Patent Publication Number: US-2010108297-A1

Title: Heat Pipe and Making Method Thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a heat pipe and making method thereof, and more particularly, to a heat pipe applied to a light emitting diode (LED) for heat dissipating and making method thereof 
     2. Description of the Prior Art 
     With the vigorous development of technology, many electrical products have unsolved heat-dissipating problems. For example, when the central processing unit (CPU) of the computer operates, it will generate a lot of heat. Once the heat can not be removed, the operation of the system will be seriously affected. The heat pipe plays important role in the heat-dissipating part of the CPU of the computer. Especially, when the usage space of the electrical apparatus gradually becomes smaller, the heat-dissipating device which can efficiently dissipate heat and fully use the space to dissipate heat becomes more important. 
     The conventional heat pipe heat-dissipating is always using a metallic block material, wherein a heat plane is formed on the metallic block material by staggering a plurality of heat pipes. However, the heat generated by the electric component located upon the heat plane needs to be transmitted to the heat pipes indirectly through the metallic block material, therefore, the heat-dissipating efficiency of this heat-dissipating mechanism will be limited to the physical property of the metallic block material, and difficult to be improved. If the electric component is directly located on the heat pipe (since the diameter of the heat pipe is limited in a general electric apparatus), the heat pipe can not load a larger electric component or a group of electric components. Using the vapor chamber can directly solve the narrow deposing area problem, however, extra device is needed to dissipate the heat from the electric component, such as a heat-dissipating fin. And, the deposing space needed for the above-mentioned vapor chamber and its heat-dissipating fin is still too larger to the electric apparatus only having a smaller space. 
     Accordingly, the invention is to provide a heat pipe having different cross-section areas and making method thereof to provide an effective and rapid heat-dissipating mechanism for the electric component with larger heat area or a group of electric components to solve the problems mentioned above. 
     SUMMARY OF THE INVENTION 
     A scope of the present invention is to provide a heat pipe and making method thereof. 
     Another scope of the present invention is to provide a heat pipe having different cross-section areas applied to a light emitting diode (LED) for heat dissipating and making method thereof. 
     The heat pipe of the invention is applied to a light emitting diode (LED) for heat dissipating. The heat pipe comprises a tube, a chamber, and a porous capillary diversion layer. The tube has a first open, and the diameter of the tube is smaller than 10 mm. The chamber has a second open, and the second open and the first open are tight joined together to form a sealed space via the tube and the chamber. The porous capillary diversion layer is formed in the tube and the chamber. Wherein, the sealed space contains a working fluid, and a cross-section area of the chamber is larger than a cross-section area of the tube. 
     In an embodiment, the tube and the chamber are formed in one piece. In another embodiment, the chamber is formed by a concave and an upper cover. The upper cover is engaged with the concave and the upper cover has the second open. The concave can be made through a process of powder metallurgy, stamping, injection molding, casting, or machining. In an embodiment, the chamber has a flat end for deposing a general electric component. 
     In an embodiment, the porous capillary diversion layer is made by sintering a copper powder, a nickel powder, a silver powder, a metallic powder plated with copper, nickel, silver, or other similar metallic powders. 
     In another embodiment, the porous capillary diversion layer comprises a metallic pellet layer and a metallic net body. The metallic pellet layer is formed on the inner wall of the tube and the inner wall of the chamber by sintering, and the metallic net body is disposed upon the metallic pellet layer. 
     In another embodiment, the porous capillary diversion layer comprises a wavy carped metal cloth and a flat metal net fabric layer. Besides, the wavy carped metal cloth is spread on the inner wall of the tube and the inner wall of the chamber, and the flat metal net fabric layer is disposed on the wavy carped metal cloth, wherein the wavy carped of the wavy carped metal cloth is in a form of triangle, rectangle, trapezium, or wave. 
     In another embodiment, the porous capillary diversion layer comprises a plurality of tiny notches formed on the inner wall of the tube and the inner wall of the chamber. 
