JP4654637B2 - Manufacturing method of aluminum electrolytic capacitor - Google Patents

Description

  The present invention relates to an aluminum electrolytic capacitor used in various electronic devices and a method for manufacturing the same.

  A general aluminum electrolytic capacitor includes an anode foil in which a dielectric oxide film is formed by anodic oxidation on a surface of which an effective surface area is expanded by etching the aluminum foil, and a cathode foil in which the effective surface area is expanded by etching the aluminum foil. Is wound through a separator to form a capacitor element. The capacitor element is impregnated with a driving electrolyte, and the capacitor element is housed in a metal case. The opening of the metal case is sealed by a sealing body. It has a sealed configuration.

  As the driving electrolyte, a solution in which ethylene glycol or γ-butyrolactone is used as a main solvent and an ammonium salt of an organic acid is added to the main solvent is often used, and as a sealing body, styrene butadiene rubber (SBR), Many are made of ethylene propylene rubber (EPM) and butyl rubber (IIR).

  In recent years, with the downsizing, digitization, and high reliability of electronic devices, there has been a strong demand for miniaturization of the needs for users of aluminum electrolytic capacitors. To that end, anode foil and cathode foil used for aluminum electrolytic capacitors It is necessary to increase the capacitance per unit area.

  In order to increase the effective surface area of the anode foil and the cathode foil and increase the capacitance per unit area, it is generally chemically performed in an aqueous hydrochloric acid solution to which an acid forming a film such as sulfuric acid, nitric acid, phosphoric acid, and oxalic acid is added. Alternatively, it can be achieved by electrochemically performing etching treatment, and by devising and improving conditions such as the electrolyte composition and current density of the etching treatment, the capacitance and mechanical strength of the anode foil and cathode foil We are trying to improve the characteristics.

For example, Patent Documents 1 and 2 are known as prior art document information relating to the invention of this application.
Japanese Patent Laid-Open No. 02-189912 Japanese Patent Laid-Open No. 2003-96599

  However, in the conventional aluminum electrolytic capacitor, the expansion of the electrostatic capacity by the etching process of the anode foil and the cathode foil needs to increase the dispersibility of the pits that can be formed by the etching process as much as possible. Since the liquid resistance increases, efficient etching is approaching its limit. In particular, the cathode foil has a thin aluminum foil thickness of 20 to 50 μm, and it is difficult to improve the expansion of the effective area by the etching process.

  In addition, a lead wire is attached to the cathode foil for extracting the electric charge. However, a potential difference is generated between the lead wire and the cathode foil, current flows and causes corrosion, and there is a problem in the life characteristics of the aluminum electrolytic capacitor.

  In order to solve this problem, formation of about 2 V is performed on the surface of the cathode foil to reduce the flowing current, or the potential difference from the lead wire is reduced by using a foil deposited with TiN or the like.

  When chemical conversion is formed on the surface of the cathode foil, the capacitance of the cathode foil is lowered, the capacitance of the anode foil cannot be sufficiently drawn, and the capacitance of the aluminum electrolytic capacitor is reduced. Further, in the case of a foil on which TiN or the like is vapor-deposited, there is a problem that it is difficult to introduce industrially because the vapor deposition process is complicated.

  The present invention solves the above-mentioned conventional problems, and improves the capacitance of the cathode foil, reduces the potential difference between the lead wire and the cathode foil, and improves performance and size with excellent life characteristics. An object of the present invention is to provide an aluminum electrolytic capacitor.

In order to achieve the above object, the present invention provides a method for manufacturing an aluminum electrolytic capacitor comprising: preparing an anode foil in which an aluminum foil is etched to form a dielectric oxide film; and a specific surface area on the surface of the aluminum foil. preparing a cathode foil obtained by forming a porous carbon layer having a specific surface area of 50~360m ² / g containing 10 to 77 wt% of activated charcoal 140~400m ² / g, and the anode and cathode foils A capacitor element is formed by winding through a separator, the capacitor element is impregnated with a driving electrolyte, and the capacitor element is housed in a metal case, and the opening of the metal case is sealed with a sealing body It is set as the manufacturing method provided with the process to do.

