Patent Publication Number: US-2011061933-A1

Title: Flat cable for use with an electronic device

Description:
BACKGROUND OF THE INVENTION 
     This is directed to a flat cable for use with an electronic device. In particular, this is directed to a USB cable supported by a flexible circuit. 
     Cables used to connect electronic devices to other components can include a conductive medium between connectors. The conductive medium typically includes one or more wires (e.g., four wires) placed within a non-conductive enclosure for protecting the wires from undesired electrical events and from damage. In some cases, the cable can be constructed by molding a sheath around wires, or by extruding a sheath that into which the wires can be threaded. The resulting cable can have a circular or elliptical cross-section, which can allow the cable to bend equally well or near-equally well in all directions. In some cases, however, the connector coupled to the wires can have a specific orientation and be more susceptible to damage or failure when the cable bends in a particular direction or orientation relative to the connector (e.g., when a cable bends away from a first connector contact and towards an opposite connector contact). In addition, the manufacturing approach used to connect individual wires to the connector (e.g., soldering) can be susceptible to bending or other cable movement in particular orientations. 
     SUMMARY OF THE INVENTION 
     This is directed to a flat cable for connecting electronic devices. In particular, this is directed to a cable in which a flex circuit is used to couple connectors forming the cable. 
     Many electronic cables are constructed from several distinct wires connected to connectors and surrounded by a non-conductive sheath. The resulting cable can have a circular or elliptical cross-section, which allows the cable to bend in any direction. This may not be desirable, however, as bending in some directions can stress the coupling between the wires and the connectors. 
     Instead of using wires, a cable can be constructed using a flex as the conductive material between the connectors. Such a flattened or ribbon-like cable can be less prone to tangle, can roll more easily for storage, and can provide controlled bending in two directions (e.g., as opposed to unhindered bending in all directions). The flex can be coupled to connectors using any suitable approach. In some embodiments, a connector can be coupled to the flex by soldering, SMT, or any other suitable process. Alternatively, the connector can be embedded within the flex traces (e.g., expose particular traces in a particular pattern to form a connector). 
     In some embodiments, an electrical circuit can be embedded within the flex as part of the cable. For example, the cable can include an integrated circuit for electrostatic discharge (ESD), an LED, power detection, or any other suitable purpose. In one implementation, the cable can include an embedded circuit for multiplexing signals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention, its nature and various advantages will be more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of a cable using wires as a conductive portion in accordance with one embodiment of the invention; 
         FIG. 2  is a schematic view of an illustrative flex-based cable in accordance with one embodiment of the invention; 
         FIG. 3  is a cross-sectional view of a portion of the cable of  FIG. 2  in accordance with one embodiment of the invention; 
         FIG. 4  is a top view of the cable of  FIG. 2  in accordance with one embodiment of the invention; 
         FIGS. 5A and 5B  are perspective views of the connector of the cable of  FIG. 2  in accordance with one embodiment of the invention; 
         FIG. 6  is a schematic view of the flex of the cable of  FIG. 2  being placed in a carrier in accordance with one embodiment of the invention; 
         FIG. 7  is a schematic view of an illustrative cable having incorporated circuitry in accordance with one embodiment of the invention; and 
         FIG. 8  is a flowchart of an illustrative process for creating a cable using a flex in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Different electronic devices can be connected to each other to transfer power, data, or combinations of these using one or more cables having connectors that can be coupled to the different devices. For example, a cable can include connectors of the same type (e.g., USB connectors) or of different types (e.g., a USB connector and a 30-pin connector). The cables can have any suitable number of channels, including for example a number set by the type of connector used for the wire. Each channel can be constructed using different approaches, including for example from individual wires enclosed by a sheath. The individual wires can be connected to connectors using any suitable approach, including for example soldering, SMT, or combinations of these. In some cases, however, the connector can bend relative to the wires at angles that cause high stresses to build up, and can increase the chance or rate of failure of the wire-connector junction. 
       FIG. 1  is a cross-sectional view of a cable using wires as a conductive portion in accordance with one embodiment of the invention. Cable  100  can include individual conductive wires  110  each serving as a channel to conduct different signals across the cable. In particular, each wire  110  can provide a signal between different connectors integrated or connected at each end of cable  100 . To avoid shorting or interference between adjacent wires, each wire  110  can be surrounded by a non-conductive sheath. Alternatively, wires  110  can be enclosed within sheath  120  such that non-conductive material  122  electrically isolates each wire  110 . Sheath  120  can also be used to maintain the distribution of the wires in cable  100 . Sheath  120  can have any suitable cross-section, including for example a circular or elliptical cross section. 
