WO2012073360A1 - Insulating sheet and laminated structure - Google Patents

Abstract

Provided is an insulating sheet that can increase handleability and storage stability in an uncured state and, further, can increase heat dissipation characteristics and adhesiveness of the cured article after curing. This insulating sheet is used to make a thermal conductor with thermal conductivity of 10 W/m·K or greater adhere to an electrically conductive layer. This insulating sheet contains a polymer with weight average molecular weight of 10000 or greater, a curable compound that has a molecular weight of 1200 or less and has an epoxy group or oxetanyl group, a curing agent, and an inorganic filler. In 100 wt% of the insulating sheet, the content for the inorganic filler is 60 wt% or greater and 95 vol% or less. In 100 wt% of the insulating sheet, the content for nitrogen atoms included in components in the insulating sheet excluding the inorganic filler is 0.3 wt% to less than 3.0 wt%.

Description

Insulating sheet and laminated structure

The present invention relates to an insulating sheet used for adhering a thermal conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer, and more specifically, handling property and storage stability in an uncured state. The present invention relates to an insulating sheet that is high and has high adhesiveness and heat dissipation of a cured product after curing, and a laminated structure using the insulating sheet.

In electronic devices and communication devices, printed wiring boards having an insulating layer are used. The insulating layer is formed using a paste-like or sheet-like insulating adhesive material.
As an example of the above-mentioned insulating adhesive material, the following patent document 1 discloses an insulating adhesive in which a glass cloth is impregnated with an adhesive composition containing an epoxy resin, an epoxy resin curing agent, a curing accelerator, an elastomer and an inorganic filler. A sheet is disclosed.

An insulating adhesive material that does not contain glass cloth is also known. For example, the example of Patent Document 2 below includes an insulating adhesive containing bisphenol A type epoxy resin, phenoxy resin, phenol novolac, 1-cyanoethyl-2-phenylimidazole, γ-glycidoxypropyltrimethoxysilane, and alumina. Agents are disclosed. Here, examples of the epoxy resin curing agent include tertiary amines, acid anhydrides, imidazole compounds, polyphenol resins, and mask isocyanates.

JP 2006-342238 A JP-A-8-332696

In the insulating adhesive sheet described in Patent Document 1, a glass cloth is used in order to improve handling properties. With an insulating adhesive sheet including glass cloth, it is difficult to make a thin film, and various processes such as laser processing or drilling are difficult. Moreover, since the heat conductivity of the hardened | cured material of the insulation adhesive sheet containing a glass cloth is comparatively low, sufficient heat dissipation may not be obtained. Furthermore, special impregnation equipment must be prepared for impregnating the glass cloth with the adhesive composition.

In the insulating adhesive described in Patent Document 2, since glass cloth is not used, the sheet itself is not self-supporting in an uncured state. For this reason, the handling property of the insulating adhesive is low.

Also, in recent years, the downsizing and high performance of electrical equipment are progressing. For this reason, in the printed wiring board used for the said electronic device and communication apparatus, multilayering and a thin film are progressing, and the mounting density of an electronic component is high. Along with this, a large amount of heat is easily generated from the electronic components, and the need to dissipate the generated heat is increasing. In order to dissipate heat, the insulating layer of the printed wiring board needs to have high thermal conductivity.

In order to impart high thermal conductivity to the insulating layer, for example, a large amount of filler having high thermal conductivity with a thermal conductivity of 10 W / m · K or more is added to the insulating adhesive material for forming the insulating layer. A filling method is generally employed. However, if a large amount of filler is filled, the adhesiveness of the insulating layer tends to be low. Furthermore, the adhesive of the above-mentioned insulating adhesive material containing a large amount of filler is likely to be lowered and peeled off, particularly in applications where a member to be bonded provided with a fine wiring pattern is bonded for miniaturization and high performance. There is a problem that it is easy.

In order to impart high thermal conductivity to the insulating layer, a method of blending a filler such as alumina having high thermal conductivity with a thermal conductivity of 10 W / m · K or more is used in the insulating adhesive material. . Alumina is also used in the insulating adhesive described in Patent Document 2. However, the workability of the cured product of the insulating adhesive material containing alumina may be low.

The object of the present invention is used to adhere a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer, and can improve handling and storage stability in an uncured state, Furthermore, it is providing the insulating sheet which can make high heat dissipation of the hardened | cured material after hardening, and can also make adhesiveness of hardened | cured material high, and a laminated structure using this insulating sheet.

A limited object of the present invention is to provide a highly workable insulating sheet and a laminated structure using the insulating sheet. A further limited object of the present invention is to provide an insulating sheet having high adhesion of a cured product to a bonding target member provided with a fine wiring pattern, and a laminated structure using the insulating sheet.

A further limited object of the present invention is to provide an insulating sheet having high heat resistance, voltage resistance and moisture resistance, and a laminated structure using the insulating sheet.

According to a wide aspect of the present invention, there is provided an insulating sheet used for bonding a thermal conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer, wherein the polymer has a weight average molecular weight of 10,000 or more. A curable compound having a molecular weight of 1200 or less and having an epoxy group or an oxetanyl group, a curing agent, and an inorganic filler, and the content of the inorganic filler is 60% by weight or more in 100% by weight of the insulating sheet, 95% by weight or less, and in 100% by weight of the insulating sheet, the content of nitrogen atoms contained in the insulating sheet excluding the inorganic filler is 0.3% by weight or more and less than 3.0% by weight. An insulating sheet is provided.

In a specific aspect of the insulating sheet according to the present invention, at least one of the polymer, the curable compound, and the curing agent contains a nitrogen atom. On the other specific situation of the insulating sheet which concerns on this invention, the said hardening | curing agent contains a nitrogen atom.

The polymer preferably has an aromatic skeleton. Further, the curable compound preferably has an aromatic skeleton.
The polymer is preferably a phenoxy resin or an epoxy resin.

In another specific aspect of the insulating sheet according to the present invention, the curable compound has a hydroxyl group equivalent of 6000 or more.

The inorganic filler is preferably at least one selected from the group consisting of alumina, synthetic magnesite, crystalline silica, boron nitride, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, magnesium carbonate and magnesium oxide. . The inorganic filler preferably contains spherical alumina. The inorganic filler preferably contains alumina having a purity by fluorescent X-ray analysis of 90.0% or more and 99.0% or less. The inorganic filler preferably contains spherical alumina or crushed alumina having a purity by fluorescent X-ray analysis of 90.0% or more and 99.0% or less.

In another specific aspect of the insulating sheet according to the present invention, an elastomer that is a poly (meth) acrylic ester is further included. The elastomer is preferably a polymer using butyl (meth) acrylate.

The curing agent preferably contains at least one of dicyandiamide and imidazole compounds.
On the specific situation with the insulating sheet which concerns on this invention, the said hardening | curing agent contains a dicyandiamide. In another specific aspect of the insulating sheet according to the present invention, the curing agent includes an imidazole compound.

The laminated structure according to the present invention includes a heat conductor having a thermal conductivity of 10 W / m · K or more, an insulating layer laminated on at least one surface of the heat conductor, and the heat conduction of the insulating layer. A conductive layer laminated on the surface opposite to the surface on which the body is laminated, and the insulating layer is formed by curing an insulating sheet configured according to the present invention. The heat conductor is preferably a metal.

An insulating sheet according to the present invention includes a polymer having a weight average molecular weight of 10,000 or more, a curable compound having a molecular weight of 1200 or less and having an epoxy group or an oxetanyl group, a curing agent, and an inorganic filler. Content of the said inorganic filler in 100 weight% is 60 weight% or more and 95 weight%, Content of the nitrogen atom contained in the component except the said inorganic filler in 100 weight% of insulating sheets Is 0.3% by weight or more and less than 3.0% by weight, the handling property and storage stability of the insulating sheet in the uncured state can be increased, and the heat dissipation of the cured product after curing is further increased. And the adhesion of the cured product can be increased.

FIG. 1 is a partially cutaway front sectional view schematically showing a laminated structure according to an embodiment of the present invention.

