Abstract:
An electromagnetic interference shield system, is provided. Each EMI shield may include a frame providing the structure around the electronic device components to be shielded, and a cover operative to be placed over the frame to prevent electromagnetic radiation from passing over the frame. Each frame may be coupled to a circuit board, and enclose electronic components in need of shielding. Each cover may be coupled to its corresponding frame using at least one snap that extends from the periphery of the cover towards the frame and circuit board. To minimize the space taken by the EMI shields, the snaps of adjacent covers may be offset or staggered so that opposing snaps engage voids left between snaps of the opposing cover, thus reducing the space needed between adjacent EMI shields by up to the width of a snap.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/112,729, filed Apr. 30, 2008, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention is directed to an interlocking electromagnetic interference (EMI) shield system for use in an electronic device. 
     Many electronic devices include various electronic components that emit electromagnetic radiation. To prevent disturbances of the electronic components, EMI shields may be provided in the electronic device. For example, the electronic device components may be placed in a conductive box (e.g., a metallic box) that prevents radiation from escaping the box. As another example, the enclosure in which the electronic components are placed may be coated with a metallic or conductive paint. 
     Although these solutions for reducing electromagnetic interferences may be effective, they may take up significant space, especially in view of the size of particular electronic components. For example, a lot of space is used to surround a small electrical circuit on all sides with a metallic box. When several electronic components of an electronic device need to be individually shielded, even more space is used to surround each component with individual conductive boxes. There is a need, therefore, for an EMI shielding system that takes up little space while providing sufficient and effective EMI shielding. 
     SUMMARY OF THE INVENTION 
     An interlocking EMI shield system for protecting components of an electronic device from electromagnetic interferences is provided. 
     An interlocking EMI shield is provided. Each EMI shield may be constructed from a frame that is coupled to a circuit board or other electronic device structural component, and a cover that is placed over the frame. The frame may be coupled to the circuit board using any suitable approach, including for example soldering, a mechanical fastener, an adhesive, or a snapping mechanism. The frame may include walls extending around the periphery the shield, and a lip extending from the top edge of the walls towards the center of the shield (e.g., to provide additional structural support). The walls may include one or more snaps, tabs, apertures or indentations for receiving a corresponding element from the cover. 
     Each cover may include a substantially flat surface operative to be placed over the frame. To couple the cover to the frame, the cover may include several snaps extending vertically from the cover surface towards the circuit board to which the frame is coupled. The snaps may be biased towards the walls of the frame such that the snaps are operative to engage the walls upon coupling of the cover to the frame. In some embodiments, the snaps may include, one or more tabs, prongs, or other elements to engage a counterpoint in the wall of the frame. 
     Each cover may include any suitable number of snaps. For example, each cover may include several snaps, each separated by a particular distance (e.g., at least by the width of a snap). The snaps may have the same or different sizes, and be distributed evenly or unevenly along the periphery of the cover. To reduce the space taken by the shields, the snaps of shields placed adjacent in the electronic device (e.g., having edges placed almost in contact) may be offset or staggered such that a snap of a first EMI shield may extend into an indentation of the second EMI shield (e.g., in between two snaps extending from the second EMI shield), while a snap of the second EMI shield may extend into an indentation of the first EMI shield (e.g., in between two snaps extending from the first EMI shield). Using this staggered approach, space of at least the thickness of one snap may be, saved for other components of the electronic device, or to further reduce the size of the electronic device. 
