GB2460071A

GB2460071A - Printed Circuit Board Including a RFID device

Info

Publication number: GB2460071A
Application number: GB0808869A
Authority: GB
Inventors: Nigel Patrick Rogers
Original assignee: LYNCOLEC Ltd
Current assignee: LYNCOLEC Ltd
Priority date: 2008-05-15
Filing date: 2008-05-15
Publication date: 2009-11-18
Also published as: GB0808869D0

Abstract

A printed circuit board (14) includes an RFID device (12) embedded between layers (4) of the circuit board as an anti-counterfeiting or product tracking means. The circuit board may be formed by laying up multiple layers of pre-preg material (4, 8) and copper layers (2, 10) and subjecting to heat and pressure. The RFID device is preferably interposed between layers of fibre material that are bonded with resin. The RFID contains a memory that stores a unique identifier of the PCB and an antenna for receiving an interrogation signal and transmitting the PCB's identifier. The RFID tag may facilitate remote inspection of images of the PCB (14) as it is being made, for example by sending the images over the internet to a customer. The circuit board may be used in the aerospace industry.

Description

Printed Circuit Board Including Anti-Counterfeiting Means

Background of the Invention

The present invention concerns printed circuit boards including anti-counterfeiting means and/or identification code data and a method of manufacturing such printed circuit boards, with particular application in the aerospace industry.

In certain industries, including in particular the aerospace industry, it is important to be able to trace reliably the origins of a printed circuit board (PCB) in order to ensure quality control and to avoid use of counterfeit components. Means provided to enable a manufacturer and other parties in a supply chain to track, and trace the origins of, a PCB during its lifetime have previously included marking the PCB with a unique code. The unique code may for example be in the form of a serial number, bar-code or the like. Simply marking products with a visible code is however prone to counterfeiting and tampering. There is a need therefore to provide a more sophisticated means of tracing and tracking the origins of a PCB.

In the aerospace industry it has been proposed to use RFID tags to enable ready access to information concerning the various components used on a product. Simply attaching an RFID tag to a particular component has the benefit of enabling simple manufacture of such a component and tag combination (using existing manufacturing methods and attaching the tag as a final bolt-on step) , but suffers from potential disadvantages such as ease of tampering and damage to the tag and possible vulnerability to counterfeiting by those determined to produce counterfeit components.

US 2006/0109119 discloses an RFID tag fabricated on a printed circuit board. The disclosure of US 2006/0109119 relates to the fabrication of an RFID tag circuit onto a PCB, * -2-or onto a whole layer of a multi-layer PCB. In order to adapt an existing PCB design it is therefore necessary either to change the layout of a layer of the PCB to make room for an RFID tag circuit, or alternatively to add a further layer to the printed circuit board, the layer being dedicated to the RFID tag circuit. Either alternative has disadvantages, namely either time-consuming redesign of a circuit or addition of a whole new layer to the printed circuit board which may be undesirable as a result of space, flexibility or mass constraints.

The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved printed circuit board including anti-counterfeiting means and/or an improved method of manufacturing a printed circuit board including anti-counterfeiting means. Alternatively or additionally, the present invention seeks to provide a printed circuit board which allows product tracking but which removes the need to add serial numbers on the exterior of the circuit board.

Summary of the Invention

The present invention provides a printed circuit board including an identification device embedded wholly within the circuit board, the device including antenna means for receiving and transmitting data, a memory on which there is stored a unique identity reference, and a control unit arranged to transmit via the antenna means data representing the unique identity reference in response to an interrogation signal received by the antenna. The identification device may form part of an anti-counterfeiting means. The identification device may form part of an anti-tampering means. The identification device may facilitate product tracking.

* . -3-By embedding the identification device wholly within the circuit board, the identification device is protected from possible damage or tampering. Furthermore, it is hoped that the extra difficulties associated with embedding an identification device wholly within the circuit board, as opposed to simply attaching an identification device onto the circuit board at the end of the assembly process, will deter counterfeiters. As a result of being embedded wholly within the circuit board, the identification device is spaced apart from all external surfaces of the circuit board.

