Abstract:
This invention id related to a heat dissipation device comprises a case having a heat dissipation path, a backflow path, a first link path, and a second link path for working fluid to circulate therein. The heat dissipation path and the backflow path are positioned in the different height levels individually. The working fluid will not be more easily have turbulence. The reduction of heat dissipation efficiency will be improved. And the working fluid will not be necessary to limit covering the liquid state and gaseous state both.

Description:
BACKGROUND  
       [0001]     The invention relates to heat dissipation devices and fabrication methods thereof, and in particular to a heat dissipation device and fabrication method thereof, wherein the heat dissipation device has paths for working fluid to circulate therethrough to dissipate heat.  
         [0002]     Transistors per unit area on the electronic devices are currently becoming more and densely disposed. However, this inevitably increases heat. Accordingly, to keep devices within effective working temperatures, most methods conducted to dissipate heat utilize extra fans or heat sinks. Additionally, heat pipes can transmit heat across a considerable distance via small cross-section and temperature difference without requiring any additional power supply. Thus, under economic considerations of power supply and space utilization, heat pipes have become one of the most widely used heat dissipation devices.  
         [0003]     As shown in  FIG. 1 , a heat pipe  1  comprises a case  10 , a wick structure  16 , and working fluid. While flowing in the vicinity of a first portion  100  of the case  10 , the working fluid absorbs heat emitted from a heat source (not shown) and changes from a liquid state to a gaseous state. The working fluid, as shown by arrows  11  in  FIG. 1 , flows further toward a second portion  101  capable of heat dissipation and is immediately cooled and condensed to the original liquid state. Simultaneously, the working fluid adheres to the wick structure  16  located on the inner side of the housing  10 . Through capillary attraction provided by the wick structure  16  redrawing the working fluid to the first portion  100 , as shown by arrows  12  in  FIG. 1 , the working fluid can absorb heat and vaporize again. This thermal cycle generates a heat-transmitting direction  15  to the heat dissipation device  1 .  
         [0004]     The working fluid described in heat dissipation device  1  requires monitoring its working states. For example, since the working fluid transmits heat from the first portion  100  to the second portion  101  of the heat dissipation device  1  by utilizing changes between liquid and gaseous states. The heat dissipation device is limited by the housing of heat dissipation device  1  providing only space for working fluid circulating therein without limiting the flow direction of the working fluid. Further, the design may generate turbulence with only limited heat dissipation efficiency of the device. Thus, an improved heat dissipation device should be considered as an important subject in the future.  
       SUMMARY  
       [0005]     The invention provides a heat dissipation device comprising paths for working fluid circulating therein and dissipating heat.  
         [0006]     The invention provides a heat dissipation device comprising a case having a first portion, a second portion and a working fluid. Moreover, a heat dissipation path is disposed in the vicinity of the second portion of the case, and a backflow path is disposed in the vicinity of the first portion of the case. A first link path connects one end of the heat dissipation path with one end of the backflow path and a second link path connects the other end of the heat dissipation path with the other end of the backflow path, wherein the working fluid absorbs heat while circulating through the backflow path and dissipates heat while circulating through the heat dissipation path.  
         [0007]     A plane formed by the heat dissipation path is different from that formed by the backflow path.  
         [0008]     The heat dissipation device comprises a partition disposed between the heat dissipation path and the backflow path.  
         [0009]     The partition comprises dissipation space comprising a first dissipation path connected with the heat dissipation path as well as a second dissipation path connected with the backflow path.  
         [0010]     The partition comprises dissipation space comprising a third dissipation path connected with the first link path as well as a fourth dissipation path connected with the second link path.  
         [0011]     The second link path is annularly disposed outside the first link path.  
         [0012]     The working fluid flows through the backflow path, the first link path, the heat dissipation path, the second link path in this order and finally back to the backflow path.  
         [0013]     The case is of metal or nonmetal materials.  
         [0014]     The invention provides a method for fabricating a heat dissipation device comprising forming a heat dissipation path, a backflow path, a first link path, and a second link path on a board, and bending and fixing the board with a bending line disposed to form a heat dissipation device.  
         [0015]     The invention provides a method for fabricating a heat dissipation device, comprising forming a heat dissipation path, a first link path, and a second link path on a first board, forming a backflow path, a first link path, and a second link path on a second board, and gluing and fixing the side of the first board having the heat dissipation path with the side of the second board having the backflow path to form a heat dissipation device.  
         [0016]     After bending and fixing the board or gluing and fixing the boards, the heat dissipation path and the backflow path are interactively independent.  
