Sheet, method for producing same, metal-clad laminate, circuit substrate, and antenna

Abstract

Provided is a sheet having a small change in relative permittivity due to a temperature change. A sheet in which the rate of change in the relative permittivity in the temperature range of-50 DEG C to 150 DEG C is 0.020 or less.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a sheet, a method for manufacturing the same, a metal-clad laminate, a substrate for a circuit, and an antenna. BACKGROUND

[0002] For a printed wiring board for high frequencies, a printed wiring board for high frequencies with a small transmission loss is required. In such a printed wiring board for high frequencies, a substrate used for an antenna of a millimeter wave radar for a mobile body is required to have a small change in relative dielectric constant caused by a change in temperature.

[0003] In Patent Literatures 1 to 3, it is disclosed that two or more fillers are used in combination with a fluororesin as an electronic substrate material.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2020-050860

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. 2020-037662

[0008] Patent Literature 3: Japanese Patent Application Laid-Open No. 2023-028091 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] The temperature of the environment in which a dielectric is used changes, and as a result, the dielectric properties of the dielectric change, which greatly affects the performance of a circuit and an antenna. Therefore, it is preferable that the dielectric properties do not greatly change due to a change in temperature. The purpose of the present disclosure is to provide a sheet having a small change in relative dielectric constant caused by a change in temperature in order to minimize the influence on the performance of an antenna.

[0011] MEANS FOR SOLVING THE PROBLEMS

[0012] The present disclosure relates to a sheet characterized in that the rate of change in relative dielectric constant in the temperature range of -50 to 150°C is 0.020 or less, and two or more fillers are contained.

[0013] The coefficient of linear expansion (CTE) of the above-described sheet is preferably 70 ppm / K or less.

[0014] The value of the dielectric loss tangent of the above-described sheet at 10 GHz is preferably 0.0015 or less.

[0015] The thickness of the above-described sheet is preferably 5 to 250 pm.

[0016] The above-described sheet preferably contains a fluororesin.

[0017] The fluororesin is preferably polytetrafluoroethylene.

[0018] The filler preferably has a band gap of 2 eV or more.

[0019] The content of the filler relative to the total amount of the sheet is preferably 30% by mass or more.

[0020] The filler preferably contains at least two selected from the group consisting of silicon dioxide, aluminum oxide, boron nitride, and zirconium oxide.

[0021] The filler is preferably two of silicon dioxide and aluminum oxide.

[0022] The silicon dioxide is preferably a spherical particle.

[0023] The silicon dioxide is preferably a silicon dioxide particle treated with a silane coupling agent.

[0024] The silane coupling agent preferably has an aminopropyl group.

[0025] The average particle diameter of the silicon dioxide particle is preferably 10 μm or less.

[0026] The average particle diameter of the aluminum oxide is preferably 10 μm or less.

[0027] The compounding amount of the aluminum oxide relative to the total amount of the aluminum oxide and the silicon dioxide is preferably 10 to 50% by mass.

[0028] The present disclosure also relates to a method for manufacturing the sheet, characterized by performing film formation after mixing the fluororesin and the filler.

[0029] The present disclosure also relates to a method for manufacturing the sheet, characterized by performing film formation using a composition consisting essentially of fluororesin particles and filler particles containing at least silicon dioxide particles and aluminum oxide particles.

[0030] The present disclosure also relates to a metal-clad laminate, characterized by having the sheet as a necessary layer, with a metal foil layer on both sides or on one side.

[0031] The metal foil is preferably copper.

[0032] The present disclosure also relates to a substrate for a circuit, characterized by having the metal-clad laminate.

[0033] The present disclosure also relates to an antenna, characterized by being formed from the substrate for a circuit.

[0034] The antenna is preferably a millimeter wave antenna for a mobile body.

[0035] Effects of the Invention

[0036] The sheet of the present disclosure has the following excellent effect: the change in the relative dielectric constant due to temperature change is small, and thus in applications such as antennas for millimeter wave radars for mobile bodies, in which temperature change is large, changes in performance due to temperature change do not occur. DETAILED DESCRIPTION

[0037] Hereinafter, the present disclosure will be described in detail.

[0038] The present disclosure is a sheet characterized in that the rate of change in the relative dielectric constant in the temperature range of -50 to 150°C is 0.020 or less. That is, the relative dielectric constant does not change in such a wide temperature range of -50 to 150°C. Therefore, the sheet has less change in electrical properties.

[0039] In recent years, circuits formed in fine have increased, such as antennas for millimeter wave radars, and in the case of such circuits, even if the relative dielectric constant changes slightly, the electrical characteristics change, and thus, sometimes, abnormal operation occurs.

[0040] In the field of mobile body applications, communication is required to have high precision. Therefore, by using a sheet in which the relative dielectric constant hardly changes in such a wide temperature range as described above, abnormality in communication can be prevented.

[0041] In other fields, as the wiring substrate is increasingly developed in high density and thin lines, it is also very important to reduce the rate of change in the relative dielectric constant in order to prevent abnormal operation. The present disclosure is used to improve such problems that have not been achieved in the related art. Note that in the present disclosure, the rate of change in the relative dielectric constant is a value measured by the method described in the examples.

[0042] The rate of change in the relative dielectric constant in the temperature range of -50 to 150°C is preferably 0.020 or less, more preferably 0.018 or less, and further preferably 0.016 or less. In addition, the lower limit thereof is not particularly limited, and for example, can be 0.001 or more.

[0043] The sheet of the present disclosure preferably has a coefficient of linear expansion (CTE) of 70 ppm / °C or less. Thus, by using a sheet having a small coefficient of linear expansion, even in the case of use under conditions in which temperature change is large, the dimensional stability is excellent, and stable performance can be obtained, which is preferable from this aspect. The CTE is more preferably 50 ppm / °C or less, and further preferably 40 ppm / °C or less. The lower limit of the CTE is not particularly limited, and for example, is preferably set to 10 ppm / °C or more, and more preferably 18 ppm / °C.

[0044] The wafer disclosed herein preferably has a dielectric loss tangent of 0.0015 or less at 10 GHz. Such a wafer is preferred in terms of low dielectric loss and low overall loss. The aforementioned dielectric loss tangent is a value measured at 20°C, and more specifically, a value measured using the method described in the embodiments.

[0045] The dielectric loss tangent at 10 GHz is more preferably 0.0012 or less, and even more preferably 0.0011 or less. The lower limit of the dielectric loss tangent at 10 GHz is not particularly limited, and for example, it can be set to 0.00001 or more.

[0046] The thickness of the aforementioned sheet is preferably 5 to 250 μm. By setting it within this range, it can be suitably used in metal-clad laminates. Even thin sheets of this disclosure can fully achieve their purpose. The aforementioned thickness is more preferably less than 230 μm, and even more preferably less than 200 μm. Furthermore, it is more preferably thicker than 15 μm, and even more preferably thicker than 30 μm.

[0047] The composition of the sheet disclosed herein is not particularly limited, but it preferably contains resin and filler. By producing such a sheet, the specific physical properties described above can be obtained. Hereinafter, the resin and filler will be described in detail.

