Electrically insulating substrate

A precursor for an electrically insulating substrate having a glazed porcelain surface for receiving electrical circuitry thereon;

• comparatively low thermal coefficient of expansion;
• comparatively high thermal conductivity for heat dissipation;
• good electrical insulation properties;
• and sufficient mechanical strength for subsequent use in a microelectronic circuit having surface mounted devices disposed thereon;
• which comprises:
• a first plurality of porcelain green sheets having a relatively low linear thermal coefficient of expansion matched to the linear thermal coefficient of expansion of the surface mounted devices to be subsequently mounted upon the substrate;
• and a second plurality of fine mesh wire cloth sheets for mechanical strength and high thermal conductivity;
• said second plurality of fine mesh wire cloth sheets interleaved between the first plurality of porcelain green sheets to separate the fine mesh wire sheets by at least one porcelain green sheet to provide electrical insulation between the wire cloth sheets, wherein the interleaved porcelain green sheets and the fine mesh wire cloth sheets have been compressed against one another at a somewhat elevated temperature with sufficient pressure to form a laminated substrate, for subsequent firing at a further elevated temperature sufficient to form at least one outermost glazed porcelain surface.