JP3500929B2 - Aluminum electrolytic capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum electrolytic capacitor used in various electronic devices.

[0002]

2. Description of the Related Art Generally, in an aluminum electrolytic capacitor, a belt-shaped aluminum foil is chemically or electrochemically etched to increase the surface area of the aluminum foil, and the aluminum foil is formed in a chemical conversion solution such as ammonium borate. Anode aluminum foil that has been subjected to a treatment to form an aluminum oxide layer on the surface, and an aluminum foil for a cathode that has only been subjected to an etching treatment, with a separator made of manila fiber or the like being interposed therebetween. To form a capacitor element.

This capacitor element is impregnated with an electrolytic solution for driving an electrolytic capacitor, and then housed in a bottomed cylindrical outer case having an opening made of aluminum or the like. Is equipped with a sealing member containing synthetic rubber, and the outer case is closed by drawing.

Lead wires for pulling out the respective electrodes to the outside are connected to the aluminum foil for the anode and the aluminum foil for the cathode by means of stitching, ultrasonic welding or the like. These lead-out leads consist of a round bar made of aluminum and a connection part that comes into contact with the electrode foil.Furthermore, an external connection part made of a solderable metal is fixed to the tip of the round bar by means such as welding. There is.

It is known that various electrolytic solutions for impregnating a capacitor element for driving an electrolytic capacitor are used depending on the performance of the electrolytic capacitor. Among them, as an electrolytic solution having high conductivity and good low temperature characteristics and excellent thermal stability, a solvent containing γ-butyrolactone, tetraalkylammonium as a basic component and a carboxylic acid as an acid component are used as an electrolyte. A salt in which a so-called quaternary ammonium salt is dissolved (JP-A-62-2)
No. 64615) or, more recently, as an electrolytic solution having the same performance, a salt containing a base having an alkyl-substituted amidine group as an electrolyte and a carboxylic acid as an acid component in a solvent containing γ-butyrolactone. The one in which a so-called amidine salt is dissolved (see re-published patent international publication number WO95 / 15572) is known.

The aluminum used for the aluminum foil for the cathode varies depending on the use of the constituent capacitor, but the purity is about 99.20% and the purity is 99.95.
About% is selected and used. Generally, in the case of aluminum having a purity of about 99.20%, a metal having a nobler potential than aluminum such as copper is intentionally added for the purpose of increasing the surface area during etching.

Further, as a special treatment method for the aluminum foil for the cathode, titanium or titanium is used for the purpose of preventing the electrolyte solution from leaking to the outside due to electrochemical alteration of the electrolyte solution in which the quaternary ammonium salt is dissolved. A part where a nitride layer such as zirconium is formed on the surface of the aluminum foil for the cathode, and the spontaneous potential of the aluminum foil for the cathode is intentionally brought into contact with the electrolyte solution of the extraction lead connected to the aluminum foil for the cathode. The cathode of the local battery formed between the aluminum foil for the cathode and the lead lead electrically connected to the aluminum foil for the cathode in the electrolytic solution by changing the potential to a nobler side than the natural potential of Is devised so as to displace the lead-out lead toward the aluminum foil side for the cathode, not at the portion of the lead-out that comes into contact with the electrolytic solution (Japanese Patent Laid-Open No. H8-78242).
No. 264392), or a portion that comes into contact with the electrolytic solution by performing a surface treatment with a silane coupling agent, a fluororesin, or the like on the surface of the connection portion that contacts the round bar portion of the extraction lead made of aluminum and the electrode foil. Which improves the insulating property of the cathode and thereby suppresses the local battery reaction formed between the aluminum foil for the cathode and the lead lead electrically connected to the aluminum foil for the cathode in the electrolytic solution. (See Japanese Patent Laid-Open No. 9-129508) and the like are known.

[0008]

The electrolytic solution in which the above-mentioned quaternary ammonium salt is dissolved has high conductivity, good low-temperature characteristics, and excellent thermal stability. The electrolytic solution tends to easily leak from the through hole for leading out the cathode lead-out lead in the sealing member. Therefore, while the aluminum electrolytic capacitor using this electrolytic solution has excellent electrical performance,
The leakage of the electrolytic solution may contaminate the printed circuit board of the device in which this capacitor is mounted.

