JPS62256423A - 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 The present invention relates to a solid electrolytic capacitor (J) that uses lead dioxide as a conductor and has good performance.

" Wataru Tatsudate I Solid electrolytic capacitors using lead dioxide as a conductor layer are known, for example, as described in Japanese Patent Publication No. 58-21414. However, in the conventional solid electrolytic capacitor described above, the method of forming lead dioxide on the oxide film is by thermally decomposing the reaction mother liquor containing lead ions, so the oxide film may crack thermally. Moreover, there is a problem of chemical damage caused by generated gas. Therefore, when a voltage is applied to this solid electrolytic capacitor, current may concentrate on the defective portion of the oxide film, causing dielectric breakdown. Therefore, in order to increase the reliability of the withstand voltage, the formation voltage must be increased 3 to 5 times the rated voltage, and in order to obtain the desired volume, a large anode body with a large surface area must be used. The problem is that you don't get it.

Furthermore, as described in Japanese Patent Publication No. 49-29374, a method is known in which lead dioxide is formed on an oxide film by chemical precipitation. However, this method
When chemically depositing lead dioxide, silver ions are required as a catalyst, so silver or silver compounds adhere to the dielectric oxide film, resulting in a reduction in insulation resistance.

The purpose of the present invention is to produce a tan δ (tan δ) film in which a conductive layer of lead dioxide is provided on an oxide film without using a thermal decomposition reaction and without using a catalyst that adversely affects capacitor performance. The object of the present invention is to provide a β1-body electrolytic capacitor with low dielectric loss tangent) and low leakage current.

As a result of various studies in order to solve the drawbacks of the above-mentioned conventional techniques, the inventors of the present invention have conducted oxidation by chemical precipitation from a reaction mother liquor containing a lead-containing compound and hydrogen peroxide and/or a calcium-based compound. The present inventors have discovered that the above object can be extremely effectively achieved by forming a 3jp electric layer of lead dioxide on the film, and a solid electrolytic capacitor with good performance can be obtained, and the present invention has been completed.

That is, according to the present invention, there is provided a solid electrolytic capacitor characterized in that the conductor layer is lead dioxide chemically precipitated from a reaction mother liquor containing a lead-containing compound, hydrogen peroxide, and/or a calcium-based compound. provided.

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

The solid electrolytic capacitor of the present invention has a structure in which a portion of the conductive layer of lead dioxide has entered the pores of the oxide film of the valve metal foil, wire, or sintered body.

A solution containing a lead-containing compound, hydrogen peroxide, and/or a calcium-based compound is used as a reaction mother liquor for forming a conductive layer of lead dioxide on the oxide film by chemical precipitation.

The solvent used to prepare the reaction mother liquor may be any solvent as long as it dissolves the lead-containing compound and the hydrogen peroxide and/or calcium-based compound, and generally water or an organic solvent miscible with water is used. It will be done.

Typical examples of lead-containing compounds used in the present invention include oxine, acetylacetone, and chelate-forming compounds such as meconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin compounds, crown compounds, and cryptate compounds. Lead-containing compounds with atoms in coordinate or ionic bonds, lead citrate, lead acetate,
Basic lead acetate, lead borofluoride, lead acetate hydrate, lead nitrate,
Lead chloride, lead bromide, lead perchlorate, lead chlorate, Leadsa,...
7 a, 8, 6, silicon chloride I, bromine. Lead, etc. can be mentioned.

These lead-containing compounds are appropriately selected depending on the solvent used. Moreover, these lead-containing compounds may be used in combination of two or more types.

sO in the reaction mother liquor of lead-containing compounds! is preferably within the range of 0.05 mol/II from the concentration that gives a saturated solution. If the concentration of the lead-containing compound in the reaction mother liquor is less than 0.05 mol/j, a solid electrolyte with good performance cannot be obtained, and the concentration of the lead-containing compound in the reaction mother liquor exceeds the saturated solubility. In this case, there is no benefit from adding weight.

Representative examples of calcium-based compounds used in the present invention include calcium hypochlorite, calcium chlorite, calcium chlorate, calcium perchlorate, and the like. These calcium-based compounds are appropriately selected depending on the solvent used. Further, two or more of these calcium-based compounds may be used in combination.

