Abstract:
A heat dissipation device adapted for cooling an electronic device mounted on a printed circuit board comprises a base plate adapted for being thermally attached to the electronic device and a clip attached on a top face of the base plate. The base plate comprises two protruding poles protruding downwardly from a bottom face thereof. The protruding poles are capable of extending through the printed circuit board, thereby establishing a location for the heat dissipation device on the printed circuit board. The clip fastens the heat dissipation device on the printed circuit board after the location for the heat dissipation device on the printed circuit board has been established.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure relates to heat dissipation devices, and particularly to a heat dissipation device for cooling an electronic device. 
         [0003]    2. Description of Related Art 
         [0004]    With the continuing improvements in the power of electronic components such as central processing units (CPUs), the heat dissipation requirements of such components are attracting increasing attention. Usually a heat sink is installed on a printed circuit board for cooling an electronic device mounted on the printed circuit board. The heat sink typically includes a base thermally contacting the electronic device, and a plurality of fins set on the base. The printed circuit board may be located inside a computer chassis, and the interior space of the computer chassis where the heat sink and the printed circuit board are received is often very limited. 
         [0005]    In order to meet the requirements of the layout of a particular computer chassis, the base of the heat sink is typically designed to have a suitable asymmetric shape, and the base is installed on the printed circuit board using screws. However, due to the asymmetric structure of the base, the screws are liable to tightened onto the printed circuit board to different degrees of torque. When this happens, one end of the base is prone to tilt with respect to the electronic device, such that the base is skewed relative to the electronic device. That is, the base does not maintain uniform intimate thermal contact with the electronic device. 
         [0006]    What is needed, therefore, is a heat dissipation device for cooling an electronic device which can overcome the limitations described. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is an isometric, assembled view of a heat dissipation device in accordance with one embodiment of the disclosure, showing the heat dissipation device ready to be mounted on a printed circuit board. 
           [0009]      FIG. 2  is an inverted view of the heat dissipation device of  FIG. 1 . 
           [0010]      FIG. 3  is an isometric, exploded view of the heat dissipation device of  FIG. 1 . 
           [0011]      FIG. 4  is an inverted view of the heat dissipation device shown in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIGS. 1 and 2 , a heat dissipation device in accordance with an embodiment of the disclosure is provided for cooling an electronic device  42  mounted on a printed circuit board  40 . The heat dissipation device includes a heat sink  10 , a fan  20  mounted on the heat sink  10 , and a clip  30  clamping the heat sink  10  on the printed circuit board  40 . 
         [0013]    Also referring to  FIGS. 3 and 4 , the heat sink  10  includes a base plate  12 , a heat conducting plate  14  mounted at a bottom of the base plate  12 , a fin assembly  16  mounted at a top of the base plate  12 , and a heat pipe  18  thermally contacting the base plate  12 , the heat conducting plate  14  and the fin assembly  16 . The heat conducting plate  14  thermally contacts the electronic device  42  on the printed circuit board  40 . The printed circuit board  40  defines two through holes  44 , and forms two locking loops  46  around the electronic device  42 . The heat pipe  18  is flat and bent into a V-shape, and includes an evaporating section  182  and a condensing section  184 . 
         [0014]    The base plate  12  is made of metal such as aluminum, and the heat conducting plate  14  is made of metal such as copper. Thus the heat conducting plate  14  has a thermal conductivity larger than that of the base plate  12 . The base plate  12  is substantially flat, and can be divided into a generally arch-shaped first part and a generally rectangular second part. An arc-shaped edge of the first part can be considered to integrally and overlappingly adjoin a corner of the second part of the base plate  12 , giving the base plate  12  as a whole an asymmetric, irregular shape. The first part of the base plate  12  forms a Y-shaped fixing seat  122  at a center thereof. Three first air inlets  120  are defined in the first part of the base plate  12  around the fixing seat  122 , the first air inlets  120  being spaced from each other. The fixing seat  122  defines three fixing holes  1220  in its three branches, for fixing of the fan  20  thereon. Three fixing portions  123  are formed at intervals along an outer edge of a top face of the first part of the base plate  12 . Each fixing portion  123  defines a through hole  1230  therein. 
