JPH06310381A - Electrolytic capacitor and tab terminal thereof - Google Patents

Abstract

PURPOSE:To prevent driving electrolyte from leaking out of an electrolytic capacitor by a method wherein an anodized film is formed, at least, on the round bar of a terminal tab by the use of forming liquid wherein one or more chemical compounds which contain phosphorus and one more inorganic acids or salts or organic acids are mixed together. CONSTITUTION:Water solution of orthophosphoric acid and boric acid is controlled in pH value by ammonia into a forming bath. The aluminum flat 3 and the aluminum round bar 2 of a terminal tab 1 are dipped into the forming bath, a lead-out wire 4 welded to the round bar 2 is made to serve as an anode, a counter electrode is provided in the forming bath, and a voltage is applied between the electrodes to perform a forming treatment. An anodized film is formed on the flat 3 and the round bar 2 of the tab terminal 1. By this setup, a round bar is enhanced in corrosion resistance to driving electrolyte, and driving electrolyte is prevented from leaking out of an electrolytic capacitor.

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 and a tab terminal for the electrolytic capacitor.

[0002]

2. Description of the Related Art In an aluminum electrolytic capacitor, a driving electrolytic solution is impregnated into a capacitor element formed by winding an aluminum anode foil and an aluminum cathode foil with a separator paper, and the capacitor element together with a rubber sealing body is made of an aluminum outer case. It has a structure in which it is hermetically sealed by being incorporated inside and the outer case being sealed.

Tab terminals as lead-out terminals are fixed to each of the anode foil and the cathode foil by caulking or the cold weld method and are drawn out through the through holes of the rubber sealing body.

As shown in FIG. 1, the tab terminal 1 comprises a round bar 2 made of aluminum, a flat part 3 obtained by flattening the round bar 2, and a lead wire 4 welded to the round bar 2. Become. The lead wire 4 is made of CP wire (copper-coated steel wire), and the surface thereof may be plated with solder or tin. A welded portion of the round bar portion 2 and the lead wire 4 is indicated by 5.

The flat portion 3 of the tab terminal 1 is fixed to the anode foil or the cathode foil, and the round bar portion 2 is fitted into the through hole of the rubber sealing body.

In recent years, in order to improve the characteristics of the capacitor, a driving electrolytic solution used for an electrolytic capacitor has been made highly conductive or stable at high temperatures.

For example, a solution obtained by dissolving a quaternary ammonium salt of O-phthalic acid or a quaternary ammonium salt of maleic acid as a solute in a solvent such as γ-butyrolactone or ethylene glycol is used as a driving electrolyte. ing.

[Problems to be Solved by the Invention]

Such a driving electrolyte solution containing a quaternary ammonium salt of a carboxylic acid as a solute has a low viscosity and is active, and it can be removed from a minute gap between the rubber sealing body and the round bar portion of the tab terminal. Was likely to occur.

Particularly, in the vicinity of the tab terminal fixed to the cathode foil, the pH of the driving electrolytic solution becomes strong alkaline due to the application of the electric field. Due to this phenomenon, the round bar portion of the tab terminal was corroded, and the driving electrolytic solution was likely to leak to the outside from between the rubber sealing body and the tab terminal.

Therefore, as the tab terminal on the cathode side, a tab terminal on which an anodic oxide film is formed by chemical conversion treatment with an adipic acid type aqueous solution or a boric acid type aqueous solution may be used, but in order to improve the corrosion resistance of the tab terminal. Was still insufficient.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present inventors have conducted various studies and experiments, and as a result, among the compounds containing phosphorus in at least the round bar portion of the tab terminal fixed to the cathode foil side. When an anodic oxide film is formed by a chemical conversion solution in which one or more of them is mixed with an inorganic acid or a salt thereof or one or more of an organic acid or a salt thereof, especially for a driving electrolyte containing a quaternary ammonium salt as a solute. It has been found that excellent corrosion resistance can be imparted.

In the present invention, the anodic oxide film may be formed not only on the round bar portion of the tab terminal but also on the flat portion.

In the formation for forming the anodic oxide film, the flat portion and the round bar portion of the tab terminal are immersed in a formation bath,
It is preferable that the lead wire serves as an anode, a counter electrode is arranged in the chemical conversion bath, and a direct current voltage is applied to the treatment.

