BACKGROUND  
       [0001]     1. Field  
         [0002]     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.  
         [0003]     2. Prior Art  
         [0004]     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.  
         [0005]     A conventional heat dissipation device comprises a heat sink and at least a pair of heat pipes. The heat sink comprises a base and a plurality of fins extending from the base. The base defines two grooves 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 one of the grooves and a condensing portion inserted in the top fins. The base absorbs heat produced by the electronic component and transfers heat directly to the fins through the heat pipes. By the provision of the heat pipes, heat dissipation efficiency of the heat dissipation device is improved.  
         [0006]     However, due to structural limitation, the contact area between the heat pipes and the fins is limited, which results in that the heat removal efficiency by the prior art heat dissipation device still cannot meet the increasing heat removing requirement for the up-to-the minute heat-generating electronic devices.  
       SUMMARY OF THE INVENTION  
       [0007]     What is needed is a heat dissipation device with heat pipes which has an improved heat dissipation efficiency.  
         [0008]     A heat dissipation device in accordance with a preferred embodiment of the present invention comprises a heat sink and at least one serpent heat pipe. The heat sink comprises a base contacting with an electrical component, a heat dissipation fins group extending from the base and a cover attached to the heat dissipation fins group. The heat dissipating fins group defines a notch at one side thereof. Evaporating and condensing portions of the at least one serpent heat pipe are respectively connected to the base and the cover, and a middle portion of the heat pipe is accommodated in the notch and thermally engages with the heat dissipating fins group.  
         [0009]     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  
       [0010]      FIG. 1  is an assembled view of a heat dissipation device in accordance with a preferred embodiment of the present invention;  
         [0011]      FIG. 2  is an exploded view of  FIG. 1 ;  
         [0012]      FIG. 3  is a view similar to  FIG. 1  with some parts thereof removed to more clearly show relationship between heat pipes and heat dissipation fins of the heat dissipation device; and  
         [0013]      FIG. 4  is a side view of  FIG. 1 , showing heat transferring paths of the heat dissipation device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]      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 , heat pipes  22 ,  24  and a fan assembly  30  located beside the heat sink  10 .  
         [0015]     Referring to  FIGS. 2-3 , the heat sink  10  comprises a base  12 , a cover  16  spaced opposite to the base  12 , and a heat dissipating fins group  14  sandwiched between the base  12  and the cover  16 . The base  12  has a bottom surface for being attached to an electrical component (not shown) and a top surface opposite to the bottom surface. The base  12  defines a pair of first grooves  120  in the top surface and a pair of first screw holes  122  at a pair of opposite sides thereof. The cover  16  defines a pair of second grooves  160  on a bottom surface thereof and a pair of second screw holes  162  at a pair of opposite sides thereof. The heat dissipating fins group  14  comprises a plurality of spaced heat dissipating fins  140 . The spaced heat dissipating fins  140  define a plurality of air passageways  143  therebetween. Each heat dissipation fin  140  defines a cutout at a side thereof (see  FIG. 3 ). An abutting flange  142  laterally extends from the heat dissipation fin  140  around the cutout for contacting the heat pipe  22 . The cutouts together form a notch  148  at a side of the heat dissipating fins group  14 . The notch  148  comprises a first section  1480  and a second section  1482  along the lateral direction wherein the first section  1480  adjacent to a right side of the heat dissipation device as seen from  FIG. 1 , and is shorter than the second section  1482  along the lateral direction. Furthermore, the first section  1480  has an inner portion that is larger than that of the second section, thereby facilitating mounting of the heat pipe  22  in the notch  148 . A bottom surface of the heat dissipating fins group  14  defines a first channel  144  corresponding to the first grooves  120 . The first channel  144  cooperates with the first grooves  120  to form a first passage  44 . A top surface of the heat dissipating fins group  14  defines a pair of second channels  146  corresponding to the