JP2017143094A - Heat sink, thermoelectric conversion module, method of manufacturing heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sink of high productivity and high heat dissipation, and a thermoelectric conversion module using the same.SOLUTION: A heat sink 40A has a structure where a base 10 and a heat dissipation fin 23, each composed of a porous metal, are integrated. In the heat sink 40A, a porous metal having a relatively low porosity is used for composing the base 10. Meanwhile, a porous metal having a relatively high porosity is used for composing the heat dissipation fin 23, so that a fluid 30 such as air or water can be fed inside, as a refrigerant. More specifically, porosity of the porous metal in the heat dissipation fin 23 is higher than that of the porous metal in the base 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heat sink, a thermoelectric conversion module using the heat sink, and a heat sink manufacturing method.

  In recent years, various devices and devices using heat generating elements such as semiconductor devices have been improved in performance and size, and accordingly, the heat generation density of the devices and devices has increased. Generally, a heating element such as a semiconductor device in an apparatus or an apparatus not only cannot maintain its performance when exceeding a predetermined temperature, but may be damaged in some cases. For this reason, appropriate temperature management by cooling or the like is necessary, and there is a strong demand for a technique for efficiently cooling a heat generating element such as a semiconductor device in which the amount of heat generated increases with improvement in processing performance.

  In such a technical background, as a method for efficiently cooling a heat generating element such as a semiconductor device, mounting a heat sink which is an enlarged heat transfer surface is widely performed. By flowing air, water, or the like as a cooling medium through the heat sink, it is possible to efficiently remove heat from a heating element such as a semiconductor device.

  As a method of manufacturing the heat sink, it is common to separately manufacture the heat dissipating fins and the base portion and braze them together. However, in such a manufacturing method, there is a problem that productivity is low because a process of brazing the heat dissipating fin and the base portion is necessary. Therefore, in order to solve such problems, a heat sink in which a heat radiating fin and a base portion are integrated has been proposed. For example, in the prior art described in Patent Document 1 below, by impregnating a ceramic into a ceramic sintered body whose porosity changes in the heat transfer direction, the substrate and the fin are integrated, and high thermal conductivity and low thermal expansion coefficient are obtained. It is said that the heat dissipation board provided can be manufactured in one step.

JP 2001-105124 A

  In the above-described conventional technology, the mounting surface of the semiconductor element corresponding to the base portion is formed of a ceramic single layer, and thus has a lower thermal conductivity than metal. Therefore, there is a problem that the heat exchange performance is lower than that of a general metal heat sink.

A heat sink according to the present invention includes a base portion made of a porous metal and a heat radiating fin made of a porous metal using the same metal as the base portion. The porosity is higher than the porosity of the porous metal in the base portion.
A thermoelectric conversion module according to the present invention includes the above heat sink and a thermoelectric element to which the heat sink is attached.
The method of manufacturing a heat sink according to the present invention includes preparing a first base having a predetermined porosity and a second base having a higher porosity than the first base, and the first base and the Metal powder is adhered to the second substrate, and the first substrate and the second substrate to which the metal powder is adhered are heated to a temperature equal to or higher than the melting point of the metal powder in contact with each other. To remove the first substrate and the second substrate and to bond the particles of the metal powder, thereby producing a heat sink in which the same porous metals having different porosities are integrated. To do.

  ADVANTAGE OF THE INVENTION According to this invention, a heat sink with high productivity and heat exchange performance and a thermoelectric conversion module using this can be provided.

It is a flowchart which shows the manufacturing process of the heat sink which concerns on one Embodiment of this invention. It is a perspective view which shows the outline | summary of the heat sink which concerns on the 1st Embodiment of this invention. It is the side view which looked at the heat sink which concerns on the 1st Embodiment of this invention from the flow direction of the fluid. It is a perspective view which shows the outline | summary of the heat sink which concerns on the 2nd Embodiment of this invention. It is the side view which looked at the heat sink concerning the 2nd Embodiment of this invention from the flow direction of the fluid. It is a perspective view which shows the outline | summary of the heat sink which concerns on the 3rd Embodiment of this invention. It is a perspective view which shows the outline | summary of the heat sink which concerns on the 4th Embodiment of this invention. It is a perspective view which shows the outline | summary of the thermoelectric conversion module which concerns on the 5th Embodiment of this invention. It is a side view of the thermoelectric conversion module which concerns on the 5th Embodiment of this invention.