[0048] (Fluoropolymer)

[0049] The compositions disclosed herein contain fluoropolymers. Fluoropolymers have low dielectric properties, and are therefore suitable for the purposes of this disclosure.

[0050] The fluoropolymers that can be used in this disclosure are not particularly limited, and 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 with a molecular weight of less than 300,000 [LMW-PTFE]. One type or a mixture of two or more can be used. From the viewpoint of low dielectric properties, polytetrafluoroethylene resin (PTFE) is particularly preferred. PTFE preferably has fibrillary properties. Fibrillary PTFE refers to PTFE that can be extruded from unburned polymer powder paste.

[0051] PTFE can be modified polytetrafluoroethylene (hereinafter referred to as modified PTFE), homopolymer polytetrafluoroethylene (hereinafter referred to as homopolymer PTFE), or a mixture of modified PTFE and homopolymer PTFE. It should be noted that, from the perspective of maintaining the moldability of polytetrafluoroethylene, the content of modified PTFE in the polymeric PTFE is preferably 10% by mass or more and 98% by mass or less, more preferably 50% by mass or more and 95% by mass or less. Homopolymer PTFE is not particularly limited, and Japanese Patent Application Publication Nos. 53-60979, 57-135, 61-16907, 62-104816, 62-190206, 63-137906, and 2000-143727 are preferred. Homopolymer PTFE disclosed in Japanese gazettes, Japanese Patent Application Publication Nos. 2002-201217, International Publication Nos. 2007 / 046345, 2007 / 119829, 2009 / 001894, 2010 / 113950, and 2013 / 027850. Among them, homopolymer PTFE disclosed in Japanese Patent Application Publication No. 57-135, Japanese Patent Application Publication No. 63-137906, Japanese Patent Application Publication No. 2000-143727, Japanese Patent Application Publication No. 2002-201217, International Publication No. 2007 / 046345, International Publication No. 2007 / 119829, and International Publication No. 2010 / 113950, which have high tensile properties, is preferred.

[0052] Modified PTFE consists of TFE and monomers other than TFE (hereinafter referred to as modified monomers). Examples of modified PTFE include PTFE uniformly modified using modified monomers, PTFE modified at the initial stage of polymerization, and PTFE modified at the end of polymerization; there is no particular limitation. Preferably, modified PTFE is a TFE copolymer obtained by polymerizing a trace amount of monomers other than TFE together with TFE, within a range that does not significantly impair the properties of the TFE homopolymer. Modified PTFE may preferably be those disclosed in Japanese Patent Application Publication No. 60-42446, Japanese Patent Application Publication No. 61-16907, Japanese Patent Application Publication No. 62-104816, Japanese Patent Application Publication No. 62-190206, Japanese Patent Application Publication No. 64-1711, Japanese Patent Application Publication No. 2-261810, Japanese Patent Application Publication No. 11-240917, Japanese Patent Application Publication No. 11-240918, International Publication No. 2003 / 033555, International Publication No. 2005 / 061567, International Publication No. 2007 / 005361, International Publication No. 2011 / 055824, and International Publication No. 2013 / 027850. Among them, modified PTFE with high tensile properties is preferred, as disclosed in Japanese Patent Application Publication No. 61-16907, Japanese Patent Application Publication No. 62-104816, Japanese Patent Application Publication No. 64-1711, Japanese Patent Application Publication No. 11-240917, International Publication No. 2003 / 033555, International Publication No. 2005 / 061567, International Publication No. 2007 / 005361, and International Publication No. 2011 / 055824.

[0053] Modified PTFE comprises TFE-based TFE units 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, more preferably 0.01% to 0.30% by mass. The total monomer units are the portion of the modified PTFE molecular structure derived from all monomers.

[0054] There are no particular limitations on the modified monomers as long as they can copolymerize with TFE. Examples include perfluoroolefins such as hexafluoropropylene (HFP); chlorofluoroolefins such as trifluorochloroethylene (CTFE); hydrofluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF); perfluorovinyl ethers; perfluoroalkyl ethylene (PFAE); and ethylene. One or more modified monomers can be used.

[0055] There are no particular limitations on perfluorovinyl ethers; for example, perfluorounsaturated compounds represented by the following general formula (1) can be cited.

[0056] CF2 = CF - ORf···(1)

[0057] In the formula, Rf represents a perfluorinated organic group.

[0058] In this specification, a perfluorinated organic group is an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The aforementioned perfluorinated organic groups may contain ether oxygen.

[0059] Examples of perfluorovinyl ethers (PAVEs) include perfluoro(alkyl vinyl ethers) in which Rf is a perfluoroalkyl group having 1 to 10 carbon atoms in the general formula (1) above. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5. Examples of perfluoroalkyl groups in PAVEs include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, and perfluorohexyl. Perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE) are preferred as PAVEs.

[0060] The term "perfluoroalkyl ethylene (PFAE)" is not specifically limited; examples include perfluorobutylethylene (PFBE) and perfluorohexylethylene (PFHE).

[0061] The modifying monomer used in modified PTFE is preferably selected from at least one of the group consisting of HFP, CTFE, VDF, PAVE, PFAE and ethylene.

[0062] The aforementioned fluoropolymers are preferably non-melt processable. Non-melt processable means that even when heated above its melting point, the resin does not possess sufficient fluidity and cannot be molded using the melt molding methods commonly used in resin production. PTFE meets this requirement.

[0063] In this disclosure, a non-melt-processable fluoropolymer is preferably used, and fluoropolymer sheets are formed by fibrillating it. This molding method is described below.

[0064] The preferred SSG value for the PTFE is 2.0 to 2.3. Using such PTFE readily yields PTFE films with high strength (cohesive strength and puncture strength per unit thickness). High molecular weight PTFE has long molecular chains, making it difficult to form a structure with regularly arranged molecular chains. In this case, the length of the amorphous portion increases, and the degree of molecular entanglement increases. It is believed that with a high degree of molecular entanglement, the PTFE film is less prone to deformation under applied loads, exhibiting excellent mechanical strength. Furthermore, using high molecular weight PTFE readily yields PTFE films with small average pore size.

[0065] The lower limit of the aforementioned SSG is more preferably 2.05, and even more preferably 2.1. The upper limit of the aforementioned SSG is more preferably 2.25, and even more preferably 2.2.

[0066] Standard specific gravity [SSG] is obtained by preparing a sample according to ASTM D-4895-89 and determining the specific gravity of the sample by the water displacement method.

[0067] In this embodiment, the molecular weight (number average molecular weight) of the PTFE constituting the PTFE powder is, for example, in the range of 2 million to 12 million. The lower limit of the molecular weight of PTFE can be 3 million or 4 million. The upper limit of the molecular weight of PTFE can be 10 million.

[0068] Methods for determining the number-average molecular weight of PTFE include methods based on standard specific gravity and methods utilizing dynamic viscoelasticity during melting. The method based on standard specific gravity can be performed using samples molded according to ASTM D-4895 98 via the water displacement method according to ASTM D-792. The method utilizing dynamic viscoelasticity is described, for example, by S. Wu in Polymer Engineering & Science, 1988, Vol. 28, 538 and the same paper, 1989, Vol. 29, 273.

