JP7766701B2 - Metal-clad laminate and laminate used for said metal-clad laminate - Google Patents

Description

The present invention relates to a metal-clad laminate and a laminate for use in the metal-clad laminate.

In recent years, as communication speeds and capacity have increased in communication devices such as smartphones, the circuit boards used in these devices are required to have low electrical signal loss, finer circuit pattern pitches, and more precise, fine circuit formation.
Metal-clad laminates, which are the main material of circuit boards, are metal-clad laminates (e.g., copper-clad laminates (CCL)) in which a metal film is laminated on the surface of a base film made of insulating resin, and the like, are also required to have performance similar to that of the above-mentioned circuit boards.
Various improved metal clad laminates (for example, copper clad laminates (CCL)) have been proposed (see, for example, Patent Document 1).

JP 2011-14801 A

As mentioned above, printed wiring boards, including metal-clad laminates, are required to transmit large amounts of data at high speeds, and progress is being made in their ability to handle high frequencies. To enable printed wiring boards to handle high frequencies, it is necessary to reduce high-frequency transmission loss, which is affected by the dielectric properties of the base film and the surface roughness of the conductor. Therefore, there is a demand for low-dielectric base films and conductors with low surface roughness.
Methods for achieving a conductor with low surface roughness include forming the conductor on the surface of a low-dielectric substrate by dry processes such as vapor deposition or sputtering, or by wet processes such as plating. Compared with the method of thermocompression bonding a metal foil (e.g., copper foil) with a certain surface roughness, these methods depend on the surface roughness of the substrate film, so the surface roughness of the conductor can be reduced by using a substrate film with high smoothness.
However, low-dielectric substrate films require high processing temperatures and adjustment of resin orientation to exhibit heat resistance, and their poor processability makes it difficult to produce smooth low-dielectric substrate films. Furthermore, because the resin that constitutes a low-dielectric substrate film has a molecular skeleton with low polarity, it is difficult to achieve adhesion with metal layers formed by dry processes such as vapor deposition and sputtering, or by wet processes such as plating. Furthermore, if the smoothness of a low-dielectric substrate film is increased, this adhesion may be further reduced.
Therefore, it is desired to provide a metal-clad laminate that can reduce the transmission loss of electrical signals and has excellent adhesion between the metal film and the substrate film.

The present invention aims to provide a metal-clad laminate that adheres well to even low-dielectric substrate films with poor adhesion, and that also has good adhesion to metal layers formed by dry processes such as vapor deposition and sputtering, or wet processes such as plating.
Another object of the present invention is to provide a laminate in which a resin layer is formed on a substrate film, which is used to form the metal-clad laminate.

As a result of extensive research to solve the above problems, the inventors discovered that the above problems could be solved by disposing a layer of a resin composition containing a silane coupling agent with a specific surface roughness (Rz) between the metal film and the substrate film, and thus completed the present invention.

The present invention includes the following aspects.
[1] A laminate having a substrate film and a layer made of a resin composition containing a silane coupling agent,
the surface roughness (Rz) of the layer made of the resin composition is 1 μm or less,
The laminate has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.005 or less under a frequency condition of 28 GHz.
[2] The laminate according to [1], wherein the surface roughness (Rz) is 0.5 μm or less.
[3] The laminate according to [1] or [2], wherein the silane coupling agent is contained in an amount of 0.1 to 20 parts by mass per 100 parts by mass of the resin composition.
[4] The laminate according to any one of [1] to [3], wherein the silane coupling agent is a silane coupling agent containing any one of functional groups selected from the group consisting of an imidazole skeleton, a triazole skeleton, a triazine skeleton, an olefin skeleton, a mercapto group, a maleic anhydride skeleton, an imide skeleton, and an amino group.
[5] The laminate according to any one of [1] to [4], wherein the silane coupling agent has a melting point of 100°C or less.
[6] The laminate according to any one of [1] to [5], wherein the silane coupling agent is a silane coupling agent having a butadiene skeleton.
[7] The laminate according to any one of [1] to [6], wherein the resin composition further contains a maleimide resin.
[8] The laminate according to [7], wherein the weight average molecular weight of the maleimide resin is 5,000 to 100,000.
[9] The laminate according to [8], wherein the weight average molecular weight of the maleimide resin is 5,000 to 40,000.
[10] The laminate according to any one of [1] to [9], wherein the resin composition further contains oxazine.
[11] The laminate according to any one of [1] to [10], wherein the layer made of the resin composition is a cured film obtained by curing a coating film made of the resin composition.
[12] The laminate according to any one of [1] to [11], wherein the layer made of the resin composition has a thickness of 20 μm or less.
[13] The laminate according to any one of [1] to [12], wherein the surface roughness (Rz) of the base film is 1 to 4 μm.
[14] The laminate according to any one of [1] to [13], wherein the base film contains a filler.
[15] The laminate according to [14], wherein the filler has an average particle size of 20 μm or less.
[16] The laminate according to [14] or [15], wherein the filler contains at least one of mica, talc, boron nitride (BN), and silica.
[17] The laminate according to any one of [14] to [16], wherein the filler has a plate-like shape.
[18] The laminate according to any one of [1] to [17], wherein the mass ratio of Si element to carbon atom (Si/C) on the surface of the substrate film is 3% or more as measured by an electron probe microanalyzer (EPMA).
[19] The laminate according to any one of [1] to [18], wherein the base film contains a polyarylene ether ketone (PAEK) resin.
[20] A metal-clad laminate obtained by laminating a metal film on a layer made of the resin composition of the laminate according to any one of [1] to [19],
The metal-clad laminate is a metal film formed by at least one of plating, sputtering, and vapor deposition.
[21] The metal-clad laminate according to [20], wherein the metal film is a copper metal film.
[22] A printed wiring board comprising the laminate according to any one of [1] to [19].
[23] A shielding film comprising the laminate according to any one of [1] to [19].
[24] A printed wiring board with a shielding film comprising the laminate according to any one of [1] to [19].

According to the present invention, it is possible to provide a metal-clad laminate that adheres well to low-dielectric substrate films with poor adhesion, and that also has good adhesion to metal layers formed by dry processes such as vapor deposition and sputtering, or wet processes such as plating.
Furthermore, according to the present invention, it is possible to provide a laminate in which a resin layer is formed on a substrate film, which is used to form the metal-clad laminate.

1 is a cross-sectional view showing an example of the configuration of a metal-clad laminate of the present invention. FIG. 2 is a cross-sectional view showing another example of the configuration of the metal-clad laminate of the present invention.

