WO2011114380A1

WO2011114380A1 - Process for production of aluminum electrode plate for electrolytic capacitor

Info

Publication number: WO2011114380A1
Application number: PCT/JP2010/001967
Authority: WO
Inventors: 片野雅彦; 小林達由樹; 吉田祐也; 矢久間一
Original assignee: 日本軽金属株式会社
Priority date: 2010-03-18
Filing date: 2010-03-18
Publication date: 2011-09-22
Also published as: JPWO2011114380A1; JP5532122B2

Abstract

Disclosed is a process for producing an aluminum electrode plate for an electrolytic capacitor, which enables the production of such an electrode plate having a thick etching layer and high electrostatic capacitance per unit projected area in a simple manner. In the process, aluminum plates (10) are respectively placed between electrodes (20) that are placed in an etching solution to achieve the alternating current etching while flowing the etching solution into an etching chamber (35) that is partitioned by each of the electrodes (20) and each of the aluminum plates (10) at a flow rate of 0.002 to 0.015 m/s, thereby forming an etching layer having an etching depth of 70 μm or more on one surface. The flow rate is a value calculated by the following formula: v (flow rate) = Q/S (wherein S represents the cross section area of the etching chamber (35); and Q represents the amount of the etching solution supplied to the etching chamber (35) per unit of time).

Description

Method for producing aluminum electrode plate for electrolytic capacitor

The present invention relates to a method for producing an aluminum electrode plate for electrolytic capacitors by AC etching of an aluminum plate.

When an aluminum electrode used for an aluminum electrolytic capacitor is manufactured by alternating current etching, in principle, an aluminum foil or an aluminum plate is disposed between two electrodes disposed in an etching solution, and an alternating current is formed between the two electrodes. An electric current is applied to form an etching layer on the surface of the aluminum foil or aluminum plate. An aluminum electrolytic capacitor is required to have a high capacitance per projected unit area as one of its required performances. In order to realize such required performance, the pits of the etching layer are deep and the CV product is high. There is a need for a large electrolytic capacitor electrode plate.

In AC etching, aluminum is dissolved mainly by hydrochloric acid in the etching solution and AC current, and pits are formed on the aluminum plate. The pits grow with the processing time and accumulate densely to form a spongy pit aggregate, and the thickness of the etching layer increases. On the other hand, dissolved aluminum ions are highly concentrated in the pit. Therefore, when the depth of the pit exceeds a certain level, the highly concentrated aluminum ions cause unnecessary dissolution of the aluminum by the etching solution and electrolysis, thereby hindering the growth of the pit aggregate. That is, when the thickness of the etching layer is increased, the shallow portion of the pit aggregate is broken, and the pit aggregate cannot be maintained in a preferable shape. According to the experiments by the present inventors, when the thickness of the etching layer reaches about 70 μm, the growth of the pit aggregate tends to be significantly hindered.

Patent Document 1 discloses a method for producing an aluminum electrode for an electrolytic capacitor, in which an aluminum plate is etched from below the aluminum plate provided between the electrodes while mixing and supplying air bubbles to the etching solution. According to this manufacturing method, it is possible to suppress the progress of the excessive etching during the formation of the etching layer and suppress the destruction of the fine porous structure. Therefore, the aluminum electrode for electrolytic capacitors with a high electrostatic capacity can be manufactured.

JP 2009-105191 A

However, in the method described in Patent Document 1, although the progress of excessive etching can be suppressed, bubbles mixed with the etching solution gather in the upper part of the aluminum plate when performing batch operation, and the removal work and the defoaming work are very large. There is a problem that it takes time and effort.

In view of the above problems, an object of the present invention is to obtain an electrode plate for an aluminum electrolytic capacitor having a high capacitance per projected unit area even when the etching layer is formed thick without much effort. An object of the present invention is to provide a method for manufacturing an aluminum electrode plate for electrolytic capacitors.

In order to solve the above problems, in the method for producing an aluminum electrode plate for electrolytic capacitors according to the present invention, one or more electrodes and at least one surface of the electrodes are contained in an etching solution stored in an etching tank having a bottom wall. When performing AC etching in a batch manner by arranging one or more aluminum plates facing each other,
With respect to the channel space sandwiched between the electrode and the aluminum plate, an etchant having an aluminum ion concentration lower than the etchant from the lower side to the upper side of the channel space is expressed by the following condition 0.002 m / s ≤ Flow velocity v ≤ 0.015m / s
v = Q ÷ S
v: Flow velocity S: Cross-sectional area of the channel space Q: Supply an etching solution to the channel space at a unit time per unit time, and form an etching layer with a depth of 70 μm or more per side on the aluminum plate. It is characterized by.

In the present invention, “an etching solution having a low aluminum ion concentration” means that the aluminum ion concentration is zero.

In the present invention, the flow velocity v is as follows: 0.004 m / s ≦ flow velocity v ≦ 0.010 m / s
It is more preferable to set to.

