WO2014091648A1

WO2014091648A1 - Production method for solid electrolytic capacitor element

Info

Publication number: WO2014091648A1
Application number: PCT/JP2013/005649
Authority: WO
Inventors: 内藤　一美; 正二矢部
Original assignee: 昭和電工株式会社
Priority date: 2012-12-11
Filing date: 2013-09-24
Publication date: 2014-06-19
Also published as: JPWO2014091648A1; JP5731720B2

Abstract

A solid electrolytic capacitor element is obtained using a method which includes: a step in which a surface of a positive electrode body comprising a valve action metal such as tungsten is subjected to electrolytic oxidation and chemically converted into a dielectric layer; a step in which electrolytic polymerization is used to form, upon the dielectric layer, a semiconductor layer comprising a conductive polymer; a step in which an electrode layer is formed upon the semiconductor layer; and a step in which an oxidant having an oxygen release function such as potassium persulfate and ammonium persulfate is supplied to the semiconductor layer or the dielectric layer.

Description

Method for manufacturing solid electrolytic capacitor element

The present invention relates to a method for manufacturing a solid electrolytic capacitor element. More specifically, the present invention relates to a method for manufacturing a solid electrolytic capacitor element in which an increase in leakage current is small during standing for a long time without sealing.

The solid electrolytic capacitor element is, for example, a dielectric layer made of a metal oxide by electrolytically oxidizing a sintered body of valve action metal powder such as tantalum, niobium, tungsten, etc. in an electrolyte aqueous solution such as phosphoric acid. And a semiconductor layer is formed on the dielectric layer by electrolytic polymerization or the like, and an electrode layer is further formed on the semiconductor layer. In such a manufacturing process, various proposals have been made in order to improve the characteristics of the solid electrolytic capacitor element.

For example, Patent Document 1 discloses that a fixed layer for supplying oxygen by applying a voltage is formed on a dielectric layer, and a voltage application process is performed after the capacitor is completed.
Patent Document 2 discloses that after the semiconductor layer is formed, the carbon layer and the silver paste layer are formed after impregnation with an acidic solution of water or an organic solvent in which an organic acid is dissolved. Patent Document 2 states that an organic acid produces an action as a dopant, and the conductivity of the semiconductor layer is improved. Moreover, the voltage application process is performed in the state immersed in the organic acidic solution.

JP 2007-173454 A JP 2007-242932 A

A solid electrolytic capacitor is manufactured by sealing the solid electrolytic capacitor element with a resin or the like. If a solid electrolytic capacitor element obtained by a conventional method is left as it is without sealing with resin or the like, the leakage current (hereinafter sometimes abbreviated as LC) may increase. If a repair process such as aging is performed after resin sealing the solid electrolytic capacitor element, the LC can be lowered to some extent. However, if the LC becomes significantly high, it is difficult to reduce the LC to a predetermined value or less even if the repair process is performed.

Also, the time from the completion of the manufacturing process of the solid electrolytic capacitor element to the start of the resin sealing process may be different for each manufacturing lot. In that case, the LC of the solid electrolytic capacitor may vary due to the difference in the standing time of the solid electrolytic capacitor element. In particular, in a solid electrolytic capacitor manufactured from an anode body mainly composed of tungsten, the magnitude of the LC variation due to the difference in the standing time is remarkable.

An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor element in which an increase in leakage current is small during standing for a long time without sealing.

The present inventors diligently studied to achieve the above object. As a result, an invention including the following aspects has been completed.

[1] A step of electrolytically oxidizing a surface of an anode body made of a valve metal to form a dielectric layer, a step of forming a semiconductor layer made of a conductive polymer on the dielectric layer, and the semiconductor layer A method of manufacturing a solid electrolytic capacitor element, comprising: forming an electrode layer on the substrate; and supplying an oxidant having an oxygen releasing function to the semiconductor layer or the dielectric layer.

[2] The step of supplying includes the step of bringing a solution containing an oxidizing agent having an oxygen releasing function into contact with a solution obtained in the step of forming the semiconductor layer or the step of forming an electrode layer. The manufacturing method as described.
[3] What is obtained in the step of forming the electrode layer is partly in a region where the electrode layer is not formed on the semiconductor layer,
The supplying step includes the step of bringing the region into contact with a solution containing an oxidant having an oxygen releasing function, according to [1] or [2].
[4] The manufacturing method according to [3], wherein the supplying step includes immersing the region in a solution containing an oxidizing agent having an oxygen releasing function.

