Dielectric medium, copper-clad laminate, and method for manufacturing dielectric medium and copper-clad laminate

Abstract

The present disclosure provides a dielectric which has excellent electrical characteristics and does not cause copper foil expansion when a copper-clad laminate is manufactured using the dielectric, and a method for manufacturing the dielectric. Also provided are: a copper-clad laminate using the dielectric; and a method for producing the copper-clad laminate. The dielectric is characterized in that the amount of residual organic matter is 500 [mu] g / g or less. A metal-clad laminate has the dielectric and a metal foil.

Description

Technical Field

[0001] The present disclosure relates to dielectrics, copper-clad laminates, and methods of making the same. Background Art

[0002] High-frequency printed wiring boards are required to have low transmission loss. Patent Documents 1 to 4 describe the use of fluororesins mixed with fillers as wiring board materials for such high-frequency printed wiring boards.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 63-259907

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2008-7607

[0007] Patent Document 3: International Publication No. 2021 / 024883

[0008] Patent Document 4: International Publication No. 2021 / 235460 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The present disclosure aims to provide a dielectric having excellent electrical properties and preventing expansion of copper foil when a copper-clad laminate is produced using the dielectric, and a method for producing the same. Furthermore, the present disclosure aims to provide a copper-clad laminate using the dielectric and a method for producing the same.

[0011] Means for solving problems

[0012] The present disclosure relates to a dielectric, characterized in that the residual organic matter is 500 μg / g or less.

[0013] The dielectric preferably comprises a resin and an inorganic filler.

[0014] The resin is preferably a fluororesin.

[0015] The fluororesin is preferably non-melt-processable.

[0016] It is preferable that part or all of the fluororesin be polytetrafluoroethylene (PTFE).

[0017] The standard specific gravity (SSG) of the polytetrafluoroethylene is preferably 2.0 to 2.3.

[0018] The inorganic filler is preferably at least one selected from the group consisting of silica, titanium oxide, magnesium oxide, aluminum oxide, and forsterite.

[0019] It is preferred that part or all of the inorganic filler be silicon dioxide.

[0020] The content of the silicon dioxide relative to the total amount of the dielectric is preferably 30% by mass or more.

[0021] Preferably, the resin is polytetrafluoroethylene (PTFE), the inorganic filler is silica, and the content of silica relative to the total amount of the dielectric is 50% by mass or more and 65% by mass or less.

[0022] The average particle size of the silicon dioxide is preferably 0.1 to 10 μm.

[0023] Preferably, the surface of the silicon dioxide is coated with a silane coupling agent.

[0024] Preferably, the fluororesin is in the form of particles with an average particle size of 0.05 to 1000 μm.

[0025] The present disclosure also relates to a metal-clad laminate having the dielectric and a metal foil.

[0026] The present disclosure also relates to a copper-clad laminate having the dielectric and a copper foil.

[0027] The surface roughness Rz of at least the surface of the copper foil that is bonded to the dielectric is preferably 2.0 μm or less.

[0028] The copper foil is preferably rolled copper or electrolytic copper.

[0029] The dielectric loss tangent of the dielectric at 10 GHz is preferably 0.0015 or less.

[0030] The thickness of the dielectric is preferably 5 μm to 250 μm.

[0031] The present disclosure also relates to a method for producing the dielectric, characterized in that fluororesin particles and an inorganic filler are mixed to form a film.

[0032] In the above-mentioned production method, it is preferred to form a film using a composition consisting essentially of fluororesin particles and an inorganic filler.

[0033] The present disclosure also relates to a method for manufacturing the copper-clad laminate, characterized in that a dielectric and copper foil are stacked, heated in the range of 180°C to 390°C, and press-formed in a vacuum or in an inert gas atmosphere at a pressure in the range of 1 kN to 100 kN.

[0034] The present disclosure also relates to a circuit substrate, characterized by comprising the dielectric or the copper-clad laminate.

[0035] Effects of the Invention

[0036] The dielectric material disclosed herein has a low dielectric constant and low loss, and is excellent in electrical properties. Furthermore, when a copper-clad laminate is produced using the dielectric material disclosed herein, expansion of the copper foil does not occur. DETAILED DESCRIPTION

[0037] The present disclosure is described in detail below.

[0038] In the field of high-frequency printed wiring boards, demands for ever-higher levels of low dielectric constant and low loss performance have been increasing in recent years. Meanwhile, extensive research has been conducted on dielectrics made by mixing fillers into resins such as fluororesins.

[0039] The present disclosure provides a dielectric having a specific residual organic matter content, thereby satisfying low dielectric constant and low loss and having excellent electrical characteristics. Furthermore, when a copper-clad laminate is manufactured using the dielectric, copper foil does not expand.

[0040] When dielectrics are formed by coating or paste extrusion, they often contain residual organic matter from extrusion aids such as dispersants or hydrocarbon oils used during molding. Excessive amounts of residual organic matter in the dielectric can cause expansion of the copper foil due to volatile components during the manufacture of the copper-clad laminate, resulting in variations in the properties of the copper-clad laminate. For example, expansion of the copper foil can occur if the dielectric is not dried well during manufacturing, if a high amount of silane coupling agent is used, or if an anti-aging agent is added to improve stability.

[0041] Patent Document 2 describes that using a petroleum-based hydrocarbon solvent with a high fractionation temperature (180-250°C) as a processing aid in the production of fluororesin sheets reduces the solvent's volatilization during rolling. However, the specific content of volatile organic components in the dielectric layer of a copper-clad laminate is not described. Consequently, the optimal amount of residual organic matter in dielectrics has not been fully investigated.

[0042] The present disclosure has discovered the optimal amount of residual organic matter contained in a dielectric. The dielectric of the present disclosure is characterized in that the amount of residual organic matter is 500 μg / g or less.

[0043] The amount of residual organic matter in the dielectric is preferably 300 μg / g or less, more preferably 200 μg / g or less, and even more preferably 100 μg / g or less.

[0044] In the present disclosure, the amount of residual organic matter is a value measured by the following method.

[0045] <Pre-processing>

[0046] The dielectric material was cut into 10 mm squares and sealed in a heating container. The generated gas was collected in an adsorption tube during heating under the following conditions. A blank was prepared by performing the same operation without the dielectric material.

[0047] <Heating conditions>

[0048] Heating temperature: 280°C, heating time: 30 minutes, heating atmosphere: nitrogen atmosphere

[0049] <Thermal Desorption GC / MS Measurement>

[0050] A standard curve was prepared from the absolute amount of the standard and the obtained peak area values ​​for quantification.

