metallic smart card with radio-frequency antenna and method for manufacturing such a smart card

Abstract

The present invention relates to a smart card comprising: - a metallic layer including a cavity and a junction connecting the cavity to an edge of the card; - an RF chip; - an RF antenna electrically connected to the RF chip by a conductive physical connection, the antenna being disposed on a non-conductive layer deposited on the metallic layer, the RF chip being disposed at the level of the metallic layer and comprising: - a first set of turns routed along the periphery of the card, including at least one turn extending towards the interior of the card, and electrically connected to: - a second set of turns routed outside said cavity, along the edges of said cavity; - the turns of the two sets of turns being arranged such that the current flows in the same direction in both sets of turns. Figure for the abstract: Fig. 1B.

Description

Title of the invention: Metallic smart card with radio frequency antenna and method for manufacturing such a smart card technical field

[0001] The invention relates to the field of smart cards and more particularly to metallic smart cards capable of operating in contactless mode. Prior art

[0002] The use of smart cards (or microcircuit cards) is now widespread in everyday life. Such cards are used, for example, as bank cards, loyalty cards, access cards, etc., and can take various forms depending on their respective uses. Smart cards can be designed to perform various types of functions, including carrying out transactions, such as banking transactions (payment transactions, transfers, etc.), authentication transactions, etc.

[0003] As is known, a smart card generally comprises a card body equipped with an electronic chip configured to exchange signals with the outside world and perform various functions depending on the intended use of the card. To this end, smart cards are equipped with communication means enabling interaction with the outside world, typically with an NFC reader or external reader.

[0004] Traditionally, a smart card is designed to cooperate with an external NFC reader by means of external contacts accessible on the surface of the card. An external NFC reader can thus position appropriate contact pins on the external contacts of the card in order to establish contact communication.

[0005] Recently, contactless smart cards have experienced increasing growth due to the speed and simplicity of contactless transactions. To achieve this, contactless cards incorporate a radio frequency (RF) antenna that allows the exchange of RF signals with an external NFC reader (for example, using NFC, or Near Field Communication). This RF antenna is generally composed of a plurality of conductive loops extending into the body of the card.

[0006] The structure and appearance of smart cards can vary depending on the case. Metallic smart cards, in particular, are experiencing growing interest due to their attractive aesthetic appearance (metallic reflections, brushed surface effect, etc.), the high-quality printing they can provide (the considerable weight of the metal, high-end aesthetics), and the prestigious connotation associated with them for their users. This is due in particular to their significant weight and the printing Because of the high quality they convey, these cards are preferred by some users as a social marker and differentiating element.

[0007] However, it has been observed that the presence of metal in the body of a smart card poses major difficulties when the card incorporates an RF antenna to operate in contactless mode. The metal acts as electromagnetic shielding and blocks or interferes with the RF signals exchanged by the RF antenna with the outside world. The metal present in the card body can thus disrupt contactless communication between a smart card and an external NFC reader and hinder, for example, the completion of a contactless transaction (payment or otherwise).

[0008] A known solution is to use a ferrite layer between the antenna and the metal foil. Although simple, this solution makes the manufacture of the card complex and the card can only communicate with the interrogating reader from one side.

[0009] Another relevant solution is to use a small antenna inserted inside or superimposed on a cavity (free of metal) made in a metal sheet, the cavity being connected to the outer edge of the metal layer by means of a slot. In this configuration, the metal layer surrounds the NFC antenna and therefore has a larger physical surface area than the antenna and generally occupies the entire size of the card.

[0010] Since the magnetic field lines are closed lines, the magnetic interrogation field incident on the surrounding metallic layer, in such a topology, will therefore be diverted from the metal: the magnetic field lines at the periphery of the metal will be diverted outwards while the lines near the cavity will be diverted inwards, thus passing through the area of ​​the antenna and adding to the normal magnetic flux passing through the antenna, making its effective area larger than in the case where it would have been used without this surrounding metal.

[0011] Although the technology described above exhibits good NFC performance, it may suffer from a technical limitation inherent in its topology. Indeed, the card provides performance similar to that of a Class 2 ISO 14443 antenna or even smaller (higher classes), i.e., mediocre load modulation values ​​and a relatively high activation threshold field strength, which limits the interoperability performance of these cards with different NFC card readers. More generally, in such a topology, the antenna insertion area is compromised by the mechanical integrity of the card, which is directly related to the cavity area: the smaller the cavity, the better the mechanical behavior of the card and the more modest the RF behavior, and vice versa.

