Dielectric materials, copper-clad laminates, and methods for manufacturing the same.

Abstract

The present invention provides a dielectric material with excellent electrical properties and a method for manufacturing the same, which prevents blistering of the copper foil during the production of copper-clad laminates using the dielectric material. Furthermore, it provides a copper-clad laminate using this dielectric material and a method for manufacturing the same. [Solution] A dielectric characterized by having a residual organic matter content of 500 μg / g or less. A metal-clad laminate having the dielectric and a metal foil.

Description

Technical Field

[0001] The present disclosure relates to dielectrics, copper-clad laminates, and methods for manufacturing them.

Background Art

[0002] In high-frequency printed wiring boards, there is a demand for high-frequency printed wiring boards with low transmission loss. In such high-frequency printed wiring boards, the use of a fluororesin blended with a filler as a wiring board material is described in Patent Documents 1 to 4.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a dielectric having excellent electrical properties and not causing copper foil swelling during the production of a copper-clad laminate using the dielectric, and a method for producing the same. Furthermore, an object of the present disclosure is to provide a copper-clad laminate using this dielectric and a method for producing the same.

Means for Solving the Problems

[0005] The present disclosure is a dielectric characterized in that the residual organic matter is 500 μg / g or less. Preferably, the dielectric contains a resin and an inorganic filler.

[0006] The resin is preferably a fluororesin. The aforementioned fluororesin is preferably non-melt processable. Preferably, the fluororesin is made up of polytetrafluoroethylene (PTFE) in part or in whole.

[0007] The polytetrafluoroethylene is preferably of a standard specific gravity (SSG) of 2.0 to 2.3.

[0008] The inorganic filler is preferably at least one selected from the group consisting of silica, titanium oxide, magnesium oxide, alumina, and forsterite. Preferably, the inorganic filler is partially or entirely silica. It is preferable that the silica content relative to the total dielectric material is 30% by mass or more.

[0009] Preferably, the average particle size of the silica is 0.1 to 10 μm. Preferably, the silica has its surface coated with a silane coupling agent.

[0010] The fluororesin is preferably in the form of particles, with an average particle size of 0.05 to 1000 μm.

[0011] This disclosure also relates to a metal-clad laminate having the dielectric and a metal foil. This disclosure also relates to a copper-clad laminate having the dielectric and copper foil. Preferably, the surface roughness Rz of at least the surface of the copper foil that adheres to the dielectric is 2.0 μm or less. The copper foil is preferably rolled copper or electrolytic copper.

[0012] It is preferable that the dielectric loss tangent value of the dielectric material at 10 GHz is 0.0015 or less. The thickness of the dielectric material is preferably 5 to 250 μm.

[0013] The present disclosure is also a method for manufacturing the dielectric, which is characterized by forming a film by mixing fluororesin particles and an inorganic filler. It is preferable that the manufacturing method forms a film using a composition consisting essentially of fluororesin particles and an inorganic filler.

[0014] The present disclosure is also a method for manufacturing the copper-clad laminate, which is characterized by laminating a dielectric and a copper foil, heating in the range of 180 to 390°C, and press-molding under vacuum or in an inert gas atmosphere at a pressure in the range of 1 to 100 kN. The present disclosure is also a circuit board having the dielectric or the copper-clad laminate.

Advantages of the Invention

[0015] The dielectric of the present disclosure has a low dielectric constant and low loss, excellent electrical properties, and when a copper-clad laminate is manufactured using the dielectric of the present disclosure, no swelling of the copper foil occurs.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present disclosure will be described in detail. In the field of high-frequency printed wiring boards, in recent years, increasingly high-level performance of low dielectric constant and low loss has been required. On the other hand, many studies have been conducted on dielectrics obtained by blending fillers into resins such as fluororesins.

[0017] The present disclosure provides a dielectric that satisfies the performance of low dielectric constant and low loss and has excellent electrical properties by setting the content of residual organic substances in the dielectric within a specific range, and a dielectric that does not cause swelling of the copper foil when manufacturing a copper-clad laminate using the dielectric.

[0018] When a dielectric is formed by painting or paste extrusion, it often contains residual organic substances derived from extrusion aids such as dispersants and hydrocarbon oils used during the forming process. If the amount of residual organic substances in the dielectric is too high, bulges or other issues may occur on the copper foil due to volatile components during the production of the copper-clad laminate, resulting in variations in the characteristics of the copper-clad laminate. For example, bulges may occur on the copper foil when the drying during the dielectric manufacturing process is weak, when the amount of silane coupling agent is high, or when an antioxidant is added to improve stability. In Patent Document 2, it is described that when using a petroleum-based hydrocarbon solvent with a high fractional distillation temperature (180 - 250 °C) as a processing aid in the production of a fluororesin sheet, the solvent is difficult to volatilize during the rolling operation. However, the specific content of organic volatile components in the dielectric layer of the copper-clad laminate is not described. Thus, until now, the appropriate amount of residual organic substances in the dielectric has not been sufficiently studied.

[0019] This disclosure has found the optimal amount of residual organic substances contained in the dielectric. The dielectric of this disclosure is characterized in that the amount of residual organic substances is 500 μg / g or less. The amount of residual organic substances 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.

[0020] In this disclosure, the above amount of residual organic substances is a value measured by the following method. <Pretreatment> The dielectric was cut into 10 mm squares, sealed in a heating container, and the generated gas when heated under the following conditions was collected in an adsorption tube. An operation blank was prepared by performing the same operation without the dielectric. <Heating Conditions> Heating temperature: 280 °C, heating time: 30 minutes, heating atmosphere: under a nitrogen atmosphere <Thermal Desorption GC / MS Measurement> A calibration curve was created from the absolute amount of the standard product and the obtained peak area value, and quantification was performed. <gc ms> Equipment: GC7890A+5975C (Agilent) Column: DB-5MS (Agilent J&W) Carrier gas: He, Column temperature: 40°C → 300°C Detector: MS, Ion source temperature: 230°C, Scan range: m / z 29~600 Standard product: Dodecane

[0021] In this disclosure, the lower limit of the residual organic matter content of the dielectric is preferably 3 μg / g, more preferably 5 μg / g, and even more preferably 7 μg / g. If the amount of residual organic matter in the dielectric is too low, the sheet shape may not be maintained.

[0022] In this disclosure, the dielectric material used to measure the amount of residual organic matter may be a dielectric material obtained by etching the copper foil of a copper-clad laminate in which a dielectric material and copper foil are laminated.

[0023] The dielectric material of this disclosure is composed of a resin. In the case of a fluororesin, the dielectric material of this disclosure preferably contains an inorganic filler.

[0024] (resin) The resin is preferably at least one selected from the group consisting of fluororesins, polyimides, modified polyimides, liquid crystal polymers (LCPs), polyphenylene sulfides, cycloolefin polymers, polystyrene, epoxy resins, bismaleimides, polyphenylene oxides, modified polyphenylene ethers, polyphenylene ethers, and polybutadiene. The dielectric material of this disclosure preferably contains a fluororesin. Since fluororesins have low dielectric properties, they can be suitably used for the purposes of this disclosure.

[0025] (Fluororesin) The fluororesin used in this disclosure is preferably in particulate form. 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 more, and even more preferably 0.1 μm or more. 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. Using such materials offers the advantage of superior moldability and dispersibility. The average particle size here is measured according to ASTM D 4895.

[0026] 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 more, and even more preferably 1 μm or more. The upper limit of the volume-based cumulative 50% diameter of the fluororesin particles is preferably 35 μm or less, and even more preferably 30 μm or less. Using such materials offers the advantage of excellent moldability and dispersibility. Note that the volume-based cumulative 50% diameter mentioned here is the value measured using a laser diffraction particle size analyzer.

