JP2000182906A - Electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the resistance of a sealing body against internal pressure increase when it is exposed to a high temperature during reflow soldering and to normally operate a safety valve when abnormality occurs, by providing an internal stress relaxing member projecting from the bottom surface of the sealing body at least on the side facing a capacitor element. SOLUTION: A cylindrical projection 13 projecting downwards from the bottom surface of a sealing body 3 is provided thereon as an internal stress relaxing member. Further, a lead wire 2 is inserted into the interior thereof. By disposing the cylindrical projection 13 on the bottom surface of the sealing body 3 in such a manner, a stress is generated within the sealing body 3 with the stress from the outside toward the center thereof, and also a stress in the other direction, specifically downward direction is generated. Thus, deformation of the sealing body 3 can be prevented even if the internal pressure increases when reflow soldered at a high temperature. Namely, flipping out of the upper surface of the sealing body 3 can be prevented even if the internal stress concentration occurs in the sealing body 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor, and more particularly, to a high-reliability electrolytic capacitor obtained by improving a sealing body of a case. The electrolytic capacitor of the present invention particularly relates to a chip-type aluminum electrolytic capacitor that can be advantageously used in electronic devices and the like.

[0002]

2. Description of the Related Art Capacitors are one of the general electric components, and are widely used in various electric products and electronic devices, mainly for power supply circuits and noise filters for digital circuits. Further, there are various types of electrolytic capacitors currently used, and examples thereof include aluminum electrolytic capacitors and wet-type tantalum electrolytic capacitors.

In electronic equipment and the like, a chip-type aluminum electrolytic capacitor is generally used, and a chip-type aluminum electrolytic capacitor typically has a configuration as shown in FIG. . An electrolytic capacitor as shown can generally be manufactured as follows: etching a high purity aluminum foil to increase its surface area and then anodic oxidizing the surface of the aluminum foil. A coated anode foil and a cathode foil whose surface has been etched are produced. Next, the obtained anode foil and cathode foil are arranged to face each other, and a separator (separating paper) is interposed between the foils to form a laminate.
An element having a structure obtained by winding the laminate, that is, a capacitor element 1 is manufactured. Subsequently, the obtained capacitor element 1 is impregnated with an electrolytic solution, and the capacitor element 1 impregnated with the electrolytic solution is placed in a case (generally made of aluminum) 4.
And the opening of the case 4 is closed with the elastic sealing body 3. In the lead wire through hole (not shown) of the sealing body 3,
As shown, two lead wires 2 are inserted, and the gap between the through holes is sealed.

[0004] In such a chip type aluminum electrolytic capacitor, as an electrolytic solution, ethylene glycol (EG, boiling point: 198 ° C) or γ-butyrolactone (GB) is used.
L, boiling point 204 ° C.). In addition, natural rubber (NR), styrene butadiene (SB)
R), an elastic rubber such as ethylene propylene terpolymer (EPT) is used.

In order to mount the chip-type electrolytic capacitor on a circuit board, it is necessary to expose the chip-type electrolytic capacitor to a solder reflow process during the manufacture of an electronic device or the like. In other words, the circuit board on which the electrolytic capacitor and other electronic components are mounted is mounted by soldering,
After being put into a reflow furnace (a processing furnace for melting solder and soldering electronic components), it is necessary to heat at a reflow temperature of about 230 to 240 ° C. for several minutes (usually about 3 minutes). .

At the time of such reflow, the inside pressure of the electrolytic solution having a boiling point lower than the reflow temperature is exposed to a state close to the vapor pressure inside the chip-type electrolytic capacitor. When the pressure increases inside the electrolytic capacitor, the internal pressure F is applied to the bottom surface of the sealing member 3 as shown in FIG. Concentration occurs, and as shown by the dotted line A, a problem of deformation of the sealing body such as the upper surface of the sealing body 3 popping out occurs. If such a deformation occurs in the sealing body, it will come into contact with other parts placed adjacent to the capacitor, causing a short circuit, and a gap will be formed in the lead wire through hole, causing electrolyte leakage. In addition, the stress generated when the sealing body is deformed acts on the internal elements of the capacitor to break down the element form and induce deterioration in characteristics. For example, since the electrolyte once leaked to the outside due to liquid leakage does not return to the inside of the capacitor, the amount of electrolyte held in the capacitor after reflow and cooling is insufficient, and not only can the capacitor characteristics not be maintained, Deterioration of characteristics cannot be avoided. In addition, when the sealing body expands and deforms during reflow, the lead wire previously fixed to the sealing body moves as the deformation occurs, and there is a problem that surface mounting is not properly performed.