Details of the present invention will be described below.
The insulating sheet which concerns on this invention is an insulating sheet used in order to adhere | attach the heat conductor whose heat conductivity is 10 W / m * K or more to a conductive layer. The insulating sheet according to the present invention includes a polymer (A) having a weight average molecular weight of 10,000 or more, a curable compound (B) having a molecular weight of 1200 or less and having an epoxy group or oxetanyl group, and a curing agent (C). And an inorganic filler (D). In 100% by weight of the insulating sheet, the content of the inorganic filler (D) is 60% by weight or more and 95% by weight or less. In 100% by weight of the insulating sheet, the content of nitrogen atoms contained in the component excluding the inorganic filler (D) in the insulating sheet is 0.3% by weight or more and less than 3.0% by weight.

By adopting the above composition, the handling property and storage stability of the insulating sheet in an uncured state can be increased, the heat dissipation of the cured product obtained by curing the insulating sheet can be increased, and the cured product Adhesiveness can also be increased. In particular, even if the adhesion target member contains copper, the adhesion of the cured product to the adhesion target member containing copper can be sufficiently increased. In particular, even if the content of the inorganic filler (D) is large and the content of the nitrogen atom is within the above range even when the content is 60% by weight or more, handling properties, storage stability, adhesiveness and heat dissipation are improved. The balance can be improved sufficiently. Furthermore, the conventional hardened | cured material of an insulating sheet has low adhesiveness with respect to the adhesion target member generally provided with the fine wiring pattern. Since the insulating sheet according to the present invention has the above composition, the adhesiveness of the cured product can be sufficiently increased even for a member to be bonded provided with fine wiring.

Furthermore, by adopting the above composition, the heat resistance, voltage resistance and moisture resistance of the cured product of the insulating sheet can be improved. In addition, by adopting the above composition, the workability of the cured product of the insulating sheet can be improved.

In 100% by weight of the insulating sheet, the content of nitrogen atoms contained in the component excluding the inorganic filler (D) in the insulating sheet is more preferably 0.4% by weight or more, more preferably 2% by weight or less. Preferably it is 1 weight% or less. When the content of the nitrogen atom is 0.4% by weight or more, the adhesion to copper and the adhesion to the adhesion target member provided with the fine wiring pattern are further enhanced. When the nitrogen atom content is 2.5% by weight or less, the storage stability of the insulating sheet in an uncured state is further enhanced.

The nitrogen atom content does not include the nitrogen atom content contained in the inorganic filler (D). The nitrogen atom content includes the nitrogen atom content contained in the polymer (A), the curable compound (B), and the curing agent (C). Furthermore, the content of nitrogen atoms includes the content of nitrogen atoms contained in the elastomer (E) described later. The nitrogen atom content is the nitrogen atom content in the components in the insulating sheet (excluding the inorganic filler (D)).

In order to enhance the handling property, storage stability, adhesiveness, heat resistance, voltage resistance and moisture resistance in a balanced manner, the insulating sheet according to the present invention includes a polymer (A), a curable compound (B), and a curing agent ( It is preferable that at least one of C) contains a nitrogen atom. The polymer (A) may or may not contain nitrogen. The curable compound (B) may or may not contain nitrogen. The curing agent (C) may or may not contain nitrogen. In order to improve the handling property, storage stability, adhesiveness, heat resistance, voltage resistance and moisture resistance in a balanced manner, in order to further improve the adhesiveness, it is preferable that the curing agent (C) contains a nitrogen atom. .

From the viewpoint of enhancing the flexibility of the cured product and further improving the reliability of the thermal cycle, the insulating sheet according to the present invention is a poly (meth) acrylic ester in addition to the components (A) to (D). It is preferable to further contain an elastomer (E). The elastomer (E) may or may not contain nitrogen atoms. (Meth) acrylic acid indicates acrylic acid and methacrylic acid.
Hereinafter, first, the detail of each component contained in the insulating sheet which concerns on this invention is demonstrated.

(Polymer (A))
The polymer (A) contained in the insulating sheet according to the present invention is not particularly limited as long as the weight average molecular weight is 10,000 or more. From the viewpoint of further improving the heat resistance of the cured product, the polymer (A) preferably has an aromatic skeleton. When the polymer (A) has an aromatic skeleton, the polymer (A) may have an aromatic skeleton in any part of the whole polymer, and may have in the main chain skeleton. , May be present in the side chain. The polymer (A) preferably has an aromatic skeleton in the main chain skeleton. In this case, the heat resistance of the cured product of the insulating sheet is further increased. As for a polymer (A), only 1 type may be used and 2 or more types may be used together.

The aromatic skeleton is not particularly limited. Specific examples of the aromatic skeleton include naphthalene skeleton, fluorene skeleton, biphenyl skeleton, anthracene skeleton, pyrene skeleton, xanthene skeleton, adamantane skeleton, and bisphenol A skeleton. Of these, a biphenyl skeleton or a fluorene skeleton is preferable. In this case, the heat resistance of the hardened | cured material of an insulating sheet becomes still higher.

As the polymer (A), a curable resin such as a thermoplastic resin and a thermosetting resin can be used. The polymer (A) is preferably a curable resin.
The thermoplastic resin and thermosetting resin are not particularly limited. Examples of the thermoplastic resin and thermosetting resin include thermoplastic resins such as polyphenylene sulfide, polyarylate, polysulfone, polyethersulfone, polyetheretherketone, and polyetherketone. In addition, as the thermoplastic resin and the thermosetting resin, thermoplastic polyimide, thermosetting polyimide, benzoxazine, and a heat-resistant resin group called super engineering plastics such as a reaction product of polybenzoxazole and benzoxazine, etc. Can be used. As for the said thermoplastic resin and the said thermosetting resin, only 1 type may respectively be used and 2 or more types may be used together. Either one of a thermoplastic resin and a thermosetting resin may be used, and a thermoplastic resin and a thermosetting resin may be used in combination.

The polymer (A) is preferably an epoxy resin, a styrene polymer, a (meth) acrylic polymer or a phenoxy resin, more preferably an epoxy resin or a phenoxy resin, and further preferably a phenoxy resin. . By using this preferable polymer, the cured product of the insulating sheet is hardly oxidized and deteriorated, and the heat resistance is further enhanced. In particular, the use of epoxy resin or phenoxy resin further increases the heat resistance of the cured product, and the use of phenoxy resin further increases the heat resistance of the cured product.

The epoxy resin is preferably an epoxy resin other than phenoxy resin. Examples of the epoxy resin include styrene skeleton-containing epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, biphenol type epoxy resin, naphthalene type epoxy resin, fluorene type epoxy resin. , Phenol aralkyl type epoxy resin, naphthol aralkyl type epoxy resin, dicyclopentadiene type epoxy resin, anthracene type epoxy resin, epoxy resin having adamantane skeleton, epoxy resin having tricyclodecane skeleton, and epoxy resin having triazine nucleus in skeleton Etc.

As the styrene polymer, specifically, a homopolymer of a styrene monomer, a copolymer of a styrene monomer and an acrylic monomer, or the like can be used. Of these, styrene polymers having a styrene-glycidyl methacrylate structure are preferred.

Examples of the styrene monomer include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, p-ethyl styrene, pn- Butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4-dimethyl Examples include styrene and 3,4-dichlorostyrene.

Examples of the acrylic monomer include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, Examples include butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate. It is done.

The phenoxy resin is specifically a resin obtained by reacting, for example, an epihalohydrin and a divalent phenol compound, or a resin obtained by reacting a divalent epoxy compound and a divalent phenol compound.

The phenoxy resin comprises a bisphenol A skeleton, a bisphenol F skeleton, a bisphenol A / F mixed skeleton, a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton, and a dicyclopentadiene skeleton. It is preferred to have at least one skeleton selected from the group. Among these, the phenoxy resin preferably has at least one skeleton selected from the group consisting of a bisphenol A skeleton, a bisphenol F skeleton, a bisphenol A / F mixed skeleton, a naphthalene skeleton, a fluorene skeleton, and a biphenyl skeleton. Preferably, it has at least one skeleton of a fluorene skeleton and a biphenyl skeleton. By using the phenoxy resin having these preferable skeletons, the heat resistance of the cured product of the insulating sheet is further increased.

The phenoxy resin preferably has a polycyclic aromatic skeleton in the main chain. The phenoxy resin preferably has at least one skeleton of the skeletons represented by the following formulas (11) to (16) in the main chain.

In the above formula (11), R _{1 s} may be the same or different and are a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom, and X ₁ is a single bond, having 1 to 7 divalent hydrocarbon group, —O—, —S—, —SO ₂ —, or —CO—.

In the above formula (12), R _1a may be the same or different and is a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom, and R ₂ is a hydrogen atom, carbon number 1 A hydrocarbon group having 1 to 10 carbon atoms or a halogen atom, R ₃ is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, and m is an integer of 0 to 5.

In the above formula (13), R _1b may be the same or different from each other, and is a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom, and R ₄ is the same or different from each other. It may be a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom, and l is an integer of 0 to 4.

In the above formula (15), R ₅ and R ₆ are a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogen atom, and X ₂ is —SO ₂ —, —CH ₂ —, —C (CH ₃ ) _2. -Or -O-, and k is 0 or 1.

As the polymer (A), for example, a phenoxy resin represented by the following formula (17) or the following formula (18) is preferably used.

In the above formula (17), A ₁ has a structure represented by any of the above formulas (11) to (13), and the structure thereof is 0 to 60 mol%, the structure represented by the above formula (12) is 5 to 95 mol%, and the structure represented by the above formula (13) is 5 to 95 mol%, and A ₂ is a hydrogen atom or the above formula And n ₁ is an average value of 25 to 500. In the formula (17), the structure represented by the formula (11) may not be included.

In the above formula (18), A ₃ has a structure represented by the above formula (15) or the above formula (16), and n ₂ is a value of at least 21 or more.
The glass transition temperature Tg of the polymer (A) is preferably 60 ° C. or higher, more preferably 90 ° C. or higher, preferably 200 ° C. or lower, more preferably 180 ° C. or lower. When the Tg of the polymer (A) is not less than the above lower limit, the resin is hardly thermally deteriorated. When the Tg of the polymer (A) is not more than the above upper limit, the compatibility between the polymer (A) and another resin is increased. As a result, the handling property of the insulating sheet in an uncured state is further improved, and the heat resistance of the cured product of the insulating sheet is further increased.

When the polymer (A) is a phenoxy resin, the glass transition temperature Tg of the phenoxy resin is preferably 95 ° C or higher, more preferably 110 ° C or higher, preferably 200 ° C or lower, more preferably 180 ° C or lower. When the Tg of the phenoxy resin is not less than the above lower limit, the thermal deterioration of the resin can be further suppressed. When the Tg of the phenoxy resin is not more than the above upper limit, the compatibility between the phenoxy resin and the other resin is increased. As a result, the handling property of the insulating sheet in an uncured state and the heat resistance of the cured product of the insulating sheet are further enhanced.

The weight average molecular weight of the polymer (A) is 10,000 or more. The weight average molecular weight of the polymer (A) is preferably 30000 or more, more preferably 40000 or more, preferably 1000000 or less, more preferably 250,000 or less. When the weight average molecular weight of the polymer (A) is not less than the above lower limit, the insulating sheet is hardly thermally deteriorated. When the weight average molecular weight of the polymer (A) is not more than the above upper limit, the compatibility between the polymer (A) and another resin is increased. As a result, the handling property of the insulating sheet in an uncured state is further improved, and the heat resistance of the cured product of the insulating sheet is further increased.

The polymer (A) may be added as a raw material, or may be a polymer produced by utilizing a reaction in each step such as stirring, coating, and drying during the production of the insulating sheet of the present invention. Good.

From the viewpoint of further improving the handleability of the insulating sheet in an uncured state, the hydroxyl group equivalent of the polymer (A) is preferably less than 6000. From the viewpoint of further improving the handleability of the insulating sheet in an uncured state, the hydroxyl equivalent of the polymer (A) is preferably 300 or more, more preferably 5500 or less, and even more preferably 5000 or less. It is preferable that the hydroxyl equivalent of the polymer (A) is not more than the above upper limit, and the hydroxyl equivalent of the curable compound (B) is not less than the lower limit described later.

The hydroxyl group equivalent of the polymer (A) is determined by calculating the amount of hydroxyl group based on the total amount of the polymer (A) by W mol% using a high performance liquid chromatograph mass spectrometer (LC-MS) or ¹ H-nuclear magnetic resonance spectrum ( ¹ H-NMR). As a value determined by the following formula.
Hydroxyl equivalent = (weight average molecular weight / W) × 100

The content of the polymer (A) is 20% by weight or more and 60% by weight or less in the total 100% by weight of the total resin components (hereinafter sometimes abbreviated as “total resin component X”) contained in the insulating sheet. It is preferable. The content of the polymer (A) in 100% by weight of the total resin component X is more preferably 30% by weight or more, and more preferably 50% by weight or less. When the content of the polymer (A) is at least the above lower limit, the handling properties of the insulating sheet in an uncured state are further improved. Dispersion | distribution of an inorganic filler (D) becomes easy that content of a polymer (A) is below the said upper limit. The total resin component X refers to the total of the polymer (A), the curable compound (B), the curing agent (C), and other resin components added as necessary. The total resin component X does not include the inorganic filler (D). The total resin component X includes an elastomer (E) that is a poly (meth) acrylic acid ester.

(Curable compound having epoxy group or oxetanyl group (B))
The curable compound (B) contained in the insulating sheet according to the present invention is not particularly limited as long as it has a molecular weight of 1200 or less and has an epoxy group or an oxetanyl group. As the curable compound (B) having an epoxy group or oxetanyl group, a conventionally known epoxy compound or oxetane compound can be used. The curable compound (B) is preferably a monomer. The curable compound (B) is cured by the action of the curing agent (C). As for a curable compound (B), only 1 type may be used and 2 or more types may be used together.

The curable compound (B) may contain an epoxy compound (B1) having an epoxy group, or may contain an oxetane compound (B2) having an oxetanyl group.
From the viewpoint of further improving the heat resistance and dielectric breakdown characteristics of the cured product, the curable compound (B) preferably has an aromatic skeleton.

Specific examples of the epoxy compound (B1) having an epoxy group include an epoxy monomer having a bisphenol skeleton, an epoxy monomer having a dicyclopentadiene skeleton, an epoxy monomer having a naphthalene skeleton, an epoxy monomer having an adamantane skeleton, and an epoxy having a fluorene skeleton. Examples of the monomer include an epoxy monomer having a biphenyl skeleton, an epoxy monomer having a bi (glycidyloxyphenyl) methane skeleton, an epoxy monomer having a xanthene skeleton, an epoxy monomer having an anthracene skeleton, and an epoxy monomer having a pyrene skeleton. These hydrogenated products or modified products may be used. As for an epoxy compound (B1), only 1 type may be used and 2 or more types may be used together.

Examples of the epoxy monomer having a bisphenol skeleton include an epoxy monomer having a bisphenol A type, bisphenol F type, or bisphenol S type bisphenol skeleton.

Examples of the epoxy monomer having a dicyclopentadiene skeleton include dicyclopentadiene dioxide and a phenol novolac epoxy monomer having a dicyclopentadiene skeleton.

Examples of the epoxy monomer having a naphthalene skeleton include 1-glycidylnaphthalene, 2-glycidylnaphthalene, 1,2-diglycidylnaphthalene, 1,5-diglycidylnaphthalene, 1,6-diglycidylnaphthalene, 1,7-diglycidyl. Examples include naphthalene, 2,7-diglycidylnaphthalene, triglycidylnaphthalene, and 1,2,5,6-tetraglycidylnaphthalene.

Examples of the epoxy monomer having an adamantane skeleton include 1,3-bis (4-glycidyloxyphenyl) adamantane and 2,2-bis (4-glycidyloxyphenyl) adamantane.

Examples of the epoxy monomer having a fluorene skeleton include 9,9-bis (4-glycidyloxyphenyl) fluorene, 9,9-bis (4-glycidyloxy-3-methylphenyl) fluorene, and 9,9-bis (4- Glycidyloxy-3-chlorophenyl) fluorene, 9,9-bis (4-glycidyloxy-3-bromophenyl) fluorene, 9,9-bis (4-glycidyloxy-3-fluorophenyl) fluorene, 9,9-bis (4-Glycidyloxy-3-methoxyphenyl) fluorene, 9,9-bis (4-glycidyloxy-3,5-dimethylphenyl) fluorene, 9,9-bis (4-glycidyloxy-3,5-dichlorophenyl) Fluorene and 9,9-bis (4-glycidyloxy-3,5-dibromophenyl) Fluorene, and the like.

Examples of the epoxy monomer having a biphenyl skeleton include 4,4'-diglycidylbiphenyl and 4,4'-diglycidyl-3,3 ', 5,5'-tetramethylbiphenyl.

Examples of the epoxy monomer having a bi (glycidyloxyphenyl) methane skeleton include 1,1′-bi (2,7-glycidyloxynaphthyl) methane, 1,8′-bi (2,7-glycidyloxynaphthyl) methane, 1,1′-bi (3,7-glycidyloxynaphthyl) methane, 1,8′-bi (3,7-glycidyloxynaphthyl) methane, 1,1′-bi (3,5-glycidyloxynaphthyl) methane 1,8'-bi (3,5-glycidyloxynaphthyl) methane, 1,2'-bi (2,7-glycidyloxynaphthyl) methane, 1,2'-bi (3,7-glycidyloxynaphthyl) And methane and 1,2′-bi (3,5-glycidyloxynaphthyl) methane.

Examples of the epoxy monomer having a xanthene skeleton include 1,3,4,5,6,8-hexamethyl-2,7-bis-oxiranylmethoxy-9-phenyl-9H-xanthene.

Specific examples of the oxetane compound (B2) having an oxetanyl group include, for example, 4,4′-bis [(3-ethyl-3-oxetanyl) methoxymethyl] biphenyl, 1,4-benzenedicarboxylate bis [(3- Ethyl-3-oxetanyl) methyl] ester, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, and oxetane-modified phenol novolac. As for an oxetane compound (B2), only 1 type may be used and 2 or more types may be used together.

The molecular weight of the curable compound (B) is 1200 or less. The molecular weight of the curable compound (B) is preferably 200 or more, preferably 600 or less, more preferably 550. When the molecular weight of the curable compound (B) is not less than the above lower limit, the volatility of the curable compound (B) is lowered, and the handleability of the insulating sheet is further enhanced. When the molecular weight of the curable compound (B) is not more than the above upper limit, the adhesiveness of the cured product is further enhanced. Furthermore, the insulating sheet is hard and not easily brittle, and the adhesiveness of the cured product is further enhanced.

In the present specification, the molecular weight in the curable compound (B) means a molecular weight that can be calculated from the structural formula when it is not a polymer and when the structural formula can be specified. Means weight average molecular weight.

From the viewpoint of further improving the handleability of the insulating sheet in the uncured state, the hydroxyl group equivalent of the curable compound (B) is preferably 6000 or more. In addition, when the hydroxyl equivalent of the curable compound (B) is 6000 or more, even if curing proceeds during storage, the insulating sheet does not crack at the time of handling, and the insulating sheet in an uncured state Storage stability is also sufficiently high.

From the viewpoint of further improving the handleability and storage stability of the insulating sheet in an uncured state, the hydroxyl equivalent of the curable compound (B) is more preferably 6500 or more, further preferably 7000 or more, and particularly preferably 15000. That's it.

The hydroxyl group equivalent of the curable compound (B) is determined by the amount of hydroxyl group relative to the entire curable compound (B) by high performance liquid chromatography mass spectrometer (LC-MS) or ¹ H-nuclear magnetic resonance spectrum ( ¹ H-NMR). Is a value determined by the following formula.
Hydroxyl equivalent = (weight average molecular weight / W) × 100

In the total 100% by weight of all the resin components X, the content of the curable compound (B) is preferably 10% by weight or more and 60% by weight or less. The content of the curable compound (B) in 100% by weight of the total resin component X is more preferably 20% by weight or more, and more preferably 50% by weight or less. When the content of the curable compound (B) is not less than the above lower limit, the adhesiveness and heat resistance of the cured product are further increased. When the content of the curable compound (B) is not more than the above upper limit, the handling property of the insulating sheet is further enhanced.

(Curing agent (C))
The curing agent (C) contained in the insulating sheet according to the present invention is not particularly limited as long as the insulating sheet can be cured. The curing agent (C) is preferably a thermosetting agent. As for a hardening | curing agent (C), only 1 type may be used and 2 or more types may be used together.

In order to improve the handling property, storage stability, adhesiveness, heat resistance, voltage resistance and moisture resistance in a well-balanced manner and to further improve the adhesiveness, the curing agent (C) is a dicyandiamide and imidazole compound. It is preferable to contain at least one of the above, more preferably dicyandiamide, and more preferably both dicyandiamide and an imidazole compound. By using a dicyandiamide or an imidazole compound, it is easy to contain a lot of nitrogen atoms in the insulating sheet. The curing agent (C) may be dicyandiamide or an imidazole compound. By using dicyandiamide, the adhesiveness of the cured product of the insulating sheet is further enhanced. From the viewpoint of further improving the heat resistance of the cured product and shortening the curing time, the curing agent (C) preferably contains an imidazole compound.

Examples of the imidazole compound include 2-undecylimidazole, 2-heptadecylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl- 2-methylimidazole, 1-benzyl-2-phenylimidazole, 1,2-dimethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-un Decylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6- [2 ' -Mechi Imidazolyl- (1 ′)]-ethyl-s-triazine, 2,4-diamino-6- [2′-undecylimidazolyl- (1 ′)]-ethyl-s-triazine, 2,4-diamino-6- [2′-Ethyl-4′-methylimidazolyl- (1 ′)]-ethyl-s-triazine, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine Isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-dihydroxymethylimidazole, etc. Can be mentioned.

From the viewpoint of effectively improving the handling property and storage stability of the insulating sheet in an uncured state, and the adhesiveness of the cured product, the content of nitrogen atoms is preferably 10 in 100% by weight of all atoms in the curing agent. % By weight or more, more preferably 20% by weight or more, preferably 30% by weight or more, more preferably 80% by weight or less.

From the viewpoint of effectively enhancing the handleability and storage stability of the insulating sheet in an uncured state and the adhesiveness of the cured product, the content of nitrogen atoms contained in the curing agent (C) in 100% by weight of the insulating sheet The amount is preferably 0.3% by weight or more, more preferably 0.4% by weight or more, more preferably 2% by weight or less.

When the curing agent (C) is only an imidazole compound, the content of nitrogen atoms contained in the imidazole compound in the insulating sheet 100% by weight is preferably 1.3% by weight or more, more preferably 2% by weight. % Or more.

In the total 100% by weight of all the resin components X, the content of the curing agent (C) is preferably 10% by weight or more and 40% by weight or less. In the total 100% by weight of all the resin components X, the content of the curing agent (C) is more preferably 12% by weight or more, and more preferably 25% by weight or less. When the content of the curing agent (C) is not less than the above lower limit, it is easy to sufficiently cure the insulating sheet. When the content of the curing agent (C) is not more than the above upper limit, it becomes difficult to generate an excessive curing agent (C) that does not participate in curing. For this reason, the heat resistance and adhesiveness of hardened | cured material become still higher.

Dicyandiamide in a total of 100% by weight of the total resin component X in order to improve the handling property, storage stability, adhesiveness, heat resistance, voltage resistance and moisture resistance in a balanced manner and to further improve the adhesiveness. The total content of imidazole and imidazole compound is preferably 10% by weight or more, more preferably 12% by weight or more, preferably 40% by weight or less, more preferably 25% by weight or less.

When dicyandiamide and imidazole compound are used in combination, the insulating sheet preferably contains dicyandiamide and imidazole compound in a weight ratio of 1:99 to 99: 1, and 90:10 to 10:90. More preferred. When the blending ratio of dicyandiamide and imidazole compound is within the above range, handling property, storage stability, adhesiveness, heat resistance, voltage resistance, and moisture resistance can be effectively improved in a balanced manner, and further adhesiveness can be improved. Can be further increased.

