FI115224B - A process for electrolytically producing thin functional copper films and a product made by the process - Google Patents

Description

115224

METHOD FOR THE PRODUCTION OF THIN FUNCTIONAL COPPER FILMS BY ELECTROLYTICS AND THE PRODUCT OBTAINED BY THE METHOD

This invention relates to a process for the production of thin copper wells electrolytically. An arcuate anode formed from at least one part is immersed in the electrolysis tank and above it is provided a rotating cathode drum on which a copper well deposited by the electrolyte is adhered. The surface of the cathode drum is covered with an electrically insulating layer, and the functional copper wells are deposited at exposed, conductive sites. Above the electrolyte surface, the films are removed from the drum and subjected to further treatment. The invention also relates to a product made by the process.

15 In many technical applications, thin films with good electrical conductivity are required. These include, for example, inductive sensors and antennas for various electrotechnical applications. In current methods, thin film '·. in order to achieve a functional shape, most of the previously fabricated metal foil is etched or cut off.

. · · ·; 20

The detector stickers are active (functional) elements consisting of a microcircuit, their various (ROM, RAM, EPROM, etc.) memories (microchip) and an antenna, which are laminated inside a plastic or other suitable surface material. They are activated by an external RF or UF field and thus do not require a power source, although they may be present in some cases. Identification stickers can be used to identify objects (products, persons, animals, etc.) by using memory data stored in an integrated circuit. The detection is done at a distance that can vary from a few. ···. millimeters to a few meters. In detection, the antenna provides an electrical current to the 30 microchips in the field of the reader. Labels may be disposable, such as those used in food and other consumer packaging, which will be destroyed after use, or may be used for continuous use, such as banking, personal, or other ID applications.

A typical sensor antenna is 20 to 50 µm thick and has a surface area of 10 to 5 50 mm x 10 to 100 mm. The printed antenna is generally manufactured by screen printing technology. The electrical conductivity is created by a conductive powder, which may be, for example, silver, copper or graphite. In addition to printed antennas, antennas are currently manufactured e.g. by coiling, evaporating, electrolytically or chemically thin copper wire. Chemically unneeded portions of the coating metal are etched from the various single-shaft copper wells to produce the shape of the antenna coil. The etched portion may well exceed 50%. As the removal of excess metal requires its own work steps, it is always sought in the art to provide a functional antenna that is as close as possible to the final shape (NNS = near net shape) at the outset of manufacture.

A method for producing a thin film by electrolytic precipitation is known in the prior art. The method comprises a rotating cathode drum in an electrolysis pool and an arcuate anode 20 in one or more sections at the bottom of the pool. The electrolyte is fed between the anode and the cathode and as a result a copper foil precipitates on the surface of the cathode drum. When the deposited foil rises above the electrolyte, it is removed from the cathode and subjected to further processing. The method has been developed since the 1930s and is described, for example, in U.S. Patent No. 2,044,415 and U.S. Patent Application Serial No. 25, 2002/5363.

* I

However, electrolytic foil manufacturing is focused on manufacturing. v. a continuous foil, for example, for the manufacture of antennas and integrated circuits. ···. excess metal is etched off. Etching occurs after * · 30 foil is laminated to, for example, a PVC substrate. A resistor is coated on the copper foil and exposed through a mask of the desired shape. The exposed resist is developed and the portion of the copper foil outside the resist is etched away. After that, resist! is removed from the surface of the remaining copper foil product. The foil product is, for example, an IC chip or an antenna for a detector.

115224 3 5 For the purpose of electrolytically fabricating sensor antennas and other functional, ultra-thin copper products, a method is now in place for electrolysis to precipitate functional products of the desired shape directly onto the cathode surface. The surface of the rotating cathode drum is covered with an electrically insulating layer so that the exposed, conductive ίο points are in the shape of the desired product. In the following, when referring to a functional product, only the antenna is referred to, although the desired product may be other than the detector antenna (e.g., the conductive part of the integrated circuit). The electric current density used and the rotation speed of the drum determine the thickness of the resulting copper layer. Current density and rotation speed can vary within wide limits. The invention also relates to a product made by the process.

