Metal-clad laminates

Abstract

The present invention provides a metal-clad laminate that reduces transmission loss of electrical signals, enables finer pitch of circuit patterns, enables high-precision formation of fine circuits, and exhibits excellent metal film adhesion. The metal-clad laminate comprises a coating film and a metal film sequentially laminated on a base film, wherein the metal film is formed by at least one of plating, sputtering, and vapor deposition, and the coating film has a surface roughness (Rz) of 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 increasing communication speeds and capacities in communication devices such as smartphones, circuit boards used in these devices are required to have low electrical signal loss, finer pitch circuit patterns, and high-precision and microscopic circuit formation.

[0003] Metal-clad laminates, which are the main materials of circuit boards, and metal-clad laminates (e.g., copper-clad laminates (CCLs)) formed by laminating a metal film on the surface of a base film containing a so-called insulating resin are also required to have the same performance as the above-mentioned circuit boards.

[0004] Various improved metal-clad laminates (for example, copper-clad laminates (CCL)) have been proposed (for example, see Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-14801 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In order to reduce the transmission loss of electric signals, it is effective to smooth the surface of the metal film that serves as the transmission path of the electric signals. However, if the surface of the metal film is smooth, the adhesion (adhesion) between the metal film and other layers becomes a problem.

[0010] Therefore, it is desired to provide a metal-clad laminate that can reduce transmission loss of electric signals and has excellent adhesion between a metal film and a base film.

[0011] However, to date, there has not been a metal-clad laminate that has a metal film on a smooth surface that can reduce the transmission loss of electrical signals, has good adhesion of the metal film, can achieve fine pitch of circuit patterns, can form fine circuits with high precision, and can fully meet all these requirements.

[0012] Therefore, an object of the present invention is to provide a metal-clad laminate having a metal film with a smooth surface capable of reducing transmission loss of electric signals, wherein the metal film has good adhesion, enables finer pitch of circuit patterns, and can form fine circuits with high precision.

[0013] Means for solving problems

[0014] The present inventors have repeatedly conducted in-depth research to solve the above-mentioned problems and have found that the above-mentioned problems can be solved by making the metal film a metal film formed by at least one of plating (Japanese: メッキ), sputtering and vapor deposition (Japanese: evaporation), and arranging a coating film with a specific surface roughness (Rz) between the metal film and the base film, thereby completing the present invention.

[0015] The present invention includes the following aspects.

[0016] [1] A metal-clad laminate comprising a coating film and a metal film sequentially stacked on a base film, wherein the metal film is formed by at least one of plating, sputtering and vapor deposition, and the surface roughness (Rz) of the coating film is less than 1 μm.

[0017] [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.

[0018] [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.

[0019] [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.

[0020] [5] The metal-clad laminate according to any one of [1] to [4], wherein the coating film contains a thermosetting resin.

[0021] [6] The metal-clad laminate according to any one of [1] to [5], wherein the coating film comprises at least one of an epoxy resin, a polyimide resin, and a bismaleimide resin.

[0022] [7] The metal-clad laminate according to any one of [1] to [6], wherein the coating film has a thickness equal to or greater than the surface roughness (Rz) of the base film × 0.8.

[0023] [8] The metal-clad laminate according to any one of [1] to [7], wherein the metal film has a thickness of 0.05 μm to 10 μm.

[0024] [9] The metal-clad laminate according to any one of [1] to [8], wherein the base film has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.004 or less.

[0025]

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

[0026]

[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.

[0027]

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

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

[0028]

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

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

[0029]

[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 silicon dioxide.

[0030]

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

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

[0031]

[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.

[0032]

[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.

[0033]

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

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

[0034]

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

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

[0035]

[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.

[0036] Effects of the Invention

[0037] According to the present invention, a metal-clad laminate can be provided having a metal film with a smooth surface capable of reducing transmission loss of electric signals. The metal film has good adhesion, enables finer pitch of circuit patterns, and enables formation of fine circuits with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a cross-sectional view showing an example of the structure of the metal-clad laminate of the present invention.

[0039] Figure 2 This is a cross-sectional view showing another example of the structure of the metal-clad laminate of the present invention. DETAILED DESCRIPTION

[0040] 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 of one embodiment of the present invention and the present invention is not limited to these contents.

