CN116477635A

CN116477635A - Low dielectric amorphous silica powder, method for producing same, slurry, resin composition, prepreg, and printed wiring board

Info

Publication number: CN116477635A
Application number: CN202310079578.XA
Authority: CN
Inventors: 糸川肇; 田口雄亮; 野村龙之介; 浦中宗圣
Original assignee: Shin Etsu Chemical Co Ltd
Current assignee: Shin Etsu Chemical Co Ltd
Priority date: 2022-01-21
Filing date: 2023-01-17
Publication date: 2023-07-25
Also published as: KR20230113158A; TW202342369A; JP2023106883A

Abstract

The invention provides a low dielectric amorphous silica powder with very small dielectric loss tangent, and a surface-treated low dielectric silica powder; silica with less agglomerationA slurry; a silica-containing resin composition which can achieve both tensile strength and dielectric loss tangent; prepregs and printed wiring boards containing silica. A low dielectric amorphous silica powder using VMC silica, wherein the average particle diameter is 0.1 to 1.5 [ mu ] m, and the specific surface area is 1.5 to 20m ² The total content of alkali metal and alkaline earth metal is 700ppm or less, the silanol amount is 100ppm or less, the specific gravity is 2.2, the dielectric loss tangent at 10GHz is 0.0007 or less, and the (dielectric loss tangent at 40 GHz)/(dielectric loss tangent at 10 GHz) is 2.0 or less.

Description

Low dielectric amorphous silica powder, method for producing same, slurry, resin composition, prepreg, and printed wiring board

Technical Field

The present invention relates to a low dielectric amorphous silica powder having a very small dielectric loss tangent in a high frequency region, a surface-treated low dielectric silica powder, a silica slurry having little aggregation, a silica-containing resin composition, a silica-containing prepreg, and a printed wiring board.

Background

Currently, next-generation communication systems (millimeter wave region of 26GHz to 80 GHz) such as 5G are popular, and development of next-generation communication systems such as 6G is also started, and it is desired to realize high-speed, high-capacity, low-delay communication as above. In order to realize these communication systems, materials for high frequency bands of 3 to 80GHz are required, and transmission loss must be reduced as a countermeasure against noise. In addition, with the increase in performance and high-speed communication of information terminals such as smart phones, it is strongly desired that the sealing materials for semiconductors such as printed wiring boards and underfills used are highly densified and extremely thinned, and that the dielectric characteristics, particularly the dielectric loss tangent, be reduced.

The transmission loss of the known signal is as described by Edward a.wolff equation: transmission lossAs shown by δ, the smaller the dielectric constant (ε) and the dielectric loss tangent (tan δ), the more the loss is suppressed. In particular, it is known from the above equation that the contribution of dielectric loss tangent (tan δ) to the transmission loss is large.

As a method for reducing the dielectric loss tangent of a sealing material for semiconductors such as a printed wiring board and an underfill, a method of adding an inorganic powder having a dielectric loss tangent lower than that of a resin is generally used. However, an inorganic powder having a dielectric loss tangent of 0.001 or less in the millimeter wave region is hardly known.

As one of typical general-purpose inorganic powders, silica powder is a material having a small expansion coefficient and excellent insulating and dielectric properties as an inorganic powder added to a resin. Although silica powder is similar in composition to quartz glass, it has inferior dielectric characteristics to quartz glass. It is considered that if dielectric characteristics, particularly dielectric loss tangent, can be reduced to the original level of quartz glass, it is expected that the silica powder will be developed in a wide range of applications as a sealing material for a semiconductor or the like for high-speed communication, a substrate for high-speed communication, or a filler for an antenna substrate or the like, which will be expected to be greatly developed in the future. In addition, the reduction in the thickness of the substrate is also expected to reduce the particle size of the silica powder itself, and in the case of a joint film application, the average particle size is expected to be 2 μm or less, and in the case of a prepreg application, the silica powder needs to intrude into the filament, and therefore the average particle size is expected to be 1 μm or less.

In patent document 1, although the production of low silanol silica is performed by heat treatment in an atmosphere having a low water vapor partial pressure, only the reduction rate of silanol groups is mentioned, the silanol amount of the silica after the treatment is not measured, and no mention is made of dielectric loss tangent.

In patent document 2, silica glass fibers produced by a sol-gel method are subjected to a heat treatment, and silica glass fibers having a moisture content of 1000ppm or less are produced. However, although the moisture content of the silica glass fiber after the heat treatment is described, the silanol amount and the dielectric loss tangent are not mentioned.

Although the relationship between the amount of moisture in the silica glass fiber and the dielectric loss tangent is shown, the amount of silanol is not described, and the dielectric loss tangent is also measured using a printed circuit board using silica glass fiber and PTFE, and therefore, the correlation between the amount of silanol and the dielectric loss tangent of glass fiber is not clear.

