Patent Publication Number: US-7901221-B1

Title: Universal serial bus ground clip

Description:
BACKGROUND 
     Universal Serial Bus (USB) connections are in widespread use for enabling communication between electronic devices. As the form factor of these electronic devices shrinks, the connectors associated with USB have shrunk as well. Micro USB (MUSB) connectors are now available. 
     MUSB connectors, however, can be challenging to install in small form factor devices. Creating an effective electrical ground connection between the MUSB receptacle and a grounding surface, such as an electrically conductive device cover, backplane, printed circuit board, etc., allows the USB connection to operate as designed and reduces the likelihood of device damage due to electrostatic discharge (ESD) or high voltage pulse (HVP). 
     It can be difficult to achieve ground USB receptacles in small form factor devices with limited interior volume. It is particularly challenging to achieve an effective, reliable and cost effective electrical ground in low profile applications such as, for example, e-book readers, cellular telephones, portable media players, laptops, netbooks, and the like. 
     Existing electronic devices have used conductive foam to establish a ground. However, the conductive foam cannot be easily repositioned and may not be sufficiently conductive to prevent an ESD or HVP. In existing low profile applications, grounding springs are too large to fit in the available space and/or too flimsy to establish a satisfactory ground against the grounding surface. 
     Conductive foam and existing grounding springs may also push back excessively during assembly. This push back complicates alignment of parts and increases the force necessary to mate parts together during assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items. 
         FIG. 1  shows an illustrative Micro Universal Serial Bus (MUSB) grounding system including a grounding clip. 
         FIG. 2  shows a perspective illustration of the grounding clip shown in the MUSB grounding system of  FIG. 1 . 
         FIG. 3  shows the illustrative MUSB grounding clip from  FIG. 1  from another perspective. 
         FIG. 4  is a left side view of the illustrative MUSB grounding clip of  FIG. 1 . 
         FIG. 5  is a front view of the illustrative MUSB grounding clip of  FIG. 1 . 
         FIG. 6  shows another illustrative implementation of an MUSB grounding clip. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     In small form factor devices with limited interior volume and/or low profile applications, such as e-book readers, cellular telephones, portable media players, laptops, netbooks, and the like, achieving an effective, reliable and cost effective electrical ground between a micro Universal Serial Bus (MUSB) receptacle and a grounding surface can be difficult. 
     This application describes a low profile form-factor grounding clip of conductive material to achieve an effective, reliable, and cost effective electrical ground connection between a MUSB receptacle in an electronic device and the grounding surface. The clip uses an interference fit to produce positive engagement between the MUSB receptacle, and has a spring tab to engage a conductive grounding surface, such as a cover, housing, ground plane, etc. The clip may also have locating features to aid in alignment during assembly. 
     The clip also facilitates assembly. By positively engaging to the MUSB receptacle, the clip is not loose during assembly. This allows multiple attempts at assembly of the device grounding surface, without risk of dislodging the grounding clip. Thus, the grounding clip assures a reliable electrical ground connection. The profile and placement of the spring tab reduces or eliminates pushback during assembly of the grounding surface towards the MUSB receptacle. 
     Generally, the MUSB connection utilizes a plug and a complimentary receptacle. For example, an electronic device having a printed circuit board (PCB) may have a receptacle affixed thereto for transmission of data and/or power to or from the device. A cable may connect an external device to the receptacle. This connection to external devices introduces a potential pathway for electrostatic discharge (ESD) or high voltage pulses (HVPs). Grounding the MUSB receptacle provides protection against ESD and HVP events. 
     In low profile devices, there may be limited space to provide a ground connection to a conductive cover, housing, ground plane, etc., which goes over the receptacle. Existing USB connections make use of conductive foam. However, this makes removal and repositioning of the conductive cover, housing, ground plane, etc., difficult. Furthermore, conductive foam may not provide the level of conductivity required to adequately ground the device. Similarly, existing grounding springs positioned on the grounding cover or affixed to the top of the receptacle have been flimsy, prone to breakage, and may be easily dislocated during assembly, thus failing to produce the desired ground connection. 
     The grounding clips disclosed herein are designed to fit around a MUSB receptacle. The grounding clips snap onto the receptacle using interference features such as dimples or tabs. On the top of the grounding clip a spring tab extends to make contact with the conductive ground surface above the receptacle. The spring tab may also be located on one of the other sides of the clip, and may extend outward to make contact with an adjacent ground surface, such as the side of a case. 
     On the front of the grounding clip, locating features or prongs may extend downwards to provide a positive alignment relative to the PCB. The device cover may be installed once the grounding clip is snapped onto the receptacle. This design makes removal or repositioning of the device cover possible, while still producing the desired ground connection upon reassembly. 
     While the grounding clip is described in the context of a grounding clip for a MUSB receptacle, grounding clips may also be used to ground other types of receptacles, such as standard USB connections, serial port connections, IEEE 1394 connections, and the like. 
     Grounding Clip Having a Back and Also Front Locating Features 
       FIG. 1  shows an illustrative MUSB grounding system  100 . PCB  102  is shown with a MUSB receptacle  104  affixed. Holes  106  or detents are typically present on both the left and right vertical sides of the receptacle  104 . 
     An illustrative grounding clip  108  placed down onto receptacle  104  is shown. Once placed around receptacle  104 , an engagement feature retains the grounding clip  108  on receptacle  104 . In one example, this engagement feature may be a dimple on one surface and a hole  106  or detent on the other. A grounding surface  110  above the grounding clip  108  may be brought into contact with a portion of grounding clip  108  to make the ground connection. 
