Resin composition, cured resin product, and composite molded product

Abstract

To provide a resin composition that has high strength and excellent moisture-absorption reflow resistance and reduces the risk of the interfacial detachment caused by thermal expansion and contraction when the resin composition is combined with a metal sheet to form a multilayer body.SOLUTION: A resin composition comprises a resin and an aggregated inorganic filler, wherein a cured product of the resin composition shows a weight increase of 0.80% or less at 85°C and 85% RH, and wherein the storage modulus of the cured product of the resin composition excluding the inorganic filler is 1.0×107 Pa or more at 200°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a cured resin, and a composite molded article having a cured part made of the cured resin composition and a metal part. The resin composition, cured resin, and composite molded article of the present invention can be suitably used, for example, as a heat dissipation sheet for a power semiconductor device. [Background technology]

[0002] In recent years, power semiconductor devices used in various fields such as railways, automobiles, and general home appliances are shifting from conventional Si power semiconductors to power semiconductors using SiC, AlN, GaN, etc. in order to become smaller, lower cost, and more efficient. Power semiconductor devices are generally used as a power semiconductor module in which a plurality of semiconductor devices are arranged on a common heat sink and packaged.

[0003] Various issues have been raised in the practical application of such power semiconductor devices. One of these is the issue of dissipating heat generated by the devices. This issue generally affects the reliability of power semiconductor devices, which are capable of achieving high output and high density by operating at high temperatures. There are concerns that the heat generated by device switching will reduce reliability.

[0004] In recent years, heat generation due to the increasing density of integrated circuits has become a major problem, especially in the electrical and electronics fields, and how to dissipate heat has become an urgent issue.

[0005] One method to solve this problem is to use highly thermally conductive ceramic substrates such as alumina substrates and aluminum nitride substrates as heat dissipation substrates on which power semiconductor devices are mounted. However, ceramic substrates have drawbacks such as being easily cracked by impact and being difficult to make thin and compact.

[0006] Therefore, heat dissipation sheets using a resin such as a highly thermally conductive epoxy resin and a highly thermally conductive inorganic filler have been proposed. For example, Patent Document 1 proposes a heat dissipation resin sheet containing a resin with a Tg of 60°C or less and a boron nitride filler, in which the content of the boron nitride filler is 30 vol% or more and 60 vol% or less.

[0007] However, conventional heat dissipation resin sheets made of inorganic filler-containing resin compositions have the following problems when applied to power semiconductors.

[0008] (1) Power semiconductors require high voltage and large current flow, making voltage resistance important. However, conventional heat dissipation resin sheets do not have sufficient voltage resistance for use in power semiconductors.

[0009] (2) When a laminated heat dissipation sheet is made by laminating a substrate such as copper foil to improve thermal conductivity, the interface is prone to peeling due to thermal expansion and contraction caused by the large amount of heat generated during use. In the case of a ceramic substrate, the substrate is integrated with the copper plate by sintering, so peeling at the interface is unlikely to occur. However, in the case of a heat-dissipating resin sheet, the integration is achieved by thermocompression bonding of the cured film, so peeling at the interface is likely to occur.

[0010] To prevent interfacial delamination due to expansion and contraction, it is conceivable to increase the degree of crosslinking of the epoxy resin to increase the strength of the cured product. Increasing the degree of crosslinking requires increasing the epoxy equivalent of the epoxy resin. In this case, the addition reaction between the epoxy groups of the epoxy resin and active hydrogen increases the hydroxyl group concentration, and as this concentration increases, the moisture absorption rate tends to increase. An increase in the moisture absorption rate of the epoxy resin reduces the insulating properties of the cured product and also reduces the voltage resistance performance under high-temperature and high-humidity conditions. For this reason, this approach was considered undesirable.

[0011] One of the processes for assembling power semiconductor modules is the solder reflow process. In this process, the temperature of components is rapidly raised to melt the solder and join the metal components together. This reflow process can cause degradation of the components used in the module, resulting in, for example, interfacial peeling between the cured material and the metal, or a decrease in insulation performance, which can reduce the reliability of the power semiconductor module. Additionally, components can absorb moisture during storage prior to the reflow process, significantly accelerating component degradation during the solder reflow process and further reducing the performance of the resulting power semiconductor module. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-36415 Summary of the Invention [Problem to be solved by the invention]

[0013] An object of the present invention is to provide a resin composition and cured resin that have high strength, excellent moisture absorption reflow resistance, and reduced problems of interfacial peeling associated with thermal expansion and contraction when laminated with a metal plate, as well as a composite molded product using this resin composition. [Means for solving the problem]

[0014] The present inventors have discovered a resin composition containing an aggregated inorganic filler, wherein the weight increase rate of the resin composition after curing at 85°C and 85% RH is 0.80% or less, and the storage modulus of the cured product of the resin composition excluding the inorganic filler at 200°C is 1.0 × 10 7 It has been discovered that a cured resin material made from a resin composition having a tensile strength of 100 Pa or more has high insulating properties after a moisture absorption reflow test in which a reflow test is performed after storage under high-temperature and high-humidity conditions (hereinafter, this property may be referred to as "moisture absorption reflow resistance"), and can also solve the problem of interfacial peeling. The present inventors have also found that by using a cured resin having a storage modulus and a weight gain rate within specific ranges, excellent moisture absorption reflow resistance can be achieved and the problem of interfacial peeling can be resolved.

[0015] The present invention provides the following.

[0016] [1] A resin composition containing a resin and an aggregated inorganic filler, wherein the weight gain of the resin composition after curing at 85°C and 85% RH is 0.80% or less, and the storage modulus of the cured product of the resin composition excluding the inorganic filler at 200°C is 1.0 × 10 7 The resin composition has a viscosity of 100 Pa or more.

[0017] [2] The resin composition contains an epoxy resin having three or more epoxy groups per molecule. The resin composition according to [1],

[0018] [3] The resin composition according to [1] or [2], wherein the resin composition contains an epoxy resin having a biphenyl structure and a weight-average molecular weight of 10,000 or more.

[0019] [4] The resin composition according to [3], wherein the epoxy resin having a biphenyl structure and a weight average molecular weight of 10,000 or more further has at least one structure selected from the group consisting of a structure represented by the following structural formula (1) and a structure represented by the following structural formula (2):

[0020] [ka]

[0021] (In formula (1), R 1 and R 2 Each represents an organic group, and in formula (2), R 3 represents a divalent cyclic organic group.

[0022] [5] The resin composition according to [3] or [4], wherein the content of the epoxy resin having a biphenyl structure and a weight average molecular weight of 10,000 or more is 1% by weight or more and 50% by weight or less, based on 100% by weight of the solid content of the resin composition excluding the inorganic filler.

[0023] [6] The resin composition according to any one of [2] to [5], wherein the content of the epoxy resin having three or more epoxy groups per molecule is 10% by weight or more and 50% by weight or less, based on 100% by weight of the solid content of the resin composition excluding the inorganic filler.

[0024] [7] The resin composition according to any one of [2] to [6], wherein the molecular weight of the epoxy resin having three or more epoxy groups per molecule is 800 or less.

[0025] [8] The resin composition according to any one of [1] to [7], further comprising a compound having a heterocyclic structure containing a nitrogen atom.

[0026] [9] The resin composition according to any one of [1] to [8], wherein the agglomerated inorganic filler is agglomerated particles of boron nitride.

[0027]

[10] The resin composition according to [9], wherein the agglomerated boron nitride particles have a house-of-cards structure.

[0028]

[11] A composite molded article having a cured product part made of a cured product of the resin composition according to any one of [1] to

[10] and a metal part.

[0029]

[12] A semiconductor device having the composite molding according to

[11] .

[0030]

[13] A cured resin product using a resin composition containing a resin and an aggregated inorganic filler, wherein the weight gain at 85°C and 85% RH is 0.80% or less, and the storage modulus at 200°C after curing of the resin composition excluding the inorganic filler is 1.0 × 10 7 The cured resin has a hardness of 100 Pa or more. [Effects of the Invention]

[0031] The resin composition of the present invention has high strength and excellent resistance to moisture absorption and reflow, and when laminated with a metal plate, there is almost no problem of interfacial peeling due to thermal expansion and contraction.

[0032] The cured resin of the present invention has high strength and excellent resistance to moisture absorption and reflow, and when laminated with a metal plate, it is almost free from the problem of interfacial peeling that occurs with thermal expansion and contraction.

[0033] The resin composition and cured resin of the present invention, as well as a composite molded product using this resin composition, can be suitably used as a heat dissipation sheet for a power semiconductor device, and a highly reliable power semiconductor module can be realized. DETAILED DESCRIPTION OF THE INVENTION

[0034] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments and can be practiced in various modified forms within the scope of the gist thereof.

[0035] [Resin composition] The resin composition of the present invention contains a resin and an aggregated inorganic filler, and the weight increase rate of the resin composition after curing at 85°C and 85% RH is 0.80% or less, and the storage modulus of the cured product of the resin composition excluding the inorganic filler at 200°C is 1.0 × 10 7 Pa or more.

[0036] In the present invention, the term "resin composition" refers to an uncured composition, for example, a composition in a state before curing in a molding and pressurizing step, etc. More specifically, examples include a slurry resin composition to be subjected to a coating step described below, a sheet that has been subjected to a coating step, and a sheet that has been subjected to a step of coating, drying, etc. before curing.

[0037] In the present invention, the term "cured resin" refers to a cured product in which the exothermic peak obtained when the temperature is increased from 40°C to 250°C at a rate of 10°C / min using a differential scanning calorimeter (DSC) is 10 J / g or less.

[0038] In the present invention, the resin composition excluding the inorganic filler refers to components other than the inorganic filler in the resin composition. The inorganic filler will be described later, and includes both aggregated inorganic filler and non-aggregated inorganic filler (non-aggregated inorganic filler).

[0039] In the present invention, the "solid content" in the resin composition refers to all components in the resin composition other than the solvent.

[0040] The resin composition of the present invention may contain "other components" other than the resin and the aggregated inorganic filler, as long as the effects of the present invention are not impaired. Examples of other components include non-aggregated inorganic fillers, curing agents, curing catalysts, solvents, surface treatment agents such as silane coupling agents, insulating carbon components such as reducing agents, viscosity modifiers, dispersants, thixotropy-imparting agents, flame retardants, colorants, organic fillers, and organic solvents. In particular, the inclusion of a dispersant makes it possible to form a uniform cured resin product, thereby improving the thermal conductivity and dielectric breakdown properties of the resulting cured resin product. Specific examples of these "other components" that may be contained in the resin composition of the present invention will be described later.

