Abstract:
A method for making a hybrid contact/non-contact or non-contact smart card which includes a support ( 10,11 ) on which is produced an antenna, two card bodies ( 32, 42, 34, 44 ) on either side of the support, each of the card bodies including at least one thermoplastic layer, and one chip ( 30 ) or module connected to the antenna. The method includes the following steps: depositing a layer of a material having a major amount of resin on a predetermined zone ( 12,13 ) of the antenna support; making the antenna which includes screen-printing turns ( 14.15 ) and two connection pads ( 16,18,17,19 ) of conductive polymer ink on the zone previously produced on the support, and subjecting the support to a heat treatment to cure the ink.

Description:
TECHNICAL FIELD 
   The present invention relates to hybrid contact-contactless smart card or contactless smart cards antennae manufacturing methods and relates particularly to a manufacturing method for the antenna of a smart card on a thermoplastic support and the smart card obtained by said method. 
   BACKGROUND 
   Contactless smart cards or hybrid contact-contactless smart cards are equipped mainly with an antenna embedded in the card and an electronic module connected to the antenna. These cards allow the exchange of information with the outside by remote, and therefore contactless, electromagnetic coupling, between their antenna and a second antenna located in the associated reader. In the case of a hybrid card, this exchange may also be done by electrical transmission of data between the flush contacts of the card&#39;s electronic module and the contacts of a reader&#39;s reading head into which the card is inserted. These cards are now used in many sectors. In this manner, in the transport sector, they are used as a means of access to the transport network. This is also the case for bank cards. Hybrid or contactless cards are used in all types of debit/credit account operations, a recent example being the electronic wallet. Many companies have also developed identification means for their personnel using contactless smart cards. 
   The electronic module inserted into the hybrid contact-contactless or contactless smart card is used for developing, storing and processing the information. The connection of the electronic module and the antenna is one of the significant manufacturing problems for smart cards. The dimensions required by the usual standards for smart cards makes their manufacture that much more tricky when an electronic module and an antenna connected together have to be inserted. 
   The manufacture of antennae by a screen-printing method using conductive ink has allowed the manufacturing constraints to be considerably reduced. Several antennae are screen printed at a time by one or more deposits of conductive ink such as silver and this makes this first step of manufacturing hybrid or contactless smart cards much faster and less expensive than methods used previously. Furthermore, the manufacturing of a screen printed antenna enables a very great adherence to be obtained for the antenna on its thermoplastic support and thus partly overcome the problem of detection of the antenna contacts during the connection step of the module and the antenna in the case of hybrid smart cards. 
   Unfortunately, the drawbacks of this type of antenna appear during the second manufacturing step of the card, which consists in laminating the various layers with plastic material that make up the card on either side of the antenna support. As the material flow is significant during the lamination step as a result of the high pressure and temperature, the antenna&#39;s shape factor is not maintained. The conductive ink forming the antenna contains only 15% of binder, which results in a mechanical strength that is insufficient in temperature and pressure conditions of the order of 180° C. and 280 bar. As a result, there appear variations in the electrical parameters (inductance and resistance) of the antenna and this results in malfunctions. In addition, it is not uncommon to experience antenna breakage in areas where strong shear stresses are present. This is particularly the case in corners and at electrical bridges. 
   The document WO 01/95252 describes a contactless smart card including an antenna on a support, and the antenna may be made by printing using conductive ink. The invention described particularly concerns a strip of smart cards consisting of a support strip (1) whose softening temperature is at least 110° C., preferably 180° C., and a cover strip whose softening temperature is not greater than 110° C. It also concerns a method used to manufacture this smart card strip. This method consists in manufacturing this smart card strip in the form of a continuous strip made up of a support strip and a cover strip fixed to one another. 
   The document EP 1 189 168 also describes a contactless smart card including an antenna on a support, the antenna and the chip being supported by biodegradable material. 
   SUMMARY OF THE INVENTION 
   This is why the purpose of this invention is to provide a hybrid contact-contactless or contactless smart card whose antenna screen printed on a thermoplastic support is not subjected to any damage during the manufacturing process of the card and particularly in the lamination step. 