[5] The manufacturing method according to any one of [2] to [4], further including a step of removing the solution from the electrode layer surface after the supplying step.
[6] The manufacturing method according to [3], wherein the supplying step includes impregnating a solution containing an oxidizing agent having an oxygen releasing function from the region.
[7] The production method according to any one of [2] to [6], wherein the solution containing the oxidizing agent contains a solvent containing 80% by mass or more of water.

[8] The production method according to any one of [2] to [7], wherein the solution containing an oxidizing agent contains the oxidizing agent in an amount of 0.1% by mass or more and saturated solubility or less with respect to the solvent.
[9] The production method according to any one of [2] to [8], wherein the temperature of the solution in the supplying step is 20 to 60 ° C.
[10] The oxidizing agent having an oxygen releasing function is at least one selected from the group consisting of a manganese (VII) compound, a chromium (VI) compound, a halogen acid compound, a persulfate compound, and an organic peroxide. ] The production method according to any one of [9] to [9].
[11] The production method according to any one of [1] to [9], wherein the oxidizing agent having an oxygen releasing function is a persulfuric acid compound.
[12] The manufacturing method according to any one of [1] to [11], wherein the anode body is a sintered body of tungsten powder.

When a conventional solid electrolytic capacitor element is left unsealed for a long time, LC (leakage current) may fluctuate greatly. On the other hand, according to the manufacturing method of the present invention, it is possible to obtain a solid electrolytic capacitor element in which an increase in leakage current is small while left for a long time without sealing. Also, by using such a solid electrolytic capacitor element, the variation in leakage current between production lots of solid electrolytic capacitors is reduced.
The effect of the manufacturing method of the present invention is particularly remarkable in a solid electrolytic capacitor element using an anode body made of a sintered body of tungsten powder.

It is a conceptual diagram which shows the cross section of the element obtained through the process of forming a semiconductor layer on a dielectric material layer. It is a conceptual diagram which shows the cross section of the element obtained through the process of forming an electrode layer (carbon layer) on a semiconductor layer. It is a conceptual diagram which shows the cross section of the element obtained through the process of forming an electrode layer (a carbon layer and a metal layer) on a semiconductor layer. It is a conceptual diagram which shows the state which immersed the element shown in FIG. 3 in the solution containing an oxidizing agent.

A method for manufacturing a solid electrolytic capacitor element according to an embodiment of the present invention includes a step of electrolytically oxidizing a surface of an anode body made of a valve action metal to form a dielectric layer, and electrolytic polymerization on the dielectric layer. A step of forming a semiconductor layer made of a conductive polymer, a step of forming an electrode layer on the semiconductor layer, and a step of supplying an oxidant having an oxygen release function to the semiconductor layer or the dielectric layer. .

The anode body is manufactured from a valve action metal or its alloy. Examples of the valve action metal include aluminum, tantalum, niobium, titanium, and tungsten. Here, the anode body preferably has 99% by mass or more of the valve metal element in the total amount of metal elements. Alloys include those in which a part of the valve metal is chemically bonded to other metals or non-metals.

In order to increase the area of the dielectric layer, the anode body is preferably porous. The porous anode body can be obtained, for example, by sintering a raw material powder made of a valve action metal or a conductive oxide thereof. The raw material powder has a 50% particle diameter (D50) in the volume-based cumulative particle size distribution of preferably 0.1 to 1 μm, more preferably 0.1 to 0.7 μm, and even more preferably 0.1 to 0.3 μm. . The raw material powder may be granulated powder. The granulated powder can be produced, for example, by sintering and pulverizing raw powder composed of an ungranulated valve action metal or a conductive oxide thereof. Further, the granulated powder may be produced by sintering and pulverizing the granulated powder once produced. The granulated powder has a 50% particle size (D50) in a volume-based cumulative particle size distribution of preferably 20 to 200 μm, more preferably 26 to 180 μm.

The valve action metal powder, particularly tungsten powder, preferably contains silicon, boron, phosphorus, oxygen and / or nitrogen. The method for incorporating these elements into the metal powder is not particularly limited. For example, when producing granulated powder from tungsten powder, silicon source such as silicon powder, boron source such as boric acid, phosphorus source such as phosphoric acid, oxygen source such as oxygen gas and / or nitrogen source such as nitrogen gas The method by adding or introduce | transducing is mentioned.