     Each end of cable  100  can include a connector operative to engage an electronic device. Each connector can include several conductive pins assigned to conduct particular signals (e.g., data channels, power, or ground signals), each of which can be connected to a corresponding wire, such that pins of opposite connectors assigned to the same signal are connected via a wire. Cable  100  can include any suitable type of connector, including for example a USB connector, 30-pin connector, display connector, power connector, or combination of these. Because the wires of the cable are provided in a circular or elliptical configuration, the cable can bend equally in all directions or orientations. If an interface between a connector and a wire is less resistant to bending or twisting along a particular orientation, the cable may be susceptible to failure. 
     To reduce stress points on the cable-connector interface, the channels of the cable can be constructed to favor bending of the cable in one or more particular orientations. For example, the cable can be constructed such that the channels have a non-circular cross-section (e.g., a flatter profile). In one implementation, the conductive element of the cable can include conductive traces printed on a flex.  FIG. 2  is a schematic view of an illustrative flex-based cable in accordance with one embodiment of the invention.  FIG. 3  is a cross-sectional view of a portion of the cable of  FIG. 2  in accordance with one embodiment of the invention.  FIG. 4  is a top view of the cable of  FIG. 2  in accordance with one embodiment of the invention. Cable  200  can include connectors  202  and  204  at opposite ends of flex  210 . For example, cable  200  can include 30-pin connector  202  and USB connector  204 , or any other suitable type of connector (e.g., a FireWire connector). Flex  210  can include any suitable number of conductive traces between connectors  202  and  204 , including for example four distinct traces. In other cases, the size of the flex (e.g., the width of the flex) or the number of conductive channels or paths required for each connector can determine the number of conductive traces included in flex  210 , as well as the size of flex  210 . The length of flex  210  can be selected based on any suitable criteria, including for example the required signal strength for transferring signals between the connectors, industrial design considerations, user interaction considerations, or any other suitable criteria. In one implementation, the length of flex  210  can be in the range of 50 cm to 200 cm, such as 150 cm. 
     Flex  210  can be coupled to each of connectors  202  and  204  using any suitable approach. In one embodiment, flex  210  can be connected to a connector (e.g., connector  202 ) using soldering, SMT, or a combination of these and other processes for making an electrical connection.  FIGS. 5A and 5B  are perspective views of the connector of the cable of  FIG. 2  in accordance with one embodiment of the invention. As shown in  FIG. 5A , flex  210  can be coupled to connector  202  using soldering. In particular, each exposed trace  212  of flex  210  can be connected to a corresponding contact or pin of connector  202 . Once the flex is electrically connected to connector  202 , protective boot  203  can be placed over the flex-connector interface to protect the coupling. In some embodiments, protective boot  203  can form part of the connector (e.g., an enclosure that is inserted in an electronic device to ensure the alignment of the connector pins with the corresponding connector housing of the electronic device). 
     In some embodiments, portions of flex  210  can be exposed, or alternatively conductive elements can be placed on flex  210  to form a connector. As seen from  FIGS. 2 and 4 , flex  210  can include several conductive elements  206  exposed on the surface of flex  210 . Each conductive element can have a particular size and position on the flex, for example set by a standard defining the connector attributes. In the example of cable  200 , conductive elements  206  can include four distinct contact pads positioned and sized in accordance with the USB connector specification. Conductive elements  206  can be constructed from any suitable material and using any suitable process, including for example from copper connected to traces located within flex  210 . 
     To protect and support flex  210 , cable  200  can include carrier  220 .  FIG. 6  is a schematic view of the flex of the cable of  FIG. 2  being placed in a carrier in accordance with one embodiment of the invention. Carrier  220  can be constructed from any suitable material, including for example plastic, metal, a composite material, silicon, or any other suitable material. In some cases, carrier  220  can form a housing into which flex  210  can be placed and retained, for example using an adhesive, press fit, engaging member, molding (e.g., double shot process when several distinct sections of the carrier), or any other suitable approach. In the example of  FIG. 6 , carrier  220  is shown covering only one planar surface of flex  210 , and part of the side walls of flex  210  (e.g., extending near or up to the height of the flex, but not higher than the flex). In some cases, carrier  220  can instead or in addition cover the entirety of flex  210  (e.g., serving as a sheath, similar to cables constructed using wires). 
