JP2001035753A - Aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor, where a charging/discharging- resistance performance and resistance to ripple current performance are significantly improved. SOLUTION: At least one surface of a cathode lead tab 22 is roughened to provide a lead tab having a larger electrostatic capacity, avoiding high voltage at the lead tab and its vicinity at discharge. So, no film is generated at the cathode lead tab 22 and its vicinity, even if it is subjected to a severe ripple application test or charge/discharge test, thus preventing generation of gas in an electrolytic capacitor.

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 mounted on various electric / electronic devices.

[0002]

2. Description of the Related Art Among various types of capacitors, an aluminum electrolytic capacitor (hereinafter referred to as an electrolytic capacitor) is
As shown in FIG. 1, a capacitor element 2 in which an anode foil, a cathode foil and a separator are wound, and a bottomed cylindrical aluminum capacitor case 3 containing the capacitor element 2
And a sealing member 4 made of synthetic resin for closing the open end side of the capacitor case 3. An anode terminal 41 and a cathode terminal 42 are formed on the outer end surface of the sealing body 4, and lower ends of these terminals 41 and 42 are formed as anode internal terminals 43 and cathode internal terminals 44, respectively. 21 and the cathode tab terminal 22 are electrically connected. Here, each of the anode tab terminal 21 and the cathode tab terminal 22 is cut out from an aluminum plate of about 200 μm. These tab terminals 21,
Among them, a cathode tab terminal 22 that is not subjected to anodization is used, and an anode tab terminal 21 that is subjected to anodization is used. A thick aluminum foil made of plain without being subjected to surface roughening such as etching is used.

In both the anode tab terminal 21 and the cathode tab terminal 22, the electrical connection with the anode foil or the cathode foil is made by connecting the anode foil 26 and the cathode foil 27 to the surface of the anode foil 26 and the cathode foil 27 as shown in FIG. This is performed by crimping 5 (or welding) in a state where the tab terminal 21 and the cathode tab terminal 22 are overlapped.

The behavior of the electrolytic capacitor 1 when charging / discharging occurs is as follows. In the electrolytic capacitor 1, the cathode foil 27 is formed by etching a aluminum foil having a thickness of, for example, 20 μm to 50 μm and then performing a film generation process of about several volts by anodic oxidation. In some cases, a film that does not perform a strong film-forming treatment may be used. However, even when a film is not forcibly formed, the surface of the aluminum foil reacts with moisture in the atmosphere or moisture in the electrolytic solution to about 1.0 V. A film having a pressure resistance is generated. For this reason, the capacitance of the electrolytic capacitor is made up of the combined capacitance of the capacitance of the anodic foil oxide film and the capacitance of the cathode foil in series connection that maintains the withstand voltage. Here, the capacitance per unit area of the anode foil is Ca (μF / cm ² ), the capacitance per unit volume of the cathode foil is Cc (μF / cm ² ), and the voltage at which the electrolytic capacitor 1 is charged. Is V, this voltage
When the voltages sharing V between the anode side and the cathode side are Va and Vc, the voltage Vc 'applied to the cathode foil 27 at the time of discharge.
Becomes [Equation 1].

[0005]

(Equation 1)

If the voltage applied to the cathode foil 27 at the time of discharge is too high, undesired phenomena occur, such as formation of a film on the cathode foil 27 and generation of gas in the capacitor. Accordingly, if a voltage at which a film is not formed on the cathode foil 27 even when a voltage is applied to the cathode foil 27 during discharge is V ′, it is necessary to satisfy [Equation 2] during discharge.

[0007]

(Equation 2)

Here, since Va = V−Vc, [Equation 3] is derived from the above equation.

[0009]

(Equation 3)

If the above [Equation 3] is satisfied, no film is formed on the cathode foil 27 even if a voltage is applied to the cathode foil during discharge. Therefore, in the related art, a film having a large capacitance or a withstand voltage of an oxide film that would be generated on the cathode foil 27 by charging / discharging current is previously formed as the cathode foil 27 so as to satisfy [Equation 3]. In order to improve the ripple resistance and the charge / discharge performance of the electrolytic capacitor 1 by using, for example, a material such as a cathode foil 27 or an anode foil 26, an electrolytic solution, and a separator, a response is mainly made. Have been.

