Glass cloth, prepreg, and printed circuit board

Abstract

Provided is a glass cloth capable of reducing skew when used in a printed circuit board. This glass cloth has glass fibers serving as warp and weft. The ratio σt / σy of the standard deviation σt of the glass strand thickness of the warp to the standard deviation σy of the glass strand thickness of the weft of the glass cloth is within a range from 0.3 to 0.9.

Description

Glass cloth, prepreg and printed wiring board

[0001] The present invention relates to a glass cloth, a prepreg, and a printed wiring board.

[0002] In general, the propagation velocity of a transmission line formed on a printed wiring board is affected by the dielectric constant of the surrounding substrate. For example, in the case of a microstrip line, the propagation velocity is expressed by the following equation: V = C / ε ｅｆｆ １／２ In the above formula, C is the speed of light, ε ｅｆｆ is the effective dielectric constant of the substrate.

[0003] In recent years, advances in electronic devices have led to demand for high-capacity, high-speed data communication technology, and reducing the delay time difference (skew) between differential wiring has become important for increasing communication speeds.

[0004] In the glass-cloth prepreg used in the printed wiring board, the dielectric properties of the glass and resin are different, so the density of the resin and glass cloth affects the transmission of communication signals. For example, if differential wiring is arranged in a sparse glass area and a dense glass area, the difference in effective dielectric constant causes skew in the transmission signal between the wiring, resulting in a deterioration of transmission characteristics.

[0005] Conventionally, as a method for improving the density of the glass cloth and reducing the skew, a technique for uniforming the density of the glass by opening the glass cloth and reducing the gaps in the glass cloth has been known (see, for example, Patent Document 1).

[0006] Japanese Patent Application Laid-Open No. 2006-232952

[0007] However, in order to stably perform the opening process of the glass cloth, it is necessary to apply tension to the warp threads of the glass cloth while transporting it. Therefore, the warp threads are more difficult to open than the weft threads, and when differential wiring is arranged in the warp direction, the influence of the density of the glass fibers is likely to occur. Furthermore, when the glass cloth has a certain thickness, the influence of the density of the glass fibers is likely to become greater, which causes the disadvantage of large skew in printed wiring boards using glass cloth-containing prepregs.

[0008] An object of the present invention is to provide a glass cloth that can eliminate such inconveniences and reduce skew when used in a printed wiring board.

[0009] The present inventors have conducted extensive research into means for reducing skew in printed wiring boards that use glass cloth-reinforced prepregs, and as a result have found that even when warp yarns are less likely to be spread apart than weft yarns, skew in the printed wiring board can be reduced by keeping the variation in strand thickness between warp yarns and weft yarns within a certain range. It is believed that this is because, by suppressing the variation in thickness of warp yarns, which are less likely to be spread apart, while allowing the thickness of weft yarns to vary to a certain extent, the glass fibers are distributed appropriately and localized dense states can be avoided, but this speculation does not limit the present invention.

[0010] In order to achieve the above object, the glass cloth of the present invention is a glass cloth having glass fibers as warp and weft, characterized in that the ratio σt / σy of the standard deviation σt of the glass strand thickness of the warp to the standard deviation σy of the glass strand thickness of the weft of the glass cloth is in the range of 0.3 to 0.9.

[0011] The glass cloth of the present invention can reduce skew of the printed wiring board by having a ratio σt / σy of the standard deviation σt of the thickness of the warp glass strands to the standard deviation σy of the thickness of the weft glass strands of the glass cloth within the above range.

[0012] In the glass cloth of the present invention, if the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness of the glass cloth exceeds 0.9, the skew of the printed wiring board cannot be reduced. On the other hand, in the glass cloth of the present invention, it is technically difficult to make the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the glass strand thickness less than 0.3.

[0013] In addition, the glass cloth of the present invention preferably has a spread area ratio S calculated by the following formula (1) using the weave density Wt of warp yarns, the average warp width Bt, the weave density Wy of weft yarns and the average weft width By in the range of 90 to 100%.

[0014] The glass cloth of the present invention, when having the spread area ratio S in the above range, can further reduce the skew of the printed wiring board.

[0015] In addition, the glass cloth of the present invention preferably has a ratio Rt / Ry of the maximum-minimum difference Rt, which is the difference between the maximum and minimum values ​​of the thickness of the warp glass strands, to the maximum-minimum difference Ry, which is the difference between the maximum and minimum values ​​of the thickness of the weft glass strands, in the range of 0.3 to 0.9.

[0016] The glass cloth of the present invention, when having the ratio Rt / Ry within the above range, can further reduce the skew of the printed wiring board.

