JPH0638385B2 - Method for manufacturing electrode foil for aluminum electrolytic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electrode foil for an aluminum electrolytic capacitor, especially an anode foil.

[Prior Art] As an electrode foil for an aluminum electrolytic capacitor, an etched aluminum foil having a chemical conversion film formed thereon is used. Generally, since the driving electrolyte contains about 1 to 20% of water, in order for the electrolytic capacitor to stably operate at high temperature, the chemical conversion film on the surface of the anode foil has water resistance and It must be chemically stable against the water content of the liquid. Then, in order to impart water resistance to the chemical conversion film, it is known to immerse the foil in an aqueous solution of phosphoric acid or its salt in the final step of chemical conversion to attach phosphate ions to the foil surface.

[Problems to be Solved by the Invention] Using such a chemical conversion foil having phosphate ions attached thereto, the other cathode foil is wound through a separator to manufacture a capacitor element, which is impregnated with a driving electrolytic solution, Even if the electrolytic capacitor enclosed in the case was manufactured, the tangent of the loss angle was large in the initial characteristics and the leakage current was large in the high temperature no-load test, so it could not be improved yet.

[Means for Solving the Problems] The present invention is intended to reduce such leakage current by first immersing the foil in an aqueous solution of hypophosphorous acid or a salt thereof to form hypophosphite ions. Is a chemical bond.

The concentration of hypophosphorous acid or its salt in an aqueous solution is 0.05.
The liquid temperature is preferably 5 to 5 wt% and the liquid temperature is preferably 20 to 50 ° C.
Further, the immersion treatment time of the foil is preferably 0.5 to 7 minutes.

Next, according to the present invention, in order to reduce the tangent of the loss angle, a foil chemically bound with hypophosphite is used in the range of 180 to 500.
The firing is performed in an atmosphere of ° C. 180
If it is less than ° C, the tangent of the loss angle cannot be reduced. The firing atmosphere may be air, and the firing time is preferably 30 seconds to 10 minutes.

[Examples] Hereinafter, a method for producing an electrode foil according to the present invention and an electrolytic capacitor using the same will be described.

Example 1 (A) An aluminum etching foil having a purity of 99.99% and a thickness of 100 μm was used. In this case, the etching magnification was about 20 times that of the unetched flat foil.

(B) This aluminum etching foil was heat treated in pure water at a liquid temperature of 98 ° C. or higher for 9 minutes.

(C) An aluminum etching foil is immersed in an aqueous solution of boric acid 80 g / and ammonium borate 0.05 g / in a liquid temperature of 85 ° C., and a current density of 10 mA / cm ² is applied to increase the formation voltage to 380 V. Application was carried out for 40 minutes for chemical conversion.

(D) Liquid temperature of the aluminum etching foil after chemical conversion is 70
C., soak in ammonia water adjusted to pH 7-9 for 3 minutes,
Depolarization treatment was performed.

(E) Heat treatment was performed for 2 minutes in a heating atmosphere of 500 ° C.

(F) Immerse again in an aqueous solution under the same conditions as in (C) above,
A current having a current density of 10 mA / cm ² was flown to raise the formation voltage to 380 V, and the same voltage was applied for 13 minutes for re-formation.

(G) The same heat treatment as in (E) above was performed.

(H) The chemical conversion treatment of (F) above is repeated, but in this case, the application time of the chemical conversion voltage was 3 minutes.

(I) Immersion in an aqueous solution of 0.3 wt% of ammonium hypophosphite at a liquid temperature of 35 ° C. for 4 minutes.

(J) This foil was fired in the air at 200 ° C. for 1 minute and 30 seconds to obtain a formed foil.

(K) This formed foil was used as an anode foil, and the other cathode foil was wound around a separator to form a capacitor element. Then, this capacitor element is impregnated with an ethylene glycol-based electrolytic solution and sealed in a case, and the rated voltage is 250 V · 30.
A μF electrolytic capacitor was manufactured.

<Example 2> In the step (J) of Example 1, the firing temperature of 200 ° C was 30%.
An electrolytic capacitor of the same rating was manufactured in the same manner as in Example 1 except that the temperature was changed to 0 ° C.

<Example 3> In the step (J) of Example 1, the firing temperature of 200 ° C. was set to 40.
An electrolytic capacitor of the same rating was manufactured in the same manner as in Example 1 except that the temperature was changed to 0 ° C.

<Example 4> In the step (J) of Example 1, a firing temperature of 200 ° C. was set to 50.
An electrolytic capacitor of the same rating was manufactured in the same manner as in Example 1 except that the temperature was changed to 0 ° C.

Example 5 An electrolytic capacitor of the same rating was manufactured in the same manner as in Example 1 except that sodium hypophosphite was used instead of ammonium hypophosphite in the step (I) of Example 1.

<Example 6> An electrolytic capacitor having the same rating was produced in the same manner as in Example 1 except that calcium hypophosphite was used instead of ammonium hypophosphite in the step (I) of Example 1.

<Comparative Example 1> Ammonium hypophosphite in the step (I) of Example 1
An electrolytic capacitor of the same rating was produced in the same manner as in Example 1 except that an aqueous solution of 85 wt% ammonium phosphate 25 m / m2 was used in place of the 0.3 wt% aqueous solution.

<Comparative Example 2> The firing temperature of 200 ° C. in the step (J) of Example 1 was set to 15
An electrolytic capacitor of the same rating was manufactured in the same manner as in Example 1 except that the temperature was changed to 0 ° C.

Next, the characteristic results of the no-load test when the electrolytic capacitors of Examples 1 to 6 and Comparative Examples 1 and 2 of the present invention thus manufactured were left in an atmosphere of 105 ° C. for 500 hours, together with initial characteristics. It is shown in Table 1.

[Effects] According to the chemical conversion foil of the present invention, as can be seen from Table 1, it is possible to provide an electrolytic capacitor capable of reducing the tangent of the loss angle of the initial characteristics and the leakage current after the high temperature no-load test. .

Claims (1)

[Claims] 1. An aluminum electrolytic capacitor, which comprises forming an etched aluminum foil, immersing it in an aqueous solution of hypophosphorous acid or a salt thereof, and then firing it in an atmosphere of 180 to 500 ° C. Method for manufacturing electrode foil.