Method for manufacturing heat sink

Abstract

The present invention provides a method for manufacturing a heat sink, which comprises: a step of coating a coating liquid A containing a thermosetting compound A and inorganic particles A on a substrate; a step of coating a coating liquid B containing a thermosetting compound B and inorganic particles B on the liquid surface of the coating liquid A; and a step of thermally curing the thermosetting compound A and the thermosetting compound B, wherein the content of inorganic particles with a particle size greater than 10 μm in the inorganic particles A is 70% by mass or more relative to the total mass of the inorganic particles A, and the content of inorganic particles with a particle size of less than 10 μm in the inorganic particles B is 80% by mass or more relative to the total mass of the inorganic particles B, and the step of coating the coating liquid A and the step of coating the coating liquid B are performed simultaneously.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a heat sink. Background Art

[0002] As electronic devices become more high-performance, it is necessary to efficiently release the heat generated in the various components that make up the electronic devices. For example, in power devices, CPUs (Central Processing Units) or light-emitting diode (LED) backlights, there are devices that generate heat above 150°C. If the heat generated from the heating element as described above accumulates inside the electronic device, it may sometimes cause adverse conditions such as malfunction of the electronic device. Therefore, various technologies have been studied to release the heat generated from the heating element.

[0003] Japanese Patent Application Laid-Open No. 2013-43111 discloses a method for manufacturing a laminated body, wherein a plurality of water-based inks containing organic synthetic polymer compounds are extruded simultaneously to stack a plurality of ink layers, and when stacking the ink layers, insoluble or insoluble substances are generated between adjacent ink layers to hinder mixing between the ink layers, and then, after coating the stacked ink layers on a substrate while maintaining the stacked structure, the ink layers are cooled to reduce the fluidity of a portion or all of the ink layers, and then the ink layers are dried and fixed, thereby manufacturing a laminated body in which components of the ink containing organic synthetic polymer compounds are stacked in layers on a substrate. Japanese Patent Application Laid-Open No. 2013-43111 discloses a method for manufacturing a heat dissipation film using the above method.

[0004] Japanese Patent Gazette No. 2017-94541 discloses a thermosetting sheet comprising a thermosetting compound, a thermosetting agent and nanotubes, wherein the nanotubes are locally present in the thickness direction of the thermosetting sheet and have a first region and a second region in which the content of the nanotubes is higher than that of the first region, and the second region is located on the surface of the thermosetting sheet.

[0005] Japanese Patent Gazette No. 2011-70930 discloses a multilayer insulating sheet that can be bonded to a bonding object by thermal curing. The multilayer insulating sheet comprises at least: a first layer containing a first filler; and a second layer, which is stacked on one surface of the first layer and is a surface layer and contains a second filler. The first filler contained in the first layer is at least one selected from the group consisting of magnesium oxide, zinc oxide, aluminum nitride and magnesium carbonate, and the second filler contained in the second layer is at least one selected from the group consisting of aluminum oxide, silicon dioxide, zirconium oxide and boron nitride.

[0006] Japanese Patent Application Publication No. 2005-354002 discloses a multilayer thermally conductive sheet comprising a first acrylic thermally conductive sheet layer and a second acrylic thermally conductive sheet layer disposed on one surface or both surfaces of the first acrylic thermally conductive sheet layer, wherein the first acrylic thermally conductive sheet layer is a layer having an Asker C hardness of 60 or more and formed by curing a first composition containing a hydrated metal compound at a ratio of 10% by volume or more, and the second acrylic thermally conductive sheet layer is a layer having an Asker C hardness of 50 or less and formed by curing a second composition containing a hydrated metal compound at a ratio of 5% by volume or more, and the thickness of the first acrylic thermally conductive sheet layer is less than half of the total thickness. Summary of the invention

[0007] Technical issues to be solved by the invention

[0008] In the past, gaps (pores) with low thermal conductivity were sometimes formed in heat sinks. If the proportion of the gaps contained in the heat sink increases, the thermal conductivity of the heat sink may be reduced. In addition, inorganic particles are sometimes used as components in the heat sink to improve thermal conductivity. However, the proportion of gaps generated in heat sinks containing inorganic particles as thermal conductive materials tends to be high. Therefore, it is believed that, for example, even by the techniques described in Japanese Patent Publication No. 2013-43111, Japanese Patent Publication No. 2017-94541, Japanese Patent Publication No. 2011-70930, and Japanese Patent Publication No. 2005-354002, it is particularly difficult to fully reduce the gaps in heat sinks containing inorganic nitride particles.

[0009] The present invention has been accomplished in view of the above circumstances.

[0010] An object of one aspect of the present invention is to provide a method for manufacturing a heat sink capable of forming a heat sink with fewer gaps.

[0011] Means for solving technical problems

[0012] Means for solving the above-mentioned problems include the following aspects.

[0013] <1> A method for manufacturing a heat sink, comprising: a step of coating a coating liquid A containing a thermosetting compound A and inorganic particles A on a substrate; a step of coating a coating liquid B containing a thermosetting compound B and inorganic particles B on the liquid surface of the coating liquid A; and a step of thermally curing the thermosetting compound A and the thermosetting compound B, wherein the content of inorganic particles having a particle size greater than 10 μm in the inorganic particles A is 70% by mass or more relative to the total mass of the inorganic particles A, and the content of inorganic particles having a particle size of less than 10 μm in the inorganic particles B is 80% by mass or more relative to the total mass of the inorganic particles B, and the step of coating the coating liquid A and the step of coating the coating liquid B are performed simultaneously.

[0014] <2> according to <1> The method for manufacturing the heat sink, wherein:

[0015] The content of inorganic particles having a particle size larger than 100 μm in the inorganic particles A is 70% by mass or more relative to the total mass of the inorganic particles A.

[0016] <3> according to <1> or <2> The method for manufacturing the heat sink, wherein:

[0017] In the coating liquid A, the content of the inorganic particles A is 100 to 600 parts by mass based on 100 parts by mass of the thermosetting compound A.

[0018] <4> according to <1> to <3> The method for manufacturing a heat sink as described in any one of the above, wherein:

[0019] In the coating liquid B, the content of the inorganic particles B is 100 to 800 parts by mass based on 100 parts by mass of the thermosetting compound B.

[0020] <5> According to <1> to <4> The method for manufacturing a heat sink as described in any one of the above, wherein:

[0021] The average particle size of the inorganic particles A is 50 μm to 150 μm.

[0022] <6> according to <1> to <5> The method for manufacturing a heat sink as described in any one of the above, wherein:

[0023] The average particle size of the inorganic particles B is 1 μm to 10 μm.

[0024] <7> according to <1> to <6> The method for manufacturing a heat sink as described in any one of the above, wherein:

[0025] The inorganic particles A and the inorganic particles B are each independently boron nitride particles or aluminum oxide particles.

[0026] <8> according to <1> to <7> The method for manufacturing a heat sink as described in any one of the above, wherein:

[0027] The thermosetting compound A includes at least one selected from the group consisting of epoxy compounds, phenol compounds, imide compounds, melamine compounds, isocyanate compounds, urethane compounds, acrylate compounds, and methacrylate compounds.

[0028] <9> according to <1> to <8> The method for manufacturing a heat sink as described in any one of the above, wherein:

[0029] The thermosetting compound B includes at least one selected from the group consisting of epoxy compounds, phenol compounds, imide compounds, melamine compounds, isocyanate compounds, urethane compounds, acrylate compounds, and methacrylate compounds.

[0030] Effects of the Invention

[0031] According to one aspect of the present invention, a method for manufacturing a heat sink capable of forming a heat sink with fewer gaps can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic cross-sectional view showing an example of a coating device. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present invention will be described in detail. In addition, the present invention is not limited to the following embodiments at all, and can be implemented with appropriate changes within the scope of the purpose of the present invention.

