Patent Publication Number: US-2019174659-A1

Title: Ciruit board assembly and shielding device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 106142436, filed on Dec. 4, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a circuit board assembly and a shielding device, and particularly to a circuit board assembly and a shielding device that prevent electromagnetic interference. 
     2. Description of Related Art 
     Electromagnetic radiation and distribution of electromagnetic field generated during operations of electronic products and electrical equipment affect performance of other electronic devices, apparatus or elements. Such phenomenon is called electromagnetic interference (EMI). Due to increase of operational frequency of electronic devices and miniaturization of manufacturing process, the number of electronic components on the printed circuit board is highly increased, which causes serious electromagnetic interference and degrades the performance of the electronic devices. Hence, how to prevent electromagnetic interference in each electronic component during the operation is a significant issue. 
     SUMMARY 
     The invention discloses electronic assemblies, which prevent electromagnetic interference via overlapped a heat dissipating member and a shielding frame. 
     The invention discloses a shielding frame adapted to be disposed on a circuit board for prevention of electromagnetic interference. 
     A circuit board assembly includes a circuit board, a shielding frame, a chip, and a heat dissipating member. The shielding frame is fixed to and protrudes from the circuit board. The shielding frame includes a first encircled positioning portion that is away from the circuit board. The chip is disposed on the circuit board and located in the shielding frame. The heat dissipating member is detachably disposed on the shielding frame, and includes a plate and a second encircled positioning portion that is disposed on the plate. When the heat dissipating member is disposed on the circuit board, the plate leans against the shielding frame and covers the chip, the second encircled positioning portion and the first encircled positioning portion correspond with each other in shape and position, so as to position the plate and the shielding frame. 
     According to an embodiment of the invention, the second encircled positioning portion is an encircled groove. The first encircled positioning portion is an encircled protrusion that corresponds to the encircled groove. 
     According to an embodiment of the invention, the first encircled positioning portion has a bent section in contact with a bottom wall of the encircled groove. 
     According to an embodiment of the invention, the shielding frame is electrically connected to a ground terminal of the circuit board. 
     According to an embodiment of the invention, the circuit board assembly further includes a plurality of fixing members. The heat dissipating member further includes a plurality of through holes that are formed at a surrounding of the second encircled positioning portion. The fixing members individually pass through the through holes, and are fixed to the circuit board and are electrically connected to a ground terminal of the circuit board. 
     A circuit board assembly includes a circuit board, a shielding frame, a chip, and a heat dissipating member. The shielding frame is fixed to and protrudes from the circuit board. The chip is disposed on the circuit board and is located in the shielding frame. The heat dissipating member is detachably disposed on the shielding frame. When the heat dissipating member is disposed on the circuit board, the heat dissipating member leans against the shielding frame and covers the chip, and the shielding frame overlaps the heat dissipating member at a junction in a radiation direction from a center of the chip. 
     A shielding device is adapted to be disposed on a circuit board and cover a chip that is disposed on the circuit board. The shielding device includes a shielding frame and a heat dissipating member. The shielding frame includes a first encircled positioning portion. The heat dissipating member includes a plate and a second encircled positioning portion that is disposed on the plate. The second encircled positioning portion and the first encircled positioning portion correspond with each other in shape and position, so as to position the plate and the shielding frame. When the shielding device is disposed on the circuit board, an encircled abutting section of the shielding frame connected to the first encircled positioning portion leans against the circuit board, and the shielding frame and the heat dissipating member cooperatively cover the chip. 
     According to an embodiment of the invention, the second encircled positioning portion is an encircled groove. The first encircled positioning portion is an encircled protrusion that corresponds to the encircled groove. 
     According to an embodiment of the invention, the first encircled positioning portion has a bent section in contact with a bottom wall of the encircled groove. 
     According to an embodiment of the invention, the plate has a first surface and a second surface opposite the first surface. The second encircled positioning portion is located at the first surface. The heat dissipating member further includes a plurality of fins located at the second surface. 
