JPH07201679A - Aluminum electrolytic capacitor - Google Patents

Abstract

PURPOSE:To provide a highly efficient aluminum electrolytic capacitor by eliminating the defect of liquid leakage regarding an aluminum electrolytic capacitor used for a household appliance, etc. CONSTITUTION:Electrolytic solution 4 is prevented from leaking and a highly efficient aluminum electrolytic capacitor is provided by forming an alkali-proof insulating film 11 in a part in contact with a sealing body 7 of an external extension line 3 connected to a capacitor element 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum electrolytic capacitor used for home electric appliances, office automation equipment, communication equipment, automobile parts and the like.

[0002]

2. Description of the Related Art A conventional aluminum electrolytic capacitor of this type will be described with reference to the drawings. FIG. 5 shows what is called the smallest chip capacitor among conventional aluminum electrolytic capacitors, and has a performance guaranteed for 2000 hours at 105 ° C.

In FIG. 5, reference numeral 17 is a capacitor element in which an anode foil and a cathode foil to which external lead wires 18 are respectively connected are wound with a separator interposed therebetween, 19 is an electrolytic solution, 20 is an aluminum case, and 21 is a seat plate. 22 is polyethylene tetrafluoride 23 and butyl rubber or ethylene / propylene rubber 2
4 is a sealing body made of a composite body of 4 and is inserted into the upper surface portion of the aluminum case 20 in a press-fit state by inserting the external lead wire 18, and fulfills a sealing function by drawing and bending the aluminum case 20.

FIG. 6 also shows a conventional aluminum electrolytic capacitor, which is a chip capacitor in which the sealing body 22 of FIG. 5 is composed of a sealing body 25 formed by compression molding butyl rubber, and the performance is guaranteed for 2000 hours at 85 ° C. Is to have.

Further, the rubber of the sealing body 22 or 25 contains filler such as carbon black to which a silicate system such as clay is added, calcium carbonate and the like.

FIG. 7 shows an external lead wire 18 used in the conventional aluminum electrolytic capacitor shown in FIGS. 5 and 6, and an internal tangential lead wire made of an aluminum wire provided with a capacitor element connecting portion 26. The wire 27 and an external lead wire 28 composed of a CP wire are formed by joining at a weld 29.

[0007]

However, although the above-mentioned conventional aluminum electrolytic capacitors have been developed to have high performance in the electrolytic solution 19 and the electrolyte, the capacitor characteristics have been greatly improved, but in recent years, the environment in which the equipment is used becomes more severe. As a result, liquid leakage defects are increasing.

This liquid leakage failure has been a serious drawback that not only the capacitor characteristics (electrostatic capacity, Tan δ) disappear but also the printed circuit board is damaged.

Further, in the chip capacitor, there is a problem that the sealing bodies 22 and 25 are deformed due to a high temperature of 200 ° C. or more and an increase in internal pressure in the solder reflow process.

The present invention solves these conventional problems,
It is an object of the present invention to provide a high-performance aluminum electrolytic capacitor which solves liquid leakage failure and deformation of the sealing body.

[0011]

In order to solve the above problems, an aluminum electrolytic capacitor of the present invention comprises a capacitor element in which an anode foil and a cathode foil connected to an external lead wire are wound with a separator interposed therebetween, and this capacitor element. In an aluminum electrolytic capacitor having an open upper surface containing the electrolyte and a sealing body inserted through the external lead wire into the upper surface of the aluminum case, the external lead wire is connected to at least the cathode foil. Also, an alkali resistant insulating coating made of phenol resin, fluororesin, polyparaxylylene, ceramic coating, or the like is formed on a portion of the external lead wire that contacts the sealing body.

[0012]

With this configuration, the alkali-resistant insulating coating formed on the portion of the external lead wire inserted through the sealing body in contact with the sealing body suppresses all electrical and chemical reactions including migration of ions. It is possible to prevent the occurrence of liquid leakage even on the side of the cathode where the problem is remarkable.

[0013]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an aluminum electrolytic capacitor according to the same embodiment. In FIG. 1, 1 is an anode foil in which an external lead wire 2 on the anode side and an external lead wire 3 on the cathode side are respectively connected (see FIG. (Not shown) and a cathode foil (not shown) wound around a separator (not shown), 4 is an electrolytic solution, 5 is an aluminum case, and 6 is a seat plate.

Reference numeral 7 designates a sealing body made of a composite of polyethylene tetrafluoride 8 and butyl rubber or ethylene / propylene rubber 9, which is inserted into the upper surface of the aluminum case 5 through the external lead wires 2 and 3 in a press-fitted state. The aluminum case 5 has a sealing function by drawing and bending.

