Glass cloth, prepreg, and printed wiring board

Abstract

The present invention relates to a glass cloth, a prepreg, and a printed wiring board. The glass cloth of the present invention is woven from glass filaments, the glass constituting the glass filaments has a bulk dielectric loss tangent of 0.0010 or less, the glass cloth has a loss on ignition value of 0.01 mass% or more and less than 0.12 mass%, and the glass cloth has a void count of 180 or less after 5 minutes of immersion in castor oil.

Description

Technical Field

[0001] This invention relates to glass cloth, prepreg, and printed wiring boards. Background Technology

[0002] Currently, the high performance of information terminals such as smartphones and the high-speed communication represented by 5G are developing. Against this backdrop, especially for printed circuit boards (PCBs) used in high-speed communication, there is a demand not only for improved heat resistance, which has always been required, but also for further improvements in the dielectric properties of their insulating materials (e.g., lower dielectric loss tangent). Similarly, there is a desire to improve the dielectric properties of the prepregs used in the insulating materials of PCBs, as well as the glass fibers and glass cloth contained within those prepregs.

[0003] To achieve low dielectric properties in insulating materials, methods for constructing insulating materials using prepregs made by impregnating glass cloth with a low dielectric resin (hereinafter referred to as "matrix resin") are known (Patent Documents 1 and 2). Patent Documents 1 and 2 describe how end-modified polyphenylene ethers with vinyl or methacryloyloxy groups are beneficial for low dielectric properties and heat resistance, and how the modified polyphenylene ether is used as a matrix resin.

[0004] Furthermore, to improve the dielectric properties of prepregs, a method for constructing prepregs using low-dielectric glass is also known (Patent Document 3). In Patent Document 3, glass fibers with a SiO2 content of 98% to 100% by mass are used. Moreover, Patent Document 3 describes a method for constructing prepregs using low-dielectric glass cloth, which possesses various requirements such as surface treatment with a silane coupling agent having unsaturated double bond groups and a loss on ignition value of 0.12% to 0.40% by mass. Additionally, as coupling agents, aminosilanes or aminosilane hydrochlorides are known, for example (Patent Document 4).

[0005] Furthermore, patent documents 5 and 6 report fiber-opening techniques for glass cloth using water pressure from a water jet machine or similar device, and fiber-opening techniques for glass cloth using ultrasonic waves or similar methods. By performing fiber-opening treatment on the glass cloth, it is difficult for air bubbles, known as voids, to form in the prepreg and printed wiring board. It is known that reducing voids can improve the heat resistance and insulation of the printed wiring board; therefore, the fiber-opening process is important in the manufacturing process of glass cloth.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2019 / 065940

[0009] Patent Document 2: International Publication No. 2019 / 065941

[0010] Patent Document 3: Japanese Patent Application Publication No. 2018-127747

[0011] Patent Document 4: Japanese Patent Application Publication No. 2016-98135

[0012] Patent Document 5: Japanese Patent Application Publication No. 2009-263824

[0013] Patent Document 6: Japanese Patent Application Publication No. 2020-158945 Summary of the Invention

[0014] The problem the invention aims to solve

[0015] However, there is room for further research in Patent Documents 1 and 2 regarding the possibility of achieving further improvements in dielectric properties. For example, Patent Documents 1 and 2 do not consider the use of low-dielectric glass as described in Patent Document 3. Furthermore, Patent Document 3 describes problems with glass having a SiO2 composition of 98% to 100% by mass from a practical point of view. Therefore, it is desirable to provide other methods for using such glass fibers to appropriately provide glass cloth and thus prepreg.

[0016] Furthermore, if aminosilane or aminosilane hydrochloride as described in Patent Document 6 is used as a silane coupling agent, delamination easily occurs at the interface between the glass cloth and the matrix resin. As a result, it becomes difficult to ensure various properties. Therefore, from the viewpoint of further improving dielectric properties, there is also room for research on the glass cloth described in Patent Document 4. In other words, it is desirable to provide a new method for achieving low dielectric loss tangent for glass cloth, different from the method of reducing silanol groups present on the surface of the glass cloth as described in Patent Document 4.

[0017] Furthermore, the inventors discovered that quartz glass has a higher hardness than other types of glass, and therefore the glass cloth made of quartz glass yarn cannot be sufficiently split by the conventional fiber splitting process described in Patent Documents 5 and 6.

[0018] Therefore, the object of the present invention is to provide a glass cloth and prepreg that can suitably obtain the advantages of low-dielectric glass, represented by quartz glass cloth, and surface treatment of glass fibers using a specific silane coupling agent, and can achieve improved dielectric properties (e.g., reduced dielectric loss tangent). Furthermore, the object of the present invention is to provide printed wiring boards, integrated circuits, and electronic devices that can also achieve improved insulation reliability and heat resistance by using glass cloth processed in a manner that results in higher fiber openness compared to conventional methods. Moreover, the object of the present invention is to provide a method for processing glass to suitably obtain the aforementioned glass cloth.

[0019] Solution for solving the problem

[0020] To address the aforementioned problems, the inventors conducted in-depth research, focusing on the type and amount of silane coupling agent chemically bonded to the surface of low-dielectric glass when using glass fibers. They discovered that by controlling the type and amount of silane coupling agent chemically bonded to the glass surface, the heat resistance of the resulting printed wiring board can be ensured, while the dielectric loss tangent of the glass cloth can be appropriately reduced. Furthermore, they found that by using, for example, dry ice blasting to open the glass cloth, the amount of silane coupling agent adhering can be reduced, while simultaneously improving the insulation reliability and heat resistance of the printed wiring board, thus completing the present invention. A portion of the embodiments of the present invention is illustrated below.

[0021] [1] A type of glass cloth, which is made of glass fibers.

[0022] The bulk dielectric loss tangent of the glass constituting the glass filament is below 0.0010.

[0023] The loss on ignition of the glass cloth is greater than 0.01% by mass and less than 0.12% by mass.

[0024] The number of voids in the glass cloth after 5 minutes of impregnation with castor oil is less than 180.

[0025] [2] The glass cloth according to Project 1, wherein the void reduction rate of the glass cloth after 1 minute to 5 minutes when impregnated with castor oil is more than 70%.

[0026] [3] A type of glass cloth, which is a glass cloth woven from glass fibers.

[0027] The bulk dielectric loss tangent of the glass constituting the glass filament is below 0.0010.

[0028] The loss on ignition of the glass cloth is greater than 0.01% by mass and less than 0.12% by mass.

[0029] When the glass cloth is impregnated with castor oil, the void reduction rate is more than 70% from 1 minute to 5 minutes later.

[0030] [4] The glass cloth according to item 1 or 2, wherein the number of voids in the glass cloth after 5 minutes of impregnation with castor oil is less than 160.

[0031] [5] The glass cloth according to item 2 or 3, wherein the void reduction rate of the glass cloth after 1 minute to 5 minutes when impregnated with castor oil is more than 80%.

[0032] [6] The glass cloth according to any one of items 1 to 5, wherein the bulk dielectric loss tangent of the glass constituting the glass filament is 0.0008 or less.

[0033] [7] The glass cloth according to any one of items 1 to 6, wherein the silicon (Si) content in the glass filament is 95.0% to 100% by mass, converted to silicon dioxide (SiO2).

[0034] [8] The glass cloth according to any one of items 1 to 7, wherein the silicon (Si) content in the glass filament is 99.0% to 100% by mass, converted to silicon dioxide (SiO2).

[0035] [9] The glass cloth according to any one of items 1 to 8 has been surface treated.

[0036]

[10] The glass cloth according to item 9, wherein the surface treatment is performed using a silane coupling agent having the structure shown in the following general formula (1).

[0037] X(R) 3-n SiY n ···(1)

[0038] In the formula,

[0039] X is an organic functional group containing one or more unsaturated double bonds with free radical reactivity.

[0040] Y is an alkoxy group on its own.

[0041] n is an integer from 1 to 3.

[0042] R is each independently selected from at least one group chosen from the group consisting of methyl, ethyl, and phenyl.

[0043]

[11] The glass cloth according to item 10, wherein X in the general formula (1) has (meth)acryloyloxy and does not contain an amino group.

[0044]

[12] The glass cloth according to any one of items 1 to 11, wherein the loss on ignition of the glass cloth is less than 0.10% by mass.

[0045]

[13] The glass cloth according to any one of items 1 to 12, wherein the nitrogen content per unit mass is less than 0.004% by mass.

[0046]

[14] The glass cloth according to any one of items 1 to 13, wherein the dielectric loss tangent of the glass cloth at 10 GHz, as determined by the resonance method, is greater than 0 and less than 0.0008.