     In another embodiment, the porous capillary diversion layer comprises a plurality of tiny notches and a metallic sintered layer, the tiny notches are formed on the inner wall of the chamber, and the metallic sintered layer is formed on the inner wall of the tube and the metallic sintered layer is welded with the tiny notches. 
     The heat pipe making method of the invention comprises the steps of: (a) providing a tube having a first open and a third open; (b) providing a chamber having a second open; (c) tightly joining the first open of the tube and the second open of the chamber together to form a semi-finished heat pipe; (d) vacuuming the semi-finished heat pipe; and (e) sealing the third open. Wherein the inner wall of the semi-finished heat pipe comprises a porous capillary diversion layer; the semi-finished heat pipe contains a working fluid; the cross-section area of the chamber is larger than the cross-section area of the tube. And, the working fluid is poured into the semi-finished heat pipe before or after step (d) is performed. Additionally, in the step (c), the tight joining is performed through a process of welding, soldering, machine fastening, or gluing. 
     The step (b) of the heat pipe making method of the invention can comprise the steps of: providing a concave; providing an upper cover having the second open; and engaging the upper cover and the concave to form the chamber. The concave can be made through a process of powder metallurgy, stamping, injection molding, casting, or machining. And, a first sintered metal layer can be formed on the concave, a second sintered metal layer can be formed on the upper cover, and the first sintered metal layer is engaged with the second sintered metal layer. Or, a plurality of first tiny notches is formed on the concave, a plurality of second tiny notches is formed on the upper cover, and the plurality of first tiny notches is engaged with the plurality second of tiny notches. Then, the porous capillary diversion layer is formed when the concave and the tube are engaged. 
     In an embodiment, a sintered metallic powder layer is formed on the inner wall of the chamber. The porous capillary diversion layer is formed by the following steps of: interposing a center pillar into the semi-finished heat pipe from the third open and the center pillar is approximately tightly against the sintered metallic powder layer; filling a first metallic powder between the center pillar and the semi-finished heat pipe; performing a sintering process to make the first metallic powder and the metallic powder mutually welded to form the porous capillary diversion layer; and getting the center pillar out of the semi-finished heat pipe. 
     In another embodiment, the inner wall of the chamber has a plurality of tiny notches. The porous capillary diversion layer is formed by the following steps of: interposing a center pillar into the semi-finished heat pipe from the third open and the center pillar is approximately tightly against the plurality of tiny notches; filling a second metallic powder between the center pillar and the semi-finished heat pipe; 
     performing a sintering process to make the second metallic powder and the plurality of tiny notches mutually welded to form the porous capillary diversion layer; and getting the center pillar from the semi-finished heat pipe. By the way, in the two above-mentioned embodiments, the first metallic powder or the second metallic powder is a copper powder, a nickel powder, a silver powder, a metallic powder plated with copper, nickel, silver metal powder, or other metallic powders. 
     In another embodiment, a machining process is used to make the plurality of tiny notches on the inner wall of the tube and the inner wall of the chamber to form the porous capillary diversion layer. 
     In another embodiment, the porous capillary diversion layer is formed by the following steps of: sintering a plurality of metallic pellets on the inner wall of the tube and the inner wall of the chamber; and disposing a metallic net body on the plurality of metallic pellets to form the porous capillary diversion layer. 
     In another embodiment, the porous capillary diversion layer is formed by the following steps of: laying a wavy carped metal cloth on the inner wall of the tube and the inner wall of the chamber; and disposing a flat metal net fabric layer on the wavy carped metal cloth to form the porous capillary diversion layer. 
     Another heat pipe making method of the invention comprises the steps of: (A) providing a first tube having an open and a closed end; (B) shrinking the neck of the first tube to form a chamber and a second tube, and the chamber and the second tube are mutually through, wherein the chamber comprises the closed end, the second comprises the open; (C) vacuuming the chamber and the second tube; and (D) sealing the open. Wherein, the inner wall of the chamber and the inner wall of the second tube comprise a porous capillary diversion layer; the chamber and the second tube contain a working fluid; a cross-section area of the chamber is larger than the cross-section area of the second tube. Wherein step (B) is operated in a temperature range from 400° C. to 600° C. 
     In an embodiment, after step (A) is performed, the porous capillary diversion layer is formed on the inner wall of the first tube. The porous capillary diversion layer is formed by the following steps of: disposing a first metallic powder into the first tube; interposing a center pillar into the first tube from the open and the center pillar is approximately tightly against on the first metallic powder; filling a second metallic powder between the center pillar and the inner wall of the first tube; performing a sintering process to make the first metallic powder and the second metallic powder mutually welded to form the porous capillary diversion layer; and getting the center pillar out of the first tube. 
     Accordingly, the invention is to provide a heat pipe having different cross-section areas and making method thereof to provide an effective and rapid heat-dissipating mechanism for the electric component, with larger heat area or a group of electric components, disposed on the flat end of the heat pipe. 
     The objective of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         FIG. 1  illustrates a cross-sectional view of the not-finished heat pipe of a first preferred embodiment. 
         FIG. 2A  illustrates a cross-sectional view of a semi-finished heat pipe of the first preferred embodiment. 
         FIG. 2B  illustrates a cross-sectional view that a center pillar is interposed into the semi-finished heat pipe of the first preferred embodiment. 
         FIG. 2C  illustrates a cross-sectional view that a first metallic powder is filled between the center pillar and the semi-finished heat pipe of the first preferred embodiment. 
         FIG. 2D  illustrates a cross-sectional view of a semi-finished heat pipe of the first preferred embodiment. 
         FIG. 2E  illustrates a cross-sectional view of the heat pipe of the first preferred embodiment. 
         FIG. 3A  illustrates a partial cross-sectional view of a first open of the heat pipe and a second open of the heat pipe of an embodiment. 
         FIG. 3B  illustrates a partial cross-sectional view that a first open of the heat pipe and a second open of the heat pipe are engaged of the embodiment. 
         FIG. 3C  illustrates a partial cross-sectional view that a first open of the heat pipe and a second open of the heat pipe of an embodiment. 
         FIG. 3D  illustrates a partial cross-sectional view that a first open of the heat pipe and a second open of the heat pipe are engaged of the embodiment. 
         FIG. 3E  illustrates a cross-sectional view of the chamber of the heat pipe of the above-mentioned embodiment. 
         FIG. 4A  illustrates a cross-sectional view of a semi-finished heat pipe of a second preferred embodiment. 
         FIG. 4B  illustrates a cross-sectional view that a center pillar is interposed into the semi-finished heat pipe of the second preferred embodiment. 
         FIG. 4C  illustrates a cross-sectional view that a second metallic powder is filled between the center pillar and the semi-finished heat pipe of the second preferred embodiment. 
         FIG. 4D  illustrates a cross-sectional view of the heat pipe of the second preferred embodiment. 
         FIG. 4E  illustrates a cross-sectional view that the heat pipe has not finished of an embodiment. 
         FIG. 4F  illustrates a cross-sectional view that the heat pipe has not finished of the embodiment. 
         FIG. 4G  illustrates a cross-sectional view of the heat pipe of the embodiment. 
         FIG. 4H  illustrates a cross-sectional view of the chamber of the heat pipe of the above-mentioned embodiment. 
         FIG. 5  illustrates a cross-sectional view of the heat pipe of a third preferred embodiment. 
         FIG. 6  illustrates a cross-sectional view of the heat pipe of a fourth preferred embodiment. 
         FIG. 7  illustrates a cross-sectional view of the heat pipe of a fifth preferred embodiment. 
         FIG. 8A  illustrates a cross-sectional view of a first tube of the heat pipe of a sixth preferred embodiment. 
         FIG. 8B  illustrates a cross-sectional view that after the first tube is shrank the neck of the sixth preferred embodiment. 
         FIG. 8C  illustrates a cross-sectional view of the heat pipe of the sixth preferred embodiment. 
         FIG. 8D  illustrates a cross-sectional view that a first metallic powder is filled into the first tube of the sixth preferred embodiment. 
         FIG. 8E  illustrates a cross-sectional view that the center pillar is interposed into the first tube of the sixth preferred embodiment. 
         FIG. 8F  illustrates a cross-sectional view that a second metallic powder between the center pillar and the first tube of the sixth preferred embodiment. 
         FIG. 8G  illustrates a cross-sectional view of the first tube of the sixth preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to  FIG. 1 .  FIG. 1  illustrates a cross-sectional view of the not-finished heat pipe  1  according to a first preferred embodiment of the invention. The heat pipe  1  includes a tube  12  and a chamber  14 . The tube  12  has a first open  122  and a third open  124 . The chamber  14  has a second open  142  and a flat end  144 . The cross-section area of the chamber  14  is larger than the cross-section area of the tube  12 . Wherein, the cross-section area of the chamber  14  means the cross-section area near the flat end  144 . The diameter of the tube  12  is smaller than 10 mm. 
     The second open  142  of the chamber  14  and the first open  122  of the tube  12  are tightly joined together to form a semi-finished heat pipe  16 , as shown in  FIG. 2A . The tight joining can be performed through a process of welding, soldering, machine fastening, or gluing. 
     According to the first preferred embodiment, a sintered metallic powder layer  182  has been formed on the inner wall of the chamber  14 , as shown in  FIG. 2A . After the tight joining is performed, a center pillar C 1  is interposed into the semi-finished heat pipe  16  from the third open  124 , and the center pillar C 1  is approximately tightly against the sintered metallic powder layer, as shown in  FIG. 2B . Then, a first metallic powder  184  is filled between the center pillar C 1  and the semi-finished heat pipe  16 , as shown in  FIG. 2C . The first metallic powder  184  can be a copper powder, a nickel powder, a silver powder, a metallic powder plated with copper, nickel, silver, or other similar metallic powders. 
     Next, a sintering process is performed to make the first metallic powder  184  and the sintered metallic powder  182  mutually welded to form a porous capillary diversion layer  18 . At last, the center pillar C 1  is gotten out of the semi-finished heat pipe  16 , as shown in  FIG. 2D . Before the third open  124  is sealed, it needs to vacuum the semi-finished heat pipe  16  and pour a working fluid L 1  into the semi-finished heat pipe  16 . The sequences of pouring the working fluid L 1  and vacuuming the gas can be exchanged. The third open  124  can be shrunk before vacuuming, so that the following sealing can be smoothly performed. Finally, after the third open  14  is sealed, the heat pipe  1  is finished, as shown in  FIG. 2E . 
     By the way, the tight joining should avoid over-damaging the porous capillary diversion layer. In the first preferred embodiment, the second open  124  of the chamber has no sintered metallic powder layer  182  (please refer to  FIG. 2A ). Therefore, during the tight joining process, the damage to the sintered metallic powder layer  182  is unnecessary to be considered, and a general welding process or a general soldering process can be used. However, it should be still noted, after the tight joining, the inner wall of the chamber  14  and the inner wall of the tube  12  should keep joining smoothly, so that the following first metallic powder  184  can be smoothly sintered, and the first metallic powder  184  and the sintered metallic powder  182  can be mutually welded to form the porous capillary diversion layer  18 . 
