Abstract:
A contactless smart card includes a card body, an antenna and an integrated circuit chip connected to the antenna&#39;s connecting terminals. The connecting terminals of the antenna are further connected to conductive via holes emerging at the card surface. A junction based on an electrically conductive substance is flush with the card surface and connects the conductive via holes. The electrically conductive substance is designed to be removed by scraping, and prevents the card from being used until it is removed.

Description:
This disclosure is based upon, and claims priority from French Application No. 98/12386, filed on Oct. 2, 1998 and International Application No. PCT/FR99/02246, filed Sep. 22, 1999, which was published on Apr. 13, 2000 in a language other than English, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a smart card or “chip card” provided with inhibiting means. 
     The invention relates more particularly to a contactless smart card comprising a card body, an antenna and, connected to the connection terminals of said antenna, an integrated-circuit chip. Such cards are designed to perform: various debit operations in public-transport vehicles, and in particular in subways, i.e. underground railways, buses, or trains; banking operations; telephone calls; or various identification operations. Such operations are performed by means of electromagnetic coupling between the card and receiver or reader equipment. The coupling can be implemented in read mode or in read/write mode. 
     In a particularly common application, such smart cards, be they provided with contacts or be they contactless, are used as means for paying for a service. Each time the corresponding service is used, at least one unit of value is decremented from the initial stock of units of value loaded in the memory of the smart card. Such applications are to be found, for example, in telephone cards and in photocopier cards. Such a smart cards thus initially contains in its memory a given number of units of value corresponding to the maximum credit. 
     In most applications in which the smart card is used as payment means, the card used is of the type having contacts and in which conductive tracks are connected to the integrated-circuit chip, and make it possible for the card to be electrically connected to a reader. 
     In which case, in order to guarantee to the user that the card purchased by him or her has the maximum number of units of value, it is necessary merely to wrap the card in a sealed jacket, e.g. in the form of cellophane wrapping, thereby preventing any electrical contact with the conductive tracks. 
     When the card is a contactless card, that solution is not satisfactory. The cellophane jacket cannot prevent interchange of information that takes place remotely between the card and a reader. Therefore, when the card is a contactless smart card, a sealed jacket cannot guarantee that the card has not been used previously. 
     SUMMARY OF THE INVENTION 
     An object of the invention is therefore to provide a novel smart card design in which inhibiting means are provided that make it possible to prevent any fraudulent use of the card prior to it being used for the first time by an authorized user. 
     To this end, the invention provides a contactless smart card comprising a card body, an antenna and, connected to the connection terminals of said antenna, an integrated-circuit chip, said smart card being characterized in that the connection terminals of the antenna are further connected to conductive through holes opening out on the surface of the card, and in that a junction based on an electrically conductive substance, and designed to be removed by being scratched off before the card is used for the first time, is disposed flush with the surface of the card, and interconnects the conductive through holes. 
     According to another characteristic of the invention, the card further comprises a two-faced electronics module received in a cavity provided in the card body, the antenna and the integrated-circuit chip being supported by a first face of said electronics module, the conductive through holes connected to the connection terminals of the antenna being provided through the thickness of said module, and the junction interconnecting the conductive through holes being provided on the second face of said module, said second face being flush with the surface of the card. 
     According to yet another characteristic of the invention, the antenna extends throughout the plane of the card body, the antenna and the integrated-circuit chip are embedded in the card body, and the conductive through holes connected to the connection terminals of the antenna are provided through the thickness of the card body so that they open out on its surface. 
     According to yet another characteristic of the invention, the electrically conductive substance used to form the junction is an ink based on epoxy charged with silver particles or with carbon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will appear on reading the following description given by way of non-limiting example and with reference to the accompanying figures, in which: 
     FIG. 1 is a plan view of a contactless smart card in a first embodiment of the invention; 
     FIG. 2 is a view from beneath a two-faced electronics module used in the contactless smart card of FIG. 1; 
     FIG. 3 is a section view of the module of FIG. 2; 
     FIG. 4 is a plan view of the electronics module of FIGS. 2 and 3; and 
     FIG. 5 is a section view of a contactless smart card in a second embodiment of the invention, while it is being manufactured. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1 to  4  are different views of the component elements of a contactless smart card or “chip card”  10  in a first embodiment of the invention. This smart card  10  comprises a card body which is generally made of a plastics material by injection molding or by lamination, for example. It further comprises inhibiting means for preventing it from being used so long as they have not been deactivated. More particularly, the card  10  has a junction  26  flush with its surface. This junction  26  is formed of an electrically conductive substance, e.g. by screen-printing with a conductive ink, and it interconnects the terminals of an antenna (not shown in FIG. 1) via conductive through holes  28 . Thus, the junction  26  flush with the surface of the card  10  makes it possible to short-circuit the terminals of the antenna. In this state, the card  10  is thus unusable. This junction thus makes it possible to detect whether the card has already been used. 
     When a user wishes to put the card into service, either, as soon as it has been purchased, or when it is to be used for the first time, the user therefore removes this junction  26 . To remove the junction, the user merely needs to scratch it off since the electrically conductive substance used is formulated such that it adheres poorly to the substrate. The conductive substance is, for example, an ink based on epoxy charged with silver particles or with carbon. 
