Fluororesin substrate laminate

Abstract

To provide a fluorine resin substrate laminate having low hygroscopicity and excellent low dielectric constant and low dielectric loss tangent, and in which transmission loss in a high frequency region can be reduced.SOLUTION: A fluorine resin substrate laminate for a high frequency circuit comprises a fluorine resin substrate and an adhesive layer provided on the fluorine resin substrate, and the adhesive layer comprises a resin composition comprising (A) a maleimide compound having a saturated or unsaturated bivalent hydrocarbon group and (B) an aromatic maleimide compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluororesin substrate laminate for use in high frequency circuits. [Background technology]

[0002] The speed and capacity of signals used in electronic devices such as mobile phones, their base station equipment, servers, routers, and other network infrastructure equipment, and large-scale computers are increasing year by year. Accordingly, the printed wiring boards used in these electronic devices must be able to handle higher frequencies, creating a demand for substrate materials with low dielectric constants and low dielectric loss tangents that can reduce transmission loss. In recent years, in addition to the electronic devices mentioned above, new systems using high-frequency wireless signals have been put into practical use or planned for use in the ITS field (automotive and transportation systems) and in indoor short-range communications. It is expected that there will be an increasing demand for low-transmission-loss substrate materials for the printed wiring boards used in these devices.

[0003] Furthermore, in light of recent environmental concerns, there has been a growing demand for the mounting of electronic components using lead-free solder and halogen-free flame retardancy, so printed wiring board materials are required to have higher heat resistance and flame retardancy than ever before.

[0004] Conventionally, resins such as polyphenylene ether (PPE), polyimide (PI), liquid crystal polymer (LCP), and fluororesin have been used for printed wiring boards that require low transmission loss (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 58-69046 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-255059 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-60449 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-171480 Summary of the Invention [Problem to be solved by the invention]

[0006] Fluororesins are known to have low moisture absorption and excellent low dielectric constants and low dielectric loss tangents. However, fluororesins such as polytetrafluoroethylene (PTFE) have poor adhesion to metal foils, making it difficult to laminate them with metal foils with low surface roughness (e.g., low-roughness copper foil). Therefore, when fluororesin substrates are used in the high-frequency range, transmission loss tends to increase compared to substrates made of PPE, PI, LCP, etc.

[0007] An object of the present invention is to provide a fluororesin substrate laminate that has low moisture absorption, an excellent low dielectric constant and low dielectric loss tangent, and is capable of reducing transmission loss in the high frequency range. [Means for solving the problem]

[0008] One aspect of the present disclosure relates to a fluororesin substrate laminate for use in high-frequency circuits, comprising: a fluororesin substrate; and an adhesive layer provided on the fluororesin substrate, wherein the adhesive layer comprises a resin composition containing (A) a maleimide compound having a saturated or unsaturated divalent hydrocarbon group and (B) an aromatic maleimide compound. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a fluororesin substrate laminate that has low moisture absorption, an excellent low dielectric constant and low dielectric loss tangent, and is capable of reducing transmission loss in the high frequency range. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of a fluororesin substrate laminate. [Figure 2]1 is a schematic cross-sectional view showing one embodiment of a fluororesin substrate laminate. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In this specification, the high frequency range refers to the range of 0.3 GHz to 300 GHz, and in particular, refers to the range of 3 GHz to 300 GHz.

[0012] <Fluororesin substrate laminate> 1 is a schematic cross-sectional view showing one embodiment of a fluororesin substrate laminate for use in a high-frequency circuit, which includes a fluororesin substrate 1 and an adhesive layer 2 provided on the fluororesin substrate 1.

[0013] [Adhesive layer] The adhesive layer 2 according to this embodiment contains a resin composition containing (A) a maleimide compound having a saturated or unsaturated divalent hydrocarbon group and (B) an aromatic maleimide compound. The adhesive layer 2 not only has excellent adhesion to the fluororesin substrate 1, but also to the metal foil described below. This reduces the transmission loss of the fluororesin substrate laminate in the high frequency range.

[0014] The thickness of the adhesive layer 2 is not particularly limited, and may be, for example, 1 to 200 μm, 3 to 180 μm, 5 to 150 μm, 10 to 100 μm, or 15 to 80 μm. By setting the thickness of the adhesive layer 2 within the above range, the high-frequency characteristics of the laminate according to this embodiment can be more easily improved.

[0015] The adhesive layer 2 may be formed by applying the resin composition to the fluororesin substrate 1, or by preparing a resin film of the resin composition and laminating the resin film on the fluororesin substrate 1. The resin film refers to an uncured or semi-cured film-like resin composition. Each component contained in the resin composition will be described in detail below.

[0016] ((A) Maleimide Compound Having a Saturated or Unsaturated Divalent Hydrocarbon Group) The maleimide compound having a saturated or unsaturated divalent hydrocarbon group according to this embodiment may be referred to as component (A). Component (A) is a compound having (a) a maleimide group and (c) a saturated or unsaturated divalent hydrocarbon group. The (a) maleimide group may be referred to as structure (a), and the (c) saturated or unsaturated divalent hydrocarbon group may be referred to as structure (c). By using component (A), a resin composition having excellent high-frequency characteristics and adhesiveness may be obtained.

[0017] In addition to Structure (a) and Structure (c), Component (A) may further have (b) a divalent group having at least two imide bonds. (b) A divalent group having at least two imide bonds is sometimes referred to as Structure (b).

[0018] The (a) maleimide group is not particularly limited and may be a general maleimide group. The (a) maleimide group may be bonded to an aromatic ring or an aliphatic chain, but from the viewpoint of dielectric properties, it is preferably bonded to a long-chain aliphatic chain (for example, a saturated hydrocarbon group having 8 to 100 carbon atoms). When component (A) has a structure in which the (a) maleimide group is bonded to a long-chain aliphatic chain, the high-frequency properties of the resin composition can be further improved.