Patent document 3 describes a heat-treated silica powder using fused silica, but no description is made about silanol, and the relation between the amount of silanol and dielectric loss tangent is still not clear. The dielectric loss tangent was measured only at frequencies around 35 to 40GHz, and the dielectric loss tangent at other frequencies was unknown. In addition, fused silica is not suitable for producing silica having a particle diameter of 1.5 μm or less, and fused silica having a particle diameter of 1.5 μm or less is hardly known. In the future, a silicon dioxide powder of 1.5 μm or less is required for a thinned substrate, and therefore, there is a problem that it cannot be applied. In addition, it is difficult for the fused silica to reduce the concentration of metal impurities, particularly alkali metals and alkaline earth metals, in the composition, and when a large amount of alkali metals and alkaline earth metals are contained, amorphous quartz is heated to form cristobalite. Cristobalite is known to be carcinogenic, and cristobalite-containing silica is not preferred in public health. Further, silica produced by the melt method contains silica having a fine particle diameter, and aggregation between fine particles is likely to occur, and the fluidity may be adversely affected when the silica is kneaded with a resin.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2-289416

Patent document 2: japanese patent laid-open No. 5-170483

Patent document 3: japanese patent No. 6793282

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a low dielectric amorphous silica powder having a very small dielectric loss tangent and a surface-treated low dielectric silica powder; a silica-containing resin composition which can achieve both tensile strength and dielectric loss tangent; a silica slurry with less agglomeration; prepregs and printed wiring boards containing silica.

Means for solving the problems

The present inventors have conducted intensive studies to achieve the above object and as a result, found that: if the specific silica powder prepared by the VMC method (Vaporized Metal Combus t ion Method: deflagration method) is heated at 700 to 1200 ℃ to reduce the silanol amount in the silica powder, reduce the dielectric loss tangent, and further reduce the silanol amount even at a high frequency of 40GHz, deterioration of the dielectric loss tangent can be suppressed. In addition, it is known that phase transition of silica powder to cristobalite, which is a carcinogenic substance, can be suppressed at the time of heating to obtain amorphous silica powder having a specific gravity of 2.2, and the present invention has been completed.

Further, it has been found that a silica-containing resin composition obtained by mixing the low dielectric amorphous silica powder, a surface-treated low dielectric silica powder obtained by treating the surface of the low dielectric amorphous silica powder with a silane coupling agent, or a silica slurry in which the low dielectric amorphous silica powder is dispersed with a resin can achieve both tensile strength and dielectric loss tangent, and the present invention has been completed.

Accordingly, the present invention provides the following inventions.

1. A low dielectric amorphous silica powder using VMC silica, wherein,

the average grain diameter is 0.1-1.5 mu m,

specific surface area of 1.5-20 m ² /g，

The total content of alkali metal and alkaline earth metal is 700ppm or less,

the silanol amount is 100ppm or less,

the specific gravity of the mixture is 2.2,

the dielectric loss tangent is 0.0007 or less at 10GHz,

(dielectric loss tangent at 40 GHz)/(dielectric loss tangent at 10 GHz) is 2.0 or less.

2. The low dielectric amorphous silica powder according to claim 1, wherein the total content of U (uranium) and Th (thorium) is 0.3ppb or less.

3. The method for producing a low dielectric amorphous silica powder according to 1 or 2, comprising a step of heating a silica powder produced by a VMC method at 700 to 1100 ℃.

4. A surface-treated low dielectric silica powder obtained by treating the surface of the low dielectric amorphous silica powder according to any one of claims 1 to 3 with a silane coupling agent, wherein,

the treatment concentration of the silane coupling agent is 0.5 to 1.5 times of the theoretical amount of the silicon dioxide powder silane coupling agent for forming a single molecular layer,

the dielectric loss tangent is 0.0010 or less at 10GHz,

5. A silica slurry comprising the low dielectric amorphous silica powder according to claim 1 or the surface-treated low dielectric silica powder according to claim 4 dispersed in an organic solvent.

6. A silica-containing resin composition which is the low dielectric amorphous silica powder according to claim 1, the surface-treated low dielectric silica powder according to claim 4, or a mixture of the silica slurry and the resin according to claim 5.

7. A silica-containing prepreg comprising the silica-containing resin composition according to claim 6 and a glass cloth.

8. A printed wiring board using the silica-containing prepreg according to 7.

ADVANTAGEOUS EFFECTS OF INVENTION

In the case of the low dielectric amorphous silica powder of the present invention, the dielectric loss tangent is extremely small and does not deteriorate even at high frequencies. In addition, the low dielectric amorphous silica powder having an average particle diameter of 1.5 μm or less can be provided even for the reduction of the thickness of a substrate for 5G use in the future.

Further, the silica-containing resin composition obtained by mixing the low dielectric amorphous silica powder, the surface-treated low dielectric silica powder obtained by treating the surface of the low dielectric amorphous silica powder with a silane coupling agent, or a silica slurry in which the low dielectric amorphous silica powder is dispersed with a resin can achieve both tensile strength and dielectric loss tangent.

Drawings

Fig. 1 is a graph showing a relationship between the amount of silica powder and the dielectric loss tangent (10 GHz).

Detailed Description

The present invention will be described in detail below.

VMC silica powder

The silica powder which is a raw material of the low dielectric amorphous silica powder of the present invention is VMC silica prepared by the VMC method (hereinafter, silica prepared by the VMC method may be referred to as VMC silica). The VMC method uses the principle of dust explosion. According to the VMC method, a large amount of oxide particles are instantaneously obtained. For example, when a silica powder is obtained, a metal silica powder may be charged. The particle diameter of the silica powder obtained can be adjusted by adjusting the particle diameter, the amount of the metal silicon powder to be charged, the flame temperature, and the like. The metal silicon can be subjected to a refining step, and is effective in reducing the amount of the alpha ray source (U, th), iron, and aluminum of the refined silica powder.

