GB2262105A

GB2262105A - Manufacturing circuit components by depositing material at an angle on contoured surface

Info

Publication number: GB2262105A
Application number: GB9125707A
Authority: GB
Inventors: Vaughan Neil Kitchin; John Forshaw
Original assignee: Marconi Electronic Devices Ltd; Plessey Semiconductors Ltd
Current assignee: Marconi Electronic Devices Ltd; Plessey Semiconductors Ltd
Priority date: 1991-12-03
Filing date: 1991-12-03
Publication date: 1993-06-09
Anticipated expiration: 2011-12-03
Also published as: GB9125707D0; GB2262105B

Abstract

A circuit component, such as a pick-up coil for use in security tags or bank cards bearing on-board processing capability, is manufactured by forming a contoured pattern in a surface of a substrate 1, and depositing conductive material 3 at an angle to the substrate, preferably by evaporation, such that parts are shadowed from deposition and form insulating regions in the finished component, whilst other parts will have a deposit of conductive material. The contoured pattern, which may be formed by impressing a tool to the substrate when in a deformable state or less suitably by injection moulding, may comprise rectangular ridges or have a saw-tooth profile. The substrate may be a polycarbonate and the conductive material may be aluminium, copper or gold. A protective plastics layer may be applied over the electrically conductive material. In one embodiment the circuit component is a pick-up coil which is laid down on a substrate which also bears a processor to which the coil is arranged to supply power. Such a coil may act as an antenna. In another embodiment the coil is laid down on a substrate which also bears optically readable tracks as on a compact disc which is associated with a processor incorporating an identification code so as to act as an anti-theft device. <IMAGE>

Description

Method of Manufacturinq Circuit Components This invention relates to a method of manufacturing circuit components and more particularly, but not exclusively, for manufacturing a coil used as a pick-up coil for providing power in a circuit.

There are many actual and potential usages for portable tokens or cards bearing on-board processing capability. For example, security tags can carry individual codings to permit access of the bearer to restricted areas when he inputs a corresponding coding at a fixed installation at an entrance point. It is also proposed to use cards having on-board processing for banking applications and as tickets for travel or entertainment venues.

It is often desirable to provide power to such on-board processors by means of a pick-up coil which interacts with a fixed processor station either alone or as a supplement to batteries carried by the card.

At present, a pick-up coil for use with a portable card is manufactured by first drawing out conductive material as a wire, for example copper wire. The wire is then coated with a transformer varnish to provide insulation and is wound on a former to obtain the required configuration, glue being applied to maintain it in shape. Typically, the coil is rectangular and planar.

The present invention arose from consideration of the manufacture of pick-up coils particularly for use with portable tags but it is envisaged that the invention may have wider uses.

According to the invention, a method of manufacturing a circuit component comprises the steps of: forming a contoured pattern in a surface of a substrate; and depositing electrically conductive material in a direction at an angle to the surface such that parts of the surface are coated with conductive material and parts are shadowed from deposition, the shadowed parts being electrically insulating in the finished component.

The method may be particularly advantageously employed where the component to be manufactured is a coil, and especially where the coil is substantially planar such as the type used as pick-up coils and/or antennas in.portable tags or tokens. However, the method may also be advantageously used in the manufacture of other circuit components. By employing a method in accordance with the invention, a coil may be fabricated which is particularly thin compared to currently available coils and, because of its support by a substrate, is robust and resistant to bending or twisting of the tag or card with which it is incorporated.

The deposition of electrically conductive material is preferably by evaporation although other directional techniques could be used. As the material is laid down at an angle to the surface and hence to the contours of the pattern, the conductive material will tend to be deposited on some faces of the pattern in preference to others which are shadowed by the raised parts of the pattern. The conductive material may be aluminium, copper, gold or some similar metal.

