Laminates and circuit boards

Abstract

The objective is to provide a laminate with high peel strength of an insulating layer against a metal base layer, and a circuit board obtained therefrom. [Solution] A laminate comprising a metal base layer and an insulating layer disposed on the metal base layer, wherein the insulating layer contains a resin and a thermally conductive filler, the thermally conductive filler contains boron nitride aggregate particles and aluminum oxide particles, the ratio of the content of aluminum oxide particles to the content of boron nitride aggregate particles is 0.1 to 5.0 or more, and the D50 particle diameter of the boron nitride aggregate particles is greater than 20 μm.

Description

Technical Field

[0001] The present invention relates to a laminate and a circuit board.

Background Art

[0002] Various circuit boards have been put into practical use as circuit boards for forming hybrid integrated circuits by mounting electronic and electrical components such as semiconductor elements. Circuit boards are classified into resin circuit boards, ceramic circuit boards, metal base circuit boards, etc. based on the substrate material.

[0003] Resin circuit boards are inexpensive but have low thermal conductivity of the substrate, so they are limited to applications that use relatively small power. Ceramic circuit boards are suitable for applications that use relatively large power due to the characteristics of ceramics such as high insulation reliability and heat resistance, but have the disadvantage of being expensive. On the other hand, metal base circuit boards have intermediate properties between the two and are suitable for general-purpose applications that use relatively large power, such as applications for inverters for refrigerators, inverters for commercial air conditioners, power supplies for industrial robots, and power supplies for automobiles.

[0004] For example, Patent Document 1 discloses a method for obtaining a circuit board excellent in stress relaxation property, heat resistance, moisture resistance, and heat dissipation property by using a circuit board composition containing a specific epoxy resin, a curing agent, and a thermally conductive filler as essential components.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Replacing ceramic circuit boards with metal-based circuit boards is expected to improve productivity. Furthermore, ceramic circuit boards have the drawback of being prone to solder cracking during thermal cycling; however, replacing them with metal-based circuit boards is expected to suppress the occurrence of solder cracks.

[0007] When manufacturing such a metal-based circuit board, a laminate is prepared comprising a metal base layer and an insulating layer placed on the metal base layer. Then, a copper foil is placed on the insulating layer, and the circuit is formed by etching the copper foil through a resist layer formed on the copper foil. However, if the peel strength of the insulating layer against the metal base layer in the laminate is low, the insulating layer may peel off when the manufactured metal-based circuit board is attached by screws or the like.

[0008] The present invention has been made in view of the above-mentioned problems, and aims to provide a laminate with high peel strength of an insulating layer against a metal base layer, and a circuit board obtained therefrom. [Means for solving the problem]

[0009] In other words, the present invention is as follows: [1] It comprises a metal base layer and an insulating layer disposed on the metal base layer, The insulating layer comprises a resin and a thermally conductive filler. The thermally conductive filler comprises boron nitride aggregate particles and aluminum oxide particles. The ratio of the content of aluminum oxide particles to the content of boron nitride aggregate particles is 0.1 to 5.0. The D50 particle diameter of the boron nitride aggregated particles is greater than 20 μm. Laminated structure. [2] The ratio of the D50 particle diameter of the aluminum oxide particles to the D50 particle diameter of the boron nitride aggregate particles is 0.2 to 2.0. The laminate described in [1]. [3] The D50 particle size of the aluminum oxide particles is 5 to 60 μm. The laminate described in [1] or [2]. [4] The ratio of the D90 particle diameter to the D10 particle diameter of the aluminum oxide particles is 1.0 to 15. A laminate as described in any one of items [1] to [3]. [5] The crushing strength of the boron nitride aggregated particles is 6 to 20 MPa. The orientation index of the boron nitride aggregate particles is 5 to 20. A laminate as described in any one of items [1] to [4]. [6] The aluminum oxide particles include spherical aluminum oxide particles. A laminate as described in any one of items [1] to [5]. [7] The thickness of the insulating layer is 90 μm or more. A laminate as described in any one of items [1] to [6]. [8] It comprises a metal base layer, a metal circuit layer, and an insulating layer disposed between the metal base layer and the metal circuit layer, The insulating layer comprises a resin and a thermally conductive filler. The thermally conductive filler comprises boron nitride aggregate particles and aluminum oxide particles. The ratio of the content of aluminum oxide particles to the content of boron nitride aggregate particles is 0.1 to 5.0. The D50 particle diameter of the boron nitride aggregated particles is greater than 20 μm. Circuit board. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a laminate with high peel strength of an insulating layer against a metal base layer, and a circuit board obtained therefrom. [Brief explanation of the drawing]

[0011] [Figure 1]It is a schematic cross-sectional view of the laminate of the present embodiment. [Figure 2] It is a schematic cross-sectional view of the circuit board of the present embodiment.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. However, the present invention is not limited to this, and various modifications are possible without departing from the gist thereof. In the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. Also, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0013] 1. Laminate The laminate of the present embodiment includes a metal base layer and an insulating layer disposed on the metal base layer. The insulating layer contains a resin and a heat conductive filler. The heat conductive filler contains boron nitride aggregated particles and aluminum oxide particles. The ratio of the content of aluminum oxide particles to the content of boron nitride aggregated particles is 0.1 to 5.0, and the D50 particle diameter of the boron nitride aggregated particles exceeds 20 μm.

[0014] FIG. 1 shows a schematic cross-sectional view of the laminate of the present embodiment. As shown in FIG. 1, the laminate 1 includes a metal base layer 11 and an insulating layer 12 disposed on one surface of the metal base layer 11, and may include a metal foil layer 13 disposed on the surface of the insulating layer 12 opposite to the metal base layer 11. In this laminate 1, the metal base layer 11 and the metal foil layer 13 are isolated by the insulating layer 12 and are kept electrically insulated from each other.

[0015] Note that the laminate of the present embodiment may be a laminate having insulating layers 12 disposed on both surfaces of the metal base layer 11 and having the metal base layer 11 as a core.

[0016] In a laminate as shown in Figure 1, the adhesion between the metal base layer and the insulating layer is low, and if the insulating layer peels off from the metal base layer, dielectric breakdown may occur starting from that point. Specifically, circuit boards made using the above laminate may be fixed with screws or the like by forming screw holes, but the laminate may be tightened by fasteners such as screws, which may cause the insulating layer to peel off.

[0017] Upon investigation into this point, it was found that while boron nitride aggregate particles have excellent thermal conductivity, they have low affinity with resins, and using them in large quantities tends to reduce the adhesion of the insulating layer to the metal base layer. Therefore, in this embodiment, boron nitride aggregate particles of a predetermined particle size with excellent thermal conductivity are used in combination with aluminum oxide particles that contribute to improved thermal conductivity and adhesion. This makes it possible to provide a laminate with predetermined thermal conductivity and high peel strength of the insulating layer to the metal base layer. In this embodiment, when referring to peel strength, it means the peel strength of the insulating layer to the metal base layer.

[0018] The following provides a detailed explanation of each layer.

[0019] 1.1. Metal base layer The metal base layer is the base or core layer of the laminate and may conduct heat from the circuit to the housing or heat sink. The metal base layer is distinguished from the metal foil layer in that it does not form a circuit.

