Resin composition, resin film, resin film with support, printed wiring board, and semiconductor package

Abstract

Provided are: a resin composition which contains a radical polymerization initiator and achieves both curability and embedding properties in a circuit board; a resin film using the resin composition; a resin film with a support; a printed wiring board; and a semiconductor package. Specifically, the resin composition contains (A) a maleimide resin, (B) an inorganic filler, (C) a radical polymerization initiator, and (D) a polymerization inhibitor.

Description

Resin composition, resin film, supported resin film, printed wiring board, and semiconductor package

[0001] The present embodiment relates to a resin composition, a resin film, a resin film with a support, a printed wiring board, and a semiconductor package.

[0002] In recent years, the miniaturization and high performance of electronic devices have led to advances in wiring density and integration in the fields of printed wiring boards and semiconductor packages. Insulating materials such as thermosetting resins are used in these electronic devices as encapsulants for semiconductor chips and substrate materials for printed wiring boards. However, stress can occur during component mounting due to the difference in thermal expansion coefficients between the insulating material and the semiconductor chip. This stress is thought to cause warping of the semiconductor package, potentially reducing reliability. Therefore, a method of blending an inorganic filler into an insulating material containing maleimide resin has been used to bring the thermal expansion coefficient of the insulating material closer to that of the semiconductor chip.

[0003] However, maleimide resins tend to have poor embeddability in circuit boards due to their high minimum melt viscosity. Under these circumstances, a resin composition containing (A) an epoxy resin and (B) a maleimide compound containing at least one of an alkyl group having 5 or more carbon atoms and an alkylene group having 5 or more carbon atoms has been proposed as a resin composition with a low minimum melt viscosity (see Patent Document 1).

[0004] JP 2023-067987 A

[0005] The method of Patent Document 1 has the problem of imposing significant limitations on the type of maleimide resin that can be used to enhance embeddability in circuit boards. Patent Document 1 also describes that a peroxide-based curing accelerator is preferred as the curing accelerator, but the present inventors have conducted extensive research into this point and found that resin compositions containing a substance that functions as a radical polymerization initiator, such as a peroxide-based curing accelerator, tend to have reduced embeddability in circuit boards, while resin compositions that do not contain a radical polymerization initiator tend to have poor curability, making it difficult to achieve both embeddability in circuit boards and curability.

[0006] In view of the current situation, an object of the present embodiment is to provide a resin composition that contains a radical polymerization initiator and yet has both embeddability in circuit boards and curability, as well as a resin film, a resin film with a support, a printed wiring board, and a semiconductor package that use the resin composition.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems and have found that the problems can be solved by the embodiments described in this specification. These embodiments include the following embodiments [1] to

[15] . [1] A resin composition comprising: (A) a maleimide resin; (B) an inorganic filler; (C) a radical polymerization initiator; and (D) a polymerization inhibitor. [2] The resin composition according to the above [1], wherein the component (A) is one or more selected from the group consisting of maleimide resins having one or more N-substituted maleimide groups and derivatives of the maleimide resins. [3] The resin composition according to the above [2], wherein the maleimide resin having one or more N-substituted maleimide groups is a maleimide resin having a molecular structure containing a fused ring of an aromatic ring and an aliphatic ring and having two or more N-substituted maleimide groups. [4] The resin composition according to any one of [1] to [3] above, wherein the content of the (D) component is 1 to 90 parts by mass per 100 parts by mass of the (C) component. [5] The resin composition according to any one of [1] to [4] above, further comprising (E) a compound that is liquid at 25°C, has a reactive group, and has a molecular weight of 1,000 or less. [6] The resin composition according to [5] above, wherein the reactive group of the (E) component is one or more reactive groups selected from a vinyl group, an allyl group, a maleimide group, a (meth)acryloyl group, an epoxy group, a hydroxyl group, a carboxy group, and an amino group. [7] The resin composition according to [5] or [6] above, wherein the (E) component has two or more reactive groups per molecule. [8] The resin composition according to any one of [5] to [7] above, wherein the (E) component is a di(meth)acrylic acid ester. [9] The resin composition according to any one of [5] to [8] above, wherein the content of the component (E) relative to the total amount (100% by mass) of the components (A), (B), and (E) is 1 to 20% by mass.

[10] The resin composition according to any one of [1] to [9] above, further comprising (F) an elastomer having a molecular weight of more than 1,000.

[11] A resin film comprising the resin composition according to any one of [1] to

[10] above.

[12] A supported resin film having a support and the resin film according to

[11] above.

[13] A printed wiring board having a cured product of the resin composition according to any one of [1] to

[10] above or a cured product of the resin film according to

[11] above.

[14] A semiconductor package having a cured product of the resin composition according to any one of [1] to

[10] above or a cured product of the resin film according to

[11] above.

[15] The semiconductor package according to

[14] above, comprising a semiconductor chip encapsulated in a cured product of the resin composition.

[0008] According to the present embodiment, it is possible to provide a resin composition that contains a radical polymerization initiator and yet has both embeddability in circuit boards and curability, as well as a resin film, a resin film with a support, a printed wiring board, and a semiconductor package that use the resin composition.

[0009] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. For example, a numerical range "X to Y" (X and Y are real numbers) means a numerical range that is equal to or greater than X and equal to or less than Y. In this specification, the term "X or greater" means X and a numerical value that exceeds X. In addition, the term "Y or less" in this specification means Y and a numerical value that is less than Y. The lower limit and upper limit of a numerical range described in this specification can be arbitrarily combined with the lower limit or upper limit of another numerical range. In the numerical ranges described in this specification, the lower limit or upper limit of that numerical range may be replaced with a value shown in the examples.

[0010] Unless otherwise specified, each component and material exemplified in this specification may be used alone or in combination of two or more types. In this specification, when a resin composition contains multiple substances corresponding to each component, the content of each component means the total amount of the multiple substances present in the resin composition unless otherwise specified. In this specification, the term "resin composition" refers to a mixture of two or more components containing a resin component, and also includes a mixture of the mixture in a B-stage state. However, the type and content of each component in a B-stage resin composition refers to the type and content of each component before the B-stage state is reached, i.e., the type and amount of the component blended when producing the resin composition.

[0011] In this specification, the term "solid content" refers to components in the resin composition other than the organic solvent described below, and components that are liquid at room temperature around 25° C. are also considered to be solid content. Furthermore, the term "resin component" is defined as all components among the solid content constituting the resin composition, excluding inorganic compounds such as (B) inorganic filler described below.

[0012] In this specification, "(meth)acrylate" means "acrylate" and its corresponding "methacrylate." Similarly, "(meth)acrylic" means "acrylic" and its corresponding "methacrylic," and "(meth)acryloyl" means "acryloyl" and its corresponding "methacryloyl."

[0013] In this specification, the "molecular weight" of a compound means, when the compound is not a polymer and the structural formula of the compound can be identified, the molecular weight that can be calculated from the structural formula, and when the compound is a polymer, it means the number average molecular weight.

[0014] The number average molecular weight in this specification refers to a value measured in terms of polystyrene by gel permeation chromatography (GPC). Specifically, the number average molecular weight in this specification can be measured by the method described in the examples.

[0015] The mechanism of action described in this specification is speculation and does not limit the mechanism by which the resin composition according to this embodiment exhibits its effects.

[0016] Any combination of the features described in this specification is also included in this embodiment.

[0017] [Resin Composition] The resin composition of the present embodiment is a resin composition containing: (A) a maleimide resin; (B) an inorganic filler; (C) a radical polymerization initiator; and (D) a polymerization inhibitor.

[0018] In this embodiment, being liquid at 25°C means that the viscosity calculated by the following measurement method is 100,000 mPa·s or less. <Viscosity Measurement Method> Apparatus: E-type viscometer Cone rotor: 1°34' x R24 Temperature: 25°C Sample amount: 1.0 mL Rotation speed: 20 rpm Hereinafter, in this specification, viscosity at 25°C means the viscosity measured by the above method.

[0019] The resin composition of this embodiment, which contains (A) maleimide resin, improves the low thermal expansion of the resin composition by including (B) an inorganic filler, and the curing reaction can be sufficiently promoted by the (C) radical polymerization initiator. The radicals generated by the (C) radical polymerization initiator cause the polymerization reaction of the resin composition to proceed rapidly, increasing the viscosity rate and resulting in curing with insufficient embedding properties for the circuit board. However, it is believed that the (D) polymerization inhibitor traps the radicals, temporarily preventing the viscosity increase of the molten resin film during heat curing, allowing the resin film to embed in accordance with the irregularities of the circuit board. It is then inferred that once the temperature has risen to a certain level and the (D) polymerization inhibitor has disappeared, the polymerization reaction by the (C) radical polymerization initiator proceeds, resulting in curing to a degree sufficient for forming an insulating layer. However, even if this inference is inaccurate, it does not adversely affect the scope of this embodiment. It is not common to use a (C) radical polymerization initiator that promotes the polymerization reaction in combination with a (D) polymerization inhibitor that suppresses the polymerization reaction. However, by incorporating these in combination in the resin composition of this embodiment, it is possible to obtain a resin composition that has both embeddability in circuit boards and curability, even while containing a radical polymerization initiator. The present inventors have attempted to improve embeddability in circuit boards by changing the type of resin component without using the (D) polymerization inhibitor, but this resulted in the sacrifice of other properties such as dielectric properties. Below, each component that may be contained in the resin composition of this embodiment will be described in order.

[0020] <(A) Maleimide Resin> The (A) maleimide resin may be any compound having a maleimide group, and is not otherwise particularly limited. However, it is preferably at least one selected from the group consisting of maleimide resins having one or more N-substituted maleimide groups and derivatives of such maleimide resins. In the following description, "at least one selected from the group consisting of maleimide resins having one or more N-substituted maleimide groups and derivatives of such maleimide resins" may be simply referred to as "maleimide-based resin." In the following description, a maleimide resin having one or more N-substituted maleimide groups may be referred to as a "maleimide resin (AX)." In addition, a derivative of a maleimide resin having one or more N-substituted maleimide groups may be referred to as a "maleimide resin derivative (AY)."

[0021] (Maleimide Resin (AX)) The maleimide resin (AX) is not particularly limited as long as it has one or more N-substituted maleimide groups. From the viewpoint of the peel strength and heat resistance of copper foil, the maleimide resin (AX) is preferably an aromatic maleimide resin having two or more N-substituted maleimide groups, and more preferably an aromatic bismaleimide resin having two N-substituted maleimide groups. In this specification, the term "aromatic maleimide resin" refers to a compound having an N-substituted maleimide group directly bonded to an aromatic ring. In this specification, the term "aromatic bismaleimide resin" refers to a compound having two N-substituted maleimide groups directly bonded to an aromatic ring. In this specification, the term "aromatic polymaleimide resin" refers to a compound having three or more N-substituted maleimide groups directly bonded to an aromatic ring. In this specification, the term "aliphatic maleimide resin" refers to a compound having an N-substituted maleimide group directly bonded to an aliphatic hydrocarbon.

[0022] From the viewpoints of dielectric properties, peel strength of copper foil, and heat resistance, the maleimide resin (AX) is preferably a maleimide resin having a molecular structure containing a condensed ring of an aromatic ring and an aliphatic ring and having two or more N-substituted maleimide groups (hereinafter, this may be referred to as "maleimide resin (A1)").

[0023] [Maleimide Resin (A1)] From the viewpoints of dielectric properties, copper foil peel strength, and heat resistance, the maleimide resin (A1) is preferably an aromatic maleimide resin having a molecular structure containing a condensed ring of an aromatic ring and an aliphatic ring and having two or more N-substituted maleimide groups. Furthermore, the maleimide resin (A1) is more preferably an aromatic bismaleimide resin having a molecular structure containing a condensed ring of an aromatic ring and an aliphatic ring and having two N-substituted maleimide groups.

[0024] From the viewpoints of dielectric properties, copper foil peel strength, and ease of production, the fused ring contained in the maleimide resin (A1) preferably has a fused bicyclic structure, and more preferably an indane ring. The maleimide resin (A1) containing an indane ring is preferably an aromatic bismaleimide resin containing an indane ring. The indane ring may have a substituent. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a hydroxyl group, and a mercapto group.

[0025] The maleimide resin (A1) preferably contains a divalent group represented by the following general formula (A1-1):

[0026] (In the formula, R ａ１ is an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a hydroxyl group, or a mercapto group. ａ１ is an integer from 0 to 3. ａ２ ~R ａ４ are each independently an alkyl group having 1 to 10 carbon atoms. * represents a bonding site.

