Epoxy resin composition for interlayer insulation, resin sheet for interlayer insulation, laminate for circuit board, metal base circuit board and power module

Abstract

Provided are: an epoxy resin composition for interlayer insulation, which has excellent adhesion heat resistance and is capable of maintaining good voltage resistance at a high level; a resin sheet for interlayer insulation; a laminate for a circuit board; a metal base circuit board; and a power module.　An epoxy resin composition for interlayer insulation according to an embodiment of the present invention contains an epoxy resin, an epoxy-modified polybutadiene compound, and an aromatic amine compound, wherein the epoxy-modified polybutadiene compound contains a repeating unit represented by general formula (I), a repeating unit represented by general formula (II), and a repeating unit represented by general formula (III), and also contains at least one among a repeating unit represented by general formula (i), a repeating unit represented by general formula (ii), and a repeating unit represented by general formula (iii).

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin composition for interlayer insulation, an interlayer insulation resin sheet, a laminate for circuit boards, a metal base circuit board, and a power module. [Background technology]

[0002] Recent advances in electronics technology have been remarkable, with rapid progress being made in improving the performance and miniaturization of electrical and electronic devices. Accordingly, the metal-based circuit boards used in these devices, which are compatible with high-density mounting, are becoming smaller and denser than ever before. Therefore, improvements in various aspects of the performance of metal-based circuit boards are being sought, and a wide range of efforts are being made to meet these demands.

[0003] Up until now, resin compositions using epoxy resins have been widely used as resin compositions for insulating layers constituting metal base circuit boards. For example, Patent Document 1 discloses a resin composition in which a specific phenolic curing agent, a phenoxy resin, and rubber particles are added to an epoxy resin-containing composition, as a resin composition capable of providing an insulating layer with high interfacial adhesion strength with a plated conductor layer even when the surface roughness of the insulating layer is small.

[0004] Furthermore, Patent Document 2 discloses that, in an insulating layer having a phase-separated structure consisting of a sea phase of epoxy-modified acrylic rubber and an island phase of epoxy resin, by adjusting the average domain size of the island phase and the compounding ratio of the epoxy-modified acrylic rubber to the epoxy resin, a printed wiring board is provided that includes an insulating layer that combines the excellent characteristics of both resin components.

[0005] Epoxy resin compositions are also widely used as sealing materials in electronic device components, and various improvements have been made to satisfy the performance requirements of sealing materials. For example, Patent Document 3 discloses a solvent-free epoxy resin composition containing a liquid epoxy resin, a liquid aromatic amine-based curing agent, an epoxidized polybutadiene compound, and an inorganic filler as an encapsulating epoxy resin composition with excellent adhesion under high temperature and high humidity conditions. In this composition, the epoxidized polybutadiene compound used is an epoxidized butadiene rubber composed of butadiene-derived vinyl-1,2 bond repeating units and 1,2 bond repeating units in which these repeating units have been epoxidized.

[0006] On the other hand, because resins have low thermal conductivity, research is also being conducted widely on increasing the thermal conductivity of insulating layers in metal-based circuit boards by adding inorganic fillers to the insulating layers. For example, Patent Document 4 discloses that boron nitride and aluminum oxide are added to the insulating layer as inorganic fillers to increase thermal conductivity, while the proportion of boron nitride in the inorganic filler is limited to 35% by volume or less in order to increase the adhesive strength between the metal foil and the insulating layer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-254709 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-79367 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-254709 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-91179 Summary of the Invention [Problem to be solved by the invention]

[0008] Metal base circuit boards are required to have heat resistance that can withstand the solder reflow treatment that occurs during element mounting. Therefore, the interlayer insulating epoxy resin compositions used in the insulating layers of metal base circuit boards are required to have even better heat resistance than the encapsulating epoxy resin compositions used in the encapsulating members. Furthermore, as the demand for heat resistance in metal base circuit boards has become increasingly strict due to factors such as the rise in solder reflow temperatures in recent years, the insulating layers of metal base circuit boards are required to have further improved adhesion heat resistance and voltage resistance.

[0009] An object of the present invention is to provide an epoxy resin composition for interlayer insulation, an interlayer insulating resin sheet, a laminate for circuit boards, a metal base circuit board, and a power module which have excellent heat resistance and can maintain good voltage resistance even after, for example, solder reflow treatment. [Means for solving the problem]

[0010] According to a first aspect of the present invention, there is provided an epoxy resin composition for interlayer insulation, comprising an epoxy resin, an epoxy-modified polybutadiene compound, and an aromatic amine compound, wherein the epoxy-modified polybutadiene compound comprises a repeating unit represented by the following general formula (I), a repeating unit represented by the following general formula (II), and a repeating unit represented by the following general formula (III), and the epoxy resin composition comprises at least one of a repeating unit represented by the following general formula (i), a repeating unit represented by the following general formula (ii), and a repeating unit represented by the following general formula (iii):

[0011] [ka]

[0012] The epoxy resin composition for interlayer insulation according to this embodiment may contain at least bisphenol A diglycidyl ether as the epoxy resin.

[0013] The epoxy resin composition for interlayer insulation according to this embodiment may contain a compound represented by the following general formula (IV) as the aromatic amine compound.

[0014] [ka]

[0015] In general formula (IV), R1 represents an alkyl group, m represents an integer of 2 or more, n represents an integer of 0 or more, and m and n satisfy m+n≦6. When n is 2 or more, multiple R1s may be the same or different.

[0016] The epoxy resin composition for interlayer insulation according to this embodiment may contain a boron-phosphorus complex represented by the following general formula (V) and a phosphorus compound represented by the following general formula (VI).

[0017] [ka]

[0018] In general formula (V), R2 and R3 each independently represent an alkyl group, r represents an integer of 0 to 5, and s represents an integer of 0 to 5. When r is an integer of 2 or greater, multiple R2s may be the same or different. When s is an integer of 2 or greater, multiple R3s may be the same or different.

[0019] [ka]

[0020] In general formula (VI), R4 represents an alkyl group or an alkoxy group, and t represents an integer of 0 to 5. When t is an integer of 2 or more, multiple R4s may be the same or different.

[0021] The epoxy resin composition for interlayer insulation according to this embodiment may contain an inorganic filler.

[0022] According to a second aspect of the present invention, there is provided a resin sheet for interlayer insulation, which comprises a cured product of the above-mentioned epoxy resin composition for interlayer insulation and has a phase-separated structure in which a discontinuous phase containing the above-mentioned epoxy-modified polybutadiene compound is dispersed in a continuous phase containing the above-mentioned epoxy resin.

[0023] The interlayer insulating resin sheet according to this embodiment may have a first glass transition temperature Tg1 derived from the epoxy-modified polybutadiene compound of −5°C or lower, and a second glass transition temperature Tg2 derived from the epoxy resin of 175°C or higher.

[0024] According to a third aspect of the present invention, there is provided a laminate for a circuit board comprising a metal substrate, an insulating layer provided on at least one surface of the metal substrate, and a metal foil provided on the insulating layer, wherein the insulating layer is the interlayer insulating resin sheet.