[0051] <gc ms>

[0052] Device: GC7890A+5975C (Agilent)

[0053] Column: DB-5MS (Agilent J&W)

[0054] Carrier gas: He, column temperature: 40℃→300℃

[0055] Detector: MS, ion source temperature: 230°C, scan range: m / z 29-600

[0056] Standard: Dodecane

[0057] In the present disclosure, the lower limit of the amount of residual organic matter in the dielectric is preferably 3 μg / g, more preferably 5 μg / g, and even more preferably 7 μg / g.

[0058] If the amount of residual organic matter in the dielectric is too small, the sheet shape may not be maintained.

[0059] In the present disclosure, the dielectric whose residual organic matter amount is measured may be the dielectric obtained by etching the copper foil of a copper-clad laminate in which the dielectric and the copper foil are stacked.

[0060] The dielectric of the present disclosure is composed of a resin. In the case of a fluororesin, the dielectric of the present disclosure preferably contains an inorganic filler.

[0061] (resin)

[0062] The resin is preferably at least one selected from the group consisting of fluororesin, polyimide, modified polyimide, liquid crystal polymer (LCP), polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, modified polyphenylene ether, polyphenylene ether, and polybutadiene.

[0063] The dielectric of the present disclosure preferably contains a fluororesin. Since fluororesin has low dielectric properties, it can be suitably used for the purpose of the present disclosure.

[0064] (Fluororesin)

[0065] The fluororesin used in the present disclosure is preferably in a granular form.

[0066] The average particle size of the fluororesin particles is preferably 0.05 to 1000 μm. The lower limit of the average particle size of the fluororesin particles is more preferably 0.07 μm or greater, and even more preferably 0.1 μm or greater. The upper limit of the average particle size of the fluororesin particles is preferably 700 μm or less, and even more preferably 500 μm or less.

[0067] The use of such fluororesin particles has the advantages of excellent moldability and dispersibility. It should be noted that the average particle size here is a value measured in accordance with ASTM D 4895.

[0068] The volume-based cumulative 50% diameter of the fluororesin particles is preferably 0.05 to 40 μm. The lower limit of the volume-based cumulative 50% diameter of the fluororesin particles is more preferably 0.7 μm or greater, and even more preferably 1 μm or greater. The upper limit of the volume-based cumulative 50% diameter of the fluororesin particles is preferably 35 μm or less, and more preferably 30 μm or less.

[0069] The use of such fluororesin particles has the advantages of excellent moldability and dispersibility. Note that the volume-based cumulative 50% diameter herein is a value measured by a laser diffraction particle size distribution analyzer.

[0070] The fluororesin particles used in the present disclosure are not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE), tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] copolymer [FEP], TFE / alkyl vinyl ether copolymer [PFA], TFE / HFP / alkyl vinyl ether copolymer [EPA], TFE / chlorotrifluoroethylene [CTFE] copolymer, TFE / ethylene copolymer [ETFE], polyvinylidene fluoride [PVdF], and tetrafluoroethylene having a molecular weight of 300,000 or less [LMW-PTFE]. One type may be used alone, or two or more types may be mixed.

[0071] The fluororesin particles used in the present disclosure are preferably non-melt-processable.

[0072] Non-melt-processability refers to a resin that lacks sufficient fluidity even when heated above its melting point, making it impossible to mold using conventional melt molding methods. PTFE meets this characteristic.

[0073] In addition, from the perspective of low dielectric properties, PTFE is particularly preferred. PTFE preferably has fibrillar properties. PTFE with fibrillar properties refers to PTFE that can be paste-extruded or powder-calendered from unfired polymer particles.

[0074] It is preferable that a part or all of the fluororesin is PTFE.

[0075] Modified PTFE comprises TFE units based on TFE and modified monomer units based on modified monomers. The modified monomer units are part of the molecular structure of the modified PTFE and are derived from the modified monomers. The modified PTFE preferably comprises 0.001% to 0.500% by mass of the modified monomer units, and more preferably 0.01% to 0.30% by mass of the total monomer units. The total monomer units are derived from all monomers in the molecular structure of the modified PTFE.

[0076] The modifying monomer is not particularly limited as long as it can copolymerize with TFE. Examples thereof include perfluoroolefins such as hexafluoropropylene (HFP); chlorofluoroolefins such as chlorotrifluoroethylene (CTFE); hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF); perfluorovinyl ether; perfluoroalkylethylene (PFAE); ethylene. The modifying monomers used may be one or more.

[0077] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorounsaturated compounds represented by the following general formula (1).

[0078] CF2=CF-ORf···(1)

[0079] (Wherein, Rf represents a perfluoroorganic group.)

[0080] In this specification, a perfluoroorganic group is an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0081] Examples of perfluorovinyl ethers include perfluoro(alkyl vinyl ether) (PAVE) in which Rf in the general formula (1) is a perfluoroalkyl group having 1 to 10 carbon atoms. The perfluoroalkyl group preferably has 1 to 5 carbon atoms. Examples of perfluoroalkyl groups in PAVE include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, and perfluorohexyl. Preferred PAVEs include perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE).

[0082] The perfluoroalkylethylene (PFAE) is not particularly limited, and examples thereof include perfluorobutylethylene (PFBE) and perfluorohexylethylene (PFHE).

[0083] The modifying monomer in the modified PTFE is preferably at least one selected from the group consisting of HFP, CTFE, VDF, PAVE, PFAE, and ethylene.

[0084] In the present disclosure, it is preferred to use such a non-melt-processable fluororesin and produce a fluororesin sheet by a molding method that fibrillates the fluororesin. This molding method will be described later.

[0085] The standard specific gravity (SSG) of the above-mentioned PTFE is preferably 2.0 to 2.3. When using such PTFE, it is easy to obtain a PTFE membrane with high strength (cohesive force and puncture strength per unit thickness). Since the PTFE with a large molecular weight has a long molecular chain, it is difficult to form a structure in which the molecular chains are regularly arranged. In this case, the length of the amorphous portion increases, and the degree of entanglement between the molecules increases. It is believed that when the degree of entanglement between the molecules is high, the PTFE membrane is not easily deformed for the applied load and shows excellent mechanical strength. In addition, when using the PTFE with a large molecular weight, it is easy to obtain a PTFE membrane with a small average pore size.

[0086] The lower limit of the SSG is more preferably 2.05, and even more preferably 2.1. The upper limit of the SSG is more preferably 2.25, and even more preferably 2.2.

[0087] Standard specific gravity [SSG] is obtained by measuring the specific gravity of a sample prepared in accordance with ASTM D-4895-89 by the water displacement method.