In the electrolytic capacitor 9 shown in FIG. 1, the end of the opening of the case 4 is curled to increase the sealing strength of the sealing body 3 in order to prevent the deformation of the sealing body. However, it is difficult to completely prevent the deformation of the sealing body during reflow by simply improving such a case.Also, although not shown, the capacitor is inclined and mounted due to the warpage of the attached insulating plate. The problem also arises. Japanese Patent Application Laid-Open No. 8-293435 discloses that in order to prevent a capacitor from being mounted at an angle, a ceramic reinforcing member is disposed from the outside of a sealing member so as to contact the sealing member. It is described that the curl at the end of the case is pressed, but this electrolytic capacitor has not yet achieved a satisfactory effect despite its complicated structure and complicated manufacturing. In particular, none of the above-mentioned electrolytic capacitors can satisfy the recent high demands for electrolytic capacitors as described below.

[0008]

In recent chip-type electrolytic capacitors, as a result of meeting the requirement of Pb-free for pollution-free, the temperature condition of the solder reflow is from 250 to 260.
The temperature has become even higher, and it has become necessary to further improve the heat resistance of the electrolytic capacitor. An object of the present invention is to recognize such a recent technical background, and can withstand a pressure rise inside a capacitor when exposed to a high temperature in a solder reflow process. An object of the present invention is to provide a high-temperature, long-life, and highly reliable electrolytic capacitor that can contribute to the improvement of characteristics and can operate a safety valve normally even when the internal pressure of the capacitor increases when an abnormality occurs. .

[0009]

According to the present invention, there is provided, in accordance with the present invention, a capacitor element formed from opposing anode and cathode foils and a separator interposed between the foils. And an electrolytic capacitor comprising an electrolytic solution impregnated in the capacitor element, and having a structure in which an opening of a case accommodating the capacitor element is sealed by a sealing body, wherein the sealing body is
At least on the side facing the capacitor element, the electrolytic capacitor may be provided with an internal stress relaxation member protruding from the bottom surface of the sealing body.

[0010] In the electrolytic capacitor of the present invention, the internal stress relaxation member attached to the bottom surface of the sealing member so as to protrude therefrom can be preferably formed integrally with the sealing member. Although it can be widely changed within the scope of the present invention, it is preferably a cylindrical projection having a diameter smaller than the diameter of the bottom surface of the sealing body, and the surface of the cylindrical projection is spherical even if it is flat. It may be. Further, the internal stress relaxation member may be a hemispherical projection having a diameter equal to or smaller than the diameter of the bottom surface of the sealing body instead of the columnar projection. In the practice of the present invention, the shape and dimensions of the internal stress relaxation member can be appropriately selected such that the internal stress of the sealing body is relaxed in an optimal form.

In forming the internal stress relaxation member, it is also important what material is used to form the member. That is, the internal stress relaxation member needs to have sufficient electrolytic solution impermeability and elasticity in order to obtain the desired effect, similarly to the material of the sealing body. Suitable materials for the internal stress relieving member are not limited to those listed below, but include a ternary copolymer of isobutylene, isoprene and divinylbenzene, a ternary copolymer of ethylene and propylene and cyclopentadiene, and a fluororesin. And rubber composite materials, and others.

[0012]

FIG. 3 is a sectional view showing a preferred example of an electrolytic capacitor according to the present invention. The illustrated electrolytic capacitor 10 is a chip-type aluminum electrolytic capacitor, and has a structure in which a capacitor element 1 impregnated with an electrolytic solution is housed in a metal case 4, and the opening of the case 4 is closed with a sealing body 3. The size of such an electrolytic capacitor is usually about 4 to 6 mm in diameter × about 4 mm in length.
5 to 6.5 mm, and the explosion-proof valve is usually about 8 mm in diameter.
Installed on capacitors with mm or more.

