JPH0722080B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention is a semiconductor layer formed on a dielectric film layer by electrolytic oxidation from an electrolytic solution containing a high concentration of lead ions to deposit and form a lead dioxide layer. The present invention relates to a method for producing a good solid electrolytic capacitor.

2. Description of the Related Art As described in, for example, JP-A-54-12447, first, manganese nitrate is thermally decomposed to form a manganese dioxide layer on a dielectric film layer, and then this is applied at a low concentration (for example, 0.1
A method is known in which a lead dioxide layer is formed on a manganese dioxide layer by electrolytic oxidation by immersing it in a solution containing lead ions.

Problems to be Solved by the Invention However, in the above method, since a thermal reaction is performed when forming the manganese dioxide layer, thermal cracking of the dielectric film and chemical damage due to generated gas are unavoidable.

Further, in the above method, a solid electrolytic capacitor is prepared by directly forming a semiconductor layer containing only lead dioxide by electrolytic oxidation from an electrolytic solution containing a low concentration of lead ions on a dielectric film layer having no manganese dioxide layer. Even if an attempt is made, the semiconductor layer of lead dioxide does not adhere sufficiently on the dielectric film layer, and only a capacitor having an extremely low capacity and a large loss coefficient can be obtained.

Therefore, an object of the present invention is to provide a solid electrolytic capacitor having good adhesion between the dielectric film and the semiconductor layer of lead dioxide, an extremely large capacitance, and a small loss coefficient.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to solve the above-mentioned drawbacks of the prior art, and as a result, by specifying the lead ion concentration in the electrolytic solution within a certain range, the dielectric film layer It has been found that the adhesion of the lead dioxide semiconductor layer to the top is improved and the above-mentioned object can be achieved very effectively, and the present invention has been completed.

That is, the gist of the present invention is characterized in that a lead dioxide layer is deposited and formed on a dielectric coating layer by electrolytic oxidation from an electrolytic solution containing lead ions of 0.2 mol / l to a saturated solubility as a semiconductor layer. This is a method for manufacturing a solid electrolytic capacitor.

The dielectric film in the present invention means an oxide film of a valve metal foil such as aluminum, tantalum, niobium or a sintered body, which is well known in the art, and can be obtained by a known method.

The electrolytic solution for forming lead dioxide on the dielectric film by electrolytic oxidation is an aqueous solution containing lead ions or an organic solvent solution. This electrolytic solution may contain a known electrolyte in order to improve the ionic conductivity of the electrolytic solution.

The lead ion species is not particularly limited, and may be any compound as long as it gives a lead ion species in the electrolytic solution, for example, lead citrate, lead acetate, basic lead acetate, lead borofluoride, lead acetate hydrate, Examples include lead nitrate, tetraethyl lead, tetraphenyl lead, lead acetylacetone, lead oxine, and the like. Two or more kinds of compounds that give these lead ion species may be mixed and used.

Any organic solvent may be used as long as it dissolves the compound that gives the lead ion species, and examples thereof include ethyl alcohol, glycerin, benzene, dioxane and chloroform.

These organic solvents may be used as a mixture of two or more,
Further, an organic solvent which is compatible with water may be used as a mixture with water.

The lead ion concentration in the electrolytic solution is from 0.2 mol / l to the saturated solubility, preferably from 0.5 mol / l to the saturated solubility, more preferably from 0.9 mol / l to the saturated solubility. If the concentration of lead ions exceeds the concentration that gives the saturated solubility, the merit of increasing the amount is not recognized, and if the concentration of lead ions is lower than 0.2 mol / l, the concentration of lead ions in the electrolyte is Since it is too thin, the semiconductor layer of lead dioxide produced by electrolytic oxidation does not sufficiently adhere to the dielectric film, and the solid electrolytic capacitor having a very low capacity and a large loss coefficient is obtained.

The electrolytic oxidation in the present invention is carried out by a conventionally known method such as a constant current method, a constant voltage method, or a constant current method and a constant voltage method alternately. As for the electrolysis apparatus and its operating method, conventionally known apparatuses and operating methods are adopted. The time and temperature of electrolytic oxidation cannot be specified unconditionally because it varies depending on the type of valve metal that has the dielectric coating used, the actual area of the dielectric coating, the type of lead ion species used, the electrolytic oxidation conditions, etc. , Determined by preliminary experiments conducted in advance.

The solid electrolytic capacitor manufactured by the method of the present invention,
Compared with a solid electrolytic capacitor in which a lead dioxide semiconductor layer is deposited and formed on a dielectric film layer by electrolytic oxidation from an electrolytic solution containing a low concentration of lead ions, it has the following advantages.

If a valve metal foil having the same dielectric film is used, an extremely high capacity solid electrolytic capacitor can be manufactured.

Since the adhesion between the dielectric film layer and the lead dioxide semiconductor layer is good, the loss factor is small.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The characteristic values of the solid electrolytic capacitors of each example are shown in the table.

Example A lead acetate trihydrate aqueous solution having a lead acetate trihydrate concentration of 1.9 mol / l was used as a high-pressure etching aluminum chemical conversion foil (capacity when an ethylene glycol-ammonium adipate-based electrolyte solution was used, 10 μF / 10 cm ² ) was immersed except for the terminal portion. Using carbon as a cathode, a current was applied for 30 minutes at a current density of 1 mA / cm ² , and a lead dioxide layer was formed on the etched aluminum conversion foil having a dielectric film. The formed foil was taken out of the electrolytic solution, thoroughly washed with water, and then dried under reduced pressure at 100 ° C. for 1 hour. Next, a silver paste was applied on the lead dioxide layer and dried, and then the cathode was taken out by soldering and sealed with a resin to produce a solid electrolytic capacitor.

Comparative Example A solid electrolytic capacitor was produced in the same manner as in the example, except that an aqueous solution of lead acetate trihydrate having a lead acetate trihydrate concentration of 0.1 mol / l was used.

Claims (1)

[Claims] 1. A solid electrolytic capacitor characterized in that a lead dioxide layer is deposited and formed as a semiconductor layer on a dielectric film layer by electrolytic oxidation from an electrolytic solution containing lead ions of 0.2 mol / l to saturation solubility. Manufacturing method.