TWI787657B - Glass cloth, prepreg, and printed wiring board - Google Patents

Abstract

The present invention provides a low-dielectric glass cloth that can suppress weft skew while keeping the thickness below 16 μm. Also, the present invention provides a prepreg and a printed wiring board in which the difference in signal propagation speed between a plurality of transmission lines is reduced. The glass cloth of the present invention is composed of glass filaments including a plurality of glass filaments as warps and wefts, and has a thickness of not less than 8 μm and not more than 16 μm, and the presence of wefts in the longitudinal direction obtained by formula (1) The ratio Y is between 75% and 90%, Y=F/(25000/G)×100・・・(1) (where, F is the width of the weft yarn (μm), and G is the weaving density of the weft yarn ( root/25 mm)) The sum of the width of the warp and the weft is 380 μm to 500 μm, and the density of the glass constituting the above warp and the above weft is 2.10 g/cm ³ or more 2.50 g/cm ³ or less.

Description

Glass cloth, prepreg, and printed wiring board

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

In most printed wiring boards, a copper foil is used to form a transmission line on an insulator layer composed of a glass cloth and a matrix resin composition. Glass cloth used in printed wiring boards is formed by flat weaving glass filaments in the warp and weft directions. Therefore, in an insulator layer made of glass cloth and a resin composition, the presence ratio of glass is high at the portion where the filaments intersect, and the presence ratio of resin is high at the portion where the filaments are not overlapped or where there is no filament. Generally, there is a difference between the dielectric constant of the glass in the glass cloth and the dielectric constant of the resin composition. Therefore, it is known that there is a difference between the signal propagation speed in the transmission line passing through the part where the glass content ratio is high, and the signal propagation speed in the transmission line passing through the part where the resin composition ratio is high. Therefore, in an electronic circuit that needs to synchronize multiple signals, when the signal arrival time deviates, signal processing may fail.

In recent years, as the information and communication society has become more and more developed, it has become necessary to perform data communication and/or signal processing with large capacity and high speed, and the transmission speed of signals is getting higher and higher. The signal speed exceeds 10 Gbps, and continues to increase to 28 Gbps and 56 Gbps and other Gigabit areas. The higher the signal speed, the greater the influence of the above-mentioned signal propagation speed difference, and the stronger the demand for reducing the signal propagation speed difference. Here, it is known that when a pair of wirings are formed on the same insulator layer, since the dielectric constant differs between the portion where the ratio of glass is high and the portion where the ratio of resin is high as described above, each The propagation speed of the signal transmitted in the wiring is affected by the positional relationship between the transmission line and the glass cloth. Therefore, in Patent Documents 1 to 3, there are proposed techniques for reducing the variation in propagation velocity due to the positional relationship between the glass cloth and the transmission line. Specifically, Patent Document 1 discloses a technique of making the line width 75% to 95% of the distance between filaments of the glass cloth. Patent Document 2 discloses a technology for making the spacing between glass filaments and the spacing between signal lines consistent. Patent Document 3 discloses a technique for making the distance between the glass filaments and the wiring width 50%.

As other attempts to reduce the difference in signal propagation speed, it is also proposed to reduce the dielectric constant of glass cloth to reduce the difference in dielectric constant between it and the resin, so as to reduce the portion where the ratio of glass is high. The difference in the dielectric constant of the part with a higher ratio of resin. For example, the low-dielectric glass cloth disclosed in Patent Document 7 contains more B ₂ O ₃ in the glass composition than the conventionally used E glass cloth, and at the same time adjusts the preparation of other components such as SiO ₂ amount, thereby achieving a low dielectric constant.

On the other hand, in recent years, in order to realize the high function, small size and light weight of digital devices, the printed wiring boards used are also required to be smaller, thinner, and higher in density. As methods for miniaturization, thinning, and high density, methods of reducing the thickness of glass cloth used as a base material and increasing the number of layers of a multilayer printed wiring board are mentioned. Here, in order to achieve high performance, compactness and light weight of cutting-edge smartphones and wearable devices, for example, the thickness of glass cloth is desired to be as thin as 16 μm or less. In Patent Documents 4 to 6, glass cloths having a relatively thin thickness are disclosed. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-130860 [Patent Document 2] International Publication No. 2016/117320 [Patent Document 3] International Publication No. 2017/159649 [Patent Document 4] Japanese Patent No. 3756066 [Patent Document 5] Japanese Patent No. 4446754 [Patent Document 6] Japanese Patent No. 5936726 [Patent Document 7] Japanese Patent Laid-Open No. 11-292567

[Problem to be solved by the invention]

The glass filaments that make up the glass cloth have the characteristic of weft skew. Especially in the thinner glass cloth, the glass filaments are thinner than the thicker glass cloth, so the width of the warp and weft is generally narrower, and the intersection point of the warp and weft The contact area between warp and weft is small. Therefore, the binding force between the warp and the weft is weakened. For example, in the manufacturing process of glass cloth or the step of manufacturing prepreg using glass cloth, even if there is a slight deviation in the parallelism of the rollers that transport the glass cloth, at this time, The tension acting on the warp also produces a difference in the width direction, that is, in the CD (Cross Direction, transverse) direction. Originally, the warp and weft should intersect at right angles, but as a result, there is a problem of weft skew, that is, the weft is inclined or bent. In addition, in the process of manufacturing the prepreg, when the resin is impregnated and coated, it passes through a narrow slit in order to control the amount of resin attached. In this step, the load acts on the glass cloth unevenly in the width direction, so It is prone to the problem of weft skew.

The thinner the thickness of the glass cloth, and the fewer the number of filaments constituting the glass cloth, the more obvious the weft skew will be. In particular, when the glass composition is controlled for low dielectric properties, specifically, when the glass composition is adjusted by increasing the amount of B ₂ O ₃ blended in the glass composition, the specific gravity of the glass constituting the glass filament is reduced, and the rigidity of the glass filament is weakened. tendency. The lower the density of the glass, the lower the rigidity of the glass, and the more obvious the weft skew. Therefore, as disclosed in Patent Documents 1 to 3, in the method of trying to reduce the difference in signal propagation speed by considering the arrangement of the transmission line of the glass filaments, there is the following problem: the positional relationship between the transmission line and the glass filaments due to the weft inclination of the glass filaments Deviation and/or unevenness occurs, making it difficult to precisely control the signal propagation speed.

The glass cloth specifically disclosed in Examples 1 to 4 of Patent Document 4 is the following glass cloth, which is measured at 10 locations for a 100 m long glass cloth with an average value of 3 to 5 mm. , with a thickness of 10-12 μm. Patent Document 4 discloses that the average value of the amount of weft skew is small. However, because the amount of weft skew is usually uneven, if there is a part with a large weft skew, there will be a transmission line with a large change in signal propagation speed. In electronic circuits that need to synchronize multiple signals, signal processing occurs. Fault.

The glass cloth specifically disclosed in Examples 1 to 5 of Patent Document 5 is the following glass cloth. The average value of the weft skew measured in units of 10 m for a 100 m long glass cloth is 1 to 3 mm, and the thickness is It is 17-21 μm. In the glass cloth described in Patent Document 5, adjacent filaments are arranged substantially without gaps in order to improve the small hole formability. Therefore, it is necessary to use glass filaments with a large number of filaments, and it is difficult to reduce the thickness of the glass cloth.

The glass cloth specifically disclosed in the examples of Patent Document 6 is made of thin glass filaments (lighter than ECBC3000, BC3750, BC5000, BC6000) with the mass of both warp and weft below 1.65×10 ^-6 kg/m. , the width of the warp and weft is also narrow. Therefore, the mutual binding force at the intersecting points of the warp and weft is weak, and the same as the previous glass cloth, it is easy to cause weft skew.

The present invention was made in view of the above problems, and an object thereof is to provide a low-dielectric glass cloth capable of suppressing weft skew while maintaining a thickness of 16 μm or less. Moreover, the object of this invention is to provide the prepreg and printed wiring board which reduced the signal propagation velocity difference of several transmission lines using the said glass cloth. [Technical means to solve the problem]

The inventors of the present invention conducted intensive research to solve the above-mentioned problems, and found that the low-dielectric glass cloth satisfies the ratio of the weft yarns in the longitudinal direction, the sum of the width of the warp yarns and the width of the weft yarns in a specific range , the occurrence of weft skew can be suppressed while the thickness is maintained at 16 μm or less, and the present invention has been completed. Also, the inventors of the present invention found that the presence ratio of the weft yarns in the longitudinal direction is in a specific range, and the low-dielectric glass cloth with the weft skew amount of the weft yarns and the spacing between the weft yarns satisfies a specific relationship, when it is made into a printed wiring board. , can make the change of the glass existence rate in the insulator layer through which the transmission line arranged in parallel to the weft can be suppressed to a smaller distance and become longer, so the change of the signal propagation speed can be reduced, thus completing the this invention.

