Method for manufacturing heat dissipation substrate, and heat dissipation substrate

Abstract

This disclosed manufacturing method comprises: a step for forming a non-metal inorganic bonding layer 20 by applying a first paste, which contains at least a first thermally-conductive material and a non-metal inorganic bonding material, to the surface of a ceramic base material 10 and then performing heating; a step for forming a resin layer 30 by applying a second paste, which contains at least a second thermally-conductive material and a thermoplastic resin, to the surface of the non-metal inorganic bonding layer 20 and then performing heating; and a step for bonding the interface of each of the non-metal inorganic bonding layer 20, the resin layer 30, and a metal plate 40 by performing heating while pressing the metal plate 40 against the surface of the resin layer 30. In this manufacturing method, the non-metal inorganic bonding layer 20, which has suitable bondability to each layer, is interposed between the ceramic base material 10 and the resin layer 30. As a result, bondability at the interface of each layer constituting the heat dissipation substrate 1 can be improved.

Description

Heat dissipation substrate manufacturing method and heat dissipation substrate

[0001] The technology disclosed herein relates to a method for manufacturing a heat dissipation substrate and a heat dissipation substrate. This international application claims priority to Japanese Patent Application No. 2024-53920, filed on March 28, 2024, the entire contents of which are incorporated herein by reference.

[0002] In recent years, semiconductors with high heat generation, such as SiC power semiconductors, have come to be used in response to demands for even higher performance in power devices. When using such semiconductors with high heat generation, heat countermeasures are important, and therefore substrates with high heat dissipation properties are sometimes used. This heat dissipation substrate has, for example, a laminated structure in which multiple thermally conductive members are stacked. An electrical circuit is provided on one side of the heat dissipation substrate, and a cooling device is attached to the other side of the heat dissipation substrate. This allows heat generated on the circuit side to be transferred to the cooling device side via the heat dissipation substrate. As a result, the temperature rise of the semiconductor can be suppressed.

[0003] Patent Document 1 discloses an example of a heat dissipation substrate. The heat dissipation substrate described in Patent Document 1 includes a thermally conductive substrate, an insulating layer laminated on one side of the thermally conductive substrate, and a circuit layer on the insulating layer. The thermally conductive substrate in Patent Document 1 includes a thermally conductive material such as graphite. The insulating layer also includes resin and ceramic particles. This heat dissipation substrate uses the above-mentioned materials for the thermally conductive substrate, thereby reducing the thermal expansion coefficient of the entire substrate. Furthermore, ceramic particles dispersed in the insulating layer improve the thermal conductivity of the insulating layer. Furthermore, the technology described in Patent Document 1 recommends forming an adhesive layer between the thermally conductive substrate and the insulating layer to prevent gaps from forming between the thermally conductive substrate and the insulating layer. The adhesive layer described in Patent Document 1 is a cured product of a thermosetting resin.

[0004] Japanese Patent Application Publication No. 2020-136577

[0005] Incidentally, some heat dissipation substrates are used as circuit boards. These circuit boards require high insulation properties from the viewpoint of high-speed transmission and signal propagation efficiency. In this case, the substrate of the heat dissipation substrate must be made of ceramic (e.g., alumina) with excellent insulation properties, rather than a conductive material such as graphite. This ceramic substrate has very low adhesion to resin. Therefore, when attempting to join the substrate and a metal component via a resin layer (insulating layer or adhesion layer), there is a risk of peeling at the interface between the substrate and the resin layer.

[0006] The technology disclosed herein has been made to solve such problems, and aims to provide a technology that improves the bonding strength of each layer in a heat dissipation substrate that uses a ceramic substrate as the base material.

[0007] In order to solve the above-mentioned problems, a method for manufacturing a heat dissipation substrate having the following configuration is provided.

[0008] The manufacturing method disclosed herein includes the steps of: forming a non-metallic inorganic bonding layer on the surface of a ceramic substrate by applying a first paste containing at least a first thermally conductive material and a non-metallic inorganic bonding material to the surface of the ceramic substrate and then heating the applied paste; forming a resin layer on the surface of the non-metallic inorganic bonding layer by applying a second paste containing at least a second thermally conductive material and a thermoplastic resin to the surface of the non-metallic inorganic bonding layer and then heating the applied paste; and bonding the resin layer and the metal plate by heating the resin layer while pressing the metal plate against the surface of the resin layer.

[0009] In the manufacturing method described above, a non-metallic inorganic bonding layer is interposed between the substrate (ceramic substrate) and the resin layer. This non-metallic inorganic bonding layer uses a non-metallic inorganic bonding material that has suitable bonding properties with both ceramics and resins. This improves bonding at the interface of each layer that constitutes the heat dissipation substrate after manufacture. Furthermore, in this manufacturing method, a thermally conductive material is added to each of the first paste and the second paste. This improves the thermal conductivity of the resin layer and the non-metallic inorganic bonding layer after manufacture. As a result, a heat dissipation substrate that exhibits excellent overall heat dissipation properties can be realized, despite the use of a ceramic substrate with relatively low thermal conductivity.

[0010] In one embodiment of the manufacturing method disclosed herein, the first thermally conductive material is D ５０ The non-metallic inorganic bonding layer contains at least metal particles having a particle diameter of 0.1 μm or more and 2.0 μm or less and an average aspect ratio of 1.0 or more and 1.5 or less, thereby further improving the thermal conductivity of the non-metallic inorganic bonding layer.

[0011] In one aspect of the manufacturing method disclosed herein, the content of the first thermally conductive material is 80 wt % or more and 90 wt % or less when the total mass of the first paste is 100 wt %, thereby achieving high levels of both thermal conductivity and bondability of the non-metallic inorganic bonding layer.

[0012] In one embodiment of the manufacturing method disclosed herein, the non-metallic inorganic bonding material is ceramic or glass, which can exhibit excellent bonding properties to both the ceramic substrate and the resin layer.

[0013] In one embodiment of the manufacturing method disclosed herein, the ceramic contains at least one selected from the group consisting of copper oxide, zinc oxide, lead oxide, cadmium oxide, antimony oxide, bismuth oxide, vanadium oxide, silicon oxide, and molybdenum oxide, which exhibit particularly excellent bonding properties to both the ceramic substrate and the resin layer.

[0014] In one aspect of the manufacturing method disclosed herein, the glass is SiO ２ Glass, SiO ２ -Al ２ O ３ Glass, SiO ２ -Bi ２ O ３ Glass, SiO ２ -Y ２ O ３ Glass, SiO ２ -B ２ O ３ Glass, SiO ２ -ZnO-based glass, SiO ２ -ZrO ２ The glass contains at least one selected from the group consisting of glass-based glass, which exhibits particularly excellent bonding properties to both the ceramic substrate and the resin layer.

[0015] In one embodiment of the manufacturing method disclosed herein, the second thermally conductive material is D ５０ The resin layer contains at least first particles having a particle diameter of 2 μm or more and 5 μm or less and an average aspect ratio of 3 or more. By adding these first particles, the thermal conductivity and heat resistance of the resin layer can be significantly improved.

[0016] In addition, in an embodiment in which the second thermally conductive material includes the first particles, the second thermally conductive material is ５０ It is preferable that the second thermally conductive material further contains second particles having a particle diameter of 0.01 μm or more and 1 μm or less and an average aspect ratio of less than 2. In this way, the second thermally conductive material containing both the first particles and the second particles can form a suitable thermally conductive network within the resin layer, thereby further improving the thermal conductivity of the resin layer.

[0017] In an embodiment in which the second thermally conductive material contains both the first particles and the second particles, the content of the first particles is preferably 70 wt % to 90 wt % and the content of the second particles is preferably 10 wt % to 30 wt % when the total mass of the second thermally conductive material is 100 wt %, which allows a more suitable thermally conductive network to be formed within the resin layer.

[0018] In one embodiment of the manufacturing method disclosed herein, the thermoplastic resin includes at least one selected from the group consisting of a polyimide resin, a PES resin, a silicone resin, and a polyamide resin. These thermoplastic resins exhibit particularly excellent bonding properties to both the non-metallic inorganic bonding layer and the metal plate.