The identification device may be arranged to receive and transmit signals at radio frequencies. The identification device may be in the form of an RFID device. The identification device may be in the form of a prefabricated device, for example a prefabricated RFID device manufactured as a stand-alone component. The prefabricated device preferably performs no function other than that of an identification device. The prefabricated device will typically be smaller than, for example less than 5% of the volume of, the PCB. The board (or other equivalent means) on which the identification device is fabricated preferably has an upper surface having an area which is less than 10% of the area of the upper surface of the PCB.

The antenna means may consist of a single antenna.

Alternatively, the antenna means may comprise more than one antenna.

The identification device may include a power source for powering the control unit, such as for example a battery.

Preferably, the identification device includes a power unit arranged to convert the electromagnetic radiation carrying an interrogation signal into electrical energy for powering the control unit. A passive REID tag is characterised by having such a power unit. The antenna may perform the function not only of receiving and transmitting signals but also assist in converting the electromagnetic radiation into electrical energy for powering the control unit.

The identification device is preferably a stand-alone component separate from any circuits that the circuit board might ever form. The circuit board will typically comprise conductive paths for forming one or more circuits independent of the identification device. Components may be electrically connected to such conductive paths. Preferably, all of such conductive paths are electrically isolated from the identification device. Preferably, none of such conductive paths run in the same plane in the circuit board as the identification device. The conductive paths may be formed on a plurality of different layers in the board. The printed circuit board may for example be a multilayer PCB. The printed circuit board may comprise a core layer having conductive material on at least one of its bottom and top surfaces, and preferably both surfaces. The PCB may be formed from more than 10, and possibly more than 20, layers of material.

The printed circuit board preferably comprises layers of fibre material bonded with resin and the identification device is preferably interposed between two fibre layers. The identification device may be directly interposed between two fibre layers. In such a case, the two fibre layers are bonded directly to each other in certain regions of the circuit board. Alternatively, the identification device may be separated from at least one of the two fibre layers by another layer of material.

The identification device is preferably relatively thin.

The identification device may have a maximum thickness of less than 0.15mm. The identification device may have a maximum thickness of about 0.1mm or less. Each of the two fibre layers, between which the identification device is interposed may have a thickness of between 0.08mm and 0.18mm, and preferably between 0.1mm and 0.14mm. Each of the two fibre layers preferably has a resin content of between 50% and 60%, by weight. Each of the two fibre layers preferably have a fibre density of between 100 x 100 ends per 5cm and 130 x 130 ends per 5cm (the number of weft and warp thread ends being counted in a 5cm by 5cm square) . The number of weft thread ends per 5cm is preferably no more than 10% different (and more preferably no more than 5% different) from the number of weft thread ends per 5cm.

The printed circuit board may have an average thickness of less than 2mm.

The memory is preferably an electronic memory device.

The memory may be in the form of write-once read-many memory.

The unique identity reference may be hard-wired into the memory.

The control unit may comprise a processor. The control unit could alternatively be in the form of a simple electronic circuit.

According to a further aspect of the present invention, there is provided a multilayer printed circuit board including a product tracking device in the form of a prefabricated passive RFID tag sandwiched between two layers of fibre reinforced composite material. The RFID tag may be wholly embedded within the POB. There may be a continuous region that completely surrounds the RFID tag in which the two layers between which the RFID tag is sandwiched are directly bonded together. The product tracking device may be in the form of an anti-counterfeiting device.

The present invention also provides a method of manufacturing a printed circuit board comprising fibre-reinforced composite material, the method including performing the following steps: laying up a plurality of layers of material for forming the circuit board, the layers including fibre layers and a * -6-layer comprising electrically conductive material for forming at least part of the circuit of the printed circuit board, arranging an identification device between two fibre layers, the identification device including antenna means for receiving and transmitting data, a memory on which there is stored a unique identity reference, and a processor arranged to transmit via the antenna means data representing the unique identity reference in response to an interrogation signal received by the antenna, providing resin material for bonding together the fibre layers, and applying pressure and heat to the lay-up so formed thereby bonding the layers together.

