Heat dissipation substrate

Abstract

To provide a heat dissipation substrate that maintains thermal conductivity while improving mechanical properties. [Solution] The heat dissipation substrate 1 comprises a metal member 10 mainly composed of copper and a ceramic member 20 mainly composed of aluminum nitride. The metal member 10 has a composite part 30 made of carbon material and copper inside, and the shape of the carbon material is a mesh made of woven carbon fibers.

Description

[Technical Field]

[0001] This disclosure relates to a heat dissipation substrate. [Background technology]

[0002] In recent years, many heat dissipation substrates have been proposed for mounting semiconductor elements such as power elements, in order to efficiently dissipate heat from semiconductor elements. For example, the heat dissipation substrate described in Japanese Patent Application Publication No. 2024-81995 comprises an insulating layer, a heat sink bonded to the back surface of the insulating layer, a circuit pattern bonded to the surface of the insulating layer, and a chip as a semiconductor element that acts as a heat source during operation. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-81995 [Overview of the project] [Problems that the invention aims to solve]

[0004] Heat dissipation substrates are sometimes formed by joining a ceramic component to a metal component such as copper. Silicon nitride and aluminum nitride can be used as the ceramic component. Aluminum nitride has a higher thermal conductivity than silicon nitride, but a lower coefficient of thermal expansion. Therefore, when using a heat dissipation substrate in which aluminum nitride and a metal component are joined, thermal strain occurs between the components as the temperature of the semiconductor element rises, leading to problems such as the aluminum nitride component delaminating from the metal component.

[0005] This disclosure aims to provide a heat dissipation substrate that improves mechanical properties while maintaining thermal conductivity. [Means for solving the problem]

[0006] The heat dissipation substrate of this disclosure comprises a metal member mainly composed of copper and a ceramic member mainly composed of aluminum nitride, wherein the metal member has a composite portion made of a carbon material and the copper inside, and the shape of the carbon material is a mesh woven from carbon fibers. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a heat dissipation substrate that improves mechanical properties while maintaining thermal conductivity. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing an example of a heat dissipation substrate according to an embodiment. [Figure 2] Figure 2 is an explanatory diagram illustrating the configuration of the heat dissipation substrate corresponding to Examples 1 to 15 and Comparative Examples 1 to 5. [Modes for carrying out the invention]

[0009] First, embodiments of this disclosure will be listed and described. (1) The heat dissipation substrate of the present disclosure comprises a metal member mainly composed of copper and a ceramic member mainly composed of aluminum nitride, wherein the metal member has a composite portion made of a carbon material and the copper inside, and the shape of the carbon material is a mesh made of woven carbon fibers.

[0010] The coefficient of thermal expansion of copper is 17.0 × 10⁻⁶. -6 The thermal expansion coefficient of aluminum nitride is 4.6 × 10⁻⁶ / K, and the thermal expansion coefficient of aluminum nitride is 4.6 × 10⁻⁶. -6 The coefficient of thermal expansion of the two materials is / K, and their coefficients of thermal expansion are significantly different from each other. The heat dissipation substrate according to this disclosure has a composite portion in which a carbon material made of a mesh of woven carbon fibers and copper are combined inside a metal member mainly composed of copper. Such a composite portion can maintain the thermal conductivity due to copper while bringing its thermal expansion closer to that of aluminum nitride. Therefore, the heat dissipation substrate according to this disclosure can improve mechanical properties while maintaining thermal conductivity.

[0011] (2) In the heat dissipation substrate according to (1), it is preferable that the carbon material is formed of pitch-based carbon fibers.

[0012] When the carbon material is formed using pitch-based carbon fibers among carbon fibers, the heat dissipation substrate can exhibit more excellent heat dissipation performance.

[0013] (3) In the heat dissipation substrate according to (1) or (2), a carbide phase in which a dissimilar metal material different from copper and carbon are bonded is formed on the surface of the carbon material, and the dissimilar metal material preferably contains at least one of Ti, V, Cr, Mn, Fe, Zr, and W.

[0014] In this case, since the carbon material and copper are more likely to be compatible in the composite part, etc., the vibration durability of the heat dissipation substrate is improved.

[0015] (4) In the heat dissipation substrate according to any one of (1) to (3), the thermal conductivity of the composite part is 280 W / m·K or more, and the coefficient of thermal expansion of the composite part is preferably 7.5×10 -6 / K or less.

[0016] In this case, the thermal conductivity of the composite part is relatively high and the thermal expansibility is relatively low. As a result, the heat dissipation substrate can exhibit excellent performance in both heat dissipation and durability.

[0017] (5) In the holding device according to any one of (1) to (4), the thermal conductivity of the ceramic member is preferably 180 W / m·K or more.

[0018] In this case, since the thermal conductivity of the ceramic member is relatively high, the heat dissipation substrate can exhibit excellent heat dissipation performance.

[0019] <Configuration of Heat Dissipation Substrate 1> The heat dissipation substrate 1 according to the present disclosure will be described with reference to FIG. 1. As shown in FIG. 1, the heat dissipation substrate 1 includes a metal member 10 and a ceramic member 20. The overall thickness T of the heat dissipation substrate 1 shown in FIG. 1 is not particularly limited, but is preferably 900 μm or more and 1100 μm or less.