[0017] In addition, in the glass cloth of the present invention, it is preferable that the warp width openness Lt calculated by the following formula (2) is in the range of 60 to 83%, and the weft width openness Ly calculated by the following formula (3) is in the range of, for example, 85% or more.

[0018] The glass cloth of the present invention can reduce the skew of the printed wiring board even when the warp width spread ratio Lt and the weft width spread ratio Ly are within the above ranges.

[0019] Furthermore, the glass cloth of the present invention preferably has a thickness in the range of 18 to 100 μm. Even if the glass cloth of the present invention has a thickness in the above range, it can reduce skew of the printed wiring board.

[0020] The prepreg of the present invention is characterized by containing the glass cloth of the present invention. By containing the glass cloth of the present invention, the prepreg of the present invention can reduce skew of the printed wiring board.

[0021] In this case, the prepreg of the present invention preferably has a difference between the dielectric constant of the glass cloth and the dielectric constant of the matrix resin of the prepreg in the range of 1.5 to 3.0. Even if the difference between the dielectric constant of the glass cloth and the dielectric constant of the matrix resin of the prepreg is in the range of 1.5 to 3.0, the prepreg of the present invention can reduce the influence on the transmission of communication signals in the printed wiring board caused by the density of the resin and the glass cloth.

[0022] The printed wiring board of the present invention is characterized by including the prepreg of the present invention. By including the prepreg of the present invention, the printed wiring board of the present invention can reduce skew.

[0023] Next, the embodiment of the present invention will be described in more detail.

[0024] The glass cloth of this embodiment is a glass cloth having glass fibers as warp and weft, and the glass fibers are glass strands made of a plurality of glass filaments.

[0025] In the glass cloth of this embodiment, the ratio σt / σy of the standard deviation σt of the glass strand thickness of the warp to the standard deviation σy of the glass strand thickness of the weft of the glass cloth is in the range of 0.3 to 0.9, preferably in the range of 0.35 to 0.85, more preferably in the range of 0.35 to 0.71, even more preferably in the range of 0.5 to 0.71, and most preferably in the range of 0.6 to 0.71. The glass strand thickness of the weft and the glass strand thickness of the warp of the glass cloth can be measured by the method described later.

[0026] Furthermore, the glass cloth of the present embodiment preferably has a spread area ratio S calculated from the warp weave density Wt, the warp average width Bt, the weft weave density Wy, and the weft average width By using the following formula (1): The warp and weft widths of the glass cloth can be measured by the method described later, and the warp average width Bt and the weft average width By can be calculated from the measured warp and weft widths, respectively.

[0027] The spread area ratio S is more preferably in the range of 95 to 100%, further preferably in the range of 96 to 99.9%, and most preferably in the range of 98.5 to 99.9%.

[0028] The weave density Wt of the warp yarns and the weave density Wy of the weft yarns are not particularly limited, but can each be in the range of 20 to 120 threads / 25 mm. The weave density Wt of the warp yarns and the weave density Wy of the weft yarns may be different from each other. The weave density Wt of the warp yarns is more preferably in the range of 30 to 110 threads / 25 mm, even more preferably in the range of 40 to 100 threads / 25 mm, and most preferably in the range of 50 to 70 threads / 25 mm. The weave density Wy of the weft yarns is more preferably in the range of 30 to 110 threads / 25 mm, even more preferably in the range of 40 to 100 threads / 25 mm, and most preferably in the range of 50 to 70 threads / 25 mm.

[0029] In addition, in the glass cloth of the present embodiment, it is preferable that the ratio Rt / Ry of the maximum-minimum difference Rt, which is the difference between the maximum and minimum values ​​of the thickness of the warp glass strands, to the maximum-minimum difference Ry, which is the difference between the maximum and minimum values ​​of the thickness of the weft glass strands, is in the range of 0.3 to 0.9.

[0030] The ratio Rt / Ry is more preferably in the range of 0.4 to 0.9, even more preferably in the range of 0.4 to 0.8, and most preferably in the range of 0.6 to 0.7.

[0031] In addition, in the glass cloth of the present embodiment, it is preferable that the warp width openness Lt calculated by the following formula (2) is in the range of 60 to 83%, and the weft width openness Ly calculated by the following formula (3) is in the range of 85% or more.

[0032] The warp width openness Lt is more preferably in the range of 63 to 83%, even more preferably in the range of 63 to 75%, and most preferably in the range of 63 to 68%. The weft width openness Ly is more preferably in the range of 88% or more, even more preferably in the range of 90% or more, and most preferably in the range of 95% or more.

[0033] The warp width openness Lt and the weft width openness Ly can be calculated from the warp and weft widths measured by the methods described below.