[0069] The refractive index of the aforementioned PTFE is preferably in the range of 1.2 to 1.6. This refractive index is preferable from the perspective of low dielectric strength. The refractive index can be adjusted within this range by methods such as adjusting polarizability and the flexibility of the main chain. The lower limit of the aforementioned refractive index is more preferably 1.25, more preferably 1.30, and most preferably 1.32. The upper limit of the aforementioned refractive index is more preferably 1.55, more preferably 1.50, and most preferably 1.45.

[0070] The refractive index mentioned above is a value measured using a refractometer (Abbemat 300).

[0071] In addition, the maximum endothermic peak temperature (crystal melting point) of the above-mentioned PTFE is preferably 340±7℃.

[0072] PTFE can be either low-melting-point PTFE with a maximum peak temperature of less than 338°C on the endothermic curve of the crystal melting curve measured by differential scanning calorimetry, or high-melting-point PTFE with a maximum peak temperature of more than 342°C on the endothermic curve of the crystal melting curve measured by differential scanning calorimetry.

[0073] Low-melting-point PTFE is a powder manufactured through emulsion polymerization. It possesses the aforementioned maximum endothermic peak temperature (crystal melting point), a dielectric constant (ε) of 2.08–2.2, and a dielectric loss tangent (tanδ) of 1.9 × 10⁻⁴. 4 ~4.0×10- 4 As commercially available products, examples include POLYFLON FINE POWDER F201, F203, F205, F301, and F302 manufactured by Daikin Industries, Ltd.; CD090 and CD076 manufactured by Asahi Glass Co., Ltd.; and TF6C, TF62, and TF40 manufactured by DuPont.

[0074] High-melting-point PTFE powder is also a powder manufactured through emulsion polymerization. It possesses the aforementioned maximum endothermic peak temperature (crystal melting point), a dielectric constant (ε) of 2.0–2.1, and a dielectric loss tangent (tanδ) of 1.6 × 10⁻⁶. 4 ~2.2×10- 4 Overall, the price is low. Examples of commercially available products include POLYFLON FINE POWDER F104 and F106 manufactured by Daikin Industries, Ltd.; CD1, CD141, and CD123 manufactured by Asahi Glass Co., Ltd.; and TF6 and TF65 manufactured by DuPont.

[0075] It should be noted that the average particle size of the powder formed by the secondary agglomeration of two PTFE polymer particles is preferably 250 μm to 2000 μm. In particular, from the perspective of improving the flowability during mold filling in preforming, granulated powder obtained by solvent granulation is preferred.

[0076] PTFE powder with the above parameters can be obtained by existing manufacturing methods. For example, it can be manufactured according to the manufacturing methods described in International Publication No. 2015 / 080291, International Publication No. 2012 / 086710, etc.

[0077] (filler)

[0078] The fillers that can be used in this disclosure are not particularly limited, and examples include one or more organic fillers selected from aromatic polyamide fibers, polyphenylene ester, polyphenylene sulfide, polyimide, polyetheretherketone, polyphenylene oxide, polyamide, and fully aromatic polyester resins; and one or more inorganic fillers selected from ceramics, talc, mica, alumina, tin oxide, titanium oxide, silicon dioxide, calcium carbonate, calcium oxide, magnesium oxide, zirconium oxide, potassium titanate, glass fiber, glass sheets, glass beads, silicon carbide, calcium fluoride, boron nitride, barium sulfate, molybdenum disulfide, and calcium carbonate whiskers. The sheets of this disclosure utilize two or more of these fillers.

[0079] Of these, at least two are particularly preferred from the group consisting of silicon dioxide, aluminum oxide, boron nitride and zirconium oxide.

[0080] The temperature variation of dielectric loss tangent and relative permittivity is greatly influenced by the band gap of the filler. Essentially, a low dielectric loss tangent can be achieved by using compounds with a large band gap. Therefore, compounds with suitable band gap ranges are particularly preferred. Preferred band gap ranges are 2 eV or higher, followed by 3 eV or higher, then 3.5 eV or higher, and then 4 eV or higher. More preferably, fillers with 4.5 eV or higher, further preferably 5 eV or higher, and especially preferably 6 eV or higher are used. Furthermore, from the perspective of producing sheets with small temperature variations in dielectric constant, it is particularly preferred to use two or more of these fillers in combination. Among these, silica and alumina are most preferred. The band gap is calculated using a UV-2600 UV-Vis spectrophotometer (manufactured by Shimadzu Corporation) by measuring the diffuse reflectance spectrum. The measurement results are retrieved using the spectral data from the bandgap calculation Excel macro. After selecting "photometric value (transmittance / reflectance)" and "n value (type of migration process)", the range that can approximate a straight line near the inflection point is specified as the tangent, and the bandgap value based on the Tauc curve is calculated.

[0081] When silicon dioxide and aluminum oxide are used together, since both have a large band gap of 5eV or more, the temperature change of the relative permittivity can be significantly reduced by using them together.

[0082] When the filler is a combination of silica and alumina, the silica particles are preferably spherical. Spherical particles are preferred because they are easier to process uniformly during pore-forming, have a smaller specific surface area, and exhibit lower transmission losses.

[0083] The aforementioned spherical silica particles refer to particles whose shape is close to that of a perfect sphere. Specifically, the sphericity is preferably 0.80 or higher, more preferably 0.85 or higher, further preferably 0.90 or higher, and most preferably 0.95 or higher. Regarding sphericity, it is determined by taking photographs using SEM and observing the area and perimeter of the particles, using the formula (sphericity) = {4π × (area) ÷ (perimeter)}. 2 The value is calculated from the given value. The closer it is to 1, the closer it is to a perfect sphere. Specifically, the average value measured on 100 particles using an image processing device (Spectris Co., Ltd.: FPIA-3000) is used.

[0084] For the spherical silica particles used in this disclosure, when integrating the volume from the side with smaller particle size, D90 / D10 is preferably 2 or more (preferably 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 preferably 1.6 or more). D50 / D10 is preferably 1.5 or more (more preferably 1.6 or more). Furthermore, D50 is more preferably 5 μm or less. Since small-sized spherical silica particles may enter the gaps between large-sized spherical silica particles, excellent filling properties are achieved, and flowability is improved. In particular, as for particle size distribution, it is preferable that the frequency on the side with smaller particle size is higher compared to the Gaussian curve. Particle size can be measured using a particle size distribution measuring device based on laser diffraction scattering. Additionally, since coarse particles make it difficult to thin the sheet, it is preferable to remove coarse particles with a specified particle size or larger using a filter or the like.

[0085] In this disclosure, the surface area of ​​the packing (m²) 2 The surface area ( / g) is a value based on the BET method, and can be measured using a "Macsorb HM model-1208" (manufactured by MACSORB). It should be noted that when the tablets of this disclosure contain two or more fillers, the overall surface area measured for the mixed fillers is within the above-mentioned range.

[0086] The average particle size of the aforementioned silica particles is preferably 10 μm or less. When the average particle size of the silica particles is 10 μm or less, the surface roughness of the sheet becomes lower, which is therefore preferable. The upper limit of the average particle size of the silica particles is more preferably 8 μm or less, and even more preferably 5 μm or less. It should be noted that the average particle size here refers to the D50 value measured using a laser analytical particle size analyzer.

