Metal-clad laminate

Abstract

Provided is a metal-clad laminated plate in which transmission loss of electrical signals can be reduced, the fineness in pitch of a circuit pattern can be increased, and a very fine circuit can be formed with high precision, the metal-clad laminated plate having exceptional adhesion of a metal film.　A metal-clad laminated plate obtained by laminating a coating film and a metal film on a substrate film in the stated order, wherein: the metal film is formed by at least one formation process from among plating, sputtering, and deposition; and the surface roughness (Rz) of the coating film is 1 μm or less.

Description

Technical Field

[0001] The present invention relates to a metal-clad laminate.

Background Art

[0002] In recent years, with the increase in communication speed and capacity in communication devices represented by smartphones, circuit boards used in these communication devices are required to have low loss of electrical signals, fine pitch of circuit patterns, and high-precision and fine circuit formation. For metal-clad laminates, which are the main materials of circuit boards, that is, metal-clad laminates in which a metal film is laminated on the surface of a base film made of an insulating resin (for example, copper-clad laminates (CCL)), the same performance as the above circuit boards is required. Metal-clad laminates (for example, copper-clad laminates (CCL)) with various improvements have been proposed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to reduce the transmission loss of electrical signals, it is effective that the surface of the metal film serving as the transmission path of the electrical signals is smooth. However, when the surface of the metal film is smooth, the adhesion (adhesiveness) between the metal film and other layers becomes a problem. Therefore, there is a demand for providing a metal-clad laminate that can reduce the transmission loss of electrical signals and has excellent adhesion between the metal film and the base film.

[0005] However, there has been no metal-clad laminate having a smooth-surface metal film capable of reducing the transmission loss of electrical signals, with good adhesion of the metal film, and further capable of achieving a fine pitch of circuit patterns and forming a high-precision and fine circuit, which can fully satisfy all these requirements.

[0006] Therefore, an object of the present invention is to provide a metal-clad laminate having a smooth-surface metal film capable of reducing the transmission loss of electrical signals, with good adhesion of the metal film, capable of achieving a fine pitch of circuit patterns, and capable of forming a high-precision and fine circuit.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by forming the metal film by at least one of plating, sputtering, and vapor deposition, and disposing a coating film having a specific surface roughness (Rz) between the metal film and the base film, thus completing the present invention.

[0008] The present invention includes the following aspects. [1] A metal-clad laminate in which a coating film and a metal film are laminated in this order on a base film, wherein the metal film is a metal film formed by at least one of plating, sputtering, and vapor deposition, and the surface roughness (Rz) of the coating film is 1 μm or less. [2] The metal-clad laminate according to [1], wherein the coating film and the metal film are laminated on both sides of the base film, and are laminated in the order of metal film, coating film, base film, coating film, and metal film. [3] The metal-clad laminate according to [1] or [2], wherein the surface roughness (Rz) of the base film is 1 μm or more and 10 μm or less. [4] The metal-clad laminate according to any one of [1] to [3], wherein the surface roughness (Rz) of the metal film is 0.5 μm or less. [5] The metal-clad laminate according to any one of [1] to [4], wherein the coating film is made of a thermosetting resin. [6] The metal-clad laminate according to any one of [1] to [5], wherein the coating film contains at least one of an epoxy resin, a polyimide resin, or a bismaleimide resin. [7] The metal-clad laminate according to any one of [1] to [6], wherein the film thickness of the coating film is 0.8 times or more the surface roughness (Rz) of the base film. [8] The metal-clad laminate according to any one of [1] to [7], wherein the film thickness of the metal film is 0.05 μm or more and 10 μm or less. [9] The metal-clad laminate according to any one of [1] to [8], wherein the relative permittivity of the base film is 3.5 or less and the dielectric loss tangent is 0.004 or less.

[10] The metal-clad laminate according to any one of [1] to [9], wherein the relative permittivity of the coating film is 3.5 or less and the dielectric loss tangent is 0.004 or less.

[11] The metal-clad laminate according to any one of [1] to

[10] , wherein the coefficient of thermal expansion (CTE) of the base film is 50 ppm or less.

[12] The metal-clad laminate according to any one of [1] to

[11] , wherein the base film is a liquid crystal polymer (LCP) film, a polyether ether ketone (PEEK) film, a tetrafluoroethylene perfluoroalkyl (PFA) film, or a polyphenylene sulfide (PPS) film.

