Abstract: A mechanically sound electrically stable substrate for use in an electrical laminate wherein the substrate supports at least one electrically conductive metallic layer. The substrate portion comprises a woven glass cloth base pad which is interposed between a pair of outer substrate layers of a polyester mat. The polyester mat comprises a mat of spunbonded continuous filament polyester fibers, preferably polyethylene terephthalate fibers, calendered, with the fibers including a mixture of bulk fibers of relatively high melting point retained in place or bonded by a binder fiber of essentially the same polyester material but with a relatively lower melting point. In fabrication, the mat, along with the glass cloth, is saturated with a curable resin, for example a heat curable resin, preferably polybutadiene, which is cured in-situ.