JP2006332157A - Aluminum foil for electrolytic capacitor electrode and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide aluminum foil for electrolytic capacitor electrode, in which defect distribution in an oxide film is uniform, dispersibility of bits is sufficient, invalid dissolution on a material surface is little and improved electrostatic capacity can be obtained. <P>SOLUTION: Aluminum foil comprises 0.1 to 2.0 ppm of Pb. Ratio P/O of phosphorous detection strength and oxygen detection strength on a surface of aluminum foil, which is measured by fluorescent X ray emission spectrum analysis, is 1.5 to 3.0 after last annealing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides an aluminum foil for electrolytic capacitor electrodes having increased capacitance and a method for producing the same.

  Along with the downsizing of electronic components, there is a demand for improved capacitance for the aluminum foil for electrolytic capacitor electrodes incorporated in electronic components. To increase the surface area after etching the aluminum foil for electrolytic capacitor electrodes Many attempts have been made.

  In order to increase the surface area after etching, it is effective to improve pit dispersibility (reduction of pits that become coalesced and become ineffective dissolution), suppress surface dissolution, make the pit length uniform, etc. Many attempts have been made, including optimization, improvement of dispersibility of crystalline oxides, and addition of pit starting points by sputtering and printing, but due to technical and cost problems, application to mass-produced materials has progressed. The current situation is not.

  The inventors have studied the chemical treatment before final annealing as a technique that can be industrially mass-produced and can simultaneously achieve improvement in pit dispersibility and suppression of surface dissolution. In order to improve the pit dispersibility, it is only necessary to dissolve and remove the uneven oxide film on the surface of the material after the foil rolling. The surface strain that promotes the preferential growth of the (100) orientation introduced in (1) is removed, and coarse different orientation crystal grains are formed after the final annealing.

  In order to solve this problem, the inventors include a metal ion that is more noble than aluminum in a strong alkali and preferentially deposits the metal ion on the surface of the material, thereby changing the dissolution form from full dissolution to local dissolution. Although a technique (Japanese Patent Application No. 2003-124800) has been found, it requires a neutralization treatment to remove metal ions deposited on the surface of the material, which is difficult in terms of cost.

In addition, in order to remove the contaminated layer and the non-homogeneous oxide film after cold rolling to form a stable homogeneous surface oxide layer and obtain an aluminum foil with excellent etching characteristics, the aluminum foil after foil rolling Has been proposed (see Patent Document 1), in which a method of treating the substrate with an acid solution containing one or more acids including sulfuric acid, hydrochloric acid, and phosphorus element, and then annealing is proposed. is not.
JP 2005-15916 A

  As a result of further testing and investigation on the technique for improving the etching characteristics, the inventors have used an aluminum foil containing Pb and applied an acid treatment with a phosphoric acid solution so that the surface of the aluminum foil is not uniform. It has been found that by removing the oxide film, generating a specific amount of phosphorus-containing film on the surface, and further specifying the annealing conditions, it is possible to reliably improve the characteristics.

  The present invention has been made on the basis of the above knowledge, and the purpose thereof is to improve the uniformity of defect distribution in the oxide film, good pit dispersibility, less ineffective dissolution of the material surface, and the like. An object of the present invention is to provide an aluminum foil for an electrolytic capacitor electrode and a method for producing the same, which can obtain a capacitance.

  An aluminum foil for an electrolytic capacitor electrode according to claim 1 for achieving the above object is an aluminum foil containing Pb: 0.1 to 2.0 ppm, which is analyzed by fluorescent X-ray emission spectroscopy after final annealing. The ratio P / O of the measured phosphorus detection intensity and oxygen detection intensity on the surface of the aluminum foil is 1.5 to 3.0.

The method for producing an aluminum foil for an electrolytic capacitor electrode according to claim 2 comprises contacting an aluminum foil containing Pb: 0.1 to 2.0 ppm after foil rolling with a phosphoric acid solution having a concentration of 1 to 5%, After the surface of the steel was treated so that the dissolution loss ΔW was 0.03 to 0.30 g / m ^2, it was annealed in an inert gas atmosphere at a temperature of 510 to 570 ° C. and measured by fluorescent X-ray emission spectrometry. A ratio P / O of phosphorus detection intensity and oxygen detection intensity on the surface of the aluminum foil is set to 1.5 to 3.0.