[0012] French patent application FR 3 131 034 A1 describes a smart card operating in both contact and contactless modes. This smart card comprises two antennas Inductively coupled antennas are arranged on either side of a metallic layer. One antenna is positioned on the front of the smart card, and the other is positioned on the back of the card on a plastic layer to mitigate interference from the metallic layer on the transmitted signal. However, the inductive coupling of the two antennas can lead to losses in the energy of the transmitted signal. Therefore, there is a need to improve the power of the transmitted signal in the context of metallic smart cards. Description of the invention

[0013] The present invention relates to a smart card comprising: - a card body formed at least in part by a metallic layer said metallic layer comprising a recessed area formed of a cavity and a junction connecting the cavity to a peripheral edge of the smart card; - an electronic module including an RF chip; - at least one RF antenna electrically connected to the RF chip by a conductive physical connection, the antenna being disposed on a non-conductive layer deposited on the metallic layer, the RF chip being disposed on the metallic layer and comprising - a first set of turns routed along the perimeter of the board, this set including at least one turn extending towards the inside of the board, and electrically connected to - a second set of turns routed outside said cavity, along the edges of said cavity, - the turns of the two sets of turns being arranged so that the current flows in the same direction in the first set of turns and in the second set of turns.

[0014] Thus, advantageously, compared to French patent application FR 3 131 034 A1, having only one antenna on one side of the card can advantageously reduce the energy losses induced by the coupling required when two antennas are present, thereby resulting in a stronger signal intensity. Furthermore, such a configuration limits phase distortions, since the signal is transmitted directly from the antenna wire to the chip (there is no reactive inductive coupling). This phase distortion presents a complexity for the chip at the level of demodulation of the received signal, which leads to communication errors with the reader or even a total loss of communication.

[0015] According to certain embodiments, eddy currents are produced under the effect of an incident magnetic field to which the card is subjected, the turns of the first set of turns and the turns of the second set of turns being wound so that said current and the eddy currents circulate in the same direction in the second set of turns, and in phase with the incident magnetic field.

[0016] According to some embodiments, said electronic module is positioned in said cavity.

[0017] According to some embodiments, the center of said cavity is located at the geometric center of the smart card.

[0018] According to some embodiments, said cavity is rounded or rectangular in shape and centered on the center of the smart card.

[0019] According to some embodiments, said cavity is rounded in shape, centered on the center of the smart card and has a diameter of 20mm.

[0020] According to some embodiments, the surface of said cavity represents an area substantially equal to 1.5% of the surface of the metallic layer.

[0021] According to some embodiments, the cavity comprises a dielectric material selected from wood, or ceramic, or rigid rubber.

[0022] According to some embodiments, the format of the smart card conforms to the ID1 format.

[0023] According to another aspect, the present invention relates to a method for manufacturing a smart card from a card body formed at least in part by a metallic layer - formation in said metallic layer of at least one area obviously formed by a cavity connected by a junction to a peripheral edge of the smart card, - assembly of an electronic module comprising an RF chip, - deposition of at least two insulating layers on either side of the metallic layer, - formation of an antenna electrically connected to the RF chip by a conductive physical connection on one of said insulating layers comprising - a first set of turns routed along the perimeter of the board, this set including at least one turn extending towards the inside of the board, and electrically connected to - a second set of turns routed outside said cavity, along the edges of said cavity, - the turns of the two sets of turns being arranged so that the current flows in the same direction in the first set of turns and in the second set of turns.

[0024] Other features and advantages of the present invention will become apparent from the description given below, with reference to the accompanying drawings which illustrate an example of an embodiment without any limiting character. Brief description of the drawings

[0025] [Fig. 1a] Fig. 1a represents a profile view of the layers of a smart card assembled according to the embodiment of the invention in Figure 1b,

[0026] Figure 1b Figure 1b shows a front view of a smart card according to certain embodiments of the invention,

[0027] [Fig. 2a] [Fig. 2a] shows a front view of a contactless smart card according to an embodiment of the invention,

[0028] [Fig. 2b] [Fig. 2b] shows a front view of a contactless smart card according to an embodiment of the invention,

[0029] [Fig. 3a] [Fig. 3a] shows a front view of a contactless smart card according to an embodiment of the invention,

[0030] [Fig. 3b] [Fig. 3b] shows a front view of a contactless smart card according to an embodiment of the invention,

[0031] [Fig.4] Fig.4 represents the currents flowing on the card according to an embodiment of the present invention.

