Abstract:
Methods for producing cost effective and reliable antennas for wireless devices are disclosed. The antennas are formed by applying a conductive layer to one or both sides of a carrier sheet. The combination of the carrier sheet and the conductive layer are then formed into one or more three-dimensional antenna structures in a thermoforming process. This -technique enables high volume production of antennas in a fast, reliable, and cost-efficient manner. The plurality of antennas formed in this fashion may then be separated by a cutting apparatus to obtain individual antennas that are ready for integration into myriad communication devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of priority of U.S. Provisional Application Ser. No. 61/037,278 titled “Methods for Forming Antennas Using Thermoforming” filed Mar. 17, 2008, the contents of which are hereby incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates generally to the field of wireless communication. In particular, the present invention relates to antennas and methods for forming antennas for use in wireless communications. 
       BACKGROUND OF THE INVENTION 
       [0003]    With the proliferation of wireless products and services, device manufacturers are forced to aggressively pursue cost reduction opportunities in the manufacturing and assembly of wireless device components. Reduction of costs associated with wireless antennas may thus be an important factor in staying competitive. Implementation of a cost-effective antenna may become even more critical as new features and functionalities are added to wireless devices that require more sophisticated antennas. 
         [0004]    An internal antenna for a wireless device is typically manufactured as either a stamped metal element or as a flex-circuit antenna on a plastic carrier. Both technique suffer from high cost of production. The stamped metal element and the plastic carrier both require expensive and time consuming tooling for high volume production. Furthermore, while the flex-circuit antenna may be readily fabricated using a standard etching process, this technique is typically a more expensive solution compared to a stamped metal element. 
       SUMMARY OF THE INVENTION 
       [0005]    It is the goal of the various embodiments of the present invention to provide methods of forming cost effective and reliable wireless antennas in one aspect of the invention, a method for forming an antenna comprises providing a non-conductive carrier sheet, applying a conductive layer to at least a portion of the carrier sheet, and forming one or more antennas by thermoforming the carrier sheet and the conductive layer. In one embodiment, the conductive layer is applied to one side of the carrier sheet, while in another embodiment the conductive layer is applied to both sides of the carrier sheet. 
         [0006]    In another embodiment, the applying of the conductive layer comprises at least one of a printing, attaching, and deposition of the conductive layer in one embodiment, the printing is conducted in accordance with a stencil printer. According to another embodiment, the carrier sheet comprises a plastic sheet. In yet another embodiment, the forming produces a plurality of three-dimensional antennas that are separated into individual antenna structures with a cutting apparatus. 
         [0007]    in another embodiment, the plurality of antennas are situated in a two dimensional array and, in another embodiment, the forming produces one or more two-dimensional antenna patterns. The antenna patterns may comprise one or more folding lines for shaping the patterns into one or more three-dimensional antenna structures. In one embodiment, one or more of the folding lines is produced using a laser cutter. 
         [0008]    In yet another embodiment, the forming produces one or more antennas on a tape portion of a tape-on-reel package. In another embodiment, the forming further produces one or more protrusions for connecting at least one of a ground and an electrical feed associated with the antennas to a circuit board. The one or more protrusions fit into one or more depressions on the circuit board. In another embodiment, the forming further produces one or more contact bumps for connecting at least one of a ground and an electrical feed associated with the antennas to a circuit board. 
         [0009]    In another embodiment, the one or more antennas further comprise one or more metal clips for connecting at least one of a ground and an electrical feed associated with the antennas to a circuit board. In one embodiment, the connecting is effected in accordance with one or more through holes on the circuit board while in another embodiment, the connecting is effected in accordance with one or more pads on the circuit board. In another embodiment, one or more metal springs are used for connecting at least one of a ground and an electrical feed associated with the antennas to a circuit board. In another embodiment, the thermoforming comprises vacuum forming. In yet another embodiment, the applying is carried out after thermoforming the carrier sheet. 
         [0010]    Another aspect of the present invention relates to an antenna comprising a non-conductive portion, a conductive portion positioned on at least a portion of the non-conductive portion, and one or more protrusions in at least the conductive portion for connecting at least one of a ground and an electrical feed associated with the antenna to a circuit board. The antenna may be formed by applying a conductive layer to a non-conductive carrier sheet and thermoforming the carrier sheet and conductive layer. The antenna may also be formed by thermoforming a non-conductive carrier sheet and applying a conductive layer to the thermoformed carrier sheet. 
