JPS6159714A - Composite dielectric capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is for bypassing various electric circuits, for coupling,
This invention relates to a composite dielectric capacitor used for noise limiters and the like.

(Conventional configuration and its problems) Conventional capacitors using inorganic materials are generally represented by ceramic capacitors. FIG. 1 is a sectional view of this ceramic capacitor. In the figure, 1 is a dielectric material made by mixing barium titanate powder and an organic binder into a green sheet, which is cut into a certain shape and dimension and heated at a high temperature of 900°C to 1400'C. By firing, the mixed organic binder is decomposed and removed, a thin plate of barium titanate is made, an electrode material is applied to this, and the electrode is fired again to form the electrode M2, and the lead wire 3 is connected to the electrode layer 2. It was used as a capacitor.

A is an enlarged view of the dielectric 1, and 4 is barium titanate particles, the particle size of which is 0.02 μm to 20 μm.

This method uses a heavy binder of 5 to 20% by weight for the work up to firing and for forming the sheet.
The organic binder should be as cheap as possible, easy to process into sheets, and easily decomposed during firing. However, although such barium titanate capacitors have large capacitance and excellent heat resistance, they must be fired at high temperatures, and physical and chemical changes occur during this firing process.
In order to produce the desired capacitance, various complicated controls are required, resulting in high costs.

Figure 2 is a cutaway diagram of a film capacitor using an organic polymer.
A metal thin film such as an aluminum vapor deposited film 6 is formed on both sides of the body 5, and a lead 117 is connected to it. However, since organic polymer materials have a low dielectric constant, the film is made as thin as possible and is made up of several tens of layers or more. This had the disadvantage of increasing the cost because it required multiple layers of winding, several hundred layers, to ensure capacitance.

(Objective of the Invention) An object of the present invention is to eliminate the drawbacks of the conventional example, to provide a capacitor that does not require high-temperature firing, and is smaller and cheaper than a film capacitor.

(Structure of the Invention) The composite dielectric capacitor of the present invention is based on barium titanate,
A homogeneous mixture of an inorganic fine powder material with a high dielectric constant such as strontium titanate, titanium oxide, tantalum oxide, or aluminum oxide and a heat-resistant organic polymeric dielectric material is used in the form of a film or A dielectric material is formed into a sheet, and a counter electrode is formed on the dielectric material.

In addition, as organic polymer materials, polymer materials such as polyimide, polyamide, fluorine, polysulfonic acid, epoxy, and polypropylene are made into a solution or viscous state in an organic solvent, and then an inorganic high dielectric constant is added to the solution or viscous material. The organic solvent is evaporated and the organic polymer is cured to form a thin coating film, or it is formed into a sheet and used as a dielectric film.

(Description of Embodiment) An embodiment of the present invention will be described based on FIGS. 3 and 4.

A substance is made by uniformly mixing a fine inorganic powder with a high dielectric constant and a heat-resistant organic dielectric material, and this is used as a dielectric material in the form of a film or coating, and a counter electrode is formed on this. The organic dielectric material has the function of binding inorganic particles with a high dielectric constant and the function of a dielectric. High dielectric constant inorganic material is a high dielectric constant coating film.

Alternatively, it serves the function of securing the sheet and increasing heat resistance.

The capacitance of a capacitor is expressed by the following formula.

A(1) An organic film having a dielectric constant ε of about 2 to 6 is used as a dielectric material for a capacitor. Therefore, as can be seen from equation (1), ε = 2 to 6, which is a small value t. Therefore, in order to increase the capacitance C, the film thickness d must be made as thin as possible, and the surface area A must be increased by using multilayer winding. Must be.

On the other hand, inorganic dielectrics have a very high dielectric constant, ε=8 to 2,000, as compared to organic films.

However, it is difficult to form a thin film, and although the dielectric constant is very high, the thickness d of the film in equation (1) is much larger than that of an organic film, so the capacitance is lower than the dielectric constant. cannot be made large.

The present invention takes advantage of the good coating and film properties of organic polymers and the high dielectric constant of inorganic dielectrics, and also improves heat resistance compared to conventional film capacitors without using the complicated method of firing. Furthermore, it can be used as a film with a high dielectric constant or as a coating, allowing the production of small capacitors at low cost.

