Abstract: A base material for a printed circuit of the present disclosure includes a base film containing polyimide as a main component, and a conductor layer formed on at least one surface of the base film. The conductor layer includes a metal sintered layer formed on the base film and an electroless plating layer formed on the metal sintered layer, and in the base film, a number of voids having a maximum width of 5 ?m or more in plan view is 10 or less per a reference unit area of 0.25 mm2 on a surface of the base film.

Abstract: A substrate for a printed wiring board, the substrate includes a base film containing polyimide as a main component and a sinter layer disposed on at least a portion of a surface of the base film and containing copper nanoparticles. The base film contains a nitrogen atom bonded to a copper atom of the copper nanoparticles, an average number of the nitrogen atom bonded to the copper atom per unit area of the surface of the base film on which the sinter layer is disposed is 2.6×1018 atoms/m2 to 7.7×1018 atoms/m2, and the average number is an average number calculated for a measurement region estimated to have a thickness of 3 nm from a measurement value of the surface of the base film measured by X-ray photoelectron spectroscopy.