Abstract:
A heat sink includes a heat receiving part for receiving heat from the outside, a first radiating part, connected to said heat receiving part, which forms a first air channel, and radiates the heat from said heat receiving part using air that passes through the first air channel, and a second radiating part, located apart from said heat receiving part and connected to said first radiating part, said second radiating part forming a second air channel which the air that has passed the first air channel enters, the second air channel being narrower than the first air channel, said second radiating part radiating the heat from said first radiating part.

Description:
This application is a continuation based on PCT International Application No. PCT/JP00/09374, filed on Dec. 20, 2000, which is hereby incorporated by reference herein in its entirety as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to heat radiator mechanisms, and more particularly to a heat radiator mechanism for radiating the heat from an exoergic circuit element or exoergic component mounted in an electronic apparatus. The present invention is suitable, for example, for a heat sink that radiates the heat from various exoergic circuit elements on a printed board in a personal computer (“PC”). 
     PCs are broadly available in the market as a typical information processor. A motherboard or main board in the PC is mounted with various circuit components such as a CPU socket, a variety of memory (sockets), a chipset, an expansion slot, and a BIOS ROM, and directly affects performance and functions of the PC. 
     Recent PCs tend to include an increased number of exoergic components and to generate more calorific values from them as various circuit components mounted on the motherboard provide higher speed and performance. The heat destabilizes operations of circuit components, and finally lowers the operational performance of a PC. Therefore, the PC provides the motherboard with a heat radiator mechanism called a heat sink in order to thermally protect the exoergic components and other circuit components mounted directly or via a socket or the like on the motherboard. 
     A description will be given of a conventional typical heat sink  500  with reference to FIGS. 18 and 19, and another conventional heat sink  600  with reference to FIGS. 20 and 21. Here, FIGS. 18 and 19 are schematic side and plane views of the heat sink  500 . FIGS. 20 and 21 are schematic side and plane views of the heat sink  600 . The heat sink typically includes plural cooling or radiating fins (or sometimes called “fin assembly”) made of a material having high heat conductivity, and cools exoergic components by forced or spontaneous air cooling. The heat sink  500  includes a base  510  placed on an exoergic component (not shown) mounted on a motherboard (not shown), and a radiating part  520  that includes plural parallel plate-shaped fins  522  that extend from the base  510  perpendicular to the motherboard or in a direction Z in FIG.  18 . The head sink  600  includes a base  610  placed on an exoergic component (not shown) mounted on a motherboard (not shown), and a radiating part  620  that includes plural pinholder-shaped fins  522  that extend from the base  610  perpendicular to the motherboard or in a direction Z in FIG.  20 . 
     A fan-cum-heat sink that includes a fan has been proposed to enhance a cooling effect of the heat sink. The fan-cum-heat sink provides forced-air cooling to the heat sink with air currents produced by a fan. 
     A higher speed and more functions of various circuit elements have drastically increased the calorific values from the circuit elements, and required the heat sink to have higher heat radiation performance. Conceivably, this request would be met by increasing surface areas of the radiating parts  520  and  620  in the conventional heat sinks  500  and  600 . 
     A conceivable way of increasing the surface area of the radiating part  520  or  620  is to narrow an interval or pitch between fins  522  or  622  and increase the number of fins  522  or  622  per unit area and/or to thicken each fin  522  or  622 . Both of these methods eventually narrow a pitch, and reduce the air convection that passes between the fins  522  or  622 , lowering the cooling efficiency at center parts of the bases  510  and  610  (this condition is sometimes called “increased pressure loss” in this application). 
     It is also conceivable to extend the height of the fins  522  or  622  in the height direction or direction Z to increase the surface area of the radiating part  520  or  620 . However, the fin  522  or  622  has such a temperature gradient in the direction Z that the excessively high fin  522  or  622  has lowered heat exchanger effectiveness and cooling efficiency on its top. In order to rectify this shortcoming, it is also conceivable to replace a material of the fin  522  or  622  with a material having high heat conductivity for the reduced temperature gradient in the height direction or the direction Z. For example, it is conceivable to replace aluminum, typically used for the fins  522  and pins  622 , which has heat conductivity of 203 W/m·K with copper that has heat conductivity of 372 W/m·K. However, copper needs anti-oxidant coating, and complexes the manufacture process. In addition, copper is heavier than aluminum and an undesirable material to be attached to a top of the component. The length in the direction Z is restricted by the mounting space limitation in the PC. 
