Abstract:
A strain-resistant electrical connection and a method of making the same is provided. An antenna ( 36, 38 ) or other conductive lead is connected to a circuit ( 32 ) in a manner that makes the connection more resistant to mechanical stresses such as movement or rotation of the antenna ( 36, 38 ) or conductive lead relative to the circuit ( 32 ). The antenna ( 36, 38 ) or conductive lead is at least partially coiled to provide additional ability to withstand mechanical stresses. The antenna ( 36, 38 ) or conductive lead may be encase along with is connected circuit in an elastomeric material.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates to a strain and/or fatigue-resistant antenna connection and a method of making the same. More specifically, the present invention provides for a robust connection at an antenna connection point associated with an RFID device that makes the connection more resistant to fatigue failure caused by mechanical stresses such as movement or rotation of the antenna relative to the circuit. In the present invention, the antenna may be coiled or otherwise shaped to provide additional ability to accommodate mechanical strain without failure In certain embodiments, an elastomeric material may be configured around the antenna and the RFID circuit so as to create a protective region for the antenna and RFID device. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electronics integrated within a tire or other product offer potential advantages such as asset tracking and measurement of physical parameters as, for example, temperature and pressure. Often many of these systems rely on a wireless data link to communicate with an information system outside of the vehicle. Such information systems may include, as non-limiting examples, on-board computer systems, drive-by interrogators, or hand-held interrogators. In addition, the types of data communicated over such wireless data links are wide and varied and include such as not only the previously mentioned temperature and pressure but also other physical parameters such as tire rotation speed as well as data corresponding to manufacturing data and a host of other information. What ever the type of data transmitted, the wireless data link requires an antenna to be attached to the electronics in the tire. If the electronics and/or antenna are adhered to the tire rubber, flexing of the tire, either due to the tire building process or normal use can cause the antenna to separate from the electronics due to cracking, breaking, or fatigue. 
         [0003]    The present invention primarily concerns physical factors such as mechanical stress leading to fatigue, which in turn can cause a circuit malfunction by physically breaking or weakening a specific part of the circuit. A typical location for such malfunction is at or near the point of connection of a wire, lead, or other conductor to an electrical circuit. In circumstances where the wire and the connected-to circuit may move or rotate relative to one another, the wire may incur a concentration of mechanical stress and/or fatigue at or near the point of connection to the circuit. Mechanical stresses such as repeated bending or twisting, for example, can lead to a weakening of the wire until a break occurs. 
         [0004]      FIG. 1  provides an example of the problem addressed. In  FIG. 1 , lead  20  is connected to a printed circuit board  22  by a soldered connection  24 . As lead  20  is twisted (as illustrated by arrow A), repeatedly bent (as illustrated by arrows B and C), or placed into tension or compression (arrow D), a concentration of stress occurs at or near the point of connection  26 . Over time, as lead  20  is exposed to repeated mechanical cycles that provide for this concentration of stress, lead  20  may eventually weaken due to repeated deformation or cyclical movement. As a result, lead  20  will likely suffer a fatigue failure (or break) either at or near point of connection  26 . 
       SUMMARY 
       [0005]    Various features and advantages of the invention will be set forth in part in the following description, or may be apparent from the description. 
         [0006]    The present invention provides a robust electrical connection for an antenna for an RFID device and a method of creating such connection that is resistant to mechanical stresses that can occur when a wire or lead is twisted or caused to bend repeatedly about its connection to a circuit. Generally speaking, with the present invention, methodologies are provided that provide a reduction in the stress and strain involving an antenna near its point of connection to an RFID device although, of course, the same principles may be applied to any electrical connection to any electrical device without limitation to antennae and RFID devices. In a first exemplary embodiment of the present subject matter, antenna elements are provided that include at least a coiled portion near the connection point to the RFID device. 
         [0007]    In one exemplary method of the present invention, a process for creating a fatigue-resistant antenna connection is provided in which a coiled wire antenna is soldered or otherwise secured to an anchor point such that at least a portion of the coils of the coiled wire antenna are free of solder, or other securing agent, allowing some amount of stretching in the non-secured coils to allow reduced stress and/or strain on the actual antenna connection point. 
         [0008]    In another exemplary embodiment of the present subject matter, methodologies are disclosed allowing the coupling of differing form factor wires to be used as antenna components for RFID devices. 
         [0009]    In still another exemplary embodiment of the present subject matter, a temporary mounting configuration is provided lends support to the antenna and RFID devices during a manufacturing process. 
         [0010]    In yet another exemplary embodiment of the present subject matter, the RFID device and antenna elements are encased in an elastomer material to provide physical protection for the RFID device as well as to assist in lessening stress on the antenna to RFID device connection point. 
         [0011]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A full and enabling disclosure of the present subject matter, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
           [0013]      FIG. 1  illustrates an example of an electrical connection in which a lead is soldered to a printed circuit board; 
           [0014]      FIG. 2  illustrates an example of an antenna connection in which a coiled antenna wire is soldered to a printed circuit board; 
           [0015]      FIG. 3  illustrates another example of an antenna connection in which a partially coiled antenna wire is soldered to a printed circuit board; 
           [0016]      FIG. 4  illustrates an exemplary mounting method according to the present subject matter; and 
           [0017]      FIG. 5  illustrates another exemplary mounting method according to the present subject matter. 
       
    
    
       [0018]    Repeat use of reference characters throughout the present specification and appended drawings is intended to represent same or analogous features or elements of the invention. 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0019]    Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations. 
