Film-attached base material and method for manufacturing film-attached base material

Abstract

To provide a base material with a film having a heat radiation film excellent in thermal shock resistance.SOLUTION: There is provided a film-coated substrate including a substrate and a heat radiation film, wherein the heat radiation film is provided on at least a part of a surface of the substrate and includes a first region containing a ceramic as a main component and functioning as a matrix and a second region containing diamond as a main component, and a surface roughness (arithmetic average roughness Ra) of a surface of the heat radiation film opposite to the substrate is 0.5 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film-coated substrate and a method for producing a film-coated substrate. [Background technology]

[0002] In recent years, heat dissipation materials using diamond, which has high thermal conductivity, as a filler have been produced. Patent Document 1 describes a heat dissipation composition containing a polymer matrix and diamond particles. Patent Document 2 describes a heat dissipation member in which multiple diamond particles are dispersed in a metal matrix containing copper. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-023255 [Patent Document 2] International Publication No. 2023210395 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the polymer matrix as in Patent Document 1 has a large difference in the coefficient of linear thermal expansion from diamond, leaving room for improvement in thermal shock resistance. Also, even with a metal matrix whose main component is copper as in Patent Document 2, the difference in the coefficient of linear thermal expansion from diamond remains, resulting in insufficient thermal shock resistance. [Means for solving the problem]

[0005] According to one aspect of the present invention, there is provided a film-coated substrate comprising a substrate and a heat dissipation film, the heat dissipation film being disposed on at least a portion of the surface of the substrate and including a first region having a ceramic as its main component and functioning as a matrix, and a second region having a diamond as its main component, and the surface roughness (arithmetic mean roughness Ra) of the heat dissipation film on the surface opposite the substrate is 0.5 μm or less.

[0006] According to this aspect, it is possible to provide a film-coated substrate having a heat-dissipating film that is excellent in thermal shock resistance. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram schematically showing a cross section of a film-coated substrate. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described. For each numerical range presented in this specification, the proportion of the film-coated substrate or the like that satisfies the numerical range is preferably about 85% or more, more preferably about 90% or more, and even more preferably about 95% or more, or may be 100%. [Substrate with film] First, a film-coated substrate according to one embodiment will be described. Figure 1 is a diagram schematically showing a cross section of a film-coated substrate. 1 includes a substrate 2 and a heat dissipation film 3. The heat dissipation film 3 is provided on at least a part of a surface (front surface) 21 of the substrate 2. The substrate 2 supports the heat dissipation film 3. The shape and material of the substrate 2 are not particularly limited, and various modes can be adopted depending on the application of the film-coated substrate 1.

[0009] Examples of the external shape of the substrate 2 include a rectangular parallelepiped, a square pillar, a cylindrical pillar, a rectangular pillar, a flat plate, a circular tube, a square tube, a film, etc. The microstructure of the substrate 2 may be, for example, a structure without pores, or a structure with pores such as a porous, honeycomb, mesh, sponge, or monolithic structure. The shape of the surface 21 of the base material 2 on which the heat dissipation film 3 is formed may be, for example, a curved surface, a flat surface, or the like, depending on the shape of the base material 2.

[0010] The material of the substrate 2 is not particularly limited, but examples thereof include ceramic materials, metal materials, glass materials, carbon materials, resin materials, and semiconductor materials. Examples of ceramic materials include alumina (Al2O3), mullite (Al2O3·SiO2), zirconia (ZrO2), titania (TiO2), yttria (Y2O3), aridil (Al2O3, ZrO2), yttria-stabilized zirconia (Y2O3, ZrO2), silicon nitride (Si3N4), sialon (Si3N4·Al2O3), and silicon carbide (SiC). Examples of metal materials include aluminum or aluminum alloys, iron, stainless steel, titanium, and nickel. Resin materials may be thermosetting or thermoplastic resins. Examples of resins include polypropylene, polyethylene, polyurethane, polystyrene, polyamide, polyimide, and polytetrafluoroethylene. Examples of semiconductor materials include silicon, germanium, gallium arsenide, gallium nitride, and indium phosphide.

[0011] A heat dissipation film 3 is provided on the surface 21 of the base material 2. The thickness of the heat dissipation film 3 is not particularly limited, but is preferably about 1 μm or more and 500 μm or less. The thickness of the heat dissipation film 3 is, for example, the arithmetic mean value of thicknesses measured at at least three locations by cross-sectional observation of the heat dissipation film 3 using an SEM (scanning electron microscope). 1, the cross section of the heat dissipation film 3 has a first region 32 mainly composed of ceramic and a second region 33 mainly composed of diamond. The second region 33 is dispersed or concentrated in the first region 32. Here, the first region 32 also functions as a matrix that holds the second region 33.

[0012] The area of ​​a portion of a certain region that is made of a specific material (for example, the area of ​​the portion of the first region 32 that is made of ceramic) can be obtained by photographing a cross section of the heat dissipation film 3 with a scanning electron microscope (SEM) and analyzing the resulting cross-sectional image. Alternatively, if the material cannot be identified using an SEM, an elemental mapping image of the cross section of the heat dissipation film 3 can be obtained using a scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDX) method, and the area of ​​the mapped portion that shows the ceramic can be obtained by image analysis. In this case, analysis can be performed on cross-sectional images at any five locations, and the arithmetic average of the areas at those five locations can be obtained as the area of ​​the portion made of ceramic. The areas described herein below can be obtained in a similar manner. Furthermore, when the proportion of the area of ​​the cross-section of the heat dissipation film 3 that is made up of a certain substance is approximately 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, or 99% or more, the substance is said to be "the main component."

