Electronic module for a smart card provided with a display screen, and method for manufacturing same

Abstract

The invention relates to an electronic module (1) for a smart card, comprising a flexible printed circuit (2) having a rear face on which electronic components (4, 5, 6, 7) are mounted and a front face on which a display screen (3) is mounted, wherein the electronic module (1) further comprises at least one protective layer (13a, 13b, 13c) for protecting the display screen (3), characterised in that it comprises a spacer (14) surrounding the periphery of the display screen (3).

Description

Title: Electronic module for smart card provided with a display screen, and its manufacturing method

[0001] The present invention relates to an electronic module for a smart card, its manufacturing method, as well as the smart card obtained after integration of this electronic module into a card body.

[0002] The electronic module according to the invention is particularly suitable for smart cards capable of displaying a dynamic security cryptogram called “dCVV”, an acronym for the English expression “dynamic Card Verification Value”. This smart card will then be called a “dynamic CVV card” or more simply a “dCVV card”. STATE OF THE ART

[0003] A dCVV card is intended to provide greater security for e-commerce transactions using a dynamic code and to improve users' online shopping experience, compared to older cards that simply had a fixed verification code known as "Card Verification Value", also known as CVV, which is a fixed code printed on the body of the card.

[0004] Popular dCVV cards feature a 3-digit display embedded on the back of some standard credit cards. Instead of the conventional static 3-digit CVV code printed on the chip card, which can be easily duplicated, this easy-to-use dynamic code solution prevents so-called “Card Not Present” fraud and is likely to give consumers, merchants, and banks more confidence in their online transactions. For example, the so-called “eSecu” dynamic CVV card is a classic EMV contactless payment card that displays a dynamic value that automatically refreshes based on a time-varying One Time Password (OTP).

[0005] The first smart cards equipped with a display screen planned to integrate the screen into the structure of the card body. Such an implementation is described in document D1 = EP 2 541 471 A1. It describes a method for manufacturing a smart card provided with an information zone, in which printed information is superimposed with a display screen, in particular of the AMOLED type, capable of displaying a one-time use code (OTP), as well as with other components (battery, control button, etc.).

[0006] The AMOLED display screen is laminated directly between layers of the card body. This means that all layers of the card body, including the one carrying the display screen, are subjected to the pressures and temperatures of the card body lamination steps, which may damage the display screen. The display may be flush with an external surface of the card body, so that it remains exposed to all physical or chemical attacks. But the document also provides that the layer of the card body carrying the display may be covered with a covering layer whose optical transmission rate is chosen to make the appearance of the card body homogeneous when the display is off.This covering layer is not designed to protect the display against humidity or shocks, so the lifespan of the display remains precarious, especially if the display used is of the “paper” type, which is particularly sensitive to humidity.

[0007] Similarly, document D2 = US 2016 / 0260005 A1 also describes a smart card structure provided with a display screen. Here again, the card body comprises a flexible substrate on which is fixed a multi-component module integrating in particular a screen integrated in a transparent resin, the assembly being laminated between transparent layers of the card body using a heat-activatable resin. It follows that the multi-component module, including the display screen, is fully subjected to pressure and temperature constraints during the manufacture of the card body.

[0008] After smart cards with a laminated screen between the layers of the card body, smart cards with an electronic reporting module, itself integrating a display, appeared. Such an embodiment is described in document WO 2021 / 206780 A1 (Ellipse). The electronic module has both a contact terminal block on the front panel, compliant with the ISO 7816 standard, and a screen on the rear panel for displaying the dCVV code. This type of module, called "all in one", has the advantage of integrating all the electronic components necessary for the operation of the smart card, in particular the microelectronic chip and its software application, particularly of the banking type, as well as the screen for displaying the dCVV code.

[0009] In principle, this architecture is therefore simple and allows such a module to be integrated with all the necessary electronic components in a cavity of the card body, without requiring the integration of discrete electronic components distributed on a printed circuit integrated into the card body.

[0010] However, this known architecture poses new technical problems in practice. A first problem that arises is to obtain a solution that allows the electronic module to be integrated and bonded into the machined cavity of the card body while maintaining sufficient transparency of the cavity bottom to allow good readability of the screen after its integration into the cavity of the card body. The screen located on the back of the electronic module must in fact be clearly visible on the back of the smart card, given that the front face of this electronic module is occupied by a terminal block of electrical contacts that are opaque.

