Heat dissipation materials

Abstract

A heat dissipation member according to the present invention comprises a planar metal-silicon carbide composite that contains aluminum. The heat dissipation member further comprises: at least one through-hole passing through the planar metal-silicon carbide composite in the thickness direction; a taper portion where the inner diameter of the through-hole gradually increases toward the outer side on the perimeter of one or both ends of the through-hole; a metal portion containing aluminum and formed on the surface of the interior of the through-hole; and a screw hole formed in the metal portion.

Description

[Technical field]

[0001] The present invention relates to a heat dissipation member. [Background technology]

[0002] Various developments have been made so far regarding heat dissipation members. For example, the technology described in Patent Document 1 is known as this type of technology. Patent Document 1 discloses a plate-shaped heat dissipation component including an Al-SiC composite body formed by impregnating a silicon carbide porous body with aluminum, a fixing hole penetrating the Al-SiC composite body, and an aluminum coating layer formed on the inner surface of the fixing hole and over the entire outer peripheral edge of the Al-SiC composite body (FIG. 2, paragraph 0012, etc. of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-299532 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has become clear that there is room for improvement in the plate-shaped heat dissipation component described in Patent Document 1 above in terms of ease of screw tightening. [Means for solving the problem]

[0005] As a result of intensive research based on this knowledge, the inventor discovered that by forming a screw hole in a metal part containing aluminum within a through hole having a tapered portion, the ease of screw tightening in such a screw hole can be improved, and thus completed the present invention.

[0006] According to one aspect of the present invention, there is provided the following heat dissipation member. 1. A heat dissipation member comprising a flat plate of a metal-silicon carbide composite material containing aluminum, At least one through hole penetrating the flat metal-silicon carbide composite in a plate thickness direction; A tapered portion around one or both ends of the through hole, in which the inner diameter of the through hole gradually increases toward the outside; a metal portion including aluminum formed on an inner surface of the through hole; A screw hole formed in the metal part; A heat dissipation member comprising: 2. The heat dissipation member according to 1., A heat dissipation member, wherein the angle of the tapered portion is 0.2° or more and 7° or less. 3. A heat dissipation member according to 1. or 2., The heat dissipation member is configured so that, when the maximum diameter of the through hole is D1 and the diameter of the screw hole is D2, D2 / D1 satisfies 0.1 to 0.9. 4. A heat dissipation member according to any one of 1. to 3., A heat dissipation component comprising a plating layer formed on a surface of the metal portion inside the screw hole. 5. The heat dissipation member according to 4., A heat dissipation component configured such that, in a cross-sectional view of the through hole, when the thickness of the metal portion is W1 and the thickness of the plating layer inside the screw hole is W2, W2 / W1 satisfies 0.001 or more and 0.04 or less. 6. A heat dissipation member according to any one of 1. to 5., A heat dissipation member comprising a plating layer provided on a main surface side of the heat dissipation member. 7. The heat dissipation member according to 6., The heat dissipation member, wherein the plating layer is a Ni plating layer containing Ni element. 8. A heat dissipation member according to any one of 1. to 7., A heat dissipation member comprising an aluminum-containing metal layer provided on a main surface of the heat dissipation member. 9. A heat dissipation member according to any one of 1. to 8., A heat dissipation component having an average thermal expansion coefficient from 25°C to 150°C of 4 ppm / K or more and 12 ppm / K or less. 10. A heat dissipation member according to any one of 1. to 9., The heat dissipation member has a thermal conductivity in a plate thickness direction at 25°C of 150 W / m·K or more and 300 W / m·K or less. Effect of the Invention

[0007] According to the present invention, a heat dissipation member that is easy to tighten with screws is provided. [Brief description of the drawings]

[0008] [Figure 1] 1A and 1B are diagrams illustrating an example of a heat dissipation member ((a) is a top view, and (b) is a cross-sectional view). [Diagram 2] FIG. 1 is a diagram (cross-sectional view) illustrating a schematic example of an electronic device. [Diagram 3] 4A to 4C are perspective views each showing a schematic example of a manufacturing process for the heat dissipation member of the present embodiment. [Figure 4] 3(c) is a cross-sectional view taken along the line AA in FIG. [Diagram 5] 1A to 1C are cross-sectional process views that diagrammatically show an example of an impregnation process when a tapered portion is present. [Figure 6] 1A to 1C are cross-sectional process views that diagrammatically show an example of an impregnation process when there is no tapered portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings, similar components are given similar reference numerals and their explanations will be omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to the actual dimensional ratios.

[0010] Unless otherwise specified, the term "approximately" used in this specification means that a range taking into consideration manufacturing tolerances, assembly variations, and the like, is included unless otherwise specified. Unless otherwise specified, for various numerical values ​​(especially measured values) in this specification that may change depending on temperature, values ​​at room temperature (25° C.) can be used. In this specification, the symbol "to" indicates that the upper and lower limits are included, unless otherwise specified.

[0011] The heat dissipation member of this embodiment will be generally described.

