Patent Publication Number: US-2007102143-A1

Title: Heat dissipation module and heat pipe thereof

Description:
This Non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application Nos. 094138665 filed in Taiwan, Republic of China on Nov. 4, 2005, the entire contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The invention relates to a heat dissipation module, and in particular to a heat dissipation module having a heat pipe with high dissipation efficiency.  
      2. Related Art  
      With the continuous progress of the industrial technology, the number of the transistors on unit area of an electronic element is increasing, which result in the increase of the heat produced during working time. Also, the working frequency of the electronic element becomes higher, and the switch loss during the transistor changing status (on/off) is also increasing. Thus, heat generated by the electronic element grows. If the heat can not be dissipated adequately, it will lower the operating speed of the chip or even damage the chip. In order to enhance the heat dissipation efficiency of the electronic element, a heat sink is frequently applied to the electronic element so as to dissipate heat to external environment by direct conduct and also a fan is applied in facilitating the dissipation by proving airflow.  
      Because a heat pipe can transfer a lot of heat by a considerable distance with a quite small cross-sectional area and a quite small temperature difference and the heat pipe can work without external power supply, the heat pipe has become one of the most widely used heat conducting elements in the electronic heat dissipation product.  
       FIG. 1  is a schematically cross-sectional view showing a conventional column-like heat pipe. The conventional column-like heat pipe  10  includes a main body  12  which has one open end and one close end, and a top cover  14  combined with the main body  12  to form an airtight hollow chamber.  
      The main body  12  is an integrally formed with a sidewall portion  122  and a bottom portion  124 . There are wicks  16   a  and  16   b  respectively formed on the inner wall of the main body  12  (i.e., the inner surfaces of the sidewall portion  122  and the bottom portion  124 ). The heat pipe  10  is filled with a working fluid “W”. When the column-like heat pipe  10  is used in practice, the bottom portion  124  directly contacts a heat source (not shown, such as a electronic element) located below the heat pipe  10  so as to dissipate the heat generated by the heat source. The bottom portion  124  of the column-like heat pipe  10  is an evaporating end, while the sidewall portion  122  and the top cover  14  are condensing ends. The working fluid “W” at the evaporating end absorbs heat and evaporates into a vaporized working fluid and naturally flows toward the condensing end under the influence of the pressure difference. Then, the vaporized working fluid releases the latent heat at the condensing end and condenses into the liquid working fluid “W”. The condensed working fluid further flows back to the evaporating end by the capillary forces of the wicks  16   a  and  16   b , and the procedures circulate again and again to achieve the effect of heat dissipation.  
      However, when the wicks  16   a  and  16   b  of the column-like heat pipe  10  are formed by powder sintering, the wick  16   b  on the bottom portion  124  and the wick  16   a  on the sidewall portion  122  are commonly filled with powder and then sintered but no wick is additionally formed on the inner surface of the top cover  14  under the limitation of the sintering mold and the manufacturing factors. Thus, the working fluid “W” condensed at the top cover  14  cannot flow back, and the condensing end “B” at the top cover  14  becomes invalid, thereby decreasing the fluctuation of the mass of the working fluid “W” in the heat pipe  10  and thus decreasing the heat conducting efficiency and the whole heat resistance of the heat pipe  10 .  
      If it is desired to form a wick on the inner surface of the top cover  14 , powder has to be filled within the evaporating end and the condensing end simultaneously and then be sintered. Thus, the controls of the shape of the wick and the powder particles become difficult, so the manufacturing processes cannot be utilized to achieve this object. Consequently, if the inner surface of the top cover  14  has to be formed with the wick, a copper mesh may be inserted such that a mesh wick is formed. However, because the wick at the top cover  14  and the wick  16   a  on the sidewall portion  122  are not manufactured simultaneously and pertain to different kinds of wicks (one is a powder sintering wick, and the other is a mesh wick), the connection between these two different wicks is poor such that the working fluid cannot smoothly flow to the sidewall portion  122  from the top cover  14  owing to lacking enough capillary force there between. Thus, the overall heat dissipation property of the heat pipe  10  deteriorates.  
      Thus, it is an important subject of the invention to provide a heat pipe which has a low cost and can be manufactured easily so as to solve the above-mentioned problems.  
     SUMMARY OF THE INVENTION  
      In view of the foregoing, the invention is to provide a heat dissipation module and a heat pipe thereof with advantages of low cost and simple manufacture procedures. In addition, the invention solve the problem of poor connection between the sidewall portion and the top cover of the column-like heat pipe in the prior art. The invention also effectively enlarges heat exchanging area of the heat pipe and enhances the overall heat dissipation efficiency.  