[0047]

[15] The glass cloth according to any one of items 1 to 14, wherein the dielectric loss tangent at 10 GHz, as determined by the resonance method, is greater than 0 and less than 0.0005.

[0048]

[16] A prepreg comprising a glass cloth as described in any one of items 1 to 15, and a matrix resin impregnated in the glass cloth.

[0049]

[17] The prepreg according to item 16 also contains an inorganic filler.

[0050]

[18] A printed wiring board comprising the prepreg described in item 16 or 17.

[0051]

[19] An integrated circuit comprising the printed wiring board described in item 18.

[0052]

[20] An electronic device comprising the printed wiring board described in item 18.

[0053] The effects of the invention

[0054] According to the present invention, glass cloth and prepregs can be provided that offer the advantages of suitable low-dielectric glass and surface treatment of glass fibers using specific silane coupling agents, and can achieve improved dielectric properties (e.g., reduced dielectric loss tangent). Furthermore, according to the present invention, the prepregs can also be used to provide printed wiring boards, integrated circuits, and electronic devices that also achieve improved heat resistance. Detailed Implementation

[0055] Hereinafter, embodiments of the present invention (hereinafter referred to as "this embodiment") will be described, but the present invention is not limited thereto and various modifications can be made without departing from its spirit.

[0056] In this embodiment, the numerical range indicated by "~" represents a range of values ​​including the values ​​before and after "~" as both the lower and upper limits. Furthermore, in this embodiment, within a range of numerical values ​​described in a stepwise manner, the upper or lower limit value of a certain range can be replaced with the upper or lower limit value of another range described in a stepwise manner. Moreover, in this embodiment, the upper or lower limit value of a certain range can also be replaced with the values ​​shown in the embodiments. Furthermore, in this embodiment, the term "process" not only refers to an independent process, but also includes any process that can achieve its function, even if it cannot be clearly distinguished from other processes.

[0057] [Glass cloth]

[0058] [Overall Composition]

[0059] The glass cloth of this embodiment is woven from glass fibers, the bulk dielectric loss tangent of the glass constituting the glass fibers is 0.0010 or less, the weight loss on ignition of the glass cloth is 0.01% by mass or more and less than 0.12% by mass, and the number of voids in the glass cloth after 5 minutes of impregnation with castor oil is 180 or less. Furthermore, it is preferable that the void reduction rate after 1 minute to 5 minutes of impregnation with castor oil is 70% or more.

[0060] In addition, the second glass cloth in this embodiment is woven from glass fibers, the bulk dielectric loss tangent of the glass constituting the glass fibers is 0.0010 or less, the weight loss on ignition of the glass cloth is 0.01% by mass or more and less than 0.12% by mass, and the porosity reduction rate after 1 minute to 5 minutes when impregnated with castor oil is 70% or more.

[0061] It should be noted that the number of voids after 5 minutes of impregnation of the glass cloth with castor oil is preferably 160 or less. In addition, the void reduction rate after 1 minute to 5 minutes of impregnation of the glass cloth with castor oil is preferably 80% or more.

[0062] Therefore, a glass cloth and prepreg can be provided that can improve dielectric properties (e.g., reduce the dielectric loss tangent) and enhance the heat resistance and insulation reliability of printed wiring boards. Furthermore, through this embodiment, the aforementioned glass cloth having a dielectric loss tangent close to that of the bulk dielectric loss tangent of glass can be obtained.

[0063] The glass cloth of this embodiment can be woven using glass fibers (e.g., glass fibers composed of multiple long glass filaments) as warp and weft yarns. Examples of the weaving structures of the glass cloth include plain weave, basket weave, satin weave, and twill weave. A plain weave structure is preferred.

[0064] The preferred warp and weft yarn density of the glass cloth constituting this embodiment is 10 yarns / inch to 120 yarns / inch (= 10 to 120 yarns / 25.4 mm), more preferably 40 yarns / inch to 100 yarns / inch. If the yarn density is within the above range, the effects of this invention are easily obtained.

[0065] In this embodiment, the unit area weight (mass of the glass cloth) is preferably 8 g / m². 2 ~250g / m 2 More preferably 8g / m 2 ~100g / m 2 Further preferred is 8g / m 2 ~80g / m 2 The preferred value is 8g / m 2 ~50g / m 2If the weight per unit area of ​​the glass cloth is within the above-mentioned range, the effects of the present invention can be easily obtained.

[0066] [Glass fiber]

[0067] The glass fibers constituting the glass cloth of this embodiment can be obtained from low-dielectric glass. Specifically, the bulk dielectric loss tangent of the glass constituting the glass fibers is 0.0010 or less. By using such glass fibers, the dielectric properties of the resulting glass cloth can be improved. From the viewpoint of improving the dielectric properties of the resulting glass cloth, the bulk dielectric loss tangent of the glass is preferably 0.0008 or less, more preferably 0.0006 or less, even more preferably 0.0005 or less, and particularly preferably 0.0003 or less.

[0068] The Si content of the glass filament, calculated as SiO2, is preferably in the range of 95.0% to 100% by mass, more preferably 99.0% to 100% by mass, further preferably 99.5% to 100% by mass, and particularly preferably 99.9% to 100% by mass, when the bulk dielectric loss tangent is below 0.0010. By using this glass filament, the dielectric properties of the resulting glass cloth can be improved.

[0069] The bulk dielectric loss tangent of the glass constituting the glass cloth of this embodiment is in the range of 0.0010 or less, more preferably in the range of 0.0008 or less, even more preferably in the range of 0.0005 or less, and particularly preferably in the range of 0.0004 or less. The bulk dielectric loss tangent of the glass constituting the glass cloth can be measured by the method described in the examples.

[0070] The average filament diameter of the glass filaments constituting the glass fiber is preferably 2.5 μm to 9.0 μm, more preferably 2.5 μm to 7.5 μm, even more preferably 3.5 μm to 7.0 μm, and even more preferably 3.5 μm to 6.0 μm, particularly preferably 3.5 μm to 5.0 μm. If the filament diameter is smaller than the above values, the breaking strength of the filaments decreases, and the resulting glass cloth is prone to fuzzing. Furthermore, if the filament diameter exceeds the above values, the mass of the glass cloth increases, making it difficult to transport or process. Moreover, if the average filament diameter of the glass filaments is within the above range, the effects of the present invention are easily obtained.

[0071] For the glass cloth of this embodiment, from the viewpoint of improving adhesion with the resin used in the prepreg, it is preferable to have the glass fibers surface-treated. The glass fibers can be surface-treated, for example, using titanate-based coupling agents or silane coupling agents. From the viewpoint of easily modifying the functional groups of the resin suitable for each prepreg, it is preferable to use silane coupling agents for surface treatment.

[0072] The nitrogen content per unit mass of the glass cloth is preferably less than 0.004% by mass. This nitrogen content is based, for example, on the amount of amino-containing components in the silane coupling agent. It should be noted that the nitrogen content per unit mass of the glass cloth can be 0 or more.

[0073] [Silane coupling agent]

[0074] The silane coupling agent used in this embodiment preferably has the structure shown in the following general formula (1):

[0075] X(R) 3-n SiY n ···(1)

[0076] (in the formula,

[0077] X is an organic functional group containing one or more unsaturated double bonds with free radical reactivity.

[0078] Y is an alkoxy group on its own.

[0079] n is an integer from 1 to 3.

[0080] R is independently selected from the group consisting of methyl, ethyl, and phenyl groups.

[0081] By using silane coupling agents of general formula (1) to treat the surface of glass cloth, the insulation reliability and heat resistance of printed wiring boards can be easily improved.

[0082] Furthermore, the silane coupling agent of general formula (1) preferably has a (meth)acryloyloxy group in its molecular structure and does not contain an amino group. Silane coupling agents containing an amino group in extremely small amounts or without an amino group have high hydrophobicity. By using such a highly hydrophobic silane coupling agent to surface treat glass filaments as low-dielectric glass, peeling at the interface between the resulting glass cloth and the matrix resin can be suppressed, resulting in improvements in various properties, including dielectric properties (e.g., insulation). It should be noted that in this specification, both the case of surface treatment of glass filaments using a silane coupling agent and the case of surface treatment of glass cloth using a silane coupling agent are included in the concept of surface treatment of glass filaments using a silane coupling agent. There is no particular limitation on the method for evaluating whether an amino group is present; a method using gas chromatography is known. By measuring the amount of nitrogen dioxide produced due to thermal decomposition using a gas chromatograph, it is possible to determine whether the silane coupling agent contains an amino group. Specifically, if the nitrogen content per unit mass of the glass cloth is less than 0.004% by mass, it can be determined that the silane coupling agent does not contain amino groups. It should be noted that the nitrogen content per unit mass of the glass cloth can be 0 or higher. In cases where the amino-containing component in the silane coupling agent is extremely small or absent, depending on the measurement method, baseline distortion may lead to negative values ​​for the "content of amino-containing components in the silane coupling agent" and consequently, the "nitrogen content per unit mass of the glass cloth." However, if the principle of a trace amount of nitrogen per unit mass of the glass cloth is met, this situation is also included in the concept of "less than 0.004% by mass."