The contours of the pattern and the angle at which conductive material is directed onto the pattern govern the final component configuration, although subsequent processing steps may be used to refine the distribution of conductive material. A contoured pattern may be readily imposed on a substrate surface by, for example, impressing a tool into it when in a deformable state. Using such a technique, it is possible to produce the shaped surface rapidly for a large number of substrates and with good accuracy and repeatability. Another suitable technique to produce the required substrate surface configuration would be to use injection moulding but this tends to be more expensive as it requires more elaborate tooling and includes additional processing stages.

The substrate is conveniently of a plastics material and may be formed in its contoured pattern using methods already in use in the compact disc manufacturing technology.

As the tools and plant required to form such contoured patterns in substrates are already available, the costs involved in adopting a method in accordance with the invention are relatively low.

The electrically conductive material is supported by the substrate on which it is laid down and hence it is not necessary to use sufficient for the material to be self-supporting, in contrast to conventionally fabricated coils. This leads to considerable savings in material costs where large scale production is required. The use of a thin layer of conductive material does not result in any appreciable loss in conductivity over that possible with a conventional wound coil.

A method in accordance with the invention lends itself to large volume production and, for example, where the circuit component is a coil reduces manufacturing time as the winding process is eliminated.

The substrate advantageously consists solely of electrically insulating material. However, the substrate may be mainly of conductive material on which an electrically insulating layer is laid down prior to deposition of the conductive material on the contoured surface. This technique, however, results in an extra processing step being required.

The pattern may be sufficiently deep compared to the angle at which the material is laid down that the areas which are to form insulating regions in the finished component have substantially no conductive material incident on them.

However, it may be necessary to include an additional processing step after deposition to remove some of the conductive material, for example, by etching.

The surface contours may be of a regular pattern or irregular depending on the configuration of the finished component.

In one advantageous method in accordance with the invention, the contoured pattern comprises substantially rectangular ridges, this being a particularly convenient configuration to produce. The width and depth of the ridges may be chosen in combination with the angle at which conductive material is deposited to give the desired effect.

In an alternative method in accordance with the invention, the contoured surface has a saw-tooth profile.

It may be desirable in some circumstances to use a more complicated pattern in which shielding of parts of the substrate from deposition is achieved -when the angle of deposition is normal to the major plane of the substrate.

It may be advantageous to include an additional step of laying down a protective coating on the electrically conductive material after deposition. The material is then protected against scratching and attack by surface contaminants.

In one preferred method, the circuit component is a pick-up coil which is laid down on a substrate which also bears a processor to which the coil is arranged to supply power. The coil may in addition or alternatively act as an antenna for receiving and/or transmitting signals. For example, modulated energy may be received by the coil from a radiating base station to which a reply is transmitted also via the coil.

In another method in accordance with the invention, the coil is laid down on a substrate which also bears optically readable tracks as on a conventional compact disc. The coil may be associated with a processor or other store which incorporates an identification code enabling the provenance of compact discs to be traced. This may act as an anti-theft device by enabling distribution routes to be checked.

Some ways in which the invention may be performed are now described by way of example with reference to the accompanying drawings in which: Figures 1 to 4 schematically illustrate processing steps in manufacturing a pick-up coil for use on a security tag; Figure 5 illustrates an intermediate stage in an alternative method in accordance with the invention; and Figure 6 schematically shows a compact disc incorporating a coil formed in accordance with the present invention.

A coil for use on a security tag to provide power to processing chips and which also acts as an antenna is formed on a substrate 1 of a plastics material of the type used as a substrate for compact discs. The substrate 1 is of a polycarbonate which is spun onto a disc. A tool 2 is pressed into the substrate 1, as shown in Figure 1, when it is in a deformable state to provide a ridged configuration having a pitch of approximately 1.5 microns and a depth of 120 nanometres. The substrate is then allowed to harden. In this particular embodiment, the ridge pattern is uniform and is rectangular in plan view.