      To achieve the above, a heat pipe of the invention includes a main body, a base, a first wick, a second wick and a working fluid. The main body has a top portion and a sidewall portion disposed around the top portion. When the base and the main body are assembled, the base and the main body are combined to form a closed chamber, and the base is disposed corresponding to the top portion. The working fluid is filled within the closed chamber. The base has an uneven surface facing the top portion, and the first wick is disposed on the sidewall portion and the top portion of the main body. The second wick is disposed on the uneven surface of the base and connected to the first wick.  
      As mentioned above, the sidewall portion and the top portion may be integrally formed as a single piece. Alternatively, the sidewall portion and the top portion are two separate components and are combined together to form the main body. The uneven surface of the base is formed with at least one protrusion, and the cross section of the protrusion on the base has a rectangular, semi-circular semi-spherical, arc, triangular, quadrangular or trapezoidal shape. The protrusions on the uneven surface of the base constitute a checkerboard pattern, an array pattern, a symmetrical pattern or an asymmetrical pattern.  
      The second wick is disposed on the uneven surface of the base such that the second wick faces the top portion and forms a plane. The second wick has a first thickness H 1  and a second thickness H 2 , which is relatively smaller than the first thickness H 1 , in a direction perpendicular to the base. Or, the second wick is disposed along an uneven surface profile of the base and the thickness of the second wick has a uniform or varied thickness. Moreover, the inner surface of the sidewall portion may have even or uneven profiles. The inner surface of the sidewall portion is formed with at least one protrusion. The cross section of the protrusion on the sidewall portion constitutes a sawtooth ring pattern, a continuous semi-circular pattern or any other patterns constituted by the equivalent structure.  
      The sidewall portion of the main body has a shape like a hollow tube. The main body and the base are made of a material with high thermal conductivity, such as copper, silver, aluminum or alloy thereof. The material of the first wick and the second wick may be a plastic material, a metallic material, an alloy or a porous non-metallic material, and be formed by way of sintering, adhering, filing and depositing or any combinations thereof. The working fluid W may be an inorganic compound, pure water, alcohol, ketone, liquid metal, refrigerant, an organic compound or any mixtures thereof.  
      The invention also provides a heat dissipation module including a heat pipe and a plurality of fins, which are connected to and disposed around the heat pipe. The heat pipe includes a main body, a base, a first wick, a second wick and a working fluid. The main body has a top portion and a sidewall portion disposed around the top portion. When the base and the main body are assembled, the base and the main body are combined to form a closed chamber, and the base is disposed corresponding to the top portion. The base has an uneven surface, which faces the top portion, and the first wick is disposed on the sidewall portion and the top portion of the main body. The second wick is disposed on the uneven surface of the base and connected to the first wick. The working fluid is filled within the closed chamber.  
      The fins are manufactured by way of aluminum extrusion, pressing or other methods. The fins may be disposed in a horizontal interval distribution, a vertically interval distribution, a slantingly interval distribution, a radial distribution, or other distributions. The fins are disposed around the heat pipe and connected to the heat pipe. The fins are connected to the heat pipe by a way selected from welding, embedding, engaging or adhering. The heat pipe is embedded in and/or engaged with the fins by way of hot mounting. Alternatively, a soldering paste, a grease or a material capable of serving as a thermal conductive interface may be coated between the fins and the heat pipe.  
      In the heat dispassion module, the heat pipe may contact the heat source directly or indirectly through an external carrier to the fins. The carrier is a solid metal block, and the heat source is an electronic element, such as a CPU (Central Processing Unit), a transistor, a server, an advanced graphics card, a hard disk, a power supply, a mobile control system, a multimedia electronic mechanism, a wireless communication transceiver station or an advanced game machine, which generates the heat. In addition, a fan may be applied to the heat dissipation module, which facilitate heat dissipation more quickly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein:  
       FIG. 1  is a schematically cross-sectional view showing a conventional column-like heat pipe;  
       FIG. 2  is a schematic illustration showing a heat pipe according to the preferred embodiment the invention;  
       FIGS. 3A and 3B  are schematic illustrations showing the uneven surfaces of the base in  FIG. 2 ;  
       FIGS. 3C and 3D  are two schematic illustrations showing the base and the second wick in the  FIG. 2 ;  
       FIG. 4  is a schematic illustration showing another heat pipe according to the preferred embodiment of the invention;  
       FIGS. 5A  to  5 C are schematic illustrations showing assembling process of a heat pipe of  FIG. 4 ;  
       FIG. 6A  is a schematic illustration showing another sidewall portion of the column-like heat pipe of  FIG. 4 ;  
       FIG. 6B  is a top view of the sidewall portion of the column-like heat pipe of  FIG. 6A ; and  
       FIGS. 7A and 7B  are two schematic illustrations showing the column-like heat pipe applied into a heat dissipation module according to the preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.  
