PRINTED WIRING BOARD

摘要

In manufacturing a double-layered or a multi-layered printed wiring board, a layer of metamorphic substance, which is created by transmuting a substrate material, is formed on an inner wall of a hole during a perforation process of the substrate utilizing radiation energy. The layer of metamorphic substance prevents conductive materials constituting electrical connection means formed on the inner wall of the hole from dispersing over a surface of the substrate or permeating into the substrate.