JP2005051273A - Aluminum electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable aluminum electrolytic capacitor that can prevent the electrolytic solution from leaking out from the capacitor although the solution has a possibility of leaking out from the capacitor when a strong basic component produced in the cathode section of the capacitor erodes, particularly, the cathode lead or a sealing material brought into contact with the lead in the case where the capacitor is continuously used in an energized state in a high-moisture atmosphere. <P>SOLUTION: The aluminum electrolytic capacitor having a rated voltage of ≤100 V is provided with a capacitor element using aluminum foil as electrodes, the drive electrolytic solution containing water at a rate of 20-90 wt%, and a bottomed cylindrical case housing the capacitor elements impregnated with the electrolytic solution. The capacitor is also provided with a sealing material which seals the opening of the case. The freezing point of the electrolytic solution is adjusted to ≤-10°C, and the chlorine content of the sealing material is adjusted to ≤300 ppm. In addition, the ratio of the impedance under the condition of -10°C and 100 kHz to the impedance under the condition of 20°C and 100 kHz is adjusted to ≤4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a highly reliable aluminum electrolytic capacitor having a low moisture content and having a low moisture content, having a low moisture content, having a low appearance change and a characteristic deterioration even when used at a high temperature for a long time. It is.

  As shown in FIG. 1, in the conventional aluminum electrolytic capacitor, an aluminum foil having a dielectric layer formed by an anodic oxidation treatment is used as an anode foil 2 after a surface enlargement treatment by an etching treatment, and the anode foil 2 and the cathode foil 3 are formed. A capacitor element 1 is formed by impregnating a drive electrolyte (hereinafter referred to as electrolyte) with a separator 4 such as manila hemp or kraft paper interposed between them, and forming a capacitor element 1. After the aluminum case 5 is inserted, the opening of the aluminum case 5 is sealed with a sealing material 6 made of rubber. The electrolytic solution draws out the electrostatic capacitance by closely contacting the roughened anode foil 2, and further, the leakage current can be kept low because the dielectric layer of the aluminum oxide film can be repaired by the chemical conversion ability of the electrolytic solution. It has a function. Among the characteristics of the electrolyte, electrical conductivity has a great influence on the impedance performance of the capacitor.

  In view of the above, in particular, low-voltage grade low impedance aluminum electrolytic capacitors with a rated temperature of 105 ° C. or higher and a rated voltage of 100 V or lower use γ-butyrolactone, which is excellent in low-temperature characteristics and chemical conversion, as a solvent. Electrolytic solutions having high electrical conductivity and being stable even at high temperatures using a quaternary ammonium salt as an electrolyte have been used.

For example, Patent Document 1 and Patent Document 2 are known as prior art document information related to the present invention.
Japanese Patent Laid-Open No. 62-145713 Japanese Patent Laid-Open No. 62-145715

  However, when an aluminum electrolytic capacitor using an electrolytic solution in which a quaternary ammonium salt of phthalic acid or maleic acid is dissolved in the above-mentioned γ-butyrolactone solvent is used continuously in a humid atmosphere, a strong alkali component is generated at the cathode portion. In particular, there is a possibility that the electrolyte solution leaks outside the capacitor due to erosion of the cathode lead and the sealing material 6 in contact with the cathode lead.

  In order to avoid such a problem, it is effective to use an electrolyte that generates little alkali even when energized, that is, an electrolyte that uses ethylene glycol and water as a solvent and an ammonium salt such as ammonium adipate as an electrolyte. .

  In addition, since an electrolyte using a γ-butyrolactone solvent has a flash point of around 100 ° C., an abnormal voltage or reverse voltage is applied to the aluminum electrolytic capacitor due to an abnormal operation of an electronic device, and a safety valve is activated. It could not be said that there was no risk of ignition when the liquid spouted.

  On the other hand, in a low-pressure class aluminum electrolytic capacitor having a guaranteed temperature of 85 ° C. and a rated voltage of 100 V or less, a mixed solvent with water added for the purpose of increasing the electrical conductivity of ethylene glycol is used as the solvent of the electrolytic solution. Although an electrolytic solution using an ammonium salt such as ammonium as an electrolyte can be used, in an aluminum electrolytic capacitor using this type of electrolytic solution, at a temperature equal to or higher than the boiling point of water (100 ° C.), which is one of the solvent components. It is difficult to maintain electrical performance for a long period of time. For example, in a rated voltage application test at a temperature of 110 ° C., due to an increase in internal pressure due to the influence of a large amount of hydrogen gas resulting from a hydration reaction between aluminum and water, Within 1000 hours, the safety valve on the bottom part will be activated within a time, or in a no-load standing test at a temperature of 110 ° C. Problem such as over 5000 percent change rate + leakage current value after the test with respect to the period leakage current has occurred.

