Glass cloth, prepreg, and printed circuit board

Abstract

The object of this invention is to provide a low-dielectric glass cloth that imparts excellent insulation reliability to a prepreg, and a prepreg and a printed circuit board using the low-dielectric glass cloth. The glass cloth of this invention is constructed by using glass yarn comprising a plurality of glass filaments as warp and weft yarns, and in the following formula (1), the weight reduction coefficient, calculated as the product of the weight reduction rate of the glass components during a heat treatment at 380°C for 2 hours and the average radius of the aforementioned glass filaments, is 0.38 to 0.9, and the whiteness is 95 or higher. Weight reduction coefficient = (1) the aforementioned weight reduction rate (%) × the aforementioned average radius of the glass filaments (μm)...(1)

Description

Technical Field

[0001] This invention relates to a glass cloth, a prepreg, and a printed circuit board. Prior Technology

[0002] With the rapid development of information and communication technology in recent years, data communication and / or signal processing have begun to be carried out at high capacity and high speed, leading to a significant increase in the dielectric constant of printed circuit boards used in electronic devices. Therefore, many low-dielectric glass cloths have been proposed for use in the construction of printed circuit boards.

[0003] For example, the low dielectric glass cloth disclosed in Patent Document 1, compared with the previously commonly used E glass cloth, has a large amount of B2O3 added to the glass composition, while adjusting the amount of other components such as SiO2, thereby achieving a low dielectric constant. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2007-262632 Summary of the Invention

[0005] [The problem the invention aims to solve] If the B2O3 content in the glass yarn is increased to reduce the dielectric constant of the glass cloth, the elastic modulus of the glass yarn will decrease, making it easier for the glass yarn to be cut during the manufacturing process. Therefore, as described in Patent Document 1, a coating treatment is performed using a sizing agent during the spinning or warping of the glass fiber bundle, and a treatment called heat cleaning is performed after weaving to remove the organic matter, i.e., the sizing agent, adhering to the glass fiber bundle.

[0006] As described in Patent Document 1, conventionally performed thermal cleaning methods include batch thermal cleaning at 350-500°C or continuous thermal cleaning through a heating furnace at a high temperature of 550-700°C. However, it is known that if such thermal cleaning methods are applied to low-dielectric glass cloth, the resulting glass cloth will contain prepreg with poor insulation reliability.

[0007] The present invention was made in view of the above-mentioned problems, and its purpose is to provide a low-dielectric glass cloth that can impart excellent insulation reliability to the prepreg, as well as a prepreg and a printed circuit board using the low-dielectric glass cloth. [Technical means to solve the problem]

[0008] In order to solve the above-mentioned problems, the inventors conducted intensive research and found that by setting the whiteness of a glass yarn with a specific tendency to reduce weight, the above-mentioned problems can be solved, thus completing the present invention.

[0009] That is, the present invention is as follows. [1] A type of glass cloth, It is constructed by using glass yarn containing multiple glass filaments as both warp and weft yarns, and In the following formula (1), the weight reduction coefficient, calculated as the product of the weight reduction rate originating from the glass composition during the heat treatment at 380°C for 2 hours and the average radius of the aforementioned glass monofilament, is 0.38 or more and 0.9 or less. Weight reduction factor = the weight reduction ratio (%) × the average radius of the glass filament (μm) ... (1) Whiteness is above 95. [2] As described in [1], the glass cloth, among which The above-mentioned glass cloth The Si content, converted from SiO2, is 40-60% by mass. The B content, calculated as B2O3, is 15-30% by mass. [3] As described in [1] or [2], the glass cloth, in which The above Fe content is calculated as 0.001~0.10% by mass in Fe2O2 form. [4] As described in any of [1] to [3], its glass cloth, It has a dielectric constant of less than 5.0 at a frequency of 1 GHz. [5] A prepreg having: The glass cloth described in any of [1] to [4]; and The glass cloth contains an impregnated matrix resin. [6] A printed circuit board, It possesses the glass cloth described in any of [1] to [4]. [Effects of the Invention]

[0010] According to the present invention, a low-dielectric glass cloth that can impart excellent insulation reliability to a prepreg, as well as a prepreg and a printed circuit board using the low-dielectric glass cloth, can be provided. Implementation

[0011] The following describes in detail the embodiments of the present invention (hereinafter referred to as "the present embodiments"), but the present invention is not limited thereto and various changes can be made without departing from its spirit.

[0012] [Glass cloth] The glass cloth of this embodiment is composed of glass yarn containing a plurality of glass filaments as warp and weft yarns, and in the following formula (1), the weight reduction coefficient, calculated as the product of the weight reduction rate of the glass components during the heat treatment at 380°C for 2 hours and the average radius of the glass filaments, is 0.38 or more and 0.90 or less, and the whiteness is 95 or more. Weight reduction factor = weight reduction ratio (%) × average radius of glass fiber (μm) ... (1)

[0013] It is known that when using low-dielectric-constant glass cloth obtained through previous thermal cleaning, printed circuit boards with poor insulation reliability are obtained. The greater the low-dielectric effect of the glass cloth, the worse the insulation reliability tends to be. The reason for this is unclear, but one reason is believed to be that the flame-retardant reaction products of the sizing agent, which should be removed by heating during thermal cleaning, are not removed and remain on the glass cloth. That is, it is speculated that the components constituting the low-dielectric glass cloth have a certain catalytic effect, modifying the sizing agent into flame-retardant components, which are difficult to remove. This situation was not observed in previous E-glass cloths, etc. It is believed that when the residual amount is the same, the reduction in insulation reliability is more significant in low-dielectric glass cloths than in E-glass cloths, etc. Furthermore, low-dielectric glass cloths tend to have glass-constant components that easily volatilize at high temperatures, thus limiting the possibility of insufficient high-temperature treatment during thermal cleaning. Therefore, in this embodiment, a glass cloth with a specific tendency to reduce weight is specified.

