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1. WO2020141331 - IMPROVEMENTS IN OR RELATING TO FLEXIBLE ELECTRONICS

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

IMPROVEMENTS IN OR RELATING TO FLEXIBLE ELECTRONICS

Technical Field of the Invention

The present invention relates to improvements in or relating to electronics. In particular the present invention relates to a process for manufacturing electronics and most particularly to a printing-based process for manufacturing electronics.

Background to the Invention

There is now an increasing demand for simple low-cost electronics, in particular electronics that can be readily incorporated into many different forms of products and packaging for products. This allows additional functions, such as tracking and monitoring functions to be implemented.

One particular example is the incorporation of electronic RF tags (or NFC tags) into packaging for food and/or beverage products. RF tags typically comprise an antenna tuned to a specific RF frequency. Detection of an attenuation in said frequency between a dedicated transmitter and receiver can indicate the presence of a tag and hence a tagged product. In other examples, the tag may be provided with energy scavenging means operable to scavenge energy from the received RF signals which power up an integrated circuit containing data such as serial numbers, date of manufacturer and other identifiers. This can provide additional information about the tag and hence the tagged product.

To produce a suitable simple low-cost antenna, it is known to print conductive ink onto a non-conductive substrate, the ink printed in a pattern corresponding to the conductive track required to act as an antenna. Whilst this does provide a workable solution, there are a number of issues that need to be addressed to formulate a functional ink. In particular, it is necessary to select suitable ink constituents that address the requirements of the ink for the application in terms of conductivity, resistivity, capacitance, or other property. The ink or coating must be suitable to be applied using standard application or printing techniques to reduce costs. An additional requirement is that the ink formulation is tailored to enable the ink to be applied to the substrate via one of the typical aforementioned print application methods. In this context, the viscosity of an ink is an important parameter. The drying or curing of the ink is also considered during the process. To enable the drying or polymerization of the ink, certain enhancing constituents are added to the formulation and these will be chosen based on the drying technology. Furthermore, it is necessary to consider adhesion of the ink to the substrate under all of the conditions to which the printed product will be exposed.

In many instances, it is convenient if the tags, or at least the antennas for the tags or power harvesting devices, can be flexible. Whilst this can be achieved by using a flexible rather than a rigid substrate, this applies further constraints to the ink. For instance, the applied ink or coating when cured must be flexible enough to function correctly even when the substrate is not flat.

Following ink formulation, before commercial use can commence, the ink must pass a qualification process. This process involves loading up the sample ink on a typical print platform and printing samples which are then evaluated under a wide range of conditions. The ink must deliver the desired functionality, it must adhere well to the substrate and will need to maintain these properties as the substrate is flexed or bent in a certain orientation which will be pre-defmed. If new ink properties are required, then as the new formulation is being developed, the qualification process begins again.

In addition to the above, the use of conductive inks presents a contamination hazard for the packaged food/beverage. Accordingly, before any such ink is used, it must undergo extensive migration testing to ensure that ink particles do not migrate to the food or beverage contained within the packaging. Inks are required to be suitable for secondary food contact and under no circumstances should any food contamination be present as a result of the application of the ink.

It is therefore an object of the present invention to provide a new process for manufacturing simple low-cost electronics that at least partially overcomes or alleviates the above problems.

Summary of the Invention

According to a first aspect of the present invention there is provided a method of manufacturing an electronic assembly, the process comprising the steps of: providing a substrate; printing an adhesive pattern onto a surface of the substrate, the adhesive pattern corresponding to one or more desired conductive tracks; pressing conductive

foil onto the adhesive pattern; curing the adhesive such that the foil adheres to the adhesive pattern; removing the non-adhered foil; and folding the substrate after removal of the foil.

The present invention thus provides a process by which a simple low-cost electronic assembly may be produced without using conductive ink. This ensures that the contamination risk associated with conductive inks is eliminated and is thus of particular benefit when the assembly is incorporated into packaging for food/beverages or the like. The printing formulation is an adhesive, which only needs to be qualified once for a wide range of substrates. This opens up new applications for digital printing of simple low-cost electronic circuits which were previously unavailable due to the complexity of deploying functional inks on digital printing equipment. Furthermore, the use of folded substrates allows more complex functionality to be implemented, including but not limited to capacitive components. Capacitive assemblies may, where appropriate be used as energy storage circuits.

