JP2000077271A - Electrolytic solution for driving electrolytic capacitor and electrolytic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deformation of the external appearance of an electrolytic capacitor due to thermal stresses during surface mounting, eliminate the failures in soldering during mounting thereby, and improve the reliability at high temperature and high moisture as well as impedance at low temperatures. SOLUTION: This electrolytic solution contains a 1,3-dimethyl-2- imidazolidinone, a sub-solvent and an organic acid salt, and the sub-solvent is an organic solvent having a boiling point of 20 deg.C or higher, and the organic acid salt has an hydrogen ion concentraction of 1.0×10-13 mol/dm3 or more (measured at 30 deg.C), when a 1 wt.% aqueous solution of a base or a hydroxide of base comprising the organic acid salt is adjusted.

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 electrolytic capacitor used for various electrolytic capacitors and an electrolytic capacitor using the same.

[0002]

2. Description of the Related Art As a conventional electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution), a solution in which an ammonium salt of boric acid or adipic acid is dissolved as an electrolyte in ethylene glycol is known.

[0003] Further, as an electrolyte having excellent low-temperature characteristics,
Low viscosity N, N-dimethylformamide or γ at low temperature
-An organic or inorganic acid or a salt thereof dissolved in butyrolactone as an electrolyte is used. An electrolytic solution using triethylamine or diethylamine salt as an electrolyte (JP-A-54-1024) is known. I have. Further, an electrolyte using a quaternary ammonium salt of maleic acid or citraconic acid as an electrolyte (Japanese Patent Publication No. 3-6646) or an electrolyte using a quaternary ammonium salt of an aromatic carboxylic acid as an electrolyte (Japanese Patent Publication No. -8092) and the like. In addition, an electrolytic solution using a carboxylate of a quaternized compound having an alkyl-substituted amidine group as an electrolyte (republished patent international publication number WO95 / 15572), a so-called amidine-based electrolytic solution, and the like are known.

As an electrolyte using an organic solvent having a high boiling point, 3-methyl-1,3-oxazolidine-2-
And an electrolyte containing 1,3-dimethyl-2-imidazolidinone (JP-A-62-266817 and JP-A-6-547).
No. 1) is known.

[0005]

However, the above-mentioned conventional electrolytic solution in which an ammonium salt of boric acid or adipic acid is dissolved in ethylene glycol, or a triethylamine salt, a diethylamine salt or a quaternary amine in N, N-dimethylformamide or γ-butyrolactone. Electrolytic solutions in which quaternary ammonium salts or quaternary salts of compounds having an alkyl-substituted amidine group are dissolved as electrolytes do not have sufficient boiling points (heat resistance) of these solvents, and these constitute an electrolytic capacitor (hereinafter referred to as a capacitor). When used as a surface-mounted component, the appearance of the surface may be deformed due to an increase in internal pressure, depending on the heat treatment conditions during surface mounting (soldering temperature and time required to pass through a reflow furnace). In some cases, poor soldering occurred.

In an electrolyte containing a quaternary ammonium salt, when an electrochemical reaction occurs inside the capacitor due to the strong alkalinity of the electrolyte base, a strong alkaline substance is generated near the negative electrode, and the strong alkaline substance is generated. The substance reduces the sealing force of the elastic body, which is the sealing body of the capacitor, and as a result, the electrolyte may leak to the outside under high temperature and high humidity conditions.

In an electrolyte containing 3-methyl-1,3-oxazolidin-2-one and 1,3-dimethyl-2-imidazolidinone, the boiling point of the solvent is relatively high. As described above, the appearance of the capacitor is not easily deformed due to an increase in the internal pressure of the capacitor due to thermal stress at the time of surface mounting, but the freezing point of the solvent itself is high and 0 ° C. or higher (3-methyl-1,3-oxazolidin-2-one). Solidification point: 15 ° C .; 1,3-dimethyl-2-imidazolidinone: 8 ° C.). There is a problem that an electrolytic capacitor having low conductivity and good impedance at low temperature cannot be formed.

