GB2588382A

GB2588382A - Method of manufacturing a smart card

Info

Publication number: GB2588382A
Application number: GB1914884.0A
Authority: GB
Inventors: Colussi Steven; Snell Devin
Original assignee: Zwipe AS
Current assignee: Zwipe AS
Priority date: 2019-10-15
Filing date: 2019-10-15
Publication date: 2021-04-28
Also published as: GB201914884D0

Abstract

An electronic circuit inlay 30 for a smartcard is provided by a substrate formed of plastic and a fibre reinforced epoxy composite. The electronics inlay 30 also comprises contacts 32 for electrical connection to a smart card component, with holes 42 provided through the substrate 30 adjacent to the contacts 32. Formation of a card body includes laminating the electronic circuit inlay between first (22, figure 4) and second (24, figure 4) layers of material, which causes the 1st and 2nd materials (22, 24 figure 4) to be bonded together around the circuit layer 30 and also through holes 42 in the substrate 30. The preferred smartcard includes a biometric fingerprint sensor 40 in a cavity 50 and processing modules 37, 38. The substrate preferably comprises polyamide, polyethylene terephthalate (PET), glycol modified PET (PETG), polytetrafluoroethylene (PTFE) or glass reinforced epoxy (FR-4). A solder mask 39 is preferably formed around the contacts 32, especially a printed or sprayed liquid or dry film photoimageable mask (LPSM, DFSM) 39. Smart or integrated circuit cards can identify and authenticate the user preventing unauthorised use of credit cards.

Description

METHOD OF MANUFACTURING A SMART CARD

The present invention relates to a method of manufacturing a smart card. A smart card, sometimes known as an integrated circuit card, is a pocket-sized card with an embedded electronic circuit. A smart card typically contains volatile and non-volatile memory and microprocessor components.

Smart cards are often manufactured by hot lamination of a circuit assembly between two layers of plastic to form a card body. Polyvinyl chloride (PVC) is commonly used for this purpose as it softens before it oxidises and, at suitably high temperatures and pressures, will flow and conform to the shape of components of the circuit assembly. When using PVC, or similar substances, the laminating temperatures required for hot lamination can be as high as 250°C.

Smart cards provide a way of authenticating the bearer of the card and carrying a secure message from the card to a reader. For example, if a "non-small' credit card were to be lost or stolen, an unauthorised user would be able to use the credit card until the credit card is cancelled. Conversely, a "smart" credit card may include additional levels of security that would prevent such use by an unauthorised user. One such security measure that may be used with a smart card is the analysis of biometric data to positively identify the bearer of the card.

A biometric security measure may be added to a smart card through the addition of a biometric sensor, such as a fingerprint sensor, on the card. In the case of a fingerprint sensor, when the card is to be used, the bearer presents their finger or thumb to the sensor which then positively authenticates the owner of the finger or thumb before performing an action permitted only to be performed by the card owner, such as authorising a payment.

One technique used for incorporating a biometric sensor into a smart card comprises the use of a circuit inlay, where an electronic circuit assembly composed of a number of electronic components in electrical communication with each other are arranged on the surface of a substrate layer, formed from a heat-resistant material such as polyamide or FR4. This circuit inlay is encapsulated within a card body, commonly formed from PVC, during lamination. The biometric sensor, and optionally other components, may be then attached to the card after lamination so as to be exposed from the surface of the card to enable the user to interact with the sensor.

A possible failure mode of such cards is that the laminated layers of the card, i.e. the inlay substrate material and the card body material, may delaminate when the card is repeatedly bent or flexed, thereby allowing them to separate. The separating of these layers can cause electronic components mounted on the surface of the card body to be lifted away from the substrate, thereby causing the electrical connection between those electrical components and the remainder of the electronic circuit to be broken.

The present invention seeks to reduce problems associated with delamination within a smart card.

Viewed from a first aspect, the present invention provides a method of manufacturing a smart card, comprising: forming a card body by laminating an electronic circuit inlay between a first layer of material and a second layer of material to bond the first and second layers of material together around the electronic circuit inlay; wherein the electronic circuit inlay comprises a substrate made from one or more of a plastics material and a fibre reinforced epoxy composite material, contacts on the substrate for electrical connection to a smart card component, and one or more holes through the substrate adjacent to the contacts; and wherein the laminating causes the first layer of material to be bonded to the second layer of material through the one or more holes in the substrate.

With the method described above, a smart card is formed with a mechanical connection between the first and second layers of material due to the bond formed through the one or more holes in the substrate. Advantageously, this bond reduces the degree to which the layers of the smart card can separate from one another in the event of delamination. Moreover, by arranging the holes through the substrate adjacent to the contacts, the degree to which the layers can separate at the contacts in the event of delamination is minimised. Thus, when a smart card component is electrically connected to the contacts, the electrical connection between the component and the contacts is less likely to be damaged or broken by delamination of the smart card.

A solder mask may be formed on the substrate around the contacts prior to lamination. A solder mask prevents unintended electrical bridges from forming between the contacts and/or other components on the electronic circuit inlay. A solder mask commonly has openings to expose the contacts and allow for electrical connections to be made with the electronic circuit inlay via the contacts. Whilst substrates formed from plastics material and a fibre reinforced epoxy composite material usually bond well during lamination, it has been found that solder masks often bond poorly during lamination. Consequently, regions where solder masks are used (i.e. surrounding the electrical contacts) are particularly prone to delamination. Electrical connections to contacts surrounded by a solder mask are therefore particularly prone to damage caused by delamination. By providing additional bonding between the laminated layers adjacent to contacts in regions where a solder masks is present, these electrical connections can be protected from damage caused by such delamination.

