Resin-coated metal foil and laminates

Abstract

To provide a resin-coated metal foil that can achieve both low thermal resistance and high insulation reliability. [Solution] The resin-coated metal foil 1 comprises a metal layer 2, a first resin layer 31 derived from a first resin composition, and a second resin layer 32 derived from a second resin composition. The ratio of the thickness of the first resin layer 31 to the thickness of the second resin layer 32 is less than 10%. The second resin composition contains an inorganic filler (C2) including a thermally conductive filler (C2-1). The content of the thermally conductive filler (C2-1) is 80 to 97% by mass of the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the 1 to 25 μm range and the 0.05 to 1 μm range in the particle size distribution. The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) is less than the content of the inorganic filler (C2), or does not contain an inorganic filler (C1). The maximum height roughness of the metal layer 2 is 2.3 μm or less.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to a resin-coated metal foil and a laminate, and more specifically to a resin-coated metal foil comprising a metal layer and a resin layer, and a laminate comprising a metal layer and an insulating layer.

BACKGROUND ART

[0002] Patent Document 1 discloses a resin-coated metal foil comprising a metal foil, a first resin layer, and a second resin layer formed from a thermosetting resin composition in a semi-cured state. The first resin layer is a layer formed by depositing a polyimide composition containing a polyimide resin having an imide ring closure ratio of 80% or more and a weight average molecular weight of 30000 or more. The aforementioned thermosetting resin composition contains an epoxy resin and a thermoplastic resin having a weight average molecular weight of 30000 or more.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] In the prior art, as a method for reducing the thermal resistance of the insulating layer formed by curing the resin layer of the resin-coated metal foil of Patent Document 1, addition of a thermally conductive filler to the resin layer may be mentioned. However, the more the thermally conductive filler is filled into the resin layer, the lower the thermal resistance of the insulating layer formed by curing the resin layer becomes, but on the other hand, there is a risk that the insulation reliability may decrease. That is, the insulating layer formed by curing the resin layer of the resin-coated metal foil of Patent Document 1 has a problem that it is difficult to achieve both low thermal resistance and high insulation reliability at the same time.

[0005] An object of the present disclosure is to provide a resin-coated metal foil and a laminate that can achieve both low thermal resistance and high insulation reliability. [Means for solving the problem]

[0006] A resin-coated metal foil according to one aspect of the present disclosure comprises a metal layer, a first resin layer containing a semi-cured product or a cured product of a first resin composition superimposed on the metal layer, and a second resin layer containing a second resin composition or a semi-cured product of a second resin composition superimposed on the first resin layer. The thickness of the first resin layer is 0.1 μm or more and less than 5 μm. The ratio of the thickness of the first resin layer to the thickness of the second resin layer is less than 10%. The first resin composition contains an epoxy resin (A1) and a curing agent (B1). The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content of the thermally conductive filler (C2-1) is 80% by mass or more and 97% by mass or less of the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the ranges of greater than 1 μm and 25 μm or less, and 0.05 μm or more and 1 μm or less, in the volume-based particle size distribution obtained by laser diffraction and scattering. The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of the inorganic filler (C2) relative to the total amount of the second resin composition, or the inorganic filler (C1) is not contained. The maximum height roughness (Rz) of the surface of the metal layer that overlaps with the first resin layer is 2.3 μm or less.

[0007] A laminate according to one aspect of the present disclosure comprises a metal layer, a first insulating layer containing a cured product of a first resin composition superimposed on the metal layer, and a second insulating layer containing a cured product of a second resin composition superimposed on the first insulating layer. The thickness of the first insulating layer is 0.1 μm or more and less than 5 μm. The ratio of the thickness of the first insulating layer to the thickness of the second insulating layer is less than 10%. The first resin composition contains an epoxy resin (A1) and a curing agent (B1). The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content of the thermally conductive filler (C2-1) is 80% by mass or more and 97% by mass or less of the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the ranges of greater than 1 μm and 25 μm or less, and 0.05 μm or more and 1 μm or less, in the volume-based particle size distribution obtained by laser diffraction and scattering. The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of the inorganic filler (C2) relative to the total amount of the second resin composition, or the inorganic filler (C1) is not contained. The maximum height roughness (Rz) of the surface of the metal layer that overlaps with the first insulating layer is 2.3 μm or less. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide resin-coated metal foils and laminates that can achieve both low thermal resistance and high insulation reliability. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing a resin-coated metal foil according to an embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing a laminate according to the embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view showing the evaluation laminate of the embodiment. [Figure 4] Figure 4 is a schematic plan view showing the test pattern of the embodiment. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure are described below. However, this disclosure is not limited to the embodiments described below. The embodiments described below are only a part of the various embodiments of this disclosure, and various modifications are possible depending on the design, as long as the objectives of this disclosure are achieved. The figures referenced below are all schematic diagrams, and the dimensional ratios of the components in the figures do not necessarily reflect the actual dimensional ratios. The mechanisms of operation of the embodiments may be described below, but the descriptions of the mechanisms of operation include those based on speculation, and this disclosure is not bound by the descriptions of the mechanisms of operation below.

[0011] 1. Overview As mentioned above, the more thermally conductive fillers are added to the resin composition, the lower the thermal resistance of the insulating layer formed by the resin composition may be. On the other hand, this may reduce the insulating reliability of the formed insulating layer.

[0012] One of the causes of reduced insulation reliability is the migration of ionic impurities along the surface of thermally conductive fillers within the resin composition. Therefore, means to restrict the migration of ionic impurities are required.

[0013] Therefore, based on the above-mentioned causes, the inventors diligently conducted research and succeeded in developing a resin-coated metal foil and a laminate formed from this resin-coated metal foil that can achieve both low thermal resistance and high insulation reliability.

[0014] The resin-coated metal foil 1 according to the embodiment of this disclosure comprises a metal layer 2, a first resin layer 31 containing a semi-cured or cured product of the first resin composition superimposed on the metal layer 2, and a second resin layer 32 containing a second resin composition or a semi-cured product of the second resin composition superimposed on the first resin layer 31. The thickness of the first resin layer 31 is 0.1 μm or more and 5 μm. The ratio of the thickness of the first resin layer 31 to the thickness of the second resin layer 32 is less than 10%. The first resin composition contains an epoxy resin (A1) and a curing agent (B1). The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content of the thermally conductive filler (C2-1) is 80% by mass or more and 97% by mass or less of the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the ranges greater than 1 μm and 25 μm or less, and 0.05 μm or more and 1 μm or less, in the volume-based particle size distribution determined by laser diffraction and scattering. The first resin composition contains inorganic filler (C1), and the content of inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of inorganic filler (C2) relative to the total amount of the second resin composition, or it does not contain inorganic filler (C1). The maximum height roughness (Rz) of the surface of the metal layer 2 overlapping with the first resin layer 31 is 2.3 μm or less.

