Glass cloth, prepreg, and printed circuit board

Abstract

The present disclosure aims to provide a glass cloth which can achieve excellent dielectric properties, can suppress an increase in dielectric loss tangent over time, and can achieve excellent solder heat resistance for a resin substrate produced using the glass cloth. The glass cloth of the present disclosure is a glass cloth in which glass yarns are woven, the glass cloth is surface-treated with a surface treatment agent, a difference between a dielectric loss tangent at 10 GHz of the glass cloth and a bulk dielectric loss tangent at 10 GHz of a glass constituting the glass yarns (the dielectric loss tangent - the bulk dielectric loss tangent) is less than 0.00000, and a white spot P of the glass cloth is 10 / m 2 The following.

Description

Technical Field

[0001] This disclosure relates to glass cloth, prepreg, and printed circuit boards, etc. Background Technology

[0002] Currently, the high performance of information terminals such as smartphones and the high speed of communication, represented by 5G, are constantly developing. Along with this, for printed circuit boards used in high-speed communication, there is a significant trend towards lower dielectric constants and lower dielectric loss tangents in the insulating materials used to reduce transmission losses. Furthermore, there is a pursuit of higher levels of insulation reliability than ever before.

[0003] Examples of insulating materials for printed circuit boards used in high-speed communications are reported in Patent Documents 1 and 2. Specifically, in Patent Documents 1 and 2, a prepreg is obtained by crosslinking a terminally modified polyphenylene ether or the like with a vinyl or methacryloxy radical through a free radical reaction, thereby impregnating a cured low-dielectric thermosetting resin (hereinafter collectively referred to as "matrix resin") into a glass cloth, which is then dried. Laminated boards are known to be formed by laminating the prepreg thus obtained and curing it by heating and pressurizing. Patent Documents 1 and 2 achieve low dielectric constant and low dielectric loss tangent as laminates by combining them with glass cloth having a low dielectric constant and a low dielectric loss tangent.

[0004] Here, to reduce the dielectric loss tangent of the glass cloth, Patent Documents 3 and 4 report methods to reduce the amount of silanol groups on the glass surface by heating the silica glass cloth at high temperatures. Patent Document 5 reports a method to reduce the silanol groups present on the surface of the glass cloth through surface treatment, thereby reducing the dielectric loss tangent of the glass cloth. Patent Document 6 reports a packaging method for quartz glass cloth to suppress the time-dependent increase in the dielectric loss tangent of the quartz glass cloth.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2019 / 065940

[0008] Patent Document 2: International Publication No. 2019 / 065941

[0009] Patent Document 3: Japanese Patent Application Publication No. 2021-63320

[0010] Patent Document 4: Japanese Patent Application Publication No. 2021-195689

[0011] Patent Document 5: Japanese Patent Application Publication No. 2020-194888

[0012] Patent Document 6: Japanese Patent No. 7375902 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] However, there is a strong demand for the creation of a technology that can further reduce the dielectric loss tangent of glass cloth compared to the prior art described in Patent Documents 1 to 6.

[0015] In addition, for glass cloth, there are situations where not only excellent dielectric properties are required, but also various properties of the resulting resin substrate (such as resistance to soldering heat) are required.

[0016] Furthermore, there is a strong demand for a technology that can suppress the time-dependent increase of the dielectric loss tangent, even without employing the method of packaging quartz glass cloth in a prescribed manner as described in Patent Document 6.

[0017] The purpose of this disclosure is to provide a glass cloth that can: achieve excellent dielectric properties, suppress the increase of dielectric loss tangent over time, and achieve excellent soldering heat resistance for resin substrates made using the glass cloth.

[0018] Furthermore, the purpose of this disclosure is to provide prepregs and printed circuit boards made using the aforementioned glass cloth, and also to provide a method for manufacturing the aforementioned glass cloth.

[0019] Solution for solving the problem

[0020] One aspect of the present invention is described below. [1]

[0022] A type of glass cloth, which is a glass cloth woven from glass yarn.

[0023] The glass cloth was surface-treated with a surface treatment agent.

[0024] The difference between the dielectric loss tangent of the glass cloth at 10 GHz and the bulk dielectric loss tangent of the glass constituting the glass yarn at 10 GHz (the dielectric loss tangent - the bulk dielectric loss tangent) is less than 0.00000.

[0025] The white spots on the glass cloth are 10 per m. 2 the following. [2]

[0027] According to the glass cloth described in Project 1, the silicon (Si) content in the glass yarn is 95.0~100% by mass, calculated as silicon dioxide (SiO2). [3]

[0029] According to Project 1 or 2, the glass cloth wherein the average open fiber ratio calculated from the yarn widths of the warp and weft yarns of the glass cloth exceeds 40%. [4]

[0031] The glass cloth according to any one of items 1 to 3, wherein the bulk dielectric loss tangent is less than 0.002. [5]

[0033] The glass cloth according to any one of items 1 to 4, wherein the surface treatment agent comprises a silane coupling agent. [6]

[0035] According to the glass cloth described in Project 5, the molecular weight of the silane coupling agent is 250~1000. [7]

[0037] According to item 5 or 6, the glass cloth wherein the silane coupling agent contains at least one group selected from the group consisting of epoxy, amino, aromatic vinyl, acryloyl and methacryloyl in its molecule. [8]

[0039] The glass cloth according to any one of items 5 to 7, wherein the surface treatment agent comprises two or more silane coupling agents with different molecular weights. [9]

[0041] The glass cloth according to any one of items 1 to 8, wherein the loss on ignition of the glass cloth is 0.01 to 0.5 by mass.

[10]

[0043] The glass cloth according to any one of items 1 to 9 is a constituent material of the printed circuit board.

[11]

[0045] A prepreg comprising glass cloth and thermosetting resin as described in any one of items 1 to 10.

[12]

[0047] A printed circuit board comprising the prepreg described in item 11.

[13]

[0049] An integrated circuit comprising the printed circuit board described in item 12.

[14]

[0051] An electronic device comprising the printed circuit board described in item 12.

[15]

[0053] A method for manufacturing glass cloth, comprising:

[0054] The weaving process involves weaving glass yarn to obtain glass cloth; and

[0055] In the surface treatment process, after the glass yarn is degreased, it is then surface-treated with a surface treatment solution.

[0056] The dielectric loss tangent of the surface-treated glass cloth at 10 GHz is lower than that of the untreated glass cloth at 10 GHz.

[16]

[0058] According to the method for manufacturing glass cloth described in Project 15, the surface treatment liquid is prepared by adding an acidic aqueous solution to a silane coupling agent used as a surface treatment agent.

[17]

[0060] According to the manufacturing method of glass cloth described in item 15 or 16, the surface treatment process includes:

[0061] The process of controlling the temperature and pH of the surface treatment solution, and the process of filtering the surface treatment solution.

[18]

[0063] The method for manufacturing glass cloth according to any one of items 15 to 17, wherein, after the surface treatment step, it further includes a step of opening the glass yarn.

[19]

[0065] The method for manufacturing glass cloth according to any one of items 15 to 18, wherein after the surface treatment step, the method further includes a step of inspecting white spots on the glass cloth.

[0066] The effects of the invention

[0067] According to this disclosure, a glass cloth can be provided that can: achieve excellent dielectric properties, suppress the increase of dielectric loss tangent over time, and achieve excellent soldering heat resistance for resin substrates made using the glass cloth.

[0068] Furthermore, according to this disclosure, it is possible to provide prepregs, printed circuit boards, integrated circuits, and electronic devices made using the aforementioned glass cloth, and also to provide a method for manufacturing the aforementioned glass cloth. Attached Figure Description

[0069] Figure 1 This is a diagram used to illustrate the white spots in this embodiment. Detailed Implementation

[0070] Hereinafter, embodiments of the present disclosure (hereinafter referred to as "this embodiment") will be described. However, the present invention is not limited to this embodiment only, and various modifications can be made without departing from its spirit.

[0071] In this specification, when multiple structures represented by the same symbol exist within the same formula, each structure can be selected independently unless otherwise specified, and they can be the same or different from each other. When multiple structures represented by the same symbol exist within different formulas, each structure can be selected independently unless otherwise specified, and they can be the same or different from each other. In this specification, all measurements are performed according to the methods described in the embodiments unless otherwise specifically stated. In this specification, the upper or lower limit values ​​within the numerical range described in stages can be replaced with the upper or lower limit values ​​within the corresponding numerical range described in other stages, and further, can be replaced with the corresponding values ​​described in the embodiments.

[0072] In this specification, the term "process" is included not only when it is an independent process, but also when it cannot be clearly distinguished from other processes, as long as the function of the process is achieved. In the accompanying drawings, scales, shapes, and lengths are sometimes exaggerated for clarity.

[0073] [Glass cloth]

[0074] The glass cloth in this embodiment is a glass cloth woven from glass yarn, for example, a glass cloth woven from glass yarn formed by multiple glass filaments as warp and weft yarns.

[0075] In one embodiment of this invention,

[0076] The glass cloth was surface-treated with a surface treatment agent.

[0077] The difference between the dielectric loss tangent of the glass cloth at 10 GHz and the bulk dielectric loss tangent of the glass constituting the glass yarn at 10 GHz (the dielectric loss tangent minus the bulk dielectric loss tangent) is less than 0.00000.

[0078] The number of white spots in the fiberglass cloth is 10 per square meter. 2 The following (e.g., 10.0 pieces / m) 2 the following).

