Patent Abstract:
An electrical connector for interconnecting a display to a printed circuit board is disclosed. One application of the invention provides connection between a liquid crystal display (“LCD”) and a circuit board. The connector is capable of serving a dual function as both a lightguide that disperses light for the display, and as an electrical connector for interconnection of the display with the circuit board. A leg member is mounted on the connector, and the leg member includes a row of contact feet for electrical communication. The connector may include a plurality of spaced apart U-shaped strip members mounted in parallel upon a leg member, with contact feet that extend upwardly to resiliently mate with contact pads of the display and downwardly to resiliently mate with contact pads of a printed circuit board.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to electrical connectors in general, and more particularly to electrical connectors used to interconnect a display device such as a liquid crystal display (“LCD” or “LCD&#39;s”) to a circuit board, in a stacked configuration.  
           [0002]    Prior art methods and devices are known for interconnecting electronic assemblies. Such methods and devices are used to connect relatively small components to adjacent electronic components, such as circuit boards. A significant problem with conventional methods and devices for interconnecting LCD&#39;s to their respective associated electronic components is the limited space afforded for such connections and assembled components.  
           [0003]    To reduce the overall size of the end product, it is desirable to vertically “stack” such components when possible. LCD&#39;s may be arranged in a vertically stacked arrangement. LCD&#39;s often are provided in association with a lightguide device that is incorporated into the stack and adapted for distributing light around the periphery of an LCD. A typical LCD assembly mounted upon a cellular telephone, for example, includes an upper display portion and a lower circuit board portion. Sandwiched between the LCD and the circuit board is the optical lightguide. Occasionally, a connector is provided between the LCD and circuit board (i.e. adjacent the lightguide device).  
           [0004]    Historically, LCD&#39;s have employed connections which appear on the underside of the display, with a semiconductor chip located away from the display, such as on the circuit board itself. However, modern assemblies sometimes include a mounted semiconductor chip on the glass of the upper display. A chip mounted on the glass of the upper display is helpful in some instances because it reduces the overall number of contact pads that must be provided on the lower surface of the LCD, due to the lesser number of communications that must be made external to the LCD in that instance.  
           [0005]    Connectors designed to interconnect an LCD with a circuit board typically have been comprised of elastomeric or foam material that springs back when compressed. For example, U.S. Pat. No. 5,709,576 to Lippmann discloses an elastomeric connector that couples terminal pads of an LCD with corresponding terminal pads of a printed wiring board. Sense pads are located on the terminal strips and arranged so that a continuity test on substantially opposed contact pads will verify pad alignment. In some applications, the tendency of such elastomeric materials to resume their original shape after deformation is relied upon as a means to hold contacts in close association within the sandwich structure.  
           [0006]    Elastomeric connectors may feature solderless contacts that connect the electrical contact pads on the LCD display with those on the printed circuit board. However, such elastomers sometimes lose their elasticity. Sometimes, electrical connection becomes faulty in such LCD&#39;s after a period of time. Elastomeric materials of this type may comprise rubbery or foamed materials that lose some of their elasticity due to age, heat, or a combination of age and heat. When a loss of elasticity occurs, the electrical connection, which depends upon such elasticity to hold contacts in resilient communication with each other, may become faulty. Slight movement of the elastomeric connector at high temperatures or in the presence of vibration may cause undesirable conductivity problems.  
           [0007]    It is quite often difficult to solder or connect terminals or connectors between adjacent components without bridging adjacent terminals with solder. Also, it is difficult to maintain and ensure the correct relative position (sometimes called “registration”) between the components during the manufacturing process and in subsequent use of the end product.  
           [0008]    What is needed in the industry is a connector that is capable of integration with a lightguide in a reliable and compact arrangement. A display which is provided in a reliable connector and lightguide system that facilitates long term and reliable use of display devices at elevated heat and vibrational conditions would be very desirable. A system that facilitates reliable registration of electrical contacts during manufacture and use is needed.  
         SUMMARY OF THE INVENTION  
         [0009]    In the invention, an electrical connector for interconnecting a display (such as an LCD) to a circuit board is provided in a stacked configuration. The connector comprises an insulating body, the body being comprised of a material that is capable of providing light to illuminate the display. In some applications, this light emitting structure is called a “lightguide”. Furthermore, a leg member is provided as part of the connector. The leg member is disposed on the insulating body, and includes an outer surface that is configured for disposition adjacent to a circuit board to which the display has been electronically connected. Furthermore, at least one connector element is configured with the insulating body.  