In the method for producing an aluminum electrolytic capacitor of the present invention, a porous carbon layer having a specific surface area of 50 to 360 m ² / g containing 10 to 77% by weight of activated carbon having a specific surface area of 140 to 400 m ² / g on the surface of the aluminum foil. By having a step of preparing a cathode foil formed with a cathode foil, the capacitance of the cathode foil can be increased without increasing the effective surface area of the cathode foil, and the potential difference between the lead wire and the cathode foil can be reduced. Therefore, since the current flowing through the cathode foil is suppressed, the corrosion resistance of the cathode foil is improved, and an effect is obtained that a long-life and downsized aluminum electrolytic capacitor can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a partially cutaway perspective view of an aluminum electrolytic capacitor according to an embodiment of the present invention. In the figure, an anode foil 11 in which a dielectric oxide film is formed by anodic oxidation on the surface of an aluminum foil which has been expanded by etching and an anode lead 15 for extraction is connected, and porous carbon containing activated carbon in the aluminum foil. A capacitor element 19 is formed by winding a cathode foil 12 having a layer formed and connected to a lead-out cathode lead 16 through a separator 13, and impregnating the capacitor element 19 with a driving electrolyte 14. Thereafter, the metal case 18 is inserted into an aluminum metal case 18 and the opening of the metal case 18 is sealed with a sealing plate 17.

  The anode foil 11 is subjected to an etching process in order to increase the effective surface area. This etching process is performed chemically or electrochemically (AC application or DC application) in an aqueous hydrochloric acid solution to which an acid that forms a film such as sulfuric acid, nitric acid, phosphoric acid, or oxalic acid is added. Among them, the AC foil is mainly used for the anode foil of low-voltage aluminum electrolytic capacitors. In many etching tanks, the etching temperature is changed by changing the liquid temperature, frequency, and time. Form. In addition, the etching process of the anode foil 11 used for medium and high pressures is performed by generating tunnel-like pits in the former etching process and expanding the pits to a diameter suitable for the working voltage of the aluminum electrolytic capacitor in the latter etching process. Form.

The cathode foil 12 has been conventionally etched to increase the effective surface area in the same manner as the anode foil 11, but the cathode foil 12 of the present invention has an aluminum foil surface of 50 to 360 m ² / g or more. A porous carbon layer having a specific surface area is coated.

The porous carbon layer contains at least activated carbon, and by containing 10 to 77 % by weight of the activated carbon, a porous carbon layer having a specific surface area of 50 to 360 m ² / g can be formed.

  The cathode foil 12 can prevent corrosion of the aluminum foil by forming a phosphoric acid film on the surface of the aluminum foil before forming the porous carbon layer or on the surface of the porous carbon layer.

  By using this cathode foil 12 for an aluminum electrolytic capacitor, it is possible to provide a high performance and miniaturized aluminum electrolytic capacitor excellent in corrosion resistance.

  The driving electrolyte solution 14 includes a polar solvent and a solute containing at least one of an inorganic acid, an organic acid, an inorganic acid salt, and an organic acid salt.

  Examples of the polar solvent include ethylene glycol, propylene glycol, 1,4-butanediol, glycerin, polyoxyalkylene polyol (polyethylene oxide having a molecular weight of 200 or less, polypropylene oxide, polyoxyethylene / oxypropylene glycol, and two or more kinds thereof. Combined use), furan solvent (2,5-dimethoxytetrahydrofuran, etc.), sulfolane solvent (sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, etc.), carbonate solvent (propylene carbonate, ethylene carbonate, diethyl carbonate, styrene carbonate, dimethyl) Carbonate or methyl ethyl carbonate), lactone solvent (γ-butyrolactone, γ-valerolactone, δ-valerolactone, 3-methyl-1, - oxaziridine-2-one, 3-ethyl-1,3-oxazolidin-2-one, etc.), imidazolidinone solvent (1,3-dimethyl-2-imidazolidinone, etc.), pyrrolidone solvents.

  The solute contains one or more of an inorganic acid, an organic acid, an inorganic acid salt, and an organic acid salt. Among them, preferred are boric acid, phosphoric acid, azelaic acid, adipic acid, glutaric acid, phthalic acid, Examples thereof include dibasic acids such as maleic acid, benzoic acid, 5,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 1,6-decanedicarboxylic acid, and salts thereof. Moreover, as said salt, ammonium salt, amine salt, quaternary ammonium salt, amidine type salt, etc. can be used.

  The separator 13 is a cellulosic fiber paper, a mixed paper or a laminated paper thereof, and the cellulosic fiber paper includes at least one of Manila hemp, craft, hemp, esparto, and cotton. Furthermore, a nonwoven fabric made of a synthetic resin material such as polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, or rayon can also be used.

  Since the fiber spacing is apparently dense and has a large number of fine through-holes, the electrical conductivity of the electrolyte is not lowered, so that the resistance loss can be reduced as a capacitor, Short circuit resistance can be improved.

The separator 13 weighs in the range of 1 to 60 g / m ² . When the separator 13 having a low weight is used, a short circuit is caused and stable characteristics cannot be maintained. If the weight is too high, the equivalent series resistance is increased.

  The separator 13 may be subjected to a paper strength enhancing process for the purpose of improving the tensile strength of the separator 13. By applying this paper strength enhancing process, the tensile strength can be improved and the short-circuit resistance can be further improved.