[0041] The following definitions of terms apply throughout this specification and claims.

[0042] The film thickness of a base film, coating film, metal film, etc. is a value obtained by observing a cross section of a measurement object using a microscope, measuring the thickness at five locations, and averaging the measured values.

[0043] (Metal-clad laminate)

[0044] 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.

[0045] The metal film is formed by at least one of plating, sputtering, and vapor deposition.

[0046] The surface roughness (Rz) of the coating film is 1 μm or less.

[0047] Figure 1 This is a cross-sectional view showing an example of the structure of the metal-clad laminate of the present invention.

[0048] The metal-clad laminate 1 includes a base film 2 , a coating film 3 , and a metal film 4 , which are stacked in this order.

[0049] In addition, the metal-clad laminate of the present invention may have a coating film and a metal film laminated on both sides of the base film.

[0050] Figure 2 Another example of the structure of the metal-clad laminate of the present invention is shown.

[0051] Figure 2 The metal-clad laminate 1 of the present invention shown is formed by laminating a metal film 4a, a coating film 3a, a base film 2, a coating film 3b, and a metal film 4b in this order.

[0052] <Base film>

[0053] In the present invention, the substrate film is not particularly limited and can be appropriately selected according to the purpose. For example, insulating resin films such as polyimide film, polyetheretherketone (PEEK) film, polyetherketone (PEK) film, polyetherketoneketone (PEKK) film, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) film, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) film, tetrafluoroethylene-ethylene copolymer (ETFE) film, polyphenylene sulfide (PPS) film, aromatic polyamide film, polyethylene naphthalate film, liquid crystal polymer film (LCP), and mixtures thereof can be mentioned. Among them, polyetheretherketone (PEEK) film, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) film, polyphenylene sulfide (PPS) film, and liquid crystal polymer (LCP) film are preferred from the viewpoints of adhesion and electrical properties.

[0054] The base film may contain a filler. The filler will be described in detail below.

[0055] "filler"

[0056] The base film may contain a filler to impart various functions to the base film, such as strength, insulation, heat resistance, and adjustment of the coefficient of thermal expansion (CTE). Examples of fillers include inorganic fillers and organic fillers, which may be used alone or in combination.

[0057] Examples of the inorganic filler include mica, talc, boron nitride, magnesium oxide, silica, diatomaceous earth, titanium oxide, and zinc oxide. Among them, inorganic fillers such as mica, talc, boron nitride, magnesium oxide, and silica are preferred.

[0058] The organic filler is not particularly limited, and examples thereof include organic particles of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, polyimide, polyether ketone, polyether ether ketone, and polymethyl methacrylate.

[0059] The inorganic filler and the organic filler may be selected from the above and used alone or in combination of two or more. When two or more are combined, the inorganic filler and the organic filler may be combined.

[0060] As the shape of filler, it is not particularly limited and can be suitably selected according to purpose.For example, the inorganic filler can be a spherical inorganic filler, or a non-spherical inorganic filler, and from the viewpoint of thermal expansion coefficient (CTE), film strength, it is preferably a non-spherical inorganic filler. The shape of the non-spherical inorganic filler is as long as it is the three-dimensional shape beyond spherical (roughly true spherical), and for example, plate-like, flaky, columnar, chain-like, fibrous etc. can be enumerated. Wherein, from the viewpoint of thermal expansion coefficient (CTE), film strength, preferably plate-like, flaky inorganic filler, more preferably plate-like inorganic filler.

[0061] In the case of a plate-like or flaky inorganic filler, the average particle size in the planar direction is preferably 0.05 μm or more and 20 μm or less, preferably 0.1 μm or more and 15 μm or less, preferably 0.1 μm or more and 10 μm or less, more preferably 0.1 μm or more and 7 μm or less. In addition, from the viewpoint of the coefficient of thermal expansion (CTE) and film strength, 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, preferably 20 or more and 500 or less, and preferably 40 or more and 500 or less.

[0062] When the average particle size of the filler is 20 μm or less, the surface roughness of the base film can be reduced, and a smooth coating film can be easily formed.

[0063] When the aspect ratio is 5 or more, it is easy to sufficiently reduce the CTE.

