Method of manufacturing organic substrate used for printed circuits

A method of manufacturing an organic substrate used for printed circuits, which comprises the steps of forming through-holes in a porous raw material provided with free tackness films and having compressive shrinkage comprising a composite material of a non-woven fabric and a thermosetting resin, filling electro-conductive paste into said through-holes, and also increasing composition ratio of the electro-conductive material with respect to a binder in the electro-conductive paste, separating the free tackness films from said porous raw material filled with the electro-conductive paste in the through-holes thereof, applying metal foils onto the surface of said porous raw material from which said free tackness films have been separated, and then compressing said porous raw material applied with said metal foils through heating and pressurization so as to make more compact, the electro-conductive material in said electro-conductive paste.

A method of manufacturing a multilayer circuit board which comprises the steps of:

• producing circuit boards each by forming circuit patterns on opposite surfaces of a printed circuit organic substrate obtained by the steps of forming through-holes in a porous material provided with cover films and having compressive shrinkage, filling electro-conductive paste into said through-holes, separating the cover films from said porous raw material filled with the electro-conductive paste in the through-holes thereof, applying metal foils onto the surfaces of said porous raw material from which said free tackness porous raw material applied with said metal foils through heating and pressurization.
• producing an intermediate connecting member by forming through-holes in the porous raw material and filling electro-conductive paste into said through-holes, and then
• holding said intermediate connecting member between at least one pair of said circuit boards for subsequent heating and pressurization thereof.