[0013] Diamond is known to have an extremely small coefficient of linear thermal expansion. Ceramics are generally known to have a smaller coefficient of linear thermal expansion than metals such as copper and iron, and polymers such as thermosetting resins and thermoplastic resins. By using ceramics and diamond as the materials for the heat dissipation film 3, the difference in the coefficient of linear thermal expansion between the materials that make up the heat dissipation film 3 can be reduced. In other words, even when temperatures change drastically, damage such as cracks and peeling is unlikely to occur at the interface between the materials, making it possible to provide a heat dissipation film 3 with excellent thermal shock resistance.

[0014] Examples of ceramics that can be used include alumina (AlO), cermet (TiC-TiN), sialon (SiN-AlO), aluminum nitride (AlN), boron nitride (BN), gallium nitride (GaN), silicon carbide (SiC), titanium carbide (TiC), boron carbide (BC), titanium boride (TiB), zirconium boride (ZrB), and silicon nitride (SiN). Among these, aluminum nitride (AlN), boron nitride (BN), gallium nitride (GaN), silicon carbide (SiC), titanium boride (TiB), and zirconium boride (ZrB) are more preferred. These ceramics have a relatively small difference in coefficient of linear thermal expansion from diamond, improving the thermal shock resistance of the heat dissipation film 3. Furthermore, their high thermal conductivity allows the heat dissipation film 3 to exhibit excellent heat dissipation.

[0015] That is, the ceramic to be used preferably has a coefficient of linear thermal expansion of about 0 to 15, more preferably about 0 to 10, and even more preferably about 0 to 8. This makes it easier to impart sufficient thermal shock resistance to the heat dissipation film 3. The ceramics used preferably have a thermal conductivity at room temperature of about 10 W / mK to 500 W / mK, more preferably about 20 W / mK to 500 W / mK, and even more preferably about 50 W / mK to 500 W / mK, which allows the heat dissipation film 3 to sufficiently dissipate heat from the substrate 2.

[0016] In the configuration of Patent Document 1, the thermal conductivity of the polymer matrix portion is low, and there is a possibility that the heat dissipation performance is insufficient. On the other hand, the film-coated substrate 1 provided with the heat dissipation film 3 containing ceramics as described above can have excellent heat dissipation performance.

[0017] Furthermore, it is preferable that the ceramic has a property of being difficult to conduct electricity (that is, a large volume resistivity), which allows the heat dissipation film 3 to function as a non-conductive film. The configuration of Patent Document 2 has a problem in that the matrix portion is a metal containing copper, and therefore cannot be used in applications requiring insulation. On the other hand, the heat dissipation film 3 of the present disclosure can be used in applications requiring insulation, because ceramics having the desired conductivity can be selected for the matrix. In this case, the volume resistivity is 10 5 Ω cm or more 10 18 It is preferable that the resistance is about Ω·cm or less, and 10 8 Ω cm or more 10 18 It is more preferable that the resistivity is about Ω·cm or less.

[0018] In this specification, the coefficient of linear thermal expansion may be that obtained in accordance with JIS R 1618:2002. Alternatively, the coefficient of linear thermal expansion of the material particles may be simply used as the coefficient of linear thermal expansion of each region or substance in the heat dissipation film 3. In this case, the coefficient of linear thermal expansion of the material particles may be measured, for example, by in-situ XRD, which measures the crystal lattice constant of the particles while heating, or the value listed in the specifications accompanying the purchase of the material particles may be used. The thermal conductivity can be obtained by the thermoreflectance method using a laser in accordance with JIS R 1689:2018. In this case, the thermal conductivity can be calculated based on the thickness of the heat dissipation film 3 obtained by cross-sectional observation using an SEM. Alternatively, the thermal conductivity of the material particles may be simply used as the coefficient of linear thermal expansion of each region or substance in the heat dissipation film 3. In this case, the thermal conductivity of the material particles may be measured by the flash method in accordance with JIS R 1611:2010, for example, or the value listed in the specifications provided when the material particles were purchased may be used. The coefficient of linear thermal expansion and the thermal conductivity are each the arithmetic mean of the test results at five locations (or five times).

[0019] The first region 32 may contain one or more substances as long as they have the properties described above. In addition to ceramics, they may also contain other ceramics or materials other than ceramics. Furthermore, the ceramic may contain a mixture of two or more of a crystalline portion, a microcrystalline portion, and an amorphous (non-crystalline) portion. Here, the microcrystalline portion refers to a portion made up of crystals with a crystallite size of 20 nm or less.

[0020] The diamond contained in the second region 33 may be, for example, a single crystal diamond such as natural diamond or synthetic diamond, polycrystalline diamond, or diamond-like carbon. Of these, it is preferable to use a single crystal diamond including natural diamond or synthetic diamond. This can further improve the heat dissipation performance of the heat dissipation film 3.

[0021] The ratio of the coefficient of linear thermal expansion of first region 32 to the coefficient of linear thermal expansion of second region 33 is preferably about 0.5 or more and 10 or less, and more preferably about 1 or more and 5 or less. In this way, the difference in the coefficient of linear thermal expansion between the ceramic and diamond contained in heat dissipation film 3 is sufficiently small, thereby improving the thermal shock resistance of heat dissipation film 3. It is particularly preferable that the ratio between the coefficients of linear thermal expansion of the components contained in the heat-dissipating film 3 satisfies the above-mentioned numerical range.

