FR2741010A1 - Manufacture of two-layer card incorporating integrated circuit - Google Patents

Abstract

The process brings together two layers (30,42) of thermally fusible plastic, between which an electronic unit (32) is inserted with connections (e.g. 34) to a conductive winding (14). The integrated circuit (4) is enclosed in a module (38) containing all other components of the electronic unit, and is linked to the connections by wires (10). The module is symmetrical about its median plane (40) so that the pressure exerted on it by the two layers during hot-pressing is uniform over its upper and lower faces (50,52). The layers are softened sufficiently for bonding together without loss of planarity of their outer surfaces (46,48).

Description

CARD COMPRISING AN ELECTRONIC UNIT
AND METHOD FOR MANUFACTURING SUCH A CARD
The present invention relates to a card comprising an electronic unit electrically connected to a winding formed by at least one turn of conductive material, in other words to a coil. The invention also relates to a method of manufacturing such a card.

 The use of integrated circuit cards as a means of identification or banking transaction in particular has rapidly spread. Relatively recently, the generation of cards without external contact and comprising a coil allowing an electromagnetic coupling with an external communication device is developing significantly. As the applications become more and more numerous, the need for integrated circuits of ever larger dimensions arises. The integration of an electronic unit, comprising an electronic circuit of relatively large dimensions and electrically connected to a coil, inside a card having a relatively small thickness, presents technical difficulties of implementation. present invention, it is intended to obtain a card as mentioned above using a heating press or hot rolling. Such a manufacturing process has the advantage of being relatively inexpensive and makes it possible to obtain exterior surfaces of the card of very good quality.

 It will be noted that, particularly in the case of integrated circuits of relatively large dimensions, it is not easy and not recommended to solder the two ends of a winding forming a coil directly on the integrated circuit as has already been proposed with integrated circuits. of relatively small dimensions.

 However, particularly in the case of embodiments with an integrated circuit of relatively large dimensions, the integrated circuit is advantageously arranged in a protection module associated with two external electrical contact pads to ensure the electrical connection with a winding, these two pads being connected electrically to the integrated circuit by a technology known to those skilled in the art.

 Using FIGS. 1 to 3, a card will be described below, produced by the Applicant on an experimental basis, having an electronic unit electrically connected to a coil according to a usual technique.

 The electronic unit 2 comprises an electronic circuit 4 disposed on a substrate 6 provided with a metallization defining two first contact pads 8 on which are welded two wires 10 for electrical connection between the substrate 6 and the integrated circuit 4. The aforementioned metallization also defines two second contact pads 12 on which the two ends of the winding 14 are respectively welded defining a coil. The first electrical contact pads are respectively connected to the second electrical contact pads by means of metal tracks.

 In order to protect the integrated circuit 4 and the connection wires 10, it is conventionally provided to cover them with a resin 16. During the manufacture of the electronic unit 2, the resin 16 is generally brought in using a nozzle allowing a drop of resin to be deposited on the integrated circuit and on the connection wires. After hardening of the resin 16, the outer surface of this hardened resin is substantially spherical. It thus defines a kind of dome or dome on the substrate 6 which initially extends in a horizontal plane (Figure 1).

According to the manufacturing process envisaged by the
Applicant, provision is made to provide a first outer layer 18 formed of a hot-melt material, in particular a plastic material, then to provide on this first outer layer the electronic module 2 electrically connected to the coil 14. Next, a second planar outer layer 20 is applied to the first planar outer layer 18, to the electronic unit 2 and to the coil 14. Using a heating press (not shown), a pressure symbolized by the arrow 22 on the FIG. 1 is exerted on the outer layers 18 and 20. The heat provided by the heating press serves to at least partially melt the outer layers 18 and 20. The resulting card is shown in FIG. 3.

The Applicant has observed that the substrate 6 is generally curved concave and located inside a depression 24 formed in the first outer layer 18. The protective resin 16 is in turn located at least partially in a recess 26 formed in the second outer layer 20.

 The process for manufacturing cards which has just been described has a very low industrial yield. In fact, many of the cards tested do not work. Analyzes have shown that, in several cases, the integrated circuit 4 is damaged.