The electrolytic solution in which an amidine salt is dissolved is a solution in which the easiness of leaking out of the electrolytic solution is greatly improved by improving the above-mentioned problems of the quaternary ammonium salt.
Although electrolyte leakage under high temperature environment could be improved, in the long-term reliability test under severer high temperature-high humidity combined environment, the electrolyte leakage was suppressed to be practically sufficient. However, the capacitor must be constructed by using butyl rubber mixed with a special vulcanization method and a special filler, and therefore there is a problem that it is not versatile and the cost of the capacitor is high.

As a special treatment method for an aluminum foil for a cathode, a nitride layer of titanium, zirconium or the like is formed on the aluminum foil for a cathode, and the natural potential of the aluminum foil for the cathode is intentionally changed to the cathode side. The aluminum foil for the cathode in the electrolytic solution and the extraction lead electrically connected to the aluminum foil for the cathode in the electrolytic solution by changing the natural potential of the portion of the outgoing lead that contacts with the electrolytic solution to a noble side. The method of changing the cathode of the local battery formed between the two to the aluminum foil side for the cathode instead of the portion of the extraction lead that contacts the electrolytic solution is also a method for coating the aluminum foil for the cathode with metal nitride. Since it is special and expensive, it has problems in terms of mass productivity and cost.

Further, the surface of the round bar portion of the lead-out lead made of aluminum and the connection portion contacting the electrode foil is subjected to a surface treatment with a silane coupling agent, a fluororesin or the like to insulate the portion in contact with the electrolytic solution. Improve
As a result, the method of suppressing the local battery reaction formed between the aluminum foil for the cathode and the extraction lead electrically connected to the aluminum foil for the cathode in the electrolytic solution is also a step in the process of forming the insulating layer. Since it requires time and labor and the material used is expensive, there is a problem in terms of mass productivity and cost.

The present invention solves the above-mentioned conventional problems. It is possible to easily improve the leakage of the electrolytic solution in a high temperature-high humidity environment without using a special butyl rubber sealing material, and to improve the mass productivity. It is an object of the present invention to provide a highly reliable aluminum electrolytic capacitor capable of supplying lead wires at high cost and at low cost.

[0013]

In order to achieve the above object, the aluminum electrolytic capacitor of the present invention uses, as an anode, an aluminum foil having an aluminum oxide layer formed as a dielectric on the surface thereof, to which an extraction lead made of aluminum is connected. , A capacitor element constituted by winding an aluminum foil to which an extraction lead made of aluminum is connected as a cathode, and winding the anode and the cathode with a separator interposed therebetween, and an electrolytic solution impregnated in the capacitor element. And a bottomed outer case for accommodating the capacitor element, and a sealing member for sealing the opening of the outer case, wherein lithium, potassium, sodium, barium, magnesium, strontium is added to the aluminum of the lead on the cathode side. , Calcium, beryllium The total content of the elements is at least 0.01%, and the spontaneous potential of the cathode-side lead lead in the electrolytic solution is -0.15 V or less with respect to the potential of the saturated calomel electrode. According to this configuration, leakage of the electrolytic solution under high temperature-high humidity environment can be easily improved without using a special butyl rubber sealing material, and the mass productivity is high and low. It is possible to obtain a highly reliable aluminum electrolytic capacitor that can supply the extraction lead at a cost.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is characterized in that an extraction lead made of aluminum is connected to an extraction lead made of aluminum and an aluminum foil having an aluminum oxide layer as a dielectric formed on the surface thereof is used as an anode. A capacitor element configured by winding an aluminum foil to which leads are connected as a cathode, and winding the anode and the cathode with a separator interposed therebetween, an electrolytic solution impregnated in the capacitor element, and the capacitor element. A bottomed outer case for accommodating and a sealing member for sealing the opening of the outer case, wherein lithium, potassium, sodium, barium, magnesium, strontium, calcium, beryllium is added to the aluminum of the lead on the cathode side. The total content of one or more selected elements Is contained in .01% or more ranges, and natural potential in the electrolyte in the cathode side out lead are relative to the potential of a saturated calomel electrode -0.1
The voltage is set to 5 V or less, and according to this configuration,
Since it is possible to bring the natural potential in the electrolytic solution of the cathode side extraction lead close to the natural potential in the electrolytic solution of the portion of the aluminum foil for the cathode that contacts the electrolytic solution, the aluminum foil for the cathode in the electrolytic solution, The electromotive force of the local battery formed between the aluminum foil for the cathode and the extraction lead electrically connected to the aluminum foil can be reduced, and the current generated thereby can be remarkably reduced. It is possible to suppress the electrochemical alteration of. As a result, it is possible to easily improve the leakage of the electrolytic solution in a high temperature-high humidity environment without using a special butyl rubber sealing member, and it is possible to supply lead wires at a low cost with high mass productivity. It is possible.

