Smart card antenna with optimized coupling and its manufacturing process
Patent Information
- Application Number
- FR2022007807
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-07-28
- Publication Date
- 2025-07-11
- Estimated Expiration
- 2042-07-28
AI Technical Summary
Existing smart card antennas face challenges in achieving optimal electromagnetic coupling with the electronic module due to positioning tolerances during assembly, especially when using thick modules, leading to degraded radio frequency performance.
The solution involves creating an internal concentrator turn on the antenna insert that opens directly into the cavity and is wider than other turns, compensating for positioning tolerances by being flush with the side walls, ensuring close proximity to the electronic module's antenna turns.
This configuration enhances electromagnetic coupling between the concentrator and module antennas, improving radio frequency performance regardless of module thickness, by minimizing the distance between internal and external turns.
Smart Images
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Abstract
Description
Description Title of the invention: Smart card antenna with optimized coupling and its manufacturing process
[0001] — The invention relates to antennas of the type used for smart cards with contactless operation or mixed contact and contactless operation or for other safety documents that may use such antennas. State of the art
[0002] — The antennas known for such smart cards are generally integrated into a multilayer antenna insert comprising a substrate typically made of plastic material often PET (polyethylene terephthalate) type with antenna tracks made by etching layers of aluminum, as well as a stack of several thin layers also made of plastic.
[0003] — The antenna is generally configured in the form of two sets of turns, forming a first antenna called ID1 antenna whose turns are large close to the size of the smart card, intended to be coupled electromagnetically with an external reader, and a second antenna called a concentrator antenna (again more simply referred to as the concentrator). This concentrator antenna is intended to be coupled electromagnetically with the antenna of the electronic module, and it is electrically connected in series or parallel with the antenna in the format said ID1.
[0004] — A network of adjustable capacities integrated into the two antennas called ID] and concentrator allows the entire antenna system to resonate at a determined operating frequency. We therefore understand by antenna system, the ID antenna], the concentrator antenna, and the adjustable capacities allowing to adjust the resonant frequency of the antenna insert.
[0005] — The aforementioned antenna system is electromagnetically coupled to an electronic module electronics also having an antenna, arranged on the periphery of the electronic module electronics and called the module antenna, whether for example the electronic module electronics of a contactless smart card, or that of an electronic passport. The module antenna is limited in terms of number of turns by the small size of the electronic module, which must also receive a microelectronic chip and possibly standardized galvanic contacts of type ISO 7816-2, for example for so-called dual cards, which have mixed contact and contactless operation.
[0006] — In known embodiments of antenna inserts, the antenna ID1 and the concentrator are produced in particular by very narrow engraved aluminum tracks arranged on a PET substrate, and the adjustment capabilities are realized by metal panels located on either side of the booster antenna substrate. The turns of the IDI and concentrator antennas can be made on one side of the insert, or on both sides. To close the electrical circuit, it is customary to use a 'crimp' in English terminology, namely an electrical connection made by crimping or stamping to connect metal pads located on either side of the antenna insert substrate. In this known embodiment, the metal tracks of the antennas typically have a thickness of around 10 to 30 micrometers, and the thickness of the dielectric substrate is around 25 to 38 micrometers, which makes it possible to obtain radiofrequency operating performances in accordance with the standards in force (ISO 14443 and 10373-6). The invention will be described with reference to the usual terminology of the components of a contactless smart card or a dual smart card, it being understood that it can be transposed without limitation to other products of different formats, such as electronic passports. The electronic module of the smart card is inserted, in a known manner, into a cavity made in the card body, in particular by machining using a milling cutter. This cavity comprises two zones of different depths, namely a zone called P2, which corresponds to the deepest machining and in which the encapsulation droplet that protects the microelectronic chip of the module is housed, and a zone called P1, which corresponds to a less deep machining and which delimits a zone on which the peripheral antenna of the electronic module rests. The module cavity is machined when all the layers of the smart card have been assembled, and the antenna insert is sandwiched between the outer layers of the card body. For a standard-thickness module, i.e., a module with a thickness of around 500 micrometers, the machining of the P2 area generally passes through the antenna insert, which is located at a depth of around 400 micrometers, while the shallower machining of the P1 area does not reach the depth of the antenna insert. In order not to damage the turns of the ID1 and concentrator antennas of the