JPH11233377A - Electrolytic capacitor drive electrolyte and electrolytic capacitor provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain an electrolytic capacitor from changing in external appearance by a method, wherein the electrolytic capacitor is provided with an electrolyte which has a structure where organic acid salt is dissolved as the electrolyte into an organic solvent which contains specific solvent components. SOLUTION: An electrolytic capacitor drive electrolyte has a structure, where organic acid salt is dissolved as electrolyte into organic solvent which contains N,N'-dimethyl propylene urea. The organic acid of the organic acid salt is carboxylic acid, and carboxylic acid is one or more elements selected from alkyl or nitro-substitution products of maleic acid, phthalic acid, adipic acid, benzoic acid or compounds of them. The base of the organic acid salt is constituted of one or more elements selected from among ammonium, tertiary amine, quaternary ammonium, compound with alkyl-substituted amidine group, and quaternary salt of compound with alkyl-substituted amidine group. With this setup, an electrolytic capacitor can be restrained from increase in the inner pressure.

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 an electrolytic capacitor used in various electronic devices 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 an ethylene glycol solvent is known.

[0003] Further, as an electrolyte having excellent low-temperature characteristics,
A solution in which an organic acid or an inorganic acid or a salt thereof is dissolved as an electrolyte in γ-butyrolactone having a low viscosity at a low temperature is used. An electrolytic solution using triethylamine or diethylamine salt as an electrolyte (Japanese Patent Application Laid-Open No. 54-1024) Gazettes) are known. Also, 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. -809
No. 2) is also known.

Further, as a solvent for an electrolytic solution having a high boiling point,
N, N'-dimethyl-2-imidazolidinone (Japanese Unexamined Patent Publication No.
No. -5471) is known.

[0005]

However, in the above-mentioned conventional electrolytic solution, an electrolytic solution in which an ammonium salt of boric acid or adipic acid is dissolved in an ethylene glycol solvent, or γ-butyrolactone or N, N′-dimethyl-2-imidazo is used. In the case of electrolytic solutions in which triethylamine salt, diethylamine salt, or quaternary ammonium salt was dissolved as an electrolyte in liginone, the boiling points (heat resistance) of these solvents were not sufficient, and these were used to form electrolytic capacitors and used as surface mount components. If
Depending on the heat treatment conditions during surface mounting (soldering temperature and time required to pass through a reflow furnace), the internal pressure may increase and deform the appearance, resulting in poor soldering during mounting. was there.

The present invention has been made to solve the above-mentioned conventional problems, and it is intended to suppress the deformation of the appearance 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. It is an object of the present invention to provide an electrolytic solution for driving an electrolytic capacitor and an electrolytic capacitor using the same.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an electrolytic solution for driving an electrolytic capacitor having a structure in which an organic acid salt is dissolved as an electrolyte in an organic solvent containing N, N'-dimethylpropyleneurea. And an electrolytic capacitor using the same. According to this configuration, since N, N'-dimethylpropylene urea having a high boiling point is contained as a solvent component, the electrolytic solution is less likely to be vaporized even in a high-temperature atmosphere, and an increase in internal pressure can be suppressed. Can suppress the deformation of the external appearance, thereby improving the poor soldering at the time of mounting.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The first aspect of the present invention relates to an electrolytic solution for driving an electrolytic capacitor having a structure in which an organic acid salt is dissolved as an electrolyte in an organic solvent containing N, N'-dimethylpropyleneurea. According to this configuration, since N, N'-dimethylpropylene urea having a high boiling point is contained as a solvent component, the electrolytic solution is not easily vaporized even in a high-temperature atmosphere. An increase in pressure can be suppressed, and as a result, the appearance deformation of the electrolytic capacitor can be suppressed, thereby having an effect of improving soldering failure during mounting.

According to a second aspect of the present invention, in the first aspect of the invention, the organic acid of the organic acid salt is a carboxylic acid. It is possible to obtain an electrolytic solution having an excellent chemical conversion property of a certain anodic oxide film, and it is possible to obtain an electrolytic capacitor having a low leakage current and a high reliability when an electrolytic capacitor is formed using this electrolytic solution.

