JP2007299916A - Manufacturing method of electrode foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode foil for an aluminum electrolytic capacitor which improves water resistance of the electrode foil. <P>SOLUTION: In the manufacturing method of the electrode foil for the electrolytic capacitor including an anodic oxidation process which forms an oxide film on an etched aluminum foil by anodic oxidation, the aluminum foil is immersed in phosphorus processing liquid including condensed phosphoric acid and/or condensed phosphate after or in the course of the anodic oxidation process, wherein in the phosphorus processing liquid, only the condensed phosphoric acid and/or the condensed phosphate may be blended, but moreover, orthophosphoric acid and/or orthophosphate may be blended. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an electrode foil for electrolytic capacitors, and particularly relates to a low-pressure electrode foil.

In an aluminum electrolytic capacitor, when water is mixed in the driving electrolyte and the specific resistance of the electrolyte is reduced, the electrode foil is required to have more water resistance. Therefore, conventionally, in the final step of chemical conversion treatment, immersion in an acidic solution is performed to increase the water resistance of the anodized film (for example, see Non-Patent Document 1).
By Nagata Isaya, “Electrolyte Cathode Aluminum Electrolytic Capacitor”, Nippon Electric Storage Industrial Co., Ltd., February 24, 1997, P311-319

Today, with the miniaturization and thinning of electronic devices, there is an increasing demand for miniaturization of aluminum electrolytic capacitors. Further, a capacitor having a low series equivalent resistance is required. Therefore, a large amount of water is blended in the electrolytic solution to reduce the specific resistance of the electrolytic solution, and accordingly, higher water resistance is required for the electrode foil.
However, in order to further reduce the equivalent series resistance, there is a problem that the water resistance of the anodized film is insufficient in the conventional method.

  In view of the above problems, an object of the present invention is to provide a method for producing an electrode foil for an electrolytic capacitor that can further improve the water resistance of the electrode foil.

  In order to solve the above-mentioned problems, in the present invention, in the method for producing an electrode foil for an electrolytic capacitor having an anodizing step of forming an oxide film by anodic oxidation on an etched aluminum foil, or after the anodizing step, In the middle of the anodizing step, the aluminum foil is immersed in a phosphorus treatment solution containing condensed phosphoric acid and / or condensed phosphate.

In the present invention, examples of the condensed phosphoric acid include pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, hexametaphosphoric acid, and the like, and examples of the condensed phosphate include sodium pyrophosphate (Na ₄ P ₂ O ₇ ), acidic pyrroline. Sodium phosphate (Na ₂ H ₂ P ₂ O ₇ ), sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ), sodium tetrapolyphosphate (Na ₆ P ₄ O ₁₃ ), sodium hexametaphosphate ((NaPO ₃ ) _n ), acidic sodium hexametaphosphate _{({Na x H y (PO} 3) x + y} n) , and the like.

  In the present invention, the phosphoric treatment solution has a configuration in which at least one of, for example, metaphosphoric acid, sodium metaphosphate, or potassium metaphosphate is blended as the condensed phosphoric acid or the condensed phosphate. can do.

  In this invention, it is preferable that the total compounding quantity of the said condensed phosphoric acid or / and the said condensed phosphate in the said phosphorus treatment liquid is 5.0-50 g / L.

  In the present invention, it is preferable that orthophosphoric acid and / or orthophosphate is further added to the phosphating solution. In this case, the total amount of the condensed phosphoric acid or / and the condensed phosphate in the phosphorus treatment solution is 20 to 50 g / L, and the orthophosphoric acid and / or the orthophosphoric acid in the phosphorus treatment solution It is preferable that the total amount of the salt is 1.5 to 7.5 g / L.

In the present invention, after the anodizing step or during the anodizing step, the aluminum foil is immersed in a phosphoric acid treatment solution containing condensed phosphoric acid or / and condensed phosphate, so that phosphoric acid is applied to the surface layer portion of the anodized film. The amount of adsorption increases. For this reason, the water resistance of the anodized film can be improved without reducing the capacitance.
Moreover, an unnecessary film | membrane can be removed by immersion in a phosphoric acid processing liquid, and an electrostatic capacity can also be aimed at. Therefore, it is possible to provide an electrolytic capacitor having a large electrostatic capacity and high temperature reliability even in a low-pressure small-sized product.

