Metal smart card with dual optimized communication interface

Abstract

The invention relates to a smart card with a dual contact and contactless communication interface, comprising a card body (20) including an electronic module (4) provided with a contact terminal block and an antenna (30) for radio frequency communication with the antenna of a contactless reader, said card body (20) including a metallic element (11) adapted to increase the weight of the card body (20), characterized in that said metallic element (11) is a composite metallic element, configured to minimize the eddy currents induced in the card body (20) when the smart card (1) is placed in the electromagnetic field of a contactless reader. Figure for the Abstract: Figure 4

Description

Title of the invention: Optimized dual-interface metal smart card

[0001] The present invention relates to a smart card with a dual contact and contactless communication interface, provided with a card body essentially made of metal. STATE OF THE ART

[0002] In the field of smart cards, particularly those used for banking applications, part of the demand tends to focus, for reasons of better handling and increased differentiation, on cards heavier than traditional smart cards with plastic bodies.

[0003] Some known smart cards have a metallic layer on only one side of the card, the other side being uncoated but equipped with an antenna enabling communication with a remote reader via radio frequency. However, due to the shielding effect of the metallic layer, the radio frequency communication is degraded. In particular, tests have shown that with this type of smart card, it is impossible to comply with certain standards such as those imposed by the so-called EMVCo specifications, which impose mechanical, electrical, and radio frequency communication quality requirements.

[0004] To overcome this problem and maintain good radio frequency communication quality regardless of the smart card's orientation relative to the remote reader, it was proposed in document FR3032294A1 to construct the smart card using a metallic insert placed between two outer sheets, each equipped with an antenna and a ferrite layer. This arrangement maintains good communication quality as required by EMVCo type specifications, but the manufacturing process for this type of card is relatively complex and expensive. Furthermore, in this embodiment, the metallic insert is located between outer layers of the plastic card and is therefore not directly visible from the outside, which does not contribute to creating sufficient differentiation in perception compared to cards made entirely of plastic.

[0005] To address this, document FR3089659A1 presented a dual-interface metal smart card with two external aluminum plates surrounding a cavity housing a microelectronic module. This structure actively enhances the card's radio frequency communication capabilities, despite the presence of aluminum layers.

[0006] However, the smart cards thus obtained weigh approximately 8 grams due to the use of aluminium, which is certainly greater than the weight of a card with a plastic body, but is still considered insufficient for the market segment of so-called "premium" smart cards, which must have a target weight of more than 12 grams, while having external faces customizable by laser engraving or other means, and while remaining compatible with the banking standards known as EMVCo.

[0007] It is therefore necessary to propose a contactless smart card or a dual communication interface card having a higher weight than known smart cards, but while retaining its communication properties and ability to be graphically personalized. PURPOSE OF THE INVENTION

[0008] The invention aims to provide a new smart card structure capable of satisfying the conflicting requirements of increased weight to reach a weight greater than 12 grams, while exhibiting a contactless communication capability conforming to the requirements of EMVCo type specifications.

[0009] Another objective of the invention is to offer such a smart card while maintaining a simple structure that is easy to mass-produce at a reduced cost and with very high reliability.

[0010] Another object of the invention is, given the high cost of ferrite, to reduce the ferrite surface area required to compensate for the presence of metal in the card. SUBJECT OF THE INVENTION

[0011] In principle, the smart card according to the invention requires the integration of heavy elements, such as metal plate elements, in particular made of steel or tungsten alloy for example, into certain areas of the card body.

[0012] However, without adequate countermeasures, the integration of a monolithic metallic element would likely severely impair the radio frequency communication capabilities of the smart card. Indeed, when the smart card is placed in the magnetic field of a contactless reader, a monolithic metallic element such as a steel plate would induce significant eddy currents, which would impair the radio frequency communication capability.

[0013] In order to remedy this new problem, the invention provides particular measures to limit eddy currents in the metallic elements added to the card body.