  Hereinafter, a heat sink according to an embodiment of the present invention will be described in detail. First, the manufacturing method of the porous metal (porous metal) used in order to comprise the heat sink of this embodiment is demonstrated. As described below, the porous metal used in the heat sink of the present embodiment is manufactured by attaching a metal powder to a structure called a base, heating it to melt the metal powder, and removing the base. Is done.

  FIG. 1 is a flowchart showing a manufacturing process of a heat sink according to an embodiment of the present invention. In step S10, a base body and metal powder used for manufacturing the porous metal are prepared, and each is installed at a predetermined position in a manufacturing apparatus (not shown).

[Substrate]
A fine mesh-like skeleton is three-dimensionally connected to the substrate installed in step S10, and a structure having a large number of pores (voids) inside is used. This substrate is for supporting metal powder on the surface of the skeleton. In addition, since a base | substrate should decompose | disassemble and lose | disappear when heated, it is preferable to be comprised, for example with resin. Specifically, polyurethane foam is most commonly used as the substrate, but silicone resin or polyester resin foam can also be used. Alternatively, as long as it has the above-described structure and can be removed by heating, the substrate may be configured using other materials.

  As will be described later, in step S10, it is necessary to prepare and install a plurality of types of substrates having different porosity from each other in order to form the porous metal constituting the base portion and the radiation fin in the heat sink of the present invention. is there. The porosity of these substrates is selected according to the porosity of the porous metal constituting the heat sink to be manufactured.

[Metal powder]
The metal powder installed in step S10 is for adhering to the resin skeleton of the substrate. In consideration of the balance between thermal conductivity and specific gravity, for example, aluminum powder is preferably used as the metal powder. Alternatively, instead of aluminum powder, aluminum alloy powder previously alloyed by adding a component that strengthens aluminum may be used. For example, when an aluminum alloy powder obtained by alloying Al with an alloying element such as Cu, Mn, Mg, or Si is used, the skeleton of an aluminum-based porous body that is a porous metal is formed of an aluminum alloy. Therefore, the strength can be improved as compared with the case of using aluminum powder. Note that by adding alloying elements such as Cu, Mn, Mg, and Si to Al, the thermal conductivity is slightly lower than in the case of Al alone, but the thermal conductivity is sufficiently high to constitute a heat sink. Can be maintained. As the aluminum powder or the aluminum alloy powder, a commercially available powder such as one having an oxide film (alumina: Al ₂ O ₃ ) of about 10 mm on the surface can be used. Alternatively, other types of metal powder may be used.

  The metal powder such as aluminum powder or aluminum alloy powder is preferably as fine as possible in order to adhere closely to the fine resin skeleton surface of the substrate. As the particle size of the metal powder increases, the mass of each particle increases, which makes it difficult to adhere closely to the resin skeleton surface of the substrate, and also tends to drop off from the substrate even after adhesion. From such a viewpoint, in the production of the porous metal according to the present embodiment, it is preferable to use, for example, a metal powder having an average particle size of 50 μm or less as the metal powder to be attached to the resin skeleton of the substrate. Furthermore, it is preferable that the average particle size is 50 μm or less and does not contain powder having a particle size exceeding 100 μm. However, since Al is an active metal, it is difficult to handle an excessively fine powder. From this viewpoint, when using aluminum powder or aluminum alloy powder, it is preferable to use one having an average particle diameter of 1 μm or more, for example.

[Adhesion process]
In the attaching step of step S20, metal powder such as aluminum powder or aluminum alloy powder is attached to the resin skeleton of the substrate. Various methods conventionally used can be applied in this attaching step. The typical method is described below.