[0027] R in the above general formula (A1-1) ａ１Examples of the alkyl group having 1 to 10 carbon atoms represented by R include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. These alkyl groups may be either linear or branched. ａ１ Examples of the alkyl group contained in the alkyloxy group having 1 to 10 carbon atoms and the alkylthio group having 1 to 10 carbon atoms represented by the formula (I) include the same alkyl groups as those having 1 to 10 carbon atoms described above. ａ１ Examples of the aryl group having 6 to 10 carbon atoms represented by R include a phenyl group and a naphthyl group. ａ１ Examples of the aryl group contained in the aryloxy group having 6 to 10 carbon atoms and the arylthio group having 6 to 10 carbon atoms represented by the formula (R) include the same as the aryl group having 6 to 10 carbon atoms described above. ａ１ Examples of the cycloalkyl group having 3 to 10 carbon atoms represented by the formula (A1-1) include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, and a cyclodecyl group. ａ１ is an integer from 1 to 3, R ａ１ From the viewpoint of solubility in organic solvents and reactivity, the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms.

[0028] R ａ２ ~R ａ４ Examples of the alkyl group having 1 to 10 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. These alkyl groups may be either linear or branched. Among these, R ａ２ ~R ａ４ is preferably an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. ａ１ is an integer from 0 to 3, and n ａ１ When R is 2 or 3, multiple R ａ１ They may be the same or different.

[0029] Among the above, the divalent group represented by the general formula (A1-1) is, from the viewpoint of ease of production, ａ１ is 0, and R ａ２ ~R ａ４ is a methyl group, and a divalent group represented by the following formula (A1-1a) is preferred, and a divalent group represented by the following formula (A1-1a') and a divalent group represented by the following formula (A1-1a'') are more preferred.

[0030] (In the formula, * represents a binding site.)

[0031] The maleimide resin (A1) containing a divalent group represented by the above general formula (A1-1) is preferably represented by the following general formula (A1-2), from the viewpoints of dielectric properties, copper foil peel strength, heat resistance, and ease of production:

[0032] (In the formula, R ａ１ ~R ａ４ and n ａ１ is the same as in the general formula (A1-1). ａ５ are each independently an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a nitro group, a hydroxyl group, or a mercapto group. ａ２ are each independently an integer of 0 to 4. ａ３ is a number between 0.95 and 10.0.)

[0033] In the general formula (A1-2), multiple R ａ１ Multiple n ａ１ R ａ５ Multiple n ａ２ Each of the n may be the same or different. ａ３ If R exceeds 1, multiple R ａ２ R ａ３ R ａ４ Each of the two may be the same or different.

[0034] R in the above general formula (A1-2) ａ５ Examples of the alkyl group having 1 to 10 carbon atoms represented by R include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. These alkyl groups may be either linear or branched. ａ５ Examples of the alkyl group contained in the alkyloxy group having 1 to 10 carbon atoms and the alkylthio group having 1 to 10 carbon atoms represented by the formula (I) include the same alkyl groups as those having 1 to 10 carbon atoms described above. ａ５ Examples of the aryl group having 6 to 10 carbon atoms represented by R include a phenyl group and a naphthyl group. ａ５ Examples of the aryl group contained in the aryloxy group having 6 to 10 carbon atoms and the arylthio group having 6 to 10 carbon atoms represented by the formula (R) include the same as the aryl group having 6 to 10 carbon atoms described above. ａ５ Examples of the cycloalkyl group having 3 to 10 carbon atoms represented by the formula (I) include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, and a cyclodecyl group. ａ５ From the viewpoints of solubility in organic solvents and ease of production, the alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group.

[0035] n in the above general formula (A1-2) ａ２ is an integer of 0 to 4, and from the viewpoints of compatibility with other resins, dielectric properties, peel strength of the copper foil, and ease of production, is preferably an integer of 1 to 3, more preferably 2 or 3, and even more preferably 2. ａ２ When n is 1 or more, the benzene ring and the N-substituted maleimide group have a twisted conformation, and intermolecular stacking is suppressed, which tends to further improve the solubility in organic solvents. ａ２ When R is 1 or more, ａ５ The substitution position of n in the above general formula (A1-2) is preferably the ortho position relative to the N-substituted maleimide group.ａ３ From the viewpoints of dielectric properties, peel strength of the copper foil, solubility in organic solvents, handling properties, and heat resistance, n is preferably a number from 0.98 to 8.0, more preferably a number from 1.0 to 7.0, and even more preferably a number from 1.1 to 6.0. ａ３ represents the average number of structural units containing an indane ring.

[0036] From the viewpoints of dielectric properties, peel strength of copper foil, solubility in organic solvents, and ease of production, the maleimide resin (A1) represented by the above general formula (A1-2) is more preferably represented by the following general formula (A1-3) or the following general formula (A1-4):

[0037] (In the formula, R ａ１ ~R ａ５ and n ａ１ and n ａ３ is the same as in the general formula (A1-2) above.

[0038] (In the formula, R ａ１ ~R ａ４ and n ａ１ and n ａ３ is the same as in the general formula (A1-2) above.

[0039] Examples of the maleimide resin (A1) represented by the general formula (A1-3) include a maleimide resin represented by the following general formula (A1-3-1), a maleimide resin represented by the following general formula (A1-3-2), and a maleimide resin represented by the following general formula (A1-3-3).

[0040] (In the formula, n ａ３ is the same as in the general formula (A1-2) above.

[0041] Examples of the maleimide resin (A1) represented by the general formula (A1-4) above include aromatic bismaleimide resins containing an indane ring, represented by the following general formula (A1-4-1), from the viewpoints of dielectric properties, peel strength of copper foil, solubility in organic solvents, and ease of production:

[0042] (In the formula, n ａ３ is the same as in the general formula (A1-2) above.

[0043] The number average molecular weight of the maleimide resin (A1) is not particularly limited, but from the viewpoints of compatibility with other resins, peel strength of copper foil, and heat resistance, it is preferably 600 to 3,000, more preferably 800 to 2,000, and even more preferably 1,000 to 1,500.

[0044] The method for producing the maleimide resin (A1) is not particularly limited, and known methods can be used and applied. For example, the maleimide resin (A1) can be produced by reacting an intermediate amine compound containing a fused ring of an aromatic ring and an aliphatic ring with maleic anhydride.

[0045] The maleimide resin (AX) may be a maleimide resin (A2) other than the above-mentioned maleimide resin (A1) (hereinafter, may be abbreviated as "maleimide resin (A2)").

[0046] [Maleimide Resin (A2)] The maleimide resin (A2) is preferably a maleimide resin represented by the following general formula (A2-1).

[0047] (In the formula, X ａ１１ is a divalent organic group that does not contain a fused ring of an aromatic ring and an aliphatic ring.

[0048] X in the above general formula (A2-1) ａ１１ is a divalent organic group that does not contain a condensed ring of an aromatic ring and an aliphatic ring. ａ１１ Examples of the divalent organic group represented by formula (A2-2) below, a divalent group represented by formula (A2-3) below, a divalent group represented by formula (A2-4) below, a divalent group represented by formula (A2-5) below, and a divalent group represented by formula (A2-6) below are given.

[0049] (In the formula, R ａ１１ is an aliphatic hydrocarbon group having 1 to 5 carbon atoms or a halogen atom. ａ１１ is an integer from 0 to 4. * represents a binding site.)

[0050] R in the above general formula (A2-2) ａ１１Examples of the aliphatic hydrocarbon group having 1 to 5 carbon atoms represented by include alkyl groups having 1 to 5 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, and n-pentyl; alkenyl groups having 2 to 5 carbon atoms, and alkynyl groups having 2 to 5 carbon atoms. The aliphatic hydrocarbon group having 1 to 5 carbon atoms may be either linear or branched. The aliphatic hydrocarbon group having 1 to 5 carbon atoms is preferably an aliphatic hydrocarbon group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. In the above general formula (A2-2), n ａ１１ is an integer of 0 to 4, and from the viewpoint of availability, is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0. ａ１１ is an integer of 2 or more, a plurality of R ａ１１ They may be the same or different.

[0051] (In the formula, R ａ１２ and R ａ１３ are each independently an aliphatic hydrocarbon group having 1 to 5 carbon atoms or a halogen atom. ａ１２ n is an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, an ether group, a sulfide group, a sulfonyl group, a carbonyloxy group, a keto group, a single bond, or a divalent group represented by the following general formula (A2-3-1): ａ１２ and n ａ１３ are each independently an integer of 0 to 4. * represents a binding site.

[0052] R in the above general formula (A2-3) ａ１２ and R ａ１３Examples of the aliphatic hydrocarbon group having 1 to 5 carbon atoms represented by include alkyl groups having 1 to 5 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, and n-pentyl; alkenyl groups having 2 to 5 carbon atoms, and alkynyl groups having 2 to 5 carbon atoms. The aliphatic hydrocarbon group having 1 to 5 carbon atoms may be either linear or branched. From the viewpoints of compatibility with other resins and suppressing gelation of the product during the reaction, the aliphatic hydrocarbon group having 1 to 5 carbon atoms is preferably an aliphatic hydrocarbon group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0053] X in the above general formula (A2-3) ａ１２ Examples of the alkylene group having 1 to 5 carbon atoms represented by include a methylene group, a 1,2-dimethylene group, a 1,3-trimethylene group, a 1,4-tetramethylene group, a 1,5-pentamethylene group, etc. The alkylene group having 1 to 5 carbon atoms is preferably an alkylene group having 1 to 3 carbon atoms, more preferably an alkylene group having 1 or 2 carbon atoms, and even more preferably a methylene group.

[0054] X in the above general formula (A2-3) ａ１２ Examples of the alkylidene group having 2 to 5 carbon atoms represented by include an ethylidene group, a propylidene group, an isopropylidene group, a butylidene group, an isobutylidene group, a pentylidene group, an isopentylidene group, etc. Among these, an alkylidene group having 2 to 4 carbon atoms is preferred, an alkylidene group having 2 or 3 carbon atoms is more preferred, and an isopropylidene group is even more preferred.

[0055] n in the above general formula (A2-3) ａ１２ and n ａ１３ are each independently an integer of 0 to 4, and from the viewpoints of availability, compatibility with other resins, and suppression of gelation of the product during the reaction, are preferably integers of 1 to 3, more preferably 1 or 2, and even more preferably 2. ａ１２ +n ａ１３From the viewpoints of availability, compatibility with other resins, and suppression of gelation of the product during the reaction, n is preferably an integer of 1 to 8, more preferably an integer of 2 to 6, and even more preferably 4. ａ１２ or n ａ１３ is an integer of 2 or more, a plurality of R ａ１２ R ａ１３ They may be the same or different from each other.

[0056] X in the above general formula (A2-3) ａ１２ The divalent group represented by formula (A2-3-1) is as follows:

[0057] (In the formula, R ａ１４ and R ａ１５ are each independently an aliphatic hydrocarbon group having 1 to 5 carbon atoms or a halogen atom. ａ１３ is an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, an ether group, a sulfide group, a sulfonyl group, a carbonyloxy group, a keto group, or a single bond. ａ１４ and n ａ１５ are each independently an integer of 0 to 4. * represents a binding site.

[0058] R in the above general formula (A2-3-1) ａ１４ and R ａ１５ Examples of the aliphatic hydrocarbon group having 1 to 5 carbon atoms represented by include alkyl groups having 1 to 5 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, and n-pentyl; alkenyl groups having 2 to 5 carbon atoms, and alkynyl groups having 2 to 5 carbon atoms. The aliphatic hydrocarbon group having 1 to 5 carbon atoms may be either linear or branched. As the aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aliphatic hydrocarbon group having 1 to 3 carbon atoms is preferred, an alkyl group having 1 to 3 carbon atoms is more preferred, and a methyl group is even more preferred. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0059] X in the above general formula (A2-3-1) ａ１３Examples of the alkylene group having 1 to 5 carbon atoms represented by include a methylene group, a 1,2-dimethylene group, a 1,3-trimethylene group, a 1,4-tetramethylene group, a 1,5-pentamethylene group, etc. The alkylene group having 1 to 5 carbon atoms is preferably an alkylene group having 1 to 3 carbon atoms, more preferably an alkylene group having 1 or 2 carbon atoms, and even more preferably a methylene group.

[0060] X in the above general formula (A2-3-1) ａ１３ Examples of the alkylidene group having 2 to 5 carbon atoms represented by include an ethylidene group, a propylidene group, an isopropylidene group, a butylidene group, an isobutylidene group, a pentylidene group, an isopentylidene group, etc. Among these, an alkylidene group having 2 to 4 carbon atoms is preferred, an alkylidene group having 2 or 3 carbon atoms is more preferred, and an isopropylidene group is even more preferred.

