Abstract:
Disclosed is a cooling apparatus for a semiconductor component having a coolant inlet flow path on a coolant flow path connecting a coolant inlet and a coolant outlet, the coolant inlet flow path having a diffuser shape, in which its cross-sectional area increases from a coolant inlet to a portion where cooling fins start to appear. In the cooling apparatus, the coolant inlet flow path meets the following equation: 
       ω= D {3/2+sin(α( x−A ))}.
 
     Here, ω is the radius of the diffuser, D is the diameter of the coolant inlet, x is a distance from the coolant inlet toward the cooling fins, α is an expansion slope coefficient of the diffuser in radians, and the sine of (α·A) is 1. 
     In the cooling apparatus for a compact and integrated semiconductor component, since the diffuser-shaped coolant inlet flow path extending from the coolant inlet to the cooling fins is designed in an optimal shape, it is possible to improve cooling efficiency and to reduce flow resistance to coolant flow.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a cooling apparatus for semiconductor components, and more particularly, to a cooling apparatus for semiconductor components having an optimal coolant inlet flow path structure capable of improving cooling efficiency and reducing resistance to coolant flow. This application claims priority from Korean Patent Application No. 10-2009-0069794 on Jul. 30, 2009 in the Korean Intellectual Property Office (KIPO), the disclosure of which is incorporated herein by reference in its entirety. 
         [0003]    2. Description of the Related Art 
         [0004]    With the recent requirements of compact design and improvement in the degree of integration of various elements of electronic components, power consumed by each component increases and high heat is generated in electronic elements. If heat generated in a semiconductor component during operation is not appropriately dissipated, the life time of the component may decrease while the performance of the component is rapidly deteriorated, and furthermore, the whole system may become damaged. Actually, about 70% to 75% of defective of semiconductor components have been caused by heat. 
         [0005]    Therefore, in order to minimize the problems caused by heat, it is required maximally dissipate heat generated in various high-integration semiconductor components. Typical mechanism for removing heat is a heat-sink having a group of cooling fins is attached to a semiconductor chip or a ceramic substrate. 
         [0006]    Examples of various variables related to the heat dissipation performance of a cooling apparatus having a heat sink include the shape and length of a cooling fin, the area of a heat-transfer surface of the cooling fin, the inlet geometry of a coolant and flow field, etc. 
         [0007]    A cooling apparatus for a semiconductor component should be configured to make a semiconductor component capable of operating at a predetermined temperature or lower when maximum power is applied during a predetermined time period after the semiconductor component reaches temperature saturation by continuous rated power. To this end, all various variables related to the heat dissipation performance should be appropriately adjusted. 
         [0008]    In particular, the shape of a coolant inlet flow path is examined the effects on cooling efficiency and resistance to coolant flow. Recently, in order to minimize pressure energy loss of a coolant the inlet geometry of a cooling system is designed in a diffuser shape. A reverse flow or stall phenomenon depends on a diffuser divergence angle and whether a diffuser shape is a cone shape or a straight pipe, which affects the stability degree of flow. 
         [0009]    In a case of an incompressible fluid, according to the energy conversion between pressure energy and kinetic energy, a decrease in a cross-sectional area causes an increase in the kinetic energy and a decrease in the pressure energy (Bernoulli&#39;s theorem). According to the related art, there is supposed a coolant inlet flow path structure having a structure in which, in order to enable coolant flowing into a cooling apparatus for a semiconductor component to overcome the resistance of cooling fins for heat transfer in a flow path, the cross-sectional area of the flow path is enlarged to compensate pressure. However, in this case, since reserve flow and vortex occurs, the effect is less dominant in improving cooling efficiency and reducing resistance to coolant flow. For this reason, it is difficult to form a coolant inlet flow path having a high cooling efficiency and small resistance to flow. 
         [0010]    Therefore, in order to improve the heat dissipation performance of a small-sized high-density semiconductor component, it is required to develop a coolant inlet flow path structure improving the cooling efficiency of a cooling apparatus and reducing resistance to coolant flow. 
       SUMMARY OF THE INVENTION 
       [0011]    In order to solve the above-mentioned problems, it is an object of the present invention to provide a cooling apparatus for a semiconductor component having an optimal coolant inlet flow path structure capable of improving cooling efficiency and reducing resistance to coolant flow. 
         [0012]    According to an aspect of the present invention, it is provided a cooling apparatus for a semiconductor component having a coolant inlet flow path on a coolant flow path connecting a coolant inlet and a coolant outlet, the coolant inlet flow path having a diffuser shape in which its cross-sectional area increases from the coolant inlet to a portion where cooling fins start to appear. In the cooling apparatus, the coolant inlet flow path meets the following equation: 
         [0000]      ω= D{ 3/2+sin(α( x−A ))}.
 