           [0010]    In one embodiment of the invention, the connector element may comprise a first contact foot that extends beyond the outer surface of the leg member, to enable electrical communication with the liquid crystal display. Furthermore, a second contact foot extends beyond the outer surface of the leg member for electrical communication with a circuit board. In this embodiment, the connector is positioned for registration of the connector elements with electrical contacts that are located on the display and the circuit board.  
           [0011]    In one embodiment of the invention, the connector element includes a “U-shaped” member with a first end and a second end, wherein the U-shaped member has an arm portion with contact feet defined on the first end and contact feet defined on the second end. The connector element also comprises a closed-end that wraps around and fits upon the leg member configured in the body.  
           [0012]    In another embodiment of the invention, the connector includes an opening that is provided in the body itself. Furthermore, the leg member includes a plurality of connector elements that are aligned and separated from the body. The opening in the body is located at least partially between the leg member and the body. During manufacturing operations, connector elements provided on a carrier strip are aligned over the leg member of the body, and then crimped down upon the leg member. The carrier strip portion is knocked out of the opening (or space) within the body that is adjacent to the leg member, leaving an opening.  
           [0013]    At least one embodiment of the invention includes connector elements that comprise strip members which are bent into a closed-end and oppositely facing arms configuration. The contact feet are defined on the arms, and at least one of the arms is adapted for applying a resilient force to electrical contacts of the LCD.  
           [0014]    Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. The invention will be described in greater detail below through preferred embodiments as illustrated in the attached Figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The following Figures illustrate the invention:  
         [0016]    [0016]FIG. 1 is a perspective view of the connector assembly in a disassembled mode in which the parts are shown separated from each other for easy identification;  
         [0017]    [0017]FIG. 2 shows an integrated display assembly in which the parts are integrated as they would be in a finished product;  
         [0018]    [0018]FIG. 3 is a perspective view of the underside of the assembly, wherein the portions of the assembly are separated for identification;  
         [0019]    [0019]FIG. 4 is a top view of the connector (sometimes called a “lightguide”) of the invention;  
         [0020]    [0020]FIG. 5 is an end view of the connector shown in FIG. 4;  
         [0021]    [0021]FIG. 6 is a side view of the connector shown in FIGS.  4 - 5 ;  
         [0022]    [0022]FIG. 7 is a cross-sectional side view taken along lines X-X of FIG. 4 of the insulating body;  
         [0023]    [0023]FIG. 8 is an alternative embodiment of the invention showing a cross-sectional side view of a device having the upper contacts provided flat against the leg member and available for adhesive bonding to contact pads of the display device.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    Reference will now be made in detail to the presently preferred 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 in another embodiment to yield still a further embodiment. It is intended that the present invention include such modifications and variations.  
         [0025]    Radio telephones, sometimes called cellular telephones, have become increasing popular for both personal and commercial use. Radio telephones have become increasingly smaller to provide more convenient storage and portability. Consequently, the space or “real estate” on circuit boards within such telephones has become limited and valuable.  
         [0026]    A lightguide is a structure provided within an illuminated electronic device such as a radio telephone that may be utilized to illuminate a key pad of translucent keys by way of a light source that is internal to the device. The lightguide also may be utilized to support a key pad and a liquid crystal display for a radio telephone. In some designs, a lightguide is placed directly on a circuit board for hosting electronic components to generate and receive telecommunications signals. As a result, the lightguide may occupy a significant amount of circuit board real estate. Thus, circuit board space beneath a lightguide may be generally unusable for hosting electronic components.  
         [0027]    One or more wall portions may depend from a face of the lightguide to maintain a spaced apart relationship between the lightguide and the circuit board. These wall portions may be configured to contact the circuit board face to thereby define one or more compartments between the circuit board face and the lightguide face when the lightguide is secured within a housing.  
         [0028]    A key pad may be secured to the lightguide and may comprise a plurality of translucent keys. The keys may extend through the housing to facilitate operation of the radio telephone by a user. Each key also may extend through the lightguide. The end of each key may be engaged with a respective contact pad on the circuit board face, depending upon the particular configuration adopted in that cellular telephone.  
