Multilayer circuit board and manufacturing method thereof
Holes having the same diameter as via holes are formed in predetermined positions in advance when forming wiring patterns on releasable carriers. The carriers with the wiring patterns are bonded on an insulating material, and a laser beam is irradiated from the side of the carrier using the holes in the wiring pattern as a laser mask to form via holes in the insulating material. The via holes and the holes in the carrier are then filled with a conductive paste. With the holes in the carrier that are matched in position with the via holes, lands in the conductor layers are precisely positioned relative to the via holes. A multilayer circuit board thus produced has lower electrical connection resistance and excellent mountability with improved performances. Also a manufacturing method thereof is achieved.
1. A multilayer circuit board comprising:
an insulating film comprising two opposing sides;
two adhesive layers, one on each of the opposing sides of said two opposing sides of the insulating film;
a pair of conductor layers opposite to each other, and each of said pair of conductor layers being embedded in one of said two adhesive layers;
a first hole formed in truncated conical shape through the insulating film and said two adhesive layers;
a second hole formed in at least one of the pair of conductor layers to be coaxial with the first hole; and
a conductive paste filled in the first hole and second hole compressed accompanying with the embedding of the pair of conductor layers and in conductive contact with said pair of conductor layers.
2. The multilayer circuit board according to claim 1 , wherein the core board is united with a second wiring board to form a multilayer circuit board, the second wiring board comprising an insulating material and a conductor layer forming wiring patterns on one side of the insulating material, a via hole being formed through the insulating material and the conductor layer and filled with a conductive paste for interconnection, and a hole coaxial with the via hole being formed in the conductor layer.
3. The multilayer circuit board according to claim 1 , wherein each of the pair of conductor layers includes the second hole.
4. The multilayer circuit board according to claim 1 , wherein diameters at a portion wherein said second hole and said first hole contact are the same.