   The purpose of the invention is thus a manufacturing method for an antenna of a hybrid contact-contactless or contactless smart card that includes a support on which the antenna is made, two card bodies on each side of the support, each of the card bodies consisting of at least one thermoplastic layer, and a chip or a module connected to the antenna. This method includes the steps of: 
   depositing a layer of a material mainly consisting of resin on a predetermined zone of the antenna support, 
   manufacturing the antenna, consisting in screen printing turns and two connection pads of electrically conductive polymer ink on a zone prepared beforehand on the support and subjecting the support to heat treatment in order to bake the ink. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The purposes, objects and characteristics of the invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which: 
       FIG. 1  represents the preliminary deposition step of resin on the antenna support of a hybrid contact-contactless smart card, 
       FIG. 2  represents the antenna screen printed on its support of a hybrid contact-contactless smart card, 
       FIGS. 3   a  and  3   b  represent a cross-section of the hybrid contact-contactless smart card after the first and second steps of lamination respectively, 
       FIG. 3   c  represents a cross-section of a hybrid contact-contactless smart card with its module, 
       FIG. 4  represents the preliminary step of resin deposition on the antenna support of a contactless smart card, 
       FIG. 5  represents the antenna screen printed on the support of a contactless smart card, and 
       FIGS. 6   a ,  6   b , and  6   c  represent a section of the contactless smart card after the module deposition, the first and second steps of lamination respectively. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   According to  FIG. 1 , resin is deposited on the antenna support  10  made of thermoplastic material of a hybrid contact-contactless smart card on a zone  12  corresponding to the location of the antenna and connection pads of the antenna with the module. The details of the shape of the zone  12  do not constitute a limitation for the invention, the main constraint being that the zone  12  defines the location where the conductive ink forming the turns and the connection pads of the antenna will be printed afterwards. Zone  12  is preferably slightly larger than the antenna&#39;s imprint as can be seen on the following  FIGS. 2 and 5 . The thickness of the resin layer applied is of the order of 5 μm. 
   According to a preferred embodiment of a hybrid contact-contactless smart card antenna shown in  FIG. 2 , the antenna is screen printed on zone  12  of the antenna support  10  in several passes and in reverse order compared with the standard screen printing method. The first pass consists in screen printing the two connection pads  16  and  18  of the antenna to the module and the electric bridge  20 , commonly referred to as “cross-over”. The second pass consists in screen printing an insulating strip  22  on top of the cross-over. The third screen printing pass consists in screen printing the turns of the antenna  14 . A fourth pass is provided to add a layer of ink on the connection pads  16  and  18 . The thickness of the conductive ink layer is of the order of 50 μm. The turns of the antenna  14  connect the connection pad  18  located at one end of the cross-over  20  and the other end of the cross-over  20  where the connection pad  16  is located. The ink forming the entire antenna is a conductive polymer type ink, doped with conductive components such as silver, copper or carbon. The antenna support  10  is then subjected to a heat treatment to cure the ink. 
   The following step consists in laminating two layers or sheets of thermoplastic material on the antenna support as shown in  FIG. 3   a . This first lamination step consists in welding by hot press moulding on each side of the antenna support  10  two homogenous layers of thermoplastic material  32  and  34  with a thickness of 100 μm. The temperature and the pressure reached are of the order of 180° C. and 280 bar respectively. During this first lamination step, the temperature must be sufficient for the material that makes up the sheets  32  and  34  to soften and melt completely so as to trap the raised designs of the antenna supports such as those caused by turns and antenna contacts. In this manner, during lamination, the antenna support  10  is trapped in the thermoplastic mass of layers  32  and  34 . 
   The second lamination stage of various layers that make up the card consist in laminating two card bodies on each side of the antenna support obtained after the first lamination step with reference to  FIG. 3   b . This second step, carried out after a certain duration corresponding to the time required for the thermoplastic layers  32  and  34  to solidify, consists in welding two thermoplastic layers  42  and  44 , of equal thickness of about 260 μm, constituting the body of the card on the thermoplastic layers  32  and  34 , by hot press moulding. The two card bodies  42  and  44  were previously printed using the customized graphic image of the card. The temperature and pressure necessary for this lamination step are of the order of 120° C. and 150 bar respectively. 
   The two lamination steps described previously may be replaced by a single lamination step consisting in welding, by hot press moulding, on each side of the antenna support at least two thermoplastic layers, corresponding for example to layers  32  and  42  on one side and  34  and  44  on the other side constituting the two card bodies, without deviating from the scope of the invention. 
   The card obtained after one or more lamination steps is therefore made up of a support  10  and two card bodies located on either side of the support, each card body being made of at least one thermoplastic layer and preferably at least two thermoplastic layers  32  and  42  on one side of the support and  34  and  44  on the other side. 
   In reference to  FIG. 3   c , the last manufacturing step for the hybrid contact-contactless card is the installation of the module. A cavity  26  designed to receive the module consisting of the chip  30  and the double-sided circuit  28  is milled in one of the card bodies. The milling operation also enables the bonding pads  16  and  18  between the antenna and the module to be removed. The milling operation is carried out in the card body which is opposite the antenna support face with the screen printed imprint, that is to say in the card body which is in contact with the side of the support that do not bear the screen printed antenna. In this manner, during the milling operation, the antenna support is milled before the ink. 
   The module is glued in place. Two different adhesives are used. Two spots of conductive glue  36  and  38  are used to connect the module to the antenna contacts. A ring of glue  40  such as cyanoacrylate glue secures the perimeter of the module to the card. 
   The method according to the invention, presents the advantage of making the detection of the antenna easier during the milling step that consists in exposing the antenna&#39;s connection pads to connect the electronic module. While the antenna&#39;s screen printed connection pads may be almost completely cut into during milling of the cavity, there is no risk they will become detached from their support. 
