Abstract:
A method of manufacture of a wristband includes the steps of providing a bottom substrate. First circuit elements are deposited on the bottom substrate. A dielectric material is deposited at predetermined areas on the bottom substrate. A remainder of the circuit is deposited on the bottom substrate and dielectric materials. A transponder chip is secured to the bottom substrate to form a transponder. A second substrate is affixed to the bottom substrate such that the dielectric material and transponder are disposed between the bottom substrate and second substrate.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 11/488,278, filed Jul. 18, 2006, which claims the benefit of U.S. Provisional Application No. 60/700,695, filed on Jul. 18, 2005. 
         [0002]    The entire teachings of the above applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    Disposable wristbands have long been used for such things as identification, access control, age verification, among other purposes. Such wristbands have typically been made from materials such as polyester, paper, or vinyl. The physical presence of a wristband of particular color or design is used to identify the wearer as a member of a particular group. These colored wristbands have been used to control access to restricted areas or for other purposes in large crowded venues such as a sports stadium. For example, patrons who provide proof of legal drinking age are issued a wristband of a particular color, to indicate that they have permission to access a beer sales area. 
         [0004]    In recent years, such wristbands have been augmented with Radio Frequency Identification (RFID) technology. RFID extends the usefulness of such wristbands, as they can each be programmed with a unique code that quickly and easily identifies the wearer. RFID also adds new functionality to such wristbands. As one example, they can be used to locate the wearer. Thus, with the installation of appropriate radio location equipment, a lost child wearing an RFID wristband can be easily found, or prevented from leaving an amusement park unless accompanied by an authorized adult. 
         [0005]    RFID wristbands are also used to allow the purchase of items without the exchange of currency or need for a credit/debit card, or to allow secure communication and monetary exchange among patrons. With this type of RFID wristband, a patron can request the wristband be credited for purchases up to a preselected amount. Purchases can then be made by presenting the wristband at a special RFID reader, instead of using cash or credit/debit cards. These wristbands can also be coded so that a wearer would be prevented from making certain purchases, or from making a single purchase above a chosen limit. This feature can be used to control purchases by children, for example, so they are encouraged to spend their allotted funds wisely. 
         [0006]    However, even such RFID wristbands are susceptible to misuse and unauthorized use. Some wristbands are easily removed, and yet still function after removal. A wristband that still functions after it has been removed provides the opportunity for patrons to exchange wristbands. This could provide patrons with the opportunity to give access to a restricted area to an unauthorized patron. A patron issued an “adult” wristband that allows access to beer sales, for example, could remove and give or sell that wristband to a patron not of legal drinking age. As another example, a thoughtlessly discarded wristband that still has funds credited to it could be retrieved and used by an unauthorized individual to purchase goods or services using someone else&#39;s account. 
       SUMMARY OF THE INVENTION 
       [0007]    Wristbands of the type described above are typically intended to be disposable, and may only be used for a few hours. As such, what is needed is a way to manufacture such a wristband to include RFID functionality and security features, without greatly impacting the overall cost. 
         [0008]    The method of manufacture of the wristband includes providing a bottom substrate. First circuit elements are deposited on the bottom substrate. The first circuit elements are cured. A dielectric material is deposited at predetermined areas on the bottom substrate. A remainder of the circuit is deposited on the bottom substrate and dielectric materials. A transponder chip is secured to the bottom substrate to form a transponder. A second substrate is affixed to the bottom substrate such that the dielectric material and circuitry are disposed between the bottom substrate and second substrate. 
         [0009]    The present invention is a design and a construction technique for such a wristband. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0011]      FIG. 1  is a plan view of one embodiment of a wristband according to the present invention not showing a top substrate; 
           [0012]      FIG. 2  is a cross section of the wristband; 
           [0013]      FIGS. 3A and 3B  are an exploded view of the wristband showing a top layer and bottom layer; 
           [0014]      FIG. 4  is a top plan view of the top layer; 
           [0015]      FIG. 5  is a top plan view of the bottom layer of the wristband of  FIG. 1  illustrating the antenna and placement of the RFID integrated circuit chip; 
           [0016]      FIGS. 6A through 6D  are a top plan, side elevation, bottom plan and perspective view respectively of one embodiment of a snap insert portion to be used with the wristband of  FIG. 1 ; 
           [0017]      FIGS. 7A through 7D  are a top plan, sectional, bottom plan and perspective view respectively of one embodiment of a snap retainer portion to be used with the snap insert portion of  FIGS. 6A-6D ; 
           [0018]      FIG. 8  is a view of a crossover portion illustrating how a circuit trace can connect to a terminal of an RFID integrated circuit chip, without shorting, to conductors of the antenna portion in accordance with one embodiment according to the present invention; 
           [0019]      FIG. 9  is a flow chart for the processing steps used to manufacture the wristband in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    A description of example embodiments of the invention follows. 
