Wire Bond Failures in Power Modules Available to Purchase

Power modules are key components for traction applications, railway locomotives, streetcars and elevators, all of which are equipped with Insulated Gate Bipolar Transistor (IGBT) modules. In this application field, a highly reliable system is of uppermost interest. Reliability tests show that wire bonding and soldering may cause the modules to fail. The packaging setup is a multilayer system in which different materials are soldered together. During a temperature swing caused by self-heating and/or by changes in the ambient temperature, the layers expand differently. This generally causes shear forces at the terminations of joint interfaces finally leading to material fatigue and shorter life. In this paper, we give an overview of the wire bonding technique used in power modules and discuss the mechanisms and failure modes associated with it.