Materials, process, and electrode design optimization of B-stage $Epoxy/BaTiO_3$ Embedded Capacitors

Abstract

B-stage epoxy/$BaTiO_3$ embedded capacitor films(ECFs) have been investigated in terms of high dielectric constant, low viscosity, and high curing on-set temperature. Using selected ECFs, embedded capacitors were fabricated and ECFs thickness, capacitance density, and thickness uniformity were investigated depending on process parameters and electrode design, respectively. In terms of material properties, basically ECFs must have high dielectric constant to get high capacitance density and ECFs must have low viscosity and high curing on-set temperature during the lamination process to have enough flow behaviors. As process parameters, suitable temperature and pressure are applied and electrode spacing and size need to be considered in terms of electrode design to get uniform ECFs thickness. In this study, effects of $BaTiO_3$ sizes and contents on the dielectric constant, viscosity, and curing behaviors of ECFs were investigated. ECFs filled with four different $BaTiO_3$ sizes and contents were fabricated, and the viscosities of those were measured with a rheometer at various temperature and time conditions. In addition, their curing behaviors were also analyzed with a differential scanning calorimeter (DSC) at same temperature and time conditions. According to the results, the viscosities of ECFs decreased as temperature increased before curing on-set temperature, and they abruptly increased with epoxy curing reaction. Besides, decreases of $BaTiO_3$ sizes resulted in increases of the viscosities of ECFs and decreases of curing on-set temperature, and the viscosities of ECFs increased and curing on-set temperature decreased as $BaTiO_3$ contents increased. Also, capacitance and thickness of ECFs were measured with as LCR meter and alpha-step, respectively in order to calculate dielectric constant. Dielectric constant of ECFs increased with increasing $BaTiO_3$ sizes and contents. Effects of process parameters and electrode design on the fabrication of embe...