JP2000030983A - Polarizable aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizable aluminum electrolytic capacitor which has no leakage of the electrolyte for driving even if an active chemical is used for the electrolyte. SOLUTION: This polarizable aluminum electrolytic capacitor is constituted of a capacitor element 2 made by winding an anode foil and a cathode foil with electrolytic paper between, a rubber sealing body 5 with its terminal insertion holes 51, 52 fit with aluminum round bars 31, 41 of an anode lead terminal 3 and a cathode lead terminal 4 extracted from the anode foil and the cathode foil respectively, and an aluminum case 6 which seals the capacitor element 2 impregnated with the nonaqueous electrolyte for driving including quaternary ammonium salt or imidazolinium salt, together with the sealing body 5. As for the cathode foil, an aluminum foil applied with chemical conversion treatment at the formation voltage between 0.1 V and 5 V after etching is used. As the material of the rubber sealing body 5, butyl rubber using magnesium silicate as a filler is used.

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. More specifically, the present invention relates to a technique for preventing a driving electrolyte from leaking from an aluminum electrolytic capacitor.

[0002]

2. Description of the Related Art FIGS. 1 and 2 are an explanatory view showing components of an aluminum electrolytic capacitor and a sectional view of the aluminum electrolytic capacitor, respectively. As shown in FIGS. 1 and 2, a small aluminum electrolytic capacitor generally includes a capacitor element 2 wound between an anode foil and a cathode foil via electrolytic paper, and an anode foil and a cathode foil of the capacitor element 2. The rubber sealing member 5 in which the aluminum round bar portions 31 and 41 of the extracted anode lead terminal 3 and cathode lead terminal 4 are fitted in the terminal insertion holes 51 and 52, respectively, and a capacitor impregnated with a driving electrolyte. And an aluminum case 6 for sealing the element 2 together with the rubber sealing body 5.

[0003] In recent years, aluminum electrolytic capacitors have also been required to have low loss and low impedance characteristics in order to cope with the development of digital circuits and the like. An important technique for meeting these demands is mainly to reduce the specific resistance of the driving electrolyte impregnated in the capacitor element. The driving electrolyte satisfying this requirement includes γ-butyrolactone alone or a mixed solvent of γ-butyrolactone as a main solvent and ethylene glycol mixed therein, such as a quaternary ammonium salt of o-phthalic acid or maleic acid. Is used as a solute.

[0004] Such a driving electrolyte solution using an organic solvent is drastically lost after passing through a rubber sealing body in a high-temperature atmosphere, and such a loss causes remarkable deterioration of capacitor characteristics. Therefore, when such a driving electrolyte is used, various design considerations have been made in terms of airtightness, such as using butyl rubber having low gas permeability as a rubber sealing member.

[0005]

However, in the aluminum electrolytic capacitor using the above-mentioned driving electrolytic solution, a new problem not pointed out in the conventional aluminum electrolytic capacitor has been pointed out. That is, when the aluminum electrolytic capacitor is used for a long time in a loaded state or left for a long time in a no-load state, the driving electrolyte leaks from the terminal insertion hole on the cathode side of the rubber sealing body and leaks. This is a problem that the wiring pattern causes a short circuit on the circuit board due to the driving electrolyte solution.

Accordingly, an object of the present invention is to realize a polar aluminum electrolytic capacitor which does not cause leakage of the electrolytic solution even when the above-mentioned active chemical is used for the driving electrolytic solution.

[0007]

Means for Solving the Problems The present invention is based on new findings obtained from various studies conducted to prevent the driving electrolyte from leaking from the terminal insertion hole on the cathode side of the rubber sealing body. The present invention is based on an aluminum round bar portion of a lead terminal that is in contact with a terminal insertion portion on the cathode side of a rubber sealing body and an electrode potential difference of a cathode foil connected to the terminal. That is, in the conventional polar aluminum electrolytic capacitor, the cathode foil has a lower electrode potential than the aluminum round bar portion of the lead terminal connected thereto,
A local battery is formed by the cathode foil and the aluminum round bar. Therefore, in the conventional polar aluminum electrolytic capacitor, the electrode reaction at the round bar portion of the lead terminal on the cathode side causes alkalinization of the driving electrolyte near the round bar portion. As a result, alkali deterioration of the rubber sealing body in contact with the driving electrolyte near the round bar portion of the lead terminal on the cathode side, that is, the rubber elasticity of the inner surface of the terminal insertion hole is reduced, and the driving electrolyte from this portion is reduced. Liquid leakage will occur.