Further, lithium, potassium, sodium, barium, magnesium, strontium, calcium, which are contained in aluminum of the extraction lead on the cathode side,
The total content of one or more elements selected from beryllium is set to 0.01% or more, and lithium, potassium, sodium, barium, magnesium, strontium, calcium contained in aluminum of the lead on the cathode side is contained. , When the total content of one or more elements selected from beryllium is less than 0.01%, the aluminum foil for the cathode in the electrolytic solution and the drawer electrically connected to the aluminum foil for the cathode This is not preferable because the effect of lowering the electromotive force of the local battery formed between the leads is lost.

The invention according to claim 2 is the electrolyte of the electrolytic solution.
In the bases that compose
The hydrogen ion concentration in an aqueous solution can be calculated by
The hydroxide concentration is 1% by weight and the measurement temperature is 30 ° C.
Hour, 1.0 × 10^-13Mol / dm³It was made above
According to this configuration, the configuration and the combination according to claim 1 are combined.
By combining them, electrolyte leakage can be prevented by using a special butyl resin.
It can be easily improved without using a sealing material
It is a thing. Hydrogen ion concentration is 1.0 × 10 ^-13Mol /
dm³A strongly basic base of less than
An electrolyte of ammonium or tetraalkylphosphonium)
The electrolytic solution consisting of
In a reliability test for a long period, leakage resistance is practically sufficient.
In order to ensure that the special
Butyl rubber must be used to form capacitors.
It is difficult to improve leakage of electrolyte easily
It is a good thing.

An embodiment of the present invention will be described below with reference to the drawings. The basis of the aluminum electrolytic capacitor of the present invention is to connect an extraction lead 1 made of aluminum as shown in FIG. 1, and use an aluminum foil having an aluminum oxide layer as a dielectric on the surface as an anode, and make an extraction lead made of aluminum. A capacitor element 3 configured by winding an aluminum foil to which 2 is connected as a cathode, and winding the anode and the cathode with a separator interposed therebetween; an electrolytic solution impregnated in the capacitor element 3; An outer case 4 having a bottom for accommodating the capacitor element 3 and a sealing member 5 for sealing the opening of the outer case 4 are provided, and lithium, potassium, sodium, barium, magnesium is added to the aluminum of the lead 2 on the cathode side. , One or more selected from strontium, calcium and beryllium The total content of the elements is 0.01% or more, and the natural potential of the cathode-side lead lead 2 in the electrolytic solution is -0.15 V or less with respect to the potential of the saturated calomel electrode. It is the one.

As the sealing member 5 of the aluminum electrolytic capacitor of the present invention, butyl rubber having excellent chemical resistance is desirable.
Examples of the vulcanization method of butyl rubber include peroxide vulcanization using a peroxide such as dicumyl peroxide as a vulcanizing agent, resin vulcanization using a resin such as an alkylphenol formalin as a vulcanizing agent, and a quinone compound vulcanizing agent. It is known that quinoid vulcanization, etc. used for the above, and inorganic compounds such as aluminum silicate and calcium carbonate are known as fillers to be added to butyl rubber, but any vulcanization method and butyl rubber mixed with filler are used. However, the effect is recognized.

The electrolytic solution of the aluminum electrolytic capacitor of the present invention is preferably an electrolytic solution containing γ-butyrolactone as a solvent, which has high conductivity and good low temperature characteristics. If necessary, γ-butyrolactone may be mixed with water or an alcohol such as ethylene glycol or glycerin as a subsolvent. In this case, the potential of the lead lead 2 on the cathode side in the electrolytic solution is the potential of the saturated calomel electrode. With respect to −0.
It should be in the range of 15V or less.