The present invention is to solve such a conventional problem, and suppresses the appearance deformation of the electrolytic capacitor due to the thermal stress at the time of surface mounting, thereby improving the poor soldering at the time of mounting and improving the high temperature. An object of the present invention is to provide an electrolytic solution for driving an electrolytic capacitor capable of improving the reliability under high humidity conditions and improving the impedance performance at a low temperature, and an electrolytic capacitor using the same.

[0009]

In order to solve the above-mentioned problems, the present invention comprises 1,3-dimethyl-2-imidazolidinone, a co-solvent and an organic acid salt, and the co-solvent has a boiling point of 200.
An organic solvent having a hydrogen ion concentration of 1.0 × 10 ⁻¹³ when a 1% by weight aqueous solution of a base or a hydroxide of the base constituting the organic acid salt is prepared.
An electrolytic solution for driving an electrolytic capacitor having a constitution of not less than mol / dm ³ (however, the measurement temperature is 30 ° C.) and an electrolytic capacitor using the same.

According to the present invention, 1,3 having a high boiling point
-Since dimethyl-2-imidazolidinone is contained as a solvent component, the electrolytic solution is less likely to evaporate even in a high-temperature atmosphere, and a rise in internal pressure can be suppressed. As a result, the appearance deformation of the electrolytic capacitor can be suppressed, thereby mounting. It is possible to improve poor soldering at the time.

Further, by containing a co-solvent, 1,3-
A freezing point lowering effect is exhibited by mixing with dimethyl-2-imidazolidinone, and an electrolytic solution that does not coagulate even at −25 ° C. or lower can be formed, so that the electrical conductivity of the electrolytic solution in a low temperature range can be improved. . At this time, by limiting the boiling point of the sub-solvent to 200 ° C. or higher, the effect of suppressing an increase in internal pressure in a high-temperature atmosphere, which is a feature of 1,3-dimethyl-2-imidazolidinone, is not impaired.

Further, the property of the organic acid salt is adjusted to a hydrogen ion concentration of 1.0 × 10 ^-13 mol / d when a 1% by weight aqueous solution of a base or a hydroxide of the base constituting the organic acid salt is adjusted.
Since the alkalinity of the electrolyte base can be weakened by setting m ³ or more (however, the measurement temperature is 30 ° C.), even when an electrochemical reaction occurs inside the capacitor, a strong alkaline substance is hardly generated in the vicinity of the negative electrode. Therefore, the sealing force of the elastic body, which is the sealing body of the electrolytic capacitor, is not reduced, so that the leakage of the electrolytic solution to the outside can be prevented, and the reliability of the electrolytic capacitor under high temperature and high humidity can be improved. it can.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 of the present invention comprises 1,3-dimethyl-2-imidazolidinone, a co-solvent and an organic acid salt, and the co-solvent having a boiling point of 200 ° C. or higher. An organic solvent, and the property of the organic acid salt is such that a hydrogen ion concentration of 1.0 × 10 ⁻¹³ mol / d when a 1% by weight aqueous solution of a base or a hydroxide of the base constituting the organic acid salt is prepared.
m ³ or more (however, the measurement temperature is 30 ° C.).
Since 1,3-dimethyl-2-imidazolidinone is contained as a solvent component, the electrolytic solution is less likely to vaporize even in a high-temperature atmosphere, and an increase in internal pressure can be suppressed.
This has the effect that deformation of the appearance of the electrolytic capacitor can be suppressed, and thereby defective soldering during mounting can be improved.

Further, by containing a co-solvent, 1,3-
A freezing point lowering effect by mixing with dimethyl-2-imidazolidinone is exhibited, and an electrolyte that does not solidify even at −25 ° C. or lower can be formed, so that the conductivity of the electrolyte at low temperatures can be improved, At that time, the boiling point of the secondary solvent was set to 200
C. or higher, 1,3-dimethyl-2
-Does not impair the effect of imidazolidinone, which suppresses an increase in internal pressure in a high-temperature atmosphere.

