JPH11345518A - Composite dielectric material and dielectric antenna using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide composite dielectric materials having good electrical characteristics, excellent machinability and formability, and a small specific gravity and a dielectric antenna which uses the composite dielectric materials. SOLUTION: A dielectric antenna 1 comprises an antenna base 2 in the form of a rectangular solid, an input electrode 4, a radiation electrode 5, and a ground electrode 6. A composite syndiotactic polystyrene and dielectric ceramic are used for forming the antenna base 2. A perovskite type oxide ferroelectric of high frequency and small Tan δ, such as CaTiO3 , SrTiO3 , and BaTiO3 , and their mixture, or BaO-Nd2 O3 -TiO2 or the like, is used as the dielectric ceramic. The addition of the dielectric ceramic is set within the range of 5 to 60 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite dielectric material and a dielectric antenna using the composite dielectric material.

[0002]

2. Description of the Related Art Mobile communication devices such as mobile phones and wireless LAs
As a surface mount type dielectric antenna used for N, an antenna composed of a single derivative ceramic or a single resin has been proposed (see Japanese Patent Application Laid-Open No. 9-98015).

[0003]

In recent years, along with the reduction in weight and size of mobile communication devices such as mobile phones,
Demands for weight reduction and miniaturization of dielectric antennas are also increasing. However, the conventional antenna made of a single derivative ceramic or the antenna made of a single resin has the following disadvantages.

[0004] In the case of an antenna made of a single dielectric ceramic, it takes a long time for the forming step and the sintering step, and the workability and the formability are inferior, making it difficult to produce an antenna having a complicated shape. In addition, there is also a problem that the specific gravity of the derivative ceramic is so large that it cannot cope with the weight reduction of the antenna. On the other hand, in the case of an antenna made of a single resin, the specific gravity of the resin is small and the moldability and workability are excellent, but there is a problem that the antenna cannot be miniaturized due to its small relative dielectric constant.

It is an object of the present invention to provide a composite dielectric material having good electrical characteristics, excellent workability and moldability, and a small specific gravity, and a dielectric antenna using this composite dielectric material. is there.

[0006]

In order to achieve the above object, a composite dielectric material according to the present invention is characterized by comprising syndiotactic polystyrene and a dielectric ceramic. Here, the content of the dielectric ceramic is
5 to 60% by volume. The dielectric antenna according to the present invention includes a composite dielectric material including the syndiotactic polystyrene and the dielectric ceramic, and a radiation electrode and a ground electrode provided on a surface of the composite dielectric material, respectively. It is characterized.

With the above structure, syndiotactic polystyrene has a low tan δ and a small specific gravity, so that a composite dielectric material composed of syndiotactic polystyrene and a dielectric ceramic has the same relative dielectric constant as a single ceramic material. Lighter than a dielectric material composed of In addition, since this composite dielectric material is a mixed material of resin and ceramic, it is more excellent in workability and moldability than a dielectric material consisting of a single ceramic. On the other hand, since dielectric ceramics have a large relative dielectric constant, dielectric antennas using a composite dielectric material composed of syndiotactic polystyrene and dielectric ceramics are better than dielectric antennas using a dielectric material composed of resin alone. It becomes small.

Further, the composite dielectric material according to the present invention is characterized in that a plating film is provided on the surface. The dielectric antenna according to the present invention includes a composite dielectric material including the syndiotactic polystyrene and the dielectric ceramic, and a radiation electrode and a ground provided on a surface of the composite dielectric material, the radiation electrode including a plated film, and a ground. Electrodes. When electrodes are required to be formed on a plurality of surfaces as in the case of a dielectric antenna, plating is performed at the same time on the plurality of surfaces by performing plating, so that the amount of work for forming the electrodes is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a composite dielectric material according to the present invention and a dielectric antenna using the composite dielectric material will be described with reference to the accompanying drawings.

As shown in FIG. 1, the dielectric antenna 1 comprises
Rectangular parallelepiped antenna base 2, input electrode 4, radiation electrode 5
And a ground electrode 6. As a material of the antenna base 2, a composite material of syndiotactic polystyrene (hereinafter, referred to as SPS) and a dielectric ceramic is used. SPS is used because it has excellent solvent resistance and heat resistance while maintaining good dielectric properties at a high frequency of general atactic polystyrene (common PS). Although those having low tan δ and heat resistance include PTFE-based resins and liquid crystal polymers, these materials are inferior to SPS in terms of moldability and material composite.

On the other hand, dielectric ceramics have t
CaTiO ₃ , SrTiO ₃ , BaTiO with small an δ
_{For example,} a perovskite-based oxide ferroelectric such as ₃ or a mixture thereof, or BaO—Nd ₂ O ₃ —TiO ₂ is used. And the addition amount of the dielectric ceramic is 5 to 60.
% (In other words, the amount of SPS added is 40 to
95% by volume).

