Abstract:
An electrical gasket provides an electrical seal between first and second components in an electrical module. The electrical gasket includes an attachment portion for fixedly attaching the electrical gasket to one of the first and second components and a plurality of spring members for engaging the other of the first and second components to make mechanical and electrical contact between the first and second components such that the electrical seal is provided between the first and second electrical components. One of the components of the module can be an EMI shield or printed circuit board of the module, and another of the components can be the module housing.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    This application relates to electronic equipment, and, in particular, to radio-frequency interference (RFI) and/or electromagnetic interference (EMI) shielding in electronic equipment. 
         [0003]    2. Discussion of Related Art 
         [0004]    Electronic systems or modules can typically include one or more printed circuit boards (PCBs) populated with electronic circuits and devices. The PCB(s) can be contained within a housing which can have one or more covers which mate together to enclose the PCB(s). Similarly, one or more of the PCB(s) can mate with one or more of the covers of the housing. In some electronic systems or modules, it is important that the internal electronic circuitry be shielded from RFI and EMI, both to prevent RFI and/or EMI in the external environment from interfering with the internal electronic circuitry and to prevent the electronic systems or modules from emitting signals into the external environment. 
         [0005]    Typically, to prevent RFI and/or EMI, the mating covers of the housing and/or the mating covers and PCB(s) of the system are made of or coated with a conductive material. When the covers are mated together or when the PCB(s) and cover(s) are mated together, an electrical gasket, which can also include a conductive material, can be interposed between them to provide an electrical seal. Also, one or more shield devices can be installed in the assembly in electrical contact with the housing to shield the internal electronic circuitry. As a result, the circuitry can be completely enclosed by conductive material, which can be connected to the electrical ground of the system. This results in a complete shield against RFI and EMI. 
         [0006]    Shields are typically fabricated using a conductive material such as metal or a plastic which absorbs and/or reflects electromagnetic radiation. In some applications, the absorptive and conductive plastic shield is preferred over the purely conductive, e.g., metallic, shield. In order to implement electrical contact between the shield and the housing, a soft conductive gasket can be over-molded to the shield. However, in order to over-mold the soft conductive gasket in applications in which the plastic shield is used, a high-temperature plastic material must be used as the shield material instead of a low-temperature plastic, which results in higher cost. 
       SUMMARY 
       [0007]    According to one aspect, an electrical gasket for providing an electrical seal between first and second components in an electrical module is provided. The electrical gasket includes an attachment portion for fixedly attaching the electrical gasket to one of the first and second components. The electrical gasket also includes a plurality of spring members for engaging the other of the first and second components to make mechanical and electrical contact between the first and second components such that the electrical seal is provided between the first and second electrical components. 
         [0008]    In some exemplary embodiments, the electrical gasket comprises a plastic material. 
         [0009]    In some exemplary embodiments, the electrical gasket comprises a metallic material. 
         [0010]    In some exemplary embodiments, the one of the first and second components to which the gasket is fixedly attached is a shield for providing at least a portion of the electrical module with electromagnetic interference (EMI) shielding. 
         [0011]    In some exemplary embodiments, the one of the first and second components to which the gasket is fixedly attached is a printed circuit board. 
         [0012]    In some exemplary embodiments, the other of the first and second components is at least a portion of a housing of the electrical module. 
         [0013]    According to another aspect, an electrical module is provided. The electrical module includes a housing and a component in the housing. The electrical module also includes an electrical gasket fixedly attached to the component in the housing, the electrical gasket comprising a plurality of spring members for engaging the housing to make mechanical and electrical contact between the component and the housing such that an electrical seal is provided between the component and the housing. 
         [0014]    In some exemplary embodiments, the electrical gasket comprises a plastic material. 
         [0015]    In some exemplary embodiments, the electrical gasket comprises a metallic material. 
         [0016]    In some exemplary embodiments, the component to which the gasket is fixedly attached is a shield for providing at least a portion of the electrical module with electromagnetic interference (EMI) shielding. 
         [0017]    In some exemplary embodiments, the component to which the gasket is fixedly attached is a printed circuit board. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The foregoing and other features and advantages will be apparent from the more particular description of preferred embodiments, as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the inventive concept. 
           [0019]      FIG. 1  includes a schematic perspective exploded view of an electronic system or module of the type to which the present inventive concept can be applied. 
           [0020]      FIG. 2  includes a schematic cross-sectional diagram of a shield as illustrated in  FIG. 1 , taken along line A-A′ of  FIG. 1 , having a conventional electrical gasket over-molded on the shield of  FIG. 1 . 
