JP2000030976A - Polarizable aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize the polarizable aluminum electrolytic capacitor which is free of a leak of an electrolyte, even when active chemicals are used as a driving electrolyte. SOLUTION: Of the polarized aluminum electrolytic capacitor having a capacitor element 2 wound between anode foil and cathode foil across electrolytic paper, a rubber sealing body 5 having aluminum-made round rod parts 31 and 42 of an anode lead terminal 3 and a cathode lead terminal 4, led out of the anode foil and cathode foil of the capacitor element 2, fitted in terminal insertion holes 51 and 52 respectively, and an aluminum-made case 6 which seals the capacitor element 2 impregnated with the driving electrolyte containing a quaternary ammonium salt or an imidazolium salt together with the rubber sealing body 5, the round rod part 41 uses a cathode lead terminal 4 made of Al-Cu alloy, Al-Mg alloy, or Al-Zn alloy.

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, and a driving electrolyte solution is used.

[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.

Based on such findings, the present invention is characterized in that the polarity of the local battery is reversed to prevent leakage of the driving electrolyte. 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. And a capacitor element impregnated with a driving electrolyte containing a quaternary ammonium salt or an imidazolinium salt are sealed together with the rubber sealing member. And the round bar portion on the cathode lead terminal side comprises an aluminum-copper (Al-Cu) alloy, an aluminum-magnesium (Al-Mg) alloy, and an aluminum-zinc (A).
It is characterized by being formed of an aluminum alloy such as an l-Zn) alloy.

[0009] The aluminum alloy referred to in the present specification is:
It refers to an alloy that is more potential than the aluminum foil used as the cathode foil in the driving electrolyte. In the present invention, the round bar portion on the cathode lead terminal side is made of an Al-Cu alloy, A
Since the cathode foil is formed of an aluminum alloy such as an l-Mg alloy or an Al-Zn alloy, the electrode potential of the cathode foil is higher than that of the aluminum round bar portion of the cathode lead terminal. Therefore,
Even if a local battery is formed by the round bar portion of the lead terminal on the cathode side and the cathode foil, an electrode reaction occurs on the surface of the round bar portion such that alkalizing proceeds in the driving electrolyte around the round bar portion. Absent. 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, when the round bar portion of the cathode lead terminal is formed of an aluminum alloy such as an Al-Cu alloy, an Al-Mg alloy, or an Al-Zn alloy, the electrode potential becomes lower than that of the cathode foil because of the alloy itself. Rather than being affected by the electrode potential, aluminum oxide (natural oxide film) is generated in the air on the surface of the round bar using such an alloy, while the cathode foil It is considered that the surface is oxidized during the manufacturing process or the like and is stabilized in potential.

[0011]

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 solution.
Next, using this driving electrolyte, rated voltage 16 V, capacitance 330 μF, case size 10 mm, length 12.5
mm aluminum electrolytic capacitor is manufactured. The cathode foil used here was obtained by subjecting an aluminum foil having a purity of 99% to AC etching in an aqueous hydrochloric acid solution.

[0012] In the embodiment, as the round rod portion of the cathode lead terminal side described with reference to FIGS. 1 and 2, Al ₉₀ -Cu
₁₀ alloy, Al ₉₀ -Mg ₁₀ alloy, used as formed from bar material made of Al ₉₀ -Zn ₁₀ alloy. On the other hand, in the conventional example, a cathode lead terminal having a round bar portion formed from a normal aluminum bar material having a purity of 99% is used. In the present invention, since there is no restriction on the material of the round bar portion on the anode lead terminal side, a round bar portion made of normal aluminum having a purity of 99.9% is used. Regardless of whether the cathode side or the anode side, the connection between the electrode foil and the lead terminal is performed by caulking with a tab formed integrally with the round bar part. Are the same.

