JP2019031750A - Glass cloth, prepreg and print circuit board - Google Patents

Abstract

To provide a glass cloth capable of suppressing both delamination and occurrence of pinhole; and a prepreg and a print circuit board obtained by using the glass cloth.SOLUTION: A glass cloth is obtained by weaving a glass yarn composed of a plurality of glass filaments as the warp and weft yarns. In the glass cloth, a basket hole area coefficient (K) determined from the following formula is 2,000 or more to 15,000 or less; and at least one of a gap between adjoining warp yarns and a gap between adjoining weft yarns is 40 μm or more, or both the gap between adjoining warp yarns and the gap between adjoining weft yarns are 36 μm or more: K=B/((Ct+Cy)/W)..(formula); where B represents the total area (mm) of the basket holes per 1 m, Ct represents the weaving density (number/25 mm) of the warp, Cy represents the weaving density (number/25 mm) of the weft, and W represents the mass (g/m) of the glass cloth per 1 m.SELECTED DRAWING: None

Description

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

Currently, along with the high performance and high speed communication of information terminals such as smartphones, the printed wiring boards used are becoming increasingly dense and extremely thin, and are also becoming increasingly low dielectric constant and low dielectric loss tangent. .
As an insulating material of this printed wiring board, a laminated board obtained by laminating a prepreg obtained by impregnating a glass cloth with a thermosetting resin such as an epoxy resin (hereinafter referred to as “matrix resin”) and curing by heating and pressing. Is widely used. Examples of common glass cloth include E glass cloth (see Patent Document 1). The dielectric constant of the matrix resin used in the above high-speed communication substrate is about 3, whereas the dielectric constant of E glass cloth is about 6.7. It is becoming.

  Therefore, low dielectric constant glass cloths such as D glass, NE glass, L glass, and silica glass (Q glass) having a glass composition different from that of E glass have been proposed (for example, Patent Document 2). Due to this low dielectric constant, the conductor circuit is made thicker from the viewpoint of impedance matching, and further, the number of through holes and the number of inner via holes accompanying the increase in the density and the number of multilayers occurs. Improving fillability such as through holes is necessary to maintain heat resistance.

  At the same time, as the transmission speed increases, the frequency increases further, and the glass cloth is used to improve the instability of the transmission speed called Skew due to the non-uniformity of the glass cloth. The surface direction is made uniform by reducing the density, particularly the portion without glass yarn.

JP 2001-329449 A JP 2006-232952 A

However, with the homogenization of the surface direction, the matrix resin is applied in a butter coat shape centering on the glass cloth, and the lack of impregnation of the complementary resin layers on the front and back surfaces becomes obvious. There is a problem that delamination (that is, swelling and cracks) occurs. The occurrence of delamination indicates that the embedding property in a complicated conductor circuit or the like is low, and the insulation reliability as a material of the printed wiring board is lowered.
Further, when a prepreg is produced by impregnating a resin using a glass cloth, pinholes are generated at a certain frequency, and the quality of the prepreg may be deteriorated.

  The present invention has been made in view of the above problems, and in a glass cloth in which the glass yarn-free portion in the glass cloth and the uniformity in the surface direction are optimized, delamination is suppressed, and a pinhole An object of the present invention is to provide a glass cloth that can simultaneously suppress the occurrence of selenium, and a prepreg and a printed wiring board using the glass cloth.

  As a result of studies to solve the above problems, the present inventors have determined that the total area of the basket holes suitable for the mass and density of various glass cloths is within a predetermined range, and the gap between adjacent glass yarns is predetermined. It was found that the above-mentioned problems can be solved by being within the range, and the present invention has been completed.

That is, the present invention is as follows.
[1]
A glass cloth formed by weaving glass yarns composed of a plurality of glass filaments as warps and wefts,
The basket hole area coefficient (K) calculated by the following formula is 2,000 to 15,000, and
At least one of the adjacent warp gaps or the adjacent weft gaps is 40 μm or more, or
A glass cloth having a gap between adjacent warps and a gap between adjacent wefts of 36 μm or more;
K = B / ((Ct + Cy) / W) where B is the total area (mm ² ) of basket holes per m ² ,
Ct is the woven fabric density of warp (lines / 25mm),
Cy is the fabric density of the weft yarn (lines / 25mm),
W is a glass cloth weight per ^{1m 2 (g / m 2)} . ).
[2]
The glass cloth according to [1], which has a dielectric constant of 5.5 or less.
[3]
A prepreg comprising the glass cloth according to [1] or [2] and a matrix resin impregnated in the glass cloth.
[4]
A printed wiring board comprising the prepreg according to [3] in at least one layer.