[0019] There are no particular limitations on the structure (b), but examples include groups represented by the following formula (I): The structure (b) is a group that does not have a maleimide group.

[0020] [ka]

[0021] In formula (I), R1 represents a tetravalent organic group. R1 is not particularly limited as long as it is a tetravalent organic group, but from the viewpoint of ease of handling, it may be, for example, a hydrocarbon group having 1 to 100 carbon atoms, a hydrocarbon group having 2 to 50 carbon atoms, or a hydrocarbon group having 4 to 30 carbon atoms.

[0022] R1 may contain a substituted or unsubstituted siloxane moiety, such as a structure derived from dimethylsiloxane, methylphenylsiloxane, or diphenylsiloxane.

[0023] When R1 is substituted, examples of the substituent include an alkyl group, an alkenyl group, an alkynyl group, a hydroxyl group, an alkoxy group, a mercapto group, a cycloalkyl group, a substituted cycloalkyl group, a heterocyclic group, a substituted heterocyclic group, an aryl group, a substituted aryl group, a heteroaryl group, a substituted heteroaryl group, an aryloxy group, a substituted aryloxy group, a halogen atom, a haloalkyl group, a cyano group, a nitro group, a nitroso group, an amino group, an amido group, -CHO, -NR x C(O)-N(R x )2, -OC(O)-N(R x ) 2, acyl group, oxyacyl group, carboxyl group, carbamate group, sulfonamide group, etc. x represents a hydrogen atom or an alkyl group. One or more of these substituents can be selected depending on the purpose, application, etc.

[0024] R1 is preferably, for example, a tetravalent residue of an acid anhydride having two or more anhydride rings in one molecule, i.e., a tetravalent group obtained by removing two acid anhydride groups (-C(=O)OC(=O)-) from an acid anhydride. Examples of acid anhydrides include compounds described below.

[0025] From the viewpoint of mechanical strength, R1 is preferably aromatic, and more preferably a group obtained by removing two acid anhydride groups from pyromellitic dianhydride. That is, structure (b) is more preferably a group represented by the following formula (III).

[0026] [ka]

[0027] From the viewpoint of fluidity and circuit embedding ability, it is preferable that a plurality of structures (b) are present in component (A). In this case, the structures (b) may be the same or different. The number of structures (b) in component (A) is preferably 2 to 40, more preferably 2 to 20, and even more preferably 2 to 10.

[0028] From the viewpoint of dielectric properties, the structure (b) may be a group represented by the following formula (IV) or (V).

[0029] [ka]

[0030] [ka]

[0031] Structure (c) is not particularly limited and may be linear, branched, or cyclic. From the viewpoint of high-frequency characteristics, structure (c) is preferably an aliphatic hydrocarbon group. Furthermore, the saturated or unsaturated divalent hydrocarbon group may have 8 to 100 carbon atoms. Structure (c) is preferably an optionally branched alkylene group having 8 to 100 carbon atoms, more preferably an optionally branched alkylene group having 10 to 70 carbon atoms, and even more preferably an optionally branched alkylene group having 15 to 50 carbon atoms. When structure (c) is an optionally branched alkylene group having 8 or more carbon atoms, the molecular structure is easily three-dimensional, increasing the free volume of the polymer and facilitating low density. In other words, the dielectric constant can be reduced, which facilitates improving the high-frequency characteristics of the resin composition. Furthermore, when component (A) has structure (c), the flexibility of the resin composition is improved, and the handleability (tackiness, cracking, powder shedding, etc.) and strength of the adhesive layer (resin film) produced from the resin composition can be improved.

[0032] Examples of the structure (c) include alkylene groups such as nonylene, decylene, undecylene, dodecylene, tetradecylene, hexadecylene, octadecylene, and nonadecylene; arylene groups such as benzylene, phenylene, and naphthylene; arylene alkylene groups such as phenylenemethylene, phenyleneethylene, benzylpropylene, naphthylenemethylene, and naphthyleneethylene; and arylene dialkylene groups such as phenylenedimethylene and phenylenediethylene.

[0033] From the viewpoints of high frequency characteristics, low thermal expansion characteristics, adhesion to conductors, heat resistance, and low moisture absorption, a group represented by the following formula (II) is particularly preferred as structure (c).

[0034] [ka]

[0035] In formula (II), R2 and R3 each independently represent an alkylene group having 4 to 50 carbon atoms. From the viewpoint of further improving flexibility and ease of synthesis, R2 and R3 each independently represent an alkylene group having 5 to 25 carbon atoms, more preferably an alkylene group having 6 to 10 carbon atoms, and even more preferably an alkylene group having 7 to 10 carbon atoms.

[0036] In formula (II), R4 represents an alkyl group having 4 to 50 carbon atoms. From the viewpoint of further improving flexibility and ease of synthesis, R4 is preferably an alkyl group having 5 to 25 carbon atoms, more preferably an alkyl group having 6 to 10 carbon atoms, and even more preferably an alkyl group having 7 to 10 carbon atoms.

[0037] In formula (II), R5 represents an alkyl group having 2 to 50 carbon atoms. From the viewpoint of further improving flexibility and ease of synthesis, R5 is preferably an alkyl group having 3 to 25 carbon atoms, more preferably an alkyl group having 4 to 10 carbon atoms, and even more preferably an alkyl group having 5 to 8 carbon atoms.

