JP2003151857A - Solid-state electrolytic capacitor and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrodeless solid-state electrolytic capacitor which assures an excellent high frequency characteristic, temperature characteristic and reliability characteristic. SOLUTION: This solid-state electrolytic capacitor is comprised of a capacitor element 20 wherein a dielectric material oxide film 12 is formed to an etching foil, and thereafter it is wound via a separator 13 between a pair of electrode foils 11 to form the electrolytic dielectric material oxide film on the cutting plane of the pair of electrode foils 11 in order to form a conductive polymer layer 14 of at least chemical oxide polymer to the area between the pair of electrode foils 11 and to the cutting plane; a cylindrical metal case 18 having a bottom for accommodating the capacitor element 20; and a sealing material 17 to seal the opening end of the metal case 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-polar solid electrolytic capacitor in which a conductive polymer is held on a capacitor element wound around a pair of electrode foils having a dielectric oxide film formed thereon via a separator, and a method for manufacturing the same. It is a thing.

[0002]

2. Description of the Related Art In recent years, with the digitization of electrical equipment,
The capacitors are also required to be small in size and large in capacity and have low impedance in the high frequency region. Conventionally, there are plastic capacitors, mica capacitors, and monolithic ceramic capacitors used in the high frequency region, but it is said that these capacitors are large in size and it is difficult to increase the capacity.

On the other hand, as a large capacity capacitor, there is an electrolytic capacitor such as an aluminum electrolytic capacitor or an aluminum or tantalum solid electrolytic capacitor. These capacitors can realize a large capacity because the oxide film serving as a dielectric is extremely thin, but on the other hand, the oxide film is likely to be damaged, and therefore an electrolyte for repairing the oxide film must be provided between the capacitor and the cathode.

In the above-mentioned aluminum electrolytic capacitor, an aluminum foil is subjected to an etching treatment to form a anodic oxidation conversion film, and an aluminum foil is subjected to an etching treatment. A cathode foil is wound between the anode foil and a separator to form a liquid electrolyte. It is used by impregnating the separator. Since this liquid electrolyte is ionic conductive and has a large specific resistance, loss is large, impedance frequency characteristics and temperature characteristics are significantly inferior, and further liquid leakage and evaporation are unavoidable, and capacity decreases and loss increases with time. Have a problem that occurs.

Further, since tantalum solid electrolytic capacitors use manganese dioxide as an electrolyte,
Although the problems of temperature characteristics and changes with time such as capacity and loss are improved, the frequency characteristics of loss and impedance are inferior to those of the multilayer ceramic capacitor or film capacitor because manganese dioxide has a relatively high specific resistance.

In recent years, a heterocyclic monomer such as pyrrole or thiophene is used as a supporting electrolyte to carry out electrolytic oxidative polymerization to produce a conductive polymer containing an anion of the supporting electrolyte as a dopant, which is used as an electrolyte (true cathode). A solid electrolytic capacitor having excellent characteristics and temperature characteristics has been proposed.

[0007]

However, a solid electrolytic capacitor using the above-mentioned conductive polymer as an electrolyte and an oxide film of a valve metal as a dielectric cannot avoid having a polarity, and a circuit and There was a problem that it could not be used on a circuit in which the voltage direction changed from time to time, and the polarity had to be distinguished even when mounting.

Further, the above-mentioned film capacitor having the electrodeposited polyimide thin film dielectric on the etching foil is non-polar, but the dielectric constant of polyimide is about 3, which is 1/3 of aluminum oxide, and 9 minutes of tantalum oxide. Therefore, it cannot be said that the volumetric efficiency is sufficiently high.

Further, when a conductive polymer is formed on the surface of a dielectric by electrolytic oxidation polymerization, it is necessary to make it conductive, and manganese dioxide is used for that purpose. To form this manganese dioxide, 30 manganese nitrate is used.
Although a method of thermally decomposing at a high temperature of about 0 ° C. was used, there was a problem that the dielectric film was easily damaged at that time.

Further, impurities of low molecular weight may be attached to the surface of the conductive polymer by electrolytic oxidation polymerization, and the adhesion with the colloidal graphite layer for forming a cathode laminated thereon is formed. There is also a problem that the peel strength is weak and peeling easily occurs.

The present invention solves the above-mentioned conventional problems, and can be used in a circuit in which the direction of alternating current or voltage changes from time to time, and high frequency characteristics, temperature characteristics, and reliability without the need to distinguish the polarity during mounting. An object is to provide a nonpolar solid electrolytic capacitor having excellent characteristics and a method for manufacturing the same.

[0012]

In order to achieve this object, the invention according to claim 1 of the present invention is a method for forming a dielectric oxide film on an etching foil and thereafter cutting the electrode foil between a pair of electrode foils. The electrode dielectric foil was wound around the separator with a separator, and an electrolytic dielectric oxide film was formed on the cut surface of the pair of electrode foils to form a chemically oxidatively polymerizable conductive polymer layer between and between the pair of electrode foils. A capacitor element, a cylindrical metal case having a bottom for accommodating the capacitor element, and a sealing material for sealing the open end of the metal case are provided. It can be used in a circuit whose direction changes from time to time, and has an effect of being excellent in high frequency characteristics, temperature characteristics, and reliability characteristics that do not require distinction in polarity during mounting.

According to a second aspect of the present invention, in the first aspect of the present invention, the conductive polymer layer is made of chemically polymerized polypyrrole, polyaniline, polythiophene, polyethylenedioxythiophene polystyrene sulfonic acid and derivatives thereof. Therefore, a conductive polymer layer having high conductivity can be easily formed, and it has an effect of excellent impedance characteristics and temperature characteristics in a high frequency range.

According to a third aspect of the present invention, a capacitor element is formed by forming a dielectric oxide film on an etching foil, and then winding the dielectric oxide film between the pair of electrode foils cut into a predetermined width with a separator interposed therebetween. Subsequently, the capacitor element is dipped in an electrolyte solution to form an electrolytic dielectric oxide film on the cut surface of the pair of electrode foils, and the capacitor element is dipped in a conductive polymerization solution to form the pair of electrode foils. After forming a chemically oxidatively polymerizing conductive polymer layer on the gap and the cut surface, insert this capacitor element into a cylindrical metal case with a bottom, and seal the open end of this metal case with a sealing material. The manufacturing method is based on the above method, and since the electrolytic dielectric oxide film can be uniformly formed on the surface of the pair of electrode foils and the cut surface thereof, it is a solid having excellent high frequency characteristics, temperature characteristics and reliability characteristics. It has the effect of being able to stably produce a solution capacitor.

According to a fourth aspect of the present invention, in the invention according to the third aspect, one or both of a pair of electrode foils is used as an anode when the electrolytic dielectric oxide film is formed with an electrolyte solution, and the electrolyte is used. The cathode is a solid conductive material immersed in a solution-containing container and / or an electrolyte solution, and an electrolytic dielectric oxide film having no defects is formed on a cut surface of a pair of electrode foils. It has the effect that it can be formed.

According to a fifth aspect of the invention, in the invention according to the third aspect, the electrolyte solution contains at least one or more selected from boric acid, phosphoric acid, carboxylic acid and these compounds as an electrolyte, and has a pH of 3 The manufacturing method is an aqueous solution of ~ 9, and has an action of forming a dense and uniform electrolytic dielectric oxide film.

According to a sixth aspect of the present invention, in the third aspect of the present invention, the electrolytic dielectric oxide film is formed on the cut surface of the pair of electrode foils by using different electrolyte solutions for each electrode foil. The electrode dielectric oxide film of the pair of electrode foils is different, so that each electrolytic dielectric oxide film is retained even when a reverse voltage is applied. It has the effect that

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are a partial cross-sectional perspective view showing the structure of the solid electrolytic capacitor of the present invention and an enlarged conceptual view of the essential part of the capacitor element. As shown in FIGS. A capacitor element 20 is produced by winding a pair of electrode foils 11 having a dielectric oxide film 12 formed on the foil by anodic oxidation with a separator 13 interposed therebetween, and a cut surface of the pair of electrode foils 11 of the capacitor element 20. An electrolytic dielectric oxide film (not shown) is formed on the conductive polymer layer 14 between the pair of electrode foils 11 and on the cut surface.
To form the capacitor element 20.

The capacitor element 20 is housed in a cylindrical metal case 18 having a bottom, and the open end of the metal case 18 is led out from each of the pair of electrode foils 11 by a rubber sealing member 17 for external extraction. It is configured by sealing 15 and 16 so as to penetrate the sealing material 17.

Then, the lead 1 pulled out from the sealing material 17
5, 5 and 16 were passed through the insulating seat plate 19, and the flattened portion on the lower surface of the insulating seat plate 19 was bent to form a surface-mounted solid electrolytic capacitor.

Next, a concrete example of the embodiment of the present invention will be described.

(Example 1) An aluminum foil was subjected to an etching treatment to roughen its surface to prepare an etching foil, and a dielectric oxide film (formation voltage 30V) was formed on the surface of this etching foil by anodizing treatment. The electrode foil was obtained by cutting into a size of. Two pieces of this electrode foil are prepared, a lead terminal is attached to each of the pair of electrode foils, and a nonwoven fabric separator (thickness 50 μm, weighing 25 g is provided between the pair of electrode foils.
/ M ² ) and a capacitor element was obtained by winding (capacitor at a frequency of 120 Hz when the capacitor element was impregnated with a 10 wt% ethylene glycol solution of ammonium adipate was 250 μF). ).

Subsequently, the above capacitor element was immersed in an electrolyte solution of a 5% ammonium borate aqueous solution (pH 4) contained in a stainless steel container, both lead terminals were used as anodes, and a stainless steel container was used as cathodes. An electrolytic dielectric oxide film was formed on the surface of the electrode foil and the cut surface thereof.

Subsequently, the capacitor element was mixed with a solution containing 1 part of ethylenedioxythiophene which is a heterocyclic monomer, 2 parts of ferric p-toluenesulfonate which is an oxidizing agent, and 4 parts of n-butanol which is a polymerization solvent. After that, the conductive polymer layer of polyethylenedioxythiophene was formed between the pair of electrode foils and the cut surface thereof by leaving it for 60 minutes at 85 ° C.

Subsequently, this capacitor element was washed with water and dried, and then a resin-vulcanized butyl rubber sealing material (consisting of 30 parts of butyl rubber polymer, 20 parts of carbon, and 50 parts of inorganic filler, sealing material hardness: 70 IRHD [International Rubber Hardness Units))
After enclosing it in a bottomed cylindrical aluminum case, the opening is sealed by curling, and both lead terminals led out from the anode foil and cathode foil are passed through an insulating seat plate made of polyphenylene sulfide, and the lead wire A flat mount type solid electrolytic capacitor was produced by bending the part into a flat shape (size: diameter 10 mm × height 8 mm).

(Example 2) Surface mounting was performed in the same manner as in Example 1 except that the electrolytic dielectric oxide film was formed by using an electrolyte solution of a 0.5% ammonium phosphate aqueous solution (pH 3). Type solid electrolytic capacitor was produced.

(Embodiment 3) A surface mount type is carried out in the same manner as in Embodiment 1 except that the electrolytic dielectric oxide film is formed by using an electrolyte solution of 2% ammonium adipate aqueous solution (pH 8). A solid electrolytic capacitor was produced.

(Embodiment 4) In the above Embodiment 1, the electrolytic dielectric oxide film of one electrode foil is formed by using an electrolytic solution of a 5% ammonium borate aqueous solution (pH 4) and the electrolytic dielectric material of the other electrode foil is used. A surface mount type solid electrolytic capacitor was produced in the same manner as in Example 1 except that an oxide solution was formed by using an electrolyte solution of a 2% ammonium adipate aqueous solution (pH 9).

(Example 5) In the above Example 1, the conductive polymer layer was added with a polypyrrole fine particle (average particle size 800 nm) of an electron conductive polymer of 5.0% by weight and a surfactant. Formed by using the above aqueous solution, polyethylenedioxythiophene was further prepared using a solution containing 1 part of ethylenedioxythiophene, 2 parts of ferric iron p-toluenesulfonate as an oxidant and 4 parts of n-butanol as a polymerization solvent. A surface mount type solid electrolytic capacitor was produced in the same manner as in Example 1 except that the conductive polymer layer of thiophene was formed.

Example 6 In Example 1, the conductive polymer layer was prepared by adding 1.0 mol / l of pyrrole to an aqueous solution containing 10 wt% of ethylene glycol and 0.25 of sodium alkylnaphthalenesulfonate as a dopant.
A conductive solution prepared by dissolving and adjusting so as to have a mol / l was used, and an aqueous solution containing 10 wt% of ethylene glycol in the oxidizing agent solution was used as an oxidizing agent.
I) 0.75 mol / l, sodium alkylnaphthalene sulfonate as a dopant 0.05 mol / l
l, except that the capacitor element was formed by dissolving sulfuric acid as an additive to a concentration of 0.75 mol / l and adjusting the capacitor element by alternately immersing the capacitor element in the conductive solution and the oxidizing solution five times. A surface mount type solid electrolytic capacitor was manufactured in the same manner as in Example 1.

(Example 7) In Example 1, the conductive polymer layer was formed by immersing it in an aqueous solution in which 3 wt% of sulfonated polyaniline was dissolved, and then 1 part of ethylenedioxythiophene and an oxidizing agent p. -Surface mount type, in the same manner as in Example 1 except that a conductive polymer layer of polyethylenedioxythiophene was formed using a solution containing 2 parts of ferric toluenesulfonate and 4 parts of n-butanol as a polymerization solvent. The solid electrolytic capacitor of was produced.

(Comparative Example) In the above-described Example 1, only one lead terminal of the pair of electrode foils was used as an anode, and a stainless steel container was used as a cathode for anodic oxidation, and electrolysis was performed on the surface of one electrode foil and its cut surface. A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the dielectric oxide film was formed (the other electrode foil was not provided with the electrolytic dielectric oxide film).