[0015] The resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1, having the above-described configuration, can achieve both low thermal resistance and high insulation reliability. This is presumed to be due to the following mechanism.

[0016] The first resin layer 31 is interposed between the metal layer 2 and the second resin layer 32. Further, the first resin composition contains an inorganic filler (C1), and the content ratio of the inorganic filler (C1) relative to the total amount of the first resin composition is smaller than the content ratio of the inorganic filler (C2) relative to the total amount of the second resin composition, or the first resin composition contains no inorganic filler (C1). As a result, migration of ionic impurities generated in the second resin layer 32 from the second resin layer 32 to the metal layer 2 can be restricted. Therefore, the resin-attached metal foil 1 including the first resin layer 31 and the laminate 10 formed from the resin-attached metal foil 1 can have high insulation reliability.

[0017] The second resin composition forming the second resin layer 32 contains an inorganic filler (C2) including a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content ratio of the thermally conductive filler (C2-1) is 80 mass% or more and 97 mass% or less relative to the total amount of the second resin composition. As a result, the thermal resistance of the resin-attached metal foil 1 including the second resin layer 32 and the laminate 10 formed from the resin-attached metal foil 1 can be reduced.

[0018] The ratio of the thickness of the first resin layer 31 to the thickness of the second resin layer 32 is less than 10%, and the thickness of the first resin layer 31 is 0.1 μm or more and 5 μm or less. That is, the proportion of the second resin layer 32, which can have high thermal conductivity with respect to the entire resin-attached metal foil 1, is large. Thereby, the resin-attached metal foil 1 including the first resin layer 31 and the laminate 10 formed from the resin-attached metal foil 1 can have improved insulation reliability and reduced thermal resistance.

[0019] The thermally conductive filler (C2-1) has at least one peak in each of the range of more than 1 μm and 25 μm or less and the range of 0.05 μm or more and 1 μm or less in the volume-based particle size distribution measured by a laser diffraction / scattering method. Therefore, the thermally conductive filler (C2-1) in the second resin layer 32 can be in thermal contact. Accordingly, the thermal resistance of the resin-attached metal foil 1 including the second resin layer 32 and the laminate 10 formed from the resin-attached metal foil can be reduced.

[0020] The maximum height roughness (Rz) of the surface of the metal layer 2 that overlaps with the first resin layer 31 is 2.3 μm or less. As a result, the metal layer 2 and the second resin layer 32 are not brought close to each other, and the movement of ionic impurities can be restricted by the first resin layer 31. Therefore, the resin-attached metal foil 1 and the laminate 10 formed from the resin-attached metal foil 1 can have high insulation reliability.

[0021] From the above, the resin-attached metal foil 1 according to the embodiment of the present disclosure and the laminate 10 formed from the resin-attached metal foil 1 can achieve both low thermal resistance and high insulation reliability.

[0022] Further, the thermal resistance between two cross sections of an object having a thickness T and a cross-sectional area A at the two cross sections facing each other in the thickness direction is calculated from the following formula.

[0023] (Thermal resistance) = (Thickness T) / {(Thermal conductivity) × (Cross-sectional area A)} Therefore, from the above formula, the thermal conductivity and the thermal resistance of an object having a certain dimension are in a reciprocal relationship. Accordingly, reducing thermal resistance is synonymous with increasing thermal conductivity. That is, the resin-attached metal foil 1 according to the embodiment of the present disclosure and the laminate 10 formed from the resin-attached metal foil 1 can be rephrased as being capable of achieving both high thermal conductivity and high insulation reliability.

[0024] The maximum height roughness (Rz) is defined in JIS B 0601:2013, and indicates the surface roughness of the target object.

[0025] 2. Details Hereinafter, the resin-attached metal foil 1 and the laminate 10 according to the embodiment will be described with reference to the drawings. Note that the arrows indicating the respective directions in the respective drawings are not intended to define the directions when the resin-attached metal foil 1 and the laminate 10 are used, but are merely described for easy understanding of the description and have no substantial meaning. The X axis, the Y axis, and the Z axis are orthogonal to each other. Hereinafter, viewing along the Z axis is referred to as XY plan view.

[0026] 2.1 Resin-attached metal foil The resin-coated metal foil 1 according to this embodiment has thickness in the Z-axis direction and is a thin film that extends in the X-axis and Y-axis directions (see Figure 1). The resin-coated metal foil 1 comprises a metal layer 2, a first resin layer 31, and a second resin layer 32. The first resin layer 31 and the second resin layer 32 are sometimes collectively referred to as the resin layer 3.

[0027] 〔composition〕 (metal layer) The metal layer 2 is located on at least one of the outermost layers in the thickness direction of the resin-coated metal foil 1. Examples of the metal layer 2 include metal foil and metal film.

[0028] The material of the metal foil and metal film is not particularly limited, but examples include copper (Cu), aluminum (Al), stainless steel, nickel (Ni), and nichrome. The manufacturing method of the metal foil and metal film is not particularly limited, but examples include electrolytic methods and rolling methods. The metal film may also be formed by plating, steaming, etc.

[0029] The maximum height roughness (Rz) of the surface of the metal layer 2 overlapping with the first resin layer 31 is 2.3 μm or less. If this maximum height roughness exceeds 2.3 μm, the protruding portion of the metal layer 2 may pierce and become embedded in the first resin layer 31. This may cause the metal layer 2 and the second resin layer 32 to come into contact, potentially hindering the effect of the first resin layer 31 in restricting the movement of ionic impurities. As a result, unexpected conductivity may occur, potentially reducing the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1. This maximum height roughness is preferably 2.2 μm or less, and more preferably 2.1 μm or less. Alternatively, this maximum height roughness may be, for example, 0.1 μm or more.

[0030] The surface of the metal layer 2 that overlaps with the first resin layer 31 may be treated with a matte finish, corona treatment, antistatic treatment, plasma treatment, silane coupling agent treatment, etc.

[0031] (1st resin layer) The first resin layer 31 is superimposed on the metal layer 2. Specifically, the first resin layer 31 is superimposed on one side of the metal layer 2 (the side in the negative Z-axis direction). The first resin layer 31 may also be superimposed on and bonded to the metal layer 2.

[0032] The thickness ratio of the first resin layer 31 is less than 10% of the thickness of the second resin layer 32. This can reduce the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1. This ratio is preferably 8% or less, and more preferably 5% or less. This ratio is, for example, 0.1% or more.

[0033] The thickness of the first resin layer 31 is 0.1 μm or more. In this case, the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can be improved. This thickness is preferably 0.5 μm or more, and more preferably 1.0 μm or more. The thickness of the first resin layer 31 is less than 5.0 μm. In this case, the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can be reduced. This thickness is preferably 4.5 μm or less, and more preferably 4.0 μm or less.

[0034] The first resin layer 31 includes a semi-cured product or a cured product of the first resin composition.

[0035] <First resin composition> The first resin composition contains epoxy resin (A1) and a curing agent (B1).