   According to a preferred embodiment of a contactless smart card antenna shown in  FIG. 4 , resin is deposited on the thermoplastic antenna support  11  of a contactless smart card on zone  13  corresponding to the location of the antenna and the connection pads of the antenna with the module. The resin zone  13  of a pure contactless smart card is reversed in relation to the resin zone  12  of a hybrid contact-contactless smart card. This special feature is inherent in the subsequent steps of the manufacture of the contactless card. Thus, the second step of the manufacturing method of a contactless smart card on its support that consists in screen printing the antenna through several passes of conductive ink is not performed in the same order as for the manufacturing step of the hybrid contact-contactless smart card antenna. The essential characteristic of the method of embodiments of the invention being that the antenna is manufactured on zone  12  or  13  where resin has been deposited previously, this characteristic is present in the production of the antenna support according to the invention, regardless of the subsequent use of the card. 
   According to a preferred embodiment of a contactless smart card antenna shown in  FIG. 5 , the antenna is screen printed by conductive ink in several passes. The first pass consists in screen printing the turns  15  of the antenna and the two connection pads  17  and  19  of the antenna. The second pass consists in screen printing an insulating strip  23  to allow the turns of the antenna to overlap without electrical contact. The third pass consists in screen printing the electric bridge or cross-over  21 . A fourth pass is provided to add a layer of ink on the connection pads  17  and  19 . The turns  15  of the antenna connect the connection pad  19  at one of the ends of the cross-over  21  and the other end of the cross-over  21  up to the connection pad  17 . 
   According to  FIG. 6   a , the module  31  containing the chip is placed upside down so that the connections of the card are in contact with the connection pads  17  and  19  of the antenna. A perforated thermoplastic sheet  25  is placed on the antenna support  11  so that the module  31  faces the opening made previously in the sheet  25  and to avoid any extra thickness due to the module. 
   As for the lamination steps of the various layers that make up the card bodies of a hybrid contact-contactless smart card, the first lamination step of a contactless smart card is shown in  FIG. 6   b . This first lamination step consists in welding by hot press moulding two homogenous layers of thermoplastic on either side of the antenna support  11 , one layer  35  on the thermoplastic layer  25  and one layer  33  on the face of the antenna support  11  that do not bear the antenna. During this first lamination step, the temperature must be sufficient for the material that makes up the sheets  25 ,  33  and  35  to soften and melt completely so as to trap the module  31  and the antenna. In this manner, during lamination, the antenna support  11  is trapped in the thermoplastic mass of layers  25 ,  33  and  35 . 
   The second lamination step of various layers that make up the card involves laminating two bodies of the card on each side of the antenna support obtained after the first lamination step with reference to  FIG. 6   b . This second step, consists in welding two thermoplastic layers  43  and  45 , constituting the card bodies, on the thermoplastic layers  33  and  35 , by hot press moulding. The two card bodies  43  and  45  were previously printed with the customized graphic image of the card. 
   The two lamination steps described previously may be replaced by a single lamination step consisting in welding, by hot press moulding on each side of the antenna support at least two thermoplastic layers, corresponding for example to layers  35  and  45  on one side and  33  and  43  on the other side and constituting the two card bodies, without deviating from the scope of the invention. 
   The thermoplastic material used for all layers that make up the smart cards and mentioned in this document is preferably polyvinyl chloride (PVC), but could also be polyester (PET, PETG), polypropylene (PP), polycarbonate (PC) or acrylonitrile-butadiene-styrene (ABS). 
   The resin placed on zones  12  and  13  of the antenna support prior to printing of the antenna is used for its properties for the temperature and pressure of the first lamination step in relation to the same properties of the support on which it is applied. In particular, resin is used because it is dimensionally stable and because it remains hard during the first lamination step in relation to the plastic material on which it is placed. At 180° C. and at 280 bar, the plastic material of the antenna support melts and thus softens whereas resin is stable. In this manner, the circuit consisting of the antenna, connection pads and possibly the chip in the case of a contactless smart card, fixed on the support, is on a stable and hard base formed by the resin. During lamination, it is this entire base that moves in relation to its support and thereby, the antenna&#39;s shape factor is maintained as the latter is not subjected to shear stresses between the two top and bottom thermoplastic layers and therefore does not fracture. The resin provides the circuit with an overall stiffness during all the manufacturing steps of the card as it can withstand the temperature and pressure of various manufacturing steps of the smart card without losing its shape. The resin is deposited on zones  12  or  13  by a rapid and profitable method such as offset printing, screen printing, heliography or flexography. For this reason and for the sake of cost, the resin used may be rosin or an epoxy acrylate type resin. These resins are used in the manufacture of inks. The inks consist of about 70% varnish, 20% pigments and 10% additives such as wax, driers, thinners. Varnish contains vegetable oils, oil thinners and resins. The method according to the invention is carried out by depositing a material mainly consisting of resin. Advantageously, the method is carried out with an offset type ink consisting mainly of an epoxy acrylate type resin or consisting mainly of a rosin.