The average particle diameter of the VMC silica powder is preferably 0.1 to 1.5. Mu.m, and more preferably 0.3 to 1.0. Mu.m. The average particle diameter is a volume average particle diameter (cumulative average diameter D) by a laser diffraction scattering method ₅₀ (median particle diameter)), a particle diameter/particle shape analyzer SYNC manufactured by microtracbl corporation, or the like can be used as the apparatus.

The specific surface area of the VMC silica powder is preferably 1.5-20 m ² Preferably 3.0 to 10m ² And/g. The specific surface area is determined by N ₂ BET1 point method for measuring gas adsorption amount. By adjusting the average particle diameter and specific surface area of the VMC silica powder, the average particle diameter and specific surface area of the low dielectric amorphous silica powder can be adjusted.

When the total content of alkali metal and alkaline earth metal in the VMC silica powder is 700ppm or less in terms of mass, cristobalite is not formed in the step of heat treatment, and a low dielectric amorphous silica powder having 700ppm or less in terms of mass of alkali metal and alkaline earth metal can be obtained. From the viewpoint of more suppressing the formation of cristobalite, the alkali metal and alkaline earth metal are more preferably 500ppm or less in terms of mass conversion. The content of the alkali metal and the alkaline earth metal was measured by the method described in examples.

In the present invention, alkali metal means lithium, sodium, potassium, rubidium, cesium, francium, or the like, excluding hydrogen, among elements belonging to the first main group in the periodic table. The alkaline earth metal means calcium, strontium, barium, and radium other than beryllium and magnesium among elements belonging to the second main group in the periodic table.

The total content of U (uranium) and Th (thorium) in the VMC silica powder is preferably 0.3ppb or less in terms of mass conversion.

Low dielectric amorphous silica powder

The low dielectric amorphous silica powder has an average particle diameter of 0.1 to 1.5. Mu.m, preferably 0.3 to 1.0. Mu.m. If the average particle diameter is smaller than 0.1. Mu.m, the specific surface area is large, and a large amount of resin cannot be filled, and if it exceeds 1.5. Mu.m, the filling property into narrow portions such as the inter-filament portions of the glass cloth is poor, and there is a problem such as unfilling. Further, when the low dielectric amorphous silica powder is used as an underfill material or a filler for a high-speed substrate, the average particle diameter is preferably 0.1 to 1.0. Mu.m, more preferably 0.1 to 0.5. Mu.m. In order to improve the fluidity, processability, and other properties of the low dielectric amorphous silica powder, low dielectric amorphous silica powder having different average particle diameters may be mixed with the low dielectric amorphous silica powder.

The specific surface area of the low dielectric amorphous silicon dioxide powder is 1.5-20 m ² Preferably 3.0 to 10m ² /g。

The total content of alkali metal and alkaline earth metal in the low dielectric amorphous silica powder is preferably 700ppm or less, more preferably 350 to 700ppm, and may be 0ppm.

In order to prevent malfunction of the substrate due to radiation, the total content of U (uranium) and Th (thorium) in the low dielectric amorphous silica powder is preferably 0.3ppb or less, more preferably 0.2 to 0.3ppb, and may be 0ppb by mass conversion. Thus, by suppressing the impurity concentration to be low, a more preferable silica powder such as dielectric characteristics of the low dielectric amorphous silica powder is obtained. The concentration of the impurities may be measured by atomic absorption spectrometry, inductively Coupled Plasma (ICP) emission spectrometry, or the like, and the details are described in examples.

The low dielectric amorphous silica powder of the present invention is useful as a sealing material for semiconductors for high-speed communications, a filler for printed wiring boards such as substrates for high-speed communications and antenna substrates, and has a dielectric loss tangent (10 GHz) of 0.0007 or less. In order to obtain a low dielectric amorphous silica powder having such a dielectric loss tangent, a method of heat-treating a VMC silica powder is mentioned.

Method of manufacture

The heating temperature for reducing the dielectric loss tangent is preferably 700 to 1200 ℃, more preferably 800 to 1100 ℃, still more preferably 900 to 1100 ℃. As the heating method, a method of heating the silica powder using an electric heating furnace, a muffle furnace, or the like is exemplified.

The heating treatment time of the VMC silica powder varies depending on the heating temperature, and is preferably from 30 minutes to 72 hours, more preferably from 1 hour to 24 hours, and even more preferably from 2 hours to 12 hours in practice. The cooling to room temperature after heating may be slow cooling or rapid cooling. The optimization can be suitably performed in such a manner that the VMC silica in a molten state is not crystallized.

The heating atmosphere is not particularly limited in the atmosphere of air, inert gas such as nitrogen, and the like, and is usually carried out under normal pressure or air in consideration of cost and the like.

Whether or not the heat-treated VMC silica powder is amorphous can be confirmed by XRD or the like, and as a method for easier confirmation, the determination can be made by measuring the specific gravity of the low dielectric amorphous silica powder. Since the specific gravity of the amorphous silica powder was 2.2 and the specific gravity of the cristobalite was 2.3, it was found that the formation of cristobalite was not performed if the specific gravity after heating was still 2.2. The specific gravity was measured based on JIS Z8807:2012, a measurement of true specific gravity.

By analyzing the silanol amount in the heat-treated VMC silica powder by infrared spectroscopic analysis, it can be confirmed whether the desired dielectric characteristics have been achieved.

Dipoles caused by polarization in the GHz band are known to induce induction in response to an electric field. Therefore, it is critical to reduce polarization from the structure for dielectric characteristics in the GHz band to be reduced.