Thus, performance of the method of the present invention will produce a printed circuit board including an identification device positioned between two fibre layers bonded together by resin. Preferably, the identification device is positioned between two fibre layers so that the identification device is embedded wholly within the circuit board.

In view of the heat and pressure needed to bond together the layers of material the characteristics of the layers of material forming the circuit board need to be selected with care. If the fibre layers adjacent to the identification device are too thin or too flexible, then the lack of effective cushioning may cause unacceptably high stress concentrations in the identification device when pressure is applied, leading to possible damage to the identification device. On the other hand, if the fibre layers adjacent to the identification device are too thick or too inflexible, then the bonding between layers in the region of the identification device may be adversely affected. Also, such inflexibility in the layers adjacent to the identification device may also result in stress concentrations in the identification device during the application of heat and pressure.

The method may include a step of creating a unique identity reference for the printed circuit board and then storing on the memory of the identification device a unique identity reference. Alternatively, the identification device may be provided in a form in which the unique identity reference is already stored in the memory of the device.

The method may include a step of recording in an electronic database the unique identity reference stored on the memory of the identification device associated with the printed circuit board together with other data concerning the printed circuit board. The other data may include data of manufacture, and the name of the company to which the PCB is being supplied. Alternatively, or additionally, such other data may be recorded on the memory of the identification device. Further amendments or additions to the data recorded on the memory of the identification device may be made during the lifetime of the PCB.

The step of applying pressure and heat to the lay-up may include exposing the lay-up to a pressure of greater than lOkPa for a period of greater than a minute, and preferably for greater than ten minutes, and possibly greater than an hour.

The step of applying pressure and heat to the lay-up may include exposing the lay-up to heat such that the internal temperature of the lay-up reaches at least 150° Celsius for at least a minute, and preferably for greater than ten minutes, and possibly greater than an hour.

The layers of material may include at least two layers of electrically conductive material. The circuit board manufactured by the method is preferably a multi-layer board.

The method may include a step of providing a core layer of fibre-reinforced composite material on which there are * -8-included electrically conductive tracks arid then sandwiching the core layer between other layers. The layers of material may comprise conductive material on one or both faces of the core layer.

Each fibre layer may comprise a layer of glass cloth.

Each fibre layer may be in the form of a sheet of pre-preg material. The steps of providing the fibre layers and of providing the resin material for bonding together the fibre layers may be performed simply by means of providing one or more sheets of pre-preg material.

The step of arranging the identification device between two fibre layers may be performed by sandwiching the identification device between two layers of pre-preg.

The particular sizes and dimensions of the various constituent parts that together enable the method to be performed may need to be chosen carefully to enable the method to be performed adequately. The identification device may have a maximum thickness of less than 0.15mm. The identification device may have a footprint having an area of less than 10 cm2, and preferably less than 5 cm2. The printed circuit board may have an average thickness of less than 2mm.

The printed circuit board may have a footprint having an area greater than that of the identification device, typically at least an area that is two times greater than that of the identification device. Each layer of pre-preg may have a thickness of between 0.08mm and 0.18mm and a resin content of between 50 and 60%, by weight. Each fibre layer is preferably formed of cloth which preferably has a thickness (without resin and before pressing) of between 0.06mm and 0.15mm, preferably about 0.1mm. Each fibre layer is preferably formed of pre-preg cloth which has a thickness (with resin, after pressing) of between 0.08mm and 0.18mm, preferably about 0.11mm. S -9-

Each fibre layer is preferably formed of cloth which preferably has a weight of between 80 gm2 and 200 gm2, preferably about 110 gm2.

According to yet a further aspect of the invention there is provided a method of facilitating remote inspection of the manufacture of a printed circuit board including a step of manufacturing a printed circuit board ordered by a customer.

