JP6102424B2 - Cooling structure - Google Patents

Description

  The present invention relates to a cooling structure for cooling electronic devices such as semiconductors and motors.

As this type of prior art, there is one disclosed in Patent Document 1 under the name of “cooling device”.
The cooling device disclosed in Patent Document 1 includes a plurality of heat dissipating members extending in a direction away from the electronic component, and the cooling fluid passes between the heat dissipating members so that the electronic component Cooling is performed, and the lengths of the plurality of heat dissipating members are formed so as to become shorter as the heat conduction temperature due to heat generation of the electronic component becomes lower.

  In addition, it is described that the lengths of the plurality of heat dissipating members are formed so as to be shorter from the central part toward the end part along the flow direction of the cooling fluid.

JP 2003-8264 A

  However, the cooling device described in Patent Document 1 performs cooling by extending a plurality of heat dissipating members in a direction away from the electronic component and increasing a contact area with the heat dissipating member. Yes, it is an obstacle to miniaturization.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cooling structure that can reduce pressure loss and improve heat transfer, and can be reduced in size and simplified.

The cooling structure according to the present invention for solving the above-described problems cools a heating element by causing a cooling fluid to flow in contact with the heating element or a substrate on which the heating element is arranged.
Then, the heating fluid flowing in contact with the cooling fluid or the first fluid contact surface of the substrate on which the heating element is disposed and the second fluid contacting surface opposite to the first fluid contact surface, A vortex flow generator that extends in a direction intersecting the flow direction and generates a vortex flow according to the flow rate of the cooling fluid is formed, respectively.
The vortex flow generation unit is a plurality of concave portions arranged at predetermined intervals,
Empirical formula of the pipe friction coefficient calculated from the shear velocity uτ = (τω / ρ) 1/2 calculated from the shear stress τω and fluid density ρ, and the flow velocity u, density ρ, and Reynolds number Re. Cf = τω / (0.5ρu2) = 0.73Re−0.25 and the dimensionless value W + = Wuτ / ν using kinematic viscosity ν are set to 25 to 300 .

  In this configuration, the two vortex flow generating portions formed to face each other, the first flow contact surface that is in contact with the cooling fluid of the heating element or the substrate on which the heating element is disposed, and the first flow contact. A vortex flow is generated in the cooling fluid flowing in the vicinity of the second flow contact surface facing the surface.

  According to the present invention, the two vortex flow generating portions formed to face each other cause a vortex flow in the cooling fluid flowing in the vicinity of the first flow contact surface and the second flow contact surface. The pressure loss can be reduced and the heat transfer can be improved, and the size and simplification can be achieved.

It is explanatory drawing which shows the structure of the cooling system to which the cooling structure which concerns on one Embodiment of this invention is applied. (A) is sectional drawing which follows the II line | wire shown in FIG. 1 which shows the structure of the inverter which makes a part of cooling system, (B) is explanatory drawing of the flow-contact surface of a cooler. It is sectional drawing which follows the II-II line | wire shown to FIG. 2 (A). It is the elements on larger scale which show the detail of two vortex flow production | generation parts. It is a graph which shows the relationship between a heat transfer coefficient and pressure loss. 3 is a bar graph showing heat transfer performances of Comparative Example 1, Comparative Example 2, Reference Example 1, and Example 1. FIG. (A) is explanatory drawing which shows the vortex flow generation part which concerns on a 1st modification, (B) is explanatory drawing which shows the vortex flow generation part which concerns on a 2nd modification, (C) is 3rd Explanatory drawing which shows the vortex flow generation part which concerns on a modification, (D) is explanatory drawing which shows the vortex flow generation part which concerns on a 4th modification.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings. FIG. 1 is an explanatory diagram showing a configuration of a cooling system to which a cooling structure according to an embodiment of the present invention is applied, and FIG. 2 (A) shows a configuration of an inverter forming a part of the cooling system, shown in FIG. Sectional drawing along the II line, (B) is explanatory drawing of the flow-contact surface of a cooler. 3 is a cross-sectional view taken along the line II-II shown in FIG. 2A, and FIG. 4 is a partially enlarged view showing details of two vortex flow generators.

  As shown in FIG. 1, the cooling system A according to an example includes a radiator 10, a water-cooled motor 11, a DC-DC converter 12, an inverter 20, an electric pump 13, and a controller B.

