A thermodynamic study of phase equilibria in the Sn-Bi-Pb solder system

As a basis for the design and development of low-temperature solder alloys, the thermodynamic calculation of phase equilibria has been carried out on the binary Bi-Pb and ternary Sn-Bi-Pb systems over the entire composition range. The Gibbs free energy of individual phases has been approximated using the sub-regular solution model and thermodynamic parameters for each phase have been evaluated using available experimental information on phase boundaries and other related thermodynamic properties. The calculated phase diagrams and thermodynamic quantities of the Bi-Pb binary system show good agreement with the experimental data, and the liquidus projection and vertical sections in the Sn-Bi-Pb ternary system are well reproduced using assessed thermodynamic parameters derived in this work.