metal smart card with radio frequency antenna and method of manufacturing such a smart card

Abstract

The present invention relates to a smart card comprising:- a metal layer comprising 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 arranged on a non-conductive layer deposited on the metal layer, the RF chip being arranged at the metal layer and comprising - a first set of turns routed along the periphery of the card, comprising at least one turn extending towards the inside 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 so that the current flows in the same direction in both sets of turns. Figure for abstract: Fig. 1B.

Description

Title of the invention: metal smart card with radiofrequency antenna and method of manufacturing such a smart card Technical field

[0001] The invention relates to the field of smart cards and relates more particularly to metal 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 formats depending on their respective uses. Smart cards can be designed to perform various types of functions, in particular to carry out transactions, such as banking transactions (payment transactions, transfer transactions, etc.), authentication transactions, etc.

[0003] As is known, a smart card generally comprises a card body which is equipped with an electronic chip configured to exchange signals with the outside and perform various functions depending on the desired use of the card. To do this, smart cards are provided with communication means allowing interaction with the outside, 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 popularity due to the increased 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 (e.g., near field NFC for "Near Field Communication" in English). This RF antenna is generally composed of a plurality of conductive turns that extend into the body of the card.

[0006] The structure and appearance of smart cards can vary depending on the case. Metal smart cards are particularly enjoying growing interest due in particular to the attractive aesthetic appearance of these cards (metallic reflections, brushed surface effect, etc.), the quality impression that they can provide (appreciable weight of the metal, high-end aesthetics), or the connotation of prestige associated with them for their users. Due in particular to their significant weight and the printing Due to the high quality they give off, these cards are favored by some users to serve as a social marker and a 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. The metal present in the card body can thus disrupt the contactless communications of a smart card with an external NFC reader and, for example, interfere with the completion of a contactless transaction (payment or other).

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

[0009] Another relevant solution is to use a reduced-size antenna inserted inside or superimposed with a cavity (absence 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 that of the antenna and generally occupies the entire size of the card.

[0010] Since the magnetic field lines are closed lines, the interrogating magnetic field incident on the surrounding metal layer, in such a topology, will therefore be diverted away from the metal: the magnetic field lines at the periphery of the metal will be diverted outwards while the lines close to the cavity will be diverted inwards, thus crossing the area of ​​the antenna and adding to the normal magnetic flux crossing the antenna, making its effective area larger than if it had been used without this surrounding metal.

[0011] Although the technology described above exhibits good NFC behavior, it may suffer from a technical limitation inherent in its topology. Indeed, the card provides performance similar to that of an ISO 14443 Class 2 or even smaller (higher classes) antenna, i.e. poor load modulation values ​​and a relatively high activation threshold field level, which limits the interoperability performance of these cards with the various 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] Patent application FR 3 131 034 A1 describes a smart card operating in both contact and contactless mode. This smart card comprises two antennas coupled by induction and arranged on each side of a metal layer. One of the antennas is positioned on the front side of the smart card and the other is positioned on the back side of the card on a plastic layer, in order to overcome the interference induced by the metal layer on the transmitted signal. The inductive coupling of the two antennas can however lead to losses in the energy of the transmitted signal. There is therefore a need to improve the power of the transmitted signal in the context of metal smart cards. Presentation of the invention

[0013] The present invention relates to a smart card comprising: - a card body formed at least in part by a metal layer, said metal layer comprising a recess area formed by a cavity and a junction connecting the cavity to a peripheral edge of the smart card; - an electronic module comprising an RF chip; - at least one RF antenna electrically connected to the RF chip by a conductive physical connection, the antenna being arranged on a non-conductive layer deposited on the metal layer, the RF chip being arranged at the metal layer and comprising - a first set of turns 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 coils 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 patent application FR 3 131 034 A1, the fact of having only one antenna present on a single face of the card can advantageously make it possible to reduce the energy losses induced by the coupling necessary when two antennas are present, thus making it possible to obtain a stronger signal intensity. In addition, such a configuration limits phase distortions, because the signal is transmitted directly from the antenna wire to the chip (there is no reactive coupling by induction). 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 in such a way 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 certain embodiments, said electronic module is positioned in said cavity.