[0083] Here, the inventors speculate that one reason for the increase in the dielectric loss tangent of the glass cloth is the presence of unwanted components that are directly physically attached to the surface of the glass filament without forming chemical bonds with it. Examples of unwanted components include, for instance, residues or modifications of silane coupling agents that are not thoroughly washed away and are directly physically attached to the surface of the glass filament without forming chemical bonds. From the viewpoint of suppressing the residue and generation (modification) of such unwanted components that should be reduced from the surface of the glass filament, it is preferable that X in general formula (1) is an organic functional group containing one or more unsaturated double bond groups with free radical reactivity and not containing an amino group.

[0084] In general formula (1), X does not contain an amino group. For example, X in general formula (1) preferably does not contain amines such as primary amines, secondary amines, tertiary amines, or ammonium cations such as quaternary ammonium cations. As a result, the amount of silane coupling agent chemically bonded to the surface of the glass fiber can be appropriately controlled, and the dielectric properties of the glass cloth can be appropriately improved. In addition, the heat resistance of the obtained printed wiring board can also be ensured.

[0085] To stabilize the glass cloth, it is preferable that at least one of the multiple Ys in general formula (1) is an alkoxy group with 1 to 5 carbon atoms (an alkoxy group with 1, 2, 3, 4 or 5 carbon atoms). More preferably, half or all of the multiple Ys are alkoxy groups with 1 or more carbon atoms and 5 or fewer carbon atoms.

[0086] The silane coupling agent shown in general formula (1) can be used alone or in combination with two or more silane coupling agents. For example, two or more silane coupling agents with different X values ​​in general formula (1) can be used in combination. In addition, two or more silane coupling agents with different R values ​​in general formula (1) can be used in combination.

[0087] The content of the silane coupling agent of general formula (1) in the silane coupling agent used for surface treatment of glass fibers is preferably 95.0% to 100% by mass, more preferably 96.5% to 100% by mass, further preferably 98.0% to 100% by mass, even more preferably 99.0% to 100% by mass, and particularly preferably 99.9% to 100% by mass. Therefore, it is easier to improve various properties, including dielectric properties, of the resulting glass cloth. The silane coupling agent used in this embodiment may contain silane coupling agents other than those shown in general formula (1) (other silane coupling agents), or may contain components other than silane coupling agents within the scope of this invention.

[0088] The molecular weight of the silane coupling agent represented by general formula (1) is preferably 100 to 600, more preferably 150 to 500, and even more preferably 200 to 450. It is preferable to use a combination of multiple silane coupling agents with different molecular weights within the above range as the silane coupling agent. This allows for suitable surface treatment of glass fibers using different types of silane coupling agents, and increases the density of the silane coupling agent on the glass surface. Consequently, there is a tendency to further improve the reactivity with the matrix resin. When using a combination of multiple silane coupling agents with different molecular weights, it is preferable that at least two of the silane coupling agents are represented by general formula (1) and fall within the above molecular weight range.

[0089] The silane coupling agent represented by general formula (1) is preferably nonionic. For example, X in general formula (1) preferably has at least one group selected from the group consisting of vinyl and (meth)acryloyloxy, more preferably (meth)acryloyloxy. This ensures suitable reactivity with the matrix resin and easily improves the heat resistance and reliability of the printed wiring board. It should be noted that (meth)acryloyloxy includes at least one of methacryloyloxy and acryloyloxy.

[0090] As silane coupling agents represented by general formula (1), vinyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 5-hexenyltrimethoxysilane, and acryloyloxypropyltrimethoxysilane are preferred, for example. The effects of the present invention are readily obtained with these silane coupling agents. Including the above, the following silane coupling agents can be listed as silane coupling agents represented by general formula (1).

[0091] [Table 1]

[0092] X Y n R vinyl Carbon number 1, 2, 3, 4, 5 1 At least one of methyl, ethyl and phenyl vinyl Carbon number 1, 2, 3, 4, 5 2 At least one of methyl, ethyl and phenyl vinyl Carbon number 1, 2, 3, 4, 5 3 At least one of methyl, ethyl and phenyl Methacryloyloxy Carbon number 1, 2, 3, 4, 5 1 At least one of methyl, ethyl and phenyl Methacryloyloxy Carbon number 1, 2, 3, 4, 5 2 At least one of methyl, ethyl and phenyl Methacryloyloxy Carbon number 1, 2, 3, 4, 5 3 At least one of methyl, ethyl and phenyl Acryloyloxy Carbon number 1, 2, 3, 4, 5 1 At least one of methyl, ethyl and phenyl Acryloyloxy Carbon number 1, 2, 3, 4, 5 2 At least one of methyl, ethyl and phenyl Acryloyloxy Carbon number 1, 2, 3, 4, 5 3 At least one of methyl, ethyl and phenyl

[0093] [Weight loss on ignition of glass cloth]

[0094] In this embodiment, the weight loss on ignition of the glass cloth is 0.01% by mass or more and less than 0.12% by mass. Therefore, a printed wiring board with good insulation and a lower dielectric loss tangent can be provided. The weight loss on ignition is an indicator that indirectly reflects the amount of silane coupling agent used for surface treatment of the glass cloth, and can be measured according to the method described in JIS R 3420.

[0095] The weight loss on ignition of the glass cloth is preferably 0.01% by mass or more and 0.10% by mass or less, more preferably 0.02% by mass or more and 0.09% by mass or less, and even more preferably 0.03% by mass or more and 0.08% by mass or less. If the weight loss on ignition exceeds the above values, there is a tendency for an excessive amount of silane coupling agent chemically bonded to the surface of the glass filaments. In this case, the dielectric loss tangent of the glass cloth, and consequently the dielectric loss tangent of the resulting printed wiring board, tends to decrease. On the other hand, if the weight loss on ignition is less than the above values, there is a tendency for an insufficient amount of silane coupling agent bonded to the surface of the glass filaments. In this case, the heat resistance of the resulting printed wiring board tends to deteriorate.

[0096] In this regard, as described above, low-dielectric glass is used as the glass fiber, and the nitrogen content per unit mass of the glass cloth is preferably less than 0.004% by mass, more preferably less than 0.0035%, further preferably less than 0.003%, and particularly preferably less than 0.0025%. Generally, due to the high hardness of SiO2, glass cloth using low-dielectric glass is sometimes indicated to be prone to brittle fracture. However, by ensuring good compatibility between the low-dielectric glass and the type of silane coupling agent used for its surface treatment, and by keeping the weight loss on ignition of the glass cloth within the aforementioned range, the glass cloth of this embodiment can further reduce the possibility of brittle fracture.

[0097] [Method for determining the dielectric loss tangent of glass cloth]

[0098] The dielectric properties of the glass cloth in this embodiment can be measured using the resonance method. A preferred measuring device for the resonance method is a split cylindrical resonator. Compared to conventional methods that evaluate dielectric properties by fabricating a printed circuit board as the test sample, the resonance method allows for simpler and more accurate measurements. This is not limited to theoretical reasons, but is because the resonance method is suitable for evaluating low-loss materials in the high-frequency region. Other methods for evaluating dielectric properties besides the resonance method include, for example, the lumped constant method or the reflection transmission method. However, the lumped constant method is complex because it requires two electrodes to clamp the test sample to form a capacitor. Furthermore, in the reflection transmission method, when evaluating low-loss materials, the effect of port matching characteristics is easily observed, making it difficult to accurately evaluate the dielectric loss tangent of the sample.

[0099] When measuring the dielectric properties of the glass cloth of this embodiment, which can be applied to printed wiring boards, especially printed wiring boards for high-speed communications, the measurable range of the measuring equipment is preferably a range suitable for both the frequency dielectric constant (Dk) and the dielectric loss tangent (Df). For example, Dk is preferably 1.1 Fm. -1 ~50Fm -1 The range is more preferably 1.5 Fm. -1 ~10Fm -1 The range is further preferably 2.0 Fm. -1 ~5Fm -1 The range. Furthermore, Df is preferably 1.0 × 10⁻⁶. -6 ~1.0×10 -1 The range is more preferably 1.0 × 10 -5 ~5.0×10 -1 The range is further preferably 5.0 × 10 -5 ~1.0×10 -2 The range.

[0100] The measurable frequency of the measuring device is preferably 10 GHz or higher. If the frequency is 10 GHz or higher, it is possible to evaluate the characteristics within a frequency band region envisioned in the case of glass cloth actually used as a printed wiring board for high-speed communication.