  Hereinafter, the present invention will be specifically described based on examples.

[Examples 1-7]
The etched aluminum foil was formed by applying a voltage at 85 ± 2 ° C. in a chemical solution containing 80 g / L ammonium adipate and 1.5 g / L adipic acid, and increasing the voltage to 22 V. Apply laminarization, re-chemical conversion, etc. (anodic oxidation process).

  Next, as shown in Table 1, immersion was performed at 25 ± 1 ° C. for 1 minute in a phosphorous treatment solution composed of an aqueous solution containing sodium hexametaphosphate (sodium metaphosphate) in respective weights, to form a chemical conversion foil (for electrolytic capacitors). Electrode foil) is obtained.

  In addition, as Comparative Examples 1, 2, and 3, a phosphoric acid treatment solution composed of an aqueous solution of phosphoric acid (orthophosphoric acid) (each weight is 1.5 g / l, 4.5 g / l, 7.5 g / l) is used. Immerse under the same conditions to obtain a chemical conversion foil.

Next, after measuring the film withstand voltage (Vt) of the chemical conversion foils of Examples 1 to 7 and Comparative Examples 1 to 3, the VT characteristics of the samples immersed in boiling pure water for 60 minutes (in the chemical conversion solution) Voltage-time characteristic when 1.0 mA / cm ^{2 was} applied), and a water resistance test for measuring the time until the Vt value was reached, and the capacitance was measured. The results are shown in Table 1.

  As can be seen from Table 1, for example, the aluminum electrode foil for electrolytic capacitors obtained under the conditions of Examples 2 to 6 had a Vt value as compared with Comparative Example 1 (blending amount of orthophosphoric acid 1.5 g / L). It can be seen that the arrival time until is reduced by 0.48 to 0.53 times, and the water resistance of the film is improved. Moreover, in the aluminum electrode foil for electrolytic capacitors obtained on the conditions of Examples 2-6, it turns out that an electrostatic capacitance is increasing.

  On the other hand, as in Comparative Examples 2 and 3, when the amount of orthophosphoric acid is 4.5 g / L and 7.5 g / L, the amount of phosphate radicals on the electrode foil surface layer is increased and the water resistance is improved. However, the capacitance is significantly reduced. Therefore, when both water resistance and electrostatic capacity are compared with Comparative Examples 2 and 3, it can be said that the amount of orthophosphoric acid is excellent under the conditions according to Examples 2 to 6 of the present invention.

In Example 1 where the amount of sodium hexametaphosphate was 1.0 g / L, the effect of improving water resistance was not sufficient, and in Example 7 where the amount of sodium hexametaphosphate was 70.0 g / L, Capacity is decreasing.
Therefore, the blending amount of sodium hexametaphosphate is preferably in the range of 5.0 to 50.0 g / L. According to this condition, the amount of phosphate in the surface layer portion can be increased 5.61 to 29.5 times. In addition, the capacitance can be improved.

[Examples 8 to 26]
In the same manner as in Examples 1 to 7, a voltage was applied to an etched aluminum foil at 85 ± 2 ° C. in a chemical solution in which ammonium adipate 80 g / L and adipic acid 1.5 g / L were dissolved. Then, the voltage is raised until formation, followed by depolarization, re-forming treatment, etc. (anodic oxidation step).

  Next, immersion was performed at 25 ± 1 ° C. for 1 minute in a phosphorous treatment solution comprising an aqueous solution containing sodium hexametaphosphate (sodium metaphosphate) and orthophosphoric acid having the addition amounts shown in Table 2 to form a chemical conversion foil (electrode foil for electrolytic capacitors) )

  Next, as in Examples 1 to 7, the chemical conversion foils of Examples 8 to 26 were immersed in boiling pure water for 60 minutes, and then subjected to VT characteristics (a low current was applied in the chemical conversion liquid). Voltage-time characteristics), and a water resistance test for measuring the time required to reach a predetermined voltage (Vt value), and the capacitance was measured. The results are shown in Table 2.