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

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

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

[0020] According to certain embodiments, the surface area of ​​said cavity represents a surface area substantially equal to 1.5% of the surface area of ​​the metal layer.

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

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

[0023] According to another aspect, the present invention relates to a method of manufacturing a smart card from a card body formed at least in part by a metal layer - formation in said metal layer of at least one recessed area 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 metal layer, - forming 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 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 coils 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 characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an exemplary embodiment thereof 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 of Figure 1b,

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

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

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

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

[0030] [Fig. 3b] [Fig. 3b] represents 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 of manufacturing a smart card according to certain embodiments of the invention. Description of the embodiments

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

[0034] As indicated previously, a contactless smart card is configured by nature to communicate in contactless mode with the outside, more particularly with an external NFC reader. For this purpose, a contactless smart card incorporates a radiofrequency (RF) antenna to exchange (receive and / or transmit) RF signals with an external NFC reader. Such a smart card may also have the capacity to operate in contact mode, using external contacts provided for this purpose on the surface of the card: these are then referred to as “dual” cards (or cards with a dual communication interface), these cards thus being capable of operating in contactless mode and in contact mode.

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

[0036] In the following examples, it is considered that the smart card is a bank card, such as a payment card for example. This smart card may comply with the ISO 7816 standard and may operate according to the EMV standard, although neither of these aspects is mandatory to implement the invention. More generally, the invention applies to any metal smart card configured to implement a transaction in contactless mode, including EMV cards or smart cards using another transaction standard, for example the NFC standard (according to for example ISO14443-2, ISO 10373-6, ISO 15693, “EMV Contactless Certification”). Generally, the smart card of the invention may be configured to carry out a transaction of any type, such as banking transactions (payment, transfer, debit transactions, etc.), authentication transactions, etc.

[0037] Unless otherwise indicated, elements common or similar to 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)", "second(s)", etc.) are used in this document by arbitrary convention to enable different elements (such as keys, devices, etc.) implemented in the embodiments described below to be identified and distinguished.

[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] A card in ID1 format 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 can for example be adapted to cards used in the automotive sector.

[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 card CD1 comprises a metal layer 103 comprising a recessed area (absence of metal, or cavity) 104 in which a substrate 105 is housed (inserted). The metal layer covers the entire surface of the card CD1. 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 metal layer to its adjacent layers. According to other embodiments, this material may also be a material for stiffening the assembly, such as dielectric ceramics, stone-based materials or wood-based materials. This material can also be a transparent material, for example tempered glass or polycarbonate, so that the card can be seen through.

[0044] The recess area 104 is an opening or through area provided in the metal layer 103. The shape and dimensions of this recess area 104 may be adapted as appropriate as illustrated in the following figures. The cavity may have a regular shape such as a rectangle, a circle or any other geometric shape, regular or irregular.

[0045] According to certain embodiments, the cavity may be round in shape and have a diameter equal to 1 cm. According to certain embodiments, the surface area of ​​the cavity may represent approximately 1.5% of the metal 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 makes it possible to improve the homogeneity of the structure of the card and consequently to improve its robustness or solidity. The cavity can however be eccentric according to the width or the length of the card, which can be interesting when the RFID tags take irregular geometric shapes.

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

[0048] The smart card CD1 also comprises two layers of dielectric resin 102a and 102b which make it possible to isolate the metal layer 103 from the other layers of the card and in particular which make it possible to consolidate the smart card CD1 and weld / bond the metal layer to its possible lower and upper adjacent layers.

[0049] An RFID antenna is implemented on a separate physical layer 106, parallel to the plane that includes the metal layer 103. The layer 106 may be a layer made of polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET) or other plastic derivatives used in the smart card field. In the following figures, in which the layers do not appear, the antenna is also implanted in the layer 106.