As the chemical conversion liquid for the chemical conversion treatment, an aqueous solution obtained by mixing one or more of phosphorus-containing compounds with one or more of an inorganic acid or a salt thereof or an organic acid or a salt thereof is used. preferable. The chemical conversion conditions such as the chemical conversion liquid temperature, applied voltage, current density, and voltage application time can be appropriately selected.

Examples of compounds containing phosphorus include orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid and salts thereof. . As the inorganic acid, boric acid, sulfuric acid, nitric acid,
Examples thereof include silicic acid, tungstic acid or salts thereof.

Examples of the organic acid include monocarboxylic acid, dicarboxylic acid, oxyacid and salts thereof. As the monocarboxylic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, acrylic acid, undecylenic acid, benzoic acid and the like are preferable.

The dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid, maleic acid,
Fumaric acid, phthalic acid, isophthalic acid, terephthalic acid and the like are preferable.

The oxyacids include glycolic acid, lactic acid, hydroacrylic acid, α-oxybutyric acid, glyceric acid, tartronic acid, malic acid, tartaric acid, citric acid, salicylic acid,
Preferred are oxybenzoic acid, gallic acid, mandelic acid, tropic acid and the like.

In the present invention, in addition to the above-mentioned chemical conversion treatment, the tab terminal is obtained by subjecting an aluminum round bar wire to chemical conversion treatment using the above-mentioned chemical conversion liquid to form an anodic oxide film on the surface thereof, and then a part thereof. It is also possible to manufacture by forming a flat portion by pressing and welding a leader wire to the round bar portion. Further, the chemical conversion treatment described above may be performed again on this tab terminal.

The tab terminal according to the present invention can be used not only on the cathode side but also on the anode side. In the present invention, on the surface of the anodic oxide film of the round bar portion of the tab terminal, for the purpose of further improving the corrosion resistance of the anodic oxide film and the adhesive strength with the rubber sealing body, silane-based, aluminum-based, titanium A system coupling agent may be applied, or another resin film may be formed.

[0021]

[Example] <Example 1>

The tab terminal shown in FIG. 1, the diameter of the round bar is 2.0.
mm, the same length 6 mm, the flat portion width 2.5 mm, the same thickness 0.35 mm, and the same length 15 mm were prepared.

On the other hand, an aqueous solution containing 0.01% by weight of orthophosphoric acid and 8% by weight of boric acid was adjusted to pH 7 with ammonia and the liquid temperature was maintained at 50 ° C. to prepare a chemical conversion bath. The flat portion and the round bar portion of the tab terminal were immersed in this chemical conversion bath, the lead wire was used as an anode, a counter electrode was placed in the chemical conversion bath, and a voltage of 150 V was applied for 2 hours for chemical conversion treatment. An anodized film was formed on the flat portion and round bar portion of the tab terminal. The chemical conversion current value measured 2 hours after the start of chemical conversion was 10 μA.

Next, after washing the tab terminals, a system liquid (85 ° C.) consisting of 10% by weight of tetramethylammonium hydroxide, 40% by weight of γ-butyrolactone and 50% by weight of water.
The flat portion and the round bar portion of the tab terminal were immersed therein for 200 hours, and the weight change of the tab terminal was measured. The amount of film dissolution of the tab terminal was 0.15 mg / cm ² . <Example 2>

In place of the chemical conversion bath of Example 1, orthophosphoric acid 0.
An aqueous solution containing 1% by weight and 1% by weight of citric acid was adjusted to pH 7 with ammonia and the liquid temperature was maintained at 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 15 μA. The amount of film dissolution of the tab terminal was 0.10 mg / cm ² . <Example 3>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 0.5% by weight of ammonium phosphate and 5% by weight of ammonium adipate was maintained at a liquid temperature of 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment is performed in the same manner as in Example 1, and
The weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 15 μA. The amount of film dissolution of the tab terminal was 0.23 mg / cm ² . <Example 4>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 2% by weight of ammonium phosphate and 3% by weight of ammonium tartrate was maintained at a liquid temperature of 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 20 μA. The amount of film dissolution of tab terminals is 0.20
It was mg / cm ² . <Example 5>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 0.1% by weight of sodium metaphosphate and 0.5% by weight of sodium borate was maintained at a liquid temperature of 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment is performed in the same manner as in Example 1, and
The weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 10 μA. The amount of film dissolution of the tab terminal was 0.30 mg / cm ² . <Example 6>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 0.05% by weight of ammonium pyrophosphate and 0.2% by weight of ammonium silicate was maintained at a liquid temperature of 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 10 μA. The amount of film dissolution of the tab terminal was 0.35 mg / cm ² . <Example 7>