[0079] According to this embodiment, a glass cloth can be provided that can: achieve excellent dielectric properties, suppress the increase of dielectric loss tangent over time, and achieve excellent soldering heat resistance for resin substrates (printed circuit boards) made using the glass cloth. The glass cloth of this embodiment is suitable as a constituent material for manufacturing prepregs, printed circuit boards, integrated circuits, and electronic devices.

[0080] The inventors of this application conducted in-depth research and focused on glass cloth that underwent surface treatment after being degreased at high temperatures. The inventors were the first to discover that glass cloth with a lower dielectric loss tangent than the bulk phase has very few silanol groups on its surface, making it difficult to absorb moisture present in the storage environment. Therefore, even without special packaging, the increase in the dielectric loss tangent of the glass cloth over time can be suppressed.

[0081] Furthermore, it was found that in order to obtain glass cloth with a dielectric loss tangent lower than that of the bulk glass phase, surface treatment with a highly hydrophobic surface treatment agent is preferable. However, such surface treatment agents exhibit significantly poor dispersibility and / or compatibility in water, thus easily generating appearance defects such as "white spots" on the surface of the glass cloth. Since white spots hinder the interfacial adhesion between the glass cloth and the resin, it is preferable to provide glass cloth with excellent appearance quality and a dielectric loss tangent lower than that of the bulk phase.

[0082] According to a preferred embodiment of the glass cloth, even surface treatment agents (e.g., specified silane coupling agents) lacking dispersibility and / or compatibility in water can have their appearance quality improved by finding a method for stable dispersion in water. In this case, it is easy to provide a glass cloth whose dielectric loss tangent is lower than that of the bulk phase of the glass, and furthermore, even without special packaging, the increase in the dielectric loss tangent of the glass cloth over time is easily suppressed. Furthermore, it is easy to provide a glass cloth with excellent solder heat resistance to resin substrates.

[0083] [Dielectric loss tangent]

[0084] (Dielectric loss tangent of glass cloth)

[0085] In this embodiment, the glass cloth preferably has a dielectric loss tangent of 0.0020° or less at 10 GHz. With such a glass cloth, prepregs and printed circuit boards with improved dielectric properties can be provided. From the viewpoint of improving dielectric properties, the dielectric loss tangent of the glass cloth at 10 GHz is preferably 0.0015° or less, 0.0010° or less, 0.0007° or less, 0.0006° or less, 0.0005° or less, 0.0004° or less, 0.0003°, 0.0002°, 0.00019°, 0.00018°, 0.00017°, 0.00016°, 0.00015°, 0.00014°, 0.00013°, 0.00012°, or 0.00011° or less. The dielectric loss tangent of the glass cloth can exceed 0°.

[0086] (Method for determining the dielectric loss tangent)

[0087] For the glass cloth of this embodiment, the dielectric loss tangent at 10 GHz is determined by using a split cylindrical resonator (using the resonance method), specifically by the method described in the embodiment.

[0088] According to this method, measurements can be performed easily, simply, and with good accuracy compared to existing methods that involve fabricating a substrate as a test sample and evaluating its dielectric properties. The reason for this, not limited to theory, is that the resonance method is suitable for evaluation in the high-frequency region, and is particularly suitable for evaluating low-loss materials.

[0089] Other methods for evaluating dielectric properties besides the resonance method include the lumped constant method and the reflection transport method. However, the lumped constant method requires two electrodes to clamp the sample to form a capacitor, which can easily complicate the operation. Furthermore, in the reflection transport method, the matching characteristics of the aperture become strongly apparent when evaluating low-loss materials, making it difficult to accurately evaluate the dielectric loss tangent of the sample.

[0090] As can be seen from the above, the dielectric loss tangent of glass cloth can be easily and accurately measured by using the method of resonance, specifically by the method described in the embodiments.

[0091] For glass cloth used in printed circuit boards, especially glass cloth used in high-speed communication printed circuit boards, the measuring equipment for determining its dielectric properties preferably has a specified measurable range. For example, regarding the dielectric constant (Dk) and dielectric loss tangent (Df), the measuring equipment preferably has Dk = 1.1 Fm, respectively. -1 ~50Fm -1 and Df=1.0×10 -6 ~1.0×10 -1The measurable range, more preferably having Dk=1.5Fm -1 ~10Fm -1 and Df=1.0×10 -5 ~5.0×10 -1 The measurable range is further preferably defined by Dk=2.0Fm. -1 ~5Fm -1 and Df=5.0×10 -5 ~1.0×10 -2 The measurable range.

[0092] Furthermore, the measuring equipment used to determine dielectric properties is preferably capable of measuring frequencies of 10 GHz or higher. If the measurable frequency is 10 GHz or higher, it is easier to evaluate the characteristics in the frequency band region, especially the characteristics in the frequency band region envisioned in the actual use of glass cloth for printed circuit boards for high-speed communications.

[0093] The preferred area for measuring dielectric properties is 10 mm². 2 The above is preferred, with 15mm being more ideal. 2 The above is further preferred to be 20mm. 2 Therefore, it is easy to improve the reliability of the obtained measurement results, and thus, it is easy to determine whether the obtained measurement results are within the range of the pre-set reference values.

[0094] The thickness of the sample is preferably 3μm to 300μm, more preferably 5μm to 200μm, and even more preferably 7μm to 150μm.

[0095] (Bulk dielectric loss tangent)

[0096] In the glass cloth of this embodiment, the bulk dielectric loss tangent of the glass raw material constituting the glass cloth at 10 GHz is measured by using a split cylindrical resonator (a method using resonance), specifically by the method described in the embodiments. Here, the glass raw material may be, for example, glass yarn, glass filament, or other types of glass.

[0097] The bulk dielectric loss tangent at 10 GHz is preferably 0.002 or less, more preferably 0.0015 or less, even more preferably 0.001 or less, even more preferably 0.0005 or less, and particularly preferably 0.0004 or 0.0002 or less. This makes it easier to achieve the effects of this disclosure.

[0098] (Method for controlling the dielectric loss tangent of glass cloth)

[0099] The dielectric loss tangent of glass cloth can be controlled, for example, by removing deterioration and residues present on the surface of the glass cloth, or by surface treatment of the glass cloth with a surface treatment agent that can reduce the dielectric loss tangent of the glass cloth.

[0100] Here, the deteriorated substance and the residue, etc., are in one manner, for example, as described below (i) to (ii):

[0101] (i) Deterioration caused by the thermal oxidation of the sizing agent physically adhering to the glass surface.

[0102] (ii) Residues or modifications of a surface treatment agent that are physically attached to the glass surface without forming chemical bonds and remain on the surface even after water washing.

[0103] (The difference between the dielectric loss tangent and the bulk dielectric loss tangent)

[0104] In the glass cloth of this embodiment, the difference (the dielectric loss tangent - the bulk dielectric loss tangent) is less than 0.00000. This relationship is achieved when the bulk dielectric loss tangent is greater than the dielectric loss tangent by more than 0.00000. The methods for measuring the dielectric loss tangent and the bulk dielectric loss tangent, and the methods for controlling them, are as described above.

[0105] From the viewpoint of easily achieving the effects of this disclosure, the dielectric loss tangent (the dielectric loss tangent of the above-mentioned dielectric loss angle - the dielectric loss tangent of the above-mentioned bulk phase) is preferably -0.00002 or less, more preferably -0.00003 or less, even more preferably -0.00004 or less, even more preferably -0.00005 or less, even more preferably -0.00006 or less or -0.00007 or less, and particularly preferably -0.00008 or less. The dielectric loss tangent of the glass cloth can exceed -0.0002.

[0106] [Glass yarn]

[0107] Glass yarn can be composed of multiple glass filaments. By weaving glass yarn as both warp and weft yarns, glass cloth can be produced.

[0108] [Average filament diameter]

[0109] The average filament diameter of the glass filament is preferably 2.5 to 9.0 μm, more preferably 2.5 to 7.5 μm, even more preferably 3.5 to 7.0 μm, even more preferably 3.5 to 6.0 μm, and particularly preferably 3.5 to 5.0 μm.

[0110] [Density]

[0111] The fiberglass yarn (warp and weft) that constitutes the fiberglass cloth is preferably 10 to 120 yarns / inch (=10 to 120 yarns / 25.4 mm), more preferably 40 to 100 yarns / inch, and even more preferably 40 to 100 yarns / inch.

[0112] [Weight per unit area]

[0113] The preferred unit area weight of glass cloth is 8~250g / m². 2 More preferably 8~100g / m 2 A further preferred value is 8~80g / m 2 The preferred concentration is 8~50g / m³. 2 .

[0114] [Types of Glass]

[0115] Conventionally, the glass cloth used in prepregs (laminates) typically uses glass raw materials known as E-glass (alkali-free glass). However, the glass cloth in this embodiment can use glass raw materials such as L-glass, NE-glass, D-glass, L2-glass, T-glass, silica glass, and quartz glass. From the viewpoint of excellent dielectric properties, glass raw materials such as L-glass, L2-glass, silica glass, and quartz glass are preferred, with silica glass and quartz glass being particularly preferred. Furthermore, from the viewpoint of improving the dimensional stability of the laminate containing the glass cloth, glass raw materials such as S-glass, T-glass, silica glass, and quartz glass are preferred, with silica glass and quartz glass being particularly preferred.

[0116] In the glass yarn constituting the glass cloth, the silicon (Si) content, converted to silicon dioxide (SiO2), is preferably 95.0~100% by mass or 99.0~100% by mass, more preferably 99.5~100% by mass, and even more preferably 99.9~100% by mass. A particularly preferred method is for the SiO2 composition of the glass yarn constituting the glass cloth to exceed 99.9% by mass. When the Si content is 95.0% by mass or higher, it is easy to ensure the dielectric properties of the glass cloth and the dimensional stability of the laminate.

