JP2021097132A - Heat sink - Google Patents

Abstract

To provide a heat sink with high heat dissipation performance.SOLUTION: A heat sink 1 includes a base plate 2 and a plurality of fins 3 provided on the base plate 2 so as to project in the thickness direction thereof. The base plate 2 has anisotropy in its thermal conductivity in the plane direction. In the top view of the base plate 2, the fin 3 extends in a direction intersecting the maximum thermal conductivity direction A in the plane direction of the base plate 2.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heat sink that dissipates heat from a heating element such as a heating element.

Here, in the present specification and claims, in order to make it easier to understand the configuration of the heat sink according to the present invention, the side of the heat sink where the heating element is installed is the upper side of the heat sink, and the opposite side is the lower side of the heat sink. The plane direction perpendicular to the thickness direction of the base plate of the heat sink is called the plane direction of the base plate.

Further, in the present specification and claims, unless otherwise specified in the text, the term "aluminum" is used to mean both pure aluminum and aluminum alloy, and the term "copper" is used as pure copper and. It is used to include both copper alloys.

As a metal-carbon particle composite material, for example, as described in Japanese Patent No. 5150905 (Patent Document 1) and (Patent Document 5145591 (Patent Document 2)), a plurality of metal layers and carbon fiber layers are alternately laminated. A metal-carbon fiber composite material that is joined and integrated in the state of being joined is known. Further, according to International Publication No. 2009/051094 (Patent Document 3), metal-scales using scaly graphite particles as carbon particles are known. The state graphite particle composite material is disclosed.

As other patent documents disclosed about the metal-carbon particle composite material, Japanese Patent Application Laid-Open No. 2015-25158 (Patent Document 4), Japanese Patent Application Laid-Open No. 2015-217655 (Patent Document 5), and Japanese Patent Application Laid-Open No. 2017-888913 (Patent Document 4). Document 6) and the like are known.

The metal-carbon particle composite material described above has anisotropy in thermal conductivity, and is expected to be used as a material for members requiring high thermal conductivity.

By the way, a cooling device that cools a heat-generating element (eg, a semiconductor element) as a heat-generating body generally includes a heat sink that dissipates heat from the heat-generating element. This heat sink is required to have high thermal conductivity in order to obtain high heat dissipation performance. Therefore, it is possible to use a metal-carbon particle composite material as a heat sink material in JP-A-2017-220039 (Patent Document 7), JP-A-2019-41076 (Patent Document 8), and JP-A-2019-176091 (Patent Document 7). It is proposed in Patent Document 9).

Japanese Patent No. 5150905 Japanese Patent No. 5145591 International Publication No. 2009/051094 Japanese Unexamined Patent Publication No. 2015-25158 Japanese Unexamined Patent Publication No. 2015-217655 JP-A-2017-888913 Japanese Unexamined Patent Publication No. 2017-220039 JP-A-2019-41076 Japanese Unexamined Patent Publication No. 2019-176091

In recent years, as the performance of heat-generating elements has improved and the amount of heat generated has increased, heat sinks have been required to have higher heat dissipation performance.

Therefore, an object of the present invention is to provide a heat sink having high heat dissipation performance.

The present invention provides the following means.

1) A base plate and a plurality of fins provided on the base plate so as to project in the thickness direction thereof are provided.
The base plate has anisotropy in its thermal conductivity in the plane direction.
A heat sink in which the fins extend in a direction intersecting the plane direction of the base plate with respect to the maximum thermal conductivity direction in the top view of the base plate.

2) The heat sink according to item 1 above, wherein the plurality of fins include at least one of a straight fin and a wave fin.

3) The heat sink according to the above item 1 or 2, wherein a first metal-carbon particle composite material containing a metal matrix and carbon particles dispersed in the metal matrix is used as the material of the base plate.

4) The heat sink according to item 3 above, wherein the longest axial direction of the carbon particles of the first composite material is oriented in the thickness direction of the base plate.

5) The heat sink according to item 3 or 4 above, wherein aluminum is used as the metal of the metal matrix of the first composite material.

6) The heat sink according to any one of the above items 1 to 5, wherein a second metal-carbon particle composite material containing a metal matrix and carbon particles dispersed in the metal matrix is used as the material of the fins.