According to a third aspect of the present invention, in the second aspect, the carboxylic acid is maleic acid, phthalic acid,
It is composed of at least one selected from the group consisting of adipic acid, benzoic acid, and alkyl or nitro-substituted products of these compounds. According to this configuration, the conductivity is high and the thermal conductivity changes. Since an electrolytic solution having a small amount can be formed, when an electrolytic capacitor is formed with this electrolytic solution,
In addition to being able to reduce the leakage current, it has the effect of obtaining an electrolytic capacitor with low loss and little change in performance during a heat resistance test.

A fourth aspect of the present invention is the composition according to any one of the first to third aspects, wherein the base of the organic acid salt is an ammonium, tertiary amine, quaternary ammonium, or alkyl-substituted amidine group. And at least one selected from the group consisting of quaternary salts of compounds having an alkyl-substituted amidine group. According to this configuration, an electrolytic solution having a small thermal conductivity change can be formed. Since it is possible, when configuring an electrolytic capacitor with this electrolytic solution,
This has the effect that an electrolytic capacitor with little change in performance during a heat resistance test can be configured.

According to a fifth aspect of the present invention, the quaternary salt of the compound having an alkyl-substituted amidine group is an imidazole compound, a benzimidazole compound, an alicyclic amidine compound (a pyrimidine compound, an imidazoline). Compound), which is one or more selected from the group of compounds). According to this configuration, it is possible to form an electrolyte which has a high conductivity and hardly generates an alkali due to an electrochemical change. In addition to reducing the performance change during a heat resistance test when configuring an electrolytic capacitor, a highly reliable electrolytic capacitor that has low loss and can prevent liquid leakage from the lead wire on the negative potential side Has the effect of being able to.

[0013] The invention according to claims 6 and 7 provides:
An electrolytic capacitor using the electrolytic solution for driving an electrolytic capacitor according to any one of claims 1 to 5, and a configuration in which the electrolytic capacitor is a surface mount type. Taking advantage of the high boiling point of the electrolyte solution containing '-dimethylpropylene urea and the low vapor pressure in the temperature range of 200 ° C or higher, there is little appearance deformation even in a high-temperature atmosphere This has the effect that an electrolytic capacitor with less soldering defects during mounting can be constructed.

According to an eighth aspect of the present invention, there is provided the electrolytic capacitor according to the sixth or seventh aspect, wherein a lead-free metal layer is provided on at least a part of a surface layer of a lead wire portion of the electrolytic capacitor. According to this configuration, lead is often used as a solder component as a plating material for the lead portion of electronic components, but in recent years, it has been desired to reduce its use from the viewpoint of global environmental protection. Although it is technically possible to plate the leads of electronic components with a metal that is not used, if the lead plating material is a metal that does not use lead, the conventional method is used to mount electronic components on printed circuit boards. Unless a higher temperature is applied than when mounting electronic components with leads that have a lead-containing metal plating layer, mounting failure (poor bonding between the lead wire plating layer and the solder layer on the printed circuit board side) occurs To solve this problem, the electrolyte containing N, N'-dimethylpropylene urea takes advantage of its high boiling point and low vapor pressure in a temperature range of 200 ° C. or more, and has little appearance deformation even in a high-temperature atmosphere. When mounting components, it is possible to construct an electrolytic capacitor with less soldering failure during board mounting, so even if the lead surface layer is plated with a metal that does not contain lead, there is no problem of mounting failure Has an action.

Hereinafter, an embodiment of the present invention will be described. First, examples of the tertiary amine used in the electrolytic solution of the present invention include trialkylamines [trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl n-propylamine, dimethylisopropylamine, methylethyl n-propylamine, methylethyl Ethyl isopropylamine, diethyl n-propylamine, diethyl isopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.), a phenyl group-containing amine [dimethylphenylamine, methylethylphenylamine, Diethylphenylamine, etc.].

Of these, preferred are trialkylamines having high conductivity, and more preferred are at least one selected from the group consisting of triethylamine, dimethylethylamine, methyldiethylamine and triethylamine having high conductivity.

Examples of the quaternary ammonium used in the electrolytic solution of the present invention include tetraalkylammoniums [tetramethylammonium, trimethylethylammonium, dimethyldiethylammonium, methyltriethylammonium, tetraethylammonium, trimethyl n-propylammonium. , Trimethyl isopropyl ammonium, dimethyl ethyl n-propyl ammonium, dimethyl ethyl isopropyl ammonium, methyl diethyl n-propyl ammonium, methyl diethyl isopropyl ammonium, triethyl isopropyl ammonium, triethyl n-propyl ammonium, tetra n-propyl ammonium, tetra isopropyl ammonium, tetra isopropyl ammonium n-butylammonium, tetra-t
tert-butylammonium], phenyltrialkylammonium [trimethylphenylammonium,
Dimethylethylphenylammonium, triethylphenylammonium, etc.].