         [0021]      FIG. 1  is a general illustration of a disabling Radio Frequency Identification (RFID) wristband  300  constructed according to the presenting invention. Wristband  300  is in the form of an elongated band  310  with opposite ends  314 ,  316  that are brought together and fastened to form a closed loop around a wearer&#39;s wrist or other body part. 
         [0022]    Wristband  300  contains a transponder  32 , which is comprised of an antenna  30  operatively coupled to a Radio Frequency Identification (RFID) circuit  22 . Antenna  30  is coupled to one or more conductive wires acting as transponder disabling wires  34  such that current will flow through conductive wire(s)  34  in the path illustrated by arrow  330  when transponder  32  is functioning. In the illustrated embodiment, conductive wire(s)  34  include a top conductor  35  and a bottom conductor  36 , which are joined at a node  37 . As will be described in more detail below, if a discontinuity becomes present in any of transponder disabling wires  34 , then transponder  32  will become disabled. Hence, conductive wire  34  is also referred to herein as a transponder disabling wire  34 . 
         [0023]    Wristband  300  also preferably includes a mechanical non-reusable tamper-resistant locking mechanism  320  to fasten band  310  upon itself at end  314  and to prevent the user from attempting to open the locking mechanism  320  to remove the wristband  300  without rendering those tampering efforts visually evident. 
         [0024]    Locking mechanism  320  comprises a barbed peg  318  disposed on band  310  at end  314 . A locking hole  322  is disposed on flap  28  at end  314  of band  310  across a fold line  26  from barbed peg  318 . A number of adjustment openings or adjustment holes  24  extend along band  310  in a direction towards end  316 . Adjustment holes  24  are used to adjust the wristband  300  to conform to body parts of different circumferences. 
         [0025]    When ends  314 ,  316  are brought together, the barbed peg  318  is arranged to pass through a selected hole  24  as required for a snug fit. The flap  28  is then folded along imaginary fold line  26  and barbed peg  318  is then passed through locking hole  322 . Peg  318  is shaped to resist removal from the locking hole  322  without also destroying the locking mechanism  320  and rendering it incapable of being refastened. Alternatively, or in addition, adjustment holes  24  can be designed to replace or supplement locking hole  322  by configuring them in such a way that attempts to remove the wristband from the barbed peg  318  would also destroy the hole  24 , thereby disabling the wristband and rendering it incapable of being refastened. 
         [0026]    As mentioned previously, wristband  300  also includes a transponder  32 . Transponder  32  contains an antenna  30  and an RFID integrated circuit (IC) chip  22 . The transponder  32  responds to an RF interrogation signal and in response emits an RF signal representative of information pre-stored or preprogrammed into RFID integrated circuit chip  22 . For example, the information could include the date the wristband  300  is issued, the date the wristband  300  expires and will no longer be usable for access, the age status of the wearer, and whether the wristband  300  can be used for purchasing goods or services. Any other desired information, depending on the context in which the wristband is to be used, may be pre-stored or pre-programmed in the transponder. The signal may also be used to access information stored in a database. 
         [0027]    Being a passive-type RFID, the transponder  32  also derives a power signal from antenna  30  that supplies power to the rest of the RFID integrated circuit chip  22 . In the preferred embodiment, the antenna  30  has the form of a continuous electrically conductive coil. 
         [0028]    One or more transponder disabling wires  34  also extend away from the area occupied by the transponder  32 . The transponder disabling wires  34  form an electrically conductive path, from antenna  30  out to end  316  and back to antenna  30 , along substantially the entire length of the band  12  of wristband  300 . As will be explained in detail below, the transponder disabling wires  34  are arranged to connect the components of transponder  32  and/or form portions of the components themselves, such that transponder disabling wires  34  must remain intact for the transponder  32  to operate. 