[0101] The preferred measurement area is 10 mm². 2 The above is preferred, with 15mm being more ideal. 2 The above is further preferred to be 20mm. 2 In conclusion, measuring the dielectric properties of glass cloth over a larger area improves the reliability of inspection results.

[0102] The thickness of the measurable sample is preferably 3 μm to 300 μm, more preferably 5 μm to 200 μm, and even more preferably 7 μm to 150 μm. This improves the reliability of the inspection results for glass cloth.

[0103] Based on the bulk dielectric loss tangent, the dielectric loss tangent of the glass cloth can be estimated to a certain extent, and vice versa. On the other hand, the dielectric loss tangent of the glass cloth sometimes differs from that of the bulk dielectric loss tangent. The main reasons for this difference, while not expected to be theoretically constrained, include, for example: (1) the generation of thermal oxides and deterioration products of the sizing agent physically adhering to the surface of the glass fibers; (2) the residue and generation of unwanted components that are not thoroughly washed away, physically adhering to the surface of the glass fibers but not forming chemical bonds with the surface of the glass fibers. Therefore, by selecting the type of sizing agent and optimizing various conditions in the manufacturing process of the glass cloth, the dielectric loss tangent of the glass cloth can be controlled within the above-mentioned range.

[0104] In this embodiment, the dielectric loss tangent of the glass cloth measured at 10 GHz using the above-described resonance method is preferably 0.0008 or less, more preferably 0.0005 or less, even more preferably 0.00045 or less, even more preferably 0.000425 or less, and particularly preferably 0.0004 or less. With such a glass cloth, a prepreg capable of improving dielectric properties can be provided.

[0105] [Impregnation properties of glass cloth]

[0106] In this embodiment, the number of voids after 5 minutes of impregnation with castor oil on the first glass cloth is 180 or less. This results in good impregnation properties between the glass cloth and the resin, thus improving the insulation and heat resistance of the printed wiring board. The number of voids after 5 minutes is preferably in the range of 160 or less, more preferably 140 or less, even more preferably 120 or less, even more preferably 110 or less, and particularly preferably 100 or less. The fewer the voids after 5 minutes, the better the impregnation and the stronger the adhesion between the glass cloth and the resin. Therefore, even with a small amount of surface treatment agent adhering to the surface of the glass cloth, a printed wiring board with good insulation reliability and heat resistance can be provided. To achieve a void number of 180 or less after 5 minutes of impregnation with castor oil, this can be achieved, for example, by treating the glass cloth with the silane coupling agent shown in the above general formula (1), by dry ice blasting, or by fiber-opening methods such as bending.

[0107] When the first glass cloth of this embodiment is impregnated with castor oil, the void reduction rate after 1 minute to 5 minutes is preferably 70% or more. Furthermore, it is preferably in the range of 80% or more, more preferably in the range of 82% or more, even more preferably in the range of 84% or more, even more preferably in the range of 86% or more, and particularly preferably in the range of 88% or more. The number of voids can be measured using the method described in the examples.

[0108] In this embodiment, the void reduction rate of the second glass cloth impregnated with castor oil is 70% or more after 1 minute to 5 minutes. Therefore, the glass cloth and resin exhibit good impregnation properties, thereby improving the insulation and heat resistance of the printed wiring board. The void reduction rate after 1 minute to 5 minutes is preferably in the range of 80% or more, more preferably in the range of 82% or more, further preferably in the range of 84% or more, even more preferably in the range of 86% or more, and particularly preferably in the range of 88% or more. A higher void reduction rate after 1 minute to 5 minutes means that voids in the glass cloth fibers are more easily eliminated in processes such as impregnating the glass cloth with resin as a varnish or processing the printed wiring board by heating and pressurizing the prepreg, thus improving the adhesion between the glass cloth and the resin. Furthermore, by improving the adhesion between the glass cloth and the resin, even with a small amount of surface treatment agent adhering to the surface of the glass cloth, a printed wiring board with good insulation reliability and heat resistance can be provided. To achieve a void reduction rate of over 70% from 1 minute to 5 minutes after castor oil impregnation, this can be achieved, for example, by treating the glass cloth with the silane coupling agent shown in the above general formula (1), by dry ice blasting, or by fiber opening methods such as bending. The void reduction rate can be measured using the methods described in the examples.

[0109] [Method for manufacturing glass cloth]

[0110] The manufacturing method of the first glass cloth in this embodiment includes a glass processing method.

[0111] The glass processing method of this embodiment includes:

[0112] Process (A) reduces the amount of sizing agent in glass fibers with a bulk dielectric loss tangent of less than 0.0010;

[0113] Process (B) reduces the silane coupling agent from the glass cloth in such a manner that the loss on ignition is 0.01% by mass or more and less than 0.12% by mass; and

[0114] Process (C) involves opening the glass cloth in such a way that the number of voids after 5 minutes of impregnation with castor oil is less than 180.

[0115] Therefore, it is possible to provide a glass cloth and prepreg that can improve the dielectric properties and heat resistance of printed wiring boards.

[0116] The manufacturing method of the second glass cloth in this embodiment includes a glass processing method.

[0117] The glass processing method of this embodiment includes:

[0118] Process (A) reduces the amount of sizing agent in glass fibers with a bulk dielectric loss tangent of less than 0.0010;

[0119] Process (B) reduces the silane coupling agent from the glass cloth in such a manner that the loss on ignition is 0.01% by mass or more and less than 0.12% by mass; and

[0120] Process (C) involves opening the glass cloth in such a way that the void reduction rate after 1 minute to 5 minutes when the glass cloth is impregnated with castor oil is more than 70%.

[0121] Therefore, a glass cloth and prepreg that can improve dielectric properties and heat resistance of printed wiring boards can be provided.

[0122] The glass processing method of this embodiment can be applied to glass fibers, and also to glass cloth. In other words, the process of weaving glass fibers to obtain glass cloth can be set before, during, or after the glass processing method of this embodiment. It should be noted that in the glass processing method of this embodiment, "reduction" means, for example, removing at least a portion of the sizing agent or silane coupling agent, allowing for the generation of residues that are not completely removed.

[0123] The process (A) that reduces the amount of sizing agent may, for example, include:

[0124] The desizing process (heating and degreasing process) involves heating the glass at a temperature of 650℃ to 1000℃.

[0125] Therefore, it is easy to reduce the amount of sizing agent in the glass. By reducing the amount of thermally oxidized deterioration products of the sizing agent remaining in the form of physical adhesion to the glass surface, it is easy to effectively suppress the rise of the dielectric loss tangent of the resulting glass cloth.

[0126] Heating of the glass cloth can be carried out sequentially or continuously in a closed or open system, or a combination of closed and open systems. From a productivity point of view, it is particularly preferred to use a device with an unwinding mechanism and a winding mechanism to heat the glass cloth in a roll-to-roll manner.

[0127] In the case of a closed system, from the viewpoint of heating means, it is preferable to place the glass cloth inside the heating furnace, and / or from the viewpoint of storage space and heating range, it is preferable to heat the glass cloth while storing it in a wound state. Furthermore, from the viewpoint of improving the removal efficiency of organic matter or shortening the removal time of organic matter, it is preferable to heat the glass cloth while conveying it inside the heating furnace.

[0128] In the case of an open system, from the viewpoint of the heated area, it is preferable to heat the glass cloth while it is being fed. The glass cloth can be fed using, for example, an unwinding mechanism and a winding mechanism.

[0129] [Heating Furnace]

[0130] The heating method for the furnace is not limited to a specific method; any method that can heat the glass cloth to a surface temperature higher than 650°C is acceptable. Various methods such as electric heaters and burners can be considered. In addition, multiple methods can be combined for heating. Heating the glass cloth in an environment with an oxygen concentration of 10% or higher is preferred. For this purpose, a gas-fired single-radiant tube burner or an electric heater is preferred.

[0131] From the perspective of heating efficiency, the heating furnace preferably has means for venting the gas generated inside the furnace and / or means for air circulation. Gas venting means may include, for example, nozzles, gas pipes, orifices, exhaust valves, etc. Air circulation means may include, for example, fans, air conditioning equipment, etc.

[0132] In addition, in order to efficiently remove organic matter adhering to the surface of the glass cloth, a continuous method that allows the glass cloth to be continuously passed through the heating furnace while being heated is preferred, rather than an intermittent method that winds the glass fiber fabric onto a core and heats the glass cloth at a specific atmosphere temperature.

[0133] To thoroughly remove organic matter adhering to the surface of the glass cloth, the surface temperature of the glass cloth is preferably above 650°C, more preferably above 700°C, even more preferably above 750°C, and particularly preferably above 800°C. The surface temperature of the glass cloth can be measured, for example, using a thermocouple or a non-contact thermometer.