Exemplary solder masks may comprise an epoxy solder mask, a liquid photoimageable solder mask (LPSM) ink, or a dry film photoimageable solder mask (DFSM). Forming the solder mask may comprise screen printing or spraying the solder mask onto the substrate.

The substrate may be formed from polyamide, PET (Polyethylene terephthalate), PETG (Polyethylene terephthalate glycol-modified), PTFE (Polytetrafluoroethylene) or FR-4 grade glass-reinforced epoxy laminate. These materials are advantageous when using lamination, as they bond well to other plastics materials commonly using in laminated smart cards, such as polyvinyl chloride (PVC) and polyurethane (PU).

Preferably, the one or more holes are each positioned a distance of less than 5 mm from an edge of the contacts. More preferably, the one or more holes are each positioned a distance of less than 1 mm from an edge of the contacts. Positioning the one or more holes close to the contacts means that the bond between the first and second layer of materials can be formed close to the contacts, thereby minimising the degree to which the layers of the smart card adjacent the contacts can separate in the event of delamination. Accordingly, a component that is connected to the contacts is less likely to become electrically detached from the contacts due to delamination of the smart card in the region surrounding the contacts.

A cavity may be formed in the card body by the forming of the card body such that the contacts are exposed by the cavity. For example, a mold may be pressed into the first and/or second layer of material during lamination to deform the layer and form the cavity. The pressure exerted by the mold may force material to disperse, forming the cavity. This is particularly advantageous when hot a lamination technique is used since the layer of material may soften and be more readily deformed under the pressure exerted by the mold.

Alternatively, a cavity may be formed in the preformed card body to expose the contacts. That is to say, a cavity may be formed in the card body after formation of the card body in order to expose the contacts. Forming the cavity may comprise removing material from the preformed card body, for example by using a precision end mill or a laser mill.

The substrate may not be exposed by formation of the cavity. That is to say, the contacts may extend from the substrate, such that an upper surface of each of the contacts is closer to the upper surface of the smartcard than an upper surface of the substrate. Thus, the cavity may expose the contacts whilst the substrate remains encapsulated by the material of the card body, i.e. such that a layer of the material of the card body will be present between the substrate and an electronic component inserted into the cavity.

The method may further comprise installing a smart card component in the cavity. An electrical connection is preferably formed between the smart card component and the electronic circuit inlay via the contacts. The smart card component may be a contact pad or a biometric sensor, such as a fingerprint sensor. When the smart card component is a biometric sensor, it is preferably for identification of an authorised user of the smart card. For instance, the smart card may be arranged to be allow operation of the smart card and/or access to sensitive data stored on the smart card only when the biometric sensor provides an indication of an authorised user.

The contacts may comprise electrically conductive extension members that extend away from the substrate of the electronic circuit inlay. For example, the extension members may be formed from a metallic solder. The metallic solder preferably has a melting temperature over 200°C, and preferably below 300°C.

Alternatively, the extension members may comprise metallic elements mounted to the substrate, such as via surface mount technology. The extension members may extend from the substrate by at least 200pm and preferably at least 300pm.

The extension members should be sufficiently high to raise the electronic component such that its upper surface is substantially flush with an upper surface of the smart card. Smart cards usually have a thickness of less than 1mm, and commonly about 0.76mm in accordance with international standard ISO 7810. Thus, the extension members will usually extend from the substrate by less than about 500pm, and often less than about 400pm.

The first layer of material may be bonded to the second layer of material via hot lamination. The laminating is preferably performed at a temperature sufficient to soften the first and second layers of material but below the melting point of the first and second layers of material such that the first and second layers do not become molten. The laminating may be performed at a temperature between 60°C and 220°C. Preferably the laminating is performed at a temperature below 200°C, more preferably below 160°C. For example, the laminating may be performed at a temperature between 60°C and 80°C, between 80°C and 120°C, or between 120°C and 200°C.

The first layer of material may be bonded to the second layer of material via an adhesive. For example, a thermoplastic adhesive, such as a heat activated film sheet, may be used to bond the first and second layers of material to each other through the one or more holes in the substrate. Alternatively, a thermoset adhesive, such as epoxy, may be poured through the one or more holes in the substrate to bond the first and second layers of material to each other. In addition, or alternatively, the adhesive may bond the first and/or second layers of material to the substrate. Alternatively, material of the first and/or second layers of material may form the bond between the first layer of material and the second layer of material such that the first and second layers of material are directly bonded to each other. For example, the material of the first and/or second layer of material may be heated, for instance via a hot lamination process, to cause the material to soften or melt and to extend through the one or more holes in the substrate. Once cooled, the material of the first and/or second layers may harden thereby forming the bond between the first and second layers of material.

In some embodiments, the first layer of material may be bonded to the second layer of material via cold lamination. In such embodiments, the first layer of material may be bonded to the second layer of material via an adhesive that cures at a temperature below about 60°C.

The first and second layers of material may be formed from a plastics material. Exemplary plastics materials include polyvinyl chloride (PVC), polyethylene (PE), polyester and acrylonitrile-butadiene-styrene (ABS).

The smart card preferably conforms to the physical characteristics of format ID-1, ID-2 or ID-3 as defined by ISO/IEC 7810. For example, the electronic card may be an ID-1 format card and may have a width of between 85.47 mm and 85.72 mm, and a height of between 53.92 mm and 54.03 mm. The electronic card may have a thickness less than 0.84 mm, and preferably of about 0.76 mm (e.g. ± 0.08 mm).