The laminate of the present invention and the metal-clad laminate of the present invention formed using the laminate will be described in detail below, but the description of the constituent elements described below is an example of one embodiment of the present invention and is not limited to these contents.
The following definitions of terms apply throughout the specification and claims.
The film thickness of the substrate film, the layer made of the resin composition, the metal film, etc. is determined by observing the cross section of the object to be measured using a microscope, measuring the thickness at five points, and averaging the measured values.

(Laminate)
The laminate of the present invention has a substrate film and a layer made of a resin composition containing a silane coupling agent.
The surface roughness (Rz) of the layer made of the resin composition is 1 μm or less.
The laminate has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.005 or less under the condition of a frequency of 28 GHz.

<Base film>
In the present invention, the substrate film is not particularly limited and can be appropriately selected depending on the purpose, but is preferably formed from a resin with excellent dielectric properties. Examples of resins with excellent dielectric properties include polyarylene ether ketone (PAEK) resins such as polyether ether ketone (PEEK) resin, polyether ketone (PEK) resin, polyether ketone ketone (PEKK) resin, and polyether ketone ether ketone ketone (PEKEKK) resin, polyimide, modified polyimide, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyphenylene sulfide (PPS), polyphenylene ether (PPE), syndiotactic polystyrene (SPS), aramid, polyethylene naphthalate, and liquid crystal polymer (LCP).
Among these, from the viewpoints of heat resistance and electrical properties, polyarylene ether ketone (PAEK) resins such as polyether ether ketone (PEEK) resins, modified polyimides, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether copolymers (PFA), polyphenylene sulfide (PPS), and liquid crystal polymers (LCP) are preferred. From the viewpoint of excellent dimensional stability, polyarylene ether ketone (PAEK) resins and liquid crystal polymers (LCP) are more preferred. Polyether ether ketone (PEEK) resins are even more preferred because they have good filler dispersibility and can achieve compatibility with other properties even when the storage modulus of the substrate film is adjusted by changing the amount of filler added.
The substrate film may be made of an alloy containing a plurality of resins.
The base film may contain a filler, which will be described in detail below.

<<Filler>>
The substrate film may contain a filler to impart various functions to the substrate, such as strength, insulation, heat resistance, adjustment of the coefficient of thermal expansion (CTE), storage modulus, etc. Examples of the filler include inorganic fillers and organic fillers, which may be used alone or in combination.

Examples of inorganic fillers include mica, talc, boron nitride, magnesium oxide, silica, diatomaceous earth, titanium oxide, and zinc oxide. From the viewpoint of being able to impart the above functions without deteriorating the dielectric loss tangent, inorganic fillers such as mica, talc, boron nitride, magnesium oxide, and silica are preferred.

The organic filler is not particularly limited, but examples include organic particles of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, olefin polymer, polyamide, polycarbonate, polyimide, polyether ketone, polyether ether ketone, polymethyl methacrylate, liquid crystal polymer, polytetrafluoroethylene, etc. From the viewpoint of improving the dielectric properties of the substrate film, polystyrene, olefin polymer, liquid crystal polymer, and polytetrafluoroethylene are preferred.

The inorganic filler and organic filler may be selected from the above and used alone, or two or more may be used in combination. When two or more types are combined, they may be a combination of an inorganic filler and an organic filler.

The shape of the filler is not particularly limited and can be appropriately selected depending on the purpose. For example, the filler may be a spherical filler or a non-spherical filler, but from the viewpoint of the coefficient of thermal expansion (CTE), a non-spherical filler is preferred. The shape of the non-spherical filler may be any three-dimensional shape other than a sphere (approximately a perfect sphere), and examples thereof include plate-like, scale-like, columnar, chain-like, and fibrous shapes. Among these, from the viewpoints that the coefficient of thermal expansion (CTE) can be adjusted even with a small amount and that flexibility can be achieved, plate-like and scale-like fillers are preferred, and plate-like fillers are more preferred.
The average particle size of the filler is preferably 0.05 μm or more and 20 μm or less, preferably 0.1 μm or more and 15 μm or less, more preferably 0.1 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 7 μm or less. If the average particle size of the filler is 0.05 μm or more, the filler is well dispersible and can effectively impart the above functions. If the average particle size of the filler is 0.1 μm or more, the effect of the aspect ratio of the non-spherical filler becomes effective. If the average particle size of the filler is 20 μm or less, the inclusion of coarse particles is reduced, making it possible to thin the substrate film. If the average particle size of the filler is 10 μm or less, the surface roughness of the substrate film can be reduced, making it easier to form a layer made of a smooth resin composition.
Furthermore, the aspect ratio (average major axis length/average minor axis length), which means the planar direction and thickness of the non-spherical filler, is preferably 5 or more and 500 or less, more preferably 10 or more and 500 or less, from the viewpoint of the coefficient of thermal expansion (CTE).
If the aspect ratio is 5 or more, it is easy to make the CTE sufficiently small.
The larger the aspect ratio, the easier it is to adjust the CTE, but it is difficult to increase the aspect ratio while reducing the particle size, and the cost of the filler tends to increase, so it is desirable to keep the aspect ratio at 500 or less.

[Measurement of average particle size and aspect ratio]
The average particle size and aspect ratio of the inorganic filler can be determined, for example, by observation using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and averaging measured values at three or more locations. The average particle size and aspect ratio of the inorganic filler present in a film (layer) can be determined, for example, by embedding the film in an epoxy resin, then subjecting the cross section of the film to ion milling using an ion milling device to prepare a sample for cross-section observation, and observing the cross section of the obtained sample using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and averaging measured values at three or more locations.
The average particle size of the organic filler can be determined by observing a cut surface of the substrate film with an electron microscope, measuring the maximum diameters of at least 10 particles, and calculating the average value as the average dispersed particle size when dispersed in the resin of the substrate film by melt-kneading and dispersion.

The filler content in the base film is preferably 1% by volume or more and 30% by volume or less, and more preferably 3% by volume or more and 25% by volume or less.

It is preferable that the mass ratio of Si element to carbon atoms (Si/C) on the surface of the substrate film is 3% or more when measured using an electron probe microanalyzer (EPMA). For example, if the substrate film contains an inorganic filler that protrudes from the surface of the substrate film, the silane coupling agent acts on the inorganic filler that protrudes from the surface, resulting in strong adhesion. Therefore, it is preferable that measurement using an electron probe microanalyzer (EPMA) shows that the mass ratio of Si element to carbon atoms on the surface of the substrate film is 3% or more.

