Abstract:
The heat dissipating structure mainly includes a heat dissipating base, one or several heat dissipating fins, and a fixing frame. It can improve the ratio of fin&#39;s height to width, to increase the effective heat transfer area, and to promote the cooling capacity, especially for electronic elements. About the manufacturing method, it includes three steps: machining, inserting and injecting. So, the manufacturing method is simple and the required machines are general.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat dissipating structure and its manufacturing method. In accordance with the present invention, the heat transfer capacity of the heat dissipating structure is increased. 
     2. Description of the Prior Art 
     Referring to FIG. 1, there is shown a conventional heat dissipating structure made of extruded aluminum. It includes a heat dissipating base  11  and a plurality of heat dissipating fins  12  extending upwardly therefrom. The heat dissipating base  11  and these heat dissipating fins  12  are integrally formed. However, because of limitations inherent to the extruded aluminum mold, the ratio of the fin&#39;s height to width cannot be too large. Each fin cannot be very thin; and, the fins&#39; distribution is quite limited. Therefore, some designs of fins cannot be realized. Given the development of electronic elements with high working rates, a new technology is needed to overcome the disadvantages of the conventional heat dissipating fins made of extruded aluminum. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a heat dissipating structure having increased heat transfer capacity. Particularly, an object is to improve the ratio of the fin&#39;s height to width, so as to increase the effective heat transfer area, and enhance the cooling capacity. 
     The other object of the present invention is to provide a manufacturing method for the heat dissipating structure that is simple and may be carried out without special machines. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a conventional structure having heat dissipating fins made of extruded aluminum; 
     FIGS. 2A and 2B respectively show a perspective view of the present invention and an enlarged view of a selected portion thereof; 
     FIGS. 3A and 3B respectively show a side view of the heat dissipating fins and an enlarged view of a selected portion thereof; 
     FIGS. 4A and 4B respectively show a front view of a heat dissipating fin and an enlarged view of a selected portion thereof; 
     FIGS. 5A and 5B respectively show a front view of another type of a heat dissipating fin and an enlarged view of a selected portion thereof; 
     FIGS. 6A,  6 B, and  6 C respectively show a perspective view of a second preferred embodiment and two enlarged views of two selected portions thereof; 
     FIGS. 7A and 7B respectively show a side view of the second preferred embodiment and an enlarged view of a selected portion thereof; and, 
     FIG. 8 is a flow chart showing steps of a manufacturing procedure in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 2A,  2 B,  3 A, and  3 B, there is shown a first preferred embodiment of the present invention. The heat dissipating structure generally comprises a heat dissipating base  21 , a plurality of heat dissipating fins  22 , and a fixing frame  23 . 
     The heat dissipating base  21  and the heat dissipating fins  22  are not integrally formed. The heat dissipating base  21  has an upper surface. The upper surface has several substantially parallel slots  211 . Each slot  211  has a width D slightly less than a thickness H of an inserting portion  224  of the heat dissipating fin  22 , so that it will allow a heat dissipating fin  22  to tightly insert therein. This then increases the heat transfer capacity of the heat dissipating structure—that is, to improve the ratio of the fin&#39;s height to width, to increase the effective heat transfer area, and to enhance the structure&#39;s cooling capacity. 
     The heat dissipating fins  22  are plural plate-like structures, and the bottom portions of these heat dissipating fins  22  are defined as the inserting portions  224 . 
     To accommodate the fixing frame  23 , fixing recesses  212  are disposed near peripheral edges of the upper surface of the heat dissipating base  21 . The fixing frame  23  is used for securing said heat dissipating fins  22  on the heat dissipating base  21 . The fixing frame  23  is formed by initially introducing a melt fixing material inside the fixing recesses  212  and thereafter cooling. As the material forms as a solid, it forms the fixing frame  23  that secures the heat dissipating fins  22  on the heat dissipating base  21 . 
     Furthermore, as shown in FIGS. 4A,  4 B,  5 A, and  5 B, two protruded flanges  221  are respectively disposed on opposing sides of each heat dissipating fin  22 . Each protruded portion  221  is formed with a fixing hole  222  or a notch  223  for enhancing the contacting area and reinforcing the coupling between the heat dissipating base  21  and the heat dissipating fins  22 . That is, the melt fixing material can flow through these fixing holes  222  or notches  223 . When the melt fixing material is cooled and formed as a solid, it becomes the solid fixing frame  23  which can firmly secure the heat dissipating fins  22  to the heat dissipating base  21 . This prevents loose fins from causing poor heat transfer capacity. 
     Because the thickness of the heat dissipating base  21  cannot be overly thick, the depth of the slots  211  cannot be overly deep. If the height of the heat dissipating fin  22  is too great, the inserted heat dissipating fins  22  will become loose due to vibration or some external force. Thus, the resulting contact between parts may become poor. Consequently, a reduction in heat transfer capacity may result. 
     The fixing frame  23  is useful in overcoming this problem. The melt fixing material will cover the protruded portions  221  of the heat dissipating fins  22 . Once it cools and solidifies to form the fixing frame  23 , the coupling of the fins  22  to the base  21  is reinforced. This improves the ratio of the fin&#39;s height to width, so as to increase the effective heat transfer area, and to enhance the cooling capacity. 
     Referring to FIGS. 6A,  6 B,  6 C,  7 A, and  7 B, a second preferred embodiment of the present invention is shown. In this example, the heat dissipating fins  22  form a single wave-like plate structure and their bottom portions define inserting portions  224 . These inserting portions  224  firmly insert into the corresponding slots  211  of the heat dissipating base  21 . Because other elements are effectively the same as those shown in the first preferred embodiment, further description of those elements is omitted. As shown in FIG. 8, the manufacturing method for the present invention comprises the following steps: 
     (1) Machining  31 : A plurality of slots  211  are cut on an upper surface of the heat dissipating base  21 ; a fixing recess  212  is cut near a peripheral edge of the upper surface of the heat dissipating base  21 ; and, the heat dissipating fin and formed, then tightly inserted into the corresponding slots  211 . 
     (2) Inserting  32 : The heat dissipating fin(s)  22  are forced into tight insert within the corresponding slots  211  of the heat dissipating base  21 . 
     (3) Injecting  33 : A melt fixing material is injected inside the fixing recesses  212  and then cooled until it forms a solid. This results in the fixing frame  23  that secures said heat dissipating fin(s)  22  on said heat dissipating base  21 . 
     Practically, if the fixing material is a plastic material, the above steps can be simplified and completed by these three kinds of machines: a computer/numerical controlled machine (like CNC machine), a pressing machine, and a plastic injection machine with corresponding molds. In order to increase the overall heat transfer capacity, the fixing material may be a heat-conductible plastic, or any other metal or non-metal material with higher heat conductibility. Also, the heat dissipating base  21  and heat dissipating fins  22  may be made of copper (Cu), aluminum (Al), copper alloy, aluminum alloy, or the like. 
     The following Table, Table 1, shows the testing results after testing three samples on a computer&#39;s central processing unit (CPU). The area of the CPU for test purposes was 10*12 mm 2 , and the actual energy consumption of the CPU was 18.24 W. The fan&#39;s size was 50*50 mm 2 . The fan&#39;s flowing rate was 12 cfm, and its static pressure was 3.8 mmH 2 O. The temperature of the environment was 45° C. The heat resistance value is defined as the heat resistance between the internal temperature of the CPU and the point above the CPU 30 mm in the air. 
     