  The method for producing an aluminum foil for electrolytic capacitor electrodes according to claim 3 is characterized in that, in claim 2, contact is made with a phosphoric acid solution having a concentration of 1 to 5% and a temperature of 20 to 80 ° C. for 1 to 30 seconds.

  According to the present invention, by contacting the surface of the hard aluminum foil produced by the processes consisting of hot rolling → cold rolling → intermediate annealing → addition rolling with a phosphoric acid solution having a specific concentration before final annealing, When the surface layer portion of the material containing the non-uniform oxide film generated in the previous step is dissolved and removed to form a uniform phosphorus-containing film, and then the final annealing is performed in a vacuum or in an inert gas atmosphere, the (100) surface becomes While accumulating at a high density, the lead added to the material is concentrated on the surface and defects are uniformly introduced into the oxide film.

  As a result, the aluminum foil for electrolytic capacitor electrodes manufactured according to the present invention has a uniform defect distribution in the oxide film, good pit dispersibility, and the phosphorus-containing film formed on the surface of the material is in the initial stage of DC etching. In order to suppress surface dissolution, there is little ineffective dissolution on the surface of the material, and electrostatic capacity and bending strength are improved simultaneously.

  In the present invention, an aluminum foil containing Pb: 0.1 to 2.0 ppm is used. If Pb is less than 0.1 ppm, the surface concentration of Pb by the final annealing becomes non-uniform, and an unetched portion is generated after DC etching, resulting in a decrease in capacitance. If Pb exceeds 2.0 ppm, the surface concentration of Pb due to the final annealing increases, so that surface dissolution occurs in the initial stage of DC etching, and tunnel pits extending in the direction perpendicular to the foil thickness decrease, resulting in a decrease in capacitance. A more preferable content range of Pb is 0.3 to 0.8 ppm.

  The aluminum foil can contain Si: 5 to 60 ppm and Fe: 5 to 60 ppm as other components, or can further contain Cu: 30 to 80 ppm. Si and Fe are inevitable impurities of aluminum, but if Si and Fe are less than 5 ppm, coarse grains may be generated. If it exceeds 60 ppm, different orientation crystal grains grow and the (100) plane occupancy tends to decrease. Become.

  Cu has an effect of increasing the pit length, but if it is less than 30 ppm, the effect is not sufficient, and if it exceeds 80 ppm, accumulation of the (100) plane is inhibited. A more preferable content range of Cu is 40 to 60 ppm.

  The aluminum foil according to the present invention is characterized in that, after the final annealing, the ratio P / O of the phosphorus detection intensity and the oxygen detection intensity on the surface of the aluminum foil measured by fluorescent X-ray emission spectrometry is 1.5 to 3.0. And The ratio P / O between the phosphorus detection intensity and the oxygen detection intensity is an index indicating the degree of generation of the phosphorus-containing film. When the P / O is less than 1.5, the amount of phosphorus-containing film generated is small, so the initial stage of DC etching When the P / O exceeds 3.0, the generated phosphorus-containing coating becomes non-uniform and the number of coarse defects in the coating increases, resulting in a capacity improvement effect. Disappear.

The aluminum foil for electrolytic capacitor electrodes of the present invention is manufactured by hot rolling, cold rolling, intermediate annealing, foil rolling, aluminum degreasing in accordance with a conventional method, followed by alkali degreasing, followed by concentration. Contact with 1-5% phosphoric acid solution, treat aluminum foil surface so that dissolution loss ΔW is 0.03 to 0.30 g / m ² , wash with water, dry, then in inert gas atmosphere The ratio P / O of the phosphorus detection intensity and the oxygen detection intensity on the aluminum foil surface measured by fluorescent X-ray emission spectroscopic analysis is 1.5 to 3.0, which is performed by annealing at a temperature of 510 to 570 ° C. To do.