<<Other ingredients>>
In the present invention, the substrate film may contain any known additives as necessary, such as antioxidants, light stabilizers, ultraviolet absorbers, crystal nucleating agents, plasticizers, and dispersants for fillers.

<<Characteristics of the base film>>
The thickness of the substrate film is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10 μm to 250 μm.

The surface roughness (Rz) of the substrate film is not particularly limited and can be appropriately selected depending on the purpose. However, taking into consideration various conditions such as the type and content of the filler contained in order to impart various functions to the substrate film, the manufacturing method, etc., the surface roughness (Rz) of the substrate film is 1 μm or more. On the other hand, in order to set the surface roughness (Rz) of the layer made of the resin composition formed on the substrate film within the desired range, the surface roughness (Rz) of the substrate film is preferably 10 μm or less. In other words, the surface roughness (Rz) of the substrate film is preferably 1 μm or more and 10 μm or less, and more preferably 1 μm or more and 4 μm or less. If it is 4 μm or less, the surface roughness of the layer made of the resin composition is easily reduced, and if it is 1 μm or more, the area where the inorganic filler is exposed on the surface of the substrate film increases, and by acting strongly with the silane coupling agent, the interlayer adhesion between the substrate film and the layer made of the resin composition can be ensured.
In this specification, the surface roughness (Rz) (including the surface roughness (Rz) of the substrate film, the surface roughness (Rz) of the layer made of a resin composition containing a silane coupling agent, and the surface roughness (Rz) of the metal film) refers to the ten-point average roughness of the film surface. The ten-point average roughness Rz indicates the RzJIS described in Appendix JA of JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009), and can be determined based on the method described in JIS B 0601:2013 Appendix JA JA.2 a).

[Measurement of ten-point average roughness Rz]
The ten-point average roughness Rz (μm) of the surface of the sheet is obtained by measuring the roughness curve of the test piece using a laser microscope, measuring 10 samples from this roughness curve based on the method described in JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009) Annex JA JA.2 a), and calculating the average value.

The dielectric constant and dielectric dissipation factor of the base film are not particularly limited and can be selected appropriately depending on the purpose, but in order to reduce transmission loss of electrical signals, it is preferable that the dielectric constant be 3.5 or less and the dielectric dissipation factor be 0.005 or less.

[Relative permittivity and dielectric loss tangent]
The relative dielectric constant and dielectric loss tangent of the substrate film can be measured by the open resonator method using a network analyzer MS46122B (manufactured by Anritsu Corporation) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM Corporation) under conditions of a temperature of 23°C, a humidity of 50% RH, and a frequency of 28 GHz.

The coefficient of thermal expansion (CTE) of the base film is not particularly limited and can be selected appropriately depending on the purpose. However, from the viewpoint of preventing curling during the production of printed wiring boards, it is preferable that the CTE be, for example, 50 ppm or less in order to reduce the difference in the coefficient of thermal expansion between the base film and the metal to be bonded.
The thermal expansion coefficient can be measured in a tensile mode using a thermomechanical analyzer (Hitachi High-Tech Science Corporation, product name: SII//SS7100) with a load of 50 mN, by increasing the temperature from 25°C to 250°C at a rate of 5°C/min, measuring the change in dimension with temperature, and determining the linear expansion coefficient from the slope in the range from 25°C to 125°C.

The surface of the substrate film may be treated by corona treatment, plasma treatment, or ultraviolet treatment to improve adhesion to the layer made of the resin composition.

<Layer made of resin composition>
The layer made of the resin composition is formed, for example, by forming a film of the resin composition and curing the coating film made of the resin composition.
The surface roughness (Rz) of the layer made of the resin composition is 1 μm or less.
The surface roughness (Rz) of the layer made of the resin composition is preferably 0.01 μm or more and 1 μm or less, more preferably 0.01 μm or more and 0.5 μm or less, and even more preferably 0.01 μm or more and 0.25 μm or less. The method for measuring the surface roughness (Rz) is as described above in the section "Characteristics of the base film."
When the surface roughness (Rz) of the layer made of the resin composition is 0.01 μm or more, a metal-clad laminate having excellent adhesion to a metal film can be obtained. When the surface roughness (Rz) of the layer made of the resin composition is 1 μm or less, the metal-clad laminate can be used for printed wiring boards used for communication in the 6 GHz band of the fifth-generation mobile communication system. When the surface roughness (Rz) of the layer made of the resin composition is 0.5 μm or less, the metal-clad laminate can be used for printed wiring boards used for communication in the 28 GHz band of the fifth-generation mobile communication system. When the surface roughness (Rz) of the layer made of the resin composition is 0.25 μm or less, the metal-clad laminate can be used for printed wiring boards used for communication in the millimeter wave band of 30 GHz or more.
The resin composition is preferably made of a thermosetting resin.
Examples of thermosetting resins include phenolic resins, epoxy resins, urea resins, melamine resins, unsaturated polyester resins, polyurethane resins, polyimide resins, silicone resins, and maleimide resins. Among these, from the viewpoints of heat resistance, adhesion, and dielectric properties, at least one of epoxy resins, polyimide resins, and maleimide resins is preferred.
In the present invention, the resin composition includes a silane coupling agent.

<<Epoxy resin>>
Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, and hydrogenated versions thereof; glycidyl ester-based epoxy resins such as phthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid glycidyl ester, tetrahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, and trimellitic acid triglycidyl ester; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ester, and the like. Examples of epoxy resins that can be used include, but are not limited to, glycidyl ether-based epoxy resins such as glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, polyglycidyl ether of sorbitol, and polyglycerol polyglycidyl ether; glycidyl amine-based epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil. Additionally, novolac-type epoxy resins such as xylene structure-containing novolac epoxy resins, naphthol novolac-type epoxy resins, phenol novolac epoxy resins, o-cresol novolac epoxy resins, and bisphenol A novolac epoxy resins can also be used.

Further examples of epoxy resins that can be used include brominated bisphenol A-type epoxy resins, phosphorus-containing epoxy resins, fluorine-containing epoxy resins, dicyclopentadiene-skeleton-containing epoxy resins, naphthalene-skeleton-containing epoxy resins, anthracene-type epoxy resins, tertiary butylcatechol-type epoxy resins, triphenylmethane-type epoxy resins, tetraphenylethane-type epoxy resins, biphenyl-type epoxy resins, and bisphenol S-type epoxy resins. These epoxy resins may be used alone or in combination of two or more.