[0011] Also known from document WO2021 / 091587 (Ellipse) is an electronic module comprising integrated electronic elements, and intended to be used in smart cards. The electronic module comprises a face provided with contacts intended to cooperate with the contacts of a smart card reader. The smart card also comprises a display screen, either on the electronic module itself, or arranged next to it on one face of the smart card. However, the electronic module described in this document does not itself comprise a screen protection layer, which does not make it possible to protect the screen during the handling phases before and during assembly of the module in a smart card body. Such protection would however be necessary, in particular against humidity, in particular when bistable screens such as electronic paper type screens must be used. PURPOSE OF THE INVENTION

[0012] The general aim of the invention is to propose a new structure of electronic module for contactless smart card, and a smart card provided with such a module, the front face of which has a display screen (also simply called display), in particular for displaying a dynamic CVV code, and which is capable of solving all the technical problems mentioned above. By front face of the electronic module, we will designate the face of the module which remains visible after insertion of the module into the body of a smart card. The rear face of the module will then be the one which will be invisible after transfer of the module into the body of the smart card.

[0013] One of the main objectives of the invention is to propose an all-in-one module, comprising a display screen on the front face, and means for protecting this screen directly integrated into the module, in particular means of protection against humidity, which will allow it to be handled without risk upstream of the chip card assembly phase, and during this phase.

[0014] Another object of the invention is to propose an electronic module constituting a subassembly of the smart card integrating both the display screen, protective layers for this screen, and a spacer to protect the module and its screen during the application of pressure for bonding the module in a cavity of the card body. This module must thus provide a complete functional assembly manufactured separately from the card body and which simply needs to be placed in a cavity of the card body.

[0015] The invention also aims to propose a method for manufacturing such an electronic module, and a smart card using such an electronic module. SUBJECT OF THE INVENTION

[0016] In principle, the invention consists of proposing an electronic module provided with a display on the front face and comprising protective layers for the display directly integrated into the electronic module. For this purpose, the front and rear faces of the display are protected by protective layers located on the module, in particular for protection against humidity. Thus, the visible front face of the module's display is surmounted by a first protective layer forming part of the module, and intended to protect the display against humidity and other external aggressions such as ultraviolet radiation or shocks.

[0017] The back side of the module's screen, invisible from the outside of the smart card, will also be protected either by a protective layer similar to that of the front side, or by a copper layer.

[0018] The protective layers chosen will depend on the technology chosen for the display screen and its specific weaknesses.

[0019] In addition, the display screen will be surrounded on its periphery by a plastic spacer chosen to withstand the application of pressure and temperature during the steps of inserting the electronic module into a smart card body.

[0020] The invention therefore relates to an electronic module intended to be inserted into a cavity of a smart card and comprising a flexible printed circuit having a rear face on which electronic components are fixed and a front face on which a display screen is fixed, said electronic module being characterized on the one hand in that it comprises at least a first protective layer for the display screen located on the front face of said electronic module and at least a second protective layer for the display screen located on the rear face of said electronic module, the display screen of the electronic module being integrated between said first and second protective layers, and said electronic module being characterized on the other hand in that it comprises a spacer surrounding the periphery of the display screen. In this way, the display screen is sandwiched between the front and rear protective layers of the module.

[0021] According to one embodiment, said display screen is an electronic paper type screen.

[0022] According to one embodiment, said at least one protective layer is a layer of protection against humidity, UV radiation, or shocks.

[0023] According to one embodiment, the electronic module comprises a first transparent protective layer located on the front face of the module and surmounting the display screen. This protective layer is made of a material such as polyimide or a PET treated to form a barrier against humidity.

[0024] According to one embodiment, said first protective layer has a three-dimensional shape and covers the upper face and the side edges of the display screen, and extends under said spacer.

[0025] Alternatively, said first protective layer has a flat shape and covers the entire front face of the electronic module, including the upper face of the spacer.

[0026] According to one embodiment, the module has a gap between the periphery of the display screen and the internal circumference of the spacer, this gap being filled with a filling material to avoid empty areas inside the electronic module likely to weaken the latter.

[0027] Preferably, the electronic module includes a second protective layer located on the rear face of the module and integrated into the flexible printed circuit.

