JP3252313B2 - Etching method of aluminum foil for electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for etching an aluminum foil for an electrolytic capacitor.

[0002]

2. Description of the Related Art Generally, aluminum electrode foils for electrolytic capacitors are usually subjected to electrolytic etching and chemical etching alone or in combination for the purpose of increasing the effective surface area. In, tunnel-shaped pits penetrating the aluminum foil are formed in a direction perpendicular to the foil surface. Since ion conduction to the cathode foil is performed through the through pits, the foil can be used for a so-called double anode in which two foils are stacked. However, in the “penetration type” in which the penetration pits occupy the majority, there is a problem that the foil strength is low and the foil is cut off when winding the electrode foil as the capacitor element. On the other hand, a so-called "core remaining type" in which a "core" portion having no pit of about 5 to 20% of the thickness is left near the center of the thickness of the aluminum foil.
However, although there is no through pit, the mechanical strength is high, but there is a problem that it cannot be used for a double anode.
In order to further increase the effective surface area for miniaturization of the electrolytic capacitor, the number of tunnel-like pits due to etching must be increased, but the increase in the number of tunnel-like pits increases the amount of corrosion, This leads to a decrease in the mechanical strength of the foil. In particular, when the number of tunnel-like pits is increased in a “penetrating type” foil, the mechanical strength is significantly reduced. On the other hand, the "core-remaining type" foil has the advantage that the effective core area can be increased because the "core" portion remains, so that the mechanical strength decreases little and the number of tunnel-like pits can be easily increased. In order to maintain the mechanical strength of the foil while increasing the effective surface area, a method of forming a non-etched linear or band-shaped non-corroded portion on the surface of the foil has been conventionally proposed.

[0003]

However, the provision of linear or strip-shaped non-corroded portions has the disadvantage that the effective surface area is prevented from being increased accordingly. When the effective surface area is increased by increasing the amount of corrosion, the mechanical strength of the foil is reduced, so that the foil is brittle and fragile when used for chemical conversion. It is necessary to increase the radius of curvature for winding by increasing the diameter of the core, but when increasing the diameter of the winding core, useless space is created in the center of the capacitor element, and the volume of the capacitor relative to the capacitance is reduced. It has the disadvantage of low efficiency, and it has been extremely difficult to simultaneously resolve the conflicting effects of increasing the effective surface area and maintaining mechanical strength. Therefore, an object of the present invention is to solve the above-described conventional difficult problem.

[0004]

Means for Solving the Problems In the conventional penetration type aluminum electrode foil, a tunnel pit formed in order to increase the effective surface area is extended deeply until it penetrates the foil. Not all pits formed in the foil penetrate the foil, some of which extend beyond the center of the foil thickness but are non-penetrating. Also, the degree of penetration required for the double anode is not necessarily required to penetrate all the pits. If the number of penetration pits can be reduced, a decrease in mechanical strength can be prevented accordingly. When the number of through pits is extremely reduced, the degree of penetration may be deteriorated. In such a case, a method of providing a step of selectively increasing the thickness of only the through pits can maintain a sufficient degree of penetration. From these facts, in the etching method for manufacturing the through-type aluminum electrode foil, it has been devised to separately form the through pit and the non-through pit.

That is, the method of manufacturing an aluminum foil for an electrolytic capacitor according to the present invention comprises a first step of electrochemically etching with a direct current in an aqueous solution containing at least chlorine ions to form through pits. A second step of electrochemically etching with a direct current in an aqueous solution containing at least chloride ions and sulfate ions to form non-penetrating pits; A third step of enlarging the pits already formed by chemically or chemically etching the aluminum foil for an electrolytic capacitor, the method comprising the steps of: (a) forming a current density of 40 to 70 mA in the first step; / Cm
² , the quantity of electricity is 1.2 to 3.6 C / cm ² , and the liquid temperature is 65
８５85 ° C. or / and in the second step,
The current density of the etching is 250 to 350 mA / cm ² ,
Amount of electricity 12~24C / cm ^2, a liquid temperature of 65 to 85 ° C.
And / or when the third step is performed electrochemically, the current density is 10 to 300 mA / c
m ² , electricity amount 6-42 C / cm ² , liquid temperature 60-8
The temperature is 5 ° C., and when the third step is performed chemically, the liquid temperature is in the range of 60 to 85 ° C. and the etching time is in the range of 3 to 30 minutes.

