FR3013483A1 - METHOD FOR MANUFACTURING A RADIOFREQUENCY DEVICE AND ASSOCIATED RFID CARD - Google Patents

Abstract

This method of manufacturing a device comprising a body comprising at least one substrate is characterized in that it comprises: a fixing step (E100), on a face of a first substrate of the body, of a first antenna; whose ends are intended to be electrically connected to a microcircuit; and a step of printing (E200) at least one circuit of a second antenna on at least one face of a second substrate of the body of the device, said antennas being intended to be electromagnetically coupled.

Description

BACKGROUND OF THE INVENTION The invention relates to the general field of radio identification (in English Radio Frequency Identification or RFID). It relates more specifically to the field of the manufacture of radiofrequency devices such as passports or RFID cards (non-contact or dual interface) which consist of at least one RFID chip, an antenna and at least one substrate . In known manner, there are at least two methods of fixing an antenna on a substrate during the manufacture of a radiofrequency device. The first method is to deposit directly on the substrate the constituent elements of the antenna and then to fix them using ultrasound or other means exerting local heating.

This method is known in English as "wire-embedded technology". The accuracy of the positioning of the antenna obtained by this method is slightly inferior to that obtained by the approach presented below. On the other hand, it makes it possible to obtain RFID cards having a good resistance to mechanical tests, in particular to bending, as well as good radiofrequency performances. However, the costs of producing a map by this approach are high. The second method consists in printing, for example by means of a conductive ink, by screen printing, by ink jet or by any other printing means, directly on the substrate the constituent elements of the antenna. This second method limits the production waste, in particular for the controlled printing systems (in English "Drop On Demand"). This production method is also very flexible, has good reproducibility and easily adapts to the quantities to be produced, even when these are low as in the case of the production of prototypes. It also allows to obtain higher production rates than in the case of a fixation for example by ultrasound at lower production costs. However, this second method has several disadvantages. First, the radio frequency performance obtained for the same antenna pattern are lower, of the order of 20 to 30% compared to those obtained for an antenna fixed for example by ultrasound. Then, the resistance of the printed antennas does not comply with the mechanical criteria of the standardized resistance tests of radio frequency devices. In particular, the use of conductive inks chosen for their good conductivity does not make it possible to obtain good flexural strength, for example for RFID cards. Indeed it has not been found to date a satisfactory solution to achieve the connection between the ends of a screen-printed antenna and the microcircuit of the RFID chip. The material deposited at the ends of the screen-printed antenna to form the contact pads must have characteristics (adhesion, conductivity, flexural strength and cost) determined, and which, to date, have not been optimally achieved . It is thus common that the links between the printed antenna and the pads intended to be connected to the RFID chip break during the bending tests. There is therefore a need for a flexible and economical solution offering a manufacturing process easily adaptable to change the parameters of the antenna, while simultaneously ensuring a good electrical connection between the antenna and the microcircuit of the RFID chip. OBJECT AND SUMMARY OF THE INVENTION The present invention aims in particular to solve the aforementioned drawbacks of the prior art. More specifically, the invention relates, in a first aspect, to a method of manufacturing a device comprising a body comprising at least one substrate. This method is characterized in that it comprises: a step of fixing, on a face of a first substrate of the body, a first antenna whose ends are intended to be electrically connected to a microcircuit; and a step of printing at least one circuit of a second antenna on at least one face of a second substrate of the card body, the antennas are intended to be electromagnetically coupled.

It should be noted that within the meaning of the invention, the fixing step is not a printing step. In other words, the first antenna is not printed on the first substrate. Thanks to these provisions, a manufacturing process is obtained for which it is easy to modify the parameters of the screen-printed antenna while guaranteeing the radiofrequency performance of the first antenna and its good electrical connection with the microcircuit of the RFID chip. In a particular embodiment, a single substrate is used. In this case, the first antenna is fixed on the first face of the substrate, while the circuit of the second antenna is printed on the second face of the substrate. In another particular embodiment, the two substrates are different and the body of the device is then obtained by assembling together at least the first and the second substrate.