[0025] According to a fourth aspect of the present invention, there is provided a metal base circuit board laminate comprising a metal substrate, an insulating layer provided on at least one surface of the metal substrate, and a circuit pattern provided on the insulating layer, wherein the insulating layer is the interlayer insulating resin sheet.

[0026] According to a fifth aspect of the present invention, there is provided a power module comprising the above metal base circuit board. [Effects of the Invention]

[0027] According to the present invention, there are provided an epoxy resin composition for interlayer insulation, an interlayer insulating resin sheet, a laminate for circuit boards, a metal base circuit board, and a power module which have excellent heat resistance and can maintain good voltage resistance even after, for example, solder reflow treatment. [Brief explanation of the drawings]

[0028] [Figure 1]2 is a graph showing the behavior of the storage modulus (E'), loss modulus (E"), and loss tangent (tan δ) for an interlayer insulating resin sheet according to one embodiment of the present invention. [Figure 2] 1 is a photographic image of a fracture surface of a cured product of an epoxy resin composition for interlayer insulation according to one embodiment of the present invention. [Figure 3] 1 is a photographic image of a fracture surface of a cured product of a comparative epoxy resin composition using an epoxy-modified polybutadiene compound that does not contain 1,4 bond repeating units. [Figure 4] 1 is a perspective view schematically showing a laminate for a circuit board according to an embodiment of the present invention; [Figure 5] 2. FIG. 3 is a cross-sectional view of the circuit board laminate taken along line II-II shown in FIG. [Figure 6] 1 is a cross-sectional view schematically showing a metal base circuit board according to an embodiment of the present invention; [Figure 7] 1 is a cross-sectional view schematically showing a power module according to an embodiment of the present invention; [Figure 8] FIG. 1 is a cross-sectional view schematically showing a conventional power module. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following describes embodiments of the present invention in the following order: a first embodiment is an epoxy resin composition for interlayer insulation; a second embodiment is an interlayer insulation resin sheet; a third embodiment is a laminate for a circuit board; a fourth embodiment is a metal base circuit board; and a fifth embodiment is a power module. These embodiments are more specific embodiments of any of the above aspects. Note that the following includes descriptions with reference to the drawings, and in the drawings referenced therein, elements having the same or similar functions are given the same reference numerals, and duplicate descriptions are omitted. Also, the dimensional ratios and shapes in each drawing may differ from the actual objects.

[0030] <Epoxy resin composition for interlayer insulation> The epoxy resin composition for interlayer insulation according to the first embodiment (hereinafter also referred to as "epoxy resin composition") contains an epoxy resin, an epoxy-modified polybutadiene compound, and an aromatic amine compound.

[0031] (epoxy resin) One or more known epoxy resins can be used as the epoxy resin. Examples of epoxy resins include bisphenol-type epoxy resins, phenol novolac-type epoxy resins, ortho-cresol novolac-type epoxy resins, biphenyl-type epoxy resins, dicyclopentadiene-type epoxy resins, diphenylfluorene-type epoxy resins, and halogen-, amino-, or alkyl-substituted versions of these epoxy resins; aromatic / aliphatic ring-containing epoxy resins such as glycidyl ester-type epoxy resins, naphthalene-type epoxy resins, and heterocyclic epoxy resins; isocyanate-modified epoxy resins; diarylsulfone-type epoxy resins; hydroquinone-type epoxy resins; hydantoin-type epoxy resins; and epoxy resins (polyepoxy compounds) containing two or more epoxy groups per molecule, such as resorcinol diglycidyl ether, triglycidyl-p-aminophenol, m-aminophenol triglycidyl ether, tetraglycidylmethylenedianiline, (trihydroxyphenyl)methane triglycidyl ether, and tetraphenylethane tetraglycidyl ether.

[0032] Among the above, bisphenol-type epoxy resins are preferably used as the epoxy resin in terms of the ease of handling of the curable resin composition and the heat resistance of the cured product. Specific examples of bisphenol-type epoxy resins include bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, and bisphenol AD-type epoxy resins. Among these, bisphenol A-type epoxy resins are more preferably used, and bisphenol A-type diglycidyl ether is even more preferably used, in terms of the ease of handling of the curable resin composition and the heat resistance of the cured product.

[0033] The epoxy resin preferably used in this embodiment has a weight-average molecular weight (Mw) of, for example, 100 to 10,000, and, for example, 200 to 5,000. When the weight-average molecular weight (Mw) of the epoxy resin is within the above range, the resin flows during adhesion and easily conforms to irregularities, and voids are easily removed, which is preferable from the viewpoints of adhesion strength and withstand voltage. Here, the weight-average molecular weight is a polystyrene-equivalent value measured by GPC (gel permeation chromatography).

[0034] The epoxy resin preferably used in this embodiment has an epoxy equivalent of, for example, 50 or more and 2000 or less, and, for another example, 100 or more and 1000 or less. When the epoxy equivalent of the epoxy resin is within the above range, the time required for curing is shortened and a high Tg is obtained.

[0035] (Epoxy-modified polybutadiene compound) The epoxy-modified polybutadiene compound is an epoxy-modified butadiene rubber obtained by epoxy-modifying a polymer (butadiene rubber) made of 1,3-butadiene. This butadiene rubber is a polymer obtained by addition polymerization of the conjugated diene monomer 1,3-butadiene. Therefore, the epoxy-modified polybutadiene compound used in this embodiment (hereinafter, may be referred to as "epoxy-modified butadiene rubber") contains, in its main chain, repeating units derived from trans-1,4-bonded butadiene represented by the following general formula (I), repeating units derived from cis-1,4-bonded butadiene represented by the following general formula (II), and repeating units derived from vinyl-1,2-bonded butadiene represented by the following general formula (III), depending on the bonding mode of the monomers.

[0036] [ka]

[0037] The epoxy-modified polybutadiene compound used in this embodiment has at least one of the repeating units represented by the above general formulas (I) to (III) epoxidized. That is, the epoxy-modified polybutadiene compound according to this embodiment contains, as the epoxidized butadiene-derived repeating unit, at least one of a 1,4-bond repeating unit represented by the following general formula (i), a 1,4-bond repeating unit represented by the following general formula (ii), and a 1,2-bond repeating unit represented by the following general formula (iii):

[0038] [ka]

[0039] Hereinafter, repeating units belonging to Group A consisting of repeating units represented by general formulas (I), (II), (i) and (ii) are referred to as "1,4-bond repeating units", and repeating units belonging to Group B consisting of repeating units represented by general formulas (III) and (iii) are referred to as "1,2-bond repeating units".

