WO2005056881A1

WO2005056881A1 - Method of manufacturing thin foils on a carrier web and the product manufactured with this method

Info

Publication number: WO2005056881A1
Application number: PCT/FI2004/000747
Authority: WO
Inventors: Yrjö LEPPÄNEN
Original assignee: Outokumpu Oyj
Priority date: 2003-12-12
Filing date: 2004-12-09
Publication date: 2005-06-23
Also published as: FI20031819A0; FI115775B

Abstract

The invention relates to a method of manufacturing thin metal or metal alloy foils by electrodeposition onto a carrier web. The surface of the carrier web is partially covered with a non-conducting layer and foils of the desired form are deposited onto the conducting points that remain bare. The carrier web is carried to an electrodeposition bath, where there are at least one anode and a cathode. The carrier web rotates around support rolls and the cathode, and the foil deposited from the salt solution attaches itself onto the carrier web. The carrier web is brought to electrodeposition as a reel and foils are also coiled after the formation of individual foils onto a carrier web reel for further processing, which can be performed in the desired location.

Description

METHOD OF MANUFACTURING THIN FOILS ON A CARRIER WEB AND THE PRODUCT MANUFACTURED WITH THIS METHOD

The invention relates to a method of manufacturing thin metal or metal alloy foils by electrodeposition onto a carrier web. The surface of the carrier web is partially covered with a non-conducting layer and foils of the desired form are deposited onto the conducting points that remain bare. The carrier web is taken to an electrodeposition bath, where there are at least one anode and a cathode. The carrier web rotates around support rolls and the cathode, and the foil deposited from the salt solution attaches itself onto the carrier web. The carrier web is brought to electrodeposition as a reel and foils are also coiled after the formation of individual foils onto a carrier web reel for further processing, which can be performed in the desired location.

Thin foils with good electrical conductivity properties are needed in several technical applications. These include for example inductive sensors and antennas for various kinds of electronic applications. In the present methods, the majority of earlier manufactured metallic foil is etched or cut away in order to obtain the functional form of the foil.

Smart labels (ID tags) are the active (functional) elements of microcircuits, their various memories (ROM, RAM, EPROM etc.) (microchip) and antenna, which are laminated inside plastic or some other suitable surface material. They are activated by the effect of an external RF or UF field and therefore do not need a power source, although they may indeed have one in some cases. Smart labels may be used to identify items (products, people, animals etc.) by utilizing the data stored in the memory of the microcircuits. Identification occurs at a distance, which may vary from a few millimetres to several metres. During identification, the antenna produces an electric current to the microchip in the field of the reader. The labels may be single- use, such as labels on food supply and other consumer goods packaging, and be destroyed after use, or they may be designed for permanent use, such as bank, personal and other ID applications.

The typical smart label antenna is 5 - 50 μm thick and has a surface area of 10 - 50 mm x 10 - 100 mm. A printed antenna is generally manufactured using the serigraphy technique. Electroconductivity is created with conductive powder, which can be for instance silver, copper or graphite. In addition to printed antennas, antennas are manufactured at present by winding thin copper wire, by vapourizing, electrolytically or chemically. When making the shape of the antenna coil the unnecessary part of the surface metal manufactured in different ways from continuous copper foil is etched away chemically. The part to be etched away can well be over 50%. Since removing the superfluous metal requires a separate work stage, the aim in the industry has always been to achieve a functional antenna, which even in the preliminary stages of production is as NNS (near net shape) as possible.

In the prior art a method is known for producing a thin foil by electrolytic deposition. In the method there is a rotating cathode drum in an electrolysis tank and a curved anode made of one or more parts on the bottom of the tank. The electrolyte is fed between the anode and the cathode and as a result a copper foil is deposited on the surface of the cathode drum. When the electrodeposited foil rises above the electrolyte, it is removed from the cathode and taken for further processing. The method has been developed since the 1930s and is described for instance in US patent 2,044,415 and US patent application 2002/5363.

Electrolytic foil manufacture has focused, however, on producing a continuous foil, of which the superfluous metal is etched away for instance in the manufacture of antennas and microcircuits. Etching occurs after the foil has been laminated to for example a PVC substrate. A resist is applied on top of the copper foil, and it is exposed into the desired form through a mask. The exposed resist is developed and the section of copper foil left outside the resist is etched away. After this, the resist is removed from the surface of the remaining copper foil product. The foil product is for example a microcircuit current conductor or a smart label antenna.

US patent 4,053,370 describes a method whereby printed circuit patterns are fabricated electrolytically. In the method, the surface of an endless strip is covered with an insulating layer so that the electricity-conductive parts that remain exposed are of the desired product shape. The strip is placed in an electrolytic bath and rolled around a cathode drum. The electrolysis tank contains an acidic copper salt or electrolyte. Anodes are also immersed in the tank, which are preferably at different distances from the cathode drum and thus the strip onto which the circuit patterns are deposited. The first anode is nearer the web, which facilitates the majority of the pattern to be deposited as a dense crystal structure. The second anode is located further away from the strip and as a result a rougher surface layer is obtained on top of the pattern. A rougher surface helps the adhesion of the pattern to the adhesive laminate.

