Space charge behaviour of epoxy composites for printed circuit boards

Space charge profiles of several epoxy composites were observed under DC electric fields. In aramid/epoxy composites, positive internal charges moved to the cathode, and negative internal charges moved to the anode, and then hetero-charge distributions were formed. The electric field near the surface of the specimen, therefore, was increased to more than twice the strength of the average applied field. Since the internal charge behaviour determines the internal electric field distribution, the space charge measurement is useful for the insulation design as well as reliability testing of printed circuit boards, especially for those of multilayer and embedded boards.