Patent Publication Number: US-2013239410-A1

Title: Method for manufacturing heat pipe

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure generally relates to heat pipes and, particularly, to a method for manufacturing a heat pipe. 
     2. Description of Related Art 
     With the continuing development of electronic technology, electronic components are made to have smaller sizes and higher frequencies. However, issues of heat dissipation are also raised accordingly. In order to cool the electronic components, heat dissipation devices, such as heat pipes, are used to dissipate heat from the electronic components. 
     A typical heat pipe includes a tube, a wick structure received in the tube, and a working fluid sealed in the tube. The heat pipe is generally manufactured by cutting a long pipe into several tubes, forming a wick structure in each tube, filling working liquid in each tube, vacuuming each tube, and sealing each tube. Some types of the heat pipes may further be bended or flattened to have predetermined shapes. The manufacturing processes of the heat pipes may be difficult. Furthermore, during flattening or bending, the wick structure may be destroyed or even dropped from the inner wall of the tube, thereby affecting the heat transferring capability of the heat pipe. 
     What is needed, therefore, is a means which can address the limitations described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the various views. 
         FIG. 1  is an isometric view of a heat pipe of manufactured by a method in accordance with a first embodiment of the present disclosure. 
         FIG. 2  is a cross section of the heat pipe of  FIG. 1 , taken along line II-II thereof. 
         FIG. 3  shows a semi-finished product of the heat pipe of  FIG. 2 . 
         FIG. 4  is similar to  FIG. 3 , but showing a semi-finished product of a heat pipe manufactured by a method in accordance with a second embodiment of the present disclosure. 
         FIG. 5  is similar to  FIG. 3 , but showing a semi-finished product of a heat pipe manufactured by a method in accordance with a third embodiment of the present disclosure. 
         FIG. 6  is similar to  FIG. 3 , but showing a semi-finished product of a heat pipe manufactured by a method in accordance with a fourth embodiment of the present disclosure. 
         FIG. 7  is similar to  FIG. 3 , but showing a semi-finished product of a heat pipe manufactured by a method in accordance with a fifth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-2 , a heat pipe  10  manufactured by a method in accordance with a first embodiment of the present disclosure is shown. The heat pipe  10  includes a tube  11 , a wick structure  12  formed in the tube  11 , and a working liquid (not shown) received in the tube  11 . 
     The tube  11  is made by sintering an upper blank  111  and a lower blank  112  together as shown in  FIG. 3 . In detail, a kind of mixture is firstly provided. The mixture includes metal powder blended with organic cement. The metal powder may be made of materials selected from copper, aluminum, copper alloy, aluminum alloy, Fe—Ni alloy, stainless steel, titanium alloy, nickel alloy, aluminum oxide, zirconium oxide and so on. A diameter of the particulate of the metal powder may range from 0.5 to 20 μm, wherein 5˜15 μm is preferable for this embodiment. The organic cement is made of flowable resin materials, such as polyethylene, vinyl acetate and so on. A volume ratio of the metal powder to the organic cement is 2:3˜7:3. 
     The metal powder and the organic cement are mixed by a mixing roll, to thereby form the mixture. The mixture is a plastic fluid where the metal powder is uniformly distributed in the organic cement. Alternatively, the plastic fluid may be further granulated or grinded according to requirements of next manufacturing processes. 
     The plastic fluid is further injected into a mold to form a plurality of blanks  111 ,  112 . In this embodiment, the tube  11  is constructed by joining the upper and lower blanks  111 ,  112  together. Each of the upper and lower blanks  111 ,  112  has a U-shaped cross section. Each of the upper and lower blanks  111 ,  112  has a wick structure  12  formed on an inner face thereof. The wick structure  12  includes a plurality of protrusions  122  and a plurality of grooves  121  between the protrusions  122 . The protrusions  122  of the wick structure  12  may be formed with each of the upper and lower blanks  111 ,  112  as a single monolithic piece. Alternatively, the protrusions  122  may be attached on the inner face of the upper and lower blanks  111 ,  112  after the blank  111 ,  112  is molded. 
     The upper and lower blanks  111 ,  112  are further debinded to release the organic cement from the sintered metal powder. In this embodiment, the upper and lower blanks  111 ,  112  are debinded under a high temperature so that the organic cement is heated to gas escaping from the metal powder. Alternatively, other treating methods, such as siphonage-thermal debinding or solvent-thermal debinding, may also be used in this step. 
     The upper and lower blanks  111 ,  112  are finally sintered to join together. Gaps between the particulates of the metal powder are eliminated during heating the metal powder under a high temperature. Thus, the upper and lower blanks  111 ,  112  are firmly fixed to each other to form the entire tube  11 . The tube  11  has a closed end  110  and an open end  113  opposite to the closed end  110 . The open end  113  gradually shrinks in a direction away from the closed end  110 . The tube  11  may be further machined by thermal treatment or surface treatment to improve an appearance thereof. 
     The tube  11  is filled with the working liquid from the open end  113 . The working liquid may be selected from materials such as water, alcohol, acetone or the like. The tube  11  is then vacuumed through the open end  113  to exhaust air in the tube  11 . Finally, the open end  113  of the tube  11  is sealed to form a hermetic space within the tube  11 . 
     The tube  11  manufactured by this method can directly form a predetermined shape. Thus, the typical manufacturing processes for shaping the conventional heat pipe, such as cutting, bending or flattening, are undesired for the heat pipe  10  of the present disclosure. Accordingly, the heat pipe  10  of the present disclosure can be made more easily. Furthermore, the simplification of the manufacturing processes of the present disclosure can protect the wick structure  12  of the heat pipe  10  from being destroyed or even dropped from the tube  11  during bending or flattening. Therefore, the quality of the heat pipe  10  is improved. 
     In order to facilitate joint of the upper and lower blanks  111 ,  112  before sintering, some positioning structures may be formed on the upper and lower blanks  111 ,  112 . For example,  FIG. 4  shows an upper blank  111   a  forming an inclined bottom face  1110  and a lower blank  112   a  forming an inclined top face  1111 . The inclined top face  1111  of the lower blank  112   a  matches the inclined bottom face  1110  of the upper blank  111   a,  whereby the upper and lower blanks  111   a,    112   a  can be positioned relative to each other more conveniently.  FIG. 5  shows an upper blank  111   b  forming an annular outer protrusion  1110   b  on a bottom face thereof and a lower blank  112   b  forming an annular inner protrusion  1111   b  on a top face thereof. The annular outer protrusion  1110   b  of the upper blank  111   b  can fittingly surround the annular inner protrusion  1111   b  of the lower blank  112   b  to position the upper and lower blanks  111   b,    112   b  together.  FIG. 6  shows an upper blank  111   c  defining an annular groove  1110   c  in a bottom face thereof and a lower blank  112   c  forming an annular protrusion  1111   c  on a top face thereof. The annular protrusion  1111   c  of the lower blank  112   c  can be received in the groove  1110   c  of the upper blank  111   c  to position the upper and lower blanks  111   c,    112   c  together.  FIG. 7  shows an upper blank  111   d  having an outer diameter equal to or slightly less than an inner diameter of a lower blank  112   d.  Thus, the upper blank  111   d  can be fittingly received in the lower blank  112   d  to position the upper and lower blanks  111   d,    112   d  together. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.