[0012] In addition to the dielectric ceramic and SPS, a dispersant such as a lubricant such as stearic acid or a titanate coupling agent may be added as an additive in order to improve melt kneading properties and moldability. . Further, a coupling agent treatment may be performed in order to increase the bonding strength between the dielectric ceramic and the SPS and increase the mechanical strength of the antenna base 2. These additives are added to such an extent that tan δ is not reduced.

The input electrode 4 is provided at the front end of the antenna base 2. The radiation electrode 5 is provided at the center of the upper surface of the antenna base 2 and extends linearly in the longitudinal direction of the antenna base 2. The length of the radiation electrode 5 is λ / 4 (λ:
Center wavelength in the antenna base 2). One end 5 a of the radiation electrode 5 faces the input electrode 4 at a predetermined interval 7. The other end 5 b of the radiation electrode 5 is electrically connected to a ground electrode 6 provided on substantially the entire lower surface of the antenna base 2 around the back end surface of the antenna base 2. These electrodes 4 to 6 are made of Ag, Pd, Ag-P
It is made of d, Au, Cu, or the like, and is formed by applying and baking a conductive paste, or by plating, sputtering, vapor deposition, or the like.

In the dielectric antenna 1 having the above-described strip line configuration, the specific gravity of the SPS is small, so that the weight of the antenna base 2 can be reduced. Incidentally, in the case of antenna bases having the same relative dielectric constant, the specific gravity of the antenna base 2 of the present embodiment is reduced by about 50% as compared with the antenna base made of a dielectric ceramic alone. Since the dielectric ceramic has a large relative dielectric constant, the antenna base 2 can be reduced in size. That is, the center wavelength λ in the antenna base 2 is represented by the following equation (1). λ = λ ₀ / ε _r ^1/2 (1) (λ ₀ : Propagation wavelength in vacuum) On the other hand, the relative permittivity of the antenna base 2 of the present embodiment is 3 to 3.
It is about 0, which is larger than the relative dielectric constant of about 2 for an antenna base made of a resin alone. Therefore, according to the above equation (1), the length (= λ / 4) of the radiation electrode 5 of the present embodiment can be shorter than the length of the radiation electrode formed on the antenna base made of a single resin. As a result, the size of the dielectric antenna 1 can be reduced. Further, the antenna base 2 has a low tan.
The dielectric antenna 1 has stable antenna characteristics because it is made of a composite dielectric material of SPS of δ and dielectric ceramic.
Can be obtained.

Next, a first method of manufacturing the dielectric antenna 1 will be described.
An example will be described. As a material of the antenna base 2, S
PS (manufacturer: Idemitsu Oil Co., Ltd.) and a CaTiO ₃ powder having a relative dielectric constant of 180 at 1 GHz are weighed at a predetermined capacity ratio, and after coarse mixing, a twin-screw extruder with a cylinder temperature kept at 300 ° C. Was used to make composite material pellets. Here, the particle size of the ceramic powder such as CaTiO ₃ is set to 0.1 from the viewpoint of dispersibility and dielectric uniformity after molding.
About 1 to 100 μm is preferable. Using the pellets, a rectangular parallelepiped antenna base 2 of 15 mm × 7 mm × 4 mm was formed by an injection molding method. The injection molding method is employed because it can easily and quickly respond to a dielectric antenna having a complicated shape. At the time of injection molding, it is only necessary to apply heat enough to melt the SPS, and a temperature of 1000 ° C. or more is not required as in ceramic firing. A on the surface of the molded antenna base 2
The input electrode 4, the radiation electrode 5, and the ground electrode 6 were formed by a printing method using a g-based conductive paste.

Table 1 is a table showing the results of measuring the variation of the relative dielectric constant, tan δ and specific gravity by changing the capacity ratio of SPS to CaTiO ₃ in various ways. However, as a sample for measuring the relative permittivity, a 50 mm × 50 mm × 1 mm plate prepared by the above-described manufacturing method was used.
In the measurement, the relative dielectric constant and ta
A perturbation method for calculating nδ was used.

[0017]

[Table 1]

According to Table 1, the content of CaTiO ₃ is 5-6.
In the case of 0% by volume, the antenna base 2 having a large relative dielectric constant, a low tan δ, and a small specific gravity can be obtained. However, when the content of CaTiO ₃ exceeds 60% by volume, the resin does not sufficiently wet the ceramic in the melt-kneading step, as shown in the sample number, resulting in poor dispersibility. In addition, injection molding cannot be performed because of low fluidity. Also, like the sample number,
When the content of CaTiO ₃ is less than 5% by volume, the relative dielectric constant does not increase.

Next, a second method of manufacturing the dielectric antenna 1 will be described.
An example will be described. As a material for the antenna base 2, in order to be able to apply plating to the surface of the antenna base 2,
Etchable with acid or alkali and dielectric properties,
SPS with highly dispersed material that does not adversely affect moldability
And a dielectric ceramic are prepared. Here, as the material dispersed in the SPS and capable of being etched with an acid or an alkali, inorganic materials include silicates, phosphates, sulfates, carbonates, carbonates of alkaline earth metals, and the like of Group II elements. is there. Organic materials include rubber and elastomer such as butadiene rubber.

