Wetting of Sn-0.7Cu solder alloy on different substrates at different temperatures

In this paper, the wettability of Sn-0.7Cu solder alloy on different substrates (Cu, Cu/Ni, Cu/Ni/Au and Cu/Ni/Ag) at different temperatures (530 K, 560 K and 590 K respectively) were investigated by microstructural observations, phase analysis and wetting tests. The results showed that the wettability of Sn-0.7Cu solder alloy improved with the increase of reflowing temperature due to the decrease of viscosity of molten Sn-0.7Cu alloy. The wettability of Sn-0.7Cu solder alloy on Cu/Ni/Au and Cu/Ni/Ag substrates is better than that of Cu substrate due to the rapid dissolution rates of Au/Ag in molten Sn-0.7Cu alloy. While, because the growth rate of intermetallic compound on Ni substrate is lower than that of Cu substrate, the wettability of Sn-0.7Cu solder alloy on Cu substrate is better than that of Cu/Ni substrate.