[0040] [ka]

[0041] While the epoxy-modified polybutadiene compound used in Patent Document 3 is an epoxy-modified butadiene rubber composed only of 1,2-bond repeating units, the epoxy-modified polybutadiene compound used in the present embodiment contains 1,4-bond repeating units in addition to 1,2-bond repeating units, as described above. That is, the epoxy-modified polybutadiene compound contains, as an essential requirement, 1,4-bond repeating units represented by general formulas (I) and (II) from among the 1,4-bond repeating units belonging to Group A, and optionally contains 1,4-bond repeating units represented by general formulas (i) and (ii). The epoxy resin composition according to the present embodiment, which contains an epoxy-modified polybutadiene compound containing such 1,4-bond repeating units as an epoxy-modified butadiene rubber component used in combination with an epoxy resin, can provide an interlayer insulating resin sheet that has high adhesion heat resistance, as described below, and that can maintain good voltage resistance even after, for example, solder reflow treatment.

[0042] In this embodiment, the compounding ratio (molar ratio) of the 1,4 bond repeating unit to the 1,2 bond repeating unit contained in the epoxy-modified polybutadiene compound is, in one example, preferably 5:5 to 0.5:9.5, and in another example, more preferably 4:6 to 1:9.

[0043] The epoxy-modified polybutadiene compound containing 1,4 bond repeating units can be a commercially available product or one produced by a known method. The epoxy-modified polybutadiene compound preferably used in this embodiment has a number average molecular weight (Mn) of, for example, 500 to 10,000, and for another example, 1,000 to 7,000. When the number average molecular weight of the epoxy-modified polybutadiene compound is within the above range, it is easily soluble in a solvent and can impart appropriate flexibility.

[0044] The epoxy-modified polybutadiene compound preferably used in the present embodiment has an epoxy equivalent of, for example, 50 or more and 500 or less, and, in another example, 100 or more and 350 or less. When the epoxy equivalent of the epoxy-modified polybutadiene compound is within the above range, it is preferable because the adhesive strength with the epoxy resin upon phase separation can be appropriately adjusted.

[0045] In the present embodiment, the compounding ratio of the epoxy-modified polybutadiene compound in the epoxy resin composition may be, for example, 5 parts by mass or more and 40 parts by mass or less, and in another example, 10 parts by mass or more and 30 parts by mass or less, when the total amount of the epoxy resin, the aromatic amine compound, and the epoxy-modified polybutadiene compound is 100 parts by mass.

[0046] (aromatic amine compounds) The epoxy resin composition according to the present embodiment contains an aromatic amine compound as a curing agent. The aromatic amine compound preferably has two or more amino groups substituted on the aromatic ring, and preferably contains, for example, an aromatic amine compound represented by the following general formula (IV):

[0047] [ka]

[0048] In general formula (IV), R1 represents an alkyl group, m represents an integer of 2 or more, n represents an integer of 0 or more, and m and n satisfy m+n≦6. When n is an integer of 2 or more, multiple R1s may be the same or different.

[0049] m, which represents the number of amino groups substituted on the benzene ring, is from 2 to 6, and may be from 2 to 5, or may be 2 or 3, or may be 2. When m is 2, the arrangement of the two amino groups on the benzene ring is preferably meta or ortho relative to one of the amino groups.

[0050] R1 is an arbitrary substituent for the benzene ring. The number of carbon atoms in the alkyl group represented by R1 may be 1 to 4, or may be 1 or 2. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. n, which represents the number of R1 substituted on the benzene ring, is 0 or more and 4 or less, or may be 0 or more and 3 or less, or may be 1 or more and 3 or less.

[0051] The aromatic amine compound represented by general formula (IV) has a small steric hindrance, and therefore has an excellent effect of improving curability, and can exhibit sufficient performance even in a short curing time. In addition, the aromatic amine compound represented by general formula (IV) is liquid at room temperature, and therefore easily soluble in solvents and easy to handle.

[0052] Specific examples of the aromatic amine compound represented by general formula (IV) include diethyltoluenediamine represented by the following formula: [ka] Examples of the amino groups include 1,2-phenylenediamine, 1,3-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,3-diaminotoluene, 3,4-diaminotoluene, 2,4,6-trimethyl-1,3-phenylenediamine, 1,2,4-triaminobenzene, 4,5-dimethyl-1,2-phenylenediamine, 1,4-phenylenediamine, and 2,3,5,6-tetramethyl-1,4-phenylenediamine.

[0053] The aromatic amine compounds represented by general formula (IV) may be used alone or in combination of two or more. There are no particular restrictions on the production of these aromatic amine compounds, and commercially available products can be used.

[0054] In the present embodiment, the blending ratio of the aromatic amine compound represented by general formula (IV) in the epoxy resin composition may be, for example, 5 parts by mass or more and 50 parts by mass or less, and in another example, 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the total of the epoxy resin and the aromatic amine compound.

[0055] (curing accelerator) The epoxy resin composition according to this embodiment preferably contains a curing accelerator. Examples of the curing accelerator that can be used in this embodiment include a boron-phosphorus complex represented by the following general formula (V):

[0056] [ka]

[0057] In general formula (V), R2 and R3 each independently represent an alkyl group, r represents an integer of 0 to 5, and s represents an integer of 0 to 5. When r is an integer of 2 or greater, multiple R2s may be the same or different. When s is an integer of 2 or greater, multiple R3s may be the same or different.

[0058] R2 and R3 are optional substituents for the benzene ring. Specific examples of the alkyl group represented by R2 and R3 include a methyl group and an ethyl group.

[0059] r, which represents the number of R2 substituted on the benzene ring on which the P atom is substituted, is from 0 to 5, may be from 0 to 3, may be from 0 to 2, or may be 0 or 1. When r is 1, the position of the alkyl group represented by R2 may be any of the ortho, meta, and para positions relative to the P atom.

[0060] The number s, which represents the number of R3 substituted on the benzene ring on which the B atom is substituted, is 0 or more and 5 or less, and may be 0 or more and 3 or less, or may be 0 or more and 2 or less.

[0061] Specific examples of the boron-phosphorus complex represented by general formula (V) include triphenylphosphine triphenylborate (TPP-S) and tris-para-methylphenylphosphine triphenylborate (TPTP-S), which are represented by the following formulas: In TPTP-S, the methyl group may be positioned at any of the ortho, meta, and para positions relative to the P atom.

[0062] [ka]

[0063] In one embodiment, the epoxy resin composition according to the present embodiment preferably contains TPP-S and / or TPTP-S as a curing accelerator.

[0064] The boron-phosphorus complex represented by general formula (V) may be used alone or in combination of two or more. There is no particular limitation on the production of the boron-phosphorus complex represented by general formula (V), and commercially available products may be used.

[0065] In the present embodiment, the blending ratio of the boron-phosphorus complex represented by general formula (V) in the epoxy resin composition may be, for example, 0.01 parts by mass or more and 5 parts by mass or less, and in another example, 0.1 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the total of the epoxy resin, the aromatic amine compound, and the epoxy-modified polybutadiene compound.

[0066] Other curing accelerators that may be contained in the epoxy resin composition according to this embodiment include phosphorus compounds represented by the following general formula (VI): In this embodiment, the phosphorus compound represented by the following general formula (VI) is preferably used in combination with the boron-phosphorus complex represented by the above-mentioned general formula (V).

[0067] [ka]

[0068] In general formula (VI), R4 represents an alkyl group or an alkoxy group, and t represents an integer of 0 to 5. When t is an integer of 2 or more, multiple R4s may be the same or different.