         [0017]     Before bending and fixing the board or gluing and fixing the boards, a partition is disposed between the heat dissipation path and the backflow path and after bending and fixing the board, the heat dissipation path and the backflow path are interactively independent.  
         [0018]     The heat dissipation path, the backflow path, the first link path, and the second link path are formed simultaneously.  
         [0019]     The heat dissipation path comprises a plurality of recessions and a plurality of protrusions arranged in sequence and the backflow path also comprises a plurality of recessions and a plurality of protrusions arranged in sequence; when the board is bent (or glued) and fixed, the protrusions of the heat dissipation path are received in the corresponding recessions of the backflow path and the protrusions of the backflow path are received in the corresponding recessions of the heat dissipation path in order to form the heat dissipation device.  
         [0020]     The recessions are complementary to the protrusions.  
         [0021]     The protrusions comprise hooks and the recessions comprise grooves and while the protrusions of the heat dissipation path are received in the corresponding recession portions of the backflow path, the hooks of the protrusions joint the grooves of the recessions to bend and fix the board to form the heat dissipation device.  
         [0022]     The protrusions comprise hooks and the recessions comprise grooves and while the protrusions of the backflow path are received in the corresponding recessions of the heat dissipation path, the hooks of the protrusions joint the grooves of the recessions to bend and fix the board to form the heat dissipation device.  
         [0023]     The shapes of the recessions and the protrusions are trapezoid, rectangle, triangular, circular, or irregular.  
         [0024]     Formation of the heat dissipation path, the backflow path, the first link path, and the second link path is accomplished by molding, punching, MEMS, etching, or other conventional means such as drilling, milling, digging or a combination thereof. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0025]     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0026]      FIG. 1  is a cross section of a conventional heat dissipation device;  
         [0027]      FIG. 2A  is a top-viewed cross section of an embodiment of a heat dissipation device of the present invention;  
         [0028]      FIG. 2B  is a side-viewed cross section of an embodiment of a heat dissipation device of the present invention;  
         [0029]      FIG. 2C  is a cross section along A-A′ line in  FIG. 2A ;  
         [0030]      FIG. 2D  is a cross section of another embodiment of a heat dissipation device of the present invention;  
         [0031]      FIG. 2E  is a cross section along A-A′ line in  FIG. 2A ;  
         [0032]      FIG. 2F  is a cross section of another embodiment of a heat dissipation device of the present invention;  
         [0033]      FIG. 2G  is a cross section along A-A′ line in  FIG. 2A ;  
         [0034]      FIG. 3A-3D  are cross sections of various heat dissipation paths of the present invention;  
         [0035]      FIG. 4A  is a three-dimensional diagram of a fabrication method of a heat dissipation device of the present invention;  
         [0036]      FIG. 4B  is a three-dimensional diagram of another fabrication method of a heat dissipation device of the present invention;  
         [0037]      FIG. 5A  is a side-viewed cross section of an embodiment of accomplishing a heat dissipation device of the present invention;  
         [0038]      FIG. 5B  is a side-viewed cross section of an embodiment of accomplishing a heat dissipation device of the present invention along A-A′ line in  FIG. 2A ;  
         [0039]      FIG. 5C  is a side-viewed cross section of an embodiment of accomplishing another heat dissipation device of the present invention;  
         [0040]      FIG. 5D  is a side-viewed cross section of an embodiment of accomplishing another heat dissipation device of the present invention along A-A′ line in  FIG. 2A ;  
         [0041]      FIG. 5E  is a side-viewed cross section of an embodiment of accomplishing another heat dissipation device of the present invention along A-A′ line in  FIG. 2A ; and  
         [0042]      FIG. 5F  is a side-viewed cross section of an embodiment of accomplishing another heat dissipation device of the present invention along A-A′ line in  FIG. 2A . 
     
    
     DETAILED DESCRIPTION  
       [0043]     As shown in  FIG. 2A , in the first embodiment of the invention, a heat dissipation device  2  comprises a case  20 , at least one heat dissipation path  21 , at least one backflow path  22 , a first link path  23 , and a second link path  24 , wherein the case may comprise metal or nonmetal materials and the heat dissipation path  21 , the backflow path  22 , the first link path  23 , and the second link path  24  are disposed in the case  20  having working fluid therein. Moreover, the first link path  23  connects one end of the heat dissipation path  21  with one end of the backflow path  22 . The second link path  24  connects the other end of the heat dissipation path  21  with the other end of the backflow path  22 . As shown by arrows  210  and  220  in  FIG. 2A , the working fluid flows through the backflow path  22 , the first link path  23 , the heat dissipation path  21 , the second link path  24 , and finally back to the backflow path  22 . In  FIG. 2A , the heat dissipation path  21  is shown in real lines and the backflow path  22  is shown in dotted lines. Thus, it can be seen that the heat dissipation path  21  and the backflow path  22  are at different height levels. Namely, a plane formed by the heat dissipation path  21  is different from that formed by the backflow path  22 .  
