JP4571014B2 - Electrolytic solution for driving aluminum electrolytic capacitors - Google Patents

Description

The present invention relates to an electrolytic solution for driving an aluminum electrolytic capacitor (hereinafter referred to as an electrolytic solution).

  In general, in an aluminum electrolytic capacitor, a high-purity aluminum foil is electrochemically etched to increase the surface area, and then subjected to a chemical conversion treatment in a chemical conversion solution such as an ammonium borate aqueous solution or an ammonium adipate aqueous solution. A capacitor element obtained by inserting and winding a separator between an anode foil having an oxide film formed on the surface and a cathode foil etched with an aluminum foil, impregnated with an electrolytic solution, and then made of a metal cylinder The case is housed, and the opening of the cylindrical case is sealed with elastic rubber and sealed by drawing the sealed portion.

In recent years, with the progress of digitalization of electronic components, the demand for low loss and low impedance of aluminum electrolytic capacitors has increased, and the electrolyte used for aluminum electrolytic capacitors has a high conductivity (low specific resistance). Development is underway.
Conventionally, low-pressure electrolytes have been made of ethylene glycol as the main solvent and ammonium salts such as adipic acid and benzoic acid as solutes. A method for reducing the specific resistance of the liquid has been proposed (see, for example, Patent Documents 1 and 2).
Japanese Patent No. 3366267 (page 1-10) Japanese Patent No. 3366268 (page 1-21)

  However, when the amount of water in the electrolyte is increased, the water in the electrolyte and the aluminum electrode foil cause a hydration reaction. As a result, there is a problem that the electrical characteristics of the aluminum electrolytic capacitor are remarkably deteriorated, and the leakage current is increased particularly under a high temperature no load condition. Such a hydration reaction becomes conspicuous as the amount of water in the electrolyte increases. For this reason, there is a problem that reliability cannot be sufficiently maintained if an attempt is made to reduce the specific resistance of the electrolytic solution by increasing the amount of water.

  In view of the above problems, the object of the present invention is to suppress the hydration reaction of the aluminum electrode foil even when the amount of water in the electrolytic solution is increased in order to reduce the specific resistance of the electrolytic solution. An object of the present invention is to provide an electrolytic solution capable of maintaining the reliability of an electrolytic capacitor.

The present invention is an invention that has been achieved as a result of various studies in order to solve the above problems, and is intended to apply alkylthiols or salts thereof to an electrolytic solution.
That is, in the electrolytic solution for driving an aluminum electrolytic capacitor according to the present invention, at least an organic carboxylic acid or a salt thereof and an alkylthiol or a salt thereof represented by the following chemical formula in a solvent containing ethylene glycol and water. The amount of water is 30 to 70 wt% with respect to the entire electrolyte solution, and the amount of the alkylthiols is 0.01 to 2.0 wt% with respect to the entire electrolyte solution. And

  In the above formula, the type of R2 may be any of a configuration that is the same in any of a plurality of carbons that constitute the main chain and a configuration that is different in a plurality of carbons that constitute the main chain.

  Here, as the alkylthiols, n-octanethiol, n-nonanethiol, n-decanethiol, 2,6,8-trihydroxy-1-decanethiol, 8-hydroxy-1-octanethiol, 12- Examples include mercapto-1-dodecylamine, 10-epoxy-1-octadecanethiol, and salts thereof.

  In the present invention, the organic carboxylic acid is, for example, at least one of formic acid, malonic acid, succinic acid, and adipic acid.

  In the present invention, it is preferable that the electrolytic solution further contains at least one of orthophosphoric acid, phosphorous acid, and hypophosphorous acid. The electrolytic solution may contain at least one of monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monopropyl phosphate, dipropyl phosphate, monoethylene glycol phosphate, and diethylene glycol phosphate. preferable.

In addition, various additives generally used in capacitor driving electrolytes can be added to the electrolytic solution according to the present invention for the purpose of reducing leakage current, improving withstand voltage, and absorbing gas.
Examples of additives include boric acid compounds, polyhydric alcohols, polyvinyl alcohol, polyethylene glycol, high molecular compounds typified by polypropylene glycol, and nitro compounds.

  The thiol group of the alkyl thiols distributed to the electrolytic solution according to the present invention has a strong adsorptivity to metal, and the thiol group is oriented on the surface of the aluminum electrode foil to form a monomolecular film. By forming such a film, it is possible to suppress the hydration deterioration reaction of the aluminum electrode foil in a high temperature atmosphere even when the amount of water added is large, and it is possible to improve the characteristics and reliability of the electrolytic capacitor. it can.

