Abstract:
A device comprises a printed circuit board including a plurality of electric components mounted thereto and a shielding element for one of shielding the electric components from electric signals outside the device and shielding electric components outside the device from electric signals within the device in combination with an elastomeric gasket forming a first electrically conductive path between the shielding element and a contacting surface of the gasket and a spacer element a first surface of which contacts the printed circuit board, a second surface of the spacer element contacting the contacting surface of the gasket, the spacer element defining a second electrically conductive path between the first and second surfaces thereof to couple the first and second electrically conductive paths to electrically couple the shielding element to the printed circuit board.

Description:
BACKGROUND INFORMATION  
       [0001]     Components of an electronic device which enable the device to perform its functions (e.g., internal circuitry) are often referred to as critical components. Such critical components including, for example, discrete and integrated components, are typically arranged in close configuration on a circuit board. Often it is required that the circuit board and the critical components be disposed within shielding structures to prevent unwanted electrical emissions from seeping out or in. It is also often required that the critical components be disposed below electrical circuit signals or grounding paths of the circuit board.  
         [0002]     Also included in the circuit board are contact positions, which are necessarily connected to a variety of other structures. The contact positions are particularly useful for shielding and grounding functions and are generally formed of materials of relatively high conductivity and corrosion resistance. However, the contact positions are often required to be placed around the critical components, and thus may be difficult to access.  
         [0003]     A printed circuit assembly may directly incorporate conductive and/or corrosion resistant materials directly into its structure in order to form the contact positions. However, such integration results in high production and replacement costs.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention is directed to a device comprising a printed circuit board including a plurality of electric components mounted thereto and a shielding element for one of shielding the electric components from electric signals outside the device and shielding electric components outside the device from electric signals within the device in combination with an elastomeric gasket forming a first electrically conductive path between the shielding element and a contacting surface of the gasket and a spacer element a first surface of which contacts the printed circuit board, a second surface of the spacer element contacting the contacting surface of the gasket, the spacer element defining a second electrically conductive path between the first and second surfaces thereof to couple the first and second electrically conductive paths to electrically couple the shielding element to the printed circuit board. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is an exemplary embodiment of a system according to the present invention;  
         [0006]      FIG. 2A  is an exemplary embodiment an open circuit system according to the present invention;  
         [0007]      FIG. 2B  is an exemplary embodiment of a closed circuit system according to the present invention;  
         [0008]      FIG. 3A  is another exemplary embodiment of a system according to the present invention;  
         [0009]      FIG. 3B  is another exemplary embodiment of a system according to the present invention; and  
         [0010]      FIG. 3C  is another exemplary embodiment of a system according to the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0011]     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are provided with the same reference numerals. The present invention provides a system to electrically couple contact points on a printed circuit board (“PCB”) to a secondary structure.  
         [0012]     As shown in  FIG. 1  an exemplary embodiment of the device according to the present invention includes a spacer element (e.g., an interface  240 ) mounted on a PCB  260 . The interface  240  is secured to the PCB  260 , for example, with solder  250 . The interface  240  contacts an electrically conductive elastomeric gasket  220  at a contact surface  230 . The elastomeric gasket  220  also contacts a structure  210  to which it is secured by for example, adhesive, compression, mechanical fasteners, etc. To simplify manufacturing, the interface  240  is preferably sized and shaped similarly to other components coupled to the PCB  260 . For example, the interface  240  may be equivalent in size to an “0603” surface mount component, measuring 0.060″L×0.030″W×0.030″H.  
         [0013]     The interface  240  is made from one or more materials, at least one of which is conductive. For instance, the interface may be substantially composed of a non-conductive material, such as plastic, with selected portions of the surface coated with a highly conductive material, such as gold. Those skilled in the art will understand that the coated portions may be limited to those areas which are required to conduct electricity. Specifically, all or a part of a surface of the interface  240  which contacts the conductive elastomeric gasket  220  will be coated with conductive material as will all or part of the surface of the interface  240  which contacts the PCB  260 . Furthermore, one or more paths of conductive material will join these areas of electrical contact between the interface  240  and the gasket  220  and between the interface  240  and the PCB  260 . Alternatively, the interface  240  may be a mass formed of one or more conductive materials. In a further exemplary embodiment, the interface  240  may be formed of one or more conductive materials with a hollow core. As would be understood by those of skill in the art, the conductive material(s) used in any of these embodiments will preferably be selected based on cost and/or desired performance criteria. For example, lead/tin, copper, gold, silver, or any other conductive material may be used.  
         [0014]     Before the solder  250  is applied to the PCB  260  to secure the interface  240 , the PCB  260  may be coated. The coating may be applied to exposed metal portions of the PCB  260 , and may be any of a variety of types. For example, the coating may be organic solder preservative (“OSP”), electroless nickel/immersion gold (“ENIG”), immersion tin, immersion silver, etc. In a conventional system, the coating may serve as the electrical coupling between the PCB and the elastomeric gasket, and thus the coating would have to be highly conductive. However, according to the present invention, an electrical connection between the PCB  260  and the elastomeric gasket  220  is provided by the interface  240 . Thus, it is not necessary for the coating to provide the electrical coupling, and a lower cost coating with lower conductivity, such as OSP, may be used without being cleaned. Because the OSP does not require cleaning to enhance its conductivity, a manufacturing step is eliminated and manufacturing costs are decreased.  