[0088] The refractive index of the above-mentioned PTFE is preferably within the range of 1.2 to 1.6. By having such a refractive index, it is preferred in terms of low dielectric constant. The refractive index can be set within the above-mentioned range by adjusting the polarizability, the flexibility of the main chain, etc. The lower limit of the above-mentioned refractive index is more preferably 1.25, more preferably 1.30, and most preferably 1.32. The upper limit of the above-mentioned refractive index is more preferably 1.55, more preferably 1.50, and most preferably 1.45.

[0089] The above-mentioned refractive index is a value measured using a refractometer (Abbemat 300).

[0090] The granular PTFE preferably contains 50% by mass or more of polytetrafluoroethylene resin having a secondary particle size of 500 μm or more, more preferably 80% by mass or more. The PTFE having a secondary particle size of 500 μm or more within this range has the advantage of being able to produce a high-strength composite sheet.

[0091] By using PTFE having a secondary particle size of 500 μm or more, a composite sheet having lower electrical resistance and high toughness can be obtained.

[0092] The lower limit of the secondary particle size is more preferably 300 μm, and further preferably 350 μm. The upper limit of the secondary particle size is more preferably 700 μm or less, and further preferably 600 μm or less. The secondary particle size can be determined, for example, by sieving.

[0093] Furthermore, the maximum endothermic peak temperature (crystalline melting point) of the PTFE is preferably 340±7°C.

[0094] The PTFE may be low-melting-point PTFE having a maximum peak temperature of 338°C or lower in an endothermic curve on a crystalline melting curve measured by a differential scanning calorimeter, or high-melting-point PTFE having a maximum peak temperature of 342°C or higher in an endothermic curve on a crystalline melting curve measured by a differential scanning calorimeter.

[0095] Low melting point PTFE particles are particles produced by emulsion polymerization and have the above-mentioned maximum endothermic peak temperature (crystalline melting point), a dielectric constant (ε) of 2.08 to 2.2, and a dielectric loss tangent (tanδ) of 1.9×10 -4 ~4.0×10 -4 Examples of commercially available products include Polyflon Fine Powder F201, F203, F205, F301, and F302 manufactured by Daikin Industries, Ltd.; CD090 and CD076 manufactured by Asahi Glass Industries, Ltd.; and TF6C, TF62, and TF40 manufactured by DuPont.

[0096] High melting point PTFE particles are also produced by emulsion polymerization, and have the above-mentioned maximum endothermic peak temperature (crystalline melting point), a dielectric constant (ε) of 2.0 to 2.1, and a low dielectric loss tangent (tanδ) of 1.6×10 -4 ~2.2×10 -4 Examples of commercially available products include Polyflon Fine Powder F104 manufactured by Daikin Industries, Ltd.; CD1, CD141, and CD123 manufactured by Asahi Glass Industries, Ltd.; and TF6 and TF65 manufactured by DuPont.

[0097] The average particle size of the particles formed by secondary aggregation of two PTFE particles is preferably generally 250 μm to 2000 μm. In particular, granulated particles obtained by granulation using a solvent are preferred from the viewpoint of improving fluidity during mold filling during premolding.

[0098] (filler)

[0099] Inorganic fillers that can be used in the present disclosure are not particularly limited, and examples thereof include one or more inorganic fillers selected from the group consisting of ceramics, talc, mica, aluminum oxide, zinc oxide, tin oxide, titanium oxide, silicon oxide, calcium carbonate, calcium oxide, magnesium oxide, potassium titanate, forsterite, glass fibers, glass flakes, glass beads, silicon dioxide, calcium fluoride, boron nitride, barium sulfate, molybdenum disulfide, and potassium carbonate whiskers. Two or more of these may also be used in combination.

[0100] Among these, at least one selected from the group consisting of silica, titanium oxide, magnesium oxide, aluminum oxide, or forsterite is particularly preferred. Alternatively, a combination thereof is preferred. Particularly preferably, the inorganic filler is partially or entirely silica.

[0101] The shape of the inorganic filler is not particularly limited, and a spherical shape, a crushed shape, etc. can be mentioned. Among them, a spherical shape is preferred. If it is a spherical shape, it is easy to process uniformly during the hole processing, has a small specific surface area, and is preferred in terms of low transmission loss.

[0102] The spherical filler is a filler whose particle shape is close to a true sphere. Specifically, the sphericity is preferably 0.80 or more, more preferably 0.85 or more, further preferably 0.90 or more, and most preferably 0.95 or more. Regarding sphericity, a photograph is taken with an SEM, and the area and perimeter of the particles observed thereby are calculated by (sphericity) = {4π × (area) ÷ (perimeter) 2}. The closer to 1, the closer to a true sphere. Specifically, the average value of 100 particles measured using an image processing device (Spectris Co., Ltd.: FPIA-3000) is used.

[0103] In the present disclosure, the average particle size of the filler is preferably 0.1 μm to 10 μm. It should be noted that the average particle size here refers to the D50 value measured using a laser diffraction particle size distribution analyzer. If the average particle size is less than 0.1 μm, filler aggregation occurs, which tends to prevent the achievement of sufficient effects. Furthermore, if the average particle size exceeds 10 μm, thin film formation tends to be difficult.

[0104] The average particle size of the spherical silica particles used in the present disclosure is preferably 0.1 to 10 μm.

[0105] In addition, the spherical silica particles used in the present disclosure are preferably such that, when the volume is accumulated from the side with the smaller particle size, D90 / D10 is 2 or more (desirably 2.3 or more, 2.5 or more), and D50 is 10 μm or less. Furthermore, D90 / D50 is preferably 1.5 or more (more desirably 1.6 or more). D50 / D10 is preferably 1.5 or more (more desirably 1.6 or more). Since the spherical silica particles with a small particle size can enter the gaps between the spherical silica particles with a large particle size, the filling property is excellent and the fluidity can be improved. In particular, as a particle size distribution, it is preferred that the frequency of the side with a smaller particle size is larger than that of the Gaussian curve. The particle size can be measured using a laser diffraction scattering particle size distribution measuring device. In addition, it is preferred to remove coarse particles with a particle size greater than a specified value using a filter or the like.

[0106] The water absorption of the spherical silica is preferably 1.0% or less, more preferably 0.5% or less. The water absorption is based on the mass of the dry spherical silica. The water absorption is measured by placing a dry sample at 40°C and 80% RH for one hour and then measuring the water content generated by heating to 200°C using a Karl Fischer moisture analyzer.

[0107] The spherical silica particles can also be measured by heating the dielectric sheet at 600° C. in air atmosphere for 30 minutes to burn off the fluororesin, taking out the spherical silica particles, and then measuring the above parameters using the above methods.