[0134] [Contact components for heating glass cloth]

[0135] As a method for heating glass cloth, the aforementioned heating furnace can be used, but from the viewpoint of low operating costs, the glass cloth can also be heated by bringing a component heated to a specified temperature into contact with the glass cloth.

[0136] The shape of the contact component is not particularly limited, as long as it can heat the surface temperature of the glass cloth to exceed 650°C. From the perspective of ease of glass cloth transport, a roller shape is preferred. As a component capable of heating the glass cloth in a roller shape, a roller that can be used in high-temperature areas, has relatively low temperature unevenness in the width direction, and heats by induction heating is preferred. When heating the glass cloth using the contact component, it is assumed that the temperature of the contact component is approximately equal to the surface temperature of the glass cloth.

[0137] In addition, in order to remove the carbon deposits that adhere to the heating roller as the glass cloth is continuously heated, the heating roller method described above is preferably a method that includes a mechanism for removing dirt or foreign matter adhering to the roller, such as a scraper.

[0138] The process (B) of attaching the silane coupling agent may include, for example, at least one of the following processes:

[0139] The coating process uses a treatment solution with a concentration of 0.1% to 0.5% by mass to attach the silane coupling agent to the surface of the glass.

[0140] The fixing process involves heating and drying to fix the silane coupling agent onto the glass surface.

[0141] In addition, in order to reduce silane coupling agent residues and modifiers that cannot be reduced by water, the glass cloth can be easily surface-treated by washing with a highly hydrophobic organic solvent or an organic solvent with hydroxyl groups that has a high affinity for silane coupling agent residues and modifiers after the fixed process.

[0142] As a method for applying the treatment solution to glass in the coating process, the following methods can be used: (a) immersing or passing the glass in the treatment solution stored in a bath (hereinafter referred to as "immersion method"), and (b) applying the treatment solution to the glass using a roller coater, die coater, or gravure coater. When using the immersion method, it is preferable to set the immersion time of the glass in the treatment solution to 0.5 seconds or more and 1 minute or less. Furthermore, after applying the treatment solution to the glass, the solvent contained in the treatment solution can be heated and dried using methods such as hot air or electromagnetic waves.

[0143] The concentration of the treatment solution is preferably 0.1% to 0.5% by mass, more preferably 0.1% to 0.45% by mass, and even more preferably 0.1% to 0.4% by mass. This makes it easier to perform suitable surface treatment on the glass.

[0144] In the fixing process, to ensure sufficient reaction between the silane coupling agent and the glass, the heating and drying temperature is preferably 80°C or higher, more preferably 90°C or higher. Furthermore, to prevent the deterioration of the organic functional groups in the silane coupling agent, the heating and drying temperature is preferably 300°C or lower, more preferably 180°C or lower.

[0145] As a method for removing silane coupling agent residues and modifiers, known methods such as immersion and spraying can be used, and heating and cooling can also be performed as needed. To prevent the dissolved glass cloth residue from re-adhering, the washed glass cloth is preferably desiccated using a squeeze roller or similar method before final drying. There are no particular limitations on the organic solvent used; for example, highly hydrophobic organic solvents include:

[0146] Saturated chain aliphatic hydrocarbons such as n-pentane, isopentane, n-hexane, isohexane, n-heptane, isoheptane, n-octane, isooctane, 2,2,4-trimethylpentane (isooctane), n-nonane, isononane, n-decane, isodecanane, 2,2,4,6,6-pentamethylheptane (isododecane);

[0147] Cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, and other saturated cyclic aliphatic hydrocarbons;

[0148] Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, and triethylbenzene;

[0149] Halogen-containing solvents such as chloroform, dichloromethane, and dichloroethane.

[0150] Organic solvents with high affinity for silane coupling agent modifiers include: alcohols such as methanol, ethanol, and butanol; ketones such as acetone and methyl ethyl ketone; and ethers such as methyl ethyl ether and diethyl ether.

[0151] Amides such as N,N-dimethylformamide and N,N-dimethylacetamide;

[0152] Dimethyl sulfoxide, etc. From the viewpoint of making the dielectric loss tangent of the obtained glass cloth close to the dielectric loss tangent of the bulk phase, aromatic hydrocarbons, alcohols, or ketones are preferred, and methanol is more preferred. Therefore, as the washing liquid in the final washing process, a washing liquid with methanol as the main component (50% or more, or 60% or more, of methanol per 100% mass of the washing liquid) is preferably used.

[0153] In the final drying process, the amount of washing liquid used in the aforementioned final washing process can be reduced. From the viewpoint of easily reducing the amount of washing liquid through drying, the boiling point of the washing liquid used in the aforementioned final washing process is preferably below 120°C. Drying can be performed by heating or air drying. It should be noted that when using an organic solvent as the washing liquid, from a safety point of view, heating drying using hot air drying with low-pressure steam or heat transfer oil as the heat source is preferred. The drying temperature is preferably above the boiling point of the washing liquid, and from the viewpoint of suppressing the deterioration of the silane coupling agent, it is preferably below 180°C.

[0154] Examples of fiber-opening processes (C) for glass cloth include: fiber-opening treatment by applying water pressure to the obtained glass cloth; fiber-opening treatment using high-frequency vibration with water (e.g., degassed water, ion-exchanged water, deionized water, electrolyzed cation water, or electrolyzed anion water) as the medium; processing by applying pressure with rollers; processing by dry ice blasting; and bending processing with a low radius of curvature. This fiber-opening treatment can be performed simultaneously with weaving or after weaving. It can be performed before or after hot cleaning, or simultaneously with hot cleaning, or simultaneously with or after the surface treatment process (B). From the viewpoint of controlling the number of voids after 5 minutes of castor oil impregnation and the rate of void reduction from 1 minute to 5 minutes after castor oil impregnation, it is necessary to increase the processing force in the fiber-opening process. Therefore, dry ice blasting or bending processing is preferred as a fiber-opening method for glass cloth made of glass fibers with high glass hardness.

[0155] Dry ice blasting is a method of injecting (blowing) dry ice particles with a diameter of 5 to 300 μm from a height of 5 to 1000 mm at an air pressure of 0.05 to 1 MPa. More preferably, it is a method of injecting dry ice particles with a diameter of 5 to 300 μm from a height of 5 to 600 mm at an air pressure of 0.1 to 0.5 MPa. By operating within this range, quality problems such as fiberglass breakage will not occur, and improved impregnation is expected.

[0156] The bending process involves passing the filaments through a roller with a radius of curvature R = 2.5 mm or less, preferably R = 2.0 mm or less, at least two times, and preferably more than ten times, to open the fibers. If the radius of curvature R = 2.5 mm or less, the adhesion between the filaments caused by the sizing agent or silane coupling agent can be effectively removed, and an improvement in impregnation can be easily expected.

[0157] The method for manufacturing the glass cloth in this embodiment may include:

[0158] The weaving process of weaving glass fibers to obtain glass cloth.

[0159] The glass cloth manufacturing method of this embodiment may have a weaving process before the covering process, a weaving process between the covering process and the final washing process, or a weaving process after the final washing process.

[0160] Furthermore, the method for manufacturing the glass cloth in this embodiment may include at least one of the following steps as needed:

[0161] The residual slurry reduction process reduces the amount of modified sizing agent remaining in the desizing process; and

[0162] The fiber opening process involves opening the glass fibers in the glass cloth after the weaving process.

[0163] In the residual slurry reduction process, the following methods can be used: dry cleaning such as plasma irradiation and ultraviolet ozone; wet cleaning such as high-pressure water washing, organic solvent washing, nano-bubble water washing, and ultrasonic water washing; and heated cleaning at a higher temperature than the heated deslurry process. In addition, multiple methods can be combined. In particular, in the residual slurry reduction process, it is preferable to perform short-time heated cleaning by passing glass fibers or glass cloth in roll-to-roll through a heating furnace at a temperature of 800°C or higher.

[0164] The glass cloth manufacturing method of this embodiment described above can appropriately reduce unwanted components that are considered to increase the dielectric loss tangent. Furthermore, it is easy to apply a silane coupling agent to the surface of each glass filament constituting the glass fiber. In addition, by strengthening the fiber-opening process of the glass fiber, the heat resistance and insulation reliability of the printed wiring board can be improved.

[0165] [Prepreg]

[0166] The prepreg of this embodiment contains the aforementioned glass cloth and a matrix resin impregnated in the aforementioned glass cloth. Therefore, a prepreg with fewer voids can be provided.

[0167] Thermosetting or thermoplastic resins can be used as the base resin. If possible, both can be used in combination, and other resins may also be included.

