JPS63245917A - Manufacture of solid electrilytic 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 Industrial Application The present invention relates to a method for manufacturing a solid electrolytic capacitor using a complex oxide having a provskite 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 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 large shapes, making it difficult to increase the capacity, and multilayer ceramic capacitors Capacitors have the disadvantage that the smaller they are, the larger their capacity becomes, the worse their temperature characteristics become, and the more expensive they become.

On the other hand, known high-capacity type capacitors include aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. These capacitors can achieve large capacitance because the anodic oxide film that serves as the dielectric can be made very thin, but on the other hand, the oxide film is easily damaged, so damage must be repaired between the oxide film and the cathode. It is necessary to provide electrolytes and electrolytes for this purpose. In an aluminum dry electrolytic capacitor, etched positive and negative electrode aluminum foils are wound up with a paper separator in between, and the separator is impregnated with a liquid electrolyte. For this reason, capacitance decreases and losses (tan δ) occur over time due to electrolyte leakage, evaporation, etc.
At the same time, it has drawbacks such as extremely poor high frequency characteristics and low temperature characteristics due to the ionic conductivity of the electrolyte.

In addition, for aluminum and tantalum solid electrolytic capacitors,
Manganese dioxide is used as a solid electrolyte to improve the drawbacks of the above-mentioned aluminum dry electrolytic capacitors. This solid electrolyte is obtained by immersing an anode element in a manganese nitrate aqueous solution and thermally decomposing it at a temperature of around 350°C. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as electrolyte leakage at high temperatures or performance degradation caused by solidification at low temperatures, and it has better frequency and temperature characteristics than capacitors using liquid electrolytes. is shown, but
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. There is.

Problems to be Solved by the Invention In order to solve the above problems, in recent years, the organic semiconductor T
It has been proposed to use CNQ salt.

TCNQ salt has high conductivity and anodic oxidation properties, so
Capacitors with good high frequency characteristics and large capacitance are possible.

However, with capacitors using TCNQ salt, it is difficult to obtain a high withstand voltage, and reliability is also affected when left at high temperatures, such as generation of harmful HCN gas, change in capacity, and increase in leakage current. There are some points that need to be improved. Each of the capacitors mentioned above has its own difficulties in the manufacturing process in terms of manufacturing thin shapes with excellent characteristics.

In view of the above-mentioned conventional problems, the present invention aims to improve the reliability of high frequency characteristics and life when left at high temperatures.

Means for Solving the Problems The method for manufacturing a solid electrolytic capacitor according to the present invention uses a mixed conductive material 5 of electrons and oxygen ions having a perovskite structure.
On the thin film of the complex oxide represented by rxLat-xcol-xCo1-a, a thin film is formed by sputtering or ion plating, using a metal oxide with valve action to serve as a dielectric film as an electrode. By forming this, the above object is achieved.

Function The present invention uses a composite oxide having a perovskite structure as a solid electrolyte, which has an electrical resistance that is 1 to 3 orders of magnitude lower than Mn0z or TCNQ salts, which are solid electrolytes that provide capacitors with excellent high frequency characteristics. By using this, a core dench with low impedance and an improved usable limit frequency can be provided, and a thin capacitor having excellent heat resistance f2 and good reliability even at high temperatures can be obtained.

5rzLa1-zcol-yFey 03-a of the present invention
The composite oxide, which is a mixed conductive material represented by
In order to reduce electrical resistance and improve high frequency characteristics, δ≦0.5. x= (Ity)/2 Qriy
It is desirable that <1, and metals with valve action include AI, Ta, Ti, Nb, Mo, W
selected from among. The perovskite-type composite oxide thin film described above can also be produced by sputtering or ion plating, but
When obtaining a film with a thickness greater than or equal to
A fine powder made by calcining Fe oxide, carbonic acid, acetic acid, or nitric acid compound in an appropriate weight ratio in an air atmosphere at 900'C is made into pellets by adding a small amount of a polymer binder and its solvent, and using a pressing method. and set it to 1200°
By performing final firing at around C, a film with low specific resistance can be obtained. A specific resistance value of 1 to 10 ohms can be easily obtained. This 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 oxide film produced by sputtering or ion plating is superior to that of TeNQ salts. The capacitors made as described above exhibit good high temperature stability.

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

Perovskite type composite oxides include Sro and 5La.
o,5CoO3-δ was selected. A thin film of this material was produced as follows. A mixture of starting materials lanthanium acetate, strontium acetate, and cobalt acetate was heated to 450
Pyrolysis was carried out at ~500°C, followed by a phase reaction at 900'C. The fired product thus obtained was pulverized into pellets using a pressing method using an aqueous polyvinyl alcohol solution as a binder, and then again
After the binder was thermally decomposed at around °C, firing was performed at 1200 °C. δ is 0.0 as determined by iodometry
It was 5. The specific resistance value was 3 x 10-4Ω·cm.

The film thickness was about 1 chick. On this, an Al2O5 film with a thickness of 200 to 300 mm was formed by RF sputtering, and on top of that, an AI film was deposited as an electrode by DC sputtering (approximately 1 μm thick).The capacitor characteristics of this material were measured. At a frequency of I KHz, the capacitance was 0.15 pF and tan δ was 8%.The impedance at I MHz was as low as about 10 mΩ, indicating excellent high frequency characteristics. It was found that the capacitor characteristics did not change much even if the capacitor was left at 130°C for a long time, indicating that it is a capacitor with excellent heat resistance.The dielectric film contains oxide films of Ta, Ti, Nb, Mo, and W. An equivalent capacitor was obtained by using the above method.The same effect was also obtained by using an ion plating method instead of the sputtering method to form the valve metal oxide and the valve metal thin film.

Effects of the Invention In summary, the invention uses a composite oxide having a perovskite structure, which is a mixed electron-ion conductor with low electrical resistance, as a solid electrolyte, and sputters a valve metal oxide and a thin film of the metal onto this membrane. The present invention provides a method for manufacturing a solid electrolytic capacitor manufactured by the ion plating method, which has the advantage of providing a capacitor with excellent high frequency characteristics and excellent heat resistance.

Claims (3)

[Claims] (1) Chemical formula Sr_xLa_1_-_xCo_1_-_
A solid electrolyte characterized by depositing an oxide of a metal having a valve action as a thin film on a thin film of a composite oxide having a perovskite structure represented by yFe_yO_3_-_δ by sputtering or ion plating. Method of manufacturing capacitors. (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) Valve metal is Al, Ti, Ta, Nb, Mo,
The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is made of W.