This invention also extends to a corresponding smart card. Accordingly, viewed from another aspect, the present invention provides a smart card comprising: an electronic circuit inlay interposed between a first layer of material and a second layer of material, the electronic circuit inlay comprising a substrate made from one or more of a plastics material and a fibre reinforced epoxy composite material, contacts on the substrate for electrical connection to a smart card component, and one or more holes through the substrate adjacent to the contacts, wherein the first layer of material and the second layer of material are bonded together around the electronic circuit inlay and through the holes in the substrate, thereby forming a card body; a cavity formed in the card body and exposing the contacts; and a smart card component received in the cavity and connected to the contacts by an electrical connection.

As discussed above in relation to the first aspect, the bond between the first and second layers of material forms a mechanical connection between these layers through the one or more holes in the substrate. This advantageously reduces the degree to which the layers of the smart card will separate and delaminate, in particular in the region surrounding the one or more holes in the substrate. By arranging the holes through the substrate adjacent to the contacts, the region of the smart card around the contacts that is susceptible to damage caused by delaminafion is minimised. Thus, the electrical connection between the smart card component and the contacts is less likely to be damaged or broken by delamination of the smart card.

The substrate may be formed from polyamide, PET (Polyethylene terephthalate), PETG (Polyethylene terephthalate glycol-modified), PTFE (Polytetrafluoroethylene) or FR-4 grade glass-reinforced epoxy laminate. The electronic circuit inlay may comprise a solder mask arranged on the substrate around the contacts. The solder mask may comprise an epoxy solder mask, a liquid photoimageable solder mask (LPSM) ink, or a dry film photoimageable solder mask (DFSM).

Preferably, the one or more holes are each positioned a distance of less than 5 mm from an edge of the contacts, more preferably less than 1 mm from an edge of the contacts. Positioning the holes close to the contacts ensures that the bond between the first and second layers of material is formed close to the contacts, thereby minimising the area around the contacts that is susceptible to delamination.

The cavity may not extend to the substrate of the electronic circuit inlay. The smart card component may be a contact pad or a biometric sensor. In a preferred embodiment, the smart card component is a fingerprint sensor. When the smart card component is a biometric sensor, it is preferably arranged for identification of an authorised user of the smart card. For instance, the smart card may be arranged to be allow operation of the smart card and/or access to sensitive data stored on the smart card only when the biometric sensor provides an indication of an authorised user.

The contacts may comprise electrically conductive extension members that extend away from the substrate of the electronic circuit inlay. The extension members may be formed from a metallic solder. The metallic solder preferably has a melting temperature over 200°C, and preferably below 300°C. In an alternative embodiment, the extension members may comprise metallic elements mounted to the substrate, such as via surface mount technology. The extension members may extend from the substrate by at least 200 pm, and optionally by at least 300pm. The extension members may extend from the substrate by less than 500 pm, and optionally less than 400pm The first layer of material and the second layer of material may be bonded together via an adhesive. For example, a thermoplastic adhesive, such as a heat activated film sheet, may be used to bond the first and second layers of material to each other through the one or more holes in the substrate. Alternatively, a thermoset adhesive, such as epoxy, may bond the first and second layers of material to each other. In addition, or alternatively, the adhesive may bond the first and/or second layers of material to the substrate.

In an alternative embodiment, the first and second layers of material may be directly bonded to each other through the one or more holes in the substrate.

Preferably, the electronic card conforms to the physical characteristics of format ID-1, ID-2 or ID-3 as defined by ISO/IEC 7810. For example, the electronic card may be an ID-1 format card and may have a width of between 85.47 mm and 85.72 mm, and a height of between 53.92 mm and 54.03 mm. The electronic card may have a thickness less than 0.84 mm, and preferably of about 0.76 mm (e.g. ± 0.08 mm).

Certain preferred embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which: Figure 1 shows a cross section though a first embodiment of a smart card including a biometric sensor; Figure 2 shows a plan view of an electronic circuit assembly for a smart card; Figure 3 shows a detailed view of contacts of the electronic circuit assembly; Figure 4 shows a plurality of layers for the manufacture of a body of the smart card of Figure 1; Figure 5 shows the body of the smart card of Figure 1 after lamination; Figure 6 shows the card body having a cavity for insertion of the biometric sensor; Figure 7 shows the insertion of the biometric sensor into the cavity in the card body; Figure 8 shows a cross section through a second embodiment of a smart card including a biometric sensor; and Figure 9 shows a plurality of layers for the manufacture of a body of the smart card of Figure 8.

The accompanying drawings are not to scale and certain features have been emphasised.

Figure 1 shows a cross section through a smart card 10 including a biometric sensor 40, where the smart card 10 is capable of performing biometric verification of a bearer of the smart card 10.

The smart card 10 comprises a card body 20, an electronic circuit inlay 30 embedded within the card body 20, and a biometric sensor 40 received within a cavity 50 in the card body 20 and electrically connected to the electronic circuit inlay 30 The card body 20 is a laminated card body, i.e. formed from a plurality of layers of material. The layers of material include at least a first layer of material 22 and a second layer of material 24 with the electronic circuit inlay 30 interposed between the first and second layers of material 22, 24. The layers of material 22, 24 are preferably formed from polyvinyl chloride (PVC). However, other suitable materials for lamination include polyester, acrylonitrile-butadiene-styrene (ABS), polycarbonate, and many other suitable plastics. Additionally, plasticisers or dyes may be added to one or more of the layers of material to achieve a desired look and feel. Optionally, additional layers may be provided between and/or outside of the first and second layers of material 22, 24.