    
    
     
       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 an exploded perspective view of an illustrative EMI shield in accordance with one embodiment of the invention; 
         FIG. 2  is a top perspective view of an exploded EMI shield assembly in accordance with one embodiment of the invention; 
         FIG. 3  is a perspective view of an EMI shield assembly coupled to a circuit board in accordance with one embodiment of the invention; 
         FIG. 4  is a perspective view of a detail of the EMI shield assembly of  FIG. 3  along the boundary between the EMI shields in accordance with one embodiment of the invention; 
         FIG. 5  is a top view of a detail of the EMI shield assembly of  FIG. 3  along the boundary between the EMI shields in accordance with one embodiment of the invention; 
         FIGS. 6A-6D  are top views of a detail of an EMI shield assembly along the boundary between EMI shields in accordance with one embodiment of the invention; and 
         FIG. 7  is a top view of a detail of an EMI shield assembly along the boundary between EMI shields in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an exploded perspective view of an illustrative EMI shield assembly in accordance with one embodiment of the invention. EMI shield assembly  100  may be formed from first EMI shield  108  that includes frame  110  and cover  120 , and second EMI shield  138  that includes frame  140  and cover  150 . Each of frames  110  and  140  may include side walls  112  and  142 , and upper lip or returns  114  and  144 , respectively. Side wells  112  and  142  may be operative to be coupled to circuit board  130  of an electronic device to form the side walls of box, for example surrounding electronic components. Side walls  112  and  142  may be coupled to circuit board  130  using any suitable approach. For example, side walls  112  and  142  may be soldered into circuit board  130 , snapped or clipped into a structural element of circuit board  130  (e.g., snaps extending in apertures in the circuit board, or snaps coupling to a receiving element incorporated in the circuit board), coupled using an adhesive or tape, or using any other suitable approach. In some embodiments, frames  110  and  140  may be combined into a single frame having a separating wall (e.g., along boundary  115 ) onto which distinct covers  120  and  150  may be attached. 
     Frames  110  and  140  may be placed on any suitable portion of circuit board  130 . For example, frames  110  and  140  may be placed to surround specific electronic device components  132  incorporated in circuit board  130 . In particular, frames  110  and  140  may be placed around different components  132  that emit electromagnetic radiation, or that are susceptible to electromagnetic radiation. If circuit board  130  includes two different components  132 , both emitting electromagnetic radiation, and both susceptible to each other&#39;s emissions, each may be surrounded by one of frames  110  and  140  to prevent or reduce electromagnetic interferences to the operation of components  132 . In addition, using two separate EMI shields  108  and  138  with separate covers  120  and  150  that can be individually removed may allow for access to particular components  132  (e.g., for repair) without disturbing other components that may be sensitive to interferences from the exposed components. 
     To prevent radiation from escaping over the end of side wall  112  and  142 , respectively, covers  120  and  150  may be placed over frames  110  and  140 , respectively. Once the covers are placed over the frames, components  132  are enclosed in all directions by the cover, side walls and circuit board, thus preventing interfering radiation from escaping and damaging other components  132 . Covers  120  and  150  may include a substantially flat surface  122  and  152  operative to be placed over each of frames  110  and  140 . Covers  120  and  150  may have any suitable boundaries, including for example boundaries that substantially follow side walls  112  and  142 , respectively. By providing covers that do not extend past, or minimally extend past side walls  110  and  140 , the space required in the electronic device for covers  120  and  150  may be minimized. 
     Covers  120  and  150  may be coupled to frames  110  and  140  using any suitable approach. In some embodiments, covers  120  and  150  may include snaps  124  and  154  extending from flat surfaces  122  and  152 . For example, snaps  124  and  154  may extend orthogonally (e.g., vertically) from surfaces  122 , and be located at the periphery of surfaces  122  and  154 . By being located at the periphery, snaps  124  and  154  may be substantially aligned with side walls  112  and  142 , respectively, such that the snaps may engage a portion of the side walls. Snaps  124  and  154  may include one or more mechanisms for engaging side walls  112  and  142 . For example, snaps  124  and  154  may be elastically biased towards side walls  112  and  142  such that snaps  124  and  154  may deflect when they are placed over frames  110  and  140 , respectively, thus creating an interference or frictional fit. As another example, snaps  124  and  154  may include a tab or protrusion  126  and  156 ; respectively, operative to engage a corresponding indentation or tab  116  and  146 , respectively, in the side wall. As still another example, a tape, adhesive or mechanical fastener (e.g., a screw passing through snaps  124  and  154  and engaging side walls  112  and  142 , respectively) may be used to secure snaps  124  and  154  to frames  110  and  140 , respectively. 