[0019] Another aspect of the technology disclosed herein provides a heat dissipation substrate, which includes a ceramic substrate, a non-metallic inorganic bonding layer bonded to a surface of the ceramic substrate and having a first metal sintered body fixed thereto with a non-metallic inorganic bonding material, a resin layer bonded to the surface of the non-metallic inorganic bonding layer and having a second metal sintered body fixed thereto with a thermoplastic resin, and a metal plate bonded to the surface of the resin layer.

[0020] The heat dissipation substrate disclosed herein has a ceramic substrate and a metal plate bonded via a non-metallic inorganic bonding layer and a resin layer. A heat dissipation substrate having such a configuration can ensure sufficient adhesion at the interfaces between the ceramic substrate, the non-metallic inorganic bonding layer, the resin layer, and the metal plate. Furthermore, in this heat dissipation substrate, the non-metallic inorganic bonding layer and the resin layer contain metal sintered bodies. These sintered bodies are sintered bodies of the thermally conductive material contained in the first paste and the second paste. These sintered bodies can improve the thermal conductivity of the resin layer and the non-metallic inorganic bonding layer.

[0021] In one aspect of the manufacturing method disclosed herein, the second metal sintered body has elongated regions with an average aspect ratio of 3 or more and spherical regions with an average aspect ratio of less than 2, and the multiple elongated regions are connected via the spherical regions. As described above, the second thermally conductive material containing both the first particles and the second particles forms a suitable thermally conductive network within the resin layer. Specifically, in the resin layer after heating, a second metal sintered body (thermal conductive network) is formed that has elongated regions derived from the first particles and spherical regions derived from the second particles. In this second metal sintered body, the multiple elongated regions are connected via the spherical regions. This further improves the thermal conductivity of the resin layer.

[0022] FIG. 1 is a flowchart illustrating a manufacturing method according to this embodiment. FIG. 2 is a cross-sectional view illustrating a first bonding step in the manufacturing method according to this embodiment. FIG. 3 is a cross-sectional view illustrating a second bonding step in the manufacturing method according to this embodiment. FIG. 4 is a cross-sectional view illustrating a heat pressing step in the manufacturing method according to this embodiment. FIG. 5 is a cross-sectional view schematically illustrating an example of a heat dissipation substrate after manufacturing. FIG. 6 is a cross-sectional SEM photograph of the heat dissipation substrate of Example 1. FIG. 7 is a cross-sectional SEM photograph of the heat dissipation substrate of Example 2.

[0023] Preferred embodiments of the technology disclosed herein are described below. Matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (e.g., methods for preparing various pastes) can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Furthermore, the notation "A to B" indicating a numerical range in this specification means "greater than or equal to A and less than or equal to B," and includes values ​​greater than A and less than B.

[0024] [Method for Manufacturing Heat Dissipating Substrate] An embodiment of a method for manufacturing a heat dissipating substrate disclosed herein will now be described. FIG. 1 is a flowchart illustrating the manufacturing method according to this embodiment. FIG. 2 is a cross-sectional view illustrating a first bonding step in the manufacturing method according to this embodiment. FIG. 3 is a cross-sectional view illustrating a second bonding step in the manufacturing method according to this embodiment. FIG. 4 is a cross-sectional view illustrating a heat pressing step in the manufacturing method according to this embodiment. Also, FIG. 5 is a cross-sectional view schematically illustrating an example of a heat dissipating substrate after manufacturing.

[0025] 1, the manufacturing method according to this embodiment includes a first joining step S10, a second joining step S20, and a hot pressing step S30. Each step will be described below.

[0026] 1. First Bonding Step S10 In this step, a first paste is applied to the surface of the ceramic substrate 10 and then heated. This forms a non-metallic inorganic bonding layer 20 on the surface of the ceramic substrate 10 (see FIG. 2). The various materials used in this step and the treatments performed in this step are described below.

[0027] (1) Ceramic substrate 10 In the manufacturing method according to this embodiment, a ceramic substrate 10 with excellent insulating properties is used as the substrate for the heat dissipation substrate. This makes it possible to sufficiently ensure the high-speed transmission properties and signal propagation efficiency required for circuit boards. Conventionally known ceramics can be used for this ceramic substrate 10. Examples of ceramics used here include metal nitrides (nitride-based ceramics), metal oxides (oxide-based ceramics), as well as metal borides, fluorides, hydroxides, carbonates, phosphates, and metal carbides (carbide-based ceramics). Specific examples of nitride-based ceramics include silicon nitride (Si ３ N ４ ), aluminum nitride (AlN), etc. Specific examples of oxide ceramics include alumina (Al ２ O ３ ) etc.

[0028] (2) First Paste The first paste contains at least a first thermally conductive material and a non-metallic inorganic bonding material. The components of the first paste will be described below.

[0029] (2-a) First Thermal Conductive Material In this specification, the term "thermal conductive material" refers to a powder material containing inorganic particles (hereinafter referred to as "thermal conductive particles") with excellent thermal conductivity. The term "first thermal conductive material" refers to the thermal conductive material contained in the first paste. The thermal conductive particles here are not limited to a specific material, and can be selected without particular limitation from known inorganic materials having a certain level of thermal conductivity or higher. Examples of such inorganic materials include silver (Ag), copper (Cu), aluminum (Al), iron (Fe), nickel (Ni), palladium (Pd), and platinum (Pt). The inorganic material for the thermal conductive material may also be an alloy containing the above-mentioned metal elements (such as an Ag-Pd alloy, an Ag-Pt alloy, an Ag-Cu alloy, or a Cu-Ni alloy). The inorganic material for the thermal conductive material is not limited to the above-mentioned metal-based materials. For example, the inorganic material may be alumina (Al). ２ O ３ ), zirconia (ZrO ２ ), silica (SiO ２The thermal conductive material may be a ceramic such as aluminum nitride (AlN), boron nitride (BN), or silicon nitride (SiN), or a carbon-based material such as carbon or diamond. Among the above, silver (Ag) and copper (Cu) have particularly excellent heat resistance and thermal conductivity, making them particularly suitable for use as thermal conductive materials. The thermal conductive material may also be a mixture of multiple types of thermally conductive particles made of different inorganic materials.

[0030] D of the first thermal conductive material ５０ The particle size is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.2 μm or more, and particularly preferably 0.3 μm or more. ５０ As the particle diameter increases, the heat resistance of the first paste (non-metallic inorganic bonding layer 20 in FIG. 2) after heating improves, and the amount of shrinkage during heating tends to decrease. ５０ The upper limit of the particle size is preferably 3 μm or less, more preferably 2 μm or less, even more preferably 1.5 μm or less, and particularly preferably 1 μm or less. ５０ As the particle diameter becomes smaller, the film density of the non-metallic inorganic bonding layer 20 after heating tends to improve. ５０ The "particle diameter" refers to the cumulative 50% particle diameter based on the number in the particle size distribution of a plurality of particles (for example, 100 particles) extracted from an image of the bonding material taken using a field emission scanning electron microscope (FE-SEM).

[0031] Furthermore, the average aspect ratio of the first thermally conductive material is preferably 1.0 or more. Meanwhile, the average aspect ratio of the first thermally conductive material is preferably 2.0 or less, more preferably 1.5 or less, even more preferably 1.3 or less, and particularly preferably 1.2 or less. As the thermally conductive particles in the first thermally conductive material become shorter, the film density of the non-metallic inorganic bonding layer 20 after heating tends to improve. Note that, in this specification, "average aspect ratio" refers to the average value of the maximum dimension / minimum dimension of a plurality of particles. In other words, the average maximum dimension, average minimum dimension, and average aspect ratio here are values ​​that indicate the average shape of the particles contained in the thermally conductive material. As a specific measurement procedure, for example, a scanning electron microscope (SEM) is used to observe a predetermined number of particles contained in the paste (for example, at least 100 particles (preferably 200 to 300 particles) selected at random), and the maximum and minimum dimensions of each particle are determined. Next, the maximum dimension of each particle is divided by the minimum dimension to calculate the maximum dimension / minimum dimension (aspect ratio) of each particle. The maximum dimensions, minimum dimensions, and aspect ratios of the predetermined number of particles are then arithmetically averaged. By the above procedure, the average maximum dimension, minimum dimension, and average aspect ratio can be determined.