         [0013]    Here, ω is the radius of the diffuser, D is the diameter of the coolant inlet, x is a distance from the coolant inlet toward the cooling fins, α is an expansion slope coefficient of the diffuser in radians, and the sine of (α·A) is 1. 
         [0014]    The range of x may be 0≦x≦6.5D. 
         [0015]    Further, the range of A may be 3D≦A≦3.5D and the range of a may meet π/7D≦α≦π/6D. 
         [0016]    A number of cooling fins may be grouped to form a heat sink in the coolant flow path. 
         [0017]    The heat sink may be connected to a semiconductor component corresponding to the heat sink. 
         [0018]    According to another aspect of the present invention, it is provided a cooling apparatus for a semiconductor component including: a main body comprising a coolant flow path extending from a coolant inlet to a coolant outlet; and a number of cooling fins formed in the coolant inlet flow path to cross the coolant flow path. In this cooling apparatus, the coolant flow path includes a coolant inlet flow path formed in a diffuser shape whose cross-sectional area increases from the coolant inlet to a portion where the cooling fins start to appear and whose profile is a curve. 
         [0019]    The curve may be a sine function graph shape. 
         [0020]    A number of cooling fins may be grouped to form a heat sink in the coolant flow path. 
         [0021]    The heat sink may be connected to a semiconductor component corresponding to the heat sink. 
         [0022]    In the cooling apparatus for compact and integrated semiconductor components according to the embodiment of the present invention, since the diffuser-shaped coolant inlet flow path extending from the coolant inlet to the cooling fins is designed in an optimal shape, it is possible to improve cooling efficiency and to reduce resistance to coolant flow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a perspective view schematically illustrating a cooling apparatus for semiconductor components according to an exemplary embodiment of the present invention; 
           [0024]      FIG. 2  is a planar cross-sectional view illustrating the internal of the cooling apparatus shown in  FIG. 1 ; 
           [0025]      FIG. 3  is a drawing illustrating a variation in a flow field in cases (a) and (b) of where the coolant inlet flow path CP has different curved expanding pipe shapes; 
           [0026]      FIG. 4  is a drawing illustrating a variation in a flow field in cases (a) and (b) of where the coolant inlet flow path CP has different linear expanding pipe shapes; 
           [0027]      FIG. 5  is a drawing illustrating a temperature distribution around individual heat sinks when the shape of the coolant inlet flow path CP is a curved expanding pipe; 
           [0028]      FIG. 6  is a drawing illustrating a temperature distribution around individual heat sinks when the shape of the coolant inlet flow path CP is a linear expanding pipe; 
           [0029]      FIG. 7  is a plot illustrating temperature variations during a time period when the maximum continuous rated power is applied to comparison examples having various shapes of the coolant inlet flow paths; and 
           [0030]      FIG. 8  is a plot illustrating an equation representing the shape of the coolant inlet flow path CP according to the exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. 
         [0032]      FIG. 1  is a perspective view schematically illustrating a cooling apparatus for semiconductor components according to an exemplary embodiment of the present invention.  FIG. 2  is a planar cross-sectional view illustrating the internal of the cooling apparatus in shown  FIG. 1 . As shown in the drawings, a cooling apparatus  100  has a coolant inlet  120  formed on one side of a main body  110 , an coolant outlet  130  formed on another side of the main body  110 , and a coolant flow path  125  connecting the coolant inlet  120  and the coolant outlet  130 . A number of semiconductor components  140  are attached to the top surface of the main body  110 . 
         [0033]    Inside the main body  110 , as shown in  FIG. 2 , a coolant flow path  125  is formed to extend from the coolant inlet  120  to the coolant outlet  130 . In the coolant flow path  125 , there are provided a number of heat sinks H 1 , H 2 , H 3 , H 4 , H 5 , and H 6  including cooling fin groups. Each of the cooling fin groups is composed of a number of cooling fins F which are provided to cross the coolant flow path  125  and are connected to the semiconductor components  140 . The coolant flow path comprise a coolant inlet flow path CP having a diffuser shape, in which its cross-sectional area increases from the coolant inlet to a portion where cooling fins F of the heat sink H 1  (hereinafter, referred to as a first heat sink) start to appear. 
         [0034]    Meanwhile, a difference in heat dissipation performance according to whether the shape of the coolant inlet flow path CP is a curved expanding pipe or a linear expanding pipe occurs. The difference will be described below in detail. 
