JP2003109859A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor having a low ESR characteristic. SOLUTION: The electrolytic capacitor contains an electrolyte for an electrolytic capacitor having an aggregate including γbutyrolactone and quaternary salt of cyclic amidine compound in a capacitor element comprising an anodic foil and a cathodic foil having a foil width of 4.5 to 7 mm, and a foil length of 220 to 400 mm. Thus, resistance of the electrode foil and resistance of the electrolyte between electrode foils are reduced to have a low ESR characteristic. Furthermore, since the electrolytic capacitor employs an electrolyte having a good high temperature characteristic, it has satisfactory heat resistance and suits to surface mounting.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrolytic capacitor.

[0002]

2. Description of the Related Art Generally, an aluminum electrolytic capacitor has the following structure. That is, the strip-shaped high-purity aluminum foil is chemically or electrochemically etched to surface-expand, and the surface-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, the anode foil having the oxide film layer formed on the surface of the aluminum foil and the cathode foil having the surface-treated aluminum foil of the same high purity are wound around the separator to form a capacitor element. Then, this capacitor element is impregnated with a driving electrolytic solution and housed in a metal case having a bottomed cylindrical shape. Further, a sealing body made of elastic rubber is housed in the opening end of the outer case, and the opening end of the outer case is closed by drawing to form an aluminum electrolytic capacitor.

The electrolytic solution impregnated into the capacitor element of a small-sized, low-voltage aluminum electrolytic capacitor is as follows:
Conventionally, using ethylene glycol as the main solvent, adipic acid,
It is known to use ammonium salts such as benzoic acid as a solute, or use γ-butyrolactone as a main solvent and a quaternized cyclic amidinium salt such as phthalic acid and maleic acid as a solute.

On the other hand, downsizing and high functionality of electronic information equipment,
In order to improve productivity, surface mounting of electronic parts has progressed, and the electrolytic capacitors described above are also required to be of the surface mounting type. The surface mount type electrolytic capacitor is formed by attaching the electrolytic capacitor prepared as described above to the pedestal. Since such a surface mount type electrolytic capacitor is required to be downsized, the foil width and foil length of the electrode foil should not be made as small as possible. In addition, the surface mount type electrolytic capacitor is mounted by reflow soldering.
Since it is exposed to a high temperature of 00 ° C or higher, heat resistance is required.

By the way, in recent years, electronic information devices have been digitized, and the driving frequency of a microprocessor (MPU), which is the heart of these electronic information devices, has been further increased. Along with this, the increase in power consumption has progressed,
The problem of reliability due to heat generation has become apparent, and the drive voltage has been reduced as a countermeasure. Here, a DC-DC converter called a voltage control module (VRM) is widely used as a circuit for supplying high-precision power to a microprocessor, and a series equivalent resistance ( Many capacitors with low ESR are used. As the capacitor having this low ESR characteristic, electrolysis using an electrolytic solution for an electrolytic capacitor which uses γ-butyrolactone having the above-mentioned low specific resistance characteristic as a main solvent and a quaternized cyclic amidinium salt such as phthalic acid or maleic acid as a solute. Capacitors are widely used.

However, the driving frequency of the microprocessor is remarkably increased, the power consumption is increased accordingly, and in order to cope with this, it is required to increase the power supplied from the capacitor to prevent the voltage drop. That is, it is necessary to be able to supply a large amount of electric power in a short time, and for this reason, the electrolytic capacitor is required to have a large capacity, a small size, a low voltage, and an ESR characteristic lower than ever. In order to reduce the specific resistance of the electrolytic solution for electrolytic capacitors, there is an attempt to further reduce the specific resistance of the electrolytic solution by adding a large amount of water to the electrolytic solution, but since it has poor heat resistance, it is used for surface mounting. I can't.

[0007]

As described above, there is a limit in reducing the ESR of the capacitor by improving the electrolytic solution for the electrolytic capacitor, and it is difficult to further reduce the ESR.

The present invention has been made to solve the above problems, and provides an electrolytic capacitor having a low ESR.

[0009]

In order to solve the above problems, in an electrolytic capacitor using an electrolytic solution having a low specific resistance, by optimizing the foil width and foil length of the electrode foil, It has been found that the ESR can be further reduced.