insert, it is therefore necessary that no track is located in the P2 area which will be machined. But in order to ensure good electromagnetic coupling between the concentrator antenna of the insert and the antenna of the electronic module, it is also necessary that the turns of the concentrator are as close as possible to the turns of the antenna of the electronic module. Coupling is defined by the geometric similarity between two antennas as well as their respective distance. Thus, to define the interaction between the concentrator antenna and the module antenna, the greater the distance separating one from the other, the poorer the coupling will be, which will lead to degraded performance. The first inner turns of the concentrator are therefore the most important and must be find the closest turns of the antenna of the module to maximize these performances, and have as many turns as possible in a minimum of space. These two simultaneous conditions are already difficult to achieve for a standard thickness module, given the positioning tolerances of the antenna insert during the assembly of the smart card layers, which are of the order of 1 to 2 mm. They become even more difficult to achieve when the module used is a so-called "thick" module, namely a module that requires a cavity whose two zones P1 and P2 are deep, and both require machining that crosses the layers of the antenna insert. This is typically the case for so-called "dCVV" type modules (acronym for "Dynamic Card Verification Value" in English terminology), for which the two depths of zones P1 and P2 are located beyond 500 micrometers.In this case, the turns of the concentrator antenna cannot be located close enough to the turns of the electronic module, which results in poor radio frequency communication performance of known smart cards equipped with such modules. Aims of the invention A general aim of the invention is therefore to propose an improved antenna insert structure, in particular for the body of a contactless smart card or for an electronic passport, and which is free from the aforementioned drawbacks. Another more specific aim of the invention is to propose an antenna insert structure for a contactless smart card or equivalent, ensuring optimized coupling with the antenna of an electronic module intended to be integrated into the card body, independently of the thickness of the module, that is to say in particular whether it is a standard module, or a so-called “thick” module, in particular of the dCVV type having a thickness of more than 500 micrometers. Another aim of the invention is to propose a method of manufacturing a smart card using the optimized antenna insert according to the invention. Summary of the invention According to the principle of the invention, the solution to the aforementioned problem consists in creating on the antenna insert an internal concentrator turn which opens directly into the cavity, on the side walls thereof, and which is wider than the others, in any case sufficiently wide to compensate for the positioning tolerance of the antenna insert between the other layers of the card body, when assembling the antenna insert with the other layers of the smart card. To make this wider internal turn, a blank of concentrator is made with a substantially solid central metal zone, then the insert with this blank is placed between the other layers of the card body, and finally the cavity of the card body as well as the substantially solid central metal zone of the antenna insert, so that after machining, there remains on the antenna insert an internal concentrator turn which opens directly into the cavity and which is flush with the side walls thereof. Thus, the enlarged internal turn which remains after machining the module cavity makes it possible both to absorb the positioning tolerances of the antenna insert in the card body, and to bring this internal turn of the concentrator as close as possible to the turns of the antenna of the electronic module, as will be visible in the figures. This method and this concentrator antenna configuration can be advantageously used regardless of the P1 or P2 zone of the module which passes through the antenna insert, i.e. whether it is a standard module or a thick module. The invention therefore relates to an antenna insert for a smart card with contactless operation or mixed contact and contactless operation, intended to be interposed between external layers of a smart card body, said antenna insert comprising a substrate and on at least one face of said substrate, turns of a concentrator intended to be electromagnetically coupled with the turns of an antenna of an electronic module arranged in a cavity of the card body, characterized in that said concentrator comprises at least one internal turn which opens into the cavity and which is flush with the internal side walls of said cavity of the smart card body. According to a preferred embodiment, said internal turn of the concentrator is wider than the other turns of the concentrator. According to an advantageous embodiment, the width of said internal turn of the concentrator is greater than the value of the positioning tolerance of the antenna insert between the external layers of a smart card body. This makes it possible to compensate for the lateral positioning tolerance of the insert between the layers of a smart card body and to prevent the internal turns of the concentrator from being cut during the machining of the cavity. According to one embodiment, when the positioning tolerance of the antenna insert in the card body is less than 2 mm, the width of said internal turn is greater than approximately 2.2 mm. According to one