Method for manufacturing heat dissipation member

Abstract

To provide a method of manufacturing a heat dissipation member excellent in manufacturing stability.SOLUTION: A method of manufacturing a heat dissipation member comprising a plate-formed metal-silicon carbide-based composite body containing aluminum according to the present invention, includes: a preparation step of preparing a plate-formed silicon carbide-based porous body; a hole forming step of forming at least one or more through-holes penetrating through the plate-formed silicon carbide-based porous body in a plate-thickness direction; an impregnation step of filling aluminum in a molten state within the through-hole while impregnating it into the plate-formed silicon carbide-based porous body, in a state the plate-formed silicon carbide-based porous body is sandwiched at both sides by spacers; and a taper forming step, between the hole forming step and the impregnation step, for forming a tapered portion where the inner diameter of the through-hole gradually spreads outward around one or both ends of the through-hole.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Various developments have been made on heat dissipation members. For example, the technology described in Patent Document 1 is known as an example of 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 (see, for example, Figure 2 and paragraph 0012 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-299532 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that the method for manufacturing a plate-shaped heat dissipation component described in Patent Document 1 leaves room for improvement in terms of manufacturing stability. [Means for solving the problem]

[0005] The inventors' investigations have revealed that many voids occur in the aluminum coating layer inside the fixing holes after molten aluminum is impregnated into the fixing holes in the silicon carbide porous body of Patent Document 1. This is thought to be due to the formation of individual or connected bubble-like voids due to an insufficient supply of molten aluminum to the holes.

[0006] As a result of intensive research based on this knowledge, the inventors discovered that by using a tapered portion provided at the end of the through hole as a flow path for the molten aluminum, the supply of molten aluminum to the through hole can be improved and the occurrence of cavities can be suppressed, leading to the completion of the present invention.

[0007] According to the present invention, A method for manufacturing a heat dissipation member having a flat metal-silicon carbide composite plate containing aluminum, comprising: a preparation step of preparing a flat silicon carbide porous body; a hole forming step of forming at least one through hole penetrating the flat silicon carbide porous body in a plate thickness direction; an impregnation step of filling the through holes with molten aluminum while the flat silicon carbide porous body is sandwiched between spacers on both sides; Including, a taper forming step between the hole forming step and the impregnation step, in which a tapered portion is formed around one or both ends of the through hole such that the inner diameter of the through hole gradually widens toward the outside; A method for manufacturing a heat dissipation member is provided. [Effects of the Invention]

[0008] According to the present invention, a method for manufacturing a heat dissipation member with excellent manufacturing stability is provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams ((a) and (b)) schematically illustrating an example of a heat dissipation member. [Figure 2] FIG. 1 is a diagram (cross-sectional view) schematically illustrating an example of an electronic device. [Figure 3] 1A to 1C are perspective views schematically illustrating an example of a manufacturing process for the heat dissipation member of the present embodiment. [Figure 4] FIG. 3(c) is a cross-sectional view taken along the line AA in FIG. [Figure 5]10A to 10C are cross-sectional process views schematically illustrating an example of an impregnation process when a tapered portion is present. [Figure 6] 10A to 10C are cross-sectional process views schematically illustrating an example of an impregnation process when no tapered portion is provided. [Figure 7] 1 is a diagram showing the state inside a through-hole of Example 1. FIG. [Figure 8] FIG. 10 is a diagram showing the state inside a through-hole of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted where appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional proportions.

[0011] Unless otherwise explicitly stated, the term "approximately" used in this specification means that a range is included taking into consideration manufacturing tolerances, assembly variations, and the like, unless otherwise explicitly stated. 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, unless otherwise specified, the symbol "to" indicates that the upper and lower limits are included.

[0012] A method for manufacturing the heat dissipation member of this embodiment will be outlined below.

[0013] The method for manufacturing a heat dissipation member of this embodiment is for manufacturing a heat dissipation member having a flat metal-silicon carbide composite containing aluminum, and includes a preparation step of preparing a flat silicon carbide porous body, a hole formation step of forming at least one through hole that penetrates the flat silicon carbide porous body in the plate thickness direction, and an impregnation step of sandwiching both sides of the flat silicon carbide porous body with spacers and filling the through holes while impregnating the inside of the flat silicon carbide porous body with molten aluminum, and includes a taper formation step between the hole formation step and the impregnation step of forming a tapered portion around one or both ends of the through hole, the inner diameter of the through hole gradually widening outward.