7) The heat sink according to item 6 above, wherein aluminum is used as the metal of the metal matrix of the second composite material.

The present invention has the following effects.

In the previous item 1, in the top view of the base plate, the fins extend in a direction intersecting the maximum thermal conductivity direction in the plane direction of the base plate, so that the heat transferred from the heating element to the base plate is transferred to the base plate in the plane direction of the base plate. Since it is easy to spread over the entire area, the heat dissipation performance of the heat sink can be improved.

In item 2 above, the heat dissipation performance of the heat sink can be further improved by including at least one of the straight fin and the wave fin in the plurality of fins.

In item 3 above, since the first metal-carbon particle composite material is used as the material of the base plate, the heat dissipation performance of the heat sink can be further improved.

In item 4 above, since the longest axial direction of the carbon particles of the first composite material is oriented in the thickness direction of the base plate, the heat conduction rate from the heat sink to the fins is high, so that the heat dissipation performance of the heat sink is further improved. Can be done.

In item 5, since aluminum is used as the metal of the metal matrix of the first composite material, the weight of the heat sink can be reduced and the workability of the base plate can be improved.

In item 6 above, since the second metal-carbon particle composite material is used as the fin material, the thermal conductivity of the fin itself can be enhanced, and thereby the heat dissipation performance of the heat sink can be further enhanced. it can.

In item 7, since aluminum is used as the metal of the metal matrix of the second composite material, the weight of the heat sink can be reduced and the workability of the fins can be improved.

FIG. 1 is a side view schematically showing a heat sink according to the first embodiment of the present invention. FIG. 2 is a perspective view schematically showing the heat sink. FIG. 3 is a top view schematically showing the heat sink. FIG. 4 is a perspective view schematically showing scaly graphite particles as carbon particles. FIG. 5 is a partially enlarged cross-sectional perspective view schematically showing a part of the base plate of the heat sink. FIG. 6 is a perspective view schematically showing a heat sink according to a reference embodiment of the present invention. FIG. 7 is a partially enlarged cross-sectional perspective view schematically showing a part of the base plate of the heat sink according to the second embodiment of the present invention. FIG. 8 is a partially enlarged cross-sectional perspective view schematically showing a part of the base plate of the heat sink according to the third embodiment of the present invention. FIG. 9 is a top view schematically showing a heat sink according to a fourth embodiment of the present invention.

Some embodiments of the present invention will be described below with reference to the drawings.

1 to 5 are diagrams for explaining the heat sink 1 according to the first embodiment of the present invention. FIG. 6 is a diagram for explaining the heat sink 1A according to the reference embodiment of the present invention.

As shown in FIG. 1, the heat sink 1 of the first embodiment cools the heating element 20 by dissipating the heat generated in the heating element (shown by the alternate long and short dash line) 20 to the cooling medium (not shown). It is a thing.

As shown in FIGS. 1 and 2, the heat sink 1 includes a flat plate-shaped base plate 2 and a plurality of fins 3. The base plate 2 is arranged substantially horizontally. The top view shape of the base plate 2 is a rectangular shape (more specifically, a rectangular shape) as shown in FIG.

In FIG. 2, the arrows “X”, “Y” and “Z” indicate the width direction, the length direction and the thickness direction of the base plate 2, respectively. The same applies to other drawings.

The plurality of fins 3 are provided on the base plate 2 so as to project downward as one side in the thickness direction Z of the base plate 2. Further, the fins 3 continuously extend in a predetermined direction of the base plate 2. The direction in which the fin 3 extends will be described later.

The heating element 20 includes a heating element such as a semiconductor element, and is installed on the base plate 2 (specifically, the upper surface 2a of the base plate 2) in a state of being in contact with and fixed to the base plate 2.

In this heat sink 1, the cooling medium flows between two fins 3, 3 adjacent to each other 4. The heat of the heating element 20 is sequentially conducted from the heating element 20 to the base plate 2 and the fins 3 and dissipated from the fins 3 to the cooling medium. As the cooling medium, a coolant (eg, water, long-life coolant), a cooling gas (eg, air), or the like is used.

