Rapid Cu6Sn5 growth at liquid Sn/solid Cu interfaces

In situ observations of the reaction between solid Cu in contact with molten Sn-0.7 wt.% Cu were achieved using a synchrotron X-ray imaging technique. It was found that, upon wetting, the rapid dissolution of Cu adjacent to the solid-liquid interface was followed by near-instantaneous interfacial intermetallic compound (IMC) formation. The kinetics of IMC formation were also elucidated. The results provide direct experimental evidence of the sequence of events in the dissolution reaction and subsequent diffusion, and in particular of the growth mechanisms of the IMC layer.