The sintered body is obtained by pressure-molding raw material powder to obtain a molded body and firing it in a furnace. In order to facilitate pressure molding, a binder may be mixed with the raw material powder. Various conditions such as the amount of powder and the molding apparatus can be appropriately set so as to obtain a desired molding density and the like. The anode body has a porosity of preferably 40 to 60% by volume. The anode body preferably has a rectangular parallelepiped shape. At least one of the eight corners of the rectangular parallelepiped may be chamfered or rounded.

When forming the raw material powder, an anode lead wire can be embedded in the molded body and planted to serve as a terminal of the anode body. As the anode lead wire, a metal such as tungsten, tantalum, niobium, or an alloy wire thereof can be used. Further, the anode lead wire can be welded and connected to the sintered body later. A metal plate or metal foil may be planted or welded to the sintered body instead of the metal wire.

Electrolytic oxidation can be performed according to a known procedure. In electrolytic oxidation, for example, the anode body is immersed in a chemical formed by dissolving an electrolyte such as nitric acid, sulfuric acid, phosphoric acid, oxalic acid, or adipic acid and, if necessary, an oxygen supply agent such as hydrogen peroxide or ozone. This is done by applying a voltage to this. The voltage is applied between the anode body (anode) and the counter electrode (cathode). Energization of the anode body can be performed through the planted anode lead wire. The electrolytic oxidation may be repeated a plurality of times. By this electrolytic oxidation, the surface of the sintered body (the surface of the pores in the sintered body and the outer surface of the sintered body) can be formed into a dielectric layer. In this electrolytic oxidation, a part of the anode lead wire can also be formed into a dielectric layer. The dielectric layer is made of a metal oxide constituting the anode body. An electrolyte, an additive, or the like may enter the dielectric layer during electrolytic oxidation.

After the chemical conversion treatment, the sintered body is washed with pure water. By this washing, the chemical conversion liquid is removed as much as possible. It is preferable to perform a high-temperature drying treatment after water removal. Drying is performed at a temperature above the boiling point of water, preferably at 160 ° C or higher. The upper limit of the temperature during drying is preferably 250 ° C. More preferable drying is first performed at a temperature of 105 ° C. or higher and lower than 160 ° C., and then performed at a temperature of 160 ° C. or higher and 230 ° C. or lower. When drying is performed at such a temperature, the capacity in the low and high frequency ranges increases by about 10 to 15%. The drying time is not particularly limited as long as the stability of the dielectric layer can be maintained, and is preferably 10 minutes to 2 hours, more preferably 20 minutes to 60 minutes. The chemical conversion treatment may be performed again after drying. The re-chemical conversion treatment can be performed under the same conditions as the first chemical conversion treatment. After the re-chemical conversion treatment, pure water washing, water removal and drying can be performed as described above.

Next, a semiconductor layer is formed on the dielectric layer. The semiconductor layer used in the conventional solid electrolytic capacitor element can be used without limitation. As shown in FIG. 1, the semiconductor layer 3 includes a part of the anode lead wire in the vicinity of the sintered body on which the dielectric layer 2 is formed, the pore surface in the sintered body, and the dielectric present on the outer surface of the sintered body. It is preferable to form so as to cover the body layer 2. In addition, it is thought that the element | device obtained through the process of forming a semiconductor layer has sufficient pores for an oxidant solution described later to permeate.

The semiconductor layer 3 is preferably made of a conductive polymer. As the conductive polymer, polypyrrole or a derivative thereof, polythiophene or a derivative thereof (for example, a polymer of 3,4-ethylenedioxythiophene), polysulfide or a derivative thereof, polyfuran or a derivative thereof, polyaniline or a derivative thereof And polymers such as derivatives thereof. The semiconductor layer made of a conductive polymer may include a plurality of layers having different types of conductive polymers and the formation method. The conductive polymer layer can also be obtained by electrolytic polymerization or the like.

An electrode layer is formed on the semiconductor layer. The electrode layer is preferably formed of a carbon layer and a metal layer in this order. The electrode layer is preferably not formed on the surface (cross section XX) where the anode lead wire is implanted.
The carbon layer can be formed by depositing a carbon paste on the semiconductor layer and then drying and curing it.
The carbon paste contains conductive carbon, a resin, a solvent, and other additives as necessary. Examples of the additive include an oxidizing agent, a dispersant, and a pH adjuster.
The carbon paste can be attached by various methods depending on the shape of the anode body. Specifically, the carbon paste can be attached by immersing the anode body in which the semiconductor layer is formed in the carbon paste bath, or by transferring the carbon paste attached to the base material onto the semiconductor layer. .

The dried carbon paste is dried at a temperature not lower than the boiling point of the solvent, preferably 100 ° C. or higher. The upper limit of the temperature during drying is preferably 160 ° C. More preferable drying is performed at a temperature of 105 ° C. or higher and lower than 150 ° C. When drying is performed at such a temperature, the solvent can be appropriately removed and a homogeneous carbon layer can be formed. The drying time is not particularly limited as long as the solvent can be removed, and is preferably 5 minutes to 2 hours, more preferably 15 minutes to 30 minutes. Drying may be performed in the air or in a stream of inert gas such as argon gas or nitrogen gas. By carrying out under reduced pressure up to about 10 kPa, drying can be completed at a lower temperature or in a shorter time. Considering mass production industrially, it is preferable to carry out at atmospheric pressure from the viewpoint of cost. The chemical conversion treatment may be performed again after drying. The re-chemical conversion treatment can be performed under the same conditions as the first chemical conversion treatment. After the re-chemical conversion treatment, pure water washing, solvent removal, and drying can be performed in the same manner as described above. The drying and curing conditions can be appropriately set by combining the above conditions.

Furthermore, a metal layer can be formed on the carbon layer as necessary. The metal layer can be formed by depositing a conductive metal paste, such as silver, or by plating a conductive metal.

In the manufacturing method of the present invention, an oxidizing agent having an oxygen releasing function is supplied to the semiconductor layer or the dielectric layer. In order to supply the oxidant to the semiconductor layer or the dielectric layer, for example, a solution containing an oxidant having an oxygen releasing function in an element (FIG. 1) obtained through a step of forming a semiconductor layer on the dielectric layer (Hereinafter also referred to as an oxidant solution), a method of contacting an oxidant solution with an element (FIG. 2) obtained through a step of forming a carbon layer on a semiconductor layer, and a top of the carbon layer And a method of bringing an oxidant solution into contact with an element (FIG. 3) obtained through a step of forming a metal layer. The semiconductor layer or dielectric layer is impregnated with the oxidant solution by contact with the oxidant solution.
For contact with the oxidant solution, a means for immersing the element obtained in each step in the oxidant solution, or a means for applying, spraying or dropping the oxidant solution to the element obtained in each step is adopted. Can do. In order to supply the oxidant solution to the semiconductor layer or the dielectric layer, at least the oxidant solution is brought into contact with a region where the electrode layer is not formed on the semiconductor layer, for example, a region indicated by 8 in FIG. Is preferred.
In the present invention, from the viewpoint of production efficiency and the like, it is preferable to immerse an element obtained through a step of forming an electrode layer on a semiconductor layer in an oxidant solution. In the immersion in the oxidizer solution, as shown in FIG. 4, the planted surface of the anode lead wire (cross section XX (the electrode layer is not formed on this surface)) is the oxidizer solution. It is preferable that the element is submerged so as to be immersed in 9. By immersing in the oxidant solution, the oxidant can be efficiently supplied to the semiconductor layer or the dielectric layer of the device.

As the oxidizing agent having a function of releasing oxygen, at least one selected from the group consisting of a manganese (VII) compound, a chromium (VI) compound, a halogen acid compound, a persulfate compound, and an organic peroxide is preferable. Specifically, manganese (VII) compounds such as permanganate; chromium (VI) compounds such as chromium trioxide, chromate, dichromate; perchloric acid, chlorous acid, hypochlorous acid and And halogen acid compounds such as salts thereof; organic acid peroxides such as peracetic acid, perbenzoic acid and salts and derivatives thereof; and persulfuric acid compounds such as persulfuric acid and salts thereof. Of these, persulfate compounds such as ammonium persulfate, potassium persulfate, and potassium hydrogen persulfate are preferred from the viewpoints of ease of handling, stability as an oxidizing agent, and water solubility. These oxidizing agents can be used alone or in combination of two or more.
The amount of the oxidizing agent contained in the oxidizing agent solution is preferably 0.1% by mass or more and saturated solubility or less, more preferably 0.5% by mass or more and 20% by mass or less, and further preferably 0.5% by mass with respect to the solvent. % To 10% by mass. If the amount of the oxidizing agent is too small, a plurality of immersions and dryings are necessary to obtain a desired effect, and the production efficiency tends to decrease.