Reference numeral 10 designates a reinforcing plate for preventing deformation of the sealing body, which is inserted through the external extraction lines 2 and 3 and closely adhered to the upper surface of the sealing body 7, and 11 denotes the sealing body 7 of the external extraction line 3 on the cathode side. It is an insulating coating formed on the contacting portion.

FIG. 2 shows an external lead wire 3 on the cathode side used in the aluminum electrolytic capacitor of the present invention shown in FIG. 1, and the external lead wire 3 on the cathode side is the capacitor element connecting portion 12a. Internal lead wire 12 made of aluminum wire and external lead wire 13 made of CP wire
Are joined together at the welded portion 14, and the insulating coating 11 is formed on the portion where the external lead wire 3 on the cathode side is in contact with the sealing body 7.
Is formed.

It is necessary that the insulating coating 11 does not significantly swell with respect to the electrolytic solution 4, is resistant to alkali, and has no pinhole.

Further, the insulating coating 11 formed on the aluminum wire or the CP wire is required to have sufficient adhesiveness and strength to withstand the stress when the external lead wires 2 and 3 are inserted into the sealing body 7 at high speed.

Further, as a material for forming the insulating coating 11, phenol resin, fluororesin, polyparaxylylene, ceramic paint, etc. are suitable.

Further, by preliminarily alumite-treating the portion of the external lead wire 3 where the insulating coating 11 is formed, the adhesion and insulating properties of the insulating coating 11 can be improved.

As described above, by forming the alkali-resistant insulating coating 11 on the portion of the cathode-side external lead wire 3 which is in contact with the sealing body 7 without pinholes, the external lead wire 3 and the electrolytic solution 4 are separated from each other. Then, electrical including movement of ions,
It is possible to suppress all chemical reactions, and particularly to prevent liquid leakage from occurring on the side of the external lead wire 3 on the cathode side where this reaction is remarkable.

(Embodiment 2) An aluminum electrolytic capacitor according to a second embodiment of the present invention will be described below.

In this embodiment, the rubber 9 (any one of butyl rubber, ethylene / propylene rubber, and a composite of butyl rubber and ethylene / propylene rubber) used for the sealing body 7 of the aluminum electrolytic capacitor described in the first embodiment is used. The present invention is related to the filler contained in (1) and is the same as that of the first embodiment except for this, and therefore detailed description thereof will be omitted and only different portions will be described.

Generally, silicate (clay), calcium carbonate (talc) and the like are often used as the filler contained in the rubber 9. However, since these are easily attacked by alkali, the electrolyte 4 is permeated. In order to induce liquid leakage failure, an alkali resistant material such as silica, alumina or boron nitride is used as the above filler, and a scale-like filler 15 is used to further enhance the effect.
Is to be used.

However, merely containing these fillers 15 does not react with butyl rubber or ethylene propylene rubber and therefore does not have the function of suppressing the swelling of the rubber 9, and in order to obtain the function of suppressing the swelling of the rubber 9. Rubber 9
It is necessary to react the filler 15 with the filler 15. Therefore, as shown in (Chemical formula 1), the reaction product (ceramic paint) of colloidal silica and alkyl silicate is added to the filler 1
It is possible to form a ceramic coating of 2 μm or less on the surface of the filler 15 by adding it to No. 5 and mixing and stirring.
However, if it is applied thickly to 2 μm or more, partial film cracking occurs and the effect is reduced.

[0027]

[Chemical 1]

3 (a) and 3 (b) are partially enlarged sectional views showing a state of the filler 15 contained in the rubber 9.
FIG. 1A shows a rubber-like scale-like filler 1 that is alkali-resistant.
5 is contained, but in this state, the filler 15
A space portion 16 is generated at the peripheral edge of and the filler 15 is in contact with the rubber 9 through the space portion 16 and therefore does not react.

FIG. 3B shows a state in which the rubber 9 contains the filler 15 having a ceramic coating formed on the surface thereof. The colloidal silica formed on the surface of the filler 15 is reacted with the alkyl silicate. The coating film formed from the ceramic paint, which is the reaction product, penetrates into the molecule of butyl rubber or ethylene propylene rubber and shows a strong bond.