In the next stage of the production process, conductive material, in this case aluminium, is evaporated onto the contoured surface of the substrate 1 at an oblique angle to the surface, as indicated in Figure 2 by the arrow. This results in a layer 3 of aluminium being laid down on the upper surfaces 4 of the ridges and also on their vertical sides 5 facing the direction of the source of the aluminium. In this embodiment, the aluminium layer is approximately 800 Angstroms thick. The shadowed sides 6 of the ridges are shielded from the aluminium as it is directed onto the substrate 1 and thus remain substantially free from it.

After the conductive material has been deposited on the surface of the contoured pattern, a plastics material 7 is laid down over the upper surface of the substrate as shown and cured using ultra-violet radiation. The layer 7 protects the conductive regions and provides additional rigidity to the finished device.

Figure 4 schematically illustrates in plan view a security tag incorporating a pick-up coil and antenna manufactured in accordance with the invention. In this embodiment, the coil/antenna 8 occupies part of the surface area and is rectangular in configuration. Other parts of the tag are occupied by micro-processors 9 and 10 and connecting conductive tracks. The coil/antenna 8 is carried by a substrate 11 on which the micro-processors 9 and 10 are also carried. However, it may be formed on a separate substrate which is then assembled onto a larger board carrying the necessary circuitry.

In another method in accordance with the invention, the steps carried out during manufacture are similar to those described with reference to Figures 1, 2 and 3 but in this case, the contoured pattern applied to the substrate 12 is of case, the contoured pattern applied to the substrate 12 is of a saw-tooth profile as shown in Figure 6. Parts 13 of the surfaces of the substrate which face towards the direction from which conductive material is directed are shadowed by adjacent regions of substrate and thus no conductive material is deposited thereon. Other portions 14 are exposed to the conductive material and in consequence a layer is produced in these areas.

A pick-up coil for supplying power to processor circuitry may be incorporated in a conventional compact disc arrangement as illustrated in Figure 6. The coil may also act as an antenna being arranged to radiate a response to an interrogating signal. The disc 15 bears grooves 16 which contain information which is laser readable to reconstitute information stored on the disc. The outer region of the disc is occupied by a coil 17 which is produced in accordance with the invention and which is connected to a micro-processor 18 containing information regarding the place of manufacture of the disc, its supply route and any other data which may be of interest.

Claims

1. A method of manufacturing a circuit component comprising the steps of: forming a contoured pattern in a surface of a substrate; and depositing electrically conductive material in a direction at an angle to the surface such that parts ofthe surface are coated with conductive material and parts are shadowed from deposition, the shadowed parts being electrically insulating in the finished component.

2. A method as claimed in claim 1 wherein the circuit component is a coil.

3. A method as claimed in claim 2 wherein the coil is a pick-up coil.

4. A method as claimed in claim 2 or 3 wherein the coil is an antenna.

5. A method as claimed in claim 2, 3 or 4 wherein the coil is substantially planar.

6. A method as claimed in any preceding claim wherein the electrically conductive material is deposited by evaporation.

7. A method as claimed in any preceding claim wherein the contoured pattern comprises substantially rectangular ridges.

8. A method as claimed in any of claims 1 to 6 wherein the contoured pattern is of a substantially saw-tooth profile.

9. A method as claimed in any preceding claim and including the step of removing some of the deposited electrically conductive material to form electrically insulating regions.

10. A method as claimed in any preceding claim and including the step of applying a protective layer over the electrically conductive material.

11. A method as claimed in any preceding claim wherein the substrate is of a plastics material.

12. A method as claimed in any preceding claim and including the step of forming the contoured pattern by pressing a tool into the substrate.

13. A method as claimed in any preceding claim and including the step of mounting a processing circuit on the substrate and forming a connection between the processing circuit and the component.

14. A method as claimed in any preceding claim wherein the substrate bears contoured regions providing optically readable information.

15. A method substantially as illustrated in and described with reference to the accompanying drawings.

16. A portable tag comprising a coil manufactured in accordance with a method as claimed in any of claims 1 to 15.