Smart card with visible metal face

Abstract

The invention relates to a smart card (1) with a dual contact and contactless communication interface, comprising a card body (2) comprising an electronic module (11) arranged in a cavity of the card body and provided on its upper face with a contact terminal block and on its lower face with a microelectronic chip protected by a drop of coating resin (13), and said card body (2) comprising on one of its faces a visible metal sheet (3) capable of increasing the weight of the card body (2), a layer (7) provided with a card body antenna (32), and a ferrimagnetic insulating layer (6) interposed between said metal sheet (3) and said card body antenna layer (7), characterized in that said card body (2) further comprises a layer (5) of electrically insulating material arranged between the metal sheet (3) and the ferrimagnetic insulating layer (6),configured to absorb thickness tolerances of the electronic module (11) and the metal sheet (3). Figure for Abstract: Figure 9,

Description

Title of the invention: Title Smart card with visible metal face

[0001] The present invention relates to a smart card with a dual contact and contactless communication interface, provided with a card body having at least one essentially metallic visible face. STATE OF THE ART

[0002] In the field of smart cards, in particular those used for banking applications, part of the demand tends to concentrate, for reasons of better handling and increased differentiation, on cards made heavier than traditional smart cards with plastic bodies, by the integration of a metal layer.

[0003] Generally speaking, chip cards made heavier using a metal layer must meet several contradictory requirements. They must in fact incorporate sufficient metal to produce a tangible weighting and a clearly perceptible differentiation compared to plastic cards. But the metal produces an electromagnetic shielding effect, or at the very least disturbances in the radiofrequency communication performance of this type of chip card with a remote contactless reader. However, this communication performance must be compatible with a set of standards, such as those provided for by the so-called EMVCo specifications which impose mechanical and electrical requirements, but also radiofrequency communication quality criteria.

[0004] Some of the known smart cards have a metal layer on only one side of the card, the other side not being covered with metal but provided with an antenna allowing communication with a remote reader by radio frequency. However, due to the shielding effect of the metal layer, radio frequency communication with the reader is degraded. In particular, tests have shown that with this type of smart card, it was until now impossible to comply with certain standards such as those imposed by the so-called EMVCo specifications mentioned above.

[0005] In order to overcome this problem and maintain good radiofrequency communication quality regardless of the orientation of the smart card relative to the remote reader, it has been proposed in document FR3032294A1 to construct the smart card using a metal insert placed between two external sheets each provided with an antenna and a ferrite layer. This arrangement makes it possible to maintain a communication quality compatible with EMVCo type specifications, but the method for producing this type of card is relatively complex and expensive. Furthermore, in this embodiment, the metal insert is located between external layers of the card made of plastic, and therefore it is not directly visible from the outside, which does not contribute to creating sufficient perceptual differentiation compared to cards made entirely of plastic.

[0006] In order to remedy this, document FR3089659A1 presented a metal smart card with a dual communication interface, provided with two external aluminum plates surrounding a cavity receiving a microelectronic module powered by a battery. This structure makes it possible to actively improve the radiofrequency communication capabilities of the card, despite the presence of the external aluminum layers.

[0007] However, the smart cards thus obtained weigh approximately 8 grams due to the use of aluminum, which is certainly greater than the weight of a card having a plastic body, but this weight is still considered insufficient for the market segment of so-called "premium" or high-end smart cards, which must have a target weight of more than 12 grams, while having external faces that can be personalized by laser engraving or other means, and while remaining compatible with the so-called EMVCo banking standards.

[0008] According to another smart card described in document WO2019136436A1, the card body comprises a metal layer provided with a cutout of a size larger than that of the electronic module, in which is inserted an intermediate piece made of plastic, which in turn receives an electronic module provided with a small antenna which is coupled with a main antenna arranged in the card body. This structure makes it possible to marginally improve the radiofrequency communication performance, but since the intermediate piece made of plastic is visible around the module, it is necessary to cover the metal face and the intermediate piece with a masking layer, which detracts from the desired metallic appearance. In addition, this more complex structure requires additional manufacturing operations, which negatively impact the manufacturing yield and the cost of this smart card.