[0020] The metal member 10 forms the core material of the heat dissipation substrate 1. The metal member 10 can be mainly composed of a metal such as copper (Cu) or aluminum (Al), and forms a plate-like body made of metal having a predetermined thickness. In the present embodiment, the metal member 10 is mainly composed of copper. In this specification, "mainly composed of" means that the content ratio of that component is the highest. That is, "mainly composed of" means that it may not contain any substances other than that component, or may contain a trace amount (for example, an amount corresponding to inevitable impurities) of substances other than that component that does not affect the functions and effects of the heat dissipation substrate 1 according to the present disclosure. The thickness of the metal member 10 is not particularly limited, but is preferably 300 μm or more and 400 μm or less.

[0021] The metal member 10 has a composite part 30 composed of a carbon material and copper inside it. The inventor of the present disclosure has attempted to improve the mechanical strength of the heat dissipation substrate 1 while maintaining the heat dissipation performance derived from copper by providing the composite part 30 inside the metal member 10 in the heat dissipation substrate 1 including the metal member 10 mainly composed of copper and the ceramic member 20 described later. The composite part 30 is a part in the metal member 10 where copper, which is the main component of the metal member 10, and the carbon material are mixed. The composite part 30 is arranged in layers along a direction orthogonal to the thickness direction of the metal member 10 inside the metal member 10. In this specification, "orthogonal" includes arrangements in a mode that is recognized as substantially orthogonal.

[0022] A material made of carbon (C) is used as the carbon material constituting the composite part 30. Within the composite part 30, the carbon material can be arranged in the copper constituting the metal member 10 in various shapes such as powder or granules, fibers, plates, and mesh. In this specification, the carbon material of the mesh is made by weaving carbon fibers together so that there are multiple meshes (gaps, openings). In this embodiment, this mesh is formed by bundling carbon fibers having a thickness of about 7 μm to 10 μm to a thickness of about 0.3 mm to 0.5 mm, and weaving these bundles together. The mesh has a planar shape that extends with a predetermined thickness. The thickness of the mesh is about 0.7 mm. The mesh may be flexible.

[0023] The composite portion 30 is formed by sandwiching a carbon material between two plate-shaped copper pieces and joining them by applying pressure in the thickness direction. As an example of such pressure welding, ultrasonic pressure welding may be performed.

[0024] In the process of forming the composite part 30, powdered or granular carbon material is placed between two plate-shaped copper sheets and pressed together. In this pressing process, the powdered or granular carbon material is scattered within the composite part 30 so as the plate-shaped copper sheets stretch due to the pressing, it spreads in a direction perpendicular to the thickness direction of the metal member 10. In the process of forming the composite part 30, fibrous carbon material is pressed together while placed side by side between two plate-shaped copper sheets. If the fibrous carbon material is a long fiber having a predetermined length, the long fiber carbon material is arranged within the composite part 30 so that the direction in which its fiber length extends is perpendicular to the thickness direction of the metal member 10. In addition to long fibers, fibrous carbon material also includes short fibers, also called chopped fibers or choppers, which are obtained by cutting (chopping) long carbon fibers. When the carbon material is in the form of short fibers, the short-fiber carbon material is scattered throughout the composite portion 30 during the process of forming the composite portion 30, similar to the case of powdered or granular carbon material. During the process of forming the composite portion 30, the mesh carbon material is placed between two plate-shaped copper pieces and pressed together. As a result, within the composite portion 30, the mesh carbon material is arranged such that each surface of the mesh carbon material is aligned in a direction perpendicular to the thickness direction of the metal member 10.

[0025] In this embodiment, it is preferable that the carbon material has continuous portions in which the carbon constituting the carbon material extends continuously along a direction perpendicular to the thickness direction of the composite portion 30, and discontinuous portions in which the carbon constituting the carbon material does not extend continuously. In this case, within the composite portion 30, the discontinuous portions of the carbon material are filled with the metal material constituting the metal member 10.

[0026] Specifically, the shape of the carbon material according to this embodiment is a mesh. In the mesh-shaped carbon material, the mesh portion (the portion where the wires forming the mesh are arranged) corresponds to the continuous portion mentioned above. Also, the mesh opening portion (the opening formed between the mesh) corresponds to the discontinuous portion mentioned above. When the mesh carbon material is placed inside the composite portion 30, copper is filled into the mesh opening portion formed in the mesh. It is preferable that the mesh openings (voids, openings) of the mesh are uniformly formed at a predetermined pitch on the surface of the mesh. The mesh opening ratio, that is, the ratio of the area of ​​the discontinuous portion (the portion where the mesh is formed) to the total area of ​​the mesh when viewed in a plane, is set to approximately 50% to 80%.

[0027] Carbon fibers are broadly classified into two types based on their raw materials: PAN-based carbon fibers, which use polyacrylonitrile as a raw material, and pitch-based carbon fibers, which use coal tar pitch or petroleum-based pitch as a raw material. PAN-based carbon fibers are characterized by their high strength. Pitch-based carbon fibers are characterized by their high elastic modulus and higher thermal conductivity than PAN-based carbon fibers. It is preferable that the carbon material of the mesh be formed from pitch-based carbon fibers.