[0032] [Fig.5] Fig.5 represents a method for manufacturing a smart card according to certain embodiments of the invention. Description of the implementation methods

[0033] The invention relates to metallic smart cards configured to operate in contactless mode, and also relates to a method for manufacturing such smart cards. In this document, a "metallic smart card" means a smart card comprising a metal or a combination (alloy) of metals, for example in the form of a metallic layer or a plurality of metallic layers.

[0034] As previously mentioned, a contactless smart card is inherently configured to communicate wirelessly with the outside world, more specifically with an external NFC reader. To this end, a contactless smart card incorporates a radio frequency (RF) antenna to exchange (receive and / or transmit) RF signals with an external NFC reader. Such a smart card may also be capable of operating in contact mode, using external contacts provided for this purpose on the card's surface: these are then referred to as "dual" cards (or cards with a dual communication interface), as these cards are thus capable of operating in both contactless and contact modes.

[0035] There is currently strong user demand for metallic smart cards, particularly for the reasons mentioned above (aesthetics, high-quality printing, prestige, etc.). It is especially desirable to produce smart cards in which the majority (or a significant portion) of the card body is made of metal, or at least in which the card body includes a metallic plate (or layer). metallic), in order to obtain a certain uniformity and quality in the visual and aesthetic appearance of the card.

[0036] In the following examples, the smart card is considered to be a bank card, such as a payment card. This smart card may conform to ISO 7816 and may operate according to the EMV standard, although neither of these aspects is mandatory for implementing the invention. More generally, the invention applies to any metallic smart card configured to implement a contactless transaction, including EMV cards or smart cards using another transaction standard, for example, the NFC standard (according to, for example, ISO 14443-2, ISO 10373-6, ISO 15693, "EMV Contactless Certification"). In general, the smart card of the invention can be configured to perform any type of transaction, such as banking transactions (payment, transfer, debit transactions, etc.), authentication transactions, and so on.

[0037] Unless otherwise indicated, common or similar elements in several figures bear the same reference signs and have identical or similar characteristics, so that these common or similar elements are generally not described again for the sake of simplicity.

[0038] The terms "first(s)" (or first(s)), "second(s)", etc.) are used in this document by arbitrary convention to allow identification and distinction of different elements (such as keys, devices, etc.) implemented in the embodiments described below.

[0039] In the examples given, the smart card is in the ID1 format of a credit card, although other forms are conceivable for implementing the invention.

[0040] An ID1 format card has dimensions of 85.60 mm x 53.98 mm x 0.76 mm.

[0041] In other embodiments, the card has a format smaller than the ID1 format and For example, it can be adapted to cards used in the automotive field.

[0042] Figures 1a and 1b respectively represent a front view and an exploded view of a smart card 1 according to certain embodiments of the invention.

[0043] The CD1 card comprises a metallic layer 103 including a recessed area (absence of metal, or cavity) 104 into which a substrate 105 is housed (inserted). The metallic layer covers the entire surface of the CD1 card. A dielectric material, or substrate, is used to fill the cavity. This material may be the resin used to bond the layers together, and in particular to bond the metallic layer to its adjacent layers. According to other embodiments, this material may also be a material used to stiffen the assembly, such as dielectric ceramics, stone-based materials, or wood-based materials. This material It can also be a transparent material, for example tempered glass or polycarbonate, so as to allow you to see through the card.

[0044] The recessed area 104 is an opening or through-hole formed in the metallic layer 103. The shape and dimensions of this recessed area 104 can be adapted as needed, as illustrated in the following figures. The cavity can have a regular shape such as a rectangle, a circle, or any other regular or irregular geometric shape.

[0045] According to some embodiments, the cavity may be round and have a diameter of 1 cm. According to some embodiments, the surface area of ​​the cavity may represent approximately 1.5% of the metallic surface area.

[0046] The center of the cavity is preferably located at the geometric center of the smart card, as in the EMVCO standards for IDL-type cards. This advantageously improves the homogeneity of the card's structure and consequently its robustness. However, the cavity can be offset depending on the width or length of the card, which can be beneficial when RFID tags have irregular geometric shapes.

[0047] The metal layer 103 may be made of a single metal, such as stainless steel, aluminum, copper, or gold, for example, or of an alloy of several different metals or any other material coated with a thick metal layer resonating at the HF RFID frequency (13.56 MHz band). The metal layer 103 may comprise a plurality of metal sublayers.

[0048] The CD1 smart card also includes two layers of dielectric resin 102a and 102b which allow the metal layer 103 to be isolated from the other layers of the card and in particular which allow the CD1 smart card to be consolidated and the metal layer to be welded / glued to its possible lower and upper adjacent layers.

