Three-dimensional multi-layer circuit structure and method for forming the same

A three dimensional multi-layer circuit structure is formed by partially etching a foil having a coating. A pre-circuit is formed by providing a metal foil, applying a photodefinable photoresist to each side of the metal foil, selectively exposing and developing the photoresist leaving exposed areas and unexposed areas and, plating the unexposed areas with a second metal. The pre-circuit is placed in an etching solution and removed after the etching solution partially etches the metal foil to undercut the second metal. The partially etched pre-circuit is then bent into a predetermined shape. The partially etched pre-circuit is then inserted into a mold cavity so that at least one surface of the circuit structure is adjacent to the mold. The mold is filled with a polymer resin so that the polymer resin encapsulates at least a portion of the partially etched pre-circuit and substantially fills the undercut. The molded circuit structure is then removed from the mold and the metallic foil is further etched to complete the forming of the circuit.