JPH07240117A - Composite dielectric and its manufacture - Google Patents

Abstract

PURPOSE:To improve the moisture resistance of a composite dielectric consisting of an inorganic powder, a fluororesin and an inorganic fiber base material by covering the inorganic powder with an inorganic film mainly containing silica, and treating its surface with a specified coupling agent. CONSTITUTION:An inorganic powder having a specific dielectric constant of 2.0 or more is covered with an inorganic film mainly containing silica, and its surface is treated with a phenyl silane and/or fluorine silane coupling agent. A composite dielectric consisting of the surface-treated inorganic powder, a fluorine resin and an inorganic fiber base material is improved in the adhesion between the inorganic powder and the fluororesin, and minimized in change of electric characteristic such as dielectric tangent by moisture absorbing treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite dielectric used in electronic parts such as a printed circuit board and a method for manufacturing the same.

[0002]

2. Description of the Related Art In the advanced information society, information transmission tends to be faster and higher frequency. In the fields of mobile radio such as car phones and personal radios, satellite broadcasting, satellite communication, CATV, etc., downsizing of devices is being promoted, and accordingly, microwave circuit elements such as dielectric resonators are also being promoted. Miniaturization is strongly desired.

The size of the microwave circuit element is based on the wavelength of the electromagnetic wave used. The wavelength λ of the electromagnetic wave propagating through the dielectric having the relative permittivity ε _r is λ = λ ₀ / (ε _r ) ^0.5 when the propagation wavelength in vacuum is λ ₀ . Therefore, when the microwave circuit element is formed on the printed circuit board, the higher the relative dielectric constant of the board used, the smaller the circuit element. Moreover, when the relative permittivity of the substrate is high, electromagnetic energy is concentrated in the substrate, which is convenient because there is little electromagnetic wave leakage.

As the above-mentioned printed circuit board, for example, as disclosed in Japanese Patent Application Laid-Open No. 3-5140, it is composed of a fluorine resin and glass cloth to which an inorganic powder having a high relative dielectric constant (barium titanate or the like) is added. Laminates are known. Such a circuit board is attracting attention because it is superior to a ceramic-based board made of alumina or the like in that it has a large area and is excellent in workability such as cutting and hole processing.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In the above-mentioned substrate composed of inorganic powder, fluororesin and glass cloth, when inorganic powder having a relative dielectric constant of 20 or more is used, the fluororesin is formed in the molding process. Since it is difficult to firmly adhere to the inorganic powder, there is a problem with respect to moisture resistance that moisture enters the interface during processing or use of the substrate and significantly changes electrical characteristics such as dielectric loss tangent.

In view of the above circumstances, it is an object of the present invention to improve the moisture resistance of a substrate composed of an inorganic powder having a relative dielectric constant of 20 or more, a fluororesin and a glass cloth. That is, the present invention is a composite dielectric comprising an inorganic powder having a relative permittivity of 20 or more, a fluororesin, and an inorganic fiber base material, and having a small change in electrical characteristics such as dielectric loss tangent due to moisture absorption treatment. It is intended to provide a body and a method for manufacturing the body.

[0007]

The composite dielectric of the present invention comprises:
In a composite dielectric comprising an inorganic powder having a relative dielectric constant of 20 or more, a fluororesin and an inorganic fiber base material, the inorganic powder is coated with an inorganic coating containing silica as a main component, And / or an inorganic powder that has been surface-treated with a fluorine-based silane coupling agent.

Further, the method for producing a composite dielectric according to the third aspect of the present invention is characterized in that silica is deposited from the supersaturated solution of silica on the surface of the inorganic powder to form an inorganic film containing silica as a main component. The method for producing a composite dielectric according to claim 1 or 2.

According to a fourth aspect of the present invention, in the method for producing a composite dielectric, the inorganic powder is treated with a treatment liquid obtained by hydrolyzing a silicon alkoxide, and then 300 to 1,000.
The method for producing a composite dielectric according to claim 1 or 2, wherein heat treatment is performed at a temperature in the range of ° C to form an inorganic film containing silica as a main component.