[0049] An RFID antenna is implemented on a separate physical layer 106, parallel to the plane comprising the metallic layer 103. Layer 106 can be made of polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET), or other plastic derivatives used in the smart card industry. In the following figures, where the layers are not shown, the antenna is also embedded in layer 106.

[0050] The metallic layer 103 is electrically isolated from the antenna by the adjacent layer 102b. The ATI antenna comprises a plurality of turns, a more explicit front view of which will be described with reference to Figure 1b.

[0051] The CD1 smart card also includes a first layer of plastic material 101a and a second plastic layer 101b, one of the purposes of which is to protect the internal layers of the CD1 smart card. The optional layers 101a and 101b are, for example, made of polycarbonate and preferably transparent. These layers may be present for aesthetic reasons, for example to allow printing on the card, and / or for security reasons necessary in the field of smart cards, particularly security documents. Additional layers, usually plastic layers, may be added according to the needs of smart card designers.

[0052] The smart card also includes an RF electronic chip 110. The RF chip 110 is considered to be contained (or embedded) in an electronic module 111, the latter being inserted into the card body 100. The electronic module 111 is, for example, positioned in a cavity 108 formed in the recess 104, or more precisely in the substrate 105 contained within the recess 104, intended to house the electronic module 111. Thus, the RF chip 110 is positioned in the recess 104.According to other embodiments, the chip 110 is not inserted into a cavity 108 but positioned above (opposite) the substrate 105. It should be noted, however, that various arrangements of the RF chip 110 are possible. In particular, variants are possible in which the RF chip 110 is not located in, or opposite, the recessed area 110.

[0053] The smart card further includes an HF RFID antenna disposed on layer 106 and comprising two windings STE1 and SET2 described later with reference to figure 1b.

[0054] According to a particular example, the card body 100 and more generally the CD1 smart card is devoid of ferrite, which simplifies the manufacture of the card.

[0055] Figure 1b represents a front view of the CD1 map, for example when looking at the map from above layer 101a.

[0056] A slot 112 connects the cavity to a peripheral edge of the metal frame 113 (edge ​​of the metal layer 103). This slot 112 is present on the card shown in Figure 1 but not visible in a cross-sectional view. More precisely, this slot 112, which also constitutes a second recessed area, forms a connection between the outer edge of the card and the recessed area 104. The metal frame 113 follows the shape of the slot to join the edge of the cavity 104. In other words, the metal layer is present over the entire surface of the card, except for the surfaces of the cavity 104 and the slot 112.

[0057] The HF RFID antenna is routed so that it comprises two sets of turns SET1 and SET2 such that -The first assembly SET1 is routed to the outer periphery of the CD1 card, along the metal edge of the card; this assembly includes at least one turn which then joins or extends towards the interior of the card - the second assembly SET2 is routed to the outer periphery of the cavity and includes at least one turn that unfolds around the cavity, or in other words, on the outer edge of the cavity -the two sets SET1 and SET2 being electrically connected -the turns being arranged or wound so that the current flows in the same direction in the first set and in the second set.

[0058] In other words, the RF antenna is electrically connected to the RF chip by a conductive physical connection, and the antenna is disposed on a non-conductive layer deposited on the metallic layer, the RF chip being disposed at the level of the metallic layer and comprises - a first set of turns SET1 routed along the perimeter of the board, this set including at least one turn extending towards the inside of the board, and electrically connected to - a second set of SET2 turns routed outside the cavity, along the edges of the cavity, - the turns of the two sets of turns being arranged so that the current flows in the same direction in the first set of turns and in the second set of turns.

[0059] According to some embodiments, the distance between the outermost loop of the card and the edge of the card is between 100 and 200 pm.

[0060] According to some embodiments, the turn of the SET2 winding, closest to the cavity, is positioned as close as possible according to the positioning tolerances of the layers.

[0061] The antenna windings are physically located on a non-conductive layer 106 and not on the metallic layer 103. In other words, the second SET2 assembly is routed to the area of ​​the non-conductive layer 106 located on the outer periphery of the cavity, the cavity being located in the metallic layer below the non-conductive layer.

[0062] The HF RFID antenna is connected to the chip using techniques well known to those skilled in the art and not detailed here. More specifically, the electronic chip is connected on one side to the end of the outermost turn of the CD1 board, of the SET1 turn assembly, and on the other side to the end of the turn closest to the edge of the cavity of the SET2 turn assembly.

[0063] As illustrated in Figures 1a and 1b, the CD1 smart card comprises two sets of turns such that -The first assembly SET1 is routed to the outer periphery of the CD1 card, along the metal edge of the card; this assembly includes at least one turn which then joins or extends towards the interior of the card - the second assembly SET2 is routed to the outer periphery of the cavity and includes at least one turn that unfolds around the cavity -the two sets SET1 and SET2 being electrically connected -the turns being arranged or wound so that the current flows in the same direction in the first set and in the second set.