         [0035]      FIG. 3  is a drawing illustrating a variation in a flow field in cases (a) and (b) of where the coolant inlet flow path CP has different curved expanding pipe shapes.  FIG. 3  shows a flow field in a case of (a) where the ratio of a measurement location y to the diameter H hs  (=22.5 mm) of a portion of the coolant flow path  125  where the heat sink H 1  is positioned, that is, y/H hs  is 0.3, and a flow field in a case of (b) where the ratio of the measurement location y to the diameter H hs  (=22.5 mm) of the portion of the coolant flow path  125  where the heat sink H 1  is positioned, that is, y/H hs  is 0.7. Here, the measurement location y represents a distance from the top surface of the heat sink H 1 , having the cooling fins F attached thereto, to the bottom of the heat sink H 1 . 
         [0036]    As shown in  FIG. 3 , when the ratio y/H hs  is 0.3, the flow field is uniformly generated; however, when the ratio y/H hs  is 0.7, a reserve flow phenomenon occurs in a wide range from a portion where cooling fins F start to appear to the inlet. 
         [0037]      FIG. 4  is a drawing illustrating a variation in a flow field in cases (a) and (b) of where the coolant inlet flow path CP has different linear expanding pipe shapes.  FIG. 4  shows a flow field in a case of (a) where the ratio of a measurement location y to the diameter H hs  (=22.5 mm) of the portion of the coolant flow path  125  where the heat sink H 1  is positioned, that is, y/H hs  is 0.3, and a flow field in a case of (b) where the ratio of the measurement location y to the diameter H hs  (=22.5 mm) of the portion of the coolant flow path  125  where the heat sink H 1  is positioned, that is, y/H hs  is 0.7. Similarly, the measurement location y represents a distance from the top surface of the heat sink H 1 , having the cooling fins F attached thereto, to the bottom of the heat sink H 1 . 
         [0038]    Referring to  FIG. 4 , when the shape of the coolant inlet flow path CP is a linear expanding pipe, vortex is formed partially between the cooling fins F, in particular, in a portion where cooling fins F start to appear; however, reserve flow is not formed when the ratio y/H hs  is 0.3 or 0.7. 
         [0039]    As shown in the cases (a) and (b) of  FIG. 3 , when the shape of the coolant inlet flow path CP is a curved expanding pipe, heat energy generated by a heat emission element can be effectively removed through circulating flows caused by the occurrence of vortex or reserve flow. 
         [0040]    This difference in the heat-transfer performance according to the shape of the coolant inlet flow path CP will be described in more detail. 
         [0041]      FIG. 5  is a drawing illustrating a temperature distribution around individual heat sinks H 1 , H 2 , H 3 , H 4 , H 5 , and H 6  provided in a coolant flow path  125  of a cooling apparatus when the shape of the coolant inlet flow path CP is a curved expanding pipe.  FIG. 6  is a drawing illustrating a temperature distribution around individual heat sinks H 1 , H 2 , H 3 , H 4 , H 5 , and H 6  provided in a coolant flow path  125  of a cooling apparatus when the shape of the coolant inlet flow path CP is a linear expanding pipe. In  FIGS. 5 and 6 , numerical values inside the heat sinks represent temperatures (° C.). 
         [0042]    As easily seen from the temperature distributions shown in  FIGS. 5 and 6 , the temperatures around the individual heat sinks when the shape of the coolant inlet flow path CP is a curved expanding pipe are lower than those when the shape of the coolant inlet flow path CP is a linear expanding pipe. 
         [0043]    The following Table 1 shows a cooling performance comparison between the case where the shape of the coolant inlet flow path CP is a curved expanding pipe and the case where the shape of the coolant inlet flow path CP is a linear expanding pipe. 
         [0044]    Numerical values in Table 1 are checked results on whether a temperature of a power semiconductor component is equal to or lower than a target temperature (120° C.) due to heat dissipation on a first condition that the maximum rated power is applied 30 seconds after a power semiconductor component of an IGBT (integrated gate bipolar transistor module for MCU (motor control unit) and HDC (high side DC/DC converter) reaches temperature saturation by continuous rated power and on a second condition that electrical energy exceeding maximum rated power by 30% is applied 30 seconds after a power semiconductor component of an IGBT module for MCU (motor control unit) and HDC (high side DC/DC converter) reaches temperature saturation by continuous rated power. Here, the IGBT module is a power module of a driving system mounted a 40 kw diesel engine-motor hybrid electrical vehicle (HEV). 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 First condition 
                 Second condition 
               
