CIRCUIT SUBSTRATE MANUFACTURING METHOD

A circuit substrate manufacturing method comprises a core substrate preparing step, a first molding step, and a second molding step. The core substrate preparing step includes preparing a core substrate comprising an insulation layer containing a thermoplastic resin, a first circuit formed on one surface of the insulation layer, and a planar metal layer bonded to the other surface of the insulation layer. The first molding step includes arranging and integrally laminating, in this order, a first adhesive layer, including a resin component with a softening point lower than the softening point of the thermoplastic resin, and a first metal foil, on a first surface on which the first circuit of the core substrate has been arranged. The second molding step includes patterning the metal layer onthe laminated body obtained in the first molding step, to form a second circuit on a second surface on which said metal layer was arranged, and then arranging and integrally laminating, in this order, a second adhesive layer