  According to the present invention, there is provided a glass cloth capable of producing a substrate such as a prepreg and a printed wiring board that can suppress delamination and pinholes, or a laminated board thereof (hereinafter also simply referred to as “substrate”). can do. Moreover, according to this invention, the prepreg and printed wiring board using this glass cloth can be provided.

  Hereinafter, the embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to this, and various modifications are possible without departing from the scope of the present invention. It is.

〔Glass cloth〕
The glass cloth of this embodiment is a glass cloth formed by weaving glass yarns composed of a plurality of glass filaments as warps and wefts.

In the glass cloth of the present embodiment, the basket hole area coefficient (K) obtained by the following formula is 2,000 or more and 15,000 or less, and the gap between at least adjacent warps or wefts is 40 μm or more. Or the gap between the warp and the weft is 36 μm or more.
That is, the glass cloth of the present embodiment has a basket hole area coefficient (K) obtained by the following formula of 2,000 or more and 15,000 or less, and
At least one of the adjacent warp gaps or the adjacent weft gaps is 40 μm or more, or
The gap between adjacent warps and the gap between adjacent wefts are both 36 μm or more.

K = B / ((Ct + Cy) / W) where B is the total area (mm ² ) of basket holes per m ² ,
Ct is the woven fabric density of warp (lines / 25mm),
Cy is the fabric density of the weft yarn (lines / 25mm),
W is a glass cloth weight per ^{1m 2 (g / m 2)} . )

As the glass cloth used for the laminate, glass called E glass (non-alkali glass) is usually used. In the glass cloth of this embodiment, L glass having a dielectric constant of 5.5 or less, NE Glass, D glass, silica glass, quartz glass and the like are preferably used. By using these glasses, a glass cloth having a low dielectric constant is obtained, and stabilization of the transmission signal is achieved.
The dielectric constant of the glass cloth of this embodiment becomes like this. Preferably it is 5.5 or less, More preferably, it is 5.0 or less.

The basket hole in this embodiment refers to a gap between warp and weft.
In general, when a high-mass glass cloth is manufactured using a glass yarn having a large count indicating the thickness of the yarn, the area of the basket hole tends to be small. On the other hand, when glass yarn with a small count is used, the basket hole area tends to increase. Also, even if yarns of the same count and the same fabric density are used, the basket hole area varies depending on the opened state (that is, the degree of flatness of the yarn), etc., and especially glass yarn with a small count is used. If so, the difference will be significant.
The weight of the glass cloth, and the area and total area of the basket hole are closely related to the count of the glass yarn and the density of the fabric, and it is necessary to derive an appropriate basket hole area in various glass cloth styles. is there. By setting the basket hole area coefficient (K) calculated by dividing the total area of the basket hole by the value obtained by dividing the total fabric density of the warp and weft by the mass of the glass cloth, In addition to the size of each area and the total area of the basket hole, it is possible to optimize the area of the glass cloth basket hole in consideration of the yarn count and the fabric density that determine the mass of the glass cloth.
Furthermore, by setting the gap between at least adjacent warps or adjacent wefts to 40 μm or more, or the gap between adjacent warps and adjacent wefts to 36 μm or more, the shape of the basket hole can be optimized.

That is, by setting the basket hole area coefficient (K) and the gap between adjacent yarns within a specific range, the glass cloth basket hole area and shape are optimized, and the basket hole area coefficient (K) is the pinhole of the prepreg. It was found that it is important for quality and suppression of substrate delamination. The area of the basket hole here refers to a glass cloth roll drawn out, cut out 100 mm × 100 mm from an arbitrary position, and the surface of the glass cloth is observed with a scanning electron microscope. Measured from the gap between the two, it indicates the average area. Furthermore, the total area of the basket holes refers to a value obtained by multiplying the number of basket holes per 1 m ² by the average area, calculated from the fabric density.
Specifically, the total area of the basket hole can be determined by the method described in the examples.

