Abstract:
A heat sink, cooling member, semi-conductor substrate cooling system, computer and method for providing sufficient cooling performance through a heat sink is provided. In part, there is provided a heat sink having a radiating portion for diffusing the heat conducted from a heat source and a blasting fan for blasting air to a duct-like structure formed by the radiating portion. Moreover, rates of airflows in the duct-like structure are averaged so that air circulates through all portions in the duct-like structure by forming a high-wind-pressure portion and a low-wind-pressure portion having wind pressures different from each other when air is blasted by the blasting fan in the duct-like structure and using the high-wind-pressure portion as a high-density area having a high arrangement density of radiating fins compared to the low-wind-pressure portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat sink, a cooling member, a semiconductor-substrate cooling system, a computer, and a radiation method, and more particularly to an apparatus, method and system for efficiently radiating heat generated in a CPU, or the like, of a computer. 
     2. Description of Related Art 
     As is known, because a temperature rise of a central processing unit (hereafter referred to as CPU) of a computer is directly related to the performance of the CPU, it is often desirable to attempt to diffuse the heat generated in the CPU and cool the CPU. 
     To improve cooling of the CPU, it is often necessary to increase the size of a radiating portion to be situated in relation to the CPU so as to contact to allow heat transfer. It is also known to position a fan in close proximity to the CPU such that the fan may provide air flow to a radiating portion, and/or the rotational speed of the fan may be increased to increase air flow. However, each of these options, increasing the size of the radiating portion and the fan, and increasing the rotational speed of the fan, are not preferred implementations as the former opposes the present trends of downsizing computer footprints and sizes, and the latter causes additional problems such as noise. 
     As shown in FIGS. 9 and 10, a heat sink  101  is set forth radiates heat generated in a CPU. FIG. 9 is an illustration showing a structure of the heat sink  101  and FIG. 10 is a sectional view taken along a line V—V in FIG.  9 . As shown in FIG. 9, the heat sink  101  is constituted by integrally forming a radiating portion  102  for radiating and diffusing the heat generated in a CPU and a centrifugal-fan-type blasting portion  103  for blasting air to the radiating portion  102 . The radiating portion  102  is provided with a substrate portion  104  formed of a flat member made of copper, a radiating fin  106  protruded to one flat face  104   a  of the substrate portion  104 , both end margins  104   b  of the substrate portion  104 , and a side-plate portion  107  rising from the both margin ends  104   b.  Moreover, as shown in FIG. 10, the radiating portion  102  is provided with an upper-plate portion  108  formed so as to cover the substrate portion  104  from the top. Therefore, as shown in FIG. 10, the radiating portion  102  forms a duct-like space  112  for the substrate portion  104 , side-plate portion  107 , and upper-plate portion  108  to surround the radiating fin  106 . Moreover, as shown in FIG. 10, the heat sink  101  is positioned so that a CPU  111  provided on the motherboard  110  of the computer directly contacts a flat face  104   c  opposite to a flat face  104   a  of the substrate portion  104 . 
     At the time of driving the blasting portion  103  while setting the heat sink  101  as shown in FIG. 10, an airflow generated by the blasting portion  103  passes through the duct-like space  112  and exhausted to the outside from the exit portion  112   a  (refer to FIG. 10) of the duct-like space  112 . However, the heat generated in the CPU  111  is conducted to the substrate portion  104  and moreover conducted up to the radiating fin  106 . In this case, because the substrate portion  104  and radiating fin  106  are cooled by the airflow supplied from the centrifugal fan, it is possible to diffuse the heat generated in the CPU  111 . 
     The centrifugal-fan-type blasting portion  103  is constituted so as to blast air in Y direction tilted by a predetermined angle from X direction which is an extending direction of the radiating portion  102  (extending direction of the duct-like space  112 ) as shown in FIG.  9 . However, to maximize a radiation effect, the radiating fin  106  is formed on the entire surface of the substrate portion  104  and the air resistance along the substrate portion  104  in the duct-like space  112  is almost uniform. Therefore, at the time of driving the blasting portion  103 , a portion where an airflow occurs is restricted to a portion to which air is directly blasted from the blasting portion  103  (e.g. area a in FIG. 9) and air stays in a portion (e.g. area b in FIG. 9) deviated from the blasting direction (Y direction) viewed from the blasting portion  103 . 