Using a lead terminal having such a round bar portion, 500 electrolytic capacitors are manufactured respectively, and after aging treatment, a rated voltage is applied in a high temperature and high humidity atmosphere at a temperature of 85 ° C. and a humidity of 85%. 200 no-load standing test
The test was performed for 0 hour, and the state of leakage of the driving electrolyte was confirmed for each capacitor sample after the test. Table 1 and Table 2 show the results.
Shown in

[0014]

[Table 1]

[0015]

[Table 2] As shown in Table 1 and Table 2, Al-Cu alloy, Al-Mg alloy, Al-Zn
It has been found that in the case of an aluminum electrolytic capacitor using an alloy, leakage of the driving electrolyte does not occur and high reliability can be obtained. In addition, in place of the tetraethylammonium phthalate, tetraethylammonium maleate,
In the evaluation performed with the driving electrolyte using other quaternary ammonium salts such as phthalate or maleate of tetramethylammonium, the round bar portion on the cathode lead terminal side also showed an Al-Cu alloy, Al
It was confirmed that no leakage of the driving electrolyte occurred in the aluminum electrolytic capacitor using the -Mg alloy or the Al-Zn alloy. Example 2 Next, 15% by weight of a phthalic acid salt of imidazolinium 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, a rated voltage of 16 V, a capacitance of 33
An electrolytic capacitor having a size of 0 μF, a case size of 10 mm, and a length of 12.5 mm is manufactured. The cathode foil used here was obtained by subjecting an aluminum foil having a purity of 99% to AC etching in an aqueous hydrochloric acid solution. Again, as round bar portion of the cathode lead terminal side described with reference to FIGS. 1 and 2, as in Example 1, Al ₉₀ -Cu ₁₀ alloy, Al ₉₀ -Mg ₁₀ alloy, Al ₉₀ -Zn ₁₀ Alloy A rod formed from a rod made of, for example, a rod formed of a normal aluminum rod having a purity of 99% is used as a conventional example. For the round bar portion on the anode lead terminal side, one formed from a normal aluminum bar material having a purity of 99.9% is used.

500 electrolytic capacitors are manufactured using the lead terminals having such a round bar portion, and after aging treatment, a rated voltage is applied in a high-temperature and high-humidity atmosphere at a temperature of 85 ° C. and a humidity of 85%. , 700 no-load test
The test was performed for 0 hour, and the state of leakage of the driving electrolyte was confirmed for each capacitor sample after the test. Tables 3 and 4 show the results.
Shown in

[0017]

[Table 3]

[0018]

[Table 4] As shown in Tables 3 and 4, Al-Cu alloy, Al-Mg alloy, Al-Zn
It has been found that the aluminum electrolytic capacitor using the alloy does not cause the leakage of the driving electrolyte, and that high reliability can be obtained. [Other Examples] In addition to the above evaluations, various round bar portions were examined by changing the alloy composition. However, the round bar portion of the cathode lead was made of an aluminum alloy so that the round bar portion was formed of a cathode foil. It was confirmed that when the electrode potential in the driving electrolyte was lower than that in the driving electrolyte, leakage of the driving electrolyte from the cathode side could be prevented.

[0019]

As described above, as described above, 4
In using the driving electrolyte containing a quaternary ammonium salt or an imidazolinium salt, in the present invention, a cathode lead terminal whose round bar portion is formed of an aluminum alloy is used. Therefore, according to the present invention, the electrode potential on the surface of the cathode foil becomes more noble in the driving electrolyte than at the round bar portion of the cathode lead terminal, so that leakage of the driving electrolyte can be reliably 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 51, 52 Terminal insertion hole of rubber sealing body

Claims (2)

[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. And the capacitor element impregnated with a driving electrolyte containing a quaternary ammonium salt or imidazolinium salt is sealed together with the rubber sealing member. A polar aluminum electrolytic capacitor having a case and the case, wherein the round bar portion on the cathode lead terminal side is formed of an aluminum alloy. 2. The aluminum electrolytic capacitor according to claim 1, wherein the aluminum alloy is any one of an aluminum-copper alloy, an aluminum-magnesium alloy, and an aluminum-zinc alloy.