[0014] Furthermore, in this embodiment, the whiteness of the glass cloth is also adjusted. The glass cloth of this embodiment is obtained through a desizing step, as described below, by removing the sizing agent adhering to the glass yarn. In this desizing step, the sizing agent adhering to the glass yarn is removed by heat treatment of the glass cloth. However, in glass cloths that are difficult to heat treat as described above, the removal of the sizing agent is insufficient, leaving residue on the glass cloth. An investigation of this residue revealed that there is relatively little sizing agent residue on the surface of the glass cloth, and even if residue remains, it is mostly a whitish gray substance that is easily and smoothly removed physically. In contrast, it is known that in the complex areas of the glass yarn, such as the weave (the intersection of warp and weft yarns), there is a greater amount of darker-colored, viscous substance that is difficult to remove. It can be inferred that in the complex areas of the glass yarn, the sizing agent is not easily removed, and viscous substances (reaction products of flame retardancy) are generated during heat treatment. Further research revealed that this viscous substance has relatively high hygroscopicity, which increases the hygroscopicity of the glass cloth and reduces insulation reliability. Moreover, it was found that the parts of the glass cloth that tend to lose weight are particularly prone to moisture absorption. If the viscous substance adheres to these parts, it will further reduce insulation reliability.

[0015] In this embodiment, whiteness is used as an indicator of the amount of viscous material, and a specific whiteness value or higher is specified for the glass cloth that meets a certain weight reduction tendency. This provides a glass cloth that imparts excellent insulation reliability to printed circuit boards. The structure of this embodiment will be described in more detail below.

[0016] (Weight reduction factor) The weight reduction factor (hereinafter also referred to as "weight reduction factor"), which is the product of the weight reduction rate of the glass component and the average radius of the glass filaments when the glass cloth is heated at 380°C for 2 hours, is 0.38 to 0.90, preferably 0.42 to 0.85, and even more preferably 0.46 to 0.80.

[0017] "Weight reduction rate derived from glass components" refers to the weight reduction rate during heat treatment at 380°C for 2 hours, which is caused by the disappearance of glass components due to volatilization during the heat treatment. As described below, when surface treatment agents such as silane coupling agents are attached to the glass cloth, or when a large amount of organic impurities are attached, the weight reduction rate in this embodiment is calculated after removing the physically adsorbed surface treatment agents such as silane coupling agents or organic impurities with a good solvent such as alcohol or acetone. Therefore, the weight reduction rate of the glass cloth after heat treatment to remove these attached components that decompose at 380°C is the weight reduction rate derived from glass components.

[0018] Furthermore, it was confirmed that the weight reduction rate depends on the diameter of the glass fiber. The weight reduction rate varies with the diameter of the glass fiber; the smaller the diameter, the greater the weight reduction. On the other hand, the product of the weight reduction rate and the fiber radius is not affected by the fiber diameter and remains approximately a fixed value. Therefore, in this embodiment, the weight reduction coefficient is standardized using the fiber diameter.

[0019] Since the weight reduction factor is 0.38 or higher, maintaining this state makes the material susceptible to the influence of hygroscopic viscous substances, which can easily lead to a decrease in the insulation reliability of the obtained prepreg. Specifically, assuming the residual amount of viscous substances is the same, the decrease in insulation reliability tends to be more pronounced in low-dielectric glass cloths than in E-glass cloths with a smaller weight reduction factor. In contrast, in this embodiment, whiteness is used as an indicator of the residual amount of viscous substances. By defining and combining the weight reduction tendency and whiteness within specific ranges, the insulation reliability of the obtained printed circuit board can be improved. Furthermore, by having a weight reduction factor of 0.90 or lower, the hygroscopicity of the glass itself is not excessive, thus suppressing a significant decrease in insulation reliability.

[0020] The method for determining the weight reduction rate can be performed in the following order. First, place the glass cloth in a dryer at 105℃±5℃ and dry for 60 minutes. Then, transfer the glass cloth to a desiccator and allow it to cool until room temperature. After cooling, weigh the glass cloth in units of less than 0.1 mg (glass cloth weight a). Next, heat the glass cloth at 380℃ for 2 hours. Then, transfer the glass cloth to a desiccator and allow it to cool until room temperature. After cooling, weigh the glass cloth in units of less than 0.1 mg (glass cloth weight b after heat treatment). Then, calculate the weight reduction due to heat treatment and use the following formula (2) to calculate the weight reduction rate (%). Weight reduction rate (%) = (ab) / a × 100···(2)

[0021] The weight reduction rate obtained in the above manner is preferably 0.05~0.7%, more preferably 0.1~0.5%, and even more preferably 0.12~0.4%. Since the weight reduction rate is 0.05% or higher, maintaining this state can easily lead to a decrease in insulation reliability. However, by adjusting the whiteness as described below, in this embodiment, the decrease in insulation reliability can be suppressed, and, depending on the composition of the glass cloth, a glass cloth with a lower dielectric constant can also be obtained. Furthermore, by keeping the weight reduction rate below 0.7%, a significant decrease in insulation reliability can be suppressed.

[0022] Next, the average diameter of the glass filaments constituting the glass cloth is measured according to JIS R3420, and the average filament diameter, which is half of the filament diameter, is calculated. In this embodiment, when simply referred to as glass filament, it refers to a single glass filament. Furthermore, the average radius of the glass filament used to calculate the weight reduction factor is the average radius before heat treatment. The average radius of the glass filament calculated in this way is preferably 1.25~4.5 μm, more preferably 1.5~3.75 μm, and even more preferably 1.75~2.7 μm.