[0014] According to the manufacturing method of this embodiment, it is possible to suppress the occurrence of voids formed inside the through-holes, thereby improving the manufacturing stability in manufacturing the heat dissipation member.

[0015] Although the details of the mechanism of porosity reduction are unclear, it is speculated as follows. FIG. 5 is a process cross-sectional view illustrating the impregnation process when a taper forming process is included, and FIG. 6 is a process cross-sectional view illustrating the impregnation process when a taper forming process is not included.

[0016] 5 and 6 show 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 and 1b is usually placed in the space within a mold, and heated and melted aluminum, i.e., molten aluminum 3, is supplied. The supplied molten aluminum 3 impregnates the interior of the silicon carbide porous body 2, and at this time, due to differences in latent heat of solidification, the molten aluminum impregnated inside the silicon carbide porous body 2 and that present near its surface solidify first, becoming solidified aluminum 3b. In this case, the flow path of the molten aluminum 3 supplied later is blocked by the solidified solidified aluminum 3b, making it difficult for the molten aluminum 3 to move through the interior of the silicon carbide porous body 2 or near its surface.

[0017] The through-hole 40 in FIG. 6(a) is formed by a general method such as drilling, and has a cylindrical structure with a uniform hole diameter in the thickness direction of the silicon carbide porous body 2 without any tapered portion. FIG. 6(a) shows a state in which the flow 3a of the molten aluminum 3 is obstructed 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 is present, and has difficulty passing near the surface around the end of the through hole 40. As a result, the amount of molten aluminum 3 moving into the through hole 40 is insufficient. If the molten aluminum 3 in the through hole 40 solidifies under such conditions, many voids 4 will be generated inside the through hole 40, as shown in FIG. 6(b). Metal contraction that occurs during cooling is also thought to be one factor in the formation of the voids 4.

[0018] 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 forms 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 improved compared to FIG. 6(a). Therefore, a sufficient amount of molten aluminum 3 can be supplied into the through hole 40. When the molten aluminum 3 in the through hole 40 solidifies in this state, as shown in FIG. 5(b), the generation of voids 4 in the metal portion 32 inside the through hole 40 can be suppressed.

[0019] Fig. 1(a) is a plan view schematically showing an 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 indicated by a solid line, and the outer edge of a metal layer 30 is indicated by a dotted line.

[0020] The heat dissipation member 10 of FIGS. 1(a) and 1(b) includes a metal-silicon carbide composite 20 formed by impregnating the silicon carbide porous body 2 with molten aluminum 3 and solidifying it in the impregnation step. In the metal-silicon carbide composite 20, a screw hole 60 is formed in the metal portion 32 that was filled into 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 screws or the like.

[0021] The screw hole 60 has excellent mechanical strength because the surrounding structure is formed of a silicon carbide porous body. Furthermore, the screw hole 60 has a structure that allows for easy screw fastening because the inner surface is made of the metal portion 32b containing aluminum. Aluminum is a flexible metal material that is easier to form thread grooves in than silicon carbide. Therefore, screws and the like can be fixed in close contact with the metal portion 32a, thereby increasing the joining strength.

[0022] FIG. 2 is a cross-sectional view schematically 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 screws 64 into screw holes 60. Other members can be detachably fixed to the heat dissipation member 10 having the screw holes 60 using the screws 64.

[0023] 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 tightly contacting state to the metal portion 32a located on the tapered portion 50. The thickness of the metal portion 32a is thicker than in the case of a non-tapered structure, so the head of the screw 64 can be tightly contacted. 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. In addition, distortion caused by the difference in the linear expansion coefficient between aluminum and silicon carbide can be suppressed.

[0024] Each step of the method for manufacturing the heat dissipation member of this embodiment will be described in detail below.

[0025] 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.

[0026] An example of a method for manufacturing the heat dissipation member 10 includes a preparation step of preparing a flat silicon carbide porous body, a hole formation step of forming at least one through hole that penetrates the flat silicon carbide porous body in the plate thickness direction, a taper formation step of forming a tapered portion around one or both ends of the through hole, the inner diameter of the through hole gradually widening outward, and an impregnation step of filling the through holes with molten aluminum while impregnating the inside of the flat silicon carbide porous body with spacers on both sides.