[0036] ≪Epoxy resin≫ The epoxy resin (A1) is a compound having one or more epoxy groups as functional groups in one molecule. Preferably, the epoxy resin (A1) has two or more epoxy groups in one molecule. In this case, the reactivity of the curing reaction of the first resin composition is increased, and the glass transition temperature of the cured product of the first resin composition can be further increased.

[0037] The epoxy resin (A1) is not particularly limited, but examples include trisphenolmethane type epoxy resin, naphthalene type epoxy resin, biphenyl aralkyl type epoxy resin, biphenyl type epoxy resin, and dicyclopentadiene type epoxy resin. Among these, the epoxy resin (A1) is preferably a trisphenolmethane type epoxy resin. A trisphenolmethane type epoxy resin has three phenylmethane skeleton epoxy groups in one molecule. Thus, because the trisphenolmethane type epoxy resin has a high epoxy group concentration, the glass transition temperature of the cured product of the first resin composition can be further increased.

[0038] ≪Hardening agent≫ The curing agent (B1) is a compound that reacts with the epoxy resin (A1) to form a crosslinked (cured) structure, and is a component that can increase the glass transition temperature of the cured product of the first resin composition. The curing agent (B1) is not particularly limited, but examples include phenolic resins and dicyandiamides. A phenolic resin is preferred as the curing agent (B1).

[0039] Phenolic resins are compounds having one or more phenolic hydroxyl groups as functional groups in one molecule. Preferably, phenolic resins have two or more phenolic hydroxyl groups in one molecule.

[0040] The phenolic resin is not particularly limited, but examples include biphenyl aralkyl phenolic resins, long-chain alkylphenolic resins, phenyl aralkyl phenolic resins, novolac phenolic resins, cresol novolac phenolic resins, bisphenol A novolac phenolic resins, naphthalene phenolic resins, tetrakisphenol phenolic resins, and phosphorus atom-containing phenolic resins. Among these, the phenolic resin is preferably at least one selected from the group consisting of biphenyl aralkyl phenolic resins and long-chain alkylphenolic resins. Biphenyl aralkyl phenolic resins can impart flame retardancy, heat resistance, and adhesion to the cured product of the first resin composition. Long-chain alkylphenolic resins can impart low viscosity and high fluidity to the first resin composition.

[0041] The functional group equivalent of the curing agent (B1) relative to the functional group equivalent of the epoxy resin (A1) (functional group equivalent of curing agent (B1) / functional group equivalent of epoxy resin (A1)) is preferably 0.3 or more and 1.3 or less, and more preferably 0.4 or more and 1.0 or less. A ratio of 0.3 or more in this equivalence ratio can further suppress the decrease in the glass transition temperature of the cured product of the first resin composition. A ratio of 1.3 or less in this equivalence ratio can suppress the increase of polar groups such as hydroxyl groups, and can further improve the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1.

[0042] Inorganic fillers The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) relative to the total amount of the first resin composition is less than or not present than the content of the inorganic filler (C2) relative to the total amount of the second resin composition. In this case, the movement of ionic impurities from the second resin layer 32 to the metal layer 2 can be restricted, and the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can be improved. The content of the inorganic filler (C1) relative to the total amount of the first resin composition is, for example, 0% by mass or more and 70% by mass or less.

[0043] The inorganic filler (C1) is not particularly limited, but examples include silica fillers such as synthetic silica filler, fused silica filler, or crystalline silica filler, talc filler, boehmite filler, magnesium hydroxide filler, aluminum hydroxide filler, magnesium hydroxide filler, aluminum silicate filler, magnesium silicate filler, zinc molybdate filler, calcium molybdate filler, clay filler, and mica filler. The inorganic filler (C1) contained in the first resin composition may be one type or two or more types.

[0044] The inorganic filler (C1) may be surface-treated with a coupling agent. Such coupling agents are not particularly limited, but examples include vinyltriethoxysilane, vinyltrimethoxysilane, methacryloxypropylmethyldimethoxysilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropylethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, glycidoxypropyltriethoxysilane, 8-glycidoxyoctyltrimethoxysilane, isocyanatetopropyltriethoxysilane, and the like. The silane coupling agent used may be a single type or a combination of two or more types.

[0045] Elastomer The first resin composition may further contain elastomer (D1). Elastomer (D1) can enhance the adhesion of the first resin composition and increase the toughness of the cured product. This is because elastomer (D1) has sufficient dispersibility in the first resin composition and can impart flexibility to the cured product of the first resin composition.

[0046] The elastomer (D1) is not particularly limited, but examples include polyvinyl acetal resin, styrene-butadiene resin, butadiene resin, isoprene resin, silicone resin, acrylic resin, methacrylic resin, styrene resin, etc. The elastomer (D1) may contain only one type or two or more types.

[0047] The elastomer (D1) content is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on the total amount of the first resin composition. The elastomer (D1) content is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, based on the total amount of the first resin composition. Within the above range, the fluidity of the first resin composition can be suppressed during the molding of the laminate 10, and the first resin layer 31 can be adjusted to a suitable thickness.

[0048] <Phosphorus-containing flame retardant> The first resin composition may or may not contain a phosphorus-containing flame retardant. When the first resin composition contains a phosphorus-containing flame retardant, the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can achieve both high thermal conductivity and high insulation reliability while enhancing flame retardancy. When the first resin composition does not contain a phosphorus-containing flame retardant, the occurrence of ion migration can be particularly suppressed, so the movement of ions from the second resin layer 32 to the metal layer 2 can be particularly suppressed, and the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can be particularly enhanced.

[0049] <<Other ingredients>> The first resin composition may contain other components besides those listed above. Such components are not particularly limited, but examples include curing accelerators.

[0050] A curing accelerator can accelerate the curing reaction of the first resin composition. While not particularly limited, examples of curing accelerators include imidazole compounds such as 2-ethyl-4-methylimidazole.

[0051] (2nd resin layer) The second resin layer 32 is superimposed on the first resin layer 31. Specifically, the second resin layer 32 is superimposed on the surface of the first resin layer 31 opposite to the surface facing the metal layer 2 (the surface in the negative Z-axis direction). The second resin layer 32 may also be superimposed on and bonded to the first resin layer 31.

[0052] The second resin layer 32 includes the second resin composition or a semi-cured product of the second resin composition.

[0053] <Second resin composition> The second resin composition contains epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2).

[0054] ≪Epoxy resin≫ Epoxy resin (A2) is the same as epoxy resin (A1). Therefore, the effects and preferred structures when epoxy resin (A2) is included are the same as those described for epoxy resin (A1) above. For this reason, the description of epoxy resin (A2) may be omitted as appropriate.

[0055] ≪Hardening agent≫ The curing agent (B2) is the same as that of curing agent (B1). Therefore, the effects and preferred structure when curing agent (B2) is included are the same as those described for curing agent (B1) above. For this reason, the description of curing agent (B2) may be omitted as appropriate.

