Patent attributes
A circuit substrate includes a core substrate having a cavity penetrating through the substrate, a metal block accommodated in the cavity of the substrate, a first build-up layer laminated on first side of the substrate and including insulating resin layers such that the first build-up layer is covering first surface of the block from the first side, and a second build-up layer laminated on second side of the substrate and including insulating resin layers such that the second build-up layer is covering second surface of the block from the second side. The first build-up layer includes an electronic component mounting structure formed on outermost portion of the first build-up layer, and the block is formed such that the first and second surfaces have roughened surfaces, respectively, and that the roughened surface of the first surface has surface roughness different from surface roughness of the roughened surface of the second surface.