The method described in US patent 4,053,370 is based on the fact that the insulation of the endless strip, the formation of the circuit patterns and the removal of the patterns are all performed in the same unit. When circuit patterns are deposited in the same place where the circuit boards are produced, this is a practical solution. On the other hand however, it is more important that the pattern formed on the carrier substrate can be transferred attached to the carrier substrate and transported to its permanent location at a later date.

Now a method is presented for the fabrication by electrodeposition of smart label antennas and other functional, very thin and highly electro-conductive products, whereby functional products of the desired final shape are deposited directly onto the surface of a carrier web revolving around one or more cathode rolls. Highly electroconductive material is used for the products such as copper, silver or gold, but in some connections the metal could also be nickel. The metal or metal alloy is in the electrodeposition tank as a metal salt solution, so that highly electroconductive foils are deposited from it electrolytically. Thin electroconductive aluminium foil is used as the carrier web on top of which the antenna is deposited. The carrier web is brought to electrolysis as a reel and the antennas are also coiled after the formation of antennas onto a carrier web reel for further treatment, which can be performed in the desired location. Later when we mention antennas we are referring to any functional product, not only a smart label antenna (for example the conductive component of a microcircuit). When we use the term electrodeposition or electrolytic deposition in the text, it means the same thing.

The essential features of the invention will be made apparent in the attached claims.

In the first stage of antenna fabrication, antenna-shaped patterns are made on top of the carrier web, aluminium foil, using a suitable method, for instance a printing method, where the shape of the future antenna is left unprotected. The insulating treatment of the carrier web is performed either in the same unit as the subsequent electrodeposition or in a separate unit. In the following stage the carrier web on the reel is straightened out and carried to an electrolyte bath, where the antenna shape is deposited on top of the untreated part of the surface of the web. The electric current density used and the speed of rotation of the drum determine the thickness of the copper layer that is generated. The current density and speed of rotation may vary within a wide range. The antenna may be further coated with fine-grained copper and/or brass or the antenna surface may itself be oxidized with a method of the prior art. Coating and oxidation increase the adhesiveness of the operating substrate. When the antenna has received the desired shape and further treatment, the carrier web is coiled onto the reel from which the antennas are attached in a separate work stage to a laminate or other operating substrate. After this, the carrier web is peeled off the operating substrate.

The method according to the invention is described further by means of the attached drawings, where

Figure 1 is a principle drawing of a method according to the invention, where the antenna is formed on to a carrier web to be coiled, and Figure 2 presents a principle drawing of another embodiment of the invention.

Figure 1 shows that a carrier web 1 made of aluminium foil is brought on a reel 2 for electrolytic deposition. Before this, antenna-shaped patterns are formed on top of the carrier web, so that the antenna shape remains uncovered and an insulating layer is formed on the other parts. Where necessary, insulating treatment can of course be carried out just prior to electrodeposition. The insulation of the surface can be carried out for example using the printing technique, by painting or gluing an insulating foil onto the surface of the carrier web. The carrier web is taken by means of support rolls 3 to the electrodeposition tank 4, which is equipped in at least one part with a forming anode 5 and a rotating roll-like cathode 6. The electrodes are connected to a power supply (not shown in detail in the figure). The tank 4 contains electrolyte 7, which in the example case is a copper salt solution, for instance copper sulphate solution, which includes necessary additives. As mentioned above, the salt solution may also be a salt solution of some other metal or metal compound. The electrolyte is made to circulate in the space between the anode and the cathode and from there back to the tank outside the anode. Thin, antenna-shaped, pattern foils 8 of a few micrometers thick are deposited from the electrolyte onto the surface of the surface-treated carrier web. The pattern foils are marked in the drawing much larger than they are in relation to the manufacturing equipment. The washing and drying of the antennas are known in the technique as such so they are not shown in detail in the drawing.

Surface treatment may be performed to the antennas formed on top of the carrier web. The surface treatment stage may be for instance electrolytic copper plating or electrolytic brassing in a tank 9, in which there are a cathode drum 6 and anode 5 of the same type as in the actual antenna deposition treatment. The electrolyte solution is selected in accordance with the desired coating. The surface treatment of the antennas makes the antennas adhere better to the operating substrate. After further treatment, the antenna-containing carrier web is rolled onto a reel 10 via support rolls 3 for further processing. When the antennas are left on the carrier web, it is easy to deliver them on reels to a further manufacturer, who can peel off the antennas from the carrier web and attach them to the operating substrate of their choice.

