Abstract:
An EMI shielded system in which a motherboard is permanently shielded behind a shielding plate defining an aperture for each corresponding connector carried by the motherboard so as to allow expansion cards or the like to be connected to the motherboard without having to unshield the latter. The expansion cards are preferably separately mounted and shielded within respective loading cartridges.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electronic equipment, such as computers and, more particularly, to an apparatus and method for providing electromagnetic interference (EMI) shielding to some of the electrical components of an electronic device. 
     2. Description of the Prior Art 
     Electronic components, such as printed circuit boards, generate electromagnetic interference (EMI) radiation. Such EMI radiation must be substantially prevented from escaping outwardly through the housing in which the electronic components are mounted. Moreover, it is also desirable that the EMI radiation generated by the electronic components be contained to avoid interfering with the operation of other electronic components. To this end, it has been proposed to mount printed circuit boards within a metallic chassis upon which a cover can be installed to provide EMI shielding. However, when it is desired to connect peripheral electronic devices, such as expansion cards, to the main printed circuit board of the device, one has first to remove the cover and thus unshield the main printed circuit board to have access to the electrical connectors thereof. The unshielded main printed circuit board can then be operatively connected to the peripheral device. 
     It would be desirable to have a new shielding structure in which individual electronic components are shielded from one another and are adapted to be connected to each other without having to be unshielded. 
     SUMMARY OF THE INVENTION 
     It is therefore an aim of the present invention to provide a shielding method and apparatus in which individual electronic components can be operatively connected without having to be unshielded. 
     It is also an aim of the present invention to provide a new shielding apparatus which facilitates the connection of an expansion card to a main printed circuit board of an electronic device. 
     It is a further aim of the present invention to provide a shielding apparatus for reducing the risk that respective electronic components of two electronic devices be damaged during installation procedures. 
     Therefore, in accordance with the present invention, there is provided a computer chassis in combination with a motherboard having at least one electrical connector extending from a surface thereof and to which additional electronic components are operatively connectable, comprising a support structure for supporting the motherboard, an EMI shield overlying said surface of said motherboard for shielding the motherboard from other electronic components, said support structure defining on a side of said shield opposite to said motherboard a space for receiving the additional electronic components, and at least one aperture defined in said shield for exposing said at least one electrical connector of the motherboard, thereby allowing the motherboard to be operatively connected to the additional electronic components without having to be unshielded. 
     In accordance with a further general aspect of the present invention, there is provided an electromagnetic interference (EMI) radiation shielded system for connecting at least one expansion card to a main printed circuit board of an electronic device, comprising a chassis, a main printed circuit board mounted within the chassis, an EMI shield overlying the main circuit board and defining one corresponding aperture for each electrical connector extending from the main printed circuit board, an EMI shielded loading cartridge housing an expansion card having at least one exposed connector accessible from outside said loading cartridge, said chassis defining a space for receiving said loading cartridge in a position wherein said at least one exposed connector of said expansion card operatively mates with a corresponding exposed connector of said main printed circuit board. 
     In accordance with a further general aspect of the present invention, there is provided a method of shielding interconnectable electronic components, comprising the steps of: mounting a first electronic component within a chassis behind an electromagnetic interference (EMI) shield defining one corresponding aperture for each electrical connector carried by the first electronic component, mounting a second electronic component in an EMI shielding module with a connector of said second electronic component remaining accessible from outside of said shielding module, mounting said EMI shielding module within said chassis with corresponding connectors of said first and second electronic components in mating engagement. 
     In accordance with a further general aspect of the present invention, there is provided a method of shielding electronic components, comprising the steps of: providing a number of electronic components on a planar board, providing an electromagnetic interference (EMI) radiation shielding plate, defining in said shielding plate one corresponding aperture for each electrical connector extending from said planar board, mounting said planar board and said shielding plate within a chassis with said shielding plate overlying said planar board and each said electrical connector in registry with a corresponding aperture in said shielding plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which: 
     FIG. 1 is a perspective view of a new apparatus for EMI shielding electronic components in accordance with a first embodiment of the present invention; 
     FIG. 2 is a side elevational view, partly in cross-section, of the apparatus of FIG. 1; and 
     FIG. 3 is a front cross-sectional view of the apparatus of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now referring to FIG. 1, an apparatus for EMI shielding interconnectable electronic components while allowing the components to be operatively connected together without having to be unshielded will be described. 