The dielectric constant is represented by the following Claus ius-Mossot t i formula, and the molar polarizability and molar volume are factors. Thus, decreasing polarization and increasing molar volume are critical in decreasing dielectric constant.

Dielectric constant= [1+2 (Σpm/Σvm) ]/[1- (Σpm/Σvm) ]

( Pm: molar polarizability of atomic group, vm: molar volume of atomic groups )

In addition, the dielectric loss tangent (tan δ) is a delay of the dielectric response to an ac electric field, and the relaxation of the dipole orientation in the GHz band is a major factor. Therefore, in order to reduce the dielectric loss tangent, a method of eliminating the dipole (having a structure close to a nonpolar structure) is conceivable.

As is clear from the above, in the present invention, the concentration of hydroxyl groups (silanol) as polar groups is suppressed to be low as a method for decreasing the dielectric characteristics of silica particles in the GHz band.

From the above point of view, in the present invention, the silanol amount (si—oh) concentration in the VMC silica powder after heat treatment is 100ppm or less, preferably 80ppm or less, more preferably 60ppm or less, and may be 0ppm or less in terms of mass.

The hydroxyl group (Si-OH) concentration in the silica powder was measured by infrared spectroscopic analysis at 3680cm ^-1 The transmittance of the nearby peak was quantified. This is due to 3680cm ^-1 Since the nearby infrared absorption is attributed to internal silanol (see patent document 1), a polar group affecting dielectric loss tangent is determined based on the characteristic absorption bandI.e. silanol, and quantified. Thereby, the degree of the decrease in the dielectric loss tangent can be estimated more specifically. It should be noted that the flow is 3740cm ^-1 Since the infrared absorption of the isolated silanol in the vicinity (see patent document 1) is negligible in the present invention, it is only about 3680cm as described above ^-1 By measuring the transmittance of the nearby peaks, the decrease in dielectric loss tangent can be sufficiently estimated.

The transmission loss of the signal is as the Edward A.Wolff formula: transmission lossAs shown, the smaller the dielectric constant (epsilon) and the dielectric loss tangent (tan delta), the more the loss is suppressed. In particular, the contribution of dielectric loss tangent (tan δ) to transmission loss is large. Therefore, a lower dielectric loss tangent is required.

The dielectric loss tangent of 10GHz can be set to the original level of quartz powder, namely, below 0.0007 by the heat treatment of the invention. The low dielectric amorphous silica powder of the present invention has a dielectric loss tangent of 0.0007 or less, preferably 0.0006 or less, more preferably 0.0005 or less, and may be 0.0003 or less at 10 GHz.

By reducing the silanol amount in the low dielectric amorphous silica powder by heat treatment at a high frequency around 40GHz, deterioration of the dielectric loss tangent can be suppressed, and the (dielectric loss tangent at 40 GHz)/(dielectric loss tangent at 10 GHz) can be made 2.0 or less. In order to suppress transmission loss at higher frequencies, the low dielectric amorphous silica powder of the present invention has a dielectric loss tangent of (40 GHz)/(dielectric loss tangent at 10 GHz) of preferably 1.8 or less, and more preferably 1.0 to 1.5.

Since the low dielectric amorphous silica powder obtained by the heat treatment is partially fused silica powder due to the treatment temperature, coarse particles and agglomerated particles exceeding 100 μm are removed by a sieve after crushing the powder by a crushing device such as a ball mill. The low dielectric silica powder thus obtained is preferably used by removing coarse particles exceeding 100 μm with a sieve (e.g., 150 mesh sieve).

Surface-treated low dielectric silicon dioxide powder

The surface-treated low dielectric amorphous silica powder can be obtained by treating the surface of the low dielectric amorphous silica powder with a coupling agent such as a silane coupling agent. The surface treatment with the silane coupling agent is used for firmly adhering the resin to the surface of the low dielectric silica powder when the surface of the low dielectric amorphous silica powder treated at a high temperature is coated with the silane coupling agent to produce a resin composition or the like.

As the silane coupling agent, a known silane coupling agent is used, preferably an alkoxysilane, more preferably 1 or 2 or more selected from γ -aminopropyl trimethoxysilane, γ -aminopropyl triethoxysilane, N- β -aminoethyl- γ -aminopropyl trimethoxysilane, N- β -aminoethyl- γ -aminopropyl triethoxysilane, γ -methacryloxypropyl trimethoxysilane, γ -methacryloxypropyl triethoxysilane, 3-methacryloxypropyl trimethoxysilane, and trifluoropropyl trimethoxysilane.

The concentration of the silane coupling agent is 0.5 to 1.5 times the theoretical amount of the silane coupling agent to form a single molecular layer on the low dielectric amorphous silica powder (hereinafter, the low dielectric amorphous silica powder of the present invention may be referred to as silica powder). The theoretical amount is determined based on the following formula from the specific surface area of the treated silica powder and the minimum coated area of the silane coupling agent.

[ mathematics 1]

In the present invention, the silane coupling treatment is performed at 0.5 to 1.5 times the theoretical amount obtained by the above formula. If the ratio is less than 0.5 times, poor adhesion to the resin may occur. On the other hand, if the amount exceeds 1.5 times, the dielectric loss tangent may be deteriorated due to the polar group of the silane coupling agent itself. By performing the treatment between 0.5 and 1.5 times, the silane coupling agent is uniformly adhered, and not only a more uniform protective effect is provided on the surface of the low dielectric amorphous silica powder, but also the treatment is easy, and the resin used for manufacturing a substrate or the like can be uniformly mixed without unevenness.