[0027] In the preparation step, a silicon carbide porous body 2b in the shape of a flat plate as shown in FIG. 3(a) is produced.

[0028] There are no particular limitations 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, alumina, or the like as a binder to silicon carbide (SiC) powder as a raw material, mixing, molding, and firing at 800°C or higher. As a method for forming the material into a flat plate, any known method can be appropriately applied, such as dry pressing, wet pressing, extrusion molding, injection molding, casting, or sheet molding followed by punching.

[0029] A high SiC content in the silicon carbide porous body is preferable because it increases thermal conductivity and reduces 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, preferably having an average particle size of 40 μm or more, and that the relative density of the SiC preform is preferably in the range of 55% to 75%.

[0030] The strength of the silicon carbide porous body (SiC preform) is preferably a bending strength of 3 MPa or more to prevent cracking during handling and impregnation. The average particle size can be measured by calculating the average diameter of 1,000 particles using a scanning electron microscope (e.g., JEOL "JSM-T200" model) and an image analyzer (e.g., Nippon Avionics Co., Ltd.). The relative density can be measured by the Archimedes method or the like.

[0031] It is preferable to adjust the particle size of the SiC powder, which is the raw material for the silicon carbide porous body (SiC preform), by using a suitable combination of coarse powder and fine powder, etc. This makes it easier to achieve both high strength for the silicon carbide porous body (SiC preform) and high thermal conductivity for the final heat dissipation member. Specifically, a mixed powder containing (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% to 80% by mass for (i) and 20% to 60% by mass for (ii).

[0032] Silicon carbide porous bodies (SiC preforms) can be obtained by degreasing and firing a compact of a mixture of SiC powder and a binder. If the firing 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 higher, regardless of the firing atmosphere. However, firing in an oxidizing atmosphere at a temperature above 1100°C may accelerate oxidation of SiC, resulting in a decrease in the thermal conductivity of the metal-silicon carbide composite. Therefore, firing in an oxidizing atmosphere at a temperature of 1100°C or less is preferred. 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.

[0033] When forming silicon carbide porous bodies (SiC preforms) into a predetermined shape, changes in curvature due to drying can be prevented by drying each preform individually or by using spacers such as carbon with the same shape as the preforms between the SiC preforms. Furthermore, by carrying out the same treatment for firing as for drying, it is possible to prevent changes in shape due to changes in the internal structure.

[0034] If necessary, at least one surface of the silicon carbide porous body (SiC preform) may be machined to have an outwardly convex curved shape using 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.

[0035] In the preparation step, the outer periphery of the silicon carbide porous body 2b is processed as necessary to form the silicon carbide porous body 2 having a desired outer periphery structure as shown in Fig. 3(b). Specifically, cutout portions 22 may be formed by excluding a portion of at least four corners of the silicon carbide porous body 2.

[0036] The peripheral processing may be performed by, but is not limited to, ordinary machining, grinding, water jet machining, laser machining, or electrical discharge machining.

[0037] Subsequently, in the hole forming step, through holes 40 are formed penetrating the plate-like silicon carbide porous body 2 in the plate thickness direction. A plurality of through holes 40 shown in FIG. 3(b) are formed in the peripheral portion of the silicon carbide porous body 2. Specifically, it is preferable to provide the through holes 40 in at least four corners of the silicon carbide porous body 2. The through holes 40 can be formed by machining such as drilling.

[0038] 3(c) is formed at one or both ends of the through-hole 40. Specifically, it is preferable to provide a tapered portion 50 at each of both ends of all of the through-holes 40.

[0039] 4, a taper machining tool (tool 5) with a predetermined angle is used, and the hole diameter D1 (taper diameter) and height H (taper height) of the tapered portion 50 can be controlled by adjusting the depression 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 prevent voids from being generated in the through-holes 40 when the metal-silicon carbide composite 20 is impregnated with metal.

[0040] The taper diameter is, for example, +6 to +40 mm relative to the hole diameter D0 of the through-hole 40, preferably +10 to +36 mm, and more preferably +14 to +32 mm. Alternatively, when the taper diameter is D1 and the hole diameter of the through-hole 40 is D0, D1 / D0 may be, for example, 1.5 to 16, preferably 2 to 15, and more preferably 3 to 14. The taper diameter is defined as the maximum diameter D1 of the through-hole 40 in one of the cross-sectional views of the heat dissipation member 10 in FIG.