[0009] It is therefore necessary to propose a contactless or dual communication interface smart card having a higher weight than known smart cards, while having optimal radio frequency communication properties and suitability for graphic personalization. PURPOSE OF THE INVENTION

[0010] The invention therefore aims to propose a new smart card structure having a metallic external face and which is capable of satisfying the contradictory requirements of an increased weight which can reach a weight greater than 12 grams with, for example, steel or a metallic material of equivalent density. or higher than that of steel, while providing contactless communication capability that meets the requirements of EMVCo type specifications.

[0011] Another aim of the invention is to propose such a smart card while retaining a simple structure that is easy to manufacture in large series at a reduced cost and with very high reliability, such as the transfer and fixing of the electronic module in a cavity of the card body. SUBJECT OF THE INVENTION

[0012] In principle, the smart card according to the invention has a structure that is optimized in several aspects, in particular with regard to the material in which planes called PI, P2 of the cavity of the card body receiving the electronic module must be machined, the dimensioning and positioning of the opening of the metal layer and the ferrite layer of the card body, and the choice of the type of ferrite used to protect the electromagnetic field lines allowing coupling between the antenna of the card body and the antenna of the module.

[0013] The subject of the invention is therefore a smart card as defined in the claims.

[0014] According to one embodiment, the electronic module of this smart card comprises contact terminals connected to the antenna of the card body by galvanic connections.

[0015] According to an alternative embodiment, said electronic module comprises a module antenna, inductively coupled with said antenna of the antenna layer of the card body.

[0016] According to one embodiment, said layer of electrically insulating material is made of PVC, PET, PETG or polycarbonate.

[0017] According to one embodiment, the electronic module is inserted into a cavity of the card body having a first machining plane denoted PI located in the layer of insulating material and a second machining plane denoted P2 located in or under the ferritic complex.

[0018] According to one embodiment, the machining of said second machining plane P2 passes through the ferrimagnetic insulating layer and extends into one or more lower layers, leaving a residual thickness of the card body of at least 50 μm.

[0019] Preferably, said layer of insulating material is secured to the metal sheet by a layer of heat-activatable adhesive.

[0020] According to one embodiment, said insert comprises a through cavity or not, machined to a depth noted P2 and capable of receiving said drop of coating resin located on the lower face of the electronic module.

[0021] According to a preferred embodiment, the opening of the ferrimagnetic layer has a surface area slightly smaller than the surface area of ​​the cavity of depth PI and has a edge slightly offset by a certain offset towards the inside of the cavity of depth PI relative to the edge of the cavity of depth PI of the metal layer, so as to ensure that a part of the ferrimagnetic layer is always positioned opposite the metal foil, despite the relative positioning tolerances of the ferrimagnetic layer and the metal layer. Said offset is for example 0.4 to 1.6 mm, preferably of the order of 0.8 mm.

[0022] According to one embodiment, the ferrimagnetic insulating layer is constituted by a ferritic complex configured in the form of a sheet comprising a layer of sintered ferrite surrounded on either side by a layer of thermo-activatable adhesive ("hotmelt"). In this case, the thickness of the layer of sintered ferrite is preferably between 30 and 200 micrometers.

[0023] According to one embodiment, the sintered ferrite layer has, at a frequency of 13.56 MHz, a complex permeability having a value of p' greater than 150, preferably of the order of 170, and a value of p” less than 10, preferably of the order of 2.