The printed circuit board may be manufactured in accordance with any aspect of the invention described herein.. The method according to this aspect of the invention advantageously includes a step of filming images of the printed circuit board whilst it is being manufactured. The method advantageously includes a step of detecting, for example by means of sending an interrogation signal, the unique identity reference stored on the memory of the identification device of the printed circuit board being filmed. The method advantageously includes a step of associating the unique identity reference stored on the memory of the identification device of the printed circuit board with a unique customer reference assigned to the customer. The method advantageously includes a step of electronically sending, to a remote user, images of the printed circuit board in response to receipt of electronic data that identifies at least one of the customer and the printed circuit board. The customer may therefore view remotely images of the printed circuit board during or shortly after it is being manufactured.

The step of sending images may be conducted automatically. The step of sending images may be conducted substantially in real time. The method may include a step of receiving a request, for example an electronic request, to view images relating to a particular circuit board or a particular group of circuit boards. The request may be sent over the internet. The images may be sent over the internet.

The transmission of data over the internet is preferably conducted in a secure manner, for example by means of encrypting the data.

The electronic data identifying the customer and/or the printed circuit board may include data verifying that the user has permission to view the images. The method may include a step of verifying that the user has permission to view the images before such images are sent. The method may include a step of indicating to a user that images will not be sent to the user in response to a failure to verify that the user has permission to view the images of a printed circuit board ordered by a particular customer.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figure 1 shows a schematic sectional side view of separate layers for forming a PCB according to a first embodiment of the invention; Figure 2 shows a schematic sectional side view of the layers of Figure 1 bonded together in the form of a finished PCB; and Figure 3 shows a schematic diagram illustrating a second embodiment of the invention facilitating remote inspection of the FOB of Figures 1 and 2.

O -11-

Detailed Description

Figure 1 shows a plurality of layers of material for forming a printed circuit board (PCB) . The layers include a top layer 2 of copper foil, two upper layers 4 of pre-preg material, an inner core layer 6, two lower layers of pre-preg material and a bottom layer 10 of copper foil. The inner core layer 6 is in the form of a pre-formed fibre reinforced composite material on which upper and lower conducting layers 6a, 6b have been etched. The inner core has a thickness of about 1.06mm. The material forming the bulk of the core layer 6 (between the copper layers 6a and 6b) is formed of fibre glass material (layers of glass fibre cloth cured in a resin matrix) The layers of pre-preg material 4, 8 are in the form of 2116 pre-preg layers. 2116 pre-preg material comprises a single ply of woven glass cloth impregnated with a blended epoxy resin which is then partly polymerised to a SB-stage".

The cloth thickness before impregnation with resin is about 0.089mm having a weight of about 109 g per square meter. The weight of the material including resin is about 196 g per square meter. The number of strand ends per 5 cm of 2116 pre-preg is 118 x 114. The resin content of the material is about 55%.

2116 pre-preg material is particularly suitable for use in the present method of manufacturing PCB, with an integrated RFID tag because the pre-preg is very even in terms of the thread count and the strand size. For example, the warp and weft are almost identical in terms of thread count. It is also suitable as a result of the filament diameter and strand size. If the strand size were significantly thicker, the bonding between the pre-preg layers in the region of the RFID tag might be adversely affected. Also, if the strand thickness were either significantly thinner or significantly thicker, the RFID tag might be crushed and damaged under the heat and pressure applied. For example, a trial using 1080 pre-preg material (a finer class of pre-preg having a fine weave and a low pressed ply thickness) th RFID tag was damaged. In this case it is believed that the chip was damaged as a result of lack of cushioning by the pre-preg material as a result of the thinness of the layers. Also, a trial using 7628 pre-preg material (a thicker and more rigid material) also resulted in damage to the RFID tag. On this occasion it is believed that the lack of flexibility resulted in stress concentrations during application of pressure in the region of the RFID tag. Thus, the choice of pre-preg material must be thick enough to provide cushioning and even distribution of pressure across the layer of pre-preg material during application of pressure, but not so thick that the layer is too rigid. Similar thread counts in the warp and weft directions is also considered to be important.

