KR20230132699A - Glass cloth - Google Patents

Abstract

[Project] Provide a glass cloth with low dielectric tangent at 10 to 40 GHz, low transmission loss, and easy processing.
[Solution] A silane coupling agent is attached to a glass cloth made of glass fiber with a softening point of 1,000 to 1,600°C and an amount of Si-OH group of less than 1,000 ppm, in an amount of 0.001% by mass or more and less than 1.0% by mass with respect to the glass cloth. Glass cloth.

Description

Glass cloth{GLASS CLOTH}

The present invention relates to glass cloth with excellent dielectric properties and processability.

Currently, with the increased performance and high-speed communication of information terminals such as smartphones, the printed wiring boards used are becoming denser and thinner, and low dielectric constants, especially low dielectric tangents, are progressing significantly.

As an insulating material for printed wiring boards, a laminated board obtained by impregnating glass cloth with a thermosetting resin such as an epoxy resin (hereinafter referred to as “matrix resin”), laminating prepregs and curing them under heat and pressure is widely used. The dielectric constant of the matrix resin used in high-speed communication boards is about 3, while the dielectric constant of general E glass cloth is about 6.7, and the problem of high dielectric constant in laminates is becoming more and more evident.

In addition, it is known that the signal transmission loss is improved as the material with smaller dielectric constant (ε) and dielectric tangent (tanδ) is shown by the Edward A. Wolff equation: transmission loss ∝√ε×tanδ. In particular, the equation above It is known that the contribution of dielectric tangent (tanδ) to transmission loss is large.

For this reason, glass cloths with improved dielectric properties such as D glass, NE glass, and L glass with glass compositions different from E glass have been proposed (Patent Documents 1 to 3).

However, from the viewpoint of achieving sufficient transmission speed performance in future 5G communication applications, etc., there is a need for improvement even in these low-dielectric characteristic glass cloths with excellent low dielectric constant and low dielectric tangent. Therefore, by setting the amount of SiO ₂ in the glass composition to approximately 100% by mass, achieving further low dielectric constant and low dielectric tangent was considered, and the development of a glass cloth with the amount of SiO ₂ included at approximately 100% by mass was conducted. (Patent Document 4). However, in Patent Document 4, although there is mention of low dielectric constant, there is no mention of dielectric tangent, which contributes to transmission loss, making low dielectric tangent a difficult task.

As for transmission loss, it is known that the presence of Si-OH groups significantly reduces transmission efficiency because the absorption of Si-OH vibration overtones is at 1.4㎛, and reduction of Si-OH groups is an effective technique for reducing transmission loss. am.

As a method of lowering the dielectric tangent, the use of synthetic quartz glass was developed (Patent Document 5). However, in Patent Document 5, although there is a description of up to 10 GHz, the dielectric tangent in the millimeter wave range of 30 GHz to 300 GHz, which is recently required, is not described. In addition, synthetic quartz glass is expensive, and when used for 5G communication purposes, which are expected to spread in the future, cost issues arise.

Additionally, Patent Document 5 describes ease of processability when used as a multilayer substrate as an advantage of using synthetic quartz glass, but points out a drawback of poor processability with natural quartz glass materials.

Japanese Patent Application Publication No. 5-170483 Japanese Patent Application Publication No. 2009-263569 Japanese Patent Application Publication No. 2009-19150 Japanese Patent Application Publication No. 2018-197411 Japanese Patent No. 4336086 Publication

The present invention was made in consideration of the above problems, and its purpose is to provide a glass cloth that has a low dielectric tangent at 10 to 40 GHz, a small transmission loss, and is easy to process.

As a result of intensive research to achieve the above object, the present inventors have found that a specific amount of a silane coupling agent was attached to a glass cloth using glass fibers with a softening point of 1,000 to 1,600°C and an amount of Si-OH groups of less than 1,000 ppm. It was discovered that Shikin Glass Cloth could solve the above problem, and the present invention was achieved. More specifically, as a method to suppress transmission loss in high-speed communications such as 5G, which will increase in the future, further improvement in the dielectric tangent characteristics of the glass cloth used in the substrate is sought, for example, from 10 GHz to 40 GHz. The dielectric tangent can be set to 0.002 or less, and the ratio of 40 GHz/10 GHz can be set to 2.0 or less, thereby achieving a significantly greater effect of suppressing transmission loss due to the dielectric tangent characteristic.

Accordingly, the present invention provides a glass cloth.

