Ultrarapid formation of homogeneous Cu₆Sn₅ and Cu₃Sn intermetallic compound joints at room temperature using ultrasonic waves

Homogeneous intermetallic compound joints are demanded by the semiconductor industry because of their high melting point. In the present work, ultrasonic vibration was applied to Cu/Sn foil/Cu interconnection system at room temperature to form homogeneous Cu₆Sn₅ and Cu ₃Sn joints. Compared with other studies based on transient-liquid- phase soldering, the processing time of our method was dramatically reduced from several hours to several seconds. This ultrarapid intermetallic phase formation process resulted from accelerated interdiffusion kinetics, which can be attributed to the sonochemical effects of acoustic cavitation at the interface between the liquid Sn and the solid Cu during the ultrasonic bonding process.