The water-cooled motor 11, the DC-DC converter 12, the inverter 20, and the electric pump 13 are connected to the output side of the controller B and are appropriately controlled.
The controller B includes a CPU (Central Processing Unit), an interface circuit, and the like, and exhibits a required function by executing a predetermined program.

  The inverter 20 shown in the present embodiment is a power converter that electrically generates AC power from DC power. As shown in FIG. 2A, the water jacket 21, a cooler 22 as a base material, In this structure, an insulating material 23, a bus bar 24 made of copper or the like, a solder layer 25, a heat buffer plate 26 made of copper / molybdenum, a solder layer 27, and a semiconductor chip 30 as a heating element are sequentially laminated. Yes.

The water jacket 21 has a U-shaped cross-section with an open upper surface, and the cooler 22 to which the cooling structure according to the embodiment of the present invention is applied so as to close the upper surface opening 21a. It is placed.
The water jacket 21 has a cooling fluid inflow side wall 21d with an inflow port 21e for allowing cooling fluid to flow in, and a cooling fluid outflow side wall 21f with an outflow port for allowing cooling fluid to flow out. 21 g is formed.
A cooling fluid flows through the water jacket 21 in the direction indicated by “α” in FIGS. 1 and 2 through the inlet 21e and the outlet 21g.

The cooler 22 is formed as a plate body, and the cooling structure according to the embodiment of the present invention is adopted for the first flow contact surface 22 a facing the water jacket 21.
A cooling structure according to an embodiment of the present invention has a function of cooling a semiconductor chip 30 by causing a cooling fluid to flow through a cooler 22 as a base material on which a semiconductor chip 30 as a heating element is disposed. It is.

  In the present embodiment, the first flow contact surface 22a that flows into the cooling fluid of the cooler 22 in which the semiconductor chip 30 is disposed and the second flow contact surface 21b that faces the first flow contact surface 22a. The vortex flow generators C1 and C2 are formed that extend in a direction intersecting the flow direction α of the cooling fluid and generate a vortex flow according to the flow rate of the cooling fluid.

A semiconductor chip 30 as a heating element is placed on the cooler 22 through the insulating material 23, bus bar 24, solder layer 25, buffer plate 26, and solder layer 27.
The buffer plate 26 is for buffering the difference in linear expansion coefficient with the semiconductor chip 30.

The vortex flow generating portion C1 is formed by continuously forming a plurality of semicircular grooves 22b as concave portions on the flow contact surface 22a of the cooler 22 at a predetermined interval.
In the present embodiment, two adjacent grooves 22b, 22b are formed at a predetermined interval at which the inner walls that define them intersect.

“To form the recesses (grooves 22b) continuously” includes not only the arrangement in which the inner walls of adjacent recesses (grooves 22b) intersect but also the form in which the inner walls of these adjacent recesses do not intersect. .
In the case where the inner walls of the recesses do not intersect with each other, it is preferable that the ends of the inner walls of adjacent recesses are smoothly continuous with a curved surface or the like. In this way, if the ends of the inner wall are smoothly continuous with a curved surface or the like, it is easy to process.

“Inner walls intersect” means that when the recesses (grooves 22b) have a semicircular cross section, the inner wall surfaces are arranged in the first flow as in the case where they are arranged at a constant interval for each of these diameter dimensions. In addition to a mode of contacting on the contact surface 22a, a mode of arranging at intervals equal to or smaller than the diameter dimension is included. In this case, the inner peripheral wall surfaces of adjacent grooves intersect at the first flow contact surface 22a and below.
The cross-sectional shape of the recess is not limited to the semicircular cross-section described above, and may be irregular, and may be arranged in combination.
That is, it is sufficient if it is a recess that generates a vortex according to the flow rate of the cooling fluid.

The “predetermined interval” includes both a constant interval and a plurality of concave portions that are all or a part of which are irregularly spaced.
By arranging two adjacent grooves 22b, 22b at a predetermined interval where the inner walls that define them intersect each other, more grooves 22b can be formed, and more vortex flows can be generated. it can.

(1) The maximum height H (see FIG. 2) of the groove (concave portion) 22b is calculated from the Reynolds number Re and the representative length d, which are flow conditions, and the laminar low layer thickness δ _b = 63.5 near the wall surface. / (Re ^7/8 ) × d.

