Design and Materials of Antiferroelectric Capacitors for High Density Power Electronic Applications

Abstract:
For high-density power electronic systems with miniaturized system size and high efficiency, and for lowest possible cost, a balancing of the semiconductor switching speed, frequency of switching, current density, and ripple and overshoot voltages is necessary. The specifications of supporting passive components, in particular the DC-link capacitors, have to follow the trends, and therefore miniaturized, low ESR, low ESL, high current and high temperature capacitors are required. The technology limits for capacitors with respect to high current, high voltages, high temperatures, high frequencies, and by cost items are discussed, and the tools and technologies are defined that are capable to extend it. New ceramic material combinations are proposed, and their combination with innovative capacitor designs are described. The new ceramics are PLZT based anti-ferroelectrics with high switching field, which are capable for copper inner electrode for the multilayer construction and are fired in reducing atmosphere. For the outer connecting electrode, a sputter method to deposit the conductor on the ceramic surface is used as high reliability design tool. Silver sintering of a flexible termination or of a press-fit connector is already well accepted as material and design in power electronics, and their application to capacitors with the new materials and inner designs is discussed. A cost forecast for high volume production scale is given. The result is a good economic perspective for future use of the new material-design combinations in high-density power electronic systems. Emerging applications in power electronics are described, where the benefits resulting from the new technologies are made evident. The integration of DC-link capacitors with new material and design into modules is discussed. Comparisons of the film capacitor technology, the Barium-Titanate based, and the PLZT based MLCCs (multilayer ceramic capacitors), including the cost estimate show that there is a big future potential of the antiferroelectric material in the new design, and in turn also for innovations in high density electronic power packages.