Early stages of intermetallic compound formation and growth during lead-free soldering

We investigate the early stages of the morphological evolution of intermetallic compounds (IMCs) during lead-free soldering involving liquid Sn-based solder and Cu substrate considering the heterogeneous nucleation of the IMCs. The simulation is performed through the multi-phase-field approach [20,25]. Initially, the liquid Sn-based solder and the Cu substrate are considered to be at metastable local equilibrium. Nucleation at the solder/substrate interface is modeled by considering it to be a Poisson process. The phase-field simulation accounts for variations in grain boundary diffusion in the g phase and interface energies between the g phase and liquid solder, and uses these variations to investigate the multiplicity of soldering reactions, and make comparisons with previous work [23]. The simulations address the kinetics of the IMC growth during lead-free soldering under the effect of nucleation at an early stage, illustrating the variation in Cu substrate thickness, IMC thickness and number of grains that nucleate or disappear due to grain growth-induced coalescence.