[13] The metal-clad laminate according to any one of [1] to

[12] , wherein the base film contains a filler.

[14] The metal-clad laminate according to any one of [1] to

[13] , wherein the filler contains at least one of mica, talc, boron nitride (BN), magnesium oxide, and silica.

[15] The metal-clad laminate according to any one of [1] to

[14] , wherein the filler has a plate-like shape.

[16] The metal-clad laminate according to any one of [1] to

[15] , wherein the aspect ratio of the filler is 5 or more and 500 or less.

[17] The metal-clad laminate according to any one of [1] to

[16] , wherein the average particle size of the filler is 20 μm or less.

[18] The metal-clad laminate according to any one of [1] to

[17] , wherein the coating film contains a filler.

[19] The metal-clad laminate according to any one of [1] to

[18] , wherein the metal film is a copper metal film.

[20] The metal-clad laminate according to any one of [1] to

[19] , wherein the surface of the base film and / or the coating film is subjected to corona treatment, plasma treatment, or ultraviolet treatment. [Advantages of the Invention]

[0009] According to the present invention, there is provided a metal-clad laminate having a smooth surface metal film capable of reducing transmission loss of an electrical signal, having good adhesion of the metal film, capable of achieving a fine pitch of a circuit pattern, and capable of forming a high-precision and fine circuit. [Brief Description of the Drawings]

[0010]

Figure 1

Figure 2

[0011] Hereinafter, the metal-clad laminate of the present invention will be described in detail. However, the description of the constituent elements described below is an example as one embodiment of the present invention and is not limited to these contents. The following definitions of terms apply throughout this specification and the claims. The film thicknesses of the base film, the coating film, the metal film, etc. are values obtained by observing the cross-section of the measurement object using a microscope, measuring the thicknesses at five locations, and averaging them.

[0012] (Metal-clad laminate) The metal-clad laminate of the present invention is formed by laminating a coating film and a metal film in this order on a base film. The metal film is a metal film formed by at least one of plating, sputtering, and vapor deposition. The surface roughness (Rz) of the coating film is 1 μm or less.

[0013] 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 base film 2, a coating film 3, and a metal film 4, and these are laminated in this order. Also, in the metal-clad laminate of the present invention, the coating film and the metal film may be laminated on both sides of the base film. 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 laminated in the order of a metal film 4a, a coating film 3a, a base film 2, a coating film 3b, and a metal film 4b.

[0014] <Base film> In the present invention, the base film is not particularly limited and can be appropriately selected according to the purpose. For example, polyimide film, polyether ether ketone (PEEK) film, polyether ketone (PEK) film, polyether ketone ketone (PEKK) film, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA) film, tetrafluoroethylene - hexafluoropropylene copolymer (FEP) film, tetrafluoroethylene - ethylene copolymer (ETFE) film, polyphenylene sulfide (PPS) film, aramid film, polyethylene naphthalate film, and liquid crystal polymer film (LCP), and insulating resin films such as mixture films thereof can be mentioned. Among these, from the viewpoints of adhesiveness and electrical properties, polyether ether ketone (PEEK) film, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA) film, polyphenylene sulfide (PPS) film, and liquid crystal polymer (LCP) film are preferable. The base film can contain a filler. Hereinafter, the filler will be described in detail.

[0015] <<Filler>> The base film can contain a filler in order to impart various functions such as adjusting the strength, insulation, heat resistance, and coefficient of thermal expansion (CTE) of the base material. Examples of the filler include inorganic fillers and organic fillers, and these can be used alone or in combination.

[0016] Examples of the inorganic filler include mica, talc, boron nitride, magnesium oxide, silica, diatomaceous earth, titanium oxide, zinc oxide, etc. Among them, inorganic fillers such as mica, talc, boron nitride, magnesium oxide, and silica are preferred.

[0017] The organic filler is not particularly limited, and examples thereof include organic particles such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, polyimide, polyether ketone, polyether ether ketone, and polymethyl methacrylate.

[0018] The inorganic filler and the organic filler may be selected from the above and used alone, or two or more thereof may be used in combination. When two or more are combined, a combination of an inorganic filler and an organic filler may also be used.