      Referring to  FIG. 2 , it is a schematic illustration showing a column-like heat pipe according to the preferred embodiment of the invention. The heat pipe  20  includes a main body  22 , a base  28 , a first wick  26   a  and a working fluid W. The main body  22  has a top portion  224  and a sidewall portion  222  disposed around the top portion  224  and the sidewall portion  222 , the top portion  224  may be integrally formed as a single piece, i.e. the main body  22 . When the base  28  and the main body  22  are assembled, the base  28  and the main body  22  are combined to form a closed chamber, and the base  28  is disposed corresponding to the top portion  224 . The working fluid W is filled within the closed chamber.  
      The base  28  has an uneven surface  281 , which is formed with at least one protrusion  282 , and the cross section of the protrusion  282  on the uneven surface  281  of the base has a rectangular, semi-circular semi-spherical, arc, triangular, quadrangular or trapezoidal shape. Herein, it is to be noted that the pattern and the number of the protrusion(s)  282  formed on the uneven surface  281  of the base  28  are not particularly limited. As shown in  FIG. 3A , there are several protrusions  282  formed on the base  28 . As shown in  FIG. 3B , there is only one protrusion  282 . The protrusions  282  on the base  28  constitute a checkerboard pattern, an array pattern, a symmetrical pattern or an asymmetrical pattern.  
      The first wick  26   a  is disposed on the sidewall portion  222  and top portion  224 , and the second wick  26   b  is disposed on the uneven surface  281  of the base  28  and connected to the first wick  26   a . Referring to  FIG. 3C , it is a schematic illustration showing the base and the second wick of  FIG. 2 . The second wick  26   b  is disposed along the profile of the uneven surface  281  of the base  28 . The second wick  26   b  has a uniform thickness or a varied thickness. It is to be noted that the pattern and the number of the protrusion(s) formed on the uneven surface  281  of the base  28  are not particularly limited. For example, in  FIG. 3C , several protrusions  282  are disposed on the base  28 , but there is only one single protrusion  282  disposed on the base, as shown in  FIG. 2 .  
      In  FIG. 3D , it is a schematic illustration showing another base and the first wick disposed thereon. The second wick  26   b  is disposed over the uneven surface  281  of the base  28  such that the second wick  26   b  facing the top portion  224  forms a plane. The second wick  26   b  has a first thickness H 1  and a second thickness H 2  which is relatively smaller than the first thickness H 1  in a direction perpendicular to the base  28 . The first thickness H 1  is the thickness of the second wick  26   b  on the uneven surface  281  of the base  28  without any protrusion  282 . The second thickness H 2  is the thickness of the second wick  26   b  on the uneven surface  281  with the protrusion  282 . It is to be noted that the pattern and the number of the protrusion(s) formed on the inner surface of the base are not particularly limited. That is to say, the several protrusions  282  are formed on the base  28  in  FIG. 3D  is taken as an example, which is different from that of  FIG. 2  only illustrating the single protrusion  282  for the purpose of clarity.  
      When the heat pipe  20  is actually used, the base  28  directly contacts a heat source (not shown) located below the heat pipe  20  so as to conduct the heat, which is generated by the heat source, away from the heat source. Alternatively, the heat pipe  20  may contact the heat source through an external carrier (not shown) located below the heat pipe  20  and above the heat source. When the heat pipe  20  is disposed above the heat source, the working fluid at the second wick  26   b  (i.e., the evaporating end) near the heat source absorbs the heat generated by the heat source and becomes a vaporized working fluid. The vaporized working fluid flows to the condensing end naturally under the action of the pressure difference, and then releases the latent heat at the first wick  26   a  (i.e., the condensing end B) of the end away from the heat source and becomes the liquid working fluid. The liquid working fluid W flows back to the evaporating end by the capillary force provided by the second wick  26   b . The circulation repeats to continuously dissipate heat of the heat source.  
