The Formation of Nano Compounds during Sn/Cu Wetting

When soldering copper-based chips in electronic industry, the growth of tin whisker on Sn/Cu interface under compressive stress was caused by nano-size intermetallic compounds (IMC), Cu₆Sn₅. Reactive wetting process of Cu substrate by pure Sn was observed in an experimental device, and its kinetic mechanism was investigated by performing molecular dynamics calculations. When Sn/Cu wetting was assisted with ultrasonic vibrations, the vertical growth of nano-size Cu₆Sn₅ particles won solid-liquid interface was inhibited, so the occurrence of a new compound Cu₃Sn in ultrasonic wetting which changed the morphology of interface, was beneficial to eliminate tin whisker on Sn/Cu interface. (paper)