Dielectric medium and manufacturing method thereof

Abstract

The purpose of the present invention is to obtain: a dielectric in which the frequency dependence of the relative dielectric constant in a terahertz high-frequency band (110 GHz to 330 GHz) of the relative dielectric constant is reduced; and a method for producing the dielectric. A dielectric medium having a slope of a relative dielectric constant (Dk) measured in a J band of a Fabry-Perot resonator with respect to a frequency from 220 GHz to 330 GHz of 0.00001 to 0.0005 (inclusive).

Description

Technical Field

[0001] The present disclosure relates to a dielectric and a method for manufacturing the same. Background Art

[0002] In a high-frequency printed wiring board, a high-frequency printed wiring board with low transmission loss is required. In such a high-frequency printed wiring board, it is known to use a fluororesin film (Patent Document 1, etc.). In addition, Patent Documents 2 and 3 describe using a fluororesin mixed with a filler as a wiring substrate material.

[0003] Furthermore, Patent Document 4 discloses using a fluororesin composition in which spherical silica particles are mixed in a fluororesin for a circuit substrate.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-8260

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 63-259907

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2022-510017

[0009] Patent Document 4: International Publication No. 2020 / 145133 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] An object of the present disclosure is to obtain a dielectric and a method for manufacturing the same that reduce the frequency dependence of the relative dielectric constant in the terahertz high-frequency band (110 GHz to 330 GHz).

[0012] Furthermore, an object is to provide a dielectric and a method for manufacturing the same with small anisotropy of the relative dielectric constant.

[0013] Furthermore, an object is to provide a dielectric and a method for manufacturing the same with a small dielectric loss tangent in the high-frequency band.

[0014] Means for Solving the Problems

[0015] The present disclosure relates to a dielectric characterized in that the slope of the relative dielectric constant (Dk) measured in the J band of a Fabry-Perot resonator with respect to the frequency from 220 GHz to 330 GHz is 0.00001 or more and 0.0005 or less.

[0016] The present disclosure also relates to a dielectric, characterized in that the 90° anisotropy in the planar direction of the relative dielectric constant (Dk) at 170 GHz measured in the J band of a Fabry - Perot resonator is 0.02 or less.

[0017] The present disclosure also relates to a dielectric, characterized in that the dielectric loss tangent (Df) at 220 GHz measured in the J band of a Fabry - Perot resonator is 0.00153 or less.

[0018] The present disclosure also relates to a dielectric, characterized in that the dielectric loss tangent (Df) at 330 GHz measured in the J band of a Fabry - Perot resonator is 0.00165 or less.

[0019] The above dielectric preferably contains a resin and spherical fillers.

[0020] The above fillers are preferably at least one selected from the group consisting of silica, titanium oxide, alumina, and forsterite.

[0021] The above fillers are preferably only spherical silica.

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

[0023] The above resin is preferably a fluororesin.

[0024] The above fluororesin preferably contains at least one polymer selected from the group consisting of polytetrafluoroethylene resin, tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene - hexafluoropropylene copolymer as part or all.

[0025] The above dielectric is preferably obtained using fluororesin particles with a primary particle size of 0.05 μm to 10 μm as raw materials.

[0026] The volume - based cumulative 50% diameter of the above fluororesin particles is preferably 0.05 μm to 40 μm.

[0027] The above dielectric is preferably used for a printed circuit board for the terahertz band, a dielectric material for the terahertz band, or a laminated circuit board for the terahertz band.

[0028] The above dielectric preferably has a sheet shape.

[0029] The present disclosure also relates to a method for manufacturing the above dielectric, characterized in that it has a step of mixing fluororesin particles and fillers to form a film.

[0030] The method for manufacturing the above dielectric preferably only mixes fluororesin particles and fillers without adding other components to form a film.

[0031] The present disclosure also relates to a copper-clad laminate that includes a copper foil and the above-described dielectric as essential layers.

[0032] The present disclosure also relates to a circuit board, characterized by including the above copper-clad laminate.

[0033] Effects of the Invention

[0034] The dielectric of the present disclosure can reduce the frequency dependence of the relative dielectric constant in the terahertz high-frequency band.

[0035] Furthermore, it is possible to reduce the anisotropy of the relative dielectric constant.

[0036] Furthermore, it is possible to reduce the dielectric loss tangent in the high-frequency band. Detailed Embodiments

[0037] The present disclosure will be described in detail below.

[0038] In recent years, due to the high-frequency trend of electronic products, performance corresponding to high frequencies is also required in wiring boards.

[0039] First, in the high-frequency band, it is not preferable to have a difference in relative dielectric constant based on frequency. Such a dielectric requires changing the wiring width of the copper wiring for each frequency when forming a copper-clad laminate, making the wiring complicated. Additionally, when the wiring width cannot be changed, it can only be used at a specific frequency.

[0040] Therefore, in order to avoid such a situation, it is necessary to obtain a dielectric with a small frequency dependence of the relative dielectric constant.

[0041] Second, it is desirable to obtain a dielectric with a small anisotropy of the relative dielectric constant in the high-frequency band.

[0042] If there is anisotropy in the relative dielectric constant, when forming a copper-clad laminate, when the copper wiring is designed to be other than straight, it is necessary to change the wiring width according to its direction, which is not preferable in this regard.

[0043] Furthermore, it is preferable that the dielectric loss tangent (Df) is low for each frequency such as 220 GHz to 330 GHz. Dielectrics formed of fluororesins are used to obtain a low-loss material with a small transmission loss of high-frequency signals by using a dielectric with a low dielectric loss tangent. Therefore, a dielectric with a small value of the dielectric loss tangent is preferable. In the present disclosure, the aim is to obtain a dielectric having these properties.

[0044] (Frequency Dependence of Relative Dielectric Constant)

[0045] The slope of the relative dielectric constant (Dk) of the first dielectric of the present disclosure measured in the J band of the Fabry - Perot resonator with respect to the frequency from 220 GHz to 330 GHz is 0.00001 or more and 0.0005 or less.

[0046] That is, it means that the frequency dependence of the relative dielectric constant in the high - frequency band is small.

[0047] In the present disclosure, the relative dielectric constant and the dielectric loss tangent are obtained by measuring the relative dielectric constant (Dk) and the dielectric loss tangent (Df) at each frequency using a network analyzer (N5290a, manufactured by Keysight Technologies) and a Fabry - Perot resonator (manufactured by EM labs) under the conditions of room temperature of 25 °C and humidity of 50%.

[0048] Furthermore, the slope of the relative dielectric constant is calculated by plotting the values of the relative dielectric constant from 220 GHz to 330 GHz.

[0049] If the above - mentioned slope is 0.00001 or more and 0.0005 or less, it is not necessary to change the wiring width of the copper wiring for each frequency when manufacturing the copper - clad laminate. In addition, it can be used in a wide range of frequencies. The above upper limit is more preferably 0.0004, and further preferably 0.0002.

[0050] (Anisotropy of relative dielectric constant)

[0051] The 90° anisotropy in the plane direction of the relative dielectric constant (Dk) of the second dielectric of the present disclosure at 170 GHz is 0.02 or less.

[0052] That is, it means that the anisotropy of the relative dielectric constant in the high - frequency band is small.