Therefore, due to the heat and pressure during solder reflow,
It becomes difficult for the electrolytic solution 4 to enter the molecule of the rubber 9, and the swelling of the rubber 9 becomes small. Filler 15 thus treated
Since the rubber reacts with the rubber 9, the swelling property with respect to the electrolytic solution 4 is improved, and changes in the capacitor characteristics during energization and heating are reduced.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a perspective view showing a reinforcing plate 10 used in the aluminum electrolytic capacitor according to the same embodiment. This reinforcing plate 10 is the aluminum electrolytic capacitor described in the first embodiment with reference to FIG. Used for external lead wires 2, 3
Is inserted at the time of assembling so as to be closely attached to the upper surface of the sealing body 7, and fixed by processing the aluminum case 5. Therefore, the reinforcing plate 10 needs to have an outer diameter smaller than the inner diameter of the aluminum case 5 and larger than the inner diameter for curling the upper end of the aluminum case 5.

Further, since it is desirable that the reinforcing plate 10 has a small deformation with respect to the heat pressure in the solder reflow, it is necessary to use a material having a heat deformation temperature of 250 ° C. or higher.

It is also necessary that the electrolytic solution 4 does not swell and dissolve when it adheres. Therefore, FRTP (glass fiber reinforced thermoplastic) is suitable. For example, nylon 46, nylon 66, PPS, PEEK, aromatic polyester, liquid crystal polymer and the like can be used.

The thickness of the reinforcing plate 10 is restricted by product specifications and curl characteristics, but a thickness of about 0.1 to 0.5 mm can be used, and the bending strength is proportional to the cube of the thickness. Needless to say, the deformation becomes smaller.

The reinforcing plate 10 is made of glass fiber 30
When prepared with 0.3 mmt of PPS filled with 10% and placed on the upper surface of the sealing body 7, the Young's modulus at 200 ° C. of PPS is 5 times larger than that of polyethylene tetrafluoride, so that the reinforcing plate 10 is not used. The amount of deformation during solder reflow is reduced to ⅕ compared to the case where only the sealing body 7 made of fluorinated polyethylene 8 and rubber 9 is used.

In the case of the rubber 9 alone, there is no heat deformation temperature and the deformation by heat and pressure is large, but when cooled, it returns to a state close to the original state, but it is difficult to return, but it is difficult to return. The reinforcing plate 10 is provided on the sealing body 7 which is a composite of
It is effective for preventing the deformation of the sealing body 7 by using the combination of.

(Fourth Embodiment) The fourth embodiment of the present invention will be described below.

In this embodiment, the smallest chip capacitor among the aluminum electrolytic capacitors was prototyped based on the first to third embodiments.

(1) A chip capacitor having a diameter of 4 mm and a withstand voltage of 16 V and 10 μF was prototyped according to the following specifications.

(1-1) Cathode lead wire: Phenol resin (trade name Sumilac PC1: made by Sumitomo Bakelite) was applied in a width of 2 mm at the center of the sealing portion, dried at 100 ° C. for 10 minutes, and baked at 160 ° C. for 30 minutes. Was performed to form a coating film having a thickness of 10 μm.

(1-2) Sealing body: A laminated sheet of 0.8 mmt tetrafluorinated polyethylene and 0.35 mmt ethylene / propylene rubber mixed with flaky alumina (average particle size 5 μm) as a rubber filler was manufactured as a trial. Then, punching processing was performed to manufacture the sealing body 7 as a prototype.

(1-3) Reinforcing plate: An outer diameter of 3.5 mm, a thickness of 0.3 mmt, and a reinforcing plate having two lead holes provided in PPS.
(Manufactured by Dainippon Ink Co., Ltd .: trade name FZ1140: 40% glass fiber).

Except for the above-mentioned three members, 100 chip capacitors were prototyped without changing the conventional process products and process conditions.

(2) A chip capacitor having a diameter of 6 mm, a withstand voltage of 10 V, and a resistance of 100 μF was prototyped according to the following specifications.

(2-1) Cathode lead wire: A polyparaxylylene film having a thickness of 3 μm and a thickness of 3 μ was formed by a vapor phase method centering on a position in contact with the sealing body 7. The area where the coating is not desired was made by masking.

(2-2) Sealing body: 0.8 mmt tetrafluorinated polyethylene, 0.35 mmt butyl rubber laminate sheet, quartz powder having a particle size of 2 to 3 μm was added as a rubber filler after the following treatment.

Colloidal silica (40% soln) 35 Ethyl silicate 10 Acetic acid 0.1 50 ° C. for 30 minutes Mixing and stirring The above mixture was mixed 1: 1 by weight with a mixture of water: isopropyl alcohol = 1: 1 to prepare a ceramic paint. Was completed.

Quartz powder 1 kg Ceramic coating 0.1 kg After kneading with a kneader, drying is performed at 150 ° C. for 20 minutes.