The basket hole area coefficient (K) is 2,000 or more and 15,000 or less, preferably 3,000 or more and 14,000 or less, more preferably 4,000 or more and 14,000 or less, and further preferably It is 12,500 or more and 13,500 or less.
When the basket hole area coefficient (K) is less than 2,000, when a prepreg is made by impregnating a glass cloth with a resin, the basket hole area is one by one with respect to the relationship between the constituted glass yarn and the fabric density. The surface uniformity of the glass cloth is improved, but impregnation of the matrix resin on both sides of the glass cloth is difficult, and delamination occurs when the resulting prepreg is used for lamination. It tends to be easy to do.
In addition, when the basket hole area coefficient (K) is larger than 15,000, each basket hole area becomes larger with respect to the relationship between the glass yarn and the woven fabric density, and when the prepreg is obtained, Occurrence and non-uniformity in the surface direction tend to occur.
At the same time, if the gap between at least adjacent warps or wefts is less than 40 μm, or if the gap between both adjacent warps and adjacent wefts is less than 36 μm, it is more difficult to impregnate the front and back matrix resins that complement each other with a glass cloth as the center. In particular, delamination tends to occur easily when a resin having a low melt viscosity is combined and laminated using the obtained prepreg.
That is, the basket hole area coefficient (K) is 2,000 or more and 15,000 or less, and at least the adjacent warp or the weft gap is 40 μm or more, or the adjacent warp and the adjacent weft have a gap. When the thickness is 36 μm or more, pinholes are less likely to occur and delamination is less likely to occur when a prepreg and a laminate are manufactured from a glass cloth. A pinhole refers to a void defect that occurs without resin being buried in the basket hole portion. Usually, when the area of the basket hole is reduced, pinholes are less likely to be generated, but impregnation with the front and back matrix resins complementing each other centering on the glass cloth becomes difficult, and delamination is likely to occur during high-temperature multilayer molding.

  The basket hole area coefficient (K) can be controlled to 2,000 or more and 15,000 or less by controlling the fabric density of the glass yarn constituting the glass cloth, the mass of the glass cloth, and the total area of the basket hole. it can.

Examples of the method for controlling the total area of the basket hole and the gap between adjacent yarns include a method of managing tension and processing conditions in the steps of warping, weaving, deglueing, processing, and opening. .
Specifically, the tension and processing conditions are managed by monitoring the tension of all warp yarns that make up the glass cloth, removing warp yarns whose tension falls outside the control value, the amount of glue attached during aging, weaving Examples thereof include a method in which the number of rotations at the time, the temperature increase rate at the time of de-glue, and the water pressure in the fiber opening process are made constant.
By setting the warp tension within a certain range, the converging state of the warp can be controlled, and the yarn width can be kept constant. In addition, by making the amount of glue adhered during aging constant, the opening effect in the opening process can be controlled, and the warp and weft widths can be kept constant. Further, by making the number of rotations during weaving constant, the tension of the weft can be controlled, the opening effect in the opening process can be controlled, and the weft width can be kept constant. In addition, by setting the rate of temperature increase during de-glue to a certain range, the amount of residual glue after the de-glue process can be controlled, the spread effect in the spread process can be controlled, and the warp and weft thread widths are constant. Can be kept in. Further, by making the water pressure in the fiber opening process constant, the fiber opening effect can be controlled, and the warp and weft yarn widths can be kept constant.

By managing these tensions and processing conditions, the total area of the basket hole and the gap between adjacent yarns can be controlled.
The total area of the basket hole is controlled to be small by increasing the water pressure in the opening process. The water pressure in the fiber opening process may be appropriately adjusted according to the fabric density and the mass of the glass cloth. For example, when the mass of the glass cloth is small, the water pressure may be reduced.

The mass (also referred to as basis weight) of the glass cloth can be controlled by adjusting the number of filaments constituting the glass yarn. The larger the number of filaments, the larger the mass of the glass cloth.
The mass of the glass cloth may be adjusted so that the basket hole area coefficient (K) is 2,000 or more and 15,000 or less, but is usually 5 to 200 g / m ² , preferably 10 to 150 g / m ² . There, more preferably 15 to 100 / m ^2.
Specifically, the mass of the glass cloth can be determined by the method described in Examples.

As for the fabric density, a glass yarn having a suitable fabric density may be appropriately selected so that the basket hole area coefficient (K) is 2,000 or more and 15,000 or less. The fabric density is usually 5 to 100/25 mm, preferably 20 to 80/25 mm, and more preferably 40 to 70/25 mm.
Specifically, the fabric density can be determined by the method described in Examples.

