JPS63126211A - Manufacture of solid electrolytic 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 Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor using a composite oxide having a vaporskite structure as a solid electrolyte.

BACKGROUND OF THE INVENTION In recent years, with the digitization of electrical equipment circuits, there has been an increasing demand for O2 capacitors used therein that have low impedance in the high frequency range and are small and large in capacity. Conventionally, plastic film capacitors, mica capacitors, and multilayer ceramic capacitors have been used as capacitors for high frequency ranges, but film capacitors and mica capacitors have thick shapes, making it difficult to increase the capacitance. , layered ceramic capacitors have the disadvantage that the smaller and larger the capacitance, the worse the temperature characteristics and the higher the price.On the other hand, aluminum dry electrolytic capacitors are known as large capacitance type capacitors. Alternatively, there are aluminum or tank solid electrolytic capacitors.In these capacitors, the anodic oxide film that serves as the dielectric material can be made very thin, making it possible to achieve large capacity, but on the other hand, the oxide film is easily damaged. Therefore, it is necessary to provide an electrolyte between the oxide film and the cathode to repair the damage.In aluminum dry electrolytic capacitors, etched positive and negative electrode aluminum foils are wound up through a paper separator, and a liquid The separator is impregnated with electrolyte.

For this reason, capacitance decreases and losses (tan δ) increase over time due to electrolyte leakage, evaporation, etc., and at the same time, high frequency characteristics and low temperature characteristics deteriorate significantly due to the ionic conductivity of the electrolyte. It has the following disadvantages. Furthermore, in aluminum and tantalum solid electrolytic capacitors, manganese dioxide is used as the solid electrolyte in order to improve the drawbacks of the above-mentioned aluminum dry electrolytic capacitors. This solid electrolyte is produced by immersing the anode element in a manganese nitrate aqueous solution.
It is obtained by thermal decomposition at a temperature of around 350°C. In the case of this capacitor, since the electrolyte is solid, there may be disadvantages such as electrolyte leakage at high temperatures and performance degradation due to solidification at low temperatures (and better frequency and temperature characteristics than capacitors using liquid electrolytes). However, due to damage to the oxide film due to thermal decomposition of manganese nitrate and the high resistivity of manganese dioxide, the impedance or loss in the high frequency range is more than an order of magnitude higher than that of multilayer ceramic capacitors or plastic film capacitors. value.

In order to solve the above problem, in recent years, the organic semiconductor T
It has been proposed to use CNQ salt. Since TCNQ salt has high conductivity and anodic oxidation properties, a capacitor with good high frequency characteristics and large capacity can be formed.

Problems to be Solved by the Invention However, capacitors using TCNQ salt do not have a high withstand voltage (or are not reliable when left at high temperatures), producing harmful HCN gas and reducing the capacity. There are some issues that need to be improved, such as changes and an increase in leakage current.

Each of the above-mentioned capacitors has its own difficulties in the manufacturing process in terms of manufacturing capacitors with excellent characteristics and thin shapes.

The present invention solves the above-mentioned conventional problems, and aims to improve high frequency characteristics and reliability of life when left at high temperatures.・Means for Solving the Problems The present invention achieves the above object, and the technical means thereof is to use a mixed conductive material of electrons and oxygen ions having a perovskite structure, such as a material represented by 5rxLa, -, Co1-, Fey034. It is formed in a square shape on the oxide film which becomes the dielectric film formed on the valve metal by a sputtering method in an atmosphere of a mixed gas of Ar and 02.

Function The present invention uses as a solid electrolyte a composite oxide having a perovskite structure, which has an electrical resistance 1 to 2 orders of magnitude smaller than that of Mr,2 or TCNQ salt, which is an electrolyte that provides a capacitor with excellent high frequency characteristics. A capacitor with low impedance and improved limit frequency can be provided. In addition, it has excellent heat resistance and exhibits good reliability even at high temperatures.

Further, in the present invention, the mixed conductive material satisfies δ<0.5 and x=(1+y)/2.0≦y≦1 in order to reduce electrical resistance and provide excellent high frequency characteristics. It is preferable to use Al, Ti1Ta, Nb, or Mo as the anode forming the capacitor.

