JP2000294464A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor which has excellent high- temperature reflow characteristics. SOLUTION: Solvent that contains γ-butyrolactone is used as electrolyte for this capacitor. Furthermore, an elastic body is used, where the elastic body is formed through a manner where alkylphenol resin is added as a vulcanizing agent to butyl rubber polymer formed of copolymer of isobutylene and isoprene butyl and partially crosslinked butyl rubber polymer formed of copolymer of isobutylene, isoprene, and divinylbenzene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electrolytic capacitor.

[0002]

2. Description of the Related Art An electrolytic capacitor generally has the following configuration. That is, a high-purity aluminum foil formed in a belt shape is chemically or electrochemically etched to enlarge the surface, and the expanded aluminum foil is subjected to a chemical conversion treatment in a chemical conversion solution such as an ammonium borate aqueous solution. By doing so, a capacitor element is formed by winding, via a separator, an anode foil having an oxide film layer formed on the surface of an aluminum foil and a cathode foil having a high-purity aluminum foil expanded. The capacitor element is impregnated with a driving electrolyte, and is housed in a metal bottomed cylindrical outer case. Further, a sealing body made of elastic rubber is housed at the opening end of the outer case, and the opening end of the outer case is sealed by drawing to form an electrolytic capacitor.

[0003] Conventionally, as an electrolytic solution impregnated in a capacitor element of a small-sized, low-pressure electrolytic capacitor, ethylene glycol as a main solvent, adipic acid,
Known are those in which an ammonium salt such as benzoic acid is used as a solute or those in which γ-butyrolactone is used as a main solvent and a quaternized cyclic amidinium salt such as phthalic acid or maleic acid is used as a solute.

[0004]

In recent years, environmental problems have been increasing, but in the field of electronic components, lead contained in solder used for mounting has become a problem. That is,
There is a demand for using a lead-free solder contained in conventional solder. However, such a solder containing no lead has a higher melting point than conventional solders, and therefore requires a higher solder reflow temperature during mounting. However, the conventional electrolytic capacitor has a problem in that, when this high-temperature solder reflow is performed, blisters of the sealing rubber and detachment from the outer case occur, which makes it impossible to cope with the problem.

Accordingly, an object of the present invention is to improve this problem and to provide an electrolytic capacitor capable of coping with high-temperature solder reflow.

[0006]

An electrolytic capacitor according to the present invention comprises a capacitor element formed by winding an anode foil, a cathode foil and a separator, and impregnated with a driving electrolyte, and an outer case for accommodating the capacitor element. Equipped with a sealing body for closing the opening of the outer case, using an electrolyte comprising a solvent containing γ-butyrolactone as the driving electrolyte,
And a butyl rubber polymer composed of a copolymer of isobutylene and isoprene as the sealing body, and a partially cross-linked butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene, and an elastic body obtained by adding an alkylphenol resin as a vulcanizing agent. It is characterized by using.

Further, mica is added to the elastic body.

[0008] The present invention is characterized in that an electrolytic solution using a salt containing a quaternized cyclic amidinium ion as a cation component as a solute is used.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

The sealing body of the present invention includes a butyl rubber polymer composed of a copolymer of isobutylene and isoprene, a partially crosslinked butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene, and an alkylphenol resin as a vulcanizing agent. Is used.

The mixing ratio of such an elastic material is 10 to 60 parts of a butyl rubber polymer composed of a copolymer of isobutylene and isoprene, and 40 to 40 parts of a butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene. 90 parts, alkylphenol resin 1
20 parts are preferred.

Further, mica can be used as an additive.

Then, the following electrolytic solution is used.

The electrolytic solution of the present invention contains γ-butyrolactone. In addition, a protic polar solvent, an aprotic solvent, and a mixture thereof can be used. Examples of the protic polar solvent include monohydric alcohols (ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols and oxyalcohol compounds (ethylene glycol , Propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, etc.)
And the like. Examples of aprotic polar solvents include amides (N-methylformamide, N, N─dimethylformamide, N─ethylformamide, N, N
{Diethylformamide, N} methylacetamide,
N, N─dimethylacetamide, N─ethylacetamide, N, N-diethylacetamide, hexamethylphosphoric amide, etc., lactones (δ-valerolactone, γ-valerolactone, etc.), sulfolane (sulfolane, 3-methyl) Sulfolane, 2,4-dimethylsulfolane, etc.), cyclic amides (N-methyl-2-pyrrolidone,
Ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitrile type (acetonitrile, etc.), oxide type (dimethylsulfoxide, etc.), 2-
Imidazolidinone [1,3-dialkyl-2-imidazolidinone (1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3
-Di (n-propyl) -2-imidazolidinone, etc.),
1,3,4-trialkyl-2-imidazolidinone (1,3,4-trimethyl-2-imidazolidinone and the like)] and the like.

