Patent Publication Number: US-2007095510-A1

Title: Heat-pipe type heat sink

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to a heat sink, and more particularly to a heat-pipe type heat sink for dissipating heat generated by electronic components.  
     DESCRIPTION OF RELATED ART  
      Referring to U.S. Pat. No. 6,435,266, a conventional heat-pipe type heat sink is shown. The heat sink includes a plurality of fins and a heat pipe extending through the fins. Each of the fins defines a larger hole, and a smaller hole above the larger hole. The smaller hole partially connects with the larger hole at a bottom end thereof. Two projections are formed at the joint of the smaller and the larger holes and extend towards each other, thereby forming a neck portion at that joint.  
      In assembly of the heat sink, the heat pipe extends through the larger holes of the fins, while a solder stick extends through the smaller holes of the fins. The solder stick is heated to a melting point so that the molten solder flows into the larger holes and fills in clearances formed between the heat pipe and the fins. The molten solder is cooled so as to firmly bond the heat pipe to the fins to complete the assembly of the heat sink.  
      In the assembly of the heat sink, a part of the molten solder sticks to the projections of the neck portions of the fins, when the molten solder flows towards the larger holes. When that part of the molten solder is cooled, a plurality of solder beads is formed at the projections of the neck portions of the fins. These solder beads do not have any help regarding the thermal connection of the heat pipe and the fins. Furthermore, they adversely affect the aesthetic appearance of the heat sink. The projections hinder the molten solder from smoothly and fully flowing into the larger holes. This results in a possible incomplete connection between the heat pipe and the fins. Thus, an improvement is required to overcome the defects of the prior art.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a heat-pipe type heat sink for dissipating heat generated by electronic components. According to a preferred embodiment of the present invention, the heat-pipe type heat sink includes a plurality of fins each defining at least a through hole therein, at least a heat pipe extending through the through holes of the fins, and soldering material filled in spaces formed between the heat pipe and the fins. Sidewall of the through hole forms a first fringe contacting with the heat pipe, and a second fringe smoothly connecting with the first fringe. The second fringe includes two guide portions, which are capable of guiding the molten soldering material flowing towards the first fringe to fill in the spaces to bond the heat pipe to the fins after the molten soldering material is cooled. The through hole has a shape of a teardrop. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the present invention 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 invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is an exploded, isometric view of a heat-pipe type heat sink according to a preferred embodiment of the present invention;  
       FIG. 2  is an assembled view of the heat-pipe type heat sink of  FIG. 1 ;  
       FIG. 3  is a cross sectional view of the heat-pipe type heat sink of  FIG. 2 , taken along line III-III thereof; and  
       FIG. 4  is an isometric view of a fin of the heat-pipe type heat sink of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring to  FIGS. 1 through 3 , a heat-pipe type heat sink  10  according to a preferred embodiment of the present invention is shown. The heat-pipe type heat sink  10  includes a base  12 , a fin assembly  14  disposed on the base  12 , and three heat pipes  16  extending through the fin assembly  14 . Each of the heat pipes  16  includes a linear-shaped evaporator section  162 , a condenser section  161  parallel to the evaporator section  162 , and an arc-shaped adiabatic section  163  integrally connected with the evaporator and condenser sections  162 ,  161 . The evaporator and condenser sections  162 ,  161  of the heat pipe  16  respectively contact with a heat-generating electronic component  18  and the fin assembly  14  for transferring heat therebetween.  
      The fin assembly  14  includes a plurality of parallel fins  140 , and is divided into three portions, i.e. a first portion  14   a , a second portion  14   b , and a third portion  14   c . Each fin  140  of the first portion  14   a  of the fin assembly  14  includes a rectangular-shaped main body  141 , and four flanges  142  extending backwardly from upper and bottom sides of the main body  141 . The fins  140  of the first portion  14   a  of the fin assembly  14  are stacked together with the flanges  142  of a front fin  140  abutting against the main body  141  of a rear fin  140 . Each fin  140  of the second and third portions  14   b ,  14   c  of the fin assembly  14  includes a rectangular-shaped main body  141 , and two flanges  142  extending forwardly from upper and bottom sides of the main body  141 . The fins  140  of the second and third portions  14   b ,  14   c  of the fin assembly  14  are stacked together with the flanges  142  of a rear fin  140  abutting against the main body  141  of a front fin  140 . A plurality of air passages are formed between two adjacent fins  140 , allowing the airflow to pass therethrough. The main body  141  of each fin  140  of the first portion  14   a  of the fin assembly  14  defines three through holes  143  therein, allowing the condenser sections  161  of the heat pipes  16  extending therethrough. Three collars  144  extend forwardly from peripheries of the through holes  143 , contacting with the condenser sections  161  of the heat pipes  16 . The main body  141  of each fin  140  of the second portion  14   b  of the fin assembly  14  defines three U-shaped slots  148  in a bottom thereof, for allowing the adiabatic sections  163  of the heat pipes  16  extending therethrough. A bottom portion of the base  12  defines three parallel grooves  121  therein, for receiving the evaporator sections  162  of the heat pipes  16  therein. The heat-generating electronic component  18  is mounted to the bottom surface of the base  12  and directly contacting with the evaporator sections  162  of the heat pipes  16 . Alternatively, there may be a heat absorbing plate sandwiched between the evaporator sections  162  of the heat pipes  16  and the heat-generating electronic component  18  to transfer heat therebetween.  