     It is also conceivable to attach a fan to a heat sink to enhance the heat conductivity, but this deteriorates energy saving aspect and economical efficiency of the heat sink. 
     Thus, some parameters should be considered which include the pressure loss instead of merely increasing the surface area of the fin in order to enhance the heat radiation efficiency in a heat sink. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is a general object of the present invention to provide a novel and useful heat radiator mechanism and electronic apparatus having the same in which the above disadvantages are eliminated. 
     Another exemplified and more specific object of the present invention is to provide a heat radiator mechanism and electronic apparatus having the same, which comparatively inexpensively enhance the entire heat radiation efficiency taking into account some parameters including pressure loss. 
     A heat sink of one embodiment according to the present invention includes a heat receiving part for receiving heat from the outside, a first radiating part, connected to the heat receiving part, which forms a first air channel, and radiates the heat from the heat receiving part using air that passes through the first air channel, and a second radiating part, located apart from the heat receiving part and connected to the first radiating part, the second radiating part forming a second air channel which the air that has passed the first air channel enters, the second air channel being narrower than the first air channel, the second radiating part radiating the heat from the first radiating part. This heat sink may radiate the heat from the heat receiving part using the first and second radiating parts. The first radiating part forms the first air channel, and radiates the heat as a result of that the air passes through the first air channel. The air that has passed through the first air channel may enter the second air channel of the second radiating part narrower than the first air channel, and the second radiating part may radiate the heat using the air convection. The second radiating part is spaced from the first radiating part by a predetermined distance that contributes to definition of the first air channel at the first radiating part. The first radiating part of the heat sink includes, for example, plural fins, and the second radiating part is provided between two fins, thereby maintaining the second air channel. The sufficiently large second air channel may be maintained by providing the second radiating part with second fin thinner than the first fin. Moreover, this heat sink forms a surface area of the second radiating part larger than that of the first radiating part, maintains the sufficiently wide heat radiation area and enhances the heat radiation effect. The heat sink includes a side plate that encloses the second radiating part and defines an air channel, so as to assist the second radiating part in radiating the heat. The second radiating part includes a first part near a center, and a second part, located outside the first part, which has a larger surface area than the first part. A wide heat radiation area may be obtained by forming the first part larger than the second part that promotes the air convection. A similar operation may be obtained by making the second part longer than the first part in the height direction. Alternatively, the first part longer than the second part in the height direction would promote the air convection at the first part and enhance the heat radiation efficiency. The convection at the second radiating part may be promoted and the heat radiation efficiency may be promoted by forming a notch in the thin plate, and raising the notch to form a raised piece as a bent projection and disturb the airflow. This notch may connect adjacent second air channels. The increased number of pillar parts and a shape of the pillar part would promote the air convection and enhance the heat radiation efficiency. 
     An electronic apparatus of another embodiment according to the present invention includes a printed board mounted with an exoergic component, and a heat sink, provided on the printed board, which cools the exoergic component, wherein the heat sink includes a heat receiving part for receiving heat from the outside, a first radiating part, connected to the heat receiving part, which forms a first air channel, and radiates the heat from the heat receiving part using air that passes through the first air channel, and a second radiating part, located apart from the heat receiving part and connected to the first radiating part, the second radiating part forming a second air channel which the air that has passed the first air channel enters, the second air channel being narrower than the first air channel, the second radiating part radiating the heat from the first radiating part. This electronic apparatus has the above heat sink, and exhibits similar operations to those of the heat sink. 
     Other objects and further features of the present invention will become readily apparent from the following description of the embodiments with reference to accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view near a heat sink as one embodiment according to the present invention that is applied to a motherboard in a PC. 
     FIG. 2 is a schematic top view of the heat sink shown in FIG.  1 . 
     FIG. 3 is a schematic sectional view of the heat sink shown in FIG. 2 taken along line X—X. 
     FIG. 4 is a schematic sectional view of the heat sink shown in FIG. 2 taken along line Y—Y. 
     FIG. 5 is a schematic top view of the heat sink having a plate-shaped fin as a variation of a pillar part shown in FIG.  1 . 
     FIG. 6 is a schematic sectional view of the heat sink shown in FIG. 5 taken along line X—X. 
     FIG. 7 is a schematic sectional view of the heat sink shown in FIG. 5 taken along line Y—Y. 
