JP2022001690A - Glass cloth, prepreg and print circuit board - Google Patents

Abstract

To provide: a glass cloth capable of fabricating a high-quality substrate in which delamination hardly occurs; a prepreg using the same; and a print circuit board.SOLUTION: A glass cloth is obtained by weaving a glass thread composed of a plurality of glass filaments as the warp and weft. The glass filament has the average filament diameter of 3.0-4.5 μm and the glass filament number of 20-50. The picking densities of the warp and weft composed of the glass cloth each are 70-130/inch. The glass cloth has the thickness of 7-13 μm and the maximum area of basket holes present in the glass cloth is 50,000 μm2 or less.SELECTED DRAWING: None

Description

The present invention relates to glass cloths, prepregs, and printed wiring boards.

At present, with the increasing functionality of electronic devices, the density and thickness of printed wiring boards used are remarkably increasing.
As the insulating material of this printed wiring board, a laminated board obtained by impregnating a glass cloth with a thermosetting resin such as an epoxy resin (hereinafter referred to as "matrix resin") and laminating a prepreg obtained by laminating and heat-pressing curing. Is widely used. In particular, in cutting-edge smartphones and wearable devices, printed wiring boards are downsized, and glass cloth, which is a constituent material, is required to have high quality, high performance, and ultra-thinness.

The diameter of the glass filament constituting the glass cloth is generally designed to have a minimum diameter of 3 μm or more from the viewpoint of safety and reduction of environmental load. Therefore, each glass cloth maker performs various processing to embody the ultra-thinning of the glass cloth (see, for example, Patent Documents 1 to 4).

Japanese Patent No. 4446754 Japanese Patent No. 5905150 Japanese Patent No. 6020764 Japanese Patent No. 5936726

However, there is still room for improvement in the future ultra-thin printed wiring boards from the viewpoint of achieving sufficient quality and performance. Specifically, in order to thin the insulating layer of the printed wiring board, a glass cloth having a thickness of 13 μm or less is used, and the mass of the resin (g) with respect ^{to RC (mass of the substrate including the glass cloth (g / m 2)).} When the mass ratio of / m ² ) is 65% by mass or less, there is a problem that pinholes occur at a constant frequency when the prepreg is produced, and delamination occurs when the prepreg is mounted at a high temperature.

In fact, the glass cloth disclosed in Patent Document 2 has a problem that pinholes occur when RC is 69% by mass or less.

Further, in the glass cloth disclosed in Patent Document 4, since glass fibers having different thicknesses are used for the warp and weft, there is a problem that anisotropy is likely to occur during mounting at a high temperature.

The present invention has been made in view of the above problems, and is a high-quality board that is less likely to cause delamination (the "board" is a concept including a prepreg, a printed wiring board, a laminated board thereof, and the like. It is an object of the present invention to provide a glass cloth capable of producing the above glass cloth, a prepreg using the glass cloth, and a printed wiring board.

As a result of studies for solving the above-mentioned problems, the present inventors have found that a predetermined glass cloth can solve the above-mentioned problems, and have completed the present invention.

That is, the present invention is as follows.
[1]
A glass cloth made by weaving glass threads composed of a plurality of glass filaments as warps and wefts.
The average filament diameter of the glass filament is 3.0 to 4.5 μm.
The number of the glass filaments is 20 to 50, and the number of the glass filaments is 20 to 50.
The driving densities of the warp and weft constituting the glass cloth are independently 70 to 130 threads / inch, respectively.
The thickness of the glass cloth is 7 to 13 μm, and the thickness of the glass cloth is 7 to 13 μm.
The maximum area of the basket hole existing in the glass cloth is 50,000 μm ² or less.
Glass cloth.
[2]
The glass cloth according to [1], wherein the maximum value of the air permeability is 250 cm ³ / cm ^{2 / sec or less.}
[3]
The glass cloth according to [1] or [2], wherein the degree of opening of the yarn widths of the warp and weft is 90% or more independently.
[4]
The glass cloth according to any one of [1] to [3], wherein the minimum yarn widths of the warp and weft are 100 μm or more independently.
[5]
The glass cloth according to any one of [1] to [4], wherein the maximum width of the basket hole is 120 μm or less.
[6]
The glass cloth according to any one of [1] to [5], wherein the surface of the glass thread is treated with a plurality of kinds of silane coupling agents.
[7]
A prepreg comprising the glass cloth according to any one of [1] to [6] and a matrix resin impregnated in the glass cloth.
[8]
A printed wiring board having the prepreg according to [7].

