JP2009105190A - Manufacturing apparatus of electrode foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing apparatus of electrode foil for electrolytic capacitors that suppresses excessive etching and has high electrostatic capacity per unit area. <P>SOLUTION: The manufacturing apparatus of electrode foil for electrolytic capacitors allows a strip of aluminum foil to run between electrodes in an etching tank filled with an etching liquid and etches the aluminum foil by applying voltage between the electrodes. In the manufacturing apparatus of electrode foil for electrolytic capacitors, a circulation pipe is arranged for circulating the etching liquid to the plurality of etching tanks and a minute bubble generator for mixing minute bubbles into the etching liquid is interposed at one portion of the circulation pipe. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus for producing an electrode foil for an electrolytic capacitor used when producing an electrode foil for an electrolytic capacitor used in various electronic devices.

  Electrolytic capacitors are required to be smaller in size with the recent miniaturization of electronic devices. In order to reduce the size of the electrolytic capacitor, it is necessary to increase the capacitance per unit area of the aluminum foil used for this, and with this configuration, it is possible to save resources and reduce raw material costs. It will be possible.

  In order to increase the capacitance per unit area of the aluminum foil, the surface of the aluminum foil is roughened by immersing the aluminum foil in an acidic aqueous solution and chemically or electrically etching it. A method of expanding the surface area is used.

  When such an etching process is performed, the surface area of the aluminum foil generally increases and the capacitance increases, but the mechanical strength of the aluminum foil itself decreases as the etching proceeds. Therefore, it is necessary to increase the surface area while maintaining the foil strength by controlling the location and shape of the etching pits to be formed by adjusting the voltage to be applied.

  In particular, in the production of a low-voltage electrolytic capacitor electrode foil, a method of performing an etching process by applying an AC voltage between the electrodes is generally performed in order to form fine etching pits.

  FIG. 3 shows a cross section of an etching tank for etching a conventional low-voltage electrolytic capacitor electrode foil. The etching tank 32 is filled with an etching solution 33 of an acidic aqueous solution mainly composed of hydrochloric acid, and a pair of electrode plates 34 a and 34 b for etching the aluminum foil 31 are disposed. A voltage is applied from the AC power source 37 to the pair of electrode plates 34a and 34b.

  Further, a circulation hose and a pump 38 for circulating the etching solution 33 around the outer periphery of the etching tank 32 are arranged.

  The aluminum foil 31 advances in the direction of the arrow A, is conveyed into the etching tank 32 via the inlet roller 35a, and passes through between the pair of electrode plates 34a and 34b via the inner roller 36 so that the etching process is performed. Applied. The etched aluminum foil 31 is once washed in the washing tank 39 via the outlet roller 35b, and proceeds to the next etching tank (not shown).

  When this etching process is performed, a large number of fine cubic pits connected in a cluster form from the surface toward the inside of the aluminum foil 31 are formed. Has a sponge-like porous structure. At this time, the mechanical strength is ensured by leaving the core in the center of the aluminum foil 31. Ideally, the pits should have a high density and uniformity, and a small deviation in pit diameter.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2000-30979 A

  In the conventional etching method, since aluminum ions are concentrated at the beginning due to the formation of complex ions of aluminum ions at the pit tip, the aluminum is easily dissolved, so that the amount of etching can be reduced. As the pits are formed in the depth direction, the surface area increases.

  However, as the etching progresses, the concentration of aluminum ions inside the pits increases in a rate-dependent manner toward diffusion from the inside of the foil toward the surface, and the reaction resistance increases conversely. And the inside of the pit is blocked, so that it becomes difficult to form the pit gradually in the depth direction.

  Therefore, as the surface area of the aluminum foil is increased, the vicinity of the surface is gradually excessively etched, the porous structure already formed is destroyed, and the capacity per etching loss is reduced.

  In order to solve this problem, methods such as adjusting the voltage to be applied as the etching progresses have been taken, but the hydrogen ion concentration of the etching solution has not been sufficiently controlled, and it has become an ideal state. The setting was not made.

  Further, as one method for solving such a problem, a method for suppressing excessive etching by adding an additive to the etching solution 33 has been proposed. As an additive, an acid other than hydrochloric acid previously contained in the etching solution 33, for example, sulfuric acid, is used, and a film is formed on the surface of the aluminum foil 31 by anions generated by dissociation of the acid added as the additive. Thus, it is difficult to etch and suppresses excessive etching.

  However, since the etching solution 33 contains hydrochloric acid in advance, when the hydrogen ion concentration of the etching solution 33 is high, the acid added as an additive is not easily dissociated, and the effect is hardly exhibited. There was a problem. In addition, in an acidic aqueous solution with a low hydrogen ion concentration, the effect of the additive tends to appear, but it is difficult to increase the etching magnification, and there is a problem that the capacitance cannot be increased by increasing the surface area. .