       
         
               
               
               
               
             
           
               
                   
               
               
                   
                 Conventional 
                 The present 
                 The present 
               
               
                   
                 structure made by 
                 invention 
                 invention 
               
               
                 Type 
                 Extruded 
                 made by 
                 made by 
               
               
                 Specification 
                 Aluminum 
                 copper (Cu) 
                 aluminum (Al) 
               
               
                   
               
             
             
               
                 Base dimensions 
                 L61*W51*H5 
                 L50*W52*H5 
                 L50*W52*50 
               
               
                 (mm) 
               
               
                 Fin dimensions 
                 L51*WO.86*H25 
                 L44*W1*H50 
                 L44*WO.3*H50 
               
               
                 (mm) 
               
               
                 Fin number 
                 19 
                 21 
                 30 
               
               
                 Fin interval (mm) 
                 2.45 
                 1.25 
                 1.276 
               
               
                 Ration of fin&#39;s 
                 29 
                 50 
                 166.67 
               
               
                 height to width 
               
               
                 Total area of fins 
                 46943 
                 95424 
                 113296 
               
               
                 (mm) 
               
               
                 Fan position 
                 blowing upward 
                 side blowing 
                 side blowing 
               
               
                 CPU&#39;s max. 
                 87.84 
                 76.28 
                 72.54 
               
               
                 temperature (° C.) 
               
               
                 Analytical Heat 
                 1.26 
                 0.92 
                 0.81 
               
               
                 Resistance 
               
               
                 (° C./W) 
               
               
                 Experimental 
                 1.28 
                 1.01 
                 0.90 
               
               
                 Heat Resistance 
               
               
                 (° C./W) 
               
               
                   
               
             
          
         
       
     
     From the results shown in Table 1, it is clearly apparent that the performance of the present invention is better than that of a conventional extruded aluminum structure. 
     Thus, an improvement in the ratio of the fin&#39;s height to width is realized. An increase in the effective heat transfer area, and an enhancement in the cooling capacity for electronic elements are also realized.