[0019] The shape of the filler is not particularly limited and can be appropriately selected according to the purpose. For example, the inorganic filler may be a spherical inorganic filler or a non-spherical inorganic filler, but from the viewpoints of the coefficient of thermal expansion (CTE) and film strength, a non-spherical inorganic filler is preferred. The shape of the non-spherical inorganic filler may be any three-dimensional shape other than spherical (substantially true spherical), and examples thereof include plate-like, scaly, columnar, chain-like, fibrous, etc. Among them, from the viewpoints of the coefficient of thermal expansion (CTE) and film strength, plate-like and scaly inorganic fillers are preferred, and plate-like inorganic fillers are more preferred. In the case of plate-like or flaky inorganic fillers, the average particle size in the planar direction is preferably 0.05 μm or more and 20 μm or less, more preferably 0.1 μm or more and 15 μm or less, desirably 0.1 μm or more and 10 μm or less, and even more desirably 0.1 μm or more and 7 μm or less. Also, the aspect ratio (average major axis length / average minor axis length) representing the planar direction and thickness is preferably 5 or more and 500 or less, more preferably 20 or more and 500 or less, desirably 40 or more and 500 or less, from the viewpoints of the coefficient of thermal expansion (CTE) and film strength. If the average particle size of the filler is 20 μm or less, the surface roughness of the base film can be reduced, making it easier to form a smooth coating film. If the aspect ratio is 5 or more, it is easy to sufficiently reduce the CTE. Although it is easier to adjust the CTE as the aspect ratio increases, 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 set it to 500 or less.

[0020] [Measurement of average particle size and aspect ratio] The average particle size and aspect ratio of the inorganic filler can be obtained, for example, by observing using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and taking the average of the measured values at three or more locations. Regarding the average particle size and aspect ratio of the inorganic filler present in the film (layer), for example, after embedding the film in an epoxy resin, ion milling of the film cross-section is performed using an ion milling device to prepare a cross-section observation sample, and the cross-section of the obtained sample is observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and can be obtained from the average of the measured values at three or more locations. Also, the average particle size of the organic filler can be obtained as the average dispersion particle size when dispersed in the resin of the base film by melt kneading and dispersion, by observing the cut surface of the base film with an electron microscope and measuring the maximum diameters of at least 10 particles and taking the average value.

[0021] The content of the filler 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.

[0022] <<Other components>> In the present invention, the base film may optionally contain known additives as required. Examples of the additives include antioxidants, light stabilizers, ultraviolet absorbers, crystal nucleating agents, plasticizers, dispersants for fillers, and the like.

[0023] <<Properties of the base film>> The film thickness of the base film is not particularly limited and can be appropriately selected according to the purpose, but it is preferably 10 μm to 250 μm.

[0024] The surface roughness (Rz) of the base film is not particularly limited and can be appropriately selected according to the purpose. However, considering various conditions such as the type and content of the filler contained to impart various functions to the base film, the surface roughness (Rz) of the base film is 1 μm or more. On the other hand, in order to make the surface roughness (Rz) of the coating film formed on the base film within a desired range, the surface roughness (Rz) of the base film is preferably 10 μm or less. That is, the surface roughness (Rz) of the base film is preferably 1 μm or more and 10 μm or less. In this specification, the surface roughness (Rz) refers to the ten-point mean roughness of the film surface. The ten-point mean roughness Rz can be determined based on JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009).

[0025] [Measurement of ten-point mean roughness Rz] The ten-point mean roughness Rz (μm) of the surface of the sheet is obtained by measuring the roughness curve of the test piece using a laser microscope, and measuring 10 samples each from this roughness curve based on JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009), and obtaining their average value.

[0026] The relative permittivity and dielectric loss tangent of the base film are not particularly limited and can be appropriately selected according to the purpose. However, for the reason of reducing the transmission loss of the electrical signal, the relative permittivity is preferably 3.5 or less, and the dielectric loss tangent is preferably 0.004 or less.

[0027] [Relative permittivity and dielectric tangent] The relative permittivity and dielectric tangent of the base film can be measured by the open resonator method under the conditions of a temperature of 23°C and a frequency of 28 GHz using a network analyzer MS46122B (manufactured by Anritsu Corporation) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM Corporation).

[0028] The coefficient of thermal expansion (CTE) of the base film is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoint of preventing curl after lamination, for the reason of reducing the difference in the coefficient of thermal expansion from the metal to be laminated, for example, it is preferably 50 ppm or less. The measurement of the coefficient of thermal expansion can be carried out by the tensile mode using a thermomechanical analyzer [product name: SII / / SS7100 manufactured by Hitachi High-Tech Sciences Corporation], with a load of 50 mN and a heating rate of 5°C / min. The temperature is raised from 25°C to 250°C at a rate of 5°C / min, the temperature change of the dimensions is measured, and the coefficient of linear expansion is obtained from the slope in the range from 25°C to 125°C.