The base plate 2 has anisotropy in its thermal conductivity in the plane direction. A metal-non-metal particle composite material is used as the material of the base plate 2, that is, the base plate 2 is made of a metal-non-metal particle composite material. Hereinafter, this metal-non-metal particle composite material for the base plate 2 is also referred to as a “first composite material”.

As shown in FIG. 5, the first composite material contains a metal matrix 8 and non-metal particles 7 as a filler. The non-metal particles 7 have anisotropy in thermal conductivity and are dispersed in the metal matrix 8. The above-mentioned anisotropy of the thermal conductivity of the base plate 2 in the plane direction is expressed by the anisotropy of the thermal conductivity of the non-metal particles 7 itself and the orientation of the non-metal particles 7.

In the first composite material, aluminum, copper, or the like is used as the metal of the metal matrix 8. Carbon particles and the like are used as the non-metal particles 7.

The carbon particles include carbon fibers (eg, pitch-based carbon fibers, PAN-based carbon fibers), scaly graphite particles, scaly graphite particles, expanded graphite particles, and pyrolyzed graphite particles (eg, highly oriented pyrolyzed graphite particles). At least one selected from the group can be used. As carbon particles, scaly graphite particles are particularly preferably used because they have high thermal conductivity.

The method for producing the first composite material is not limited. For example, as a method for producing a first composite material, a laminate obtained by laminating a plurality of coated foils coated with non-metal particles on a metal foil is heat-sintered (eg, hot-press sintered device, discharge plasma). A method of producing the first composite material by heating and sintering with a sintering apparatus) can be mentioned.

In the first embodiment, in detail, aluminum is used as the metal of the metal matrix 8 of the first composite material, and scaly graphite particles 7a are used as the non-metal particles (carbon particles) 7 of the first composite material. Has been done. Therefore, the first composite material is an aluminum-carbon particle composite material in detail, and an aluminum-scaly graphite particle composite material in more detail. By using aluminum as the metal of the metal matrix 8, the weight of the heat sink 1 can be reduced and the workability of the base plate 2 can be improved.

“D” in FIG. 4 indicates the longest axial direction of the scaly graphite particles 7a as the non-metal particles (carbon particles) 7. The longest axial direction D of the non-metal particles 7 such as the scaly graphite particles 7a and its length mean the longest axis of the non-metal particles 7 and its length. Therefore, when the non-metal particles 7 are, for example, carbon fibers 7b (in the case of the second and third embodiments described later), the longest axis of the non-metal particles 7 means the fiber axis of the carbon fibers 7b, and the non-metal particles 7 The length of the longest axial direction D of 7 means the fiber length of the carbon fiber 7b. “E” in FIG. 4 indicates the width direction of the scaly graphite particles 7a as the non-metal particles (carbon particles) 7.

Here, in the following, the plane direction perpendicular to the thickness direction of the scaly graphite particles 7a is referred to as the plane direction of the scaly graphite particles 7a.

The scaly graphite particles 7a have anisotropy in thermal conductivity. Specifically, in general, the thermal conductivity of the scaly graphite particles 7a in the thickness direction is low, and the thermal conductivity of the scaly graphite particles 7a in the planar direction (that is, the longest axial direction D and the width direction E of the scaly graphite particles). Is expensive.

The particle size of the non-metal particles 7 is not limited, and the average length of the non-metal particles 7 in the longest axial direction D is preferably 0.10 mm or more. The reason is that the interfacial thermal resistance between the non-metal particles 7 and the metal matrix 8 can be reliably reduced, thereby reliably increasing the thermal conductivity of the base plate 2. The upper limit of the average length of the non-metal particles 7 in the longest axial direction D is not limited, and is usually 2.0 mm.

The aspect ratio of the non-metal particles 7 is not limited, but in general, the larger the aspect ratio of the non-metal particles 7, the higher the thermal conductivity of the non-metal particles 7, so that the average aspect ratio of the non-metal particles 7 is generally high. It is preferably 30 or more. The upper limit of this average aspect ratio is not limited, and is, for example, 200.