[0087] The aforementioned silica particles may be silica particles treated with a silane coupling agent. By performing surface treatment beforehand, the aggregation of silica particles can be suppressed, and the silica particles can be well dispersed in the wafer.

[0088] As for the aforementioned silane coupling agent, there are no particular limitations, and any known surface treatment can be used. Specifically, examples include treatments using silane coupling agents with reactive functional groups such as epoxy silanes, amino silanes, isocyanate silanes, vinyl silanes, acrylate silanes, hydrophobic alkyl silanes, phenyl silanes, and fluorinated alkyl silanes, as well as plasma treatments and fluorination treatments.

[0089] Examples of silane coupling agents include epoxy silanes such as γ-epoxypropoxypropyltriethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, aminosilanes such as aminopropyltriethoxysilane and N-phenylaminopropyltrimethoxysilane, isocyanate silanes such as 3-isocyanatepropyltrimethoxysilane, vinyl silanes such as vinyltrimethoxysilane, and acryloylsilanes such as acryloyloxytrimethoxysilane. Among these, silane coupling agents having an aminopropyl group are preferred.

[0090] The aforementioned spherical silica particles can be made from commercially available silica particles that meet the above properties. Examples of commercially available silica particles include, for instance, Denka fused silica FB grade (manufactured by Denka Corporation), Denka fused silica SFP grade (manufactured by Denka Corporation), EXCELICA (manufactured by Tokuyama Corporation), high-purity synthetic spherical silica ADMAFINE (manufactured by Admatechs Corporation), ADMANANO (manufactured by Admatechs Corporation), and ADMAFUSE (manufactured by Admatechs Corporation).

[0091] When the silica particles mentioned above are silica particles treated with silane coupling agent, there is no particular limitation on the amount of treatment. Relative to the amount of silica particles coated, it is preferably in the range of 0.1 to 1.5% by mass, more preferably in the range of 0.15 to 1.0% by mass.

[0092] The alumina described above has good electrical insulation and thermal conductivity. As alumina particles, their shape and size are not particularly limited, and any known alumina particles can be used. More specifically, the average particle size is preferably 10 μm or less. When the average particle size of the alumina particles is 10 μm or less, the surface roughness of the sheet becomes lower, which is therefore preferable. The upper limit of the average particle size of the alumina particles is more preferably 5 μm or less, and even more preferably 4 μm or less. Furthermore, the lower limit of the average particle size of the alumina particles is not particularly limited, but is preferably 0.5 μm or more. If the average particle size is less than 0.5 μm, there is a tendency to fail to obtain a sufficient effect due to filler agglomeration. It should be noted that the method for measuring the average particle size here is the same as the method for measuring the silica particles described above. The alumina particles can be surface-treated particles or untreated particles. Furthermore, the BET specific surface area (m² / g) is preferably 1.0 to 5.0, more preferably 1.2 to 4.0, and particularly preferably 1.4 to 3.2. The oil absorption capacity (ml / 100g) is preferably 10-40, more preferably 15-30, and particularly preferably 20-27. The pH is preferably 7-10, more preferably 8-10, and particularly preferably 9.

[0093] The mixing ratio of the silane particles and alumina particles is not particularly limited. For example, the amount of alumina mixed in is preferably 10 to 50% by mass relative to the total amount of alumina and silicon dioxide. More preferably, it is 12 to 40% by mass, and even more preferably, it is 13% to 35% by mass. By setting it within the above range, it is possible to produce a sheet with a small temperature change in relative permittivity, which is preferred.

[0094] The aforementioned alumina particles can be commercially available alumina particles that meet the above properties. Examples of commercially available alumina particles include LS-210B and LS-110F manufactured by Nippon Light Metals Co., Ltd.

[0095] The wafers disclosed herein preferably contain filler at a ratio of 30% or more by mass relative to the total wafer weight. This mixing amount is preferred in terms of maintaining a low dielectric constant and low loss while also achieving low thermal expansion. More preferably, the mixing amount is 35% or more by mass, further preferably 50% or more by mass, and even more preferably 55% or more by mass. There is no particular upper limit to the filler mixing amount, but it is preferably 70% or less by mass, more preferably 68% or less by mass, and even more preferably 65% ​​or less by mass.

[0096] (Methods for manufacturing the film)

[0097] The film disclosed herein can be obtained by mixing the above-mentioned fluororesin particles and fillers and then forming a film. The manufacturing method is not limited and can be carried out by paste extrusion molding, powder calendering, etc.

[0098] As described above, the fluoropolymer used in the sheets of this disclosure is preferably a non-melt-processable fluoropolymer. When using such a fluoropolymer, it is preferable to mold it into sheets by fibrillating powdered PTFE, which is used as a raw material.

[0099] The powdered PTFE described above preferably uses PTFE with a primary particle size of 0.05–10 μm. Using such PTFE offers advantages such as excellent formability and dispersibility. It should be noted that the primary particle size here is a value determined according to ASTM D 4895.

[0100] The aforementioned powdered PTFE preferably contains 50% by mass or more of polytetrafluoroethylene resin with a secondary particle size of 500 μm or more, and more preferably 80% by mass or more. By ensuring that the PTFE has a secondary particle size of 500 μm or more falls within this range, it has the advantage of being able to produce high-strength compound tablets. Using PTFE with a secondary particle size of 500 μm or more, compound tablets with lower electrical resistance and greater toughness can be obtained.

[0101] The lower limit of the aforementioned secondary particle size is more preferably 300 μm, and even more preferably 350 μm. The upper limit of the aforementioned 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.

[0102] For the aforementioned powdered PTFE, from the viewpoint of obtaining sheets with higher strength and excellent homogeneity, the average primary particle size is preferably 50 nm or more. More preferably, it is 100 nm or more, further preferably 150 nm or more, and particularly preferably 200 nm or more. The larger the average primary particle size of PTFE, the better it is to suppress the rise of paste extrusion pressure and the better the formability when using the powder for paste extrusion molding. There is no particular upper limit, and it can be 500 nm. From the viewpoint of productivity in the polymerization process, 350 nm is preferred.

[0103] Regarding the aforementioned average primary particle size, a calibration curve is prepared using an aqueous dispersion of PTFE obtained through polymerization. This curve compares the transmittance of 550 nm of projected light per unit length relative to the aqueous dispersion with a polymer concentration adjusted to 0.22% by mass with the average primary particle size determined by measuring the directional diameter in a transmission electron microscope image. The transmittance of the aqueous dispersion being measured can be determined based on the calibration curve.

[0104] The PTFE used in this disclosure can have a core-shell structure. Examples of PTFEs with a core-shell structure include, for instance, modified PTFE, which contains a core of high molecular weight polytetrafluoroethylene (PTFE) and a shell of lower molecular weight PTFE or modified PTFE. Examples of such modified PTFEs include, for instance, the PTFE described in Japanese Patent Application Publication No. 2005-527652.

[0105] There are no particular limitations on the specific methods for paste extrusion molding and powder calendering molding; the following describes the common methods.