[0034] In the present invention, the numerical range represented by "to" refers to a range including the numerical values ​​recorded before and after "to" as the lower limit and the upper limit. In the numerical range recorded in stages in the present invention, the upper limit or lower limit recorded in a certain numerical range can be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical range recorded in the present invention, the upper limit or lower limit recorded in a certain numerical range can be replaced by the value shown in the embodiment.

[0035] In the present invention, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition unless otherwise specified.

[0036] In the present invention, a combination of two or more preferred aspects is a more preferred aspect.

[0037] In the present invention, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0038] In the present invention, "mass %" and "weight %" have the same meaning, and "parts by mass" and "parts by weight" have the same meaning.

[0039] In the present invention, the “total solid content mass” refers to the total mass of components excluding the solvent.

[0040] <Method for manufacturing heat sink>

[0041] The method for manufacturing a heat sink involved in the present invention includes: a step of coating a coating liquid A containing a thermosetting compound A and inorganic particles A on a substrate (hereinafter also referred to as "coating step A"); a step of coating a coating liquid B containing a thermosetting compound B and inorganic particles B on the liquid surface of the above-mentioned coating liquid A (hereinafter also referred to as "coating step B"); and a step of thermally curing the above-mentioned thermosetting compound A and the above-mentioned thermosetting compound B (hereinafter also referred to as "thermal curing step"). Relative to the total mass of the above-mentioned inorganic particles A, the content of inorganic particles with a particle size greater than 10μm in the above-mentioned inorganic particles A is 70% by mass or more, and relative to the total mass of the above-mentioned inorganic particles B, the content of inorganic particles with a particle size of less than 10μm in the above-mentioned inorganic particles B is 80% by mass or more, and the step of coating the above-mentioned coating liquid A and the step of coating the above-mentioned coating liquid B are performed simultaneously.

[0042] According to the method for manufacturing a heat sink according to the present invention, a heat sink with few voids can be formed. The reason why the method for manufacturing a heat sink according to the present invention exhibits the above-mentioned effect is not clear, but it is presumed as follows.

[0043] As one of the reasons for the generation of a large number of voids in a heat sink containing inorganic particles as a thermally conductive material, it is believed that the inorganic particles (especially inorganic nitride particles) contained in the heat sink have low affinity with thermosetting compounds. It is also believed that if the inorganic particles have low affinity with thermosetting compounds, voids are generated starting from surface defects such as depressions during the formation of the heat sink. In addition, in heat sinks, inorganic particles with large particle sizes are sometimes used to obtain excellent thermal conductivity. However, if the particle size of the inorganic particles is large, surface defects such as depressions are easily generated, so the generation of voids tends to increase. Therefore, it is believed that, for example, in a method of simultaneously applying multiple inks in multiple layers as described in Japanese Patent Publication No. 2013-43111, it is difficult to suppress the generation of voids during the formation of the heat sink. Furthermore, even in the so-called sequential coating method (a method in which another coating liquid is overlapped and coated on a coating film formed by coating a coating liquid and then drying it), inorganic particles having a large particle size may be exposed due to the surface of the previously formed coating film being dissolved by the other coating liquid, so that surface defects such as dents are easily generated.

[0044] In the method for manufacturing a heat sink according to the present invention, the above-mentioned steps are included, and the coating step A and the coating step B are performed simultaneously, so that a coating material including the coating liquid A and the coating liquid B can be formed at once, so that the problem of sequential coating, that is, the exposure of inorganic particles with a large particle size during the coating process can be suppressed, and in the above-mentioned coating material, the inorganic particles B including inorganic particles with a particle size of 10 μm or less can be arranged on the inorganic particles A including inorganic particles with a particle size of more than 10 μm. By suppressing the exposure of inorganic particles with a large particle size during the coating process and allowing the inorganic particles with a particle size of 10 μm or less to be locally present near the surface of the coating material, the surface area of ​​each inorganic particle present near the surface of the above-mentioned coating material can be reduced, so even when the affinity between the inorganic particles and the thermosetting compound is low, the generation of surface defects such as dents can be suppressed. Therefore, according to the method for manufacturing a heat sink according to the present invention, a heat sink with fewer voids can be formed.

[0045] Hereinafter, each step of the method for manufacturing a heat sink according to the present invention will be described.

[0046] [Coating step A]

[0047] The method for manufacturing a heat sink according to the present invention includes a step of coating a coating liquid A containing a thermosetting compound A and inorganic particles A on a substrate (coating step A). ​​By including the coating step A in the method for manufacturing a heat sink according to the present invention, inorganic particles having a particle size greater than 10 μm can be locally present in a region on the substrate side of the coating formed on the substrate. Therefore, the thermal conductivity of the heat sink can be improved.

[0048] 〔Base material〕

[0049] Examples of the substrate include a metal substrate and a release liner.

[0050] Examples of the metal substrate include an iron substrate, a copper substrate, a stainless steel substrate, an aluminum substrate, an alloy substrate containing magnesium, and an alloy substrate containing aluminum. Among the above, the metal substrate is preferably a copper substrate.

[0051] Examples of release liner include paper (e.g., kraft paper, glassine paper, and premium paper), resin films (e.g., polyolefins and polyesters), and laminated paper formed by laminating paper and resin films. Examples of polyolefins include polyethylene and polypropylene. Examples of polyesters include polyethylene terephthalate (PET).

[0052] The paper used as the release liner may be a release-treated paper. The release-treated paper may be formed by, for example, further performing a release treatment on one or both sides of a sealing-treated paper. The sealing treatment may be performed using, for example, clay or polyvinyl alcohol. The release treatment may be performed using, for example, a silicone resin.

[0053] The thickness of the substrate is not limited and may be appropriately set within a range of, for example, 10 μm to 300 μm.

[0054] 〔Coating liquid A〕

[0055] The coating liquid A contains a thermosetting compound A and inorganic particles A. Hereinafter, each component contained in the coating liquid A will be described.

[0056] (Thermosetting compound A)

[0057] Thermosetting compound A is a compound that can be cured by chemical reaction under heating conditions, and unless otherwise specified, includes a compound that forms a molecular skeleton of a product (i.e., a cured product) in a thermal curing reaction. Thermosetting compound A may be a single compound that is thermally cured, or a compound that is thermally cured by using two or more compounds in combination, or a compound that is thermally cured in the presence of a known additive.

[0058] The form of the thermosetting compound A is not limited to a monomer, and includes, for example, an oligomer, a prepolymer, and a polymer. From the viewpoint of easily adding a function such as heat resistance, the thermosetting compound A is preferably a monomer.

[0059] The thermosetting compound A is not limited, and known thermosetting compounds can be used. Examples of the thermosetting compound A include epoxy compounds, phenol compounds, imide compounds, melamine compounds, isocyanate compounds, urethane compounds, acrylate compounds, and methacrylate compounds. The above compounds also include thermosetting resins described below.

[0060] From the viewpoint of curability and film quality, the thermosetting compound A preferably contains at least one selected from the group consisting of epoxy compounds, phenol compounds, imide compounds, melamine compounds, isocyanate compounds, urethane compounds, acrylate compounds and methacrylate compounds, more preferably contains at least one selected from the group consisting of epoxy compounds, phenol compounds, acrylate compounds and methacrylate compounds, further preferably contains at least one selected from the group consisting of epoxy compounds and phenol compounds, and particularly preferably contains epoxy compounds.

[0061] From the viewpoint of curability and film quality, the thermosetting compound A is preferably at least one selected from the group consisting of epoxy compounds, phenol compounds, imide compounds, melamine compounds, isocyanate compounds, urethane compounds, acrylate compounds and methacrylate compounds, more preferably at least one selected from the group consisting of epoxy compounds, phenol compounds, acrylate compounds and methacrylate compounds, further preferably at least one selected from the group consisting of epoxy compounds and phenol compounds, and particularly preferably an epoxy compound.

