Abstract:
A heat dissipation fan includes a fan frame, a bearing assembly, a stator and a rotor. The fan frame includes a base and a central tube. The central tube includes an open top end and an open bottom end. The base defines a receiving concave at a bottom surface thereof. The receiving concave communicates with the central hole. A top wall is formed by the base over the concave. A sidewall is formed between the top wall and the bottom surface of the base and surrounds the concave. A plurality of first locking units extend from the top wall into the receiving concave. The bearing assembly includes an oil sealing cover for sealing the open bottom end of the central tube. The oil sealing cover includes a plurality of second locking units which are detachably interlocked with the first locking units to mount the oil sealing cover to the base.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to heat spreaders, and more particularly to a heat spreader for transferring heat of a heat generating electronic component and a heat dissipation device using same. 
         [0003]    2. Description of Related Art 
         [0004]    Nowadays, heat sinks are used in electronic products for dissipating heat generated by electronic components such as CPUs. Typically, a heat spreader made of metals having a high thermal conductivity is configured for distributing and transferring heat from the CPU to the heat sink. The heat spreader is arranged to have an intimate contact with the electronic component and absorbs heat therefrom. 
         [0005]    However, the electronic components are made to be more powerful while occupying a smaller size. Thus, a contacting area between the electronic component and the heat spreader is decreased as the size of the electronic component decreases. Therefore, a heat flux density between a contacting portion of the heat spreader and other portions of the heat spreader is increased. As the CPU operates faster and faster, and, therefore generates larger and larger amount of heat, the conventional heat spreader, which transfers heat via heat conduction means, cannot transfer heat to the heat sink uniformly to meet the increased heat dissipating requirement of the CPU. 
         [0006]    For the foregoing reasons, therefore, there is a need in the art for a heat spreader which overcomes the above-mentioned problems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an assembled, isometric view of a heat dissipation device in accordance with a first embodiment. 
           [0008]      FIG. 2  is an exploded view of the heat dissipation device of  FIG. 1 . 
           [0009]      FIG. 3  is a cross-section of the heat dissipation device of  FIG. 1 , taken along line III-III thereof. 
           [0010]      FIG. 4  is an exploded view of a heat spreader of a heat dissipation device in accordance with a second embodiment. 
           [0011]      FIG. 5  is a cross-section of a heat dissipation device in accordance with a third embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Reference will now be made to the drawing figures to describe the present heat dissipation device in detail. 
         [0013]    Referring to  FIGS. 1 and 2 , a heat dissipation device  10  in accordance with a first embodiment of the disclosure is shown. The heat dissipation device  10  is mounted on a heat generating electronic component  40  such as a CPU (central processing unit), a North Bridge chip or an LED (light emitting diode) to dissipate heat therefrom. The heat dissipation device  10  includes a heat spreader  20  and a heat sink  30  mounted on the heat spreader  20 . 
         [0014]    The heat spreader  20  has a flat type configuration and is rectangular shaped when viewed from above. The heat spreader  20  includes a main plate  21  and a first and a second end covers  23  located at front and rear sides of the main plate  21 , respectively. The main plate  21  has a flat rectangular bottom surface  212  ( FIG. 3 ) contacting the electronic component  40  and an opposite top surface  211 . The main plate  21  defines a plurality of through holes  25  in an interior thereof. The through holes  25  are parallel to and spaced from each other. The through holes  25  are arranged side by side along a left-to-right direction of the main plate  21 . Each of the through holes  25  has a circular cross section and includes an evaporator section at a middle portion of the main plate  21  and two condenser sections adjacent to the front and rear sides of the main plate  21 , respectively. A first and a second receiving grooves  24  are defined at the front and rear sides of the main plate  21 , respectively. The receiving grooves  24  are concaved inwardly from the front and rear sides of the main plate  21 . Each of the through holes  25  extends horizontally along a front-to-rear direction of the main plate  21  to communicate the first receiving groove  24  with the second receiving groove  24 . An annular wick structure  26  ( FIG. 3 ) is disposed in each of the through holes  25  and contacts an inner surface of the main plate  21 . The wick structures  26  are selected from a porous structure such as grooves, sintered powder, screen mesh, or bundles of fiber to provide capillary force in the through holes  25 . The through holes  25  can be provided with different kinds of wick structure therein, according to the actual heat dissipation requirement. Each of the receiving grooves  24  is rectangular and elongated. A diameter of each of the through holes  25  is smaller than a height of the receiving grooves  24 . A width of an occupying region of the through holes  25  along the left-to-right direction of the main plate  21  is smaller than a length of the receiving groove  24 . 
         [0015]    Each of the end covers  23  includes a rectangular sealed portion  231  and a plurality of connecting portions  233  extending horizontally from an inner side surface of the sealed portion  231  towards the main plate  21 . The sealed portion  231  of each end cover  23  has a size substantially equal to a size of each of the first and the second receiving grooves  24  of the main plate  21 . Each of the connecting portions  233  is column. The connecting portions  233  of each of the end covers  23  are paralleled to and spaced from each other. The connecting portions  233  are arranged along a left-to-right direction of the inner side surface of the sealed portion  231  and face the through holes  25  correspondingly. Number of the connecting portions  233  of each of the end covers  23  equals to the number of the through holes  25  of the main plate  21 . A diameter of each of the connecting portions  233  is slightly larger than the diameter of each of the through holes  25 . The connecting portions  233  of the end covers  23  can be inserted into distal ends of the through holes  25 , respectively. Thus, the end covers  23  connect with the main plate  21  by interference fit of the connecting portions  233  in the through holes  25 . Accordingly, the distal ends of each through hole  25  are sealed by the connecting portions  233  of the end covers  23 , respectively. 
