New non‐reinforced substrates for use as embedded capacitors

As CPUs increase in performance, the number of passive components on the surface of circuit boards also increases dramatically. To reduce the number of components, as well as improve the electrical performance (i.e. reduce inductance), designers are increasingly embedding capacitive layers in the PCB. The majority of the products in use utilize reinforced epoxy laminates. These products are relatively easy to handle, but the thickness and Dk limit the effectiveness of the layer to perform as a capacitor. Other materials are being developed that are thinner (and thus increase capacitance), but either have problems with dielectric breakdown strength, handling or offer only a marginal improvement over existing materials. This paper describes new non‐reinforced substrates for use as embedded capacitance layers that address these issues. The material selection process, substrate processing and electrical performance are reviewed.