Abstract:
A heat sink and a power source unit employing the same can minimize leakage of plosive outside of the power source unit upon failure of semiconductor parts and can restrict leakage flashing, foreign odor, smoke and so forth which is possibly caused upon occurrence of failure of the semiconductor parts. The heat sink has a heat radiating casing housing therein a semiconductor part forming a power source unit therein, and whereby sealing the semiconductor part within the casing.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a power source used for a computer or the like. More particularly, the invention relates to a heat sink and a power source unit employing the same which can minimize leakage of plosive outside of the power source unit upon failure of semiconductor parts and can restrict leakage flashing, foreign odor, smoke and so forth which is possibly caused upon occurrence of failure of the semiconductor parts.  
           [0003]    2. Description of the Related Art  
           [0004]    In the power source unit to be used in computers or the like, a switching MOSFET which is a semiconductor part frequently causing failure, is employed. Since the switching MOSFET operates at high voltage and high power, large plosive and momentary spark should be caused upon occurrence of failure. Adapting to such failure, the power source unit is designed not to cause fire on the basis of safety standard.  
           [0005]    [0005]FIG. 3 is a perspective view of the conventional type heat sink. The heat sink  1  shown in FIG. 3 is formed with a flat plate form aluminum plate  1   a  with a plurality of fins  1   b . The heat sink  1  thus constructed is mounted expending substantially perpendicularly to planes of a printed circuit board. A semiconductor part  3 , such as a switching MOSFET, is secured on an aluminum plate  2  at back surface portion for performing cooling by radiating heat of the semiconductor part  3  by the heat sink  1 .  
           [0006]    In case of the power source unit using the heat sink  1 , the semiconductor part per se is mounted on the printed circuit board in bare condition within the power source unit. Since the power source unit is cooled by air, ventilation opening is formed in a casing. On the other hand, in case of the computer or the like, since the power source unit is mounted at a position facing outside of a main body, the semiconductor part (switching MOSFET) of the power source unit cannot be said as being shielded.  
           [0007]    Therefore, since the switching MOSFET caused failure at high frequency, burst is caused in the switching MOSFET, plosive should directly cause leakage to outside of the main body. Then, user may hear large plosive, may see momentary spark flying out or smoke flowing out of the computer or the like, or may feel foreign odor to cause serious discomfort for the user. Nowadays, concern for product liability is growing, even though occurrence of spark does not lead to occurrence of fire actually, such failure should cause degradation of credibility to result in re-calling of whole products.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention has been worked out in view of the problems set forth above. It is therefore an object of the present invention to provide a heat sink can minimize leakage of plosive outside of the power source unit upon failure of semiconductor parts and can restrict leakage flashing, foreign odor, smoke and so forth which is possibly caused upon occurrence of failure of the semiconductor parts, and a power source unit employing such heat sink.  
           [0009]    According to the first aspect of the present invention, a heat sink comprises:  
           [0010]    a heat radiating casing housing therein a semiconductor part forming a power source unit therein, and whereby sealing the semiconductor part within the casing.  
           [0011]    In the preferred construction, fins may be provided on an outer surface of the casing. The semiconductor part may be mounted on the inner surface of the casing. The casing may be mounted on a printed circuit board and the semiconductor part is connected to the printed circuit board. At least one of side walls of the casing may be formed with a nonflammable transparent plate. The semiconductor part may generate plosive upon failure of semiconductor part. In this case, a sound deadening sheet of nonflammable material may be fitted on an inner surface of the casing.  
           [0012]    According to the second aspect of the present invention, a power source unit comprises a heat sink constructed as set forth above. Namely, the power source unit includes a box shaped heat sink housing therein a semiconductor part forming a power source unit therein, and whereby sealing the semiconductor part within the heat sink.  
           [0013]    As set forth above, with the heat sink and the power source unit employing the same seals the semiconductor part, such as switching MOSFET with the box shaped heat sink to insulate from the outside of the heat sink. Therefore, even when failure is caused in the semiconductor part, plosive thus generated can be suppressed within the heat sink so as not to reach a user&#39;s ears, and flash, foreign odor, smoke and so forth will never leak out. Thus, failure of semiconductor part will never provoke anxiety of the user. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the preferred embodiment of the present invention, which, however, should not be taken to be limitative to the invention, but are for explanation and understanding only.  