[0041] <Storage modulus> The storage modulus at 200°C after curing of the resin composition of the present invention excluding the inorganic filler is 1.0 × 10 7 The storage modulus is 1×10 Pa or more. 7 If the compressive strength is less than Pa, the strength of the cured resin product (hereinafter simply referred to as "cured resin product") obtained by curing the resin composition of the present invention will be low, and as a result, in a moisture absorption reflow test, voids will be generated inside, resulting in a decrease in insulating performance, and in the case of a composite molded product having a cured product part made of the cured resin composition of the present invention and a metal part, peeling may occur at the interface between the metal part and the cured product part. From the viewpoint of maintaining performance after moisture absorption and reflow testing, this storage modulus is 1.3 × 10 7 Pa or more, and 1.5 × 10 7Pa or more is more preferable, and 1.7 × 10 7 It is more preferable that the viscosity is 100 Pa or more. On the other hand, the storage modulus is 5 × 10 9 Pa or less, and 9 Pa or less is more preferable, and 5×10 8 It is more preferable that the storage modulus is equal to or less than the above upper limit. When the storage modulus is equal to or less than the above upper limit, excessive internal stress generated by the moisture absorption reflow test can be suppressed, and cracking of the obtained cured resin and interfacial peeling between the metal part and the cured resin part tend to be suppressed. Furthermore, when the storage modulus is within the above range, the cured resin composition can easily penetrate into the irregularities of the metal, which is the adherend described below, and the cured resin that has penetrated into the irregularities exhibits a strong anchor effect, which tends to improve the adhesion between the metal and the cured resin.

[0042] Controlling the storage modulus after curing to fall within the above-mentioned specific range can be achieved, for example, by introducing a rigid structure such as an aromatic ring into the components that make up the resin-containing component, or by introducing a polyfunctional component having multiple reactive groups to increase the crosslink density of the cured product, as described below.

[0043] The curing conditions for the resin composition of the present invention excluding the inorganic filler when measuring the storage modulus are as shown in the examples described later, namely, the temperature is increased from 25°C at a rate of 14°C per minute to 120°C, held at this temperature for 30 minutes, then increased at a rate of 7°C per minute to 175°C, held at this temperature for 30 minutes, then increased at a rate of 7°C per minute to 200°C, and held at this temperature for 10 minutes.

[0044] The storage modulus may be measured by any conventionally known method, and specifically, the method described in the Examples section below can be mentioned.

[0045] <Weight increase rate> After curing, the resin composition (containing the inorganic filler) of the present invention exhibits a weight gain of 0.8% or less at 85°C and 85% RH. If the weight gain exceeds 0.8%, the object of the present invention, namely, maintaining high insulating properties and preventing interfacial peeling after a moisture absorption reflow test, cannot be achieved. From the viewpoints of maintaining high insulating properties after a moisture absorption reflow test and preventing interfacial peeling, the smaller this weight gain rate is, the more preferable, and it is preferably 0.75% or less, and more preferably 0.7% or less. The lower limit of the weight gain rate is not particularly limited, but from the viewpoints of achieving both strength and insulating performance of the resin cured product and film formability, it is, for example, 0.2% or more.

[0046] There are various possible causes of the weight increase of the cured resin, but it is important to control the weight increase due to moisture absorption. The present invention is based on the finding that the problems of the present invention can be solved by providing a resin composition with a weight increase rate at 85°C and 85% RH after curing that falls within the above-mentioned specific range.

[0047] A resin composition having a weight gain rate within a specific range at 85°C and 85% RH can be obtained by, for example, introducing a highly hydrophobic structure such as an aliphatic skeleton or an aromatic ring into the resin component of the resin composition. This can be achieved by controlling the weight gain rate.

[0048] The weight gain of the resin composition of the present invention at 85° C. and 85% RH after curing is measured by the method described in the Examples section below.

[0049] <Resin> The resin contained in the resin composition of the present invention is not particularly limited as long as it has a specific storage modulus and weight gain rate after curing. For example, it may be a resin that is cured by heat or light in the presence of a curing agent or a curing catalyst. In particular, a thermosetting resin is preferred from the viewpoint of ease of production.

[0050] Specific examples of the resin include epoxy resins, phenolic resins, polycarbonate resins, unsaturated polyester resins, urethane resins, melamine resins, urea resins, and maleimide resins. Among these, epoxy resins are preferred from the viewpoints of viscosity, heat resistance, moisture absorption, and ease of handling. Examples of epoxy resins include epoxy group-containing silicon compounds, aliphatic epoxy resins, bisphenol A or F epoxy resins, novolac epoxy resins, alicyclic epoxy resins, glycidyl ester epoxy resins, multifunctional epoxy resins, and polymeric epoxy resins.

[0051] The resin composition of the present invention preferably contains 5 wt% or more of resin, more preferably 30 wt% or more, and even more preferably 50 wt% or more of resin, based on 100 wt% of the solid content of the resin composition excluding the inorganic filler. The resin composition of the present invention more preferably contains 99 wt% or less of resin, based on 100 wt% of the solid content of the resin composition excluding the inorganic filler. When the resin content is equal to or greater than the lower limit, moldability is improved, and when it is equal to or less than the upper limit, the content of other components can be ensured, which tends to improve thermal conductivity.

[0052] (epoxy resin) Epoxy resin is a general term for compounds that have one or more oxirane rings (epoxy groups) in the molecule. The oxirane rings (epoxy groups) contained in epoxy resins can be either alicyclic epoxy groups or glycidyl groups.

[0053] The epoxy resin used in the present invention may be an aromatic oxirane ring (epoxy group)-containing compound. Specific examples thereof include bisphenol-type epoxy resins obtained by glycidylating bisphenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol AD, tetramethylbisphenol S, and tetrafluorobisphenol A; biphenyl-type epoxy resins; epoxy resins obtained by glycidylating dihydric phenols such as dihydroxynaphthalene and 9,9-bis(4-hydroxyphenyl)fluorene; epoxy resins obtained by glycidylating trisphenols such as 1,1,1-tris(4-hydroxyphenyl)methane; epoxy resins obtained by glycidylating tetrakisphenols such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane; and novolac-type epoxy resins obtained by glycidylating novolacs such as phenol novolac, cresol novolac, bisphenol A novolac, and brominated bisphenol A novolac.

[0054] The resin composition of the present invention preferably contains 20% by weight or more, and more preferably 45% by weight or more, of an epoxy resin based on 100% by weight of the resin contained in the resin composition of the present invention. There is no particular upper limit to the content of the epoxy resin in the resin composition of the present invention, and the epoxy resin may be contained in 100% by weight of the total resin components. The epoxy resin may be within the above range. By including the above range, it becomes easier to control the high elasticity and weight gain rate of the cured product of the resin composition, and the storage modulus and weight gain rate tend to fall within the above-mentioned specific ranges.

[0055] ((Multifunctional epoxy resin)) The resin composition of the present invention preferably contains an epoxy resin having three or more oxirane rings (epoxy groups) in one molecule (hereinafter, sometimes referred to as a "multifunctional epoxy resin"). By including a multifunctional epoxy resin in the resin composition of the present invention, it becomes possible to introduce highly polar oxirane rings (epoxy groups) at a high density. This increases the effects of physical interactions such as van der Waals forces and hydrogen bonds, which tends to improve the adhesion between the metal and the cured resin in the composite molded product. Furthermore, by including a polyfunctional epoxy resin, the storage modulus of the cured resin tends to be more easily adjusted to fall within the above-mentioned specific range, and the adhesion between the metal and the cured resin tends to be improved. Furthermore, by improving the reactivity of the oxirane ring (epoxy group), the amount of hydroxyl groups during the curing reaction can be reduced, and an increase in moisture absorption can be suppressed.

[0056] The polyfunctional epoxy resin may be used alone or in combination of two or more kinds.

[0057] A polyfunctional epoxy resin is an epoxy resin having three or more oxirane rings (epoxy groups) in one molecule, preferably four or more oxirane rings (epoxy groups) in one molecule. There is no particular upper limit to the number of oxirane rings (epoxy groups) in one molecule of a polyfunctional epoxy resin, but 10 or less is preferred, 8 or less is more preferred, and 6 or less is particularly preferred. When the number of oxirane rings (epoxy groups) in one molecule is within this range, adhesion between metal and cured resin is improved and an increase in moisture absorption tends to be suppressed.

[0058] The oxirane ring (epoxy group) is more preferably a glycidyl group from the viewpoints of reaction rate and heat resistance.

[0059] The resin composition of the present invention contains a polyfunctional epoxy resin having multiple oxirane rings (epoxy groups), particularly glycidyl groups, in one molecule, which tends to improve the crosslink density of the cured product and increase the strength of the resulting cured resin. As a result, when internal stress is generated in the cured resin during a moisture absorption reflow test, the cured resin maintains its shape without deformation or fracture, which tends to suppress the generation of voids and other gaps in the cured resin.

[0060] The molecular weight of the polyfunctional epoxy resin is not particularly limited, but is preferably 1000 or less, more preferably 800 or less, and even more preferably 600 or less. The molecular weight of the polyfunctional epoxy resin is preferably 100 or more, and more preferably 150 or more. When the molecular weight of the polyfunctional epoxy resin is within the above range, the storage modulus at 200°C of the cured resin after curing of the resin composition can be 1.0 × 10 7 It tends to be easier to achieve a value of 0.1 Pa or higher.

[0061] Specifically, EX321L, DLC301, DLC402, etc. manufactured by Nagase ChemteX Corporation can be used as the polyfunctional epoxy resin.

[0062] The content of the polyfunctional epoxy resin in the resin composition of the present invention is not particularly limited, but is preferably 5% by weight or more, more preferably 10% by weight or more, based on 100% by weight of the solid content of the resin composition excluding the inorganic filler. It is also preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less. It is further preferably 5% by weight or more and 50% by weight or less, even more preferably 10% by weight or more and 40% by weight or less, and even more preferably 10% by weight or more and 30% by weight or less. When the content of the polyfunctional epoxy resin is above the lower limit, the aforementioned advantages resulting from the inclusion of the polyfunctional epoxy resin are not obtained. On the other hand, by ensuring that the content of the polyfunctional epoxy resin is equal to or less than the above upper limit, it is possible to suppress the moisture absorption of the cured resin material and to improve the strength performance of the cured resin material, thereby achieving both of these performances.

[0063] ((Specific epoxy resin)) The resin in the resin composition of the present invention preferably contains an epoxy resin having a biphenyl structure and a weight average molecular weight of 10,000 or more (hereinafter, sometimes referred to as a "specific epoxy resin").

[0064] In the following description, the term "organic group" refers to any group containing carbon atoms. Examples of the organic group include alkyl groups, alkenyl groups, and aryl groups, which may be substituted with halogen atoms, groups containing heteroatoms, or other hydrocarbon groups.