As described above, the base plate 2 has anisotropy in its thermal conductivity in the plane direction. Specifically, as shown in FIGS. 2 and 3, in the first embodiment, the direction A of the highest thermal conductivity in the thermal conductivity in the plane direction of the base plate 2 (hereinafter, this direction A is the plane of the base plate 2). The maximum thermal conductivity direction A) is set in the length direction Y of the base plate 2. The direction B of the lowest thermal conductivity in the plane direction of the base plate 2 (hereinafter, this direction B is referred to as the lowest thermal conductivity direction B in the plane direction of the base plate 2) is set in the width direction X of the base plate 2. There is. The maximum thermal conductivity direction A in the plane direction and the minimum thermal conductivity direction B in the plane direction of the base plate 2 intersect with each other, and are orthogonal to each other in detail in the first embodiment.

In the base plate 2 having such an anisotropic thermal conductivity, as shown in FIG. 5, the longest axial direction D and the width direction E of the scaly graphite particles 7a of the first composite material are the width direction X (the width direction X of the base plate 2). That is, it is oriented in the plane direction perpendicular to the plane direction of the base plate 2 (the lowest thermal conductivity direction B) (that is, the plane direction parallel to the length direction Y and the thickness direction Z of the base plate 2), and is scaly. The thickness direction of the graphite particles 7a is oriented in the width direction X of the base plate 2 (that is, the minimum thermal conductivity direction B in the plane direction of the base plate 2). In this case, the thermal conductivity in the length direction Y of the base plate 2 (that is, the maximum thermal conductivity in the plane direction of the base plate 2) and the thermal conductivity in the thickness direction Z of the base plate 2 are the thermal conductivity in the width direction X of the base plate 2. Higher than the rate (ie, the lowest thermal conductivity of the base plate 2 in the plane direction).

As shown in FIGS. 1 and 2, the plurality of fins 3 have the same shape and the same size as each other. As shown in FIG. 3, in the top view of the base plate 2, the fins 3 are continuously in the direction intersecting the maximum thermal conductivity direction A (that is, the length direction Y of the base plate 2) in the plane direction of the base plate 2. Along with the extension, the fins 3 are arranged in parallel at equal intervals in the maximum thermal conductivity direction A (that is, the length direction Y of the base plate 2) in the plane direction of the base plate 2, and in this state, the fins 3 are arranged in parallel with the base plate 2 (specifically, the base plate 2). It is joined to the lower surface 2b) of 2 by brazing.

Further, the fin 3 is a straight fin 3A, that is, the fin 3 extends straight and continuously in a direction intersecting the maximum thermal conductivity direction A in the plane direction of the base plate 2. Two fins 3, 3 adjacent to each other are parallel.

“F” in FIG. 3 indicates the central axis of the fin 3 (straight fin 3A) in the top view of the base plate 2. “Θ” is an angle formed by the maximum thermal conductivity direction A in the plane direction of the base plate 2 and the central axis F of the fins 3 (straight fins 3A) in the top view of the base plate 2. The preferable range of θ will be described later.

The material of the fin 3 is not limited, and as the material of the fin 3, for example, a metal such as aluminum or copper is used, or a metal-non-metal particle composite material is used. Hereinafter, this metal-non-metal particle composite material for fin 3 is also referred to as a “second composite material”.

As the second composite material, a material of the same type as the above-mentioned first composite material is preferably used. When a second composite material is used as the material for the fins 3, the heat dissipation performance of the heat sink 1 can be improved. Further, when aluminum is used as the metal of the metal matrix of the second composite material, the weight of the heat sink 1 can be reduced and the workability of the fins 3 can be improved.

Further, in the fin 3, the orientation direction of the carbon particles (eg, scaly graphite particles) of the second composite material is not limited, and preferably the longest axial direction D of the carbon particles is the protruding direction of the fin 3 with respect to the base plate 2. It is preferably oriented in G (see FIG. 2). In this case, since the heat conducted from the base plate 2 to the fins 3 is rapidly conducted toward the tip of the fins 3, the heat dissipation performance of the heat sink 1 can be further improved.

Next, the advantages of the heat sink 1 of the first embodiment will be described below in comparison with the heat sink 1A according to the reference embodiment shown in FIG. In FIG. 6, each element of the heat sink 1A of the present reference embodiment has the same reference numerals as those used in the heat sink 1 of the first embodiment.