[0023] Furthermore, the glass cloth used in the above-mentioned method for determining the weight loss ratio can be appropriately pretreated. For example, in the glass cloth drawn from the intermediate roll after self-sizing treatment (hot cleaning), there are no adhering substances on the glass fibers, so it can be directly used in the above-mentioned method for determining the weight loss ratio.

[0024] On the other hand, when determining the weight reduction ratio by taking glass cloth coated with surface treatment agents such as silane coupling agents as the object, the surface treatment agents such as silane coupling agents that are physically adsorbed can be removed by washing with good solvents such as alcohols and acetone beforehand, and then the weight reduction coefficient can be determined by the above method.

[0025] Furthermore, "physically adsorbed silane coupling agents" refers to silane coupling agents attached to glass fibers, not silane coupling agents that are chemically bonded to glass fibers. In contrast, silane coupling agents that are chemically bonded to glass fibers are called "chemically adsorbed silane coupling agents."

[0026] Furthermore, when the glass cloth contains organic impurities (such as starch-based sizing agents applied during the glass yarn manufacturing process, combustion residues of the sizing agents applied in the early stage during the hot cleaning step), the organic impurities attached to the glass cloth can be removed in advance by washing with alcohols, acetone, etc., and then the weight reduction factor can be calculated by the above method.

[0027] The above-mentioned cleaning process removes physically adsorbed silane coupling agents or organic impurities, not chemically adsorbed silane coupling agents. However, even after heating at 380°C for 2 hours, chemically adsorbed silane coupling agents will not decompose, or even if some decompose, it will not exceed the error range. Therefore, in the determination of the weight reduction rate in this embodiment, it is not necessary to remove chemically adsorbed silane coupling agents through pretreatment.

[0028] Furthermore, based on the viewpoint of simplifying the determination of whether pretreatment is required, the weight loss rate can be measured using glass cloth that has been pre-washed with good solvents such as alcohols or acetone. In this way, whether it is glass cloth drawn from the middle roll after self-de-sizing treatment (heat cleaning) or glass cloth with physically adsorbed silane coupling agents or organic impurities, the weight loss rate can be measured in the same state.

[0029] Alternatively, when determining the aforementioned weight reduction coefficient, the amount of surface treatment agent or organic impurities before and after heating can be quantified, and the weight reduction due to the surface treatment agent can be subtracted from the obtained weight reduction to obtain the weight reduction coefficient originating from the glass component. As a method for determining the weight reduction due to the surface treatment agent, known methods such as the quantitative method for silane coupling agents described in Japanese Patent No. 6472082 can also be used.

[0030] The weight reduction factor can be adjusted by increasing or decreasing the content of relatively volatile components, such as B, in the glass cloth. Similarly, it can be adjusted by increasing or decreasing other components.

[0031] Furthermore, the weight reduction factor can also be adjusted by adjusting the space filling rate of the glass in the glass cloth (weave density or thickness), adjusting the dissociation of the monofilaments constituting the glass yarn bundle through fiber opening processing, adjusting the monofilament diameter of the glass yarn used, etc., and can also be adjusted by increasing or decreasing the opportunity for the glass surface to be exposed to a high-temperature gas atmosphere. That is, the weight reduction factor is not solely determined by the composition of the glass cloth.

[0032] (Whiteness) The whiteness should be 95 or higher, preferably 95.5 or higher, even better 96 or higher, and ideally 97 or higher. Furthermore, there is no specific upper limit to the whiteness, but the upper limit reflects the hue of the glass itself, and is approximately 99.5. A whiteness of 95 or higher further improves insulation reliability. Whiteness can be measured according to JIS 2000 L1916, the method for determining the colorimetry of fiber products.

[0033] Furthermore, whiteness can be improved by reducing the amount of sizing agent (or paste) used, increasing the heat treatment temperature, changing the composition of the sizing agent, or changing the composition of the glass cloth.

[0034] (composition) The composition of the glass cloth of this embodiment will now be described. Furthermore, the composition of the glass cloth is synonymous with the composition of the glass yarn constituting the glass cloth. In the composition of the glass cloth of this embodiment, the Fe content, calculated as Fe2O3, is preferably 0.001% by mass or more and 0.10% by mass, more preferably 0.001% by mass or more and 0.08% by mass, and even more preferably 0.01% by mass or more and 0.05% by mass. By having an Fe content of 0.10% by mass or less, the insulation reliability of the obtained prepreg can be further improved. This is presumably because by reducing the Fe content, which is considered to have more general catalytic activity, to a specific range, the modification of the sizing agent into a flame-retardant component can be suppressed. There is no particular limitation on the lower limit of the Fe content, which is 0.001% by mass or more. The Fe content can be adjusted according to the amount of raw materials used in the production of glass fibers, the refining and removal of raw materials using magnetic filters, or the addition of Fe.

[0035] The Si content of the glass cloth, converted from SiO2, is preferably 40-60% by mass, more preferably 45-55% by mass, and even more preferably 47-53% by mass, with a value of 48-52% by mass. Si is the component that forms the skeletal structure of the glass yarn. With a Si content of 40% by mass or more, the strength of the glass yarn is further improved, and the tendency for glass cloth breakage to be suppressed in subsequent steps such as the manufacturing process of the glass cloth and the manufacturing of the prepreg. Furthermore, with a Si content of 40% by mass or more, there is a tendency for the dielectric constant of the glass cloth to be further reduced. On the other hand, with a Si content of 60% by mass or less, the viscosity during melting is further reduced during the manufacturing process of the glass fibers, resulting in glass fibers with a more homogeneous glass composition, and thus the glass cloth becomes less prone to breakage. The Si content can be adjusted according to the amount of raw materials used in the production of glass fibers.