[0014] The invention therefore relates to a smart card with a dual contact and contactless communication interface, comprising a card body having an electronic module provided with a contact box and an antenna for radio frequency communication with the antenna of a contactless reader, said card body comprising a metallic element capable of increasing the weight of the card body, characterized in that said metallic element is a composite metallic element, configured to minimize eddy currents induced in the card body when the smart card is placed in the electromagnetic field of a contactless reader.

[0015] By composite metallic element, we mean any metallic structure or structure incorporating metal, which is not monolithic and which is specifically configured to be the site of eddy currents much lower than those which would be induced in a monolithic metallic plate.

[0016] Preferably, said composite metallic element extends over the essential part of the surface of the card body.

[0017] According to an advantageous embodiment, said composite metal element has a density greater than 1.4 grams per cm3 (which corresponds to the density of plastic materials usually used in the manufacture of smart cards), and this density is preferably greater than 2.7 grams per cm3.

[0018] According to an advantageous embodiment, the composite character of the metallic element can be achieved by dividing the element into a plurality of smaller unitary metallic elements, electrically insulated from each other.

[0019] According to one embodiment, said unitary metal elements of the composite metal element are configured in the form of unitary metal plates in the shape of squares, juxtaposed to one another.

[0020] According to one embodiment, said unitary metal elements of the composite metal element are configured in the form of juxtaposed metal crossbars and provided with a central cutout suitable for limiting eddy currents in each metal crossbar.

[0021] According to one embodiment, said unitary metal elements of the composite metal element are configured in the form of unitary metal plates in the shape of adjacent hexagons, so that the eddy currents induced along the adjacent edges of two contiguous hexagons flow in opposite directions, thus reducing the eddy currents induced in each hexagon.

[0022] In this case, said unitary metal plates in the shape of hexagons can be solid, or arranged in the form of a metal track interlaced with recesses.

[0023] In other embodiments of the invention, it is possible to replace the unit metal plates with another structure, for example by configuring the composite metal element in the form of a resin layer incorporating filings of a metallic material, in particular iron filings, or by structuring the composite metal element in the form of one or more metal sheets. Honeycomb-structured tallics.

[0024] Whatever the geometric configuration of the composite metal element, it will preferably use heavy elements, in stainless steel or alloy, in particular tungsten alloy.

[0025] The smart card according to the invention using a composite metallic element will then comprise a card body formed by a stack comprising at least one layer of plastic material, an insert provided with an antenna, a ferrite layer, a composite metallic element in one of the forms described above, and an aluminum cover provided with a cavity receiving an electronic module. This module may simply be connected to the antenna of the card body, or may have its own antenna directly on the module, as known per se.

[0026] According to one embodiment of the smart card according to the invention, the ferrite layer may be located in the same plane of the card body as the composite metal element and juxtaposed to it. Alternatively, the ferrite layer may be interposed between the insert carrying the antenna of the card body and the composite metal element.

[0027] In order to limit the amount of ferrite to be used, the invention provides for the placement of the ferrite layer only opposite the antenna of the card body and the antenna of the electronic module, when the latter has its own antenna.

[0028] Depending on the embodiment of the smart card, the composite metallic element integrated into the card body will have a thickness of between 50 and 250 micrometers. DETAILED DESCRIPTION