The principle drawing in Figure 2 shows another circulation method for a carrier web in an electrodeposition bath. Patterns in the shape of an antenna are formed on top of the carrier web 1 so that the places for the antenna remain bare and an insulating layer is formed on the other parts. The carrier web 1 is brought to the electrodeposition stage on a reel 2. There is an electrolyte 7 in the tank 4, which in the case of the example is a copper salt solution, for instance copper sulphate solution, which includes necessary additives. In this alternative several plate-like, upright anodes 11 are located in the tank. The carrier web moves between the anodes by means of the rolllike cathodes 12 situated above the tank and the support rolls 13 situated in the tank. The anodes are situated between the cathode rolls. The electrodes are connected to a power supply (not shown in the drawing). As a result of this treatment the antenna patterns of the desired shape are deposited on top of the carrier web. If surface treatment is required on top of the antenna patterns, it can be made in the corresponding method to that described in connection with Figure 1 , using either one or more cathode rolls. When inexpensively priced aluminium foil is used as carrier web, the various fabrication stages of the antenna can be differentiated in specialized units. Thus one unit may handle surface treatment, the next the formation of antennas and the third the forming of smart labels. The foil thickness is chosen according to need, but in general the foil thickness is in the range of 10 - 500 micrometres. It is preferable to route the aluminium foil back to smelting for example after peeling off the antennas. Foil that is wrapped around a reel in the transportation stage protects the antennas from the effect of the environment.

Claims

PATENT CLAIMS

1. A method for the fabrication of thin foils using a carrier web (1), of which the surface is partially insulated with an electricity-insulating layer, whereby the web is carried to an electrodeposition, having equipped with an anode (5, 1 1 ) and a roll-like cathode (6,12), around which the carrier web revolves, and whereby a salt solution of a highly electroconductive metal or metal alloy is used as electrolyte, characterised in that the carrier web (1 ) is brought to electrolytic deposition on a reel (2), in which deposition functional metal or metal alloy foils (8) are deposited on the points of the web that remain bare and conduct current, and that the web onto which the functional foils (8) are deposited, are rolled onto a reel (10) for transfer to the processing unit, where the foils are attached to the operating substrate.

2. A method according to claim 1 , characterised in that the carrier web (1 ) is aluminium foil. 3. A method according to claim 1 or 2, characterised in that the thickness of the carrier web (1 ) is 10 - 500 micrometres.

4. A method according to any of preceding claims 1 - 3, characterised in that the insulation treatment of the carrier web surface and the electrodeposition are carried out in different units.

5. A method according to any of preceding claims 1 - 3, characterised in that the insulation treatment of the carrier web surface and the electrodeposition are carried out in the same unit.

A method according to any of preceding claims 1 - 5, characterised in that the highly electroconductive metal is copper or a copper alloy.

7. A method according to any of preceding claims 1 - 5, characterised in that the highly electroconductive metal is silver or a silver alloy.

8. A method according to any of preceding claims 1 - 5, characterised in that the highly electroconductive metal is gold or a gold alloy.

9. A method according to any of preceding claims 1 - 5, characterised in that the highly electroconductive metal is nickel or a nickel alloy.

10. A method according to any of preceding claims 1 - 9, characterised in that after the electrodeposition stage the carrier web (1 ) is routed to a surface treatment stage, where the functional foils (8) are coated with copper.

1 1. A method according to any of preceding claims 1 - 9, characterised in that after the electrodeposition stage the carrier web (1 ) is routed to a surface treatment stage, where the functional foils (8) are coated with brass.

12. A method according to any of preceding claims 1 - 9, characterised in that after the electrodeposition stage the carrier web (1 ) is routed to a surface treatment stage, where the functional foils (8) are oxidized.

13. A method according to any of preceding claims 1 - 12, characterised in that electrolytic deposition is carried out in a tank (4), which is equipped with a rotating cathode drum (6), and at least one anode (5) located below it, whereby the carrier web (1 ) rolls around the cathode drum and is transferred from one reel (2) to the next (10).

14. A method according to any of preceding claims 1 - 12, characterised in that electrolytic deposition is carried out in a tank (4), which is equipped with at least one plate-like, upright anode (1 1 ) and at least two roll-like cathodes (12) located above the tank and support rolls (13) situated in the tank, via which the carrier web (1 ) travels from one reel (2) to the next (10).

15. A functional foil, characterised in that highly electroconductive metal or metal alloy foils (8) are formed by electrodeposition on the surface of a carrier web (1 ), where said surface is partially insulated by an electricity-insulating layer, and foils (8) of the desired shape are deposited onto the points of the web that remain bare and conduct current.

16. A foil according to claim 15, characterised in that the functional foil forms a smart label antenna.

17. A foil according to claim 15, characterised in that the functional foil is a microcircuit current conductor.

18. A foil according to any of preceding claims 15 - 17, characterised in that the thickness of the foil is 5 - 50 micrometres.

19. A foil according to any of preceding claims 15 - 18, characterised in that the highly electroconductive metal is copper or a copper alloy.

20. A foil according to any of preceding claims 15 - 18, characterised in that the highly electroconductive metal is silver or a silver alloy.

21. A foil according to any of preceding claims 15 - 18, characterised in that the highly electroconductive metal is gold or a gold alloy.

2. A foil according to any of preceding claims 15 - 18, characterised in that the highly electroconductive metal is nickel or a nickel alloy.