         [0029]    In one embodiment, one or more of the transponder disabling wires  34  may function as part of antenna  30 . In such an embodiment, consideration should be given to the distance between the sections of the loop antenna and transponder disabling wires  34  in order to minimize inductance that can lead to possible interference with the operation of the other components of transponder  32 . 
         [0030]    Transponder disabling wires  34  are preferably, but not necessarily, made from printed conductive ink that is robust enough to withstand normal handling but fragile enough that they will be broken if a user attempts to remove the wristband. Alternatively, transponder disabling wires  34  may be a thin wire such as copper wire, a thin foil, or other suitable electrically conductive material that will form an electrically continuous path but will break as a result of tampering. Forming transponder disabling wires  34  with frangible zones, where stresses from tampering attempts are most likely to occur, may facilitate breakage of the transponder disabling wires. Of course, if the user attempts to remove the wristband  300  with a cutting implement, the conductor forming transponder disabling wires  34  will also be severed. 
         [0031]    Turning attention to  FIG. 2 , in a preferred embodiment the wristband is formed from two layers of a polymeric substrate material such as PET or other flexible plastic material. However, Dupont Teflon™, Teslin® or vinyl are examples of other possible materials. For comfort reasons it is preferred to have at least the bottom layer  220 , which forms the substrate for the entire wristband  300 , exhibit a low coefficient of friction and generally flexible nature, as it is that layer that will most likely come in close contact to the wearer&#39;s skin. 
         [0032]    As described in detail below, the bottom layer  220  is used as a substrate on which are printed a circuit  230  that includes certain elements of transponder  32  such as the antenna  30  and certain circuit wiring, such as the disabling wire(s)  34 . Conductive ink is used to form the antenna  30  and wiring  34 . 
         [0033]    The top layer  210  is typically formed of the same material as the bottom layer  220 . It is used as a cover-lay for the wristband, and should readily accept printing inks so that identifying graphics, advertisements, or the like, can be printed thereon. 
         [0034]    A pressure sensitive adhesive (PSA)  240  is used to bind the top  210  and bottom  220  layers. Alternative sealing techniques may also be used, such as heat sealing, radio-frequency sealing, ultrasound sealing, or a hot-melt adhesive. 
         [0035]    Turning to  FIGS. 3A-7D  wristband  300  is described in greater detail.  FIG. 3A  shows an exploded view of the wristband prior to assembly of the two layers  210 ,  220 . The bottom layer  220  is seen with the printed side up, after installation of the RFID integrated circuit chip  22 , but prior to installation of snap insert  418  that includes the barbed peg  318  described above, and also prior to installation of snap retainer  422  that includes part of the locking hole  322 . 
         [0036]    A slit  352 , formed by matching slits  352   a,    352   b,  is formed in or near end  314  of wristband  300  to accommodate any extra length of band material from far end  316  after the band is fastened together. Flaps  28   a,    28   b  form flap  28  when bottom  220  is joined to top  210 . 
         [0037]      FIG. 3B  is a more detailed view illustrating more view of the wristband in the area of the antenna and the integrated circuit chip showing a crossover and more detail of the fastener. Hole A is shown for snap insert  418  and hole B for snap retainer  422 . Corresponding holes C and D are formed in top layer  210  to receive snap insert  418  and snap retainer  422 . 
         [0038]    As seen in  FIGS. 6A-6C , snap insert  418  includes a base  420  and a peg  318  extending from base  420 . Base  420  is significantly greater in diameter than peg  318  and significantly greater in diameter than either one of hole A or hole D. In this way, when assembled, as discussed below, base  420  anchors peg  318  to wristband  300 . 
         [0039]    Similarly, as seen  FIGS. 7A-7D , snap retainer  422  includes a locking hole  320  formed in a base  424 . Base  424  has a diameter substantially greater than the diameter of the opening to hole  322  and substantially greater than the diameter of holes B and C. In this way, base  424  anchors snap retainer  422  to wristband  300  when assembled. It should be noted that the interior of hole  322  is sloped towards a retaining portion  324  to receive the surfaces of barbed peg  318 , but prevent barbed peg  318  from being removed from receiving portion  324 . 