[0106] (Paste extrusion molding)

[0107] The manufacturing method of the above-mentioned sheet may include: a step of mixing PTFE powder obtained using a hydrocarbon-based surfactant with an extrusion aid (1a); a step of extruding the resulting mixture into a paste (1b); a step of calendering the extrudate obtained by extrusion (1c); a step of drying the calendered sheet (1d); and a step of firing the dried sheet to obtain a molded body (1e). The above-mentioned paste extrusion molding may also be carried out by adding conventionally known additives such as pigments and fillers to the above-mentioned PTFE powder.

[0108] There are no particular limitations on the extrusion aids mentioned above; commonly known extrusion aids can be used. For example, hydrocarbon oils can be cited.

[0109] (Powder Calendering)

[0110] The aforementioned sheets can also be formed by powder calendering. Powder calendering is a method of forming sheets by applying shear force to resin powder to fibrillate it. Then, a firing process can be included to obtain the molded body.

[0111] More specifically, it can be obtained by a manufacturing method having the following steps: In step (1), shear force is applied while mixing the raw material composition containing fluoropolymer and filler; Step (2) involves shaping the mixture obtained through step (1) into a block shape; and The process (3) involves calendering the blocky mixture obtained through the above process (2) into sheet form.

[0112] It should be noted that when forming sheets by calendering powder in this way, it is preferable to mix only fluoropolymer particles and inorganic fillers for forming.

[0113] When manufacturing sheets using the powder calendering method described above, it is preferable to use a composition substantially composed of fluoropolymer particles and filler particles to form the film, without any liquid components. It should be noted that "substantially composed of fluoropolymer particles and filler particles" means that the content of components other than the fluoropolymer particles and the filler particles is 3% by mass or less relative to the total composition.

[0114] For the sheet disclosed herein, surface treatment can be performed to improve the adhesion strength to the copper foil. The specific method for surface treatment of the sheet is not particularly limited and can be performed by any known method. The surface treatment of the sheet can employ conventional discharge treatments such as plasma discharge treatment, corona discharge treatment, glow discharge treatment, and sputtering treatment. Plasma treatment is preferred.

[0115] Plasma treatment involves etching the fluororesin on the outer surface of the wafer by bringing plasma into contact with the wafer, and adding oxygen atoms, nitrogen atoms, etc. to the outer surface of the wafer.

[0116] For example, by introducing oxygen, nitrogen, hydrogen, helium, argon, etc. into the discharge atmosphere, the surface free energy can be controlled.

[0117] Alternatively, the surface to be modified can be exposed to an atmosphere of an inactive gas containing organic compounds, and a high-frequency voltage can be applied between the electrodes to generate a discharge, thereby generating active species on the surface. Then, functional groups of organic compounds or graft polymerizable organic compounds can be introduced to modify the surface.

[0118] Organic compounds among the aforementioned inactive gases containing organic compounds can be categorized as polymeric or non-polymeric organic compounds containing oxygen atoms. Examples include: vinyl esters such as vinyl acetate and vinyl formate; acrylates such as glycidyl methacrylate; ethers such as vinyl ethyl ether, vinyl methyl ether, and glycidyl methyl ether; carboxylic acids such as acetic acid and formic acid; alcohols such as methanol, ethanol, phenol, and ethylene glycol; ketones such as acetone and methyl ethyl ketone; carboxylic acid esters such as ethyl acetate and ethyl formate; and acrylic acids such as acrylic acid and methacrylic acid. Among these, vinyl esters, acrylates, and ketones are preferred from the perspective of their resistance to surface deactivation after modification, i.e., their long lifespan. Vinyl acetate and glycidyl methacrylate are particularly preferred.

[0119] The concentration of organic compounds in the inactive gas containing organic compounds varies depending on their type and the type of fluororesin to be surface-treated, typically ranging from 0.1 to 3.0% by capacity, preferably from 0.1 to 1.0% by capacity, more preferably from 0.15 to 1.0% by capacity, and even more preferably from 0.30 to 1.0% by capacity. The discharge conditions are appropriately selected based on the degree of surface treatment targeted, the type of fluororesin, and the type or concentration of organic compounds. Typically, a discharge rate of 50 W·min / m is used. 2 ~1500W·min / m 2 Optimal 70W·min / m 2 The above 1400W·min / m 2 The discharge process is performed within the following range. The processing temperature can be any temperature within the range of 0°C to 100°C. However, to avoid elongation, wrinkling, etc. of the sheet, it is preferable to perform the process at 80°C or below.

[0120] (Layered structure)

[0121] The sheet disclosed herein can be used as a sheet for printed wiring substrates and laminated with other substrates.

[0122] The sheet disclosed herein can be used as a substrate for circuit boards and laminated with metal foil. It can also be manufactured as a laminate in which metal foil is bonded to one or both sides of the sheet. This disclosure also describes a metal-clad laminate in which the sheet is a necessary layer and has metal foil layers on one or both sides.

[0123] Examples of metal foils used in this disclosure include copper foil, gold foil, silver foil, platinum foil, and ruthenium foil. Among these, copper foil is preferred due to its low conductor loss.

[0124] This disclosure also pertains to a copper-clad laminate, characterized in that copper foil is bonded to one or both sides of the aforementioned sheet. As described above, the sheet of this disclosure is particularly suitable for use as a printed wiring substrate, and therefore suitable for use as such a copper-clad laminate.

[0125] The copper foil described above preferably has an Rz of 2.0 μm or less. That is, the sheet disclosed herein exhibits excellent adhesion to copper foil with high smoothness, such as an Rz of 2.0 μm or less. Furthermore, the copper foil only needs to have an Rz of 2.0 μm or less on the side that is bonded to the sheet; the Rz value of the other side is not particularly limited. The copper foil described above preferably uses copper foil with high smoothness, such as an Rz of 2.0 μm or less, further Rz of 1.6 μm or less, and further Rz of 1.0 μm or less. The Rz described above is the sum of the highest point (maximum peak height: Rp) and the deepest point (maximum valley depth: Rv). The surface roughness described above is the ten-point average roughness specified in JIS-B0601. In this specification, the Rz described above is the value measured using a surface roughness meter (trade name: SURFCOM 470A, manufactured by Tokyo Seiki Co., Ltd.) with a measurement length of 4 mm.

[0126] The thickness of the copper foil is not particularly limited, but is preferably in the range of 1μm to 100μm, more preferably in the range of 5μm to 50μm, and even more preferably in the range of 9μm to 35μm.

[0127] The copper foil mentioned above is not specifically limited; examples include rolled copper foil and electrolytic copper foil.

[0128] There are no particular limitations on the copper foil with an Rz of 2.0 μm or less, and commercially available copper foil can be used. Examples of commercially available copper foil 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.).

[0129] To improve the adhesion strength with the sheet disclosed herein, the copper foil may be surface treated.

[0130] The surface treatment described above is not particularly limited and can include silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, etc., with plasma treatment being preferred. The reactive functional group used as the silane coupling agent is not particularly limited, but from the perspective of adhesion to the resin substrate, it is preferable to have at least one terminal group selected from amino, (meth)acryloyl, mercapto, and epoxy groups. Furthermore, the hydrolyzable group is not particularly limited, and examples include alkoxy groups such as methoxy and ethoxy. The copper foil used in this disclosure can be formed with an anti-rust layer (such as an oxide film like chromate) and a heat-resistant layer.