[0027] The fluororesin particles used in this disclosure are not particularly limited, but examples 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 (LMW-PTFE) with a molecular weight of 300,000 or less. They may be used individually or mixed with two or more other types.

[0028] The fluororesin particles used in this disclosure are preferably non-melt processable. Non-melt-processable means that even when heated above its melting point, the resin does not have sufficient fluidity and cannot be molded using the melt molding methods commonly used for resins. PTFE falls into this category. Furthermore, from the viewpoint of low dielectric properties, PTFE is particularly preferred. PTFE with fibril properties is preferred. Fibril-possessed PTFE refers to PTFE that can be formed from unfired polymer particles through paste extrusion or powder rolling.

[0029] It is preferable that the fluororesin is partly or entirely PTFE.

[0030] PTFE may be modified polytetrafluoroethylene (hereinafter referred to as modified PTFE), homopolytetrafluoroethylene (hereinafter referred to as homoPTFE), or a mixture of modified PTFE and homoPTFE. The content of modified PTFE in polymer PTFE is preferably 10% to 98% by weight, and more preferably 50% to 95% by weight, from the viewpoint of maintaining good moldability of polytetrafluoroethylene. Homo-PTFE is not particularly limited, and homo-PTFE disclosed in Japanese Patent Publication No. 53-60979, Japanese Patent Publication No. 57-135, Japanese Patent Publication No. 61-16907, Japanese Patent Publication No. 62-104816, Japanese Patent Publication No. 62-190206, Japanese Patent Publication No. 63-137906, Japanese Patent Publication No. 2000-143727, Japanese Patent Publication No. 2002-201217, International Publication No. 2007 / 046345, International Publication No. 2007 / 119829, International Publication No. 2009 / 001894, International Publication No. 2010 / 113950, International Publication No. 2013 / 027850, etc., can be suitably used. Among these, homo-PTFE disclosed in Japanese Patent Publication No. 57-135, Japanese Patent Publication No. 63-137906, Japanese Patent Publication No. 2000-143727, Japanese Patent Publication No. 2002-201217, International Publication No. 2007 / 046345, International Publication No. 2007 / 119829, International Publication No. 2010 / 113950, etc., which have high stretchability, is preferred.

[0031] Modified PTFE consists of TFE and monomers other than TFE (hereinafter referred to as modified monomers). Modified PTFE can be uniformly modified by the modified monomer, modified in the early stages of the polymerization reaction, or modified in the final stages of the polymerization reaction, but is not limited to these. Preferably, modified PTFE is a TFE copolymer obtained by polymerizing TFE along with a small amount of monomers other than TFE, within a range that does not significantly impair the properties of the TFE homopolymer. Modified PTFE can preferably be those disclosed in, for example, Japanese Patent Publication No. 60-42446, Japanese Patent Publication No. 61-16907, Japanese Patent Publication No. 62-104816, Japanese Patent Publication No. 62-190206, Japanese Patent Publication No. 64-1711, Japanese Patent Publication No. 2-261810, Japanese Patent Publication No. 11-240917, Japanese Patent Publication No. 11-240918, International Publication Brochure No. 2003 / 033555, International Publication Brochure No. 2005 / 061567, International Publication Brochure No. 2007 / 005361, International Publication Brochure No. 2011 / 055824, International Publication Brochure No. 2013 / 027850, etc. Among these, modified PTFE disclosed in Japanese Patent Publication No. 61-16907, Japanese Patent Publication No. 62-104816, Japanese Patent Publication No. 64-1711, Japanese Patent Publication No. 11-240917, International Publication No. 2003 / 033555, International Publication No. 2005 / 061567, International Publication No. 2007 / 005361, International Publication No. 2011 / 055824, etc., which have high stretchability, is preferred.

[0032] Modified PTFE contains TFE units based on TFE and modified monomer units based on modified monomers. Modified monomer units are a part of the molecular structure of modified PTFE that originates from the modified monomer. Modified PTFE preferably contains modified monomer units in an amount of 0.001 to 0.500% by mass of the total monomer units, and more preferably in an amount of 0.01 to 0.30% by mass. The total monomer units are the parts of the molecular structure of modified PTFE that originate from all monomers.

[0033] The modified monomer is not particularly limited as long as it can copolymerize with TFE, and examples 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, etc. One or more modified monomers may be used.

[0034] Perfluorovinyl ethers are not particularly limited and include, for example, perfluorounsaturated compounds represented by the following general formula (1). CF2 = CF - ORf ... (1) (In the formula, Rf represents a perfluoroorganic group.)

[0035] In this specification, a perfluoroorganic group is an organic group in which all hydrogen atoms bonded to a carbon atom are replaced with fluorine atoms. The above perfluoroorganic group may have an ether oxygen.

[0036] Examples of perfluorovinyl ethers include perfluoro(alkyl vinyl ether) (PAVE) in which Rf in the above general formula (1) is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5. Examples of perfluoroalkyl groups in PAVE include perfluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, and perfluorohexyl group. Perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE) are preferred PAVEs.

[0037] The perfluoroalkylethylene (PFAE) mentioned above is not particularly limited and includes, for example, perfluorobutylethylene (PFBE), perfluorohexylethylene (PFHE), and the like.

[0038] In modified PTFE, the modified monomer is preferably at least one selected from the group consisting of HFP, CTFE, VDF, PAVE, PFAE, and ethylene.

[0039] The PTFE used in this disclosure may have a core-shell structure. Examples of PTFE having a core-shell structure include modified polytetrafluoroethylene, which contains a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene in the particles. Examples of such modified polytetrafluoroethylene include the polytetrafluoroethylene described in Japanese Patent Publication No. 2005-527652.

[0040] In this disclosure, it is preferable to use a fluororesin that is non-melt processable and to form a fluororesin sheet by a molding method that fibrillates it. The molding method will be described later.

[0041] The above-mentioned PTFE preferably has a standard specific gravity (SSG) of 2.0 to 2.3. Using such PTFE makes it easier to obtain PTFE films with high strength (cohesive force and puncture strength per unit thickness). PTFE with a large molecular weight has long molecular chains, making it difficult to form a structure in which the molecular chains are regularly arranged. In this case, the length of the amorphous region increases, and the degree of entanglement between molecules increases. When the degree of entanglement between molecules is high, the PTFE film is less likely to deform under applied load and is thought to exhibit excellent mechanical strength. Furthermore, using PTFE with a large molecular weight makes it easier to obtain PTFE films with a small average pore size.

[0042] The lower limit of the above SSG is more preferably 2.05, and even more preferably 2.1. The upper limit of the above SSG is more preferably 2.25, and even more preferably 2.2.

[0043] Standard specific gravity (SSG) is determined by preparing a sample in accordance with ASTM D-4895-89 and measuring the specific gravity of the obtained sample using the water displacement method.

[0044] The PTFE described above preferably has a refractive index within the range of 1.2 to 1.6. Having such a refractive index is preferable in that it is a low dielectric material. The refractive index can be set within the above range by methods such as adjusting the polarizability and the flexibility of the main chain. The lower limit of the refractive index is more preferably 1.25, more preferably 1.30, and most preferably 1.32. The upper limit of the refractive index is more preferably 1.55, more preferably 1.50, and most preferably 1.45. The refractive index mentioned above was measured using a refractometer (Abbemat 300).

[0045] In this embodiment, the molecular weight (number-average molecular weight) of the PTFE constituting the PTFE particles is, for example, in the range of 2 to 12 million. The lower limit of the molecular weight of PTFE may be 3 million or 4 million. The upper limit of the molecular weight of PTFE may be 10 million.