<<Maleimide resin>>
Examples of maleimide resins include 1-methyl-2,4-bismaleimidebenzene, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-m-toluylene bismaleimide, N,N'-4,4-biphenylene bismaleimide, N,N'-4,4-(3,3'-dimethyl-biphenylene)bismaleimide, N,N'-4,4-(3,3'-dimethyldiphenylmethane)bismaleimide, N,N'-4,4-(3,3'-diethyldiphenylmethane)bismaleimide, N,N'-4,4-diphenylmethane bismaleimide, N,N'-4,4-diphenylpropane bismaleimide, N,N'-4,4-diphenylether bismaleimide, and N,N'-3,3-diphenylsulfone bismaleimide.
Further examples include modified maleimides obtained by modifying the above maleimide resins with a compound having a primary amine, and polymers obtained by chain extension of amine-modified products such as dimer acid or trimer acid with maleic anhydride or pyromellitic acid.
As the maleimide resin, commercially available compounds can be used, and specifically, for example, BMI-3000, BMI-1500, BMI-2550, BMI-1400, BMI-2310, BMI-3005, BMI-689, BMI-2500, BMI-6000, BMI-6100, and the like manufactured by DESIGNER MOLECURES Inc. can be suitably used.

In the present invention, the weight-average molecular weight of the maleimide resin contained in the resin composition is preferably 5,000 to 100,000, and more preferably 5,000 to 40,000. A weight-average molecular weight of 5,000 or more improves the leveling properties of the resin composition layer during film formation, reducing the surface roughness of the resin composition layer. A weight-average molecular weight of 100,000 or less imparts appropriate flexibility to the cured resin composition and allows it to exhibit excellent adhesion. Heat resistance is also improved. A weight-average molecular weight of 40,000 or less improves the solubility of the maleimide resin with other additives and the dispersibility of fillers, etc., allowing for both improved performance and reduced surface roughness.

<<Silane coupling agent>>
By incorporating a silane coupling agent into the resin composition, as shown in the examples below, it is possible to improve the adhesion (adhesion) between the layer made of the resin composition and the substrate film, and between the layer made of the resin composition and the metal film described below, and it is possible to produce a metal-clad laminate with good adhesion.

The silane coupling agent used in the present invention is not particularly limited as long as it can produce a metal-clad laminate with good adhesion, and can be selected appropriately depending on the purpose. Examples include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, and 3-methacryloxypropylmethyldimethoxysilane. Acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, hexamethyldisilazane, 3-(2-aminoethylaminopropyl)dimethoxymethylsilane, 3 -(2-aminoethylaminopropyl)trimethoxysilane, 2-(2-aminoethylthioethyl)diethoxymethylsilane, 2-(2-aminoethylthioethyl)triethoxysilane, 3-[2-(2-aminoethylaminoethylamino)propyl]trimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane Examples of such silane include silane, 3-isocyanatepropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, imidazolylalkyl-trialkoxysilane, diphenyldimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, trifluoropropyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyltriethoxysilane, and phenyltriethoxysilane.

In the present invention, the silane coupling agent is preferably a silane coupling agent containing any one of the following functional groups: an imidazole skeleton, a triazole skeleton, a triazine skeleton, an olefin skeleton, a mercapto group, a maleic anhydride skeleton, an imide skeleton, or an amino group. When a silane coupling agent containing any of these groups is added, adhesion can be improved even with a small amount. When a maleimide resin is contained in a resin composition, a silane coupling agent containing such a group can improve heat resistance by reacting with the maleimide resin or acting as a reaction accelerator.
In the present invention, the silane coupling agent is preferably in a liquid state at 100° C. If the silane coupling agent is in a liquid state at 100° C., when an attempt is made to form a metal film on a layer made of a resin composition by sputtering, the temperature of the surface of the layer made of the resin composition rises due to collision of metal particles, and at a surface temperature of about 100° C. that is often observed in sputtering, the alkoxysilane group and the above-mentioned functional group are more likely to be oriented at the interface with the metal film, thereby improving adhesion.
Furthermore, in the present invention, the silane coupling agent is preferably a silane coupling agent having a butadiene skeleton. When the silane coupling agent has a butadiene skeleton, when a maleimide resin is contained in the resin composition, the maleimide resin and the silane coupling agent having a butadiene skeleton can be crosslinked, thereby improving the crosslink density and forming a layer made of a resin composition having improved heat resistance, adhesion strength, and flexibility.
Examples of silane coupling agents having a butadiene skeleton include "X-12-1281A,""X-12-1281A-ES,""X-12-1287A,""X-12-1267B," and "X-12-1267B-ES" manufactured by Shin-Etsu Chemical Co., Ltd.

The content of the silane coupling agent in the resin composition is preferably 0.1 to 20 parts by mass per 100 parts by mass of the resin composition. If the content of the silane coupling agent is equal to or greater than the above-mentioned lower limit, adhesion strength is improved. If the content of the silane coupling agent exceeds the above-mentioned upper limit, adverse effects may occur, such as bleed-out of the silane coupling agent that has not reacted with the maleimide resin, or compatibility deterioration resulting in increased surface roughness.

In addition, the layer made of the resin composition may contain other components such as fillers and various additives.

<<Filler>>
The layer made of the resin composition may contain a filler to improve heat resistance, control fluidity, etc. The type of filler is not particularly limited and can be appropriately selected depending on the purpose. For example, the fillers described above in the <<Filler>> section, which are described as fillers contained in the base film, can be used.
The average particle size of the filler contained in the layer made of the resin composition is preferably 0.01 μm to 20 μm, more preferably 0.01 μm to 10 μm, and even more preferably 0.01 to 5 μm.

The content of the filler in the layer made of the resin composition is preferably 0.1% by volume or more and 50% by volume or less, and more preferably 1% by volume or more and 25% by volume or less.
Since the layer made of the resin composition is required to have a surface smoother than the base film, it is preferable that the average particle size of the filler used is smaller than that of the base film and that the content is small.

<<Other ingredients>>
In addition to the above-mentioned thermosetting resin, silane coupling agent, and filler, the resin composition may contain a tackifier, a flame retardant, a curing agent, a curing accelerator, a heat aging inhibitor, a leveling agent, an antifoaming agent, a pigment, a solvent, etc., to an extent that does not affect the functions of the resin composition. Among these, it is preferable to contain oxazine as a curing agent.

