NOVELTY - A primary polyimide precursor solution containing a polyamic acid and a solvent is cast or applied on a support and then heated. The primary polyimide precursor solution contains an organic material which is different from the polyamic acid and the solvent. The maximum temperature of heating is less than the volatilization temperature of the organic material but not more than the volatilization temperature of the polyimide, to obtain polyimide film.    USE - Manufacture of polyimide film e.g. substrate for solar cells and printed circuit boards (all claimed). Uses include but are not limited to flat display panel, semiconductor ink, aircraft, electromagnetic induction, wireless local area network, liquid crystal panel, resistor ink and dielectric material ink.    ADVANTAGE - The polyimide film is efficiently manufactured with favorable film formability, and excellent strength and electroconductivity, and high adhesiveness.    DETAILED DESCRIPTION - A primary polyimide precursor solution containing a polyamic acid and a solvent is cast or applied on a support and then heated. The primary polyimide precursor solution contains an organic material which is different from the polyamic acid and the solvent. The volatilization temperature of organic material is less than the volatilization temperature of a polyimide obtained by imidizing the polyamic acid. The maximum temperature of heating is less than the volatilization temperature of the organic material but not more than the volatilization temperature of the polyimide, to obtain polyimide film. During the process the polyimide is formed by heating the primary polyimide precursor solution cast or applied on the support, the organic material undergoes phase separation from the phase of the polyimide precursor and is thermally decomposed or vaporized by heating, and removed from the polyimide film. INDEPENDENT CLAIMS are included for the following:    (1) polyimide film; and    (2) printed circuit board, which has electroconductive pattern formed on the substrate containing polyimide film.