[0032] Furthermore, when the total mass of the first paste is 100 wt%, the content of the first thermally conductive material is preferably 65 wt% or more, more preferably 70 wt% or more, even more preferably 75 wt% or more, and particularly preferably 80 wt% or more. As the content of the first thermally conductive material increases, the thermal conductivity of the non-metallic inorganic bonding layer 20 tends to improve. On the other hand, the upper limit of the content of the first thermally conductive material is preferably 96 wt% or less, more preferably 94 wt% or less, even more preferably 92 wt% or less, and particularly preferably 90 wt% or less. By reducing the content of the first thermally conductive material, it becomes easier to ensure the content of the non-metallic inorganic bonding material. This makes it easier to improve the bonding properties of the non-metallic inorganic bonding layer 20.

[0033] (2-b) Non-metallic inorganic bonding material The non-metallic inorganic bonding material forms the non-metallic inorganic bonding layer 20 by undergoing a heat treatment. At this time, the non-metallic inorganic bonding material chemically reacts with the ceramic substrate 10 to form a complex oxide, thereby bonding the ceramic substrate 10 and the non-metallic inorganic bonding layer 20. The non-metallic inorganic bonding material can be appropriately selected from conventionally known non-metallic inorganic materials, taking into consideration the bonding properties to the components of the ceramic substrate 10 and the resin layer 30 (see FIG. 3). Examples of this non-metallic inorganic bonding material include ceramic and glass. Examples of ceramics that can be used for the non-metallic inorganic bonding material include copper oxide, zinc oxide, lead oxide, cadmium oxide, antimony oxide, bismuth oxide, vanadium oxide, silicon oxide, manganese oxide, and molybdenum oxide. Examples of glass that can be used for the non-metallic inorganic bonding material include SiO ２ Glass, SiO ２ -Al ２ O ３ Glass, SiO ２ -Bi ２ O ３ Glass, SiO ２ -Y ２ O ３ Glass, SiO ２ -B ２ O ３ Glass, SiO ２ -ZnO-based glass, SiO ２ -ZrO ２ These non-metallic inorganic bonding materials can exhibit particularly excellent bonding properties to both the ceramic substrate 10 and the resin layer 30. Note that the term "X-based glass" as used herein refers to glass containing a compound represented by X as the main component (typically containing 75 mol % or more in terms of oxide).

[0034] Next, the non-metallic inorganic bonding material D ５０The particle diameter is preferably 5 μm or less, more preferably 4 μm or less, even more preferably 3 μm or less, and particularly preferably 2 μm or less. As the non-metallic inorganic bonding material becomes smaller, the non-metallic inorganic bonding materials tend to react with each other during heat treatment, which makes it easier to form the non-metallic inorganic bonding layer 20. On the other hand, if the non-metallic inorganic bonding material becomes too small, aggregation of inorganic particles (first thermal conductive material, non-metallic inorganic bonding material) occurs in the first paste, which tends to increase the paste viscosity. From this perspective, the D of the non-metallic inorganic bonding material ５０ The particle size is preferably 0.001 μm or more, more preferably 0.005 μm or more, even more preferably 0.01 μm or more, and particularly preferably 0.02 μm or more. ５０ The particle diameter is D of the first thermal conductive material. ５０ It is preferable that the particle size is smaller than the particle size, thereby making it possible to form a non-metallic inorganic bonding layer 20 with even better adhesion to the ceramic substrate 10.

[0035] The shape of the nonmetallic inorganic bonding material is not particularly limited. That is, the average aspect ratio of the nonmetallic inorganic bonding material may be 1.0 or more. On the other hand, the average aspect ratio of the nonmetallic inorganic bonding material may be 5 or less, 4 or less, 3 or less, or 2 or less. As the nonmetallic inorganic bonding material approaches a spherical shape, the nonmetallic inorganic bonding material tends to be more easily dispersed in the first paste.

[0036] Furthermore, when the total mass of the first paste is 100 wt%, the content of the non-metallic inorganic bonding material is preferably 0.01 wt% or more, more preferably 0.05 wt% or more, even more preferably 0.1 wt% or more, and particularly preferably 0.2 wt% or more. As the content of the non-metallic inorganic bonding material increases, the bonding strength of the non-metallic inorganic bonding layer 20 tends to improve. Meanwhile, the upper limit of the content of the non-metallic inorganic bonding material is preferably 10 wt% or less, more preferably 6 wt% or less, even more preferably 4 wt% or less, and particularly preferably 2 wt% or less. Reducing the content of the non-metallic inorganic bonding material makes it easier to ensure the content of the first thermally conductive material. As a result, the thermal conductivity of the non-metallic inorganic bonding layer 20 is more easily improved.

[0037] (2-c) Organic Solvent The first paste in this embodiment contains an organic solvent. Any conventionally known organic solvent can be used as this organic solvent without any particular restrictions. It is preferable to select an organic solvent for the first paste that can suitably disperse the first thermally conductive material and the non-metallic inorganic bonding material and that evaporates easily during heat treatment. Examples of such organic solvents include alcohol-based solvents such as terpineol, texanol, dihydroterpineol, and benzyl alcohol; glycol-based solvents such as ethylene glycol and diethylene glycol; glycol ether-based solvents such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and triethylene glycol dimethyl ether; ester-based solvents such as isobornyl acetate, ethyl diglycol acetate, butyl glycol acetate, butyl diglycol acetate, butyl cellosolve acetate, butyl carbitol acetate (diethylene glycol monobutyl ether acetate), γ-butyrolactone, methyl benzoate, and propylene carbonate; hydrocarbon-based solvents such as toluene and xylene; aprotic polar solvents such as N-methylpyrrolidone (NMP), and mineral spirits. The first paste may contain two or more of the above-mentioned organic solvents.

[0038] Furthermore, when the total mass of the first paste is 100 wt%, the content of the organic solvent is preferably 1 wt% or more, more preferably 2 wt% or more, even more preferably 3 wt% or more, and particularly preferably 5 wt% or more. As the content of the organic solvent increases, the preparation of the first paste becomes easier, which contributes to improving productivity. On the other hand, the upper limit of the content of the organic solvent is preferably 20 wt% or less, more preferably 18 wt% or less, even more preferably 16 wt% or less, and particularly preferably 15 wt% or less. As the content of the organic solvent decreases, a first paste that is more easily adhered to the ceramic substrate 10 can be obtained.

[0039] (2-d) Other Components The first paste may contain any of the conventional additives known to be used in bonding pastes of this type, without particular limitation, as long as they do not significantly impair the effect of the technology disclosed herein (improved bonding properties). For example, the first paste may contain binders, dispersants, thickeners, plasticizers, defoamers, antioxidants, preservatives, colorants (pigments, dyes, etc.), etc.

[0040] For example, it is preferable that the first paste contains a binder. This can improve the adhesion of the first paste to the ceramic substrate 10. This binder can be any conventionally known resin component used to increase the viscosity of a paste, without any particular restrictions. Specific examples of this binder include cellulose-based polymers, acrylic resins, epoxy resins, phenolic resins, alkyd resins, polyvinyl alcohol, and rosin resins. Among these, cellulose-based polymers such as ethyl cellulose are particularly suitable as binders for the first paste because they have excellent combustion decomposition properties when heated.

[0041] Furthermore, when the total mass of the first paste is 100 wt%, the binder content is preferably 0.1 wt% or more, more preferably 0.5 wt% or more, even more preferably 1 wt% or more, and particularly preferably 2 wt% or more. As the binder content increases, adhesion to the ceramic substrate 10 tends to improve. On the other hand, the upper limit of the binder content is preferably 10 wt% or less, more preferably 8 wt% or less, even more preferably 6 wt% or less, and particularly preferably 5 wt% or less. By reducing the binder content, it becomes easier to ensure the contents of other components. As a result, it becomes easier to improve the thermal conductivity and bonding properties of the non-metallic inorganic bonding layer 20.

[0042] (3) Processing Procedure Next, the processing procedure of the first bonding step S10 will be specifically described. As described above, in the first bonding step S10, the first paste is applied to the surface of the ceramic substrate 10 and then heated.

