Fabrication and characterization of embedded capacitors in printed circuit boards using B-stage epoxy/BaTiO3 composite embedded capacitor films (ECFs)

Embedded capacitor technology is one of the methods to miniaturize and to obtain higher performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been of great interest as embedded capacitor materials for packaging applications, because they have good processability and compatibility with printed circuit boards (PCB), in addition to high dielectric constant. In this study, we have demonstrated the fabrication of prototype-scale embedded capacitors in manufacturing scale PCBs using multi-layer PCB build-up process. Specially formulated B-stage epoxy/BaTiO₃ embedded capacitor films (ECFs) were used as not only an adhesive between two copper clad laminates (CCLs) but also capacitor dielectrics for embedded capacitors. The total thickness of PCB included embedded capacitor was below 250 mum. Dielectric properties of epoxy/BaTiO₃ ECFs were measured at 100 kHz using a LCR meter, and the dielectric properties at high frequency were measured using devices specially designed for correcting stray effect around capacitors. High temperature storage test at 150degC, high temperature /humidity test with 60degC/60RH% condition, and reflow process at 260degC were performed to evaluate the reliability of prototype-size embedded capacitors. In summary, fabrication of B-stage epoxy/BaTiO₃ composite embedded capacitors in prototype-scale 405 times 508 mm PCBs using CCL was successfully demonstrated using conventional PCB manufacturing processes, and their dielectric properties and reliability were evaluated.