Abstract:
The invention is to provide a method for making a heat pipe with a flat end. The method comprises the steps of (a) providing a first tube, including a first open end and a second open end; (b) providing a second tube, including a third open end and a flat closed end; (c) seal jointing the second open end of the first tube and the third open end of the second tube to form a third tube; (d) forming a porous capillary diversion layer on the inner wall of the third tube; (e) injecting a working fluid into the third tube; (f) vacuuming the third tube, and (g) sealing the first open end.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a heat pipe and a manufacturing method thereof, and more particularly, the heat pipe has a flat end so that an electrical device can be smoothly connected onto the flat end of the heat pipe. 
         [0003]    2. Description of the Prior Art 
         [0004]    With the development of technology, many electronic products face the problem of heat-dissipating. For example, a lot of heat is generated when the central processing unit of a computer is operated. If the heat is not removed, the operation of the entire system will be impacted. Therefore, the heat pipe plays an important role in the heat-dissipating of the central processing unit in the computer. 
         [0005]    The well-known method of manufacturing a sintering heat pipe is to seal one end of a metal tube in a high temperature fusing way. Then, a metal rod is put in the tube and a metal powder is infilled in the tube. After the sintering process, the metal rod is removed and then the heat pipe is done. Please refer to  FIG. 1 .  FIG. 1  shows the partial cross-sectional view of the heat pipe A 1  in the prior art. As shown in  FIG. 1 , the metal pipe manufactured in this way has a round sealing end and a thicker wall, and the inner wall of the metal pipe lacks of capillary. Therefore, only the wall of the present heat pipe can be used and the end part of the heat pipe is not able to be used. 
         [0006]    Therefore, the main aim of the invention is to provide a heat pipe and manufacturing method thereof. Herewith an electrical device can be smoothly connected onto the flat end of the heat pipe. 
       SUMMARY OF THE INVENTION 
       [0007]    In order to achieve the above-mentioned aim and solve the above-mentioned drawback, the invention provides a heat pipe and manufacturing method thereof. Herewith an electrical device can be smoothly connected onto the flat end of the heat pipe. 
         [0008]    The heat pipe according to the invention comprises a first tube and a second tube. The first tube has a first end and a second end; the second tube has a third end and the flat end. The first tube can be a hollow metal tube, and the first end and the second end are both open. The third end of the second tube and the second end of the first tube are sealed and connected so that a third tube is formed by the first tube and the second tube. The sealing process can a soldering process, a welding process, a mechanical buckling process, or an agglutinating process. In addition, the second tube can be made by a powder metallurgy process, a punching process, an injection molding process, a casting process, or a machining process. The flat end can be in a flat form or in a concave form. It depends on the practical application. 
         [0009]    According to the invention, a multi-hole capillary conducting layer is formed on the inner wall of the third tube. A working fluid is injected into the third tube from the first end of the first tube and the heat pipe is formed by sealing. Before the sealing, the heat pipe must be vacuumed to let the inside of the heat pipe reach a necessary vacuum so that the working fluid can work normally. 
         [0010]    In addition, the multi-hole capillary conducting layer can be made by the following methods, but not limited by these methods. In the first method, a first metal powder is put into the third tube (at this time, the first end of the first tube is not sealed yet). Then, a center bar is inserted into the third tube from the first end and the center bar is against the first metal powder and a second metal powder is infilled between the center bar and the third tube. Afterward, a sintering process is performed to weld the first metal powder and the second metal powder to form the multi-hole capillary conducting layer. At last, the center bar is drawn out from the third tube. By the way, the first metal powder can be replaced by a sintered metal powder layer. 
         [0011]    In the second method, a plurality of fine notches is on the inner wall of the third tube. The procedures of the second method are as follows. At first, a metal powder is put into the third tube (at this time, the first end of the first tube is not sealed yet). Then, a center bar is inserted into the third tube from the first end and the center bar is against the metal powder. Afterward, a sintering process is performed to weld the metal powder and the plurality of fine notches to form the multi-hole capillary conducting layer. At last, the center bar is drawn out from the third tube. 