Further, the properties of the organic acid salt are adjusted to a hydrogen ion concentration of 1.0 × 10 ^-13 mol / d when a 1% by weight aqueous solution of a base or a hydroxide of the base constituting the organic acid salt is adjusted.
By setting m ³ or more (however, the measurement temperature is 30 ° C.), the alkalinity of the electrolyte base can be limited to a low level, so that even when an electrochemical reaction occurs inside the capacitor, a strong alkaline substance is hardly generated near the negative electrode, For this reason, since the sealing force of the elastic body, which is the sealing body of the electrolytic capacitor, is not reduced, leakage of the electrolytic solution to the outside can be prevented, and the reliability of the electrolytic capacitor under high temperature and high humidity can be improved. Can be.

According to a second aspect of the present invention, in the first aspect, the mixing ratio of 1,3-dimethyl-2-imidazolidinone and the co-solvent is 1,3-dimethyl-2-imidazoline.
Imidazolidinone: co-solvent = 80-20: 20-80. According to this configuration, 1,
The solidification point generated by mixing 1,3-dimethyl-2-imidazolidinone with a sub-solvent, without impairing the effect of suppressing internal pressure rise in a high-temperature atmosphere, which is a feature of 3-dimethyl-2-imidazolidinone. Since the electrolytic solution does not solidify even at −40 ° C. or lower due to the drop effect, it has an effect that an electrolytic solution having high conductivity at low temperatures can be formed. In addition, when the mixing ratio of the two kinds of organic solvents is more than 1,3-dimethyl-2-imidazolidinone: subsolvent = 80: less than 20, the low temperature of 1,3-dimethyl-2-imidazolidinone is low. It is not preferable because the influence of coagulation becomes apparent and the electrolyte coagulates in a temperature range of −40 ° C. or higher. In addition, 1,3-dimethyl-2-imidazolidinone: a co-solvent of less than 20: in the range of more than 80, the feature of 1,3-dimethyl-2-imidazolidinone such as a low vapor pressure at a high temperature is sufficient. And the internal pressure is not sufficiently suppressed, and as a result, the degree of external deformation of the capacitor may increase, which is not preferable.

According to the third and fourth aspects of the present invention, in the first or second aspect, the co-solvent is a 3-alkyl-1,3-oxazolidin-2-one (more specifically, a 3-alkyl-1,3-oxazolidin-2-one). Methyl-1,3-oxazolidin-2-one:
1,3-dialkyl-2-imidazolidinone other than 1,3-dimethyl-2-imidazolidinone (more specifically, 1,3-diethyl-2-imidazolidinone: boiling point 236) C, 1,3-dipropyl-2-imidazolidinone: boiling point 255 ° C, 1-methyl-3-ethyl-2-imidazolidinone: boiling point 230 ° C), 1,3,4
-Trialkyl-2-imidazolidinone (more specifically, 1,3,4-trimethyl-2-imidazolidinone:
Boiling point 241 ° C), 1,3,4,5-tetraalkyl-2
-Imidazolidinones (more specifically 1,3,4,5
-Tetramethyl-2-imidazolidinone (more specifically, 1,3,4,5-tetramethyl-2-imidazolidinone: boiling point 249 ° C), cyclic lactone (more specifically, γ-butyrolactone : Boiling point 204 ° C.), polyhydric alcohol (more specifically, ethylene glycol: boiling point 20)
1 ° C., glycerin: boiling point 290 ° C.), and carbonate (more specifically, ethylene carbonate: boiling point 238 ° C., propylene carbonate: boiling point 242 ° C.). If the electrolyte is composed of at least one selected from a group of solvents having a high boiling point as a sub-solvent, a freezing point lowering effect is exhibited by mixing with 1,3-dimethyl-2-imidazolidinone, and the solidification occurs even at -25 ° C or lower. Can improve the conductivity at low temperatures, and by limiting the boiling point of the sub-solvent to 200 ° C. or higher, 1,3-dimethyl-2-imidazolide It has the effect of not impairing the suppression of internal pressure rise and drop in a high-temperature atmosphere, which is a characteristic feature of non-equipment.