[0131] Surface-treated copper foil having a surface treatment layer formed from the aforementioned silane compound on its surface can be manufactured as follows: after preparing a solution containing the silane compound, the copper foil is surface-treated using the solution, thereby manufacturing the copper foil.

[0132] To improve adhesion to the resin substrate, the copper foil may have a roughening treatment layer on its surface. It should be noted that if the roughening treatment may reduce the performance required by this disclosure, the number of roughening particles electrodeposited on the copper foil surface may be reduced, or the roughening treatment may be omitted altogether.

[0133] To enhance various properties, one or more layers selected from the group consisting of heat-resistant treatment layers, rust-proof treatment layers, and chromate treatment layers can be placed between the copper foil and the surface treatment layer. These layers can be single layers or multiple layers.

[0134] The metal-clad laminate disclosed herein may further have layers other than metal foil and sheet. These layers other than metal foil and sheet are preferably at least one selected from the group consisting of polyimide, modified polyimide, liquid crystal polymer, polyphenylene sulfide, cyclic olefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, modified polyphenylene ether, polyphenylene ether, and polybutadiene.

[0135] There are no particular limitations on the layers other than the metal foil and sheet, as long as they are made of the aforementioned resin. Furthermore, the thickness of these layers other than the metal foil and sheet is preferably in the range of 12.5 to 260 μm.

[0136] In the metal-clad laminate disclosed herein, the metal layer can be formed on one side or both sides of the roll film. Methods for forming the metal layer include laminating (adhering) metal foil onto the surface of the roll film, vapor deposition, and plating. A method for laminating the metal foil is hot pressing. The hot pressing temperature can be from -150°C to +40°C (the melting point of the sheet). The hot pressing time is, for example, 1 minute to 30 minutes. It can be manufactured by using a hot pressing pressure of 0.1 MPa to 10 MPa.

[0137] The application of the metal-clad laminate disclosed herein is not particularly limited, and it is used as a circuit board. A printed circuit board (PCB) is a plate-shaped component used to electrically connect and fix electronic components such as semiconductors and capacitor chips within a limited space. The structure of the PCB formed from this metal-clad laminate is not particularly limited. The PCB can be any of a rigid substrate, a flexible substrate, or a rigid-flexible substrate. The PCB can be any of a single-sided substrate, a double-sided substrate, or a multilayer substrate (such as a build-up substrate). It is particularly suitable for use as a flexible substrate or a rigid substrate. It is particularly suitable for use as a PCB for high-frequency applications above 10 GHz.

[0138] As a circuit board, there are no particular limitations; the aforementioned metal-clad laminate can be used and manufactured using conventional methods.

[0139] In the metal-clad laminate disclosed herein, the metal foil layer can be formed on one side or both sides of the roll sheet. Methods for forming the metal foil layer include laminating (adhering) metal foil to the surface of the roll sheet, vapor deposition, and plating.

[0140] As a method for laminating the aforementioned metal foil, hot pressing can be used. The hot pressing temperature can range from -150°C to +40°C, which is the melting point of the sheet. The hot pressing time can be, for example, 1 minute to 30 minutes.

[0141] For example, the method for manufacturing a copper-clad laminate is characterized by stacking the aforementioned sheet with a metal foil, heating it at 180–390°C, and pressing it under a vacuum or an inert gas atmosphere at a pressure of 0.5–5 MPa.

[0142] When the above-described laminate is obtained, the sheet of this disclosure is used for bonding copper foil on one or both sides. As described above, the sheet of this disclosure has excellent adhesion. Therefore, it also exhibits excellent adhesion to copper foil with high smoothness (Rz 2.0 μm or less).

[0143] For copper foil used in circuit boards, a certain degree of unevenness has traditionally been imparted to the surface to ensure adhesion to the insulating layer. However, in high-frequency applications, unevenness on the surface of the copper foil can cause signal loss, and is therefore undesirable. The aforementioned laminate can achieve suitable adhesion even to copper foil with high smoothness, making it a suitable laminate for use as a circuit board.

[0144] The laminate used for circuit boards is also a type of laminate characterized by having a metal foil layer and the aforementioned sheet. The laminate may further include a substrate layer. The substrate layer is not particularly limited, but preferably includes a fabric layer made of glass fiber or a resin film layer.

[0145] The aforementioned fiberglass fabric layer is composed of glass cloth, glass nonwoven fabric, or the like. Commercially available glass cloth can be used, and treatment with a silane coupling agent is preferred to improve its affinity with fluoropolymers. Examples of glass cloth materials include E-glass, C-glass, A-glass, S-glass, D-glass, NE-glass, and low-dielectric-constant glass; E-glass, S-glass, and NE-glass are preferred for ease of acquisition. The fiber weave can be plain weave or twill weave. The thickness of the glass cloth is typically 5μm to 90μm, preferably 10μm to 75μm, and a glass cloth thinner than the sheet used is preferable.

[0146] The aforementioned laminate can use glass nonwoven fabric as the fabric layer composed of glass fibers. Glass nonwoven fabric is a substance formed by bonding short glass fibers together with a small amount of binder compound (resin or inorganic material), or a substance that maintains its shape by winding the short glass fibers without using a binder compound; commercially available products can be used. The diameter of the glass short fibers is preferably 0.5 μm to 30 μm, and the fiber length is preferably 5 mm to 30 mm. Specific examples of binder compounds include epoxy resin, acrylic resin, cellulose, polyvinyl alcohol, fluoropolymers, and inorganic materials such as silica compounds. The amount of binder compound used is typically 3% to 15% by mass relative to the glass short fibers. Examples of glass short fiber materials 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 typically 50 μm to 1000 μm, preferably 100 μm to 900 μm. It should be noted that the thickness of the glass nonwoven fabric in this application refers to the value measured using the digital gauge DG-925 (load 110 g, face diameter 10 mm) manufactured by Ono Instrument Co., Ltd., in accordance with JIS P8118:1998. To improve the affinity with fluoropolymers, the glass nonwoven fabric can be treated with a silane coupling agent.

[0147] Most glass nonwoven fabrics have a porosity of over 80%, which is very high. Therefore, it is preferable to use glass nonwoven fabrics that are thicker than those made of fluoropolymer sheets and to use them under pressure for compression.

[0148] The aforementioned fabric layer made of glass fiber can be a layer formed by laminating glass cloth and glass nonwoven fabric. This allows for the combination of their respective properties, resulting in suitable properties. The aforementioned fabric layer made of glass fiber can also be in the form of a resin-impregnated prepreg.

[0149] In the above-mentioned laminate, the fabric layer and sheet made of glass fiber can be bonded at the interface, and the sheet can also be partially or completely impregnated into the fabric layer made of glass fiber.

[0150] Alternatively, the fluoropolymer composition can be impregnated into a fabric made of glass fiber to produce a prepreg. The resulting prepreg can then be further laminated with the sheets disclosed herein. In this case, the fluoropolymer composition used in making the prepreg is not particularly limited, and the sheets disclosed herein can also be used.

[0151] As the resin film used as the substrate layer, a heat-resistant resin film or a thermosetting resin film is 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.

