Transfer including an electrical component

A conductive transfer and method of producing the conductive transfer is described. The conductive transfer comprises two non-conductive layers and a conductive layer between the two non-conductive layers and at least one electrical component in electrical communication with the conductive layer. The conductive layer includes a power trace for providing a power source to the electrical component and a data trace for providing the electrical component with an electrical signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom Patent Application number 18 15 292.6, filed on 19 Sep. 2018, the whole contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a conductive transfer and a method of producing a conductive transfer.

Conductive transfers such as that disclosed by the applicant in patent publication GB 2 555 592 provide a means by which thin, lightweight, washable and stretchable conductive elements can be incorporated into flexible items, for example, wearable items such as items of clothing.

Printed circuit boards (PCBs) are also known in the art as providing suitable circuits by surface mount technology which can provide complex functionality including electronic components and are utilized in electronic devices to provide such functionality.

Combining electronic components having functionality into wearable items is traditionally problematic, and this is typically solved by providing a removable component that does not need to be thin, lightweight, washable or flexible. Such devices can be cumbersome or suffer loss of functionality when incorporated into wearable items such as clothing.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a conductive transfer in accordance with claim1.

According to a second aspect of the present invention, there is provided a method of producing a conductive transfer in accordance with claims17.

In an embodiment, a further step of curing the bonding material is performed after the at least one electrical component has been placed. The bonding material may be any suitable conductive adhesive or a solder paste. When a solder paste is utilized, the conductive transfer is cured in a reflow oven so as to melt the solder paste, which then solidifies on cooling.

The steps of printing each of the layers involve printing the layer onto a substrate or transfer film, and, following completion, the conductive transfer can be transferred or applied to a suitable surface or article typically by means of application of heat and/or pressure.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. The detailed embodiments show the best mode known to the inventor and provide support for the invention as claimed. However, they are only exemplary and should not be used to interpret or limit the scope of the claims. Their purpose is to provide a teaching to those skilled in the art. Components and processes distinguished by ordinal phrases such as “first” and “second” do not necessarily define an order or ranking of any sort.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

A conductive transfer according to the present invention is configured to be incorporated into a wearable item. In the example ofFIG. 1, a wearable item incorporating a conductive transfer in accordance with the present invention is shown and described.

Wearable item101, in this example illustrated as a jacket, such as a hi-vis jacket, comprises a conductive transfer having an electrical component in electrical communication with a conductive layer of the conductive transfer.

As the conductive transfer is incorporated into wearable item101, wearable item101appears functionally similar to a conventional jacket. However, wearable item101comprises a plurality of electrical components102and103which in this case are a plurality of illuminating devices, for example, light-emitting diodes (LEDs). Each plurality of electrical components102and103are associated with a conductive transfer incorporated into jacket101in accordance with the present invention. The conductive transfer is in electrical communication with a driving controller104which is incorporated into the wearable item and is configured to provide power and suitable signals to the conductive transfers, and consequently, each of the electrical components. It is appreciated that driving controller104may be hidden internally in jacket101rather than being externally visible.

It is appreciated that wearable item101can be any suitable wearable item other than a jacket, for example, a pair of shorts, vest, hat or other wearable item. Furthermore, it is anticipated that the conductive transfer as described herein may be incorporated into any other suitable article or device. For example, a conductive transfer as described herein may form part of a larger electronic device comprising several components including the conductive transfer.

In an alternative embodiment to that ofFIG. 1, the electrical component comprises a sensing device which is configured to measure a required parameter. For example, the sensing device may be configured to measure temperature, heat flow, light, sound, touch, biomedical data, physiological data, environmental conditions or electromagnetic waves. In one embodiment, a sensing device configured to measure environmental conditions involves measuring pollutants or gasses such as carbon monoxide so as to provide an alert to a user. In a further embodiment, the electrical component is configured to provide stimulation and is incorporated into a wearable item so as to provide stimulation to the wearer for medical purposes for example.