[0028] According to one embodiment, said flexible printed circuit of the module comprises two dielectric layers interposed with three metal layers interconnected by conductive vias, and said second protective layer is then constituted by a continuous portion of one of said metal layers of the flexible printed circuit.

[0029] Alternatively, the electronic module comprises a second protective layer located on the rear face of the module, made of a layer of polyimide or PET treated to form a moisture barrier, and this second protective layer extends under the display screen and under the spacer.

[0030] This second layer of protection can be configured to encompass the entire back face of the module, including the passive electronic components.

[0031] The spacer preferably has a thickness corresponding to the thickness of the display screen. The spacer is arranged below the peripheral zone of the upper protective layer. It is made of a plastic material chosen to withstand the pressure and temperature of the steps of fixing the electronic module in a smart card body. It is in particular made of PET or polyimide. The plastic spacer can be coated on its upper face with a thin metal layer, allowing heat to dissipate during the insertion of the module. This thin metal layer is optionally provided with a graphic personalization pattern.

[0032] The invention also relates to a method of manufacturing an electronic module as described above, characterized in that it comprises steps consisting of:

[0033] - Supply a flexible printed circuit having an upper face and a lower face and comprising a dielectric core and two metal layers arranged on either side around the dielectric core;

[0034] - Place a lower protective layer on the upper side of the flexible printed circuit;

[0035] - Connecting a display screen above said lower protective layer with passive components located on the underside of the flexible printed circuit;

[0036] - Position a spacer around the display screen;

[0037] - Place a top protective layer over the display screen and spacer;

[0038] - Laminate the different components together using hot lamination.

[0039] The invention also relates to a smart card comprising a card body formed by a stack of layers secured to each other, and a cavity intended to receive an electronic module, said cavity having a first peripheral zone of depth P1 and a second central zone of depth P2 greater than P1, this smart card being characterized in that it comprises an electronic module as defined above. DETAILED DESCRIPTION

[0040] The invention will be described in more detail with the aid of the drawings, in which: Figures 1 and 2 represent a first embodiment of an electronic module according to the invention, this module being represented respectively in sectional view () and in top view (); La represents a sectional view of a second embodiment of the electronic module according to the invention; La represents a sectional view of a third embodiment of the electronic module according to the invention; La represents a sectional view of a fourth embodiment of the electronic module according to the invention; La represents a partial sectional view of a smart card integrating an electronic module conforming to the ; La represents a partial sectional view of a smart card integrating an electronic module conforming to the.

[0041] Identical elements of the different embodiments described will be designated by the same numerical references.

[0042] We refer to the. The electronic module 1 comprises a flexible printed circuit 2, also called “flex” for simplification, on a front face of which is mounted a display screen or display 3 and on the rear face of which are mounted electronic components 4, 5, 6, 7. These comprise in particular, in a known manner, a secure identification component hosting the software applications of the smart card, a display control circuit, and one or more passive components such as resistors or capacitors.

[0043] In the various embodiments of the module 1, the display 3 may be of different types. But it will preferably be a bistable display of the electronic paper type, also known as "papiel", or "e-paper" in English terminology. This type of display does not require backlighting and therefore does not need any energy to leave a text or an image displayed after its power supply has been cut off. On the other hand, this type of display contains a gel which makes it sensitive to humidity. It is therefore particularly important that the module itself has an optimized structure to protect the display against any exposure to humidity, throughout the manufacturing cycle of the electronic module and the smart card which will receive it.If the display screen is properly protected on the module itself, it becomes less important, or even unnecessary, for the card body to have specific screen protection means, which simplifies the structure of the card body compared to some prior art structures mentioned above.

[0044] In order to solve the problem of protecting the display directly by the module, the electronic module 1 according to the invention comprises protective layers directly integrated into its structure. This may be at least one transparent protective layer on the front face of the module, and preferably also a protective layer on the rear face of the electronic module.