According to the heat sink 1 of the first embodiment, as described above, in the top view of the base plate 2 (see FIG. 3), the fins 3 (straight fins 3A) have the highest thermal conductivity direction A (straight fin 3A) in the plane direction of the base plate 2. That is, it extends in a direction intersecting the length direction Y) of the base plate 2.

Therefore, when the heat generated in the heating element 20 is transferred from the heating element 20 to the base plate 2 of the heat sink 1, the heat is the maximum thermal conductivity in the plane direction of the base plate 2 from the contact portion of the base plate 2 with the heating element 20. In addition to conducting mainly in the direction A, it also conducts in the direction in which the fins 3 extend at the connection portion 2c of the base plate 2 with the fins 3 (that is, the lowest thermal conductivity direction B in the plane direction of the base plate 2). Therefore, the heat transferred from the heating element 20 to the base plate 2 tends to spread over the entire plane direction of the base plate 2. Then, this heat is conducted from the base plate 2 to substantially all the fins 3 and dissipated from these fins 3 to the cooling medium. That is, there are many fins 3 that contribute to heat dissipation to the cooling medium. Therefore, the heat dissipation performance of the heat sink 1 is high.

On the other hand, in the heat sink 1A of the present reference embodiment, in the top view of the base plate 2, the fins 3 (straight fins 3A) are relative to the maximum thermal conductivity direction A (that is, the length direction Y of the base plate 2) in the plane direction of the base plate 2. It extends continuously in the parallel direction and is arranged in parallel at equal intervals in the lowest thermal conductivity direction B (that is, the width direction X of the base plate 2) in the plane direction of the base plate 2.

Therefore, when the heat generated in the heating element 20 is transferred from the heating element 20 to the base plate 2 of the heat sink 1A, the heat is the maximum thermal conductivity in the plane direction of the base plate 2 from the contact portion of the base plate 2 with the heating element 20. It conducts mainly in the direction A, but since the fins 3 extend in a direction parallel to the maximum thermal conductivity direction A in the plane direction of the base plate 2, the minimum thermal conductivity direction B in the plane direction of the base plate 2 Hard to conduct. Therefore, the heat transferred from the heating element 20 to the base plate 2 is difficult to spread in the entire plane direction of the base plate 2, and the number and parts of the fins 3 that contribute to heat dissipation to the cooling medium are larger than those of the heat sink 1 of the first embodiment. There are few. Therefore, the heat dissipation performance of the heat sink 1A is lower than that of the heat sink 1 of the first embodiment.

In the heat sink 1 of the first embodiment, the angle θ formed by the maximum thermal conductivity direction A in the plane direction of the base plate 2 and the central axis F of the fins 3 is 90 ° ± in the top view of the base plate 2 (see FIG. 3). It is preferably in the range of 30 °. In this case, the heat transferred from the heating element 20 to the base plate 2 is surely spread over the entire plane direction of the base plate 2, so that the heat dissipation performance of the heat sink 1 can be surely improved. The more preferable range of θ is 90 ° ± 15 °, and the particularly preferable range of θ is 90 °. When θ is 90 °, the fin 3 (more specifically, the central axis F of the fin 3) extends in a direction orthogonal to the maximum thermal conductivity direction A in the plane direction of the base plate 2.

Further, since the fin 3 is a straight fin 3A, the heat dissipation performance of the heat sink 1 can be further improved.

Further, since the first metal-carbon particle composite material (specifically, the metal-scaly graphite particle composite material) is used as the material of the base plate 2, the heat dissipation performance of the heat sink 1 can be further improved.

FIG. 7 is a diagram for explaining a heat sink according to a second embodiment of the present invention, FIG. 8 is a diagram for explaining a heat sink according to a third embodiment of the present invention, and FIG. 9 is a diagram for explaining a fourth embodiment of the present invention. It is a figure explaining the heat sink which concerns on. In these figures, each element of the heat sink is designated by the same reference numerals as those used in the heat sink 1 of the first embodiment. Hereinafter, each of the heat sinks of the second to fourth embodiments will be described focusing on the differences from the heat sink 1 of the first embodiment.