embodiment, the concentrator is a single-sided antenna, all of whose turns are arranged on a single face of the substrate of the insert, and which comprises a single internal turn opening into the cavity. According to an alternative embodiment, the concentrator is a double-sided antenna, the turns of which are distributed between the two opposite faces of the substrate of the antenna insert and are connected in series or in parallel by means of a via or a crimp type crimping, said concentrator comprising two internal turns on either side and other side of the substrate and opening into the cavity. The invention also relates to a method for manufacturing a smart card provided with an antenna insert as defined above, characterized in that it comprises steps consisting of: Produce a rough antenna insert on at least one side of a substrate having a substrate carrying several turns of etched aluminum and a solid central part not engraved; Arranging said antenna insert blank between outer layers and the laminate together to form a card body; Machine one face of the card body to form a cavity intended to receive an electronic module, said cavity passing through said solid central part of the antenna insert blank and said substrate, such that said portion central leaves after machining of the cavity an internal spiral of concentrator which is flush with the internal side walls of the cavity; Apply a layer of adhesive to the periphery of the module. Report and fix in said cavity an electronic module provided on its pe- array of tracks of a module antenna, so that these antenna tracks of the module are adjacent to the internal track of the hub, or opposite of said internal track of the concentrator. Other characteristics and advantages of the invention will appear on reading the detailed description and the attached drawings in which: Figures 1A to 1D illustrate a sectional view of a known smart card during cavity milling and module insertion phases standard thickness; [Fig.1E] shows a top view of the relative positioning of the coils of a single-sided concentrator and the antenna turns of the module figures 1A to 1D; Figures 2A to 2C illustrate a sectional view of a known smart card during cavity milling and thick module insertion phases dCVV type; [Fig.2D] shows a top view of the relative positioning of the coils of the concentrator and turns of the antenna of the module of figures 2A to 2C; Figures 3A to 3D illustrate various views of a smart card according to the invention during phases of milling the cavity and inserting a thick electronic module in the cavity; [Fig.3E] shows a top view of the relative positioning of the coils of the concentrator and turns of the antenna of the module of figures 3A to 3D; Figures 4A to 4D illustrate various views of a smart card according to the invention, provided with a single-sided antenna insert, during phases of milling of the cavity and insertion of a standard thickness module; [Fig.4E] shows a top view of the relative positioning of the coils of the concentrator and turns of the antenna of the module of Figures 4A to 4D; Figures 5A to 5D illustrate various views of a smart card according to the invention, provided with a double-sided concentrator antenna insert during cavity milling and thick module insertion phases; [Fig.5E] shows a top view of the relative positioning of the coils of the concentrator and antenna turns of the module of Figures 5A to 5D; Detailed description We refer to Figure 1 which shows the manufacturing steps of a dual chip card provided with an antenna insert 1 according to the state of the art. This antenna insert provided with turns 3 forming a concentrator, the other turns shown are part of other components of the insert, such as for example an antenna in ID1 format. This antenna insert | is first laminated between external layers 2 so as to obtain a card body 5 ([Fig. 1 A]). After lamination of the card body, a cavity 6 is machined using a milling cutter 7 in this card body S ([Fig. 1B]). The milling cutter 7 machines a cavity portion to a depth P2 and another wider cavity portion, to a depth P1.The depth P2 being greater than half the thickness of the card body 5, this machining passes through the antenna insert 1, which implies that the internal turn 3a of the concentrator 3 must be located at a certain distance 15 from the internal lateral wall of the cavity machined at the depth P2 ([Fig.1D]), so that the machining of the zone P2 does not damage the concentrator 3, and in particular its internal turn 3a, during this machining. Once the cavity 6 has been machined, an electronic chip card module 9 is inserted therein (figures 1C, ID). This comprises, in a known manner, a substrate 10 on which contacts are arranged, in particular in ISO 7816-2 format, and under which a microelectronic chip 11 is fixed, protected by a drop of coating resin 12. This electronic module 9 is fixed in the cavity 6 using a layer of adhesive 13 placed between the antenna 14 of the electronic module 9 and the bottom of the cavity 6 at the depth P1 (figures IC, 1D). As appears more clearly on the 1D enlargement of [Fig.1C], the lateral positioning tolerance of the antenna insert 1 requires keeping a certain distance 15 between the internal turn 3a of the concentrator 3, and the lateral internal walls 17 of the cavity 6, in order not to risk cutting the internal turn 3a of the concentrator during the machining of the cavity 6.This distance 15 introduces an offset between the turns of the concentrator 3 and the turns of the antenna 14 of the module, which is detrimental to a good coupling coefficient between . the antenna 14 of the electronic module and the concentrator 3. The positioning