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 inside which copper is made of a dissimilar metal material different from copper and copper, and the thermal expansion coefficient of the dissimilar metal material is 10 × 10 -6 The temperature is less than or equal to / K, and the shape of the dissimilar metal materials is either perforated foil or a mesh made of woven wires.

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 inside it made of a dissimilar metal material different from the copper and the copper, and the thermal expansion coefficient of the dissimilar metal material is 10 × 10 -6 The temperature is less than or equal to / K, and the shape of the dissimilar metal material is perforated foil or a mesh woven from wires. [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 and the performance evaluation results 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 inside it made of a dissimilar metal material different from the copper and the copper, and the coefficient of thermal expansion of the dissimilar metal material is 10 × 10 -6 The temperature is less than or equal to / K, and the shape of the dissimilar metal material is perforated foil or a mesh woven from wires.

[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 both is / K, and the coefficients of thermal expansion of both are significantly different from each other. The heat dissipation substrate according to this disclosure has a metal member mainly composed of copper, with a 10 × 10 inside. -6It has a composite part in which a mesh incorporating a perforated foil or wire formed of a dissimilar metal material below / K and copper are combined. Such a composite part can bring the coefficient of thermal expansion closer to that of aluminum nitride while retaining the thermal conductivity attributed to copper. Therefore, the heat dissipation substrate according to the present disclosure can improve mechanical properties while retaining thermal conductivity.

[0011] (2) In the heat dissipation substrate according to (1), it is preferable that the dissimilar metal material contains at least one of Mo and W.

[0012] The dissimilar metal material contains at least one of Mo and W, which has a relatively low coefficient of thermal expansion and a relatively high thermal conductivity. Thereby, the heat dissipation substrate can exhibit excellent performance in both heat dissipation and durability.

[0013] (3) In the heat dissipation substrate according to (1) or (2), the metal member is joined to the ceramic member, and the composite part preferably extends and is arranged in a layered manner in a direction orthogonal to the thickness direction within a range of 10 μm or more and 30 μm or less in the thickness direction from the joining interface between the metal member and the ceramic member.

[0014] By arranging the composite part at a position relatively close to the joining interface between the metal member and the ceramic member, a sudden change in the thermal conductivity and the coefficient of thermal expansion at the joining interface is suppressed. Therefore, the heat dissipation substrate can suppress the occurrence of thermal strain between the metal member and the ceramic member and the peeling of the ceramic member from the metal member as the temperature rises.

[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 section is maintained at a relatively high level, while its thermal expansion is kept relatively low. As a result, the heat dissipation substrate can exhibit excellent performance in terms of both heat dissipation and durability.

[0017] (5) In the holding device described in any of (1) to (4), it is preferable that the thermal conductivity of the ceramic member is 180 W / m·K or higher.

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

[0019] <Heat dissipation substrate 1 configuration> The heat dissipation substrate 1 according to this disclosure will be described with reference to Figure 1. As shown in Figure 1, the heat dissipation substrate 1 comprises a metal member 10 and a ceramic member 20. The overall thickness T of the heat dissipation substrate 1 shown in Figure 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 metals such as copper (Cu) and aluminum (Al), and is a metal plate-like body having a predetermined thickness. In this embodiment, the metal member 10 is mainly composed of copper. In this specification, "main component" means that the content ratio of that component is the highest. That is, "main component" means that it does not have to contain any other substances, or it may contain other substances in trace amounts (for example, amounts corresponding to unavoidable impurities) that do not affect the function and effect of the heat dissipation substrate 1 according to this disclosure. The thickness of the metal member 10 is not particularly limited, but it is preferably 300 μm or more and 400 μm or less.