[0065] The specific epoxy resin having a biphenyl structure and a weight-average molecular weight of 10,000 or more preferably further has at least one structure selected from the structure represented by the following structural formula (1) (hereinafter, sometimes referred to as "Structure (1)") and the structure represented by the following structural formula (2) (hereinafter, sometimes referred to as "Structure (2)").

[0066] [ka]

[0067] (In formula (1), R 1 and R 2 Each represents an organic group, and in formula (2), R 3 represents a divalent cyclic organic group.

[0068] Furthermore, the specific epoxy resin may be an epoxy resin having a structure represented by the following structural formula (3) (hereinafter, sometimes referred to as "structure (3)").

[0069] [ka]

[0070] (In formula (3), R 4 , R 5 , R6 , R 7 each independently represents an organic group having a molecular weight of 15 or more.

[0071] In the above formula (1), R 1 and R 2 At least one of them is preferably an organic group having a molecular weight of 16 or more, particularly a molecular weight of 16 to 1000. Examples include alkyl groups such as ethyl, propyl, butyl, pentyl, hexyl, and heptyl, and aryl groups such as phenyl, tolyl, xylyl, naphthyl, and fluorenyl.

[0072] R 1 and R 2 may both be organic groups with a molecular weight of 16 or more, or one may be an organic group with a molecular weight of 16 or more and the other may be an organic group with a molecular weight of 15 or less or a hydrogen atom. 1 and R 2 One of the groups is an organic group having a molecular weight of 16 or more and the other an organic group having a molecular weight of 15 or less, and it is particularly preferable that one of the groups is a methyl group and the other a phenyl group, as this makes it easier to control the handling properties such as the viscosity of the resin and from the viewpoint of the strength of the cured product.

[0073] In equation (2), R 3 is a divalent cyclic organic group, which may be an aromatic ring structure such as a benzene ring structure, a naphthalene ring structure, or a fluorene ring structure, or an aliphatic ring structure such as cyclobutane, cyclopentane, or cyclohexane, and may independently have a substituent such as a hydrocarbon group or a halogen atom.

[0074] R 3 The divalent bond may be a divalent group on a single carbon atom or on different carbon atoms. Preferred examples include divalent aromatic groups having 6 to 100 carbon atoms and divalent groups derived from cycloalkanes having 2 to 100 carbon atoms, such as cyclopropane and cyclohexane. 3is particularly preferably a 3,3,5-trimethyl-1,1-cyclohexylene group represented by the following structural formula (4) from the viewpoint of controlling the handleability of the resin, such as viscosity, and strength of the cured product.

[0075] [ka]

[0076] In equation (3), R 4 , R 5 , R 6 , R 7 are each independently an organic group having a molecular weight of 15 or more. Preferably, they are alkyl groups having a molecular weight of 15 to 1000, and particularly preferably R 4 , R 5 , R 6 , R 7 It is preferable that all of the groups be methyl groups from the viewpoint of controlling the handling properties such as the viscosity of the resin and the strength of the cured product.

[0077] The specific epoxy resin is preferably an epoxy resin containing either one of Structure (1) or Structure (2) and a biphenyl structure, and more preferably an epoxy resin containing either one of Structure (1) or Structure (2) and Structure (3). When the specific epoxy resin contains these structures, it tends to be possible to suppress the moisture absorption of the cured product and simultaneously achieve the strength retention performance of the resin composition.

[0078] Such specific epoxy resins are generally made of bisphenol A or bisphenol F Compared to epoxy resins with a skeletal structure, these resins contain a large amount of hydrophobic hydrocarbon and aromatic structures. Therefore, by blending specific epoxy resins, the moisture absorption of the cured product of the resin composition can be reduced. From the viewpoint of reducing the amount of moisture absorption, it is preferable that the specific epoxy resin contains a large amount of the hydrophobic structures (1), (2), and (3).

[0079] The weight-average molecular weight of the specific epoxy resin is preferably 10,000 or more, more preferably 20,000 or more, and even more preferably 25,000 or more, and is preferably 80,000 or less, more preferably 70,000 or less, and even more preferably 60,000 or less.

[0080] The specific epoxy resin is preferably more hydrophobic, and specifically, the epoxy equivalent of the specific epoxy resin is preferably larger, preferably 3,000 g / equivalent or more, more preferably 4,000 g / equivalent or more, and even more preferably 5,000 g / equivalent or more, and the epoxy equivalent of the specific epoxy resin is preferably 20,000 g / equivalent or less, and more preferably 5,000 g / equivalent or more and 20,000 g / equivalent or less.

[0081] The weight average molecular weight of the epoxy resin is a value calculated as polystyrene as measured by gel permeation chromatography. The epoxy equivalent is defined as "the weight of an epoxy resin containing one equivalent of epoxy groups" and can be measured in accordance with JIS K7236.

[0082] Such specific epoxy resins may be used alone or in combination of two or more thereof. The specific epoxy resin may have a plurality of epoxy groups.

[0083] The content of the specific epoxy resin in the resin composition of the present invention is not particularly limited, but is preferably 5% by weight or more, more preferably 10% by weight or more, based on 100% by weight of the solid content of the resin composition excluding the inorganic filler. Also, it is preferably 50% by weight or less, more preferably 40% by weight or less. By keeping the content of the specific epoxy resin at or below the upper limit, the storage modulus of the cured product tends to be improved or maintained, and reflow resistance tends to be improved. By keeping the content of the specific epoxy resin at or above the lower limit, the resin composition becomes easier to apply, and the resulting cured resin tends to have flexibility.

[0084] ((Content ratio of specific epoxy resin to multifunctional epoxy resin)) In particular, it is preferable that the resin composition of the present invention contains both a specific epoxy resin and a polyfunctional epoxy resin as epoxy resins, in order to achieve both high elasticity and low moisture absorption in the cured product of the resin composition.

[0085] When the resin composition of the present invention contains both a specific epoxy resin and a polyfunctional epoxy resin, the content ratio of the specific epoxy resin to the polyfunctional epoxy resin is not particularly limited, but is preferably specific epoxy resin:polyfunctional epoxy resin = 10-90:90-10 (weight ratio), more preferably 20-80:80-20 (weight ratio), and particularly preferably 30-70:70-30 (weight ratio). When the content ratio of the specific epoxy resin to the polyfunctional epoxy resin is within this range, it becomes easier to control the storage modulus and weight gain rate described above within appropriate ranges.

[0086] ((Other epoxy resins)) The resin composition of the present invention may contain an epoxy resin other than the specific epoxy resin and the polyfunctional epoxy resin. The epoxy resin other than the specific epoxy resin and the polyfunctional epoxy resin contained in the resin composition of the present invention is not particularly limited, but for example, bisphenol A and epoxy resins obtained by glycidylating tetrakisphenols such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane; novolac-type epoxy resins obtained by glycidylating novolacs such as phenol novolac, cresol novolac, bisphenol A novolac, and brominated bisphenol A novolac; and silicone-containing epoxy resins.

[0087] <Inorganic filler> In the present invention, inorganic fillers include agglomerated inorganic fillers and non-agglomerated inorganic fillers.

[0088] The resin composition of the present invention comprises an aggregated inorganic filler. The resin composition of the present invention may contain a non-agglomerated inorganic filler in addition to the agglomerated inorganic filler. The non-agglomerated inorganic filler also includes a spherical filler, which will be described later.

[0089] The inclusion of the aggregated inorganic filler in the resin composition of the present invention enables the thermal conductivity and insulating properties of the cured resin product to be improved and the linear expansion coefficient to be controlled. In particular, in the pressurization step described below, the aggregated inorganic fillers deform as they come into contact with each other, and the surface contact forms more heat conduction paths, resulting in a cured resin product with high thermal conductivity. Furthermore, the deformation of the aggregated inorganic filler effectively removes gaps or voids between the fillers, improving insulating properties.

[0090] The resin composition of the present invention contains a resin and an inorganic filler, and by using the aforementioned epoxy resin suitable for the present invention in combination with the aggregated inorganic filler, the deformed state of the filler can be maintained even after the aggregated inorganic filler is deformed in the pressurizing step described below. Furthermore, by keeping the weight gain rate of the resin composition of the present invention within the aforementioned specific range after curing, the deformed state of the filler can be maintained even after the moisture absorption reflow step.

[0091] When the resin composition and cured resin contain only a single filler such as silica or alumina, even after the pressurization step, the contact between the fillers is point contact, and an effective heat conduction path cannot be formed. Furthermore, the gaps or voids between the fillers cannot be removed, and the insulation properties may be reduced.

[0092] The agglomerated morphology of the agglomerated inorganic filler can be confirmed by a scanning electron microscope (SEM).

[0093] (Agglomerated inorganic filler) As the agglomerated inorganic filler, an electrically insulating filler can be used, and examples thereof include those composed of at least one type of inorganic particles selected from the group consisting of metal carbides, metal oxides, and metal nitrides.

[0094] Examples of metal carbides include silicon carbide, titanium carbide, and tungsten carbide. Examples of metal oxides include magnesium oxide, aluminum oxide, silicon oxide, calcium oxide, zinc oxide, yttrium oxide, zirconium oxide, cerium oxide, ytterbium oxide, and sialon (ceramics composed of silicon, aluminum, oxygen, and nitrogen). Examples of metal nitrides include boron nitride, aluminum nitride, and silicon nitride. .

[0095] In particular, when used in applications requiring insulation, such as power semiconductors, agglomerated inorganic fillers should have a volume resistivity of 1×10 13 Ω·cm or more, especially 1×10 14 It is preferable that the inorganic particles constituting the aggregated inorganic filler be made of an inorganic compound with excellent insulating properties of Ω·cm or more. In particular, the inorganic particles constituting the aggregated inorganic filler are preferably made of a metal oxide and / or a metal nitride, since the cured resin has sufficient electrical insulating properties.

[0096] Specific examples of such metal oxides and metal nitrides include alumina (Al2O3, volume resistivity 1×10 14 Ω·cm), aluminum nitride (AlN, volume resistivity 1×10 14 Ω·cm), boron nitride (BN, volume resistivity 1×10 14 Ω·cm), silicon nitride (Si3N4, volume resistivity 1×10 14 Ω·cm), silica (SiO2, volume resistivity 1×10 14 Among them, alumina, aluminum nitride, boron nitride, and silica are preferred, and alumina and boron nitride are particularly preferred.

[0097] There are no particular limitations on the method or degree of agglomeration of the agglomerated inorganic filler. The aggregated inorganic filler may be surface-treated with a surface treatment agent, and known surface treatment agents can be used.