<<<Oxazine>>
The resin composition preferably contains an oxazine, more specifically, a benzoxazine resin, because it reacts with the resin in the resin composition, particularly with the maleimide resin when the resin composition contains a maleimide resin, to increase the crosslink density of the resin composition, thereby enabling the resin composition to exhibit high adhesion to an adherend and heat resistance in a cured product of the resin composition.
Examples of benzoxazine resins include 6,6-(1-methylethylidene)bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine) and 6,6-(1-methylethylidene)bis(3,4-dihydro-3-methyl-2H-1,3-benzoxazine), and two or more of these may be used in combination. A phenyl group, a methyl group, a cyclohexyl group, or the like may be bonded to the nitrogen of the oxazine ring. Specific examples of benzoxazine resins include "Benzoxazine Fa,""BenzoxazineP-d," and "Benzoxazine ALP-d," all manufactured by Shikoku Chemical Industry Co., Ltd., and "CR-276" and "BZ-LB-MDA," all manufactured by Tohoku Chemical Industry Co., Ltd.

The thickness of the layer made of the resin composition is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and particularly preferably 3 μm or more. When the thickness of the layer made of the resin composition is equal to or greater than the above-mentioned lower limit, sufficient uniformity can be maintained to smooth the surface of the substrate film. The thickness of the layer made of the resin composition is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 20 μm or less, and particularly preferably 10 μm or less. When the thickness of the layer made of the resin composition is 100 μm or less, the layer made of the resin composition is easily applied. When the thickness of the layer made of the resin composition is 50 μm or less, the printed wiring board can be made thinner. When the thickness of the layer made of the resin composition is 20 μm or less, stress concentration in the layer made of the resin composition can be reduced, and adhesion can be improved. Furthermore, when the thickness of the layer made of the resin composition is 10 μm or less, the properties of the polyether ether ketone, which has a low CTE in the thickness direction, are not impaired in a laminate laminated with a resin film containing polyether ether ketone as a substrate film.
Furthermore, from the viewpoint of smoothing the surface of the base film by the layer made of the resin composition, thereby smoothing the surface of the metal film as well, and thereby achieving a desired low loss of electrical signals, the film thickness of the layer made of the resin composition is preferably at least 0.7 times the value of the surface roughness (Rz) μm of the base film, more preferably at least 1 time the value of the surface roughness (Rz) μm of the base film, and even more preferably at least 1.2 times the value of the surface roughness (Rz) μm of the base film.

The relative dielectric constant and dielectric dissipation factor of the layer made of the resin composition are not particularly limited and can be selected appropriately depending on the purpose, but for the purpose of reducing transmission loss of electrical signals, it is preferable that the relative dielectric constant is 3.5 or less and the dielectric dissipation factor is 0.004 or less.
The methods for measuring the relative dielectric constant and the dielectric loss tangent are as described in the section "<<Characteristics of the base film>>" for the base film above.

The surface of the layer made of the resin composition may be treated by corona treatment, plasma treatment, or ultraviolet treatment to improve adhesion to the metal film.

<<Method of manufacturing layer made of resin composition>>
The layer made of the resin composition can be formed by forming a film of the resin composition and curing the coating film made of the resin composition.
The resin composition can be produced by mixing an epoxy resin, a polyimide resin, a maleimide resin, or the like with a silane coupling agent and other components. The mixing method is not particularly limited as long as the resin composition is homogeneous. Since the resin composition is preferably used in the form of a solution or dispersion, a solvent is usually also used.
Examples of the solvent include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone; aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene; esters such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; and aliphatic hydrocarbons such as hexane, heptane, cyclohexane, and methylcyclohexane. These solvents may be used alone or in combination of two or more.
When the resin composition is a solution or dispersion containing a solvent (resin varnish), coating onto a substrate film and formation of a coating film can be carried out smoothly, and a coating film made of the resin composition having the desired thickness and surface roughness can be easily obtained.
When the resin composition contains a solvent, the solid content is preferably in the range of 3 to 80% by mass, more preferably 10 to 50% by mass, from the viewpoint of workability including the formation of a coating film. When the solid content is 80% by mass or less, the viscosity of the solution is appropriate, and uniform coating is easy.
In a more specific embodiment of the method for producing a coating film, a resin varnish containing the above-mentioned resin composition, a silane coupling agent, and a solvent is applied to the surface of a substrate film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer to form a B-stage coating film. Here, the B-stage coating film refers to a state in which the resin composition is in an uncured state or a semi-cured state in which a portion has begun to cure, and refers to a state in which the curing of the resin composition further progresses by heating, etc.
Here, the method for applying the resin varnish onto the substrate film is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include spraying, spin coating, dipping, roll coating, blade coating, doctor roll method, doctor blade method, curtain coating, slit coating, screen printing, inkjet method, and dispensing method.
The coating film in the B-stage state can be further subjected to heating or the like to form a cured coating film, that is, a layer made of the resin composition.

<Characteristics of the laminate>
The laminate has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.005 or less under the condition of a frequency of 28 GHz.
The methods for measuring the relative dielectric constant and the dielectric loss tangent are as described in the section "<<Characteristics of the base film>>" for the base film above.

(Metal-clad laminate)
The metal-clad laminate of the present invention comprises a metal film laminated on a layer made of the resin composition of the laminate of the present invention.
In a metal-clad laminate, a layer made of a resin composition and a metal film are laminated in this order on a substrate film.
The metal film is preferably formed by at least one of plating, sputtering, and vapor deposition.
In addition, the metal-clad laminate of the present invention may have a layer made of a resin composition and a metal film laminated on both sides of a substrate film.
In this case, the metal-clad laminate is formed by laminating a metal film, a layer made of a resin composition, a substrate film, a layer made of a resin composition, and a metal film in this order.

FIG. 1 is a cross-sectional view showing an example of the configuration of the metal-clad laminate of the present invention.
The metal-clad laminate 1 has a substrate film 2, a layer 3 made of a resin composition, and a metal film 4, which are laminated in this order.
FIG. 2 shows another example of the configuration of the metal-clad laminate of the present invention.
The metal-clad laminate 1 of the present invention shown in FIG. 2 is formed by laminating a metal film 4a, a layer 3a made of a resin composition, a substrate film 2, a layer 3b made of a resin composition, and a metal film 4b in this order.