         [0012]    The third method is to make a plurality of fine notches on the inner wall of the third tube by a machining process to form the multi-hole capillary conducting layer. 
         [0013]    The fourth method is to sinter a plurality of metal particles on the inner wall of the third tube. And then a metal mesh is set upon the plurality of metal particles to form the multi-hole capillary conducting layer. 
         [0014]    The fifth method is to lay an undulant metal cloth upon the inner wall of the third tube. And then a smooth metal mesh cloth layer is set upon the undulant metal cloth to form the multi-hole capillary conducting layer. 
         [0015]    The first metal powder and the second metal powder in the first method and the metal powder in the second method can be a copper powder, a nickel powder, a silver powder, a copper-plated powder, a nickel-plated powder, a silver-plated powder, or any other similar metal powder. Besides, the first tube and the second tube can be made of a copper, a nickel, a silver, or any other similar metal. 
         [0016]    In addition, if a plurality of fine notches are formed upon both of the inner wall of the first tube and the inner wall of the second tube, the multi-hole capillary conducting layer is formed by the fine notches of the inner wall of the first tube and the inner wall of the second tube after the first tube and the second tube are sealed. Any further process is not necessary. And, the inner wall of the flat end of the heat pipe is not necessary to comprise the multi-hole capillary conducting layer. Therefore, in the above-mentioned condition, the inner wall of the flat end of the second tube is not limited by the plurality of fine notches. 
         [0017]    To sum up, the heat pipe according to the invention has a flat end so that an electrical device can be smoothly connected onto the flat end of the heat pipe. More specifically, a multi-hole capillary conducting layer can be set upon the inner wall of the flat end of the heat pipe to let the working fluid circulate more smoothly and make the heat-dissipating effect of the electrical device better. 
         [0018]    The advantage and spirit of the invention may be further understood by the following recitations together with the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         [0019]      FIG. 1  shows a partial cross-sectional view of a heat pipe in the prior art. 
           [0020]      FIG. 2A  shows a cross-sectional view of a first tube according to a preferred embodiment. 
           [0021]      FIG. 2B  shows a cross-sectional view of a second tube according to the preferred embodiment. 
           [0022]      FIG. 2C  shows a cross-sectional view of a second tube according to an embodiment. 
           [0023]      FIG. 3A  shows a cross-sectional view of a third tube according to the preferred embodiment. 
           [0024]      FIG. 3B  shows a cross-sectional view of the third tube after the soldering process according to an embodiment. 
           [0025]      FIG. 3C  shows a cross-sectional view of the third tube after the welding process according to an embodiment. 
           [0026]      FIG. 3D  shows an exploded cross-sectional view of the first tube and the second tube according to an embodiment. 
           [0027]      FIG. 3E  shows a cross-sectional view of the third tube after the welding process according to the embodiment. 
           [0028]      FIG. 3F  shows a cross-sectional view of the third tube after the spiral agglutinating process according to an embodiment. 
           [0029]      FIG. 3G  shows a cross-sectional view of the third tube after the wedging process according to an embodiment. 
           [0030]      FIG. 3H  shows a cross-sectional view of the third tube according to an embodiment. 
           [0031]      FIG. 4A  shows a cross-sectional view of putting a first metal powder into the third tube according to the first method. 
           [0032]      FIG. 4B  shows a cross-sectional view of inserting a center bar into the third tube and the center bar is against the first metal powder according to the first method. 
           [0033]      FIG. 4C  shows a cross-sectional view of a multi-hole capillary conducting layer formed upon the inner wall of the third tube according to the first method. 
           [0034]      FIG. 4D  shows a cross-sectional view of inserting a center bar into the third tube and the center bar is against a metal powder according to the second method. 
           [0035]      FIG. 4E  shows a cross-sectional view of the third tube after a machining process according to the third method. 
           [0036]      FIG. 4F  shows a cross-sectional view of a plurality of metal particles and a metal mesh set upon the third tube according to the fourth method. 
           [0037]      FIG. 4G  shows a cross-sectional view of an undulant metal cloth and a smooth metal mesh cloth layer set on the third tube according to the fifth method. 