That is, the present invention is as follows. [1] A glass cloth composed of glass filaments including a plurality of glass filaments as warp and weft, with a thickness of 8 μm to 16 μm, and the weft in the longitudinal direction obtained by formula (1) The existence ratio Y of the yarn is 75% to 90%, Y=F/(25000/G)×100・・・(1) (In the formula, F is the width of the weft yarn (μm), G is the width of the weft yarn Weaving density (root/25 mm)) The sum of the width of warp and weft is 380 μm or more and 500 μm or less, and the density of the glass constituting the above warp and weft is 2.10 g/cm ³ or more 2.50 g/ ^cm3 or less. [2] The glass cloth as in [1], where the elongation in the warp direction when a load of 5 N is applied to the warp direction per 25 mm width is the same as when a load of 5 N is applied to the weft direction per 25 mm width The sum of the resulting elongation in the weft direction is 0.50% or less. [3] A glass cloth composed of glass filaments including a plurality of glass filaments as warp and weft, with a thickness of 8 μm to 16 μm, and the weft in the longitudinal direction obtained by formula (1) The existence ratio Y of the yarn is 75% to 90%, Y=F/(25000/G)×100・・・(1) (In the formula, F is the width of the weft yarn (μm), G is the width of the weft yarn Weaving density (threads/25 mm)) The weft inclination of the weft is less than the value obtained by dividing 10 times the distance between wefts (μm) by 500 mm. The density of the glass constituting the above-mentioned warp and above-mentioned weft is Above 2.10 g/ ^cm3 and below 2.50 g/ ^cm3 . [4] The glass cloth as in [3], wherein the weft skew of the weft is equal to or less than the value obtained by dividing 5 times the distance between wefts (μm) by 500 mm. [5] The glass cloth as in [3], wherein the weft skew of the weft is not more than the value obtained by dividing 2.5 times the distance between wefts (μm) by 500 mm. [6] The glass cloth as in [3], wherein the weft skew of the weft is not more than the value obtained by dividing 1.0 times the distance between wefts (μm) by 500 mm. [7] The glass cloth according to any one of [3] to [6], wherein the sum of the width of the warp and the width of the weft is 380 μm or more and 500 μm or less. [8] For glass cloth as in [7], the elongation in the warp direction when a load of 5 N is applied to the warp direction per 25 mm width is the same as when a load of 5 N is applied to the weft direction per 25 mm width The sum of the resulting elongation in the weft direction is 0.50% or less. [9] The glass cloth of [1] or [2], wherein the ratio of the section height in the warp direction to the section height in the weft direction is not less than 90% and not more than 110%. [10] The glass cloth according to any one of [3] to [6], wherein the sum of the width of the warp and the width of the weft is not less than 380 μm and not more than 500 μm, and the height of the section in the direction of the warp and the width of the weft are The ratio of the section height in the direction is not less than 90% and not more than 110%. [11] The glass cloth according to any one of [1] to [10], wherein the dielectric constant at 10 GHz is 5 or less. [12] The glass cloth according to any one of [1] to [11], wherein the average mass per unit length of the warp is 1.40×10 ^-6 kg/m or more and less than 1.60×10 ^-6 kg/m , the average mass per unit length of the weft exceeds 1.65×10 ^-6 kg/m and is less than 3.00×10 ^-6 kg/m, and the average mass per unit length of the weft is relative to the average mass per unit length of the warp The average mass ratio (weft/warp ratio) is 1.20 or more and 1.50 or less. [13] The glass cloth according to any one of [1] to [12], wherein the average number of filaments of the warp and weft are substantially the same, and the average filament diameter of the warp is not less than 3.7 μm and not more than 4.3 μm, The average filament diameter of the weft is 4.2 μm to 5.3 μm, and the ratio of the average filament diameter of the weft to the average filament diameter of the warp (weft/warp ratio) is 1.07 to 1.40. [14] The glass cloth according to any one of [1] to [12], wherein the average filament diameters of the warp and weft are substantially the same, and the average number of filaments of the warp is not less than 45 and not more than 70, The average number of filaments of the weft is 55 to 80, and the ratio of the average number of wefts to the average number of warps (weft/warp ratio) is greater than 1.25 and not more than 1.50. [15] A prepreg comprising: the glass cloth according to any one of [1] to [14]; and a matrix resin. [16] The prepreg according to [15], wherein the difference between the dielectric constant at 10 GHz of the glass constituting the glass cloth and the dielectric constant at 10 GHz of the cured product of the matrix resin is 3 or less. [17] The prepreg according to [15], wherein the difference between the dielectric constant at 10 GHz of the glass constituting the glass cloth and the dielectric constant at 10 GHz of the cured product of the matrix resin is 2 or less. [18] The prepreg according to [15], wherein the difference between the dielectric constant at 10 GHz of the glass constituting the glass cloth and the dielectric constant at 10 GHz of the cured product of the matrix resin is 1 or less. [19] A printed wiring board having the prepreg according to any one of [15] to [18]. [Effect of Invention]

According to the present invention, it is possible to provide a low-dielectric glass cloth capable of suppressing weft skew while maintaining a thickness of 16 μm or less. When the glass cloth of the present invention is made into a printed wiring board, the deviation of the positional relationship between the glass filament and the transmission line can be reduced. Also, according to the present invention, it is possible to provide a prepreg and a printed wiring board having a small difference in signal propagation speed among a plurality of transmission lines.

Hereinafter, an embodiment 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 changes can be made within a range not departing from the gist. In addition, the dielectric constant in this embodiment represents the value measured in the 10 GHz frequency band by the cavity resonator perturbation method (cavity resonator perturbation method/manufactured by Kanto Electronics Applied Development Co., Ltd.).

＜Glass Cloth＞ (thickness) The glass cloth of this embodiment is a glass cloth having a thickness of not less than 8 μm and not more than 16 μm, which is composed of glass filaments including a plurality of glass filaments as warps and wefts. By making the thickness 16 μm or less, the number of layers of the multilayer printed wiring board can be increased, and the density of the transmission line can be increased while maintaining the thickness of the multilayer printed wiring board. The thinner the thickness of the glass cloth, the better, but because the thickness becomes thinner, the glass filaments that constitute it need to be made into filaments, so the strength of the glass cloth tends to decrease and weft skewing tends to occur. With a thickness of 8 μm or more, the strength of the glass cloth can be maintained and the occurrence of weft skew can be suppressed.

(Weft Occupancy) In the glass cloth of this embodiment, the presence ratio of the weft in the longitudinal direction is 75% or more and 90% or less. The presence ratio of the weft in the length direction is also called the weft occupancy rate, which is calculated according to formula (1), which is the value Y obtained by dividing the weft width by the weft spacing. Y＝F/(25000/G)×100・・・(1) (In the formula, F is the width of the weft yarn (μm), and G is the weaving density of the weft yarn (root/25 mm)) The wire width of the weft is to use a microscope to observe the glass cloth sample with a size of 100 mm × 100 mm from the surface, calculate the width of all wefts, and divide the total by the total number of such wefts to obtain the average value. At this time, when the width of the weft yarn varies within the sample, the width at the widest point is set as the width of the weft yarn.

One of the present embodiments is a glass cloth, which is composed of glass filaments including a plurality of glass filaments as warps and wefts, and has a thickness of 8 μm to 16 μm, and the longitudinal direction obtained by formula (1) The ratio Y of the above weft yarns is 75% to 90%, Y=F/(25000/G)×100・・・(1) (where, F is the width of the weft yarn (μm), G is Weaving density of weft yarns (roots/25 mm)) The sum of the width of the warp yarns and the weft yarns is 380 μm or more and 500 μm or less, and the density of the glass constituting the above-mentioned warp yarns and the above-mentioned weft yarns is 2.10 g/cm Above ³ and below 2.50 g/ ^cm3 . The said glass cloth is also called glass cloth P.

(the sum of the width of the warp and the width of the weft) The sum of the width of the warp yarns and the width of the weft yarns in the glass cloth P of this embodiment is not less than 380 μm and not more than 500 μm, preferably not less than 380 μm and not more than 480 μm, more preferably not less than 400 μm and not more than 480 μm. Since the sum of the width of the warp and the width of the weft is 380 μm or more, the contact area between the warp and the weft becomes larger at the point where the warp and the weft intersect. Therefore, by increasing the friction area between the warp and weft, the mutual binding force is strengthened, and weft skew can be suppressed. Since the sum of the width of the warp and the weft is 500 μm or less, the mutual binding force between the warp and the weft at the intersecting point of the warp and the weft does not become too strong, and the warp and weft Silk has room to move moderately. Therefore, in the thin glass cloth with a thickness of 16 μm or less, when stress is applied, the warp and weft move based on the intersecting point, and the stress is relieved, thereby suppressing the occurrence of wrinkles and breakage.

Also, the line width generally used in multilayer wiring boards and the like is about 0.1 mm. Therefore, in the glass cloth having a weft yarn occupancy rate of 75% to 90%, in order to suppress the change in the glass existence rate of the insulator layer through which the transmission line arranged in parallel to the weft yarn passes, the weft yarn width should be larger than that of the weft yarn. It is preferably at most 300 μm, and the sum of the width of the warp and weft is preferably at most 500 μm. When the sum of the warp width and the weft width is 380 μm or more and 500 μm or less, it is possible to obtain a glass cloth with excellent handleability without wrinkle and weft skew.

(sum of elongation) The glass cloth of this embodiment is preferably the elongation in the warp direction when a load of 5 N is applied to the warp direction per 25 mm width, and the weft value generated when a load of 5 N is applied to the weft direction per 25 mm width. The sum of elongation in the filament direction is 0.50% or less. The sum of the elongations is more preferably 0.48 or less, and a further preferred range is 0.45 or less. Here, the elongation of the glass cloth is a value obtained as follows.