The invention according to claims 5 and 6 is characterized in that, in the invention according to any one of claims 1 to 4, the organic acid of the organic acid salt is replaced with a carboxylic acid (more specifically, maleic acid,
Phthalic acid, cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, adipic acid, benzoic acid or one or more selected from the group consisting of alkyl or nitro-substituted compounds of the above compounds). Therefore, when an electrolytic capacitor is formed using the electrolytic solution according to this configuration, it is possible to obtain an electrolytic capacitor having excellent impedance performance and little performance change during a heat resistance test, in addition to being able to reduce leakage current. It has the action of:

The invention according to claims 7 and 8 is characterized in that, in the invention according to any one of claims 1 to 6, the base of the organic acid salt is replaced with ammonium, a secondary amine (specifically, diethylamine or the like). ), Tertiary amines (specifically, triethylamine, methyldiethylamine, diethylethylamine, dimethylpropylamine, etc.), compounds having an alkyl-substituted amidine group (specifically, 1,4,5,6-tetrahydropyrimidine, etc.), A quaternary salt of a compound having an alkyl-substituted amidine group (specifically, one or more selected from the group consisting of imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) According to this configuration, the nature of the base is 1% by weight of the base or the hydroxide of the base. The solution is the hydrogen ion concentration at the time of adjusting the 1.0 × 10 ^-13 mol / dm ³ or more (when representing a hydrogen ion concentration at pH values, means pH13 below) in order to be, electrochemical reaction occurs In addition to this, an electrolytic solution in which a strong alkali substance is unlikely to be generated in the vicinity of the negative electrode can be formed, and since the conductivity is high, when an electrolytic capacitor is formed using this electrolytic solution, the impedance performance is excellent and the lead on the negative electrode side is formed. This has the effect that a highly reliable electrolytic capacitor in which liquid leakage from the line portion is unlikely to occur can be configured.

The invention according to claims 9 and 10 is an organic solvent containing the aforementioned 1,3-dimethyl-2-imidazolidinone, a co-solvent and an organic acid salt, wherein the co-solvent has a boiling point of 200 ° C. or more. And the property of the organic acid salt is such that the hydrogen ion concentration when a 1% by weight aqueous solution of a base or a hydroxide of the base constituting the organic acid salt is prepared is 1.0 × 10 ⁻¹³ mol / dm ^3.
An electrolytic capacitor (more specifically, an electrolytic capacitor for surface mounting) is formed by using the electrolytic solution for driving an electrolytic capacitor described above. According to this configuration, a high boiling point having the above-described electrolytic solution, By making use of the characteristics such as low vapor pressure in the temperature range of 200 ° C or higher, there is little deformation in appearance even in a high temperature atmosphere, and when it is used as a surface mount component, configure an electrolytic capacitor with few soldering defects during board mounting. It has the effect of being able to.

According to an eleventh aspect of the present invention, in the invention according to the ninth or tenth aspect, the elastic body used for the sealing body of the electrolytic capacitor is a peroxide-vulcanized and / or resin-vulcanized butyl rubber, and Has at least a part of hardness of 75 IRHD (international rubber hardness unit) or more. According to this configuration, the peroxide-cured and / or resin-cured butyl rubber elastic body has excellent alkali resistance. Therefore, when the 1% by weight aqueous solution of the base or the hydroxide of the base is adjusted to the electrolyte base, the hydrogen ion concentration becomes 1.0%.
As long as a material having a density of at least × 10 ^-13 mol / dm ³ (measured at a temperature of 30 ° C.) is used, the sealing force does not decrease over time. This has the effect that a highly reliable electrolytic capacitor that is difficult to leak can be formed. In addition, by setting the hardness of at least a part of the elastic body to 75 IRHD (international rubber hardness unit) or more, it is possible to suppress the appearance deformation of the sealing surface, which tends to occur when the internal pressure increases, with physical strength. As a result, as a result, the appearance deformation of the electrolytic capacitor can be suppressed, thereby further improving the soldering failure at the time of mounting.

