Packaging of 15-kV Silicon Carbide Half-Bridge Module Enabled by a Nonlinear Resistive Polymer Nanocomposite Field-Grading Coating

Emerging medium-voltage silicon carbide devices offer the potential to achieve more efficient and compact power electronics for grid-Tied applications. However, the lack of an effective insulation solution for packaging the devices has slowed their widespread adoption. In this work, a 15-kV silicon carbide MOSFET half-bridge module was designed and fabricated. The module was built by silver-sintering the device chips on an aluminum nitride direct-bond-copper substrate with 1.0-mm thick ceramic. The insulation of the module was enhanced by coating a nonlinear resistive polymer nanocomposite along the electrode edges on the substrate prior to silicone-gel encapsulation. The field-grading effect of the coating was tested on aluminum nitride direct-bond-copper substrates. The coated substrates showed an average partial discharge inception voltage of 20.2 kVpeak, which is 85% higher than the uncoated ones and 33% higher than the devices' rated voltage. Finally, prototypes of the modules with functional 15-kV dice were fabricated and tested. The blocking capability of the devices were unchanged after packaging. The fabricated modules in this work will serve as testbed for evaluating the coating's effectiveness under fast pulse-width modulation excitations during switching tests.