Using the method described in JIS R3420 General Test Method for Glass Test and Item 7.4 Tensile Strength, measure the elongation when tension is applied to the glass cloth in the warp or weft direction. In the method stipulated in the JIS, a test piece with a width of about 30 mm and a length of about 250 mm is selected from the warp and weft directions of the woven fabric, so that the yarns at both ends of the test piece have a spread width of about 25 mm, ensuring about 150 mm gripping interval is installed on the gripping part, stretched at a stretching speed of about 200 mm/min, and the load at the time of breaking is obtained. In this embodiment, in order to improve the measurement accuracy, the stretching speed is set at about 10 mm/min, and the width of the selected test piece is set at about 35 mm, and stretching is carried out under the same conditions as the method stipulated by the above-mentioned JIS. In the test, the displacement of the glass cloth when a load of 5 N is applied to the width of 25 mm is determined, and the value obtained by the following formula (2) is defined as "the elongation of the glass cloth". Elongation = {(load time interval - no load time interval)/no load time interval}×100 (2)

The inventors of the present invention have studied the relationship between the woven fabric structure of glass cloth and the ease of weft skew occurrence, and found that there is a relationship between the "elongation of the initial deformation region" and the ease of weft skew occurrence when tensile tension is applied. Relatedly, if the "elongation of the initial deformation area" is made less than a specific range, the occurrence of weft skew can be significantly suppressed when glass cloth is usually processed.

Fig. 1 shows the elongation measurement results of the 1017 type of L glass (glass cloth G obtained in Comparative Example 1), which is usually used as a thin glass cloth for printed wiring boards, that is, a glass cloth with a thickness of 14 μm. That is the load-elongation curve. The characteristic of the load-elongation curve of the 1017 type glass cloth of L glass is that the elongation of the weft is greater than that of the warp, and the slope is low near the displacement of 0-0.2%, and then gradually increases until about 0.4%, 0.4% Later, it swings upwards to become a fixed slope. The area with a lower slope reflects that there is a gap between the weft and warp at the point where the weft and warp intersect, and they are not in sufficient contact with each other. Therefore, the weft is greatly stretched by a very weak stretching tension Until it becomes a close state, that is, a tight state. The next area where the slope gradually becomes higher is the area where the crimp of the warp yarn increases and the crimp of the weft yarn continues to stretch. Then swing up and the region where the slope becomes fixed is the region where the weft itself elongates and produces elastic deformation.

As mentioned above, the weft yarn of 1017 cloth of L glass has an initial deformation area before causing elastic deformation within a very weak tensile tension range of 5 N per 25 mm, and the elongation of the initial deformation area gradually increases . Compared with the previous glass cloth such as the 1017 model of L glass, the elongation of the initial deformation region of the glass cloth of the present embodiment is smaller. The load-elongation curve of the glass cloth C obtained in Example 3 is shown in FIG. The elongation of the glass cloth C of the present invention is also small when a maximum of 5 N is applied in the weft direction, and the elongation of the initial deformation area is suppressed to be small. This implies that the binding force between the warp and weft is stronger at the point where the warp and weft intersect. Thin glass cloth, especially glass cloth with a thickness of 16 μm or less, usually uses thin glass filaments with a filament diameter of 4.0 μm or less and a filament number of 50 or less in order to express its thickness. Therefore, warp and weft The mutual binding force at the crossing point of the yarn is weak, and the weft is prone to be skewed, but the sum of the elongation of the glass cloth is 0.50% or less, so it tends to become the following glass cloth, that is, the distance between the warp and the weft is increased. Mutual binding forces at the crossing points inhibit the occurrence of latitude.

As described above, by making the elongation in the weft direction when a load of 5 N is applied in the weft direction per 25 mm width and the elongation in the warp direction when a load of 5 N is applied in the warp direction per 25 mm width If the sum of the elongation ratios is 0.50% or less, it can be made into a glass cloth, that is, the mutual binding force at the intersecting point of the warp and weft becomes high, and weft skew is less likely to occur. On the other hand, the lower limit of the sum of elongations is preferably at least 0.30%, more preferably at least 0.33%, and still more preferably at least 0.35%. With the sum of the elongation ratios being 0.30% or more, glass cloth having a woven fabric structure tends to cause deformation caused by stress applied to the glass cloth to be reversible due to the structure of the glass cloth based on the intersecting point of the warp and weft. Changes are alleviated, thereby suppressing wrinkle generation and breakage. When the sum of the elongation is in the range of 0.30% to 0.50%, there is a tendency that a glass cloth with no wrinkle or weft and excellent handleability can be obtained.

In addition, one of the present embodiments is a glass cloth, which is composed of glass filaments including a plurality of glass filaments as warps and wefts, and has a thickness of 8 μm or more and 16 μm or less, and is obtained by using formula (1). The presence ratio Y of the weft yarn in the length direction is 75% to 90%, Y=F/(25000/G)×100・・・(1) (where, F is the width of the weft yarn (μm), G is the weaving density of the weft yarn (root/25 mm)) The weft inclination of the weft yarn is the value obtained by dividing the value obtained by dividing 10 times the weft yarn spacing by 500 mm, and the density of the glass that constitutes the above warp yarn and the above weft yarn 2.10 g/cm ³ or more and 2.50 g/cm ³ or less. The said glass cloth is also called glass cloth Q.

The weft skew of the weft is preferably less than the value obtained by dividing the value of 5 times the weft spacing by 500 mm, and even less than the value obtained by dividing the value of 2.5 times the weft spacing by 500 mm. The value obtained by dividing 1.0 times the wire spacing by 500 mm or less. Here, the unit of "weft spacing" in "the value obtained by dividing 10 times, 5 times, 2.5 times, or 1.0 times the weft spacing by 500 mm" is μm.

Also, regarding the weft yarn occupancy rate and the weft skew amount, the occupancy rate is preferably 77% to 87%, and the weft skew amount is preferably less than the value obtained by dividing 5 times the weft yarn spacing by 500 mm. The occupancy rate is even higher. It is preferably above 79% and below 85%. The weft skew is more preferably the value obtained by dividing the value of 2.5 times the weft spacing by 500 mm. The occupancy is further preferably between 80% and below 84%. Preferably, the value obtained by dividing 1.0 times the weft spacing by 500 mm is less than the value obtained. The distance between the wefts in this embodiment refers to the distance between the wefts constituting the glass cloth, and the distance between the wefts in this specification also includes the width of the weft itself. Here, Fig. 3 is a schematic diagram showing the intervals between wefts in the glass cloth. a is the wire width, and b is the weft spacing. Also, the weft spacing is calculated based on the weaving density G (root/25 mm) of the weft. Specifically, when the unit of the spacing is mm, the weft spacing can be calculated based on 25/G (mm), when When the unit of the interval is μm, the weft interval can be calculated from 25000/G (μm).

By dividing the weft yarn occupancy rate from 75% to 90% and the weft skew amount is the value obtained by dividing the value of 10 times the weft yarn spacing by 500 mm, when making a printed wiring board, parallel to the weft yarn Changes in the glass ratio in the insulator layer through which the transmission line is arranged are suppressed to be small, so there is a tendency to reduce fluctuations in signal propagation speed.

Here, when the weft yarn occupancy rate is more than 75% to 90%, if the value obtained by dividing the value obtained by dividing 10 times the weft yarn spacing by 500 mm, the weft can be arranged parallel to the weft yarn. The deviation between the transmission line and the weft is suppressed to be small. Specifically, the deviation of the transmission line from the weft can be suppressed to a range smaller than 0.5 times the weft interval, so that the distance around the transmission line can be reduced. The glass presence ratio is maintained at the same transmission path becomes longer. The smaller the amount of weft skew, the better. Ideally, the amount of weft skew is zero, but it may exceed zero.

The "inclination amount" in the description of this case refers to the maximum value among Z _N (Z ₀ , Z ₁ and Z ₂ ) defined by the following formula (I).

Z _N ＝|(Y _{N + 1} -Y _N )/(X _{N + 1} -X _N )| (I) (In the formula, N is 0~2, when the value of X _{N + 1} -X _N is 0 , Z _N is 0)

In the formula, X ₀ ~ X ₃ and Y ₀ ~ Y ₃ are in the form of combination of (X ₀ , Y ₀ ), (X ₁ , Y ₁ ), (X ₂ , Y ₂ ), and (X ₃ , Y ₃ ) Behavior is defined as shown below. The glass cloth, or prepreg, or printed wiring board containing multiple warps and multiple wefts is used as the tested sample, and the warp direction of the tested sample is set as the Y direction, and the direction perpendicular to the Y direction The direction of X is set as the X direction, and for the weft extending from the first warp to the second warp among the first and second warps located at both ends of the tested sample, it is defined that the first warp and the above-mentioned weft The contact point is used as the origin (0, 0), that is, the Y-axis and X-axis of (X ₀ , Y ₀ ). Also, with the point of contact between the second warp and the above-mentioned weft as the end point (X ₃ , Y ₃ ), take the point where the coordinate Y of the above-mentioned weft on the X-axis and Y-axis takes the maximum value and the minimum value One of them is set as (X ₁ , Y ₁ ), and the other is set as (X ₂ , Y ₂ ). In this case, (X 0 , Y 0 ), (X ₀ , Y ₀ ) and (X 0 ₁ , Y ₁ ), (X ₂ , Y ₂ ) and (X ₃ , Y ₃ ).

Hereinafter, referring to FIGS. 4 to 6 , the calculation methods of Z ₀ , Z ₁ , and Z ₂ are exemplarily shown. 4 to 6 are schematic diagrams showing one form of weft. The shape of the weft in this embodiment is not limited to the shape of the weft shown in FIGS. 4 to 6 .

