Phase equilibria of Sn-In based micro-soldering alloys

The phase equilibria of Sn-In-X (X = Ag, Bi, Sb, Zn), the most basic inform ation necessary for the development of Pb-free micro-soldering alloys, were studied using the CALPHAD method. Thermodynamic analyses for describing th e Gibbs energies of the constituent phases were made by optimizing the obta ined data on the experimental phase diagrams, and such data in the literatu re, including data on thermochemical properties. The present results combin ed with the thermodynamic database which was recently developed by our grou p [I. Ohnuma et al., J. Electron. Mater. 28, 1164 (1999)] provide various i nformation on phase equilibria such as liquidus and solidus surfaces, isoth ermal and vertical section diagrams, mole fractions of the phase constituti ons, etc., and thermodynamic properties such as activity, heat of mixing, s urface energy, viscosity, etc., in multi-component soldering alloy systems including the elements of Pb, Pi, Sn, Sb, Cu, Ag, Zn, and In. Typical examp les for the phase diagrams and thermodynamic properties of Sn-In-X ternary systems are shown. The application of the database to the alloy design for Pb-free solders is also presented.