The sealing body 3 used in the electrolytic capacitor 10 shown in FIG. 3 has a shape as shown in FIG. That is, the sealing body 3 has a columnar projection 13 projecting downward from the bottom surface thereof, and a lead wire 2 shown in FIG. It has a hole 5. The cylindrical projection 13 of the sealing body 3 can function as an internal stress relaxation member in the present invention. Further, a sealing body 3 is provided at the end of the opening of the case 4.
Curl 14 is applied to increase the sealing strength.
Note that the illustrated electrolytic capacitor 10 is an example, and the present invention can be advantageously applied to a structure other than such a wound structure.

The electrolytic capacitor shown in FIG. 3 can be manufactured, for example, as follows. First, using a high-purity aluminum foil as a raw material, the surface is etched to increase the surface area, and then the surface of the aluminum foil is anodized to form an oxide film on the anode foil, and the surface is etched. To produce a cathode foil with an increased surface area. Next, the obtained anode foil and cathode foil are arranged to face each other, and a separator (separation paper) is interposed between the foils to form a laminate, and an element having a structure in which the laminate is wound up, That is, a capacitor element is manufactured. Subsequently, the obtained capacitor element is impregnated with an electrolytic solution, the capacitor element impregnated with the electrolytic solution is housed in a case (generally made of aluminum) as described above, and the opening of the case is closed with a sealing body. . In addition, two lead wires are inserted into the lead wire through-holes of the sealing body, and they are completely sealed so that the electrolyte does not leak.

The electrolytic capacitor of the present invention as described above can solve the disadvantages of the conventional electrolytic capacitor described above with reference to FIG. That is, when solder is reflowed at a high temperature of about 250 to 260 ° C. on a circuit board on which a capacitor or the like is mounted, a pressure rise inside the capacitor occurs due to the solder reflow temperature to which the capacitor is exposed, as shown in FIG. Furthermore, even if the internal pressure F is applied to the bottom surface of the sealing body 3, it is possible to prevent the deformation of the sealing body. That is, even if stress concentration as indicated by an arrow occurs inside the sealing body 3, a dotted line A in FIG.
It is possible to prevent the problem of the protrusion of the upper surface of the sealing body 3 as indicated by. This is because, in the case of the sealing body 3 used in the present invention, the cylindrical projection 13 is arranged as an internal stress relaxation member on the bottom surface (the side facing the capacitor element). From the center to the center (see arrow) and the stress in other directions, especially downward (see arrow B), the stress concentration problem that was difficult to solve in the prior art. This is because it can be avoided. Therefore, the use of the electrolytic capacitor of the present invention eliminates the problem of short-circuit and the problem of electrolyte leakage due to the protrusion of the sealing body, and also ensures the normal and proper operation of the safety valve.

To further explain the electrolytic capacitor according to the present invention, the aluminum foil used as the anode foil and the cathode foil is preferably a high-purity aluminum foil having a purity of 99% or more. The anode foil can be preferably formed by electrochemically etching an aluminum foil, anodizing to form an oxide film on the surface, and then attaching an electrode lead tab. Further, the cathode foil can be formed by etching the aluminum foil and then attaching a lead tab for leading the electrode. The cathode foil is not subjected to anodic oxidation.

The capacitor element can be obtained by winding the anode foil and the cathode foil formed as described above, with the surfaces of the anode foil and the cathode foil facing each other via the above-mentioned separator paper. The separator paper used for producing the capacitor element is not particularly limited, but is preferably a paper produced from a naturally-occurring cellulose material, for example, manila hemp or vegetation pulp. For such a separator paper, for example, paper produced by using a pulp of a plant as a raw material and subjecting the raw pulp to a dust removing step, a washing step, a beating step, a paper making step, and the like can be advantageously used. In addition, use of paper derived from synthetic fibers is also conceivable, but such paper is not preferable because heat resistance is poor or halogen ions contained therein cause corrosion of the capacitor.