         [0044]      FIG. 2B  is a side-viewed cross section along the heat dissipation path  21  of the heat dissipation device  2 . The backflow path  22  of the heat dissipation device  2  is disposed in the vicinity of a first portion  200  of the case  20  and the first portion  200  may be disposed in the vicinity of a heat source (not shown); the heat dissipation path  21  is disposed in the vicinity of a second portion  201  of the case  20  and the second portion  201  may be disposed in a location with relatively lower temperature than the heat source. Accordingly, when flowing along backflow path  22 , the working fluid absorbs heat dissipated by the heat source. Further, the working fluid flows along the heat dissipation path  21  through a first link path  23 , conducting heat through the second portion  201  of the case  20 , and finally returning to the backflow path  22  through the second link path  24 . Through the cycle, heat is conducted away in the direction as shown by arrow  25 .  
         [0045]      FIG. 2C  is a cross-section along A-A′ line in  FIG. 2A . The plane formed by the heat dissipation path  21  is different from that formed by the backflow path  22 . Moreover, in this embodiment, the bottom of the plane formed by the heat dissipation path  21  and the top of the plane formed by the backflow path  22  are precisely located at the same height level such that the fabrication method of the heat dissipation device is therefore simplified. However, the invention is not limited thereto. It will work when the heat dissipation path  21  and the backflow path  22  disposed at different height levels; even the bottom of the plane of the heat dissipation path  21  is lower than the top of plane of the backflow path  22 . Furthermore, as shown in  FIG. 2D  and  FIG. 2E , when the bottom of the plane formed by the heat dissipation path  21  is higher than the top of the plane formed by the backflow path  22 , the heat dissipation path  21  and the backflow path  22  are completely isolated and their arrangement density may be increased to dissipate more heat per unit area. In this invention, the heat dissipation path  21  and the backflow path  22  are not linked except by their ends through the first link path  23  and the second link path  24 .  
         [0046]     Additionally, the heat dissipation device  2  further comprises a dissipation space  27 , as shown in  FIG. 2F-2G . The dissipation space  27  comprises a plurality of first dissipation paths  272  linked to the heat dissipation path  21  and a plurality of second dissipation paths  271  linked to the backflow path  22 . When circulating in the heat dissipation device  2 , especially through the backflow path  22 , the working fluid may absorb heat from the heat source to be vaporized. The vapor flows through the second dissipation paths  271  to the dissipation space  27 , then through the first dissipation paths  272  to the heat dissipation path  21 , dissipating heat via the heat dissipation path  21 , and flowing back along the backflow path  22  through the second link path  24 . An alternative design of the dissipation space  27  may further comprise a plurality of third dissipation paths  273  linked to the first link path  23  and a plurality of fourth dissipation paths  274  linked to the second link path  24  such that the dissipation paths of the steamed working fluid are increased, thereby improving heat dissipation efficiency of the heat dissipation device  2  of the invention.  
         [0047]     In the mentioned embodiment, the plane formed by the heat dissipation path  21 , as shown in  FIG. 3A , is radial. Furthermore, the heat dissipation path  21  is radiated. Additionally, one end of the heat dissipation path  21  in the vicinity of center is connected to the first link path  23  and the other end in the vicinity of outside is connected to the second link path  24 . Preferably, the second link path  24  is annularly disposed outside the first link path  23  and the plane formed by the backflow path  22  may follow that of the heat dissipation path  21 ; however, the shape of the plane of the heat dissipation path  21  is not limited. As shown in  FIGS. 3B and 3C , the shape may be an arc shape, or an alternate shape. Further, referring to  FIG. 3D , the heat dissipation device  2  ma, include two groups of heat dissipation paths  21 ′ and  21 ″, two first link paths  23 ′ and  23 ″, and two second link paths  24 ′ and  24 ″ coordinating with each other to form two heat dissipation areas. Like the other embodiments, the heat dissipation device  2  with two-group arrangement provides the same heat dissipation effect and the distribution of the backflow paths is the same as that of the heat dissipation paths.  