When the electrolytic solution of the aluminum electrolytic capacitor of the present invention contains water as a sub-solvent, it is preferably 10% by weight or less based on the weight part of the electrolytic solution. By adjusting the amount of water contained, it becomes easy to adjust the potential of the lead lead 2 on the cathode side in the electrolytic solution. However, if the amount of water exceeds 10% by weight, the generation of gas due to corrosion of aluminum becomes large and the characteristics of the aluminum electrolytic capacitor are significantly deteriorated, which is not preferable.

As the base constituting the electrolyte of the electrolytic solution of the aluminum electrolytic capacitor of the present invention, tertiary amines (trimethylamine, triethylamine, ethyldimethylamine,
Examples thereof include diethylmethylamine), imidazole compounds quaternized with an alkyl group having 1 to 11 carbon atoms or an arylalkyl group, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds). Specifically, 1-methyl-1, which has high conductivity,
8-diazabicyclo [5,4,0] undecene-7,1
-Methyl-1,5-diazabicyclo [4,3,0] nonene-5,1,2,3-trimethylimidazolinium,
1,2,3,4-tetramethylimidazolinium, 1,
2-dimethyl-3-ethylimidazolinium, 1,3-
Dimethyl-2-ethyl-imidazolinium, 1,3,4
-Trimethyl-2-ethylimidazolinium, 1,3-
Dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2- (3'heptyl) imidazolinium, 1,
3-dimethyl-2-dodecylimidazolinium, 1,
2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium, 1,3-dimethylimidazolium, 1,3
-Dimethylbenzimidazolium is preferred. Of these, particularly preferable is 1,2,3,4-tetramethylimidazolinium, which has high conductivity and is thermally stable.

If necessary, various additives may be mixed with the electrolytic solution of the aluminum electrolytic capacitor of the present invention. By adding an additive, the potential of the cathode side extraction lead 2 in the electrolytic solution can be adjusted, and it becomes easy to adjust the potential to −0.15 V or less with respect to the potential of the saturated calomel electrode. . Examples of the additive include phosphorus compounds (phosphoric acid, phosphoric acid ester, etc.), boron compounds (boric acid, borate [ammonium borate, etc.], complex compounds of boric acid and polysaccharides [mannite, sorbit, etc.]), Nitro compounds (p-nitrophenol, m-nitrophenol, o-nitrophenol, p-nitrobenzoic acid, m-nitrobenzoic acid, o-nitrobenzoic acid, 3-
Nitrophthalic acid, 4-nitrophthalic acid, etc.), organic acids (maleic acid, o-phthalic acid, benzoic acid, adipic acid,
Resorcylic acid).

Table 1 shows the constituent materials of the aluminum electrolytic capacitors of Embodiments 1 to 11 of the present invention and Comparative Examples 1 and 2. The method for measuring the contained metal in the cathode side lead was to completely dissolve the cathode side lead by immersing it in an aqueous hydrochloric acid solution, and measure this by high frequency inductively coupled plasma emission spectrometry. , The detection amount per unit weight of the lead-out lead on the immersed cathode side.

[0024]

[Table 1]

Table 2 shows the natural potential in the electrolytic solution of the extraction lead on the cathode side of the aluminum electrolytic capacitors of Embodiments 1 to 11 of the present invention and Comparative Examples 1 and 2, and the aluminum for the cathode in the electrolytic solution. Foil (Purity 99.9
%) And the extraction lead electrically connected to the aluminum foil for the cathode, and the current generated by the local battery is measured at a temperature of 25 ° C.

[0026]

[Table 2]

As is clear from (Table 2), in the aluminum electrolytic capacitors according to the first to eleventh embodiments of the present invention,
It can be seen that the natural potential of the lead-out lead 2 on the cathode side in the electrolytic solution is within -0.15 V with respect to the potential of the saturated calomel electrode. Also, it can be seen that the generated current of the local battery is small.

Next, using the constituent materials of the aluminum electrolytic capacitors of Embodiments 1 to 11 of the present invention and Comparative Examples 1 and 2, an anode foil, a separator made of manila fiber, and an outer case made of aluminum, a rated voltage is used. An aluminum electrolytic capacitor having a capacitance of 220 μF and a size of φ8.0 mm × L11.2 mm was prepared. And each of the 10 aluminum electrolytic capacitors has a temperature of 85 ° C.-a relative humidity of 85.
A voltage of 25 V is continuously applied in an environment of% RH 50
A reliability test was performed for 00 hours, and the state of the sealing rubber surface of the capacitor after the test was examined. The results (Table 3)
Shown in.