The dielectric loss tangent of the surface-treated low dielectric silica powder is 0.0010 or less, preferably 0.0080 or less at 10 GHz.

The dielectric loss tangent (40 GHz)/(dielectric loss tangent at 10 GHz) is 2.0 or less, more preferably 1.8 or less, and still more preferably 1.0 to 1.5.

The average particle diameter, the total amount of alkali metal and alkaline earth metal, the specific gravity, and the like are preferably in the same ranges as those of the low dielectric amorphous silica powder.

Silica slurry

The surface-treated low dielectric silica powder can be dispersed in an organic solvent and then crushed to prepare a silica slurry. If the silica powder is directly added to the resin, the silica powder is aggregated in a large amount, and therefore it is necessary to carry out the crushing treatment with 3 rolls or the like after the addition. However, since the silica slurry has silica powder dispersed in an organic solvent, a crushing treatment is not required after the addition to the resin, and thus is suitable in the production of a substrate or the like.

As the organic solvent of the silica slurry, a known organic solvent may be used, and may be selected from toluene, anisole, cyclohexanone, and the like. The boiling point of the organic solvent is preferably 100 to 200 ℃, and if it is lower than 100 ℃, it is not preferable that a sufficient amount of liquid cannot be maintained due to thermal volatilization at the time of crushing. If the boiling point is 200 ℃ or higher, drying at a high temperature is required in the subsequent step, and oxidation degradation of the resin proceeds, which is not preferable.

The disruption of the silica slurry may be selected from a bead mill, a ball mill, a cavitation mill, and the like. The crushing time during crushing is appropriately adjusted according to the crushing method, and is preferably stopped at the moment when the aggregation disappears. The agglomeration can be confirmed by measuring the particle size distribution by a laser diffraction method or the like. The low dielectric amorphous silica powder before crushing is preferably uniform in particle size, and if it contains a fine silica powder or the like, it cannot be crushed smoothly, and there is a possibility that the silica powder aggregates when it is added to the resin.

Resin composition containing silica

The silica-containing resin composition of the present invention is the low dielectric amorphous silica powder, the surface-treated low dielectric silica powder, or a mixture of the silica slurry and a resin. Examples of the resin include epoxy resin, silicone resin, polyimide resin, teflon (registered trademark) resin, maleimide resin, polyphenylene ether resin, and the like, and as a filler, a thermosetting resin and a thermoplastic resin may be blended.

In particular, in the case of using the surface-treated low dielectric silica powder, the tensile strength of the resin cured sheet of the resin composition is preferably 1.5 times or more, more preferably 1.6 times or more, as compared with the tensile strength when the low dielectric silica powder not treated with the silane coupling agent is used instead of the surface-treated low dielectric silica powder. The upper limit is not particularly limited, and is about 1.7 times.

The amount of the low dielectric amorphous silica powder, the surface-treated low dielectric silica powder, or the silica slurry blended in the silica-containing resin composition is preferably 10 to 80% by volume, and more preferably 25 to 50% by volume, calculated as the low dielectric amorphous silica powder conversion. The blending amount of the resin is preferably 50 to 75% by volume. In addition, a curing agent, a solvent, and the like may be blended.

Prepreg containing silicon dioxide

The resin composition containing the low dielectric amorphous silica powder, the surface-treated low dielectric silica powder, and the silica slurry is impregnated into a fiber base material and then heated and dried, so that the resin composition can be used as a silica-containing prepreg.

As the fiber base material, a known fiber base material used for a laminate can be used. Examples thereof include inorganic fibers such as E glass, S glass, T glass, NE glass, and Q glass (quartz glass); organic fibers such as polyethylene, polyester, polyamide, polytetrafluoroethylene, and the like. The number of these may be 1 alone or 2 or more. Among them, from the viewpoint of dielectric characteristics, inorganic fibers are preferable, and T glass, NE glass, and Q glass are more preferable.

The thickness of the fibrous base material is not particularly limited, but is preferably 5 to 500. Mu.m, more preferably 10 to 100. Mu.m, and still more preferably 20 to 80. Mu.m. When the amount is within this range, a silica-containing prepreg excellent in flexibility, low in warpage and high in strength can be obtained. In order to improve dielectric characteristics and affinity for resins, these fiber substrates may be surface-treated with a silane coupling agent or the like.

The content of the resin composition in the silica-containing prepreg is not particularly limited, but is preferably 20 to 90% by volume, more preferably 30 to 80% by volume, and still more preferably 40 to 70% by volume. If the amount is within this range, the adhesion strength to the conductor can be improved while maintaining the dielectric characteristics and reducing warpage.

The thickness of the silica-containing prepreg of the present invention is not particularly limited, but is preferably 10 to 500. Mu.m, more preferably 25 to 300. Mu.m, and still more preferably 40 to 200. Mu.m. If the amount is within this range, the copper-clad laminate can be produced satisfactorily.

The silica-containing prepreg of the present invention may be pre-cured (B-staged) by heating. The method of B-staging is not particularly limited, and for example, the cyclic imide resin composition of the present invention may be dissolved in a solvent, impregnated into a fiber base material, dried, and then heated at a temperature of 80 to 200℃for 1 to 30 minutes to thereby cause B-staging.

Printed wiring board

By using the above-mentioned prepreg containing silica, a printed wiring board having a small transmission loss can be produced. Specifically, the silica-containing prepreg of the present invention can be used as a copper-clad laminate by stacking copper foil and pressing the stacked copper foil to heat-cure the stacked copper foil. The method for producing the copper-clad laminate is not particularly limited, and it can be produced by, for example, using 1 to 20, preferably 2 to 10, of the above-mentioned silica-containing prepregs, disposing copper foil on one or both surfaces thereof, and then pressing and heat-curing the copper foil.

The thickness of the copper foil is not particularly limited, but is preferably 3 to 70. Mu.m, more preferably 10 to 50. Mu.m, and still more preferably 15 to 40. Mu.m. If the amount is within this range, a multilayered copper-clad laminate with high reliability can be molded. The molding conditions of the copper-clad laminate are not particularly limited, and for example, multi-stage press, multi-stage vacuum press, continuous molding, autoclave molding machine and the like can be used, and molding can be performed at a temperature of 100 to 400 ℃, a pressure of 1 to 100MPa, and a heating time of 0.1 to 4 hours. The prepreg containing silica, copper foil, and wiring board for inner layer of the present invention may be combined and molded to form a copper-clad laminate.

The method of the circuit processing is not particularly limited, and examples thereof include a circuit forming process such as a hole forming process, a metal plating process, and an etching process of a metal foil. Further, a build-up method of sequentially stacking the resin composition of the present invention, a prepreg containing silica, and a copper foil may be used to manufacture a printed wiring board.

Examples

The present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the examples.

I: low dielectric amorphous silica powder

Example I-1

Silica powder SO-C2 (average particle diameter 0.5 μm, specific surface area 6 m) manufactured by Admatechs company and prepared by VMC method ² /g) was heated at 1100℃for 5 hours using an electric furnace, FO-810 manufactured by Yamato scientific Co.

Example I-2

Except that the silica powder was changed to silica powder SO-E2 (average particle diameter 0.5 μm, specific surface area 6 m) manufactured by Admatechs company and prepared by VMC method ² Heating was performed in the same manner as in example I-1 except for/g).

Example I-3

The preparation was carried out in the same manner as in example I-2 except that the heating temperature of example I-2 was changed to 700 ℃.

Example I-4

Except that the silica powder was changed to silica powder SO-C1 (average particle diameter 0.3 μm, specific surface area 15 m) manufactured by Admatechs company and prepared by VMC method ² Heating was performed in the same manner as in example I-1 except for/g).

Example I-5

Except that the silica powder was changed to silica powder SO-C4 (average particle diameter 1.1 μm, specific surface area 5m, manufactured by Admatechs Co., ltd. Prepared by VMC method ² Heating was performed in the same manner as in example I-1 except for/g).

Comparative example I-1

The silica powder SO-E2 used in example I-2 was used as it is without heat treatment.

Comparative example I-2

The preparation was carried out in the same manner as in example I-2 except that the heating temperature of example I-2 was changed to 500 ℃.

Comparative example I-3

The preparation was carried out in the same manner as in example I-2 except that the heating temperature of example I-2 was changed to 1300 ℃. The physical properties cannot be measured due to the fusion.

Comparative example I-4

Except that the silica powder was changed to silica powder F-205 (average particle diameter 5.5 μm, specific surface area 6m, manufactured by Fumi tec Co., ltd. By the melt method ² Heating was performed in the same manner as in example I-1 except for/g). Forming cristobalite.

Physical properties of the silica powders prepared in example I and comparative example I are shown in table 1.

TABLE 1

I I: surface-treated low dielectric silicon dioxide powder

Example I I-1

To the low dielectric amorphous silica powder prepared in example I-2, 0.5 times the theoretical amount required for forming a single film with 3-methacryloxypropyl trimethoxysilane (KBM-503 (manufactured by Xinyue chemical Co.), was added, and after stirring for 5 minutes with an FM mixer manufactured by Nippon COKE Industrial Co., ltd.), the powder was cured at room temperature for 3 days.

Example I-2

The process was carried out in the same manner as in example I I-1 except that the amount of 3-methacryloxypropyl trimethoxysilane (KBM-503) added was changed to 1.0 times the theoretical amount required for forming a single film.

Example I I-3

The process was carried out in the same manner as in example I I-1 except that the amount of 3-methacryloxypropyl trimethoxysilane (KBM-503) added was changed to 1.5 times the theoretical amount required for forming a single film.

Comparative example I I-1

The process was carried out in the same manner as in example I I-1 except that the amount of 3-methacryloxypropyl trimethoxysilane (KBM-503) added was changed to 0.25 times the theoretical amount required for forming a single film.

Comparative example I-2

The process was carried out in the same manner as in example I I-1 except that the amount of 3-methacryloxypropyl trimethoxysilane (KBM-503) added was changed to 2.0 times the theoretical amount required for forming a single film.

Comparative example I-3

Silica powder YA050C (average particle diameter 0.05 μm, specific surface area 65 m) manufactured by Admatechs company and prepared by sol-gel method ² /g) was heated at 1100℃for 5 hours using an electric furnace, FO-810 manufactured by Yamato scientific Co. To the heated silica powder, 1.0 times the theoretical amount required for forming a single film with 3-methacryloxypropyl trimethoxysilane (KBM-503) was added, and after stirring for 5 minutes with an FM mixer manufactured by the Nippon COKE Industrial Co., ltd., aging was carried out at room temperature for 3 days. Physical properties of the surface-treated silica powders prepared in example I I and comparative example I I are shown in table 2.