[0064] The larger the aspect ratio, the easier it is to adjust the CTE. However, it is difficult to increase the aspect ratio while reducing the particle size, and the cost of the filler tends to increase. Therefore, it is preferably set to 500 or less.

[0065] [Measurement of average particle size and aspect ratio]

[0066] The average particle size and aspect ratio of the inorganic filler can be determined by, for example, observing with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and averaging the values measured at three or more locations. It should be noted that the average particle size and aspect ratio of the inorganic filler present in the film (layer) can be determined by, for example, embedding the film with an epoxy resin, then performing ion milling of the film cross section using an ion milling device to prepare a sample for cross-sectional observation, observing the cross section of the obtained sample using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and averaging the values measured at three or more locations.

[0067] The average particle size of the organic filler can be determined by observing the cross section of the substrate film with an electron microscope and measuring the average value of the maximum diameters of at least 10 particles as the average dispersed particle size when the filler is dispersed in the resin of the substrate film by melt kneading and dispersion.

[0068] 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.

[0069] <<Other ingredients>>

[0070] In the present invention, the base film may contain any known additives as needed. Examples of the additives include antioxidants, light stabilizers, ultraviolet absorbers, crystal nucleating agents, plasticizers, and filler dispersants.

[0071] <<Base Film Characteristics>>

[0072] The film thickness of the base film is not particularly limited and can be appropriately selected depending on the intended purpose, but is preferably 10 μm to 250 μm.

[0073] The surface roughness (Rz) of the substrate film is not particularly limited and can be appropriately selected depending on the intended purpose. However, considering various factors such as the type and content of fillers contained to impart various functions to the substrate film, the surface roughness (Rz) of the substrate film is preferably 1 μm or greater. On the other hand, to ensure that the surface roughness (Rz) of the coating film formed on the substrate film falls 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 greater and 10 μm or less.

[0074] In this specification, surface roughness (Rz) refers to the ten-point average roughness of the film surface. The ten-point average roughness Rz can be determined based on JIS B 0601: 2013 (ISO 4287: 1997 Amd. 1: 2009).

[0075] [Measurement of ten-point average roughness Rz]

[0076] The ten-point average roughness Rz (μm) of the sheet surface was obtained as follows: a roughness curve was measured for each test piece using a laser microscope. Based on the roughness curve, 10 samples were measured in accordance with JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009) to determine the average value.

[0077] The relative dielectric constant and dielectric loss tangent of the base film are not particularly limited and may be appropriately selected depending on the intended purpose. However, from the perspective of reducing transmission loss of electrical signals, the relative dielectric constant is preferably 3.5 or less and the dielectric loss tangent is preferably 0.004 or less.

[0078] [Relative dielectric constant and dielectric loss tangent]

[0079] The relative dielectric constant and dielectric loss tangent of the base film can be measured using a network analyzer MS46122B (manufactured by Anritsu Corporation) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM Corporation) by an open resonator method at a temperature of 23° C. and a frequency of 28 GHz.

[0080] The coefficient of thermal expansion (CTE) of the base film is not particularly limited and may be appropriately selected depending on the intended purpose. For example, it is preferably 50 ppm or less from the viewpoint of preventing curling after lamination and from the perspective of minimizing the difference in thermal expansion coefficient with the metal to be laminated.

[0081] The coefficient of thermal expansion can be measured as follows: using a thermomechanical analyzer (manufactured by Hitachi High-Technologies Corporation, product name: SII / / SS7100) in tensile mode, the temperature is increased from 25°C to 250°C at a load of 50 mN and a heating rate of 5°C / min., the temperature change of the dimensions is measured, and the linear expansion coefficient is calculated from the slope in the range from 25°C to 125°C.

[0082] The surface of the base film may be surface-treated by corona treatment, plasma treatment, or ultraviolet treatment for the purpose of improving adhesion with the coating film.

[0083] <Coating>

[0084] The surface roughness (Rz) of the coating film is 1 μm or less. The method for measuring the surface roughness (Rz) is as described in the above-mentioned "Properties of the Base Film" section.

[0085] By setting the surface roughness (Rz) of the coating film to 1 μm or less, a metal film with a smooth surface can be formed as will be seen in the examples described below. In such a metal-clad laminate capable of reducing transmission loss, the metal film can also have excellent adhesion.