1. A glass cloth made of glass fiber with a softening point of 1,000 to 1,600°C and an amount of Si-OH group of less than 1,000 ppm, with a silane coupling agent attached in an amount of 0.001% by mass or more but less than 1.0% by mass with respect to the glass cloth. .

2. Glass cloth based on 1, which has a dielectric tangent of 0.002 or less from 10 GHz to 40 GHz and a dielectric tangent ratio of 2.0 or less from 40 GHz/10 GHz.

3. Glass cloth based on 1 or 2, wherein the amount of SiO ₂ in the glass fiber is 99.9% by mass or more.

4. The glass cloth according to any one of 1 to 3, wherein the glass cloth has a thickness of 200 μm or less.

5. The glass cloth according to any one of 1 to 4, wherein the mass per unit area is 4 to 300 g/m ² .

According to the present invention, a glass cloth with excellent dielectric tangent properties and processability can be obtained.

(Form for carrying out the invention)

Hereinafter, the present invention will be described in detail, but these embodiments are presented as exceptions, and it goes without saying that various modifications are possible as long as they do not deviate from the technical idea of the present invention. The glass cloth of the present invention is a glass cloth made of glass fiber with a softening point of 1,000 to 1,600°C and an amount of Si-OH group of less than 1,000 ppm, and a silane coupling agent is attached at an adhesion rate of 0.001 mass% or more and less than 1.0 mass%. It is a glass cloth (hereinafter, it may be described as an attached glass cloth of the present invention).

[glass fiber]

The glass fiber of the present invention has a softening point of 1,000 to 1,600°C and an amount of Si-OH groups of less than 1,000 ppm.

Even if glass has the same composition, its structure and physical properties are different depending on the heat treatment or cooling rate during the treatment. This is influenced by the process by which the glass cools from a completely molten state, but the virtual temperature is different if the cooling rate is different. If the cooling rate is slow, there is sufficient time for structural relaxation, and the virtual temperature follows the actual temperature and falls. On the other hand, when the cooling rate is fast, the virtual temperature increases as it moves away from the actual temperature of the glass. Additionally, as a change that occurs as the virtual temperature increases, the softening point decreases. The softening point of the glass fiber of the present invention is 1,000 to 1,600°C, preferably 1,000 to 1,400°C, and more preferably 1,050 to 1,200°C. In addition, the softening point is a value measured by pulling the glass fiber in the radial direction using a thermomechanical analysis device (TMA).

The Si-OH group content of the glass fiber of the present invention is less than 1,000 ppm (mass). In addition, the method for measuring the content of Si-OH groups is the method described in the Examples. A correlation has been confirmed between the viscosity (Pa·s) of the glass and the OH content, and it is known that the viscosity decreases as the OH content increases. As the viscosity decreases, the softening point also decreases. Although the OH content can increase the elongation of heat treatment in acid hydrogen salt, if it is excessively increased, a problem occurs in that the dielectric tangent deteriorates. The softening point and the amount of Si-OH groups can be adjusted by the glass fiber manufacturing method.

The SiO ₂ content of the glass fiber is preferably 99.9% by mass or more, and may be 100% by mass. Methods for producing quartz glass raw material ingots include electric melting method using quartz as a raw material, flame melting method, direct synthesis method using silicon tetroxide as a raw material, plasma synthesis method, soot method, or sol-gel method using alkyl silicate as a raw material. However, it is not limited to these manufacturing methods as long as the SiO ₂ compounding amount is 99.9 mass%. In particular, the electric melting method using quartz as a raw material, the plasma synthesis method using silicon tetroxide as a raw material, and the soot method are preferable because they rarely contain silanol groups (Si-OH) as impurities.

The fiber diameter ϕ of the glass fiber is preferably 3 to 10 μm, and more preferably 3.5 to 10 μm. The dielectric tangent of the glass fiber from 10 GHz to 40 GHz is preferably 0.002 or less, and more preferably 0.0015 or less. Additionally, it is required that the amount of change in dielectric tangent is small, so it is preferable that the ratio of 40 GHz/10 GHz is 2.0 or less.

In order to achieve both processability and dielectric tangent properties, the glass material is stretched at a speed of 300 m/min or more, more preferably 400 m/min or more, with the fiber diameter being 10 times or more, more preferably 20 times or more, than the target fiber diameter. Glass fiber with low dielectric tangent and easy processing can be obtained.

