JPH0638384B2 - Method for manufacturing aluminum etching foil for electrolytic capacitors - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an aluminum etching foil for an electrolytic capacitor, and more specifically to a heat treatment step thereof.

[Conventional technology]

When the aluminum foil for electrolytic capacitors is etched and then heat-treated, the electrostatic capacity after formation is improved. This heat treatment method includes, for example, a method of heating in a dry atmospheric gas, which is introduced in JP-B-45-32857, and an inert gas (Ar, N) as disclosed in JP-A-53-26960. ₂ etc.) There is a method of heating in an atmosphere.

[Problems to be Solved by the Invention]

However, the heat treatment in dry atmospheric gas has a drawback that the leakage current after chemical formation is significantly increased, although the capacitance is improved. On the other hand, the etching foil heat-treated in an inert gas atmosphere has an improved capacitance, and the leakage current after chemical formation is at a level lower than that of the non-heat-treated foil.

By the way, heat treatment in an inert gas atmosphere is usually
The etching foil is wound into a coil, and it is put in a heating furnace.The surface natural hydrated film of the etching foil causes a dehydration reaction during the heating process, and the water generated is between the layers of the etching foil coil. Especially concentrate on the edges. As a result,
Since the ends of the coil come into contact with a large amount of water, a hydration reaction occurs, and not only the ends have a poor appearance but also an uneven hydrated film is formed on the end surfaces. As a result, the leakage current after chemical formation remarkably increases, so that the end portion is conventionally cut off, and there is a drawback that the yield is poor.

The present invention has been made in view of the above conventional circumstances, and an object thereof is to prevent a hydration reaction at the end of the coil when the etching foil is wound into a coil and heat-treated in an inert gas atmosphere. Another object of the present invention is to provide a method of manufacturing an aluminum etching foil for electrolytic capacitors, which is capable of obtaining uniform characteristics over the entire width direction.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, the aluminum foil for electrolytic capacitors is etched and then wound into a coil, and prior to heat treatment in an inert gas atmosphere, the same aluminum etched into a coil is etched. The foil is preheated in a heating furnace in an inert gas atmosphere at a predetermined temperature to dehydrate the natural hydrated film formed on the surface of the foil, and at the time of the preheating, the inside of the heating furnace is decompressed at least once to 1 atm or less. After that, it is characterized by returning to the inert gas atmosphere again.

The above object can also be achieved by raising the temperature of the inside of the heating furnace to a predetermined preheating temperature in a state where the pressure inside the heating furnace is reduced to 1 atm or less, and then making the inside of the heating furnace an inert gas atmosphere. It

In this case, the preheating temperature is preferably in the range of 200 to 450 ° C.

[Action]

By reducing the pressure to 1 atm or less as described above, the water dehydrated by preheating is discharged to the outside of the coil.

〔Example〕

 Hereinafter, examples of the present invention will be described together with comparative examples.

Example 1 A pre-etched aluminum etching foil was wound into a coil and placed in a heating furnace, which was heated to 200 ° C. in a N ₂ gas atmosphere.
Depressurize to orr, return to N ₂ gas atmosphere again, then 500
The temperature was raised to 0 ° C. and heat treatment was performed for 2 hours.

Example 2 The same aluminum etching foil as in Example 1 was wound into a coil and placed in a heating furnace and heated to 450 ° C. in a N ₂ gas atmosphere. The pressure was reduced, the atmosphere was returned to the N ₂ gas again, the temperature was then raised to 500 ° C., and heat treatment was performed for 2 hours.

Example 3 The same aluminum etching foil as in Example 1 was wound into a coil and placed in a heating furnace and heated to 450 ° C. in an N ₂ gas atmosphere. After returning to a ₂ gas atmosphere, the temperature was raised to 500 ° C. and heat treatment was performed for 2 hours.

"Example 4" Example 1 and Turn placed in a heating furnace up the same aluminum etching foil into a coil, where the furnace was vacuum from the start to 10 torr, and heated to 300 ° C., N ₂
In a gas atmosphere, the temperature was raised to 550 ° C. and heat treatment was performed for 6 hours.

[Comparative Example 1] The same aluminum etching foil as in Example 1 was wound in a coil shape and preheated at 500 ° C.
In N ₂ gas atmosphere for 2 hours.

[Comparative Example 2] The same aluminum etching foil as in Example 1 was wound into a coil and placed in a heating furnace and heated to 480 ° C in an N ₂ gas atmosphere. The pressure was reduced, the atmosphere was returned to the N ₂ gas again, the temperature was then raised to 500 ° C., and heat treatment was performed for 2 hours.

For each of the above-mentioned Examples and Comparative Examples, the capacitance (μF) after formation of 50 V at the coil center and coil ends
/ Cm ² ) and the leakage current (μA / cm ² ) after forming 50 V are shown in the following table.

In Comparative Example 1, since preheating was not performed,
The capacitance at the end of the coil is lower than that at the center of the coil, and the leakage current is significantly increased. Further, when the preheating temperature is increased to 480 ° C. as in Comparative Example 2, the natural hydrated film on the surface of the etching foil is sufficiently dehydrated, but on the other hand, since the treatment temperature is high, a large amount of air oxide film is formed. As a result, the characteristics are the same as those of Comparative Example 1.

On the other hand, in Examples 1 to 4, the natural hydrated film formed on the surface of the etching foil was dehydrated by preheating, and the moisture was removed outside the coil by depressurization. The capacitance and the leakage current at the coil end have almost the same value. In particular, it can be seen from Example 4 that the same effect can be obtained by raising the temperature in the furnace to a predetermined preheating temperature under reduced pressure and then using an inert gas atmosphere.

〔The invention's effect〕

As described above, according to the present invention, the aluminum etching foil is preheated in the coiled state prior to the heat treatment in the inert gas atmosphere by winding the aluminum etching foil in a coil, By appropriately performing the pressure reduction treatment, the hydration reaction of the coil end portion is prevented, and the aluminum etching foil for electrolytic capacitors having uniform characteristics over the entire width direction is manufactured.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuji Kawasaki 2-2-1 Tsujido Shinmachi, Fujisawa-shi, Kanagawa Elner Co., Ltd. No. 1 Elner Co., Ltd. (72) Inventor Mikio Sasaki 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Asahi Glass Co., Ltd.

Claims (3)

[Claims] 1. An aluminum foil for an electrolytic capacitor is etched and then wound in a coil shape, and prior to heat treatment in an inert gas atmosphere, the aluminum etched foil wound in a coil shape is kept at a predetermined temperature. Preheating is performed in a heating furnace in an active gas atmosphere to dehydrate the natural hydrated film formed on the surface, and the heating furnace is depressurized at least once to 1 atm or less at the time of preheating, and then inert again. A method for producing an aluminum etching foil for an electrolytic capacitor, which comprises returning to a gas atmosphere. 2. An aluminum foil for an electrolytic capacitor is etched and then wound into a coil, and prior to heat treatment in an inert gas atmosphere, the coiled aluminum etching foil is placed in a heating furnace. The aluminum for electrolytic capacitors, characterized in that the inside of the heating furnace is heated to a predetermined preheating temperature in a state where the inside of the heating furnace is depressurized to 1 atm or less, and then the inside of the heating furnace is made an inert gas atmosphere. Etching foil manufacturing method. 3. The method for producing an aluminum etching foil for an electrolytic capacitor according to claim 1, wherein the preheating temperature is in the range of 200 to 450 ° C.