[0098] The aggregated inorganic filler may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0099] As the agglomerated inorganic filler, it is preferable to use the following agglomerated boron nitride particles, from the viewpoint of effectively achieving the above-mentioned effects of using the agglomerated inorganic filler. The agglomerated boron nitride particles may be used in combination with inorganic fillers of different shapes and types.

[0100] (Boron nitride agglomerated particles) Boron nitride has high thermal conductivity, but because it is flaky, it has excellent thermal conductivity in the planar direction but high thermal resistance in the direction perpendicular to the plane. Agglomerated particles made by aggregating these flaky particles into spherical shapes are preferable because they are easy to handle.

[0101] In agglomerated particles of boron nitride, in which particles of boron nitride are stacked like cabbage, the radial direction of the agglomerated particles is the direction in which the thermal resistance is greatest. As the boron nitride agglomerated particles, it is preferable that the boron nitride particles are aligned in the planar direction so that the radial direction of the agglomerated particles is the direction of good thermal conductivity.

[0102] The boron nitride agglomerated particles also preferably have a house-of-cards structure. The "house of card structure" is described, for example, in Ceramics 43 No. 2 (published by the Ceramic Society of Japan in 2008), and refers to a structure in which plate-like particles are layered in a complex manner without being oriented. More specifically, boron nitride agglomerated particles having a house of card structure are aggregates of boron nitride primary particles, and have a structure in which the flat surfaces and end surfaces of the primary particles are in contact with each other to form, for example, a T-shaped aggregate.

[0103] The boron nitride agglomerated particles used in the present invention are particularly preferably agglomerated particles of boron nitride having the above-mentioned house-of-card structure. By using agglomerated particles of boron nitride having a house-of-card structure, thermal conductivity can be further increased.

[0104] The new Mohs hardness of the boron nitride agglomerated particles is not particularly limited, but is preferably not more than 5. There is no particular lower limit to the new Mohs hardness of the boron nitride agglomerated particles, but it is, for example, 1 or more.

[0105] When the new Mohs hardness is 5 or less, the particles dispersed in the resin composition tend to come into surface contact with each other, forming heat conduction paths between the particles and tending to improve the thermal conductivity of the cured resin.

[0106] The volume average particle diameter of the boron nitride agglomerated particles is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more. The volume average particle diameter of the boron nitride agglomerated particles is preferably 100 μm or less, more preferably 90 μm or less. When the volume average particle diameter is equal to or greater than the above lower limit, the interparticle interface in the resin composition and the cured resin is suppressed, which tends to reduce thermal resistance and obtain high thermal conductivity. When the volume average particle diameter is equal to or less than the above upper limit, the cured resin tends to obtain surface smoothness.

[0107] The volume average particle size of the boron nitride agglomerated particles means the particle size at which the cumulative volume reaches 50% when a cumulative curve is drawn, with the volume of the powder used for measurement being 100%. The volume average particle size can be measured by a wet method using a laser diffraction / scattering particle size distribution analyzer or the like on a sample prepared by dispersing aggregated particles in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer, or by a dry method using a Malvern "Morphologi." The same applies to the volume average particle diameter of the spherical inorganic filler described below.

[0108] (Agglomerated inorganic filler content) The content of the aggregated inorganic filler in the resin composition of the present invention is preferably 30% by weight or more, more preferably 40% by weight or more, and even more preferably 45% by weight or more, based on 100% by weight of the solid content of the resin composition. Furthermore, the content of the aggregated inorganic filler in the resin composition of the present invention is preferably 99% by weight or less, more preferably 90% by weight or less, and even more preferably 80% by weight or less, based on 100% by weight of the solid content of the resin composition. When the content of the aggregated inorganic filler is equal to or greater than the above-mentioned lower limit, the effect of improving thermal conductivity and the effect of controlling the linear expansion coefficient due to the inclusion of the aggregated inorganic filler tend to be sufficiently obtained. When the content of the aggregated inorganic filler is equal to or less than the above-mentioned upper limit, the moldability of the resin composition and the cured resin product, and the interfacial adhesion of the composite molded product tend to be improved.

[0109] (Non-agglomerating inorganic filler) The resin composition of the present invention may contain, as the inorganic filler, a non-agglomerated inorganic filler together with an agglomerated inorganic filler.

[0110] The non-agglomerated inorganic filler preferably includes a spherical inorganic filler having a thermal conductivity of 10 W / m·K or more, preferably 15 W / m·K or more, more preferably 20 W / m·K or more, for example, 20 to 30 W / m·K, and a new Mohs hardness of 3.1 or more, for example, 5 to 10. By using such a spherical inorganic filler in combination with the above-mentioned agglomerated inorganic filler, the adhesive strength to metal and heat dissipation properties of the obtained resin cured product can be improved.

[0111] Here, "spherical" means anything that is generally recognized as spherical; for example, an average circularity of 0.4 or more may be considered spherical, or an average circularity of 0.6 or more may be considered spherical. Usually, the upper limit of the average circularity is 1. The circularity can be measured by image processing the projected image, and can be measured, for example, with an FPIA series from Sysmex Corporation.

[0112] The spherical inorganic filler is preferably at least one selected from the group consisting of alumina, synthetic magnesite, silica, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, and magnesium oxide. Use of these preferred spherical inorganic fillers can further improve the heat dissipation properties of the resulting cured resin product.

[0113] The volume average particle diameter of the spherical inorganic filler is preferably in the range of 0.5 μm or more and 40 μm or less. A volume average particle diameter of 0.5 μm or more allows the resin and inorganic filler to flow easily during hot molding, which is thought to enhance the interfacial adhesive strength of the composite molded product of the present invention. Furthermore, an average particle diameter of 40 μm or less makes it easier to maintain the dielectric breakdown characteristics of the cured resin.

[0114] When an agglomerated inorganic filler and a non-agglomerated inorganic filler are used in combination as the inorganic filler, the content ratio of the agglomerated inorganic filler to the non-agglomerated inorganic filler in the resin composition is not particularly limited, but is preferably 90:10 to 10:90 by weight, and more preferably 80:20 to 20:80.

[0115] The total content of the agglomerated inorganic filler and non-agglomerated inorganic filler in the resin composition of the present invention is preferably 30% by weight or more, more preferably 40% by weight or more, and even more preferably 50% by weight or more, based on 100% by weight of the solid content of the resin composition. The total content of the agglomerated inorganic filler and non-agglomerated inorganic filler in the resin composition of the present invention is preferably 99% by weight or less, more preferably 90% by weight or less, and even more preferably 80% by weight or less, based on 100% by weight of the solid content of the resin composition.

[0116] <Other ingredients> The resin composition of the present invention may contain other components in addition to those described above, provided that the effects of the present invention are not impaired. Examples of such other components include a compound having a heterocyclic structure containing a nitrogen atom, a curing agent, a curing catalyst, a surface treatment agent such as a silane coupling agent that improves the interfacial adhesion strength between an inorganic filler and a resin, an insulating carbon component such as a reducing agent, a viscosity modifier, a dispersant, a thixotropy-imparting agent, a flame retardant, a colorant, an organic filler, an organic solvent, and a thermoplastic resin. The presence or absence of other components in the resin composition of the present invention and the content ratio thereof are not particularly limited as long as they do not significantly impair the effects of the present invention.

[0117] (Compounds having a heterocyclic structure containing a nitrogen atom) The resin composition of the present invention may contain a compound having a heterocyclic structure containing a nitrogen atom.

[0118] The inclusion of a compound having a heterocyclic structure containing a nitrogen atom (hereinafter, sometimes referred to as a "nitrogen-containing heterocyclic compound") tends to have the effect of improving the adhesion between a cured resin product obtained from the resin composition of the present invention and a metal. That is, when the resin composition or the cured resin product is composited with a metal, the nitrogen-containing heterocyclic compound is located at the interface between the resin composition or the cured resin product and the metal, thereby improving the adhesion between the resin composition or the cured resin product and the metal. From this perspective, it is more preferable that the nitrogen-containing heterocyclic compound has a low molecular weight so that the nitrogen-containing heterocyclic compound can easily remain at the interface between the resin composition or the cured resin product and the metal. The molecular weight of the nitrogen-containing heterocyclic compound is preferably 1,000 or less, more preferably 500 or less. There is no particular lower limit to the molecular weight of the nitrogen-containing heterocyclic compound, but it is preferably 60 or more, more preferably 70 or more.

[0119] Examples of the heterocyclic structure of the nitrogen-containing heterocyclic compound include structures derived from imidazole, triazine, triazole, pyrimidine, pyrazine, pyridine, and azole. The nitrogen-containing heterocyclic compound may have a plurality of heterocyclic structures simultaneously in one molecule. From the viewpoint of improving the insulating properties of the resin composition and adhesion to metals, nitrogen-containing heterocyclic compounds The imidazole compounds and triazine compounds are preferred.

[0120] Preferable imidazole compounds and triazine compounds as the nitrogen-containing heterocyclic compounds include, for example, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino- Examples thereof include 6-[2'-ethyl-4'methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, and 2,4-diamino-6-methacryloyloxyethyl-s-triazine isocyanuric acid adduct.

[0121] Among these, structures derived from imidazole and triazine are particularly preferred, with triazine-derived structures being particularly preferred. As the heterocyclic structure of the nitrogen-containing heterocyclic compound, a structure derived from 1,3,5-triazine is particularly preferred. The structure may also have a plurality of these exemplified structural moieties. By having the above structure, the nitrogen-containing heterocyclic compound tends to have high resin compatibility and a high reaction activation temperature. Therefore, the curing rate and post-curing physical properties can be easily adjusted, which tends to improve the storage stability of the resin composition and further improve the adhesive strength after hot molding.

[0122] The nitrogen-containing heterocyclic compound may contain a curing catalyst, which will be described later, depending on the structure, and therefore the resin composition of the present invention may contain a nitrogen-containing heterocyclic compound as a curing catalyst.

[0123] The nitrogen-containing heterocyclic compounds may be used alone or in combination of two or more.

[0124] The content of the nitrogen-containing heterocyclic compound is preferably 0.001 wt% or more, more preferably 0.1 wt% or more, and even more preferably 0.5 wt% or more, based on 100 wt% of the solid content of the resin composition excluding the inorganic filler. The content of the nitrogen-containing heterocyclic compound is preferably 10 wt% or less, more preferably 7 wt% or less, and even more preferably 5 wt% or less, based on 100 wt% of the solid content of the resin composition excluding the inorganic filler. By keeping the content of the nitrogen-containing heterocyclic compound within the above range, it tends to be easier to control the storage modulus and weight gain rate within the aforementioned specific ranges.