     For the purposes of example, the present EMI shielding apparatus is herein described in the form of a computer system  10  comprising a support structure or a chassis  12  adapted to house electronic components, such as a main printed circuit board or motherboard  14  (FIGS.  2  and  3 ), as well as other electronic devices adapted to be plugged into the motherboard  14 . More specifically, as illustrated in FIG. 1, the chassis  12  is adapted to removably receive a number of side by side EMI shielded loading cartridges or units, one of which is shown at  16 . Each loading cartridge  16  houses an electronic component, such as an expansion card  18 , to be operatively connected to the motherboard  14 . 
     As seen in FIGS. 1 to  3 , the chassis  12  is preferably of a metallic sheet construction and includes spaced-apart L-shaped side walls  20 . Each side wall  20  has a front upstanding portion  22  and an elongated bottom portion  24  extending integrally rearwardly from a bottom end of the front upstanding portion  22 . A top wall structure  26  extends between the front upstanding portions  22  of the L-shaped side walls  20  and defines a front bay through which the loading cartridges  16  can be removably inserted into the chassis  12 . 
     As seen in FIG. 2, the top wall structure  26  can include a horizontal plate  25  having front and rear upwardly folded end portions  29 . The horizontal plate  25  is fastened to inturned lip portions  31  (FIG. 3) projecting laterally inwardly from the upper edges of the front upstanding portions  22  of the side walls  20 . A cover plate  33  can also be secured to the lips  31  between the front and rear upwardly folded end portions  29  of the horizontal plate  25 . 
     Inturned mounting lips  27  (FIGS. 2 and 3) project laterally inwardly from the bottom edges of the elongated bottom portions  24  of the L-shaped side walls  20 . Holes (not shown) are defined in the mounting lips  27  for allowing the chassis  12  to be securely mounted to a support surface (not shown). 
     The chassis  12  further includes a bottom EMI shielding plate  28  mounted between the L-shaped side walls  20  for overlying the top surface of the motherboard  14 . The EMI shielding plate  28  is preferably fastened to the L-shaped side walls  20  by means of threaded fasteners, such as screws. According to a construction of the present invention, the shielding plate  28  is also permanently secured in parallel to the motherboard  14  at a distance from the top surface thereof by means of a plurality of fasteners, such as rivets  30 , extending therebetween, thereby allowing the motherboard  14  and the shielding plate  28  to be assembled as a single unit to the interconnected side walls  20 , which act as a support structure therefor. 
     As best seen in FIG. 2, the EMI shielding plate  28  is provided with front and rear downwardly depending lip portions  32 . The lip portions  32  cooperate with the side wall  20  to form a transverse electromagnetic mode (TEM) radiation edge shielding for the motherboard  14  to prevent the passage of EMI radiation outwardly of the chassis  12 . Electromagnetic interference radiation discharged from the electronic components mounted on the top planar surface of the substrate of the motherboard  14  are prevented from escaping from above by the horizontal portion of the shielding plate  28  overlying the motherboard  14 . By so mounting the motherboard  14  of an electronic device, such as a computer, behind an EMI shielding plate  28  with the edges of the motherboard  14  peripherally surrounded by an EMI shielding structure, it becomes possible to substantially entirely shield the motherboard  14  from electromagnetic interference radiation. 
     As best shown in FIG. 1, one aperture  34  is defined in the EMI shielding plate  28  for each corresponding electrical connector  36  extending from the top surface of the motherboard  14 . This advantageously allows peripheral electronic devices to be connected to the motherboard  14  without having to unshield the latter. Each aperture  34  is preferably sized so as to generally correspond to the contour of the associated connector  36 . 
     As shown in FIGS. 1 and 3, a number of pairs of top and bottom guide channels  38  and  40  in the form of slotted guides are respectively defined in the top horizontal plate  25  and the bottom shielding plate  28  adjacent each row of connectors  36  for slidably receiving the loading cartridges. 
     Each loading cartridge  16  is preferably of the type disclosed in co-pending U.S. patent application Ser. No. 09/689,732 filed on Oct. 13, 2000, the content of which is herein incorporated by reference. 