[0028] The surface of the carbon material of the mesh may be coated with a dissimilar metal material other than copper. The coating of the dissimilar metal material on the surface of the carbon material of the mesh may be performed by coating the surface of the carbon fibers prepared for forming the mesh with the dissimilar metal material. Alternatively, the dissimilar metal material may be coated on the surface of the mesh after it has been formed by weaving the carbon fibers. There are no limitations on the coating methods used, but for example, CVD, vapor deposition, particle dipping, etc., may be employed.

[0029] The metallic materials constituting the dissimilar metallic material may be selected from a variety of metals or alloys. The metals or alloys constituting the dissimilar metallic material may exist on the surface of the mesh without bonding with the carbon forming the mesh of the carbon material. The metals or alloys constituting the dissimilar metallic material present on the surface of the mesh of the carbon material may be solid-dissolved in the copper present in the composite part 30. Alternatively, the metals or alloys constituting the dissimilar metallic material present on the surface of the mesh of the carbon material may form a eutectic with the copper present in the composite part 30. In this embodiment, it is preferable that a carbide phase of the dissimilar metallic material is formed on the surface of the carbon material of the mesh by bonding between the dissimilar metallic material coated on the surface of the carbon material of the mesh and the carbon constituting the mesh. As the dissimilar metallic material that forms the carbide phase on the surface of the carbon material of the mesh, for example, metals such as Ti (titanium), V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Zr (zirconium), and W (tungsten) can be used.

[0030] The composite portion 30 containing such carbon material is defined as a portion of the metal member 10 that is 30 μm or less from the end of the carbon material adjacent to the bonding interface I and the end opposite to that end, in the thickness direction of the metal member 10. The thickness of the composite portion 30 is not particularly limited, but it is preferably 30 μm or more and 120 μm or less.

[0031] The thermal conductivity of the composite portion 30 is preferably 280 W / m·K or higher. In this embodiment, the carbon material has a lower thermal conductivity than copper. Therefore, the thermal conductivity of the composite portion 30 will not exceed the thermal conductivity of copper, which is 350 W / m·K. The thermal conductivity of the composite portion 30 is derived by adding the value obtained by multiplying the volume ratio of copper contained in the composite portion 30 by the thermal conductivity of copper, and the value obtained by multiplying the volume ratio of carbon material contained in the composite portion 30 by the thermal conductivity of carbon material. In this embodiment, the thermal expansion coefficient of the composite portion 30 is 7.5 × 10 -6 It is preferable that the temperature is 1 / K or less. In this embodiment, the carbon material has a lower coefficient of thermal expansion than copper. Therefore, the coefficient of thermal expansion of the composite part 30 will not be lower than the coefficient of thermal expansion of the carbon material.

[0032] The ceramic member 20 is a plate-like body having a predetermined thickness, mainly composed of a ceramic material. The ceramic member 20 is provided to provide insulation in the thickness direction of the heat dissipation substrate 1. The ceramic member 20 may include oxide-based ceramic materials such as alumina (Al2O3) or non-oxide-based ceramic materials such as silicon nitride (Si3N4) or aluminum nitride (AlN). In this embodiment, the ceramic member 20 is a sintered body mainly composed of aluminum nitride. The ceramic member 20 mainly composed of aluminum nitride has lower mechanical strength than the ceramic member mainly composed of silicon nitride, but has higher thermal conductivity. The inventors of this disclosure have attempted to improve the mechanical strength of the heat dissipation substrate 1 while maintaining the heat dissipation performance derived from copper and aluminum nitride, in a heat dissipation substrate 1 comprising a metal member 10 having the aforementioned composite portion 30 inside and a ceramic member 20 mainly composed of aluminum nitride. In this embodiment, the thermal conductivity of the ceramic member 20, which is made of a sintered body mainly composed of aluminum nitride, is preferably 180 W / m·K or higher.

[0033] As shown in Figure 1, the ceramic member 20 is arranged in a laminated manner between the two metal members 10. While there are no particular restrictions on the thickness of the ceramic member 20, it is preferably 300 μm to 450 μm. The interface between the metal member 10 and the ceramic member 20 is joined to each other by means of pressure welding or brazing.

[0034] The composite portion 30 described above is arranged in layers within the metal member 10, extending in a direction perpendicular to the thickness direction of the metal member 10. In other words, the composite portion 30 is arranged in layers within the metal member 10 so as to extend in a direction along the direction in which the bonding interface I extends. The position of the end of the composite portion 30 that is close to the bonding interface I in the thickness direction of the heat dissipation substrate 1 relative to the bonding interface I, that is, the length from the bonding interface I to the composite portion 30, is defined as position L, as shown in Figure 1. In this embodiment, it is preferable that position L is in the range of 10 μm to 300 μm.

[0035] <Manufacturing method for heat dissipation substrate 1> An example of a method for manufacturing the heat dissipation substrate 1 is described below. First, the metal member 10 and the ceramic member 20 are manufactured.

[0036] The method for manufacturing the metal member 10 is as follows. First, two copper plates are prepared to form the metal member 10. A carbon material is also prepared. As mentioned above, the carbon material can take various forms, such as powder, granules, fibers, plates, and mesh. The carbon material having each of these forms is sandwiched between the two copper plates. These are then subjected to ultrasonic pressure welding under pressure in the thickness direction to obtain a metal member 10 having a composite portion 30 inside.