As described above, the electrolytic capacitor of the present invention is characterized by the shape of the sealing member for sealing the case of the capacitor, whereby a remarkable effect unique to the present invention can be obtained. The essential component of the sealing body used in the present invention is that an internal stress relaxation member is attached to the bottom surface of the sealing body so as to protrude therefrom.
The shape and size of the internal stress relaxation member can be appropriately selected so that the internal stress of the sealing body is relaxed in an optimal form.

The internal stress relieving member is preferably formed integrally with the sealing body and from the same or substantially the same material, and its shape and dimensions may vary widely within the scope of the present invention. However, preferably, it is a columnar projection having a diameter smaller than the diameter of the bottom surface of the sealing body, and the surface of the columnar projection may be flat or spherical. Such a columnar projection may have, for example, the shape as described above with reference to FIG.

In the present invention, instead of the columnar projections, projections of other shapes can be advantageously used as internal stress relaxing members. For example, the internal stress relieving member may be a hemispherical protrusion having a diameter equal to or smaller than the diameter of the bottom surface of the sealing body. FIG. 6 shows an internal stress relaxation member of this embodiment, in which a dome-shaped hemispherical projection 23 is integrally attached to the bottom surface of the sealing body 3 having the lead wire through hole 5 so as to project therefrom. Have been. Note that the illustrated hemispherical projection 23 is
Although it has the same diameter as the bottom surface of the sealing body, instead of such a projection, it has a diameter smaller than the bottom surface of the sealing body 3 and has a structure in which a hemispherical projection protrudes from the center of the bottom surface. You may have.

Further, in the case of the sealing body used in the present invention, the upper surface, that is, the surface opposite to the surface having the above-mentioned internal stress relaxation member is not particularly limited, and therefore, has an arbitrary shape. Alternatively, it can have a configuration. In general, the upper surface of the sealing body is preferably flat. The sealing body used in the electrolytic capacitor of the present invention has various hardness as long as its material is high in hardness, has a suitable rubber elasticity, is impermeable to electrolyte, and has good airtightness as a sealing body. It can be formed from conventional materials. Suitable sealing materials include, for example, natural rubber (NR), styrene butadiene (SB)
R), ethylene propylene terpolymer (EPT), and elastic rubbers such as isobutylene / isoprene rubber (IIR). It is also preferable to use isobutylene-isoprene rubber (IIR) because the airtightness is high and the electrolyte does not permeate as vapor. In particular, vulcanized IIR having better heat resistance,
For example, it is more preferable to use IIR such as sulfur vulcanization, quinoid vulcanization, resin vulcanization, and peroxide vulcanization. Resin vulcanization IIR is particularly preferred.

Further, in practicing the present invention, instead of the above-mentioned sealing material, a resin material plate (for example, a fluororesin plate such as a PTFE plate) having airtightness and sufficiently high strength may be used. A composite material in which rubber is bonded can also be advantageously used for forming the sealing body. In the electrolytic capacitor of the present invention, a common electrolytic solution can be arbitrarily used as the electrolytic solution for driving the electrolytic capacitor. The electrolytic solution is generally composed of an electrolyte and a solvent in which the electrolyte is dissolved.
G) as a main solvent, N, N-dimethylformamide (DMF), γ-butyrolactone (GB
L) and the like. As mentioned above, it is desirable to use an electrolytic solution having a lower specific resistance in order to improve the capacitor characteristics, particularly to achieve a lower impedance of the capacitor.

Electrolytes that can be used particularly advantageously in the practice of the present invention are those that the present inventors have recently invented. That is, the electrolytic solution uses a solvent having a high water concentration, which is a mixture of an organic solvent and water, as a solvent for dissolving the electrolyte in the electrolytic solution. As the organic solvent used in this electrolytic solution, a protic solvent or an aprotic solvent can be used alone or in any combination. Examples of suitable protic solvents include alcohol compounds. Also,
Specific examples of the alcohol compound that can be advantageously used here include, but are not limited to, those listed below, ethyl alcohol, propyl alcohol, monohydric alcohols such as butyl alcohol, ethylene glycol, Examples thereof include dihydric alcohols (glycols) such as diethylene glycol, triethylene glycol and propylene glycol, and trihydric alcohols such as glycerin. Examples of suitable aprotic solvents include lactone compounds. Also,
Specific examples of the lactone compound that can be advantageously used here include, but are not limited to, those listed below, and γ-butyrolactone and other intramolecularly polarized compounds. In the practice of the present invention, when using one or more selected from a protic solvent and an aprotic solvent, more specifically, one protic solvent may be used,
One kind of aprotic solvent may be used, plural kinds of protic solvents may be used, plural kinds of aprotic solvents may be used, or one or more kinds of protic solvents may be used. A mixed system of one or more aprotic solvents may be used.

