Frequency behavior of embedded epoxy/SrTiO3 composite capacitor materials

Epoxy/BaTiO₃ composites have been of great interest as embedded capacitor materials, mainly due to high dielectric constant of ceramic powders, and good process compatibility of epoxy with printed circuit boards (PCBs). However, one of the potential problems of epoxy/BaTiO₃ composite is the dielectric relaxation at GHz range. In this paper, epoxy/SrTiO₃ composite ECFs were fabricated for high frequency applications. Dielectric constants of epoxy/SrTiO₃ composite embedded capacitor films with various SrTiO₃ particles loading for three different commercial SrTiO ₃ powders were measured from 100 Hz to 1 MHz, and experimental data at 100 kHz were fitted to the Lichtenecker equation for the prediction of the effective dielectric constant of SrTiO₃ powders in epoxy/SrTiO₃ composite ECFs. Using a rectangular cavity resonator method, dielectric constants of epoxy/SrTiO ₃ composite ECFs were measured at GHz range (1-10 GHz). At GHz frequencies, dielectric constants of epoxy/SrTiO₃ composite ECFs were nearly constant. In contrast, epoxy/BaTiO₃ composite ECFs showed significant decrease of dielectric constants above 5GHz. Therefore, it is concluded that epoxy/SrTiO₃ composite ECFs cab be more effectively to be applied for high frequency applications.