Patent ID: 8518203

Claim:
A method of manufacturing a wiring substrate, comprising: preparing two stacked bodies, each of the two stacked bodies comprising two first carriers and a first insulating layer, each of the first carriers comprising a first carrier plate, a first peeling layer and a first metallic foil provided on one surface side of the first carrier plate via the first peeling layer, the two first carriers being stacked with each other such that the respective first metallic foils of the two first carriers are opposed to each other via the first insulating layer; forming a joined body by joining the first carrier plates on one surface side of the stacked bodies to a joining layer such that the two stacked bodies are joined via a joining layer; peeling the first carrier plates provided on both sides of the joined body to expose respective first metallic foils of the two first carriers on both sides of the joined body, and forming first conductor patterns from the respective first metallic foils that are exposed by the peeling the first carrier plates, the first conductor patterns are formed to be electrically connected to the first metallic foils of the first carriers via vias that pass through the first insulating layers in the joined body, the first conductor patterns being thicker than the first metallic foils; providing second carriers, each of which comprises a second carrier plate, a second peeling layer and a second metallic foil provided on one surface side of the second carrier plate via the second peeling layer, to the first conductor patterns via second insulating layers such that the first conductor patterns are opposed to the second metallic foils of the second carriers respectively, the first conductor patterns being thicker than the second metallic foils; forming two substrates, each of which has a first surface side defined by one first metallic foil of the first carrier and a second surface side defined by one second metallic foil of the second carrier, the first surface side being opposite to the second surface side, by peeling the first and second carrier plates of the first and second carriers from the peeling layers of the first and second carriers; and forming second conductor patterns, which are connected electrically to the first conductor patterns via vias that pass through the first and second insulating layers respectively, from the first and second metallic foils defining the first and second surface sides, respectively, of the substrate.