[0034] Furthermore, the thickness of the glass cloth of the present embodiment is preferably in the range of 18 to 100 μm, more preferably in the range of 25 to 90 μm, even more preferably in the range of 30 to 80 μm, and most preferably in the range of 30 to 50 μm.

[0035] The thickness of the glass cloth is an average value of measured values ​​when the thickness is measured at 15 points on the glass cloth with a micrometer in accordance with JIS R 3420:2013.

[0036] The glass cloth of this embodiment is woven using the glass fibers (glass strands) as warp and weft, and can be produced, for example, as follows.

[0037] First, a predetermined glass batch (glass raw material) is melted and fiberized to obtain glass filaments. The diameter of the glass filaments is not particularly limited, but for printed wiring board applications, it is preferably in the range of 10 μm or less, more preferably in the range of 8 μm or less, and particularly preferably in the range of 3 to 7 μm.

[0038] The glass filaments are bundled into glass fibers by a method known per se, for example, in a number ranging from 25 to 500, preferably from 40 to 300. Note that spinning refers to the process of melting a glass batch, fiberizing it to obtain glass filaments, and then bundling a plurality of these glass filaments to obtain glass fibers (glass strands).

[0039] The mass per unit length of the glass fiber (glass strand) is preferably in the range of 2 to 30 g / 1000 m, more preferably in the range of 4 to 25 g / 1000 m, and even more preferably in the range of 4 to 15 g / 1000 m.

[0040] The glass composition of the glass fiber is not particularly limited, but examples thereof include an E-glass composition, a high-strength, high-elasticity glass composition, a high-elasticity, easily manufacturable glass composition, a low-dielectric-constant, low-dielectric-loss-tangent glass composition, etc. For high-speed communication applications, a low-dielectric-constant, low-dielectric-loss-tangent glass composition is preferred, and examples thereof include NE-glass, L-glass, D-glass, etc.

[0041] The E-glass composition is the most commonly used glass composition, and contains SiO in the range of 52.0 to 56.0 mass % based on the total amount of glass fibers. ２ and Al in the range of 12.0 to 16.0 mass% ２ O ３ and a total of 20.0 to 25.0 mass% of MgO and CaO, and 5.0 to 10.0 mass% of B. ２ O ３ Includes:

[0042] The high-strength, high-elastic modulus glass composition contains SiO in the range of 60.0 to 70.0 mass % based on the total amount of glass fibers. ２ and Al in the range of 20.0 to 30.0 mass% ２ O ３ and MgO in the range of 5.0 to 15.0 mass % and Fe in the range of 0 to 1.5 mass %. ２ O ３ and a total of 0 to 0.2 mass% of Na ２ O.K. ２ O and Li ２ The high strength, high modulus glass composition preferably contains Fe in the range of 0.15 to 1.50 mass %. ２ O ３ and ZrO in the range of 0.01 to 0.10 mass %. ２ and a total of 0.02 to 0.20 mass% of Na ２ O.K. ２ O and Li ２ O.

[0043] The high elastic modulus, easily manufacturable glass composition contains SiO in the range of 57.0 to 60.0 mass % based on the total amount of glass fibers. ２ and Al in the range of 17.5 to 20.0 mass% ２ O ３8.5 to 12.0 mass% MgO, 10.0 to 13.0 mass% CaO, and 0.5 to 1.5 mass% B ２ O ３ and a total of 98.0 mass% or more of SiO ２ , Al ２ O ３ , MgO and CaO.

[0044] The low dielectric constant and low dielectric loss tangent glass composition contains SiO in the range of 48.0 to 62.0 mass % based on the total amount of glass fibers. ２ and B in the range of 17.0 to 26.0 mass% ２ O ３ and Al in the range of 9.0 to 18.0 mass% ２ O ３ 0.1 to 9.0 mass% CaO, 0 to 6.0 mass% MgO, and 0 to 0.5 mass% Na in total. ２ O.K. ２ O and Li ２ O and TiO in the range of 0 to 5.0 mass% ２ and SrO in the range of 0 to 6.0 mass %, and F in the range of 0 to 3.0 mass % in total. ２ and Cl ２ and P in the range of 0 to 6.0 mass%. ２ O ５ Includes:

[0045] The content of each component of the glass composition described above can be measured using an ICP optical emission spectrometer for the light element Li, and using a wavelength dispersive X-ray fluorescence analyzer for the other elements. Specifically, the content of each component of the glass composition can be measured as follows.

