Patent Publication Number: US-2007102147-A1

Title: Heat dissipation apparatus and method for manufacturing the same

Description:
DESCRIPTION  
      1. Technical Field  
      The present invention relates generally to heat dissipation apparatuses and, more particularly, to a heat dissipation apparatus having improved heat dissipation efficiency used in an electronic device and a method for manufacturing the heat dissipation apparatus.  
      2. Discussion of Related Art  
      With the development of electronic science, operational frequencies of electronic components such as CPUs have become higher and higher, and as a result more energy is consumed and more heat is generated. As a result, it has become necessary to use a powerful heat dissipation device to dissipate the heat generated by the electronic components.  
      A typical heat dissipation apparatus generally includes a base and a number of cooling fins attached to the base. The base and the cooling fins can be made of a metal having high heat conductivity. Such metal can be, for example, copper, aluminium, etc. Advantageously, the base is made of a highly heat-conductive material such as copper, and the cooling fins are made of aluminium which can be easily processed to form a variety of shapes.  
      Such devices are usually disposed on a heat source for dissipating heat generated by the heat source through a combination of heat conduction and convection. Firstly, heat generated by the heat source is conducted to the atmosphere at a surface of the device by conduction; secondly, the heat dissipates into atmosphere by convection.  
      However the highly heat-resistant interfaces between the base and the cooling fins make the heat resistance of the heat dissipation apparatus relatively high, and heat dissipation efficiency of the heat dissipation device is therefore unsatisfactory.  
      Thus, there is a desire to develop a heat dissipation apparatus that has a low heat resistance between the base and the cooling fins, so as to improve the heat dissipation efficiency.  
     SUMMARY  
      In one embodiment, a heat dissipation apparatus includes a base member and a number of cooling fins. Each of the cooling fins includes a main part and a foot part embedded in the base member, the foot part includes a first portion extending from the main part in the extension direction of the main part (i.e., forming a continuation of the main body) and at least one second portion extending at an angle from the first portion.  
      In one embodiment, a method for manufacturing a heat dissipation apparatus, the method comprising the steps of: providing a base member and a plurality of cooling fins each having a main part and a foot part, the foot part including a first portion extending from the main part in the extension direction of the main part and a second portion extending at an angle from the first portion; defining a number of grooves on the base member in a manner so as conform to a shape of the foot parts of the cooling fins; and pressing the foot parts of the cooling fins into the corresponding grooves at a high temperature and a high pressure.  
      This and other features and advantages of the present invention as well as the preferred embodiments thereof and a heat dissipation apparatus and techniques for fabricating heat dissipation apparatus in accordance with the invention will become apparent from the following detailed description and the descriptions of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the present apparatus and method 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 and method. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views  
       FIG. 1  is a schematic, cross sectional schematic view of a heat dissipation apparatus in accordance with a first preferred embodiment;  
       FIG. 2  is a schematic, cross sectional view of the heat dissipation apparatus disposed on a heat source;  
       FIG. 3  is a schematic, cross sectional view of a heat dissipation apparatus in accordance with a second preferred embodiment;  
       FIG. 4  is a schematic, cross sectional view of a heat dissipation apparatus in accordance with a third preferred embodiment;  
       FIG. 5  is a schematic, cross sectional view of a heat dissipation apparatus in accordance with a fourth preferred embodiment;  
       FIG. 6  is a flow chart of a method for manufacturing a heat dissipation apparatus in accordance with another preferred embodiment; and  
       FIG. 7  is a schematic, cross sectional view of a base member for manufacturing the heat dissipation apparatus. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Referring now to  FIG. 1 , a heat dissipation apparatus  10  in accordance with the first preferred embodiment includes a base member  12  and a number of cooling fins  14 . Each of the cooling fins  14  includes a main part  141  and a foot part  142  embedded in the base member  12  by using a process such as, for example, hot pressing and metallurgical means. such as, for example, placing the cooling fins  14  in liquid metal and then cooling the liquid to form the base member  12  with the cooling fins  14  embedded therein. Each foot part  142  includes a first portion  143  and a second portion  144 . The first portion  143  extends straightly from the main part  141  along a longitudinal extension direction of the main part  141 . The second portion  144  extends at an angle from the first portion  143 . Thus, the first portion  143  and the second portion  144  form an obtuse angle to each other. The base member  12  and the cooling fins  14  are made of a metal or an alloy having high heat conductivity, such as copper, aluminium or copper-aluminium alloy.  
      Referring to  FIG. 2 , the heat dissipation apparatus  10  can be used for dissipating heat from a heat source  16 . The heat source  16  is an electronic component such as a microprocessor. When the heat dissipation apparatus  10  is disposed on the heat source  16 , heat generated in the heat source  16  is conducted to the main part  141  of the heat dissipation apparatus  10  through the foot part  142  and is dispersed into the ambient air. In the preferred embodiment, that the foot part  142  is inserted into the base member  12  using a process such as, for example, hot pressing, improves a contact area between the base member  12  and the foot part  142 , and heat resistance between the base member  12  and the foot part  142  is decreased as a result.  
      Referring to  FIG. 3 , a heat dissipation apparatus  20  in accordance with a second embodiment is similar to that of the first embodiment except that each foot part  242  is composed of a first portion  243  and a second portion  244  extending perpendicularly to the first portion  243  so as to form “L” shaped cooling fins.  
      Referring to  FIG. 4 , a heat dissipation apparatus  30  in accordance with a third embodiment is similar to that of the first embodiment except that each foot part  342  includes a first portion  343  and a second portion  344  perpendicular to the first portion  343 . The first portion  343  of each foot part  342  is connected to a center of the second portion  344  so as to form inverted “T” shaped cooling fins.  
      Referring to  FIG. 5 , the heat dissipation apparatus  40  in accordance with a fifth embodiment shown is similar to that of the second embodiment except that a base member  42  defines a vapor chamber  422  therein and a number of cooling fins  44  extending from the base member with a portion of each cooling fin being embedded in an upper portion of the base member  42  using a process such as, for example, hot pressing. The vapor chamber  422  contains a fluid  424  for facilitating heat conduction evenly from the base member  42  to the cooling fins  44 . The fluid  424  can be a low boiling point fluid such as alcohol, acetone and ammonia, a high boiling point fluid such as water or any combination thereof. In order to decrease the boiling point of the fluid  424 , the vapor chamber  422  should preferably be vacuumized to a pressure in the range from 10-3 Pa to 10-2 Pa.  
      In use, the base member  42  works as a heat pipe, i.e., the fluid  424  in the vapor chamber  422  is vaporized after absorbing heat generated from a heat source (not shown), the vapor flows from one end of the vapor chamber  422  to another end and discharges heat quickly. Thus, the heat is evenly transferred to the upper portion of the base member  42  and is conducted to the cooling fins  44  uniformly.  
      The heat dissipation apparatus in accordance with the aforementioned embodiments can be made by the following method. Take the heat dissipation apparatus  20  for example, referring to  FIG. 6  and  FIG. 7 , the method includes the steps of: 
          Step 1, providing a base member and a number of cooling fins each having a foot part  242  at an extremity thereof, wherein the foot part  242  includes a first portion  243  and a second portion  244  perpendicular to the first portion  242 ;     Step 2, defining a number of grooves on the base member in a manner so as conform to a shape of the foot part  242  of the cooling fins; and     Step 3, pressing the foot parts  242  of the cooling fins into the grooves  222  at a high temperature and a high pressure.        