           [0038]      FIG. 5  shows a schematic diagram of using a fine tube to inject a working fluid into the third tube according to the preferred embodiment. 
           [0039]      FIG. 6  shows a cross-sectional view of the heat pipe according to the preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]    In a preferred embodiment according to the invention, the manufacturing method of a heat pipe  1  provides a first tube  12  and the first tube  12  is a hollow metal tube, as shown in  FIG. 2A .  FIG. 2A  shows a cross-sectional view of the first tube  12 . The first tube  12  has a first open end  122  and a second open end  124 . Then, the method provides a second tube  14  and the second tube  14  is also a metal tube, as shown in  FIG. 2B .  FIG. 2B  shows a cross-sectional view of the second tube  14 . The second tube  14  has a third open end  142  and the flat end  144 . The second tube  14  can be formed by punching a metal board, but not limited to this way. For example, the second tube  14  can also be made by injecting, molding, casting, sintering, or second manufacturing. It should be noticed that a flat area is on the surface of the flat end  144  so that an electrical device can be set on the flat end  144 . However, the shape of the flat end  144  is not necessary to be a flat form. It depends on the practical applications. In an embodiment, the flat end  144 ′ can be in a concave form or the second tube  14  can be a “T” form; namely, the cross-section of the flat end  144 ′ is larger than the cross-section of the second tube  14 ′ to match different electrical device configuration, as shown in  FIG. 2C .  FIG. 2C  shows a cross-sectional view of the second tube  14 ′ according to the embodiment. The cross-sectional view shows the second tube  14  is in the “T” form. The shapes of the second tube  14  can be easily made by combining the above-mentioned processes, so it is not described again here. 
         [0041]    It should be noticed that if the second tube  14  is made by a punching process, then  FIG. 2C  should be modified. This is well-known to those skilled in the art, so it is not described again here. In addition, the material of the first tube  12  and that of the second tube  14  are not necessary to be the same. And, the cross-section of the first tube  12  and that of the second tube  14  are not necessary to be in a round form. It depends on the practical applications. For example, the shape of the cross-section can be a rectangle or a triangle. In principle, the cross-section of second open end  124  of the first tube  12  should match that of third open end  142  of the second tube  14 . 
         [0042]    Then, the second open end  124  of the first tube  12  and the third open end  142  of the second tube  14  are sealed to form a third tube  16 , as shown in  FIG. 3A .  FIG. 3A  shows the cross-sectional view of the third tube  16 . The sealing process can be a soldering process, a welding process, a mechanical buckling process, an agglutinating process, or any other process which can seal two items. By the way,  FIG. 3A  is only a schematic diagram, and it does not show that the sealing process belongs to which one of the above-mentioned processes. Each of the different sealing processes will be explained by the following embodiments respectively. However, it is not limited to the embodiments in practical applications. 
         [0043]    In an embodiment, the sealing process is a soldering process. A “V” shape groove can be reserved in advance at the sealing point between the second open end  124  of the first tube  12  and the third open end  142  of the second tube  14 . The groove can be used for infilling the solder S so that the solder S will not protrude the surface of the third tube  16  too much, as shown in  FIG. 3B .  FIG. 3B  shows the cross-sectional view of the third tube  16  after the soldering process is performed. However, the method of the invention is not limited to this embodiment. For example, in certain designs, the protrusion caused by the soldering process can be used to connect to the electrical device. It should be noticed that the soldering process is not the only requirement. In principle, after the soldering process, the inner wall of the first tube  12  and the inner wall of the second tube  14  should be as continually smooth as possible for the sake of the formation of the multi-hole capillary conducting layer, but it is not limited to this case. This is because the plane discontinuities allowed by the formation of different conducting layers are also diverse. 
         [0044]    In an embodiment, the sealing process is a welding process. The sealing point of the second open end  124  of the first tube  12  and the third open end  142  of the second tube  14  is in a sawtooth form so that the second open end  124  and the third open end  142  can be further fused, as shown in  FIG. 3C .  FIG. 3C  shows the cross-section view of the third tube  16  after the welding process is performed. It should be noticed that the sawtooth form should be vanished after the welding process, but it is still shown in  FIG. 3C . 