[0117] [Weaving Structure]

[0118] Examples of weaving structures for glass cloth include plain weave, square plain weave, satin weave, and twill weave, with plain weave being more preferred.

[0119] [Surface treatment agent (surface treatment liquid)]

[0120] The surface treatment liquid may contain a surface treatment agent. In this embodiment, the surface treatment is performed, for example, by using a surface treatment liquid.

[0121] Previously, it was believed that if a common surface treatment agent (such as a common silane coupling agent) is used, the dielectric loss tangent of the glass cloth will increase due to the surface treatment.

[0122] Regarding this point, the inventors of this application conducted research and found that by using a highly hydrophobic surface treatment agent (such as a highly hydrophobic silane coupling agent) to treat the glass surface, moisture present in the storage environment is not easily adsorbed onto the glass surface. As a result, even without special packaging methods, it is easy to suppress the time-dependent increase of the dielectric loss tangent of the glass cloth.

[0123] In this disclosure, "a highly hydrophobic surface treatment agent (a highly hydrophobic silane coupling agent)" is defined as follows: an aqueous solution prepared by mixing an aqueous solution of acetic acid at a concentration of 0.3% by mass and a surface treatment agent (silane coupling agent) at a concentration of 0.8% by mass is stirred at room temperature of 25°C for 3 hours. At this time, the surface treatment agent (silane coupling agent) is in a state where it is not dissolved or is unevenly dispersed in the aqueous solution, for example, the surface treatment agent (silane coupling agent) is separated in the aqueous solution as oil droplets and oil films.

[0124] (molecular weight)

[0125] The molecular weight of the surface treatment agent, such as the molecular weight of the silane coupling agent, is preferably 250 to 1000, more preferably 270 to 800, further preferably 300 to 750, and particularly preferably 350 to 700.

[0126] It should be noted that when using two or more surface treatment agents (e.g., silane coupling agents), it is preferable that the weighted average of the molecular weights of each surface treatment agent, weighted by the mass of each agent, is within the above-mentioned range, and more preferably that the total molecular weights of all the various surface treatment agents used are within the above-mentioned range.

[0127] For example, when a surface treatment agent is formulated with 0.5% by mass and 1.0% by mass of silane coupling agents with molecular weights of 300 and 500, respectively, its weighted average value is calculated as follows:

[0128] The weighted average is calculated as follows: ={(300×0.5) / (0.5+1.0)} + {(500×1.0) / (0.5+1.0)} = 433.

[0129] (Silane coupling agent)

[0130] In this embodiment, the surface treatment agent preferably includes a silane coupling agent.

[0131] That is, the glass yarn (including glass filaments) constituting the glass cloth is preferably surface-treated with a silane coupling agent.

[0132] Surface treatment agents, for example, include silane coupling agents represented by the following formula (1):

[0133] X 3-n SiY n …(1)

[0134] (In the formula, X is independently selected to contain different organic functional groups, and is composed of functional groups having a total of 2 or more carbonyl groups and a total of 2 or more unsaturated carbon double bonds in X; Y is independently alkoxy groups; and n is an integer of 1 or more and 3 or less.) Therefore, the difference between the dielectric loss tangent of the glass cloth and the dielectric loss tangent of the glass phase (the above dielectric loss tangent - the above bulk phase dielectric loss tangent) is less than 0.00000, thereby easily suppressing the time-dependent increase of the dielectric loss tangent of the glass cloth.

[0135] The silane coupling agent preferably contains at least one group selected from the group consisting of epoxy, amino, acryloyl, and methacryloyl groups in its molecule. For example, from the viewpoint of easily improving adhesion to the resin, the above-mentioned X preferably contains at least one group selected from the group consisting of epoxy, amino, aromatic vinyl, acryloyl, and methacryloyl groups.

[0136] Regarding Y, from the viewpoint of the stability of the surface treatment of glass cloth, alkoxy groups with 1 to 5 carbon atoms (1, 2, 3, 4 or 5 carbon atoms) are preferred as Y.

[0137] As a silane coupling agent contained in a surface treatment agent, the silane coupling agent shown in formula (1) above can be used alone or in multiple forms. For example, two or more different silane coupling agents described above can be used in combination.

[0138] Examples of silane coupling agents represented by general formula (1) include 4-(trimethoxysilyl)phenyl 2-methyl-2-propenoate.

[0139] 1-[2-(Trimethoxysilyl)ethyl]pentyl 2-methyl-2-propenoate

[0140] [4-[2-(Trimethoxysilyl)ethyl]phenyl]methyl 2-propenoate

[0141] N-2-Propen-1-yl-N-[3-(trimethoxysilyl)propyl]-2-oxiranemethanamine

[0142] 3-(Ethenyloxy)-2-[(trimethoxysilyl)oxy]propyl 2-propenoate

[0143] 6-[[[3-(Trimethoxysilyl)propyl]amino]carbonyl]-2-naphthalenyl 2-methyl-2-propenoate

[0144] 3-[2-(trimethoxysilyl)ethyl]tricyclo[3.3.1.1] 3,7 [3-[2-(Trimethoxysilyl)ethyl]tricyclo[3.3.1.1] 3,7 ]dec-1-yl 2-methyl-2-propenoate),

[0145] 4'-[(4-methylphenyl)[4-[2-(trimethoxysilyl)ethyl]phenyl]amino][1,1'-biphenyl]-4-yl 2-methyl-2-propenoate

[0146] Trimethoxy[3-(7-oxabicyclo[4.1.0]hept-3-ylmethoxy)propyl]silane

[0147] 1,3-Bis(2-oxiranylmethyl)-5-[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione

[0148] N 1 -[10-(trimethoxysilyl)decyl]-1,3-phenylenediamine (N 1 -[10-(Trimethoxysilyl)decyl]-1,3-benzenedimethanamine), etc.

[0149] The silane coupling agent that can be used can be appropriately adjusted according to the dielectric loss tangent of the glass cloth before surface treatment and the matrix resin used in the resin substrate. Of course, the silane coupling agent shown in formula (1) above can also be used in combination with silane coupling agents other than the silane coupling agent shown in formula (1) above.

[0150] On the other hand, it is preferable to use two or more silane coupling agents represented by the above formula (1) with different molecular weights. By using two or more silane coupling agents with different molecular weights, the density of the treatment agent on the glass surface tends to increase, resulting in a tendency for further improvement in reactivity with the matrix resin.

[0151] [Average fiber open density of glass cloth]

[0152] The average open fiber degree of the glass cloth is preferably 38% or more or more than 40%, more preferably more than 43%, further preferably more than 46%, more than 50%, more than 53%, more than 56%, or more than 60%, and particularly preferably more than 65%. When the average open fiber degree of the glass cloth is 38% or more, it is easy to suppress air bubbles, which are called voids, remaining in the glass yarn bundles during the fabrication of the resin substrate. As a result, it is less likely to have an adverse effect on the soldering heat resistance and insulation reliability.

[0153] It should be noted that the intermolecular forces of the silane coupling agent shown in formula (1) tend to be relatively strong. Therefore, compared with silane coupling agents other than those shown in formula (1), the impregnation of the matrix resin in the glass cloth tends to become unfavorable. Therefore, for glass cloths surface-treated with the silane coupling agent shown in formula (1), from the viewpoint of fully improving their insulation reliability, the average open fiber degree is preferably 38% or more or more than 40%.

[0154] [Weight loss on ignition of glass cloth]

[0155] From the viewpoint of easily reducing the dielectric loss tangent of the glass cloth, the weight loss on ignition of the glass cloth is preferably 0.01~0.5% by mass, or 0.01~0.4% by mass, or 0.01~0.3% by mass, more preferably 0.02~0.25% by mass, further preferably 0.03~0.22% by mass, even more preferably 0.03~0.17% by mass, and particularly preferably 0.04~0.15% by mass. When the weight loss on ignition is 0.01% by mass or more, it is easy to ensure the adhesion between the resin and the glass cloth in the resulting prepreg. In this case, it is easy to ensure heat resistance and insulation reliability when manufacturing printed circuit boards. When the weight loss on ignition of the glass cloth is less than 0.5% by mass, it is easy to avoid the presence of surface treatment agents (or their residues) that are physically attached to the glass cloth surface without forming chemical bonds, surface treatment agents (or their residues) that cannot be reduced from the glass cloth surface by water washing, and / or their modifiers on the glass cloth surface in large quantities. In this case, it is easy to achieve a low dielectric loss tangent for the glass cloth.

[0156] [White spots on the glass cloth]

[0157] White stains (white spots) are sometimes observed on the surface of surface-treated glass cloth. These white spots can easily repel the matrix resin used in the prepreg production, and therefore may cause poor appearance of the resulting prepreg.

[0158] The current understanding is that the cause of these white spots is unknown.

[0159] Regarding this point, the inventors have clarified that one of the aforementioned white spots is an aggregate or a modified form of a highly hydrophobic surface treatment agent (e.g., a highly hydrophobic silane coupling agent).

[0160] In particular, the inventors of this application have clarified that the silane coupling agent shown in formula (1) above has strong hydrophobicity, and therefore tends to easily form aggregates. In addition, when the solvent in the surface treatment solution contains water, the frequency of white spots in the surface-treated glass cloth tends to increase (e.g., 10.0 spots / m). 2 above).

[0161] To suppress white spots, as described below, it is appropriate to use methods such as preparing the surface treatment solution using prescribed methods, managing the temperature and pH of the surface treatment solution, and filtering the surface treatment solution to remove aggregates in the surface treatment solution.