[0041] Here, the hole diameter D0 of the through-hole 40 means the smallest diameter in the plate thickness direction. 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, but is, for example, 4 to 10 mm, preferably 5 to 9 mm, and more preferably 6 to 8 mm.

[0042] The taper height is, for example, 0.2 to 1 mm, preferably 0.3 to 0.8 mm, and more preferably 0.4 to 0.6 mm. The taper height is defined as the distance (height H) between an auxiliary line L1 drawn along the main surface of the silicon carbide porous body 2 and an auxiliary line L2 drawn through the end of the tapered portion 50 inside the through hole 40 in one of the cross-sectional views of the heat dissipation member 10 in Figure 2.

[0043] The taper angle is, for example, 0.2 to 5°, preferably 0.3 to 4°, and more preferably 0.4 to 3°. By setting the content to the upper limit or less, it is possible to prevent a decrease in the mechanical strength of the metal-silicon carbide composite 20. It is also possible to prevent distortion caused by the difference in the linear expansion coefficients between aluminum and silicon carbide. By setting the content to the lower limit or more, it is possible to improve the manufacturing stability of the heat dissipation member 10. The taper angle is defined as the angle (θ) formed between an 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.

[0044] 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 in a direction perpendicular to the main surface of silicon carbide porous body 2 (hereinafter referred to as the "main surface-perpendicular direction") 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.

[0045] Furthermore, tapered portion 50 may have a plurality of separated portions that are separated from each other when viewed in 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 individually provided. Furthermore, when viewed from the direction perpendicular to the main surface, a part of tapered portion 50 may have an extension that protrudes further toward the outer edge than the other parts. The outer edge or extension of tapered portion 50 may reach the outer periphery of silicon carbide-based porous body 2, but from the viewpoint of mechanical strength, it is preferable that it be located inside the outer periphery.

[0046] The tapered surface of tapered portion 50 in the cross-sectional view of silicon carbide-based porous body 2 may be linear or curved, and may have one or more steps or grooves within the surface. Specifically, the tapered surface in the cross-sectional view of silicon carbide-based porous body 2 in Fig. 2 may be linear. This improves the flow 3a of molten aluminum 3.

[0047] Subsequently, 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.

[0048] 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 infiltrates into the voids of silicon carbide-based porous body 2 and fills through-holes 40. In FIG. 5(b), after cooling, metal-silicon carbide composite 20 containing aluminum is obtained. At this time, the metal is cooled inside through-holes 40, and metal portions 32 are filled.

[0049] There are no particular limitations on the spacers 1a and 1b, as long as they allow for the release of the obtained metal-silicon carbide composite 20. A laminated structure of silicon carbide porous bodies, in which another silicon carbide porous body and another spacer are further disposed on the spacer 1a, may be used in the impregnation step.

[0050] Here, it is preferable to preheat the silicon carbide porous body 2 before 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 molten metal into the silicon carbide porous body (SiC preform) as quickly as possible after it has been set in the mold.

[0051] 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 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 poured into it to form a surface metal layer. As another example, a surface metal layer can be formed by arranging one or more of alumina or silica fibers, spherical particles, and crushed particles directly on the surface of a SiC preform and then impregnating the surface with a metal. In this case, the content of the material consisting of one or more of alumina or silica fibers, spherical particles, and crushed particles 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 it with metal, or by adding grooves or the like to the surface of the SiC preform in advance.

[0052] The pressure of the molten metal to be pressed is not particularly limited as long as the metal is sufficiently impregnated, but is, for example, 30 MPa or more.

[0053] In order to allow the metal (preferably aluminum or an alloy containing aluminum) to fully penetrate into the voids of the preform, it is preferable that the melting point of the metal to be impregnated is appropriately low. In this respect, an aluminum alloy containing 7% by mass or more and 25% by mass or less of silicon is preferred. Furthermore, by adding 0.2% by mass or more and 5% by mass or less of magnesium, the bond between the silicon carbide grains and the metal portion becomes stronger, which is preferable. There are no particular restrictions on the metal components other than aluminum, silicon, and magnesium in the aluminum alloy, as long as the properties are not significantly changed, and for example, copper may be included.