[0061] X in the above general formula (A2-3-1) ａ１３ Among the above options, alkylidene groups having 2 to 5 carbon atoms are preferred, alkylidene groups having 2 to 4 carbon atoms are more preferred, and an isopropylidene group is even more preferred.

[0062] n in the above general formula (A2-3-1) ａ１４ and n ａ１５ are each independently an integer of 0 to 4, and from the viewpoint of availability, are each preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0. ａ１４ or n ａ１５ is an integer of 2 or more, a plurality of R ａ１４ R ａ１５ They may be the same or different from each other.

[0063] X in the above general formula (A2-3) ａ１２ Among the above options, an alkylene group having 1 to 5 carbon atoms, an alkylidene group having 2 to 5 carbon atoms, or a divalent group represented by general formula (A2-3-1) above is preferable, an alkylene group having 1 to 5 carbon atoms is more preferable, and a methylene group is even more preferable.

[0064] (In the formula, n ａ１６is an integer from 0 to 10. * represents a binding site.)

[0065] n in the above general formula (A2-4) ａ１６ is preferably an integer of 0 to 5, more preferably an integer of 0 to 4, and even more preferably an integer of 0 to 3, from the viewpoint of availability.

[0066] (In the formula, n ａ１７ is a number from 0 to 5. * represents a binding site.)

[0067] (In the formula, R ａ１６ and R ａ１７ are each independently a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms. ａ１８ is an integer from 1 to 8. * represents a binding site.)

[0068] R in the above general formula (A2-6) ａ１６ and R ａ１７ Examples of the aliphatic hydrocarbon group having 1 to 5 carbon atoms represented by include alkyl groups having 1 to 5 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, and n-pentyl; alkenyl groups having 2 to 5 carbon atoms; and alkynyl groups having 2 to 5 carbon atoms. The aliphatic hydrocarbon group having 1 to 5 carbon atoms may be either linear or branched. ａ１８ is an integer of 1 to 8, preferably an integer of 1 to 5, more preferably an integer of 1 to 3, and even more preferably 1. ａ１８ is an integer of 2 or more, a plurality of R ａ１６ R ａ１７ They may be the same or different from each other.

[0069] The maleimide resin (A2) is preferably a polymaleimide resin represented by the following general formula (A2-7).

[0070] (In the formula, X ａ１４ are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms, and n ａ１９ is an integer from 2 to 5.

[0071] X in the above general formula (A2-7)ａ１４ Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (A2-3) include divalent aliphatic hydrocarbon groups such as alkylene groups having 1 to 5 carbon atoms and alkylidene groups having 2 to 5 carbon atoms; and divalent hydrocarbon groups containing an aromatic hydrocarbon group represented by the following general formula (A2-8). Examples of the alkylene group having 1 to 5 carbon atoms include a methylene group, a 1,2-dimethylene group, a 1,3-trimethylene group, a 1,4-tetramethylene group, and a 1,5-pentamethylene group. The alkylene group having 1 to 5 carbon atoms is preferably an alkylene group having 1 to 3 carbon atoms, more preferably an alkylene group having 1 or 2 carbon atoms, and even more preferably a methylene group. The alkylidene group having 2 to 5 carbon atoms is preferably an alkylidene group having 2 to 4 carbon atoms, more preferably an alkylidene group having 2 or 3 carbon atoms, and even more preferably an isopropylidene group.

[0072] (In the formula, Ar ａ１ is a divalent aromatic hydrocarbon group, and X ａ１５ and X ａ１６ are each independently a divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms. * represents a bonding site.

[0073] X in the above general formula (A2-8) ａ１５ and X ａ１６ The divalent aliphatic hydrocarbon group having 1 to 5 carbon atoms represented by X in the above general formula (A2-7) is ａ１４ Examples of the alkylene group having 1 to 5 carbon atoms and the alkylidene group having 2 to 5 carbon atoms mentioned above are as follows. Among these, a methylene group is preferred. ａ１ Examples of the divalent aromatic hydrocarbon group represented by are a phenylene group, a naphthylene group, a biphenylene group, and an anthranylene group. Of these, a biphenylene group is preferred. Examples of the biphenylene group include a 4,2'-biphenylene group, a 4,3'-biphenylene group, a 4,4'-biphenylene group, and a 3,3'-biphenylene group. Of these, a 4,4'-biphenylene group is preferred.

[0074] Among the above options, X in the general formula (A2-7) ａ１４is preferably a divalent hydrocarbon group containing an aromatic hydrocarbon group represented by the above general formula (A2-8), and in the above general formula (A2-8), X ａ１５ and X ａ１６ is a methylene group and Ar ａ１ More preferably, the divalent hydrocarbon group is a 4,4'-biphenylene group.

[0075] n in the above general formula (A2-7) ａ１９ is an integer of 2 to 5, preferably an integer of 2 to 4, and more preferably 2 or 3.

[0076] Examples of the maleimide resin (A2) include aromatic bismaleimide resins, aromatic polymaleimide resins, aliphatic maleimide resins, etc. Specific examples of the maleimide resin (A2) include N,N'-ethylene bismaleimide, N,N'-hexamethylene bismaleimide, N,N'-(1,3-phenylene)bismaleimide, N,N'-[1,3-(2-methylphenylene)]bismaleimide, N,N'-[1,3-(4-methylphenylene)]bismaleimide, N,N'-(1,4-phenylene)bismaleimide, bis(4-maleimidophenyl)methane, bis(3-methyl-4-maleimidophenyl)methane, 3,3'-dimethyl-5,5'-diethyl- 4,4'-diphenylmethane bismaleimide, bis(4-maleimidophenyl)ether, bis(4-maleimidophenyl)sulfone, bis(4-maleimidophenyl)sulfide, bis(4-maleimidophenyl)ketone, bis(4-maleimidocyclohexyl)methane, 1,4-bis(4-maleimidophenyl)cyclohexane, 1,4-bis(maleimidomethyl)cyclohexane, 1,4-bis(maleimidomethyl)benzene, 1,3-bis(4-maleimidophenoxy)benzene, 1,3-bis(3-maleimidophenyl) bis[4-(3-maleimidophenoxy)phenyl]benzene, bis[4-(4-maleimidophenoxy)phenyl]methane, bis[4-(4-maleimidophenoxy)phenyl]methane, 1,1-bis[4-(3-maleimidophenoxy)phenyl]ethane, 1,1-bis[4-(4-maleimidophenoxy)phenyl]ethane, 1,2-bis[4-(3-maleimidophenoxy)phenyl]ethane, 1,2-bis[4-(4-maleimidophenoxy)phenyl]ethane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]butane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]butane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 4,4-bis(3-maleimidophenoxy)biphenyl, 4,4-bis(4-maleimidophenoxy)biphenyl, bis[4-(3-maleimidophenoxy)phenyl]ketone, bis[4-(4-maleimidophenoxy)phenyl]ketone, bis(4-maleimidophenyl)disulfide, bis[4-(3-maleimidophenoxy)phenyl]sulfide, bis[4-(4-maleimidophenoxy)phenyl]sulfide, bis[4-(3-maleimidophenoxy)phenyl]sulfide sulfoxide, bis[4-(4-maleimidophenoxy)phenyl]sulfoxide, bis[4-(3-maleimidophenoxy)phenyl]sulfone, bis[4-(4-maleimidophenoxy)phenyl]sulfone, bis[4-(3-maleimidophenoxy)phenyl]ether, bis[4-(4-maleimidophenoxy)phenyl]ether, 1,4-bis[4-(4-maleimidophenoxy)-α,α-dimethylbenzene 1,3-bis[4-(4-maleimidophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-maleimidophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(3-maleimidophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(4-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene, 1,3- Examples of such maleimide include bis[4-(4-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(3-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene, polyphenylmethane maleimide, and biphenylaralkyl maleimide.

[0077] (Maleimide Resin Derivative (AY)) The maleimide resin derivative (AY) is preferably an aminomaleimide resin having a structural unit derived from the above-mentioned maleimide resin (AX) and a structural unit derived from a diamine compound (hereinafter, sometimes abbreviated as "aminomaleimide resin (A3)").

[0078] [Aminomaleimide Resin (A3)] The aminomaleimide resin (A3) has a structural unit derived from the maleimide resin (AX) and a structural unit derived from a diamine compound (hereinafter sometimes abbreviated as "diamine compound (a)").

[0079] <Structural Units Derived from Maleimide Resin (AX)> Examples of the structural units derived from the maleimide resin (AX) include structural units formed by a Michael addition reaction of at least one N-substituted maleimide group among the N-substituted maleimide groups contained in the maleimide resin (AX) with an amino group contained in a diamine compound. The structural units derived from the maleimide resin (AX) contained in the aminomaleimide resin (A3) may be of one type alone or two or more types.

[0080] The content of the structural unit derived from the maleimide resin (AX) in the aminomaleimide resin (A3) is not particularly limited, but is preferably 5 to 95% by mass, more preferably 30 to 93% by mass, and even more preferably 60 to 90% by mass. When the content of the structural unit derived from the maleimide resin (AX) in the aminomaleimide resin (A3) is within the above range, the dielectric properties and film handling properties tend to be better.

[0081] <<Structural Units Derived from Diamine Compound (a)>> Examples of the structural units derived from the diamine compound (a) include structural units formed by a Michael addition reaction of one or both of the two amino groups contained in the diamine compound (a) with an N-substituted maleimide group contained in the maleimide resin (AX). The structural units derived from the diamine compound (a) contained in the aminomaleimide resin (A3) may be of one type alone or may be of two or more types.

[0082] The content of the structural units derived from the diamine compound (a) in the aminomaleimide resin (A3) is not particularly limited, but is preferably 5 to 95 mass%, more preferably 7 to 70 mass%, and even more preferably 10 to 40 mass%. When the content of the structural units derived from the diamine compound (a) in the aminomaleimide resin (A3) is within the above range, the dielectric properties, heat resistance, flame retardancy, and glass transition temperature tend to be better.

[0083] As the diamine compound (a), for example, the same amine compounds having at least two primary amino groups in one molecule as those described in JP 2020-200406 A can be used. Specific examples of the diamine compound (a) include 4,4'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ketone, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4 '-Diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis(3-aminophenoxy)benzene , 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 1,3-bis[1-[4-(4-aminophenoxy)phenyl]-1-methylethyl]benzene, 1,4-bis[1-[4-(4-aminophenoxy)phenyl]-1-methylethyl]benzene, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline aromatic diamine compounds such as 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 3,3'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, and 9,9-bis(4-aminophenyl)fluorene; and amine-modified siloxane compounds having a primary amino group.

[0084] In the aminomaleimide resin (A3), the —NH ２ Group derived from the group (-NH ２The equivalent ratio (Ta2 / Ta1) of the total equivalent (Ta2) of the groups derived from N-substituted maleimide groups of the maleimide resin (AX) to the total equivalent (Ta1) of the groups derived from N-substituted maleimide groups of the maleimide resin (AX) is not particularly limited, but is preferably 0.05 to 10, more preferably 0.5 to 7, and even more preferably 1 to 5, from the viewpoints of dielectric properties, heat resistance, flame retardancy, and glass transition temperature. ２ The group derived from the group is —NH ２ The group derived from the N-substituted maleimide group of the maleimide resin (AX) also includes the N-substituted maleimide group itself.

[0085] The number average molecular weight of the aminomaleimide resin (A3) is not particularly limited, but from the viewpoints of handleability and moldability, it is preferably 400 to 10,000, more preferably 500 to 5,000, and even more preferably 600 to 2,000.

[0086] The aminomaleimide resin (A3) can be produced, for example, by the method described in “(A) Method for producing modified maleimide resin” in JP-A-2020-200406.

[0087] Among the (A) maleimide resins described above, from the viewpoints of dielectric properties, peel strength of copper foil, and heat resistance, the (A) maleimide resin is preferably a maleimide resin that contains a condensed ring of an aromatic ring and an aliphatic ring in its molecular structure and has two or more N-substituted maleimide groups.

[0088] The maleimide resin (A) preferably has a viscosity at 25°C measured by the above-mentioned method of more than 100,000 mPa·s, and more preferably is solid at 25°C.

[0089] (Content of (A) Maleimide Resin) In the resin composition of this embodiment, the content of the (A) maleimide resin is not particularly limited, but is preferably 3 to 80 mass %, more preferably 5 to 60 mass %, even more preferably 5 to 40 mass %, and particularly preferably 5 to 25 mass %, relative to the total solid content (100 mass %) in the resin composition of this embodiment. When the content of the (A) maleimide resin is at least the above-mentioned lower limit, the heat resistance, moldability, processability, low thermal expansion, and copper foil peel strength tend to be better. On the other hand, when the content of the (A) maleimide resin is at most the above-mentioned upper limit, the dielectric properties tend to be better.