(2) The opening width W of the groove 22b is calculated from the shear rate u _τ = (τ _ω / ρ) ^1/2 calculated from the shear stress _tw and the fluid density ρ, the flow velocity u, the density ρ, and the Reynolds number Re. An empirical formula for tube friction coefficient C _f = τ _ω /(0.5ρu ² ) = 0.73Re ^−0.25 and kinematic viscosity ν is used to make the dimension W ⁺ = Wu _τ / ν is 25 to 300. The range.

(3) The maximum height H of the groove 22b is made smaller than the distance X (see FIG. 2) from the flow contact surface 22a to the opposite flow contact surface 21b.
(4) The representative length d = 4 A / L calculated from the minimum channel cross-sectional area A of the channel cross-section orthogonal to the flow direction α of the cooling fluid and the maximum wetting slip length L is increased.
The minimum flow path cross-sectional area A is a cross-sectional area defined by the contour line segments L1, L2, L3, and L4 shown in FIG.
The contour line segments L1 and L3 have a length corresponding to the interval between the tops of the convex portions 21d and 22c, and the contour line segments L2 and L4 are the lengths of the grooves 21c and 22b. The projections 21d and 22c (see FIG. 4) are passed through.
As shown in FIG. 3, the “wetting contact length L” is the length of the contour line in contact with the cooling fluid in the flow path section defined by the contour line segments L5, L6, L7, and L8.
The contour line segments L5 and L7 have a length corresponding to the distance between the bottoms of the recesses 22b and 21c, and the contour line segments L6 and L8 are the lengths of the grooves 21c and 22b. It passes through the bottom of the recesses 21d and 22c.

(5) Although the representative length d = 4 A / L is set to 0.004 or more, the representative length d = 4 A / L is preferably set to 0.007 or more.
(6) A value W + obtained by making the width of the inner portion of the direction β perpendicular to the flow direction α of the cooling fluid in the groove 22b dimensionless is in the range of 40 to 150.

(7) The length of the convex portion with respect to the flow direction α of the cooling fluid becomes smaller toward the tip on the convex portion side, the region where the tip of the convex portion is flat with respect to the flow direction is small, and the uneven shape is the cooling fluid. It is continuous with respect to the flow direction.

The vortex flow generator C2 extends in a direction intersecting the flow direction α of the cooling fluid and generates a vortex flow according to the flow speed of the cooling fluid, as with the vortex flow generator C1 described above. It is formed on the bottom wall surface (second flow contact surface) 21b of the water jacket 21.
In other words, the vortex flow generating portion C2 is formed on the bottom wall surface (second flow contact surface) 21b that is in flow contact with the cooling fluid and is opposed to the first flow contact surface 22a of the cooler 22. ing.

The vortex flow generation part C2 is formed by forming a semicircular groove 21c as a plurality of recesses on the bottom wall surface 21b at a predetermined interval.
In the present embodiment, the two adjacent grooves 21c and 22b are formed at a predetermined interval at which the inner walls that define them intersect, and satisfy the above conditions (1) to (7). ing.

In the present embodiment, as shown in FIG. 4, the grooves 22b and 21c having a constant curvature as the plurality of recesses described above, and the protrusions 21d formed between these grooves 22b and 21c, 22c is coupled to the first and second flow contact surfaces 22a and 21b at a constant interval P1.
The convex portions 21d and 21c are formed from curved surfaces having a radius of curvature of 0.2 mm or more at each end.

By forming each tip of the convex portions 21d and 22c formed between adjacent concave portions into a curved surface having a constant radius of curvature, wear due to erosion can be suppressed and processing of the vortex flow generating portions C1 and C2 can be performed. It can be done easily.
In addition, the occurrence of mold cracking and chipping can be suppressed, and since there is no corner at the tip of the convex portion, the average film thickness can be easily managed.
Furthermore, when the curvature radius of each front-end | tip of convex part 21d, 22c shall be 0.2 mm or more, it is preferable when performing wire cut electric discharge machining.