  The average filament diameter of the glass filament in this embodiment is preferably 3.0 to 9.0 μm. Moreover, the number of filaments of the glass yarn in this embodiment is preferably 20 to 400. Furthermore, the thickness of the glass cloth is preferably 7 to 200 μm.

  The woven structure of the glass cloth is not particularly limited, and examples thereof include a woven structure such as a plain weave, a nanako weave, a satin weave, and a twill weave. Furthermore, a mixed woven structure using different types of glass yarn may be used. Among these, a plain weave structure is preferable.

  The glass yarn (including the glass filament) constituting the glass cloth is preferably surface-treated with a silane coupling agent. As the silane coupling agent, for example, a silane coupling agent represented by the following general formula (1) is preferably used.

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 bond group, Y is independently an alkoxy group, and n is 1 or more and 3 or less. R 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 three of an amino group and an unsaturated double bond group, and X has at least four of an amino group and an unsaturated double bond group. More preferably, it is an organic functional group.
Any form can be used as the alkoxy group, but an alkoxy group having 5 or less carbon atoms is preferable for stabilizing the glass cloth.

  Specific examples of silane coupling agents 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 hydrochloride, N-β- (N-benzylaminoethyl) -γ-aminopropyltriethoxysilane and its hydrochloride, γ- ( 2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, aminopropyltrimethoxysilane, vinyltrimethoxysilane, methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, etc. These known simple substances or a mixture thereof.

The molecular weight of the silane coupling agent is preferably 100 to 600, more preferably 150 to 500, and still more preferably 200 to 450.
Among these, it is preferable to use two or more silane coupling agents having different molecular weights. By treating the glass yarn surface with two or more types of silane coupling agents having different molecular weights, the treatment agent density on the glass surface is increased, and the reactivity with the matrix resin tends to be further improved.
The ignition loss value of the glass cloth is preferably 0.10% by mass or more and 1.20% by mass or less, more preferably 0.11% by mass or more and 1.10% by mass or less, and further preferably 0.12% by mass. It is not less than 1.00% by mass.

  When the ignition loss value is 0.10% by mass or more and 1.2% by mass or less, the transportability (handling property) of the prepreg can be improved as compared with the prior art. In addition, it is possible to suppress a decrease in insulation reliability of the substrate resulting from the resin and glass cloth being easily peeled off at the interface, and it is possible to suppress a decrease in insulation reliability of the substrate resulting from the penetration of the plating solution into the glass cloth There is a tendency.

  The “ignition loss value” 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, the glass cloth is transferred to a desiccator, left for 20 minutes, and allowed to cool to room temperature. After standing to cool, the glass cloth is weighed 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 the muffle furnace, the glass cloth is transferred to a desiccator, left for 20 minutes, and allowed to cool to room temperature. After standing to cool, the glass cloth is weighed in units of 0.1 mg or less. The amount of silane coupling agent treated with glass cloth is defined by the ignition loss value obtained by the above measurement method.

[Glass cloth manufacturing method]
The method for producing the glass cloth of the present embodiment is not particularly limited. For example, the surface of the glass filament is almost completely covered with the treatment liquid having a silane coupling agent concentration of 0.1 to 3.0 wt%. A method having a covering step of covering with, a fixing step of fixing the silane coupling agent to the surface of the glass filament by heat drying, and a fiber opening step of opening the glass yarn of the glass cloth are preferably mentioned.
As the solvent for dissolving or dispersing the silane coupling agent, either water or an organic solvent can be used, but water is preferably used as the main solvent from the viewpoint of safety and protection of the global environment. As a method for obtaining a treatment liquid containing water as a main solvent, a method in which a silane coupling agent is directly added to water, an organic solvent solution is prepared by dissolving the silane coupling agent in a water-soluble organic solvent, and then the organic solvent solution is used. Any one of the methods of adding to water is preferable. In order to improve the water dispersibility and stability of the silane coupling agent in the treatment liquid, a surfactant may be used in combination.

As a method of applying the treatment liquid to the glass cloth, (a) a method of storing 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, Or the method of apply | coating a process liquid directly to glass cloth with a gravure coater etc. is possible. When applying by the immersion method (a), the immersion time of the glass cloth in the treatment liquid is preferably selected to be 0.5 seconds or more and 1 minute or less.
In addition, examples of the method for heating and drying the solvent after applying the treatment liquid to the glass cloth include known methods such as hot air and electromagnetic waves.

