High capacitance, large area, thin film, nanocomposite based embedded capacitors

This paper discusses 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 times 18 inch or 19.5 inch times24 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 degC) and 1400 cycles DTC (deep thermal cycle)