[0046] Methods for measuring the number-average molecular weight of PTFE include determining it from standard specific gravity and measuring it using dynamic viscoelasticity during melting. The method using standard specific gravity can be performed using a sample molded in accordance with ASTM D-4895 98 and the water displacement method in accordance with ASTM D-792. The method using dynamic viscoelasticity is described, for example, by S. Wu in Polymer Engineering & Science, 1988, Vol.28, 538, and in the same publication, 1989, Vol.29, 273.

[0047] The above-mentioned particulate PTFE preferably contains 50% by mass or more of polytetrafluoroethylene resin with a secondary particle diameter of 500 μm or more, and more preferably 80% by mass or more. Having PTFE with a secondary particle diameter of 500 μm or more within this range has the advantage of enabling the production of a highly strong composite sheet. By using PTFE with a secondary particle size of 500 μm or larger, a composite sheet with lower resistance and greater toughness can be obtained.

[0048] The lower limit of the secondary particle size is more preferably 300 μm, and even more preferably 350 μm. The upper limit of the secondary particle size is more preferably 700 μm or less, and even more preferably 600 μm or less. The secondary particle size can be determined, for example, by sieving.

[0049] The above-mentioned particulate PTFE is preferably such that the average primary particle diameter is 50 nm or more, in order to obtain a dielectric sheet with higher strength and superior homogeneity. More preferably, it is 100 nm or more, even more preferably 150 nm or more, and particularly preferably 200 nm or more. The larger the average primary particle size of PTFE, the lower the increase in paste extrusion pressure when using the powder for paste extrusion molding, resulting in superior moldability. There is no particular upper limit, but it may be 500 nm. From the viewpoint of productivity in the polymerization process, 350 nm is preferable.

[0050] The above average primary particle diameter can be determined by creating a calibration curve using an aqueous dispersion of PTFE obtained by polymerization, adjusting the polymer concentration to 0.22% by mass, and comparing the transmittance of 550 nm projected light per unit length of the aqueous dispersion with the average primary particle diameter determined by measuring the directional diameter in transmission electron microscope images. The transmittance of the aqueous dispersion to be measured is then measured, and the average primary particle diameter can be determined based on the above calibration curve.

[0051] Furthermore, the PTFE described above preferably has a maximum endothermic peak temperature (crystal melting point) of 340±7℃.

[0052] The PTFE may be low-melting-point PTFE, where the maximum peak temperature of the endothermic curve on the crystal melting curve measured by differential scanning calorimeter is 338°C or lower, or high-melting-point PTFE, where the maximum peak temperature of the endothermic curve on the crystal melting curve measured by differential scanning calorimeter is 342°C or higher.

[0053] Low-melting-point PTFE particles are particles produced by polymerization using an emulsion polymerization method, possess the aforementioned maximum endothermic peak temperature (crystal melting point), a dielectric constant (ε) of 2.08-2.2, and a dielectric loss tangent (tan δ) of 1.9 × 10⁻¹⁰. -4 ~4.0×10 -4 Examples of commercially available products include Polyflon Fine Powder F201, F203, F205, F301, and F302 from Daikin Industries, Ltd.; CD090 and CD076 from Asahi Glass Industrial Co., Ltd.; and TF6C, TF62, and TF40 from DuPont.

[0054] High-melting-point PTFE particles are also particles produced by polymerization using the emulsion polymerization method, and possess the aforementioned maximum endothermic peak temperature (crystal melting point), dielectric constant (ε) of 2.0-2.1, and dielectric loss tangent (tanδ) of 1.6 × 10⁻¹⁰. -4 ~2.2×10 -4 The overall levels are low. Examples of commercially available products include Polyflon Fine Powder F104 from Daikin Industries, Ltd.; CD1, CD141, and CD123 from Asahi Glass Industrial Co., Ltd.; and TF6 and TF65 from DuPont.

[0055] Furthermore, the average particle size of the particles obtained by secondary aggregation of both PTFE particles is usually preferably 250 to 2000 μm. In particular, granulated particles obtained by granulation using a solvent are preferred because they have improved fluidity when filling the mold during pre-molding.

[0056] PTFE with particle shapes that satisfy the parameters described above can be obtained by conventional manufacturing methods. For example, it can be manufactured by following the manufacturing methods described in International Publication No. 2015-080291 and International Publication No. 2012-086710, etc.

[0057] (Filler) The inorganic fillers that can be used in this disclosure are not particularly limited and include one or more inorganic fillers selected from ceramics, talc, mica, alumina, zinc oxide, tin oxide, titanium oxide, silicon oxide, calcium carbonate, calcium oxide, magnesium oxide, potassium titanate, forsterite, glass fibers, glass fragments, glass beads, silica, calcium fluoride, boron nitride, barium sulfate, molybdenum disulfide, and potassium carbonate whiskers. Two or more of these may be used in combination. Among these, it is particularly preferable that at least one is selected from the group consisting of silica, titanium oxide, magnesium oxide, alumina, or forsterite. Alternatively, it is preferable that a combination thereof is included. In particular, it is preferable that the inorganic filler is partially or entirely silica.

[0058] The inorganic filler described above is not limited in shape and can be spherical, crushed, or otherwise. Among these, a spherical shape is preferred. A spherical shape is preferable because it is easy to process uniformly during drilling, has a small specific surface area, and has low transmission loss.

[0059] The spherical fillers described above refer to particles whose shape is close to a perfect sphere. Specifically, a sphericity of 0.80 or higher is preferred, 0.85 or higher is more preferred, 0.90 or higher is even more preferred, and 0.95 or higher is most preferred. Sphericity is calculated by taking a picture with a scanning electron microscope (SEM) and using the area and perimeter of the observed particle as a value calculated using the formula (sphericity) = {4π × (area) ÷ (perimeter)²}. The closer to 1, the closer to a perfect sphere. Specifically, the average value measured for 100 particles using an image processing device (Spectris Corporation: FPIA-3000) is adopted.

[0060] In this disclosure, the inorganic filler preferably has an average particle diameter of 0.1 to 10 μm. The average particle diameter here refers to the D50 value measured by a laser diffraction particle size analyzer. If the average particle diameter is less than 0.1 μm, aggregation of the inorganic filler tends to occur, resulting in insufficient effectiveness. Furthermore, if the average particle diameter exceeds 10 μm, the sheet tends to become less thin.

[0061] The silica particles used in this disclosure preferably have an average particle diameter of 0.1 to 10 μm. Furthermore, the spherical silica particles used in this disclosure preferably have a D90 / D10 of 2 or more (preferably 2.3 or more and 2.5 or more) and a D50 of 10 μm or less when the volume is accumulated from the smallest particle size. Moreover, it is preferable that the D90 / D50 is 1.5 or more (more preferably 1.6 or more). It is preferable that the D50 / D10 is 1.5 or more (more preferably 1.6 or more). This allows smaller spherical silica particles to fill the gaps between larger spherical silica particles, resulting in excellent packing performance and high fluidity. In particular, it is preferable that the frequency of smaller particle sizes is higher in the particle size distribution compared to a Gaussian curve. The particle size can be measured using a laser diffraction scattering particle size distribution analyzer. It is also preferable that coarse particles with a particle size larger than a predetermined size are removed by a filter or the like.

[0062] The spherical silica described above preferably has a water absorption of 1.0% or less, and more preferably 0.5% or less. The water absorption is based on the mass of the spherical silica when dry. The water absorption is measured by leaving a dry sample at 40°C and 80% RH for 1 hour, and then measuring the moisture generated by heating to 200°C using a Karl Fischer moisture analyzer.