According to the present invention, it is possible to provide a glass cloth capable of producing a substrate having high quality and less likely to cause delamination, a prepreg using the glass cloth, and a printed wiring board.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited thereto, and various modifications can be made without departing from the gist thereof. Is.

〔Glass cloth〕
The glass cloth of the present embodiment is a glass cloth obtained by weaving a glass thread composed of a plurality of glass filaments as a warp and a weft.
Further, in the glass cloth of the present embodiment, the average filament diameter of the glass filament is 3.0 to 4.5 μm, the number of the glass filaments is 20 to 50, and the warp and weft constituting the glass cloth. And the driving density of the warp and weft is 70 to 130 threads / inch independently, the thickness of the glass cloth is 7 to 13 μm, and the maximum area of the basket hole existing at an arbitrary position of the glass cloth. However, ^{it is 50,000 μm 2} or less.

When the maximum area of the basket hole is 50,000 μm ² or less, pinholes are remarkably less likely to occur when the glass cloth is impregnated with resin to prepare a prepreg. The maximum area of the basket hole is preferably 45,000 μm ² or less, more preferably 40,000 μm ² or less.
The minimum area of the basket hole is preferably not 3,000 microns ² or more, more preferably to 4,000 ² or more, still more preferably 5,000 .mu.m ² or more. Since the minimum area of the basket hole is 3,000 μm ² or more, delamination tends to be less likely to occur.

Furthermore, the average area of the basket holes, preferably, 5,000 .mu.m ² or more and 20,000 ² or less, more preferably, 6,000Myuemu ² or more and 19,000M ² or less, more preferably 7, It is 000 μm ² or more and 18,000 m ² or less. Average area of the basket hole is 5,000 .mu.m ² or more, by at 20,000 ² below, pinholes hardly occurs, and tend to delamination hardly occurs.

The basket hole in the present embodiment refers to a gap sandwiched between the warp and weft, and the pinhole refers to a void defect generated without the resin being buried in the basket hole portion.
Normally, when the average area of basket holes is reduced, pinholes are less likely to occur, but the amount of resin applied is reduced, and delamination is likely to occur during high-temperature mounting. In the present invention, it has been found that the maximum area of the basket hole is more important for the pinhole quality of the prepreg and the suppression of the occurrence of delamination of the substrate than the size of the average area of the basket hole. The maximum area of the basket hole here means that the glass cloth roll is pulled out, 100 mm × 100 mm is cut out from an arbitrary position, the surface of the glass cloth is observed with a scanning electron microscope, and the area of all the basket holes is measured. It refers to the area of the basket hole that was the largest among them.

As a method of reducing the maximum area of the basket hole while keeping the average area of the basket hole constant, for example, a method of managing tension and processing conditions in the processes of warping, weaving, deglazing, processing, and opening of fibers. Can be mentioned.
As a method of controlling the tension and the processing condition, specifically, a method of monitoring the tension of all the warps constituting the glass cloth and removing the warp whose tension deviates from the control value, the amount of glue adhered during aging, and weaving. Examples thereof include the number of rotations at the time, the rate of temperature rise at the time of degluing, and a method of keeping the water pressure in the fiber opening process constant.