[0029] The invention will be described in more detail with reference to the drawings, in which: - Fig. 1 represents a plan view of the inside of a known metallic smart card. - Figures 2A, 2B, 2C represent exploded perspective, plan, and section views of another metallic smart card according to the prior art. - Fig. 3 represents a schematic diagram illustrating the appearance of eddy currents in the metallic parts of a known smart card conforming to figures 1 or 2, under the effect of the electromagnetic field of a contactless reader. - Fig. 4 schematically represents the metallic part of a smart card, configured according to a first embodiment of the invention, namely with a composite metallic element formed by a plurality of small unitary metallic elements integrated into the card body. - Fig. 5 represents one embodiment of the unitary metal elements of Fig. 4, in the shape of a cross. - Fig. 6 represents a first embodiment of a composite metallic element formed by a juxtaposition of solid metallic hexagons intended to be incorporated into the body of the smart card according to the invention. - Fig. 7 represents a second embodiment of a composite metallic element formed by a juxtaposition of hollow metallic hexagons intended to be incorporated into the body of the smart card according to the invention. - Fig. 8 represents another embodiment of a composite metallic element, in the form of a honeycomb metallic structure intended to be incorporated into the body of the smart card according to the invention. - Fig. 9 represents iron filings intended to be incorporated into a mixture to form a composite metallic element intended to limit eddy currents in the body of the smart card according to the invention. - Fig. 10 represents a cross-sectional view of a first embodiment of a smart card according to the invention, using a composite metallic element according to one of figures 4 to 9. - Fig. 11 represents a cross-sectional view of a second embodiment of a smart card according to the invention, using a composite metallic element according to one of figures 4 to 9. - Fig. 12 represents a plan view of an embodiment of the smart card according to the invention, with a card body conforming to Fig. 11.

[0030] In [Fig. 1] a plan view of an internal face of the body of a known metallic smart card 1 is shown. It has on its external face (not shown) a metallic layer, and on its internal face a ferrite layer 10 of a large surface area (shown in black) which covers almost the entire surface of the card, with the exception of the area of ​​the electronic module 4 and the area of ​​the antenna 12 of the card body.

[0031] In such a smart card 1 with a predominantly metallic body, the use of a ferrite layer 10 makes it possible to deflect the incident electromagnetic field lines from a contactless card reader. Indeed, ferrite has a very high magnetic permeability which allows it to modify the field lines, so that the external metallic plate has minimal influence on the radio frequency communication capability of the smart card. However, this known solution suffers from an economic problem, since ferrite is a very expensive material.

[0032] In order to obtain a metallic smart card without ferrite, a smart card such as that shown in Figure 2 has been proposed in the prior art. It comprises a card body formed by two aluminum sheets 2, 3 in which cavities are provided to receive, on the one hand, the electronic module 4, and on the other hand, a battery 8 intended to power the electronic module. In other In terms of electromagnetic shielding, the effect induced by the aluminum foils 2,3 is compensated for by the use of an active power supply circuit, since the electromagnetic field of the contactless reader is insufficient to overcome the disruptive effect of the aluminum foils on the power supply and radio frequency communication of the smart card. This known solution is therefore more complex than that of [Fig. 1] and requires additional machining of the card body. Furthermore, the cards thus obtained weigh approximately 8 grams, certainly more than a card with a plastic body, but still well below the weight of at least 12 grams sought by the market for high-end metallic smart cards.

[0033] In order to resolve these conflicting requirements, the invention therefore sought to provide a metallic card using significantly less ferrite than the card in [Fig. 1], while using a more economical metal than ferrite and heavier than aluminum in the card body, and while maintaining good radio frequency communication capabilities with a contactless reader. This last requirement implies finding a metallic structure that is less prone to the appearance of eddy currents in the card body in the presence of the electromagnetic field of the card reader.

[0034] As illustrated schematically in [Fig. 3], in the presence of a monolithic metallic card body 2, the excitation current of the contactless reader generates a significant destructive electromagnetic excitation field, which creates eddy currents in the metallic card body 2 corresponding to an induced electromagnetic field. In the absence of countermeasures, this induced field severely disrupts or even destroys the radio frequency communication capability of the card body's antenna.

[0035] According to a principle illustrated schematically in [Fig. 4], the invention provides for the incorporation into the card body of a composite metallic element 11, formed by a set of small individual metallic elements 12, particularly made of steel, juxtaposed to one another but electrically insulated from each other. The principle is that by replacing a continuous conductive surface with a discontinuous set of smaller, insulated metallic surfaces, the resulting eddy currents in each individual metallic element 12 generate a much weaker magnetic field, and one that is less destructive to the magnetic field required for radio frequency communication between the reader and the smart card.

[0036] In the embodiment of [Fig. 4], these individual metal elements 12 are square, for example, on the order of 5 millimeters on each side, but other shapes are possible. In this configuration, the electromagnetic field of the card reader causes the appearance in each individual metal element 12 of a much weaker eddy current than in the case of a metal plate 2 the size of the card body. Furthermore, as shown schematically by the arrows 13, the currents induced the along adjacent edges 14 of the different metallic squares 12 circulate in opposite directions, and the induced fields then tend to cancel each other out at many points.

[0037] According to another embodiment shown schematically in [Fig. 5], the individual square-shaped metal elements 12 can be replaced by cross-shaped metal elements 15, preferably having a central cross-shaped slot 16. Here again, the eddy currents (shown schematically by arrows 13) would be lower than in the case of a metal plate the size of a smart card, and the eddy currents induced in two adjacent cross-shaped elements 15 would produce only a very small destructive field.

[0038] According to another advantageous embodiment shown schematically in [Fig. 6], the metal squares 12 of [Fig. 4] can be replaced by solid, juxtaposed metal hexagons 17. Here again, the field of the contactless reader generates eddy currents in the different metal hexagons 17, which tend to cancel each other out in pairs along the sides of adjacent hexagons 17, thus greatly reducing the electromagnetic field that could interfere with radio frequency communication with the reader.

[0039] According to an alternative embodiment shown in [Fig.7], the juxtaposed hexagonal metal elements 17 are not solid, but hollow, and made in the form of metal tracks 18 whose external parts have a hexagonal shape, and the tracks 18 are separated by recesses 19.

[0040] Another possible configuration of metallic element is the honeycomb metallic structure 28 shown schematically in [Fig.8]. In order to increase the electrical resistance of this structure and thus reduce eddy currents, it would also be possible to stack several thin honeycomb metallic grids 28 such as that shown in [Fig.8], insulated from each other.

[0041] Another solution under consideration would be to produce a composite metallic element, not in the form of a set of small, juxtaposed individual metal plates, but rather a heavy element formed by incorporating iron filings (shown in [Fig. 9]) into a binder such as a resin, so as to form a composite plate based on binder and iron filings, in proportions that can be easily determined by those skilled in the art according to the desired weight. This makes it possible to substantially increase the weight of the card body, with a low manufacturing cost, while avoiding the generation of harmful eddy currents, since the iron filings do not have a continuous metallic surface susceptible to eddy currents that could destroy the electromagnetic field used for communication.

[0042] Regardless of the geometry of the unit elements used to form a composite metallic element 11 to be integrated into the card body, ferrite may only be used in limited areas corresponding to the parts of the card body which are the most sensitive from an electromagnetic point of view, namely in particular at the right of the turns of the antenna of the card body and / or the antenna of the electronic module of the smart card.

[0043] The composite metal element 11 configured according to one of the embodiments described in relation to Figures 3 to 9 can then be used to incorporate it into the card body, in particular between the different layers thereof.

[0044] Two concrete embodiment examples are shown in Figures 10 and 11. The thicknesses of the card body 20 and its layers have been greatly exaggerated compared to those of a real smart card, for the sake of clarity of representation.

[0045] In [Fig. 10], the card body 20 consists of a lower sheet 21 of plastic material, in particular transparent PVC, surmounted by a printed PVC layer 22, and an aluminum cover 25 delimiting a "pocket" into which other layers of material are incorporated, namely a plastic insert 23 carrying aluminum tracks (not shown) forming the antenna of the card body 20. The various layers are bonded together by thin layers of adhesive 29 as known per se. The card body 20 naturally includes a cavity 27 into which an electronic module (not shown) will be inserted. The insert layer 23 carrying the antenna of the card body is surmounted by a ferrite layer 24 limited to the antenna area (as seen in the top view in [Fig. 12]).This ferrite layer 24 is surmounted by a composite metallic element 11 such as those described in connection with figures 4 to 9, namely juxtaposed square metallic elements 12 or hexagonal metallic elements 17, a metallic honeycomb structure 28, or a composite plate incorporating iron filings.