           [0021]      FIG. 3  includes a schematic cross-sectional diagram of a shield as illustrated in  FIG. 1 , taken along line A-A′ of  FIG. 1 , with an integral electrical gasket, according to some exemplary embodiments. 
           [0022]      FIG. 4  includes a schematic cross-sectional diagram of the shield of  FIG. 3 , installed in the base cover illustrated in  FIG. 1 , along with an exemplary PCB illustrated in  FIG. 1 , according to some exemplary embodiments. 
           [0023]      FIGS. 5 and 6  include schematic top views of shields with integral electrical gaskets, according to some exemplary embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    It will be noted that, throughout this application, RFI and EMI will be used interchangeably. It will be understood that the present inventive concept and the exemplary embodiments are applicable to shielding for both RFI and EMI. 
         [0025]      FIG. 1  includes a schematic perspective exploded view of an electronic system or module  10  of the type to which the present inventive concept can be applied. Referring to  FIG. 1 , electronic module  10  can include a bottom or base cover  12  having vertical walls  20 , which have inner surfaces  24  and outer surfaces  22 . Base cover  12  also includes a lower inner surface  26 . Base cover  10  can be formed of a conductive material such as a metal, for example, aluminium. Alternatively, base cover  10  can be formed of a nonconductive material  25  such as plastic coated with a conductive material such as conductive paint. 
         [0026]    Module  10  can also include one or more printed circuit boards (PCBs)  14 , which can be mounted within base cover  12 . The PCB(s)  14  can be fixedly attached to base cover  12  on fixed spacers or standoffs or bosses (not shown), such as by screws and threaded holes in standoffs or bosses, an adhesive material, or other fixed attachment means. PCB(s)  14  can include one or more integrated circuits and/or discrete electronic components, collectively referred to herein as PCB devices  28 , which are mounted on a top side  30  of PCB  14 . It should be noted that PCB devices  28  could also be mounted to a bottom side  31  of PCB  14 , or PCB devices  28  could be mounted on both top side  30  and bottom side  31  of PCB  14 . 
         [0027]    PCBs  14  can include conductive patterns for connecting PCB devices  28  to each other and to the external environment as required. The conductive patterns can be printed on one or more layers or surfaces of PCBs  14 . Part of the conductive patterns can include a conductive trace  32 , which can be formed on top side  30  and/or bottom side  31  of PCB  14 . Conductive trace  32  can be connected to a system ground and, therefore, can serve as a ground plane on PCB  14 . 
         [0028]    Module  10  can also include a shield  16 , which provides shielding for RFI and EMI. Shield  16  is illustrated in  FIG. 1  as having a generic rectangular shape, but it will be understood that shield  16  can be made to have any shape desirable for the particular application. Shield  16  can be made of a plastic, EMI-absorptive and/or conductive material. Alternatively, shield  16  can be made of a conductive material such as a metal, e.g., aluminium. In some configurations, shield  16  can be installed in module  10  over PCB(s)  14  to provide EMI shielding for PCB devices  28 . In some configurations, shield  16  is located on and makes electrical and mechanical contact with conductive trace  32  on PCB(s)  14 . 
         [0029]    Module  10  also includes a top cover  18 , which is fixedly attached to base cover  22  to complete the housing or enclosure of module  10 . Top cover  18  can be attached to base cover  12  by screws and threaded holes (not shown), heat-stake pins, an adhesive, molded clip or clamp mating arrangements in top cover  18  and base cover  12  (not shown) or other known fixed attachment means. 
         [0030]    In many applications, such as where module  10  is an automotive radar sensor module, it is desirable to form an electrical seal between components of the system, including, for example, between multiple PCBs  14  and/or between one or more PCBs  14  and one or more covers  12  and  18  of the housing, and/or between one or more shields  16  and one or more covers  12  and  18  of the housing, and/or between one or more shields  16  and one or more PCBs  14 . To that end, it is often desirable to form an electrical gasket to facilitate formation of an electrical seal. 
         [0031]      FIG. 2  includes a schematic cross-sectional diagram of a shield as illustrated in  FIG. 1 , taken along line A-A′ of  FIG. 1 , having a conventional electrical gasket over-molded on the shield of  FIG. 1 . Referring to  FIG. 2 , to achieve electrical contact between PCB  14  and shield  16  and the housing of module  10 , a soft conductive gasket  50  is over-molded to a wall  52  of the metal/conductive or plastic EMI-absorptive/conductive shield  16 . When shield  16  is installed in base cover  12 , electrical gasket  50  makes electrical and mechanical contact with inner surface  24  of wall  12  to electrically seal shield  16  to base cover  12 . However, as mentioned above, in many cases, the plastic absorptive/conductive shield  16  will be preferred over the metallic conductive shield  16 . In the case of a plastic shield  16 , in order to over-mold the soft and conductive electrical gasket  50  onto shield  16 , a high-temperature plastic material must be used for shield  16 , which is more expensive than a low-temperature plastic material. 
