In Situ Measurement of Wire-Bond Strain in Electrically Active Power Semiconductors

Thermal-mechanical displacement/strain in power semiconductor devices is investigated using electronic speckle pattern interferometry (ESPI). Validated models for thermal-mechanical strain are key to improving the reliability of power electronics modules. ESPI is a noncontact optical technique capable of providing surface displacement measurements with submicrometer resolution. The significant contribution of this paper is an experimental methodology by which wire-bond displacement/strain can be measured in an active device. Simultaneous in-plane and out-of-plane measurements are combined to accurately measure the displacement field across the wire-bond interface, while decoupling thermal-mechanical deformation not related to wire-bond strain (such as base plate thermal expansion). Experimental results verify the electrical-loss-driven thermal-mechanical displacement/strain in an electrically active discrete insulated gate bipolar transistor switching at 5 kHz.