DETERMINATION OF COMPONENT ACTIVITIES OF TERNARY Sn-Ag-Au SYSTEM: A POTENTIAL LEAD –FREE SOLDER.

Abstract

Thermodynamic activities of the components binary liquid Ag-Au, Au-Sn, and Ag Sn which are subsystems of ternary lead –free solder Sn-Ag-Au at 800 K, 823 K, and 1250 K were determined using the molecular interaction volume model (MIVM) respectively. Based on the good agreement obtained between the experimental data and the calculated activities of the constituents of the binary alloys, the molecular interactions volume model has been employed to predict the activity of Sn content in the ternary Sn-Ag-Au systems at 973 K along the three cross- sections with constant molar ratio of 2:1, 1:1, and 1:2, respectively. The activity of Sn in ternary liquid Sn-Ag-Au was found to show a negative deviation from ideality across the entire concentration range. Due to the fairly comparable calculated results obtained at 973 K with the experimental data, the activity values for all the three components in ternary Sn-Ag-Au were further predicted at different temperatures of 1073 K, 1173 K, 1273 K, and 1373 K kept at molar ratio of 1:2, 1:1 and 2:1 across the three sections, respectively. This research showed that the model employed is reliable and economical for predicting the thermodynamic activities for ternary alloys.