Hereinafter, embodiments of the present invention will be described. The basis of the present invention is to contain 1,3-dimethyl-2-imidazolidinone, a co-solvent and an organic acid salt, and the sub-solvent is an organic solvent having a boiling point of 200 ° C. or higher, and the properties of the organic acid salt are as follows: 1 of the base or the hydroxide of the base that constitutes the organic acid salt
The hydrogen ion concentration when adjusting the aqueous solution by weight is 1.0 ×
An electrolytic solution for driving an electrolytic capacitor having a ^{concentration of} 10 ⁻¹³ mol / dm ³ or more (at a measurement temperature of 30 ° C.) and an electrolytic capacitor using the same.

Examples of the tertiary amine used in the electrolyte of the present invention include trialkylamines [trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl n-propylamine, dimethylisopropylamine, methylethyl n-propylamine, Methylethylisopropylamine, diethyl n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.] phenyl group-containing amine [dimethylphenylamine, methylethylphenylamine, Diethylphenylamine, etc.].

Of these, preferably, the conductivity is high.
Trialkylamine, and more preferably one or more selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine, which have high conductivity.

Examples of the compound having an alkyl-substituted amidine group used in the electrolytic solution of the present invention include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds). Specifically, 1,8-diazabicyclo [5,4,0] undecene-7 and 1,5-diazabicyclo [4,3,0] nonene can provide a capacitor having high conductivity and excellent impedance performance. 5,1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline,
1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2- (3'heptyl)
Preferred are imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, and 1-methylbenzimidazole.

Examples of the quaternary salt of the compound having an alkyl-substituted amidine group used in the electrolyte of the present invention include those having 1 carbon atom.
Imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) quaternized with alkyl groups or arylalkyl groups of Nos. 1 to 11;

Specifically, it is possible to provide a capacitor having high conductivity and excellent impedance performance.
1,8-diazabicyclo [5,4,0] undecene-
7,1-methyl-1,5-diazabicyclo [4,3
0] nonene-5,1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4 -Trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2- (3'heptyl) imidazolinium, 1,3-dimethyl-2-dodecylimidazo Linium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, 1,3
-Dimethylbenzimidazolium is preferred.

Examples of the organic acid used in the electrolytic solution of the present invention include: polycarboxylic acid (divalent to tetravalent): aliphatic polycarboxylic acid [saturated polycarboxylic acid, for example, oxalic acid, malonic acid, succinic acid, glutaric acid] Adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid: unsaturated polycarboxylic acids such as maleic acid, fumaric acid, and icotanic acid]; Alicyclic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid;
1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.], hexahydrophthalic acid; alkyl (1 to 3 carbon atoms) or nitro-substituted polycarboxylic acids such as citraconic acid, dimethylmaleic acid, Nitrophthalic acid (3-nitrophthalic acid, 4-nitrophthalic acid); and sulfur-containing polycarboxylic acids such as thiopropionic acid; monocarboxylic acids; aliphatic monocarboxylic acids (1 to 30 carbon atoms) [saturated monocarboxylic acids such as formic acid Acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid: unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid Oleic acid]; aromatic monocarboxylic acids such as benzoic acid, o
-Nitrobenzoic acid, p-nitrobenzoic acid, cinnamic acid, naphthoic acid; oxycarboxylic acids such as salicylic acid, mandelic acid and resorcinic acid, of which maleic having high conductivity and being thermally stable are preferred. Acids, phthalic acid, cyclohexanecarboxylic acid, cyclohexene-1,2-dicarboxylic acid, adipic acid, and benzoic acid.

The ratio of the organic acid to the base constituting the electrolytic solution is usually 4 to 11, preferably 6 to 11 as the pH of the electrolytic solution.
-9. Outside this range, the spark voltage of the electrolyte decreases.

The electrolyte of the present invention may contain water as required. Its content is usually less than 5% based on the weight of the electrolyte. More preferably, it is less than 1%. If the water content is 5% or more, the solder heat resistance is significantly reduced due to the effects of the boiling point and vapor pressure of water.