Some components of the electronic circuit inlay 30 may protrude from the surface of the electronic circuit inlay 30. Therefore, the lower surface of the first layer of material 22 of the exemplary smart card 10 is shaped to conform to the shape of the electronic circuit inlay 30. In this way, the first layer of material 22 fits closely over the top of the electronic circuit inlay 30 and the outer surface of the card body 20 is flat with no bulges at the locations of the electronic components.

The biometric sensor 40 is a fingerprint sensor having a scanning surface 41 that is exposed from the surface of the smart card 10 and is preferably substantially flush with the surface of the smart card 10. The exposed scanning surface 41 permits a user of the card to present their finger or thumb to the scanning surface 41. The biometric sensor 40 is received within the cavity 50, which extends through the material of the card body 20 to expose contacts 32 provided on the electronic circuit inlay 30. The biometric sensor 40 is electrically connected to the electronic circuit inlay 30 via the contacts 32.

Figure 2 is a schematic illustration of the electronic circuit inlay 30 within the smart card 10. The edge of the card body 20 is shown in dotted lines. Section line A-A illustrates the plane along which the cross-section of Figure 1 is taken.

The electronic circuit inlay 30 comprises a substrate 31 on which a plurality of electronic components are mounted and electrically interconnected. Contacts 32 are provided on the substrate 31 and electrically connected to the electronic components. The electrical interconnection between the electronic components and the contacts 32 is not shown, but may be provided by any suitable means, such as a printed circuit. The substrate 31 is preferably made from a flexible material capable of withstanding the lamination process, such as polyamide or FR-4 grade glass-reinforced epoxy laminate. Conductive traces providing the electrical interconnection between the electronic components may be formed from copper on the substrate 31, for example, by etching a suitable pattern onto a copper cladding formed on the substrate 31.

The electronic circuit inlay 30 includes at least a biometric processing module 37 comprising a processor and a memory for performing biometric verification of the user. In this example, the electronic circuit inlay 30 also includes a card processing module 38, such as a secure element 38, for controlling interaction between the smart card 10 and an external system, for example to authorise particular actions, such as financial transitions. The biometric processing module 37 and the secure element 38 are encapsulated within the material of the card body 20, i.e. they are each completely surrounded by the material of the card body 20.

The memory of the biometric processing module 37 is arranged to store biometric reference data corresponding to an authorised bearer of the smart card 10. The biometric reference data may, in the case where the biometric sensor 40 is a fingerprint sensor, comprise a reference fingerprint image or a set of reference minutiae corresponding to a reference fingerprint.

The processor of the biometric processing module 37 is arranged to verify the biometric data acquired by the biometric sensor 40 and to responsively control operation of the smart card 10. Particularly, the processor is arranged to compare the biometric data stored on the memory to the biometric data acquired by the biometric sensor 40. Thus, the processor of the biometric processing module 37 is arranged to determine if the user of the smart card 10 is an authorised user based on biometric data captured by the biometric sensor 40.

Once the processor of the biometric processing module 37 has determined that the user of the smart card 10 is an authorised user, the processor may authorise the user of the smart card 10 to perform an action. For example, if the smart card 10 acts as a bank card, authorisation of the user may allow for financial transactions to be made using the smart card 10, for example via the card processing module 38. Certain functionality of the card processing module 38 may otherwise be disabled until the processor verifies the identity of the user of the smart card 10.

The processor may authorise the use of the smart card 10 for only a predetermined time after the user has been verified, for example up to 5 seconds after the user has been verified. Alternatively, the processor may be arranged to authorise use of the smart card 10 only whilst data is being acquired by the biometric sensor 40. For example, when the biometric sensor 40 is a fingerprint sensor, the processor may be arranged to authorise use of the smart card 10 only when an authorised user has a finger in contact with the fingerprint sensor 40.

The card processing module 38 may provide card functionalifies, such as communicating data stored on the smart card 10 to a suitable reader subject to verification of the bearer of the smart card 10 by the biometric processing module 37. The card processing module 38 may comprise a memory arranged to store information associated with the smart card 10 and/or a bearer of the smart card 10. For example, this may include a name or other identifier of the bearer of the smart card 10, account information of the bearer of the smart card 10, an access level of the bearer of the smart card 10, etc. The smart card 10 is preferably arranged such that the biometric data acquired by the biometric sensor 40 and the reference biometric data stored on the memory of the biometric processing module 37 are never transferred from the smart card 10 during normal operation.

The electronic circuit inlay 30 in the illustrated example also includes an antenna 35. The antenna 35 may be used to communicate with a card reader, which is external to card 10. This type of smart card 10 is known as a contactless or non-contact smart card 10. In this embodiment, the antenna 35 is formed on the substrate 31 of the inlay, and may be formed as part of the printed circuit.

However, in other embodiments, the antenna may be a separate component. In the illustrated example, the smart card 10 is a hybrid smart card, and the electronic circuit inlay 30 additionally comprises a contact pad 36 for physical connection to a contact reader.

The location of the contact pad 36 is shown in dotted lines in Figure 2. A contact surface of the contact pad 36 will be exposed from the surface of the smart card 10 so that it is substantially flush with the surface of the smart card 10.

The card processing module 38 is connected to both the antenna 35 and the contact pad 36 for communication. In some embodiments, the electronic circuit inlay 30 may include only the antenna 35 or only the contact pad 36.

The electronic circuit inlay 30 is arranged to power the biometric processing module 37, the card processing module 38 and the biometric sensor 40 using power supplied either via contact pad 36 from a device external to the smart card 10 or via the antenna 35 when it is energised by a card reader. The electronic circuit inlay 30 may, in some embodiments, alternatively or additionally include a battery (not shown) which is configured to power one or more of the components of the electronic circuit inlay 30.