[0037] The method for producing the ceramic member 20 is as follows: Aluminum nitride powder is prepared, and a mixture of this powder with an organic binder, an appropriate amount of dispersant, and various additives such as plasticizers is added. An organic solvent is then added to this mixture and mixed in a ball mill to produce a slurry. This slurry is formed into a sheet using a casting device. Alternatively, this slurry may be granulated by spray drying, and the resulting granulated powder may be press-molded into a sheet. The resulting molded body is heated to 400°C to 500°C in an air or nitrogen gas atmosphere to remove hydrocarbon components added as an organic binder and degrease the molded body. The degreased molded body is heated to a high temperature in a nitrogen gas atmosphere to form a sintered aluminum nitride body. The resulting sintered body is then appropriately molded to obtain the ceramic member 20. Furthermore, the thermal conductivity of the ceramic member 20 can be changed by controlling the purity of the grain boundaries by changing the sintering temperature at which the unsintered aluminum nitride body is sintered, whether or not a pressure sintering process such as discharge plasma sintering is used in combination with sintering, and the type and amount of sintering aid added during sintering.

[0038] After the metal member 10 and the ceramic member 20 are manufactured separately, the ceramic member 20 is arranged in a laminated manner between the two metal members 10. At this time, the composite portion 30 inside the metal member 10 is made to extend in a direction along the direction in which the bonding interface I between the metal member 10 and the ceramic member 20 extends. The laminated metal member 10 and the ceramic member 20 are then pressed together in the respective thickness directions of the metal member 10 and the ceramic member 20 to join them. In this way, the heat dissipation substrate 1 is manufactured. [Examples]

[0039] The present disclosure will be described in further detail below based on the examples. However, the present disclosure is not limited in any way by these examples.

[0040] <Examples 1-15> (Fabrication of metal component 10) In Examples 1-4, a mesh made of PAN-based carbon fibers was prepared as the carbon material. In Examples 5-7, a mesh made of pitch-based carbon fibers was prepared as the carbon material. In Examples 1-4 and 5-7, the amount of mesh constituting the carbon material was varied.

[0041] In Examples 8 and 15, the carbon material prepared was a mesh formed from pitch-based carbon fibers with a Ti carbide phase (titanium carbide phase) formed on its surface. In Example 9, the carbon material prepared was a mesh formed from pitch-based carbon fibers with a Zr carbide phase (zirconium carbide phase) formed on its surface. In Example 10, the carbon material prepared was a mesh formed from pitch-based carbon fibers with a Cr carbide phase (chromium carbide phase) formed on its surface. In Example 11, the carbon material prepared was a mesh formed from pitch-based carbon fibers with a Mn carbide phase (manganese carbide phase) formed on its surface. In Example 12, the carbon material prepared was a mesh formed from pitch-based carbon fibers with a W carbide phase (tungsten carbide phase) formed on its surface. In Example 13, the carbon material prepared was a mesh formed from pitch-based carbon fibers with an Fe carbide phase (iron carbide phase) formed on its surface. In Example 14, a carbon material was prepared in which a carbide phase of V (vanadium carbide phase) was formed on the surface of a mesh made of pitch-based carbon fibers.

[0042] Figure 2 shows the type (PAN-based or pitch-based), shape, presence or absence of a carbide phase, and, in the case where a carbide phase is formed, the type of dissimilar metal material forming the carbide phase, thermal expansion coefficient, and thermal conductivity of each carbon material related to Examples 1 to 15.

[0043] Each of these carbon materials was sandwiched between two copper plates, and the sandwiched material was subjected to ultrasonic pressure welding to obtain a metal member 10 having a composite portion 30 inside, as described in Examples 1 to 15.

[0044] (Fabrication of ceramic component 20) Aluminum nitride powder was prepared, and a mixture of this powder with an organic binder, an appropriate amount of dispersant, and various additives such as plasticizers was added. An organic solvent was then added to this mixture and mixed in a ball mill to produce a slurry. This slurry was formed into a sheet using a casting device. The resulting molded body was degreased by heating it to 400°C to 500°C in an air or nitrogen gas atmosphere to remove hydrocarbon components added as an organic binder. The degreased molded body was then heated to a high temperature in a nitrogen gas atmosphere to form a sintered aluminum nitride body. The resulting sintered body was then appropriately molded to obtain a ceramic member 20.

[0045] (Joining of metal member 10 and ceramic member 20) The ceramic member 20 was arranged in a laminated manner between the two metal members 10. In this arrangement, the composite portion 30 inside the metal member 10 was made to extend in a direction along the direction in which the bonding interface I between the metal member 10 and the ceramic member 20 extends. The metal member 10 and the ceramic member 20 were joined by applying pressure in the respective thickness directions of the metal member 10 and the ceramic member 20. In this way, the heat dissipation substrate 1 according to Examples 1 to 15 was manufactured.