[0012] The heat dissipation member of this embodiment is a heat dissipation member comprising a flat metal-silicon carbide composite containing aluminum, and is provided with at least one through hole penetrating the flat metal-silicon carbide composite in the thickness direction, a tapered portion around one or both ends of the through hole, in which the inner diameter of the through hole gradually widens toward the outside, a metal portion containing aluminum formed on the inner surface of the through hole, and a screw hole formed in the metal portion.

[0013] Fig. 1(a) is a plan view showing a schematic example of the configuration of a heat dissipation member 10, and Fig. 1(b) is a cross-sectional view taken along the line BB in Fig. 1(a). In Fig. 1(a), the outer edge of a metal-silicon carbide composite 20 is shown by a solid line, and the outer edge of a metal layer 30 is shown by a dotted line.

[0014] The heat dissipation member 10 in FIGS. 1(a) and 1(b) includes a metal-silicon carbide composite 20 formed by impregnating molten aluminum 3 into a silicon carbide porous body 2 and solidifying the molten aluminum 3 in the above-mentioned impregnation step. In the metal-silicon carbide composite 20, a screw hole 60 is formed in the metal portion 32 filled in the through hole 40 in the above impregnation step. The screw holes 60 are used when joining the heat dissipation member 10 to another member (for example, a plastic case) with a screw or the like.

[0015] The inner surface of the screw hole 60 is made of a metal part 32b containing aluminum. Aluminum is a flexible metal material that is easier to form a screw groove in than silicon carbide. Therefore, the screw or the like can be fixed by being in close contact with the metal part 32a, thereby increasing the joining strength. Therefore, the screw hole 60 has a structure that is excellent in terms of ease of tightening the screw. Moreover, the screw hole 60 is formed such that the periphery of the metal portion 32b made of a soft metal material is covered with a silicon carbide-based porous body, so that the screw hole 60 has a structure excellent in mechanical strength.

[0016] FIG. 2 is a cross-sectional view illustrating an example of the configuration of the electronic device 100. As shown in FIG. 2 has a structure in which a case 80 is joined to a heat dissipation member 10 by inserting a screw 64 into a screw hole 60. The heat dissipation member 10 having the screw hole 60 can be detachably fixed to another member using the screw 64.

[0017] 2 is formed around both ends of the through hole 40, and is configured so that the inner diameter of the through hole 40 gradually widens outward. The head of the screw 64 is fixed in a state of tight contact with the metal part 32a on the tapered part 50. Since the thickness of the metal part 32a is thicker than in the case of a non-tapered structure, the head of the screw 64 can be tightly attached to the metal part 32a. This improves the ease of tightening the screw in the screw hole 60 in the through hole 40. On the other hand, the hole diameter D2 of the screw hole 60 is smaller than the maximum hole diameter (hole diameter D1) of the tapered portion 50. That is, the volume ratio of aluminum to silicon carbide in the vicinity of the through hole 40 can be reduced. This makes it possible to suppress a decrease in the mechanical strength of the metal-silicon carbide composite 20. Also, distortion caused by the difference in linear expansion coefficient between aluminum and silicon carbide can be suppressed.

[0018] FIG. 5 is a process cross-sectional view illustrating the impregnation process when a taper forming process is included. FIG. 5 shows an impregnation step in which molten aluminum 3 is impregnated into the silicon carbide porous body 2 (preform) having the through-holes 40 formed therein. In this impregnation step, the silicon carbide porous body 2 sandwiched between spacers 1a, 1b is usually placed in the space within the mold, and heated and melted aluminum, i.e., molten aluminum 3, is supplied. The supplied molten aluminum 3 impregnates the silicon carbide porous body 2, and at this time, due to the difference in latent heat of solidification, the aluminum impregnated inside the silicon carbide porous body 2 and the aluminum present in the vicinity of its surface solidify first to become solidified aluminum 3b. In this case, the flow path of the molten aluminum 3 supplied later is blocked by the solidified aluminum 3b that has solidified first, making it difficult for the molten aluminum 3 to move through the silicon carbide porous body 2 or the vicinity of its surface.

[0019] The through-hole 40 in FIG. 6(a) is formed by a general method such as by using a drill, and has a cylindrical structure with a uniform hole diameter in the plate thickness direction of the silicon carbide-based porous body 2 without a tapered portion. FIG. 6(a) shows a state in which the flow 3a of the molten aluminum 3 is hindered by the solidified aluminum 3b that has solidified earlier. This is because the molten aluminum 3 cannot move inside the silicon carbide porous body 2 where the solidified aluminum 3b exists, and has difficulty passing near the surface around the end of the through hole 40. Therefore, the supply amount of the molten aluminum 3 moving to the through hole 40 is insufficient. If the molten aluminum 3 in the through hole 40 solidifies in such a state, many voids 4 will be generated inside the through hole 40, as shown in FIG. 6(b). Another factor in the formation of the voids 4 is thought to be metal contraction during cooling.