[0069] R4 is an optional substituent for the benzene ring. Specific examples of the alkyl group represented by R4 include a methyl group, an ethyl group, and a propyl group. Specific examples of the alkoxy group represented by R4 include a methoxy group and a butoxy group.

[0070] t, which represents the number of substitutions of R4 on the benzene ring, is 0 or more and 5 or less, and may be 0 or more and 4 or less, or 0 or more and 2 or less, or may be 0.

[0071] A specific example of the phosphorus compound represented by general formula (VI) is triphenylphosphine (TPP) represented by the following formula. [ka]

[0072] The phosphorus compound represented by the general formula (VI) may be used alone or in combination of two or more. There is no particular limitation on the production of the phosphorus compound represented by the general formula (VI), and commercially available products may be used.

[0073] When the epoxy resin composition according to the present embodiment contains an aromatic amine compound represented by general formula (IV) as a curing agent, and a boron-phosphorus complex represented by general formula (V) and a phosphorus compound represented by general formula (VI) as curing accelerators, the voltage resistance, adhesion, and heat resistance of the cured film obtained in a short curing time are all significantly improved. The reason for this is not entirely clear, but it is speculated as follows: Namely, the resin curing reaction does not proceed at room temperature, and a rapid curing reaction occurs only when heated. This allows the molecular weight to be sufficiently increased in a short time during the drying process, and is easy to control, allowing the film to have an appropriate melt viscosity during pressing.

[0074] In the present embodiment, the compounding ratio of the phosphorus compound represented by general formula (VI) in the epoxy resin composition may be, for example, 0.01 parts by mass or more and 5 parts by mass or less, and in another example, 0.05 parts by mass or more and 5 parts by mass or less, when the total amount of the epoxy resin, aromatic amine compound, and epoxy-modified polybutadiene compound is taken as 100 parts by mass.

[0075] In determining the amount of the phosphorus compound represented by general formula (VI), it is preferable to take into consideration the amount of the boron-phosphorus complex represented by general formula (V). In one embodiment, [total mass of the phosphorus compound represented by general formula (VI) / total mass of the boron-phosphorus complex represented by general formula (V)] is preferably in the range of 0.002 to 5, and more preferably in the range of 0.1 or more and less than 1.

[0076] Furthermore, the total compounding ratio of the boron-phosphorus complex represented by general formula (V) and the phosphorus compound represented by general formula (VI) in the epoxy resin composition may be, for example, 0.5 parts by mass or more and 10 parts by mass or less, and in another example, 1 part by mass or more and 10 parts by mass or less, when the total of the epoxy resin, aromatic amine compound, and epoxy-modified polybutadiene compound is taken as 100 parts by mass.

[0077] (Inorganic filler) The epoxy insulating composition according to the present embodiment preferably contains an inorganic filler. Examples of the inorganic filler include alumina, aluminum nitride, boron nitride, silicon nitride, magnesium oxide, and silicon oxide. It is preferable to use one or more types selected from these.

[0078] In systems in which the epoxy resin composition according to this embodiment contains an inorganic filler, the presence of the inorganic filler tends to suppress the exothermic reaction accompanying curing. Specifically, problems may arise, such as the curing reaction being slowed down due to the absorption of reaction heat by the inorganic filler, or the curing reaction of the thermosetting resin being inhibited depending on the surface functional groups of the inorganic filler. For this reason, a surface-treated inorganic filler may be used, or it is preferable to use an inorganic filler in an appropriate combination with the curing accelerator described above. For example, the surface of the inorganic filler may be modified with a functional group capable of chemically bonding with the thermosetting resin through a reaction, or with a functional group highly compatible with the thermosetting resin (e.g., cyanate group, epoxy group, amino group, hydroxyl group, carboxyl group, vinyl group, styryl group, methacryl group, acrylic group, ureido group, mercapto group, sulfide group, isocyanate group, etc.). For example, silane coupling treatment or plasma treatment may be used.

[0079] When the epoxy resin composition according to the present embodiment contains an inorganic filler, the compounding ratio (total compounding ratio when two or more types are contained) is preferably 30 to 90% by volume, more preferably 50 to 85% by volume, based on the total volume of the epoxy resin, epoxy-modified polybutadiene compound, and aromatic amine compound. If the filling ratio is too low, the desired thermal conductivity cannot be obtained, and the inorganic filler tends to precipitate. On the other hand, if the filling ratio is too high, the viscosity becomes too high, making it difficult to obtain a uniform coating film, which may lead to an increase in pore defects.

[0080] The epoxy resin composition according to this embodiment contains at least a predetermined amount of boron nitride (BN) as an inorganic filler. By adjusting the proportion of boron nitride in the inorganic filler to a predetermined value or greater, heat-resistant adhesion can be further improved. Specifically, the proportion of the inorganic filler in the total volume of the epoxy resin, epoxy-modified polybutadiene compound, and aromatic amine compound in the epoxy resin composition is 50% by volume or more and 85% by volume or less. In this case, the proportion of boron nitride in the inorganic filler (hereinafter also referred to as the "BN ratio") is preferably 60% by volume or more, thereby further improving heat-resistant adhesion. The BN ratio is more preferably 65% ​​by volume or more, and even more preferably 70% by volume or more.

[0081] This is surprising considering that it is well known that, because boron nitride has almost no functional groups on its surface that contribute to adhesion with resins, the adhesive strength tends to decrease as the proportion of boron nitride in the inorganic filler increases (see, for example, paragraphs 0078 and 0123 of the claims of Patent Document 4). This phenomenon is presumed to be an effect brought about by the combined use of an epoxy-modified polybutadiene compound and boron nitride, and details will be provided below.

[0082] From the viewpoint of adhesion heat resistance, the upper limit of the BN ratio in the inorganic filler is not particularly limited. The upper limit of the BN ratio may be 100 vol% in one example, 95 vol% in another example, and 90 vol% in yet another example. Note that a BN ratio of 100 vol% refers to the case where only boron nitride is contained as the inorganic filler.

[0083] (solvent) The epoxy resin composition according to this embodiment preferably contains a solvent. An interlayer insulating resin sheet made of a cured product of the epoxy resin composition according to this embodiment has a phase-separated structure in which a discontinuous phase containing an epoxy-modified polybutadiene compound is dispersed in a continuous phase containing an epoxy resin. To form this phase-separated structure, the epoxy resin and the epoxy-modified polybutadiene compound are preferably dissolved in the solvent and uniformly dispersed in each other in a compatible state in the solvent-containing epoxy resin composition. When the epoxy resin and the epoxy-modified polybutadiene compound are heated in this state to proceed with curing, the epoxy resin and the amine curing agent react with each other, increasing their molecular weight and forming a continuous phase, while the epoxy-modified polybutadiene compound, which is less reactive than them, partially aggregates to form a discontinuous phase.