[0046] First, glass cloth is cut to an appropriate size, placed in a platinum crucible, and melted in an electric furnace at a temperature of 1400 to 1650°C for 6 hours while stirring, to obtain a homogeneous molten glass. If organic matter is attached to the surface of the glass cloth or if glass fibers are contained mainly as a reinforcing material in the organic matter (resin), the glass cloth is used after removing the organic matter by, for example, heating in a muffle furnace at 300 to 650°C for 2 to 24 hours.

[0047] The molten glass is then poured onto a carbon plate to produce glass cullet, which is then crushed and powdered to produce glass powder. The light element Li is quantitatively analyzed using an ICP optical emission spectrometer after the glass powder is thermally decomposed with acid. The other elements are quantitatively analyzed using a wavelength dispersive X-ray fluorescence analyzer after the glass powder is molded into a disk shape using a press.

[0048] Quantitative analysis using a wavelength-dispersive X-ray fluorescence analyzer can be performed by the following method. First, the content of each component in a measurement sample is measured using the fundamental parameter method. Next, based on the measurement results, at least three calibration curve samples are prepared and analyzed using the calibration curve method. The content of each component in the calibration curve samples can be quantitatively analyzed using an ICP optical emission spectrometer. Next, these quantitative analysis results are converted into oxides to calculate the content and total amount of each component, and the content (mass %) of each component described above can be determined from these values.

[0049] Next, the glass cloth of this embodiment can be obtained by weaving the glass fibers (glass strands) as warp or weft using a known loom. Examples of the loom include a jet loom such as an air jet or water jet loom, a shuttle loom, and a rapier loom. Examples of the weaving method used with the loom include plain weave, satin weave, sash weave, and twill weave, with plain weave being preferred from the viewpoint of production efficiency.

[0050] During the weaving process, a sizing agent can be used to bundle the glass filaments and protect the glass fibers (glass strands). Examples of the sizing agent include starch-based or PVA (polyvinyl alcohol)-based film-forming agents. The sizing agent may contain an oil or a softener.

[0051] In the glass cloth of the present embodiment, the amount of the sizing agent attached to 100 parts by mass of the glass fiber yarn is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.3 to 3 parts by mass, and even more preferably in the range of 0.5 to 2 parts by mass.

[0052] The glass cloth of the present embodiment may be subjected to a fiber-opening treatment after weaving, and further to a deoiling treatment and a surface treatment. The fiber-opening treatment, the deoiling treatment, and the surface treatment may be performed in any order.

[0053] Examples of the opening treatment include a process for widening the yarn width of the warp and weft yarns by applying a tension in the range of 30 to 500 N to the warp yarns of the glass cloth of this embodiment while using the pressure of a fluid such as a water jet having a surface pressure in the range of 1 to 8 MPa (high-pressure water opening treatment), a process for opening by water jet pressure such as a general-purpose spray, a process for opening by high-frequency vibration such as ultrasonic waves using a liquid as a medium, and a process for opening by applying pressure with a roll.

[0054] The deoiling treatment may be, for example, a treatment in which the glass cloth of the present embodiment is placed in a heating furnace at an atmospheric temperature in the range of 300 to 500°C for a period in the range of 40 to 80 hours, and organic matter adhering to the glass fibers is thermally decomposed.

[0055] The surface treatment may include a treatment in which the glass cloth is immersed in a silane coupling agent or a solution containing the silane coupling agent and a surfactant, excess water is squeezed out, and the glass cloth is then heated and dried at a temperature in the range of 90 to 120°C for a time in the range of 1 to 10 minutes.

[0056] Examples of the silane coupling agent include aminosilane, ureidosilane, chlorosilane, epoxysilane, mercaptosilane, vinylsilane, (meth)acrylicsilane, phenylsilane, styrylsilane, and isocyanatesilane. In this embodiment, the silane coupling agent may be used alone or in combination of two or more.

[0057] Examples of aminosilanes include γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-N'-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-anilinopropyltrimethoxysilane.

[0058] Examples of ureidosilane include γ-ureidopropyltriethoxysilane.

[0059] Examples of chlorosilanes include γ-chloropropyltrimethoxysilane.

[0060] Examples of epoxy silanes include β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.

[0061] Examples of mercaptosilane include γ-mercaptotrimethoxysilane and γ-mercaptopropyltrimethoxysilane.

[0062] Examples of vinylsilanes include vinyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, and N-benzyl-β-aminoethyl-γ-aminopropyltrimethoxysilane.

[0063] Examples of the (meth)acrylic silane include γ-acryloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

[0064] Examples of phenylsilane include phenyltrimethoxysilane.

[0065] The styrylsilane may include p-styryltrimethoxysilane.

[0066] Examples of isocyanate silanes include γ-isocyanate propyl triethoxy silane.

[0067] Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. In this embodiment, the surfactants may be used alone or in combination of two or more.