     In addition, if the second open  142  of the chamber  14  has the sintered metallic powder  182 , the used joining process or the using condition will be limited. For example, it is not suitable to directly use a welding process or a soldering process in this case. However, if the joining is well-designed, the welding process or the soldering process can be used. Please refer to  FIG. 3A .  FIG. 3A  illustrates a partial cross-sectional schematic diagram of the first open  122  and the second open  142  according to an embodiment. The first open  122  includes a joining plane  1222  and a welding portion  1224 . The second open  142  includes a joining plane  1422  and a welding portion  1424 . The joining planes  1222  and  1442  are tightly cohered to each other. The joining planes  1222  and  1442  are both inclined planes. After the joining planes  1222  and  1442  are cohered, the welding portions  1224  and  1424  will form a concave to provide the filling material welding. After the tight joining is finished, only the welding portions  1224  and  1424  are affected to be filled with a welding material P thereon, the joining planes  1222  and  1442  are not affected, so that the inner wall of the chamber  14  and the inner wall of the tube  12  can be still smoothly connected, and the sintered metallic powder  182  of the second open  142  of the chamber  14  can not be damaged, as shown in  FIG. 3B . 
     Furthermore, please refer to  FIG. 3C .  FIG. 3C  illustrates a partial cross-sectional view of the first open  122  and the second open  142  according to another embodiment. The first open  122  includes a joining plane  1222  and a welding portion  1224 . The second open  142  includes a joining plane  1422  and a welding portion  1424 . The joining planes  1222  and  1442  both comprise a protrusion  1224   a ,  1424   a  and a concave  1224   b ,  1424   b.  After the joining planes  1222  and  1442  are cohered, the joining planes  1222  and  1442  are tightly cohered to each other, the protrusions  1224   a ,  1424   a  are mutually weld through a heating process or a soldering process, and the concaves  1224   b  and  1424   b  are fully filled. After the tight joining is finished, only the welding portions  1224  and  1424  are affected, the joining planes  1222  and  1442  are not affected, so that the inner wall of the chamber  14  and the inner wall of the tube  12  can be still smoothly connected, and the sintered metallic powder  182  of the second open  142  of the chamber  14  will not be damaged, as shown in  FIG. 3D . The dotted line circles in  FIG. 3D  show the soldering regions of the welding portions  1224  and  1424 . Of course, if the first open  122  and the second open  142  are joined by a screw thread locking method, the above-mentioned effects due to heat will not exist. But the sealing effect of the tight joining should be noticed. 
     It should be mentioned that in the above-mentioned embodiment, the chamber  14  can include a concave  146  and an upper cover  148 . The concave  146  includes the flat end  144  and the upper cover  148  includes the second open  142 . A first sintered metal layer  1822  is formed on the concave  146 . A second sintered metal layer  1824  is formed on the upper cover  148 . The upper cover  148  and the concave  146  are engaged to form the chamber  14 , and the sintered metallic powder layer  182  is formed by the first sintered metal layer  1822  and the second sintered metal layer  1824 . Additionally, the casing body of the concave  146  itself can be made through a process of powder metallurgy, stamping, injection molding, casting, or machining. 
     Please refer to  FIG. 4A .  FIG. 4A  illustrates a cross-sectional view of the not-finished heat pipe  2  according to a second preferred embodiment. The making method of the heat pipe  2  is approximately same with the heat pipe  1  of the first preferred embodiment, so it will no longer be explained again here. Then, the forming method of the porous capillary diversion layer  28  of the heat pipe  2  will be introduced in detail. 
     As shown in  FIG. 4A , the inner wall of the chamber  24  of the heat pipe  2  has a plurality of tiny notches  282 . A center pillar C 2  is interposed into a semi-finished heat pipe  26  from the third open  224  of the tube  22  of the heat pipe  2 , and the center pillar C 2  is approximately tightly against the plurality of tiny notches  282 , as shown in  FIG. 4B . Then, a second metallic powder is filled between the center pillar C 2  and the semi-finished heat pipe  26 , as shown in  FIG. 4C . Next, a sintering process is performed to make the second metallic powder  284  and the plurality of tiny notches  282  mutually welded to form the porous capillary diversion layer  28 . Finally, the center pillar C 2  is gotten out of the semi-finished heat pipe  26 . And, the heat pipe  2  is formed after sealing the third open  224 , as shown in  FIG. 4D . 