The present invention will be described in detail below. As the inorganic powder having a relative dielectric constant of 20 or more used in the present invention,
The average particle diameter is preferably 0.3 to 10 μm, and the kind thereof is not particularly limited as long as the relative dielectric constant is 20 or more. Examples of the inorganic powder having a relative dielectric constant of 20 or more that can be used in the present invention include titanium oxide (TiO ₂ etc.), barium titanate (BaTi _0.7 Zr _0.3 O ₃ etc.), strontium titanate (SrTiO ₃ ). , PbTi _0.5 Zr
Titanium-based inorganic powder containing titanium element such as _0.5 O ₃ system, Pb (Mg _2/3 Nb _2/3 ) O ₃ system, Ba (Sn _x Mg)
_Examples thereof include powders having a perovskite type crystal structure (or a complex perovskite type crystal structure) such as _y Ta _z ) O ₃ type and Ba (Zr _x Zn _y Ta _z ) O ₃ type.
(Note that x, y, and z represent positive numbers such that x + y + z = 1.) There is no particular limitation on the shape of the inorganic powder that can be used in the present invention, and for example, spherical particles or blocks of various shapes can be used. A unilateral shape or the like can be used.

The fluororesin used in the present invention includes
Although not particularly limited, tetrafluoroethylene resin (melting point 320 to 335 ° C.), tetrafluoroethylene-hexafluoropropylene copolymer resin (melting point 260 to 280 ° C.),
Like a tetrafluoroethylene-perfluorovinyl ether copolymer resin (melting point 302 to 310 ° C.), the melting point is 2
A material having a temperature of 50 ° C. or higher is preferable because it is less likely to be deformed during soldering. Since these fluorine-based resins have a property of low loss at high frequencies, the composite dielectric of the present invention is suitable for use in high frequencies.

As the inorganic fiber base material used in the present invention,
Although not particularly limited, examples thereof include base materials such as glass cloth and glass mat. Further, it is desirable that the inorganic fiber base material is subjected to a surface treatment with a phenylsilane-based and / or fluorine-based silane coupling agent in order to improve the adhesion with the fluorine-based resin.

In the present invention, the inorganic coating film containing silica as the main component may be such that 50% by weight or more of the component is a silica component, and the manufacturing method thereof is not particularly limited and will be described later, for example. It can be produced by the method according to claim 3 or 4 of the present invention.

In the present invention, it is important that the inorganic powder coated with the inorganic coating containing silica as the main component is subjected to a surface treatment with a phenylsilane-based and / or fluorine-based silane coupling agent. . As described above, the inorganic powder coated with the inorganic coating containing silica as the main component is not subjected to the coupling agent treatment directly on the inorganic powder, but is subjected to the coupling agent treatment. Due to the configuration that the silane coupling agent to be used is a phenylsilane-based and / or fluorine-based silane coupling agent, the composite dielectric of the present invention has extremely excellent moisture resistance. The method of treating the coupling agent is not particularly limited, but while stirring the inorganic powder coated with the inorganic coating containing silica as the main component with a Henschel Misser or the like, the surface of the inorganic powder is treated. A dry treatment method of dropping the coupling agent treatment liquid, a wet treatment method of immersing the inorganic powder in the coupling agent treatment liquid, and then scattering the solvent of the treatment liquid can be used. The amount of the coupling agent blended is preferably 0.05 to 5% by weight based on the weight of the inorganic powder. It should be noted that not all of the blended coupling agents adhere to the surface of the inorganic powder,
In order to obtain the composite dielectric having excellent moisture resistance, which is the object of the present invention, it is preferable to add the coupling agent in an amount within the above range.

