Abstract:
An electronic module or label which is adapted to be rendered adhesive including a support film having an insulative film and at a communication interface disposed on the insulative film, at least one microcircuit, the communication interface being connected to the microcircuit by connections, an adhesive tape including an activatable adhesive adhered to the insulative film and a perforation coinciding with a predetermined area of the support film that includes the microcircuit and connections, a coating resin protecting the microcircuit and the connections and covering the predetermined area within the perforation. The adhesive tape can also include a removable protective film. After removing the removable protective film, the module or label can be adhered to a card body, forming a electronic card such as a smart card. In other embodiments, adhesive is applied to the support film so as to form a delimitation in which the coating resin is applied.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of application Ser. No. 09/534,053, filed on Mar. 24, 2000, which is based upon, and claims priority from, French Patent Application No. 97/12445, filed Sep. 26, 1997. The entire contents of these applications are incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention relates to electronic modules to be integrated into an electronic card, such as a smart card, an electronic label, or the like.  
           [0003]    The electronic module includes at least one microcircuit and an interface which can be a contact terminal assembly in the case of conventional contact-type smart cards or one or more antennas providing contactless communication in the case of contactless smart cards and electronic labels. In the case of hybrid smart cards, the interface includes a contact terminal assembly and an antenna.  
         BACKGROUND  
         [0004]    Several types of electronic modules and methods for forming electronic modules and some associated drawbacks are described in U.S. patent application Ser. No. 09/534,053.  
           [0005]    The problem addressed by the invention is that of providing a simple, reliable and economic method of fabricating electronic modules for electronic cards.  
           [0006]    The proposed solution aims not only to reduce the number of process steps but also to eliminate the use of consumables. To this end, the principle of the invention is to use the adhesive employed for fixing as a barrier to or delimiter of the coating resin.  
         SUMMARY  
         [0007]    To this end, a method is described for fabricating at least one electronic module or label which is adapted to be rendered adhesive, the module or label including a support film, at least one microcircuit and at least one interface of the contact and/or antenna type connected together by connections and disposed on the support film, a coating resin protecting at least said microcircuit and said connections, the coating resin being disposed over a predetermined area, and an external activatable adhesive. The method includes the following steps:  
           [0008]    a) an insulative film is supplied including at least one contact and/or antenna type interface,  
           [0009]    b) an adhesive tape is supplied including an activatable adhesive and a removable protective film, said tape including at least one perforation corresponding to the area of the resin on the module or label,  
           [0010]    c) the adhesive tape is applied to the support film so that said perforation coincides with the area of the resin and said adhesive is activated so that it fixes the tape to the film, and  
           [0011]    d) the coating resin is dispensed over the intended area at least within the perforation and in contact with the perforation, the microcircuit having been fixed to the support film connected to the interface after one of the preceding steps.  
           [0012]    In the case of series fabrication of media provided with an electronic module, such as smart cards, or with a label, and the preceding steps are performed, the support film and the tape being provided in roll form, the former including a plurality of interfaces, the latter including a plurality of perforations. The protective layer is then removed from the adhesive tape and the modules or labels are cut out before gluing them to a support of the body of the card by activating the adhesive tape.  
           [0013]    This method is particularly advantageous for fabricating smart cards since no dedicated consumable material is used for shuttering the resin, because the fixing adhesive is used for this purpose, and the number of process steps is reduced, because the separate operation of depositing the barrier is eliminated. Also, equipment and processes known in the art are used, which facilitates industrial application.  
           [0014]    Minimising the number of process steps increases efficiency and reduces fabrication cost.  
           [0015]    In the case of small microcircuits, for which a barrier is not normally used, the method increases the volume of resin around the connecting wires and thus provides a form of packaging which is more rigid and therefore more resistant to mechanical stresses (repeated bending and twisting). This increase in reliability is achieved with no increase in unit cost.  
           [0016]    The adhesive tape can be applied to the support film at various stages, including before gluing the microcircuits to the support film, after gluing the microcircuits and before connecting them, or after connecting them.  
           [0017]    According to another feature of the invention, the total thickness of the adhesive tape with its external protective layer is at least equal to the intended thickness of the protective or coating resin. This enables the resin to be well contained or to the required height.  
           [0018]    The height of the barrier is, preferably matched to the required height of the resin simply by varying the thickness of the protective film. Thus a very thin layer of adhesive can be used, which is preferable in particular in the fabrication of smart cards in respect of the gluing or the dynamic behaviour of the module relative to the cavity.  