         [0032]    According to the inventive concept, rather than over-molding a gasket onto shield  16 , an electrical gasket is integrally formed with the shield.  FIG. 3  includes a schematic cross-sectional diagram of a shield as illustrated in  FIG. 1 , taken along line A-A′ of  FIG. 1 , with an integral electrical gasket, according to some exemplary embodiments. Referring to  FIG. 3 , electrical gasket  150  is molded as a part of shield  116 , preferably in a single molding process, that is, the same molding process used to form shield  116 . 
         [0033]      FIG. 4  includes a schematic cross-sectional diagram of shield  116  of  FIG. 3 , installed in base cover  12  illustrated in  FIG. 1 , along with an exemplary PCB  14  illustrated in  FIG. 1 , according to some exemplary embodiments. Referring to  FIGS. 3 and 4 , electrical gasket  150  is configured in the form of a plurality of spring fingers, also referred to herein as “comb-pins,” which are urged outwardly toward inner surface  24  of wall  20  of base cover  12 . As illustrated in  FIG. 3 , the spring fingers of electrical gasket  150  are in a quiescent, non-compressed state. However, as illustrated in  FIG. 4 , when shield  116  is installed in base cover  12 , the spring fingers are urged against inner surface  24  of wall  20 , such that electrical contact is made between shield  116  and wall  20 , and shield  116  is held in place in base cover  12  by the spring force of the spring fingers against wall  20 . Electrically conductive contact is made to conductive wall  20  or conductive coating, e.g., paint  25 , on inner surface  24  of wall  20 . 
         [0034]    As further illustrated in the exemplary configuration of  FIG. 4 , shield  116 , held in place by the spring fingers of electrical gasket  150 , can be located over PCB  14 , which can be mounted in stationary fashion in base cover  12  on spacers, standoffs or integral bosses  54 , on bottom surface  26  of base cover  12 , which support PCB  14  at its bottom side or bottom surface  31 . Additionally, conductive trace  32  on top side or top surface  30  of PCB  14  can be in contact with shield  116  as illustrated. Hence, shield  116  with integral electrical gasket  150  can provide EMI shielding for PCB  14 . 
         [0035]    It will be noted that the assembly configurations depicted in  FIGS. 1-4  are exemplary only and are intended to illustrate the concept and certain embodiments of the shield with integral electrical gasket according to the present disclosure. It will be understood that PCBs may be different in configuration and quantity than as illustrated and described. In fact, the shield and integrated electrical gasket of the inventive concept need not be applied to a system having any PCBs. It may be applied to any system having any kind of device in which shielding is desirable. PCBs are used herein merely as illustrative examples of such devices. Also, the particular assembly illustrated herein, i.e., a PCB over a cover, and a shield with integral electrical gasket over the PCB, is used merely as an illustrative example. Shield  116  may be above or below any number of PCBs and/or devices, and above or below any kind of cover or partition or wall or barrier used in an electrical module in which shielding is desired. The particular configuration of the shielding, electrical gasket and/or devices requiring shielding will depend upon the particular application in which the inventive concept is being employed. In fact, the electrical gasket does not necessarily need to be formed on the shield. According to some exemplary embodiments, the electrical gasket of the inventive concept can be formed directly on the device or devices, i.e., integrated circuits, PCBs, waveguides, conductors, etc., for which EMI shielding is being provided. 
         [0036]      FIGS. 5 and 6  include schematic top view of shields with integral electrical gaskets, according to some exemplary embodiments. Referring to  FIG. 5 , a shield  116 A with narrow spring fingers or narrow comb-pin pattern  158 A is illustrated. Referring to  FIG. 5 , a shield  116 B with wide spring fingers or wide comb-pin pattern  158 B is illustrated. According to exemplary embodiments, since the electrical contact portion of the electrical gasket is molded along with the component being sealed, e.g., shield  116 , almost no extra cost is introduced into producing the shield. With proper design of the thickness of the contact area of the comb-pin, spring-finger structure, the comb-pin structure provides a desired predetermined contact through the pressure of the shield on the housing cover, while being sufficiently strong to prevent breakage, such as while being pressed into the housing cover during assembly. Also, with no over-molding process, no high-temperature plastic is required, also resulting in reduced cost. 
         [0037]    While the present inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present inventive concept as defined by the following claims.