[0006] Between the first step and the second step, the through pit formed in the first step is enlarged by electrochemically or chemically etching in an aqueous solution containing at least nitrate ions or chlorine ions. An additional intermediate step is provided.

[0007]

The embodiments of the present invention will be described below in detail.
In the first step, the concentration of chlorine ions in the aqueous solution is adjusted to 1
0 to 80 g / 1, the concentration of aluminum ions in the range of 1 to 5 g / 1, and the current density of 40 to 70 mA.
/ Cm ² , the liquid temperature is 65 to 85 ° C., and the quantity of electricity is 1.2 to 3.6 C / cm ² .

In the above, the chlorine ion concentration is 1
If it is less than 0 g / 1, the necessary number of through pits will not be generated, and if it exceeds 80 g / 1, the number of pits generated will be excessive. Therefore, a preferable range is 10 to 80 g / l. If the content is less than 1 g / 1, aluminum ions in the solution increase due to the dissolved aluminum, and the liquid component is not stable. If the content exceeds 5 g / 1, the number of pits decreases, so that the preferred range is 1 to 5
g / l is appropriate, and if the liquid temperature is lower than 65 ° C., the pits do not form a tunnel and thus do not penetrate.
If the temperature exceeds 100 ° C., the number of generated pits becomes excessive. Therefore, a preferable range is 65 to 85 ° C., and if the current density is less than 40 mA / cm ² , the number of generated pits is small, and 70 mA / cm ² is reduced. If it exceeds, the pits do not penetrate. Therefore, a preferable range is 40 to 70 mA / cm ² , and if the electric quantity is less than 1.2 C / cm ² , the number of pits generated is small and the pits do not penetrate.
If it is more than 3.6 C / cm ² , the number of penetrating pits becomes excessive. Therefore, a preferable range is 1.2 to 3.6 C / cm ^2.
Is appropriate.

Next, in the second step, the concentration of chloride ions in the aqueous solution is set in the range of 10 to 30 g / 1, the concentration of sulfate ions is set in the range of 350 to 500 g / 1, and the concentration of aluminum ions is set in the range of 5 to 20 g / 1. / 1, a current density of 250 to 350 mA / cm ² , and a liquid temperature of 65 to
The temperature is 85 ° C., and the amount of electricity is 12 to 24 C / cm ² .

In the above, the chlorine ion concentration is 1
If it is less than 0 g / 1, the required number of non-penetrating pits will not be generated, and if it exceeds 30 g / 1, the dissolution of the surface will proceed simultaneously with the formation of the pits and the capacity will be reduced. If the sulfate ion concentration is less than 350 g / 1, the pits penetrate, and if it exceeds 500 g / 1, the length of the pits becomes too short, and a larger effective surface area can be obtained. Therefore, the preferred range is 350 to 500 g / l. If the aluminum ion is less than 5 g / 1, the aluminum ion in the liquid increases due to the dissolved aluminum, and the liquid component is not stable. If it exceeds 20 g / 1, the number of pits decreases, so that a preferable range is 5 to 20 g / l. Pits not like a tunnel, 8
When the temperature exceeds 5 ° C., the length of the pit becomes short, and a larger effective surface area cannot be obtained.
85 ° C. is appropriate, and the current density is 250 mA / c.
If less than m ² pits will pass through, 350mA
If it exceeds / cm ² , formation of pits and dissolution of the surface proceed simultaneously to reduce the effective surface area. Therefore, the preferable range is 250 to 350 mA / cm ² , and the electric charge is less than 12 c / cm ² . If not, a sufficient number of pits cannot be obtained, and if it exceeds 24 C / cm ² , adjacent pits overlap, leading to a decrease in the effective surface area. Therefore, a preferable range is 12 to 24 C / c.
m ² is appropriate.