[0064] A slot 112 connects the cavity 104 to a peripheral edge of the metal frame 113. More precisely, this slot 112, as described above, is, in this embodiment, parallel to the longer edge of the card and centered with respect to the two edges of the card. According to a variant, the slot is parallel to the shorter edge of the card and centered with respect to the two edges of the card. According to other embodiments, which can also be applied to the embodiments described in the other figures, the slot can follow a different path on the card, any geometric routing being possible.

[0065] Figures 2 to 4 represent different embodiments of the present invention by proposing different shapes of cavity 104.

[0066] Figure 2a represents an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely at the center (or substantially at the center) of the cavity 104.

[0067] The cavity 104 is circular in shape and centered on the card and its diameter is 20 mm.

[0068] A slot 112 connects the cavity 104 to a peripheral edge of the metal frame 113. More precisely, this slot 112, as described above, is, in this embodiment, parallel to the longer edge of the card and centered with respect to the two edges of the card. According to a variant, the slot is parallel to the shorter edge of the card and centered with respect to the two edges of the card. As mentioned above, the slot 112 can follow any geometric path that allows the cavity 104 to be connected to the metal edge of the card.

[0069] As mentioned previously, the CD1 smart card comprises two sets of turns such that -The first assembly SET1 is routed to the outer periphery of the CD1 card, along the metal edge 113 of the card; this assembly includes at least one turn which then joins or extends towards the interior of the card - the second assembly SET2 is routed to the outer periphery of cavity 104 and includes at least one turn that unfolds around cavity 104 - the two assemblies SET1 and SET2 being electrically connected -the turns being arranged or wound so that the current flows in the same direction in the first set and in the second set.

[0070] Figure 2b represents an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely at the center (or substantially at the center) of the cavity 104.

[0071] The cavity 104 is circular in shape and centered on the card and its diameter is 10 mm.

[0072] A slot 112 connects the cavity 104 to a peripheral edge of the metal frame 113. More precisely, this slot 112, as described above, is, in this embodiment, parallel to the longer edge of the card and centered with respect to the two edges of the card. According to a variant, the slot is parallel to the shorter edge of the card and centered with respect to the two edges of the card. As mentioned above, the slot 112 can follow any geometric path that allows the cavity 104 to be connected to the metal edge of the card.

[0073] As mentioned previously, the CD1 smart card comprises two sets of turns such that -The first assembly SET1 is routed to the outer periphery of the CD1 card, along the metal edge 113 of the card; this assembly includes at least one turn which then joins or extends towards the interior of the card - the second assembly SET2 is routed to the outer periphery of cavity 104 and includes at least one turn that unfolds around cavity 104 - the two assemblies SET1 and SET2 being electrically connected -the turns being arranged or wound so that the current flows in the same direction in the first set and in the second set.

[0074] Figure 3a represents an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely at the center (or substantially at the center) of the cavity 104.

[0075] The cavity 104 is rectangular in shape and centered on the card. Its width is 7 mm and its length is 12 mm. It extends parallel to the edges of the smart card CD1, its length being along the axis of the length of the smart card.

[0076] A slot 112 connects the cavity 104 to a peripheral edge of the metal frame 113. More precisely, this slot 112, as described above, is, in this embodiment, parallel to the longer edge of the card and centered with respect to the two edges of the card. According to a variant, the slot is parallel to the shorter edge of the card and centered with respect to the two edges of the card. As mentioned above, the slot 112 can follow any geometric path that allows the cavity 104 to be connected to the metal edge of the card.

[0077] As mentioned previously, the CD1 smart card comprises two sets of turns such that -The first assembly SET1 is routed to the outer periphery of the CD1 card, along the metal edge 113 of the card; this assembly includes at least one turn which then joins or extends towards the interior of the card - the second assembly SET2 is routed to the outer periphery of cavity 104 and includes at least one turn that unfolds around cavity 104 -the two sets SET1 and SET2 being electrically connected -the turns being arranged or wound so that the current flows in the same direction in the first set and in the second set.

[0078] Figure 3b represents an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely at the center (or substantially at the center) of the cavity 104.

[0079] The cavity 104 is rectangular in shape and centered on the card. Its width is 5 mm and its length is 25 mm. It extends parallel to the edges of the smart card CD1, its length being along the axis of the length of the smart card.