[0036] The boron (B) content of the glass cloth, converted from B₂O₃, is preferably 15-30% by mass, more preferably 17-28% by mass, further preferably 20-27% by mass, further preferably 21-25% by mass, and further preferably 21.5-24% by mass. With a B content of 15% by mass or higher, there is a tendency for a further decrease in the dielectric constant. Furthermore, with a B content of 30% by mass or lower, moisture absorption resistance is improved, and there is a tendency for a further improvement in insulation reliability. The B content can be adjusted according to the amount of raw material used in the glass fiber production. Moreover, in cases where changes may occur during glass fiber production, the feed rate can be adjusted in advance to anticipate these situations.

[0037] The preferred Fe content of the glass cloth is 0.001~0.1% by mass, more preferably 0.001~0.07% by mass, and even more preferably 0.001~0.05% by mass. Here, the Fe content is a value calculated using F². By keeping the Fe content within the above range, there is a tendency to further suppress the breakage of the glass cloth. There is no limitation on the reasons for suppressing the breakage of the glass cloth by adjusting the Fe content, but the following viewpoints exist. Fe reduces the viscosity of the molten glass during the glass manufacturing process. Therefore, by having a specific range of Fe content, when metallic components such as Fe are incorporated into the glass structure, they will be uniformly dispersed rather than localized, thereby forming a uniform glass. It is believed that by uniformly dispersing Fe, the aforementioned effect of inhibiting the modification of sizing agents into flame-retardant components can be more effectively manifested. The Fe content can be adjusted according to the amount of raw materials used in the production of glass fibers.

[0038] Furthermore, glass fibers may contain other compositions besides those mentioned above. There are no particular limitations on these other compositions; examples include Al, Ca, Mg, P, Na, K, Ti, and Zn.

[0039] The Al content of the glass cloth, converted to Al2O3, is preferably 10-20% by mass, more preferably 12-18% by mass, and even more preferably 14-17% by mass. Within the above-mentioned Al content range, there is a tendency for further improvement in electrical properties and strength. The Al content can be adjusted according to the amount of raw material used in the production of glass fibers.

[0040] The Ca content of the glass cloth, converted to CaO, is preferably 1.0~6.0% by mass, more preferably 2.0~5.0% by mass, and even more preferably 2.5~4.0% by mass. With a Ca content of 1.0% by mass or higher, the viscosity during melting is further reduced during the glass fiber manufacturing process, tending to produce glass fibers with a more homogeneous glass composition. Furthermore, with a Ca content of 6.0% by mass or lower, there is a tendency to further increase the dielectric constant. The Ca content can be adjusted according to the amount of raw materials used in glass fiber production.

[0041] The Mg content of the glass cloth, converted from MgO, is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, further preferably 0.01 to 1.0% by mass or less, further preferably 0.05 to 0.5% by mass or less, and further preferably 0.05 to 0.3% by mass or less. With a Mg content of 5.0% by mass or less, during the fiber opening or surface treatment steps in glass cloth manufacturing, the glass cloth is less prone to breakage when passing through extrusion rollers or clamping rollers in a wet state. Furthermore, phase separation during glass fiber manufacturing is suppressed, further improving the moisture resistance of the obtained glass fibers. As a result, the obtained printed circuit board is less affected by high humidity environments, reducing the environmental dependence of the dielectric constant. The Mg content can be adjusted according to the amount of raw materials used in glass fiber production.

[0042] The phosphorus (P) content of the glass cloth, converted from P₂O₅, is preferably 1.0 to 7.0% by mass, more preferably 2.0 to 6.0% by mass, and even more preferably 3.0 to 6.0% by mass, and even more preferably 3.0 to 5.5% by mass. With a P content of 1.0% by mass or higher, there is a tendency for the dielectric constant to decrease further. Furthermore, with a P content of 7.0% by mass or lower, during the fiber-opening or surface-treatment steps in glass cloth manufacturing, the glass cloth is less prone to breakage when passing through extrusion rollers or clamping rollers in a wet state. Moreover, phase separation during glass fiber manufacturing is suppressed, further improving the moisture resistance of the obtained glass fibers. Therefore, the resulting printed circuit board is less affected by high-humidity environments, reducing the environmental dependence of the dielectric constant. The P content can be adjusted according to the amount of raw material used in glass fiber production.

[0043] Furthermore, the aforementioned contents can be determined using ICP (inductively coupled plasma) emission spectrometry. Specifically, regarding the Si and B contents, the weighed glass cloth sample can be decomposed under pressure with sodium hydroxide, dissolved in dilute nitric acid, filtered, and then the insoluble components can be dissolved with sodium carbonate. The filtrates are then combined and diluted to a final volume, and the resulting sample is analyzed using ICP emission spectrometry.

[0044] Regarding the Fe, Al, Ca, Ma, and P contents, the weighed glass cloth sample can be decomposed by heating with perchloric acid, nitric acid, hydrochloric acid, and hydrogen fluoride, then dissolved by heating with dilute aqua regia, filtered, and the filtrate diluted to a final volume. Subsequently, the undissolved components are decomposed by heating with sulfuric acid, nitric acid, hydrochloric acid, and hydrogen fluoride, and the solution is then determined. The obtained sample is then analyzed by ICP emission spectroscopy. Furthermore, the ICP emission spectroscopy instrument can be the PS3520VDD II manufactured by Hitachi High-Tech Science.

[0045] Furthermore, regarding the fluoride (F) content, a weighed glass cloth sample can be burned in a tubular electric furnace, and the generated gas can be absorbed into an absorbent liquid. The fluoride ions (F-) in this solution can then be determined using an ion chromatography system to ascertain the fluoride content in the sample. Moreover, the combustion apparatus can be an automated sample combustion device (AQF-2100S) manufactured by Mitsubishi Chemical Analytech, and the measuring instrument can be an ICS-1500 ion chromatography system manufactured by Thermo Fisher Scientific.