(1) Wet method This method creates a dispersion liquid in which a metal powder is dispersed in a dispersion medium, and immerses the base material in the dispersion liquid, and then dries the base material, so that the metal powder is applied to the skeleton surface of the base body. It is the method of making it adhere. As the dispersion medium, for example, a volatile liquid such as alcohol, or a liquid in which water is used as a solvent and a binder is dissolved therein can be used. In this case, a dispersant may be added to the dispersion medium so that the metal powder does not settle in the dispersion. Moreover, as a dispersion medium, you may use the solution of high molecular organic substances, such as a phenol resin.

(2) Dry method In this method, metal powder is applied to the skeleton surface of the substrate by imparting adhesiveness to the substrate and swinging the substrate in the powder of the metal powder or spraying the metal powder on the substrate. It is the method of attaching. In this method, for example, an adhesive solution such as an acrylic or rubber adhesive or an adhesive resin solution such as a phenol resin, an epoxy resin, or a furan resin is applied to the surface of the substrate to provide the substrate with adhesiveness. it can.

  As will be described later, in step S20, in order to form the porous metal constituting the base portion and the radiating fin in the heat sink of the present invention, a plurality of types of substrates installed in step S10 are in contact with each other. It is necessary to attach metal powder to these substrates. Alternatively, after attaching the metal powder in step S20, these substrates may be brought into contact with each other.

[Heating process]
In the heating process of step S30, the substrate on which the metal powder such as aluminum powder or aluminum alloy powder is adhered to the skeleton surface in the adhesion process of step S20 is heated to a temperature equal to or higher than the melting point of the metal powder in a non-oxidizing atmosphere. . In the temperature raising process up to this melting point, the resin substrate is decomposed, removed and disappears.

When aluminum powder or aluminum alloy powder is used as the metal powder, when the heating temperature exceeds the melting point of aluminum (660.4 ° C.) or the melting point of the aluminum alloy, the inside of each particle of these metal powders melts. That is, the surface of the aluminum powder or aluminum alloy powder is covered with the oxide film (alumina: Al ₂ O ₃ ) as described above. Since the melting point of alumina is 2072 ° C., which is higher than the melting point of aluminum or aluminum alloy, each particle of aluminum powder or aluminum alloy powder melts the inner aluminum or aluminum alloy without melting the oxide film on the surface. . The aluminum or aluminum alloy thus melted inside each particle breaks the oxide film on the surface and wets and covers the powder surface, and is mixed and bonded between the particles. At this time, the oxide film formed on the powder surface serves as a substitute skeleton, and the shape of the base skeleton is maintained. Further, the surface of the skeleton is relatively smooth due to the surface tension of the molten aluminum or molten aluminum alloy bonded to each other between the particles, so that the neck portion disappears and becomes a continuous metal surface. As a result, a porous metal having a structure similar to that of the substrate is generated.

  On the other hand, when the heating temperature is lower than the melting point of aluminum or aluminum alloy, a strong oxide film formed on the surface of these metal powders serves as a barrier, and bonding due to diffusion between particles of the powder is hindered. Sintering does not progress. Accordingly, the heating temperature needs to be higher than the melting point of aluminum or aluminum alloy.

Here, when the atmosphere in the heating step is an oxidizing atmosphere such as air, the molten aluminum or molten aluminum alloy exposed by breaking the oxide film is immediately oxidized, and this wets and covers the powder surface. As a result, mixing of molten aluminum or molten aluminum alloy generated from each particle of the powder is prevented, and bonding between the particles is inhibited. For this reason, it is desirable that the atmosphere in the heating step be a non-oxidizing atmosphere such as nitrogen gas or inert gas. Further, in the above heating step, since the purpose is not to remove the oxide film on the surface of the aluminum powder or aluminum alloy powder, it is not necessary to be a reducing atmosphere such as hydrogen gas or hydrogen mixed gas. However, since the reducing atmosphere is also a non-oxidizing atmosphere, the atmosphere in the heating process may be a reducing atmosphere. Furthermore, it is good also as a pressure reduction atmosphere (vacuum atmosphere) whose pressure is a predetermined value, for example, 10 < ^-3 > Pa or less.