[0080] A slot 112 connects the cavity 104 to a peripheral edge of the metal frame 113. More precisely, this slot 112, as described above, is, in this embodiment, parallel to the longer edge of the card and centered with respect to the two edges of the card. According to a variant, the slot is parallel to the shorter edge of the card and centered with respect to the two edges of the card. As mentioned above, the slot 112 can follow any geometric path that allows the cavity 104 to be connected to the metal edge of the card.

[0081] As mentioned previously, the CD1 smart card comprises two sets of turns such that -The first assembly SET1 is routed to the outer periphery of the CD1 card, along the metal edge 113 of the card; this assembly includes at least one turn which then joins or extends towards the interior of the card - the second assembly SET2 is routed to the outer periphery of cavity 104 and includes at least one turn that unfolds around cavity 104 -the two sets SET1 and SET2 being electrically connected -the turns being arranged or wound so that the current flows in the same direction in the first set and in the second set.

[0082] Fig. 4 illustrates the flow of currents on a CD1 smart card as described in the embodiments of the preceding figures.

[0083] Eddy currents are produced under the effect of a magnetic field FL1 to which the smart card is subjected. Such a magnetic field is generated in this example (Figure 1b) by an external terminal T1 with which the smart card CD1 cooperates in contactless mode. When the smart card CD1 is exposed to the magnetic field FL1, eddy currents circulate in the form of loops of current (primary loops and secondary loops) on the surface of the metallic layer 103. The phenomenon of the formation of eddy currents is known to those skilled in the art and will therefore not be described in detail in this document.

[0084] Eddy currents circulate in closed loops. The outermost loop relative to the center of the board, of the set of turns SET2, is the longest loop and therefore the most dominant in terms of energy carried.

[0085] In [Fig.4], it is assumed that the magnetic field generated by the terminal Tl is perpendicular to the card and directed from the back to the front of the card, the card being represented viewed from its front face.

[0086] When the card is placed in the electromagnetic field of an HF RFID reader that interrogates it (operating in the 13.56 MHz RFID frequency band), eddy currents are generated on the metallic surface as a reaction effect opposing the applied magnetic field. The eddy currents flow in closed loops; the outermost (largest) loop, corresponding to the longest path of the eddy currents, is the most significant loop in terms of energy transported.

[0087] In the present invention, because the winding loops of the antenna assembly SET1 face the outer periphery of the metal layer, and since these traces are parallel to the metal layer, an image current IA is formed in these loops. Considering the conceptual diagram in [Fig. 4], the eddy currents are represented by the arrows IM, showing the outermost current loop IM on the metal frame. The arrows IA represent the image current IA in the antenna. As shown in [Fig. 4], the induced current flows from the SET2 winding assembly located on the outer periphery of the board to the SET1 winding assembly located on the outer periphery of the cavity 104. As illustrated, the induced current flows from the outermost loops (assembly 1) to the innermost loops (assembly 2) that encircle the metal-free area of ​​the cavity.

[0088] The turns of the SET2 and SET1 assembly are wound so that the image current IA and the eddy currents IM flow in the same direction in the SET2 winding, in phase with the incident magnetic field, as illustrated in [Fig. 4]. This is made possible in particular by the presence of the metal frame 113 along the slot 112, which connects the metal frame located on the outer edge of the card to the metal frame located at the periphery of the cavity 104.

[0089] Assuming that the magnetic field follows the direction mentioned above, the current IA flowing in the turns of the SET1 and SET2 antenna assembly flows counterclockwise, in the same direction, provided that the turns of the SET1 and SET2 assemblies are wound in the same direction. The dominant eddy current in the outermost loop (i.e., closest to the metal frame on the outer periphery of the board) opposes the incident magnetic field and therefore flows clockwise through the top, bottom, left, and right sides of the metal frame in the SET1 loop assembly, but counterclockwise in the SET2 loops. Thus, in the vicinity of cavity 104, where the RF chip is located, the energy is greater than elsewhere on the board due to the energy of the electrical current IA, the eddy currents on the periphery of the board flowing through the SET1 loop, the eddy currents near the cavity flowing through the SET2 loop, and the energy induced by the magnetic field flowing inside the cavity, all of which are in phase and add together.Thus, the available energy may be greater in the cavity, therefore at the level of the RF 110 chip, than on the rest of the smart card, thereby facilitating the coupling between the smart card and the external terminal Tl and thus the communication between the smart card and the terminal Tl.

[0090] We must supply the harvested energy to the RF chip, attempting to harvest as much energy as possible. Indeed, the card's only energy source comes from the magnetic field of the interrogator reader. This energy has an amplitude and a phase. Part of this magnetic field incident on the card passes directly through the cavity, and the phase of this energy is an important parameter to consider.