[0063] The spherical silica can also be obtained by heating a dielectric sheet at 600°C for 30 minutes in an atmospheric environment to burn off the fluororesin, extracting the spherical silica particles, and then measuring the above parameters using the method described above.

[0064] The spherical silica mentioned above may be any commercially available silica particles that satisfy the properties described above. 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 Corporation), High Purity Synthetic Spherical Silica Particles AdmaFine (manufactured by Admatex Co., Ltd.), Admanano (manufactured by Admatex Co., Ltd.), and AdmaFuse (manufactured by Admatex Co., Ltd.).

[0065] The above-mentioned titanium dioxide, magnesium oxide, and alumina have higher dielectric constants (Dk) compared to silica, and can therefore be added to adjust the dielectric constant (Dk). Examples of commercially available titanium dioxide include CR-EL (manufactured by Ishihara Sangyo Co., Ltd.) and HT0210 (manufactured by Toho Titanium Co., Ltd.). Examples of commercially available magnesium oxide include RF-10CS and RF-10C-45μm (manufactured by Ube Materials Co., Ltd.). Examples of commercially available alumina include LS-110F and LS-210B (manufactured by Nippon Light Metal Co., Ltd.).

[0066] The inorganic fillers, particularly silica particles, are preferably surface-treated. By pre-treating the surface, aggregation of the inorganic fillers, especially silica particles, can be suppressed, and the inorganic fillers, especially silica particles, can be well dispersed in the resin composition.

[0067] The above surface treatment can be performed by appropriately selecting the type and amount of surface treatment agent. The above surface treatment is not particularly limited, and any known treatment can be used. Specifically, examples include treatment with silane coupling agents such as epoxysilanes, aminosilanes, isocyanatesilanes, vinylsilanes, acrylicsilanes, hydrophobic alkylsilanes, phenylsilanes, and fluorinated alkylsilanes having reactive functional groups, plasma treatment, and fluorination treatment.

[0068] Examples of the silane coupling agents mentioned above include epoxysilanes such as γ-glycidoxypropyltriethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, aminosilanes such as aminopropyltriethoxysilane and N-phenylaminopropyltrimethoxysilane, isocyanatesilanes such as 3-isocyanatetopropyltrimethoxysilane, vinylsilanes such as vinyltrimethoxysilane, and acrylicsilanes such as acryloxytrimethoxysilane.

[0069] In this disclosure, among surface-treated silica particles, it is preferable to use silica particles whose surfaces are coated with a silane coupling agent.

[0070] When treating with a silane coupling agent, it is preferable that the amount of silane coupling agent treated is 3% by mass or less relative to the inorganic filler, especially the silane particles. If the amount of silane coupling agent treated is large, blistering tends to occur in the copper foil during the manufacture of the copper-clad laminate.

[0071] (dielectric) The dielectric material of this disclosure is composed of the resin described above and preferably contains an inorganic filler and fluororesin particles. If necessary, it may also contain components other than the inorganic filler and fluororesin particles, or it may consist 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 material. In particular, it is preferable to use a dielectric that is substantially composed of fluororesin particles and inorganic fillers. "Substantially composed of fluororesin particles and inorganic fillers" means that the content of inorganic fillers and components other than fluororesin particles is 3% by mass or less relative to the total amount of the dielectric.

[0072] The inorganic filler content relative to the total dielectric material is preferably 30% by mass or more. Within this range, the coefficient of thermal expansion of the dielectric material can be controlled to a low level. Furthermore, the silica content relative to the total dielectric material is preferably 30% by mass or more. The lower limit of the inorganic filler content is more preferably 35% by mass, and even more preferably 40% by mass. On the other hand, the upper limit of the inorganic filler content is preferably 65% ​​by mass.

[0073] The dielectric material of this disclosure may contain an anti-aging agent. As an antioxidant, any antioxidant commonly used in the resin industry can be used without any particular limitations. However, it is preferable to use at least one antioxidant selected from the group consisting of phenolic antioxidants, amine antioxidants, phosphorus antioxidants, and sulfur-based antioxidants, as this can greatly improve the oxidation resistance of the resulting dielectric without inhibiting the crosslinking reaction. Among these, phenolic antioxidants and amine antioxidants are preferred, with phenolic antioxidants being particularly preferred.

[0074] Examples of phenolic antioxidants include dibutylhydroxytoluene, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,4-di-t-amyl-6-(1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl)phenyl acrylate, 3,5-di-t-butyl-4-hydroxyanisole, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2'-methylene-bis(4-methyl-6-t-butylphenol), 4,4'-butylidene-bis(6-t-butyl-m-cresol), and 3,9-bis(2-(3-(3-t-butyl Examples include (-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, tetrakis(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenylpropionate)methane [i.e., pentaerythrimethyl-tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenylpropionate)], 6-(4-hydroxy-3-methyl-5-t-butylanilino)-2,4-bisoctylthio-1,3,5-triazine, and 2-octylthio-4,6-bis-(3,5-di-t-butyl-4-oxyanilino)-1,3,5-triazine.

[0075] Examples of amine-based anti-aging agents include 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine and 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonic acid-bis-(1,2,2,6,6-pentamethyl-4-piperidyl).

[0076] Examples of phosphorus-based anti-aging agents include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, tris(dinonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylenediphosphite, and cyclic neopentanetetraylbis(isodecyl phosphite).

[0077] Examples of sulfur-based anti-aging agents include dilauryl 3,3-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3-thiodipropionate, laurylstearyl 3,3-thiodipropionate, pentaerythritol-tetrakis-(β-lauryl-thio-propionate), and 3,9-bis(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane.

[0078] These anti-aging agents can be used individually or in combination of two or more. The amount of antioxidant is preferably 3 ppm or less relative to the total amount of dielectric material. Within this range, it will not affect the amount of residual organic matter in the dielectric material. Furthermore, in the case of dielectric materials with high heat resistance, such as fluororesins, it is not necessary to add an antioxidant.

[0079] The dielectric material of this disclosure is typically used in sheet form. The dielectric material described above preferably has a thickness of 5 to 250 μm. Even if the dielectric material of this disclosure is thin, it can sufficiently achieve its purpose. From this viewpoint, it is more preferable that the thickness be less than 200 μm, and even more preferable that it be less than 150 μm.

[0080] The dielectric material of this disclosure preferably has a dielectric loss tangent (Df) of 0.0015 or less at 10 GHz. Having a dielectric loss within this range is preferable because it results in low dielectric loss. 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.

[0081] The dielectric material of this disclosure preferably has a relative permittivity (Dk) of 3.5 or less at 10 GHz. This range is preferable because it results in low dielectric loss. The upper limit of the relative permittivity (Dk) is more preferably 3.2, and even more preferably 3.1. On the other hand, the lower limit of the relative permittivity (Dk) is more preferably 2.0, and even more preferably 2.5.

[0082] In this specification, the relative permittivity (Dk) and dielectric loss tangent (Df) at 10 GHz were determined by measuring Dk and Df at 25°C and 10 GHz using a split-cylinder type dielectric constant / dielectric loss tangent measuring device (manufactured by EM lab).

[0083] Furthermore, it is preferable that the coefficient of thermal expansion (CTE) is 100 ppm / K or less. This range is preferable because it results in a dielectric sheet with low shrinkage and excellent dimensional stability. The upper limit of the coefficient of thermal 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 thermal expansion (CTE) is more preferably 5 ppm / K, and even more preferably 10 ppm / K.