[0024] The invention also relates to a method for producing a smart card as defined above, comprising steps consisting of: - arranging on a first face of an antenna layer a first face of heat-activatable adhesive of a ferrimagnetic insulating layer provided with an opening; - insert an insert into the opening of the ferrimagnetic insulating layer; - place a layer of insulating material on a second thermo-activatable adhesive face of the ferrimagnetic insulating layer; - placing a layer of heat-activated adhesive on the second face of the antenna layer, and a layer of plastic material printed on this layer of adhesive; - possibly prefixing together the ferritic complex, the antenna layer, the insulating material and the printed layer, using ultrasonic spot welds capable of locally activating said thermo-activatable adhesives; - place one side of a metal sheet glued with a layer of adhesive on the layer of insulating material; - place a transparent protective layer on the free side of the printed layer; - hot laminating the stack of all the layers so as to obtain a multi-layer card body; - machine a cavity in the card body from the outer face of the metal layer and insert an electronic chip card module into it. DETAILED DESCRIPTION

[0025] The invention will be described in more detail with the aid of the drawings, in which: - [Fig. 1] represents a sectional view in the area of ​​the electronic module, of a first degraded embodiment of a smart card according to the invention, only partially resolving the problem posed. - [Fig. 2] represents a sectional view of an embodiment of a smart card according to the invention, partially resolving the problem posed, but improved compared to the embodiment of [Fig. 1]. - [Fig.3] represents a sectional view of an embodiment of a smart card similar to that of [Fig.2], but in which the connection between the antenna of the card body and the electronic module is made by a galvanic connection. - [Fig.4] shows a plan view of the upper metal layer of a metal layer smart card body according to the state of the art. - [Fig.5] shows an enlarged view of a portion of the edge of the cavity of the card body of [Fig.4]. - [Fig.6] shows a plan view of the upper metal layer of a metal layer smart card body according to the invention. - [Fig.7] shows an enlarged view of a portion of the cavity edge of a card body of [Fig.6], with the metal layer and the ferrite layer well aligned. - [Fig.8] shows an enlarged view of a portion of the cavity edge of a card body of [Fig.6], with the metal layer and the ferrite layer misaligned. - [Fig.9] represents a sectional view of an embodiment of a smart card according to the invention, making it possible to obtain a cavity edge as represented in [Fig.7]. - [Fig. 10] represents a sectional view of a sintered ferrimagnetic insulating layer according to the state of the art. - [Fig. 11] represents a sectional view of a sintered ferrimagnetic insulating layer used in the body of a smart card according to the invention.

[0026] Referring to [Fig.l]. A partial longitudinal section of a smart card is shown, in the area of ​​the electronic module, with layer thicknesses exaggerated compared to reality, for greater clarity.

[0027] Identical elements in different figures are designated by the same reference numbers.

[0028] The smart card 1 comprises a card body 2 composed of a stack of layers, namely, starting from the top, a metal layer 3, an adhesive layer 4, for example a heat-activated adhesive forming the mechanical connection between the metal layer 3 and a layer 5 made of plastic, in particular PVC, PET, PETG or polycarbonate. A ferrite-based complex 6, also called a ferritic complex, is interposed between the layer 5 and a layer 7 containing the metal turns of an antenna (not shown) of the card body. This ferritic complex 6 is formed by a ferrite layer 6a taken between two adhesive layers 6b constituted for example by a heat-activated adhesive, also called a "hotmelt" in English terminology. Ferrite is a ferrimagnetic material which has the particularity of modifying the path taken by the electromagnetic field lines.To ensure the proper radiofrequency operation of the smart card, the ferrite-based complex 6 must be placed between the metal layer 3 and the antenna layer 7 of the card body. It then limits the shielding effect of the metal layer 3 with respect to the antenna of the card body. Next comes an adhesive layer 8 ensuring the mechanical connection between the antenna layer 7 and a layer 9 intended to be printed, for example in PVC, followed finally by a transparent protective layer 10.

[0029] The electronic module 11 comprises, in a well-known manner, a dielectric substrate 12 which carries on its lower face a microelectronic chip (not visible), protected by a drop of coating resin 13. As it is a module for a card with contactless operation or mixed contact and contactless operation, it also comprises a module antenna whose turns 14 surrounding the area of ​​the microelectronic chip can be seen.

