JPH06188158A - Capacitor - Google Patents

Abstract

PURPOSE:To obtain a nonpolar capacitor wherein its capacity is high, its high- frequency characteristic value is good and its cost is low by a method wherein an aluminum or tantalum foil or rod which is provided with a fine hole on the surface is used as one electrode and a semiconductor layer which is formed on a dielectric layer composed of an oxide of tantalum is used as the other electrode. CONSTITUTION:Many fine holes 2 are made on both faces of a foil 1. An oxide layer 3 of tantalum is formed as a dielectric layer at the inside of the fine holes 2 and along the surface of the foil. A semiconductor layer 4 is formed on the back of the oxide layer 3 of tantalum. In addition, a dielectric layer 5 is attached to the back of the semiconductor layer 4, the whole is sealed with a sealing resin 6, lead terminals 7, 7 are attached to the foil and the dielectric layer, they are extracted by the sealing resin, and a capacitor product is formed. Thereby, the capacity of the capacitor product is larger than that of an aluminum electrolytic capacitor, the product is reliable and the cost can be made lower than that of a tantalum electrolytic capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high capacity capacitor having a dielectric layer of tantalum oxide.

[0002]

2. Description of the Related Art Conventionally, a tantalum electrolytic capacitor is formed by using an oxide film provided on the surface of a tantalum foil, a rod, a sintered body or the like as a dielectric. Such a tantalum electrolytic capacitor has a small size and a large capacity, and is widely used in industry due to the stability of the dielectric.

On the other hand, the aluminum electrolytic capacitor has an oxide film formed on the surface of an aluminum foil, a rod, a sintered body or the like as a dielectric. Since such an aluminum electrolytic capacitor is inexpensive and can have a large capacity, it is also used in various fields.

[0004]

However, tantalum electrolytic capacitors are somewhat expensive in material and aluminum electrolytic capacitors are somewhat unreliable due to dielectric instability. Further, since both capacitors generally have polarities, there is a disadvantage that they are not suitable for certain applications.

Further, with the recent trend toward smaller, lighter, thinner electronic devices, there is also a demand for capacitors having smaller size and higher capacity. The present inventor, as a result of earnest research to solve the above problems, as a result of providing pores or voids on the surface to increase the surface area of an aluminum or titanium foil, rod or sintered body. It has been discovered that excellent characteristics can be obtained by using, for example, a capacitor.

The present invention was completed based on the above findings, and an object of the present invention is to provide a nonpolar capacitor having a high capacity, a good high frequency characteristic value, and a low price.

[0007]

The present invention has been made to achieve the above object, and the gist thereof is to use, as one electrode, an aluminum or titanium foil or rod having pores on the surface thereof. A tantalum oxide provided inside and along the surface of a hole serves as a dielectric layer, a capacitor having a semiconductor layer provided on the dielectric layer as the other electrode, and a sintered body containing aluminum or titanium as a main component. There is provided a capacitor in which one electrode is used, a tantalum oxide provided along the inside and the surface of the void of the sintered body is used as a dielectric layer, and the semiconductor layer provided on the dielectric layer is used as the other electrode.

The present invention will be described in detail below. FIG. 1 is a vertical cross-sectional view showing an embodiment of a capacitor according to the present invention using a foil. The foil 1 is provided with a large number of pores 2 on both sides. On the surface of the foil 1 having pores, a tantalum oxide layer 3 is provided as a dielectric layer along the inside of the pores 2 and along the foil surface, and on the back surface of the tantalum oxide layer 3,
The semiconductor layer 4 is provided to form the capacitor of the present invention. A dielectric layer 5 is attached to the back surface of the above-mentioned 4, and the whole is sealed with a sealing resin 6, and lead terminals 7 and 7 are attached to the foil and the conductor layer and pulled out by the sealing resin. To form a capacitor product.

For one of the electrodes of the present invention, an aluminum or titanium foil, a rod, or a sintered body containing aluminum or titanium as a main component is used.

A method of forming pores or voids in such a metal for the purpose of increasing the surface area is as follows. In the case of a foil or a rod, for example, by etching, or in the case of a sintered body, it is sintered. It can be formed by

The size and depth of the pores and the volume of the voids can be changed by the etching method, the sintering pressure, the temperature, etc., and along the inner surface of such pores or voids and the metal surface. An oxide of tantalum, which will be described later, is formed.

As an etching method, for example, in the case of aluminum, a direct current-applied or alternating-current-applied electrolytic etching method generally used in the electrolytic capacitor industry can be used.

The tantalum oxide layer formed as the dielectric oxide film layer of the present invention is, for example, a tantalum halide, a tantalum / acetonylacetonate salt, an alkoxide salt, a carboxylate salt, a carbonate salt or an oxine salt. It is provided by oxidizing a complex salt or a complex salt of tantalum and another metal such as cadmium.