  The paper strength enhancing process can be performed by applying or impregnating the separator 13 with an aqueous solution of starch, vegetable gum, carboxyalkyl cellulose, polyoxyethylene phthalate, or the like.

  In addition, since the nonwoven fabric of the synthetic resin material can be formed into a sheet by a thermal bonding method or a mechanical entanglement method without using an adhesive for bonding fibers during sheeting, its melting point is also high. Even under soldering mounting conditions exceeding 250 ° C., it is difficult for the separator fiber to be cut or ESR increased due to heat shrinkage of the resin, and a low ESR aluminum electrolytic capacitor having excellent solder heat resistance can be obtained.

  The sealing plate 17 is at least one of ethylene-propylene-diene terpolymer rubber (EPDM), butane rubber (IIR), urethane rubber (U), silicone rubber (Q), and chlorosulfonated polyethylene rubber (CSM). The sealing plate 17 can be obtained by adding a vulcanizing agent, a vulcanization aid, a reinforcing material and a filler, a deterioration preventing agent, and the like, kneading, and then molding.

  Hereinafter, specific examples will be described.

Example 1
[Production of anode foil]
An aluminum foil having a thickness of 100 μm and a purity of 99.98% is used, and pretreatment is performed by dipping in a 90 ° C. aqueous solution having a phosphoric acid concentration of 1.0 wt% for 60 seconds.

  Next, the aluminum foil is immersed in an electrolytic solution at a temperature of 30 ° C. adjusted to 5 wt% hydrochloric acid, 2 wt% aluminum chloride, 0.1 wt% sulfuric acid, and 0.2 wt% phosphoric acid, and an alternating current is applied to perform etching treatment. It was divided into four stages.

  Next, an immersion treatment for 100 seconds was performed with an aqueous solution of 10 wt% sulfuric acid at 60 ° C., and a heat treatment was performed at 250 ° C. for 120 seconds to produce an etching foil serving as an anode foil.

  Next, the etching foil was subjected to a chemical conversion treatment by applying a DC voltage of 19 V in a 15% ammonium adipate aqueous solution to obtain an anode foil.

[Preparation of cathode foil]
Activated carbon powder (BET specific surface area: 140 m ² / g) having an average particle diameter of 5 μm, carbon black having an average particle diameter of 0.05 μm and polytetrafluoroethylene (hereinafter abbreviated as PTFE) as a conductivity imparting agent are 10: 2: A water-soluble binder solution mixed and dispersed at a weight ratio of 1 is sufficiently kneaded with a kneader, and then a water dispersion solvent is added little by little to further knead to prepare a paste.

  Next, a cathode foil having a porous carbon layer formed by applying the paste to a thickness of 10 μm on one surface of an aluminum foil having a thickness of 30 μm and a purity of 99.9% and drying at 150 ° C. Obtained.

The activated carbon content in the porous carbon layer was 77% by weight, and the specific surface area was 140 m ² / g.

[Drive electrolyte]
The composition of the driving electrolyte is shown below (hereinafter referred to as driving electrolyte A).

Ethylene glycol: 85% by weight
Phosphoric acid: 2% by weight
1,6-decanedicarboxylic acid: 12% by weight
p-Nitrobenzoic acid: 1% by weight
[Production of aluminum electrolytic capacitors]
A capacitor element is formed by winding the anode foil and the cathode foil through a separator made of Manila paper. The capacitor element is impregnated with the driving electrolyte A and stored in a metal case. After sealing with a resin vulcanized butyl rubber sealing plate (30 parts butyl rubber polymer, 20 parts carbon, 50 parts inorganic filler, sealing board hardness: 70 IRHD [international rubber hardness unit]), it is opened by curling treatment. The part was sealed to produce an aluminum electrolytic capacitor (size: diameter 10 mm × height 16 mm, rated 400 WV 6.8 μF).

(Example 2)
An aluminum electrolytic capacitor was prepared in the same manner as in Example 1 except that the activated carbon of the porous carbon layer was formed using activated carbon powder having an average particle size of 5 μm (BET specific surface area: 220 m ² / g). Was made.

The specific surface area of the porous carbon layer was 210 m ² / g.

(Example 3)
Aluminum electrolytic capacitor in the same manner as in Example 1 except that the activated carbon of the porous carbon layer in Example 1 was formed using activated carbon powder having an average particle size of 5 μm (BET specific surface area: 400 m ² / g). Was made.

The specific surface area of the porous carbon layer was 360 m ² / g.

Example 4
In Example 1, an aluminum electrolytic capacitor was produced in the same manner as in Example 1 except that the weight ratio of activated carbon to carbon black and polyester resin was 7: 5: 1 and an organic dispersion solvent was used.