[0090] <(B) Inorganic Filler> By including the inorganic filler (B), the resin composition of the present embodiment tends to easily obtain better low thermal expansion, heat resistance, and flame retardancy. The inorganic filler (B) may be used alone or in combination of two or more.

[0091] (B) Examples of inorganic fillers include silica, alumina, titanium oxide, mica, beryllia, barium titanate, potassium titanate, strontium titanate, calcium titanate, aluminum carbonate, magnesium hydroxide, aluminum hydroxide, aluminum silicate, calcium carbonate, calcium silicate, magnesium silicate, silicon nitride, boron nitride, clay, talc, molybdic acid compounds (such as zinc molybdate), aluminum borate, and silicon carbide.Among these, from the viewpoint of low thermal expansion, heat resistance, and flame retardancy, silica, alumina, mica, and talc are preferred, and silica and alumina are more preferred.Examples of silica include precipitated silica produced by a wet method and having a high water content, and dry-process silica produced by a dry method and containing almost no bound water.Examples of dry-process silica include crushed silica, fumed silica, fused silica, and the like, depending on the production method.

[0092] The average particle diameter of the (B) inorganic filler is not particularly limited, but from the viewpoint of the dispersibility and fine wiring properties of the (B) inorganic filler, it is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm, even more preferably 0.2 to 5 μm, and particularly preferably 0.3 to 3 μm. In this specification, the average particle diameter of the (B) inorganic filler refers to the particle diameter at the point corresponding to 50% volume when a cumulative frequency distribution curve of particle diameters is calculated assuming the total volume of the particles to be 100%. The average particle diameter of the (B) inorganic filler can be measured, for example, using a particle size distribution measuring device using a laser diffraction scattering method. The shape of the (B) inorganic filler can be spherical, crushed, etc., with spherical being preferred.

[0093] The resin composition of this embodiment may contain a coupling agent for the purpose of improving the dispersibility of the inorganic filler (B) and the adhesion to the organic component. Examples of the coupling agent include a silane coupling agent and a titanate coupling agent. Among these, a silane coupling agent is preferred. Examples of the silane coupling agent include an aminosilane coupling agent, a vinylsilane coupling agent, an acrylic silane coupling agent, a methacrylsilane coupling agent, and an epoxysilane coupling agent.

[0094] When the resin composition of this embodiment contains a coupling agent, the (B) inorganic filler may be surface-treated with the coupling agent. Specifically, the surface treatment method for the (B) inorganic filler may be an integral blending method in which the (B) inorganic filler is blended into the resin composition and then a coupling agent is added, or a method in which the (B) inorganic filler is previously surface-treated with a coupling agent in a dry or wet manner. Among these, from the viewpoint of more effectively exhibiting the characteristics of the (B) inorganic filler, a method in which the (B) inorganic filler is previously surface-treated with a coupling agent in a dry or wet manner is preferred. In order to improve dispersibility in the resin composition, the (B) inorganic filler may be previously dispersed in an organic solvent to form a slurry, and then mixed with other components.

[0095] (Content of (B) Inorganic Filler) In the resin composition of this embodiment, the content of the (B) inorganic filler is not particularly limited, but is preferably 20 to 90 mass%, more preferably 40 to 80 mass%, even more preferably 45 to 75 mass%, and particularly preferably 50 to 70 mass%, relative to the total solid content (100 mass%) of the resin composition. When the content of the (B) inorganic filler is equal to or greater than the above lower limit, low thermal expansion, heat resistance, and flame retardancy tend to be more favorable. On the other hand, when the content of the (B) inorganic filler is equal to or less than the above upper limit, formability and copper foil peel strength tend to be more favorable.

[0096] <(C) Radical Polymerization Initiator> The resin composition of this embodiment contains a radical polymerization initiator (C). By containing the radical polymerization initiator (C), the polymerization reaction upon heating is accelerated, and as a result, the resin composition can be cured to a degree sufficient for use as an insulating layer. Furthermore, by containing the radical polymerization initiator (C), the resin composition of this embodiment tends to improve the solder heat resistance and chemical resistance of the cured resin film. The radical polymerization initiator decomposes into a compound having an unpaired electron when exposed to energy such as light or heat. The radical polymerization initiator (C) may be used alone or in combination of two or more types.

[0097] Examples of the radical polymerization initiator (C) include organic peroxides such as dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, 1,3-di(t-butylperoxyisopropyl)benzene, and α,α-bis(t-butylperoxy-m-isopropyl)benzene; inorganic peroxides such as potassium persulfate, sodium persulfate, and ammonium persulfate; and azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2'-dimethylvaleronitrile). The radical polymerization initiator (C) may be any of organic peroxides, inorganic peroxides, and azo compounds, but is preferably an organic peroxide.

[0098] (Content of (C) Radical Polymerization Initiator) In the resin composition of this embodiment, the content of the (C) radical polymerization initiator is not particularly limited, but is preferably 0.05 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, even more preferably 0.5 to 3 parts by mass, and particularly preferably 1.0 to 2.5 parts by mass, relative to 100 parts by mass of the total amount of the resin components. When the content of the (C) radical polymerization initiator is at least the above-mentioned lower limit, the above-mentioned effects of the (C) component tend to be more easily obtained. Furthermore, when the content of the (C) radical polymerization initiator is at most the above-mentioned upper limit, storage stability tends to be better.

[0099] <(D) Polymerization inhibitor> The resin composition of this embodiment contains (D) a polymerization inhibitor. By containing (D) a polymerization inhibitor, the (D) polymerization inhibitor traps radicals generated by the (C) radical polymerization initiator, temporarily preventing thickening of the molten resin film during heat curing, and making it easier to embed the resin film in accordance with the irregularities of the circuit board. One type of (D) polymerization inhibitor may be used alone, or two or more types may be used in combination.

[0100] The polymerization inhibitor (D) is not particularly limited, but from the viewpoint of embeddability in circuit boards, a hindered amine compound is preferred. Examples of hindered amine compounds include piperidine derivatives such as compounds having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton, compounds having a 2,2,6,6-tetramethylpiperidine skeleton, compounds having a 2,2,6,6-tetramethylpiperidine-N-alkyl skeleton, and compounds having a 2,2,6,6-tetramethylpiperidine-N-acyl skeleton. Among these, from the viewpoint of embeddability in circuit boards, compounds having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton are preferred.

[0101] Examples of compounds having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton include 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 4,4'-[(1,10-dioxo-1,10-decanediyl)bis(oxy)]bis[2,2,6,6-tetramethyl]-1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate, and decanedioic acid bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl)ester.

[0102] (D) The polymerization inhibitor may be a commercially available product. The hindered amine compounds are also commercially available, including "ADEKA STAB LA-7RD" (2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl) (manufactured by ADEKA Corporation); "IRGASTAB UV 10" (4,4'-[(1,10-dioxo-1,10-decanediyl)bis(oxy)]bis[2,2,6,6-tetramethyl]-1-piperidinyloxy) (CAS. 2516-92-9), "TINUVIN 123" (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (all manufactured by BASF Corporation); "FA-711HM" and "FA-712HM" (2,2,6,6-tetramethylpiperidinyl methacrylate, manufactured by Resonac Corporation); and "TINUVIN 111FDL”, “TINUVIN 144”, “TINUVIN 152”, “TINUVIN 292”, “TINUVIN 765”, “TINUVIN 770DF”, “TINUVIN 5100”, “SANOL LS-2626", "CHIMASSORB 119FL", "CHIMASSORB 2020 FDL", "CHIMASSORB 944 FDL", "TINUVIN 622 Examples of commercially available compounds include "LA-52," "LA-57," "LA-62," "LA-63P," "LA-68LD," "LA-77Y," "LA-77G," "LA-81," and "LA-82" (1,2,2,6,6-pentamethyl-4-piperidyl methacrylate) and "LA-87" (all manufactured by ADEKA Corporation). Of the commercially available compounds listed above, "LA-82" is a compound having the 2,2,6,6-tetramethylpiperidine-N-methyl skeleton, and "ADEKA STAB LA-7RD" is a compound having the 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton.

[0103] The polymerization inhibitor other than the hindered amine compound is not particularly limited, but examples thereof include p-methoxyphenol, hydroquinone, hydroquinone monomethyl ether (MEHQ), cresol, t-butylcatechol, 3,5-di-t-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), and phenothiazine. The (D) polymerization inhibitor can also be selected from polymerization inhibitors other than the hindered amine compound. Furthermore, the hindered amine compound can also be used in combination with a polymerization inhibitor other than the hindered amine compound. Note that hindered amine compounds tend to have a greater effect of improving embeddability in circuit boards than polymerization inhibitors other than the hindered amine compound.

[0104] (Content of (D) Polymerization Inhibitor) In the resin composition of this embodiment, the content of the (D) polymerization inhibitor is preferably 1 to 90 parts by mass, more preferably 3 to 80 parts by mass, even more preferably 5 to 75 parts by mass, particularly preferably 7 to 70 parts by mass, and most preferably 13 to 70 parts by mass, relative to 100 parts by mass of the (C) component. It may be 20 to 70 parts by mass, 30 to 70 parts by mass, 35 to 70 parts by mass, or 40 to 65 parts by mass. When the content of the (D) polymerization inhibitor is equal to or greater than the above-mentioned lower limit, radicals generated by the (C) radical polymerization initiator are easily trapped efficiently, temporarily preventing thickening of the molten resin film during heat curing, and enabling the resin film to be embedded in accordance with the irregularities of the circuit board. When the content of the (D) polymerization inhibitor is equal to or less than the above-mentioned upper limit, the effect of the (C) radical polymerization initiator, i.e., the polymerization reaction, is promoted after the (D) polymerization inhibitor disappears, and as a result, the insulating layer tends to be cured to a sufficient degree. The content of the (D) polymerization inhibitor may be 0.001 to 1 part by mass, 0.003 to 0.8 parts by mass, 0.005 to 0.5 parts by mass, 0.01 to 0.4 parts by mass, 0.03 to 0.4 parts by mass, 0.05 to 0.3 parts by mass, or 0.08 to 0.3 parts by mass, relative to 100 parts by mass of the total amount of the resin components.

[0105] <(E) Compound that is liquid at 25°C, has a reactive group, and has a molecular weight of 1,000 or less> The resin composition of this embodiment may contain (E) a compound that is liquid at 25°C, has a reactive group, and has a molecular weight of 1,000 or less (hereinafter, may be abbreviated as (E) reactive liquid compound). When the resin composition of this embodiment contains (E) reactive liquid compound, the flexibility of the resin film increases, and the resin film (resin film before curing) tends to be less likely to tear. The (E) reactive liquid compound is not particularly limited as long as it is a compound that is liquid at 25°C, has a reactive group, and has a molecular weight of 1,000 or less. One type of (E) reactive liquid compound may be used alone, or two or more types may be used in combination.

[0106] The reactive liquid compound (E) preferably has two or more reactive groups per molecule, more preferably 2 to 5, even more preferably 2 to 4, and particularly preferably 2 or 3. When the number of reactive groups is within the above range, excellent flexibility tends to be easily obtained while volatilization during heat curing is more effectively suppressed.

[0107] The molecular weight of the (E) reactive liquid compound is 1,000 or less, preferably 100 to 800, more preferably 150 to 600, and even more preferably 200 to 400. When the molecular weight of the (E) reactive liquid compound is equal to or greater than the above-mentioned lower limit, volatilization of the (E) reactive liquid compound before the resin composition is heat-cured tends to be easily suppressed. Furthermore, when the molecular weight of the (E) reactive liquid compound is equal to or less than the above-mentioned upper limit, better flexibility tends to be easily obtained.

[0108] The viscosity of the (E) reactive liquid compound at 25°C is preferably 1 to 5,000 mPa·s, more preferably 2 to 1,000 mPa·s, and even more preferably 4 to 500 mPa·s. When the viscosity of the (E) reactive liquid compound at 25°C is equal to or greater than the above-mentioned lower limit, the volatilization of the (E) reactive liquid compound tends to be easily suppressed. Furthermore, when the viscosity of the (E) reactive liquid compound at 25°C is equal to or less than the above-mentioned upper limit, better flexibility tends to be easily obtained. The viscosity of the (E) reactive liquid compound at 25°C can be measured by the measurement method described above.

[0109] The reactive group of the (E) reactive liquid compound is preferably one or more reactive groups selected from the group consisting of a vinyl group, an allyl group, a maleimide group, a (meth)acryloyl group, an epoxy group, a hydroxyl group, a carboxyl group, and an amino group. As the reactive group, a (meth)acryloyl group and an epoxy group are more preferred, and a (meth)acryloyl group is even more preferred from the viewpoint of facilitating the attainment of better dielectric properties.