[0038] From the viewpoint of fluidity and circuit embedding ability, it is preferable that a plurality of structures (c) are present in component (A). In this case, the structures (c) may be the same or different. For example, it is preferable that 2 to 40 structures (c) are present in component (A), more preferably 2 to 20 structures (c), and even more preferably 2 to 10 structures (c).

[0039] The content of component (A) in the resin composition is not particularly limited. From the viewpoint of heat resistance, the content of component (A) is preferably 2 to 98 mass % relative to the total mass of the resin composition, more preferably 10 to 50 mass %, and even more preferably 10 to 30 mass %.

[0040] The molecular weight of component (A) is not particularly limited. From the viewpoints of handleability, flowability, and circuit embedding ability, the weight average molecular weight (Mw) of component (A) is preferably 500 to 10,000, more preferably 1,000 to 9,000, even more preferably 1,500 to 9,000, still more preferably 1,500 to 7,000, and particularly preferably 1,700 to 5,000.

[0041] The Mw of the component (A) can be measured by gel permeation chromatography (GPC).

[0042] The GPC measurement conditions are as follows: Pump: L-6200 type [manufactured by Hitachi High-Technologies Corporation] Detector: L-3300 type RI [Hitachi High-Technologies Corporation] Column oven: L-655A-52 [Hitachi High-Technologies Corporation] Guard column and column: TSK Guardcolumn HHR-L + TSKgel G4000HHR + TSKgel G2000HHR [all manufactured by Tosoh Corporation, product names] Column size: 6.0 x 40 mm (guard column), 7.8 x 300 mm (column) Eluent: tetrahydrofuran Sample concentration: 30 mg / 5 mL Injection volume: 20μL Flow rate: 1.00mL / min Measurement temperature: 40℃

[0043] There are no particular restrictions on the method for producing component (A). Component (A) may be produced, for example, by reacting an acid anhydride with a diamine to synthesize an amine-terminated compound, and then reacting the amine-terminated compound with excess maleic anhydride.

[0044] Examples of acid anhydrides include pyromellitic anhydride, maleic anhydride, succinic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride. Depending on the purpose, application, etc., one type of acid anhydride may be used alone, or two or more types may be used in combination. As described above, a tetravalent organic group derived from an acid anhydride such as those listed above can be used as R1 in the above formula (I). From the viewpoint of better dielectric properties, the acid anhydride is preferably pyromellitic anhydride.

[0045] Examples of diamines include dimer diamine, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 1,3-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-diamino-3,3'-dihydroxybiphenyl, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, polyoxyalkylenediamine, and [3,4-bis(1-aminoheptyl)-6-hexyl-5-(1-octenyl)]cyclohexene. Depending on the purpose, application, etc., one type of diamine may be used alone, or two or more types may be used in combination.

[0046] The component (A) may be, for example, a compound represented by the following formula (XIII). [ka]

[0047] In the formula, R and Q each independently represent a divalent organic group. R can be the same as in the structure (c) above, and Q can be the same as R1 above. Furthermore, n represents an integer of 1 to 10.

[0048] A commercially available compound can also be used as component (A). Examples of commercially available compounds include products manufactured by Designer Molecules Inc., specifically BMI-1500, BMI-1700, BMI-3000, BMI-5000, and BMI-9000 (all trade names). From the viewpoint of obtaining better high-frequency characteristics, it is more preferable to use BMI-3000 as component (A).

[0049] ((B) Aromatic Maleimide Compound) The aromatic maleimide compound (B) according to this embodiment may be referred to as component (B). Component (B) is a maleimide compound different from component (A). A compound that can be classified as both component (A) and component (B) is considered to belong to component (A). However, when two or more compounds that can be classified as both component (A) and component (B) are included, one of them is considered to belong to component (A) and the remaining compounds are considered to belong to component (B). For example, a compound having an aromatic ring contained in the group represented by formula (I) may be considered component (A), and a compound having an aromatic ring other than the aromatic ring contained in the group represented by formula (I) may be considered component (B). The use of component (B) can reduce the hygroscopicity of the resin composition. A cured product of a resin composition containing components (A) and (B) can maintain good dielectric properties while improving low hygroscopicity by containing a polymer having structural units composed of component (A), which has low dielectric properties, and structural units composed of component (B), which has low hygroscopicity.

[0050] Component (B) preferably has a lower thermal expansion coefficient than component (A). Examples of component (B) having a lower thermal expansion coefficient than component (A) include maleimide group-containing compounds having a lower molecular weight than component (A), maleimide group-containing compounds having more aromatic rings than component (A), and maleimide group-containing compounds having a shorter main chain than component (A).

[0051] The content of component (B) in the resin composition is not particularly limited. From the viewpoint of low moisture absorption and dielectric properties, the content of component (B) is preferably 1 to 95 mass %, more preferably 3 to 90 mass %, and even more preferably 5 to 85 mass %, based on the total mass of the resin composition.

[0052] The blending ratio of the (A) component to the (B) component in the resin composition is not particularly limited. From the viewpoint of low moisture absorption and dielectric properties, the mass ratio of the (A) component to the (B) component, (B) / (A), is preferably 0.01 to 3, more preferably 0.03 to 2, and even more preferably 0.05 to 1.

[0053] The component (B) is not particularly limited as long as it has an aromatic ring. Because aromatic rings are rigid and have low thermal expansion, the use of a component (B) having an aromatic ring can reduce the thermal expansion coefficient of the resin composition. The maleimide group may be bonded to either an aromatic ring or an aliphatic chain, but from the viewpoint of low thermal expansion, it is preferable that the maleimide group be bonded to an aromatic ring. Furthermore, the component (B) may be a polymaleimide compound containing two or more maleimide groups. One type of component (B) may be used alone, or two or more types may be used in combination.