In the heat sink of the second embodiment shown in FIG. 7, an aluminum-carbon fiber composite material (first composite material) is used as the material of the base plate 2. That is, in this first composite material, carbon fibers 7b are used as carbon particles (non-metal particles 7).

In the base plate 2, the longest axial direction D of the carbon fibers 7b of the first composite material (that is, the fiber axial direction of the carbon fibers 7b) is oriented in the length direction Y of the base plate 2. Therefore, the maximum thermal conductivity direction A in the plane direction of the base plate 2 is the length direction Y of the base plate 2, and the minimum thermal conductivity direction B in the plane direction of the base plate 2 is the width direction X of the base plate 2. Further, the thermal conductivity of the base plate 2 in the length direction Y is higher than the thermal conductivity of the base plate 2 in the width direction X and the thickness direction Z.

In the heat sink of the third embodiment shown in FIG. 8, an aluminum-carbon fiber composite material (first composite material) is used as the material of the base plate 2. That is, in this first composite material, carbon fibers 7b are used as carbon particles (non-metal particles 7).

In the base plate 2, the longest axial direction D of the carbon fibers 7b of the first composite material (that is, the fiber axial direction of the carbon fibers 7b) is oriented in the thickness direction Z of the base plate 2. Further, the carbon fiber dispersion layer 10 in which carbon fibers 7b are dispersed in the aluminum matrix (as the metal matrix 8) of the first composite material, and aluminum in which carbon particles such as carbon fibers 7b are substantially not present in the aluminum matrix. A plurality of layers 11 (as metal layers) are alternately laminated in the width direction X of the base plate 2.

When the carbon fiber dispersion layer 10 and the aluminum layer 11 are arranged in this way, the thermal conductivity in the length direction Y of the base plate 2, which is the thermal conductivity in the direction in which the aluminum layer 11 extends continuously, is the carbon fiber dispersion. It is higher than the thermal conductivity in the width direction X of the base plate 2, which is the thermal conductivity in the stacking direction of the layer 10 and the aluminum layer 11.

Therefore, the maximum thermal conductivity direction A in the plane direction of the base plate 2 is the length direction Y of the base plate 2, and the minimum thermal conductivity direction B in the plane direction of the base plate 2 is the width direction X of the base plate 2. Further, as described above, since the longest axial direction D of the carbon fibers 7b (the fiber axial direction of the carbon fibers 7b) is oriented in the thickness direction Z of the base plate 2, the thermal conductivity in the thickness direction Z of the base plate 2 Is higher than the thermal conductivity in the length direction Y of the base plate 2, which is the maximum thermal conductivity direction A in the plane direction of the base plate 2.

In this heat sink, since the longest axial direction D of the carbon fibers 7b (the fiber axial direction of the carbon fibers 7b) is oriented in the thickness direction Z of the base plate 2, the thermal conductivity from the base plate 2 to the fins is high. Therefore, the heat dissipation performance of the heat sink can be further improved.

In the heat sink 1 of the fourth embodiment shown in FIG. 9, each fin 3 is a wave fin 3B, that is, the fin 3 is relative to the maximum thermal conductivity direction A in the plane direction of the base plate 2 in the top view of the base plate 2. It extends continuously in a wavy direction in the direction of intersection. The preferable range of θ is the same as that of the heat sink 1 of the first embodiment described above.

Although some embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can be variously modified without departing from the gist of the present invention.

For example, in the heat sink 1 of the first embodiment, the fins 3 are joined to the base plate 2 (specifically, the lower surface 2b of the base plate 2) by a joining means such as brazing, but in the heat sink according to the present invention, in addition to the above. For example, the fins may be integrally formed on the base plate by forging or the like.

Specific examples and comparative examples of the present invention are shown below. In order to make it easier to understand the following embodiment, the embodiment will be described with reference to each element of the heat sink 1 of the first embodiment. However, the present invention is not limited to the following examples. In the following examples, the thermal conductivity of each part of the heat sink is the thermal conductivity at room temperature (20 ° C.).

<Example>
In this embodiment, the heat sink 1 of the first embodiment shown in FIGS. 1 to 5 was manufactured by the following method.

