JP2000036439A - Polarized aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a polarized aluminum electrolytic capacitor where electrolyte is prevented from leaking outside, even if active chemicals are used as driving electrolyte. SOLUTION: This electrolytic capacitor is equipped with a capacitor element 2 formed by rolling an anode foil and a cathode foil interposing an electrolytic paper between them, a rubber sealer 5 provided with insertion holes 51 ands 52, in which the aluminum round rods 31 and 41 of an anode lead terminal 3 and a cathode lead terminal 4 led out from the anode foil and the cathode foil are inserted, and an aluminum case 2 which seals up the capacitor element 2 impregnated with a driving electrolyte solution, that contains quaternary ammonium salt or imidazollinium salt with the rubber sealer 4. In this case, an aluminum foil where Ti is deposited on its surface of a thickness of several tens to several thousands of nm by sputtering is used as the cathode foil.

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.

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 a case in which a Ti (titanium) film is formed on an etched aluminum (Al) foil surface as the cathode foil.

In the present invention, the cathode foil having a Ti film formed on the surface of the edging-treated aluminum foil is used.
The electrode potential of the cathode foil becomes more noble than 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, the electrode reaction on the surface of the round bar portion such that alkalizing in the driving electrolyte around the round bar portion proceeds. Does not occur.
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.

The cathode foil used here is a cathode foil in which several tens of nm to several thousand nm of Ti are sputter-formed on the surface of an aluminum foil. If the thickness of Ti is too small, aluminum is considerably exposed. The direction of the current of the local battery cannot be reliably reversed, and the effect of preventing leakage of the electrolyte cannot be sufficiently obtained. On the other hand, even if the film thickness of Ti exceeds several thousand nm, further improvement in the effect of preventing leakage of the electrolytic solution cannot be expected from the viewpoint of the electrode potential, and only the cost increases.

[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.
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 sample used here has a film thickness of 5 nm and 10 nm on the surface of the etched aluminum foil.
m, 100 nm, 500 nm, 1000 nm and 20
It is formed by sputtering 00 nm of Ti. In addition,
As the aluminum foil, a foil obtained by subjecting a 40 μm aluminum foil having a purity of 99% to AC electrolytic etching in a 6% hydrochloric acid solution was used.

As a comparative example, a cathode foil obtained by subjecting a conventionally used Al foil to an etching treatment, that is, a 40 μm aluminum foil having a purity of 99%, was subjected to alternating current electrolytic etching in a 6% hydrochloric acid solution. The one not sputtered with Ti was used. After 500 electrolytic capacitors were produced using these cathode foils, respectively, 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 leaving test was performed for 2000 hours. The state of 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 electrolytic capacitor using a cathode foil formed by spattering tens of nm to several thousand nm of Ti on an aluminum foil does not cause leakage of the driving electrolyte and high reliability is obtained. Turned out to be. In addition, in place of the tetraethylammonium phthalate, tetraethylammonium maleate,
In the evaluation performed with a driving electrolyte using another quaternary ammonium salt such as phthalate or maleate of tetramethylammonium, a foil obtained by sputtering Ti on an aluminum foil was also used as the cathode foil. It was confirmed that leakage of the driving electrolyte did not occur in the aluminum electrolytic capacitor. 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 solution. 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 sample used here also has a film thickness of 5 nm and 10 nm on the etched aluminum foil surface.
m, 100 nm, 500 nm, 1000 nm and 20
It is formed by sputtering 00 nm of Ti. In addition,
As the aluminum foil, a foil obtained by subjecting a 40 μm aluminum foil having a purity of 99% to AC electrolytic etching in a 6% hydrochloric acid solution was used.

For comparison, a cathode foil obtained by etching a conventionally used Al foil, that is, a 40 μm aluminum foil having a purity of 99%, was subjected to alternating current electrolytic etching in a 6% hydrochloric acid solution. The one not sputtered with Ti was used. After 500 electrolytic capacitors were produced using these cathode foils, respectively, 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 leaving test was performed for 8000 hours. The state of 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 electrolytic capacitor using a cathode foil formed by spattering Ti having a thickness of several tens of nm to several thousand nm on an aluminum foil does not cause leakage of the driving electrolyte and high reliability is obtained. Turned out to be. [Other Examples] In addition, Ti on the surface of aluminum foil
In forming the film, in addition to sputtering, evaporation,
Alternatively, polyvinyl alcohol in which Ti particles are dispersed may be applied to the etched aluminum foil surface.

[0022]

As described above, as described above, 4
When a driving electrolyte containing a quaternary ammonium salt or an imidazolinium salt is used, the driving electrolyte is leaked in the conventional cathode foil. However, as in the present invention, Ti is added to the etched aluminum foil. By using the cathode foil with the film formed, the electrode potential on the cathode foil surface is made noble in the driving electrolyte from the round bar part of the cathode lead terminal, so that the leakage of the driving electrolyte is reliably prevented. can do. 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;
And a case for sealing the capacitor element impregnated with a driving electrolyte containing either a secondary ammonium or an imidazolinium salt together with the rubber sealing body. A polar aluminum electrolytic capacitor, characterized in that a titanium film is formed on the surface of an aluminum foil.