[0056] Inorganic fillers Inorganic filler (C2) is similar to inorganic filler (C1) in terms of preferred compounds and coupling agents used. However, inorganic filler (C2) differs from inorganic filler (C1) in that it contains thermally conductive filler (C2-1). Therefore, the similarities between inorganic filler (C2) and inorganic filler (C1) will be omitted as appropriate, and the difference, thermally conductive filler (C2-1), will be explained in detail.

[0057] As described above, the inorganic filler (C2) includes a thermally conductive filler (C2-1). The thermal conductivity of the thermally conductive filler (C2-1) is 10 W / (m·K) or higher. Therefore, the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can be reduced. A higher thermal conductivity of the thermally conductive filler (C2-1) is preferable because it can reduce the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1, but the practical upper limit is, for example, 300 W / (m·K) or less.

[0058] The thermally conductive filler (C2-1) preferably includes at least one selected from the group consisting of magnesium oxide filler, aluminum nitride filler, and aluminum oxide filler. In this case, the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can be further reduced.

[0059] The thermally conductive filler (C2-1) has at least one peak in each of the ranges of greater than 1 μm and less than or equal to 25 μm, and the range of greater than or equal to 0.05 μm and less than or equal to 1 μm, in the volume-based particle size distribution measured by laser diffraction and scattering. In other words, the thermally conductive filler (C2-1) is a mixture of particles that show a peak in the range of greater than 1 μm and less than or equal to 25 μm in the volume-based particle size distribution measured by laser diffraction and scattering (hereinafter also referred to as particle group (I)) and particles that show a peak in the range of greater than or equal to 0.05 μm and less than or equal to 1 μm in the volume-based particle size distribution measured by laser diffraction and scattering (hereinafter also referred to as particle group (II)). As a result, in the second resin composition, particles of particle group (II) can intersect with particles of particle group (I), allowing the thermally conductive filler (C2-1) to come into thermal contact with each other. Therefore, the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can be reduced.

[0060] The thermal conductive filler (C2-1) preferably contains a first thermal conductive filler and a second thermal conductive filler (C2-2). The median diameter of the first thermal conductive filler is preferably greater than 1 μm and 25 μm or less, more preferably 4 μm or more and 20 μm or less. The median diameter of the second thermal conductive filler (C2-2) is preferably 0.05 μm or more and 1 μm or less, more preferably 0.1 μm or more and 0.4 μm or less. That is, when the thermal conductive filler (C2-1) contains a first thermal conductive filler and a second thermal conductive filler (C2-2), the first thermal conductive filler is particle group (I), and the second thermal conductive filler (C2-2) is particle group (II). As a result, thermal contact between the first thermally conductive fillers via the second thermally conductive filler (C2-2) in the second resin composition can be further promoted, thereby reducing the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1.

[0061] In this disclosure, "median diameter" refers to the 50% integrated value of the volume-based particle size distribution obtained by laser diffraction and scattering. The median diameter may also be referred to as D50.

[0062] The content of the thermally conductive filler (C2-1) is 80% by mass or more of the total amount of the second resin composition. This content of 80% by mass or more can reduce the thermal resistance of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1. This content is preferably 82% by mass or more, and more preferably 84% by mass or more. The content of the thermally conductive filler (C2-1) is 97% by mass or less of the total amount of the second resin composition. This content of 97% by mass or less can suppress an increase in the viscosity of the second resin composition and improve its fluidity. This content is preferably 96% by mass or less, and more preferably 95% by mass or less.

[0063] <<Other ingredients>> The second resin composition may contain other components besides those listed above. Such components are not particularly limited, but examples include curing accelerators, flame retardants, coupling agents, dispersants, ion scavengers, heavy metal deactivators, and flow regulators.

[0064] The curing accelerator can accelerate the curing reaction of the second resin composition, similar to the contents of the first resin composition described above. The curing accelerator is not particularly limited, but examples include imidazole compounds such as 2-ethyl-4-methylimidazole.

[0065] The flame retardant can enhance the flame retardancy of the cured product of the second resin composition. While not particularly limited, examples of flame retardants include phosphorus-based flame retardants, halogen-based flame retardants, and inorganic flame retardants. A halogen-free phosphorus-based flame retardant is more preferable.

[0066] A coupling agent can improve the adhesion between the cured product of the first resin composition and the cured product of the second resin composition. The inorganic fillers listed above (C1) can be used as coupling agents.

[0067] The dispersant can uniformly disperse the inorganic filler (C2) in the second resin composition. The dispersant is not particularly limited, but examples include wetting dispersants.

[0068] The metal deactivator can suppress the degradation of the second resin composition by forming a complex with active metal ions (e.g., copper ions) that promote oxidative degradation in the second resin composition. The metal deactivator is not particularly limited, but examples include hydrazide derivatives, oxalic acid derivatives, salicylic acid derivatives, etc.

[0069] The ion scavenger can further improve the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 by capturing ionic impurities in the second resin composition and suppressing ion migration. The ion scavenger is not particularly limited, but examples include hydrotalcite.

[0070] The fluidity modifier adjusts the second resin composition to an appropriate fluidity, thereby enabling the second resin layer 32 to be formed with a uniform thickness. Furthermore, as in this embodiment, even if the second resin composition is highly filled with a thermally conductive filler (C2-1), the fluidity modifier can impart appropriate fluidity to the second resin composition during molding. This can suppress the generation of voids in the second resin composition. Because the generation of voids can be suppressed in this way, the occurrence of partial discharge within the second resin composition can be suppressed, which can further reduce the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1. The fluidity modifier is not particularly limited, but examples include polyether ester types.

[0071] [Effects and Effects] In the resin-coated metal foil 1, the first resin layer 31 is interposed between the metal layer 2 and the second resin layer 32. This can restrict the movement of ionic impurities in the resin-coated metal foil 1, thereby suppressing the occurrence of ion migration.

[0072] Furthermore, the resin-coated metal foil 1 does not necessarily have to contain a phosphorus-containing flame retardant in its first resin composition. When the first resin composition does not contain a phosphorus-containing flame retardant, the occurrence of ion migration can be particularly suppressed.

[0073] Furthermore, the resin-coated metal foil 1 has a maximum height roughness (Rz) of 2.3 μm or less for the metal layer 2. As a result, the metal layer 2 and the second resin layer 32 are not in close proximity, and the effect of the first resin layer 31 in restricting the movement of ionic impurities can be fully realized.

[0074] Thus, the resin-coated metal foil 1 can restrict the movement of ionic impurities within it, thereby suppressing the occurrence of ion migration. Consequently, the insulation reliability of the resin-coated metal foil 1 and the laminate 10 formed from it can be improved.

