JP7837469B2 - Heat dissipation member, method for manufacturing a heat dissipation member, and vacuum valve - Google Patents

Description

This disclosure relates to a heat dissipation member, a method for manufacturing a heat dissipation member, and a vacuum valve.

For electrical and electronic equipment equipped with heat-generating components such as LEDs (Light-Emitting Diodes) and ICs (Integrated Circuits), the increasing heat generation due to higher power output has made heat dissipation technology increasingly important. In particular, automotive electronic components housed in sealed enclosures for dust and water protection, or vacuum valves in space and power equipment used in vacuum environments, face the problem of difficulty in heat dissipation through air convection.

Therefore, conventional heat dissipation technologies, such as natural air cooling using aluminum heatsinks and forced air cooling using electric fans, do not provide sufficient heat dissipation.

Therefore, in recent years, a highly efficient heat dissipation technology that utilizes the thermal radiation of ceramics by applying a ceramic coating to metal components has attracted attention, particularly for products where heat dissipation is difficult with conventional heat dissipation technologies.

For example, Patent Document 1 discloses a heat dissipation material characterized by a substrate formed from a composite material consisting of ceramics and aluminum, and an anodized layer formed on at least one surface of the substrate.

Japanese Patent Publication No. 2008-255410

However, while the method disclosed in Patent Document 1 above makes it possible to form a metal oxide film on the surface of a component made of light metals (Al, Mg) to impart infrared radiation properties, it has been difficult to form a metal oxide film on the surface of heavy metals such as copper, which are widely used as conductive components in electrical and electronic equipment, to impart infrared radiation properties.

This disclosure provides a technology to solve the above-mentioned problems, and aims to provide a heat dissipation member, a method for manufacturing the heat dissipation member, and a vacuum valve that have excellent adhesion between the substrate and the coating layer and high emissivity without reducing the conductivity of the substrate.

Furthermore, the heat dissipation member of this disclosure is
A heat dissipation member having a base material mainly composed of copper and a coating layer covering the surface of the base material, wherein the coating layer has a ceramic layer mainly composed of an oxide of a metal element with a greater ionization tendency than copper, and a diffusion layer is present at the interface between the base material and the coating layer in which the metal element is diffused into the copper, and the metal element is zinc or nickel.
Furthermore, the heat dissipation member of this disclosure is
A heat dissipation member having a base material mainly composed of copper and a coating layer covering the surface of the base material, wherein the coating layer has a ceramic layer mainly composed of an oxide of a metal element with a higher ionization tendency than copper, and has a diffusion layer at the interface between the base material and the coating layer in which the metal element is diffused into the copper,
The coating layer has a metal layer made of the metal element between the substrate and the ceramic layer.
Furthermore, the method for manufacturing the heat dissipation member of this disclosure is
The method includes the steps of forming a metal plating layer as a coating layer on the substrate and oxidizing the metal plating layer by heat treatment to form the ceramic layer.
Furthermore, the vacuum valve of this disclosure is
The heat dissipation member is provided on at least one of the surfaces of the fixed electrode rod and the movable electrode rod.

According to the heat dissipation member, the method for manufacturing the heat dissipation member, and the vacuum valve disclosed herein,
This invention provides a heat dissipation member, a method for manufacturing the heat dissipation member, and a vacuum valve that offer excellent adhesion between the substrate and the coating layer, as well as high emissivity, without reducing the conductivity of the substrate.

This is a schematic cross-sectional view of the heat dissipation member according to Embodiment 1. This is a schematic cross-sectional view showing another example of the coating layer according to Embodiment 1. This is a schematic cross-sectional view showing an example of the crystal structure of the coating layer according to Embodiment 1. This is a schematic cross-sectional view showing another example of the crystal structure of the coating layer according to Embodiment 1. This is a schematic cross-sectional view showing the alloy layer formed in the diffusion layer of the heat dissipation member according to Embodiment 1. This is a schematic cross-sectional view showing another example of the alloy layer according to Embodiment 1. This is a schematic cross-sectional view of a heat dissipation member in which a metal layer remains on the coating layer according to Embodiment 1. This is a flowchart showing the manufacturing process of the heat dissipation member according to Embodiment 1. This diagram shows the configurations of Examples 1 to 5 of the heat dissipation member according to Embodiment 1. This diagram shows the configurations of Examples 6 to 8 of the heat dissipation member according to Embodiment 1. This diagram shows the configuration of the heat dissipation members for Comparative Examples 1 to 3. This is a schematic cross-sectional view of a vacuum valve according to Embodiment 2. This diagram shows the configurations of Examples 9 to 13 of the heat dissipation member according to Embodiment 3.

Embodiment 1.
The heat dissipation member and the method for manufacturing the heat dissipation member according to Embodiment 1 will be described below with reference to the figures. In the following description and drawings, various "layers" will be mentioned and described, but each "layer" does not have a strict boundary.
Figure 1 is a schematic cross-sectional view of the heat dissipation member 100 according to Embodiment 1.
The heat dissipation member 100 consists of a copper base material 2 (hereinafter simply referred to as base material 2), a coating layer 3, and a diffusion layer 4.

The base material 2 constituting the heat dissipation member 100 is preferably made of a copper-based material because it has excellent thermal and electrical conductivity and is cost-effective. For example, in addition to pure copper, copper alloys such as brass and cupronickel can be used.

In particular, for applications requiring high thermal and electrical conductivity, pure copper is preferred, with a volume resistivity of 2.5 μΩ·cm or less, and more preferably 1.8 μΩ·cm or less. Furthermore, when use in a high vacuum is anticipated, oxygen-free copper is preferred among pure coppers. By using oxygen-free copper, it is possible to prevent a decrease in vacuum due to the release of oxygen dissolved in the copper.