Favorable solvents used for the oxidant solution include water-soluble solvents such as water, methanol and ethanol. As the solvent used in the present invention, a solvent containing 80% by mass or more of water is preferable, a solvent containing 90% by mass or more of water is more preferable, and a solvent containing 95% by mass or more of water is more preferable. It is preferable to add a small amount of a water-soluble solvent such as ethanol since the surface tension of the solution is lowered and the penetration into the anode body pores is increased.

The solution temperature at the time of contacting with the oxidant solution is preferably lower than the boiling point of the solvent and high from the viewpoint of dissolving a large amount of the oxidant, but if the temperature is too high, it is necessary to replenish the solvent evaporation frequently. Therefore, it is preferably 20 ° C. to 60 ° C., more preferably 25 ° C. to 50 ° C., and further preferably 30 ° C. to 50 ° C. The contact time with the oxidant solution is determined from a preliminary experiment or the like in consideration of the size of the anode body.

It is preferable to remove the solution from the electrode layer surface after the step of contacting with the oxidant solution. The removal of the oxidant solution can be performed, for example, by a method of immersing in water except for the surface on which the anode lead wire is planted. The temperature of water when immersed in water is preferably 20 ° C. to 60 ° C. The time for immersing in water is determined from a preliminary experiment in consideration of the size of the anode body. This immersion in water is thought to leave the oxidant supplied to the semiconductor layer or dielectric layer of the capacitor element as it is, and remove the oxidant from the electrode layer surface. It is preferable not to dry the oxidant solution adhering to the capacitor element between the step of immersing in the oxidant solution and the step of immersing in water. Once the oxidant is precipitated by drying of the oxidant solution, it is difficult to redissolve in water. Therefore, the oxidant may remain on the electrode layer surface even when immersed in water. Since the oxidizing agent may hinder the conductivity, the electric resistance between the electrode layer and the external terminal tends to increase.

Then, dry to remove water. Prior to drying, drying may be performed after immersing in a water-soluble solvent such as ethanol to promote water evaporation.

A solid electrolytic capacitor element is obtained through the above steps. According to the manufacturing method of the present invention, the oxidant solution that has entered from the semiconductor layer formed on the surface where the lead wire is implanted is supplied to the semiconductor layer or the dielectric layer through the pores in the anode body. Thereafter, when the solvent is removed from the solution, oxygen supplied from the oxidizing agent is considered to contribute to the standing stability of the dielectric layer.

Next, a cathode lead is electrically connected to the electrode layer, and a part of the cathode lead is exposed outside the exterior of the electrolytic capacitor to become a cathode external terminal. On the other hand, an anode lead is electrically connected to the anode body via an anode lead wire, and a part of the anode lead is exposed outside the exterior of the electrolytic capacitor and becomes an anode external terminal. A normal lead frame can be used to attach the cathode lead and the anode lead. Subsequently, the exterior can be formed by sealing with a resin or the like to obtain a solid electrolytic capacitor. The solid electrolytic capacitor thus produced can be subjected to an aging treatment as desired. The obtained solid electrolytic capacitor can be used by being mounted on various electric circuits or electronic circuits.

Hereinafter, the present invention will be described more specifically with reference to examples. Note that these are merely illustrative examples, and the present invention is not limited by these.

Various characteristics were measured as follows.
(Leak current)
2.5 V was applied to the capacitor element at room temperature. When 15 seconds passed from the start of voltage application, the current value (leakage current) of the circuit from the positive terminal of the power source to the anode lead wire of the capacitor element, the electrode layer of the capacitor element, and the negative terminal of the power source was measured. The average of the measured values for 40 capacitor elements randomly selected was calculated.

(Elemental analysis)
The element content in the anode body was determined by ICP emission analysis using ICPS-8000E (manufactured by Shimadzu Corporation). Further, the amount of nitrogen and the amount of oxygen in the anode body were determined by a thermal conductivity method and an infrared absorption method, respectively, using an oxygen / nitrogen analyzer (TC600 manufactured by LECO). The average of the measured values for three randomly selected anode bodies was calculated.