[0029] The surface of the base film may be surface-treated by corona treatment, plasma treatment, or ultraviolet treatment for the reason of improving the adhesion to the coating film.

[0030] [Coating film] The surface roughness (Rz) of the coating film is 1 μm or less. The measurement method of the surface roughness (Rz) is as described in the above section of <<Properties of the base film>>. Since the surface roughness (Rz) of the coating film is 1 μm or less, as will be apparent from the examples described later, a smooth metal film can be formed, and in such a metal-clad laminate with reduced transmission loss, a metal-clad laminate with excellent adhesion of the metal film can be obtained.

[0031] The coating film is formed by forming and curing a resin composition. The resin composition for forming the coating film preferably consists of a thermosetting resin. Examples of the thermosetting resin include, for example, phenol resin, epoxy resin, urea resin, melamine resin, unsaturated polyester resin, polyurethane resin, polyimide resin, silicone resin, bismaleimide resin, etc. Among them, from the viewpoints of heat resistance, adhesion, and dielectric properties, it is preferable that the coating film contains at least any one of epoxy resin, polyimide resin, or bismaleimide resin.

[0032] <<Epoxy resin>> Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, or hydrogenated products thereof; glycidyl ester type epoxy resins such as diglycidyl phthalate, diglycidyl isophthalate, diglycidyl terephthalate, glycidyl p-hydroxybenzoate, diglycidyl tetrahydrophthalate, diglycidyl succinate, diglycidyl adipate, diglycidyl sebacate, triglycidyl trimellitate, etc.; glycidyl ether type epoxy resins such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenyl glycidyl ether ethane, triphenyl glycidyl ether ethane, polyglycidyl ether of sorbitol, polyglycidyl ether of polyglycerol, etc.; glycidyl amine type epoxy resins such as triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane, etc.; linear aliphatic epoxy resins such as epoxidized polybutadiene, epoxidized soybean oil, etc., but are not limited thereto. Also, novolak type epoxy resins such as xylene structure-containing novolak epoxy resin, naphthol novolak type epoxy resin, phenol novolak epoxy resin, o-cresol novolak epoxy resin, bisphenol A novolak epoxy resin, etc. can also be used.

[0033] Furthermore, as examples of the epoxy resin, brominated bisphenol A type epoxy resin, phosphorus-containing epoxy resin, fluorine-containing epoxy resin, epoxy resin containing dicyclopentadiene skeleton, epoxy resin containing naphthalene skeleton, anthracene type epoxy resin, tertiary butyl catechol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, biphenyl type epoxy resin, bisphenol S type epoxy resin, etc. can be used. These epoxy resins may be used alone or in combination of two or more.

[0034] <<Bismaleimide resin>> Examples of the bismaleimide resin include 1-methyl-2,4-bismaleimidebenzene, N,N'-m-phenylenebismaleimide, N,N'-p-phenylenebismaleimide, N,N'-m-tolylene 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, N,N'-3,3-diphenylsulfone bismaleimide, etc. As the bismaleimide resin, commercially available compounds can also be used. Specifically, for example, BMI-3000, BMI-1500, BMI-2550, BMI-1400, BMI-2310, BMI-3005, etc. manufactured by DESIGNER MOLECURES Inc. can be preferably used. Furthermore, modified bismaleimide obtained by modifying the above bismaleimide resin with a compound having a primary amine, etc. can be mentioned.

[0035] In addition, the coating film can also contain other components such as fillers and various additives.

[0036] <<Filler>> The coating film can contain fillers for improving heat resistance, controlling fluidity, etc. The type of filler is not particularly limited and can be appropriately selected according to the purpose. For example, the fillers described in the above <<Filler>> column, which are described as the fillers contained in the above base film, can be used. As for the average particle size of the filler contained in the coating film, it is preferably 0.01 μm to 20 μm, more preferably 0.01 μm to 10 μm, and desirably 0.01 to 5 μm so that the surface roughness (Rz) of the coating film satisfies 1 μm or less.

[0037] The content of the filler in the coating film is preferably 0.1% by volume or more and 25% by volume or less, and more preferably 1% by volume or more and 20% by volume or less. Since the coating film is required to have a higher surface smoothness 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 the content is less.