     However, as it is difficult to completely cool the radiating fin  106  at a portion deviated from the blasting direction (Y direction) viewed from the blasting portion  103 , the cooling performance is less than that desired. 
     Moreover, since it is impossible to completely cool the portion deviated from the blasting direction (Y direction) as described above, a temperature rise occurs at this portion and heat is conducted up to the housing of the computer through a screwed portion  113  formed on the radiating portion  102 . For such a situation, the surface temperature of the computer housing rises and availability of a user may be lost. 
     SUMMARY OF THE INVENTION 
     Accordingly, there is a need for an apparatus, method and system that overcomes the problems discussed above. The present invention provides an apparatus, method and system having efficient cooling performance, even for a compact structure, while suppressing a temperature rise of the housing of a computer. 
     According to one embodiment, the present invention is a heat sink, comprising: a radiating plate for radiating heat conducted from a heat source; a ventilation area formed along said radiating plate; and a blasting fan for blasting air to said ventilation area, wherein a high-wind-pressure portion and a low-wind-pressure portion having wind pressures different from each other when air is blasted by the blasting fan are formed in the ventilation area and wind-force losing members for losing the wind pressures are provided for the ventilation area, and the wind-force losing members are densely provided for the high-wind-pressure portion compared to the low-wind-pressure portion. 
     In this embodiment, because the high-wind-pressure portion has a large pressure loss and the low-wind-pressure portion has a small pressure loss in the ventilation area, wind pressures in the ventilation area are averaged. Therefore, rates of airflows generated by the blasting fan are averaged in the ventilation area and as a result, an airflow is generated in any portion in the ventilation area. In this case, it is possible to use a radiating fin or the like for radiation as a wind-force-losing member. 
     In this embodiment, when the ventilation area is formed like a duct, the blasting direction by the blasting fan tilts by a predetermined angle from the extending direction of the ventilation area, the high-wind-pressure portion is provided in the blasting direction of the blasting fan viewed from the blasting fan, and the low-wind-pressure portion is provided in a direction other than the blasting direction viewed from the blasting fan, it is possible to set a blasting direction independently of the extending direction of the duct-like ventilation area. Additionally, as used herein, the term “duct-like” includes not only a completely cylindrical shape but also a half-duct-like shape, that is, a half-cylindrical shape. 
     Moreover, when the low-wind-pressure portion is provided for separate positions at the both sides of the high-wind-pressure portion viewed from a tangential line of the blasting direction to the blasting fan, an airflow along the blasting-directional tangent also moves to the low-wind-pressure side and air is blasted to both the high- and low-wind-pressure portions. 
     Furthermore, when a portion of the radiating plate facing the low-wind-pressure portion is flatly formed, it is possible to minimize the pressure loss of this portion. Therefore, it is possible to easily generate a pressure-loss difference between the low- and high-wind-pressure portions by providing the wind-force losing member for the only high-wind-pressure portion. 
     Furthermore, the present invention, in a further embodiment, is a cooling member having a cooling member body contacting a heat source and forming a duct-like structure and a plurality of radiating fins fixed to the cooling-member body and protruded to the inside of the duct-like structure in which a high-density area and a low-density area different from each other in radiating-fin arrangement density are formed. 
     In this embodiment, by making radiating-fin arrangement densities different in the duct-like structure, a portion having a large air resistance and a portion having a small air resistance are formed in the duct-like structure and thereby a pressure loss is made different for each portion and thus, it is possible to suppress a flow-rate difference due to the difference between wind pressures working in the duct-like structure. Therefore, particularly when an airflow having a direction intersecting with the extending direction of the duct-like structure is generated in the duct-like structure, it is preferable to form the high-density area in an air-flow generation area and the low-density area in a portion other than the generation area. 
     In this embodiment, airflow is generated through blasting by a blasting fan or through attraction of air by any attracting means. Moreover, the duct-like structure includes not only a perfect cylindrical shape but also a half-duct shape, that is, a semi-cylindrical shape. 
     Moreover, in this embodiment, when a radiating fin is positioned so as to extend in the direction same as the extending direction of the duct-like structure, the extending direction of the radiating film tilts from a blasting direction. Also in this case, however, it is possible to uniform the flow rate in the duct-like structure. 
