Patent Publication Number: US-2010126701-A1

Title: Plate-type heat pipe and method for manufacturing the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to plate-type heat pipes and, more particularly, to a plate-type heat pipe with enhanced heat dissipation efficiency. The plate-type heat pipe has a wick structure therein; the wick structure has a cross-section with a varied thickness. 
     2. Description of Related Art 
     Generally, plate-type heat pipes efficiently dissipate heat from components such as central processing units (CPU). Referring to  FIGS. 7-8 , a conventional plate-type heat pipe comprises a top plate  100 , a base plate  101  engaging the top plate  100 , and a wick structure  102  of uniform thickness mounted on the base plate  101 . A heat absorbing portion  103  extends downwardly from a center portion of the base plate  101 , contacting the heat-generating components. When heat from a component enters the plate-type heat pipe via its heat absorbing portion  103 , working fluid in the wick structure  102  absorbs the heat and vaporizes. If the wick structure  102  is too thick, the vapor remains therein, increasing heat resistance of the heat pipe and raising a temperature of the base plate  101 , possibly inflicting damage thereon. If the wick structure  102  is too thin, the working fluid vaporizes too quickly, damaging the wick structure  102 . 
     It is therefore desirable to provide a plate-type heat pipe which has a wick structure of optimum thickness to engage the plate-type heat pipe. 
    
    
     