[0046] The elastic modulus of the glass cloth is preferably 50-70 GPa, more preferably 50-63 GPa, further preferably 53-63 GPa, and even more preferably 53-60 GPa. The lower the elastic modulus of the glass cloth, the easier it is to break. Therefore, with an elastic modulus of 50 GPa or higher, during the manufacturing steps of the glass cloth, such as the fiber opening or surface treatment steps, the glass cloth tends to be less prone to breakage when passing through extrusion rollers or clamping rollers in a wet state. Furthermore, in subsequent steps such as the manufacturing of the prepreg, the glass cloth tends to be less prone to breakage when passing through a slit to control the resin impregnation amount. Also, with an elastic modulus of 70 GPa or lower, there is a tendency for the dielectric constant to decrease further. The elastic modulus can be measured using the method described in the examples. Furthermore, the elastic modulus can be adjusted by utilizing the composition of the glass cloth.

[0047] The dielectric constant of the glass cloth in this embodiment is preferably 5.0 or less, more preferably 4.7 or less, further preferably 4.5 or less, and even more preferably 4.0 or less at a frequency of 1 GHz. Furthermore, in this embodiment, when referring to the dielectric constant, unless otherwise specified in advance, it refers to the dielectric constant at a frequency of 1 GHz.

[0048] (constitute) Glass yarn is obtained by bundling multiple strands of glass yarn and twisting as needed, glass cloth is obtained by weaving the above-mentioned glass yarn as warp and weft yarn. Classify glass yarn as complex filament and glass filament as monofilament.

[0049] The mean diameters of the glass filaments constituting the warp and weft yarns are each independently preferably 2.5~9 μm, more preferably 3.0~7.5 μm, and by extension 3.5~5.4 μm. By resorting to the average diameter of the glass filaments being within the above range, there is a tendency to further improve the processability when processing the obtained substrate using a mechanical drill or carbon dioxide gas laser, UV-YAG (Ultraviolet-Yttrium Aluminum Garnet, ultraviolet-titanium aluminum garnet) laser. Printed circuit boards capable of achieving thin and high-density packages. In particular, if the average diameter becomes less than 5.4 μm, the weight reduction under the same heating time increases, thus there is a tendency to improve the hygroscopicity of the glass cloth itself, in addition, the increase in the surface area of ​​the glass filament per unit volume, thus the increase in the adhesion of the sticky material derived from the hygroscopicity of the sizing agent, promotes the hygroscopicity of the glass cloth, therefore, the improvement effect of the insulation reliability of the present embodiment becomes more important. Also, by means of an average diameter of 2.5 μm or more, there is a tendency to not easily produce breakage when the glass cloth is in a wet state by extrusion roller or clamp roller, etc., in the fabrication step of glass cloth such as fiber opening step or surface treatment step. Furthermore, in subsequent steps such as the fabrication of the prepreg, there is also a tendency to not easily produce breakage when passing the glass cloth through the slit for the purpose of controlling the dip content of the resin into the glass cloth.

[0050] The weaving density of warp and weft yarns constituting the glass fabric is preferably 30~120 book / 25 mm, preferably 40~110 book / 25 mm, and further preferably 50~100 book / 25 mm.

[0051] The thickness of the glass cloth is preferably 8~100 μm, preferably 10~70 μm, and further preferably 12~50 μm. By resorting to the thickness of the glass cloth within the above range, there is a tendency to obtain thin and relatively high strength glass cloth. Further, the weight reduction factor depends on the area of ​​the glass cloth, on the diameter of the threads constituting the glass cloth, and therefore, it is difficult to depend on the thickness. The tendency is maintained at least within the above-mentioned thickness range.

[0052] The fabric weight (weight per unit area) of glass cloth is preferably 8~250g / m2, preferably 8~100g / m2, and further preferably 8~50g / m2, especially 8~35g / m2.

[0053] There are no particular limitations on the weave structure of glass cloth; examples include plain weave, square plain weave, satin weave, and twill weave. Among these, plain weave is preferred.

[0054] (Surface treatment) Fiberglass cloth can also be surface-treated using surface treatment agents. There are no particular limitations on surface treatment agents; for example, silane coupling agents can be used, and water, organic solvents, acids, dyes, pigments, surfactants, etc., can also be used as needed.

[0055] There are no particular limitations on silane coupling agents; for example, compounds represented by formula (1) can be cited. X(R)3-nSiYn···(1) (In formula (1), X is an organic functional group having at least one of the amino group and unsaturated double bond group, Y is an alkoxy group, n is an integer of 1 to 3, and R is a group selected from the group consisting of methyl, ethyl and phenyl).

[0056] X is preferably an organic functional group having at least three of the following: an amino group and an unsaturated double bond group; X is more preferably an organic functional group having at least four of the following: an amino group and an unsaturated double bond group.

[0057] The aforementioned alkoxy group can be used in any form, but from the viewpoint of stabilizing the glass cloth, an alkoxy group with 5 or fewer carbon atoms is preferred.

[0058] As silane coupling agents, examples include N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane and its hydrochloride, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropylmethyldimethoxysilane and its hydrochloride, N-β-(N-di(vinylbenzyl)aminoethyl)-γ-aminopropyltrimethoxysilane and its hydrochloride, and N-β-(N-di(vinylbenzyl)aminoethyl)-N-γ-(N-vinylbenzyl)-γ-aminopropyltrimethoxysilane and its hydrochloride. Its hydrochloride, N-β-(N-benzylaminoethyl)-γ-aminopropyltrimethoxysilane and its hydrochloride, N-β-(N-benzylaminoethyl)-γ-aminopropyltriethoxysilane and its hydrochloride, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropyltriethoxysilane, aminopropyltrimethoxysilane, vinyltrimethoxysilane, methacryloxypropyltrimethylsilane, acryloxypropyltrimethoxysilane and other known monomers, or mixtures thereof.