  The upper limit of the heating temperature may be any temperature that exceeds the melting point of the aluminum powder or aluminum alloy powder adhered to the substrate. However, when heating at a temperature greatly exceeding the melting point, extra energy is required, and the viscosity of molten aluminum or aluminum alloy is lowered, so that the shape is easily lost. Therefore, it is preferable that the heating temperature not exceed the melting point, for example, up to the melting point + 100 ° C.

  When the heating process in step S30 is completed, the produced porous metal is cooled in step S40, and then the manufacturing process in FIG. 1 is completed.

  The three-dimensional network structure of the porous metal (aluminum-based porous body) manufactured by the above manufacturing method is such that the three-dimensional network structure of the substrate is maintained as it is. Therefore, by changing the three-dimensional network structure of the substrate, the three-dimensional network structure of the porous metal can be changed, and the porosity and pore size of the entire porous metal can be adjusted to the desired ones. Is possible. Specifically, a porous metal of 6 to 80 ppi (cell number / 25.4 mm) can be easily produced by setting the porosity to 85 to 95% and the pore size to 30 to 4000 μm.

  In the case where the aluminum-based porous body is composed of an aluminum alloy, a method of using a mixed powder obtained by mixing an aluminum powder and another metal powder as a raw material powder is also conceivable. For example, an aluminum-based mixed powder in which a component (Cu, Mg, etc.) that generates a eutectic liquid phase with Al is added to an aluminum powder as a simple powder or an aluminum alloy powder can be used as a raw material powder. The aluminum-based porous body can be manufactured by attaching this aluminum-based mixed powder to the surface of a substrate having a three-dimensional network structure and performing sintering at a temperature at which a eutectic liquid phase is generated. However, in such a manufacturing method, the distribution of the component elements in the aluminum-based porous material becomes non-uniform, and the aluminum oxide does not disperse inside the skeleton, so that it is difficult to obtain a desired strength.

  On the other hand, the distribution of the component elements in the aluminum-based porous material becomes uniform by using, as the raw material powder, the aluminum prealloy powder in which the component elements are alloyed in advance as described above instead of such a mixed powder. . In addition, aluminum oxide resulting from the manufacturing method is dispersed inside the skeleton. For this reason, high intensity | strength can be obtained compared with the method of sintering by a eutectic liquid phase using said aluminum type mixed powder.

  In addition, it is possible to arbitrarily change the shape of the porous metal by blowing a relatively high-speed gas on the porous metal or utilizing the centrifugal force or the weight of the porous metal itself during the heating step. it can. For example, a curved surface can be provided on the front surface, and the rear surface can be changed to a long and thin shape.

  Next, the heat sink of the present invention configured using the porous metal manufactured by the manufacturing method described above will be described.

(First embodiment)
FIG. 2 is a perspective view showing an outline of the heat sink 40A according to the first embodiment of the present invention. As shown in FIG. 2, the heat sink 40 </ b> A of the present embodiment has a structure in which the base portion 10 and the heat radiating fins 23 each made of a porous metal are integrated.

  The heat sink 40A is manufactured by integrally forming the porous metal constituting the base portion 10 and the porous metal constituting the radiating fins 23 using the manufacturing method as described above. Specifically, in step S10 of FIG. 1, a base for forming a porous metal to be the base portion 10 and a base for forming the porous metal to be the heat radiating fins 23 are prepared, and these are mutually connected. Installed in production equipment in contact with each other. Thereafter, in the attaching step of step S20, metal powder, preferably aluminum powder or aluminum alloy powder, is attached to each substrate. Alternatively, these substrates may be in contact with each other after the metal powder is deposited. With this contact state, these substrates are subjected to the heating process of step S30 to remove the substrate and bind the particles of the metal powder. As a result, a heat sink in which the base portion 10 and the radiation fins 23 are integrated as shown in FIG. 40A can be manufactured.