[0110] Specific examples of the (E) reactive liquid compound having a (meth)acryloyl group as the reactive group include (meth)acrylic acid esters such as mono(meth)acrylic acid esters, di(meth)acrylic acid esters, and tri- or higher functional (meth)acrylic acid esters.

[0111] Examples of mono(meth)acrylate esters include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, pentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, dodecyl(meth)acrylate, lauryl(meth)acrylate, tridecyl(meth)acrylate, stearyl(meth)acrylate, and the like. Examples of the acrylate include methyl (meth)acrylate, ...

[0112] Examples of di(meth)acrylic acid esters include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, tricyclodecane di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate. Examples of the di(meth)acrylate include 2-[5-ethyl-5-[(acryloyloxy)methyl]-1,3-dioxane-2-yl]-2,2-dimethylethyl acrylate, ...

[0113] Examples of the tri- or higher functional (meth)acrylic acid ester include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0114] Among the above options, the (meth)acrylic acid ester is preferably a di(meth)acrylic acid ester. As the di(meth)acrylic acid ester, a diacrylic acid ester represented by the following general formula (E-1) or a dimethacrylic acid ester represented by the following general formula (E-2) is preferred, and a dimethacrylic acid ester represented by the following general formula (E-2) is more preferred.

[0115] (In the formula, R ｅ１ is an alkylene group having 1 to 20 carbon atoms.

[0116] R in the above general formulas (E-1) and (E-2) ｂ１The number of carbon atoms in the alkylene group having 1 to 20 carbon atoms represented by is preferably 4 to 18, more preferably 6 to 15, and even more preferably 8 to 12. Examples of the alkylene group having 1 to 20 carbon atoms include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tetradecylene group, and a pentadecylene group. The alkylene group may be linear, branched, or cyclic, but is preferably linear.

[0117] (Content of (E) Reactive Liquid Compound) In the resin composition of this embodiment, the content of the (E) reactive liquid compound is not particularly limited, but is preferably 1 to 20 mass%, more preferably 1 to 15 mass%, even more preferably 2 to 10 mass%, and particularly preferably 3 to 8 mass%, relative to the total amount (100 mass%) of the (A), (B), and (E) components. When the content of the (E) reactive liquid compound is equal to or greater than the above-mentioned lower limit, the resin film of this embodiment can have excellent flexibility, and the resin film (resin film before curing) tends to be less likely to tear. Furthermore, when the content of the (E) reactive liquid compound is equal to or less than the above-mentioned upper limit, the generation of volatile components during heat curing tends to be more easily suppressed.

[0118] <(F) Elastomer Having a Molecular Weight of More than 1,000> The resin composition of this embodiment may further contain (F) an elastomer having a molecular weight of more than 1,000 (hereinafter, sometimes abbreviated as "(F) elastomer"). By containing (F) elastomer, the resin composition of this embodiment tends to easily obtain better dielectric properties. Here, "elastomer" means a polymer having a glass transition temperature of 25°C or less as measured by differential scanning calorimetry in accordance with JIS K6240:2011. One type of (F) elastomer may be used alone, or two or more types may be used in combination.

[0119] The molecular weight of the (F) elastomer exceeds 1,000, preferably 1,050 to 500,000, more preferably 1,100 to 350,000, and even more preferably 1,150 to 200,000. When the molecular weight of the (F) elastomer is equal to or greater than the above lower limit, the heat resistance and other properties of the resulting resin composition tend to be more readily maintained. On the other hand, when the molecular weight of the (F) elastomer is equal to or less than the above upper limit, the dielectric properties and copper foil peel strength of the resulting resin composition tend to be more readily improved.

[0120] Preferred examples of the elastomer (F) include a conjugated diene polymer (F1), a modified conjugated diene polymer (F2), a styrene-based elastomer (F3), etc. Preferred embodiments of these components will be described below.

[0121] (Conjugated diene polymer (F1)) In this specification, the term "conjugated diene polymer" refers to a polymer of a conjugated diene compound. The resin composition of this embodiment tends to have better dielectric properties by containing the conjugated diene polymer (F1). The conjugated diene polymer (F1) may be used alone or in combination of two or more.

[0122] Examples of conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. The conjugated diene polymer (F1) may be a polymer of one type of conjugated diene compound, or a copolymer of two or more types of conjugated diene compounds. The conjugated diene polymer (F1) may also be a copolymer of one or more types of conjugated diene compounds and one or more types of monomers other than conjugated diene compounds. When the conjugated diene polymer (F1) is a copolymer, the polymerization mode is not particularly limited, and may be any of random polymerization, block polymerization, and graft polymerization.

[0123] From the viewpoints of compatibility with other resins and dielectric properties, the conjugated diene polymer (F1) is preferably a conjugated diene polymer having multiple vinyl groups in its side chains. The number of vinyl groups in one molecule of the conjugated diene polymer (F1) is not particularly limited, but from the viewpoints of compatibility with other resins and dielectric properties, it is preferably 3 or more, more preferably 5 or more, and even more preferably 10 or more. The upper limit of the number of vinyl groups in one molecule of the conjugated diene polymer (F1) is not particularly limited, but may be 100 or less, 80 or less, or 60 or less.

[0124] Examples of the conjugated diene polymer (F1) include polybutadiene having a 1,2-vinyl group, butadiene-styrene copolymer having a 1,2-vinyl group, and polyisoprene having a 1,2-vinyl group. Among these, from the viewpoints of dielectric properties and heat resistance, polybutadiene having a 1,2-vinyl group and butadiene-styrene copolymer having a 1,2-vinyl group are preferred, and polybutadiene having a 1,2-vinyl group is more preferred. Furthermore, as the polybutadiene having a 1,2-vinyl group, a polybutadiene homopolymer having a 1,2-vinyl group is preferred. The butadiene-derived 1,2-vinyl group contained in the conjugated diene polymer (F1) is a vinyl group contained in a butadiene-derived structural unit represented by the following formula (F1-1):

[0125]

[0126] When the conjugated diene polymer (F1) is a polybutadiene having a 1,2-vinyl group, the content of structural units having a 1,2-vinyl group relative to all structural units derived from butadiene constituting the polybutadiene (hereinafter, sometimes referred to as the "vinyl group content") is not particularly limited, but from the viewpoints of compatibility with other resins, dielectric properties, and heat resistance, it is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 85 mol% or more. Furthermore, the upper limit of the vinyl group content is not particularly limited, and may be 100 mol% or less, 95 mol% or less, or even 90 mol% or less. The structural unit having a 1,2-vinyl group is preferably a butadiene-derived structural unit represented by the above formula (F1-1). From the same viewpoint, the polybutadiene having a 1,2-vinyl group is preferably a 1,2-polybutadiene homopolymer.

[0127] The number average molecular weight of the conjugated diene polymer (F1) is not particularly limited, but from the viewpoints of compatibility with other resins, dielectric properties, and heat resistance, it is preferably 1,050 to 3,000, more preferably 1,100 to 2,000, and even more preferably 1,150 to 1,500.

[0128] (Modified Conjugated Diene Polymer (F2)) The modified conjugated diene polymer (F2) is a polymer obtained by modifying a conjugated diene polymer. By containing the modified conjugated diene polymer (F2), the resin composition of the present embodiment tends to have good heat resistance and low thermal expansion properties, while also being more likely to obtain excellent dielectric properties. The modified conjugated diene polymer (F2) may be used alone or in combination of two or more types.

[0129] For example, from the viewpoints of compatibility with other resins, dielectric properties, and conductor adhesion, the modified conjugated diene polymer (F2) is preferably a modified conjugated diene polymer obtained by modifying (f1) a conjugated diene polymer having a vinyl group in a side chain (hereinafter, sometimes abbreviated as "conjugated diene polymer (f1)") with (f2) a maleimide resin having two or more N-substituted maleimide groups (hereinafter, sometimes abbreviated as "maleimide resin (f2)").

[0130] As the conjugated diene polymer (f1), for example, the conjugated diene polymer having a vinyl group in a side chain described above as the conjugated diene polymer (F1) can be used, and preferred embodiments are also the same. The conjugated diene polymer (f1) may be used alone or in combination of two or more.

[0131] As the maleimide resin (f2), for example, a maleimide resin having two or more N-substituted maleimide groups as described above for the maleimide resin (AX) can be used, and preferred embodiments are also similar. One type of maleimide resin (f2) may be used alone, or two or more types may be used in combination.

[0132] The modified conjugated diene polymer (F2) preferably has, in its side chain, a substituent (hereinafter, sometimes referred to as "substituent (x)") formed by a reaction between a vinyl group in the conjugated diene polymer (f1) and an N-substituted maleimide group in the maleimide resin (f2). From the viewpoints of compatibility with other resins, dielectric properties, low thermal expansion, and heat resistance, the substituent (x) is preferably a group containing a structure represented by the following general formula (F2-1) or (F2-2) as a structure derived from the maleimide resin (f2).

[0133] (In the formula, X ｆ１ is a divalent group obtained by removing two N-substituted maleimide groups from the maleimide resin (f2), and * ｆ１ is the site of bonding to the carbon atom derived from the vinyl group that the conjugated diene polymer (f1) has in its side chain. ｆ２ is the site of attachment to another atom.)

[0134] The modified conjugated diene polymer (F2) preferably has a substituent (x) and a vinyl group (y) in its side chain. The extent to which the substituent (x) is present in the modified conjugated diene polymer (F2) can be determined by the extent to which the vinyl groups of the conjugated diene polymer (f1) have been modified by the maleimide resin (f2) (hereinafter, this may be referred to as the "vinyl group modification rate"). The vinyl group modification rate is not particularly limited, but from the viewpoints of compatibility with other resins, dielectric properties, low thermal expansion, and heat resistance, it is preferably 20 to 70%, more preferably 30 to 60%, and even more preferably 35 to 50%. Here, the vinyl group modification rate is a value determined by the method described in the Examples. The vinyl group (y) is preferably a 1,2-vinyl group possessed by a structural unit derived from butadiene.

[0135] The number average molecular weight of the modified conjugated diene polymer (F2) is not particularly limited, but from the viewpoints of compatibility with other resins, dielectric properties, low thermal expansion, and heat resistance, it is preferably 1,100 to 6,000, more preferably 1,300 to 4,000, and even more preferably 1,500 to 2,000.

[0136] The modified conjugated diene polymer (F2) can be produced by reacting a conjugated diene polymer (f1) with a maleimide resin (f2). The method for reacting the conjugated diene polymer (f1) with the maleimide resin (f2) is not particularly limited. For example, the modified conjugated diene polymer (F2) can be obtained by charging the conjugated diene polymer (f1), the maleimide resin (f2), a reaction catalyst, and an organic solvent into a reaction vessel and reacting them while heating, keeping the temperature, stirring, or the like, as necessary. The reaction temperature for the above reaction is preferably 70 to 120°C, more preferably 80 to 110°C, and even more preferably 85 to 105°C, from the viewpoints of workability and suppressing gelation of the product during the reaction. The reaction time for the above reaction is preferably 0.5 to 15 hours, more preferably 1 to 10 hours, and even more preferably 3 to 7 hours, from the viewpoints of productivity and allowing the reaction to proceed sufficiently. However, these reaction conditions can be adjusted appropriately depending on the types of raw materials used, and are not particularly limited.

[0137] Examples of organic solvents used in the reaction include alcohol-based solvents such as methanol, ethanol, butanol, butyl cellosolve, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbon-based solvents such as toluene, xylene, and mesitylene; ester-based solvents such as methoxyethyl acetate, ethoxyethyl acetate, butoxyethyl acetate, and ethyl acetate; and nitrogen-containing solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. These organic solvents may be used alone or in combination. Among these, toluene is preferred from the viewpoint of resin solubility.

[0138] When the reaction is carried out in an organic solvent, the total content of the conjugated diene polymer (f1) and the maleimide resin (f2) in the reaction solution is not particularly limited, but is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and even more preferably 20 to 50% by mass. When the total content of the conjugated diene polymer (f1) and the maleimide resin (f2) is equal to or greater than the above-mentioned lower limit, a good reaction rate is obtained and productivity tends to be improved. On the other hand, when the total content of the conjugated diene polymer (f1) and the maleimide resin (f2) is equal to or less than the above-mentioned upper limit, better solubility is obtained, stirring efficiency is improved, and gelation of the product during the reaction tends to be more effectively suppressed.

