Method for fabricating a wiring substrate by electroplating a wiring film on a metal base

1. Field of the Invention The present invention relates to a method for fabricating a wiring substrate by forming an insulating film on a metal base having openings on the metal base at positions corresponding to metal bumps to be formed later; forming at least one layer of wiring on the base made of a metal through the insulating film, the layer of wiring having a wring film formed thereon by electroplating; and selectively etching the base. The insulating film can be a liquid photosensitive polyamide, the wiring layer can be copper and the wiring film can be a conductive layer selected from the group consisting of Ni-P and Ni. In the present invention, the wiring layer can be formed through the insulating film in contact with the metal base at the openings in the insulating film and in contact with the insulating film where there are no openings in the insulating film.