     Based on the above, when the heat dissipating member is disposed on the circuit board, the plate of the heat dissipating member leans against the shielding frame and covers the chip. One of the second encircled positioning portion and the first encircled positioning portion extends along a normal direction of the plate to another one of the second and first encircled positioning portions, so as to overlap each other. According to the present invention, the shielding frame and the plate of the heat dissipating member lean against each other and are used for covering the chip. Via integration of the plate and the shielding frame, transmission of electromagnetic radiation can be blocked to prevent influence of electromagnetic interference on operational performance of the chip. 
     In addition, according to the present invention, the shielding device includes the heat dissipating member and the shielding frame, and the plate of the heat dissipating member is configured as an upper cover of the shielding frame. That is, the shielding frame of the present invention is not required to have an additional upper cover, so as to reduce size of the shielding frame and reduce production cost. 
     To make the aforementioned more comprehensible, several embodiments accompanied with drawings are described in detail as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1A  is an exploded perspective view of a circuit board assembly according to an embodiment of the invention. 
         FIG. 1B  is another exploded perspective view of the circuit board assembly of  FIG. 1A . 
         FIG. 2A  is an assembled side view of the circuit board assembly of  FIG. 1A . 
         FIG. 2B  is an exploded side view of the circuit board assembly of  FIG. 1A . 
         FIG. 3A  is a sectional view of the circuit board assembly of  FIG. 1A . 
         FIG. 3B  is a partial enlarged view of an area A 1  in  FIG. 3A . 
         FIGS. 3C and 3D  are partial enlarged views of areas A 2  and A 3 , respectively, which replace the area A 1  in other embodiments. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     In general, electromagnetic interference which is a common phenomenon exists in electronic devices. For example, there are many kinds of high-efficiency electronic components disposed on the computer motherboard, such as central processing unit (CPU), computer memory, southbridge chip, northbridge chip, and graphics processing unit, etc. During operations, the abovementioned electronic components generate electromagnetic fields and electromagnetic radiation that outwardly emit, which render disturbance between the electronic components, thus degrading operational performance thereof. 
     An embodiment according to the present invention is directed to a circuit board assembly, which prevents electromagnetic interference and is effectively reduced in size. The detail description is recited as follows. 
       FIG. 1A  is an exploded perspective view of a circuit board assembly according to an embodiment of the invention.  FIG. 1B  is another exploded perspective view of the circuit board assembly of  FIG. 1A .  FIG. 2A  is an assembled side view of the circuit board assembly of  FIG. 1A .  FIG. 2B  is an exploded side view of the circuit board assembly of  FIG. 1A . 
     Referring to  FIGS. 1A, 1B, 2A, and 2B , an embodiment of the circuit board assembly  100  includes a circuit board  110 , a shielding frame  120 , a chip  130 , and a heat dissipating member  140 . The circuit board  110  is, for example, a printed circuit board, and is adapted to be applied in all types of electronic devices. In this embodiment, the circuit board  110  can be configured as a computer motherboard or a mobile phone motherboard, but is not limited thereto. In other embodiments, the circuit board  110  may be a motherboard in any electronic device that has all electronic components disposed thereon. 
     The shielding frame  120  is, for example, a hollow frame body, and includes two openings. When the shielding frame  120  is fixed to the circuit board  110 , the circuit board  110  covers one of the openings of the shielding frame  120 , and the shielding frame  120  extends outwardly and protrude from the circuit board  110 . The chip  130  is disposed on the circuit board  110  and is located in the shielding frame  120 . In this embodiment, the chip  130  is, for example, a central processing unit (CPU) or other electronic components. 
     The heat dissipating member  140  is detachably disposed on the shielding frame  120  and is fixed to the circuit board  110 . The heat dissipating member  140  covers the other opening of the shielding frame  120 , and is adapted to contact the chip  130  in order to achieve heat conduction and dissipation. In this embodiment, when the shielding frame  120  and the heat dissipating member  140  are simultaneously disposed on the circuit board  110 , such disposition are configured as a shielding device that is adapted to accommodate the chip  130  and prevent electromagnetic interference. 