In the present invention, the ratio of the inorganic powder having a relative dielectric constant of 20 or more, the fluororesin and the inorganic fiber base material is not particularly limited and may be appropriately selected depending on the desired performance of the composite dielectric. However, usually, the inorganic powder having a relative dielectric constant of 20 or more is 5 to 75% by volume, and the fluororesin is 25
It is preferable that the content of the inorganic fiber base material is in the range of ˜95% by volume and the inorganic fiber base material is in the range of 5 to 70% by volume.

The compounding method for obtaining the compound dielectric of the present invention is not particularly limited,
For example, it can be performed as follows. That is, coated with an inorganic film containing silica as a main component, further, the inorganic powder that has been subjected to a coupling agent treatment, impregnated with an inorganic fiber substrate in a mixed liquid that is uniformly mixed in a dispersion of a fluororesin, After drying, a prepreg is obtained, a predetermined number of the obtained prepregs are laminated, and further, a metal foil such as a copper foil or an aluminum foil is arranged on both sides or one side of the prepreg, which is heated and pressed to form a copper-clad laminate. Plates (a type of composite dielectric) can be manufactured.

Next, a method for manufacturing the composite dielectric according to claim 3 of the present invention will be described. In this manufacturing method, the silica component-containing material is dissolved in a hydrosilicofluoric acid solution or the like to obtain a saturated solution of silica, and the saturated solution is then heated, for example, by adding a boric acid solution. , Make a supersaturated solution of silica. Then, silica is deposited on the surface of the inorganic powder from the supersaturated solution of silica to form an inorganic film containing silica as a main component. Examples of this precipitation method include a method in which an inorganic powder is added to a supersaturated solution of silica and allowed to stand to precipitate silica on the surface of the inorganic powder.

Next, a method for manufacturing the composite dielectric according to claim 4 of the present invention will be described. In this manufacturing method, the inorganic powder is treated with a treatment liquid obtained by hydrolyzing silicon alkoxide. Examples of this treatment method include a wet treatment method in which the inorganic powder is immersed in the treatment liquid and then the solvent is scattered, and a dry method in which the treatment liquid is dropped on the surface of the inorganic powder while stirring the inorganic powder with a Henschel mixer or the like. Can be done using.
Then, after treating the inorganic powder with the treatment liquid, it is important to perform heat treatment in order to remove the organic component and densify the inorganic film containing silica as a main component. The temperature of this heat treatment is preferably carried out in the temperature range of 300 to 1000 ° C. If the temperature is lower than 300 ° C., the inorganic film may not be sufficiently densified, and if the temperature exceeds 1000 ° C., the inorganic powders are burned together. In some cases, this may cause a problem that the labor of crushing becomes great.

[0019]

[Function] Since the silica-based inorganic coating is highly reactive with the phenylsilane-based or fluorine-based silane coupling agent, the inorganic powder is coated with the silica-based inorganic coating. The surface treatment with a system and / or fluorine-based silane coupling agent functions to improve the adhesion between the inorganic powder and the fluorine-based resin.

[0020]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples.

Example 1 First, hydrosilicofluoric acid (H ₂
SiF ₆ (manufactured by Nacalai Tesque, Inc.) was added water to 2 mol /
1000 ml of an aqueous solution of 1 l was prepared, and 20 g of silica gel corresponding to SiO ₂ was put into this aqueous solution to obtain a saturated solution of silica. Then, 5 ml of an aqueous solution of boric acid having a concentration of 0.5 mol / l was added in a state where the obtained saturated solution of silica was heated to 35 ° C., and the silica was supersaturated in the hydrosilicofluoric acid solution. A solution was made. Next, in a solution in which the silica is supersaturated, an average particle size of 2 μm,
100 g of titanium oxide powder having a relative dielectric constant of 104 was added, and then the mixture was left for 5 hours to deposit an inorganic film containing silica as a main component on the surface of the titanium oxide powder. Then, the titanium oxide powder having the surface on which the inorganic film containing silica as a main component was formed was taken out from the hydrofluoric acid solution and dried sufficiently.

