Patent Publication Number: US-2009231825-A1

Title: Electromagnetic shielding device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an electromagnetic shielding device. 
     2. Description of the Related Art 
       FIG. 1  illustrates an electronic device employing a conventional electromagnetic shielding device that includes a circuit board  1  and a metal cover  2 . The circuit board  1  has a component-mounting surface  101  mounted with a plurality of electronic components  102 , and a looped solder pad  103  attached to the component-mounting surface  101  and disposed to surround the electronic components  102 . The metal cover  2  is mounted on the circuit board  1  using surface mounting techniques, and has a top wall  201 , and a looped surrounding wall  202  connected integrally to a periphery of the top wall  201 . The surrounding wall  202  has one end connected electrically and fixedly to the solder pad  103 . It is noted that the solder pad  103  is disposed so that there is preferably a distance (w) between the electronic components  102  and a looped inner surface of the surrounding wall  202  of the metal cover  2 . 
     However, in order to attach fully the solder pad  103  to the component-mounting surface  101 , a looped peripheral region  104  of the component-mounting surface  101  is preferably maintained between the solder pad  103  and a periphery of the circuit board  1  such that a distance (w 1 ) is formed between a looped outer surface of the surrounding wall  202  of the metal cover  2  and the periphery of the circuit board  1 . As a result, the circuit board  1  has a relatively large size, thereby impeding miniaturization of the electronic device. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the present invention is to provide an electromagnetic shielding device that can overcome the aforesaid drawbacks of the prior art. 
     According to one aspect of the present invention, there is provided an electromagnetic shielding device that comprises: 
     a base board having a top surface adapted to be mounted with an electronic component thereon, a bottom surface opposite to the top surface and having an area larger than that of the top surface, and a looped surrounding surface interconnecting peripheries of the top and bottom surfaces, the looped surrounding surface having an inclined upper surface portion extending outwardly and downwardly from the periphery of the top surface; 
     a looped solder pad attached to the inclined upper surface portion of the looped surrounding surface of the base board; and 
     a metal cover mounted on the base board, and having a top wall, and a looped surrounding wall extending downwardly from a periphery of the top wall, the looped surrounding wall having a bottom end connected electrically and fixedly to the looped solder pad such that the metal cover cooperates with the base board so as to define an inner receiving space therebetween for receiving the electronic component. 
     According to another aspect of the present invention, there is provided an electromagnetic shielding device that comprises: 
     a base board having a top surface adapted to be mounted with an electronic component thereon, a bottom surface opposite to the top surface and having an area larger than that of the top surface, and a looped surrounding surface interconnecting peripheries of the top and bottom surfaces, the looped surrounding surface having a vertical upper surface portion extending downwardly from the periphery of the top surface, a vertical lower surface portion extending upwardly from the periphery of the bottom surface, and a horizontal intermediate surface portion interconnecting a lower end of the vertical upper surface portion and an upper end of the vertical lower surface portion; 
     a looped solder pad attached to the vertical upper surface portion and the horizontal intermediate surface portion of the looped surrounding surface of the base board; and 
     a metal cover mounted on the base board, and having a top wall, and a looped surrounding wall extending downwardly from a periphery of the top wall and connected electrically and fixedly to the looped solder pad such that the metal cover cooperates with the base board so as to define an inner receiving space therebetween for receiving the electronic component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic sectional view of an electronic device employing a conventional electromagnetic shielding device; 
         FIG. 2  is a schematic sectional view showing an electronic device employing the first preferred embodiment of an electromagnetic shielding device according to the present invention; 
         FIG. 3   a  to  3   c  are perspective views illustrating how the electronic device is fabricated; 
         FIG. 4  is a schematic sectional view illustrating a final step of fabricating the electronic device; and 
         FIG. 5  is a schematic sectional view showing an electronic device employing the second preferred embodiment of an electromagnetic shielding device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure. 
     Referring to  FIG. 2 , the first preferred embodiment of an electromagnetic shielding device according to the present invention is shown to be embodied in an electronic device, such as a wireless communication electronic device. The electromagnetic shielding device includes a base board  10 , a looped solder pad  12 , and a metal cover  20 . 
     The base board  10 , such as a rectangular circuit board, has a top surface  111  adapted to be mounted with a plurality of electronic components  13  of the electronic device thereon, a bottom surface  112  opposite to the top surface  111  and having an area larger than that of the top surface  111 , and a looped surrounding surface  113  interconnecting peripheries of the top and bottom surfaces  111 ,  112 . In this embodiment, the looped surrounding surface  113  has an inclined upper surface portion  114  extending outwardly and downwardly from the periphery of the top surface  111 , and an upright lower surface portion  115  having an upper end connected to a lower end of the inclined upper surface portion  114 . 
     The looped solder pad  12  is attached to the inclined upper surface portion  114  of the looped surrounding surface  113  of the base board  10  by plating techniques. 