[0053] Furthermore, the 90° anisotropy in the plane direction of the relative dielectric constant is obtained by measuring the relative dielectric constant (Dk) at 170 GHz in the plane directions of 0° and 90° using a network analyzer (N5290a, manufactured by Keysight Technologies) and a Fabry - Perot resonator (manufactured by EM labs) under the conditions of room temperature of 25 °C and humidity of 50%, and calculating the difference.

[0054] If the above - mentioned anisotropy is 0.02 or less, it is preferable in that when the copper wiring is designed to be other than a straight line, it is not necessary to change the wiring width according to its direction. The above upper limit is more preferably 0.018, and further preferably 0.016.

[0055] (Dielectric loss tangent (Df) at 220 GHz)

[0056] The dielectric loss tangent of the third dielectric of the present disclosure is 0.00153 or less at 220 GHz. That is, by having such a dielectric loss tangent, there is an effect of low loss with small transmission loss of high-frequency signals. The above upper limit is more preferably 0.00152, and further preferably 0.00151. The above lower limit is not particularly limited, and more preferably 0.

[0057] It should be noted that in this specification, the dielectric loss tangent is measured using a network analyzer (N5290A, manufactured by Keysight Technologies) and a Fabry - Perot resonator (manufactured by EM labs) under the conditions of room temperature of 25 °C and humidity of 50%.

[0058] (Dielectric loss tangent (Df) at 330 GHz)

[0059] The dielectric loss tangent of the fourth dielectric of the present disclosure is 0.00165 or less. That is, by having such a dielectric loss tangent, there is an effect of low loss with small transmission loss of high-frequency signals. The above upper limit is more preferably 0.00164, and further preferably 0.00163. The above lower limit is not particularly limited, and more preferably 0.

[0060] The dielectric of the present disclosure can have any one of the above first to fourth properties, can also have two or more properties, and can also have all the properties.

[0061] (Dielectric)

[0062] The dielectric of the present disclosure is not particularly limited as long as it satisfies any of the above parameters, and is preferably a composition containing spherical fillers and fluororesin. In such a composition, by adjusting the composition as needed, a dielectric that satisfies the above parameters can be made. Hereinafter, the spherical fillers and fluororesin that can be used in such a dielectric will be described in detail.

[0063] (Fluororesin)

[0064] The fluororesin sheet of the present disclosure contains fluororesin. Since the fluororesin has low dielectric properties, it can be suitably used for the purpose of the present disclosure.

[0065] The fluororesin that can be used in the present disclosure is not particularly limited, and examples thereof include polytetrafluoroethylene [PTFE], tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] copolymer [FEP], TFE / alkyl vinyl ether copolymer [PFA], TFE / HFP / alkyl vinyl ether copolymer [EPA], TFE / trifluorochloroethylene [CTFE] copolymer, TFE / ethylene copolymer [ETFE], polyvinylidene fluoride [PVdF], tetrafluoroethylene with a molecular weight of 300,000 or less [LMW - PTFE], etc. One kind can be used, or two or more kinds can be mixed.

[0066] From the aspect of low dielectric properties, the above fluororesin is preferably polytetrafluoroethylene resin (PTFE), tetrafluoroethylene [TFE] / hexafluoropropylene [HFP] copolymer [FEP], or TFE / alkyl vinyl ether copolymer [PFA], and particularly preferably polytetrafluoroethylene resin (PTFE). PTFE preferably has fibrillarity. PTFE with fibrillarity refers to PTFE capable of paste extrusion of unfired polymer powder.

[0067] (Polytetrafluoroethylene)

[0068] PTFE can be modified polytetrafluoroethylene (hereinafter referred to as modified PTFE), or homopolymer polytetrafluoroethylene (hereinafter referred to as homopolymer PTFE), or a mixture of modified PTFE and homopolymer PTFE. It should be noted that, from the aspect of well maintaining the moldability of polytetrafluoroethylene, the content ratio of modified PTFE in high molecular PTFE is preferably 10% by weight or more and 98% by weight or less, more preferably 50% by weight or more and 95% by weight or less. There is no particular limitation on homopolymer PTFE, and homopolymer PTFE disclosed in, for example, Japanese Patent Application Laid-Open No. 53-60979, Japanese Patent Application Laid-Open No. 57-135, Japanese Patent Application Laid-Open No. 61-16907, Japanese Patent Application Laid-Open No. 62-104816, Japanese Patent Application Laid-Open No. 62-190206, Japanese Patent Application Laid-Open No. 63-137906, Japanese Patent Application Laid-Open No. 2000-143727, Japanese Patent Application Laid-Open No. 2002-201217, International Publication Pamphlet No. 2007 / 046345, International Publication Pamphlet No. 2007 / 119829, International Publication Pamphlet No. 2009 / 001894, International Publication Pamphlet No. 2010 / 113950, International Publication Pamphlet No. 2013 / 027850, etc. can be preferably used. Among them, homopolymer PTFE disclosed in Japanese Patent Application Laid-Open No. 57-135, Japanese Patent Application Laid-Open No. 63-137906, Japanese Patent Application Laid-Open No. 2000-143727, Japanese Patent Application Laid-Open No. 2002-201217, International Publication Pamphlet No. 2007 / 046345, International Publication Pamphlet No. 2007 / 119829, International Publication Pamphlet No. 2010 / 113950, etc., which has high tensile properties, is preferred.

[0069] Modified PTFE is composed of TFE and monomers other than TFE (hereinafter referred to as modified monomers). Examples of modified PTFE include PTFE uniformly modified with modified monomers, PTFE modified in the initial stage of the polymerization reaction, and PTFE modified in the final stage of the polymerization reaction, and there is no particular limitation. Modified PTFE is preferably a TFE copolymer obtained by polymerizing a small 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 can be preferably used, for example, as disclosed in Japanese Patent Laid-Open No. 60-42446, Japanese Patent Laid-Open No. 61-16907, Japanese Patent Laid-Open No. 62-104816, Japanese Patent Laid-Open No. 62-190206, Japanese Patent Laid-Open No. 64-1711, Japanese Patent Laid-Open No. 2-261810, Japanese Patent Laid-Open No. 11-240917, Japanese Patent Laid-Open No. 11-240918, Pamphlet of International Publication No. 2003 / 033555, Pamphlet of International Publication No. 2005 / 061567, Pamphlet of International Publication No. 2007 / 005361, Pamphlet of International Publication No. 2011 / 055824, Pamphlet of International Publication No. 2013 / 027850, etc. Among them, modified PTFE disclosed in Japanese Patent Laid-Open No. 61-16907, Japanese Patent Laid-Open No. 62-104816, Japanese Patent Laid-Open No. 64-1711, Japanese Patent Laid-Open No. 11-240917, Pamphlet of International Publication No. 2003 / 033555, Pamphlet of International Publication No. 2005 / 061567, Pamphlet of International Publication No. 2007 / 005361, Pamphlet of International Publication No. 2011 / 055824, etc., which has high tensile properties, is preferred.

[0070] Modified PTFE contains TFE units based on TFE and modified monomer units based on modified monomers. The modified monomer units are part of the molecular structure of modified PTFE and are parts derived from modified monomers. Modified PTFE preferably contains 0.001% by weight to 0.500% by weight of modified monomer units based on all monomer units, and preferably contains 0.01% by weight to 0.30% by weight. All monomer units are parts derived from all monomers in the molecular structure of modified PTFE.