The electrolytic capacitor of the present invention contains an electrolytic solution containing γ-butyrolactone and a quaternary salt of a cyclic amidine compound in a capacitor element having the following anode foil and cathode foil. That is, the electrode foil used in the present invention has a foil width of 4.5 to 7 m, preferably 5.0 to 6.0 mm, and a foil length of 220 to 400 mm, preferably 300 to 40.
It is 0 mm. If the foil width is less than this range, the effect of ESR reduction is small, and if it exceeds this range, the height of the electrolytic capacitor becomes large and exceeds the allowable range for surface mounting. Further, if the foil length is less than this range, the effect of reducing ESR is small, and if it exceeds this range, the effect of reducing ESR is small and the volume efficiency is rather deteriorated.

By using the above-mentioned electrode foil of the present invention and an electrolytic solution having a low specific resistance containing the electrolytic solution containing γ-butyrolactone and a quaternary salt of a cyclic amidine compound, an unprecedented low ESR characteristic can be obtained. An electrolytic capacitor having the same can be realized.

Further, in the electrolytic capacitor constructed by winding the above-mentioned electrode foil, the width and length of the electrode foil of the capacitor can be increased. It is preferable because a long condition can be realized.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described. An aluminum foil is roughened by AC etching in an etching solution composed of an aqueous solution of hydrochloric acid or the like to form an etching foil, which is used as a cathode foil. further,
In order to form a dielectric film on the surface of this etching foil, it is subjected to chemical conversion in a chemical conversion solution such as a phosphoric acid aqueous solution and used as an anode foil. In the present invention, the foil width of such an electrode foil is 4.5 to 7 m, preferably 5.0 to 6.0.
mm, and the foil length is 220 to 400 mm, preferably 3
It is set to 00 to 400 mm.

An anode lead terminal and a cathode lead terminal are attached to the above anode foil and cathode foil, and they are wound via a separator. Here, as the separator, manila paper, kraft paper, glass separator, or the like, or non-woven fabric made of synthetic fiber such as vinylon or polyester, or a porous separator can be used. Then, the capacitor element thus formed is impregnated with an electrolytic solution containing γ-butyrolactone of the present invention and a quaternary salt of a cyclic amidine compound, and housed in a metal case having a tubular shape with a sealing rubber at the opening end. Attach and seal by caulking.

The quaternary salt of a cyclic amidine compound is a salt having a cation obtained by quaternizing a cyclic amidine compound as a cation component.

Examples of the acid serving as an anion component include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, benzoic acid, toluic acid, enanthic acid and malonic acid.

Examples of tetraalkylammonium as a cation component include tetramethylammonium, trimethylethylammonium, dimethyldiethylammonium, triethylmethylammonium, tetraethylammonium and the like. Further, a cation obtained by quaternizing a cyclic amidine compound means N, N, N'-
Examples of the cation obtained by quaternizing a cyclic compound having a substituted amidine group, and the cyclic compound having an N, N, N′-substituted amidine group include the following compounds. That is, an imidazole monocyclic compound (1-methylimidazole, 1,
2-Dimethylimidazole, 1,4-dimethyl-2-ethylimidazole, imidazole analogues such as 1-phenylimidazole, 1-methyl-2-oxymethylimidazole, oxyalkyl derivatives such as 1-methyl-2-oxyethylimidazole , Nitro and amino derivatives such as 1-methyl-4 (5) -nitroimidazole and 1,2-dimethyl-4 (5) -nitroimidazole), benzimidazole (1-methylbenzimidazole, 1-methyl-2-benzyl) Benzimidazole), compounds having a 2-imidazoline ring (1-methylimidazoline,
1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-phenylimidazoline, etc.),
Compounds having a tetrahydropyrimidine ring (1-methyl-1,4,5,6-tetrahydropyrimidine, 1,2-
Dimethyl-1,4,5,6-tetrahydropyrimidine,
1,8-diazabicyclo [5.4.0] undecene-
7,1,5-diazabicyclo [4.3.0] nonene etc.)
Etc.

The content of γ-butyrolactone in the above electrolytic solution is 60 to 90 wt% in the electrolytic solution, preferably 65 to 85.
If the content is less than this range, the spark voltage decreases, and if it exceeds this range, the specific resistance increases. . Further, the content of the quaternary salt of the cyclic amidine compound is 15 to 40 wt%, preferably 20 to 35 wt%, and if it is less than this range, the specific resistance increases.
If it exceeds this range, the spark voltage will decrease.

Further, for the purpose of stabilizing the life characteristics of the electrolytic capacitor, nitrophenol, nitrobenzoic acid, nitroacetophenone, nitrobenzyl alcohol, 2-
(Nitrophenoxy) ethanol, nitroanisole,
Aromatic nitro compounds such as nitrophenetol, nitrotoluene and dinitrobenzene can be added.