           [0019]    The coating material, which is a resin, can be dispensed in various ways, in particular by spraying, screenprinting, positive displacement dispensing (Glob Top), etc.  
           [0020]    Positive displacement dispensing provides total control of the predetermined quantity of resin deposited and consequently its thickness. Unlike spraying, this technique provides total control over the dispensing region on the support film, in particular in the intended area within any form of perforation, barrier or delimitation.  
           [0021]    A variant of the method differs from the previous embodiment described above in that it includes the following steps:  
           [0022]    b) an activatable adhesive with no external protective film is supplied,  
           [0023]    c) the adhesive is deposited so that it is distributed over all of the support film and defines a delimitation around said area and said adhesive is activated so that it adheres to the support film, and  
           [0024]    d) the coating resin is dispensed over the intended area inside said delimitation so that the coating resin stops spreading when it comes into contact with it, the microcircuit having been fixed to the support film and connected to the interface after one of the preceding steps.  
           [0025]    This eliminates the need for a protective film and the step of removing such film prior to fixing.  
           [0026]    For fixing the module or antenna to a support, a method can include a step of activating the adhesive prior to or at the same time as it is applied to and pressed onto said support.  
           [0027]    The support is preferably a smart card or token body incorporating a cavity adapted to receive at least one microcircuit, its connections and the coating resin.  
           [0028]    Embodiments of the invention also include an electronic module or label obtained by the above methods. In the case of an electronic module including an antenna, the antenna can be formed on the rear face of the support film, in which case the module includes a second adhesive tape applied to the rear face of the support film.  
           [0029]    This second adhesive tape constitutes a protective layer for the antenna.  
           [0030]    The invention further provides an electronic label incorporating an electronic module in which the interface is an antenna and which is obtained by the above method. A label of this kind is constituted entirely by the electronic module, which is not “carded” and retains the external protective layer. The adhesive tape is advantageously used to fix the label to a product support.  
           [0031]    An adhesive electronic label of low unit cost is obtained in this way.  
           [0032]    To stiffen the label, the adhesive tape can be reinforced, for example with glass fibres.  
           [0033]    The invention further provides a smart card or token made by the methods according to the invention.  
           [0034]    According to one feature of the invention, a standard smart card can be obtained by enclosing the module entirely within a support cavity, in particular a card body, so that the module is flush with the surface of the support.  
           [0035]    According to one advantageous feature of the invention, the smart card or token includes a cavity adapted to receive at least one microcircuit, its connections and said coating resin and the support film is fixed to the surface of said support outside the cavity. Thus it is easy to fix a large label or module (interface with an antenna size of a few centimeters) to a card body without requiring a specific wide cavity on the support film.  
           [0036]    The invention further provides a spool of support film carrying a plurality of modules or labels obtained by the methods described above.  
           [0037]    Other features and advantages of the invention will emerge from the following description which is given by way of illustrative and non-limiting example, and with reference to the accompanying drawings, in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0038]    [0038]FIG. 1 shows the operation of depositing the adhesive tape,  
         [0039]    [0039]FIGS. 2 and 3 show the “carding” operation for both embodiments of the barrier,  
         [0040]    [0040]FIGS. 4A to  4 G shows a method in accordance with the invention of fabricating smart cards,  
         [0041]    [0041]FIGS. 5A to  5 G shows a first method for forming an electronic module, and  
         [0042]    FIGS.  6 - 8  show other embodiments of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]    In a conventional method of making an electronic module for use in a smart card, microcircuits are cut out from a wafer and glued to a support film. Interface connections are made to constitute the electronic module.  
         [0044]    Then, if the microcircuit is large and rectangular, a barrier is formed on the support film around the electronic module obtained in the above manner. The barrier can be a pressed metal frame glued to the support film or a polymer, such as epoxy or polyester resin, or silicone, which can be deposited by a deposition technique using a syringe (“dispensed”) or by screenprinting.  
         [0045]    A drop of resin for mechanically protecting the electronic module is then deposited on the support film in the area delimited by the barrier.  
         [0046]    An adhesive film is then applied around the electronic module coated with the drop of protective resin ready for the operation of inserting the electronic module into the body of the smart card.  