Printing of the adhesive may take place by any suitable process. Suitable processes include, but are not limited to screen printing, gravure, flexograohic printing or the like. The adhesive may be any suitable adhesive. In many embodiments, the adhesive is a food-safe adhesive. This allows the process to be used to manufacture electronics for use in food/beverage packaging.

In one particular embodiment, printing is achieved by inkjet printing. This can be achieved by use of an inkjet printing head supplied with a suitable adhesive. This has the benefit of being able to print detailed patterns and of enabling different patterns to be produced in successive printing actions. This can allow for rapid changes in the nature of or number of assemblies produced or for assemblies to be produced on demand. In such embodiments, the adhesive is an adhesive compatible with ink jet printing techniques. Examples of such inkjet compatible adhesives include but are not limited to aqueous jettable adhesives, monofunctional acrylate esters, and the like.

In some embodiments, the adhesive may be selected to have particular electrical properties. These properties may be particular dielectric or resistive properties.

The curing may take place after foil application and prior to foil removal. The curing may be achieved by any suitable process including but not limited to thermal curing, UV curing, low energy electron beam curing, photonic curing, air curing or the like. In the context of the present invention, low energy electron beam curing is preferred as this can cure adhesives reliably through a wide range of foil and functional film layers. Additionally, low energy electron beam curing is often quicker than other curing techniques and can penetrate thicker foils and substrates.

The foil may be formed from any suitable conductive material. Examples of suitable foil materials include but are not limited to copper, silver, graphene, and the like.

The substrate may be rigid. Alternatively, the substrate may be flexible. Beneficially, in such cases, the present invention further provides a method of manufacturing functional flexible electronics.

The substrate may be formed from any suitable non-conductive material. Examples of suitable substrate materials include but are not limited to polymers, paper, woven fabrics, non-wovens, timber, silicon, composite materials, or the like.

In some embodiments, the substrate may be conductive. In such embodiments, the substrate may comprise a conductive foil, metal, or graphene.

The substrate may be subject to pre-treatment which may be a corona treatment, atmospheric plasma treatment, or application of a suitable primer prior to adhesive printing. This can improve the wettability and tailor the surface energy and chemistry of the substrate so as to ensure a good bond between the adhesive and the supporting substrate.

The substrate thickness may be selected such that the substrate is sufficiently structurally intact for the intended use and sufficiently thin such that it is sufficiently flexible for the intended use. The substrate thickness may thus vary depending upon the substrate material and the intended use. Solid components and rigid substrates may also benefit from this technique as it allows the addition of circuits to existing components and parts.

The substrate may be provided in an elongate strip. This can enable a series of separate conductive traces to be printed on the same substrate. The method may include the step of cutting the substrate to separate conductive traces. In such embodiments, successive patterns may be repeated or may vary.

The method may include the step of printing one or more additional adhesive patterns onto a surface of the substrate or onto the foil after initial foil removal. This can aid the construction of more complex assemblies. The additional adhesive may be of the same type or a different type to the initial adhesive.

In such embodiments, the additional adhesive pattern may correspond to one or more desired conductive tracks and/or additional adhesive required to construct the assembly. Where the adhesive pattern does correspond to one or more desired conductive tracks, the method may include the steps of pressing conductive foil onto the adhesive pattern such that the foil adheres to the adhesive pattern; and removing the non-adhered foil in such embodiments, the additional adhesive pattern may be subject to curing as necessary.

The method may include the step of printing adhesive and subsequently applying and removing foil on both sides of the substrate. This can facilitate the construction of more complex electronics. The application of adhesive and foil to both surfaces may take place in parallel but is preferably achieved sequentially. In such embodiments, where suitable, the method may include applying additional layers of adhesive or additional layers of adhesive and foil to one or both sides of the substrate.

The folding of the substrate may facilitate conductive connection or capacitive interaction between different parts of the adhered foil. The method may include the step of making multiple folds of the substrate. This may facilitate multiple conductive connections or capacitive interactions between different parts of the foil. This can facilitate the formation of more complex assemblies.

Additionally or alternatively, the method may include the stacking together of one or more substrates with conductive tracks. Use of stacked substrates allows more complex functionality to be implemented, including but not limited to capacitive

components. Capacitive assemblies may, where appropriate be used as energy storage circuits.

Folded or stacked substrates may be retained in position by the additional adhesive pattern or by application of adhesive, as required. The adhesive may be an adhesive ink. Additionally or alternatively, folded or stacked substrates may be retained in position by use of alternative techniques including but not limited to micro-welding, soldering, conductive epoxy or adhesives or the use of fixing elements such as clamps, clips, and pinning devices and the like.