[0008] Based on such findings, the present invention is to reverse the polarity of the local battery to promote the alkalizing of the driving electrolyte in contact with the rubber sealing member near the round bar of the lead terminal on the cathode side. And preventing the leakage of the driving electrolyte by improving the alkali resistance itself of the rubber sealing body. That is, in the present invention, a capacitor element wound between an anode foil and a cathode foil via electrolytic paper, and aluminum of an anode lead terminal and a cathode lead terminal drawn out from the anode foil and the cathode foil of the capacitor element. Rubber seals each of which has a round bar portion made of a metal, and a capacitor element impregnated with a non-aqueous driving electrolyte containing a quaternary ammonium salt or imidazolinium salt. A polar aluminum electrolytic capacitor having a case to be sealed together with butyl rubber containing magnesium silicate as a filler as the rubber sealing member, and having a withstand voltage of 0.1 V or more after etching as the cathode foil. It is characterized by using an aluminum foil having a coating formed thereon.

[0009] The non-aqueous driving electrolyte referred to in the specification of the present application is different from an ethylene glycol-water driving electrolyte containing 10% or more of water, in which no water is added or not.
Alternatively, it refers to a driving electrolyte of 5% or less even when blended. In the field of aluminum electrolytic capacitors, a technique of forming a film on a cathode foil by a chemical conversion treatment or the like has conventionally used a driving electrolyte obtained by dissolving an ammonium salt (NH ₄ salt) in an ethylene glycol-water solvent. When used, it has been used as a technique for preventing hydration deterioration of the cathode foil or reduction of the capacity of the cathode foil during charge / discharge, but in the present invention, a non-aqueous system containing a quaternary ammonium salt or an imidazolinium salt is used. The first characteristic of the aluminum electrolytic capacitor using the driving electrolyte solution is that a cathode foil having a film formed by a method such as chemical conversion treatment is used.

In the present invention, since a cathode foil having a film formed thereon is used, the electrode potential of the cathode foil is higher than that of an aluminum round bar portion of a cathode lead terminal. Therefore, the current from the local battery composed of the round bar portion and the cathode foil of the lead terminal on the cathode side flows from the round bar portion to the cathode foil, so that the driving electrolyte around the round bar portion of the lead terminal has Alkalinization does not progress. Therefore, the rubber sealing body in contact with the driving electrolyte near the round bar portion of the cathode-side lead terminal does not deteriorate with alkali, that is, the rubber elasticity of the inner surface of the terminal insertion hole does not decrease. Electrolyte leakage can be prevented. Here, the withstand voltage of the film formed on the cathode foil varies depending on the material and shape of the round bar portion of the lead terminal to be used and the type of the driving electrolyte.
V or more is necessary. However, when the formation voltage exceeds 5 V, it is not very effective because it only causes a decrease in the cathode capacity.

Further, conventionally, butyl rubber using calcium carbonate, calcium silicate or the like as a filler has been used, but the present invention has a second feature in that butyl rubber using magnesium silicate as a filler is used. Having. As a result, the alkali resistance of the rubber sealing body has been improved, so that even if the drive electrolyte in contact with the rubber sealing body in the vicinity of the round bar portion of the cathode-side lead terminal is slightly alkalized,
The rubber seal does not deteriorate. Therefore, leakage of the driving electrolyte can be prevented.

[0012]

Embodiments of the present invention will be described.
The structure of the aluminum electrolytic capacitor used here is as described with reference to FIG. 1 and FIG. Example 1 First, 15% by weight of a phthalic acid salt of tetraethylammonium as a main solute was blended with a solvent containing γ-butyrolactone as a main component to prepare a driving electrolyte.
Next, using this driving electrolyte, rated voltage 16 V, capacitance 330 μF, case size 10 mm, length 12.5
mm electrolytic capacitor is manufactured.

The cathode foil according to the embodiment used here is obtained by subjecting an aluminum foil having a purity of 99% to AC electrolytic etching in a 6% hydrochloric acid solution, and then applying 0.05V, 0.5V, 1.0V.
V, 1.5 V, 2.0 V, and 5.0 V. As a conventional example, an unformed cathode foil obtained by etching an Al foil was used. Further, butyl rubber using magnesium silicate as a filler was used as the rubber sealing body according to the example, and butyl rubber used as a filler of calcium carbonate was used as the rubber sealing body according to the conventional example.