In a particular embodiment, the device is an RFID card. The invention then proposes to manufacture this RFID card, formed of plastic and in accordance with the ISO / IEC 7810 and ISO / IEC 14443 standard of thickness of the order of 0.76 mm, using an equivalent antenna formed of two antennas electromagnetically coupled.

Each of these two antennas is fixed by separate manufacturing processes, including one printing, on the same substrate or on different substrates of the RFID card, thus advantageously taking advantage of the intrinsic characteristics of each of the two methods used. The substrates may be plastic substrates, for example of the polyvinyl chloride (PVC), polyethylene or other type, or in another material. These substrates are separate layers that are intended to be assembled to form the card body. It should be noted that no restriction is made on the composition of the substrates. These may be of the same nature or of different natures depending on the intended application. Advantageously, the invention is compatible with the main possible modes of fixing an antenna on the first substrate. Thus, it can, for example, be manufactured by directly depositing the constituent elements of the antenna, a sheathed copper wire for example, and then fixing them by the so-called "wireembedded" method. The ends of the encrusted antenna are electrically connected to the microcircuit of the RFID chip by physical means known to those skilled in the art, such as copper pads in contact with the end of the antenna on the one hand and on the other hand electrically connected to the microcircuit via a conductive adhesive and gold son, or protruding conductive alloy. These methods of connection between the antenna and the RFID chip are known by the card manufacturers and exhibit good flexural strength. This particular approach guarantees the first substrate, and if necessary all of the two assembled substrates, a good mechanical strength. On the other hand, the antenna deposited on the first substrate thus has radiofrequency performances higher than those which would have been obtained by another method. The second antenna is printed on the second substrate, which makes the manufacture of this second antenna and substrate assembly more economical, easier to produce, very reproducible and adaptable. Very advantageously, the printing on the second substrate can be done by screen printing, flexography, heliography, inkjet or any other conductive ink printing means. The conductive ink used may be composed of, for example, metal particles (typically silver, copper or carbon) suspended in a polymer resin or an intrinsically conductive polymer resin. Very advantageously, no restriction is imposed on the assembly of the two substrates which can thus be made by rolling, gluing or by any other means known to those skilled in the art. In a particular embodiment of the invention, the electromagnetic coupling between the two antennas is in the form of a mutual inductance coupling. Such an electromagnetic coupling of the two antennas makes it possible from the radiofrequency performances of the first antenna to obtain for the equivalent antenna 35, formed by all the two coupled antennas, the desired radio frequency performance for a particular application. In other words, the manufacturing method, which is the subject of the invention, makes it possible to use identical first substrate and first antenna pairs for the production of radiofrequency devices, for example an RFID card, used in different applications. The adaptation of a radiofrequency device to a particular application is performed by specifying the second antenna so as to obtain, after electromagnetic coupling with the first antenna, the desired radio frequency characteristics (resonant frequency, antenna range, etc.). for the particular application envisaged. The second antenna is then printed either on the second face of the first substrate or on a second substrate which is then assembled with the first substrate.

In addition, in the latter case, the manufacturing method according to the invention allows the stacking and assembly of one (or more) other substrate (s) or one (or more) film (s). ) Plastic (s) with the first and the second substrate. Advantageously, when one (or more) other (s) substrate (s) or plastic film (s) are inserted between the first and second substrate, the coupling between the two antennas is then through the or substrates or plastic films, the insertion of which makes it possible to increase the distance between the first and second substrates; distance which constitutes an additional parameter or degree of freedom when specifying the electromagnetic coupling between the two antennas. Thus, compared to prior methods of manufacture, the method that is the subject of the present invention is more flexible and more economical while guaranteeing the mechanical strength and the expected radio frequency performance of the devices produced.