         [0040]      FIG. 8  illustrates still more detail of the construction of the wristband  300  near the antenna  30  and the RFID integrated circuit chip  22 . The antenna  30  is defined as a set of individual wire traces  380 - 1 ,  380 - 2 ,  380 -n that form a wire coil; wire traces  380  thus form a progressively smaller loop within a single printed circuit layer. 
         [0041]    However, it is necessary to connect one terminal  371  of the chip  22  to one end of the antenna coil  30 , and another terminal  372  of the chip  22  to the other end of the antenna coil  30  and/or the transponder disabling wires  34  (in the illustrated embodiment, the transponder disabling wired  34  is connected to terminal  372 , so that transponder disabling wires  34  is placed in electrical series with the coiled traces  380 ). 
         [0042]    To allow for this, without having the individual wire traces  380  of antenna  30  short against one another, a dielectric is used to form a crossover or bridge  390 . As such, another conductive trace  385  can be placed over the dielectric bridge  390 , completing the connection to terminal  371 . 
         [0043]      FIG. 9  illustrates the steps of a process that can be used to manufacture the wristband  300 . Reference can be made back to  FIGS. 2-8  while examining the steps of the process. 
         [0044]    In a first step  900  of the process, a conductive ink is printed in a first pattern to define elements of the antenna  30  and the disabling wire  34  on the substrate formed by bottom layer  220 . The substrate that forms bottom layer  220  is preferably pre-treated, such as by heating, such that further processing will not warp or shrink the substrate once circuit manufacturing has begun. 
         [0045]    After the first printing step, a curing step  902  is performed, wherein heat and/or ultraviolet light is applied to cure the conductive ink on bottom layer  220 . 
         [0046]    In a next step  904 , a dielectric material is applied in selected areas over the cured bottom layer. The dielectric is used to isolate certain conductive portions of the circuitry from other portions. For example, the dielectric is formed in the area of crossover or bridge  390 . However, it can also be used in other areas for other bridge elements. It may be also desirable to use dielectric to isolate other circuitry and/or define vias between multiple printed circuit layers on bottom layer  220 . For example, a serpentine pattern used for the transponder disabling wire  34  that encircles the holes may be defined on multiple printed circuit layers isolated by such dielectric. 
         [0047]    The dielectric layer is then cured via UV light or heat in step  906 , depending on the nature of the dielectric material. 
         [0048]    Next, another printing step  908  may be used to print a second set of conductive traces that define further circuitry such as the crossover trace  385  on crossover or bridge  390  or conductive vias between printed layers, followed by a curing step  910 . 
         [0049]    Additionally, electronic components may be formed in steps. For example, a capacitor may be formed in steps  904  through  910  by printing two conductive parallel plates separated by dielectric layers, as is well understood in the art. 
         [0050]    Additional dielectric layers and conductive ink layers may be patterned as desired to provide further circuitry definition by repeating steps  904  through  910 . 
         [0051]    In a next step  912 , the RFID integrated circuit chip  22  is placed in the proper location on the bottom layer  220 . The RFID integrated circuit chip  22  is preferably held in place in the desired location using a z-axis conductive adhesive, anisotropic conductive adhesive (ACA), or non-conductive paste (NCP). Alternatively, the RFID integrated circuit chip  22  may be connected using a soldering technique if proper steps are taken not to melt bottom layer  220 . The RFID integrated circuit chip  22  can be any one of any number of different commercial off the shelf RFID integrated circuit chips, such as those available from Texas Instruments or Philips. 
         [0052]    As desired, additional electronic components may be placed on bottom layer  220  in step  912  such as a thin-film battery. 
         [0053]    In lamination steps  913 ,  914 , and  916  the top layer  210  is laminated to the bottom layer  220  using a pressure sensitive adhesive (PSA) type adhesive. The adhesive may be applied first to one layer or the other, and then the two layers subjected to pressure such as by rollers. If no pre-treatment of the adhesive is required, then the cover layer  210  may come pre-coated with a PSA. Lamination integrity should be maintained such that no voids or vacancies or separation of layers occurs and/or damage to the RFID integrated circuit chip  22 . 