FIG. 3 is a cross-sectional view of a composite dielectric capacitor according to the present invention. As shown in the enlarged view (B) in the same figure, 11 is a high dielectric constant inorganic material, and materials such as barium titanate, strontium titanate, titanium oxide, tantalum oxide, and aluminum oxide are suitable for this material. These materials can be easily dispersed as fine powders,
Make particles that are easy to form into a coating film. The particle size is preferably as fine as 5 μm or less. 12 is an organic polymer, which is a heat-resistant material such as polyimide resin, polyamide resin, polyester resin, epoxy resin, polysulfonic acid resin, polypropylene resin, or fluororesin, and can be liquefied or viscous using an organic solvent. The mixing ratio of the inorganic material 11 to the organic polymer material 12 may vary slightly depending on the type of material, but the weight ratio is 0.
A ratio of 5-2:8-9.5 is suitable. 13 is a mixture of these substances. To improve the dielectric constant of the mixed substance 13, increase the proportion of the inorganic material 11, and when desired coating properties, sheet properties, and film strength, increase the proportion of the organic polymer material 12. increase.

The organic polymer material 12 must be made into a solution with an organic solvent, and the inorganic material 11 must be mixed and kneaded to form a uniform substance. Kneading is carried out using an agate ball mill. In order to stabilize the characteristics of the capacitor, it is necessary to mix it sufficiently uniformly. 14 is a metal electrode layer formed on the page surface of the mixed substance 13, and 15 is a lead wire connected to the metal electrode layer.

(1) Experimental Example 1 FIG. 4 is a sectional view of a capacitor of Experimental Example 1 according to the present invention. 9 g of barium titanate was mixed with 1 g of polyimide resin and mixed in an agate mortar for about 2 hours using an organic solvent and PMF as a solvent to create a homogeneous mixed liquid 16, and a gold vapor deposited layer 17 prepared in advance was formed on the aluminum. It was applied to a thickness of about 50 μm on a metal plate 18, air-dried, and then cured at a temperature of 200° C. for about 2 hours. Thereafter, a gold vapor deposition layer 17 was formed thereon, and a composite dielectric capacitor was constructed as a counter electrode. 20μF at 120Hz
A capacitance of /aJ was obtained and a tan δ of 1.2% was obtained. (The capacitance of polyimide alone is O, OSμF
/a&, tan δ is 0.5%. ) (2) Experimental example 2 1.5 g of polyester resin in 8.5 g of barium titanate
The mixed organic solvent was made into a viscous liquid by using DMF as in Experimental Example 1, and after thorough kneading, a composite dielectric capacitor was constructed in the same manner as in Experimental Example 1. A vapor-deposited metal was provided on the counter electrode, and as a result of measuring the characteristics at 1201 (z), the capacitance was 12 μF/ad, and the tan δ was 0.8%. (The capacitance of the polyester resin alone was 0. ．．
03μF, tan δ is 0. It is brocade. ) (3) Experimental Example 3 A composite dielectric capacitor was constructed under exactly the same conditions as Experimental Example 1 by mixing 8 g of titanium oxide and 2 g of polyimide, and 12
The results of measuring capacitance and tanδ at 0Hz are as follows:
The capacitance was 1.3 μF/j, and the tan was 60.5%.

In addition, we immersed it in a solder bath at 260°C for 10sac and measured the change in characteristics, and found that the capacitance was 1.2μF.
/al, tan δ was 0.56%, and there was almost no change in properties, and it was confirmed that the film had excellent heat resistance.

(Effects of the Invention) According to the present invention, a mixed dielectric material with a high dielectric constant can be obtained by mixing an inorganic high dielectric material into an organic polymer, and also has heat resistance. This has the effect of providing an E-type capacitor with low cost.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional capacitor using an inorganic material, Fig. 2 is a sectional view of a capacitor using the same organic material, and Fig. 3 is a sectional view of a composite dielectric capacitor according to an embodiment of the present invention. , FIG. 4 is a sectional view of the composite dielectric capacitor of Experimental Example 1. 1.5...dielectric, 2.14...electrode layer, 3,
7.15.19... Lead wire, 4... Barium titanate particles, 6... Aluminum vapor deposited film, 11... High dielectric constant inorganic material, 12... Organic polymer material, 13. ...Mixed substance, 16...Mixed liquid, 1
7... Gold vapor deposited layer, 18... Aluminum metal plate. Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1 (A) Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) Homogeneously combine fine powder materials with inorganic high dielectric constants such as barium titanate, strontium titanate, titanium oxide, tantalum oxide, and aluminum oxide, and heat-resistant organic polymeric dielectric materials. 1. A composite dielectric capacitor characterized in that a mixed mixture is used as a dielectric material in the form of a film or sheet, and a counter electrode is formed on the dielectric material. (2) As organic polymer materials, polymer materials such as polyimide, polyamide, fluorine, polysulfonic acid, epoxy, polyester, and polypropylene are made into a solution or viscous form with an inducing solvent. The method is characterized in that an inorganic powder having a high dielectric constant is mixed, the organic solvent is evaporated and the organic polymer is cured to form a thin coating film, or it is formed into a sheet and used as a dielectric film. A composite dielectric capacitor according to claim (1).