Patent Publication Number: US-2011067844-A1

Title: Planar heat pipe

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention generally relates to heat dissipation devices, particularly to heat pipes. 
     2. Related Art 
     Integrated circuits (ICs) are broadly applied in various industrial equipments, measurement instruments and computers. With the development of electronic industries, ICs work at higher and higher frequencies and then generate more and more heat. ICs tend to damage if overheating. Conventional heat dissipation devices simply employing fins are not enough to satisfy requirement of heat dissipation of modern ICs. Thus heat pipes become popular in heat dissipation devices. Conventional heat pipes are tubular in shape and composed of a metallic tube, a wick structure arranged in the tube and a working fluid injected in the tube. The heat pipes can rapidly transfer a large amount of heat by phase change of the working fluid. 
     However, modern electronic devices tend toward lighter, thinner, shorter and smaller than ever. Conventional heat pipes become hard to be applied in a limited space. On the other hand, a heat pipe connecting a heat source to a heat sink usually must make a turn to evade other components. This situation has the design of heat dissipation become difficult. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a planar heat pipe which can only occupy a flat space and easily evade other components for increasing the space utilization. 
     To accomplish the above object, the planar heat pipe of the invention includes: 
     a metallic tube composed of two flat extensions located at two ends thereof and a shrinked intermediate structure connecting between the flat extensions; 
     a wick structure arranged in the metallic tube; 
     a working fluid in the metallic tube; and 
     a support element in the metallic tube for supporting the wick structure to attach the metallic tube. 
     In above structure, the flat extensions can be separately attached to a heat source and a heat sink. The flat extensions can be accommodated in a very flat space. And the intermediate structure can be provided with a turn to evade other components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the original shape of the metallic tube; 
         FIG. 2  shows the metallic tube which has been shrinked; 
         FIG. 3  shows the metallic tube which has been pressed into a flat shape; 
         FIG. 4  shows the metallic tube which has been provided with the wick structure; 
         FIG. 5  is a cross-section view of the metallic tube with the support element; 
         FIG. 6  shows the metallic tube which has been sealed; 
         FIG. 7  shows an application of the planar heat pipe associated with a heat source; and 
         FIG. 8  is a cross-section view of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The planar heat pipe of the invention includes a metallic tube  10  composed of two flat extensions  11 ,  12  and an intermediate structure  13 , a wick structure  20 , a working fluid  30  and a support element  40 . 
     Please refer to  FIG. 1 . A circular metallic tube  10  is used to be an original material of a heat pipe. The metallic tube  10  is made of material with great thermo-conductivity such as, but not limited to, copper. 
     Please refer to  FIGS. 2 and 3 . The flat extensions  11 ,  12  are located at two ends of the metallic tube  10  and the intermediate structure  13  is located between the two flat extensions  11 ,  12 . 
     The intermediate structure  13  is made by a shrink process. The shrink process can be preferably performed by the tube spinning. The intermediate structure  13  is elongated with maintaining a circular cross-section. The intermediate structure  13  still keeps hollow even if it has been elongated. Two tapering portions  111 ,  121  are formed between the intermediate structure  13  and the extensions  11 ,  12 . The tapering portions  111 ,  121  taper from the extensions  11 ,  12  to the intermediate structure  13 . 
     The intermediate structure  13  may be made with a turn to satisfy real requirements. The embodiment shown in the drawings is with a turn. As can be seen in  FIG. 3 , a turn  131  is formed in the intermediate structure  13 . The metallic tube  10  is pressed to become flat, i.e. the extensions  11 ,  12 , tapering portions  111 ,  121 , intermediate structure  13  and turn  131  are deformed into a flat shape. This flat shape can make the heat pipe accommodated in a thin space. 
     Please refer to  FIGS. 4-6 . The wick structure  20  is disposed in the metallic tube  10  through an opening thereof. The wick structure  20  attaches an inner side of the metallic tube  10 . A gas passage is remained in the metallic tube  10 . The wick structure  20  is made of porous material such as sintered powder. 
     The working fluid  30  is injected in the metallic tube  10  through its opening. The working fluid is absorbed by the wick structure  20  due to the capillary force. The total volume of the injected working fluid  30  is equal to the total volume of all pores of the wick structure  20 . 
     The support element  40  is disposed in the metallic tube  10  to prevent the metallic tube from caving. The support element  40  pushes the wick structure  20  to attach the inner side of the metallic tube  10 . 
     The metallic tube  10  must be degassed before its opening is sealed because the gas inherently filled in the metallic tube  10 , such as air, does not involve the phase change of the working fluid  30 . A heat pipe can not work normally if the gas has not been degassed. 
     Please refer to  FIGS. 7 and 8 . Either of the flat extensions  11 ,  12  serves as an evaporating section for attaching a heat source  50 . The evaporating section can attach the heat source  50  planarly and tightly due to its flat shape. The other one of the flat extensions  11 ,  12  serves as a condensing section for attaching a fin set  60 . The intermediate structure  13  is smaller than the flat extensions  11 ,  12  so that it can easily pass through or evade other components. 
     The flat extensions  11 ,  12  can be easily accommodated in a limited space such as a laptop computer. On the other hand, the evaporating section may be further extended to attach more heat sources. So the manufacturing costs can be reduced. 
     Although the present invention has been described with reference to the foregoing preferred embodiment, it will be understood that the invention is not limited to the details thereof. Various equivalent variations and modifications can still occur to those skilled in this art in view of the teachings of the present invention. Thus, all such variations and equivalent modifications are also embraced within the scope of the invention as defined in the appended claims.