[0020] The metal material constituting the metal base layer is not particularly limited, but examples include aluminum, aluminum alloys, copper, copper alloys, iron, and stainless steel. Among these, aluminum, aluminum alloys, copper, and copper alloys are preferred. When aluminum or aluminum alloys are used as the metal base layer, the adhesion to the insulating layer tends to be lower compared to copper, etc., therefore the present invention is preferred. The metal base layer may be composed of one metal material, or it may be composed of two or more metal materials. Furthermore, the metal base layer may have a single-layer structure or a multi-layer structure.

[0021] The thickness of the metal base layer 11 is preferably 0.1 to 5.0 mm, 0.3 to 4.0 mm, or 0.5 to 3.0 mm. When the thickness of the metal base layer 11 is within the above range, the mechanical strength and heat dissipation characteristics of the laminate tend to be further improved.

[0022] 1.2. Insulating layer The insulating layer is located between the metal base layer and the metal foil layer, insulating them from each other, and, when used as a circuit board, conducting heat generated on the metal circuit layer (metal foil layer) side to the metal base layer. Such an insulating layer contains a resin and a thermally conductive filler, and may also contain a surfactant, an ion scavenger, and a curing accelerator as needed.

[0023] The insulating layer may be a cured resin composition, a semi-cured state (Stage B), or a fully cured state (Stage C).

[0024] The thickness of the insulating layer is preferably 50 μm or more, 90 μm or more, or 150 μm or more. Alternatively, the thickness of the insulating layer is preferably 500 μm or less, 300 μm or less, or 250 μm or less. A thickness of 50 μm or more in the insulating layer tends to improve insulation reliability. Furthermore, a thickness of 300 μm or less in the insulating layer tends to improve heat dissipation.

[0025] 1.2.1. Resin Examples of resins include silicone resins, epoxy resins, phenolic resins, cyanate resins, melamine resins, urea resins, thermosetting polyimide resins, and unsaturated polyester resins.

[0026] In general, the term "resin" can refer to the monomer or prepolymer before polymerization, or to the polymer after polymerization, depending on the context. However, in this specification, "resin" shall refer to the polymer after polymerization. On the other hand, when referring to the monomer or prepolymer before polymerization, the term "compound" shall be used, for example, "epoxy compound" or "phenol compound."

[0027] In other words, epoxy resins are not particularly limited, but for example, resins obtained by the reaction of an epoxy compound with a curing agent; phenolic resins are resins obtained by the reaction of a resol or novolac with a curing agent; and cyanate resins are resins obtained by the homopolymerization or copolymerization of a cyanate compound. The same applies to silicone resins, melamine resins, urea resins, thermosetting polyimide resins, and unsaturated polyester resins.

[0028] Among these, epoxy resin is preferred. Using such a resin tends to improve peel strength, as well as insulation reliability and thermal conductivity.

[0029] As for epoxy compounds, any compound having two or more epoxy groups in one molecule can be used, and the type is not particularly limited. Specific examples include bisphenol A type epoxy compounds, bisphenol E type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, bisphenol A novolac type epoxy compounds, biphenyl type epoxy compounds, phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, xylene novolac type epoxy compounds, polyfunctional phenol type epoxy compounds, naphthalene type epoxy compounds, naphthalene skeleton-modified novolac type epoxy compounds, naphthylene ether type epoxy compounds, phenol aralkyl type epoxy compounds, anthracene type epoxy compounds, trifunctional phenol type epoxy compounds, tetrafunctional phenol type epoxy compounds, triglycidyl isopropyl alcohol Examples of epoxy compounds include anurates, glycidyl ester type epoxy compounds, alicyclic epoxy compounds, dicyclopentadiene novolac type epoxy compounds, biphenyl novolac type epoxy compounds, phenol aralkyl novolac type epoxy compounds, naphthol aralkyl novolac type epoxy compounds, aralkyl novolac type epoxy compounds, biphenyl aralkyl type epoxy compounds, naphthol aralkyl type epoxy compounds, dicyclopentadiene type epoxy compounds, polyol type epoxy compounds, phosphorus-containing epoxy compounds, compounds in which double bonds of glycidylamine, butadiene, etc. have been epoxidized, compounds obtained by the reaction of hydroxyl-containing silicone resins with epichlorohydrin, or halides thereof. These epoxy compounds can be used individually or in combination of two or more.

[0030] Among these, epoxy compounds having a naphthalene skeleton, such as naphthalene-type epoxy compounds, naphthalene skeleton-modified novolac-type epoxy compounds, and naphthylene ether-type epoxy compounds, are preferred.

[0031] Examples of curing agents used with epoxy compounds include amino compounds having two or more amino groups in one molecule, acid anhydride compounds, or phenol compounds having two or more hydroxyl groups in one molecule.

[0032] The phenol compounds are not particularly limited, but examples include bisphenol A type phenol compounds, bisphenol E type phenol compounds, bisphenol F type phenol compounds, bisphenol S type phenol compounds, phenol novolac compounds, bisphenol A novolac type phenol compounds, glycidyl ester type phenol compounds, aralkyl novolac type phenol compounds, biphenyl aralkyl type phenol compounds, cresol novolac type phenol compounds, polyfunctional phenol compounds, naphthol compounds, naphthol novolac compounds, polyfunctional naphthol compounds, anthracene type phenol compounds, naphthalene skeleton-modified novolac type phenol compounds, phenol aralkyl type phenol compounds, naphthol aralkyl type phenol compounds, dicyclopentadiene type phenol compounds, biphenyl type phenol compounds, alicyclic phenol compounds, polyol type phenol compounds, phosphorus-containing phenol compounds, hydroxyl group-containing silicone compounds, and the like. These phenol compounds can be used individually or in combination of two or more.

[0033] Among these, bisphenol-type phenol compounds, such as bisphenol A type phenol compounds, are preferred.

[0034] The resin content is preferably 70% by mass or more, 80% by mass or more, or 85% by mass or more, relative to the total amount of resin solids in the insulating layer. A resin content of 70% by mass or more tends to improve peel strength and insulation reliability. Alternatively, the resin content is preferably 99% by mass or less, 97% by mass or less, or 95% by mass or less, relative to the total amount of resin solids in the insulating layer. A resin content of 99% by mass or less tends to improve thermal conductivity.

[0035] In this embodiment, "resin solids in the insulating layer" refers to the components of the insulating layer excluding the thermally conductive filler.

[0036] 1.2.2. Thermally conductive fillers The thermally conductive filler comprises boron nitride aggregate particles and aluminum oxide particles, and may optionally include other thermally conductive fillers. By using boron nitride aggregate particles and aluminum oxide particles in combination, peel strength can be further improved while maintaining insulation reliability and thermal conductivity.

[0037] In this embodiment, agglomerated boron nitride particles having a predetermined particle size are used. "Agglomeration" refers to the state in which primary particles have aggregated into secondary particles. Primary boron nitride particles have a flattened shape, and tend to have poor thermal conductivity in the thickness direction and excellent thermal conductivity in the plane direction. Such flattened primary boron nitride particles tend to be oriented in the plane direction. By using boron nitride, which has anisotropy in terms of thermal conductivity, as agglomerated particles, thermal conductivity is improved by contact between boron nitride particles, and it becomes easier to form heat conduction paths in any direction, thus tending to further improve thermal conductivity. In addition, by using agglomerated particles, the proportion of primary particles lying flat in the plane direction of the thermal conductive sheet is reduced, and the thermal resistance in the thickness direction is decreased. The secondary particles may be spherical or irregularly shaped lumps.