[0075] The resin-coated metal foil 1 contains an inorganic filler (C2) which includes a thermally conductive filler (C2-1) with a thermal conductivity of 10 W / (m·K) or more, in the second resin composition that forms the second resin layer 32. The content of the thermally conductive filler (C2-1) is 80% by mass or more and 97% by mass or less of the total amount of the second resin composition. Furthermore, in the resin-coated metal foil 1, the ratio of the thickness of the first resin layer 31 to the thickness of the second resin layer 32 is less than 10%. In other words, the proportion of the second resin layer 32 that can reduce the thermal resistance is large relative to the entire resin-coated metal foil 1.

[0076] Furthermore, the thermally conductive filler (C2-1) has at least one peak in each of the ranges of greater than 1 μm and less than or equal to 25 μm, and between 0.05 μm and less than or equal to 1 μm, in the volume-based particle size distribution obtained by laser diffraction and scattering, indicating that thermally conductive filler (C2-1) can make thermal contact.

[0077] Thus, the resin-coated metal foil 1 includes a second resin layer 32 in which thermal resistance is reduced due to thermal contact between the thermally conductive fillers (C2-1). Furthermore, the proportion of the second resin layer 32 in the resin-coated metal foil 1 is large. Therefore, the resin-coated metal foil 1 and the laminate 10 formed from the resin-coated metal foil 1 can have reduced thermal resistance.

[0078] As described above, the resin-coated metal foil 1 according to the embodiment can achieve both low thermal resistance and high insulation reliability. Furthermore, by using the resin-coated metal foil 1 as a build-up material, for example, by layering the resin-coated metal foil 1 on a core material 14 such as a wiring board and heating and pressurizing it, a laminate 10 that can achieve both low thermal resistance and high insulation reliability can be easily manufactured.

[0079] 2.2 Laminate The laminate 10 according to this embodiment has thickness in the Z-axis direction and is plate-shaped, extending in the X-axis and Y-axis directions (see Figure 2). The laminate 10 comprises a metal layer 12, a first insulating layer 131, and a second insulating layer 132. The first insulating layer 131 and the second insulating layer 132 are sometimes collectively referred to as the insulating layer 13.

[0080] 〔composition〕 (metal layer) The metal layer 12 corresponds to the metal layer 2 of the resin-coated metal foil 1. Therefore, the preferred material, preferred numerical range, etc., of the metal layer 12 are the same as those of the metal layer 2 of the resin-coated metal foil 1 described above. For this reason, the description of the metal layer 12 may be omitted as appropriate.

[0081] The maximum height roughness (Rz) of the surface of the metal layer 12 that overlaps with the first insulating layer 131 is 2.3 μm or less. This maximum height roughness of 2.3 μm or less can improve the insulation reliability of the laminate 10.

[0082] (First insulating layer) The first insulating layer 131 corresponds to the first resin layer 31 of the cured resin-coated metal foil 1. The first insulating layer 131 differs from the first resin layer 31 only in that it does not contain the semi-cured material of the first resin composition. Therefore, the preferred material, preferred numerical range, and other details of the first insulating layer 131 are the same as those of the first resin layer 31 of the resin-coated metal foil 1 described above. For this reason, the description of the first insulating layer 131 may be omitted as appropriate.

[0083] The first insulating layer 131 is superimposed on the metal layer 12. Specifically, the first insulating layer 131 is superimposed on one side of the metal layer 12 (the side in the negative Z-axis direction). The first insulating layer 131 may also be superimposed on and bonded to the metal layer 12.

[0084] The thickness ratio of the first insulating layer 131 is less than 10% of the thickness of the second insulating layer 132. This can reduce the thermal resistance of the laminate 10.

[0085] The thickness of the first insulating layer 131 is 0.1 μm or more. In this case, the insulation reliability of the laminate 10 can be further improved. The thickness of the first insulating layer 131 is less than 5.0 μm. In this case, the thermal resistance of the laminate 10 can be further reduced.

[0086] The first insulating layer 131 contains a cured product of the first resin composition. The first resin composition contains an epoxy resin (A1) and a curing agent (B1).

[0087] The first resin composition contains an inorganic filler (C1), and the content of inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of inorganic filler (C2) relative to the total amount of the second resin composition, or it does not contain inorganic filler (C1). This can improve the insulation reliability of the laminate 10.

[0088] The first resin composition may further contain elastomer (D1). When elastomer (D1) is included, the elastomer (D1) content is preferably 10% by mass or more and 95% by mass or less of the total amount of the first resin composition. Within this range, the fluidity of the first resin composition can be suppressed when molding the laminate 10, and the first insulating layer 131 can be adjusted to a suitable thickness.

[0089] The first resin composition may or may not contain a phosphorus-containing flame retardant. When the first resin composition contains a phosphorus-containing flame retardant, the laminate 10 can achieve both high thermal conductivity and high insulation reliability while enhancing flame retardancy. When the first resin composition does not contain a phosphorus-containing flame retardant, the occurrence of ion migration can be particularly suppressed, thereby particularly suppressing the movement of ions from the second insulating layer 132 to the metal layer 2, and the insulation reliability of the laminate 10 can be particularly enhanced.

[0090] (Second insulating layer) The second insulating layer 132 corresponds to the second resin layer 32 of the cured resin-coated metal foil 1. The second insulating layer 132 differs from the second resin layer 32 only in that it contains cured material of the second resin composition and does not contain uncured or semi-cured material of the second resin composition. Therefore, the preferred material, preferred numerical range, and other details of the second insulating layer 132 are the same as those of the second resin layer 32 of the resin-coated metal foil 1 described above. For this reason, the description of the second insulating layer 132 may be omitted as appropriate.

[0091] The second insulating layer 132 is superimposed on the first insulating layer 131. Specifically, the second insulating layer 132 is superimposed on the surface of the first insulating layer 131 opposite to the surface facing the metal layer 12 (the surface in the negative Z-axis direction). The second insulating layer 132 may also be superimposed on and bonded to the first insulating layer 131.

[0092] The second insulating layer 132 contains a cured product of the second resin composition. The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more.

[0093] The content of the thermally conductive filler (C2-1) is 80% by mass or more and 97% by mass or less of the total amount of the second resin composition. If the content is 80% by mass or more, the thermal resistance of the laminate 10 may be reduced. If the content is 97% by mass or less, the increase in viscosity of the second resin composition may be suppressed and the fluidity may be improved. Therefore, the thickness of the second insulating layer 132 can be formed uniformly.

[0094] The thermally conductive filler (C2-1) preferably includes at least one selected from the group consisting of magnesium oxide filler, aluminum nitride filler, and aluminum oxide filler. In this case, the thermal resistance of the laminate 10 can be further reduced.

[0095] The thermally conductive filler (C2-1) has at least one peak in each of the ranges of greater than 1 μm and less than or equal to 25 μm, and the range of greater than or equal to 0.05 μm and less than or equal to 1 μm, in the volume-based particle size distribution obtained by laser diffraction and scattering. In other words, the thermally conductive filler (C2-1) is a mixture of particle group (I) that shows a peak in the range of greater than 1 μm and less than or equal to 25 μm in the volume-based particle size distribution obtained by laser diffraction and scattering, and particle group (II) that shows a peak in the range of greater than or equal to 0.05 μm and less than or equal to 1 μm in the volume-based particle size distribution obtained by laser diffraction and scattering. As a result, in the second resin composition, particles of particle group (II) can intersect with particles of particle group (I), allowing the thermally conductive filler (C2-1) to come into thermal contact. Therefore, the thermal resistance of the laminate 10 can be reduced.

[0096] The median diameter of the first thermally conductive filler is preferably greater than 1 μm and less than or equal to 25 μm. The median diameter of the second thermally conductive filler (C2-2) is preferably between 0.05 μm and 1 μm. As a result, thermal contact between the thermally conductive fillers (C2-1) in the second resin composition is further promoted, which can further reduce the thermal resistance of the laminate 10.

[0097] (Core material) The laminate 10 may further comprise a core material 14 (see Figure 2). The core material 14 is not particularly limited, but examples include printed circuit boards. The core material 14 has thickness in the Z-axis direction and is plate-shaped, extending in the X-axis and Y-axis directions. The core material 14 comprises an insulating substrate 15 and a conductive layer 16.

[0098] <Insulating substrate> The insulating substrate 15 is an electrically insulating substrate. The insulating substrate 15 has thickness in the Z-axis direction and is plate-shaped, extending in the X-axis and Y-axis directions. The insulating substrate 15 is superimposed on the second insulating layer 132. Specifically, the insulating substrate 15 is superimposed on the side of the second insulating layer 132 opposite to the side facing the first insulating layer 131 (the side in the negative Z-axis direction). The insulating substrate 15 may also be superimposed on and bonded to the second insulating layer 132.

[0099] <Conductor layer> The conductor layer 16 includes at least one of a signal layer for transmitting electrical signals, a power layer for supplying power, and a ground layer for maintaining ground potential. The conductor layer 16 is bonded to the insulating substrate 15. Specifically, the conductor layer 16 is bonded to one side of the insulating substrate 15 (the side in the positive Z-axis direction). The conductor layer 16 may also be bonded to the other side of the insulating substrate 15 (the side in the negative Z-axis direction). In Figure 2, the conductor layer 16 is embedded within the second insulating layer 132. However, the conductor layer 16 is not in contact with the first insulating layer 131. Thus, the thickness of the conductor layer 16 is thinner than the thickness of the second insulating layer 132. The thickness of the conductor layer 16 is not particularly limited, but for example, it is 12 μm or more and 210 μm or less.

[0100] [Effects and Effects] The laminate 10 according to this embodiment can be easily manufactured by using resin-coated metal foil 1 as a build-up material. That is, the laminate 10 can be manufactured from resin-coated metal foil 1 that can achieve both low thermal resistance and high insulation reliability. Therefore, the laminate 10 can achieve both high thermal conductivity and high insulation reliability. The method for manufacturing the laminate 10 is not particularly limited, but for example, it can be carried out by stacking resin-coated metal foil 1 on a core material 14 such as a wiring board and heating and pressurizing it.

[0101] 3. Appearance As is clear from the embodiments described above, this disclosure includes the following aspects. In the following, reference numerals are enclosed in parentheses solely to indicate their correspondence with the embodiments.

[0102] The resin-coated metal foil (1) according to the first embodiment comprises a metal layer (2), a first resin layer (31) containing a semi-cured or cured product of the first resin composition superimposed on the metal layer (2), and a second resin layer (32) containing a second resin composition or a semi-cured product of the second resin composition superimposed on the first resin layer (31). The thickness of the first resin layer (31) is 0.1 μm or more and less than 5 μm. The ratio of the thickness of the first resin layer (31) to the thickness of the second resin layer (32) is less than 10%. The first resin composition contains an epoxy resin (A1) and a curing agent (B1). The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content of the thermally conductive filler (C2-1) is 80% to 97% by mass of the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the ranges of greater than 1 μm and 25 μm or less, and 0.05 μm to 1 μm or less, in the volume-based particle size distribution by laser diffraction and scattering method. The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of the inorganic filler (C2) relative to the total amount of the second resin composition, or it does not contain an inorganic filler (C1). The maximum height roughness (Rz) of the surface of the metal layer (2) that overlaps with the first resin layer (31) is 2.3 μm or less.

[0103] According to this embodiment, the resin-coated metal foil (1) can achieve both low thermal resistance and high insulation reliability.

[0104] In the second embodiment, the resin-coated metal foil (1) comprises, in the first embodiment, at least one thermally conductive filler (C2-1) selected from the group consisting of magnesium oxide filler, aluminum nitride filler, and aluminum oxide filler.

[0105] The resin-coated metal foil (1) according to the third embodiment, in the first or second embodiment, comprises a thermal conductive filler (C2-1) comprising a first thermal conductive filler and a second thermal conductive filler (C2-2) having a median diameter smaller than the median diameter of the first thermal conductive filler (the value of 50% of the integrated value in the volume-based particle size distribution by laser diffraction-scattering method). The median diameter of the first thermal conductive filler is greater than 1 μm and 25 μm or less. The median diameter of the second thermal conductive filler (C2-2) is 0.05 μm or more and 1 μm or less.

[0106] The resin-coated metal foil (1) according to the fourth embodiment is such that, in any one of the first to third embodiments, the first resin composition does not contain a phosphorus-containing flame retardant.

[0107] The resin-coated metal foil (1) according to the fifth embodiment further contains an elastomer (D1) in any one of the first to fourth embodiments. The elastomer (D1) content is 10% by mass or more and 95% by mass or less with respect to the total amount of the first resin composition.

[0108] The laminate (10) according to the sixth embodiment comprises a metal layer (12), a first insulating layer (131) containing a cured product of a first resin composition superimposed on the metal layer (12), and a second insulating layer (132) containing a cured product of a second resin composition superimposed on the first insulating layer (131). The thickness of the first insulating layer (131) is 0.1 μm or more and less than 5 μm. The ratio of the thickness of the first insulating layer (131) to the thickness of the second insulating layer (132) is less than 10%. The first resin composition contains an epoxy resin (A1) and a curing agent (B1). The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content of the thermally conductive filler (C2-1) is 80% to 97% by mass of the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the ranges of greater than 1 μm and 25 μm or less, and 0.05 μm to 1 μm or less, in the volume-based particle size distribution by laser diffraction and scattering method. The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of the inorganic filler (C2) relative to the total amount of the second resin composition, or it does not contain an inorganic filler (C1). The maximum height roughness (Rz) of the surface of the metal layer (12) that overlaps with the first insulating layer (131) is 2.3 μm or less.

[0109] According to this embodiment, the laminate (10) can achieve both low thermal resistance and high insulation reliability.