[0050] The metal layer 103 is electrically insulated 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 FIG. 1b.

[0051] The smart card CD1 also comprises a first layer of plastic material 101a and a second plastic layer 101b, one of the objectives of which is to protect the internal layers of the smart card CD1. The layers 101a and 101b, optional, are for example made of polycarbonate and preferably transparent. These layers may in particular 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 and in particular security documents. Additional layers, usually plastic layers, may be added according to the needs of the smart card designers.

[0052] The smart card also comprises an RF electronic chip 110. It is considered that the RF chip 110 is included (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 area 104, or more precisely in the substrate 105 included in the recess area 104, intended to accommodate the electronic module 111. Thus, the RF chip 110 is positioned in the recess area 104.According to other embodiments, the chip 110 is not inserted into a cavity 108 but positioned above (facing) the substrate 105. Note, however, that various arrangements of the RF chip 110 are possible. Variants are notably possible in which the RF chip 110 is not arranged in, or facing, the recess area 110.

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

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

[0055] Figure 1b shows a front view of the card CD1, for example when looking at the card above the 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 FIG. 1 but not visible in a sectional view. More precisely, this slot 112, which also constitutes a second recess area, constitutes a connection between the outer edge of the card and the recess 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 set SET1 is routed on the outer periphery of the card CD1, along the metal edge of the card, this set comprises at least one turn which then joins or is deployed towards the inside of the card - the second set SET2 is routed on the outer periphery of the cavity and comprises at least one turn which is deployed 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 metal layer, the RF chip being disposed at the metal layer and comprises - 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 SET2 coils 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 certain embodiments, the distance between the outermost turn of the card and the edge of the card is between 100 and 200 pm.

[0060] According to certain 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 metal layer 103. In other words, the second set SET2 is routed on the area of ​​the non-conductive layer 106 located at the outer periphery of the cavity, the cavity being located in the metal layer located under the non-conductive layer.

[0062] The HF RFID antenna is connected to the chip by techniques well known to those skilled in the art and not detailed here. More precisely, the electronic chip is connected on the one hand to the end of the outermost turn to the card CD1, of the set of turns SET1, and on the other hand to the end of the turn closest to the edge of the cavity of the set of turns SET2.

[0063] As illustrated in Figures 1a and 1b, the smart card CD1 comprises two sets of turns such that -the first set SET1 is routed on the outer periphery of the card CD1, along the metal edge of the card, this set comprises at least one turn which then joins or is deployed towards the inside of the card - the second set SET2 is routed on the outer periphery of the cavity and comprises at least one coil which is deployed 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 previously, is in this embodiment, parallel to the largest edge of the card and centered relative to the two edges of the card. According to a variant, the slot is parallel to the smallest edge of the card and centered relative 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 another path on the card, any geometric routing being able to be envisaged.

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

[0066] [Fig. 2a] shows an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely in the center (or substantially in 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 previously, is in this embodiment, parallel to the largest edge of the card and centered relative to the two edges of the card. According to a variant, the slot is parallel to the smallest edge of the card and centered relative to the two edges of the card. As mentioned previously, the slot 112 can follow any geometric path making it possible to connect the cavity 104 to the metal edge of the card.

[0069] As mentioned previously, the smart card CD1 comprises two sets of turns such that -the first set SET1 is routed on the outer periphery of the card CD1, along the metal edge 113 of the card, this set comprises at least one turn which then joins or is deployed towards the inside of the card - the second set SET2 is routed on the outer periphery of the cavity 104 and comprises at least one turn which is deployed around the 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.

[0070] [Fig. 2b] shows an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely in the center (or substantially in 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 previously, is in this embodiment, parallel to the largest edge of the card and centered relative to the two edges of the card. According to a variant, the slot is parallel to the smallest edge of the card and centered relative to the two edges of the card. As mentioned previously, the slot 112 can follow any geometric path making it possible to connect the cavity 104 to the metal edge of the card.