         [0015]    The second part of the base plate  12  has a protrusion  124  extending from a top face thereof, corresponding to the electronic device  42  located below the base plate  12 . The protrusion  124  is generally elongated and extends along a diagonal direction of the second part of the base plate  12 . The protrusion  124  along its extension direction defines a narrow slot  1240 , and the clip  30  is placed in the narrow slot  1240 . Two fixing plates  1242  are fixed to two ends of the protrusion  124  for fixing the clip  30  in the narrow slot  1240 . Each of two ends of the protrusion  124  defines two locking holes  1244 , which are located at two sides of the narrow slot  1240 , respectively. Each fixing plate  1242  defines two through holes  1246  corresponding to the locking holes  1244 . Four screws  1247  extend through the through holes  1246  of the fixing plates  1242  and engage in the locking holes  1244  of the protrusion  124 , to fasten the fixing plates  1242  on the protrusion  124 . The middle of the protrusion  124  is higher than the two opposite ends thereof, and the middle of the narrow slot  1240  is shallower than the two opposite ends thereof. 
         [0016]    The first part and the second part of the base plate  12  respectively define a first groove  125  and a second groove  128  in top faces thereof, for receiving the evaporating section  182  and the condensing section  184  of the heat pipe  18 , respectively. The first groove  125  is located adjacent to the fixing seat  122 , and the second groove  128  intersects the protrusion  124  at a position corresponding to the electronic device  42 . The second groove  128  defines a rectangular through hole  1280  in a bottom thereof. The second part of the base plate  12  defines a rectangular groove  126  in a bottom face thereof, in communication with the second groove  128 . The heat conducting plate  14  is received in the rectangular groove  126 , and a bottom face of the evaporating section  182  of the heat pipe  18  thermally contacts a top face of the heat conducting plate  14 . Four fixing posts  1260  extend downwardly from an inner face of the rectangular groove  126  near four corners of the rectangular groove  126 . The heat conducting plate  14  defines four through holes  140  in four corners thereof, corresponding to the four fixing posts  1260 . Four screws  142  extend through the through holes  140  of the heat conducting plate  14  and engage in the fixing posts  1260 , to fasten the heat conducting plate  14  in the rectangular groove  126  of the base plate  12 . 
         [0017]    The second part of the base plate  12  has two protruding poles  127  extending downwardly from two diagonal corners of the bottom face thereof. A connection line between the two protruding poles  127  goes across and is symmetrical about the center of the electronic device  42 . The projection of the protrusion  124  of the base plate  12  on the printed circuit board  40  intersects the connection line between the two protruding poles  127 . Each protruding pole  127  includes a larger, upper pole section  1272  extending downwardly from the bottom face of the base plate  12 , and a smaller, lower pole section  1274  extending downwardly from the upper pole section  1272 . The upper pole section  1272  has a diameter larger than that of the lower pole section  1274 , such that an annular step (not labeled) is formed between the upper pole section  1272  and the lower pole section  1274 . A bottom of the upper pole section  1272  is configured to abut the top face of the printed circuit board  40 . The lower pole section  1274  has a diameter approximately equal to that of the through hole  44  of the printed circuit board  40 . 
         [0018]    Before the clip  30  is used to mount the heat dissipation device on the printed circuit board  40 , the lower pole sections  1274  of the protruding poles  127  can extend through the through holes  44  of the printed circuit board  40  to position the heat dissipation device on the printed circuit board  40  in advance. The upper pole section  1272  of each protruding pole  127  has a height equal to a height of the electronic device  42 , so that the heat conducting plate  14  can thermally and intimately contact the electronic device  42  and is prevented from excessively pressing the electronic device  42 . 
         [0019]    The fin assembly  16  includes a plurality of fins  162  stacked together. The fins  162  are made of metal such as aluminum, copper or an alloy thereof, and are spaced from each other. A groove (not labeled) is defined in a bottom of the fin assembly  16 , and the condensing section  184  of the heat pipe  18  is received in the groove and thermally contacts the fin assembly  16 . 
