A method includes providing a mandrel having an electrical conduit electroformed in the mandrel. The second side of the electrical conduit is blackened while in the mandrel to create a black layer on the electrical conduit. The mandrel is aligned in a flatness fixture such that the mandrel is substantially flat. The mandrel remains flat and in a fixed relationship to the flatness fixture throughout the method. A beam of a laser is controlled toward the black layer. The beam has laser parameters including a power output, a frequency and a mark speed, and selected by setting the power output and the mark speed then determining the frequency. The beam removes a plurality of the portions of the black layer. Each removed portion of the plurality of the portions has a thickness equal to the black layer thickness, and a portion area of 9 mm2 to 18 mm2.