Interfacial Characterization and Bonding Mechanism of Ultrasonic Wedge Bonding

The joining mechanism of ultrasonic wedge bonding was investigated by chemical etching method. Compared to peeling-off method, the advantage of chemical etching method not only reflected the characters of the bond interface, but also indicated the physical process and bonding mechanism of the interconnection between the metal wire and metallization. It was found that the evolution and characters of the bond interface were affected heavily by the bonding parameters. The lateral and longitudinal joint marks were observed. The former were perpendicular to the direction of the ultrasonic vibration, and distributed at the periphery of the bond interface with some periodicity, which were the metallurgical joining parts. However, the later were parallel to the vibration directions locating at the bond center. The features above had important influence on the bond resistance. The mechanism was ascribed to the stress evolution and distribution during bonding process