[0071] The modified monomer is not particularly limited as long as it can copolymerize with TFE, and examples thereof include perfluoroolefins such as hexafluoropropylene (HFP); fluorochloroolefins such as chlorotrifluoroethylene (CTFE); hydrogen-containing fluorinated olefins such as trifluoroethylene and vinylidene fluoride (VDF); perfluoro vinyl ethers; perfluoroalkyl ethylene (PFAE), ethylene, etc. The modified monomer used can be one kind or a plurality of kinds.

[0072] There is no particular limitation on the perfluoro vinyl ether. For example, perfluoro unsaturated compounds represented by the following general formula (1) can be cited, etc.

[0073] CF 2 =CF-ORf···(1)

[0074] In the formula, Rf represents a perfluoro organic group.

[0075] In this specification, the perfluoro organic group is an organic group in which all hydrogen atoms bonded to carbon atoms are replaced by fluorine atoms. The above perfluoro organic group may have an ether oxygen.

[0076] As the perfluoro vinyl ether, for example, perfluoro(alkyl vinyl ether) (PAVE) in which Rf in the above general formula (1) is a perfluoroalkyl group having 1 to 10 carbon atoms can be cited. The number of carbon atoms of the perfluoroalkyl group is preferably 1 to 5. As the perfluoroalkyl group in PAVE, for example, perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl, etc. can be cited. As PAVE, perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE) are preferred.

[0077] There is no particular limitation on the above perfluoroalkyl ethylene (PFAE), and for example, perfluorobutyl ethylene (PFBE), perfluorohexyl ethylene (PFHE), etc. can be cited.

[0078] As the modifying monomer in the modified PTFE, at least 1 kind selected from the group consisting of HFP, CTFE, VDF, PAVE, PFAE, and ethylene is preferred.

[0079] The above fluororesin is preferably not melt-moldable. Not being melt-moldable means that even when heated above the melting point, the resin does not have sufficient fluidity and cannot be molded by the melt molding methods commonly used in resins.

[0080] In the present disclosure, it is preferable to use such a non-melt-moldable fluororesin, and a fluororesin sheet is made by a fibrillation molding method thereof. This molding method will be described later.

[0081] The above PTFE preferably has an SSG of 2.0 to 2.3. If such PTFE is used, it is easy to obtain a PTFE film having high strength (cohesion and puncture strength per unit thickness). PTFE having a large molecular weight has long molecular chains, so it is difficult to form a structure in which the molecular chains are regularly arranged. In this case, the length of the amorphous part increases, and the degree of entanglement of molecules increases. It is considered that when the degree of entanglement of molecules is high, the PTFE film is not easily deformed by the applied load and exhibits excellent mechanical strength. In addition, if PTFE having a large molecular weight is used, it is easy to obtain a PTFE film having a small average pore size.

[0082] The lower limit of the above SSG is more preferably 2.05, and further preferably 2.1. The upper limit of the above SSG is more preferably 2.25, and further preferably 2.2.

[0083] The standard specific gravity [SSG] is obtained by preparing a specimen in accordance with ASTM D - 4895 - 89 and measuring the specific gravity of the obtained specimen by the water displacement method.

[0084] In this embodiment, the molecular weight (number - average molecular weight) of PTFE constituting the PTFE powder is, for example, in the range of 2 million to 12 million. The lower limit value of the molecular weight of PTFE can be 3 million or 4 million. The upper limit value of the molecular weight of PTFE can be 10 million.

[0085] As a method for measuring the number - average molecular weight of PTFE, there are a method obtained from the standard specific gravity (Standard Specific Gravity) and a measurement method using the dynamic visco - elasticity during melting. The method obtained from the standard specific gravity can be implemented by using a sample molded in accordance with ASTM D - 4895 98 and the water displacement method in accordance with ASTM D - 792. The measurement method using dynamic visco - elasticity is described, for example, by S. Wu in Polymer Engineering & Science, 1988, Vol. 28, 538 and in this literature 1989, Vol. 29, 273.

[0086] In addition, the maximum endothermic peak temperature (crystal melting point) of the above PTFE is preferably 340 ± 7 °C.

[0087] PTFE can be low - melting - point PTFE with the maximum peak temperature of the endothermic curve on the crystal melting curve measured by a differential scanning calorimeter being 338 °C or lower, and high - melting - point PTFE with the maximum peak temperature of the endothermic curve on the crystal melting curve measured by a differential scanning calorimeter being 342 °C or higher.

[0088] The low - melting - point PTFE is a powder produced by polymerization by the emulsion polymerization method, having the above - mentioned maximum endothermic peak temperature (crystal melting point), with the dielectric constant (ε) being 2.08 - 2.2 and the dielectric loss tangent (tanδ) being 1.9×10 -4 ~4.0×10 -4 . As commercially available products, for example, POLYFLON FINE POWDER F201, F203, F205, F301, F302 manufactured by Daikin Industries, Ltd.; CD090, CD076 manufactured by Asahi Glass Co., Ltd.; TF6C, TF62, TF40 manufactured by DuPont Co., etc.

[0089] The high melting point PTFE powder is also a powder manufactured by emulsion polymerization, having the above-mentioned maximum endothermic peak temperature (crystal melting point), with a dielectric constant (ε) of 2.0 to 2.1 and a dielectric loss tangent (tanδ) of 1.6×10 -4 ~2.2×10 -4 , being overall low. As commercially available products, for example, POLYFLON FINE POWDER F104, F106 manufactured by Daikin Industries, Ltd.; CD1, CD141, CD123 manufactured by Asahi Glass Co., Ltd.; TF6, TF65 manufactured by DuPont Co., etc. can be cited.

[0090] It should be noted that the average particle diameter of the powder formed by secondary aggregation of two PTFE polymer particles is usually preferably 250 μm to 2000 μm. In particular, from the aspect of improving the fluidity during mold filling at the time of preforming, granulated powder obtained by granulating using a solvent is preferably used.

[0091] PTFE in the powder shape satisfying 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 pamphlet, International Publication No. 2012 / 086710 pamphlet, etc.

[0092] (Fluororesin capable of melt molding)

[0093] As described above, the dielectric of the present disclosure is most preferably polytetrafluoroethylene resin. On the other hand, a fluororesin capable of melt molding can also be used to obtain a molded body having the above parameters. From such a viewpoint, the fluororesin capable of melt molding will also be described in detail below.

[0094] The fluororesin is more preferably a fluororesin capable of melt molding, and examples thereof include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), copolymer having chlorotrifluoroethylene (CTFE) unit (CTFE copolymer), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV), tetrafluoroethylene-vinylidene fluoride copolymer, etc.

[0095] Among these fluororesins capable of melt molding, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are preferred.

[0096] The glass transition temperature of the resin constituting the fluororesin film is preferably 40 °C or higher. If it is 40 °C or higher, for example, when storing the rolled film at room temperature, deformation at ambient temperature is less likely to occur, which is preferable from this aspect. More preferably, it is 60 °C or higher, and further preferably 80 °C or higher. The above upper limit is not particularly limited, and from the aspect of adhesiveness, it is preferably 200 °C or lower, more preferably 160 °C, and further preferably 120 °C or lower.

