JPH0277109A - Electrolyte for driving electrolyte capacitor - Google Patents

Abstract

PURPOSE:To prevent occurrence of short circuit between electrodes without a decline in electric characteristics and obstructing the miniaturization of the title capacitor even when copper is contained in the aluminum electrode foil of the capacitor by adding ethylenediamine tetraacetate to a solution prepared by dissolving an organic acid or its salt in a mixture of one or two or more specific kinds of solutions by more than a prescribed wt.%. CONSTITUTION:Ethylenediamine tetraacetate(EDTA) is added to a solution prepared by dissolving an organic acid or its salt in a mixture solvent of one or two or more kinds selected out of polyhydric alcohol, such as ethylene glycol, diethylene glycol, etc., monoalcohol, such as methyl alcohol, ethyl alcohol, etc., and water by >=0.01wt.%. The electrolyte thus prepared prevent re-precipitation of copper, because the EDTA forms a firm soluble complex salt together with copper ions dissolving in the electrolyte from aluminum electrode foil.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as electrolytic solution).

2. Description of the Related Art Conventionally, an electrolytic solution in which an organic acid such as adipic acid or a salt thereof is dissolved in a solvent mainly composed of ethylene glycol has been frequently used.

Problems to be Solved by the Invention In an electrolytic solution using such an ammonium salt of an organic acid, if a capacitor is left for a long period of time, if copper is contained in the aluminum electrode foil, the copper will dissolve. Further, redeposition occurs, and if this redeposition is significant, a short circuit occurs between the electrodes, resulting in a loss of capacitor function.

Countermeasures have been taken, such as using thick separators to ensure the distance between electrodes, but this has resulted in a decline in electrical characteristics and has become an obstacle to miniaturization.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses one or two of polyhydric alcohols such as ethylene glycol and diethylene glycol, monoalcohols such as methyl alcohol and ethyl alcohol, and water. A solution made by dissolving an organic acid or its salt in a mixed solvent of more than one type,
0.01% by weight or more of ethylenediaminetetraacetic acid (
This is an electrolyte solution for an electrolytic capacitor characterized by adding EDTA (hereinafter referred to as EDTA).

Function The electrolytic solution of the present invention prevents redeposition of copper by forming a strong soluble complex salt between the copper ions eluted from the aluminum electrode foil during the night of electrolysis and EDTA.

Examples Below, examples of the present invention will be described using ethylene glycol as the main solvent.
A normal electrolytic solution containing 0% by weight, 15% by weight of water, and 715% by weight of ammonium adipate, and EDTA in this electrolytic solution.
A copper piece was immersed in an electrolytic solution containing
Table 1 shows the results of measuring the amount of copper eluted over time by atomic absorption.

Note that the size of the same piece (99.9%) was 1 x 4 x 51 squares, and the amount of electrolyte was 10 m/bin.

Table 1 From Table 1, it was confirmed that the addition of 0.01% by weight or more of EDTA was effective in suppressing the amount of dissolved copper ions.

Furthermore, using an aluminum foil containing 1% copper as a cathode and using the above-mentioned electrolyte, a rated voltage of 16W V220μF was applied.
Table 2 shows the number of short banks that occurred when a capacitor was manufactured and subjected to a high temperature load test at 95° C. for 2000 hours.

Table 2 Table 2 also confirms that the addition of EDTA has the effect of preventing short circuits between electrodes due to dissolution and redeposition of copper.

Further, the test was repeated by changing the type of solvent, the blending ratio, and the type and concentration of the organic acid salt, and the effect of the above-mentioned additive was confirmed under all conditions.

It should be noted that if the additive is less than 0.01% by weight, the effect will not be sufficient, and if the amount exceeds the saturation concentration, it is not preferable.

As is clear from the results beyond the effects of the invention, ethylene glycol,
In a mixed solvent of one or more of polyhydric alcohols such as diethylene glycol, monoalcohols such as methyl alcohol and ethyl alcohol, and water,
The electrolytic solution for electrolytic capacitors, which is characterized by adding EDTA to a solution prepared by dissolving an organic acid, has problems such as deterioration of electrical characteristics and hindrance to miniaturization even when copper is contained in the aluminum electrode foil. It is possible to prevent short circuits between electrodes without causing problems, and is of great industrial and practical value.

Claims (1)

[Claims] A solution of an organic acid or its salt dissolved in a mixed solvent of one or more of polyhydric alcohols such as ethylene glycol and diethylene glycol, monoalcohols such as methyl alcohol and ethyl alcohol, and water. An electrolytic solution for driving an electrolytic capacitor, characterized in that .01% by weight or more of ethylenediaminetetraacetic acid is added.