grains, consequently decreasing the temporal growth exponent of the IMC layer.