Further, for the purpose of improving the safety of the electrolytic capacitor, a nonionic surfactant, a polyhydric alcohol and ethylene oxide which can improve the withstand voltage of the electrolytic solution, and / or
Alternatively, a polyoxyalkylene polyhydric alcohol ether compound obtained by addition polymerization of propylene oxide, or polyvinyl alcohol can be added.

Further, by adding boric acid, a polysaccharide (mannite, sorbit, pentaerythritol, etc.), a complex compound of boric acid and a polysaccharide, colloidal silica, etc. to the electrolytic solution for electrolytic capacitors of the present invention, The voltage can be improved.

An oxycarboxylic acid compound or the like may be added for the purpose of reducing the leakage current.

The electrolytic capacitor of the present invention formed as described above has a low ESR characteristic and can prevent the leakage of liquid which has been observed in conventional quaternary salts.

An insulating layer such as a ceramic coating layer made of Al ₂ O ₃ , SiO ₂ , ZrO ₂ or the like is formed on at least the surface of the round bar portion of the lead wire, or an aqueous solution of ammonium borate or ammonium phosphate is formed. An aluminum oxide layer formed by anodizing treatment with an aqueous solution or an aqueous solution of ammonium adipate can be formed. This can also enhance the liquid leakage prevention effect.

In the electrolytic capacitor of the present invention,
As a cathode electrode foil, a metal nitride selected from titanium nitride, zirconium nitride, tantalum nitride, and niobium nitride, or a metal selected from titanium, zirconium, tantalum, and niobium is conventionally known such as a vapor deposition method, a plating method, and a coating method. A cathode electrode foil coated by the known method can be used. Here, the portion to be covered may cover the entire surface of the cathode electrode foil, or if necessary, a part of the cathode electrode foil, for example, only one surface of the cathode electrode foil may be covered with metal nitride or metal. . This can enhance the effect of preventing electrolyte leakage. Since the surface mount electrolytic capacitor is small and the rubber thickness is small and the round bar portion of the lead wire is small accordingly, the leakage preventing effect is small. Therefore, the metal nitride or the cathode electrode foil coated with metal is used. Is more preferable.

[0026]

EXAMPLES Specific examples of the electrolytic capacitor of the present invention will be described below. (Example 1) An aluminum foil is roughened by alternating-current etching, and further subjected to chemical conversion for forming a dielectric oxide film to prepare an anode foil of the present invention. Further, the aluminum foil is similarly roughened by AC etching, and titanium nitride is deposited on the surface to form a cathode foil. The anode foil and the cathode foil are wound around a separator to form a capacitor element.

In the capacitor element configured as described above,
Impregnate the electrolytic solution for driving the aluminum electrolytic capacitor. The capacitor element impregnated with this electrolytic solution is housed in a bottomed cylindrical aluminum outer case, a butyl rubber sealing body is inserted into the open end of the outer case, and the end of the outer case is squeezed. By doing so, the aluminum electrolytic capacitor is sealed.

The electrolyte used here had a composition of 75 parts of γ-butyrolactone and 25 parts of 1-ethyl-2,3-dimethylimidazolinium phthalate.

The foil width and foil length of the electrode foil used here and their respective ESRs are shown in (Table 1).

[0030]

[Table 1]

As can be seen from (Table 1), the ESR of the electrolytic capacitors of Examples 1 to 3 of the present invention is as low as 45 to 67 mΩ. Especially the foil width is 5.5mm and the foil length is 2
Example 2 of 50 mm, foil width 6.0 mm, foil length 400
Example 3 of mm has an ESR of 50 mΩ or less,
We have realized an electrolytic capacitor with unprecedented low ESR characteristics.

On the other hand, Comparative Example 1 in which the foil width is 4.5 mm or less is 90 mΩ, and Comparative Example 2 in which the foil length is 220 mm or less.
Shows 80 mΩ, which shows the effect of the electrolytic capacitor of the present invention.

[0033]

As described above, according to the present invention, it is possible to provide an electrolytic capacitor having an unprecedented low ESR characteristic.

Claims (2)

[Claims] 1. A foil width of 4.5 to 7 mm and a foil length of 200 to
An electrolytic capacitor containing an electrolytic solution containing γ-butyrolactone and a quaternary salt of a cyclic amidine compound in a capacitor element having a 400 mm anode foil and a cathode foil. 2. The electrolysis according to claim 1, wherein the capacitor element is formed by winding a separator between the anode foil provided with the anode drawing means and the cathode foil provided with the cathode drawing means. Capacitors.