By setting the tension of the warp in a certain range, the focused state of the warp can be controlled and the width of the warp can be kept constant. Further, by keeping the amount of glue adhered during the pacing period constant, the fiber opening effect in the fiber opening step can be controlled, and the yarn widths of the warp and weft can be kept constant. Further, by keeping the rotation speed at the time of weaving constant, the tension of the weft can be controlled, the opening effect in the fiber opening step can be controlled, and the yarn width of the weft can be kept constant. Further, by setting the temperature rise rate at the time of degluing within a certain range, the amount of residual glue after the degluing step can be controlled, the fiber opening effect in the fiber opening process can be controlled, and the yarn widths of the warp and weft are constant. Can be kept at. Further, by making the water pressure in the fiber-spreading process constant, the fiber-spreading effect can be controlled, and the yarn widths of the warp and weft can be kept constant.
By managing these tensions and processing conditions, it is possible to reduce the maximum area of the basket hole while keeping the average area of the basket hole constant.

The maximum value of the air permeability of the glass cloth in this embodiment ^{is preferably 250 cm 3} / cm ² / sec or less. When the maximum value of the air permeability is 250 cm ³ / cm ² / sec or less, the pinhole quality of the prepreg can be greatly improved. The maximum value of the air permeability is more preferably 240 cm ³ / cm ² / sec or less, and further preferably 230 cm ³ / cm ² / sec or less.
The minimum value of the air permeability is preferably 50 cm ³ / cm ² / sec or more, more preferably 60 cm ³ / cm ² / sec or more, and further preferably 70 cm ³ / cm ² / sec or more. When the minimum value of the air permeability is 50 cm ³ / cm ² / sec or more, the occurrence of delamination tends to be suppressed.

The air permeability in the present embodiment is an air permeability that can be measured according to the method described in JIS R 3420.
Specifically, as the testing machine / equipment, a manual type or automatic type testing machine of the Frangial type testing machine is used. Place the glass cloth test piece on one end of the cylinder and press it with a clamp to attach it. In the case of the manual type, air is sucked in so that the inclined type oil barometer shows the pressure of 124.5 Pa by the adjusting resistor, and the pressure indicated by the vertical type oil barometer when adjusting the suction fan, and the air hole used. The amount of air passing through the test piece cm ³ / cm ² / sec is calculated from the type of air pressure.
The same measurement method is measured at three points in the width direction of the glass cloth, and the maximum and minimum values of air permeability are obtained.
Examples of the method for adjusting the air permeability include a method of controlling tension and processing conditions in the steps of warping, weaving, degluing, processing, and opening.

In the present embodiment, the degree of opening of the yarn widths of the warp and weft of the glass cloth is preferably 90% or more independently. When the openness of the warp and weft is 90% or more, the pinhole quality and the occurrence of delamination can be improved, and the rigidity of the substrate can be increased. The openness of the warp and weft is more preferably 91% or more, still more preferably 92% or more.
The upper limit of the openness of the warp and weft is preferably 120% or less, more preferably 115% or less, and further preferably 110% or less. When the upper limit of the openness of the warp and weft is 120% or less, the area of the basket hole can be made constant, and the pinhole quality tends to be improved.

The fibrous opening degree [%] in the present embodiment is a value calculated by the yarn width [μm], the filament diameter [μm], and the number of filaments [line] as shown in the following equation.
Openness [%] = thread width [μm] ÷ (filament diameter [μm] x number of filaments [lines]) x 100

Examples of the method for adjusting the degree of defibration include a method of controlling tension and processing conditions in the steps of warping, weaving, degluing, processing, and defibration.

The minimum yarn width of the warp and weft in the present embodiment is preferably 100 μm or more, more preferably 110 μm or more, still more preferably 120 μm or more, independently from the viewpoint of improving the pinhole quality. be.
The maximum yarn width of the warp and weft in the present embodiment is preferably 240 μm or less, more preferably 230 μm or less, still more preferably 220 μm or less, independently from the viewpoint of suppressing the occurrence of delamination. Is.
The yarn width of the warp and weft is a method of adjusting the average filament diameter of the glass filament and the number of glass filaments, and a method of controlling tension and processing conditions in the processes of warping, weaving, degluing, processing, and opening. Can be adjusted by.