[0043] (3-a) Coating Treatment In this step, the first paste described above is first coated on the upper surface 10b of the ceramic substrate 10. The means for coating the first paste is not particularly limited, and any conventionally known method can be used without particular limitation. Examples of such coating methods include various printing methods such as screen printing, gravure printing, offset printing, and inkjet printing, as well as doctor blade and spray methods. The area where the first paste is coated may be the entire upper surface 10b of the ceramic substrate 10, or a portion of the upper surface 10b of the ceramic substrate 10.

[0044] In this process, it is preferable to adjust the amount of the first paste applied so that the non-metallic inorganic bonding layer 20 has a predetermined thickness after heating. Specifically, the amount of the first paste applied is adjusted so that the film thickness of the non-metallic inorganic bonding layer 20 after heating is 1 μm or more. The film thickness of the non-metallic inorganic bonding layer 20 after heating may be 2 μm or more, preferably 4 μm or more, more preferably 5 μm or more, even more preferably 6 μm or more, and particularly preferably 8 μm or more. As the film thickness of the non-metallic inorganic bonding layer 20 increases, adhesion to the ceramic substrate 10 tends to further improve. The upper limit of the film thickness of the non-metallic inorganic bonding layer 20 after heating is not particularly limited and may be 500 μm or less, 250 μm or less, 100 μm or less, 50 μm or less, or 25 μm or less.

[0045] (3-b) Heat Treatment Next, the first paste applied to the ceramic substrate 10 is heated under predetermined conditions. This removes the organic solvent, binder, and the like. Furthermore, the non-metallic inorganic bonding material reacts with the first thermally conductive material and the ceramic substrate 10 to produce a complex oxide. The non-metallic inorganic bonding material then solidifies as the temperature decreases after the heat treatment. This forms a non-metallic inorganic bonding layer 20 on the surface of the ceramic substrate 10. As will be described in detail later, this non-metallic inorganic bonding layer 20 is a layer in which a first metal sintered body (a sintered body of the first thermally conductive material) is fixed with the non-metallic inorganic bonding material.

[0046] The heating temperature in this step is set to a temperature appropriate for the nonmetallic inorganic bonding material. That is, the heating temperature is not limited to a specific temperature and can be appropriately changed depending on the reaction temperature between the nonmetallic inorganic bonding material and the ceramic substrate 10. Specifically, when the reaction temperature of the nonmetallic inorganic bonding material is X°C, the heating temperature in the first bonding step S10 is preferably set to X±10°C (more preferably X±5°C). This allows the nonmetallic inorganic bonding material, the first thermally conductive material, and the ceramic substrate 10 to react with each other to appropriately generate a complex oxide. As a result, the ceramic substrate 10 and the nonmetallic inorganic bonding layer 20 are firmly bonded together. For example, when copper oxide is used as the nonmetallic inorganic bonding material, the heating temperature is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 700°C or higher, and particularly preferably 800°C or higher. On the other hand, the upper limit of the heating temperature in the first bonding step S10 is preferably 1200°C or less, more preferably 1100°C or less, even more preferably 1000°C or less, and particularly preferably 900°C or less. This can prevent the metal-inorganic bonding material from flowing out due to excessive heating. The heating time (the time during which the maximum temperature is maintained) is preferably 5 to 20 minutes (preferably 8 to 14 minutes).

[0047] 2. Second Bonding Step S20 Next, in the second bonding step S20, a second paste is applied to the surface of the non-metallic inorganic bonding layer 20 and then heated. As a result, as shown in Fig. 3, a resin layer 30 can be formed on the surface of the non-metallic inorganic bonding layer 20. The second paste used in this step and each treatment performed in this step will be described below.

[0048] (1) Second Paste As described above, the second bonding step S20 uses a second paste containing at least a second thermally conductive material and a thermoplastic resin. The components of the second paste will be described below.

[0049] (1-a) Second Thermal Conductive Material In this specification, the term "second thermal conductive material" refers to the thermal conductive material contained in the second paste. Like the first thermal conductive material described above, this second thermal conductive material can be selected without particular limitation from known thermal conductive materials having a certain level of heat resistance and thermal conductivity. A detailed description of this thermal conductive material will be omitted to avoid redundancy. Furthermore, the thermal conductive material of the first thermal conductive material and the thermal conductive material of the second thermal conductive material may be the same or different. However, using the same thermal conductive material for the first and second thermal conductive materials tends to improve the bonding at the interface between the non-metallic inorganic bonding layer 20 and the resin layer 30.

[0050] The second thermal conductive material has an aspect ratio and D ５０ It is preferable that the resin layer 30 contains a plurality of thermally conductive particles with different particle sizes, which can greatly improve the thermal conductivity of the resin layer 30. This will be described in detail below.

[0051] (First particle) First, the second thermal conductive material is D ５０ It is preferable to contain first particles having a particle diameter of 2 μm or more and 5 μm or less and an average aspect ratio of 3 or more. This significantly improves the heat resistance and thermal conductivity of the resin layer 30. Specifically, if the thermally conductive particles are spaced apart within the resin layer 30, heat applied to the resin layer 30 is more likely to pass through the thermoplastic resin. Because the thermoplastic resin described below is a resin material with low thermal conductivity, the thermal conductivity of the resin layer 30 may be reduced. In contrast, the use of non-spherical particles (first particles) having a particle diameter greater than a certain level and a high aspect ratio facilitates the formation of a thermally conductive network within the resin layer 30 in which multiple thermally conductive particles are connected to one another. As a result, thermal conduction via the thermally conductive particles is promoted, thereby improving the thermal conductivity of the resin layer 30.

[0052] The average aspect ratio of the first particles is preferably 3.2 or more, more preferably 3.5 or more, even more preferably 3.7 or more, and particularly preferably 4 or more. This allows for the formation of a more suitable thermally conductive network. On the other hand, the upper limit of the average aspect ratio of the first particles is not particularly limited, and may be 10 or less, 8.5 or less, 8 or less, 7 or less, 6 or less, or 5.5 or less. Furthermore, the first particles may have any of the above-mentioned average aspect ratios, and the specific shape is not particularly limited. Specific examples of the shape of the first particles include flakes (scales), needles, rods, plates, and ellipsoids.

[0053] Also, D of the first particle ５０ The particle diameter is preferably 4.9 μm or less, more preferably 4.8 μm or less, even more preferably 4.7 μm or less, and particularly preferably 4.6 μm or less. ５０ The lower limit of the particle diameter is not particularly limited from the viewpoint of improving thermal conductivity. ５０ If the particle diameter is too small, the first particles tend to aggregate with each other. In this case, it is difficult to form an appropriate heat conduction network. From this viewpoint, the D ５０ The lower limit of the particle size is set to 2 μm or more (preferably 2.3 μm or more, more preferably 2.5 μm or more, and particularly preferably 2.8 μm or more).

[0054] (Second Particles) When the first particles are added to the second thermally conductive material, it is preferable to add second particles having the following structure. ５０The second particles are spherical particles with a particle diameter of 0.01 μm or more and 1 μm or less and an average aspect ratio of less than 2. This further improves the thermal conductivity of the resin layer 30. Specifically, the second particles are smaller spherical particles than the first particles. When these first particles and second particles are mixed, a complex thermal conduction network is formed in which large non-spherical particles are connected via the small spherical particles. This further improves the thermal conductivity of the resin layer 30. Furthermore, when the position of the thermally conductive particles within the resin layer 30 becomes more complex, the thermoplastic resin and the thermally conductive particles are firmly bonded together due to an anchor effect. This also contributes to improving the bonding strength of the resin layer 30.

[0055] The average aspect ratio of the second particles is preferably 1.8 or less, more preferably 1.5 or less, and particularly preferably 1.3 or less. This allows for the formation of a more suitable heat conduction network. Meanwhile, the lower limit of the average aspect ratio of the second particles is 1 or more (i.e., a perfect sphere).