Generally, methods for forming a ceramic coating layer 3 on a copper substrate include sputtering, which requires a complex vacuum process, and thermal spraying, which requires an ultra-high temperature process.

However, with these methods, it is difficult to uniformly form the coating layer 3 on the surface of components with complex shapes, and the adhesion to the copper substrate may be weak. Another method involves coating with a resin composite material in which ceramic fillers are mixed into a resin matrix, but this method has the disadvantage of poor adhesion to the copper substrate and the generation of resin decomposition gases in a vacuum, making it unsuitable for heat dissipation components used in a vacuum.

Therefore, in the heat dissipation member 100 of this embodiment 1, a plating film made of a metal element is formed on the surface of the base material 2, and a ceramic coating layer 3 is easily formed on the base material 2 by oxidizing the plating film in air. In this case, by using a plating film made of a metal element with a higher ionization tendency than copper, when oxidized in air, only the plating film is oxidized, the base material 2 is not oxidized, and the thermal conductivity and electrical conductivity of the base material 2 do not decrease. In this specification, the coating layer 3 refers to the portion of the plating film applied to the base material 2, and the oxidized portion within the coating layer 3 is specifically referred to as the ceramic layer. In some cases, the entire coating layer 3 may be a ceramic layer, and in other cases, as described later, only a portion of the coating layer 3 may be a ceramic layer.

Furthermore, by forming a diffusion layer 4 between the coating layer 3 and the substrate 2, where metal elements are mutually diffused, the adhesion between the substrate 2 and the coating layer 3 is strengthened. Therefore, the heat dissipation member 100 of this embodiment 1 has excellent adhesion to the coating layer 3 and high emissivity, resulting in excellent heat dissipation without reducing the conductivity of the substrate 2.

The coating layer 3 constituting the heat dissipation member 100 plays a role in improving the infrared radiation performance of the heat dissipation member 100. Therefore, it is preferable that it be made of a ceramic material with high emissivity. Furthermore, in the oxidation treatment step, which is one of the processes for forming the coating layer 3 on the substrate 2, it is preferable that it be an oxide of a metal element with a higher ionization tendency than copper, from the viewpoint of preventing oxidation of the substrate 2. For example, ceramic materials such as zinc oxide, silica, and nickel oxide are used.

In particular, when applied to a heat dissipation member 100 where heat dissipation performance is important, zinc oxide with even higher radiation performance is preferable. By using zinc oxide, a heat dissipation member with even higher heat dissipation performance can be obtained. Furthermore, when considering the use of the heat dissipation member in a high vacuum, or when the heat dissipation member is used after undergoing a heat treatment process under a high vacuum, such as vacuum brazing, nickel oxide using nickel with a low vapor pressure is preferable from the viewpoint of preventing evaporation of metal elements in a vacuum.

By using nickel oxide, it is possible to obtain a highly reliable heat dissipation component that has high heat dissipation properties and does not cause evaporation of metal components in a vacuum.
Figure 2 is a schematic cross-sectional view showing another example of the coating layer 3.
As shown in Figure 2, the coating layer 3 may be made of two different ceramic materials to form a laminated structure of coating layer 3A (first coating layer) and coating layer 3B (second coating layer). By making the coating layer 3 a two-layer laminated structure, a coating layer 3A with a coefficient of thermal expansion closer to that of the substrate 2 than the upper coating layer 3B can be formed on the lower layer on the substrate 2 side, and a coating layer 3B with a higher emissivity than coating layer 3A can be formed on the upper layer.

This allows for the formation of a coating layer 3 that exhibits even greater adhesion to the substrate 2 and higher radiation performance. It is even more preferable that the ceramic layer, which is the coating layer 3 of the heat dissipation member in this embodiment, be crystalline.

By using a crystalline ceramic layer as the coating layer 3, the thermal conductivity within the ceramic layer is increased, and heat is efficiently transferred to the ceramic layer responsible for radiation, thus improving radiation performance. The crystalline state of the ceramic layer can be confirmed by X-ray diffraction. If diffraction peaks due to the crystalline structure are observed in the X-ray diffraction pattern, it can be confirmed as crystalline; if only a halo pattern is observed, it can be confirmed as amorphous.

Furthermore, the thickness of the coating layer 3 is preferably 0.5 μm or more and 20 μm or less, and more preferably 1 μm or more and 10 μm or less. If the thickness is less than 0.5 μm, sufficient radiation performance may not be obtained. On the other hand, if the film thickness exceeds 20 μm, the ceramic layer becomes brittle, and problems such as peeling may occur during long-term use.

Figure 3 is a schematic cross-sectional view showing an example of crystalline grains 6 in the coating layer 3.
Figure 4 is a schematic cross-sectional view showing another example of the crystalline grains 6 of the coating layer 3.
The ceramic layer, which is the coating layer 3, can be a dense film made of polycrystalline crystalline grains 6 as shown in Figure 3, or a porous film containing many voids 7 (micropores) between the crystalline grains 6 as shown in Figure 4, as long as it does not impede the radiation performance. From the viewpoint of adhesion to the substrate 2, it is best to choose the type of ceramic layer depending on its material. When using a ceramic layer with a large difference in thermal expansion coefficient from the substrate 2, a porous ceramic layer is preferable in order to alleviate thermal stress, which is a factor that impedes adhesion.

For example, when using zinc oxide, which has a low coefficient of thermal expansion, for the ceramic layer (coating layer 3), making the ceramic layer porous lowers the apparent elastic modulus of the ceramic layer, making it less likely for thermal stress to occur due to the difference in thermal expansion between the substrate 2 and the ceramic layer. Therefore, it becomes possible to further strengthen the adhesion with the substrate 2.