     By breaking this junction  26 , it is possible to remove the short-circuit of the antenna so that remote communication between the card and a reader is made possible. 
     In this first embodiment, the card  10  is provided with a cavity  11  in which an electronics module  20  is inserted. The electronics module  20  is shown diagrammatically in FIGS. 2 to  4  respectively in a view from beneath it, in section, and in a plan view. It has two faces  21  and  22 . A first face  21  supports an antenna  25  and an integrated-circuit chip  27  connected to the connection terminals of the antenna. This first face  21  is designed to be received in the bottom of the cavity  11  in the card body  10 . FIG. 2 shows a view from beneath the module  20 , i.e. a view of said first face  21  of the module  20 , which face is designed to be received in the bottom of the cavity in the card body  10 . FIG. 4 is a plan view of the module, i.e. a view of the second face  22  of the module  20 , which face is designed to come flush with the surface of the card body  10 . However, in FIG. 4, the antenna  25  and the chip  27  are shown in dashed lines. 
     The antenna  25  may be formed by printing with conductive ink, by using a conventional pad-printing method or offset printing method, for example. This antenna  25  is implemented conventionally in the form of a continuous conductor which is wound in a rectangular spiral made up of a certain number of turns disposed concentrically and extending in the plane of the first face  21  of the electronics module  20 . The two ends of the antenna conductor  25  respectively form an external terminal  23  and an internal terminal  24 , via which terminals the antenna is connected to two contact tabs of an integrated-circuit chip  27 . This chip  27  is mounted on the antenna using a conventional well-known mounting technique, such as mounting of the “flip-chip” type, for example, or of some other type. 
     Two orifices  28  are provided through the thickness of the module  20 , facing the connection terminals  23 ,  24  of the antenna. They are disposed so as to lead through to the second face  22  of the electronics module  20 . These orifices are metal-plated using a method of screen-printing with a conductive ink, so as to obtain conductive through holes or “plated through holes”  28  that are connected electrically to the connection terminals  23 ,  24  of the antenna  25 . This conductive ink screen-printing step also makes it possible to form the junction  26  flush with the second face  22  of the module and interconnecting the two conductive through holes  28 . Thus, the conductive through holes  28  and the junction  26  may be formed simultaneously. This junction  26  makes it possible to interconnect the two terminals  23 ,  24  of the antenna  25  via the conductive through holes  28 , thereby creating a short-circuit making the card unusable. 
     In the example described above, the antenna  25  is described as being a winding of a continuous conductor whose ends respectively form an internal terminal and an external terminal. In a variant embodiment, it is possible to form the antenna in some other manner. For example, it may be in the form of a winding having two external terminals or having two internal terminals. In which case, the turns of the winding overlap, and to prevent them from short-circuiting, care is taken, during manufacture of the antenna, to separate the overlapping turns with insulating patches. 
     Another contactless smart card, in a second embodiment of the invention, is shown diagrammatically while it is being manufactured in the section view of FIG.  5 . In this second embodiment, the smart card, referenced  30 , does not have a cavity or an electronics module. 
     In this case, the card body  30  is made up of at least two sheets of plastics material  39 ,  40  to the dimensions (width, length) of the card to be made. An antenna  35  is printed on a first sheet  40  by a well-known printing technique of the offset printing or pad-printing type, for example. The antenna  35  is in the form of a continuous conductor that is wound in a rectangular spiral having a certain number of turns disposed concentrically and that extends in the entire plane of the sheet  40  constituting the card body  30  The ends  33 ,  34  of the antenna conductor  35  form connection terminals to which two contact tabs of an integrated-circuit chip  37  are connected. 
     Two orifices are provided through the thickness of the card body, facing the connection terminals  33 ,  34  of the antenna  35 , so that they open out on an external face  32  of the card body  30 . These orifices are then metal plated using a printing deposition method, e.g. by screen-printing with a conductive ink, so as to form conductive through holes, i.e. plated through holes,  38 . Such a screen-printing method makes it possible, in a first step, to form a junction  36  at the surface of the external face  32  of the card body, in order to interconnect the connection terminals  33 ,  34  of the antenna  35  via the conductive through holes  38 . 
     An optionally transparent second sheet  39  is then mounted on the sheet  40  so as to protect the antenna  35  and the integrated-circuit chip  37 , and so as to embed them in the card body  30 . The second sheet  39  is mounted using a well-known conventional method, e.g. lamination. 
     Thus, the smart card  30  has a top face  32  that supports a junction  36  making it possible to inhibit, i.e. prevent, operation of the smart card by short-circuiting the antenna via conductive through holes  38 . By means of the presence of said junction, the user knows that the card has not yet been used, and that the number of units of value in the memory is thus at its maximum. 
     In order to activate the card, the user merely needs to scratch off the junction  26  so as to destroy it, thereby removing the short-circuit. The conductive ink is formulated in a manner such that it adheres poorly to the surface of the card body. For example, it is based on epoxy charged with silver particles or with carbon.