High-temperature lead-free SnSb solders: Wetting reactions on Cu foils and phased-in Cu-Cr thin films

We report the soldering behaviors of high-temperature (300 degrees C) lead-free SnSb alloys on Cu foils and phased-in Cu-Cr thin films. By increasing the Sb content from 5 to 15 wt%, the solder surface became rougher and the wetting angle decreased from 50 degrees to 20 degrees on the Cu foils. Interfacial compounds were found to be Cu6Sn5 and Cu3Sn. The Cu6Sn5 showed a scallop-type morphology, whereas the Cu3Sn had a layer-type morphology, The growth of the latter was found to be diffusion Limited. On phased-in Cu-Cr thin films, the solders showed much lower wetting angles than on the Cu foils, but the dewetting phenomenon was observed after 1 min of reflow time in the 85Sn15Sb alloy. In comparison, we found no dewetting of the high-temperature 95Pb5Sn solder.