[0125] When a curing catalyst described later is contained in a nitrogen-containing heterocyclic compound due to its molecular structure, the total amount including the content thereof is preferably within the above range. When the content of the nitrogen-containing heterocyclic compound is equal to or greater than the above lower limit, the above effects of containing this compound can be sufficiently obtained, and when it is equal to or less than the above upper limit, the reaction proceeds effectively, improving the crosslinking density, increasing the strength, and further improving the storage stability.

[0126] (hardening agent) The resin composition of the present invention may contain a curing agent.

[0127] Although not particularly limited, preferred curing agents are phenolic resins, acid anhydrides having an aromatic or alicyclic skeleton, or hydrides of such acid anhydrides or modified products of such acid anhydrides. By using these preferred curing agents, it is possible to obtain a cured resin product having an excellent balance of heat resistance, moisture resistance, and electrical properties.

[0128] The curing agent may be used alone or in combination of two or more kinds.

[0129] The phenol resin is not particularly limited. Specific examples of the phenol resin include phenol novolac, o-cresol novolac, p-cresol novolac, t-butylphenol novolac, dicyclopentadiene cresol, polyparavinylphenol, bisphenol A-type novolac, xylylene-modified novolac, decalin-modified novolac, poly(di-o-hydroxyphenyl)methane, poly(di-m-hydroxyphenyl)methane, and poly(di-p-hydroxyphenyl)methane. In order to further improve the flexibility and flame retardancy of the resin composition and to improve the mechanical properties and heat resistance of the cured resin, novolac-type phenolic resins having a rigid main chain skeleton and phenolic resins having a triazine skeleton are preferred. A phenolic resin having an allyl group is preferred in order to improve the flexibility of the uncured resin composition and the toughness of the cured resin.

[0130] Commercially available phenolic resins include MEH-8005, MEH-8000H, and NEH-8015 (all manufactured by Meiwa Kasei Co., Ltd.), YLH903 (manufactured by Mitsubishi Chemical Corporation), LA-7052, LA-7054, LA-7751, LA-1356, and LA-3018-50P (all manufactured by Dainippon Ink & Chemicals Co., Ltd.), and PSM6200, PS6313, and PS6492 (manufactured by Gun-ei Chemical Industry Co., Ltd.).

[0131] The acid anhydride having an aromatic skeleton, the water-added product of the acid anhydride, or the modified product of the acid anhydride is not particularly limited. Specific examples include SMA Resin EF30 and SMA Resin EF60 (both manufactured by Sartomer Japan), ODPA-M and PEPA (both manufactured by Manac), Ricadit MTA-10, Ricadit TMTA, Ricadit TMEG-200, Ricadit TMEG-500, Ricadit TMEG-S, Ricadit TH, Ricadit MH-700, Ricadit MT-500, Ricadit DSDA, and Ricadit TDA-100 (all manufactured by New Japan Chemical Co., Ltd.), EPICLON B4400, and EPICLON B570 (all manufactured by Dainippon Ink and Chemicals Co., Ltd.).

[0132] The acid anhydride having an alicyclic skeleton, the hydration product of the acid anhydride, or the modified product of the acid anhydride is preferably an acid anhydride having a polyalicyclic skeleton, the hydration product of the acid anhydride, or the modified product of the acid anhydride, or an acid anhydride having an alicyclic skeleton obtained by the addition reaction of a terpene compound with maleic anhydride, the hydration product of the acid anhydride, or the modified product of the acid anhydride.Specific examples include Ricadit HNA and Ricadit HNA-100 (both manufactured by New Japan Chemical Co., Ltd.), and Epicure YH306 and Epicure YH309 (both manufactured by Mitsubishi Chemical Corporation).

[0133] The resin composition of the present invention may or may not contain a curing agent, and when the resin composition of the present invention contains a curing agent, the content of the curing agent is not particularly limited.

[0134] When the resin composition of the present invention contains a curing agent, it is preferably contained in an amount of 0.5 to 70% by weight, particularly 0.5 to 55% by weight, based on 100% by weight of the solid content of the resin composition excluding the inorganic filler. When the content of the curing agent is equal to or greater than the lower limit, sufficient curing performance can be obtained, and when it is equal to or less than the upper limit, the reaction proceeds effectively, improving the crosslink density and increasing the strength, and further This improves film-forming properties. Furthermore, when the resin composition contains a curing agent, the amount is preferably 0 to 55% by weight equivalent relative to the epoxy equivalent in the resin composition. By being in this range, the reaction proceeds effectively, the crosslinking density can be improved, strength can be increased, and film formability tends to be improved.

[0135] (curing catalyst) The resin composition of the present invention may contain a curing catalyst. In order to adjust the curing rate and the physical properties of the cured product, it is preferable to contain a curing catalyst together with the curing agent.

[0136] The curing catalyst is not particularly limited, but is appropriately selected depending on the type of resin and curing agent used. Specific examples of the curing catalyst include linear or cyclic tertiary amines, organic phosphorus compounds, quaternary phosphonium salts, diazabicycloalkenes such as organic acid salts, etc. Organometallic compounds, quaternary ammonium salts, metal halides, etc. can also be used. Examples of organometallic compounds include zinc octoate, tin octoate, and aluminum acetylacetone complex. These may be used alone or in combination of two or more.

[0137] When the resin composition of the present invention contains a curing catalyst, the curing catalyst is preferably contained in an amount of 0.1 to 10 wt %, particularly 0.1 to 5 wt %, based on 100 wt % of the solids content of the resin composition excluding the inorganic filler. When the content of the curing catalyst is equal to or greater than the lower limit, the progress of the curing reaction can be sufficiently promoted, resulting in good curing. When the content of the curing catalyst is equal to or less than the upper limit, the curing rate is not too fast, and therefore the storage stability of the resin composition of the present invention can be improved.

[0138] (solvent) The resin composition of the present invention may contain an organic solvent, for example, to improve the coatability when the resin composition is subjected to a coating step to form a sheet-like cured resin product.

[0139] Examples of organic solvents that may be contained in the resin composition of the present invention include methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether acetate, butyl acetate, isobutyl acetate, and propylene glycol monomethyl ether. These organic solvents may be used alone or in combination of two or more.

[0140] When the resin composition of the present invention contains an organic solvent, the content thereof is appropriately determined depending on the handleability of the resin composition when producing a cured resin product, the shape before curing, drying conditions, etc. When the resin composition of the present invention is in the form of a slurry to be subjected to the coating step described below, the organic solvent is preferably used so that the solid content of the resin composition of the present invention becomes 10 to 90% by weight, particularly 40 to 80% by weight. When the resin composition of the present invention is in the form of a sheet that has been subjected to processes such as coating and drying, the solid content of the resin composition of the present invention is preferably 95% by weight or more, and more preferably 98% by weight or more.

[0141] (dispersant) The resin composition of the present invention may contain a dispersant. When the resin composition of the present invention contains a dispersant, it becomes possible to form a uniform cured resin product, and the thermal conductivity and dielectric breakdown characteristics of the obtained cured resin product may be improved.

[0142] The dispersant preferably has a functional group containing a hydrogen atom capable of hydrogen bonding. When the dispersant has a functional group containing a hydrogen atom capable of hydrogen bonding, the thermal conductivity and dielectric breakdown characteristics of the resulting cured resin can be further improved. Examples of functional groups containing a carboxyl group include a carboxyl group (pKa=4), a phosphate group (pKa=7), and a phenol group (pKa=10).

[0143] The pKa of the functional group containing a hydrogen atom capable of hydrogen bonding is preferably in the range of 2 to 10, more preferably in the range of 3 to 9. A pKa of 2 or more allows the acidity of the dispersant to fall within an appropriate range, which may facilitate suppression of the reaction of the epoxy resin in the resin component. Therefore, when an uncured molded product is stored, the storage stability tends to be improved. A pKa of 10 or less tends to adequately function as a dispersant, and the thermal conductivity and dielectric breakdown characteristics of the cured resin product tend to be sufficiently improved.

[0144] The functional group containing a hydrogen atom capable of forming a hydrogen bond is preferably a carboxyl group or a phosphate group, which can further improve the thermal conductivity and dielectric breakdown characteristics of the cured resin.

[0145] Specific examples of the dispersant include polyester-based carboxylic acids, polyether-based carboxylic acids, polyacrylic-based carboxylic acids, aliphatic-based carboxylic acids, polysiloxane-based carboxylic acids, polyester-based phosphoric acids, polyether-based phosphoric acids, polyacrylic-based phosphoric acids, aliphatic-based phosphoric acids, polysiloxane-based phosphoric acids, polyester-based phenols, polyether-based phenols, polyacrylic-based phenols, and polysiloxane-based phenols. The dispersant may be used alone or in combination of two or more kinds.

[0146] (organic filler, thermoplastic resin) The resin composition of the present invention may contain an organic filler and / or a thermoplastic resin. By containing an organic filler or a thermoplastic resin in the resin composition of the present invention, the resin composition may be given appropriate elongation, the generated stress may be alleviated, and the occurrence of cracks in a temperature cycle test may be suppressed.

[0147] Any commonly known thermoplastic resin can be used as the thermoplastic resin, for example, vinyl polymers such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, (meth)acrylic resin, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, etc., polyesters such as polylactic acid resin, polyethylene terephthalate, polybutylene terephthalate, etc., polyamides such as nylon and polyamidoamine, polyvinyl acetal resins such as polyvinyl acetoacetal, polyvinyl benzal, polyvinyl butyral resin, ionomer resin, polyphenylene ether, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyacetal, ABS resin, LCP (liquid crystal polymer), fluororesin, urethane resin, silicone resin, various elastomers, or modified products of these resins.

[0148] The thermoplastic resin may be uniform in the resin phase of the cured resin product, or may be phase-separated and have a recognizable shape. If the thermoplastic resin is phase-separated, the shape of the thermoplastic resin in the cured resin product may be particulate or fibrous. In this way, if the shape of the thermoplastic resin is recognizable in the cured resin product, the thermoplastic resin may be recognized as an organic filler. However, in the present invention, organic fillers refer to natural products such as wood flour, cellulose which may be modified, starch, various organic pigments, etc., and thermoplastic resins are not included in the organic fillers.

[0149] When the thermoplastic resin or organic filler is insoluble in the resin, the viscosity of the resin composition is prevented from increasing, and when the resin composition is formed into a sheet as described later, the smoothness of the sheet surface can be improved. In this case, by simultaneously mixing the thermoplastic resin and organic filler that are insoluble in the resin with a large amount of inorganic filler, the component phase that is thermoplastic and has good elongation can be efficiently obtained. The resin can be easily dispersed in the cured resin, which helps to relieve stress, and therefore the occurrence of cracks in the cured resin can be suppressed without reducing the elastic modulus of the cured resin. From these viewpoints, preferred thermoplastic resins are polyamide resins such as nylon and cellulose resins, with polyamide resins such as nylon being particularly preferred.