Instead of the chemical conversion bath of Example 1, triphosphoric acid 0.
An aqueous solution containing 1% by weight and 1.5% by weight of acrylic acid was adjusted to pH 7 with ammonia and the liquid temperature was maintained at 50 ° C. to prepare a chemical conversion bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 12 μA. The amount of film dissolution of the tab terminal was 0.18 mg / cm ² . <Example 8>

Instead of the chemical conversion bath of Example 1, tetraphosphoric acid 0.
An aqueous solution containing 2% by weight and 1% by weight of valeric acid was adjusted to pH 7 with sodium hydroxide, and the liquid temperature was maintained at 50 ° C.
It was a chemical bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. Formation start 2
The formation current value after 20 hours was 20 μA. The amount of film dissolution of the tab terminal was 0.30 mg / cm ² . <Example 9>

Instead of the chemical conversion bath of Example 1, phosphorous acid 0.
An aqueous solution containing 02% by weight and 1% by weight of caproic acid was adjusted to pH 7 with ammonia, and the liquid temperature was maintained at 50 ° C.
It was a chemical bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. Formation start 2
The formation current value after 12 hours was 12 μA. The amount of film dissolution of the tab terminal was 0.23 mg / cm ² . <Example 10>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 0.2% by weight of hypophosphorous acid and 2% by weight of adipic acid was adjusted to pH 7 with ammonia and the liquid temperature was maintained at 50 ° C. And Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 10 μA. The amount of film dissolution of the tab terminal was 0.30 mg / cm ² . <Example 11>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 1% by weight of sodium polyphosphate and 1% by weight of sodium azelate was maintained at a liquid temperature of 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment is performed in the same manner as in Example 1, and
The weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 10 μA. The amount of film dissolution of the tab terminal was 0.18 mg / cm ² . <Example 12>

Instead of the chemical conversion bath of Example 1, orthophosphoric acid 0.
An aqueous solution consisting of 1% by weight, 0.2% by weight of hypophosphorous acid and 2% by weight of malonic acid was adjusted to pH 7 with ammonia and the liquid temperature was maintained at 50 ° C. to obtain a chemical bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 15 μA. The amount of film dissolution of the tab terminal is 0.15mg / cm ²
Met. <Example 13>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 0.05% by weight of ammonium phosphite, 1% by weight of ammonium adipate and 0.5% by weight of ammonium borate was maintained at a liquid temperature of 50 ° C. It was a bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation is 10μ
It was A. The amount of film dissolution of the tab terminal is 0.30 mg / c
It was m ² . <Comparative Example 1>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 0.5% by weight of ammonium phosphate was maintained at a liquid temperature of 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 230 μA. The amount of film dissolution of the tab terminal was 0.25 mg / cm ² . <Comparative example 2>

Instead of the chemical conversion bath of Example 1, an aqueous solution of 0.1% by weight of hypophosphorous acid was adjusted to pH 7 with ammonia,
The liquid temperature was maintained at 50 ° C. to form a chemical bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation is 310μ
It was A. The amount of film dissolution of the tab terminal is 0.35 mg / c
It was m ² . <Conventional example 1>

Instead of the chemical conversion bath of Example 1, an aqueous solution containing 5% by weight of ammonium adipate was maintained at a liquid temperature of 50 ° C. to obtain a chemical conversion bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 20 μA. The amount of film dissolution of the tab terminal was 2.80 mg / cm ² . <Conventional example 2>

8% by weight of boric acid was used instead of the chemical conversion bath of Example 1.
The aqueous solution of was maintained at a liquid temperature of 50 ° C. and used as a chemical bath. Other than that, the chemical conversion treatment was performed in the same manner as in Example 1, and the weight change of the tab terminal was measured. The formation current value 2 hours after the start of formation was 10 μA. The amount of film dissolution of the tab terminal is 2.95m
It was g / cm ² .

