| 摘要 |
PROBLEM TO BE SOLVED: To efficiently form a via hole with no remaining insulating resin residue, etc., between layers, by etching/removing an insulating resin residue remaining at the bottom part of a blind hole together with a part of a conductor layer. SOLUTION: A connection opening part of a wiring board between a copper foil and a circuit-constituted printed board, where a copper foil and a polyimide adhesive sheet of insulating resin are laminated on the circuit-constituted wiring board, is etched to form a fine opening in a desired pattern. Further, with the copper foil as a work mask, carbon dioxide laser beam 5 is projected almost over the entire surface, so that a blind hole 6 for connecting the copper foil and the circuit-constituted wiring board is opened. With a soft etching liquid put in a stainless vat, a laminated wiring board is submerged in it and irradiated with ultrasonic wave for better penetration of the soft etching liquid, and the copper foil at a lower layer is etched and, at the same time, a resin remaining on the bottom surface of hole is removed. As a result, a plate tight-contact characteristics at the bottom surface of an inner-layer copper foil is improved for forming a via hole of high reliability. |
