Class I Multi-Layer Ceramic Capacitors (MLCCs) Performance as Wide Band Gap (WBG) Snubbers in Hard Switching Applications

Abstract

There is increased interest in packaging snubber capacitors close to Wide Band Gap (WBG) device switches to improve performance, ultimately being most effective packaged inside power modules. The performance of Multi-Layer Ceramics Capacitors (MLCCs) at the higher switching frequencies used by Wide Band Gap (WBG) devices are not well documented in the literature with respect to dV/dt capability. In this work the internal current stresses induced by high dV/dt pulses in low capacitance, high voltage rated MLCCs (> 500 VDC) used as snubbers in WBG device switching cells was studied. Electrode current densities > 2 ×109 A/m2 were calculated for dV/dt transients > 50 V/nS observed during fast switching with a double pulse test setup. ANSYS® Maxwell® EM Models provide insight into internal MLCC electric fields and current density for these excitations. Post stress measurements show these MLCCs are not degraded. This study will help provide guidance on capacitor selection for different customer snubber applications.