The amount of film dissolution of the tab terminals of Examples 1 to 13 is extremely small at 0.15 to 0.35 mg / cm ² , whereas the amount of film dissolution of Conventional Examples 1 and 2 is 2.80 to 2. 9
It is as large as 5 mg / cm ^2, and it can be seen that it is deteriorated.
In addition, when comparing Comparative Examples 1 and 2 with Examples 1 to 13,
It is understood that the formation current value is large and the formation electricity cost is large, which is not preferable.

Next, the tab terminals subjected to the chemical conversion treatment in Examples 1 to 13, Comparative Examples 1 and 2 and Conventional Examples 1 and 2 were fixed to the anode foil and the cathode foil, respectively, and the anode foil, the cathode foil and the separator paper were interposed. To make a capacitor element.

Γ-butyrolactone 75 was used for the capacitor element.
And a driving electrolyte solution containing 25% by weight of O-tetraethylammonium phthalate was impregnated.

A capacitor element was assembled in an aluminum outer case together with a butyl rubber sealing body, and the diameter was 12.5 m.
m, length 25 mm, rated voltage 25 V, electrostatic capacity 1000
20,000 μF electrolytic capacitors were prototyped.

A rated voltage was applied to these electrolytic capacitors for 2000 hours in an atmosphere of a temperature of 60 ° C. and a humidity of 95%. Then, the leakage state of the electrolytic solution between the tab terminal and the through hole of the rubber sealing body was visually inspected.

As a result of the inspection, there was no liquid leakage in the electrolytic capacitors using the tab terminals of Examples 1 to 13 and Comparative Examples 1 and 2. However, eight electrolytic capacitors were leaking in the electrolytic capacitor using the tab terminal of Conventional Example 1. Further, in the electrolytic capacitor using the tab terminal of Conventional Example 2, 10 leaked.

【The invention's effect】

In the present invention, the round bar portion of the tab terminal is
One or more compounds containing phosphorus and one or more of inorganic acids or salts thereof or organic acids or salts thereof are mixed to form an anodized film which has been subjected to chemical conversion treatment. Corrosion resistance to the driving electrolyte is improved, and leakage of the driving electrolyte inside can be prevented.

Therefore, it is possible to provide a highly reliable electrolytic capacitor.

[Brief description of drawings]

FIG. 1 is a schematic view showing a tab terminal.

[Explanation of sign]

 1 tab terminal 2 round bar part 3 flat part 4 lead wire 5 welded part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyuki Adachi 2-2-1 Tsujido Shinmachi, Fujisawa City, Kanagawa Elna Co., Ltd. (72) Manabu Kazuhara 2-2-1 Tsujido Shinmachi, Fujisawa City, Kanagawa Prefecture No. Erna Co., Ltd.

Claims (2)

[Claims] 1. A driving electrolytic solution containing a quaternary ammonium salt as a solute in a capacitor element formed by winding an aluminum anode foil having tab terminals fixed thereto and an aluminum cathode foil having tab terminals fixed thereto with a separator paper interposed therebetween. In an electrolytic capacitor in which the capacitor element is impregnated and incorporated in an outer case together with a rubber sealing body, at least the tab terminal fixed to the aluminum cathode foil is made of one or more compounds containing phosphorus, an inorganic acid or An electrolytic capacitor having an anodized film which has been subjected to a chemical conversion treatment with a chemical conversion liquid in which a salt thereof or an organic acid or one or more of the salts is mixed. 2. A tab terminal for an electrolytic capacitor comprising a round bar of aluminum, a flat flat section of the same aluminum, and a lead wire welded to the round bar, wherein at least the round bar has phosphorus. Characterized by forming an anodized film which has been subjected to a chemical conversion treatment with a chemical conversion liquid in which one or more of the contained compounds and one or more of an inorganic acid or a salt thereof or an organic acid or a salt thereof are mixed. Tab terminal for electrolytic capacitors.