On the other hand, when nickel oxide, which has a small difference in thermal expansion coefficient with the substrate 2, is used for the ceramic layer, the thermal stress generated at the interface with the substrate 2 is small, even without making the ceramic layer porous, and the possibility of delamination is reduced.

Therefore, selecting a dense ceramic layer with high strength is preferable from the viewpoint of improving the mechanical strength of the coating layer 3.

A diffusion layer 4 is formed at the interface between the substrate 2 and the coating layer 3, where the metallic components of the oxides of the metal elements constituting the coating layer 3 are diffused. A ternary metal oxide system of Ni, Cu, and O may be formed in the diffusion layer 4. By forming the diffusion layer 4, the adhesion between the substrate 2 and the coating layer 3 is improved through chemical effects.

Figure 5 is a schematic cross-sectional view showing the alloy layer 8 formed on the diffusion layer 4 of the heat dissipation member 100.
Figure 6 is a schematic cross-sectional view showing another example of the alloy layer 8.
Furthermore, from the viewpoint of improving the adhesion between the substrate 2 and the coating layer 3, it is even more preferable that an alloy layer 8 of copper and the metallic component of the oxide of the metal element constituting the coating layer 3 is formed in the diffusion layer 4. The formation of the alloy layer 8 provides stronger chemical adhesion. In this case, the alloy layer 8 does not have to be formed as a continuous film of uniform thickness at the interface between the substrate 2 and the coating layer 3, but may be formed partially.

For example, when nickel oxide is used for the oxide layer, the alloy layer 8 is a Cu-Ni alloy. Since Cu and Ni are completely dissolved, the ratio of Cu to Ni in the Cu-Ni alloy can be any ratio. Furthermore, the ratio of Cu to Ni in the Cu-Ni alloy is not limited to a single ratio; as shown in Figure 6, it may have a gradient where the copper ratio gradually increases from the upper alloy layer 8a to the alloy layer 8b and alloy layer 8c on the substrate 2 side. When such a gradient is applied, the thermal expansion coefficient of the entire alloy layer 8 also has a gradient, so it acts as a buffer layer for thermal stress relaxation, further contributing to improved adhesion between the substrate 2 and the coating layer 3. Also, when zinc oxide is used for the coating layer 3, the alloy layer is a Cu-Zn alloy.

Figure 7 is a schematic cross-sectional view of the heat dissipation member 100 in which the metal layer 5 remains on the coating layer 3.
As shown in Figure 7, it is even more preferable that the heat dissipation member 100 has a metal layer 5 remaining between the ceramic layer 3S, which is an oxide layer constituting the coating layer 3, and the substrate 2, with the same metal component as the coating layer 3 remaining. The metal layer 5 is the lower layer portion of the metal that was plated to form the coating layer 3, which remained unoxidized during the oxidation treatment.

By leaving the unoxidized metal layer 5, a metal layer 5 with a thermal expansion coefficient intermediate between that of the substrate 2 and the ceramic layer 3S remains beneath the coating layer 3. This has the effect of mitigating thermal stress caused by the difference in thermal expansion coefficients between the substrate 2 and the coating layer 3, and further improving the adhesion between the substrate 2 and the metal layer 5. For example, when nickel oxide is used as the oxide layer for the coating layer 3, the metal layer is a nickel layer.

Furthermore, when zinc oxide is used for the ceramic layer 3S as the coating layer 3, the metal layer 5 is a zinc layer. When the heat dissipation member 100, in which the above-mentioned metal layer 5 is formed between the substrate 2 and the ceramic layer 3S, is used in a high vacuum, or after undergoing a heat treatment process under a high vacuum such as vacuum brazing, a nickel layer with a lower vapor pressure than copper is preferred to prevent evaporation of the metal layer 5. The thickness of the metal layer 5 is not particularly limited, but from the viewpoint of manufacturability, 1 μm to 10 μm is preferred.

Next, an example of a method for manufacturing the heat dissipation member 100 of this embodiment will be described.
Figure 8 is a flowchart showing the manufacturing process of the heat dissipation component 100.
First, copper is processed into the desired shape and dimensions to create the base material 2 (step S01). The shape of the base material 2 can be any shape that can function as a heat dissipation member, such as a plate, cylinder, or fin shape.

The dimensions of the base material 2 are determined considering the thickness of the coating layer 3 to be formed in a later process. Furthermore, when manufacturing a heat dissipation member 100 with strict dimensional tolerances, the base material 2 may be coated with another metal and then surface polished for fine dimensional adjustment. Surface grinding improves surface smoothness and dimensional accuracy. The base material 2 is preferably a copper-based material; for example, in addition to pure copper, copper alloys such as brass and cupronickel can be used.

In particular, for applications requiring high thermal and electrical conductivity, pure copper is preferred, with a volume resistivity of 2.5 μΩ·cm or less, and more preferably 1.8 μΩ·cm or less. Furthermore, if use in a high vacuum is anticipated, oxygen-free copper is preferred among pure coppers.

Next, the surface of the substrate 2 is plated to form a plating layer (step S02). The plating film formed on the surface of the substrate 2 is preferably made of a metal element with a higher ionization tendency than copper, from the viewpoint of preventing oxidation of the substrate 2. For example, zinc, silica, nickel, etc., can be used. By using a plating film made of a metal element with a higher ionization tendency than copper, when oxidized in air, only the plating film oxidizes, the substrate 2 remains unoxidized, and the thermal conductivity and electrical conductivity of the substrate 2 do not decrease.

The plating process can be carried out using any known method, including electroless plating or electrolytic plating. From the viewpoint of adhesion between the substrate 2 and the plating layer, electroplating is even more preferable. Furthermore, the pretreatment for the plating process can be carried out using known methods such as degreasing, acid cleaning, or water washing, depending on the type of plating selected. For example, in electroplated nickel, a plating method using a Watt bath or a sulfamic acid bath can be used, but from a cost viewpoint, plating using a Watt bath is preferable.