The SPS and the dielectric ceramic were weighed at a predetermined volume ratio, and after roughly mixing, composite pellets were prepared using a twin-screw extruder in which the cylinder temperature was kept at 300 ° C. Using the pellets, a rectangular parallelepiped antenna base 2 was formed by an injection molding method. This antenna base 2
Is degreased and etched with chromic acid to roughen the entire surface of the antenna base 2. Next, after activating by a catalyst (for example, palladium chloride or the like) and implanting the catalyst over the entire surface of the antenna base 2, an electroless copper plating process is performed to form a plating film over the entire surface of the antenna base 2.

Further, an unnecessary plating film is removed by etching, using a photolithography method to leave a necessary portion of the plating film. Thus, the dielectric antenna 1 in which the input electrode 4, the radiation electrode 5, and the ground electrode 6 are provided on the surface of the antenna base 2 is obtained. Thereafter, a peeling test was performed on the electrodes 4 to 6 made of a copper plating film, and it was confirmed that these electrodes 4 to 6 had good adhesion.

Further, a third example of the method of manufacturing the dielectric antenna 1 will be described. Primary molded article 1 as shown in FIG.
1 is molded by a method such as an injection molding method. In the primary molded article 11, an input electrode portion 12 on which the input electrode 4 is formed on the surface in a later step, a radiation electrode portion 13 on which the radiation electrode 5 is formed on the surface, and a ground electrode 6 are formed on the surface. The ground electrode portion 14 is integrally joined. The material of the primary molded article 11 is a composite dielectric material composed of SPS and dielectric ceramic in which a material which can be etched with the acid or alkali described in the second example and has no adverse effect on the dielectric properties and moldability is highly dispersed. It is.

After the primary molded article 11 is degreased, it is etched with chromic acid to roughen the entire surface of the primary molded article 11. After the primary molded article 11 is washed with water and dried, the primary molded article 11 is inserted into the cavity of the mold. Next, the same composite dielectric material as the primary molded product 11 is filled in the cavity, and the secondary molded product 18 shown in FIG. 3 is molded. The secondary molded product 18 includes the input electrode portion 12 of the primary molded product 11,
The radiation electrode section 13 and the ground electrode section 14 are exposed on the outer surface. Next, the catalyst was activated to implant the catalyst only on the primary molded product 11 exposed on the surface of the secondary molded product 18, and then subjected to electroless plating. As a result, the input electrode portion 12, the radiation electrode portion 13, and the ground electrode portion 14 exposed on the surface of the
Only to obtain a dielectric antenna 1 as shown in FIG.

It should be noted that the composite dielectric material according to the present invention and the dielectric antenna using the composite dielectric material are not limited to the above embodiment, but can be variously modified within the scope of the invention.

[0025]

As is apparent from the above description, according to the present invention, since the composite dielectric material is composed of syndiotactic polystyrene and dielectric ceramic, when the dielectric constant is the same, This composite dielectric material can be made lighter than a dielectric material consisting of a single ceramic. In addition, since this composite dielectric material is a mixed material of resin and ceramic, it is more excellent in workability and moldability than a dielectric material consisting of a single ceramic. On the other hand, since dielectric ceramics have a large relative dielectric constant, dielectric antennas using a composite dielectric material composed of syndiotactic polystyrene and dielectric ceramics are better than dielectric antennas using a dielectric material composed of resin alone. Can be downsized. Furthermore, a dielectric antenna using a composite dielectric material composed of a low tan δ syndiotactic polystyrene and a dielectric ceramic can have stable antenna characteristics.

Further, since the composite dielectric material can be formed with a plating film on its surface, when it is necessary to form a radiation electrode or a ground electrode on a plurality of surfaces as in a dielectric antenna, the composite dielectric material can be formed on a plurality of surfaces. At the same time, a plating film is formed, and the amount of work for forming an electrode can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a dielectric antenna according to the present invention.

FIG. 2 is a perspective view showing an example of a method for manufacturing the dielectric antenna shown in FIG.

FIG. 3 is a perspective view showing a manufacturing step following FIG. 2;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 dielectric antenna 2 antenna base 4 input electrode 5 radiation electrode 6 ground electrode

Claims (4)

[Claims] 1. A composite dielectric material comprising a syndiotactic polystyrene and a dielectric ceramic. 2. The method according to claim 1, wherein the dielectric ceramic is 5 to 60% by volume.
The composite dielectric material according to claim 1, wherein 3. The composite dielectric material according to claim 1, wherein a plating film is provided on the surface. 4. The composite dielectric material according to any one of claims 1, 2 and 3, and a radiation electrode and a ground electrode provided on a surface of the composite dielectric material, respectively. A dielectric antenna, comprising: