JP7735666B2 - Resin composition, prepreg, resin-coated metal foil, laminate, printed wiring board, and semiconductor package - Google Patents

Description

This disclosure relates to resin compositions, prepregs, resin-coated metal foils, laminates, printed wiring boards, and semiconductor packages.

2. Description of the Related Art With the rapid spread of electronic information devices, electronic devices are becoming smaller and thinner, and there is an increasing demand for higher density and higher functionality in the printed wiring boards mounted thereon.
High density printed wiring boards can be suitably achieved by reducing the thickness of the glass cloth serving as the substrate, for example, to a thickness of 30 μm or less, and so prepregs equipped with such glass cloth have recently been developed and marketed.

On the other hand, with the progress of increasing density of printed wiring boards, it is becoming increasingly difficult to ensure the heat resistance, insulating reliability, and adhesion between the wiring and the substrate of printed wiring boards. Therefore, wiring board materials used in high-density and high-performance printed wiring boards tend to be required to have properties such as heat resistance, electrical insulating properties, long-term reliability, and adhesiveness. Furthermore, flexible printed wiring boards, which are one type of high-density and high-performance printed wiring boards, are required to have properties such as flexibility and low elasticity in addition to the above properties.
Furthermore, because printed wiring boards for automotive use are exposed to harsh temperature environments, preventing solder cracks at the connection points between ceramic components and the board is a major challenge, requiring even higher heat resistance.

Under these circumstances, a resin composition containing (A) an acrylic polymer, (B) a thermosetting resin, and (C) an active ester curing agent has been proposed with the aim of providing a resin composition that has a sufficiently low modulus of elasticity, high elongation, insulation reliability, heat resistance, and adhesion to metal foil, while also exhibiting a low dielectric constant and low dielectric loss tangent (see Patent Document 1).

Japanese Patent Application Laid-Open No. 2019-199537

However, although resin compositions containing a thermoplastic resin such as an acrylic polymer and a thermosetting resin can have low elasticity due to the thermoplastic resin such as an acrylic polymer, the inclusion of the thermoplastic resin tends to reduce heat resistance, making it difficult to use the compositions as materials for in-vehicle printed wiring boards.
Therefore, the present inventors have considered further improving the heat resistance of a resin composition containing an acrylic polymer (A) and a thermosetting resin (B) by adding a thermosetting resin having a specific structure as the thermosetting resin (B). However, they have found that some thermosetting resins having the specific structure have very poor compatibility with the acrylic polymer (A), making it difficult to even prepare a varnish with good varnish properties.

The object of the present disclosure is to provide a resin composition that uses (A) a thermosetting resin that is compatible with acrylic polymers, and that has a sufficiently low modulus of elasticity, adhesion to metal foil, and high heat resistance sufficient to withstand use as a material for automotive printed wiring boards. It is also an object of the present disclosure to provide prepregs, resin-coated metal foils, laminates, printed wiring boards, and semiconductor packages that use the resin composition.

The present disclosure includes the following [1] to [14].
[1] A resin composition containing (A) an acrylic polymer and (B) a thermosetting resin,
A resin composition, wherein the (B) thermosetting resin contains an epoxy resin, and the epoxy resin contains (b1) an epoxy resin having a naphthalene skeleton and a weight average molecular weight of 450 or less.
[2] The resin composition according to the above [1], wherein the (A) acrylic polymer is an acrylic polymer containing a structural unit derived from a (meth)acrylic acid ester represented by the following general formula (A1):

(In the formula, R ^A1 represents a hydrogen atom or a methyl group, and R ^A2 represents an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group.)
[3] The resin composition according to [1] or [2] above, wherein the weight average molecular weight of the (A) acrylic polymer is 100,000 to 1,500,000.
[4] The resin composition according to any one of [1] to [3] above, wherein the content of the (A) acrylic polymer is 5 to 50 parts by mass per 100 parts by mass of the total solid content of the resin composition.
[5] The resin composition according to any one of [1] to [4] above, wherein the content of the (b1) component is 100 to 180 parts by mass per 100 parts by mass of the (A) acrylic polymer.
[6] The resin composition according to any one of the above [1] to [5], further comprising (C) a filler.
[7] The resin composition according to the above [6], wherein the filler (C) is an inorganic filler.
[8] The resin composition according to any one of the above [1] to [7], further comprising (D) a curing agent.
[9] The resin composition according to any one of the above [1] to [8], further comprising (E) a curing accelerator.
[10] A prepreg comprising the resin composition according to any one of [1] to [9] above and a substrate.
[11] A resin-coated metal foil having a layer of the resin composition according to any one of [1] to [9] above on the metal foil.
[12] A laminate comprising the prepreg according to [9] above or the resin-coated metal foil according to [10] above.
[13] A printed wiring board comprising the laminate according to [11] above.
[14] A semiconductor package comprising the printed wiring board according to [12] above and a semiconductor element.

According to the present disclosure, it is possible to provide a resin composition having a sufficiently low elastic modulus, adhesion to metal foil, and high heat resistance sufficient to withstand use as a material for in-vehicle printed wiring boards. Furthermore, it is possible to provide a prepreg, a resin-coated metal foil, a laminate, a printed wiring board, and a semiconductor package using the resin composition.
The thermosetting resin contained in the resin composition of this embodiment includes (A) an epoxy resin that has good compatibility with the acrylic polymer, and therefore it is possible to prepare a varnish that has good varnishability.