of the turns of the concentrator 3, in particular its internal turn 3a, appears in solid lines in [Fig.1E] which is a top view (in which the ISO contacts of the module are not shown), and the turns of the antenna 14 of the electronic module are shown in broken lines. The problem of creating an offset 15 persists when replacing the standard electronic module used in Figure 1, with a thicker module which requires a cavity whose depths P1, P2 are both located beyond the depth where the antenna insert 1 is located, as visible in Figure 2, in particular Figures 2C and 2D. In order to overcome this problem, the invention proposes the structure and method shown diagrammatically in Figure 3. As shown in [Fig.3A], an antenna insert blank 21a is used which comprises, in a known manner, a concentrator formed by its turns 3 at its periphery, the center of the concentrator being formed initially by a substantially solid metal central part 16. The right part of [Fig.3A] simply represents a top view of the area of the concentrator 3, with a hatched part corresponding to the future position of the module 9. Once the antenna insert blank 21a is laminated between the external layers 2 of the card body, the cavity 6 of the card body is machined as shown diagrammatically in [Fig.3B], which has the effect of eliminating the solid central part 16 of the antenna insert blank 21a, leaving an internal concentrator turn 3a in line with the cavity 16 which opens directly into the cavity 6, and which is flush with the lateral internal walls 17 of the cavity 6. An antenna insert 21 in accordance with the invention is then obtained, integrated between the external layers 2 of the card body 5. Then an electronic module 9 provided with its antenna 14 is inserted in the cavity in a known manner. As visible in [Fig.3D] which represents an enlargement of [Fig.3C], and in the top view in [Fig.3E], we observe that there is almost no distance between the external turn of the antenna 14 of the module and the internal turn 3a of the antenna insert 21 (apart from the very small clearance allowing the module 9 to be inserted into the cavity 6). In fact these two turns 3a and 14 are now contiguous, and simply positioned at potentially different depths.In any case, for an electronic module 9 of given thickness, these two turns are now much closer than in the configuration of figures 1 and 2, since the distance 15 ([Fig.1D]) due to the lateral positioning tolerance of the insert in the card body has been eliminated. This increased proximity between the turns of the concentrator 3 and the turns 14 of the antenna of the electronic module 9 makes it possible to obtain a much better coupling between the antenna of the electronic module and the antenna of the antenna insert. In addition, the distance between the internal turn 3a of the concentrator 3 and the external turn of the antenna 14 of the module is now . constant, for a given module type. Figures 4A to 4D are similar to Figures 3A to 3D, except that the electronic module 9 used is a standard thickness module, so that the area P1 of the cavity 6 does not pass through the antenna insert 21. As can be seen in [Fig.4B], in this case, only the machining at depth P2 passes through the antenna insert 21. As a result, the internal turn 3a of the concentrator is now directly opposite the turns 14 of the antenna of the electronic module, which produces optimal coupling ([Fig.4D]). Figure 5 is similar to Figure 3, except that the antenna insert 21 now comprises a double-sided concentrator, the turns 3, 4 of which are distributed on either side of the insert substrate. In this case, we start with a concentrator blank 21a provided with two substantially solid central metal zones 16, one on each face of the substrate. For the use of a thick electronic module, a cavity 6 is then machined ([Fig.SB]) whose two zones P1, P2 pass through the insert blank, which eliminates the solid central metal zones 16 from the two faces of the concentrator blank, leaving internal turns 3a, 4a remaining on the internal side walls 17 of the cavity ([Fig.5D]) which open into said cavity 6, which again minimizes the distance between these internal turns 3a, 4a of the double-sided concentrator 3, 4 and the turns 14 of the antenna of the electronic module, thus improving the coupling between the double-sided concentrator and the antenna 14 of the module. Advantages of the invention Ultimately, the invention makes it possible to achieve the set goals. In particular, it makes it possible to eliminate the negative influence of the positioning tolerances of the antenna insert on the communication performance of a smart card provided with an antenna insert according to the invention, by bringing the internal turns of the concentrator closer to the turns of the antenna of the module, which has the effect of increasing the coupling factor between these two antennas. Furthermore, the distance between the internal turn 3a of the hub 3 and the external turn of the antenna 14 of the module is now constant, for a given type of module. The new structure does not require any significant modification to the process for assembling the antenna inserts into the card bodies. Only the manufacturing process for the inserts is modified, using a hub blank with a substantially solid metal center portion before a machining phase that removes this substantially solid metal center portion and finalizes the geometry of the hub and the antenna insert. This method and this concentrator antenna configuration can be advantageously used regardless of the zone P1, P2 of the module which passes through the antenna insert and regardless of the machining depths of the module cavity.