[0022] Furthermore, the ratio of the coefficient of linear thermal expansion of the first region 32 to the coefficient of linear thermal expansion of the substrate 2 is preferably approximately 0.5 or more and 10 or less, and more preferably approximately 1 or more and 5 or less. Since the difference in the coefficient of linear thermal expansion between the first region 32 functioning as a matrix and the substrate 2 is thus sufficiently small, the adhesion of the heat dissipation film 3 to the substrate 2 is less likely to deteriorate during thermal shock. In other words, the thermal shock resistance of the heat dissipation film 3 is further improved.

[0023] The second regions 33 are preferably distributed across the thickness of the heat dissipation film 3. This allows heat from the substrate 2 to be efficiently transferred to the surface 31 of the heat dissipation film 3 opposite the substrate 2. In addition, the first regions 32, which function as a matrix, tend to firmly hold the second regions 33, thereby preventing or suppressing the diamond from detaching from the heat dissipation film 3.

[0024] The second regions 33 may also be distributed across the in-plane direction of the heat dissipation film 3. This allows heat from the substrate 2 to be transferred evenly in the in-plane direction to the heat dissipation film 3 and easily dissipated from the surface 31. Furthermore, the second regions 33 containing diamond are held firmly by the first regions 32, so that the diamond (second regions 33) can be prevented or suppressed from detaching from the heat dissipation film 3.

[0025] Furthermore, it is preferable that the area of ​​the second region 33, which is mainly composed of diamond, varies widely. In this case, second regions 33 having a narrower area (i.e., diamonds with a smaller diameter) can be embedded around second regions 33 having a wider area (i.e., diamonds with a larger diameter). This allows the second regions 33 having a wider area to quickly dissipate heat from the substrate 2. Furthermore, since the proportion of diamond in the heat dissipation film 3 is increased, the heat dissipation efficiency of the heat dissipation film 3 as a whole can also be improved.

[0026] In the cross section of the heat dissipation film 3, when the area of ​​the first region 32 is X and the area of ​​the second region 33 is Y, Y / X is preferably approximately 0.05 to 19, and more preferably approximately 0.1 to 15. In this way, by including a high proportion of the second region 33, which is mainly composed of diamond, the thermal conductivity of the heat dissipation film 3 is improved, and heat can be efficiently dissipated from the substrate 2. Furthermore, the presence of an appropriate amount of the first region 32, which functions as a matrix, can prevent or suppress the diamond from separating from the heat dissipation film 3. As described above, the area of ​​the first region 32 and the area of ​​the second region 33 can be obtained by SEM image analysis of the cross section of the heat dissipation film 3 or by analysis of an element mapping image by SEM-EDX method.

[0027] The porosity of the heat dissipation film 3 is preferably about 10% or less, and more preferably about 5% or less. A heat dissipation film 3 with such a small porosity prevents the heat conduction path from the base material 2 from being blocked by voids, and allows efficient transfer and release of heat via the first region 32 and the second region 33, which have high thermal conductivity. The porosity of the heat dissipation film 3 may be about 0% or more and 10% or less, or about 0% or more and 5% or less. The porosity of the heat dissipation film 3 can be obtained as follows. First, an SEM image of the cross section of the heat dissipation film 3 is obtained. The brightness threshold of the obtained SEM image is adjusted using image analysis software to binarize the image so that the heat dissipation film 3 (bright areas) and the voids (dark areas) are separated. The ratio of the number of void pixels to the number of pixels of the heat dissipation film 3 is then determined as the porosity.

[0028] Furthermore, the surface roughness (arithmetic mean roughness Ra) of the surface (surface) 31 of the heat dissipation film 3 opposite the substrate 2 is approximately 1.3 μm or less, approximately 1 μm or less, or approximately 0.5 μm or less, preferably approximately 0.4 μm or less, more preferably approximately 0.3 μm or less, and particularly preferably approximately 0.2 μm or less. Thus, a small surface roughness (arithmetic mean roughness Ra) of the surface of the heat dissipation film 3 can be expected to have the effect of smoothing the conduction path of heat generated by the substrate 2. Therefore, the efficiency of heat dissipation from the substrate 2 is improved. For example, when another heat dissipation member or the like is bonded to the surface 31 of the heat dissipation film 3, the adhesion between the surface 31 and the bonding surface of the other heat dissipation member can be improved, thereby improving heat transfer from the film-coated substrate 1 to the heat dissipation member.

[0029] The surface roughness (arithmetic mean roughness Ra) of face 31 may be about 0.005 μm or more, about 0.01 μm or more, about 0.03 μm or more, or about 0.05 μm or more. A relatively large surface roughness (arithmetic mean roughness Ra) has the advantage of increasing the area of ​​heat dissipation film 3 that comes into contact with air. The upper and lower limit values ​​of the surface roughness (arithmetic mean roughness Ra) of face 31 can be appropriately combined, and may be, for example, approximately 0.005 μm or more and 1.3 μm or less, approximately 0.005 μm or more and 1 μm or less, approximately 0.005 μm or more and 0.5 μm or less, approximately 0.01 μm or more and 0.4 μm or less, approximately 0.03 μm or more and 0.3 μm or less, or approximately 0.005 μm or more and 0.2 μm or less.

