JP5067100B2 - Electrolytic capacitor - Google Patents

Description

  The present invention relates to an electrolytic capacitor.

  The electrolytic capacitor generally has the following configuration. That is, a high-purity aluminum foil formed in a band shape is chemically or electrochemically etched to expand the surface, and the expanded aluminum foil is subjected to chemical conversion in a chemical conversion solution such as an aqueous ammonium borate solution. By doing so, a capacitor element is formed by winding an anode foil in which an oxide film layer is formed on the surface of the aluminum foil and a cathode foil obtained by enlarging the same high-purity aluminum foil through a separator. The capacitor element is impregnated with a driving electrolyte solution and stored in a metal bottomed cylindrical outer case. Further, a sealing body made of elastic rubber is accommodated in the opening end portion of the outer case, and the opening end portion of the outer case is sealed by drawing to constitute an electrolytic capacitor.

  In addition, as an electrolytic solution impregnated in a capacitor element of a small-sized, low-pressure electrolytic capacitor, conventionally, an ethylene glycol as a main solvent and an ammonium salt such as adipic acid or benzoic acid as a solute, or γ Known are those having butyrolactone as a main solvent and quaternized cyclic amidinium salts such as phthalic acid and maleic acid as solutes.

In recent years, as the functions of a control circuit have increased in in-vehicle applications, the number of electronic components used in the control circuit has increased and the mounting space has been reduced, and it has become a situation that must be mounted close to the engine room. Under such conditions, the maximum operating temperature of the aluminum electrolytic capacitor is required to be 125 ° C. instead of 105 ° C. as in the past. In addition, environmental problems are increasing, and there is a demand to remove lead contained in solder used for mounting. However, such lead-free solder has a higher melting point than conventional solder, and therefore the solder reflow temperature during mounting must be increased. In order to meet the requirements for such high temperature use and high temperature reflow characteristics, an electrolyte solution comprising a solvent containing sulfolane is used, and a butyl rubber polymer comprising a copolymer of isobutylene and isoprene as a sealing body, and isobutylene, isoprene and divinylbenzene. An electrolytic capacitor using an elastic body in which an alkylphenol resin is added as a vulcanizing agent to a partially cross-linked butyl rubber polymer made of a copolymer is disclosed (Patent Document 1).
JP 2000-294465 A

   However, the precision of the operation of such a control circuit is required even in a cold region specification of −40 ° C. For that purpose, the stability of ESR after a high temperature test of 125 ° C. is required, and the patent The electrolytic capacitor of Document 1 cannot answer such a request.

  Therefore, an object of the present invention is to provide an electrolytic capacitor that has good reflow characteristics, can withstand use at 125 ° C., and has good ESR stability after a high-temperature test.

The electrolytic capacitor of the present invention includes a capacitor element in which an anode foil, a cathode foil, and a separator are wound and impregnated with a driving electrolyte, an outer case that houses the capacitor element, and an opening of the outer case is sealed And an impregnating amount of the electrolytic solution with respect to the capacitor element is a liquid that can be impregnated in the capacitor element, using an electrolytic solution composed of a solvent containing 30 to 50 wt% sulfolane and γ-butyrolactone as the driving electrolytic solution. It is characterized by being in the range of 75 to 95% of the maximum capacity.

    An alkylphenol resin is added as a vulcanizing agent to a butyl rubber polymer made of a copolymer of isobutylene and isoprene as a sealing body and a partially crosslinked butyl rubber polymer made of a copolymer of isobutylene, isoprene and divinylbenzene. And

    Since the electrolytic capacitor of the present invention uses an electrolytic solution composed of a solvent containing sulfolane as the driving electrolytic solution, the reflow characteristics are good, and the amount of impregnation of the electrolytic solution into the capacitor element can be impregnated in the capacitor element. Since it is in the range of 75 to 95% of the maximum capacity of the liquid, the ESR characteristic at −40 ° C. after the high temperature test at 125 ° C. is good.