      Because the main body  20  and the bases  28  are two separate components, the uneven surface  281  of the base  28  can be manufactured to form an uneven surface easily, so that the contact area between the base  28  and the second wick  26   b  is increased to enhance the evaporating efficiency of heat pipe  20 . Moreover, the first wick  26   a  disposed on the sidewall portion of the main body  22  and the second wick  26   b  disposed on the uneven surface  281  of the base  28  are disposed separately so as to enlarge the exposed surface area of the wick and to enhance the evaporating efficiency of the working fluid W and thus to enhance the heat dissipation performance of the heat pipe  20  at the evaporating end.  
      The main body  22  and the base  28  are made of a material with high thermal conductivity, such as Copper, silver, aluminum or alloy thereof. The first wick  26   a  and the second wick  26   b  may be made by plastic material, a metallic material, an alloy and a porous non-metallic material, and formed by way of sintering, adhering, filling and depositing or any combinations thereof. The working fluid W may be an inorganic compound, pure water, alcohol, ketone, liquid metal, refrigerant, an organic compound or any mixtures thereof.  
      The sidewall portion  222  and the top portion  224  may be integrally formed as a single piece and combined together to form the main body  22 . Alternatively, the sidewall portion  222  has a shape of hollow tube, the sidewall portion  222  and the top portion  224  may be two separate components and be further combined together to form the main body  22 . Refer to  FIGS. 4 , and  5 A to  5 C, another column-like heat pipe  40  is disclosed including a main body  42 , a base  48 , a first wick  46   a  and a working fluid W.  
      The main body  42  has a top portion  424  and a sidewall portion  422  disposed around the top portion  424 . Different from the previously mentioned heat pipe  20  of  FIG. 2 , the sidewall portion  422  and the top portion  424  of the main body  42  are two separate components, which are connected by way of welding, embedding, engaging or adhering to form a main body  42 . Then, the first wick  46   a  is disposed on the inner surfaces of the sidewall portion  422  and top portion  424 , while the second wick  46   b  is disposed on the uneven surface of the base  48 . After the wicks are combined, the base  48  and the main body  42  are combined together, which makes a closed chamber in the heat pipe  40 . The heat pipe  40  may have the same technological features as those of the heat pipes  20  of  FIG. 2 , and detailed descriptions thereof will be omitted.  
      In addition to the configuration of the uneven surface of the base  28 ,  48 , it is feasible to configure the inner surface of the top portion or the inner surface of the sidewall portion of the main body  22  into uneven surfaces so as to enlarge the exposed surface area of the second wick  26   b . That is, the inner surface of the top portion  224  and/or  424  or the inner surface of the sidewall portion  222  and/or  422  may have even or uneven profiles.  
      As shown in  FIG. 4 , the inner surface of the top portion  424  is formed with a plurality of protrusions, and the protrusions may constitute a checkerboard pattern, an array pattern, a symmetrical pattern or an asymmetrical pattern. The first wick  46   a  is disposed on the inner surface of the top portion  424  such that the first wick  46   a  facing the base  48  forms a plane, and the first wick  46   a  has a third thickness H 3  and a fourth thickness H 4  relatively smaller than the third thickness H 3  in a direction perpendicular to the top portion  424 .  
      Referring to  FIG. 6A , it is a schematic illustration showing another sidewall portion of the column-like heat pipe of  FIG. 4 . As shown in the example of  FIG. 6A , the base  68  and the sidewall portion  622  have uneven surfaces. Similar to the bases  28 ,  48  of  FIGS. 2 and 4 , the uneven surface of the base  68  and the inner surface of the sidewall portion  622  are respectively formed with at least one protrusion  682   a  and at least one protrusion  682   b . The cross section of the protrusion  682   b  on the sidewall portion  622  constitutes a sawtooth ring pattern ( FIG. 6B ), a continuous semi-circular pattern or any other patterns constituted by the equivalent structure.  FIG. 6B  is a top view showing the sidewall portion of the column-like heat pipe of  FIG. 6A . Herein, it is to be noted that the patterns and numbers of the protrusions  682   a  and  682   b  formed on the uneven surface  681  of the base  68  and the inner surface of the sidewall portion  622  are not particularly limited. One single protrusion or multiple protrusions may be formed. Multiple protrusions  682   a  on the base  68  constitute a checkerboard pattern, an array pattern, a symmetrical pattern or an asymmetrical pattern.  