Electrical components in accordance with the invention, notwithstanding the examples listed above, may also be printed components. Examples include, but are not limited to, resistors, capacitors, transistors, cooling elements including Peltier coolers, sensors for determining touch, pressure, light, heat flux or temperature. In some embodiments, the conductive transfer may include a combination of both printed electrical components and physical electrical components.

A method of producing a conductive transfer suitable for the applications described in respect ofFIG. 1is illustrated diagrammatically inFIG. 2.

At step201, a first non-conductive layer is printed using a conventional ink screen-printing process to create a suitable pattern such as that which will be described in respect ofFIG. 3. In the embodiment, the first non-conductive layer is printed directly onto a substrate or transfer film. The first non-conductive layer is subsequently cured and dried at step202in anticipation of step203.

At step203, a first conductive layer is printed over the first non-conductive layer. This conductive layer will be described further with respect toFIG. 4and comprises a power trace and a data trace.

The conductive layer is subsequently cured at step204. At step205, a second non-conductive layer is printed over the first conductive layer such that the first conductive layer is positioned between the first non-conductive layer and the second non-conductive layer. As will be explained further in respect ofFIG. 5, openings may be included in the second non-conductive layer to coincide with the at least one electrical component. At step206, the second non-conductive layer is cured by heating and/or drying.

At step207, an adhesive layer is printed over the conductive and non-conductive layers to enable transfer of the conductive transfer to a surface or article such as a wearable item as previously described. The adhesive layer may also include corresponding openings to second non-conductive layer, again to coincide with the at least one electrical component. The adhesive layer may be cured following its application by means of an additional curing step as required.

Once the conductive transfer has been produced by means of steps201to207, a bonding material is applied to the first conductive layer at step208. The bonding material is applied such that the bonding material is in electrical contact with the first conductive layer. This can be achieved by suitable openings in the second non-conductive layer and the adhesive layer as described herein. At step209, at least one electrical component is attached to the conductive transfer by placing the at least one electrical component in contact with the bonding material.

In an embodiment, the bonding material comprises a conductive adhesive comprising a resin and a metallic material such as silver. It is appreciated that other suitable conductive adhesives of alternative compositions may also be utilized. In an alternative embodiment, the bonding material comprises a solder paste. A suitable solder paste comprising metal alloys is a supplied as a low-temperature solder paste by Qualitek, Wirral, United Kingdom.

The bonding material can be applied in any suitable manner to the conductive layer. It is possible to hand-place a quantity of conductive adhesive onto the conductive layer. However, in order to ensure accurate placement of the electrical component, it is also suitable to utilize a pick-and-place machine to dispense the bonding material. The pick-and-place machine in this embodiment is supplied with a syringe containing the bonding material, and configured to dispense a predetermined quantity of the bonding material at a particular position on the conductive layer.

As an alternative, a method of stencil printing which comprises printing the bonding material through a stencil can be utilized. A printer is supplied with a metal stencil which provides openings where the bonding material is required. The printer passes across the stencil, which is loaded with bonding material, such that the bonding material is pushed through the stencil into the required position on the conductive layer. This is particularly suitable for more complex circuits which may require several points of application of bonding material for several different components, for example.

Once applied, the bonding material may then be cured. In the example utilizing solder paste as the bonding material, the transfer is placed into an oven known as a reflow oven. The metal in the solder paste melts and consequently secures the electrical component(s) into place before solidifying on cooling. In the conductive adhesive example, the conductive transfer may also be placed into an oven for curing.

In further embodiments, it is possible to utilize a combination of solder paste and conductive adhesive. In an example embodiment, the solder paste may be stencil printed and the conductive adhesive may be dispensed by the pick-and-place machine.

The electrical component can be attached to the conductive transfer by alternative means. In an embodiment, the step of attaching at least one electrical component comprises utilizing a pick-and-place machine to position the electrical component(s). Pick-and-place machines of this type function by having a plurality of components, typically supplied on a reel of tape, which are removed from the reel by means of a moveable head which is programmed to place the component on a particular part of the conductive transfer. In some embodiments, a plurality of moveable heads may be provided to enable more complex electrically functional conductive transfers to be manufactured.