[0150] When the thermoplastic resin observed in the cured resin is in the form of particles, the upper limit of the average particle size is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. By controlling the average particle size of the particulate thermoplastic resin in the cured resin to the above upper limit or less, it is possible to produce sheet-shaped cured products of various thicknesses without causing a decrease in thermal conductivity. The average particle size of the particulate thermoplastic resin is determined by observing the cross section of the cured resin and averaging the longest diameters of any 20 particles.

[0151] <Cured resin> The cured resin product of the present invention is a cured resin product using a resin composition containing an inorganic aggregated filler, wherein the cured resin product has a weight increase rate of 0.80% or less at 85°C and 85% RH, and the storage modulus of the resin composition excluding the inorganic filler at 200°C after curing is 1.0 × 10 7 It is more than Pa.

[0152] In the present invention, the term "resin composition" refers to an uncured resin composition containing an aggregated inorganic filler and a resin. While not particularly limited, the resin composition is preferably a mixture of an aggregated inorganic filler, a thermosetting resin component such as an epoxy resin, a curing agent for curing the resin, a curing catalyst serving as a curing aid, and the like, and more preferably contains a compound having a heterocyclic structure containing a nitrogen atom. Examples of the resin composition include the resin compositions described above. The resin composition excluding the inorganic filler refers to the components in the resin composition other than the inorganic filler. The resin, curing agent, curing catalyst, compound having a heterocyclic structure containing a nitrogen atom, inorganic filler, inorganic aggregate filler, and other components have the same meanings as those of the resin composition described above, and the preferred ranges thereof are also the same.

[0153] The term "cured resin" as used herein refers to a product obtained by curing a resin composition. The cured resin of the present invention is in a state in which the exothermic peak obtained when the temperature is increased from 40°C to 250°C at a rate of 10°C / min by DSC is 10 J / g or less. The method for obtaining the cured resin product of the present invention is not particularly limited, and examples thereof include a method for obtaining the product by curing the above-mentioned resin composition.

[0154] [Storage modulus] The storage modulus of the resin composition after curing, excluding the inorganic filler, at 200°C is 1.0 x 10 7 From the viewpoint of maintaining performance after moisture absorption and reflow testing, the storage modulus is 1.3 × 10 7 Pa or more, and 1.5 × 10 7 Pa or more is more preferable, and 1.7 × 10 7 On the other hand, the storage modulus is more preferably 5×10 Pa or more. 9 Pa or less, and 9 Pa or less is more preferable, and 5×10 8 It is more preferable that the viscosity is 0.05 Pa or less. By ensuring that the storage modulus is equal to or less than the above upper limit, excessive internal stress that occurs during a moisture absorption reflow test can be suppressed, and cracking of the resulting cured resin product and interfacial peeling between the metal and the cured resin product tend to be suppressed. When the storage modulus is within the above range, the cured resin product can easily penetrate into the irregularities of the metal, which is the adherend described below, and the cured resin product that has penetrated into the irregularities exhibits a strong anchor effect, which tends to improve the adhesion between the metal and the cured resin product.

[0155] In this way, in order to control the storage modulus of the resin of the cured resin to a specific range, This can be achieved by introducing a rigid structure such as an aromatic ring into the components constituting the resin composition used to obtain the cured product, or by introducing a polyfunctional component having multiple reactive groups to increase the crosslink density of the cured product. Alternatively, this can be achieved by obtaining a cured resin product using the above-mentioned resin composition.

[0156] The storage modulus may be measured by any conventionally known method, and specifically includes the method described in the Examples section below.

[0157] [Weight increase rate] The cured resin (containing an inorganic filler) of the present invention exhibits a weight gain of 0.8% or less at 85°C and 85% RH. If the weight gain exceeds 0.8%, the object of the present invention, namely, maintaining high insulating properties and preventing interfacial peeling after a moisture absorption reflow test, cannot be achieved. From the viewpoint of maintaining high insulating properties and preventing interfacial peeling after a moisture absorption reflow test, the smaller this weight increase rate is the better, preferably 0.75% or less, and more preferably 0.7% or less. The lower limit of the weight gain rate is not particularly limited, but is, for example, 0.2% or more from the viewpoint of achieving both strength and insulating performance of the cured resin and film formability. Although there are various possible causes of the weight increase of the cured resin, it is important to control the weight increase due to moisture absorption. The present invention has found that the problems of the present invention can be solved by setting the moisture content within the above specific range.

[0158] A cured resin product having a weight gain rate within a specific range at 85°C and 85% RH can be obtained, for example, by controlling the weight gain rate by introducing a highly hydrophobic structure such as an aliphatic skeleton or an aromatic ring into the constituent components. Alternatively, the cured resin product can be obtained by using the above-mentioned resin composition.

[0159] The weight gain of the cured resin of the present invention at 85° C. and 85% RH is measured by the method described in the Examples section below.

[0160] [Production of Resin Composition and Cured Resin] The method for producing the resin composition of the present invention and the cured resin product of the present invention will be described below by taking as an example a method for producing a sheet-shaped cured resin product made from the resin composition of the present invention.

[0161] The sheet-shaped cured resin product can be produced by a commonly used method, for example, by preparing the resin composition of the present invention, molding it into a sheet, and curing it.

[0162] The resin composition of the present invention can be obtained by uniformly mixing the inorganic aggregate filler, the resin, and other components added as needed by stirring or kneading. For mixing, a general kneading device such as a mixer, a kneader, or a single-screw or twin-screw kneader can be used. Heating may be performed during mixing, if necessary.

[0163] The order of mixing the components may be any as long as there are no particular problems such as the occurrence of reaction or precipitation, but examples thereof include the following methods. A resin is mixed and dissolved in an organic solvent (e.g., methyl ethyl ketone) to prepare a resin liquid, and a thoroughly mixed inorganic aggregate filler and other components are added to the obtained resin liquid and mixed. After that, an organic solvent is further added to adjust the viscosity and mixed, and then additives such as a curing agent, a curing accelerator, or a dispersant are further added and mixed.

[0164] The prepared resin composition can be formed into a sheet by any commonly used method. For example, when a resin composition has plasticity and fluidity, the resin composition can be molded into a desired shape by curing the resin composition while it is placed in a mold, for example, by injection molding, injection compression molding, extrusion molding, compression molding, or vacuum compression molding.

[0165] The solvent in the resin composition can be removed by a known heating method such as using a hot plate, a hot air oven, an IR heating oven, a vacuum dryer, or a high-frequency heater.

[0166] A sheet-like cured resin product can also be obtained by cutting a cured resin composition into a desired shape.

[0167] A sheet-like cured resin product can also be obtained by forming a slurry resin composition into a sheet by a doctor blade method, a solvent casting method, an extrusion film formation method, or the like.

[0168] An example of a method for producing a sheet-shaped cured product using this slurry resin composition will be described below.

[0169] <Coating process> First, a slurry resin composition is applied to the surface of a substrate to form a coating film (a sheet-like resin composition).

[0170] A coating film is formed on a substrate using a slurry resin composition by a dip method, a spin coating method, a spray coating method, a blade method, or any other method. A coating device such as a spin coater, a slit coater, a die coater, or a blade coater can be used to apply the slurry resin composition. Such a coating device can uniformly form a coating film of a predetermined thickness on the substrate.

[0171] As the substrate, a copper plate or copper foil or a PET film, as described below, is generally used, but there is no limitation thereto.

[0172] <Drying process> The coating film formed by applying the slurry resin composition is dried at a temperature of usually 10 to 150°C, preferably 25 to 120°C, and more preferably 30 to 110°C to remove the solvent and low molecular weight components. When the drying temperature is equal to or lower than the upper limit, curing of the resin in the slurry resin composition is suppressed, and the resin in the sheet-shaped resin composition tends to flow and voids tend to be easily removed in the subsequent pressurizing step.When the drying temperature is equal to or higher than the lower limit, the solvent can be effectively removed, and productivity tends to be improved.

[0173] The drying time is not particularly limited and can be adjusted appropriately depending on the state of the slurry resin composition, the drying environment, etc. The drying time is preferably 1 minute or more, more preferably 2 minutes or more, even more preferably 5 minutes or more, still more preferably 10 minutes or more, particularly preferably 20 minutes or more, and most preferably 30 minutes or more. The drying time is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 4 hours or less, and particularly preferably 2 hours or less. When the drying time is equal to or greater than the lower limit, the solvent can be sufficiently removed, and the residual solvent tends to be prevented from forming voids in the cured resin. When the drying time is equal to or less than the upper limit, productivity tends to be improved, and production costs tend to be reduced.

[0174] <Pressure process> After the drying step, it is desirable to subject the obtained sheet-shaped resin composition to a pressure step for the purposes of bonding the aggregated inorganic fillers together to form heat conduction paths, eliminating voids and gaps within the sheet, improving adhesion to the substrate, etc.

[0175] The pressurizing step is desirably carried out by applying a load of 2 MPa or more to the sheet-shaped resin composition on the substrate. The load is preferably 5 MPa or more, more preferably 7 MPa or more, and even more preferably 9 MPa or more. The load is preferably 1500 MPa or less, more preferably 1000 MPa or less, and even more preferably 800 MPa or less. By setting the load during pressing to the above upper limit or less, the secondary particles of the aggregated inorganic filler are not destroyed, and a sheet having high thermal conductivity and no voids in the sheet-like cured resin can be obtained. By setting the load to the above lower limit or more, good contact between the aggregated inorganic filler particles is achieved, making it easier to form thermal conduction paths, and a cured resin product having high thermal conductivity can be obtained.

[0176] The heating temperature of the sheet-shaped resin composition on the substrate in the pressurizing step is not particularly limited. The heating temperature is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. The heating temperature is preferably 300°C or lower, more preferably 250°C or lower, even more preferably 200°C or lower, still more preferably 100°C or lower, and particularly preferably 90°C or lower. By carrying out the pressurizing step within this temperature range, the melt viscosity of the resin in the sheet-shaped resin composition can be reduced, and voids and gaps in the cured resin can be further reduced. Furthermore, by heating at or below the upper limit, decomposition of organic components in the sheet-shaped resin composition and the cured resin and voids caused by residual solvent tend to be suppressed.

[0177] The time for the pressurizing step is not particularly limited. The time for the pressurizing step is preferably 30 seconds or more, more preferably 1 minute or more, even more preferably 3 minutes or more, and particularly preferably 5 minutes or more. The time for the pressurizing step is preferably 1 hour or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less. By keeping the pressurizing time at or below the upper limit, the production time for the cured resin can be reduced, which tends to reduce production costs.By keeping the pressurizing time at or above the lower limit, voids and gaps in the cured resin can be sufficiently removed, which tends to improve heat transfer performance and voltage resistance characteristics.

