Computational investigation of intermetallic compounds (Cu6Sn5 and Cu3Sn) growth during solid-state aging process

Computational investigations of the morphological evolution and growth kinetics for intermetallic compounds (IMCs, Cu6Sn5 and Cu3Sn) formed during reaction and aging between Sn-based solder and a copper substrate are presented. Cu-substrate, Cu3Sn (ɛ phase) and Cu6 Sn5 (η phase) layers (or grains), as well as the Sn-liquid phase (or Sn-solid phase) are considered during the soldering (solid-state aging) process. In the simulation, interface regions are defined by the coexistence of two or more phases (at triple points) at a computational grid point. The simulation is performed through the multiphase-field approach. In the phase-field simulation, the grain boundary (GB) diffusion of the η phase as well as the interfacial energy between this phase and the solder alloy are treated as model parameters. Variation of these parameters allows the investigation of the effects of short-circuit diffusion paths and GB wetting on the morphological evolution of the IMC layers. The simulations addresses the growth kinetics of the two IMC layers (Cu6Sn5 and Cu3Sn) during the two processes up to 14 h, illustrating the variation of η and ɛ IMC thickness and the number of η and ɛ grains as the microstructure coarsens.