[0020] In contrast, the through hole 40 in FIG. 5(a) has tapered portions 50 around both ends, where the inner diameter of the through hole 40 gradually widens outward. In FIG. 5(b), the tapered portion 50 of the through hole 40 becomes a flow path that is not blocked by the solidified aluminum 3b that has solidified earlier. The molten aluminum 3 can move around the end of the through hole 40 through this flow path. As a result, the flow 3a of the supplied molten aluminum 3 is better than that in FIG. 6(a). Therefore, a sufficient amount of molten aluminum 3 can be supplied into the through hole 40. In this state, when the molten aluminum 3 in the through hole 40 solidifies, it is possible to suppress the generation of voids 4 in the metal portion 32 inside the through hole 40, as shown in FIG. 5(b).

[0021] In this manner, the formation of voids 4 is suppressed in metal portion 32b in through hole 40. For this reason, the thread formed on the surface of metal portion 32b, which is the inner surface of screw hole 60, is less likely to be crushed when the screw is tightened. Therefore, in the heat dissipation member 10 of this embodiment, the screws can be easily fastened into the screw holes 60 .

[0022] Each step of the method for producing a heat dissipation member according to this embodiment will be described in detail below.

[0023] A method for manufacturing the heat dissipation member 10 of this embodiment will be described with reference to FIGS. FIG. 3 is a perspective view showing a schematic example of a manufacturing process for a heat dissipation member, FIG. 4 is a cross-sectional view taken along the line AA in FIG. 3(c), and FIG. 5 is a cross-sectional view showing a schematic example of an impregnation process.

[0024] In the preparation step, a flat silicon carbide porous body 2b as shown in FIG. 3(a) is produced.

[0025] There is no particular limitation on the method for producing the silicon carbide porous body (SiC preform), and it can be produced by a known method. For example, it can be produced by adding silica or alumina as a binder to silicon carbide (SiC) powder as a raw material, mixing, forming, and firing at 800°C or higher. The method for forming the sheet can be appropriately selected from known methods, such as dry pressing, wet pressing, extrusion molding, injection molding, casting, and sheet molding followed by punching.

[0026] A high SiC content in the silicon carbide porous body is preferable because it increases the thermal conductivity and decreases the thermal expansion coefficient, but if the SiC content is too high, the aluminum alloy may not be sufficiently impregnated. For practical purposes, it is preferable that the SiC preform contains 40 mass % or more of coarse SiC particles having an average particle size of preferably 40 μm or more, and that the relative density of the SiC preform is preferably in the range of 55% to 75%.

[0027] The strength of the silicon carbide porous body (SiC preform) is preferably 3 MPa or more in bending strength to prevent cracking during handling or impregnation. The average particle size can be measured by calculating the average value of the diameters of 1000 particles using a scanning electron microscope (e.g., JEOL "JSM-T200 type") and an image analyzer (e.g., Nippon Avionics Co., Ltd.). The relative density can be measured by the Archimedes method or the like.

[0028] It is preferable to adjust the particle size of the SiC powder, which is the raw material of the silicon carbide porous body (SiC preform), by appropriately combining coarse powder and fine powder, etc. This makes it easier to achieve both the strength of the silicon carbide porous body (SiC preform) and high thermal conductivity of the heat dissipation member finally obtained. Specifically, a mixed powder of (i) coarse SiC powder having an average particle size of 40 μm to 150 μm and (ii) fine SiC powder having an average particle size of 5 μm to 15 μm is suitable. Here, the ratio of (i) to (ii) in the mixed powder is preferably 40% by mass to 80% by mass for (i) and 20% by mass to 60% by mass for (ii).

[0029] Silicon carbide porous bodies (SiC preforms) can be obtained by degreasing and sintering a molded body of a mixture of SiC powder and a binder added. If the sintering temperature is 800°C or higher, it is easy to obtain silicon carbide porous bodies (SiC preforms) with a bending strength of 3 MPa or more, regardless of the sintering atmosphere. However, in an oxidizing atmosphere, firing at a temperature exceeding 1100° C. may accelerate the oxidation of SiC, resulting in a decrease in the thermal conductivity of the metal-silicon carbide composite. Therefore, in an oxidizing atmosphere, firing at a temperature of 1100° C. or less is preferable. The firing time may be appropriately determined according to conditions such as the size of the silicon carbide porous body (SiC preform), the amount put into the firing furnace, and the firing atmosphere.

[0030] When forming silicon carbide porous bodies (SiC preforms) into a specific shape, changes in curvature due to drying can be prevented by drying each preform one by one, or by using spacers such as carbon with the same shape as the preform between the SiC preforms. Also, by carrying out the same treatment as drying for firing, it is possible to prevent changes in shape due to changes in the internal structure.

[0031] If necessary, at least one surface of the silicon carbide porous body (SiC preform) may be machined to have a curved shape that is convex toward the outside, for example, by a cutting / grinding tool such as a lathe. Not only one surface but also both surfaces of the silicon carbide porous body (SiC preform) may be machined. In this way, by performing machining (cutting) at the preform stage, there is no need to use special tools for cutting after metal impregnation, and there is an advantage that the degree of curvature and flatness can be easily controlled.

[0032] In the preparation step, the outer periphery of the silicon carbide-based porous body 2b is processed as necessary to form the silicon carbide-based porous body 2 having a desired outer periphery structure as shown in Fig. 3(b). Specifically, at least four corners of the silicon carbide-based porous body 2 may be partially removed to form cutout portions 22.