[0038] The D50 particle diameter of boron nitride aggregated particles is greater than 20 μm, preferably 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, and 42 μm or more. The upper limit of the D50 particle diameter of boron nitride aggregated particles is preferably 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, and 50 μm or less. When the D50 particle diameter of boron nitride aggregated particles is greater than 20 μm, peel strength and thermal conductivity tend to be further improved. Also, when the D50 particle diameter of boron nitride aggregated particles is 100 μm or less, insulation reliability tends to be further improved.

[0039] In this embodiment, "D50 particle diameter" refers to the median diameter, which is the value at which the cumulative distribution reaches 50% on the volume-based cumulative distribution curve. Similarly, D10 particle diameter and D90 particle diameter refer to the values ​​at which the cumulative distribution reaches 10% and 90%, respectively, on the volume-based cumulative distribution curve.

[0040] The crushing strength of the boron nitride aggregate particles is preferably 6 to 20 MPa, 7 to 18 MPa, 8 to 16 MPa, or 9 to 14 MPa. Because the crushing strength is within the above range, in the pressurization step of the thermal conductive sheet manufacturing method described later, the boron nitride aggregate particles deform along with the resin flow, making void formation less likely. Therefore, peel strength is improved, thermal resistance in the thickness direction is further reduced, void formation is eliminated, and insulation reliability tends to improve.

[0041] In this embodiment, the crushing strength refers to the value measured in accordance with the description in JIS R 1639-5:2007 "Fine ceramics - Method for measuring granular properties - Part 5: Crushing strength of a single granule". The crushing strength σ (unit: MPa) of a single agglomerated particle is calculated using the formula σ = α × P / (π × d²) from the values ​​of the dimensionless number α (α = 2.48), which changes depending on the position within the agglomerated particle, the crushing test force P (unit: N), and the particle size d (unit: μm). The measurement shall be performed on 20 or more agglomerated particles, and the value at the point of cumulative failure rate of 63.2% shall be calculated. A micro-compression tester can be used for the measurement. As a micro-compression tester, for example, the "MCT-210" (product name) manufactured by Shimadzu Corporation can be used.

[0042] The orientation index of the boron nitride aggregate particles is preferably 5 to 20, 6 to 15, or 7 to 10. Having the orientation index within this range tends to further reduce the thermal resistance in the thickness direction.

[0043] In this embodiment, the "orientation index" refers to a value measured according to the following method. An X-ray diffraction measurement is performed on a thermally conductive sheet containing boron nitride aggregate particles to obtain the X-ray diffraction spectrum of the boron nitride aggregate particles in the thermally conductive sheet, and peak intensities I(002) and I(100) corresponding to the (002) plane and (100) plane are obtained from the said X-ray diffraction spectrum. The orientation index [I(002) / I(100)] of the boron nitride aggregate particles can be calculated using the obtained peak intensities. As an X-ray diffractometer, for example, "ULTIMA-IV" (product name) manufactured by Rigaku Corporation can be used.

[0044] The content of boron nitride aggregated particles is preferably 10-60% by volume, 15-55% by volume, 20-50% by volume, and 25-45% by volume, relative to 100% by volume of the insulating layer. Peel strength tends to be further improved when the content of boron nitride aggregated particles is 60% by volume or less. Furthermore, thermal conductivity tends to be further improved when the content of boron nitride aggregated particles is 10% by volume or more.

[0045] The aluminum oxide particles may be polyhedral or spherical. Among these, spherical aluminum oxide particles are preferred. This tends to further improve peel strength and insulation reliability.

[0046] The D50 particle diameter of the aluminum oxide particles is preferably 5 μm or larger, 7.5 μm or larger, 10 μm or larger, 12.5 μm or larger, or 15 μm or larger. Alternatively, the D50 particle diameter of the aluminum oxide particles may be 60 μm or smaller, 50 μm or smaller, 40 μm or smaller, 30 μm or smaller, or 20 μm or smaller. When the D50 particle diameter of the aluminum oxide particles is within the above range, peel strength is improved, and peel strength and insulation reliability tend to be further improved.

[0047] The D10 particle diameter of the aluminum oxide particles is preferably 1.0 μm or larger, 2.5 μm or larger, 5.0 μm or larger, 10 μm or larger, or 15 μm or larger. Alternatively, the D10 particle diameter of the aluminum oxide particles is preferably 50 μm or smaller, 40 μm or smaller, 30 μm or smaller, 20 μm or smaller, 10 μm or smaller, or 5.0 μm or smaller. The D10 particle diameter of the aluminum oxide particles may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values.

[0048] The D90 particle diameter of the aluminum oxide particles is preferably 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, or 45 μm or more. Alternatively, the D90 particle diameter of the aluminum oxide particles is preferably 80 μm or less, 70 μm or less, 60 μm or less, 55 μm or less, 50 μm or less, 45 μm or less, or 40 μm or less. The D90 particle diameter of the aluminum oxide particles may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values.

[0049] The ratio of the D90 particle diameter to the D10 particle diameter of the aluminum oxide particles (D90 / D10) is preferably 1.5 or more, 2.0 or more, 3.0 or more, 5.0 or more, 7.5 or more, or 10 or more. Alternatively, the ratio (D90 / D10) may be 15 or less, 12.5 or less, 10 or less, 7.5 or less, or 8 or less. The ratio (D90 / D10) may be determined by any combination of any one of the above-mentioned lower limit candidate values ​​and any one of the above-mentioned upper limit candidate values. When the ratio (D90 / D10) is within the above range, peel strength is improved and insulation reliability tends to be further improved.

[0050] The ratio of the D50 particle diameter of aluminum oxide particles to the D50 particle diameter of boron nitride aggregate particles is preferably 0.2 to 2.0, 0.3 to 1.5, 0.4 to 1.0, or 0.5 to 0.95. When the ratio of the D50 particle diameter of aluminum oxide particles to the D50 particle diameter of boron nitride aggregate particles is within the above range, peel strength is improved, and insulation reliability and thermal conductivity tend to be further improved.

[0051] The aluminum oxide particle content is preferably 10-60% by volume, 15-55% by volume, 20-50% by volume, and 25-45% by volume, relative to 100% by volume of the insulating layer. Having an aluminum oxide particle content within these ranges tends to improve peel strength, as well as insulation reliability and thermal conductivity.

[0052] The total content of aluminum oxide particles and boron nitride aggregate particles is preferably 1 to 30% by volume, 3 to 20% by volume, and 5 to 15% by volume, relative to 100% by volume of the insulating layer. When the total content of aluminum oxide particles and boron nitride aggregate particles is within the above range, peel strength is improved, and insulation reliability and thermal conductivity tend to be further improved.

[0053] The ratio of aluminum oxide particles to boron nitride aggregate particles is 0.1 to 5.0, preferably 0.2 to 2.5, 0.3 to 1.5, and 0.4 to 0.95. When the ratio of aluminum oxide particles to boron nitride aggregate particles is within the above range, peel strength is improved, and insulation reliability and thermal conductivity tend to be further enhanced.