It should be noted that the manufacturing method, object of the invention, adapts advantageously to all the shapes and dimensions of antennas that can be used for the manufacture of radio frequency devices, including RFID cards. In particular, in the latter case, the antennas can be designed and positioned to conform to the ID-1, 2FF or 3FF formats of ISO / IEC 7810 and ISO / IEC 14443. In particular, it is possible to guarantee the presence of an embossing area (embossing area) of 5 lines in accordance with the ID-1 format of the RFID cards. Correlatively, according to a second aspect, the invention provides an RFID card comprising a card body comprising at least one substrate and: a first antenna fixed on one side of a first substrate of the card body, the ends of the first antenna being electrically connected to an RFID chip; and a second antenna having a circuit printed on at least one side of a second substrate of said card body, the antennas being electromagnetically coupled. In a first particular embodiment of an RFID card according to the invention, the second substrate is constituted by the first substrate. In this case, the first antenna is fixed on the first face 15 of the substrate, while the circuit of the second antenna is printed on the second face of the substrate. The circuit of the second antenna is also connected to two conductive plates positioned vis-à-vis, each on a different face of the substrate and capacitively coupled so as to form a capacitor. In a second particular embodiment of an RFID card according to the invention, the two substrates are different and the second antenna consists of two circuits connected together at one end by a metallized hole made in the second substrate. Each of the two circuits is printed on a different face of the second substrate. On the other hand, the second end of each circuit is connected to a first capacitor. This capacitance is formed by two capacitively coupled plates positioned facing each other on a different face of the second substrate. This capacitance provides a parameter for adjusting and optimizing the characteristics of the antenna, in particular for adjusting the resonance frequency as requested for a particular application of the RFID card. Very advantageously, this particular embodiment makes it possible to produce antennas occupying a smaller area on the RFID card, which makes it easier to guarantee the existence of a zone, standardized or not, of relief writing. , while having the radio frequency performance of a larger antenna.

In a third particular embodiment of an RFID card according to the invention, the two substrates are different and the second antenna is connected to two first conductive plates also located on the second substrate. A third substrate, intended to be inserted between the first and the second substrate, also comprises two second conductive plates connected to one another by a conductive element and positioned vis-a-vis the first conductive plates. In this way during the step of assembling the third substrate between the first substrate and the second substrate, the first two plates and the second two plates are facing each other and form two capacitors which constitute with the turns a resonant assembly. The magnetic coupling between the two antennas is through the third substrate, the thickness of which can be chosen as a function of the desired coupling between the two antennas.

The invention also aims, in a third aspect, at a kit for manufacturing an RFID card body, characterized in that: a first antenna, the ends of which are intended to be electrically connected to an RFID chip, is fixed on a face of a first substrate of the kit; and a circuit of a second antenna is printed on at least one face of a second substrate of the kit, the antennas being intended to be electromagnetically coupled.

BRIEF DESCRIPTION OF THE DRAWINGS Particular features and advantages of the present invention will become apparent from the detailed description given in the figures in which: FIG. 1 represents in flow chart form the main steps implemented by the method of manufacturing a device; radio frequency; FIG. 2 represents an RFID card within the meaning of the invention according to a first embodiment; FIG. 3 represents an exploded view of an RFID card according to the invention according to a second embodiment; FIG. 4 represents an exploded view of an RFID card in the sense of the invention according to a third embodiment; FIG. 5 represents a stack of several substrates and of several protective plastic films forming an RFID card within the meaning of the invention. DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS OF THE INVENTION FIG. 1 represents, in flowchart form, the main steps implemented by the method of manufacturing a radiofrequency device according to the invention. We start from two substrates Si and S2 prepared beforehand. The second substrate S2 is optionally constituted by the first substrate Si. It should be noted that no restriction is formulated on the nature of the composition of the two substrates Si and S2. These may be of the same nature or of different natures depending on the intended application. In a first step E100, the first antenna Al is fixed on the first substrate Si and its ends are connected to a chip of an RFID chip.

In a particular embodiment of the invention, the fixing of the first antenna Al is done using the so-called "wireembedded technology" method. Of course, other modes of attachment of the antenna Al can be used, depending on the desired characteristics of the radio frequency device.

In a second step E200, the second antenna A2 is printed by means of a conductive ink, for example composed of silver particles suspended in a polymer resin, on the substrate S2. In a particular embodiment, the second substrate S2 is constituted (or merged) by the first substrate Si. In this case, the first antenna is fixed on the first face of the substrate Si, while the circuit of the second antenna is printed. on the second face of the Si substrate. The term "circuit" means all the turns inductively coupled with the first antenna. The printing can be done by screen printing, flexography, heliography, inkjet or by any other means of printing.