(Inorganic filler (D))
The inorganic filler (D) contained in the insulating sheet according to the present invention is not particularly limited as long as the thermal conductivity is 10 W / m · K or more. By using this inorganic filler (D), the thermal conductivity of the cured product can be increased. As a result, the heat dissipation of the cured product is increased. As for an inorganic filler (D), only 1 type may be used and 2 or more types may be used together.

If the thermal conductivity of the inorganic filler (D) is smaller than 10 W / m · K, it is difficult to sufficiently increase the thermal conductivity of the cured product. The thermal conductivity of the inorganic filler (D) is preferably 15 W / m · K or more, more preferably 20 W / m · K or more. The upper limit of the thermal conductivity of the inorganic filler (D) is not particularly limited. Inorganic fillers having a thermal conductivity of about 300 W / m · K are widely known, and inorganic fillers having a thermal conductivity of about 200 W / m · K are easily available.

The inorganic filler (D) is at least one selected from the group consisting of alumina, synthetic magnesite, crystalline silica, boron nitride, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, magnesium carbonate and magnesium oxide. Is preferable, and at least one selected from the group consisting of alumina, crystalline silica, boron nitride, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, magnesium carbonate and magnesium oxide is more preferable. By using these preferable fillers, the heat dissipation of the cured product can be further enhanced. The magnesium carbonate is different from synthetic magnesite.

The inorganic filler (D) is preferably at least one selected from the group consisting of spherical alumina, crushed alumina and spherical aluminum nitride, and more preferably spherical alumina or spherical aluminum nitride. By using these preferable fillers, the heat dissipation of the cured product can be further enhanced.

The inorganic filler (D) may be a spherical filler or a crushed filler. The inorganic filler (D) is particularly preferably spherical. In the case of a spherical filler, since it can be filled with high density, the heat dissipation of the cured product is further enhanced.

In order to effectively improve the heat dissipation and workability of the cured product, the inorganic filler (D) preferably contains spherical alumina. The inorganic filler (D) preferably contains 50% by weight or more of spherical alumina, preferably 75% by weight or more, and contains 100% by weight or less. All of the inorganic filler (D) may be spherical alumina.

In order to effectively improve the heat dissipation and workability of the cured product, the inorganic filler (D) is made of alumina having a purity (alumina purity) by fluorescent X-ray analysis of 90.0% or more and 99.0% or less. It is preferable to include. In addition, when the purity exceeds 99.0%, the workability tends to be low. When the purity is 90.0% or more, the heat dissipation of the cured product is further enhanced. The inorganic filler (D) preferably contains 50% by weight or more of alumina having a purity of 90.0 to 99.0%, preferably 75% by weight or more, and contains 100% by weight or less. All of the inorganic fillers (D) may be alumina having a purity of 90.0 to 99.0%. The purity (%) is the content (%) of alumina in 100% of the inorganic filler which is alumina to be blended. In other words, alumina whose purity by fluorescent X-ray analysis is 90.0% or more and 99.0% or less is an inorganic substance whose purity by alumina X-ray analysis is 90.0% or more and 99.0% or less. It is a filler.

In order to further improve the workability of the cured product, the inorganic filler (D) preferably contains spherical alumina or crushed alumina whose purity by fluorescent X-ray analysis is 90.0% or more and 99.0% or less. . The inorganic filler (D) preferably contains 50% by weight or more of spherical alumina or crushed alumina having a purity of 90.0 to 99.0%, preferably 75% by weight or more, and contains 100% by weight or less. All of the inorganic fillers (D) may be spherical alumina or crushed alumina having a purity of 90.0 to 99.0%.

Crushed filler may be mentioned as the crushed filler. The crushed filler can be obtained, for example, by crushing a massive inorganic substance using a uniaxial crusher, a biaxial crusher, a hammer crusher, a ball mill, or the like. By using the crushed filler, the filler in the insulating sheet is likely to have a structure that is bridged or effectively brought close together. Therefore, the thermal conductivity of the cured product of the insulating sheet is further increased. Moreover, the crushed filler is generally cheaper than a normal filler. For this reason, the cost of an insulating sheet can be reduced by using the crushed filler.

The average particle size of the crushed filler is preferably 12 μm or less. When the average particle size is 12 μm or less, it is easy to disperse the crushed filler in the insulating sheet at a high density, and the dielectric breakdown characteristics of the cured product of the insulating sheet are further enhanced. The average particle size of the crushed filler is more preferably 10 μm or less, and preferably 1 μm or more. When the average particle size of the crushed filler is not less than the above lower limit, it is easy to fill the crushed filler with high density.

The aspect ratio of the crushed filler is not particularly limited. The aspect ratio of the crushed filler is preferably 1.5 or more and 20 or less. Fillers with an aspect ratio of less than 1.5 are relatively expensive. Therefore, the cost of the insulating sheet increases. When the aspect ratio is 20 or less, filling of the crushed filler is easy.

The aspect ratio of the crushed filler can be determined, for example, by measuring the crushed surface of the filler using a digital image analysis type particle size distribution measuring device (trade name: FPA, manufactured by Nippon Luft).

When the inorganic filler (D) is a spherical filler, the average particle diameter of the spherical filler is preferably 0.1 μm or more and 40 μm or less. When the average particle size is 0.1 μm or more, the inorganic filler (D) can be easily filled at a high density. When the average particle size is 40 μm or less, the dielectric breakdown characteristics of the cured product are further enhanced.

The above-mentioned “average particle diameter” is an average particle diameter obtained from a volume average particle size distribution measurement result measured with a laser diffraction particle size distribution measuring apparatus.

The new Mohs hardness of the inorganic filler (D) is preferably 12 or less, more preferably 9 or less. When the new Mohs hardness of the inorganic filler (D) is 9 or less, the workability of the cured product is further enhanced.

From the viewpoint of further improving the workability of the cured product, since the new Mohs hardness is 9 or less, the inorganic filler (D) was selected from the group consisting of synthetic magnesite, crystalline silica, zinc oxide, and magnesium oxide. It is preferable that there is at least one.

In order to sufficiently improve the heat dissipation of the cured product, the content of the inorganic filler (D) in 100% by weight of the insulating sheet is 60% by weight or more. Moreover, content of the inorganic filler (D) in 100 weight% of insulating sheets is 95 weight% or less. The content of the inorganic filler (D) in 100% by weight of the insulating sheet is preferably 90% by weight or less, more preferably 85% by weight or less, still more preferably 80% by weight or less, and particularly preferably 70% by weight or less. When the content of the inorganic filler (D) is not more than the above upper limit, the handling property of the insulating sheet and the workability of the cured product are further enhanced.

(Elastomer (E))
The elastomer (E) contained in the insulating sheet according to the present invention is a poly (meth) acrylic ester. The elastomer (E) that is the poly (meth) acrylate is not particularly limited. As the elastomer (E), for example, a conventionally known poly (meth) acrylic acid ester elastomer and particulate poly (meth) acrylic acid ester as a core and the core covered with a shell can be used. Elastomers are compounds that exhibit rubber elasticity near room temperature. Only one type of elastomer (E) may be used, or two or more types may be used in combination.

As a polymerization component for obtaining an elastomer (E) which is a poly (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate Hexyl (meth) acrylate and 2-ethylhexyl (meth) acrylate.

Other examples of polymerization components for obtaining an elastomer (E) that is a poly (meth) acrylic acid ester include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and maleic anhydride And epoxy group-containing monomers such as glycidyl acrylate and allyl glycidyl ether.

From the viewpoint of further improving the thermal cycle reliability of the cured product, the elastomer (E) which is a poly (meth) acrylic acid ester is preferably a polymer using butyl (meth) acrylate, and butyl methacrylate is used. More preferred is a polymer. The “polymer” includes a copolymer.

The elastomer (E) may be included in the form of rubber particles. By adding the elastomer (E) in the form of rubber particles, the stress relaxation property and flexibility of the insulating sheet can be enhanced without impairing the heat resistance.