[0030] The electronic module 11 is inserted into a machined cavity of the card body 2 which typically comprises two machining planes, namely a first machining plane denoted PI defining a first cavity portion receiving the substrate 12 of the electronic module 11, and a second machining plane P2 machined more deeply and forming a second smaller and deeper cavity portion in which the drop of coating resin 13 which protects the chip is positioned.

[0031] In the case of a smart card with mixed contact and contactless operation, the electronic module 11 cannot be buried under the metal layer 3 because it must operate by contact with the contacts of a smart card reader.

[0032] Furthermore, to ensure proper radiofrequency operation of the electronic module 11, several other conditions must be met. It is necessary to prevent the periphery of the electronic module 11, namely the area of ​​the electronic module 11 which surrounds the drop of coating resin 13 and which receives the turns of the antenna 14 from bearing on the metal layer 3, which requires that the machining of the first portion of the cavity must pass through the metal layer 3, which means that the machining plane PI is located below the lower face of the metal layer 3.

[0033] For this purpose, the invention provides that the machining plane PI of the cavity of the electronic module 11 is located in a layer 5 of plastic material, in particular PVC, PET, PETG or equivalent, making it possible to absorb the tolerance of the machining depth necessary for the plane PI of the cavity, as shown in [Fig. 1]. This machining tolerance may in particular be due to the fact of using electronic modules whose thickness may vary from one manufacturer to another or from one module reference to another. In practice, this layer 5 of plastic material has a thickness of between 50 and 100 μm.

[0034] However, this structure according to [Fig.l] is not yet optimal, insofar as the machining of the plane P2 of the cavity leaves a portion 15 of the ferrimagnetic layer 6 under the antenna 14 of the electronic module 11, which risks interfering with the field lines of this antenna. To remedy this problem, the invention provides for adopting the structure shown in [Fig.2].

[0035] The structure of the smart card 1 of [Fig.2] differs from that of [Fig.l], insofar as the ferrimagnetic layer 6 comprises, in the area located under the electronic module 11, an opening 40 which is filled by an insert 16 made of plastic material, in particular PVC. This insert 16 makes it possible to fill the opening 40 of the layer 6 while avoiding a fining of this layer in the opening 40 during the assembly of the card. In addition, by choosing for the insert 16 a plastic material which does not disturb the field lines or even which concentrates or improves them, it allows an optimal electromagnetic coupling between the antenna 14 of the module 11 and the antenna 7 of the card body.

[0036] The structure of the chip card 1 of [Fig. 3] differs from that of [Fig. 1] insofar as the electronic module 11 does not have its own antenna, but output pads 30 of the electronic module 11 are connected to ends of the antenna 32 of the card body, by means of galvanic connections 31, for example in the form of metallized vias arranged through the insulating layer 5 and the ferrimagnetic insulating layer 6.

[0037] Another technical problem may still arise with a metal layer chip card like that of [Fig. 2]. As shown in Figures 4 and 5, the positioning tolerances during the stacking of the layers of the card body 2 may result in a slight offset 17, especially visible in [Fig. 5], between the edge 18 of the cavity of the metal layer 3, and the edge 19 of the opening 40 made in the ferrimagnetic layer 6.

[0038] In this case, this offset 17 can have a significant impact on the radiofrequency performance of the smart card. Indeed, this horizontal offset 17, in the plane of the card body, is penalizing, the metal no longer being masked in this area by the ferrimagnetic material. However, such offsets are definitely present in manufacturing processes consisting of superimposing layers and assembling them together.

[0039] In order to overcome this problem, the invention provides for ensuring, as shown in Figures 6 to 8, that despite manufacturing tolerances, the edge 19 of the opening 40 made in the ferrimagnetic material is always slightly offset by an offset 17 towards the inside of the cavity provided for the module, beyond the edge 18 of the cavity made in the metal layer 3. In other words, the invention provides for the cavity in the layer 6 to be less extensive than that provided for the electronic module, which makes it possible to have in all cases a safety margin 17 to absorb the positioning tolerances of the layer 6 relative to the metal layer 3.