Of these, tetraalkylammonium having high conductivity is preferable, and tetramethylammonium, trimethylethylammonium, dimethyldiethylammonium, methyltriethylammonium and tetraethylammonium having high conductivity are more preferable. One or more selected from the following.

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, which can provide an electrolytic capacitor having high conductivity and low loss.
4,0] undecene-7,1,5-diazabicyclo [4,3,0] nonene-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) imidazoline, 1-methyl-2-dodecylimidazoline,
1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, 1-methylbenzimidazole are preferred.

Examples of the quaternary salt of the compound having an alkyl-substituted amidine group used in the electrolytic solution of the present invention include an imidazole compound quaternized with an alkyl or arylalkyl group having 1 to 11 carbon atoms, and a benzoate. Imidazole compounds and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds). Specifically, 1-methyl-1,8-diazabicyclo [5,4,0] undecene can provide a capacitor having high conductivity and low loss.
7,1-methyl-1,5-diazabicyclo [4,3
0] nonene-5,1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,3-dimethyl-2-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 Preferred are rhinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium and 1,3-dimethylbenzimidazolium.

Examples of the organic acid used in the electrolytic solution of the present invention include polycarboxylic acids (divalent to tetravalent): aliphatic polycarboxylic acids [saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, and the like] Glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-
Decanedicarboxylic acid, 5,6-decanedicarboxylic acid: unsaturated polycarboxylic acid such as maleic acid, fumaric acid, icotanic acid]; aromatic polycarboxylic acid such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, Pyromellitic acid; alicyclic polycarboxylic acids such as tetrahydrophthalic acid (such as cyclohexane-1,2-dicarboxylic acid) and hexahydrophthalic acid; alkyl (1 to 3 carbon atoms) or nitro-substituted products of these polycarboxylic acids For example, citraconic acid, dimethylmaleic acid, nitrophthalic acid (3-nitrophthalic acid, 4-nitrophthalic acid); and sulfur-containing polycarboxylic acids such as thiopropionic acid; monocarboxylic acids; 30) [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 acid, for example, acrylic acid, methacrylic acid, oleic acid]; aromatic monocarboxylic acid, for example, benzoic acid, o-nitrobenzoic acid, p-nitrobenzoic acid, cinnamon Acids, naphthoic acids; oxycarboxylic acids such as salicylic acid, mandelic acid, resorcinic acid.

Of these, preferred are maleic acid, phthalic acid, adipic acid and benzoic acid, which have high conductivity and are thermally stable.

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

Further, the electrolytic solution 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 may be mixed with another organic solvent compatible with N, N'-dimethylpropyleneurea as a secondary solvent for the purpose of improving low-temperature characteristics and discharge voltage. good.

Examples of the secondary solvent include polyhydric alcohol solvents; ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, glycerin, polyoxyalkylene polyol, and lactone solvents; γ-butyrolactone, γ-valerolactone; δ-valerolactone, 3-methyl-1,3-oxazolidine-
2-one, 3-ethyl-1,3-oxazolidine-2-
On, N, N′-dimethyl-2-imidazolidinone,
N, N'-diethyl-2-imidazolidinone, N, N '
-Di-n-propyl-2-imidazolidinone, N, N'-
Diisopropylimidazolidinone, 1,3,4-trimethyl-2-imidazolidinone, amide solvent; N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N-methylacetamide, ether solvent; methylal , 1,2-dimethoxyethane, 1
-Ethoxy-2-methoxyethane, 1,2-diethoxyethane, nitrile solvents; acetonitrile, 3-methoxypropionitrile, furan solvents; 2,5-dimethoxytetrahydrofuran, 2-imidazolidinone solvents;
A single solvent of 1,3-dimethyl-2-imidazolidinone or a mixed solvent of two or more thereof is exemplified. In the case of a mixed solvent system, the content of the secondary solvent is desirably 20 parts or less based on 100 parts of N, N'-dimethylpropyleneurea. When the content of the secondary solvent exceeds 20 parts, the boiling point of the electrolytic solution is affected by that of the secondary solvent, so that a sufficient effect cannot be obtained.