     FIG. 8 is a schematic top view of the heat sink having a plate-shaped fin as a variation of a pillar part shown in FIG.  1 . 
     FIG. 9 is a schematic sectional view of a variation of a thin plate of a radiating part in the heat sink shown in FIG.  1 . 
     FIG. 10 is an enlarged perspective view of a circle shown in FIG.  9 . 
     FIG. 11 is a schematic perspective top view of a heat sink having a thin plate as a variation of a thin plate shown in FIG.  1 . 
     FIG. 12 is a schematic plane view of a variation of a side plate of the heat sink shown in FIG.  1 . 
     FIG. 13 is one schematic side view of the heat sink shown in FIG.  12 . 
     FIG. 14 is another schematic side view of the heat sink shown in FIG.  12 . 
     FIG. 15 is a schematic sectional view of the heat sink shown in FIG. 1 provided with a cavity. 
     FIG. 16 is a schematic sectional view of the heat sink shown in FIG. 15 provided with a fan. 
     FIG. 17 is a view that compares cooling performance of a conventional heat sink with that of the inventive heat sink. 
     FIG. 18 is a schematic side view of a structure of the conventional heat sink. 
     FIG. 19 is a schematic top view of the heat sink shown in FIG.  18 . 
     FIG. 20 is a schematic side view of a structure of the conventional heat sink. 
     FIG. 21 is a schematic top view of the heat sink shown in FIG.  20 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A description will now be given of a heat sink as a radiator mechanism of one embodiment according to the present invention, with reference to FIGS. 1 to  4 . FIG. 1 is a schematic perspective view near a heat sink  100  as one embodiment according to the present invention that is applied to a motherboard  200  in a PC  300 . FIG. 2 is a schematic top view of the heat sink  100 . FIG. 3 is a schematic sectional view of the heat sink  100  shown in FIG. 2 taken along line X—X. FIG. 4 is a schematic sectional view of the heat sink  100  shown in FIG. 2 taken along line Y—Y. The same element in each figure is designated by the same reference numeral, and a duplicate description thereof will be omitted. The reference numeral with an alphabet generally denotes a variation, and the reference numeral without an alphabet generalizes all the same reference numerals with different alphabets. 
     The heat sink  100  is placed on a CPU  210  (which includes an MPU and any other processor irrespective of its name) as an exoergic component mounted on the motherboard  200  shown in FIG.  1 . The heat sink  100  includes a heat receiving part  110 , a pillar part  120 , a radiating part  130 , and side plate  170 . 
     The heat receiving part  110  thermally contacts an exoergic component outside the heat sink  100  and receives heat from it. The instant embodiment places the heat receiving part  110  directly on the CPU  210 , but the present invention allows the heat receiving part  110  to indirectly contact the CPU  210  via a certain member. The heat receiving part  110  has a rectangular plate shape in the instant embodiment, but may have an arbitrary shape according to shapes of exoergic components to be connected to the heat receiving part  110 . The heat receiving part  110  has a bottom area surface (e.g., 40 mm×40 mm) that is approximately the same as or larger than the top surface area of the CPU  210  so that it may receive heat from the entire surface of the CPU  210 . The thickness of the heat receiving part  110  is not limited, but the heat receiving part  110  preferably is made as thin as possible for effective heat conduction to the pillar  120 , which will be described later. The heat receiving part  110  is made, for example, of such a material having high thermal conductivity as aluminum. 
     The heat receiving part  110  has a heat receiving surface  112  as a surface that surface-contacts the CPU  210 , a heat radiator surface  114  as a surface opposite to the heat receiving surface  112  and at the side of the pillar  120 , and four side surfaces  116 . The inventive heat sink  100  absorbs the heat generated from the CPU  210  through the heat generating surface  112 , and transfers the heat to the pillar part  120  at the heat radiator surface  114 . Of course, the heat receiving part  110  may radiate the heat at the heat radiator surface  114  and side surfaces  116 . The heat receiving part  110  may be formed integral with the pillar part  120 , or formed independent of the pillar part  120  and then jointed together. 
     The pillar part  120  serves as a first heat radiator part that radiates the heat from the heat receiving part  110 , and conducts part of the heat received from the heat receiving part  110  to the heat radiator part  130 . The pillar part  120  of the instant embodiment is made of plural approximately T-shaped plate-shaped fins  122  which are arranged in parallel. However, as described below with reference to FIG. 8, the inventive plate-shaped fins  122  do not have to be necessarily arranged in parallel. As described below with reference to FIG. 5, the present invention does not limit the shape of the pillar part  120  to a plate shape, and may use the pillar part  120  with a pin shape or any other shape. 