      In step 1, each of the cooling fins includes a main part extending from the first portion of the foot part. The base member and the cooling fins are made of a material having high heat conductivity such as copper, aluminium, or copper-aluminium alloy.  
      In step 2, the grooves are configured for receiving the foot part  242 . In order to increase the contact area between the foot parts  242  and the base member, the grooves are shaped so as to tightly accommodate the foot parts  242 . Referring now to  FIG. 7 , each of the grooves  222  includes a first space  224  and a second space  226 . The first space  224  is used for receiving the first potion  243 . The second space  226  is used for receiving the second portion  244 . The grooves  222  can be made by cutting or electrostatic discharging process. A size of the grooves should be less than that of the foot part  242 , and preferably the size of the grooves should be approximately 0.2% to 5% less than that of the foot part  242 .  
      In step 3, the temperature can be in a range from 500 to 600 degrees Celsius. Preferably, the pressure should be in the range from 600 to 1200 kilo-Newtons/metre2. This step can be performed by stamping/pressing. That is, the cooling fins  54  can be stamped into the grooves from the side surface of the base member  52  using a stamper. At such a high temperature and under such a high pressure, the atoms on the surface of the cooling fins and the grooves mix across the gap between the cooling fins and the grooves thus form an copper-aluminium alloy layer between the base member and the cooling fins.  
      The heat dissipation apparatus  20  can also be manufactured by using a metallurgical means, such as, for example, melting a metal material of the base member to a liquid in a mold and then inserting the cooling fins into the liquid, cooling the liquid and the cooling fins thereby obtaining the heat dissipation apparatus  20 . Alternatively, a number of grooves are formed on the base member in a manner so as conform to a shape of the foot part  242  of the cooling fins, a mold is disposed on the base member, the mold and the grooves cooperatively define a number of chambers having the shape of the cooling fins, then a liquid of the metal material of the cooling fins is placed in the chambers, when the liquid is cooled the heat dissipation apparatus  20  is obtained.  
      Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the invention. Variations may be made to the embodiments without departing from the spirit of the invention as claimed. The above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention.