FR2764414A1 - NON-CONTACT CHIP CARD MANUFACTURING PROCESS - Google Patents

Abstract

The invention concerns smart cards, and more particularly those capable operating without contact with an antenna integrated in the card, including mixed cards having standard contacts. The manufacturing method comprises the following operations: assembling superposed plastic sheets by enclosing within the layers an antenna (22) comprising two conductive access zones (60, 24; 62, 26); opening a cavity in the assembly top surface, and exposing the conductive access zones during said opening; gluing an electronic module (M) in the cavity, the module having on its bottom surface, facing inside the cavity, conductive ranges (72) coming into electric contact with the antenna conductive access zones. The antenna conductive access zones consist of the antenna two conductive ends (24, 26) coated with conductive adhesive (60, 62). The conductive adhesive is deposited on the antenna ends after opening the cavity.

Description

NON-CONTACT CHIP CARD MANUFACTURING METHOD
The invention relates to the manufacture of smart cards, more particularly cards capable of operating without contact using an antenna integrated in the card. Under this name contactless card ", we will consider on the one hand cards that can communicate with the outside only through the antenna, and also and above all mixed cards that can communicate with the outside either by through the antenna or via standard standardized contacts.

 Such cards are intended to carry out various operations, such as, for example, banking operations, telephone communications, identification operations, debit operations or recharging of account units, and all kinds of operations which can be carried out either by inserting the card in a reader or remotely by electromagnetic coupling (in principle of the inductive type) between a transmission-reception terminal and a card placed in the zone of action of this terminal.

 Contactless cards should preferably have standardized dimensions identical to those of conventional smart cards with contacts. This is obviously particularly essential for mixed cards, and it is desirable for cards operating only without contact.

 The usual standard 150 7810 defines a card 85 mm long, 54 mm wide, and 0.76 mm thick. The contacts are flush with well-defined positions on the surface of the card.

 These standards impose severe constraints for manufacturing. The very small thickness of the card is in particular a major constraint, even more severe for contactless cards than for cards simply provided with contact, since it is necessary to provide for the incorporation of an antenna in the card.

 The technical problems which arise are problems of positioning the antenna relative to the card, since the antenna occupies almost the entire surface of the card, problems of positioning of the integrated circuit module (comprising the chip and its contacts ) which ensures the electronic functioning of the card, and problems of precision and reliability of the connection between the module and the antenna; finally, mechanical strength, reliability and manufacturing cost constraints must be taken into account.

 The object of the invention is to propose a manufacturing method which makes it possible to best resolve the various constraints of dimensioning, manufacturing precision, mechanical strength, and more generally reliability, cost and card manufacturing efficiency.

For this, a method of manufacturing a smart card is proposed according to the invention, comprising the following steps:
- assembly of superimposed plastic sheets by enclosing in the superposition an antenna comprising two conductive access zones;
- opening of a cavity in an upper face of the assembly, and updating of the conductive access zones during this opening;
bonding of an electronic module into the cavity, the module having on its underside, turned towards the interior of the cavity, conductive pads coming into electrical contact with the conductive access zones of the antenna.

 The conductive access areas of the antenna will preferably be constituted by the ends, covered with conductive adhesive, of an antenna conductor. This conductive adhesive will in principle be deposited after opening the cavity, but it could also be deposited between two phases of a rolling carried out in several passes.

 Preferably, the sheet assembly comprises a sheet provided with perforations coming above the ends of the antenna, the perforations being updated during the opening of the cavity and conductive adhesive being deposited in these perforations.

 As will be seen, the electronic module can be of the single-sided or double-sided type, and, in the latter case, it can advantageously be provided that it is a double-sided circuit without contact via between the two faces, with wires welded between the chip and the conductors on both sides. Whatever the embodiment of the module, provision is preferably made for the cavity to define a housing in the shape of the module, so that the conductors of the module are flush with the upper surface of the card and thus constitute the access contacts to the card. smart.

 The antenna conductor is preferably a conductor printed on an insulating sheet, but it could also consist of a wound wire enclosed in the assembly of plastic sheets.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows and which is given with reference to the appended drawings in which
- Figures 1 to 5 show the successive operations of the method according to the invention in one embodiment;
- Figure 6 shows the constitution of a double-sided electronic module without via conductors between the two faces;
- Figures 7 to 9 show the method according to the invention in a second embodiment.

 In general, contactless smart cards will be made by gluing (hot or cold lamination) of plastic sheets into which the antenna conductor will have been inserted or inserted, then opening of a cavity in the sheets assembled to create a housing for an integrated circuit module therein, or to complete an already partially created housing, and positioning of the module so that two conductive pads of the module come into electrical contact with two ends of the antenna conductor , either directly or most often via a conductive adhesive.

 Figures 1 to 5 show a first embodiment of the method according to the invention.

 We start from several plastic sheets, here four sheets 10, 20, 30, 40, which are superimposed by hot or cold rolling to join them together.

We could use only two or three superimposed sheets as we will see later. The rolling operation consists in pressing the sheets flat against each other in the possible presence of binding substances between the sheets. Cutting the card to standard dimensions can be done either before or after the laminating operation, preferably after.