[0086] The coating film is formed by forming a resin composition into a film and curing it.

[0087] The resin composition for forming the coating film preferably contains a thermosetting resin.

[0088] Examples of thermosetting resins include phenolic resins, epoxy resins, urea resins, melamine resins, unsaturated polyester resins, polyurethane resins, polyimide resins, silicone resins, and bismaleimide resins. Among these, from the viewpoints of heat resistance, adhesion, and dielectric properties, a coating film comprising at least one of epoxy resins, polyimide resins, and bismaleimide resins is preferred.

[0089] Epoxy resin

[0090] Examples of epoxy resins include: bisphenol A epoxy resin, bisphenol F epoxy resin, or resins obtained by hydrogenating these; glycidyl ester epoxy resins such as diglycidyl phthalate, diglycidyl isophthalate, diglycidyl terephthalate, glycidyl p-hydroxybenzoate, diglycidyl tetrahydrophthalate, diglycidyl succinate, diglycidyl adipate, diglycidyl sebacate, and triglycidyl trimellitate; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether Examples of epoxy resins include, but are not limited to, glycidyl ether epoxy resins such as 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, polyglycidyl ethers of sorbitol, and polyglycidyl ethers of polyglycerol; glycidyl amine epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil. Furthermore, novolac epoxy resins containing a xylene structure, naphthol novolac epoxy resins, phenol novolac epoxy resins, o-cresol novolac epoxy resins, and bisphenol A novolac epoxy resins may also be used.

[0091] Furthermore, examples of epoxy resins include brominated bisphenol A epoxy resins, phosphorus-containing epoxy resins, fluorine-containing epoxy resins, dicyclopentadiene skeleton-containing epoxy resins, naphthalene skeleton-containing epoxy resins, anthracene-type epoxy resins, tert-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.

[0092] <<Bismaleimide resin>>

[0093] Examples of the bismaleimide resin include 1-methyl-2,4-bismaleimide benzene, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-m-toluene 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.

[0094] As the bismaleimide resin, a commercially available compound may be used. Specifically, for example, BMI-3000, BMI-1500, BMI-2550, BMI-1400, BMI-2310, and BMI-3005 manufactured by DESIGNER MOLECURES Inc. can be preferably used.

[0095] Furthermore, there can be mentioned modified bismaleimide obtained by modifying the above-mentioned bismaleimide resin with a compound having a primary amine.

[0096] Furthermore, the coating film may contain other components such as fillers and various additives.

[0097] "filler"

[0098] The coating film may contain a filler in order to improve heat resistance, control fluidity, etc. The type of filler is not particularly limited and may be appropriately selected according to the purpose. For example, the fillers described in the "Filler" column above as fillers contained in the above-mentioned base film may be used.

[0099] The average particle size of the filler contained in the coating film is preferably 0.01 to 20 μm, more preferably 0.01 to 10 μm, and even more preferably 0.01 to 5 μm, so that the surface roughness (Rz) of the coating film satisfies 1 μm or less.

[0100] 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.

[0101] Since the coating film is required to have higher surface smoothness than the base film, the filler used preferably has an average particle size smaller than that of the base film and a smaller content.

[0102] <<Other ingredients>>

[0103] In addition to the above-mentioned thermosetting resin and filler, the resin composition may also contain a tackifier, flame retardant, curing agent, curing accelerator, coupling agent, heat aging inhibitor, leveling agent, defoaming agent, pigment and solvent to the extent that the function of the resin composition is not affected.

[0104] The thickness of the coating film is not particularly limited and can be appropriately selected depending on the intended purpose. For example, it is preferably 1 to 100 μm, more preferably 3 to 70 μm, further preferably 5 to 50 μm, and even more preferably 5 to 20 μm. If the coating film thickness is 1 μm or greater, sufficient uniformity can be maintained to smooth the surface of the substrate film. If it is 100 μm or less, the peel strength between the substrate film, the coating film, and the metal film can be enhanced.

[0105] In addition, from the viewpoint of using the coating to smooth the surface of the substrate film and then smooth the surface of the metal film to obtain the desired low loss of the electrical signal, the film thickness of the coating is preferably at least 0.8 times the value of the surface roughness (Rz) μm of the substrate film, more preferably at least 1 times the value of the surface roughness (Rz) μm of the substrate film, and further preferably at least 1.2 times the value of the surface roughness (Rz) μm of the substrate film.