[0097] The melting point of the above PFA is preferably 180 °C to 340 °C, more preferably 230 °C to 330 °C, and further preferably 280 °C to 320 °C. The above melting point is the temperature corresponding to the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10 °C / minute using a differential scanning calorimeter [DSC].

[0098] As the above PFA, there is no particular limitation, and a copolymer having a molar ratio of TFE unit to PAVE unit (TFE unit / PAVE unit) of 70 / 30 or more and less than 99.5 / 0.5 is preferred. A more preferred molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, and a further preferred molar ratio is 80 / 20 or more and 98.5 / 1.5 or less. If the TFE unit is too small, the mechanical properties tend to decrease; if too much, the melting point is too high and the moldability tends to decrease. The above PFA may be a copolymer composed only of TFE and PAVE, and a copolymer in which the monomer units derived from monomers capable of copolymerizing with TFE and PAVE are 0.1 mol% to 10 mol% and the total of the TFE unit and the PAVE unit is 90 mol% to 99.9 mol% is also preferred. As monomers capable of copolymerizing with TFE and PAVE, HFP, CZ 3 Z 4 = CZ 5 (CF 2 )nZ 6 (wherein Z 3 , Z 4 and Z 5 are the same or different and represent a hydrogen atom or a fluorine atom, Z 6 represents a hydrogen atom, a fluorine atom or a chlorine atom, and n represents an integer of 2 to 10) vinyl monomers shown, and CF 2 = CF - OCH 2 -Rf 7 (wherein Rf 7 represents a perfluoroalkyl group having 1 to 5 carbon atoms) alkyl perfluoro vinyl ether derivatives shown, etc. As other copolymerizable monomers, for example, cyclic hydrocarbon monomers having an acid anhydride group, etc. As acid anhydride monomers, it is possible to cite itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, maleic anhydride, etc. Acid anhydride monomers may be used alone or in combination of two or more.

[0099] The melt flow rate (MFR) of the above-mentioned PFA is preferably from 0.1 g / 10 min to 100 g / 10 min, more preferably from 0.5 g / 10 min to 90 g / 10 min, and still more preferably from 1.0 g / 10 min to 85 g / 10 min. It should be noted that in this specification, MFR is the value measured according to ASTM D3307 under the conditions of a temperature of 372 °C and a load of 5.0 kg.

[0100] The above-mentioned FEP is not particularly limited. A copolymer having a molar ratio of TFE units to HFP units (TFE units / HFP units) of 70 / 30 or more and less than 99 / 1 is preferred. A more preferred molar ratio is 70 / 30 or more and 98.9 / 1.1 or less, and an even more preferred molar ratio is 80 / 20 or more and 97 / 3 or less. If the amount of TFE units is too small, the mechanical properties tend to decrease; if too large, the melting point is too high and the moldability tends to decrease. The FEP is also preferably a copolymer in which monomer units derived from monomers capable of copolymerizing with TFE and HFP are 0.1 mol% to 10 mol%, and the total of TFE units and HFP units is 90 mol% to 99.9 mol%. Examples of monomers capable of copolymerizing with TFE and HFP include alkyl perfluoro vinyl ether derivatives. Examples of other copolymerizable monomers include cyclic hydrocarbon monomers having an acid anhydride group. Examples of acid anhydride monomers include itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, maleic anhydride, etc. The acid anhydride monomers can be used alone or in combination of two or more.

[0101] The melting point of the above-mentioned FEP is preferably from 150 °C to 320 °C, more preferably from 200 °C to 300 °C, and still more preferably from 240 °C to 280 °C. The above melting point is the temperature corresponding to the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10 °C / min using a differential scanning calorimeter [DSC].

[0102] The MFR of the above-mentioned FEP is preferably from 0.01 g / 10 min to 100 g / 10 min, more preferably from 0.1 g / 10 min to 80 g / 10 min, still more preferably from 1 g / 10 min to 60 g / 10 min, and particularly preferably from 1 g / 10 min to 50 g / 10 min.

[0103] The fewer the functional groups of the above fluororesin, the better, especially the fewer the number of unstable end groups. Such fluororesins have methods of being produced by adjusting the conditions during production (polymerization reaction), methods of reducing the number of unstable end groups by subjecting the polymerized fluororesin to fluorine gas treatment, heat treatment, supercritical gas extraction treatment, etc. From the aspect of excellent treatment efficiency, part or all of the unstable end groups are converted to -CF 3In terms of becoming a stable terminal group, fluorine gas treatment is preferred. If a fluororesin with a reduced number of unstable terminal groups is used, it is preferred in terms of reducing the electrostatic tangent and the loss of electrical signals.

[0104] The number of the above-mentioned unstable terminal groups is not particularly limited, and relative to 10 main chain carbon atoms of the fluororesin 6 pieces, it is preferably 450 or less, more preferably 250 or less, further preferably 100 or less, and most preferably 50 or less. Considering the effect of reducing the dielectric loss tangent, it is preferably less than 10, and further preferably 5 or less.

[0105] As the unstable terminal group, specifically, -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), hydroxyl group (-CH 2 OH, etc.), -CONH 2 , -COOR (R = CH 3 etc.), -CF 2 H, -OCOO-R (such as n-propyl carbonate), etc. functional groups can be cited.

[0106] The number of unstable terminal groups is specifically measured by the following method. First, the above-mentioned fluororesin is melted and compression molded to produce a film with a thickness of 0.25 mm to 0.3 mm. The film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the above-mentioned fluororesin, and a differential spectrum from the background spectrum of completely fluorinated and non-functional groups is obtained. According to the following formula (A), the number of unstable terminal groups per 1×10 6 carbon atoms in the above-mentioned fluororesin is calculated from the absorption peak of specific functional groups shown in the differential spectrum.

[0107] N = I×K / t(A)

[0108] I: Absorbance

[0109] K: Correction coefficient

[0110] t: Thickness of the film (mm)

[0111] For reference, regarding the unstable terminal groups in this specification, the absorption frequency, molar extinction coefficient, and correction coefficient are shown in Table 1. In addition, the molar extinction coefficient is determined from the FT-IR measurement data of low molecular weight model compounds.

[0112] [Table 1]

[0113]

[0114] The above-mentioned fluorination treatment can be carried out by bringing an unfluorinated fluororesin into contact with a fluorine-containing compound.

[0115] The fluorine-containing compound mentioned above is not particularly limited, and a fluorine radical source that generates fluorine radicals under fluorination treatment conditions can be cited. As the above-mentioned fluorine radical source, F 2 gas, CoF 3 , AgF 2 , UF 6 , OF 2 , N 2 F 2 , CF 3 OF, halogen fluoride (such as IF 5 , ClF 3 ), etc.

[0116] The above-mentioned fluorine radical sources such as F 2 gas can be at a concentration of 100%, but from the aspect of safety, it is preferably mixed with an inert gas and diluted to 5% by mass to 50% by mass for use, and more preferably diluted to 15% by mass to 30% by mass for use. As the above-mentioned inert gas, nitrogen, helium, argon, etc. can be cited, and from the aspect of economy, nitrogen is preferred.