[0162] The preferred frequency of white spots in the glass cloth is 7.0 spots / m. 2 Below, more preferably 4.0 pieces / m 2 The following is a further preferred option: 2.0 units / m 2Below or 0.1 per m 2 The following is a preferred option: 0.05 pieces / m 2 The following applies. Therefore, it is easy to achieve prepregs with excellent appearance. The frequency of white spots in the glass cloth can exceed 0 per m. 2 . s

[0163] [Method for manufacturing glass cloth]

[0164] One aspect of this embodiment is a method for manufacturing the glass cloth described above in this embodiment.

[0165] The manufacturing method of this embodiment includes:

[0166] The weaving process involves weaving glass yarn to obtain glass cloth; and

[0167] In the surface treatment process, after degreasing the glass yarn, a surface treatment solution is used to treat the glass yarn.

[0168] The dielectric loss tangent of the surface-treated glass cloth at 10 GHz is lower than that of the untreated glass cloth at 10 GHz.

[0169] Here, the manufacturing method of this embodiment may optionally include the following steps:

[0170] The process of reducing the fiber binding agent adhering to the glass yarn by heating it (heating degreasing process)

[0171] The process of washing glass yarn with water (finishing and cleaning process), and / or

[0172] The process of opening glass yarn (fiber opening process).

[0173] At least one of the surface treatment process, fiber opening process, and finishing cleaning process can be performed on the glass yarn before the process of weaving the glass yarn to obtain glass cloth (weaving process), or it can be performed on the glass cloth after the weaving process. Furthermore, the order of the heating degreasing process, surface treatment process, fiber opening process, and finishing cleaning process can be interchanged. When the cleaning process is performed after the weaving process, the fiber opening process can be combined with the cleaning process using high-pressure water spray, etc. It should be noted that the composition of the glass cloth usually does not change before and after fiber opening.

[0174] [Heating and degreasing process]

[0175] In this process, heating the glass yarn reduces the amount of fiber binding agent (sizing agent) and its residues, as well as their modifiers, adhering to the glass yarn, and preferably removes them. By performing a heating degreasing process, a surface treatment layer can be formed on the surface of the glass yarn (glass filament) while reducing organic matter that can increase the dielectric loss tangent, thus facilitating the production of glass cloth with excellent dielectric properties.

[0176] As a means of oil removal by heating, known methods (heating means, heating medium, heating mechanism, heating device and heating components, etc.) can be used.

[0177] As a method of heating and degreasing, for example, there is a known method of heating glass cloth at a temperature of 600~1600℃.

[0178] In the heat treatment process, by heating the glass cloth blank, whose softening point is above 900°C, within a temperature range of 600~1600°C, damage to the glass cloth is easily suppressed, and the dielectric loss tangent of the glass cloth is easily reduced. From the viewpoint of suppressing the time-dependent increase in the dielectric loss tangent of the glass cloth, it is preferable to fully dehydrate and condense the silanol groups present on the glass surface within a range that does not adversely affect the surface treatment process, which is the next step. By reducing the amount of silanol groups on the glass surface to below a certain level, the adsorption of moisture from the air can be suppressed, and as a result, the effects of this disclosure are easily achieved.

[0179] From the viewpoint of effectively achieving the effects of this disclosure, the heating degreasing temperature is preferably 700-1500°C, more preferably 800-1400°C, even more preferably 900-1300°C, and particularly preferably 1000-1200°C. When the heating degreasing temperature is above 600°C, the sizing agent and other substances adhering to the glass cloth blank can be easily and effectively removed, thus making it easier to produce glass cloth with excellent dielectric properties. When the heating degreasing temperature is below 1600°C, devitrification of the glass can be easily suppressed, and as a result, it is easier to prevent a decrease in the strength of the glass cloth.

[0180] The heating time is preferably less than 1 hour or less than 30 minutes, more preferably less than 15 minutes, and even more preferably less than 5 minutes. Heating the glass cloth at high temperature for an extended period can easily cause a dehydration condensation reaction of the silanol groups on the glass surface. From the viewpoint of effectively removing sizing agents, the heating time can be, for example, more than 1 second, more than 5 seconds, more than 10 seconds, or more than 15 seconds.

[0181] In the case of heating and degreasing glass cloth in a closed system, from the viewpoint of achieving suitable heating using heating methods, it is preferable to place the glass cloth inside a heating furnace. Furthermore, from the viewpoint of maximizing the efficiency of storage space and heating range, it is preferable to heat the glass cloth while storing it in a rolled-up state. Moreover, from the viewpoint of improving the removal efficiency of organic matter and shortening the removal time of organic matter, it is also preferable to heat the glass cloth while it is being conveyed inside the heating furnace. The conveying of the glass cloth can, for example, be carried out by a combination of a winding mechanism and a roll-up mechanism.

[0182] In the case of heating and degreasing glass cloth in an open system, from the viewpoint of ensuring the heated area, it is preferable to heat the glass cloth while it is being fed. The glass cloth can be fed, for example, by a combination of a winding mechanism and a roll-up mechanism.

[0183] The method of heating and degreasing is not limited to the above.

[0184] As another method for the heating and degreasing process, the following methods are also known:

[0185] Methods of heating in a vacuum or a gas with a dew point below 15°C, where the heating amount expressed as heating temperature (°C) × heating time (h) above 100°C is 450 (°C·h) or higher (where the highest heating temperature is 100~600°C).

[0186] (Heating method)

[0187] As heating methods, options include furnaces, electric heaters, and burners, with gas-fired single-radiant-tube burners or electric heaters being preferred. Various heating methods can be combined.

[0188] From the viewpoint of efficiently removing organic matter adhering to the surface of glass cloth, a continuous heating method is preferred over an intermittent method in which the glass cloth wound around the core is heated at a predetermined atmosphere temperature, where the glass cloth is continuously passed through a heating furnace while being heated. Even more preferred is a method that allows for continuous cleaning of the glass cloth using cleaning water with low metal ion content, such as reverse osmosis (RO) water or ion-exchange water.

[0189] When the sodium ions adhering to the glass cloth exceed a specified amount, heating the de-oiled glass cloth above 700°C can sometimes reduce the tensile strength of the glass cloth due to devitrification of the quartz glass. To suppress devitrification, washing the glass cloth with water containing less than 20 ppm of sodium ions before heating for de-oiling easily reduces the amount of sodium ions on the glass surface. In this case, even if de-oiling is performed at temperatures above 700°C, devitrification of the quartz glass is easily suppressed. By maintaining the strength of the glass cloth after de-oiling, wrinkles and / or damage to the glass cloth during surface treatment processes can be easily prevented.

[0190] From the viewpoint of achieving the desired effects of this disclosure, the sodium ion content of the cleaning water can be less than 18 ppm, less than 15 ppm, less than 12 ppm, less than 10 ppm, or less than 7 ppm. The sodium ion content is preferably 0 ppm, but it can also exceed 0.

[0191] Any known cleaning method that can remove sodium ions from the glass surface is acceptable for cleaning glass cloth with a sodium ion content of 20 ppm or less. Examples include ultrasonic methods (e.g., methods using ultrasonic transducers), spray-based methods (e.g., high-pressure spray-based methods), and steam spray methods. From the viewpoint of cost-effective processing, a preferred method is to immerse the glass cloth in a tank containing cleaning water (water with a sodium ion content of 20 ppm or less), remove excess cleaning water using a squeeze roller, and then dry the glass cloth. In this case, the immersion time can be, for example, 2 seconds or more, 5 seconds or more, 10 seconds or more, 15 seconds or more, or 120 seconds or less, 90 seconds or less, 60 seconds or less, and 45 seconds or less.

[0192] The method for producing water with a sodium ion content of 20 ppm or less can be a known method. For example, methods such as filtration using an RO membrane or deionization using an ion exchange resin are considered. "Water with a sodium ion content of 20 ppm or less" may include other liquid components (liquids other than water; etc.) without hindering the effects of the present invention.

[0193] From the viewpoint that it is easy to promote the dehydration condensation reaction of silanol groups on the glass surface, it is preferable to set the surrounding environment as dry as possible from the time of heating and degreasing until the temperature of the glass cloth surface drops to below 100°C, that is, to reduce the moisture in the surrounding area during heating and degreasing.

[0194] Methods for reducing ambient moisture during heating and degreasing include introducing dry air into the furnace, creating a vacuum inside the furnace, and introducing inert gases such as nitrogen into the furnace. When heating and degreasing is performed while glass cloth is being conveyed, introducing inert gases such as nitrogen into the furnace is preferred.

[0195] [Surface treatment process]

[0196] In the surface treatment process, a surface treatment liquid containing a surface treatment agent with a molecular weight of 200 or higher is used to treat the glass yarn.

[0197] Methods for treating glass fiber with a surface treatment liquid (e.g., coating the glass fiber with a surface treatment liquid) include:

[0198] (1) A method of conveying a glass cloth while immersing it in a surface treatment liquid that has accumulated in a bath (hereinafter referred to as the "immersion method");

[0199] (2) Methods such as directly applying the surface treatment liquid to the glass cloth using a roller coater, die coater, or gravure coater. When using the immersion method, the immersion time of the glass cloth in the surface treatment liquid is preferably selected to be 0.5 seconds or more and 1 minute or less.

[0200] In the method of this embodiment, the surface treatment step involves surface treating the glass yarn with a specified surface treatment agent, particularly a specified silane coupling agent (in one embodiment, a silane coupling agent advantageous from the viewpoint of reducing the dielectric loss tangent of the glass cloth). The silane coupling agent used in the method of this embodiment is more hydrophobic than general silane coupling agents.