     The metal cover  20  is mounted on the base board  10  using surface mounting techniques, and has a top wall  21 , and a looped surrounding wall  22  extending downwardly from a periphery of the top wall  21 . The looped surrounding wall  22  has a bottom end  221  connected electrically and fixedly to the looped solder pad  12  such that the metal cover  20  cooperates with the base board  10  so as to define an inner receiving space therebetween for receiving the electronic components  13 . 
       FIGS. 3   a ,  3   b ,  3   c  and  4  illustrate how the electronic device employing the electromagnetic shielding device of the first preferred embodiment is fabricated. Firstly, a rectangular substrate  100  is provided, wherein the substrate  100  has a top surface  110  formed with four open-ended slots  1100  having a V-shaped cross-section. The slots  1100  are respectively adjacent to and parallel to four sides of the substrate  100 . Each slot  1100  is defined by first and second flat surfaces  1101 ,  1102  opposite to each other, as shown in  FIG. 3   a . It is noted that a central portion  1103  of the top surface  110  of the substrate  100  defined among the four slots  1100  serves as the top surface  111  of the base board  10  of  FIG. 2 . Central portions of the first flat surfaces  1101  of the substrate  100  constitute the inclined upper surface portion  114  of the looped surrounding surface  113  of the base board  10  of  FIG. 2 . Then, a solder material  200  is plated on the first and second flat surfaces  1101 ,  1102  of the substrate  100 , as shown in  FIG. 3   b . It is noted that the solder material  200  plated on the portions of the first flat surfaces  1101  of the substrate  100  constitutes the looped solder pad  12  of  FIG. 2 . Subsequently, the electronic components  13  are mounted on the central portion  1103  of the top surface  110  of the substrate  100  (see  FIG. 3   c ). Thereafter, the metal cover  20  is covered over the portion  1103  of the top surface  110  of the substrate  100 , and is mounted on the substrate  100  using surface mounting techniques, as shown in  FIG. 4 . Finally, an unnecessary peripheral portion of the substrate  100  is cut off such that the electronic device is completed. 
     In such a configuration, the solder pad  12  is attached to the inclined upper surface portion  114  of the looped surrounding surface  113  of the base board  10  without requiring the looped peripheral region  104  present in the aforesaid conventional electromagnetic shielding device of  FIG. 1 . In addition, a distance (w 2 ) (see  FIG. 2 ) between a looped outer surface  223  of the surrounding wall  22  of the metal cover  20  and the upright lower surface portion  115  of the looped surrounding surface  113  of the base board  10  is much less than the distance (w 1 ) in  FIG. 1 . As a result, the base board  10  has a relatively small size, thereby facilitating miniaturization of the electronic device. Furthermore, due to the presence of the inclined upper surface portion  114 , the metal cover  20  can be accurately positioned on the base board  10  during assembly. 
       FIG. 5  illustrates the second preferred embodiment of an electromagnetic shielding device according to this invention, which is a modification of the first preferred embodiment. In this embodiment, the looped surrounding surface  119  of the base board  10 ′ has a vertical upper surface portion  116  extending downwardly from the periphery of the top surface  111 , a vertical lower surface portion  117  extending upwardly from the periphery of the bottom surface  112 , and a horizontal intermediate surface portion  118  interconnecting a lower end of the vertical upper surface portion  116  and an upper end of the vertical lower surface portion  117 . 
     In addition, the looped solder pad  12 ′ has a vertical pad portion  121  attached to the vertical upper surface portion  116  of the looped surrounding surface  119  of the base board  10 ′, and a horizontal pad portion  122  connected to a lower end of the vertical pad portion  121  and attached to the horizontal intermediate surface portion  118  of the looped surrounding surface  119  of the base board  10 ′. As a result, the bottom end  221  of the looped surrounding wall  22  of the metal cover  20  is in electrical contact with the horizontal pad portion  122  of the looped solder pad  12 ′. The looped surrounding wall  22  of the metal cover  20  further has a looped inner surface  222  in electrical contact with the vertical pad portion  121  of the looped solder pad  12 ′. 
     In such a configuration, the solder pad  12 ′ is attached to the vertical upper surface portion  116  and the horizontal intermediate surface portion  118  of the looped surrounding surface  119  of the base board  10 ′ without requiring the looped peripheral region  104  present in the aforesaid conventional electromagnetic shielding device of  FIG. 1 . In addition, a distance (w 3 ) between the looped outer surface  223  of the looped surrounding wall  22  of the metal cover  20  and the vertical lower surface portion  117  of the looped surrounding surface  119  of the base board  10 ′ is much less than the distance (w 1 ) in  FIG. 1 . As a result, the base board  10 ′ has a relatively small size, thereby facilitating miniaturization of the electronic device. Furthermore, due to the presence of the vertical upper surface portion  116  and the horizontal intermediate surface portion  118 , the metal cover  20  can be accurately positioned on the base board  10 ′ during assembly. 
     While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.