Patent ID: 7438969

Claim:
A multilayer printed wiring board comprising: a substrate; a plated through-hole formed in the substrate; a solvent-free insulative filling material filled in the plated through-hole; a conductor layer plated on an exposed surface of the solvent-free insulative filling material; an insulating layer formed on a surface of the conductor layer; a conductive pattern layer formed on a surface of the insulating layer; and a via conductor connecting the conductor layer and the conducting pattern layer; wherein the solvent-free insulative filling material includes a filler, a thermosetting epoxy resin, a curing catalyst and a dicyandiamide curing agent, wherein the filling material has cured with a uniform composition without localizing at least the filler, the thermosetting epoxy resin and the dicyandiamide curing agent, wherein the plated through-hole has a diameter between 50 μm and 200 μm, wherein the dicyandiamide curing agent is used to reduce deterioration in adhesive strength between the solvent-free insulative filling material and the conductor layer, wherein the curing catalyst comprises a urea compound; and wherein the filler is substantially spherical particles having an average particle size of 0.1 to 12 μm and a maximum particle size of 75 μm or smaller.