     More particularly, the illustrated loading cartridge  16  generally comprises a sliding member  42 , a metallic mounting plate  44  movably mounted on an inner surface of the sliding member  42 , an actuator in the form of a lever  46  adapted to be manually actuated to displace the mounting plate  44  up and down on the inner surface of the sliding member  42 , and an EMI shielding cover  48  adapted to be removably mounted to the mounting member  44  for joint movement therewith. As seen in FIG. 2, a number of clamping members  50 ,  52  and  54  are provided on the mounting plate  44  for readily releasably securing the expansion card  18  thereon without the help of any tool. According to the illustrated embodiment, the first two clamping members  50  and  52  are adjustably mounted in selected diagonal slots  56  defined in the mounting plate  44 . The clamping members  50  and  52  can be releasably secured in position at a desired location in selected slots  56  in accordance with the dimensions of the expansion card  18 . Any appropriate locking mechanism known in the art can be used for that purpose. Each clamping member  50 / 52  includes a lever  58  which can be manually pivoted for wedging the expansion card  18  behind a rib  60  forming part of the clamping member  50 / 52 , as shown in FIG.  2 . 
     The third clamping member  54  is pivotally mounted to a front bracket  62  extending integrally from the mounting plate  44  for movement into a slot  64  (FIG. 1) defined in a front plate  66  fixedly secured to the sliding member  42 . By rotating the clamping member  54  into a substantially vertical position, as shown in FIG. 2, a forwardly projecting tongue  68  (FIG. 1) of the expansion card  18  is wedged between a bottom surface of the bracket  62  and a wedge surface  70  (FIG. 1) of the clamping member  54 . 
     A handle  72  is mounted at the end of the lever  46 . The handle  72  is provided with a latch  74  (FIG. 2) releasably engageable into a corresponding catch  76  (FIG. 1) defined in a horizontal locking surface  78  extending integrally forwardly from the front shielding lip portion  32  of the shielding plate  28 . 
     The sliding member  42  is provided in the form of a plate having a top guiding edge  80  slidably insertable into and out of the top guide channel  38  and a bottom guiding structure  82  provided in the form of an elongated channel  84  configured to slidably receive one edge of the bottom guide channel  40  (see FIG.  3 ). As shown in FIG. 2, the channel  84  is formed by a continuous top rib  86  and a bottom row of ribs  88  extending laterally at right angles from a bottom portion of the inner surface of the sliding member  42 . 
     The EMI shielding cover  48  and the mounting plate  44  form a EMI shielding enclosure for the expansion card  18  disposed in the internal spaced defined thereby. As shown in FIG. 3, the so formed EMI shielded enclosure defines a bottom opening for allowing the connectors  90  depending downwardly from the lower edge of the expansion card  18  to be operatively connected to the corresponding connectors  36  of the motherboard  14  without having to unshield the expansion card  18  or directly manipulate the same. As the expansion card  18  is shielded in its loading cartridge  16  and the motherboard  14  behind the shielding plate  28 , there is virtually no risk that one of the electronic components carried by the motherboard  14  or the expansion card  18  be damaged as a result of an electrostatic shock during the installation of the expansion card  18 . 
     When it is desired to operatively connect an expansion card  18  to the motherboard  14 , one has first to attach the expansion card  18  to the mounting plate  44  via the clamping members  50 ,  52  and  54 . Then, the EMI shielding cover  48  is secured to the mounting plate  44  to shield the expansion card  18 . Thereafter, the sliding member  42  is slidably inserted into the top and bottom guide channels  38  and  40  and slidably displace to a fully inserted position wherein the connectors  90  of the expansion card  18  are in register with the corresponding connectors  36  of the motherboard  14 . Once the loading cartridge  16  has been fully inserted, the lever  46  is pivoted to lower the connectors  90  of the expansion card  18  into engagement with the underlying connectors  36  of the shielded motherboard  14 . As seen in FIG. 2, the latch  74  is engaged with the associated catch  76  when the lever  46  is pivoted to an operative position, wherein the connectors  90  and  36  are operatively connected. Accidental withdrawal of the expansion card  18  from the chassis  12  is further prevented by the connector receiving projections  92  extending laterally from the mounting plate  44  to receive the corresponding connector  36  therebetween once the connector  90  has been lowered into engagement with the underlying connector  36 , as illustrated in FIG.  2 . 
     The shielding plate  28 , the mounting plate  44  and the shielding cover  48  are also preferably made of a heat conductive material to dissipate the heat generated by the operating electronic components.