In Figure 4, the origin (X ₀ , Y ₀ ), the point of the maximum value of Y (X ₁ , Y ₁ ), and the point of the minimum value of Y (X ₂ , Y ₂ ) are arranged in sequence on the weft , and the end point (X ₃ , Y ₃ ). Z ₀ is calculated by substituting two adjacent points (X ₀ , Y ₀ ) and (X ₁ , Y ₁ ) into the above formula (I), and Z ₁ is calculated by substituting the adjacent two points ( X ₁ , Y ₁ ) and (X ₂ , Y ₂ ) are substituted into the above formula (I) to calculate, and Z ₂ is calculated by taking two adjacent points (X ₂ , Y ₂ ) and (X ₃ , Y ₃ ) is substituted into the above-mentioned formula (I) and calculated.

In Figure 5, the origin (X ₀ , Y ₀ ), the point of the maximum value of Y (X ₁ , Y ₁ ), and the point of the minimum value of Y (X ₂ , Y ₂ ) are arranged in sequence on the weft , and the end point (X ₃ , Y ₃ ), where (X ₂ , Y ₂ ) and (X ₃ , Y ₃ ) represent the same coordinates. Z ₀ , Z ₁ , and Z ₂ can be calculated in the same manner as in the description of FIG. 4 above. Furthermore, since (X ₂ , Y ₂ ) and (X ₃ , Y ₃ ) represent the same coordinate, Z ₂ takes the value 0 in the above formula (I).

In Figure 6, the origin (X ₀ , Y ₀ ), the point of the maximum value of Y (X ₁ , Y ₁ ), and the point of the minimum value of Y (X ₂ , Y ₂ ) are arranged in sequence on the weft , and the end point (X ₃ , Y ₃ ), where (X ₀ , Y ₀ ) and (X ₁ , Y ₁ ) represent the same coordinates, and (X ₂ , Y ₂ ) and (X ₃ , Y ₃ ) represent The same coordinates, Z ₀ , Z ₁ , and Z ₂ can be calculated in the same manner as in the description of FIG. 4 above. Furthermore, since (X ₀ , Y ₀ ) and (X ₁ , Y ₁ ) represent the same coordinate, Z ₀ takes a value of 0 in the above formula (I), and Z ₂ also takes a value of 0.

The amount of weft skew described in Examples of Patent Documents 4 and 5 is an average value obtained by measuring a plurality of points. On the other hand, in this embodiment, the maximum value is used as the amount of weft skew in this embodiment. The reason is that in an electronic circuit that needs to synchronize multiple signals, even if the arrival time of a signal in one circuit deviates, it may cause a signal processing failure.

The sum of the width of the warp yarns and the width of the weft yarns in the glass cloth Q of this embodiment is preferably not less than 380 μm and not more than 500 μm, more preferably not less than 380 μm and not more than 480 μm, more preferably not less than 400 μm and not more than 480 μm the following. Since the sum of the width of the warp and the weft is 380 μm or more, at the intersecting point of the warp and weft, the contact area between the warp and weft becomes larger, and the mutual binding force is enhanced, which can Suppress weft skew. Since the sum of the width of the warp and the weft is 500 μm or less, the binding force between the warp and the weft at the intersecting point of the warp and weft does not become too strong, and the warp and weft There is room for the threads to move moderately. Therefore, in the thin glass cloth with a thickness of 16 μm or less, the warp and the weft move around the intersecting point when stress is applied, thereby relieving the stress, thereby suppressing the generation of wrinkles and broken.

In addition, the line width used in multilayer wiring boards is usually about 0.1 mm. Therefore, in the glass cloth with a weft yarn occupancy rate of 75% to 90%, in order to suppress the transmission line arranged parallel to the weft yarn The variation of the glass existence ratio of the insulator layer passing through, the width of the weft is preferably 300 μm or less, so the sum of the width of the warp and the weft is preferably 500 μm or less. When the sum of the warp width and the weft width is 380 μm or more and 500 μm or less, it is possible to obtain a glass cloth with excellent handleability without wrinkle and weft skew.

The glass cloth Q of this embodiment is preferably such that the sum of the width of the warp and the width of the weft is 380 μm or more and 500 μm or less, and the warp direction generated when a load of 5 N is applied to the warp direction per 25 mm width The sum of the elongation in the weft direction and the elongation in the weft direction when a load of 5 N is applied to the weft direction per 25 mm width is 0.50% or less

(Section height ratio of warp and weft) In the glass cloth of this embodiment, the ratio of the cross-sectional height in the warp direction to the cross-sectional height in the weft direction is preferably not less than 90% and not more than 110%. The ratio of the section height in the warp direction to the section height in the weft direction is more preferably from 92% to 108%, and more preferably from 95% to 105%. The cross-sectional height in the warp direction is the cross-sectional height of the glass cloth when the cross-sectional image of the glass cloth is observed in such a way that four or more adjacent warp wires enter continuously. Similarly, the cross-sectional height in the weft direction is the cross-sectional height of the glass cloth when the cross-sectional image of the glass cloth is observed in such a way that four or more adjacent wefts enter continuously. Since the ratio of the cross-sectional height in the warp direction to the cross-sectional height in the weft direction is 90% to 110%, the presence of glass and resin composition in the Z-axis direction, that is, in the thickness direction, at the position where glass filaments exist in the insulator layer The uniformity becomes better, and therefore, the variation in the signal propagation speed tends to be reduced.

The glass cloth Q of this embodiment is preferably such that the sum of the width of the warp and the width of the weft is 380 μm or more and 500 μm or less, and the ratio of the height of the section in the direction of the warp to the height of the section in the direction of the weft is more than 90%. Below 110%.

(Density of glass) The density of the glass constituting the glass cloth of this embodiment is 2.10 g/cm ³ to 2.50 g/cm ³ , preferably 2.15 g/cm ³ to 2.45 g/cm ³ , more preferably 2.20 More than g/cm ³ and less than 2.40 g/cm ³ . The specific gravity of E-glass cloth that has been generally used so far is 2.54 g/cm ³ . In order to reduce the dielectric constant and dielectric loss factor of the glass cloth, it is necessary to change the composition of the glass. Compared with the E glass cloth, the low dielectric glass contains more substances with relatively small specific gravity such as B ₂ O ₃ . Therefore, the density of glass becomes smaller, and the rigidity of glass filaments also becomes smaller. Also, if glass filaments with low density and weak rigidity are used, deformation such as weft skewing will easily occur in the glass cloth. With a density of 2.10 g/cm ³ or more, the occurrence of weft skew can be effectively suppressed in the thread width structure of this embodiment. By making the density of the glass 2.50 g/cm ³ or less, the low dielectric property is excellent.

As mentioned above, more substances with relatively small specific gravity such as B ₂ O ₃ are prepared, that is, the composition of the glass is controlled, so that the density of the glass is controlled at 2.10 g/cm ³ or more and 2.50 g/cm ³ or less range. The glass composition can be appropriately adjusted, for example, as long as it has the following compositions. The Si content of the glass cloth is, in terms of SiO ₂ , preferably 40 to 60 mass%, more preferably 45 to 55 mass%, further preferably 47 to 53 mass%, and 48 to 52 mass%. The B content of the glass cloth is, in terms of B ₂ O ₃ , preferably 15 to 30% by mass, more preferably 17 to 28% by mass, further preferably 20 to 27% by mass, further preferably 21 to 25% by mass , and more preferably 21 to 24% by mass. The Al content of the glass cloth is, in terms of Al ₂ O ₃ , preferably from 10 to 20% by mass, more preferably from 11 to 18% by mass, and still more preferably from 12 to 17% by mass. The Ca content of the glass cloth is, in terms of CaO, preferably 4 to 12% by mass, more preferably 5 to 10% by mass, more preferably 6 to 9% by mass. As another composition, for example, Mg, P, Na, K, Ti, Zn, etc. may be contained. The glass composition can be adjusted according to the amount of raw materials used to make glass filaments.

(Mass of Glass Fiber) In the glass cloth of this embodiment, it is preferable that the mass per unit length of the warp is 1.40×10 ^-6 kg/m or more and less than 1.60×10 ^-6 kg/m, and the mass per unit length of the weft is The mass exceeds 1.65×10 ^-6 kg/m and is 3.00×10 ^-6 kg/m or less, and the ratio of the average mass per unit length of the weft to the average mass per unit length of the warp, that is, the weft The ratio to the warp (weft/warp ratio) is not less than 1.20 and not more than 1.50. The mass per unit length of the warp yarn, the mass per unit length of the weft yarn, and the ratio of the above-mentioned average mass are preferably warp yarns; more than 1.40×10 ^-6 kg/m and less than 1.57×10 ^-6 kg/m m, weft yarn; more than 1.65×10 ^-6 kg/m and less than 2.80×10 ^-6 kg/m, weft/warp ratio; more than 1.17 and less than 1.79, respectively, and more preferably warp yarn; 1.40×10 ^-6 kg More than 1.55×10 -6 kg/m and less than 1.55×10 ^-6 kg/m, weft yarn; more than 1.70×10 ^-6 kg/m and less than 2.50×10 ^-6 kg/m, weft/warp ratio; more than 1.21 and less than 1.62.

For glass cloth, in the manufacturing process, a physical load is applied in the step of adjusting the coating amount of the silane agent after dipping and coating the silane treatment agent, or in the fiber opening process step. In addition, in the case of prepreg coating using glass cloth, a physical load is applied to the glass cloth during the step of adjusting the amount of resin varnish after impregnation coating and drying the resin varnish. In order to stably and continuously convey the glass cloth without cutting it in the above steps, it is preferable that the warp yarns have a certain strength or more. For this reason, it is preferable to use glass yarns of 1.40×10 ^-6 kg/m or more. On the other hand, by using glass filaments with an average mass per unit length of less than 1.60×10 ^-6 kg/m as warps, the thickness can be maintained at 16 μm or less, and the weaving density can be increased to, for example, 90 or more , There is a tendency to inhibit the generation of pinholes.

By using glass filaments whose average mass per unit length exceeds 1.65×10 ^-6 kg/m as the weft, the rigidity of the weft is enhanced, and the tendency of weft skewing can be easily reduced. The greater the mass per unit length of the glass filaments used for the weft, the better because it is superior in rigidity, but in order to suppress the thickness of the glass cloth to 16 μm or less, it is preferable to have an average mass per unit length of 3.00×10 ^-6 Below kg/m.

Also, when the mass ratio of the weft and warp is 1.20 or more, the difference between the rigidity of the weft and the rigidity of the warp becomes large, so even when the weft is thin and has no rigidity, It is also possible to suppress the undulation of the weft yarn to be small during the weaving process, and the weft yarn and the warp yarn intersecting the weft yarn are in a close contact state with less gaps. In addition, the undulating state of the weft inserted in a non-constraint state varies according to the unevenness of the thread tension acting on the warp in the weaving step, but since the difference in rigidity between the warp and weft becomes larger, it is possible to The variation of the undulation structure of the weft is suppressed to be small. Therefore, there is a tendency that the fluctuation of "the elongation of the initial deformation region" when tensile tension is applied is small, and a glass cloth with a small weft skew can be stably obtained. Furthermore, the undulation of the weft becomes smaller, and on the contrary, the undulation of the warp becomes larger. As a result, there is a tendency that the crimp amplitude of the weft and warp is close, and the crimp amplitude of the warp can be adjusted to 50% of the thickness of the glass cloth. % to 80%, and adjust the crimp amplitude of the weft to be within the range of 60% to 90% of the thickness of the glass cloth.

On the other hand, by keeping the mass ratio of the weft and warp below 1.50, the rigidity difference between the warp and the weft is prevented from becoming too large, and the undulating structure of the weft is maintained moderately, so that the gap between the warp and the weft does not become too large. The undulation structure produces a large difference, so it tends to prevent the anisotropy and warpage of the dimensional stability of the printed wiring board due to the difference in rigidity between the warp and the weft. With the mass per unit length of the warp, the mass per unit length of the weft, and the mass ratio of the weft to the warp within the above-mentioned ranges, there is a tendency that the dimensional stability of printed wiring boards can be prevented. Anisotropy and warpage, and can reduce the "elongation of the initial deformation region" to a specific range when tensile tension is applied.

(average filament diameter, average filament number) In the glass cloth of this embodiment, the average number of filaments of the warp and weft is preferably substantially the same, and the average filament diameter of the warp is not less than 3.7 μm and not more than 4.3 μm, and the average filament diameter of the weft is not less than 4.2 μm 5.3 μm or less, the ratio of the average filament diameter of the weft to the average filament diameter of the warp (weft/warp ratio) is not less than 1.07 and not more than 1.30.

With the average number of filaments and the average filament diameter of the warp and weft within the above range, there is a tendency to maintain the thickness of the glass cloth below 16 μm and prevent the anisotropy of the dimensional stability of the printed wiring board And warping, and improve the rigidity of the weft direction, suppress weft skew. The average filament diameter of the warp and weft, and the weft/warp ratio of the average filament diameter are more preferably warp; 3.8 μm to 4.2 μm, weft; 4.3 μm to 5.2 μm, average Weft/warp ratio of filament diameter; 1.08 to 1.25, respectively, and more preferably warp; 3.9 μm to 4.1 μm, weft; 4.4 μm to 5.1 μm, average filament diameter of weft/warp Silk ratio: above 1.09 and below 1.20.

The average number of filaments in the warp and weft is substantially the same, which means that the ratio of the number of filaments in the warp to the number of filaments in the weft (ratio of weft/warp) is in the range of 0.94 to 1.06. When the weft/warp ratio of the average number of filaments is 0.94 to 1.06, the effect of making the filament diameter of the weft larger, that is, the rigidity in the weft direction tends to be excellent. Moreover, in this embodiment, when the average number of filaments of a warp and a weft is substantially the same, it is preferable to set the number of filaments of a warp and a weft to 60 or less. By setting the number of filaments to less than 60, it is easy to diffuse the filaments by physical processing in the glass cloth manufacturing process, so that the distribution of the filaments in the Z direction of the glass strands is less, so it is easy to reduce the thickness of the glass cloth . In order to reduce the thickness of the glass cloth, the fewer the number of filaments the better, but from the viewpoint of the strength and handleability of the glass cloth, when the average number of filaments of the warp and weft is substantially the same, the filament The lower limit of the number is preferably 44 or more, more preferably 46 or more, and still more preferably 48 or more.

In the glass cloth of this embodiment, the average filament diameters of the warp and weft are preferably substantially the same, and the average filament number of the warp is 43 to 70, and the average filament number of the weft is 55 or more. 80 or less, the ratio of the average number of filaments of the weft to the average number of filaments of the warp (weft/warp ratio) is greater than 1.25 and not more than 1.50. With the average number of filaments and the average filament diameter of the warp and weft within the above range, there is a tendency to maintain the thickness of the glass cloth below 16 μm and prevent the dimensional stability of the printed wiring board from being anisotropic. Irregularity and warpage, and increase the rigidity of the weft direction to suppress weft skew. The average number of filaments of warp and weft, and the range of their ratio (weft/warp ratio) are more preferably warp; 43 to 65, weft; 57 to 75, average length The weft/warp ratio of the number of filaments; 1.27 to 1.45, respectively, and preferably warp; 45 to 60, weft; 60 to 70, the average weft/warp ratio of filaments ; Above 1.30 and below 1.40.

The average filament diameters of the warp and weft are substantially the same, which means that the ratio of the filament diameter of the warp to the filament diameter of the weft (weft/warp ratio) is in the range of 0.95 to 1.05. When the weft/warp ratio of the average filament diameter is in the range of 0.95 to 1.05, the effect of increasing the number of weft filaments, that is, the rigidity in the weft direction tends to be excellent. Also, in the present embodiment, when the average filament diameters of the warp and weft are substantially the same, the filament diameters of the warp and weft are preferably 3.8 μm or more. When the average filament diameter of the warp and weft is 3.8 μm or more, the rigidity of the glass cloth tends to be enhanced. In order to enhance the rigidity of the glass cloth, the larger the diameter of the filament, the better, but from the perspective of the thickness of the glass cloth, when the average filament diameters of the warp and weft are substantially the same, the average diameter of the warp and weft The upper limit of the filament diameter is preferably at most 4.4 μm, more preferably at most 4.3 μm, and still more preferably at most 4.2 μm.

The glass filaments constituting the glass cloth of this embodiment are not particularly limited, and low dielectric constant glasses such as D glass, L glass, NE glass, and silica glass (Q glass) can be used. By using glass fiber yarns with a dielectric constant close to that of the impregnated resin as the warp and weft, there is a tendency that the unevenness of the dielectric constant can be further alleviated. From the viewpoint of alleviating the unevenness of the dielectric constant, the dielectric constant of the glass cloth is preferably 5.0 or less, more preferably 4.5 or less.

The weaving structure of the glass cloth is not particularly limited, and examples thereof include weaving structures such as plain weave, caviar weave, satin weave, and twill weave. Furthermore, a mixed weave structure using different types of glass filaments may also be used. Among them, a plain weave structure is preferable.

In addition, the glass cloth of laminates used in printed wiring boards, etc., is usually surface treated with a treatment solution containing a silane coupling agent. As the silane coupling agent, a commonly used silane coupling agent can be used, and acids and dyes can also be added as needed. , pigments, surfactants, etc.

As the silane coupling agent, for example, a silane coupling agent represented by formula (2) is preferably used. X(R) _3-n SiY _n・・・ (2) In formula (2), X is an organic functional group having at least one of an amine group and an unsaturated double bond group, and Y are each independently an alkoxy group , n is an integer ranging from 1 to 3, and R are independently selected from the group consisting of methyl, ethyl and phenyl.

X is preferably an organic functional group having at least 3 or more of an amine group and an unsaturated double bond group, and X is more preferably an organic functional group having at least 4 or more of an amine group and an unsaturated double bond group. As the above-mentioned alkoxy group, any form can be used, but an alkoxy group having 5 or less carbon atoms is preferable from the viewpoint of stabilizing the glass cloth.

As the silane coupling agent, specifically, 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, Acryloxy A known single component such as propyltrimethoxysilane, or a mixture thereof.

The molecular weight of the silane coupling agent is preferably from 100 to 600, more preferably from 150 to 500, and still more preferably from 200 to 450. Among them, it is preferable to use two or more kinds of silane coupling agents with different molecular weights. By using two or more silane coupling agents with different molecular weights to treat the glass fiber surface, the density of the treatment agent on the glass surface tends to increase, and the reactivity with the matrix resin is further improved.

The loss on ignition of the glass cloth is preferably from 0.10% by mass to 2.00% by mass, more preferably from 0.12% by mass to 1.50% by mass, still more preferably from 0.15% by mass to 1.20% by mass. The loss on ignition of glass cloth is an index to indirectly evaluate the surface treatment amount of silane coupling agent on glass cloth. If the loss on ignition value is more than 0.10% by mass, the silane coupling agent will uniformly surface-treat the glass cloth, and the texture of the glass cloth will be strong, and weft skewing will not easily occur, so it is preferable. If the loss on ignition is 2.00% or less, the texture of the glass cloth remains moderately soft, so it is less likely to wrinkle, which is better. The loss on ignition value of the glass cloth is a value calculated according to the method described in JIS R 3420.

＜How to make glass cloth＞ The manufacturing method of the glass cloth of this embodiment is not particularly limited. For example, a method including the following steps can be preferably mentioned: a coating step, which uses a silane coupling agent with a concentration of 0.1 to 3.0 wt% of the silane coupling agent. The treatment solution almost completely covers the surface of the glass filaments; the fixing step is to fix the silane coupling agent on the surface of the glass filaments by heating and drying; and the fiber opening step is to open the glass fibers of the glass cloth.

As a 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 of obtaining a treatment liquid with water as the main solvent, any one of the following methods is preferred, that is, the method of directly putting the silane coupling agent into water, and dissolving the silane coupling agent in a water-soluble organic solvent. A method of throwing the organic solvent solution into water after dissolving it in an organic solvent. In order to improve the water dispersibility and stability of the silane coupling agent in the treatment liquid, a surfactant can also be used in combination.

As the method of applying the silane coupling agent treatment solution to the glass cloth, there are (a) a method of storing the treatment solution in a bath, dipping the glass cloth and passing it through; (b) using a roll coater or die coating Cloth machine, gravure coater, etc., which directly coat the treatment liquid on the glass cloth, etc. In the case of coating by the method (a) above, it is preferable to select the immersion time of the glass cloth in the treatment liquid to be 0.5 second or more and 1 minute or less.

Moreover, well-known methods, such as hot air and electromagnetic waves, can be mentioned as a method of heat-drying a solvent after apply|coating a silane coupling agent treatment liquid on a glass cloth. The heating and drying temperature is preferably above 90°C, more preferably above 100°C, so that the silane coupling agent and the glass can fully react. In addition, in order to prevent deterioration of the organic functional group possessed by the silane coupling agent, the heating and drying temperature is preferably 300°C or lower, more preferably 200°C or lower.

Also, the method of fiber opening in the fiber opening step is not particularly limited, and examples include methods of fiber opening processing of glass cloth using spray water (high-pressure water fiber opening), vibration washing machines, ultrasonic water, pad dyeing machines, and the like. . In order to keep the total area of the square mesh within a certain range, it is preferable to use spray water to carry out the fiber opening step. When spraying water for fiber opening, it is sufficient to set the water pressure appropriately, but in order to adjust the total area of the square mesh in the glass cloth, it is preferable to fix the water pressure. Here, "fixing the water pressure" means reducing the difference between the spray water pressure set for fiber opening and the maximum and minimum values of the actual water pressure. Before and after the fiber opening step, there may be a step of performing heat drying.

＜Prepreg＞ One of this embodiment is a prepreg which has the glass cloth and matrix resin described in this embodiment. The prepreg system of this embodiment is a prepreg with less weft skew and a thinner thickness, which is preferably used as a prepreg for printed wiring boards. Here, the dielectric constant difference between the glass cloth and the matrix resin is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.0 or less. The smaller the difference in permittivity, the better, and the lower limit of the permittivity needs to be 0 or more. By reducing the dielectric constant difference between the glass cloth and the cured resin, even in the case of unevenness in the presence of glass and resin in the insulator layer, it is possible to alleviate the inhomogeneity of the dielectric constant. Reduces the tendency to vary in signal propagation velocity.

The prepreg using the glass cloth of this embodiment can be manufactured by a conventional method. As a method of manufacturing the prepreg of this embodiment, for example, the following method can be mentioned: After impregnating the glass cloth of this embodiment with a varnish obtained by diluting a matrix resin like epoxy resin with an organic solvent, the organic solvent is dried in a drying oven. volatilize, and harden the thermosetting resin to a B-stage state, that is, a semi-cured state, to obtain a resin-impregnated prepreg. As the matrix resin, bismaleimide resin, cyanate resin, unsaturated polyester resin, polyimide resin, bismaleimide triazine resin (also known as BT resin), functionalized polyphenylene ether resin and other thermosetting resins; polyphenylene ether resin, polyetherimide resin, liquid crystal polymer of fully aromatic polyester (also known as LCP), polybutadiene, Thermoplastic resins such as fluororesins; or their mixed resins, etc. From the viewpoint of improving dielectric properties, heat resistance, solvent resistance, and press-formability, it may be a resin obtained by modifying a thermoplastic resin with a thermosetting resin.

In addition, the matrix resin can also be mixed with inorganic fillers such as silicon dioxide and aluminum hydroxide, flame retardants such as bromine-based, phosphorus-based, and metal hydroxides, other silane coupling agents, heat stabilizers, antistatic agents, etc. Resins for additives, UV absorbers, pigments, colorants, lubricants, etc.

＜Printed Wiring Board＞ One of this embodiment is a printed wiring board which has the prepreg of this embodiment. The printed wiring board of this embodiment can be made into a printed wiring board in which the variation in the positional relationship between the glass filament and the transmission line is small, and the signal propagation speed difference between the plurality of transmission lines is small. Here, the dielectric constant difference between the glass cloth and the matrix resin is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.0 or less. The smaller the difference in permittivity, the better, and the lower limit of the permittivity needs to be 0 or more. By reducing the dielectric constant difference between the glass cloth and the resin after hardening, even when the existence ratio of the glass in the insulator layer and the existence ratio of the resin composition are uneven, the unevenness of the dielectric constant can be alleviated , Therefore, there is a tendency to reduce the fluctuation of the signal propagation speed.

The printed wiring board of this embodiment can be manufactured by a conventional method. For example, a double-sided printed wiring board can be manufactured through the following steps. The above steps are to apply a single or multiple prepreg volume layers of this embodiment, attach copper foil to both surfaces of the obtained laminate, and heat and press A step of making a copper-clad laminate by hardening it; a step of making a circuit pattern including copper foil on both surfaces of the copper-clad laminate; and then forming a through hole to ensure electrical connection between the circuit patterns on the two surfaces step. [Example]

Hereinafter, the present invention will be specifically described by way of examples. The physical properties of the glass cloths in Examples and Comparative Examples were measured in accordance with JIS R3420. The elongation in the warp direction and the elongation in the weft direction of the glass cloth are measured according to the method based on JIS 3420. In addition, the weft amount of the glass cloth was measured by the above-mentioned method based on JIS L1096.

<Example 1> As the warp, L glass filaments with an average filament diameter of 4.0 μm, a number of filaments of 50, a twist number of 1.0 Z, and a mass per unit length of 1.46×10 ^-6 kg/m were used. The wire diameter is 4.5 μm, the number of filaments is 50, the number of twists is 1.0 Z, and the mass per unit length is 1.83×10 ^-6 kg/m. mm, weft 70 / 25 mm weaving density to weave glass cloth. Furthermore, the density of L glass (composition: SiO ₂ : 51%, Al ₂ O ₃ : 13%, CaO: 8%, B ₂ O ₃ : 23%) constituting the glass cloth is 2.30 g/cm ³ . The glass cloth obtained as gray cloth was heat-treated at 400°C for 24 hours to desize it. Then, the glass cloth was impregnated with N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane as a silane coupling agent; SZ6032 (manufactured by Toray Dow Corning Co.) In the treatment liquid, the liquid was pressurized and dried at 120°C for 1 minute, and fiber opening was carried out by a high-pressure water sprayer to obtain a glass cloth A with a mass of 10.7 g/m ² and a thickness of 13 μm. The widths of the warp and weft of glass cloth A are 140 μm and 286 μm respectively, the occupancy rate of the weft is 80%, the elongation in the warp direction is 0.22%, and the elongation in the weft direction is 0.27%. The ratio of the section height in the direction of the weft to the section height in the weft direction is 0.97. The weft of glass cloth A is 3 mm, and it is a glass cloth with excellent handleability. The glass cloth A was processed into a width of 650 mm for the coating test, and the epoxy resin varnish was used for prepreg coating. Furthermore, the epoxy resin varnish is formulated with 80 parts by mass of low brominated bisphenol A type epoxy resin, 20 parts by mass of cresol novolak type epoxy resin, 2 parts by mass of dicyandiamide, 2-ethyl-4-formaldehyde 0.2 parts by mass of imidazole and 100 parts by mass of 2-methoxy-ethanol were prepared. Transport the glass cloth at a speed of 3 m/min, impregnate the glass cloth A in the epoxy resin varnish, scrape off the excess varnish through the adjusted slit so that the resin content reaches 68% by mass, and then dry it at the drying temperature Drying was carried out at 170° C. for a drying time of 1 minute and 30 seconds, and the epoxy resin was semi-cured (B-staged) to obtain a prepreg A. The prepreg A was cut into a size of 550 mm × 550 mm, and then copper foil with a thickness of 35 μm was placed on both surfaces of the prepreg A, and then compression molding was performed at 175°C and 40 kgf/cm ² to obtain the substrate A . The obtained substrate A was subjected to etching treatment, and processed so that copper foil lines with a width of 200 μm and the warp wires were arranged at right angles to obtain an evaluation substrate A. Taking the position 2 cm away from the end of the copper foil wire as a reference, the deviation between the copper foil wire and the weft is evaluated within 0.5 times of the distance between the weft wires, and the result is 70 mm.