In the present invention, one or a plurality of electrodes and an aluminum plate facing at least one surface of the electrode are arranged in the etching solution, and one surface of the aluminum plate or an aluminum plate is passed through the alternating current between the facing electrode and the aluminum plate. AC etching is performed on both sides. In the present invention, the method of applying an alternating current between the electrode and the aluminum plate to be etched is not limited. As a result of various studies on the flow of the etching solution during the etching process, the inventors of the present application supplied the flow rate of the etching solution passing through the surface of the aluminum plate to be etched as a predetermined speed, and set the aluminum ion concentration of this etching solution. It has been found that an aluminum electrode plate for an aluminum electrolytic capacitor having a high CV product can be obtained when the aluminum ion concentration is set lower than the aluminum ion concentration in the etching tank, and the present invention has been completed.

That is, in the present invention, the etching solution is caused to flow in the flow path space between the electrode and the aluminum plate at a flow rate of 0.002 to 0.015 m / s. Here, in the present invention, when the flow rate of the etching solution is S, the cross-sectional area of the channel space is S, and the amount of etching solution supplied to the channel space per unit time is Q, v (flow rate) = Q ÷. It is defined as a value calculated by S. More preferably, this flow rate is 0.004 to 0.010 m / s. According to such a configuration, although it is estimated, the aluminum ions in the pits are stably moved out of the pits by the flow of the etching solution and easily removed, and as a result, the etching is performed deeply without destroying the preferable pit shape. It can be carried out. Further, a difference in aluminum ion concentration occurs inside and outside the pit, and the aluminum ion is easily diffused outside the pit. Thereby, aluminum ions can be efficiently removed from the pits. Therefore, even when the etching layer is formed thick, an aluminum electrolytic capacitor electrode plate having a large CV product and a high capacitance per projected unit area can be obtained. In addition, this makes it possible to realize a large-capacitance capacitor and achieve downsizing of the device. In addition, since the workability at the time of manufacture is good and can be easily manufactured, and the operation of removing bubbles and the operation of defoaming are unnecessary, an effect that the manufacturing apparatus and incidental facilities are not complicated can be obtained.

According to the study of the inventors of the present application, when the flow rate of the etching solution is less than 0.002 m / s, the flow of the etching solution in contact with the aluminum plate becomes extremely low, and the discharge amount of aluminum ions from the pit is extremely small. As a result, when a deep etching layer is formed, the shape of the pit in the shallow portion is destroyed, and the electrostatic capacity is lowered. On the other hand, when the flow velocity exceeds 0.015 m / s, a turbulent flow is generated in the etching solution, the flow becomes unstable, and the movement of aluminum ions becomes unstable. In addition, since the etching layer formed so far also melts, the pit shape is destroyed as a result, and the electrostatic capacity is lowered. Therefore, it is preferable to set the flow velocity as described above.

In the present invention, the etching solution supplied to the flow path space is preferably a mixture of an etching solution overflowing from the etching tank and an etching solution having a lower aluminum ion concentration than the etching solution. According to such a configuration, the overflowed etchant can be reused as a regenerated etchant.

In the present invention, it is preferable that an etching solution supply port for supplying the etching solution toward the channel space sandwiched between the aluminum plate and the electrode is provided in the bottom wall portion of the etching tank. According to such a configuration, the flow of the etching solution is evenly formed in the entire channel space, and the etching solution flows smoothly from the lower end to the upper end of the channel space. Therefore, aluminum ions can be efficiently removed from the pits on the entire surface of the aluminum plate, and uniform etching can be performed. At this time, an etchant supply port for supplying the etchant toward the flow path space on one side of the aluminum plate, and an etchant supply for supplying the etchant toward the flow path space on the other side It is good also as a structure which provided the opening | mouth. According to this configuration, the aluminum plate can be etched on both sides.

The aluminum electrode plate for electrolytic capacitors to which the present invention is applied is used, for example, as an anode of an aluminum electrolytic capacitor in which a functional polymer is used as an electrolyte. That is, the aluminum electrode plate for electrolytic capacitors to which the present invention is applied is used for an electrolytic capacitor in which a dielectric film is formed on the surface and a functional polymer layer is formed on the dielectric film.

In the present invention, the aluminum ions in the pits are stably moved out of the pits and easily removed by flowing the etching solution in the flow path space between the electrode and the aluminum plate at a flow rate of 0.002 to 0.015 m / s. In addition, a difference in the concentration of aluminum ions occurs inside and outside the pit, and the aluminum ions are easily diffused outside the pit. Thereby, aluminum ions can be efficiently removed from the pits. As a result, deep etching can be performed without destroying the preferred pit shape. Therefore, even when the etching layer is formed thick, an aluminum electrolytic capacitor electrode plate having a large CV product and a high capacitance per projected unit area can be obtained. In addition, this makes it possible to realize a large-capacitance capacitor and achieve downsizing of the device. In addition, since the workability at the time of manufacture is good and can be easily manufactured, and the operation of removing bubbles and the operation of defoaming are unnecessary, an effect that the manufacturing apparatus and incidental facilities are not complicated can be obtained.