[0117] The conditions of the above-mentioned fluorination treatment are not particularly limited, and the molten fluororesin can be brought into contact with the fluorine-containing compound, but usually it can be carried out at a temperature below the melting point of the fluororesin, preferably 20°C to 220°C, more preferably 100°C to 200°C. The above-mentioned fluorination treatment is usually carried out for 1 hour to 30 hours, preferably 5 hours to 25 hours. The above-mentioned fluorination treatment is preferably a treatment in which the unfluorinated fluororesin is brought into contact with fluorine gas (F 2 gas).

[0118] In this specification, the content of each monomer unit constituting the fluororesin can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and fluorescent X-ray analysis according to the type of monomer.

[0119] (Spherical filler)

[0120] The dielectric of the present disclosure preferably contains a filler. Mixing a filler is particularly preferred in terms of being able to reduce the linear expansion coefficient.

[0121] The fillers that can be used in the present disclosure are not particularly limited, and examples thereof include one or more organic fillers selected from aromatic polyamide fibers, polyphenyl esters, polyphenylene sulfides, polyimides, polyether ether ketones, polyphenylenes, polyamides, and wholly aromatic polyester resins; 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, glass fibers, glass flakes, glass beads, silicon carbide, calcium fluoride, boron nitride, barium sulfate, molybdenum disulfide, forsterite, and potassium carbonate whiskers; and the like. Two or more of them can also be used in combination.

[0122] Among them, from the aspect of low loss, at least one selected from the group consisting of silicon oxide, titanium oxide, alumina, and forsterite is particularly preferred. Further, silicon oxide is most preferred.

[0123] The above spherical filler is particularly preferably composed only of spherical silicon oxide. As described above, the purpose of blending fillers is to reduce the linear expansion coefficient. However, if fillers with high anisotropy are blended, it is difficult to satisfy the above properties of the dielectric. The above spherical silicon oxide is preferred in terms of small anisotropy and frequency dependence of the relative dielectric constant.

[0124] The above spherical silicon oxide particles refer to particles whose particle shape is close to a perfect sphere. Specifically, the sphericity is preferably 0.80 or more, more preferably 0.85 or more, further preferably 0.90 or more, and most preferably 0.95 or more. Regarding the sphericity, a photograph is taken using SEM, and based on the area and perimeter of the observed particles, it is calculated as the value calculated by (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 Co., Ltd.: FPIA-3000) is adopted.

[0125] For the spherical silicon oxide particles used in the present disclosure, when integrating the volume from the smaller particle size side, D90 / D10 is preferably 2 or more (preferably 2.3 or more, 2.5 or more), and D50 is 10 μm or less. Further, 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). Since spherical silicon oxide particles with a small particle size may enter the gaps between spherical silicon oxide particles with a large particle size, the filling property is excellent and the fluidity can be improved. In particular, as the particle size distribution, it is preferably that the frequency on the side with a smaller particle size is larger compared to the Gaussian curve. The particle size can be measured using a laser diffraction scattering type particle size distribution measuring device. In addition, it is preferable to remove coarse particles with a specified particle size or more using a filter or the like.

[0126] The water absorption of the above spherical silica particles is preferably 1.0% or less, more preferably 0.5% or less. The water absorption is based on the mass of the silica particles when dry. In the measurement of water absorption, a sample in a dry state is placed at 40°C and 80% RH for 1 hour, and the water generated by heating at 200°C is measured using a Karl Fischer moisture meter, and thus calculated.

[0127] In addition, for the above spherical silica particles, the dielectric can also be heated in an air atmosphere at 600°C for 30 minutes to burn off the fluororesin, and after taking out the spherical silica particles, the above parameters can be measured by the above method.

[0128] The silica particles used in the present disclosure can be surface-treated. By performing surface treatment in advance, aggregation of the silica particles can be suppressed, and the silica particles can be well dispersed in the resin composition. In addition, it is also preferable in terms of being able to reduce the dielectric loss tangent.

[0129] The above surface treatment is not particularly limited, and any known surface treatment can be used. Specifically, for example, treatment with a silane coupling agent such as epoxy silane, amino silane, isocyanate silane, vinyl silane, acrylic silane, hydrophobic alkyl silane, phenyl silane, fluorinated alkyl silane, etc. having reactive functional groups, plasma treatment, fluorination treatment, etc. can be cited.

[0130] Examples of the above silane coupling agents include epoxy silanes such as γ-glycidoxypropyltriethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, amino silanes such as aminopropyltriethoxysilane and N-phenylaminopropyltrimethoxysilane, isocyanate silanes such as 3-isocyanatopropyltrimethoxysilane, vinyl silanes such as vinyltrimethoxysilane, acryloyl silanes such as acryloyloxytrimethoxysilane, etc.

[0131] The above spherical silica particles can use commercially available silica particles that satisfy the above properties. Examples of commercially available silica particles include Denka fused silica FB grade (manufactured by Denka Co., Ltd.), Denka fused silica SFP grade (manufactured by Denka Co., Ltd.), EXCELICA (manufactured by Tokuyama Corporation), high-purity synthetic spherical silica ADMAFINE (manufactured by Admatechs Co., Ltd.), ADMANANO (manufactured by Admatechs Co., Ltd.), ADMAFUSE (manufactured by Admatechs Co., Ltd.), etc.

[0132] More specifically, it is particularly preferred to perform surface treatment using aminopropylsilane, aminosilane, vinylsilane, hydrophobic alkylsilane, phenylsilane, 3-mercaptopropylsilane, 3-acryloxypropylsilane, 3-methacryloxypropylsilane, p-styrylsilane, silylpropyl succinic anhydride, 3-isocyanatepropylsilane, 2-(3,4-epoxycyclohexyl)ethylsilane, etc.

[0133] By performing surface treatment using these silane coupling agents, the polar functional groups present on the surface of the filler react, and the amount of polar functional groups decreases, so the electrical properties are excellent.

[0134] (Composition)

[0135] The dielectric of the present disclosure contains the above-mentioned filler and fluororesin. If necessary, it may contain components other than the filler and fluororesin, or may be composed only of the filler and fluororesin. The content of components other than the filler and fluororesin is preferably 10% by weight or less.

[0136] In the dielectric of the present disclosure, the content of the filler is preferably 70% by weight or less with respect to the total amount of the composition. By containing the filler in such a range, the coefficient of linear expansion can be reduced, which is preferable in terms of easy molding.

[0137] The lower limit of the compounding amount of the above-mentioned filler is not particularly limited, and is preferably 40% by weight from the aspect of being able to reduce the coefficient of linear expansion.

[0138] The above upper limit is more preferably 68% by weight, further preferably 65% by weight. The above lower limit is more preferably 40% by weight, further preferably 45% by weight.

[0139] The coefficient of linear expansion of the dielectric of the present disclosure is preferably 10 to 100 (ppm / °C). By being within the above range, it is preferable from the aspect of becoming a dielectric with low shrinkage and excellent dimensional stability. The above upper limit is more preferably 90, further preferably 80. The above lower limit is more preferably 12, further preferably 15. Regarding the coefficient of linear expansion in this specification, TMA measurement using TMA-7100 (manufactured by Hitachi High-Tech Science Corporation) was performed in the tensile mode. As the sample piece, a piece cut to a length of 20 mm, a width of 5 mm, and a thickness of 0.1 mm to 0.5 mm was used, the distance between the chucks was set to 10 mm, and the coefficient of linear expansion was obtained from the displacement amount of the sample at -10°C to 160°C while applying a load of 49 mN and at a heating rate of 2°C / minute.

