ON THE SN-BI-AG TERNARY PHASE-DIAGRAM

The selection and evaluation of Pb-free solders requires information t hat is best determined through a knowledge of ternary and higher order phase diagrams. As part of an ongoing program on Pb-free solder phase diagrams at the National Institute of Standards and Technology, a the rmodynamic model is formulated for the Sn-Bi-Ag phase diagram. Thermod ynamic functions for the various phases obtained by fitting measured d ata for the three constituent binary systems are extrapolated to the t ernary system using the method of Muggianu. Modeling results are compa red to preliminary experimental data for the ternary system and are ap plied in the calculation of the solidification path.