| 摘要 |
PROBLEM TO BE SOLVED: To improve connection reliability and to form a high-precision circuit board by plate-sealing a small-bore end part of a tapered through-hole for combination with a tapered through-hole, where front/rear and/or an inner-layer circuit is connected. SOLUTION: A tapered through-hole 3 is formed by laser work at a place which is to be a through-hole with no copper foil layer 2 or a place, which is to be a through-hole where the copper foil layer 2 is oxidized. Here, the bore of a small bore end part of the tapered through-hole 3 is 20-50μm, while that of a large-bore end part being larger than the small-bore end part by at least 10μm, with a maximum bore being 150μm. After laser hole-working, the tapered through-hole 3 is plated for conduction between copper layers, while a through-hole 6 whose small-bore end part is sealed with a plating metal is formed. The inside wall surface of the tapered through-hole 3 is plated to form a metal layer, while the small-bore end part is sealed with a plating metal for combination of through-holes in the same and/or opposite directions. |