[0021] The metal member 10 has a composite portion 30 inside it, which is made of a dissimilar metal material different from copper and copper. 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 in the heat dissipation substrate 1 by providing a composite portion 30 inside the metal member 10 in a heat dissipation substrate 1 which comprises a metal member 10 mainly composed of copper and a ceramic member 20 described later. The composite portion 30 is the part of the metal member 10 in which copper, which is the main component of the metal member 10, and the dissimilar metal material are mixed. The composite portion 30 is arranged in layers inside the metal member 10 along a direction perpendicular to the thickness direction of the metal member 10. In this specification, "perpendicular" also includes arrangements that are substantially perceived as orthogonal.

[0022] As the dissimilar metal materials constituting the composite part 30, a metallic material consisting of a metal or an alloy is used. The metallic material constituting the dissimilar metal materials is not particularly limited as long as it has a predetermined thermal conductivity and coefficient of thermal expansion. As dissimilar metal materials, for example, metals such as Ti (titanium), Cr (chromium), Fe (iron), Co (cobalt), Ni (nickel), Zr (zirconium), Mo (molybdenum), La (lanthanum), W (tungsten), Re (rhenium), and alloys such as iron-nickel-cobalt alloy (Fe-Ni-Co), iron-nickel alloy (Fe-Ni), chromium steel (Fe-Cr), molybdenum-lanthanum alloy (Mo-La), tungsten-rhenium alloy (W-Re), molybdenum-zirconium alloy (Mo-Zr), and tungsten-nickel-iron alloy (W-Ni-Fe) can be used. In this embodiment, as the dissimilar metal material, its coefficient of thermal expansion is 10 × 10 -6 Materials with a temperature of / K or less should be used. The dissimilar metal material preferably contains at least one of Mo and W.

[0023] Within the composite portion 30, dissimilar metal materials can be arranged in the copper constituting the metal member 10 in various forms, such as powders or granules, wires, meshes, plates, and foils. In this specification, a mesh is defined as a wire or other wire material of dissimilar metal materials woven together to have multiple meshes (gaps, openings). The mesh constituting the dissimilar metal materials has a planar shape that extends to a predetermined thickness. The thickness of the mesh constituting the dissimilar metal materials is approximately 0.5 mm to 1.0 mm. The mesh constituting the dissimilar metal materials may be flexible.

[0024] In this specification, "plate-like" refers to a plate-like body having a thickness of approximately 1 mm. In this specification, "foil" refers to a material that is thinner than a plate, for example, with a thickness of 200 μm or less. In this embodiment, the foil constituting the dissimilar metal material has a thickness of approximately 10 μm to 100 μm.

[0025] The composite portion 30 is formed by sandwiching a dissimilar metal 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.

[0026] In the process of forming the composite part 30, dissimilar metal materials in powder or granular form are placed between two plate-shaped copper sheets and pressed together. In this pressing process, the powder or granular dissimilar metal materials are scattered within the composite part 30 so as the plate-shaped copper sheets stretch due to the pressing, they spread in a direction perpendicular to the thickness direction of the metal member 10. In the process of forming the composite part 30, wire-shaped dissimilar metal materials are pressed together while placed side by side between two plate-shaped copper sheets. As a result, the wire-shaped dissimilar metal materials are arranged within the composite part 30 so that their longitudinal direction is perpendicular to the thickness direction of the metal member 10. In the process of forming the composite part 30, mesh, plate-shaped, and foil-shaped dissimilar metal materials are placed between two plate-shaped copper sheets and pressed together. As a result, the dissimilar metal materials, such as mesh, plates, and foils, are arranged within the composite portion 30 such that the surfaces of each of the dissimilar metal materials are aligned in a direction perpendicular to the thickness direction of the metal member 10.

[0027] In this embodiment, the dissimilar metal material is configured to have a continuous portion in which the metal material constituting the dissimilar metal material extends continuously along a direction perpendicular to the thickness direction of the composite portion 30, and a discontinuous portion in which the metal material constituting the dissimilar metal material does not extend continuously. In this case, within the composite portion 30, the discontinuous portion of the dissimilar metal material is filled with the metal material constituting the metal member 10.