The plating layer may be formed in a single plating treatment or in multiple plating treatments. Furthermore, as shown in Figure 2, the coating layer 3 may be formed in a laminated structure of ceramic layers of different materials, or a laminated structure of plating films of different materials. The thickness of the plating layer in the electrolytic plating treatment can be appropriately adjusted by conditions such as the applied electric field strength and the immersion time in the treatment solution, and a thickness of 1 μm to 30 μm is preferred, and 2 μm to 20 μm is more preferred.

If the thickness is less than 1 μm, variations in thickness may result in areas with extremely thin plating. Furthermore, if it exceeds 30 μm, the plating may become more prone to peeling.
Next, the plating layer is heat-treated in air and oxidized to form a coating layer 3 (ceramic layer 3S) (step S03).

The heat treatment method only requires that the plating layer be oxidized in the presence of oxygen, and batch-type electric furnaces, belt-type electric furnaces, etc., can be used. The oxidation temperature should be appropriately selected depending on the type of plating film chosen, and can also be determined by referring to the Ellingham diagram, which is an index of the oxidation-reduction temperatures of metals.

For example, if zinc plating is selected, oxidation treatment at 400°C to 600°C is preferred, and 450°C to 550°C is more preferred. Furthermore, if nickel plating is selected, 600°C to 850°C is preferred, and 650°C to 750°C is more preferred. In addition, the thickness of the ceramic layer formed by oxidation of the plating layer is preferably 0.5 μm to 20 μm, and more preferably 1 μm to 10 μm. The thickness of the ceramic layer can be adjusted as appropriate by changing the temperature and time of the oxidation treatment.

Furthermore, the metal layer 5 between the substrate 2 and the ceramic layer 3S can be formed by selecting heat treatment conditions that do not completely oxidize the plating layer. The diffusion layer 4 is formed during the oxidation treatment by the mutual diffusion of metal elements from the substrate 2 and the plating layer near the interface between the substrate 2 and the plating layer. Depending on the heat treatment conditions, the mutually diffused metal elements can also undergo a chemical reaction to form an alloy layer 8 within the diffusion layer 4.

Next, the details of the heat dissipation member 100 will be described by examples and comparative examples, but this disclosure is not limited thereto.
Figure 9 shows the configurations of the heat dissipation member 100 in Examples 1 to 5.
Figure 10 shows the configurations of the heat dissipation member 100 in Examples 6 to 8.
Figure 11 shows the configuration of the heat dissipation members for Comparative Examples 1 to 3.
Each figure shows the configuration of the heat dissipation member, including the presence or absence of a base material, coating layer, diffusion layer, alloy layer, and metal layer, and the performance evaluation results show a relative evaluation to Example 1.

[Example 1]
A sheet of oxygen-free copper (C1020) (50 mm x 50 mm x 5 mm) was prepared as the base material 2, and a nickel plating layer with a thickness of 0.3 μm was formed on the surface of the base material 2 by electroplating.
Next, using a batch-type electric furnace, the plated layer was oxidized by heat treatment at 700°C in air for 40 minutes to obtain an evaluation heat dissipation member 100 having a coating layer 3 (all ceramic layers) with a thickness of 0.3 μm and an alloy layer 8.

[Example 2]
The procedure was the same as in Example 1, except that the nickel plating layer was formed to a thickness of 3 μm, the process was heat-treated in air at 700°C for 9 hours, and the coating layer 3 (all ceramic layers) had a thickness of 3 μm.

[Example 3]
The procedure was the same as in Example 1, except that the nickel plating layer was formed to a thickness of 18 μm, the process was heat-treated in air at 800°C for 13 hours, and the coating layer 3 (all ceramic layers) had a thickness of 18 μm.

[Example 4]
The procedure was the same as in Example 1, except that the nickel plating layer was formed to a thickness of 25 μm, the process was heat-treated in air at 800°C for 18 hours, and the coating layer 3 (all ceramic layers) had a thickness of 25 μm.

[Example 5]
The procedure was the same as in Example 1, except that the nickel plating layer was formed to a thickness of 3 μm, the coating layer 3 consisted of a ceramic layer 3S with a thickness of 1.5 μm and a metal layer 5 with a thickness of 1.5 μm.

[Example 6]
The procedure was the same as in Example 1, except that the nickel plating layer was formed to a thickness of 8 μm, the coating layer 3 consisted of a ceramic layer 3S with a thickness of 2.5 μm and a metal layer 5 with a thickness of 5.5 μm.

[Example 7]
A plate material (50 mm x 50 mm x 5 mm) of oxygen-free copper (C1020) was prepared as base material 2, and a zinc plating layer with a thickness of 3 μm was formed on the surface of base material 2 by electroplating.
Next, using a batch-type electric furnace, the plated layer was oxidized by heat treatment at 500°C in air for 12 hours to obtain an evaluation heat dissipation member 100 having a 3 μm thick coating layer 3 (all ceramic layers), a diffusion layer 4, and an alloy layer 8.

[Example 8]
The procedure was the same as in Example 7, except that the zinc plating layer was formed to a thickness of 6 μm, the material was heat-treated in air at 500°C for 7 hours, and the coating layer 3 consisted of a ceramic layer 3S with a thickness of 2 μm and a metal layer 5 with a thickness of 4 μm.

[Comparative Example 1]
A plate material (50 mm x 50 mm x 5 mm) of oxygen-free copper (C1020) was prepared as the base material 2, and a heat dissipation member for evaluation was obtained without forming a coating layer on the surface.

[Comparative Example 2]
A plate material (50 mm x 50 mm x 5 mm) of oxygen-free copper (C1020) was prepared as base material 2. Without plating the surface, a heat dissipation member for evaluation was obtained by heat treatment at 500°C in air for 12 hours using a batch-type electric furnace.