  In the heat sink 40A, a porous metal having a relatively low porosity is used as the porous metal constituting the base portion 10. Therefore, the base part 10 can be regarded as a substantially solid metal body. On the other hand, as the porous metal constituting the radiating fin 23, a metal having a relatively high porosity is used so that a fluid 30 such as air or water can flow inside as a refrigerant. That is, the porosity of the porous metal in the radiating fin 23 is higher than the porosity of the porous metal in the base portion 10. By configuring the heat sink 40A as described above, the base portion 10 of the heat sink 40A can be easily fixed to a heat generating body such as a semiconductor module to be radiated through a heat conductive sheet, a heat conductive grease, an adhesive, or the like. And by arrange | positioning the radiation fin 23 in the fluid 30, heat exchange can be performed between a heat generating body and the fluid 30, and a heat generating body can be removed efficiently. Contrary to the above, the heat sink 40A may be attached to the endothermic object, and the heat of the fluid 30 may be taken into the endothermic object via the heat sink 40A.

  FIG. 3 is a side view of the heat sink 40 </ b> A according to the first embodiment of the present invention viewed from the flow direction of the fluid 30. This side view shows the internal structure of the base portion 10 and the heat radiating fins 23.

  As shown in FIG. 3, the heat radiating fins 23 are made of a porous metal having a network structure 20 made of a fine metal and cavities 21 existing in the gaps of the network structure 20. When the temperature of the fluid 30 is higher than the temperature of the network structure 20 due to the fluid 30 flowing in the cavity 21, heat is transferred from the network structure 20 to the fluid 30. On the other hand, when the temperature of the fluid 30 is lower than the temperature of the network structure 20, heat is transferred from the fluid 30 to the network structure 20. Thereby, heat exchange can be performed efficiently between the radiation fins 23 and the fluid 30. In addition, in order to ensure the heat transfer area of the radiation fin 23, it is preferable that the porous metal which comprises the radiation fin 23 has a comparatively high porosity. For example, a porous metal having a porosity of about 95% can be used as the radiation fins 23.

  Similarly to the heat radiating fins 23, the base portion 10 is also made of a porous metal having a network structure and a cavity. Here, as shown in FIG. 3, the mesh structure in the base portion 10 is denser than the mesh structure 20 in the radiating fin 23, and there are few cavities existing in the gap. That is, the porous metal that forms the base portion 10 has a lower porosity than the porous metal that forms the radiating fins 23. For example, a porous metal having a porosity of about 50% can be used as the base portion 10. Thereby, as the heat transfer performance of the base part 10, the heat transfer performance comparable to a solid metal body can be obtained.

  As described above, the heat sink 40A of the present embodiment includes the base portion 10 made of a porous metal and the heat radiation fins 23 made of a porous metal using the same metal as the base portion 10. And the porosity of the porous metal in the radiation fin 23 is higher than the porosity of the porous metal in the base portion 10. Thereby, the heat sink 40A with high productivity and high heat exchange performance can be realized.

  In the heat sink 40A of the present embodiment described above, the thickness of the base portion 10, that is, the height in the vertical direction in the figure, is smaller than the thickness of the radiating fins 23 as shown in FIGS. preferable. Thus, heat transfer from the base portion 10 to the heat radiation fins 23 can be efficiently performed, the heat transfer area of the heat radiation fins 23 can be improved, and the heat sink 40A having high heat exchange performance can be obtained.

(Second Embodiment)
FIG. 4 is a perspective view showing an outline of a heat sink 40B according to the second embodiment of the present invention. Compared with the heat sink 40A of FIG. 2 described in the first embodiment, the heat sink 40B of the present embodiment shown in FIG. 4 has three heat radiating fin layers 231, 232, and 233 stacked and joined to each other. Is different. For the radiating fin layers 231 to 233, porous metals having different densities are used. That is, the porosity of the porous metal in the radiating fin 23 is configured to change along the thickness direction of the radiating fin 23.

  In general, when a refrigerant such as air or water is flowed through the heat radiation fins 23 as the fluid 30, the heat radiation amount of the heat radiation fins 23 decreases as the distance from the base portion 10 that is the heat receiving portion increases. This is called the fin efficiency of the radiating fin. In the heat sink 40B of the present embodiment, in consideration of the fin efficiency of the heat radiating fins 23, as shown in FIG. 4, the heat radiating fins 23 to 233 using porous metals having different densities are stacked. The density of the porous metal in is changed along the vertical direction. Here, it is preferable to select a porous metal used for the radiation fin layers 231 to 233 so that the density of the radiation fins 23 decreases as the distance from the base portion 10 increases, that is, the porosity increases.