[0054] Examples of the component (B) include 1,2-dimaleimidoethane, 1,3-dimaleimidopropane, bis(4-maleimidophenyl)methane, bis(3-ethyl-4-maleimidophenyl)methane, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, 2,7-dimaleimidofluorene, N,N'-(1,3-phenylene)bismaleimide, N,N'-(1,3-(4-methylphenylene))bismaleimide, bis(4-maleimidophenyl)sulfone, bis(4-maleimidophenyl)sulfide, bis(4-maleimidophenyl)ether, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(3-(3-maleimidophenoxy)phenoxy)benzene, bis( bis(4-maleimidophenyl)ketone, 2,2-bis(4-(4-maleimidophenoxy)phenyl)propane, bis(4-(4-maleimidophenoxy)phenyl)sulfone, bis[4-(4-maleimidophenoxy)phenyl]sulfoxide, 4,4'-bis(3-maleimidophenoxy)biphenyl, 1,3-bis(2-(3-maleimidophenyl)propyl)benzene, 1,3-bis(1-(4-(3-maleimidophenoxy)phenyl)-1-propyl)benzene, bis(maleimidocyclohexyl)methane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, and bis(maleimidophenyl)thiophene. In order to further reduce the moisture absorption and the thermal expansion coefficient, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane may be used as component (B). In order to further increase the breaking strength and metal foil peel strength of the resin film formed from the resin composition, 2,2-bis(4-(4-maleimidophenoxy)phenyl)propane may be used as component (B).

[0055] From the viewpoint of moldability, a compound represented by the following formula (VI) may be used as component (B).

[0056] [ka]

[0057] In formula (VI), A4 represents a residue represented by the following formula (VII), (VIII), (IX) or (X), and A5 represents a residue represented by the following formula (XI): From the viewpoint of low thermal expansion, A4 may be a residue represented by the following formula (VII), (VIII) or (IX).

[0058] [ka]

[0059] In formula (VII), R 10 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or a halogen atom.

[0060] [ka]

[0061] In formula (VIII), R 11 and R 12 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or a halogen atom, and A6 represents an alkylene group or alkylidene group having 1 to 5 carbon atoms, an ether group, a sulfide group, a sulfonyl group, a ketone group, a single bond, or a residue represented by the following formula (VIII-1):

[0062] [ka]

[0063] In formula (VIII-1), R 13 and R 14 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 5 carbon atoms or a halogen atom, and A7 represents an alkylene group having 1 to 5 carbon atoms, an isopropylidene group, an ether group, a sulfide group, a sulfonyl group, a ketone group or a single bond.

[0064] [ka]

[0065] In formula (IX), i is an integer of 1 to 10.

[0066] [ka]

[0067] In formula (X), R 15 and R 16 each independently represents a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and j is an integer of 1 to 8.

[0068] [ka]

[0069] In formula (XI), R 17 and R 18 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, or a halogen atom, and A8 represents an alkylene group or alkylidene group having 1 to 5 carbon atoms, an ether group, a sulfide group, a sulfonyl group, a ketone group, a fluorenylene group, a single bond, a residue represented by the following formula (XI-1) or a residue represented by the following formula (XI-2):

[0070] [ka]

[0071] In formula (XI-1), R 19 and R 20 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or a halogen atom, and A9 represents an alkylene group having 1 to 5 carbon atoms, an isopropylidene group, an m-phenylenediisopropylidene group, a p-phenylenediisopropylidene group, an ether group, a sulfide group, a sulfonyl group, a ketone group, or a single bond.

[0072] [ka]

[0073] In formula (XI-2), R 21 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or a halogen atom; A 10 and A 11 each independently represents an alkylene group having 1 to 5 carbon atoms, an isopropylidene group, an ether group, a sulfide group, a sulfonyl group, a ketone group, or a single bond.

[0074] Component (B) may be a compound having an amino group and a maleimide group from the viewpoints of solubility in organic solvents, high-frequency characteristics, high adhesion to conductors, etc. The compound having an amino group and a maleimide group can be obtained, for example, by subjecting a bismaleimide compound and an aromatic diamine compound having two primary amino groups to a Michael addition reaction in an organic solvent.

[0075] Examples of aromatic diamine compounds include 4,4'-diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyl-diphenylmethane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, and 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline. These may be used alone or in combination of two or more.

[0076] From the viewpoints of high solubility in organic solvents, high reaction rate during synthesis, and high heat resistance, the aromatic diamine compound may be 4,4'-diaminodiphenylmethane or 4,4'-diamino-3,3'-dimethyl-diphenylmethane.

[0077] Examples of organic solvents include alcohol compounds such as methanol, ethanol, butanol, butyl cellosolve, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and mesitylene; ester compounds such as methoxyethyl acetate, ethoxyethyl acetate, butoxyethyl acetate, and ethyl acetate; and nitrogen-containing compounds such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. One organic solvent may be used alone, or two or more organic solvents may be used in combination. Among these, methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether, N,N-dimethylformamide, and N,N-dimethylacetamide are preferred from the viewpoint of solubility.

[0078] (catalyst) The resin composition according to this embodiment may further contain a catalyst for accelerating the curing of component (A). The content of the catalyst is not particularly limited, but may be 0.1 to 5% by mass based on the total mass of the resin composition. Examples of the catalyst that can be used include peroxides and azo compounds.

[0079] Examples of peroxides include dicumyl peroxide, dibenzoyl peroxide, 2-butanone peroxide, tert-butyl perbenzoate, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, bis(tert-butylperoxyisopropyl)benzene, and tert-butyl hydroperoxide. Examples of azo compounds include 2,2'-azobis(2-methylpropanenitrile), 2,2'-azobis(2-methylbutanenitrile), and 1,1'-azobis(cyclohexanecarbonitrile).