During manufacture of a PCB the layers 2, 4, 6, 8, 10 of the PCB are built up to form a layup. In the present embodiment an RFID tag 12 is positioned between the two upper layers 4 of pre-preg material. As will be seen in Figure 1, the edge of the prefabricated RFID device 12 is spaced apart from the left-hand edge of the pre-preg material 4. The position of the RFID tag 12 needs to be chosen in view of the layout of the conductive tracks on the conducting layers 2, 6a, 6b, 10 and also in view of positioning of components on or in the PCB that might interfere with the RFID tag 12. For example, if holes need to be drilled through the PCB after it is formed, the RFID tag 12 must obviously not be positioned near to where a hole needs to be drilled.

It is also important that the tag 12 is positioned so that it is wholly embedded within the pre-preg layers 4 and bounded on all sides by bonded pre-preg 4. If the RFID tag 12 * -13-were positioned on the outside surface of the finished PCB, it might be susceptible to damage or tampering. Also, if the RFID tag 12 is embedded within the PCB but is positioned directly on the edge of the PCB so that it is not surrounded on all sides by pre-preg layers 4 bonded together then there may be problems associated with the delamination of the layers 4 of the PCB in the region of the shared edge.

The RFID tag 12 is in the form of a RFID device including an antenna, memory on which a unique identification code is stored, and a control unit for causing a signal to be transmitted via the antenna with details of the identification code stored on the memory, if and when the control unit detects that an interrogation signal has been received via the antenna. The RFID device 12 in the present embodiment is in the form of a passive RFID tag requiring no external power source. The electrical power required for causing a return signal in response to receipt of an interrogation signal is derived from the electromagnetic radiation energy carrying the interrogation signal. Such passive RFID tags are readily available in prefabricated form. In the present embodiment the RFID is provided with a unique identification code already stored in the memory. The memory in this embodiment is a write once read many times memory and no other data is stored in the memory of the RFID device. The memory may therefore be very simple in form. The copper layers 2, 10 have a thickness of about 20 microns, but may in other embodiments have other thicknesses; typical thicknesses ranging from 9 to 70 microns.

The RFID tag has a thickness of about 0.1mm arid a rectangular footprint measuring 25mm x 12mm.

Once the layers 2, 4, 6, 8, 10 for forming the PCB have been arranged and aligned to the form the laup, the layup is exposed to heat and pressure in an autoclave device. In the present embodiment the pressure applied is 20 ton per square foot at a temperature of 180° Celsius for a period of 90 minutes. Figure 2 shows the FOB 14 comprising the various layers 2, 4, 6, 8, 10 once they have been bonded together.

Each layer of pre-preg material 4, 8 in the finished FOB has a pressed ply thickness of about 0.113mm. The finished PCB has a thickness of about 1.6mm. After the FOB has been cured in the autoclave, an RFID reader device is used to test the function of the RFID tag 12. The unique code assigned to the tag 12 of the circuit board 14 is then stored in a computer database together with other data concerning the characteristics of the manufacture, such other data including the date of manufacture, the details of the customer and a brief description of the type of FOB produced. If ever there are queries concerning the history or origins of the FOB the unique identification code stored on the memory of the RFID tag 12 can then be used to extract details from the database to provide the information required, or to reveal that the FOB in question is a counterfeit board or one produced by another supplier/manufacturer. The data concerning the history of the FOB 14 may of course be supplied to other parties within the supply chain.

The curing of the layers of the FOB may be carried out as a batch process such that other FOBs are formed simultaneously. In such cases the layers for forming individual FOBs may themselves be arranged in a stack, being separated by suitable separator plates before heat and pressure is applied.

The copper layers 2, 10 may subsequently be etched to provide further conductive tracks on the multilayer FOB device in accordance with standard techniques known in the art.

