JP2001244144A - Aluminium electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminium electrolytic capacitor which can significantly raise the charging/discharging resistance performance and ripple current resistance performance of the electrolytic capacitor. SOLUTION: An aluminium electrolytic capacitor formed by impregnating a capacitor element, which is formed by winding or laminating an anode foil connected electrically with an anode tab terminal and a cathode foil connected electrically with a cathode tab terminal via a separator, with an electrolyte for drive is characterized in that a deposited layer is formed by depositing valve metallic particles on the surface, which comes into contact with at least the separator, of the cathode tab terminal, the deposited layer is formed into a sponge shape, the deposit thickness of the deposited layer is set at 2.0 to 10.0 μm and the particle diameter of the metal particles is set at 0.020 to 0.200 μm.

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, and more particularly to a tab terminal.

[0002]

2. Description of the Related Art As shown in FIGS. 1 and 3, an aluminum electrolytic capacitor (hereinafter, referred to as an electrolytic capacitor) houses a capacitor element 2 in which an anode foil, a cathode foil and a separator are wound, and the capacitor element 2 is housed. A capacitor case 3 made of aluminum having a bottomed cylindrical shape and a sealing body 4 made of synthetic resin for sealing the open end side of the capacitor case 3 are provided. An anode terminal 41 is provided on the outer end surface of the sealing body 4.
And a cathode terminal 42, and these terminals 41, 4
The lower end of 2 has an anode internal terminal 43 and a cathode internal terminal 4
4, an anode tab terminal 21 and a cathode tab terminal 22 drawn from the capacitor element 2 are electrically connected. Here, the anode tab terminal 21 and the cathode tab terminal 22
In each case, aluminum foil of about 200 μm was cut. Of these tab terminals 21 and 22, the cathode tab terminal 22 that has not been subjected to a chemical conversion treatment is used, while the anode tab terminal 21 that has been subjected to a chemical conversion treatment is used. The tab terminals 21 and 22 are also made of aluminum foil not subjected to surface processing.

[0003] 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, 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 pressure-resistant film is formed. For this reason,
The capacitance of the electrolytic capacitor is composed of the combined capacitance of the anode foil capacitance and the cathode foil capacitance that maintain the withstand voltage in series connection.

Here, the electrostatic capacity per unit area of the anode foil is Ca (μF / cm ² ), the electrostatic capacity per unit volume of the cathode foil is Cc (μF / cm ² ), and the electrolytic capacitor 1 is charged. The applied voltage is V, the voltages shared by the anode side and the cathode side are Va and Vc, and the cathode foil and the charges accumulated in the cathode foil at this time are Qa and Qc. When discharging the charged electrolytic capacitor, the capacitance of the anode foil and the capacitance of the cathode side are connected in parallel. Therefore, the remaining charge that is not discharged becomes Qa-Qc, and the voltage Vc 'applied to the cathode foil 27 at the time of discharge becomes [Equation 1].

[0006]

(Equation 1)

Here, if the voltage applied to the cathode foil 27 at the time of discharging is too high, undesired phenomena occur, such as formation of a film on the cathode foil 27 and generation of gas in the capacitor. Therefore, if a voltage at which no film is 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.

[0008]

(Equation 2)

Here, since Va = V−Vc, [Equation 3] is derived from [Equation 2].

[0010]

(Equation 3)

If this [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.

Conventionally, a cathode foil having a large capacitance or an oxide film that would be generated on the cathode foil 27 by charging / discharging current is determined in advance so as to satisfy [Equation 3]. In order to improve the ripple resistance and charge / discharge performance of the electrolytic capacitor 1 by using a film that has been formed, the development or improvement of materials such as the cathode foil 27 or the anode foil 26, the electrolyte, and the separator is mainly performed. Has been done.

[0013]

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 the experiment repeatedly performed by the inventor of the present application, the electrolytic capacitor 1 subjected to the ripple resistance test and the charge / discharge 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. It has been newly found that since a film-forming reaction takes place, gas is generated in the capacitor, causing problems such as explosion-proof valve operation caused by an increase in internal pressure.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrolytic capacitor capable of greatly improving charge / discharge resistance and ripple current resistance by preventing the formation of a film on the cathode side during discharge. It is in.

[0015]

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 single time and periodically is provided. 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, valve metal particles are vapor-deposited on the above-mentioned cathode tab terminal, and further formed into a sponge shape.
The capacitance per unit area of the cathode tab terminal can be increased. Therefore, even if a ripple current far exceeding the permissible ripple is applied to the electrolytic capacitor in a single time period, or in an electrolytic capacitor used in a charge / discharge circuit having a large voltage difference and a short period, the cathode tab terminal And there is no high voltage around it. Therefore, no film is formed on and around the cathode tab terminal, so that gas generation in the capacitor can be prevented.

That is, the driving electrolyte is applied to a capacitor element in which an anode foil to which an anode tab terminal is electrically connected and a cathode foil to which a cathode tab terminal is electrically connected are wound or laminated via a separator. An aluminum electrolytic capacitor obtained by impregnating an aluminum electrolytic capacitor, wherein valve metal particles are vapor-deposited on at least a surface of the cathode tab terminal in contact with the separator.

An aluminum electrolytic capacitor characterized in that the valve metal particles are sponge-deposited.

The vapor deposition thickness of the valve metal particles is 2.0 to 1
An aluminum electrolytic capacitor having a thickness of 0.0 μm.

The particle diameter of the valve metal particles is 0.020 to
An aluminum electrolytic capacitor having a thickness of 0.200 μm.