The electrolyte of the present invention has improved low-temperature characteristics,
Other organic solvents compatible with 1,3-dimethyl-2-imidazolidinone may be mixed as a sub-solvent for the purpose of improving the discharge voltage, but the boiling point of the sub-solvent needs to be 200 ° C. or higher. .

The electrolyte of the present invention may be mixed with various additives as necessary. Examples of the additives include phosphorus compounds [phosphoric acid, phosphoric acid ester, etc.], boric acid compounds [boric acid, complex compounds of boric acid and polysaccharides (mannitol, sorbite, etc.), boric acid and polyhydric alcohols. (Ethylene glycol, glycerin, etc.)], a nitro compound [o-nitrobenzoic acid, m-nitrobenzoic acid,
p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, etc.]. The addition of these additives increases the spark voltage of the electrolyte, which may be preferable.

The content of the electrolyte in the electrolytic solution of the present invention is usually 10 to 95% by weight, preferably 20 to 90% by weight based on the weight of the electrolytic solution. Outside this range, the conductivity will drop significantly.

Next, specific embodiments of the present invention will be described, but the present invention is not limited thereto.
Hereinafter, all parts are by weight.

Table 1 shows the compositions of the electrolytic solutions of Embodiments 1 to 6 of the present invention and Comparative Examples 1 to 5 as comparative examples.

[0036]

[Table 1]

A surface-mount type aluminum electrolytic capacitor (rated voltage: 4 V-capacitance: 220 μF, size: φ6 mm × L5.5 mm) using the electrolytes of the first to sixth embodiments of the present invention and the conventional examples 1 to 5 )created. Peroxide vulcanized butyl rubber (hardness: 75 IRHD) was used as the sealing rubber. The surface of the lead wire of the aluminum electrolytic capacitor was plated with Sn-Bi as a main component without containing lead. Each of the 100 aluminum electrolytic capacitors was mounted on an epoxy board (thickness: 2 mm) and passed through a solder reflow furnace. The appearance deformation rate at this time is shown in (Table 2). In addition, the time of the epoxy substrate after passing through the solder reflow furnace-
The temperature profiles are shown in FIGS. The mounting condition in FIG. 2 is a condition in consideration of mounting with Sn-Ag-Bi solder (solder containing no lead in consideration of environmental effects). Heat stress is greater. The temperature was measured indirectly based on the starting force of a thermocouple bonded to an epoxy substrate.

[0038]

[Table 2]

In Comparative Example 1, the solvent is γ-butyrolactone and does not contain 1,3-dimethyl-2-imidazolidinone, so that the solder heat resistance is poor. In Comparative Example 2, the content of 1,3-dimethyl-2-imidazolidinone in the solvent was 19
%, There was no soldering failure under the condition (FIG. 1), but under the condition of more thermal stress (FIG. 2),
Since the content of 1,3-dimethyl-2-imidazolidinone in the solvent is as small as less than 20%, the influence of the vapor pressure of γ-butyrolactone becomes significant, and poor soldering occurs. In Comparative Example 4, although the content of 1,3-dimethyl-2-imidazolidinone in the solvent was 80%, the boiling point of N, N-dimethylformamide as the auxiliary solvent was 153 ° C.
And less than 200 ° C., so that 1,3-dimethyl-2-
Insufficient soldering has occurred without taking advantage of the inherent effects of imidazolidinone, such as low vapor pressure at high temperatures.

As is clear from Table 2, the aluminum electrolytic capacitors using the electrolytic solutions of the first to sixth embodiments of the present invention are the same as those of the prior art examples 1 to 2 and 4. In comparison with the above, it is clear that under any conditions, there is no deformation of the appearance of the condensate due to the thermal stress at the time of mounting, and it is possible to improve the poor soldering at the time of mounting.
In addition, resin sealing vulcanized butyl rubber (hardness: 80I
RHD), the same effect is obtained.
The effect of the present invention is particularly remarkable in such a sealed body of a peroxide-cured butyl rubber and / or a resin-cured butyl rubber having a hardness of 75 IRHD or more.