  FIG. 5 is a side view of the heat sink 40B according to the second embodiment of the present invention viewed from the flow direction of the fluid 30. FIG. This side view shows the internal structure of the base portion 10 and the internal structure of the radiation fin layers 231 to 233 of the radiation fin 23.

  The radiating fin layers 231 to 233 are each composed of a porous metal having a network structure 20 made of a fine metal and a cavity 21 existing in a gap between the network structure 20. As shown in FIG. 5, a porous metal having the highest density, that is, the lowest porosity is used for the first radiating fin layer 231 closest to the base portion 10. On the other hand, a porous metal having the lowest density, that is, the highest porosity is used for the third radiating fin layer 233 farthest from the base portion 10. For example, porous metals having a porosity of about 75%, 85%, and 95% can be used as the radiation fin layers 231, 232, and 233, respectively. Thereby, heat exchange can be favorably performed between the radiation fins 23 and the fluid 30.

  Or you may select the porous metal used for the radiation fin layers 231-233 so that a density may become high, so that a porosity may become low, so that it may leave | separate from the base part 10 contrary to the above. As described above, when the density of the radiating fins 23 is decreased as the distance from the base portion 10 increases, more fluid 30 is contained in the radiating fins 23 on the blade tip side of the radiating fins 23, that is, on the side away from the base portion 10. Flowing. Therefore, there is a concern that the fluid 30 flows out to the upper part in the middle of passing through the radiating fins 23 and heat exchange cannot be performed appropriately between the radiating fins 23 and the fluid 30. In order to suppress this, contrary to the example of FIG. 5, in the radiation fin layers 231 to 233, the density of the radiation fins 23 increases as the distance from the base portion 10 increases, that is, the porosity decreases. What is necessary is just to set the density of a porous metal.

  As described above, in the heat sink 40 </ b> B of the present embodiment, the porosity of the porous metal in the radiating fin 23 is changed along the thickness direction of the radiating fin 23. Thereby, the structure of the radiation fin 23 can be optimized in consideration of fin efficiency and heat transfer. In the above example, the porosity of the porous metal in the radiating fin 23 is changed in three stages along the thickness direction of the radiating fin 23, but the present invention is not limited to this. The porosity of the porous metal in the radiating fin 23 can be changed in an arbitrary number of steps or continuously along the thickness direction of the radiating fin 23.

(Third embodiment)
FIG. 6 is a perspective view showing an outline of a heat sink 40C according to the third embodiment of the present invention. The heat sink 40C of the present embodiment shown in FIG. 6 has four base blocks 101, 102, 103, and 104 overlapped and joined in the horizontal direction as compared with the heat sink 40A of FIG. 2 described in the first embodiment. The base part 10 is different. For the base blocks 101 to 104, porous metals having different densities are used. That is, the porosity of the porous metal in the base portion 10 is configured to change along the surface direction of the base portion 10.

  When the heating element to which the heat sink 40C is attached is a semiconductor element such as a CPU, the outer dimension of the heat sink 40C mounted immediately above the heating element is generally larger than the outer dimension of the heating element in order to increase the heat dissipation area. For this reason, there is a concern that expanded thermal resistance from the heating element is generated in the base portion 10 of the heat sink 40C, and heat is not transmitted to the end portions or the four corners of the base portion 10. In order to solve this problem, in the heat sink 40C of the present embodiment, as shown in FIG. 6, base blocks 101 to 104 using porous metals having different densities are arranged along the flow direction of the fluid 30, The density of the porous metal in the base part 10 is changed along the flow direction of the fluid 30. Here, by making the density of the porous metal in the base blocks 102 and 103 in contact with the heating element higher than that of the base blocks 101 and 104, the heat received from the heating element can be sufficiently obtained in the width direction of the base portion 10. Can tell. On the contrary, the density of the porous metal in the base block 101 located on the inlet side of the fluid 30 and the base block 104 located on the outlet side of the fluid 30 may be made higher than that of the base blocks 102 and 103. Good. Thereby, the heat generated by the heating element can be sufficiently transmitted to the end portion and the four corners of the base portion 10.

