Large Cu wire wedge bonding process for power devices

Abstract

Due to the high cost of gold, Cu-wire bonding is being used more and more on fine-pitch, high-pin-count IC devices. Medium-size Cu wire (>;1mil) has been used for bonding on power devices for years but has not become a popular interconnect option. Recently, however, successful bonding of large (16-mil) Cu wire on specifically metallized IGBTs was reported. Some of these devices showed 10 times the power-cycling life-span of standard Al wire bonded to Al die metallization. In order to develop and make this process production capable, K&S has developed a new Cu bond head that delivers bond forces, wire clamp forces, and ultrasonic power that are significantly higher than those typically achieved with Al wire. This rear-cut head is compatible with most current power-module designs. A modified V-groove bond tool for use with the new head enables bond shear and pull strengths that are 1.0 and 1.5 times the wire's tensile strength respectively.