<Metal film>
The metal film is formed by at least one of plating, sputtering, and vapor deposition.
When a metal film is formed on a layer made of a resin composition having a surface roughness (Rz) of 1 μm or less by at least one of plating, sputtering, and vapor deposition, a metal film with a smooth surface can be formed.
Furthermore, metal films formed by these methods allow for finer pitch circuit patterns and the formation of highly accurate, fine circuits.
The plating method and the sputtering method may be used separately or in combination. For example, when using them in combination, a thin copper film may be formed by sputtering, and then a copper film may be formed by electrolytic copper plating.

The metal that constitutes the metal film is not particularly limited and can be selected appropriately depending on the purpose, but examples include one selected from the group consisting of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, or an alloy containing one or more of these. Of these, copper and alloys containing copper are preferred from the standpoints of shielding properties and economy.

As mentioned above, methods for forming metal films include at least one of plating, sputtering, and vapor deposition. More specifically, examples include vapor deposition films formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion beam vapor deposition, electron beam vapor deposition, etc.) or chemical vapor deposition, and plated films formed by plating. Among these, vacuum deposition films or sputtered films formed by vacuum film formation methods (vacuum vapor deposition, sputtering, etc.), or plated films formed by electrolytic plating, are preferred because of their excellent in-plane conductivity. Sputtered films are even more preferred because of their improved adhesion due to the anchoring effect and increased surface temperature.

The thickness of the metal film is preferably 0.05 μm to 10 μm, more preferably 0.1 to 10 μm, and even more preferably 0.5 to 10 μm, from the viewpoint of ensuring sufficient electrical signal transmission characteristics and enabling a good fine pitch of the circuit pattern.
The surface roughness (Rz) of the metal film on the surface not in contact with the layer made of the resin composition is not particularly limited and can be selected appropriately depending on the purpose, but for example, it is preferably 0.5 μm or less for the purpose of reducing transmission loss of electrical signals.

<Effects of metal-clad laminates>
Although it is difficult to smooth the surface of a substrate film due to the filler contained in the substrate film or for reasons of manufacturing the substrate film, by forming a layer made of a resin composition on the substrate film, a smooth metal film can be laminated, thereby reducing transmission loss. Moreover, since a layer made of a resin composition is provided, even if a smooth metal film is used, a metal-clad laminate having excellent adhesion between the substrate film and the metal film can be obtained. Furthermore, in the present invention, since a silane coupling agent is contained in the layer made of the resin composition, even better adhesion between the substrate film and the metal film can be achieved.
Furthermore, by forming the metal film on the laminate of the present invention by at least one of plating, sputtering, and vapor deposition, it is possible to obtain a metal-clad laminate that allows for fine-pitched circuit patterns and the formation of highly accurate, fine circuits.

<Film Thickness of Metal-Clad Laminate>
The film thickness of the metal-clad laminate is not particularly limited and can be appropriately selected depending on the purpose, but for example, it is preferably 10 μm or more and 300 μm or less, more preferably 10 μm or more and 200 μm or less, and even more preferably 10 μm or more and 150 μm or less. If the film thickness of the metal-clad laminate is equal to or greater than the lower limit of the above range, it can have excellent handleability and ensure strength. Furthermore, if it is equal to or less than the upper limit of the above range, it can be made lighter, thinner, shorter, and more flexible.

<Metal-clad laminate manufacturing method>
A layer made of a resin composition is formed on a substrate film.
A metal film is formed on the surface of the layer made of the resin composition opposite to the substrate film.
A more specific method for forming a layer made of a resin composition is as described above in the section <<Method for producing a layer made of a resin composition>>, in which a resin varnish containing a resin composition, a silane coupling agent, and a solvent is applied to the surface of a substrate film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer to form a coating film. The coating film can be further cured by heating or the like to form a layer made of a resin composition.
The method for applying the resin varnish is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include spraying, spin coating, dipping, roll coating, blade coating, doctor roll method, doctor blade method, curtain coating, slit coating, screen printing, inkjet method, and dispensing method.
Examples of methods for forming the metal film include vacuum film formation methods (vacuum deposition, sputtering) and electrolytic plating methods.
From the viewpoint of being able to form a metal film having a desired film thickness and surface shape, a method of forming a vapor deposition film by vacuum deposition, a method of forming a plated film by electrolytic plating, a method of forming a sputtered film by sputtering, or a method of combining sputtering and plating by performing sputtering followed by electrolytic plating can be used to form a metal film.

When the metal-clad laminate of the present invention is a metal-clad laminate having a layer of a resin composition and a metal film on both sides of a substrate film as shown in Figure 2, a layer of a resin composition and a metal film can be formed on one side of the substrate film by the method described above, and then a layer of a resin composition and a metal film can be formed on the other side of the substrate film by the same method. Alternatively, a method can be used in which layers of a resin composition are formed on both sides of the substrate film together, and then metal films placed on top of the layers of a resin composition are also formed on both sides together.

When the substrate film and/or layer made of the resin composition is a substrate film or layer made of the resin composition that has been surface-treated by corona treatment, plasma treatment, ultraviolet treatment, or the like, for example, a substrate film may be prepared, the surface of the prepared substrate film may be surface-treated, and a layer made of the resin composition may be formed on the surface-treated substrate film by the method described above. Alternatively, after forming a layer made of the resin composition, the surface of the layer made of the resin composition may be surface-treated, and then a metal film may be formed by the method described above.

In addition to using the laminate of the present invention to produce the above-mentioned metal-clad laminate, the laminate of the present invention can also be used to produce the printed wiring boards, shielding films, and printed wiring boards with shielding films described below.

(Printed wiring board)
A preferred embodiment of the laminate according to the present invention is a printed wiring board in which copper wiring is formed on a layer made of a resin composition in the laminate according to the present invention.
A printed wiring board can be obtained by forming an electronic circuit on the copper-clad laminate.
The printed wiring board is formed by laminating a base film and copper wiring using the laminate, and is composed of the base film, a layer made of a resin composition, and copper wiring in this order. The layer made of a resin composition and the copper wiring may be formed on both sides of the base film.
For example, a printed wiring board is manufactured by using a heat press or the like to attach a coverlay film via an adhesive layer to a surface having wiring portions.
The printed wiring board according to the present invention uses the low-dielectric resin composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.
A method for producing the printed wiring board according to the present invention includes, for example, contacting the adhesive layer of the laminate with copper wiring, performing thermal lamination at 80°C to 200°C, and then curing the layer made of the resin composition by after-curing. The after-curing conditions can be, for example, 100°C to 200°C and 30 minutes to 4 hours. The shape of the copper wiring is not particularly limited, and an appropriate shape can be selected as desired.