[0056] Also, D of the second particle ５０ The particle diameter is preferably 0.9 μm or less, and particularly preferably 0.8 μm or less. This allows the second particles to easily enter the gaps between the first particles, making it easier to form a suitable heat conduction network inside the resin layer 30. On the other hand, the D of the second particles ５０ If the particle diameter is too small, the second particles aggregate, making it difficult for the second particles to enter the gaps between the first particles. ５０ The particle size is set to 0.01 μm or more (preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.15 μm or more, and particularly preferably 0.2 μm or more).

[0057] In addition, the surfaces of the second particles are preferably coated with an organic protective layer. This can suppress aggregation of the second particles. It has also been confirmed that when an organic protective layer is formed on the surface of microparticles of 1 μm or less, the second particles are sintered by heating at a temperature lower than the melting point of the second particles. This allows the first particles to be sintered via the second particles even at low temperatures that do not burn off the thermoplastic resin. While not limiting the technology disclosed herein, this phenomenon is presumed to be due to the decomposition of the organic protective layer during heating and the reduction of the surfaces of the second particles. The components of the organic protective layer are not particularly limited, and conventionally known organic components used to protect this type of inorganic particles can be used without particular limitation.

[0058] When the second thermally conductive material contains both the first particles and the second particles, it is preferable that the content of the first particles be 70 wt% to 90 wt% (preferably 75 wt% to 85 wt%) and the content of the second particles be 10 wt% to 30 wt% (preferably 15 wt% to 25 wt%). This allows the first particles and the second particles to be mixed in an appropriate balance, thereby forming a more optimal thermally conductive network within the resin layer 30.

[0059] (Other Thermally Conductive Particles) The second thermally conductive material may contain thermally conductive particles other than the first particles and the second particles. Examples of the other thermally conductive particles include third particles, which are spherical particles larger than the second particles, fourth particles, which are non-spherical particles smaller than the first particles, and fifth particles, which have an aspect ratio intermediate between the first and second particles. Specifically, the third particles may be D ５０ The fourth particle refers to a thermally conductive particle having a particle diameter of more than 1 μm and an average aspect ratio of less than 2. ５０The first and second particles refer to thermally conductive particles having a particle diameter of less than 2 μm and an average aspect ratio of 3 or greater. The fifth particles refer to thermally conductive particles having an average aspect ratio of 2 or greater but less than 3. Even when these thermally conductive particles are included, a resin layer 30 with favorable performance can be formed. However, from the viewpoint of forming a thermally conductive network with the first and second particles, the content of the other thermally conductive particles is preferably 20 wt % or less, more preferably 10 wt % or less, even more preferably 5 wt % or less, and particularly preferably 1 wt % or less. From the viewpoint of forming a more favorable thermally conductive network, it is preferable that the thermally conductive material does not contain any thermally conductive particles other than the first and second particles (the content of other thermally conductive particles is 0 wt %).

[0060] (1-b) Thermoplastic Resin The thermoplastic resin is softened and solidified through a heat treatment to form the resin layer 30. The thermoplastic resin can be appropriately selected from conventionally known thermoplastic resins, taking into consideration the bonding strength between the non-metallic inorganic bonding layer 20 and the metal plate 40 (see FIG. 4). If the glass transition point of the thermoplastic resin is too low, the bonding layer 40 may soften due to temperature increases during use of the electronic component. Therefore, the glass transition point of the thermoplastic resin is set to 150°C or higher (preferably 170°C or higher, more preferably 180°C or higher, even more preferably 190°C or higher, and particularly preferably 200°C or higher). On the other hand, a thermoplastic resin with a too high glass transition point is difficult to sufficiently soften through the heat treatment described below, which may result in a decrease in the bonding strength of the resin layer 30. Therefore, the glass transition point of the thermoplastic resin is set to 300°C or lower (preferably 290°C or lower, more preferably 280°C or lower).

[0061] The thermoplastic resin is not particularly limited as long as its glass transition point is within an appropriate range, and conventionally known thermoplastic resins can be used without any particular limitation. Specific examples of thermoplastic resins include polyimide resin, PES resin, silicone resin, and polyamide resin. By using these thermoplastic resins, a resin layer 30 with excellent bonding properties can be easily formed. Furthermore, from the perspective of the performance of the resin layer 30, the weight-average molecular weight of the thermoplastic resin is not particularly limited. However, the viscosity of the second paste tends to increase as the weight-average molecular weight of the thermoplastic resin increases. For this reason, the weight-average molecular weight of the thermoplastic resin is preferably 5,000 or more, more preferably 10,000 or more, and particularly preferably 20,000 or more. This allows for a second paste that is easily adhered to the interface of the non-metallic inorganic bonding layer 20 to be obtained. On the other hand, the weight-average molecular weight of the thermoplastic resin is preferably 500,000 or less, more preferably 300,000 or less, even more preferably 200,000 or less, and particularly preferably 100,000 or less. This allows for a second paste that is easily applied to the non-metallic inorganic bonding layer 20 to be obtained.

[0062] Furthermore, when the total mass of the second paste is 100 wt%, the content of the thermoplastic resin is preferably 1 wt% or more, more preferably 2.5 wt% or more, and particularly preferably 5 wt% or more. As the content of the thermoplastic resin increases, the bonding strength of the resin layer 30 tends to improve. On the other hand, the upper limit of the content of the thermoplastic resin is preferably 20 wt% or less, more preferably 15 wt% or less, and particularly preferably 10 wt% or less. By reducing the content of the thermoplastic resin, it becomes easier to ensure the content of the second thermally conductive material. As a result, it becomes easier to improve the thermal conductivity of the resin layer 30.

[0063] (1-c) Organic Solvent The second paste in this embodiment also contains an organic solvent. As with the first paste, the second paste can also use any conventionally known organic solvent without any particular restrictions. A detailed description of this organic solvent will be omitted to avoid redundancy. The organic solvents for the first paste and the second paste may be the same or different. It is preferable that the organic solvent for the second paste be one that can appropriately form a paste from a mixture containing a thermoplastic resin. From this perspective, an ester-based solvent such as γ-butyrolactone is particularly preferable as the organic solvent for the second paste. The content of the organic solvent in the second paste is also not particularly limited. For example, when the entire second paste is 100% by mass, the content of the organic solvent may be 1% by mass to 70% by mass, 5% by mass to 60% by mass, or 10% by mass to 50% by mass. However, the content of the organic solvent is not limited to the above range and may be appropriately adjusted to achieve a viscosity that facilitates application to the surface of the non-metallic inorganic bonding layer 20.

[0064] (1-d) Other Components As with the first paste, the second paste can also use conventionally known additives without particular limitations, as long as they do not significantly impair the effect of the technology disclosed herein (improvement of bondability). Details of such additives have already been described, so duplicated descriptions will be omitted.

[0065] (2) Processing Procedure Next, the processing procedure of the second bonding step S20 will be specifically described. As described above, in the second bonding step S20, the second paste is applied to the surface of the non-metallic inorganic bonding layer 20 and then heated.

[0066] (2-a) Coating Method As in the first bonding step S10, the second bonding step S20 can employ any conventional coating method (such as screen printing) without any particular restrictions. The coating area of ​​the second paste may be the entire upper surface 20b of the non-metallic inorganic bonding layer 20, or may be a part of the upper surface 10b of the non-metallic inorganic bonding layer 20.

[0067] In this process, it is preferable to adjust the amount of the second paste applied so that the resin layer 30 after production has a predetermined thickness. The amount of the second paste applied is preferably adjusted so that the thickness of the resin layer 30 after heating is 5 μm or more (more preferably 20 μm or more, and particularly preferably 30 μm or more). A resin layer 30 with a sufficient thickness can function as a buffer layer between the metal plate 40 and the ceramic substrate 10. On the other hand, the upper limit of the thickness of the resin layer 30 is not particularly limited and may be 500 μm or less, 250 μm or less, or 100 μm or less.

[0068] (2-b) Heating Conditions Next, the second paste applied to the non-metallic inorganic bonding layer 20 is heated under predetermined conditions. This removes the organic solvent and solidifies the second paste. This forms a resin layer 30 on the surface of the non-metallic inorganic bonding layer 20. As will be described in detail later, this resin layer 30 is a layer in which a second metal sintered body (a sintered body of a second thermally conductive material) is fixed with a thermoplastic resin. Then, when the second bonding step S20 is performed, a laminate 50 is produced in which the ceramic substrate 10, the non-metallic inorganic bonding layer 20, and the resin layer 30 are laminated in this order.