[0080] (inorganic filler) The resin composition according to this embodiment may further contain an inorganic filler. By adding any suitable inorganic filler, the adhesive layer can be improved in low thermal expansion properties, high elastic modulus, heat resistance, flame retardancy, and the like. Examples of inorganic fillers include silica, alumina, titanium oxide, mica, beryllia, barium titanate, potassium titanate, strontium titanate, calcium titanate, aluminum carbonate, magnesium hydroxide, aluminum hydroxide, aluminum silicate, calcium carbonate, calcium silicate, magnesium silicate, silicon nitride, boron nitride, calcined clay, talc, aluminum borate, and silicon carbide. These may be used alone or in combination of two or more.

[0081] There are no particular limitations on the shape and particle size of the inorganic filler. The particle size of the inorganic filler may be, for example, 0.01 to 20 μm or 0.1 to 10 μm. The particle size refers to the average particle size, which is the particle size at the point corresponding to 50% volume when a cumulative frequency distribution curve is calculated based on particle size, with the total volume of the particles being 100%. The average particle size can be measured using a particle size distribution measuring device using a laser diffraction scattering method.

[0082] When an inorganic filler is used, its amount is not particularly limited, but for example, the content of the inorganic filler is preferably 3 to 75 volume % and more preferably 5 to 70 volume % based on the total solid content in the resin composition. When the content of the inorganic filler in the resin composition is within the above range, good curability, moldability, and chemical resistance are easily obtained.

[0083] When an inorganic filler is used, a coupling agent can be used in combination as needed to improve the dispersibility of the inorganic filler and its adhesion to organic components. Examples of the coupling agent that can be used include silane coupling agents and titanate coupling agents. These can be used alone or in combination of two or more. The amount of coupling agent added can be, for example, 0.1 to 5 parts by mass or 0.5 to 3 parts by mass per 100 parts by mass of the inorganic filler used. Within these ranges, there is little deterioration in various properties, making it easier to effectively utilize the benefits of using the inorganic filler.

[0084] When a coupling agent is used, a so-called integral blending method may be used in which the inorganic filler is blended into the resin composition and then the coupling agent is added, but a method in which the inorganic filler is previously surface-treated with the coupling agent by a dry or wet method is preferred. By using this method, the characteristics of the inorganic filler can be more effectively exhibited.

[0085] (thermosetting resin) The resin composition of this embodiment may further contain a (C) thermosetting resin (hereinafter, sometimes referred to as "component (C)") different from components (A) and (B). Note that compounds that can be classified as components (A) or (B) are not considered to belong to component (C). By including component (C), the low thermal expansion properties of the resin composition can be further improved. Examples of component (C) include epoxy resins and cyanate ester resins. One type of component (C) may be used alone, or two or more types may be used in combination.

[0086] Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, alicyclic epoxy resins, aliphatic linear epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, phenol aralkyl epoxy resins, naphthol novolac epoxy resins, naphthol aralkyl epoxy resins, and other naphthalene skeleton-containing epoxy resins, difunctional biphenyl epoxy resins, biphenyl aralkyl epoxy resins, dicyclopentadiene epoxy resins, and dihydroanthracene epoxy resins. From the viewpoint of high-frequency characteristics and thermal expansion characteristics, naphthalene skeleton-containing epoxy resins or biphenyl aralkyl epoxy resins may also be used.

[0087] Examples of cyanate ester resins include 2,2-bis(4-cyanatophenyl)propane, bis(4-cyanatophenyl)ethane, bis(3,5-dimethyl-4-cyanatophenyl)methane, 2,2-bis(4-cyanatophenyl)-1,1,1,3,3,3-hexafluoropropane, α,α'-bis(4-cyanatophenyl)-m-diisopropylbenzene, cyanate ester compounds of phenol-added dicyclopentadiene polymers, phenol novolac cyanate ester compounds, and cresol novolac cyanate ester compounds. Considering the overall balance of low cost, high-frequency characteristics, and other properties, 2,2-bis(4-cyanatophenyl)propane may also be used.

[0088] (hardening agent) When the resin composition according to this embodiment contains the component (C), it may further contain a curing agent for the component (C). This allows the reaction to proceed smoothly when obtaining a cured product of the resin composition, and also makes it possible to appropriately adjust the physical properties of the cured product of the obtained resin composition. One type of curing agent may be used alone, or two or more types may be used in combination.

[0089] Examples of curing agents for epoxy resins include polyamine compounds such as diethylenetriamine, triethylenetetramine, diaminodiphenylmethane, m-phenylenediamine, and dicyandiamide; polyphenol compounds such as bisphenol A, phenol novolac resin, cresol novolac resin, bisphenol A novolac resin, and phenol aralkyl resin; acid anhydrides such as phthalic anhydride and pyromellitic anhydride; carboxylic acid compounds; and active ester compounds.

[0090] Examples of curing agents for cyanate ester resins include monophenol compounds, polyphenol compounds, amine compounds, alcohol compounds, acid anhydrides, and carboxylic acid compounds.

[0091] (curing accelerator) The resin composition according to the present embodiment may further contain a curing accelerator depending on the type of component (C). Examples of curing accelerators for epoxy resins include imidazole-based curing accelerators, BF3 amine complexes, and phosphorus-based curing accelerators. From the viewpoints of the storage stability of the resin composition, the handleability of the semi-cured resin composition, and solder heat resistance, imidazole-based curing accelerators and phosphorus-based curing accelerators are preferred.