[0038] <<Other Components>> In addition to the above-mentioned thermosetting resin and filler, the resin composition can contain an adhesion promoter, a flame retardant, a curing agent, a curing accelerator, a coupling agent, a heat aging inhibitor, a leveling agent, an antifoaming agent, a pigment, a solvent, etc. to such an extent that it does not affect the function of the resin composition.

[0039] The film thickness of the coating film is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably 1 to 100 μm, more preferably 3 to 70 μm, still more preferably 5 to 50 μm, and more desirably 5 to 20 μm. If the film thickness of the coating film is 1 μm or more, sufficient uniformity can be maintained to smooth the surface of the base film, and if it is 100 μm or less, the peel strength between the base film, the coating film, and the metal film can be made strong. Also, from the viewpoint of smoothing the surface of the base film with the coating film and thereby also smoothing the surface of the metal film to obtain low loss of a desired electrical signal, the film thickness of the coating film is preferably 0.8 times or more the value of the surface roughness (Rz) μm of the base film, more preferably 1 time or more the value of the surface roughness (Rz) μm of the base film, and even more preferably 1.2 times or more the value of the surface roughness (Rz) μm of the base film.

[0040] The relative permittivity and the dielectric loss tangent of the coating film are not particularly limited and can be appropriately selected according to the purpose. However, for the reason of reducing the transmission loss of the electrical signal, the relative permittivity is preferably 3.5 or less and the dielectric loss tangent is preferably 0.004 or less. The measuring method of the relative permittivity and the dielectric loss tangent is as described in the column of <<Properties of the Base Film>> of the above base film.

[0041] The surface of the coating film may be surface-treated by corona treatment, plasma treatment, or ultraviolet treatment for the reason of improving the adhesion to the metal film.

[0042] <<Manufacturing Method of the Coating Film>> The coating film can be manufactured by forming a resin composition into a film. The resin composition can be manufactured by mixing an epoxy resin, a polyimide resin, a bismaleimide resin, etc. with other components. The mixing method is not particularly limited as long as the resin composition becomes uniform. Since the resin composition is preferably used in a solution or dispersion state, usually a solvent is 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 (resin varnish) containing a solvent, coating on the base film and formation of the coating film can be smoothly carried out, and a coating film having a desired thickness and surface roughness can be easily obtained. When the resin composition contains a solvent, from the viewpoint of workability including formation of the coating film, the solid content concentration is preferably in the range of 3 to 80% by mass, more preferably 10 to 50% by mass. When the solid content concentration is 80% by mass or less, the viscosity of the solution is appropriate and it is easy to coat uniformly. As a more specific embodiment of the method for producing the coating film, a resin varnish containing the above resin composition and solvent is applied to the surface of the base 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 coating film being in the B-stage means that the resin composition is in an uncured state or a semi-cured state in which a part has started to cure, and is a state in which the curing of the resin composition further proceeds by heating or the like. Here, the method of applying the resin varnish on the base film is not particularly limited and can be appropriately selected according to the purpose. For example, spray method, spin coating method, dip method, roll coating method, blade coating method, doctor roll method, doctor blade method, curtain coating method, slit coating method, screen printing method, inkjet method, dispensing method, etc. can be mentioned. The above B-stage coating film can be further heated etc. to form a cured coating film.

[0043] <metal film> The metal film is formed by at least one of plating, sputtering, and vapor deposition. By forming a metal film on a coating film with 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. In addition, the metal film formed by these forming methods enables fine pitch of the circuit pattern and formation of a fine circuit with high precision. The plating forming method and the sputtering forming method may be used separately or in combination. For example, in the case of combined use, a thin copper film can be laid by sputtering and then a copper film can be formed by electrolytic copper plating.

[0044] The metal constituting the metal film is not particularly limited and can be appropriately selected according to the purpose. For example, one selected from the group consisting of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, or an alloy containing any one or more of these can be mentioned. Among them, from the viewpoints of shielding property and economy, copper and alloys containing copper are preferable.

[0045] As a method for forming a metal film, as described above, at least one of plating, sputtering, and vapor deposition can be mentioned. More specifically, for example, a vapor deposition film formed by physical vapor deposition (such as vacuum vapor deposition, sputtering, ion beam vapor deposition, electron beam vapor deposition, etc.) or chemical vapor deposition, a plating film formed by plating, etc. can be mentioned. Among them, a vacuum vapor deposition film or a sputtering film formed by a vacuum film forming method (such as a vacuum vapor deposition method or a sputtering method), or a plating film formed by an electrolytic plating method is preferable from the viewpoint of excellent conductivity in the plane direction.