The electrolytic capacitor of the present invention uses water as a solvent component of the electrolytic solution in addition to the organic solvent. Particularly, the electrolytic solution of the present invention contains a relatively large amount of water. Electrolyte solution. In the present invention, the use of such a solvent lowers the freezing point of the solvent, thereby improving the impedance characteristics of the electrolyte at low temperatures, and is indicated by a low impedance ratio between low and normal temperatures. Good low-temperature characteristics can be realized. The content of water in the electrolyte is preferably in the range of 20 to 80% by weight, and the remainder is an organic solvent. When the water content is less than 20% by weight or more than 80% by weight, the degree of freezing point drop of the electrolytic solution becomes insufficient, and it becomes difficult to obtain good low-temperature characteristics of the electrolytic capacitor. A more preferred water content in the solvent is 3
The range of 0 to 80% by weight, with the most preferred water content being in the range of 45 to 80% by weight.

As the electrolyte dissolved in the electrolyte, an organic acid, preferably a carboxylic acid or a salt thereof, or an inorganic acid or a salt thereof is used. These electrolyte components may be used alone or A combination of more than one species may be used. Examples of carboxylic acids that can be used as the electrolyte component include, but are not limited to, those listed below, formic acid, acetic acid, propionic acid, butyric acid, p-
Includes monocarboxylic acids such as nitrobenzoic acid, salicylic acid and benzoic acid, and dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, phthalic acid and azelaic acid For example, carboxylic acids having a functional group such as a hydroxyl group such as citric acid and oxybutyric acid can be used.

Examples of the inorganic acids which can also be used as the electrolyte component are not limited to those listed below, but include phosphoric acid, phosphorous acid, hypophosphorous acid, boric acid, and sulfamic acid. Etc. are included. Further, various salts can be used as the salts of the carboxylic acids or inorganic acids as described above, and suitable salts include, for example, ammonium salts, sodium salts, potassium salts, amine salts, and alkyl ammonium salts. And so on. Among such salts, it is more preferable to use an ammonium salt.

In addition, when an inorganic acid or a salt thereof is used as an electrolyte in the practice of the present invention, a decrease in the freezing point of the electrolyte can be expected, which can contribute to further improvement of the low-temperature characteristics of the electrolyte. The use of an inorganic acid or a salt thereof is also notable in that if a nitro compound is used as an additive, the ability to absorb hydrogen gas derived from the nitro compound can be maintained for a long period of time.

According to the study of the present inventors, when an electrolyte such as an inorganic acid or a salt thereof is used in combination with the above-mentioned electrolyte such as a carboxylic acid or a salt thereof, they are used alone. As compared with the case, the effect that the life of the electrolytic capacitor can be significantly extended can also be obtained. Furthermore, in conventional electrolytic capacitors, due to problems such as electric conductivity, inorganic acid-based electrolytes have been mainly used for medium to high voltage (160 to 500 volt) type electrolytic capacitors. When the electrolyte is used in combination, it can be advantageously used even in a low-voltage (less than 160 volt) type electrolytic capacitor.

The amount of the electrolyte used in the electrolyte depends on various factors such as the characteristics required for the electrolyte and the capacitor finally obtained, the type and composition and amount of the solvent used, and the type of the electrolyte used. Accordingly, the optimal amount can be appropriately determined. The electrolytic solution used in the electrolytic capacitor of the present invention is, in particular, an electrolytic solution having a specific composition as described above, that is, a solvent comprising 20 to 80% by weight of an organic solvent and 80 to 20% by weight of water, The following specific additives (1) to (5) are used alone or in combination with an electrolyte solution containing at least one electrolyte selected from the group consisting of an acid or a salt thereof and an inorganic acid or a salt thereof. A more remarkable effect can be obtained by the addition.

