Patent ID: 7417195

Claim:
A circuit board having a flat plate shaped first board part and a flat plate shaped second board part disposed stacked on a partial region of this first board part, said circuit board characterized in that said first board part and said second board part each comprise a substrate formed in a flat plate shape, a plurality of interconnection patterns arranged inside said substrate so as to form a plurality of layers in its thickness direction, and a plurality of interlayer connection parts disposed inside said substrate for connecting interconnection patterns belonging to different layers, at least one of the substrate of said first board part and the substrate of said second board part comprises a thermoplastic resin substrate made only of a thermoplastic resin, said first board part and said second board part are joined at their respective stacked regions by the thermoplastic resin, a plurality of first interconnection patterns are disposed on said stacked region of said first board part, a plurality of second interconnection patterns are disposed on said stacked region of said second board part so as to form pairs with said plurality of first interconnection patterns, and between the pairs of said first interconnection patterns and said second interconnection patterns, interboard connection parts are formed from a connection material which at a temperature applied to melt the thermoplastic resin melts at least partially and electrically connects the first and second interconnection patterns together.