     Furthermore, when the extending direction of a radiating fin tilts toward the low-density area rather than an air-flow generating direction viewed from an air-flow generating area, it is possible to attract an airflow toward the low-pressure low-density area deviated from the air-flow generating area and therefore, it is possible to preferably pass the airflow along the radiating fin. 
     In a further embodiment, the present invention can be regarded a semiconductor-substrate cooling system comprising a radiating member having a flat portion and a centrifugal fan set adjacently to the radiating member, in which the nozzle of the centrifugal fan opens at one end margin of the flat face of the flat portion and the flat face of the flat portion has a high-resistance area and a low-resistance area having air resistances different from each other when air is blasted from the centrifugal fan. 
     Thus, by forming portions having air resistances different from each other on the flat face of the flat portion of a radiating member, it is possible to uniform a flow rate because of the difference between air resistances even if an airflow generated by the centrifugal fan acts on the radiating member in a non-uniform manner. 
     Moreover, in this embodiment, by forming the high-resistance area in the blasting direction by the centrifugal fan viewed from the nozzle of the centrifugal fan and the low-resistance area at the high-resistance area side viewed from the blasting direction, it is possible to supply some of the airflow generated by the centrifugal fan not only to the high-resistance area but also to the low-pressure low-resistance area. 
     Furthermore, at the time of forming the high-resistance area so that its width viewed from the nozzle becomes almost equal to the diameter of the centrifugal fan, even if enlarging the radiating member compared to the diameter of the centrifugal fan, it is possible to preferably supply an airflow to the whole radiating member by using the enlarged portion as the low-resistance area. 
     Furthermore, in a further embodiment, the present invention is a computer having a central processing unit for performing operations, a cooling system for cooling the central processing unit, and a housing for housing the central processing unit and the cooling system, in which the cooling system contacts the central processing unit and has a radiating member having a flat portion and a blasting portion for blasting air to the plat face of the flat portion and the flat portion is formed so that the roughness of the plat face of the flat portion differs in accordance with the difference between wind pressures working when air is blasted by a blasting portion. 
     According to the above embodiment, as configured, it is possible to uniformly cool the radiating member of the cooling system and suppress the temperature of the central processing unit. 
     Moreover, when fins are arranged on the flat face of the flat portion of the radiating member of the cooling system, it is possible to easily adjust the roughness of the flat-portion surface by adjusting the roughness of the flat face of the flat portion in accordance with the arrangement density of the arranged fins. 
     Furthermore, in this embodiment, if areas having a roughness different from each other are adjacently arranged viewed from the extending direction of a fin, it is possible to generate an airflow from a blasting portion in directions other than the extending direction of the fin by using the difference between air-flow pressure losses due to the difference between each roughness. 
     Furthermore, in this embodiment, when the blasting portion and the radiating portion are integrally formed, it is possible to downsize the cooling system. 
     Furthermore, in a still further embodiment, the present invention is a radiating method of radiating the heat conducted from a heat source by using a radiating member, comprising forming the surface of a radiating member so that the air resistance of a part of the surface becomes smaller than that of other portion and generating an airflow along the surface of the radiating member toward the other portion so that the airflow passes through the part of the surface decreased in air resistance and also flows in the direction intersecting with the air-flow generating direction. 
     Thus, at the time of blasting air to the radiating member, it is possible to decrease the air resistance of a part of the radiating member and use the part as a path for preferably supplying air to the whole radiating member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other aspects, features, and advantages of the present invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which: 
     FIG. 1 is a top view of a heat sink according to an embodiment of the present invention; 
     FIG. 2 is a back view of the heat sink in FIG. 1; 
     FIG. 3 is a right side view of the heat sink in FIG. 1; 
     FIG. 4 is a perspective view showing a state of setting the heat sink shown in FIG. 1 in the housing of a personal computer, according to an embodiment of the present invention; 
     FIG. 5 is a sectional view of the heat sink in FIG. 1, taken along a line I—I in FIG. 1; 
     FIG. 6 is a sectional view of the heat sink in FIG. 1, taken along a line II—II in FIG. 1; 
     FIG. 7 is a sectional view of the heat sink in FIG. 1, taken along a line III—III in FIG. 1; 
     FIG. 8 is a sectional view of the heat sink in FIG. 1, taken along a line IV—IV in FIG. 1; 
     FIG. 9 is a top view showing a conventional heat sink; and, 
     FIG. 10 is a sectional view of the conventional heat sink in FIG. 9, taken along a line V—V in FIG.  9 . 
