Lifting-Off of Al Bonding Wires in IGBT Modules Under Power Cycling: Failure Mechanism and Lifetime Model

Lifting-off of Al bonding wires is one common failure mode of insulated-gate bipolar transistor (IGBT) modules during long-time operation. In the present work, the failure mechanism of Al wires lifting-off was investigated and the major factors were discussed based on both experiments and finite element (FE) simulations. It indicates that lifting-off of Al-wires is mainly determined by the interfacial thermal stress at the bonding interface. Thermal expansion of Al-wires and thermal mismatch of Al-Si interfaces contribute to the interfacial thermal stress which is affected by the resistance heat of Al-wires and power loss of Si-chips. Accordingly, a new lifetime model for the Al wires lifting-off failure mode of IGBT modules is proposed and verified through power cycling tests. The conduction current I-c, the heating time t(ON), and the junction temperature swing Delta T-j are three major factors for the fatigue life model of IGBTs under Al wires lifting-off failure mode.