Development of thermodynamic database for micro-soldering alloys

Recent progress on the database of calculated phase diagrams in micro-solde ring alloy systems, which consist of Pb, Bi, Sn, Sb, Cu, Ag, In and Zn, is presented. Experimental determination of phase equilibria was conducted in several binary, ternary and quaternary systems by DSC, EDX and X-ray diffra ction techniques. Based on these experiments as well as on previous data on phase diagrams and thermo-chemical properties such as activity, heat of mi xing and enthalpy of formation, the various thermodynamic parameters For de scribing the Gibbs energies of the different constituent phases were optimi zed and evaluated by the CALPHAD (CALculation of PHAse Diagrams) method. Th e database provides a variety of key information on liquidus and solidus su rfaces, isothermal and vertical section diagrams, and mole fractions of the phase constitutions of multi-component soldering alloys. Thermodynamic pro perties of the surface tension and viscosity of the liquid phase can also b e predicted. Moreover, a non-equilibrium solidification process using the S cheil model was simulated. Several phase diagrams of Pb-bearing and Pb-free solders are presented. The database is expected to be a powerful tool and an indispensable resource for the development of new Pb-free solders.