Predicting the Cu₆Sn₅ Growth Kinetics During Thermal Aging of Cu-Sn Solder Joints Using Simplistic Kinetic Modeling

Accumulation of intermetallic compounds (IMC), such as Cu₆Sn₅, adversely impacts the solder joint toughness. Therefore, a basic understanding of the factors that determine the growth kinetics of IMC under distinct operating conditions is warranted to improve the reliability of microelectronic devices. However, predicting the growth of IMC involves tedious experiments or large-scale 3D phase-field simulations, both of which are labor- and resource-intensive techniques. Here, we present simple approaches that couple material thermodynamics with diffusional kinetics for predicting the isothermal growth characteristics of Cu₆Sn₅ in Cu-Sn alloy for temperatures ranging from 145°C to 230°C. While our calculations can reproduce the kinetics of growth obtained from experiments, they also indicate the limited role of IMC/Sn interfacial curvature in determining the rate at which the IMC layer thickens. The reported parametric study, while contrasting the uni- and bidirectional Cu₆Sn₅ growth rates, highlights the utility of combined thermodynamic-kinetic 1D approaches in predicting steady-state growth velocity of IMCs in Cu-Sn alloys.