[0046] <Comparative Examples 1-5> In Comparative Example 1, PAN-based carbon short fibers (choppers) were prepared as the carbon material. The carbon short fibers had a thickness of 10 μm and a length of 100 μm to 150 μm. In Comparative Example 2, a plate (a plate without holes) of Ti, a dissimilar metal material, was prepared. In Comparative Example 3, a foil (a foil without holes) of Fe, a dissimilar metal material, was prepared. In this specification, a plate refers to a plate-like body formed with a thickness of, for example, about 1 mm. Also, in this specification, a foil refers to a material thinner than a plate, for example, with a thickness of 200 μm or less. In this embodiment, a foil with a thickness of approximately 10 μm to 100 μm was used. In Comparative Example 4, a Ti wire, a dissimilar metal material, was prepared. The Ti wire had a length of 300 μm to 600 μm, and the length of the Ti wire was the same as the length of the copper plate. In Comparative Example 5, carbon powder was prepared as the carbon material. The particle size of the carbon powder was set to 80 nm.

[0047] By sandwiching carbon materials and dissimilar metal materials of shapes other than these mesh shapes between two copper plates and ultrasonically pressing the sandwiched material, metal members having a composite portion inside, as shown in Comparative Examples 1 to 5, were obtained. In Comparative Examples 2 and 3, the dissimilar metal materials, which are in the form of plates or foils, are arranged within the composite portion 30 such that the surfaces of each plate-shaped or foil-shaped dissimilar metal material are aligned in a direction perpendicular to the thickness direction of the metal member 10. The other manufacturing procedures are the same as in Examples 1 to 15.

[0048] Furthermore, the dissimilar metal materials in the form of plates or foils in Comparative Examples 2 and 3 do not have openings like the mesh in the carbon materials of Examples 1 to 15. That is, the dissimilar metal materials in Comparative Examples 2 and 3 have only continuous portions and are formed in a shape without discontinuous portions. In addition, the carbon material in Comparative Example 1 is short carbon fibers, and the composite part 30 using this is formed in which the short carbon fibers are scattered within the copper in a direction perpendicular to the thickness direction of the metal member 10. In addition, the dissimilar metal material in Comparative Example 4 is a Ti wire, and this wire is not woven with other wires. Therefore, the composite part 30 using this is formed in which multiple wires are scattered within the copper in a direction perpendicular to the thickness direction of the metal member 10. In addition, the carbon material in Comparative Example 5 is carbon powder, and the composite part 30 using this is formed in which the powdered carbon is scattered within the copper in a direction perpendicular to the thickness direction of the metal member 10.

[0049] The configurations of Examples 1 to 15 and Comparative Examples 1 to 5 are shown in Figure 2. As shown in Figure 2, in all of Examples 1 to 15 and Comparative Examples 1 to 5, the main component of the metal member 10 is copper, and the thermal expansion coefficient of this copper is 17.0 × 10⁻⁶. -6 It is 350 W / m·K, and its thermal conductivity is 350 W / m·K.

[0050] Figure 2 shows the thermal expansion coefficient and thermal conductivity of the carbon material or dissimilar metal material used in the composite parts 30 of Examples 1-15 and Comparative Examples 1-5, corresponding to the type of carbon material or the material and shape of the dissimilar metal material. Figure 2 also shows the thermal expansion coefficient and thermal conductivity of the composite parts 30 for Examples 1-15 and Comparative Examples 1-5.

[0051] Furthermore, as shown in Figure 2, in all of Examples 1 to 15 and Comparative Examples 1 to 5, the main component of the ceramic member 20 is aluminum nitride. As mentioned above, the thermal conductivity of the ceramic member 20 can be changed by the sintering temperature at which the unsintered aluminum nitride body is sintered, whether or not a pressure sintering process such as discharge plasma sintering is used in combination during sintering, and the type and amount of sintering aid added during sintering. As shown in Figure 2, the thermal conductivity of the ceramic member 20 was 150 W / m·K in Examples 1 to 13 and Comparative Examples 1 to 5, 180 W / m·K in Example 14, and 200 W / m·K in Example 15.

[0052] <Rating> The following evaluations were performed on each sample related to Examples 1-15 and Comparative Examples 1-5.

[0053] (Evaluation of the heat dissipation performance of the heat dissipation substrate) To evaluate the heat dissipation performance of the heat dissipation substrates, each of the heat dissipation substrates 1 from Examples 1 to 15 and each of the heat dissipation substrates from Comparative Examples 1 to 5 were processed to a thickness of 1.5 mm in accordance with JIS R1611, and their thermal conductivity was measured by the laser flash method. The results showed that the higher the thermal conductivity, the better the heat dissipation performance of the heat dissipation substrate. For comparison, a sample was prepared consisting of a 0.5 mm thick plate made of sintered aluminum nitride sandwiched between two 0.5 mm thick pure copper plates, and the thermal conductivity of this comparison sample was also measured. The percentage decrease in the thermal conductivity of each of the heat dissipation substrates 1 from Examples 1 to 15 and each of the heat dissipation substrates from Comparative Examples 1 to 5 compared to the thermal conductivity measured for the comparison sample was calculated and evaluated. In the "Heat Dissipation Performance" column of the heat dissipation substrates in Figure 2, these evaluation results are shown. △: A decrease of 50% or more ○: Decrease of 40% or more but less than 50% ◎: Decrease of 30% or more but less than 40% ☆: Decrease of less than 30% These are indicated by the symbols △, ○, ◎, and ☆. △ represents the lowest level of heat dissipation performance of the heat dissipation substrate, ○ is higher than △, ◎ is higher than ○, and ☆ is higher than ◎. In the "Heat Dissipation Performance" column of Figure 2, the measured values ​​of the thermal conductivity of each heat dissipation substrate 1 for Examples 1 to 15 and each heat dissipation substrate for Comparative Examples 1 to 5 are also shown.