One advantage provided by means of embedding an RFID tag in a circuit board, in the manner described above with reference to Figures 1 and 2, is that the circuit board may then be tracked reliably during subsequent manufacturing steps. Figure 3 shows a second embodiment of the invention in which a PCB 14 is manufactured in such a way that the customer, or someone authorised by the customer, can view the PCB as it is being made by means of a secure data transfer over the internet. The steps of the method of this embodiment are described below.

A customer orders one or more printed circuit boards according to a particular specification. Other customers may also place orders for one or more printed circuit boards according to different specifications. Each customer is assigned a unique customer refrence in a database stored on a central computer system 24 in the premises where the PCBs are made.

For each PCB being produced, the printed circuit board 14 is initially manufactured in accordance with the method of the first embodiment as described above and thus each PCB 14 includes an embedded RFID tag 12. The RFID tag 12 of each PCB 14 has a unique code, the RFID tags typically being provided in sets with sequential codes hard-written into the RFID tags in each set.

Further manufacturing/assembly steps are performed in an assembly line. The assembly line comprises a plurality of work areas 20a, 20b. For example, components may be added to, and then soldered to, the PCB. During these further manufacturing/assembly steps, images (preferably video images) of the printed circuit board are filmed at each station 20a, 20b by a camera 16. Images from the cameras 16 are sent to the central computer system 24. An RFID scanner 18 at each station also detects, by means of sending an interrogation signal and interpreting a response signal from the RFID tag 12, the unique identity reference stored on the RFID tag of the printed circuit board 14 at the station.

Data concerning the unique identity reference of the PCB at each station is collected by the central computer system 24. The computer system 24 holds various data concerning each * -16-PCB including for example details of the customer, the type of PCB, the deadline for delivery, the purchase order number, the job number and the RFID's unique identity code. It will be appreciated that in the database each PCB may be assigned an RFID code before the RFID is embedded in the PCB.

A computer user, acting under the permission of a customer, is able to view images 14', on a remote computer 22, of the CBs 14 being made to order for the customer. The user enters via a secure Internet connection a user name and password on a program running on the central computer 24. The central computer 24 identifies the customer and from both the database stored on the computer system 24 and the data sent from the RFID scanners 18 ascertains which if any stations 20a, 20b have PCBs at them that are being made for the customer. The user then receives details of any PCB5 being made that can be viewed, and possibly details of other PCBs previously made (possibly with archived images for viewing) or POBs to be made in the future. The user can then select a camera to view live images of the PCB being processed at one of the assembly stations 20a, 20b. In response to such a request, the central computer 24 automatically streams live images via the secure internet connection to the remote computer 22.

The method of this embodiment allows a customer to automatically view live images of his product being produced whilst denying access to such images by others.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

The layers forming the PCB could be greater or fewer in number. The invention has application to single layer PCBs, * -17-that is a PCB having a single conductive layer but being manufactured from at least two layers of pre-preg material.

Whilst glass cloth based pre-preg material has been described, other materials, such as carbon fibre, may be appropriate in certain applications. The memory of the RFID tag could be re-writable and could be used to store other data.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

