JPS62268122A - 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] Industrial applications The present invention relates to a solid electrolytic converter with good performance.

BACKGROUND OF THE INVENTION Metals with valve action (hereinafter referred to as valve metals) such as tantalum, aluminum, niobium, and titanium are used as the anode substrates of conventional solid electrolytic capacitors, and among these, tantalum and aluminum are often used. ing.

For example, in a solid electrolytic capacitor that uses aluminum as the anode base, the anode body is formed by forming an aluminum oxide film as a dielectric on a sintered body of aluminum powder, as shown in Figure 4. It is constructed by forming a semiconductor layer and further laminating a conductor layer on this semiconductor layer. Manganese dioxide produced by thermal decomposition of manganese nitrate is mostly used as a semiconductor layer.

Problems to be Solved by the Invention However, in such conventional techniques, the process is complicated because thermal decomposition is performed several times, and the conductivity of manganese dioxide is less than to-1s, cll-1, so There was a problem in that the equivalent series resistance value in the frequency range was large and undesirable.

Means and operation for solving the problems The present invention solves the above problems, and the gist thereof is to have an oxide film layer that is partially electrically and mechanically connected to and integrated with the anode terminal. In N sheets (N is a positive integer of 2 or more) of valve metal etching foils, a semiconductor layer is sequentially provided on the oxide WA layer, a conductor layer is provided on the semiconductor layer, and a common cathode terminal is further provided on the conductor layer. A solid electrolytic capacitor equipped with

In the solid electrolytic capacitor of the present invention, since the semiconductor layer is made of lead dioxide or lead dioxide and lead sulfate,
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As shown in the figure, due to the stacked parallel configuration, the combined resistance value of the equivalent circuit is 1/N as shown in FIG. 2, and the equivalent series resistance value in the high frequency range is extremely small. Furthermore, the process for producing such a conductor layer is also extremely simple and industrially advantageous.

The solid electrolytic capacitor of the present invention will be explained below.

As the valve metal substrate used as the anode, any metal having a valve action may be used, such as aluminum, tantalum, niobium, titanium, and alloys using these as substrates. Of these, it is advantageous to use aluminum.

The oxide layer on the surface of the anode substrate may be an oxide layer of the anode substrate itself provided on the surface layer of the anode substrate, or may be another dielectric oxide layer provided on the surface of the anode substrate. You can. Among these, a layer made of an oxide of the anode valve metal itself is preferable. In either case, a conventionally known method can be used to provide the oxide layer.

For example, when using aluminum foil as the anode substrate,
By electrochemically etching the surface of aluminum foil and further electrochemically treating it in an aqueous solution of boric acid and ammonium borate, an oxide layer consisting of alumina dielectric is formed on the aluminum foil, which is the anode substrate. Ru.

Note that N sheets (N is a positive integer of 2 or more) of the anode valve metal substrates are partially electrically and mechanically connected to the anode terminal by caulking, high-frequency bonding, etc. before and after providing the oxide layer, and are combined. be done.

Although there is no particular $11 ffl in the composition and manufacturing method of the half-half layer used in the present invention, the height of the capacitor is 17;
To improve wave performance, use lead dioxide or carbon dioxide.

It is preferable to use lead and lead sulfate as main components, and to produce it by, for example, a conventionally known electrochemical deposition method or chemical deposition method.

Methods for providing a semiconductor layer containing lead dioxide as a main component include a chemical deposition method and an electrochemical deposition method.

Examples of the chemical precipitation method include a method of chemically precipitating from a solution containing a lead-containing compound and an oxidizing agent.

Typical examples of lead-containing compounds include chelate-forming compounds such as oxine, acetylacetone, pyromeconic acid, salicylic acid, alipurin, polyvinyl acetate, porphyrin compounds, crown compounds, and cributate compounds, in which a lead atom forms a coordinate bond or ionic bond. lead-containing compounds, lead citrate, lead acetate, basic vinegar pH lead, lead chloride,
Lead bromide, perchlorine Fi! ! Lead, chlorine M lead, lead length Luffamate, silicon hexafluoride chain, lead bromate, lead borofluoride, lead acetate hydrate, nitrate Pl! Examples include lead. These lead-containing compounds are appropriately selected depending on the solvent used for the reaction mother liquor. Further, two or more of these lead-containing compounds may be used in combination. In the reaction, the concentration of the lead-containing compound in the solution is within the range of 0.05 mol/1 from the concentration that gives saturated solubility, preferably within the range of 0.1 mol/1 from the concentration that gives saturated solubility. , more preferably within the range of 0.5 mol/1 from the concentration that provides saturation solubility. The concentration of lead-containing compounds in the reaction mother liquor is 0.05 mol/f
If it is less than J, a solid electrolytic capacitor with good performance cannot be obtained. Further, if the concentration of the lead-containing compound in the reaction mother liquor exceeds the saturation solubility, no merit will be observed by addition of the mother liquor.

Typical examples of oxidizing agents include quinone, chloranil,
Pyridine-N-oxide, dimethyl sulfoxide, chromic acid, potassium permanganate, selenium oxide,
Examples include mercury acetate, vanadium oxide, sodium chlorate, ammonium persulfate, potassium persulfate, sodium persulfate, ferric chloride, "A" hydrogen oxide, mustard powder, and benzoyl peroxide.

These oxidizing agents may be appropriately selected depending on the solvent used. Further, two or more oxidizing agents may be used in combination. The proportion of the oxidizing agent used is preferably within the range of 5 to 01 times the mole of the lead-containing compound used. If the proportion of the oxidizing agent used is more than 5 times the mole of lead-containing compounds, there is no cost advantage, and
If the amount is less than twice the molar amount, a solid electrolytic capacitor with good performance cannot be obtained.

As a method for forming a semiconductor layer containing lead dioxide as a main component, for example, a reaction mother liquor is prepared by mixing a solution in which a lead-containing compound is dissolved and a solution in which an oxidizing agent is dissolved. An example of this method is to immerse the anode substrate to chemically deposit the anode.

On the other hand, examples of electrochemical deposition methods include the method previously proposed by the present inventors in which lead dioxide is deposited by electrolytic oxidation in an electrolytic solution containing high IIa lead ions (patent application Publication number 61-26952).

There are no particular restrictions on the type of lead ion to be used, and any compound that provides lead ion types in the electrolyte may be used, such as lead citrate, lead oversalt, lead acetate, basic lead acetate, and fluoroborate. Examples include lead, lead nitrate, lead chloride, lead bromide, lead bromate, lead chlorate, lead sulfamate, lead silicon hexafluoride, tetraethyl lead, tetraphenyl lead, acetylacetone, and lead oxine. Two or more of these compounds providing lead ion species may be used in combination.

The electrolytic solution for forming a semiconductor layer containing lead dioxide as a main component by electrolytic oxidation is an aqueous solution containing lead ions or an organic solvent solution containing lead ions. This electrolyte may contain a known electrolyte to improve the ionic conductivity of the electrolyte.

The paid solvent used in the specific solvent solution may be any solvent as long as it dissolves the compound that provides the above lead ion species, such as ethyl alcohol, glycerin, benzene, dioxane, chloroform, and the like. Two or more of these paid solvents may be used as a mixture, and a separate solvent that is compatible with water may be used as a mixture with water.

The lead ion concentration in the electrolyte ranges from 0.2 mol/1 to a temperature that provides saturated solubility, preferably from 0.5 mol/1 to saturated solubility, and more preferably from 0.9 mol/1 to saturated solubility. be. When the temperature of lead ions exceeds the concentration that provides saturation solubility, no merit is observed by adding R. Also, if the lead ion concentration is lower than 0.2 mol/1, the concentration of lead ions in the electrolyte is too low and the electric current is low. The disadvantage is that the semiconductor layer of lead dioxide produced by oxidation does not adhere sufficiently onto the oxide layer of the anode substrate, resulting in only a solid electrolytic capacitor having an extremely low 8 coefficient and a large n lapse coefficient.

Electrolytic oxidation is carried out using conventionally known methods, such as a constant current method, a constant voltage method, a pulse method, or alternately a constant current method and a constant voltage method. Furthermore, conventionally known devices and operating methods are employed as the electrolysis device and its operating method. The time and temperature of electrolytic oxidation cannot be determined unconditionally because they vary depending on the type of anode substrate used, the actual area of the oxide film, the type of lead ion species used, the conditions of electrolytic oxidation, etc., and preliminary experiments should be carried out in advance. It is preferable to decide based on

On the other hand, if the semiconductor layer is composed of a layer whose main components are lead dioxide, which originally plays the role of a semiconductor, and lead sulfate, which is an insulating material, l
By adding tAM lead, the leakage current value of the capacitor can be reduced. On the other hand, the combination of lead nitrate lowers the electrical conductivity of the semiconductor layer, resulting in a higher equivalent series resistance value, but it is not possible to achieve and maintain a high level of performance compared to conventional solid electrolytic capacitors. It was discovered by the present invention. Therefore, when the semiconductor layer is composed of a mixture of lead dioxide and lead sulfate, 10 parts by weight or more of lead dioxide
Good condensation performance can be achieved and maintained over a wide range of compositions, including 90 parts by weight or less of lead sulfate for less than 20 to 50 parts by weight of lead dioxide. 80 to 50 parts by weight, furthermore, 25 to 50 parts by weight of lead dioxide
The balance between the leakage current value and the equivalent series resistance value is particularly good in the range of 75 to 65 weight parts of lead sulfate relative to the 35jT7&i part. If the amount of lead dioxide is less than 10 parts by weight, the conductivity deteriorates and the equivalent series resistance becomes large, and 8 companies do not appear sufficiently.

