JPH07245246A - Drive electrolyte of electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enhance the reliability upon a high tension aluminum electrolytic capacitor at high temperature. CONSTITUTION:0.01%-5.0wt% of ester borate of pentitol group is added to an electrolyte comprising molten boric acid and organic acid or salt thereof using ethylene glycol as a main solvent. Through these procedures, the high reliable electrolyte displaying extremely stable characteristic of leakage current in a life test for a long time at high temperature can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for driving an aluminum electrolytic capacitor (hereinafter referred to as electrolytic solution).

[0002]

2. Description of the Related Art Conventionally, ethylene glycol has been used as an electrolytic solution for aluminum electrolytic capacitors for medium and high voltage.
A so-called ethylene glycol boric acid-based electrolytic solution in which boric acid or ammonium borate is dissolved is often used. Further, an electrolytic solution using an ammonium salt of a dibasic acid having 8 to 22 carbon atoms is also known for the purpose of improving reliability at high temperatures.

[0003]

However, the electrolytic capacitor using the electrolytic solution as described above has a drawback that the leakage current becomes large because the oxide film forming ability of the electrolytic solution is not good, and the reliability at high temperature is high. Was not enough.

[0004]

In order to solve this problem, the present invention uses 0.01% by weight of an electrolytic solution containing ethylene glycol as a main solvent and boric acid and an organic acid or salts thereof dissolved therein. This is an electrolytic solution of an electrolytic capacitor, which is obtained by adding 5.0 wt% of a boric acid ester of pentitols. The pentitols are characterized by comprising arabitol, ribitol, or xylitol.

[0005]

The borate ester of pentitols has a hydrophilic group, -OH, and is well compatible with the defective portion of the dielectric film, and has the action of quickly repairing the film defect. . Therefore, the ability of the aluminum electrode foil to form an oxide film is enhanced, and the capacitor can be used in a wide temperature range.

[0006]

EXAMPLES Next, specific examples of the present invention will be described.
Table 1 shows a comparison of the composition, specific resistance and spark generation voltage of the electrolytic solution used in the examples of the present invention with the conventional product.

[0007]

[Table 1]

Table 2 shows the sample No. of the conventional example shown in Table 1. Electrolytes 1 and 2 and sample No. of the example of the present invention. The following shows the results of a high temperature no-load storage test for 1000 hours at an ambient temperature of 105 ° C. on an aluminum electrolytic capacitor rated at 400 V and 220 μF, which was manufactured using 3, 4, and 5 electrolytic solutions. The values in Table 2 are all average values of 20 samples, and the unit of capacitance is μ
The unit of F and leakage current is μA.

[0009]

[Table 2]

All of the samples using the electrolytic solution of the embodiment of the present invention have a capacity change rate, ta, in a high temperature unloaded test.
The improvement effect was verified without any problems in nδ, leakage current and appearance. As is apparent from the above-mentioned examples, the aluminum electrolytic capacitor of the present invention using the electrolytic solution containing the borate ester of the pentitols of the present invention has a significantly suppressed increase in leakage current. From the results of various experiments, the addition amount of boric acid ester of pentitols was 0.1.
If it is 5 to 5.0 wt%, this effect is effective and sufficient for practical use. If it exceeds 5.0 wt%, the solubility in the electrolytic solution is remarkably deteriorated, and if it is less than 0.01 wt%, the effect is obtained. Is not enough. Therefore, the addition amount of boric acid ester of pentyl is 0.1 to 5.0 w with respect to the electrolytic solution.
t% is suitable. In addition to the above-described examples, polyhydric alcohols such as ethylene glycol and propylene glycol, or organic solvents such as N, N-dimethylformamide and γ-butyrolactone are mixed with monocarboxylic acid such as formic acid and acetic acid. The same results were obtained by repeating the experiment with an electrolyte solution containing carboxylic acid, boric acid, phosphoric acid, or one or more of these salts as a solute at various mixing ratios.

[0011]

INDUSTRIAL APPLICABILITY As described above, the electrolytic solution of the present invention to which the borate ester of pentitols is added shows an extremely stable characteristic of leakage current in an aluminum electrolytic capacitor even when left at high temperature for a long time, and is reliable. It is highly effective and has great industrial and practical value.

Claims (2)

[Claims] 1. A boric acid ester of pentitols is added in an amount of 0.01% to 5.5% to an electrolytic solution containing ethylene glycol as a main solvent and boric acid and an organic acid or salts thereof dissolved therein.
An electrolytic solution for driving an electrolytic capacitor, characterized in that 0 wt% is added. 2. The pentitols are arabitol,
Alternatively, it is a ribitol or a xylitol, and an electrolytic solution for driving an electrolytic capacitor.