[0092] (thermoplastic resin) The resin composition according to the present embodiment may further contain a thermoplastic resin in order to improve the handleability of the resin film. The type of thermoplastic resin is not particularly limited, and the molecular weight is also not limited, but in order to further improve compatibility with component (A), it is preferable that the number average molecular weight (Mn) of the thermoplastic resin is 200 to 60,000.

[0093] From the viewpoint of film-forming properties and moisture absorption resistance, the thermoplastic resin is preferably a thermoplastic elastomer. Examples of the thermoplastic elastomer include saturated thermoplastic elastomers, such as chemically modified saturated thermoplastic elastomers and unmodified saturated thermoplastic elastomers. Examples of the chemically modified saturated thermoplastic elastomers include styrene-ethylene-butylene copolymers modified with maleic anhydride. Specific examples of chemically modified saturated thermoplastic elastomers include Tuftec M1911, M1913, and M1943 (trade names, manufactured by Asahi Kasei Corporation). On the other hand, examples of unmodified saturated thermoplastic elastomers include unmodified styrene-ethylene-butylene copolymers. Specific examples of unmodified saturated thermoplastic elastomers include Tuftec H1041, H1051, H1043, and H1053 (trade names, manufactured by Asahi Kasei Corporation).

[0094] From the viewpoints of film-forming properties, dielectric properties, and moisture absorption resistance, it is more preferable that the saturated thermoplastic elastomer has a styrene unit in the molecule. In this specification, a styrene unit refers to a unit in a polymer derived from a styrene monomer, and a saturated thermoplastic elastomer refers to a structure in which the aliphatic hydrocarbon moieties other than the aromatic hydrocarbon moieties of the styrene unit are all constituted by saturated bonding groups.

[0095] The content of styrene units in the saturated thermoplastic elastomer is not particularly limited, but is preferably 10 to 80 mass %, more preferably 20 to 70 mass %, in terms of the mass percentage of styrene units relative to the total mass of the saturated thermoplastic elastomer. When the content of styrene units is within the above range, the film tends to have excellent appearance, heat resistance, and adhesiveness.

[0096] A specific example of a saturated thermoplastic elastomer having a styrene unit in its molecule is a styrene-ethylene-butylene copolymer, which can be obtained, for example, by hydrogenating the unsaturated double bonds of the butadiene-derived structural units of a styrene-butadiene copolymer.

[0097] The content of the thermoplastic resin is not particularly limited, but from the viewpoint of further improving the dielectric properties, it may be 0.1 to 15 mass%, 0.3 to 10 mass%, or 0.5 to 5 mass% of the total solid content of the resin composition.

[0098] (Flame retardant) The resin composition according to the present embodiment may further contain a flame retardant. The flame retardant is not particularly limited, but a bromine-based flame retardant, a phosphorus-based flame retardant, a metal hydroxide, or the like is preferably used. One type of flame retardant may be used alone, or two or more types may be used in combination.

[0099] Examples of brominated flame retardants include brominated epoxy resins such as brominated bisphenol A epoxy resins and brominated phenol novolac epoxy resins; brominated additive flame retardants such as hexabromobenzene, pentabromotoluene, ethylene bis(pentabromophenyl), ethylene bistetrabromophthalimide, 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane, tetrabromocyclooctane, hexabromocyclododecane, bis(tribromophenoxy)ethane, brominated polyphenylene ether, brominated polystyrene, and 2,4,6-tris(tribromophenoxy)-1,3,5-triazine; and brominated reaction flame retardants containing unsaturated double bond groups such as tribromophenylmaleimide, tribromophenyl acrylate, tribromophenyl methacrylate, tetrabromobisphenol A dimethacrylate, pentabromobenzyl acrylate, and brominated styrene.

[0100] Examples of phosphorus-based flame retardants include aromatic phosphate esters such as triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, cresyl di-2,6-xylenyl phosphate, and resorcinol bis(diphenyl phosphate); phosphonate esters such as divinyl phenylphosphonate, diallyl phenylphosphonate, and bis(1-butenyl) phenylphosphonate; phosphinate esters such as phenyl diphenylphosphinate, methyl diphenylphosphinate, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivatives; phosphazene compounds such as bis(2-allylphenoxy)phosphazene and dicresyl phosphazene; and phosphorus-based flame retardants such as melamine phosphate, melamine pyrophosphate, melamine polyphosphate, melam polyphosphate, ammonium polyphosphate, phosphorus-containing vinylbenzyl compounds, and red phosphorus. Examples of metal hydroxide flame retardants include magnesium hydroxide and aluminum hydroxide.

[0101] The resin composition according to the present embodiment can be obtained by uniformly dispersing and mixing the above-described components. The preparation means, conditions, etc. of the resin composition are not particularly limited. For example, the resin composition may be produced by thoroughly and uniformly stirring and mixing predetermined amounts of the components using a mixer or the like, kneading the mixture using a mixing roll, extruder, kneader, roll, extruder, etc., and then cooling and pulverizing the resulting kneaded mixture.

[0102] The dielectric constant of the cured product (cured adhesive layer) of the resin composition according to this embodiment is not particularly limited, but from the viewpoint of suitable use in the high frequency band, the dielectric constant at 10 GHz is preferably 3.6 or less, more preferably 3.1 or less, and even more preferably 3.0 or less. The lower limit of the dielectric constant is not particularly limited, but may be, for example, about 1.0. Furthermore, from the viewpoint of suitable use in the high frequency band, the dielectric loss tangent of the cured product of the resin composition is preferably 0.004 or less, more preferably 0.003 or less. The lower limit of the dielectric constant is not particularly limited, but may be, for example, about 0.0001. The dielectric constant and dielectric loss tangent can be measured by the methods shown in the examples described below.