     The pillar fins  122  stand erect from the heat radiator surface  114 , and a vent  128  shown in FIG. 1 is connected between two fins  122 . The vent  128  is connected to the outside, and maintains, with two fins  122 , a first air channel for cooling. The first air channel contributes to air cooling to the heat radiator surface  114 , fins  122 , and heat radiator part  130 , which will be described later. 
     Referring to FIG. 3, the plate-shaped fin  122  of this embodiment has an approximately T-shape, and includes a lower part  123  (below a dotted line in FIG. 3) formed as wide as the heat receiving part  110 , and an upper part  124  (above the dotted line in FIG. 3) connected to the heat radiator part  130  and formed wider than the lower part  123 . The lower part  123  has a height h, for example, of about 7 mm. The height h of zero would eliminate the vents  128 , and undesirably enlarge the pressure loss. The height h having a value near zero would reduce the vents  128 , and undesirably enlarge the pressure loss. The height h differs depending upon use or nonuse of a fan, even when the same heat radiator effect is expected. As will be described later, the heat radiator part  130  is spaced from the heat receiving part  110  by the height h. As detailed later, as shown in FIG. 2, the instant embodiment forms the upper part  124  and the heat radiator part  130  larger than the top surface of the heat receiving part  110 . Therefore, when the height h becomes zero, the upper part  124  and heat radiator part  130  undesirably prevent a memory and other circuit elements from being mounted in a space  202  shown in FIG. 1 adjacent t the CPU  210  on the motherboard  200 . Therefore, the height h of about 5 mm or larger, more preferably 7 to 10 mm, is necessary even when the fan is used. 
     The upper part  124  of the pillar part  120  is wider (e.g., about 60 mm) than the lower part  123 , and maintains a wide heat radiator area. A shape of the plate-shaped fin  122  of this embodiment is exemplary for this advantage, and the present invention may use a trapezoid-shaped plate-shaped fin. 
     As shown in FIGS. 1 and 4, the pillar part  120  of the instant embodiment is made of five plate-shaped fins  122 . The number of plate-shaped fins  122  is exemplary, and the present invention is not limited to this number. An interval d between adjacent plate-shaped fins  122  defines the above first air channel to the heat radiator part  130 . As the airflow is in proportion to product between the height h and the interval d, the interval d is determined for the intended airflow. The interval d is set to, for example, about 7 to 11 mm, and 9 mm in the instant embodiment. As shown in FIG. 4, each plate-shaped fin  122  has the same size and shape with a common thickness t in the instant embodiment. As the thickness t increases, the surface area of the fin  122  generally increases, narrowing the interval d. The excessively small thickness t would enlarge the temperature gradient to the tip (or top in FIG. 4) of the pillar part  120 , and lower the heat conduction performance and thus the heat conductivity from the pillar part  120  to the heat radiator part  130 . The thickness t was set in view of this point. The thickness t is set, for example, about 1 to 2 mm, and about 2 mm in the instant embodiment. 
     The pillar part  120  is made, for example, of such a material having high thermal conductivity as aluminum. As discussed above, the pillar part  120  may be formed integral with the heat receiving part  110 . When the pillar part  120  is formed as a single member, the pillar part  120  is provided on the side of the heat receiving surface  114  of the heat receiving part  110  through such means as adhesion and welding. 
     As discussed above, the pillar part  120  is not limited to the above T shape, and may include a plate-shaped fin  122 , as shown in FIGS. 5 to  7 , which divides one plate-shaped fin  122  into plural pieces using slits  125 . Here, FIG. 5 is a schematic top view of the heat sink  100  having a plate-shaped fin  122   b  as a variation of a pillar part  120  shown in FIG.  1 . FIG. 6 is a schematic sectional view of the heat sink  100  shown in FIG. 5 taken along line X—X. FIG. 7 is a schematic sectional view of the heat sink  100  shown in FIG. 5 taken along line Y—Y. 