[0201] Here, as described above, the inventors of this application have realized that when the solvent in the surface treatment solution contains water, there is a tendency for aggregates of the surface treatment agent to be easily generated. In addition, when the solvent in the surface treatment solution contains water, the frequency of white spots in the surface-treated glass cloth tends to increase.

[0202] The inventors of this application have discovered that, in a specified surface treatment solution, for example by performing the following (A) to (C), white spots on glass cloth can be suppressed.

[0203] (A) Add a solvent (e.g., a weakly acidic aqueous solution of the mother liquor) to the surface treatment agent;

[0204] (B) Control the temperature and / or pH of the surface treatment solution during surface treatment;

[0205] (C) Filter the surface treatment solution during surface treatment.

[0206] (A) Preparation of surface treatment solution

[0207] Common silane coupling agents have excellent compatibility with water and good dispersibility in water. Therefore, they are prepared by adding small amounts of silane coupling agent at a time while stirring slightly acidic water with a pH of around 3 to 5.

[0208] On the other hand, in the method of this embodiment, a pre-solution of the surface treatment agent can be obtained by adding a surfactant and a small amount of solvent for hydrolyzing the silane coupling agent (the solvent added here is, for example, a 60% aqueous solution of acetic acid) to a diluted solution obtained by diluting the surface treatment agent with a small amount of methanol. It should be noted that the solvent added to the pre-solution is for hydrolyzing the hydroxyl groups of the silane coupling agent, and the amount of solvent added is preferably adjusted according to the amount of hydrolysis. Furthermore, by adding a small amount of an aqueous solution (also referred to as "mother liquor" in this disclosure) adjusted to pH 3-4 to the pre-solution while stirring, the surface treatment agent can be uniformly dispersed in the aqueous solution. In this case, it is easier to suppress aggregates in the surface treatment solution.

[0209] From the viewpoint of easily suppressing white spots, the content of silane coupling agent relative to the surface treatment liquid is preferably in the range of 0.01 to 2.0% by mass, more preferably in the range of 0.01 to 1.8% by mass, even more preferably in the range of 0.02 to 1.5% by mass, even more preferably in the range of 0.02 to 1.3% by mass, and particularly preferably in the range of 0.02 to 1.0% by mass. When the content of silane coupling agent exceeds 2.0% by mass, the amount of silane coupling agent adhering to the glass cloth becomes excessive, thus easily increasing the dielectric loss tangent of the glass cloth. In addition, there are relatively more silanol groups not bonded to the glass, thus easily absorbing moisture from the air, resulting in an increase in the dielectric loss tangent of the glass cloth over time. On the other hand, when the content of silane coupling agent is less than 0.01% by mass, the amount of silane coupling agent adhering to the glass cloth is too small, thus the reaction between the silane coupling agent and the matrix resin is difficult to proceed fully, which can easily have an adverse effect on the solder heat resistance of the substrate.

[0210] As a surfactant, its composition and quantity can be appropriately modified according to the type and amount of surface treatment agent. Any of the following can be used: nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Different types of surfactants can also be used in combination.

[0211] The amount of surfactant relative to the surface treatment agent (e.g., silane coupling agent) is preferably 0.2 to 10% by mass, more preferably 0.4 to 9% by mass, even more preferably 0.6 to 8% by mass, and particularly preferably 1 to 6% by mass. By ensuring that the amount of surfactant meets the above range, the silane coupling agent can be easily and uniformly dispersed.

[0212] Examples of nonionic surfactants include glycerol fatty acid esters, sorbitol fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polyoxypropylene glycol, fatty acid polyethylene glycol esters, polyoxyethylene sorbitol fatty acid esters, and fatty acid alkanolamides.

[0213] Examples of anionic surfactants include fatty acid monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acylsarcosine salts, N-acylglutamate salts, dialkyl sulfosuccinates, alkane sulfonates, α-olefin sulfonates, linear alkylbenzene sulfonates, alkylbenzene sulfonates, naphthalene sulfonate-formaldehyde condensates, alkylnaphthalene sulfonates, N-methyl-N-acyl taurate, alkyl sulfates, polyoxyethylene alkyl ether sulfates, oleic acid sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and polyoxyethylene alkylphenyl ether phosphates.

[0214] Examples of cationic surfactants include monoalkylamine salts, dialkylamine salts, trialkylamine salts, alkyltrimethylammonium chloride, and alkylbenzalkonium chloride.

[0215] Examples of amphoteric surfactants include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolium betaine, alkyl betaine, fatty acid amylpropyl betaine, alkyl diethylenetriaminoacetic acid, and alkyl amine oxides.

[0216] (B) Temperature and / or pH control of surface treatment solution

[0217] From the viewpoint of suppressing aggregates in the surface treatment solution, it is preferable to control the temperature of the surface treatment solution at 10~30°C during surface treatment, more preferably at 13~27°C, even more preferably at 15~25°C, and particularly preferably at 17~23°C.

[0218] Furthermore, during surface treatment, the pH of the surface treatment solution may sometimes fluctuate due to trace amounts of impurities such as alkali metals contained in the glass cloth. From the viewpoint of suppressing aggregates in the surface treatment solution, it is preferable to minimize the fluctuation range of the pH of the surface treatment solution. During surface treatment, it is preferable to control the pH of the surface treatment solution at 2.5 to 5.5, more preferably at 2.8 to 5.2, and even more preferably at 3.0 to 5.0. As a method for controlling the pH within the specified range, for example, the method of bubbling carbon dioxide in the surface treatment solution can be cited.

[0219] The temperature and pH of the surface treatment solution can be controlled individually or both. From the viewpoint of effectively suppressing aggregates in the surface treatment solution, it is preferable to control both the temperature and pH of the surface treatment solution.

[0220] Here, "temperature control of surface treatment liquid" refers to the following concept: it includes not only operations that raise and / or lower the temperature of the surface treatment liquid, but also operations that maintain the temperature of the surface treatment liquid at a specified value, and operations that detect the temperature to determine whether the temperature of the surface treatment liquid falls within a specified range.

[0221] In addition, "pH control of surface treatment solution" refers to any of the following concepts: it includes not only operations that raise and / or lower the pH of the surface treatment solution, but also operations that maintain the pH of the surface treatment solution to a specified value, and operations that detect the pH to determine whether the pH of the surface treatment solution falls within a specified range.

[0222] (C) Filtration of surface treatment solution

[0223] From the viewpoint of reliably capturing aggregates in the surface treatment solution, it is preferable to filter the surface treatment solution during surface treatment. In this case, it is preferable to circulate the surface treatment solution while simultaneously capturing any aggregates that may form in the solution through filtration.

[0224] From the viewpoint of improving the collection efficiency of aggregates, it is preferable to perform filtration in multiple stages. For example, a preferred method is the following two-stage filtration: after removing the aggregates once using a filter with a coarser mesh, the surface treatment liquid is filtered again using a filter with a finer mesh than the first filter. This multi-stage filtration method makes it easier to prevent filter clogging, and consequently, it helps to avoid interruptions in the glass cloth manufacturing process.

[0225] (Drying process)

[0226] The surface treatment process may also include: a process of drying the solvent contained in the surface treatment liquid after coating the glass yarn (drying process).

[0227] According to the drying process, the surface treatment agent can be easily fixed to the surface of the glass yarn (the surface of the glass filament), especially to the surface of each individual glass yarn (the surface of each individual glass filament). As a method for drying the solvent, for example, methods of drying by heating can be cited, specifically, known methods such as heating by hot air and electromagnetic waves can be cited.

[0228] From the viewpoint of ensuring sufficient reaction between the surface treatment agent and the glass, the drying temperature is preferably 80°C or higher, more preferably 90°C or higher. Furthermore, from the viewpoint of preventing the deterioration of the organic functional groups present in the surface treatment agent, the drying temperature is preferably 300°C or lower, more preferably 180°C or lower.

[0229] [Fiber Opening Process]

[0230] The manufacturing method of this embodiment preferably includes a fiber opening process after the surface treatment process.

[0231] Examples of fiber-opening methods in the fiber-opening process include using water spray (high-pressure water fiber opening), vibrating washing machines, ultrasonic water, and cloth rolling machines to open glass cloth. During this fiber-opening process, by reducing the tension applied to the glass cloth, the yarn width of the glass yarn can be easily increased. Furthermore, it is easier to remove surface treatment agents that are not chemically bonded to the glass surface to a certain extent. To suppress the decrease in tensile strength of the glass cloth caused by the fiber-opening process, it is preferable to implement measures such as reducing friction of the contact components during glass yarn weaving, optimizing the sizing agent, and increasing the adhesion amount of the sizing agent.

[0232] [Cleaning Process]

[0233] As a cleaning process (finishing cleaning process), methods can be used to reduce the residues and modifiers of surface treatment agents that have not formed chemical bonds with the surface of the glass filaments. For example, methods such as cleaning glass yarn with organic solvents can be used. By performing a cleaning process, even when using glass raw materials with high silicon (Si) content, such as quartz glass, it is easy to adjust the difference between the dielectric loss tangent of the obtained glass cloth and the bulk dielectric loss tangent to within a specified range.

[0234] As a cleaning process, in order to reduce the aforementioned residues that are difficult to reduce with water, it is preferable to use a highly hydrophobic organic solvent for cleaning. In addition, it is preferable to use an organic solvent with high affinity for silane coupling agent residues with hydroxyl groups for cleaning.