[0046] The embodiment of the card body 20 of [Fig.11] is similar to that of [Fig.10], except that the composite metal element 11 is no longer superimposed with the ferrite zone 24, but juxtaposed with it in the same plane.

[0047] In [Fig. 12] the arrangement of the various elements of the card body 20 of [Fig. 11] is shown in a top view. It can be seen that the composite metallic element 11, which adds weight to the smart card, is arranged over the entire surface of the card body 20, with the exception of area 27 of the electronic module 7 and the peripheral area occupied by the antenna 30. The ferrite 24 occupies the peripheral area of ​​the card body, substantially overlapping with the area occupied by the antenna 30. ADVANTAGES OF THE INVENTION

[0048] The invention achieves the stated objectives. Tests have shown that radio frequency communication with a contactless reader is of good quality regardless of the card's orientation, and remains compliant with EMVCo specifications.

[0049] The metallic faces of the smart card according to the invention are solid, without compromising the quality of radio frequency communication. They provide the smart card a beautiful appearance, a weight of more than 12 grams in line with the needs of the premium card market, and a good grip.

[0050] The manufacture of the composite metal elements 11 and the assembly of the components is simple and low cost.

[0051] In conclusion, the smart card according to the invention works in the same way as a plastic card or a known heavy card, but it also fully complies with the EMVCo standard.

Claims

Claims

1. 1 - Smart card with dual contact and contactless communication interface, comprising a card body (20) comprising an electronic module (4) provided with a contact terminal block and an antenna (30) intended for radiofrequency communication with the antenna of a contactless reader, said card body (20) comprising a composite metal element (11) capable of increasing the weight of the card body (20), said composite metal element (11) being configured in the form of a plurality of smaller unitary metal elements (15) electrically insulated from each other,characterized in that said unitary metal elements (15) of the composite metal element (11) are configured in the form of juxtaposed metal crosspieces (15) provided with a central cutout (16) capable of limiting the eddy currents in each metal crosspiece (15) when the smart card (1) is placed in the electromagnetic field of a contactless reader.,

2. 2 - Chip card according to claim 1, characterized in that said composite metal element (11) extends over most of the surface of the card body.

3. 3 - Chip card according to claim 1 or claim 2, characterized in that said composite metal element (11) has a density greater than 1.4 grams per cm3, and preferably greater than 2.7 grams per cm3.

4. - Smart card according to any one of the preceding claims, characterized in that said composite metal element (11) comprises elements made of stainless steel or alloy, in particular tungsten alloy.

5. 5 - Smart card according to any one of the preceding claims, characterized in that it comprises a card body (20) formed by a stack comprising at least one layer of plastic material (21, 22), an insert (23) provided with an antenna (30), a ferrite layer (24), a composite metal element (11), and an aluminum cover (25) provided with a cavity (27) receiving an electronic module.

6. 6 - Chip card according to claim 5, characterized in that the ferrite layer (24) is located in the same plane of the card body (20) as the composite metal element (11) and juxtaposed with it.

7. 7 - Chip card according to claim 5, characterized in that the ferrite layer (24) is interposed between the insert (23) carrying the antenna (30) and the composite metal element (11).

8. 8 - Chip card according to one of claims 5 to 7, characterized in that the ferrite layer (24) is arranged only opposite the antenna (30) of the card body (20) and the antenna of the electronic module.

9. 9 - Smart card according to any one of the preceding claims, characterized in that said composite metal element (11) integrated into the card body (20) has a thickness of between 50 and 250 micrometers.

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