High-temperature thick Al wire bonding technology for high-power modules

In order to enhance the strength of thick Al wire bonds while eliminating damage, we have developed a new high-temperature thick Al wire bonding technology. The 300-μm-diameter Al wires were bonded to Al pads on an insulated gate bipolar transistor (IGBT) chip at varying substrate temperatures and ultrasonic powers. Al wire bonds joined at 423 K with 2.0 W ultrasonic power exhibited high bonding strength compared to those joined at room temperature with 5.0 W power. The main reason for the high bonding strength exhibited by the high-temperature bonding process with low ultrasonic power may be the ease of deformation of Al wires and Al electrode films which results in the enhancement of the true bonded area between Al wires and Al electrode films. We also confirmed that Si damage did not occur during this high temperature bonding process using low ultrasonic power. High-temperature thick Al wire bonding technology is considered to be a promising candidate for the production of reliable IGBT modules.