[0062] As the epoxy compound, there is no limitation as long as it is a compound having an oxirane group. From the viewpoint of curability and film quality, the epoxy compound is preferably a compound having at least 2 oxirane groups in one molecule, more preferably an aromatic compound having at least 2 oxirane groups in one molecule, and particularly preferably a compound represented by the following formula (I).

[0063] [Chemical formula 1]

[0064]

[0065] In formula (I), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 Each independently represents a hydrogen atom or an alkyl group.

[0066] In formula (I), R 1 , R 2 , R 3, R 4 , R 5 , R 6 , R 7 and R 8 The alkyl group represented by is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0067] In formula (I), preferably R 1 , R 4 , R 5 and R 8 are independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R 2 , R 3 , R 6 and R 7 is a hydrogen atom. In formula (I), more preferably R 1 , R 4 , R 5 and R 8 are independently a hydrogen atom or a methyl group, R 2 , R 3 , R 6 and R 7 A hydrogen atom.

[0068] The compound represented by the above formula (I) can be obtained as, for example, YX4000 manufactured by Mitsubishi Chemical Corporation.

[0069] When the coating liquid A used in the present invention contains an epoxy compound, it is preferred that the coating liquid A further contain a phenol compound from the viewpoint of curability. That is, the thermosetting compound A preferably contains at least an epoxy compound and a phenol compound.

[0070] The phenol compound is not limited as long as it is a compound having a phenolic hydroxyl group. From the viewpoint of curability and film quality, the phenol compound is preferably a polyphenol compound, and more preferably a compound represented by the following formula (II).

[0071] [Chemical formula 2]

[0072]

[0073] In formula (II), R 11 and R 12 Each independently represents a hydrogen atom, an alkyl group or a hydroxyl group, and R 13 , R 14 , R 15 and R 16 Each independently represents a hydrogen atom or an alkyl group.

[0074] In formula (II), R 11and R 12 Each independently is preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxyl group, and more preferably a hydrogen atom or a hydroxyl group.

[0075] In formula (II), R 13 , R 14 , R 15 and R 16 Each independently is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.

[0076] The compound represented by the above formula (II) can be obtained as QE-2405 manufactured by Combi-Blocks Inc., for example.

[0077] In addition, examples of the thermosetting compound A include the epoxy resin monomer and acrylic resin monomer described in paragraph 0028 of Japanese Patent No. 4118691, the epoxy compounds described in paragraphs 0006 to 0011 of Japanese Patent Publication No. 2008-13759, and the epoxy resin monomer described in paragraphs 0032 to 0100 of Japanese Patent Publication No. 2013-227451.

[0078] Thermosetting compound A also includes thermosetting resins. Thermosetting resins are not limited, and known thermosetting resins can be used. Examples of thermosetting resins include epoxy resins, phenolic resins, polyimide resins, cresol resins, melamine resins, unsaturated polyester resins, isocyanate resins, and thermosetting polyurethane resins.

[0079] Among the above, the thermosetting resin is preferably an epoxy resin from the viewpoint of having a small thermal expansion coefficient and excellent heat resistance and adhesiveness.

[0080] The epoxy resin is not limited, and a known epoxy resin can be used. Examples of the epoxy resin include bifunctional epoxy resins and novolac epoxy resins.

[0081] Examples of the bifunctional epoxy resin include bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin.

[0082] Examples of the novolac epoxy resin include a phenol novolac epoxy resin and a cresol novolac epoxy resin.

[0083] The thermosetting compound A preferably has a polymerizable group. The polymerizable group in the thermosetting compound A is preferably at least one polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, an oxirane group (also referred to as an epoxy group) and a vinyl group, and an oxirane group is more preferred.

[0084] Thermosetting compound A may have a single polymerizable group or may have more than two polymerizable groups. Furthermore, the number of polymerizable groups in the thermosetting compound A may be one or more than two. From the viewpoint of excellent heat resistance of the cured product, the number of polymerizable groups in the thermosetting compound A is preferably more than two, more preferably more than three. The upper limit of the number of polymerizable groups in the thermosetting compound A is not limited. The number of polymerizable groups in the thermosetting compound A is usually less than 8.

[0085] The thermosetting compound A preferably contains a compound having at least one polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, an oxirane group, and a vinyl group, and more preferably contains a compound having an oxirane group.

[0086] From the viewpoint of easily adding functions such as heat resistance, the molecular weight of the thermosetting compound A is preferably 10,000 or less, more preferably 5,000 or less, further preferably 1,000 or less, and particularly preferably 600 or less.

[0087] There is no lower limit on the molecular weight of the thermosetting compound A. The molecular weight of the thermosetting compound A may be appropriately set within the range of, for example, 100 or more, preferably 200 or more.

[0088] The coating liquid A may contain a single thermosetting compound A or two or more thermosetting compounds A.

[0089] From the viewpoint of thermal conductivity of the heat sink, dispersibility of the inorganic particles and film quality, the content of the thermosetting compound A is preferably 10% to 50% by mass, more preferably 20% to 50% by mass, and particularly preferably 20% to 40% by mass, relative to the total solid content in the coating liquid A.

[0090] (Inorganic particles A)

[0091] There is no limitation on the inorganic particles A, and known inorganic particles can be used. Examples of the inorganic particles A include inorganic nitride particles and inorganic oxide particles.

[0092] Examples of the inorganic nitride constituting the inorganic nitride particles include boron nitride (BN), carbon nitride (C 3 N 4 ), silicon nitride (Si 3 N 4 ), gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), chromium nitride (Cr 2 N), copper nitride (Cu 3 N), iron nitride (Fe 4 N or Fe3 N), lanthanum nitride (LaN), lithium nitride (Li 3 N), magnesium nitride (Mg 3 N 2 ), Molybdenum Nitride (Mo 2 N), niobium nitride (NbN), tantalum nitride (TaN), titanium nitride (TiN), tungsten nitride (W 2 N.W.N 2 or WN), yttrium nitride (YN) and zirconium nitride (ZrN).

[0093] From the viewpoint of thermal conductivity of the heat sink, the inorganic nitride particles are preferably inorganic nitride particles containing at least one atom selected from the group consisting of boron atoms, aluminum atoms and silicon atoms, more preferably inorganic nitride particles containing at least one atom selected from the group consisting of boron atoms and aluminum atoms, and particularly preferably inorganic nitride particles containing boron atoms.

[0094] From the viewpoint of thermal conductivity of the heat sink, the inorganic nitride particles are preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles, aluminum nitride particles, and silicon nitride particles, more preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles and aluminum nitride particles, and particularly preferably boron nitride particles.

[0095] Examples of the inorganic oxide constituting the inorganic oxide particles include zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), silicon oxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), iron oxide (Fe 2 O 3 , FeO or Fe 3 O 4 ), copper oxide (CuO or Cu 2 O), zinc oxide (ZnO), yttrium oxide (Y 2 O 3 ), niobium oxide (Nb 2 O 5 ), molybdenum oxide (MoO 3 ), indium oxide (In 2 O 3 or In 2 O), tin oxide (SnO 2 ), Tantalum Oxide (Ta 2 O 5 ), tungsten oxide (WO 3 or W 2 O 5 ), lead oxide (PbO, PbO 2 ), bismuth oxide (Bi2 O 3 ), cerium oxide (CeO 2 or Ce 2 O 3 ), antimony oxide (Sb 2 O 3 or Sb 2 O 5 ), germanium oxide (GeO 2 or GeO), lanthanum oxide (La 2 O 3 ) and ruthenium oxide (RuO 2 ).

