Abstract:
A thermal module includes a substrate and a heat pipe integrally embedded in the substrate by insert molding technique. An end of the heat pipe protrudes laterally out of the substrate. The heat pipe includes a tube, a wick structure attached to an inner surface of the tube and a working fluid filled in the tube. A method for manufacturing the thermal module includes following steps: providing a tube with a wick structure attached to an inner surface thereof, an end of the tube being open; placing the tube into a mold; injecting a molten metal into the mold to form a substrate with the tube being integrally embedded in the substrate and the open end of the tube protruding laterally out of the substrate; filling a working fluid into the tube via the open end; sealing the open end of the tube.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a thermal module and a manufacturing method of the thermal module. 
         [0003]    2. Description of Related Art 
         [0004]    With continuing development of electronic technology, heat-generating electronic components such as CPUs (central processing units) are generating more and more heat which requires immediate dissipation. Generally, thermal modules are attached to the electronic components to provide such dissipation. 
         [0005]    A conventional thermal module includes a substrate, a fin assembly and a plurality of heat pipes connecting the fin assembly with the substrate. The substrate defines a plurality of elongated recesses for receiving the evaporator sections of the heat pipes. The evaporator sections of the heat pipes are respectively received in the recesses of the substrate and fixed to the substrate by soldering. Usually, a thermal interface material such as thermal grease is applied in the recesses to reduce air gaps between the heat pipes and the substrate. In manufacturing the thermal module, the substrate is defined with the recesses, and the heat pipes are assembled to the recesses of the substrate, which is time-consuming and complex. Furthermore, due to a technical restriction, the thermal grease can not be uniformly filled in a gap between the heat pipes and the substrate, which increases a heat resistance of the thermal module, and a heat dissipation capability of the thermal module is thus greatly reduced. 
         [0006]    Therefore, a thermal module having a high heat dissipation capability and a simple manufacturing process is desired to overcome the above described shortcomings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an isometric view of a thermal module according to a first embodiment. 
           [0008]      FIG. 2  is a cross-sectional view of the thermal module of  FIG. 1 , taken along a line II-II thereof. 
           [0009]      FIG. 3  is a flow chart showing a method for manufacturing the thermal module of  FIG. 1 . 
           [0010]      FIG. 4  shows a mold and plural tubes for forming the thermal module according to the method of  FIG. 3 . 
           [0011]      FIG. 5  is a bottom plan view of a thermal module according to a second embodiment. 
           [0012]      FIG. 6  is an isometric view of a thermal module according to a third embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring to  FIGS. 1 and 2 , the thermal module  100  includes a substrate  12  and a plurality heat pipes  16  integrally embedded in the substrate  12  by insert molding technique. The substrate  12  is made of metal such as aluminum which has a high heat conductivity coefficient. The substrate  12  is rectangular, including a planar bottom surface  122  adapted for contacting with a heat-generating electronic component (not shown) and a planar top surface  124  opposite to the bottom surface  122 . 
         [0014]    The heat pipes  16  have the same shape and structure. The heat pipes  16  each are elongated. Each of the heat pipes  16  includes a tube  162 , a wick structure  164  received in the tube  162  and a working fluid (not shown) filled in the tube  162 . The tube  162  is made of metal with high heat conductivity coefficient, such as copper. The tube  162  is hollow, defining a chamber  163  therein. The working fluid with a relatively low boiling point is filled in the chamber  163 . The wick structure  164  is attached to an inner surface of the tube  162  surrounding the chamber  163 . The wick structure  164  may be sintered powder, tiny grooves, or screen mesh. In this embodiment, the wick structure  164  is sintered powder. The wick structure  164  defines a plurality of pores therein which generate a capillary force to the working fluid. 
         [0015]    The heat pipes  16  are parallel to and evenly spaced from each other in the substrate  12 . Each of the heat pipes  16  extends from one lateral side of the substrate  12  to an opposite lateral side of the substrate  12  with two distal ends of each of the heat pipes  16  protruding laterally out of the substrate  12 . The heat pipes  16  each are flat, and thus a planar contacting surface  161  is formed at a bottom side of each of the heat pipes  16 . The contacting surfaces  161  of the heat pipes  16  are coplanar with the bottom surface  122  of the substrate  12 . 
         [0016]    Referring to  FIGS. 3 and 4 , in a method of manufacturing the thermal module  100 , a plurality of hollow tubes  162   a  each with a wick structure  164   a  attached to an inner surface thereof are firstly provided, wherein one end of each of the tubes  162   a  is open, and the other end of each of the tubes  162   a  is sealed. A mold  18  is provided and the tubes  162   a  are positioned in the mold  18 . A molten metal is injected into the mold  18  to form the substrate  12  wherein the tubes  162   a  are integrally embedded in the substrate  12  with two ends of each of the tubes  162   a  protruding laterally out of the substrate  12 . The tubes  162   a  together with the substrate  12  are then taken out from the mold  18 . Each of the tubes  162   a  is vacuumed and a working fluid is filled into each of the tubes  162   a  via the open end of each of the tubes  162   a , and then the open end of each of the tubes  162   a  is sealed to form the heat pipes  16 . Thus, the thermal module  100  with the heat pipes  16  integrally embedded in the substrate  12  is formed. 