Titanium oxide powder 99 whose surface obtained by the above procedure is coated with an inorganic film containing silica as a main component.
A phenylsilane-based silane coupling agent (TSL8173 manufactured by Toshiba Silicone Co., Ltd.) was used at a ratio of 1 part by weight based on 1 part by weight, and the coupling agent treatment was performed by the wet treatment method described above.

The above inorganic powder that has been treated with the coupling agent is treated with a tetrafluoroethylene resin (D-
2) and a tetrafluoroethylene-hexafluoropropylene copolymer resin (manufactured by Daikin Industries, Ltd .: ND-1) in a weight ratio of 4: 1.
The inorganic powder was mixed in the dispersion mixed in 1) so that the content of the inorganic powder was 20% by volume with respect to the fluororesin, and the mixture was mixed to prepare a varnish for impregnation.

On the other hand, as the glass cloth, 2 parts by weight of a phenylsilane type silane coupling agent (manufactured by Toshiba Silicone Co .: TSL8173) is used for 98 parts by weight of the glass cloth.
Having a thickness of 100, which is surface-treated with
A μm plain woven glass cloth was used.

The above-mentioned impregnating varnish was thoroughly stirred, then impregnated into the above plain woven glass cloth and fired at 370 ° C. to obtain a prepreg. The weight ratio of the glass cloth in this prepreg was 42% by weight. Four prepregs obtained were stacked, and copper foil (thickness 18μ
m) is placed at a temperature of 400 ° C. and a pressure of 30 kg / cm ² for 6
Double-sided copper-clad laminate (composite dielectric) after pressure molding for 0 minutes
Was produced.

Example 2 The same as Example 1 except that the silica was supersaturated and the titanium oxide powder was allowed to stand in the hydrosilicofluoric acid solution for 3 hours. To prepare a double-sided copper-clad laminate.

(Example 3) In Example 1, except that strontium titanate having a relative dielectric constant of 100 or more was used as the inorganic powder to be added to the hydrosilicofluoric acid solution in which silica was supersaturated. A double-sided copper-clad laminate was prepared in the same manner as in Example 1.

(Example 4) Example 4 was carried out except that a fluorine-based silane coupling agent (TSL8233 manufactured by Toshiba Silicone Co., Ltd.) was used instead of the phenylsilane-based silane coupling agent as the coupling agent. Example 1
A double-sided copper-clad laminate was prepared in the same manner as. The fluorinated silane coupling agent was used in both cases of treating the inorganic powder and the glass cloth with the coupling agent.

(Example 5) The same as Example 1 except that the titanium oxide powder having the inorganic coating film containing silica as the main component was formed on the surface in the following manner. Then, a double-sided copper-clad laminate was prepared.

As a method for obtaining a titanium oxide powder on which an inorganic film is formed, first, in a weight ratio, silicon tetraethoxide (manufactured by Nacalai Tesque, Inc.): Water: methanol: acetic acid is 10: 10: 100: 0.1. A solution was prepared so as to be as follows, and then stirred for 10 minutes to hydrolyze silicon tetraethoxide to prepare a treatment liquid in which silicon alkoxide was hydrolyzed. Next, 100 g of the same titanium oxide powder as that used in Example 1 was added to this treatment liquid,
After stirring for 15 minutes, the titanium oxide powder was taken out, sufficiently dried in air, and then the obtained treated titanium oxide powder was heat-treated at 500 ° C. for 2 hours to form an inorganic film containing silica as a main component on the surface. Thus, a titanium oxide powder in which is formed is obtained.

(Example 6) In Example 5, the treatment liquid obtained by hydrolyzing the silicon alkoxide was prepared in a weight ratio of silicon tetraethoxide (manufactured by Nacalai Tesque): water: methanol: acetic acid 20:10. : 100:
A double-sided copper-clad laminate was produced in the same manner as in Example 5 except that the thickness was adjusted to 0.1.

(Comparative Example 1) The step of coating the titanium oxide powder with the inorganic coating containing silica as the main component in Example 1 was omitted, and the phenylsilane silane coupling agent was used for the titanium oxide powder. A double-sided copper-clad laminate was produced in the same manner as in Example 1 except that the coupling agent treatment was directly carried out.

(Comparative Example 2) The step of coating the titanium oxide powder with the inorganic film containing silica as the main component in Example 4 was omitted, and the titanium oxide powder was directly coated with a fluorine-based silane coupling agent. A double-sided copper-clad laminate was produced in the same manner as in Example 4 except that the coupling agent treatment was directly carried out.

(Comparative Example 3) In Example 1, except that the titanium oxide powder on the surface of which an inorganic film containing silica as a main component was formed was not treated with a coupling agent using a silane coupling agent. A double-sided copper-clad laminate was prepared in the same manner as in Example 1.

(Comparative Example 4) In Example 1, a phenylsilane-based silane coupling agent was used as a coupling agent for treating the titanium oxide powder on the surface of which an inorganic film containing silica as a main component was formed. change,
A double-sided copper-clad laminate was produced in the same manner as in Example 1 except that an epoxysilane-based silane coupling agent (TS8350 manufactured by Toshiba Silicone Co., Ltd.) was used. For the treatment of the glass cloth with the coupling agent, a phenylsilane-based silane coupling agent was used as in Example 1.

As described above, the relative permittivity before and after the PCT treatment (moisture absorption treatment) at 135 ° C., 3 atm (vapor pressure) and 2 hours for each double-sided copper-clad laminate obtained in Examples and Comparative Examples The dielectric loss tangent was measured, and the obtained results are shown in Tables 1 and 2. The relative permittivity and the dielectric loss tangent were measured at measurement frequencies f of 1 KHz and 3 GHz.

[0037]

[Table 1]

[0038]

[Table 2]

As can be seen from Tables 1 and 2, the copper clad laminates of the Examples are stable with very little change in the value of the dielectric loss tangent before and after the PCT treatment (moisture absorption treatment) as compared with the Comparative Examples. It was confirmed that the moisture resistance was improved.

[0040]

As described above, in the composite dielectric material according to the present invention, the inorganic powder having a relative dielectric constant of 20 or more is coated with an inorganic film containing silica as a main component, and further, a phenylsilane-based material. According to the present invention, since a surface treatment with a fluorine-based silane coupling agent is carried out, a composite dielectric material comprising an inorganic powder having a relative dielectric constant of 20 or more, a fluorine-based resin and an inorganic fiber substrate is used. In addition, there is little change in the dielectric loss tangent due to the moisture absorption treatment, that is, the moisture resistance is improved, and a composite dielectric useful in applications such as a printed circuit board can be obtained.

Further, according to the method for producing a composite dielectric of the present invention, a composite dielectric useful in the above-mentioned applications such as a printed circuit board can be produced.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiyoshiro Yamakawa 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (4)

[Claims] 1. A composite dielectric comprising an inorganic powder having a relative dielectric constant of 20 or more, a fluororesin and an inorganic fiber substrate, wherein the inorganic powder is coated with an inorganic film containing silica as a main component, A composite dielectric, which is an inorganic powder that has been surface-treated with a phenylsilane-based and / or fluorine-based silane coupling agent. 2. The composite dielectric according to claim 1, wherein the inorganic powder is a titanium-based inorganic powder. 3. The composite dielectric according to claim 1, wherein silica is deposited on the surface of the inorganic powder from a supersaturated solution of silica to form an inorganic film containing silica as a main component. Production method. 4. An inorganic powder is treated with a treatment liquid obtained by hydrolyzing a silicon alkoxide, and then 300 to 100.
The method for producing a composite dielectric according to claim 1 or 2, wherein heat treatment is performed at a temperature in the range of 0 ° C to form an inorganic film containing silica as a main component.