Development of Film-on-Foil Ceramic Dielectrics for Embedded Capacitors for Power Inverters in Electric Drive Vehicles

Advanced power inverters for electric drive vehicles require capacitors that operate under high voltage at under-hood temperatures and have minimal footprint. This need can be realized by embedding ceramics with high dielectric constant within a printed wire board (PWB). The “film-on-foil” approach, where the high-dielectric-constant ceramic is first deposited on base-metal foil, is a promising method for embedding the capacitors within a PWB. We have deposited lead lanthanum zirconium titanate (PLZT) on nickel foils and characterized the samples in the temperature range between -50 and 250 °C. The measured dielectric constants varied with temperature: from ≈700 at -50 °C to ≈2200 at 250 °C. The dielectric loss remained fairly constant at ≈0.05–0.08. At 300 V bias, a dielectric constant of ≈110 and dielectric loss of ≈0.004 were measured. Hysteresis loop analysis showed an energy density of ≈85 J/cm3. The fabrication procedures and dielectric properties of the PLZT film-on-foils will be described in this paper.