[0028] Specifically, the shape of the dissimilar metal material according to this embodiment is a perforated foil or mesh, which is a foil with holes (openings) formed therein. The holes formed in the perforated foil penetrate the foil in the thickness direction. When the shape of the dissimilar metal material is a perforated foil, the portion of the perforated foil without holes corresponds to the continuous portion mentioned above. Also, the portion of the perforated foil with holes corresponds to the discontinuous portion mentioned above. When the perforated foil is placed inside the composite portion 30, copper is filled into the holes formed in the perforated foil. Preferably, the holes formed in the perforated foil are formed uniformly at a predetermined pitch on the surface of the perforated foil. In this embodiment, the opening ratio of the perforated foil, that is, the ratio of the area of ​​the discontinuous portion (the portion with holes) to the total area of ​​the perforated foil when viewed in a planar view, is set to approximately 50% to 70%.

[0029] When the shape of dissimilar metal materials is a mesh, 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 meshes) corresponds to the discontinuous portion mentioned above. When the mesh is arranged inside the composite portion 30, copper is filled into the mesh opening portion formed in the mesh. It is preferable that the mesh openings (openings) of the mesh are formed uniformly 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 70%.

[0030] Furthermore, when dissimilar metal materials are in the form of plates and foils, and no holes are formed in the plates and foils, the dissimilar metal materials are considered to have only continuous portions and no discontinuous portions.

[0031] The composite portion 30 containing such dissimilar metal materials is defined as a portion of the metal member 10 that is 30 μm or less from the end of the dissimilar metal 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.

[0032] The thermal conductivity of the composite portion 30 is preferably 280 W / m·K or higher. In this embodiment, the dissimilar metal material mainly consists of a metal or alloy having 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 the dissimilar metal material contained in the composite portion 30 by the thermal conductivity of the dissimilar metal material. In this embodiment, the thermal expansion coefficient of the composite portion 30 is 7.5 × 10⁻⁶. -6 It is preferable that the value is less than or equal to / K.

[0033] 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. A sintered body mainly composed of aluminum nitride has lower mechanical strength but higher thermal conductivity compared to a sintered body mainly composed of silicon nitride. 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 the heat dissipation substrate 1, which comprises 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.

[0034] 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 pressure welding or brazing.

[0035] 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 such that it extends in a direction along the direction in which the bonding interface I extends. In this embodiment, it is preferable that the composite portion 30 is arranged within the metal member 10 in a range of 10 μm to 300 μm in the thickness direction from the bonding interface I.

[0036] <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.

[0037] The method for manufacturing the metal member 10 is as follows. First, two copper plates are prepared to form the metal member 10. Also, dissimilar metal materials are prepared. As mentioned above, the dissimilar metal materials can take various forms, such as powder or granules, wire, mesh, plate, and foil. The dissimilar metal materials having each of these forms are sandwiched between the two copper plates. These are then subjected to ultrasonic pressure welding by applying pressure in the thickness direction to obtain the metal member 10 having a composite portion 30 inside.

[0038] 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.

[0039] 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]

[0040] 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.

[0041] <Examples 1-15> (Fabrication of metal component 10) In Example 1, a mesh of iron-nickel-cobalt alloy (Fe-Ni-Co) was prepared as the dissimilar metal material. The composition of the iron-nickel-cobalt alloy in Example 1 was Fe: 54 mass%, Ni: 29 mass%, and Co: 17 mass%. In Example 2, a perforated foil of iron-nickel alloy (Fe-Ni) was prepared as the dissimilar metal material. A perforated foil is a foil with multiple holes (voids) that penetrate through the foil. The composition of the iron-nickel alloy in Example 2 was Fe: 65 mass%, and Ni: 35 mass%. In Example 3, a perforated foil of Ti was prepared as the dissimilar metal material. In Example 4, a perforated foil of chromium steel (Fe-Cr) was prepared as the dissimilar metal material. The chromium steel in Example 4 was 10Cr, and its composition was Fe: 90 mass%, and Cr: 10 mass%.