[0168] Examples of thermosetting resins include:

[0169] (a) An epoxy resin, which is formed by reacting and curing a compound having an epoxy group with a compound having at least one group selected from the group consisting of amino, phenol, acid anhydride, hydrazide, isocyanate, cyanate and hydroxyl groups that react with the epoxy group.

[0170] (b) A free radical polymerizable curing resin, which is formed by curing a compound having at least one group selected from the group consisting of allyl, methacrylate, and acrylic acid;

[0171] (c) Maleimide triazine resin, which is formed by reacting and curing a compound having a cyanate ester group with a compound having a maleimide group;

[0172] (d) Thermosetting polyimide resin, which is formed by reacting maleimide compound with amine compound to cure;

[0173] (e) Benzoxazine resins, which are formed by crosslinking and curing compounds having benzoxazine rings through heating polymerization; etc.

[0174] It should be noted that, in obtaining (a) epoxy resin, the compound can be reacted without a catalyst. Alternatively, catalysts with reaction catalytic ability, such as imidazole compounds, tertiary amine compounds, urea compounds, and phosphorus compounds, can be added to facilitate the reaction. Furthermore, in obtaining (b) free radical polymerization type cured resin, thermally decomposable catalysts or photodecomposable catalysts can be used as reaction initiators.

[0175] Examples of thermoplastic resins include: polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, aromatic polyamide, polyetheretherketone, thermoplastic polyimide, insoluble polyimide, polyamide-imide, and fluoropolymers. As an insulating material for printed wiring boards used in high-speed communications, polyphenylene ether or modified polyphenylene ether with high free radical reactivity is preferred.

[0176] When the matrix resin used in high-speed communication printed wiring boards has vinyl or methacrylic groups, silane coupling agents with functional groups that have relatively high hydrophobicity and participate in free radical reactions such as methacrylic groups have good compatibility with the matrix resin.

[0177] As described above, thermosetting resins and thermoplastic resins can be used in combination. Furthermore, the prepreg may contain inorganic fillers. Inorganic fillers are preferably used in combination with thermosetting resins, and examples include: aluminum hydroxide, zirconium oxide, calcium carbonate, alumina, mica, aluminum carbonate, magnesium silicate, aluminum silicate, silica, talc, short glass fibers, aluminum borate, and silicon carbide. Inorganic fillers can be used alone or in combination of two or more.

[0178] Printed wiring board

[0179] The printed wiring board of this embodiment contains the aforementioned prepreg. Therefore, a printed wiring board with excellent insulation reliability can be provided.

[0180] [Integrated Circuits and Electronic Equipment]

[0181] Furthermore, integrated circuits and electronic devices incorporating the aforementioned printed wiring board are also embodiments of this embodiment. Integrated circuits and electronic devices obtained using the printed wiring board of this embodiment exhibit excellent characteristics.

[0182] Example

[0183] Next, the present invention will be described in detail through examples and comparative examples. The present invention is not limited to the following examples.

[0184] Methods for determining the weight per unit area (mass of fabric)

[0185] The mass of the cloth is calculated by cutting it to a specific size and dividing its mass by the sample area. In this embodiment, the glass cloth is cut into 10cm pieces.2 The dimensions of the glass cloth were determined, and its mass was measured to calculate the weight per unit area of ​​each glass cloth.

[0186] [Method for determining converted thickness]

[0187] Since glass cloth is a discontinuous planar body with air between the glass fibers, the equivalent thickness is calculated by dividing the weight per unit area (mass of the cloth) of each piece of glass cloth by its density. Specifically, the equivalent thickness is calculated according to the following formula (3):

[0188] Conversion thickness (μm) = Weight per unit area (g / m²) 2 )÷Density (g / cm³) 3 )···(3)

[0189] The converted thickness value was used for the determination by the resonance method.

[0190] [Method for determining the dielectric loss tangent]

[0191] The dielectric loss tangent of each glass cloth was determined according to IEC 62562. Specifically, glass cloth samples, taken to the dimensions required for measurement using a split cylindrical resonator, were stored in a constant temperature and humidity oven at 23°C and 50% RH for at least 8 hours. Then, the dielectric properties of the stored samples were measured using a split cylindrical resonator (manufactured by EM Labs) and an impedance analyzer (manufactured by Agilent Technologies). Five measurements were performed on each sample, and the average value was obtained. Additionally, the thickness of each sample was measured using the aforementioned converted thickness. Similarly, a glass plate with the same composition as each glass cloth and a thickness of 300 μm or less was prepared, and the bulk dielectric loss tangent was also measured based on the thickness value obtained from the thickness measurement of this glass plate. Furthermore, IEC 62562 primarily specifies methods for measuring the dielectric properties of fine ceramic materials used in microwave circuits at microwave frequencies.

[0192] [Method for determining the loss on ignition of glass cloth]

[0193] According to JIS R3420, the weight loss on ignition of the glass cloth was calculated.

[0194] [Methods for determining nitrogen content]

[0195] The surface-treated glass cloth was heated to approximately 800°C for 1 minute, and the amount of nitrogen dioxide in the generated gas was determined by gas chromatography. A specific amount of acetanilide (C8H9NO) was similarly heated to approximately 800°C for 1 minute beforehand, and the amount of nitrogen dioxide generated at this time was used as a comparison. The nitrogen content (mass%) per unit mass of the surface-treated glass cloth was then determined. The determination was performed using a SUMIGRAPH NC-90A (manufactured by Sumitomo Chemical Analysis Center).

[0196] The molecular weight of acetanilide is 135.17.

[0197] The nitrogen ratio of acetanilide is 10.36%.

[0198] That is, the nitrogen content per unit mass of glass cloth is calculated based on the following formula.

[0199] Nitrogen content per unit mass of glass cloth =

[0200] [{mass of acetanilide × (nitrogen ratio of acetanilide / 100)} / peak area of ​​nitrogen dioxide produced from acetanilide] × {(peak area of ​​nitrogen dioxide produced by glass cloth / mass of glass cloth) × 100}

[0201] [Methods for determining permeability]

[0202] Samples were taken to ensure the glass cloth had a size of 50mm x 50mm or larger. The sampling was performed without bending or contact with the measurement area. The sampled glass cloth was impregnated in castor oil (manufactured by Hayashi Junya Kogyo Co., Ltd.) for a specified time at a liquid temperature of 24–26°C, and the number of voids was counted for evaluation. A high-precision camera (frame size: 5120 x 5120 pixels) was positioned perpendicular to the glass cloth, and LED lights (PowerFlash-bar type illumination manufactured by CCS Co., Ltd.) were used as the light source, illuminating the glass cloth from both sides from a position 15cm away from its front side, clamping it in place. The number of voids larger than 160μm existing between the glass filaments within a 32mm x 32mm field of view was then counted, and the average of three measurements was taken as the void count. Voids correspond to the portion not impregnated with the matrix resin. Therefore, a lower void count in the glass cloth indicates excellent impregnation with the matrix resin.

[0203] Here, regarding the "porosity reduction rate (%) from 1 minute to 5 minutes after castor oil impregnation",

[0204] Let A be the number of pores in the glass cloth after it has been soaked in castor oil for 1 minute.

[0205] Let B be the number of pores in the glass cloth after it has been soaked in castor oil for 5 minutes.

[0206] It can be calculated using the formula “{(AB) / A}×100(%)”.

[0207] [Glass cloth]

[0208] (Grey Fabric A)

[0209] The fabric is woven using glass fibers with a SiO2 content greater than 99.9% by mass on an air-jet loom with a weave density of 66 warp threads / 25mm and 68 weft threads / 25mm. The warp threads are made of quartz glass with an average filament diameter of 5.0μm, 100 filaments, and a twist count of 1.0Z. Similarly, the weft threads are also made of quartz glass with an average filament diameter of 5.0μm, 100 filaments, and a twist count of 1.0Z.

[0210] (Grey Fabric B)

[0211] The fabric is woven using glass fibers with a SiO2 content greater than 99.9% by mass on an air-jet loom at a weaving density of 54 warp threads / 25mm and 54 weft threads / 25mm. It should be noted that the weaving is performed to achieve a fabric width of 1300mm. The warp threads are made of quartz glass with an average filament diameter of 5.0μm, 200 filaments, and a twist count of 1.0Z. Similarly, the weft threads are also made of quartz glass with an average filament diameter of 5.0μm, 200 filaments, and a twist count of 1.0Z.

[0212] (Grey Fabric C)

[0213] The fabric is woven using E-glass yarn with a weave density of 66 warp threads / 25mm and 68 weft threads / 25mm. The warp threads are E-glass yarns with an average filament diameter of 5.0μm, 100 filaments, and a twist count of 1.0Z. Similarly, the weft threads are also E-glass yarns with an average filament diameter of 5.0μm, 100 filaments, and a twist count of 1.0Z.

[0214] (Example 1)

[0215] Fabric A was heat-treated at 900°C for 60 seconds to desizing (heating and degreasing process). Next, a treatment solution was prepared containing 0.3% by mass of 3-methacryloyloxypropyltrimethoxysilane (silane coupling agent A) as Z6030 (manufactured by Dow Toray) dispersed in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution at a linear speed of 1.5 m / min, and after extruding the liquid, it was heat-dried at 130°C for 60 seconds to fix the silane coupling agent (fixation process). The dried fabric was then irradiated in water at a frequency of 25 kHz and an output power of 0.50 W / cm².2 The glass cloth is then subjected to ultrasonic treatment to reduce excess silane coupling agent physically adhering to it (washing process), followed by drying at 130°C for 1 minute (drying process). Next, 5–50 μm dry ice particles are uniformly sprayed onto the entire glass cloth at an air pressure of 0.4 MPa, thereby performing fiber-opening treatment (fiber-opening treatment by dry ice spraying), thus obtaining the glass cloth. The converted thickness is calculated based on the unit area weight and density of the obtained glass cloth, and the dielectric loss tangent of the glass cloth is measured.

[0216] (Example 2)

[0217] Fabric A was desized by heat treatment at 600°C for 60 seconds. Next, a treatment solution was prepared containing 0.1% by mass of 3-methacryloyloxypropyltrimethoxysilane (silane coupling agent A) dispersed in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution at a linear speed of 1.5 m / min, and after extrusion, it was dried at 130°C for 60 seconds to fix the silane coupling agent. The dried fabric was then irradiated in water at a frequency of 25 kHz and an output power of 0.50 W / cm². 2 The glass cloth is subjected to ultrasonic treatment to reduce excess silane coupling agent physically adhering to it, and then dried at 130°C for 1 minute. Then, 5–50 μm dry ice particles are uniformly sprayed onto the entire glass cloth at an air pressure of 0.5 MPa, thereby performing fiber opening treatment to obtain the glass cloth. The converted thickness is calculated based on the unit area weight and density of the obtained glass cloth, and the dielectric loss tangent of the glass cloth is measured.

[0218] (Example 3)

[0219] Fabric A was desized by heat treatment at 900°C for 60 seconds. Next, a treatment solution was prepared containing 0.3% by mass of Z6161 (manufactured by DowToray) as 5-hexenyltrimethoxysilane (silane coupling agent B) dispersed in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution at a linear speed of 1.5 m / min, and after extrusion, it was dried at 130°C for 60 seconds to fix the silane coupling agent. The dried fabric was then irradiated in water at a frequency of 25 kHz and an output power of 0.50 W / cm². 2 The glass cloth is subjected to ultrasonic treatment to reduce excess silane coupling agent physically adhering to it, and then dried at 130°C for 1 minute. Then, 5–50 μm dry ice particles are uniformly sprayed onto the entire glass cloth at an air pressure of 0.5 MPa, thereby performing fiber opening treatment to obtain the glass cloth. The converted thickness is calculated based on the unit area weight and density of the obtained glass cloth, and the dielectric loss tangent of the glass cloth is measured.

[0220] (Example 4)

[0221] Fabric A was desized by heat treatment at 900°C for 60 seconds. Next, a treatment solution was prepared by dispersing 0.15% by mass of Z6030 (manufactured by Dow Toray) as 3-methacryloyloxypropyltrimethoxysilane (silane coupling agent A) and 0.15% by mass of Z6161 (manufactured by Dow Toray) as 5-hexenyltrimethoxysilane (silane coupling agent B) in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution at a linear velocity of 1.5 m / min, and after extruding the liquid, it was heat-dried at 130°C for 60 seconds to fix the silane coupling agents. The dried fabric was then irradiated in water at a frequency of 25 kHz and an output power of 0.50 W / cm². 2 The glass cloth is subjected to ultrasonic treatment to reduce excess silane coupling agent physically adhering to it, and then dried at 130°C for 1 minute. Then, 5–50 μm dry ice particles are uniformly sprayed onto the entire glass cloth at an air pressure of 0.2 MPa, thereby performing fiber opening treatment to obtain the glass cloth. The converted thickness is calculated based on the unit area weight and density of the obtained glass cloth, and the dielectric loss tangent of the glass cloth is measured.

[0222] (Example 5)

[0223] Except that the solvent used in ultrasonic cleaning was changed from water to methanol, the glass cloth was obtained using the same method as in Example 1. After calculating the equivalent thickness based on the unit area weight and density of the obtained glass cloth, the dielectric loss tangent of the glass cloth was measured.

[0224] (Example 6)

[0225] Fabric B was desized by heat treatment at 1000°C for 20 seconds. Next, a treatment solution was prepared containing 0.15% by mass of 3-methacryloyloxypropyltrimethoxysilane (silane coupling agent A) dispersed in pure water adjusted to pH 3 with acetic acid. The fabric was immersed in the treatment solution at a linear velocity of 1.5 m / min, and after extrusion, it was dried at 130°C for 60 seconds to fix the silane coupling agent. The dried fabric was then irradiated in methanol solvent at a frequency of 25 kHz and an output power of 0.50 W / cm². 2 The glass cloth is subjected to ultrasonic treatment to reduce excess silane coupling agent physically adhering to it, and then dried at 130°C for 1 minute. Then, 5–50 μm dry ice particles are uniformly sprayed onto the entire glass cloth at an air pressure of 0.45 MPa, thereby performing fiber opening treatment to obtain the glass cloth. The converted thickness is calculated based on the unit area weight and density of the obtained glass cloth, and the dielectric loss tangent of the glass cloth is measured.

[0226] (Comparative Example 1)

[0227] The concentration of the treatment solution was changed to 0.7% by mass, and the fiber-opening treatment was not performed by dry ice blasting. Otherwise, the glass cloth was obtained using the same method as in Example 1. After calculating the equivalent thickness based on the unit area weight and density of the obtained glass cloth, the dielectric loss tangent of the glass cloth was measured.

[0228] (Comparative Example 2)

[0229] The concentration of the treatment solution was set to 0.04% by mass, and the fiber-opening treatment was not performed by dry ice blasting. Otherwise, the glass cloth was obtained using the same method as in Example 1. After calculating the converted thickness based on the unit area weight and density of the obtained glass cloth, the dielectric loss tangent of the glass cloth was measured.

[0230] (Comparative Example 3)

[0231] A treatment solution containing 0.15% by mass of Z6032 (manufactured by Toray Dow Corning Co., Ltd.) as N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride (silane coupling agent C) was used, and fiber opening treatment was not performed by dry ice blasting. Otherwise, the glass cloth was obtained by the same method as in Example 1. After calculating the converted thickness based on the unit area weight and density of the obtained glass cloth, the dielectric loss tangent of the glass cloth was measured.

[0232] (Comparative Example 4)

[0233] The concentration of the treatment solution was set to 0.35% by mass, and fiber opening treatment was not performed by dry ice blasting. Otherwise, the glass cloth was obtained in the same manner as in Comparative Example 3. After calculating the equivalent thickness based on the unit area weight and density of the obtained glass cloth, the dielectric loss tangent of the glass cloth was measured.

[0234] (Comparative Example 5)

[0235] The fiber opening process was performed using a columnar water jet from a 1.4 MPa high-pressure water jet. Otherwise, the glass cloth was obtained using the same method as in Example 1. After calculating the equivalent thickness based on the unit area weight and density of the obtained glass cloth, the dielectric loss tangent of the glass cloth was measured.

[0236] (Comparative Example 6)

[0237] Using fabric C, the glass cloth was heated at 400°C for 72 hours to remove oil, and otherwise obtained using the same method as in Example 1. After calculating the equivalent thickness based on the unit area weight and density of the obtained glass cloth, the dielectric loss tangent of the glass cloth was measured.

[0238] [How to manufacture laminated boards]

[0239] For the glass cloth obtained in the examples and comparative examples, 45 parts by weight of polyphenylene ether (manufactured by SABIC, SA9000), 10 parts by weight of triallyl isocyanurate, 45 parts by weight of toluene, and 0.6 parts by weight of 1,3-di(tert-butylisopropylbenzene) were added to a stainless steel container and stirred at room temperature for 1 hour to prepare a varnish. The glass cloth was impregnated with the prepared varnish and then dried at 115°C for 1 minute to obtain a prepreg. Eight sheets of the obtained prepreg were overlapped, and then copper foil with a thickness of 12 μm was overlapped on top and bottom, and the mixture was dried at 200°C and 40 kg / cm². 2 The laminate is heated and pressurized for 120 minutes to obtain a laminated plate.