TABLE 2

I I: silica slurry

Example I I I-1

30 parts of anisole manufactured by Tsuku chemical Co., ltd was added to 70 parts of the surface-treated low dielectric silicon dioxide powder prepared in example I I-2, and the powder was crushed for 7 minutes at a flow rate of 16m/s using a bead mill Aqua TURBO TZ-10 manufactured by FRUND-TURBO Co.

Comparative example I I I-1

A portion of the cristobalite-forming heated silica powder prepared in comparative example I-4 was added with 1 time of the theoretical amount required for forming a single film with KBM-503, stirred with an FM mixer manufactured by the Nippon COKE Industrial Co., ltd, and cured at room temperature for 3 days. Then, the mixture was crushed by a bead mill under the same conditions as in example I I I-1.

Comparative example I I I-2

The heated sol-gel silica powder prepared in comparative example I I-3 was crushed by a bead mill under the same conditions as in example I I I-1.

Physical properties of the silica slurries prepared in example ii and comparative example ii are shown in table 3.

TABLE 3

The physical properties were measured as follows.

1. Average particle diameter

Particle size distribution was measured by using a particle size/particle shape analyzer SYNC manufactured by microtracB EL, and the volume average particle size (cumulative average diameter D) ₅₀ (median particle diameter)) as the average particle diameter.

2. Specific surface area

The measurement was performed by the BET method using Tris tar II Plus 3030 manufactured by Shimadzu corporation.

3. Confirmation of formation of cristobalite (specific gravity)

Using a full-automatic true density measuring device Macpycno manufactured by MOUNTECH corporation, based on JIS Z8807:2012, the true specific gravity of the heated silica powder was measured. If the specific gravity of the silica powder is 2.2, it is determined that cristobalite formation is not performed, and if it is 2.3, it is determined that cristobalite formation is performed.

4. Method for measuring contents of alkali metal, alkaline earth metal and U, th

1g of the silica powder was accurately weighed into a Teflon (registered trademark) beaker, 5mL of hydrofluoric acid and 2mL of nitric acid were added thereto, and the mixture was allowed to stand for 30 minutes. Then heating and dissolving on a heating plate, and finally drying and solidifying the mixture. To this, 2.5mL of nitric acid was added, the residue in the beaker was dissolved, and the mixture was transferred to a 25mL volumetric flask, diluted with water, and the content of alkali metal, alkaline earth metal, U, th, etc. contained in the silica powder was measured by using HP4500 type ICP-MS manufactured by the company Hei Analyt ical Sys tems.

5. Determination of silanol amount

A sample obtained by filling an aluminum plate having a thickness of 0.15cm with a silica powder until the silica powder was scraped was prepared, and the infrared absorption spectrum of the obtained sample was measured by a diffuse reflection method using a Fourier transform infrared spectrometer (IRAaffinity ty-1S) and a diffuse reflection measuring apparatus (DRS-8000A), to measure 3680cm due to hydroxyl group ^-1 Transmittance T of the nearby peak. Based on the obtained transmittance value, absorbance A was obtained by applying the Lambert-Beer law shown below. Absorbance a= -Log10T

T＝3680cm ^-1 Transmittance in the vicinity

Then, from the absorbance obtained by the above formula, the silanol amount C (ppm) in the silica powder was obtained by the following formula.

C＝100/d(cm)×A

Epsilon: molar absorptivity (molar absorptivity of silanol epsilon=77.5 dm) ³ /mol cm), d: thickness of sample (optical path length) (0.15 cm)

6. Method for measuring dielectric loss tangent

The method for calculating the dielectric loss tangent of the low dielectric amorphous silica powder at 10GHz is shown by way of example I-1. A varnish was prepared by mixing, dispersing and dissolving low dielectric amorphous silica powder in an anisole solvent containing SLK-3000 (trade name manufactured by Xinyue chemical industry Co., ltd.) as a low dielectric maleimide resin and dicumyl peroxide (Percumyl D: manufactured by Nitro oil Co., ltd.) as a radical polymerization initiator of a curing agent in the proportions shown in Table 4 below. The low dielectric amorphous silica powder was added so as to be 0%, 11.1%, 33.3% and 48.1% by volume with respect to the low dielectric maleimide resin, and the resultant mixture was drawn to a thickness of 200 μm by a bar coater, and the resultant mixture was dried at 80℃for 30 minutes to remove anisole solvent, whereby an uncured maleimide resin composition was prepared.

TABLE 4

The prepared uncured maleimide resin composition was put into a 60mm×60mm×100 μm mold, cured at 180℃for 10 minutes under 30MPa by manual pressing, and then completely cured at 180℃for 1 hour by a dryer to prepare a resin cured sheet. The resin cured sheet was cut into a size of 50mm×50mm, and the dielectric loss tangent at 10GHz was measured using a dielectric resonator frequency of SPDR (Spl i t post dielectric resonators) (manufactured by Keys ight Technology corporation).

As shown in fig. 1, a straight line of the dielectric loss tangent of the volume% vs of the silica powder was prepared from a graph obtained by taking the volume% of the silica powder on the horizontal axis and taking the measured dielectric loss tangent on the vertical axis with respect to the obtained dielectric loss tangent value. The straight line was extrapolated, and the dielectric loss tangent of 100% of the silica powder was taken as the value of the dielectric loss tangent of the low dielectric amorphous silica powder of example 1-1.