[0040] [Fig.7] corresponds to the case where the stacking of the layers has been done nominally, that is to say without positioning offset between the metal layer and the ferrimagnetic layer 6. Consequently, the internal limit 19 of the ferrimagnetic material around the opening 40 is offset regularly over the entire periphery of the opening 40, towards the inside, by a uniform offset 17, relative to the internal limit 18 of the metal layer.

[0041] This ideal case does not occur in practice depending on the positioning tolerances of the metal layer and the ferrimagnetic layer. As shown in [Fig.8], in the event of misalignment between the metal layer 3 and the layer 6, the offset of the boundary 19 of the layer 6 towards the inside of the opening 40 allows a positive or zero offset 17 to remain everywhere, meaning that the ferrimagnetic material always covers the metal throughout the perimeter of the opening 40. In this way, any exposure of the metal 3 is avoided. It is better to have ferrimagnetic material between the module and the antenna than exposed metal. In practice, it is found that an offset 17 in a range of 0.4 mm to 1.6 mm, preferably approximately 0.8 mm, allows very good results to be obtained.

[0042] A final technical problem to be solved is linked to the structure of the ferrimagnetic material 6 and in particular to its capacity for adhesion to the adjacent layers 5 and 7. This must be sufficient to withstand delamination forces standardized according to the ISO 7810 standard, of at least 3.5 N / cm.

[0043] As shown in [Fig.10], in the current state of the art, outside the field of smart cards, sintered or unsintered ferrite sheets 20 are used, encapsulated on either side between layers 21 of pressure-sensitive adhesive (denoted "PSA" in English terminology) topped by layers 22 of PET. This structure is commonly used in the field of wireless charging systems. contact or to protect electronic circuits from external aggression in systems such as cars or mobile phones. But it is not suitable for the field of smart cards because it would not have sufficient adhesion to layers 5, 7 ([Fig.2]) of the smart card, the risk of delamination of the card body being then high, which is even more prohibitive for a premium card.

[0044] To overcome this problem, the invention provides for the ferrimagnetic insulating layer 6 to preferably use a ferritic complex using sintered ferrite 23, as shown diagrammatically in [Fig. 11]. Sintered ferrite is not used to date in the smart card industry, and it imposes particular constraints because of its powdery texture and its embodiment in small sheets. In order to make it compatible with smart card manufacturing processes, the invention provides for the sintered ferrite to be encapsulated between external adhesive layers 24 of the “hotmelt” type, for example made of PUR (polyurethane), POR (polyolefin), Epoxy or Acrylic to form a suitable ferritic complex 6. The external layer 24 in “hot melt” is implemented hot, the adhesive material being inserted into the pores of the sintered ferrite, which ensures maximum cohesion of the ferritic complex 6, much greater than that of the complex 6 of [Fig.10].Furthermore, the ferritic complex 6 of [Fig. 11] has a lesser thickness than the known complexes, which in the context of a smart card with a metal layer allows, at constant total thickness, to increase the thickness of the metal layer 3, and therefore to make the smart card heavier.

[0045] Ultimately, this new ferrimagnetic layer structure in the form of a sintered ferritic complex 6 exhibits both high adhesion with the adjacent layers 5 and 7 of the smart card, and maximum efficiency in guiding the electromagnetic field lines.

[0046] Indeed, ferrite (not to be confused with ferrite) is a material with the characteristics of having a very high resistivity (approximately 108 Ohms per meter, or 1014 times more than aluminum), making eddy currents negligible, while having a high magnetic susceptibility. Its shielding action is therefore not focused on destroying the harmful magnetic field, but on reorienting it.

[0047] In the industrial world, ferrites are characterized by a complex permeability characterized by values ​​#' and #" representing on the one hand the eddy current losses at a given frequency, for example 13.56 MHz, and on the other the capacity to deflect field lines at the same given frequency. The smaller #" is, the lower the magnetic losses, i.e. the eddy current losses, and the larger # ' is, the greater the capacity to modify the field lines.