The method may include the step of mounting one or more integrated circuits on the substrate. The integrated circuits may be electrically connected to the one or more conductive tracks. The mounting may take place by use of adhesive or by use of any suitable alternative fixing techniques, including but not limited to micro-welding, soldering, conductive epoxy or adhesives or the use of fixing elements such as clamps, clips, and pinning devices and the like.

The integrated circuits may be packaged integrated circuits. The integrated circuits may be application specific integrated circuits. The integrated circuits may be adapted to perform any necessary function including but not limited to receiving, recording or transmitting data, processing data, reading or controlling sensors, controlling output devices or the like.

The method includes the additional step of providing a protective layer over the substrate surface to which the foil is affixed. The protective layer may be a lacquer or over print varnish (OPV). Examples of suitable lacquer or OPVs include but are not limited to over print varnishes used in the converting industry to protect surface printed images in the flexible food packaging sector, or encapsulation coatings used to protect flexible circuits, sensors and solar cells from the environment. Alternatively, the protective layer may be in the form of a film applied over the surface. Examples of suitable films include but are not limited to PE, PP, PET and the like. In embodiments where the protective layer is a film, an adhesive may be provided between the film and the electronic assembly. The adhesive may be applied to either the film or the electronic assembly as appropriate.

The protective layer may be applied by any suitable applicator, including but not limited to a brush, roller or one or more spray nozzles. The protective layer may be cured after application. This may be the case where the protective layer is an OPV. In embodiments where adhesive is provided between a film comprising the protective layer and the electronic assembly, the adhesive may be cured. The curing may be achieved by any suitable process including but not limited to thermal curing, UV curing, low energy electron beam curing, photonic curing, air curing or the like.

In some embodiments, the protective layer may be adapted to retain folded and/or stacked portions of the substrate and/or one or more additional integrated circuits mounted on the substrate in the appropriate position.

According to a second aspect of the present invention there is provided an apparatus for manufacturing an electronic assembly, the apparatus comprising: a printing unit operable to apply an adhesive pattern onto a surface of the substrate, the adhesive pattern corresponding to one or more desired conductive tracks; a foil applicator operable to press conductive foil onto the adhesive pattern; an adhesive curing unit operable to cure the applied adhesive such that the foil adheres to the adhesive pattern; a foil de-applicator operable to remove the non-adhered foil; and means for folding the substrate after removal of the foil..

The apparatus of the second aspect of the invention may incorporate any or all features of the method of the first aspect of the present invention as desired or as appropriate.

The substrate may be rigid. Alternatively, the substrate may be flexible. Beneficially, in such cases, the present invention further provides for the manufacture of functional flexible electronics.

The adhesive curing unit may comprise a heater, UV light source, photonic source or low energy electron beam source as appropriate.

The apparatus may comprise a substrate supply for retaining and supplying the substrate. Where the substrate is non-conductive, it may comprise any one of: polymers, paper, woven fabrics, non-wovens, timber, silicon, composite materials, or the like. Where the substrate is flexible, the substrate supply may comprise a reel upon which an elongate strip of substrate is wound. Alternatively, a sheet feed system may be provided to feed successive sheets of substrate to the apparatus.

The apparatus may comprise a surface treatment unit or other pre-treatment unit.

The apparatus may comprise substrate transport means for transporting the substrate past the successive components of the apparatus. The substrate transport means may be operable to transport the substrate from the substrate supply to the other components of the apparatus. The substrate transport means may comprise one or more belts or rollers. Any of or all of said one or more belts or rollers may be powered.

The foil applicator may comprise a roller adapted to press against the substrate and be rotated by the substrate as it is transported past the foil applicator. The foil de applicator may comprise a roller adapted to press against the substrate and be rotated by the substrate as it is transported past the foil de-applicator. The foil may be provided in an elongate strip. The elongate strip may comprise a foil layer and a backing layer.

The apparatus may comprise a foil supply for retaining and supplying the foil. The foil supply may comprise a reel upon which the elongate strip of foil is wound. Subsequent to the foil de-applicator, the foil may be transported to a foil store. The foil store may comprise a reel upon which used foil strips are stored. The used foil strips may subsequently be collected for recycling or the like.