second grooves  160 . Each second channel  146  cooperates with a corresponding second groove  160  to form a second passage  46 . The heat pipe  22  is S-shaped and the heat pipe  24  is U-shaped. The heat pipe  22  comprises three parallel heat-exchange portions, namely a first parallel-portion  220 , a second parallel-portion  222  and a third parallel-portion  224 . The first parallel-portion  220  and the third parallel-portion  224  are respectively accommodated in a corresponding first groove  120  and a corresponding second groove  160  by means of soldering. An upper turning corner of a connecting-portion between the first parallel-portion  220  and the second parallel-portion  222  is accommodated in the first section  1480 . The second parallel-portion  222  is inserted in the second section  1482  and is soldered to and thermally contacts with the flanges  142 . The U-shaped heat pipe  24  comprises an evaporating portion  240  and a condensing portion  244 . The evaporating portion  240  and the condensing portion  244  are respectively accommodated in corresponding first and second grooves  120 ,  160 . The fan assembly  30  comprises a fan  32  and a fan holder  34 . The fan holder  34  has a pair of flanges  340  on a pair of opposite sides thereof. Each flange  340  defines holes  342  corresponding to the first, second screw holes  122 , 162 . Screws (not shown) are used to extend through the holes  342  and screwed into the screw holes  122 ,  162 , whereby the fan assembly  30  is attached to a rear side of the heat dissipating fins group  14 . An airflow generated by the fan  32  flow through the air passageways  143  to take heat away therefrom. In the present invention, the cover  16  is soldered to a top surface of the heat dissipating fins group  14  and the base is soldered to a bottom surface of the heat dissipating fins group  14 . The first-parallel portion  220  of the S-shaped heat pipe  22  and the evaporating portion  240  of the U-shaped heat pipe  24  are soldered in the first grooves  120  and the first channel  144  so that the portions  220 ,  240  are thermally connected with the base  12  and the heat dissipating fin group  14 . The third-parallel portion  224  of the S-shaped heat pipe  22  and the condensing portion  244  of the U-shaped heat pipe  24  are soldered in the second grooves  160  and the second channels  144  so that the portions  224 ,  244  are thermally connected with the cover  16  and the heat dissipating fin group  14 .  
         [0016]     Referring to  FIG. 4 , heat transferring paths of the heat dissipation device are shown, the base  12  absorbs heat and a major part of the heat is directly transferred to the first parallel-portion  220  of the heat pipe  22  and the evaporating portion  240  of the heat pipe  24 . The first parallel-portion  220  is an evaporating portion of the heat pipe  22 . A minor part of the heat is conducted upwardly through the fins  140 . The major part of the heat received by the heat pipes  22 ,  24  causes liquid in the portions  220 ,  240  thereof to evaporate into vapor. The vapor flows upwardly as shown by arrows in the heat pipes  22 ,  24 . Following the upward movement of the vapor, the major part of the heat is transmitted to the fins  140  in contact with the heat pipes  22 ,  24 . Finally the vapor is condensed into liquid in the condensing portion  244  and the third-parallel portion  224  (which is a condensing portion of the heat pipe  22 ) and returns to the first-parallel portion  220  and the evaporating portion  240  of the heat pipes  22 ,  24  along wick structures of the heat pipes  22 ,  24 .  
         [0017]     In the present invention, by the use of the S-shaped and U-shaped heat pipes  22 ,  24 , and the specially designed heat dissipating fins group  14 , the contacting areas between the heat pipes  22 ,  24  and the fins  140  are significantly increased, whereby heat transferred by the heat pipes  22 ,  24  can be more efficiently taken away, thereby meeting the requirement of heat dissipation of up-to-the minute electronic devices.  
         [0018]     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.
A heat dissipation device includes a heat sink ( 10) and at least a serpent heat pipe ( 22). The heat sink ( 10) comprises a base ( 12) contacting with an electrical component, a heat dissipation fins group ( 14) secured to the base ( 12) and a cover ( 16) attached to a top of the heat dissipation fins group ( 14). The heat dissipating fins group ( 14) defines a notch ( 148) at one side thereof. Two end portions of the heat pipe ( 22) are respectively connected to the base ( 12) and the cover ( 16), and a middle portion of the heat pipe ( 22) is accommodated in the notch ( 148).