Multiphase Field Simulations of Intermetallic Compound Growth During Lead-Free Soldering

Abstract

A multiphase field simulation of the morphological evolution of the intermetallic compounds (IMCs) formed during the reaction between liquid Sn-based solder and a copper substrate is presented. The Cu-substrate, Cu 3 Sn (∈ phase), and Cu 6 Sn 5 (η phase) layers (or grains), as well as the Sn-liquid phase are considered. Interfaces are defined by the presence of more than one phase at a given point of the computational domain. The interface structure is determined by assuming that all components of coexisting phases within the interfacial region have equal chemical potentials, which are in turn calculated from CALPHAD thermodynamic databases. Fast grain boundary (GB) diffusion in the η IMC layer, η grain coarsening and growth with growth/shrinkage of ∈ grains, and dissolution of Cu from the substrate will be discussed and compared with previous works. The simulation will address the kinetics of the IMC growth during soldering and the influence of fast GB diffusion on the concurrent coarsening of Cu 3 Sn and Cu 6 Sn 5 grains. The kinetic behavior of the substrate/ IMC/solder system as a function of model parameters will also be presented.