  The heating and drying temperature is preferably 90 ° C. or higher, and more preferably 100 ° C. or higher so that the reaction between the silane coupling agent and glass is sufficiently performed. Moreover, in order to prevent deterioration of the organic functional group which a silane coupling agent has, heat drying temperature becomes like this. Preferably it is 300 degrees C or less, More preferably, it is 200 degrees C or less.

In addition, the opening method in the opening step is not particularly limited, and examples thereof include a method of opening a glass cloth with spray water (high-pressure water opening), vibrowasher, ultrasonic water, mangle and the like. . In order to keep the total area of the basket hole in a certain range, it is preferable to perform the opening process with spray water.
In the case of opening with spray water, the water pressure may be set as appropriate, and the water pressure is preferably constant in order to adjust the total area of the basket holes present in the glass cloth. Here, making the water pressure constant means reducing the difference between the water pressure of the spray set for carrying out the fiber opening and the maximum value and the minimum value of the actual water pressure. You may have the process of heat-drying also before and after the opening process.

[Prepreg]
The prepreg of this embodiment has the glass cloth and a matrix resin impregnated in the glass cloth. Thereby, it is possible to provide a prepreg excellent in pinhole quality and suppressed in the occurrence of substrate delamination.

  As the matrix resin, either a thermosetting resin or a thermoplastic resin can be used. The thermosetting resin is not particularly limited. 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 is cured by reacting with a compound having at least one of the above, without a catalyst, or by adding a catalyst having a reaction catalytic ability such as an imidazole compound, a tertiary amine compound, a urea compound, or a phosphorus compound. A resin; b) a radical polymerization curable resin in which a compound having at least one of an allyl group, a methacryl group, and an acryl group is cured using a thermal decomposition catalyst or a photodecomposition catalyst as a reaction initiator; c D) a maleimide triazine resin cured by reacting a compound having a cyanate group with a compound having a maleimide group; Imide compounds, thermosetting polyimide resin is cured by reacting an amine compound, a; benzoxazine resin to crosslink cured by thermal polymerization of a compound having e) benzoxazine ring are exemplified.

  The thermoplastic resin is not particularly limited. For example, polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyether sulfone, polyarylate, aromatic polyamide, polyether ether ketone, thermoplastic polyimide, insoluble polyimide, Examples include polyamide imide and fluororesin. Moreover, you may use together a thermosetting resin and a thermoplastic resin.

[Printed wiring board]
The printed wiring board of this embodiment has the prepreg. As a result, it is possible to provide a printed wiring board that is of high quality and in which the occurrence of delamination is suppressed.

  Next, the present invention will be described in more detail with reference to examples and comparative examples. The present invention is not limited in any way by the following examples.

Example 1
Glass cloth (glass filament average filament diameter 5.0 μm, number of filaments 100, warp fabric density 65/25 mm, weft fabric density 67/25 mm, mass 26 g / m ² ) N-β- (N -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Toray Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water opening was performed with a spray adjusted to a water pressure of 5.0 ± 0.1 kg / cm ² and heat-dried to obtain a product with a loss on ignition value of 0.6%.

(Example 2)
Glass cloth (glass filament average filament diameter 5.0 μm, number of filaments 200, warp fabric density 52.5 / 25 mm, weft fabric density 52.5 / 25 mm, mass 41.5 g / m ² ) N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Toray Dow Corning Co., Ltd .; Z6032) was immersed in water and dried by heating. Next, high-pressure water-spreading was performed with a spray whose water pressure was adjusted to 5.0 ± 0.1 kg / cm ² and heat-dried to obtain a product with a loss on ignition value of 0.4%.

(Comparative Example 1)
Glass cloth (average filament diameter of glass filament 5.0 μm, number of filaments 100, warp fabric density 55/25 mm, weft fabric density 55/25 mm, mass 22 g / m ² ) N-β- (N -Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Toray Dow Corning Co., Ltd .; Z6032) was immersed in a treatment solution dispersed in water and dried by heating. Next, high-pressure water-spreading was performed with a spray whose water pressure was adjusted to 5.0 ± 0.3 kg / cm ² and heat-dried to obtain a product with a loss on ignition value of 0.6%.

