A method is disclosed for applying an electrical conductor to an electrically insulating substrate, which comprises providing a flexible membrane with a pattern of groove formed on a first surface thereof, and loading the grooves with a composition comprising conductive particles. The composition is, or may be made, electrically conductive. Once the membrane is loaded, the grooved first surface of the membrane is brought into contact with a front or/and back of the substrate. A pressure is then applied between the substrate and the membrane(s) so that the composition loaded to the grooves adheres to the substrate. The membrane(s) and the substrate are separated and the composition in the groove is left on the surface of the electrically insulating substrate. The electrically conductive particles in the composition are then sintered to form a pattern of electrical conductors on the substrate, the pattern corresponding to the pattern formed in the membrane(s).