[0084] In this specification, the coefficient of linear expansion was determined by performing TMA measurements in tensile mode using a TMA-7100 (manufactured by Hitachi High-Tech Science Corporation). A sheet cut to a length of 20 mm and a width of 5 mm was used as the sample piece, with the distance between the chucks set to 10 mm, and the linear expansion coefficient was determined from the displacement of the sample from 0 to 150°C while applying a load of 49 mN and heating at a rate of 2°C / min.

[0085] (Method of manufacturing dielectrics) The dielectric material of this disclosure can be obtained by mixing the above-mentioned fluororesin particles and inorganic fillers and forming a film. This disclosure also provides a method for producing a derivative by mixing fluororesin particles and inorganic fillers and forming a film. While the manufacturing method is not limited, it can be carried out by methods such as paint molding, paste extrusion molding, and powder rolling.

[0086] The above-mentioned painting and molding methods include spray painting, roll painting, painting with a doctor blade, dip painting, impregnation painting, spin flow painting, curtain flow painting, coating with a bar coater, gravure coating, microgravure coating, and die coating.

[0087] As described above, it is preferable to use a non-melt-processable fluororesin as the dielectric material of this disclosure. When such a fluororesin is used, it is preferable to form it into a sheet by fibrillating the powdered PTFE used as the raw material.

[0088] While there are no specific limitations on the methods used for paste extrusion molding and powder rolling molding, general methods are described below.

[0089] (Paste extrusion molding) The above method for manufacturing the sheet may include the steps of: mixing fluororesin particles, for example, PTFE powder obtained using a hydrocarbon surfactant, an inorganic filler, and an extrusion aid (1a); paste extrusion molding of the obtained mixture (1b); rolling the extruded product obtained by extrusion molding (1c); drying the rolled sheet (1d); and firing the dried sheet to obtain a molded body (1e). The paste extrusion molding described above can also be carried out by adding conventionally known additives such as pigments and fillers to the fluororesin particles.

[0090] The above-mentioned extrusion aids are not particularly limited and generally known ones can be used. Examples include hydrocarbon oils.

[0091] In the drying step (1d) of the sheet after rolling, it is preferable to set the drying temperature to 100°C or higher and 300°C or lower, and the drying time to 15 minutes or higher and 1 hour or lower, in order to reduce the amount of residual organic matter in the dielectric.

[0092] (Powder rolling) Powder rolling is a method of forming resin powder into a sheet by applying shear force to cause fibrillation. The process may then include a step of firing to obtain a molded body. More specifically, (1) A step in which shear force is applied while mixing a raw material composition containing fluororesin particles and fillers. Step (2) involves forming the mixture obtained in step (1) into a bulk form, and Step (3) involves rolling the bulk mixture obtained in step (2) into a sheet. Examples include manufacturing methods that have the following characteristics. Furthermore, the process may include a step (4) in which the sheet-like material obtained above is baked at 200 to 400°C for 1 to 60 minutes. Also, step (2) can be omitted.

[0093] When manufacturing a sheet using the powder rolling molding method described above, it is preferable to form the film using a composition that substantially consists of fluororesin particles and an inorganic filler. Alternatively, it is preferable to mix only fluororesin particles and inorganic fillers and then mold the product.

[0094] (Other resins) Examples of liquid crystal polymers (LCPs) include thermoplastic liquid crystal polyesters, or thermoplastic liquid crystal polyesteramides in which amide bonds are introduced thereto. Furthermore, liquid crystal polymers may be polymers in which imide bonds, carbonate bonds, carbodiimide bonds, isocyanate-derived bonds such as isocyanurate bonds, or aromatic polyesteramides are further introduced. Polymers having a rigid structure, such as naphthoic acid, are also preferred.

[0095] Polyimides are a general term for polymers that contain imide bonds in their repeating units, and may also refer to aromatic polyimides in which aromatic compounds are directly linked by imide bonds. Modified polyimides are polymers that contain imide bonds in repeating units, which have reduced water absorption compared to polyimides. Polyphenylene sulfide is a crystalline thermoplastic resin with a simple linear structure in which benzene rings (p-phenylene groups) and sulfur atoms (sulfide bonds) are alternately bonded. Cycloolefin polymers are polymers that have a cyclic structure in their polymer chains, and can be polymerized by ring-opening metathesis polymerization or coordination polymerization.

[0096] Polystyrene is a polymer obtained by polymerizing styrene, and includes syndiotactic polystyrene and other types in which stereoregularity is controlled and crystallinity is imparted. Epoxy resins are thermosetting synthetic resins with reactive epoxy groups at their ends; the most representative example is a copolymer of bisphenol A and epichlorohydrin. Various polyamines and acid anhydrides are used as curing agents. Bismaleimide resins are high-performance thermosetting addition-type polyimides. They can generally be synthesized by condensing phthalic anhydride and an aromatic diamine in a molar ratio of 2:1 to produce bismaleimide, and then adding more diamines to the terminal double bonds of the bismaleimide via Michael addition. Polyphenylene oxide is a thermoplastic resin produced from 2,6-disubstituted phenols by oxidative coupling polymerization.

[0097] Polyphenylene ether (PPE) is a resin made from a blend of polyphenylene oxide (PPO) and polystyrene, possessing toughness and rigidity while also exhibiting impact resistance at low temperatures. Polyphenylene ether is a plastic that possesses characteristics such as heat resistance, flame retardancy, and chemical resistance. Modified polyphenylene ethers are a general term for polymer alloys formed by mixing polyphenylene ether (PPE), an amorphous engineering plastic, with other resins. Because the main chain consists of benzene rings linked by ether bonds, these resins exhibit excellent hydrolysis resistance. Polybutadiene is a type of general-purpose synthetic rubber produced by the polymerization of 1,3-butadiene, and is a material with excellent elasticity, abrasion resistance, and low-temperature properties.

[0098] Other molding methods for resins other than the fluororesins mentioned above include melt extrusion molding, casting molding, inflation molding, calendering, injection molding, vacuum / pressure molding, compression molding, and press molding. In each molding method, residual organic matter can be reduced by controlling the molding temperature and molding time. In the case of a method for producing resins other than fluororesins, it is preferable to mold either the resin alone or a composition containing the resin and an inorganic filler.

[0099] (Heat compression molding) A method for manufacturing a liquid crystal polymer film preferably comprises at least the following steps: a heat treatment step in which a laminate, in which both sides of a thermoplastic liquid crystal polymer film are sandwiched between a pair of heat-resistant release supports, is heat-treated at a temperature of (HT+15) to (HT+70)°C, relative to the heat distortion temperature (hereinafter sometimes referred to as HT) of the thermoplastic liquid crystal polymer film before the heat treatment step, under predetermined pressure; and a peeling step in which the pair of heat-resistant release supports are peeled off the laminate to obtain a thermoplastic liquid crystal polymer film.

[0100] In the heat treatment process, a liquid crystal polymer film obtained by extrusion molding (e.g., inflation method) is used, and a laminate in which both sides of this liquid crystal polymer film are sandwiched between a pair of heat-resistant release supports is subjected to heat treatment at a specific temperature under predetermined pressure. Because the liquid crystal polymer molecules on the front and back surfaces of the skin layer are subjected to shear force during this heat treatment, the dielectric constant in the thickness direction of the liquid crystal polymer film after the heat treatment process can be controlled to a desired range. Furthermore, the heat treatment process also makes it possible to reduce residual organic matter in the liquid crystal polymer. The heat-resistant release supports disposed on both sides of the liquid crystal polymer film may be of the same type or different types, as long as the objective is achieved, but it is preferable that they be of the same type.

[0101] (Copper-clad laminate) The dielectric material of this disclosure can be used as a sheet for printed circuit boards, laminated with other substrates.