[Comparative Example 3]
A plate material (50 mm x 50 mm x 5 mm) of oxygen-free copper (C1020) was prepared as the base material 2, and a nickel oxide target was sputtered onto its surface using the sputtering method to obtain an evaluation heat dissipation member having a coating layer with a thickness of 2 μm.

Next, the heat dissipation members obtained in the above examples and comparative examples were evaluated as follows.
(1) Emissivity For the heat dissipation members obtained in Examples 1 to 8 and Comparative Examples 1 to 3 described above, the surface emissivity was measured using an emissivity measuring device as an indicator of heat dissipation performance.
The emissivity results are shown in Figure 9 as relative values of the emissivity obtained for the heat dissipation members of each example or comparative example ([emissivity obtained for the heat dissipation members of each example or comparative example] / [emissivity obtained for the heat dissipation member of Example 1]), with the emissivity obtained for the heat dissipation member 100 of Example 1 as the reference.

(2) Cycas Strength The cycas strength of the coating layer 3 was measured as an indicator of adhesion for the heat dissipation members obtained in Examples 1 to 8 and Comparative Examples 1 to 3 described above. The results of this cycas strength are shown in Figures 9 to 11 as relative values of the cycas strength obtained for the heat dissipation members of each example or comparative example (value of [cycas strength obtained for the heat dissipation members of each example or comparative example] / [cycas strength obtained for the heat dissipation member of Example 1]) with the cycas strength obtained for the heat dissipation member of Example 1 as the reference.

(3) Volume resistivity of base material 2 The volume resistivity of base material 2 was evaluated using the four-terminal method for the heat dissipation members obtained in Examples 1 to 8 and Comparative Examples 1 to 3 described above. If the obtained volume resistivity value was the same as the volume resistivity of untreated oxygen-free copper (1.65 μΩ·cm), it was marked as ○, and if it increased by 10% or more, it was marked as ×.

(4) Evaporation of metal components in a vacuum The heat dissipation members obtained in Examples 1 to 8 and Comparative Examples 1 to 3 described above were subjected to heat treatment (800°C) in a high vacuum (10⁻³ Pa) simulating brazing conditions using a vacuum heating furnace, and the presence or absence of evaporation of metal components was investigated. The presence or absence of evaporation was evaluated by EPMA (Electron Probe Micro Analyzer) analysis of the cross-section and XRD (X-ray Diffraction) analysis of the surface before and after heat treatment. If there was no change in the elemental distribution and XRD pattern of the metal layer, it was evaluated as no evaporation; if there was a change, it was evaluated as evaporation.

As shown in Figures 9 and 10, the heat dissipation members 100 of Examples 1 to 8 use nickel and zinc, which have a higher ionization tendency than the base material 2, resulting in good volume resistivity of the base material 2. Furthermore, the large ratio of emissivity and the high ratio of cycas strength indicate good heat dissipation and adhesion strength.

On the other hand, in Comparative Example 1, which lacks a coating layer, the heat dissipation is extremely low. Furthermore, in Comparative Example 2, where the surface of the substrate 2 was oxidized directly, the copper oxide film formed on the surface of the substrate 2 peeled off, indicating that it did not form a coating.

Therefore, heat dissipation was not improved. Furthermore, in Comparative Example 3, where nickel oxide was coated onto the surface of substrate 2 by sputtering, it can be seen that the adhesion was very low because there was no diffusion layer on substrate 2 and therefore no chemical adhesion.

Furthermore, comparing Examples 1-4 with Example 5, it can be seen that the heat dissipation is even better when the nickel oxide in the coating layer 3 is crystalline. Also, comparing Examples 1-4 with Example 6, it can be seen that Example 6, which has a thick metal layer 5 between the ceramic layer 3S and the substrate 2 to mitigate the difference in thermal expansion, has even better adhesion between the coating layer 3 and the substrate 2.

Focusing on the difference in the material of the coating layer 3, zinc oxide exhibits even better heat dissipation than nickel oxide. However, focusing on the presence or absence of evaporation of metal components in a vacuum, a comparison between Example 6 and Example 8, both of which have a metal layer 5, shows that the nickel oxide in Example 6 does not undergo evaporation of metal components in a vacuum and is suitable for use in high vacuum. On the other hand, the zinc oxide in Example 8 undergoes evaporation of metal components in a vacuum and is not suitable for use in high vacuum.

According to the heat dissipation member 100 of Embodiment 1,
In a heat dissipation member having a base material mainly composed of copper and a coating layer covering the surface of the base material, the coating layer has a ceramic layer mainly composed of an oxide of a metal element with a higher ionization tendency than copper, and a diffusion layer is present at the interface between the base material and the coating layer in which the metal element is diffused into the copper, and the metal element is zinc or nickel, it is possible to obtain a heat dissipation member with excellent adhesion between the base material 2 and the coating layer 3 and high emissivity without reducing the conductivity of the base material 2. Furthermore, oxidation of the base material 2 can be prevented.

Furthermore, in a heat dissipation member having a base material mainly composed of copper and a coating layer covering the surface of the base material, the coating layer has a ceramic layer mainly composed of an oxide of a metal element with a greater ionization tendency than copper, and at the interface between the base material and the coating layer, there is a diffusion layer in which the metal element is diffused into the copper, and the coating layer has a metal layer made of the metal element between the base material and the ceramic layer. Therefore, by leaving an unoxidized metal layer 5 on the base material 2 side within the coating layer 3, there is a metal layer 5 having a thermal expansion coefficient intermediate between the thermal expansion coefficients of the base material 2 and the coating layer 3, and the effect of mitigating thermal stress due to the difference in thermal expansion coefficients between the base material 2 and the coating layer 3 is obtained.