[0091] Furthermore, it is also important to reduce losses. Since the present disclosure is based on the antenna topology and energy harvesting from eddy currents on the metal plate, minimizing energy losses is achieved through appropriate routing of the antenna assemblies / loops such that the energy harvested by these loops is greater than the intrinsic ohmic losses of the wires. Another parameter for minimizing losses is to keep the harvested energy in phase with that of the source, i.e., the magnetic field of the interrogator through the cavity area.

[0092] It should be noted that the eddy current loops are everywhere on the metallic layer, forming large and small loops. The larger a loop is, the greater its energy.

[0093] A set of eddy current loops, not shown in the figure, encircles the cavity in opposite phase to the incident magnetic field: this means that there is a set of eddy current loops around the cavity (disregarding the narrow slit), with the electric current flowing in a clockwise direction. Since the cavity area is the reference for this energy balance across the map and is in fact the main region where energy passes from one domain to the other, there is a high concentration of current in this area. zone: wherever there is a transition from one energy domain to another, there is a high concentration of current. By energy domain, we mean: the energy domain that is in phase with the incident energy source (including the directly incident part of the source) and the energy domain that is out of phase (180-degree phase shift), the latter being related to the reaction effect of eddy currents. It is therefore essential to collect the energy of these eddy currents and bring it into phase with the antenna routing system by means of the second set of loops around the cavity. This satisfies the two conditions mentioned above. In fact, if we imagine the set of loops around the cavity as shown in [Fig. 4] and, by hypothesis, consider them as not being in direct contact with the metal of the metal plate, but in the metal-free zone (the cavity), the loops as shown in [Fig. 4]4] are much more effective than having them in the cavity.

[0094] The routing of the antenna through these two sets of loops, as well as the presence of a slot opening onto the cavity, ensures that the induced current (IA) flowing in the SET2 loops and the eddy current at the periphery of the cavity are in the same direction, both in phase with the incident magnetic field.

[0095] In order to mechanically consolidate the card, it may be considered to fill the cavity with a robust dielectric material such as wood, ceramic, or rigid rubber.

[0096] During tests carried out on the different cavity shapes, it was found that the embodiment of [Fig. 3a], in which the cavity is round, 20 mm in diameter, and centered on the geometric center of the board, gives the best results, making it possible to obtain, for a magnetic field of 0.75 A / m, a charge modulation higher than that required by the standard. The charge modulation obtained for a magnetic field of 0.75 A / m is approximately 377 mV, the value required by the standard being 25 mV.

[0097] The embodiments described in Figures 3b, 4a, and 4b cannot achieve such high charge modulation values ​​regardless of the magnetic field strength. The embodiment in Figure 4b, in which the cavity is rectangular, centered on the geometric center of the board, and measures 5 mm by 25 mm, with the length of the cavity aligned with the length of the board, can achieve results lower than those of [Fig. 3a] but higher than the others. Next in order of performance is the embodiment of [Fig. 3b], followed by that of Figure 4a. However, all embodiments achieve results significantly higher than those required by ISO 14443-2.

[0098] It can therefore be seen that the card implementing any one of the embodiments of the present invention can, on the one hand, trigger an activation of the card very quickly and, on the other hand, with a very large modulation amplitude, and thus provide performance superior to state-of-the-art solutions.

[0099] Figure 5 schematically represents a method for manufacturing a CD1 smart card according to certain embodiments of the invention. The preceding description of the CD1 smart card according to various embodiments with reference to Figures 1-4 applies by analogy to the manufacturing method illustrated in Figure 5.

[0100] During a supply step S2, a card body 100 comprising a metal layer 103 as previously described is formed (or supplied). In particular, this card body 100 is formed at least in part by a metal layer 103, this metal layer 103 comprising a recessed area 104 opening onto a peripheral edge of the metal layer via a junction 112, as already described. In particular, a metal frame is formed by the metal layer 103 at the edge of the card, the junction, and the cavity, forming a continuous metal edge surrounding the peripheral edge, the junction, and the cavity.

[0101] According to one embodiment, two recessed areas 104 and 104' can be formed in the metal layer 103, only the recessed area 104 opening onto the peripheral edge of the metal layer 103 via the junction 112. The second cavity 104' can be intended to house an RF chip.

[0102] According to one variant, the electronic module is not positioned in a cavity.

[0103] During an S4 step, an RF electronic module is implanted either in cavity 104 or outside a cavity.