The apparatus may comprise foil transport means for transporting the foil to the applicator and de-applicator. The foil transport means may comprise one or more belts or rollers. Any of or all of said one or more belts or rollers may be powered

The means for folding the substrate may comprise a roller, a gripping arm, or any other suitable components. The means for folding the substrate may be operable to enable multiple folds of a single substrate, where desired or appropriate. In one example, the means for folding may be adapted from a pouch making machine as is known in the relevant art.

Subsequent to the foil de-applicator, the apparatus may be provided with a protective layer applicator. The applicator may comprise a roller brush or one or more spray nozzles operable to apply a protective lacquer or over print varnish to the assembly. The apparatus may further comprise a protective layer curing unit for curing the protective layer. The protective layer curing unit may comprise a heater, UV light source or low energy electron beam source as appropriate.

Subsequent to the foil de-applicator, the substrate may be transported to a substrate store. Where the substrate is flexible, the substrate store may comprise a reel upon which substrate with formed conductive tracks is wound. This can enable multiple successive conductive tracks to be provided on a single reel for transport to an alternative processing apparatus.

In alternative embodiments, subsequent to the foil de-applicator, the substrate may be transported to a substrate cutter. The substrate cutter may be operable to cut individual conductive tracks from the substrate. The cutter may comprise a blade or a laser beam, or other slitting device.

According to a third aspect of the present invention there is provided an electronic assembly, the component comprising: a flexible substrate; an adhesive pattern applied on at least one surface of the substrate, the adhesive pattern corresponding to one or more desired conductive tracks; a conductive foil adhered on top of the adhesive pattern; and wherein the assembly comprises a folded substrate.

The assembly of the third aspect of the present invention may incorporate any or all features of the first two aspects of the present invention.

The substrate may be rigid. Alternatively, the substrate may be flexible. Beneficially, in such cases, the present invention further provide a functional flexible electronic assembly.

The substrate may be non-conductive or may be conductive. Where the substrate is conductive, it may comprise foil, metal, or graphene. The assembly may comprise an additional adhesive pattern printed over the substrate and/or foil. The assembly may include an additional conductive foil adhered to the additional adhesive pattern. The assembly may include an adhesive pattern and an adhered conductive foil on both sides of the substrate.

The substrate may comprise multiple folds. The assembly may comprise multiple layers of substrate stacked together. Such assemblies may comprise resistive, inductive and capacitive components capacitive components may be used for energy storage.

The assembly may include one or more additional integrated circuits mounted on the substrate. The integrated circuits may be electrically connected to the one or more conductive tracks. The mounting may take place by use of adhesive or by use of any suitable alternative fixing techniques, including but not limited to micro-welding, soldering, epoxy or adhesives or the use of fixing elements such as clamps, clips, and pinning devices and the like.

The integrated circuits may be packaged integrated circuits. The integrated circuits may be application specific integrated circuits. The integrated circuits may be adapted to perform any necessary function including but not limited to receiving, recording or transmitting data, processing data, reading or controlling sensors, controlling output devices or the like.

The assembly may comprise a protective layer. The protective layer may be adapted to retain folded and/or stacked portions of the substrate and/or one or more additional integrated circuits mounted on the substrate in the appropriate position.

The assembly comprise an antenna. The assembly may comprise part of an RF tag or an NFC tag. The assembly may comprise part of an energy scavenging device.

The assembly may comprise a touch sensor. In particular, the assembly may comprise a capacitive touch sensor.

The assembly may comprise a loudspeaker coil. The assembly may comprise part of a loudspeaker. In such embodiments, the assembly may be mounted adjacent to a suitable magnet. Additionally or alternatively, the assembly may be mounted on a substrate spaced apart from another article or substrate so as to provide a vibration chamber.

The assembly may comprise a device or part of a device integrated into packaging. In particular, the packaging may be food or beverage packaging. The assembly may comprise a device or part of a device integrated into a greetings card or the like.

According to a fourth aspect of the present invention there is provided an item of packaging incorporating an electronic assembly according to the third aspect of the present invention.

The item of packaging may incorporate any or all features of the third aspect of the present invention as desired or as appropriate.

Detailed Description of the Invention

In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 illustrates schematically an electronic assembly (a) in plan view and (b) in cross-section along line A- A;

Figure 2 is a schematic illustration of the steps involved in manufacturing an electronic assembly of figure 1;

Figure 3 is a schematic illustration of an embodiment of an apparatus for carrying out the method of figure 2 using a flexible substrate so as to provide an electronic assembly of figure 1;

Figure 4 is a schematic illustration of an alternative embodiment of an apparatus for carrying out the method of figure 2 using a flexible substrate so as to provide an electronic assembly of figure 1;

Figure 5 illustrates schematically alternative embodiments for applying a protective layer to an electronic assembly;

Figure 6 illustrates schematically cross-sectional views of alternative circuit assembly constructions achievable by applying variations of the method of figure 2;

Figure 7 illustrates schematically using cross-sectional views (a) and (b) construction of an electronic assembly by use of folding;

Figure 8 illustrates schematically using plan views (a), (b) construction of an electronic assembly by use of folding;

Figure 9 illustrates schematically construction of an electronic assembly by use of a folding means comprising rollers;

Figure 10 illustrates an assembly comprising a double spiral coil according to the present invention;

Figure 11 is a schematic illustration of a touch sensor according to the present invention;

Figure 12 illustrates schematically the construction of a combined touch sensor and loudspeaker according to the present invention using (a) a plan view (a) and (b) a schematic cross-section.

Turning now to figure 1 a simple low-cost electronic assembly 1 comprises a substrate 2, an adhesive pattern 3 applied on at least one surface of the substrate 2, the adhesive pattern 3 corresponding a desired conductive track; and a conductive foil 4 applied on top of the adhesive pattern. The substrate 2 can be any suitable non-conductive material, typically polymer, paper or the like. The thickness of the substrate 2 is selected depending upon the material such that it has sufficient strength for the intended use. In some embodiments, the substrate 2 may be flexible, this therefore provides a flexible electronic assembly 1.

As is shown best in figure la, the foil forms a conductive track 4 such that the electronic assembly 1 can be used as an electronic device in its own right or as a component of a larger electronic device. As one example, the assembly 1 may comprise an antenna for an electronic tag, for instance a power harvesting antenna

As illustrated in figure 2, the assembly 1 may be manufactured by the following steps. At step SI, the substrate 2 is optionally treated with plasma to improve wettability of the surface. At step S2, an adhesive 3 is applied to the surface of the substrate 2 in a pattern corresponding to a desired conductive track. Subsequently at step S3, conductive foil 4 is applied to the adhesive 3. The foil 4 may be pressed on to the adhesive 3, hence pressing the adhesive 3 onto the substrate 2, during the application step S3 or during an optional separate pressing step S4. If necessary, the adhesive 3 is cured at step S5.

At this stage, the adhesive 3 has bonded to both foil 4 and substrate 2. Accordingly, the foil 4 that is not in contact with the adhesive 3 can then be pulled away from the substrate 2 at step S6. If the foil 4 is provided on a backing layer, this can be achieved by pulling away the backing layer. Following the pulling away of the unbonded foil, a flexible circuit assembly 1 is provided at step S7, the assembly having a conductive track defined by the foil 4 bonded to the adhesive 3.

Whilst not shown in figure lb, an optional protective layer can be applied over the assembly 1 as an encapsulation method. Typically, this might be in the form of a lacquer or over print varnish (OPV) and may be applied by a brush, roller, spray nozzles or inkjet. Alternatively, the protective layer may be in the form of a film applied over the surface with a laminating adhesive in between. In either event, the protective layer is applied after the conductive track 4. Optional methods for application of a protective layer is discussed further in relation to figure 5 below.

In the event that the substrate 2 is flexible, the assembly 1 can be manufactured using an apparatus 100 as shown in figure 3. An elongate strip of substrate 2 is provided on a supply reel 110. The substrate 2 is transported from the supply means past a printing unit 120, a foil applicator 130, a curing unit 140 and a foil de-applicator 150. The substrate 2 is transported by the action of substrate transport means comprising one or more rollers 101-106. Optionally, as is shown in figure 3, the substrate 2 is subjected to plasma treatment by a plasma treatment unit 109.

The printing unit 120 in the embodiment of figure 3 comprises a print roller 121 to which is applied an adhesive pattern 122 by a gravure roller 123. In the present instance, the gravure roller 123 is an etched roller, the etching corresponding to the desired adhesive pattern. As the print roller 121 rotates in a direction opposite to that of transport roller 103, the substrate 2 passes between the print roller 121 and the transport roller 103 and adhesive 3 is applied to the substrate 2 in the desired pattern.