Such a tantalum compound is melted or dissolved in an appropriate solvent, introduced into the above-mentioned pores or voids, and then oxidized to form tantalum along the pores or voids and the metal surface. An oxide layer is formed. In this case, in order to introduce the tantalum oxide without blocking the pores or voids, it is necessary to consider the introduction conditions, the diameter of the pores, etc., and the conditions etc. are determined by preliminary experiments. .

In the present invention, examples of the conductor layer formed on the dielectric layer include TCNQ salt, a conductive polymer represented by polypyrrole or lead dioxide, a mixture of lead dioxide and lead sulfate, and the like. Of these, lead dioxide or a mixture of lead dioxide and lead sulfate is preferable because it has heat resistance, has a wide electrical conductivity, and is inexpensive. Further, two or more kinds of the above-mentioned semiconductor layers may be used.

Examples of the method for providing the semiconductor layer on the above-mentioned pores or voids and the dielectric layer on the metal surface include a method of melting and introducing the semiconductor, a method of manufacturing the semiconductor on the dielectric layer, and the like.

Of these, the method of producing a semiconductor on a dielectric layer is preferable, and in particular, the method of producing a semiconductor previously proposed by the present inventors by a chemical deposition method (JP-A-62-25).
6423 and JP-A-63-51621) are preferable.

Further, a conductor layer may be provided on the semiconductor layer in order to improve electrical contact. As the conductor layer, for example, solidification of the conductive paste, plating, metal deposition,
It can be provided by forming a heat resistant conductive resin film or the like.

The capacitor of the present invention configured as described above is made into a capacitor product for various uses by, for example, a resin mold, a resin case, a metal outer case, a resin dipping, an outer case such as a laminate film. You can

[0020]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. The characteristic values of the capacitors of each example are collectively shown in Tables 1 and 2.

Example 1 A lead wire having terminals crimped thereto was connected to a length of 1 cm,
An aluminum foil with a width of 3 mm and a thickness of 90 μm is used as an anode,
The surface of the foil is electrochemically etched with a direct current,
An aluminum foil having pores with a diameter of 3.6 μm and a depth of 20 μm on the entire surface was obtained. This aluminum foil was immersed in an alcohol solution of tantalum pentachloride, pulled up, and then water was poured to oxidize the tantalum pentachloride to form an oxide layer of tantalum in the pores and on the surface of the aluminum foil. Next, the aluminum foil on which the dielectric was formed was immersed in a mixed solution of an aqueous solution of lead acetate trihydrate of 2 mol / l and an ammonium persulfate solution of 4 mol / l only 3 mm from the lower end, and the temperature was changed to 60 ° C.
It was left for 20 minutes. After this operation was performed 3 times, a silver paste was applied on the generated semiconductor layer made of lead dioxide and lead sulfate, the terminal lead wires were taken out, and the resin was sealed to produce a capacitor.

Example 2 In Example 1, tantalum acetonylacetone salt was used in place of tantalum pentachloride, and at the same time, it was oxidized with ammonium persulfate 4 aqueous solution to form tantalum oxide. A capacitor was produced in the same manner as in Example 1 except that a lead acetate aqueous solution aluminum foil (1/1) was dipped and a lead dioxide layer was provided by an electrolytic reaction with a platinum electrode.

Example 3 In Example 1, a titanium foil was used in place of the aluminum foil, pores having a diameter of 5 μm and a depth of 10 μm were formed on the entire surface, and tantalum pentachloride was replaced with chloroform of oxine salt of tantalum. Dip titanium foil in the solution and pull up 750
A capacitor was produced in the same manner as in Example 1 except that the tantalum oxide was formed by oxidizing at 0 ° C.

Comparative Example 1 An aluminum foil similar to that of Example 1 was electrochemically treated in an aqueous solution of boric acid and ammonium borate to form an alumina dielectric layer. Lower surface of this aluminum foil 3 mm ×
Wrap only the 3 mm part in a separator containing an ethylene glycol-ammonium adipate-based electrolyte,
It was placed in a metal case and sealed with atactic polypropylene.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

As described above, the capacitor of the present invention has a larger capacity than aluminum electrolytic capacitors, is more reliable, and is cheaper than tantalum electrolytic capacitors.
Further, it has many advantages such as good high frequency performance and high utility value because it has no polarity.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a capacitor according to the present invention using a foil.

[Explanation of symbols]

 1 Foil 2 Pore 3 Tantalum Oxide Layer 4 Semiconductor Layer 5 Conductor Layer 6 Sealing Resin 7 Lead Terminal

Claims (2)

[Claims] 1. An aluminum or titanium foil or rod having pores on the surface is used as one electrode, and a tantalum oxide provided inside and along the surface of the pores is used as a dielectric layer on the dielectric layer. A capacitor, characterized in that the semiconductor layer provided on the other side is used as the other electrode. 2. A sintered body containing aluminum or titanium as a main component is used as one electrode, and a tantalum oxide provided inside and along the surface of the void of the sintered body is used as a dielectric layer. A capacitor, wherein the semiconductor layer provided on the layer is used as the other electrode.