(50% particle size)
The particle size distribution was measured by a laser diffraction scattering method using HRA 9320-X100 manufactured by Microtrack, and the 50% particle size (D50) in the volume-based cumulative particle size distribution was determined.

Example 1
(Production of sintered body)
Tungsten trioxide was reduced with hydrogen to obtain a primary tungsten powder having a 50% particle size of 0.5 μm (particle size distribution range: 0.1 μm to 1 μm). This powder was mixed with 0.3% by mass of silicon powder having a 50% particle diameter of 60 nm. The mixed powder was heated at 1250 ° C. under reduced pressure for 30 minutes. After returning to room temperature, the lump is crushed, and the particle size is 87 μm (particle size distribution range is 26 μm to 180 μm, and the mesh openings in the mass distribution by sieving have peaks in the range of 53 to 63 μm and 106 to 125 μm). Granulated powder was obtained.

The granulated powder was pressed and solidified using a TAP-2R molding machine manufactured by Seken Co., Ltd. to produce a molded body. At the time of this molding, a tantalum wire (anode lead wire) having a diameter of 0.29 mmφ and a length of 9.8 mm was embedded in 3.8 mm, and 6 mm outside was planted.
The obtained molded body was placed in a vacuum firing furnace and sintered at a temperature of 1520 ° C. for 20 minutes. Thereafter, the temperature was lowered to room temperature. A plurality of hexahedron sintered bodies having a size of 1.0 mm × 1.5 mm × 4.5 mm (lead wires were planted on a 1.0 mm × 1.5 mm surface. 3.8 mm inside and 6 mm outside) were produced.
The ratio of the sintered body density to the green body density was 1.06. The mass of the anode body excluding the anode lead wire was 60 ± 2 mg.

[Formation of dielectric layer (chemical conversion treatment)]
i) Electrolytic oxidation A 3 mass% ammonium persulfate aqueous solution was prepared as a chemical conversion solution. The chemical conversion liquid was put into a stainless steel container. The sintered body was hung by holding the tip of the anode lead wire. The suspended sintered body was immersed in the chemical forming solution from the surface on which the entire sintered body and the anode lead wire were erected to a position where the lead wire 3.5 mm was sunk. The lead wire was connected to the anode, the container was connected to the cathode, and a voltage of 10 V was applied for 6 hours in the chemical liquid at a liquid temperature of 50 ° C.
ii) Water washing-water removal-drying Subsequently, washing with pure water was performed to remove the chemical conversion liquid in the pores of the sintered body. Thereafter, most of the water adhering to the surface (including the surface in the pores) was removed by soaking in ethanol and stirring. It was pulled from ethanol and dried at 190 ° C. for 30 minutes. The surface of the sintered body was formed into a tungsten trioxide dielectric layer.

[Lamination of semiconductor layers]
i) Immersion step The sintered body on which the dielectric layer was formed was hung by holding the tip of the anode lead wire. In a 10% by mass ethylenedioxythiophene (hereinafter abbreviated as EDOT) ethanol solution, the anode lead wire 0.2 mm sinks from the surface on which the entire sintered body and anode lead wire are planted. Soaked into position. It pulled up from the ethanol solution and dried at room temperature. Next, the sintered body suspended in a 10% by mass aqueous solution of toluenesulfonic acid iron was immersed from the surface on which the entire sintered body and the anode lead wire were planted to a position where the lead wire was sinked by 0.2 mm. The EDOT was reacted by pulling up from the aqueous solution and allowing to stand at 60 ° C. for 10 minutes. This series of operations was repeated three times to obtain a treated body.

