| abstract |
An object of the present invention is to provide a low warpage property, flexibility, and sealing material required for a protective film of a flexible wiring board without causing penetration of a plating component into the edge of the protective film and without diffusing the plating layer into the wiring. Provided is a flexible wiring board using a resin paste for a protective film of a flexible wiring board excellent in adhesion, solvent resistance and chemical resistance, heat resistance, electrical characteristics, moisture resistance, workability and economy. The following formula: A resin paste containing a resin, which is a thermosetting resin containing a polyurethane structure, and inorganic fine particles containing silica fine particles, and a non-nitrogen-containing polar solvent, is printed on a wiring pattern subjected to Sn plating on a flexible wiring board. And a step of forming a protective film by thermally curing the resin paste by heating at 80 to 130 ° C. [Selection figure] None |