[0030] Furthermore, the surface roughness (maximum height roughness Rz) of the surface (surface) 31 of the heat dissipation film 3 opposite the substrate 2 is preferably about 10 μm or less, about 7 μm or less, more preferably about 6 μm or less, about 4 μm or less, or about 3 μm or less, and even more preferably about 2 μm or less, or about 1 μm or less. Thus, a small surface roughness (maximum height roughness Rz) of the surface 31 of the heat dissipation film 3 means that there is little damage such as cracks and interconnected voids on the surface 31 of the heat dissipation film 3, and therefore the heat dissipation effect of the heat dissipation film 3 can be fully exerted. In addition, the mechanical strength of the heat dissipation film 3 is easily improved.

[0031] The surface roughness (maximum height roughness Rz) of face 31 may be about 0.05 μm or more, about 0.1 μm or more, about 0.15 μm or more, or about 0.3 μm or more. The upper and lower limit values ​​of the surface roughness (maximum height roughness Rz) of face 31 can be combined as appropriate, and may be, for example, approximately 0.05 μm or more and 10 μm or less, approximately 0.05 μm or more and 7 μm or less, approximately 0.1 μm or more and 6 μm or less, approximately 0.1 μm or more and 4 μm or less, approximately 0.1 μm or more and 3 μm or less, approximately 0.15 μm or more and 2 μm or less, or approximately 0.3 μm or more and 1 μm or less.

[0032] The surface roughness (arithmetic mean roughness Ra) and the surface roughness (maximum height roughness Rz) of the surface 31 can be obtained using a surface profiler in accordance with JIS B 0651:2001 (ISO3274:1996).

[0033] The scratch hardness of the heat dissipation film 3 measured by the pencil method is preferably 4H or more, and more preferably 6H or more. The scratch hardness may be, for example, about 9H or less, but may also be harder than 9H. That is, the scratch hardness may be about 4H or more but 9H or less, or about 6H or more but 9H or less. By satisfying such values, damage such as cracks and chips is unlikely to occur in the heat dissipation film 3. Furthermore, the mechanical strength of the entire film-coated substrate 1 is improved. The scratch hardness by the pencil method can be obtained in accordance with JIS K 5600-5-4:1999 (ISO / DIS 15184:1996). Herein, when obtaining the scratch hardness, the test is also performed using 7H, 8H, and 9H pencils as defined in JIS S 6006:2020.

[0034] Furthermore, as described for ceramics, it is more preferable that the heat dissipation film 3 has the property of being difficult to conduct electricity (i.e., the volume resistivity of the film-coated substrate 1 is high), which allows the heat dissipation film 3 to function as a non-conductive film. Specifically, the volume resistivity of the film-coated substrate 1 is 10 4 Ω cm or more 10 18 It is preferable that the resistance is Ω·cm or less, and 10 8 Ω cm or more 10 18 It is more preferable that the resistance is about Ω·cm or less, and 10 12 Ω cm or more 10 18 It is more preferable that the resistivity is about Ω·cm or less. By satisfying such a value, it is possible to impart sufficient insulating performance (non-conductivity) to the film-coated substrate 1.

[0035] The lower limit of the volume resistivity of the heat dissipation film 3 is 10 4 About Ω cm or more, 10 6 About Ω cm or more, 10 8 Ω·cm or more, or 10 12 The upper limit is 10 20 About Ω cm or less, 10 18 About Ω cm or less, 10 12 Less than Ω cm or 1010 The lower and upper limits of the numerical ranges can be combined in any manner. The volume resistivity may be that obtained in accordance with JIS C 2141: 1992. The volume resistivity is the arithmetic average of the test results at five locations.

[0036] [Method of manufacturing film-coated substrate] Next, a description will be given of a method for producing the film-coated substrate 1. In this specification, a case where the heat dissipation film 3 is formed on the entire surface 21 of the flat substrate 2 will be described as an example. The method for manufacturing the film-coated substrate 1 includes a preparation step of preparing a substrate 2 and a powder (mixed particles) containing diamond particles and ceramic particles, and a film formation step of spraying the powder onto the substrate 2 to form a heat dissipation film 3 containing diamond and ceramic on the surface of the substrate 2, thereby obtaining the film-coated substrate 1.

[0037] (preparation process) First, a base material 2 and a powder containing diamond particles and ceramic particles are prepared. The base material 2 and the powder may be prepared by purchasing commercially available products, or may be prepared by oneself. The substrate 2 can be prepared by various methods, such as cutting a flat base material or heat-treating (degreasing and firing) a molded body containing the particles and binder that make up the substrate 2.

[0038] The powder can also be prepared by various methods. Among the powders, ceramic particles can be prepared by physical methods such as pulverization or chemical methods such as hydrothermal synthesis. Diamond particles can be prepared by, for example, pulverizing purchased or prepared diamond blocks. The diamond preferably contains single-crystal diamond, and more preferably is substantially composed of single-crystal diamond alone. This can further improve the thermal conductivity of the heat dissipation film 3, as described above for the film-coated substrate 1.

[0039] The ceramic particles may be two or more types of particles with different average particle sizes (for example, small particles and large particles). That is, the particle size distribution of the ceramic powder, which is an aggregate of ceramic particles, may have two or more maximum values. For example, the average particle size of the small particles is preferably about 10 nm to 700 nm, more preferably about 30 nm to 600 nm, and the average particle size of the large particles is preferably about 500 nm to 50 μm, more preferably about 700 nm to 30 μm.

