Abstract:
An electronic module and method of making an electronic module include a printed circuit board (PCB) having a surface, at least one conductive trace being formed on the surface. A housing element for mechanically mating with the PCB includes at least one mating surface aligned with the conductive trace on the PCB when the PCB and the housing element are mechanically mated, the mating surface comprising a plurality of alternating protrusions and spaces between the protrusions. An electrical gasket is formed on the mating surface of the housing element such that the electrical gasket conforms with the protrusions and spaces on the mating surface of the housing element and is disposed between the mating surface of the housing element and the conductive trace on the surface of the PCB when the housing element and the PCB are mechanically mated, such that the electrical gasket provides an electromagnetic interference (EMI) seal between the mating surface of the housing element and the conductive trace on the first surface of the PCB.

Description:
BACKGROUND 
     1. Technical Field 
     This application relates to electronic equipment, and, in particular, to radio-frequency interference (RFI) and/or electromagnetic interference (EMI) shielding in electronic equipment, and methods of making electronic equipment with RFI and EMI shielding. 
     2. Discussion of Related Art 
     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. 
     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. 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. 
     In some electrical systems with such a shielding configuration, such as, for example, automotive radar sensor systems/modules, the gasket interposed between a PCB within the module and a cover of the module creates mechanical stresses on the PCB when it is attached to the housing cover. These stresses can cause damage to the PCB and can adversely affect the quality of the electrical seal and, therefore, performance of the system. 
     SUMMARY 
     According to one aspect, an electronic module is provided. The electronic module includes a printed circuit board (PCB) having a surface, at least one conductive trace being formed on the surface. The module also includes a housing element for mechanically mating with the PCB, the housing element comprising at least one mating surface aligned with the conductive trace on the PCB when the PCB and the housing element are mechanically mated, the mating surface comprising a plurality of alternating protrusions and spaces between the protrusions. An electrical gasket is formed on the mating surface of the housing element such that the electrical gasket conforms with the protrusions and spaces on the mating surface of the housing element and is disposed between the mating surface of the housing element and the conductive trace on the surface of the PCB when the housing element and the PCB are mechanically mated, such that the electrical gasket provides an electromagnetic interference (EMI) seal between the mating surface of the housing element and the conductive trace on the first surface of the PCB. 
     In some exemplary embodiments, the electronic module is an automotive radar sensor module. 
     In some exemplary embodiments, the housing element is formed of a material comprising metal. In some exemplary embodiments, the metal is aluminum. 
     In some exemplary embodiments, the housing element is formed of a plastic material. 
     In some exemplary embodiments, the housing element comprises a conductive coating. In some exemplary embodiments, the conductive coating is conductive paint. 
     In some exemplary embodiments, the electrical gasket comprises a soft conductive elastomer material. 
     In some exemplary embodiments, the protrusions and spaces on the mating surface of the housing element have a sawtooth pattern. 
     In some exemplary embodiments, the protrusions and spaces on the mating surface of the housing element have a substantially rectangular shape. 
     In some exemplary embodiments, the protrusions and spaces on the mating surface of the housing element have a substantially trapezoidal shape. 
     According to another aspect, a method of making an electronic module is provided. The method includes: forming at least one conductive trace on a surface of a printed circuit board (PCB); forming at least one mating surface on a housing element for mechanically mating with the PCB, the at least one mating surface being formed to be aligned with the conductive trace on the PCB when the PCB and the housing element are mechanically mated, the mating surface being formed with a plurality of alternating protrusions and spaces between the protrusions; and forming an electrical gasket on the mating surface of the housing element such that the electrical gasket conforms with the protrusions and spaces on the mating surface of the housing element and is disposed between the mating surface of the housing element and the conductive trace on the surface of the PCB when the housing element and the PCB are mechanically mated, such that the electrical gasket provides an electromagnetic interference (EMI) seal between the mating surface of the housing element and the conductive trace on the first surface of the PCB. 
     In some exemplary embodiments, the electronic module is an automotive radar sensor module. 