       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 several views. 
         FIG. 1  is a cross-section showing a plate-type heat pipe formed in a mold in accordance with a first embodiment of the disclosure. 
         FIG. 2  is a cross-section of the plate-type heat pipe of  FIG. 1 . 
         FIG. 3  is a cross-section showing a plate-type heat pipe formed in a mold in accordance with a second embodiment of the disclosure. 
         FIG. 4  is a cross-section of the plate-type heat pipe of  FIG. 3 . 
         FIG. 5  is a cross-section showing a plate-type heat pipe formed in a mold in accordance with a third embodiment of the disclosure. 
         FIG. 6  is a cross-section of the plate-type heat pipe of  FIG. 5 . 
         FIG. 7  is an exploded, cross-section of a related plate-type heat pipe. 
         FIG. 8  is an assembled view of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-2 , a method for manufacturing a plate-type heat pipe  10  in accordance with a first embodiment of the disclosure is detailed as follows. 
     A bowl-shaped base plate  11  and a covering plate  13  are provided. The base plate  11  comprises a central heat absorbing plate  112 , a pair of extending plates  114  angling upwardly from opposite ends of the heat absorbing plate  112 , two engaging plates  116  extending outwardly from ends of the extending plates  114  respectively and facing apart, and two sidewalls  118  extending upwardly from ends of the engaging plates  116 . 
     A mold  15  is provided. The mold  15  comprises a first mold  151  and a second mold  153 . The first mold  151  encloses the base plate  11  therein. The first mold  151  and the base plate  11  define a first cavity  152  therebetween. The second mold  153  encloses the covering plate  13  therein. The second mold  153  and the covering plate  13  define a second cavity  154  therebetween. A cross-section of the second cavity  154  is rectangular. The first cavity  152  comprises a first receiving portion  1522  corresponding to a central portion of the heat absorbing plate  112  of the base plate  11 , two second receiving portions  1524  angling outwardly from opposite ends of the first receiving portion  1522  and corresponding to lateral portions of the heat absorbing plate  112  and the extending plates  114  of the base plate  11 , and two third receiving portions  1526  extending outwardly from ends of the second receiving portions  1524  and corresponding to the engaging plates  116  of the base plate  11 . The first, second and third receiving portions,  1522 ,  1524 ,  1526  connect and communicate with each other in series. A cross-section of the first receiving portion  1522  is rectangular. A cross-section of the second receiving portion  1524  is pentagonal. The third receiving portion  1526  comprises a first connecting portion  1526   a  angling outwardly from an end of the second receiving portion  1524  and a second connecting portion  1526   b  extending outwardly from an end of the first connecting portion  1526   a . A cross-section of the first connecting portion  1526   a  of the third receiving portion  1526  is trapezoidal. A cross-section of the second connecting portion  1526   b  of the third receiving portion  1526  is rectangular. The second receiving portion  1524  of the first cavity  152  is deeper than the first receiving portion  1522 . Depth of the second receiving portion  1524  first increases and then decreases along a laterally outwardly direction. The third receiving portion  1526  is deeper than the second receiving portion  1524  of the first cavity  152 . Depth of the first connecting portion  1526   a  of the third receiving portion  1526  of the first cavity  152  increases from an inner end connected with the second receiving portion  1524  to an outer end opposite to the inner end. An inner end of the second connecting portion  1526   b  is of the same depth as the outer end of the first connecting portion  1526   a.    
     A first metal powder is filled into the first cavity  152  and a second metal powder is filled into the second cavity  154 . The first and second metal powder are copper powder. Particle size of the first metal powder is less than that of the second metal powder. The first metal powder filled in the first cavity  152  and the second metal powder filled in the second cavity  154  are heated to a high temperature, sufficient to execute sintering, to obtain a sintered first wick structure  16  securely fixed to a top surface of the base plate  11  and a sintered second wick structure  17  securely fixed to a bottom surface of the covering plate  13 . The first wick structure  16  and the second wick structure  17  are porous, with apertures of the first wick structure  16  fewer than those of the second wick structure  17 . The first wick structure  16  comprises a first adhering portion  161  securely fixed to a top surface of the central portion of the heat absorbing plate  112  of the base plate  11 , two second adhering portions  163  securely fixed to top surfaces of the lateral portions of the heat absorbing plate  112  and the extending plates  114  of the base plate  11 , and two third adhering portion  165  securely fixed to top surfaces of the engaging plates  116  of the base  11 . The third adhering portion  165  receives a first joining portion  1651  in the first connecting portion  1526   a  and a second joining portion  1653  in the second connecting portion  1526   b  of the third receiving portion  1526  of the first cavity  152 . A top surface of the second adhering portion  163  and a top surface of the first joining portion  1651  of the third adhering portion  165  of the first wick structure  16  are coplanar. 
     The first mold  151  and the second mold  153  of the mold  15  are removed from the first and second wick structures  16 ,  17  respectively. The base plate  11  with the first wick structure  16  attached thereto and the covering plate  13  with the second wick structure  17  attached thereto are assembled together. A chamber  18  is defined between the first and second wick structures  16 ,  17  and the chamber  18  is vacuumed and filled with a working fluid (not shown) such as water, alcohol, methanol, or the like, and sealed. The disclosed plate-type heat pipe  10  is thus obtained. In this state, opposite ends of the second wick structure  17  and the second joining portions  1653  of the third adhering portions  165  of the first wick structure  16  are combined. 
     In this embodiment, a cross-section of the first adhering portion  161  of the first wick structure  16  is rectangular. A cross-section of the second adhering portion  163  of the first wick structure  16  is pentagonal. A cross-section of the first joining portion  1651  of the third adhering portion  165  of the first wick structure  16  is trapezoidal. A cross-section of the second joining portion  1653  of the third adhering portion  165  of the first wick structure  16  is rectangular. A cross-section of the second wick structure  17  is rectangular. The first adhering portion  161  of the first wick structure  16  is thinner than the second wick structure  17 . Work fluid contained in the first adhering portion  161  of the first wick structure  16  absorbs heat and is vaporized quickly to generate vapor. The vapor then reaches the second wick structure  17 . The second adhering portion  163  of the first wick structure  16  is thicker than the first adhering portion and thins from a central portion to distal ends thereof. Third adhering portion  165  thickens from an inner end connected with the second adhering portion  163  to an outer end opposite to the inner end. The second and third adhering portions  163 ,  165  collect condensate work fluid from the second wick structure  17 . When generated heat enters the plate-type heat pipe  10  via heat absorbing portion  112 , the work fluid contained in the first adhering portion  161  of the first wick structure  16  absorbs the heat and vaporizes, and the working fluid contained in the second and third adhering portions  163 ,  165  of the first wick structure  16  flows to the first adhering portion  161 . 
     Referring to  FIGS. 3-4 , a plate-type heat pipe  20  is manufactured using the method previously described, differing only in that configuration of the first connecting portion  2526   a  of the first cavity  252  is different from that of the first connecting portion  1526   a  of the first cavity  152  of the first embodiment. The first connecting portion  2526   a  is shallower than the first connecting portion  1526   a  of the first embodiment. A joint of the first connecting portion  2526   a  and the second receiving portion  2524  defines a hollow protruding portion  2517  thereof. The protruding portion  2517  angles upwardly from the joint of the first joining  2526   a  and the second receiving portion  2524 . The first joining portion  2651  of first wick structure  26  is thinner than the first joining portion  1651  of the first wick structure  16  of the first embodiment. A step is formed at a joint of the first joining portion  2651  and the second adhering portion  263 . 
     Referring to  FIGS. 5-6 , a plate-type heat pipe  30  is manufactured using the method previously described, differing only in that configuration of the first connecting portion  3526   a  of the first cavity  352  is different from that of the first connecting portion  1526   a  of the first cavity  152  of the first embodiment. A cross-section of an outer end of the first connecting portion  3526   a  is rectangular. The outer end of the first connecting portion  3526   a  is shallower than an outer end of the first connecting portion  1526   a . Thus, a cross-section of an outer end of a first joining portion  3651  of the first wick structure  36  is rectangular. The outer end of the first joining portion  3651  is thinner than the first joining portion  1651  of the first embodiment. A chamber  38  of the plate-type heat pipe  30  is larger than the chamber  18  of the plate-type heat pipe  10  of the first embodiment. Therefore, the vaporized work fluid contained in the chamber  38  is cooled quickly and the heat dissipation efficiency of the plate-type heat pipe  30  is enhanced. 
     It is believed that the disclosed embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.