(Shielding film)
A preferred embodiment of the laminate according to the present invention is a shielding film.
Shielding film is a film used to shield various electronic devices, such as computers, mobile phones, and analytical equipment, in order to cut out electromagnetic noise that can affect these devices and cause them to malfunction. It is also called electromagnetic wave shielding film.
The electromagnetic wave shielding film is formed by laminating, for example, an adhesive layer, a metal layer, and the laminate of the present invention, wherein the layer made of the resin composition of the laminate of the present invention and the metal layer are in contact with each other.
The shielding film according to the present invention uses the low-dielectric resin composition of the present invention, and therefore is capable of high-speed transmission in electronic devices and also has excellent adhesive stability to electronic devices.

(Printed wiring board with shielding film)
A preferred embodiment of the laminate according to the present invention is a printed wiring board with a shielding film.
A printed wiring board with a shielding film is a printed wiring board having a printed circuit provided on at least one surface of the substrate, and the electromagnetic wave shielding film is attached to the printed wiring board.
A printed wiring board with a shielding film includes, for example, a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and the electromagnetic wave shielding film.
The printed wiring board with a shielding film according to the present invention uses the low-dielectric resin composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.

The present invention will be described in further detail below with reference to examples, but the scope of the present invention is not limited to these examples. In the following, parts and percentages are by weight unless otherwise specified.

(Base Material Production Example 1)
100 parts by mass of polyether ether ketone (PEEK) resin (381G: manufactured by Victrex) and 45 parts by mass of synthetic mica (MK-100PGDS: manufactured by Katakura Agricorp) were mixed, and the mixture was extruded in a twin-screw kneader to produce pellets. The synthetic mica used had an average particle size of 4.4 μm and an aspect ratio of 41.9.
The obtained pellets were charged into a single-screw extruder equipped with a 900 mm wide T-die, melt-kneaded, and continuously extruded from the T-die to obtain a PEEK substrate film with a thickness of 100 μm (Substrate A-1).
The surface roughness (Rz) of this PEEK substrate film was measured using a laser microscope and found to be Rz: 3.63 μm.
The CTE of this PEEK substrate film in the thickness direction was measured and found to be 48 ppm/°C.
The mass ratio of Si element to carbon atom (Si/C) on the surface of this PEEK substrate film was measured by an electron probe microanalyzer (EPMA) and was found to be 12.91%.
The measurement results for the substrate A-1 obtained in Production Example 1 are shown in Table 1 below.

(Base Material Production Examples 2 and 3)
Substrates A-2 to A-3 were prepared by changing the conditions for substrate A-1 in Production Example 1 and adjusting the production conditions as shown in Table 1 below. The measurement results for substrates A-2 to A-3 obtained in Production Examples 2 and 3 are shown in Table 1 below.

(Components used in the resin composition)
<Bismaleimide resin>
The product used was "SLK-3000-T50" manufactured by Shin-Etsu Chemical Co., Ltd. It had a solid content of 50%, a solvent of toluene, a number average molecular weight of 7,725, a weight average molecular weight of 12,545, and a softening point of 40°C.
<Bismaleimide resin>
The product used was "SLK-1500-T80" manufactured by Shin-Etsu Chemical Co., Ltd. It had a solid content of 80%, a solvent of toluene, a number average molecular weight of 3,257, a weight average molecular weight of 5,040, and a softening point of 45°C.
<Silane coupling agent>
The product used was "X-12-1281A" manufactured by Shin-Etsu Chemical Co., Ltd. It is a silane coupling agent with a styrene-butadiene polymer structure and is in a liquid state at room temperature.
<Silane coupling agent>
The product used was "VD-5" manufactured by Shikoku Chemicals Corporation. It is a silane coupling agent with a triazine skeleton and a melting point of 85°C.
<Silane coupling agent>
The product used was "2MUSIZ" manufactured by Shikoku Chemicals Corporation. This is a silane coupling agent with an imidazole skeleton. It is in a liquid state at room temperature.
<Silane coupling agent>
The product used was "KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd. It is a silane coupling agent with an epoxy backbone and is in a liquid state at room temperature.
<Curing agent>
The product was "Perhexa 25O" manufactured by NOF Corporation, with a solid content of 50%.
<Curing agent: benzoxazine resin>
A product name "ALP-d" (liquid) manufactured by Shikoku Chemicals Corporation was used.

(Resin Composition Blending Example 1)
A bismaleimide resin (SLK-3000-T50: Shin-Etsu Chemical Co., Ltd.), a bismaleimide resin (SLK-1500-T80: Shin-Etsu Chemical Co., Ltd.), a silane coupling agent (X-12-1281A: Shin-Etsu Chemical Co., Ltd.), a curing agent (Perhexa 25O: NOF Corporation), toluene, and methyl isobutyl ketone (MIBK) were mixed according to the formulation in Table 2 below to obtain a coating solution (coating liquid) B-1.
The solid content ratio in the applied layer after the solvent was dried from the coating film of the resin composition is shown in Table 3 below.

(Resin Composition Formulation Examples 2 to 7)
Resin compositions B-2 to B-7 were prepared by changing the conditions for resin composition B-1 in formulation example 1 as shown in Table 2 below. The measurement results for resin compositions B-2 to B-7 obtained in formulation examples 2 to 7 are shown in Table 2 below.
For Blend Examples 2 to 7, the solid content ratio in the applied layer after the solvent was dried from the coating film of the resin composition is also shown in Table 3 below.

Example 1
The surface of the PEEK substrate film of Production Example 1 was subjected to a corona treatment, and the coating solution of Formulation Example 1 was applied to the surface-treated PEEK substrate film to a film thickness of 5 μm, and then the solvent component was volatilized to dry the coating film.
The coating was cured by aging at 80°C for 72 hours.
At this stage, the surface roughness (Rz) of the surface of the layer (coating film) made of the resin composition was measured, and the relative dielectric constant and dielectric loss tangent of the laminate having the PEEK substrate film and the layer made of the resin composition were measured under the condition of a frequency of 28 GHz.

[Relative permittivity and dielectric loss tangent]
The relative dielectric constant and dielectric loss tangent of the adhesive layer were measured using a network analyzer MS46122B (manufactured by Anritsu) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM) by the open resonator method at a temperature of 23°C and a frequency of 28 GHz.

