JPS62126624A - Solid electrolytic 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 the Invention The present invention relates to a solid electrolytic capacitor with good performance having a conductor layer of vanadium trioxide formed by chemical deposition on a dielectric film layer.

2. Description of the Related Art Solid electrolytic capacitors having conductive layers made of manganese dioxide have been known. However, in this solid electrolytic capacitor, the dielectric film (oxide film) is
There is a problem in that the metal is thermally cracked and furthermore, it is chemically damaged by the generated gas. Therefore, when a voltage is applied to this solid electrolytic capacitor, current may concentrate at the defective portion of the dielectric film, causing dielectric breakdown. Therefore, in order to increase the reliability of the withstand voltage, the formation voltage must be increased to 3 to 5 times the rated voltage, and in order to obtain the specified capacity, a large anode body with a large surface area must be used. The problem is that there is no.

As a method to solve these drawbacks, a method is known in which tetracyanthine methane salt, which is an organic semiconductor, is used as a conductive substance (Japanese Patent Application Laid-Open No. 173928/1983, etc.); Disadvantages include that the cost of salt is extremely high, and because it is salt, it is unstable against moisture.

Problems to be Solved by the Invention The objects of the present invention are to provide a method that is low in cost, has a small loss factor by forming a conductive layer on a dielectric film layer by chemical precipitation without using a thermal decomposition reaction, and An object of the present invention is to provide a solid electrolytic capacitor with good performance and low leakage current.

Means to Solve the Problems As a result of intensive study, the inventors have found that the above object can be effectively achieved by forming a conductive layer of vanadium trioxide on the dielectric film layer by chemical precipitation. This discovery led to the present invention. That is, according to the present invention, Panazo trioxide A formed by chemical precipitation on the dielectric film layer
A solid electrolytic capacitor having a conductor layer is provided.

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

A solution containing metavanadate ions and a reducing agent is used as a reaction mother liquor for forming a conductor layer of pananium trioxide on a dielectric film layer by chemical precipitation.

There are no particular restrictions on the metavanadate ion species and the reducing agent, and representative examples of compounds that provide metavanadate ion species include sodium metapanacinate, ammonium metavanadate, and the like. On the other hand, typical examples of the reducing agent include lithium aluminum hydride, sodium borohydride, tributyl tin hydride, hydrazine, and zinc sodium hypophosphite. Two or more of these compounds and reducing agents that provide metavanadate ion species may be used in combination.

The concentration of metavanadate ion in the reaction mother liquor is preferably within the range of 0.003 mol/l from the concentration that provides saturated solubility. When the concentration of metavanadate ions in the reaction mother liquor is lower than 0.03 mol/l, there is a problem that the concentration of metavanadate ions in the mother liquor is too low and the number of coatings must be increased. Further, when the concentration of metavanadate ion in the reaction mother liquor exceeds the saturated solubility, no merit is observed by adding an increased amount. On the other hand, the concentration of the reducing agent in the reaction mother liquor is preferably within the range of 3 to 0.5 in terms of molar ratio to metavanadate ions. If the concentration of the reducing agent in the reaction mother liquor is more than 3 in molar ratio to metavanadate ions, unreacted reducing agent remains, resulting in high costs; If it is less than 05, unreacted metavanadate ions remain and the conductivity deteriorates, which is not preferable.

The reaction mother liquor may be used by simultaneously dissolving the compound that provides metavanadate ion species and the reducing agent in a solvent, or by separately preparing solvent solutions of the compound that provides metavanadate ion species and the reducing agent in advance. It may be used by mixing immediately before use.

The solvent used may be any solvent as long as it dissolves the compound providing the metavanadate ion species and the reducing agent, and generally water or an organic solvent is used. The solvent is
It is appropriately selected depending on the compound providing the metavanadate ion species and the type of reducing agent used.

The solid electrolytic capacitor of the present invention is produced by applying a reaction mother liquor containing metavanadate ions and a reducing agent to a valve metal such as aluminum, tantalum, or dioxide having a dielectric film, or by applying a reaction mother liquor containing metavanadate ions and a reducing agent. immersing the valve metal in the reaction mother liquor and allowing the reaction mother liquor to enter the vj dielectric film;
He who is left alone is manufactured by washing with water and drying. The temperature at which it is left to stand is preferably within the range of room temperature to 100°C.

The standing time varies depending on the leaving temperature and cannot be determined unconditionally, but is usually determined as appropriate by observing and judging the degree of vanadium trioxide formation.

Effects of the Invention The solid electrolytic capacitor of the present invention has the following advantages over conventionally known solid electrolytic capacitors.

■ Since a conductive layer of pananium trioxide can be formed on the dielectric film layer without heating to high temperatures, there is no risk of damaging the dielectric film of the anode, and there is no need to perform anodization (re-forming) for repair. Nor.

Therefore, the rated voltage can be increased several times higher than before.
In order to obtain a capacitor with the same capacity and rated voltage, the shape can be made smaller compared to conventional capacitors.

■Low leakage current.

■ Capacitors with high withstand voltage can be manufactured.

■ The conductivity of pananium trioxide is 1O~100s'cl
n'', which is sufficiently high, the impedance is low.

■Good high frequency characteristics.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that the characteristic values of the solid electrolytic capacitors on each side are shown in the table.

Example 1 Aluminum foil with a thickness of 100 μm (purity 99.99 cm)
was used as an anode, and the surface of the foil was electrochemically etched by alternating direct current and alternating current, with an average pore diameter of 2 μm.
The specific surface area was 12 m2/9. The etched aluminum foil was then electrochemically treated in an ammonium borate solution to form a thin layer of dielectric (alumina) on the aluminum foil.

Concentrated potassium of ammonium metavanadate 0.6 mol/
The concentration of the aqueous solution of L and sodium borohydride is 1.
A reaction mother liquor was obtained by mixing 0 mol/l aqueous solution. This reaction mother liquor was immediately applied to the dielectric thin layer described above and left under reduced pressure for 3 hours, whereby a vanadium trioxide layer was formed on the dielectric thin layer. Next, the vanadium trioxide layer was thoroughly washed with water and then dried under reduced pressure at 110° C. for 3 hours. After applying carbon paste on the vanadium trioxide layer and drying it, silver paste was further applied on top of it and dried. Next, after soldering the lead wires, the capacitor was packaged with a mold to produce a solid electrolytic capacitor.

Example 2 In Example 1, the concentration of sodium metavananoate was 0.9 instead of the aqueous solution of ammonium metavanadate and the aqueous solution of sodium boronohydride as the reaction mother liquor.
mol/l aqueous solution and the concentration of sodium hypophosphite is 1.
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that a 5 mol/l aqueous solution was used.

Comparative Example 1 A solid electrolytic capacitor was manufactured by forming manganese dioxide on an aluminum foil having the same dielectric layer as in Example 1 by thermally decomposing conventionally known manganese nitrate at t-300°C.

table Medium value at 120Hz Value at m-50V

Claims (2)

[Claims] (1) A solid electrolytic capacitor having a conductive layer of vanadium trioxide formed by chemical deposition on a dielectric film layer. (2) The solid electrolytic capacitor according to claim (1), wherein the reaction mother liquor for chemically precipitating vanadium trioxide is a solution containing metavanadate ions and a reducing agent.