[0042] In Example 5, a mesh of Mo was prepared as the dissimilar metal material. In Example 6, a mesh of W was prepared as the dissimilar metal material. In Example 7, a mesh of molybdenum lanthanum alloy (Mo-La) was prepared as the dissimilar metal material. The composition of the molybdenum lanthanum alloy in Example 7 was Mo: 90 mass%, La: 10 mass%.

[0043] In Example 8, a mesh of tungsten-rhenium alloy (W-Re) was prepared as the dissimilar metal material. The tungsten-rhenium alloy in Example 8 had a composition of W: 97% by mass and Re: 3% by mass. In Example 9, a mesh of molybdenum-zirconium alloy (Mo-Zr) was prepared as the dissimilar metal material. The composition of the molybdenum-zirconium alloy in Example 9 had a composition of Mo: 97% by mass and Zr: 3% by mass. In Example 10, a mesh of tungsten-nickel-iron alloy (W-Ni-Fe) was prepared as the dissimilar metal material. The composition of the tungsten-nickel-iron alloy in Example 10 had a composition of W: 90% by mass, Ni: 5% by mass, and Fe: 5% by mass.

[0044] In Examples 11 to 15, Mo meshes were prepared as dissimilar metal materials. The material properties (mass % ratio), shape, thermal expansion coefficient, and thermal conductivity of each of these dissimilar metal materials in Examples 1 to 15 are shown in Figure 2.

[0045] Each of these dissimilar metal 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.

[0046] (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.

[0047] (Joining of metal member 10 and ceramic member 20) The ceramic member 20 was arranged in a laminated manner between two metal members 10. In this case, 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 thickness direction of each 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. In each of the heat dissipation substrates 1 according to Examples 1 to 15, 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 called position L, as shown in Figure 1. The value of this position L is shown in the composite portion column of Figure 2. The position L of the composite portion 30 relative to the bonding interface I was determined by measuring the length between the end of the composite portion 30 that is close to the bonding interface I and the bonding interface I at multiple points on the end of the composite portion 30 that is close to the bonding interface I, and averaging these measurements.

[0048] <Comparative Examples 1 - 5> In Comparative Example 1, a Ni mesh was prepared as the dissimilar metal material. In Comparative Example 2, a Ti plate (a plate without holes) was prepared as the dissimilar metal material. In Comparative Example 3, an Fe foil (a foil without holes) was prepared as the dissimilar metal material. In Comparative Example 4, a Ti wire was prepared as the dissimilar metal material. The thickness of the Ti wire was set to be 400 μm or more and 600 μm or less, and the length of the Ti wire was made the same as the length of the plate-shaped copper. In Comparative Example 5, Ti powder was prepared as the dissimilar metal material. The particle size of the Ti powder was set to be 15 μm or more and 30 μm or less.

[0049] By sandwiching each of these dissimilar metal materials between two copper plates and subjecting the sandwiched materials to ultrasonic pressure welding, metal members according to Comparative Examples 1 - 5, each having a composite part inside, were obtained. The other manufacturing procedures were the same as those in Examples 1 - 15.

[0050] Note that openings such as holes and meshes like those in the dissimilar metal materials according to Examples 1 - 15 are not provided in the dissimilar metal materials according to Comparative Examples 2 and 3. That is, the dissimilar metal materials according to Comparative Examples 2 and 3 have only continuous parts and are formed in a shape without discontinuous parts. Also, the dissimilar metal material according to Comparative Example 4 is a Ti wire, and this wire is not braided with other wires. Therefore, the composite part 30 formed using this is formed such that a plurality of wires are scattered in the copper in a direction orthogonal to the thickness direction of the metal member 10. Further, the dissimilar metal material according to Comparative Example 5 is Ti powder, and the composite part 30 formed using this is formed such that the powdered Ti is scattered in the copper in a direction orthogonal to the thickness direction of the metal member 10.

