Patent ID: 8866022

Claim:
A printed wiring board comprising: a first insulating layer; a second insulating layer; wiring patterns made of copper foil, which are alternately laminated on the first and the second insulating layers; and a resin-filled layer provided only at a side of the first insulating layer between the wiring patterns, wherein the first and the second insulating layers include at least resin, glass woven fabric and/or nonwoven fabric, and inorganic filler whose content is 30 vol. % or more and 70 vol. % or less with respect to the insulating layer, the inorganic filler has solubility with respect to an acid solution of more than pH5 or alkaline solution of less than pH10, the inorganic filler includes at least one material selected from aluminum hydroxide, silicon nitride, tin oxide, zirconium silicate, magnesium hydroxide, magnesium carbonate, calcium carbonate, calcium hydroxide, barium carbonate, and barium hydroxide, and the resin-filled layer includes a plurality of pores formed at the side of the first insulating layer and a resin product formed by filling the pores with resin of the second resin layer.