(1) Chelating compounds such as ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid monohydrate (CyDTA), dihydroxyethylglycine ( DH
EG), ethylenediaminetetrakis (methylenephosphonic acid) (EDTPO), diethylenetriamine-N,
N, N ', N ", N" -pentaacetic acid (DTPA), diaminopropanoltetraacetic acid (DPTA-OH), ethylenediaminediacetic acid (EDDA), ethylenediamine-N, N'
-Bis (methylenephosphonic acid) hemihydrate (EDDP
O), glycol ether diamine tetraacetic acid (GEDT)
A), hydroxyethylethylenediamine triacetic acid (ED
TA-OH) and the like. Chelating compounds are generally used in 0.0
It is preferable to add in the range of 1 to 3% by weight. Such a chelate compound can prolong the life of the capacitor by suppressing the hydration reaction of the aluminum (Al) electrode foil of the low impedance capacitor, and improve the low temperature characteristics of the electrolytic capacitor. The change in impedance at a low temperature is reduced), and effects such as improvement in corrosion resistance can be obtained.

(2) Sugars, for example, glucose, fructose, xylose, galactose and the like. Generally, saccharides are preferably added in the range of 0.01 to 5% by weight. Such saccharides reduce the hydration reaction of the Al electrode foil of low impedance capacitors, prolong the life of the capacitors, suppress the decomposition and activation of electrolytes such as carboxylic acids by adding saccharides, and improve the low temperature characteristics of electrolytic capacitors. (Since the solvent has a composition close to the antifreeze state, the change in impedance between room temperature and low temperature is small).

(3) Hydroxybenzyl alcohol, for example, 2-hydroxybenzyl alcohol, L-glutamic acid diacetate or a salt thereof. This additive is generally
It is preferable to add in the range of 0.01 to 5% by weight.
Such additives can be used in the low impedance capacitor A
(1) Longer life of the capacitor by suppressing the hydration reaction of the electrode foil and improvement of the low temperature characteristics of the electrolytic capacitor (since the solvent has a composition close to the antifreeze state, the change in impedance between room temperature and low temperature is small). Can bring.

(4) Nitro compounds such as nitrophenols such as p-nitrophenol, nitrobenzoic acids such as p-nitrobenzoic acid, dinitrobenzoic acid, nitroacetophenones such as p-nitroacetophenone and nitroanisole group. Generally, it is preferable to add the nitro compound in the range of 0.01 to 5% by weight. Such a nitro compound has a remarkable hydrogen gas absorbing effect and an action of inhibiting the element from being corroded by an action of a halogenated hydrocarbon used for cleaning a printed circuit board, for example, trichloroethane (in other words, an action of obtaining halogen). Action).

(5) Gluconic acid, gluconolactone and the like.
Generally, this additive is preferably added in the range of 0.01 to 5% by weight. When this additive is added to the electrolyte solution of the present invention, it has additional effects unique to the present invention, such as longer life of the electrolytic capacitor, improvement of low-temperature characteristics, and excellent hydrogen gas absorption effect. As a result, a remarkable effect such as improvement in corrosion resistance can be further obtained.

Further, in addition to the above-mentioned additives,
Additives commonly used in the field of aluminum electrolytic capacitors or other electrolytic capacitors may be further added.
Suitable conventional additives include, for example, mannitol, silane coupling agents, water-soluble silicones, polymer electrolytes, and the like.

