JPH0770442B2 - Electrolytic solution for driving electrolytic capacitors - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for driving an electrolytic capacitor which has excellent low temperature characteristics and is stable at high temperatures.

Conventional technology An electrolytic capacitor with a structure in which a chemically etched aluminum anode foil and cathode foil wound with separator paper is impregnated with electrolytic solution, and this element is housed in an aluminum case using rubber packing is used. Conventionally, there is known one using an electrolytic solution in which a solvent such as an ammonium salt of carboxylic acid is dissolved in a mixed solvent of ethylene glycol and water.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An electrolyte containing a solute of ammonium salt of carboxylic acid in a mixed solvent of ethylene glycol and water has an increased viscosity at low temperature and deteriorates the low temperature characteristics of the capacitor.

Further, in a load test in a high temperature atmosphere, the anodic oxide film of the capacitor, the cathode foil, and the like generate hydrogen gas that reacts with water, and the pressure inside the capacitor may increase, resulting in destruction.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides 95-50 wt% γ-butyrolactone, 2-20 wt% methanol or ethanol.
%, Ethylene glycol 3 to 30 wt%, and a mixed solvent consisting of 3 components at respective weight ratios, 5 to 30 wt% of a metal salt of borodisalicylic acid and 1 to 10 wt% of a metal salt of maleic acid are dissolved. Is an electrolytic solution for driving an electrolytic capacitor.

Action γ-butyrolactone as an electrolytic solution of an aluminum electrolytic capacitor, in a mixed solvent consisting of methanol or ethanol and ethylene glycol, by dissolving the metal salt of borodisalicylic acid and maleic acid, the specific resistance is relatively small even at low temperatures, The electrolytic capacitor using this suppresses the capacitance decrease and tan δ increase, and exhibits stable characteristics in reliability tests such as high temperature load tests.

Examples Hereinafter, specific examples of the present invention will be described.

The electrolytic solution of the present invention (sample description) is shown in Table 1 as an example. Nos. A, B, C, and D) as comparative samples, the composition ratios of the respective electrolytic solutions of the conventional electrolytic solution (sample symbol E),
The specific resistance at 30 ° C and -55 ° C is shown.

Table 2 shows the low temperature characteristics of the capacitors using the electrolyte solutions A, B, C, D and E. All sample capacitors are rated
35WV 220μF aluminum electrolytic capacitor.

Table 3 shows the results of the high temperature load life test of capacitors using the above electrolytes A, B, C, D and E in a 105 ° C. atmosphere.

As is apparent from the above-mentioned Examples, electrolysis obtained by dissolving a metal salt of borodisalicylic acid and a metal salt of maleic acid as a solute in a mixed solvent of γ-butyrolactone, methanol or ethanol and ethylene glycol of the present invention. Aluminum electrolytic capacitors using liquids have significantly improved low temperature characteristics and high temperature load life. From the results of various experiments, when the content of borodisalicylic acid is less than 5 wt%, the specific resistance of the electrolytic solution is high, and when it exceeds 30 wt%, precipitation occurs at low temperature. Similarly, when the metal salt of maleic acid is less than 1 wt%, the specific resistance of the electrolytic solution is high, and when it exceeds 10 wt%, precipitation occurs at low temperatures. If the amount of methanol or ethanol is less than 2 wt%, the low-temperature specific resistance of the electrolyte is high, and if it exceeds 20 wt%, the vapor pressure at high temperature becomes high, and if the capacitor is left in a high temperature atmosphere, the internal pressure rises. Destroy the capacitor case. If ethylene glycol is less than 3 wt%, the metal salt of maleic acid cannot be dissolved, and if it exceeds 30 wt%, the viscosity of the electrolytic solution at low temperature becomes high and the specific resistance at low temperature becomes high. Further, although the potassium salt is shown in the above-mentioned Examples, similar results can be obtained for a calcium salt, a sodium salt and a mixture of these three kinds of salts, and various mixing ratios of each solvent and solute can be mixed within limits. Repeated experiments with different ratios gave similar results.

EFFECTS OF THE INVENTION As described above, the electrolytic solution for driving the electrolytic capacitor according to the present invention maintains extremely stable characteristics from a low temperature to a high temperature as compared with the conventional one, and a highly reliable electrolytic capacitor can be obtained.

Claims (3)

[Claims] 1. Gamma-butyrolactone 95-50 wt%, methanol or ethanol 2-20 wt%, ethylene glycol 3
An electrolytic solution for driving an electrolytic capacitor, characterized in that metal salts of borodisalicylic acid and maleic acid are dissolved in a mixed solvent having a weight ratio of ˜30 wt%. 2. A drive for an electrolytic capacitor according to claim 1, wherein at least one of potassium salt, calcium salt and sodium salt is dissolved as a metal salt of borodisalicylic acid and maleic acid. Electrolyte. 3. The electrolytic capacitor according to claim 2, wherein 5 to 30 wt% of the metal salt of borodisalicylic acid and 1 to 10 wt% of the metal salt of maleic acid are dissolved in the mixed solvent. Electrolyte for driving.