    
    
     DETAILED DESCRIPTION 
     The use of figure reference labels in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the interpretation of the claims. Such labeling is not to be construed as necessarily limiting the scope of those claims to the embodiments shown in the corresponding figures. The preferred embodiments of the present invention and its advantages are best understood by referring to the drawings, like numerals being used for like and corresponding parts of the various drawings. 
     FIGS. 1,  2 , and  3  are a top view, a back view, and a side view in order for explaining a heat sink (cooling system)  1  of this embodiment, respectively. The heat sink  1  shown in FIGS. 1 to  3  is set in the housing  3  of a notebook-type personal computer  2  as shown in FIG. 4 while turning the face shown in FIG. 1 toward a mother board  4  and has a function for cooling a CPU (Central Processing Unit)  5  fixed onto the mother board  4 . 
     As shown in FIGS. 1 and 2, the heat sink  1  is provided with a radiating portion (cooling member and radiating member)  7  for radiating heat in contact with the CPU  5  and a blasting fan (blasting portion and centrifugal fan)  8  for blasting air to the radiation portion  7 . 
     The radiating portion  7  is provided with a flat copper radiating plate (cooling-member body and flat portion)  10 . The radiating plate  10  is so configured such that one end margin  11   a  of a flat face  11  at one side of the radiating plate  10  contacts with the blasting fan  8 , and there are provided rising-wall portions  12 ,  12  at end margins  11   b.  End margins  11   b  are opposed to one another at this end margin  11   a.  Furthermore, there are provided a CPU contact portion  13  and a plurality of radiating fins (wind-force losing member)  14 ,  14  between the rising-wall portions  12 ,  12  of the same members. Additionally there are provided sponges  15 ,  15  along the rising-wall portions  12 ,  12 . 
     FIGS. 5 to  8  are vertical sectional views taken along lines I—I, II—II, III—III, and IV—IV in FIG.  1 . These illustrations also show positions of the motherboard  4  and CPU  5  at the time of setting the heat sink  1  on the motherboard  4 . 
     As shown in FIGS. 5 to  8 , when setting the heat sink  1  on the mother board  4 , the CPU  5  is located in a space surrounded by the radiating plate  10 , rising-wall portions  12  and  12 , sponges  15  and  15 , and mother board  4 . That is, in this case, the radiating portion  7  forms a duct-like structure (ventilation area)  17  surrounding the CPU  5  together with the mother board  4  and the CPU contact portion  13  and radiating fins  14  are set in the duct-like structure  17  so as to protrude to the inside of the structure  17 . Moreover, as shown in FIG. 6, the CPU contact portion  13  is formed so as to directly contact with the CPU  5  when setting the heat sink  1  on the motherboard  4 . Furthermore, as shown in FIG. 1, the extending direction (direction A in FIG. 1) of the radiating fins  14  is the same as the extending direction (direction B in FIG. 1) of the duct-like structure  17 . 
     On the other hand, as shown in FIG. 1, the blasting fan  8  is formed as a centrifugal fan. The blasting fan  8  blasts air from its nozzle  18  in the direction of the arrow C in FIG.  1  and thereby, an airflow can be generated in the duct-like structure  17 . The blasting direction (direction C) tilts from the extending direction (direction B) of the duct-like structure  17  by a predetermined angle q. 
     Furthermore, as shown in FIG. 1, a high-resistance area  19  having a large air resistance (large roughness) because the radiating fins  14  are formed and a low-resistance area  20  having a small air resistance (small roughness) compared to the high-resistance area  19  because the low-resistance area  20  is flattened with no radiating fins  14  formed are formed on the flat face  11  of the radiating plate  10 . That is, the roughness of the flat face  11  is adjusted in accordance with the arrangement density of the radiating fins  14  arranged on the flat face  11  in the radiating portion  7 . 
     In this case, the high-resistance area  19  extends in the same direction as the extending direction (direction B) of the duct-like structure  17  and the extending direction (direction A) of the radiating fins  14  by having the width R 2  almost equal to the diameter R 1  of the blasting fan  8  and moreover, the low-resistance area  20  is formed on a portion (width-enlarged portion  21 ) where the width of the low-resistance area  20  is enlarged compared to the diameter R of the blasting fan  8 . Therefore, the low-resistance area  20  is located at the side of the high-resistance area  19  when viewed from the extending direction (direction A) of the duct-like structure  17  and the blasting direction (direction C) of the blasting fan  8 . 