[0084] Therefore, the solvent used in the epoxy resin composition is preferably one that can dissolve the epoxy resin and the epoxy-modified polybutadiene compound. Examples of such solvents include amide solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide, and N-methyl-2-pyrrolidone (NMP), ether solvents such as 1-methoxy-2-propanol and ethylene glycol monomethyl ether, ketone solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone, and cyclopentanone, and aromatic solvents such as toluene and xylene. The solvents may be used alone or in combination.

[0085] (Other ingredients) The epoxy resin composition according to the present embodiment may further contain other components, such as coupling agents, such as silane coupling agents and titanium coupling agents, ion adsorbents, anti-settling agents, hydrolysis inhibitors, leveling agents, and antioxidants.

[0086] <Interlayer insulation resin sheet> The interlayer insulating resin sheet according to the second embodiment is a sheet-like member made of a cured product of the epoxy resin composition for interlayer insulation according to the first embodiment described above, and can be obtained, for example, by heating and curing a coating made of an epoxy resin composition containing a solvent. The interlayer insulating resin sheet according to this embodiment has a phase-separated structure in which a discontinuous phase containing an epoxy-modified polybutadiene compound is dispersed in a continuous phase containing an epoxy resin layer. The mechanism by which such a phase-separated structure is formed is as described above. That is, from a compatible state in which the epoxy resin and the epoxy-modified polybutadiene compound are dissolved in a solvent and uniformly dispersed, curing proceeds by heating, and the molecular weight of the epoxy-modified polybutadiene compound partially increases, increasing its viscosity and forming a discontinuous phase. The lower-viscosity epoxy resin forms a continuous phase (sea component), thereby forming a phase-separated structure (sea-island structure) in which discontinuous phases (island components) containing the epoxy-modified polybutadiene compound are dispersed in the continuous phase (sea component) containing the epoxy resin.

[0087] The interlayer insulating resin sheet according to this embodiment is formed from the epoxy resin composition according to the first embodiment and contains the above-mentioned epoxy-modified polybutadiene compound containing 1,4-bond repeating units, and therefore has excellent heat-resistant adhesion and can maintain good voltage resistance even after, for example, solder reflow treatment. The mechanism behind this is explained below based on the behavior of the loss tangent (tan δ) obtained by dynamic mechanical analysis (DMA).

[0088] In the interlayer insulating resin sheet according to this embodiment, the glass transition temperature Tg can be determined by dynamic viscoelasticity measurement (DMA). Specifically, a dynamic viscoelasticity measuring device is used to determine the storage modulus (E') and loss modulus (E") of a test specimen of the interlayer insulating resin sheet while changing the measurement temperature. The temperature showing the peak top (maximum value) of the loss tangent (tan δ), which is expressed as the ratio (E" / E') of the loss modulus (E") to the storage modulus (E'), is defined as the glass transition temperature Tg of the interlayer insulating resin sheet.

[0089] In the loss tangent (tanδ) of the resin sheet for interlayer insulation having a phase-separated structure including a continuous phase of an epoxy resin and a discontinuous phase of an epoxy-modified polybutadiene compound that is incompatible with the epoxy resin, there are a first peak of the first glass transition temperature Tg1 derived from the epoxy-modified polybutadiene compound and a second peak of the second glass transition temperature Tg2 derived from the epoxy resin. Here, the first glass transition temperature Tg1 and the second glass transition temperature Tg2 have a relationship of Tg1 < Tg2. Hereinafter, the first glass transition temperature Tg1 derived from the epoxy-modified polybutadiene compound is also referred to as "Tg1 of the epoxy-modified butadiene rubber phase", and the second glass transition temperature Tg2 derived from the epoxy resin is also referred to as "Tg2 of the epoxy resin phase", etc.

[0090] FIG. 1 is a graph showing the behavior of the storage modulus (E'), loss modulus (E"), and loss tangent (tanδ) obtained by dynamic viscoelasticity measurement (DMA) for a resin sheet for interlayer insulation manufactured using the epoxy resin composition according to the first embodiment. Specifically, it is a graph showing the behavior of the storage modulus (E'), loss modulus (E"), and loss tangent (tanδ) obtained by dynamic viscoelasticity measurement (DMA) for an insulating layer (resin sheet for interlayer insulation) manufactured using the epoxy resin composition 1 prepared in Example 1 described later. This insulating layer contains bisphenol A type diglycidyl ether as an epoxy resin and contains an epoxy-modified butadiene rubber containing a 1,4-bond repeating unit and a 1,2-bond repeating unit as an epoxy-modified polybutadiene compound.

[0091] As a result of intensive research by the present inventors, when using an epoxy-modified polybutadiene compound further containing a 1,4-bond repeating unit compared to using an epoxy-modified polybutadiene compound composed of a 1,2-bond repeating unit used in Patent Document 3 as an epoxy-modified butadiene rubber component incompatible with the epoxy resin, it has been found that Tg1 of the epoxy-modified butadiene rubber phase shifts to the low-temperature side, Tg2 of the epoxy resin phase shifts to the high-temperature side, and the difference between Tg1 and Tg2 becomes larger.

[0092] The lower the Tg1 of this epoxy-modified butadiene rubber phase, the lower the thermal expansion in the temperature range from Tg1 to Tg2 of the epoxy resin phase. Furthermore, since thermal expansion increases rapidly in the temperature range higher than Tg2, the higher the Tg2 of the epoxy resin phase, the more likely it is that low expansion can be maintained. A larger difference between Tg1 and Tg2 in this way can further limit the thermal expansion of the insulating layer (interlayer insulating resin sheet) until it reaches Tg2 of the epoxy resin phase during processing such as a solder reflow process. This improves the adhesion heat resistance of the interlayer insulating resin sheet according to this embodiment, making it possible to maintain a high level of excellent voltage resistance. Hereinafter, a larger difference between Tg1 and Tg2 is referred to as "low thermal expansion."

[0093] As described above, when boron nitride (BN) is used as an inorganic filler in combination with an epoxy-modified polybutadiene compound, the adhesion heat resistance is further improved when a predetermined amount of boron nitride (BN) is blended into the epoxy resin composition and the ratio of boron nitride to the inorganic filler (BN ratio) is increased. In this case, the inventors have confirmed that the difference between Tg1 and Tg2 is further increased, further reducing the thermal expansion of the insulating layer.

[0094] In the interlayer insulating resin sheet according to this embodiment, the first glass transition temperature Tg1 derived from the epoxy-modified polybutadiene compound is, in one example, −5° C. or lower, and in another example, −10° C. or lower. The second glass transition temperature Tg2 derived from the epoxy resin is, in one example, 175° C. or higher, and in another example, 180° C. or higher.

[0095] The fact that the resin sheet for insulating layer according to this embodiment has a phase-separated structure containing a continuous phase of the epoxy resin and a discontinuous phase of the epoxy-modified polybutadiene compound can be confirmed by the fact that the first peak at the first glass transition temperature Tg1 derived from the epoxy-modified polybutadiene compound and the second peak at the second glass transition temperature Tg2 derived from the epoxy resin do not overlap with each other, as shown in the loss tangent (tanδ) in FIG. 1 .

