Abstract:
A conductive layer is applied to a thermoformed plastic component to form an integrated antenna assembly. The conductive layer is on a flexible layer and adhered or attached to the rigid thermoformed plastic carrier. Features are designed into the thermoformed plastic carrier to provide electrical contacts from the conductive layer to the circuit board of the communication device and to mechanically attach the carrier to the circuit board. Multiple conductive layers can be applied to a multi-layered thermoformed structure to form a multi-antenna assembly.

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 fabricating 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 techniques suffer from a 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 not suited for high-volume and cost-efficient production needs. 
       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 present invention, a method for forming an antenna comprises the steps of; pre-forming a carrier element by thermoforming a non-conductive sheet material into a three-dimensional configuration; providing the pre-formed carrier element, a dielectric thin-sheet material, and a conductive material; applying the conductive material to the thin-sheet material to form a conductive layer on the thin-sheet material; and attaching the thin-sheet material to at least one surface of the pre-formed carrier element. The resulting assembly is an integrated antenna and carrier ready for assembly into a wireless device or other communication system. In a preferred embodiment, the carrier element can be pre-formed by using a vacuum forming process to form a non-conductive sheet material into a three-dimensional carrier element. 
         [0006]    In one embodiment of the present invention, the conductive layer can comprise a conductive ink, for example a silver ink. Alternatively, the conductive layer can comprise one or more deposited metals, one or more conductive films, or any other conductive material. The conductive layer formed on a thin-sheet material can be referred to as an antenna element. 
         [0007]    In another embodiment, the dielectric thin-sheet material can be stretchable, bendable, or flexible. The antenna element on the flexible sheet can be placed on the top surface of the thermoformed carrier element. This results in the conductive element on the outer surface of the integrated antenna assembly. 
         [0008]    In another embodiment, the antenna element on the flexible sheet is placed on the bottom surface of the thermoformed carrier element. This provides a more cosmetic finish and mechanical protection for the conductive layer. 
         [0009]    In yet another embodiment, the antenna element can be placed on both the top and bottom surfaces of the carrier element. 
         [0010]    In another embodiment, the applying of the conductive layer comprises at least one of a printing, depositing, or placing of the conductive material on at least one surface of the dielectric thin-sheet material. 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 carrier elements that are separated into individual carrier element structures with a cutting apparatus. 
         [0011]    In another embodiment, multiple antenna elements, each on flexible sheets can be stacked on a thermoformed carrier to form a multi-antenna assembly. In another embodiment, multiple thermoformed carriers, each with an antenna element on a flexible sheet attached thereto, can be stacked to form a multi-antenna assembly. 
         [0012]    In another embodiment, multiple thermoformed carriers for the same or different antenna functions are combined in the same assembly. Antenna elements of the same or differing design and function are applied to the thermoformed carriers to complete a multi-antenna suite for a communication device. 
         [0013]    In another embodiment, the thermoformed carriers are fabricated in sheet form, with carriers formed in a one or two dimensional array. In another embodiment, the thermoformed carriers are formed using a tape and reel method, where single or multiple carriers in columns are thermoformed and placed into a reel. The antennas on flexible thin-sheets are attached to the thermoformed carriers subsequent to fabrication of the carriers. 
         [0014]    Another aspect of the present invention is the method of forming one or more raised areas on the edge of the thermoformed carrier for making contact with the circuit board. Feed and/or ground connections for the antenna element wrap around the edge of the thermoformed carrier, with the raised area providing pressure contact with the feed and ground pads on the circuit board of the communication device. 
         [0015]    Another aspect of the present invention is a thermoformed plastic carrier with an opening cut or etched into a portion of the carrier. A conductive layer is wrapped around the edge of the opening, with the conductive layer on both upper and lower surfaces of the carrier. This assembly can be positioned between two thermoformed antenna assemblies and used to make electrical connection between the thermoformed antennas. 
         [0016]    In another embodiment, bumps are formed on the plastic sheet at the desired locations of the feed and ground points of the antenna. Positive pressure contact is made between the feed and ground bumps and the circuit board. 
         [0017]    In another embodiment, metal clips are used to connect the feed and ground locations on the thermoformed antenna to plated-thru holes on the circuit board. In another embodiment, a conductive pad on the circuit board can replace the plated-thru hole. 
         [0018]    Another aspect of the present invention relates to an antenna comprising a non-conductive portion, a conductive portion, and one or more protrusions for connecting at least one of a ground and an electrical feed associated with the antenna to a circuit board. The antenna is fabricated by pre-forming a carrier element using a thermoforming, or preferably a vacuum forming process; providing the pre-formed carrier element, a dielectric thin-sheet material, and a conductive material; applying the conductive material to the thin-sheet material to form a conductive layer on the thin-sheet material; and attaching the thin-sheet material to at least one surface of the pre-formed carrier element. 
         [0019]    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 
         [0020]      FIG. 1  illustrates an exemplary flow diagram in accordance with an example embodiment of the present invention. 