[0040] The average particle size of the particles can be, for example, the particle size at 50% of the cumulative size measured using a particle size distribution analyzer based on a laser diffraction / scattering method. Alternatively, the average particle size of the particles can be determined by arithmetically averaging the equivalent area circle diameters obtained in accordance with JIS Z8827-1:2018 (ISO 13322-1:2014) based on images acquired using a scanning electron microscope (SEM).

[0041] In the film formation process, a powder containing ceramic particles and diamond particles is sprayed toward the surface 21 of the substrate 2 on which the film is to be formed, thereby forming (depositing) the film. The particles in the powder sprayed toward the surface 21 of the substrate 2 collide with and deposit on the surface 21 of the substrate 2, thereby forming the heat dissipation film 3 on said surface 21. In particular, the ceramic particles act as a matrix to hold the diamond particles in place by being deformed, broken, etc., and adhering during the process of forming the heat dissipation film 3.

[0042] At this time, if the collision energy when the particles collide with the substrate 2 is insufficient, the particles will not be able to adhere to the surface 21, and therefore will not be able to form the heat dissipation film 3. The higher the kinetic energy of the sprayed particles, the higher the collision energy. When the ceramic particles contain two or more types of particles with different average particle sizes, the large diameter particles impart collision energy to the entire powder, while the small diameter particles easily form a dense heat dissipation film 3 in the film formation step.

[0043] Here, although large-diameter particles contribute to imparting collision energy, they may impair the density and uniformity of the heat-dissipating film 3, and therefore it is preferable that they are less likely to be incorporated into the heat-dissipating film 3. In the film formation process, many large-diameter particles are repelled without being deposited on the substrate 2, but by mixing under the following conditions, it is possible to appropriately reduce the number of large-diameter particles incorporated into the heat-dissipating film 3. Furthermore, by including a sufficient amount of large-diameter particles, it is possible to impart appropriate collision energy to the powder, thereby facilitating the formation of the heat-dissipating film 3.

[0044] That is, the loose bulk density of the prepared ceramic particles is 0.3 g / cm 3 It is preferable that the concentration is about 0.4 g / cm or more. 3 It is more preferable that the temperature is about the same or higher. The loose bulk density can be measured according to JIS K 7365: 1999 (ISO 60: 1977) or a method conforming thereto. That is, ceramic particles are gently poured into a 100 mL container using a funnel without applying any external physical force (tapping, pushing, etc.), and the weight of the ceramic particles when the container is leveled is divided by the volume (100 mL) to obtain the loose bulk density.

[0045] Furthermore, when the cumulative 10% diameter in the volume-based particle size distribution of the ceramic particles is defined as cD10 and the cumulative 90% diameter is defined as cD90, it is preferable that cD10 is about 0.05 μm or more and 1.0 μm or less, and cD90 is about 0.8 μm or more and 5 μm or less, and more preferably cD10 is about 0.1 μm or more and 0.8 μm or less, and cD90 is about 1 μm or more and 4 μm or less. These values ​​are examples of particularly preferred ranges and can be combined with each other. This particle size distribution can be measured, for example, using a particle size distribution analyzer using a laser diffraction / scattering method. Based on the obtained particle size distribution, the particle size at 10% cumulative from the smallest particle size can be calculated as cD10, and the particle size at 90% cumulative from the smallest particle size as cD90.

[0046] The prepared diamond particles preferably have a broad particle size distribution. Specifically, when the cumulative 10% diameter of the volume-based particle size distribution of diamond particles is dD10 and the cumulative 90% diameter is dD90, dD10 is preferably 0.05 μm or more and 1.0 μm or less, and dD90 is 0.8 μm or more and 5 μm or less, and more preferably dD10 is 0.1 μm or more and 0.8 μm or less, and dD90 is 1 μm or more and 4 μm or less. These values ​​are examples of particularly preferred ranges and can be combined with each other. By satisfying these conditions, as described above, it is possible to appropriately increase the variation in the area of ​​the second region 33, which is mainly composed of diamond, and to expect to improve the heat dissipation efficiency of the heat dissipation film 3. dD10 and dD90 can be obtained in the same manner as cD10 and cD90.

[0047] The resulting ceramic particles and diamond particles are then mixed wet or dry to prepare a powder. The proportion of diamond particles in the powder is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 30% by mass or less. By mixing at such a proportion, the ratio of the first region 32 to the second region 33 in the cross section of the heat dissipation film 3 can be set to the value described above in the description of the film-coated substrate 1.

[0048] (film formation process) Next, powder is sprayed onto the surface 21 of the substrate 2 to form the heat dissipation film 3 containing diamond and ceramics. In the film formation process, the powder is preferably sprayed onto the substrate 2 by an aerosol deposition method. The use of the aerosol deposition method has the advantages of broadening the range of materials that can be used to form the heat dissipation film 3, improving the bonding reliability of the formed heat dissipation film 3, and increasing the density of the heat dissipation film 3. Furthermore, since the film can be formed at room temperature, it is also suitable from the viewpoint of reducing power consumption.

[0049] Ceramics are generally difficult to process and somewhat unsuitable for forming thin films. Furthermore, there are technical obstacles to using them in combination with diamond, which is even more difficult to process. However, after extensive research, the inventors discovered that aerosol deposition can be used to particularly effectively form a heat dissipation film 3 including a first region 32 as a matrix primarily composed of ceramic and a second region 33 primarily composed of diamond. In other words, when the aerosol deposition method is employed, it is possible to obtain a heat-dissipating film 3 that satisfies the preferable ranges of the values ​​presented for the film-coated substrate 1 .