Furthermore, since the diffusion layer contains an alloy layer composed of copper and the aforementioned metal element, an even stronger chemical adhesion between the coating layer 3 and the substrate 2 can be obtained.

Furthermore, since the aforementioned metal element has a lower vapor pressure than copper, it can prevent the evaporation of the metal element in a vacuum, such as in a vacuum valve.

Furthermore, since the thickness of the ceramic layer is between 0.5 μm and 20 μm, the heat dissipation member 100 can achieve both high radiation performance and durability.

Furthermore, since the volume resistivity of the substrate is 2.5 μΩ·cm or less, it can be used in applications requiring high thermal and electrical conductivity.

Furthermore, since the oxide of the aforementioned metal element is crystalline, it can form a ceramic layer with high heat dissipation properties.

Furthermore, since the coating layer consists of two layers, and the thermal expansion coefficient of the first coating layer on the substrate side is closer to the thermal expansion coefficient of the substrate than the thermal expansion coefficient of the upper second coating layer, a coating layer 3 with even better adhesion to the substrate 2 can be formed.

Furthermore, since the emissivity of the second coating layer is higher than that of the first coating layer, a coating layer 3 with even higher radiation performance can be formed.

Furthermore, according to the manufacturing method of the heat dissipation member 100 according to Embodiment 1,
Since the process includes the steps of forming a metal plating layer as a coating layer on the substrate and oxidizing the metal plating layer by heat treatment to form the ceramic layer, it is possible to form a ceramic layer 3S, a metal layer 5, and an alloy layer 8 of optimal thickness according to the application.

Embodiment 2.
The vacuum valve according to Embodiment 2 will be described below with reference to the figures.
Figure 12 is a schematic cross-sectional view of the vacuum valve 50.
The vacuum valve 50 comprises an insulating cylinder 51, a fixed end plate 52, a movable end plate 53, a fixed electrode rod 54, a movable electrode rod 55, a bellows 56, a fixed contact 57, a movable contact 58, and a coating layer 59. The vacuum container 50A, which is the housing, includes a cylindrical insulating cylinder 51 and fixed end plates 52 and movable end plates 53 fixed to both ends of the insulating cylinder 51 by brazing. A metal arc shield 51A is positioned in the middle of the insulating cylinder 51.

The fixed electrode rod 54 is provided by passing through the fixed end plate 52 and is attached to the fixed end plate 52 by brazing. The movable electrode rod 55 passes through the movable end plate 53 and is joined to the movable end plate 53 by brazing via a bellows 56, and is provided to move freely in the axial direction Z.

A fixed contact 57 is brazed to the end of the fixed electrode rod 54 that is on the movable electrode rod 55 side. Similarly, a movable contact 58 is brazed to the end of the movable electrode rod 55 that is on the fixed electrode rod 54 side.

A drive device (not shown) is attached to the end of the movable electrode rod 55 outside the vacuum container 50A. When the movable electrode rod 55 is driven, the bellows 56 expands and contracts, causing the movable contact 58 and the fixed contact 57 to open and close while maintaining a vacuum inside the vacuum container.

As shown in Figure 12, when the contacts of the vacuum valve 50 are closed and current is supplied, the fixed electrode rod 54, movable electrode rod 55, fixed contact 57, and movable contact 58 inside the vacuum container become heat-generating parts.

In Embodiment 2, the fixed electrode rod 54 and the movable electrode rod 55 of the vacuum valve 50 are equipped with a coating layer 59 on their surfaces and also serve the role of the heat dissipation member 100 described in Embodiment 1, which dissipates heat by radiation in a vacuum, thus incorporating the configuration of the heat dissipation member 100. In this way, the vacuum valve 50 has excellent heat dissipation performance.
Although the description of the vacuum valve 50 describes a vacuum valve 50 with a fixed electrode rod 54 and a movable electrode rod 55 having a coating layer 29 on their surfaces, the coating layer 59 only needs to be present on the surface of at least one of the two electrode rods, the fixed electrode rod 54 or the movable electrode rod 55.

According to the vacuum valve 50 of Embodiment 2,
Since it includes a fixed electrode rod and a movable electrode rod, each having the aforementioned heat dissipation member on its surface,
We can provide vacuum valves with excellent heat dissipation and durability.

Embodiment 3.
The following describes the heat dissipation member and the method for manufacturing the heat dissipation member according to Embodiment 3. Note that for parts other than those described below, the same configuration as in Embodiment 1 is effective.
The base material 2 constituting the heat dissipation member 100 in this embodiment is preferably made of a copper-based material because it has excellent thermal and electrical conductivity and is cost-effective. For example, in addition to pure copper, copper alloys such as brass and cupronickel can be used.

In particular, for applications requiring high thermal and electrical conductivity, pure copper is preferred, with a volume resistivity of 2.5 μΩ·cm or less, and more preferably 1.8 μΩ·cm or less. Furthermore, when use in a high vacuum is anticipated, oxygen-free copper is preferred among pure coppers. By using oxygen-free copper, it is possible to prevent a decrease in vacuum due to the release of oxygen dissolved in the copper.

In the heat dissipation member 100 of this third embodiment, a plating film made of nickel, a metallic element with a greater ionization tendency than copper, is formed on the surface of the substrate 2, and a ceramic coating layer is easily formed on the substrate 2 by oxidizing the plating film in air. Generally, the plating solution used for nickel plating contains sulfur components, and therefore the nickel plating film also contains sulfur components. The sulfur components contained in the nickel film affect the oxidation-reduction potential of the nickel film, and if it contains a large amount of sulfur components, the nickel film becomes very easily oxidized.