[0036]

Next, the present invention will be further described with reference to examples.
It goes without saying that the examples given here are intended to illustrate the invention, but not to limit it. Example 1 The following 4 was used to manufacture an electrolytic capacitor.
Various types of sealing bodies were produced. [Sealing body 1] (Example of the present invention) After preparing a ternary copolymer of isobutylene, isoprene and divinylbenzene, vulcanizing the resin, a disk with cylindrical projections as shown in FIG. A projection with a diameter of 3 mm is added to the sealing rubber, height h = 1.5 mm)
A sealing body in the shape of was prepared. [Sealing body 2] (Example of the present invention) After preparing a ternary copolymer of isobutylene, isoprene and divinylbenzene, and vulcanizing the resin, a disc with hemispherical projections as shown in FIG. A projection was provided to the sealing rubber to form a sealing body having a height h = 1.5 mm). [Sealing body 3] (Comparative example) A ternary copolymer of isobutylene, isoprene and divinylbenzene was prepared, and after resin vulcanization, a disc having no projection as described with reference to FIGS. 1 and 2 was used. (A conventional sealing rubber for a condenser having a diameter of 5 mm and a height h = 1.3 mm) was prepared. [Sealing body 4] (Comparative example) A three-component copolymer of isobutylene, isoprene and divinylbenzene was prepared and cured with a resin, and thereafter, a disk having no projection as described with reference to FIGS. 1 and 2. (A conventional sealing rubber for a condenser having a diameter of 5 mm and a height h = 1.5 mm) was prepared. Example 2 Each of the sealing bodies 1 to 4 prepared in Example 1 was used to form a wound structure of 6.3 WV-47 μF (diameter 5
A chip-type aluminum electrolytic capacitor (mm × 6 mm in length) was manufactured according to the following procedure.

First, an aluminum foil is electrochemically etched and anodized to form an oxide film on the surface.
Thereafter, a lead tab for extracting an electrode was attached to produce an aluminum anode foil. Next, another aluminum foil was also electrochemically etched, and then a lead tab for extracting an electrode was attached to produce an aluminum cathode foil.
Subsequently, a separator was sandwiched between the anode foil and the cathode foil and wound to form a capacitor element. The separating paper used here is paper manufactured using Manila hemp as a raw material. Then, the capacitor element is impregnated with an electrolytic solution having the following composition: 75 parts by weight of γ-butyrolactone and 25 parts by weight of monotetramethylammonium phthalate. Then, a lead tab for extracting an electrode is placed in a bottomed aluminum case. Of the case, and the opening of the case was sealed with the elastic sealing body prepared in Example 1.

The heating profile for each aluminum electrolytic capacitor (20 each) is as follows: 1. Starting from room temperature and heating to 150 ° C. 2. Continue the temperature of 150 ° C. for 120 seconds measured from the start of heating; 3. After 120 seconds measured from the start of heating, continue heating further until peak temperature (230 ° C., 240 ° C. or 250 ° C.) is reached, and After reaching the peak temperature, the substrate was left to cool, and a simulated solder reflow test was performed according to. The appearance of the sealing body of each capacitor was visually observed, and the number of capacitors having swelling or other abnormalities was recorded. The results as shown in Table 1 below were obtained.

Table 1 Test capacitor peak temperature (° C.) (No. of sealing body) 230 240 250 1 (Example of the present invention) 0/200 0/20 0/20 2 (Example of the present invention) 0/20 0/20 0/20 3 (Comparative Example) 0/20 3/20 15/204 (Comparative Example) 0/200 0/20 8/20 Example 3 Each of the sealing bodies 1 to 4 prepared in Example 1 was used. 6.3WV-47μF of the winding structure (diameter 5
A chip-type aluminum electrolytic capacitor (mm × 6 mm in length) was manufactured according to the procedure described in Example 2. In addition,
In this example, the following composition: ethylene glycol 45% by weight, water 40% by weight, ammonium adipate 14.4% by weight, ethylenediaminetetraacetic acid 0.5% by weight, and D 酢 酸 gluconic acid-δ-lactone 0.1% by weight %, And a heating profile as follows: 1. Starting from room temperature and heating to 150 ° C. 2. Continue the temperature of 150 ° C. for 120 seconds measured from the start of heating; 3. After 120 seconds measured from the start of heating, continue heating further until peak temperature (220 ° C., 230 ° C. or 240 ° C.) is reached, and After reaching the peak temperature, the substrate was left to cool, and a simulated solder reflow test was performed according to. The second below
The results as shown in the table were obtained. Table 2 Test capacitor peak temperature (° C.) (No. of sealing body) 220 230 240 1 (Example of the present invention) 0/20 0/20 2/20 2 (Example of the present invention) 0/20 0/20 1/20 3 (Comparative Example) 2/20 8/20 20/204 (Comparative Example) 0/20 4/20 10/20 As can be understood from the results described in Tables 1 and 2 above, the present invention When a sealing body with a projection is used in accordance with the above, an abnormality such as swelling can be prevented in contrast to a conventional sealing body without a projection. In addition, when the conventional sealing body having no projection is used, the occurrence of abnormalities increases as the peak temperature increases, and when the thickness of the sealing body increases, the occurrence of abnormalities is slightly reduced. Can be suppressed, but not perfect.