Claims
Claims
1. A smart card with contactless operation or mixed contact and contactless operation, comprising a smart card body (5) and an antenna insert (21) interposed between external layers (2) of said smart card body (5), said antenna insert (21) comprising a substrate and on at least one face of said substrate, turns of a concentrator (3, 4) intended to be electromagnetically coupled with the turns of an antenna (14) of an electronic module (9) arranged in a cavity (6) of the card body (5), characterized in that said concentrator (3, 4) comprises at least one internal turn (3a, 4a) which opens into the cavity (6) and which is flush with the internal side walls (17) of said cavity (6) of the smart card body (5).
2. Smart card according to claim 1, characterized in that said internal turn (3a, 4a) of the concentrator (3,4) of the antenna insert (21) is wider than the other turns of the concentrator.
3. Smart card according to claim 2, characterized in that the width of said internal turn (3a, 4a) of the concentrator (3, 4) is greater than the value of the positioning tolerance of the antenna insert (21) between the external layers (2) of a smart card body (5).
4. Smart card according to claim 3, characterized in that when the positioning tolerance of the antenna insert (21) in the card body (5) is less than 2 mm, the width of said internal turn (3a, 4a) is greater than 2.2 mm.
5. Smart card according to any one of the preceding claims, characterized in that the concentrator (3) is a single-sided antenna, all of the turns of which are arranged on a single face of the substrate of the antenna insert (21), and which comprises a single internal turn (3a) opening into the cavity (6) of the card body (5).
6. Smart card according to any one of claims 1 to 4, characterized in that the concentrator of the insert (21) is a double-sided antenna, the turns (3, 4) of which are distributed between the two opposite faces of the substrate of the antenna insert (21) and are connected in series or in parallel by means of a via, a crimp or a capacitor, said concentrator comprising two internal turns (3a, 4a) opening into the cavity (6) of the card body (5).
7. A method of manufacturing a smart card according to any one of claims 1 to 6, characterized in that it comprises steps consisting of: - Producing an antenna insert blank (21a) comprising a substrate (21) having several antenna turns (3, 4) made of etched aluminum and a substantially solid central part (16) which is not etched; - Arranging said antenna insert blank (21a) provided with its antennas (3, 4) between external layers (2) and laminating them together to form a card body (5); - Machining a face of the card body (5) to form a cavity (6) intended to receive an electronic module (9), said cavity (6) passing through said solid central part (16) of the antenna insert blank (21a), so that said central part (16) forms, after machining the cavity (9), an internal concentrator turn (3a, 4a) which is flush with the internal side walls (17) of the cavity (6);- Deposit a layer of adhesive (13) on the periphery of the electronic module (9); - Transfer and fix in said cavity (6) an electronic module (9) provided on its periphery with tracks (14) of a module antenna, so that these antenna tracks of the module are adjacent to the internal track (3a, 4a) of the concentrator (3, 4), or opposite said internal turn (3a, 4a) of the concentrator.;