[0045] According to one embodiment (figures 1, 3), the flexible printed circuit 2 comprises two dielectric layers 8 interposed with three metal layers 10a, 10b, 10c in particular made of copper, interconnected by conductive vias 11, 12. A first protective layer 13a is arranged on the front face of the module, above the display 3, and a second protective layer 13b is arranged on the rear face of the module. In this case, this second protective layer 13b is constituted by a continuous part of one of said metal layers of the flexible printed circuit, namely a continuous part of the middle metal layer 10b. The middle metal layer 10b forms at the periphery of the module the turns of an antenna of the module, and in the central part of the module, it has a continuous zone forming a second protective layer 13b, intended to block the rise of humidity towards the display 3 from the rear face of the module.In the embodiment of the, the electronic module 1 comprises a first transparent protective layer 13a covering the upper face of the display. This protective layer 13a is in particular made of transparent polyimide or other materials capable of constituting a barrier to humidity and UV radiation, such as a PET benefiting from a treatment with an inorganic material, in particular mineral. This protective layer 13a has a thickness of a few micrometers, in particular approximately 50 micrometers.

[0046] The surface of the display 3 is smaller than the surface of the module 1, leaving a crown free around the display 3. In order to be able to apply to the module the necessary temperatures and pressures when it is inserted into a smart card body, the electronic module 1 according to the invention further comprises a spacer 14 surrounding the periphery of the display 3, capable of protecting the display 3 against an application of these inserting temperatures and pressures. This spacer 14 is made of plastic, epoxy glass, polyimide or another material capable of withstanding the temperatures and pressures applied when the module is inserted into a card body. The thickness of the spacer 14 is chosen so that the level of the upper face of the spacer 14 corresponds to the level of the upper face of the display 13.Furthermore, the thickness of the spacer 14 is an adjustment parameter making it possible to produce in a smart card a cavity whose depth P1 (figures 6, 7) is adapted either for a galvanic connection or for a connection by inductive coupling with a concentrator antenna. The copper or aluminum antenna circuits are then preferably placed at the level of the neutral fiber of the smart card, which makes it possible to limit the bending stresses and to increase the durability of the smart card.

[0047] In the embodiment shown in, the first transparent protective layer 13a extends to the periphery of the electronic module 1, and the spacer 14 is arranged below the peripheral zone of the upper protective layer 13a, which reinforces the protection of the display 3 against possible infiltration of humidity from the front face of the module.

[0048] Preferably, in the embodiment of the, the gap between the periphery of the display 3 and the internal circumference 16 of the spacer 14 is filled with a filling material 17, for example a thermosetting resin or glue, making it possible to avoid empty areas inside the module and likely to weaken it.

[0049] Optionally, the electronic module 1 may include a thin metal layer 15 on the upper face of the spacer 14, to improve its resistance to mechanical friction and its external appearance. This metal layer 15 then preferably has an internal edge chamfered towards the transparent protective layer 13a, which makes it possible to improve the visual appearance of the module. This metal layer 15 may optionally be accompanied by a logo or a graphic personalization pattern.

[0050] In the embodiment shown in, the upper transparent protective layer 13a is three-dimensional, instead of being flat as in. In this way, the transparent protective layer 13a surmounts the display 3, then folds back on the peripheral sides of the display 3 and passes in its periphery under the spacer 14. The spacer 14 can also be bi-material or bi-layer, for example with a metallic upper layer provided with an engraved pattern visible from the outside of the module.

[0051] According to another embodiment (figures 4, 5), the flexible printed circuit 2 comprises a single dielectric core 8 and only two metal layers 10a, 10b located on either side of the dielectric core 8 and interconnected with each other by conductive vias 11. The metal layers 10a and 10b are discontinuous because they are only used to make antenna turns or connections between the electronic components 4, 5, 6, 7 and the display 3. They are therefore devoid of a continuous part which could act as a rear protective layer of the display 3. In the case shown in, the absence of a continuous metal layer is compensated either by a second flat protective layer 13b made of plastic material, in particular polyimide, directly integrated under the display screen. In this embodiment, the protective layer 13b is located directly under the display 3 and extends under the spacer 14.In this way, the display 3 is sandwiched between the two protective layers 13a, 13b made of plastic. In the case shown in, the absence of a continuous metal layer is compensated by a second three-dimensional protective layer 13c made of plastic integrated in the lower part of the electronic module and encompassing the passive components 4, 5, 6, 7 of the module. The protective layers of plastic 13a, 13b; 13c are preferably surface-treated with an inorganic material to give them a very high level of insulation against humidity, necessary for e-paper technology screens.