[0108] The spherical silica can be made of commercially available silica particles that satisfy the above-mentioned properties. Examples of commercially available silica particles include Denka fused silica FB grade (manufactured by Denka Co., Ltd.), Denka fused silica SFP grade (manufactured by Denka Co., Ltd.), Excelica (manufactured by Tokuyama Co., Ltd.), and high-purity synthetic spherical silica particles such as Admafine (manufactured by Admatechs Co., Ltd.), Admanano (manufactured by Admatechs Co., Ltd.), and Admafuse (manufactured by Admatechs Co., Ltd.).

[0109] The titanium oxide, magnesium oxide, and aluminum oxide have a higher relative dielectric constant (Dk) than silicon dioxide, and therefore can be added to adjust the relative dielectric constant (Dk). Commercially available titanium oxide includes CR-EL (manufactured by Ishihara Sangyo Co., Ltd.) and HT0210 (manufactured by Toho Titanium Co., Ltd.). Commercially available magnesium oxide includes RF-10CS and RF-10C-45μm (manufactured by Ube Materials Co., Ltd.). Commercially available aluminum oxide includes LS-110F and LS-210B (manufactured by Nippon Light Metal Co., Ltd.).

[0110] The inorganic filler, especially the silica particles, is preferably surface-treated. This surface treatment can suppress aggregation of the inorganic filler, especially the silica particles, and allow the inorganic filler, especially the silica particles, to be well dispersed in the resin composition.

[0111] The surface treatment can be performed by appropriately selecting the type and treatment amount of the surface treatment agent.

[0112] The surface treatment is not particularly limited and any known treatment may be used. Specifically, for example, treatment with a silane coupling agent such as epoxy silane, amino silane, isocyanate silane, vinyl silane, acrylic silane, hydrophobic alkyl silane, phenyl silane, or fluorinated alkyl silane having a reactive functional group, plasma treatment, or fluorination treatment may be used.

[0113] Specific examples of the silane coupling agent include epoxy silanes such as γ-glycidoxypropyltriethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, amino silanes such as aminopropyltriethoxysilane and N-phenylaminopropyltrimethoxysilane, isocyanate silanes such as 3-isocyanatepropyltrimethoxysilane, vinyl silanes such as vinyltrimethoxysilane, and acrylic silanes such as acryloxytrimethoxysilane.

[0114] In the present disclosure, among the surface-treated silica particles, silica particles whose surfaces are coated with a silane coupling agent are preferably used.

[0115] When treated with a silane coupling agent, the amount of the silane coupling agent used is preferably 3% by mass or less relative to the inorganic filler, particularly the silica particles. A large amount of the silane coupling agent used may cause the copper foil to swell during the production of the copper-clad laminate.

[0116] (Dielectric)

[0117] The dielectric disclosed herein is composed of the aforementioned resin, preferably containing an inorganic filler and fluororesin particles. Depending on the needs, it may contain components other than the inorganic filler and fluororesin particles, or it may be composed solely of the inorganic filler and fluororesin particles. The content of components other than the inorganic filler and fluororesin particles is preferably 10% by mass or less relative to the total amount of the dielectric.

[0118] Particularly preferred are dielectrics consisting essentially of fluororesin particles and inorganic fillers. It should be noted that "essentially consisting of fluororesin particles and inorganic fillers" means that the content of components other than the inorganic filler and fluororesin particles is 3% by mass or less relative to the total amount of the dielectric.

[0119] The content of the inorganic filler relative to the total amount of the dielectric is preferably 30% by mass or more. Within this range, the linear expansion coefficient of the dielectric can be controlled to be low.

[0120] Furthermore, the content of silicon dioxide relative to the total amount of the dielectric is preferably 30% by mass or more.

[0121] The lower limit of the content of the inorganic filler is more preferably 35% by mass, and further preferably 40% by mass. On the other hand, the upper limit of the content of the inorganic filler is preferably 65% ​​by mass.

[0122] The dielectric of the present disclosure may have an anti-aging agent.

[0123] As an antioxidant, any antioxidant commonly used in the resin industry can be used without particular limitation. However, the use of at least one antioxidant selected from the group consisting of phenolic antioxidants, amine antioxidants, phosphorus antioxidants, and sulfur antioxidants is preferred because it can significantly improve the resistance to oxidative degradation of the resulting dielectric without hindering the crosslinking reaction. Among these, phenolic antioxidants and amine antioxidants are preferred, with phenolic antioxidants being particularly preferred.

[0124] Examples of the phenolic antioxidant include dibutylhydroxytoluene, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,4-di-tert-amyl-6-(1-(3,5-di-tert-amyl-2-hydroxyphenyl)ethyl)phenyl acrylate, 3,5-di-tert-butyl-4-hydroxyanisole, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 4,4'-butylene-bis(6-tert-butyl-m-cresol), 3,9-bis(2-(3-( 3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, tetrakis(methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenylpropionate)methane [i.e., pentaerythritolmethyl-tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionate), 6-(4-hydroxy-3-methyl-5-tert-butylanilino)-2,4-bisoctylthio-1,3,5-triazine, 2-octylthio-4,6-bis-(3,5-di-tert-butyl-4-oxyanilino)-1,3,5-triazine, and the like.

[0125] Examples of amine-based antioxidants include 1-[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine and bis-(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-n-butylmalonate.

[0126] Examples of the phosphorus-based antioxidant include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, tris(dinonylphenyl) phosphite, tris(2,4-di-tert-butylphenyl) phosphite, 2,2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 4,4'-butylene-bis(3-methyl-6-tert-butylphenyl-di-tridecyl) phosphite, 4,4'-diphenylenediphosphite tetrakis(2,4-di-tert-butylphenyl), and cycloneopentanylate tetraylbis(isodecyl phosphite).

[0127] Examples of sulfur-based antioxidants include dilauryl 3,3-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3-thiodipropionate, pentaerythritol-tetrakis-(β-lauryl-thio-propionate), and 3,9-bis(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane.

[0128] These anti-aging agents can be used alone or in combination of two or more.

[0129] The amount of the antioxidant relative to the total amount of the dielectric is preferably below 3 ppm. If this range is reached, the amount of residual organic matter in the dielectric will not be affected. In addition, in the case of a dielectric having high heat resistance such as a fluororesin, the antioxidant may not be added.

[0130] The dielectric material disclosed herein is generally used in the form of a sheet.

[0131] The thickness of the dielectric is preferably 5 μm to 250 μm. The dielectric disclosed herein can fully achieve its purpose even if it is thin. From this perspective, it is more preferably less than 200 μm, and even more preferably less than 150 μm.

[0132] The dielectric loss tangent (Df) at 10 GHz of the dielectric of the present disclosure is preferably 0.0015 or less. Setting it within this range is preferred in terms of low dielectric loss.