[0069] The heating temperature in this step is set to a temperature depending on the type of organic solvent. That is, the heating temperature in the second bonding step S20 is not limited to a specific temperature and can be changed appropriately depending on the type of organic solvent. For example, the heating temperature in the second bonding step S20 is preferably 50°C or higher, more preferably 100°C or higher, and particularly preferably 130°C or higher. This allows the resin layer 30 to be properly formed. On the other hand, the upper limit of the heating temperature in the second bonding step S20 is preferably 200°C or lower, more preferably 180°C or lower. This allows the outflow of the thermoplastic resin due to excessive heating to be suppressed. Furthermore, the heating time (the time during which the maximum temperature is maintained) in the second bonding step S20 is preferably 10 to 60 minutes.

[0070] 4 , in this step, the metal plate 40 is heated while being pressed against the surface 30a of the resin layer 30. This bonds the interfaces between the non-metallic inorganic bonding layer 20, the resin layer 30, and the metal plate 40. As a result, a heat dissipation substrate 1 (see FIG. 5 ) can be manufactured in which the ceramic base material 10 and the metal plate 40 are bonded via the non-metallic inorganic bonding layer 20 and the resin layer 30.

[0071] Specifically, as shown in FIG. 4 , this process uses a press equipped with a lower press plate PD and an upper press plate PU. The laminate 50 produced in the second joining process S20 is placed on the lower press plate PD. The orientation of the laminate 50 is adjusted so that the lower surface of the laminate 50 (the lower surface 10a of the ceramic substrate 10) is in contact with the lower press plate PD. Next, a metal plate 40 is placed on the upper surface of the laminate 50 (the upper surface 30b of the resin layer 30). In this state, the upper press plate PU is lowered to contact the upper surface 40b of the metal plate 40. This sandwiches the laminate 50 and the metal plate 40 between the lower press plate PD and the upper press plate PU. The laminate 50 and the metal plate 40 are then heated while applying pressure along the stacking direction of the laminate 50. This softens the thermoplastic resin in the resin layer 30. The softened resin layer 30 is then pressed against the lower surface 40a of the metal plate 40 by the pressure from the press. When the heating is stopped in this state and the temperature of the resin layer 30 is lowered, the upper surface 30b of the resin layer 30 and the lower surface 40a of the metal plate 40 are firmly bonded together. The softened resin layer 30 is also pressed against the upper surface 20b of the non-metallic inorganic bonding layer 20. This further improves the bonding strength at the interface between the lower surface 30a of the resin layer 30 and the lower surface 20b of the non-metallic inorganic bonding layer 20. This produces a heat dissipation substrate 1 in which the ceramic base material 10, the non-metallic inorganic bonding layer 20, the resin layer 30, and the metal plate 40 are laminated in this order (see FIG. 5 ).

[0072] The heating temperature in the heat-pressing step S30 is preferably set to a temperature taking into consideration the glass transition temperature Y of the thermoplastic resin of the resin layer 30. For example, when a polyimide resin is used as the thermoplastic resin, the heating temperature in the heat-pressing step S30 is preferably 200°C or higher, and more preferably 250°C or higher. This allows the layers to be more firmly bonded. On the other hand, the upper limit of the heating temperature in the heat-pressing step S30 is preferably 500°C or lower, more preferably 400°C or lower, and particularly preferably 300°C or lower.

[0073] Furthermore, the heating time in the heat pressing step S30 is preferably 15 minutes or more, more preferably 20 minutes or more, and particularly preferably 30 minutes or more. This prevents a decrease in bonding strength due to insufficient softening of the thermoplastic resin. Furthermore, in this heat pressing step S30, the layers can be sufficiently bonded even if the heating time is set to 120 minutes or less (preferably 90 minutes or less, more preferably 60 minutes or less). By achieving such a short bonding process, environmental impact and manufacturing costs can be significantly reduced.

[0074] In the hot pressing step S30, it is preferable to adjust the pressure conditions so that the surface pressure on the laminate 50 and the metal plate 40 is 5 MPa or more (particularly preferably 15 MPa or more). This prevents gaps from forming at the interfaces of the layers, thereby further improving the bonding strength at the interfaces of the layers. On the other hand, the upper limit of the surface pressure in the hot pressing step S30 may be 200 MPa or less, 150 MPa or less, 100 MPa or less, or 50 MPa or less.

[0075] The foregoing describes one embodiment of the method for manufacturing a heat dissipating substrate disclosed herein. In this manufacturing method, a non-metallic inorganic bonding layer 20 is formed on the surface of a ceramic substrate 10, and then a resin layer 30 is formed on the surface of the non-metallic inorganic bonding layer 20. Then, a metal plate 40 is pressed against the surface of the resin layer 30 while being heated. This bonds the interfaces between the ceramic substrate 10, the non-metallic inorganic bonding layer 20, and the resin layer 30, and the metal plate 40. In this manufacturing method, the non-metallic inorganic bonding layer 20 is interposed between the ceramic substrate 10 and the resin layer 30. This non-metallic inorganic bonding layer 20 exhibits favorable bonding properties to both the ceramic substrate 10 and the resin layer 30. As a result, bonding properties at the interfaces of the layers constituting the heat dissipating substrate 1 can be improved. Furthermore, in this manufacturing method, a thermally conductive material is added to the material (first paste) for the non-metallic inorganic bonding layer 20 and the material (second paste) for the resin layer 30. This improves the thermal conductivity of the resin layer 30 and the non-metallic inorganic bonding layer 20 after manufacturing. As a result, it is possible to realize a heat dissipation substrate 1 that exhibits excellent heat dissipation properties as a whole, despite the use of a ceramic base material 10 with a relatively low thermal conductivity.

[0076] [Heat Dissipating Substrate] Next, a description will be given of the manufactured heat dissipating substrate 1. As shown in Fig. 5 , the heat dissipating substrate 1 according to this embodiment has a ceramic base 10 and a metal plate 40 bonded to each other via a non-metallic inorganic bonding layer 20 and a resin layer 30.

[0077] (1) Ceramic Substrate The heat dissipation substrate 1 according to this embodiment uses a ceramic substrate 10. Details of this ceramic substrate 10 have already been described, so a duplicated description will be omitted. The ceramic substrate 10 has excellent insulating properties, and therefore, unlike conductive substrates, can be suitably used for circuit boards that require high-speed transmission and efficient signal propagation.

[0078] (2) Non-metallic Inorganic Bonding Layer The non-metallic inorganic bonding layer 20 is a layer formed by solidifying the first paste. This non-metallic inorganic bonding layer 20 is bonded to the surface of the ceramic substrate 10. The non-metallic inorganic bonding layer 20 is a layer in which a first metal sintered body is fixed with a non-metallic inorganic bonding material. Because the non-metallic inorganic bonding layer 20 uses a non-metallic inorganic bonding material (ceramic, glass, etc.) as a bonding component, it exhibits favorable bonding properties to the ceramic substrate 10. The non-metallic inorganic bonding layer 20 also contains a first metal sintered body formed by sintering the first thermally conductive material of the first paste. This allows the non-metallic inorganic bonding layer 20 to exhibit excellent thermal conductivity. The non-metallic inorganic bonding material is solidified while filling the gaps in the first metal sintered body. As a result, the non-metallic inorganic bonding layer 20 is a dense layer in which the first metal sintered body is fixed with the non-metallic inorganic bonding material (see FIG. 6 ). Such a dense layer exhibits particularly excellent thermal conductivity.

[0079] (3) Resin Layer The resin layer 30 is bonded to the surface of the non-metallic inorganic bonding layer 20. The resin layer 30 is a layer in which a second metal sintered body is fixed with a thermoplastic resin. Because the resin layer 30 uses a thermoplastic resin as a bonding component, it exhibits favorable bonding properties between the non-metallic inorganic bonding layer 20 and the metal plate 40. The resin layer 30 also contains a second metal sintered body formed by sintering the second thermally conductive material of the second paste. This allows the resin layer 30 to exhibit excellent thermal conductivity despite being a layer of solidified thermoplastic resin. The thermoplastic resin adheres to the periphery of the second metal sintered body. The thermoplastic resin bonds the interfaces between the second metal sintered bodies, the interface between the second metal sintered body and the non-metallic inorganic bonding layer 20, and the interface between the second metal sintered body and the metal plate 40. As a result, the resin layer 30 is a more porous layer than the non-metallic inorganic bonding layer 20 (see FIG. 6 ).