[0068] Examples of nonionic surfactants include ethylene oxide propylene oxide alkyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene-polyoxypropylene block copolymers, alkyl polyoxyethylene-polyoxypropylene block copolymer ethers, polyoxyethylene fatty acid esters, polyoxyethylene fatty acid monoesters, polyoxyethylene fatty acid diesters, polyoxyethylene sorbitan fatty acid esters, glycerol fatty acid ester ethylene oxide adducts, polyoxyethylene castor oil ethers, hydrogenated castor oil ethylene oxide adducts, alkylamine ethylene oxide adducts, fatty acid amide ethylene oxide adducts, glycerol fatty acid esters, polyglycerin fatty acid esters, pentaerythritol fatty acid esters, sorbitol fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyhydric alcohol alkyl ethers, fatty acid alkanolamides, acetylene glycol, acetylene alcohol, ethylene oxide adducts of acetylene glycol, and ethylene oxide adducts of acetylene alcohol.

[0069] Examples of cationic surfactants include alkyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, alkyldimethylethylammonium ethyl sulfate, higher alkylamine salts (acetates, hydrochlorides, etc.), ethylene oxide adducts of higher alkylamines, condensates of higher fatty acids and polyalkylenepolyamines, salts of esters of higher fatty acids and alkanolamines, salts of higher fatty acid amides, imidazoline-type cationic surfactants, and alkylpyridinium salts.

[0070] Examples of anionic surfactants include higher alcohol sulfates, higher alkyl ether sulfates, α-olefin sulfates, alkylbenzene sulfonates, α-olefin sulfonates, reaction products of fatty acid halides and N-methyltaurine, dialkyl sulfosuccinates, higher alcohol phosphates, and phosphate salts of higher alcohol ethylene oxide adducts.

[0071] Examples of amphoteric surfactants include amino acid type amphoteric surfactants such as alkali metal salts of alkylaminopropionic acid, betaine type amphoteric surfactants such as alkyldimethylbetaine, and imidazoline type amphoteric surfactants.

[0072] Next, the prepreg of this embodiment can be obtained by impregnating at least a portion of the glass cloth of this embodiment with a resin by a method known per se and semi-curing it.

[0073] In the prepreg of this embodiment, the difference between the dielectric constant of the glass cloth of this embodiment and the dielectric constant of the matrix resin of the prepreg is preferably in the range of 1.5 to 3.0, more preferably in the range of 1.6 to 2.8, even more preferably in the range of 1.7 to 2.6, and particularly preferably in the range of 1.9 to 2.5.

[0074] When the glass fibers (glass strands) have a glass composition such as the E-glass composition, a high-strength, high-elasticity glass composition, a high-elasticity, easily manufacturable glass composition, or a low-dielectric-constant, low-dielectric-loss-tangent glass composition, the glass cloth of this embodiment has a relative dielectric constant in the range of 3.0 to 7.0, preferably in the range of 3.5 to 6.0, and more preferably in the range of 4.0 to 5.0, at a measurement frequency of 10 GHz.

[0075] In this case, examples of the matrix resin having a relative dielectric constant difference within the above range from the glass cloth of this embodiment include epoxy resin, polyphenylene ether resin, maleimide resin, cycloolefin polymer resin, ODV resin, etc. For high-speed communication applications, the matrix resin is preferably a thermosetting resin with low dielectric properties, and examples of such thermosetting resins include modified polyphenylene ether and reactive low-molecular-weight polyphenylene ether.

[0076] The printed wiring board of this embodiment can be obtained by curing the prepreg of this embodiment, laminating multiple sheets of the cured prepreg, and then hot-pressing the laminate with copper foil, such as low-roughness electrolytic copper foil, on top and bottom of the prepreg to form a copper-clad laminate, which can then be patterned to form a desired wiring pattern. The patterning can be performed by a known method such as photolithography.

[0077] Next, examples of the present invention and comparative examples will be described.

[0078] [Example 1] In this example, first, a glass cloth conforming to IPC4412 standard #1078 (yarn used: D500 (fiber diameter 5.0 μm, yarn weight 10.1 g / 1000 m), warp weave density: 53 threads / 25 mm, weft weave density: 53 threads / 25 mm, weight per unit area: 43 g / m) was prepared using glass fibers (glass strands) formed by bundling 200 glass filaments having a low dielectric constant and low dielectric loss tangent glass composition and a relative dielectric constant of 4.7 (measurement frequency 10 GHz) as warp and weft yarns. ２ ) was woven.

[0079] The warp yarns used for the glass cloth were yarns that had been coated with a glass fiber protective agent (sizing agent) in the warping process and then dried by pressing the warp yarns against a drum-type cylinder whose surface was kept at 120°C.