       FIG. 3A  is a sectional view of the circuit board assembly of  FIG. 1A .  FIG. 3B  is a partial enlarged view of an area A 1  in  FIG. 3A . 
     Referring to  FIGS. 3A and 3B , in this embodiment, the shielding frame  120  includes a first encircled positioning portion  121 , an encircled abutting section  121   a , and a bent section  122 . The first encircled positioning portion  121  extends in a direction away from the circuit board  110 . The encircled abutting section  121   a  is connected to the first encircled positioning portion  121 , and extends to the circuit board  110  until it leans against the circuit board  110 . The bent section  122  is formed on an inner edge of the first encircled positioning portion  121 , and is spaced apart from the circuit board  110 . The heat dissipating member  140  includes a plate  141  and a second encircled positioning portion  142 . The plate  141  faces the circuit board  110 . The second encircled positioning portion  142  is disposed on the plate  141 . In this embodiment, the second encircled positioning portion  142  and the first positioning portion  141  correspond with each other in shape and position, so as to position the plate  141  and the shielding frame  120 . 
     When the heat dissipating member  140  is disposed on the circuit board  110 , the plate  141  leans against the bent section  122  of the shielding frame  120  and covers the chip  130 , and one of the second encircled positioning portion  142  and the first encircled positioning portion  121  extends along a normal direction (Dn) of the plate  141  to the other one thereof, in order to allow the first encircled positioning portion  121  and the second encircled positioning portion  142  overlap each other in a horizontal direction (Dp) that is perpendicular to the normal direction (Dn). 
     Referring to  FIGS. 3A and 3B , in this embodiment, the first encircled positioning portion  121  is, for example, an encircled protrusion. The second encircled positioning portion  142  is, for example, an encircled groove that corresponds to the encircled protrusion. The encircled protrusion and the encircled groove have corresponding polygonal shapes. The encircled protrusion may extend along the normal direction (Dn) into the encircled groove such that the encircled protrusion and the encircled groove have an overlapped area in the horizontal direction (Dp), and that the bent section  122  is in contact with a bottom wall (W 1 ) and a side wall (W 2 ) which is perpendicular to the bottom wall (W 1 ) for mutually positioning. Specifically, the part of the shielding frame  120  extending into the second encircled positioning portion  142  or not protruding out of a first surface (S 1 ) of the plate  141  is the first encircled positioning portion  121  (i.e., the encircled protrusion). The part of the shielding frame located out of the second encircled positioning portion  142  (i.e., the encircled groove) or protruding out of the first surface (S 1 ) of the plate  141  is the encircled abutting section  121   a.    
     In another embodiment, the first encircled positioning portion may be configured as an encircled groove formed on the shielding frame. The second encircled positioning portion may be configured as an encircled protrusion formed on the plate. When the heat dissipating member is disposed on the circuit board, the encircled groove may extend along the normal direction to accommodate the encircled protrusion, such that the encircled protrusion protrudes into the encircled groove, and that the shielding frame is in contact with the plate around the encircled protrusion for mutually positioning. The present invention is not limited thereto. 
     Referring to  FIGS. 1A and 1B , the plate  141  has the first surface (S 1 ) and a second surface (S 2 ) opposite to the first surface (S 1 ). The second encircled positioning portion  142  is located at the first surface (S 1 ). The heat dissipating member  140  further includes a plurality of fins  143  and a heat dissipating pad  144 . The fins  143  are located at the second surface (S 2 ) and are spaced apart from each other. Air is capable of passing through a space between any adjacent two of the fins  143  so each of the fins  143  is adapted to dissipate heat of the plate  141  to environment, which is absorbed from the chip  130 . The heat dissipating pad  144  (shown in  FIGS. 2B and 3A ) is disposed on the first surface (S 1 ) of the plate  141 , and is located at an inner side between the shielding frame  120  and the second positioning portion  142 . The heat dissipating pad  144  has a surface contacting the chip  130 , and such disposition improves thermal conductivity of the head dissipating member  140  relative to the chip  130 . Referring to  FIG. 3B , in this embodiment, the heat dissipating pad  144  is, for example, thermal grease or other heat-conductive materials. Specifically, the height difference (T) in the normal direction (Dn) exists between the bottom wall (W 1 ) of the second encircled positioning portion  142  and the first surface (S 1 ) of the plate  141 . 