One embodiment of the present disclosure is described in detail below, but the present disclosure is not limited to the following embodiment.

In the numerical ranges described herein, the upper or lower limit of the numerical range may be replaced with the values shown in the examples. In addition, the lower and upper limits of a numerical range can be arbitrarily combined with the lower or upper limit of another numerical range. In the expression "AA to BB," the numerical values AA and BB at both ends are included as the lower and upper limits, respectively, of the numerical range.
In this specification, for example, the expression "10 or more" means 10 or a numerical value exceeding 10, and this also applies when the numerical values are different. Furthermore, for example, the expression "10 or less" means 10 or a numerical value less than 10, and this also applies when the numerical values are different.
Furthermore, unless otherwise specified, each of the components and materials exemplified in this specification may be used alone or in combination of two or more. In this specification, when a plurality of substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified.

In this specification, the term "solid content" refers to components in a resin composition other than water and volatile substances such as the solvent described below. In other words, the solid content includes substances that are liquid, syrup-like, or waxy at around 25°C, and does not necessarily mean that they are solid.
Any combination of the descriptions in this specification is also included in the present disclosure and the present embodiment.

[Resin composition]
One of the present embodiments is a resin composition containing (A) an acrylic polymer (hereinafter also referred to as "component (A)") and (B) a thermosetting resin (hereinafter also referred to as "component (B)"), wherein the (B) thermosetting resin contains an epoxy resin, and the epoxy resin contains (b1) an epoxy resin (hereinafter also referred to as "component (b1)") that has a naphthalene skeleton and a weight-average molecular weight of 450 or less.
Hereinafter, each component contained in the resin composition of the present embodiment will be described in detail in order.

<(A) Acrylic Polymer>
The component (A) is an acrylic polymer, more specifically, a polymer containing a (meth)acrylic acid ester as a monomer. In this embodiment, the term "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid."
The acrylic polymer (A) may be used alone or in combination of two or more thereof.

The (A) acrylic polymer can also be said to be an acrylic polymer containing structural units derived from a (meth)acrylic acid ester, and is preferably an acrylic polymer containing structural units derived from a (meth)acrylic acid ester represented by the following general formula (A1):

(In the formula, R ^A1 represents a hydrogen atom or a methyl group, and R ^A2 represents an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group.)

The number of carbon atoms in the alkyl group represented by R ^A2 is preferably 1 to 20, more preferably 1 to 15, and even more preferably 2 to 10. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a 2-ethylhexyl group. The alkyl group may have a substituent. Examples of the substituent on the alkyl group include a cycloalkyl group, a hydroxyl group, a halogen atom, an oxygen-containing hydrocarbon group, and a nitrogen-containing cyclic group. The total number of carbon atoms in the cycloalkyl-substituted alkyl group is preferably 6 to 13, and more preferably 7 to 10. Examples of the cycloalkyl-substituted alkyl group include a norbornylmethyl group and a tricyclodecylethyl group.
The number of carbon atoms in the cycloalkyl group represented by R ^A2 is preferably 6 to 13, and more preferably 7 to 10. Examples of the cycloalkyl group include a cyclohexyl group, a norbornyl group, a tricyclodecanyl group, an isobornyl group, and an adamantyl group. Among these, a norbornyl group, a tricyclodecanyl group, and an isobornyl group are preferred as the cycloalkyl group.
The number of carbon atoms in the aryl group represented by R ^A2 is preferably 6 to 13, more preferably 6 to 10. Examples of the aryl group include a phenyl group and a nonylphenyl group.
The number of carbon atoms in the aralkyl group represented by R ^A2 is preferably 7 to 15, more preferably 7 to 11. Examples of the aralkyl group include a benzyl group and a 4-methylbenzyl group.

Specific examples of (A) acrylic polymers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobutyl (meth)acrylate, ethylene glycol methyl ether (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, isobornyl (meth)acrylate, tricyclo[5.2.1.0(2,6)]dec-8-yl (meth)acrylate, isodecyl (meth)acrylate, octadecyl (meth)acrylate, lauryl (meth)acrylate, allyl (meth)acrylate, norbornylmethyl (meth)acrylate, tricyclodecylethyl (meth)acrylate, phenyl (meth)acrylate, nonylphenyl (meth)acrylate, benzyl (meth)acrylate, and 4-methylbenzyl (meth)acrylate.

The acrylic polymer (A) is not particularly limited, but is preferably an acrylic polymer having a crosslinkable functional group. Examples of the acrylic polymer having a crosslinkable functional group include a copolymer of a (meth)acrylic acid ester and a copolymerizable monomer having a crosslinkable functional group (hereinafter simply referred to as a "crosslinkable copolymerizable monomer"). The crosslinkable copolymerizable monomer preferably has a crosslinkable functional group such as a carboxy group, a hydroxyl group, an amino group, a vinyl group, a glycidyl group, or an epoxy group. Among these, from the viewpoints of low moisture absorption and heat resistance, an epoxy group is preferred as the crosslinkable functional group.
The crosslinkable copolymerizable monomer is preferably a compound having a double bond.