[0152] Heat-resistant resin films and thermosetting resin films may contain reinforcing fibers. There are no particular limitations on the reinforcing fibers, but glass cloth, especially low dielectric constant type reinforcing fibers, is preferred.

[0153] The dielectric properties, coefficient of linear expansion, and water absorption rate of the heat-resistant resin film and thermosetting resin film are not particularly limited. For example, the dielectric constant at 20 GHz is preferably 3.8 or less, more preferably 3.4 or less, and even more preferably 3.0 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 linear expansion is preferably 100 ppm / ℃ or less, more preferably 70 ppm / ℃ or less, and even more preferably 40 ppm / ℃ or less. The water absorption rate is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less.

[0154] The application of the metal-clad laminate disclosed herein is not particularly limited, and it can be used as a circuit substrate. This disclosure also pertains to a circuit substrate having the aforementioned metal-clad laminate.

[0155] A circuit board is a plate-shaped component used to electrically connect, configure, and fix electronic components such as semiconductors and capacitor chips within a limited space. There are no particular limitations on the configuration of the circuit board formed from the sheet or metal-clad laminate of this disclosure. The circuit board can be any of a rigid substrate, a flexible substrate, or a rigid-flexible composite substrate. The circuit board can be any of a single-sided substrate, a double-sided substrate, or a multilayer substrate (such as a laminated substrate). It is particularly suitable for use with flexible and rigid substrates. When the sheet of this disclosure does not contain glass fiber or a cloth made of glass fiber, it is suitable for use with flexible substrates.

[0156] In particular, it is suitable for use as a printed circuit board for high frequencies above 10 GHz.

[0157] In this disclosure, the high-frequency circuit is not only composed of circuits that transmit only high-frequency signals, but also includes circuits that transmit signals other than high-frequency signals, such as a transmission path that converts high-frequency signals into low-frequency signals and outputs the generated low-frequency signals to the outside, and a transmission path that supplies power for driving high-frequency corresponding components. Furthermore, it can also be used as a circuit board for antennas, filters, etc.

[0158] This disclosure also describes an antenna formed from the aforementioned circuit board. A millimeter-wave antenna oriented towards moving objects such as automobiles and aircraft is particularly preferred.

[0159] As a circuit substrate, there are no particular limitations; the aforementioned metal-clad laminate can be used and manufactured using conventional methods.

[0160] The sheet and metal-clad laminate disclosed herein are used as electrical and electronic components. Examples include antennas used in electronic devices such as ETC, GPS, wireless LAN and mobile phones, connectors for high-speed transmission, CPU sockets, millimeter-wave and quasi-millimeter-wave radars such as anti-collision radars, RFID tags, capacitors, inverter components, cable sheathing materials, insulating materials for secondary batteries such as lithium-ion batteries, speaker diaphragms, etc.

[0161] Examples of high-speed communication substrates include base station antenna substrates, antenna distribution substrates, RRH (Remote Radio Head) substrates for the wireless portion of wireless base stations, substrates for the control unit or baseband unit (BBU) of wireless base stations, high-speed communication transceiver substrates, RNC (Radio Network Controller) substrates, high-speed transmitter substrates, high-speed receiver substrates, high-speed signal multiple-loop substrates, WiFi substrates for 60GHz bands, and data transmission substrates used by servers in data centers. Furthermore, examples of high-speed communication substrates include antenna substrates, such as substrates for Massive MIMO antennas required for high-capacity communication standards beyond 5G. Additionally, examples include microwave-based space-transmission wireless power supply antennas.

[0162] The sheet disclosed herein has good adhesion to the unroughened copper foil with low transmission loss, thus improving the gain when an antenna is obtained by processing a copper-clad laminate containing the sheet of this disclosure and the unroughened copper foil, making it particularly suitable for antennas.

[0163] The sheet disclosed herein can be used not only as an insulator for substrates, but also as an insulator for signal line sheathing. For example, it can be used as an insulating sheathing material (e.g., an insulating tube) for waveguides transmitting high-speed signals, QSFP cables for high-speed LANs, coaxial cables (e.g., SFP+ cables, QSFP+ cables, etc.) for high-speed communication applications, and coaxial cables for low-loss applications.

[0164] In the context of using the aforementioned high frequencies, materials used in communication equipment, such as connectors and housings, require stable electrical characteristics such as a low relative permittivity (εr) and a low dielectric loss tangent (tanδ). The sheet disclosed herein can also be used as an insulating material for such applications.

[0165] The sheet disclosed herein can also be used as an insulating material for printed wiring boards of connectors that require soldering. The sheet disclosed herein has excellent heat resistance, therefore it is less prone to problems even at the high temperatures during soldering.

[0166] In dielectric waveguide circuits, materials with low dielectric loss are required for low-loss transmission of high-frequency millimeter or submillimeter waves. The sheet disclosed herein can also be used as an insulating material for dielectric waveguide circuits transmitting millimeter waves, submillimeter waves, etc. Examples of dielectric waveguide circuits include cylindrical dielectric lines, square dielectric lines, elliptical dielectric lines, tubular dielectric lines, image lines, island image lines, trapped image lines, ridge waveguides, strip dielectric lines, reverse striplines, H-shaped waveguides, and non-radioactive dielectric lines (NRD waveguides), etc.

[0167] In this disclosure, "mobile body" refers to all means and methods related to movement and transport, including cars, buses, taxis, trucks, motorcycles, bicycles, two-wheeled vehicles such as bicycles with prime movers, railways, vehicles for the elderly, and compact personal mobility vehicles for one person. Furthermore, it is not necessarily limited to objects moving on the ground, but can also include objects moving in the air or water.

[0168] Example

[0169] The present disclosure will now be described in detail based on the embodiments. Unless otherwise specified in the following embodiments, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0170] (Examples 1-9, Comparative Examples 1-3)

[0171] Sheet manufacturing method (paste extrusion molding)

[0172] Weigh the specified amounts of PTFE powder (average particle size: 500 μm, apparent density: 460 g / L, standard specific gravity: 2.17), silica particles (Admatechs: SC6500-SQ, average particle size: 2.1 μm), and alumina particles (Nippon Light Metals Co., Ltd.: LS-210B (average particle size: 3.2 μm) or LS-110F (average particle size: 1.13 μm)) according to the proportions shown in Table 1, and mix them using a mixer in the presence of dry ice. The mixing temperature is below -10°C.

[0173] Add 21 wt% oil (Isopar H) to the obtained mixed powder, mix, and mature for about 5 hours.

[0174] The cured composition was pre-formed under a pressure of 3 MPa, and the pre-formed body was extruded at 40°C and 50 mm / min to obtain an extruded sample.

[0175] The extruded sample was calendered using two rollers (roller gap: set to 500-80 μm) to obtain a sample with a film thickness of 125 μm. It was dried at 200 °C for 2 hours and then fired at 360 °C for 15 minutes to obtain a sheet.

[0176] (Comparative Example 4)

[0177] Zinc oxide particles (manufactured by Hakusui Tech: DW-4, average particle size: 4 μm) were used instead of alumina particles, and otherwise, the same sheets were obtained as in Examples 1-9 and Comparative Examples 1-3.