[0110] The laminate (10) according to the seventh embodiment, in the sixth embodiment, comprises at least one thermally conductive filler (C2-1) selected from the group consisting of magnesium oxide filler, aluminum nitride filler, and aluminum oxide filler.

[0111] The laminate (10) according to the eighth embodiment, in the sixth or seventh embodiment, comprises a thermal conductive filler (C2-1) comprising a first thermal conductive filler and a second thermal conductive filler (C2-2) having a median diameter smaller than the median diameter of the first thermal conductive filler (the 50% cumulative value in the volume-based particle size distribution by laser diffraction-scattering method). The median diameter of the first thermal conductive filler is greater than 1 μm and 25 μm or less. The median diameter of the second thermal conductive filler (C2-2) is 0.05 μm or more and 1 μm or less.

[0112] In the laminate (10) according to the ninth embodiment, the first resin composition does not contain a phosphorus-containing flame retardant, in any one of the sixth to eighth embodiments.

[0113] In the laminate (10) according to the tenth embodiment, the first resin composition further contains elastomer (D1) in any one of the sixth to ninth embodiments. The content of elastomer (D1) is 10% by mass or more and 95% by mass or less, based on the total amount of the first resin composition. [Examples]

[0114] The present disclosure will be described in detail below with reference to examples. However, the present disclosure is not limited to the following examples.

[0115] 1. Preparation of the first resin composition and the second resin composition Each component was blended in the amounts shown in Tables 1 and 2, and methyl ethyl ketone was used as the solvent. The mixture was stirred and mixed to homogenize it, resulting in a first resin composition in a varnish state.

[0116] Similarly, each component was blended in the amounts shown in Tables 1 and 2, and methyl ethyl ketone was used as the solvent. The mixture was stirred and mixed to homogenize it, resulting in a varnish-like second resin composition with a solid content concentration of 90-99% by mass.

[0117] The details of the components used in the preparation of the first and second resin compositions are as follows.

[0118] (Epoxy resin) -Epoxy resin #1: Manufactured by Nippon Kayaku Co., Ltd., product name: EPPN502H, trisphenolmethane type epoxy resin, epoxy equivalent 158-178 g / eq. -Epoxy resin #2: Manufactured by DIC Corporation, product name: HP-7250, trisphenolmethane type epoxy resin, epoxy equivalent weight 150-180 g / eq.

[0119] (Hardening agent) -Hardening agent #1: Manufactured by UBE Corporation, product name: MEHC-7403H, biphenyl aralkyl type phenolic resin, hydroxyl group equivalent 132 g / eq. -Hardening agent #2: Manufactured by Gun-ei Chemical Industry Co., Ltd., product name: Resitopp ELP83H, long-chain alkyl liquid phenol resin, hydroxyl group equivalent 226 g / eq.

[0120] (Inorganic filler) - Thermally conductive filler #1:1: Manufactured by Nippon Steel Chemical & Material Co., Ltd., product name; AZ10-20, aluminum oxide filler, D50; 8~10μm - Thermally conductive filler #2: Manufactured by Ube Arterial Co., Ltd., Product name: RF-10CS, Magnesium oxide filler, D50; 5~10μm - Thermally conductive filler #3: Manufactured by Tokuyama Corporation, product name: HF-10c, aluminum nitride filler, D50: 16~22μm - Thermally conductive filler #4: Manufactured by Admatex Co., Ltd., product name: AO-502, aluminum oxide filler, D50; 0.2~0.3μm -Other inorganic fillers: Huber Engineered Materials, product name: Kemgard 501, calcium molybdate composite, D50: 3.7 μm.

[0121] (Elastomer) - Elastomer #1: Manufactured by Sekisui Chemical Co., Ltd., product name: Esrec KS-23Z, polyvinyl acetal resin.

[0122] (Other ingredients) - Curing accelerator: Manufactured by Shikoku Chemicals Co., Ltd., Product name: 2E4MZ, Chemical name: 2-ethyl-4-methylimidazole -Flame retardant: Manufactured by Fushimi Pharmaceutical Co., Ltd., product name: FP-100, phosphazene-based flame retardant (non-halogen flame retardant) - Coupling agent: Manufactured by Shin-Etsu Chemical Co., Ltd., Product name: KBM-4803, Silane coupling agent, Chemical name: 8-Glycidoxyoctyltrimethoxysilane - Dispersant: BYK-Chemie, product name; BYK-W903, wetting dispersant - Ion scavenger: Manufactured by Toagosei Co., Ltd., Product name: IXEPLAS-A1, Inorganic ion scavenger, Hydrotalcite-based - Heavy metal deactivator: Manufactured by ADEKA Corporation, Product name: ADEKA Stab CDA-10, Chemical name: N,N'-Bis「3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl」hydrazine - Flow regulator: Manufactured by Kusumoto Kasei Co., Ltd., product name: Disparon 3350EF, polyether ester type, phosphorus atom-free.

[0123] 2. Preparation of resin-coated metal foil (Example 1) First, a surface-treated electrolytic copper foil (manufactured by Furukawa Electric Industry Co., Ltd., product name "FV-WS", nominal thickness 35 μm, size 550 mm x 700 mm, maximum height roughness Rz 2.0 μm of the contact surface) was prepared as the metal layer.

[0124] The first resin composition was applied to one side of this metal layer and heated at 200°C for 3 to 5 minutes to dry and partially cure the first resin composition, forming a first resin layer with a thickness of 1.2 μm.

[0125] Next, the second resin composition was applied to the side of the first resin layer opposite to the side in contact with the metal layer, and the second resin composition was heated and dried at 150°C for 2 to 5 minutes to form a second resin layer with a thickness of 100 μm. After the resin layer was formed, it was cut to a size of 515 mm × 340 mm to produce resin-coated metal foil.

[0126] (Examples 2 and 3) A resin-coated metal foil was prepared using the same procedure as in Example 1, except that the thickness of the first resin layer was set to 2.4 μm.

[0127] (Comparative Examples 1-4) Except for using surface-treated electrolytic copper foil (manufactured by Furukawa Electric Industry Co., Ltd., product name "F2-WS", nominal thickness 35 μm, size 550 mm x 700 mm, maximum height roughness Rz 2.5 μm of the contact surface) as the metal layer, and forming the first resin layer to the thickness shown in Table 2, a resin-coated metal foil was prepared using the same procedure as in Example 1.

[0128] 3. Preparation of evaluation laminates The evaluation laminate 10A shown in Figure 3 was fabricated. The details of the fabrication procedure are described below.

[0129] First, a double-sided copper-clad laminate (manufactured by Panasonic Industries, Ltd., product name "R-1566S", thickness 400 μm, copper foil thickness 105 μm, size 515 mm x 340 mm) was prepared as the core material 14. This double-sided copper-clad laminate is a high heat-resistant halogen-free multilayer substrate material that has an insulating substrate 15 and copper foil on both surfaces of the insulating substrate 15. By etching the copper foil on both surfaces of this double-sided copper-clad laminate, a conductive layer 16 (16a, 16b) with the test pattern (comb pattern) shown in Figure 4 was formed in an XY plan view.