The biometric sensor 40 is electrically connected to the electronic circuit inlay 30 via the contacts 32 provided on the electronic circuit inlay 30. The contacts 32 are arranged to align with contacts 45 on the biometric sensor 40, when the biometric sensor 40 is in place. These contacts 32, 45 enable the electrical connection of the biometric sensor 40 to the electronic circuit inlay 30, and allow electrical communication between the biometric sensor 40 and components of the electronic circuit inlay 30. The contacts 32 particularly facilitate data communication with the biometric processing module 37 and power supply from the battery, the contact pad 36 or the antenna 35, as appropriate.

In this exemplary embodiment, the contacts 32 comprise electrically-conductive extension members 33 formed on conductive pads 34 of the electronic circuit inlay. The contacts 32 are shown in detail in Figure 3. The conductive extension members 33 extend away from the electronic circuit inlay 30 in a direction that is generally perpendicular to the face of the smart card 10. In this example, the extension members 33 are formed from a metallic solder material that can withstand a hot lamination process. Exemplary solder materials include tin-based or a copper-based solders having a melting temperature over about 200°C (so as to withstand lamination), but below 300°C (so as to still be easily soldered). The extension members 33 are preferably formed as solder blobs on the conductive pads 34 of the electronic circuit inlay 30 so as to extend in a direction substantially perpendicular to the surface of the electronic circuit inlay 30. The conductive pads 34 may be made of gold or may be gold plated. The extension members 33 have a height of about 300pm to 400pm and do not need to be completely uniform as they will be milled to a flat surface after lamination.

Whilst in this example the conductive extension members 33 are formed from a metallic solder material, it will be appreciated that they may be formed of any material suitable for enabling electrical connection of the biometric sensor 40 to the electronic circuit inlay 30. For example, the extension members 33 may comprise metallic target discs mechanically connected to the contacts 32, for instance via surface mount technology.

A solder mask 39 is arranged on the surface of the electronic circuit inlay 30 around the contacts 32. The solder mask 39 comprises a non-conductive layer of material applied to the surface of the substrate 31 to surround the contacts 32 to prevent unintended electrical bridges from forming between the contacts 32 and/or between other electrically conductive components of the electronic circuit inlay 30. Openings are provided in the solder mask 39 to allow for electrical connection between the biometric sensor 40 and the electronic circuit inlay 30 via the contacts 32. The solder mask 39 may comprise an epoxy liquid solder mask, a liquid photoimageable ink solder mask (LPSM) or a dry film photoimageable solder mask (DFSM).

The presence of the solder mask 39 on the substrate 31 is particularly beneficial in the present example, in which unintended electrical bridges may form between the conductive pads 34 and/or between other electrically conductive components of the electronic circuit inlay 30 during formation of the extension members 33. In this example, the solder mask 39 is arranged on the substrate 31 around the conductive pads 34 to prevent unintended electrical bridges from forming. The openings in the solder mask 39 to expose the conductive pads 34 to allow for the extension members 33 to be formed and electrically connected to the contact pads 34, thereby allowing for electrical connection between the biometric sensor 40 and the electronic circuit inlay 30 via the conductive pads 34.

As can be seen in Figure 3, the solder mask 39 may partially cover the conductive pads 34. This may be the case when the openings in the solder mask 39 are smaller in area than the conductive pads 34 and/or when the openings are a different shape to the conductive pads 34. Alternatively, a perimeter of an opening may align with a perimeter of a conductive pad 34 so that the solder mask 39 does not cover the conductive pad 34.

Whilst the solder mask 39 is important for avoiding unintentional electrical bridges from forming, it has been found that the material of the solder mask 39 bonds poorly to common materials used for the card body 20, such as PVC. Consequently, the smart card 10 is especially prone to delamination at the locations where the solder mask 39 is present. This is problematic where a large solder mask 39 is used, for example at the biometric sensor 40, which is a relatively large component.

Where delamination occurs, the biometric sensor 40 may be lifted off of the electronic circuit inlay 30, thereby breaking the electrical connection between the biometric sensor 40 and the electronic circuit inlay 30.

It has been proposed to solve this problem by mechanically connecting the first and second layers 22, 24 of the card body 20 adjacent the contacts 32, such that a delamination region is minimised and the biometric sensor 40 cannot be lifted as far off the electronic circuit inlay 30.

To achieve this, a plurality of holes 42 are provided through the substrate 31 of the electronic circuit inlay 30 adjacent to contacts 32, either passing through or outside of the solder mask 30. These holes 42 enable the first layer of material 22 and the second layer of material 24 to bond to one another through the holes 42. The provision of the one or more holes 42 in this way can strengthen the bond between the first and second layers of material 22, 24 and therefore increase the structural integrity of the card body 20.

The holes 42 are positioned close to the contacts 32 to minimise the delamination region around the contacts 32. For example, each of the holes 42 may be positioned a distance of less than 5 mm, or less than 1 mm from an edge of a contact 32.

The holes 42 in the substrate 31 can be seen in plan in Figure 2. In this example, six holes 42 are provided through the substrate 31 adjacent to four contact pads 42. The holes 42 are arranged on two opposing sides of each contact pad 34. This arrangement provides holes 42 between adjacent contact pads 34, thereby minimising the delamination region. Whilst in this example only one hole 42 is arranged in a space between adjacent contact pads 34, in other examples more than one hole may be arranged in the space between adjacent contact pads 34. For example, two, three, or more holes 42 may be arranged in a space between adjacent contact pads 34.