         [0011]    Those skilled in the art will appreciate that various embodiments discussed above, or parts thereof, may be combined in a variety of ways to create further embodiments that are encompassed by the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates an exemplary flow diagram in accordance with an example embodiment of the present invention; 
           [0013]      FIG. 2  illustrates an exemplary flow diagram in accordance with an embodiment of the present invention; 
           [0014]      FIG. 3  illustrates an antenna in accordance with an exemplary embodiment of the present invention; 
           [0015]      FIG. 4  illustrates an exemplary antenna in accordance with an embodiment of the present invention; 
           [0016]      FIG. 5(   a ) illustrates a tape strip corresponding to a tape-and-reel system; 
           [0017]      FIG. 5(   b ) illustrates a plurality of antennas in accordance with an exemplary embodiment of the present invention; 
           [0018]      FIG. 6  illustrates an antenna in accordance with an exemplary embodiment of the present invention; 
           [0019]      FIG. 7  illustrates an antenna in accordance with an exemplary embodiment of the present invention; 
           [0020]      FIG. 8  illustrates an antenna in accordance with an exemplary embodiment of the present invention; 
           [0021]      FIG. 9  illustrates an antenna in accordance with an exemplary embodiment of the present invention; and 
           [0022]      FIG. 10  illustrates an antenna in accordance with an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    In the following description, for purposes of explanation and not limitation, details and descriptions are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from these details and descriptions. 
         [0024]    The antennas and methods described in accordance with embodiments of the present invention reduce the number of components in a wireless antenna to a as few as a single component, and thus significantly reduce the complexity and costs associated with antenna fabrication. Embodiments of the invention achieve this goal by manufacturing cost-effective antenna structures using a thermoforming process. Thermoforming may refer to the process of forming a thermoplastic sheet into a three-dimensional shape by clamping the sheet in a frame, heating it to render it soft and pliable, then applying differential pressure to make the sheet conform to the shape of a mold or die positioned below the frame. When the pressure is applied entirely by vacuum, the process is called ‘vacuum forming.’ 
         [0025]    In accordance with the various embodiments of the present invention, prior to vacuum forming, a conductive antenna pattern may be printed, deposited, or placed (hereinafter, collectively referred to as ‘applied’) on a plastic sheet or other nonconductive carrier material. The conductive antenna pattern may be applied to one or both sides of the plastic carrier. In some applications, however, it may be advantageous to use the plastic sheet as a protective layer by applying the antenna pattern to the bottom of the plastic carrier. This configuration, which may also provide an enhanced cosmetic appearance, can be used to implement an integrated contact point between the antenna terminals and the circuit board of the wireless device. Once the conductive material is applied to the plastic carrier, the vacuum forming process, or other processes for providing a pressure differentiated forming, creates one or more low cost antennas with an integrated plastic carrier. A laser or other cutting mechanism may be used to subsequently cut out individual finished antenna structures that are now ready to be integrated into various communication devices. 
         [0026]    The conductive pattern may be applied using a variety of techniques, including, but not limited to, printing conductive (e.g., silver) inks, placing or attaching copper or aluminum sheets, or depositing copper or other conductive materials on the plastic sheet using electro-deposition or similar techniques. The conductive material may be any one of silver, copper, aluminum, gold, or other conductive elements or composites. In one embodiment, the antenna pattern may be cut, punched, or etched onto the conductive material prior to it application to the plastic sheet. It should also be noted that the choice of non-conductive material is not limited to plastic, and it may comprise any material that can be formed by the thermoforming process. 
         [0027]      FIG. 1  illustrates a flow diagram of an antenna forming process in accordance with an exemplary embodiment of the present invention. This exemplary embodiment uses a stencil printer to print the conductive antenna pattern on a non-conductive carrier. Step  100  includes providing the conductive ink for printing. Step  102 , which may be carried out at the same time as Step  100 , includes providing the carrier, which may comprise a non-conductive material such as plastic. However, as noted earlier, the carrier may include any suitable material other than plastic that can be utilized in the thermoforming process. In Step  104 , printing of the conductive antenna pattern on the carrier takes place. The printing process may be carried out using, for example, a Surface Mount Technology (SMT) stencil printer that is used in the manufacturing of electronic circuit boards. Alternatively, screening techniques and apparatus may be used for printing the conductive pattern on the carrier. Furthermore, depending on the antenna design specifications and preferences, the conductive pattern may be printed on one or both sides of the carrier sheet. 