It is explanatory drawing which shows typically the manufacturing method and manufacturing apparatus of the aluminum electrode plate for electrolytic capacitors to which this invention is applied. 4 is a graph showing a CV product of an etching plate manufactured under the etching conditions of Example 1. FIG. 6 is a graph showing a CV product of an etching plate manufactured under the etching conditions of Example 2. It is a graph which shows the relationship between the thickness of the etching layer in Example 1, and the maximum increase rate of a CV product. It is explanatory drawing of the image analysis photograph of the etching board manufactured on the etching conditions to which this invention is applied, and the outline of an etching pit. It is explanatory drawing of the image analysis photograph of the etching board manufactured on the etching conditions of the comparative example, and the outline of an etching pit.

Embodiments of the present invention will be described with reference to the drawings.

(Configuration of manufacturing equipment for aluminum electrode plates for electrolytic capacitors)
FIG. 1 is an explanatory view schematically showing an example of a production apparatus (etching apparatus) for an aluminum electrode plate for electrolytic capacitors to which the present invention is applied. FIG. 1 shows an etching apparatus in which five electrodes are arranged in an etching apparatus and can etch a total of four aluminum plates. The number of electrodes can be three or more, but can be two.

As shown in FIG. 1, a batch type manufacturing apparatus (hereinafter referred to as an etching apparatus 100) of an aluminum electrode plate for electrolytic capacitors to which the present invention is applied includes an etching tank 30 in which a hydrochloric acid-based etching solution 40 described later is stored, The power supply device 80 includes three or more electrodes 20 arranged to face each other in the etching solution 40. The electrode 20 is made of a conductor such as carbon or platinum that does not dissolve in electrolysis in an etching solution. The etching tank 30 is made of an insulator such as resin.

In the etching apparatus 100 of the present embodiment, the power supply apparatus 80 is connected to the

electrodes

20a and 20e disposed at both ends of the three or more electrodes 20, and an alternating current is provided between the two

electrodes

20a and 20e. Apply.

In addition, the aluminum plates 10 are disposed between the electrodes 20 facing each other in the three or more electrodes 20, and the electrodes 20 and the aluminum plates 10 are alternately disposed. That is, in the etching apparatus 100, the electrode 20 (electrode 20a), the aluminum plate 10 (aluminum plate 10a), the electrode 20 (electrode 20b), the aluminum plate 10 (aluminum plate 10b), the electrode 20 (electrode 20c), and the aluminum plate 10 ( The aluminum plate 10c), the electrode 20 (electrode 20d), the aluminum plate 10 (aluminum plate 10d), and the electrode 20 (electrode 20e) are arranged in this order while facing each other. Here, the electrode 20 has a width dimension larger than that of the aluminum plate 10.

In the etching apparatus 100 configured as described above, when an alternating current is applied between the

electrodes

20a and 20e disposed at both ends, both surfaces of any aluminum plate 10 are AC etched. At that time, among the three or more electrodes 20, the

electrodes

20b, 20c, 20d other than the

electrodes

20a, 20e arranged at both ends are not connected to the power supply device 80 and are in an electrically floating state. The aluminum plates 10 are divided from each other, and the aluminum plate 10 is not connected to the power supply device 80 by wiring. For this reason, the aluminum plate 10 is in an electrically floating state.

In such a configuration, since the

electrodes

20b, 20c, 20d other than the

electrodes

20a, 20e disposed at both ends and the aluminum plate 10 disposed between the electrodes 20 do not need to be fed, the apparatus configuration is simple. Thus, no trouble is required in maintenance such as replacement of the electrode 20. Furthermore, since it is only necessary to connect the wiring to only some of the electrodes 20, a situation in which the balance of the wiring resistance to each electrode 20 is not lost does not occur. Therefore, the etching current density for the aluminum plate 10 is stable. The above describes the case where there are three or more electrodes 20 and the aluminum plate is in an electrically floating state with the power supply device 80. However, there are two electrodes 20 and one or more aluminum plates 10 between them. One electrode 20 may be provided, and one aluminum plate 10 may be provided. Thus, when the electrode 20 and the aluminum plate 10 are one each and it is one to one, the electrode 20 (20a) and the aluminum plate 10 (10a) will be connected to AC power supply, and the aluminum plate 10 (10a) Etching only on one side. In the present application, the number of electrodes 20, the number of aluminum plates 10, and the electrical connection method with the power supply device 80 are not limited.

In the etching apparatus 100 of this embodiment, a plurality of plate portions 36 are formed in the etching tank 30 on both

side walls

32 and 33 facing each other at a predetermined interval. An electrode shielding portion 51 is formed to block between the inner wall and the electrode 20. In this embodiment, the electrode shielding portions 51 are formed on both sides of the electrode 20 in the width direction. Further, the electrode shielding part 51 is formed in a slit shape extending in the vertical direction while being opened inside, and the slit is an electrode holding slit into which both end portions in the width direction of the electrode 20 are inserted. . Further, in the etching apparatus 100 of this embodiment, the etching tank 30 is formed with an aluminum plate shielding part 52 that closes between the inner wall of the etching tank 30 and the aluminum plate 10 by the plate part 36. In this embodiment, the aluminum plate shielding portions 52 are formed on both sides of the aluminum plate 10 in the width direction. Further, the aluminum plate shielding portion 52 is formed in a slit shape extending in the vertical direction while being opened inside, and the slit is used for holding an aluminum plate into which both end portions in the width direction of the aluminum plate 10 are inserted. It is a slit.

