High Voltage Package Encapsulants

With significant strides being made on wide bandgap (WBG) semiconductor devices for high-power electronics, there is a concurrent need for packaging encapsulants with reliable performance in a rigorous operational environment. The WBG power devices are set to be fielded in electric vehicles, aircrafts, spacecrafts, and energy producing systems where working conditions can see temperatures in the range of 200–400 °C. Based on silicon carbide or gallium nitride, these newer semiconductors with higher power densities can be produced in smaller sizes, operate at higher voltages, and provide greater efficiency in switching frequencies than conventional silicon. Commercial encapsulants, which are based on either epoxy or silicone material, fall short in their thermal properties for use in WBG power electronics. The role of an encapsulant is to electrically insulate and protect the electronic assembly from moisture, corrosion, dirt, and mechanical disturbances. Additionally, operating under higher voltages (>1kV) will enhance localized electric fields and increase the activity of partial discharges, or the localized breakdown of the insulation system by small sparks of current. It is thus essential that the encapsulating material exhibits high thermal stability, and towards this end, TRI Austin will continue the development and characterization of cyanate ester resin formulations for next-generation power devices. Materials developed in Phase I will be optimized for processing and targeted properties and the down-selected candidates will undergo extensive testing to establish long-term performance for a successful prototype.