[0235] As cleaning methods, known methods such as immersion and spraying can be used, and cleaning can be performed while heating or cooling as needed. In order to prevent the dissolved glass cloth residue from re-adhering, it is preferable to use a pressing roller or similar device to reduce excess solvent before finishing and drying of the cleaned glass cloth.

[0236] Suitable organic solvents, such as highly hydrophobic organic solvents, include 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, and 2,2,4,6,6-pentamethylheptane (isododecane); saturated cyclic aliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, and ethylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, and triethylbenzene; and halogenated solvents such as chloroform, dichloromethane, and dichloroethane.

[0237] Examples of organic solvents with high affinity for surface treatment agents (such as silane coupling agents) include alcohols such as methanol, ethanol, and butanol; ketones such as acetone and methyl ethyl ketone; ethers such as methyl ethyl ether and diethyl ether; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; and dimethyl sulfoxide.

[0238] From the viewpoint that the difference between the dielectric loss tangent of the obtained glass cloth and the dielectric loss tangent of the bulk phase can be easily adjusted to within a specified range, aromatic hydrocarbons, alcohols or ketones are preferred, and methanol is more preferred.

[0239] In the manufacturing method of this embodiment, in order to reduce the organic solvent after cleaning, it is preferable to include a step of drying the cleaned glass cloth (post-cleaning drying step). From the viewpoint that it is easy to reduce organic solvent by drying, the organic solvent used in cleaning preferably has a boiling point of 120°C or below. In the drying of organic solvent, known methods such as heating drying and air drying can be used.

[0240] In the post-cleaning drying process, when heating is used to reduce organic solvents, from a safety perspective, hot air drying using low-pressure steam or hot oil as the heat source is preferred. The drying temperature is preferably above the boiling point of the cleaning solvent, and from the viewpoint of suppressing the deterioration of the silane coupling agent, it is preferably below 180°C.

[0241] [Optional Process]

[0242] In addition to the steps described above, the manufacturing method of this embodiment may optionally include other steps.

[0243] Other processes include, for example, the process of processing glass cloth into slits (slit processing process).

[0244] (Inspection or measurement process)

[0245] In addition, as another step, the step of inspecting white spots on the glass cloth can be listed. The manufacturing method of this embodiment, by including this step, easily produces the glass cloth of this embodiment.

[0246] [Prepreg]

[0247] The prepreg of this embodiment contains glass cloth, matrix resin, and inorganic filler. The prepreg of this embodiment can be manufactured using the glass cloth described above as the glass cloth. Thus, prepregs with various excellent properties (e.g., prepregs with low porosity) are provided.

[0248] As the base resin, any type of thermosetting resin or thermoplastic resin can be used. Thermosetting resins and thermoplastic resins can be used in combination.

[0249] Examples of thermosetting resins include:

[0250] (a) An epoxy resin is formed by reacting a compound having an epoxy group with a compound having at least one of an amino group, phenolic group, acid anhydride group, acylhydrazine group, isocyanate group, cyanate group, and hydroxyl group that reacts with the epoxy group under catalyst-free conditions, or by adding a catalyst with reaction catalytic ability such as an imidazole compound, tertiary amine compound, urea compound, or phosphorus compound, and then curing it.

[0251] (b) A free radical polymerizable curing resin, which is formed by using a thermally decomposable catalyst or a photodecomposable catalyst as a reaction initiator and curing a compound having at least one of allyl, methacrylate, and acrylic groups;

[0252] (c) Maleimide triazine resin, which is formed by reacting a compound having a cyanate ester group with a compound having a maleimide group and then curing it;

[0253] (d) Thermosetting polyimide resin, which is formed by reacting maleimide compound with amine compound and then curing it;

[0254] (e) Benzoxazine resins, which are formed by crosslinking and curing compounds having benzoxazine rings through heating polymerization; etc.

[0255] Examples of thermoplastic resins include polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, aromatic polyamide, polyetheretherketone, thermoplastic polyimide, insoluble polyimide, polyamide-imide, LCP, polyester, fluoropolymer, etc.

[0256] Prepregs may contain inorganic fillers. Examples of inorganic fillers 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 in combination with thermosetting resins.

[0257] Printed Circuit Board

[0258] The printed circuit board of this embodiment includes a prepreg. In particular, the printed circuit board of this embodiment is manufactured using the prepreg described above as the prepreg. Therefore, printed circuit boards with various excellent properties (e.g., printed circuit boards with excellent insulation reliability) are provided.

[0259] [Integrated Circuits and Electronic Equipment]

[0260] The integrated circuit of this embodiment includes the printed circuit board described in this embodiment. Furthermore, the electronic device of this embodiment includes the printed circuit board described in this embodiment. Thus, various integrated circuits and electronic devices with excellent characteristics are provided.

[0261] Example

[0262] Hereinafter, examples and comparative examples are provided to further illustrate this embodiment. However, this embodiment is not limited to the examples described below. Various manufacturing, measurement, and evaluation methods were performed in the examples and comparative examples using the following methods.

[0263] [thickness]

[0264] According to section 7.10 of JIS R 3420, using a micrometer, slowly rotate the mandrel until it is parallel to the measuring surface and gently touches it. Read the scale after the ratchet clicks three times. It should be noted that JIS R 3420 specifies general test methods for glass fibers and products such as glass cloth using glass fibers.

[0265] [Weight per unit area]

[0266] Samples are obtained by cutting glass cloth to a specified size. The weight per unit area is calculated by dividing the mass of the sample by its area. Here, samples are obtained by cutting glass cloth into 10cm × 10cm pieces, and their mass is measured to determine the weight per unit area (g / m²). 2 ).

[0267] [Thickness Conversion]

[0268] Glass cloth is a discontinuous planar body composed of air and glass. Therefore, by dividing the weight per unit area of ​​each piece of glass cloth by the density of glass, the equivalent thickness required for measurement using the resonance method can be calculated.

[0269] The calculation formula is as follows: Converted thickness (μm) = Weight per unit area (g / m²) 2 ) ÷ Density of glass (g / cm³) 3 ).

[0270] [Dielectric loss tangent]

[0271] According to IEC 62562, the dielectric loss tangent of each glass cloth was measured. Specifically, glass cloth samples of the required dimensions for measurement in each split cylindrical resonator were conditioned in a constant temperature and humidity oven at 23°C and 50%RH for 8 hours. Then, the dielectric properties at 10 GHz were measured using a split cylindrical resonator (EM LABO) and an impedance analyzer (Agilent Technologies). Five measurements were performed on each sample, and the average value was calculated. The thickness of each sample was calculated using the aforementioned converted thickness. It should be noted that IEC 62562 primarily specifies the method for measuring the dielectric properties of fine ceramic materials used in microwave circuit dielectric substrates in the microwave band.

[0272] [Bulk dielectric loss tangent]

[0273] A glass plate of the same type and composition as the glass cloths whose dielectric loss tangent was measured was prepared, with a thickness of 300 μm. Then, using the thickness obtained from the thickness measurement of the glass plate, the bulk dielectric loss tangent at 10 GHz was measured by the same method as the dielectric loss tangent measurement described above.

[0274] [Difference in dielectric loss tangent (the above dielectric loss tangent - the above bulk dielectric loss tangent)]

[0275] Based on the dielectric loss tangent and the bulk dielectric loss tangent obtained by the above measurement method, the difference of the dielectric loss tangent (the dielectric loss tangent - the bulk dielectric loss tangent) is calculated.

[0276] [Increase in dielectric loss tangent over time]

[0277] Due to the presence of moisture in the storage environment, the dielectric loss tangent of the glass cloth will increase. Using a constant temperature and humidity chamber, the glass cloth was stored for one week in a high temperature and high humidity environment (40℃, relative humidity 90%). The increase in dielectric loss tangent over time before and after storage was calculated as (dielectric loss tangent after storage - dielectric loss tangent before storage).

[0278] (condition)

[0279] Storage conditions: 40℃×90%RH

[0280] Storage period: 1 week

[0281] Dielectric loss tangent: The measurement method described above for [dielectric loss tangent]

[0282] [Loss on Ignition]

[0283] According to JIS R3420, the loss on ignition of the glass cloth was calculated. Specifically, the glass cloth was dried at 110℃±5℃ for 60 minutes. Then, it was transferred to a desiccator and allowed to cool naturally at room temperature for 20 minutes. The mass of the test piece was then weighed to a unit of 0.1 mg (A mg). The dried test piece was then heat-treated at 625℃±20℃ for 20 minutes. Next, it was transferred to a desiccator and allowed to cool naturally for 20 minutes. The mass of the test piece was then weighed to a unit of 0.1 mg (B mg). The loss on ignition was calculated using the following formula, rounded to the fourth decimal place, and expressed as a third decimal place.

[0284] Loss on ignition (%) = (A(mg) - B(mg))) / A(mg) × 100

[0285] [Average filament diameter of glass yarn]

[0286] The cross-sections of 30 strands of glass yarn at any position were observed using a scanning electron microscope. The average value was calculated, and the average filament diameter was determined.

[0287] [Average fiber opening degree]

[0288] The open fiber density of the warp yarns in glass cloth is calculated using the following formula:

[0289] The opening degree of the warp yarn (%) = [warp width (μm) / {number of warp filaments × diameter of warp filaments (μm)}] × 100.

[0290] In addition, the open fiber density of the weft yarns of the glass cloth is calculated using the following formula:

[0291] The opening degree of the weft yarn (%) = [weft yarn width (μm) / {number of weft yarn filaments × diameter of weft yarn filaments (μm)}] × 100.