     Furthermore, referring to  FIGS. 1A and 1B , the circuit board assembly  100  further includes a plurality of fixing members  150 . The heat dissipating member  140  further has a plurality of through holes (O). The through holes (O) are through the first surface (S 1 ) and the second surface (S 2 ) of the plate  141  and are formed at a periphery of the second encircled positioning portion  142 . The circuit board  110  has a plurality of securing holes (H) individually corresponding with the through holes (O), and a ground terminal (G). The fixing member  150  are, for example, screws, and individually pass through the through holes (O) and are fixed into the securing holes (H) of the circuit board  110 . The ground terminal (G) is electrically connected to an inner surface of each of the securing holes (H). In this embodiment, the heat dissipating member  140  is made of, for example, metal, and is electrically connected to the ground terminal (G) of the circuit board  110  via the securing members  150 . The shielding frame  120  is made of, for example, metal, and is mounted to the circuit board  110  by a welding process, and is electrically connected to the ground terminal (G). The plate  141  of the heat dissipating member  140  and the shielding frame  120  are electrically connected to each other so the plate  141  and the shielding frame  120  that surround the chip  130  can conduct static electricity to ground. 
     Referring to  FIGS. 1A, 3A, and 3B , during the operation of the chip  130 , electromagnetic radiation (E 1 ) radiates from the center, the chip  130 , toward the plate  141  and an inner side of the shielding frame  120 . External electromagnetic radiation (E 2 ) travels in another radiation direction toward an outer side of the shielding frame  120 . The radiation directions of the electromagnetic radiation (E 1 , E 2 ) are, for example, parallel to the horizontal direction (Dp), or form angles with the horizontal direction (Dp) Since part of the shielding frame  120  extends into the second encircled positioning portion  142  (i.e., the encircled groove) of the plate  141 , the first encircled positioning portion  121  (i.e., the encircled protrusion) and the side wall (W 2 ) of the second encircled positioning portion  142  (i.e., the encircled groove) overlap, and the bent section  122  abuts against the bottom wall (W 1 ). The bottom wall (W 1 ) of the second encircled positioning portion  142  and the first surface (S 1 ) of the plate  141  have a height difference (T) in the normal direction (Dn) in between. The electromagnetic radiation (E 1 , E 2 ) propagates in Light of Sight (LOS). During the propagation, since the electromagnetic radiation (E 1 ) cannot turn 90 degrees to enter the second encircled positioning portion  142  (i.e., the encircled groove) of the plate  141  in the normal direction (Dn), and cannot turn 90 degrees to pass through the bottom wall (W 1 ) and the bent section  122  in the horizontal direction (Dp), the electromagnetic radiation (E 1 ) propagating outwardly from the chip  130  is blocked by the plate  141  and the shielding frame  140 . In other embodiments, a gap of a certain dimension may exist between the bottom wall (W 1 ) and the bent section  122 . Since the transmission of the electromagnetic radiation (E 1 ) is limited to be LOS propagation, the electromagnetic radiation (E 1 ) cannot turn twice to pass through the gap. 
     In addition, when the electromagnetic radiation (E 1 ) contacts the plate  141  and the shielding frame  120 , it is guided to the ground terminal (G) of the circuit board  110 , in order to prevent outward emission of the electromagnetic radiation (E 1 ). Similarly, when the external electromagnetic radiation (E 2 ) travels toward the chips  130  along the plate  141  and the circuit board  110 , the electromagnetic radiation (E 2 ) cannot turn 90 degrees to enter the second encircled positioning portion  142  (i.e., the encircled groove) of the plate  141  in the normal direction (Dn), and cannot turn 90 degrees to pass through the bottom wall (W 1 ) and the bent section  122  in the direction opposite to the horizontal direction (Dp). The electromagnetic radiation (E 2 ) is blocked by the plate  141  and the shielding frame  120 . When the electromagnetic radiation (E 2 ) contacts the plate  141  and the shielding frame  120 , it is guided to the ground terminal (G) of the circuit board  110 , in order to prevent the electromagnetic radiation (E 2 ) from affecting the operation of the chip  130 . Therefore, the shielding frame  120  can prevent the chip  130  from negative affect caused by electromagnetic interference. 
