Laminates and circuit boards

Abstract

The objective is to provide a laminate that is less prone to delamination of the insulating layer at high temperatures and has excellent thermal conductivity, and a circuit board obtained therefrom. [Solution] A laminate comprising a metal base layer, a metal foil layer, and an insulating layer disposed between the metal base layer and the metal foil layer, wherein the insulating layer contains a resin and a thermally conductive filler, the thermally conductive filler contains boron nitride aggregate particles, and the difference |α1-α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer at 25-100°C is 11 ppm / °C or less.

Description

Technical Field

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

Background Art

[0002] To form a hybrid integrated circuit by mounting electronic and electrical components such as semiconductor elements, various circuit boards have been put into practical use so far. 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 composition for a circuit board containing specific epoxy resin, curing agent, and thermal 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 disposed 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. In such laminates and circuit boards, the insulating layer may delaminate from the metal base layer due to differences in the coefficients of thermal expansion of each layer at high temperatures.

[0008] This invention has been made in view of the above-mentioned problems, and aims to provide a laminate that is less prone to peeling of the insulating layer at high temperatures and has excellent thermal conductivity, 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, a metal foil layer, and an insulating layer disposed between the metal base layer and the metal foil layer, The insulating layer comprises a resin and a thermally conductive filler. The thermally conductive filler comprises boron nitride aggregated particles, The difference |α1-α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer at 25-100°C is 11 ppm / °C or less. Laminated structure. [2] The three-dimensional surface roughness Sa1 of the surface of the metal base layer in contact with the insulating layer is 0.05 μm or more. The laminate described in [1]. [3] The aluminum content of the metal base layer is 70 to 95% by weight relative to the total amount of the metal base layer. The laminate described in [1] or [2]. [4] The crushing strength of the boron nitride aggregated particles is 5.0 MPa or more. A laminate as described in any one of items [1] to [3]. [5] The particle size D90 of the boron nitride aggregate particles is 50-150 μm. A laminate as described in any one of items [1] to [4]. [6] The content of the thermally conductive filler is 40 to 70% by volume relative to the total volume of the insulating layer. A laminate as described in any one of items [1] to [5]. [7] The difference |α1-α3| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α3 of the metal foil layer is 0.30 to 10 ppm / ℃. A laminate as described in any one of items [1] to [6]. [8] The glass transition temperature of the insulating layer is 150°C or higher. A laminate as described in any one of items [1] to [7]. [9] The insulating layer contains an inorganic ion scavenger containing at least one element selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn. The content of the inorganic ion scavenger is 0.1 to 50% by mass relative to the total amount of resin solids in the insulating layer. A laminate as described in any one of items [1] to [8].

[10] The insulating layer comprises a copolymer having an anionic group (meth)acrylic monomer unit A, a cationic group (meth)acrylic monomer unit B, and (meth)acrylic monomer units C other than (meth)acrylic monomer unit A and (meth)acrylic monomer unit B. The content of the copolymer is 0.01 to 10 parts by mass per 100 parts by mass of the thermally conductive filler. A laminate as described in any one of items [1] to [9].

[11] A metal base layer, a metal circuit layer, and an insulating layer disposed between the metal base layer and the metal circuit layer, wherein the insulating layer contains a polymer and a thermally conductive filler, the thermally conductive filler contains boron nitride agglomerated particles, [ the content of the boron nitride agglomerated particles is 40 to 70% by volume based on the total volume of the insulating layer, and the difference |α1 - α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer is 11 ppm / °C or less. Circuit board.

Effect of the Invention

[0010] According to the present invention, it is possible to provide a laminate in which peeling of the insulating layer hardly occurs at high temperatures and which has excellent thermal conductivity, and a circuit board obtained thereby.

Brief Description of the Drawings

[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, but the present invention is not limited thereto, and various modifications are possible without departing from the gist thereof. In the drawings, the same reference numerals will be given to the same elements, and overlapping descriptions will be 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 this embodiment comprises a metal base layer, a metal foil layer, and an insulating layer disposed between the metal base layer and the metal foil layer, wherein the insulating layer contains a resin and a thermally conductive filler, the thermally conductive filler contains boron nitride aggregate particles, and the difference |α1-α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer at 25-100°C is 11 ppm / °C or less.

[0014] Figure 1 shows a schematic cross-sectional view of the laminate of this embodiment. As shown in Figure 1, the laminate 1 comprises a metal base layer 11 and an insulating layer 12 disposed on one surface of the metal base layer 11, and may also 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 maintain an electrically insulated state from each other.

[0015] In addition, the laminate of this embodiment may be a laminate in which insulating layers 12 are arranged on both sides of the metal base layer 11, with the metal base layer 11 serving as the core.

[0016] In a laminate as shown in Figure 1, the thermal conductivity of the insulating layer can be improved by using boron nitride aggregate particles as a thermally conductive filler. However, it has been found that using boron nitride aggregate particles reduces the adhesion of the insulating layer, making it easier for delamination to occur between the metal base layer and the insulating layer due to thermal expansion at high temperatures.

[0017] Therefore, in this embodiment, the difference |α1-α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer at 25-100°C is defined. This makes it possible to provide a laminate that is less prone to delamination of the insulating layer at high temperatures and has excellent thermal conductivity, and a circuit board obtained therefrom. Each layer will be described in detail below.

[0018] 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.

[0019] 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 such as A1050, A5052, A4045, A2218, and A2219, copper, and copper alloys such as C1100, C1020, and C4621 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., so the present invention is particularly preferred.

[0020] When an aluminum alloy is used as such a metal base layer, the aluminum content is preferably 70-95% by weight, 75-94% by weight, 80-93% by weight, or 85-92% by weight relative to the total amount of the metal base layer. The present invention is preferred because an aluminum content within the above range makes it easier for a difference in thermal expansion to occur with the metal foil layer, such as copper.

[0021] Furthermore, the surface of the metal base layer may be subjected to surface treatments such as corona treatment or anodizing. The metal base layer may be composed of one type of metal material, or it may be composed of two or more types of metal materials. Also, the metal base layer may have a single-layer structure or a multi-layer structure.

[0022] The coefficient of thermal expansion α1 of the metal base layer is preferably 15-27 ppm / °C, 16-26 ppm / °C, 16.5-25 ppm / °C, 17-24 ppm / °C, 17.5-23 ppm / °C, 18-22 ppm / °C, or 18.5-21 ppm / °C. The present invention is preferred because the coefficient of thermal expansion α1 of the metal base layer being within the above range makes it easier for a difference in thermal expansion to occur with the metal foil layer such as copper.

[0023] Furthermore, the difference |α1-α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer at 25-100°C is 11 ppm / °C or less, preferably 0-10.5 ppm / °C, 0.30-10 ppm / °C, 0.50-9.0 ppm / °C, 0.75-8.0 ppm / °C, 1.0-7.0 ppm / °C, and 2.0-6.0 ppm / °C. The present invention is preferred when the difference |α1-α2| is 0 ppm / °C or more, as this makes delamination more likely at high temperatures. Also, when the difference |α1-α2| is 11 ppm / °C or less, the delamination resistance tends to be further improved.

[0024] Furthermore, the difference |α1-α3| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α3 of the metal foil layer is preferably 0.30-10 ppm / °C, 0.50-7.5 ppm / °C, 0.75-5.0 ppm / °C, and 1.00-3.0 ppm / °C. The present invention is preferred when the difference |α1-α3| is 0.30 ppm / °C or more, as this makes delamination more likely at high temperatures. Also, when the difference |α1-α3| is 10 ppm / °C or less, the delamination resistance tends to be further improved.

[0025] The coefficient of linear thermal expansion may be measured in accordance with JIS Z 2285. Furthermore, the coefficient of linear thermal expansion can be appropriately adjusted depending on the selected metal, or, in the case of an alloy, its composition.

[0026] The three-dimensional surface roughness Sa1 of the surface of the metal base layer in contact with the insulating layer is preferably 0.05 μm or more, 0.07 μm or more, 0.10 μm or more, 0.15 μm or more, 0.20 μm or more, and 0.25 μm or more. When the three-dimensional surface roughness Sa1 is 0.05 μm or more, the adhesion between the insulating layer and the metal base layer is further improved, and the peel resistance tends to be further improved. Alternatively, the three-dimensional surface roughness Sa1 is preferably 1.0 μm or less, 0.90 μm or less, 0.80 μm or less, 0.70 μm or less, and 0.60 μm or less. If the three-dimensional surface roughness Sa1 is high, the insulating layer may not be able to fully penetrate the valleys of the surface irregularities, creating voids, which may actually be the starting point for a decrease in adhesion. However, when the three-dimensional surface roughness Sa1 is 1.0 μm or less, the insulating layer can penetrate into the valleys of the surface irregularities, which tends to further improve peel resistance.

[0027] The three-dimensional surface roughness Sz1 of the surface of the metal base layer in contact with the insulating layer is preferably 0.1 to 15 μm, 0.3 to 12.5 μm, 0.5 to 10 μm, 0.8 to 7.5 μm, or 1.0 to 5.0 μm. When the three-dimensional surface roughness Sz1 is within the above range, peel resistance tends to be further improved, similar to Sa described above.

[0028] The three-dimensional surface roughness Sdr1 of the surface of the metal base layer in contact with the insulating layer is preferably 0.001 to 1.000, 0.005 to 0.900, 0.010 to 0.800, or 0.015 to 0.850. When the three-dimensional surface roughness Sdr1 is within the above range, peel resistance tends to be further improved, similar to Sa described above.

[0029] In this embodiment, instead of two-dimensional surface roughness which measures only irregularities along a specific direction, three-dimensional surface roughness which measures the irregularities of the surface is used. By using three-dimensional surface roughness, the roughness of the surface as a whole can be evaluated, and a surface that suppresses delamination can be represented more appropriately. Three-dimensional surface roughness can be measured in accordance with ISO 25178. In this specification, Sa is a parameter that indicates the arithmetic mean height of the three-dimensional surface, Sz is a parameter that indicates the maximum height of the three-dimensional surface, and Sdr is a parameter that indicates how much the unfolded area (surface area) of the defined region has increased relative to the area of ​​the defined region.

[0030] Furthermore, there are no particular limitations on the method for adjusting the three-dimensional surface roughness Sa, Sz, and Sdr. For example, it may be adjusted by polishing treatments such as surface polishing, lapping, and buffing, as well as by chemical treatments such as pickling and etching, and surface treatments such as plating and vapor deposition.

[0031] The value of the difference in linear expansion coefficients |α1-α2| (|α1-α2| / Sa1) relative to the three-dimensional surface roughness Sa1 is preferably 5 to 100, 7.5 to 90, 10 to 80, 12.5 to 70, or 15 to 60. When the value (|α1-α2| / Sa1) is 5 or greater, the three-dimensional surface roughness Sa1 tends to be relatively larger than the difference in linear expansion coefficients |α1-α2|, which tends to improve the adhesion between the insulating layer and the metal base layer and further improve peel resistance. Furthermore, there is no particular upper limit to the value (|α1-α2| / Sa1), but when it is 100 or less, the insulating layer can penetrate into the valleys of the surface irregularities, which tends to further improve peel resistance.

[0032] The thickness of the metal base layer is preferably 0.1 to 5.0 mm, 0.3 to 4.0 mm, 0.5 to 3.0 mm, or 1.0 to 2.5 mm. When the thickness of the metal base layer is within the above range, the mechanical strength and heat dissipation characteristics of the laminate tend to improve.

[0033] 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.

[0034] The insulating layer may be a cured resin composition, a semi-cured state (Stage B), or a fully cured state (Stage C).

[0035] The glass transition temperature of the insulating layer is preferably 100°C or higher, 125°C or higher, 150°C or higher, and 175°C or higher. A glass transition temperature of 100°C or higher tends to suppress softening of the insulating layer and the resulting delamination at high temperatures. Furthermore, there is no particular upper limit to the glass transition temperature of the insulating layer, but for example, it may be 300°C or lower, 250°C or lower, 225°C or lower, and 200°C or lower.

[0036] 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.

[0037] 1.2.1. Resin Examples of resins include silicone resins, epoxy resins, phenolic resins, cyanate resins, melamine resins, urea resins, polyimide resins, and unsaturated polyester resins.

[0038] 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."

[0039] In other words, epoxy resins are resins obtained by the reaction of epoxy compounds with a curing agent, for example; phenolic resins are resins obtained by the reaction of resol or novolac with a curing agent; and cyanate resins are resins obtained by the homopolymerization or copolymerization of cyanate compounds. The same applies to silicone resins, melamine resins, urea resins, polyimide resins, and unsaturated polyester resins.

[0040] Among these, epoxy resin is preferred. Using such a resin tends to improve peel resistance, insulation reliability, and thermal conductivity.

[0041] 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.

[0042] Among these, epoxy compounds having a naphthalene skeleton, such as bisphenol-type epoxy compounds, naphthalene-type epoxy compounds, naphthalene skeleton-modified novolac-type epoxy compounds, and naphthylene ether-type epoxy compounds, are preferred.

[0043] 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. Among these, phenol compounds are preferred.

[0044] 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, novolac type phenol 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.

[0045] The resin content may preferably be 75% 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. When the resin content is 75% by mass or more, peel resistance tends to be further improved and insulation reliability tends to be further improved. Alternatively, the resin content may preferably be 99% by mass or less, 98% by mass or less, or 95% by mass or less, relative to the total amount of the insulating layer. When the resin content is 99% by mass or less, thermal conductivity tends to be further improved.

[0046] In this embodiment, "resin solids in the insulating layer" refers to the components of the insulating layer excluding the thermally conductive filler.

[0047] 1.2.2. Thermally conductive fillers The thermally conductive filler includes boron nitride aggregate particles and may include other thermally conductive fillers as needed. The use of boron nitride aggregate particles further improves thermal conductivity.

[0048] In this embodiment, boron nitride aggregated particles are used. "Aggregation" refers to the state in which primary particles aggregate 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 aggregated 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 aggregated particles, the proportion of primary particles lying flat in the plane direction of the laminate is reduced, and the thermal resistance in the thickness direction is decreased. The secondary particles may be spherical or irregularly shaped lumps.

[0049] While larger boron nitride aggregate particles are preferable from the standpoint of thermal conductivity, an increase in coarse particles can lead to a decrease in insulation reliability.

[0050] From this perspective, the D10 particle size of the boron nitride aggregated particles is preferably 1.0 to 25 μm, 1.5 to 20 μm, 2.5 to 15 μm, or 5.0 to 10 μm.

[0051] The D50 particle size of the boron nitride aggregated particles is preferably 35-75 μm, 40-70 μm, 45-65 μm, or 50-60 μm.

[0052] The D90 particle size of the boron nitride aggregated particles is preferably 50-150 μm, 55-125 μm, 65-100 μm, or 70-90 μm.

[0053] The ratio of the D90 particle diameter to the D10 particle diameter (D90 / D10) is preferably 5.0 to 20, 7.5 to 17.5, and 10 to 15.

[0054] When the D10 particle diameter, D50 particle diameter, D90 particle diameter, and ratio (D90 / D10) are all within the above ranges, thermal conductivity and insulation reliability tend to improve.

[0055] 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.

[0056] The crushing strength of the boron nitride aggregate particles is preferably 5.0 MPa or higher, 6.0 to 20 MPa, 7.0 to 18 MPa, 8.0 to 16 MPa, and 9.0 to 14 MPa. A crushing strength of 5.0 MPa or higher tends to suppress the decrease in thermal conductivity caused by the pulverization of the boron nitride aggregate particles during the pressurization step of the laminate manufacturing method described later.

[0057] 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.

[0058] The content of boron nitride aggregated particles is preferably 40-70% by volume, 45-65% by volume, or 50-60% by volume, relative to 100% by volume of the insulating layer. When the content of boron nitride aggregated particles is 70% by volume or less, peel resistance tends to be further improved and insulation reliability tends to be further improved. Also, when the content of boron nitride aggregated particles is 40% by volume or more, thermal conductivity tends to be further improved.

[0059] Other thermally conductive fillers are not particularly limited, but examples include aluminum oxide, aluminum nitride, silicon nitride, silicon oxide, zinc oxide, silica, aluminum hydroxide, magnesium oxide, and carbon.

[0060] 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.

[0061] 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.

[0062] The total content of the thermally conductive filler is preferably 40-70% by volume, 45-65% by volume, or 50-60% by volume relative to the total volume of the insulating layer. A thermally conductive filler content of 40% by volume or more tends to improve thermal conductivity. Conversely, a thermally conductive filler content of 70% by volume or less tends to improve insulation reliability.

[0063] Furthermore, the content of resin solids excluding thermally conductive fillers is 30-60% by volume, 35-55% by volume, and 40-50% by volume, relative to the total volume of the insulating layer.

[0064] 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 dispersibility of thermally conductive fillers and improvement of thermal conductivity.

[0065] 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").

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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 groups in which a halogen group is bonded to the carbon atom at the α position of a carboxyl group.

[0071] 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.

[0072] 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 methylacrylate, 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 methylacrylate, and 2-acrylamido-2-methylpropanesulfonic acid, and more preferably acrylic acid.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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).

[0078] 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.

[0079] 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.

[0080] Examples of (meth)acrylic monomers having a siloxane group include α-butyl-ω-(3-methacryloxypropyl)polydimethylsiloxane.

[0081] 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.

[0082] Examples of (meth)acrylic monomers having a phosphate ester group include (meth)acryloyloxyethyldialkyl phosphates.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 contained in 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 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The surfactant content is preferably 2.0% by mass or more, 3.0% by mass or more, and 4.0% 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, 9.0% by mass or less, and 8.0% by mass or less, relative to the total amount of resin solids in the insulating layer. A surfactant content of 10% by mass or less tends to further improve peel resistance. Furthermore, a surfactant content of 2.0% by mass or more tends to further improve insulation reliability.

[0096] 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.

[0097] 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.

[0098] The ion scavenger may contain, for example, at least one element selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn, or it may contain at least one element 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.

[0099] 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.).

[0100] 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.).

[0101] 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.).

[0102] 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.

[0103] 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.

[0104] The ion scavenging agent content is preferably 1.0 to 10% by mass, 1.5 to 7.5% by mass, 2.0 to 5.0% by mass, or 2.5 to 4.0% 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.

[0105] 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.

[0106] 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, triphenylphosphinetriphenylborane, and tetraphenylphosphonium dicyanamide. Examples include phosphorus compounds such as tetraphenylphosphonium tetra(4-methylphenyl)borate; and imidazole compounds such as 1-benzyl-2-phenylimidazole, 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.

[0107] The content of the curing accelerator is preferably 0.10 to 2.00% by mass, 0.50 to 1.75% by mass, and 0.75 to 1.50% by mass, relative to the total amount of resin solids in the insulating layer.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] The coefficient of thermal expansion α3 of the metal foil layer is preferably 15-25 ppm / °C, 16-22.5 ppm / °C, 16.5-20 ppm / °C, or 17-19 ppm / °C. The present invention is preferred because the coefficient of thermal expansion α3 of the metal foil layer being within the above range makes it easier for a difference in thermal expansion to occur with the metal base layer such as aluminum or an aluminum alloy.

[0112] 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.

[0113] 2. Method for manufacturing laminates The manufacturing method of the laminate according to this embodiment is not particularly limited as long as it includes a first lamination step of laminating an insulating layer on a metal base layer and a second lamination step of further laminating a metal foil layer on the insulating layer, and may optionally include a preparation step of preparing a resin composition for constituting the insulating layer.

[0114] In the preparation process, the resin composition before curing may be obtained by mixing monomers, curing agents, and thermally conductive fillers that make up the resin, as well as optional components such as surfactants and ion scavengers. The mixing method is not particularly limited, but examples include using a planetary agitator, a universal mixing agitator, a kneader, a hybrid mixer, etc.

[0115] 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.

[0116] The method for curing the resin composition is not particularly limited, but one example is a method of curing the resin composition by heating. The heating conditions, such as the heating temperature and heating time, are set appropriately according to the type of resin and curing agent, the desired curing state, etc. The heating treatment may be carried out in one stage or in multiple stages. In addition, the resin composition may be pressed in the planar direction during heating. The insulating layer may be a B-stage sheet in a semi-cured state or a C-stage sheet in a fully cured state.

[0117] For example, in the first lamination step, a resin composition may be applied in a sheet-like manner onto a release sheet, heated to form an insulating layer for the B stage, the insulating layer for the B stage may be laminated onto a metal base layer, and then heated under pressure.

[0118] In the second lamination process, a metal foil layer is further laminated on the insulating layer. During lamination, the metal base layer, insulating layer, and metal foil layer may be heated under pressure. At this time, the insulating layer of the B stage may be fully cured. The pressurizing conditions may be, for example, 5 to 20 MPa. The heating conditions may be, for example, 130 to 230°C. Furthermore, the pressurizing and heating time may be, for example, 1 to 10 hours.

[0119] 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, wherein the insulating layer contains a polymer and a thermally conductive filler, the thermally conductive filler contains boron nitride aggregate particles, the content of boron nitride aggregate particles is 40 to 70 volume percent of the total volume of the insulating layer, and the difference |α1-α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer is 11 ppm / ℃ or less.

[0120] 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.

[0121] 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.

[0122] 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 film may be formed on the metal foil layer, the resist film may be formed into a desired pattern, and then the metal foil layer may be etched with an etching solution. This makes it possible to form a circuit of any shape. 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]

[0123] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples. Unless otherwise specified, the measurement temperature will be 25°C. The unit of the coefficient of linear expansion will be ppm / °C.

[0124] [Preparation example: Synthesis of surfactants] 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) (toluene:2-propanol = 7:3 (volume ratio)) were added as initiators, and the autoclave was purged with nitrogen. Subsequently, 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 20,000.

[0125] 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.

[0126] 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)

[0127] (Example 1) 80.26% by mass of a naphthalene-type epoxy compound (HP-4032D, manufactured by DIC Corporation, epoxy compound B) and 9.93% by mass of a phenol novolac compound (VH-4150, manufactured by DIC Corporation, curing agent) were stirred at 170°C to dissolve the curing agent. In response, a resin composition was prepared by adding boron nitride aggregated particles (Denka Co., Ltd., D50 particle size 40 μm, thermal conductivity 150 W / m·K, aggregated BN) as a thermally conductive filler, 8.66 mass% of an ion scavenger (IXEPLAS-B1 (Zr, Bi-based), average particle size 0.4 μm, manufactured by Toagosei Co., Ltd.), 0.68 mass% of a curing accelerator A (1-benzyl-2-phenylimidazole (1B2PZ), manufactured by Shikoku Chemicals Co., Ltd.), and 0.48 mass% of a curing accelerator B (triphenylphosphine (TPP), manufactured by Hokko Chemical Co., Ltd.). The mixture was stirred and mixed in a planetary mixer for 15 minutes. The amount of boron nitride aggregated particles was set to 60 volume% of the layer volume of the insulating layer.

[0128] The obtained resin composition was applied to a polyethylene terephthalate (PET) film to a thickness of 200 μm after curing, and heated and dried at 100°C for 50 minutes to produce a semi-cured body.

[0129] The prepared cured body (insulating layer) was peeled from the PET film and placed on the roughened surface of a metal plate (1.5 mm thick aluminum plate: A4045 material) that would serve as the metal base layer. A metal foil (500 μm thick copper foil: C1100 material) 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 10 MPa using a press machine. This fully cured the insulating layer and obtained a laminate.

[0130] Next, a circular resist film with a diameter of 20 mm was formed on the metal foil layer, and the metal foil layer was etched using a sulfuric acid-hydrogen peroxide mixed solution as the etching solution. After removing the resist film and washing and drying, a metal-based circuit board having a circular electrode (copper foil) with a diameter of 20 mm was obtained.

[0131] (Examples 2-7, Comparative Examples 1-5) As shown in Table 1, laminates and circuit boards were obtained in the same manner as in Example 1 or 2, except that the materials of each component used and the metal base layer were changed.

[0132] The metal materials used in the metal base layer shown in Table 1 are as follows, and their definitions conform to JIS H 3100 (copper and copper alloy sheets and strips) and JIS H 4000 (aluminum and aluminum alloy sheets and strips). C1100 Tough Pitch Copper A1050: Aluminum content 99.5% or higher A4050 Al-Si alloy, aluminum content approximately 90% A2218 Al-Cu-Mg alloy, aluminum content approximately 95% A2219 Al-Cu-Mg alloy, aluminum content approximately 95%. A5052 Al-Mg alloy, aluminum content approximately 96-98%.

[0133] In Comparative Example 2, A1050 material that had been buffed to adjust its roughness was used as the metal base layer.

[0134] The three-dimensional surface roughness Sa, Sz, and Sdr of the metal materials used in the metal base layer and metal foil layer were measured in accordance with ISO 25178 using a shape analysis laser microscope (VK-X1000 Series).

[0135] (Measurement of particle size) The particle size of the thermally 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 thermally 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.

[0136] The boron nitride aggregated particles used in the examples had particle diameters of 6 μm for D10, 42 μm for D50, and 76 μm for D90.

[0137] (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%.

[0138] (Coefficient of linear expansion) Based on JIS Z 2285, the linear thermal expansion coefficients α1 of the insulating layer, α2 of the metal base layer, and α3 of the metal foil layer were measured.

[0139] (Glass transition temperature of the insulating layer) The B-stage insulating layer prepared as described above was peeled from the PET film, sandwiched between the release surfaces of a PET film treated with a release agent, and further sandwiched between metal plates (2.0 mm thick copper plates). The sheet was then heated and cured at 180°C for 410 minutes under a surface pressure of 10 MPa using a press machine until completely cured. The resulting insulating layer was cut out with a diamond cutter to obtain a plate-shaped measurement sample measuring 0.13 mm × 5 mm × 40 mm. The glass transition temperature of this measurement sample was measured using the DMA method (JIS K 0129 (2005)) with a dynamic viscoelasticity analyzer (T&A Instruments, "RSA 3"). Measurements were taken in the temperature range of 40°C to 300°C under conditions of a frequency of 1 Hz and a heating rate of 7.5°C / min.

[0140] (Thermal conductivity) The B-stage-shaped insulating layer prepared as described above was heat-cured at 180°C for 410 minutes under a surface pressure of 10 MPa using a press machine to produce an insulating layer sheet with dimensions of 10 mm in length, 10 mm in width, and 0.5 mm in thickness. The thermal diffusivity α was measured using the laser flash method, and the thermal conductivity λ was evaluated using the following formula. λ = α × Cp × ρ

[0141] In the above formula, the specific heat Cp was calculated from DSC measurements. Furthermore, the specific gravity ρ of the laminate was calculated using the following formula by measuring the weight of the sheet in air and in distilled water at a temperature of 25°C and a pressure of 1013 hPa using the specific gravity measurement kit AD-1653 (product name) from A&D Co., Ltd. ρ = A / (AB) × (ρ0 - d) + d (In the formula, A is the mass of the insulating layer in air, B is the mass of the insulating layer in distilled water, ρ0 is the density of distilled water, and d is the density of air.)

[0142] (Peel resistance test) The metal-based circuit board having a 20 mm diameter circular electrode (copper foil) obtained as described above was heated to a predetermined temperature and then heated in a solder bath for a predetermined time. After cooling to room temperature, it was observed using an ultrasonic flaw detection device (Fine SAT III) to check for the presence or absence of delamination. Processing conditions A: Solder bath temperature 285°C, heating time 5 minutes Processing conditions B: Solder bath temperature 200°C, heating time 5 minutes The evaluation result when no delamination was observed under both treatment conditions A and B is denoted as A, and the evaluation result when no delamination was observed under treatment condition B only is denoted as B.

[0143] (Insulation reliability: Reliability evaluation by high-temperature, high-pressure bias test (Vt)) For the laminate obtained as described above, the time until dielectric breakdown was measured under test conditions of applying a DC voltage of 10kV between the metal foil layer and the metal base layer in a 150°C environment. The time until dielectric breakdown was defined as the time from the start of voltage application until the leakage current value measured by the withstand voltage tester exceeded 10mA.

[0144] [Table 1] -:Not measured

[0145] [Table 2] -:Not measured [Industrial applicability]

[0146] The laminate of the present invention has industrial applicability as a material for metal-based circuit boards. [Explanation of Symbols]

[0147] 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, a metal foil layer, and an insulating layer disposed between the metal base layer and the metal foil layer, The insulating layer comprises a resin and a thermally conductive filler. The thermally conductive filler comprises boron nitride aggregated particles, The difference between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer at 25 to 100°C, |α1 - α2|, is 11 ppm / °C or less. Laminated structure.

2. The three-dimensional surface roughness Sa1 of the surface of the metal base layer in contact with the insulating layer is 0.05 μm or more. The laminate according to claim 1.

3. The aluminum content of the metal base layer is 70 to 95% by weight relative to the total amount of the metal base layer. The laminate according to claim 1.

4. The crushing strength of the boron nitride aggregated particles is 5.0 MPa or higher. The laminate according to claim 1.

5. The particle size D90 of the boron nitride aggregated particles is 50 to 150 μm. The laminate according to claim 1.

6. The content of the thermally conductive filler is 40 to 70% by volume relative to the total volume of the insulating layer. The laminate according to claim 1.

7. The difference |α1-α3| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α3 of the metal foil layer is 0.30 to 10 ppm / °C. The laminate according to claim 1.

8. The glass transition temperature of the insulating layer is 150°C or higher. The laminate according to claim 1.

9. The insulating layer contains an inorganic ion scavenger containing at least one element selected from the group consisting of Al, Mg, Bi, Zr, Sb, and Zn. The content of the inorganic ion scavenger is 0.1 to 50% by mass relative to the total amount of resin solids in the insulating layer. The laminate according to claim 1.

10. The insulating layer comprises a copolymer having an anionic group (meth)acrylic monomer unit A, a cationic group (meth)acrylic monomer unit B, and (meth)acrylic monomer units C other than (meth)acrylic monomer unit A and (meth)acrylic monomer unit B. The content of the copolymer is 0.01 to 10 parts by mass per 100 parts by mass of the thermally conductive filler. The laminate according to claim 1.

11. 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 polymer and a thermally conductive filler. The thermally conductive filler comprises boron nitride aggregated particles, The content of the boron nitride aggregated particles is 40 to 70% by volume relative to the total volume of the insulating layer. The difference |α1 - α2| between the linear expansion coefficient α1 of the metal base layer and the linear expansion coefficient α2 of the insulating layer is 11 ppm / °C or less. Circuit board.

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