  As described above, in the conventional etching method of the aluminum foil 31, the etching state is adjusted by adjusting the applied voltage or the like to adjust the formation position of the pits or adding an additive to the etching solution 33. However, no setting has been made in consideration of the relationship between the hydrogen ion concentration and the progress of etching in the depth direction, and the relationship between the hydrogen ion concentration and the passivation property of the additive. Therefore, excessive etching near the surface of the aluminum foil 31 is suppressed to prevent the porous structure from being destroyed, and an aluminum electrode foil for an electrolytic capacitor having a high capacitance per unit area cannot be manufactured.

  This invention solves the said problem and provides the manufacturing apparatus of the electrode foil for electrolytic capacitors which can obtain the electrode foil for electrolytic capacitors with the high electrostatic capacitance per unit area.

  To achieve the above object, the present invention provides an electrode foil for an electrolytic capacitor in which a strip-shaped aluminum foil is run between electrodes in an etching tank filled with an etching solution, and the aluminum foil is etched by applying a voltage between the electrodes. In the manufacturing apparatus, an electrolytic capacitor electrode in which a circulation pipe for circulating an etching solution is arranged in the plurality of etching tanks, and a fine foam generation device for mixing fine bubbles in the etching solution is interposed in a part of the circulation pipe A foil manufacturing apparatus is provided.

  The fine bubble generator includes a pump that circulates an etching solution and a supply port that supplies gas, and generates fine bubbles by a swirling flow. The fine bubbles are bubbles of 50 μm or less.

  According to the present invention, an infinite number of fine bubbles can be interposed in the etching solution by disposing a fine bubble generating device that mixes fine bubbles in the etching solution of the etching tank, and the fine bubbles have a diameter of 50 μm or less. Since the microbubbles diffuse the aluminum ions and aluminum complex generated when the aluminum foil is etched into the etching solution, the increase of the aluminum ion concentration in the pit can be suppressed, and the etching is performed. Etching pits can be formed without hindering the progress of the etching. As a result, excessive etching in the vicinity of the surface of the aluminum foil can be suppressed to prevent the porous structure from being destroyed, and an electrolytic capacitor electrode foil having a high capacitance per unit area can be manufactured.

  If the diameter of the fine bubbles exceeds 50 μm, it is difficult to suppress an increase in the aluminum ion concentration in the pit.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an apparatus for manufacturing an electrode foil for an electrolytic capacitor according to an embodiment of the present invention. In FIG. 1, an etching bath 12 is filled with an acidic aqueous solution containing hydrochloric acid as a main component and at least one or more of sulfuric acid, oxalic acid, phosphoric acid or the like as an additive. In addition, a circulation hose 19 that circulates the etching solution 13 around the outer periphery of the etching tank 12, and a fine bubble generator 18 that takes in air from the compressor 20 into the etching solution 13 in the circulation hose 19 to generate fine bubbles. The etching solution 13 containing fine bubbles of 50 μm or less generated there is sent into the etching tank 12. For this reason, the etching solution 13 in the etching tank 12 includes a large number of fine bubbles.

  In addition, since the etching solution 13 is circulated through the fine bubble generator 18 by the circulation hose 19, a certain amount of fine bubbles interposed in the etching solution 13 in the etching tank 12 can be secured constantly.

  The fine bubble generating device 18 is a device that uses a centrifugal force generated by a swirling flow to make the swirling central portion a negative pressure to self-suck air, a pressurized liquid and gas introducing portion, and a cylindrical bubble generating space. And a device using ultrasonic waves can be used.

  Among these, the device based on the method of self-priming air by using the centrifugal force generated by the swirling flow to make the swirling center negative pressure has a small bubble diameter of 10 to 40 μm, high oxygen dissolution efficiency, and the device itself is compact. , Gas does not coalesce or absorb, stays in a single gas for a long time, has a relatively long life, and has a very slow ascent rate, so it has excellent dispersibility and diffusibility in liquid It has the characteristics.

  Also, the aluminum foil 11 is a belt-like roll, and the aluminum foil 11 is conveyed between a pair of electrodes 14a arranged in the etching tank 12 via a traveling roller 15a, and further the rollers in the tank. 16 is passed between the pair of electrodes 14b through 16 and washed once in the washing tank 21 through the traveling roller 15b. A plurality of etching tanks 12 and washing tanks 21 are provided to perform etching treatment, and finally, dechlorination treatment is performed and dried to obtain the etched aluminum foil 11.

  The present invention is not limited to the number of etching tanks 12, and it is preferable to use 3 to 6 etching tanks 12 in order to obtain an electrode foil for an electrolytic capacitor having a high capacitance per unit area.

  Here, when the aluminum foil 11 is etched between the pair of electrodes 14 a and 14 b disposed in the etching tank 12, the aluminum foil 11 is subjected to aluminum by a voltage applied from the AC power supply 17 to the pair of electrodes 14 a and 14 b. The foil 11 is etched.

  This etching process forms a large number of fine cubic pits connected in a cluster from the surface of the aluminum foil 11 toward the inside thereof. At that time, by performing the etching process with the etching solution 13 in which fine bubbles are interposed, aluminum ions and aluminum complexes generated in the pits are diffused into the etching solution 13 by the action of the fine bubbles, so that the aluminum ions in the pits. An increase in concentration can be suppressed, and a large number of etching pits can be formed without hindering the progress of etching.