[0133] The upper limit of the dielectric loss tangent (Df) is more preferably 0.0012, and even more preferably 0.0011. On the other hand, the lower limit of the dielectric loss tangent (Df) is preferably 0.00001.

[0134] The dielectric material disclosed herein preferably has a relative dielectric constant (Dk) of 3.5 or less at 10 GHz. Setting the relative dielectric constant within this range is preferred in terms of low dielectric loss.

[0135] The upper limit of the relative dielectric constant (Dk) is more preferably 3.2, and even more preferably 3.1. On the other hand, the lower limit of the relative dielectric constant (Dk) is preferably 2.0, and even more preferably 2.5.

[0136] The relative dielectric constant (Dk) and dielectric loss tangent (Df) at 10 GHz in this specification were determined by measuring Dk and Df at 25° C. and 10 GHz using a split-cylinder dielectric constant / dissipation tangent measuring apparatus (manufactured by EM lab).

[0137] Furthermore, the coefficient of linear expansion (CTE) is preferably 100 ppm / K or less. This range is preferred for achieving a dielectric sheet with low shrinkage and excellent dimensional stability. The upper limit of the coefficient of linear expansion (CTE) is more preferably 70 ppm / K, and even more preferably 50 ppm / K. On the other hand, the lower limit of the coefficient of linear expansion (CTE) is more preferably 5 ppm / K, and even more preferably 10 ppm / K.

[0138] Regarding the linear expansion coefficient in this specification, TMA measurement is performed in the tensile mode using a TMA-7100 (manufactured by Hitachi High-Tech Science Corporation). As a sample piece, a piece cut into a length of 20 mm and a width of 5 mm is used. The distance between the chucks is set to 10 mm. The linear expansion coefficient is determined from the displacement of the sample at 0°C to 150°C while applying a load of 49 mN and heating at a rate of 2°C / min.

[0139] (Method for manufacturing dielectric)

[0140] The dielectric of the present disclosure can be obtained by mixing the above-mentioned fluororesin particles with an inorganic filler and forming the mixture into a film. The present disclosure also relates to a method for producing a dielectric obtained by mixing the fluororesin particles with an inorganic filler and forming the mixture into a film.

[0141] The production method is not limited and can be carried out by coating molding, paste extrusion molding, powder calendering molding, etc.

[0142] Examples of the coating method include spray coating, roll coating, coating with a doctor blade, dip coating, impregnation coating, rotary flow coating, curtain flow coating, coating with a bar coater, gravure coating, micro gravure coating, and die coating.

[0143] As described above, the fluororesin used in the dielectric of the present disclosure is preferably a non-melt-processable fluororesin. When such a fluororesin is used, it is preferably formed into a sheet by fibrillating powdered PTFE as a raw material.

[0144] The specific methods of paste extrusion molding and powder calendering molding are not particularly limited, and general methods are described below.

[0145] (Paste extrusion molding)

[0146] The method for producing the above-mentioned sheet may include: a step (1a) of mixing fluororesin particles, for example, PTFE powder obtained using a hydrocarbon-based surfactant, an inorganic filler and an extrusion aid; a step (1b) of subjecting the obtained mixture to paste extrusion molding; a step (1c) of calendering the extrudate obtained by extrusion molding; a step (1d) of drying the calendered sheet; and a step (1e) of calendering the dried sheet to obtain a molded body.

[0147] The paste extrusion molding may be performed by adding conventionally known additives such as pigments and fillers to the fluororesin particles.

[0148] The extrusion aid is not particularly limited, and a generally known extrusion aid can be used, for example, hydrocarbon oil.

[0149] In the step (1d) of drying the rolled sheet, the drying temperature is preferably set to 100°C to 300°C and the drying time is preferably set to 15 minutes to 1 hour in order to reduce the amount of residual organic matter in the dielectric.

[0150] (Powder calendering molding)

[0151] Powder calendering is a method of applying shear force to resin powder to fibrillate it, thereby forming it into a sheet shape. Subsequently, a step of calendering to obtain a molded body may be included.

[0152] More specifically, a production method including the following steps can be mentioned:

[0153] A step (1) of applying a shear force while mixing a raw material composition containing fluororesin particles and a filler;

[0154] a step (2) of forming the mixture obtained in the above step (1) into a block; and

[0155] A step (3) of rolling the bulk mixture obtained in the above step (2) into a sheet shape.

[0156] Furthermore, the process may include a step (4) of firing the sheet obtained above at 200° C. to 400° C. for 1 minute to 60 minutes.

[0157] Alternatively, step (2) may be omitted.

[0158] When the sheet is produced by the above-mentioned powder calendering method, it is preferable to form the film using a composition consisting essentially of fluororesin particles and an inorganic filler.

[0159] Alternatively, it is preferable to mix only the fluororesin particles and the inorganic filler and then form the mixture.

[0160] (Other resins)

[0161] Liquid crystal polymers (LCPs) include, for example, thermoplastic liquid crystal polyesters or thermoplastic liquid crystal polyester amides into which amide bonds have been introduced. Liquid crystal polymers may also be polymers obtained by further introducing an isocyanate-derived bond, such as an imide bond, a carbonate bond, a carbodiimide bond, or an isocyanurate bond, into aromatic polyesters or aromatic polyester amides. Furthermore, polymers having a rigid structure, such as naphthoic acid, are preferred.

[0162] Polyimide is a general term for polymers containing imide bonds in repeating units, and is generally an aromatic polyimide formed by directly linking aromatic compounds through imide bonds.

[0163] The modified polyimide is a polymer containing an imide bond in a repeating unit, which reduces the water absorption of the polyimide.

[0164] Polyphenylene sulfide is a crystalline thermoplastic resin having a simple linear structure in which benzene rings (p-phenylene groups) and sulfur atoms (sulfide bonds) are alternately bonded.

[0165] Cycloolefin polymers are polymers with a cyclic structure in the polymer chain, which can be polymerized by ring-opening metathesis polymerization or coordination polymerization.

[0166] Polystyrene is a polymer formed by polymerizing styrene, and also includes syndiotactic polystyrene, which controls stereoregularity and imparts crystallinity.

[0167] Epoxy resins are thermosetting synthetic resins with reactive epoxy groups at the ends. The most representative example is a copolymer of bisphenol A and epichlorohydrin. Various polyamines and acid anhydrides can also be used as curing agents.

[0168] Bismaleimide resin is a high-performance, thermosetting, addition-type polyimide. It is typically synthesized by condensing phthalic anhydride with an aromatic diamine in a 2:1 molar ratio to form bismaleimide, followed by Michael addition of more diamine to the terminal double bond of the bismaleimide.

[0169] Polyphenylene ether is a thermoplastic resin made from 2,6-disubstituted phenols by oxidative coupling polymerization.