Examples of the crosslinkable copolymerizable monomer include monomers having a carboxy group, such as acrylic acid and methacrylic acid; monomers having an epoxy group, such as glycidyl acrylate and glycidyl methacrylate; monomers having a hydroxyl group, such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; monomers having an amino group, such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate; monomers having an amide group, such as acrylamide, methacrylamide, dimethylacrylamide, and dimethylmethacrylamide; and monomers having a nitrile group, such as acrylonitrile. These may be used alone or in combination. Among these, from the viewpoint of electrical insulation reliability, monomers having a carboxy group, monomers having an epoxy group, monomers having a hydroxyl group, and monomers having an amino group are preferred. From the viewpoints of low moisture absorption and heat resistance, monomers having an epoxy group are more preferred, and glycidyl acrylate and glycidyl methacrylate are even more preferred.

The acrylic polymer (A) may also be a copolymer of a (meth)acrylic acid ester and a polymerizable monomer selected from the group consisting of N-vinylpyrrolidone acrylate, N-vinylpyrrolidone methacrylate, N-acryloylmorpholine, N-methacryloylmorpholine, aromatic vinyl compounds, N-substituted maleimide compounds, and (meth)acrylic acid esters other than those represented by the general formula (A1) above.
Although there are no particular limitations, it is preferable that the acrylic polymer (A) does not have a nitrile group.

When the (A) acrylic polymer is a copolymer of a (meth)acrylic acid ester and a crosslinkable copolymerizable monomer, the amount of the (meth)acrylic acid ester used is preferably 70 to 99.5 parts by mass, more preferably 80 to 98 parts by mass, and even more preferably 90 to 97 parts by mass, per 100 parts by mass of the total amount of the (meth)acrylic acid ester and the crosslinkable copolymerizable monomer.
The amount of the crosslinkable copolymer monomer used is preferably 0.5 to 30 parts by mass, more preferably 2 to 25 parts by mass, and even more preferably 3 to 20 parts by mass, relative to 100 parts by mass of the total amount of the (meth)acrylic acid ester and the crosslinkable copolymer monomer. By setting the amount within such a range, heat resistance, adhesive strength with the metal foil, insulation reliability, etc. tend to be further improved.
In all raw material monomers of the acrylic polymer (A), the total content of the (meth)acrylic acid ester and the crosslinkable copolymerizable monomer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may be 100% by mass.

When the (A) acrylic polymer has epoxy groups, its epoxy equivalent is preferably 2,000 to 18,000 g/eq, more preferably 2,000 to 8,000 g/eq. When the epoxy equivalent is 2,000 g/eq or more, the storage modulus does not become too large and the dimensional stability of the substrate tends to be maintained, while when it is 18,000 g/eq or less, the decrease in the glass transition temperature of the cured product is suppressed and the heat resistance of the substrate is sufficiently maintained.
The epoxy equivalent of the (A) acrylic polymer can be adjusted by appropriately adjusting the copolymerization ratio when glycidyl (meth)acrylate is copolymerized with another monomer copolymerizable therewith.
Commercially available examples of the acrylic polymer (A) having an epoxy group include "HTR-860" (trade name, manufactured by Nagase ChemteX Corporation, epoxy equivalent weight: 2,900 g/eq) and "KH-CT-865" (trade name, manufactured by Hitachi Chemical Co., Ltd., epoxy equivalent weight: 3,300 g/eq).

The weight-average molecular weight (Mw) of the (A) acrylic polymer is preferably 100,000 to 1,500,000, and from the viewpoint of improving low modulus and elongation, more preferably 300,000 to 1,300,000, and even more preferably 300,000 to 1,100,000. If the weight-average molecular weight of the (A) acrylic polymer is equal to or greater than the above-mentioned lower limit, the (A) acrylic polymer and the (B) thermosetting resin tend not to be completely compatible with each other and a phase-separated structure tends to be easily formed, whereas if the weight-average molecular weight is equal to or less than the above-mentioned upper limit, the (A) acrylic polymer tends to be easily dissolved in a solvent and to have excellent handleability and dispersibility.
The acrylic polymer (A) may be a combination of two or more types having different weight average molecular weights.
In this specification, the weight average molecular weight refers to a value measured by gel permeation chromatography (GPC) analysis using tetrahydrofuran (THF) as a solvent, and is expressed in terms of standard polystyrene.

The (A) acrylic polymer may be in powder or liquid form at 25°C, but is preferably in liquid form from the viewpoints of excellent solubility in solvents and dispersibility of the (A) acrylic polymer in the resin composition. From the viewpoint of improving the dispersibility of the (A) acrylic polymer in the resin composition, it is preferable to use the (A) acrylic polymer in a state where the above-mentioned compound is dispersed in a solvent.

The content of the (A) acrylic polymer in the resin composition of this embodiment is not particularly limited, but is preferably 5 to 50 parts by mass, more preferably 10 to 45 parts by mass, even more preferably 15 to 40 parts by mass, and particularly preferably 15 to 35 parts by mass, per 100 parts by mass of the total solids content of the resin composition. When the content of the (A) acrylic polymer is at or above the above lower limit, the excellent characteristics of the (A) acrylic polymer, low elasticity and flexibility, tend to be sufficiently obtained. On the other hand, when the content is at or below the above upper limit, heat resistance and sufficient adhesive strength with the metal foil are obtained.