[0052] The embodiment of figures 4 and 5 makes it possible to do without a flex 2 with three metal layers, so that the flex 2 is simplified, thinner and less expensive, since it now only comprises one dielectric layer 8 and two metal layers 10a, 10b.

[0053] La represents a schematic view in partial section of a smart card 20 integrating an electronic module 1 according to la or la, provided with a flex 2 with a double layer of dielectric 8 and three metal layers. Conventionally, the body of the smart card 20 comprises external layers 20a, 20b made of plastic, and an insert 21 provided with an antenna 22 of the card body allowing communication with an antenna of a remote reader (not shown). The card body 20 formed by the layers 20a, 20b also comprises in a known manner a cavity 23 having a first zone of depth P1 receiving the periphery of the electronic module 1, and a second zone of depth P2 greater than P1 and receiving the central part of the module 1, thicker and provided with the electronic components 4, 5, 6, 7.

[0054] In the embodiment shown in, the electronic module 1 comprises an antenna 24 whose turns are positioned opposite certain turns of the antenna 22 of the card body, so as to be able to be electromagnetically coupled with them. The periphery of the lower face of the module 1 is fixed to the bottom of the area of ​​the cavity of depth P1 by a heat-activatable adhesive 25, of the “hotmelt” type in English terminology.

[0055] Despite the presence of the display 3 and the protective layers 13a, 13b, the structure of the module 1 is particularly thin, compatible with a cavity 23 of depth P1 less than or equal to 320 micrometers and depth P2 less than or equal to 620 micrometers.

[0056] The smart card 20 of the comprises an electronic module 1 according to the, even thinner than that of figures 1 and 3, due to the use of a flex 2 with only two metal layers 10a, 10b, the display 3 of the module being protected on its front face by a first transparent protective layer 13a made of plastic, and on its rear face by a second protective layer 13b also made of plastic. The module 1 used is without antenna, and is glued in the cavity 23 of the smart card 20 using an anisotropic conductive adhesive 26, making it possible to establish a galvanic connection between the connections of the electronic components 4,5,6,7 located on the metal layer of the flex, and the connections 25 of the module.

[0057] In practice, given their different variants, the electronic modules 1 can therefore be designed to be compatible with an inductive, capacitive or direct connection with the communication device of the card body.

[0058] In a concrete embodiment, the protective layers 13a, 13b or 13c have a thickness of the order of 50 µm, the spacer 14 has a thickness of the order of 130 µm, the flex 2 with two metal layers has a thickness of the order of 90 µm, the flex 2 with three metal layers has a thickness of the order of 160 µm, the hotmelt adhesive 25 or the ACF 26 has a thickness of approximately 30 µm once pressed. The module 1 has a total thickness of approximately 600 µm. In total, the smart card 20 integrating the module 1 according to the invention then has a typical thickness of 800 + / - 40 µm. ADVANTAGES OF THE INVENTION

[0059] The invention achieves the set objectives. In particular, it has the advantage of integrating a display screen in an easily readable manner into an electronic module, while directly integrating means for protecting this screen onto the electronic module.

[0060] The display screen of the module allows in particular the display of a dCVV code on the visible surface of a smart card integrating such an electronic module. However, the invention is applicable to other types of smart cards and applications, as long as the smart card has a display screen.

[0061] The invention makes it possible to protect the module display well behind an upper protective layer located above the display and a lower protective layer located behind the display. Thus, the module display is well protected directly on both sides of the module, against external aggressions, in particular against humidity, and this during the entire manufacturing cycle of the module and the smart card, and without impairing the good visibility of the screen. This makes it possible in particular to use bistable displays of the electronic paper type which are particularly thin and energy-saving, but sensitive to humidity.

[0062] The integration of the electronic module with its screen is particularly clean, without requiring buttons or other components in the card body or on its surface.

[0063] Ultimately, the solution according to the invention makes it possible to advantageously replace dCVV cards which embed the screen and its control electronics on a PCB substrate located in the card body, away from the electronic module.

[0064] A smart card provided with a module according to the invention can be manufactured using a method using proven, reliable and economical techniques, including machining a cavity in the card body, then transferring and gluing the electronic module in the cavity, thus avoiding the problems associated with laminating a card body including a display between the layers of the card body.

[0065] The resulting smart card is fully compatible with the existing credit card system, easy to deploy for both merchants and users.

