Patent Publication Number: US-2007095509-A1

Title: Heat dissipation having a heat pipe

Description:
BACKGROUND  
      1. Field of the Invention  
      The present invention relates generally to a heat dissipation device, and more particularly to a heat dissipation device using heat pipes for enhancing heat removal from heat-generating components.  
      2. Related Art  
      As computer technology continues to advance, electronic components such as central processing units (CPUs) of computers are being made to provide faster operational speeds and greater functional capabilities. When a CPU operates at high speed in a computer enclosure, its temperature can increase greatly. It is desirable to dissipate the heat quickly, for example by using a heat dissipation device attached to the CPU in the enclosure. This allows the CPU and other electronic components in the enclosure to function within their normal operating temperature ranges, thereby assuring the quality of data management, storage and transfer.  
      A conventional heat dissipation device comprises a heat sink and a heat pipe. The heat sink comprises a base and a plurality of fins extending from the base. The base defines a groove in the top surface thereof, and bottom surface of the base is attached to an electronic component. Each heat pipe has an evaporating portion accommodated in the groove and a condensing portion inserted in the fins. The base absorbs heat produced by the electronic component and transfers the heat directly to the fins through the heat pipe. By the provision of the heat pipe, heat dissipation efficiency of the heat dissipation device is improved.  
      In order to further improve the heat dissipation efficiency, it is an efficient way to increase the number of the heat pipe such as two or more. However, it will increase the cost of the heat dissipation device using more heat pipes, and the conventional heat dissipation device has low ratio of performance to cost.  
     SUMMARY OF THE INVENTION  
      What is needed is a heat dissipation device with a heat pipe which has a high ratio of performance to cost.  
      A heat dissipation device in accordance with a preferred embodiment of the present invention comprises a heat sink and a heat pipe. The heat sink comprises a base, a fins group extending from the base, and a cover contacting with the fins group. The heat pipe surrounds the fins group and thermally connects with the base and the cover. The heat pipe has a generally rectangular shape with two juxtaposed free end portions sandwiched between the base and the fins group, a top portion parallel to the free end portions and sandwiched between the cover and the fins group, and two connecting portions interconnecting two ends of the top portion and the free end portions, respectively. The free end portions are constructed as an evaporator for the heat pipe, and the top portion is constructed as a condenser for the heat pipe.  
      Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an assembled view of a heat dissipation device in accordance with a preferred embodiment of the present invention;  
       FIG. 2  is an exploded view of  FIG. 1 ; and  
       FIG. 3  is an enlarged view of a heat pipe of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       FIG. 1  shows a heat dissipation device in accordance with a preferred embodiment of the present invention. The heat dissipation device comprises a heat sink  10  and a heat pipe  20 .  
      Referring also to  FIG. 2 , the heat sink  10  comprises a base  12 , a cover  14  spaced opposite to the base  12 , and a fins group  16  sandwiched between the base  12  and the cover  14 . A bottom surface of the base  12  is used for being attached to an electrical component (not shown). The base  12  defines a pair of first grooves  120  in a top surface thereof. The cover  14  defines a second groove  140  in a bottom surface thereof. The fins group  16  comprises a plurality of spaced heat dissipating fins  160 . The spaced heat dissipating fins  160  define a plurality of air passageways  162  therebetween. Airflow flows through the air passageways  162  to take heat away from the fins  160 . A bottom surface of the fins group  16  defines a first channel  164  corresponding to the first grooves  120 . The first channel  164  cooperates with the first grooves  120  to form a first passage. A top surface of the fins group  16  defines a second channel  166  corresponding to the second groove  140 . The second channel  166  cooperates with the second groove  140  to form a second passage.  
      The heat pipe  20  has a rectangular shape and surrounds the top and bottom faces and two sides of the fins group  16 . Referring to  FIG. 3 , the heat pipe  20  comprises two juxtaposed free end portions  202 ,  204  at a bottom thereof, and a top portion  206  parallel to the free end portions  202 ,  204 . The heat pipe  20  further comprises two connecting portions  208  interconnecting two opposite ends of the top portion  206  and the free end portions  202 ,  204 , respectively. The two connecting portions  208  are perpendicular to the top and free end portions  206 ,  202 ,  204  and parallel to each other. In the preferred embodiment, the free end portions  202 ,  204  are constructed as evaporators of the heat pipe  20  which absorb heat from the electrical component via the  12 , and the top portion  206  is constructed as a condenser for the heat pipe  20 , which is used for dissipating the heat to the fins  160 . Furthermore, in the preferred embodiment, the cover  14  is soldered to the top surface of the fins group  16  and the base  12  is soldered to the bottom surface of the fins group  16 . The free end portions  202 ,  204  of the rectangle-shaped heat pipe  20  are soldered in the first passage defined by the first grooves  120  and the first channel  164  so that the free end portions  202 ,  204  are thermally connected with the base  12  and the fins group  16 . The top portion  206  of the rectangle-shaped heat pipe  20  is soldered in the second passage defined by the second groove  140  and the second channel  166  so that the top portion  206  is thermally connected with the cover  14  and the fins group  16 . The connecting portions  208  are disposed at the opposite sides of the fins group  16 .  
      In operation of the heat dissipation device of the preferred embodiment, the base  12  absorbs the heat from the electronic component and a major part of the heat is directly transferred to the free end portions  202 ,  204  of the heat pipe  20 . The free end portions  202 ,  204  are evaporating portions of the heat pipe  20 . A minor part of the heat is conducted upwardly to the fins  160  via a soldering connection between the fins  160  and the base  12 . The major part of the heat received by the heat pipe  20  causes liquid in the free end portions  202 ,  204  thereof to evaporate into vapor. The vapor flows upwardly along the two connecting portions  208  simultaneously. Then the vapor is condensed into liquid in the top portion  206  (which is a condensing portion of the heat pipe  20 ). The condensed liquid returns to the free end portions  202 ,  204  along wick structures in the heat pipe  20 . Thus, the major part of the heat is transferred to the cover  14  and the fins  160  to be dissipated into surrounding environment.  
      In the preferred embodiment, the heat pipe  20  comprises two connecting portions  208  disposed at opposite sides of the fins group  16  and connecting the free end portions  202 ,  204  and the top portion  206 . The heat pipe  20  can thereby transfer the heat from the base  12  to the cover  14  along the two connecting portions  208  simultaneously, whereby the heat dissipation efficiency of the heat pipe  20  is the same as using two U-shaped heat pipes. Furthermore, the cost of two U-shaped heat pipes is much more than that of the one heat pipe  20 . Therefore, the heat dissipation device of the present invention has a better ratio regarding performance to cost. In an alternative embodiment, the cover can be used to contact with the electronic component. For this, the top portion  206  is constructed as an evaporator and the free end portions  202 ,  204  are constructed as condensers for the heat pipe  20 .  
      It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.