[0103] From the viewpoint of suppressing warpage of the laminate, the thermal expansion coefficient of the cured product of the resin composition is preferably 10 to 90 ppm / ° C., more preferably 10 to 45 ppm / ° C., and even more preferably 10 to 40 ppm / ° C. The thermal expansion coefficient can be measured in accordance with IPC-TM-650 2.4.24.

[0104] The method for producing the resin film is not limited. For example, the resin film may be obtained by applying a resin composition to a supporting substrate and drying the resulting resin layer. Specifically, the resin composition may be applied to a supporting substrate using a kiss coater, roll coater, comma coater, or the like, and then dried in a heating and drying oven or the like at a temperature of, for example, 70 to 250°C, preferably 70 to 200°C, for 1 to 30 minutes, preferably 3 to 15 minutes. This allows for the production of a resin film in which the resin composition is semi-cured.

[0105] The semi-cured resin film can be further heated in a heating furnace at a temperature of, for example, 170 to 250° C., preferably 185 to 230° C., for 60 to 150 minutes to thermally cure the resin film.

[0106] The thickness of the resin film is not particularly limited, but may be 0.01 to 2.0 times, 0.05 to 1.0 times, or 0.1 to 0.9 times the thickness of the fluororesin substrate. When the thickness of the resin film is 2.0 times or less, the dielectric constant of the laminate is easily reduced. When the thickness of the resin film is 0.01 times or more, the rigidity and dimensional stability of the laminate are easily improved. The thickness of the resin film may be, for example, 1 to 200 μm, 3 to 180 μm, 5 to 150 μm, 10 to 100 μm, or 15 to 80 μm.

[0107] The supporting substrate is not particularly limited, but is preferably at least one selected from the group consisting of glass, metal foil, and PET film. When the resin film has a supporting substrate, storage properties and handling properties when used to produce a laminate tend to be improved.

[0108] [Fluororesin substrate] Examples of fluororesin that constitute the fluororesin substrate 1 include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-perfluoroalkoxyethylene polymer (PFE), tetrafluoroethylene-hexafluoropropylene polymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE).The fluororesin substrate is preferably a substrate containing polytetrafluoroethylene, as this has better high-frequency characteristics.

[0109] The dielectric constant (Dk) of the fluororesin substrate may be 2.2 to 3.5 or 2.8 to 3.1. The dielectric dissipation factor (Df) of the fluororesin substrate may be 0.0010 to 0.0020 or 0.0010 to 0.0013. The thermal expansion coefficient of the fluororesin substrate in the base material direction may be 30 or less or 20 or less. To improve the insulation reliability and antenna characteristics of the laminate, the thickness of the fluororesin substrate may be 100 μm or more, 110 μm or more, or 120 μm or more, and may be 12,700 μm or less, 6,350 μm or less, or 2,540 μm or less.

[0110] [Metal foil] A metal foil can be further laminated on a fluororesin substrate laminate comprising a fluororesin substrate and an adhesive layer. Fig. 2 is a schematic cross-sectional view showing one embodiment of a fluororesin substrate laminate comprising a metal foil. The laminate comprises a fluororesin substrate 1, an adhesive layer 2 provided on the fluororesin substrate 1, and a metal foil 4 laminated on the adhesive layer 2. The fluororesin substrate 1 and the metal foil 4 are bonded via the adhesive layer 2.

[0111] The metal foil according to this embodiment may be a metal foil with a low surface roughness (low-roughening metal foil). The surface roughness of the metal foil may be 0.05 to 2 μm, 0.1 to 1.5 μm, or 0.15 to 1 μm. The thickness of the metal foil may be 5 to 105 μm, 8 to 70 μm, 10 to 40 μm, or 10 to 20 μm. Electrolytic copper foil may be used as the metal foil from the viewpoint of peel strength.

[0112] The fluororesin substrate laminate including the metal foil may be produced by forming an adhesive layer 2 on a fluororesin substrate 1 and then laminating a metal foil 4 on the adhesive layer 2, or by laminating the fluororesin substrate 1, a resin film, and a metal foil 4 in this order. The fluororesin substrate laminate according to this embodiment may be a laminate in which adhesive layers 2 are formed on both sides of a fluororesin substrate 1 and a metal foil 4 is laminated on the adhesive layer 2.

[0113] <Laminate> According to this embodiment, a metal-clad laminate can be produced by providing a laminate having a resin layer containing a cured product of a resin composition and a conductor layer.

[0114] The method for producing a metal-clad laminate is not limited. For example, one or more of the above-mentioned resin films are laminated on both sides of a fluororesin substrate, and a metal foil serving as a conductor layer is placed on at least one side. The resulting laminate is heated and pressurized, for example, at a temperature of 170 to 250°C, preferably 185 to 230°C, and at a pressure of 0.5 to 5.0 MPa for 60 to 150 minutes, to obtain a metal-clad laminate having a metal foil on at least one side of a resin layer serving as an insulating layer. Heating and pressurization can be carried out, for example, under conditions of a vacuum degree of 10 kPa or less, preferably 5 kPa or less, and is preferably carried out in a vacuum to improve efficiency. Heating and pressurization are preferably carried out for 30 minutes from the start to the end of molding. A metal-clad laminate may also be produced by placing a metal foil 4 on adhesive layer 2 of a fluororesin substrate comprising fluororesin substrate 1 and adhesive layer 2, and then heating and pressurizing the resulting fluororesin substrate.