[0054] Other thermally conductive fillers are not particularly limited, but examples include aluminum nitride, silicon nitride, silicon oxide, zinc oxide, silica, aluminum hydroxide, magnesium oxide, and carbon.

[0055] Other thermally conductive fillers may be aggregated particles formed by the aggregation of primary particles. For example, using a thermally conductive filler with anisotropic thermal conductivity as aggregated particles improves thermal conductivity through contact between the thermally conductive fillers and facilitates the formation of heat conduction paths in any direction, thus tending to further improve thermal conductivity.

[0056] The content of other thermally conductive fillers is preferably 0 to 20% by volume, 0 to 15% by volume, 0 to 10% by volume, 0 to 5% by volume, and 0 to 3.0% by volume, relative to 100% by volume of the insulating layer. Furthermore, other thermally conductive fillers may not be included.

[0057] 1.2.3. Surfactants While there are no particular limitations on the surfactant as long as it is conventionally known, amphoteric surfactants are preferred from the viewpoint of improving the dispersibility of thermally conductive fillers and the peel strength.

[0058] Such amphoteric surfactants are not particularly limited, but examples include those having an anionic group (meth)acrylic monomer unit A (hereinafter also referred to as "unit A," and the monomer that gives unit A is also referred to as "monomer A") and a cationic group (meth)acrylic monomer unit B (hereinafter also referred to as "unit B," and the monomer that gives unit B is also referred to as "monomer B"). Furthermore, amphoteric surfactants may also have a nonionic monomer unit other than (meth)acrylic monomer unit A and (meth)acrylic monomer unit B, namely (meth)acrylic monomer unit C (hereinafter also referred to as "unit C," and the monomer that gives unit C is also referred to as "monomer C").

[0059] Furthermore, surfactants may have (meth)acrylic monomer units (unit X) that possess both anionic and cationic groups. In this case, unit X is considered to correspond to both unit A and unit B. In other words, a surfactant having unit X is considered to have both unit A and unit B.

[0060] In this specification, "monomer" means a monomer having a polymerizable group before polymerization. "Monomer unit" means a structural unit derived from the monomer that constitutes a surfactant. "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. "(meth)acrylic monomer" means acrylic monomers and their corresponding methacrylic monomers, and similar expressions such as "(meth)acryloyl group" have the same meaning.

[0061] The surfactant may have one or more units A, B, and C. The surfactant may be a random copolymer or a block copolymer. Monomers A, B, and C may each be monomers having one (meth)acryloyl group (monofunctional (meth)acrylic monomers) or monomers having two or more (meth)acryloyl groups (polyfunctional (meth)acrylic monomers), and preferably monofunctional (meth)acrylic monomers.

[0062] The anionic group possessed by unit A is, for example, one or more selected from the group consisting of a carboxyl group, a phosphoric acid group, a phenolic hydroxyl group, and a sulfonic acid group. From the viewpoint of further improving the dispersibility of the thermally conductive filler, the anionic group is preferably one or more selected from the group consisting of a carboxyl group, a phosphoric acid group, and a phenolic hydroxyl group.

[0063] Unit A preferably further comprises an electron-withdrawing group bonded to an anionic group, from the viewpoint of further improving the dispersibility of the thermally conductive filler. The electron-withdrawing group has the effect of stabilizing the anion of the anionic group. Examples of electron-withdrawing groups include halogen groups (also called halogeno groups). Examples of anionic groups to which electron-withdrawing groups are bonded include a group in which a halogen group is bonded to the carbon atom at the α position of a carboxyl group.

[0064] Unit A does not need to have an electron-donating group bonded to the anionic group. Electron-donating groups can destabilize the anion of the anionic group. An example of an electron-donating group is the methyl group.

[0065] Examples of monomer A include acrylic acid, methacrylic acid, acid phosphooxypropyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolyoxypropylene glycol monomethacrylate, phosphoric acid-modified epoxy acrylate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 4-hydroxyphenyl acrylate, 4-hydroxyphenyl meacrylate, 2-methacryloyloxyethyl succinic acid, and 2-acrylamido-2-methylpropanesulfonic acid. From the viewpoint of further improving the dispersibility of the thermally conductive filler, monomer A is preferably one or more selected from the group consisting of acrylic acid, 2-methacryloyloxyethyl phosphate, 4-hydroxyphenyl meacrylate, and 2-acrylamido-2-methylpropanesulfonic acid, and more preferably acrylic acid.

[0066] The cationic group possessed by unit B is, for example, one or more selected from the group consisting of primary amino groups, secondary amino groups, tertiary amino groups, and quaternary ammonium bases. From the viewpoint of further improving the dispersibility of the thermally conductive filler, the cationic group is preferably a tertiary amino group.

[0067] Unit B preferably further comprises an electron-donating group bonded to a cationic group, from the viewpoint of further improving the dispersibility of the thermally conductive filler. The electron-donating group has the effect of stabilizing the cation of the cationic group. An example of an electron-donating group is a methyl group. An example of a cationic group to which an electron-donating group is bonded is a group in which a methyl group is bonded to the carbon atom at the α position of an amino group.

[0068] Unit B does not need to have an electron-withdrawing group bonded to a cationic group. Electron-withdrawing groups can destabilize the cation of the cationic group. An example of an electron-withdrawing group is a carboxyl group.

[0069] Examples of monomer B include 1-aminoethyl acrylate, 1-aminopropyl acrylate, 1-aminoethyl methacrylate, 1-aminopropyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, t-butylaminoethyl (meth)acrylate, dimethylaminoethyl methacrylate quaternary salt, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, and dimethylaminoethyl acrylate benzyl chloride quaternary salt. From the viewpoint of further improving the dispersibility of the thermally conductive filler, monomer B is preferably one or more selected from the group consisting of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate and 2,2,6,6-tetramethyl-4-piperidyl methacrylate, and more preferably 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate.

[0070] Unit C is a (meth)acrylic monomer that does not contain either a cationic or anionic group. In addition to the (meth)acryloyl group, unit C may have an amphiphilic group, a hydrophobic group, or a hydrophilic group. An example of an amphiphilic group is an oxyalkylene group. An example of a hydrophobic group is a siloxane group and a hydrocarbon group. An example of a hydrophilic group is a phosphate ester group. Note that the hydrocarbon group referred to here does not include the methyl group that constitutes the methacryloyl group (the same applies to the hydrocarbon group in unit C below).

[0071] Unit C has one or more selected from the group consisting of oxyalkylene groups, siloxane groups, and hydrocarbon groups, from the viewpoint of affinity or compatibility between the surfactant and the resin, and more preferably has one or more selected from the group consisting of siloxane groups and hydrocarbon groups.

[0072] Examples of (meth)acrylic monomers having an oxyalkylene group include ethoxycarbonylmethyl (meth)acrylate, phenol ethylene oxide modified (meth)acrylate, phenol (ethylene oxide 2 molar modified) (meth)acrylate, phenol (ethylene oxide 4 molar modified) (meth)acrylate, paracumylphenol ethylene oxide modified (meth)acrylate, nonylphenol ethylene oxide modified (meth)acrylate, nonylphenol (ethylene oxide 4 molar modified) (meth)acrylate, nonylphenol (ethylene oxide 8 molar modified) (meth)acrylate, nonylphenol (propylene oxide 2.5 molar modified) acrylate, 2-ethylhexylcarbitol (meth)acrylate, ethylene oxide modified phthalic acid (meth)acrylate, ethylene oxide modified succinic acid (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate.