In the etching apparatus 100 configured as described above, when the electrode 20 is inserted into the electrode shielding portion 51 and the aluminum plate 10 is inserted into the aluminum plate shielding portion 52, the etching tank 30 includes the electrode 20 and the aluminum plate 10. A plurality of etching chambers 35 (channel spaces) are partitioned. Here, with respect to the plurality of etching chambers 35, a plurality of etching solution supply ports 55 for supplying an etching solution for each etching chamber 35 are provided. In the present embodiment, the plurality of etching solution supply ports 55 are opened at the bottom wall 34 among the wall surfaces of the etching tank 30. Accordingly, an etching solution supply port 55 that opens toward each of the two etching chambers 35 (channel spaces) located on both sides of the aluminum plate 10 is provided at the bottom of the etching tank 30. It has been. More specifically, an etchant supply port 55 for supplying an etchant toward the etching chamber 35 (flow path space) on one side of the aluminum plate 10 and an etching chamber 35 (flow) on the other side of the aluminum plate 10. An etchant supply port 55 for supplying an etchant toward the (road space) is provided.

In the etching tank 30, the etching solution supply ports 55 communicate with the plurality of etchant supply ports 55 on the side opposite to the side on which the electrode 20 is disposed with respect to the bottom wall 34 where the etchant supply ports 55 open. An etching solution supply path 38 is defined. The etchant supply path 38 is provided with a plurality of partition plates 53, and the etchant supply path 38 is partitioned into individual chambers 381 corresponding to the etch chamber 35 on a one-to-one basis by the partition plates 53. Adjacent private chambers 381 are formed independently. As described above, the individual chambers 381 are completely separated by the partition plate 53, so that electrical influences between the plurality of etching chambers 35 are more reliably prevented.

A plurality of overflow ports 61 (etching solution outlets) are formed near the upper end of the side wall 33 in the etching tank 30, and the overflow ports 61 allow the etching solution to overflow from each of the plurality of etching chambers 35. . On the outer surface side of the sidewall 33 of the etching tank 30, a recovery path 39 for recovering the overflowing etching solution at a position below the overflow port 61 is configured.

The etching apparatus 100 of this embodiment includes an etching liquid circulation device 62 for adjusting a component of a part of the overflowing etching liquid and re-supplying it to the etching tank. The etching liquid circulation device 62 connects an overflow tank 63 provided below the recovery path 39, a circulation flow path 64 connected to the bottom of the overflow tank 63, a downstream portion of the circulation flow path 64, and each individual chamber 381. A pipe 42 is provided. The downstream portion of the circulation flow path 64 extends along the arrangement direction of the individual chambers 381 of the etching solution supply path 38, and each pipe 42 is connected to this portion. Each pipe 42 is provided with a flow rate adjusting valve 65 (flow rate adjusting means) for controlling the amount of etching solution supplied from the circulation flow path 64 to each individual chamber 381.

The etching liquid circulation device 62 includes a pipe 66 (outflow means) for extracting a part of the etching liquid in the overflow tank 63, and a fixed amount extraction valve 67 (outflow means) for adjusting the amount of extraction from the pipe 66. It has. Further, a pipe 68 (inflow means) for joining the etching liquid for component adjustment supplied from the outside to the upstream portion of the circulation flow path 64 and a fixed amount for adjusting the supply amount of the etching liquid from the pipe 68. And a supply valve 69 (inflow means). The etchant circulation device 62 is configured to be able to control the flow rate and opening / closing timing of the flow rate adjusting valve 65, the fixed amount removal valve 67 and the fixed amount supply valve 69. For example, the amount of liquid extracted from the pipe 66 and the amount supplied from the pipe 68 are controlled to be the same, and the amount of liquid in the etching tank 30 is kept constant. Further, it controls how much of the etching solution flowing into the overflow tank 63 in a certain time is extracted and replaced with the etching solution from the pipe 68.

In the etching solution circulation device 62, the entire amount of the etching solution that has flowed into the recovery passage 39 flows into the overflow tank 63, and then a part of the etching solution is withdrawn via the pipe 66. 64 is mixed with the etchant newly flowing from the pipe 68. Then, the mixed etching solution (hereinafter referred to as a regenerated etching solution) is supplied to each individual chamber 381 via each pipe 42. The etching solution supply ports 55 provided in the individual chambers 381 are open near both sides sandwiching the lower end portion of the aluminum plate 10. Therefore, the etching solution supplied from the etching solution supply port 55 to the etching chamber 35 flows from the bottom to the top along the surface of the aluminum plate 10.

(Method for producing aluminum electrode plate for electrolytic capacitor)
In this embodiment, the aluminum plate 10 is used, for example, to constitute an anode (an aluminum electrode plate for an electrolytic capacitor) of an aluminum electrolytic capacitor in which a functional polymer such as polypyrrole, polythiophene, or polyaniline is used as an electrolyte. That is, after the aluminum plate 10 is etched, an anodic oxide film is formed on the surface thereof, and the aluminum plate 10 is used as an anode of an aluminum solid electrolytic capacitor.