[0046] From the viewpoint of ensuring sufficient electrical signal transmission characteristics and enabling a good fine pitch of the circuit pattern, the film thickness of the metal film is preferably 0.05 μm to 20 μm, desirably 0.1 to 15 μm, and desirably 0.5 to 10 μm. The surface roughness (Rz) of the surface of the metal film on the surface not in contact with the coating film is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably 0.5 μm or less for the reason of reducing the transmission loss of the electrical signal.

[0047] <Effect of Metal-Clad Laminated Plate> The base film may contain a filler, or it is difficult to smooth the surface of the base film for reasons in the manufacture of the base film. However, by forming a coating film with a surface roughness (Rz) of 1 μm or less on the base film, the surface of the metal film can be smoothed and the transmission loss can be reduced. Furthermore, the adhesion between the coating film and the metal film can also be made good. Since the metal film formed on the coating film is a thin-film metal film formed by at least one of plating, sputtering, and vapor deposition, the fine pitch of the circuit pattern and the formation of a fine and precise circuit with high accuracy can be achieved.

[0048] <Film Thickness of Metal-Clad Laminated Plate> The film thickness of the metal-clad laminate is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably 10 μm or more and 300 μm or less. If the film thickness of the metal-clad laminate is at least the lower limit value of the above range, it has excellent handleability and can ensure strength. Also, if it is at most the upper limit value of the above range, it can be made thinner, lighter, shorter, and more flexible.

[0049] <Method for manufacturing metal-clad laminate> A coating film is formed on a base film. A metal film is formed on the surface of the coating film opposite to the base film. As a more specific method for forming the coating film, as described in the column of the <<Method for manufacturing coating film>> above, a resin varnish containing a resin composition and a solvent is applied to the surface of the base 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 heated or the like to form a cured coating film. The method for applying the resin varnish is not particularly limited and can be appropriately selected according to the purpose. For example, spray method, spin coating method, dip method, roll coating method, blade coating method, doctor roll method, doctor blade method, curtain coating method, slit coating method, screen printing method, inkjet method, dispensing method, etc. can be mentioned. Examples of the method for forming the metal film include a method by a vacuum film forming method (vacuum evaporation, sputtering), a method by an electroplating method, etc. From the point that a metal film having a desired film thickness and surface shape can be formed, a method of forming a vapor deposition film by vacuum evaporation, a method of forming a plating film by electroplating, a method of forming a sputter film by sputtering, or a method of forming a metal film using both sputtering and electroplating by performing electroplating after sputtering can be used.

[0050] When the metal-clad laminate of the present invention is a metal-clad laminate in which a coating film and a metal film are provided on both sides of a base film as shown in FIG. 2, for one side of the base film, the coating film and the metal film are formed by the method described above. Then, for the other side of the base film, the coating film and the metal film can be formed in the same manner. Alternatively, a method may be used in which the coating films on both sides of the base film are formed together, and then the metal films disposed on the coating films are also formed together on both sides.

[0051] When the base film and / or the coating film uses a base film or a coating film surface-treated by corona treatment, plasma treatment, ultraviolet treatment, etc., for example, after preparing the base film, the surface of the prepared base film is surface-treated, and then a coating film is formed on the surface-treated base film by the method described above. Further, after forming the coating film, the surface of the coating film is surface-treated, and then a metal film is formed by the method described above.

Example

[0052] The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In the following, parts and % are based on mass unless otherwise specified.

[0053] (Example 1) <Base film> Polyetheretherketone (PEEK) resin (Victrex Granules 450G: manufactured by Victrex) and synthetic mica (Micromica MK100: manufactured by Katakura Agrico Co., Ltd.) were mixed so that the synthetic mica was 15% by volume, and the mixture was extruded with a twin-screw extruder to produce pellets. The average particle size of the synthetic mica used was 4.9 μm, and the aspect ratio was 30 to 50. The obtained pellets were put into a single-screw extruder with a T-die having a width of 900 mm and melt-kneaded, and continuously extruded from the T-die to obtain a PEEK film with a thickness of 100 μm (film Rz: 6.4 μm, CTE 30 ppm).