[0106] The relative dielectric constant and dielectric loss tangent of the coating film are not particularly limited and may be appropriately selected depending on the intended purpose. However, from the perspective of reducing transmission loss of electrical signals, the relative dielectric constant is preferably 3.5 or less and the dielectric loss tangent is preferably 0.004 or less.

[0107] The relative dielectric constant and dielectric loss tangent are measured as described in the "Base Film Properties" section of the above-mentioned base film.

[0108] In order to improve the adhesion with the metal film, the surface of the coating film may be surface treated by corona treatment, plasma treatment, or ultraviolet treatment.

[0109] <<Coating Film Manufacturing Method>>

[0110] The coating film can be produced by forming the resin composition into a film.

[0111] The resin composition can be produced by mixing an epoxy resin, a polyimide resin, a bismaleimide resin, or the like with other components. The mixing method is not particularly limited as long as the resin composition becomes uniform. The resin composition is preferably used in the form of a solution or dispersion, and therefore a solvent is generally used.

[0112] Examples of the solvent include alcohols such as methanol, ethanol, isopropanol, n-propanol, isobutanol, n-butanol, 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.

[0113] When the resin composition is a solution or dispersion containing a solvent (resin varnish), coating on a substrate film and formation of a coating film can be smoothly performed, and a coating film having a desired thickness and surface roughness can be easily obtained.

[0114] When the resin composition contains a solvent, the solid content concentration is preferably in the range of 3 to 80% by mass, more preferably 10 to 50% by mass, from the viewpoint of workability including film formation. When the solid content concentration is 80% by mass or less, the viscosity of the solution is moderate, making uniform coating easy.

[0115] In a more specific embodiment of the method for producing a coating film, a resin varnish containing the above-mentioned resin composition 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 in a B-stage state. Here, the coating film being in a B-stage state means that the resin composition is in an uncured state or a semi-cured state where it has partially begun to cure, and refers to a state where the curing of the resin composition has further progressed by heating or the like.

[0116] Here, the method for coating the resin varnish on the substrate film is not particularly limited and can be appropriately selected according to the purpose. For example, spraying, spin coating, dipping, roller coating, blade coating, doctor roll coating, blade coating, curtain coating, slit coating, screen printing, inkjet coating, dispensing, etc. can be mentioned.

[0117] The coating film in the B-stage state can be further heated or the like to form a cured coating film.

[0118] <Metal Film>

[0119] The metal film is formed by at least one of plating, sputtering, and vapor deposition.

[0120] By forming a metal film on a coating film having a surface roughness (Rz) of 1 μm or less by at least one of plating, sputtering, and vapor deposition, a metal film having a smooth surface can be formed.

[0121] Furthermore, metal films formed by these formation methods can achieve finer pitches of circuit patterns and form fine circuits with high precision.

[0122] Plating and sputtering can be used alone or in combination. For example, a thin copper film can be deposited by sputtering and then formed by electrolytic copper plating.

[0123] The metal constituting the metal film is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include one selected from the group consisting of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, or an alloy containing at least one of these. Among these, copper and alloys containing copper are preferred from the viewpoints of shielding properties and economic efficiency.

[0124] As described above, the method for forming the metal film may include at least one of plating, sputtering, and vapor deposition. More specifically, examples include vapor-deposited 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 vapor-deposited films or sputtered films formed by vacuum film-forming methods (vacuum vapor deposition, sputtering, etc.), or plated films formed by electroplating are preferred due to their excellent surface conductivity.

[0125] From the viewpoint of ensuring sufficient electric signal transmission characteristics and achieving a good fine pitch of the circuit pattern, the thickness of the metal film is preferably 0.05 μm to 20 μm, more preferably 0.1 to 15 μm, and even more preferably 0.5 to 10 μm.

[0126] The surface roughness (Rz) of the metal film on the side not in contact with the coating film is not particularly limited and may be appropriately selected depending on the intended purpose. For example, from the perspective of reducing transmission loss of electric signals, it is preferably 0.5 μm or less.