         [0016]    Alternatively, the diameter of each of the connecting portions  233  can be slightly smaller than the diameter of each of the through holes  25 . Solders can be sprayed on an outer surface of connecting portions  233  or the inner surface of the main plate  21  at the distal ends of the through holes  25 , thus the end covers  23  and the main plate  21  can be connected with each other by soldering. A plurality of hermetical channels are thus formed in the interior of the main plate  21  by the through holes  25 . The wick structures  26  are layered on the inner surfaces of the hermetically channels. Subsequently, the hermetically channels are evacuated and then injected with working medium  29  therein which has a lower boiling point and is compatible with the wick structures  26 . The working medium  29  can be selected from a liquid such as water, alcohol, or methanol. 
         [0017]    The heat sink  30  includes a plurality of parallel fins  31  arranged side by side on the top surface  211  of the base plate  21 . Each of the fins  31  extends along the same direction as the through holes  25 . That is, each of the fins  31  extends along the front-to-rear direction of the main plate  21 . Referring to  FIG. 3 , each of the fins  31  includes a plate-shaped main body  311  and a flange  312  extending perpendicularly from a bottom end of the main body  311  to a neighboring fin  31 . The flanges  312  cooperatively form a planar bottom surface at a bottom side of the heat sink  30  for increasing a contacting area between the top surface  211  of the main plate  21  and the heat sink  30 . 
         [0018]    In operation of the heat dissipation device  10 , the electronic component  40  is disposed under and has an intimate contact with a central portion of the bottom surface  212  of the main plate  21 . A substantially rectangular shaped heating area  27  is formed at the central portion of the bottom surface  212  of the heat spreader  20 , absorbing heat from the electronic component  40 . A spreading area  28  surrounding the heating area  27  is thus formed at an outer periphery of the heat spreader  20  for transferring the heat to the heat sink  30  and dissipating the heat to surrounding environment. 
         [0019]    The working medium  29  contained in the evaporator sections of the through holes  25  corresponding to the heating area  27  vaporizes due to the heat absorbed from the electronic component  40 . The vapor then spreads to fill the hermetically channels of the main plate  21 , and wherever the vapor comes into contact with the condenser sections of the through holes  25  corresponding to the spreading area  28  of the main plate  21 , it releases its latent heat of vaporization and condenses. Simultaneously, the vapor moves upwardly to transfer the heat to the fins  31  above the heating area  27 . The heat is therefore spread on the entire heat spreader  20  quickly and uniformly, and thus can be evenly transferred to each fin  31  of the heat sink  30  for dissipating to surrounding environment. The condensate returns to the heating area  27  due to the capillary forces generated by the wick structures  26 . Thereafter, the condensate continues to vaporize and condense, thereby removing the heat generated by the electronic component  40 . 
         [0020]    In the present heat spreader  20 , the main plate  21  defines the plurality of through holes  25  containing working fluid and wick structure  26  therein, the heat generated by the heat generating electronic component  40  can be quickly absorbed by the working medium  29  contained in through holes  25 , since the lowest heat resistance between the electronic component  40  and the main plate  21  and the large contacting areas between wick structures  26  and the main plate  21 . The through holes  25  and the wick structures  26  thereof help the working medium  29  contained in the main plate  21  to horizontally move in the main plate  21  from the heating area  27  of the heat spreader  20  to the spreading area  28  due to their low heat resistance. The through holes  25  and the wick structures  26  thereof also help the heat transfer to the fins  31  on the top surface  211  of the heat spreader  20  with low heat resistance, and therefore mounts of heat generated by the electronic component  40  is quickly and effectively transferred to different portions of the heat sink  30  far from the electronic component  40 . This increases the heat transfer capability of the heat spreader  20  greatly, and thereby increasing the heat dissipation efficiency of the heat dissipation device  10 . 
         [0021]      FIG. 4  is an exploded view of a heat spreader  20   a  in accordance with a second embodiment of the disclosure, differing from the previous heat spreader  20  only in that a main plate  21   a  defines one receiving groove  24  at a front side and forms a close surface at a rear side, through holes  25   a  defined in an interior of the main plate  21   a  each have an open end communicated with the receiving groove  24  and a close end corresponding to the close rear surface, and accordingly only one end cover  23  is in included at the front side of the main plate  21   a  for sealing the open ends of the through holes  25   a.    
         [0022]      FIG. 5  is a cross-section of a heat dissipation device  10   b  in accordance with a third embodiment of the disclosure, differing from the previous heat dissipation device  10  only in that the fins  31   b  and the main plate  21   b  of the heat spreader  20   b  are integrally formed by extrusion, and each of the fins  31   b  includes a plate-shaped main body  311   b  extending upwardly and perpendicularly from a top surface  211   b  of the main plate  21   b . In the present heat dissipation device  10   b , lower heat resistance between the main plate  21   b  and the fins  31   b  can be obtained, and thus heat transfer to the fins  31   b  on the top surface  211   b  of the main plate  21   b  can be very quick for further increasing the heat dissipation efficiency of the heat dissipation device  10   b.    
         [0023]    It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.