 The sheet 10, below the stack, constitutes a rear covering of the smart card.

 The sheet 20 carries a printed circuit antenna 22, that is to say a conductor deposited and engraved, or screen printed, on the sheet. The antenna 22 generally makes several turns following the outer periphery of the card, in order to cut off as large an electromagnetic flux as possible.

The antenna has two ends 24 and 26 slightly spaced from each other. The spacing is chosen according to the conductive areas of the electronic module that will be inserted in the card.

 The sheet 30 preferably comprises two perforations 34 and 36 each located above a respective end, 24, 26, of the antenna. The electrical contact between the antenna and the integrated circuit module will be made through these perforations.

 Finally, the sheet 40 constitutes a coating on the front face of the chip (FIG. 1).

 The rolling operation makes it possible to constitute, from the four sheets, a plastic plate 50 in which the antenna 22 and its ends 24, 26 are enclosed, the latter being below the perforations 34, 36 (FIG. 2).

 A cavity 52 is then hollowed out having the general shape of the electronic module which must be inserted therein, the depth of the cavity being such that the external access contacts of the module, which will become the access contacts of the card for the insertion in a contact reader, flush with the upper surface of the board. In the general case, the cavity has a double bowl shape with two flat bottoms, one of the bottoms, 54, being shallower, the other, 56, being deeper. The shallower part reaches above the ends 24 and 26, while the deeper part is located entirely between the ends.

 The cavity is preferably formed by two successive milling operations. After formation of the cavity, the ends 24 and 26 of the antenna conductor are accessible through the perforations 34 and 36; this means that the depth of the bottom 54 is at least sufficient to pierce the entire thickness of the sheet 40 and reach the sheet 30 and its perforations (FIG. 3).

 A drop of conductive glue 60, 62 is then preferably placed in each of the perforations 34 and 36.

The ends of the antenna thus covered constitute the conductive zones of access to the antenna (FIG. 4).

 Then, the electronic module M is installed containing the integrated circuit ensuring the electronic operation of the smart card. This module can be a single-sided printed circuit module or a double-sided printed-circuit module, and in the latter case it can have two possible configurations to which we will return later. A module M is shown in FIG. 4 above the cavity 52. In this example it is a double-sided printed circuit module comprising upper conductors 70 on the face which will be turned towards the outside of the cavity and lower conductors 72 on the face which will face the interior of the cavity. The conductors are formed on an insulating sheet and via conductors connect the upper and lower conductors. A chip embedded in a protective resin 74 is mounted on the underside and connected to the conductors 72 (and thereby the conductors 70).

 The module fits in the cavity 52 which has been machined to its dimensions. Figure 5 shows the module mounted in the card. Two conductive pads on the underside of the module, arranged just above the ends 24, 26 of the antenna, are electrically connected to these two ends by means of the conductive adhesive present in the perforations 34 and 36.

 The conductive adhesive keeps the module in place, but it is also possible to envisage additional support by a non-conductive adhesive deposited in the bottom of the cavity or on the underside of the module outside the places reserved for contact with the antenna ends. An anisotropic conductive adhesive, leading perpendicular to the adhesive layer but not parallel to the layer can also be used to avoid short-circuits between certain electrical parts of the module or the antenna which must not be connected together. This anisotropic adhesive could be deposited both in the perforations 34, 36 and in the rest of the cavity 52 without special precautions.

 The method can also be easily used with a single-sided integrated circuit module. In this case, the chip is placed on a metal grid whose upper face will constitute the access contacts of the smart card and whose lower face, facing the antenna ends, will allow connection with these ends by glue. conductive. This metal grid will generally be covered, on the lower side, by an insulating sheet. The insulating sheet is perforated where contact must be made with the antenna, the other conductive parts of the underside of the grid preferably being protected either by this insulating sheet or by the chip protection resin.

 In a particularly advantageous variant embodiment, the module consists of a double-sided printed circuit carrying the integrated circuit chip, but this double-sided circuit is produced without a conductor between the conductors of the two faces, which makes it less expensive.

 Figure 6 shows in detail the realization of such a double-sided module without via. The module comprises an insulating sheet 80 with first conductors 70 deposited and etched on its upper face (external face when the module is placed in the card), and second conductors 72 deposited and etched on the lower face.

The first conductors will serve as access contacts for the smart card. The second are intended to ensure the connection of the chip with the antenna. The integrated circuit chip 82 is bonded to the underside and is connected by wires welded on the one hand directly to conductors on the underside and on the other hand, through openings in the insulating sheet, at the rear. conductors 70 of the upper face.

 More specifically, two welded connecting wires start from the chip and lead to two conductors 72 on the underside, these conductors being intended to be connected to the ends of the antenna. Only one of these wires, 84, is shown in FIG. 6. And other connecting wires leave the chip and are soldered to the rear of the conductors 70 of the upper face in order to provide the accesses of the card in a reader with contacts. Only one of these welded wires, 86, is shown in FIG. 6.