The activated carbon content in the porous carbon layer was 54% by weight, and the specific surface area was 110 m ² / g.

(Example 5)
In Example 1, an aluminum electrolytic capacitor was produced in the same manner as in Example 1 except that the weight ratio of activated carbon, carbon black, and polyester resin was 4: 8: 1 and an organic dispersion solvent was used.

The activated carbon content in the porous carbon layer was 30% by weight and the specific surface area was 65 m ² / g.

(Example 6)
In Example 1, the weight ratio of activated carbon to carbon black and polyester resin was 1.3: 10.7: 1, and an aluminum electrolytic capacitor was prepared in the same manner as in Example 1 except that an organic dispersion solvent was used. Produced.

The content of activated carbon in the porous carbon layer was 10% by weight, and the specific surface area was 50 m ² / g.

(Example 7)
An aluminum electrolytic capacitor in the same manner as in Example 1 except that the aluminum foil used for the cathode foil was immersed in a 2% aqueous ammonium phosphate solution and a phosphate film was formed on the surface. Was made.

(Example 8)
In Example 1, the aluminum foil used for the cathode foil was roughened with a 10% aqueous hydrochloric acid solution and then immersed in a 2% aqueous ammonium phosphate solution to form a phosphate film on the surface. An aluminum electrolytic capacitor was produced in the same manner as in Example 1 except that.

Example 9
In Example 1, an aluminum electrolytic capacitor was produced in the same manner as in Example 1 except that the driving electrolyte solution having the following composition (hereinafter referred to as driving electrolyte solution B) was used (size: 10 mm diameter x 16 mm height, rated 16 WV 330 μF).

γ-butyl lactone: 43% by weight
Sulfolane: 40% by weight
Phthalic acid: 5% by weight
Triethylamine: 12% by weight
(Comparative Example 1)
An aluminum electrolytic capacitor was prepared in the same manner as in Example 1 except that the surface of the aluminum foil as a cathode foil was roughened with a 10% hydrochloric acid aqueous solution and then heat-treated at 350 ° C. for 1 minute. Was made.

(Comparative Example 2)
An aluminum electrolytic capacitor was produced in the same manner as in Comparative Example 1 except that the driving electrolytic solution B was used as the driving electrolytic solution in Comparative Example 1.

  The aluminum electrolytic capacitors of Examples 1 to 9 and Comparative Examples 1 and 2 were subjected to initial characteristics (capacity, tan δ, leakage current (LC)) and a high temperature load test at 105 ° C. The results are shown in (Table 1).

  As is clear from Table 1, the aluminum electrolytic capacitors of Examples 1 to 9 are superior to the aluminum electrolytic capacitors of the comparative examples in the initial characteristics and the high temperature load test at 105 ° C. In Examples 1 to 3 of this (Table 1), the surface area of the porous carbon layer of the cathode foil was changed, but as the surface area of the porous carbon layer increased, the capacity increased and tan δ and LC also increased. Is lower than Comparative Example 1.

  Further, by making the activated carbon of the porous carbon layer 10% by weight or more, the capacity is higher than that of Comparative Example 1, and tan δ and LC are also low.

  If the specific surface area of the activated carbon is large, the amount of activated carbon in the porous carbon layer can be reduced, but if the amount of activated carbon is less than 10% by weight, a high capacity cannot be obtained.

  Further, even if the driving electrolyte is changed from the solvent of ethylene glycol to the solvent of γ-butyllactone, the capacitor characteristics are excellent as compared with the comparative examples.

The aluminum electrolytic capacitor of the present invention increases the capacitance of the cathode foil without enlarging the effective surface area of the cathode foil by coating the surface of the cathode foil with a porous carbon layer having a specific surface area of 50 m ² / g or more. And the potential difference between the lead wire and the cathode foil can be reduced, so that the current flowing through the cathode foil is suppressed, so that the corrosion resistance of the cathode foil is improved, and the lifetime and size of the aluminum electrolytic capacitor are reduced. Can be obtained.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Anode foil 12 Cathode foil 13 Separator 14 Driving electrolyte 15 Anode lead 16 Cathode lead 17 Sealing plate 18 Metal case 19 Capacitor element

Claims (1)

A step of preparing an anode foil in which a dielectric oxide film is formed by etching an aluminum foil, and 50 to 360 m ² containing 10 to 77% by weight of activated carbon having a specific surface area of 140 to 400 m ² / g on the surface of the aluminum foil. A cathode foil in which a porous carbon layer having a specific surface area of / g is prepared, and the anode foil and the cathode foil are wound through a separator to form a capacitor element. A method for manufacturing an aluminum electrolytic capacitor, comprising: impregnating a liquid; and housing the capacitor element in a metal case, and sealing an opening of the metal case with a sealing body.

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