Study on the soldering in partial melting state (1) - analysis of surface tension and wettability

This paper introduces the partial melting process for solder application and characterization of its feasibility using Pb-Sn, Ag-Sn, Sn-Cu, Sn-In and Sn-Bi alloys. In order to show that the liquid phase in the semi-liquid state maintains the similar wettability as the single-phase liquid, the wetting balance tests are conducted with varying temperatures and compositions. The results are then compared with the surface tension of liquid, both measured and calculated, to examine the correlation. The results from this investigation indicate that the partial melting can yield satisfactory solder joints as long as the liquid phase acquires sufficient chemical activity. At a condition where the partial melting is effective, a direct correlation between the wettability and the surface tension is found to exist. All alloys except two, Sn-Bi and Sn-In, are found to show a reasonable wettability in semi-liquid state.