               
                 Shape of coolant inlet flow path 
                 (° C.) 
                 (° C.) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Curved expanding pipe 
                 99.4 
                 111.75 
               
               
                 Linear expanding pipe 
                 103.24 
                 117.38 
               
               
                   
               
             
          
         
       
     
         [0045]    Referring to Table 1, when the shape of the coolant inlet flow path CP is a curved expanding pipe, the coolant inlet flow path CP is at temperatures remarkably lower than the target temperature (120° C.) due to heat dissipation on both of the first and second conditions and also has the highest temperature remarkably lower than when the shape of the coolant inlet flow path CP is a linear expanding pipe. 
         [0046]    Moreover, it can be verified that the case where the shape of the coolant inlet flow path CP is a curved expanding pipe is much more effective than the case where the shape of the coolant inlet flow path CP is a linear expanding pipe in that an error between a result obtained by fabricating a trial product and performing performance estimation and a temperature distribution of an actual product is about maximum 7% and design considering a safety factor is inevitable in the case where the shape of the coolant inlet flow path CP is a linear expanding pipe. 
         [0047]    In the exemplary embodiment of the present invention, considering the case where the shape of the coolant inlet flow path CP is a curved expanding pipe is much more effective than the case where the shape of the coolant inlet flow path CP is a linear expanding pipe, curved expanding pipes having various curve profiles have been formed and their effects have been verified. 
         [0048]      FIG. 7  is a graph illustrating temperature variations during a time period when the maximum continuous rated power is applied after a power semiconductor component of an IGBT module for MCU (motor control unit) and HDC (high side DC/DC converter), which is a power module of a driving system, reaches temperature saturation by continuous rated power, in comparison examples having various shapes of coolant inlet flow paths CP. 
         [0049]    In the drawing, first to fifth comparison examples represent cases where the profiles of coolant inlet flow paths CP are a linear function graph shape, a cosine function graph shape, an ellipse function graph shape, a sine function graph shape, and a parabolic function graph shape, respectively. As can be seen from the test results, the fourth comparison example in which the profile of the coolant inlet flow path CP is a sine function graph shape has the lowest pressure resistance and the highest cooling performance. 
         [0050]    As described above, considering that the coolant inlet flow path CP having a curved expanding pipe shape has better cooling performance and the profile of a sine function graph shape has the lowest pressure resistance and the highest cooling performance, in the embodiment of the present invention, the shape of the coolant inlet flow path CP is limited as follows. 
         [0051]    When w is the radius of the diffuser, D is the diameter of the coolant inlet, x is a distance from the coolant inlet toward the cooling fins, a is an expansion slope coefficient of the diffuser in radians, and the sine of (α·A) is 1; the shape of the coolant inlet flow path CP according to the embodiment of the present invention is determined to be a shape meeting the following Equation 1. When the sine of (α·A) is 1, ‘A’ means an x value of an inflexion point in a sine function appearing in Equation 1. 
         [0000]      ω= D{ 3/2+sin(α( x−A ))}  [Equation 1]
 
