Patent Description:
As the development of biometric devices for identity verification, and in particular of fingerprint sensing devices, has led to devices which are made smaller, cheaper and more energy efficient, the range of applications for such devices is increasing.

In particular fingerprint sensing has been adopted more and more in, for example, consumer electronic devices, due to small form factor, relatively beneficial cost/performance factor and high user acceptance.

Capacitive fingerprint sensing devices, built based on CMOS technology for providing the fingerprint sensing elements and auxiliary logic circuitry, are increasingly popular as such sensing devices can be made both small and energy efficient while being able to identify a fingerprint with high accuracy. Thereby, capacitive fingerprint sensors are advantageously used for consumer electronics, such as portable computers, tablets and mobile phones. There is also an increasing interest in using fingerprint sensors in smartcards to enable biometric identification in a card such as a bank card where other types of biometric systems are not applicable.

Fingerprint sensors can be included in a smartcard by adding them after a smartcard has been produced, by a so-called mill and drill process and surface mounting the sensor module into the hole created in the surface of the card. This requires the fabrication of robust fingerprint sensors that are prepared for the wear and tear of being exposed at the surface of a smartcard.

However, it is still desirable to explore additional methods for integrating a biometric sensor in a smartcard, in particular in terms of cost reduction which is in part linked to the complexity of the manufacturing process.

<CIT> describes a flexible electronic card comprising a fingerprint module arranged in a cavity formed in the card body, the fingerprint module being housed in the cavity and flush with the upper surface of the card body.

<CIT> relates to a capacitive fingerprint sensing device comprising a semiconductor substrate and an array of sensing elements formed on the semiconductor substrate.

<CIT> describes a fingerprint sensor module comprising a fingerprint sensor device and an antenna embedded in a substrate of the fingerprint sensor module.

<CIT> describes a smartcard comprising a fingerprint reader.

In view of above-mentioned and other drawbacks of the prior art, it is an object of the present invention to provide an improved smartcard comprising a fingerprint sensor module.

According to a first aspect of the invention, there is provided a smartcard comprising: a plurality of smartcard substrate layers; an antenna layer comprising an antenna; a fingerprint sensor module embedded in the smartcard substrate layers and connected to the antenna layer, the fingerprint sensor module being configured to receive energy and communicate with a reading device via the antenna, and wherein the fingerprint sensor module is galvanically isolated from an outside of the smartcard.

A smartcard can be considered to be any card comprising functionality such as biometric sensing, and smartcards may be used as payment cards, identification cards, access cards and in other applications where a card with built-in functionality is desirable. In the present context, the smartcard comprises a fingerprint sensor module connected to an antenna, but this does not exclude that other features are included in the smartcard.

The present invention is based on the realization that it is advantageous to provide a smartcard where the fingerprint sensor module is galvanically isolated within the smart card. The present invention thereby describes a solution for how to form a smartcard comprising a galvanically isolated fingerprint sensor module.

By embedding the fingerprint sensor module, greater mechanical and electrical protection for the electronics in the sensor module is provided. The production of the smartcard is also simplified by connecting the sensor module directly to the antenna that powers the smartcard. Thereby, even if the user holds a large electrical charge, there will be no path for the charge to damage neither the fingerprint sensor nor any other electronic component in the card or a payment terminal with which the card is in contact.

The invention is enabled by a fingerprint sensor which is capable of operating without an electrical connection to the user, and thereby without a bezel or any other external electrode. Such a fingerprint sensor without a bezel is described in <CIT>.

The fingerprint sensor module comprises at least a fingerprint sensor having an active sensing surface, and the fingerprint sensor may advantageously be a capacitive fingerprint sensor comprising an array of electrically conductive sensing elements. A capacitive fingerprint sensor should be understood to further comprise sensing circuitry connected to sensing elements for reading a signal from the sensing elements. The sensing circuitry may in turn comprise or be connected to readout circuitry for providing a result of the sensing device to an external device for further processing, which in the present case may be included in the fingerprint sensor module. The fingerprint sensor module may also comprise additional passive or active components.