1 ·

The essential features of the invention will be apparent from the appended claims.

20: * · · As the cathode drum rotates, antennas deposited on the drum surface and reaching the desired thickness will rise from the electrolyte bath above the surface. The surface of the drum and its antennas are rinsed and dried. Thereafter, the surface of the drum is brought into contact with a continuous support web 25 which is provided with an adhesive surface at least on the side that comes into contact with the antennas. The antennas adhere to the adhesive surface, and when the support web is led away from the cathode drum, the antennas release from the surface of the drum and remain on the support web surface. The portion of the surface of the drum where the antennas have been removed will go again, ···. electrolyte and a new antenna grows there, so the process is continuous. The support web 30 preferably forms the other side of the sensor to be manufactured. A microchip is attached to the antenna and a suitable web is also attached to one side of the antenna, whereby the antenna and the microchip are sandwiched between two supporting webs.

4, 115224

The process according to the invention is further illustrated by the accompanying drawing 1, which is a schematic drawing of electrolysis.

As shown in Figure 1, the electrolysis vessel 1 is provided with a curved anode 2 and a rotating cathode 3 consisting of at least one part. The cathode is centered 4 connected to a power source (not shown in detail). The surface of the cathode drum has been treated by some prior art insulating method such that it is electrically conductive only at the antenna patterns, the rest being electrically insulating. Insulation of the cathode surface may be effected, for example, by printing technique, painting or gluing an insulating film to the surface of the cathode drum. The electrolysis pool contains electrolyte 5, which in this case is a copper salt solution, for example a copper sulphate solution with the necessary additives. The electrolyte is placed in the space between the rotating anode and the i 15 cathode and from there back to the pool anode! outside. On the surface of the surface treated cathode, electrolyte forms an antenna-shaped thin film of a few tens of micrometres »* · · in pattern, which is marked in relation to · for resolution. much larger than what they are when they are formed. Washing and drying the antennas are known per se and are not illustrated in detail in the figure.

A support web 7 is rotated with the upper part of the cathode drum which rotates' / ·; on its support rollers 8, 9. At least the surface above the support web is provided with an adhesive surface, but the adhesive surface covered by the protective material may also be provided on one side of the web. The functional membranes 6 are adhered; '' *: To the support web and at the same time lead to further processing.

. ··. The functional copper well is electrolytically formed on the surface of the cathode drum 30 partially covered with an electrically insulating layer, and the functional copper wells are deposited on exposed, conductive sites. The functional copper well is preferably a detector antenna.

Claims (8)

115224 A method for making thin copper wells electrolytically by immersing a curved anode (2) formed by at least one part 5 in an electrolytic vessel (1) and above which a rotatable cathode drum (3) is disposed, over which the copper well precipitated by the electrolyte (5) drum and is further processed, characterized in that the surface of the cathode-drum is covered with an electrically insulating layer and the functional copper wells (6) are deposited at exposed, conductive points. Method according to Claim 1, characterized in that the cathode drum is brought into contact with the continuous support web (7) above the electrolyte surface, which is provided with an adhesive surface at least on the side that comes into contact with the copper wells (6). «* · Method according to Claim 1 or 2, characterized in that • above the electrolyte surface, the surface of the cathode drum and the copper wells (6) therein are rinsed and dried before removing the membranes from the cathode. * · A method according to any one of the preceding claims, characterized in that the functional copper well forms the antenna of the detector sticker »*» 25. »* · ►» »* · * ·: 5. A method according to any one of the preceding claims, characterized in that v. of contact with functional copper wells. · ·. the support web (7) forming part of the sensor sticker. t »* Method according to Claim 5, characterized in that the microchip of the tag sticker is attached to the support money in connection with the antenna. 30, 115224 7. Functional copper well, characterized in that the copper well is formed electrolytically on the surface of the cathode drum partially covered by an electrically insulating layer, and the functional copper wells (6) are deposited on exposed, conductive sites. Functional copper well according to claim 7, characterized in that the copper well is an antenna for the sensor sticker. 10