     In some embodiments, carrier  220  can include distinct portions having different mechanical or physical characteristics. For example, carrier  220  can include flexible portion  221  that allows cable  200  to be bent or rolled for storage, and rigid portion  222  that does not deflect to be inserted into an electronic device as part of a connector. In some cases, flexible portion  221  can have different levels of flexibility such that different regions of cable  200  can bend in different manners. For example, carrier  220  may allow the cable to bend in any manner between the connectors, but may become partially rigid and restrict the bending orientations of the cable adjacent to the connectors (e.g., only allow bending out of the flex plane near the connectors). 
     In some embodiments, flex  210  can be surrounded or enclosed by a sheath for aesthetic purposes. Alternatively, carrier  220  and the top surface of flex  220  can be finished to provide an aesthetically pleasing cable. In some cases, flex  210  can instead or in addition include a cosmetic coating such that the flex remains visible as a cosmetic element of the cable. 
     In some embodiments, the functionality of the cable can be increased or enhanced by taking advantage of the flex used as the conductive channel between the cable connectors. In particular, the flex can include intermediate or additional traces between the connectors for supporting circuitry embedded within the connector.  FIG. 7  is a schematic view of an illustrative cable having incorporated circuitry in accordance with one embodiment of the invention. Cable  700  can include flex  701  providing channels for signals between connectors  702  and  704 . Flex  701  can have any suitable number of traces along different paths, including for example traces connecting contact pins or regions of connectors  702  and  704 . In some cases, flex  701  can instead or in addition include one or more intermediate traces that do not extend between the connectors. Instead, the one or more intermediate traces may be coupled to circuitry  710  embedded within the flex. Circuitry  710  can perform any suitable operation for cable  700 , including for example detect and control power use (e.g., block power surges or shorts), encrypt or decrypt transmitted signals, multiplex received signals for a single channel (e.g., when providing signals between a connector having few pins and a connector having a larger number of pins), repeat received signals for transmission over larger distances, provide an indication of signal transfers to a user (e.g., via a LED), indicate whether a cable can be safely disconnected (e.g., using one or more LEDs), or combinations of these. 
     To prevent damage to circuitry  710  due to bending cable  700 , a more rigid cover or carrier can be placed over flex  701  in the region adjacent to circuitry  710 . For example, a carrier having variable stiffness can be placed around flex  701  such that the portion of flex supporting circuitry  710  remains substantially immobile. In some embodiments, flex  701  can itself include one or more additional layers of structural material, traces, vias or other elements (e.g., in the flex stack) to provide electrical or mechanical functionality. For example, flex  701  can include an additional layer of structural material to ensure consistent electrical connections between the circuitry and the flex, as well as additional traces for connecting the circuitry to the flex. As another example, flex  701  can include several layers of conductive and non-conductive material to provide integrated electromagnetic shielding (e.g., the additional traces of the flex shield circuitry  710 ). 
       FIG. 8  is a flowchart of an illustrative process for creating a cable using a flex in accordance with one embodiment of the invention. Process  800  can begin at step  802 . At step  804 , traces can be drawn on a flex. For example, traces connecting opposite ends of the flex can be drawn. As another example, traces within the flex for supporting embedded circuitry can be drawn. The traces can be provided using any suitable conductive material, including for example copper. At step  806 , connectors can be coupled to the flex. For example, individual pins of connectors can be coupled to individual traces of the flex. The connectors can be the same or different, and connected to particular traces such that data, power or both can be transmitted across the flex between the connectors. At step  808 , circuitry can be integrated in the flex. For example, circuitry (e.g., a chip) can be placed on the flex such that traces drawn on the flex connect appropriate pins of the circuitry. The circuitry can provide any suitable functionality, including for example detecting and controlling power use, repeating, encrypting, decrypting, or multiplexing transmitted signals, providing an indication of signal transfers, or combinations of these. At step  810 , the flex can be placed in a carrier. The carrier can be selected based on mechanical, electrical, or cosmetic considerations. For example, a carrier can be selected to allow bending of the flex cable in particular regions and along particular orientations, while providing an aesthetically pleasing cable. Process  800  can then end at step  812 . 
     The previously described embodiments are presented for purposes of illustration and not of limitation. It is understood that one or more features of an embodiment can be combined with one or more features of another embodiment to provide systems and/or methods without deviating from the spirit and scope of the invention.