[0292] Using the calculated warp yarn openness (%) and weft yarn openness (%), the average openness is calculated using the following formula:

[0293] Average fiber opening degree (%) = {fiber opening degree of warp yarn (%) + fiber opening degree of weft yarn (%)} / 2.

[0294] (Number of filaments for each warp and weft yarn)

[0295] When calculating the average fiber opening, the number of filaments of the warp and weft yarns is determined by observing a cross-sectional image of the glass yarn. Specifically, a cross-sectional image of the glass yarn used as the warp (or weft) is obtained, and the number of filaments of that warp (or weft) yarn is measured in the cross-sectional image.

[0296] Similarly, the image acquisition and filament number measurement of the glass yarn were repeated, and the average of the 5 measurements was used as the filament number of the warp (or weft) yarn.

[0297] (warp width and weft width)

[0298] When calculating the average fiber opening, the warp width and weft width are determined using the following method.

[0299] First, cut five glass cloth test pieces with dimensions of 70mm in the warp direction and 70mm in the weft direction from the glass cloth.

[0300] The cut test pieces were observed vertically at 100x magnification using a microscope. For each test piece, the width of 250 warp (or weft) yarns was randomly measured, and the average value of the 250 warp (or weft) yarn widths was calculated. This average value was then used as the warp width (or weft width).

[0301] [Glass cloth P]

[0302] The warp and weft yarns were composed of glass yarn with a SiO2 content exceeding 99.9% by mass. Specifically, glass yarns with an average filament diameter of 5.0 μm, 100 filaments, and a twist of 1.0 Z were used as the warp and weft yarns, respectively. Then, 2000 m of plain-weave glass cloth was woven using an air-jet loom with a weaving density of 66 warp yarns / 25 mm and 68 weft yarns / 25 mm, and a cloth width of 1300 mm. It should be noted that the bulk dielectric loss tangent of the glass constituting the glass yarn used was 0.00020° at 10 GHz.

[0303] [Glass Cloth Q]

[0304] The warp and weft yarns were composed of glass yarn with a SiO2 content exceeding 99.9% by mass. Specifically, glass yarns with an average filament diameter of 5.0 μm, 200 filaments, and a twist of 1.0 Z were used as the warp and weft yarns, respectively. Then, 2000 m of plain-weave glass cloth was woven using an air-jet loom with a weaving density of 54 warp yarns / 25 mm and 54 weft yarns / 25 mm, and a cloth width of 1300 mm. It should be noted that the bulk dielectric loss tangent of the glass constituting the glass yarn used was 0.00020° at 10 GHz.

[0305] [Glass cloth R]

[0306] The warp and weft yarns were composed of glass yarn with a SiO2 content exceeding 99.9% by mass. Specifically, glass yarns with an average filament diameter of 4.0 μm, a filament count of 50, and a twist count of 1.0 Z were used as the warp and weft yarns, respectively. Then, 2000 m of plain-weave glass cloth was woven using an air-jet loom with a weaving density of 95 warp yarns / 25 mm and 95 weft yarns / 25 mm, and a cloth width of 1300 mm. It should be noted that the bulk dielectric loss tangent of the glass constituting the glass yarn used was 0.00020° at 10 GHz.

[0307] [Preparation of Surface Treatment Solution]

[0308] Prepare the surface treatment solution according to the following methods 1) to 5).

[0309] 1) Weigh the silane coupling agent.

[0310] 2) Mix the methanol weighed in the same amount as in 1) above with the silane coupling agent weighed in 1) above to prepare a silane coupling agent solution.

[0311] 3) Mix the silane coupling agent solution with 0.8% by mass of polyoxyethylene alkyl ether relative to the silane coupling agent, and then stir. After stirring for 1 minute, add an aqueous acetic acid solution (60% by mass) at 20% by mass relative to the silane coupling agent to the silane coupling agent solution. This hydrolyzes the silane coupling agent.

[0312] 4) Prepare a stock solution of acetic acid aqueous solution (pH=3~4). Separately, stir the silane coupling agent solution (pre-solution) obtained in 3) above at room temperature (20~25°C) for 15 minutes. At this time, add the stock solution dropwise to the stirring silane coupling agent solution to disperse the silane coupling agent. The amount of stock solution added (dropping rate) is set to allow all the stock solution to be added dropwise over 10 minutes.

[0313] 5) After step 4) above, stir the silane coupling agent solution at room temperature of 20~25℃ for 2 hours to obtain the surface treatment solution.

[0314] In the "process of adding a solvent to a surface treatment agent to prepare a surface treatment solution" disclosed herein, the "solvent" is, in one embodiment, the aforementioned mother liquor. Here, an example of the mother liquor is a weakly acidic aqueous solution with a pH of 3 to 4 added to disperse the hydrolyzed silane coupling agent.

[0315] [Examples and Comparative Examples]

[0316] (Example 1)

[0317] The glass cloth P is washed with ion-exchanged water and then dried. This removes alkali metal ions and other contaminants adhering to the surface of the glass cloth. Then, the glass cloth is conveyed and heated for 5 minutes in a furnace with the set temperature adjusted to 1000°C for degreasing (heating degreasing process). It should be noted that the above-mentioned heating degreasing is carried out in a nitrogen atmosphere in the furnace.

[0318] 4-(Trimethoxysilyl)phenyl 2-methyl-2-propenoate (CAS NO: 2097368-37-9, molecular weight = 282.36, silane coupling agent A) was used as a silane coupling agent. The surface treatment solution was prepared by the above method so that the concentration of silane coupling agent in the surface treatment solution was 0.4% by mass.

[0319] The heated and degreased glass cloth is then immersed in the resulting surface treatment solution. Excess solution is then squeezed out using an NBR rubber roller at a pressure of 0.3 MPa. The glass cloth is then heated and dried at 130°C for 1 minute, thereby fixing the silane coupling agent to the surface of the glass cloth.

[0320] In this embodiment, during the surface treatment of the glass cloth, temperature management (e.g., cooling) is performed so that the temperature of the surface treatment solution is in the range of 17~23°C. Additionally, during the surface treatment of the glass cloth, carbon dioxide is bubbled into the surface treatment solution so that the pH of the surface treatment solution is in the range of 3.0~4.0.

[0321] In this embodiment, an HDCII filter (manufactured by Nihon Pall Ltd.) is used to filter the surface treatment liquid used in the surface treatment of the glass cloth. Specifically, the surface treatment liquid is first passed through a filter with a mesh size of 10 μm, and then further passed through a filter with a mesh size of 4.5 μm. This captures any aggregates that may be present in the surface treatment liquid. The filtered surface treatment liquid is then used for the surface treatment of the glass cloth.

[0322] Apply 3.0 kg / cm² of spray to the surface-treated glass cloth using a spray nozzle. 2 The pressure is used to perform high-voltage fiber opening. Then, the fiber is irradiated in water at a frequency of 25kHz and an output power of 0.50W / cm². 2 The glass cloth is further split by ultrasonic waves, which reduces excess silane coupling agent physically adhering to it. It is then dried by heating at 130°C for 1 minute. Through these processes, 2000m of surface-treated glass cloth is obtained.

[0323] (Example 2)

[0324] [4-[2-(Trimethoxysilyl)ethyl]phenyl]methyl 2-propenoate (CAS NO: 141813-20-9, molecular weight = 310.42, silane coupling agent B) was used as the silane coupling agent. Otherwise, 2000m glass cloth was obtained by the same method as in Example 1.

[0325] (Example 3)

[0326] 6-[[[3-(Trimethoxysilyl)propyl]amino]carbonyl]-2-naphthalenyl 2-methyl-2-propenoate (CAS NO: 1537868-42-0, molecular weight = 417.53, silane coupling agent C) was used as the silane coupling agent. Otherwise, 2000m glass cloth was obtained by the same method as in Example 1.

[0327] (Example 4)

[0328] Using 1,3-bis(2-epoxyethoxymethyl)-5-[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (1,3-Bis(2-oxiranylmethyl)-5-[3-(trimethoxysilyl)propyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione) (CAS NO: 1331829-87-8, molecular weight = 403.46, silane coupling agent D) as the silane coupling agent, 2000m glass cloth was obtained by the same method as in Example 1.

[0329] (Example 5)

[0330] Use N 1 -[10-(trimethoxysilyl)decyl]-1,3-phenylenediamine (N 1 -[10-(Trimethoxysilyl)decyl]-1,3-benzenedimethanamine)(CAS NO: 149048-51-1, molecular weight = 396.64, silane coupling agent E) was used as the silane coupling agent. Otherwise, 2000m glass cloth was obtained by the same method as in Example 1.

[0331] (Example 6)

[0332] Using 4'-[(4-methylphenyl)[4-[2-(trimethoxysilyl)ethyl]phenyl]amino][1,1'-biphenyl]-4-yl 2-methyl-2-propenoate (CAS NO: 1266672-96-1, molecular weight = 567.75, silane coupling agent F) as the silane coupling agent, a 2000m surface-treated glass cloth was obtained by the same method as in Example 1.

[0333] (Example 7)

[0334] Glass cloth Q was used instead of glass cloth P, and otherwise 2000m glass cloth was obtained by the same method as in Example 1.

[0335] (Example 8)

[0336] 2000m of glass cloth was obtained by using glass cloth R instead of glass cloth P, except that the same method as in Example 1 was used to obtain the glass cloth.

[0337] (Example 9)

[0338] Surface treatment was performed without filtering the surface treatment liquid, and otherwise, 2000m glass cloth was obtained by the same method as in Example 3.