In the electrolytic solution for driving an aluminum electrolytic capacitor according to the present invention, at least an organic carboxylic acid or a salt thereof and an alkylthiol or a salt thereof are blended in a solvent in which ethylene glycol and water are blended. It is preferable that a compounding quantity is 30-70 wt% with respect to the whole electrolyte solution. Moreover, it is preferable that the compounding quantity of alkylthiols is 0.01-2.0 wt% with respect to the whole electrolyte solution.
Here, examples of the organic carboxylic acid include formic acid, malonic acid, succinic acid, and adipic acid.
Furthermore, the electrolyte includes orthophosphoric acid, phosphorous acid, hypophosphorous acid, monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monopropyl phosphate, dipropyl phosphate, monoethylene glycol phosphate, It is preferable that at least one of diethylene glycol phosphate is blended.

Hereinafter, examples of the present invention will be described more specifically. First, an electrolytic solution was prepared with the composition shown in Table 1, and the specific resistance at 30 ° C. was measured. The results are shown in Table 1. In Table 1, components A to E are the following alkylthiols A: n-octanethiol B: n-nonanethiol C: n-decanethiol D: 2, 6, 8-trihydroxy-1-decane Thiol E: 8-hydroxy-1-octanethiol.

  Next, using the electrolytic solution shown in Table 1, 10 aluminum electrolytic capacitors each having a rating of 6.3 V-1500 μF (φ10 × 12.5 mmL) were produced, and initial characteristics were measured for capacitance, tan δ, and leakage current. Thereafter, a DC 6.3 V load test (3000 hours) was performed at 105 ° C., and the results shown in Table 2 were obtained.

In Table 2, when water content is the same, for example, Comparative Example 2 having a water content of 50 wt% is compared with Examples 1 to 6, aluminum using the electrolytic solution of Conventional Example 2 to which no alkylthiols are added. Compared with the electrolytic capacitor, the reliability of the aluminum electrolytic capacitor using the electrolytic solutions of Examples 1 to 6 to which alkylthiols were added in the DC application test for 3000 hours is improved.
In particular, the aluminum electrolytic capacitor using the electrolytic solution of Conventional Example 2 has deteriorated electrical characteristics and valve expansion after a 3000-hour DC application test. In the aluminum electrolytic capacitor using the electrolytic solution of Examples 2 to 5, Even after the DC application test for 3000 hours, the electrical characteristics show good values.

  Here, when the blending amount of the alkylthiols is less than 0.01 wt% (Example 1) with respect to the entire electrolyte solution, the effect of suppressing the leakage current is not sufficient, and exceeds 2.0 wt% (Example 6). ) And the optimum addition amount for the suppression effect of the hydration reaction, causing a decrease in electrical characteristics. Therefore, the blending amount of the alkylthiols is preferably in the range of 0.01 to 2.0 wt% with respect to the entire electrolyte solution.

  Moreover, when the blending amount of water is less than 30 wt% with respect to the entire electrolyte solution, low specific resistance is not sufficient (Example 12), and when the blending amount exceeds 70 wt%, low specific resistance is achieved, It can be seen that the reliability characteristics are significantly deteriorated and the effect of suppressing the hydration reaction by alkylthiols is reduced (Example 16). Therefore, the blending amount of moisture is preferably 30 to 70 wt% with respect to the entire electrolytic solution.

Further, in addition to the above examples, even when any of ammonium adipate, ammonium succinate, ammonium formate, and ammonium malonate was used as the organic carboxylic acid, the DC application test 3000 was caused by the effect of suppressing the hydration reaction by alkylthiols. It was confirmed that good electrical characteristics were exhibited even after time.
In addition, phosphorous acid, hypophosphorous acid, monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monopropyl phosphate, dipropyl phosphate, monoethylene glycol phosphate, phosphoric acid When at least one of diethylene glycol was blended, the effect of suppressing the hydration reaction by alkylthiols was further enhanced, and it was confirmed that good electrical characteristics were exhibited even after 5000 hours of DC application test.

  In addition, this invention is not limited to the said Example, The general addition used for the electrolyte solution which melt | dissolved the various solutes illustrated previously individually or more than one, and also for the drive electrolyte solution of an aluminum electrolytic capacitor The same effect as in the above examples was also obtained with the electrolyte added with the agent.

Claims (4)

In a solvent in which ethylene glycol and water are blended, at least an organic carboxylic acid or a salt thereof and an alkyl thiol or a salt thereof represented by the following chemical formula are blended ,
The blending amount of water is 30 to 70 wt% with respect to the whole electrolyte solution,
The amount of alkyl thiols, driving electrolyte for an aluminum electrolytic capacitor, which is a 0.01 to 2.0% relative to the total electrolyte.

2. The electrolytic solution for driving an aluminum electrolytic capacitor, wherein the organic carboxylic acid according to claim 1 is at least one of formic acid, malonic acid, succinic acid, and adipic acid . 3. The electrolytic solution for driving an aluminum electrolytic capacitor according to claim 1 , further comprising at least one of orthophosphoric acid, phosphorous acid, and hypophosphorous acid . 4. The method according to claim 1 , further comprising: monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monopropyl phosphate, dipropyl phosphate, monoethylene glycol phosphate, and diethylene glycol phosphate. An electrolytic solution for driving an aluminum electrolytic capacitor, comprising at least one kind .