[0054] As the aluminum alloy, it is possible to preferably use alloys for casting, such as AC4C, AC4CH, and ADC12.

[0055] Incidentally, in order to remove distortion caused during the impregnation, annealing may be performed on the metal-silicon carbide composite 20. The annealing may be performed, for example, at a temperature of about 400° C. to 550° C. for 10 minutes or longer.

[0056] In this manner, the heat dissipation member 10 of this embodiment is obtained.

[0057] It should be noted that 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 this embodiment, the surface metal layer may have 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 treatment or a blasting treatment.

[0058] Furthermore, after the impregnation step, a step of forming screw holes may be carried out on the obtained heat dissipation member 10. In the screw hole forming step, a screw hole is formed in the metal portion 32 formed by filling the inside of the through hole 40 with aluminum, as shown in FIG. 5(b).

[0059] 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 thread formed on the inner surface.

[0060] In the cross-sectional view of the heat dissipation member 10, the diameter of the screw 64 is D2, and the maximum diameter of the through-hole 40 is D1. D2 / D1 is, for example, 0.5 to 0.95, preferably 0.6 to 0.9, and more preferably 0.7 to 0.8.

[0061] 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 known electroless Ni-P plating or Ni-B plating techniques.

[0062] 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). In this case, in a cross-sectional view of the through hole 40, the thickness of the metal portion 32b is represented as W1, and the thickness of the plating layer inside the screw hole 62 is represented 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.

[0063] The heat dissipation member 10 of this embodiment will be described in detail.

[0064] 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.

[0065] 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 (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.

[0066] 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 below, it is preferable that the screw holes 62 are provided in the metal layer 30a formed in the cutout portions 22 at at least four corners of the heat dissipation member 10. The screw holes 62 are used when joining the heat dissipation member 10 to other heat dissipation parts (for example, heat dissipation fins) with screws or the like.

[0067] 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. By appropriately joining the heat dissipation member 10 (element mounting board) of this embodiment to another heat dissipation member (heat dissipation fin, etc.), the heat can be efficiently released.

[0068] 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 side 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 facing upward, 10 to 80% of the area of ​​the heat dissipation member 10 is covered with the electronic element 90.

[0069] The heat dissipation member 10 is preferably substantially rectangular. 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 into a rounded shape rather than a right-angled shape (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 rounded, the point where the straight lines of the short and long sides intersect when the short and long sides 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 "vertex" as the start point or end point.

[0070] 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 to 6 mm or less, and preferably 3 to 5 mm or less. 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.

[0071] The heat dissipation member 10 has an average thermal expansion coefficient of, for example, 4 to 12 ppm, preferably 4 to 10 ppm, from 25° C. to 150° C. This can prevent 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 using a thermal dilatometer in accordance with JIS R1618 at a temperature decrease rate of 5° C. / min or less.

[0072] The thermal conductivity of the heat dissipation member 10 in the thickness direction at 25° C. is, for example, 150 to 300 W / m·K, and preferably 180 to 300 W / m·K.

[0073] 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. Furthermore, the alloy may be, for example, an aluminum alloy containing 7 to 25 mass % of silicon (Si). 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.

[0074] When the metal-silicon carbide composite 20 is an aluminum-silicon carbide composite, aluminum is contained as the 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.

[0075] The metal contained in the metal layer 30 may be of the same type 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.

[0076] The thickness of the metal layer 30 is, for example, 10 to 300 μm, or preferably 30 to 150 μm. By making the thickness equal to or greater than the above lower limit, it is possible to improve the film strength of metal layer 30. By making the thickness equal to or less than the above upper limit, it is possible to suppress 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.

[0077] 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, nitride ceramics such as silicon nitride and aluminum nitride, oxide ceramics such as aluminum oxide and zirconium oxide, carbide ceramics such as silicon carbide, boride ceramics such as lanthanum boride, etc. Among these, aluminum nitride, silicon nitride, and aluminum oxide are preferred from the viewpoints of insulation, strength of bonding with the metal layer 13, mechanical strength, etc.

