JPH0247818A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To sharply improve film breakdown strength (leakage currents) so as to contribute to miniaturization and low loss advancement by forming an oxide film on the surface of a valve acting metallic electrode, and sticking organic metallic salt such as alkoxide, etc., onto the oxide film, and heating it in the wet atmosphere so as to form a solid electrolyte. CONSTITUTION:Though solid electrolyte excellent in heat resistance is formed by applying solution in which organic metallic salt such as alkoxide, etc., is dissolved in xylene, or the like onto the surface of a valve acting metallic electrode consisting of aluminum foils treated by chemical conversion, and doing heat treatment after setting, steam is sent in at the time of formative reaction when metallic alcoholate transforms into a metallic oxide on a dielectric film so as to make the metallic oxide to be formed a one which contains crystal water to prevent damage and deterioration of the dielectric film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a solid electrolytic capacitor by improving the method of forming a solid electrolyte.

Prior Art The conventional method for forming a solid electrolyte involves immersing a valve metal having an oxide film in a manganese nitrate solution, then subjecting it to thermal decomposition treatment, and depositing manganese dioxide on the electrode.

Problems to be Solved by the Invention However, when a manganese dioxide layer is formed on an electrode, it is generally immersed in a manganese nitrate solution and then thermally decomposed, so that the anodic oxide film is damaged by one member. It was necessary to perform thermal decomposition and reconstitution. Further, it is necessary to perform chemical conversion at a voltage three to four times higher than the rated voltage, which is a major negative factor in miniaturization.

Means for Solving the Problems In order to solve the above problems, the present invention uses an organic metal salt such as an alkoxide that has little chemical action on the oxide film, and further heats the metal oxide to form the solid electrolyte. This method of manufacturing a solid electrolytic capacitor is characterized in that the effect of preventing deterioration of the oxide film is further enhanced by performing the treatment operation in steam.

That is, a solid electrolyte is formed by forming an oxide film on the surface of a valve metal electrode, depositing an organic metal salt such as an alkoxide on the oxide film, and heat-treating it in a humid atmosphere to form a solid electrolyte. This is a method of manufacturing an electrolytic capacitor. The alkoxide is characterized in that it is an organic metal salt containing manganese, tin, or lead.

A solution of an organic metal salt such as a functional alkoxide dissolved in xylene or the like is applied onto the surface of a valve metal electrode made of chemically treated aluminum foil, and thermally decomposed by heat treatment after insertion, resulting in heat resistance. A solid electrolyte with excellent properties can be formed. The general formula for the thermal decomposition reaction of the alkoxide at that time is shown by the following formula.

M (OR) n -1111→ MOnzz
+ ROR where, M: Metal element R: Organic substance such as an alkyl group However, since this manufacturing method involves a reaction on a metal oxide film, which is a dielectric, it inevitably induces an interaction with the oxide film. On the other hand, in the absence of the above-mentioned mutual reaction, the bonding property between the metal oxide, which is the solid electrolyte, and the oxide film, which is the dielectric, decreases, leading to an increase in tan δ. Therefore,
Although tan δ is good in this manufacturing method, it is necessary to improve the film breakdown voltage.

As a result of various studies, the inventors of the present invention discovered that when water vapor is introduced into a dielectric film during the formation reaction in which a metal alcolade becomes a metal oxide, the metal oxide that is formed contains crystal water. It has become clear that when crystallization water enters into manganese dioxide, tin oxide, and lead oxide, damage and deterioration of the dielectric film can be significantly prevented. In addition, in terms of bonding with the dielectric film, the ion exchange reaction of the crystal water strengthened the mutual bonding, making it possible to reduce loss.

EXAMPLE As an electrode for an anode, an aluminum foil etched to a surface magnification of approximately 100 times was subjected to 14V chemical conversion.

This electrode foil was immersed in the organic metal salt solution shown in Table 1, pulled up, dried at 125°C for 5 minutes, and then baked in an atmosphere of 350°C for 10 minutes. (Conventional example) Similarly, saturated steam at 350° C. was blown during the above baking process for 10 minutes in a humidified atmosphere. (Method of the present invention) This dipping-drying-baking process was repeated three times for both the conventional method and the method of the present invention.

After that, colloidal carbon was applied, a cathode lead was attached using silver paste, epoxy sealing was performed, and aging was performed.

Table 1 Table 2 The capacitor rating is IOV, 33 μF, and the product characteristics are shown in Table 2. The numerical values in Table 2 are the average values of 10 samples.

Effects of the Invention As shown in Table 2, the electrolytic capacitor manufactured by the manufacturing method of the present invention significantly improves the film withstand voltage (leakage current) and at the same time induces a significant decrease in tan δ, resulting in miniaturization and low loss. You can make a big contribution. Moreover, it can be easily mass-produced and has great industrial and practical value.

Claims (1)

[Claims] A solid electrolytic capacitor characterized in that an oxide film is formed on the surface of a valve metal electrode, an organic metal salt such as an alkoxide is attached on the oxide film, and a solid electrolyte is formed by heat treatment in a humid atmosphere. manufacturing method.