Examples 1 to 1 of the present invention produced as described above
7 and the solid electrolytic capacitor of the comparative example, the capacitance (measurement frequency 120 Hz), tan δ (measurement frequency 1
20 Hz), leakage current (2 minutes value after application of rated voltage of 16 V), and reverse leakage current (2 minutes value after application of DC 5 V) are shown in Table 1.

[0035]

[Table 1]

The number of tests is 50 in each case.
The average value is shown.

As is clear from Table 1, the solid electrolytic capacitors of Examples 1 to 7 of the present invention have high conductivity after the electrolytic dielectric oxide film is formed on the surfaces of the pair of electrode foils and the cut surfaces thereof. Since the molecular layer is formed, the characteristics of capacitance, tan δ, and leakage current are superior to those of the comparative example.

Although the dielectric oxide films of the pair of electrode foils are made equal (formation voltage 30V), when the reverse voltage of the circuit using the aluminum electrolytic capacitor is low, the dielectric oxide film of one of the electrode foils is low. The capacitance can be increased by lowering the formation voltage of the electrode foil than that of one of the electrode foils.

Although a non-woven fabric separator was used as the separator, a non-woven fabric composed mainly of synthetic resin is preferred among the non-woven fabric separators, and a non-woven fabric of polyethylene terephthalate resin or polybutylene terephthalate resin is most suitable.

[0040]

As described above, in the solid electrolytic capacitor of the present invention, the dielectric oxide film is formed on the etching foil, and then the electrode foil is cut between the pair of electrode foils and cut into a predetermined width. A capacitor element having a dielectric oxide film formed on the cut surface of the electrode foil and at least a conductive polymer layer formed between the pair of electrode foils and on the cut surface, and a bottomed cylindrical metal housing the capacitor element. It is composed of a case and a sealing plate that seals the open end of this metal case.It shows no polarity and can be used in circuits in which the direction of AC or voltage changes from time to time. It is possible to obtain a solid electrolytic capacitor which is excellent in high frequency characteristics, temperature characteristics and reliability characteristics without concern about connection.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view showing a configuration of a solid electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is an enlarged conceptual diagram of the main part of the capacitor element.

[Explanation of symbols]

11 electrode foil 12 Dielectric oxide film 13 separator 14 Chemically polymerizable conductive polymer layer 15,16 leads 17 Sealing material 18 metal cases 19 Insulation seat 20 Capacitor element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01G 9/24 C 9/05 G (72) Inventor Hiroki Kusagiya 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Munehiro Morukuma 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshihiro Watanabe 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A dielectric oxide film is formed on an etching foil, which is then wound with a separator between a pair of electrode foils cut into a predetermined width, and an electrolytic dielectric oxide film is formed on the cut surface of the pair of electrode foils. A capacitor element formed by forming a chemically oxidatively polymerizing conductive polymer layer between the pair of electrode foils and on the cut surface, a cylindrical metal case having a bottom for housing the capacitor element, and opening of the metal case. A solid electrolytic capacitor having a sealing material for sealing the ends. 2. The solid electrolytic capacitor according to claim 1, wherein the conductive polymer layer is polypyrrole, polyaniline, polythiophene, polyethylenedioxythiophene polystyrenesulfonic acid and derivatives thereof obtained by chemical oxidative polymerization. 3. A capacitor element is formed by forming a dielectric oxide film on an etching foil, and winding the dielectric foil between a pair of electrode foils cut into a predetermined width with a separator interposed therebetween.
Subsequently, the capacitor element is dipped in an electrolyte solution to form an electrolytic dielectric oxide film on the cut surface of the pair of electrode foils, and the capacitor element is dipped in a conductive polymerization solution to form the electrode foil pair. After forming a chemically oxidatively conductive polymer layer on the gaps and cut surfaces, insert this capacitor element into a cylindrical metal case with a bottom, and seal the open end of this metal case with a sealing material. Capacitor manufacturing method. 4. When forming an electrolytic dielectric oxide film with an electrolyte solution, one or both of a pair of electrode foils is used as an anode, and a container containing the electrolyte solution and / or a solid conductive material immersed in the electrolyte solution. The method for producing a solid electrolytic capacitor according to claim 3, wherein the organic substance is a cathode. 5. The solid electrolytic capacitor according to claim 3, wherein the electrolytic solution contains at least one selected from boric acid, phosphoric acid, carboxylic acid, and compounds thereof as an electrolyte and is an aqueous solution having a pH of 3-9. Production method. 6. The production of a solid electrolytic capacitor according to claim 3, wherein when forming the electrolytic dielectric oxide film on the cut surfaces of the pair of electrode foils, different electrolytic solutions are used for the respective electrode foils. Method.