[0102] This disclosure also relates to a metal-clad laminate having the dielectric and metal foil described above. Examples of the above-mentioned metals include copper, stainless steel, aluminum, iron, silver, gold, and ruthenium. Alloys of these metals can also be used. Among these, copper is preferred.

[0103] The present disclosure also relates to a copper-clad laminate having the dielectric material described above and copper foil. It may also be a copper-clad laminate characterized by having copper foil bonded to one or both sides of the dielectric material described above. As described above, the dielectric material containing fluororesin of the present disclosure is particularly suitable for use in printed circuit board applications, and therefore can be suitably used as such a copper-clad laminate.

[0104] The dielectric material in the copper-clad laminate preferably has a dielectric loss tangent (Df) of 0.0015 or less at 10 GHz. This range is preferable because it results in low dielectric loss. 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.

[0105] The dielectric in the copper-clad laminate preferably has a thickness of 5 to 250 μm. Even if the dielectric of this disclosure is thin, it can sufficiently achieve its purpose. From this viewpoint, it is more preferable that it be less than 200 μm, and even more preferable that it be less than 150 μm.

[0106] The copper foil described above preferably has a surface roughness Rz of 2.0 μm or less. That is, the dielectric material of this disclosure has excellent adhesion to copper foil with a high smoothness of Rz of 2.0 μm or less. Furthermore, the copper foil only needs to have an Rz of 2.0 μm or less on at least the side that adheres to the fluororesin film described above, and the Rz value of the other side is not particularly limited. The above Rz is the sum of the highest point (maximum peak height: Rp) and the deepest point (maximum valley depth: Rv). The above surface roughness is the ten-point average roughness specified in JIS-B0601. In this specification, the above Rz is the value measured using a surface roughness meter (product name: Surfcom 470A, manufactured by Tokyo Seiki Co., Ltd.) with a measurement length of 4 mm.

[0107] The thickness of the copper foil is not particularly limited, but is preferably in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm, and even more preferably in the range of 9 to 35 μm.

[0108] The copper foils mentioned above are not particularly limited; for example, rolled copper foil, electrolytic copper foil, etc., are examples.

[0109] The copper foil with an Rz of 2.0 μm or less is not particularly limited, and commercially available foils can be used. Examples of commercially available copper foils with 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 & Powder Industry Co., Ltd.) and electrolytic copper foil CF-V9S-SV-18 (thickness 18 μm / Rz 1.5 μm) (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.).

[0110] The copper foil described above may be surface-treated to enhance its adhesion strength to the dielectric material of this disclosure.

[0111] The above surface treatment is not particularly limited, but may include silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, etc. The reactive functional group of the silane coupling agent is not particularly limited, but from the viewpoint of adhesion to the resin substrate, it is preferable that it has at least one selected from amino groups, (meth)acrylic groups, mercapto groups, and epoxy groups at its terminal end. The hydrolyzable group is not particularly limited, but may include alkoxy groups such as methoxy groups and ethoxy groups. The copper foil used in this disclosure may have a rust-preventive layer (such as an oxide film like chromate), a heat-resistant layer, etc. formed on it.

[0112] Surface-treated copper foil having a surface treatment layer of the above-mentioned silane compound on the surface of the copper foil can be manufactured by preparing a solution containing the silane compound and then surface-treating the copper foil with this solution.

[0113] The copper foil described above may have a roughened layer on its surface, for example, to improve adhesion to the resin substrate. Furthermore, if the roughening treatment is likely to degrade the performance required in this disclosure, the amount of roughening particles electrodeposited onto the copper foil surface may be reduced or the roughening treatment may be omitted as necessary.

[0114] Between the copper foil and the surface treatment layer, one or more layers selected from the group consisting of a heat-resistant treatment layer, a rust-preventive treatment layer, and a chromate treatment layer may be provided from the viewpoint of improving various properties. These layers may be a single layer or multiple layers.

[0115] The copper-clad laminate of this disclosure may further have layers other than copper foil and dielectric. The layer other than the copper foil and dielectric is preferably made of at least one resin selected from the group consisting of polyimide, modified polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, modified polyphenylene ether, polyphenylene ether, and polybutadiene.

[0116] These layers other than the copper foil and dielectric are not particularly limited as long as they are made of the resin described above. Furthermore, it is preferable that the thickness of these layers other than the copper foil and dielectric is in the range of 12.5 to 260 μm.

[0117] In the copper-clad laminate of this disclosure, the copper layer may be formed on one or both sides of the roll-shaped sheet. Methods for forming the copper layer include laminating (adhering) copper foil to the surface of the roll-shaped sheet, vapor deposition, and plating. Methods for laminating copper foil include hot pressing. The hot pressing temperature can range from the melting point of the dielectric film (-150°C) to the melting point of the dielectric film (+40°C). The hot pressing time is, for example, 1 to 30 minutes. The hot pressing pressure can be set from 0.1 to 10 MPa.

[0118] This disclosure also relates to a method for manufacturing a copper-clad laminate, characterized by laminating a dielectric and a copper foil, heating them in the range of 180 to 390°C, and press-molding them under a vacuum or inert gas atmosphere at a pressure in the range of 1 to 100 kN. Press molding under these conditions prevents degradation of the dielectric material and allows for adhesion to the copper foil.

[0119] The copper-clad laminate of this disclosure is not particularly limited in its application and can be used as a circuit board. This disclosure is also a circuit board having the dielectric or the copper-clad laminate. A circuit board is a plate-shaped component used to electrically connect electronic components such as semiconductors and capacitor chips, while simultaneously arranging and fixing them within a limited space. The configuration of the circuit board formed from the derivative or copper-clad laminate of this disclosure is not particularly limited. The circuit board may be a rigid board, a flexible board, or a rigid-flexible board. The circuit board may be single-sided, a single-sided board, a double-sided board, or a multilayer board (such as a pull-up board). It is particularly suitable for use as a flexible board or a rigid board. It is especially suitable for use as a printed circuit board for high frequencies of 10 GHz or higher.

[0120] The method for manufacturing the circuit board is not particularly limited, and it can be manufactured by a general method using the copper-clad laminate described above.

[0121] The dielectrics and copper-clad laminates of this disclosure are used as electrical and electronic components. Examples include antennas used in electronic and communication equipment such as ETC, GPS, wireless LAN, and mobile phones; high-speed transmission connectors; CPU sockets; millimeter-wave and sub-millimeter-wave radars such as collision avoidance radar; RFID tags; capacitors; inverter components; cable sheathing materials; insulating materials for secondary batteries such as lithium-ion batteries; and speaker diaphragms.

[0122] Examples of high-speed communication compatible boards include base station antenna boards, antenna distribution boards, boards for RRH (Remote Radio Head), which is the wireless portion of a wireless base station, boards for the control unit or baseband unit (BBU: Base Band Unit) of a wireless base station, high-speed communication transceiver boards, RNC (Radio Network Controller) boards, high-speed transmitter boards, high-speed receiver boards, high-speed signal multiplexing circuit boards, WiFi boards using the 60GHz band, and data transfer boards used in servers for data centers. In addition, examples of high-speed communication compatible boards include antenna boards, such as boards for ultra-high-capacity antennas (Massive MIMO) required for the large-capacity communication required by standards from 5G onwards.

[0123] Insulating films can be used not only as insulators for substrates but also as insulators for signal line coatings. For example, they can be used as insulating coatings (e.g., insulating tubes) for waveguides that transmit high-speed signals, QSFP cables for high-speed LANs, coaxial cables for high-speed communication (e.g., SFP+ cables, QSFP+ cables, etc.), and coaxial cables for low loss.