         [0029]    In general, the invention as disclosed herein may be used with any other electronic device that includes a display. It is not required that the display be of the liquid crystal type, and essentially any display mechanism that is capable of communicating electrically with a connector could be employed in the application of the invention. In conventional use, the assembly consists of a printed circuit board, a lightguide, and a connector that may be comprised of elastomeric materials. The connector is assembled with the lightguide, and therefore the lightguide and the connector are provided together in a one piece unit. The elastomeric portion may include a rubber or flexible connector that compresses and makes contact between ITO pads (Indian Tin Oxide). ITO Pads are small contact areas on the surface of the display that provide an electrical communication path between the connector and the display. Furthermore, the lightguide acts to disperse light around the outside of the display to highlight the display during use at nighttime, or during low light conditions.  
         [0030]    In the invention, a lightguide connector combination is provided to perform a dual function. First, the combination component operates as a light dispersal device, and second, it operates as a connector and insulator. In the manufacture of the invention, it is possible to assemble contacts directly upon the lightguide, which can eliminate the need for an elastomer in the use of the invention, and also eliminates the assembly operation of the elastomer into the lightguide. This saves manufacturing time and effort, and reduces costs.  
         [0031]    The retention device and leg member used in the invention relates to another co-pending U.S. patent application that is directed to other types of connector assemblies i.e., co-pending U.S. patent application entitled “Low Profile Electrical Connectors for Microphones”, filed on Jul. 15, 1999, (U.S. Ser. No. 09/354,402).  
         [0032]    Turning to FIG. 1, a connector assembly  21  is shown in perspective view in which a liquid crystal display (LCD) is shown in the upper part of the Figure. A connector  23  is shown below the liquid crystal display  22 , the connector  23  having an insulating body  24  that is adapted to mate or connect with a circuit board  26 . Connector elements  27  are provided in a row along a leg member  25  on the connector  23 . The connector  23  has an insulating body  24  that is adapted to disperse light around the edges to illuminate the liquid crystal display  22  when the assembly is integrated. Registration hole  29   a  is adapted for receipt of the alignment pin  37   a , which mates the connector elements  27  exactly in correct registration with contact pads  28  of the circuit board  26 .  
         [0033]    [0033]FIG. 2 shows the integrated display assembly  32  which comprises the components seen in FIG. 1 when completely mated together in an operable unit. A liquid crystal display (LCD)  22  emits light from its upper surface as emitted light  31 . Furthermore, the leg member  25  is shown immediately below the liquid crystal display  22 , and the circuit board  26  forms the bottom portion of the integrated display assembly  32 .  
         [0034]    [0034]FIG. 3 shows an exploded view of the connector assembly  21  from the bottom, revealing the circuit board  26  having registration holes  29   a - b  on its lower surface. Furthermore, the leg member  25  of the connector  23  is shown, having alignment pin  37   b  which is adapted for insertion into registration hole  29   b . Furthermore, liquid crystal display  22  receives light from the connector  23 . Connector elements  27  located along the leg member  25  are adapted to interact with contact pads  38  of the liquid crystal display  22  on the upper surface of the connector  23 , and the connector elements  27  interact with the circuit board  26  below the surface of the connector  23 .  
         [0035]    In FIG. 4, a top view of the connector  23  is shown. The insulating body  24  includes along one side a leg member  25  having connector elements  27  spaced along the leg member  25 . On opposite sides of the insulating body  24 , registration features  39   a  and  39   b  are shown, which are opposite registration features  39   c  and  39   d . The registration features  39   a - d  are provided to interlock the connector  23  with corresponding features located on the edge of circuit board  26  (not shown in FIG. 4). These registration features  39   a - d  ensure that the connector  23  is provided at exactly the right location to mate the connector elements  27  with their corresponding contact pads on both the liquid crystal display  22  and the circuit board  26 . Furthermore, the registration features  39   a - d  also assist in securing the connector  23  to avoid unnecessary vibration or movement during use of the device.  
         [0036]    [0036]FIG. 5 shows an end view of the connector  23  shown in FIG. 4, with connector elements  27  along the leg member  25 , which is attached to the insulating body  24 . On either side of the connector  23  are alignment pins  37   a - b . Furthermore, registration features  39   a  and  39   c  are seen on the edge of the connector  23 .  