[0078] An Ag—Cu-based brazing filler metal is preferable as the brazing filler metal for joining the metal layer 30 and the ceramic substrate 92. That is, the brazing filler metal is preferably a mixture of Ag powder, Cu powder, and the like. The brazing filler metal may contain Sn or In for the purpose of improving wettability with the ceramic plate. The brazing filler metal preferably contains an active metal from the viewpoint of enhancing reactivity with the ceramic plate. Examples of the active metal include titanium, zirconium, hafnium, niobium, etc. Titanium is preferred because it has high reactivity with aluminum nitride substrates and silicon nitride substrates and can achieve extremely high bonding strength.

[0079] The type of solder 70 is not particularly limited, but for example, lead-tin eutectic solder or lead-free solder can be used.

[0080] 1, the heat dissipation member 10 may have a plating layer formed on the main surface 30A side of the heat dissipation member 10, specifically on the outermost surface, which can improve the bondability with the solder.

[0081] The plating layer may contain at least one of Ni, Au, and Ag, and is preferably a Ni plating layer containing Ni.

[0082] The thickness of the plating layer is, for example, 3 to 15 μm, and preferably 4 to 10 μm. By setting the thickness to the above lower limit or more, the coating stability of the plating layer can be improved. By setting the thickness to the above upper limit or less, 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.

[0083] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. Below, examples of reference forms are added. 1. A method for manufacturing a heat dissipation member having a flat metal-silicon carbide composite plate containing aluminum, comprising: a preparation step of preparing a flat silicon carbide porous body; a hole forming step of forming at least one through hole penetrating the flat silicon carbide porous body in a plate thickness direction; an impregnation step of filling the through holes with molten aluminum while the flat silicon carbide porous body is sandwiched between spacers on both sides; Including, a taper forming step between the hole forming step and the impregnation step, in which a tapered portion is formed around one or both ends of the through hole such that the inner diameter of the through hole gradually widens toward the outside; A method for manufacturing a heat dissipation member. 2. A method for manufacturing the heat dissipation member according to 1., The method for producing a heat dissipation member, wherein the angle of the tapered portion is 0.2 to 5°. 3. A method for producing a heat dissipation member according to 1. or 2., The method for manufacturing a heat dissipation member includes, after the impregnation step, a step of forming a screw hole in a metal portion formed by filling the inside of the through hole with aluminum. 4. A method for manufacturing the heat dissipation member according to 3., A method for manufacturing a heat dissipation member, wherein when the maximum diameter of the through holes is D1 and the diameter of the screw holes is D2, D2 / D1 satisfies 0.001 to 0.04. 5. A method for producing a heat dissipation member according to any one of 1. to 4., The method for manufacturing a heat dissipation member includes, after the impregnation step, a plating step of forming a plating layer on the main surface side of the heat dissipation member. 6. A method for manufacturing a heat dissipation member according to 5., The method for manufacturing a heat dissipation member, wherein the plating layer is a Ni plating layer containing Ni element. 7. A method for producing a heat dissipation member according to any one of 1. to 6., The method for producing a heat dissipation member, wherein the heat dissipation member has an average thermal expansion coefficient from 25°C to 150°C of 4 to 12 ppm / K. 8. A method for producing a heat dissipation member according to any one of 1. to 7., The method for producing a heat dissipation member, wherein the heat dissipation member has a thermal conductivity in the plate thickness direction at 25°C of 150 to 300 W / m·K. [Example]

[0084] 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.

[0085] <Manufacture of heat dissipation components> (Formation of silicon carbide porous body) First, the following silicon carbide powder A, silicon carbide powder B, and silica sol were mixed in a stirring 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

[0086] The resulting mixture was placed in a mold and press-molded at a pressure of 10 MPa to obtain a plate-shaped compact measuring 135 mm x 75 mm x 5.0 mm. The resulting compact was fired in air at 900°C for 2 hours to obtain a silicon carbide-based porous body with a relative density (bulk density) of 65% by volume.

[0087] (Through hole / tapered portion forming process) Through holes were formed at the four corners of the silicon carbide porous body using a drill. Next, a tapering 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.

[0088] (Metal impregnation) The machined silicon carbide porous body was sandwiched on both sides between carbon-coated stainless steel plates measuring 170 mm x 100 mm x 0.8 mm, and laminated. Next, 6mm 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 2Nm 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. A 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 100 MPa for 20 minutes. This allowed the silicon carbide porous body to be impregnated with the aluminum alloy.

[0089] 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 way, an aluminum-silicon carbide composite was obtained.