[0124] When using such high frequencies, electrical components such as connectors and materials used in communication equipment such as casings require stable electrical properties such as a low relative permittivity (εr) and a low dielectric loss tangent (tanδ). Insulating films can also be used as insulating materials for such materials.

[0125] The insulating film can also be used as an insulating material for connector printed circuit boards that require soldering. Because the insulator has excellent heat resistance, problems are less likely to occur even at the high temperatures during soldering.

[0126] In dielectric waveguides, materials with low dielectric loss are required to transmit high-frequency millimeter waves or submillimeter waves with low loss. Dielectric films can also be used as insulating materials for dielectric waveguides that transmit millimeter waves, submillimeter waves, etc. Examples of dielectric waveguides include cylindrical dielectric lines, rectangular dielectric lines, elliptical dielectric lines, tubular dielectric lines, image lines, insulator image lines, trapped image lines, rib guides, strip dielectric lines, reverse strip lines, H guides, and non-radiative dielectric lines (NRD guides).

[0127] A laminate for circuit boards is also a laminate characterized by having a copper foil layer, the dielectric layer described above, and a base layer. The base layer is not particularly limited, but it is preferable to have a fabric layer made of glass fibers or a resin film layer.

[0128] The above-mentioned fabric layer made of glass fibers is a layer made of glass cloth, glass nonwoven fabric, etc. Commercially available glass cloth can be used, and it is preferable that it has been treated with a silane coupling agent to enhance its affinity with the fluororesin. Examples of glass cloth materials include E glass, C glass, A glass, S glass, D glass, NE glass, and low dielectric constant glass, but E glass, S glass, and NE glass are preferred due to their availability. The weave of the fibers can be plain weave or twill weave. The thickness of the glass cloth is usually 5 to 90 μm, preferably 10 to 75 μm, but it is preferable to use one that is thinner than the fluororesin film used.

[0129] The above laminate may use a glass nonwoven fabric as a fabric layer made of glass fibers. A glass nonwoven fabric is made by fixing short glass fibers with a small amount of binder compound (resin or inorganic substance), or by maintaining its shape by entangling the short glass fibers without using a binder compound, and commercially available products can be used. The diameter of the short glass fibers is preferably 0.5 to 30 μm, and the fiber length is preferably 5 to 30 mm. Specific examples of binder compounds include resins such as epoxy resin, acrylic resin, cellulose, polyvinyl alcohol, and fluororesin, as well as inorganic substances such as silica compounds. The amount of binder compound used is usually 3 to 15% by mass relative to the short glass fibers. Examples of materials for the short glass fibers include E glass, C glass, A glass, S glass, D glass, NE glass, and low dielectric constant glass. The thickness of the glass nonwoven fabric is usually 50 μm to 1000 μm, and is preferably 100 to 900 μm. Furthermore, the thickness of the glass nonwoven fabric in this application refers to the value measured using a digital gauge DG-925 (load 110 grams, face diameter 10 mm) manufactured by Ono Sokki Co., Ltd., in accordance with JIS P8118:1998. To improve the affinity with fluororesin, the glass nonwoven fabric may be treated with a silane coupling agent.

[0130] Since most glass nonwoven fabrics have a very high void ratio of 80% or more, it is preferable to use a material that is thicker than the dielectric sheet and to compress it by pressure before use.

[0131] The above-mentioned fabric layer made of glass fibers may be a layer formed by laminating glass cloth and glass nonwoven fabric. This allows the properties of each material to be combined to obtain desirable properties. The above-mentioned glass fiber fabric layer may be in the form of a prepreg impregnated with resin.

[0132] The above laminate may have a glass fiber fabric layer and a fluororesin film bonded at the interface, or part or all of the fluororesin film may be impregnated into the glass fiber fabric layer. Furthermore, a prepreg may be prepared by impregnating a glass fiber fabric with a fluororesin composition. A fluororesin film of the present disclosure may be further laminated onto the prepreg obtained in this manner. In this case, the fluororesin composition used to prepare the prepreg is not particularly limited, and the fluororesin film of the present disclosure may also be used.

[0133] As the resin film used as the base layer, heat-resistant resin films and thermosetting resin films are preferred. Examples of heat-resistant resin films include polyimide, modified polyimide, liquid crystal polymer, and polyphenylene sulfide. Examples of thermosetting resins include epoxy resin, bismaleimide, polyphenylene oxide, modified polyphenylene ether, polyphenylene ether, and polybutadiene. The heat-resistant resin film and the thermosetting resin film may contain reinforcing fibers. The reinforcing fibers are not particularly limited, but glass cloth, especially of the low dielectric type, is preferred.

[0134] The dielectric properties, coefficient of thermal expansion, and water absorption of the heat-resistant resin film and thermosetting resin film are not particularly limited, but for example, the dielectric constant at 20 GHz is preferably 3.8 or less, more preferably 3.4 or less, and even more preferably 3.2 or less. The dielectric loss tangent at 20 GHz is preferably 0.0030 or less, more preferably 0.0025 or less, and even more preferably 0.0020 or less. The coefficient of thermal expansion is preferably 100 ppm / °C or less, more preferably 70 ppm / °C or less, and even more preferably 40 ppm / °C or less. The water absorption is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less. [Examples]

[0135] The present disclosure will now be described in detail based on the following examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0136] (Examples 1-4, Examples 6-9) (Paste extrusion) Fluororesin particles and silica were weighed separately so that the silica content matched the amounts shown in Table 1, and then mixed in a mixer in the presence of dry ice. The temperature during mixing was below -10°C. The resulting mixture was mixed with 18-23% oil (isoper H) and aged for about 5 hours. The matured composition was pre-molded under a pressure of 3 MPa, and the pre-molded body was extruded at 40°C and 50 mm / min to obtain an extruded sample. The extruded sample was rolled using two rolls (roll gap set to 500-80 μm) to obtain a sample with a thickness of 125 μm. This sample was then dried at 200°C for 1 hour and fired at 360°C for 10 minutes to obtain a dielectric sheet.

[0137] The fluororesin particles (PTFE) used in each example have the following properties. Average particle size: 500μm Apparent density: 460g / L Standard specific gravity: 2.17

[0138] In each example, the silica used was as follows, as shown in Table 1: as spherical silica, Admatex SC6500-SQ (average particle size 2.1 μm), Admatex SC6500-SQ (average particle size 2.1 μm) surface-treated with 3-aminopropyltriethoxysilane (treatment amount 1 mass%), or Admatex SC2500-SQ (average particle size 0.5 μm); as crushed silica, Ryusen ZA-30 or Ryusen ZA-30 surface-treated with a mixture of phenyltrimethoxysilane and aminoethylaminopropyltrimethoxysilane in a 9:1 ratio at a treatment amount of 1 mass%.

[0139] (Example 5) (Powder rolling) Predetermined amounts of fluoropolymer powder (PTFE) and silica were weighed in the proportions shown in Table 1 and stirred twice for 30 seconds each at setting 6 in a Wonder Crusher at room temperature. The resulting powder was rolled using two rolls (roll gap set to 100 μm) to obtain a sample with a film thickness of 130 μm, and a dielectric sheet was obtained by firing at 360°C for 10 minutes.