  As described above, in the heat sink 40C of this embodiment, the porosity of the porous metal in the base portion 10 is changed along the surface direction of the base portion 10. Thereby, the heat flow in the surface direction of the base part 10 can be adjusted, and the structure of the base part 10 can be optimized. In the above example, the porosity of the porous metal in the base portion 10 is changed in four steps along the surface direction of the base portion 10, but the present invention is not limited to this. The porosity of the porous metal in the base portion 10 can be changed in any number of steps or continuously along the surface direction of the base portion 10.

(Fourth embodiment)
FIG. 7 is a perspective view showing an outline of a heat sink 40D according to the fourth embodiment of the present invention. The heat sink 40D of this embodiment shown in FIG. 7 dissipates heat by overlapping three heat dissipating fin blocks 235, 236, and 237 in the horizontal direction and joining them compared to the heat sink 40A of FIG. 2 described in the first embodiment. The difference is that the fins 23 are configured. Porous metals having different densities are used for the radiation fin blocks 235 to 237, respectively. That is, the porosity of the porous metal in the radiating fin 23 is configured to change along the surface direction of the radiating fin 23.

  Generally, the heat exchange performance of the radiating fin 23 is higher as it is closer to the inlet side of the fluid 30, and the temperature of the fluid 30 is increased by receiving heat radiated from the radiating fin 23. The heat exchange performance of the is reduced. In order to solve this problem, in the heat sink 40D of the present embodiment, as shown in FIG. 7, the heat dissipating fin blocks 235 to 237 using porous metals having different densities are arranged along the flow direction of the fluid 30. The density of the porous metal in the heat radiating fins 23 is changed along the flow direction of the fluid 30. Here, the density of the porous metal in the radiating fin block 235 located on the inlet side of the fluid 30 is maximized, and the density of the porous metal in the radiating fin blocks 236 and 237 is increased from there to the outlet side of the fluid 30. Decrease sequentially. Thereby, the heat flow toward the inlet side of the fluid 30 can be increased, and the heat exchange performance of the radiation fins 23 can be improved. Contrary to the above, the density of the porous metal in the radiating fin block 235 located on the inlet side of the fluid 30 is made the lowest, and from there toward the outlet side of the fluid 30, the porosity in the radiating fin blocks 236 and 237 is set. The density of the solid metal may be increased sequentially. Thereby, the heat radiation amount from the radiation fins 23 can be leveled with respect to the flow direction of the fluid 30, and the temperature distribution in the heat generating body such as a CPU to which the heat sink 40D is attached can be made uniform.

  As described above, in the heat sink 40 </ b> D of the present embodiment, the porosity of the porous metal in the radiating fin 23 is changed along the surface direction of the radiating fin 23. Thereby, the heat flow in the surface direction of the radiation fin 23 can be adjusted, and the structure of the radiation fin 23 can be optimized. In the above example, the porosity of the porous metal in the radiating fin 23 is changed in three stages along the surface direction of the radiating fin 23, but the present invention is not limited to this. The porosity of the porous metal in the radiating fin 23 can be changed in an arbitrary number of steps or continuously along the surface direction of the radiating fin 23.

(Fifth embodiment)
FIG. 8 is a perspective view showing an outline of a thermoelectric conversion module 50 according to the fifth embodiment of the present invention. The thermoelectric conversion module 50 of this embodiment shown in FIG. 8 is configured by combining any one of the heat sinks 40A to 40D described in the first to fourth embodiments with the thermoelectric element 51.

  The thermoelectric element 51 directly converts heat energy into electric energy. The thermoelectric element 51 is configured by, for example, arranging a P-type thermoelectric element and an N-type thermoelectric element in contact with each other, and uses a mechanism in which a current flows due to a thermoelectric effect according to a temperature difference between the two ends, and heat energy is obtained. To electrical energy. In the thermoelectric conversion module 50, any of the heat sinks 40 </ b> A to 40 </ b> D composed of the base portion 10 and the heat radiating fins 23 each using the porous metal as described above is connected to the thermoelectric module 60 via the heat conduction grease 60 that is a heat transfer elastomer. It is attached to one side of the element 51. On the other side of the thermoelectric element 51, a cold / hot source 70 is attached. As the cold source 70, a water cooling jacket of a water cooling system or the like can be used.