[0096] In addition to the loss tangent (tan δ), the presence of the phase-separated structure in the interlayer insulation resin sheet according to this embodiment can also be confirmed by microscopic observation and / or scattering measurement. In the case of microscopic observation, the phase-separated structure can be confirmed by a scanning electron microscope (SEM), atomic force microscope, optical microscope, transmission electron microscope, or the like. In the case of scattering measurement, the phase-separated structure can be confirmed by grazing incidence small-angle X-ray scattering measurement, elemental analysis, energy dispersive X-ray analysis, electron probe microanalyzer, X-ray photoelectron spectroscopy, or the like. As will be described in detail later, FIG. 2 is a photograph of a fracture surface of a cured product of the epoxy resin composition for interlayer insulation according to this embodiment that does not contain an inorganic filler, and it can be seen that a phase-separated structure is formed.

[0097] When the interlayer insulating resin sheet according to this embodiment contains an inorganic filler, the inorganic filler is present in both the discontinuous phase and the continuous phase, i.e., the inorganic filler may be present in either the discontinuous phase or the continuous phase.

[0098] <Laminate for circuit boards> A circuit board laminate according to a third embodiment includes a metal substrate, an insulating layer formed on at least one side of the metal substrate, and a metal foil formed on the insulating layer. FIG. 4 is a perspective view schematically illustrating the circuit board laminate according to this embodiment, and FIG. 5 is a cross-sectional view of the circuit board laminate shown in FIG. 4 taken along line II-II. The circuit board laminate 10 shown in FIGS. 4 and 5 has a three-layer structure in which an insulating layer 12 is formed on one side of a metal substrate 11, and a metal foil 13 is formed on the insulating layer 12. In other embodiments, the circuit board laminate 10 may have a five-layer structure in which insulating layers 12 are formed on both sides of a metal substrate 11, and a metal foil 13 is further formed on each insulating layer 12. In FIGS. 4 and 5, the X and Y directions are parallel to the main surfaces of the metal substrate 2 and perpendicular to each other, and the Z direction is the thickness direction perpendicular to the X and Y directions. While FIGS. 4 and 5 show a rectangular circuit board laminate 10 as an example, the circuit board laminate 10 may have other shapes.

[0099] In the circuit board laminate 10, the metal substrate 11 is made of, for example, a single metal or an alloy. Examples of materials that can be used for the metal substrate 11 include aluminum, iron, copper, an aluminum alloy, and stainless steel. The metal substrate 11 may further contain a non-metal such as carbon. For example, the metal substrate 11 may contain aluminum composited with carbon. The metal substrate 11 may have a single-layer structure or a multi-layer structure.

[0100] The metal substrate 11 has a high thermal conductivity. Typically, the metal substrate 11 has a thermal conductivity of 60 W·m -1 ·K -1 The metal substrate 11 has a thermal conductivity of 0.2 mm to 5 mm or more. The metal substrate 11 may be flexible or may not be flexible. The thickness of the metal substrate 11 may be in the range of 0.2 mm to 5 mm, for example.

[0101] The metal foil 13 is provided on the insulating layer 12. The metal foil 13 faces the metal substrate 11 with the insulating layer 12 sandwiched therebetween. The metal foil 13 is made of, for example, a single metal or an alloy. The material of the metal foil 13 can be, for example, copper or aluminum. The thickness of the metal foil 13 can be, for example, in the range of 10 μm to 500 μm.

[0102] The insulating layer 12 is an interlayer insulating resin sheet according to the second embodiment, which is a cured product of the epoxy resin composition according to the first embodiment. Therefore, the insulating layer 12 has a phase-separated structure containing a continuous phase of the epoxy resin and a discontinuous phase of the epoxy-modified polybutadiene compound. The storage modulus (E') of the insulating layer 12, obtained by dynamic mechanical analysis (DMA), exhibits the behavior shown in FIG. 1. The insulating layer 12 has a large difference between the first glass transition temperature Tg1 derived from the epoxy-modified polybutadiene compound and the second glass transition temperature Tg2 derived from the epoxy resin, and thus has excellent heat-resistant adhesion and can maintain good voltage resistance to a high degree. The thickness of the insulating layer 12 may be, for example, in the range of 50 μm to 300 μm.

[0103] The circuit board laminate 10 can be produced, for example, by the following method. First, the epoxy resin composition for interlayer insulation according to the present embodiment is applied to at least one of the metal substrate 11 and the metal foil 13 to form a coating film. The epoxy resin composition can be applied by, for example, roll coating, bar coating, or screen printing. It may be applied continuously or as a single plate. The coating film is dried as necessary.

[0104] Next, the metal substrate 11 and the metal foil 13 are stacked together with the coating film sandwiched between them, and then they are hot-pressed together to obtain the circuit board laminate 10.

[0105] In this method, a coating film is formed by applying the epoxy resin composition according to this embodiment to at least one of the metal substrate 11 and the metal foil 13. However, in another embodiment, a coating film may be formed in advance by applying the epoxy resin composition to a substrate such as a PET film and drying it, and then this coating film may be thermally transferred to one of the metal substrate 11 and the metal foil 13.

[0106] <Metal-based circuit board> Next, a metal base circuit board according to a fourth embodiment will be described. FIG. 6 is a cross-sectional view schematically showing a metal base circuit board according to a fourth embodiment. The metal base circuit board 20 shown in FIG. 6 includes a metal substrate 11, an insulating layer 12, and a circuit pattern 13a, in this order. The metal base circuit board 20 is obtained from the circuit board laminate 10 according to the third embodiment shown in FIGS. 4 and 5, and the circuit pattern 13a is obtained by patterning the metal foil 13 of the circuit board laminate 10. This patterning can be achieved, for example, by forming a mask pattern on the metal foil 13 and removing exposed portions of the metal foil 13 by etching. The metal base circuit board 20 can be obtained, for example, by patterning the metal foil 13 of the circuit board laminate 10 as described above, and then performing processing such as cutting and drilling as necessary.

[0107] The metal base circuit board 20 according to this embodiment is obtained from the circuit board laminate 10 described above, and has an insulating layer 12 made of the interlayer insulating resin sheet according to the second embodiment. Therefore, the metal base circuit board 20 has excellent heat-resistant adhesion and can maintain good voltage resistance even after, for example, solder reflow treatment.

[0108] <Power module> 7 is a cross-sectional view schematically showing a power module 100 according to a fifth embodiment. This power module 100 includes a metal base circuit board 20 according to the fourth embodiment, which includes a metal substrate 11, an insulating layer 12, and a circuit pattern 13a. Therefore, the power module 100 according to this embodiment has excellent heat-resistant adhesion and can maintain good voltage resistance even after, for example, solder reflow processing. In the current situation where heat generation temperatures are on the rise as power devices become more powerful, modules according to the embodiments of the present invention can be suitably used in temperature ranges that conventional power modules could not handle.

[0109] In the power module 100 shown in FIG. 7, 101 denotes a power device, 102 denotes a solder layer, 103 denotes a heat dissipation sheet, and 104 denotes a heat sink.