 The embodiment which has been described in FIGS. 1 to 6 uses a lamination of four sheets of plastic material. It will be understood that the sheets 10 and 20 can be replaced by a single sheet 20, possibly thicker, and likewise the sheets 30 and 40 can be replaced by a single sheet 30, possibly thicker. In the latter case, the perforations 34 and 36 are flush with the surface of the laminated wafer 50; the perforations are then updated regardless of the depth of the bottom 54 of the cavity.

 In another alternative embodiment, the deposits of conductive adhesive 60 and 62 can be made before gluing the upper sheet 40 on the sheet 30, but after gluing the sheet 30 on the sheet 20. The lamination is done in this case by two passages, the adhesive deposit being carried out between the two passages. The glue is then enclosed in the perforations 34 and 36 and is exposed during the machining of the cavity 52. We can then, if desired, put a dose of glue on the perforations 34 and 36 already filled with glue , before installing the electronic module.

 In another alternative embodiment, represented in FIG. 7, it is provided that a non-stick substance is placed between two sheets of the assembly in the region provided for the cavity so as to prevent the sticking of the two sheets in this region and to facilitate the removal of material in this region during the opening of the cavity; one of the sheets is that which carries the antenna so that the opening of the cavity exposes the ends of the antenna. More specifically, the upper sheet 30 does not have perforations 34 and 36 but has, above the cavity 52 this non-stick substance 90 which will prevent the sheet 30 from sticking to the ends of the antenna. After lamination, the plastic of the sheet 30 is torn off where it is not adherent, exposing the contacts and partially establishing the cavity 52 (FIG. 8).

 The final shape of the cavity can be obtained by machining, in particular to define a deeper part.

A drop of conductive glue can then be deposited on the ends of the antenna conductor before bonding the module (Figure 9).

 Finally, in some cases it may be preferable to use a wound wire antenna rather than an antenna printed on an insulating sheet. In this case, the coiled antenna is pressed against a sheet of plastic material similar to the sheet 20 and is thus locked in the smart card during hot or cold lamination. Perforations such as 34 and 36 can be provided in the sheet 30, but they are not compulsory because it can be provided that the ends of the coiled antenna are exposed during the machining operation of the cavity. This solution is indeed possible due to the fact that the wound wire is thicker than the printed conductor and that machining can therefore be limited when the wire is exposed. A drop of conductive glue can then be placed on the ends of the exposed wire before installing the electronic module.

Claims (9)

 1. Method for manufacturing a smart card comprising the following steps  - assembly of superimposed plastic sheets (10, 20, 30, 40) by enclosing in the superposition an antenna (22) comprising two conductive access zones (60, 24; 62, 26);  - opening a cavity (52) in an upper face of the assembly, and updating the conductive access zones during this opening;  bonding of an electronic module (M) in the cavity, the module having on its underside, turned towards the interior of the cavity, conductive pads (72) coming into electrical contact with the conductive access zones of the 'antenna.  2. The manufacturing method according to claim 1, characterized in that the conductive access zones of the antenna consist of two conductive ends (24, 26) of the antenna covered with conductive adhesive (60, 62).  3. Manufacturing method according to claim 2, characterized in that the conductive adhesive is deposited on the ends of the antenna after opening of the cavity.  4. Manufacturing method according to one of claims 2 and 3, characterized in that the sheet assembly comprises a sheet (30) provided with perforations (34, 36) coming above the ends of the antenna, the perforations being updated during the opening of the cavity and the conductive adhesive (60, 62) being deposited in these perforations.  5. Manufacturing method according to claim 2, characterized in that the assembly comprises at least one sheet (20) carrying the conductive antenna (22), a sheet (30) provided with perforations (34, 36) above the ends (24, 26) of the antenna, and an upper closure sheet (40), in that the first two sheets are assembled first (20, 30), conductive adhesive is deposited in the perforations, and the third sheet (40) is assembled, then, when the cavity is opened, the conductive adhesive appears, and the electronic module is put in place.  6. Manufacturing method according to one of claims 1 to 5, characterized in that the electronic module (M) comprises an integrated circuit chip (82) and a double-sided printed circuit without via conductors between the two faces, the double-sided circuit comprising an insulating sheet (80) on one side of the first conductors (70) intended to serve as access contacts for the smart card and on the other face of the second conductors (72) intended to be connected to the antenna, connection wires (86) being welded between the chip and the first conductors (70) through openwork areas of the insulating sheet and other connection wires (84) being welded between the chip and the second conductors (72) without passing through the insulating sheet.  7. The manufacturing method according to one of claims 1 to 6, characterized in that the antenna is produced in the form of a conductor printed on one of the plastic sheets (20) of the assembly.  8. Manufacturing method according to one of claims 1 to 6, characterized in that the antenna is produced in the form of a wound wire.  9. The manufacturing method according to claim 1, characterized in that a non-stick substance (90) is placed between two sheets of the assembly in the region provided for the cavity so as to prevent the sticking of the two sheets in this region and to facilitate the removal of material in this region when opening the cavity, one of the sheets carrying the antenna so that the opening of the cavity exposes the antenna ends.