[0073] Examples of (meth)acrylic monomers having a siloxane group include α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane.

[0074] Examples of (meth)acrylic monomers having hydrocarbon groups include benzyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, and methoxylated cyclodecatriene (meth)acrylate.

[0075] Examples of (meth)acrylic monomers having a phosphate ester group include (meth)acryloyloxyethyldialkyl phosphates.

[0076] Monomer C may also be, for example, a (meth)acrylic monomer having a hydroxyl group. Examples of (meth)acrylic monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate.

[0077] Monomer C may be, for example, a (meth)acrylic monomer having an amide bond. Examples of (meth)acrylic monomers having an amide bond include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, diacetone(meth)acrylamide, and acryloylmorpholine.

[0078] Monomer C may be, for example, a polyfunctional (meth)acrylic monomer. Examples of polyfunctional (meth)acrylic monomers include 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexadiol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, 2-ethyl-2-butyl-propanediol (meth)acrylate, neopentyl glycol-modified trimethylolpropane di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, 2-(1,2-cyclohexacarboxyimide)ethyl (meth)acrylate, hexanediol di(meth)acrylate, and polyfunctional (meth)acrylates having a bisphenol structure.

[0079] The content of unit A may be 0.03 mol% or more, 0.1 mol% or more, 0.5 mol% or more, 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more, or 5 mol% or more, based on 100 mol% of the total of unit A, unit B, and unit C (in other words, the total of all monomer units possessed by the surfactant; the same applies hereinafter), or it may be 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, 15 mol% or less, 10 mol% or less, or 5 mol% or less. A unit A content of 0.03 mol% or more tends to further improve the dispersibility of the thermally conductive filler. A unit A content of 70 mol% or less tends to further reduce the viscosity of the resin composition before the formation of the insulating layer, and further improve the handling properties of the resin composition.

[0080] The content of unit B may be 0.02 mol% or more, 0.05 mol% or more, 0.07 mol% or more, or 0.1 mol% or more, relative to 100 mol% of the total of units A, B, and C, and may be 20 mol% or less, 10 mol% or less, 5 mol% or less, 3 mol% or less, 1 mol% or less, 0.5 mol% or less, or 0.1 mol% or less. When the content of unit B is 0.02 mol% or more, the affinity of the surfactant to the thermally conductive filler tends to be better. When the content of unit B is 20 mol% or less, the viscosity of the resin composition before the formation of the insulating layer tends to be further reduced, and the handling properties of the resin composition tend to be further improved.

[0081] The content of unit C may be 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 92 mol% or more, or 94 mol% or more, relative to 100 mol% of the total of units A, B, and C, and may be 99.8 mol% or less, 99 mol% or less, 98 mol% or less, 97 mol% or less, 96 mol% or less, or 95 mol% or less. When the content of unit C is 10 mol% or more, the viscosity of the resin composition before the formation of the insulating layer tends to decrease further, and the handling properties of the resin composition tend to improve further. When the content of unit C is 99.8 mol% or less, the affinity of the surfactant to the thermally conductive filler tends to be better.

[0082] The total content of unit A and unit B may be 0.05 mol% or more, 0.2 mol% or more, 1 mol% or more, 2 mol% or more, 3 mol% or more, 4 mol% or more, or 5 mol% or more, relative to 100 mol% of the total of unit A, unit B, and unit C, and may be 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, 30 mol% or less, 20 mol% or less, 10 mol% or less, 8 mol% or less, or 6 mol% or less. When the total content of unit A and unit B is 0.05 mol% or more, the dispersibility of the thermally conductive filler tends to be further improved. When the total content of unit A and unit B is 90 mol% or less, the handling properties of the resin composition before the formation of the insulating layer tend to be further improved.

[0083] The molar ratio of unit A to unit B (unit A / unit B) may be 0.01 or greater, 0.9 or greater, 1 or greater, 5 or greater, 10 or greater, 20 or greater, 30 or greater, 40 or greater, or 50 or greater, and may also be 200 or less, 150 or less, 100 or less, 90 or less, 80 or less, 70 or less, 60 or less, 50 or less, 40 or less, 30 or less, 20 or less, 15 or less, or 10 or less. When the molar ratio of unit A to unit B is within the above range, the dispersibility of the thermally conductive filler tends to improve.

[0084] The weight-average molecular weight of the surfactant may be 1,000 or more, 5,000 or more, 7,000 or more, 10,000 or more, 20,000 or more, 30,000 or more, 40,000 or more, or 50,000 or more, and may also be 1,000,000 or less, 500,000 or less, 300,000 or less, 100,000 or less, 90,000 or less, 80,000 or less, 70,000 or less, or 60,000 or less. A weight-average molecular weight of 1,000 or more for the surfactant helps maintain the dispersibility of the thermally conductive filler and suppresses the increase in hardness of the insulating layer over time. A weight-average molecular weight of 1,000,000 or less for the surfactant tends to further reduce the viscosity of the resin composition and improve the handling properties of the resin composition before the insulating layer is formed. The weight-average molecular weight of surfactants is determined as the weight-average molecular weight on a standard polystyrene basis using the GPC (gel permeation chromatography) method.

[0085] Surfactants are obtained by polymerizing monomers A, B, and C using known polymerization methods. Examples of polymerization methods include radical polymerization and anionic polymerization. Radical polymerization is preferred as the polymerization method.

[0086] The polymerization initiator used in radical polymerization may be a thermal polymerization initiator or a photopolymerization initiator. Examples of thermal polymerization initiators include azo compounds such as azobisisobutyronitrile, and organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, and di-tert-butyl peroxide. Examples of photopolymerization initiators include benzoin derivatives. The polymerization initiator may also be a known polymerization initiator used in living radical polymerization such as ATRP and RAFT.

[0087] Polymerization conditions can be adjusted as appropriate depending on the type of monomer, polymerization initiator, etc. If the surfactant is a random copolymer, the monomers may be mixed beforehand before polymerization. If the surfactant is a block copolymer, the monomers may be added sequentially to the polymerization system.

[0088] The surfactant content is preferably 1.0% by mass or more, 2.0% by mass or more, and 3.0% by mass or more, relative to the total amount of resin solids in the insulating layer. Alternatively, the surfactant content is preferably 10% by mass or less, 8.0% by mass or less, and 6.0% by mass or less, relative to the total amount of resin solids in the insulating layer. A surfactant content of 5% by mass or less tends to further improve peel strength. Furthermore, a surfactant content of 0.1% by mass or more tends to further improve insulation reliability.

[0089] 1.2.4. Ion scavengers The ion scavenger is not particularly limited as long as it is a compound having ion-scavenging properties that capture at least one of a cation and anion, but it is preferably an inorganic material. In this specification, "ion-scavenging properties" means the property of adsorbing the ion to be captured onto the surface of an inorganic material, or the property of introducing the ion to be captured into the structure of an inorganic material through ion exchange between ions in the structure of the inorganic material and the ion to be captured. Examples of ions to be captured by the ion scavenger include cations such as Na ions, Cu ions, and Ag ions, and anions such as Cl ions and Br ions.