[0054] <Preparation of Resin Composition 1 for Forming a Coating Film> An alkyl bis maleimide resin (BMI - 3000, manufactured by Desiner Molecules Inc.) was dissolved in toluene so that the solid content was 50% by mass. Then, it was diluted with methyl isobutyl ketone so that the solid content became 25% by mass. A peroxide (Perk Mill D, manufactured by NOF Corporation) was added at a ratio of 2% by mass based on the solid content. These were mixed to prepare Coating Solution 1.

[0055] <Preparation of Copper - Clad Laminate> The surface of the prepared PEEK film was corona - treated. Coating Solution 1 obtained above was applied onto the surface - treated PEEK film. Then, the coating film was dried. The film thickness after drying was 7 μm. Next, the substrate film with the coating film was put into an oven at 200 °C for 1 hour to cure the coating film. At this time, the Rz of the coating film surface was 0.35 μm. A copper film (film thickness 0.1 μm) was formed on the cured coating film by sputtering. The Rz of the metal layer made of the copper film was 0.15 μm.

[0056] For the metal - clad laminate (copper - clad laminate) of Example 1 thus obtained, when the peel strength of the metal layer was measured by the following measurement method, it was 7 N / cm or more. [Peel Strength] According to the method specified in JIS K6854 - 3:1999, the peel strength of the copper - clad laminate was measured by a T - peel test at a peel rate of 300 mm / min.

[0057] Also, for the metal - clad laminate (copper - clad laminate) of Example 1, the transmission loss was measured by the following measurement method, and the transmission characteristics were evaluated according to the following criteria. [Transmission Loss Measurement Method] A microstrip line substrate (line length 50 mm) with an impedance adjusted to 50 Ω was prepared from the copper - clad laminate, and the S - parameter (S21) at 20 GHz was measured by a network analyzer. [Evaluation Criteria] 〇 (Transmission loss of 4 dB / cm or less: 20 GHz) × (Transmission loss greater than 4 dB / cm: 20 GHz)

[0058] Table 1 shows various measurement results for the base film, coating film, and metal film in the copper-clad laminate of Example 1, as well as the measurement and evaluation results of the characteristics (peel strength and transmission characteristics) of the copper-clad laminate.

[0059] (Examples 2 to 7) In Example 1, copper-clad laminates of Examples 2 to 7 were produced in the same manner as in Example 1, except that the conditions of the coating film were changed as shown in Table 1. During Examples 2 to 7, Coating Solution 2 and Coating Solution 3 used were prepared as follows.

[0060] [Preparation of Resin Composition 2 for Forming Coating Film] The dicyclopentadiene-type low-dielectric epoxy resin (HP7200H: manufactured by DIC Corporation) was dissolved in toluene so that the solid content was 50% by mass. Then, it was diluted with methyl isobutyl ketone so that the solid content became 25% by mass. The alkyl bis maleimide resin (BMI-3000: manufactured by Desiner Molecules Inc) and 2-methylimidazole (2MZ: manufactured by Shikoku Chemicals Corporation) were added so as to be 20 parts by mass and 2% by mass, respectively, with respect to the solid content of the dicyclopentadiene-type low-dielectric epoxy resin. These were mixed to prepare Coating Solution 2.

[0061] [Preparation of Resin Composition 3 for Forming Coating Film] Alkyl bismaleimide resin (BMI-3000, manufactured by Desiner Molecules Inc.) was dissolved in toluene so that the solid content was 50% by mass. Then, it was diluted with methyl isobutyl ketone so that the solid content became 25% by mass. Synthetic mica (Micro Mica MK100DS, manufactured by Katakura Agrico Co., Ltd., average particle size 3.3 μm, aspect ratio 30 to 50) and peroxide (Parkmill D, manufactured by NOF Corporation) were added to the solid content of the alkyl bismaleimide resin at ratios of 10% by volume and 2% by mass, respectively. These were mixed to prepare Coating Solution 3.

[0062] The same measurements as in Example 1 were performed on the copper-clad laminates produced in Examples 2 to 7. Table 1 shows the various measurement results for the base film, coating film, and metal film in the copper-clad laminates of Examples 2 to 7, as well as the measurement and evaluation results of the properties of the copper-clad laminates.

[0063] (Comparative Example 1) The surface of a PEEK film produced in the same manner as in Example 1 was corona-treated. A copper film (film thickness 0.1 μm) was formed on the surface-treated PEEK film by sputtering. The Rz of the metal layer made of the copper film was 6.2 μm.

