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Bjarni Bjarnason

Per Petersson

Göran Frennesson

G&ouml;ran Frennesson

Bin Xie

Jenny Sjöberg

Jenny Sj&ouml;berg

Mikael Gustavsson

Etching of copper on a card is achieved by applying an electrical voltage between a cathode () and the card (), the card () thereby forming an anode. The cathode () and the card () are immersed in an electrolyte comprising a first component, which may be reduced from a first state in the form of an ion having a metal atom with a first positive oxidation number to a second state in the form of an ion having said metal atom with a second positive oxidation number, which is less than said first positive oxidation number. A first redox potential in the electrolyte for reduction from the first to the second state is larger than a second redox potential in the electrolyte for reduction of divalent copper ions to metallic copper. During the etching metallic copper on the card is oxidized and transferred into positively charged copper ions while the first component is reduced from its first state to its second state. The quality of the etched structures on the card is improved since no metallic copper is precipitated on the cathode.

Method of etching copper on cards

In a method of etching a substrate having a surface layer of conductive material, a circuit pattern is transferred to the surface layer in a central surface area portion of the substrate by electrochemical etching. To prevent excessive current densities from forming at the periphery of the central surface area portion during the etching step, a frame adapted to attract electrical field is provided adjacent to the central surface area portion. The frame can be part of a separate frame element which is placed on the substrate before the etching step, or be incorporated in a resist coating on the substrate. The frame 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 can be incorporated in a prefabricated substrate element, to which the circuit pattern is transferred in the etching step.

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

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Vellinge, Sweden

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