JPS59193017A - Method of producing electrolytic condenser - 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 The present invention relates to a method of manufacturing capacitors by type.

Traditionally, tantalum, nioff, zirconium, and vanadium have been used as anode body materials for free-flowing capacitors.

Metals such as hafnium, titanium, and aluminum that act as valves are known, and in the past many researchers have investigated the basic characteristics of these metals alone or with alloy threads as electric control capacitors, and have thoroughly investigated their practical application. I came.

However, in order to be put to practical use as a capacitor, the leakage current of the oxide film unique to the anode material is required.

Electrical characteristics such as dielectric loss must reach a certain level, and the only electric capacitors currently in practical use use tantalum and aluminum as anode bodies.

Capacitors using tantalum as anode material have excellent electrical properties such as leakage current2 and dielectric loss9, are stable and extremely reliable, and are characterized by being compact and having large capacity. .

However, the supply of tantalum has not been able to keep up with the demand in recent years, and due to a shortage of supplies, the price of the material has significantly increased, causing product prices to rise. . On the other hand, capacitors using aluminum Rammura anode material are characterized by being inexpensive, but in addition to being more difficult to make smaller and larger capacitors, capacitors using tantalum anode material have lower electrical characteristics and stability. Inferior.

Under these circumstances, we are developing materials that have excellent electrical properties such as leakage current and dielectric loss, and are stable, as well as being able to achieve small size and large capacity, and that can be inexpensively and stably supplied. There was a strong desire to develop an electrolytic capacitor as an anode body.

As a result of being frugal, the present inventors used all powders of titanium hydride and aluminum as raw materials, and created an aluminum-titanium alloy porous sintered body made by mixing, pressing, and sintering these powders as an anode body. We have already found and proposed a porous material for electrolytic capacitors that meets these demands.

In addition, we have already proposed that when this aluminum-titanium alloy is used as an anode body, the most suitable chemical solution for anodizing is a phosphoric acid water bath.By the way, as a method for solidifying an electrolytic capacitor,
Generally, a method is used in which a manganese nitrate bath solution is impregnated into a chemical product after 1b electrode oxidation treatment, and then heated to perform thermal decomposition, and deposit manganese dioxide (Mn02) as a cathode layer on the oxide film. . In this case, the pyrolysis temperature is 20
Impregnation with manganese cuprate at 0 to 250℃.Due to the need to repeat the pyrolysis process several times, the anodic oxide film undergoes thermal deterioration during this treatment process, increasing the dielectric loss of the film. It may be stored away. Regarding this cause,
When heat is applied, some of the oxygen in the oxide film is taken away by the anode metal at the interface between the anodic oxide film and the anode metal, and as a result, donors are generated due to oxygen defects, and the interface side of the oxide film becomes partially conductive. It is said that this is to form a low resistance layer.

Such a phenomenon is also observed when anodic oxidation is performed in a phosphoric acid water bath using an aluminum-titanium alloy as an anode body, increasing the dielectric loss of the oxide film after 18=.integration.

An object of the present invention is to provide an excellent manufacturing method that prevents such thermal deterioration during solidification, that is, the dielectric loss of the anodic oxide film.

According to the invention, the anodic oxidation process is carried out in a phosphoric acid water bath up to a certain voltage lower than the final formation voltage, then in an ammonium carbonate or ammonium citrate water bath up to the final formation voltage, and then The dielectric loss (tan δ
f) are both very small, and due to the heat during solidification, ta
An excellent method for manufacturing an At-Ti alloy electrolytic contesser without an increase in nδf can be obtained.

Hereinafter, the present invention will be explained in more detail according to examples.

Example At powder with an average particle size of 3 μm and titanium hydride powder with an average particle size of 3 μm were mixed so that the atomic ratio of At and Ti was 54; 46, and after compression molding into a cylinder shape, the mixture was heated at 1070°C in a vacuum. By holding for 2 hours and performing firing and sintering, an At-Ti alloy porous body was produced and used as an anode body.