    In the present invention, an electrolytic solution comprising a solvent containing sulfolane is used as the driving electrolytic solution, and the amount of the electrolytic solution impregnated in the capacitor element is 75 to 95% of the maximum capacity of the liquid that can be impregnated in the capacitor element, preferably 80%. Although it is within the range of ˜90%, if it is less than this range, the ESR at −40 ° C. after the 125 ° C. high temperature test will increase, and if it exceeds this range, the reflow characteristics will be reduced. Here, the maximum capacity of the liquid that can be impregnated in the capacitor element was obtained from the difference in weight before and after the impregnation, assuming that the dried capacitor element was impregnated with the electrolyte under reduced pressure and the electrolyte did not adhere to the outer periphery of the capacitor element. Further, the impregnation amount of the present application was also obtained from the difference in weight before and after the capacitor element was impregnated.

    The electrolytic solution of the present invention contains sulfolane, but in addition to this, a protic polar solvent, an aprotic solvent, and a mixture thereof can be used. Protic polar solvents 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.). 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, hexamethylphosphoricamide, etc.), lactones (γ-butyrolactone, δ-valerolactone, γ-valerolactone, etc.), sulfolanes (3-methylsulfolane, 2,4 -Dimethylsulfolane, etc.), cyclic amides (N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, isobutylene carbonate, etc.), nitriles (acetonitrile, etc.), oxides (dimethyl sulfoxide, etc.), 2-imidazolidinones [1,3-di Rukyle-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, etc.)] and the like.

  In particular, when γ-butyrolactone is used, the stability of ESR at −40 ° C. after a high temperature test at 125 ° C. is good, and the content of sulfolane in the solvent is 30 to 50 wt%, preferably 30 to 40 wt%. . If it is less than this range, the amount of γ-butyrolactone transpiration increases, and if this range is exceeded, the conductivity of the electrolyte will decrease, and the ESR characteristics will both decrease.

    As the solute of the electrolytic solution, ammonium salts, quaternary ammonium salts, or amine salts of carboxylic acids such as adipic acid, formic acid, and benzoic acid can be used. The quaternary ammonium constituting the quaternary ammonium salt includes tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), pyridium (1-methylpyridium). 1-ethylpyridium, 1,3-diethylpyridium, etc.). In addition, amines constituting the amine salt include primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, monoethanolamine, etc.), 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.).

    Furthermore, 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 the salt include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, and the like.

    The quaternized cyclic amidinium ion serving as a cation component is a cation obtained by quaternizing a cyclic compound having an N, N, N′-substituted amidine group, and a cyclic compound having an N, N, N′-substituted amidine group Examples of the compound include the following compounds. Imidazole monocyclic compounds (1-methylimidazole, 1-phenylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1,2 -Imidazole homologues such as dimethylimidazole, 1,2,4-trimethylimidazole, oxyalkyl derivatives such as 1-methyl-2-oxymethylimidazole, 1-methyl-2-oxyethylimidazole, 1-methyl-4 ( 5) Nitro derivatives such as -nitroimidazole, amino derivatives such as 1,2-dimethyl-5 (4) -aminoimidazole), benzimidazole compounds (1-methylbenzimidazole, 1-methyl-2-benzimidazole, 1 -Methyl-5 (6) -nitrobenzimidazole Etc.), compounds having a 2-imidazoline 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.), 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, etc.).

    It is preferable to use a salt containing such a quaternized cyclic amidinium ion as a cation component because the conductivity of the electrolytic solution can be increased.

    Furthermore, the withstand voltage can be improved by adding boric acid, mannitol, nonionic surfactant, colloidal silica or the like to the electrolytic solution for electrolytic capacitors of the present invention.

  As the sealing body of the present invention, an alkylphenol resin was added as a vulcanizing agent to a butyl rubber polymer composed of a copolymer of isobutylene and isoprene and a partially crosslinked butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene. When an elastic body is used, the transpiration from the sealing rubber at a high temperature of the electrolytic solution is small, and the ESR characteristic after the 125 ° C. high temperature test is good.

