Abstract:
A method of making a heat sink ( 10 ) includes the following steps: providing a base ( 11 ) and a plurality of individual fins ( 13 ), and welding the fins successively to the base by ultrasonic welding method.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention generally relates to heat sinks, and more particularly to a method of making a heat sink used for dissipating heat from heat-generating components. 
         [0003]    2. Description of Related Art 
         [0004]    It is well known that heat is produced by electronic components such as integrated circuit chips during their normal operations. If the heat is not timely removed, these electronic components may overheat. Therefore, heat sinks are often used to cool these electronic components. 
         [0005]    Presently, a typical heat sink includes a base and a fin assembly attached to the base. The base thermally contacts with a heat generating electronic component. The fin assembly includes a plurality of fins joined together. The fin assembly is welded to the base via tin soldering method. However, solder and flux are required during soldering of the heat sink. Specially, when the base and the fin assembly are respectively made of different materials, such as copper and aluminum, an additional process for coating a nickel layer on welding surfaces of the base and the fin assembly is needed. Thus, the cost of the heat sink is increased and the process of making the heat sink is complicated. In addition, during the soldering process, tiny air bubbles will be formed between the fin assembly and the base, thereby increasing a heat resistance between the base and the fin assembly, which further decreases the heat dissipating efficiency of the heat sink. 
         [0006]    What is needed, therefore, is a new method of making a heat sink which can overcome the shortcomings of the prior art. 
       SUMMARY 
       [0007]    The present invention relates to a method of making a heat sink. According to a preferred embodiment of the present invention, the method of making the heat sink includes the following steps: providing a base and a plurality of individual fins, and welding the fins successively to the base by ultrasonic welding method. 
         [0008]    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 
         [0009]    Many aspects of the present 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 method. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0010]      FIG. 1  is an isometric view showing fins of a heat sink to be joined to a base of the heat sink by an ultrasonic welding process in accordance with a first embodiment of the present invention. 
           [0011]      FIG. 2  is an assembled, isometric view of the heat sink of  FIG. 1 . 
           [0012]      FIG. 3  is an isometric view showing fins of a heat sink to be jointed to a base of the heat sink by an ultrasonic welding process of a heat sink in accordance with a second embodiment of the present invention. 
           [0013]      FIG. 4  is an assembled, isometric view of the heat sink of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to  FIG. 1 , an ultrasonic welding process of a heat sink  10  in accordance with a first embodiment of the present invention is shown. Firstly, a base  11  and a plurality of individual fins  13  are provided. 
         [0015]    The base  11  has a rectangular shape. The base  11  is made of copper, which has good thermal conductivity. The base  11  has a contacting surface  111  at a top thereof. 
         [0016]    The fins  13  are made of aluminum, which has good thermal conductivity. Aluminum has a lower thermal conductivity than copper. Each fin  13  has a plate shape, and has a thickness in a range of 0.3˜0.4 mm. Each fin  13  includes a rectangular main body  133 , and a flange  134  extending vertically and outwardly from a bottom side of the main body  133 . 
         [0017]    During assembly of the heat sink  10 , the fins  13  are successively welded to the base  11  by ultrasonic welding method. Specifically, the flange  134  of each fin  13  is welded on the contacting surface  111  of the base  11  by the ultrasonic welding method. When one of the fins  13  is welded on the contacting surface  111  of the base  11 , a welding area  136  is defined at a front side of the welded one of the fins  13  for receiving another one of the fins  13  to be soldered to the base  11 . The ultrasonic welding can seamlessly join two workpieces together when the workpieces are under high-frequency ultrasonic acoustic vibrations and pressure. 
         [0018]    The ultrasonic welding method has many advantages, such as environment friendly, cleaning, energy and time saving and so on. The ultrasonic welding method not only fits for joining different materials, but also has a lower requirement with respect to the quality of the surfaces to be welded together. Oxidated and electroplated surfaces also fit for the ultrasonic welding method. Although the base  11  and the fins  13  of the heat sink  10  are respectively made of copper and aluminum, the ultrasonic welding method can easily weld the base  11  and the fins  13  together. In addition, the base  11  and the fins  13  are seamlessly welded together by the ultrasonic welding method, thereby decreasing the heat resistance between the base  11  and the fins  13 . Thus, heat dissipating efficiency of the heat sink  10  is accordingly improved. Furthermore, solder and flux are not required during the ultrasonic welding method, whereby the cost of the heat sink  10  is decreased and the process of making the heat sink  10  is simplified. 
         [0019]    In the ultrasonic welding method, a required power is increased dramatically along with an increase of the thickness of the workpiece being welded. However, in the heat sink  10 , each fin  13  has a small thickness in the range of 0.3˜0.4 mm; thus, the required power for welding each fin  13  is in an acceptable range, thereby decreasing unnecessary energy consumption. In addition, a larger welding head is generally required in the ultrasonic welding. However, in the heat sink  10 , the flanges  134  of the fins  13  are successively welded on the contacting surface  111  of the base  11  by the ultrasonic welding method. Thus, the welding head can be small. The welding area  136  defined at the front side of the fin  13  to be welded can provide an adequate enough space for the welding head to press the flange  134  of the fin  13  to be welded. Thus, the welding head can conveniently and evenly apply the pressure on the flange  134  of each fin  13  to be welded, which helps the fins  13  to have an intimate connection with the base  11 . 
         [0020]    Referring to  FIG. 2 , the heat sink  10  made by the ultrasonic welding method is shown. The fins  13  of the heat sink  10  are stacked together and parallel to each other. A bottom surface of the base  11  of the heat sink  10  thermally contacts with a heat generating component (not shown) to absorb heat therefrom, and then transfers the heat towards the fins  13 . 
         [0021]    Referring to  FIG. 3 , an ultrasonic welding process of a heat sink  20  in accordance with a second embodiment of the present invention is shown. Firstly, a base  21  and a plurality of individual fins  23  are provided. 
         [0022]    The base  21  has a cylindrical shape. The base  21  is made of copper, which has good thermal conductivity. The base  21  has a circular contacting surface  211  at a circumference thereof. 
         [0023]    The fins  23  are made of aluminum, which has good thermal conductivity. Each fin  23  has a plate shape, and has a thickness in a range of 0.3˜0.4 mm. Each fin  23  includes a main body  233 , and a flange  234  extending vertically and outwardly from an inner side of the main body  233 . The main body  233  of each fin  23  includes a lower part  237 , a middle part  238  and an upper part  239 . A length from an inner side towards an outer side of each of the lower part  237 , the middle part  238  and the upper part  239  is successively increased, thereby forming two sidesteps at an outer side of the main body  233 . 
         [0024]    During assembly of the heat sink  20 , the fins  23  are successively welded to the base  21  by ultrasonic welding method. Specially, the flange  234  of each fin  23  is welded on the contacting surface  211  of the base  21  by the ultrasonic welding method. When one of the fins  23  is welded on the contacting surface  211  of the base  21 , a welding area  236  is defined at a front side of the welded fin  23 . 
         [0025]    Referring to  FIG. 4 , the heat sink  20  made by the ultrasonic welding method is shown. The fins  23  of the heat sink  20  are radially welded to the base  21 . A bottom surface of the base  21  of the heat sink  20  thermally contacts with a heat generating component (not shown) to absorb heat therefrom, and then transfers the heat towards the fins  23 . 
         [0026]    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.