The pick-and-place machine can be suitably aligned with the printed layers by ensuring that markers are printed onto the substrate or transfer film to which the pick-and-place machine can optically align using a vision system. This provides precise placement of the electrical components which is also repeatable, and consequently suitable for mass production.

In an alternative embodiment, the step of attaching at least one electrical component comprises a method known as stamp transfer printing. The electrical components are provided on a source material and a transfer stamp, made from an elastomer, is configured to select a plurality of components and place them onto the conductive transfer. The transfer stamp is cleaned and reset so the process can be repeated.

Prior to applying the bonding material and attaching the at least one electrical component, a further step may be included to electrically test the printed conductive layers to ensure their functionality. This process may also be conducted following placement of the electrical component to test the circuit, individual electrical components and the entire system.

In order to provide mechanical protection and strength, and also to protect the at least one electrical component such that the conductive transfer as a whole can be washed in line with conventional washing practices, at step210, the at least one electrical component is encapsulated by applying an encapsulating material. The encapsulating material may comprise a resin-based material. This can be conducted by utilizing a dispensing syringe in a similar manner to the dispensing of the bonding material as previously described, or alternatively by means of screen printing or stencil printing.

In an alternative embodiment, the encapsulation can be achieved by utilizing a conformal coating machine which are conventionally used to spray coatings onto electrical circuitry. The encapsulating material may be any conventional conformal coating material with required properties for the application in question. For example, such a coating may include particular heat conductive properties so as to disperse or direct heat towards the electrical component. It is appreciated that following the application of the encapsulating material, a further curing step of the encapsulating material may be performed.

In each of the printing processes, it is appreciated that the printing may be conducted by any conventional printing process. In addition to screen-printing therefore, any one of the printing steps may comprise gravure printing, inkjet printing, laser printing, lithographic printing or any other suitable method.

Further details regarding the printed layers of the conductive transfer will now be described with respect toFIGS. 3 to 6of the application.

An example pattern of the first non-conductive layer in line with the example shown inFIG. 1is shown inFIG. 3. First non-conductive layer301is printed directly onto a substrate, which is typically in the form of a transfer film. Non-conductive layer301comprises a suitable printing ink which comprises a water-based printing ink, an ultraviolet cured printing ink, a silicone ink, a solvent based ink, a latex printing ink or any other suitable printing ink.

First non-conductive layer301presents a solid layer with openings302which, when the conductive transfer is completed, provide suitable access to the conductive layer so that an external electrical connection can be made.

A corresponding example pattern toFIG. 3of the conductive layer is shown inFIG. 4. Conductive layer401is printed over first non-conductive layer301as described inFIG. 2.

Conductive layer401comprises an electrically conductive ink comprising a metallic material. In the embodiment the electrically conductive ink comprises silver.

In the embodiment, conductive layer401comprises three separate traces. Traces402and403are configured to be power traces to enable power to be provided to an electrical component. A further trace404comprises a data trace for providing an electrical component with an electrical signal. Each trace402,403and404, lead to a connection point405which terminates at driving controller104shown inFIG. 1. Thus, the driving controller104can provide power to each of the power traces402and403via connection point405and electrical signals to data trace404.

In the embodiment, a voltage of zero volts (0V) is supplied to power trace402and a voltage of five volts (5V) is supplied to power trace403to ground. Data trace404is positioned central to each of the power traces and connects electrically to the power traces at points at which electrical components are to be attached so as to enable a voltage to be supplied to each of the electrical components. In the embodiment, conductive layer401is configured to receive nine (9) electrical components at each attachment point406.

In the embodiment, the nine (9) electrical components comprise an illuminating device as will be described further with respect toFIG. 7. In the embodiment, the illuminating devices are LEDs which are configured to receive an electrical signal from data trace404when in operation.

In an embodiment, conductive layer401comprises an antenna and is configured to provide a connection to one or more of the at least one electrical component. In a further embodiment, conductive layer401is printed as a touch sensor connectable to a touch controller. It is appreciated that these examples are not exhaustive and the conductive layer may be utilized in any suitable manner to provide an electrical circuit.