[0050] When forming the heat dissipation film 3 by aerosol deposition, the substrate 2 is attached to a stage in a chamber of a film forming apparatus (not shown) so that the surface 21 on which the heat dissipation film 3 is to be formed faces the nozzle. Aerosol is generated by mixing powder with a gas such as oxygen (O2), nitrogen (N2), argon (Ar), helium (He), or air.

[0051] Next, the chamber is depressurized. The pressure in the chamber is not particularly limited, but is preferably, for example, about 5 Pa or more and 1000 Pa or less. Then, the aerosol is sprayed from the nozzle outlet at a speed of subsonic or more and supersonic or less, causing the powder to collide with and deposit on the surface 21 of the substrate 2. At this time, the spray speed of the aerosol (powder) onto the surface 21 of the substrate 2 is preferably set to about 10 m / s or more and 1000 m / s or less, and more preferably set to about 10 m / s or more and 250 m / s or less. While the aerosol is being sprayed, the substrate 2 is moved by the XY stage to form the heat dissipation film 3 over the entire surface 21. The moving speed of the substrate 2 is preferably about 0.1 cm / sec or more and 30 cm / sec or less, and more preferably about 0.5 cm / sec or more and 20 cm / sec or less.

[0052] In this manner, the heat dissipation film 3 is formed on the surface 21 of the substrate 2, and the substrate 1 with the film is obtained. In the film formation step, the heat dissipation film 3 can also be formed by a film formation method such as electrostatic fine particle coating or cold spray instead of the aerosol deposition method. Furthermore, it may be provided in the following aspects.

[0053] (1) A film-coated substrate comprising a substrate and a heat dissipation film, the heat dissipation film being provided on at least a portion of the surface of the substrate, the heat dissipation film comprising a first region having a ceramic as its main component and functioning as a matrix, and a second region having a diamond as its main component, the surface roughness (arithmetic mean roughness Ra) of the heat dissipation film on the surface opposite the substrate being 0.5 μm or less.

[0054] (2) The film-coated substrate according to (1) above, wherein the surface roughness (maximum height roughness Rz) of the opposite surface is 3 μm or less.

[0055] (3) The film-coated substrate according to (1) or (2) above, wherein the second region is distributed across the thickness direction of the heat dissipation film.

[0056] (4) The film-coated substrate according to any one of (1) to (3) above, wherein the second regions are distributed across the in-plane direction of the heat-dissipating film.

[0057] (5) The film-coated substrate according to any one of (1) to (4) above, wherein, in a cross section of the heat dissipation film, when the area of ​​the first region is X and the area of ​​the second region is Y, Y / X is 0.05 or more and 19 or less.

[0058] (6) The film-coated substrate according to any one of (1) to (5) above, wherein the heat-dissipating film has a scratch hardness of 4H or more as measured by a pencil method.

[0059] (7) The film-coated substrate according to any one of (1) to (6) above, wherein the porosity of the heat-dissipating film is 10% or less.

[0060] (8) The film-coated substrate according to any one of (1) to (7) above, wherein the ratio of the coefficient of linear thermal expansion of the first region to the coefficient of linear thermal expansion of the second region is 10 or less.

[0061] (9) A method for producing a film-coated substrate according to any one of (1) to (8) above, comprising: a preparation step of preparing the substrate and a powder containing diamond particles and ceramic particles; and a film formation step of spraying the powder onto the substrate to form the heat dissipation film containing the diamond and the ceramic on the surface of the substrate, thereby obtaining the film-coated substrate.

[0062] (10) The method for producing a film-coated substrate according to (9) above, wherein in the film-forming step, the powder is sprayed onto the substrate by an aerosol deposition method. Of course, this is not the case.

[0063] As described above, various embodiments of the present invention have been described, but these are presented as examples and do not limit the scope of the invention in any way. The novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Such embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as set forth in the claims. [Example]

[0064] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0065] 1. Manufacturing of film-coated substrate Example 1 Substrate preparation The substrate was a silicon wafer with a thickness of 1 mm, cut into a roughly rectangular shape of 10 mm x 10 mm.

[0066] Powder preparation First, as ceramic particles, aluminum nitride (AlN) particles with an average particle size of 500 nm (thermal conductivity: 200 W / mK, coefficient of linear thermal expansion: 4.8 × 10 -6 / K). As diamond particles, artificial diamond particles with an average particle size of 100 nm (thermal conductivity: 1100 W / mK, coefficient of linear thermal expansion: 2.3 × 10 -6 / K) was prepared.

[0067] A mixture of 95 parts by mass of aluminum nitride particles and 5 parts by mass of synthetic diamond particles was placed in a container. 60 parts by mass of ethanol (concentration 99.5% by mass) was added to the container per 100 parts by mass of this mixture, and the mixture was kneaded using a planetary mixer. The kneading was carried out for 2 minutes at a revolution speed of 2000 rpm and a rotation speed of 800 rpm. The slurry obtained after kneading was left to stand at 70°C for 3 hours, and then left to stand at 100°C for 1 hour to dry. The dried product obtained by drying was pulverized in a blade mill at 20,000 rpm for 1 minute, thereby obtaining a powder.