         [0028]    Referring again to  FIG. 1 , Step  106  includes forming of the antenna by utilizing the thermoforming process. This step may be carried out using a vacuum forming apparatus, such as those utilized in, for example, the packaging industry. For example, an FDH Series vacuum forming machine, manufactured by Formech Inc., may be used. Of course, other manners of providing the necessary pressure differential may also be used and are contemplated within the scope of the present invention. In Step  108 , the thermoformed antennas are: dried. A reflow oven or other drying system is used to cure the silver ink. Finally, in Step  110 , the thermoformed antennas are cut into individual antenna assemblies that can be incorporated into wireless devices or other communication systems. The cutting (Step  110 ) may be carried out using a laser cutter or other cutting apparatus. In one example embodiment, the plurality of thermoformed antennas may reside in a two-dimensional array and are subsequently separated or cut out to form the individual antennas. 
         [0029]      FIG. 2  illustrates a flow diagram of an antenna forming process in accordance with an another embodiment of the present invention. Step  200  includes providing a conductive film or layer for producing the antenna pattern. Step  202 , which may be carried out at the:same time as Step  200 , includes providing the carrier, which is comprised of a suitable non-conductive material such as plastic. In Step  204 , the conductive pattern is applied to the non-conductive carrier using techniques such as printing, deposition, or attachment. Steps  206  through  210  are similar to those described in connection with Steps  106  to  110  of  FIG. 1 . More specifically, in Step  206 , the antennas are formed using thermoforming techniques. In Step  208 , the antennas are dried, and in Step  210 , the antennas are cut into separate antenna assemblies that can be deployed in wireless or other communication systems. While the embodiments of the present invention, as illustrated in  FIGS. 1 and 2 , describe several exemplary steps for forming the antennas of the present invention, it is understood that the scope of the antenna forming process in accordance with the embodiments of the present invention encompasses variations to the above-described antenna forming processes. For example, one or more steps of  FIGS. 1 and 2  may be removed, combined, or carried out in a different order. For example, in another embodiment, a carrier sheet may be thermoformed prior to the application of a conductive layer. In accordance with this exemplary embodiment, the conductive layer, which may be applied after the thermoforming process, can be a metalized film with an adhesive layer for attachment to the formed carrier. 
         [0030]      FIG. 3  shows an antenna  30  that may be formed in accordance with an exemplary embodiment of the present invention. The exemplary antenna  30  of  FIG. 3  comprises an external conductive pattern  31 , and is formed by applying the conductive material to the top of the plastic carrier  32  prior to thermoforming the three-dimensional antenna structure  30 . The antenna  30  may be placed on a PCB  33  or otherwise integrated into a communication device.  FIG. 4  illustrates another exemplary antenna  40  in accordance with an embodiment of the present invention. This exemplary antenna  40  comprises an internal conductive pattern (not visible in  FIG. 4 ), and may be formed by applying the conductive pattern to the bottom side of the plastic carrier  42  prior to thermoforming the three-dimensional antenna structure. The antenna  40  may be placed on a PCB  43  or otherwise integrated into a communication device. The internal conductive pattern may also be used to implement an integrated contact point between the ground and/or electrical feeds associated with the antenna  40  and the appropriate connections on the PCB  43 . 
         [0031]    In another embodiment of the present invention, tape-and-reel packaging techniques may be adapted to enable manufacturing of low cost integrated antennas. Tape-and-reel packaging comprises a carrier ‘tape’ with formed cavities for holding the SMD (surface mount device) components.  FIG. 5(   a ) illustrates an exemplary tape  50  with a plurality of formed cavities  52 . A tape-and-reel package may accommodate up to several hundreds of thousands components that may be used by pick-and-place machines for automated assembly of electronic circuit boards, for example. In accordance with an example embodiment of the present invention, the plastic ‘tape’  50  may be metalized by applying one or more antenna conductive patterns on the ‘tape’ strip prior to forming the cavities  52 . Once the cavities are formed, individual antennas may be cut out from the strip, and used for integration into communication devices.  FIG. 5(   b ) illustrates a series of exemplary antennas that are formed, in accordance with an exemplary embodiment of the present invention, by applying one or more conductive antenna patterns  54  on a tape strip  50 , prior to forming of the cavities  52 . It should be noted that while, in  FIG. 5(   b ), only the conductive antenna patterns  54  on top side of cavities  52  are visible, antenna patterns may exist on either or both sides of the formed cavities. The antennas formed in this fashion are arranged in a single column that may be placed onto a reel and cut into individual antennas at a later time. The placement of the conductive patterns on the plastic tape carrier may be accomplished using any one of the techniques described in connection with Step  104  of  FIG. 1 , or Step  204  of  FIG. 2 . 