ii) Electropolymerization process The tip of the anode lead wire was held and the treatment body was hung. The suspended treatment body was immersed in a 10 mass% EDOT ethanol solution from the surface where the entire treatment body and the anode lead wire were planted to a position where the anode lead wire 0.2 mm was sunk. The ethanol solution was pulled up. Subsequently, the anode lead wire 0.2 mm sinks from the surface on which the entire treatment body and the anode lead wire are planted in the polymer solution having a liquid temperature of 20 ° C. stored in a stainless steel (SUS303) container. Soaked into position. A voltage was applied between the anode lead wire and the container, and electrolytic polymerization was performed at 60 μA per piece for 60 minutes. The polymerization solution is obtained by dissolving supersaturated EDOT and 3% by mass of anthraquinone sulfonic acid in a solvent composed of 70 parts by mass of water and 30 parts by mass of ethylene glycol. Thereafter, the polymer solution was pulled up, washed with pure water and washed with ethanol, and then dried at 80 ° C. As shown in FIG. 1, a semiconductor layer 3 made of a conductive polymer was laminated on the surface of the dielectric layer 2. The anode lead 1 and the semiconductor layer 3 are separated by a dielectric layer 2.

iii) Post-chemical conversion step A 3% by mass aqueous ammonium persulfate solution was prepared as a chemical conversion solution. The processing body on which the semiconductor layer was formed was hung by holding the tip of the anode lead wire. The process body suspended in the chemical liquid was immersed from the surface where the entire process body and the anode lead wire were planted to a position where the anode lead wire was sinked by 0.2 mm. In the chemical solution at a liquid temperature of 20 ° C., a voltage of 7 V was applied for 15 minutes. It was pulled out from the chemical conversion liquid, washed with pure water and ethanol, and then dried.

Thereafter, the above-mentioned dipping step-electrolytic polymerization step-post-chemical conversion step was further repeated 5 times (6 times in total). The second to third electropolymerizations were carried out under the condition of 70 μA per piece. The fourth to sixth electropolymerizations were performed under the condition of 80 μA per one.

(Lamination of electrode layers)
As shown in FIG. 2, the carbon paste is attached to the treatment body on which the semiconductor layer is formed except the surface where the anode lead wire is planted, and is dried in air at 105 ° C. for 30 minutes using a constant temperature dryer. Thus, the carbon layer 4 was formed. As the carbon paste, T-602 manufactured by Nippon Graphite Co., Ltd. was used.
Next, as shown in FIG. 3, a silver paste was applied on the carbon layer 4 and dried to form a metal layer 5. The silver paste was mixed with 94% by mass of silver powder (AGC252 manufactured by Fukuda Metal Foil Powder Industry) and 6% by mass of acrylic resin (polymethyl methacrylate manufactured by Aldrich), and butyl acetate was added as a solvent so that the solid content was 30% by mass. Were used. The electrode layer is not formed on the surface (XX) where the anode lead wire of the processed body thus fabricated is planted, and the semiconductor layer is exposed.

[Immersion in oxidizer solution]
A 50 ° C. solution in which 5% by volume of ethanol was added to a 1% by mass ammonium persulfate aqueous solution was prepared as an oxidant solution.
The treated body on which the electrode layer was formed by holding the anode lead wire was hung. As shown in FIG. 4, the suspended treatment body was immersed in an oxidant solution at 50 ° C. until the semiconductor layer formed on the whole treatment body and the lead wire sinks, and left for 30 minutes. It pulled up from the oxidizing agent solution, and while the surface of the treated body did not dry, the treated body suspended in water at 30 ° C. was immersed except for the planted surface of the anode lead wire and allowed to stand for 40 minutes. . The oxidizing agent solution adhering to the electrode layer surface was removed. By these operations, an oxidizing agent was supplied to the semiconductor layer and the dielectric layer.
The treated body pulled up from water and suspended in ethanol at 23 ° C. was immersed to the position where the entire treated body and the semiconductor layer formed on the lead wire sink, and allowed to stand for 20 minutes. It pulled up from ethanol and dried at 105 degreeC.
128 solid electrolytic capacitor elements were produced as described above.

The leakage current was measured for 30 pieces of the solid electrolytic capacitor elements obtained indiscriminately, and the average (denoted as initial LC in the table) was calculated. Then, 30 of them were left in a constant temperature and humidity chamber at 35 ° C. and 80% RH for 7 days. Then, the leakage current was measured about them, and the average (it describes with LC after leaving in the table | surface) was computed. The results are shown in Table 1. The anode body had a silicon content of 2880 mass ppm, an oxygen content of 5200 mass ppm, and the total amount of elements (impurity elements) other than tungsten, silicon, and oxygen was 300 mass ppm or less.

Examples 2-4
Solid electrolytic capacitor elements were produced in the same manner as in Example 1 except that the oxidant solution was changed to that shown in Table 1, and their leakage currents were measured. The results are shown in Table 1.