     Each cover  120  and  150  may include any suitable number of snaps  124  and  154 . For example, a cover may include snaps  124  and  154  offset at distances larger than the width of a snap. In some embodiments, different snaps  124  and  154  may have different sizes, for example based on the component  132  lying adjacent the snap on circuit board  130 , or based on the position of snap relative frame  310  or  140  (e.g., a snap adjacent a corner may be wider than a snap in the middle of a wall). The snaps may also be distributed along the periphery of the cover using any suitable approach, including for example evenly, or based on the EMI shielding or structural requirements of the shield. 
     Frames  110  and  140 , and covers  120  and  150  may be manufactured from any suitable material operative to shield the components of contained within EMI shield  100  from electro-magnetic interference (e.g., from other components of the electronic device). In some embodiments, shield  100  may be constructed from an electrically conductive material such as, for example, metal (e.g., copper silver, aluminum, steel), graphite, plasma, or any other conductive material. Frames  110  and  140 , and covers  120  and  150  may include unbroken surfaces, or materials with a mesh or holes (e.g., so long as the holes are smaller than the wavelength of the radiation being kept out). 
     Because two frames  110  and  140 , and two covers  120  and  150  may be used in the same electronic device, space may be lost between each EMI shield (e.g., along boundary  115 ). To reduce the space required between adjacent EMI shields  108  and  138 , shields  108  and  138  may interlock along boundary  115 .  FIG. 2  is a top perspective view of an exploded EMI shield assembly in accordance with one embodiment of the invention. EMI shield  208  and  238  may include some or all of the features of EMI shields  108  and  138  ( FIG. 1 ) described above. Frames  210  and  240  may be coupled to circuit board  130  using any suitable approach. Covers  220  and  250  may then be placed over frames  210  and  240 , respectively, such that the electronic device components within the boundary of each frame  210  and  240  are fully enclosed. 
     Using some approaches, EMI shields  208  and  238  may be placed adjacent, and brought together until covers  220  and  250 , which form the external-most layer of the EMI shields (e.g., because tabs extending from the covers are positioned outside the side walls of the frames), are in near contact (e.g., along boundary  215 ). To save even more space, however, covers  220  and  250  may be designed to interlock. 
       FIG. 3  is a perspective view of an assembled EMI shield assembly in accordance with one embodiment of the invention. EMI shield assembly  300  may include first EMI shield  308  and second EMI shield  338  that are coupled to circuit board  330 . EMI shields  308  and  338  may include some or all of the features of any of the EMI shields described above in connection with  FIGS. 1 and 2 . First EMI shield  308  may include frame  310  to which cover  320  may be coupled, and second EMI shield  338  may include frame  340  to, which cover  350  may be coupled. Covers  320  and  350  may include snaps  324  and  354 , respectively, for engaging frames  310  and  340 , respectively. To save space between EMI shields  308  and  338  along boundary  315 , snaps  324  and  354  of covers  320  and  350 , respectively, may be arranged such that snaps  324  and  354  may interlock. 
       FIG. 4  is a perspective view of a detail of the EMI shield assembly of  FIG. 3  along the boundary between the EMI shields in accordance with one embodiment of the invention.  FIG. 5  is a top view of a detail of the EMI shield assembly of  FIG. 3  along the boundary between the EMI shields in accordance with one embodiment of the invention. By the manner in which snaps  324  and  354  are constructed, snaps  324  and  354  extend beyond the respective peripheries  321  and  351  of covers  320  and  350 , creating respective voids  326  and  356  between adjacent snaps  324  and  354 , respectively. Voids  326  and  356  may be defined, for example, by the side wall of the underlying frame, and by the width of adjacent snaps  324  or  354 . 
     By sizing and distributing snaps  324  and  354  and voids  326  and  356  judiciously, a snap  324  may extend into a void  356 , and a corresponding snap  354  may extend into a void  324  along boundary  315  (e.g., where covers  320  and  350  engage). In addition, if snaps  324  and  354  have the same width (e.g., which would likely be the case if the same material is used for both covers  320  and  350 ), the depth of each void  326  and  356  would match the width of each snap  324 , and  356  operative to engage or extend into the void. Thus, the space required between adjacent covers  320  and  350  may be reduced from the width of snap  324 , plus the width of snap  354 , plus a clearance factor to only the width of one of snaps  324  and  354 , plus a clearance factor. This allows the space between adjacent EMI shields  308  and  338  to be reduced up to by half (e.g., by the thickness of the material, for example sheet metal plus any additional distance required to clear the snaps). For example, if the width of each snap  224  or  254  is in the range of 0.12 to 0.2 mm, the savings may be for example 0.15 mm. 
