Analysis of the aging mechanism occurring at the bond-wire contact of IGBT power devices during power cycling

This paper focuses on the degradation at the wire bond contact with the metalized pad, and precisely its evolution with the power module aging. In order to induce damage in this particular zone, an accelerated power cycling test is carried out on well-suited devices. The on-state voltage (VCE) is measured during the test as an indicator of the degradation in the wire and metallization. Then, analyses of the interface wire-metallization are done with a numerical microscope and the EBSD (Electron Back-Scattered Diffraction) technique. As a result, an attempt to correlate the evolution of the degradation with the changes in the granular microstructure of the aluminium constituting the wire and metallization is proposed.