     In some exemplary embodiments, the housing element is formed of a material comprising metal. In some exemplary embodiments, the metal is aluminum. 
     In some exemplary embodiments, the housing element is formed of a plastic material. 
     In some exemplary embodiments, the method further comprises applying a conductive coating to at least a portion of the housing element. In some exemplary embodiments, the conductive coating is conductive paint. 
     In some exemplary embodiments, the electrical gasket comprises a soft conductive elastomer material. 
     In some exemplary embodiments, forming the electrical gasket comprises: dispensing a fluid gasket material onto the mating surface of the housing element such that the fluid gasket material conforms with the protrusions and spaces on the mating surface of the housing element; and allowing the fluid gasket material to dry to a solid gasket material. 
     In some exemplary embodiments, forming the at least one mating surface on the housing comprises molding the mating surface while molding the housing. 
     In some exemplary embodiments, the protrusions and spaces on the mating surface of the housing element are formed in a sawtooth pattern. 
     In some exemplary embodiments, the protrusions and spaces on the mating surface of the housing element are formed to have a substantially rectangular shape. 
     In some exemplary embodiments, the protrusions and spaces on the mating surface of the housing element are formed to have a substantially trapezoidal shape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIG. 1  includes a schematic perspective view of a portion of a top or bottom cover of a housing of a conventional electronic system or module. 
         FIG. 2  includes a schematic perspective view of an exemplary printed circuit board (PCB), which can be installed in and mated with the cover illustrated in  FIG. 1 . 
         FIG. 3  includes a schematic cross-sectional view taken along line A-A′ of  FIG. 1 . 
         FIG. 4  includes a schematic perspective view of a portion of a top or bottom cover of a housing of an electronic system or module, according to some exemplary embodiments. 
         FIGS. 5-7  include schematic cross-sectional views taken along line A-A′ of  FIG. 4 , illustrating various mating surfaces and electrical gaskets, according to exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  includes a schematic perspective view of a portion of a top or bottom cover  10  of a housing of a conventional electronic system or module. Cover  10  includes a vertical wall  12  having an inner surface  14  and an outer surface  16 , as well as a top or bottom cover surface  31 . Cover  10  can be formed of an electrically conductive material, such as a metal, e.g., aluminium. Cover  10  can alternatively be formed of a non-conductive material such as plastic and coated with a conductive material such as conductive paint. Cover  10  can also include a shelf portion  18  on which a PCB can be mounted. Shelf portion  18  can be integrally formed with cover  10  such as by being molded in the same molding step as cover  10 . Shelf  18  can include a mating surface  20 , on which an electrical gasket  21  (shown in phantom) can be disposed. The electrical gasket  21  can be made of a conductive material, such as a soft conductive elastomer material, which mates with a surface of the PCB when the PCB is installed in cover  10 . 
       FIG. 2  includes a schematic perspective view of an exemplary printed circuit board (PCB)  30 , which can be installed in and mated with cover  10  illustrated in  FIG. 1 . Referring to  FIG. 2 , PCB  30  includes a front side, or top side or device side  32  on which can be mounted one or more integrated circuits (ICs)  34  and/or discrete electronic devices  35 . ICs  34  and discrete devices  35  can be connected by a conductor pattern printed on one or more layers and/or surfaces of PCB  30 . The conductor pattern can include a conductive trace  36  formed on surface  32  of PCB  30 . Conductive trace  36  can be connected to system ground and, therefore, can be considered a ground plane formed on PCB  30 . 
     When cover  10  of  FIG. 1  and PCB  30  of  FIG. 2  are mated together, the orientation of one of cover  10  and PCB  30  is opposite to that illustrated in  FIGS. 1 and 2 , respectively. That is, for example, PCB  30  is flipped over 180 degrees such that surface  32  faces cover  10 , thus allowing conductive trace  36  on PCB  30  to make electrical contact with mating surface  20  of shelf  18  formed in cover  10  through electrical gasket  21 . When assembled, PCB  30  and cover  10  are held firmly together in place by some rigid fastening means such as, for example, screws and threaded holes (not shown), against electrical gasket  21 . The intent of this configuration is to provide an electrical seal between cover  10  and PCB  30  such that an EMI shield of ICs  34  and discrete devices  35  is provided. 
