Characterization of a Low-Cost Insulator Substrate for Traction Power Modules

Demand for cost-effective automotive traction inverters requires improved power module packaging. This paper presents a packaging method using an epoxy composite insulator applied directly to the cold plate surface, replacing Direct Bonded Copper (DBC) and Active Metal Brazed (AMB) substrates. This integration removes the substrate-to-cold plate solder interface and eliminates two material layers from the thermal path. The epoxy composite demonstrates a dielectric strength greater than 60 kV/mm. Thermal resistance (junction-to-coolant) measured approximately 0.17 K∙cm²/W. Electrical characterization showed a relative permittivity of 3.9, which is lower than standard ceramics and results in reduced parasitic capacitance. Initial thermal cycling tests indicated no significant degradation in thermal or electrical performance. These results suggest the epoxy composite insulator could be a promising alternative for traction power modules.