         [0015]     The elastomeric gasket  220  is preferably made of silicon rubber with a highly conductive silver fill dispersed throughout. However, any compliant material may be used to form the gasket  220 . Further, any highly conductive material or assembly may be used in place of the silver fill.  
         [0016]     The contact surface  230  includes a relative degree of contact resistance. Because the interface  240  is coated with corrosion resistant material, the degree of contact resistance will not degrade significantly over time. Integrity of the contact surface  230  is also enhanced as the interface  240  increases a surface area of the PCB  260  over which electrical contact is established.  
         [0017]     The elastomeric gasket  220  may take a variety of shapes and forms. For instance, the elastomeric gasket  220  may cover an entire surface of the structure  210 . Alternatively, the gasket  220  may be formed as one or more strips distributed along a surface of the structure  210 . Further, the elastomeric gasket  220  may be formed in any of a variety of shapes. For example, the gasket  220  may be substantially rectangular, conical, etc. The interface  240  eliminates the need for the elastomeric gasket  220  to be designed to extend down to the PCB  260  and contorted and maneuvered around discrete and integrated electrical components.  
         [0018]     The structure  210  may be used for a variety of applications. For example, the structure  210  may be used to shield components of the PCB  260  from electrical emissions of other components and/or to prevent the escape of electrical emissions produced by the components of the PCB  260  to surrounding areas. Alternatively, the structure  210  may serve as a ground for circuitry disposed on the PCB  260 . The structure  210  may also serve as part of a signal path. Accordingly, the structure  210  is preferably formed of sheet metal or any other conductive material possessing suitable mechanical properties.  
         [0019]      FIG. 2A  shows an embodiment of the present invention wherein, before being deformed through contact with the interface  240 , the elastomeric gasket  220  is substantially conical. As shown, the system is in an open circuit configuration with no conductive path between the PCB  260  and the structure  210 . An end of the gasket  220  distal to the structure  210  is tapered. Accordingly, an extent of the contact surface  230  between the gasket  220  and the interface  240  may be varied by adjusting an amount of compression of the gasket  220  when assembled with the PCB  260 . For example, in applications where it is desired that the interface  240  be relatively narrow, the gasket  220  will be compressed against the interface  240  only until a distal portion of the gasket  220  contacts the interface  240 . Conversely, for applications requiring a wider interface  240  such as that portrayed in  FIG. 2B , the structure  210  will be pressed against the PCB  260  until a wider portion of the gasket  220  is spread against the interface  240 , as will be described below.  
         [0020]      FIG. 2B  shows the distal end of the gasket  220  after being flattened due to compression against the interface  240  increasing the length (and width) of the contact surface  230 . As the degree of compression is increased, the area of the contact surface  230  increases.  
         [0021]      FIG. 3A  shows an embodiment of the present invention where the interface  240  is comprised of a plurality of discrete interface elements  241 . In this embodiment, the interface elements  241  are aligned in a nose-to-tail configuration. This configuration may prove beneficial in that it allows the size of each of the discrete interface elements  241  to be reduced. Further, the nose-to-tail configuration may provide improved shielding because there are relatively few gaps between the discrete interface elements  241 , and any existing gaps are fairly small.  
         [0022]      FIG. 3B  shows an alternative embodiment of the present invention wherein the interface  240  is comprised of a plurality of discrete interface elements  241  stacked on one another. Specifically, as shown in  FIG. 3B , a first interface element  241  is stacked on second and third interface elements  241  aligned similarly to the nose-to-tail configuration of  FIG. 3A . The first interface element  241  is preferably secured and electrically coupled to the second and third interface elements  241  to ensure that the elements  241  will not shift relative to one another, disrupting the electrical connections therebetween. Accordingly, a first contact surface  232  exists between the first interface element  241  and the second interface element  241 . In addition, a second contact surface  230  exists between the first interface element  241  and the elastomeric gasket  220 .  
         [0023]      FIG. 3C  shows another alternative embodiment of the present invention wherein the interface  240  comprises a plurality of discrete elements  241 . In this configuration, a first interface element  241  is positioned on the PCB  260  with a second interface element  241  stacked on the first interface element  241 . However, this embodiment differs from that of  FIG. 3B  in that the second interface element  241  is positioned at a pitch with respect to the first interface  240 . The pitch may be maintained, for example, by a mass of solder  250  disposed between the first and second interface elements  241 . Similarly to the embodiment of  FIG. 3B , first and second contact surfaces  230 ,  232  exist between the first and second interface elements  241  and the elastomeric gasket  220 . The first contact surface  230  extends between the first and second interface elements  241  with the second contact surface  232  extending between the second interface element  241  and the gasket  220 . This configuration is particularly suited for devices where the structure  210  is not intended to be parallel to the PCB  260 .  
         [0024]     The interface of the present invention facilitates the installation of electrical shielding, grounding, and signal contacts on conventional PCBs. Because of the highly conductive and corrosion resistant nature of the interface, the longevity and efficiency of the electrical connection between the PCB and a secondary component are significantly increased. Further, the installation is simplified and reduced in cost.  
         [0025]     The present invention has been described with reference to the above exemplary embodiments. One skilled in the art would understand that the present invention may also be successfully implemented if modified. Accordingly, various modifications and changes may be made to the embodiments without departing from the broadest spirit and scope of the present invention as set forth in the claims that follow. The specification and drawings, accordingly, should be regarded in an illustrative rather than restrictive sense.