[0051] The configurations of Examples 1 - 15 and Comparative Examples 1 - 5 were shown in Fig. 2. As shown in Fig. 2, for any of Examples 1 - 15 and Comparative Examples 1 - 5, the main component of the metal member 10 is copper, and the thermal expansion coefficient of this copper is 17.0×10 -6 / K, and the thermal conductivity is 350 W / m·K.

[0052] Figure 2 shows the type, shape, thermal expansion coefficient, and thermal conductivity of the dissimilar metal materials used in the composite parts 30 of Examples 1-15 and Comparative Examples 1-5. Figure 2 also shows the thermal expansion coefficient, thermal conductivity, and position L of the composite part 30 relative to the bonding interface I for each of the composite parts 30 of Examples 1-15 and Comparative Examples 1-5 using these dissimilar metal materials.

[0053] 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, 2, 6 to 13, 120 W / m·K in Example 3, 140 W / m·K in Examples 4 and 5, and 130 W / m·K in Comparative Examples 1 to 5.

[0054] <Rating> The following evaluations were performed on each sample related to Examples 1-15 and Comparative Examples 1-5.

[0055] (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 35% or more but less than 40% ☆: Decrease of less than 35% 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.

[0056] (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 room temperature so that the displacement amplitude per second of the other end, opposite to the one end, 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 ○.

[0057] (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 ○.

[0058] As shown in Figure 2, in Examples 1 to 15, where the shape of the dissimilar metal material provided inside the composite section 30 is a perforated foil or 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 2, where the shape of the dissimilar metal material provided in the composite section is a Ti plate without holes, the desired performance in terms of heat dissipation performance and thermal durability was not obtained. Furthermore, in Comparative Example 3, where the shape of the dissimilar metal material provided in the composite section is a Fe foil without holes, the desired performance in terms of heat dissipation performance, vibration durability, and thermal durability was not obtained. From these results, it can be inferred that when the dissimilar metal material is a perforated foil or mesh with discontinuous portions, the composite section 30 is formed in such a way that it can maintain thermal conductivity due to copper by filling the discontinuous portions of the dissimilar metal material in the composite section 30. On the other hand, it can be inferred that when the dissimilar metal material has only continuous portions and no discontinuous portions, the composite section will not be able to maintain thermal conductivity.

[0059] Furthermore, if thermal distortion occurs in the continuous portion of dissimilar metal materials due to temperature rise, or if distortion occurs in the continuous portion of dissimilar metal materials due to vibration, stress may be applied to the continuous portion of the dissimilar metal materials. If the dissimilar metal materials are perforated foil or mesh with discontinuous portions, copper is filled into the discontinuous portions of the dissimilar metal materials 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 dissimilar metal materials, 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.

[0060] As shown in Figure 2, in Comparative Example 4, where the dissimilar metal material in the composite portion is a Ti wire, and in Comparative Example 5, where the dissimilar metal material is a Ti powder, a certain level of heat dissipation performance was obtained, but the desired performance in terms of vibration durability and thermal durability was not obtained. From these results, it can be inferred that in order to maintain the mechanical properties of the heat dissipation substrate 1, it is not sufficient for the dissimilar metal material to be scattered within the composite portion 30, but rather it is necessary for the dissimilar metal material to be confined within the copper while maintaining to some extent the surface shape that extends along the bonding interface I. That is, when the dissimilar metal material is in the form of a perforated foil or mesh, it can be inferred that within the composite portion 30, the dissimilar metal material is confined within the copper while maintaining to some extent the surface shape that extends along the bonding interface I, and this provides the heat dissipation substrate 1 with the desired mechanical durability.