[0127] Effects of Metal-Clad Laminates

[0128] While it can be difficult to smooth the surface of a substrate film due to fillers contained in the substrate film or due to manufacturing issues, forming a coating film with a surface roughness (Rz) of 1 μm or less on the substrate film can smooth the surface of the metal film, reducing transmission loss. Furthermore, the coating film can improve adhesion between the metal film and the coating film.

[0129] The metal film formed on the coating film is formed by at least one of plating, sputtering, and vapor deposition, and thus can achieve finer pitches of circuit patterns and form fine circuits with high precision.

[0130] <Thickness of Metal-Clad Laminate>

[0131] The thickness of the metal-clad laminate is not particularly limited and can be appropriately selected depending on the intended purpose. For example, it is preferably from 10 μm to 300 μm. If the thickness of the metal-clad laminate is above the lower limit of the above range, it is easy to handle and can ensure strength. If it is below the upper limit of the above range, it can be made thinner, smaller, and more flexible.

[0132] <Method for Manufacturing Metal-Clad Laminated Sheets>

[0133] A coating film is formed on a base film.

[0134] A metal film is formed on the surface of the coating film opposite to the base film.

[0135] As a more specific method for forming a coating film, as described in the "Method for Producing Coating Film" section above, a resin varnish containing a resin composition 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 heated or the like to form a cured coating film.

[0136] The method for applying the resin varnish is not particularly limited and can be appropriately selected depending on the purpose. Examples include spraying, spin coating, dipping, roll coating, blade coating, doctor roll coating, blade coating, curtain coating, slit coating, screen printing, inkjet coating, and dispensing.

[0137] Examples of a method for forming a metal film include a method based on a vacuum film-forming method (vacuum vapor deposition, sputtering), and a method based on an electroplating method.

[0138] From the perspective of being able to form a metal film having a desired film thickness and surface shape, a method of forming a vapor-deposited film by vacuum vapor deposition, a method of forming a plated film by electroplating, a method of forming a sputtered film by sputtering, or a method of forming a metal film by a combination of sputtering and electroplating by electroplating after sputtering can be used.

[0139] The metal-clad laminate of the present invention is Figure 2 In the case of a metal-clad laminate having a coating film and a metal film respectively provided on both sides of a substrate film, the coating film and the metal film can be formed on one side of the substrate film using the above method, and then the coating film and the metal film can be formed on the other side of the substrate film using the same method. Alternatively, a method can be used in which the coating films are formed on both sides of the substrate film at once, and then the metal film disposed on the coating films is formed on both sides at once.

[0140] In the case of using a substrate film and / or coating film that has been surface-treated by corona treatment, plasma treatment, or ultraviolet treatment, for example, after preparing the substrate film, the surface of the prepared substrate film is surface-treated, and then the coating film is formed on the surface-treated substrate film by the above-mentioned method. Alternatively, after forming the coating film, the surface of the coating film is surface-treated, and then the metal film is formed by the above-mentioned method.

[0141] [Example]

[0142] The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples. In the following, parts and % are by mass unless otherwise specified.

[0143] (Example 1)

[0144] <Base film>

[0145] Polyetheretherketone (PEEK) resin (Victrex Granules 450G, manufactured by Victrex) and synthetic mica (Micromica MK100, manufactured by Katakura & Co-op Agri) were mixed so that the synthetic mica accounted for 15% by volume. The mixture was extruded using a twin-screw extruder to produce pellets. The synthetic mica used had an average particle size of 4.9 μm and an aspect ratio of 30 to 50.

[0146] The obtained pellets were fed 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 100 μm thick PEEK film (film Rz: 6.4 μm, CTE 30 ppm).

[0147] <Preparation of Coating Film-Forming Resin Composition 1>

[0148] Alkyl bismaleimide resin (BMI-3000: manufactured by Desiner Molecules Inc.) was dissolved in toluene to a solid content of 50% by mass. The mixture was then diluted with methyl isobutyl ketone to a solid content of 25% by mass. Peroxide (PERCUMYL D: manufactured by NOF Corporation) was added to a ratio of 2% by mass relative to the solid content. These were mixed to prepare coating solution 1.