(Comparative Example 2)
Glass cloth (glass filament average filament diameter 5.0 μm, number of filaments 200, warp fabric density 52.5 / 25 mm, weft fabric density 52.5 / 25 mm, mass 41.5 g / m ² ) N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride (manufactured by Toray Dow Corning Co., Ltd .; Z6032) was immersed in water and dried by heating. Next, high-pressure water-spreading was performed with a spray whose water pressure was adjusted to 10.0 ± 0.1 kg / cm ² and heat-dried to obtain a product with a loss on ignition value of 0.6%.

<Evaluation method for basket hole of glass cloth>
Using a scanning electron microscope, observe 100 mm x 100 mm at any position on the glass cloth, measure the area of all basket holes from the gap between adjacent yarns, calculate the average value, and calculate the average area of the basket holes. Asked.
Further, the total number of basket holes was calculated by calculating the number of basket holes per 1 m ² from the fabric density and multiplying by the average area of the basket holes.

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

<Evaluation method for fabric density of glass cloth>
According to JIS R 3420 7.9, the number of warp yarns and weft yarns per 25 mm was measured using a fabric disassembling mirror, and the average value of the three measurements measured in each direction was calculated as the fabric density. As sought.

<Method for evaluating mass of glass cloth>
In accordance with JIS R 3420 7.2, a test piece was collected with a cutter using a square template having an area of 100 cm ² , and the weight of the test piece was measured with a scale having a sensitivity of 0.1 mg or less. The From the measured mass and area, the mass per 1 m ² (g / m ² ) was calculated to determine the mass of the glass cloth.

<Preparation method of prepreg and evaluation method of pinhole quality of prepreg>
Polyphenylene ether resin varnish (mixture of modified polyphenylene ether resin 30 parts by weight, triallyl isocyanurate 10 parts by weight, toluene 50 parts by weight, catalyst 0.1 part by weight) is added to the glass cloth obtained in the above examples and comparative examples. A prepreg was obtained after impregnation and drying at 120 ° C. for 2 minutes. Arbitrary 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.

<Method for producing multilayer substrate>
A 0.4 mm thick double-sided board with a thickness of 35 μm copper foil was prepared as an inner layer core substrate, and a wiring pattern was prepared on the copper foils on both sides according to a conventional method to obtain an inner layer core substrate. The prepregs obtained as described above are laminated one by one on both layers of the core substrate, and a copper foil having a thickness of 12 μm is laminated on the top and bottom, and heated and pressed at 200 ° C. and 40 kg / cm ² for 60 minutes to form a multilayer. A substrate was obtained.

<Method for evaluating delamination properties of multilayer substrate>
The substrate was prepared as described above, and the copper foil on the surface was removed with an etching solution. Then, the substrate was exposed to a temperature of 121 ° C. and a humidity of 100% (2 atm) for 1 week. The substrate was immersed for 2 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 ×.

<Evaluation method of dielectric constant of substrate>
Using the prepreg prepared as described above, a substrate was prepared so that the resin content was 60% by volume, and the copper foil was removed to obtain a sample for dielectric constant evaluation. The dielectric constant of the obtained sample at a frequency of 1 GHz was measured using an impedance analyzer (manufactured by Agilent Technologies). The dielectric constant of the glass cloth was calculated from the obtained substrate dielectric constant based on the volume fraction of the glass cloth and the matrix resin dielectric constant of 2.5.

  Table 1 summarizes the evaluation results of the glass cloths produced in Examples and Comparative Examples.

  It turned out that the glass cloth of an Example has the low dielectric constant, can suppress delamination, and is excellent in pinhole quality.

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

Claims (4)

A glass cloth formed by weaving glass yarns composed of a plurality of glass filaments as warps and wefts,
The basket hole area coefficient (K) calculated by the following formula is 2,000 to 15,000, and
At least one of the adjacent warp gaps or the adjacent weft gaps is 40 μm or more, or
A glass cloth having a gap between adjacent warps and a gap between adjacent wefts of 36 μm or more;
K = B / ((Ct + Cy) / W) where B is the total area (mm ² ) of basket holes per m ² ,
Ct is the woven fabric density of warp (lines / 25mm),
Cy is the fabric density of the weft yarn (lines / 25mm),
W is a glass cloth weight per ^{1m 2 (g / m 2)} . ).   The glass cloth of Claim 1 whose dielectric constant is 5.5 or less.   A prepreg comprising the glass cloth according to claim 1 and a matrix resin impregnated in the glass cloth.   A printed wiring board comprising the prepreg according to claim 3 in at least one layer.