FIG. 5 is a graph showing the relationship between the heat transfer coefficient and the pressure loss. In FIG. 5, the relationship between the vortex flow generator C1 and the vortex flow generator C2 is as follows. In addition, a vertical axis | shaft is a heat passage coefficient and a horizontal axis is a pressure loss.
<Comparative example>
Flat-Flat ... Form in which neither the vortex flow generator C1 nor the vortex flow generator C2 is provided ... Indicated by a purple circle in the figure.
Flat-R0.2: Form in which only the vortex flow generation unit C2 is provided without providing the vortex flow generation unit C1, which is indicated by a blue circle in the drawing.
“R0.2” indicates that the radius of the groove 21c is 0.2 mm.
Flat-R0.5: Form in which the vortex flow generation unit C1 is not provided, but only the vortex flow generation unit C2 is provided ... Indicated by an orange circle in the drawing.
“R0.5” indicates that the radius of the groove 21c is 0.5 mm.
Flat-R1... Form in which only the vortex flow generation section C2 is provided without providing the vortex flow generation section C1...
“R1” indicates that the radius of the groove 21c is 1.0 mm.
<Reference example>
R0.5-Flat: Form in which only the vortex flow generator C1 is provided without providing the vortex flow generator C2, which is indicated by a purple triangle in the figure.
“R1” indicates that the radius of the groove 22b is 1.0 mm.

<Example>
R0.5-R0.2: Form in which vortex flow generators C1, 2 are provided: Indicated by blue triangles in the figure.
“R0.5” indicates that the radius of the groove 22b is 0.5 mm, and “R0.2” indicates that the radius of the groove 21c is 0.2 mm.
R0.5-R0.5... Form in which the vortex flow generators C1 and C2 are provided.
“R0.5” indicates that the radius of the groove 22b is 0.5 mm, and “R0.5” indicates that the radius of the groove 21c is 0.5 mm.
R0.5-R1... Form in which the vortex flow generators C1 and C2 are provided. Indicated by purple triangles in the figure.
“R0.5” indicates that the radius of the groove 22b is 0.5 mm, and “R1” indicates that the radius of the groove 21c is 1.0 mm.

6 is a bar graph showing the heat transfer performances of Comparative Example 1, Comparative Example 2, Reference Example 1, and Example 1. FIG.
Comparative Example 1 is “Flat-Flat” shown in FIG. 5 described above, Comparative Example 2 is “Flat-R0.5” shown in FIG. 5, Reference Example 1 is “R0.5-Flat”, and Example 1 corresponds to “R0.5-R0.5” shown in FIG.
As is apparent from FIGS. 5 and 6, the heat transfer performance is greatly improved as compared with Comparative Examples 1 and 2 described above, and the heat transfer performance is about 10% as compared with Reference Example 1. It is clear that it has improved.

According to the cooling structure having the above configuration, the following effects can be obtained.
-Two vortex flow generators formed to face each other cause a vortex flow to flow in the cooling fluid flowing in the vicinity of the heating element or the substrate on which the heating element is disposed and in the cooling fluid in the vicinity of the bottom wall surface 21b of the water jacket 21. Thus, heat transfer can be promoted.

The maximum height H of the grooves 21c and 22b (recessed portions) is set to the laminar low layer thickness δ _b = 63.5 / (Re ^{7 /} near the wall surface calculated from the Reynolds number Re and the representative length d, which are flow conditions. ⁸ ) Since it is larger than xd, heat transfer can be promoted at a thickness equal to or greater than the thickness of the laminar low layer in the vicinity of the heat generator or the cooler 22 in which the heat generator is disposed.

Shear rate - the opening width W of the recess is calculated from the shear stress tau _omega fluid density _{ρ u τ = (τ ω /} ρ) 1/2 and flow rate u, the density [rho, pipe friction factor calculated from the Reynolds number Re The value W ⁺ = Wu _τ / ν made dimensionless by using the empirical formula C _f = τ _ω /(0.5ρu ² ) = 0.73Re ^−0.25 and the kinematic viscosity ν is in the range of 25 to 300. Therefore, heat transfer efficiency can be improved.

Since the representative length d = 4 A / L calculated from the minimum channel cross-sectional area A of the channel cross-section orthogonal to the flow direction of the cooling fluid and the maximum wetting length L is 0.004 or more, wall shear In addition, the increase in pressure loss can be reduced, and at the same time the groove width and flow path height of the first and second flow contact surfaces can be reduced. A base material can be reduced in size.

-By forming the grooves intersecting the flow direction of the cooling fluid, a vortex flow can be formed in the entire direction intersecting the flow direction of the first and second flow-contact surfaces, and heat transfer is thereby achieved. Promoted.

The heat transfer performance can be further improved by setting the width of the groove opened in the surface through which the cooling fluid flows to a predetermined value.
-By making the groove continuous in the direction orthogonal to the flow direction of the cooling fluid, the frequency of vortices in the flow direction can be increased, and heat transfer can be promoted.
-By making the groove recessed in the first flow contact surface of the cooler, it is possible to further reduce the size of the heating element and the base material to which the cooling structure is applied.