[0139] As the reaction catalyst, an organic peroxide is preferred from the viewpoint of obtaining sufficient reactivity while suppressing gelation of the product during the reaction. As the organic peroxide, those exemplified as the (G) curing accelerator described below can be used. One type of reaction catalyst may be used alone, or two or more types may be used in combination. The amount of the reaction catalyst used is not particularly limited, but from the viewpoint of reaction rate and reaction uniformity, it is preferably 0.001 to 1 part by mass, more preferably 0.003 to 0.1 part by mass, and even more preferably 0.005 to 0.02 part by mass per 100 parts by mass of the total amount of the conjugated diene polymer (f1) and the maleimide resin (f2).

[0140] When the above reaction is carried out, the number of moles of side chain vinyl groups in the conjugated diene polymer (f1) (M ｖ ) the number of moles of N-substituted maleimide groups in the maleimide resin (f2) relative to the number of moles (M ｍ ) ratio (M ｍ / M ｖ ) is not particularly limited, but is preferably 0.001 to 0.5, more preferably 0.005 to 0.1, and even more preferably 0.008 to 0.05, from the viewpoints of compatibility of the resulting modified conjugated diene polymer (F2) with other resins and suppression of gelation of the product during the reaction.

[0141] <Styrene-based elastomer (F3)> The styrene-based elastomer (F3) is not particularly limited as long as it is an elastomer having a structural unit derived from a styrene-based compound. The resin composition of this embodiment tends to easily obtain better dielectric properties by containing the styrene-based elastomer (F3). The styrene-based elastomer (F3) may be used alone or in combination of two or more.

[0142] The styrene-based elastomer (F3) is preferably one having a structural unit derived from a styrene-based compound represented by the following general formula (F3-1).

[0143] (In the formula, R ｆ１ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ｆ２ is an alkyl group having 1 to 5 carbon atoms. ｆ１ is an integer from 0 to 5.

[0144] R in the above general formula (F3-1) ｆ１ and R ｆ２ Examples of the alkyl group having 1 to 5 carbon atoms represented by include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, etc. The alkyl group having 1 to 5 carbon atoms may be either linear or branched. Among these, an alkyl group having 1 to 3 carbon atoms is preferred, an alkyl group having 1 or 2 carbon atoms is more preferred, and a methyl group is even more preferred. In the above general formula (F3-1), nｆ１ is an integer of 0 to 5, preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0145] The styrene-based elastomer (F3) may contain structural units other than those derived from styrene-based compounds. Examples of structural units other than those derived from styrene-based compounds that the styrene-based elastomer (F3) may contain include butadiene-derived structural units, isoprene-derived structural units, maleic acid-derived structural units, and maleic anhydride-derived structural units. The butadiene-derived structural units and isoprene-derived structural units may be hydrogenated. When hydrogenated, the butadiene-derived structural units become structural units composed of a mixture of ethylene units and butylene units, and the isoprene-derived structural units become structural units composed of a mixture of ethylene units and propylene units.

[0146] Examples of the styrene-based elastomer (F3) include hydrogenated products of styrene-butadiene-styrene block copolymers, hydrogenated products of styrene-isoprene-styrene block copolymers, and styrene-maleic anhydride copolymers. Examples of hydrogenated products of styrene-butadiene-styrene block copolymers include SEBS, which is obtained by completely hydrogenating the carbon-carbon double bonds in the butadiene block, and SBBS, which is obtained by partially hydrogenating the carbon-carbon double bonds at 1,2-bond sites in the butadiene block. In SEBS, completely hydrogenated usually means 90% or more, 95% or more, 99% or more, or even 100% of the total carbon-carbon double bonds. In SBBS, the partial hydrogenation rate is preferably 60 to 85% of the total carbon-carbon double bonds. In the hydrogenated products of styrene-isoprene-styrene block copolymers, the polyisoprene portion is hydrogenated, resulting in SEPS. Among these, SEBS and SEPS are preferred, and SEBS is more preferred, from the viewpoints of dielectric properties, peel strength of copper foil, heat resistance, glass transition temperature, and low thermal expansion.

[0147] In the SEBS, the content of structural units derived from styrene (hereinafter, sometimes abbreviated as "styrene content") is not particularly limited, but is preferably 5 to 60 mass%, more preferably 7 to 40 mass%, and even more preferably 10 to 35 mass%.

[0148] The melt flow rate (MFR) of the SEBS is not particularly limited, but is preferably 0.1 to 40 g / 10 min, more preferably 1 to 35 g / 10 min, and even more preferably 5 to 35 g / 10 min, and may be 10 to 35 g / 10 min, or may be 20 to 35 g / 10 min, measured under conditions of 230°C and a load of 2.16 kgf (21.2 N).

[0149] Commercially available SEBS products include the Tuftec H series and Tuftec M series manufactured by Asahi Kasei Corporation, the Septon series manufactured by Kuraray Co., Ltd., and the Kraton series manufactured by Kraton Polymer Japan Co., Ltd.

[0150] The number average molecular weight of the styrene elastomer (F3) is not particularly limited, but is preferably 10,000 to 500,000, more preferably 50,000 to 350,000, and even more preferably 100,000 to 200,000.

[0151] Examples of the elastomer (F) other than the conjugated diene polymer (F1), the modified conjugated diene polymer (F2), and the styrene-based elastomer (F3) include polyolefin-based resins, polyphenylene ether-based resins, polyester-based resins, polyamide-based resins, and polyacrylic-based resins.

[0152] (Content of (F) Elastomer) When the resin composition of this embodiment contains the (F) elastomer, the content of the (F) elastomer is not particularly limited, but is preferably 1 to 40 mass %, more preferably 3 to 30 mass %, even more preferably 5 to 25 mass %, and particularly preferably 5 to 20 mass parts, relative to the total solid content (100 mass %) in the resin composition of this embodiment. When the content of the (F) elastomer is at least the above lower limit, better dielectric properties tend to be easily obtained. On the other hand, when the content of the (F) elastomer is at most the above upper limit, better heat resistance tends to be easily obtained.

[0153] The total content of one or more selected from the group consisting of the conjugated diene polymer (F1), the modified conjugated diene polymer (F2), and the styrene-based elastomer (F3) is not particularly limited, but from the viewpoint of the dielectric properties and the peel strength of the copper foil, it is preferably 60 to 100 mass%, more preferably 80 to 100 mass%, and even more preferably 90 to 100 mass%, based on the total amount (100 mass%) of the elastomer (F).

[0154] From the viewpoints of dielectric properties and compatibility, the (F) elastomer preferably contains one or more selected from the group consisting of conjugated diene polymers (F1) and modified conjugated diene polymers (F2), and a styrene-based elastomer (F3). When the (F) elastomer contains one or more selected from the group consisting of conjugated diene polymers (F1) and modified conjugated diene polymers (F2), and a styrene-based elastomer (F3), the ratio of the total content of the conjugated diene polymer (F1) and the modified conjugated diene polymer (F2) to the content of the styrene-based elastomer (F3), [[(F1)+(F2)] / (F3)], is not particularly limited, but from the viewpoints of dielectric properties and compatibility, it is preferably 0.1 to 5, more preferably 0.2 to 1, and even more preferably 0.3 to 0.7.

[0155] (G) Curing Accelerator The resin composition of this embodiment may further contain a (G) curing accelerator. The (G) curing accelerator does not contain the (C) radical polymerization initiator. By containing the (G) curing accelerator, the resin composition of this embodiment tends to have improved curability and to easily obtain better dielectric properties, heat resistance, and copper foil peel strength. One type of (G) curing accelerator may be used alone, or two or more types may be used in combination.

[0156] Examples of the (G) curing accelerator include acidic catalysts such as p-toluenesulfonic acid; amine compounds such as triethylamine, pyridine, tributylamine, and dicyandiamide; imidazole compounds such as methylimidazole, phenylimidazole, and 1-cyanoethyl-2-phenylimidazole; isocyanate-masked imidazole compounds such as the addition reaction product of hexamethylene diisocyanate resin and 2-ethyl-4-methylimidazole; tertiary amine compounds; quaternary ammonium compounds; phosphorus compounds such as triphenylphosphine; and carboxylates of manganese, cobalt, zinc, etc. Among these, from the viewpoints of curing acceleration effect and storage stability, imidazole compounds, isocyanate-masked imidazole compounds, and carboxylates are preferred, and isocyanate-masked imidazole compounds are more preferred.

[0157] (Content of (G) Curing Accelerator) When the resin composition of the present embodiment contains a (G) curing accelerator, the content of the (G) curing accelerator is not particularly limited, but is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, even more preferably 0.03 to 2 parts by mass, and particularly preferably 0.03 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of the resin components. When the content of the (G) curing accelerator is equal to or greater than the above lower limit, a sufficient curing acceleration effect tends to be easily obtained. Furthermore, when the content of the (G) curing accelerator is equal to or less than the above upper limit, storage stability tends to be better.

[0158] <Other Components> The resin composition of this embodiment may further contain, as necessary, one or more optional components selected from the group consisting of resin materials other than the above components, flame retardants, antioxidants, heat stabilizers, antistatic agents, UV absorbers, pigments, colorants, lubricants, organic solvents, and other additives. Examples of resin materials other than the above components include one or more thermosetting resins selected from the group consisting of epoxy resins, phenolic resins, cyanate resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins. The thermosetting resin is preferably one or more selected from the group consisting of epoxy resins, phenolic resins, cyanate resins, isocyanate resins, amino resins, unsaturated polyester resins, and silicone resins, more preferably one or more selected from the group consisting of epoxy resins, phenolic resins, cyanate resins, and isocyanate resins, and even more preferably one or more selected from the group consisting of epoxy resins, phenolic resins, and cyanate resins. The above-mentioned optional components may be used alone or in combination of two or more. The content of the above-mentioned optional components in the resin composition of this embodiment is not particularly limited, and they may be used as needed within a range that does not impair the effects of this embodiment. Furthermore, the resin composition of this embodiment may not contain the above-mentioned optional components depending on the desired performance.

[0159] (Resin Component Content) The resin component content in the resin composition of the present embodiment is not particularly limited, but from the viewpoints of low thermal expansion, heat resistance, flame retardancy, and copper foil peel strength, it is preferably 5 to 80 mass %, more preferably 10 to 60 mass %, and even more preferably 20 to 40 mass % relative to the total solid content (100 mass %) of the resin composition of the present embodiment.

[0160] The resin composition of this embodiment is suitable as a resin composition for forming a resin film. The resin composition of this embodiment is preferably used to form a resin film having a thickness of 10 μm or more, more preferably used to form a resin film having a thickness of 25 μm or more, more preferably used to form a resin film having a thickness of 50 μm or more, even more preferably used to form a resin film having a thickness of 80 μm or more, even more preferably used to form a resin film having a thickness of 100 μm or more, even more preferably used to form a resin film having a thickness of 130 μm or more, and particularly preferably used to form a resin film having a thickness of 150 μm or more. Note that when the resin composition of this embodiment contains the reactive liquid compound (E), the flexibility of the resin film is significantly improved, making it easy to form a resin film having the above thickness, particularly a resin film having a thickness of 50 μm or more, a resin film having a thickness of 80 μm or more, a resin film having a thickness of 100 μm or more, a resin film having a thickness of 130 μm or more, or a resin film having a thickness of 150 μm or more. Furthermore, from the viewpoint of ease of handling, the resin composition of this embodiment is preferably used to form a resin film having a thickness of 1,000 μm or less, more preferably used to form a resin film having a thickness of 700 μm or less, and even more preferably used to form a resin film having a thickness of 500 μm or less. In other words, it can be said that the resin composition of this embodiment is preferably used to form a resin film having a thickness of 10 to 1,000 μm. The lower and upper limits of the numerical range "10 to 1,000 μm" can be replaced with the preferred numerical values.

[0161] [Resin Film and Supported Resin Film] The resin film of this embodiment is a resin film containing the resin composition of this embodiment. In this specification, "containing" means that the contained substances may be contained as they are, the contained substances may have reacted with each other, or both of these aspects may be included. The resin film of this embodiment can be produced, for example, by applying the resin composition of this embodiment containing an organic solvent, i.e., a resin varnish, to a support and then heating and drying. In this way, a supported resin film having a support and the resin film of this embodiment is obtained.

[0162] Examples of the support include plastic films, metal foils, and release papers. Examples of plastic films include polyolefin films such as polyethylene, polypropylene, and polyvinyl chloride; polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate; polycarbonate films, and polyimide films. Among these, polyethylene terephthalate films are preferred from the viewpoints of economy and ease of handling. Examples of metal foils include copper foil and aluminum foil. When copper foil is used as the support, the copper foil itself can be used as the conductor layer to form a circuit. In this case, rolled copper foil, electrolytic copper foil, and the like can be used as the copper foil. When a thin copper foil is used, a copper foil with a carrier may be used to improve workability. The support may be surface-treated, such as matte-treated or corona-treated. The support may also be release-treated with a silicone resin-based release agent, an alkyd resin-based release agent, a fluororesin-based release agent, or the like. The thickness of the support is not particularly limited, but from the viewpoints of ease of handling and economy, it is preferably 10 to 150 μm, more preferably 20 to 100 μm, and even more preferably 25 to 50 μm.