[0054] (Evaluation of vibration resistance of heat dissipation substrate) As one of the evaluations of the durability performance of the heat dissipation substrates, sinusoidal vibration tests were conducted on each of the heat dissipation substrates 1 according to Examples 1 to 15 and each of the heat dissipation substrates according to Comparative Examples 1 to 5, in accordance with JIS C 60068-2-6. Specifically, 50 mm square samples were cut out from each of the heat dissipation substrates 1 according to Examples 1 to 15 and each of the heat dissipation substrates according to Comparative Examples 1 to 5. One end of the cut sample was fixed, and vibration was applied to the sample at 125°C so that the displacement amplitude per second at the other end opposite to the heat dissipation substrate was 20 mm in a direction parallel to the thickness direction of the heat dissipation substrate. In addition, the peel strength of the sample was measured before and after the sinusoidal vibration test. The percentage decrease in the peel strength of the sample after the sinusoidal vibration test compared to the peel strength of the sample before the sinusoidal vibration test was calculated and evaluated. Peel strength was measured as copper foil peel strength (peel strength) in accordance with JIS C 6481. In the "Durability Performance" section of the heat dissipation substrate in Figure 2, the "Vibration Durability" column shows the evaluation results. △: A decrease of 30% or more ○: Decrease of 20% or more but less than 30% ◎: Decrease of 10% or more but less than 20% These are indicated by the symbols △, ○, and ◎. △ represents the lowest degree of vibration resistance of the heat dissipation substrate, ○ is higher than △, and ◎ is higher than ○.

[0055] (Evaluation of thermal durability of heat dissipation substrates) As one of the evaluations of the durability performance of the heat dissipation substrate, a thermal cycling test was conducted. The thermal cycling test was carried out according to the following procedure. (1) The peel strength was measured for each of the heat dissipation substrates 1 according to Examples 1 to 15 and each of the heat dissipation substrates according to Comparative Examples 1 to 5. The peel strength was measured in the same manner as in the evaluation of vibration durability. (2) Next, a cooling cycle was repeated 1000 times, changing the temperature between -40°C and 150°C. The holding time at -40°C and the holding time at 150°C were both 1 minute. (3) Subsequently, at room temperature, the peel strength was measured for each of the heat dissipation substrates 1 according to Examples 1 to 15 and each of the heat dissipation substrates according to Comparative Examples 1 to 5. (4) The percentage decrease in peel strength of the sample after the cold and hot cycling test compared to the peel strength of the sample before the cold and hot cycling test was calculated and evaluated. Based on these evaluation results, △: A decrease of 30% or more ○: Decrease of 20% or more but less than 30% ◎: Decrease of 10% or more but less than 20% These are indicated by the symbols △, ○, and ◎. △ represents the lowest degree of vibration resistance of the heat dissipation substrate, ○ is higher than △, and ◎ is higher than ○.

[0056] As shown in Figure 2, in Examples 1 to 15, where the carbon material inside the composite section 30 is in the shape of a mesh, the evaluation results for the heat dissipation performance, vibration durability, and thermal durability of the heat dissipation substrate 1 were all good. On the other hand, in Comparative Example 1, where the carbon material inside the composite section is in the shape of short PAN-based carbon fibers, a certain level of heat dissipation performance was obtained, but the desired performance in terms of vibration durability and thermal durability was not achieved. Furthermore, in Comparative Example 5, where the carbon material inside the composite section is in the shape of carbon powder, the desired performance in terms of heat dissipation performance, vibration durability, and thermal durability was not achieved. In addition, in Comparative Example 4, where the material inside the composite section is replaced with a wire of Ti, a dissimilar metal material, a certain level of heat dissipation performance was obtained, but the desired performance in terms of vibration durability and thermal durability was not achieved.

[0057] These results suggest that, in order to maintain the mechanical properties of the heat dissipation substrate 1, it is not sufficient for the carbon material to be scattered within the composite portion 30; rather, the carbon material needs to be confined within the copper while maintaining its surface shape to some extent. When the carbon material has a mesh shape, within the composite portion 30, the copper constituting the metal member fills in the mesh openings, which are discontinuous portions, thereby confining the carbon material within the copper while maintaining its surface shape to some extent. This is presumed to provide the heat dissipation substrate 1 with the desired mechanical durability.

[0058] Furthermore, if thermal strain occurs in the continuous portion of the carbon material due to a rise in temperature, or if strain occurs in the continuous portion of the carbon material due to vibration, it is conceivable that stress will be applied to the continuous portion of the carbon material mesh. If the carbon material has discontinuous portions, copper is filled into the discontinuous portions of the carbon material in the composite portion 30. It is presumed that filling the discontinuous portions with copper will distribute the stress applied to the continuous portion of the carbon material, thereby improving the mechanical properties of the heat dissipation substrate 1. On the other hand, if the dissimilar metal materials have only continuous portions and no discontinuous portions, such stress distribution will not be achieved in the composite portion, and it is presumed that the overall mechanical properties of the heat dissipation substrate will decrease.