[0073] As mentioned previously, the smart card CD1 comprises two sets of turns such that -the first set SET1 is routed on the outer periphery of the card CD1, along the metal edge 113 of the card, this set comprises at least one turn which then joins or is deployed towards the inside of the card - the second set SET2 is routed on the outer periphery of the cavity 104 and comprises at least one turn which is deployed around the 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.

[0074] [Fig. 3a] shows an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely in the center (or substantially in 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 in 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 previously, is in this embodiment, parallel to the largest edge of the card and centered relative to the two edges of the card. According to a variant, the slot is parallel to the smallest edge of the card and centered relative to the two edges of the card. As mentioned previously, the slot 112 can follow any geometric path making it possible to connect the cavity 104 to the metal edge of the card.

[0077] As mentioned previously, the smart card CD1 comprises two sets of turns such that -the first set SET1 is routed on the outer periphery of the card CD1, along the metal edge 113 of the card, this set comprises at least one turn which then joins or is deployed towards the inside of the card - the second set SET2 is routed on the outer periphery of the cavity 104 and comprises at least one turn which is deployed around the 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] [Fig. 3b] shows an embodiment of a contactless smart card. The RF chip 110 is located in the cavity and more precisely in the center (or substantially in 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 in 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 previously, is in this embodiment, parallel to the largest edge of the card and centered relative to the two edges of the card. According to a variant, the slot is parallel to the smallest edge of the card and centered relative to the two edges of the card. As mentioned previously, the slot 112 can follow any geometric path making it possible to connect the cavity 104 to the metal edge of the card.

[0081] As mentioned previously, the smart card CD1 comprises two sets of turns such that -the first set SET1 is routed on the outer periphery of the card CD1, along the metal edge 113 of the card, this set comprises at least one turn which then joins or is deployed towards the inside of the card - the second set SET2 is routed on the outer periphery of the cavity 104 and comprises at least one turn which is deployed around the 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 circulation 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 metal 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 card, 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 T1 is perpendicular to the card and directed from the back to the front of the card, the card being represented seen from its front face.

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

[0087] In the present invention, due to the winding loops of the antenna assembly SET1 facing the outer periphery of the metal layer, as these traces are parallel to the metal layer, an image electric current IA is formed in these loops. Considering the conceptual diagram of [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 electric current IA in the antenna. As shown in [Fig.4], the induced current flows from the set of turns SET2 located on the outer periphery of the board to the set of turns SET1 located on the outer periphery to the cavity 104. As illustrated, the induced current flows from the outermost loops (set 1) to the innermost loops (set 2) which encircle the area of ​​the cavity without metal.

[0088] The turns of the assembly SET2 and SET1 are wound in such a way that the image current IA and the eddy currents IM circulate in the same direction in the winding SET2, 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 on 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 sets of the antenna flows in the opposite direction to the hands of a clock, in the same direction, provided that the turns of the SET1 and SET2 sets are wound in the same direction. The dominant eddy current, in the outermost turn (thus closest to the metal frame at the outer periphery of the board), opposes the incident magnetic field, and therefore flows clockwise through the top, bottom, left and right of the metal frame, in the set of turns SET1, but flows counterclockwise in the turns of the set SET2. Thus, in the vicinity of cavity 104, where the RF chip is located, the energy is made greater than elsewhere on the board thanks to the energy of the electric current IA, the eddy currents at the periphery of the board flowing on the set SET1, the eddy currents close to the cavity flowing on the set SET2, and the energy induced by the magnetic field flowing inside the cavity, all adding up while being in phase.Thus, the available energy may be greater in the cavity, therefore at the level of the RF chip 110, than on the rest of the smart card, thus facilitating the coupling between the smart card and the external terminal T1 and thus the communication between the smart card and the terminal T1.

[0090] We must supply the harvested energy to the RF chip, trying to harvest as much energy as possible. Indeed, the only source of energy for the card comes from the magnetic field of the interrogator reader. This energy has an amplitude and a phase. A 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 take into account.