  In order to solve these problems, various phosphorus compounds can be added to the electrolyte solution for the purpose of suppressing the hydration reaction between the electrode foil and water, and various gas absorbents can be used to absorb the generated hydrogen gas. Although a method such as adding a nitro compound has been proposed, an electrolytic solution having a high water content such that the water content exceeds 20% even using these methods is used for a long time at a temperature of 100 ° C. or higher. It was difficult to maintain the electrical performance of the capacitor (in a high voltage capacitor whose rated voltage exceeds 100V, the oxide film as a dielectric is thick and strong, so the moisture content is 20 to 25%. If an electrolyte of the order is used, the electrical performance may be stable for about 1000 to 2000 hours at a temperature of 100 ° C. or higher, but a capacitor with a rated voltage of 100 V or less has a thin oxide film. In order, these problems have not been satisfactorily resolved.).

  Furthermore, in the case where an electrolytic solution having a high electrical conductivity with a water content of 20% or more is used for a long time at a temperature of 100 ° C. or higher, an electrolyte with a low water content with a water content of less than 20% is not a problem. The chlorine in the sealing rubber causes corrosion of the anode aluminum lead in a long-time high-temperature load test, resulting in an increase in leakage current or a corrosion breakage of the anode aluminum lead.

  An object of the present invention is to solve such a conventional problem and to provide a highly reliable aluminum electrolytic capacitor.

  In order to solve the above problems, the present invention accommodates a capacitor element using an aluminum foil as an electrode, a driving electrolyte having a water content of 20 to 90 wt%, and the capacitor element impregnated with the driving electrolyte. A bottomed cylindrical case and a sealing material that seals the opening of the case, the freezing point of the driving electrolyte is −10 ° C. or less, and the chlorine content of the sealing material is the sealing material The aluminum electrolytic capacitor has a rated voltage of 100 V or less and an impedance ratio of −10 ° C. and 100 kHz with respect to the impedance at 20 ° C. and 100 kHz is 4 ppm or less.

  As described above, according to the present invention, even when used at a high temperature for a long time, there is little change in appearance and characteristic deterioration, and an abnormal voltage or reverse voltage is applied to the aluminum electrolytic capacitor due to an abnormal operation of the electronic device. High reliability and impedance performance as well as its low temperature characteristics by using a high water content electrolyte that operates and has a low risk of ignition even when the electrolyte is ejected. An aluminum electrolytic capacitor having a voltage of 100 V or less can be configured.

  The invention according to claim 1 of the present invention includes a capacitor element using an aluminum foil as an electrode, a driving electrolyte having a moisture content of 20 to 90 wt%, and the capacitor element impregnated with the driving electrolyte. A bottomed cylindrical case to be stored and a sealing material for sealing the opening of the case, the freezing point of the driving electrolyte is −10 ° C. or less, and the chlorine content of the sealing material is the sealing The impedance ratio of −10 ° C. and 100 kHz to the impedance at 20 ° C. and 100 kHz is an aluminum electrolytic capacitor having a rated voltage of 100 V or less, which is 4 or less, and has high reliability. In addition, abnormal voltage or reverse voltage is applied to the aluminum electrolytic capacitor due to abnormal operation of the electronic equipment, etc., and the safety valve is activated, and the electrolyte should be ejected. Even less risk of fire when the has an effect that it can provide an excellent aluminum electrolytic capacitor impedance characteristics and low-temperature characteristics thereof.

  In addition, when the water content of the electrolytic solution is less than 20%, the electrical conductivity at low temperature cannot be sufficiently exhibited, so that the impedance ratio of −10 ° C. and 100 kHz to the impedance at 20 ° C. and 100 kHz exceeds 4, which is not preferable. In the range where the moisture content exceeds 90%, the freezing point of the electrolyte may be higher than −10 ° C., so that the impedance performance at 20 ° C. can be ensured, but on the low temperature side of the capacitor. Is not preferable because the guaranteed temperature range becomes -10 ° C. or more and the guaranteed range is narrowed.

  In addition, when a capacitor is constructed using a sealing material having a chlorine content exceeding 300 ppm with respect to the weight of the sealing material, chlorides released from the sealing rubber are electrolyzed when a rated voltage test is performed at a temperature of 100 ° C. or higher. A large amount of water contained in the solution dissociates into ions, and as a result, the anode aluminum lead is corroded at a high temperature.

  The invention according to claim 2 is the aluminum electrolytic capacitor according to claim 1, wherein the driving electrolyte has a moisture content of 35 to 90 wt%.

  The invention according to claim 3 is the aluminum electrolytic capacitor according to claim 1 or 2, wherein the driving electrolyte contains 0.01 wt% or more of a phosphorus compound.

  According to a fourth aspect of the present invention, the sealing material is made of isobutylene isoprene rubber, ethylene propylene terpolymer, or a mixture thereof, and the international rubber hardness of any part of the sealing material is 65 to 100 IRHD. The aluminum electrolytic capacitor according to claim 2.