[0011]

However, there is a limit in improving the ripple resistance and the charge / discharge resistance of the electrolytic capacitor 1 due to the development of such basic materials. That is, in an experiment repeatedly performed by the inventor of the present application, the electrolytic capacitor 1 subjected to the ripple resistance test and the charge / discharge resistance test was investigated and analyzed. No matter how close the cathode foil 27 is to the electrolytic capacitor 1 used in the circuit applied to the battery and the charge / discharge circuit having a large voltage difference and a short cycle, the cathode tab terminal 22 and the surrounding cathode foil 27 can be used. A new finding was obtained that a gas was generated in the capacitor due to a film-forming reaction, which caused problems such as explosion-proof valve operation due to an increase in internal pressure.

Accordingly, an object of the present invention is to significantly improve charge / discharge resistance and ripple current resistance by preventing the formation of a film on the cathode side during discharge from the structure of the capacitor element. An electrolytic capacitor is provided.

[0013]

In order to solve the above-mentioned problems, the present inventor has found from a repeated experiment that a circuit in which a ripple current exceeding a permissible ripple is applied to an electrolytic capacitor in a short time and periodically. Also, the reason why the film formation reaction occurs on the cathode foil around the cathode tab terminal in the electrolytic capacitor used in the charge and discharge circuit with a large voltage difference and a short cycle is as follows:
It has been concluded that the conventional cathode tab terminal has a low capacity per unit area, so that when a discharge current flows through the cathode tab terminal, a high voltage is applied to the cathode tab terminal and its surroundings. Therefore, in the present invention, by roughening one surface of the cathode tab terminal, the capacitance per unit area of the cathode tab terminal can be increased, and a ripple current far exceeding the allowable ripple can be obtained in a short time. Even when the voltage is applied to the electrolytic capacitor periodically, or in an electrolytic capacitor used in a charge / discharge circuit having a large voltage difference and a short cycle, a high voltage is not applied to the cathode tab terminal and its surroundings. Therefore,
Since no film is formed on the cathode tab terminal and its surroundings,
Gas generation in the condenser can be prevented. Furthermore, when only one surface of the cathode tab terminal is roughened, the surface in contact with the cathode foil is flat as in the conventional case, and no bonding failure occurs.

That is, a capacitor element in which an anode foil to which an aluminum anode tab terminal is electrically connected and a cathode foil to which an aluminum cathode tab terminal is electrically connected are wound or laminated via a separator. Wherein the cathode tab terminal is roughened on at least one side thereof.

[0015] The aluminum electrolytic capacitor is characterized in that the anode tab terminal is anodized.

[0016]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross section schematically showing the structure of the electrolytic capacitor. 2 and 3 are an explanatory view showing a structure of a capacitor element used for the electrolytic capacitor according to the present embodiment, and an explanatory view showing a method of manufacturing the capacitor element, respectively. The electrolytic capacitor of the present embodiment also
Since the basic structure is common with conventional electrolytic capacitors,
Corresponding parts are denoted by the same reference numerals.

As shown in FIGS. 1 and 2, in the electrolytic capacitor 1, an anode foil 26 obtained by subjecting an etching foil to anodic oxidation (chemical conversion treatment), an etching foil having no anodic oxide film formed thereon, or a thin anodic oxide film is used. A capacitor element 2 having a cathode foil 27 formed of an etching foil formed thereon and a separator 28 wound thereon, a bottomed cylindrical aluminum capacitor case 3 accommodating the capacitor element 2, and an open end side of the capacitor case 3 And an element fixing member 30 for fixing the capacitor element 2 to the capacitor case 3. The capacitor element 2 is impregnated with a driving electrolyte. An anode terminal 41 and a cathode terminal 42 are formed on the outer end surface of the sealing body 4, and the lower ends of these terminals 41 and 42 serve as an anode internal terminal 43 and a cathode internal terminal 44. The anode tab terminal 21 and the plurality of cathode tab terminals 22 are electrically connected to each other. Here, the anode tab terminal 21 and the cathode tab terminal 22 are both cut out of a thick aluminum foil of about 200 μm. Of these tab terminals 21 and 22,
The anode tab terminal 22 is not anodized, and the anode tab terminal 21 is anodized. However, in each of the tab terminals 21 and 22, anodization is not performed. May be used.

