JP3457222B2 - Aluminum electrolytic capacitors - 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 mounted on various electric / electronic devices.

[0002]

2. Description of the Related Art Among various 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 tubular capacitor case 3 made of aluminum and accommodating the capacitor element 2.
And a synthetic resin sealing body 4 that closes 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 end portions of these terminals 41 and 42 are anode tab terminals drawn out from the capacitor element 2 as an anode internal terminal 43 and a cathode internal terminal 44. 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,
Out of 22, the cathode tab terminal 22 used is not anodized and the anode tab terminal 21 used is anodized. However, for both tab terminals 21 and 22, Plane thick aluminum foil that has not been roughened by etching is used.

Further, in both the anode tab terminal 21 and the cathode tab terminal 22, the electric 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 as shown in FIG. This is done by caulking 5 (or welding) with the tab terminal 21 and the cathode tab terminal 22 overlapped.

The behavior of the electrolytic capacitor 1 when charging / discharging occurs is as follows. In the electrolytic capacitor 1, as the cathode foil 27, an aluminum foil having a thickness of, for example, 20 μm to 50 μm is etched and then subjected to a film formation treatment of about several volts by anodic oxidation, and a case where the etching is forced only by etching. In some cases, a film that does not undergo a film formation process is used, but even when the film formation is not compulsorily performed, the aluminum foil surface reacts with water in the atmosphere or water in the electrolytic solution to reach about 1.0V. A film with pressure resistance is formed. Therefore, the electrostatic capacity of the electrolytic capacitor is composed of a combined capacity of the electrostatic capacity of the anodic foil oxide film holding the breakdown voltage and the electrostatic capacity of the cathode foil in series. 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 V, this voltage
When V and Vc are voltages shared by V on the anode side and the cathode side, respectively, a voltage Vc ′ applied to the cathode foil 27 at the time of discharging
Becomes [Equation 1].

[0005]

[Equation 1]

Here, if the voltage applied to the cathode foil 27 during discharge is too high, an unfavorable phenomenon occurs such that a film is formed on the cathode foil 27 and gas is generated in the capacitor. Therefore, if the voltage at which a film is not formed on the cathode foil 27 even if 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, conventionally, as the cathode foil 27, one having a large capacitance or the withstand voltage of the oxide film that would be generated on the cathode foil 27 by the charging / discharging current is previously formed so as to satisfy [Equation 3]. In order to improve the ripple resistance and the charge / discharge resistance of the electrolytic capacitor 1 such as the use of a capacitor, the development and improvement of materials such as the cathode foil 27 or the anode foil 26, the electrolytic solution and the separator are mainly dealt with. Came.

[0011]

However, there is a limit to improving the ripple resistance and charge / discharge resistance of the electrolytic capacitor 1 by developing such a basic material. That is, in the experiment repeated 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, and it was found that a ripple current that far exceeded the allowable ripple in a short time was periodic. For the electrolytic capacitor 1 used in the circuit applied to the battery and the charging / discharging circuit having a large voltage difference and a short cycle, no matter how close to the ideal cathode foil 27 is used, the cathode tab terminal 22 and the cathode foil 27 in the vicinity thereof are not affected. Since the film formation reaction occurs in the capacitor, gas is generated in the capacitor, which leads to new findings that malfunctions such as explosion-proof valve operation due to an increase in internal pressure occur.

Therefore, an object of the present invention is to prevent the formation of a film on the cathode side at the time of discharge from the structural aspect of the capacitor element, thereby significantly improving the charge / discharge resistance and the ripple current resistance. It is to provide an electrolytic capacitor.

[0013]

In order to solve the above-mentioned problems, the inventors of the present application have found from repeated experiments that a ripple current far exceeding the allowable ripple is applied to an electrolytic capacitor in a short time and periodically. The reason why the film formation reaction occurs on the cathode foil around the cathode tab terminal in an electrolytic capacitor used in a charge / discharge circuit with a large voltage difference and a short cycle is as follows.
It was concluded that the conventional cathode tab terminal has a low capacity per unit area, and therefore a high voltage is applied to the cathode tab terminal and its surroundings when a discharge current flows to the cathode tab terminal. Therefore, in the present invention, by processing one surface of the cathode tab terminal to be roughened, the capacitance per unit area of the cathode tab terminal can be increased, and a ripple current far exceeding the allowable ripple in a short time can be obtained. A high voltage is not applied to the cathode tab terminal and its surroundings even when it is periodically applied to the electrolytic capacitor or in the electrolytic capacitor used in the charge / discharge circuit having a large voltage difference and a short cycle. 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 joint 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 through a separator. In an aluminum electrolytic capacitor impregnated with a driving electrolytic solution, the surface of the cathode tab terminal facing the separator is roughened, and the surface in contact with the cathode foil is flat. is there.