[0090] The ion scavenger includes both anion exchangers and cation exchangers, or both ion exchangers. Anion exchangers are inorganic materials that capture anions, cation exchangers are inorganic materials that capture cations, and both ion exchangers are inorganic materials that capture both anions and cations. The ion scavenger may be used alone or in combination of two or more types. For example, the ion scavenger may include multiple anion exchangers, multiple cation exchangers, or multiple both ion exchangers.

[0091] The ion scavenger may contain, for example, at least one selected from the group consisting of Al, Mg, Bi, Zr, Sb, Sn, Ti, and Zn, or it may contain at least one selected from the group consisting of Bi, Zr, and Sb. The ion scavenger may also be, for example, an oxide, acid chloride, or hydrate thereof containing at least one of these metal elements. The ion scavenger may contain two or more of these metal elements.

[0092] Examples of anion exchangers include inorganic materials containing at least one selected from the group consisting of Al, Mg, Bi, Zr, and Zn. Specific examples of anion exchangers include IXE-500 (Bi-based), IXE-530 (Bi-based), IXE-550 (Bi-based), IXE-700 (Mg, Al-based), IXE-700F (Mg, Al-based), IXE-770 (Mg, Al-based), IXE-770D (Mg, Al-based), IXE-702 (Al-based), IXE-800 (Zr-based), and IXE-1000 (Zn-based) (all manufactured by Toagosei Co., Ltd.).

[0093] Examples of cation exchangers include inorganic materials containing at least one selected from the group consisting of Zr, Sn, and Ti. Specific examples of cation exchangers include IXE-100 (Zr-based), IXE-200 (Sn-based), IXE-300 (Sb-based), and IXE-400 (Ti-based) (all manufactured by Toagosei Co., Ltd.).

[0094] Examples of ion exchangers include inorganic materials containing at least one selected from the group consisting of Al, Mg, Bi, Zr, and Sb. Specific examples of ion exchangers include IXE-1320 (Mg, Al system), IXE-600 (Sb, Bi system), IXE-633 (Bi system), IXE-680 (Bi system), IXE-6107 (Zr, Bi system), IXE-6136 (Zr, Bi system), IXEPLAS-A1 (Zr, Mg, Al system), IXEPLAS-A2 (Zr, Mg, Al system), and IXEPLAS-B1 (Zr, Bi system) (all manufactured by Toagosei Co., Ltd.).

[0095] The average particle size of the ion scavenger is preferably 0.05 μm or larger, 0.1 μm or larger, 0.15 μm or larger, and 0.2 μm or larger. Alternatively, the average particle size of the ion scavenger is preferably 5 μm or smaller, 3 μm or smaller, 2 μm or smaller, and 1 μm or smaller. The average particle size of the ion scavenger can be measured by laser diffraction / scattering.

[0096] The content of the ion scavenger, which includes at least one selected from the group consisting of Bi, Zr, and Sb, may preferably be 80% by mass or more, 90% by mass or more, or 95% by mass or more, relative to the total amount of ion scavenger. The content of the ion scavenger, which includes at least one selected from the group consisting of Bi, Zr, and Sb, may also be 100% by mass or less, relative to the total amount of ion scavenger.

[0097] The ion scavenging agent content is preferably 1.0 to 7.0% by mass, 2.0 to 6.0% by mass, or 3.0 to 5.0% by mass, relative to the total amount of resin solids in the insulating layer. When the ion scavenging agent content is within the above range, the insulating reliability tends to improve further.

[0098] 1.2.5. Curing Accelerator The insulating layer of this embodiment may also contain a curing accelerator added from the viewpoint of promoting the polymerization reaction of the resin.

[0099] The curing accelerator is not particularly limited, but examples include organometallic salts such as bis(2,4-pentanedionato)zinc(II), zinc octoate, zinc naphthenate, cobalt naphthenate, copper naphthenate, iron acetylacetone, nickel octoate, manganese octoate; tetraphenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetraphenylborate, triphenylphosphine, tri-p-tolylphosphine, tris(4-chlorophenyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine, triphenylphosphine, triphenylborane, tetraphenylphosphine Examples include phosphorus compounds such as honium dicyanamide and tetraphenylphosphonium tetra(4-methylphenyl)borate; and imidazole compounds such as 2-phenyl-1-benzyl-1H-imidazole, 1-(1-cyanomethyl)-2-ethyl-4-methyl-1H-imidazole, 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2,4,5-triphenylimidazole.

[0100] The content of the curing accelerator is preferably 0.50 to 2% by mass and 0.75 to 1.5% by mass, relative to the total amount of resin solids in the insulating layer.

[0101] 1.2.6. Other Ingredients The resin composition may further contain other components. Examples of other components include coupling agents, leveling agents, antioxidants, defoaming agents, wetting agents, dispersants, and stabilizers.

[0102] 1.3.Metal foil layer The metal foil layer 13 is a metal foil that forms a circuit through etching or the like to become a metal circuit layer, and is constructed on the metal base layer 11 via the insulating layer 12.

[0103] The metal material constituting the metal foil layer is not particularly limited, but examples include copper, aluminum, and nickel. Among these, copper or aluminum is preferred from the viewpoint of thermal conductivity, and copper is more preferred. The metal foil layer may be composed of one metal material, or it may be composed of two or more metal materials. The metal foil layer may be a single layer structure or a multilayer structure. In Figure 1, the metal foil layer 13 is arranged over substantially the entire surface of the insulating layer 12, but the second metal layer may be arranged only on a part of the insulating layer 12.

[0104] The thickness of the metal foil layer is preferably 10 to 1000 μm, 100 to 750 μm, or 250 to 500 μm. Having the metal foil layer thickness within these ranges facilitates circuit formation and tends to improve conductivity.

[0105] 2. Method for manufacturing laminates The manufacturing method of the laminate according to this embodiment is not particularly limited as long as it has a first lamination step of laminating an insulating layer on a metal base layer, and may optionally include a preparation step of preparing a resin composition for constituting the insulating layer, and a second lamination step of further laminating a metal foil layer on the insulating layer.

[0106] In the preparation step, a thermosetting resin, a thermoconductive filler, a surfactant, and an ion scavenger (and a curing agent and other components as needed) may be mixed to obtain the resin composition before curing. The mixing method is not particularly limited, but examples include using a planetary agitator, a universal mixer, a kneader, a hybrid mixer, etc.

[0107] In the first lamination step, an insulating layer is laminated onto the metal base layer. The lamination method is not particularly limited, but for example, an insulating layer may be made by curing a resin composition and laminating the insulating layer onto the metal base layer, or an insulating layer may be formed by applying a resin composition onto the metal base layer and curing the resin composition.

[0108] The method for curing the resin composition is not particularly limited, but one example is curing the resin composition by heat treatment. The heat treatment conditions, such as heating temperature and heating time, are set appropriately according to the type of resin and curing agent, the desired curing state, etc. The heat treatment may be carried out in one stage or in two stages. In addition, the resin composition may be pressed in the planar direction during heating. The sheet-like cured body may be a B-stage sheet in a semi-cured state or a C-stage sheet in a fully cured state.