[0033] The peripheral processing may be performed by, but is not limited to, ordinary machining, grinding, water jet processing, laser processing, electric discharge processing, or the like.

[0034] Next, in the hole forming step, through holes 40 are formed penetrating in the plate-like silicon carbide-based porous body 2 in the plate thickness direction. A plurality of through holes 40 as shown in Fig. 3(b) are formed in the peripheral portion of the silicon carbide-based porous body 2. Specifically, it is preferable to provide the through holes 40 in at least four corners of the silicon carbide-based porous body 2. The through holes 40 can be formed by machining such as drilling.

[0035] 3(c) is formed at one or both ends of the through-hole 40. Specifically, it is preferable to provide the tapered portion 50 at each of both ends of all the through-holes 40. 4, a taper machining tool (tool 5) with a predetermined angle is used, and the hole diameter D1 (taper diameter) of the tapered portion 50 and the height H (taper height) of the tapered portion 50 can be controlled by adjusting the drop amount of the tool 5 and the angle of the tool 5. In addition, the angle θ (taper angle) of the tapered portion 50 can be controlled by the hole diameter D1 and the height H. By adjusting the taper diameter, taper height, and / or taper angle, it is possible to suppress the occurrence of voids in the through-holes 40 when the metal-silicon carbide composite 20 is impregnated with a metal. Here, the taper diameter (hole diameter D1) is defined as the maximum diameter of the through hole 40 in the plate thickness direction in one of the cross-sectional views of the heat dissipation member 10 in FIG. The hole diameter D0 of the through hole 40 is defined as the minimum diameter of the through hole 40 in the plate thickness direction in one of the cross-sectional views of the heat dissipation member 10 in FIG.

[0036] The taper diameter is, for example, +6 to +40 mm, preferably +8 to +36 mm, and more preferably +10 to +32 mm, relative to the minimum hole diameter (hole diameter D0) of the through-hole 40. Alternatively, the taper diameter may be configured such that hole diameter D1 / hole diameter D0 satisfies, for example, 1.5 to 16, preferably 2 to 15, and more preferably 2.3 to 14.

[0037] An example of the hole diameter D0 of the through-holes 40 can be appropriately selected depending on the area and application of the flat silicon carbide porous body 2, and is, for example, 4 to 10 mm, preferably 5 to 9 mm, and more preferably 6 to 9 mm.

[0038] The taper height is defined as the distance (height H) between an auxiliary line L1 drawn through an end of the tapered portion 50 on the front side where the through hole 40 has a maximum diameter, and an auxiliary line L2 drawn through an end of the tapered portion 50 on the inner side where the through hole 40 has a minimum diameter, in one of the cross-sectional views of the heat dissipation member 10 in FIG. 2. Note that this auxiliary line L1 may be formed along the main surface of the silicon carbide-based porous body 2. The taper height (height H) is, for example, 0.1 to 1 mm, preferably 0.2 to 0.8 mm, and more preferably 0.3 to 0.6 mm.

[0039] The taper angle is defined as the angle (θ) between the above-mentioned auxiliary line L1 and an auxiliary line L3 drawn along the tapered surface of the tapered portion 50 in one of the cross-sectional views of the heat dissipation member 10 in FIG. The taper angle (θ) is, for example, 0.2 to 7°, preferably 0.3 to 6°, and more preferably 0.4 to 5°. By setting the taper angle to the upper limit or less, it is possible to suppress a decrease in mechanical strength in the metal-silicon carbide composite 20. It is also possible to suppress distortion caused by the difference in linear expansion coefficient between aluminum and silicon carbide. Furthermore, by setting the taper angle to the lower limit or more, it is possible to improve the manufacturing stability of the heat dissipation member 10.

[0040] The shape of tapered portion 50 is not particularly limited as long as it serves as a flow path for molten aluminum 3 . The shape of tapered portion 50 when viewed from a direction perpendicular to the main surface of silicon carbide porous body 2 (hereinafter referred to as the direction perpendicular to the main surface) may have a ring-like structure surrounding through-hole 40, but is not limited to this. The outer edge shape of tapered portion 50 may be configured to be a circle, such as a perfect circle or an ellipse, or a polygon, such as a rectangle or a hexagon.

[0041] Furthermore, tapered portion 50 may have a plurality of separated portions that are separated from each other when viewed from the direction perpendicular to the main surface. That is, tapered portion 50 may have two or more flow paths for molten aluminum 3 that are provided individually. Furthermore, a part of tapered portion 50 when viewed from the direction perpendicular to the main surface may have an extension that protrudes further toward the outer edge than other parts. The outer edge or extension of tapered portion 50 may reach the outer periphery of silicon carbide-based porous body 2, but is preferably located inside the outer periphery from the viewpoint of mechanical strength.

[0042] The tapered surface of the tapered portion 50 in the cross-sectional view of the silicon carbide-based porous body 2 may be linear or curved, and may have one or more steps or grooves in the surface. Specifically, the tapered surface in the cross-sectional view of the silicon carbide-based porous body 2 in Fig. 2 may be linear. This improves the flow 3a of the molten aluminum 3.