[0140] (Method for manufacturing fluororesin sheet)

[0141] In the case where the fluororesin is polytetrafluoroethylene, the fluororesin sheet of the present disclosure can be obtained by mixing fluororesin particles with a filler and forming a film. Its manufacturing method is not limited, and it can be carried out by paste extrusion molding, powder calendering molding, etc. In the case of a fluororesin that can be melt-molded, the manufacturing method is not limited, and it can be carried out by injection molding, blow molding, blow-up molding, vacuum / compressed air molding, extrusion molding, etc. The device used in melt kneading is not particularly limited, and a twin-screw extruder, single-screw extruder, multi-screw extruder, tandem extruder, etc. can be used.

[0142] As described above, as the fluororesin used in the fluororesin sheet of the present disclosure, a fluororesin that cannot be melt-molded is preferably used. In the case of using such a fluororesin, when it is formed into a sheet, it is preferably formed by fibrillating powdery PTFE as a raw material.

[0143] The above-mentioned powdery PTFE preferably uses PTFE having a primary particle size of 0.05 μm to 10 μm. By using such PTFE, it has the advantage of excellent dispersibility. It should be noted that the primary particle size here is the value measured according to ASTM D4895.

[0144] The above-mentioned powdery PTFE preferably contains 50% by mass or more of polytetrafluoroethylene resin having a secondary particle size of 500 μm or more, and more preferably contains 80% by mass or more. By making the PTFE having a secondary particle size of 500 μm or more within this range, a binder sheet with high strength can be produced, which has advantages in this regard.

[0145] By using PTFE having a secondary particle size of 500 μm or more, a binder sheet with lower resistance and greater toughness can be obtained.

[0146] The lower limit of the above-mentioned secondary particle size is more preferably 300 μm, and further preferably 350 μm. The upper limit of the above-mentioned secondary particle size is more preferably 700 μm or less, and further preferably 600 μm or less. The secondary particle size can be obtained by, for example, a sieving method.

[0147] From the aspect of obtaining a fluororesin sheet with higher strength and excellent homogeneity, the average primary particle size of the above-mentioned powdery PTFE is preferably 50 nm or more. More preferably 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 more the increase in paste extrusion pressure can be suppressed during paste extrusion molding using this powder, and the better the moldability. The upper limit is not particularly limited and can be 500 nm. From the aspect of productivity in the polymerization process, it is preferably 350 nm.

[0148] Regarding the above average primary particle diameter, an aqueous dispersion of PTFE obtained by polymerization is used to prepare a calibration curve of the transmittance of 550 nm projection light per unit length of an aqueous dispersion with a polymer concentration adjusted to 0.22% by mass and the average primary particle diameter determined by measuring the orientation diameter in a transmission electron microscope photograph. The transmittance of the aqueous dispersion to be measured can be determined based on the above calibration curve.

[0149] The PTFE used in the present disclosure may have a core-shell structure. As the PTFE having a core-shell structure, for example, a modified PTFE containing a core of high molecular weight polytetrafluoroethylene and a shell of lower molecular weight polytetrafluoroethylene or modified polytetrafluoroethylene in particles can be mentioned. As such a modified PTFE, for example, the polytetrafluoroethylene described in Japanese Patent Application Laid-Open No. 2005-527652 can be mentioned.

[0150] The specific methods of paste extrusion molding and powder rolling molding are not particularly limited, and general methods are described below.

[0151] (Paste extrusion molding)

[0152] The method for manufacturing the above sheet may include: step (1a) of mixing PTFE powder obtained using a hydrocarbon surfactant and an extrusion aid; step (1b) of subjecting the obtained mixture to paste extrusion molding; step (1c) of calendering the extrudate obtained by extrusion molding; step (1d) of drying the calendered sheet; and step (1e) of firing the dried sheet to obtain a molded body. The above paste extrusion molding can also be carried out by adding known additives such as pigments and fillers to the above PTFE powder.

[0153] The above extrusion aid is not particularly limited, and generally known extrusion aids can be used. For example, hydrocarbon oils and the like can be mentioned.

[0154] (Powder rolling molding)

[0155] The above sheet can also be formed by powder rolling molding. Powder rolling molding is a method of fibrillating resin powder by applying a shear force thereto and thereby forming it into a sheet shape. Thereafter, it may include a step of firing to obtain a molded body.

[0156] More specifically, it can be obtained by the following manufacturing method, which has:

[0157] Step (1) of applying a shear force while mixing a raw material composition containing a fluororesin and a filler;

[0158] Step (2) of forming the mixture obtained by the above step (1) into a block; and

[0159] Step (3) is to roll the block-shaped mixture obtained in the above step (2) into a sheet-shaped form.

[0160] In addition, when forming a sheet by such powder calendering molding, it is preferable to mix only the fluororesin particles and the inorganic filler and then mold them.

[0161] (laminated body)

[0162] The dielectric material disclosed herein can be used as a sheet for a printed wiring board by being laminated on other base materials.

[0163] A copper-clad laminate can also be obtained by bonding copper foil to one or both sides of the dielectric. As described above, the film containing the fluororesin of the present disclosure can be particularly suitably used for printed wiring board applications, and thus can be suitably used as such a copper-clad laminate.

[0164] The copper foil preferably has an Rz of 1.6 μm or less. That is, the fluororesin composition of the present disclosure has excellent adhesion to a copper foil having an Rz of 1.6 μm or less and high smoothness.

[0165] Furthermore, the Rz value of the copper foil on the other side is not particularly limited as long as at least the side bonded to the fluororesin film is 1.6 μm or less.

[0166] The thickness of the copper foil is not particularly limited, but is preferably in the range of 1 μm to 100 μm, more preferably in the range of 5 μm to 50 μm, and further preferably in the range of 9 μm to 35 μm.

[0167] The copper foil is not particularly limited, and specific examples thereof include rolled copper foil and electrolytic copper foil.

[0168] The copper foil with Rz of 1.6 μm or less is not particularly limited, and commercially available products can be used. Examples of commercially available copper foil with Rz of 1.6 μm or less include electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz 0.85 μm) (manufactured by Fukuda Metal Foil Co., Ltd.).

[0169] The copper foil may be subjected to a surface treatment in order to improve the bonding strength with the fluororesin film of the present disclosure.

[0170] The above surface treatment is not particularly limited and may be silane coupling treatment, plasma treatment, corona treatment, UV treatment, electron beam treatment, etc. The reactive functional groups of the silane coupling agent are not particularly limited. From the aspect of adhesion to the resin substrate, it is preferably to have at least one selected from the group consisting of an amino group, a (meth)acryloyl group, a mercapto group, and an epoxy group at the terminal. In addition, the hydrolyzable group is not particularly limited, and examples thereof include alkoxy groups such as methoxy and ethoxy. The copper foil used in the present disclosure may be formed with an anti-rust layer (such as an oxide film such as chromate), a heat-resistant layer, etc.