[0021]

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. FIG. 2 is an explanatory diagram showing the structure of the capacitor element used for the electrolytic capacitor according to the present embodiment.
Note that the electrolytic capacitor of the present embodiment also has the same basic structure as the conventional electrolytic capacitor, and 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 etched foil and a separator 28 wound thereon; a bottomed cylindrical aluminum capacitor case 3 containing the capacitor element 2; and an open end side of the capacitor case 3 And a sealing element 4 made of synthetic resin for sealing the
And an element fixing member 30 for fixing the element. 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 cut from a thick aluminum foil of about 200 μm. Of these tab terminals 21 and 22, the cathode tab terminal 22 is not subjected to a chemical conversion treatment, while the anode tab terminal 21 is subjected to a chemical treatment. Any of the tab terminals 21 and 22 may be subjected to a chemical conversion treatment.

In this embodiment, the electrical connection between the anode tab terminal 21 and the anode foil 26 is made in the same manner as in the prior art.
The crimping 5 (or welding) or the like is performed in a state where the anode tab terminal 21 is superimposed on the surface. However, the cathode tab terminal 22 has a particle diameter of 0.02 to 0.20.
A tab terminal is used in which valve metal particles of μm are formed in a sponge shape with a thickness of 2 to 5 μm on at least the contact surface of the separator by vapor deposition.

[0024]

EXAMPLE Using a cathode tab terminal shown in Table 1, a rating of 40 was used.
Ten electrolytic capacitors each having 0 V / 1500 μF and a size of φ63 × 60 mmL were produced. Ta of electrolytic capacitor
After measuring nδ, a charge / discharge test in which charging at 400 V, charging for 1 second, and discharging for 1 second was repeated 10 million times was performed. Table 1 shows the results.

[0025]

[Table 1]

As is evident from Table 1, Examples 1 to 7 had good products tan δ and no rejects occurred in the charge / discharge test. However, in Examples 1 to 7 and Comparative Examples having a low capacitance, the results were satisfactory. In the discharge test, some products failed due to valve operation. From this result, it was found that the tab terminal capacity on which the valve metal particles were deposited was desirably 0.3 times or more the capacitance of the cathode foil.

Next, the deposition thickness of the valve metal particles was tested. FIG. 4 is a characteristic diagram of the deposition thickness, the product tan δ, and the failure rate in the charge / discharge test. According to FIG.
It turned out that 2.0-10.0 micrometers is desirable. When the vapor deposition thickness is less than 2.0 μm, the effect of withstanding the charge / discharge test is low, and when the vapor deposition thickness exceeds 10.0 μm, the product tan δ becomes high, which is problematic.

Further, the particle diameter of the valve metal particles to be deposited was examined. FIG. 5 shows a characteristic diagram of the particle diameter, product tan δ, and tab terminal capacity / cathode foil capacity magnification. From FIG. 5, if the particle diameter is less than 0.02 μm, the required capacity cannot be obtained because the particle diameter is too small.
This is a problem because nδ becomes high. Therefore, the particle size is 0.0
It turned out that 20 to 0.200 μm is desirable.

In the embodiment, aluminum and titanium are used as the valve metals to be deposited. However, the same effect as in the embodiment can be obtained by using tantalum, niobium, hafnium or the like. Further, the vapor deposition method is not limited to the vacuum vapor deposition method, and the vapor deposition may be performed in an inert gas such as argon, a rare gas such as nitrogen, or a slight oxygen atmosphere.

As the aluminum foil on which the valve metal particles are deposited, any of a roughened etching foil and a non-roughened plain foil may be used.

[0031]

As described above, in the aluminum electrolytic capacitor according to the present invention, valve metal particles are vapor-deposited on at least the surface in contact with the separator. Even if a ripple current far exceeding the allowable ripple is periodically applied to the electrolytic capacitor, and the electrolytic capacitor used in the charge / discharge circuit having a large voltage difference and a short cycle, a high voltage is applied to the cathode tab terminal and its surroundings. No voltage is applied.
Therefore, the formation of a film on the cathode tab terminal and the periphery thereof is suppressed, and a highly reliable electrolytic capacitor can be realized.

[Brief description of the drawings]

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

FIG. 2 is a structural explanatory view of a capacitor element according to an embodiment to which the present invention is applied.

FIG. 3 is a structural explanatory view of a conventional capacitor element.

FIG. 4 is a characteristic diagram showing a deposition thickness of valve metal particles, a product tan δ, and a failure rate in a charge / discharge test.

FIG. 5 is a characteristic diagram of the particle diameter of valve metal particles, product tan δ, and tab terminal capacity / cathode capacity (capacity magnification).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolytic capacitor 2 Capacitor element 3 Capacitor case 4 Sealing body 5 Caulking (or welding) 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 Anode internal terminal 44 Cathode internal terminal

Continuing on the front page (72) Inventor Nobuo Kuroki, Nichicon Corporation

Claims (4)

[Claims] An electrolytic solution for driving is applied to a capacitor element in which an anode foil to which an anode tab terminal is electrically connected and a cathode foil to which a cathode tab terminal is electrically connected are wound or laminated via a separator. An aluminum electrolytic capacitor obtained by impregnating an aluminum electrolytic capacitor, wherein valve metal particles are vapor-deposited on at least a surface of the cathode tab terminal which is in contact with the separator. 2. An aluminum electrolytic capacitor, wherein the valve metal particles according to claim 1 are deposited in a sponge shape. 3. The deposition thickness of the valve metal particles is 2.0 to 2.0.
3. The method according to claim 1, wherein the thickness is 10.0 μm.
The aluminum electrolytic capacitor as described. 4. The valve metal particles having a particle diameter of 0.020.
4 to 0.200 μm.
The aluminum electrolytic capacitor as described.