[0064] When the peel strength of the metal layer of the metal-clad laminate (copper-clad laminate) of Comparative Example 1 thus obtained was measured by the same method as in Example 1, it was 2 N / cm or less. Table 1 shows the various measurement results for the base film and metal film in the copper-clad laminate of Comparative Example 1, as well as the measurement and evaluation results of the properties of the copper-clad laminate.

[0065] (Comparative Examples 2 to 5) In Example 1, copper-clad laminates of Comparative Examples 2 to 5 were produced in the same manner as in Example 1, except that the conditions of the coating film were changed as shown in Table 1.

[0066] The same measurements as in Example 1 were performed on the copper-clad laminates produced in Comparative Examples 2 to 5. Table 1 shows various measurement results for the base film, coating film, and metal film in the copper-clad laminates of Comparative Examples 2 to 5, as well as the measurement and evaluation results of the properties of the copper-clad laminates.

[0067]

Table 1

Industrial Applicability

[0068] The metal-clad laminate of the present invention can be suitably used for the production of FPC-related products for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game machines, notebook computers, and medical instruments.

Explanation of Symbols

[0069] 1 Metal-clad laminate 2 Base film 3, 3a, 3b Coating film 4, 4a, 4b Metal film

Claims

1. A metal-clad laminate in which a coating film and a metal film are laminated in this order on a base film, wherein the metal film is a metal film formed by at least one of plating, sputtering, and vapor deposition, the surface roughness (Rz) of the coating film is 0.35 μm or more and 1 μm or less, and the film thickness of the coating film is 0.8 times or more the surface roughness (Rz) of the base film and 3 μm or more and 70 μm or less, a metal-clad laminate.

2. The metal-clad laminate according to claim 1, wherein the coating film and the metal film are laminated on both sides of the base film, and are laminated in the order of metal film, coating film, base film, coating film, and metal film.

3. The metal-clad laminate according to claim 1 or 2, wherein the surface roughness (Rz) of the base film is 1 μm or more and 10 μm or less.

4. The metal-clad laminate according to any one of claims 1 to 3, wherein the surface roughness (Rz) of the metal film is 0.5 μm or less.

5. The metal-clad laminate according to any one of claims 1 to 4, wherein the coating film is made of a thermosetting resin.

6. The metal-clad laminate according to any one of claims 1 to 5, wherein the coating film contains at least one of an epoxy resin, a polyimide resin, or a bismaleimide resin.

7. The metal-clad laminate according to any one of claims 1 to 6, wherein the film thickness of the metal film is 0.05 μm or more and 10 μm or less.

8. The metal-clad laminate according to any one of claims 1 to 7, wherein the relative dielectric constant of the base film is 3.5 or less and the dielectric tangent is 0.004 or less.

9. The metal-clad laminate according to any one of claims 1 to 8, wherein the relative dielectric constant of the coating film is 3.5 or less and the dielectric tangent is 0.004 or less.

10. The metal-clad laminate according to any one of claims 1 to 9, wherein the thermal expansion coefficient (CTE) of the base film is 50 ppm or less.

11. The metal-clad laminate according to any one of claims 1 to 10, wherein the base film is a liquid crystal polymer (LCP) film, a polyether ether ketone (PEEK) film, a tetrafluoroethylene perfluoroalkyl (PFA) film, or a polyphenylene sulfide (PPS) film.

12. The metal-clad laminate according to any one of claims 1 to 11, wherein the base film contains a filler.

13. The metal-clad laminate according to claim 12, wherein the filler contains at least one of mica, talc, boron nitride (BN), magnesium oxide, and silica.

14. The metal-clad laminate according to any one of claims 12 to 13, wherein the filler has a plate-like shape.

15. The metal-clad laminate according to any one of claims 12 to 14, wherein the aspect ratio of the filler is 5 or more and 500 or less.

16. The metal-clad laminate according to any one of claims 12 to 15, wherein the average particle size of the filler is 20 μm or less.

17. The metal-clad laminate according to any one of claims 1 to 16, wherein the coating film contains a filler.

18. The metal-clad laminate according to any one of claims 1 to 17, wherein the metal film is a copper metal film.

19. The metal-clad laminate according to any one of claims 1 to 18, wherein the surface of the base film and / or the coating film is subjected to corona treatment, plasma treatment, or ultraviolet treatment.

20. The metal-clad laminate according to any one of claims 1 to 19, wherein the film thickness of the coating film is 5 μm or more and 20 μm or less.

Images