[0110] Furthermore, compared to the conventional power module 110, an example of which is shown in Fig. 8, the power module 100 according to this embodiment has fewer constituent members (layers) and is thinner overall due to the inclusion of the metal base circuit board 20 according to this embodiment, enabling a more compact design with lower thermal resistance. Another advantage is that assembly is easy because processing such as drilling and cutting is easy.

[0111] In the conventional power module 110 shown in FIG. 8, 101 denotes a power device, 102a denotes a first solder layer, 13a denotes a circuit pattern, 105 denotes a ceramic substrate, 106 denotes a metallized layer, 102b denotes a second solder layer, 11 denotes a metal substrate, 103 denotes a heat dissipation sheet, and 104 denotes a heat sink. [Example]

[0112] <Preparation of Epoxy Resin Composition> Epoxy resin compositions 1 to 4 and 101 to 104 were prepared by the following methods. (Example 1) Bisphenol A diglycidyl ether, epoxy-modified polybutadiene compound 1, diethyltoluenediamine as a curing agent, triphenylphosphine triphenylborane as curing accelerator 1, and triphenylphosphine as curing accelerator 2 were mixed in the blending ratios shown in Table 1 below to obtain mixture 1. The figures for the blending ratios in Table 1 indicate parts by mass excluding the inorganic filler.

[0113] Next, alumina filler (Al2O3) and boron nitride filler (BN) in a volume ratio of 20:45 were added as inorganic fillers to the obtained mixture 1 so that the total amount was 65 volume % relative to the total volume of bisphenol A diglycidyl ether, aromatic amine compound, and epoxy-modified polybutadiene compound 1, thereby obtaining mixture 2.

[0114] Next, methyl ethyl ketone (MEK) was added as a solvent to the obtained mixture 2 so that the nonvolatile concentration was 79% by mass, thereby preparing an epoxy resin composition 1 (slurry) having a viscosity suitable for coating.

[0115] Details of each raw material used in the preparation of the above-mentioned mixture 1 are as follows: Bisphenol A diglycidyl ether: Product name EXE850CRP, manufactured by DIC Corporation, Mw 300-1500. Epoxy-modified polybutadiene compound 1: trade name Ricon (registered trademark) 657E, manufactured by Cray Valley Corporation, Mn approximately 1900, repeating unit: [ka]

[0116] Curing agent: Diethyltoluenediamine (trade name DETDA-80; manufactured by Lonza Co., Ltd.) represented by the following formula: [ka]

[0117] Curing accelerator 1: Triphenylphosphine triphenylborane (trade name TPP-S; manufactured by Hokko Chemical Industry Co., Ltd.) [ka]

[0118] Curing accelerator 2: Triphenylphosphine (trade name TPP; manufactured by Hokko Chemical Industry Co., Ltd.) [ka]

[0119] (Example 2) Epoxy resin composition 2 was prepared in the same manner as in Example 1, except that the compounding ratio of epoxy-modified polybutadiene compound 1 was changed to the compounding ratio shown in Table 1.

[0120] (Example 3) Epoxy resin composition 3 was prepared in the same manner as in Example 1, except that the volume ratio of alumina filler (Al2O3) and boron nitride filler (BN) (20:45) was changed to the volume ratio shown in Table 1.

[0121] (Example 4) Epoxy resin composition 4 was prepared in the same manner as in Example 2, except that the volume ratio of alumina filler (Al2O3) and boron nitride filler (BN) (20:45) was changed to the volume ratio shown in Table 1.

[0122] (Comparative Example 1) An epoxy resin composition 101 was prepared in the same manner as in Example 1, except that the epoxy-modified polybutadiene compound 1 in Example 1 was changed to the epoxy-modified polybutadiene compound 2 shown below. Epoxy-modified polybutadiene compound 2: Product name JP200, manufactured by Nippon Soda Co., Ltd., Mw 2200, repeating unit: [ka]

[0123] (Comparative Example 2) An epoxy resin composition 102 was prepared in the same manner as in Comparative Example 1, except that the compounding ratio of the epoxy-modified polybutadiene compound 2 was changed to the compounding ratio shown in Table 1.

[0124] (Comparative Example 3) Epoxy resin composition 103 was prepared in the same manner as in Comparative Example 1, except that the volume ratio of alumina filler (Al2O3) and boron nitride filler (BN) (20:45) was changed to the volume ratio shown in Table 1.

[0125] Comparative Example 4 An epoxy resin composition 104 was prepared in the same manner as in Comparative Example 2, except that the volume ratio (20:45) of the alumina filler (Al2O3) and the boron nitride filler (BN) in Comparative Example 2 was changed to the mass ratio shown in Table 1.

[0126] <Confirmation of phase separation structure> Epoxy resin compositions 1a and 101a were prepared in the same manner as in Example 1 and Comparative Example 1, respectively, except that no inorganic filler was added. The fracture surfaces of test pieces made of cured products of these epoxy resin compositions were observed under a microscope. A photograph of the fracture surface of epoxy resin composition 1a is shown in Figure 2, and a photograph of the fracture surface of epoxy resin composition 101a is shown in Figure 3. It was confirmed that a phase-separated structure was formed in both samples.

[0127] <Production of test specimen> Each epoxy resin composition prepared above was applied to a PET film using a coater, and the solvent was dried by heating at 80°C for 40 minutes to obtain a dried coating film. Each resulting coating film was thermally transferred to a 2.0 mm thick base copper, and then a 20 mm diameter, 0.5 mm thick circuit copper plate was temporarily attached to the copper plate, with the coating film sandwiched between them, facing each other, and heat-treated at 185°C for 1 hour to obtain test specimens of metal base circuit boards equipped with an insulating layer 120 μm thick.

[0128] Dynamic Mechanical Analysis (DMA) The base copper and circuit copper were removed by etching from each of the test specimens produced above to extract the insulating layer, yielding test specimens measuring 2 mm in width, 60 mm in length, and 120 μm in film thickness. Using these test specimens, dynamic viscoelasticity measurements (storage modulus (E'), loss modulus (E"), and loss tangent (tanδ)) were performed under the following conditions. The glass transition temperatures Tg1 and Tg2 obtained from the loss tangent (tanδ) for each test specimen are shown in Table 1. Tg1 is the glass transition temperature of the epoxy-modified butadiene rubber phase, and Tg3 is the glass transition temperature of the epoxy resin phase. Figure 1 shows the dynamic viscoelasticity measurement data for Example 1, selected from the dynamic viscoelasticity measurement data obtained for each test specimen.