  According to a fifth aspect of the present invention, the case is made of aluminum or an aluminum alloy, and the thickness of the bottom portion of the case is 0.30 mm or more. The aluminum electrolytic capacitor according to the first or second aspect, It is what.

  Next, the present invention will be described with specific examples.

  (Table 1), (Table 2), (Table 3), the electrolytic solution compositions of Embodiments 1 to 25 and Comparative Examples 1 to 8 of the present invention, the phosphorus compound or silicone compound adhesion amount of the separator used, and the electrode used The amount of phosphorus compound or silicone compound attached to the foil, the amount of chlorine contained in the sealing material used, the hardness of the sealing material and the surface-treated silicone compound, the thickness of the bottom surface of the aluminum case, and the compound treated on the inner surface of the aluminum case are shown.

  As a result of measuring the flash point of the electrolytic solutions of Embodiments 1 to 25 of the present invention by the Cleveland open method, it was confirmed that the test flame disappeared in the temperature range of 128 ° C to 134 ° C. Has no flash point. Moreover, as a result of leaving the electrolyte solution of Embodiment 1-25 of this invention for 24 hours in the low temperature thermostat set to the temperature of -30 degreeC, since the change of a property was not confirmed, the freezing point of electrolyte solution was It was also confirmed that it was −10 ° C. or lower.

  The chemical formulas of (Chemical Formula 1) to (Chemical Formula 8) described in (Table 1) and (Table 2) are shown below.

  (Table 4) to (Table 7) at −10 ° C./100 kHz with respect to the impedance at 20 ° C./100 kHz of the aluminum electrolytic capacitors configured using the electrolytic solutions of Embodiments 1 to 25 and Comparative Examples 1 to 8 of the present invention. Impedance ratio, rated voltage applied at a temperature of 110 ° C. for 1000 hours, and the amount of swelling at the bottom of the product after a no-load standing test, the rate of change in leakage current, the amount of solvent permeated through the sealing rubber, The state of the sealing rubber is shown. There are two types of aluminum electrolytic capacitors used in this test: rated voltage 6.3 V-capacitance 560 μF (size: φ8 × 11 L) and rated voltage 50 V—capacitance 1500 μF (size: φ16 × 35.5 L). It is. For adhesion treatment of phosphorus compounds or silicone compounds on separators (manila hemp fiber material), electrode foils and sealing rubber (resin vulcanized isobutylene isopropylene rubber [butyl rubber] materials), an aqueous solution of a phosphorus compound or silicone compound of any concentration After the separator, electrode foil, and sealing rubber were immersed therein, a drying treatment was performed at 100 ° C. for 1 hour. The amount of chlorine in the sealing rubber was measured with a total chlorine analyzer (product number: TSX-10) manufactured by Mitsubishi Chemical Corporation and converted into the amount of chlorine per weight of the sealing rubber.

  From the results of (Table 4) to (Table 7), the aluminum electrolytic capacitor of the present invention has a low impedance ratio, and even in a life test at 110 ° C., the swelling amount (L dimension change) and leakage current of the bottom surface of the aluminum case It can be seen that the rate of change of the value is small, the corrosiveness of the anode aluminum lead, and the sealing rubber does not pop out.

The partially cutaway perspective view which shows the structure of the aluminum electrolytic capacitor containing one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode foil 3 Cathode foil 4 Separator 5 Aluminum case 6 Sealing material

Claims (5)

A capacitor element using an aluminum foil as an electrode, a driving electrolyte having a water content of 20 to 90 wt%, a bottomed cylindrical case for housing the capacitor element impregnated with the driving electrolyte, and this case A sealing material for sealing the opening of
The freezing point of the driving electrolyte is −10 ° C. or lower,
The amount of chlorine contained in the sealing material is 300 ppm or less with respect to the weight of the sealing material,
An aluminum electrolytic capacitor having a rated voltage of 100 V or less, wherein the impedance ratio of −10 ° C. and 100 kHz to the impedance at 20 ° C. and 100 kHz is 4 or less. The aluminum electrolytic capacitor according to claim 1, wherein the driving electrolyte has a moisture content of 35 to 90 wt%. The aluminum electrolytic capacitor according to claim 1, wherein the driving electrolyte contains 0.01 wt% or more of a phosphorus compound. The sealing material is made of isobutylene isoprene rubber, ethylene propylene terpolymer, or a mixture thereof, and the international rubber hardness of any part of the sealing material is 65 to 100 IRHD. Aluminum electrolytic capacitor. The aluminum electrolytic capacitor according to claim 1, wherein the case is made of aluminum or an aluminum alloy, and a thickness of a bottom surface portion of the case is 0.30 mm or more.

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