Scale-like graphite particles 7a as carbon particles, 10% by mass aqueous solution of polyethylene oxide as a binder, 10% by mass aqueous solution of polyvinyl alcohol, isopropyl alcohol and water as a solvent for a binder, a dispersant, and a surface conditioner. Was placed in a mixing container and stirred and mixed with a disper to obtain a coating liquid. The viscosity of the coating liquid was 5000 mPa · s at 25 ° C.

The average length of the scaly graphite particles 7a in the longest axial direction D was 0.15 mm, and the average aspect ratio thereof was 30. The content of the scaly graphite particles 7a contained in the coating liquid was 90% by mass with respect to the total mass of the binder and the scaly graphite particles 7a.

Next, the coating liquid is applied onto the strip of aluminum foil with a roll-to-roll comma knife coater at a coating speed of 1 m / min, and the solvent in the coating liquid is dried and removed by passing through the drying furnace. did. As a result, a strip of scaly graphite particle coated foil in which scaly graphite particles 7a were coated on the strip of aluminum foil was obtained. The amount of the scaly graphite particles 7a coated on the strip of the coating foil was 30 g / m ² .

The material of the aluminum foil was aluminum alloy number 1N30 specified by JIS (Japanese Industrial Standards), and its thickness was 20 μm and its width was 300 mm.

Then, a large number of square-shaped coating foils were obtained by cutting a large number of strips of the coating foil into a square shape (its dimensions: width 80 mm × length 80 mm).

Next, the first laminated body for the base plate 2 was formed by laminating 3200 coating foils. Then, the first laminate is heated in a vacuum by a hot press sintering apparatus in the thickness direction of the first laminate (that is, the lamination direction of the coating foil) under predetermined sintering conditions. 1 The laminate was sintered. As a result, the first aluminum-scaly graphite particle composite for the base plate 2 was produced. The dimensions of this first complex were width 80 mm × length 80 mm × thickness 80 mm.

The above-mentioned sintering conditions were as follows. The sintering temperature was 620 ° C., the holding time of the sintering temperature was 3 hours, the rate of temperature rise from room temperature was 20 ° C./min, the pressing force on the first laminate was 20 MPa, and the degree of vacuum was 3 Pa. Further, the binder in the first laminate was thermally decomposed and sublimated by temporarily stopping the temperature rise while heating the first laminate from room temperature to the sintering temperature, whereby the binder was removed from the first laminate. .. The binder removal conditions applied at that time were that the heating temperature of the laminate for removing the binder was 450 ° C. and the holding time was 30 min.

Next, a flat plate-shaped base plate 2 having a width of 60 mm, a length of 60 mm, and a thickness of 2 mm was cut out from the first complex so as to have the highest thermal conductivity in the thickness direction Z.

In the base plate 2, the longest axial direction D and the width direction E of the scaly graphite particles 7a are oriented in the plane direction parallel to the length direction Y and the thickness direction Z of the base plate 2, and the thickness of the scaly graphite particles 7a. The vertical direction was oriented in the width direction X of the base plate 2. Therefore, the maximum thermal conductivity direction A in the plane direction of the base plate 2 was the length direction Y of the base plate 2, and the minimum thermal conductivity direction B in the plane direction of the base plate 2 was the width direction X of the base plate. Further, the thermal conductivity of the base plate 2 in the length direction Y and the thickness direction Z was about the same, which was higher than the thermal conductivity of the base plate 2 in the width direction X.

Further, a second laminated body for the fins 3 was formed by laminating 26 of the above-mentioned coating foils. Then, by sintering the second laminate under the same conditions as the above-mentioned sintering conditions of the first laminate, a second aluminum-scaly graphite particle composite for fin 3 was produced. The dimensions of this second complex were width 80 mm × length 80 mm × thickness 0.6 mm.

Next, 30 straight fins 3A having a width of 8 mm, a length of 50 mm, and a thickness of 0.6 mm were cut out from the second complex.

In the straight fin 3A, the longest axial direction D and the width direction E of the scaly graphite particles 7a are in the width direction of the straight fin 3A (that is, the protruding direction G of the straight fin 3A with respect to the base plate 2) and the plane direction parallel to the length direction. It was oriented.