In the third step, the concentration of nitrate ions in the aqueous solution is set in the range of 100 to 200 g / l, and the concentration of aluminum ions is set in the range of 10 to 30 g / l. In the above description, if the amount of nitrate ion is less than 100 g / l, the effect of expanding the pit is small, and if it exceeds 200 g / l, the dissolution of the surface proceeds and the capacity is reduced. Therefore, a preferable range is 100 to 200 g / l. If the amount of aluminum ion is less than 10 g / l, the stability of dissolution is poor, and if it exceeds 30 g / l, the pit expansion ability is reduced. Therefore, the preferred range is 10 to 30 g / l. As another method, the concentration of chlorine ions in the aqueous solution is 10 to 30 g / l, and the concentration of aluminum ions is 5 to 20 g / l. In the above, when the chlorine ion is less than 10 g / l, the pit enlargement effect is small, and when it exceeds 30 g / l, the surface dissolution proceeds and the effective surface area is reduced.
g / l is suitable, and aluminum ion is 5 g / l
If it is less than 5 g, the dissolution stability is poor, and if it exceeds 20 g / l, the pit expansion ability is reduced.
-20 g / l is suitable. In the third step, when the liquid temperature is 60 to 85 ° C. electrochemically, the current density is 10 to 300 mA / cm ² , and the quantity of electricity is 6 to 42 C / c.
m ² , and when chemically performed, the etching time is 3 to 3
It is assumed to be 0 minutes. In the above, the liquid temperature is 60 ° C
If it is less than 85 ° C., the pit enlargement ability is low, and if it exceeds 85 ° C., the dissolution of the surface progresses.
~ 85 ° C is suitable. Further, in the case of performing electrochemically, if the current density is less than 10 mA / cm ² , the pit expansion effect is small, and if the current density exceeds 300 mA / cm ² , the dissolution of the surface progresses.
00 mA / cm ² is appropriate, and the amount of electricity is 6 C / c.
If it is less than m ² , the pit enlargement effect is small and 42 C / c
If it exceeds m ² , the pits become too large and the non-penetrating pits, which are effective in increasing the effective surface area, are reduced. Therefore, the preferable range is 6 to 42 C / cm ² . Further, in the case of performing chemically, if less than 3 minutes, the pit enlargement effect is small, and if more than 30 minutes, the pits are too large, which leads to a decrease in non-penetrating pits, which is effective in increasing the effective surface area. 3 to 30
Minutes are appropriate.

In an intermediate step added between the first step and the second step, the concentration of nitrate ions in the aqueous solution is adjusted to 10%.
The range is 0 to 200 g / 1, and the concentration of aluminum ion is 10 to 30 g / 1.

When the amount of nitrate is less than 100 g / 1, the effect of expanding the pit is small, and when it exceeds 200 g / 1, the dissolution of the surface proceeds to reduce the effective surface area.
l is suitable, and aluminum ion is 10 g /
If it is less than 1, the stability of dissolution will be poor, and if it exceeds 30 g / 1, the pit expanding ability will be poor. Therefore, a preferable range is 10 to 30 g / l.

As another method in the intermediate step added between the first step and the second step, the concentration of chloride ion in the aqueous solution is 10 to 30 g / 1, and the concentration of aluminum ion is 5 to 20 g / 1. And

In the above, if the chlorine ion is less than 10 g / 1, the pit enlargement effect is small, and if it exceeds 30 g / 1, the dissolution of the surface proceeds and the capacity is reduced, and a preferable range is 10 to 30 g. / L is appropriate, and if the amount of aluminum ion is less than 5 g / 1, the stability of dissolution is poor, and if it exceeds 20 g / 1, the pit expansion ability is reduced.
l is appropriate.

In the intermediate step added between the first step and the second step, the temperature of the solution is set to 60 to 85 ° C., and when electrochemically performed, the current density is set to 10 to 300 ° C.
mA / cm ² , the amount of electricity is 0.6 to 6 C / cm ^2, and when the intermediate step is performed chemically, the etching time is 3 to 1
0 minutes.

In the above description, if the liquid temperature is lower than 60 ° C., the pit expansion ability is low, and if the liquid temperature is higher than 85 ° C., the dissolution of the surface proceeds, and the preferable range is 60 to 85 ° C. In the case of performing electrochemically, if the current density is less than 10 mA / cm ² , the pit expansion effect is small, and if the current density exceeds 300 mA / cm ² , the dissolution of the surface progresses.
0 mA / cm ² is appropriate. The quantity of electricity is 0.6C /
If it is less than cm ² , the pit enlargement effect is small, and 6 C / c
If it exceeds m ² , the pits become too large, leading to a decrease in non-penetrating pits which are effective in increasing the effective surface area. Therefore, a preferable range is 0.6 to 6 C / cm ² .