[0339] (Example 10)

[0340] The concentration of the surface treatment solution was adjusted to a total of 0.4% by mass, consisting of 0.2% by mass of silane coupling agent A and 0.2% by mass of silane coupling agent B. Fiber splitting using the spray nozzle was not performed; instead, an output power of 0.20 W / cm was used. 2 The fiber was opened using ultrasonic waves, and 2000m of glass cloth was obtained by the same method as in Example 1.

[0341] (Example 11)

[0342] Even if the temperature of the surface treatment solution exceeds 23°C, the surface treatment solution is not cooled, and even if the pH exceeds 4.0, carbon dioxide bubbling is not performed. Otherwise, 2000m glass cloth is obtained by the same method as in Example 3.

[0343] (Comparative Example 1)

[0344] The concentration of the surface treatment solution was adjusted to 0.9% by mass, and the heating degreasing temperature was changed to 700°C. Otherwise, 2000m of surface-treated glass cloth was obtained by the same method as in Example 1.

[0345] (Comparative Example 2)

[0346] The concentration of the surface treatment solution was adjusted to 2.5% by mass. Otherwise, 2000m of surface-treated glass cloth was obtained by the same method as in Example 1.

[0347] (Comparative Example 3)

[0348] The surface treatment solution was prepared by adding a silane coupling agent solution dropwise to the mother liquor of the acetic acid aqueous solution under stirring. The surface treatment of the glass cloth was carried out without filtering the surface treatment solution. The surface treatment solution was not cooled even if the temperature of the surface treatment solution exceeded 23°C. Carbon dioxide bubbling was not carried out even if the pH exceeded 4.0. Otherwise, 2000m glass cloth was obtained by the same method as in Example 1.

[0349] [Frequency of white spot formation]

[0350] The frequency of white spots on the surface of the glass cloth was evaluated by illuminating glass cloth of A4 size (210mm × 297mm) and above with a halogen lamp. When observing sheet-like glass cloth, a halogen lamp was placed directly above the glass cloth, and the frequency of white spot occurrence was calculated by the number of white spots and the following formula while changing the direction of observation:

[0351] Frequency of white spots (number / m) 2 = Number of white spots / {Area of ​​glass cloth (m²)} 2 )}.

[0352] In addition, when observing glass cloth rolls, on a roll-to-roll inspection table, while applying a tension of 100 N / 1300 mm and illuminating with a halogen lamp, the number of white spots generated in the glass cloth over a length of 2000 m is counted. Then, based on the inspected area and the number of white spots found during the inspection, the frequency of white spot generation is calculated according to the following formula:

[0353] Frequency of white spots (number / m) 2 = Number of white spots / {Width of glass cloth (m) × Length of glass cloth being inspected (m)}.

[0354] Figure 1 This is a photograph used to illustrate the "white spot" in this embodiment. Figure 1 (a) represents a photograph of the area without white spots. Additionally, Figure 1(b) shows a photograph of the area with white spot P.

[0355] In this embodiment, the area enclosed by the white outline observed under UV light (including the area of ​​the outline) is 0.8 cm². 2 The above defects are defined as "white spots". Here, the outline is, for example, a circle.

[0356] It should be noted that the area enclosed by the contour line is calculated using known image analysis software.

[0357] [Prepreg Manufacturing Method 1]

[0358] In this manufacturing method 1, polyphenylene ether resin is used as a raw material.

[0359] Specifically, 45 parts by weight of polyphenylene ether (manufactured by SABIC, Noryl 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) are added to a stainless steel container and stirred at room temperature for 1 hour. This produces a varnish.

[0360] After impregnating the glass cloth obtained in Examples 1-4 and 6-11 and Comparative Examples 1-3 with the prepared varnish, the prepreg was obtained after drying at 130°C for 1 minute.

[0361] [Prepreg Manufacturing Method 2]

[0362] In this manufacturing method 2, epoxy resin is used as a raw material.

[0363] Specifically, a varnish is prepared by mixing 80 parts by weight of low-brominated bisphenol A type epoxy resin, 20 parts by weight of cresol phenolic varnish type epoxy resin, 2 parts by weight of dicyandiamide, 0.2 parts by weight of 2-ethyl-4-methylimidazolium, and 100 parts by weight of 2-methoxy-ethanol.

[0364] After impregnating the glass cloth obtained in Examples 4 and 5 with the prepared varnish, it was dried at 130°C for 7 minutes to obtain the prepreg.

[0365] [Manufacturing method of polyphenylene oxide resin substrate]

[0366] The obtained prepreg samples were taken in sizes of 20cm × 20cm. Eight samples were stacked together, and then copper foil with a thickness of 12μm was stacked on the top and bottom layers. Then, the samples were subjected to a temperature of 200℃ and a pressure of 40kg / cm². 2 The resin substrate is produced by heating and pressurizing for 120 minutes.

[0367] [Manufacturing method of epoxy resin substrate]

[0368] The obtained prepreg was sampled in a size of 20cm × 20cm. Eight samples were stacked together, and then copper foil with a thickness of 12μm was stacked on the top and bottom layers. Then, it was subjected to a temperature of 195℃ and a pressure of 40kg / cm². 2 The resin substrate is produced by heating and pressurizing for 120 minutes.

[0369] [Welding heat resistance]

[0370] A laminate was obtained by removing the top and bottom copper foil layers from the resin substrate. Ten laminates were cut into 5cm x 5cm pieces. These were then heated in an autoclave at 133°C for 24 hours to absorb water. The water-absorbed laminates were then immersed in a solder bath at 288°C for 20 seconds. Each of the ten laminate samples was then visually inspected for any swelling caused by peeling at the glass cloth / resin interface.

[0371] Laminate samples exhibiting expansion due to delamination at the glass cloth / resin interface are marked as "unacceptable," and the number of such "unacceptable" laminate samples is recorded. A lower number of glass cloth samples listed in the table indicates better heat resistance.

[0372] The manufacturing conditions and evaluation results of the embodiments and comparative examples are shown in the table below. It should be noted that the glass cloth used in the embodiments can be used to manufacture prepregs, printed circuit boards (resin substrates), integrated circuits, and electronic devices using conventional methods.

[0373] [Table 1]

[0374]

[0375] [Table 2]

[0376]

[0377] According to the embodiments, a glass cloth can be provided that can: achieve excellent dielectric properties, suppress the increase of dielectric loss tangent over time, and achieve excellent solder heat resistance for resin substrates made using the glass cloth. On the other hand, Comparative Examples 1-2 cannot suppress the increase of dielectric loss tangent over time, and in Comparative Example 3, excellent solder heat resistance properties cannot be obtained.

[0378] Industrial availability

[0379] This invention can be applied to fields involving glass cloth, printed circuit boards (especially printed circuit boards for high-speed communication), etc.

[0380] Explanation of reference numerals in the attached figures

[0381] P: White spots

Claims

1. A type of glass cloth, which is a glass cloth woven from glass yarn. The glass cloth was surface-treated with a surface treatment agent. The difference between the dielectric loss tangent of the glass cloth at 10 GHz and the bulk dielectric loss tangent of the glass constituting the glass yarn at 10 GHz, i.e., the dielectric loss tangent minus the bulk dielectric loss tangent, is less than 0.00000. The white spots on the glass cloth are 10 per m. 2 the following.

2. The glass cloth according to claim 1, wherein, The silicon (Si) content in the glass yarn is 95.0~100% by mass, converted from silicon dioxide (SiO2).

3. The glass cloth according to claim 1 or 2, wherein, The average open fiber ratio calculated from the yarn widths of the warp and weft yarns of the glass cloth exceeds 40%.

4. The glass cloth according to claim 1 or 2, wherein, The bulk dielectric loss tangent is below 0.

002.

5. The glass cloth according to claim 1 or 2, wherein, The surface treatment agent contains a silane coupling agent.

6. The glass cloth according to claim 5, wherein, The molecular weight of the silane coupling agent is 250~1000.

7. The glass cloth according to claim 5, wherein, The silane coupling agent contains at least one group selected from the group consisting of epoxy, amino, aromatic vinyl, acryloyl and methacryloyl groups in its molecule.

8. The glass cloth according to claim 5, wherein, The surface treatment agent contains two or more of the silane coupling agents with different molecular weights.

9. The glass cloth according to claim 1 or 2, wherein, The loss on ignition of the glass cloth is 0.01~0.5% by mass.

10. The glass cloth according to claim 1 or 2, which is a constituent material of a printed circuit board.

11. A prepreg comprising the glass cloth as described in claim 1 or 2 and a thermosetting resin.

12. A printed circuit board comprising the prepreg of claim 11.

13. An integrated circuit comprising the printed circuit board of claim 12.

14. An electronic device comprising the printed circuit board of claim 12.

15. A method for manufacturing glass cloth, comprising: The weaving process involves weaving glass yarn to obtain glass cloth; as well as In the surface treatment process, after the glass yarn is degreased, it is surface treated with a surface treatment solution. The dielectric loss tangent of the surface-treated glass cloth at 10 GHz is lower than that of the untreated glass cloth at 10 GHz.

16. The method for manufacturing glass cloth according to claim 15, wherein, The surface treatment solution is prepared by adding an acidic aqueous solution to a silane coupling agent used as a surface treatment agent.

17. The method for manufacturing glass cloth according to claim 15 or 16, wherein, The surface treatment process includes: The process of controlling the temperature and pH of the surface treatment solution, and the process of filtering the surface treatment solution.

18. The method for manufacturing glass cloth according to claim 15 or 16, wherein, Following the surface treatment process, the process further includes a fiber-opening process for the glass yarn.

19. The method for manufacturing glass cloth according to claim 15 or 16, wherein, Following the surface treatment process, the process further includes: inspecting the white spots on the glass cloth.

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