           [0021]      FIG. 2  illustrates an integrated antenna assembly comprising a conductive antenna element attached to the top side of a thermo-formed plastic carrier. 
           [0022]      FIG. 3  illustrates an integrated antenna assembly comprising a conductive antenna element attached to the bottom side of a thermo-formed plastic carrier. 
           [0023]      FIG. 4  illustrates an integrated antenna assembly comprising a conductive antenna elements attached to both the top and bottom side of a thermo-formed plastic carrier. 
           [0024]      FIG. 5  illustrates an integrated antenna assembly comprising two thermo-formed plastic carriers, one on top of the other, with conductive antenna elements attached to both the top and bottom side of each thermo-formed plastic carrier. 
           [0025]      FIG. 6  illustrates thermoformed integrated antenna assemblies manufactured by tape and reel techniques. 
           [0026]      FIG. 7  illustrates contact clips used to establish an electrical connection between the feed and ground point of the conductive antenna element attached to the thermoformed carrier and the circuit board of the wireless system. 
           [0027]      FIG. 8  illustrates the use of a contact spring to make electrical connection between the feed and/or ground point of the conductive element and the circuit board of the wireless system. 
           [0028]      FIG. 9  illustrates integrated contact bumps used to establish an electrical connection between the feed and/or ground point of the conductive element and the circuit board of the wireless system. 
           [0029]      FIG. 10  illustrates heat stack pins which attach the thermoformed carrier to the circuit board. An embossed region is formed in the feed point region to provide rigidity to assist in applying pressure to feed legs. 
           [0030]      FIG. 11  illustrates heat stack pins which attach the thermoformed carrier to the circuit and to apply pressure to the feed legs for electrical connection. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    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. 
         [0032]    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 two components, 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, cast or die positioned below the frame. When pressure is applied entirely by vacuum, the process is called ‘vacuum forming’. 
         [0033]    In accordance with the various embodiments of the present invention, in parallel with vacuum forming the carrier, a conductive antenna pattern may be printed, deposited, or placed (hereinafter, collectively referred to as ‘applied’) on a dielectric thin-sheet. The thin sheet can be a plastic sheet or other non-conductive carrier material. The thin sheet will have a material thickness between about 0.0001 inches and about 0.0500 inches, and more preferably between about 0.0001 inches and about 0.0200 inches. The thin sheet can be bendable, flexible, stretchable, or any combination thereof. The conductive antenna pattern may be applied to one or both sides of the thermoformed plastic carrier. In some applications, however, it may be advantageous to use the plastic carrier 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 vacuum formed plastic carrier, a low cost antenna assembly is created. 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. 
         [0034]    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 conductive sheets such as 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 its 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. The conductive element, or plurality thereof, can be attached to the thermoformed carrier element by an attachment means such as a glue, adhesive, melt bond, chemical bond, solvent bond, or mechanical fit such as a friction fit. 
         [0035]      FIG. 1  illustrates a flow diagram of an antenna forming process in accordance with an exemplary embodiment of the present invention. In Step  100  this exemplary embodiment involves applying conductive ink to a dielectric thin-sheet (an example would be silver ink applied on a 0.003 inch thick Mylar® or other polyester film) that is then cured in Step  101  to form the antenna element. An antenna element can be cured using a reflow oven or other drying system to cure the conductive ink. Step  102  includes providing the carrier material, 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. The carrier material, herein referred to as a thermoformable carrier material, will have a melting temperature (T m ) between about 50.0° C. and about 500.0° C., and preferably between about 50.0° C. and about 300.0° C. The carrier material will have a relaxed state at temperatures below 50.0° C., and will be rigid in the relaxed state. In Step  104 , the antenna is attached to the thermoformed plastic carrier with an adhesive. Furthermore, depending on the antenna design specifications and preferences, the conductive pattern may be adhered to one or both sides of the thermoformed carrier. Finally, in Step  105  the thermoformed antennas are cut into individual antenna assemblies that can be incorporated into wireless devices or other communication systems. The cutting (Step  105 ) 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. 
         [0036]      FIG. 2  shows an antenna that may be formed in accordance with an exemplary embodiment of the present invention. The exemplary antenna of  FIG. 2  comprises an external conductive pattern  21 , and is formed by adhering the conductive material to the top of the plastic carrier  20 . The combination thermoformed carrier  20  and conductive pattern  21  are attached by various methods to the PCB 22 . 
         [0037]      FIG. 3  shows an antenna that may be formed in accordance with an exemplary embodiment of the present invention. The exemplary antenna of  FIG. 3  comprises an internal conductive pattern  31 , and is formed by adhering the conductive material to the bottom of the thermoformed carrier  30 . The combination thermoformed carrier  30  and conductive pattern  31  are attached by various methods to the PCB  32 . These various methods will be described in detail below. 
