Effect of liquid-liquid structure transition on solidification and wettability of Sn-0.7Cu solder

The temperature dependence of electrical resistivity (ρ-T) of a Sn-0.7Cu (wt.%) melt was measured and an abnormal change was found on the ρ-T curve within the range of 825-1066 °C. The result suggests that the melt has experienced a temperature-induced liquid-liquid structural transition (TI-LLST), and the transition is reversible after the first cycle heating. Based on the result of TI-LLST, solidification experiments and spreadability tests were carried out on the Sn-0.7Cu alloy to investigate the effect of liquid structure transition on solidification microstructure and wettability. The results show that the microstructure was refined and the wettability was improved when the samples solidified from the melt experienced TI-LLST.