In the total 100% by weight of all the resin components X, the content of the elastomer (E) is preferably 1% by weight or more, more preferably 3% by weight or more, and preferably 30% by weight or less. When the content of the elastomer (E) is equal to or more than the above lower limit, the flexibility of the cured product is further increased, and the cooling cycle reliability is further increased. When the content of the elastomer (E) is not more than the above upper limit, the heat resistance of the cured product is further increased.

(Other ingredients)
The insulating sheet according to the present invention may contain a dispersant. Use of the dispersant can further enhance the thermal conductivity and dielectric breakdown characteristics of the cured product.

The dispersant preferably has a functional group containing a hydrogen atom having hydrogen bonding properties. When the dispersing agent has a functional group containing a hydrogen atom having hydrogen bonding properties, the thermal conductivity and dielectric breakdown characteristics of the cured product can be further enhanced. Examples of the functional group containing a hydrogen atom having hydrogen bonding include a carboxyl group (pKa = 4), a phosphoric acid group (pKa = 7), a phenol group (pKa = 10), and the like.

The pKa of the functional group containing a hydrogen atom having hydrogen bonding property is preferably 2 or more, more preferably 3 or more, preferably 10 or less, more preferably 9 or less. When the pKa of the functional group is not less than the lower limit, the acidity of the dispersant does not become too high. Therefore, the storage stability of the insulating sheet is further enhanced. When the pKa of the functional group is not more than the above upper limit, the function as the dispersant is sufficiently fulfilled, and the thermal conductivity and dielectric breakdown characteristics of the cured product are further enhanced.

The functional group containing a hydrogen atom having hydrogen bonding properties is preferably a carboxyl group or a phosphate group. In this case, the thermal conductivity and dielectric breakdown characteristics of the cured product are further enhanced.

Specific examples of the dispersant include a polyester carboxylic acid, a polyether carboxylic acid, a polyacrylic carboxylic acid, an aliphatic carboxylic acid, a polysiloxane carboxylic acid, a polyester phosphoric acid, and a polyether type. Examples thereof include phosphoric acid, polyacrylic phosphoric acid, aliphatic phosphoric acid, polysiloxane phosphoric acid, polyester phenol, polyether phenol, polyacrylic phenol, aliphatic phenol, and polysiloxane phenol. As for the said dispersing agent, only 1 type may be used and 2 or more types may be used together.

In the total 100% by weight of the total resin component X, the content of the dispersant is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 20% by weight or less, more preferably 10% by weight. % By weight or less. When the content of the dispersant is not less than the above lower limit and not more than the upper limit, aggregation of the inorganic filler (D) is difficult to occur, and the heat dissipation and dielectric breakdown characteristics of the cured product are further enhanced.

In order to further improve the handleability, the insulating sheet according to the present invention may contain a base material such as glass cloth, glass nonwoven fabric, and aramid nonwoven fabric. However, even if the base material is not included, the insulating sheet has a self-supporting property at room temperature (23 ° C.) and an excellent handling property. Therefore, the insulating sheet preferably does not contain a base material, and particularly preferably does not contain glass cloth. When an insulating sheet does not contain the said base material, the thickness of an insulating sheet can be made thin and the thermal conductivity of hardened | cured material can be improved further. Furthermore, when an insulating sheet does not contain the said base material, various processes, such as a laser processing or a drilling process, can also be easily performed to an insulating sheet as needed. In addition, self-supporting means that the shape of a sheet can be maintained and handled as a sheet even if there is no support such as a PET film or copper foil.

Furthermore, the insulating sheet according to the present invention may contain a tackifier, a plasticizer, a coupling agent, a thixotropic agent, a flame retardant, a photosensitizer, a colorant, and the like as necessary.

(Insulating sheet)
The insulating sheet according to the present invention is used for bonding a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer.
The manufacturing method of the insulating sheet which concerns on this invention is not specifically limited. The insulating sheet can be obtained, for example, by forming a mixture obtained by mixing the above-described materials into a sheet shape by a method such as a solvent casting method or an extrusion film forming method. Defoaming is preferred when forming into a sheet.

The thickness of the insulating sheet is not particularly limited. The thickness of the insulating sheet is preferably 10 μm or more, more preferably 50 μm or more, further preferably 70 μm or more, preferably 300 μm or less, more preferably 200 μm or less, and still more preferably 120 μm or less. When the thickness is not less than the above lower limit, the insulating property of the cured product of the insulating sheet is increased. When the thickness is less than or equal to the above upper limit, the heat dissipation becomes high when the metal body is bonded to the conductive layer.

The glass transition temperature Tg of the insulating sheet in the uncured state is preferably 25 ° C. or lower. When the glass transition temperature is 25 ° C. or lower, the insulating sheet is hard and not easily brittle at room temperature. For this reason, the handleability of the insulating sheet in an uncured state is enhanced.

The thermal conductivity of the cured product of the insulating sheet is preferably 0.7 W / m · K or more, more preferably 1.0 W / m · K or more, and further preferably 1.5 W / m · K or more. The heat dissipation of the hardened | cured material of an insulating sheet becomes high enough that heat conductivity is more than the said minimum.

The dielectric breakdown voltage of the cured product of the insulating sheet is preferably 25 kV / mm or more, more preferably 30 kV / mm or more, still more preferably 40 kV / mm or more, still more preferably 50 kV / mm or more, and particularly preferably 80 kV / mm or more. It is. If the dielectric breakdown voltage is too low, the insulating property may be lowered when the insulating sheet is used for a large current application such as for a power element.

(Laminated structure)
The insulating sheet according to the present invention constitutes an insulating layer of a laminated structure in which a conductive layer is laminated on at least one surface of a heat conductor having a thermal conductivity of 10 W / m · K or more via an insulating layer. Is preferably used.

In FIG. 1, an example of the laminated structure using the insulating sheet which concerns on one Embodiment of this invention is shown.
The laminated structure 1 shown in FIG. 1 includes a heat conductor 2, an insulating layer 3 laminated on the first surface 2a of the heat conductor 2, and a surface on which the heat conductor 2 of the insulating layer 3 is laminated. And a conductive layer 4 laminated on the opposite surface. The insulating layer and the conductive layer are not laminated on the second surface 2b opposite to the first surface 2a of the heat conductor 2. The insulating layer 3 is formed by curing the insulating sheet according to the present invention. The heat conductivity of the heat conductor 2 is 10 W / m · K or more.

It is sufficient that the insulating layer and the conductive layer are laminated in this order on at least one surface of the heat conductor, and the insulating layer and the conductive layer are laminated in this order on the other surface of the heat conductor. Good.
In the laminated structure 1, since the insulating layer 3 has a high thermal conductivity, heat from the conductive layer 4 side is easily transmitted to the thermal conductor 2 through the insulating layer 3. In the laminated structure 1, heat can be efficiently dissipated by the heat conductor 2.

For example, after bonding a metal body to each conductive layer such as a laminated board or multilayer wiring board provided with copper circuits on both sides, copper foil, copper plate, semiconductor element or semiconductor package via an insulating sheet, the insulating sheet is cured. By doing so, the laminated structure 1 can be obtained.

The thermal conductor having a thermal conductivity of 10 W / m · K or more is not particularly limited. Examples of the heat conductor having a thermal conductivity of 10 W / m · K or more include aluminum, copper, alumina, beryllia, silicon carbide, silicon nitride, aluminum nitride, and graphite sheet. Especially, it is preferable that the heat conductor whose said heat conductivity is 10 W / m * K or more is copper or aluminum. Copper or aluminum is excellent in heat dissipation.

The insulating sheet according to the present invention is suitably used for bonding a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer of a semiconductor device in which a semiconductor element is mounted on a substrate.
The insulating sheet according to the present invention adheres a heat conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer of an electronic component device in which electronic component elements other than semiconductor elements are mounted on a substrate. Also preferably used.

When the semiconductor element is a power device element for a large current, the cured product of the insulating sheet is required to be more excellent in insulation or heat resistance. Therefore, the insulating sheet of this invention is used suitably for such a use.

Hereinafter, the present invention will be clarified by giving specific examples and comparative examples of the present invention. The present invention is not limited to the following examples.
The following materials were prepared.

