Patent ID: 6691409
Filing Date: 2004-02-17
Classification: H05K,Y10T

Abstract:
A circuit board producing method, the circuit board including not less than two wiring layers, an insulator layer for electric insulation between the wiring layers, and an inner-via-hole conductive member provided in the insulator layer in a thickness direction of the insulator layer for electric connection between the wiring layers,the circuit board producing method comprising the steps of: making an insulator layer of a composite material containing an organic resin and a material having a smaller thermal expansion coefficient than that of the organic resin so that the insulator layer includes a surface part, a core part, and a surface part laminated in the stated order, the surface part having a high content of the organic resin, the core part having a low content of the organic resin; opening an inner via hole in the insulator layer in a thickness direction of the insulator layer, and filling the inner via hole with a conductive material; providing metal foils on both sides of the insulator layer, each metal foil having a protruded portion at a predetermined position so that the position coincides with a position of the inner via hole filled with the conductive material; applying heat and pressure to external sides of the metal foils by hot pressing so that the protruded portions of the metal foils come substantially in contact with the core part of the insulator layer, to cause the inner via hole filled with the conductive material to form an inner-via-hole conductive member with a thickness substantially equal to a thickness of the core part; and etching the metal foils so as to leave the protruded portion as the land portion.