In the present embodiment, the electric connection between the anode tab terminal 21 and the anode foil 26 is made by crimping 5 (or welding) with the anode tab terminal 21 superimposed on the surface of the anode foil 26 as in the prior art. Is done by doing. However, as the cathode tab terminal 22 of the first embodiment, a tab terminal whose one surface is roughened to increase the capacitance is used, and the unprocessed surface is overlapped with the cathode foil 27 and crimped 6 (or welded). Electrically connected. As the cathode tab terminal 22 of Example 2, a tab terminal whose both surfaces were roughened was used. Further, as the cathode foil 27, any of an etching foil having no anodic oxide film formed thereon, an etching foil having a thin anodic oxide film formed thereon, and a foil having the surface of the etching foil subjected to vapor deposition or the like may be used.

[0019]

EXAMPLES The results of evaluation tests according to the present invention will be described below. φ63 × 60mm and rated 400V1500
Make electrolytic capacitor of μF. Voltage difference 150V, 0.
A charge / discharge test was performed for 25 seconds, and the results shown in Table 1 were obtained. (10 samples for each condition)

[0020]

[Table 1]

In the conventional example using the cathode tab terminal without rough surface processing, valve operation was caused, but in Examples 1 and 2 using the cathode tab terminal having rough surface processing of the present invention, no valve operation was caused. . Further, in Example 1 using the cathode tab terminal having only one surface roughened, the flat surface of the cathode tab terminal is joined to the cathode foil, so that the charge / discharge characteristics can be improved without lowering the joining strength. . And it is preferable to use an anodized terminal for the anode tab terminal in order to shorten the aging time.

The method of rough surface processing is not particularly limited, and known methods such as mechanical rough surface processing such as knurling and sand blasting, and electric or chemical etching can be used.

In the electrolytic capacitor 1 of the present embodiment having the above-described structure, the cathode tab terminal whose surface is roughened and whose capacitance is increased is opposed to the anode foil 21. Since the capacitance per area is large, the value derived from the expression on the right side of the above [Equation 3] becomes small, and even if a ripple current far exceeding the allowable ripple is applied periodically in a short time, Also, even when used in a charge / discharge circuit having a large voltage difference and a short cycle, a high voltage is not applied to the cathode tab terminal 22 and its surroundings. Therefore, even when a severe ripple application test or charge / discharge test is performed, no film is formed on the cathode tab terminal 22 and its surroundings, so that gas generation in the electrolytic capacitor 1 can be prevented.

[0024]

As described above, the aluminum electrolytic capacitor according to the present invention uses a tab terminal whose one side of the cathode tab terminal is roughened to increase the capacitance, so that the conventional cathode tab is used. A charge / discharge circuit with a large voltage difference and a short cycle even if a ripple current exceeding a permissible ripple is applied periodically in a short time because the capacitance per unit area becomes larger than the terminal. High voltage is not applied to the cathode tab terminal and its surroundings.
Therefore, no film is formed on and around the cathode tab terminal, so that gas generation in the capacitor can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure of an electrolytic capacitor.

FIG. 2 is an explanatory diagram showing a structure of a capacitor element used for an electrolytic capacitor to which the present invention has been applied.

FIG. 3 is an explanatory view showing a method of manufacturing the capacitor element shown in FIG.

FIG. 4 is an explanatory view showing a structure of a capacitor element used for a conventional electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolytic capacitor 2 Capacitor element 3 Capacitor case 4 Sealing body 5 Caulking (or welding) 8 Element winding machine 21 Anode tab terminal 22 Cathode tab terminal 26 Anode foil 27 Cathode foil 28 Separator 30 Element fixing material 41 Anode terminal 42 Cathode terminal 43 Pole internal terminal 44 Cathode internal terminal 81 Cathode tab terminal mounting area 82 Caulking device

Claims (2)

[Claims] 1. A capacitor element in which an anode foil electrically connected to an aluminum anode tab terminal and a cathode foil electrically connected to an aluminum cathode tab terminal are wound or laminated via a separator. An aluminum electrolytic capacitor obtained by impregnating a driving electrolytic solution into the aluminum electrolytic capacitor, wherein at least one surface of the cathode tab terminal is roughened. 2. The aluminum electrolytic capacitor according to claim 1, wherein said anode tab terminal is anodized.