JPS5915373B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solid electrolytic capacitor, and particularly to a method for manufacturing a solid electrolytic capacitor that can improve tan δ characteristics.

In general, in order to reduce thermal deterioration of solid electrolytic capacitors and improve their reliability, it is required to improve the tan δ.

The main factors for the tan δ of a solid electrolytic capacitor, such as a tantalum solid electrolytic capacitor, are the resistances of the tantalum anodic oxide film layer, manganese dioxide layer, carbon layer, and metal layer, as well as the contact resistance between each layer. The contact resistance between the

It is thought that the reason why the contact resistance between the manganese dioxide layer and the carbon layer increases is that the manganese dioxide layer is porous and extremely sparse, resulting in insufficient contact with the carbon layer.

Therefore, to improve tan δ, it is necessary to improve the contact between the manganese dioxide layer and the carbon layer.

In view of the above points, it is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor that can improve tan δ.

To this end, the gist of the present invention is to provide a method for manufacturing a solid electrolytic capacitor in which an anodic oxide film is formed on the surface of a metal having a valve action, and a semiconductor layer, a carbon layer, and a metal layer are sequentially formed on the anodic oxide film. , a method for producing a solid electrolytic capacitor, which comprises the steps of immersing the capacitor in a nitric acid solution and holding the capacitor in a high-temperature atmosphere after forming the semiconductor layer.

Examples of the present invention will be described below.

First, an oxide film is formed on the tantalum surface of the tantalum sintered body, and the steps of impregnation with manganese nitrate and firing are repeated to form a manganese dioxide layer.

Next, the tantalum sintered body with the manganese dioxide layer formed thereon is immersed for 3 minutes in a nitric acid solution with a concentration of 3 at a temperature of 20°C.

After immersion, it is kept in an electric furnace or gas furnace at 200°C for 3 minutes to perform heat treatment.

After the heat treatment, reconversion is performed if necessary, and then a carbon layer and a silver hash layer are formed under normal conditions, a cathode lead wire is connected with solder, and a resin coating is applied.

Table 1 shows the tan δ of the conventional manufacturing method and that of the above example.

That is, according to the present invention, tan δ is reduced by a factor of 60 in the case of 35 VμF and by about 37 in the case of 3.15 V and 100 μF, resulting in a significant improvement in tan δ.

The reason for the improvement in tan δ is considered to be that the surface of the manganese dioxide layer is altered and the contact resistance with the carbon layer is reduced.

That is, the surface of the manganese dioxide layer obtained by the conventional method is brownish-black, but the surface of the manganese dioxide layer treated according to the present invention becomes grayish-black and is altered in quality.

This alteration lowers the contact resistance, and tan δ, which accounts for a large proportion of the contact resistance, decreases.

As is clear from the results in Table 2, tan δ hardly changes as long as the temperature of the atmosphere maintained after immersion is 100° C. or higher.

This is a tantalum solid electrolytic capacitor of 3.15 V and 100 μF by immersing it in a nitric acid solution at a temperature of 20° C. and a concentration of 10 μF for 3 minutes, holding it in an atmosphere at each temperature for 3 minutes, and using the usual method.

Tan δ is almost constant at 3.1 to 3.2 factors when the temperature is 100°C or higher, but at 50°C it is 3.5 factors, which is about 10 factors larger than the former case, and when the temperature of the atmosphere is 100°C
It is more effective if it is more than that.

In addition, when immersed in a nitric acid solution with a concentration of 10 g for 3 minutes, the liquid temperature was set to 20°C, 150°C, and 100°C, respectively.
The sample was held in an atmosphere of 3.15 V and 100 μF for 3 minutes, and the tan δ was measured, and the results shown in Table 3 were obtained.

It can be seen from this that tan δ is almost constant regardless of the temperature of the nitric acid solution.

Therefore, the nitric acid solution can be processed without boiling it.
There are advantages such as ease of manufacturing.

In other words, when a tantalum sintered body is immersed in a nitric acid solution after a manganese dioxide layer has been formed, the sintered body is immersed while welded to a support (usually a stainless steel bar), so if the solution is boiling, the Production becomes difficult, as the supports are contaminated by droplets or the concentration of the solution changes greatly, making it difficult to manage, but production can be facilitated by keeping the liquid temperature at room temperature.

As described above, according to the present invention, the contact resistance between the semiconductor layer and the carbon layer can be mainly reduced, and the tan δ characteristics can be improved as a whole.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a solid electrolytic capacitor in which an anodic oxide film is formed on the surface of a metal having a valve action, and a semiconductor layer, a carbon layer, and a metal layer are sequentially formed on the anodic oxide film. A method for manufacturing a solid electrolytic capacitor, which comprises, after formation, immersing it in a nitric acid solution and further holding it in a high-temperature atmosphere. 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the temperature of the atmosphere is 100°C or higher.