Embedded capacitors provide the greatest potential benefit for high density, high speed and low voltage IC packaging. Capacitors can be embedded into the interconnect substrate (printed wiring board, flex, MCM-L, interposer) to provide decoupling, bypass, termination, and frequency determining functions. In this work, we report novel thin film technology based on barium titanate (BaTiO3)-epoxy polymer nanocomposites. In particular, we highlight recent developments on high capacitance, large area, thin film passives, their integration in PWB substrates and the reliability of the embedded capacitors. A variety of nanocomposite thin films ranging from 2 microns to 25 microns thick were processed on PWB substrates by liquid coating or printing processes. SEM micrographs showed uniform particle distribution in the coatings. The electrical performance of composites was characterized by dielectric constant (Dk), capacitance and dissipation factor (loss) measurements. Nanocomposites resulted in high capacitance density (10-100 nF/inch2) and low loss (0.02-0.04) at 1 MHz. The manufacturability of these films and their reliability has been tested using large area (13 inch X 18 inch or 19.5 inch X 24 inch) test vehicles. Reliability of the test vehicles was ascertained by IR-reflow, thermal cycling, PCT (Pressure Cooker Test ) and solder shock. Capacitors were stable after PCT and solder shock. Capacitance change was less than 5% after IR reflow (assembly) preconditioning (3X, 245 oC) and 1400 cycles DTC (Deep Thermal Cycle). This effort is an integrated approach centering on three interrelated fronts: (1) materials development and characterization; (2) fabrication and (3) design and electrical characterization at device level.