As a solute of the electrolytic solution, an ammonium salt, a quaternary ammonium salt, or an amine salt of a carboxylic acid such as adipic acid, formic acid, and benzoic acid can be used. As the quaternary ammonium constituting the quaternary ammonium salt, tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium) , 1-ethylpyridium, 1,3-diethylpyridium, etc.). Examples of the amine constituting the amine salt include primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, monoethanolamine, etc.) and secondary amines (dimethylamine, diethylamine, dipropylamine, ethylmethylamine, diphenylamine). , Diethanolamine, etc.) and tertiary amines (trimethylamine, triethylamine, tributylamine, 1,8-diazabicyclo (5,4,0) -undecene-7, triethanolamine, etc.).

Further, a salt containing a quaternized cyclic amidinium ion as a cation component can be used. Examples of the acid serving as the anion component of this salt include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, benzoic acid, toluic acid, enanthic acid, and malonic acid.

The quaternized cyclic amidinium ion serving as the cation component is a cation obtained by quaternizing a cyclic compound having an N, N, N'-substituted amidine group. The following compounds are mentioned as the cyclic compound having the compound. Imidazole monocyclic compounds (1-methylimidazole, 1-phenylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-
Methylimidazole, 1,2-dimethylimidazole,
Imidazole homologs such as 1,2,4-trimethylimidazole, oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole and 1-methyl-2-oxyethylimidazole, 1-methyl-4 (5) -nitro Nitro derivatives such as imidazole, 1,2-dimethyl-5
(4) amino derivatives such as -aminoimidazole, etc.), benzimidazole compounds (such as 1-methylbenzimidazole, 1-methyl-2-benzimidazole, 1-methyl-5 (6) -nitrobenzimidazole), 2-imidazoline Compounds having a ring (1-methylimidazoline,
1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1-methyl-2-phenylimidazoline, 1-ethyl-2-methyl-imidazoline, 1,4-
Dimethyl-2-ethylimidazoline, 1-methyl-2-
Ethoxymethylimidazoline, etc.), and compounds having a tetrahydropyrimidine ring (1-methyl-1,4,5,6-
Tetrahydropyrimidine, 1,2-dimethyl-1,4,
5,6-tetrahydropyrimidine, 1,5-diazabicyclo [4,3,0] nonene-5 and the like.

It is preferable to use such a salt having a quaternary cyclic amidinium ion as a cation component, since the conductivity of the electrolytic solution can be increased.

Further, by adding boric acid, mannitol, nonionic surfactant, colloidal silica and the like to the electrolytic solution for an electrolytic capacitor of the present invention, the withstand voltage can be improved.

The electrolytic capacitor of the present invention as described above
Good high-temperature solder reflow characteristics.

Usually, the elastic rubber used as the sealing member comes into contact with the electrolytic solution after being made as a capacitor, swells the electrolytic solution, and the elastic force is reduced.
When the temperature rises during solder reflow, the hardness and elasticity of the sealing rubber further decrease, and the sealing rubber is blistered and comes off from the outer case. However, the elastic body of the present invention has a high initial hardness, and furthermore,
Since the swellability of γ-butyrolactone is low, it is considered that this suppresses a decrease in elastic force at high temperature, but it suppresses blistering and detachment of the sealing rubber. As described above, good synthesizing action of the elastic body of the present invention and the electrolytic solution comprising the solvent containing γ-butyrolactone can realize good high-temperature solder reflow characteristics.

Further, it is considered that the addition of mica to the elastic body suppresses the evaporation of the electrolytic solution from the elastic body, but the high-temperature life characteristic at 125 ° C. is improved.

