Rapid formation of Cu-Sn intermetallic compounds by strong electric current

A new approach of rapid fabrication of intermetallic compounds (IMCs) solder joints at ambient temperature was investigated in this work. The high share strength Cu/Sn/Cu solder joints were obtained by using different strong electric currents 0.8KA, 0.9KA, 1.0KA, and 1.2KA for only about 0.2s. The Sn foils with the thickness of 10μm were used as solders. The results showed that with the current intensities increasing from 0.8KA to 1.2KA, the thickness of IMCs, Cu₆Sn₅, increased from less than 1μm to 4.2μm for 0.2s, which was induced by thermoelectric coupling interfacial interaction at the liquid solder/solid metallization interface. In addition, amount of dendritic Cu₆Sn₅ distributed in the Sn matrix at the bottom right corner of solder joint under the current intensity of 1.2KA, which was caused by the current crowding effects. Lastly, the share strengths of Cu/Sn/Cu solder joints under the rapid bonding process were improved with the bonding current increasing. The share strength was up to 51.9MPa at 1.2KA.