         [0047]    [0047]FIG. 1 shows the operation of applying the adhesive film  22 . It shows a roll  24  carrying a series of microcircuits  10  on a support film  12  and protected by an interleaved film  26 . The interleaved film  26  is removed and wound onto an auxiliary spool. A third roll  21  supplies the adhesive film  22  which is perforated by a device  28  to form cut-outs corresponding to the areas of the electronic modules coated with the drop  20  of protective resin, with the result that the adhesive film  22  is made up of frames  30  surrounding this area.  
         [0048]    The support film  12  is then cut to obtain individual electronic modules which are then glued into a recess  32  in the body  34  of the smart card by the adhesive film  22  that has just been applied. This operation is shown in FIGS.  2  and  3  for barriers  16  (a pressed metal frame) and  18  (a polymer deposited with a syringe or by screenprinting).  
         [0049]    In the case of thermosetting resins, it maybe necessary to correct the thickness of the electronic module coated with the drop  20  of protective resin before the cutting operation, for example by milling the drop  20  of protective resin.  
         [0050]    The above-mentioned technique of forming the barrier has many drawbacks. The cost of this operation is not negligible.  
         [0051]    The material used can have harmful secondary effects; if silicone is used, for example, surfaces to be glued in subsequent process steps may become polluted.  
         [0052]    A precise technique for depositing the resin must be used to prevent the resin overflowing, which leads to rejection.  
         [0053]    The use of thermosetting resins entails an additional operation of correcting the thickness of the electronic module coated with the drop  20  of protective resin.  
         [0054]    As indicated above, there are other techniques for producing the barrier which necessitate the use of a consumable material and/or additional process steps increasing fabrication cost.  
         [0055]    The present invention embodiments avoid the aforementioned drawbacks and produce an electronic module coated with the drop  20  of protective resin at reduced fabrication cost. The adhesive film employed for the subsequent “carding” operation can be used to form the barrier. There is therefore no consumable material; furthermore, the dedicated step of forming the barrier is eliminated.  
         [0056]    [0056]FIGS. 4A to  4 G shows embodiments of the electronic module which can be coated with the drop  20  of protective resin. FIGS. 4A to  4 C show the two steps of producing the support film  12 , the step of gluing on the microcircuit or chip  10  and the step of making the interface connections  14 .  
         [0057]    An adhesive tape  40  which is perforated, for example the adhesive film  22  shown in FIG. 1, can be made up of a layer  42  of adhesive covered with an external protection layer  44 , is then applied to the support film  12 . The drop  20  of protective resin is then applied, after which the external protection layer  44  is removed to glue the electronic module into the recess  32  in the body  34  of the smart card.  
         [0058]    This method uses a layer  42  of heat-activated, thermoplastic or heat-activated adhesive, for example BEIERSDORF TESA 8410 adhesive.  
         [0059]    The operation of applying the adhesive tape  40  to the support film  12  is performed before depositing the drop  20  of protective resin; it can be performed before gluing the chip  10 , before making the connections  14  or, at the latest, after this latter step. All that is required is to use techniques for gluing the chip and wiring the connections which do not require a temperature that could activate the layer  42  of adhesive.  
         [0060]    For example, a two-component glue which is crosslinked at room temperature can be used to glue the chips, or a glue which is cross-linked by ultraviolet radiation or light at a shorter wavelength (“blue light”). The “wedge bonding” technique can be used for wiring the connections, employing an aluminum wire welded ultrasonically. Another solution is “ball bonding” using suitable parameter settings and avoiding a temperature greater than 70° C. in the area of the layer  42  of adhesive.  
         [0061]    The adhesive tape  40  includes an external protection layer  44 , i.e. an external non-stick surface preventing unintentional gluing during the steps of fabrication of the electronic module.  
         [0062]    Moreover, the thickness of the adhesive tape  40  with its external protection layer  44  is chosen to be not less than the intended thickness of the drop  20  of protective resin. A thinner adhesive tape  40  can be used if the drop  20  of protective resin is deposited by a positive displacement dispensing type deposition technique providing total control of the quantity of resin deposited and consequently its thickness.  
         [0063]    The protective resin must be cross-linked at a low temperature. It can be activated by ultraviolet radiation, cross-linked by wetting or a two-component product.  
         [0064]    In the case of a thin adhesive tape, the rheological properties and the surface tension of the resin are such that a convex drop is reproducibly obtained. In other cases the term “resin” as used in the context of the invention can refer to any material adapted to protect the microcircuit and its connections.  