[0171] The surface-treated copper foil having a surface treatment layer formed of the above silane compound on the copper foil surface can be manufactured as follows: After preparing a solution containing the silane compound, the copper foil is surface-treated with this solution.

[0172] From the aspect of improving adhesion to the resin substrate, etc., the above copper foil may have a roughened treatment layer on the surface.

[0173] It should be noted that when the roughening treatment may reduce the performance required by the present disclosure, the roughening particles electrodeposited on the copper foil surface can be reduced as needed, or a method of not performing the roughening treatment can be adopted.

[0174] From the aspect of improving various properties, one or more layers selected from the group consisting of a heat-resistant treatment layer, an anti-rust treatment layer, and a chromate treatment layer can be provided between the copper foil and the surface treatment layer. These layers can be a single layer or multiple layers.

[0175] The above copper-clad laminate may further have a layer other than the copper foil and the dielectric. The layer other than the copper foil and the fluororesin film is preferably at least one selected from the group consisting of polyimide, modified polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, modified polyphenylene ether, and polybutadiene.

[0176] As long as the layer other than the copper foil and the dielectric is composed of the above resin, it is not particularly limited. In addition, the thickness of the layer other than the copper foil and the fluororesin film is preferably in the range of 12.5 μm to 260 μm.

[0177] In the above copper-clad laminate, the copper layer can be formed on one side or both sides of the rolled film. As the method for forming the copper layer, methods such as laminating (bonding) a copper foil on the surface of the rolled film, vapor deposition method, plating method, etc. can be cited. As the method for laminating the copper foil, a method using hot pressing can be cited. The hot pressing temperature can be cited as 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 minute to 30 minutes. It can be manufactured by a method with a hot pressing pressure of 0.1 MPa to 10 MPa.

[0178] The use of the above copper-clad laminate is not particularly limited, and it is used as a circuit substrate. A printed circuit board refers to a board-like component used to electrically connect electronic components such as semiconductors and capacitor chips while arranging and fixing them in a limited space. The structure of the printed circuit board formed from the present copper-clad laminate is not particularly limited. The printed circuit board can be any one of a rigid substrate, a flexible substrate, and a rigid-flexible substrate. The printed circuit board can be any one of a single-sided substrate, a double-sided substrate, and a multi-layer substrate (such as a build-up substrate). In particular, it is suitable for use in flexible substrates and rigid substrates. In particular, it can be suitably used as a printed circuit board for high frequencies of 110 GHz or higher.

[0179] There is no particular limitation as a circuit substrate, and the above copper-clad laminate can be used and manufactured by a general method.

[0180] The laminate for a circuit board can also be the following laminate, which is characterized by having a copper foil layer, the above fluororesin film, and a base material layer. There is no particular limitation for the base material layer, and it preferably has a cloth layer and a resin film layer made of glass fiber.

[0181] The cloth layer made of the above glass fiber is a layer composed of glass cloth, glass non-woven fabric, etc.

[0182] As the glass cloth, commercially available glass cloth can be used. In order to improve the affinity with the fluororesin, it is preferably treated with a silane coupling agent. As the material of the glass cloth, E glass, C glass, A glass, S glass, D glass, NE glass, low dielectric constant glass, etc. can be cited. From the aspect of easy availability, E glass, S glass, and NE glass are preferred. As the weaving method of the fiber, it can be plain weave or twill weave. The thickness of the glass cloth is usually 5 μm to 90 μm, preferably 10 μm to 75 μm, and it is preferable to use a glass cloth thinner than the fluororesin film used.

[0183] The above laminate may use a glass non-woven fabric as the fabric layer composed of glass fibers. The glass non-woven fabric is a substance obtained by bonding short glass fibers with a small amount of binder compound (resin or inorganic substance), or a substance that maintains its shape by winding 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 μm to 30 μm, and the fiber length is preferably 5 mm to 30 mm. Specific examples of the binder compound include resins such as epoxy resin, acrylic resin, cellulose, polyvinyl alcohol, fluororesin, or inorganic substances such as silica compounds. The amount of the binder compound is usually 3% by mass to 15% by mass relative to the short glass fibers. Examples of the material of the short glass fibers include E glass, C glass, A glass, S glass, D glass, NE glass, low dielectric constant glass, etc. The thickness of the glass non-woven fabric is usually 50 μm to 1000 μm, preferably 100 μm to 900 μm. It should be noted that the thickness of the glass non-woven fabric in this application refers to the value measured in accordance with JIS P8118:1998 using a digital gauge DG-925 (load 110 g, surface diameter 10 mm) manufactured by Ono Sokki Co., Ltd. In order to improve the affinity with the fluororesin, the glass non-woven fabric can be treated with a silane coupling agent.

[0184] Most of the glass non-woven fabrics have a porosity of 80% or more, which is very high. Therefore, it is preferable to use a glass non-woven fabric thicker than the sheet made of fluororesin and compress it under pressure for use.

[0185] The above fabric layer composed of glass fibers may be a layer formed by laminating a glass cloth and a glass non-woven fabric. Thus, the properties of each other are combined, and appropriate properties can be obtained.

[0186] The above fabric layer composed of glass fibers may be in the state of a prepreg impregnated with resin.

[0187] In the above laminate, the fabric layer composed of glass fibers and the fluororesin film may be bonded at the interface, and the fluororesin film may also partially or completely infiltrate into the fabric layer composed of glass fibers.

[0188] In addition, a fluororesin composition may be infiltrated into the fabric composed of glass fibers to make a prepreg. For the prepreg thus obtained, the fluororesin film of the present disclosure may be further laminated. In this case, the fluororesin composition used when making the prepreg is not particularly limited, and the fluororesin film of the present disclosure may also be used.

[0189] As the resin film used as the above-mentioned base material layer, a heat-resistant resin film and a thermosetting resin film are preferred. Examples of the heat-resistant resin film include polyimide, modified polyimide, liquid crystal polymer, polyphenylene sulfide, etc. Examples of the thermosetting resin include thermosetting resins containing epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, modified polyphenylene ether, polybutadiene, etc.

[0190] The heat-resistant resin film and the thermosetting resin film may contain reinforcing fibers. There is no particular limitation on the reinforcing fibers, and preferably, for example, glass cloth, particularly a reinforcing fiber of a low dielectric constant type.

[0191] The characteristics such as dielectric properties, coefficient of linear expansion, water absorption rate, etc. of the heat-resistant resin film and the 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 further 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 further preferably 0.0020 or less. The coefficient of linear expansion is preferably 100 ppm / °C or less, more preferably 70 ppm / °C or less, and further preferably 40 ppm / °C or less. The water absorption rate is preferably 1.0% or less, more preferably 0.5% or less, and further preferably 0.1% or less.

[0192] Examples

[0193] The present disclosure will be specifically described based on the examples below. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "mass %", respectively.

[0194] Sheet manufacturing method 1 (paste extrusion molding)

[0195] Weigh a specified amount of fluororesin powder (PTFE) and spherical silica in the ratio shown in Table 3, and mix them with a mixer in the presence of dry ice. The temperature during mixing is -10°C or lower.

[0196] Add 18 wt% - 23 wt% of oil (IP solvent 2028) to the obtained mixed powder, mix it, and cure for about 5 hours.

