The Development and Validation of a New CALPHAD Thermodynamic Database for Lead Free Solders

This presentation describes the development of a new thermodynamic database for Pb free solders using the CALPHAD methodology based on various types of available experimental data and theoretical information. This new database contains all the important Au-/Ag-/Cu-/Sn-based solder alloy phases within a 16-element framework [Ag-Al-Au-Bi-Co-Cu-Ge-In-Ni-Pb-Pd-Pt-Sb-Si-Sn-Zn] and in total 150 phases (most of them as multicomponent alloy solutions and/or intermediate compound solutions, and the rest as intermediate stoichiometric compounds) are included. The database can be used with Thermo-Calc for predicting various thermodynamic properties, stable/metastable phase equilibria and phase transformations of Au-/Ag-/Cu-/Sn-based solder systems (Pb-containing/Pb-free), and for simulating the effects of non-equilibrium solidification and micro-segregation of various soldering/brazing processes. Such predictions can be used to screen candidate solder alloys and identify unsuitable freezing temperature ranges or the presence of undesirable precipitate phases and are a useful compliment to experimental studies.