In the case where the intermediate step is performed chemically, if the etching time is less than 3 minutes, the pit enlargement effect is small, and if the etching time is more than 10 minutes, the pits are too large and the effective surface area is not greatly increased. A range of 3 to 10 minutes is appropriate as a preferable range because it leads to a decrease in penetration pits.

Next, the method of etching an aluminum foil for an electrolytic capacitor of the present invention will be described in comparison with a conventional example.

(Embodiment 1) A thickness of 104 μm, O material, 4
An aluminum foil having an N, (100) plane occupation ratio of 90% was coated with chlorine ions at 65.0 g / 1 and aluminum ions at 2.4 g /.
After the first step of DC etching at a current density of 60 mA / cm ² , an amount of electricity of 3.6 C / cm ² , and a liquid temperature of 75 ° C. in an aqueous solution containing 1, 22 g of chlorine ions as a second step
/ 1, sulfate ion 435g / 1, aluminum ion 1
Current density 300mA / c in aqueous solution containing 4g / 1
DC etching at m ² , electricity 18 C / cm ² , liquid temperature 72 ° C., and as a third step 135 g of nitrate ions
/ 1, in an aqueous solution containing 18 g / 1 of aluminum ions at a liquid temperature of 75 ° C. for 10 minutes.

(Embodiment 2) 104 μm thick, O material, 4N
Example 1 Aluminum foil having 90% (100) plane occupancy
Current density 60 mA / c in the same aqueous solution as in the first step
After the first step of DC etching at m ² , an amount of electricity of 1.4 C / cm ² and a liquid temperature of 75 ° C., a liquid temperature of 75 ° C. in an aqueous solution containing 135 g / 1 of nitrate ions and 18 g / 1 of aluminum ions as an intermediate step. Chemical etching for 5 minutes.
Then, as a second step, a current density of 300 mA / cm ² and an electric quantity of 18 C in an aqueous solution containing 22 g of chlorine ion / 1, 435 g / 1 of sulfate ion, and 14 g / 1 of aluminum ion.
/ Cm ² and a DC temperature of 72 ° C.
Is chemically etched at a liquid temperature of 75 ° C. for 10 minutes in an aqueous solution containing 135 g / 1 of nitrate ions and 18 g / 1 of aluminum ions.

(Embodiment 3) 104 μm thick, 0 material, 4N
Example 1 Aluminum foil having 90% (100) plane occupancy
After DC etching at a current density of 60 mA / cm ² , an amount of electricity of 1.8 C / cm ² and a liquid temperature of 75 ° C. in the same liquid as in the first step, 15 g / l of chlorine ions and 18 g / l of aluminum ions were used as an intermediate step. Current density 15 in aqueous solution containing
mA / cm ² , electric quantity 1.8C / cm ² , liquid temperature 65 ° C
DC etching. Next, as a second step, a current density of 300 mA / cm is set in an aqueous solution containing 22 g / l of chloride ions, 435 g / l of sulfate ions, and 14 g / l of aluminum.
^2. After DC etching at an electric quantity of 18 C / cm ² and a liquid temperature of 72 ° C., as a third step, an aqueous solution containing 15 g / l of chlorine ions and 18 g / l of aluminum ions has a current density of 100 mA / cm ² and an electric quantity of 30 C / cm ² . cm ² , liquid temperature 6
DC etching at 5 ° C. (Conventional example) An aluminum foil having a thickness of 104 m, an O material, 4N, and a (100) plane occupation ratio of 90% was prepared by using the same liquid as in the second step of the first embodiment at a current density of 100 mA / cm ² and an electric quantity of 21.
DC etching was performed at 6 C / cm ^{2 at} a liquid temperature of 68 ° C., and the same chemical etching as in the third step of Example 1 was performed. Each of the aluminum foils etched in the above embodiment and the conventional example was formed into 350 V in a boric acid aqueous solution, and a certain amount of air was formed as a bending strength and a certain amount of air as a capacitance and a mechanical strength. The time required to pass through the area was measured by air permeability (the smaller the value, the better the degree of penetration). The results shown in Table 1 were obtained.