         [0020]    The fan  20  is a centrifugal fan, and includes a fan frame  22  and an impeller  24  located inside the fan frame  22 . The impeller  24  is rotatably mounted to a Y-shaped supporting seat  242  provided at a bottom of the impeller  24 , corresponding to the fixing seat  122  of the base plate  12 . The impeller  24  is mounted on the fixing seat  122  of the base plate  12  via screws  244 . In particular, the screws  244  extend through the supporting seat  242  and engage in the fixing holes  1220  of the fixing seat  122 . The fan frame  22  includes a panel  220 , and a side wall  222  extending downwardly and vertically from an outer edge of the panel  220 . The shape of the panel  220  corresponds with the first part of the base plate  12 , and the panel  220  defines a circular second air inlet  2200  corresponding to the first air inlets  120  of the base plate  12 . The side wall  222  of the fan frame  22  forms three mounting ears  224 , corresponding to the three fixing portions  123  of the base plate  12 . Each mounting ear  224  defines a locating hole  2240 . Three screws  2242  extend through the through holes  1230  of the fixing portions  123  of the base plate  12  and engage in the locating holes  2240  of the mounting ears  224 , to fasten the fan frame  22  on the top face of the base plate  12 . Thereby, the fan frame  22  and the base plate  12  together form a space for receiving the impeller  24  therein. 
         [0021]    The clip  30  is formed by bending a resilient metal wire, and includes a middle portion  32  and two locking arms  34  extending from two ends of the middle portion  32 . The projection of the middle portion  32  on the printed circuit board  40  goes across the center of the electronic device  42 . The middle portion  32  is received in the narrow slot  1240  of the protrusion  124 , and includes a confining portion  322  and two pressing portions  324  extending downwardly and then outwardly and horizontally from two ends of the confining portion  322 . The confining portion  322  and the two pressing portions  324  are located in the same vertical plane. The confining portion  322  is received in the middle of the narrow slot  1240 , and the pressing portions  324  are received in the two ends of the narrow slot  1240 . Since the middle of the narrow slot  1240  is shallower than the two ends thereof, the clip  30  can be prevented from rotating around the middle portion  32 . Each of the locking arms  34  extends slantwise upwardly and then slantwise downwardly from a respective one of two ends of the middle portion  32 . The locking arms  34  are respectively located at two sides of the vertical plane where the middle portion  32  is located. Each locking arm  34  forms a locking hook  342  at a distal end thereof, for engaging with the locking loops  46  of the printed circuit board  40 . Thereby, the heat sink  10  is fastened on the printed circuit board  40 . 
         [0022]    In use of the heat dissipation device, the heat dissipation device is placed on the printed circuit board  40 . The lower pole sections  1274  of the protruding poles  127  of the base plate  12  extend through the two through holes  44  of the printed circuit board  40  until the upper pole sections  1272  of the protruding poles  127  abut the top face of the printed circuit board  40 . At this stage, the heat conducting plate  14  of the heat sink  10  is brought into contact with the electronic device  42 . Then, the locking hooks  342  of the clip  30  are caused to lock on the locking loops  46  on the printed circuit board  40 , thereby firmly securing the heat sink  10  on the electronic device  42 . 
         [0023]    According to the above-described configuration, the base plate  12  of the heat sink  10  of the heat dissipation device is asymmetric about the clip  30 . However, the connection line of the two protruding poles  127  goes across and is symmetrical about the center of the electronic device  42 , and the connecting line of the protruding poles  127  intersects with the clip  30 . Before the heat dissipation device is secured on the electronic device  42  by the clip  30 , the two protruding poles  127  of the heat dissipation device extend through the printed circuit board  40 . Thereby, the heat dissipation device can be located on the printed circuit board  40  in advance, and one end of the heat dissipation device can be prevented from tilting or rotating relative to the clip  30 . 
         [0024]    During operation of the heat dissipation device, the heat conducting plate  14  absorbs heat from the electronic device  42 , and then conducts the heat to the heat pipe  18  and the fin assembly  16 . The fan  20  draws air through the first air inlets  120  of the base plate  12  and the second air inlet  2200  of the fan  20  into the space formed by the fan frame  22  and the base plate  12 . The air under the action of the impeller  24  is blown through and out of the fin assembly  16 . Furthermore, because the first air inlets  120  are defined in the base plate  12 , the air can be drawn through the bottom of the base plate  12 , and the electronic device  42  below the base plate  12  can be cooled during the process of the air flowing into the first air inlets  120 . 
         [0025]    It is believed that the embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.