An aluminum electrolytic capacitor is characterized in that the anode tab terminal is anodized.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the structure of an electrolytic capacitor. 2 and 3 are an explanatory view showing a structure of a capacitor element used in the electrolytic capacitor according to the present embodiment and an explanatory view showing a method for manufacturing the capacitor element, respectively. The electrolytic capacitor of this embodiment also
Since the basic structure is common to conventional electrolytic capacitors,
Corresponding parts are designated 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 anodization (chemical conversion treatment), an etching foil having no anodization film, or a thin anodization film is used. A cathode element 27 formed of an etching foil and a capacitor element 2 around which a separator 28 is wound, a bottomed cylindrical aluminum-made capacitor case 3 and the open end side of the capacitor case 3. It has a synthetic resin sealing body 4 for closing the capacitor 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 electrolytic solution. 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, 42 serve as an anode internal terminal 43 and a cathode internal terminal 44, respectively. The anode tab terminal 21 and the plurality of cathode tab terminals 22 are electrically connected to each other. Here, each of the anode tab terminal 21 and the cathode tab terminal 22 is cut out from a thick aluminum foil having a thickness of about 200 μm. Of these tab terminals 21 and 22,
Although the cathode tab terminal 22 is not anodized and the anode tab terminal 21 is anodized, both tab terminals 21 and 22 are anodized. You may use what gave.

In the present embodiment, the electrical connection between the anode tab terminal 21 and the anode foil 26 is performed by crimping 5 (or welding) with the anode tab terminal 21 overlaid on the surface of the anode foil 26, as in the conventional case. 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). It is electrically connected. As the cathode tab terminal 22 of the comparative example, a tab terminal having both surfaces roughened was used. Further, as the cathode foil 27, either an etching foil having no anodized film formed thereon, an etching foil having a thin anodized film formed thereon, or a foil obtained by vapor deposition on the surface of the etching foil may be used.

[0019]

EXAMPLES The results of the evaluation test relating to the present invention will be described below. φ63 × 60mm, rated 400V 1500
Fabricate a μF electrolytic capacitor. Voltage difference 150V, 0.
A 25 sec charge / discharge test was performed and the results shown in Table 1 were obtained. (10 samples for each condition)

[0020]

[Table 1]

The conventional example using the cathode tab terminal without roughening caused valve actuation, but the embodiment 1 using the cathode tab terminal having only one surface roughened according to the present invention did not cause valve actuation. Furthermore, since the flat surface of the cathode tab terminal is bonded to the cathode foil, the charge / discharge characteristics can be improved without lowering the bonding strength. The anode tab terminal is preferably anodized in order to shorten the aging time.

The roughening method is not particularly limited, and known methods such as knurling, mechanical roughening such as sandblasting, and electrical or chemical etching can be used.

In the electrolytic capacitor 1 of the present embodiment thus constructed, the cathode tab terminal having the roughened surface and the increased capacitance is made to face the anode foil 21, so that the unit is smaller than the conventional cathode tab terminal 22. Since the capacitance per area is large, the value derived from the equation on the right side of the above [Equation 3] becomes small, and even if the ripple current far exceeding the allowable ripple is periodically applied within a short time, Further, 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 if a harsh ripple application test or a charge / discharge test is performed, a film is not 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, since the aluminum electrolytic capacitor according to the present invention uses the tab terminal having a large capacitance by roughening one surface of the cathode tab terminal, the conventional cathode tab terminal is used. The capacitance per unit area becomes larger than that of the terminals, and even if a ripple current far exceeding the allowable ripple is periodically applied within a short time, the charge / discharge circuit has a large voltage difference and a short cycle. , No high voltage is 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 capacitor can be prevented.

[Brief description of drawings]

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

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

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

FIG. 4 is an explanatory diagram showing a structure of a capacitor element used in a conventional electrolytic capacitor.

[Explanation of symbols]

1 Electrolytic capacitor 2 Capacitor element 3 capacitor case 4 Sealing body 5 Caulking (or welding) 8-element winder 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 Crimping device

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01G 9/008

Claims (2)

(57) [Claims] 1. 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 through a separator. An aluminum electrolytic capacitor obtained by impregnating a driving electrolytic solution with the above, wherein the surface of the cathode tab terminal facing the separator is roughened, and the surface in contact with the cathode foil is flat. 2. The aluminum electrolytic capacitor according to claim 1, wherein the anode tab terminal is anodized.