     The slit  125  between adjacent plate-shaped fins  122   b  in the direction X in FIG. 5 may be connected to the above vents  128  by dividing the plate-shaped fin  122  into plural pieces, enlarging a range of the airflow. This shape promotes the air convection and may improve the heat radiation efficiency of the heat sink  100 . The plate-shaped fin  122   b  may be provided with the slits  125  only at the upper part  124   b  so as not to reduce the heat conductivity to the radiating part  130  at the upper part  124  above the pillar part  120 , or may be provided with the slits  125  to middle part between the upper and lower parts  124  and  123   b . Understandably, similar operations and effects are available by providing the fin  122  with a notch or any other hole instead of the slit  125  and connecting the notch etc. to the above vents  128 . 
     As discussed above, the arrangement of the plate-shaped fin  122  of the pillar part  120  is not limited to a parallel and lateral arrangement. For example, as shown in FIG. 8, plural arc-shaped fins  122   c  may be arranged concentrically. Here, FIG. 8 is a schematic top view of the heat sink  100  having a plate-shaped fin  122   c  as another variation of the pillar part  120  shown in FIG.  1 . This arrangement may also exhibit similar operations of the plate-shaped fin  122  having the above structure. 
     The radiating part  130  is located at the upper part  124  of the pillar part  120 , and serves as a second radiating part that radiates the heat from the pillar part  120 . The radiating part  130  has a thin plate  132 . The instant embodiment provides the radiating part  130  between the fins  122 , but the radiating part  130  does not have to be provided between fins  122 , and may be provided onto the lower part  123  by removing the upper part  124 . As shown in FIGS. 2 and 4, the radiating part  130  respectively arranges thin plates  132  orthogonal to the heat receiving part  110  between the plate-shaped fins  122 . The radiating part  130  uses the thin plate  132  to radiate the heat absorbed from the heat receiving part  110  and transmitted to the pillar part  120 . 
     The thin plate  132  has a plate thickness smaller than the thickness t (which is 0.2 mm in this embodiment) of the plate-shaped fin  122  of the pillar  120 , and its section is bent like a corrugated shape. Of course, the thin plate  132  may have various sectional shapes, such as any other waveform shape, a U-shape, a V-shape, and a W-shape. As the thin plate  132  intends to enlarge the surface area of the pillar part  120 , the present invention covers a non-bent shape, for example a diagonally provision between two adjacent pillar parts  120 &#39;s upper parts  124 . 
     As shown in FIG. 2, the thin plate  132  forms bent portions so that they may contact the plate-shaped fin  122 , and defines a second air channel in an airflow direction from the lower part  123  of the plate-shaped fin  122  to the upper part  124  (or from the upper part  124  to the lower part  123 ). The thin plate  132  has the approximately the same size as the upper part  124  of the plate-shaped fin  122 . Such a corrugated bending interval is applied to the thin plate  132  so as not to prevent the airflow at the radiating part  130 . As shown in FIG. 2, the passages  134  as the second air channel defined by the thin plate  132  are connected to the above vents  128 . 
     The thin plate  132  radiates the heat conducted by the thin plate  132  via a contact portions with the plate-shaped fin  122 . The corrugated thin plate  132  may maintain a large surface area. In other words, the thin plate  132  expands the heat radiation area between the plate-shaped fins  122 . The thin plates  132  maintain larger heat radiation area and do not reduce the heat radiation efficiency of the heat sink  100  even when the plate-shaped fins  122  of the pillar part  120  have such a wide fin pitch as allows the uniform air convection. The thin plate  132  is thinner than the plate-shaped fin  122 , and does not prevent the air natural convection. 
     The thin plate  132  is made, for example, of such a material having high thermal conductivity as aluminum. The thin plate  132  is so thin that its weight would not be problematic, and thus may use another material having high thermal conductivity, such as copper, to enhance the heat radiation efficiency. When the thin plate  132  is made of aluminum, the thickness of the thin plate  132  is between 0.1 and 0.3 mm. When the thin plate  132  is made of copper, the thickness of the thin plate  132  is between 0.05 and 0.15 mm, about half that for aluminum. 
     Referring to FIGS. 9 and 10, the thin plate  132  may be replaced with a thin plate  132   a  that has a plurality of raised pieces  133 . FIG. 9 is a schematic sectional view of the thin plate  132   a  as a variation of the thin plate  132 . FIG. 10 is an enlarged perspective view of a circle shown in FIG.  9 . The raised piece  133  is provided on a plane area  136  of the thin plate  132   a , which is not subject to bending. The raised piece  133  is formed by forming a notch  135  in the plane area  136  of the thin plate  132   a , raising a top of the notch  135 , and deforming the plane area  136 . Each plane area  136  may form a plurality of raised pieces  133 . The raised pieces  133  are preferably formed on each plane area  136  of the thin plate  132   a . The thin plate  132   a  uses the raised pieces  133  to disturb airflow that convects on the thin plate  132 , and thus promotes turbulence and enhances the heat conductivity. Therefore, the raised pieces  133  promote the air convection on the thin plate  132   a , and assist in enhancing the heat radiation efficiency. The thin plate  132  may exhibit this operation by forming a projection on its surface, and thus is not limited to the above embodiment. 
