New Substrates for Use as Embedded Capacitors

As CPUs increase in performance, the number of passive components on the surface of the boards are increasing 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 today 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 only marginal improvement over the existing material. This paper will describe new non-reinforced substrates for use as embedded capacitance layers that address these issues. The material selection process, substrate processing and electrical performance will be reviewed.