  The thermoelectric conversion module 50 can generate electric energy by utilizing a temperature difference in various systems. For example, heat energy is directly converted into electric energy using high-temperature exhaust gas generated from an automobile or the like and a low-temperature portion of a radiator water cooling system such as an automobile. In this case, by attaching the radiation fins 23 to the high-temperature exhaust gas side generated from the automobile or the like, and attaching the cooling / heating source 70 to the low temperature part side of the radiator water cooling system such as the automobile, electric energy is generated from the thermoelectric conversion module 50, A cooling system can be constructed using this.

  FIG. 8 is a side view of a thermoelectric conversion module 50 according to the fifth embodiment of the present invention. In FIG. 8, the example at the time of combining the heat sink 40A by 1st Embodiment with the thermoelectric element 51 is shown.

  As shown in FIG. 8, the heat radiating fins 23 are made of a porous metal similar to that shown in FIG. 3, which has a network structure 20 made of a fine metal and cavities 21 existing in the gaps of the network structure 20. The radiating fins 23 have gaps through which fluid flows, and heat transfer is performed between the mesh structure 20 and the fluid. Similarly, the base portion 10 is made of a porous metal having a network structure and a cavity. The mesh structure in the base portion 10 is denser than the mesh structure 20 in the radiating fins 23 as in FIG. 3, and there are few cavities existing in the gaps. Therefore, the base portion 10 has a heat transfer performance substantially equivalent to that of a solid metal body, and can transfer heat to the efficient liquid between the thermoelectric element 51 and the heat radiating fins 23.

  As described above, the thermoelectric conversion module 50 of this embodiment includes any one of the heat sinks 40A to 40D and the thermoelectric element 51 to which the heat sink is attached. Thereby, the high-performance thermoelectric conversion module 50 with a simple structure can be realized.

  In addition, each embodiment described above may each be implemented independently, and may be combined arbitrarily. Further, the present invention is not limited to the above embodiment. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

  10: Base part, 101, 102, 103, 104: Base block, 20: Mesh structure, 21: Cavity, 23: Radiation fin, 231, 232, 233: Radiation fin layer, 235, 236, 237: Radiation fin block, 30: Fluid, 40A, 40B, 40C, 40D: Heat sink, 50: Thermoelectric conversion module, 51: Thermoelectric element, 60: Thermal conductive grease, 70: Cold source

Claims (7)

A base portion made of porous metal;
A heat dissipating fin composed of a porous metal using the same metal as the base part,
The heat sink has a higher porosity of the porous metal than the porosity of the porous metal in the base portion. The heat sink according to claim 1.
The thickness of the base part is a heat sink smaller than the thickness of the heat dissipating fins. The heat sink according to claim 1 or 2,
The porosity of the porous metal in the radiating fin is a heat sink that varies along the thickness direction of the radiating fin. The heat sink according to any one of claims 1 to 3,
A heat sink in which a porosity of the porous metal in the base portion varies along a surface direction of the base portion. The heat sink according to any one of claims 1 to 4,
The porosity of the porous metal in the radiating fin is a heat sink that varies along the surface direction of the radiating fin. A heat sink according to any one of claims 1 to 5,
A thermoelectric conversion module comprising: a thermoelectric element to which the heat sink is attached. Preparing a first substrate having a predetermined porosity and a second substrate having a higher porosity than the first substrate;
Attaching metal powder to each of the first substrate and the second substrate;
The first substrate and the second substrate to which the metal powder is attached are heated to a temperature equal to or higher than the melting point of the metal powder while being in contact with each other, thereby allowing the first substrate and the second substrate to be heated. A method of manufacturing a heat sink, in which a base is removed and the particles of the metal powder are bonded to each other, thereby manufacturing a heat sink in which the same porous metals having different porosities are integrated.

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