[0109] In the second lamination step, a metal foil layer is further laminated on the insulating layer. The lamination method is not particularly limited, but for example, the metal foil layer may be laminated on the insulating layer. In the second lamination step, the laminate may be heated under pressure. The pressure conditions may be, for example, 5 to 20 MPa. The heating conditions may be, for example, 130 to 230°C. Furthermore, the pressurized heating time may be, for example, 1 to 10 hours.

[0110] 3. Circuit board The circuit board of this embodiment comprises a metal base layer, a metal circuit layer, and an insulating layer disposed between the metal base layer and the metal circuit layer. The insulating layer contains a resin and a thermally conductive filler, and the thermally conductive filler contains boron nitride aggregate particles and aluminum oxide particles. The ratio of aluminum oxide particles to boron nitride aggregate particles is 0.1 to 5.0, and the D50 particle diameter of the boron nitride aggregate particles is greater than 20 μm.

[0111] Figure 2 shows a schematic cross-sectional view of the circuit board of this embodiment. As shown in Figure 2, the circuit board 2 according to this embodiment comprises a metal base layer 21, an insulating layer 22 disposed on one surface of the metal base layer 21, and a metal circuit layer 23 disposed on the surface of the insulating layer 22 opposite to the metal base layer 21. In this circuit board 2, the metal circuit layer 23 is, for example, a circuit processed into a predetermined pattern. There are no particular limitations on the method for forming the circuit pattern on the metal circuit layer 23, but one example is etching.

[0112] The metal base layer and insulating layer in a circuit board can be the same as those in a laminate. Furthermore, the metal circuit layer in a circuit board can be the same as the metal foil layer in a laminate in terms of material, thickness, etc., except that a circuit is formed on it.

[0113] 4. Manufacturing method of circuit boards The method for manufacturing a circuit board according to this embodiment includes a circuit formation step of forming a circuit on the metal foil layer of the laminate. In the circuit formation step, for example, a resist layer may be formed on the metal foil layer, a pattern may be formed on the resist layer, and then the metal foil layer may be etched with an etching solution. The etching solution is not particularly limited, but for example, a sulfuric acid-hydrogen peroxide mixed solution can be used. Furthermore, an optional cleaning and drying step may be included after etching. [Examples]

[0114] The present invention will be described more specifically below using examples and comparative examples. The present invention is not limited in any way by the following examples.

[0115] [Preparation example: Synthesis of surfactants] The monomers used in the synthesis of the surfactants in the examples are shown below. First, 100 parts by mass of a (meth)acrylic monomer consisting of 5 mol% acrylic acid (manufactured by Toagosei Co., Ltd.), 0.1 mol% 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (ADEKA Corporation's "ADEKA Stab LA-82"), and 94.9 mol% benzyl methacrylate (Kyoeisha Chemical Co., Ltd.'s "Light Ester BZ") was added to an autoclave equipped with a stirrer. Next, 0.5 parts by mass of azobisisobutyronitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) (relative to 100 parts by mass of the total (meth)acrylic monomer) and 1000 parts by mass of a mixed solution of toluene (reagent grade) and 2-propanol (reagent grade) as a solvent (toluene:2-propanol = 7:3 (volume ratio)) were added, and the autoclave was purged with nitrogen. After that, the autoclave was heated in an oil bath at 65°C for 20 hours to carry out radical polymerization. After polymerization was complete, the mixture was degassed under reduced pressure at 120°C for 1 hour to obtain a surfactant with a weight-average molecular weight of 58,000.

[0116] Gas chromatography analysis revealed that the polymerization rate relative to 100% of the monomer charge was over 98%. From this, it was estimated that the ratio of each monomer unit in the surfactant was approximately the same as the charge ratio of the monomers.

[0117] Furthermore, the weight-average molecular weight of the obtained surfactant was determined as the weight-average molecular weight on a standard polystyrene basis using GPC (gel permeation chromatography). The measurement conditions were as follows. High-speed GPC system: Tosoh Corporation's "HLC-8020" Columns: One 6.0mm ID x 4.0cm column of Tosoh Corporation's "TSK guardcolumn MP (xL)" and two 7.8mm ID x 30.0cm columns of Tosoh Corporation's "TSK-GELMULTIPOREHXL-M" (16,000 theoretical plates), for a total of three columns (32,000 theoretical plates in total). Developing solvent: tetrahydrofuran Detector: RI (Differential Refractive Index Meter)

[0118] (Example 1) 80.4 parts by mass of a naphthalene-type epoxy compound (manufactured by DIC Corporation, HP-4032D) as a thermosetting resin and 9.9 parts by mass of a phenol novolac compound (manufactured by DIC Corporation, VH-4150) as a curing agent were stirred at 170°C to dissolve the curing agent in the thermosetting resin. To this, 45% by volume of boron nitride aggregate particles (manufactured by Denka Co., Ltd., D50 particle size 46 μm) and 20% by volume of aluminum oxide particles (manufactured by Denka Co., Ltd., D50 particle size 37.5 μm, spherical) were added as thermoconductive fillers, with the total resin composition being 100% by volume. Furthermore, 5.5 parts by mass of the surfactant synthesized in the above manufacturing example, 3.2 parts by mass of an ion scavenger (IXEPLAS-B1 (Zr, Bi-based), average particle size 0.4 μm, manufactured by Toagosei Co., Ltd.), 0.6 parts by mass of curing accelerator 1 (1B2PZ, manufactured by Shikoku Chemicals, Inc.), and 0.4 parts by mass of curing accelerator 2 (TPP, manufactured by Hokko Chemical Industry Co., Ltd.) were added and mixed in a hybrid mixer for 8 minutes to prepare a resin composition.

[0119] The obtained resin composition was applied to a polyethylene terephthalate (PET) film to a thickness of 180 μm after curing, and heated and dried at 60°C for 30 minutes and then at 100°C for 30 minutes to produce a semi-cured body.

[0120] The prepared cured body (insulating layer) was peeled from the PET film and placed on the roughened surface of a metal plate (2.0 mm thick copper plate) that would serve as the metal base layer. The roughened surface of a metal foil (500 μm thick copper foil) that would serve as the metal foil layer was then placed on top of the cured body, and the mixture was heated and cured at 180°C for 410 minutes while applying a surface pressure of 13.3 MPa using a press machine. This fully cured the insulating layer and obtained a laminate.

[0121] Next, after masking the predetermined areas with etching resist, the copper foil was etched using a sulfuric acid-hydrogen peroxide mixed solution as the etching solution. After removing the etching resist and washing and drying, a metal-based circuit board having a 20 mm diameter circular electrode (copper foil) was obtained.

[0122] (Examples 2-4) The resin composition, cured body, and metal-based circuit board were prepared in the same manner as in Example 1, except that the composition of the thermally conductive filler was changed as shown in Table 1.