The maximum width of the basket hole in the warp and weft direction (also referred to as the maximum width of the basket hole) is preferably 120 μm or less, more preferably 115 μm or less, and further preferably 110 μm or less.
By setting the maximum width of the basket hole in the weft direction to 120 μm or less, the pinhole quality can be improved.
The minimum width of the basket hole in the warp and weft direction is preferably 50 μm or more, more preferably 60 μm or more, and further preferably 70 μm or more. By setting the minimum width of the basket hole in the weft direction to 50 μm or more, the occurrence of delamination tends to be suppressed.
The width of the basket hole in the weft direction can be adjusted, for example, by a method of controlling tension and processing conditions in the steps of warping, weaving, degluing, processing, and opening.

The cloth weight (weighting) of the glass cloth is preferably 5 to 12 g / m ² , more preferably 6 to 11 g / m ² , and further preferably 7 to 10 g / m ² . Within the above range, the obtained substrate can be made thinner, the pinhole quality can be improved, and the occurrence of delamination can be suppressed.

The woven structure of the glass cloth is not particularly limited, and examples thereof include woven structures such as plain weave, nanako weave, satin weave, and twill weave. Of these, a plain weave structure is more preferable.

The glass threads (including glass filaments) constituting the glass cloth are preferably surface-treated with a silane coupling agent. As the silane coupling agent, for example, it is preferable to use the silane coupling agent represented by the following general formula (1).

X (R) _3-n SiY _n ... (1)

In formula (1), X is an organic functional group having at least one of an amino group and an unsaturated double-bonding group, Y is an independently alkoxy group, and n is 1 or more and 3 or less. It is an integer and R is a group selected from the group consisting of a methyl group, an ethyl group and a phenyl group.

More preferably, X is an organic functional group having at least 3 or more of an amino group and an unsaturated double bond group, and X has at least 4 or more of an amino group and an unsaturated double bond group. It is more preferably an organic functional group.
Any form can be used as the above-mentioned alkoxy group, but an alkoxy group having 5 or less carbon atoms is preferable for stable treatment on the glass cloth.

Specific examples of the silane coupling agent that can be used include N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and its hydrochloride, N-β- (N-vinylbenzylaminoethyl). ) -Γ-Aminopropylmethyldimethoxysilane and its hydrochloride, N-β- (N-di (vinylbenzyl) aminoethyl) -γ-aminopropyltrimethoxysilane and its hydrochloride, N-β- (N-di) (Vinylbenzyl) Aminoethyl) -N-γ- (N-vinylbenzyl) -γ-aminopropyltrimethoxysilane and its hydrochloride, N-β- (N-benzylaminoethyl) -γ-aminopropyltrimethoxysilane And its hydrochlorides, N-β- (N-benzylaminoethyl) -γ-aminopropyltri ethoxysilane and its hydrochlorides, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-amino Ethyl) Examples thereof include known single substances such as aminopropyltriethoxysilane, aminopropyltrimethoxysilane, vinyltrimethoxysilane, metharoxypropyltrimethoxysilane, and acryloxypropyltrimethoxysilane, or mixtures thereof.

The molecular weight of the silane coupling agent is preferably 100 to 600, more preferably 150 to 500, and even more preferably 200 to 450.
Among these, it is preferable to use two or more kinds of silane coupling agents having different molecular weights. By treating the surface of the glass yarn with two or more kinds of silane coupling agents having different molecular weights, the density of the treatment agent on the glass surface tends to be high, and the reactivity with the matrix resin tends to be further improved.

The ignition loss value of the glass cloth is preferably 0.12% by mass or more and 1.0% by mass or less, more preferably 0.13% by mass or more and 0.90% by mass or less, and further preferably 0.14. It is by mass% or more and 0.80 mass% or less.
When the ignition loss value is 0.12% by mass or more and 1.0% by mass or less, the transportability (handleability) of the prepreg can be improved as compared with the conventional case. In addition, it is possible to suppress a decrease in the insulation reliability of the substrate due to the resin and the glass cloth being easily peeled off at the interface, and it is possible to suppress a decrease in the insulation reliability of the substrate due to the plating liquid permeating into the glass cloth. There is a tendency.