[Table 1]

As is clear from Table 1, Example 1 is superior to the conventional example in terms of bending strength, while having approximately the same capacitance and air permeability. In Examples 3 and 3, although there is no bending strength as in Example 1,
It is superior in bending strength and air permeability as compared with the conventional example, and demonstrates the effect of the present invention.

[0024]

According to the present invention, penetrating pits and non-penetrating pits, in other words, pits necessary for imparting penetrability to the electrode foil and pits having a large effect on increasing the effective surface area are separately formed. In order to prevent the formation of excessive through pits, it is possible to prevent a decrease in foil strength and to manufacture an aluminum foil for an electrolytic capacitor having a high mechanical strength. Can be provided.

Claims (8)

(57) [Claims] A first step of electrochemically etching with a direct current in an aqueous solution containing at least chloride ions to form through pits; and an aqueous solution containing at least chloride ions and sulfate ions. A second step of electrochemically etching with a direct current to form a non-penetrating pit; and electrochemically or chemically etching in an aqueous solution containing nitrate ions or chlorine ions to form already formed pits. In the method for etching an aluminum foil for an electrolytic capacitor, which includes a third step of enlarging the formed pits, in the first step, the etching current density is 40 to 70 mA / cm ² , and the amount of electricity is 1.2 to 3. 6C / cm ^2, a liquid temperature of 65 to 85 ° C., or / and in the second step, the current density of the etching 25 ~350mA / cm ^2, amount of electricity 1
^{2 to} 24 C / cm ² , the liquid temperature is 65 to 85 ° C., and / or when the third step is performed electrochemically, the current density is 10 to 300 mA / cm ² , and the quantity of electricity is 6 to 42 C / Cm ² , the liquid temperature is 60 to 85 ° C., and when the third step is performed chemically, the liquid temperature is 60 to 85 ° C.
An etching method for an aluminum foil for an electrolytic capacitor, wherein the etching time is in a range of from about 85 ° C to an etching time of from 3 to 30 minutes. 2. An intermediate step of electrochemically or chemically etching in an aqueous solution containing at least nitrate ions or chloride ions to enlarge a through pit between the first step and the second step. 2. The method for etching an aluminum foil for an electrolytic capacitor according to claim 1, further comprising the step of: 3. When the intermediate step is performed electrochemically, the liquid temperature is 60 to 85 ° C. and the current density is 10 to 300 m.
A / cm ^2, claim 2 electrolytic etching method of an aluminum foil for capacitor according to an electric amount in the range of 0.6~6C / cm ^2. 4. When the intermediate step is performed chemically,
3. The method for etching an aluminum foil for an electrolytic capacitor according to claim 2, wherein the liquid temperature is 60 to 85 [deg.] C. and the etching time is 3 to 10 minutes. 5. The method according to claim 1, wherein the electrolyte used in the first step contains at least 10 to 80 g / l of chloride ions and 1 to 5 g / l of aluminum ions.
The method for etching an aluminum foil for an electrolytic capacitor according to the above. 6. The electrolytic solution used in the second step is at least 10 to 30 g / l of chloride ions and 350 to 350 g of sulfate ions.
The method for etching an aluminum foil for an electrolytic capacitor according to any one of claims 1 to 5, comprising a range of 500 g / l and aluminum ions of 5 to 20 g / l. 7. In the third step, the aqueous solution contains at least 100 to 200 g / l of nitrate ions and 10 to 30 g / l of aluminum ions, or at least 10 to 30 g / l of chloride ions and 5 to 50 g of aluminum ions.
7. A method as claimed in claim 1, comprising a range of from 20 to 20 g / l.
The method for etching an aluminum foil for an electrolytic capacitor according to the above. 8. The aqueous solution used in the intermediate step contains at least 100 to 200 g / l of nitrate ions and 10 to 30 g / l of aluminum ions, or at least 10 to 30 g / l of chloride ions and 5 to 5 aluminum ions.
The method for etching an aluminum foil for an electrolytic capacitor according to any one of claims 2 to 7, wherein the method is any one of an aqueous solution containing 20 g / l.