In this embodiment, the aluminum purity in the aluminum plate 10 is 99.98% by mass or more. If it does in this way, the toughness of the aluminum plate 10 will be high, and the handling at the time of manufacturing an electrolytic capacitor will be easy. On the other hand, if the aluminum purity is less than the lower limit, the hardness increases, the toughness decreases, and damage such as cracking may occur during handling, which is not preferable. The aluminum plate 10 does not limit the content of elements other than Al (Fe, Si, Cu, Ga, V, Ni, Ti, Zr, etc.), but preferably, Fe 50 ppm or less, Cu 40 ppm or less, Si 60 ppm or less. It is good to do. The aluminum plate 10 may have various thicknesses depending on the purpose. For example, a thickness of 150 μm to 1 mm, usually 300 to 400 μm is used.

In this embodiment, the aluminum plate 10 is subjected to AC etching with a low concentration hydrochloric acid aqueous solution as a primary electrolytic treatment. As a pretreatment, it is preferable to remove the surface oxide film by performing degreasing cleaning or slight etching on the aluminum plate 10. The primary electrolytic treatment can be performed using the etching apparatus 100 described above.

For example, an aqueous solution containing 1.5 to 2.4 mol / l hydrochloric acid and 0.05 to 0.5 mol / l sulfuric acid is used as the low concentration hydrochloric acid aqueous solution used as an etching solution (electrolytic solution) in the primary electrolytic treatment. The liquid temperature is 40 to 55 ° C, the frequency is 10 to 25 Hz, the AC waveform is a sine waveform, rectangular waveform, AC / DC superimposed waveform, etc. The current density is 40 to 50 A / dm ² , and the processing time is 30 to 60 seconds. Etching is performed to form a large number of pits on the surface of the aluminum plate 10.

After the primary electrolytic treatment, the main electrolytic treatment is performed to form a spongy pit aggregate on both surfaces of the aluminum plate 10. In this embodiment, this main electrolytic treatment is performed in the etching apparatus 100 while supplying the regenerated etching solution to each etching chamber 35 by the etching solution circulation device 62. That is, in this embodiment, the manufacturing method of the present invention is applied to the main electrolytic treatment.

For example, an aqueous solution containing 4 to 6 mol / l hydrochloric acid and 0.05 to 0.5 mol / l sulfuric acid is used as the etching solution (electrolytic solution) used in the main electrolytic treatment. The etching conditions are, for example, 20 to 35 ° C., where the liquid temperature is lower than the primary electrolytic treatment, the frequency is 30 to 60 Hz, the AC waveform is a sine waveform, rectangular waveform, AC / DC superimposed waveform, etc., and the current density is the primary electrolytic treatment predetermined etching layer thickness (e.g., one side at 70μm or more, more 140μm in total of both sides) is 20 ~ 30A / dm ^2, treatment time less than set to a time that can be etched away.

Further, as etching conditions, the flow rate of the etching solution flowing from the bottom to the top along each surface of the aluminum plate 10 and the aluminum ion concentration of the regenerated etching solution supplied to each etching chamber 35 are set. . The target of the aluminum ion concentration may be 12 grams / liter or less. In the main electrolytic treatment, the etching solution supplied from the pipe 68 to the circulation channel 64 has a lower aluminum ion concentration than the etching solution in the etching tank 30, specifically, substantially contains aluminum ions. Or an etching solution whose aluminum ion concentration is increased by an etching process. Thereby, it is preferable that the aluminum ion concentration of the regenerated etching solution is lower than the etching solution in the etching tank 30. The specific concentration is set, for example, by what percentage of the aluminum ion concentration in the etching bath 30 is the reference (100%).

On the other hand, the flow velocity is preferably set to a value within the range of 0.002 to 0.015 m / s, and more preferably 0.004 to 0.010 m / s. Here, the definition of the flow velocity in this embodiment is that each etching chamber 35 is a channel space having an equal cross-sectional shape provided between the aluminum plate 10 and the electrode 20 and extending in the vertical direction. It can be considered that the value (v) calculated by the following equation (1) is assumed, where S is the channel area) and Q is the supply amount of the regenerated etching solution to each etching chamber 35 per unit time. As the supply amount Q, a flow rate per unit time flowing through each flow rate adjustment valve 65 can be used.
v (m / s) = Q (m ³ / s) ÷ S (m ² )... (1)

In this embodiment, the etching process is performed according to the above etching conditions, and the pits drilled by the primary electrolytic process are further drilled. After performing the primary electrolytic treatment and before performing the main electrolytic treatment, the main electrolytic treatment is performed by activating the pits drilled in the primary electrolytic treatment using the AC / DC superimposed waveform and then proceeding to the main electrolytic treatment. It is possible to proceed reliably. In this process, for example, the etching is performed for about 60 seconds under the condition that the duty ratio is about 0.07 to 0.09 and the current density is 12 to 17 A / dm ² . Thereby, an etching layer having a thickness of 70 μm or more can be formed.