     Moreover, because the flat face  11  of the radiating portion  7  is formed as described above, the inside of the duct-like structure  17  is divided into a high-density area (high-wind-pressure portion)  22  having a large arrangement density of the radiating fins  14  and a low-density area (low-wind-pressure portion)  23  having a small arrangement density of the radiating fins  14  (no radiating fins  14  are arranged). 
     The high-density area  22  and low-density area  23  are located adjacently to each other in the direction perpendicularly intersecting with the extending direction (direction B) of the duct-like structure  17  and also intersecting with the direction (direction D in FIG. 1) also intersecting with the blasting direction (direction C). Moreover, the high-density area  22  is formed at a portion where the pressure of an airflow generated by the blasting fan  8  is high, that is, in the blasting direction (direction C) viewed from the nozzle  18  of the blasting fan  8  and the low-density area  23  is separated at the both sides of the high-density area  22  viewed from the tangent  24  of the blasting direction (direction C) to the blasting fan  8  and formed at a low air-flow pressure compared to the high-density area  22 . 
     Therefore, as shown in FIG. 1, the high-density area  22  is located at an airflow generating area  25  in which an airflow is generated by the blasting fan  8  and the low-density area  23  is located at a portion other than the airflow generating area  25 . Moreover, the extending direction of the radiating fins  14  (direction A) is tilted toward the low-density area  23  rather than the airflow generating direction (direction C). 
     The pressure loss of the high-density area  22  increases compared to that of the low-density area  23  when airflows having the same flow rate flow downward due to the difference between arrangement densities of the radiating fins  14 . 
     A radiating method using the heat sink  1  is described below. 
     While setting the heat sink  1  formed as described above into the housing  3  of the personal computer  2  as shown in FIG. 4, the personal computer  2  is operated and simultaneously the blasting fan  8  is driven. 
     The CPU  5  generates heat when the personal computer  2  is operated and the heat is conducted to the radiating plate  10  and radiating fins  14  through the CPU contact portion  14  contacting the CPU  5 . Moreover, because the blasting fan  8  is driven, airflow is generated in the direction C in FIG. 1 from the nozzle  18  of the blasting fan  8 . 
     In this case, the high-density area  22  to which the airflow is directly blasted in the duct-like structure  17  becomes a high pressure and the low-density area  23  to which the airflow is not directly blasted becomes a low pressure. Therefore, some of the airflows from the high-density area  22  to the low-density area  23 . However, the high-density area  22  has a large pressure loss because the area  22  has a large air resistance compared to the low-density area  23  and therefore, a large flow-rate drop compared to the case of the low-density area  23  occurs in the high-density area  22 . Thereby, airflow rates are averaged in the high-density area  22  and low-density area  23 . That is, in this case, not only the high-density area  22  but also the low-density area  23  function as air paths and thereby, it is possible to supply air into the whole duct-like structure  17 . 
     Moreover, because an airflow can be generated in any one of the high-density area  22  and low-density area  23  in the duct-like structure  17 , it is possible to eliminate a stagnation area of air in the duct-like structure  17  differently from the past. That is, according to this embodiment, the flow of air in the duct-like structure  17  is optimized and as a result, it is possible to maximize the quantity of heat to be radiated from the radiating fins  14 . 
     Moreover, in the case of this embodiment, because the flow of air is optimized as described above, it is possible to minimize wind noises causing noises from the blasting fan  8  and optimize the noise characteristic of the heat sink  1 , whereby such results are depicted Table 1 below. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 CPU temperature 
                 rpm 
                 Acoustic 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Conventional 
                 93.7 
                 4380 rpm 
                 28 dB 
               
               
                 Present invention 
                 91.7 
                 4380 rpm 
                 — 
               
               
                 Present invention 
                 89.6 
                 4680 rpm 
                 28 dB 
               
               
                   
               
             
          
         
       
     
     Table 1 compares temperatures of CPUs to be cooled, revolutions per minute of blasting fans, and acoustic characteristics, that is, magnitudes of noises of blasting fans when using the conventional heat sink  101  and the heat sink  1  of this embodiment. As a result of comparing the first stage with the second stage in Table 1, it is found that the temperature of the CPU can be lowered by 2.0° C. by using the heat sink  1  of this embodiment when revolutions per minute of the blasting fans are the same (4,380 rpm). Moreover, as a result of comparing the first stage with the third stage in Table 1, it is found that the temperature of the CPU can be lowered by 4.1° C. at the same acoustic characteristic (28 dB) by using the heat sink  1  of this embodiment. 