[0080] Next, the woven glass cloth was heated at a temperature of 450°C for 60 hours to be deoiled, and then subjected to a water pressure opening treatment using a jet spray at a water pressure of 6.0 MPa. The opened glass cloth was immersed in an aqueous solution of a glass treating agent in which 3-methacryloxypropyltrimethoxysilane (manufactured by Toray Dow Corning Co., Ltd., trade name: OFS6030) and acetic acid were dispersed in water, and then heated and dried to perform a surface treatment, thereby obtaining a surface-treated opened glass cloth with a thickness of 43.2 µm.

[0081] Next, for the surface-treated spread glass cloth obtained in this example, the widths of the warp and weft yarns constituting the surface-treated spread glass cloth were measured by the method described later, and the average warp width, average weft width, spread area ratio S, warp width spread ratio Lt, and weft width spread ratio Ly were calculated. The results are shown in Table 1.

[0082] [Method of measuring yarn width] For the surface-treated spread glass cloth obtained in this example, glass cloth pieces having a size of 110 mm in length and 60 mm in width were cut out at three points in the width direction of the glass cloth (100 mm from both ends and the center) using a digital microscope (manufactured by Keyence Corporation) at a magnification of 100 times, and the warp width and weft width were measured at 100 consecutive points in each yarn direction, and the average warp width and the average weft width were calculated from the average values ​​of a total of 300 measurement points.

[0083] Next, the surface-treated spread glass cloth was cut into pieces measuring 450 mm lengthwise and 400 mm widthwise, and the resulting surface-treated spread glass cloth pieces were immersed in a modified polyphenylene ether resin varnish and pre-dried at 150°C for 10 minutes to obtain a prepreg with a resin content of 60% by mass. The modified polyphenylene ether resin varnish was prepared by adding 70 parts by mass of reactive low-molecular-weight polyphenylene ether (SABIC, trade name: SA9000, dielectric constant: 2.5 (measurement frequency: 1 MHz)), 30 parts by mass of triallyl isocyanurate (Evonik Japan, trade name: TAICROS), 1 part by mass of α,α'-di(tert-butylperoxy)diisopropylbenzene (NOF Corporation, trade name: Perbutyl P), and toluene (Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent.

[0084] Next, two sheets of the prepreg were laminated together, and low-roughness electrolytic copper foil (manufactured by Fukuda Metal Foil Co., Ltd., product name: CF-T4X-SV18, thickness 18 μm) was placed on top and bottom, and the laminate was heated and pressed in a vacuum for 1 hour under conditions of 205°C and a surface thickness of 4 MPa using a vacuum hot press (manufactured by Kitagawa Seiki Co., Ltd.) to obtain a copper-clad laminate with a plate thickness of 0.21 mm.

[0085] Next, for the copper-clad laminate obtained in this example, the strand thicknesses of the warp and weft yarns of the glass cloth contained in the copper-clad laminate were measured by the method described below, and the ratio of the standard deviation of the warp glass strand thickness σt to the standard deviation of the weft glass strand thickness σy (σt / σy) and the ratio of the maximum and minimum difference of the warp glass strand thickness Rt to the maximum and minimum difference of the weft glass strand thickness Ry were calculated. The results are shown in Table 1.

[0086] [Method for Measuring Strand Thickness] The copper-clad laminate obtained in this example was cut into a size of 14 mm x 10 mm, embedded in epoxy resin (manufactured by Cemedine Co., Ltd., product name: 1500), and the cross section was polished parallel to the warp or weft direction so that the intersections between the warp and weft yarns of the glass cloth were exposed on the surface. Using a scanning electron microscope (manufactured by JEOL Ltd., product name: IT700HR) at 300x magnification, the thickness of 30 adjacent continuous strands of the glass cloth contained in the copper-clad laminate was measured. Here, the thickness of the warp strand refers to the distance between lines drawn parallel to the weft direction from the top of the glass filament at the top of the warp yarn (glass filament) bundle and the bottom of the glass filament at the bottom of the warp yarn bundle. Similarly, the thickness of the weft strand refers to the distance between lines drawn parallel to the warp direction from the top of the glass filament at the top of the weft yarn bundle and the bottom of the glass filament at the bottom of the weft yarn bundle. The strand thickness was measured at the intersection of the warp and weft yarns. That is, when measuring the strand thickness of the warp yarns of the glass cloth, the thickness of the strand was measured at a portion where one or more weft yarns exist above or below the warp yarn bundle, and when measuring the strand thickness of the weft yarns of the glass cloth, the thickness of the strand was measured at a portion where one or more warp yarns exist above or below the weft yarn bundle.