     The raised pieces  133  on the thin plate  132   a  have an effect to introduce the air that convects on the thin plate  132   a  into the notch  135 . In other words, the airflow may be expanded simply by providing a perforation in the thin plate  132 . The air introduced through the vents  128  ascends vertical to the heat receiving part  110 , and the raised pieces  133  in the instant embodiment assist the air in passing through the notch  135 . Therefore, the raised pieces  133  also promote the air convection on the thin plate  132   a , and enhance the heat radiation efficiency. 
     The side plate  170  is a frame that encloses the plate-shaped fins  122  and the thin plate  132  located at the outermost plate-shaped fin  122 , as best shown in FIGS. 2 to  4 . The side plate  170  is formed with approximately the same thickness as the plate-shaped fin  122 . The side plate  170  has a shape by adhering four plates, or a hollow square pole. A provision of the side plate  170  would be able to prevent leakage of wind from the outermost thin plates  132 . In other words, the side plate  170  maintains the air channel, and controls the airflow at the radiating part  130  (in particular, near the thin plate  132  located at the outermost part). This side plate  170  is especially effective when the heat sink  100  is provided with a fan (not shown). The side plate  170  may radiate the heat conducted from the pillar part  120  and the thin plate  132  due to the heat conduction associated with the air convection. 
     The air convection is promoted at the side of the thin plate  132  located at both ends compared with the center part of the radiating part  130 . Therefore, as shown in FIG. 11, the outermost thin plates  132  of the plate-shaped fin  122  may be replaced with a thin plate  132   b  shown in FIG.  11 . Here, FIG. 11 is a schematic perspective top view of a heat sink  100  having the thin plate  132   b  as another variation of the thin plate  132  shown in FIG.  1 . The thin plate  132   b  is bent so that an interval smaller than the thin plate  132  between the plate-shaped fins  122 . The thin plate  132   b  has a surface area larger than that of the thin plate  132 , and thus expands the heat radiation area effectively. As discussed above, since the air convection is promoted at the side of the thin plates  132   b  located at both ends, a narrow interval of the thin plate  132   b  does not weaken the air convection. 
     The heat radiator part  130  may replace the side plate  170  with a side plate  17   a  shown in FIGS. 12 to  14 . Here, FIG. 12 is a schematic plane view of the heat sink  100  having the side plate  170   a  as a variation of the side plate  170  shown in FIG.  1 . FIG. 13 is one schematic side view of the heat sink  100  shown in FIG.  12 . FIG. 14 is another schematic side view of the heat sink  100  shown in FIG.  12 . The side plate  170   a  is formed higher than the side plate  170 , and as high as the plate-shaped fin  122 . Therefore, the side plate  170  encloses the pillar part  120  entirely. However, the side plate  170   a  at the side orthogonal to the plate-shaped fin  122  is formed as high as the side plate  170  at a portion  172  corresponding to the pillar part  120  so as not to prevent the air inflow to or near the center of the heat sink  100 . In this state, the outermost thin plate  132   c  of the pillar part  120  is longer than the thin plate  132  between the plate-shaped fins  122 . More specifically, the thin plate  132   c  is as high as the side plate  170   a . The thin plate  132   c  may be formed higher than the thin plate  132  by elongating the side plate  170   a , and the surface area of the radiating part  130  may be expanded further. As discussed, since the air convection is promoted at the side of the thin plate  132   c  located at both ends, the long side plate  170  and thin plate  132  do not weaken the air convection near the thin plate  132   c.    