<Example 2> Except that the weaving density of the wefts was set to 75 threads/25 mm, glass cloth weaving and subsequent processing were carried out in the same manner as in Example 1 to obtain a mass of 11.1 g/m ² and a thickness of 14 μm glass cloth B. The widths of the warp and weft of glass cloth B are 138 μm and 276 μm respectively, the occupancy rate of the weft is 83%, the elongation in the warp direction is 0.19%, and the elongation in the weft direction is 0.25%. The ratio of the height of the profile in the direction to the height of the profile in the direction of the weft is 1.00. The weft of glass cloth B is 1 mm, and it is a glass cloth with excellent handleability. The evaluation substrate B was produced in the same manner as in Example 1, and the distance between the copper foil line and the weft was evaluated within 0.5 times the distance between the wefts, and the result was 202 mm.

<Example 3> Except that the weaving density of wefts was set to 78 threads/25 mm, glass cloth weaving and subsequent processing were carried out in the same manner as in Example 1 to obtain a mass of 11.2 g/m ² and a thickness of 14 μm glass cloth C. The widths of the warp and weft of glass cloth C are 138 μm and 277 μm respectively, the occupancy rate of the weft is 86%, the elongation in the warp direction is 0.19%, and the elongation in the weft direction is 0.23%. The ratio of the height of the profile in the direction to the height of the profile in the direction of the weft is 1.03. The weft of glass cloth C is 0.5 mm, and it is a glass cloth with excellent handleability. The evaluation substrate C was produced in the same manner as in Example 1, and the distance between the copper foil line and the weft was evaluated within 0.5 times the distance between the wefts, and the result was 415 mm.

<Example 4> Using L glass filaments with an average filament diameter of 4.0 μm, a number of filaments of 67, a twist number of 1.0 Z, and a mass per unit length of 1.95×10 ^-6 kg/m as weft yarns, the weft yarns were The weaving density was set at 68 threads/25 mm. Except for this, glass cloth weaving and subsequent treatment were carried out in the same manner as in Example 1 to obtain glass cloth D with a mass of 11.0 g/m ² and a thickness of 13 μm. The widths of the warp and weft of glass cloth D are 150 μm and 287 μm respectively, the occupancy rate of the weft is 78%, the elongation in the warp direction is 0.19%, and the elongation in the weft direction is 0.26%. The ratio of the height of the profile in the direction to the height of the profile in the direction of the weft is 1.06. The weft of glass cloth D is 2.5 mm, and it is a glass cloth with excellent handleability. The evaluation substrate D was produced in the same manner as in Example 1, and the distance between the copper foil wire and the weft was evaluated within 0.5 times of the weft interval, and the result was 91 mm.

<Example 5> Except that the weaving density of the wefts was set to 72 threads/25 mm, glass cloth weaving and subsequent processing were carried out in the same manner as in Example 4, and a mass of 11.3 g/m ² and a thickness of 13 mm were obtained. μm glass cloth E. The widths of the warp and weft of glass cloth E are 152 μm and 285 μm respectively, the occupancy rate of the weft is 82%, the elongation in the warp direction is 0.20%, and the elongation in the weft direction is 0.25%. The ratio of the height of the profile in the direction to the height of the profile in the direction of the weft is 1.03. The weft of glass cloth E is 1.5 mm, and it is a glass cloth with excellent handleability. The evaluation substrate E was produced in the same manner as in Example 1, and the distance between the copper foil wire and the weft was controlled within 0.5 times the distance between the wefts for evaluation, and the result was 157 mm.

<Example 6> Except that the weaving density of the weft yarns was set to 75 threads/25 mm, the same method as Example 4 was used to weave glass cloth and the subsequent treatment to obtain a mass of 11.8 g/m ² and a thickness of 14 μm glass cloth F. The widths of the warp and weft of glass cloth F are 149 μm and 282 μm respectively, the occupancy rate of the weft is 85%, the elongation in the warp direction is 0.20%, and the elongation in the weft direction is 0.24%. The ratio of the height of the profile in the direction to the height of the profile in the direction of the weft is 1.03. The weft of glass cloth F is 1.5 mm, and it is a glass cloth with excellent handleability. The evaluation substrate F was produced in the same manner as in Example 1, and the distance between the copper foil wire and the weft was evaluated within 0.5 times of the weft interval, and the result was 165 mm.

<Comparative Example 1> Both the warp and the weft are made of L glass filaments with an average filament diameter of 4.0 μm, a number of filaments of 50, a twist number of 1.0 Z, and a mass per unit length of 1.47×10 ^-6 kg/m , using an air-jet loom to weave glass cloth with a weaving density of 93.5 threads/25 mm for both warp and weft. The glass cloth obtained as gray cloth was heat-treated at 400°C for 24 hours to desize it. Then, the glass cloth was impregnated with N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane as a silane coupling agent; SZ6032 (manufactured by Toray Dow Corning Co.) In the treatment solution, after pressurizing, dry at 120°C for 1 minute, and then perform fiber opening with a high-pressure water sprayer to obtain glass cloth G with a mass of 11.1 g/m ² and a thickness of 14 μm. The widths of the warp and weft of glass cloth G are 133 μm and 224 μm respectively, the occupancy rate of the weft is 84%, the elongation in the warp direction is 0.19%, and the elongation in the weft direction is 0.39%. The ratio of the height of the profile in the direction to the height of the profile in the direction of the weft is 1.14. The weft skew of glass cloth G is 7 mm, which is a glass cloth with a large weft skew. The evaluation substrate G was produced in the same manner as in Example 1, and the distance between the copper foil wire and the weft was evaluated within 0.5 times of the weft interval, and the result was 23 mm.

<Comparative Example 2> As the warp, L glass filaments with an average filament diameter of 4.0 μm, a number of filaments of 40, a twist number of 1.0 Z, and a mass per unit length of 1.17×10 ^-6 kg/m were used. The wire diameter is 4.0 μm, the number of filaments is 50, the number of twists is 1.0 Z, and the mass per unit length is 1.47×10 ^-6 kg/m. Weave glass cloth with a weaving density of 95 threads/25 mm. The gray glass cloth obtained was heated at 400° C. for 24 hours to desize it. Then, the glass cloth was impregnated with N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane as a silane coupling agent; SZ6032 (manufactured by Toray Dow Corning Co.) In the treatment solution, after pressurizing, dry at 120°C for 1 minute, and then perform fiber opening with a high-pressure water sprayer to obtain glass cloth H with a mass of 9.2 g/m ² and a thickness of 14 μm. The widths of the warp and weft of glass cloth H are 124 μm and 215 μm respectively, the occupancy rate of the weft is 82%, the elongation in the warp direction is 0.25%, and the elongation in the weft direction is 0.34%. The ratio of the section height in the direction of the weft to the section height in the weft direction is 0.97. The weft skew of the glass cloth H is 10 mm, which is a glass cloth with a large weft skew. The evaluation substrate H was produced in the same manner as in Example 1, and the distance between the copper foil line and the weft was evaluated within 0.5 times the distance between the wefts, and the result was 13 mm.

<Comparative Example 3> Both the warp and the weft are made of L glass filaments with an average filament diameter of 4.0 μm, the number of filaments is 50, the number of twists is 1.0 Z, and the mass per unit length is 1.47×10 ^-6 kg/m , using an air-jet loom to weave glass cloth with a weaving density of 85 yarns/25 mm in warp and weft. Under the tension of 4.9 N/m, the fiber-opening process (processing pressure of 196 N/cm ² ) was carried out on the obtained gray glass cloth by using a high-pressure sprinkler. Thereafter, heat treatment was performed at 400° C. for 24 hours to desizing. Next, dip the glass cloth in N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane used as a silane coupling agent; SZ6032 (manufactured by Toray Dow Corning Corporation) In the treatment liquid, press liquid and dry at 120°C for 1 minute to obtain glass cloth I with a mass of 9.7 g/m ² and a thickness of 12 μm. The chemical and physical treatment of glass cloth is based on the method of Example 2 of Patent Document 4: Japanese Patent No. 3756066. The widths of the warp and weft of glass cloth I are 185 μm and 202 μm respectively, the occupancy rate of the weft is 69%, the elongation in the warp direction is 0.27%, and the elongation in the weft direction is 0.42%. The ratio of the height of the profile in the direction to the height of the profile in the direction of the weft is 1.06. The weft skew of glass cloth I is 8 mm, which is a glass cloth with a large weft skew. The evaluation substrate I was produced in the same manner as in Example 1, and the distance between the copper foil line and the weft was evaluated within 0.5 times of the distance between the wefts, and the result was 17 mm.