The foil 4 comprises an elongate strip provided on a supply reel 131. The foil strip 3 may comprise either a foil layer alone or a foil layer upon a backing layer. The foil 4 is transported by foil transport roller 132 toward the substrate 2. Subsequently, the foil 4 is pressed against the substrate 2 by foil transport roller 133 and by substrate transport roller 102. Accordingly, the foil 4 and adhesive 3 are pressed together.

The foil 4, adhesive 3 and substrate 2 are then transported past a curing unit 140. In the present example, the curing unit is operable to illuminate the passing substrate 2, adhesive 3 and foil 4 with UV radiation or an electron beam as necessary to cure the adhesive 3. Curing the adhesive causes it to bond securely to both the substrate 2 and foil 4.

The substrate 2, adhesive 3 and foil then pass foil de-applicator 150 comprising rollers 151-153. The rollers 151-153 direct the foil strip 4 away from the substrate 2. Those areas of foil 4 bonded to the substrate 32 via the adhesive 3 remain bonded whilst the remainder of the foil strip 4 is transported away. Ultimately, the remainder of the foil strip 4 is collected on a foil store reel 154. The used foil strip may be recycled if applicable.

The foil 4 bonded to substrate 2 via adhesive 3 thereby forms an electronic assembly 1 at A. If the apparatus 100 is run continuously, a series of like assemblies 1 are formed on the substrate strip 2. Subsequently, the individual assemblies 1 may be separated and/or an optional protective layer 5 may be applied over all or part of each assembly 1. Separation can be achieved by cutting the substrate 2 using a suitable cutter (not shown) such as a blade or laser.

The skilled man will appreciate that where a rigid rather than flexible substrate 2 is used, alternative substrate supply and substrate transport means may be provided, such means adapted to supplying and transporting rigid substrates 2.

Turning now to figure 4 an alternative embodiment of apparatus 100 is shown. The embodiment of figure 4 differs from that of figure 3 in that the printing unit 120 comprises an inkjet printing head 129 supplied with inkjet compatible adhesive. Additionally, the transport means is reconfigured to comprise roller 101, 102, 107 & 108. In operation rather than a fixed adhesive pattern 122 being applied on to the print roller 121 by a gravure roller 123 for subsequent application to the substrate 2, the adhesive 3 is directly applied to the substrate 3 in a desired pattern 128. Since the inkjet print head 129 may be re-tasked as necessary, it allows the formation of multiple different patterns 128a-128c successively on the substrate strip 2 at A. This can enable the on the fly formation of different assemblies la-lc or can enable the formation of assemblies la-lc comprising different components of a compound device. Where

different assemblies are formed, the cutter (not shown) should be operable to adapt to different separation requirements. As with the embodiment of figure 3, the skilled man will appreciate that where a rigid rather than flexible substrate 2 is used, alternative substrate supply and substrate transport means may be provided, such means adapted to supplying and transporting rigid substrates 2.

Turning now to figure 5a, application of a protective layer 5 in the form of an over print varnish (OPV) or lacquer is illustrated. In the example shown a series of assemblies 1 on a substrate 2 from A in figure 3 or figure 4 are passed through an applicator 160 using transport means comprising one or more rollers 111-115. Optionally, as is shown in figure 5a, the substrate 2 is subjected to plasma treatment by a plasma treatment unit 109.

The applicator unit 160 in the embodiment of figure 5a comprises a print roller 161 to which is applied an OPV or lacquer 5 from a reservoir 164 by a gravure roller 163. In the present instance, the gravure roller 163 is a plain roller, thereby providing an even coating of OPV or lacquer. As the print roller 161 rotates in a direction opposite to that of transport roller 114, the substrate 2 passes between the print roller 161 and the transport roller 114 and an OPV or lacquer protective layer 5 is applied to the substrate 2. This provides an encapsulated circuit assembly lb at B.

Optionally, the encapsulated circuit assemblies lb may be subjected to a curing unit 140 operable to illuminate the passing substrate 2, adhesive 3, foil 4 and protective layer 5 with UV radiation or an electron beam as necessary to cure the protective layer 5 and improve boding to the assembly 1.

Turning now to figure 5b, application of a protective layer 7 in the form of a laminate film is illustrated. In the example shown a series of assemblies 1 on a substrate 2 from A in figure 3 or figure 4 are passed through an adhesive applicator 170 and a film applicator 180 using transport means comprising one or more rollers 111-115. Optionally, as is shown in figure 5a, the substrate 2 is subjected to plasma treatment by a plasma treatment unit 109.