[0043] Next, in the impregnation step, the inside of the flat silicon carbide porous body 2 is impregnated with a metal containing aluminum to obtain a metal-silicon carbide composite 20.

[0044] First, in Fig. 5(a), silicon carbide-based porous body 2, sandwiched between spacers 1a and 1b on both sides, is set in a mold, and then molten metal (metal containing aluminum) is poured into the mold. The molten metal is then pressed, so that the metal is impregnated into the voids of silicon carbide-based porous body 2, and the through-holes 40 are filled with the metal. In Fig. 5(b), after cooling, a metal-silicon carbide composite 20 containing aluminum is obtained. At this time, the metal is cooled inside through-holes 40, and metal parts 32 are filled.

[0045] There are no particular limitations on the spacers 1a and 1b, so long as they enable release of the obtained metal-silicon carbide composite 20. A laminated structure of silicon carbide-based porous bodies obtained by further arranging another silicon carbide-based porous body and another spacer on the spacer 1a may be used in the impregnation step.

[0046] Here, it is preferable to preheat the silicon carbide porous body 2 when setting it in the mold. The preheating temperature is, for example, 500° C. or higher and 650° C. or lower. In order to prevent a drop in temperature, it is preferable to pour the molten metal as soon as possible after the silicon carbide porous body (SiC preform) is set in the mold.

[0047] When the metal-silicon carbide composite 20 is obtained by impregnating the silicon carbide porous body 2 with a metal, a surface metal layer (metal layer 30) may be provided on the surface (main surface, etc.) of the metal-silicon carbide composite 20. This allows the metal layer 30 containing aluminum to be formed on one or both surfaces of the metal-silicon carbide composite 20. As an example, a mold having dimensions slightly larger than the dimensions of the SiC preform is prepared as the mold for impregnation, and the SiC preform is placed in the mold and molten metal is injected to provide a surface metal layer. As another example, a surface metal layer can be provided by arranging one or more of fibers, spherical particles, and crushed particles made of alumina or silica so as to be in direct contact with the surface of the SiC preform, and then impregnating the surface with metal. In this case, the content of the material made of one or more of fibers, spherical particles, and crushed particles made of alumina or silica in the surface metal layer is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.3% by mass or more and 2% by mass or less, based on the mass of the metal-silicon carbide composite. As yet another example, a surface metal layer can be provided by placing a thin metal plate or film on the surface of the SiC preform and then impregnating the metal, or by previously adding grooves or the like to the surface of the SiC preform.

[0048] The pressing pressure of the molten metal is not particularly limited as long as the metal is sufficiently impregnated, but is, for example, 30 MPa or more.

[0049] In order to allow a metal (preferably aluminum or an alloy containing aluminum) to fully infiltrate into the voids of the preform, it is preferable that the melting point of the impregnating metal be appropriately low. In this respect, for example, an aluminum alloy containing 7% by mass or more and 25% by mass or less of silicon is preferable. Furthermore, by containing 0.2% by mass or more and 5% by mass or less of magnesium, the bond between the silicon carbide grains and the metal part becomes stronger, which is preferable. There is no particular restriction on the metal components other than aluminum, silicon, and magnesium in the aluminum alloy as long as the characteristics are not significantly changed, and for example, copper, etc. may be contained.

[0050] As the aluminum alloy, preferably, casting alloys such as AC4C, AC4CH, and ADC12 can be used.

[0051] Incidentally, in order to remove distortion caused during the impregnation, an annealing treatment may be performed on the metal-silicon carbide composite 20. The annealing treatment may be performed, for example, at a temperature of about 400° C. to 550° C. for 10 minutes or more.

[0052] In this manner, the heat dissipation member 10 of the present embodiment is obtained.

[0053] Of course, the method for manufacturing the heat dissipation member of this embodiment is not limited to the above. For example, in the heat dissipation member 10 of the present embodiment, the surface metal layer may be of any configuration, and therefore the surface metal layer does not necessarily have to be formed. The surface of the obtained heat dissipation member 10 may be subjected to a polishing process or a blasting process.

[0054] Furthermore, in the obtained heat dissipation member 10, a step of forming a screw hole may be carried out after the above impregnation step. In the screw hole forming step, in FIG. 5(b), a screw hole is formed in the metal portion 32 formed by filling the inside of the through hole 40 with aluminum.

[0055] 1(b) includes a screw 64 formed in the metal portion 32b inside the through hole 40. The screw 64 is a blind hole, and has a screw thread formed on the inner surface.

[0056] In the cross-sectional view of the heat dissipation member 10, the hole diameter of the screw 64 is denoted as D2, and the maximum hole diameter of the through hole 40 is denoted as D1. D2 / D1 is, for example, 0.1 to 0.9, preferably 0.15 to 0.7, and more preferably 0.2 to 0.6.

[0057] Furthermore, after the impregnation step, a plating step may be performed on the obtained heat dissipation member 10. For example, a plating layer can be provided on the main surface side of the heat dissipation member 10 by a known method such as electroless Ni-P plating or Ni-B plating.