Next, the results of low-temperature conductivity measurements of the electrolytes of Embodiments 1 to 6 of the present invention and Comparative Examples 3 and 5 are shown in Table 3.

[0042]

[Table 3]

In Comparative Example 3, the solvent was 1,3-dimethyl-2
-Since it is imidazolidinone alone and does not contain a sub-solvent, the electrolyte is easily coagulated, and coagulation of the electrolyte occurs at -25 ° C. Therefore, when a capacitor is formed using the electrolyte solution of Comparative Example 3, the function of the capacitor cannot be exhibited in a temperature range of −25 ° C. or lower. In Comparative Example 5, the solvent was 3-methyl-1,3-oxazolidin-2-one alone and did not contain 1,3-dimethyl-2-imidazolidinone. The electrolyte has solidified. Therefore, when the capacitor is formed using the electrolyte solution of Comparative Example 5, the function of the capacitor cannot be exhibited in a temperature range of −25 ° C. or lower.

As is clear from Table 3, the electrolytes of the first to sixth embodiments of the present invention have higher conductivity in the low temperature range than the electrolytes of Comparative Examples 3 and 5. Is evident. Therefore, when an electrolytic capacitor is formed using the electrolytic solution according to Embodiments 1 to 6 of the present invention, the electric characteristics are good even in a low temperature range up to −40 ° C. (capacity change is small and loss increases. Less).

Further, a reliability test was conducted for 1000 hours by continuously applying a rated voltage in an atmosphere of a temperature of 85 ° C. and a relative humidity of 85% RH using an electrolytic capacitor having the same configuration. The state of the surface of the sealing body after the test (observation of presence / absence of abnormality such as electrolyte leakage) is shown in (Table 4).

[0046]

[Table 4]

In Comparative Example 2, the properties of the organic acid salt as the electrolyte were prepared by adjusting a 1% by weight aqueous solution of a hydroxide of a base constituting the organic acid salt (a 1% by weight aqueous solution of tetramethylammonium hydroxide). Hydrogen ion concentration of 1.0 × 10 ^-13
Mol / dm ³ (in this case 13.2 pH values,
However, because the measurement temperature is 30 ° C.), even if peroxide vulcanized butyl rubber having excellent alkali resistance is used for the sealing body, the sealing force decreases over time, and the lead wire on the negative electrode side even under high temperature and high humidity. Leakage from the battery, making it impossible to construct a highly reliable electrolytic capacitor.

As is evident from Table 4, the electrolytes according to Embodiments 1 to 6 of the present invention are each composed of a 1% by weight aqueous solution of a base constituting an organic acid salt (1,2,3,4-tetrafluoroethylene). Hydroxide ion addition ring-opening product of methyl imidazolinium as 3-
The hydrogen ion concentration when preparing aminopropyl-N-methylacetamide (1% by weight aqueous solution) is not less than 1.0 × 10 ⁻¹³ mol / dm ³ (in this case, the pH value is 11.2; However, since the measurement temperature is 30 ° C.), it is apparent that the sealing property of the sealing body does not decrease with time at such an alkalinity, and that a highly reliable electrolytic capacitor can be formed even under high temperature and high humidity.

As described above, by forming an electrolytic capacitor using the electrolytic solutions of Embodiments 1 to 6 of the present invention,
(1) Deformation of the appearance of the electrolytic capacitor due to thermal stress at the time of surface mounting can be suppressed, and defective soldering at the time of mounting can be improved.
(2) Good electrical characteristics at low temperatures. (3) Temperature 85
The reliability is high even in a test in an atmosphere at a temperature of 85 ° C. and a relative humidity of 85% RH. Can be satisfied at the same time.

[0050]

As described above, the electrolytic solution for driving an electrolytic capacitor of the present invention is excellent in stability at high temperatures due to the high boiling point of the solvent. As a result, the appearance deformation of the electrolytic capacitor due to thermal stress during surface mounting To improve soldering defects during mounting, improve reliability under high-temperature and high-humidity conditions, and improve impedance performance at low temperatures, and its industrial value is large. is there.

