Importance

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Abstract

A method of making a printed circuit board whereby a fine wiring pattern can be formed. A through hole is formed in a substrate, both surfaces of the substrate being covered with copper foil. The substrate is treated with a catalyst and plated with copper. The through hole is filled with an insulating material, and the copper layer on the substrate is etched so that the catalyst layer is not exposed, leaving a thinned copper layer. Then, the substrate surfaces are ground and leveled by removing any projecting insulating material. Thereafter, another copper layer is deposited on the surface of the substrate, including surface regions on the fill material and is circuitized to form a wiring pattern. Since the catalyst layer is not exposed when the copper layer on the substrate is thinned, a fine wiring pattern can be obtained without the problem of subsequent peeling of the wiring conductors, or the entrapment of air.

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First Claim