[0048] In the context of the invention, a ferrite having the following characteristics will preferably be used: p' greater than or equal to 150, preferably close to 170, and p” less than or equal to 10, preferably close to 2.

[0049] In order to manufacture a smart card according to the invention, the procedure is carried out, for example, as follows. A ferrimagnetic insulating layer 6 of suitable dimensions is prepared, in particular a complex formed by a layer of sintered ferrite 23 surrounded by layers 24 of heat-activatable adhesive, this ferritic complex 6 being provided with an opening 40 intended to receive an insert 16, and such an insert 16 is placed in the opening 40 of the ferritic complex. Separately, an antenna layer 7 is prepared and an adhesive layer 8 is superimposed on one of its faces. Then the ferritic complex 6 is placed on the face of the antenna layer 7 opposite that which carries the adhesive 8. Preferably, these first positioning operations are carried out without pre-fixing, to avoid mechanical stresses likely to generate cracks in the ferritic complex 6.Then, a layer of insulating material 5 is placed above the ferritic complex 6, provided with its layer of thermo-activatable adhesive 4. At this stage, the ferritic complex 6 is therefore caught between the insulating material 5 and the antenna layer 7. It should be noted that the positioning of the different layers 6, 5, 8, 9 can be done in relation to a skeleton (not shown) positioned according to visible markers on the antenna layer 7. Then, the layers 8, 3, 6, 5 are prefixed together using a few localized welding points obtained by an ultrasonic probe. Then, on the one hand, the metal sheet 3 is added above the adhesive 4, and on the other hand, the printed layer 9 and the transparent protective layer 10 to obtain the final stack, which is definitively assembled by hot lamination of all the layers, which completes the construction of the card body 2.It then remains to machine the planes PI and P2 of the cavity of the card body, and to transfer and glue the electronic module 11 there, according to conventional operations well known in the state of the art.

[0050] All of the above operations can be carried out for a single card, or on the contrary for a set of cards from a large sheet, in which case several smart cards 1 are obtained simultaneously and must be individualized by a final cutting operation from said sheet. ADVANTAGES OF THE INVENTION

[0051] The invention achieves the set objectives. Tests have shown that radiofrequency communication with a contactless reader is of good quality and remains compliant with EMVCo specifications regardless of the orientation of the card, and without requiring a slot in the metal layer.

[0052] The metal face 3 of the smart card according to the invention is directly visible, without requiring a masking layer as in certain prior art embodiments. of the technique. This metallic appearance is achieved without compromising the quality of radio frequency communication. It gives the smart card a beautiful appearance, a weight that can be greater than 12 grams in the case of using steel, which meets the needs of the premium card market, and a good grip.

[0053] The manufacture of the smart card according to the invention makes it possible to continue to use the conventional and proven manufacturing methods, consisting of transferring an electronic module into a cavity of the card body as well as the pre-fixing and lamination of the layers of the card body.

[0054] Ultimately, the metal-faced chip card according to the invention operates in the same way as a plastic card or a known heavy card, but it also fully complies with the EMVCo contact or contactless banking standard.

Claims

Claims

1. Smart card (1) with dual contact and contactless communication interface, comprising a card body (2) comprising an electronic module (11) arranged in a cavity of the card body and provided on its upper face with a contact terminal block and on its lower face with a microelectronic chip protected by a drop of coating resin (13), and said card body (2) comprising on one of its faces a visible metal sheet (3) capable of increasing the weight of the card body (2), a layer (7) provided with a card body antenna (32), and a ferrimagnetic insulating layer (6) interposed between said metal sheet (3) and said card body antenna layer (7), said ferrimagnetic insulating layer (6) comprising an opening (40) allowing the electromagnetic field lines to pass between an antenna (14) of the module and the antenna (32) of the card body,characterized in that said card body (2) further comprises a layer (5) of electrically insulating material arranged between the metal sheet (3) and the ferrimagnetic insulating layer (6) and configured to absorb thickness tolerances of the electronic module (11) and of the metal sheet (3), and in that said opening (40) is filled using an insert (16) configured not to disturb the field lines or to channel them between the antenna (32) of the card body and the antenna (14) of the electronic module (11).,

2. Chip card (1) according to claim 1, characterized in that the electronic module (11) comprises contact terminals (30) connected to the antenna (32) of the card body by galvanic connections (31).