     Using this approach, in a top view, it may appear as though the snaps of both covers form a single layer placed between the frames of the two EMI shields (e.g., snaps of adjacent shields are substantially or at least partially aligned). For example, a single plane may include the inner surface of snap  324  and the outer surface of an adjacent snap  354 . 
     In some embodiments, covers  320  and  350  may have different heights. For example, cover  320  may be higher than cover  350  (e.g., when coupled to frame  310 ). To allow covers  320  and  350  to engage, snaps  324  and  354  may be offset in the vertical dimension (e.g., along the height of covers  320  and  350 ). For example, snaps  324  may be located above snaps  354  when covers  320  and  350  engage because cover  320  is located above cover  350 . Thus, the void used to place snap  354  near frame  310  may not be adjacent snap  324  (e.g., at a different point on the periphery of cover  320 ), but rather underneath a snap  324  (e.g., between the bottom edge of snap  324  and circuit board  330 ). 
     Any suitable approach may be used to ensure that adjacent covers  320  and  350  engage properly. For example, covers  320  and  350  may be shaped such that only one possible engagement of covers  320  and  350  is possible. As shown clearly in  FIGS. 3-5 , boundary  315  includes angled segment  316 . Each of covers  320  and  350  may include corresponding angled portions  321  and  351 , respectively. The size and shape of angled portions  321  and  351  may render any engagement of covers  320  and  350  that does not engage angled portions  321  and  351  impossible (e.g., covers  320  and  350  cannot engage properly, and save space unless angled segment  316  is properly created). This may ensure that covers  320  and  350  are properly placed on their respective frames, and that EMI shields  308  and  338  are properly mounted. 
     Other suitable shapes may be used instead of or in addition to angled segment  316 .  FIGS. 6A-6D  are top views of a detail of an EMI shield assembly along the boundary between EMI shields in accordance with one embodiment of the invention. EMI shields  608  and  638  may include covers  620  and  650 , respectively. Cover  620  may include tabs  624  and voids  626 , and cover  650  may include tabs  654  and voids  656 . Boundary  615  between EMI shields  608  and  638  may have any suitable, non-linear shape that allows only one reasonable engagement configuration. For example, boundary  615 A includes a curved shape, boundary  615 B includes several curved shapes, boundary  615 C includes a single angle, and boundary  615 D includes a protrusion. Tabs from each cover  620  and  650  may engage along any suitable surface, including several surfaces if boundary  615  includes several surfaces (e.g., boundary  615 C includes engaging tabs along two surfaces of covers  620  and  650 ). It will be understood, however, that any other suitable shape may be used for boundary  615 . 
     As another example, snaps  324  and  354 , and corresponding voids  326  and  356  may be distributed along the periphery of each cover  320  and  350  such that, along the periphery that forms boundary  315 , at least one snap and void in each cover is sized or located such that only one possible engagement of the covers is possible.  FIG. 7  is a top view of a detail of an EMI shield assembly along the boundary between EMI shields in accordance with one embodiment of the invention. EMI shields  708  and  738  may include covers  720  and  750 , respectively. Cover  720  may include first tabs  724 , and second tab  725  that is different from first tabs  724 . Conversely, cover  750  may include first voids  756  that is different from second void  757 . When covers  720  and  750  are placed adjacent and engaged, the sizes of tabs  724  and  725 , and of voids  756  and  757  may be such that the only possible engagement of covers  720  and  750  is with tab  724  engaging void  756 , and tab  725  engaging void  757 . 
     In some embodiments, more than two adjacent EMI shields installed on a circuit board may include tabs operative to engage to save space. For example, a two-dimensional array of interlocking EMI shields may be provided, such that different sides of a particular EMI shield may engage sides of different EMI shields (e.g., every side of the center EMI shield of a 3×3 array may engage another EMI shield). This may allow more components to be individually shielded while limiting the amount of space required for each shield. 
     The above described embodiments of the present invention are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.