[0149] <Production of Copper-Clad Laminates>

[0150] The surface of the prepared PEEK film was corona treated. The coating solution 1 obtained above was applied to the surface-treated PEEK film. The coating was then dried. The film thickness after drying was 7 μm.

[0151] Next, the base film with the coating film was placed in an oven at 200° C. for 1 hour to cure the coating film.

[0152] The Rz of the coating film surface at this time was 0.35 μm.

[0153] A copper film (film thickness: 0.1 μm) was formed on the cured coating film by sputtering.

[0154] The Rz of the metal layer composed of the copper film was 0.15 μm.

[0155] The peel strength of the metal layer of the metal-clad laminate (copper-clad laminate) of Example 1 obtained in this manner was measured by the following measurement method and found to be 7 N / cm or more.

[0156] [Peel strength]

[0157] The peel strength of the copper-clad laminate was measured by a T-type peel test at a peeling speed of 300 mm / min according to the method specified in JIS K6854-3:1999.

[0158] In addition, the transmission loss of the metal-clad laminate (copper-clad laminate) of Example 1 was measured by the following measurement method, and the transmission characteristics were evaluated according to the following criteria.

[0159] [Transmission loss measurement method]

[0160] A microstrip line substrate (line length 50 mm) with an impedance adjusted to 50Ω was produced from a copper-clad laminate, and the S parameters (S21) at 20 GHz were measured using a network analyzer.

[0161] [Evaluation Criteria]

[0162] ○(Transmission loss 4dB / cm or less: 20GHz)

[0163] ×(Transmission loss greater than 4dB / cm: 20GHz)

[0164] Table 1 shows various measurement results of the base film, coating film, and metal film in the copper-clad laminate of Example 1, as well as measurement and evaluation results of the properties (peel strength and transmission properties) of the copper-clad laminate.

[0165] (Example 2 to Example 7)

[0166] In Example 1, except that the coating conditions were changed as shown in Table 1, copper-clad laminates of Examples 2 to 7 were produced in the same manner as in Example 1.

[0167] In Examples 2 to 7, coating solution 2 and coating solution 3 used were prepared as follows.

[0168] <Preparation of Coating Film-Forming Resin Composition 2>

[0169] A dicyclopentadiene-based low-dielectric epoxy resin (HP7200H: manufactured by DIC Corporation) was dissolved in toluene to a solid content of 50% by mass, and then diluted with methyl isobutyl ketone to a solid content of 25% by mass.

[0170] Alkyl bismaleimide resin (BMI-3000: manufactured by Desiner Molecules Inc.) and 2-methylimidazole (2MZ: manufactured by Shikoku Chemical) were added to the solid content of the dicyclopentadiene low dielectric epoxy resin at a ratio of 20 parts by mass and 2% by mass, respectively.

[0171] <Preparation of Coating Film-Forming Resin Composition 3>

[0172] Alkyl bismaleimide resin (BMI-3000: manufactured by Desiner Molecules Inc.) was dissolved in toluene to a solid content of 50% by mass. The mixture was then diluted with methyl isobutyl ketone to a solid content of 25% by mass. Synthetic mica (Micromica MK100DS: manufactured by Hikari Aggregate Co., Ltd.: average particle size 3.3 μm, aspect ratio 30-50) and peroxide (PERCUMYL D: manufactured by NOF Corporation) were added to the mixture at ratios of 10% by volume and 2% by mass, respectively, relative to the solid content of the alkyl bismaleimide resin. These were mixed to prepare coating solution 3.

[0173] The copper-clad laminates produced in Examples 2 to 7 were subjected to the same measurements as in Example 1.

[0174] Table 1 shows various measurement results of the base film, coating film, and metal film in the copper-clad laminates of Examples 2 to 7, as well as measurement and evaluation results of the characteristics of the copper-clad laminates.

[0175] (Comparative Example 1)

[0176] The surface of the PEEK film produced by the same method as in Example 1 was subjected to corona treatment.

[0177] A copper film (film thickness: 0.1 μm) was formed on the surface-treated PEEK film by sputtering.

[0178] The Rz of the metal layer composed of the copper film was 6.2 μm.

[0179] The peel strength of the metal layer of the metal-clad laminate (copper-clad laminate) of Comparative Example 1 obtained in this manner was measured by the same method as in Example 1 and was found to be 2 N / cm or less.