The adhesive applicator unit 170 in the embodiment of figure 5b comprises a print roller 171 to which is applied an adhesive 6 from a reservoir 174 by a gravure roller 173. In the present instance, the gravure roller 163 is a plain roller, thereby providing an even coating of OPV or lacquer. As the print roller 171 rotates in a direction opposite to that of transport roller 114, the substrate 2 passes between the print roller 171 and the transport roller 114 and an adhesive layer 6 is applied to the substrate 2

The film 7 comprises an elongate strip provided on a supply reel 181. The strip 7 may comprise either a film layer alone or a film layer upon a backing layer. The film 4 is transported by film transport roller 182 toward the substrate 2. Subsequently, the film 7 is pressed against the substrate 2 by film transport roller 183 and by substrate transport roller 115. Accordingly, the film 7 and adhesive 6 are pressed together against eth foil 4 and substrate 2. This provides an encapsulated circuit assembly lb at B.

Optionally, the film 7, adhesive 6, foil 4 and substrate 2 are then transported past a curing unit 140. In the present example, the curing unit is operable to illuminate the passing film 7, adhesive 6, foil 4 and substrate 2 with UV radiation or an electron beam as necessary to cure the adhesive 6. Curing the adhesive causes it to bond securely to both the substrate 2, foil 4 and the film 7. The skilled man will appreciate that other forms of application of a protective layer may alternatively be used if required or desired.

It is possible to form more complex assemblies 1 by repeating some of the steps of the method. For instance, this can be achieved by passing the substrate 2 through apparatus 100 on multiple occasions or by adding additional printing units 120, applicators 130 and de-applicators 150 as appropriate. For example, as is illustrated in the assembly shown in figure 6a, repetition of steps S2-S6 either by the same printing unit 120, applicator 130 and de-applicator 140 or by different units 120, 130, 150 can enable the application of an additional adhesive pattern 31 and an additional conductive foil track 41. As appropriate the additional adhesive pattern 31 and foil track 41 can lie over the original adhesive pattern 3 and foil track 4 as shown in figure 5a. The skilled man will however appreciate that the additional adhesive pattern 31 and foil conductive track 41 may not overlap or may only partially overlap the original adhesive pattern 3 and foil conductive track 4.

The example assembly shown in figure 6a can therefore provide capacitive circuit elements on the assembly. Selecting the adhesive 3, 31 with particular dielectric properties and particular thickness can enable the tuning of the capacitive components for particular applications. Alternatively, if the adhesive 3, 31 has resistive properties, such a construction can provide a resistive circuit element. Selecting the adhesive 3, 31 with particular resistive properties and particular thickness can enable the tuning of the capacitive components for particular applications.

In another example assembly shown in figure 6b, steps S2-S6 may be repeated on both sides of substrate 2 either by the same printing unit 120, applicator 130 and de applicator 140 or by different units 120, 130, 150. This provides an adhesive pattern 3, 3’ and a foil conductive trace 4, 4’ on each side of the substrate 2. The adhesive patterns 3, 3’ and foil traces 4, 4’ may be aligned on each surface as shown in figure 6b or may not be aligned as necessary. The skilled man will also appreciate that additional adhesive patterns and foil conductive tracks can be formed on either or both sides of the substrate 2 as shown in figure 6a.

A further example assembly shown in figure 6c differs from that of figure 6a in that the substrate is formed from a sheet of conductive foil 42. In this example, two overlapping adhesive patterns 3, 31 and two foil conductive tracks 4, 41 are provided on the foil sheet substrate 42. In alternative embodiments, only a single adhesive pattern 3 and track 4 may be provided, or the patterns 3, 31 and tracks 4, 41 need not overlap or one or more patterns 3’ or tracks 4‘ may be formed on the reverse side of the foil sheet 42.

The assemblies shown in figures 6b and 6c can likewise be adapted by selection of adhesive properties to implement capacitive and resistive components.

It is also possible to form more complex assemblies by additional process steps after separation. For instance, these steps might include stacking one or more (like or unlike) assemblies 1 together to form a compound assembly. Such a compound assembly may be retained in position by use of adhesive.