<(B) Thermosetting resin>
In this embodiment, component (B) contains an epoxy resin, and the epoxy resin contains "(b1) an epoxy resin having a naphthalene skeleton and a weight-average molecular weight of 450 or less." This aspect improves compatibility with component (A), making it possible to prepare a varnish with good varnish properties, and improves the heat resistance of the resin composition of this embodiment to a level that makes it durable for use as a material for automotive printed wiring boards. However, the acrylic polymer (A) and the epoxy resin are not completely compatible, and the resin composition of this embodiment tends to have a phase-separated structure in which the acrylic polymer (A) forms a sea and the epoxy resin forms islands.
From the viewpoint of compatibility with the component (A), the weight average molecular weight of the component (b1) is 450 or less, preferably 100 to 450, more preferably 150 to 350, even more preferably 200 to 300, and particularly preferably 220 to 280.
From the viewpoint of compatibility with the component (A), the epoxy equivalent of the component (b1) is preferably 150 to 350 g/eq, more preferably 180 to 300 g/eq, and even more preferably 200 to 280 g/eq.

Specific examples of the component (b1) include naphthalene-type epoxy resins, naphthol novolac-type epoxy resins, naphthol-type epoxy resins, naphthol aralkyl-type epoxy resins, naphthylene ether-type epoxy resins, etc. Among these, from the viewpoint of heat resistance, naphthalene-type epoxy resins are preferred as the component (b1).
From the viewpoint of heat resistance, the component (b1) is preferably an epoxy resin represented by any one of the following general formulas (B1) to (B3).

(In formula (B1), R ^B1 represents a hydrogen atom or an organic group.)

Examples of the organic group represented by R ^B1 in general formula (B1) above include alkyl groups such as methyl, ethyl, propyl, butyl, and pentyl; aryl groups such as phenyl, benzyl, and naphthyl; and heteroaryl groups such as pyridyl. The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. The aryl group is preferably an aryl group having 6 to 14 carbon atoms, more preferably an aryl group having 6 to 10 carbon atoms. The heteroaryl group is preferably a heteroaryl group having 5 to 14 carbon atoms, more preferably a heteroaryl group having 5 to 9 carbon atoms.
Of the above, the organic group represented by R ^B1 is preferably an alkyl group, and more preferred embodiments are as described above.

(Thermosetting resin other than the above component (b1))
The thermosetting resin other than the component (b1) (hereinafter also referred to as component (b2)) is not particularly limited, but examples thereof include epoxy resins other than the component (b1), cyanate resins, bismaleimide compounds, addition reaction products of bismaleimide compounds and diamines, isocyanate resins, triallyl isocyanurate resins, triallyl cyanurate resins, vinyl group-containing polyolefin compounds, etc. Among these, epoxy resins and cyanate resins other than the component (b1) are preferred as the component (b2).
The component (b2) may be used alone or in combination of two or more.

Epoxy resins other than component (b1) are not particularly limited, but include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, biphenyl epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, phosphorus-containing epoxy resins, aralkylene skeleton-containing epoxy resins, phenol biphenyl aralkyl epoxy resins, phenol salicylaldehyde novolac epoxy resins, lower alkyl group-substituted phenol salicylaldehyde novolac epoxy resins, dicyclopentadiene skeleton-containing epoxy resins, polyfunctional glycidylamine epoxy resins, polyfunctional alicyclic epoxy resins, and tetrabromobisphenol A epoxy resins. Among these, from the viewpoint of compatibility with the acrylic polymer (A), tetrabromobisphenol A epoxy resins, phenol novolac epoxy resins, dicyclopentadiene skeleton-containing epoxy resins, and phosphorus-containing epoxy resins are preferred as epoxy resins other than component (b1).

The weight-average molecular weight of the epoxy resin as component (b2) may be 200 to 1,000, or may be 300 to 900. When the weight-average molecular weight of the epoxy resin as component (b2) is at least the above-mentioned lower limit, the epoxy resin tends to have excellent heat resistance, and when it is at most the above-mentioned upper limit, the epoxy resin tends to have low elasticity and flexibility.
From the viewpoint of compatibility, the epoxy equivalent of the epoxy resin as component (b2) may be 150 to 500 g/eq, 150 to 450 g/eq, or 150 to 300 g/eq.

The cyanate resin may be any known cyanate resin, such as novolac cyanate resin, bisphenol A cyanate resin, bisphenol E cyanate resin, bisphenol F cyanate resin, tetramethylbisphenol F cyanate resin, or dicyclopentadiene cyanate resin. Among these, it is preferable to use one or more bisphenol A cyanate resins, from the viewpoint of compatibility with the acrylic polymer (A) when dissolved.

(Content of component (b1))
The content of the component (b1) in the epoxy resin contained in the thermosetting resin (B) is, from the viewpoint of compatibility with the component (A) and the heat resistance of the resin composition, preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 80% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more, and the upper limit of any of these may be 100% by mass.
Furthermore, the content of the component (b1) in the thermosetting resin (B) is, from the viewpoint of compatibility with the component (A) and the heat resistance of the resin composition, preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 80% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more, and the upper limit of any of these may be 100% by mass.
The thermosetting resin (B) may not contain the component (b2), which is a thermosetting resin other than the component (b).