[0115] While preferred embodiments of the present invention have been described above, these are merely examples for the purpose of explaining the present invention, and the scope of the present invention is not intended to be limited to these embodiments. The present invention can be embodied in various forms different from the above-described embodiments without departing from the spirit of the present invention. [Example]

[0116] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0117] [Resin composition] Example 1 A vessel equipped with a stirrer was charged with 104.4 g of silica slurry (manufactured by Admatechs Co., Ltd., trade name "SC-2050KNK"), 9.1 g of toluene, 21.3 g of component (A), 5.1 g of component (B), and 0.53 g of catalyst (2,5'-dimethyl-2,5-di(t-butylperoxy)hexane, manufactured by NOF Corporation, trade name "Perhexyne 25B"), and the mixture was stirred and mixed for 1 hour at 25°C. The mixture was filtered using a #200 nylon mesh to obtain a resin composition.

[0118] (Comparative Example 1) A resin composition was obtained in the same manner as in Example 1, except that component (A) was not used.

[0119] (Comparative Example 2) A resin composition was obtained in the same manner as in Example 1, except that component (B) was not used.

[0120] Component (A): A maleimide compound having a structure represented by the following formula (XII-3) (manufactured by Designer Molecules Inc., trade name "BMI-1500") was used as component (A). [ka]

[0121] Component (B): 2,2-bis(4-(4-maleimidophenoxy)phenylpropane (manufactured by Daiwa Chemical Industry Co., Ltd., trade name "BMI-4000"), an aromatic maleimide compound, was used as component (B).

[0122] [Resin film] The resin composition was applied to a PET film (manufactured by Teijin Limited, product name "G2-38", thickness: 38 μm) using a comma coater, and then dried at 130°C to produce a resin film with a PET film having a semi-cured resin layer. The thickness of the resin film (adhesive layer) was 65 μm.

[0123] [Laminate] A high-frequency PTFE substrate (Rogers, product name "RO3003", thickness: 127 μm) with both sides of the copper foil fully etched was used. Resin films with the PET film removed were placed on both sides of the PTFE substrate, and copper foil (Furukawa Electric Co., Ltd., product name "FZ-WS", thickness: 18 μm, surface roughness: 0.2 μm or less) was then laminated. Next, a plate was placed on top of the laminate, and it was heated and pressed under conditions of 200°C / 3.0 MPa / 70 minutes to produce a double-sided metal-clad laminate.

[0124] [evaluation] The double-sided metal-clad laminate and the high-frequency PTFE substrate were evaluated as follows. The results are shown in Table 1.

[0125] (Dielectric properties) The dielectric properties, namely, the relative permittivity (Dk) and the dielectric loss tangent (Df), were measured by the cavity resonator perturbation method using test pieces prepared by etching the outer copper foil of double-sided metal-clad laminates at a frequency of 10 GHz and a temperature of 25°C.

[0126] (Moisture absorption solder heat resistance) To evaluate the moisture-absorbed solder heat resistance, the copper foil on one side of a double-sided metal-clad laminate was etched and cut into 50 mm square pieces to serve as test pieces. These were then treated for 1 hour in a pressure cooker test (PCT) device (conditions: 121°C, 2.2 atmospheres), and then floated on molten solder at 288°C for 20 seconds, and the presence or absence of blistering was visually evaluated.

[0127] (Transmission loss) The copper foil on one side of the double-sided metal-clad laminate produced in Example 1 was etched to produce a microstrip line 10 cm long and 65 μm wide, and the transmission loss was measured under conditions of impedance 50 Ω, temperature 25°C, and humidity 60%. As Comparative Example 3, a high-frequency PTFE substrate (Rogers, product name "RO3003", thickness: 127 μm) was used and the transmission loss was measured in the same manner.

[0128] [Table 1] [Explanation of symbols]

[0129] 1...fluororesin substrate, 2...adhesive layer, 4...metal foil.

Claims

1. A fluororesin substrate and an adhesive layer provided on the fluororesin substrate, the adhesive layer comprises a resin composition containing (A) a maleimide compound having a saturated or unsaturated divalent hydrocarbon group and (B) an aromatic maleimide compound, The adhesive layer has a thickness of 15 to 200 μm, A fluororesin substrate laminate for a high frequency circuit, further comprising a metal foil on the adhesive layer, the metal foil having a surface roughness of 0.05 to 1 μm and a thickness of 5 to 20 μm.

2. 2. The fluororesin substrate laminate according to claim 1, wherein the fluororesin substrate is a substrate containing polytetrafluoroethylene.

3. 3. The fluororesin substrate laminate according to claim 1, wherein the aromatic maleimide compound (B) has a structure in which a maleimide group is bonded to an aromatic ring.

4. 4. The fluororesin substrate laminate according to claim 1, wherein the saturated or unsaturated divalent hydrocarbon group has 8 to 100 carbon atoms.

5. 5. The fluororesin substrate laminate according to claim 1, wherein the saturated or unsaturated divalent hydrocarbon group is a group represented by the following formula (II): 【Chemistry 1】 [In formula (II), R ２ and R ３ each independently represents an alkylene group having 4 to 50 carbon atoms; R ４ represents an alkyl group having 4 to 50 carbon atoms, and R ５ represents an alkyl group having 2 to 50 carbon atoms.]

6. 6. The fluororesin substrate laminate according to claim 1, wherein the (A) maleimide compound having a saturated or unsaturated divalent hydrocarbon group further has a divalent group having at least two imide bonds.

7. 7. The fluororesin substrate laminate according to claim 6, wherein the divalent group having at least two imide bonds is a group represented by the following formula (I): 【Chemistry 2】 [In formula (I), R １ represents a tetravalent organic group.

8. 8. The fluororesin substrate laminate according to claim 1, wherein the weight average molecular weight of the (A) maleimide compound having a saturated or unsaturated divalent hydrocarbon group is 500 to 10,000.

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