[0163] Coating devices known to those skilled in the art, such as comma coaters, bar coaters, kiss coaters, roll coaters, gravure coaters, and die coaters, can be used to apply the resin varnish. These coating devices can be selected appropriately depending on the film thickness to be formed. Drying conditions after application of the resin varnish are not particularly limited and can be determined appropriately depending on the content and boiling point of the organic solvent. For example, in the case of a resin varnish containing 40 to 60 mass% of an aromatic hydrocarbon solvent, the drying temperature is not particularly limited, but is preferably 50 to 200°C, more preferably 80 to 150°C, and even more preferably 95 to 130°C, from the viewpoints of productivity and adequately B-staging the resin composition of this embodiment. Furthermore, in the case of the resin varnish, the drying time is not particularly limited, but is preferably 1 to 30 minutes, more preferably 2 to 15 minutes, and even more preferably 3 to 10 minutes, from the viewpoints of productivity and adequately B-staging the resin composition of this embodiment.

[0164] The thickness of the resin film of this embodiment can be determined appropriately depending on the application of the resin film, but from the viewpoint of obtaining sufficient insulation reliability and enabling the embedding of semiconductor chips, etc., it is preferably 10 μm or more, more preferably 50 μm or more, even more preferably 80 μm or more, even more preferably 100 μm or more, even more preferably 130 μm or more, and particularly preferably 150 μm or more. Furthermore, from the viewpoint of handleability, the thickness of the resin film of this embodiment is preferably 1,000 μm or less, more preferably 700 μm or less, and even more preferably 500 μm or less. In other words, the thickness of the resin film of this embodiment is preferably 10 to 1,000 μm, and the lower and upper limits of this numerical range can be replaced with the preferred numerical values ​​described above.

[0165] The resin film of the present embodiment may have a protective film. The protective film is provided on the surface of the resin film of the present embodiment opposite to the surface on which the support is provided, and is used for the purpose of preventing adhesion of foreign matter and the like to the resin film and preventing scratches on the resin film.

[0166] (Tensile Modulus) The tensile modulus at 25°C of the cured product of the resin composition and the cured product of the resin film of this embodiment may be 0.5 to 2.5 GPa, 1.0 to 2.5 GPa, 1.4 to 2.5 GPa, 1.5 to 2.3 GPa, or 1.7 to 2.1 GPa. When the tensile modulus is equal to or greater than the lower limit, cracks tend to be less likely to occur during deformation due to heat or external impact. Furthermore, when the tensile modulus is equal to or less than the upper limit, warpage tends to be reduced when heat is applied to a printed wiring board or semiconductor package. Since a polymerization inhibitor is used in this embodiment, it is important to achieve high curing levels after the polymerization inhibitor disappears. The tensile modulus is a value measured at 25°C, with an initial length L0 of 20 mm and a pulling speed of 2 mm / min. More specifically, it is a value measured according to the method described in the Examples.

[0167] (Fracture strain) The higher the fracture strain of the cured product of the resin composition and the cured product of the resin film of this embodiment, the better. It is preferably 5% or more, and may be 5 to 50%, 5 to 35%, 5 to 20%, 6.0 to 10.0%, 6.5 to 9.5%, 6.8 to 9.0%, or 7.5 to 9.0%. The larger the fracture strain, the less likely cracks tend to occur during deformation due to heat or external impact. The fracture strain is measured under conditions of an environment of 25°C, an initial length L0 of 20 mm, and elongation at a tensile speed of 2 mm / min. More specifically, it is measured according to the method described in the examples.

[0168] (Minimum Melt Viscosity, Temperature Showing Minimum Melt Viscosity) The minimum melt viscosity of the resin film of this embodiment may be 500 to 1,550 Pa·s, 700 to 1,500 Pa·s, 800 to 1,400 Pa·s, 800 to 1,300 Pa·s, 800 to 1,200 Pa·s, or 800 to 1,150 Pa·s. The temperature at which the resin film of this embodiment shows its minimum melt viscosity may be 120 to 180°C, 120 to 170°C, 120 to 160°C, 130 to 180°C, 140 to 180°C, or 150 to 180°C. A small minimum melt viscosity and a high temperature at which the minimum melt viscosity is shown can be said to have excellent embeddability in circuit boards. The minimum melt viscosity and the temperature at which the minimum melt viscosity is exhibited are values ​​measured under the conditions of a temperature rise rate of 5°C / min, a jig with a diameter of 8 mm, a frequency of 1.0 Hz, and a strain of 1%, and more specifically, values ​​measured according to the method described in the examples.

[0169] (Linear expansion coefficient) The linear expansion coefficient of the cured product of the resin composition and the cured product of the resin film of this embodiment may be 10 to 27, 12 to 25, 15 to 24, 17 to 23, 17 to 22, or 17 to 20. When the linear expansion coefficient is within the above range, it can be said that the product has excellent low thermal expansion properties. This value is obtained by measuring the dimensional change in a tensile mode, at a temperature range of 30 to 300°C, at a heating rate of 5°C / min, and with a load of 4 g, and more specifically, this value is measured according to the method described in the examples.

[0170] (Peel strength of copper foil) The peel strength of the copper foil in the metal-clad laminate of this embodiment may be 0.30 to 0.70, 0.35 to 0.60, or 0.40 to 0.55. When the peel strength of the copper foil is in the above range, it can be said that the adhesion to the copper foil is excellent. The peel strength of the copper foil is a value measured in accordance with JIS C6481:1996 by peeling in a 90° direction at a pulling rate of 50 mm / min, and more specifically, a value measured according to the method described in the examples.

[0171] (Relative dielectric constant (Dk) and dielectric loss tangent (Df)) The relative dielectric constant (Dk) at 10 GHz of the cured product of the resin composition and the cured product of the resin film of this embodiment may be 3.3 or less, 3.2 or less, 3.1 or less, or 3.0 or less. The smaller the relative dielectric constant (Dk), the more preferable. The lower limit is not particularly limited, but in consideration of the balance with other physical properties, it may be 2.6 or more, or 2.8 or more. The dielectric loss tangent (Df) at 10 GHz of the cured product of the resin composition and the cured product of the resin film of this embodiment may be 0.0022 or less, 0.0020 or less, 0.0018 or less, 0.0017 or less, or 0.0016 or less. The smaller the dielectric loss tangent (Df), the more preferable. The lower limit is not particularly limited, but in consideration of the balance with other physical properties, it may be 0.0012 or more, or 0.0014 or more. Furthermore, from the viewpoint of obtaining sufficient insulation reliability and enabling embedding of semiconductor chips, etc., the resin film of this embodiment is preferably a resin film having a thickness of 150 μm or more, and a cured product of the resin film having a relative dielectric constant (Dk) of 3.3 or less and a dielectric loss tangent (Df) of 0.0022 or less at 10 GHz, and more preferred values ​​of the relative dielectric constant (Dk) and dielectric loss tangent (Df) are as described above. Note that the relative dielectric constant (Dk) and dielectric loss tangent (Df) are values ​​measured in accordance with the cavity resonator perturbation method, and more specifically, are values ​​measured by the method described in the Examples.

[0172] The resin film of this embodiment is suitable as, for example, a resin film for forming an insulating layer in a printed wiring board such as a multilayer printed wiring board, and a resin film for sealing a semiconductor in a semiconductor package.

[0173] [Printed Wiring Board] The printed wiring board of the present embodiment is a printed wiring board having a cured product of the resin composition of the present embodiment or a cured product of the resin film of the present embodiment. In other words, it can be said that the printed wiring board of the present embodiment contains the resin composition of the present embodiment or the resin film of the present embodiment.

[0174] The printed wiring board of this embodiment is preferably a multilayer printed wiring board having a cured product of the resin composition of this embodiment or a cured product of the resin film of this embodiment. That is, the multilayer printed wiring board of this embodiment includes at least a multilayer structure containing a cured product of the resin composition of this embodiment or a cured product of the resin film of this embodiment and a conductor circuit layer. Hereinafter, a method for producing the multilayer printed wiring board of this embodiment using the resin film of this embodiment will be described.

[0175] When manufacturing a multilayer printed wiring board using the resin film of this embodiment, the resin film of this embodiment is first laminated on one or both sides of a circuit board. Specifically, the resin film of this embodiment is placed on the circuit board, and then laminated onto the circuit board while applying pressure and heat using a vacuum laminator, thereby laminating the resin film of this embodiment on the circuit board. Examples of circuit boards used in multilayer printed wiring boards include glass epoxy, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates, each of which has a patterned conductor layer (circuit) formed on one or both sides. The surface of the conductor layer of the circuit board may be previously roughened by blackening or the like from the viewpoint of adhesion.

[0176] Next, if necessary, the support of the resin film is peeled off, and the resin film is then heat-cured to form an insulating layer. The heating temperature during heat-curing is not particularly limited, but is preferably 100 to 300° C., more preferably 120 to 280° C., and even more preferably 150 to 250° C. The heating time during heat-curing is not particularly limited, but is preferably 2 to 300 minutes, more preferably 5 to 200 minutes, and even more preferably 10 to 150 minutes.

[0177] After the insulating layer is formed by the above method, it may be drilled as needed. Drilling is a process in which holes are drilled in the circuit board and the formed insulating layer by a drill, laser, plasma, a combination of these, or the like to form via holes, through holes, etc. Examples of lasers used for drilling include carbon dioxide lasers, YAG lasers, UV lasers, and excimer lasers.

[0178] Next, the surface of the insulating layer may be roughened with an oxidizing agent. Furthermore, if via holes, through holes, etc. are formed in the insulating layer and the circuit board, the so-called "smear" that occurs when these holes are formed may be removed with an oxidizing agent. The roughening treatment and smear removal can be performed simultaneously. The roughening treatment can form uneven anchors on the surface of the insulating layer.

[0179] Next, a conductor layer is formed on the roughened surface of the insulating layer. The conductor layer can be formed, for example, by plating. Examples of plating methods include electroless plating and electrolytic plating. Examples of metals for plating include copper, gold, silver, nickel, platinum, molybdenum, ruthenium, aluminum, tungsten, iron, titanium, chromium, and alloys containing at least one of these metal elements. Among these, copper and nickel are preferred, and copper is more preferred. Alternatively, a method can be employed in which a plating resist having a reverse pattern to the wiring pattern is first formed, and then the wiring pattern is formed solely by electroless plating. Furthermore, an annealing treatment may be performed after the formation of the conductor layer. Annealing treatment tends to further improve and stabilize the adhesive strength between the interlayer insulating layer and the conductor layer.

[0180] As a method for patterning the conductor layer and forming a circuit, known methods such as a subtractive method, a full-additive method, a semi-additive method (SAP: Semi-Additive Process), a modified semi-additive method (m-SAP: Modified Semi-Additive Process) and the like can be used.

[0181] [Semiconductor Package] The semiconductor package of this embodiment is a semiconductor package having a cured product of the resin composition of this embodiment or a cured product of the resin film of this embodiment. That is, the semiconductor package of this embodiment can also be said to be a semiconductor package containing the resin composition of this embodiment or the resin film of this embodiment. The semiconductor package of this embodiment may be, for example, a semiconductor package having a semiconductor chip mounted on the printed wiring board of this embodiment, or may be a semiconductor package having a semiconductor chip encapsulated in a cured product of the resin film of this embodiment.

[0182] A semiconductor package having a semiconductor chip mounted on the printed wiring board of this embodiment can be manufactured, for example, by mounting a semiconductor chip, a memory, etc. on the printed wiring board of this embodiment by a known method. The printed wiring board of this embodiment used for manufacturing a semiconductor package is preferably a multilayer printed wiring board.

[0183] A semiconductor package including a semiconductor chip encapsulated in a cured resin film of this embodiment can be manufactured, for example, by the following method. First, the resin film of this embodiment is placed on the semiconductor chip. Next, the resin film is heated and melted, and the semiconductor chip is embedded in the resin composition that constitutes the resin film. Thereafter, the resin composition in which the semiconductor chip is embedded is cured by heating, thereby manufacturing a semiconductor package in which the semiconductor chip is encapsulated in a cured resin composition.

[0184] The present embodiment will be specifically described below with reference to examples, although the present embodiment is not limited to the following examples.