         [0054]    If precision lamination is required, an optional cutting stage  913  may be required to create registration holes. These registration holes will subsequently be utilized during the lamination process to precisely align top and bottom layers  210 , 220 . The registration holes may be cut using a die cut or laser process, for example. 
         [0055]    Alternatively, with more sophisticated equipment, layer alignment may be conducted by printing fiducials in an early printing stage and using a vision alignment system during lamination. 
         [0056]    In a next step  918  the outer dimensions of the wristband are defined by cutting the lamination using a die cut or laser process as before. In addition, the holes  24 , and holes for snap insert  418  and snap retainer  422  are formed. 
         [0057]    A next step  920  is to install the snap insert  418 . The snap insert  418  (e.g., the male portion of the fastener  320 ) is then placed through a hole formed in the end of the band  300 . Note the orientation of the snap insert  318  from the drawings such as FIG.  3 B—that is, the snap insert  318  should be inserted from the unprinted side of bottom layer  220 , such that the catch portion is visibly protruding on the printed side. 
         [0058]    In a next step  922 , the snap retainer  422  (the female portion of the fastener  320 ) is inserted into wristband  300 , from the same direction that the snap insert was placed. 
         [0059]    The snap portions  418 ,  422  may be inserted in steps  920 ,  922  either manually or by machine process as long as the snaps are fully inserted and secure. Optionally, snap portions  418 ,  422  may be pre joined such that only one of insertion steps  920 ,  922  need be executed to secure both snap portions  418 ,  422  to the assembly. 
         [0060]    In an alternative embodiment, an adhesive fastening mechanism may be used. This can be carried out by applying a PSA to the outer-side of top layer  310  at distal end  316  of wristband  300 . 
         [0061]    Various changes can be made to the invention without departing from its true spirit and scope. For example, in one embodiment the top layer  210  is actually made somewhat thicker than the bottom layer  220 . This places conductive circuitry into compression more readily when the wristband  300  is fastened around a wearer&#39;s wrist. That is, when such a band is installed around a wearer&#39;s wrist, with the thinner bottom layer  220  carrying the conductive components such as the RFID integrated circuit chip  22 , antenna  30 , and disabling wire  34 , these will be placed into mechanical compression rather than into mechanical tension. This is because these components are closer to the inside of bend center than the outside of the bend center. Most conductors, particularly percolation conductors such as conductive inks, are mechanically stronger in compression than in tension. As such, this construct markedly increases the durability of wristband  300 . 
         [0062]    In addition, note a further advantage of the layout described herein in having the crossover portion  390  of the circuit laid out perpendicular to a lengthwise, longest axis of the wristband  300 . This exposes the crossover  390  to less stress than it would be otherwise, alleviating a further possible failure point, and increasing robustness of the wristband  300 . 
         [0063]    It should be further noted that wristband  300  will be most susceptible to failure near the RFID integrated circuit chip  22  and cross-over  390  areas of wristband  300 . In an improvement to wristband  300 , bottom and/or top substrate  220 ,  210  are created such that they vary in thickness. This can be achieved by adding an additional layer of PET, for example, which is commonly referred to in the art as a “stiffener.” The RFID chip  22  and crossover or bridge  390  are then placed such that they are near the part of wristband  300  containing the stiffener. The stiffener causes a non-uniform distribution of stress along wristband  300 , such that more stress is concentrated away from the stiffener when wristband  300  is flexed. As such, RFID integrated circuit chip  22  and cross-over  390  are placed under less stress during wristband flexion, substantially increasing circuit durability. 
         [0064]    The antenna  30  can also be formed in other ways. For example, it can be formed by depositing copper and/or etching a copper layer. After electrodepositing a copper layer an additional over coating of tin or SnPb (solder) can be over coated to help improve the mechanical integrity of the circuit. 
         [0065]    Other configurations are possible that use crossover or bridge  390  in different ways. For example, an alternative format in which the RFID integrated circuit chip  22  may be provided from the manufacturer is on a metal bridge or “strap.” This strap is insulated on its underside such that it can be laid over the antenna in lieu of a dielectric and cross-over trace. In this manner, the crossover or bridge  390  can be achieved at the same time as the chip is placed down. This reduces the number of print passes and layers required to manufacture the device. 
         [0066]    While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.