         [0045]    In another embodiment, the second open end  124  and the third open end  142  both have a relative protrusion  1242  and  1422  for keep the sealing point continually smooth after the welding process, as shown in  FIG. 3D  and  FIG. 3E .  FIG. 3D  shows the exploded cross-sectional view of the first tube  12  and the second tube  14 .  FIG. 3E  shows a cross-sectional view of the third tube  16  after the welding process. Please refer to  FIG. 3D . The second open end  124  of the first tube  12  comprises a concavity  1244  and a surface  1246 , and the third open end  142  of the second tube  14  also comprises a concavity  1424  and a surface  1426 . When the protrusions  1242  and  1422  are fused to each other, the partial fused protrusions  1242  and  1422  can be infilled into the concavity  1244  and  1424  to make the surface  1246  and  1426  seamlessly agglutinated, as shown in  FIG. 3E . The dotted line in  FIG. 3E  indicates the fused area. In addition, the protrusions  1242  and  1422  can also be in a sawtooth form. 
         [0046]    In an embodiment, the sealing process is a mechanical buckling process. The second open end  124  of the first tube  12  and the third open end of the second tube  14  are spirally connected, as shown in  FIG. 3F .  FIG. 3F  shows the cross-section view of the third tube  16  after the spiral connection. As shown in  FIG. 3F , the second open end  124  of the first tube  12  comprises a male screw, and the third open end  142  of the second tube  14  comprises a female screw correspondingly. 
         [0047]    In practical applications, the second open end  124  of the first tube  12  can comprise a female screw, and the third open end  142  of the second tube  14  can comprise a male screw correspondingly. The screws generation step can be incorporated into the manufacturing process of the first tube  12  and the second tube  14 . In another embodiment, the second open end  124  of the first tube  12  and the third open end  142  of the second tube  14  are connected by wedging, as shown in  FIG. 3G .  FIG. 3G  shows the cross-sectional view of the third tube  16  after the wedging connection. The second open end  124  of the first tube  12  comprises a protrusion, and the third open end  142  of the second tube  14  comprises a concavity correspondingly. In general, after the wedging connection, a sealing process is performed to seal the sealing point. 
         [0048]    In an embodiment, the sealing process is an agglutinating process. A viscose is spread on the sealing point between the second open end  124  of the first tube and the third open end  142  of the second tube  14  to agglutinate them. The shape of the connecting surface of the second open end  124  and the third open end  142  is not necessary to be a plane. In general, the moderate irregular form will be helpful to enhance the agglutinating effect. The agglutinating process can be also combined with the above-mentioned processes. For example, in the spiral connection process and the wedging process, the viscose can infiltrate the sealing gap to reach the effect of sealing and enhancing the sealing strength. 
         [0049]    In the above-mentioned embodiments, the first tube  12  and the second tube  14  can be made of a copper, a nickel, a silver, or any other similar metal materials. And, the first tube  12  and the second tube  14  are not necessary to be made of the same material. 
         [0050]    In addition, in the above-mentioned embodiments, the cross-section of the second open end  124  of the first tube  12  and that of the third open end  142  of the second tube  14  are the same. However, in an embodiment, the outer diameter of the first tube  12 ′ equals or is slightly smaller than the inner diameter of the second tube  14 ′ so that the first tube  12 ′ can be inserted into the second tube  14 ′ to form the third tube  16 ′, as shown in  FIG. 3H .  FIG. 3H  shows the cross-sectional view of the third tube according to the embodiment. It should be noticed that  FIG. 3H  is only the schematic diagram of the third tube of the embodiment. The sealing of the third tube can adopt the above-mentioned sealing process, so it is not described again here. 
         [0051]    According to the preferred embodiment, after the first tube  12  and the second tube  14  are sealed, the heat pipe manufacturing method according to the invention forms a multi-hole capillary conducting layer  164  upon the inner wall of the third tube  16 . Please refer to  FIG. 5 . The multi-hole capillary conducting layer  164  can be produced via the following methods. But it is not limited to these methods in practical applications. And, the cross-section of the second open end  124  of the first tube  12  is still the same with that of the third open end  142  of the second tube  14  in the following description, but it is not limited to this case. 