In a particular embodiment and during a third step E300, the two substrates Si and S2, when they are different, are assembled, by gluing or by any other means known to those skilled in the art, to form the radio frequency device.

FIG. 2 shows an RFID card 1 within the meaning of the invention when the second substrate S2 is constituted by the first substrate Si. On the first face of the substrate Si is fixed an antenna Al, possibly adapted, formed for example of several turns whose ends are connected to studs 2, 3. The studs 2, 3 make it possible to connect the antenna Al to an RFID chip 4. In this example, the number of turns as well as their shape and their spatial positioning define the characteristics of the antenna. the antenna Al and in particular its radiofrequency properties.

On the second face of the substrate Si is printed a second circuit of a second antenna A2 (electromagnetically coupled to the antenna A1 and formed for example by a network of turns), each end of which is connected to a different plate Cla and Clb. These two plates Cla and Clb are positioned vis-a-vis each on a different face of the substrate Si, so as to form a capacitor C1. FIG. 3 shows an exploded view of an RFID card 1 'within the meaning of the invention. according to a second embodiment. For the sake of simplification, identical references are given in this figure, as well as in the following, to the elements common to the first embodiment and illustrated in FIG. 2. The RFID card consists of two different substrates Si and S2. On the first face of the substrate Si is fixed an antenna Al ', possibly adapted, formed for example of several turns whose ends are connected to studs 2, 3. The studs 2, 3 make it possible to connect the antenna Al' to a RFID chip 4. In this example, the number of turns as well as their shape and their spatial positioning define the characteristics of the antenna Al 'and in particular its radio frequency properties.

On both sides of the second substrate S2 is printed a second antenna A2 '. The second antenna A2 'is formed of two circuits A2'-1, A2'-2 (in this example: two networks of turns) each printed on a different face of the substrate S2. The two circuits are interconnected electrically and physically via a via (metallized well) 6 at one end and are interconnected electrically by their other end by a capacitor Cl '. The capacitance Cl 'is formed of two Cra and Clib plates, positioned vis-à-vis each on a different face of the second substrate S2. In addition, the two plates Cra and Crb are capacitively coupled; the set A2'-1 and A2'-2 consisting of the two circuits and capacitance Cl then forming a resonant circuit.

In this particular embodiment of the RFID card, thanks to the chosen topology of the two antennas A1 'and A2', in particular the printing of A2 'on both sides of the substrate S2, it is possible to easily guarantee the existence of an embossed writing zone 5 judiciously positioning the two plates Cra and Cl'b, for example in the upper left corner of the RFID card as shown in FIG. 3. In this example, the topologies of the two networks of turns forming the antenna A2 'are simultaneously defined by the desired characteristics of the antenna equivalent to the two antennas Al' and A2 'electromagnetically coupled, for example by mutual inductance, and by the constraint of having a write zone 5 (by example of 5 lines for the ID-1 format) in relief (embossing zone). It should be noted that the two networks of turns do not necessarily have the same topology as is apparent in FIG. 3. The two antennas A1 'and A2' are positioned so as to be electromagnetically coupled by mutual inductance (ie the flux magnetic generated by one at least partially crossing the turns of the other) so that the assembly consisting of the two antennas forms an equivalent antenna. The design of an antenna A2 'electromagnetically coupled to an antenna Al' given to obtain an equivalent antenna having particular radiofrequency characteristics (resonant frequency, range of the equivalent antenna, etc.) is known to those skilled in the art. and will not be described further here.

FIG. 4 shows an exploded view of an RFID card 1 ", consisting of three substrates Si, S2 and S3, according to a third embodiment of the invention, The first substrate Si differs from that represented in FIG. possibly by the geometric definition of the antenna Ar. On one side of the second substrate S2 is printed a second antenna A2 "electromagnetically coupled to the first antenna Ar and formed for example by a network of turns. At each end of the array of turns are arranged two first plates 10 Cra and C2a. The third substrate S3 comprises two second plates C1 "b and C2b, interconnected by a conductive element In a particular embodiment of the invention, the two second plates C1" b and C2b can also be printed on the substrate S3 .