A further corresponding example pattern for the second non-conductive layer of the conductive transfer is shown inFIG. 5. Second non-conductive layer501comprises a suitable printing ink which comprises a water-based printing ink, an ultraviolet cured printing ink, a silicone ink, a solvent based ink, a latex printing ink or any other suitable printing ink. It is anticipated that the printing ink of second non-conductive layer501is substantially similar to the printing ink of first non-conductive layer301.

In the embodiment, non-conductive layer501comprises a plurality of openings502which correspond to the attachment points406where electrical components have been attached in the process. Thus, in this way, the electrical components are not printed over by non-conductive layer501, and protrude through non-conductive layer501.

A corresponding pattern for adhesive layer601is shown inFIG. 6. Adhesive layer601is substantially similar in terms of its pattern to second non-conductive layer501. Thus, in a similar way, a plurality of openings602are included in the adhesive layer such that the electrical components are not obscured or covered by the adhesive layer.

Adhesive layer601is suitable for adhering the conductive transfer to any suitable surface or article such as the wearable item described inFIG. 1. Adhesive layer601comprises a water-based adhesive, a solvent based adhesive, a printable adhesive, a powder adhesive or any other suitable adhesive which is capable of adhering conductive transfer to a surface or article.

It is appreciated that, any one or all of the layers described in respect ofFIGS. 3 to 6comprise, in an embodiment, stretchable inks enabling the conductive transfer to be stretchable once produced. In addition, conductive layer401may be printed sinusoidally to provide increased stretchability if required.

A suitable electrical component for use in accordance with the present invention is shown inFIG. 7. A schematic illustration of an illuminating device701is shown. In the embodiment, illuminating device701comprises an integrated LED chip such as those available from Dongguang Opsco Optoelectronics Co., Ltd., China.

Illuminating device701comprises a housing702which comprises a plurality of LEDs and a controller. In the embodiment, the housing comprises three LEDs which are each a different color, red, green and blue. Illuminating device701includes four electrodes for electrical connection. One electrode provides a power source703to the controller and LEDs. A further electrode is grounded704. The remaining two electrodes are configured to receive a control signal input705and provide a control signal output706.

When attached to conductive layer401, power trace403provides a connection to power source703and power trace402provides a connection to ground704. Data trace404provides an electrical signal which travels along data trace and provides an indication of an operating configuration such as the nature of the LEDs as being off or on or their output intensity. In the embodiment, the electrical signal is provided as a modulated waveform. Each LED is configured to receive eight bits (8b) of data from the signal with twenty-four bits (24b) being received per illuminating device. The controller in each illuminating device therefore controls the amount of data received to ensure the LEDs are illuminated as required.

Thus, once attached to conductive layer401, in use, the electrical signal is sent to a first illuminating device, for example406A, which receives twenty-four bits (24b) from the data trace, before the next twenty-four bits (24b) are provided to the next illuminating device,406B.

A schematic cross-sectional view of a conductive transfer801in accordance with the present invention is shown inFIG. 8. It is appreciated that the view is for diagrammatic purposes only and not to scale.

Conductive transfer801comprises a substrate802onto which the non-conductive layers and conductive layers are printed in line with the process previously described herein. In the embodiment, substrate802is a polyester film. In an alternative embodiment, substrate802comprises a paper film, coated paper or thermoplastic polyurethane (TPU).

Conductive transfer801further comprises first non-conductive layer803, second non-conductive layer804and first conductive layer805between first non-conductive layer803and second non-conductive layer804. From the cross-sectional view shown, it can be seen that conductive transfer801comprises a plurality of electrical components806, with three across this particular cross-section. As described previously, conductive layer805comprises a power trace and a data trace for providing a power source and an electrical signal to each of the electrical components as necessary. Thus, each electrical component is in electrical communication with conductive layer805.

In the embodiment, conductive transfer801further comprises an encapsulating material807which protects each of the electrical components such as from debris, dirt, fluid or moisture. Each part of the encapsulating material807is configured to encapsulate each electrical component. Conductive transfer801further comprises an adhesive layer808which is utilized for attaching conductive transfer801to a surface or article.