These materials are combined to produce 500 electrolytic capacitors, each of which is subjected to an aging treatment. Then, a rated voltage is applied in a high-temperature and high-humidity atmosphere at a temperature of 85 ° C. and a humidity of 85%, and a no-load test is performed for 3000 times. After the test, the leakage of the driving electrolyte was confirmed for each capacitor sample after the test. The results are shown in Tables 1 and 2.

[0015]

[Table 1]

[0016]

[Table 2] As is clear from Tables 1 and 2, an aluminum foil subjected to a chemical conversion treatment of 0.1 V or more after etching was used as a cathode foil, and butyl rubber using magnesium silicate as a filler was used as a rubber sealing body. It was found that leakage of the driving electrolyte did not occur in the aluminum electrolytic capacitor, and high reliability was obtained.

A driving electrolyte using another quaternary ammonium salt such as tetraethylammonium maleate, tetramethylammonium phthalate or maleate instead of tetraethylammonium phthalate is used. In the evaluation, leakage of the driving electrolyte also occurred in the aluminum electrolytic capacitor using the cathode foil that had been subjected to chemical conversion treatment and the butyl rubber using magnesium silicate as the filler as the rubber sealing body. It was confirmed that it did not. Example 2 In a solvent containing γ-butyrolactone as a main component, a phthalate of imidazolinium was used as a main solute to form
By weight, a driving electrolyte was prepared. Next, using this driving electrolyte, a rated voltage of 16 V and a capacitance of 330 μm
F. An electrolytic capacitor having a case size of 10 mm and a length of 12.5 mm is manufactured.

The cathode foil according to the embodiment used herein was obtained by subjecting an aluminum foil having a purity of 99% to AC electrolytic etching in a 6% hydrochloric acid solution, and then applying 0.05 V, 0.5 V, 1.0 V
V, 1.5 V, 2.0 V, and 5.0 V. As a conventional example, an unformed cathode foil obtained by etching an Al foil was used. Further, butyl rubber using magnesium silicate as a filler was used as the rubber sealing body according to the example, and butyl rubber used as a filler of calcium carbonate was used as the rubber sealing body according to the conventional example.

After 500 electrolytic capacitors were produced by combining these materials and subjected to aging treatment, a rated voltage was applied in a high-temperature and high-humidity atmosphere at a temperature of 85 ° C. and a humidity of 85%, and a no-load test was performed for 8000 hours. After the test, the leakage of the driving electrolyte was confirmed for each capacitor sample after the test. The results are shown in Tables 3 and 4.

[0020]

[Table 3]

[0021]

[Table 4] As is clear from Tables 3 and 4, an aluminum foil subjected to a chemical conversion treatment of 0.1 V to 5 V after etching was used as a cathode foil, and butyl rubber using magnesium silicate as a filler was used as a rubber sealing body. In the aluminum electrolytic capacitor, it was found that leakage of the driving electrolyte did not occur and high reliability was obtained.

[0022]

As described above, in the aluminum electrolytic capacitor according to the present invention, the direction of the current caused by the local battery formed between the cathode foil and the round bar portion of the cathode lead terminal connected to the foil is determined. By reversing the rotation, the alkalinization of the driving electrolyte in contact with the rubber seal near the round bar of the lead terminal on the cathode side was prevented, and the alkali resistance of the rubber seal itself was improved. The leakage of the liquid was prevented. Therefore, the reliability of the aluminum electrolytic capacitor having low loss and low impedance characteristics can be improved, so that the present invention has great industrial and practical value.

[Brief description of the drawings]

FIG. 1 is a perspective view showing components of an aluminum electrolytic capacitor.

FIG. 2 is a vertical sectional view of the aluminum electrolytic capacitor.

[Explanation of symbols]

 2 Capacitor element 3 Anode lead terminal 4 Cathode lead terminal 5 Rubber sealing body 6 Aluminum case 31, 41 Aluminum round bar part 51, 52 Terminal insertion hole of rubber sealing body

Claims (1)

[Claims] 1. A capacitor element wound between an anode foil and a cathode foil via an electrolytic paper, and an aluminum lead terminal and a cathode lead terminal of the capacitor element drawn out from the anode foil and the cathode foil. A rubber sealing member in which each round bar portion is fitted in each terminal insertion hole;
A case in which the capacitor element impregnated with a non-aqueous driving electrolyte containing either a quaternary ammonium salt or an imidazolinium salt is sealed together with the rubber sealing body. Is a butyl rubber containing magnesium silicate as a filler, and the cathode foil is an aluminum foil formed with a film having a withstand voltage of 0.1 V or more after etching.