[0059] Furthermore, in Comparative Example 2, where the dissimilar metal material provided in the composite section was a Ti plate without holes, the desired performance in terms of heat dissipation and thermal durability was not obtained. Similarly, in Comparative Example 3, where the dissimilar metal material provided in the composite section was an Fe foil without holes, the desired performance in terms of heat dissipation, vibration durability, and thermal durability was not obtained. From these results, it can be inferred that even if the material provided in the composite section is a dissimilar metal material having higher thermal conductivity than the carbon material, if the dissimilar metal material has only continuous portions and no discontinuous portions, the composite section will not be able to maintain its thermal conductivity. In other words, it can be inferred that the performance of the heat dissipation substrate 1 is improved by making the carbon material provided in the composite section 30 a mesh shape having both continuous and discontinuous portions.

[0060] Furthermore, as shown in Figure 2, in Examples 5 to 15, where the mesh of the carbon material used in the composite part 30 is formed of pitch-based carbon fibers, the heat dissipation performance was particularly improved compared to Examples 1 to 5, where the mesh of the carbon material is formed of PAN-based carbon fibers, and good results were also obtained in terms of durability. The thermal expansion coefficient of the aluminum nitride forming the ceramic member 20 is 4.6 × 10⁻⁶. -6 The temperature is / K, and the thermal expansion coefficient of the copper forming the metal member 10 is 17.0 × 10⁻⁶. -6 The temperature is / K. When the carbon material is formed from pitch-based carbon fibers, which have relatively low thermal expansion and higher thermal conductivity than PAN-based carbon fibers, the thermal expansion coefficient of the composite part 30 can be more easily approximated by the thermal expansion coefficient of the ceramic member 20, and the thermal conductivity of the composite part 30 can also be easily improved. Furthermore, because the thermal expansion of the carbon material is relatively low, the thermal expansion coefficient of the composite part 30 can be more easily approximated by the thermal expansion coefficient of the ceramic member 20. As a result, even if the heat dissipation substrate 1 is subjected to vibration shock or thermal shock, it is thought that delamination of the ceramic member 20 from the metal member 10 at the bonding interface I is suppressed. In this way, it is estimated that the heat dissipation performance of the heat dissipation substrate 1 is improved and its durability is maintained.

[0061] Furthermore, as shown in Figure 2, in Examples 8 to 15, in which a carbide phase is formed on the surface of the carbon material in the composite portion 30, in which carbon is bonded to a dissimilar metal material containing at least one of Ti, V, Cr, Mn, Fe, Zr, and W, vibration durability was particularly improved compared to Examples 1 to 7, and good results were also obtained for other performance aspects. When a carbide phase made of a dissimilar metal material is formed on the surface of the carbon material, it is thought that the copper filling the discontinuous portions of the carbon material and the continuous portions of the carbon material become more compatible. In such cases, even if vibration is applied to the heat dissipation substrate 1, the carbon material and copper do not separate in the composite portion 30, and the state in which the carbon material is constrained by the copper is more easily maintained. As a result, it is estimated that the vibration durability of the heat dissipation substrate 1 is further improved.

[0062] Also, as shown in FIG. 2, in Examples 11 to 15 where the thermal conductivity of the composite part 30 is 280 W / m·K or more and the coefficient of thermal expansion is 7.5×10 -6 / K or less, the heat dissipation performance and cold-heat durability were further improved compared to Examples 1 to 10 where the thermal conductivity of the composite part 30 was less than 280 W / m·K and the coefficient of thermal expansion was greater than 7.5×10 -6 / K, and good results were also obtained for vibration durability. That is, it was confirmed that the heat dissipation substrate 1 can exhibit excellent heat dissipation performance and cold-heat durability because the thermal conductivity and coefficient of thermal expansion of the composite part 30 are within the above ranges.

[0063] Also, as shown in FIG. 2, in Examples 14 and 15 where the thermal conductivity of the ceramic member 20 is 180 W / m·K, the value of the thermal conductivity of the heat dissipation substrate 1 was further improved compared to Examples 1 to 13 where the thermal conductivity of the ceramic member 20 was less than 180 W / m·K. From this, it was confirmed that setting the thermal conductivity of the ceramic member 20 to 180 W / m·K or more has a more favorable influence on the heat dissipation performance of the heat dissipation substrate 1.

[0064] In this way, it has been found that by providing a composite portion 30 inside the metal member 10 in a heat dissipation substrate 1 comprising a metal member 10 mainly composed of copper and a ceramic member 20 mainly composed of aluminum nitride, a heat dissipation substrate 1 can be provided that maintains the heat dissipation performance derived from copper and aluminum nitride while improving mechanical strength. The mechanism by which such an effect is achieved is not fully understood, and it is thought that various factors are involved in combination. However, one possible reason is that the carbon material contained in the composite portion 30 has mesh shapes with continuous and discontinuous portions, and the copper forming the metal member 10 is filled in the discontinuous portions of the carbon material, thereby suppressing a rapid decrease in thermal conductivity in the composite portion 30 when heat is transferred from the metal member 10 to the ceramic member 20 via the composite portion 30. Furthermore, because the thermal expansion coefficient of carbon material is relatively small, even if thermal strain occurs between the metal member 10 and the ceramic member 20 as the temperature of the heat dissipation substrate 1 rises, it is presumed that the thermal expansion of the composite part 30 approximates that of the ceramic member 20, thereby suppressing the delamination of the ceramic member 20 from the metal member 10. It should be noted that this mechanism is based solely on presumption, and its accuracy does not affect the technical scope of this disclosure.

