A Thermal–Electrical Co-Modeling Method for Bond Wire Degradation Assessment of Power Modules Independent of Junction Temperature

Effective online bond wire degradation assessment of power modules is crucial for ensuring long-term stability. However, its electrical aging indicators are often influenced by junction temperature (Tj), and conventional Tj monitoring methods are also affected by the aging process itself, creating a contradiction. This paper proposes a thermal–electrical co-modeling method designed to reduce reliance on accurate Tj. A major challenge of the method is the traditional thermal network models, which rely on case temperature (Tc). These models are affected by thermal coupling and have a slow dynamic response, making them difficult to integrate with electrical models. To overcome this, a Tj monitoring method based on in situ sensor fabrication is employed to shorten thermal conduction path and simplify thermal network. This method results in a much faster dynamic process and is unaffected by thermal coupling, as confirmed through both theoretical analysis and finite element simulation. To validate the proposed method, bond wire degradation assessment is conducted using the on-state voltage drop (Vce). Tested in practical circuits, this design successfully enables online evaluation of bond wire degradation, which is unaffected by Tj.