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

• Homogeneous high-melting-point Cu6Sn5 and Cu3Sn intermetallic compound joints were fabricated.
• The ultrasonic joining method was utilized to fabricate intermetallic compound joints at room temperature in air.
• The processing time was dramatically reduced to only several seconds.
• The sonochemical effects of acoustic cavitation were investigated.

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 Cu3Sn 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.