Next, these anode bodies were anodized to 60V in a phosphoric acid bath solution of 05 bodies (anodization 1-■), and then all were anodized to 80V with 1 weight part of ammonium carbonate or ammonium succinate2. Anodizing was carried out in a water bath. (Anodization 1-■) Furthermore, each of the two types of anodized products with different chemical solutions used in the above-mentioned anodization 1-■ was anodized again to 80V in a 0.005 volume phosphoric acid bath solution. I made money.

(Anodization 2) For comparison, as a conventional method, 1 ft of anodization was performed in a phosphoric acid bath solution of 0.5 volume of phosphoric acid to a final chemical pressure of 80 V, and then 0.005 volume of phosphoric acid was used. 80V during acid water bath
A sample was prepared by performing anodic oxidation again.

The static capacity at 120Hz is approximately 6.
It was 8 μF.

The chemical product produced by the above three chemical conversion methods was placed in the air for 25 minutes.
After heat treatment at 0°C, 300°C, and 350°C for 30 minutes each, 30vol. %f(tanaf e m in 2SO4
The results are shown in Figure 1. ■ in Figure 1
, ■, and ■ respectively indicate the following cases.

■ ; In the case of chemical conversion using only the conventional method of phosphoric acid water bath ■ ; In the case of chemical conversion using phosphoric acid-ammonium carbonate of the present invention ■ ; In the case of chemical conversion using phosphoric acid-ammonium citrate of the present invention From Figure 1 As can be seen, the chemical conversion method according to the present invention has a smaller tanaf value after chemical formation than the conventional chemical conversion method using only a phosphoric acid water bath, and also has less negative deterioration of the chemical conversion film when heat stress is applied. In other words, it can be seen that the increase in tanaf is extremely small.

The oxide film produced by the chemical conversion method of the present inventor has a stronger bonding of oxygen ions than the oxide film produced by phosphoric acid formation, and even under heat stress, the oxygen in the film is not absorbed by the lower metal. This is thought to be because it is difficult to be taken away and the interface portion does not become a semiconductor. Next, for the beret after chemical formation,
The properties after solidification by impregnation with manganese nitrate and heating at 250° C. 6 times are shown in the table. (1st shift in the center of 30 water falcons) From the table, it can be seen that the chemical conversion method of the present invention has a higher tanaf value than the conventional method (chemical conversion method using only water bathing) even when solidified in the fruit space. It can be confirmed that the thermal deterioration of the film is small. In addition, corresponding to the small tanaf, the tanδ (1201
1z) is also smaller in the case according to the present invention. Regarding leakage current, almost the same small value was obtained in all cases. Note that the reason why the anodic oxidation is performed again in the anodic oxidation treatment is to further reduce the leakage current.

In addition, in the example, a case was shown in which phosphoric acid water bath powder (0,005 vol, %) <1 was used for the second (again) anodic oxidation, but it is also possible to use ammonium carbonate or ammonium citrate water bath powder. It was confirmed that similar results could be obtained.

As explained above, according to the mounting method of the present invention, an excellent oxidized film is produced which is resistant to heat stress during solidification as determined by thermal analysis of manganese nitrate and does not increase tanaf (film induced loss). It is possible to form a capacitor, which greatly contributes to the improvement of capacitor characteristics. Therefore, it is clear that the present invention is highly useful.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the dependence of the fatty electric loss tan δf of the chemical conversion coating on the heat treatment temperature. Figure 1

Claims (1)

[Claims] In the manufacturing method of electrolytic capacitors, in which an alloy consisting of aluminum and titanium is used as the anode metal, and after anodizing it, PJf, a solid cathode semiconductor layer, and an external cathode are sequentially formed. The process is carried out in a phosphoric acid aqueous solution up to a lower constant voltage, then in a water bath solution of ammonium carbonate or ammonium citrate until the final formation voltage, and then in a phosphoric acid water bath solution or ammonium-based water bath solution of category 2 & 1 above. 1. A method for manufacturing an electric tuning capacitor, comprising an anodizing step of once again performing anodization to the final formation voltage.