Claims

Electronic module (1) intended to be inserted into a cavity of a smart card and comprising a flexible printed circuit (2) having a rear face on which electronic components (4, 5, 6, 7) are fixed and a front face on which a display screen (3) is fixed, said electronic module (1) being characterized on the one hand in that it comprises at least a first protective layer (13a) of the display screen (3) located on the front face of said electronic module (1) and at least a second protective layer (13b; 13c) of the display screen (3) located on the rear face of said electronic module (1), the display screen (3) of the electronic module (1) being integrated between said first and second protective layers, and said electronic module (1) being characterized on the other hand in that it comprises a spacer (14) surrounding the periphery of the display screen (3). Electronic module (1) according to claim 1, characterized in that said display screen (3) is an electronic paper type screen. Electronic module (1) according to claim 1 or claim 2, characterized in that said at least one protective layer (13a, 13b, 13c) is a layer of protection against humidity, UV radiation, or shocks. Electronic module (1) according to claim 3, characterized in that said first transparent protective layer (13a) located on the front face of the module and surmounting the display screen (3) is made of a material chosen from polyimide or a PET treated to form a barrier against humidity. Electronic module (1) according to claim 4, characterized in that said first protective layer (13a) has a three-dimensional shape and covers the upper face and the lateral edges of the display screen (3), and extends under said spacer (14). Electronic module (1) according to claim 4, characterized in that said first protective layer (13a) has a flat shape and covers the entire front face of the electronic module (1). Electronic module (1) according to claim 6, characterized in that it has a gap between the periphery of the display screen (3) and the internal circumference (16) of the spacer (14), this gap being filled with a filling material (17) to avoid empty areas inside the electronic module (1). Electronic module (1) according to one of the preceding claims, characterized in that said second protective layer (13b) located on the rear face of the module is integrated into the flexible printed circuit (2). Electronic module (1) according to claim 8, characterized in that said flexible printed circuit (2) comprises two dielectric layers (8) interposed with three metal layers (10a, 10b, 10c) interconnected by conductive vias (11, 12), and in that said second protective layer (13b) is constituted by a continuous portion of one (10b) of said metal layers of the flexible printed circuit (2). Electronic module (1) according to one of claims 1 to 8, characterized in that said second protective layer (13b) located on the rear face of the module is made of a layer of polyimide or PET treated to form a moisture barrier, and extends under the display screen (3) and under the spacer (14). Electronic module (1) according to claim 10, characterized in that said second protective layer (13b) is configured so as to encompass the entirety of said rear face of the module, including said passive components (4, 5, 6, 7). Electronic module (1) according to one of the preceding claims, characterized in that the spacer (14) has a thickness corresponding to the thickness of the display screen (3). Electronic module (1) according to one of the preceding claims, characterized in that the spacer (14) is arranged below the peripheral zone of the upper protective layer (13a). Electronic module (1) according to one of the preceding claims, characterized in that the spacer (14) is made of a plastic material chosen to withstand the pressure and temperature of the steps of fixing the electronic module (1) in a smart card body (20), in particular PET or polyimide. Electronic module (1) according to claim 14, characterized in that the spacer (14) made of plastic material is coated on its upper face with a thin metallic layer (15), possibly provided with a graphic personalization pattern. A method of manufacturing an electronic module (1) according to one of the preceding claims, characterized in that it comprises steps consisting of:Providing a flexible printed circuit (2) having an upper face and a lower face and comprising a dielectric core (8) and two metal layers (10a, 10b) arranged around the dielectric core (8);Arranging a lower protective layer (13b) on the upper face of the flexible printed circuit (2);Connecting a display screen (3) above the lower protective layer (13b) with passive components (4, 5, 6, 7) located on the lower face of the flexible printed circuit;Positioning a spacer (14) around the display screen (3);Arranging an upper protective layer (13a) above the display screen (3) and the spacer (14);Laminating the various components together by hot lamination. Smart card (1) comprising a card body (2) formed by a stack of layers (20a, 20b) integral with each other, and a cavity (23) intended to receive an electronic module (1), said cavity (23) having a first peripheral zone of depth P1 and a second central zone of depth P2 greater than P1, characterized in that it comprises in said cavity (23) an electronic module (1) according to any one of the preceding claims 1 to 15.

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