[Polymer (A)]
(1) Epoxy group-containing styrene resin (manufactured by NOF Corporation, trade name: Marproof G-1010S, Mw = 100000, Tg = 93 ° C.)
(2) Bisphenol A type phenoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: E1256, Mw = 51000, Tg = 98 ° C.)
(3) High heat resistant phenoxy resin (trade name FX-293, manufactured by Toto Kasei Co., Ltd., Mw = 43700, Tg = 163 ° C.)

[Other polymers other than polymer (A)]
(1) Epoxy group-containing acrylic resin (manufactured by NOF Corporation, trade name: Marproof G-0130S, Mw = 9000, Tg = 69 ° C.)

[Curable compound (B)]
(1) Bisphenol A type liquid epoxy resin (Mitsubishi Chemical make, brand name: Epicoat 828US, Mw = 370, hydroxyl group equivalent 8800)
(2) Bisphenol F type liquid epoxy resin (Mitsubishi Chemical make, brand name: Epicoat 806L, Mw = 370, hydroxyl group equivalent 7500)
(3) Trifunctional glycidyldiamine type liquid epoxy resin (Mitsubishi Chemical Co., Ltd., trade name: Epicoat 630, Mw = 300, hydroxyl group equivalent 8200, nitrogen atom content 16% by weight)
(4) Fluorene skeleton epoxy resin (manufactured by Osaka Gas Chemical Co., Ltd., trade name: ONCOAT EX1011, Mw = 486, hydroxyl group equivalent 8500)
(5) Naphthalene skeleton liquid epoxy resin (manufactured by DIC, trade name EPICLON HP-4032D, Mw = 304, hydroxyl group equivalent 7000)

[Other curable compounds other than the curable compound (B)]
(1) Bisphenol A type solid epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: 1003, Mw = 1300, hydroxyl group equivalent 380)

[Curing agent (C)]
(1) Dicyandiamide (Nippon Carbite, trade name: DD, nitrogen atom content 66.6% by weight)
(2) Isocyanur-modified solid dispersion type imidazole (imidazole curing accelerator, manufactured by Shikoku Kasei Co., Ltd., trade name: 2MZA-PW, nitrogen atom content 44.7% by weight)
(3) Biphenyl skeleton phenol resin (Madewa Kasei Co., Ltd., trade name: MEH-7851-S)

[Inorganic filler (D)]
(1) Crushed alumina 1 (manufactured by Nippon Light Metal Co., Ltd., trade name: LS-242C, average particle size 2 μm, purity 99.9% by X-ray fluorescence analysis, thermal conductivity 36 W / m · K, new Mohs hardness 12)
(2) Crushed Alumina 2 (Kinsei Matec Co., Ltd., trade name: Seraph 02050, average particle size 2 μm, purity 98.2% by X-ray fluorescence analysis, thermal conductivity 36 W / m · K, new Mohs hardness 12)
(3) Spherical alumina (Denka Co., Ltd., trade name: DAM-10, average particle size 10 μm, purity 99.9% by X-ray fluorescence analysis, thermal conductivity 36 W / m · K, new Mohs hardness 12)
(4) Crystalline silica (manufactured by Tatsumori Co., Ltd., trade name: Crystallite CMC-12, average particle size 5 μm, thermal conductivity 10 W / m · K, new Mohs hardness 9)
(5) Boron nitride (manufactured by Showa Denko KK, trade name: UHP-1, average particle size 8 μm, thermal conductivity 60 W / m · K, new Mohs hardness 2)
(6) Aluminum nitride (manufactured by Toyo Aluminum Co., Ltd., trade name: TOYALNITE-FLX, average particle size 14 μm, thermal conductivity 200 W / m · K, new Mohs hardness 11)
(7) Silicon carbide (manufactured by Shinano Electric Smelting Co., Ltd., trade name: Shinano Random GP # 700, average particle diameter 17 μm, thermal conductivity 125 W / m · K, new Mohs hardness 13)

[Elastomer (E) which is a poly (meth) acrylic ester]
(1) MMA / BMA elastomer (manufactured by Mitsubishi Rayon Co., Ltd., trade name: KW4426, rubber fine particles having a shell formed of methyl methacrylate and a core formed of n-butyl methacrylate, average particle size of 5 μm)
(2) BMA elastomer (a polymer using n-butyl methacrylate, manufactured by Negami Kogyo Co., Ltd., trade name: Hyperl M-6003)
(3) Acrylic polymer (butyl acrylate / ethyl acrylate / acrylonitrile terpolymer, manufactured by Nagase Chemtech Co., Ltd., trade name: WS-023)

[Additive]
(1) Epoxysilane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBE403)

[solvent]
(1) Methyl ethyl ketone

(Examples 1 to 22 and Comparative Examples 1 to 5)
Using a homodisper type stirrer, each raw material was blended in the proportions shown in Tables 1 and 2 below (blending unit is parts by weight) and kneaded to prepare an insulating material.
The insulating material was applied to a release PET sheet having a thickness of 50 μm so as to have a thickness of 100 μm, and dried in an oven at 90 ° C. for 30 minutes to produce an insulating sheet on the PET sheet.

(Evaluation)
(1) Nitrogen atom content An uncured insulation sheet was thermally decomposed at a sample furnace temperature of 950 ° C. using a micro coder JM-10 manufactured by J Science Lab. The content (% by weight) of nitrogen atoms contained in the components excluding the inorganic filler in the sheet was measured.

(2) Handling property A laminate sheet having a PET sheet and an insulating sheet formed on the PET sheet was cut into a size of 460 mm x 610 mm to obtain a test sample. Using the obtained test sample, the handling property when the uncured insulating sheet was peeled from the PET sheet at room temperature (23 ° C.) was evaluated according to the following criteria.

[Handling criteria]
○: The insulating sheet is not deformed and can be easily peeled. Δ: The insulating sheet can be peeled, but the sheet is stretched or broken. ×: The insulating sheet cannot be peeled.

(3) Storage stability A laminate sheet having a PET sheet and an insulating sheet formed on the PET sheet was cut into a size of 460 mm × 610 mm to obtain a test sample. The obtained test sample was left in an oven at 50 ° C. for 24 hours. Using the test sample after being left for 24 hours, the handling property when the uncured insulating sheet was peeled from the PET sheet at room temperature (23 ° C.) was evaluated, and the storage stability was determined according to the following criteria.

[Criteria for storage stability]
◯: Insulation sheet is not deformed and can be easily peeled △: Insulation sheet can be peeled off, but chipping or cracking occurs during peeling ×: Chipping or cracking occurs during peeling and the insulating sheet cannot be peeled off

(4) Glass transition temperature Using a differential scanning calorimeter “DSC220C” (manufactured by Seiko Instruments Inc.), the glass transition temperature of the insulating sheet in an uncured state was measured at a temperature rising rate of 3 ° C./min.
(5) Thermal conductivity The thermal conductivity of the insulating sheet was measured using a thermal conductivity meter “Quick Thermal Conductivity Meter QTM-500” manufactured by Kyoto Electronics Industry Co., Ltd.

(6) Peel strength A (adhesiveness)
An insulating sheet is sandwiched between an aluminum plate having a thickness of 1 mm and a middle profile electrolytic copper foil having a thickness of 35 μm, and the insulating sheet is held at 120 ° C. for 1 hour and further at 200 ° C. for 1 hour while maintaining a pressure of 4 MPa with a vacuum press. Press-cured to form a copper-clad laminate. The copper foil of the obtained copper-clad laminate was etched to form a copper foil strip having a width of 10 mm. The copper foil was peeled from the substrate at an angle of 90 ° C. at a pulling rate of 50 mm / min, and the peel strength A was measured.

(7) Solder heat resistance test (heat resistance)
The copper-clad laminate obtained by the evaluation of (6) peeling strength A was cut out to a size of 50 mm × 60 mm to obtain a test sample. The obtained test sample was floated in a solder bath at 288 ° C. with the copper foil side facing down, and the time until the copper foil swelled or peeled off was measured and judged according to the following criteria.