These two plates C1 "b and C2b are positioned on the third substrate S3 vis-à-vis the first two plates Cra and C2a on the second substrate S2, in this way during the insertion, during step d assembly of the third substrate S3 between the first substrate Si and the second substrate S2, the first two plates Cra, C2a and the two second plates C1 "b, C2b form, by capacitive coupling, two capacitors Cr and C2 carrying out with the turns a resonant closed circuit. FIG. 5 shows a stack of substrates Si, S2, S3, 11, 12 and plastic films 7, 8, 9, 10 constituting an RFID card according to the invention.

Claims (10)

REVENDICATIONS1. A method of manufacturing a device (1, r, 1 ") comprising a body comprising at least one substrate (Si, S2), said method being characterized in that it comprises: - a fixing step (E100), on a face of a first substrate (Si) of the body, a first antenna (A1, Ar, A1 ") whose ends are intended to be electrically connected to a microcircuit; and a step of printing (E200) at least one circuit of a second antenna (A2, A2 ', A2 ") on at least one face of a second substrate (S2) of the body of the device, said antennas being intended to be electromagnetically coupled. 2. A method of manufacturing a device (1) according to claim 1, wherein the first and second substrates (Si, S2) coincide and said circuit of the second antenna is printed on a face different from that on which is fixed said first antenna. 3. A method of manufacturing a device (1 ', 1 ") according to claim 1, characterized in that it comprises, when said substrates are different, a step of assembling (E300) said substrates (Si) and ( S2) to constitute said body of said device (1 ', 1 "). 4. A method of manufacturing a device (1 ', 1 ") according to claim 3, characterized in that at least a third substrate or at least one plastic film is stacked and assembled with said first and second substrates at said assembly step (E300). 5. A method of manufacturing a device (1, 1 ', 1 ") according to one of claims 1 to 4, characterized in that the device is an RFID card and the physical characteristics of said RFID card are in accordance with the one of the formats ID-1, 2FF or 3FF according to ISO / IEC 7810. An RFID card (1, 1 ', 1 ") comprising: - a card body comprising at least one substrate (Si, S2); - a first antenna fixed on one side of a first substrate (Si) of the body of card, the ends of said first antenna being electrically connected to an RFID chip, and - a second antenna (A2, A2 ', A2 ") having a circuit which is printed on at least one side of a second substrate (Si, S2 ) of said card body, said antennas being electromagnetically coupled; 7. RFID card (1) comprising a card body according to claim 6 and characterized in that: - said second substrate (S2) is constituted by said first substrate (S1); said circuit of the second antenna is printed on a face different from that on which said first antenna is fixed; and - the ends of the circuit of said second antenna (A2) are each connected to a conductive plate (C1a, C2a); said conductive plates (C1a, C1b) being each positioned on a different face of said substrate to form a capacitance (C1). 8. RFID card (1 ') comprising a card body according to claim 6 and characterized in that - said second antenna (A2') comprises two circuits (A2'-1, A2'-2) interconnected by a first at their end, each of said circuits (A2'-1, A2'-2) being printed on a different face of said second substrate (52); said second substrate (S2) comprises a first capacitance (Cl ') formed of two conductive plates (Cra, C11) each positioned on a different face of said second substrate (S2); and the second end of each of said circuits (A2'-1, A2'-2) is connected to the conductive plate, positioned on the face of said second substrate (S2) on which this circuit is positioned. 9. RFID card (1 ") comprising a card body according to claim 6 and characterized in that: - the ends of said second antenna (A2") are each connected to a conductive plate (Cra, C2a) printed on said second substrate; and - said card body comprises at least a third substrate (S3) comprising two conductive plates (C1 "b, C2b) interconnected by a conductive element and positioned on said third substrate opposite the conductive plates (Cra , C2a) on said second substrate (S2), so that the conductive plates vis-à-vis form capacitances (Cl ", C2). 10. Kit (Si, S2) for manufacturing a card body of an RFID card according to any one of claims 6 to 9, this kit being characterized in that: - a first antenna (A1, Ar, Ar ), whose ends are intended to be electrically connected to an RFID chip, is fixed on one side of a first substrate (Si) of said kit; and - a circuit of a second antenna (A2, A2 ', A2 ") is printed on at least one face of a second substrate (S2) of said kit, said antennas being intended to be electromagnetically coupled.