The amount of hydrogen peroxide or calcium-based compound used is preferably within a range of 5 to 0.05 times the molar amount of the lead-containing compound. If the amount of hydrogen peroxide or calcium-based compound used is more than 5 times the mole, there is no cost advantage, and if it is less than 0.05 times the mole, a solid electrolytic capacitor with good performance cannot be obtained.

A method for forming a conductive layer of lead dioxide on an oxide film is, for example, an invasion method in which a reaction mother liquor is prepared by mixing a solution containing a lead-containing compound and a solution containing hydrogen peroxide and/or a calcium-based compound. , a method in which a reaction mother liquor is applied to the oxide film and chemically precipitated is mentioned.

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

■ Oxidized skin II without heating to high temperatures! Since a conductive layer of lead dioxide can be formed on the iI layer, there is no risk of damaging the oxide film of the anode, and there is no need to perform anodic oxidation (reformation) for repair.

Therefore, the rated voltage can be increased several times compared to the conventional one,
Although a capacitor with the same capacity and rated voltage can be obtained, it can be made smaller in size compared to conventional capacitors.

■Low leakage current.

■ Capacitors with high voltage resistance can be manufactured.

(2) The conductivity of the conductor layer is sufficiently high at 10 to 10 9-ax-', so the impedance is low.

■ Tan δ is small.

BACKGROUND-1-1 The present invention will be described in more detail below with reference to Examples and Comparative Examples. Note that the characteristic values of eight examples of solid electrolytic capacitors are shown in the table.

Example 1 Aluminum foil with a thickness of 100 μm (purity 99.99%)
was used as an anode, and the surface of the foil was electrochemically etched by direct current to have an average pore diameter of 2 μm and a non-surface area of 12TrL3.
/g. The etched aluminum foil was electrochemically treated in a solution of boric acid and ammonium borate to form a thin layer of dielectric material on the aluminum foil.

Next, the aluminum foil provided with the dielectric layer was immersed in a 2 mol/1 aqueous solution of lead acetate trihydrate, and 1.2 times the mol of hydrogen peroxide solution was added to the lead acetate trihydrate. added. 2
After standing for a period of time, the resulting lead dioxide layer was thoroughly washed with water to remove unreacted substances and by-products, and then dried at 120° C. for 2 hours. Next, a carbon paste was applied onto the lead dioxide layer and dried, and then a silver paste was applied thereon and dried again. A solid electrolytic capacitor was fabricated using a copper wire for the cathode and sealing it with resin.

Example 2 A solid was prepared in the same manner as in Example 1, except that instead of the aqueous solution of lead acetate trihydrate in Example 1, a saturated ethyl alcohol solution of lead acetylacetone synthesized from lead chloride and acetylacetone according to a conventional method was used. An electrolytic capacitor was manufactured.

Example 3 A solid electrolytic capacitor was produced in the same manner as in Example 1, except that an aqueous solution of lead nitrate was used instead of the aqueous solution of lead acetate trihydrate.

Example 4 A solid electrolytic condenser was produced in the same manner as in Example 1, except that a saturated aqueous solution of calcium chlorate was used instead of the hydrogen peroxide solution.

Example 5 In Example 1, hydrogen peroxide solution was added 0.5 times the mole of vinegar Mt+'l trihydrate, and calcium chlorate was added 0.2 times the mole of lead acetate trihydrate. A solid electrolytic capacitor was produced in the same manner as in Example 1 except for the addition of the following.

Comparative Example 1 An aluminum foil having the same dielectric layer as in Example 1 was coated with
A lead dioxide layer was formed by a conventionally known thermal decomposition method of an aqueous solution of lead nitrate. After repeating this operation four times, a carbon paste layer and a silver paste layer were provided in the same manner as in Example 1 to produce a solid electrolytic capacitor.

*Value at 120Hz **Value at 30V Umbrella Umbrella * Value at 101GIZ

Claims (1)

[Claims] A solid electrolytic capacitor characterized in that a conductive layer is lead dioxide chemically precipitated from a reaction mother liquor containing a lead-containing compound, hydrogen peroxide, and/or a calcium-based compound.