Polyimide - metal foil wiring boards for high frequency use

摘要

A metal foil-based layered product which can eliminate the problems caused by etchant infiltration, can be produced easily, and is sufficiently effective in reducing the permittivity of the whole insulating layer; and a process for producing the same. The process for producing the metal foil-based layered product includes the steps of: forming on a metal foil an undercoat film layer made of a poly(amic acid) which has been imidized at least partly; forming a porous, precursor layer on the undercoat film layer by a wet film-forming method using a solution containing a poly(amic acid); and imidizing at least the porous precursor layer.