The electrolyte of the present invention may be mixed with various additives as necessary. Examples of the additive include a phosphorus compound [phosphoric acid, phosphoric acid ester, etc.], a boric acid compound [boric acid, a complex compound of boric acid with a polysaccharide (mannitol, sorbit, etc.), boric acid and a polyhydric alcohol ( Nitro compounds [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 in some cases.

The content of the electrolyte in the electrolyte of the present invention is usually 1 to 80% by weight based on the weight of the electrolyte.
Preferably it is 5 to 40% by weight. 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 results of measuring the boiling points of N, N'-dimethylpropylene urea of the present invention and a conventional electrolyte solvent as a comparative example.

[0031]

[Table 1]

As is clear from Table 1, N, N'-dimethylpropylene urea of the present invention has a higher boiling point than conventional electrolyte solvents. Further, those having a higher molecular weight of the alkyl group on the nitrogen atom (for example, ethyl group, n-propyl group, isopropyl group, n
-Butyl group, tert-butyl group, etc.), the thermodynamic energy of the solvent molecule is increased, the boiling point is further increased, and the same effect is expected to be obtained.

Table 2 shows the compositions of the electrolytic solutions of Embodiments 1 to 6 of the present invention and Comparative Examples 1 to 3 as comparative examples.

[0034]

[Table 2]

Next, Embodiments 1 to 5 of the present invention will be described.
6 and a surface-mount type aluminum electrolytic capacitor (rated voltage 4 V-capacitance 220
μF, size: φ6 mm × L5.5 mm). The sealing rubber is a peroxide-cured butyl rubber (JIS-A hardness:
84 degrees). The surface of the lead wire of the aluminum electrolytic capacitor was plated with tin containing no 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 3). In addition, the time of the epoxy substrate after passing through the solder reflow furnace-
FIG. 1 shows the temperature profile. The temperature was measured indirectly from the electromotive force of a thermocouple bonded to an epoxy substrate.

[0036]

[Table 3]

As is clear from Table 3, the aluminum electrolytic capacitors using the electrolytic solutions of the first to sixth embodiments of the present invention are compared with the aluminum electrolytic capacitors using the electrolytic solutions of Conventional Examples 1 to 3. Thus, it is clear that there is no deformation of the appearance of the electrolytic capacitor due to thermal stress at the time of surface mounting, and it is possible to improve poor soldering at the time of mounting. Similar results were obtained when resin-vulcanized butyl rubber (JIS-A hardness: 87 degrees) was used as the sealing rubber, and the effect of the present invention depends on the type of sealing rubber. It turns out that it is not.

[0038]

As described above, the electrolytic solution for driving an electrolytic capacitor according to the present invention is excellent in stability at high temperatures due to the high boiling point of the electrolytic solution solvent. As a result, the electrolytic capacitor due to thermal stress during surface mounting is excellent. It suppresses external deformation and improves poor soldering during mounting, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a time-temperature characteristic of an epoxy substrate when a surface-mount type aluminum electrolytic capacitor according to an embodiment of the present invention has passed through a solder reflow furnace.

Claims (8)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor in which an organic acid salt is dissolved as an electrolyte in an organic solvent containing N, N′-dimethylpropylene urea. 2. 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. 3. The electrolytic capacitor drive according to claim 2, wherein the carboxylic acid is at least one selected from the group consisting of maleic acid, phthalic acid, adipic acid, benzoic acid, and alkyl or nitro-substituted compounds of these compounds. Electrolyte. 4. The base of an organic acid salt is one selected from the group consisting of ammonium, a tertiary amine, a quaternary ammonium, a compound having an alkyl-substituted amidine group, and a quaternary salt of a compound having an alkyl-substituted amidine group. The electrolytic solution for driving an electrolytic capacitor according to any one of claims 1 to 3, which is as described above. 5. 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. 6. An electrolytic capacitor using the electrolytic solution for driving an electrolytic capacitor according to claim 1. Description: 7. The electrolytic capacitor according to claim 6, wherein the electrolytic capacitor is a surface mount type. 8. A lead-free metal layer is provided on at least a part of a surface layer of a lead wire portion of an electrolytic capacitor.
Or the electrolytic capacitor according to 7.