Abstract: A method of applying microelectronic circuit elements, such as high definition thin-film microwave components, typically to a lower definition thick film or printed circuit board substrate. The method described involves the formation of a high definition microwave filter on the surface of a transparent, flexible carrier substrate using thin film deposition techniques, and the circuit element is then adhesive bonded face down in an appropriate position in a thick film circuit on the surface of a second, permanent substrate. The thin film circuit element is formed with contact areas which overlap cooperating portions of the thick film circuit on insertion of the circuit element to provide electrical connections. The carrier substrate may then be removed, eg by dissolving, and the overlapping contact areas may be permanently bonded together. Thus only the high definition parts of the micro-circuit need be fabricated using expensive thin film technology.