3. Smart card (1) according to claim 1, characterized in that the module antenna (14) is inductively coupled with said antenna (32) of the antenna layer (7) of the card body.

4. Smart card (1) according to any one of the preceding claims, characterized in that said layer (5) of electrically insulating material is made of PVC, PET, PETG or polycarbonate.

5. Chip card (1) according to any one of the preceding claims, characterized in that the electronic module (11) is inserted into a cavity of the card body (2) having a first machining plane noted PI located in the layer (5) of insulating material and a second machining plane noted P2 located in or under the ferrimagnetic insulating layer (6).

6. Chip card (1) according to claim 5, characterized in that the machining of said second machining plane P2 passes through the ferrimagnetic insulating layer (6) and extends into one or more lower layers (8, 9) leaving a residual thickness of the card body (2) of at least 50 μm.

7. Smart card (1) according to any one of the preceding claims, characterized in that said layer of insulating material (5) is secured to the metal sheet (3) by a layer of adhesive (4) of the heat-activatable type.

8. Smart card (1) according to one of the preceding claims, characterized in that said insert (16) comprises a cavity (41) through or not, machined to a depth noted P2 and capable of receiving said drop of coating resin (13) located on the lower face of the electronic module (11).

9. Chip card (1) according to claim 7, characterized in that the opening (40) of the ferrimagnetic insulating layer (6) has a surface area slightly smaller than the surface area of ​​the cavity of depth PI and has an edge (19) slightly offset by an offset (17) towards the inside of the cavity of depth PI relative to the edge (18) of the cavity of depth PI of the metal layer (3), so as to ensure that a part of the ferrimagnetic insulating layer (6) is always positioned opposite the metal sheet (3), despite the tolerances of relative positioning of the ferrimagnetic insulating layer (6) and the metal layer (3).

10. Smart card (1) according to claim 9, characterized in that said offset (17) is 0.4 to 1.6 mm, preferably of the order of 0.8 mm.

11. Chip card (1) according to claim 6, characterized in that the ferrimagnetic insulating layer is configured in the form of a ferritic complex (6) consisting of a sheet (6) comprising a layer (23) of sintered ferrite surrounded on either side by a layer (24) of thermo-activatable adhesive ("hotmelt").

12. Smart card (1) according to claim 11, characterized in that the thickness of the layer (23) of sintered ferrite is between 30 and 200 micrometers.

13. Chip card (1) according to claim 11 or 12, characterized in that the sintered ferrite layer (23) has, at a frequency of 13.56 MHz, a complex permeability having a value of p' greater than 150, preferably of the order of 170, and a value of p” less than 10, preferably of the order of 2.

14. Method for producing a smart card (1) according to one of the preceding claims, characterized in that it comprises steps consisting of: - arranging on a first face of an antenna layer (7) a first face of heat-activatable adhesive (24) of a ferrimagnetic insulating layer (6) provided with an opening (40); - transferring an insert (16) into said opening (40); - arranging a layer of insulating material (5) on a second face of heat-activatable adhesive (24) of the ferrimagnetic insulating layer (6); - arranging a layer of heat-activatable adhesive (8) on the second face of the antenna layer (7), and a layer of printed plastic material (9) on the layer of adhesive (8); - arranging on the layer of insulating material (5) one face of a metal sheet (3) glued with a layer of adhesive (4); - placing a transparent protective layer (10) on the free face of the printed layer (9);- joining the different layers (3,4,5,6,7,8,9,10) together by hot lamination so as to obtain a multi-layer card body (2); - machining a cavity in the card body (2) from the outer face of the metal layer and attaching an electronic module (11) there.;

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