         [0048]     Accordingly, the heat dissipation device  2  of the first embodiment of the invention comprises heat dissipation path  21  enabling the working fluid to circulate therein and along the backflow path  22 . Moreover, the heat dissipation path  21  and the backflow path  22  are located at different height levels such that the working fluid dissipates heat in the heat dissipation path  21  and absorb heat in backflow path  22  without producing turbulence. Hence, heat dissipation efficiency is increased. Additionally, the working fluid of the heat dissipation device does not require changing states between a gas state and a liquid state. Thus, the working fluid completely maintains state (gas or liquid) such that the selectivity of the working fluid is wider and more convenient for industry to use.  
         [0049]     The invention provides a method for fabricating a heat dissipation device, as shown in  FIG. 4A , comprising forming a heat dissipation path (not shown), a first link path (not shown), and a second link path (not shown) on a first board  401 , forming a backflow path  42 , a first link path  43 , and a second link path  44  on a second board  402 , and final gluing and fixing of the side of the first board  401  having the heat dissipation path with the side of the second board  402  having the backflow path  42  to form a heat dissipation device  2 , wherein the method conducted to form the heat dissipation path, the backflow path  42 , the first link path  43 , and the second link path  44  is accomplished by molding, punching, MEMS, etching, or other conventional means such as drilling, milling, digging or a combination thereof. Moreover, any means to form a recession on the first board  401  or a groove on the second board  402  can be adopted. While the first board  401  and the second board  402  are glued together, the heat dissipation path  41  and the backflow path  42  are interactively independent.  
         [0050]     Please refer to  FIGS. 5A and 5B . The first board  401  having the heat dissipation path  41  and the second board having the backflow path  42  are glued together, wherein it is obvious that only two ends of the heat dissipation path  41  and the backflow path  42  are connected to form the heat dissipation device  2  illustrated in  FIG. 2B  and  FIG. 2C . Furthermore, before the step of gluing the first board  401  and the second board  402 , a partition  49  is disposed between the heat dissipation path  41  and the backflow path  42 . After gluing the boards, even utilizing the same distribution, the heat dissipation path  41  and the backflow path  42 , as shown in  FIGS. 5C and 5D , are still interactively independent because of the partition  49 , forming the heat dissipation device  2  illustrated in  FIG. 2D  and  FIG. 2E .  
         [0051]     Further, referring to  FIG. 5E , the heat dissipation path  41  of the first board  401  comprises a plurality of recessions  410  and a plurality of protrusions  411  arranged in sequence and the backflow path  42  of the second board  402  also comprises a plurality of recessions  420  and a plurality of protrusions  421  arranged in sequence, wherein the recessions  410  correspond to the protrusions  421  and the recessions  420  correspond to the protrusions  411 . Preferably, in this embodiment, the shapes of the recessions  410 , 420  and the shapes of the protrusions  411 , 421  are trapezoid, rectangle, triangular, circular, or irregular. When the first board  401  and the second board  402  are glued together, the protrusions  411  of the heat dissipation path  41  are received in the corresponding recessions  420  of the backflow path  42  and the protrusions  421  of the backflow path  42  are received in the corresponding recessions  410  of the heat dissipation path  41  in order to form the heat dissipation device  2 .  
         [0052]     As shown in  FIG. 5F , the protrusions  411  of the first board  401  comprises hooks  412  and the recessions  420  of the second board  402  comprises grooves  422 . When the protrusions  411  of the heat dissipation path  41  are received in the corresponding recessions  420  of the backflow path  42 , the hook  412  joins the groove  422  in order to glue and fix the first board  401  and the second board  402  together. Similarly, The protrusions  421  of the second board  402  comprise hooks (not shown) and the recessions  410  of the first board  401  comprise grooves (not shown); alternatively, the first board  401  and the second board  402  may comprise the same structure to approach the same result.  
         [0053]     The invention provides another method for fabricating a heat dissipation device comprising providing a board  40 , forming a heat dissipation path  41 , a backflow path  42 , a first link path  43 , and a second link path  44  on the board, wherein the heat dissipation path  41 , the backflow path  42 , the first link path  43 , and the second link path  44  are formed by molding, punching, MEMS, etching, or other conventional means such as drilling, milling, digging or a combination thereof. Moreover, any means to form a recession portion on the board  40  can be adopted to produce the heat dissipation path  41 , the backflow path  42 , the first link path  43 , and the second link path  44 . Then, the bending and fixing the board  40  is applied in accordance with a bending line  48  to form a heat dissipation device, wherein after the board is bent and glued, the distribution of the heat dissipation path  41  and the backflow path  42  is the same as that mentioned before.  
         [0054]     The above-mentioned method of fabricating a heat dissipation device is not limited thereto. The heat dissipation device is workable if the structure and the feature are similar to the embodiment of the above-mentioned disclosed.  
         [0055]     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.