     In many systems, the flat electrical gasket  21  can introduce mechanical stresses into the PCB  30  at the junction of cover  10  and PCB  30 . These stresses can result in bending and warping of PCB  30  and/or cover  10 , such that a complete electrical seal is not provided. This results in degrading the EMI shielding provided for the system. 
       FIG. 3  includes a schematic cross-sectional view taken along line A-A′ of  FIG. 1 . Referring to  FIG. 3 , cover  10  is illustrated with vertical wall  12 , having inner surface  14  and outer surface  16 . Cover  10  includes integral shelf portion  18  having mating surface  20  for supporting PCB  30  ( FIG. 2 ). Electrical gasket  21  is disposed on mating surface  20  of shelf portion  18 . Electrical gasket  21  can be formed by dispensing a fluid electrical gasket material, which can be, for example, a soft conductive elastomer, and then allowing the fluid gasket material to dry into solid electrical gasket  21 . 
     As illustrated in  FIG. 3 , electrical gasket  21  includes a flat, continuous top surface. As a result, when PCB  30  is secured to electrical gasket  21 , PCB  30  will be forced to conform to the flat continuous surface. This can cause bending and warping stresses to be introduced into PCB  30 , which can result in damage to PCB  30  and in an incomplete electrical seal being formed by electrical gasket  21 . 
     According to some exemplary embodiments, a dispensible electrical gasket is provided which is not flat. Therefore, the PCB is not prone to the warping and bending stresses caused by a flat electrical gasket  21 .  FIG. 4  includes a schematic perspective view of a portion of a top or bottom cover  100  of a housing of an electronic system or module, according to some exemplary embodiments. In some exemplary embodiments, the system or module is a radar sensor module for an automotive radar system. Cover  100  includes a vertical wall  112  having an inner surface  114  and an outer surface  116 , as well as a top or bottom cover surface  131 . Cover  100  can be formed of an electrically conductive material, such as a metal, e.g., aluminium. Cover  100  can alternatively be formed of a non-conductive material such as plastic and coated with a conductive material such as conductive paint. Cover  100  can also include a shelf portion  118  on which PCB  30  ( FIG. 2 ) can be mounted. Shelf portion  118  can be integrally formed with cover  100  such as by being molded in the same molding step as cover  100 . Shelf  118  can include a mating surface  120 , on which an electrical gasket  121  (shown in phantom), according to exemplary embodiments, can be disposed. Electrical gasket  121  can be made of a conductive material, such as a soft conductive elastomer, which mates with a surface of PCB  30  when PCB  30  is installed in cover  100 . 
     Referring to  FIG. 4 , mating surface  120  is not a flat, smooth, continuous surface as in the conventional system illustrated in  FIG. 1 . In contrast, according to some exemplary embodiments, mating surface  120  is formed with a plurality of ribs or protrusions  132  alternating with spaces or gaps  134  between ribs or protrusions  132 . In some exemplary embodiments, electrical gasket  121  disposed on mating surface  120  at least partially conforms with ribs  132  and spaces  134  of mating surface  120 , such that electrical gasket  121  also includes ribs or protrusions  136  alternating with spaces or gaps  138  between ribs or protrusions  136 . Since electrical gasket  121  does not have a continuous, flat surface, when PCB  30  ( FIG. 2 ) is mated with cover  100 , PCB  30  does not need to conform with a flat, continuous surface. Instead, it contacts electrical gasket  121  at ribs  136 . As a result, the warping and bending stresses of the conventional system illustrated in  FIG. 1  are eliminated. According to these exemplary embodiments, an improved electrical seal is obtained. 
