Abstract:
A cooling device is constructed to include a heat sink attached to a heat generating device and adapted to absorb heat energy from the heat generating device, and at least one heat pipe mounted in the heat sink, each heat pipe having a condensing side formed at each end and disposed at a relatively lower temperature area at the heat sink and an evaporation side formed at the middle and disposed at a relatively higher temperature area at the heat sink.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a cooling device and, more particularly, to such a cooling device suitable for use in a computer to dissipate heat from heat generating elements.  
         [0003]     2. Description of Related Art  
         [0004]     Following fast development of high technology, many products have installed therein a variety of electronic elements. The heat dissipation problem of these electronic elements bother development engineers. For example, advanced computers use microprocessors of relatively higher frequency that generate much heat during operation. ICs in a electronic system may fail if heat is not quickly dissipated during operations.  
         [0005]      FIG. 5  is an exploded view of a cooling structure of semiconductor device according to the prior art, which shows a cooling structure adapted to dissipate heat from a semiconductor device  96 . The cooling structure comprises a heat sink  91 , which has a flat bottom wall disposed in close contact with the semiconductor device  96 , a plurality of cooling fins  93  upwardly extended from the top surface of the flat bottom wall, two heat pipes  92  installed on the cooling fins  93 , a heat-conductive cover  95  covered on the heat sink  91  over the cooling fins  93 , and a fan  94  mounted on the heat-conductive cover  95 .  
         [0006]     However, generally, because the amount of heat energy generated by the semiconductor device  96  gradually decreases from the center of the semiconductor device  96  toward the border and because the end condensing sides  922  and middle evaporating sides  921  of the heat pipes  92  are respectively disposed at the top side  932  and bottom side  931  of the cooling fins  93  and maintained in close contact with the cooling fins  93 , the temperature difference between the condensing sides  922  and evaporating sides  921  of the heat pipes  92  is not large enough, resulting in lower heat dissipation efficiency.  
         [0007]     Therefore, it is desirable to provide a cooling device that improves the aforesaid problems.  
       SUMMARY OF THE INVENTION  
       [0008]     It is the main object of the present invention to provide a cooling device, which has the condensing sides of each heat pipe respectively disposed at the lateral sides of the heat sink where the temperature is relatively lower, so that a significant temperature difference is produced between the condensing sides and the evaporation side of each heat pipe to improve heat dissipation efficiency.  
         [0009]     To achieve these and other objects of the present invention, the cooling device comprises a heat sink, and at least one heat pipe. The heat sink is a substantially U-shaped device comprising a flat bottom panel, two upright side panels at two opposite lateral sides of the flat bottom panel, a plurality of cooling fins respectively upwardly extended from the flat bottom panel and arranged in parallel between the upright side panels, at least one side locating groove respectively disposed at an outer surface of each the upright side panel, and at least one bottom locating groove disposed at a bottom surface of the flat bottom panel. The at least one heat pipe is respectively having a substantially U-shaped profile and received in the at least one side locating groove and the at least one bottom locating groove of the heat sink.  
         [0010]     After installation of the at least one heat pipe in the heat sink, the ends of each heat pipe form a respective condensing side, and the middle part of each heat pipe forms an evaporation side. Because the amount of thermal energy generated from the heat source (the semiconductor chip or the like) gradually reduces from the center area of the heat source toward the border area, the temperature at the lateral cooling fins is lower than the temperature at the middle cooling fins. Because the two condensing sides of each heat pipe are respectively disposed at the side panels where the temperature is relatively lower, there is a significant temperature between the side panels of the heat sink and the condensing sides of each heat pipe. Therefore, the invention greatly improves heat dissipation efficiency. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of a cooling device according to the first embodiment of the present invention.  
         [0012]      FIG. 2  is an exploded view of the cooling device according to the first embodiment of the present invention.  
         [0013]      FIG. 3  is another exploded view of the cooling device according to the first embodiment of the present invention when viewed from another angle.  
         [0014]      FIG. 4  is an exploded view of a cooling device according to the second embodiment of the present invention.  
         [0015]      FIG. 5  is an exploded view of a semiconductor device cooling structure according to the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     For easy understanding of the technical content of the present invention, the present invention will now be described by way of the following two embodiments in which the first embodiment has the heat pipes extended perpendicular to the cooling fins; the second embodiment has the heat pipes extended in parallel to the cooling fins.  
         [0017]      FIG. 1  is a perspective view showing a cooling device  1  constructed according to the first embodiment of the present invention and adapted to dissipate heat from an IC chip  9 , which generates heat when operated. Under normal status, the amount of heat gradually decreases from the center area of the IC chip  9  toward the border area thereof.  
