Abstract: A printed circuit board includes insulating layers formed by impregnating a base material with a resin and a metal foil pattern formed on a desired layer of the insulating layers. Ions for forming a hardly soluble metal salt by combining with metal ions free from a portion of the board or a sulfur-containing compound for reacting with the metal ion are present in the insulating layer or on a surface of the metal foil pattern. Furthermore, a method for producing the printed circuit board includes any one of the steps of adding the ions or the sulfur-containing compound to the resin varnish, impregnating a base material with the solution of the ions or the sulfur-containing compound, or applying the solution onto the surface of the metal foil pattern, in order to allow the ions or the sulfur-containing compound to exist in the printed circuit board.

Abstract: To address the problem of difficulty of making compatible flame retarding property and electrical and mechanical characteristics in conventional printed interconnection substrates, the present invention employs, in a substrate for printed circuit board of which the insulating material comprises a thermosetting resin composition comprising an epoxy resin main component and a curing agent, an epoxy resin containing a brominated phenol novolac type epoxy resin having a biphenyl skeleton as the main component or a curing agent containing a brominated phenol novolac type curing resin. It provides a substrate for printed circuit board which has an extremely high flame retarding property and a superior heat resistance and humidity resistance, as well as a high insulating reliability and a superior high frequency characteristic.