Therefore, when the nickel plating film is oxidized in air, a rapid oxidation reaction may occur, which can reduce the adhesion between the substrate 2 and the ceramic layer 3S constituting the coating layer 3. For this reason, in the heat dissipation member 100 of this embodiment 3, it is preferable to use a nickel plating film with a relatively low sulfur content to suppress the rapid oxidation reaction and to reduce the sulfur content of the coating layer 3 after oxidation.

Specifically, the sulfur content of the coating layer 3 in this embodiment 3 is preferably 1000 ppm or less. It is even more preferably 600 ppm or less, even more preferably 400 ppm or less, and most preferably 200 ppm or less.

The ceramic layer 3S constituting the coating layer 3 of the heat dissipation member 100 in this embodiment 3 is preferably composed of nickel oxide particles with an average particle size of 1 μm or less, and more preferably composed of nickel oxide particles with an average particle size of 0.5 μm or less. By setting the particle size of the nickel oxide particles as described above, the strength of the ceramic layer 3S is increased, and the effect of a ceramic layer 3S that is less likely to peel off from the substrate 2 is obtained.

Furthermore, from the viewpoint of further improving adhesion with the substrate 2, it is preferable that the ceramic layer 3S has a large number of micropores (the voids 7 described above). In this case, the average size of the micropores is preferably equal to or less than the average particle size of the nickel oxide constituting the ceramic layer 3S, with an average size of 1 μm or less, and more preferably 0.5 μm or less. By setting the average size of the micropores in this way, the effect of mitigating thermal stress due to the difference in thermal expansion with the substrate 2 is created without reducing the strength of the ceramic layer 3S, thereby improving the adhesion between the substrate 2 and the ceramic layer 3S.

In this embodiment 3, it is preferable that a copper-nickel alloy layer 8 is formed in the diffusion layer 4 of the heat dissipation member 100, and that the content ratio of copper to nickel constituting the alloy is within a certain range. Specifically, the ratio of copper to nickel constituting the alloy is preferably 40:60 to 60:40 by mass, and more preferably 45:55 to 55:45. By forming an alloy layer 8 with a copper-nickel content ratio within a certain range in this way, the alloy layer 8 becomes chemically stable, and even when the ceramic layer 3S becomes thicker, the adhesion to the substrate 2 can be further improved.

Next, an example of a method for manufacturing the heat dissipation member 100 of this third embodiment will be described.
The manufacturing method for the heat dissipation member 100 in this third embodiment is based on the flowchart in Figure 8, which describes the manufacturing method for the heat dissipation member 100 in the first embodiment; therefore, only the differences will be explained here.

Step S02 involves applying a plating treatment to the surface of the substrate 2 to form a plating layer. From the viewpoint of preventing oxidation of the substrate 2, nickel, a metallic element with a higher ionization tendency than copper, is used for the plating film formed on the surface of the substrate 2. From the viewpoint of adhesion between the substrate 2 and the plating layer, electroplating is preferable for the nickel plating treatment. Furthermore, pretreatment for the plating process can be carried out using known methods such as degreasing, acid cleaning, or water washing. In addition, electroplated nickel can use a Watt bath or a sulfamic acid bath, but from a cost viewpoint, plating using a Watt bath is preferable.

In electroplating nickel, a brightener is generally added to the plating solution. However, some brighteners contain large amounts of sulfur, which can lead to a large amount of sulfur being incorporated into the nickel plating layer. Sulfur can cause corrosion of the plating layer, which forms the coating layer 3. Therefore, from the viewpoint of suppressing the sulfur content of the nickel plating layer after plating, it is preferable to use a brightener that does not contain sulfur. Furthermore, if it is necessary to use a brightener containing sulfur, such as saccharin, it is preferable to use as little as possible.

Furthermore, in electroplated nickel, there are additives that incorporate carbon components into the nickel plating film after the plating process. In the heat dissipation member 100 of this embodiment 3, it is preferable to add such an additive to the plating solution and then perform the plating process. For example, it is preferable to use an additive such as butynediol.

By incorporating carbon components into the plating film, during the oxidation treatment process (step S03), when the carbon components burn and gasify, the grain growth of nickel oxide particles constituting the ceramic layer 3S is suppressed, making it easier for fine particles to form. Furthermore, as the combustion gas of the carbon components escapes, micropores are more easily formed in the ceramic layer 3S, thus enabling the formation of a coating layer 3 with even better adhesion to the substrate 2.

Specific examples are described below.
[Example 9]
The procedure was the same as in Example 1, except that a nickel plating layer was formed on the substrate 2 to a thickness of 8 μm using a plating solution to which 1 mL/L of saccharin, a brightening agent, was added, the process was heat-treated in air at 700°C for 8 hours, and the coating layer 3 consisted of a ceramic layer 3S with a thickness of 3 μm and a metal layer 5 with a thickness of 5 μm.

[Example 10]
The procedure was the same as in Example 1, except that a nickel plating layer was formed to a thickness of 8 μm using a plating solution to which 3 mL/L of saccharin, a brightening agent, was added, heat treatment was performed in air at 700°C for 7.5 hours, and a coating layer 3 consisting of a ceramic layer 3S with a thickness of 3 μm and a metal layer 5 with a thickness of 5 μm was performed.

[Example 11]
The procedure was the same as in Example 1, except that a nickel plating layer was formed to a thickness of 8 μm using a plating solution to which 5 mL/L of saccharin, a brightening agent, was added, heat treatment was performed in air at 700°C for 7.5 hours, and a coating layer 3 consisting of a ceramic layer 3S with a thickness of 3 μm and a metal layer 5 with a thickness of 5 μm was performed.

[Example 12]
The procedure was the same as in Example 1, except that a nickel plating layer was formed to a thickness of 8 μm using a plating solution to which 15 mL/L of saccharin, a brightening agent, was added, the plating was heat-treated in air at 700°C for 7.5 hours, and the coating layer 3 consisted of a ceramic layer 3S with a thickness of 3 μm and a metal layer 5 with a thickness of 5 μm.

