RECENT TOPICS IN THE FIELD OF FERROELECTRIC MATERIALS FOR BME-MLCCs

The present paper focuses on the recent direction of materials technology for Base Metal. Electrode (BME)-Multilayer Ceramic Capacitors (MLCCs). Recently, technologies are accelerating in the area of miniaturization, high capacitance, and reduction of production cost of MLCCs, in order to meet the requirements of the electronics market. In order to maintain high capacitance values with smaller case sizes, reduction in thickness and the multiplication of the dielectric layers have been advancing. Thinning dielectric layers, however, has a deleterious effect on the dielectric performance and it is considered getting closer to dimensional limit. So far, temperature stable MLCCs of high capacitance such as X7R, X7S, and X 7T specifications in EIA-S'I'D have been employing BafiO(3) based ferroelectric materials. In the case of BaTiO3 based ferroelectrics, X8R. characteristics may be a limit for temperature stable MLCCs, because Curie temperature of BaTiO3 is around 120-130 degrees C. Under these circumstances, numerous studies have been devoted to ferroelectric materials such as giant dielectric constant (K) materials, high Tf: materials of high K, and high withstanding voltage materials. In this paper, these challenges in the field of dielectric materials for MLCCs are reviewed, and a potential of filled tungsten-bronze type ferroelectrics for high capacitance BME-MLCCs of X9R specification (Delta C/C-25 <=+15%-55 similar to 200 degrees C) arc proposed.