The smartcard can be considered to be formed as a laminate structure comprising a plurality of layers, such as one or more core layers and outer layers on respective sides of the core layer(s). Typically, the smartcard will also comprise one or more electrically conductive layers embedded in the card to route signals between different parts of the card and/or to function as an antenna for power harvesting and communication.

According to one embodiment of the invention, the fingerprint sensor module may comprise contact pads on a backside of the module opposite a sensing side of the module, and wherein the contact pads are directly connected to the antenna. That the contact pads of the fingerprint sensor module are in direct contact, i.e. mechanical and physical contact, with the antenna both ensures a good electrical connection and simplifies manufacturing since no additional communication paths are required in the card.

According to one embodiment of the invention the fingerprint sensor module is a T-shaped module comprising contact pads on an extending portion of the module, the contact pads facing in the same direction as a sensing side of the module, and wherein the contact pads are directly connected to the antenna. The extending portion of the T-shaped module, sometimes referred to as wings, enables the arrangement of contact pads facing in the same direction as a sensing surface of the module, which may be advantageous in some implementations. The T-shaped module may be arranged as an inverted T, i.e. an upside-down T-shape where the sensing surface of the sensor module is facing upwards.

According to one embodiment of the invention, the antenna layer is located in the middle of the smartcard, and the fingerprint sensor module is located on one side of the antenna layer. From a mechanical stability/warpage standpoint it is preferable that the stacking of the layers in the card is as symmetrical as possible, so there is a preference of having two core layers on either side of the antenna layer which default places the antenna near the center of the card.

According to one embodiment of the invention, the fingerprint sensor module is laminated into the smartcard. The fingerprint sensor module can thereby be entirely embedded into the card and galvanically isolated using a process which is already in common use when manufacturing cards, thereby facilitating the implementation of a smartcard comprising a fingerprint sensor module.

According to one embodiment of the invention, the fingerprint sensor module comprises at least one of a secure element and a processing unit. Since the fingerprint sensor module is provided as a single module to be integrated in the smartcard, it can be advantageous to include additional components required for biometric identification and verification into the module in order to avoid having to integrate such components in the card using separate processing steps. The component may for example be a secure element, which in itself often comprises a processing unit, or a separate processing unit used in the fingerprint acquisition and verification process.

According to one embodiment of the invention smartcard comprises, in a direction from the antenna layer to an outer surface, at least one core layer, a printing layer and an outer layer, and wherein the fingerprint sensor module is arranged in an opening of the at least one core layer such that a top surface of the fingerprint sensor module is in line with a top surface of the core layer. By arranging the printing layer above the fingerprint sensor module, it is possible to provide a desirable visual appearance of the card. The printing layer may for example comprise a visual indication of the location of the active sensing area of the fingerprint sensor.

According to one embodiment of the invention, the smartcard comprises, in a direction from the antenna layer to an outer surface, at least one core layer, a printing layer and an outer layer, and wherein the fingerprint sensor module is arranged in an opening of the at least one core layer and the printing layer such that a top surface of the fingerprint sensor module is in line with a top surface of the printing layer. In some implementations it is desirable to minimize the distance between the fingerprint sensor and the card surface and this can be achieved by forming an opening on both a core layer and a printing layer so that the fingerprint sensor is only covered by an outer layer of the card. By minimizing the distance between a sensing surface and a finger, fingerprint acquisition also under more difficult conditions is facilitated.

The present invention will now be described in more detail, with reference to the appended drawings showing example embodiments of the invention, wherein:.

In the present detailed description, various embodiments of the smartcard according to the present invention are mainly described with reference to a smartcard comprising a capacitive fingerprint sensor embedded therein.

<FIG> schematically illustrates a smart card <NUM> comprising a fingerprint sensor module <NUM> according to an embodiment of the invention.

