Patent Publication Number: US-2010116467-A1

Title: Heat dissipation device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat dissipation device incorporating heat pipes and fins, and more particularly to a combination structure of the fins which is used for combining the fins and the heat pipes together. 
     2. Description of Related Art 
     Computer electronic components, such as central processing units (CPUs), generate large amounts of heat during normal operation. If the heat is not properly dissipated, it can adversely affect operational stability of the electronic components and damage associated electronic devices. A heat dissipation device is often attached to a top surface of a CPU to dissipate heat therefrom. 
     Conventionally, a heat dissipation device as shown in  FIG. 3  includes a plurality of fins  90  stacked together. A plurality of holes  91  and collars  92  extending from edges of the holes  91  are formed by punching (or other means) of the fins  90 . Heat pipes (not shown) extend through the holes  91 , with a part of outer surfaces of the heat pipes attached to the collars  92 . Solder (not shown) is filled in gaps existed between the collars  92  and the heat pipes to secure the heat pipes in the holes  91  and increase heat transfer efficiency from the heat pipes to the fins  90 . A distance, which is indicated by P 1 , is defined between every two adjacent fins  90 , functioning as a channel for air flowing therethrough. 
     Due to a limited ductility of the fins  90  which are made of metallic material, a height of the collars  92 , which is indicated by H 1  in  FIG. 3 , cannot be as high as the distance P 1 , since such a large height may result in a break of the collars  92 . Therefore, a bottom of each collar  92  is spaced from an adjacent fin  90 . The collars  92  such configured cannot retain enough solder therein, which causes the solder to flow from bottoms of the collars  92  onto an adjacent fin during the solder being filled in the gaps between the collars  92  and the heat pipes. The overflowed solder is not only a waste of material, but also a negative impact to an aesthetic appearance of the heat dissipation device. 
     What is needed, therefore, is an improved heat dissipation device which can overcome the described limitations. 
     SUMMARY OF THE INVENTION 
     A heat dissipation device includes a plurality of fins stacked together, a plurality of heat pipes extending through the fins, and solder filled in gaps between the fins and the heat pipes. Each fin includes a horizontal, flat plate defining a plurality of holes therein for extension of the heat pipes therethrough, respectively. A collar extends from a periphery of each of the holes. The collar includes a columned portion attached to an outer surface of the heat pipe, and a taper portion interconnecting the plate and the columned portion. A height of the collar approaches to a distance between two adjacent fins. The taper portion has an inner surface facing towards the heat pipe. A portion of the solder is retained in a space between the inner surface of the taper portion of the collar and the heat pipe to prevent the portion of the solder from overflowing to the horizontal, flat plate of the fin. 
     Other advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present apparatus 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 apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an assembled, isometric view of a heat dissipation device in accordance with a preferred embodiment of the disclosure. 
         FIG. 2  is a cross-sectional view of the heat dissipation device of  FIG. 1 , taken along line II-II thereof. 
         FIG. 3  is a side elevation view of a related heat dissipation device, with heat pipes thereof being removed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-2 , a heat dissipation device in accordance with a preferred embodiment of the disclosure comprises a plurality of fins  10  stacked together, and a plurality of heat pipes  20  extending through the fins  10 . Bottom ends of the heat pipes  20  are used to connect with a base (not shown) which is attached to a heat generating component (not shown), such as a CPU. Heat generated by the heat generating component is transferred by the heat pipes  20  to the fins  10  and dissipated by the fins  10  to ambient air. 