[0080] When a second thermally conductive material containing two types of thermally conductive particles (first particles and second particles) is used in the second paste, a thermally conductive network is formed in the manufactured resin layer 30, in which multiple large elongated particles (first particles) are connected via small spherical particles (second particles). This further improves the thermal conductivity of the resin layer 30. Specifically, when the second thermally conductive material containing the first particles and the second particles is sintered, a second metal sintered body having elongated regions and spherical regions is formed. The elongated regions are regions derived from the first particles and have an average aspect ratio of 3 or more. Meanwhile, the spherical regions are regions derived from the second particles and have an average aspect ratio of less than 2. The multiple elongated regions of this second metal sintered body are connected via the spherical regions. This results in the formation of a network-like second metal sintered body with excellent thermal conductivity within the resin layer 30, significantly improving the thermal conductivity of the resin layer 30.

[0081] (4) Metal Plate The metal plate 40 is a plate-shaped member bonded to the surface of the resin layer 30. Specific examples of such metal materials include copper (Cu), aluminum (Al), silver (Ag), platinum (Pt), and palladium (Pd). The metal plate 40 can be used as either a circuit component or a heat dissipation component of a heat dissipation substrate. For example, when the ceramic substrate 10 is used as a circuit component, an electronic circuit is formed on the upper surface of the ceramic substrate 10. When the laminate 50 is used as a heat dissipation component, a semiconductor with a high heat generation rate, such as a SiC power semiconductor, is attached to the upper surface of the metal plate 40, and a cooling device, such as a heat sink, is attached to the lower surface of the ceramic substrate 10. The heat dissipation substrate 1 according to this embodiment has excellent thermal conductivity due to the excellent thermal conductivity of the bonding layer between the non-metallic inorganic bonding layer 20 and the resin layer 30. The metal plate 40 can be made of a conventionally known metal material with excellent thermal conductivity.

[0082] [Other Embodiments] One embodiment of the technology disclosed herein has been described above. However, the technology disclosed herein is not limited to the above-described embodiment. The technology disclosed herein encompasses various modifications and variations of the above-described embodiment.

[0083] For example, the heat dissipation substrate 1 according to the above embodiment has a structure in which the non-metallic inorganic bonding layer 20, the resin layer 30, and the metal plate 40 are laminated on only one surface (upper surface 10b) of the ceramic base material 10. However, the technology disclosed herein is not limited to the above embodiment. That is, the heat dissipation substrate disclosed herein may have the non-metallic inorganic bonding layer, the resin layer, and the metal plate laminated on both surfaces of the ceramic base material.

[0084] However, the technology disclosed herein makes it possible to realize a heat dissipation substrate in which a metal plate is bonded to only one side of a ceramic substrate, which was previously difficult. Specifically, in a heat dissipation substrate using a ceramic substrate, the difference in thermal expansion coefficient between the metal plate and the substrate is very large. Therefore, if a metal plate is bonded to only one side of a ceramic substrate, the amount of volume change upon heating will be significantly different between the upper and lower sides of the substrate, potentially resulting in warping of the heat dissipation substrate. In contrast, the technology disclosed herein includes a flexible resin layer containing a thermoplastic resin between the ceramic substrate and the metal plate. This resin layer can reduce stress between the metal plate and the ceramic substrate, thereby minimizing the curvature of the heat dissipation substrate even when a metal plate is bonded to only one side of the ceramic substrate. In other words, the technology disclosed herein is particularly suitable for applications in which a non-metallic inorganic bonding layer, a resin layer, and a metal plate need to be laminated on only one side of the ceramic substrate.

[0085] [Test Examples] Test examples relating to the technology disclosed herein will be described below. Note that the following description is not intended to limit the technology disclosed herein to the content shown in the test examples.

[0086] 1. Sample Preparation (1) Example 1 In this sample, first, a non-metallic inorganic bonding layer was formed on the surface of a ceramic substrate. In this test, an alumina substrate (thickness: 0.3 mm) was prepared as the ceramic substrate. In addition, a paste obtained by mixing a first thermally conductive material, a non-metallic inorganic bonding material, a binder, and an organic solvent was used as the first paste for forming the non-metallic inorganic bonding layer. In addition, silver (D ５０The ceramic substrate was then coated with the first paste (particle diameter: 0.5 μm, aspect ratio: 1.0). The non-metallic inorganic bonding material was copper oxide. Ethyl cellulose was used as the binder. Diethylene glycol monobutyl ether was used as the organic solvent. The mixing ratio of the first thermal conductive material, the non-metallic inorganic bonding material, the binder, and the organic solvent was set to 85:0.5:1.5:13. The first paste was then applied to the surface of the ceramic substrate by screen printing so that the thickness of the non-metallic inorganic bonding layer after heating would be 7 μm. A heat treatment was then performed at 850°C for 10 minutes to form a non-metallic inorganic bonding layer.

[0087] Next, a resin layer was formed on the surface of the non-metallic inorganic bonding layer member. To form this resin layer, a second paste was used, which was a mixture of a second thermal conductive material, a thermoplastic resin, and an organic solvent. The second thermal conductive material was a mixed powder made by mixing first particles, which were large non-spherical particles, and second particles, which were small spherical particles. The first particles here were D ５０ The second particles are flake-shaped Ag particles (average aspect ratio: 5.5) having a particle diameter of 2.8 μm. ５０ The particles were spherical Ag particles with a particle diameter of 0.2 μm (average aspect ratio: 1.4). The mixing ratio of the first particles to the second particles was set to 90:10. Next, polyester resin (glass transition point: 70°C) was used as the thermoplastic resin. γ-butyrolactone was used as the organic solvent. The mixing ratio of the second thermal conductive material, thermoplastic resin, and organic solvent was set to 72:8:20. Next, the second paste was applied to the surface of the non-metallic inorganic bonding layer by screen printing so that the thickness of the resin layer after heating would be 20 μm. Then, a resin layer was formed by performing a heat treatment at 130°C for 15 minutes.

[0088] Next, a metal plate (copper plate) was placed on the non-metallic inorganic bonding layer, and a heat treatment was performed using a high-precision hot press (manufactured by Tester Sangyo Co., Ltd.) while applying a surface pressure of 30 MPa. The heating conditions were set to 280°C for 15 minutes. In this way, a test piece was produced in which the alumina plate and the copper plate were bonded via the non-metallic inorganic bonding layer and the resin layer.

[0089] (2) Example 2 In Example 2, a test piece in which an alumina plate and a copper plate were joined was produced according to the same procedure as in Example 1, except that the non-metallic inorganic joining layer was not formed using the first paste. That is, in Example 2, a test piece in which an alumina plate, a resin layer, and a copper plate were laminated in this order was produced.

[0090] 2. Evaluation Test In this test, the cross sections of the test pieces of Example 1 and Example 2 were observed with an electron microscope. Note that in this test, a field emission scanning electron microscope (model: JCM-7000) manufactured by JEOL Ltd. was used. An SEM photograph (magnification: 2000 times) of Example 1 is shown in FIG. 6, and an SEM photograph (magnification: 3000 times) of Example 2 is shown in FIG. 7.

[0091] As shown in Figure 7, in the heat dissipation substrate of Example 2, gaps were formed at a portion of the interface between the ceramic substrate and the resin layer. When an attempt was made to peel the heat dissipation substrate of Example 2 along the stacking direction, delamination occurred with the resin layer adhering to the copper plate. On the other hand, as shown in Figure 6, in the heat dissipation substrate of Example 1, almost no gaps were formed at the interfaces between the ceramic substrate, the non-metallic inorganic bonding layer, the resin layer, and the copper plate. Furthermore, the layers were in close contact with each other, and no delamination occurred even when attempting to peel the substrate along the stacking direction. From these points, it was found that when a ceramic substrate is used, the bonding strength of each layer can be significantly improved by interposing a non-metallic inorganic bonding layer between the resin layer and the ceramic substrate.