     As described above, in the case of this embodiment, a portion having a large pressure loss (high-density area  22 ) and a portion having a small pressure loss (low-density area  23 ) are formed in the duct-like structure  17  serving as a ventilation area by adjusting the arrangement density of the radiating fins  14  on the flat face  11  of the radiating plate  10  of the heat sink  1  by a portion having a large wind pressure and a portion having a small wind pressure. In this case, by using the portion having a small pressure loss as an air path, it is possible to uniform a flow-rate distribution in the duct-like structure  17  and optimize the flow of air in the duct-like structure  17 . Thereby, it is possible to maximize the radiating performance of the radiating portion  7  and greatly improve the cooling performance for the CPU  5 . Moreover, the noise characteristic of the heat sink  1  can be improved than ever, it is possible to raise the rpm of the blasting fan  8  and further improve the cooling performance for the CPU  5 . 
     Moreover, as described for this embodiment, even when the blasting direction (direction C) of the blasting fan  8  tilts from the extending direction (direction B) of the duct-like structure  17  and the width of the radiating plate  10  is larger than the width R 1  of the blasting fan  8 , it is possible to preferably show the performance of the heat sink  1  by using the air-flow generating area  25  by the blasting fan  8  as the high-density area  22  and the portion adjacent to the area  22  as the low-density area  23 . Therefore, even if the shape of the radiating portion  7  and the positional relation of the radiating portion  7  to the blasting fan  8  are restricted, it is possible to downsize the heat sink  1  and also secure the cooling performance of the heat sink  1  and contribute to reduction of a computer in size and improvement of the computer in performance. Moreover, these effects of this embodiment are particularly advantageous when integrally forming the radiating portion  7  and the blasting fan  8 . 
     Moreover, as described for this embodiment, by setting an area in which no radiating films  14  are formed in the duct-like structure  17  so as to be adjacent to the direction (direction D) perpendicularly intersecting with the extending direction (direction B) of the duct-line structure  17  to an area in which the radiating fins  14  are formed, it is possible to optimize an airflowing direction independently of the extending direction (direction A) of the radiating fins  14 . Therefore, it is unnecessary to complicate the arrangement of the radiating fins  14  or newly form a ventilation path in order to control the airflowing direction and it is possible to inexpensively form the compact heat sink  1  superior in cooling performance. 
     Although an embodiment of the present invention is described above, the present invention is not limited to the above embodiment, and it is understood by those skilled in the art that other configuration(s) in view of the invention are also possible. 
     For example, though the radiating portion  7  forms the duct-like structure  17  so as to surround the CPU  5  in the case of the above embodiment, it is allowed that the position of the CPU  5  is present at the outside of the duct-like structure  17 . Moreover, it is possible to conduct the heat of the CPU  5  to the radiating portion  7  through a heat pipe or the like and radiate the heat by the radiating portion  7  at a position separate from the CPU  5 . 
     Moreover, though the blasting fan  8  is integrated with the radiating portion  7  in the case of the above embodiment, it is also allowed to separate the blasting fan  8  from the radiating portion  7  and conduct an airflow generated by the blasting fan  8  to the radiating portion  7  through a duct or the like. 
     Furthermore, though air is blasted to the radiating portion  7  in the case of the above embodiment, it is also allowed to generate an airflow in the radiating portion  7  by attracting the air of the radiating portion  7 . 
     Furthermore, it is possible to select the configuration used for the above embodiment or properly change the configuration to another configuration as long as the new configuration is not deviated from the gist of the present invention. 
     As described above, according to the present invention, preferable cooling performance and noise characteristic can be realized even if a heat sink is decreased in size. Therefore, it is possible to contribute to the reduction of a computer in size and the improvement of the computer in performance by using the heat sink to cool a CPU or the like. 
     It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention as expressed in the following claims.