Another option, as is illustrated in figure 7, 8 and 9 is that the assembly 1 may be folded over. As illustrated in figure 7a, an assembly 1 is provided with an additional adhesive pattern 31 over the foil 4. If the assembly 1 is then folded as shown at figure 7b, the additional adhesive 31 will retain the assembly 1 in the folded position. The additional adhesive pattern 31 may be thinner than the adhesive pattern 3 to compensate for folding. The additional adhesive pattern 31 is selected so as to securely hold the folded assembly 1 in position so as to achieve the desired size or electronic function. For instance, folding an assembly 1 with additional adhesive 31 between foil tracks 4 can enable the formation of capacitive or resistive components on the assembly 1.

Another alterative might include the deployment of additional adhesive 31 adjacent to rather than over the foil track 4. This can enable an electrical connection to be made between different portions of the foil track 4. An example of such an assembly is shown in figure 7, which shows a simplified RFID or NFC tag. In figure 8a a conductive trace 4 has end contact 48 formed on the body portion 28 of substrate 2 and a second end contact 49 formed on the arm portion 29 of substrate 2. By making a fold along line 9, the arm portion 29 can be bent over the body portion 28 allowing the end contacts 48, 49 to come into contact as shown in figure 8b.

Turning now to figure 9, one possible embodiment of a folding means 190 is shown. In this example, the folding takes place which still on a strip of substrate 2 by use of a pair of folding rollers 191, 192. By drawing the substrate strip 2 through the folding means at a suitable orientation, the assembly 1 may be folded as required to provide a folded assembly at C. As indicated, the assembly may be a plain assembly 1 from figure 3 or figure 4 or an encapsulated assembly lb from figure 5. If the folded assembly is not encapsulated, it may be subsequently encapsulated by the methods illustrated in figure 5 or otherwise.

In some embodiments comprising folded substrates where an optional protective layer is applied, the protective layer in addition to encapsulation can help retain the folded substrate in the folded position.

The skilled man will appreciate that the invention is not confined to single folds of the substrate as illustrated in figures 7, 8 and 9 above. Where appropriate multiple folds may be used facilitating the construction of more complex components. The skilled man will further appreciate that folding can be combined with stacking and/or multiple printing steps in the construction of more complex components.

In addition to or alternatively to the above steps, an assembly may also be connected to other components or devices. In one example, this may include the connection of one or more suitable application specific integrated circuits (ASICs) to the conductive foil track 4 at appropriate positions.

Turning now to figure 10, this illustrates a coil assembly 1 comprising double spiral coil 22. in addition to antennas, such assemblies can be incorporated into touch sensors or loudspeakers as is explained further below.

Figure 11 illustrates an assembly 1 operable as a touch sensor 39. The assembly

I comprises a conductive foil track 4 in the form of a single spiral coil 21 on a substrate 2. A second substrate 25 is stacked over the first substrate 2. The second substrate 25 has an elongate conductive foil tack 45 with a bulbous end portion 46 that crosses the spiral 21 at multiple locations. Each track 4, 45 ends in a respective contact 7, 8. When a user touches the assembly 1, the capacitance of the assembly 1 is varied. This can be detected by monitoring the voltage across the respective contacts 7, 8. This voltage may be monitored by a dedicated processing unit operable to generate an output signal when the assembly is touched. The processing unit may be provided in the form of an application specific integrated circuit (ASIC) (not shown) mounted on substrate 2 and electrically connected to contacts 7,8.

Figure 12 illustrates the provision of the touch sensor assembly 39 of figure

I I on an item 30. Typically, this could be a pouch, box or the like for food or a greetings card or similar. When a user touches the assembly, the change in voltage at contacts 7,8 can be detected using an ASIC as discussed above This can trigger additional functionality from the ASIC or otherwise. In particular, if the ASIC is also operable to drive the contacts 7,8, the assembly 1 can function as a loudspeaker.

This functionality is enabled by the provision of a magnetic component 50. If magnet 50 positioned relative to the assembly 39 as shown in figure 10b, the current in the coil 21 induces a force in response to the magnetic field of magnet 50. If a current varying at an audio frequency is passed through the coil will vibrate at the audio frequency, thus producing audible sounds. To increase the volume of the audio output, the substrate 2 can be mounted on the item 30 by way of an adhesive pattern 32 printed on the reverse face of the substrate 2. If this adhesive pattern 32 is sufficiently thick, it can create a pocket behind the substrate 2 increasing the freedom of the substrate 2 to vibrate. Trapping air behind the flexible coil and sealing with the curable adhesive creates an air pocket which can increase the fidelity of sound produced on this speaker.

The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.