[0058] The heat dissipation member 10 may further include a plating layer formed on the surface of the metal portion 32b inside the screw hole 62 of FIG. 1(b). At this time, in a cross-sectional view of the through hole 40, the thickness of the metal portion 32b is designated as W1, and the thickness of the plating layer inside the screw hole 62 is designated as W2. W2 / W1 is, for example, 0.001 to 0.04, preferably 0.002 to 0.03, and more preferably 0.003 to 0.02.

[0059] The heat dissipation member 10 of this embodiment will be described in detail.

[0060] The heat dissipation member 10 in FIGS. 1( a ) and 1 ( b ) includes a flat plate-shaped metal-silicon carbide composite 20 and metal layers 30 formed on at least the front and rear surfaces of the metal-silicon carbide composite 20 . Of the two surfaces of the heat dissipation member 10, the surface on which the electronic components are mounted is referred to as a main surface 30A, and the other surface is referred to as a back surface 30B.

[0061] In one embodiment, the main surface 30A and / or the back surface 30B (ie, the surface of the heat dissipation member 10) can be a metal-silicon carbide composite 20 containing aluminum. In another embodiment, the main surface 30A and / or the back surface 30B (the surface of the heat dissipation member 10) may be a metal layer 30. For example, the main surface 30A and / or the back surface 30B of the heat dissipation member 10 preferably includes a metal layer 30 (a surface metal layer) containing aluminum. In this case, the portion of the heat dissipation member 10 other than the surface metal layer may be a metal-silicon carbide composite or the like.

[0062] 1(a) has a plurality of screw holes 62 (through holes) on its periphery. More specifically, when the heat dissipation member 10 is substantially rectangular as described later, it is preferable that the screw holes 62 are provided in the metal layer 30a formed in the cutout portions 22 at least at the four corners of the heat dissipation member 10. The screw holes 62 are used when joining the heat dissipation member 10 to another heat dissipation part (for example, a heat dissipation fin, etc.) with a screw or the like.

[0063] The electronic component may be, for example, a power semiconductor element. A large amount of heat may be released from the electronic element 90, which is a power semiconductor element, but the heat dissipation member 10 (element mounting board) of this embodiment may be appropriately joined to another heat dissipation member (heat dissipation fins, etc.) to efficiently remove the heat.

[0064] The electronic element 90 includes at least a ceramic substrate 92. In Fig. 2, the electronic element 90 has a structure in which the ceramic substrate 92 is sandwiched between two metal layers 13. The electronic element 90 is mounted on the main surface 3A of the heat dissipation member 10, for example, by soldering with solder 70. When the electronic element 90 is viewed from above with the main surface 3A of the heat dissipation member 10 as the upper surface, 10 to 80% of the area of ​​the heat dissipation member 10 is covered by the electronic element 90.

[0065] The heat dissipation member 10 is preferably substantially rectangular in shape. That is, when viewed from a direction perpendicular to the main surface 30A of the heat dissipation member 10, the shape of the heat dissipation member 10 is substantially rectangular. Here, "substantially rectangular" means that at least one of the four corners of the heat dissipation member 10 may be processed to have a rounded shape rather than a right angle (of course, the four corners may also be right angled). If at least one of the four corners of the heat dissipation member 10 is processed into a rounded shape, the point where the straight lines of the short side and long side intersect when the short side and long side are extended when the heat dissipation member 10 is viewed from above can be defined as the "vertex" of the rectangle. In this case, the "length of the short side" and the "length of the long side" of the heat dissipation member 10 can be defined with the above-mentioned "vertex" as the start point or end point.

[0066] The length and width of the heat dissipation member 1 are, for example, approximately 40 mm×90 mm to 140 mm×250 mm. The thickness of the heat dissipation member 1 is, for example, 2 mm to 6 mm, preferably 3 mm to 5 mm. If the thickness of the heat dissipation member 1 is not uniform, it is preferable that at least the thickness at the center of gravity of the heat dissipation member 1 is within the above range. Alternatively, if the thickness of the heat dissipation member 1 is not uniform, it is preferable that the thickness of each part other than the holes is within the above range.

[0067] The heat dissipation member 10 has an average thermal expansion coefficient of, for example, 4 to 12 ppm / K, and preferably 4 to 10 ppm / K at 25° C. to 150° C. This can suppress cracks and breakage caused by the difference in thermal expansion coefficient with the ceramic plate. The linear thermal expansion coefficient is the value when the temperature is decreased from 150° C. to 25° C. The linear thermal expansion coefficient can be measured with a thermal dilatometer in accordance with JIS R1618 at a temperature decrease rate of 5° C. / min or less.

[0068] The thermal conductivity of the heat dissipation member 10 in the plate thickness direction at 25° C. is, for example, 150 to 300 W / m·K, and preferably 180 to 300 W / m·K.