[0061] As shown in Figure 2, in Comparative Example 1, where the shape of the dissimilar metal material provided in the composite section is a Ni mesh, a certain level of heat dissipation performance was obtained, but the desired performance in terms of vibration durability and thermal durability was not obtained. The thermal expansion coefficient of Ni forming the mesh of the dissimilar metal material in Comparative Example 1 is 13.0 × 10⁻⁶. -6 The coefficient of thermal expansion is / K. On the other hand, among Examples 1 to 15, Example 4 uses dissimilar metal materials with the highest coefficient of thermal expansion in the composite part 30. The coefficient of thermal expansion of the chromium steel (10Cr) forming the perforated foil of the dissimilar metal materials in Example 4 is 10.0 × 10 -6 The temperature is / K. In Example 4, good performance was obtained for the heat dissipation substrate 1 in terms of heat dissipation performance, vibration durability, and thermal durability. From this, it can be concluded that in order to ensure the mechanical properties of the heat dissipation substrate 1, the dissimilar metal material must be a perforated foil or mesh, and its coefficient of thermal expansion must be 10 × 10 -6 It is derived that the temperature must be less than or equal to / K. 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 coefficient of thermal expansion of dissimilar metals is 10 × 10. -6By being below / K, the thermal expansion coefficient of the composite portion 30 becomes more easily approximated to that of the ceramic member 20. As a result, it is presumed that even if the heat dissipation substrate 1 is subjected to vibration shock or thermal shock, delamination of the ceramic member 20 from the metal member 10 at the bonding interface I is suppressed.

[0062] Furthermore, as shown in Figure 2, in Examples 5 to 15, where the dissimilar metal material used in the composite portion 30 includes at least one of Mo and W, the heat dissipation performance was particularly improved, and good results were also obtained in terms of durability, compared to Examples 1 to 4, where the dissimilar metal material is formed from a metal or alloy other than Mo and W. When the dissimilar metal material is formed including at least one of Mo and W, which has relatively low thermal expansion and relatively high thermal conductivity, it is thought that the thermal expansion coefficient of the composite portion 30 becomes easier to approximate with the thermal expansion coefficient of the ceramic member 20, and the thermal conductivity of the composite portion 30 also tends to improve. As a result, it is presumed that both the heat dissipation performance and durability of the heat dissipation substrate 1 are improved.

[0063] Furthermore, as shown in Figure 2, in Examples 8 to 15, where the composite portion 30 is positioned in a range L of 10 μm to 300 μm in the thickness direction from the bonding interface I, vibration durability was particularly improved, and other performance results were also favorable, compared to Examples 1 to 7, where the composite portion 30 is positioned in a position L exceeding 300 μm in the thickness direction from the bonding interface I. From these results, it can be inferred that by positioning the composite portion 30 at a position L relatively close to the bonding interface I within the metal member 10, abrupt changes in thermal conductivity and thermal expansion coefficient at the bonding interface I are suppressed. This is presumed to suppress the delamination of the ceramic member 20 from the metal member 10 at the bonding interface I of the heat dissipation substrate 1.

[0064] Furthermore, as shown in Figure 2, the thermal conductivity of the composite section 30 is 280 W / m·K or higher, and the coefficient of thermal expansion is 7.5 × 10 -6 In Examples 11-15, where the thermal conductivity is less than 280 W / m·K, the thermal conductivity of the composite part 30 is less than 280 W / m·K, and the coefficient of thermal expansion is 7.5 × 10 -6The heat dissipation performance and thermal durability were further improved compared to Examples 1-10, which had values ​​greater than / K, and good results were also obtained for vibration durability. In other words, it was confirmed that the heat dissipation substrate 1 exhibits excellent heat dissipation performance and thermal durability because the thermal conductivity and thermal expansion coefficient of the composite part 30 are within the above range.

[0065] Furthermore, as shown in Figure 2, in Examples 14 and 15, where the thermal conductivity of the ceramic member 20 was 180 W / m·K, 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. This confirms that having a thermal conductivity of 180 W / m·K or higher for the ceramic member 20 has an even more favorable effect on the heat dissipation performance of the heat dissipation substrate 1.