[0096] From the viewpoint of thermal conductivity of the heat sink, the inorganic oxide particles are preferably at least one inorganic oxide particle selected from the group consisting of titanium oxide particles, aluminum oxide particles, and zinc oxide particles, and are more preferably aluminum oxide particles.

[0097] From the viewpoint of thermal conductivity of the heat sink, the inorganic particles A are preferably at least one type of inorganic particles selected from the group consisting of inorganic nitride particles and inorganic oxide particles, and more preferably inorganic nitride particles.

[0098] Specifically, from the viewpoint of thermal conductivity of the heat sink, the inorganic particles A are preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles, aluminum nitride particles, silicon nitride particles, titanium oxide particles, aluminum oxide particles and zinc oxide particles, more preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles, aluminum nitride particles, silicon nitride particles and aluminum oxide particles, further preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles, aluminum nitride particles and aluminum oxide particles, particularly preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles and aluminum oxide particles, and most preferably boron nitride particles.

[0099] The average aspect ratio of the inorganic particles A is preferably 3 or more, more preferably 5 or more, and particularly preferably 8 or more. When the average aspect ratio of the inorganic particles A is within the above range, the thermal conductivity of the heat sink can be improved.

[0100] There is no upper limit on the average aspect ratio of the inorganic particles A. From the viewpoint of particle dispersibility in the coating liquid A, the average aspect ratio of the inorganic particles A is preferably 20 or less, and more preferably 15 or less.

[0101] The average aspect ratio of the inorganic particles A is measured by the following method.

[0102] (1) Using a scanning electron microscope (SEM), images of 100 randomly selected inorganic particles A are obtained.

[0103] (2) The major diameter and minor diameter of each of the above-mentioned inorganic particles A are measured respectively. In the present invention, the "major diameter of a particle" refers to the length of the longest line segment between any two points on the contour line connecting the particle. For example, in the case where the inorganic particle A is a perfect circle in the above-mentioned image, the major diameter of the inorganic particle A refers to the diameter of the inorganic particle A. Furthermore, in the present invention, the "minor diameter of a particle" refers to the length of the longest line segment between any two points on the contour line connecting the particle and being orthogonal to the line segment that determines the major diameter.

[0104] (3) The ratio of the major axis to the minor axis (major axis / minor axis) of each of the inorganic particles A is determined.

[0105] (4) The arithmetic mean of the obtained values ​​is taken as the average aspect ratio of the inorganic particles A.

[0106] The average particle size of the inorganic particles A is preferably 30 μm to 200 μm, more preferably 50 μm to 150 μm, and particularly preferably 50 μm to 100 μm. When the average particle size of the inorganic particles A is within the above range, the thermal conductivity of the heat sink can be improved.

[0107] In the present invention, the average particle size of the inorganic particles is the particle size at which the number-based accumulation in the number-based particle size distribution measured using a laser diffraction particle size distribution analyzer (e.g., MT3300II, manufactured by MicrotracBEL Corporation) becomes 50% (i.e., D50 or median particle size).

[0108] Classification is a method for adjusting the average particle size of the inorganic particles A. The average particle size of the inorganic particles A can also be adjusted by adjusting the content of inorganic particles having a particle size larger than 10 μm in the inorganic particles A.

[0109] The coating liquid A may contain the inorganic particles A alone or in combination of two or more.

[0110] In the coating liquid A, the content of the inorganic particles A is preferably 50 to 650 parts by mass, more preferably 100 to 600 parts by mass, and particularly preferably 200 to 400 parts by mass, relative to 100 parts by mass of the thermosetting compound A. When the content of the inorganic particles A is within the above range, the thermal conductivity of the heat sink can be improved.

[0111] The content of inorganic particles with a particle size greater than 10 μm in the inorganic particles A is 70% by mass or more relative to the total mass of the inorganic particles A. When the content of inorganic particles with a particle size greater than 10 μm in the inorganic particles A is within the above range, the inorganic particles with a particle size greater than 10 μm become the main heat conduction path, thereby improving the thermal conductivity of the heat sink. Here, "particle size" refers to the major diameter of the particle. The particle size of the inorganic particles is measured using a scanning electron microscope (SEM).

[0112] The content of inorganic particles having a particle size larger than 10 μm relative to the total mass of the inorganic particles A in the inorganic particles A is determined by the following method.

[0113] (1) Using a scanning electron microscope (SEM), images of 100 randomly selected inorganic particles A are obtained.

[0114] (2) The major diameter of each of the above-mentioned inorganic particles was measured.

[0115] (3) The inorganic particles are regarded as perfect circles, and the formula (4 / 3)πr is used. 3 The volume of each of the inorganic particles is calculated by the formula represented by: In the formula, π represents the circumference, and r represents the radius (1 / 2 of the major axis of the inorganic particle).

[0116] (4) The value obtained by dividing the sum of the volumes of the inorganic particles having a major diameter greater than 10 μm among the above-mentioned inorganic particles by the sum of the volumes of the above-mentioned inorganic particles (converted into a percentage) is taken as the content (mass %) of the inorganic particles having a particle size greater than 10 μm relative to the total mass of the inorganic particles A. That is, in the present invention, the volume ratio of the inorganic particles is regarded as the content ratio of the inorganic particles.

[0117] The more inorganic particles with a particle size greater than 10 μm in the inorganic particles A, the more thermal conductivity is formed. The thermal conductivity of the heat sink tends to improve. Relative to the total mass of the inorganic particles A, the content of inorganic particles with a particle size greater than 10 μm in the inorganic particles A is preferably 75% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The upper limit of the content of inorganic particles with a particle size greater than 10 μm is not limited. Relative to the total mass of the inorganic particles A, the content of inorganic particles with a particle size greater than 10 μm can be appropriately set within the range of 100% by mass or less.

[0118] Relative to the total mass of the inorganic particles A, the content of inorganic particles with a particle size greater than 100 μm in the inorganic particles A is preferably 15% by mass or more, more preferably 65% ​​by mass or more, further preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more. The thermal conductivity of the heat sink can be further improved by the content of inorganic particles with a particle size greater than 100 μm in the inorganic particles A being within the above range. There is no upper limit on the content of inorganic particles with a particle size greater than 100 μm. Relative to the total mass of the inorganic particles A, the content of inorganic particles with a particle size greater than 100 μm can be appropriately set within the range of less than 100% by mass, preferably less than 98% by mass. The content of inorganic particles with a particle size greater than 100 μm relative to the total mass of the inorganic particles A in the inorganic particles A is obtained by replacing "10 μm" with "100 μm" in the above method for calculating the content of inorganic particles with a particle size greater than 10 μm.

[0119] There is no limitation on the method for adjusting the content of inorganic particles having a particle size greater than 10 μm in the inorganic particles A, and a known method can be used. For example, inorganic particles having a particle size greater than 10 μm can be obtained by classification. In addition, inorganic particles having a particle size greater than 10 μm obtained by classification and inorganic particles having a particle size of 10 μm or less can be mixed in any proportion to adjust the content of inorganic particles having a particle size greater than 10 μm.

[0120] (Other ingredients)

[0121] The coating liquid A may contain other components in addition to the thermosetting compound A and the inorganic particles A. As other components, for example, a curing agent, a curing accelerator and a polymerization initiator may be mentioned. From the viewpoint of promoting the curing reaction, the coating liquid A preferably contains at least one selected from the group consisting of a curing agent, a curing accelerator and a polymerization initiator.

[0122] -Curing agent-

[0123] The curing agent is not limited, and a known curing agent can be used. The curing agent is preferably a compound having at least one functional group selected from the group consisting of a hydroxyl group, an amino group, a thiol group, an isocyanate group, a carboxyl group, an acryloyl group, a methacryloyl group, and a carboxylic anhydride group, and more preferably a compound having at least one functional group selected from the group consisting of a hydroxyl group, an acryloyl group, a methacryloyl group, an amino group, and a thiol group.

[0124] The curing agent is preferably a compound having two or more of the above functional groups, and more preferably a compound having two or three of the above functional groups.

[0125] Specific examples of the curing agent include amine curing agents, phenol curing agents, guanidine curing agents, imidazole curing agents, naphthol curing agents, acrylic curing agents, anhydride curing agents, active ester curing agents, benzoxazine curing agents, and cyanate curing agents. Among the above, the curing agent is preferably an imidazole curing agent, an acrylic curing agent, a phenol curing agent, or an amine curing agent.

[0126] The coating liquid A may contain a single type of curing agent, or may contain two or more types of curing agents.

[0127] When the coating liquid A contains a curing agent, the content of the curing agent is preferably 1% by mass to 50% by mass, and more preferably 1% by mass to 30% by mass, based on the total solid content mass in the coating liquid A.

[0128] -Curing accelerator-

[0129] The curing accelerator is not limited, and a known curing accelerator can be used. Examples of the curing accelerator include triphenylphosphine, 2-ethyl-4-methylimidazole, boron trifluoride amine complex, and 1-benzyl-2-methylimidazole.

[0130] The coating liquid A may contain a single type of curing accelerator, or may contain two or more types of curing accelerators.

[0131] When the coating liquid A contains a curing accelerator, the content of the curing accelerator is preferably 0.1% by mass to 20% by mass relative to the total solid content mass in the coating liquid A.

[0132] -Polymerization initiator-

[0133] The polymerization initiator is not limited, and a known polymerization initiator can be used. When the polymerizable monomer has an acryloyl group or a methacryloyl group, the polymerization initiator is preferably a polymerization initiator described in paragraph 0062 of Japanese Patent Application Publication No. 2010-125782 or a polymerization initiator described in paragraph 0054 of Japanese Patent Application Publication No. 2015-052710.

[0134] The coating liquid A may contain a single polymerization initiator or two or more polymerization initiators.

[0135] When the coating liquid A contains a polymerization initiator, the content of the polymerization initiator relative to the total solid content mass in the coating liquid A is preferably 0.1% by mass to 50% by mass.

[0136] -Solvents-

[0137] The coating liquid A may contain a solvent as another component. There is no limitation on the solvent, and a known solvent can be used. From the viewpoint of the solubility of the thermosetting compound, the solvent is preferably an organic solvent. Examples of the organic solvent include ethyl acetate, methyl ethyl ketone, dichloromethane, and tetrahydrofuran.

[0138] The coating liquid A may contain a single type of solvent or two or more types of solvents.

[0139] The content of the solvent is not limited, and can be appropriately set, for example, according to the composition of each component contained in the coating liquid A and the coating method. When the coating liquid A contains a solvent, the content of the solvent is preferably 30% to 80% by mass, more preferably 50% to 70% by mass, relative to the total mass of the coating liquid A.

[0140] (Method for producing coating liquid A)

[0141] As a method for producing the coating liquid A, for example, there can be mentioned a method of mixing the above-mentioned components. For example, the coating liquid A can be obtained by mixing a solvent, a thermosetting compound A, and inorganic particles A. The mixing method is not limited, and a known method can be used.

[0142] 〔Coating method〕

[0143] The coating method of the coating liquid A is not limited as long as the coating step A and the coating step B can be performed simultaneously, and a known method can be used. A specific embodiment of the coating method of the coating liquid A will be described later.

[0144] The coating amount of the coating liquid A is not limited and can be appropriately set according to the composition of the coating liquid A, the coating method, and the target thickness of the heat sink. The coating amount of the coating liquid A after drying is preferably 10 cm 3 / m 2 ~200cm 3 / m 2 , more preferably 30cm 3 / m 2 ~100cm 3 / m 2 .

[0145] [Coating step B]

[0146] The method for manufacturing a heat sink according to the present invention includes a step of coating a coating liquid B containing a thermosetting compound B and inorganic particles B on the liquid surface of the coating liquid A (coating step B). Since the method for manufacturing a heat sink according to the present invention includes the coating step B, inorganic particles having a particle size of 10 μm or less can be locally present near the surface of the coating formed on the substrate, so that even when the affinity between the inorganic particles and the thermosetting compound is low, the generation of surface defects such as dents can be suppressed. Therefore, the voids contained in the heat sink can be reduced.

[0147] [Coating liquid B]

[0148] The coating liquid B contains a thermosetting compound B and inorganic particles B. Hereinafter, each component contained in the coating liquid B will be described.

[0149] (Thermosetting compound B)

[0150] Thermosetting compound B is not limited, and a known thermosetting compound can be used. As thermosetting compound B, for example, the thermosetting compound described in the above "Thermosetting compound A" can be cited. The preferred embodiment of thermosetting compound B is the same as the preferred embodiment of thermosetting compound A.

[0151] The type of the thermosetting compound B may be the same as or different from the type of the thermosetting compound A, but is preferably the same as the type of the thermosetting compound A from the viewpoint of coating properties.

[0152] The coating liquid B may contain a single thermosetting compound or may contain two or more thermosetting compounds.

[0153] From the viewpoint of heat dissipation, the content of the thermosetting compound B relative to the total solid content in the coating liquid B is preferably 10 to 50% by mass, more preferably 20 to 50% by mass, and particularly preferably 20 to 40% by mass.

[0154] (Inorganic particles B)

[0155] There is no limitation on the inorganic particles B, and known inorganic particles can be used. For example, the inorganic particles B include the inorganic particles described in the above-mentioned "inorganic particles A". The preferred embodiment of the type and average aspect ratio of the inorganic particles B is the same as the preferred embodiment of the above-mentioned inorganic particles A.

[0156] The kind of the inorganic particles B may be the same as or different from the kind of the inorganic particles A, but is preferably the same as the kind of the inorganic particles A from the viewpoint of thermal conductivity.

[0157] Specifically, from the viewpoint of thermal conductivity of the heat sink, the inorganic particles A and the inorganic particles B are each independently preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles, aluminum nitride particles, silicon nitride particles, titanium oxide particles, aluminum oxide particles and zinc oxide particles, more preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles, aluminum nitride particles, silicon nitride particles and aluminum oxide particles, further preferably at least one inorganic nitride particle selected from the group consisting of boron nitride particles, aluminum nitride particles and aluminum oxide particles, particularly preferably boron nitride particles or aluminum oxide particles, and most preferably boron nitride particles.

[0158] The average particle size of the inorganic particles B is preferably 1 μm to 25 μm, more preferably 1 μm to 15 μm, further preferably 1 μm to 10 μm, and particularly preferably 1 μm to 5 μm. When the average particle size of the inorganic particles B is within the above range, the voids contained in the heat sink can be further reduced, and the thermal conductivity of the heat sink can be improved. The average particle size of the inorganic particles B is measured by following the method for measuring the average particle size of the inorganic particles A.

[0159] Classification is a method for adjusting the average particle size of the inorganic particles B. The average particle size of the inorganic particles B can also be adjusted by adjusting the content of inorganic particles having a particle size of 10 μm or less in the inorganic particles B.

[0160] In the method for manufacturing a heat sink involved in the present invention, it is preferred that the average particle size of the inorganic particles A is 50μm to 150μm, and the average particle size of the inorganic particles B is 1μm to 25μm, more preferably the average particle size of the inorganic particles A is 50μm to 150μm, and the average particle size of the inorganic particles B is 1μm to 10μm, and it is particularly preferred that the average particle size of the inorganic particles A is 50μm to 100μm, and the average particle size of the inorganic particles B is 1μm to 5μm.