[0023]

Next, embodiments of the present invention will be described in detail. An anode foil and a cathode foil are wound through a separator to form a capacitor element. The anode electrode foil is obtained by chemically or electrochemically etching an aluminum foil having a purity of 99.9% in an acidic solution and expanding the surface thereof, and then performing a chemical conversion treatment in an aqueous solution of ammonium adipate. Use an oxide film layer. As the cathode foil, a foil obtained by etching an aluminum foil having a purity of 99.9% and expanding the surface was used.

In the capacitor element configured as described above,
An electrolytic solution for driving an electrolytic capacitor is impregnated. As the electrolyte, γ-butyrolactone 75 wt%, phthalic acid 1-
Ethyl-2,3-dimethylimidazolinium 25wt%
Was used. The capacitor element impregnated with this electrolytic solution is housed in a bottomed cylindrical outer case made of aluminum, and the sealing rubber is inserted into an opening end of the outer case,
Furthermore, the electrolytic capacitor is sealed by drawing the end of the outer case.

The sealing rubber used in Example 1 was 45 parts of a butyl rubber polymer composed of a copolymer of isobutylene and isoprene, 55 parts of a partially crosslinked butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene, as in Example 1. A mixture prepared by mixing 2 parts of an alkylphenol resin, and a mixture obtained by adding 30 parts of mica to the mixture of Example 1 as Example 2 were used. In the comparative example, a conventional butyl rubber was used.

These electrolytic capacitors were heated at a preheat temperature of 150 ° C., a reflow peak temperature of 295 ° C.
The heat treatment was performed with a reflow profile of

As a result, in the comparative example, blisters of the sealing rubber and detachment from the outer case occurred. On the other hand, there was no abnormality in Examples 1 and 2, and it was found that the electrolytic capacitor of the present invention had good high-temperature reflow characteristics.

Next, a high temperature life test was performed on the electrolytic capacitors of Example 2 and Comparative Example. The rating of the electrolytic capacitor is
The test conditions were 125 ° C., a rated voltage load, and 1000 hours. The results are shown in (Table 1).

[0029]

[Table 1] (Note) Cap: Capacitance (μF), tan δ: Tangent of dielectric loss (120 Hz), LC: Leakage current (μA), ΔCap: Capacitance change rate (%)

As apparent from Table 1, in the comparative example, the decrease in capacitance after 1000 hours at 125 ° C.
The increase in anδ is also remarkable. On the other hand, using a salt having a quaternized amidinium ion as a cation component as a solute,
In Example 2 in which mica was added to the elastic body, the initial tan δ was low, and the results after 125 hours at 125 ° C. were good, indicating that use at 125 ° C. was possible.

[0031]

The electrolytic capacitor of the present invention uses an electrolytic solution comprising a solvent containing γ-butyrolactone, and comprises a butyl rubber polymer comprising a copolymer of isobutylene and isoprene, and a copolymer of isobutylene, isoprene and divinylbenzene. An elastomer obtained by adding an alkylphenol resin as a vulcanizing agent to a partially crosslinked butyl rubber polymer made of a coalesced rubber is used as a sealing rubber. By the synergistic action of these electrolytes and the elastic material used for the sealing rubber, good high-temperature reflow characteristics can be realized.

Further, by adding mica to the elastic body, an electrolytic capacitor having a specification of 125 ° C. can be realized.

When a salt having a quaternary cyclic amidinium ion as a cation component is used, the conductivity of the electrolytic solution can be increased, so that the tan δ of the capacitor can be reduced.

Claims (3)

[Claims] An anode foil, a cathode foil and a separator are wound,
And a capacitor element impregnated with a driving electrolyte,
An outer case for accommodating the capacitor element, and a sealing body for closing an opening of the outer case, using an electrolytic solution containing a solvent containing γ-butyrolactone as the driving electrolyte, and isobutylene as the sealing body An electrolytic capacitor using an elastic body obtained by adding an alkylphenol resin as a vulcanizing agent to a butyl rubber polymer composed of a copolymer of isoprene and a partially crosslinked butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene. 2. The method according to claim 1, wherein mica is added to the elastic body.
The electrolytic capacitor as described. 3. The electrolytic capacitor according to claim 1, wherein an electrolytic solution using a salt containing a quaternary cyclic amidinium ion as a cation component as a solute is used.