Next, a modified example of the vortex flow generation unit will be described with reference to FIGS. FIG. 7A is an explanatory diagram showing a vortex flow generator according to the first modification, FIG. 7B is an explanatory diagram showing a vortex flow generator according to the second modification, and FIG. Explanatory drawing which shows the vortex flow generation part which concerns on a 3rd modification, (D) is explanatory drawing which shows the vortex flow generation part which concerns on a 4th modification.
Note that the vortex flow generators C3 to C6 shown below are applicable as the vortex generators C1 and C2 described above.

The vortex flow generating part C3 according to the first modification shown in FIG. 7A is formed by forming linear grooves 40 obliquely at regular intervals in the flow direction α of the cooling fluid.
In the vortex flow generating section C4 according to the second modification shown in FIG. 5B, zigzag grooves 41 are orthogonal to the flow direction α of the cooling fluid at a constant interval.

The vortex flow generating section C5 according to the third modification shown in FIG. 3C is obtained by making the corrugated groove 42 orthogonal to the flow direction α of the cooling fluid at a constant interval.
The vortex flow generating section C6 according to the fourth modification shown in FIG. 4D is obtained by making a linear and intermittent groove 43 perpendicular to the cooling fluid flow direction α at a constant interval. .

The present invention is not limited to the above-described embodiments, and the following modifications can be made.
In the above-described embodiment, an example in which the cooling structure is applied to an inverter has been described as an example of the cooling structure that cools the heating element by circulating the cooling fluid through the base material on which the heating element is disposed. Of course, the present invention may be directly applied to a motor or the like as a heating element.

22 Cooler (base material)
30 Heating element (semiconductor chip)
C1 to C6 vortex flow generators 22a and 21b first and second flow contact surfaces

Claims (9)

In the cooling structure for cooling the heating element by flowing the cooling fluid to the heating element or the substrate on which the heating element is arranged,
Distribution of the cooling fluid on the first flow contact surface of the heating element or the base material on which the heating element is disposed and the second flow contact surface facing the first flow contact surface. A vortex flow generating section that extends in a direction intersecting with the direction and generates a vortex flow according to the flow rate of the cooling fluid is formed .
The vortex flow generation unit is a plurality of concave portions arranged at predetermined intervals,
Empirical formula of the pipe friction coefficient calculated from the shear velocity uτ = (τω / ρ) 1/2 calculated from the shear stress τω and fluid density ρ, and the flow velocity u, density ρ, and Reynolds number Re. Cf = τω / (0.5ρu2) = 0.73Re−0.25 and dimensionless value W + = Wuτ / ν using kinematic viscosity ν is 25 to 300 . The maximum height H of the recess is made larger than the laminar flow lower layer thickness δb = 63.5 / (Re7 / 8) × d near the wall surface calculated from the Reynolds number Re and the representative length d which are flow conditions. The cooling structure according to claim 1 . The cooling structure according to claim 1 or 2 , wherein the maximum height H of the concave portion is made smaller than the distance X from the opening surface to the opposing flow path surface. Claim 3 that the characteristic length d = 4A / L maximum being wetted perimeter calculated from the length L and the minimum flow path cross-sectional area A of the flow path cross section perpendicular to the flow direction of the cooling fluid and 0.004 or more Cooling structure. Wherein the characteristic length d = 4A / L maximum being wetted perimeter calculated from the length L and the minimum flow path cross-sectional area A of the flow path cross section perpendicular to the flow direction of the cooling fluid to claim 4 which is 0.007 or more Cooling structure. The cooling structure according to claim 3 or 5 , wherein a value W + obtained by making the width in a direction orthogonal to the flow direction of the cooling fluid in the recess dimensionless is in a range of 40 to 150. The cooling structure according to any one of claims 1 to 6 , wherein two adjacent concave portions are formed so that inner walls that define these intersect each other. The cooling structure according to any one of claims 1 to 7 , wherein a convex portion formed between adjacent concave portions is formed from a curved surface having a curvature radius of 0.2 mm or more at the tip of the convex portion. One of the two vortex flow generators is a groove formed in the first flow contact surface that is in contact with the cooling fluid of the heating element or the substrate on which the heating element is disposed, and the other is the first one. The cooling structure according to any one of claims 1 to 8 , wherein the cooling structure is a groove provided in a second flow contact surface facing the one flow contact surface.

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