         [0065]    After the drop  20  of protective resin has been gelled or completely cross-linked, the external protection layer  44  is removed to perform the “carding” operation in the conventional way. In the case of a thin external protection layer  44 , the thickness of the drop  20  of protection resin can be corrected by milling.  
         [0066]    [0066]FIGS. 5A to  5 G show another embodiment using a layer  42  of adhesive cross-linked by ultraviolet radiation and is based on the use of a thermosetting polymer (for example an epoxy or urethane polymer) whose polymerisation is initiated by ultraviolet radiation, possibly associated with a thermoplastic formulation (for example polyester) to render the product activatable, the product becoming tacky when heated. As shown in FIG. 5, the layer  42  of adhesive is activated by ultraviolet radiation after removing the external protection layer  44  and just before fitting it into the cavity  32  in the body  34 . It is therefore not necessary to apply a high temperature to polymerise the layer  42  of adhesive. This means that the deformation of the back of the cavity  32  usually caused by pressing at high temperature is significantly reduced compared to the use of an adhesive which is cross-linked by applying heat.  
         [0067]    The advantage of this adhesive is that it can be exposed to a temperature in the order 80 to 120° C. without degrading it; this means that a thermosetting protective resin can be cast and polymerised in the recesses formed by the perforations in the adhesive tape  40 .  
         [0068]    These method can therefore produce electronic modules including an interface of the contact terminal assembly or antenna type. In the case of an electronic module whose interface is an antenna, the invention can produce electronic labels for marking commercial products, for example in large retail outlets. Such electronic labels are used in particular to detect products entering a surveillance area. The external protection layer  44  of the labels is not removed so that users can choose whether to retain it or not. However, in a preferred embodiment aimed at series fixing of modules or labels to products such as chip supports or industrial products, the protective film must be removed before cutting. In one example, the module is cut out by a punch and transferred to an insertion tool for fixing it to the product concerned.  
         [0069]    The adhesive layer of the adhesive tape can be used for gluing the electronic label to the product.  
         [0070]    [0070]FIG. 6 shows an electronic label of this kind which includes a support film  50 , a microcircuit  52 , connections  54  to an antenna  56  consisting of metal turns deposited on the rear face of the support film  50 , and an adhesive tape  58 . The microcircuit  52  is embedded in a drop  60  of protective resin.  
         [0071]    In this case, the adhesive tape  58  produces a label of constant thickness. An adhesive tape reinforced by means of glass fibres, for example, can be used if a stronger label is required.  
         [0072]    The antenna is made of metal tape, for example copper or aluminium tape, chemically etched or stamped on a dielectric, for example glass/epoxy, polyester, polyimide, polyethylene, polypropylene.  
         [0073]    The antenna can be on the same side as the microcircuit (front face of the support film  50 ) or the other side (rear face).  
         [0074]    In the former case, as shown in FIG. 7, the adhesive tape  70  protects the turns of the antenna  72  from climatic conditions which can degrade the characteristics of the antenna, for example through corrosion, and mechanical abrasion. Also, the labels can be manipulated without interfering with operation by grounding or short-circuiting the turns.  
         [0075]    In the latter case, as shown in FIG. 8, the adhesive tape  80  forming the barrier is applied to the support film  82  and a protective film  84  protecting the antenna  86  can be applied to its rear face.  
         [0076]    The invention provides a low-cost electronic module for smart cards of the contact, contactless or hybrid type. In particular, no consumable material is used and the number of fabrication process steps is reduced.  
         [0077]    Furthermore, the method of the invention uses conventional equipment and fabrication process steps, which makes it more reliable.  
         [0078]    Also, an electronic label of great reliability in terms of mechanical strength can be obtained, also at low cost.  
         [0079]    In the embodiment of the method of the invention using an activatable adhesive ( 44 ), the adhesive can be applied in various manners, in particular in the form of stripes or spots.  
         [0080]    Likewise, the adhesive can be applied in the form of a film such as a thermofusible film. This film can be perforated like the film of the protective tape.  
         [0081]    The adhesive can be a multilayer film. The adhesive layers can be activated differently, in particular by radiation or by heat.  
         [0082]    One practical dispensing method uses the screenprinting technique.  
         [0083]    Depending on the process, when the adhesive is heat activated, the coating resin can be a single-component resin or a two-component polymer which is polymerised at a temperature of 70° C. or less.  
         [0084]    Although only preferred embodiments are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.