[0090] (Post-impregnation treatment) The outer periphery of the resulting aluminum-silicon carbide composite was machined using an NC lathe to a size of 140 mm x 80 mm. In this way, a heat dissipation member without a plating layer was obtained.

[0091] (Evaluation of softening) 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 (single or connected streaks like air bubbles) in surface photographs taken at 50 magnifications using an optical microscope. A surface photograph of Example 1 at 50 magnifications is shown in FIG. 7, and a surface photograph of Comparative Example 1 at 50 magnifications is shown in FIG. In addition, when the number of photographs (number of examinations) in different areas observed was defined as N1 and the number of photographs in which porosity was observed (number of occurrences) was defined as N2, the porosity occurrence rate was calculated based on the formula: N2 / N1 × 100%, and is shown in Table 1.

[0092] [Table 1]

[0093] The methods for producing the heat dissipation members of Examples 1 and 2 were able to suppress the occurrence of voids compared to Comparative Example 1, and therefore showed good production stability. [Explanation of symbols]

[0094] 1a spacer 1b spacer 2. Silicon carbide porous body (preform) 2a Silicon carbide porous material 2b Silicon carbide porous material 3. Molten aluminum 3a Flow 3b Solidified Aluminum 4 Loosen 5 Tool 10 Heat Dissipation Member 20 Metal-Silicon Carbide Composite 20a Metal-Silicon Carbide Composite 22 Notch 30 Metal Layer 30a Metal Layer 30A Main Surface 30B Back Surface 32 Metal Part 32a Metal Part 32b Metal Part 40 Through-Hole 50 Tapered Portion 60 Screw Hole 62 Screw Hole 64 Screw 70 Solder 80 Case 90 Electronic Component 92 Ceramic Substrate 100 Electronic Device

Claims

1. A method for manufacturing a heat dissipation member having a flat metal-silicon carbide composite plate containing aluminum, comprising: a preparation step of preparing a flat silicon carbide porous body; a hole forming step of forming at least one through hole penetrating the flat silicon carbide porous body in a plate thickness direction; an impregnation step of filling the through holes with molten aluminum while the flat silicon carbide porous body is being sandwiched between spacers on both sides; Including, a taper forming step between the hole forming step and the impregnation step, in which a tapered portion is formed around one or both ends of the through hole such that the inner diameter of the through hole gradually widens toward the outside; A method for manufacturing a heat dissipation member.

2. A method for manufacturing a heat dissipation member according to claim 1, a method for manufacturing a heat dissipation member, wherein, when the angle (θ) formed by an auxiliary line L1 drawn along the main surface of the flat silicon carbide porous body and an auxiliary line L3 drawn along the tapered surface of the tapered portion in a cross section of the heat dissipation member is defined as the angle of the tapered portion, the angle of the tapered portion is 0.2 to 5° with respect to the surface of the flat silicon carbide porous body on which the tapered portion is formed.

3. A method for manufacturing a heat dissipation member according to claim 1 or 2, The method for manufacturing a heat dissipation member includes, after the impregnation step, a step of forming a screw hole in a metal portion formed by filling the inside of the through hole with aluminum.

4. The method for manufacturing the heat dissipation member according to claim 3, When the maximum diameter of the through hole is D1 and the diameter of the screw hole is D2, the manufacturing method of the heat dissipation member is configured so that D2 / D1 satisfies 0.5 to 0.

95.

5. A method for manufacturing a heat dissipation member according to any one of claims 1 to 4, The method for manufacturing a heat dissipation member includes, after the impregnation step, a plating step of forming a plating layer on the main surface side of the heat dissipation member.

6. The method for manufacturing a heat dissipation member according to claim 5, The method for manufacturing a heat dissipation member, wherein the plating layer is a Ni plating layer containing Ni elements.

7. A method for manufacturing a heat dissipation member according to any one of claims 1 to 6, The method for manufacturing a heat dissipation member, wherein the heat dissipation member has an average thermal expansion coefficient of 4 to 12 ppm / K from 25°C to 150°C.

8. A method for manufacturing a heat dissipation member according to any one of claims 1 to 7, The method for manufacturing a heat dissipation member, wherein the heat dissipation member has a thermal conductivity in the plate thickness direction at 25°C of 150 to 300 W / m·K.

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