[0087] Next, the copper foil on one side of the copper-clad laminate obtained in this example was patterned to obtain a printed wiring board, and the skew was measured and evaluated by the method described below. The results are shown in Table 1.

[0088] [Method for Measuring and Evaluating Skew] The copper foil on one side of the copper-clad laminate obtained in this example was patterned to form eight pairs of differential microstrip lines parallel to the warp direction of the glass cloth. The wiring width was 130 μm. The spacing between the two differential lines was half the warp pitch (25,000 / Wt) of the glass cloth used, and each pair of differential wiring was offset in the weft direction by 9 / 8 of the warp pitch. This line arrangement allowed for the acquisition of skew data, including the combination of the line with the highest effective dielectric constant, where the glass component directly below the line is maximized, and the line with the lowest effective dielectric constant, where the resin component directly below the line is maximized. Skew for 100 mm of lines was measured using a network analyzer (Keysight Technologies, product name: N5227B).

[0089] From the results of the measurement, the maximum value of the skew value at eight points was evaluated as follows: ⊚ when it was less than 2.5 ps / 100 mm; ◯ when it was 2.5 ps / 100 mm or more but less than 3.5 ps / 100 mm; and × when it was 3.5 ps / 100 mm or more.

[0090] [Example 2] In this example, a glass cloth corresponding to IPC4412 standard #1280 (yarn used: D500 (fiber diameter 5.0 μm, yarn weight 10.1 g / 1000 m), warp weave density: 59 threads / 25 mm, weft weave density: 59 threads / 25 mm, weight per unit area: 48 g / m) was used. ２ The surface-treated spread glass cloth and copper-clad laminate were obtained in exactly the same manner as in Example 1, except that the above-mentioned woven fabric was woven.

[0091] Next, the warp and weft widths, strand thicknesses, and skews were measured in exactly the same manner as in Example 1, and the warp width average, weft width average, spread area ratio S, warp width spread ratio Lt, weft width spread ratio Ly, the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness, and the ratio Rt / Ry of the maximum / minimum difference Rt of the warp glass strand thickness to the maximum / minimum difference Ry of the weft glass strand thickness were calculated to evaluate the skew. The results are shown in Table 1.

[0092] Example 3 In this example, a surface-treated spread glass cloth and a copper-clad laminate were obtained in exactly the same manner as in Example 1, except that a glass cloth was woven using glass fibers (glass strands) formed by bundling 200 glass filaments having a relative dielectric constant of 4.5 (measurement frequency 10 GHz) and the fiber-opening treatment was carried out by hydraulic pressure spreading using a jet spray at a water pressure of 5.0 MPa.

[0093] Next, the warp and weft widths, strand thicknesses, and skews were measured in exactly the same manner as in Example 1, and the warp width average, weft width average, spread area ratio S, warp width spread ratio Lt, weft width spread ratio Ly, the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness, and the ratio Rt / Ry of the maximum / minimum difference Rt of the warp glass strand thickness to the maximum / minimum difference Ry of the weft glass strand thickness were calculated to evaluate the skew. The results are shown in Table 1.

[0094] [Example 4] In this example, a surface-treated spread glass cloth and a copper-clad laminate were obtained in exactly the same manner as in Example 3, except that yarns dried without contact in a chamber maintained at 120°C in the warping step were used as the warp yarns of the glass cloth, and the opening treatment was carried out by hydraulic opening using a jet spray at a water pressure of 7.0 MPa.

[0095] Next, the warp and weft widths, strand thicknesses, and skews were measured in exactly the same manner as in Example 1, and the warp width average, weft width average, spread area ratio S, warp width spread ratio Lt, weft width spread ratio Ly, the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness, and the ratio Rt / Ry of the maximum / minimum difference Rt of the warp glass strand thickness to the maximum / minimum difference Ry of the weft glass strand thickness were calculated to evaluate the skew. The results are shown in Table 1.

[0096] [Example 5] In this example, a glass cloth corresponding to IPC4412 standard #2116 (yarn used: E250 (fiber diameter 7.0 μm, yarn weight 20.2 g / 1000 m), warp weave density: 59 threads / 25 mm, weft weave density: 57 threads / 25 mm, weight per unit area: 95 g / m) was used. ２ The surface-treated spread glass cloth and copper-clad laminate were obtained in exactly the same manner as in Example 1, except that the above-mentioned woven fabric was woven.