[0178] <Curing process> The curing step for completely curing the resin composition of the present invention may be carried out under pressure or without pressure. The pressurizing step and the curing step may also be carried out simultaneously.

[0179] The load applied when the pressing step and the curing step are performed simultaneously is not particularly limited. In this case, the sheet-shaped resin composition on the substrate is preferably subjected to a load of 5 MPa or more, more preferably 7 Pa or more, even more preferably 9 MPa or more, and particularly preferably 20 MPa or more. The load is preferably 2000 MPa or less, more preferably 1500 MPa or less. By setting the load when the pressurizing step and the curing step are carried out simultaneously to the above upper limit or less, the secondary particles of the aggregated inorganic filler are not destroyed, and a sheet-like cured resin product having high thermal conductivity and no voids in the sheet-like cured resin product can be obtained. Furthermore, by setting the load to the above lower limit or more, good contact between the aggregated inorganic filler particles is achieved, making it easier to form heat conduction paths, thereby producing a cured resin product having high thermal conductivity.

[0180] When the pressing step and the curing step are carried out simultaneously, the pressing time is not particularly limited. The pressurization time is preferably 1 hour or less, more preferably 30 minutes or less, even more preferably 1 minute or more, still more preferably 3 minutes or more, and particularly preferably 5 minutes or more. The pressurization time is preferably 1 hour or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less. By keeping the pressing time at or below the upper limit, the time required to produce a sheet-shaped cured resin product can be reduced, which tends to reduce production costs.By keeping the pressing time at or above the lower limit, voids and gaps in the sheet-shaped cured resin product can be sufficiently removed, which tends to improve heat transfer performance and voltage resistance characteristics.

[0181] When the pressing step and the curing step are performed simultaneously, the heating temperature of the sheet-shaped resin composition on the substrate is not particularly limited. The heating temperature is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. The heating temperature is preferably 300°C or lower, more preferably 250°C or lower, even more preferably 200°C or lower, still more preferably 100°C or lower, and particularly preferably 90°C or lower. By setting the heating temperature to the above lower limit or higher, it is possible to reduce the melt viscosity of the resin in the sheet-shaped resin composition and eliminate voids and gaps in the cured resin product. By setting the heating temperature to the above upper limit or lower, it is possible to suppress decomposition of organic components in the sheet-shaped resin composition and the cured resin product in the sheet-shaped resin composition and voids caused by residual solvent.

[0182] When only the curing step is performed, the heating temperature of the sheet-shaped resin composition on the substrate is not particularly limited. The heating temperature is preferably 10°C or higher, more preferably 50°C or higher, and even more preferably 100°C or higher. The heating temperature is preferably 500°C or lower, more preferably 300°C or lower, even more preferably 200°C or lower, still more preferably 180°C or lower, and particularly preferably 175°C or lower. By setting the heating temperature within this temperature range, the curing reaction of the resin can be effectively promoted. By setting the heating temperature at or below the upper limit, thermal degradation of the resin can be prevented. By setting the heating temperature at or above the lower limit, the curing reaction of the resin can be more effectively promoted.

[0183] The thickness of the sheet-like cured resin thus formed is not particularly limited, but is preferably 50 μm or more, more preferably 80 μm or more, and even more preferably 100 μm or more. The thickness of the cured resin is preferably 400 μm or less, and more preferably 300 μm or less. When the thickness of the cured resin is equal to or greater than the lower limit, the voltage resistance characteristics are obtained and the breakdown voltage tends to be improved. When the thickness of the cured resin is equal to or less than the upper limit, the device can be made smaller and thinner, and the thermal resistance of the resulting cured resin (heat dissipation sheet) tends to be reduced.

[0184] [Composite molded body] The composite molded article of the present invention has a cured product part made of the cured product of the resin composition of the present invention and a metal part, and these are usually laminated together.

[0185] The metal portion may be provided on only one surface of the cured product of the present invention, or on two or more surfaces. For example, the cured product may have a metal portion on only one surface, or on both surfaces. The metal portion may also be patterned.

[0186] The composite molded article of the present invention can be produced by using a metal part as the substrate and forming the cured resin product of the present invention on this substrate according to the method described above.

[0187] In addition, the composite molded product of the present invention can be produced by peeling a sheet-like resin composition or a cured resin formed on a substrate separate from the metal part from the substrate, and then heat-pressing the resin composition or the cured resin onto a metal member that will become the metal part. It can also be manufactured.

[0188] In this case, a sheet-like resin composition or cured resin of the present invention is formed in the same manner as described above, except that a slurry of the resin composition of the present invention is applied to a substrate such as PET (polyethylene terephthalate) which may be treated with a release agent, and then the sheet-like resin composition or cured resin is peeled off from the substrate, and the sheet-like resin composition or cured resin is placed on another metal plate or sandwiched between two metal plates and pressurized to be integrated.

[0189] The metal plate may be made of copper, aluminum, nickel-plated metal, or the like, and have a thickness of about 10 μm to 10 cm. The surface of the metal plate may be physically roughened or chemically treated with a surface treatment agent, etc. From the viewpoint of adhesion between the resin composition and the metal plate, it is more preferable that the surface of the metal plate is subjected to such treatment.

[0190] [Semiconductor Devices] The composite molded article of the present invention can be used as a semiconductor device, and is particularly suitable for use in a power semiconductor device that can be operated at high temperatures to achieve high output and high density. [Example]

[0191] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. The values ​​of various conditions and evaluation results in the following examples indicate the preferred ranges of the present invention, similar to the preferred ranges in the embodiments of the present invention, and the preferred ranges of the present invention can be determined by taking into consideration the preferred ranges in the above-mentioned embodiments and the values ​​in the following examples or the ranges indicated by a combination of values ​​between the examples.

[0192] [raw materials] The raw materials used in the examples and comparative examples are as follows.

[0193] <Resin component> Resin component 1: A resin having the structure (2) (R 3 = Structure (4)) and Structure (3) (R 4 ,R 5 ,R 6 ,R 7 (=methyl group) specific epoxy resin Weight average molecular weight in polystyrene equivalent: 30,000 Epoxy equivalent: 9,000g / equivalent Resin component 2: a resin having the structure (1) (R 1 = methyl group, R 2 = phenyl group) and structure (3) (R 4 ,R 5 ,R 6 ,R 7 (=methyl group) specific epoxy resin Weight average molecular weight in polystyrene equivalent: 39,000 Epoxy equivalent: 13,000g / equivalent Resin component 3: Mitsubishi Chemical Corporation bisphenol F type solid epoxy resin containing a structure with two epoxy groups per molecule Weight average molecular weight in polystyrene equivalent: 60,000 Resin component 4: Mitsubishi Chemical Corporation, bisphenol A liquid epoxy resin containing two epoxy groups per molecule Molecular weight: approx. 370 Resin component 5: Nagase ChemteX Corporation, multifunctional epoxy resin containing a structure having four or more glycidyl groups per molecule Molecular weight: approx. 400 Resin component 6: Mitsubishi Chemical Corporation hydrogenated bisphenol A liquid epoxy resin containing two epoxy groups per molecule Molecular weight approx. 410 Resin component 7: p-aminophenol-type liquid multifunctional epoxy resin containing a structure having three or more epoxy groups per molecule, manufactured by Mitsubishi Chemical Corporation Molecular weight: approx. 290

[0194] <Inorganic filler> Inorganic filler 1: boron nitride agglomerated particles having a house-of-cards structure, produced in accordance with the method for producing boron nitride agglomerated particles disclosed in the examples of WO 2015 / 561028. New Mohs hardness: 2 Volume average particle size: 45 μm Inorganic filler 2: Spherical alumina particles manufactured by Admatechs New Mohs hardness: 9 Volume average particle size: 6.5 μm Thermal conductivity: 20-30 W / m K

[0195] <Curing agent> Hardener 1: Meiwa Kasei "MEH-8000H" Phenolic resin curing agent

[0196] <Curing catalyst> Curing catalyst 1: Shikoku Chemicals "2E4MZ-A" 2,4-Diamino-6-[2'-ethyl-4'-methylimidazolyl-(17')]-ethyl-s-triazine (Compounds having a triazine ring as a nitrogen-containing heterocyclic structure) Molecular weight: 247 Curing catalyst 2: Shikoku Chemicals "C11Z-CN" 1-Cyanoethyl-2-undecylimidazole Molecular weight: 275

[0197] [Sample preparation, measurement, and evaluation] The methods for producing the molded bodies in the examples and comparative examples, as well as the measurement conditions and evaluation methods, are as follows.

[0198] Example 1 Using a planetary stirring device, a mixture was prepared so that the solid content was 51% by weight of inorganic filler 1, 20% by weight of inorganic filler 2, and 29% by weight of components other than the inorganic filler. At this time, the weight ratio of the components other than the inorganic filler in the solid content was adjusted to the ratio shown in the Example 1 column of Table 1. Furthermore, when preparing the mixture, equal amounts of methyl ethyl ketone and cyclohexanone were used so that the mixture accounted for 63% by weight (solid content concentration) of the coating slurry.

[0199] The resulting slurry-like resin composition (slurry for sheet use) was applied to a PET substrate by doctor blade method, and after heat drying at 60°C for 120 minutes, it was pressed at 42°C and 147 MPa for 10 minutes to obtain a sheet-like resin composition with a thickness of 150 μm. The total content of methyl ethyl ketone and cyclohexanone in the sheet-like resin composition was 1 wt% or less.

[0200] Next, we used a 500μm thick sheet that had been roughened with a #120 file 100 times beforehand. The sheet-like resin composition was sandwiched between two 2,000 μm copper plates and pressed at 120° C. and 9.8 MPa for 30 minutes, then heated and pressed at 175° C. and 9.8 MPa for 30 minutes.

[0201] The composite molded product containing the copper plate and the cured resin obtained above was etched using a specified method to pattern the copper plate with a thickness of 500 μm, leaving two circular patterns with a diameter of 25 mm.

[0202] <Examples 2 to 3, Comparative Examples 1 to 4> A mixture was prepared in accordance with the method of Example 1 so that the solid content was 51% by weight of inorganic filler 1, 20% by weight of inorganic filler 2, and 29% by weight of components other than the inorganic filler. Except for adjusting the weight ratio of the components other than the inorganic filler in the solid content to the ratio shown in Table 1, a sheet-shaped resin composition and a composite molded product containing a copper plate and a cured resin were obtained in the same manner as in Example 1.