In the main electrolytic treatment, by setting the etching conditions as described above, it is possible to reduce the dissolution that does not contribute to pit formation and to form a spongy etching layer deeply. Specifically, several thousand to several hundreds of thousands of spongy pits can be drilled per square millimeter. Therefore, the aluminum electrode plate (etched plate) for an electrolytic capacitor manufactured according to the present invention is an electrode plate having a high etching magnification and a high capacitance.

The inventor of the present application considers AC etching, which is an etching method in the manufacturing method of the present application, as follows. That is, in AC etching, Al on the aluminum plate 10 becomes Al ³⁺ during the anode and dissolves and diffuses into the etching solution. A part of the generated Al ³⁺ reacts with one (OH) group at the cathode to become Al (OH) ₃ and precipitates on the pit surface, but a part of the remaining reaction product diffuses into the etching solution. Thus, it is removed outside the pit, and a part remains in the etching solution in the pit. By this series of repetitions, the etching progresses while the position of the starting point where Al is easily dissolved moves, and the aluminum plate 10 is deeply etched in a spongy manner. At this time, in the conventional AC etching, as the etching depth becomes deeper, the aluminum plate 10 becomes harder to be punched into pits, and the pit shape of the etched portion is destroyed due to an etching solution containing hydrochloric acid and other influences. Come. For this reason, if the etching process is further continued, the pit shape collapses at a shallow portion of the etching layer, and the electrostatic capacity is lowered.

Such a phenomenon is considered to occur because reaction products accumulate in the pits and the etching conditions gradually change. Therefore, the inventor of the present application sets supply conditions for the etching solution used in the main electrolytic treatment based on the following considerations. That is, if an etching solution having a lower aluminum ion concentration than the etching solution in the etching tank 30 is supplied to the surface of the aluminum plate 10, the aluminum ions in the pits are etched outside the pits due to the concentration difference of the aluminum ions inside and outside the pits. Aluminum ions are easily discharged to the liquid side, and aluminum ions that hinder the formation of pits and the progress of etching are reduced. As a result, it is considered that a spongy etching layer in which pits having a preferable shape are deeply etched and densely gathered can be formed. As a specific method for supplying an etching solution, an etching solution that has a high aluminum ion concentration by etching treatment is obtained by extracting an overflowing etching solution by a certain amount and mixing it with an etching solution from which aluminum ions have been removed. The etching solution is regenerated to a low etching solution, and is supplied again into the etching bath 30.

Furthermore, it is considered that the flow rate of the etchant flowing along the surface of the etching layer affects the pit formation. That is, if the etching solution supplied from the bottom of the etching tank 30 is made to flow from the bottom to the top along the surface of the aluminum plate 10 and the flow velocity at this time is kept at 0.002 to 0.015 m / s, the aluminum in the pit It is considered that ions are likely to move stably outside the pit. In the vicinity of the surface of the aluminum plate 10, the etching solution has a low flow rate due to the velocity gradient, and the aluminum ions in the pits are difficult to diffuse. Specifically, when the flow rate of the etching solution is less than 0.002 m / s, the discharge amount of aluminum ions from the pits decreases, and the pit shape collapses. On the other hand, when the flow velocity exceeds 0.015 m / s, turbulent flow is generated along the surface of the aluminum plate 10, so that aluminum ions cannot be stably discharged from the pits. In addition, the pit shape collapses due to turbulence. From such examination, the preferable flow velocity range is set to 0.002 to 0.015 m / s.

As described above, according to the etching apparatus 100 of this embodiment and the method for manufacturing an aluminum electrode plate for an electrolytic capacitor using the etching apparatus 100, aluminum ions in the pits are formed in the etching layer on the surface of the aluminum plate 10. Due to the flow of the etching solution, it is easily moved out of the pits and easily removed, and as a result, deep etching can be performed without destroying the preferred pit shape. In addition, the reproduction etching solution having a low aluminum ion concentration causes a difference in aluminum ion concentration between the inside and outside of the pit, and the aluminum ion is easily diffused outside the pit. Thereby, aluminum ions can be efficiently removed from the pits, and effective etching by an etching solution and electrolysis can be promoted. Therefore, an electrode plate for an aluminum electrolytic capacitor having a large CV product and a high capacitance per projected unit area can be obtained. In addition, this makes it possible to realize a large-capacitance capacitor and achieve downsizing of the device. In addition, since the workability at the time of manufacture is good and the product can be manufactured easily, and the bubble removing operation and the defoaming operation are unnecessary, the manufacturing apparatus and incidental facilities are not complicated. In addition, an electrode plate for an aluminum electrolytic capacitor can be manufactured with high productivity.

Further, in this embodiment, a part of the overflowed etching solution can be reused as a regenerated etching solution, and at this time, by controlling the ratio of the extraction amount to the total amount of the overflow solution and the mixing amount of the new etching solution. The regenerated etching solution can have a desired aluminum ion concentration. Furthermore, by supplying a regenerated etching solution from the bottom of the etching bath 30 and flowing the etching solution from the bottom to the top along the aluminum plate, the flow of the etching solution is formed uniformly in the entire flow path space, Aluminum ions can be efficiently removed from the pits on the entire surface of the aluminum plate, and uniform etching can be performed.