It is appreciated that, the embodiment shown herein is suitable for the application as described inFIG. 1. However, it is further appreciated that, in alternative embodiments, the layers of the conductive transfer could be reversed to account for the directionality of alternative electrical components. This can be achieved by transferring the whole conductive transfer onto a further substrate and utilizing a further adhesive that is responsive to ultraviolet light.

A schematic cross-sectional view of a conductive transfer901in another embodiment in accordance with the present invention is shown inFIG. 9. It is appreciated that the view is for diagrammatic purposes only and not to scale.

Conductive transfer901comprises a substrate902which is substantially similar to substrate802of conductive transfer801. Thus, substrate902may be a suitable polyester film, a paper film, coated paper or thermoplastic polyurethane (TPU).

Second conductive layer907forms an electrical connection with first conductive layer906. Third non-conductive layer905comprises an electrical pathway or via to provide the electrical connection, and in the embodiment, the electrical pathway comprises two openings908in third non-conductive layer905. Thus, when third non-conductive layer905is printed, it is printed in such a way that openings908are present and the pattern printed is broken. Thus, when conductive layer907is overprinted in line with the process described herein, the conductive ink of conductive layer907prints into the openings908thereby forming the electrical pathway and connection.

Conductive transfer901also comprises a plurality of electrical components909, with three shown across this particular cross-section.

In accordance with the invention, each electrical component is in electrical communication with at least one of conductive layers906and907and at least one of the conductive layers provides a power trace and data trace to communicate with the electrical components as necessary.

It is appreciated that, while the example ofFIG. 9shows two conductive layers, any other number of conductive layers and combination of conductive layers and non-conductive layers may be utilized so as to create electrical devices of increased complexity. This provides a cheaper and easier alternative to conventional PCBs which may include a plurality of similar layers with increased functionality, but which require significant post processing to include vias similar to the conductive pathway ofFIG. 9. In particular, this process in regard to the conductive transfer can be easily included without substantial addition to the process.

Following the production of the conductive transfer as described herein, the conductive transfer can be applied to a surface of an article such as the wearable item described in respect ofFIG. 1.FIG. 10illustrates the process of applying a conductive transfer to a surface of an article.

At step1001a conductive transfer is obtained before being positioned in a suitable location on a surface to which the conductive transfer can be applied at step1002.

Once the conductive transfer is in position, heat, pressure, or a combination of heat and pressure is applied to both the transfer and the surface at step1003. This allows the conductive transfer to adhere to the surface due to the adhesive layer of the conductive transfer.

In the embodiment, heat and pressure is applied by means of a heat press. Conventional heat presses typically comprise a rigid surface onto which the pressing is affected. This presents a problem in that damage can be caused to the electrical components on conventional machines. In one embodiment, an air-filled pad is supplied underneath the press such that, when the electrical components impact the air-filled pad they are not damaged. In an alternative embodiment, the heat press is supplied with a stencil which aligns with the at least one electrical component such that, when the force from the heat press is applied, the electrical components do not receive the force while the rest of the conductive transfer does. This can also work to protect the electrical components from heat as necessary.

Once adhered, the article now comprising the conductive transfer can be removed from the machine for applying heat and/pressure with the transfer now attached. The substrate onto which the non-conductive and conductive inks are printed can then be removed from the conductive transfer at step1004such that the article retains the conductive transfer and electrical components therein.

It is appreciated that, prior to the application of the transfer to a surface or an article, the electrical components and conductive transfer may be suitably tested for functionality to ensure they are working effectively. This allows for fully functioning conductive transfers to be provided to third parties for their own application to articles as necessary. However, it is further appreciated that further testing may also take place after the application stages to ensure the functionality of the conductive transfer following application.

Thus, the present invention allows for a transfer with increased functionality which can be applied to any suitable article having a surface and provides an electrically conductive circuit within the article with functions with an integral electrical component. The conductive transfer also retains the durability required to be able to withstand conventional cleaning or washing processes.