         [0052]    In the first method, a first metal powder P 1  is firstly put into the third tube  16 , as shown in  FIG. 4A .  FIG. 4A  shows the cross-sectional view of putting the first metal powder P 1  into the third tube  16 . Then, a center bar  2  is inserted into the third tube  16  from the first open end  122 , and the center bar is against the first metal powder P 1 , as shown in  FIG. 4B .  FIG. 4B  shows the cross-sectional view of inserting a center bar  2  into the third tube  16  and the center bar  2  is against the first metal powder P 1 . Then, a second metal powder P 2  is infilled between the center bar  2  and the third tube  16 . And, a sintering process is performed to fuse the first metal powder P 1  and the second metal powder P 2  to form the multi-hole capillary conducting layer  164 , as shown in  FIG. 4C .  FIG. 4C  shows the cross-sectional view of the multi-hole capillary conducting layer  164  formed upon the inner wall of the third tube  16 . At last, the center bar  2  is drawn out from the third tube  16 . By the way, in this method, there must be a gap between the center bar  2  and the inner wall of the third tube  16  to accommodate the second metal powder P 2 . And, the cross-section of the center bar is not necessary to be a round form. In principle, the cross-section should match the cross-section of the third tube  16 , but it is not necessary to be similar. In addition, the first metal powder P 1  and the second powder P 2  are not necessary to be the same. And, in this method, the first metal powder P 1  can also be replaced by a sintered metal powder layer.  FIG. 4B  or  FIG. 4C  shows the figure of putting the sintered metal powder layer into the third tube. The sintered metal powder layer can be made by sintering a metal powder in advance. 
         [0053]    In the second method, the inner wall of the third tube  16  already has a plurality of fine notches  166 . At first, a metal powder P 3  is put into the third tube  16 , and then a center bar  2 ′ is inserted into the third tube  16  and the center bar  2 ′ is against the metal powder P 3 , as shown in  FIG. 4D .  FIG. 4D  shows the cross-sectional view of inserting the center bar  2 ′ into the third tube  16  and the center bar  2 ′ is against the metal powder P 3 . Then, a sintering process is performed on the metal powder P 3  to form a metal sintering layer. And, the metal sintering layer and the fine notches  166  are fused to form the multi-hole capillary conducting layer  164 . At last, the center bar  2 ′ is drawn out from the third tube  16 . In the sintering process, the amount of the metal powder P 3  must be enough to be fused with the fine notches  166 . As shown in  FIG. 4D , the fine notches  166  are spread on the inner wall of the first tube  12  and the inner wall of the second tube  14 . However, in practical applications, if the depth of the second tube is shallow enough, the fine notches  166  can only be formed on the first tube  12 . But the amount of the metal powder P 3  must be enough to be fused with the fine notches  166  in the sintering process. This case can simplify the difficulties of manufacturing the second tube  14 . The fine notches  166  on the inner wall of the first tube  12  can be made via a machining process. 
         [0054]    In the third method, a machining process is directly used to make a plurality of fine notches  166 ′ on the inner wall of the third tube  16  to form the multi-hole capillary conducting layer  164 , as shown in  FIG. 4E .  FIG. 4E  shows the cross-sectional view of the third tube  16  after the machining process. It should be noticed that the multi-hole capillary conducting layer  164  can be spread on the inner wall of the flat end  144  of the second tube  14 . The fine notches  166 ′ can be generated via a cutter-cutting way, a discharging manufacturing way, or any other fine notch generating way. 
         [0055]    In the fourth method, a plurality of metal particles  168  are sintered on the inner wall of the third tube  16  to form a metal particle layer. Then, a metal mesh  170  is set on the plurality of metal particles  168  (namely the metal particle layer) to form the multi-hole capillary conducting layer  164 , as shown in  FIG. 4F .  FIG. 4F  shows the cross-sectional view of the third tube  16  after the metal mesh  170  is set. 
         [0056]    In the fifth method, an undulant metal cloth  172  is laid upon the inner wall of the third tube  16  at first. Then, a smooth metal mesh cloth layer  174  is set upon the undulant metal cloth  172  to form the multi-hole capillary conducting layer  164 , as shown in  FIG. 4G .  FIG. 4G  shows the cross-sectional view of the undulant metal cloth  172  and the smooth metal mesh cloth layer  174  set on the third tube  16 . In fact, the shape of undulance of the undulant metal cloth  172  can be a triangle, a rectangle, a trapezoid, a wave, a complex form, or any other shapes. 
         [0057]    In the above-mentioned methods, the first metal powder P 1  and the second metal powder P 2  in the first method and the metal powder P 3  in the second method can be a copper powder, a nickel powder, a silver powder, a copper-plated powder, a nickel-plated powder, a silver-plated powder, or any other similar metal powder. Similarly, the metal powder used in the sintered metal powder layer in the first method can also be one of the above-mentioned powders or a mixed powder. 
         [0058]    In addition, if a plurality of fine notches are formed upon both of the inner wall of the first tube  12  and the inner wall of the second tube  14 , the multi-hole capillary conducting layer  164  is formed by the fine notches of the inner wall of the first tube  12  and the inner wall of the second tube  14  after the first tube  12  and the second tube  14  are sealed. Any further process is not necessary to form the multi-hole capillary conducting layer  164 . And, the inner wall of the flat end  144  of the heat pipe  1  according to the invention is not necessary to comprise the multi-hole capillary conducting layer  164 . Therefore, in the above-mentioned case, the inner wall of the flat end  144  of the second tube  14  is not limited to have the plurality of fine notches. 
         [0059]    According to the preferred embodiment, after the multi-hole capillary conducting layer  164  is formed on the inner wall of the third tube  16 , a working fluid L is injected into the third tube  16  by the method of manufacturing the heat pipe  1  according to the invention. The method can use a fine tube  3  to inject the working fluid L (as shown in  FIG. 5 ), but it is not limited to this case.  FIG. 5  shows the schematic diagram of using the fine tube  3  to inject the working fluid L into the third tube  16 . The fine tube  3  is inserted into the third tube  16  from the open  176  of the third tube  16  (namely the first open end  122  of the first tube  12 ) and then the working fluid L is injected. The open  168  can be shrunk to a diameter which the fine tube  3  can be inserted so that the following processes of vacuuming and sealing the open  176  can be smoothly proceeded, as shown in  FIG. 5 . 
         [0060]    Please refer to  FIG. 6 .  FIG. 6  shows the cross-sectional view of the heat pipe  1  according to the preferred embodiment of the invention. After the injection of the working fluid L is finished, the fine tube  3  is drawn out. Then, the third tube  16  is vacuumed to reach a required vacuum degree in the third tube  16  so that the working fluid can work normally. As shown in  FIG. 6 , the open  176  is sealed to form the heat pipe  1 . However,  FIG. 6  only shows that the open  176  of the third tube  16  is sealed. In practical applications, the sealing method and the sealed cross-sectional structure are not limited to this case. The vacuuming method and the sealing method can be performed via the conventional technologies, so the conventional technologies are not described again here. In addition, the performing sequence of the injection step and the vacuuming step can also be exchanged. It depends on the design of the practical manufacturing process. 
         [0061]    The electrical device which is connected onto the flat end  144  of the heat pipe  1  according to the invention can be a light emitting diode (LED), a laser diode (LD), or an integrated circuit (IC). 
         [0062]    In conclusion, the heat pipe according to the invention has a flat end, and a multi-hole capillary conducting layer set on the inner wall of the flat end so that the working fluid can be smoothly circulated. Therefore, an electrical device can be smoothly connected onto the flat end of the heat pipe to achieve good heat-dissipating effect. 
         [0063]    With the recitations of the preferred embodiment above, the features and spirits of the invention will be hopefully well described. However, the scope of the invention is not restricted by the preferred embodiment disclosed above. The objective is that all alternative and equivalent arrangements are hopefully covered in the scope of the appended claims of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.