[Brief description of the drawings]

FIG. 1 is a diagram showing a time-temperature profile when an epoxy substrate on which an electrolytic capacitor according to the present invention is mounted is passed through a solder reflow furnace.

FIG. 2 is a diagram showing a time-temperature profile when a solder containing no lead is used.

Claims (11)

[Claims] 1. A method according to claim 1, which comprises 1,3-dimethyl-2-imidazolidinone, a co-solvent and an organic acid salt, wherein the co-solvent has a boiling point of 20.
An organic solvent having a temperature of 0 ° C. or higher, and the property of the organic acid salt is 1% by weight of the base or the hydroxide of the base constituting the organic acid salt;
The hydrogen ion concentration when preparing the aqueous solution is 1.0 × 10
An electrolytic solution for driving an electrolytic capacitor having a ^{concentration of -13} mol / dm ³ or more (at a measurement temperature of 30 ° C.). 2. The mixing ratio of 1,3-dimethyl-2-imidazolidinone and the sub-solvent is in the range of 1,3-dimethyl-2-imidazolidinone: sub-solvent = 80 to 20:20 to 80. The electrolytic solution for driving an electrolytic capacitor according to claim 1. 3. The method according to claim 1, wherein the secondary solvent is 3-alkyl-1,3-oxazolidin-2-one, 1,3-dialkyl-2-imidazolidinone, 1,3,4-trialkyl-2-imidazolidinone, 3. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the electrolytic solution is at least one selected from the group consisting of 2,3,4,5-tetraalkyl-2-imidazolidinone, cyclic lactone, polyhydric alcohol and carbonate. 4. The method according to claim 1, wherein the secondary solvent is 3-methyl-1,3-oxazolidin-2-one, 1,3-diethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone,
1-methyl-3-ethyl-2-imidazolidinone, 1,
3,4-trimethyl-2-imidazolidinone, 1,3
The electrolytic solution for driving an electrolytic capacitor according to claim 3, wherein the electrolytic solution is at least one selected from the group consisting of 4,5-tetramethyl-2-imidazolidinone, γ-butyrolactone, ethylene glycol, glycerin, ethylene carbonate, and propylene carbonate. 5. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the organic acid of the organic acid salt is a carboxylic acid. 6. The group of the carboxylic acids comprising maleic acid, phthalic acid, cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, adipic acid, benzoic acid or alkyl or nitro-substituted compounds of the above compounds. The electrolytic solution for driving an electrolytic capacitor according to claim 5, which is at least one selected from the group consisting of: 7. The compound according to claim 4, wherein the base of the organic acid salt is ammonium, a secondary amine, a tertiary amine, a compound having an alkyl-substituted amidine group, or a compound having an alkyl-substituted amidine group.
At least one selected from the group consisting of graded salts.
7. The electrolytic solution for driving an electrolytic capacitor according to any one of 6. 8. The quaternary salt of the compound having an alkyl-substituted amidine group is at least one selected from the group consisting of an imidazole compound, a benzimidazole compound, and an alicyclic amidine compound (pyrimidine compound, imidazoline compound). The electrolytic solution for driving an electrolytic capacitor according to the above. 9. A composition comprising 1,3-dimethyl-2-imidazolidinone, a co-solvent and an organic acid salt, wherein the co-solvent has a boiling point of 20.
An electrolytic capacitor which is an organic solvent having a temperature of 0 ° C. or higher and has a hydrogen ion concentration of 1.0 × 10 ^-13 or more when a 1% by weight aqueous solution of a base constituting the organic acid salt is prepared. An electrolytic capacitor that uses a driving electrolyte. 10. The electrolytic capacitor according to claim 9, wherein the electrolytic capacitor is a component for surface mounting. 11. An elastic body used for a sealing body of an electrolytic capacitor is a peroxide-vulcanized and / or resin-vulcanized butyl rubber, and at least a part of the elastic body has a hardness of 75 IRH.
D (international rubber hardness unit) or more.
An electrolytic capacitor according to item 1.