         [0032]    In accordance with another embodiment of the present invention, the conductive material may be applied to one or both sides of a carrier to form a two-dimensional sheet with a plurality of antenna patterns. The two-dimensional antenna patterns may further be folded along predetermined locations to form the final three-dimensional antenna structures. This process may be facilitated by using a cutting apparatus, such as a laser cutter, to create ‘folding’ lines on the two-dimensional antenna sheets. Alternatively, or additionally, the thermoforming process can be used to form the folding lines. The individual two-dimensional antenna structures may then be folded along these lines at any time prior to the integration of the antennas into the communication devices.  FIGS. 6   a - b  illustrate an exemplary two-dimensional antenna  60  that may be folded along a plurality of folding lines  62  to form a three-dimensional antenna structure  64  in accordance to an exemplary embodiment of the present invention. 
         [0033]      FIGS. 7   a - b  illustrate another antenna in accordance with an exemplary embodiment of the present invention. Antenna  70  is placed (or attached) to a printed circuit board (PCB)  71  or another intended device.  FIGS. 7   a - b  show a cross sectional view of a thermo-formed antenna  70  that comprises a thermoformed cylindrically shaped protrusion  72  for providing mechanical and/or electrical contact with a PCB  71 . The cylindrical protrusion  72 , or other custom-shaped feature, may be designed to fit into a cavity or depression on the circuit board. If the cavity on the circuit board is plated, then the cylindrically shaped protrusion on the antenna with conductive coating will provide electrical continuity between the antenna and circuit board. In the exemplary embodiment of  FIGS. 7   a - b , heat stacking, a process which forms a bond by partially melting a protrusion of one plastic part to provide a locking fit to another component, is used. The location that is heat stacked to the PCB may be isolated from the electrical connections for the antenna, or may be used to feed the antenna and/or provide a ground connection. In the exemplary embodiment of  FIGS. 7   a - b , the antenna comprises both an external conductive pattern  74  (that is applied to the top of the non-conductive carrier  73 ) and an internal conductive pattern  75  (that is applied to the bottom of the non-conductive carrier  73 ). In one exemplary embodiment, the antenna feed and/or ground connection may be provided through the conductive layer that surrounds the cylindrical protrusion  76 . 
         [0034]    In accordance with another embodiment of the present invention, integrated contact bumps are implemented for providing electrical connection between the feed and/or ground point of the thermoformed antenna and the circuit board of the communication system.  FIGS. 8   a - b , in accordance with an exemplary embodiment of the present invention, illustrate a PCB  83 , and a thermoformed antenna  80  that comprises an internal conductive pattern  81 , one or more heat stacking pins  82 , and one or more integrated contact bumps  84 . The one or more integrated bumps  84  are situated close to one or more heat stacking pins  82 , and comprise plastic bumps that are covered by conductive material and collectively formed in a thermoforming process. The bumps act as ‘springs,’ and are situated at desired locations to allow positive contact pressure to apply between the feed and ground points of the antenna and the appropriate locations on the PCB  83 . The contact force is a function of the plastic wall thickness and the dimensions of the bump. 
         [0035]    In accordance with another embodiment of the present invention, metalclips are used to provide a connection between the antenna feed and/or ground locations of the thermoformed antenna and the circuit board.  FIGS. 9   a - c  illustrate an exemplary embodiment comprising a thermoformed antenna  90  that is placed on a PCB  92 . The exemplary antenna  90  has an external conductive pattern  91  and one or more metallic contact clips  93  that connect the antenna feed and/or ground to the PCB  92 . The contact force is determined by the dimensions of the clip and the thickness of the antenna walls. The exemplary contact clip of  FIG. 9  comprises a stem  93 A that is designed to fit into a plated through hole of the PCB  92 . In an alternate embodiment, a contact clip with no stem (or a smaller stem) may be utilized that allows electrical contact between a conductive pad on the PCB  92  and the contact clip  93 . Soldering or a conductive epoxy can be used to maintain contact between the contact clip and pad on the circuit board. 
         [0036]    In accordance with another embodiment of the present invention, electrical contact between the feed and/or ground locations of an antenna with a circuit board may be effected using a contact spring.  FIGS. 10   a - c  illustrate an exemplary embodiment comprising a thermoformed antenna  120  that is connected to a PCB  122 . The exemplary antenna  120  has an internal conductive pattern  121  and one or more contact springs  123  that connect the feed and/ground on the internal antenna pattern to the PCB  122 . 
         [0037]    While particular embodiments of the present invention have been disclosed, it is to be understood that various modifications and combinations are possible and are contemplated within the true spirit and scope of the appended claims. There is no intention, therefore, of limitations to the exact abstract and disclosure herein presented.