(Confirmation of change in CV product depending on etching conditions)
2 to 4 show CV product data of etched plates manufactured under various etching conditions. 2 and 4 are data based on the etching conditions of Example 1, and FIG. 3 is data based on the etching conditions of Example 2. In Examples 1 and 2, the aluminum plate 10 (thickness 0.35 mm) was etched by the etching method and the etching apparatus 100 described with reference to FIG. Capacitance C and film withstand voltage V in an aqueous solution of ammonium adipate when an oxide film having a withstand voltage was formed were measured, and the value of the CV product was determined.

Example 1
In Example 1, the aluminum ion concentration ratio of the regenerated etching solution supplied to the etching chamber 35 is constant (60% of the aluminum ion concentration when the aluminum ion concentration in the etching tank 30 is 100). The change in the CV product when the flow rate v and the etching time were varied was verified. In Example 1, using the apparatus shown in FIG. 1, the aluminum purity of the aluminum plate was 99.98% by mass or more, the total projected area of the aluminum plate was 500 cm ² , the amount of electrolyte was 50 liters, and the initial aluminum ion concentration was 4 g / liter. It was. 40 parts of 100 parts of the etching liquid overflowing from the etching tank 30 are extracted, and a regenerated etching liquid obtained by newly mixing 40 parts of etching liquid in which aluminum ions are not substantially added to the remaining amount is supplied from the tank bottom. Then, an etching process was performed. The etching solution flow velocity v (supply amount Q / channel cross-sectional area S) was set to various values in the range of 0.001 to 0.020 m / s. The etching time was a time for forming an etching layer having a thickness of 60 μm, 100 μm, 140 μm, and 220 μm in total on both surfaces. The results are shown in FIG. The horizontal axis in FIG. 2 is the flow velocity (m / s), and the vertical axis is the rate of increase (%) in the CV product. The rate of increase (%) of the CV product in Example 1 indicates the ratio to this value, assuming that the CV product is 100% when the flow velocity is 0.002 m / s. Further, the four graphs in FIG. 2 correspond to four stages of etching time (total thickness of both surfaces of the etching layer).

When the etching depth of the aluminum plate etched under the etching conditions of Example 1 was observed with a microscope, the etching depth of each plate was etched to substantially the same depth on both sides. From the results of FIG. 2, it can be seen that the CV product increases as the flow rate increases, and that there is a peak in the CV product. Therefore, it is preferable to supply an etching solution having a lower aluminum ion concentration than the etching solution in the etching tank 30 as a regenerating etching solution, and to set the flow rate of the regenerating etching solution in the range of 0.002 to 0.015 m / s. It turns out that it is preferable. That is, a high CV product value is obtained under this condition.

As shown in FIG. 2, the maximum rate of increase of the CV product varies depending on the thickness of the etching layer to be formed. FIG. 4 shows the relationship between the thickness of the etching layer and the maximum rate of increase of the CV product based on the data of FIG. 2, where the horizontal axis is the thickness of the etching layer and the vertical axis is the maximum rate of increase of the CV product. It is. As shown in FIG. 4, when the inflection point is observed in the vicinity of the total thickness of both sides of the etching layer being 120 μm (60 μm on one side) and the total thickness on both sides is 140 μm (70 μm on one side) or more, the CV product The rate of increase is increasing.

(Example 2)
In Example 2, the same apparatus, the same projected area, liquid amount, and initial aluminum ion concentration as in Example 1 were used. The flow rate v (supply amount Q / channel cross-sectional area S) of the etching solution in the etching chamber 35 is constant at 0.005 m / s, and the aluminum ion concentration of the regenerated etching solution supplied to the etching chamber 35 and the etching time are varied. The change in the CV product was verified. The results are shown in FIG. The horizontal axis of FIG. 3 is the aluminum ion concentration of the regenerated etching solution (concentration ratio when the aluminum ion concentration in the etching tank 30 is 100%), and the vertical axis is the rate of increase (%) of the CV product. When the aluminum ion concentration of the etching solution is the same (100%) as in the etching tank 30, the CV product is 100%, and the ratio to this value is shown. In Example 2, the aluminum ion concentration was varied by adjusting the amount of the etching solution to be extracted and the amount of the etching solution to be mixed with respect to the overflowing etching solution in the same manner as in Example 1. In addition, the etching time was set to the time when the total thickness of both surfaces of the etching layer was 60 μm, 100 μm, 140 μm, and 220 μm, as in Example 1.

3 that the CV product is increased when the aluminum ion concentration in the regenerated etching solution is low. It can also be seen that when the total thickness of both surfaces of the etching layer exceeds 140 μm, the rate of increase of the CV product is larger than that of the thickness less than that. In FIG. 2, when the total thickness of both surfaces of the etching layer exceeds 140 μm, the CV product exceeded 106%, but from FIG. 3, when the total thickness of both surfaces is 140 μm, the aluminum ion concentration is less than 60%. It can be seen that when the CV product exceeds 106% and the total thickness of both surfaces is 220 μm, it exceeds 106% when the aluminum ion concentration is made thinner than 70%.