[0059] The molecular weight of the silane coupling agent is preferably 100-600, more preferably 150-500, and even more preferably 200-450. Preferably, two or more silane coupling agents with different molecular weights are used. By treating the surface of the glass cloth with two or more silane coupling agents with different molecular weights, the density of the surface treatment agent on the surface of the glass cloth increases, and there is a tendency to enhance its reactivity with the matrix resin.

[0060] [Manufacturing Method of Fiberglass Cloth] The manufacturing method of the glass cloth in this embodiment is not particularly limited. For example, the following method can be cited, which includes a weaving step of weaving glass yarn to obtain glass cloth, a fiber opening step of opening the glass yarn of the glass cloth, and a desizing step of removing the sizing agent attached to the glass yarn of the glass cloth. In addition, a surface treatment step using a surface treatment agent such as a silane coupling agent may also be included as needed.

[0061] The weaving method is any method that weaves the weft and warp yarns in a manner that forms a specific weaving structure; there are no particular restrictions. Furthermore, there are no particular restrictions on the fiber opening method; for example, methods such as using water spray (high-pressure water fiber opening), vibrating washing machines, ultrasonic water, and rolling mills can be used for fiber opening processing.

[0062] Furthermore, there are no particular limitations on the desizing method; for example, removing the sizing agent by heating can be used. Moreover, the sizing agent is used in weaving processes to protect the glass yarn from breakage. There are no particular limitations on this type of sizing agent; for example, starch-based binders and polyvinyl alcohol-based binders can be used. Furthermore, regarding the temperature at which the sizing agent is removed by heating, from the viewpoint of maintaining breaking strength while sufficiently removing the sizing agent, 300-500°C is preferred, more preferably 330-450°C, and even more preferably 350-430°C.

[0063] Furthermore, as a surface treatment method, examples include contacting a surface treatment agent containing a silane coupling agent with glass cloth and then drying it. Alternatively, the contact between the surface treatment agent and the glass cloth can be achieved by immersing the glass cloth in the surface treatment agent, or by applying the surface treatment agent to the glass cloth using a roller coater, a die coater, or a gravure coater. There are no particular limitations on the drying method for the surface treatment agent; for example, hot air drying or electromagnetic wave drying methods can be used.

[0064] [Prepreg] The prepreg of this embodiment includes the aforementioned glass cloth and a matrix resin composition impregnated in the glass cloth. The prepreg with the aforementioned glass cloth further enhances insulation reliability and results in a higher yield of the final product. Furthermore, due to its excellent dielectric properties and moisture resistance, it also provides a printed circuit board with minimal variation in dielectric constant, particularly under high humidity conditions, due to the influence of the operating environment.

[0065] The prepreg of this embodiment can be manufactured in accordance with conventional methods. For example, it can be manufactured by impregnating the glass cloth of this embodiment with a varnish obtained by diluting a matrix resin such as epoxy resin with an organic solvent, and then evaporating the organic solvent in a drying oven to harden the thermosetting resin to stage B (semi-hardened state).

[0066] In addition to the epoxy resins mentioned above, examples of thermosetting resins that can be used as matrix resin compositions include: bismaleimide resins, cyanate ester resins, unsaturated polyester resins, polyimide resins, BT (polybismaleimide triazine) resins, functionalized polyphenylene ether resins, etc.; thermoplastic resins such as polyphenylene ether resins, polyether amide resins, liquid crystal polymers (LCPs) of fully aromatic polyesters, polybutadiene, fluoropolymers, etc.; and mixed resins thereof. From the viewpoint of improving dielectric properties, heat resistance, solvent resistance, and compressive molding properties, resins obtained by modifying thermoplastic resins with thermosetting resins can also be used as matrix resin compositions.

[0067] Furthermore, the matrix resin composition may also contain: inorganic fillers such as silicon dioxide and aluminum hydroxide; flame retardants such as bromine-based, phosphorus-based, and metal hydroxides; other silane coupling agents; heat stabilizers; antistatic agents; ultraviolet absorbers; pigments; colorants; lubricants, etc.

[0068] Printed Circuit Board The printed circuit board of this embodiment incorporates the aforementioned glass cloth. This printed circuit board further enhances insulation reliability and results in a higher yield rate for the final product. Furthermore, due to its excellent dielectric properties and moisture resistance, it also exhibits minimal variation in dielectric constant under environmental conditions, particularly in high humidity environments. [Example]

[0069] The present invention will now be described in more detail using examples and comparative examples. The present invention is not limited to the following examples.

[0070] [Properties of Glass Cloth] The physical properties of glass cloth, specifically the thickness of the glass cloth, the diameter and number of filaments constituting the warp and weft yarns, and the weaving density (weave density) of the warp and weft yarns, are measured according to JIS R3420.