[0130] Next, the resin layers of the resin-coated metal foil prepared in "2. Preparation of resin-coated metal foil" were placed on top of both surfaces of the core material 14 and brought into contact with it. The resin layers (first resin layer and second resin layer) were cured by heating and pressurizing under the conditions of 200°C, 3 MPa, and 60 minutes, forming an insulating layer 13 (first insulating layer 131 and second insulating layer 132). After the insulating layer 13 was formed, the outermost metal layer was etched to form metal layers 12a and 12b, which have the same test pattern as the conductive layer 16 in an XY plan view, and an evaluation laminate 10A was prepared.

[0131] 4. Evaluation (thermal resistance) The resin layer of the resin-coated metal foil prepared in "2. Preparation of Resin-Coated Metal Foil" was cured at 200°C for 60 minutes. The thermal resistance of this cured resin layer was measured using a thermal properties evaluation device (Siemens, model number "T3Ster DynTIM Tester") in accordance with ASTM D5470.

[0132] The measured thermal resistance results are shown in Tables 1 and 2.

[0133] (Insulation reliability) The evaluation laminate 10A was placed in an environment of 85°C / 85%RH, and a voltage of 900V was applied between the outer metal layer 12a and the inner conductor layer 16a to measure the resistance of the insulating layer 13. From the start of voltage application, the resistance of the insulating layer 13 was 1 × 10⁻¹⁰. 7 The time it took for the resistance to drop below Ω was monitored. The results are shown in Tables 1 and 2. Note that the resistance value is 1 × 10⁻⁶. 7 The time until the value becomes less than Ω is recorded as an actual value if it is 1500 hours or less, and as ">1500(h)" if it is more than 1500 hours.

[0134] [Table 1]

[0135] [Table 2]

[0136] In the thermal resistance evaluation, the results for evaluation laminates 10A in Examples 1-3 were comparable to those of Comparative Examples 1-4. On the other hand, in the insulation reliability evaluation, the time required to reach the predetermined resistance value was longer for evaluation laminates 10A in Examples 1-3 compared to those of Comparative Examples 1-4, confirming an improvement in insulation reliability. Therefore, evaluation laminates 10A in Examples 1-3 achieve both low thermal resistance and high insulation reliability. [Explanation of Symbols]

[0137] 1. Metal foil coated with resin 2 metal layer 31 1st resin layer 32 Second resin layer 10 Laminate 12 metal layer 131 First insulating layer 132 Second insulating layer

Claims

1. The material comprises a metal layer, a first resin layer containing a semi-cured or cured product of a first resin composition superimposed on the metal layer, and a second resin layer containing a second resin composition or a semi-cured product of a second resin composition superimposed on the first resin layer. The thickness of the first resin layer is 0.1 μm or more and less than 5.0 μm. The ratio of the thickness of the first resin layer to the thickness of the second resin layer is less than 10%. The first resin composition contains an epoxy resin (A1) and a curing agent (B1), The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content of the thermally conductive filler (C2-1) is 80% by mass or more and 97% by mass or less, relative to the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the ranges greater than 1 μm and 25 μm or less, and 0.05 μm or more and 1 μm or less, in the volume-based particle size distribution obtained by laser diffraction and scattering method. The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of the inorganic filler (C2) relative to the total amount of the second resin composition, or does not contain the inorganic filler (C1). The maximum height roughness (Rz) of the surface of the metal layer that overlaps with the first resin layer is 2.3 μm or less. Metal foil coated with resin.

2. The thermally conductive filler (C2-1) includes at least one selected from the group consisting of magnesium oxide filler, aluminum nitride filler, and aluminum oxide filler. The resin-coated metal foil according to claim 1.

3. The thermally conductive filler (C2-1) includes a first thermally conductive filler and a second thermally conductive filler having a median diameter smaller than the median diameter of the first thermally conductive filler (the 50% integrated value in the volume-based particle size distribution by laser diffraction / scattering method). The median diameter of the first thermally conductive filler is greater than 1 μm and less than or equal to 25 μm. The median diameter of the second thermally conductive filler is 0.05 μm or more and 1 μm or less. The resin-coated metal foil according to claim 1.

4. The first resin composition does not contain a phosphorus-containing flame retardant. The resin-coated metal foil according to claim 1.

5. The first resin composition further contains an elastomer (D1), The content of the elastomer (D1) is 10% by mass or more and 95% by mass or less, based on the total amount of the first resin composition. The resin-coated metal foil according to claim 1.

6. The device comprises a metal layer, a first insulating layer containing a cured product of a first resin composition superimposed on the metal layer, and a second insulating layer containing a cured product of a second resin composition superimposed on the first insulating layer. The thickness of the first insulating layer is 0.1 μm or more and less than 5.0 μm. The ratio of the thickness of the first insulating layer to the thickness of the second insulating layer is less than 10%. The first resin composition contains an epoxy resin (A1) and a curing agent (B1), The second resin composition contains an epoxy resin (A2), a curing agent (B2), and an inorganic filler (C2) containing a thermally conductive filler (C2-1) having a thermal conductivity of 10 W / (m·K) or more. The content of the thermally conductive filler (C2-1) is 80% by mass or more and 97% by mass or less, relative to the total amount of the second resin composition. The thermally conductive filler (C2-1) has at least one peak in each of the ranges greater than 1 μm and 25 μm or less, and 0.05 μm or more and 1 μm or less, in the volume-based particle size distribution obtained by laser diffraction and scattering method. The first resin composition contains an inorganic filler (C1), and the content of the inorganic filler (C1) relative to the total amount of the first resin composition is less than the content of the inorganic filler (C2) relative to the total amount of the second resin composition, or does not contain the inorganic filler (C1). The maximum height roughness (Rz) of the surface of the metal layer that overlaps with the first insulating layer is 2.3 μm or less. Laminated structure.

7. The thermally conductive filler (C2-1) includes at least one selected from the group consisting of magnesium oxide filler, aluminum nitride filler, and aluminum oxide filler. The laminate according to claim 6.

8. The thermally conductive filler (C2-1) includes a first thermally conductive filler and a second thermally conductive filler having a median diameter smaller than the median diameter of the first thermally conductive filler (the 50% cumulative value in the volume-based particle size distribution obtained by laser diffraction and scattering method). The median diameter of the first thermally conductive filler is greater than 1 μm and less than or equal to 25 μm. The median diameter of the second thermally conductive filler is 0.05 μm or more and 1 μm or less. The laminate according to claim 6.

9. The first resin composition does not contain a phosphorus-containing flame retardant. The laminate according to claim 6.

10. The first resin composition further contains an elastomer (D1), The content of the elastomer (D1) is 10% by mass or more and 95% by mass or less, based on the total amount of the first resin composition. The laminate according to claim 6.

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