[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 done by 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 to minimize losses is to keep the harvested energy in phase with that of the source, i.e. the magnetic field of the interrogator across the cavity area.

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

[0093] A set of eddy current loops, which is not shown in the figure, encircles the cavity in phase opposition with the incident magnetic field: this means that there is a set of eddy current loops around the cavity (without taking into account the narrow slit), with a clockwise direction of electric current. The cavity area being the reference of this energy balance across the board and being in fact the main region where energy passes from one domain to another, there is a high concentration of current in this area: 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 the eddy currents. It is therefore of prime importance 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 not to be 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] are much more effective than having them in the cavity.

[0094] Routing 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 consolidate the card mechanically, it may be considered to fill the cavity with a robust dielectric material such as wood, ceramic, rigid rubber.

[0096] During tests carried out on the different cavity shapes, it is 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 card, presents the best results, making it possible to obtain, for a magnetic field of 0.75 A / m, a charge modulation greater 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 significant load modulation values ​​regardless of the value of the magnetic field. The embodiment of figure 4b in which the cavity is rectangular, centered on the geometric center of the card and of dimensions 5mm by 25 mm, the length of the cavity being in the same axis as the length of the card, can achieve results lower than those of [Fig. 3a] but higher than the others. Next in the order of performance, comes the embodiment of [Fig. 3b] then that of figure 4a. However, all the embodiments make it possible to obtain results significantly higher than those required by the ISO 14443-2 standard.

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

[0099] [Fig. 5] schematically represents a method of manufacturing a CD1 smart card according to certain embodiments of the invention. The above 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 [Fig. 5].

[0100] During a supply step S2, a card body 100 is formed (or supplied) comprising a metal layer 103 as previously described. In particular, this card body 100 is formed at least in part by a metal layer 103, this metal layer 103 comprising a recess zone 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 on 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 a variant, two recess zones 104 and 104' can be formed in the metal layer 103, only the recess zone 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 a variant, the electronic module is not positioned in a cavity.

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

[0104] During a step S6, insulating layers 102a and 102b are deposited on either side of the metal layer 103 in order to isolate the metal 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 field of smart cards. It may be noted that the electronic module, or the RF chip, comprises two contact points configured to be connected to an RF antenna arranged above the layer 106. Thus, perforations may exist in the layer 106 to connect contact points of the RF chip or the electronic module to the antenna.

[0105] During a step S8, an antenna is formed on the layer 106. This antenna comprises two sets of turns such that -the first set SET1 is routed on the outer periphery of the card CD1, along the metal edge 113 of the card, this set comprises at least one turn which then joins or is further deployed towards the interior of the card, - the second set SET2 is routed on the outer periphery of the cavity 104 and comprises at least one turn which is deployed around the 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.

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

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

[0108] When the module is an electronic module allowing communication with contact, then the layers 102a and 101a can be pierced 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 constitute only non-limiting examples of implementation of the invention. In particular, a person skilled in the art may envisage any adaptation or combination of the embodiments and variants described above, in order to meet a very specific need in accordance with the claims presented below.

Claims

Claims

1. Smart card (CD1) comprising: - a card body (100) formed at least in part by a metal layer (103), said metal layer comprising a recess area (104) formed by 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 arranged on a non-conductive layer deposited on the metal layer, the RF chip being arranged at the metal 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. A smart card according to claim 1, in which 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 in such a way 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 one of the preceding claims in which said electronic module is positioned in said cavity.

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

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

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

7. Smart card according to one of the preceding claims in which the surface of said cavity represents a surface substantially equal to 1.5% of the surface of the metal layer.

8. A smart card according to any preceding claim wherein the cavity comprises a dielectric material selected from wood, or ceramic, or rigid rubber.

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

10. Method for manufacturing a smart card (CD1) from a card body (100) formed at least in part by a metal layer (103) - formation (S2) in said metal layer of at least one recessed area (104) formed by 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 metal 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 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.,

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