A method of manufacturing an electronic circuit assembly that includes a number of electrically interconnected flexible films, each flexible film having a flexible electrical wiring circuit. The electrical wiring circuits are interconnected between film layers and the film layers are adhered to a molded backing structure. A first flexible film is formed with a pattern of flexible electrical wiring circuits created on at least one surface thereof. The first flexible film has a passage that provides an electrical connection through the flexible film. A second flexible film is formed with a pattern of flexible electrical wiring circuits created on a least one surface thereof. The second flexible film has an electrical interconnect feature that connects with the electrical passage on the first film and electrically connects the first film with the second film. The first flexible film is overlaid juxtaposed the second flexible film so that the passage is aligned adjacent the electrical interconnect feature. The first and second flexible films are placed within an open mold. The mold is closed and a plastic material is injected within the mold adjacent at least one surface of the first and second flexible films. The molten plastic adheres to the first and second flexible films and forms an integral backing structure. The backing structure and first and second flexible films together form the circuit assembly.