Claims 1. A printed circuit board for use in the aerospace industry including anti-counterfeiting means, wherein the anti-counterfeiting means includes an identification device embedded wholly within the circuit board, the device including antenna means for receiving and transmitting data, a memory on which there is stored a unique identity reference, and a control unit arranged to transmit via the antenna means data representing the unique identity reference in response to an interrogation signal received by the antenna.
2. A printed circuit board according to claim 1, comprising layers of fibre material bonded with resin and the identification device is interposed between two fibre layers.
3. A printed circuit board according to claim 1 or claim 2, wherein the identification device has a maximum thickness of less than 0.15mm.
4. A printed circuit board according to claim 3, when dependent on claim 2, wherein each of the two fibre layers has a thickness of between 0.03mm and 0.18mm, a fibre density of between 100 x 100 ends per 5cm and 130 x 130 ends per 5cm, and a resin content of between 50 and 60%, by weight.
5. A printed circuit board according to preceding claim, wherein the printed circuit board has an average thickness of less than 2mm.
6. A method of manufacturing a printed circuit board comprising fibre-reinforced composite material, the method including performing the following steps: laying up a plurality of layers of material for forming the circuit board, the layers including fibre layers and a layer comprising electrically conductive material for forming at least part of the circuit of the printed circuit board, arranging an identification device between two fibre layers, the identification device including antenna means for receiving and transmitting data, a memory on which there is stored a unique identity reference, and a processor arranged to transmit via the antenna means data representing the unique identity reference in response to an interrogation signal received by the antenna, providing resin material for bonding together the fibre layers, and applying pressure and heat to the lay-up so formed thereby bonding the layers together.
7. A method according to claim 6, including a step of recording in an electronic database the unique identity reference stored on the memory of the identification device associated with the printed circuit board together with other data concerning the printed ircuit board.
8. A method according to claim 6 or claim 7, wherein the step of applying pressure and heat to the lay-up includes exposing the lay-up to a pressure of greater than l0kPa for a period of greater than a minute.
9. A method according to any of claims 6 to 8, wherein the step of applying pressure and heat to the lay-up includes exposing the lay-up to heat such that the internal temperature of the lay-up reaches at least 150° Celsius for at least a minute.
10. A method according to any of claims 6 to 9, wherein the step of laying up the plurality of layers of material for forming the circuit board, includes providing a core layer of fibre-reinforced composite material on which there are included electrically conductive tracks and then sandwiching the core layer between other layers.
11. A method according to any of claims 6 to 10, wherein the identification device has a maximum thickness of less than 0.15mm, the step of laying up the plurality of layers of material for forming the circuit board is performed by means of laying up a plurality of layers of pre-preg, each layer of pre-preg having a thickness and resin content such that, after the step of applying pressure and heat to the lay-up has been completed, each layer of pre-preg has a thickness of between 0.08mm and 0.18mm, a fibre density of between 100 x 100 ends per 5cm and 130 x 130 ends per 5cm and a resin content of between 50 and 60%, by weight, and the step of arranging the identification device between two fibre layers is performed by sandwiching the identification device between two layers of pre-preg.
12. A method of facilitating remote inspection of the manufacture of a printed circuit board, the method including performing the following steps: manufacturing a printed circuit board ordered by a customer, such manufacturing including performing a method according to any of claims 6 to 11, filming images of the printed circuit board whilst it is being manufactured, detecting, by means of sending an interrogation signal, the unique identity reference stored on the memory of the identification device of the printed circuit board being filmed, associating the unique identity reference stored on the memory of the identification device of the printed circuit board with a unique customer reference assigned to the customer, sending images electronically, to a remote user, of the printed circuit board in response to receipt of electronic data that identifies at least one of the customer and the printed circuit board.
13. A method according to claim 12, wherein the step of sending images is conducted automatically and substantially in real time.
14. A method according to claim 13, wherein the electronic data identifying at least one of the customer and the printed circuit board includes data verifying that the user has permission to view the images and the method includes a step of verifying such permission before such images are sent.
15. A method according to claim 14, wherein the method includes a step of indicating to a user that images will not be sent to the user in response to a failure to verify that the user has permission to view the images of a printed circuit board ordered by a particular customer.
16. A method of facilitating remote inspection of the manufacture of a printed circuit board, the method including performing the following steps: manufacturing a printed circuit board including an RFID tag on which there is stored a unique identity reference, filming images of the printed circuit board whilst it is being manufactured, detecting, by means of sending an interrogation signal, the unique identity reference stored on the RFID tag of the printed circuit board being filmed, associating the unique identity reference stored on the RFID tag of the printed circuit board with a unique customer reference assigned to the customer, sending images electronically to a remote user of the printed circuit board in response to receipt of electronic data that identifies at least one of the customer and the printed circuit board.
17. A multilayer printed circuit board including a product tracking device in the form of a prefabricated passive RFID tag sandwiched between two layers of fibre reinforced composite material.