[Example 13]
The procedure was the same as in Example 1, except that a nickel plating layer was formed to a thickness of 8 μm using a plating solution to which 20 mL/L of saccharin, a brightening agent, was added, heat treatment was performed in air at 700°C for 7.5 hours, and a coating layer 3 consisting of a ceramic layer 3S with a thickness of 3 μm and a metal layer 5 with a thickness of 5 μm was performed.

Next, the heat dissipation members 100 obtained in Examples 9 to 13 were evaluated in the same manner as in Examples 1 to 8 and Comparative Examples 1 to 3. In addition, the sulfur content contained in the coating layer 3 was analyzed by GD-OES (Glow Discharge Optical Emission Spectrometry) analysis. The results are shown in Figure 13.
The heat dissipation members 100 in Examples 9 to 13 have a nickel oxide ceramic layer 3S and a diffusion layer 4, an alloy layer 8, and a metal layer 5, all of which are effective in improving adhesion, and therefore have excellent heat dissipation and adhesion to the substrate 2. Furthermore, it can be seen that in Examples 9 to 12, in which the sulfur content of the coating layer 3 is 1000 ppm or less, the adhesion of the coating layer 3 to the substrate 2 is even better.

According to the heat dissipation member 100 of Embodiment 1,
The aforementioned metal element is nickel, and the coating layer has a sulfur content of 1000 ppm or less.
A corrosion-resistant coating layer can be formed.

Furthermore, the aforementioned metal element is nickel.
The ceramic layer is composed of nickel oxide particles with an average particle size of 1 μm or less, and has micropores with an average size of 1 μm or less,
This process reduces thermal stress caused by differences in thermal expansion between the ceramic layer and the substrate without reducing the strength of the ceramic layer. As a result, the adhesion between the substrate and the ceramic layer is improved.

Furthermore, the aforementioned metal element is nickel.
The diffusion layer consists of a copper-nickel alloy layer with a copper-nickel content ratio of 40:60 to 60:40,
The alloy layer becomes chemically stable, and even when the ceramic layer becomes thicker, adhesion to the substrate can be improved.

While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but can be applied individually or in various combinations to the embodiments.
Accordingly, countless variations not illustrated are conceivable within the scope of the technology described herein. These include, for example, modifying, adding or omitting at least one component, or extracting at least one component and combining it with components of other embodiments.

100 Heat dissipation member, 2 Base material, 3, 3A, 3B Coating layer, 3S Ceramic layer, 4 Diffusion layer, 5 Metal layer, 50 Vacuum valve, 50A Vacuum container, 6 Crystal grains, 7 Void, 51 Insulating cylinder, 51A Arc shield, 52 Fixed end plate, 53 Movable end plate, 54 Fixed electrode rod, 55 Movable electrode rod, 56 Bellows, 57 Fixed contact, 58 Movable contact, 59 Coating layer, 8, 8a, 8b, 8c Alloy layer, Z axis direction.

Claims (14)

A heat dissipation member comprising a base material mainly composed of copper and a coating layer covering the surface of the base material, wherein the coating layer has a ceramic layer mainly composed of an oxide of a metal element with a higher ionization tendency than copper, and a diffusion layer at the interface between the base material and the coating layer where the metal element is diffused into the copper, wherein the metal element is zinc or nickel. A heat dissipation member having a base material mainly composed of copper and a coating layer covering the surface of the base material, wherein the coating layer has a ceramic layer mainly composed of an oxide of a metal element with a higher ionization tendency than copper, and has a diffusion layer at the interface between the base material and the coating layer in which the metal element is diffused into the copper,
The coating layer is a heat dissipation member having a metal layer made of the metal element between the substrate and the ceramic layer. The heat dissipation member according to claim 1 or claim 2, having an alloy layer composed of copper and the aforementioned metal element within the diffusion layer. The heat dissipation member according to claim 2, wherein the aforementioned metal element is a metal element with a lower vapor pressure than copper. The heat dissipation member according to claim 1 or claim 2 , wherein the thickness of the ceramic layer is 0.5 μm or more and 20 μm or less. The heat dissipation member according to claim 1 or claim 2 , wherein the volume resistivity of the substrate is 2.5 μΩ·cm or less. The heat dissipation member according to claim 1 or claim 2 , wherein the oxide of the metal element is crystalline. The heat dissipation member according to claim 1 or claim 2, wherein the coating layer consists of two layers, and the thermal expansion coefficient of the first coating layer on the substrate side is closer to the thermal expansion coefficient of the substrate than the thermal expansion coefficient of the upper second coating layer. The heat dissipation member according to claim 8, wherein the emissivity of the second coating layer is higher than that of the first coating layer. The aforementioned metallic element is nickel,
The heat dissipation member according to claim 1 or claim 2 , wherein the coating layer has a sulfur content of 1,000 ppm or less. The aforementioned metallic element is nickel,
The heat dissipation member according to claim 1 or claim 2 , wherein the ceramic layer is composed of nickel oxide particles with an average particle size of 1 μm or less and has micropores with an average size of 1 μm or less. The aforementioned metallic element is nickel,
The heat dissipation member according to claim 1 or claim 2 , wherein the diffusion layer is a copper-nickel alloy layer having a copper-nickel content ratio of 40:60 to 60:40. A method for manufacturing a heat dissipation member according to claim 1 or claim 2 ,
A method for manufacturing a heat dissipation member, comprising the steps of forming a metal plating layer as a coating layer on the substrate and oxidizing the metal plating layer by heat treatment to form the ceramic layer. A vacuum valve having the heat dissipation member described in claim 1 or claim 2 provided on at least one surface of either the fixed electrode rod or the movable electrode rod.