         [0038]      FIG. 4  shows antennas that may be formed in accordance with an exemplary embodiment of the present invention. The exemplary antennas of  FIG. 4  comprise external conductive patterns  41  and  42 , and are formed by adhering the conductive patterns  41  and  42  to both the top and bottom of the plastic carrier  40 . The combination thermoformed carrier  40  and conductive patterns  41  and  42  are attached by various methods to the PCB 43 . 
         [0039]      FIG. 5  shows an integrated antenna assembly consisting two thermo-formed plastic carriers  50  and  51 , one on top of the other, with conductive antenna elements  52  and  53  attached to both the top and bottom side of each thermo-formed plastic carrier. The combination thermoformed carriers  50  and  51 , and conductive patterns  52  and  53  are attached by various method to the PCB 54 . 
         [0040]    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. 6  illustrates an exemplary tape  60  with a plurality of formed cavities  61 . For example, A tape-and-reel package may accommodate up to several hundred thousand components that may be used by pick-and-place machines for automated assembly of electronic circuit boards. 
         [0041]    In accordance with another embodiment of the present invention, metal clips are used to provide a connection between the antenna feed and/or ground locations of the thermoformed antenna and the circuit board.  FIGS. 7   a - c  illustrate an exemplary embodiment comprising a thermoformed antenna  70  that is placed on a PCB  72 . The exemplary antenna  70  has an external conductive pattern  71  and one or more metallic contact clips  73  that connect the antenna feed and/or ground to the PCB  72 . The thermoformed antenna can comprise a thermoformable anchoring element, such as a contact slot  74  for engagement with a contact clip  73 . As shown in  FIG. 7   b,  the contact slot can comprise one or more depressed channels which are thermoformed into the dielectric carrier prior to attachment of the conductive layer. The contact force is determined by the dimensions of the clip and the thickness of the antenna walls. The exemplary contact clip of  FIG. 7   c  comprises a stem  73 A that is designed to fit into a plated through hole of the PCB  72 . 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  72  and the contact clip  73 . Soldering or a conductive epoxy can be used to maintain contact between the contact clip and pad on the circuit board. 
         [0042]    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 achieved using a contact spring  81 .  FIGS. 8   a - c  illustrate an exemplary embodiment comprising a thermoformed antenna  82  that is connected to a PCB  80 . The thermoformed antenna can comprise a thermoformable anchoring element, such as a contact groove. The contact groove  84  can comprise a depressed channel, an elevated channel, or a flat contact surface thermoformed into the dielectric carrier for attachment of the conductive layer. The conductive layer can be integrated into the contact groove  84 , for a flush surface finish. The contact spring  81  can engage the contact groove  84  to complete a circuit. The exemplary antenna  82  has an internal conductive pattern  83  and one or more contact springs  81  that connect the feed and/ground on the internal antenna pattern to the PCB  80 . 
         [0043]    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. 9   a - b,  in accordance with an exemplary embodiment of the present invention, illustrate a PCB  93 , and a thermoformed antenna  90  that comprises an internal conductive pattern  91 , one or more heat stacking pins  92 , and one or more integrated contact bumps  94 . The one or more integrated bumps  94  are situated close to one or more heat stacking pins  92 , and comprise a dielectric notch  95  formed in a thermoforming process. The integrated bumps  94  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  93 . The thermoformed antenna can comprise a thermoformable anchoring element, such as the thermoformed dielectric notch  95 . A thermoformed dielectric notch  95  can be thermoformed into the dielectric carrier prior to attachment of the conductive layer. The thermoformed notch  94  can be configured to engage a heat stacking pin  92  having a thermoformed dielectric notch  95  aligned with the integrated contact bump  94 . The contact force is a function of the plastic wall thickness and the dimensions of the bump. 
         [0044]    In accordance with another embodiment of the present invention, the dielectric thermoformed carrier can comprise an embossed or depressed region  105  formed into the thermoformed carrier to assist in providing positive pressure for electrical connection between antenna feed and/or ground legs and the contacts on the circuit.  FIG. 10 , in accordance with an exemplary embodiment of the present invention, illustrates a PCB, and a thermoformed antenna  100  that comprises an internal conductive pattern  101 , one or more heat stacking pins  102 , and one or more integrated contact bumps  103 . The heat stacking pins are not located close to the integrated contact bump, so an additional integrated contact bump  104  is placed perpendicular to the contact bump that intersects the silver ink pattern, to assist in providing positive contact pressure between the feed and ground points on the antenna and the appropriate locations on the PCB. In an alternative embodiment, one or more screws can be used to provide pressure between the feed and ground points on the antenna and the appropriate locations on the PCB. In another embodiment, one or more screws can be used in combination with one or more heat stacking pins. 
         [0045]    In accordance with another embodiment of the present invention,  FIG. 11 , illustrates a PCB, and a thermoformed antenna  110  that comprises an internal conductive pattern  111 , one or more heat stacking pins  112 , and one or more integrated contact bumps  113 . One of the heat stacking pins is located in close proximity to the integrated contact bump, to assist in providing positive contact pressure between the feed and ground points on the antenna and the appropriate locations on the PCB. 
         [0046]    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.