[0065] As described above, the heat dissipation substrate 1 comprises a metal member 10 mainly composed of copper and a ceramic member 20 mainly composed of aluminum nitride. The metal member 10 has a composite part 30 made of carbon material and copper inside, and the shape of the carbon material is a mesh made of woven carbon fibers.

[0066] The coefficient of thermal expansion of copper is 17.0 × 10⁻⁶. -6 The thermal expansion coefficient of aluminum nitride is 4.6 × 10⁻⁶ / K, and the thermal expansion coefficient of aluminum nitride is 4.6 × 10⁻⁶. -6The thermal expansion coefficients of the two materials are significantly different. The heat dissipation substrate 1 has a composite portion 30 inside a metal member 10 mainly composed of copper, which is a composite of a carbon material made of a mesh woven with carbon fibers and copper. Such a composite portion 30 can maintain the thermal conductivity due to copper while bringing its thermal expansion closer to that of aluminum nitride. Therefore, the heat dissipation substrate 1 can improve its mechanical properties while maintaining thermal conductivity.

[0067] The carbon material is formed from pitch-based carbon fibers.

[0068] When a carbon material is formed using pitch-based carbon fibers, the heat dissipation substrate 1 can exhibit superior heat dissipation.

[0069] A carbide phase is formed on the surface of the carbon material, in which carbon is bonded to a dissimilar metallic material different from copper. The dissimilar metallic material includes at least one of Ti, V, Cr, Mn, Fe, Zr, and W.

[0070] In this case, the carbon material and copper become more compatible in the composite section 30, which improves the vibration resistance of the heat dissipation substrate 1.

[0071] The thermal conductivity of the composite part 30 is 280 W / m·K or higher, and the thermal expansion coefficient of the composite part 30 is 7.5 × 10 -6 It is less than or equal to / K.

[0072] In this case, the thermal conductivity of the composite portion 30 is kept relatively high, and its thermal expansion is kept relatively low. As a result, the heat dissipation substrate 1 can exhibit excellent performance in terms of both heat dissipation and durability.

[0073] The thermal conductivity of the ceramic component 20 is 180 W / m·K or higher.

[0074] In this case, since the thermal conductivity of the ceramic component 20 is relatively high, the heat dissipation substrate 1 can exhibit excellent heat dissipation.

[0075] <Other Embodiments> This disclosure is not limited to the embodiments described above and in the drawings. For example, the following embodiments are also included in the technical scope of this disclosure, and furthermore, various modifications can be made without departing from the spirit of the disclosure.

[0076] (1) In the above embodiment, the heat dissipation substrate 1 is shown to have one layer of composite portion 30 made of carbon material and copper inside the metal member 10, along a direction perpendicular to the thickness direction of the metal member 10. The heat dissipation substrate 1 may have two or more layers of composite portion 30 inside the metal member 10, along a direction perpendicular to the thickness direction of the metal member 10. When the heat dissipation substrate 1 has two or more layers of composite portion 30, the position L of the composite portion 30 that is closest to the bonding interface I among the two or more layers of composite portion 30 is determined by the method described above.

[0077] (2) In the above embodiment, the carbon material mesh was made by weaving carbon material wires. The carbon material mesh may also be made by woven carbon material wires.

[0078] (3) The method for manufacturing the heat dissipation substrate 1 shown in the above embodiment is just one example, and it may be manufactured by other methods as long as the purpose of this disclosure is not impaired. [Explanation of Symbols]

[0079] 1: Heat dissipation substrate 10: Metal component 20: Ceramic component 30: Composite part

Claims

1. A heat dissipation substrate comprising a metal component mainly composed of copper and a ceramic component mainly composed of aluminum nitride, The aforementioned metal member has a composite portion inside it made of carbon material and copper, The carbon material has the shape of a mesh made of woven carbon fibers, which is used for heat dissipation substrates.

2. The heat dissipation substrate according to claim 1, wherein the carbon material is formed of pitch-based carbon fibers.

3. A carbide phase is formed on the surface of the carbon material, in which carbon is bonded to a different metal material than copper. The heat dissipation substrate according to claim 2, wherein the dissimilar metal material includes at least one of Ti, V, Cr, Mn, Fe, Zr, and W.

4. The thermal conductivity of the composite portion is 280 W / m·K or higher, and the thermal expansion coefficient of the composite portion is 7.5 × 10 －６ The heat dissipation substrate according to claim 3, wherein the temperature is less than or equal to / K.

5. The heat dissipation substrate according to any one of claims 1 to 4, wherein the thermal conductivity of the ceramic member is 180 W / m·K or higher.

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