         [0052]    In Equation 1, x meets 0≦x≦6.5D and ‘A’ meets 3D≦A≦3.5D. 
         [0053]    Specifically, the shape of the coolant inlet flow path CP greatly varies according to the ‘A’ value (the location of the inflexion point). At this time, when the ‘A’ value is small, the cross-sectional area of the flow path may be rapidly enlarged, and when the ‘A’ value is large, the cross-sectional area of the flow path may be enlarged at a location too far from the coolant inlet. For this reason, it is required to appropriately select the ‘A’ value. 
         [0054]    In the embodiment of the present invention, the ‘A’ value is designed in a range of 3D≦A≦3.5D. In this case, α meets π/7D≦α≦π/6D. 
         [0055]    Specifically, in a first case of A=3D, sin(α·A)=1 can be written as sin(α·3D)=1 and thus α·3D becomes π/2. As a result, a becomes π/6D. In a second case of A=3.5D, sin(α·A)=1 can be written as sin(α·3.5D)=1 and thus α·3.5D becomes π/2. As a result, α becomes π/7D. Considering this point, a has the range of π/7D≦α≦π/6D. 
         [0056]    In the present invention, experiments on differences in cooling performance was conducted on a condition that the range of x was set to 0≦x≦6.5D to define the upper and lower limits thereof. 
         [0057]    The following Table 2 shows a cooling performance comparison according to upper and lower limits of x. Numerical values in Table 2 are checked results on whether a temperature of a power semiconductor component is equal to or lower than a target temperature (120° C.) due to heat dissipation on the first condition that the maximum rated power is applied 30 seconds after a power semiconductor component of an IGBT module for MCU (motor control unit) and HDC (high side DC/DC converter) reaches temperature saturation by continuous rated power and on the second condition that electrical energy exceeding the maximum rated power by 30% is applied 30 seconds after a power semiconductor component of an IGBT module for MCU (motor control unit) and HDC (high side DC/DC converter) reaches temperature saturation by continuous rated power. Here, the IGBT module is a power module of a driving system mounted a 40 kw diesel engine-motor hybrid electrical vehicle (HEV). 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Lower/upper 
                 First condition 
                 Second condition 
               
               
                   
                 limits of x 
                 (° C.) 
                 (° C.) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Inventive example 
                   0/6.5D 
                 99.4 
                 111.75 
               
               
                 First experimental 
                 0/7D 
                 103.09 
                 117.51 
               
               
                 example 
               
               
                 Second experimental 
                 0/6D 
                 103.83 
                 118.59 
               
               
                 example 
               
               
                 Third experimental 
                   0/7.5D 
                 101.92 
                 117.38 
               
               
                 example 
               
               
                   
               
             
          
         
       
     
         [0058]    Referring to Table 2, the inventive example having x in a range of 0≦x≦6.5D is at temperatures remarkably lower than the target temperature (120° C.) due to heat dissipation on both of the first and second conditions, as compared with the first to third experimental examples. Therefore, it can be seen that the cooling performance of the inventive example is the most effective. 
         [0059]    Moreover, it can be verified that cooling performance is the most superior when the range of x in a range of 0≦x≦6.5D in that an error between a result obtained by fabricating a trial product and performing performance estimation and a temperature distribution of an actual product is about maximum 7% and thus design considering a safety factor is inevitable in the cases of the first to third experimental examples. 
         [0060]    Although the embodiments of the present invention have been described above with reference to the accompanying drawings, they are used in a generic and descriptive sense only and not for purposes of limitation. It will be apparent to those skilled in the art that modifications and variations can be made in the present invention without deviating from the spirit or scope of the invention.