[0097] Next, the warp and weft widths, strand thicknesses, and skews were measured in exactly the same manner as in Example 1, and the warp width average, weft width average, spread area ratio S, warp width spread ratio Lt, weft width spread ratio Ly, the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness, and the ratio Rt / Ry of the maximum / minimum difference Rt of the warp glass strand thickness to the maximum / minimum difference Ry of the weft glass strand thickness were calculated to evaluate the skew. The results are shown in Table 1.

[0098] Comparative Example 1 In this comparative example, a surface-treated glass cloth and a copper-clad laminate were obtained in exactly the same manner as in Example 1, except that no opening treatment was carried out.

[0099] Next, the warp and weft widths, strand thicknesses, and skews were measured in exactly the same manner as in Example 1, and the warp width average, weft width average, spread area ratio S, warp width spread ratio Lt, weft width spread ratio Ly, the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness, and the ratio Rt / Ry of the maximum / minimum difference Rt of the warp glass strand thickness to the maximum / minimum difference Ry of the weft glass strand thickness were calculated to evaluate the skew. The results are shown in Table 1.

[0100] In this comparative example, the spread area ratio S, the warp width spread ratio Lt, and the weft width spread ratio Ly were calculated using the widths of warp and weft yarns that had not been subjected to the spread treatment.

[0101] [Comparative Example 2] In this comparative example, a surface-treated spread glass cloth and a copper-clad laminate were obtained in exactly the same manner as in Example 1, except that the glass cloth was opened by hydraulic opening using a fan-shaped spray at a water pressure of 6.0 MPa.

[0102] Next, the warp and weft widths, strand thicknesses, and skews were measured in exactly the same manner as in Example 1, and the warp width average, weft width average, spread area ratio S, warp width spread ratio Lt, weft width spread ratio Ly, the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness, and the ratio Rt / Ry of the maximum / minimum difference Rt of the warp glass strand thickness to the maximum / minimum difference Ry of the weft glass strand thickness were calculated to evaluate the skew. The results are shown in Table 1.

[0103] [Comparative Example 3] In this comparative example, a surface-treated spread glass cloth and a copper-clad laminate were obtained in exactly the same manner as in Example 1, except that the glass cloth was spread by a non-contact ultrasonic spreading treatment in which the glass cloth was passed through water vibrated by an ultrasonic vibrator at 60 Hz.

[0104] Next, the warp and weft widths, strand thicknesses, and skews were measured in exactly the same manner as in Example 1, and the warp width average, weft width average, spread area ratio S, warp width spread ratio Lt, weft width spread ratio Ly, the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness, and the ratio Rt / Ry of the maximum / minimum difference Rt of the warp glass strand thickness to the maximum / minimum difference Ry of the weft glass strand thickness were calculated to evaluate the skew. The results are shown in Table 1.

[0105]

[0106] From Table 1, it is clear that the glass cloths of Examples 1 to 5, in which the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness is in the range of 0.3 to 0.9, can reduce skew when used in printed wiring boards.

[0107] On the other hand, it is clear that the glass cloths of Comparative Examples 1 to 3, in which the ratio σt / σy of the standard deviation σt of the warp glass strand thickness to the standard deviation σy of the weft glass strand thickness is greater than 0.9, are unable to reduce skew when used in printed wiring boards.

Claims

1. A glass cloth having glass fibers as warp and weft, characterized in that the ratio σt / σy of the standard deviation σt of the glass strand thickness of the warp to the standard deviation σy of the glass strand thickness of the weft of the glass cloth is in the range of 0.3 to 0.

9.

2. The glass cloth according to claim 1, characterized in that the glass cloth has an open area ratio S calculated from the warp weave density Wt, the warp average width Bt, the weft weave density Wy, and the weft average width By using the following formula (1) in the range of 90 to 100%.

3. The glass cloth according to claim 1, characterized in that the ratio Rt / Ry of the maximum-minimum difference Rt, which is the difference between the maximum and minimum values ​​of the thickness of the warp glass strands, to the maximum-minimum difference Ry, which is the difference between the maximum and minimum values ​​of the thickness of the weft glass strands, is in the range of 0.3 to 0.

9.

4. The glass cloth according to claim 1, characterized in that the warp width openness Lt calculated by the following formula (2) is in the range of 60 to 83%, and the weft width openness Ly calculated by the following formula (3) is in the range of 85% or more.

5. The glass cloth according to claim 1, characterized in that the glass cloth has a thickness in the range of 18 to 100 μm.

6. A prepreg comprising the glass cloth according to any one of claims 1 to 5.

7. The prepreg according to claim 6, wherein the difference between the relative dielectric constant of the glass cloth and the relative dielectric constant of the matrix resin of the prepreg is in the range of 1.5 to 3.

0.

8. A printed wiring board comprising the prepreg according to claim 6.

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