     Referring to  FIGS. 1A and 1B , in this embodiment, the shielding frame  120  further includes a plurality of locking portions  123  formed on a surface of the shielding frame  120 , which faces the circuit board  110 . The locking portions  123  are, for example, spaced-apart bumps fixed to the circuit board  110 , so as to allow the shielding frame  120  to be connected to the circuit board  110  via welding. Hence, the shielding frame  120  is electrically connected to the ground terminal (G) of the circuit board  110  via welding. 
       FIGS. 3C and 3D  are partial enlarged views of areas A 2  and A 3 , respectively, which replace the area A 1  in other embodiments. Other embodiments according to the present invention would be described as follows. It should be noted that, in the following description, components identified with numerals similar to the previous embodiment are omitted for the brevity, only those different from the previous embodiment would be disclosed in detail. 
     Referring to  FIGS. 3A, 3C and 3D , the areas (A 2 ) in  FIG. 3C  and the area (A 3 ) in  FIG. 3D  can replace the area (A 1 ) in  FIG. 3A . In other embodiments, when the heat dissipating member  140  is disposed on the circuit board  110 , the shielding frame  120 B,  120 C leans against the heat dissipating member  140  in the normal direction (Dn), and the heat dissipating member  140  covers the chip  130 . The shielding frame  120 B,  120 C overlap the heat dissipating member  140  at a junction in the radiation direction (i.e., a direction in which the electromagnetic radiation (E 1 ) radiates from the center, the chip  130 . The radiation direction is, for example, parallel to the horizontal direction (Dp) or form an angle with the horizontal direction (Dp). Specifically, referring to  FIGS. 3C and 3D , the plate  141 B,  141 C has a second encircled positioning portion  142 B,  142 C, which is an encircled protrusion extending from the plate  141 B,  141 C. When the plate  141 B,  141 C leans against the shielding frame  120 B,  120 C, the second encircled positioning portion  142 B,  142 C is, for example, located at an inner side or an outer side of the shielding frame  120 B,  120 C, such that the encircled protrusion and the shielding frame  120 B,  120 C have an overlapped area in the horizontal direction (Dp). Since the height difference exists between the gap of the shielding frame  120 B,  120 C and the plate  141 B,  141 C and the encircled protrusion, the electromagnetic radiation (E 1 ) and the electromagnetic radiation (E 2 ) cannot turn and pass through the shielding frame  120 B,  120 C and the encircled protrusion, and thus the electromagnetic interference is avoided. 
     In summary, the circuit board assembly according to the present invention is equipped with detachable shielding device, which is different from a conventional cover molded as one piece. When the heat dissipating member is disposed on the circuit board, the heat dissipating member and the shielding frame are used for preventing electromagnetic interference from affecting the chip. The shielding frame is designed to be hollow and coupled to the plate of the heat dissipating member for covering the chip, and the shielding frame and the plate overlap each other and form the gap with the height difference, so that the electromagnetic radiation cannot pass through and is blocked by the shielding frame and the plate. Moreover, the shielding frame and the plate can guide the electromagnetic radiation to the ground terminal, and thus electromagnetic interference affecting the operation of the chip is prevented. 
     In addition, the circuit board assembly of the present invention adopts the shielding device, which includes the heat dissipating member and the shielding frame and also takes the plate of the heat dissipating member as the upper cover of the shielding frame. That is, the shielding frame of the present invention is not required to be equipped with an additional upper cover, therefore, the size (i.e., thickness) of the shielding device is reduced, and the production cost is also reduced. To be specific, due to the reduced size, the circuit board assembly of the present invention can be adapted to a relatively small electronic device. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided that they fall within the scope of the following claims and their equivalents.