(Adhesion test)
A copper film (thickness: 0.1 μm) was formed by magnetron sputtering on the layer made of the resin composition of a laminate having a PEEK substrate film and a layer made of the resin composition.
The adhesion strength was measured for the metal-clad laminate (copper-clad laminate) thus obtained in Example 1. However, since the copper film was thin at 0.1 μm, if the copper film was torn during adhesion strength measurement, the adhesion strength between the copper film and the PEEK substrate could not be measured. Therefore, an adhesive layer and copper foil were laminated on the copper film to prevent the copper film from being torn, and then the adhesion between the copper film and the PEEK substrate was evaluated.
Therefore, a laminate (I) for adhesion measurement was prepared by laminating an adhesive layer and copper foil for reinforcing the copper film on the metal-clad laminate (copper-clad laminate) of Example 1 as follows.
--Laminate plate for adhesion measurement (I)--
A coating solution of an adhesive composition having the following composition was further coated onto the copper film so that the film would have a dry thickness of 25 μm, and then dried to form an adhesive layer (i).
Composition of adhesive composition: 75 parts by mass of amine-modified styrene-ethylene butylene-styrene copolymer (Tuftec MP10 manufactured by Asahi Kasei Corporation), 25 parts by mass of bismaleimide resin (SKL-3000-T50 manufactured by Shin-Etsu Chemical Co., Ltd.), and 3 parts by mass of organic peroxide (Perbutyl E manufactured by NOF Corporation).
Next, an electrolytic copper foil was laminated on the adhesive layer (i) so that the shiny side of the electrolytic copper foil was in contact with the adhesive layer (i). Thereafter, thermal lamination was performed at 120°C, and further after-curing was performed at 150°C for 60 minutes to cure the adhesive layer (i), thereby obtaining a laminate (I) for adhesion measurement.
Electrolytic copper foil: "TQ-M7-VSP" manufactured by Mitsui Mining & Smelting Co., Ltd. (thickness 12 μm, shiny surface Rz 1.27 μm, shiny surface Ra 0.197 μm, shiny surface Rsm 12.95 μm) was used.
The adhesion of a laminate (I) for adhesion measurement, which was obtained by laminating an adhesive layer for copper film reinforcement and a copper foil on the metal-clad laminate (copper-clad laminate) of Example 1 obtained as described above, was measured as follows.
Furthermore, the laminate (I) for adhesion measurement of Example 1 was stored at 150° C. for one week, and then the adhesion was measured to evaluate the degree of decrease in adhesion due to heat resistance.

[Adhesion strength (N/cm)]
The adhesion was measured by cutting the laminate (I) for adhesion measurement into a test specimen having a width of 25 mm, and measuring the peel strength when peeling the copper film (on which an adhesive layer and a copper foil were laminated) from a substrate film having a layer made of a resin composition fixed to a support at a peel speed of 0.3 m/min and a peel angle of 180° in accordance with JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets).

The measurement results for the laminate used in Example 1 and the evaluation results for the adhesion test of the laminate (I) for adhesion measurement, including the copper-clad laminate, are shown in Table 4.

(Examples 2 to 8, Comparative Example 1)
In Example 1, except that the conditions of the PEEK substrate film and the layer made of the resin composition used were changed as shown in Table 4, the copper-clad laminates of Examples 2 to 8 and Comparative Example 1, and laminates for adhesion measurement (I) containing the copper-clad laminates were prepared in the same manner as in Example 1.

The laminates (I) for adhesion measurement prepared in Examples 2 to 8 and Comparative Example 1 were evaluated in the same manner as in Example 1.
Table 4 shows the measurement results of the laminates used in Examples 2 to 8 and Comparative Example 1, as well as the evaluation results of the adhesion test of the laminate (I) for adhesion measurement.

The metal-clad laminates of the present invention produced in the examples have a smooth metal film surface, which allows for reduced transmission loss. Because a layer made of a resin composition is provided, the adhesion between the substrate film and the metal film is excellent even when a smooth metal film is used.
In particular, in the present invention, since the layer made of the resin composition contains a silane coupling agent, it is possible to achieve even stronger adhesion between the substrate film and the metal film.

The metal-clad laminate of the present invention can be suitably used in the manufacture of FPC-related products for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game consoles, laptops, and medical equipment.

1 Metal-clad laminate 2 Base film 3, 3a, 3b Layers made of resin composition 4, 4a, 4b Metal film

Claims (18)

A laminate having a substrate film and a layer made of a resin composition containing a silane coupling agent ,
the surface roughness (Rz) of the layer made of the resin composition is 1 μm or less,
the laminate has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.005 or less under a frequency condition of 28 GHz,
the silane coupling agent is a silane coupling agent having any one of an imidazole skeleton, a triazine skeleton, and a butadiene skeleton,
The resin composition comprises a maleimide resin . The laminate described in claim 1, wherein the surface roughness (Rz) is 0.5 μm or less. The laminate according to claim 1, wherein the silane coupling agent is contained in an amount of 0.1 to 20 parts by mass per 100 parts by mass of the resin composition. The laminate described in claim 1, wherein the silane coupling agent has a melting point of 100°C or less. 2. The laminate according to claim 1 , wherein the maleimide resin has a weight average molecular weight of 5,000 to 100,000. 6. The laminate according to claim 5 , wherein the maleimide resin has a weight average molecular weight of 5,000 to 40,000. The laminate according to claim 1, wherein the resin composition further contains oxazine. The laminate according to claim 1, wherein the layer made of the resin composition is a cured film formed by curing a coating film made of the resin composition. The laminate described in claim 1, wherein the layer made of the resin composition has a thickness of 20 μm or less. The laminate according to claim 1, wherein the surface roughness (Rz) of the substrate film is 1 to 4 μm. The laminate according to claim 1, wherein the substrate film contains a filler. The laminate according to claim 11 , wherein the filler has an average particle size of 20 μm or less. The laminate of claim 11 , wherein the filler comprises at least one of mica, talc, boron nitride (BN), and silica. The laminate according to claim 11 , wherein the filler has a plate-like shape. The laminate of claim 1, wherein the mass ratio of silicon to carbon atoms (Si/C) on the surface of the substrate film is 3% or more as measured by an electron probe microanalyzer (EPMA). A metal-clad laminate obtained by laminating a metal film on a layer made of the resin composition of the laminate according to any one of claims 1 to 15 ,
The metal-clad laminate is a metal film formed by at least one of plating, sputtering, and vapor deposition. 17. The metal clad laminate of claim 16 , wherein the metal film is a copper metal film. A printed wiring board comprising the laminate according to any one of claims 1 to 15 .