     By the way, the outer diameter of the center pillar C 2  is not limited by one, namely the center pillar C 2  may have different outer diameters. Please refer to  FIG. 4E .  FIG. 4E  illustrates a cross-sectional view of the not-finished heat pipe  2 ′ according to an embodiment. Compared to the second preferred embodiment, the plurality of tiny notches  282 ′ of the chamber  24 ′ of the heat pipe  2 ′ shows the same inner diameter with the tube  22 ′ of the heat pipe  2 ′, therefore, the center pillar having only one outer diameter will not be tight against the plurality of tiny notches  282 ′ and has a space existed between the center pillar and the semi-finished heat pipe  26 ′ of the heat pipe  2 ′ to contain the following added metallic powder. Under this condition, a center pillar C 2 ′ must have different outer diameters, so that one part of the center pillar C 2 ′ can be tightly against the plurality of tiny notches  282 ′ and there will be a space existed between the center pillar C 2 ′ and the heat pipe  2 ′ to contain the following added second metallic powder  284 ′. In the following sintering process, the second metallic powder  284 ′ and the plurality of tiny notches  282 ′ are mutually welded to form a porous capillary diversion layer  28 ′, as shown in  FIG. 4F . After sealing the semi-finished heat pipe  26 ′, heat pipe  2 ′ will be formed, as shown in  FIG. 4G . 
     It should be mentioned that in the above-mentioned embodiment, the chamber  24  and  24 ′ can include a concave  246  and an upper cover  248 . The upper cover  248  includes the second open  242  of the chamber  24 . A plurality of first tiny notches  2822  is formed on the concave  246 . A plurality of second tiny notches  2824  is formed on the upper cover  248 . The concave  246  and the upper cover  248  are engaged together to form the chamber  24 ,  24 ′, and the plurality of first tiny notches  2822  and the plurality of second tiny notches  2824  form the plurality of tiny notches  282 , as shown in  FIG. 4H . Additionally, the casing body of the concave  246  itself can be made through a process of powder metallurgy, stamping, injection molding, casting, or machining. 
     Please refer to  FIG. 5 .  FIG. 5  illustrates a cross-sectional view of the heat pipe  3  according to a third preferred embodiment. The making method of the heat pipe  3  is approximately same with the heat pipe  1  of the first preferred embodiment, so it will no longer be explained again here. Then, the forming method of the porous capillary diversion layer  38  of the heat pipe  3  will be introduced in detail. The porous capillary diversion layer  38  is formed through a machining process to make the plurality of tiny notches  38  on the inner wall of the tube  32  of the heat pipe  3  and the inner wall of the chamber  34  of the heat pipe  3 . For example, the plurality of tiny notches  38  can be formed on the inner wall of the semi-finished heat pipe by directly cutting via a knife. By the way, in an embodiment, since the chamber of the semi-finished heat pipe already has the plurality of tiny notches, after the tight joining is performed, the only thing needed to do is to generate the plurality of tiny notches on the other portions of the semi-finished heat pipe to form a porous capillary diversion layer. However, the connection between these two sets of tiny notches should be noticed. This chamber is always found in the combined chamber, such as a chamber assembled by a concave and an upper cover. 
     Please refer to  FIG. 6 .  FIG. 6  illustrates a cross-sectional view of the heat pipe  4  according to a fourth preferred embodiment. The making method of the heat pipe  4  is approximately the same with the heat pipe  1  of the first preferred embodiment, so it will no longer be explained again here. Then, the forming method of the porous capillary diversion layer  48  of the heat pipe  4  will be introduced in detail. Firstly, a plurality of metallic pellets  482  is sintered on the inner wall of the tube  42  of the heat pipe  4  and the inner wall of the chamber  44  of the heat pipe  4 . Then, a metallic net body  484  is disposed on the plurality of metallic pellets  482  to form the porous capillary diversion layer  48 . By the way, the plurality of metallic pellets  482  can be sintered on the inner wall of the tube  42  and the inner wall of the chamber  44  respectively. 
     Please refer to  FIG. 7 .  FIG.7  illustrates a cross-sectional view of the heat pipe  5  according to a fifth preferred embodiment. The making method of the heat pipe  5  is approximately the same with the heat pipe  1  of the first preferred embodiment, so it will no longer be explained again here. Then, the forming method of a porous capillary diversion layer  58  of the heat pipe  5  will be introduced in detail. Firstly, a wavy carped metal cloth  582  is laid on the inner wall of the tube  52  of the heat pipe  5  and the inner wall of the chamber  54  of the heat pipe  5 . Then, a flat metal net fabric layer  584  is disposed on the wavy carped metal cloth  582  to form the porous capillary diversion layer  58 . Wherein, the wavy carped of the wavy carped metal cloth  582  can be in a form of triangle, rectangle, trapezium, or wave. 
     Please refer to  FIG. 8 .  FIG. 8  illustrates a cross-sectional view of the first tube  62  of the heat pipe  6  according to a sixth preferred embodiment. The first tube  62  has an open  622  and a closed end  624 . The closed end  624  is flat. The first tube  62  has larger inner diameter, so that the following neck-shrinking process can be smoothly performed. And, because it is the tube wall of the first tube  62  shrunk by the shrinking neck process, and the tube wall will become thicker after the neck-shirking process, the wall thickness of the closed end  624  of the first tube  62 , in general applications, will be thicker than that before the neck-shirking process, so that a uniform wall thickness can be obtained after the neck-shirking process. But it is not limited to this. 
     Next, a chamber  626  and a second tube  628  are formed by shrinking the neck of the first tube  62 , and the chamber  626  and the second tube  628  are mutually through, as shown in  FIG. 8B . The chamber  626  includes the closed end  624 , and the second tube  628  includes the open  622 . A cross-section area of the chamber  626  is larger than a cross-section area of the second tube  628 . The cross-section area of the chamber  626  means the cross-section area of the closed end. In addition, the chamber  626  and the inner wall of the second tube  628  include a porous capillary diversion layer  64 . 
     Then, the chamber  626  and the second tube  628  are vacuumed, and a working fluid L 2  is poured into the chamber  626  and the second tube  628  respectively. Finally, the open  622  is sealed. Wherein, the sequence of the pouring the working fluid L 2  step and the vacuuming the gas step can be exchanged. After the open  622  is sealed, the heat pipe  6  is finished, as shown in  FIG. 8C . 
     According to the sixth preferred embodiment, the shrunk neck is heated in a temperature range from 400° C. to 600° C., or the shrunk neck is heated in a temperature range from the recrystallization temperature of the first tube  62  to the temperature that about 200° C. over the recrystallization temperature. Additionally, the porous capillary diversion layer  64  is formed on the inner wall of the first tube  62  before the neck-shrinking by the following steps of: disposing a first metallic powder  642  into the first tube  62 , as shown in  FIG. 8D ; interposing a center pillar C 3  into the first tube  62  from the open  622  and the center pillar C 3  is approximately tightly against on the first metallic powder  642 , as shown in  FIG. 8E ; filling a second metallic powder  644  between the center pillar C 3  and the inner wall of the first tube  62 ; performing a sintering process to make the first metallic powder  642  and the second metallic powder  644  mutually welded to form the porous capillary diversion layer  64 ; and getting the center pillar C 3  out of the first tube  62 , as shown in  FIG. 8G . 
     In the above-mentioned embodiment, the tube and the chamber are joined in a symmetrical method. In practical applications, the tube and the chamber can be also joined in an unsymmetrical method. For example, the tube can be connected to the edge of the chamber to meet different space limitations. 
     To sum up, the invention provides a heat pipe having different cross-section areas and making method thereof to provide an effective and rapid heat-dissipating mechanism for the electric component, with larger heat area or a group of electric components, disposed on the flat end of the heat pipe. 
     Although the present invention has been illustrated and described with reference to the preferred embodiment thereof, it should be understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.