     On the other hand, referring to FIG. 15, the heat sink  100  may have a cavity  140  different from the shape shown in FIGS. 11 to  14 . Here, FIG. 15 is a schematic sectional view of the heat sink  100  shown in FIG. 1 provided with the cavity  140 . The cavity  140  is a shape convex cavity projecting down at the side opposite to the heat receiving part  110  near the center part of the radiating part  130  and the pillar part  120 . A provision of this cavity  140  would shorten the radiating part  130  near the center part. Therefore, the air convection is promoted near the center part of the radiating part  130  and provides the enhanced heat radiation efficiency when compared with a structure without the cavity  140 . Referring to FIG. 16, this shape is effective when the fan  150  is provided  150 . FIG. 16 is a schematic sectional view of the heat sink  100  shown in FIG. 15 provided with a fan  150 . When the top of the heat sink  100  is provided with the fan  150 , the fan center part  152  is such a center of rotation of the fan  150 , and causes less air convection. However, a provision of the cavity  140  would be able to introduce the air from a fan end  154 , and improve the heat radiation efficiency of the radiating part  130  (especially at the center part). The fan  150  is also called a cooler, and protects the CPU  210  from the heat by compulsorily radiating the heat. A lid is preferably provided to reduce noises associated with a rotation of the fan  150 . 
     The fin  122  and the radiating part  130  are compulsorily cooled by rotating the fan  150  and generating the airflow. The fan  150  includes a motor portion (not shown), a propeller portion  151  fastened to the motor portion. The motor portion typically includes an axis of rotation, a bearing provided around the axis of rotation, a bearing house, and a magnet making up a motor, but since any structure known in the art may be applied to the motor portion  132 , a detailed description will be omitted. In order to prevent heat transfer to the bearing house, a thermal insulation portion is preferably formed on an inner wall surface of the bearing house. The thermal insulating portion is, for example, formed of such a material having low thermal conductivity as fluoroplastic and silicon resin thin films. 
     The propeller portion  151  includes a desired number of rotor blades each forming a desired angle. The rotor blades may be so oriented to form equal or unequal angles, and have a desired dimension. The motor portion and propeller portion  151  in the fan  150  may be separable or non-separable. An illustration of wiring connected with the fan  150  is omitted. When a perforation or intake is formed in the space  202  shown in FIG. 1, the fan  150  may take in air from the both sides of the motherboard  200  through the perforation. 
     As discussed above, the heat sink  100  includes three parts, i.e., the heat receiving part  110 , pillar part  120 , and radiating part  130 , enlarges the heat radiation area without disturbing the air convection, and improves the heat radiation efficiency. In this embodiment, the plate-shaped fin  122  of the pillar part  120  integrates the upper part  124  with the lower part  123 , although the upper part  124  may be detachable from the lower part  123  in the plate-shaped fin  122  and only the lower part  123  constructs the pillar part  120 . In other words, the radiating part  130  includes the upper part  124  of the plate-shaped fin  122  and the thin plate  132 . The radiating part  130  in this structure may properly vary its size and shape in accordance with the intended heat radiation performance. Of course, this state maintains the heat transferable from the pillar part  120  to the radiating part  130 . In use, the pillar part  120  is adhered to the radiating part  130 . 
     Referring to FIG. 17, it is apparent that the inventive heat sink  100  has superior heat radiation performance or cooling performance to that of the conventional heat sink  600 . Here, FIG. 17 is a view that compares cooling performance of the conventional heat sink  600  with that of the inventive heat sink  100 . In FIG. 17, the conventional heat sink is shown like a rhomb, the heat sink  100  shown in FIG. 1 is shown as a triangle, and the heat sink  100  shown in FIG. 12 is shown as a square. The abscissa axis denotes a fin pitch (mm), while the ordinate axis denotes the cooling performance (W). The inventive fin pitch is an interval between adjacent pillar parts. As understood from FIG. 17, the inventive heat sink  100  has superior cooling performance to that of the conventional heat sink  600 . A large fin pitch value slightly drops the cooling performance, whereas the conventional heat sink  600  remarkably lowers cooling performance with fin pitch. In other words, the enlarged fin pitch in the conventional heat sink  600  would lead to a smaller heat radiation area and clearly lower the cooling performance. It is understood that the present invention maintains the heat radiation area at the thin plates  132  and side plate  170 , and the enlarged interval between pillar parts  120  do not lower the cooling performance so much. 
     Turning back to FIG. 1, a description will be given of the PC  300  to which the inventive heat sink  100  is applicable. The PC  300  has a housing (not shown), and accommodates the motherboard  200  and a hard disc drive (“HDD”) and floppy disc drive (“FDD”) (not shown). The instant embodiment uses the desktop PC, but the PC  300  may be a tower type. The PC  300  includes a display as an output part (not shown), and a keyboard and mouse as an input part (not shown). The display, keyboard, and mouse may use any technology known in the art, and a detailed description will be omitted in this specification. 