         [0015]    In the drawings:  
         [0016]    [0016]FIG. 1 is a perspective view of the first embodiment of a heat sink and a power source unit employing the same according to the present invention;  
         [0017]    [0017]FIG. 2 is a perspective view of the second embodiment of a heat sink and a power source unit employing the same according to the present invention; and  
         [0018]    [0018]FIG. 3 is a perspective view of the prior art. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]    The present invention will be discussed hereinafter in detail in terms of the preferred embodiment of the present invention with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instance, well-known structure are not shown in detail in order to avoid unnecessary obscurity of the present invention.  
         [0020]    [0020]FIG. 1 shows the first embodiment of a heat sink and a power source unit employing the same according to the present invention. A heat sink  10  has a radiation casing  12  of the shape curving the inside of a cubic aluminum block. On outer surfaces of an upper wall and side walls of the casing  12 , a plurality of heat radiation fins  13 ,  14  and  15  are provided.  
         [0021]    A switching MOSFET  3  as semiconductor part forming the power source unit  20  is stored within the casing  12  with securing the back surface thereof on the inner surface of the side wall  12   a  of the casing  12 . Thus, the switching MOSFET  3  is sealed within the casing  12 . On the other hand, a terminal  3   a  of the switching MOSFET  3  extends through a bottom wall  12   b  of the casing  12 .  
         [0022]    The casing  12  housing the switching MOSFET  3  in a manner set forth above is secured on a printed circuit board (PCB)  16  with firmly fitting the bottom wall  12   b  on the printed circuit board  16 . Also, the switching MOSFET  3  has the terminal  3   a  connected to the printed circuit board  16 . With all of these components, a power source unit  20  is constructed.  
         [0023]    It should be noted that it is possible to provide holes in the casing  12  or the fins  13 ,  14  and  15  for securing the switching MOSFET  3  within the casing  12  from outside of the casing  12 . On the other hand, upon securing the bottom wall  12   b  of the casing  12  on the printed circuit board  16 , compound or the like may be used for enhancing firmness.  
         [0024]    By fitting a sound deadening sheet of nonflammable material on the inner surface of the casing, plosive to be generated upon bursting of the switching MOSFET  3  will never reverb to enhance noise insulation effect.  
         [0025]    With the power source unit shown in FIG. 1, a heat from the switching MOSFET as the semiconductor part is transmitted from the casing  12  of the heat sink to the fins  13 ,  14  and  15 , and is radiated to the ambient air through the outer surface of the casing  12  and the fins  13 ,  14  and  15  by a not shown forced air cooling means (e.g. air cooling fan) provided in a computer system or the like, for example. Therefore, when sufficient surface area for heat radiation is provided in the heat sink  10  by the fins  13 ,  14  and  15  and so forth, no problem will be arisen even when the switching MOSFET  3  is sealed within the casing  12 . Also, the switching MOSFET  3  can be protected against an external impact from outside of the power source unit  20  by the heat sink  10  and the printed circuit board  16 .  
         [0026]    On the other hand, upon occurrence of failure of the switching MOSFET  3 , the switching MOSFET  3  may generate large plosive, damage a mold portion or element portion and may cause flashing, foreign odor or smoking. However, plosive is insulated by the casing  12  of the heat sink  10  and thus is prevented from casing leakage. Also, external leakage of flashing, foreign odor or smoking can also be avoided successfully.  
         [0027]    In the embodiment shown in FIG. 1, since the switching MOSFET  3  is sealed by the aluminum heat sink  10 , the switching MOSFET  3  can be checked directly from outside of the heat sink. Therefore, in the second embodiment shown in FIG. 2, a nonflammable transparent plate  18  is provided in at least one side wall among side walls of the casting  12  of the heat sink  10  so that the switching MOSFET  3  in the casing may be checked from outside.  
         [0028]    It should be noted that while the fins on the upper surface of the casing  12  of the heat sink  10  in FIG. 2 is eliminated, position, number and shape of the fins may be appropriately selected. On the other hand, number, position, shape and so forth of other components should not be limited to those in the shown embodiments, but can be of any number, position, shape and so forth suitable for implementing the present invention. Therefore, although the present invention has been illustrated and described with respect to exemplary embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omission and additions may be made therein and thereto, without departing from the spirit and scope of the present invention. Therefore, the present invention should not be understood as limited to the specific embodiment set out above but to include all possible embodiments which can be embodied within a scope encompassed and equivalent thereof with respect to the feature set out in the appended claims.  
         [0029]    With the present invention set forth above, since the semiconductor parts, such as switching MOSFET or the like, are sealed by the casing to insulate from the outside of the casing, plosive to be generated upon failure of the semiconductor parts can be restricted within the heat sink to suppressed from reaching to the user&#39;s ears. Also, since flash, foreign odor, smoke or the like will never leaks out of the casing, failure will never provoke anxiety of the user.