[Criteria for solder heat resistance test]
○: No swelling or peeling even after 3 minutes △: Swelling or peeling occurs after 1 minute and before 3 minutes ×: Swelling or peeling occurs before 1 minute

(8) Moisture resistance The copper-clad laminate obtained by the evaluation of the above (6) peel strength A was cut into a size of 100 mm × 100 mm, and the copper foil was peeled off to obtain a test sample. The obtained test sample was left in an autoclave at 121 ° C., 2 atm and 100% relative humidity for 24 hours, and then the moisture resistance was evaluated by the presence or absence of occurrence of swelling or peeling of the cured product from the aluminum plate. The moisture resistance was determined according to the following criteria.

[Criteria for moisture resistance]
○: After 24 hours, no change Δ: After 24 hours, there is one bulge ×: After 24 hours, there are two or more bulges or peeling

(9) Dielectric breakdown voltage (withstand voltage)
The insulating sheet was cut into a size of 100 mm × 100 mm to obtain a test sample. The obtained test sample was cured in an oven at 120 ° C. for 1 hour and further in an oven at 200 ° C. for 1 hour to obtain a cured product of an insulating sheet. An AC voltage was applied using a withstand voltage tester (MODEL7473, manufactured by EXTECH Electronics) so that the voltage increased at a rate of 1 kV / second between the cured products of the insulating sheet. The voltage at which the cured product of the insulating sheet was broken was defined as the dielectric breakdown voltage.

(10) Workability (6) Using a drill with a diameter of 2.0 mm (RA series), a copper-clad laminate obtained by the evaluation of the peel strength A, the rotational speed of 30000 and table feed Router processing was performed at a speed of 0.5 m / min. The processing distance until the flash was generated was measured, and the workability was evaluated according to the following criteria.

[Criteria for workability]
A: Processing is possible for 20 m or more without generating burr B: Processing is possible for 10 m or more and less than 20 m without generating burr C: Processing is possible for 5 m or more and less than 10 m without generating burr D: Without generating burr 1m or more and less than 5m can be processed. E: Burrs are generated by processing less than 1m.

(11) Cooling cycle test The copper-clad laminate obtained by the evaluation of the above (6) peel strength A was cut into a size of 100 mm × 100 mm and the copper foil was peeled off to obtain a test sample.
Using the test sample, a 500-cycle or 1000-cycle thermal cycle test is performed using a one-chamber type thermal cycle tester (WINTECH NT510, manufactured by ETACH) at -40 ° C, 20 minutes, and 125 ° C for 20 minutes. It was. The presence or absence of cracks on the surface of the insulating layer formed by the insulating sheet after the test was observed with an optical microscope (TRANSFORMER-XN, manufactured by Nikon). Further, the presence or absence of peeling of the insulating layer after the test was observed with an ultrasonic flaw detector (mi-scope hyper, manufactured by Hitachi Construction Machinery Finetech). The number of test samples in which cracks or peeling occurred in 10 test samples was counted and judged according to the following criteria.

[Evaluation criteria for presence or absence of cracks or peeling after cooling cycle test]
○○: Test specimens with cracks or peeling out of 10 specimens, 0 specimens ○: Test specimens with cracking or peeling out of 10 specimens, 1 to 2 specimens Δ: Test specimens with cracks or peeling off in 10 specimens Medium, 3 to 4 specimens ×: 5 or more specimens out of 10 specimens where cracks or peeling occurred

Tables 1 and 2 below show the composition and evaluation results of the insulating material for forming the insulating sheet. * 1 indicates the content (% by weight) of the total resin component X in a total of 100% by weight. * 2 indicates the content (% by weight) of nitrogen atoms contained in the component excluding the inorganic filler in the insulating sheet in 100% by weight of the insulating sheet. “-” Indicates that evaluation is not performed.

For the insulating sheets obtained in Examples 1, 11, and 12, the following peel strength B (adhesiveness) was also evaluated. In addition, as compared with the above-described peeling strength A, in the evaluation of the following peeling strength B, since a fine wiring pattern is formed, the adhesiveness is hardly exhibited.

(6-2) Peel strength B (adhesiveness)
An insulating sheet is sandwiched between an aluminum plate having a thickness of 1 mm and a low profile electrolytic copper foil having a thickness of 18 μm, and the insulating sheet is held at 120 ° C. for 1 hour and further at 200 ° C. for 1 hour while maintaining a pressure of 4 MPa with a vacuum press. Press-cured to form a copper-clad laminate. The copper foil of the obtained copper-clad laminate was etched to form a copper foil strip having a width of 10 mm. The copper foil was peeled from the substrate at an angle of 90 ° C. at a pulling rate of 50 mm / min, and the peel strength B was measured.
The results are shown in Table 3 below.

From the results shown in Table 3, it can be seen that when spherical alumina is used, the adhesion of the cured product to the bonding target member provided with a fine wiring pattern is higher than when crushed alumina is used.

DESCRIPTION OF SYMBOLS 1 ... Laminated structure 2 ... Thermal conductor 2a ... 1st surface 2b ... 2nd surface 3 ... Insulating layer 4 ... Conductive layer

Claims (18)

1. An insulating sheet used for bonding a thermal conductor having a thermal conductivity of 10 W / m · K or more to a conductive layer,
   A polymer having a weight average molecular weight of 10,000 or more;
   A curable compound having a molecular weight of 1200 or less and having an epoxy group or an oxetanyl group;
   A curing agent;
   An inorganic filler,
   In 100% by weight of the insulating sheet, the content of the inorganic filler is 60% by weight or more and 95% by weight or less,
   The insulating sheet whose content of the nitrogen atom contained in the component except the said inorganic filler in an insulating sheet is 0.3 weight% or more and less than 3.0 weight% in 100 weight% of insulating sheets.
2. The insulating sheet according to claim 1, wherein at least one of the polymer, the curable compound, and the curing agent contains a nitrogen atom.
3. The insulating sheet according to claim 1, wherein the curing agent contains a nitrogen atom.
4. The insulating sheet according to any one of claims 1 to 3, wherein the polymer has an aromatic skeleton.
5. The insulating sheet according to any one of claims 1 to 4, wherein the curable compound has an aromatic skeleton.
6. The insulating sheet according to any one of claims 1 to 5, wherein the polymer is a phenoxy resin or an epoxy resin.
7. The insulating sheet according to any one of claims 1 to 6, wherein the curable compound has a hydroxyl group equivalent of 6000 or more.
8. The inorganic filler is at least one selected from the group consisting of alumina, synthetic magnesite, crystalline silica, boron nitride, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, magnesium carbonate, and magnesium oxide. The insulating sheet according to any one of 1 to 7.
9. The insulating sheet according to any one of claims 1 to 8, wherein the inorganic filler contains spherical alumina.
10. The insulating sheet according to any one of claims 1 to 9, wherein the inorganic filler contains alumina having a purity by fluorescent X-ray analysis of 90.0% or more and 99.0% or less.
11. The insulating sheet according to any one of claims 1 to 10, wherein the inorganic filler includes spherical alumina or crushed alumina having a purity by fluorescent X-ray analysis of 90.0% or more and 99.0% or less.
12. The insulating sheet according to any one of claims 1 to 11, further comprising an elastomer which is a poly (meth) acrylic ester.
13. The insulating sheet according to claim 12, wherein the elastomer is a polymer using butyl (meth) acrylate.
14. The insulating sheet according to any one of claims 1 to 13, wherein the curing agent contains at least one of dicyandiamide and an imidazole compound.
15. The insulating sheet according to any one of claims 1 to 14, wherein the curing agent contains dicyandiamine.
16. The insulating sheet according to any one of claims 1 to 15, wherein the curing agent contains an imidazole compound.
17. A thermal conductor having a thermal conductivity of 10 W / m · K or more;
    An insulating layer laminated on at least one surface of the thermal conductor;
    A conductive layer laminated on a surface opposite to the surface on which the thermal conductor of the insulating layer is laminated,
    A laminated structure in which the insulating layer is formed by curing the insulating sheet according to any one of claims 1 to 16.
18. The laminated structure according to claim 17, wherein the heat conductor is a metal.

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