Wiring substrate having vias

Claim 1

A wiring substrate comprising: a core substrate; penetrating filled vias formed in the core substrate, the diameters of the penetrating filled vias being the same and not more than 300 μm, the penetrating filled vias being formed into a matrix-shaped at regular intervals of not more than 2 mm; a plane pattern formed on a surface of the core substrate through an insulating layer, the plane pattern having pad portions; and connecting vias penetrating the insulating layer and electrically connecting each pad portion of the plane pattern with certain, but not all, filled vias; wherein, said core substrate is composed of a wiring body used for manufacturing a substrate in which a large number of fine metallic wires, constituting said filled vias, are embedded in parallel with the axis of a columnar body which is made in such a manner that a porous fired inorganic insulating material is impregnated with organic insulating material, and the wiring body used for manufacturing a substrate is sliced in a direction perpendicular to the axis; and said inorganic insulating material being a mixed fired body in which glass having softening point of not higher than 1000 ° C. is mixed with one or more of aluminum oxide, mullite, cordierite, silicon oxide, aluminum nitride, silicon carbide, and silicon nitride.