     As described above, in some exemplary embodiments, electrical gasket  121  at least partially conforms with ribs  132  and spaces  134  of mating surface  120 . In some embodiments, electrical gasket  121  is formed by dispensing a fluid gasket material on mating surface  120 . The fluid gasket material can be, for example, a soft conductive elastomer. The dispensed fluid gasket material conforms to the shape of mating surface  120  and is allowed to dry and solidify. The resulting electrical gasket  121  also includes ribs  136  and spaces  138 , which contact conductive trace  36  on PCB  30  ( FIG. 2 ) when the system is assembled. 
       FIGS. 5-7  include schematic cross-sectional views taken along line A-A′ of  FIG. 4 , illustrating various mating surfaces  120  and electrical gaskets  121 , according to exemplary embodiments. Referring to  FIG. 5 , cover  100 A includes vertical wall  112 , having inner surface  114 , outer surface  116  and top or bottom cover surface  131 A. Shelf  118 A includes mating surface  120 A, and electrical gasket  121 A is disposed on mating surface  120 A. Mating surface  120 A is formed to have ribs or protrusions  132 A alternating with spaces or gaps  134 A between ribs or protrusions  132 A. In the exemplary embodiment illustrated in  FIG. 5 , ribs  132 A and spaces  134 A are substantially rectangular in cross-sectional shape. Electrical gasket  121 A formed on mating surface  120 A at least partially conforms with mating surface  120 A such that electrical gasket  121 A also includes ribs or protrusions  136 A alternating with spaces or gaps  138 A between ribs or protrusions  136 A. In some embodiments, the alternating ribs  136 A and spaces  138 A can be viewed to have a modified sawtooth shape in cross-section. 
     Referring to  FIG. 6 , cover  100 B includes vertical wall  112 , having inner surface  114 , outer surface  116  and top or bottom cover surface  131 B. Shelf  118 B includes mating surface  120 B, and electrical gasket  121 B is disposed on mating surface  120 B. Mating surface  120 B is formed to have ribs or protrusions  132 B alternating with spaces or gaps  134 B between ribs or protrusions  132 B. In the exemplary embodiment illustrated in  FIG. 6 , ribs  132 B are substantially trapezoidal in cross-sectional shape. Electrical gasket  121 B formed on mating surface  120 B at least partially conforms with mating surface  120 B such that electrical gasket  121 B also includes ribs or protrusions  136 B alternating with spaces or gaps  138 B between ribs or protrusions  136 B. In some embodiments, the alternating ribs  136 B and spaces  138 B can be viewed to have a modified sawtooth shape in cross-section. 
     Referring to  FIG. 7 , cover  100 C includes vertical wall  112 , having inner surface  114 , outer surface  116  and top or bottom cover surface  131 C. Shelf  118 C includes mating surface  120 C, and electrical gasket  121 C is disposed on mating surface  120 C. Mating surface  120 C is formed to have ribs or protrusions  132 C alternating with spaces or gaps  134 C between ribs or protrusions  132 C. In the exemplary embodiment illustrated in  FIG. 7 , ribs  132 C and spaces  134 C can be viewed to have a modified sawtooth shape in cross-section. Electrical gasket  121 C formed on mating surface  120 C at least partially conforms with mating surface  120 C such that electrical gasket  121 C also includes ribs or protrusions  136 C alternating with spaces or gaps  138 C between ribs or protrusions  136 C. In some embodiments, the alternating ribs  136 C and spaces  138 C can be viewed to have a modified sawtooth shape in cross-section. 
     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. 
     For example, in  FIG. 4 , shelf portion  118  has a particular size and shape. It is shown by way of example only to be formed adjacent to the entire inner surface  114  of vertical wall  112 . It is also shown to have a web portion connecting the portions adjacent to vertical wall  112 . It will be understood that this particular configuration of shelf  118  and, therefore, mating surface  120 , is exemplary only and is intended to illustrate that shelf  118  and mating surface  120  can have any configuration, including adjacent to wall  112  and in a connecting web configuration as illustrated in  FIG. 4 , but also in other configurations, such as standing alone on surface  131  of cover  100 , or other configurations.