(Checking the etching state by image analysis)
FIGS. 5 and 6 are explanatory diagrams showing image analysis photographs of the pits on the etching plate and the contour lines of the etching pits, and FIG. / s, etching plate etched at a thickness of 220 μm on both sides of the etching layer, FIG. 6 shows the etching conditions of the comparative example (reproduction etching solution aluminum ion concentration ratio 100%, flow rate 0.005 m / s, etching layer on both sides) This is an etching plate subjected to an etching treatment with a thickness of 220 μm.

FIG. 5A is an image analysis photograph of a surface where an unstable layer on the etching plate surface is deleted to a depth of 20 μm from the surface, and FIG. 5B is an image analysis of a surface where the surface is deleted to a depth of 50 μm from the surface. The photograph, FIG. 5C, is an image analysis photograph of the surface removed from the surface to a depth of 100 μm. Similarly, FIGS. 6A to 6C are image analysis photographs of the surfaces deleted from the surface to respective depths of 20 μm, 50 μm, and 100 μm. In each photograph, a black dot-like portion represents an etching pit, and a gray portion represents an unetched portion. FIGS. 5D to 5F show the image processing of FIGS. 5A to 5C to try to extract the contour lines of the etching pits. Similarly, FIGS. 6D to 6F are obtained by trying to extract the outline of the etching pit by performing image processing on FIGS. 6A to 6C.

5 (a) to 5 (f), it can be seen that, under the etching conditions of this embodiment, the etching is almost the same at each position of 20 μm, 50 μm, and 100 μm from the surface, and deep etching is possible. Since a preferable etching state was obtained, it can be considered that in Examples 1 and 2, the increase rate of the CV product was increased.

On the other hand, as shown in FIGS. 6A to 6F, in the comparative example, the etching state is poor overall, and when the etching state at the position of 50 μm from the surface layer is compared with the etching state at the position of 100 μm from the surface layer, the etching state from the surface layer is 100 μm. There are few etched parts. That is, it can be seen that even if the etching time is long and the etching is randomly performed deeply, it does not progress to a good etching pit shape.

According to the present invention, it is possible to perform deep etching on the surface of the aluminum plate 10 without breaking a preferable pit shape. Therefore, even when the etching layer is formed thick, an aluminum electrolytic capacitor electrode plate having a large CV product and a high capacitance per projected unit area can be obtained. In addition, this makes it possible to realize a large-capacitance capacitor and achieve downsizing of the device. In addition, since the workability at the time of manufacture is good and can be easily manufactured, and the operation of removing bubbles and the operation of defoaming are unnecessary, an effect that the manufacturing apparatus and incidental facilities are not complicated can be obtained.

10 Aluminum plate 20 Electrode 30 Etching tank 32 Side wall 33 Side wall 34 Bottom wall 35 Etching chamber (channel space)
36 Plate portion 38 Etching solution supply path 381 Private chamber 39 Recovery route 40 Etching solution 42 Pipe 51 Electrode shielding portion 52 Aluminum plate shielding portion 53 Partition plate 55 Etching solution supply port 61 Overflow port (etching solution outlet)
62 Etching solution circulating device 63 Overflow tank 64 Circulating flow path 65 Flow rate adjusting valve (flow rate adjusting means)
66 Piping (outflow means)
67 Metering valve (outflow means)
68 Piping (inflow means)
69 Constant supply valve (inflow means)
80 Power supply device 100 Etching device (manufacturing device)

Claims

In performing AC etching in a batch manner by arranging one or more electrodes and one or more aluminum plates facing at least one surface of the electrodes in an etching solution stored in an etching tank of a bottomed wall,
With respect to the channel space sandwiched between the electrode and the aluminum plate, an etchant having an aluminum ion concentration lower than the etchant from the lower side to the upper side of the channel space is expressed by the following condition 0.002 m / s ≤ Flow velocity v ≤ 0.015m / s
v = Q ÷ S
v: Flow velocity S: Cross-sectional area of the channel space Q: Supply an etching solution to the channel space at a unit time per unit time, and form an etching layer with a depth of 70 μm or more per side on the aluminum plate. The manufacturing method of the aluminum electrode plate for electrolytic capacitors characterized by these.
The flow velocity v is as follows: 0.004 m / s ≦ flow velocity v ≦ 0.010 m / s
The manufacturing method of the aluminum electrode plate for electrolytic capacitors of Claim 1 characterized by the above-mentioned.
2. The etching solution supplied to the flow path space is a mixture of an etching solution overflowing from the etching tank and an etching solution having a lower aluminum ion concentration than the etching solution. The manufacturing method of the aluminum electrode plate for electrolytic capacitors as described in any one of.
The etching solution supply port for supplying the etching solution toward the channel space sandwiched between the aluminum plate and the electrode is provided in a bottom wall portion of the etching tank. 4. The method for producing an aluminum electrode plate for electrolytic capacitors according to any one of 3.