 The object of the present invention is to provide a card, comprising an electronic unit connected to a winding, which is reliable and inexpensive and to provide a process for the hot manufacture of such a card having a high industrial yield.

To this end, the present invention relates to a method of manufacturing a card comprising the following steps
I) provision of a first flat layer of hot-melt material;
II) supply to said first layer of at least one electronic unit, comprising an integrated circuit and electrical contact pads electrically connected to said integrated circuit, and of a winding formed of at least one turn of conductive material, the two ends of this winding being connected respectively to two of said electrical contact pads; said integrated circuit being housed in a module whose shape has essentially a symmetry relative to a median plane of this module;
III) provision of a second flat layer of hot-melt material on the first layer, on the electronic unit and on the winding;
IV) application of a heating press on said first and second plane layers so as to soften these first and second layers enough to weld them to each other and insert said electronic unit and said coil between these first and second layers in keeping their respective external surfaces flat.

 According to a characteristic of a first particular embodiment of the manufacturing method according to the invention, the module in which the integrated circuit is integrated contains all of the components of the electronic unit excluding the contact pads electric.

 According to an advantageous characteristic of the above-mentioned embodiment, the two electrical contact pads extend essentially in the median plane of the above-mentioned module.

 Thanks to the above characteristics, the cards obtained are reliable and the industrial yield of the process according to the invention is very good. Indeed, the fact that the integrated circuit is housed in a module whose shape has essentially a symmetry relative to a median plane of this module very greatly reduces the mechanical stresses exerted on this integrated circuit during the application of a heating press to form the map.

 From the analysis of the cards obtained according to the method described in FIGS. 1 to 3, the Applicant has found that the housing generated inside the card for the electronic module is formed partially in the lower layer and partially in the upper layer.

In the general case where the lower layer and the upper layer enveloping the electronic unit and the coil are made of the same material, the volumes taken up on the lower layer and on the upper layer to house the electronic unit naturally tend to to be equal. If on the contrary the electronic unit, in particular the module comprising the integrated circuit, did not exhibit symmetry relative to the median plane parallel to the lower and upper layers, mechanical stresses would be exerted on the module and therefore on the integrated circuit during the application of the heating press, which would result in significant damage to the integrated circuit.

 The present invention also relates to a card obtained by the above-mentioned method, that is to say a card comprising an electronic unit and a winding, formed of at least one turn of conductive material, which are inserted between two layers of hot-melt material welded together hot, the electronic unit comprising an integrated circuit and two electrical contact pads electrically connected to the integrated circuit. The two ends of the winding are electrically connected to the two electrical contact pads.

This card is characterized in that the integrated circuit is housed in a module whose shape has essentially a symmetry relative to a median plane of this module.

The present invention will be described below in detail using the appended figures, given by way of non-limiting example, in which
- Figures 1 to 3, already described, describe an embodiment of a card and its manufacturing process according to a technique previously developed by the Applicant;
- Figure 4 schematically shows an embodiment of the method according to the invention;
- Figure 5 is a top view at the line VV of Figure 4;
- Figure 6 is a partial section of a card according to one invention;
FIG. 7 is a partial section of a variant of the card shown in FIG. 6.

 Using FIGS. 4 to 6, an embodiment of the method according to the invention and the resulting card will be described below.

As shown diagrammatically in FIG. 4, the method according to the invention firstly comprises the following steps
- Provision on a work surface 28 of a first outer layer 30 of hot-melt material;
- Provision on the first outer layer 30 of an electronic unit 32 and a winding 14 formed of at least one turn of electrically conductive material. The two ends of the winding 14 are welded or bonded to two electrical contact pads 34 and 36 which belong to the electronic unit 32 and which are electrically connected to the integrated circuit 4, included in the electronic unit 32, by wires connection 10 provided for this purpose.

 The electronic unit 32 comprises a module 38 in which the integrated circuit 4 is housed. This module 38 made of plastic material formed by an overmolding technique serves to protect the integrated circuit 4 and its connections 10 to the two external contact pads 34 and 36 to module 38. Preferably, module 38 contains all the components of the electronic unit 32, with the exception of contact pads 34 and 36.

 The pads 34 and 36 are located near the median plane 40 of the module 38, the latter having a shape symmetrical with respect to the median plane 40.