[0203] <Breakdown voltage (BDV) before and after moisture absorption reflow test> <BDV before moisture absorption reflow test> The composite molded bodies prepared in the examples and comparative examples were immersed in Fluorinert FC-40 (manufactured by 3M), and an ultra-high voltage withstand voltage tester 7470 (manufactured by Keisoku Gijutsu Kenkyusho) was used to place electrodes on the patterned copper of φ25 mm, apply a voltage of 0.5 kV, and measure the voltage by increasing it by 0.5 kV every 60 seconds until dielectric breakdown occurred. For those with a BDV of 5 kV or more, the BDV was measured after the moisture absorption reflow test, but for composite molded bodies with a BDV of less than 5 kV (ND), the BDV was not measured after the moisture absorption reflow test.

[0204] <BDV after moisture absorption reflow test> The composite molded bodies prepared in the examples and comparative examples were stored in an environment of 85°C and 85% RH for 3 days using a thermo-hygrostat SH-221 (manufactured by Espec Corporation), and then heated from room temperature to 290°C in 12 minutes in a nitrogen atmosphere within 30 minutes, held at 290°C for 10 minutes, and then cooled to room temperature (moisture absorption reflow test). The breakdown voltage was then measured in the same manner as above, and a BDV of 5 kV or more was marked "Good", and a BDV of less than 5 kV was marked "Poor".

[0205] <Interface peeling after moisture absorption reflow test> The composite molded articles prepared in the examples and comparative examples were subjected to a moisture absorption reflow test in the same manner as above, and then the interface between the copper plate and the sheet-like cured resin was observed using an ultrasonic imaging device, FinSAT (FS300III) (manufactured by Hitachi Power Solutions). Measurements were performed using a 50 MHz probe with a gain of 30 dB and a pitch of 0.2 mm, with the sample placed in water. Those in which no delamination was observed at the interface were marked with an "O", and those in which delamination was observed were marked with an "X".

[0206] <Weight increase rate of cured resin> The cured resin sheets prepared in the Examples and Comparative Examples were cut into 6 cm x 7 cm test pieces, dried at 150°C for 1 hour, and their weights (a) were measured. These cured resin sheets were then stored for a fixed period of time in an environment of 85°C and 85% RH using a thermo-hygrostat SH-221 (manufactured by Espec Corporation), and their weights were measured over time. The weight gain was calculated using the following formula: Weight gain rate (%) = (ba) / a × 100

[0207] <Storage modulus of resin composition excluding inorganic filler> In the same manner as in each of the Examples and Comparative Examples, except that no inorganic filler was blended, a resin composition was prepared using a planetary stirring device, and after heat drying, the uncured resin composition was heat cured using an Anton Paar rheometer "MCR302" to measure 200 The storage modulus at °C was measured. Aluminum parallel plates were used for the measurements, and the measurement conditions were a strain of 0.3%, a frequency of 1 Hz, and a gap of 0.5 mm. The temperature profile during heat curing was as follows: starting from 25°C, the temperature was increased at 14°C per minute to 120°C, and after reaching 120°C, it was held for 30 minutes; then the temperature was increased at 7°C per minute to 175°C, and after reaching 175°C, it was held for 30 minutes; then the temperature was increased again at 7°C per minute to 200°C, and after reaching 200°C, it was held for 10 minutes. The storage modulus measured after holding at 200°C for 10 minutes was used for evaluation.

[0208] The results of the above measurements and evaluations are shown in Table 1.

[0209] [Table 1]

[0210] Table 1 shows that the cured resin of the present invention has excellent voltage resistance under high temperature and high humidity conditions, and also does not suffer from the problem of interfacial peeling under high temperature and high humidity conditions when formed into a composite molded product with a metal.

[0211] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2018-192691 filed on October 11, 2018, the entire contents of which are incorporated by reference.

Claims

1. A resin composition comprising a resin, an aggregated inorganic filler, and a compound having a heterocyclic structure containing a nitrogen atom, the weight increase rate of the resin composition after curing at 85°C and 85% RH is 0.80% or less; The storage modulus of the cured resin composition excluding the inorganic filler at 200°C is 1.0 x 10 ７ Pa or more, The resin composition comprises an epoxy resin having three or more epoxy groups per molecule; The epoxy resin contains a biphenyl structure and has a weight average molecular weight of 10,000 or more, The composite molded body produced by the following method has a dielectric breakdown voltage (BDV) of 5 kV or more after a moisture absorption reflow test measured by the following method, The resin composition wherein no interfacial peeling is observed when the composite molded body is subjected to the following moisture absorption reflow test and then interfacial peeling is checked. <Production of composite molded body> The resin composition is applied to a PET substrate, dried by heating, and then pressed at 42° C. and 147 MPa for 10 minutes to obtain a sheet-like resin composition having a thickness of 150 μm. Next, the sheet-like resin composition is sandwiched between two copper plates each having a surface previously roughened with a #120 file, and pressed at 175° C. and 9.8 MPa for 30 minutes. The resulting composite molded body containing the copper plate and the cured resin is subjected to an etching treatment to pattern the copper plate on one side. <BDV after moisture absorption reflow test> The composite molded body was stored in an environment of 85°C and 85% RH for 3 days, then heated from room temperature to 290°C in 12 minutes in a nitrogen atmosphere, held at 290°C for 10 minutes, and then cooled to room temperature (moisture absorption reflow test). After the moisture absorption reflow test, the composite molded body was immersed in insulating oil, an electrode was placed on the patterned copper, and a voltage of 0.5 kV was applied in the thickness direction of the composite molded body. The voltage was increased by 0.5 kV every 60 seconds, and the voltage at which dielectric breakdown occurred (BDV) was measured. <Interface peeling after moisture absorption reflow test> The composite molding is subjected to a moisture absorption reflow test in the same manner as above, and then the presence or absence of interfacial delamination between the copper plate and the sheet-like resin cured product is observed using an ultrasonic imaging device.

2. 2. The resin composition according to claim 1, wherein the epoxy resin having a biphenyl structure and a weight average molecular weight of 10,000 or more further has at least one structure selected from the group consisting of a structure represented by the following structural formula (1) and a structure represented by the following structural formula (2): 【Chemistry 1】 (In formula (1), R １ and R ２ Each of R represents an organic group, and the organic group is an alkyl group, an alkenyl group, or an aryl group, which may be substituted with a halogen atom or a heteroatom. ３ represents a divalent cyclic organic group, and the cyclic organic group is an aromatic cyclic group or an aliphatic cyclic group, which may independently have a hydrocarbon group or a halogen atom as a substituent.

3. 3. The resin composition according to claim 2, wherein the epoxy resin having a biphenyl structure and a weight average molecular weight of 10,000 or more has a structure represented by the following structural formula (3): 【Chemistry 2】 (In formula (3), R ４ , R ５ , R ６ , R ７ each independently represents an organic group having a molecular weight of 15 or more, and the organic group is an alkyl group, an alkenyl group, or an aryl group, which may be substituted with a halogen atom or a heteroatom.

4. The resin composition according to any one of claims 1 to 3, wherein the weight average molecular weight of the epoxy resin having a biphenyl structure and having a weight average molecular weight of 10,000 or more is 80,000 or less.

5. 5. The resin composition according to claim 1, wherein the content of the epoxy resin having a biphenyl structure and a weight average molecular weight of 10,000 or more is 1% by weight or more and 50% by weight or less, based on 100% by weight of the solid content of the resin composition excluding the inorganic filler.

6. 6. The resin composition according to claim 1, wherein the content of the epoxy resin having three or more epoxy groups per molecule is 10% by weight or more and 50% by weight or less, based on 100% by weight of the solid content of the resin composition excluding the inorganic filler.

7. The resin composition according to any one of claims 1 to 6, wherein the agglomerated inorganic filler is agglomerated boron nitride particles.

8. 8. The resin composition according to claim 7, wherein the agglomerated boron nitride particles have a house-of-cards structure.

9. A composite molded article having a cured product part made of a cured product of the resin composition according to any one of claims 1 to 8 and a metal part.

10. A semiconductor device comprising the composite compact of claim 9.

11. A cured resin product using a resin composition containing a resin, an aggregated inorganic filler, and a compound having a heterocyclic structure containing a nitrogen atom, The weight gain rate at 85°C and 85% RH is 0.80% or less, The storage modulus at 200°C after curing of the resin composition excluding the inorganic filler is 1.0 x 10 ７ Pa or more, The resin composition comprises an epoxy resin having three or more epoxy groups per molecule; The epoxy resin contains a biphenyl structure and has a weight average molecular weight of 10,000 or more, The composite molded body produced by the following method has a dielectric breakdown voltage (BDV) of 5 kV or more after a moisture absorption reflow test measured by the following method, The composite molded product is a cured resin product in which no interfacial peeling is observed when the composite molded product is subjected to the following moisture absorption reflow test and then interfacial peeling is checked. <Production of composite molded body> The resin composition is applied to a PET substrate by a doctor blade method, and after heat drying at 60°C for 120 minutes, it is pressed at 42°C and 147 MPa for 10 minutes to obtain a sheet-like resin composition having a thickness of 150 μm. Next, the above-mentioned sheet-like resin composition is sandwiched between two copper plates each having a thickness of 500 μm and 2,000 μm, the surfaces of which have been previously roughened 100 times with a #120 file, and pressed at 120°C and 9.8 MPa for 30 minutes. The temperature is then increased and the plates are pressed at 175°C and 9.8 MPa for 30 minutes. The resulting composite molded product containing the copper plate and the cured resin is subjected to an etching treatment to pattern the copper plate having a thickness of 500 μm, so that two circular patterns of φ25 mm remain. <Production of composite molded body> The resin composition is applied to a PET substrate, dried by heating, and then pressed at 42° C. and 147 MPa for 10 minutes to obtain a sheet-like resin composition having a thickness of 150 μm. Next, the sheet-like resin composition is sandwiched between two copper plates each having a surface previously roughened with a #120 file, and pressed at 175° C. and 9.8 MPa for 30 minutes. The resulting composite molded body containing the copper plate and the cured resin is subjected to an etching treatment to pattern the copper plate on one side. <BDV after moisture absorption reflow test> The composite molded body was stored in an environment of 85°C and 85% RH for 3 days, then heated from room temperature to 290°C in 12 minutes in a nitrogen atmosphere, held at 290°C for 10 minutes, and then cooled to room temperature (moisture absorption reflow test). After the moisture absorption reflow test, the composite molded body was immersed in insulating oil, an electrode was placed on the patterned copper, and a voltage of 0.5 kV was applied in the thickness direction of the composite molded body. The voltage was increased by 0.5 kV every 60 seconds, and the voltage at which dielectric breakdown occurred (BDV) was measured. <Interface peeling after moisture absorption reflow test> The composite molding is subjected to a moisture absorption reflow test in the same manner as above, and then the presence or absence of interfacial delamination between the copper plate and the sheet-like resin cured product is observed using an ultrasonic imaging device.

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