      Particularly referring to  FIG. 4 , each through hole  143  has a general shape of a teardrop. The collar  144  of each through hole  143  includes an arcuate first inner fringe  145  mated with the condenser section  161  of the heat pipe  16 , and a V-shaped second inner fringe  146  above the first inner fringe  145 . Soldering material (not shown) such as solder paste, or solder bar is filled in a space enclosed by the second inner fringe  146 . The second inner fringe  146  includes two slantwise guiding portions  147  smoothly and linearly connected with top ends of the first inner fringe  145 . The distance between the guiding portions  147  of the second inner fringe  146  is gradually increased from a top portion of the collar  144  towards the top ends of the first inner fringe  145 . The collar  144  is substantially teardrop-shaped in profile and has no projection extending from its inner fringes  145 ,  146  inwardly. The guiding portions  147  of the second inner fringe  146  guide the molten soldering material entirely and smoothly from the top portion of the collar  144  towards the first inner fringe  145  to fill in a clearance between the condenser section  161  of the heat pipe  16  and the first inner fringe  145 .  
      In assembly of the heat-pipe type heat sink  10 , the fins  140  of the fin assembly  14  are stacked together. The evaporator, the condenser, and the adiabatic sections  162 ,  161 ,  163  of the heat pipes  16  are respectively received in the grooves  121  of the base  12 , the through holes  143  of the first portion  14   a  of the fin assembly  14 , and the slots  148  of the second portion  14   b  of the fin assembly  14 . The soldering material is disposed in the spaces enclosed by the guiding portions  147  of the second inner fringes  146  and above the condenser sections  161  of the heat pipes  16 . The heat-pipe type heat sink  10  is thus preassembled. The preassembled heat-pipe type heat sink  10  is heated to a melting point of the soldering material, so that the molten soldering material is guided by the guiding portions  147  of the second inner fringes  146  towards the first inner fringes  145  and fills in clearances formed between the first inner fringes  145  and the condenser sections  161  of the heat pipes  16 . The molten soldering material is cooled so as to firmly bond the condenser sections  161  of the heat pipes  16  to the first inner fringes  145  of the fin assembly  14 . The assembly of the heat sink  10  is thus completed.  
      In the present invention, the collar  144  is teardrop-shaped in profile and has no projection extending inwardly from its inner fringes  145 ,  146 . Such projection could form a barrier preventing the molten soldering material from smoothly and entirely flowing downwards and could have solder beads formed thereon, as explained in connection with the prior art. The present invention overcomes such problems. In addition, a part of the soldering material can spread on the collars  144  of the fins  140  of the first portion  14   a  of the fin assembly  14  and bond the condenser sections  161  of the heat pipes  16  thereat to the fins  140 , which increases contacting areas between the condenser sections  161  of the heat pipes  16  and the fins  140  of the first portion  14   a  of the fin assembly  14 , and further improves heat dissipation efficiency of the heat-pipe type heat sink  10 .  
      Particularly referring to  FIG. 4 , the guiding portions  147  of the second inner fringe  146  connect with each other at a top end of the collar  144  via an arcuate tip portion  149 . Alternatively, the tip portion  149  may not be arcuate, but is sharp.  
      In the preferred embodiment of the present invention, the second inner fringe  146  is disposed above the first inner fringe  145 . Alternatively, the second inner fringe may be disposed below the first inner fringe, or on the right or the left side of the first inner fringe. In the assembly of the heat sink with such configurations, during heating thereof, the heat-pipe type heat sink needs to be rotated to a position, where the molten soldering material can be guided by gravity and the guiding portions towards the first inner fringes and evenly distributed around the condenser sections of the heat pipes. The cross section of the condenser section of the heat pipe is round-shaped in this embodiment. Alternatively, the cross section of the condenser section of the heat pipe may have any other appropriate configuration, whilst the first fringe may have a corresponding configuration mated with the condenser section of the heat pipe.  
      It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, 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.