[0069] The metal contained in the metal-silicon carbide composite 20 may be, for example, aluminum, an aluminum alloy, magnesium, or a magnesium alloy. From the viewpoint of thermal conductivity, the metal-silicon carbide composite 20 preferably contains aluminum or an aluminum alloy. As an example of the alloy, an aluminum alloy containing 7 to 25 mass% of silicon (Si) can be used. By using an aluminum alloy containing 7 to 25 mass% of silicon, it is possible to obtain the effect of promoting densification of the metal-silicon carbide composite 20.

[0070] When the metal-silicon carbide composite 20 is an aluminum-silicon carbide composite, aluminum is contained as a main component, and the content of aluminum in the metal may be, for example, 60 to 100 mass %, or 80 to 99.8 mass %. The metal contained in the aluminum-silicon carbide composite may contain, in addition to aluminum, which is the main component, one or more elements selected from the group consisting of magnesium, silicon, iron and copper, as long as the effects of the present invention are not impaired.

[0071] The metal contained in the metal layer 30 may be the same as the metal contained in the metal-silicon carbide composite 20, and may be, for example, aluminum, an aluminum alloy, magnesium, or a magnesium alloy.

[0072] The thickness of the metal layer 30 is, for example, 10 to 300 μm, or preferably 30 to 150 μm. By setting the thickness to be equal to or greater than the above lower limit, it is possible to improve the film strength of metal layer 30. By setting the thickness to be equal to or less than the above upper limit, it is possible to suppress the occurrence of warping due to the difference in thermal expansion coefficient with metal-silicon carbide composite 20. The thermal conductivity can be measured by the laser flash method in accordance with JIS R1611.

[0073] The material of the ceramic substrate 92 included in the electronic component is not particularly limited as long as it is a ceramic material. For example, it may be a nitride ceramic such as silicon nitride or aluminum nitride, an oxide ceramic such as aluminum oxide or zirconium oxide, a carbide ceramic such as silicon carbide, a boride ceramic such as lanthanum boride, etc. Among them, aluminum nitride, silicon nitride, and aluminum oxide are preferable from the viewpoints of insulation, strength of bonding with the metal layer 13, mechanical strength, etc.

[0074] An Ag--Cu based brazing material is preferable as the brazing material for joining the metal layer 30 and the ceramic substrate 92. That is, the brazing material is preferably a mixture of Ag powder, Cu powder, and the like. The brazing material may contain Sn or In for the purpose of improving wettability with the ceramic plate. The brazing material preferably contains an active metal from the viewpoint of increasing the reactivity with the ceramic plate, etc. Examples of the active metal include titanium, zirconium, hafnium, niobium, etc. From the viewpoint of high reactivity with aluminum nitride substrates and silicon nitride substrates and extremely high bonding strength, it is preferable that the brazing material contains titanium.

[0075] The type of solder 70 is not particularly limited, but for example, a lead-tin eutectic solder or a lead-free solder can be used.

[0076] 1, the heat dissipation member 10 may have a plating layer formed on the main surface 30A side, specifically, on the outermost surface, of the heat dissipation member 10. This can improve the bondability with the solder.

[0077] The plating layer may contain at least one of Ni, Au, and Ag. Among these, the plating layer is preferably composed of a Ni plating layer containing Ni.

[0078] The thickness of the plating layer is, for example, 3 to 15 μm, preferably 4 to 10 μm. By setting the thickness to be equal to or greater than the lower limit, the coating stability of the plating layer can be improved. By setting the thickness to be equal to or less than the upper limit, the occurrence of warping due to the difference in thermal expansion coefficient with the underlying layer such as the metal layer 30 can be suppressed.

[0079] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention. EXAMPLES

[0080] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0081] <Manufacture of heat dissipation components> (Formation of silicon carbide porous body) First, silicon carbide powder A, silicon carbide powder B, and silica sol were mixed in a stirrer mixer for 30 minutes to obtain a mixture. Silicon carbide powder A (manufactured by Pacific Random Co., Ltd.: NG-150, average particle size: 100 μm) 300 g Silicon carbide powder B (Yakushima Denko Co., Ltd.: GC-1000F, average particle size: 10 μm) 150 g Silica sol (Nissan Chemical Industries, Ltd.: Snowtex) 30g

[0082] The mixture obtained was poured into a mold and pressed at a pressure of 10 MPa. This resulted in a plate-shaped molded body with dimensions of 135 mm x 75 mm x 5.0 mm. The molded body obtained was fired in air at a temperature of 900°C for 2 hours to obtain a silicon carbide-based porous body with a relative density (bulk density) of 65% by volume.

[0083] (Through hole / tapered section formation process) Through holes were formed at the four corners of the silicon carbide porous body using a drill. Next, a taper machining tool (tool 5) having a predetermined angle as shown in FIG. 4 was pressed against both ends of each through hole to form a tapered portion. The dimensions of the tapered portions in Examples 1 and 2 are shown in the following Table 1. In Comparative Example 1, no tapered portion was formed. The through-hole diameters in Table 1 refer to the minimum hole diameter (D0).