[0240] [Methods for evaluating the heat resistance of laminated boards]

[0241] After removing the copper foil from the laminate obtained as described above, it was heated in an autoclave at 133°C for 62 hours to absorb water. Then, the water-absorbed laminate was immersed in a solder bath at 288°C for 20 seconds, and visual inspection was performed to check for any bulging (expansion) caused by peeling at the interface between the glass cloth and the resin. Four tests were conducted on each glass cloth. The evaluation of heat resistance is shown in Table 2. It should be noted that a lower tendency for bulging in the glass cloth indicates better heat resistance.

[0242] E(〇): None of the four laminates have bulges.

[0243] G(△): One or two laminated plates have bulges.

[0244] P(×): There is a bulge in 3 or 4 laminated plates.

[0245] [Evaluation Methods for Insulation Reliability of Laminated Boards]

[0246] Following the above procedure, a laminate with a thickness of 1.0 mm is fabricated. A wiring pattern with through-holes spaced at 0.30 mm intervals is created on the copper foil on both sides of the laminate to obtain an insulation reliability evaluation sample. A voltage of 50 V is applied to the obtained sample at 85°C and 85% RH, and the change in resistance is measured. At this point, a resistance less than 1 MΩ within 500 hours of the start of the test is considered a failure to insulate. The same measurement is performed on 10 samples, and the number of samples that do not become failures to insulate is determined.

[0247] The manufacturing conditions and evaluation results of the examples and comparative examples are shown in Table 2. It should be noted that any of the glass cloths in Examples 1 to 6 can be made into prepregs and printed wiring boards according to conventional methods.

[0248] [Table 2]

[0249]

Claims

1. A type of glass cloth, which is made of woven glass fibers. The bulk dielectric loss tangent of the glass constituting the glass filament is below 0.0010. The loss on ignition of the glass cloth is greater than 0.01% by mass and less than 0.12% by mass. The number of voids in the glass cloth after 5 minutes of impregnation with castor oil is less than 180. The number of voids was determined by the following method: The glass cloth was sampled in a size of 50mm×50mm or larger. The sampled glass cloth was soaked in castor oil for a specified time at a liquid temperature of 24-26°C. The number of voids larger than 160μm between the glass filaments within a 32mm×32mm viewing angle was counted. The average value of three measurements was taken as the void count.

2. The glass cloth according to claim 1, wherein, When the glass cloth is impregnated with castor oil, the void reduction rate is more than 70% from 1 minute to 5 minutes later.

3. The glass cloth according to claim 1, wherein, The number of voids in the glass cloth after 5 minutes of impregnation with castor oil is less than 160.

4. The glass cloth according to claim 1, wherein, The number of voids in the glass cloth after 5 minutes of impregnation with castor oil is less than 140.

5. The glass cloth according to claim 1, wherein, The number of voids in the glass cloth after 5 minutes of impregnation with castor oil is less than 120.

6. The glass cloth according to claim 1, wherein, The number of voids in the glass cloth after 5 minutes of impregnation with castor oil is less than 100.

7. A type of glass cloth, which is made of woven glass fibers. The bulk dielectric loss tangent of the glass constituting the glass filament is below 0.0010. The loss on ignition of the glass cloth is greater than 0.01% by mass and less than 0.12% by mass. When the glass cloth is impregnated with castor oil, the porosity reduction rate is over 70% from 1 minute to 5 minutes later. The reduction rate of voids in the glass cloth after 1 minute to 5 minutes of impregnation with castor oil is calculated by the following formula: {(AB) / A}×100(%); in, A represents the number of voids in the glass cloth after soaking in castor oil for 1 minute, and B represents the number of voids in the glass cloth after soaking in castor oil for 5 minutes. The number of voids was determined by the following method: The glass cloth was sampled in a size of 50mm×50mm or larger. The sampled glass cloth was soaked in castor oil for a specified time at a liquid temperature of 24-26°C. The number of voids larger than 160μm between the glass filaments within a 32mm×32mm viewing angle was counted. The average value of three measurements was taken as the void count.

8. The glass cloth according to any one of claims 2 to 7, wherein, When the glass cloth is impregnated with castor oil, the void reduction rate is more than 80% from 1 minute to 5 minutes later.

9. The glass cloth according to any one of claims 2 to 7, wherein, When the glass cloth is impregnated with castor oil, the void reduction rate is more than 86% from 1 minute to 5 minutes later.

10. The glass cloth according to any one of claims 2 to 7, wherein, When the glass cloth is impregnated with castor oil, the void reduction rate is more than 88% from 1 minute to 5 minutes later.

11. The glass cloth according to claim 1 or 7, wherein, The bulk dielectric loss tangent of the glass constituting the glass filament is less than 0.0008.

12. The glass cloth according to claim 1 or 7, wherein, The bulk dielectric loss tangent of the glass constituting the glass filament is less than 0.0006.

13. The glass cloth according to claim 1 or 7, wherein, The bulk dielectric loss tangent of the glass constituting the glass filament is less than 0.0003.

14. The glass cloth according to claim 1 or 7, wherein, The silicon (Si) content in the glass fiber, converted from silicon dioxide (SiO2), is 95.0% to 100% by mass.

15. The glass cloth according to claim 1 or 7, wherein, The silicon (Si) content in the glass fiber, converted from silicon dioxide (SiO2), is 99.0% to 100% by mass.

16. The glass cloth according to claim 1 or 7, wherein, The silicon (Si) content in the glass fiber, converted from silicon dioxide (SiO2), is 99.9% to 100% by mass.

17. The glass cloth according to claim 1 or 7, wherein it has undergone surface treatment.

18. The glass cloth according to claim 17, wherein, The surface treatment was performed using a silane coupling agent having the structure shown in the following general formula (1). X(R) 3-n Yes n (1) In the formula, X is an organic functional group containing one or more unsaturated double bonds with free radical reactivity. Y is an alkoxy group on its own. n is an integer from 1 to 3. R is each independently at least one group selected from the group consisting of methyl, ethyl, and phenyl.

19. The glass cloth according to claim 18, wherein, X in the general formula (1) has a (meth)acryloyloxy group and does not contain an amino group.

20. The glass cloth according to claim 18, wherein, At least one Y in the general formula (1) is an alkoxy group having 1 to 5 carbon atoms.

21. The glass cloth according to claim 18, wherein, In the general formula (1), more than half of the Y atoms are alkoxy groups with 1 to 5 carbon atoms.

22. The glass cloth according to claim 18, wherein, In the general formula (1), all Y are alkoxy groups with 1 to 5 carbon atoms.

23. The glass cloth according to claim 18, wherein, The molecular weight range of the silane coupling agent represented by the general formula (1) is 100 to 600.

24. The glass cloth according to claim 18, wherein, The molecular weight range of the silane coupling agent represented by the general formula (1) is 200 to 450.

25. The glass cloth according to claim 1 or 7, wherein, The loss on ignition of the glass cloth is less than 0.10% by mass.

26. The glass cloth according to claim 1 or 7, wherein, The loss on ignition of the glass cloth is greater than 0.03% by mass and less than 0.08% by mass.

27. The glass cloth according to claim 1 or 7, wherein, The nitrogen content per unit mass is less than 0.004 by mass.

28. The glass cloth according to claim 1 or 7, wherein, The dielectric loss tangent of the glass cloth at 10 GHz, as measured by the resonance method, is greater than 0 and less than 0.0008.

29. The glass cloth according to claim 1 or 7, wherein, The dielectric loss tangent at 10 GHz, as measured by the resonance method, is greater than 0 and less than 0.0005.

30. The glass cloth according to claim 1 or 7, wherein, The dielectric loss tangent at 10 GHz, as measured by the resonance method, is greater than 0 and less than 0.0004.

31. The glass cloth according to claim 1 or 7, wherein its unit area weight (mass) is 8 g / m². 2 ~50g / m 2 .

32. The glass cloth according to claim 1 or 7, wherein, The warp and weft yarns of the glass cloth have a yarn density of 40 yarns / inch to 100 yarns / inch.

33. The glass cloth according to claim 1 or 7, wherein, The average diameter of the glass filaments constituting the glass filament is 2.5 μm to 9.0 μm.

34. The glass cloth according to claim 1 or 7, wherein the thickness is 7 μm to 150 μm.

35. A prepreg comprising the glass cloth as described in claim 1 or 7, and a matrix resin impregnated in the glass cloth.

36. The prepreg according to claim 35, further comprising an inorganic filler.

37. A printed wiring board comprising the prepreg of claim 35.

38. An integrated circuit comprising the printed wiring board of claim 37.

39. An electronic device comprising the printed wiring board of claim 37.

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