Comparative Example 1
Solid electrolytic capacitor elements were produced by the same method as in Example 1 except that the immersion in the oxidant solution was not performed, and the leakage currents were measured. The results are shown in Table 1.

Examples 5 to 8 and Comparative Example 2
Change the 50% particle size of tungsten primary powder to 0.3μm (particle size distribution range 0.05-3μm), mix 3% by weight boric acid aqueous solution instead of mixing silicon powder, depressurize 125 ° C before heating at 1250 ° C Under the condition that water was removed under the condition, the temperature of the vacuum baking furnace was changed to 1500 ° C., the chemical conversion solution was changed to a 2 mass% potassium persulfate aqueous solution, the voltage during chemical conversion was changed to 12 V, and EDOT was changed to pyrrole. Solid electrolytic capacitor elements were produced in the same manner as in Examples 1 to 4 and Comparative Example 1. The results are shown in Table 2. In the anode body, the boron content was 106 mass ppm, the oxygen content was 7500 mass ppm, and the total amount of elements (impurity elements) other than tungsten, oxygen, and boron was 300 mass ppm or less.

From the above results, oxygen release is achieved by immersing the element obtained in the process of forming the semiconductor layer or the process of forming the electrode layer in a solution containing an oxidizing agent having an oxygen release function such as potassium persulfate or ammonium persulfate. It can be seen that when an oxidizing agent having a function is supplied to the semiconductor layer or the dielectric layer, a solid electrolytic capacitor element having a small increase in leakage current during standing for a long time without sealing is obtained. It can be seen that the oxidizing agent having an oxygen releasing function supplied to the semiconductor layer or the dielectric layer contributes to the stability of the dielectric layer.

1: Anode lead 2: Dielectric layer 3: Semiconductor layer 4: Carbon layer 5: Metal layer 6: A portion of the anode lead where the dielectric layer is not formed 7: Near the sintered body where the dielectric layer is formed 8: part of anode lead wire 8: region in which electrode layer is not formed on semiconductor layer 9: solution containing oxidant having oxygen releasing function XX: plane YY where anode lead is implanted Y: oxygen Level of solution containing oxidizing agent with release function

Claims

A step of electrolytically oxidizing the surface of an anode body made of a valve metal to form a dielectric layer;
Forming a semiconductor layer made of a conductive polymer on the dielectric layer;
Forming an electrode layer on the semiconductor layer;
And a step of supplying an oxidant having an oxygen releasing function to the semiconductor layer or the dielectric layer.
The manufacturing according to claim 1, wherein the supplying step includes a step of bringing a solution containing an oxidizing agent having an oxygen releasing function into contact with a solution obtained in the step of forming the semiconductor layer or the step of forming an electrode layer. Method.
What is obtained in the step of forming the electrode layer is partly a region where the electrode layer is not formed on the semiconductor layer,
The manufacturing method according to claim 1, wherein the supplying step includes bringing the region into contact with a solution containing an oxidizing agent having an oxygen releasing function.
The manufacturing method according to claim 3, wherein the supplying step includes immersing the region in a solution containing an oxidizing agent having an oxygen releasing function.
5. The manufacturing method according to claim 2, further comprising a step of removing the solution from the electrode layer surface after the supplying step.
The manufacturing method according to claim 3, wherein the supplying step includes impregnating a solution containing an oxidizing agent having an oxygen releasing function from the region.
The production method according to any one of claims 2 to 6, wherein the solution containing the oxidizing agent contains a solvent containing 80% by mass or more of water.
The production method according to any one of claims 2 to 7, wherein the solution containing the oxidizing agent contains the oxidizing agent in an amount of 0.1% by mass or more and saturated solubility or less with respect to the solvent.
The production method according to any one of claims 2 to 8, wherein the temperature of the solution in the supplying step is 20 to 60 ° C.
The oxidizing agent having an oxygen releasing function is at least one selected from the group consisting of manganese (VII) compounds, chromium (VI) compounds, halogen acid compounds, persulfate compounds, and organic peroxides. The manufacturing method as described in any one of these.
The production method according to any one of claims 1 to 9, wherein the oxidizing agent having an oxygen releasing function is a persulfuric acid compound.
The method according to any one of claims 1 to 11, wherein the anode body is a sintered body of tungsten powder.