         [0017]    Before the tubes  162   a  are positioned in the mold  18 , the tubes  162   a  each are flattened to form a contacting surface  161 . The contacting surfaces  161  of the heat pipes  16  are coplanar to the bottom surface  122  of the substrate  12  such that the contacting surfaces  161  can contact the electronic component directly, to thereby absorb heat from the electronic component directly. The open ends of the tubes  162   a  protrude laterally out of the substrate  12  such that the working fluid can be filled into the tubes  162   a  via the open end of each of the tubes  162   a , and the open end of each of the tubes  162   a  can be conveniently sealed. 
         [0018]    As the heat pipes  16  are embedded in the substrate  12  by insert molding technique, the substrate  12  needs not to define recesses therein for receiving the heat pipes  16 , and the heat pipes  16  need not to be assembled and soldered to the substrate  12 , whereby the manufacturing process of the thermal module  100  is simple and convenient. In addition, the heat pipes  16  are integrally formed with the substrate  12  with no air gaps therebetween, whereby a heat resistance between the substrate  12  and the heat pipes  16  is greatly reduced; thus, a heat dissipation efficiency of the thermal module  100  is increased accordingly 
         [0019]    During operation, the bottom surface  122  of the substrate  12  and the contacting surfaces  161  of the heat pipes  16  directly contact with the electronic component to absorb heat from the electronic component. The bottom surface  122  of the substrate  12  transfers the heat to the top surface  124  of the substrate  12 , and then the top surface  124  of the substrate  12  radiates the heat to an outside environment or a fin assembly attached on the top surface  124 . The contacting surfaces  161  of the heat pipes  16  absorb the heat and transfer the heat to the working fluid received in the chambers  163  of the heat pipes  16 , and then the working fluid in the chambers  163  absorbs the heat and evaporates, the vapor carrying the heat moves to every area of the chambers  163  and releases the heat to the substrate  12 . Thus, the heat is rapidly and uniformly spread to everywhere of the substrate  12 . Since the heat pipes  16  are integrally connected with the substrate  12  by insert molding technique, the heat pipes  16  are intimately connected with the substrate  12  with no air gaps therebetween, such that the heat can be quickly transferred to the substrate  12 , and a heat transfer capability of the thermal module  100  is thus increased accordingly. 
         [0020]      FIG. 5  shows a thermal module  200  according to an alternative embodiment. The thermal module  200  is similar to the previous thermal module  100  of the first embodiment. The thermal module  200  includes a rectangular substrate  22  and plural heat pipes  26 ,  27 . The thermal module  200  differs from the previous thermal module  100  in that the heat pipes  26 ,  27  of the thermal module  200  are different from the heat pipes  16  of the previous thermal module  100 . In this embodiment, the heat pipes  26 ,  27  includes a first heat pipe  26  and two second heat pipes  27  which have a different shape from the first heat pipe  26 . The first heat pipe  26  is linearly shaped, while the second heat pipes  27  each are bent to have a bow shape. The first heat pipe  26  is arranged centrally through the substrate  22 . The second heat pipes  27  are located at two opposite lateral sides of the first heat pipe  26 . Each of the second heat pipes  27  includes a linear portion  272  and two bent portions  271 ,  273  respectively extending slantwise from two ends of the linear portion  272  towards corners of the substrate  22 . Ends of each of the first heat pipe  26  and the second heat pipes  27  protrude laterally out of the substrate  22 . A method of manufacturing the thermal module  200  is the same as the method of manufacturing the previous thermal module  100  of the first embodiment. 
         [0021]      FIG. 6  shows a thermal module  300  according to a third embodiment. The thermal module is similar to the previous first thermal module  100 . The thermal module  300  includes a substrate  32  and a plurality of heat pipes  36 . The substrate  32  forms a bottom surface  322  and a top surface  324  opposite to the bottom surface  322 . The thermal module  300  differs from the first thermal module  100  in that a plurality of fins  34  are integrally formed on the top surface  324  of the substrate  32 , and a shape of the heat pipes  36  is different from the heat pipes  16  of the first thermal module  100 . The heat pipes  36  of the thermal module  300  each are U-shaped, including an evaporating section  362  and a condensing section  362  parallel to the evaporating section  362 . The evaporating section  362  is integrally embedded in the substrate  32 , while the condensing section  364  extends through and thermally connects with the fins  34 . The evaporating section  362  of each of the heat pipes  36  forms a planar contacting surface  361  coplanar with the bottom surface  322  of the substrate  32 . 
         [0022]    A method of manufacturing the thermal module  300  is similar to the method of manufacturing the previous thermal module  100  of the first embodiment. When the thermal module  300  is manufactured, a plurality of tubes each with a wick structure attached to an inner surface thereof are firstly provided. Each of the tubes is flat in cross section and U-shaped in profile. Each tube includes a first section used for forming the evaporating section  362  of the heat pipe  36  and a second section used for forming the condensing section  364  of the heat pipe  36 . One end of each of the tubes is open and the other end of each of the tubes is sealed. Secondly, the tubes are placed into a mold which is applied for forming the substrate  32  and the fins  34 . Thirdly, a molten metal is injected into the mold to simultaneously form the substrate  32  and the fins  34  wherein the first sections of the tubes are integrally embedded in the substrate  32  and the second sections of the tubes integrally extend through the fins  34 . Two ends of each of the tubes protrude laterally outside from the substrate  32 . Then, a working fluid is filled into the tubes via the open ends of the tubes, and finally the open ends of the tubes are sealed, to thereby form the heat pipes  36  and the thermal module  300 . 
         [0023]    It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function 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.