[0029]

[Table 3]

As is clear from (Table 3), the aluminum electrolytic capacitors prepared by using the constituent materials of the aluminum electrolytic capacitors according to the first to eleventh embodiments of the present invention are naturally formed in the electrolytic solution of the extraction lead on the cathode side. Since the electric potential can be set in the range of −0.15 V or less with respect to the electric potential of the saturated calomel electrode, the aluminum foil for the cathode and the drawer electrically connected to the aluminum foil for the cathode in the electrolytic solution. Since the electromotive force of the local battery formed between the lead and the lead can be reduced and the current generated thereby can be significantly reduced, the electrochemical alteration of the electrolytic solution can be suppressed. As a result, leakage of electrolyte under high temperature-high humidity environment can be easily improved without using special butyl rubber sealing material, and highly reliable aluminum electrolytic capacitor can be provided at a low cost by a method suitable for mass production. Is something that can be done.

[0031]

INDUSTRIAL APPLICABILITY As described above, the aluminum electrolytic capacitor of the present invention is connected with the lead-out lead made of aluminum, and the lead-out lead made of aluminum is formed by using the aluminum foil on the surface of which an aluminum oxide layer is formed as a dielectric as an anode. The aluminum foil connected to the cathode as a cathode, a capacitor element constituted by winding these anode and cathode with a separator interposed therebetween, an electrolytic solution impregnated into the capacitor element, and the capacitor element A bottomed outer case for housing and a sealing member for sealing the opening of the outer case are provided, and the cathode lead-out lead aluminum is selected from lithium, potassium, sodium, barium, magnesium, strontium, calcium and beryllium. The content of one or more elements Is contained in a range of more than a total of 0.01% Te, and natural potential in the electrolyte in the cathode side out lead are relative to the potential of a saturated calomel electrode -0.
According to this configuration, the spontaneous potential in the electrolytic solution of the lead wire on the cathode side becomes equal to the spontaneous potential in the electrolytic solution of the portion of the aluminum foil for the cathode that comes into contact with the electrolytic solution. Since they can be brought close to each other, the electromotive force of the local battery formed between the aluminum foil for the cathode and the extraction lead electrically connected to the aluminum foil for the cathode in the electrolytic solution can be reduced, Since the electric current generated thereby can be remarkably reduced, the electrochemical alteration of the electrolytic solution can be suppressed. As a result, it is possible to easily improve the leakage of the electrolytic solution in a high-temperature and high-humidity environment without using a special butyl rubber sealing material, and it is possible to supply the extraction lead with high mass productivity and at low cost. Because you can
It is possible to provide a highly reliable aluminum electrolytic capacitor at a low cost by a method suitable for mass production.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an aluminum electrolytic capacitor of the present invention.

[Explanation of symbols]

1, 2 drawer leads 3 Capacitor element 4 exterior case 5 Sealing member

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yukihiro Nitta 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Junji Ozaki 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. In-company (56) Reference JP-A-6-84710 (JP, A) JP-A-4-143242 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01G 9/008 H01G 9/035

Claims (2)

(57) [Claims] 1. An aluminum foil, to which lead-out leads made of aluminum are connected and an aluminum oxide layer formed on the surface as a dielectric, is used as an anode, and an aluminum foil to which lead-out leads made of aluminum are connected is used as a cathode. A capacitor element constituted by winding a cathode and a separator interposed therebetween, and an electrolytic solution impregnated in the capacitor element,
A bottomed outer case that houses the capacitor element, and a sealing member that seals the opening of the outer case are provided, and lithium is added to the aluminum of the lead lead on the cathode side.
One or more elements selected from potassium, sodium, barium, magnesium, strontium, calcium, and beryllium are contained in a total amount of 0.01% or more, and the cathode side extraction lead is contained in the electrolytic solution. Spontaneous potential against saturated calomel electrode potential −
Aluminum electrolytic capacitor designed to be 0.15V or less. 2. In the base constituting the electrolyte of the electrolytic solution, the hydrogen ion concentration in the aqueous solution of the base or the hydroxide of the base is 1% by weight of the base or the hydroxide of the base, and the measurement temperature is 1.0 × 10 ^-13 at 30 ℃
The aluminum electrolytic capacitor according to claim 1, wherein the molar ratio is not less than mol / dm ³ .