[0170] Polyphenylene ether (PPE) is a blend of polyphenylene ether (PPO) and polystyrene, and is a resin having toughness and rigidity as well as impact resistance at low temperatures.

[0171] Polyphenylene ether is a plastic with characteristics such as heat resistance, flame retardancy, and chemical resistance.

[0172] Modified polyphenylene ether is a general term for polymer alloys formed by mixing polyphenylene ether (PPE), an amorphous engineering plastic, with other resins. Since benzene rings are ether-bonded in the main chain, modified polyphenylene ether is a resin with excellent hydrolysis resistance.

[0173] Polybutadiene is a general-purpose synthetic rubber produced by polymerizing 1,3-butadiene. It is a material with excellent elasticity, wear resistance, and low-temperature properties.

[0174] Examples of methods for forming sheets using resins other than the above-mentioned fluororesins include melt extrusion, casting, inflation, calendaring, injection molding, vacuum / pressure molding, compression molding, and press molding. Residual organic matter can be reduced by controlling the molding temperature and molding time in each molding method.

[0175] In the case of a sheet molding method using a resin other than a fluororesin, it is preferable to mold the resin alone or to mold a composition containing the resin and an inorganic filler.

[0176] (Thermocompression molding)

[0177] The method for producing a liquid crystal polymer film preferably includes at least: a heat treatment step of heat-treating a laminate having both sides of a thermoplastic liquid crystal polymer film sandwiched between a pair of heat-resistant release supports at a temperature of (HT+15)°C to (HT+70)°C relative to the heat deformation temperature (hereinafter sometimes referred to as HT) of the thermoplastic liquid crystal polymer film before the heat treatment step under a specified pressure; and a peeling step of peeling the pair of heat-resistant release supports from the laminate to obtain the thermoplastic liquid crystal polymer film.

[0178] In the heat treatment process, a liquid crystal polymer film obtained by extrusion molding (e.g., inflation molding) is used. A laminated body, sandwiched between a pair of heat-resistant release supports on both sides of the liquid crystal polymer film, is heat treated at a specified temperature under a specified pressure. This heat treatment may be due to the shear forces applied to the liquid crystal polymer molecules on the surface and back of the surface layer, allowing the dielectric constant in the thickness direction of the liquid crystal polymer film after the heat treatment process to be controlled within a desired range. Furthermore, the heat treatment process can also reduce residual organic matter in the liquid crystal polymer.

[0179] The heat-resistant releasable supports provided on both surfaces of the liquid crystal polymer film may be of the same kind or different kinds as long as the purpose can be achieved, but are preferably of the same kind.

[0180] (Copper-clad laminate)

[0181] The dielectric material disclosed herein can be used as a sheet for a printed wiring board by being laminated with other base materials.

[0182] The present disclosure also relates to a metal-clad laminate including the above-mentioned dielectric and metal foil.

[0183] Examples of the metal include copper, stainless steel, aluminum, iron, silver, gold, and ruthenium. Alloys thereof may also be used. Among these, copper is preferred.

[0184] The present disclosure also relates to a copper-clad laminate comprising the above-mentioned dielectric and copper foil. Alternatively, the copper-clad laminate may be characterized by copper foil being bonded to one or both sides of the above-mentioned dielectric. As described above, dielectrics comprising the fluororesin of the present disclosure are particularly suitable for use in printed wiring board applications and are therefore suitable for use as such copper-clad laminates.

[0185] The dielectric loss tangent (Df) of the dielectric in the copper-clad laminate at 10 GHz is preferably 0.0015 or less. Setting it within this range is preferred in terms of low dielectric loss.

[0186] The upper limit of the dielectric loss tangent (Df) is more preferably 0.0012, and even more preferably 0.0011. On the other hand, the lower limit of the dielectric loss tangent (Df) is preferably 0.00001.

[0187] The thickness of the dielectric in the copper-clad laminate is preferably 5 μm to 250 μm. The dielectric of the present disclosure can fully achieve its purpose even if it is thin. From this perspective, it is more preferably less than 200 μm, and even more preferably less than 150 μm.

[0188] The copper foil preferably has a surface roughness Rz of 2.0 μm or less. That is, the dielectric of the present disclosure exhibits excellent adhesion to highly smooth copper foil having an Rz of 2.0 μm or less. Furthermore, the Rz value of the copper foil on the surface bonded to the fluororesin film is not particularly limited, provided that at least the Rz value of the surface bonded to the fluororesin film is 2.0 μm or less.

[0189] The Rz value is the sum of the highest peak height (maximum peak height: Rp) and the deepest valley depth (maximum valley depth: Rv). The surface roughness is the ten-point average roughness specified in JIS-B0601. In this specification, the Rz value is measured using a surface roughness meter (trade name: SURFCOM 470A, manufactured by Tokyo Seiki Co., Ltd.) with a measurement length of 4 mm.

[0190] The thickness of the copper foil is not particularly limited, but is preferably in the range of 1 μm to 100 μm, more preferably in the range of 5 μm to 50 μm, and even more preferably in the range of 9 μm to 35 μm.

[0191] The copper foil is not particularly limited, and specific examples thereof include rolled copper foil and electrolytic copper foil.

[0192] The copper foil having an Rz of 2.0 μm or less is not particularly limited, and commercially available copper foil can be used. Examples of commercially available copper foil having an Rz of 2.0 μm or less include electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil Co., Ltd.) and electrolytic copper foil CF-V9S-SV-18 (thickness 18 μm / Rz 1.5 μm) (manufactured by Fukuda Metal Foil Co., Ltd.).

[0193] The copper foil may be a copper foil subjected to surface treatment in order to improve the bonding strength with the dielectric material of the present disclosure.

[0194] In the copper-clad laminate disclosed herein, the copper layer may be formed on one or both sides of the roll sheet. Examples of methods for forming the copper layer include laminating (bonding) copper foil on the surface of the roll sheet, vapor deposition, and plating.

[0195] Examples of methods for laminating copper foil include hot pressing. The hot pressing temperature can be between -150°C (the melting point of the dielectric film) and +40°C (the melting point of the dielectric film). The hot pressing time can be, for example, 1 to 30 minutes. Production can be achieved by using a hot pressing pressure of 0.1 to 10 MPa.

[0196] The present disclosure also relates to a method for manufacturing a copper-clad laminate, characterized in that a dielectric and copper foil are stacked, heated in the range of 180 to 390° C., and press-formed in a vacuum or in an inert gas atmosphere at a pressure in the range of 1 to 100 kN.

[0197] By performing press molding under such conditions, the dielectric material can be bonded to the copper foil without deteriorating.