         [0037]    [0037]FIG. 6 shows a side view of the connector  23  of FIG. 1 and  3  in which an insulating body  24  is shown with alignment pins  37   a  and  37   c  shown on the underside of insulating body  24 . A first contact foot  41  and a second contact foot  42  extend above and below, respectively, the leg member  25  for electrical communication. The first contact foot  41  and the second contact foot  42  are provided at an angle from the leg member  25 , to afford a resilient spring action against respective contact pads.  
         [0038]    In FIG. 7, a cross-section along lines X-X shows the first embodiment (i.e.: FIGS.  1 - 6 ) in cross-section with the connector  23  in the assembled configuration  50 . In the assembled configuration  50 , the first contact foot  41  and the second contact foot  42  are pushed down to a position which is roughly parallel with the sides of the leg member  25 . An arm portion  44  and an arm portion  45  are pushed closely against the leg member  25 . Thus, the U-shaped member  43  is now in full contact with the display  22  and the circuit board  26  (not shown in FIG. 8). The display contact pad connection point  51  is shown on the upper surface of the insulating body  24 , and the circuit board contact pad connection point  52  is shown on the lower surface of the insulating body  24 . Alignment pin  37   a  is shown on the lower surface of the insulating body  24 . The opening  46  which lies between at a point roughly between the leg member  25  and the insulating body  24  is shown.  
         [0039]    In FIG. 8, a second alternate embodiment of the connector is shown, which is a cross-section taken along lines X-X (see FIG. 4). This alternative embodiment reveals an insulating body separated by an opening  146  from the leg member  125 . The opening  146  is the point at which a carrier strip (not shown) is located during manufacture of the connector  123 , in which the carrier strip is “punched out” through the opening  146  during manufacture at the point at which the “U-shaped” member  143  is secured to the leg member  125 . The U-shaped member  143  has an arm portion  144  and an arm portion  145  on either end. The arm portion  144 , in this particular configuration, is shown as a “flat beam”, rather than a formed sprung contact beam as previously shown in FIG. 6. In this particular configuration, the flat beam portion is to be bonded directly to the contact pads  38  on the liquid crystal display  22 . The bonding is accomplished using one of many commercially available conductive adhesives, of a type known to persons of skill in the art. Furthermore, a first contact foot  141  and a second contact foot  142  are provided above and below, (respectively) the insulating body  124 .  
         [0040]    When the integrated display assembly  32  is assembled as shown in FIG. 2, the connector  23  is put together by mechanically confining the sides of the connector and compressing it through its height thereby pressing the conducting elements of the connector onto contact pads  38  and contact pads  28 . The pitch between conductive elements on the connector  23  may be 0.1 mm or finer. In general, it is considered good practice to design elastomeric connection systems so that the contact pads  28  and are at least as wide as the distance spanned by three consecutive conductive elements in the connector  23  so that the space between the pads will be at least about the same width.  
         [0041]    With the structure of the retention device described herein as shown in FIG. 1, it is a relatively simple process to press the connector elements  27  onto body  24 , and particularly onto leg member  25 . The closed end of U-shaped member  43  is pressed onto the end of the leg member  25 .  
         [0042]    In a typical application of the invention, a radio telephone will include a housing, a keypad, and the connector  23  as shown in the invention which also serves as a lightguide for illuminating the keypad from a light source within the radio telephone. Furthermore, various electronic components are adapted for receiving and transmitting telecommunications signals secured to a circuit board. A face of the circuit board also includes a plurality of contact pads. The lightguide is secured within the housing in a spaced apart relationship with the circuit board to define one or more compartments between the lightguide and the circuit board face.  
         [0043]    One or more wall portions may extend from the face of the lightguide to maintain a spaced apart relationship between the lightguide and the circuit board. These wall portions may be configured to contact the circuit board face to thereby define one or more compartments between the circuit board face and the lightguide face when the lightguide is secured within the housing. For example, a wall portion may depend from the lightguide along peripheral edge portions to define a compartment between the circuit board face and the lightguide.  
         [0044]    A keypad may be secured to the lightguide and may comprise a plurality of translucent keys. Each key is a first end extending through the housing to facilitate operation of the radio telephone by a user. Each key also has a second end extending through the lightguide. The second end of each key is operably engaged with a respective contact pad on the circuit board face.  
         [0045]    It should be appreciated by those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention. It is intended that the present invention include such modifications and variations as come within the scope and spirit of the appended claims and their equivalents.

Technology Classification (CPC): 8