[0161] The coating liquid B may contain the inorganic particles B alone or in combination of two or more.

[0162] In the coating liquid B, the content of the inorganic particles B is preferably 50 to 850 parts by mass, more preferably 100 to 800 parts by mass, and particularly preferably 200 to 500 parts by mass, relative to 100 parts by mass of the thermosetting compound B. When the content of the inorganic particles B is within the above range, the voids contained in the heat sink can be further reduced, and the thermal conductivity of the heat sink can also be improved.

[0163] The content of inorganic particles with a particle size of 10 μm or less in the inorganic particles B is 80% by mass or more relative to the total mass of the inorganic particles B. When the content of inorganic particles with a particle size of 10 μm or less in the inorganic particles B is within the above range, the voids contained in the heat sink can be reduced. The content of inorganic particles with a particle size of 10 μm or less is calculated by following the method for calculating the content of inorganic particles with a particle size greater than 10 μm described in the above "coating step A".

[0164] The more the content of inorganic particles with a particle size of less than 10 μm in the inorganic particles B, the smaller the inorganic particles can be locally present in the area on the surface side of the coating, so the voids contained in the heat sink can be further reduced, and the thermal conductivity of the heat sink can also be improved. Relative to the total mass of the above-mentioned inorganic particles B, the content of inorganic particles with a particle size of less than 10 μm in the inorganic particles B is preferably 85% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit of the content of inorganic particles with a particle size of less than 10 μm is not limited. Relative to the total mass of the above-mentioned inorganic particles B, the content of inorganic particles with a particle size of less than 10 μm can be appropriately set within the range of less than 100% by mass.

[0165] There is no limitation on the method for adjusting the content of inorganic particles with a particle size of 10 μm or less in the inorganic particles B, and a known method can be used. For example, inorganic particles with a particle size of 10 μm or less can be obtained by classification. In addition, inorganic particles with a particle size of 10 μm or less obtained by classification and inorganic particles with a particle size greater than 10 μm can be mixed in any proportion to adjust the content of inorganic particles with a particle size of 10 μm or less.

[0166] (Other ingredients)

[0167] The coating liquid B may contain other components in addition to the thermosetting compound B and the inorganic particles B. As other components, for example, other components described in the above-mentioned "coating step A" can be cited. Preferred embodiments of other components in the coating liquid B are the same as the preferred embodiments of other components described in the above-mentioned "coating step A".

[0168] (Method for producing coating liquid B)

[0169] As a method for producing the coating liquid B, for example, a method of mixing the above-mentioned components can be cited. For example, the coating liquid B can be obtained by mixing a solvent, a thermosetting compound B and inorganic particles B. There is no limitation on the mixing method, and a known method can be used. As a solvent, for example, the solvents described above can be used.

[0170] 〔Coating method〕

[0171] The coating method of the coating liquid B is not limited as long as the coating step A and the coating step B can be performed simultaneously, and a known method can be used. A specific embodiment of the coating method of the coating liquid B will be described later.

[0172] The coating amount of the coating liquid B is not limited and can be appropriately set according to the composition of the coating liquid B, the coating method, and the target thickness of the heat sink. The coating amount of the coating liquid B after drying is preferably 10 cm 3 / m 2 ~200cm 3 / m 2 , more preferably 10 cm 3 / m 2 ~50cm 3 / m 2 .

[0173] [Simultaneous coating]

[0174] In the method for manufacturing a heat sink according to the present invention, a step of applying the coating liquid A (coating step A) and a step of applying the coating liquid B (coating step B) are performed simultaneously (hereinafter, also referred to as "simultaneous coating"). In the method for manufacturing a heat sink according to the present invention, unlike sequential coating, coating step A and coating step B are performed simultaneously, thereby forming a coating material containing coating liquid A and coating liquid B at the same time, thereby suppressing the exposure of inorganic particles with a large particle size during the coating process and allowing inorganic particles with a particle size of less than 10 μm to be locally present near the surface of the above-mentioned coating material. As a result, in the process of forming the heat sink, the occurrence of surface defects such as depressions can be suppressed, so that the voids contained in the heat sink can be reduced.

[0175] In the present invention, “the step of applying the coating liquid A and the step of applying the coating liquid B are performed simultaneously” means that the coating liquid A and the coating liquid B are applied simultaneously or substantially simultaneously.

[0176] Here, "substantially simultaneously" is not limited to the case of completely simultaneous, and also includes the case where the difference between the time when the coating liquid A contacts the substrate and the time when the coating liquid B contacts the liquid surface of the coating liquid A is as close as possible in consideration of the time difference that may occur in order to implement the coating step A and the coating step B (for example, the time deviation caused by the manufacturing equipment). In the method for manufacturing the heat sink involved in the present invention, the coating liquid A is coated on the substrate, and then the coating liquid B is coated on the liquid surface of the coating liquid A. Therefore, for example, depending on the coating device and the coating method, it is considered that the time when the coating liquid B contacts the liquid surface of the coating liquid A is slightly delayed compared to the time when the coating liquid A contacts the substrate. That is, in the simultaneous coating, the time deviation that may inevitably occur between the time when the coating step A is performed and the time when the coating step B is performed is allowed as long as it does not deviate from the purpose of the present invention. In the method for producing a heat sink according to the present invention, the absolute value of the difference between the time when coating liquid A contacts the substrate and the time when coating liquid B contacts the liquid surface of coating liquid A is preferably 0 to 1 second, more preferably 0 to 0.1 seconds.

[0177] Examples of coating methods used for simultaneous coating include extrusion coating, die coating, spray coating, and inkjet coating. Among the above, the coating method is preferably die coating.

[0178] As for the coating device used for simultaneous coating, as long as the coating liquid A and the coating liquid B can be coated simultaneously or substantially simultaneously, there is no limitation, and a known coating device can be used. In simultaneous coating, it is preferred to use a coating device having a discharge port capable of discharging the coating liquid A and a discharge port capable of discharging the coating liquid B to coat the coating liquid A and the coating liquid B. In addition, a coating device having a discharge port capable of discharging the coating liquid A and a coating device having a discharge port capable of discharging the coating liquid B can be used together. In simultaneous coating, it is preferred to use a slit die to coat the coating liquid A and the coating liquid B. In the case of using a slit die in simultaneous coating, it is preferred to discharge the coating liquid A and the coating liquid B from a common slit die (for example, a slit die having a discharge port capable of discharging the coating liquid A and a discharge port capable of discharging the coating liquid B).

[0179] Hereinafter, an embodiment of a coating device applied to simultaneous coating will be described with reference to the drawings.

[0180] Figure 1 It is a schematic cross-sectional view showing an example of a coating device. Figure 1 The illustrated coating device 100 has a support roll 110 and a slot die 130 .

[0181] The support roller 110 is a member that rotatably supports the substrate 120. Examples of the material constituting the support roller include stainless steel.

[0182] The diameter of the support roller 110 is not limited and may be appropriately set according to, for example, ease of coating, productivity, and manufacturing cost of the support roller. The diameter of the support roller 110 may be appropriately set within a range of, for example, 100 mm to 1000 mm.

[0183] The substrate 120 described in the above “Coating Step A” can be used as the substrate 120 . The substrate 120 is conveyed by being wound around the support roll 110 .

[0184] The slot die 130 is a member for discharging the first coating liquid 140a and the second coating liquid 140b. The coating liquid A is used as the first coating liquid 140a. The coating liquid B is used as the second coating liquid 140b.

[0185] The slot die 130 includes a block 132A, a block 132B, and a block 132C. Figure 1 As shown, the slot die 130 is formed by bringing blocks 132A, 132B, and 132C into contact with each other. Examples of the material of the blocks 132A, 132B, and 132C include stainless steel.