[0198] The copper-clad laminate disclosed herein is not particularly limited in its use, but is preferably used as a circuit substrate. The present invention also provides a circuit substrate having the above-mentioned dielectric or the above-mentioned copper-clad laminate.

[0199] A circuit substrate is a plate-like component used to electrically connect electronic components such as semiconductors and capacitor chips while being arranged and fixed in a limited space. The composition of the circuit substrate formed by the dielectric or copper-clad laminate disclosed herein is not particularly limited. The circuit substrate can be any of a rigid substrate, a flexible substrate, and a rigid-flexible substrate. The circuit substrate can be any of a single-sided substrate, a double-sided substrate, and a multi-layer substrate (laminated substrate, etc.). It is particularly suitable for use as a flexible substrate or a rigid substrate. It is particularly suitable for use as a printed circuit board for high frequencies above 10 GHz.

[0200] The method for producing the circuit board is not particularly limited, and the circuit board can be produced by a general method using the copper-clad laminate described above.

[0201] Example

[0202] The present disclosure will be described in detail below based on Examples. In the following Examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "mass %", respectively.

[0203] (Examples 1 to 4, Examples 6 to 9)

[0204] (Paste Extrusion)

[0205] Fluororesin particles and silica were weighed separately so that the silica content would be the amount shown in Table 1, and mixed using a mixer in the presence of dry ice. The temperature during mixing was -10°C or lower.

[0206] 18 to 23% of oil (Isopar H) was added to the obtained mixture, mixed, and aged for about 5 hours.

[0207] The aged composition was preformed under a pressure of 3 MPa, and the preformed body was extruded at 40° C. and 50 mm / min to obtain an extruded sample.

[0208] The extruded sample was rolled using a twin roll (roll gap: set to 500 to 80 μm) to obtain a sample with a film thickness of 125 μm. The sample was dried at 200° C. for 1 hour and fired at 360° C. for 10 minutes to obtain a dielectric sheet.

[0209] It should be noted that the fluororesin particles (PTFE) used in each example have the following properties.

[0210] Average particle size: 500 μm

[0211] Apparent density: 460g / L

[0212] Standard specific gravity: 2.17

[0213] It should be noted that, as shown in Table 1, the silica used in each example includes SC6500-SQ (average particle size 2.1 μm) manufactured by Admatechs, spherical silica obtained by surface-treating SC6500-SQ (average particle size 2.1 μm) manufactured by Admatechs with 3-aminopropyltriethoxysilane (treatment amount 1 mass %), or SC2500-SQ (average particle size 0.5 μm) manufactured by Admatechs, and crushed silica obtained by surface-treating ZA-30 manufactured by Ronson Corporation with a treatment amount of 1 mass % using a mixture of phenyltrimethoxysilane and aminoethylaminopropyltrimethoxysilane in a ratio of 9:1.

[0214] (Example 5)

[0215] (Powder Calendering)

[0216] Fluororesin powder (PTFE) and silica were weighed in the prescribed amounts according to the ratios shown in Table 1 and stirred twice at room temperature using a WonderCrusher at memory 6 for 30 seconds. The resulting powder was rolled using a twin-roller (roll gap set to 100 μm) to obtain a 130 μm thick sample. The sample was then fired at 360°C for 10 minutes to obtain a dielectric sheet.

[0217] (Comparative Examples 1 to 3)

[0218] (Paste Extrusion)

[0219] Fluororesin particles and silica were weighed separately so that the silica content would be the amount shown in Table 1, and mixed using a mixer in the presence of dry ice. The temperature during mixing was -10°C or lower.

[0220] To the obtained mixture, 18% to 23% of oil (Isopar H) was added, and in Comparative Example 2, 1000 ppm of butylated hydroxytoluene (BHT) as an antioxidant was further added, followed by mixing and aging for about 5 hours.

[0221] The aged composition was preformed under a pressure of 3 MPa, and the preformed body was extruded at 40° C. and 50 mm / min to obtain an extruded sample.

[0222] The extruded sample was rolled using a twin roll (roll gap: set to 500 to 80 μm) to obtain a sample with a thickness of 125 μm. The sample was dried under the conditions described in Table 1 and fired at 360° C. for 10 minutes to obtain a dielectric sheet.

[0223] The obtained dielectric sheets were evaluated based on the following criteria.

[0224] [Residual organic matter]

[0225] <Pre-processing>

[0226] The dielectric sheet was cut into 10 mm squares and sealed in a heating container. The generated gas during heating under the following conditions was collected in an adsorption tube. A blank was prepared by performing the same operation without inserting a sample.

[0227] <Heating conditions>

[0228] Heating temperature: 280°C, heating time: 30 minutes, heating atmosphere: nitrogen atmosphere

[0229] <Thermal Desorption GC / MS Measurement>

[0230] A standard curve was prepared from the absolute amount of the standard and the obtained peak area values ​​for quantification.

[0231] <gc ms>

[0232] Device: GC7890A+5975C (Agilent)

[0233] Column: DB-5MS (Agilent J&W)

[0234] Carrier gas: He, column temperature: 40℃→300℃

[0235] Detector: MS, ion source temperature: 230°C, scan range: m / z 29-600

[0236] Standard: Dodecane

[0237] [Dk and Df]

[0238] Dk and Df were measured at 25° C. and 10 GHz using a split-cylinder dielectric constant / dissipation factor measuring apparatus (manufactured by EM lab).

[0239] [CTE (Coefficient of Linear Expansion)]

[0240] TMA measurement was performed in tensile mode using a TMA-7100 (manufactured by Hitachi High-Tech Science Corporation). As a sample piece, a piece cut into a length of 20 mm and a width of 5 mm was used. The distance between the chucks was set to 10 mm. While applying a load of 49 mN, the temperature was increased at a rate of 2°C / min. The CTE (coefficient of linear expansion) was determined from the displacement of the sample at 0°C to 150°C.

[0241] (Manufacturing of Copper-Clad Laminate)

[0242] The dielectric sheets obtained in Examples 1 to 9 and Comparative Examples 1 to 3 were sandwiched between two sheets of electrolytic copper foil CF-V9S-SV-18 (thickness 18 μm / Rz 1.5 μm) (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.), heated at 360°C, press-molded under a pressure of 15 kN for 5 minutes under vacuum, and cooled to room temperature to obtain copper-clad laminates.

[0243] The obtained copper-clad laminates were evaluated based on the following criteria.

[0244] [Appearance of Copper-Clad Laminate]

[0245] A 100 mm×100 mm test piece was cut out from the produced copper-clad laminate and visually inspected. If swelling was observed at one or more locations, it was considered to have occurred. If no swelling was observed, it was considered to be good.

[0246] These results are shown in Table 1.