[0068] - Formation of a film on the surface of a substrate The film was formed using an aerosol deposition device. First, the four edges (four sides) of the substrate were fixed to the edges of the support surface of the stage (XY stage) with Kapton tape. The powder was then sprayed onto the surface of the substrate at about 20°C. Specifically, the powder to be sprayed was loaded into an aerosol generator, and the pressure inside a chamber containing the substrate was reduced to 5 Pa by a pump. In this state, powder was sprayed onto the substrate from a nozzle having a rectangular nozzle of 10 mm x 0.5 mm in plan view while the substrate was being moved along the in-plane directions (X direction and Y direction).

[0069] Nitrogen gas (N2) was used for transport adjustment. This nitrogen gas was supplied from a gas cylinder to an aerosol generator filled with powder, dispersing the powder in the nitrogen gas to generate an aerosol. The flow rate of the nitrogen gas was adjusted using a mass flow controller installed upstream of the aerosol generator. The aerosol was then passed through a disintegrator and a classifier and sprayed from a nozzle toward the substrate to form a film. The aerosol was sprayed from the nozzle at a speed of 250 mm / sec, and the distance from the nozzle to the surface 21 of the substrate 2 was 10 mm. The number of scans was adjusted to 12.

[0070] (Examples 2 and 3, Comparative Examples 1 and 2) A film-coated substrate was produced in the same manner as in Example 1, except that the constituent materials, masses, and particle sizes of the particles in the powder were changed as shown in Table 1.

[0071] 2. Measurement and testing

[0072] (Measuring the average thickness of the film) The average thickness of the film was determined by measuring the thickness at five points on the cross section of the film-coated substrate and calculating the arithmetic mean of the measured thicknesses. The five points were selected to be at least 20 μm apart from each other in the in-plane direction of the film. Observation and image acquisition were performed using a scanning electron microscope (SEM) while adjusting the magnification so that at least the surface of the substrate on which the film was formed could be observed from the outermost surface of the film. The acceleration voltage was set to 1.0 kV or more and 15 kV or less. Then, for the acquired images, the thickness from the surface of the substrate on which the film was formed to the outermost surface of the film was measured.

[0073] (thermal conductivity measurement) A molybdenum (Mo) layer was formed as a light-reflecting layer on the surface of the film opposite the substrate by sputtering. The thickness of the molybdenum layer was 100 nm. The film-coated substrate was then placed in a pulsed light heating thermoreflectance device, and pulsed heating light was irradiated from the substrate side. A laser diode was used as the pulsed heating light, with an average output of 100 W, a pulse width of 450 ps, ​​and a wavelength of 1064 nm. The temperature history of the film surface was then obtained by irradiating the molybdenum layer with a temperature-measuring laser and receiving the reflected light with a light-receiving device. A continuous-wave laser diode was used as the temperature-measuring laser, with an average output of 100 and a wavelength of 782 nm.

[0074] The temperature of the film surface was recorded until it reached room temperature, and a cooling curve of the film surface was created using the temperature history.Then, the time it took for the film surface temperature to reach half the difference between the maximum temperature and room temperature (i.e., the half-life) was obtained from the cooling curve. The measurement was carried out three times for each Example and Comparative Example, and the arithmetic mean of the three half-lives was taken as the heat release time.

[0075] (volume resistivity measurement) The volume resistivity of the film-coated substrate was obtained in accordance with JIS C 2141:1992 by the following procedure: Instead of measuring the resistance value using a high-insulation resistance meter, the resistance value was calculated based on the current measured using a digital microcurrent meter and the applied voltage. The thickness of the film-coated substrate was measured using a micrometer. The film-coated substrate was then inserted into an electric furnace and heated to 500°C at a rate of 5°C / min while a voltage of 1 kV was applied. At 500°C, the current flowing through the film-coated substrate in the thickness direction was measured using a digital microcurrent meter. Conductive paste was used as the electrodes, with the film surface serving as the negative electrode and the surface of the substrate opposite the film serving as the anode. The resistance value R was then calculated based on the measured current.

[0076] The volume resistivity ρ (Ω cm) is the electrode area A (cm 2 ), the thickness d (cm) of the film-coated substrate, and the resistance value R (Ω), ρ=R·A / d It was obtained by the formula: The measurement was carried out five times, and the arithmetic mean of the five volume resistivities ρ was taken as the volume resistivity of each example and comparative example. (Area ratio analysis of membrane) Observation and image acquisition were performed using a scanning electron microscope (SEM) at a magnification adjusted to allow observation of at least the surface of the substrate on which the film was formed and the outermost surface of the film. The acceleration voltage was set to 1.0 kV or more and 15 kV or less. The acquired images were then analyzed using image analysis software. In the analysis, the area of ​​the region originating from each particle was obtained, with the entire cross-sectional area of ​​the film being set to 100.

[0077] Analysis was performed at five locations that were at least 20 μm apart, and the arithmetic average of the five locations was used as the area derived from each particle. Note that since the arithmetic average was used as the area ratio of each region, the sum of the area ratios did not always equal 100. Furthermore, based on this area, the ratio Y / X of the area Y of the region (second region) mainly composed of diamond to the area X of the region (first region) mainly composed of ceramic was calculated.