<Comparative Example 4> Both the warp and the weft are made of L glass filaments with an average filament diameter of 4.0 μm, the number of filaments is 40, the number of twists is 1.0 Z, and the mass per unit length is 1.17×10 ^-6 kg/m , using an air-jet loom to weave glass cloth with a weaving density of 94.5 threads/25 mm for both warp and weft. Under the tension of 4.9 N/m, the fiber-opening process (processing pressure of 196 N/cm ² ) was carried out on the obtained gray cloth glass cloth by using high-pressure water sprinkling. Thereafter, heat treatment was performed at 400° C. for 24 hours to desizing. Next, the glass cloth was dipped in a treatment solution using SZ6032 (manufactured by Toray Dow Corning Co., Ltd.) as a silane coupling agent, pressed and dried at 120°C for 1 minute to obtain a cloth with a mass of 9.0 g/m ² and a thickness of 11 μm. Glass Cloth J. The chemical and physical treatment of glass cloth is based on the method of Example 2 of Patent Document 4: Japanese Patent No. 3756066. The widths of the warp and weft of glass cloth J are 158 μm and 177 μm respectively, the occupancy rate of the weft is 67%, the elongation in the warp direction is 0.17%, and the elongation in the weft direction is 0.37%. The ratio of the height of the section in the direction of the weft to the height of the section in the direction of the weft is 1.09. The weft skew of glass cloth J is 8 mm, which is a glass cloth with a large weft skew. The evaluation substrate J was produced in the same manner as in Example 1, and the distance between the copper foil line and the weft was controlled within 0.5 times of the weft interval for evaluation, and the result was 15 mm.

<Comparative Example 5> Using L glass filaments with an average filament diameter of 4.5 μm, a number of filaments of 50, a twist number of 1.0 Z, and a mass per unit length of 1.83×10 ^-6 kg/m as the weft, the weft The weaving density was set at 60 strands/25 mm. Except for this, glass cloth weaving and subsequent treatment were performed in the same manner as in Comparative Example 1 to obtain glass cloth K with a mass of 10.1 g/m ² and a thickness of 12 μm. The widths of the warp and weft of glass cloth K are 135 μm and 267 μm respectively, the occupancy rate of the weft is 64%, the elongation in the warp direction is 0.21%, and the elongation in the weft direction is 0.29%. The ratio of the height of the section in the direction of the weft to the height of the section in the direction of the weft is 1.09. The weft skew of glass cloth K is 6 mm, which is a glass cloth with a large weft skew. The evaluation substrate K was produced in the same manner as in Example 1, and the distance between the copper foil line and the weft was evaluated within 0.5 times the distance between the wefts, and the result was 31 mm.

Table 1 shows the properties and evaluation results of the glass cloths and substrates produced in Examples and Comparative Examples.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative Example 5 A B C D. E. f G h I J K Thickness (μm) 13 14 14 13 13 14 14 14 12 11 12 Mass (g/m ² ) 10.7 11.1 11.2 11.0 11.3 11.8 11.1 9.2 9.7 9 10.1 Warp filament width (μm) 140 138 138 150 152 149 133 124 185 158 135 Width of weft wire (μm) 286 276 277 287 285 282 224 215 202 177 267 The sum of the width of warp and weft (μm) 426 414 415 437 437 431 357 339 387 335 402 Weft Occupancy(%) 80 83 86 78 82 85 84 82 69 67 64 Elongation in the warp direction (%) when a load of 5 N is applied in the warp direction per 25 mm width 0.22 0.19 0.19 0.19 0.20 0.20 0.19 0.25 0.27 0.17 0.21 Elongation in the weft direction when a load of 5 N is applied to the weft direction per 25 mm width (%) 0.27 0.25 0.23 0.26 0.25 0.24 0.39 0.34 0.42 0.37 0.29 The sum of the elongation in the warp direction and the elongation in the weft direction (%) 0.49 0.44 0.42 0.45 0.45 0.44 0.58 0.59 0.69 0.54 0.50 Weft spacing (μm) 357 333 321 368 347 333 267 263 294 265 417 Weft skew(mm) 3 1 0.5 2.5 1.5 1.5 7 10 8 8 6 The deviation between the copper foil line and the weft is controlled within 0.5 times the distance between the wefts (mm) 70 202 415 91 157 165 twenty three 13 17 15 31 [Industrial availability]

The glass cloth of the present invention is industrially applicable as a base material used for printed wiring boards used in the electronic and electrical fields.

a: Width of weft b: Interval between wefts

FIG. 1 is a graph showing the results of measuring the elongation of glass cloth G (model 1017 of L glass) obtained in Comparative Example 1, that is, the load-elongation curve. FIG. 2 is a graph showing a load-elongation curve of glass cloth C obtained in Example 3. FIG. Fig. 3 is a schematic view showing the width of the weft yarns and the interval between the weft yarns in the glass cloth of the present embodiment. Fig. 4 is a schematic view showing one form of the glass cloth of the present embodiment, and is a view showing one form of weft yarns. Fig. 5 is a schematic view showing one form of the glass cloth of the present embodiment, and is a view showing one form of weft yarns. Fig. 6 is a schematic view showing one form of the glass cloth of the present embodiment, and is a view showing one form of weft yarns.

Claims (19)

A glass cloth comprising glass filaments including a plurality of glass filaments as warps and wefts, having a thickness of not less than 8 μm and not more than 16 μm, and having a ratio Y of the wefts in the longitudinal direction obtained by formula (1) More than 75% and less than 90%, Y=F/(25000/G)×100‧‧‧(1) (where, F is the width of the weft yarn (μm), and G is the weaving density of the weft yarn (root/ 25mm)) The sum of the width of the warp and the weft is 380 μm to 500 μm, and the density of the glass constituting the warp and the weft is 2.10 g/cm ³ to 2.50 g/cm ³ . Such as the glass cloth of claim 1, wherein the elongation in the warp direction produced when a 5N load is applied to the warp direction per 25mm width, and the elongation in the weft direction produced when a 5N load is applied to the weft direction per 25mm width The sum of the ratios is less than 0.50%. A glass cloth comprising glass filaments including a plurality of glass filaments as warps and wefts, having a thickness of not less than 8 μm and not more than 16 μm, and having a ratio Y of the wefts in the longitudinal direction obtained by formula (1) More than 75% and less than 90%, Y=F/(25000/G)×100‧‧‧(1) (where, F is the width of the weft yarn (μm), and G is the weaving density of the weft yarn (root/ 25mm)) The weft inclination of the weft is less than the value obtained by dividing 10 times the distance between the wefts (μm) by 500mm, and the density of the glass constituting the above-mentioned warp and the above-mentioned weft is 2.10g/ ^cm3 or more 2.50 g/ ^cm3 or less. The glass cloth as claimed in claim 3, wherein the weft skew of the weft is equal to or less than the value obtained by dividing 5 times the distance between wefts (μm) by 500 mm. Such as the glass cloth of claim 3, wherein the weft skew of the weft is not more than the value obtained by dividing the value obtained by dividing 2.5 times the interval (μm) between the wefts by 500 mm. Such as the glass cloth of claim 3, wherein the weft skew of the weft is not more than the value obtained by dividing 1.0 times the distance between wefts (μm) by 500 mm. The glass cloth according to any one of claims 3 to 6, wherein the sum of the width of the warp and the width of the weft is not less than 380 μm and not more than 500 μm. Such as the glass cloth of claim 7, wherein the elongation in the warp direction produced when a 5N load is applied to the warp direction per 25mm width, and the elongation in the weft direction produced when a 5N load is applied to the weft direction per 25mm width The sum of the ratios is less than 0.50%. The glass cloth of claim 1 or 2, wherein the ratio of the section height in the warp direction to the section height in the weft direction is not less than 90% and not more than 110%. The glass cloth according to any one of claims 3 to 6, wherein the sum of the width of the warp and the width of the weft is 380 μm or more and 500 μm or less, and the ratio of the height of the section in the direction of the warp to the height of the section in the direction of the weft is: Above 90% and below 110%. The glass cloth according to any one of claims 1 to 6, wherein the dielectric constant at 10 GHz is 5 or less. The glass cloth according to any one of Claims 1 to 6, wherein the average mass per unit length of warp yarns is more than 1.40×10 ^-6 kg/m and less than 1.60×10 ^-6 kg/m, and the average mass per unit length of weft yarns is The average mass per unit length exceeds 1.65×10 ^-6 kg/m and is less than 3.00×10 ^-6 kg/m, and the ratio of the average mass per unit length of the weft to the average mass per unit length of the warp ( The weft/warp ratio) is not less than 1.20 and not more than 1.50. Such as the glass cloth of any one of claims 1 to 6, wherein The average number of filaments of the warp and weft is substantially the same, and the average filament diameter of the warp is 3.7 μm to 4.3 μm, the average filament diameter of the weft is 4.2 μm to 5.3 μm, the average length of the weft The ratio of the yarn diameter to the average filament diameter of the warp (weft/warp ratio) is not less than 1.07 and not more than 1.40. The glass cloth according to any one of claims 1 to 6, wherein the average filament diameters of the warp and weft are substantially the same, and the average number of filaments of the warp is 45 to 70, and the average length of the weft is The number of filaments is not less than 55 and not more than 80, and the ratio of the average filament number of the weft to the average filament number of the warp (weft/warp ratio) is greater than 1.25 and not more than 1.50. A prepreg comprising: the glass cloth according to any one of claims 1 to 14; and a matrix resin. The prepreg according to claim 15, wherein the difference between the dielectric constant at 10 GHz of the glass constituting the glass cloth and the dielectric constant at 10 GHz of the cured product of the matrix resin is 3 or less. The prepreg according to claim 15, wherein the dielectric constant of the glass constituting the above-mentioned glass cloth at 10 GHz is the same as the hardness of the above-mentioned matrix resin The difference in dielectric constant of the compound at 10 GHz is 2 or less. The prepreg according to claim 15, wherein the difference between the dielectric constant at 10 GHz of the glass constituting the glass cloth and the dielectric constant at 10 GHz of the cured product of the matrix resin is 1 or less. A printed wiring board having the prepreg according to any one of Claims 15 to 18.

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