[0185] The number average molecular weight was measured by the following procedure. (Method for measuring number average molecular weight) The number average molecular weight was calculated by gel permeation chromatography (GPC) from a calibration curve using standard polystyrene. The calibration curve was approximated by a cubic equation using standard polystyrene: TSKstandard POLYSTYRENE (Types: A-2500, A-5000, F-1, F-2, F-4, F-10, F-20, F-40) (manufactured by Tosoh Corporation, trade name). The GPC measurement conditions are shown below. [GPC measurement conditions] Apparatus: High-speed GPC apparatus HLC-8320GPC Detector: Ultraviolet absorption detector UV-8320 [manufactured by Tosoh Corporation] Column: Guard column; TSK Guard column SuperHZ-L + column; TSKgel SuperHZM-N + TSKgel SuperHZM-M + TSKgel SuperH-RC (all manufactured by Tosoh Corporation, trade names) Column size: 4.6 x 20 mm (guard column), 4.6 x 150 mm (column), 6.0 x 150 mm (reference column) Eluent: tetrahydrofuran Sample concentration: 10 mg / 5 mL Injection amount: 25 μL Flow rate: 1.00 mL / min Measurement temperature: 40°C

[0186] [Production of Resin Compositions] Examples 1 to 5, Comparative Examples 1 and 2 Resin compositions with a solid content concentration of approximately 50% by mass were prepared by blending each of the components shown in Table 1 with toluene in the amounts shown in Table 1, and then stirring and mixing the mixture at 25° C. or while heating to 50 to 80° C. In Table 1, the unit of the blending amount of each component is parts by mass, and in the case of a solution or dispersion, this means parts by mass converted into solid content.

[0187] [Production of Resin Film] The resin composition obtained in each example was applied to one side of a 50 μm thick PET film (manufactured by Toyobo Co., Ltd., trade name "Purex A53") in a thickness such that the thickness of the resin layer after drying would be 150 μm. The resin composition was then heated and dried at 105°C for 5 minutes to bring it to a B-stage state, producing a resin film (1) with a single PET film (resin film thickness: 150 μm). The resulting resin film (1) with a single PET film was then cut into a 200 mm x 200 mm piece and stacked so that the resin films faced each other. Subsequently, a vacuum laminator was used to bond the two films together at 100°C for 5 seconds under pressure, yielding a resin film (2) with a double PET film (resin film thickness: 300 μm).

[0188] [Production of Double-Sided Copper Foil-Mounted Resin Plate] The resin film (2) with double-sided PET film obtained above was cut into a size of 90 mm long x 50 mm wide. After peeling and removing the PET films on both sides, the film was placed in a die-cut Teflon sheet with a size of 0.3 mm thick x 90 mm long x 50 mm wide. Low-profile copper foil (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "3EC-VLP-18") with a thickness of 18 μm was placed on the top and bottom of the resin film contained in the die-cut Teflon sheet. The low-profile copper foil was placed with its M side facing the resin film. Next, this pre-heat-pressure-molded laminate was subjected to heat-pressure molding at a temperature of 180°C, a pressure of 2.0 MPa, and a time of 60 minutes to mold and harden the resin film into a resin plate, thereby producing a double-sided copper foil-mounted resin plate. The thickness of the resin plate portion of the obtained double-sided copper foil-mounted resin plate was 0.3 mm.

[0189] [Measurement and Evaluation Methods] Using the resin films or double-sided copper foil-coated resin plates obtained in the above Examples and Comparative Examples, measurements and evaluations were carried out according to the following methods. The results are shown in Table 1.

[0190] (1. Method for Measuring Tensile Modulus) The copper foil was removed from the resin plate with copper foil on both sides obtained in each example by immersing it in a 10% by mass solution of ammonium persulfate (manufactured by Mitsubishi Gas Chemical Company, Inc.), a copper etching solution. The resulting resin plate was cut into a width of 10 mm, a length of 40 mm, and a thickness of 0.2 mm, and then dried at 105°C for 1 hour to prepare a test specimen. The test specimen was clamped at both ends of the long side direction between upper and lower grippers with a 20 mm gap between the grippers. Next, the tensile modulus of the test specimen was measured using a small benchtop testing machine (manufactured by Shimadzu Corporation, product name "EZ-TEST") at 25°C under the conditions of an initial length L0 of 20 mm and a tensile speed of 2 mm / min. Five similar samples were prepared, and the tensile modulus was measured under the same conditions as above. The average value was taken as the 25°C tensile modulus. Other detailed conditions and the method for calculating the tensile modulus were in accordance with the international standard ISO 5271 (1993). The larger the value, the less likely cracks will occur when the printed wiring board or semiconductor package is deformed by heat or external impact. Also, if the value is not too large, warping when heat is applied to the printed wiring board or semiconductor package tends to be small.

[0191] (2. Method for measuring breaking strain) Measurement was performed using the same method as in "1. Method for measuring tensile modulus," and the strain value at which the test piece broke was taken as the breaking strain. The larger the value, the less likely cracks will occur during deformation due to heat or external impact.

[0192] (3. Evaluation method for embeddability in circuit boards) The PET film of the resin film obtained in each example was peeled off, and the resulting overlap was 1 mm thick. The resulting sample was punched out to a diameter of 20 mm, and the melt viscosity was measured. The viscosity was measured using a rheometer (trade name: Discovery HR20, manufactured by TA Instruments Japan Co., Ltd.) under the conditions of a temperature rise rate of 3°C / min, a 20 mm diameter jig, a frequency of 1.0 Hz, and a strain of 1%. A small minimum melt viscosity and a high temperature at which the minimum melt viscosity is exhibited indicate excellent embeddability in circuit boards.

[0193] (4. Method for Measuring Linear Expansion Coefficient) The resin plate with copper foil on both sides obtained in each example was immersed in a 10% by mass solution of ammonium persulfate (manufactured by Mitsubishi Gas Chemical Company, Inc.), a copper etching solution, to remove the copper foil. The resulting resin plate was cut into a width of 0.4 mm, a length of 20 mm, and a thickness of 0.2 mm, and then dried at 105°C for 1 hour to prepare a test specimen. The test specimen was clamped at both ends of the long side direction between upper and lower grippers with a 10 mm gap between the grippers. Next, dimensional change was measured in tension mode using a thermomechanical analyzer (TMA) (manufactured by Seiko Instruments Inc., product name "SS6100") at a temperature range of 30 to 300°C, a heating rate of 5°C / min, and a load of 4 g. The average dimensional change per unit temperature from 30 to 150°C was taken as the linear expansion coefficient and evaluated according to the following evaluation criteria. A: Less than 30 ppm / °C B: 30 ppm / °C or more and less than 40 ppm / °C C: 40 ppm / °C or more

[0194] (5. Method for Measuring Copper Foil Peel Strength) The copper foil of the double-sided copper foil-covered resin sheet obtained in each example was etched into a 5 mm wide straight line, which was then dried at 105°C for 1 hour to prepare a test piece. The resulting straight line-shaped copper foil was attached to a small tabletop testing machine (manufactured by Shimadzu Corporation, product name "EZ-TEST"), and the peel strength of the copper foil was measured by peeling it off in a 90° direction in accordance with JIS C6481:1996. The pulling speed when peeling the copper foil was 50 mm / min.

[0195] (6. Method for measuring relative permittivity (Dk) and dielectric loss tangent (Df)) The resin plate with copper foil on both sides obtained in each example was immersed in a 10 mass % solution of ammonium persulfate (manufactured by Mitsubishi Gas Chemical Company, Inc.), which is a copper etching solution, to remove the copper foil. The obtained resin plate was cut into a size of 2 mm x 50 mm and dried at 105°C for 1 hour to prepare a test piece. Next, the relative permittivity (Dk) and dielectric loss tangent (Df) of the test piece were measured at an ambient temperature of 25°C and in the 10 GHz band in accordance with the cavity resonator perturbation method.

[0196] (7. Evaluation method for solder heat resistance) The resin board with copper foil on both sides obtained in each example was immersed in molten solder at 288°C for 30 seconds. Thereafter, the heat resistance of the four-layer copper-clad laminate was evaluated according to the following evaluation criteria. Good solder heat resistance can also be said to mean that the resin composition or resin film has been cured to a high level. (Evaluation criteria for heat resistance) A: No blisters were observed when visually inspected. C: Blisters were observed when visually inspected.

[0197]

[0198] The details of each component shown in Table 1 are as follows: [Component (A)] Maleimide resin 1: Aromatic bismaleimide resin containing an indane ring represented by the general formula (A1-4-1): Number average molecular weight = 1,600, solid at 25°C

[0199] [Component (B)] Silica 1: spherical silica treated with a methacrylsilane coupling agent, average particle size 2.4 μm Silica 2: spherical silica treated with a methacrylsilane coupling agent, average particle size 1.0 μm

[0200] Coupling agent: 3-methacryloxypropyltrimethoxysilane (methacrylsilane coupling agent)

[0201] [Component (C)] Organic peroxide: α,α-bis(t-butylperoxy-m-isopropyl)benzene

[0202] [Component (D)] A hindered amine compound having the following structure (a compound having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton):

[0203] [Component (E)] 1,9-nonanediol dimethacrylate: liquid at 25°C (viscosity at 25°C = 8 mPa·s), molecular weight: 296.4

[0204] [Component (F)] Conjugated diene polymer (F1): 1,2-polybutadiene homopolymer (number average molecular weight = 1,200, vinyl group content = 85% or more) Styrene-based elastomer (F3): hydrogenated styrene-based thermoplastic elastomer (styrene-ethylene-butylene-styrene copolymer), trade name "Kraton MD1653" (manufactured by Kraton Polymer Japan Co., Ltd.), styrene unit content = 31 mass%, MFR = 28 g / 10 min measured under conditions of 230°C and a load of 2.16 kgf, number average molecular weight = more than 1,000

[0205] [Component (G)] Imidazole-based curing accelerator: isocyanate-masked imidazole, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "G-8009L"

[0206] The above results demonstrate that the cured resin compositions or resin films obtained in Examples 1 to 5 exhibited favorable low thermal expansion properties, and the resin films exhibited excellent embeddability in circuit boards. Furthermore, peel strength, dielectric properties, and solder heat resistance were also favorable. While exhibiting excellent embeddability in circuit boards, the resin films were cured to a high level over time, which is thought to be why the solder heat resistance improved and high curability was achieved. On the other hand, Comparative Example 1, which used a resin composition that did not contain the hindered amine compound (D) as a polymerization inhibitor, resulted in poor embeddability in circuit boards. Furthermore, Comparative Example 2, which did not contain the hindered amine compound (D) as a polymerization inhibitor and did not contain the radical polymerization initiator (C), exhibited reduced fracture strain and peel strength, as well as reduced solder heat resistance.

Claims

1. A resin composition comprising: (A) a maleimide resin; (B) an inorganic filler; (C) a radical polymerization initiator; and (D) a polymerization inhibitor.

2. The resin composition according to claim 1, wherein component (A) is at least one selected from the group consisting of maleimide resins having one or more N-substituted maleimide groups and derivatives of said maleimide resins.

3. The resin composition according to claim 2, wherein the maleimide resin having one or more N-substituted maleimide groups is a maleimide resin containing a condensed ring of an aromatic ring and an aliphatic ring in its molecular structure and having two or more N-substituted maleimide groups.

4. A resin composition according to any one of claims 1 to 3, wherein the content of the component (D) is 1 to 90 parts by mass per 100 parts by mass of the component (C).

5. The resin composition according to any one of claims 1 to 4, further comprising (E) a compound that is liquid at 25°C, has a reactive group, and has a molecular weight of 1,000 or less.

6. The resin composition according to claim 5, wherein the reactive group possessed by component (E) is one or more reactive groups selected from the group consisting of a vinyl group, an allyl group, a maleimide group, a (meth)acryloyl group, an epoxy group, a hydroxyl group, a carboxyl group, and an amino group.

7. The resin composition according to claim 5 or 6, wherein the component (E) has two or more reactive groups in one molecule.

8. The resin composition according to any one of claims 5 to 7, wherein the component (E) is a di(meth)acrylic acid ester.

9. A resin composition according to any one of claims 5 to 8, wherein the content of the (E) component relative to the total amount (100% by mass) of the (A), (B), and (E) components is 1 to 20% by mass.

10. The resin composition according to any one of claims 1 to 9, further comprising (F) an elastomer having a molecular weight of more than 1,000.

11. A resin film comprising the resin composition according to any one of claims 1 to 10.

12. A resin film with a support, comprising a support and the resin film according to claim 11.

13. A printed wiring board having a cured product of the resin composition according to any one of claims 1 to 10 or a cured product of the resin film according to claim 11.

14. A semiconductor package comprising a cured product of the resin composition according to any one of claims 1 to 10 or a cured product of the resin film according to claim 11.

15. The semiconductor package according to claim 14, comprising a semiconductor chip encapsulated in a cured product of the resin composition.

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