         [0020]      FIGS. 2 and 3  provide illustrations of first and second exemplary embodiments of antenna connections to RFID devices according to the present subject matter. As illustrated in  FIGS. 2 and 3 , a printed circuit board  32  is shown as might be found in any electronics but, for the present subject matter, an RFID device  34  principally embodied as an integrated circuit component is illustrated. The RFID device  34  wirelessly transmits data to a remote receiver and/or receives data from a remote transmitter by way of a dipole antenna configuration consisting of antenna elements  36 ,  38 . In these exemplary embodiments, antenna elements  36 ,  38  are formed as coiled wires with two separate portions each with a different pitch, i.e., number of coil turns per unit length. 
         [0021]    A first section  36 ′,  38 ′ of antenna elements  36 ,  38  respectively in each of the  FIGS. 2 and 3  embodiments, is formed of coil turns having a higher pitch, i.e., a higher number of turns per unit length, than antenna sections  36 ″,  38 ″ of antenna element  36 ,  38 , respectively. In fact, sections  36 ″,  38 ″ of the embodiment illustrated in  FIG. 3  have a zero pitch, i.e., zero turns per unit length or, more directly, a straight wire. Antenna elements  36 ,  38  with their various coil pitches may be constructed in various manners. As non-limiting examples only, the antenna elements  36 ,  38  may be formed from a single section of wire and coiled at one end with coil turns of one pitch and at the other end with coil turns of a second (including zero) pitch. In the case of the embodiment illustrated in  FIG. 3 , the zero pitch portion may also be provided by securing a separate, straight wire to a coiled section. Such a straight wire may be soldered, butt welded or secured in any known manner. In addition, the straight wire portion may be formed from a monofilament section or a multi-strand section. Moreover the diameter of the zero pitch section may be significantly greater than that of the conductor forming the higher pitched coil portion of the antenna element. An example of this larger diameter configuration may be seen in  FIG. 5  and will be discussed more fully later. 
         [0022]    While a number of connection methodologies may be used with the present invention,  FIGS. 2 and 3  illustrate a soldered connection  40 ,  42  between antenna  36 ,  38  and RFID component  34  to printed circuit board  32 . Printed circuit board  32  has been used to illustrate this particular exemplary embodiment but the present invention is not limited to use with only a printed circuit board. As illustrated in  FIGS. 2 and 3 , the end portion of the higher pitched coils  36 ′,  38 ′ of antenna elements  36 ,  38  along with respective leads  44 ,  46  from the RFID device  34  are soldered together and to a solder pad on printed circuit board  32 . An example of the solder pad is more readily seen from the embodiments illustrated in  FIGS. 4 and 5  as will be described more fully later. 
         [0023]    The provision of two different pitches in the antenna elements offers improved performance from the RFID and antenna configuration in two respects. First, the higher pitched turns are provided in the high stress transitions zones allowing for a higher distribution of any stress applied to such portion of the antenna element. This higher pitched turns section also operates as an inductive element thereby shortening the overall length of the antenna elements for the operating frequency thereby allowing a smaller overall package to be constructed. The lower or zero pitch coil sections may be provided in lower stress areas as less stress needs to be dispersed and the lower pitch coils provides a longer antenna and, thereby, a larger target area in which to position data transmission devices. 
         [0024]    Finally, it will be noted that the RFID and antenna combinations illustrated in  FIGS. 2 and 3  are surrounded by a dotted line oval  50 . Such is meant to represent the fact that the RFID device may be completely enclosed in a suitably shaped elastomeric material to provide further protection of the RFID device. Such elastomeric material is designed to not only surround the various components of the RFID device  34  and antenna elements  36 ,  38 , but to actually fill the voids within the coil turns of the antenna elements. Elastomeric materials placed in this manner will tend to assist in minimizing movement of the antenna elements and, thereby, assist in reducing stresses applied to the elements. 
         [0025]    Third and fourth embodiments of the present subject matter will now be described with reference now to  FIGS. 4 and 5 .  FIGS. 4 and 5  both illustrate plan views of RFID and antenna configurations wherein an RFID device  34  is secured to printed circuit board  32  using industrial accepted methods. Antenna elements  36 ,  38 , as in the first and second embodiments of the present subject matter, also include portions  36 ′ and  38 ′ of higher pitched coil turns as well as section  36 ″ and  38 ″ containing lower pitched, in fact zero pitched, coil turns in the form of straight wire portions. As is apparent from examination of  FIGS. 4 and 5 , the straight wire portions  36 ″ and  38 ″ of the two embodiments differ by the substantial difference in their respective wire diameters. In both cases, however, the straight wire portions  36 ″ and  38 ″ may be provided from either solid or stranded wire segments. 
         [0026]    An additional feature in the presently illustrated embodiments of the present subject matter is shown as a plurality of perforations  70 ,  72 ,  74 ,  76  strategically placed in pairs between solder connections  40 ,  40 ′ and  42 ,  42 ′. Solder pads  60 ,  66  on each end portion of printed circuit board  32  provide securing sites where solder connections  40 ′,  42 ′ may be used to secure one end of antenna sections  36 ′,  38 ′ to one end of antenna sections  36 ″,  38 ″ respectively. As the RFID device  34  and assembled antennae are sealed in elastomeric material  50 , the portions  80 ,  82  of printed circuit board  32  between perforations  70 ,  72  and  74 ,  76  respectively, are designed to break away as the elastomeric material is cured. Breaking away of the printed circuit board portions  80 ,  82  permits coiled antenna portions  36 ′,  38 ′ to more effectively disperse any forces applied to the antenna elements that may have a negative impact on the connection points to the RFID device. 
         [0027]    Using the teachings disclosed herein, one of ordinary skill in the art will appreciate that other embodiments of the present invention exist that fall under the scope of the appended claims. In fact, it should be appreciated by those skilled in the art that modifications and variations can be made to the connection and method as described herein, without departing from the scope and spirit of the claims. It is intended that the invention include such modifications and variations as come within the scope of the appended claims and their equivalents.