[0186] The slot die 130 includes at least a slot 134 a and a pocket 136 a provided in a space defined by the wall surface of the block 132A and the wall surface of the block 132B.

[0187] The slit 134a is a flow path of the first coating liquid 140a. In the slot die 130, the slit 134a is communicated with the groove 136a, and is provided from the groove 136a toward an opening portion for discharging the first coating liquid 140a.

[0188] The groove 136a is a space for storing the first coating liquid 140a. There is no limitation on the shape of the groove 136a as long as it can store the first coating liquid 140a. Figure 1 As shown, the cross-sectional shape of the groove 136a can be roughly circular or semicircular.

[0189] The slot die 130 includes at least a slot 134 b and a groove 136 b provided in a space defined by the wall surface of the block 132B and the wall surface of the block 132C.

[0190] The slit 134b is a flow path of the second coating liquid 140b. In the slot die 130, the slit 134b is communicated with the groove 136b, and is provided from the groove 136b toward an opening for discharging the second coating liquid 140b.

[0191] The groove 136b is a space for storing the second coating liquid 140b. There is no limitation on the shape of the groove 136b as long as it can store the second coating liquid 140b. Figure 1 As shown, the cross-sectional shape of the groove 136b can be substantially circular or semicircular.

[0192] The following uses Figure 1 The die coating method of the coating apparatus 100 shown will be described. However, the method for manufacturing a heat sink according to the present invention is not limited to the following method.

[0193] exist Figure 1 In the coating apparatus 100 shown in FIG. 1 , a first coating liquid 140a and a second coating liquid 140b are discharged from an opening of a slot die 130 toward a substrate 120 conveyed by a support roller 110. Figure 1 As shown in FIG. 1 , the first coating liquid 140a is coated on the substrate while the second coating liquid 140b is coated, thereby coating the second coating liquid 140b on the liquid surface of the first coating liquid 140a. As a result, the first layer 122 formed by the first coating liquid 140a and the second layer 124 formed by the second coating liquid 140b are formed. Figure 1 In the figure, for convenience, the layer formed by the first coating liquid 140a and the second coating liquid 140b is represented as a two-layer structure (i.e., the first layer 122 and the second layer 124), but the above-mentioned layer does not necessarily have to be a two-layer structure, and can also be a single-layer structure (including a state where the boundary between the layers cannot be clearly confirmed).

[0194] In the method for producing a heat sink according to the present invention, the coating formed on the substrate by the coating liquid A and the coating liquid B can be dried as needed. As a drying method, for example, a method of applying warm air at 40° C. to 140° C. for 1 to 30 minutes can be mentioned.

[0195] [Thermal curing process]

[0196] The method for producing a heat sink according to the present invention includes a step (thermal curing step) of thermally curing the thermosetting compound A and the thermosetting compound B. By thermally curing the thermosetting compound A and the thermosetting compound B, the strength of the heat sink can be improved.

[0197] The device used in the heat curing step is not limited, and a known heating device can be used. Examples of the heating device include an electric furnace and a fan heater.

[0198] The heating temperature is not limited, and may be appropriately set, for example, according to the compositions of the coating liquid A and the coating liquid B. The heating temperature may be appropriately set, for example, within the range of 50 to 200°C.

[0199] The heating time is not limited and may be appropriately set according to the heating temperature, for example.

[0200] Furthermore, the thermal curing reaction may be a semi-curing reaction. That is, the obtained cured product may be in a so-called B-stage state (semi-cured state).

[0201] [Pressing process]

[0202] The method for manufacturing a heat sink according to the present invention preferably includes a step of pressurizing the cured product formed by the thermal curing step (hereinafter also referred to as a "pressurizing step"). By including the pressurizing step, the gaps in the heat sink can be further reduced.

[0203] There is no limitation on the pressurization method, and a known method can be used. For example, punching and calendering can be mentioned as the pressurization method. Among the above, the pressurization method is preferably calendering from the viewpoint of productivity and reduction of void ratio.

[0204] The pressure in the pressurizing step is not limited, and can be appropriately set according to the pressurizing method. For example, when the pressurizing method is calendering, the pressure (linear pressure) is preferably 50 N / m to 200 N / m, and more preferably 100 N / m to 150 N / m.

[0205] The temperature in the pressurizing step is preferably 20°C to 150°C, more preferably 25°C to 120°C.

[0206] When the pressing method is a calendering process, the conveying speed is not limited and may be appropriately set within a range of, for example, 1 m / min to 100 m / min.

[0207] <Heat sink>

[0208] The heat sink formed by the manufacturing method of the heat sink involved in the present invention has few gaps and therefore has excellent heat dissipation. Therefore, the heat sink formed by the manufacturing method of the heat sink involved in the present invention can efficiently release the heat generated in the heat source by contacting various heat generating bodies. For example, by making the heat sink contact with various components constituting an electronic device, the heat generated in the above components can be efficiently released. As the above components, for example, power devices and CPUs can be cited. In addition, the heat sink formed by the manufacturing method of the heat sink involved in the present invention can also be arranged between a heat generating body such as a power device and a heat sink such as a heat sink for use.

[0209] The thickness of the heat sink is not limited and may be appropriately set according to the application. From the viewpoint of thermal conductivity, the thickness of the heat sink is preferably in the range of 50 μm to 200 μm.

[0210] Example

[0211] Hereinafter, the present invention will be described in detail by way of Examples, but the present invention is not limited thereto. In addition, "part" and "%" are by mass unless otherwise specified.

[0212] <Example 1>

[0213] [Preparation of coating liquid A]

[0214] Coating liquid A was prepared by kneading the following components.

[0215] (Element)

[0216] Thermosetting compound A1 (compound having the following structure, molecular weight 372.42, QE-2405, manufactured by Combi-Blocks Inc.): 17 parts by mass

[0217] [Chemical formula 3]

[0218]

[0219] Thermosetting compound A2 (compound having the following structure, molecular weight 354.45, YX4000, manufactured by Mitsubishi Chemical Corporation): 34 parts by mass

[0220] [Chemical formula 4]

[0221]

[0222] Methyl ethyl ketone: 65 parts by mass

[0223] TPP (triphenylphosphine: curing accelerator): 0.6 parts by mass

[0224] Boron nitride particles (inorganic particles A, HP-40MF100, manufactured by Mizushima Ferroalloy Co., Ltd.): 46 parts by mass

[0225] [Preparation of coating liquid B]

[0226] The boron nitride particles (HP-40MF100, manufactured by MIZUSHIMA FERROALLOY CO., LTD.) used as the inorganic particles B were classified, and the content of the inorganic particles with a particle size of less than 10 μm in the inorganic particles B and the average particle size (D50) of the inorganic particles B were changed as described in Table 1. The coating liquid B was prepared by the same method as the coating liquid A.

[0227] [Manufacturing of heat sink]

[0228] Use with Figure 1The coating apparatus of the structure shown in the figure was used to simultaneously apply the coating liquid A and the coating liquid B on the release surface of the polyester film (NP-100A, thickness 100 μm, manufactured by PANAC Corporation), and then dried with warm air at 130° C. for 5 minutes to form a coating film. The coating amount of the coating liquid A after drying was adjusted to 170 cm 3 / m 2 Adjust the coating amount of coating liquid B to 30 cm after drying. 3 / m 2 Next, the coating film was thermally cured at 180° C. for 1 hour. The thermally cured coating film was subjected to calendaring under the following conditions to produce a heat sink. A pair of rollers including a rubber roller and a SUS (stainless steel) roller was used for the calendaring process.

[0229] (Conditions of calendering process)

[0230] Line pressure: 100N / m

[0231] Temperature: 80℃

[0232] ·Transmission speed: 5m / min

[0233] <Example 2 to Example 3>

[0234] In Example 1, a heat sink was produced in the same manner as in Example 1 except that the content of inorganic particles having a particle size greater than 100 μm in the inorganic particles A and the average particle size (D50) of the inorganic particles A were changed as described in Table 1 by classification operation.

