Modeling the atomic transport kinetics in high-lead solders

The atomic mobilities of Au, In, Pb, and Sn in face-centered cubic Pb-Sn and Pb-In alloys are modeled using the available literature data. A set of parameters describing the composition and temperature dependence of diffusional mobility are provided. The calculated tracer diffusivities of Pb in ternary Pb-Sn-In and Pb-Sn-Au alloys are in very good agreement with the experimental data. Using the model parameters, both tracer and chemical diffusivities can be calculated in the composition and temperature ranges where experimental data is not available. On the assumption of local equilibrium, the simulation of dissolution kinetics of Pd in liquid Pb is demonstrated. The major source of discrepancy between the calculated and experimental diffusion profiles is the uncertainty of the atomic transport kinetics data in the liquid phase. The implications of current kinetic modeling are discussed briefly.