[0180] Table 1 shows various measurement results of the base film and the metal film in the copper-clad laminate of Comparative Example 1, as well as measurement and evaluation results of the characteristics of the copper-clad laminate.

[0181] (Comparative Examples 2 to 5)

[0182] In Example 1, except that the coating conditions were changed as shown in Table 1, copper-clad laminates of Comparative Examples 2 to 5 were produced in the same manner as in Example 1.

[0183] The same measurements as in Example 1 were performed on the copper-clad laminates produced in Comparative Examples 2 to 5.

[0184] Table 1 shows various measurement results of the base film, coating film, and metal film in the copper-clad laminates of Comparative Examples 2 to 5, as well as measurement and evaluation results of the characteristics of the copper-clad laminates.

[0185] [Table 1]

[0186]

[0187] The metal film in the metal-clad laminates of the present invention produced in the Examples has a smooth surface, thereby reducing transmission loss. Furthermore, as shown in Table 1, the metal-clad laminates of the present invention exhibit excellent adhesion between the coating film and the base film and the metal film.

[0188] Industrial applicability

[0189] The metal-clad laminate of the present invention can be suitably used in the production of FPC-related products for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game consoles, notebook computers, and medical devices.

[0190] [Explanation of Reference Numerals]

[0191] 1 Metal-clad laminate

[0192] 2. Base film

[0193] 3, 3a, 3b coating

[0194] 4, 4a, 4b Metal film.

Claims

1. A metal-clad laminate comprising a coating film and a metal film laminated in this order on a substrate film. The metal film is formed by plating, The surface roughness Rz of the coating film is 0.35 μ m or more and 1 μ m or less, The thickness of the coating film is greater than or equal to the surface roughness Rz×0.8 of the substrate film and is 3 μ m and above and 70 μ m or less.

2. The metal-clad laminate according to claim 1, wherein The metal film is a metal film formed by sputtering.

3. The metal-clad laminate according to claim 1, wherein The metal film is a metal film formed by vapor deposition.

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

5. The metal-clad laminate according to claim 1, wherein The surface roughness Rz of the substrate film is 1 μ m or more and 10 μ m or less. The metal-clad laminate according to claim 1 , wherein: The surface roughness Rz of the metal film is 0.5 μ m or less.

7. The metal-clad laminate according to claim 1, wherein The coating film contains a thermosetting resin.

8. The metal-clad laminate according to claim 7, wherein: The coating film includes at least any one of epoxy resin, polyimide resin, or bismaleimide resin.

9. The metal-clad laminate according to claim 1, wherein The thickness of the metal film is 0.05 μ m or more and 10 μ m or less.

10. The metal-clad laminate according to claim 1, wherein The base film has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.004 or less.

11. The metal-clad laminate according to claim 1, wherein The coating film has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.004 or less.

12. The metal-clad laminate according to claim 1, wherein The substrate film has a coefficient of thermal expansion (CTE) of 50 ppm or less.

13. The metal-clad laminate according to claim 1, wherein The substrate film is a liquid crystal polymer (LCP) film, a polyetheretherketone (PEEK) film, a tetrafluoroethylene perfluoroalkyl (PFA) film, or a polyphenylene sulfide (PPS) film.

14. The metal-clad laminate according to claim 1, wherein The base film contains a filler.

15. The metal-clad laminate according to claim 14, wherein The filler includes at least any one selected from the group consisting of mica, talc, boron nitride BN, magnesium oxide, and silicon dioxide.

16. The metal-clad laminate according to claim 14, wherein The filler has a plate-like shape.

17. The metal-clad laminate according to claim 14, wherein The filler has an aspect ratio of 5 or more and 500 or less.

18. The metal-clad laminate according to claim 14, wherein The average particle size of the filler is 20 μ m or less.

19. The metal-clad laminate according to claim 1, wherein The coating film contains a filler.

20. The metal-clad laminate according to claim 1, wherein The metal film is a copper metal film.

21. The metal-clad laminate according to claim 1, wherein The surface of the substrate film and / or the coating film is subjected to corona treatment, plasma treatment, or ultraviolet treatment.

22. The metal-clad laminate according to claim 1, wherein The film thickness of the coating is 5 μ m and above and 20 μ m or less.

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