[0235] <Example 4 to Example 7>

[0236] In Example 1, except that the content of the inorganic particles A was changed as described in Table 1, a heat sink was produced by the same method as in Example 1.

[0237] <Example 8 to Example 11>

[0238] In Example 1, a heat sink was produced by the same method as in Example 1 except that the content of the inorganic particles B was changed as described in Table 1.

[0239] <Example 12 to Example 16>

[0240] In Example 1, a heat sink was prepared by the same method as in Example 1 except that the content of inorganic particles having a particle size greater than 100 μm in inorganic particles A, the content of inorganic particles A, the average particle size (D50) of inorganic particles A, the content of inorganic particles B, and the average particle size (D50) of inorganic particles B were changed as described in Table 1. In addition, the content of inorganic particles having a particle size greater than 100 μm in inorganic particles A, the average particle size (D50) of inorganic particles A, and the average particle size (D50) of inorganic particles B were adjusted by classification operation.

[0241] <Example 17 to Example 18>

[0242] In Example 1, a heat sink was produced in the same manner as in Example 1 except that the content of inorganic particles having a particle size of 10 μm or less in the inorganic particles B and the average particle size (D50) of the inorganic particles B were changed as described in Table 1 by classification operation.

[0243] <Comparative Example 1>

[0244] In Example 1, a heat sink was produced by the same method as in Example 1 except that the coating liquid A and the coating liquid B were applied by the following method.

[0245] Coating liquid A was applied to the release surface of a polyester film (NP-100A, 100 μm thick, manufactured by PANAC Corporation) using an applicator to a dry thickness of 170 μm, and then dried for 5 minutes using warm air at 120° C. to form a coating film. Coating liquid B was applied to the coating film using an applicator to a dry thickness of 30 μm, and then dried for 5 minutes using warm air at 120° C.

[0246] <Comparative Example 2>

[0247] In Example 1, a heat sink was produced by the same method as in Example 1 except that the content of inorganic particles having a particle size of 10 μm or less in the inorganic particles B was changed as described in Table 1 by the classification operation.

[0248] <Comparative Example 3>

[0249] In Example 1, a heat sink was produced by the same method as in Example 1 except that the content of inorganic particles having a particle size of more than 10 μm in the inorganic particles A was changed as described in Table 1 by the classification operation.

[0250] <Evaluation>

[0251] The porosity and thermal conductivity of each of the above heat sinks were evaluated by the following method.

[0252] [Porosity]

[0253] The porosity of each heat sink was measured according to the procedures described in (1) to (4) below, and the obtained porosity was evaluated according to the following criteria. The evaluation results are shown in Table 1 below.

[0254] (1) The heat sink was cut by focused ion beam (FIB).

[0255] (2) A scanning electron microscope (SEM) was used to obtain a cross-sectional image of the heat sink. Specifically, images of five viewing fields were obtained in the cross section of the heat sink. 2 ~200,000μm 2 The cross-sectional area and the void area were appropriately calculated.

[0256] (3) Based on the above images, the ratio of the void area to the cross-sectional area (void area / cross-sectional area) was calculated.

[0257] (4) The obtained values ​​were arithmetic averaged and then converted into percentage to determine the porosity of the heat sink.

[0258] (standard)

[0259] A: Less than 5%

[0260] B: 5% or more and less than 10%

[0261] C: 10% or more and less than 30%

[0262] D: 30% or more or cannot be measured

[0263] [Thermal conductivity]

[0264] The thermal conductivity of each heat sink was measured by the following method, and the obtained thermal conductivity was evaluated according to the following criteria. The evaluation results are shown in Table 1 below.

[0265] (Method for measuring thermal conductivity)

[0266] (1) The thermal diffusion coefficient in the thickness direction of the thermal conductive sheet was measured by a laser flash method using "LFA467" manufactured by NETZSCH.

[0267] (2) The specific gravity of each fin was measured using a balance "XS204" manufactured by Mettler-Toledo International Inc. (using a "solid specific gravity measurement kit").

[0268] (3) Using "DSC320 / 6200" manufactured by Seiko Instruments Inc., the specific heat of each heat sink at 25°C was determined using DSC7 software under the condition of a temperature increase of 10°C / min.

[0269] (4) The thermal conductivity of each heat sink is calculated by multiplying the specific gravity and specific heat by the obtained thermal diffusion coefficient.

[0270] (standard)

[0271] A: 14Wm -1 K -1 above

[0272] B: 8Wm -1 K -1 Above and less than 14Wm -1 K -1

[0273] C: less than 8Wm -1 K -1

[0274] D: Unable to determine

[0275]

[0276] From Table 1, it is known that each heat sink of Examples 1 to 18 has fewer voids than the heat sinks of Comparative Examples 1 to 3. It is also known that each heat sink of Examples 1 to 18 has fewer voids even when pressurized at a pressure lower than the pressure generally used in the manufacture of conventional heat sinks. It is also known that each heat sink of Examples 1 to 18 has superior thermal conductivity than the heat sinks of Comparative Examples 1 to 3.

[0277] The invention of Japanese Patent Application No. 2019-061231 filed on March 27, 2019 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each document, patent application, or technical standard was specifically and individually described as being incorporated by reference.

Claims

1. A method for manufacturing a heat sink, in, The manufacturing method comprises: A step of coating a coating liquid A containing a thermosetting compound A and inorganic particles A on a substrate; A step of applying a coating liquid B containing a thermosetting compound B and inorganic particles B on the surface of the coating liquid A; and a step of thermally curing the thermosetting compound A and the thermosetting compound B, in, The content of inorganic particles having a particle size greater than 10 μm in the inorganic particles A is 70% by mass or more relative to the total mass of the inorganic particles A. The content of inorganic particles having a particle size of 10 μm or less in the inorganic particles B is 80% by mass or more relative to the total mass of the inorganic particles B. The step of applying the coating liquid A and the step of applying the coating liquid B are performed simultaneously.

2. The method for manufacturing a heat sink according to claim 1, in, The content of inorganic particles having a particle size greater than 100 μm in the inorganic particles A is 70% by mass or more relative to the total mass of the inorganic particles A.

3. The method for manufacturing a heat sink according to claim 1 or 2, in, In the coating liquid A, the content of the inorganic particles A is 100 to 600 parts by mass relative to 100 parts by mass of the thermosetting compound A.

4. The method for manufacturing a heat sink according to claim 1 or claim 2, in, In the coating liquid B, the content of the inorganic particles B is 100 to 800 parts by mass relative to 100 parts by mass of the thermosetting compound B.

5. The method for manufacturing a heat sink according to claim 1 or claim 2, in, The average particle size of the inorganic particles A is 50 μm to 150 μm.

6. The method for manufacturing a heat sink according to claim 1 or claim 2, in, The average particle size of the inorganic particles B is 1 μm to 10 μm.

7. The method for manufacturing a heat sink according to claim 1 or claim 2, in, The inorganic particles A and the inorganic particles B are independently boron nitride particles or aluminum oxide particles.

8. The method for manufacturing a heat sink according to claim 1 or claim 2, in, The thermosetting compound A includes at least one selected from the group consisting of epoxy compounds, phenol compounds, imide compounds, melamine compounds, isocyanate compounds, urethane compounds, acrylate compounds, and methacrylate compounds.

9. The method for manufacturing a heat sink according to claim 1 or claim 2, in, The thermosetting compound B includes at least one selected from the group consisting of epoxy compounds, phenol compounds, imide compounds, melamine compounds, isocyanate compounds, urethane compounds, acrylate compounds, and methacrylate compounds.

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