[0178] (Example 10)

[0179] Flake manufacturing method (powder calendering)

[0180] Weigh PTFE powder (average particle size: 500 μm, apparent density: 460 g / L, standard specific gravity: 2.17), silica particles (Admatechs: SC6500-SQ, average particle size: 2.1 μm), and alumina particles (Nippon Light Metals Co., Ltd.: LS-210B (average particle size: 3.2 μm) or LS-110F (average particle size: 1.13 μm)) according to the mass ratios shown in Table 1, and stir twice for 30 seconds at mark 6 using Wonder Crusher at room temperature.

[0181] The mixture was calendered using two rollers (roller gap: set to 100 μm, roller temperature: 100 °C) to obtain a sample with a film thickness of 130 μm. The sample was then fired at 360 °C for 15 minutes to obtain a sheet.

[0182] The samples obtained were evaluated based on the following criteria.

[0183] [Relative permittivity (Dk) of the plate]

[0184] Using a split cylindrical dielectric constant / dielectric loss tangent measuring device (manufactured by EM Labs), the Dk was measured at 10 GHz every 10 °C from -50 °C to 150 °C.

[0185] The rate of change from -50℃ to 150℃ is calculated from the difference between the maximum and minimum values ​​of the measured Dk values.

[0186] [Dielectric loss tangent (Df) of the chip]

[0187] The dielectric constant / dielectric loss tangent was measured at 20°C and 10 GHz using a split cylindrical dielectric constant / dielectric loss tangent measuring device (manufactured by EM Labs).

[0188] [Coefficient of linear expansion (CTE)]

[0189] TMA measurements were performed in tensile mode using a TMA-7100 (manufactured by Hitachi High Technology Co., Ltd.). As a sample, a piece with a length of 20 mm, a width of 5 mm, and a thickness of 150 μm was used. The clamp spacing was set to 10 mm. While applying a load of 49 mN, the coefficient of linear expansion was determined from the displacement of the sample at a heating rate of 2 °C / min from 0 to 150 °C.

[0190] The results are shown in Table 1.

[0191] [Table 1]

[0192] The sheet obtained from Example 1 was subjected to [sheet surface treatment], [XPS measurement of sheet surface], and [peel strength measurement] under the following conditions. The results showed the following elemental composition (atomic%) in the XPS measurement: C1s: 43.4, N1s: 2.8, O1s: 7.1, F1s: 43.3, Si2p: 1.2. Furthermore, the peel strength showed a value as high as 11 N / cm, confirming high adhesion.

[0193] [Surface Treatment of Sheets]

[0194] A plate is placed between the upper and lower electrodes in a processing chamber (direct plasma surface treatment device, manufactured by Air Water Corporation) equipped with upper and lower electrodes. After the processing chamber is filled with a mixed gas atmosphere of argon, helium, nitrogen and oxygen, the surface of the plate is subjected to discharge plasma treatment for 36 seconds.

[0195] For the surface-treated slides, the elemental composition was determined using XPS.

[0196] [XPS Measurement of Film Surface]

[0197] The measurements were performed using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) PHI5000 VersaProbe II (manufactured by ULVAC-PHI Corporation).

[0198] [Peel strength test]

[0199] The copper foil (Fukuda metal foil powder CF-T9DA-SV-18, Rz=0.85μm, Rq=0.05μm) was overlapped on the top and bottom of the surface-treated sheet in a way that the treated surface was tightly bonded to the sheet. The sample was then prepared by applying pressure and heating using vacuum hot pressing (360℃·2.5MPa·300s).

[0200] The obtained sample was cut into strips 10 mm wide. Using a Tensilon universal testing machine (manufactured by Shimadzu Corporation), the unbonded part of the strip sample was held in the upper and lower chucks of the Tensilon while being stretched at a speed of 50 mm per minute. The peel strength was measured and the obtained value was taken as the peel strength.

[0201] Based on the above results, the sheet disclosed herein maintains a low dielectric loss tangent and a low CTE, and the rate of change of the relative permittivity over a temperature range of -50 to 150°C is as low as 0.020 or less. In addition, it has excellent adhesion to copper foil. Therefore, it has excellent performance in high-frequency printed wiring boards, especially as a substrate used in antennas for millimeter-wave radars facing mobile bodies.

[0202] Industrial applicability

[0203] The wafer disclosed herein is particularly suitable for use on high-frequency printed circuit boards.

Claims

1. A sheet, characterized in that, The relative permittivity varies by less than 0.020 within a temperature range of -50℃ to 150℃, and contains two or more fillers.

2. The sheet according to claim 1, wherein, The linear expansion coefficient, or CTE, of the sheet is below 70 ppm / ℃.

3. The sheet according to claim 1 or 2, wherein, The dielectric loss tangent at 10 GHz is below 0.0015.

4. The sheet according to any one of claims 1 to 3, wherein the thickness is 5 μm to 250 μm.

5. The sheet according to any one of claims 1 to 4, wherein, The sheet contains fluoropolymer.

6. The sheet according to claim 5, wherein, The fluororesin is polytetrafluoroethylene.

7. The sheet according to any one of claims 1 to 6, wherein, The band gap of the filler is above 2 eV.

8. The sheet according to any one of claims 1 to 7, wherein, The filler content relative to the total amount of the sheet is 30% by mass or more.

9. The sheet according to any one of claims 1 to 8, wherein, The filler comprises at least two selected from the group consisting of silica, alumina, boron nitride and zirconium oxide.

10. The sheet according to any one of claims 1 to 9, wherein, The fillers are silicon dioxide and aluminum oxide.

11. The sheet according to claim 9 or 10, wherein, The silicon dioxide is in the form of spherical particles.

12. The sheet according to any one of claims 9 to 11, wherein, The silica is silica particles treated with a silane coupling agent.

13. The sheet according to claim 12, wherein, Silane coupling agents contain aminopropyl groups.

14. The sheet according to any one of claims 9 to 13, wherein, The average particle size of the silica particles is less than 10 μm.

15. The sheet according to any one of claims 9 to 14, wherein, The average particle size of the alumina is less than 10 μm.

16. The sheet according to any one of claims 9 to 15, wherein, The amount of alumina mixed in is 10% to 50% by mass relative to the total amount of alumina and silicon dioxide.

17. A method for manufacturing a sheet, which is the method for manufacturing a sheet according to any one of claims 5 to 16, characterized in that, Fluoropolymer and filler are mixed and then film is formed.

18. A method for manufacturing a sheet, which is the method for manufacturing a sheet according to any one of claims 5 to 17, characterized in that, Film formation is performed using a composition substantially consisting of fluoropolymer particles and filler particles comprising at least silica particles and alumina particles.

19. A metal-clad laminate, characterized in that, The sheet as described in any one of claims 1 to 16 is a necessary layer, having a metal foil layer on one or both sides.

20. The metal-clad laminate according to claim 19, wherein, The metal foil is copper.

21. A circuit board, characterized in that, The metal-clad laminate as described in claim 19 or 20.

22. An antenna, characterized in that, It is formed from the circuit substrate as described in claim 21.

23. The antenna according to claim 22 is a millimeter-wave antenna oriented towards a moving body.

24. The wafer according to any one of claims 1 to 16, used as a circuit board.

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