[0040]

As described above, according to the present invention, when the electrolytic capacitor is exposed to a high temperature in the solder reflow step by using the sealing member having the specific shape as described above, the capacitor can be used. The sealing body can withstand the increase in the pressure generated inside the capacitor, and in the event of an abnormality, a long-life and highly reliable electrolysis can be performed so that the safety valve can operate normally against the increase in the internal pressure of the capacitor. Capacitors can be provided. Further, in this electrolytic capacitor, a low-boiling-point electrolytic solution can be used, which can contribute to improvement of capacitor characteristics.

Further, according to the present invention, even if the electrolyte contains a highly volatile solvent such as γ-butyrolactone as a main solvent, it has low impedance, excellent low-temperature characteristics, heat resistance, and airtightness. An electrolytic capacitor capable of effectively preventing the leakage of the electrolytic solution can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a conventional electrolytic capacitor.

FIG. 2 is a cross-sectional view illustrating a deformation of a sealing body occurring during use in the electrolytic capacitor of FIG.

FIG. 3 is a sectional view showing a preferred example of an electrolytic capacitor according to the present invention.

FIG. 4 is a side view showing a shape of a sealing body used in the electrolytic capacitor of FIG.

FIG. 5 is a cross-sectional view illustrating the behavior of the sealing body in the electrolytic capacitor (during use) of FIG. 3;

FIG. 6 is a side view showing another preferred example of a sealing body that can be advantageously used in the electrolytic capacitor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Capacitor element 2 ... Lead wire 3 ... Sealing body 4 ... Case 5 ... Lead wire through-hole 13 ... Cylindrical projection 14 ... Curl 23 ... Hemispherical projection

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akihiko Komatsu 1938-1, Nishi-Minawa, Oaza, Ina-shi, Nagano Rubicon Co., Ltd. In-company (72) Inventor Katsuya Karasawa 1938 Nishiminowa, Ina-shi, Nagano Prefecture 1 Rubycon Corporation

Claims (7)

[Claims] 1. A capacitor element formed from an anode foil and a cathode foil disposed opposite to each other, and a separator paper interposed between the foils, and an electrolytic solution impregnated in the capacitor element. In an electrolytic capacitor having a structure in which an opening of a case accommodating the capacitor element is sealed by a sealing body, the sealing body protrudes from a bottom surface of the sealing body at least on a side facing the capacitor element. An electrolytic capacitor comprising an internal stress relaxation member. 2. The electrolytic capacitor according to claim 1, wherein the internal stress relaxation member is a columnar projection having a diameter smaller than a diameter of a bottom surface of the sealing body. 3. The internal stress relaxation member is a hemispherical projection having a diameter equal to or smaller than a diameter of a bottom surface of the sealing body.
An electrolytic capacitor according to item 1. 4. The internal stress relaxation member comprises a three-component copolymer of isobutylene, isoprene and divinylbenzene, and a three-component copolymer of ethylene, propylene and cyclopentadiene.
The electrolytic capacitor according to any one of claims 1 to 3, wherein the electrolytic capacitor is formed from a material selected from the group consisting of a component copolymer and a composite material of a fluororesin and a rubber. 5. The electrolytic capacitor according to claim 1, wherein the electrolytic solution is a γ-butyrolactone-based electrolytic solution. 6. The electrolytic capacitor according to claim 1, wherein the electrolytic solution is an ethylene glycol-based electrolytic solution. 7. The electrolytic capacitor according to claim 1, wherein the electrolytic capacitor is a chip-type aluminum electrolytic capacitor used in an electronic device or the like.