[0066] In this way, it has been found that 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, by providing a composite portion 30 inside the metal member 10, 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 dissimilar metal materials contained in the composite portion 30 have various shapes such as perforated foil or mesh with continuous and discontinuous portions, and the copper forming the metal member 10 is filled in the discontinuous portions of the dissimilar metal materials, so that when heat is transferred from the metal member 10 to the ceramic member 20 via the composite portion 30, the rapid decrease in thermal conductivity in the composite portion 30 is suppressed. In addition, the thermal expansion coefficients of the dissimilar metal materials are 10 × 10 -6Since the temperature is below / K, it is presumed that 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, 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. However, this mechanism is based solely on estimation, and its accuracy does not affect the technical scope of this disclosure.

[0067] 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 inside which copper and a dissimilar metal material different from copper are made, and the thermal expansion coefficient of the dissimilar metal material is 10 × 10 -6 The temperature is less than or equal to / K, and the shape of the dissimilar metal materials is either perforated foil or a mesh made of woven wires.

[0068] 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 temperature is / K, and the thermal expansion coefficients of both are significantly different from each other. The heat dissipation substrate 1 has a 10 × 10 inside a metal member 10 whose main component is copper. -6 The heat dissipation substrate 1 has a composite portion 30 which is made of copper and a mesh woven from perforated foil or wire made of dissimilar metal materials with a temperature of 1 / K or lower. 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.

[0069] The dissimilar metal material includes at least one of Mo and W.

[0070] The dissimilar metal material includes at least one of Mo and W, which have relatively low thermal expansion and relatively high thermal conductivity. This allows the heat dissipation substrate to exhibit excellent performance in both heat dissipation and durability.

[0071] The metal member 10 is bonded to the ceramic member 20, and the composite portion 30 is arranged in layers in a direction perpendicular to the thickness direction within a range L of 10 μm to 300 μm in the thickness direction from the bonding interface I between the metal member 10 and the ceramic member 20.

[0072] By positioning the composite portion 30 at a location L relatively close to the bonding interface I between the metal member 10 and the ceramic member 20, abrupt changes in thermal conductivity and thermal expansion coefficient at the bonding interface I are suppressed. Therefore, the heat dissipation substrate 1 can suppress thermal strain between the metal member 10 and the ceramic member 20 as the temperature rises, preventing the ceramic member 20 from peeling off from the metal member 10.

[0073] 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.

[0074] 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.

[0075] The thermal conductivity of the ceramic component 20 is 180 W / m·K or higher.

[0076] 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.

[0077] <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 various modifications can be made without departing from the spirit of the disclosure.

[0078] (1) In the above embodiment, the heat dissipation substrate 1 is shown to have one layer of composite portion 30 made of dissimilar metal materials 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.

[0079] (2) In the above embodiment, the mesh of dissimilar metal materials was made by weaving wires of dissimilar metal materials. The mesh of dissimilar metal materials may also be made by weaving wires of dissimilar metal materials.

[0080] (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]

[0081] 1: Heat dissipation substrate 10: Metal component 20: Ceramic component 30: Composite part I: Bonding interface L: Position

Claims

1. A heat dissipation substrate comprising a metal component mainly composed of copper and a ceramic component mainly composed of aluminum nitride, The metal member has a composite portion inside it, which is made of a different metal material than the copper and the copper. The thermal expansion coefficient of the aforementioned dissimilar metal materials is 10 × 10 －６ / K or less, The heat dissipation substrate is characterized by the shape of the dissimilar metal material being either perforated foil or a mesh woven from wires.

2. The heat dissipation substrate according to claim 1, wherein the dissimilar metal material includes at least one of Mo and W.

3. The metal member is joined to the ceramic member. The heat dissipation substrate according to claim 1, wherein the composite portion is arranged in layers in a direction perpendicular to the thickness direction, within a range of 10 μm to 300 μm in the thickness direction from the bonding interface between the metal member and the ceramic member.

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 1, 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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