Next, the 30 straight fins 3A are arranged in a direction in which the straight fins 3A are orthogonal to the maximum thermal conductivity direction A (that is, the length direction Y of the base plate 2) in the plane direction of the base plate 2 (that is, the width direction X of the base plate 2). ), And is arranged in parallel at equal intervals in the maximum thermal conductivity direction A (that is, the length direction Y of the base plate 2) in the plane direction of the base plate 2. It was joined by brazing using a brazing material foil (its thickness 0.04 mm). Therefore, θ was 90 °. Further, in these straight fins 3A, the gap 4 between the two straight fins 3A and 3A adjacent to each other was 0.9 mm.

The heat sink 1 was manufactured by the above method.

A heating element 20 was joined to the central portion of the upper surface 2a of the base plate 2 of the heat sink 1 by brazing. Then, with the heating element 20 generating heat, cooling water having a temperature of 60 ° C. was flowed between the straight fins 4 of the heat sink 1 as a cooling medium at a flow velocity of 10 L / min. As a result, the temperature of the cooling water increased from 60 ° C to 86.3 ° C.

<Comparison example>
In this comparative example, the heat sink 1A of the above reference embodiment shown in FIG. 6 was manufactured by the following method.

The 30 straight fins 3A are extended so that the straight fins 3A continuously extend in a direction parallel to the maximum thermal conductivity direction A (that is, the length direction Y of the base plate 2) in the plane direction of the base plate 2 and the base plate 2 Except that it was joined to the lower surface of the base plate 2 by brazing so that it was arranged in parallel at equal intervals in the direction orthogonal to the maximum thermal conductivity direction A in the plane direction (that is, the width direction X of the base plate 2). , A heat sink 1A was manufactured in the same manner as in the above embodiment. In this heat sink 1A, θ was 0 °.

The same heating element 20 as the heating element used in the above embodiment was joined to the central portion of the upper surface 2a of the base plate 2 of the heat sink 1A by brazing. Then, with the heating element 20 generating heat, cooling water having a temperature of 60 ° C. was flowed between the straight fins 4 of the heat sink 1A under the same conditions as in the above embodiment. As a result, the temperature of the cooling water increased from 60 ° C to 85.6 ° C.

As described above, in the heat sink 1 of the example, the temperature of the cooling water is 86.3 ° C., which is higher than the temperature of the cooling water of the comparative example of 85.6 ° C. Therefore, it was confirmed that the heat dissipation performance of the heat sink 1 of the example was higher than that of the heat sink 1A of the comparative example.

The present invention can be used as a heat sink that dissipates heat from a heating element such as a heating element.

1: Heat sink 2: Base plate 3: Fins 3A: Straight fins 3B: Wave fins 7a: Scaly graphite particles (carbon particles)
7b: Carbon fiber (carbon particles)
8: Metal matrix A: Maximum thermal conductivity direction in the plane direction of the base plate B: Minimum thermal conductivity direction in the plane direction of the base plate D: Longest axial direction of carbon particles E: Width direction of carbon particles

Claims (7)

A base plate and a plurality of fins provided on the base plate so as to project in the thickness direction thereof are provided.
The base plate has anisotropy in its thermal conductivity in the plane direction.
A heat sink in which the fins extend in a direction intersecting the plane direction of the base plate with respect to the maximum thermal conductivity direction in the top view of the base plate. The heat sink according to claim 1, wherein the plurality of fins include at least one of a straight fin and a wave fin. The heat sink according to claim 1 or 2, wherein a first metal-carbon particle composite material containing a metal matrix and carbon particles dispersed in the metal matrix is used as the material of the base plate. The heat sink according to claim 3, wherein the longest axial direction of the carbon particles of the first composite material is oriented in the thickness direction of the base plate. The heat sink according to claim 3 or 4, wherein aluminum is used as the metal of the metal matrix of the first composite material. The heat sink according to any one of claims 1 to 5, wherein a second metal-carbon particle composite material containing a metal matrix and carbon particles dispersed in the metal matrix is used as the material for the fins. The heat sink according to claim 6, wherein aluminum is used as the metal of the metal matrix of the second composite material.

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