A valve metal such as W is preferable. The specific resistance of the perovskite-type composite oxide thin film used here is 10 to 10Ω・
It is within the range of (7). When performing sputtering, the substrate is generally heated or a heat treatment is performed after film formation in order to improve crystallinity and adhesion.

The better the crystallinity of the composite oxide used here, the lower the electrical resistance.In order not to destroy the oxide film that has already been formed, it is better to perform the heat treatment mildly.

Sputtering atmosphere Ar and 0. When carried out in a mixed gas of , a film with good crystallinity can be obtained without heat treatment, and an electrical resistance of 10 to 10 Ω·m can be easily obtained. In particular, when the concentration of 02 was 20-40%, a film with good crystallinity and adhesion was obtained. If the o2 concentration is high, a film with good crystallinity can be obtained, but the sputtering speed will be lower and the adhesion will be poorer. In this case, the composite oxide having a perovskite structure can serve as the solid electrolyte and the other electrode at the same time. In addition, the adhesion between this composite oxide film and the dielectric oxide film is superior to that of TCNQ salt, and the heat resistance of this material is superior to that of the oxide film, making this capacitor a good choice. It exhibits excellent high temperature stability.

Example Examples of the present invention will be described in detail below.

Sro, 5Lao, and 5Co3-δ were selected as the composite oxides.

This fired product was produced as follows. A mixture of starting materials, lanthanium acetate, strontium acetate, and cobalt acetate, was thermally decomposed at 450 to 500°C, followed by 9
It was produced by performing a solid phase reaction at a temperature of 00°C or higher. δ was found to be 0.05 as determined by iodometry. The specific resistance value was 5×10″Ωφm.

Using A1 as the valve metal, a dielectric film was prepared by performing a 75V chemical conversion treatment. A thin film of the fired product was formed on this surface by RF sputtering.

The conditions for producing the thin film were as follows: The above fired product was used in powder form as the target material, the calculated surrounding atmosphere was a mixed gas with Ar gas of 30 g of 02 gas, and the gas pressure was 10 torr.
r, and the output was 300W. The film thickness was 1.5μ. The electrical resistance when formed into a thin film was 2×10 −20·α. When we measured the capacitor characteristics using the AI gold metal anode and this solid electrolyte membrane as the other cathode, we found that:
In IKHg, the capacitance was 0.55 μF and the tan δ was 7 chi. The leakage current was about 2 μA when 10 V was applied.

The capacity achievement rate was about 85%. It was found that the impedance at IMHg was as low as 10 nΩ, and the high frequency characteristics were excellent. Even if the composition of the fired product was changed within the range mentioned above, the electrical resistance of the sample produced by sputtering was 10 to 10 Ω·m, and the same capacitor characteristics as above were exhibited. Ti, Ta, Nb, Mo,
An equivalent capacitor can be obtained using W. The properties of the electrolyte membrane were similar even when the thin film was prepared by @flow sputtering.

Further, when the capacitor characteristics produced in this way were left at 130° C. for a long time, no deterioration of the characteristics was observed, indicating that the capacitor had excellent heat resistance.

Effects of the Invention In short, the present invention uses a thin film of a composite oxide having a perovskite structure as a solid electrolyte prepared by a sputtering method in a mixed gas atmosphere of Ar and 02, thereby achieving excellent high frequency characteristics and It has the advantages that a high temperature resistant solid state capacitor can offer.

Claims (4)

[Claims] (1) One electrode made of a valve metal and the chemical formula Sr_xLa_1_-_x on the oxide surface of the valve metal.
A thin film of a composite oxide having a perovskite structure represented by Co_1_-_yFe_yO_3_-_δ
A method for manufacturing a solid electrolytic capacitor, the method comprising manufacturing a solid electrolytic capacitor by a sputtering method in an atmosphere of a mixed gas of and O_2. (2) The complex oxide satisfies 0≦y≦1, δ≦0.5,
The method of manufacturing a solid electrolytic capacitor according to claim 1, characterized in that the relationship x=(1+y)/2 is satisfied. (3) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the valve metal is any one of Al, Ti, Ta, Nb, and W. (4) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the mixed gas concentration of O_2 in the mixed gas of Ar and O_2 is 20 to 40%.