Although there are also measuring machines capable of directly measuring powder, it is difficult to remove air mixed in because silica powder is filled in a measuring tank for measurement. Therefore, in order to obtain a value in a state close to the actual use mode by excluding the influence of the air mixed in, in the present invention, the dielectric loss tangent of the silica powder is obtained by the above-mentioned measurement method. The calculations at 10 and 40GHz were also performed in the same manner in other examples and comparative examples.

Confirmation of the Effect of KBM-503 processing

The surface-treated silica powders prepared in example I-2, example II and comparative example I I were added so as to be 48.1% by volume with respect to the low dielectric maleimide resin (SLK-3000), and after 0.2 part of dicumyl peroxide was added to the low dielectric maleimide resin (SLK-3000), the resultant was drawn to a thickness of 200. Mu.m, and the resultant was put into a dryer at 80℃for 30 minutes to remove anisole solvent, whereby an uncured maleimide resin composition was prepared.

The prepared uncured maleimide resin composition was put into a 60mm×60mm×100 μm mold, cured at 180℃for 10 minutes under 30MPa by manual pressing, and then completely cured at 180℃for 1 hour by a dryer to prepare a resin cured sheet. The resin cured sheet was subjected to a tensile test by Autograph, AGS-X manufactured by Shimadzu corporation. Tensile strength was compared with the resin cured sheet containing the silica powder of example 2 which was not subjected to KBM-503 treatment.

8. Confirmation of degree of breakage of silica slurry

The silica slurries prepared in example ii and comparative example ii were mixed in an anisole solvent containing a low dielectric maleimide resin (SLK-3000) so that the silica powder was 33.3% by volume of the resin. The resultant film was stretched to a thickness of 20. Mu.m, placed in a dryer at 80℃for 30 minutes, and anisole solvent was removed to prepare a resin film having a thickness of 10. Mu.m, and the presence or absence of aggregation of the silica powder was visually confirmed.

According to Table 1, since the silica powder prepared by the VMC method has an average particle diameter of 1.5 μm or less and contains less alkali metal and alkaline earth metal, the formation of cristobalite can be prevented during heating. Further, it is known that the higher the heating temperature is, the smaller the silanol amount is and the dielectric loss tangent is lowered. In the case of a low silanol amount of the silica powder, the dielectric loss tangent at 40GHz can be suppressed to within 2.0 times the dielectric loss tangent at 10 GHz. If the heating temperature exceeds 1300 ℃, the silica is not suitable as a substrate material because of progress of fusion bonding. In addition, if a small amount of U, th silicon dioxide is used as in example I-2, malfunction of the substrate due to alpha rays can be suppressed.

As shown in table 2, the larger the amount of the silane coupling agent to be processed with respect to the heated low dielectric amorphous silica powder, the more deteriorated the dielectric loss tangent, and therefore, if the theoretical amount of the silane coupling agent to be processed is 0.5 to 1.5 times, the tensile strength and the dielectric loss tangent of the resin can be both achieved when the silane coupling agent is compounded in the resin composition. In comparative example I I-3, the theoretical amount of the silane coupling agent to be treated was 1.0 times, but the specific surface area was large, so that the required coupling agent was increased, and the dielectric loss tangent was deteriorated.

According to table 3, since the silica powder prepared by the VMC method does not contain fine silica or the like, the silica powder does not agglomerate even when added to the resin after slurrying. On the other hand, the fine silica of the silica prepared by the melting method is aggregated. In addition, since silica produced by the sol-gel method has a small particle size, it cannot be crushed in the slurry, and aggregation is confirmed.

Further, a prepreg containing silica and a printed wiring board using the same were prepared using the low dielectric amorphous silica powder of the present invention.

According to the present invention, a low dielectric amorphous silica powder, a surface-treated low dielectric silica powder, a silica slurry, and a slurry, which can cope with the reduction in thickness of a substrate for 5G use in the future, have an average particle diameter of 1.5 μm or less, have a very small dielectric loss tangent, and do not deteriorate the dielectric loss tangent even at high frequencies, can be provided. By using the silica-containing resin composition as a mixture with the resin, a remarkable effect of being able to produce a printed wiring board having very small transmission loss is expected.

The present invention is not limited to the above embodiment. The above embodiments are examples, and all embodiments having substantially the same constitution and exhibiting the same effects as the technical ideas described in the patent claims of the present invention are included in the technical scope of the present invention.

Claims

1. A low dielectric amorphous silica powder using VMC silica, wherein,

the average grain diameter is 0.1-1.5 mu m,

specific surface area of 1.5-20 m ² /g，

The total content of alkali metal and alkaline earth metal is 700ppm or less,

the silanol amount is 100ppm or less,

the specific gravity of the mixture is 2.2,

the dielectric loss tangent is 0.0007 or less at 10GHz,

3. The method for producing a low dielectric amorphous silica powder according to claim 1 or 2, comprising a step of heating a silica powder produced by a VMC method at 700 to 1100 ℃.

the dielectric loss tangent is 0.0010 or less at 10GHz,

6. A silica-containing resin composition which is the low dielectric amorphous silica powder according to claim 1, the surface-treated low dielectric silica powder according to claim 4, or the mixture of the silica slurry and the resin according to claim 5.

7. A silica-containing prepreg comprising a glass cloth and the silica-containing resin composition according to claim 6.

8. A printed wiring board using the silica-containing prepreg according to claim 7.