[0084] (Metal Impregnation) The machined silicon carbide porous body was sandwiched between carbon-coated stainless steel plates measuring 170 mm×100 mm×0.8 mm on both sides and laminated. Next, 6 mm thick steel plates were placed on both sides, connected with six M10 bolts, and tightened with a torque wrench so that the tightening torque in the surface direction was 2 Nm to form a single block. The integrated block was then preheated to 620°C in an electric furnace, and then placed in a preheated press mold with an inner diameter of 400 mm. Molten aluminum alloy containing 12% by mass of silicon and 1.0% by mass of magnesium was poured into the press mold, and pressurized at a pressure of 60 MPa for 20 minutes. This allowed the silicon carbide porous body to be impregnated with the aluminum alloy.

[0085] After the impregnation was completed, the sample was cooled to 25°C, then cut to the shape of the stainless steel plate using a wet band saw, and the sandwiched stainless steel plate was peeled off.Furthermore, to remove distortion caused by the impregnation, the sample was annealed at a temperature of 500°C for 3 hours. In this manner, an aluminum-silicon carbide composite was obtained.

[0086] (Post-impregnation treatment) The outer periphery of the resulting aluminum-silicon carbide composite was machined by an NC lathe to a size of 140 mm×80 mm. Subsequently, a screw hole (hole diameter D2: 4 mm) was formed in the metal portion formed in the through hole of the aluminum-silicon carbide composite. In this manner, a heat dissipation member without a plating layer was obtained.

[0087] (Evaluation of porosity) Each of the obtained heat dissipating members was cut, and the internal surfaces of the through holes were observed for the presence or absence of voids (individual or connected bubble-like streaks) in surface photographs taken at 50 magnifications using an optical microscope. Also, when the number of photos (number of inspections) in another area where observations were made was N1 and the number of photos in which looseness was observed (number of occurrences) was N2, the looseness occurrence rate was calculated based on the formula: N2 / N1×100% and described in Table 1.

[0088] (Ease of screwing) Using each of the obtained heat dissipation members, the workability when screwing a screw into a screw hole was evaluated. In Comparative Example 1, at four screw holes, the screw threads might be crushed and it might be impossible to tighten the screw (defect). In Examples 1 and 2, at four screw holes, compared with Comparative Example 1, the screw threads were not crushed and it was possible to easily tighten the screw (excellent).

[0089]

Table 1

[0090] It was found that the heat dissipation members of Examples 1 and 2 were less likely to have their screw threads crushed and it was easier to tighten the screws into the screw holes compared with Comparative Example 1.

[0091] This application claims priority based on Japanese Patent Application No. 2021-164568 filed on October 6, 2021, and incorporates the entire disclosure thereof herein.

Explanation of reference signs

[0092] 1a Spacer 1b Spacer 2 Silicon carbide porous body (preform) 2a Silicon carbide porous body 2b Silicon carbide porous body 3 Molten aluminum 3a Flow 3b Solidified aluminum 4 Looseness 5 Tool 10 Heat dissipation member 20 Metal-silicon carbide composite 20a Metal-silicon carbide composite 22 Cutout 30 metal layer 30a metal layer 30A main surface 30B back side 32 Metal Parts 32a Metal part 32b Metal part 40 Through hole 50 Tapered section 60 screw holes 62 screw holes 64 Screws 70 Solder 80 cases 90 Electronic Elements 92 Ceramic Substrate 100 Electronic equipment

Claims

1. A heat dissipation member including a flat metal-silicon carbide composite plate containing aluminum, At least one through hole penetrating the flat metal-silicon carbide composite in a plate thickness direction; A tapered portion around one or both ends of the through hole, in which the inner diameter of the through hole gradually increases toward the outside; a metal portion including aluminum formed on an inner surface of the through hole; A screw hole formed in the metal part; Equipped with A heat dissipation component comprising a plating layer formed on a surface of the metal portion inside the screw hole.

2. The heat dissipation member according to claim 1 , A heat dissipation member, wherein the angle of the tapered portion is 0.2° or more and 7° or less.

3. The heat dissipation member according to claim 1 or 2, A heat dissipation member configured such that, when the maximum diameter of the through hole is D1 and the diameter of the screw hole is D2, D2 / D1 satisfies 0.1 or more and 0.9 or less.

4. The heat dissipation member according to claim 1 or 2, A heat dissipation component configured such that, in a cross-sectional view of the through hole, when the thickness of the metal portion is W1 and the thickness of the plating layer inside the screw hole is W2, W2 / W1 satisfies 0.001 or more and 0.04 or less.

5. The heat dissipation member according to claim 1 or 2, A heat dissipation member comprising a plating layer provided on a main surface side of the heat dissipation member.

6. The heat dissipation member according to claim 5, The heat dissipation member, wherein the plating layer is a Ni plating layer containing Ni element.

7. The heat dissipation member according to claim 1 or 2, A heat dissipation member comprising an aluminum-containing metal layer provided on a main surface of the heat dissipation member.

8. The heat dissipation member according to claim 1 or 2, A heat dissipation member having an average thermal expansion coefficient from 25° C. to 150° C. of 4 ppm / K or more and 12 ppm / K or less.

9. The heat dissipation member according to claim 1 or 2, The heat dissipation member has a thermal conductivity in a plate thickness direction at 25°C of 150 W / m·K or more and 300 W / m·K or less.

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