  As a blending ratio of such an elastic body, 10 to 60 parts of a butyl rubber polymer made of a copolymer of isobutylene and isoprene, 40 to 90 parts of a partially crosslinked butyl rubber polymer made of a copolymer of isobutylene, isoprene and divinylbenzene, 1-20 parts of alkylphenol resin is preferred.

  The electrolytic capacitor of the present invention as described above has good reflow characteristics, and good ESR characteristics at −40 ° C. after a high temperature test at 125 ° C.

    Next, the present invention will be described in detail with reference to examples. A capacitor element is formed by winding an anode foil and a cathode foil through a separator. The anode electrode foil was obtained by subjecting an aluminum foil of 99.9% purity to chemical or electrochemical etching in an acidic solution to enlarge the surface, followed by chemical conversion treatment in an aqueous solution of ammonium adipate. What formed the oxide film layer is used. As the cathode foil, a foil obtained by etching an aluminum foil having a purity of 99.9% and expanding the surface was used.

    The capacitor element configured as described above is impregnated with an electrolytic solution for driving an electrolytic capacitor. The capacitor element impregnated with the electrolytic solution is housed in an outer case made of bottomed cylindrical aluminum, the sealing rubber is inserted into the opening end of the outer case, and the end of the outer case is drawn. To seal the electrolytic capacitor.

    Here, as the sealing rubber, 45 parts of a butyl rubber polymer made of a copolymer of isobutylene and isoprene as a resin vulcanized rubber, 55 parts of a partially crosslinked butyl rubber polymer made of a copolymer of isobutylene, isoprene and divinylbenzene, an alkylphenol resin What blended 2 parts used the conventional butyl rubber as a peroxide vulcanized rubber. The rating and size of the electrolytic capacitor are A, 10 WV-470 μF, 10 φ × 10.5 L, B, 35 WV-100 μF, 8 φ × 10.5 L.

    The composition of the electrolytic solution, sealing rubber, amount of electrolyte impregnation, ESR after high temperature test, and reflow characteristics of the electrolytic capacitor prepared here are shown in Table 1. The high temperature test is 125 ° C, rated voltage load, 2000 hours, and the reflow test conditions are preheat temperature, 150 ° C, reflow peak temperature, 250 ° C.

(Note) SL: sulfolane, GBL: γ-butyrolactone, EDMIP: 1-ethyl-2,3-dimethylimidazolinium phthalate

As can be seen from Table 1, the characteristics of the electrolytic capacitors of Examples 1 to 10 of the present invention are good. In contrast, Comparative Example 1 in which the electrolytic solution impregnation amount is 100 wt% has deteriorated reflow characteristics, and Comparative Example 2 in which 70 wt% has an increased ESR. Further, Examples 2 to 9 having a sulfolane content of 30 to 50 wt% have better ESR characteristics than those of Example 1 of 65 wt% and Example 10 of 25 wt%.

Claims (2)

A capacitor element formed by winding an anode foil, a cathode foil, and a separator and impregnated with a driving electrolyte, an exterior case that houses the capacitor element, and a sealing body that seals an opening of the exterior case, An electrolytic solution composed of a solvent containing 30 to 50 wt% sulfolane and γ-butyrolactone is used as the driving electrolytic solution. The amount of the electrolytic solution impregnated in the capacitor element is 75 to 95% of the maximum capacity of the liquid that can be impregnated in the capacitor element. Electrolytic capacitor characterized by being in the range of   An elastic body in which an alkylphenol resin is added as a vulcanizing agent to a butyl rubber polymer composed of a copolymer of isobutylene and isoprene and a partially crosslinked butyl rubber polymer composed of a copolymer of isobutylene, isoprene and divinylbenzene was used as a sealing body. The electrolytic capacitor according to claim 1.