Wiring board and a process of producing a wiring board

摘要

In a wiring board, predetermined wiring patterns which are formed on both sides of an insulation substrate are electrically connected by an electrically conductive material provided in through holes formed through the insulation substrate. The insulation substrate is composed of a resin impregnated fibrous sheet and a heat resistant film. The present invention solves the problems of the wiring board which are caused by irregularities on the surface of the resin impregnated fibrous sheet. The problems include insufficient adhesion strength between the wiring pattern and the insulation substrate or the limitation of fineness of the wiring pattern due to the irregularities on the surface of the printed wiring board which are formed upon the thermocompression bonding process.