[0123] (Comparative Example 1) 77.9 parts by mass of a naphthalene-type epoxy compound (DIC Corporation, HP-4032D) as a thermosetting resin and 9.6 parts by mass of a phenol novolac compound (DIC Corporation, VH-4150) as a curing agent were stirred at 170°C to dissolve the curing agent in the thermosetting resin. To this, 60 parts by volume of boron nitride aggregate particles (Denka Co., Ltd., D50 particle size 40 μm) were added as a thermoconductive filler, with the entire resin composition being 100 parts by volume. Furthermore, 8.2 parts by mass of the surfactant synthesized in the above production example, 3.2 parts by mass of an ion scavenger (IXEPLAS-B1), 0.7 parts by mass of curing accelerator 1 (1B2PZ, Shikoku Chemicals, Inc.), and 0.5 parts by mass of curing accelerator 2 (TPP, Hokko Chemical Industry Co., Ltd.) were added, and the mixture was stirred and mixed in a hybrid mixer for 6 minutes to prepare the resin composition.

[0124] Except for using the above-mentioned resin composition, a resin composition, a cured body, and a metal-based circuit board were prepared in the same manner as in Example 1.

[0125] (Measurement of particle size) The particle size of the thermal conductive filler was measured in accordance with the method described in JIS Z 8825:2013 "Particle Size Analysis - Laser Diffraction and Scattering Method". A laser diffraction scattering particle size analyzer (Microtrac-Bell, product name: "Microtrac MT-3300EXII") was used for the measurement. For the measurement, 2 mL of sodium hexametaphosphate aqueous solution and 200 mL of water were placed in a 300 mL beaker, 60 mg of thermal conductive filler was added, and the mixture was stirred at 100 rpm for 1 minute using a stirrer without homogenization, and the measurement was performed in the presence of aggregated particles. Water was used as the dispersant, and the refractive index was set to 1.33. The channel divisions were 129 divisions, ranging from 1408 μm to 0.021 μm. From the obtained volume-based cumulative distribution curve, the D50 particle size, D10 particle size, and D90 particle size were determined.

[0126] (Measurement of crushing strength) The crushing strength of boron nitride aggregated particles was measured in accordance with JIS R 1639-5:2007 "Fine ceramics - Method for measuring grain properties - Part 5: Single grain crushing strength". A microcompression tester (manufactured by Shimadzu Corporation, product name "MCT-210") was used for the measurement. Measurements were performed on 20 or more aggregated particles, and the value was calculated at a cumulative fracture rate of 63.2%.

[0127] (Measurement of copper foil peel strength) In accordance with JIS C 6481, the peel force (N / mm) of a copper foil laminate with metal cladding on both sides was measured when peeled at a width of 10 mm at a speed of 50 mm / min at a 90° angle. Specifically, a universal testing machine (manufactured by A&D Co., Ltd., product name: RTG-1210) was used to determine the peel strength when the insulating layer was peeled from the metal base layer at a 90° angle. The measurement was performed under the following conditions: test speed: 50 mm / min, load cell: 5 kN, measurement temperature: room temperature (20°C).

[0128] (Measurement of thermal conductivity) The thermal conductivity H of the insulating layer (unit: W / (m·K)) and the thermal diffusivity T (unit: m 2 ( / second), density D (unit: kg / m³) 3 The thermal diffusivity T was calculated using the formula H = T × D × C, with the specific heat capacity C (unit: J / (kg·K)) and ). The thermal diffusivity T was measured using the laser flash method on the evaluation laminated sheet. The measurement device used was a xenon flash analyzer (NETZSCH, product name: LFA447NanoFlash). The density D was measured by the Archimedes method. The specific heat capacity C was measured using a differential scanning calorimeter (Rigaku, device name: ThermoPlusEvoDSC8230).

[0129] (Measurement of dielectric breakdown voltage) The dielectric breakdown voltage of the laminate was measured in accordance with JIS C 2110. An AC voltage was applied to the test sample. The voltage applied to the test sample was increased from 0V at a rate (500V / s) such that dielectric breakdown occurred an average of 10 to 20 seconds after the start of voltage application. The voltage at which dielectric breakdown occurred was measured for five test samples, and the average value V5(kV) was obtained. Then, the dielectric breakdown voltage (kV / mm) was calculated by dividing the voltage V5(kV) by the thickness (mm) of the test sample. The above measurements were taken at a total of nine points within the plane of a 12cm x 12cm thermal conductive sheet: the four corners, the four midpoints of the four sides, and the center, and the average was calculated as the dielectric breakdown voltage.

[0130] [Table 1] * An insulating layer could not be formed, making various evaluations impossible.

[0131] Furthermore, in Example 1, polyhedral aluminum oxide particles were used instead of spherical aluminum oxide particles to fabricate the laminate and circuit board. As a result, the laminate and circuit board using polyhedral aluminum oxide particles had lower peel strength and a relatively lower dielectric breakdown voltage compared to the laminate and circuit board described in Example 1. In addition, the thermal conductivity was higher compared to Comparative Example 1.

[0132] Furthermore, in Example 1, instead of using boron nitride aggregated particles with a D50 particle diameter of 46 μm, boron nitride aggregated particles with a D50 particle diameter of 15 μm were used to fabricate the laminate and circuit board. As a result, the laminate and circuit board using boron nitride aggregated particles with a D50 particle diameter of 15 μm showed reduced thermal conductivity and peel strength compared to the laminate and circuit board described in Example 1. [Industrial applicability]

[0133] The laminate of the present invention has industrial applicability as a material for metal-based circuit boards. [Explanation of Symbols]

[0134] 1...Laminate, 11...Metal base layer, 12...Insulating layer, 13...Metal foil layer, 2...Circuit board, 21...Metal base layer, 22...Insulating layer, 23...Metal circuit layer.

Claims

1. It comprises a metal base layer and an insulating layer disposed on the metal base layer, The insulating layer comprises a resin and a thermally conductive filler. The thermally conductive filler comprises boron nitride aggregate particles and aluminum oxide particles. The ratio of the content of aluminum oxide particles to the content of boron nitride aggregate particles is 0.1 to 5.

0. The D50 particle diameter of the boron nitride aggregated particles is greater than 20 μm. Laminated structure.

2. The ratio of the D50 particle diameter of the aluminum oxide particles to the D50 particle diameter of the boron nitride aggregated particles is 0.2 to 2.

0. The laminate according to claim 1.

3. The D50 particle size of the aluminum oxide particles is 5 to 60 μm. The laminate according to claim 1.

4. The ratio of the D90 particle diameter to the D10 particle diameter of the aluminum oxide particles is 1.0 to 15. The laminate according to claim 1.

5. The crushing strength of the boron nitride aggregated particles is 6 to 20 MPa. The orientation index of the boron nitride aggregate particles is 5 to 20. The laminate according to claim 1.

6. The aluminum oxide particles include spherical aluminum oxide particles. The laminate according to claim 1.

7. The thickness of the insulating layer is 90 μm or more. The laminate according to claim 1.

8. It comprises a metal base layer, a metal circuit layer, and an insulating layer disposed between the metal base layer and the metal circuit layer, The insulating layer comprises a resin and a thermally conductive filler. The thermally conductive filler comprises boron nitride aggregate particles and aluminum oxide particles. The ratio of the content of aluminum oxide particles to the content of boron nitride aggregate particles is 0.1 to 5.

0. The D50 particle diameter of the boron nitride aggregated particles is greater than 20 μm. Circuit board.

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