The "ignition weight loss value" referred to here can be measured according to the method described in JIS R 3420. That is, first, the glass cloth is placed in a dryer at 110 ° C. and dried for 60 minutes. After drying, transfer the glass cloth to a desiccator, leave it for 20 minutes, and allow it to cool to room temperature. After allowing to cool, weigh the glass cloth in units of 0.1 mg or less. Next, the glass cloth is heated in a muffle furnace at 625 ° C. for 20 minutes. After heating in a muffle furnace, transfer the glass cloth to a desiccator, leave it for 20 minutes, and allow it to cool to room temperature. After allowing to cool, weigh the glass cloth in units of 0.1 mg or less. The amount of glass cloth treated with the silane coupling agent is defined by the ignition loss value obtained by the above measurement method.

Glass called E glass (non-alkali glass) is usually used as the glass cloth used for the laminated plate, but in the glass cloth of the present embodiment, L glass, NE glass, D glass, S glass, and T are used. Glass, silica glass, quartz glass, high dielectric constant glass and the like may be used. E-glass is most preferably used in terms of its low cost.

[Manufacturing method of glass cloth]
The method for producing the glass cloth of the present embodiment is not particularly limited, but for example, the surface of the glass filament is almost completely covered with the silane coupling agent by a treatment liquid having a concentration of the silane coupling agent of 0.1 to 3.0 wt%. A method having a coating step of covering with glass, a fixing step of fixing the silane coupling agent to the surface of the glass filament by heating and drying, and a fiber opening step of opening the glass thread of the glass cloth can be preferably mentioned.

As the solvent for dissolving or dispersing the silane coupling agent, either water or an organic solvent can be used, but from the viewpoint of safety and protection of the global environment, it is preferable to use water as the main solvent. As a method of obtaining a treatment liquid using water as a main solvent, a method of directly adding a silane coupling agent to water, a method of dissolving the silane coupling agent in a water-soluble organic solvent to prepare an organic solvent solution, and then using the organic solvent solution. Any method of putting it in water is preferable. It is also possible to use a surfactant in combination in order to improve the water dispersibility and stability of the silane coupling agent in the treatment liquid.

As a method of applying the treatment liquid to the glass cloth, (a) a method of collecting the treatment liquid in a bath and immersing and passing the glass cloth (hereinafter referred to as "immersion method"), (b) a roll coater, a die coater, and the like. Alternatively, a method of directly applying the treatment liquid to the glass cloth with a gravure coater or the like is possible. When applying by the dipping method of (a) above, it is preferable to select the immersion time of the glass cloth in the treatment liquid to be 0.5 seconds or more and 1 minute or less.

Further, as a method of applying the treatment liquid to the glass cloth and then heating and drying the solvent, known methods such as hot air and electromagnetic waves can be mentioned.
The heating and drying temperature is preferably 90 ° C. or higher, more preferably 100 ° C. or higher so that the reaction between the silane coupling agent and the glass can be sufficiently performed. Further, the heating and drying temperature is preferably 300 ° C. or lower, more preferably 200 ° C. or lower, in order to prevent deterioration of the organic functional group of the silane coupling agent.

The method for opening the fiber in the fiber opening step is not particularly limited, and examples thereof include a method for opening the glass cloth with spray water (high pressure water opening), vibro washer, ultrasonic water, mangle, and the like. .. In order to reduce the maximum area of the basket hole while keeping the average area of the basket hole constant, it is preferable to carry out the fiber opening step with spray water.
When the fiber is opened with spray water, the water pressure may be appropriately set, and it is preferable that the water pressure is constant in order to adjust ^{the maximum area of the basket hole existing in the glass cloth to 50,000 μm 2 or less.} Here, to make the water pressure constant means to reduce the difference between the water pressure of the spray set for carrying out the fiber opening and the maximum and minimum values of the actual water pressure.
The difference between the water pressure of the spray set for performing fiber opening and the maximum and minimum values of the actual water pressure may be less than 6% of the water pressure of the spray set for performing fiber opening. It is preferably within 5%, more preferably within 4%.
Even after the fiber opening step, it may have a step of heating and drying.

[Prepreg]
The prepreg of the present embodiment has the above glass cloth and a matrix resin impregnated in the glass cloth. This makes it possible to provide a prepreg that is thin, has excellent pinhole quality, and suppresses the occurrence of delamination of the substrate.