In this embodiment, the holes 42 are rectangular in cross section, however the holes 42 may have any suitable cross sectional shape to allow the first and second layers of material 22, 24 to bond through the holes 42. For example, the holes may have a circular cross section or irregularly shaped cross section. Furthermore, whilst Figure 2 illustrates one exemplary arrangement of holes, it will be appreciated that the advantageous effect described above can be achieved with many suitable configurations, provided that the holes are arranged close to the contacts to minimise the impact of delamination at the solder mask 39.

Figures 4 to 7 illustrate a method for the manufacture of the smart card 10 described above.

The holes 42 are cut or stamped through the substrate 31 of the electronic circuit inlay 30 adjacent to the contacts 32, although it will be appreciated that they may be formed by any suitable method. This may be performed either before or after mounting the electronic components to the substrate 31, and also before or after applying the solder mask 39 and/or the extension members 33 to the substrate 31.

A pre-lamination assembly is formed by arranging the electronic circuit inlay 30 between the first layer of material 22 and the second layer of material 24. The layers of the pre-lamination assembly may for example be held in place by a suitable adhesive or by use of a frame or jig.

It will be appreciated that the pre-lamination assembly may be for the manufacture of a single smart card 10, or may be for the manufacture of multiple smart cards 10, i.e. such that after lamination the assembly is cut into multiple, individual smart cards 10. In the latter case, multiple electronic circuit inlays 30 may be provided, for example in a grid layout, between a single first layer of material 22 and second layer of material 24.

A heat cycle is applied to the pre-lamination assembly to soften the material of the first and second layers of material 22, 24. The temperature of the heat cycle is preferably sufficient to soften the first and second layers of material 22, 24 but below the melting point of the first and second layers of material 22, 24 such that the first and second layers of material 22, 24 become tacky or sticky, but not molten. For example, where the first and second layers of material 22, 24 are PVC, this temperature may be between 60°C and 120°C. The pressure is increased along with the temperature, for example to a pressure of between 1 MPa and 8 MPa, for example approximately 6.5 MPa.

In one example, a cooling cycle is then applied to the pre-lamination assembly and the pressure is further increased by between 10% and 50%, for example by approximately 25% until the pre-lamination assembly has cooled to approximately 5°C to 20°C.

During the heat cycle the material of the first and/or second layers of material 22, 24 is caused to soften or melt and to extend through the holes 42 in the substrate 31 such that the first and second layers of material 22, 24 come into contact through the holes 42 in the substrate 31. Once cooled, the material of the first and second layers 22, 24 hardens thereby forming a bond between the first and second layers of material 22, 24 through the holes 42 in the substrate 31.

The cavity 50 is formed in the card body 20 to expose the upper ends of the extension members 33 of the electronic circuit inlay 30. The cavity 50 extends through the first layer of material 22 to expose the extension members 33 and is sized substantially in conformity with the shape of the biometric sensor 40, such that the biometric sensor 40 will fit closely within the cavity 50.

In this exemplary embodiment, the cavity 50 is milled into the first layer of material 22. This may be done using a precision end mill or a laser mill. The cavity 50 is milled to a depth sufficient to receive the biometric sensor 40 such that the sensing surface 41 of the biometric sensor 40 will be flush with the surface of the card body 20. Milling also cuts into the extension members 33 such that they form uniform, flat surfaces to which the biometric sensor 40 can be attached. The cavity 50 does not extend to the substrate 31 of the electronic circuit inlay 30. This means that when the biometric sensor 40 is received within the cavity 50 there remains material of the first layer of material 22 between the biometric sensor 40 and the substrate 31.

In the above example, the cavity 50 is formed in the card body after the lamination process. However, the cavity 50 may be formed in the card body 20 in other ways. In one example, the cavity 50 may be formed during the formation of the card body 20. For example, a mold may be pressed into the material of the card body 20 during lamination to deform the material and form the cavity 50. The pressure exerted by the mold may force material of the card body 20 to disperse during the lamination process, forming the cavity 50 in the material of the card body 20.

In another example, the card body 20 may be formed using techniques other than lamination, such as molding. For example, injection molding may be used. A protrusion in the mold may be arranged so as to prevent material covering the contacts 32, thereby forming the cavity 50 in the material of the card body 20 during formation of the card body 20. It will be appreciated that such techniques will still form a mechanical bond through the holes 42, such that delamination of the card body material from the electronic circuit inlay 30 will not break the contacts between the biometric sensor 40 and the electronic circuit inlay 30.

Figure 7 shows the biometric sensor 40 being inserted into the cavity 50. In order to install the biometric sensor 40 into the cavity 50, a fin-bismuth solder is used to form solder blobs on the contacts 45 of the biometric sensor. The biometric sensor 40 is then aligned with the cavity 50 and the biometric sensor 40 is pushed into the cavity 50 such that the contacts 45 on the biometric sensor 40 and the contacts 32 in the circuit inlay 30 are brought into electrical contact through the solder blobs.

In order to form a permanent connection between the biometric sensor 40 and the extension members 33, ultrasonic energy is used to heat the tin-bismuth solder blobs above their melting temperatures (approx. 139°C). Using tin-bismuth solder allows the components to be reflowed at a lower temperature which does not damage the materials of the card body. Tin-bismuth solder is sufficiently conducive to provide the connection needed for the biometric sensor to communicate with the components of the electronic circuit inlay 30.

Alternatively, a conductive epoxy may be applied to the surface of the extension members 33 prior to the biometric sensor 40 being inserted into the cavity 50. A suitable conductive epoxy is type SEC1222 epoxy, manufactured by Resinlab, LLC of Wisconsin USA, which cures at room temperatures (approx. 25°C). A conductive epoxy having a strongly anisotropic characteristic may be used. This is beneficial when the contacts 45 on the biometric sensor 40 are very close together because it provides the required conductivity between the biometric sensor 40 and the extension members 33 in the circuit inlay 30, whilst ensuring that even if the conductive epoxy flows between extension members 33 of adjacent contacts 32, it will not form any appreciable conductive path between them.

Interior walls 54 of the cavity 50 may be coated with an adhesive epoxy prior to the biometric sensor 40 being inserted. The adhesive epoxy seals the biometric sensor 40 in place to prevent the biometric sensor 40 from becoming dislodged and becoming disconnected from the contacts 32 of the circuit inlay 30.

The conductive epoxy and/or adhesive epoxy preferably cure without heating. However, alternatively, one or both of the conductive epoxy and adhesive epoxy may require heat curing where the curing temperature of the conductive epoxy and/or adhesive epoxy is below a safe temperature of the biometric sensor 40, for example below 60°C. Higher temperatures may be possible for short time periods and/or for different sensor types.

In some embodiments, the contact pad 36 may be installed in a similar manner as discussed above in respect of the biometric sensor 40. That is to say, the contact pad may be received within a cavity that extends through the first layer of material 22 to expose contacts 43 provided on the electronic circuit inlay 30 and arranged to align with contacts on the contact pad 36, when the contact pad 36 is in place. The contact pad 36 will be electrically connected to the contacts 43 to allow electrical communication between the contact pad and components of the electronic circuit inlay 30.

The layers of the smart card 10 formed by using this method are bonded together adjacent to the contacts 43 due to the presence of holes 44 in the substrate 31 (shown in Figure 2). This prevents the layers of the smart card 10 from separating near the contacts 43 in the event of delamination, which could otherwise cause the connection between the contact pad 36 and the contacts 43 to break. Therefore, the presence of the holes 44 acts to prevent the connection between the contact pad 36 and the contacts 43 from breaking.

In this example, the contact pads 43 are arranged in two adjacent rows of four contact pads 43. A hole 44 is provided through the substrate 31 on two opposing sides of each row of contact pads 43 such that two holes 44 are provided in a space between the two rows of contact pads 43. Each hole 44 extends a length equal to that of each of the two rows of contact pads 43.

Figure 1 shows a cross-section through the biometric sensor 40 when assembled into the smart card 10.

Whilst in the above embodiment, the first and second layers of material 22, 24 are directly bonded to each another around the substrate 31 and through the holes 42 in the substrate, in another embodiment a mechanical bond may be formed between the first and second layers of material 22, 24 via a separate adhesive.

Figure 8 shows a cross section through a smart card 10a in accordance with a second embodiment. Features corresponding to those discussed above in relation to smart card 10 are given the same reference numbers. In the below discussion of the smart card 10a only features that differ from those discussed above in relation to the smart card 10 will be described in detail.

As with the smart card 10 described above, the smart card 10a comprises a card body 20, an electronic circuit inlay 30 embedded within the card body 20, and a biometric sensor 40 received within a cavity 50 in the card body 20 and electrically connected to the electronic circuit inlay 30. However, in the smart card 10a, the electronic circuit inlay 30 is embedded within an adhesive 51 in the card body 20. That is to say, the substrate 31 and the electronic components 37, 38 are completely surrounded by the adhesive 51. The contacts 32 are exposed from the adhesive 51 to enable an electrical connection between the biometric sensor 40 and the electronic circuit inlay 30 via the contacts 32. The contacts 32 may be exposed from the adhesive 51 by, for example, formation of the cavity 50 which may extend partially into the adhesive 51.

The adhesive may be a thermoplastic adhesive, for example a heat activated film sheet.

The adhesive 51 bonds to the material of the card body 20 and extends through the holes 42 in the substrate 31. Accordingly, the material of the card body on opposing sides of the substrate 31 is mechanically bonded through the holes 42 in the substrate 31 via the adhesive 51.

A method for the manufacture of the smart card 10a will be discussed with reference to Figure 9. To avoid repetition, only the steps that differ from those discussed above in relation to smart card 10 will be described in detail.

An adhesive inlay layer 52 is formed by encasing the electronic circuit inlay 30 within a layer of adhesive 51. Any suitable manufacturing technique may be used to form the adhesive inlay layer 52, such as molding. For instance, injection molding may be used to form the adhesive 51 layer around the electronic circuit inlay 30. In addition to surrounding the electronic circuit inlay 30, the adhesive 51 of the adhesive inlay layer 52 also extends through the holes 42 in the substrate 31. A pre-lamination assembly is formed by arranging the adhesive inlay layer 52 between the first layer of material 22 and the second layer of material 24. A frame 53 is arranged around the perimeter of the adhesive inlay layer 52 and between the first and second layers of material 22, 24. Hence, the adhesive inlay layer 52 is surrounded by the frame 53, the first layer of material 22 and the second layer of material 24. The frame may be formed of the same material as the first and second layers of material 22, 24, for example PVC.

The pre-lamination assembly is heated in order to soften the adhesive 51 and thereby cause the adhesive to adhere to the first and second layers of material 22, 24 and the frame 53. Preferably, the pre-lamination assembly is heated to a temperature that is sufficiently below the melting point of the material of the frame 53 and the first and second layers of material 22, 24 such that the frame 53 and the first and second layers of material 22, 24 do not soften.

By adhering and bonding the adhesive 51 to the first and second layers of material 22, 24 and the frame 53, the adhesive acts to secure the layers of the card body 20 together. It will be appreciated that in this example a mechanical bond is formed between the first and second layers of material 22, 24 through the holes 42 in the substrate 31 via the adhesive 51.

The biometric sensor 40 may be installed in the card body 20 in the same way as discussed above in relation to the smart card 10. For instance, the cavity 50 may be formed in the card body 20 to extend through the first layer of material 22 and a portion of the adhesive 51 to expose the extension members 33. The biometric sensor 40 can then be inserted into the cavity 50, secured to the card body 20 and electrically connected to the contacts 32 in the circuit inlay 30 in the manner described above.

Whilst in the described embodiments the smart card 10 is formed by using lamination, the present invention is not limited to such. It will be appreciated by those skilled in the art the smart card 10 may be formed using other manufacturing techniques, such as molding. For instance, injection molding may be used to form the card body 20 around the electronic circuit inlay 30.

Claims

CLAIMS: 1. A method of manufacturing a smart card, comprising: forming a card body by laminating an electronic circuit inlay between a first layer of material and a second layer of material to bond the first and second layers of material together around the electronic circuit inlay; wherein the electronic circuit inlay comprises: a substrate made from one or more of a plastics material and a fibre reinforced epoxy composite material, contacts on the substrate for electrical connection to a smart card component, and one or more holes through the substrate adjacent to the contacts; and wherein the laminating causes the first layer of material to be bonded to the second layer of material through the one or more holes in the substrate.
2. A method as recited in claim 1, wherein the substrate is formed from polyamide, PET (Polyethylene terephthalate), PETG (Polyethylene terephthalate glycol-modified), PTFE (Polytetrafluoroethylene) or FR-4 grade glass-reinforced epoxy laminate.
3. A method as recited in claim 1 or 2, further comprising forming a solder mask on the substrate around the contacts prior to lamination, the solder mask having openings to expose the contacts.
4. A method as recited in claim 3, wherein forming the solder mask comprises screen printing or spraying the solder mask onto the substrate.
5. A method as recited in claim 3 or 4, wherein the solder mask comprises an epoxy solder mask, a liquid photoimageable solder mask (LPSM) ink, or a dry film photoimageable solder mask (DFSM).
6. A method as recited in any preceding claim, wherein the one or more holes are each positioned a distance of less than 5 mm from an edge of the contacts, optionally less than 1 mm.
7. A method as recited in any preceding claim, wherein a cavity is formed in the card body by the forming of the card body such that the contacts are exposed by the cavity.
8. A method as recited in any of claims 1 to 6, further comprising forming a cavity in the card body to expose the contacts.
9. A method as recited in claim 8, wherein forming the cavity comprises removing material from the card body, optionally wherein the material is removed from the preformed card body using a precision end mill or a laser mill.
10. A method as recited in any of claims 6 to 9, wherein the substrate is not exposed by formation of the cavity.
11. A method as recited in any of claims 7 to 10, further comprising installing a smart card component in the cavity and forming an electrical connection between the smart card component and the electronic circuit inlay via the contacts.
12. A method as recited in claim 11, wherein the smart card component is a contact pad or a biometric sensor, optionally wherein the biometric sensor is a fingerprint sensor.
13. A method as recited in any preceding claim, wherein the contacts comprise electrically conductive extension members that extend away from the substrate of the electronic circuit inlay.
14. A method as recited in any preceding claim, wherein the first layer of material is bonded to the second layer of material via hot lamination.
15. A method as recited in any preceding claim, wherein the first layer of material is bonded to the second layer of material via an adhesive.
16. A smart card comprising: an electronic circuit inlay interposed between a first layer of material and a second layer of material, the electronic circuit inlay comprising: a substrate made from one or more of a plastics material and a fibre reinforced epoxy composite material, contacts on the substrate for electrical connection to a smart card component, and one or more holes through the substrate adjacent to the contacts, wherein the first layer of material and the second layer of material are bonded together around the electronic circuit inlay and through the holes in the substrate, thereby forming a card body; a cavity formed in the card body and exposing the contacts; and a smart card component received in the cavity and connected to the contacts by an electrical connection.
17. A smart card as recited in claim 16, wherein the substrate is formed from polyamide, PET (Polyethylene terephthalate), PETG (Polyethylene terephthalate glycol-modified), PTFE (Polytetrafluoroethylene) or FR-4 grade glass-reinforced epoxy laminate.
18. A smart card as recited in claim 16 or 17, wherein the electronic circuit inlay comprises a solder mask arranged on the substrate around the contacts.
19. A smart card as recited in claim 18, wherein the solder mask comprises an epoxy solder mask, a liquid photoimageable solder mask (LPSM) ink, or a dry film photoimageable solder mask (DFSM)
20. A smart card as recited in any of claims 16 to 19, wherein the one or more holes are each positioned a distance of less than 5 mm from an edge of the contacts, optionally less than 1 mm.
21. A smart card as recited in any of claims 16 to 20, wherein the cavity does not extend to the substrate of the electronic circuit inlay.
22. A smart card as recited in any of claims 16 to 21, wherein the smart card component is a contact pad or a biometric sensor, optionally wherein the biometric sensor is a fingerprint sensor.
23. A smart card as recited in any of claims 16 to 22, wherein the contacts comprise electrically conductive extension members that extend away from the substrate of the electronic circuit inlay.
24. A smart card as recited in any of claims 16 to 23, wherein the first layer of material and the second layer of material are bonded together via an adhesive.