     Each fin  10  has a rectangular thin plate  11  and two flanges  12  bent downwardly from two long sides of the plate  11 . The thin plate  11  is horizontal and flat. A channel  13  is defined between every two adjacent fins  10  by the flanges  12 . The channel  13  has a height which is indicated by P in  FIG. 2 . A plurality of round holes  19  (six in this embodiment) is defined in each plate  11 . A collar  16  extends from a periphery of each hole  19 . The collar  16  has a funnel-like shape. The collar  16  comprises a columned portion  14  and a taper portion  15  interconnecting the plate  11  and the columned portion  14 . The columned portion  14  is cylindrical. The taper portion  15  is substantially a truncated cone with a small bottom thereof connecting a top of the columned portion  14 , and a big top thereof connecting the plate  11 . The collar  16  has a height in an axial direction of the hole  19  (i.e., an axial direction of the heat pipes  20 ) which is indicated by H. The height H of the collar  16  approaches to the height P of the channel  13 . That is, a distance between a bottom of the columned portion  14  and an adjacent underlying fin  10  along the axial direction of the hole  19  is very small. A height of the columned portion  14  is substantially equal to that of the taper portion  15 . 
     Each heat pipe  20  has a round cross section. The heat pipe  20  has wick structures (not shown) formed in an inner surface thereof and working fluid (not shown) contained therein. 
     In assembly, the fins  10  are stacked together. The flanges  12  of each fin  10  abut against a lower, adjacent fin  10 . Solder  30  is spread on inner surfaces of the columned portions  14  of the collars  16  of the fins  10 . The heat pipes  20  are then inserted into the holes  19  of the fins  10 . By the provision of the taper portions  15  which are located very close to the bottoms of the columned portions  14  of the corresponding upper collars  16 , excessive solder  30  which is pushed out of the columned portions  14  is immediately received in the taper portions  15 , thereby eliminating the possibility that the excessive solder  30  will drop on the flat plates  11 . Then, the fins  10  together with the heat pipes  20  are put into an oven to be heated. The solder  30  on the heat pipes  20  and located corresponding to the columned portions  14  of the collars  16  is heated to flow. The flowed solder  30  evenly fills in gaps between the inner surfaces of the columned portions  14  of the collars  16  and the heat pipes  20 . After cooled, the solidified solder  30  thermally and mechanically connects the heat pipes  20  and the columned portions  14  of the collars  16  together. The solder  30  on the heat pipes  20  and located between the columned portions  14  is heated to flow downwardly into spaces between inner surfaces of the taper portions  15  of the collars  16  and the heat pipes  20  as shown in  FIG. 2 . After cooled, the solidified solder  30  thermally and mechanically connects the taper portions  15  of the collars  16  and the heat pipes  20  together whereby the thermal and mechanical connections between the fins  10  and the heat pipes  20  are reinforced. In the present invention, by the provision of the taper portions  15  and the design that the bottom of the columned portion  14  is very close to a corresponding lower taper portion  15 , the solder  30  will not drop or flow to the horizontal, flat plate  11  to unfavorably affect an aesthetic appearance of the heat dissipation device. 
     The formation of the taper portions  15  results in an increasing of a total height H of the collars  16  along the axial direction of the heat pipes  20 . That is, the distance between bottoms of the columned portions  14  and the adjacent underlying fin  10  is decreased, which could prevent the solder  30  from spraying onto the horizontal, flat plate  11  of the adjacent underlying fin  10 . Furthermore, the taper portions  15  connect to the outer surfaces of the heat pipes  20  by the solder  30  retained in the spaces therebetween. Therefore, a contact surface between the fins  10  and the heat pipes  20  is increased, which is an advantage of enhancing the heat dissipation efficiency of the heat dissipation device. 
     The heat pipes  20  are round in this embodiment, and the collars  16  form corresponding columned portions  14  to contact with the heat pipes  20 . It is to be understood that the shape of the heat pipes  20  and the collars  16  could be potentially varied, as long as the collars  16  comprise a contacting portion attached to the heat pipes  20  and an intermediate portion interconnecting with the plate  11  and the contacting portion, wherein a cross section of the intermediate portion has a size larger than that of the contacting portion. In an alternative embodiment, the solder  30  can be replaced by thermally conductive glue. When the thermally conductive glue is used, the step of heating the fins and the heat pipes in the oven can be omitted. 
     It is believed that the present invention and its 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 invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.