Barium titanate epoxy composite dielectric materials for integrated thin film capacitors

Integration of passive components into electronic packaging will lead to further structural miniaturization, performance aid reliability improvements, as well as cost reduction in the microelectronics industry. To replace the discrete capacitors currently employed in packages with the embedded ones, suitable dielectric materials and thin film processes compatible with the PWB technology are desired. Toward this end we have been investigating a thin film technology based on barium titanate (BaTiO3)/epoxy composites, whose advantages in terms of processability, low processing temperature, and versatility make it quite promising. In this process, the homogeneous dispersion of fine-grained barium titanate into the epoxy matrix was achieved through the surface functionalization of the ceramic powders with a silane coupling agent. Particulate coatings were formulated using the functionalized barium titanate powders, bisphenol A epoxy resin, dicyandiamide, and 2-methylimidazole in an organic solvent. The composite dielectric thin layers were processed on Cu substrates by spinor dip-coating followed by curing at 175 degrees C. Electrical measurements on these capacitors demonstrate that, for composite dielectric films containing 60 vol% of barium titanate, a dielectric constant of about 40 at 1 kHz and low loss factors of less than 0.035 over a wide frequency region have been obtained. The crosslinking reaction in this hybrid system was investigated using IR spectroscopy. The curing reaction of the epoxy is not inhibited by the presence of BaTiO3 particles, but instead, it seems to proceed even faster.