  In the results shown in Table 2, when both water resistance and capacitance are compared with the comparative examples, the addition amount of sodium hexametaphosphate and orthophosphoric acid is excellent in the conditions according to Examples 8 to 26 of the present invention. I can say that.

  Moreover, among each Example, the aluminum electrode foil for electrolytic capacitors obtained from the conditions of Examples 9-11, 14-16, 19-21 has a phosphate group amount of the surface layer part of 14.2-45.1 times. As compared with the conventional example, the time to reach the Vt value is reduced by 0.45 to 0.52 times, and the water resistance of the film is improved. Furthermore, an increase in capacitance is also observed.

On the other hand, in Examples 8, 13, and 18 in which the amount of sodium hexametaphosphate was 10 g / L, the water resistance of the film was improved, but a slight decrease in capacitance was also observed. Further, in Examples 12, 17, and 22 in which the amount of sodium hexametaphosphate was 70 g / L, a slight decrease in capacitance was observed.
Further, in Examples 23 to 26 in which the blending amount of orthophosphoric acid was 0.75 g / L and 10.5 g / L, the amount of phosphate radicals in the surface layer portion was increased, and the water resistance of the film was improved, but the capacitance There is also a decrease. Therefore, the blending amount of sodium hexametaphosphate is 20.0-50.0 g / L, and the blending amount of orthophosphoric acid is suitably in the range of 1.5-7.5 g / L.

In addition, although sodium hexametaphosphate was used as the said Example, even if it is not only a sodium salt but potassium salt, the same effect can be acquired. Moreover, in the said form, although hexametaphosphate was used as condensed phosphate, you may use pyrophosphate, acidic pyrophosphate, tripolyphosphate, tetrapolyphosphate, acidic hexametaphosphate, etc.
Furthermore, it may be blended in the state of condensed phosphoric acid instead of the condensed phosphate. Orthophosphoric acid may be added in the form of a salt.

  Further, in the above actual example, after the anodizing step, the aluminum foil was immersed in a phosphorus treatment solution containing condensed phosphoric acid or / and condensed phosphate, but in the middle of the anodizing step, the aluminum foil was You may immerse in the phosphorus treatment liquid containing condensed phosphoric acid or / and condensed phosphate.

  Furthermore, the electrolytic capacitor electrode foil to which the present invention is applied has improved water resistance and capacitance, so it is not limited to electrolytic capacitors in which moisture is mixed in the electrolytic solution, but to all electrolytic capacitors. Can be used.

Claims (5)

In the method of manufacturing an electrode foil for an electrolytic capacitor having an anodizing step of forming an oxide film by anodic oxidation on an etched aluminum foil,
A method for producing an electrode foil for an electrolytic capacitor, comprising immersing an aluminum foil in a phosphorus treatment solution containing condensed phosphoric acid or / and condensed phosphate after the anodizing step or during the anodizing step.   2. The phosphoric acid treatment liquid according to claim 1, wherein at least one of metaphosphoric acid, sodium metaphosphate, or potassium metaphosphate is blended as the condensed phosphoric acid or the condensed phosphate. The manufacturing method of the electrode foil for electrolytic capacitors of description.   3. The electrode for an electrolytic capacitor according to claim 1, wherein the total amount of the condensed phosphoric acid or / and the condensed phosphate in the phosphorus treatment solution is 5.0 to 50 g / L. 4. Foil manufacturing method.   The method for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein orthophosphoric acid and / or orthophosphate is further blended in the phosphorus treatment solution. The total amount of the condensed phosphoric acid or / and the condensed phosphate in the phosphorus treatment solution according to claim 4 is 20 to 50 g / L, and
The manufacturing method of the electrode foil for electrolytic capacitors characterized by the total compounding quantity of the said orthophosphoric acid or / and the said orthophosphate in the said phosphorus treatment liquid being 1.5-7.5 g / L.