     The motherboard  200  typically includes a socket (not shown) for attaching the CPU  210  and a memory, and an expansion slot to which an expansion card is attached. Each part may be electrically connected by attaching the CPU  210  as a control part and a memory (not shown) as a main storage to the motherboard  200 . The socket for attaching the CPU  210  covers both a socket and a slot, and a shape of the socket is not limited. Similarly, a shape of the socket for the memory is not limited. 
     The motherboard  200  mounted with the CPU  210  has the heat sink  100  on the CPU  210  at the side opposite to the motherboard  200 . The heat sink  100  surface-contacts the CPU  210  through the heat receiving surface  12  of the heat receiving part  110 . The heat sink  100  and the CPU  210  are fixed together by a clip (not shown). This clip holds the heat receiving part  110  and the CPU  210  using as the vent  128  of the pillar part  120  for a perforation of the clip. The heat sink  100  may use any structure that has been discussed above, and a detailed description will be omitted. The fan  150  may be provided, as shown in FIG. 16, to the heat sink  100  at the side opposite to the CPU  210  so as to enhance the heat radiation efficiency. Whether the fan  150  is provided is optional and determined by the intended cooling performance. The fan  150  may use a type that blows up the air from the side of the heat receiving part  110  to the side of the radiating part  130 , or a type that blows up the air from the radiating part  130  to the heat receiving part  110 . 
     The PC has a HDD and FDD as an auxiliary storage. The HDD is a unit that moves an arm on a disc to which a magnetic material is attached for reading and writing. The HDD and FDD may use any technology known in the art, and a description thereof will be omitted. 
     In operation, a user of the desktop PC  300  executes a program stored in the HDD manipulating the keyboard and/or mouse. The CPU  210  downloads necessary data from the HDD and the ROM (not shown) to the memory. The heat generated from the CPU  210  transfers to the radiating part  130  of the heat sink  110  through the heat receiving part  110  and the pillar part  120 . As a result, the heat is radiated from surfaces of the thin plate  132  and side plate  170  of the radiating part  130  (air cooling). Of course, the heat is radiated from the radiating surface  114  of the heat receiving part  110  and the pillar part  120  due to the heat conduction associated with the air convection. Blast from the fan  150  shown in FIG. 16 would compulsorily cool the radiating part  130 . 
     Further, the present invention is not limited to these preferred embodiments, and a various variations and modifications may be made without departing from the spirit and scope of the present invention. If required, the side plate  170  and other members may include a hollow bottom portion having the bottom surface  124 , in which cooling water or other refrigerants (e.g., fleon, alcohol, ammonia, galden, and flon) are contained to form a heat pipe plate. In addition, the side plate  170  and other members, if necessary, may be connected with an external heat pipe, or the like. This heat pipe may include a pipe with a difference of elevation made of aluminum, stainless, copper, or the like. The pipe has a wick material made of glass fiber, reticular thin copper wire, or the like affixed inside, and under reduced pressure, stores cooling water or other refrigerants. The cooling water cools exoergic components by repeating the following cycle: having obtained heat from the exoergic components in a lower position, the cooling water is vaporized and moves up to a higher position, and then is spontaneously or forcefully cooled in the higher position, liquefied, and returns to the lower position. The heat pipe when connected to a specific exoergic source would cool the source efficiently or intensively. 
     The inventive heat sink spaces the heat receiving part from the radiating part by a certain height, and allows air inflow to the radiating part in this height. A structure that provide a weight approximately below the head with respect to the balancer section, and a structure that bends and spaces the balancer section from the disc may mechanically stabilize the weight balance of the balancer section, and effectively reduce the torsion. Moreover, use of the preamp IC for the weight would be able to improve the electric characteristics. Even when the thin plate provided on the radiating part reduces the number of pillar parts, a sufficient heat radiating area may be maintained and the heat radiating efficiency may be enhanced in comparison with the conventional one. When the thin plate is bent to form a corrugated shape and/or to form a narrow bending interval, the surface area and consequently the heat radiation area may increase. The raised pieces on the thin plate may disturb the airflow, and promote the convection at the radiating part. The increased number of the pillar parts and a shape of the pillar part may promote the air convection and improve the heat radiation efficiency.