[0092] The technology disclosed herein has been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. In other words, the technology disclosed herein encompasses the aspects described in items 1 to 12 below.

[0093] <Item 1> A method for manufacturing a heat dissipation substrate, comprising: a step of applying a first paste including at least a first thermally conductive material and a non-metallic inorganic bonding material to a surface of a ceramic base, followed by heating, to form a non-metallic inorganic bonding layer on the surface of the ceramic base; a step of applying a second paste including at least a second thermally conductive material and a thermoplastic resin to the surface of the non-metallic inorganic bonding layer, followed by heating, to form a resin layer on the surface of the non-metallic inorganic bonding layer; and a step of heating a metal plate while pressing it against the surface of the resin layer, to bond the non-metallic inorganic bonding layer, the resin layer, and the metal plate at their respective interfaces.

[0094] <Item 2> The first thermal conductive material is D ５０ Item 2. A method for manufacturing a heat dissipation substrate according to item 1, comprising at least metal particles having a particle diameter of 0.1 μm or more and 2.0 μm or less and an average aspect ratio of 1.0 or more and 1.5 or less.

[0095] <Item 3> The method for manufacturing a heat dissipation substrate according to item 1 or 2, wherein the content of the first thermal conductive material is 80 wt % or more and 90 wt % or less when the total mass of the first paste is 100 wt %.

[0096] <Item 4> The method for manufacturing a heat dissipation substrate according to any one of Items 1 to 3, wherein the nonmetallic inorganic bonding material is ceramic or glass.

[0097] <Item 5> The method for manufacturing a heat dissipation substrate according to Item 4, wherein the ceramic contains at least one selected from the group consisting of copper oxide, zinc oxide, lead oxide, cadmium oxide, antimony oxide, bismuth oxide, vanadium oxide, silicon oxide, and molybdenum oxide.

[0098] <Item 6> The glass is SiO ２ Glass, SiO ２ -Al ２ O ３ Glass, SiO ２ -Bi ２ O ３ Glass, SiO ２ -Y ２ O ３ Glass, SiO ２ -B ２ O ３Glass, SiO ２ -ZnO-based glass, SiO ２ -ZrO ２ 5. The method for manufacturing a heat dissipation substrate according to item 4, wherein the heat dissipation substrate comprises at least one selected from the group consisting of glass-based glasses.

[0099] <Item 7> The second thermal conductive material is D ５０ 7. The method for manufacturing a heat dissipation substrate according to any one of items 1 to 6, comprising at least first particles having a particle diameter of 2 μm or more and 5 μm or less and an average aspect ratio of 3 or more.

[0100] <Item 8> The second thermal conductive material is D ５０ 8. The method for manufacturing a heat dissipation substrate according to item 7, further comprising second particles having a particle diameter of 0.01 μm or more and 1 μm or less and an average aspect ratio of less than 2.

[0101] <Item 9> The method for manufacturing a heat dissipation substrate according to Item 8, wherein, when a total mass of the second thermally conductive material is 100 wt %, a content of the first particles is 70 wt % or more and 90 wt % or less, and a content of the second particles is 10 wt % or more and 30 wt % or less.

[0102] <Item 10> The bonding material for heat dissipation substrates according to any one of Items 1 to 9, wherein the thermoplastic resin comprises at least one selected from the group consisting of polyimide resin, PES resin, silicone resin, and polyamide resin.

[0103] <Item 11> A heat dissipation substrate comprising: a ceramic base; a non-metallic inorganic bonding layer bonded to a surface of the ceramic base and having a first metal sintered body fixed thereto with a non-metallic inorganic bonding material; a resin layer bonded to a surface of the non-metallic inorganic bonding layer and having a second metal sintered body fixed thereto with a thermoplastic resin; and a metal plate bonded to the surface of the resin layer.

[0104] <Item 12> The second metal sintered body has elongated regions having an average aspect ratio of 3 or more and spherical regions having an average aspect ratio of less than 2, and the plurality of elongated regions are connected via the spherical regions. The heat dissipation substrate according to item 11.

[0105] According to the technology disclosed herein, it is possible to improve the bonding strength of each layer in a heat dissipation substrate that uses a ceramic base material as the base material.

[0106] REFERENCE SIGNS LIST 1 heat dissipation substrate 10 ceramic base material 20 non-metallic inorganic bonding layer 30 resin layer 40 metal plate

Claims

1. A method for manufacturing a heat dissipation substrate, comprising: a step of applying a first paste containing at least a first thermally conductive material and a non-metallic inorganic bonding material to the surface of a ceramic substrate, followed by heating, to form a non-metallic inorganic bonding layer on the surface of the ceramic substrate; a step of applying a second paste containing at least a second thermally conductive material and a thermoplastic resin to the surface of the non-metallic inorganic bonding layer, followed by heating, to form a resin layer on the surface of the non-metallic inorganic bonding layer; and a step of heating a metal plate while pressing it against the surface of the resin layer, thereby bonding the interfaces of the non-metallic inorganic bonding layer, the resin layer, and the metal plate.

2. The first thermal conductive material is D ５０ 2. The method for producing a heat dissipation substrate according to claim 1, wherein the heat dissipation substrate contains at least metal particles having a particle diameter of 0.1 μm or more and 2.0 μm or less and an average aspect ratio of 1.0 or more and 1.5 or less.

3. The method for manufacturing a heat dissipation substrate according to claim 1, wherein the content of the first thermal conductive material is 80 wt % or more and 90 wt % or less when the total mass of the first paste is 100 wt %.

4. The method for manufacturing a heat dissipation substrate according to claim 1, wherein the non-metallic inorganic bonding material is ceramic or glass.

5. The method for manufacturing a heat dissipation substrate according to claim 4, wherein the ceramic contains at least one material selected from the group consisting of copper oxide, zinc oxide, lead oxide, cadmium oxide, antimony oxide, bismuth oxide, vanadium oxide, silicon oxide, and molybdenum oxide.

6. The glass is SiO ２ Glass, SiO ２ -Al ２ O ３ Glass, SiO ２ -Bi ２ O ３ Glass, SiO ２ -Y ２ O ３ Glass, SiO ２ -B ２ O ３ Glass, SiO ２ -ZnO-based glass, SiO ２ -ZrO ２ The method for manufacturing a heat dissipation substrate according to claim 4 , wherein the substrate comprises at least one selected from the group consisting of glass containing fluorine and fluorine-containing compounds.

7. The second thermal conductive material is D ５０ The method for manufacturing a heat dissipation substrate according to claim 1 , wherein the heat dissipation substrate comprises at least first particles having a particle diameter of 2 μm or more and 5 μm or less and an average aspect ratio of 3 or more.

8. The second thermal conductive material is D ５０ The method for manufacturing a heat dissipation substrate according to claim 7 , further comprising: second particles having a particle diameter of 0.01 μm or more and 1 μm or less and an average aspect ratio of less than 2.

9. A method for manufacturing a heat dissipation substrate as described in claim 8, wherein, when the total mass of the second thermal conductive material is 100 wt%, the content of the first particles is 70 wt% or more and 90 wt% or less, and the content of the second particles is 10 wt% or more and 30 wt% or less.

10. The method for manufacturing a heat dissipation substrate according to claim 1, wherein the thermoplastic resin includes at least one selected from the group consisting of polyimide resin, PES resin, silicone resin, and polyamide resin.

11. A heat dissipation substrate comprising: a ceramic substrate; a non-metallic inorganic bonding layer bonded to the surface of the ceramic substrate and having a first metal sintered body fixed thereto with a non-metallic inorganic bonding material; a resin layer bonded to the surface of the non-metallic inorganic bonding layer and having a second metal sintered body fixed thereto with a thermoplastic resin; and a metal plate bonded to the surface of the resin layer.

12. A heat dissipation substrate as described in claim 11, wherein the second metal sintered body has elongated regions having an average aspect ratio of 3 or more and spherical regions having an average aspect ratio of less than 2, and a plurality of the elongated regions are connected via the spherical regions.

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