Method of etching, as well as frame element, mask and prefabricated substrate element for use in such etching

In a method of etching a substrate (1) having a surface layer (3) of conductive material, a circuit pattern is transferred to the surface layer (3) in a central surface area portion (4) of the substrate (1) by electrochemical etching. To prevent excessive current densities from forming at the periphery of the central surface area portion (4) during the etching step, a frame (9) adapted to attract electrical field is provided adjacent to the central surface area portion (4). The frame (9) can be part of a separate frame element which is placed on the substrate (1) before the etching step, or be incorporated in a resist coating on the substrate (1). The frame (9) can be transferred to the resist coating by any suitable means, for example by photolithographic exposure through a mask with a suitable frame pattern. Alternatively, the frame (9) can be incorporated in a prefabricated substrate element, to which the circuit pattern is transferred in the etching step.