According to the mode of implementation of the method according to the invention described here, the following steps are then provided
- Providing a second flat outer layer 42 preferably having a thickness substantially equal to that of the first flat outer layer 30; this second layer 42 being provided on the first layer 30, the electronic unit 32 and the coil 14;
- Application of a heating press, exerting a pressure represented diagrammatically by arrow 44, on the first and second plane layers 30 and 42 so as to soften these first and second layers enough to weld them together and insert the electronic unit 32 and the coil 14 between these first and second layers 30 and 42 while keeping their respective external surfaces 46 and 48 flat.

 Since the module 38 has a plane symmetry relative to its median plane 40, the pressure exerted by the layers 30 and 42 on the module 38 during the application of the heating press is uniform, that is to say that it is relatively equal and constant on the upper face 50 and on the lower face 52 of the module 38. As a result, the module 38 essentially retains its initial shape as shown in FIGS. 4 and 5.

The integrated circuit 4 does not undergo bending forces during the application of the heating press, which significantly reduces the risk that this integrated circuit 4 will be damaged during the formation of the card shown in FIG. 6 relative to the case shown in Figure 3.

 It will be noted that the ends of the winding 14, connected to the electrical contact pads 34 and 36, have a small surface in projection in the median plane 40. Thus, if the ends of the winding 14 are not, in an alternative embodiment, located near the median plane 40 of the module 38, their influence on the displacement of material during the formation of the card is almost negligible.

 When the electronic unit 32 includes electrical contact pads leaving the module in which the integrated circuit is housed, these outer pads are preferably located near the median plane of this module and the ends of the winding 14 which are electrically connected these external contact areas are thus also located near the median plane of the module comprising the integrated circuit as shown in FIGS. 6 and 7.

 In Figure 7 is shown an alternative embodiment of the card shown in Figure 6. The references already described above will not be described again in detail here.

 The variant embodiment described in FIG. 7 differs from the embodiment described in FIG. 6 in that the module 38 in which the integrated circuit 4 is housed has a spindle-shaped section. This makes it possible to avoid mechanical stresses in the peripheral region of the module 38 during the formation of the card using a heating press.

Claims (8)

 1. Method for manufacturing a card comprising the following steps  I) provision of a first planar layer (30) of hot-melt material;  II) addition to said first flat layer of at least one electronic unit (32), comprising an integrated circuit (4) and electrical contact pads (34, 36) electrically connected to said integrated circuit, and a winding (14) formed at least one turn of conductive material, said winding having ends connected respectively to two of said electrical contact pads (34, 36), the integrated circuit being housed in a module (38) whose shape has essentially a symmetry relatively to a median plane (40) of this module ;;  III) providing a second planar layer (42) of hot-melt material on said first planar layer, on said electronic unit and on said winding;  IV) application of a heating press on said first and second flat layers so as to soften them enough to weld them to one another and deform them internally to trap said electronic unit and said winding between these first and second layers in keeping their respective external surfaces flat (46, 48).  2. Method according to claim 1, characterized in that said module (38) contains all of the components of said electronic unit (32) excluding said electrical contact pads (34, 36).  3. Method according to claim 1 or 2, characterized in that said electrical contact pads (34, 36) are located near the median plane (40) of said module (38).  4. Method according to one of claims 1 to 3, characterized in that said first and second planar layers (30, 42) have substantially the same thickness.  5. Card comprising an electronic unit (32) and a winding (14), formed of at least one turn of conductive material, which are inserted between two layers (30, 42) of hot-melt material welded together hot, said electronic unit comprising an integrated circuit (4) and electrical contact pads (34, 36) electrically connected to said integrated circuit, said winding having two ends connected respectively to two of said electrical contact pads, the card being characterized in that said integrated circuit is housed in a module (38) whose shape has essentially a symmetry relative to a median plane (40) of this module.  6. Card according to claim (5), characterized in that said module (38) contains all of the components of said electronic unit (32) excluding said electrical contact pads (34, 36).  7. Card according to claim (6), characterized in that said electrical contact pads (34, 36) are located near the median plane (40) of said module (38).  8. Card according to one of the preceding claims, characterized in that a cross section of said module (38) is fusiform.