JPH06176975A - Electrolytic capacitor and its tab terminal - Google Patents

Abstract

PURPOSE:To enhance the corrosion-resistant property of a tab terminal by a method wherein an anode oxide film by a formation liquid containing phosphorus is formed at least on a round rod part at the tab terminal which is fixed and bonded to the side of an anode foil. CONSTITUTION:The pH of an aqueous solution containing 0.15wt.% of orthophosphoric acid is adjusted, and a formation bath is formed. A flat part 3 and-a round rod part 2 at a tab terminal 1 are immersed in the formation bath, an outgoing wire 4 is used as an anode, a counter electrode is arranged the formation bath, and a formation treatment is executed. Then, tab terminals to which the formation treatment has been executed are fixed and bonded respectively to an anode foil and a cathode foil, and a capacitor element is formed by interposing the anode foil, the cathode foil and a sheet of separator paper. Thereby, the corrosion-resistant property to a driving electrolytic solution of the round rod part is enhanced, and it is possible to prevent that the driving electrolytic solution at the inside is leaked.

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.

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 inventors of the present invention have conducted various studies and experiments, and as a result, have shown that an anode made of a chemical conversion liquid containing phosphorus in at least a round bar of a tab terminal fixed to the cathode foil side. It has been found that when an oxide film is formed, excellent corrosion resistance can be imparted particularly to a driving electrolyte solution containing a quaternary ammonium salt as a solute.

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, it is preferable to use an aqueous solution containing phosphorus. The chemical conversion liquid containing phosphorus can be easily obtained by dissolving orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid or a salt thereof in water.

The chemical conversion conditions such as the chemical conversion liquid temperature, applied voltage, current density and voltage application time can be appropriately selected.

In the present invention, in addition to the above-mentioned chemical conversion treatment, the tab terminal is formed by subjecting an aluminum round rod 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.

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.

[0018]

【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 of 0.15% by weight of orthophosphoric acid was adjusted to pH 7 with ammonia and the liquid temperature was maintained at 50 ° C.
It was a chemical bath. The flat part and the round bar of the tab terminal are immersed in this formation bath, the lead wire serves as an anode, the counter electrode is arranged in the formation bath, and the current density of 10 mA / cm ² and the voltage of 150 V are applied for 2 hours to form the formation treatment. did. An anodized film was formed on the flat portion and round bar portion of the tab terminal.

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 0.20 mg / cm ² . <Example 2>

Instead of the chemical conversion bath of Example 1, an aqueous solution of 0.15% by weight of hypophosphorous 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 amount of film dissolution of the tab terminal is 0.25 mg
Was / cm ² . <Example 3>

Instead of the formation bath of Example 1, an aqueous solution containing 5% by weight of adipic acid ammonium salt and 0.15% by weight of phosphoric acid was adjusted to pH 7 with ammonia and the temperature of the solution was 50 ° C.
It was maintained 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 amount of film dissolution of the tab terminal was 0.85 mg / cm ² . <Example 4>

8% by weight of boric acid was used instead of the chemical conversion bath of Example 1.
An aqueous solution containing 0.15% by weight of phosphoric acid was adjusted to pH 7 with ammonia, and the liquid temperature was maintained at 50 ° C. to form a chemical 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 amount of film dissolution of the tab terminal was 0.90 mg / cm ² . <Comparative Example 1>

Instead of the chemical conversion bath of Example 1, an aqueous solution of ammonium adipate of 5% by weight 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 amount of film dissolution of the tab terminal was 2.80 mg / cm ² . <Comparative example 2>

8% by weight of boric acid was used instead of the chemical conversion bath of Example 1.
The solution temperature of an aqueous solution containing 0.05% by weight of ammonium borate and 50% was maintained 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 amount of film dissolution of the tab terminal was 2.85 mg / cm ² .

The tab terminals of Examples 1 to 5 are comparative examples 1 and 2.
It can be seen that the amount of film dissolution of the tab terminal is remarkably small. <Example 5>

The tab terminals subjected to the chemical conversion treatment in Example 1 were respectively fixed to the anode foil and the cathode foil, and the anode foil, the cathode foil and the separator paper were interposed to form 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
Prototypes of 20000 μF electrolytic capacitors were manufactured.

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%.

When the electrolyte leakage state between the tab terminal and the through hole of the rubber sealing body was visually inspected, none was found. <Comparative Example 3>

20000 electrolytic capacitors were manufactured in the same manner as in Example 5 except that the tab terminals fixed to the anode foil and the cathode foil were the ones subjected to the chemical conversion treatment in Comparative Example 1.

When the same test as in Example 5 was conducted, eight electrolytic capacitors were found to have electrolyte leakage.

【The invention's effect】

In the present invention, the round bar portion of the tab terminal is
Since the anodic oxide film formed by chemical conversion treatment containing phosphorus is formed, the corrosion resistance of the round bar against the driving electrolyte is improved and the leakage of the internal driving electrolyte is prevented. be able to.

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 Leader wire

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 assembled with a rubber sealing member in an outer case, at least the tab terminal fixed to the aluminum cathode foil is anodized film formed by chemical conversion treatment containing phosphorus. An electrolytic capacitor characterized by having. 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. A tab terminal for an electrolytic capacitor, characterized in that an anodized film which has been subjected to a chemical conversion treatment with a chemical conversion liquid contained therein is formed.