       FIG. 2  shows a perspective illustration of the grounding clip  108  shown in the MUSB grounding system  100 . A horizontal top surface  202  is attached to a vertical left surface  204 , a vertical right surface  206 , and a vertical back surface  208 . The vertical surfaces  204 ,  206 , and  208  may have curves  210 ,  212 , and  214 , respectively, or a roll at the bottom to ease insertion, minimize sharp edges, add structural rigidity, or any combination thereof. 
     A first locating feature  216  in the same plane as vertical left surface  204  extends downwards below the vertical left surface  204  beyond curved edge  210 . A second locating feature  218  in the same plane as vertical right surface  206  extends downwards below the vertical right surface  206  beyond curved edge  212 . The locating features aid in assembly by providing a positive alignment with the circuit board to which the receptacle is affixed. In other embodiments locating features  216  and  218  may also have a curve or roll  220  and  222 , respectively, at the bottom to ease insertion, minimize cutting, add structural rigidity, and so forth. Locating features may also be present at other locations on the clip, such as extending from the back vertical surface  208 . 
     On the horizontal top surface  202  a spring tab  224  is shown which originates from the front of the horizontal top surface  202  and extends generally towards the back surface  208  of the clip  108 . The spring tab  224  may also originate at the back of the horizontal top surface  202  and extend forwards, or originate from one or more of the vertical surfaces  204  or  206  or  208 . 
     On the vertical left surface  204  a first dimple  226  protrudes inward, towards the opposite vertical right surface  206 . The first dimple  226  is shaped to positively engage the hole  106  or detent in the receptacle  104 . Alternatively, the receptacle  104  may have a dimple to engage a corresponding hole or detent in the clip. 
     On the vertical right surface  206 , a second dimple  228  protrudes inward, towards the opposite vertical left surface  204 . The second dimple  228  is shaped to positively engage the hole  106  or detent in the receptacle  104 . Alternatively, the receptacle  104  may have a dimple to engage a corresponding hole or detent in the clip. Interference features  226  and  228  are shown as hemispherical dimples. However, other interference structures capable of producing a positive engagement are possible such as, for example, bumps, ribs, ridges, lips, slots, tracks, opposing angled surfaces, crimps, and so forth. Instead of, or in addition to, an interference structure, a threaded fastener, rivet, weld, adhesive, and/or solder may be used to engage the clip to the receptacle. 
       FIG. 3  shows the illustrative MUSB grounding clip  108  from another perspective. The back surface  208  with curve  214  is clearly shown, as is vertical right side  204 , first dimple  226  and first locating feature  216 . 
       FIG. 4  is a left side view of the illustrative MUSB grounding clip of  FIG. 1 , and  FIG. 5  is a front view of the illustrative MUSB grounding clip of  FIG. 1 .  FIGS. 4 and 5  shown an alternative configuration for the spring tab on a vertical surface. As shown in these figures, a spring tab  402  may originate from a vertical surface, such as the vertical right surface  206 , and extend generally towards the opposite side of the clip  108 . 
     Grounding Clip with No Back 
       FIG. 6  shows an illustration of an alternate implementation of a MUSB grounding clip  600 . A horizontal top surface  602  is attached to a vertical left surface  604  and a vertical right surface  606 . The left and right vertical surfaces  604  and  606  may have curves  608  and  610 , respectively, or a roll at the bottom to ease insertion, minimize cutting, add structural rigidity, or any combination thereof. 
     On the horizontal top surface  602 , a spring tab  612  is shown, which originates from the front of the horizontal top surface  602  and extends generally towards the back of the clip  600 . The spring tab  612  may also originate at the back of the horizontal top surface  602  and extend forwards, or originate from one or both of the left and right vertical surfaces  604  or  606 . 
     On the vertical left surface  604  a first dimple  614  protrudes inward, towards the opposite vertical right surface  606 . The first dimple  614  is shaped to positively engage the hole  106  or detent in the receptacle  104 . Alternatively, the receptacle  104  may have a dimple to engage a corresponding hole or detent in the clip. 
     On the vertical right surface  606 , a dimple  616  protrudes inward, towards the opposite vertical left surface  604 . The dimple  616  is shaped to positively engage the hole  106  or detent in the receptacle  104 . Alternatively, the receptacle  104  may have a dimple to engage a corresponding hole or detent in the clip. 
     While the detailed descriptions given above refer to a MUSB receptacle, the disclosed clips may be used with other form factors of USB such as Standard and Mini, as well as other types of electrical receptacles which require a ground connection. 
     The above-described clip is shown as being separate from the receptacle. However, the features of this clip may be integrated into the receptacle itself. For example, the spring tab may be integral to the top surface of the receptacle. 
     Any of the above-described clips may include cutouts or holes. These cutouts may be used to alter the stiffness or mass of the clip as desired. For example, placement of relief holes on the vertical sides and/or the top surface may reduce the force necessary to engage the clip to the receptacle. 
     The grounding clip may be comprised of material including metal (for example, beryllium copper, gold plated beryllium copper, aluminum, nickel silver, etc.), non-conducting polymer (for example, polyvinyl chloride, poly(tetrafluoroethene), etc.), conducting polymer (for example, polyaniline, poly(3-alkylthiophenes, etc.), or combinations thereof. Where the material is non-conductive, it may be plated with a conductive material. The clip may be made by stamping, milling, molding, forming, or other methods of fabrication suitable to the material chosen. 
     CONCLUSION 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the claims. Moreover, any of the features of any of the devices described herein may be implemented in a variety of materials or similar configurations.