<FIG> is a schematic cross section illustration of a smartcard <NUM> according to an embodiment of the invention. The smartcard comprises a plurality of smartcard substrate layers <NUM>, one of which is an antenna layer <NUM> comprising an antenna <NUM>. A smartcard may comprise a large number of layers, e.g. some layers referred to as core layers or foils and some referred to as overlay layers or foils. Overlay foils are typically thinner and transparent while the core foils are of a solid color, often white, and thicker. The overlay foils are typically the outer layer on both the top and bottom of the card and are designed to have a glossy or matte finish depending on the aesthetic requirements on the card. The core foil gives the physical structure and weight of the card. The number of foils that are used depend on what features are needed on the card. For example, in addition to the core foil and overlay foil you can have a "signature panel foil", a magnetic stripe foil", "security overlay foil". Several overlay foils can also be stacked together to create the desired thickness of the total card.

In the illustrated example, the smartcard <NUM> comprises, from the bottom, two overlay layers, <NUM>, <NUM>, a core layer <NUM>, an antenna layer <NUM>, an overlay layer, <NUM>, a core layer <NUM>, a printing layer <NUM> and finally an overlay layer <NUM> forming the upper surface of the smartcard <NUM>.

The smartcard <NUM> further comprises a fingerprint sensor module <NUM> embedded in the smartcard and connected to the antenna <NUM> in the antenna layer <NUM>, the fingerprint sensor module <NUM> being configured to receive energy and communicate with a reading device via the antenna <NUM>. Moreover, the fingerprint sensor module <NUM> is galvanically isolated from an outside of the smartcard, i.e. the fingerprint sensor module and any associated components such as the antenna <NUM> are fully embedded in the smartcard so that there is no conductive path from the fingerprint sensor module <NUM> to the outside of the card.

As further illustrated in <FIG>, the fingerprint sensor module <NUM> comprises contact pads <NUM> on a backside of the module <NUM> opposite a sensing side <NUM> of the module, and wherein the contact pads <NUM> are directly connected to the antenna <NUM>. The direct connection between the fingerprint sensor module <NUM> and the antenna <NUM> simplifies the manufacturing process and also ensures that there is a reliable electric connection between sensor module <NUM> and the antenna <NUM>.

<FIG> also illustrate openings <NUM> in the antenna film <NUM> at the locations of the contact pads <NUM>. The antenna film <NUM> comprises an antenna carrier in the form of a plastic material and the antenna <NUM> itself. The openings <NUM> are formed in order to be able to access the antenna with a heated tool during manufacturing as will be described in further detail when describing the manufacturing process. However, in the final card the lamination process will have melted the plastic so that the openings are partially or fully filled by surrounding melted plastic material. The openings <NUM> in <FIG> are thus provided for illustrative purposes and should not be taken to be an exact representation of a final smartcard. However, the direct connection between the contact pads <NUM> and the antenna <NUM> will still exist in the final smartcard and could be seen in a cross section of a card.

<FIG> is a flow chart outlining steps of a method of manufacturing a smartcard <NUM> and <FIG> illustrate selected steps of the method. In particular, <FIG> highlight the steps related to the contact formation between the antenna and the contact pads of the fingerprint sensor module <NUM>. The general steps of forming a smartcard using various plastic foils and hot lamination can be assumed to be well known to the skilled person and will therefore not be detailed herein.

First, a fingerprint sensor module <NUM> comprising contact pads <NUM> for contacting an antenna is provided <NUM>, followed by providing <NUM> an antenna carrier layer <NUM> illustrated in <FIG>.

Next, openings <NUM> are formed <NUM> in the antenna carrier layer <NUM> in locations corresponding to the contact pads <NUM> of the fingerprint sensor module as illustrated in <FIG>.

<FIG> illustrates forming <NUM> the conductive antenna <NUM> on the antenna carrier layer to form a complete antenna film <NUM>. The conductive antenna comprises a copper wire being arranged on the antenna carrier according to a predetermined pattern, e.g. from a CAD template. The antenna <NUM>, i.e. the copper wire, is embedded in an insulating coating in order to allow antenna crossings without short-circuiting the antenna.