[0197] Preform the cured composition under a pressure of 3 MPa, and extrude the preformed body at 40°C and 50 mm / min to obtain an extruded sample. Roll the extruded sample with a two-roll calender (roll gap: set to 500 μm - 80 μm) to obtain a sample with a film thickness of 125 μm, dry it at 200°C for 2 hours, and bake it at 360°C for 15 minutes to obtain a sheet.

[0198] Sheet manufacturing method 2 (powder rolling molding)

[0199] Weigh a specified amount of fluororesin powder (PTFE) and silica in the proportions shown in Table 3, and use a WonderCrusher to stir for 30 seconds × 2 times at room temperature with a memory of 6. Roll the obtained powder using a two-roll calender (roll gap: set to 100 μm) to obtain a sample with a film thickness of 130 μm, and bake it at 360 °C for 15 minutes to obtain a sheet.

[0200] It should be noted that the spherical silica used in each example uses SC6500-SQ (average particle size 2.1 μm) manufactured by Admatechs Co., Ltd. as the raw material, and surface treatment shown in Table 2 was performed in some examples. The spherical silica in Example 9 uses FE920D-SQ (average particle size 5.8 μm) manufactured by Admatechs Co., Ltd., and the spherical silica in Example 10 uses 20GA-C2 (average particle size 2.0 μm) manufactured by Admatechs Co., Ltd.

[0201] It should be noted that the fluororesin powder (PTFE) used has the following properties.

[0202] Average particle size: 500 μm

[0203] Apparent density: 460 g / L

[0204] Standard specific gravity: 2.17

[0205] The measurement method is based on ASTM D 4895.

[0206] [Table 2]

[0207]

[0208] [Table 3]

[0209] Mixing amount of silica Mixing amount of fluororesin Method for manufacturing the sheet Example 1 60 wt% 40 wt% Sheet manufacturing method 1 Example 2 60 wt% 40 wt% Sheet manufacturing method 1 Example 3 60 wt% 40 wt% Sheet manufacturing method 2 Example 4 60 wt% 40 wt% Sheet manufacturing method 2 Example 5 50 wt% 50 wt% Sheet manufacturing method 1 Example 6 50 wt% 50 wt% Sheet manufacturing method 1 Example 7 50 wt% 50 wt% Sheet manufacturing method 2 Example 8 50 wt% 50 wt% Sheet manufacturing method 2 Example 9 50 wt% 50 wt% Sheet manufacturing method 2 Example 10 50 wt% 50 wt% Sheet manufacturing method 2

[0210] (Etching)

[0211] Etch the copper foil of the copper foil with a resin layer (RO3003G2, NF-30) using an aqueous ferric chloride solution, wash it with flowing clean water for 2 to 5 minutes, then wash it with distilled water, and dry it in a constant temperature bath at 80 ± 3 °C for about 60 minutes to recover the monomer resin layer.

[0212] (Comparative Example 1)

[0213] Etch RO3003G2 (manufactured by Rogers Corporation), which is a commercially available copper-clad laminate, to obtain a resin layer.

[0214] (Comparative Example 2)

[0215] The resin layer was obtained by etching NF-30 (manufactured by Taconic), a commercially available copper-clad laminate.

[0216] (Evaluation method)

[0217] (Method for measuring dielectric constant and dielectric loss tangent)

[0218] Under the conditions of room temperature of 25 °C and humidity of 50%, the relative dielectric constant (Dk) and dielectric loss tangent (Df) at each frequency were measured using a network analyzer (N5290A, manufactured by Keysight Technologies) and Fabry-Perot resonators in the J band (220 GHz to 330 GHz) and D band (110 GHz to 170 GHz) (FP-J, FP-D, manufactured by EM labs).

[0219] The results are shown in Table 4.

[0220]

[0221] According to Table 4, the difference in the relative dielectric constant of the dielectrics of Examples 1 to 10 based on the frequencies from 220 GHz to 330 GHz is small. When such a dielectric is made into a copper-clad laminate, it is not necessary to change the wiring width of the copper wiring for each frequency. In addition, a dielectric with small anisotropy in the relative dielectric constant at 170 GHz can be obtained, and copper wirings other than straight lines can be freely designed.

[0222] Furthermore, it is preferable that the dielectric loss tangent (Df) is low for each frequency from 220 GHz to 330 GHz. By using a dielectric with a low dielectric loss tangent, the transmission loss from 220 GHz to 330 GHz becomes small, so it is preferable.

[0223] Industrial applicability

[0224] The dielectric of the present disclosure is particularly suitable for high-frequency printed circuit boards of 110 GHz or higher.

Claims

1. A dielectric, characterized in that, the slope of the relative dielectric constant Dk measured in the J band of the Fabry - Perot resonator with respect to the frequency from 220 GHz to 330 GHz is 0.00001 or more and 0.0005 or less.

2. A dielectric, characterized in that, the 90° anisotropy in the plane direction of the relative dielectric constant Dk at 170 GHz measured in the J band of the Fabry - Perot resonator is 0.02 or less.

3. A dielectric, characterized in that, the dielectric loss tangent Df at 220 GHz measured in the J band of the Fabry - Perot resonator is 0.00153 or less.

4. A dielectric, characterized in that, the dielectric loss tangent Df at 330 GHz measured in the J band of the Fabry - Perot resonator is 0.00165 or less.

5. The dielectric according to any one of claims 1 to 4, wherein, the dielectric comprises a resin and spherical fillers.

6. The dielectric according to claim 5, wherein, the fillers are at least one selected from the group consisting of silica, titanium oxide, alumina, and forsterite.

7. The dielectric according to claim 5 or 6, wherein, the fillers are substantially spherical silica.

8. The dielectric according to any one of claims 5 to 7, wherein, the average particle diameter of the fillers is 0.1 μm to 10 μm.

9. The dielectric according to any one of claims 5 to 8, wherein, the resin is a fluororesin.

10. The dielectric according to claim 9, wherein, the fluororesin comprises at least one polymer selected from the group consisting of polytetrafluoroethylene resin, tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene - hexafluoropropylene copolymer as part or all.

11. The dielectric according to claim 9 or 10, which is obtained by using fluororesin particles having a primary particle diameter of 0.05 μm to 10 μm as raw materials.

12. The dielectric according to claim 11, wherein, the volume - based cumulative 50% diameter of the fluororesin particles is 0.05 μm to 40 μm.

13. The dielectric according to any one of claims 1 to 12, which is used for a printed circuit board for the terahertz band, a dielectric material for the terahertz band, or a laminated circuit board for the terahertz band.

14. The dielectric according to any one of claims 1 to 13, which has a sheet shape.

15. A method for manufacturing the dielectric according to claim 14, characterized in that, fluororesin particles and fillers are mixed and formed into a film.

16. A method for manufacturing the dielectric according to claim 14, characterized in that, it has a step of mixing fluororesin particles and fillers and forming a film without adding other components.

17. A copper - clad laminate, which uses a copper foil and the dielectric according to claim 14 as essential layers, and is used for a printed circuit board for the terahertz band, a dielectric material for the terahertz band, or a laminated circuit board for the terahertz band.

18. A circuit board, characterized in that, it has the copper - clad laminate according to claim 17.

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