Thermodynamic modeling of the nickel-lead-tin system

A set of self-consistent thermodynamic model parameters is presented to des cribe the phase equilibria of nickel-lead (Ni-Pb) and nickel-tin (Ni-Sn) sy stems. Sublattice descriptions are used for thermodynamic modeling of the e ta-Ni3Sn, lambda-Ni3Sn, eta-Ni3Sn2, lambda-Ni3Sn2, and Ni3Sn4 phases. A thr ee-sublattice and a four-sublattice model are used to describe the molar Gi bbs energies of eta-Ni3Sn2 and lambda-Ni3Sn2, respectively, and also to des cribe the second-order phase transition from eta-Ni3Sn2 to lambda-Ni3Sn2. I n the majority of the cases, the agreement between the experimental data an d the calculated values is very good. Since the experimental Ni-Pb-Sn terna ry-phase diagrams are not known, several isothermal sections are calculated based on thermodynamic principles. They are of practical importance as rel ated to microelectronics soldering applications.