A sealing body 7 was manufactured by punching this sheet. (2-3) Reinforcing plate: outer diameter φ5.5 mm, thickness 0.3 mmt,
Liquid crystal polymer (Nippon Petrochemical: product name Sizer G330: glass fiber 3)
Prototype with 0%).

Except for the above-mentioned three members, trial production of 100 chip capacitors was performed without changing the conventional process products and process conditions.

(3) A chip capacitor having a diameter of 4 mm, a withstand voltage of 10 V, and a resistance of 10 μF was prototyped according to the following specifications.

(3-1) Cathode lead wire: A phenol resin film was formed in a thickness of 10 μm as in the prototype (1).

(3-2) Sealing body: In a rubber compound for butyl rubber compression molding having a thickness of 2 mm, scaly alumina (average particle diameter 3 μ) was added by ceramic coating treatment in the same manner as in the prototype (2). 150 ° C, 100
A sealing body 7 was prototyped by carrying out compression molding for 5 minutes at kg / cm ² .

Except for the above two members, 100 chip capacitors were prototyped without changing the conventional process products and process conditions.

Prototype (1)-
When the performance of (3) was measured, the capacitance change during solder reflow was -4 to -5% for the conventional product, but -3% for the prototype (1), and the prototypes (2), (3). Then -1 to
It was as small as -2%.

In a thermal shock test at -40 ° C to + 105 ° C, liquid leakage from the cathode part was confirmed after several tens of cycles in the sealing body made of polyethylene tetrafluoride and rubber.
Also, the limit is 100 cycles even for the sealed body of butyl rubber alone, but the prototype according to the present invention showed no liquid leakage even after the thermal shock test of 300 cycles.

[0058]

As described above, in the aluminum electrolytic capacitor according to the present invention, the alkali-resistant insulating film is formed by forming the alkali-resistant insulating coating on at least the portion of the cathode-side external lead wire which is in contact with the sealing body. It is possible to provide a high-performance aluminum electrolytic capacitor in which the coating film suppresses all electrical and chemical reactions including migration of ions, and liquid leakage does not occur especially on the cathode side where this reaction is remarkable.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an aluminum electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a plan view showing an external lead wire according to the embodiment.

FIG. 3 is a partially enlarged sectional view of a sealing body according to the same embodiment.

FIG. 4 is a perspective view showing a reinforcing plate according to the embodiment.

FIG. 5 is a sectional view showing the structure of a conventional aluminum electrolytic capacitor.

FIG. 6 is a sectional view showing the structure of a conventional aluminum electrolytic capacitor.

FIG. 7 is a plan view showing a conventional external lead wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor element 2 External lead wire (anode side) 3 External lead wire (cathode side) 4 Electrolyte solution 5 Aluminum case 6 Seat plate 7 Sealing body 8 Tetrafluoride polyethylene 9 Rubber 10 Reinforcing plate 11 Insulation coating 12 Internal connection lead wire 12a Capacitor element connection part 13 External lead wire 14 Weld part 15 Filler 16 Space part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Hattori 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A capacitor element in which an anode foil and a cathode foil connected to an external lead wire are wound with a separator interposed therebetween, an aluminum case having an open upper surface in which the capacitor element is housed together with an electrolytic solution, and the external lead wire is inserted. In an aluminum electrolytic capacitor having a sealing body fitted to the upper surface of an aluminum case, at least a portion of the external lead wire that is in contact with the sealing body of the external lead wire connected to the cathode foil is phenol resin, fluororesin, or polypara resin. An aluminum electrolytic capacitor with an alkali-resistant insulating coating made of xylylene, ceramic paint, etc. 2. The aluminum electrolytic capacitor according to claim 1, wherein the portion of the external lead wire where the insulating coating is formed is preliminarily anodized. 3. A butyl rubber, an ethylene / propylene rubber, or a composite of a butyl rubber and an ethylene / propylene rubber containing at least one alkali resistant filler selected from alumina, silica and boron nitride. The aluminum electrolytic capacitor according to claim 1 or 2, wherein a sealing body or a sealing body formed by laminating and bonding polyethylene tetrafluoride thereto is used. 4. The aluminum electrolytic capacitor according to claim 3, wherein an alkali resistant filler is used in which colloidal silica and an alkyl silicate are added and reacted to form a coating film. 5. The aluminum electrolytic capacitor according to claim 1, wherein a disk-shaped reinforcing plate made of glass fiber reinforced thermoplastic is disposed in close contact with the upper surface of the sealing body by inserting an external lead wire. .