[0247] (Example 10)

[0248] The copper-clad laminate of Example 5 was etched and the amount of residual organic matter in the dielectric layer recovered was measured by the following method.

[0249] (Etching)

[0250] The copper foil of the copper-clad laminate was etched with an aqueous solution of ferric chloride, washed with running water for 2 to 5 minutes, further washed with distilled water, and dried in a thermostatic bath at 80±3°C for about 60 minutes to recover the dielectric layer.

[0251] The results are shown in Table 1.

[0252] (Example 11)

[0253] A copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 70 / 30) was melt-extruded and inflation-molded to obtain a thermoplastic liquid crystal polymer film having a melting point of 325°C, a heat distortion temperature of 280°C, and a film thickness of 100 μm.

[0254] A 100 μm-thick polyimide film (linear expansion coefficient: 16 ppm / K) was used as a heat-resistant, releasable support. The resulting thermoplastic liquid crystal polymer film was sandwiched between its two surfaces with the MD and TD directions aligned. This laminate was then preheated in a vacuum hot press and heat-treated at 330°C and 3 MPa for 15 minutes. After the heat treatment, the laminate was cooled and the polyimide films were peeled off to produce a dielectric sheet.

[0255] The obtained dielectric sheets were evaluated based on the above-mentioned criteria.

[0256] The dielectric sheet was sandwiched between two sheets of electrolytic copper foil CF-V9S-SV-18 (thickness 18 μm / Rz 1.5 μm) (manufactured by Fukuda Metal Foil Industry Co., Ltd.) and press-formed under vacuum at 170°C, 3 MPa, for 60 minutes, and then cooled to room temperature to obtain a copper-clad laminate.

[0257] The obtained copper-clad laminate was evaluated based on the above-mentioned criteria.

[0258] The results are shown in Table 1.

[0259] (Example 12)

[0260] Under a nitrogen stream, 5.9 g of 2,2'-dimethyl-4,4'-diaminobiphenyl (0.028 mol) and 2.0 g of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (0.0049 mol) and N,N-dimethylacetamide were added to a 300 ml separable flask to achieve a solid content concentration of 15% by weight after polymerization, and stirred at room temperature to dissolve them. Subsequently, 12.9 g of p-biphenylene bis(trimellitic acid monoester anhydride) (0.024 mol) and 1.8 g of pyromellitic dianhydride (0.008 mol) were added, and the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution. The solution viscosity of the polyamic acid solution was 21,000 cps.

[0261] The polyamic acid solution was evenly applied to electrolytic copper foil CF-V9S-SV-18 (thickness 18 μm / Rz 1.5 μm) (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) to a thickness of approximately 50 μm after curing, and then dried by heating at 120°C for 1 hour to remove the solvent. Furthermore, a stepwise heat treatment was performed from 120°C to 360°C, and finally a vacuum press heat treatment was performed at 360°C for 20 minutes to complete imidization, thereby obtaining a copper-clad laminate.

[0262] At this time, evaluation was performed based on the above-mentioned criteria. As a result, no foaming was observed on the film surface.

[0263] Next, the copper foil of the obtained copper-clad laminate was etched in the same manner as in Example 10 to obtain a polyimide film.

[0264] The obtained polyimide film was evaluated based on the above-mentioned criteria.

[0265] The results are shown in Table 1.

[0266]

[0267] Based on the above results, the dielectric of the present disclosure improves the appearance of the copper-clad laminate.

[0268] Industrial Applicability

[0269] The dielectrics disclosed herein are particularly suitable for use in high-frequency printed circuit boards.< / gc> < / gc>

Claims

1. A dielectric, characterized in that The residual organic matter is less than 500 μg / g. The dielectric according to claim 1 , comprising a resin and an inorganic filler.

3. The dielectric according to claim 2, wherein The resin is a fluororesin.

4. The dielectric according to claim 3, wherein The fluororesin is non-melt-processable.

5. The dielectric according to claim 3 or 4, wherein A part or all of the fluororesin may be polytetrafluoroethylene (PTFE). The dielectric according to claim 5 , wherein: The standard specific gravity SSG of the polytetrafluoroethylene is 2.0 to 2.

3.

7. The dielectric according to any one of claims 2 to 6, wherein The inorganic filler is at least one selected from the group consisting of silicon dioxide, titanium oxide, magnesium oxide, aluminum oxide, and forsterite.

8. The dielectric according to any one of claims 2 to 6, wherein A part or all of the inorganic filler is silicon dioxide.

9. The dielectric according to claim 8, wherein The content of the silicon dioxide is 30% by mass or more relative to the total amount of the dielectric.

10. The dielectric according to claim 8 or 9, wherein The average particle size of the silicon dioxide is 0.1 μm to 10 μm.

11. The dielectric according to any one of claims 8 to 10, wherein The surface of the silica is coated with a silane coupling agent.

12. The dielectric according to any one of claims 3 to 11, wherein The fluororesin is in the form of particles with an average particle size of 0.05 μm to 1000 μm.

13. The dielectric according to claim 2, wherein The resin is polytetrafluoroethylene (PTFE), the inorganic filler is silica, and the content of silica relative to the total amount of the dielectric is 50% by mass or more and 65% by mass or less. 14 . A metal-clad laminate comprising the dielectric according to claim 1 and a metal foil. 15 . A copper-clad laminate comprising the dielectric according to claim 1 and a copper foil.

16. The copper-clad laminate according to claim 15, wherein The surface roughness Rz of at least the surface of the copper foil in contact with the dielectric is 2.0 μm or less.

17. The copper-clad laminate according to claim 15 or 16, wherein The copper foil is rolled copper or electrolytic copper.

18. The copper-clad laminate according to any one of claims 15 to 17, wherein The dielectric loss tangent of the dielectric at 10 GHz is 0.0015 or less.

19. The copper-clad laminate according to any one of claims 15 to 18, wherein The thickness of the dielectric is 5 μm to 250 μm.

20. A method for producing a dielectric, which is the method for producing a dielectric according to any one of claims 1 to 13, characterized in that: Fluorine resin particles and inorganic fillers are mixed to form a film.

21. The method for manufacturing a dielectric according to claim 20, wherein: The film is formed using a composition consisting essentially of fluororesin particles and an inorganic filler.

22. A method for producing a copper-clad laminate, the method for producing a copper-clad laminate according to any one of claims 15 to 19, characterized in that: The dielectric and copper foil are stacked, heated in the range of 180°C to 390°C, and press-molded in a vacuum or in an inert gas atmosphere at a pressure range of 1 kN to 100 kN.

23. A circuit substrate, characterized in that: A dielectric according to any one of claims 1 to 13 or a copper-clad laminate according to any one of claims 15 to 19.

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