  And it etches with the some etching tank 12, and finally becomes a sponge-like porous structure as a whole. Moreover, mechanical strength can be ensured by leaving a core in the center of the aluminum foil 11.

  A specific example of this embodiment will be described below.

(Example 1)
The electrode foil manufacturing apparatus shown in FIG. 1 was used as an etching tank, and the etching tank was made into five tanks. As the aluminum foil, a high-purity foil having a width of 500 mm and a thickness of 100 μm and a purity of 99.9% or more was used. Further, as the etching solution, an acidic aqueous solution having a chlorine ion concentration of 2.75N and sulfuric acid so as to have a sulfuric acid concentration of 0.1% as an additive was used.

  Then, the etching solution was filled in the final etching bath, and the etching solution was flowed into the previous etching bath to fill the respective etching baths.

  In addition, an etching solution in which innumerable fine bubbles generated from the fine bubble generator are inserted is inserted from the bottom of the etching tank, and the etching liquid is circulated through the circulation hose from the top of the etching tank.

The etching treatment of the aluminum foil was performed by adjusting the traveling speed of the aluminum foil and the AC power supply conditions so that the etching loss per unit area of the aluminum foil was 10 mg / cm ² (these conditions are the size of the etching tank). Depending on the size of the pair of electrodes. Thereafter, dechlorination treatment was performed, and an aluminum foil subjected to etching treatment was produced.

(Example 2)
In Example 1, the fine bubble generated from the fine bubble generator was etched between the pair of electrodes using a bubble induction hose 22 as shown in FIG. Except for the above, an etched aluminum foil was produced in the same manner as in Example 1.

(Comparative Example 1)
The electrode foil manufacturing apparatus shown in FIG. 3 was used as an etching tank, and the number of etching tanks was five. Further, the aluminum foil and the etching solution were the same as those in Example 1, and an aluminum foil etched in the same manner as in Example 1 was obtained under the other conditions.

  The etched aluminum foils of Examples 1 and 2 and Comparative Example 1 were formed to complete an electrode foil with a withstand voltage of 22V.

  The capacitance and mechanical strength of the obtained electrode foil for electrolytic capacitors are shown in (Table 1). The mechanical strength was subjected to a bending test (one reciprocation was performed once under the conditions of φ1.0 mm, a load of 250 g and a bending angle of 90 degrees).

  As is clear from (Table 1), an etching solution containing innumerable fine bubbles generated from the fine bubble generator is inserted from the bottom of the etching tank, and the etching liquid is circulated through the circulation hose from the top of the etching tank. By carrying out the etching process, the electrostatic capacity per unit area of the aluminum foil can be increased.

  In the first embodiment, the etchant containing the fine bubbles generated by the fine bubble generator is inserted from the bottom of the etching tank. However, the same effect can be obtained by inserting the etching liquid into the side surface of the etching tank from the bottom. Needless to say.

  In addition, although the fine bubble generating device is provided in each etching tank, the etching process in the first etching tank has a relatively short pit length, so that even if the fine bubble generating device is not provided, the electrostatic capacity higher than that of Comparative Example 1 is provided. Capacity can be obtained. Moreover, a higher electrostatic capacity than Comparative Example 1 can be obtained by providing an etching tank that performs an etching process of 60% or more of the etching weight loss.

  In the first embodiment, the low-pressure AC etching process using an AC power source has been described. However, for the medium- and high-pressure DC etching process, an etching solution in which fine bubbles generated from the fine bubble generator are interposed is used. A high electrostatic capacity can be obtained by performing an etching process.

  The present invention provides an apparatus for producing an electrode foil for an electrolytic capacitor that suppresses excessive etching and has a high capacitance per unit area, and is useful for downsizing electronic equipment.

Sectional drawing which shows the structure of the manufacturing apparatus of the electrode foil for electrolytic capacitors in Embodiment 1 of this invention Sectional drawing which shows the structure of the microbubble generator of the Example 2 Sectional drawing which shows the structure of the manufacturing apparatus of the conventional electrode foil for electrolytic capacitors

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Aluminum foil 12 Etching tank 13 Etching liquid 14a, 14b A pair of electrode plates 15a, 15b Traveling roller 16 In-tank roller 17 AC power supply 18 Fine bubble generator 19 Circulation hose 20 Compressor 21 Flush tank

Claims (4)

For electrolytic capacitors in which a pair of electrodes are arranged and a plurality of etching tanks filled with an etching solution are provided, and a voltage is applied to the pair of electrodes to run a strip-shaped aluminum foil, thereby etching the aluminum foil. In electrode foil manufacturing equipment,
An apparatus for producing an electrode foil for an electrolytic capacitor, in which a circulation pipe for circulating an etching solution is arranged in the plurality of etching tanks, and a fine bubble generating device for mixing fine bubbles in the etching solution is interposed in a part of the circulation pipe. The apparatus for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein the fine bubble generating device includes a pump for circulating the etching solution and a supply port for supplying gas, and generates fine bubbles by a swirling flow. The apparatus for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein the fine bubbles are bubbles of 50 μm or less. The apparatus for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein fine bubbles generated from the fine bubble generator are fed between the pair of electrodes.

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