[0078] (Calculation of linear thermal expansion coefficient for each region) The coefficients of linear thermal expansion of the first and second regions were calculated based on the coefficients of linear thermal expansion of the material particles and the area ratio. When the first region contains multiple ceramics, the coefficient of linear thermal expansion of each ceramic was multiplied by the area ratio of that ceramic, and the resulting value was added up to determine the coefficient of linear thermal expansion of the first region. When the first region is made of a single ceramic, the coefficient of linear thermal expansion of the material particles was used as the coefficient of linear thermal expansion of the first region. As the second region is made of only diamond, the coefficient of linear thermal expansion of the diamond particles was used as the coefficient of linear thermal expansion of the second region. Furthermore, the ratio A / B of the coefficient of linear thermal expansion A of the first region to the coefficient of linear thermal expansion B of the second region, and the ratio A / C of the coefficient of linear thermal expansion A of the first region to the coefficient of linear thermal expansion C of the substrate were calculated. C was set to 4.0 × 10, which is the general coefficient of linear thermal expansion of single crystal silicon. -6 was used.

[0079] (Porosity analysis) Observation and image acquisition were performed using a scanning electron microscope (SEM) at a magnification adjusted to allow observation of at least the surface of the substrate on which the film was formed and the outermost surface of the film. The acceleration voltage was set to 1.0 kV or more and 15 kV or less. The acquired images were then binarized using image analysis software to separate the film (bright areas) and dark areas (voids). The ratio of voids to the film area was then obtained. The proportion of voids was calculated for five locations spaced 20 μm or more apart, and the arithmetic average of the five locations was taken as the void ratio.

[0080] (Measurement of film surface roughness (arithmetic mean roughness Ra) and surface roughness (maximum height roughness Rz)) In accordance with JIS B0651:2001 (ISO3274:1996), the surface roughness (arithmetic mean roughness Ra) and surface roughness (maximum height roughness Rz) of the outermost surface of the film were measured by the following procedure. The surface roughness (arithmetic mean roughness Ra) and surface roughness (maximum height roughness Rz) were measured by sweeping the measurement needle of a surface profiler (Tokyo Seimitsu Co., Ltd., "SURFCOM130A") 1 cm while it was in contact with the outermost surface of the film. The arithmetic mean of the measurement results at three different points on the outermost surface was obtained as the surface roughness (arithmetic mean roughness Ra) and surface roughness (maximum height roughness Rz) for each example and comparative example.

[0081] (Scratch hardness test) In accordance with JIS K 5600-5-4:1999 (ISO / DIS 15184:1996), the scratch hardness of the outermost surface of the film was tested by the pencil method using the following procedure. In addition to hardnesses of 6B to 6H, tests were also conducted using pencils with hardnesses of 7H, 8H, and 9H as specified in JIS S 6006:2020. A pencil was placed in a handy pencil scratch hardness tester, placed at a 45-degree angle against the top surface of the film, and moved at a speed of 1 mm / sec over a distance of 10 mm. The test was carried out at room temperature. After the test, the hardness was determined by visually inspecting the indentation on the film. The test was carried out at five locations spaced at least 20 μm apart, and the test results that accounted for the majority were adopted.

[0082] 3.Results The measurement results of Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in the following Tables 1 and 2. Table 1 shows the powder and particles that are the materials, and Table 2 shows the films that were formed.

[0083] [Table 1]

[0084] [Table 2] [Explanation of symbols]

[0085] 1: Film-coated substrate 2: Base material 21: Face 3: Heat dissipation film 31: Face 32: First area 33: Second Area

Claims

1. A film-attached substrate, A substrate and a heat dissipation film are provided, The heat dissipation film is provided on at least a portion of the surface of the substrate, The ceramic substrate includes a first region having a ceramic as a main component and functioning as a matrix, and a second region having a diamond as a main component, The surface roughness (arithmetic mean roughness Ra) of the surface of the heat dissipation film opposite to the substrate is 0.5 μm or less. Membrane-coated substrate.

2. The film-coated substrate according to claim 1, The surface roughness (maximum height roughness Rz) of the opposite surface is 3 μm or less. Membrane-coated substrate.

3. The film-coated substrate according to claim 1, The second region is distributed across the thickness direction of the heat dissipation film. Membrane-coated substrate.

4. The film-coated substrate according to claim 1, the second region is distributed across the in-plane direction of the heat dissipation film; Membrane-coated substrate.

5. The film-coated substrate according to claim 1, In the cross section of the heat dissipation film, when the area of ​​the first region is X and the area of ​​the second region is Y, Y / X is 0.05 or more and 19 or less. Membrane-coated substrate.

6. The film-coated substrate according to claim 1, The scratch hardness of the heat dissipation film by the pencil method is 4H or more. Membrane-coated substrate.

7. The film-coated substrate according to claim 1, The porosity of the heat dissipation film is 10% or less. Membrane-coated substrate.

8. The film-coated substrate according to claim 1, a ratio of the coefficient of linear thermal expansion of the first region to the coefficient of linear thermal expansion of the second region is 10 or less; Membrane-coated substrate.

9. A method for producing a film-coated substrate according to any one of claims 1 to 8, comprising: a preparation step of preparing the substrate and a powder containing diamond particles and ceramic particles; a film-forming step of spraying the powder onto the substrate to form the heat dissipation film containing the diamond and the ceramic on the surface of the substrate, thereby obtaining the film-coated substrate. Method for manufacturing a film-coated substrate.

10. The method for producing a film-coated substrate according to claim 9, In the film forming step, the powder is sprayed onto the substrate by an aerosol deposition method. Method for manufacturing a film-coated substrate.

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