[0104] During step S6, insulating layers 102a and 102b are deposited on either side of the metallic layer 103 to isolate the metallic layer from the other non-conductive layers of the card. A layer 106 is also deposited on one of the layers 102b or 102a, such as a layer made of polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET), or other plastic derivatives used in the smart card industry. It should be noted that the electronic module, or RF chip, includes two contact points configured to be connected to an RF antenna located above layer 106. Thus, perforations may exist in layer 106 to connect contact points of the RF chip or electronic module to the antenna.

[0105] During an S8 step, an antenna is formed on layer 106. This antenna comprises two sets of turns such that -The first assembly SET1 is routed to the outer periphery of the CD1 card, along the metallic edge 113 of the card; this assembly includes at least one turn which then joins or extends towards the interior of the card, - the second assembly SET2 is routed to the outer periphery of cavity 104 and includes at least one turn that unfolds around cavity 104, - the two assemblies SET1 and SET2 being electrically connected, -the turns being arranged or wound so that the current flows in the same direction in the first set and in the second set.

[0106] As mentioned above, the end of the SET2 winding is connected to one of the contact points of the RF chip, or electronic module, and the other end of the SET1 winding is connected to the other contact point of the RF chip or electronic module so as to electrically connect the antenna to the RF chip or electronic module.

[0107] During an S10 step, protective layers 10la and 101b are arranged on either side of layer 102a and layer 106.

[0108] When the module is an electronic module enabling contact communication, then layers 102a and 101a can be drilled opposite these contact points so that these contact points are accessible by an external terminal, for example when inserting the card into a terminal.

[0109] A person skilled in the art will understand that the embodiments and variants described above are merely non-limiting examples of implementation of the invention. In particular, a person skilled in the art may consider any adaptation or combination of the embodiments and variants described above in order to meet a very specific need in accordance with the claims set forth below.

Claims

Demands

1. Smart card (CD1) comprising: - a card body (100) formed at least in part by a metallic layer (103) said metallic layer comprising a recess area (104) formed of a cavity and a junction connecting the cavity to a peripheral edge of the smart card; - an electronic module comprising an RF chip (110);- at least one RF antenna (ATI) electrically connected to the RF chip by a conductive physical connection, the antenna being disposed on a non-conductive layer deposited on the metallic layer, the RF chip being disposed at the level of the metallic layer and comprising - a first set of turns (SET1) routed along the periphery of the card, this set comprising at least one turn extending towards the inside of the card, and electrically connected to - a second set of turns (SET2) routed outside said cavity, along the edges of said cavity, - the turns of the two sets of turns being arranged so that the current flows in the same direction in the first set of turns and in the second set of turns.;

2. Smart card according to claim 1 wherein eddy currents are produced under the effect of an incident magnetic field to which the card is subjected, the turns of the first set of turns (SET1) and the turns of the second set of turns (SET2) being wound so that said current and the eddy currents flow in the same direction in the second set of turns (SET2), and in phase with the incident magnetic field.

3. Smart card according to any one of the preceding claims in which said electronic module is positioned in said cavity.

4. Smart card according to any one of the preceding claims wherein the center of said cavity is located at the geometric center of the smart card.

5. Smart card according to any one of the preceding claims wherein said cavity is rounded or rectangular in shape and centered on the center of the smart card.

6. Smart card according to any one of the preceding claims wherein said cavity is rounded in shape, centered on the center of the smart card and of diameter 20mm.

7. Smart card according to any one of the preceding claims wherein the surface area of ​​said cavity represents an area substantially equal to 1.5% of the surface area of ​​the metallic layer.

8. Smart card according to any one of the preceding claims wherein the cavity comprises a dielectric material selected from wood, or ceramic, or rigid rubber.

9. Smart card according to any one of the preceding claims, the format of which conforms to the ID1 format.

10. Method of manufacturing a smart card (CD1) from a card body (100) formed at least in part by a metallic layer (103) - formation (S2) in said metallic layer of at least one recessed area (104) formed of a cavity connected by a junction (112) to a peripheral edge (113) of the smart card, - assembly (S4) of an electronic module comprising an RF chip (110), - deposition (S6) of at least two insulating layers on either side of the metallic layer, - formation (S8) of an antenna electrically connected to the RF chip by a conductive physical connection on one of said insulating layers comprising - a first set of turns (SET1) routed along the periphery of the card, this set comprising at least one turn extending towards the interior of the card, and electrically connected to - a second set of turns (SET2) routed outside said cavity, along the edges of said cavity,- the turns of the two sets of turns being arranged so that the current flows in the same direction in the first set of turns and in the second set of turns.

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