[0129] Apparatus: Dynamic viscoelasticity measuring device (manufactured by TA Instruments) Measurement mode: Tensile mode Heating rate: 2℃ / min Frequency: 1Hz Atmosphere: N2 Temperature range: -50℃~300℃

[0130] <Adhesion heat resistance> Each test piece was left floating in a solder bath for 5 minutes to reach a temperature of 300°C, after which a scanning acoustic tomograph (SAT) was used to check for the presence or absence of peeling at the adhesive interface between the metal base substrate and the circuit board. This was repeated until peeling occurred, and the number of times it could be endured without peeling (holding times) was measured and evaluated based on the following criteria. A higher number of holding times indicates better adhesion heat resistance. The results are shown in Table 1. (Number of times held) 3 or more times: A 2 times :B 0 or 1 time: C

[0131] <Post-soldering voltage resistance> In the above-mentioned adhesion heat resistance test, each test piece was floated in a solder bath for 5 minutes at a temperature of 300°C, and this was repeated twice before measuring the withstand voltage. Note that even for test pieces in which peeling occurred under the circuit, withstand voltage measurement is possible as long as adhesion to the insulating layer is maintained. The withstand voltage was measured by increasing the voltage by 0.2 kV every 5 seconds, and the voltage at which insulation breakdown occurred was taken as the withstand voltage. The results are shown in Table 1.

[0132] [Table 1]

[0133] The results shown in Table 1 indicate that by replacing the epoxy-modified polybutadiene compound with a compound containing a repeating unit derived from 1,2-bonded butadiene and further containing a repeating unit derived from 1,4-bonded butadiene, the adhesion heat resistance is improved and a high level of voltage resistance can be maintained.

[0134] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention. [Explanation of symbols]

[0135] 10. Circuit board laminates 11 Metal substrate 12 Insulating layer 13 Metal foil 13a Circuit pattern 20 Metal-based circuit board 100 Power Module 110 Conventional power module 101 Power Devices 102 solder layer 102a First solder layer 102b Second solder layer 103 Heat dissipation sheet 104 Heatsink 105 Ceramic substrate 106 Metallized layer

Claims

1. 1. An epoxy resin composition for interlayer insulation comprising an epoxy resin, an epoxy-modified polybutadiene compound, and an aromatic amine compound, wherein the epoxy-modified polybutadiene compound comprises a repeating unit represented by the following general formula (I), a repeating unit represented by the following general formula (II), and a repeating unit represented by the following general formula (III), and further comprises at least one of a repeating unit represented by the following general formula (i), a repeating unit represented by the following general formula (ii), and a repeating unit represented by the following general formula (iii), and the epoxy resin comprises at least bisphenol A diglycidyl ether: 【Chemistry 1】

2. 2. The epoxy resin composition for interlayer insulation according to claim 1, wherein the aromatic amine compound is a compound represented by the following general formula (IV): 【Chemistry 2】 In general formula (IV), R １ represents an alkyl group, m represents an integer of 2 or more, n represents an integer of 0 or more, and m and n satisfy m+n≦6. When n is 2 or more, a plurality of R １ may be the same as or different from each other.

3. 2. The epoxy resin composition for interlayer insulation according to claim 1, which contains a boron-phosphorus complex represented by the following general formula (V) and a phosphorus compound represented by the following general formula (VI): 【Transformation 3】 In general formula (V), R ２ and R ３ each independently represents an alkyl group, r represents an integer of 0 or more and 5 or less, and s represents an integer of 0 or more and 5 or less. When r is an integer of 2 or more, a plurality of R ２ may be the same or different. When s is an integer of 2 or more, a plurality of R ３ may be the same as or different from each other. 【Chemistry 4】 In general formula (VI), R ４ represents an alkyl group or an alkoxy group, and t represents an integer of 0 to 5. When t is an integer of 2 or more, a plurality of R ４ may be the same as or different from each other.

4. 2. The epoxy resin composition for interlayer insulation according to claim 1, which contains an inorganic filler.

5. 5. The epoxy resin composition for interlayer insulation according to claim 4, wherein the inorganic filler contains at least boron nitride, the proportion of the inorganic filler in the total volume of the epoxy resin, the epoxy-modified polybutadiene compound, and the aromatic amine compound is 50% by volume or more and 85% by volume, and the proportion of the boron nitride in the inorganic filler is 60% by volume or more.

6. An interlayer insulating resin sheet comprising a cured product of an interlayer insulating epoxy resin composition, The epoxy resin composition for interlayer insulation contains an epoxy resin, an epoxy-modified polybutadiene compound, and an aromatic amine compound, and the epoxy-modified polybutadiene compound contains a repeating unit represented by the following general formula (I), a repeating unit represented by the following general formula (II), and a repeating unit represented by the following general formula (III), and also contains at least one of a repeating unit represented by the following general formula (i), a repeating unit represented by the following general formula (ii), and a repeating unit represented by the following general formula (iii): The interlayer insulating resin sheet has a phase-separated structure in which a discontinuous phase containing the epoxy-modified polybutadiene compound is dispersed in a continuous phase containing the epoxy resin, and the first glass transition temperature Tg 1 derived from the epoxy-modified polybutadiene compound is −5°C or lower, and the second glass transition temperature Tg 2 derived from the epoxy resin is 175°C or higher. 【Transformation 5】

7. The epoxy resin contains at least bisphenol A diglycidyl ether.

7. The interlayer insulating resin sheet according to claim 6, 8. The resin sheet for interlayer insulation according to claim 6, wherein the aromatic amine compound is a compound represented by the following general formula (IV): 【Transformation 6】 In general formula (IV), R 1 represents an alkyl group, m represents an integer of 2 or more, n represents an integer of 0 or more, and m and n satisfy m + n ≦ 6. When n is 2 or more, multiple R 1s may be the same or different.

9. An interlayer insulation resin sheet as described in claim 6, wherein the epoxy resin composition for interlayer insulation contains a boron-phosphorus complex represented by the following general formula (V) and a phosphorus compound represented by the following general formula (VI): 【Transformation 7】 In general formula (V), R2 and R3 each independently represent an alkyl group, r represents an integer of 0 to 5, and s represents an integer of 0 to 5. When r is an integer of 2 or greater, multiple R2s may be the same or different. When s is an integer of 2 or greater, multiple R3s may be the same or different. 【Transformation 8】 In general formula (VI), R 4 represents an alkyl group or an alkoxy group, and t represents an integer of 0 to 5. When t is an integer of 2 or more, multiple R 4 s may be the same or different.

10. An interlayer insulation resin sheet as described in Claim 6, wherein the interlayer insulation epoxy resin composition contains an inorganic filler.

11. An interlayer insulating resin sheet as described in Claim 10, wherein the epoxy resin composition for interlayer insulation contains at least boron nitride as the inorganic filler, the proportion of the inorganic filler in the total volume of the epoxy resin, the epoxy-modified polybutadiene compound and the aromatic amine compound is 50% by volume or more and 85% by volume, and the proportion of the boron nitride in the inorganic filler is 60% by volume or more.

12. 12. A laminate for a circuit board comprising a metal substrate, an insulating layer provided on at least one surface of the metal substrate, and a metal foil provided on the insulating layer, wherein the insulating layer is an interlayer insulating resin sheet according to any one of claims 6 to 11.

13. A metal base circuit board comprising a metal substrate, an insulating layer provided on at least one surface of the metal substrate, and a circuit pattern provided on the insulating layer, wherein the insulating layer is an interlayer insulating resin sheet according to any one of claims 6 to 11.

14. A power module comprising the metal base circuit board according to claim 13.

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