      Similar to the disposed way of the first wick  26   a  and the second wick  26   b  of  FIG. 2 , the first wick  66   a  is disposed on the inner surface of the sidewall portion  622  and the inner surface of the top portion  624 , and the second wick  66   b  is disposed on the uneven surface of the base  68  and connected to the first wick  66   a . The second wick  66   b  is disposed along the profile of the uneven surface of the base  68  and the second wick  66   b  has an even shape or an uneven shape. Alternatively, the second wick  66   b  is disposed on the uneven surface of the base  68 , such that the second wick  66   b  faces to the top portion  624  to form a plane. The second wick  66   b  has a first thickness H 1  and a second thickness H 2  in a direction perpendicular to the base  68 . The first thickness H 1  is relatively greater than the second thickness H 2 . The first thickness H 1  is the thickness of the second wick  66   b  on the uneven surface  681  of the base  68  without any protrusion  682   a . The second thickness H 2  is the thickness of the second wick  66   b  on the uneven surface  681  with the protrusion  682   a  as shown in  FIG. 6A . The first wick  66   a  on the sidewall portion  622  can have the same technical feature with the second wick  66   b , the detailed description is omitted.  
      Referring to  FIGS. 7A and 7B , there are two schematic illustrations showing column-like heat pipe applied into two heat dissipation modules according to the preferred embodiment of the invention. The heat dissipation module  50 A and  50 B may be applied to a heat source (not shown), and the heat pipe  20  contacts the heat source directly or indirectly through an external carrier. The heat source is an electronic element, such as a CPU (Central Processing Unit), a transistor, a server, an advanced graphics card, a hard disk, a power supply, a mobile control system, a multimedia electronic mechanism, a wireless communication transceiver station or an advanced game machine, which emits the heat. In addition, the heat dissipation module  50 A,  50 B may further be combined with a fan to dissipate heat, which is conducted by the heat dissipation module  50 A,  50 B, more quickly.  
      In  FIG. 7A , the heat dissipation module  50 A includes a heat pipe  20  and a plurality of heat dissipation fins  52   a . The heat pipe  20  may have the same technical feature of the  FIG. 2 , and the detailed description thereof is omitted. The fins  52   a ,  52   b  are manufactured by way of aluminum extrusion, pressing or other methods and are disposed around the heat pipe  20  and connected to the heat pipe  20 . The fins  52   a ,  52   b  are connected to the heat pipe  20  by way of welding, embedding, engaging or adhering. The fins  52   a ,  52   b  may directly contact the heat pipe  20 , or a soldering paste, a grease or a material capable of serving as a thermal conductive interface may be coated between the fins  52   a ,  52   b  and the heat pipe  20 .  
      Multiple fins  52   a  are disposed around the heat pipe  20  in radial distribution and connected to the heat pipe  20 . The heat pipe  20  is embedded in and/or engaged with the fins  52   a , such as the heat pipe  20  is passed through by the fins  52   a . Alternatively, as shown in  FIG. 7B , multiple fins  52   a  may be disposed in a horizontal interval distribution. However, the distribution of the fins  52   a  or  52   b  are taken for examples, the invention is not limited by these. The fins  52   a ,  52   b  also can be a vertically interval distribution, a slantingly interval distribution, or other distributions.  
      In the heat dissipation module and the heat pipe thereof according to the embodiments, the heat dissipation module and the heat pipe thereof have advantages of low cost and simple manufacture procedures. Besides, the sidewall portion and the top portion of the main body are integrally formed or may be tightly fit with each other, and then the second wicks are simultaneously disposed on the inner surfaces of the sidewall portion and the top portion. Because the wicks on the sidewall portion and the top portion are continuous, the working fluid condensed at the wick on the top portion can flow to the wick on the sidewall portion smoothly. Thus, the invention not only solves the problems of poor connection between the sidewall portion and the top cover of the conventional column-like heat pipe in the prior art, but also effectively enlarges the heat exchanging area of the column-like heat pipe and thus enhances the overall heat dissipation efficiency.  
      Moreover, the main body and the bases are two separate components, and the uneven surface of the base can be manufactured to form an uneven surface easily, so that the contact area between the base and the second wick is enlarged to enhance the evaporating efficiency of heat pipe. In addition, the first wick disposed on the sidewall portion of the main body and the second wick disposed on the uneven surface of the base are disposed separately, so it is easy to form a wick with uniform or varied thickness to enlarge the surface area of the wick and to enhance the evaporating efficiency of the working fluid and thus to enhance the heat dissipation performance of the heat pipe at the evaporating end.  
      Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.