Furthermore, the content of component (b1) in the resin composition of this embodiment is not particularly limited, but is preferably 100 to 180 parts by mass, more preferably 110 to 170 parts by mass, even more preferably 120 to 160 parts by mass, and particularly preferably 120 to 150 parts by mass, relative to 100 parts by mass of the acrylic polymer (A). When the content of component (b1) in the resin composition of this embodiment is at or above the above-mentioned lower limit, the heat resistance of the resin composition tends to be improved to a level sufficient for use as a material for automotive printed wiring boards, while when the content is at or below the above-mentioned upper limit, the resin composition tends to have excellent low elasticity and flexibility.

<(C) Filler>
The resin composition of the present embodiment may further contain a filler (C) (hereinafter also referred to as "component (C)").
The (C) filler is not particularly limited, but inorganic fillers are preferred from the viewpoint of reducing the thermal expansion coefficient and ensuring flame retardancy. Examples of inorganic fillers include silica, alumina, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, calcium oxide, magnesium oxide, aluminum nitride, aluminum borate whiskers, boron nitride, and silicon carbide. One type of (C) filler may be used alone, or two or more types may be used in combination. Among these, silica is preferred because of its low relative dielectric constant and low linear expansion coefficient. Examples of silica include synthetic silica synthesized by a wet method or a dry method, crushed silica, and fused silica.

The filler (C) may be a filler that has been subjected to a coupling treatment. The coupling agent used in the coupling treatment is preferably a silane coupling agent. Examples of silane coupling agents include aminosilane coupling agents, epoxysilane coupling agents, phenylsilane coupling agents, alkylsilane coupling agents, alkenylsilane coupling agents, alkynylsilane coupling agents, and silicone oligomer coupling agents. These may be used alone or in combination of two or more. Among these, silicone oligomer coupling agents are preferred from the standpoint of dispersibility.

The average particle size of component (C) is preferably 0.1 to 1.5 μm, more preferably 0.2 to 1.0 μm, and even more preferably 0.3 to 0.8 μm. If the average particle size of component (C) is equal to or greater than the lower limit, the filler is easily dispersed when the resin composition is made into a varnish, and aggregation tends to be less likely to occur. If the average particle size of component (C) is equal to or less than the upper limit, sedimentation of component (C) tends to be less likely to occur when the resin composition is made into a varnish.
Here, the average particle size in this embodiment refers to the particle size at a point corresponding to 50% volume when a cumulative frequency distribution curve of particle sizes is calculated, with the total volume of particles being 100%, and can be measured using a particle size distribution measuring device using a laser diffraction scattering method, or the like.

(Content of component (C))
When the resin composition of this embodiment contains a (C) filler, its content is not particularly limited, but is preferably 10 to 60 parts by mass, more preferably 15 to 50 parts by mass, and even more preferably 20 to 40 parts by mass, per 100 parts by mass of the total solid content of the resin composition. When the content of the (C) filler is equal to or greater than the above-mentioned lower limit, the linear expansion coefficient tends to be low and sufficient heat resistance tends to be obtained. When the content of the (C) filler is equal to or less than the above-mentioned upper limit, the low elasticity and flexibility inherent to the (A) acrylic polymer tend to be sufficiently obtained.

<(D) Curing Agent>
The resin composition of the present embodiment may contain a curing agent (D) (hereinafter also referred to as "component (D)").
Examples of the (D) curing agent include phenolic resins such as phenol novolac resin, cresol novolac resin, bisphenol A novolac resin, biphenyl novolac phenolic resin, and aminotriazine novolac phenolic resin; amine-based curing agents such as dicyandiamide, diaminodiphenylmethane, and diaminodiphenylsulfone; acid anhydrides such as pyromellitic anhydride, trimellitic anhydride, and benzophenonetetracarboxylic acid; active ester curing agents, etc. One type of component (D) may be used alone, or two or more types may be used in combination.
Since the resin composition of this embodiment contains the thermosetting resin (B), it is preferable that it further contains a curing agent (D) from the viewpoint of ensuring adhesive strength with the metal foil. Moreover, since the resin composition of this embodiment contains the epoxy resin as the thermosetting resin (B), it is more preferable that the curing agent (D) is a phenol resin.

((D) Content of curing agent)
When the resin composition of this embodiment contains a (D) curing agent, its content is not particularly limited, but the total amount of active groups derived from the (D) curing agent relative to the epoxy groups of the (b1) component is preferably 0.5 to 1.5 equivalents, more preferably 0.6 to 1.3 equivalents, and even more preferably 0.7 to 1.2 equivalents. When the content of the (D) curing agent is within the above range, adhesion to the metal foil, glass transition temperature, and insulating properties tend to be excellent.

<(E) Curing Accelerator>
The resin composition of the present embodiment may contain (E) a curing accelerator (hereinafter also referred to as "component (E)").
In this embodiment, since the (B) thermosetting resin contains an epoxy resin, the (E) curing accelerator preferably contains one or more compounds selected from the group consisting of amine-based compounds and imidazole-based compounds, and more preferably contains an imidazole-based compound.
Examples of the amine compounds include dicyandiamide, diaminodiphenylethane, and guanylurea.
Examples of the imidazole compounds include 2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, and benzimidazole.
The curing accelerator (E) may be used alone or in combination of two or more kinds.
When the resin composition of the present embodiment contains the curing accelerator (E), the content thereof is not particularly limited, but is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 2 parts by mass, and even more preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the total solid content of the resin composition.

<Other ingredients>
The resin composition of the present embodiment may contain, as necessary, a crosslinking agent such as a melamine resin, a flame retardant such as a phosphorus-based compound, a rubber-based elastomer, conductive particles, a coupling agent, a flow control agent, an antioxidant, a pigment, a leveling agent, an antifoaming agent, an ion-trapping agent, etc. Known components can be used as these other components.

The resin composition of this embodiment may be dissolved or dispersed in an organic solvent to form a varnish. Examples of the organic solvent include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbon-based solvents such as toluene and xylene; ester-based solvents such as methoxyethyl acetate, ethoxyethyl acetate, butoxyethyl acetate, and ethyl acetate; amide-based solvents such as N-methylpyrrolidone, formamide, N-methylformamide, and N,N-dimethylacetamide; and alcohol-based solvents such as methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monopropyl ether, and dipropylene glycol monopropyl ether. One type of organic solvent may be used alone, or two or more types may be used in combination.
The solid content concentration in the varnish is preferably from 10 to 70% by mass, more preferably from 20 to 60% by mass, and even more preferably from 35 to 60% by mass.

From the viewpoint of stress relaxation, the storage modulus at 25°C of the cured product of the resin composition of this embodiment is preferably 7.0 GPa or less, more preferably 6.5 GPa or less, and even more preferably 6.0 GPa or less. Furthermore, from the viewpoint of mechanical strength, the storage modulus may be 0.5 GPa or more, 2 GPa or more, or even 4.5 GPa or more. The curing conditions for the resin composition and the method for measuring the storage modulus are as described in the examples.

[Prepreg]
The prepreg of this embodiment contains the resin composition of this embodiment and a substrate. The prepreg can be produced, for example, by impregnating or coating the substrate with the resin composition of this embodiment in a varnish form, followed by drying to B-stage the resin composition. Here, B-staging in this specification refers to achieving the B-stage state defined in JIS K6900 (1994), and is also referred to as semi-curing.

As the substrate, a fibrous substrate such as a woven fabric or a nonwoven fabric is usually used, and the substrate is preferably a sheet-like fibrous substrate.
Examples of the material for the fiber substrate include inorganic fibers such as glass, alumina, asbestos, boron, silica alumina glass, silica glass, Tyranno, silicon carbide, silicon nitride, and zirconia; organic fibers such as aramid, polyether ether ketone, polyether imide, polyether sulfone, carbon, and cellulose; and mixtures thereof.
The thickness of the substrate is preferably 5 to 200 μm, may be 10 to 100 μm, or may be 20 to 50 μm. By setting the thickness of the substrate to the above upper limit or less, a printed wiring board that can be bent arbitrarily can be obtained, and dimensional changes due to temperature, moisture absorption, etc. during the manufacturing process can be reduced.

The prepreg production conditions are not particularly limited, but it is preferable that 80% by mass or more of the organic solvent used in the varnish has evaporated in the resulting prepreg. The drying temperature is, for example, 80 to 180°C, and the drying time is set appropriately taking into account the varnish gelation time. Furthermore, the impregnation amount of varnish is preferably an amount that results in a solids content of the resin composition of this embodiment in the resulting prepreg of 30 to 80% by mass.

The thickness of the prepreg in this embodiment is not particularly limited, and may be 10 to 200 μm, 10 to 150 μm, or 10 to 100 μm.

[Metal foil with resin]
The resin-coated metal foil of this embodiment has a layer of the resin composition of this embodiment on a metal foil. Hereinafter, the "layer of the resin composition" may be referred to as a "resin layer."
A resin-coated metal foil having a resin layer on a metal foil can be produced by applying the resin composition of this embodiment to a metal foil and then B-staging the resin composition in a drying oven. Drying conditions are not particularly limited, but the drying temperature is preferably 60 to 180°C, more preferably 80 to 140°C. The coating method is not particularly limited, but examples include coating methods using known coaters such as a die coater, comma coater, bar coater, kiss coater, and roll coater.

Examples of the metal foil of the resin-coated metal foil include copper foil, aluminum foil, tin foil, tin-lead alloy (solder) foil, nickel foil, etc., but other metal foils can also be used. Among these, copper foil is preferred. When copper foil is used as the metal foil, the grade and thickness of the copper foil may be appropriately selected depending on the circuit design of the semiconductor package to be manufactured, but copper foil with a copper content of 95% by mass or more is preferred.
Of the two surfaces of the metal foil, the surface facing the resin layer may be roughened from the viewpoint of adhesion. The roughening treatment can be performed by forming roughening particles on the surface of the metal foil. The roughening particles are preferably electrodeposited particles made of at least one element selected from the group consisting of copper, nickel, phosphorus, tungsten, arsenic, molybdenum, chromium, cobalt, and zinc, or electrodeposited particles made of an alloy containing at least one of these elements.
After the roughening treatment, secondary particles, tertiary particles, an anti-rust layer, a heat-resistant layer, or the like may be formed using at least one element selected from the group consisting of nickel, cobalt, copper, and zinc, or an alloy containing at least one of these elements, and the surface may then be subjected to a surface treatment such as a chromate treatment or a silane coupling treatment.

In the resin-coated metal foil of this embodiment, the thickness of the resin layer is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 70 μm.
In the resin-coated metal foil of this embodiment, the thickness of the metal foil is not particularly limited, but is preferably 3 to 25 μm, more preferably 5 to 22 μm, and even more preferably 10 to 20 μm.

[Laminate]
The laminate of this embodiment is a laminate containing the prepreg of this embodiment or the resin-coated metal foil of this embodiment. Note that a laminate with a metal foil disposed thereon may be referred to as a "metal-clad laminate."
The metal-clad laminate can be produced, for example, by stacking both adhesive surfaces of one prepreg of the present embodiment or two or more prepregs of a laminate so that they face the metal foil, and then heating and press-molding the laminate in a vacuum press, typically at 130 to 250°C, preferably 150 to 230°C, at a pressure of 0.5 to 10 MPa, preferably 1 to 5 MPa.
Another method for producing a metal-clad laminate is to stack two sheets of the resin-coated metal foil of this embodiment with the resin surfaces facing each other, and then vacuum press the laminate under heat and pressure molding at a temperature of typically 130 to 250° C., preferably 150 to 230° C., and a pressure of 0.5 to 10 MPa, preferably 1 to 5 MPa. For the heat and pressure molding, a multistage press, a multistage vacuum press, a continuous molding machine, an autoclave molding machine, or the like can be used.
Another method for producing a metal-clad laminate includes a method in which the resin-coated metal foil of this embodiment is laminated on both sides or one side of the prepreg of this embodiment or another prepreg so that the resin side faces the prepreg, and then heated and pressed. In this case, the prepreg may be a single prepreg, or two or more prepregs may be laminated. When two or more prepregs are laminated, different prepregs may be combined and laminated.

Metal foils used in metal-clad laminates include copper foil, aluminum foil, tin foil, tin-lead alloy (solder) foil, and nickel foil. The thickness of the metal foil can be that typically used in laminates, for example, 1 to 200 μm. Other examples include a three-layer composite foil with an intermediate layer of nickel, nickel-phosphorus, nickel-tin alloy, nickel-iron alloy, lead, or lead-tin alloy, with a 0.5 to 15 μm copper layer and a 10 to 300 μm copper layer on both sides; and a two-layer composite foil combining aluminum and copper foil.

[Printed wiring board]
The printed wiring board of this embodiment includes the laminate of this embodiment.
The printed wiring board of this embodiment can be manufactured, for example, by subjecting the metal foil of the laminate of this embodiment, i.e., a metal-clad laminate, having metal foil on one or both sides thereof to circuit processing and, if necessary, multilayer adhesive processing.

[Semiconductor package]
The present disclosure also provides a semiconductor package including the printed wiring board and semiconductor element of the present embodiment. The semiconductor package of the present embodiment can be manufactured, for example, by mounting semiconductor elements such as semiconductor chips and memories at predetermined positions on the multilayer printed wiring board of the present embodiment by a known method and encapsulating the semiconductor elements with an encapsulating resin or the like.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

Example 1, Comparative Examples 1 and 2
(Preparation of Varnish)
Of the components shown in Table 1, each component except for component (E) was blended in the amounts shown in Table 1 (the numbers in the table are parts by mass of solid content, and in the case of a solution or dispersion, are solid content equivalent amounts), dissolved in methyl isobutyl ketone, and then component (E) was blended to obtain a varnish with a non-volatile content (solid content concentration) of 50 mass%.
(Preparation of prepreg)
The varnish prepared in each example was impregnated into a glass cloth 3313 (trade name, manufactured by Nitto Boseki Co., Ltd.) having a thickness of 0.028 mm, and then heated and dried at 140°C for 10 minutes to obtain a prepreg.
(Preparation of resin-coated copper foil)
The varnish prepared in each example was applied to an electrolytic copper foil having a thickness of 18 μm, "CFT9L-UR-18" (trade name, manufactured by Fukuda Metal Foil & Powder Co., Ltd.), using a coater, and the foil was dried with hot air at 140°C for about 6 minutes to prepare a resin-coated copper foil having a resin composition layer having a thickness of 50 μm.
(Preparation of copper clad laminate)
On both sides of the four prepreg sheets, 18 μm thick electrolytic copper foil "CFT9L-UR-18" (trade name, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was placed so that the adhesive surfaces faced the prepreg, and the laminate was heated and pressed at 200°C for 60 minutes under vacuum pressing conditions of 4 MPa to produce a double-sided copper-clad laminate. Two resin-coated copper foil sheets were also placed so that the resin surfaces faced each other, and the laminate was heated and pressed at 200°C for 60 minutes under vacuum pressing conditions of 4 MPa to produce a double-sided copper-clad laminate.

[Evaluation method]
(1) Varnish properties (compatibility of each component)
The varnish properties were evaluated by placing the prepared varnish in a transparent container and visually observing its appearance after 24 hours. A varnish with a uniform hue was rated as having "good" varnish properties, while one in which separation of the varnish components was observed was rated as having "poor" varnish properties. The results are shown in Table 1.

(2) Appearance of prepreg (presence or absence of aggregates)
The appearance of the prepreg was evaluated by observing the surface of the prepreg using a 20x magnifying glass to check for the presence or absence of aggregates. Those in which aggregates were observed were marked "present," and those in which aggregates were not observed were marked "absent." The results are shown in Table 1.

(3) Storage Modulus at 25°C The storage modulus at 25°C was measured using a dynamic viscoelasticity measuring device (manufactured by UBM Co., Ltd.) by cutting a 5 mm wide x 30 mm long specimen from a double-sided copper-clad laminate made from resin-coated copper foil, which was then fully etched. A storage modulus at 25°C of 7.0 GPa or less is preferable because it indicates a good stress relaxation effect. The results are shown in Table 1.

(4) Heat Resistance Heat resistance was evaluated by cutting a double-sided copper-clad laminate made from prepreg into a 50 mm square test piece, floating it in a solder bath at 260°C, and measuring the time elapsed from that point until the test piece bulged visually. The elapsed time was measured up to 1,800 seconds. A time of 1,600 seconds or more can be said to be high enough in heat resistance to withstand use as a material for automotive printed wiring boards. The results are shown in Table 1.

(5) Copper Foil Peel Strength The copper foil peel strength was evaluated by measuring the load when a test piece was prepared by partially etching the copper foil of a double-sided copper-clad laminate made from a prepreg to form a 3 mm wide copper foil line and peeling the copper foil line at a speed of 50 mm/min in a direction 90° to the adhesive surface. If the peel load was 0.5 kN/m or more, it was determined that the adhesion to the metal foil was sufficient. The results are shown in Table 1.

The details of the components in each table are as follows:
[Component (A)]
Acrylic polymer: acrylic polymer having epoxy groups "HTR-860", weight average molecular weight = 80 x 10 ⁴ , epoxy equivalent: 2,900 g/eq (trade name, manufactured by Nagase ChemteX Corporation)
[(B) Component]
Component (b1) EPICLON HP-5000: naphthalene-based epoxy resin, weight-average molecular weight = 245 to 260 (manufactured by DIC Corporation, trade name)
Component (b2) EPICLON 153: tetrabromobisphenol A type epoxy resin (trade name, manufactured by DIC Corporation), not containing a naphthalene skeleton EPICLON HP-6000: naphthalene skeleton epoxy resin, weight average molecular weight = 540 to 580 (trade name, manufactured by DIC Corporation)
[(C) Component]
Filler: silane coupling treated fused spherical silica, average particle size 0.5 μm
[(D) Component]
Curing agent: Cresol novolac resin "KA-1165" (manufactured by DIC Corporation, product name)
[(E) component]
Curing accelerator: 2-phenylimidazole

As is clear from Table 1, in Example 1, which used the resin composition of this embodiment, a sufficiently low elastic modulus and adhesion to metal foil were obtained, and heat resistance sufficient for use as a material for printed wiring boards for automobiles was also obtained.
On the other hand, in Comparative Example 1, although the heat resistance was not low, it was insufficient for use as a material for printed wiring boards for automobiles. In Comparative Example 2, the components in the varnish separated, which was likely to result in a deterioration in physical properties, and therefore prepreg could not be produced.

Claims (14)

A resin composition containing (A) an acrylic polymer and (B) a thermosetting resin,
the weight average molecular weight of the (A) acrylic polymer is 100,000 to 1,500,000;
the (B) thermosetting resin contains an epoxy resin, and the epoxy resin contains (b1) an epoxy resin having a naphthalene skeleton, a weight average molecular weight of 100 to 450 , and an epoxy equivalent of 150 to 350 g/eq ;
The resin composition has a content of the component (b1) of 110 to 180 parts by mass per 100 parts by mass of the acrylic polymer (A). The resin composition according to claim 1, wherein the acrylic polymer (A) is an acrylic polymer containing a structural unit derived from a (meth)acrylic acid ester represented by the following general formula (A1):

(In the formula, R ^A1 represents a hydrogen atom or a methyl group, and R ^A2 represents an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group.) 3. The resin composition according to claim 1, wherein the weight average molecular weight of the acrylic polymer (A) is 300,000 to 1,100,000 . The resin composition according to any one of claims 1 to 3, wherein the content of the (A) acrylic polymer is 5 to 50 parts by mass per 100 parts by mass of the total solid content of the resin composition. The resin composition according to any one of claims 1 to 4, wherein the content of the component (b1) is 120 to 150 parts by mass per 100 parts by mass of the acrylic polymer (A). The resin composition according to any one of claims 1 to 5, further comprising (C) a filler. The resin composition according to claim 6, wherein the (C) filler is an inorganic filler. The resin composition according to any one of claims 1 to 7, further comprising (D) a curing agent. The resin composition according to any one of claims 1 to 8, further comprising (E) a curing accelerator. A prepreg comprising the resin composition according to any one of claims 1 to 9 and a substrate. A resin-coated metal foil having a layer of the resin composition described in any one of claims 1 to 9 on the metal foil. A laminate comprising the prepreg described in claim 10 or the resin-coated metal foil described in claim 11. A printed wiring board comprising the laminate of claim 12. A semiconductor package comprising the printed wiring board of claim 13 and a semiconductor element.