AbstractTernary solder alloys have come into wide use in chip bonding, printed circuit board connection, and in ceramic package sealing applications. Little is known concerning phase equilibria in many of these systems. Methods for predicting phase equilibria in the ternary (Pb+Sn)+Ag system using CAD (computer aided design) are described, and a predicted value for the ternary eutectic temperature is compared with values obtained by differential scanning calorimetry (DSC) for this system.