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AssigneeIbiden Co., Ltd.
InventorsMasaru Takada, Hiroyuki Kobayashi, Kenji Chihara, Hisashi Minoura, Kiyotaka Tsukada, Mitsuhiro Kondo
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A solder resist comprising a thermosetting resin is printed on a surface of an insulating board (7) having a conductor circuit (6). The solder resist is then heat-cured to form an insulating film (1) having a low thermal expansion coefficient. A laser beam (2) is then applied to the portion of the insulating film in which an opening is to be formed, to burn off the same portion for forming an opening (10), whereby the conductor circuit (6) is exposed. This opening may be formed as a hole for conduction by forming a metal plating film on an inner surface thereof. It is preferable that an external connecting pad be formed so as to cover the opening. The film of coating of a metal is formed by using an electric plating lead, which is preferably cut off by a laser beam after the electric plating has finished.
A printed wiring board characterized in that an upper face pattern is formed on an upper face of an insulating substrate and a lower face pattern is formed on a lower face of said insulating substrate and a hole for conductivity extends through said insulating substrate and a lower end portion of the hole is completely covered with the lower face pattern and a metallic filling material for electrically conducting said upper face pattern and said lower face pattern is arranged within the hole for conductivity;
Dependencies are inferred from the claim text.