As a method of preparing the stretched glass material, for example, a quartz glass thread with a diameter of 200 ± 100 μm and a SiO ₂ blending amount of 99.0% by mass or more is carried out by electric melting. Specifically, by melting glass with a diameter of 50 to 200 mm at 1,700 to 2,300°C and winding it into a thread shape, a glass thread with a diameter of 200 ± 100 μm can be obtained. If the melting temperature is less than 1,700°C, there is a risk that the quartz glass may not be melted, and if it exceeds 2,300°C, the viscosity may decrease too much and stable stretching may not be possible.

Since the strength of glass thread is very weak, it is desirable to apply coating to obtain the strength necessary for winding. As a coating agent, a UV curable resin having an acrylate-based functional group with excellent curability is preferable, and the coating thickness is preferably 5 μm or more. If it is less than 5 μm, there is a risk that the reinforcing effect may not be obtained due to insufficient coating thickness.

In order to increase productivity, it is desirable to cool the quartz glass from melting to coating. Cooling includes water cooling or air cooling, and it is more effective to use both. The softening point can be lowered in this process as well by heating quartz glass with a diameter of 50 to 200 mm to 1,700 to 2,300°C and cooling it.

[Glass Strand]

Glass strands can be obtained by bundling the glass fibers. For example, strands can be obtained by melting 20 to 400 quartz glass fibers in a mixed flame of oxygen and hydrogen. When manufacturing glass strands, a bundling agent is used to focus the glass strands. The binder is used in a composition based on starch, and a softener or lubricant can be added to provide functionality.

[Glass Yarn]

Glass yarn can be obtained by twisting the glass strand. The frequency of twisting is preferably 0.1 to 5.0 times per 25 mm, and more preferably 0.1 to 4.0 times.

[Glass cloth (before attachment)]

The glass yarn can be woven and a glass cloth can be obtained. The weave structure, weave density, etc. of the glass cloth are not particularly limited, but examples of the weave structure include plain weave, satin weave, serpentine weave, and twill weave. Moreover, as a straight density, for example, 10-150 pieces/25mm are mentioned.

The thickness of the glass cloth is preferably 200 μm or less, and more preferably 180 μm or less. The mass per unit area of the glass cloth is preferably 4 to 300 g/m ² , and more preferably 10 to 200 g/m ² .

The weaving method of the glass cloth is not particularly limited, but examples include an air jet loom, a water jet loom, a Repia loom, and a shuttle loom.

When weaving glass cloth, a sizing agent can be used to stabilize the weaving or suppress the generation of fluff. The sizing agent preferably contains one or more types selected from polyvinyl alcohol, polyethylene oxide, starch, polyester, and polyamide. The glass cloth may be subjected to an opening process as needed.

As the glass cloth, for example, a quartz glass cloth (1078: IPC-4412B Appendix II) made of a filament containing 99.9% by mass or more of SiO ₂ can be used.

[Glass cloth (after attachment)]

The attached glass cloth of the present invention is a glass cloth to which a silane coupling agent has been attached at an adhesion rate of 0.001 mass% or more and less than 1.0 mass%, and can be obtained by surface treating the above glass strand, glass yarn, and glass cloth with a silane coupling agent.

The adhesive glass cloth of the present invention is treated with a silane compound and a silane coupling agent (treatment agent) in order to develop the impregnability of the resin and the adhesiveness of the interface between the resin and the glass cloth. The silane coupling agent can be selected depending on the glass cloth used, and can be used alone or in combination of two or more types. As a silane coupling agent, for example, a silane coupling agent having a functional group such as a vinyl group, styryl group, methacryl group, or acrylic group is preferable. Specific examples of silane coupling agents include γ-methacryloxypropyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, Vinyltris(β-methoxyethoxy)silane, p-styryltrimethoxysilane, etc. are mentioned. Silane coupling treatment agents for epoxy resins conventionally used include epoxy-based silane coupling agents and cationic silane coupling agents. Additionally, a phenylaminosilane treatment agent that is excellent in solder heat resistance, moisture absorption resistance, copper adhesion heat resistance, and insulation reliability can also be used. Among them, a functional group containing an unsaturated group that has a stable surface to be treated and has a functional group that can chemically bond with an organic resin is preferred, for example, a vinyl-based, (meth)acrylic-based, or styryl-based silane coupling agent. As a silane coupling agent, for example, a silane coupling agent having a methacryl group (Shin-Etsu Chemical Co., Ltd. product: KBM-503: methacryloxypropyltrimethoxysilane) may be used.