         [0018]     Referring to  FIGS. 2 and 3  and  FIG. 1  again, the cooling device  1  comprises a heat sink  2 , and two heat pipes  3 . The heat sink  2  is a substantially U-shaped aluminum member having a flat bottom panel  21 , two side panels  22  respectively upwardly extended from the two opposite lateral sides of the flat bottom panel  21  and arranged in parallel, and a plurality of cooling fins  212  perpendicularly upwardly extended from the top surface of the flat bottom panel  21  and arranged in parallel between the side panels  22 . The side panels  22  each have two locating grooves  221  respectively formed in the outer surface and extended from the top side to the bottom side. The bottom panel  21  has two locating grooves  211  formed in the bottom surface and respectively connected between the two corresponding opposite locating grooves  221  at the bottom sides of the outer surfaces of the two side panels  22 .  
         [0019]     The heat pipes  3  are U-tubes received in the locating grooves  211  at the bottom panel  21  and the locating grooves  221  at the side panels  22 . According to this embodiment, the bottom panel  21  further has a transverse bottom recess  213  formed in the bottom surface and transversely extended across the locating grooves  211 . A cooling plate  4  is set in the transverse bottom recess  213  to hold the heat pipes  3  in the locating grooves  211  at the bottom panel  21 . According to this embodiment, the cooling plate  4  is a copper plate. Further, two packing plates  5  are respectively fixedly fastened to the two side panels  22  with screws  8  to hold down the heat pipes  3  in the locating grooves  221 .  
         [0020]     In order to firmly secure the heat pipes  3  to the heat sink  2 , the cooling plate  4  is made having two locating grooves  41  formed in the top surface and adapted to accommodate the heat pipes  3  after the heat pipes  3  have been received in the locating grooves  211  at the bottom panel  21 . Further, the packing plates  5  each have two locating grooves  51  corresponding to the locating grooves  221  at the side panels  22  for holding the heat pipes  3 .  
         [0021]     When installed in the heat sink  2 , the two ends of each heat pipe  3  forms a respective condensing side  31 , and the middle part of each heat pipe  3  forms an evaporation side  32 . Through the cooling plate  4 , the evaporation side  32  of each heat pipe  3  absorbs heat energy from the IC chip  9 , and transfers absorbing heat energy to the condensing side  31  at each end of the respective heat pipe  3 . At the same time, a part of heat energy is transferred from the IC chip  9  to the cooling fins  212  of the heat sink  2 .  
         [0022]     Because the center area of the IC chip  9  has the maximum amount of heat and the amount of heat is gradually reduced from the center area of the IC chip  9  toward the border area, the temperature of the cooling fins  212  near the center area of the heat sink  2  is higher than the temperature of the side panels  22 . Because the condensing sides  31  at the ends of the heat pipes  3  are respectively disposed at the side panels  22  of the heat sink  2 , there is a more temperature difference between the condensing sides  31  of the heat pipes  3  and the side panels  22  of the heat sink  2 , achieving a better heat dissipation effect.  
         [0023]     In order to make sure of the expected heat dissipation effect, the inventor examined the thermal resistance (R) of a cooling device constructed according to the aforesaid first embodiment to be 0.244. Conventional heat sinks for this purpose commonly have a thermal resistance over 0.3. Because a relatively lower thermal resistance achieves relatively better heat dissipation effect, the invention greatly improves heat dissipation effect.  
         [0024]     Referring to  FIGS. 2 and 3  again, the side panels  22  each further comprise a plurality of auxiliary cooling fins  222  that increase the heat cooling area of the heat sink  2 . Further, a heat-conductive top cover  6  may be covered on the top side of the heat sink  2  to hold an electric fan  7 , enhancing the heat dissipation effect of the cooling device.  
         [0025]      FIG. 4  is an exploded view of the second embodiment of the present invention. According to this embodiment, the heat pipes are disposed in parallel to the cooling fins. As illustrated, the heat sink  201  comprises a flat bottom panel  205 , two upright side panels  202  at two opposite lateral sides of the flat bottom panel  205 , a plurality of cooling fins  207  upwardly extended from the top surface of the flat bottom panel  205  and arranged in parallel between the upright side panels  202 , two side flanges  203  respectively transversely protruded at the upright side panels  202  at the outer side, and two bottom locating grooves  206  disposed at the bottom surface of the bottom panel  205 . The two side flanges  203  defining with the respective outer surface of each the side panels  202  the holding spaces  204 . The heat pipes  301  are respectively fastened to the holding spaces  204  between the side panels  202  and the side flanges  203  and the bottom locating grooves  206  at the bottom panel  205 . Because the condensing sides  302  of the heat pipes  301  are respectively disposed at the area having a relatively lower temperature, i.e., at the side panels  202 , there is a more temperature difference between the condensing sides  302  of the heat pipes  301  and the side panels  202  of the heat sink  201 . Therefore, this embodiment achieves the same effects.  
         [0026]     In the aforesaid two embodiments, the heat pipes may be directly welded to the heat sink to achieve better heat-transfer performance. The aforesaid second embodiment is relatively simple than the aforesaid first embodiment. Further, except the heat pipes, the heat sink is preferably made by extrusion.  
         [0027]     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.