[0071] [Weight Reduction Factor] The weight reduction factor was determined in the following order. First, the glass cloth pulled from the middle roll is placed in a dryer at 105℃±5℃ and dried for 60 minutes. Then, the glass cloth is transferred to a desiccator and allowed to cool until room temperature. After cooling, the weight of the glass cloth is measured in units of less than 0.1 mg (weight a of the glass cloth). Next, the glass cloth is heated at 380℃ for 2 hours. Then, the glass cloth is transferred to a desiccator and allowed to cool until room temperature. After cooling, the weight of the glass cloth is measured in units of less than 0.1 mg (weight b of the glass cloth after heat treatment). Then, the weight reduction due to heat treatment is calculated, and the weight reduction rate (%) is calculated according to the following formula (2). Weight reduction rate (%) = (ab) / a × 100···(2)

[0072] Subsequently, the diameter of the monofilament was determined according to Method B of JIS R3420, and half of that value was taken as the radius of the monofilament. Furthermore, although Method B of JIS R3420 randomly measures the diameter of 25 filament cross sections, here the diameter of all the monofilaments constituting the glass yarn (multifilament) was measured, and the average diameter of the filaments was calculated. The weight reduction coefficient is calculated using the weight reduction rate (%) and the average radius of the glass fiber (μm) according to the following formula (1). Weight reduction factor = weight reduction ratio (%) × average radius of glass fiber (μm) ... (1)

[0073] [Composition of Glassy Yarn] The composition of the glass cloth was determined using ICP (inductively coupled plasma) emission spectrometry. Specifically, regarding the Si and B content, a weighed glass cloth sample was decomposed under pressure with sodium hydroxide, dissolved in dilute nitric acid, filtered, and the insoluble components were dissolved in sodium carbonate. The filtrates were combined and diluted to a final volume, and the resulting sample was analyzed using ICP emission spectrometry.

[0074] Furthermore, the Fe, Al, Ca, Ma, and P contents were obtained by heating and decomposing the weighed glass cloth sample with perchloric acid, nitric acid, hydrochloric acid, and hydrogen fluoride, dissolving it in dilute aqua regia, filtering and separating the components, making up the volume of the filtrate, and then decomposing the undissolved components with sulfuric acid, nitric acid, hydrochloric acid, and hydrogen fluoride, followed by dissolution and determination. The results were then obtained by ICP emission spectroscopy analysis. Moreover, the ICP emission spectroscopy instrument used was a Hitachi High-Tech Science PS3520VDD II.

[0075] Furthermore, the fluoride (F-) content was determined by burning a weighed glass cloth sample in a tubular electric furnace, absorbing the generated gas into an absorbent liquid, and then measuring the fluoride ions (F-) in the solution using an ion chromatography system. The combustion apparatus used was an automated sample combustion device (AQF-2100S) manufactured by Mitsubishi Chemical Analytech, and the measuring instrument was an ICS-1500 ion chromatography system manufactured by Thermo Fisher Scientific.

[0076] [Measurement of Whiteness] Whiteness was measured using a spectrophotometer (CM-2600d, manufactured by Konica Minolta) according to JIS 2000 L1916, the method for determining the colorimetry of fiber products. Furthermore, the whiteness was measured with the glass cloth folded and overlapped eight times, and the average of five measurements was taken.

[0077] [Evaluation of Insulation Reliability] <Substrate Manufacturing Method> The glass cloth obtained in the Examples and Comparative Examples was impregnated with epoxy resin varnish (a mixture of 40 parts by weight of low-brominated bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation), 10 parts by weight of o-cresol type phenolic varnish epoxy resin (manufactured by Mitsubishi Chemical Corporation), 50 parts by weight of dimethylformamide, 1 part by weight of dicyandiamide, and 0.1 parts by weight of 2-ethyl-4-methylimidazole), and dried at 160°C for 2 minutes. Examples 1-3, Comparative Examples 1-6, and Reference Example 1 yielded prepregs with a resin content of 78% by weight, Example 4 yielded a resin content of 73% by weight, and Example 5 yielded a resin content of 58% by weight. These prepregs were stacked on a specific number of sheets, and then copper foil with a thickness of 12 μm was stacked on top and bottom. The substrate was heated and pressurized at 175°C and 40 kg / cm2 for 60 minutes to obtain a substrate with a thickness of approximately 0.4 mm. A circuit pattern with through holes spaced 0.15 mm apart is fabricated on the copper foil on both sides of the obtained substrate to obtain a test substrate for insulation reliability evaluation.

[0078] <Evaluation Methods for Insulation Reliability of Substrates> The obtained test substrate was subjected to a 10 V voltage in a gas atmosphere of 120°C and 85%RH, and the change in resistance was measured. Cases where the resistance did not reach 1 MΩ within 500 hours of the start of the test were considered as insulation failures.

[0079] One hundred test substrates were fabricated, and the insulation reliability of 30 prepregs selected from these substrates was determined. Based on the test results, the insulation reliability was evaluated using the following evaluation criteria. A: There is no test substrate that shows poor insulation. B: There is one prepreg indicating poor insulation. C: There are two prepregs that indicate poor insulation. D: There are more than 3 prepregs that indicate poor insulation.

[0080] [Examples 1-3] Using an air-jet loom, glass yarn with the composition shown in Table 1 (average filament diameter: 4.0 μm, number of filaments: 50) was woven to obtain glass cloth with a warp and weft yarn density of 95 yarns / 25 mm and a thickness of 14 μm. Subsequently, a heat cleaning treatment was performed at 400°C for 24 hours, followed by a fiber-opening step using high-pressure water spray to obtain an intermediate glass cloth with a width of 1280 mm and a length of 2000 m. Then, a surface treatment was performed using a silane coupling agent to produce the final glass cloth.

[0081] [Example 4] Low-dielectric glass yarn with an average filament diameter of 5.0 μm and containing 100 filaments was woven. The warp yarn weaving density was set to 65 filaments, and the weft yarn weaving density was set to 67 filaments / 25 mm to produce glass cloth. Otherwise, the glass cloth rolls were obtained in the same manner as in Example 2. The obtained glass cloth had a thickness of 30 μm, and its composition is shown in Table 1.

[0082] [Example 5] Low-dielectric glass yarn with an average filament diameter of 7.0 μm and containing 200 filaments was woven, and the warp and weft yarn weaving density was set to 52.5 filaments / 25 mm to produce glass cloth. Otherwise, the glass cloth rolls were obtained in the same manner as in Example 2. The obtained glass cloth had a thickness of 92 μm, and its composition is shown in Table 1.