[0140] (Comparative Example 1 to Comparative Example 3) (Paste extrusion) Fluororesin particles and silica were weighed separately so that the silica content matched the amounts shown in Table 1, and then mixed in a mixer in the presence of dry ice. The temperature during mixing was below -10°C. To the resulting mixture, 18-23% of oil (isoper H) was added, and in Comparative Example 2, 1000 ppm of dibutylhydroxytoluene (BHT) was added as an antioxidant and mixed, and the mixture was aged for about 5 hours. The matured composition was pre-molded under a pressure of 3 MPa, and the pre-molded body was extruded at 40°C and 50 mm / min to obtain an extruded sample. Extruded samples were rolled using two rolls (roll gap set to 500-80 μm) to obtain samples with a film thickness of 125 μm. These samples were dried under the conditions described in Table 1 and then fired at 360°C for 10 minutes to obtain dielectric sheets.

[0141] Each dielectric sheet obtained was evaluated based on the following criteria. [Residual organic matter amount] <Pre-treatment> A dielectric sheet was cut into 10 mm squares and sealed in a heating container. The generated gas was collected in an adsorption tube when heated under the following conditions. A blank was created by performing the same procedure without the sample. <Heating conditions> Heating temperature: 280°C, Heating time: 30 minutes, Heating atmosphere: Nitrogen atmosphere <Thermal desorption GC / MS measurement> A calibration curve was created from the absolute amount of the standard sample and the obtained peak area value, and quantification was performed. <gc ms> Equipment: GC7890A+5975C (Agilent) Column: DB-5MS (Agilent J&W) Carrier gas: He, Column temperature: 40°C → 300°C Detector: MS, Ion source temperature: 230°C, Scan range: m / z 29~600 Standard product: Dodecane

[0142] [Dk and Df] Dk and Df were measured at 25°C and 10GHz using a split-cylinder dielectric constant / dielectric loss tangent measuring device (manufactured by EM lab).

[0143] [CTE (Coefficient of Thermal Expansion)] TMA measurements were performed in tensile mode using the TMA-7100 (manufactured by Hitachi High-Tech Science Corporation). A sheet cut to a length of 20 mm and a width of 5 mm was used as the sample piece. The distance between the chucks was set to 10 mm, and the CTE (coefficient of linear expansion) was determined from the displacement of the sample from 0 to 150°C while applying a load of 49 mN and heating at a rate of 2°C / min.

[0144] (Manufacturing of copper-clad laminates) The dielectric sheets obtained in Examples 1-9 and Comparative Examples 1-3 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, pressed under vacuum at a pressure of 15 kN for 5 minutes, and cooled to room temperature to obtain a copper-clad laminate. Each of the obtained copper-clad laminates was evaluated based on the following criteria.

[0145] [Appearance of copper-clad laminate] A 100mm x 100mm test piece was cut from the fabricated copper-clad laminate and visually inspected. If one or more blisters were observed, it was considered to have blistered; if no blisters were observed, it was considered to be in good condition. These results are shown in Table 1.

[0146] (Example 10) The amount of residual organic matter in the dielectric layer recovered by etching the copper-clad laminate of Example 4 using the method described below was measured. (etching) The copper foil of the copper-clad laminate was etched with an aqueous ferric chloride solution, washed with running clean water for 2-5 minutes, then washed again with distilled water, and dried in a constant temperature bath at 80±3°C for approximately 60 minutes to recover the individual dielectric layers. The results are shown in Table 1.

[0147] (Example 11) A copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (molar ratio: 70 / 30) was melt-extruded and then subjected to inflation molding to obtain a thermoplastic liquid crystal polymer film with a melting point of 325°C, a heat distortion temperature of 280°C, and a film thickness of 100 μm. A 100 μm thick polyimide film (coefficient of thermal expansion: 16 ppm / K) was used as a heat-resistant release support. The obtained thermoplastic liquid crystal polymer film was sandwiched between two polyimide films with their MD and TD directions aligned to form a laminate. After preheating in a vacuum heat press, the laminate was heat-treated at 330°C for 15 minutes under a pressure of 3 MPa. After the heat treatment, the laminate was cooled and removed, and the polyimide film was peeled off to obtain a dielectric sheet. The obtained dielectric sheets were evaluated based on the above criteria. The dielectric sheet described above 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 & Powder Industry Co., Ltd.), and press-molded under vacuum at 170°C, 3 MPa, and for 60 minutes. After cooling to room temperature, a copper-clad laminate was obtained. The obtained copper-clad laminates were evaluated based on the above criteria. The results are shown in Table 1.

[0148] (Example 12) Under a nitrogen atmosphere, 5.9 g of 2,2'-dimethyl-4,4'-diaminobiphenyl (0.028 mol), 2.0 g of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (0.0049 mol), and an amount of N,N-dimethylacetamide such that the solid content concentration after polymerization was 15% by weight were added to a 300 ml separable flask and stirred at room temperature to dissolve. Next, 12.9 g of p-biphenylenebis(trimellitic acid monoester anhydride) (0.024 mol) and 1.8 g of pyromellitic acid dianhydride (0.008 mol) were added, and the polymerization reaction was carried out by continuing to stir at room temperature for 3 hours to obtain a polyamic acid solution. The viscosity of the polyamic acid solution was 21,000 cps. A polyamic acid solution was uniformly 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.) so that the thickness after curing would be approximately 50 μm. The solution was then heated and dried 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 the imidization and obtain a copper-clad laminate. Based on the above criteria, no foaming was observed on the film surface. 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. The obtained polyimide films were evaluated based on the above criteria. The results are shown in Table 1.

[0149] [Table 1]

[0150] Based on the above results, the dielectric material of this disclosure improves the appearance of the copper-clad laminate. [Industrial applicability]

[0151] The dielectric material of this disclosure can be particularly suitable for use in high-frequency printed circuit boards.< / gc> < / gc>

Claims

1. A dielectric characterized by having a residual organic matter content of 500 μg / g or less.

2. 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 the fluororesin is partially or entirely polytetrafluoroethylene (PTFE).

6. The dielectric according to claim 5, wherein the polytetrafluoroethylene has a standard specific gravity (SSG) of 2.0 to 2.

3.

7. The dielectric according to claim 2, wherein the inorganic filler is at least one selected from the group consisting of silica, titanium oxide, magnesium oxide, alumina, and forsterite.

8. The dielectric according to claim 2, wherein the inorganic filler is partially or entirely silica.

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

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

11. The dielectric according to claim 8 or 9, wherein the silica is coated on its surface with a silane coupling agent.

12. The dielectric according to claim 3 or 4, wherein the fluororesin is in the form of particles and has an average particle diameter of 0.05 to 1000 μm.

13. A metal-clad laminate having a dielectric and a metal foil as described in claim 1.

14. A copper-clad laminate having a dielectric and copper foil as described in claim 1.

15. The copper-clad laminate according to claim 14, wherein the surface roughness Rz of at least the surface of the copper foil that adheres to the dielectric is 2.0 μm or less.

16. The copper-clad laminate according to claim 14 or 15, wherein the copper foil is rolled copper or electrolytic copper.

17. The copper-clad laminate according to claim 14 or 15, wherein the dielectric loss tangent value of the dielectric at 10 GHz is 0.0015 or less.

18. The copper-clad laminate according to claim 14 or 15, wherein the thickness of the dielectric is 5 to 250 μm.

19. A method for producing a dielectric according to claim 1, characterized by mixing fluororesin particles and an inorganic filler to form a film.

20. A method for producing a dielectric according to claim 19, characterized in that a film is formed using a composition substantially consisting of fluororesin particles and an inorganic filler.

21. A method for manufacturing a copper-clad laminate according to claim 14, characterized by laminating a dielectric and copper foil, heating in the range of 180 to 390°C, and press-molding under vacuum or in an inert gas atmosphere at a pressure in the range of 1 to 100 kN.

22. A circuit board characterized by having a dielectric material as described in claim 1 or a copper-clad laminate as described in claim 14.

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