A semiconductor layer containing lead dioxide and lead oxide as main components can be formed by chemical precipitation using, for example, an aqueous solution containing lead ions and persulfate ions as a reaction mother liquid. Also,
A suitable oxidizing agent that does not contain persulfate ions may also be added.

In particular, in order to facilitate the precipitation of lead sulfate, the reaction mother liquor was
It is preferable to heat to about 100°C.

The concentration of lead ions in the mother liquor is within the range of 0.1° C. mol/l from the concentration giving saturation solubility, preferably 0.5 mol/l from the concentration giving saturation solubility. If the concentration of lead ions is higher than the concentration that gives saturation solubility, there is no advantage to adding an increased amount. Also, the concentration of lead ions is 0.1 mol/
When the lead ion concentration is lower than 1, the lead ion concentration in the mother liquor is too low, so there is a problem that the number of applications must be increased. On the other hand, the concentration of persulfate ions in the mother liquor is within the range of 5 to O.OS in terms of molar ratio to lead ions. When the concentration of persulfate ions is more than 5 in molar ratio to lead ions,
Unreacted persulfate ions remain, resulting in high costs, and the concentration of persulfate ions is 0.0 molar ratio to lead ions.
If it is less than 5, unreacted lead ions remain and conductivity deteriorates, which is not preferable.

Typical examples of compounds that provide lead ion species include citric M lead, lead perchlorate, lead nitrate, lead acetate, basic lead acetate, lead chlorate, lead sulfamate, lead silicon hexafluoride, and bromine! Examples include lead, lead chloride, lead bromide, etc. Two or more of these compounds providing lead ion species may be used in combination. On the other hand, typical examples of compounds that provide persulfate ion species include potassium persulfate, ztrium persulfate, ammonium persulfate, and the like. These overlils! Two or more compounds that provide IN ion species may be used in combination.

Examples of the oxidizing agent include hydrogen peroxide, calcium hypochlorite, calcium chlorate, calcium chlorate, and calcium perchlorate.

The conductor layer provided on the semiconductor layer can be formed by, for example, solidifying a conductive paste, plating, metal vapor deposition, or the like. As the conductive paste, silver paste, copper paste, nickel paste, aluminum paste, carbon paste, etc. are preferable, but one type or two or more types of these may be used.

When two or more types are used, they may be mixed and layered, or they may be stacked as separate layers. After applying the conductive paste dropwise, it is left in the air or heated to solidify.

Examples of plating include nickel plating, copper plating, and aluminum plating. Further, examples of the adhering metal include aluminum, copper, and the like.

The common cathode terminal can be attached to the conductive layer using, for example, a conductive paste or soldered onto the conductive layer.

Before and after attaching the common cathode terminal, the combination may be strengthened by taping or the like.

The solid electrolytic capacitor of the present invention constructed as described above can be made into a general-purpose capacitor product for various uses by, for example, exterior packaging such as resin molding, resin case, metal exterior case, resin dipping, or laminate film exterior. can.

Effects of the Invention The solid electrolytic capacitor of the present invention can be made smaller and smaller in volume than conventional electrolytic capacitors, and has good capacitor performance.

Example EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1941 Ten small pieces each having a length of 1 ctrr and a width of 0.5 ctrr were cut from etched aluminum foil that had been electrochemically etched using alternating current. These 10 pieces were laminated and an anode terminal was caulked to one end to electrically and mechanically combine the pieces. Subsequently, an alumina oxide layer was formed by electrochemical treatment in an aqueous solution of boric acid and ammonium borate, and 10 sheets of low-pressure etched aluminum chemical foil (approximately 1 μF/c112
) is 1q. Subsequently, the chemically formed foil was immersed in an aqueous solution of lead acetate at a concentration of 1'U nyl/l, and a diluted aqueous solution of hydrogen peroxide in an amount of 0.5 times the mole of lead acetate was added. After leaving it for 1 hour, the lead dioxide layer deposited on the chemically formed foil was thoroughly washed with water.
It was dried under reduced pressure at ℃. Furthermore, the chemically formed foil with the lead dioxide layer adhered to it was immersed in a silver paste bath, pulled up, and then air-dried.

A solidified silver paste layer was formed on the lead dioxide layer of the chemically formed foil. Next, I left one end where the anode terminal was not connected and taped it with a width of 0.2 mm to form a laminated state, and then put the one end where the anode terminal was not connected in a solder bath and connected the common negative 8I terminal. . After that, a solid electrolytic capacitor was manufactured using resin.