Once the antenna film <NUM> is completed with the patterned antenna, it is being flipped upside down and arranged <NUM> on the fingerprint sensor module <NUM> which is placed having the contact pads <NUM> facing upward as illustrated in <FIG>. The openings <NUM> are aligned with the contact pads <NUM> so that the antenna <NUM> is facing the contact pads <NUM> and also overlaps the contact pads <NUM>.

In the next step, the conductive antenna <NUM> is contacted with a heated tool through the openings in the antenna carrier layer <NUM> in order to melt the insulating coating at the locations of the contact pads <NUM>, thereby forming <NUM> an electrical contact between the conductive antenna <NUM> and the contact pads <NUM>. The heating tool may for example be a hot welding tip or the like which can access the exposed antenna <NUM> through the opening <NUM>. When the insulating coating is melted, a direct physical contact is formed between the conductive antenna <NUM> and the contact pad, thereby forming a good electrical connection.

Finally, the antenna film and the fingerprint sensor module are embedded <NUM> in a smartcard through lamination. Lamination may be performed in the form of hot lamination where a stack of layers together forms a body of the smartcard <NUM>.

The lamination process may also comprise using a laminating plate having a protruding portion at a position corresponding to a location of the fingerprint sensor module. This will have the effect that an indentation <NUM> is formed in the smartcard surface at the location of a sensing area of the fingerprint sensor module <NUM> as illustrated in <FIG>. The indentation is advantageous in that it will guide the user to a correct finger placement on the smartcard. Moreover, the indentation will act to protect the outer surface of the smartcard from scratches and the like at the location of the sensor.

<FIG> schematically illustrate an example embodiment of a portion of a smartcard <NUM> where the fingerprint sensor module <NUM> comprises wings <NUM>, making the cross section of the fingerprint sensor module <NUM> T-shaped, here seen as an upside-down T. The contact pads <NUM> for connecting to the antenna <NUM> are located on a backside of the sensor module same as in the previously described embodiments. Accordingly, the described configuration of a smartcard is applicable for different designs of the fingerprint sensor module.

<FIG> schematically illustrate an example embodiment of a portion of a smartcard <NUM> where the fingerprint sensor module <NUM> again comprises wings <NUM>, but where the contact pads <NUM> are located on a top side of the wings <NUM> such that the contact pads <NUM> face in the same direction as a sensing surface <NUM> of the fingerprint sensor module <NUM>. The illustrated embodiment may be advantageous in implementations where it is desirable to place the sensor with the sensing side up during the welding step, and/or if it is desirable to have the antenna closer to the surface of the card.

It would also be possible to arrange the contact pads of the fingerprint sensor module on the side of the module, either directly on the side of the module or on the side of wings of a T-shaped module. Side facing contact pads can for example be made using a so-called castellation process.

In the above description, the fingerprint sensor module is described as a single module. However, the module may comprise additional components such as a secure element (SE) and/or one or more additional active or passive components, such as a processing unit. Moreover, it is also possible to arrange one or more of the secure element and processing unit outside of the fingerprint sensor module itself, and to connect the component to the fingerprint sensor module using wiring in the smartcard. It should be noted that the fingerprint sensor module would still be galvanically isolated from an outside of the car since none of the components connected to the module have an external interface.

Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art.

Claim 1:
A smartcard (<NUM>) comprising:
a plurality of smartcard substrate layers (<NUM>);
an antenna layer (<NUM>) comprising an antenna (<NUM>); a fingerprint sensor module (<NUM>,<NUM>,<NUM>) connected to the antenna layer (<NUM>), the fingerprint sensor module being configured to receive energy and communicate with a reading device via the antenna (<NUM>), characterized in that the fingerprint sensor module (<NUM>,<NUM>,<NUM>) is embedded in the smartcard substrate layers (<NUM>), and in that the fingerprint sensor module (<NUM>,<NUM>,<NUM>) is galvanically isolated from an outside of the smartcard (<NUM>).