[0083] [Example 6] After hot cleaning, the glass cloth was washed with water in an attempt to remove any residual sizing agent residue from the hot cleaning process. Otherwise, the glass cloth rolls were obtained in the same manner as in Comparative Example 5. The composition of the obtained glass cloth is shown in Table 1.

[0084] [Compare Examples 1, 3, and 6] Except for the different composition of the glass yarn, the glass cloth rolls were obtained in the same manner as in Example 1. The composition of the obtained glass cloth is shown in Table 1.

[0085] [Comparative Example 2] The heat cleaning process was set to 48 hours, and otherwise the glass cloth rolls were obtained in the same manner as in Comparative Example 1. The composition of the obtained glass cloth is shown in Table 1.

[0086] [Comparative Example 4] The heat cleaning process was set to 48 hours, and otherwise the glass cloth rolls were obtained in the same manner as in Comparative Example 3. The composition of the obtained glass cloth is shown in Table 1.

[0087] [Comparative Example 5] Before the heat cleaning process, the glass cloth was washed with water to reduce the amount of sizing agent before the heat cleaning process. Otherwise, the glass cloth roll was obtained in the same manner as in Comparative Example 3. The composition of the obtained glass cloth is shown in Table 1.

[0088] [Reference Example 1] The composition of the glass yarn was changed to a so-called E-glass composition. Otherwise, the glass cloth roll was obtained in the same manner as in Example 1. The composition of the obtained glass cloth is shown in Table 1.

[0089] [Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Reference Example 1 Composition (mass %) Si (SiO2 conversion) 49.7 49.7 49.7 49.7 49.7 49.7 49.7 49.7 49.7 49.7 49.7 50.8 54.2 B (B2O3 conversion) twenty four twenty four twenty four twenty four twenty four twenty four twenty four twenty four twenty four twenty four twenty four 29.4 6.2 Al (Al2O3 conversion) 16.5 16.5 16.5 16.5 16.5 16.5 16.5 16.5 16.5 16.5 16.5 13.2 14.1 Ca (CaO conversion) 3.7 3.7 3.7 3.7 3.7 3.7 3.7 3.7 3.7 3.7 3.7 4 22.8 Mg (MgO conversion) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 1.3 0.8 P(P2O5 conversion) 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.2 0.0 Fe (Fe2O3 conversion) 0.08 0.04 0.01 0.04 0.04 0.130 0.420 0.420 0.130 0.130 0.130 0.08 0.430 F(F2 conversion) 0.020 0.017 0.018 0.017 0.018 0.019 0.020 0.020 0.019 0.019 0.019 0.018 0.480 Other features Weight reduction factor 0.61 0.61 0.61 0.58 0.52 0.60 0.60 0.60 0.61 0.60 0.60 0.93 0.16 Whiteness 95.6 96.2 97.0 96.4 96.8 95.2 91.0 93.3 94.0 94.4 94.6 95.4 93.9 evaluate Insulation reliability test B A A A A B D C C C C C A

[0090] When using the glass cloth of the embodiments, substrates with high insulation reliability can be obtained, and the production rate of substrates with poor insulation reliability is low. Furthermore, the glass cloth of Reference Example 1 has poor whiteness, but the production rate of substrates with poor insulation reliability is low. This means that the problem of reduced insulation reliability is not easily generated in previous E-glass and the like, and is a problem unique to low dielectric glass cloth.

[0091] On the other hand, it can be seen that the glass cloths of Comparative Examples 1 and 3 have lower whiteness and poorer insulation reliability. It is speculated that this is due to the formation of a flame-retardant viscous substance.

[0092] Furthermore, it can be seen that in Comparative Examples 2 and 4, although the whiteness was gradually improved by extending the hot cleaning treatment time to twice the original value, the improvement was not significant.

[0093] Furthermore, it can be seen that in Comparative Example 5, although an attempt was made to wash off the sizing agent before the hot cleaning process, there was no significant difference compared with Comparative Example 3. In Comparative Example 6, the glass cloth with a higher weight reduction coefficient and easier detachment of volatile components had poorer insulation reliability. [Industrial Applicability]

[0094] This invention is industrially applicable as a low-dielectric glass cloth for use in prepregs, etc.

Claims

1. A glass cloth comprising glass yarn containing a plurality of glass filaments as warp and weft yarns, wherein the weight reduction coefficient, calculated as the product of the weight reduction rate of the glass components during a heat treatment at 380°C for 2 hours and the average radius of the glass filaments, is 0.38 to 0.9, and the weight reduction coefficient is calculated as follows: Weight reduction coefficient = Weight reduction rate (%) × Average radius of the glass filaments (μm) ... (1) Whiteness is 95 or higher, Weight reduction rate is 0.05 to 0.7%, Average radius of the glass filaments is 1.25 to 4.5 μm, Si content of the glass cloth (converted from SiO2) is 40 to 60% by mass, B content (converted from B2O3) is 15 to 30% by mass, Fe content (converted from Fe2O3) is 0.001 to 0.10% by mass, and the insulation spacing obtained from the glass cloth is 0.

15. The resistance of a 1 mm substrate was measured by applying a 10 V voltage in a gas atmosphere at 120°C and 85%RH. The resistance was greater than 1 MΩ within 500 hours after the start of the measurement.

2. The glass cloth of claim 1 has a dielectric constant of 5.0 or less at a frequency of 1 GHz.

3. A prepreg comprising: a glass cloth as claimed in claim 1 or 2; and a matrix resin impregnated therein.

4. A printed circuit board having a glass cloth as claimed in claim 1 or 2.