Example 2 A laminated chemical foil similar to that in Example 1 was immersed in a 1.9 mol/p aqueous solution of lead nitrate except for a part of the anode terminal. Electrolytic oxidation was performed for 10 hours at a constant current using carbon as a cathode to form a lead dioxide layer on the chemically formed foil. The chemically formed foil was taken out from the electrolyte, thoroughly washed with water, and then dried under reduced pressure at 100° C. for 1 hour. A solid electrolytic capacitor was produced in the same manner as in Example 1.

Example 3 Vinegar M lead trihydrate 3.8 mol/Ω aqueous solution and ammonium persulfate 4. After mixing each of the Otl/9 aqueous solutions at a temperature of 50°C, a chemically formed foil similar to that in Example 1 was immersed in this mixture and heated to 80°C.
It was left at ℃ for 20 minutes. The semiconductor layer deposited on the chemically formed foil was thoroughly washed with water to remove unreacted substances, and then dried under reduced pressure at 120° C. for 1 hour. The produced semiconductor layer was composed of lead dioxide and 5A acid lead, and it was confirmed by quality analysis, X-ray analysis, and infrared spectroscopy that it contained approximately 25% by weight of lead dioxide. Subsequently, a solid electrolytic capacitor was produced in the same manner as in Example 1.

Example 4 A solid electrolytic capacitor 1 was produced in the same manner as in Example 1, except that the concentration of ammonium perllIII acid in forming the semiconductor in Example 3 was changed to 0.37 l/''. It was confirmed that the half and one body 1 at this time was a composition consisting of lead dioxide and lead sulfate, and contained approximately 35% by weight of lead dioxide.

Example 5 In Example 3, when forming a semiconductor layer, hydrogen peroxide solution was added at 0.05%.
A solid electrolytic capacitor was produced in the same manner as in Example 1, except that 57 l/l was added. It was confirmed that the semiconductor layer at this time was a composition consisting of lead dioxide and W11 lead, and that lead dioxide contained approximately 50%.

Comparative Example 1 A conventionally known sintered body of aluminum powder was used as an anode substrate to form an oxide film, and then immersed in an aqueous manganese nitrate solution for 6 hours and thermally decomposed 5 times to form a semiconductor layer made of manganese dioxide. did. After applying carbon paste and silver paste and drying, it was immersed in a solder bath and the cathode was taken out.

Next, a solid electrolytic capacitor was prepared by using resin 1.

Table 1 shows the characteristic values of the obtained capacitor.

Table 1 *Value at 120tlz Book - 1st shift at 120tlz ***Value at 20Kllz

[Brief explanation of drawings]

FIG. 1 is a sectional view of a solid electrolytic capacitor of the present invention, FIG. 2 is an equivalent circuit diagram of the solid electrolytic capacitor shown in FIG. 1, and FIG. 3 is a perspective view of a partially assembled anode base. FIG. 4 is a sectional view of a conventional solid electrolytic capacitor. 1... Anode terminal 2... Anode base 3...
Semiconductor layer 4, 5... Conductor layer 6... Solder layer 7... Anode terminal 8... Chemically formed foil
9...Semiconductor layer 10...Conductor layer
11...Cathode terminal 12...Anode terminal 13...Chemical foil patent applicant Showa Denko Co., Ltd. Agent Patent attorney Sei Kikuchi Figure 1 Figure 2 Figure 3

Claims (6)

[Claims] (1) In a valve metal etching foil of N pieces (N is a positive integer of 2 or more) having an oxide film layer partially electrically and mechanically connected to the anode terminal and combined, a semiconductor layer is formed on the oxide film layer. A solid electrolytic capacitor characterized in that conductor layers are sequentially provided on the semiconductor layer, and a common cathode terminal is further provided on the conductor layers. (2) The solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide as a main component. (3) The solid electrolytic capacitor according to claim 2, wherein the semiconductor layer containing lead dioxide as a main component is a layer electrochemically deposited from a reaction mother liquor containing lead ions. (4) The solid electrolyte according to claim 2, wherein the semiconductor layer containing lead dioxide as a main component is a layer chemically deposited from a reaction mother liquor containing a lead-containing compound and an oxidizing agent. capacitor. (5) The concentration of the lead-containing compound in the reaction mother liquor is in the range from 0.1 mol/l to the concentration that provides saturation solubility, and the oxidizing agent is in the range from 0.1 mol/l to 1 mol of the lead-containing compound. 5. A solid electrolytic capacitor according to claim 4, wherein the solid electrolytic capacitor is in the range of up to 5 moles. (6) The solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide and lead sulfate as main components.