The silane coupling treatment method is as long as the silane coupling and the glass cloth are brought into contact so as to achieve a specific adhesion amount, and the temperature, etc., is not particularly limited. The adhesion amount of the treatment agent is 0.001 mass% or more and less than 1.0 mass% (adhesion rate) with respect to the glass cloth, and is preferably 0.01 mass% or more and 0.3 mass% or less. If the adhesion amount is 1.0 mass% or more, it will cause the dielectric tangent to worsen, and if it is less than 0.001 mass%, wettability with the resin will worsen.

The dielectric tangent of the adhesive glass cloth of the present invention at 10 GHz to 40 GHz is preferably 0.002 or less, and more preferably 0.0015 or less. Additionally, it is required that the amount of change in dielectric tangent is small, and the ratio of 40 GHz/10 GHz is preferably 2.0 or less, and more preferably 1.6 or less. In particular, glass cloth used in substrates used in high-speed communications such as 5G is required to have a low dielectric tangent.

The mass per unit area of the adhesive glass cloth of the present invention is preferably 4 to 300 g/m ² , and more preferably 4 to 260 g/m ² .

The adhesive glass cloth of the present invention can be suitably used for printed circuit board prepregs or printed wiring boards that require a low dielectric tangent, and is particularly suitable for multilayer printed boards for high frequencies of 10 GHz or higher.

(Example)

Hereinafter, the present invention will be described in detail by providing examples and comparative examples, but the present invention is not limited to the following examples.

In the examples, measurement of dielectric tangent, calculation of dielectric tangent, silanol group (Si-OH) content, adhesion amount of silane coupling agent, evaluation of softening point and processability were performed by the following methods.

[Measurement of dielectric tangent]

Measurements were made using SPDR (Split post dielectric resonators) dielectric resonator frequencies for dielectric constant measurement of 10 GHz and 40 GHz.

In addition, the dielectric tangent of the examples and comparative examples represents the dielectric tangent of the attached glass cloth.

[Measurement of silanol group (Si-OH) content]

The silanol content of glass fiber and glass cloth refers to the value measured and calculated by the following method.

Using the Fourier transform infrared absorption spectrum of glass fiber and glass cloth, an infrared spectrophotometer (IRAffinity-1S) and a diffuse reflectance measurement device (DRS-8000A), the transmittance of the peak around 3680 cm ^-1 , which is a silanol group, was determined by the diffuse reflection method. T was measured. Based on the obtained transmittance value, the absorbance A was obtained by applying Lambert-Beer's law shown below.

Absorbance A = -Log10T (T=3, transmittance around 680cm ^-1 )

Next, from the absorbance determined by the above formula, the molar concentration C (mol/L) of silanol was determined by the following formula.

C=A/εL

ε: molar extinction coefficient (molar extinction coefficient of silanol ε=77.5dm ³ /mol·cm)

C: molar concentration (mol/L)

L: Thickness of sample (optical path length)

From the obtained absorbance A, the molar concentration C was calculated using the above formula.

Using the obtained molar concentration C, the content (ppm) of silanol in the glass fiber was determined by the following formula.

Silanol content (ppm) = {(C×M(Si-OH))/(d×1000)}×106

Specific gravity of glass fiber d = 2.2g/cm ³

Molecular weight of silanol M(Si-OH) = 45 g/mol

[Measurement of adhesion rate of silane coupling agent]

The attached glass cloth was heated under the conditions of 625°C for 4 hours using an electric furnace, and the change in mass before and after heating was measured. Based on the formula below, the adhesion rate (mass %) was calculated.

Adhesion rate (mass%) = (mass of attached glass cloth before heating - mass of attached glass cloth after heating) / mass of attached glass cloth before heating × 100

[Measurement of softening point]

Using a thermomechanical analysis device (TMA), the glass fiber was pulled in the diametric direction and the softening point was measured.

[Evaluation of processability]

A prepreg was produced by impregnating the adhesive glass cloth with an epoxy resin, and wettability (staining, etc.) and drill life were evaluated.

No problems with wettability (staining, etc.), drill life over 100 times: ○

Wetting problems (staining, etc.) or drill life less than 100 times: ×

[Examples 1 to 3]

A quartz glass fiber with ₂ % by mass of SiO and a softening point shown in Table 1 was stretched at a high temperature and a bundling agent was applied to prepare a quartz glass strand composed of 200 quartz glass filaments with a diameter of 5.0 μm. Next, the obtained quartz glass strand was twisted 0.4 times per 25 mm to prepare quartz glass yarn.

The obtained quartz glass yarn was set in an air jet loom, and a plain weave quartz glass cloth with a warp density of 54/25 mm and a weft density of 54/25 mm was woven. Thereafter, the bundling agent was removed by heat cleaning and then treated with a silane coupling agent (KBM-503: methacryloxypropyltrimethoxysilane) so that the adhesion amount was 0.1% by mass. The obtained treated quartz glass cloth had a thickness of 45 μm and a cloth mass of 42.5 g/m ² . The evaluation results are shown in the table below.

[Example 4]

A glass cloth was prepared in the same manner as in Example 1, and treated with a silane coupling agent (KBM-503) to obtain an adhesion amount of 0.2% by mass, thereby obtaining a treated quartz glass cloth.

[Example 5]

A glass cloth was prepared in the same manner as in Example 1, and treated with a silane coupling agent (KBM-503) to obtain an adhesion amount of 0.05% by mass, thereby obtaining a treated quartz glass cloth.

[Comparative Example 1]

A glass cloth was prepared in the same manner as in Example 1, except that E glass fiber with a softening point of 800°C and a SiO ₂ content of 53% by mass was used, and a silane coupling agent (KBM-503) was added to provide an adhesion amount of 0.1% by mass. By treating with, a treated quartz glass cloth was obtained.

[Comparative Example 2]

A glass cloth was prepared in the same manner as in Example 1, except that quartz glass fibers with a SiO ₂ content of 99.9% by mass and a Si-OH amount of more than 1,000ppm were used, and a silane coupling agent was added so that the adhesion amount was 0.1% by mass. (KBM-503) to obtain a treated quartz glass cloth.

[Comparative Example 3]

A glass cloth was prepared in the same manner as in Example 1, except that quartz glass fibers with a SiO ₂ content of 99.9% by mass and a Si-OH amount of less than 1,000ppm were used, and a silane coupling agent was added so that the adhesion amount was 1.0% by mass. (KBM-503) to obtain a treated quartz glass cloth.

[Comparative Example 4]

A glass cloth was prepared using the same quartz glass as in Example 1 with a SiO ₂ content of 99.9% by mass and a Si-OH amount of less than 1,000 ppm (untreated with a silane coupling agent).

As shown in Examples 1 to 5, the dielectric tangent of the glass cloth made of glass fiber of the present invention was less than 0.002 from 10 GHz to 40 GHz, and the ratio between 40 GHz and 10 GHz was less than 2.0.

As shown in Comparative Example 1, when glass fiber with a softening point of 800°C was used, the dielectric tangent at 10 GHz to 40 GHz was greater than 0.002.

As shown in Comparative Example 2, when glass fibers with a softening point of 990°C and a silanol content of more than 1,000 ppm were used, the dielectric tangent at 10 GHz was less than 0.002, but the dielectric tangent at 40 GHz was greater than 0.002.

As shown in Comparative Example 3, when glass fibers with a softening point of 1,200°C and a silanol content of less than 1,000 ppm were used and the adhesion amount of the silane treatment agent was 1.0 mass%, the dielectric tangent at 10 GHz was less than 0.002, but the dielectric tangent at 40 GHz was It was greater than 0.002.

As shown in Comparative Example 4, the processability was poor when glass fibers with a softening point of 1,200°C and a silanol content of less than 1,000 ppm were used and the adhesion amount of the silane treatment agent was 0%.

Claims (5)

A glass cloth made of glass fiber with a softening point of 1,000 to 1,600°C and an amount of Si-OH groups of less than 1,000 ppm, with a silane coupling agent attached to the glass cloth in an amount of 0.001% by mass or more and less than 1.0% by mass. The glass cloth according to claim 1, wherein the dielectric tangent from 10 GHz to 40 GHz is 0.002 or less, and the dielectric tangent ratio of 40 GHz/10 GHz is 2.0 or less. The glass cloth according to claim 1 or 2, wherein the amount of SiO ₂ in the glass fibers is 99.9% by mass or more. The glass cloth according to claim 1 or 2, wherein the glass cloth has a thickness of 200 μm or less. The glass cloth according to claim 1 or 2, wherein the mass per unit area is 4 to 300 g/m ² .