As the matrix resin, either a thermosetting resin or a thermoplastic resin can be used. The thermosetting resin is not particularly limited, but for example, a) a compound having an epoxy group and an amino group, a phenol group, an acid anhydride group, a hydrazide group, an isocyanate group, a cyanate group, and a hydroxyl group that react with the epoxy group. An epoxy that cures by reacting with a compound having at least one of Resin; b) A radical polymerization type curing resin in which a compound having at least one of an allyl group, a methacrylic group, and an acrylic group is cured by using a thermal decomposition type catalyst or a photodegradable type catalyst as a reaction initiator; c. ) Maleimide triazine resin in which a compound having a cyanate group and a compound having a maleimide group are reacted and cured; d) A thermosetting polyimide resin in which a maleimide compound and an amine compound are reacted and cured; e) Benzo Examples thereof include a benzoxazine resin in which a compound having an oxazine ring is cross-linked and cured by heat polymerization.

The thermoplastic resin is not particularly limited, but for example, polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyether sulfone, polyarylate, aromatic polyamide, polyether ether ketone, thermoplastic polyimide, insoluble polyimide, etc. Examples thereof include polyamide-imide and fluororesin. Further, the thermosetting resin and the thermoplastic resin may be used in combination.

[Printed wiring board]
The printed wiring board of this embodiment has the above-mentioned prepreg. This makes it possible to provide a printed wiring board having high quality and suppressing the occurrence of delamination.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

(Example 1)
Glass cloth (average filament diameter 4.0 μm of glass filament, number of filaments 40, warp density 95 / inch, weft density 95 / inch, mass 10 g / m ² ) was added to N-β- (N). -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water opening was carried out with a spray adjusted to a water pressure of 5.0 ± 0.1 kg / cm ^{2, and the product was dried by heating to obtain a product.}

(Example 2)
Glass cloth (average filament diameter 4.0 μm of glass filament, number of filaments 33, warp density 105 / inch, warp density 105 / inch, mass 9 g / m ² ) was added to N-β- (N). -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water opening was carried out with a spray adjusted to a water pressure of 5.0 ± 0.1 kg / cm ^{2, and the product was dried by heating to obtain a product.}

(Example 3)
Glass cloth (average filament diameter 3.5μm glass filaments, the number 40 filament, implantation of warp density of 110 / inch, implantation of weft density of 110 / inch, mass 7 g / m ²⁾ and, N-beta-(N -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water opening was carried out with a spray adjusted to a water pressure of 5.0 ± 0.1 kg / cm ^{2, and the product was dried by heating to obtain a product.}

(Comparative Example 1)
Glass cloth (average filament diameter 4.0 μm of glass filament, number of filaments 40, warp density 95 / inch, weft density 95 / inch, mass 10 g / m ² ) was added to N-β- (N). -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water opening was carried out with a spray adjusted to a water pressure of 5.0 ± 0.3 kg / cm ^{2, and the product was obtained by heating and drying.}

(Comparative Example 2)
Glass cloth (average filament diameter 4.0 μm of glass filament, number of filaments 33, warp density 105 / inch, warp density 105 / inch, mass 9 g / m ² ) was added to N-β- (N). -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water opening was carried out with a spray adjusted to a water pressure of 5.0 ± 0.3 kg / cm ^{2, and the product was obtained by heating and drying.}

(Comparative Example 3)
Glass cloth (average filament diameter 3.5μm glass filaments, the number 40 filament, implantation of warp density of 110 / inch, implantation of weft density of 110 / inch, mass 7 g / m ²⁾ and, N-beta-(N -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water opening was carried out with a spray adjusted to a water pressure of 5.0 ± 0.3 kg / cm ^{2, and the product was obtained by heating and drying.}

<Evaluation method of basket hole, warp width, and weft width of glass cloth>
By observing 100 mm × 100 mm at an arbitrary position of the glass cloth with a scanning electron microscope, all the warp width, the weft width, and the area of the basket hole were measured, and the average value and the maximum value were obtained.

<Evaluation method of filament diameter of glass cloth>
The cross section of 30 glass yarn bundles at an arbitrary position of the glass cloth was observed with a scanning electron microscope, the average value was calculated, and the average filament diameter was obtained.

<Evaluation method of openness>
Using the warp width, weft width, and filament diameter obtained above, the degree of fiber opening was determined by the following formula.
Openness [%] = thread width [μm] ÷ (filament diameter [μm] x number of filaments [lines]) x 100

<Evaluation method of glass cloth thickness>
According to JIS R 3420 7.10, using a micrometer, the spindle was gently rotated and lightly touched parallel to the measurement surface, and the scale after the ratchet made three sounds was read.

<Prepreg manufacturing method and prepreg pinhole quality evaluation method>
Epoxy resin varnish (40 parts by mass of low brominated bisphenol A type epoxy resin, 10 parts by mass of o-cresol type novolak epoxy resin, 50 parts by mass of dimethylformamide, 1 mass by mass of dicyandiamide) was added to the glass cloths obtained in the above Examples and Comparative Examples. , And a mixture of 0.1 parts by mass of 2-ethyl-4-methylimidazole diluted to 50 wt% with a methyl ethyl ketone solvent) was impregnated, pulled up at a speed of 2 m / min, and the gap was adjusted to 65% RC. Excess resin was scraped off through the slit, and dried at 160 ° C. for 1 minute to obtain a prepreg. Any 500 mm × 500 mm of the prepared prepreg was observed with a portable microscope, and the number of pinholes was determined. The smaller the number of pinholes, the higher the quality.

<How to make a substrate>
The prepregs obtained above were layered, and copper foils having a thickness of 12 μm were layered on top and bottom, and ^{heated and pressed at 175 ° C. and 40 kg / cm 2} for 60 minutes to obtain a laminated board.

<Evaluation method of substrate delamination>
A substrate having a thickness of 0.1 mm was prepared as described above, and after removing the copper foil with an etching solution, the substrate was exposed to a temperature of 121 ° C. and a humidity of 100% (2 atm) for 1 week, and after taking out, the substrate was taken out. It was immersed in a solder bath at 288 ° C. for 20 seconds, and the presence or absence of swelling or cracks on the substrate was visually confirmed. In Table 1, those in which no swelling or cracks were observed on the substrate were indicated by ◯, and those in which swelling or cracks were observed on the substrate were indicated by x.

The evaluation results of the glass cloth shown in Examples and Comparative Examples are summarized in Table 1.
It was found that by using the glass cloth of the example, the pinhole quality of the prepreg was excellent and the occurrence of delamination of the substrate could be suppressed.

The glass cloth of the present invention has industrial applicability as a base material used for a printed wiring board used in the electronic and electrical fields.

Claims (8)

A glass cloth made by weaving glass threads composed of a plurality of glass filaments as warps and wefts.
The average filament diameter of the glass filament is 3.0 to 4.5 μm.
The number of the glass filaments is 20 to 50, and the number of the glass filaments is 20 to 50.
The driving densities of the warp and weft constituting the glass cloth are independently 70 to 130 threads / inch, respectively.
The thickness of the glass cloth is 7 to 13 μm, and the thickness of the glass cloth is 7 to 13 μm.
The maximum area of the basket hole existing in the glass cloth is 50,000 μm ² or less.
Glass cloth. The glass cloth according to claim 1, wherein the maximum value of the air permeability is 250 cm ³ / cm ^{2 / sec or less.} The glass cloth according to claim 1 or 2, wherein the yarn widths of the warp and weft have an openness of 90% or more independently. The glass cloth according to any one of claims 1 to 3, wherein the minimum yarn width of the warp and weft is 100 μm or more independently. The glass cloth according to any one of claims 1 to 4, wherein the maximum width of the basket hole is 120 μm or less. The glass cloth according to any one of claims 1 to 5, wherein the surface of the glass yarn is treated with a plurality of types of silane coupling agents. A prepreg comprising the glass cloth according to any one of claims 1 to 6 and a matrix resin impregnated in the glass cloth. A printed wiring board having the prepreg according to claim 7.