If the loss of dissolution ΔW due to the phosphorus-containing film generation treatment performed before the final annealing is less than 0.03 g / m ² , the uneven oxide film generated in the previous process is not sufficiently removed, and uniform pit dispersibility is obtained. Therefore, the capacity improvement effect is small. Further, if ΔW exceeds 0.30 g / m ² , the surface strain that promotes the preferential growth of the (100) orientation introduced in the foil rolling is removed, and coarse different orientation crystal grains are generated after the final annealing. This is inappropriate for electrolytic capacitor electrodes.

  In the phosphorous-containing film production treatment, if the phosphoric acid concentration is less than 1%, the amount of the phosphorous-containing film produced is small and the effect is insufficient. If the phosphoric acid concentration exceeds 5%, the produced phosphorous-containing film becomes non-uniform. As a result, the number of coarse defects in the film increases, and the effect of improving the capacity cannot be obtained. In the above P / O range, the produced phosphorus-containing film becomes dense, and the effects of improving pit dispersibility and suppressing surface dissolution can be obtained at the same time.

  The phosphorus-containing film generation treatment is preferably performed in contact with a phosphoric acid solution having a phosphoric acid concentration of 1 to 5% and a liquid temperature of 20 to 80 ° C. for 1 to 30 seconds. The alkali degreasing and phosphorus-containing film generation treatment is a spray treatment, and the alkaline degreasing → water washing → phosphorus-containing film formation treatment → water washing → drying is followed by mass production without significant cost increase. It becomes possible to do.

  The final annealing conditions are preferably performed in an inert gas atmosphere at a temperature range of 510 to 570 ° C. for 1 to 60 hours. If the temperature is less than 510 ° C. or less than 1 hour, the Pb surface concentration is small, so the number of pits is reduced. In addition, the capacitance decreases. In addition, if the treatment is performed at a temperature exceeding 570 ° C. or a time exceeding 60 hours, the foil surface is strongly peeled when annealed in a coil state, and the oxide film is destroyed when peeled off. Decreases.

  In the present invention, the non-uniform oxide film that causes the concentration of pits is dissolved and removed by the phosphorus-containing film generation treatment, and the ratio P / O of phosphorus detection intensity to oxygen detection intensity is set to 1.5-3. A dense phosphorus-containing film having a density of 0 is generated to suppress surface dissolution during DC etching, pit dispersibility is improved by Pb concentration, and an increase in capacitance is achieved by a synergistic effect thereof.

  Examples of the present invention will be described below in comparison with comparative examples, and the effects of the present invention will be demonstrated. In addition, these Examples show one embodiment of this invention, and this invention is not limited to these.

Examples and Comparative Examples After using an aluminum ingot containing Pb in the amount shown in Table 1 to form a hard foil having a thickness of 110 μm according to a conventional method, a continuous spray washer (nozzle flow rate 10 L / min) was used. Then, alkaline degreasing (liquid temperature of 65 ° C. for 5 seconds) → water washing (at room temperature for 5 seconds) → phosphorus-containing film formation treatment (see Table 1 for conditions) → water washing (at room temperature for 5 seconds) was performed. During the above steps, the loss on dissolution ΔW (g / m ² ) on the surface of the aluminum foil after the phosphorus-containing film formation treatment was measured from the weight difference before and after the treatment. In addition, although the board after a process also has the increase by a phosphorus containing film production | generation, it was set as the weight after a process including this.

Next, final annealing was performed in an argon gas atmosphere at the temperature and time shown in Table 1, and the obtained foil material was mixed with a mixed acid solution of hydrochloric acid 1 mol / L and sulfuric acid 3 mol / L at a liquid temperature of 85 ° C. and a current. Etching was performed for 480 seconds under the condition of a density of 25 A / dm ² , and then it was converted to 200 V in a boric acid solution, and the capacitance was measured. The measurement results are shown in Table 1.

  Moreover, about the foil material after chemical conversion, P / O of the foil surface was measured by the fluorescent X ray emission spectroscopic analysis. Fluorescence X-ray emission spectroscopic analysis was performed by RIX-3100 manufactured by RIGAKU in a vacuum atmosphere using a Rh tube under a condition of 30 kV-130 mA. The measurement results are shown in Table 1.

  As can be seen from Table 1, all of Examples 1 to 4 according to the present invention have excellent capacitance exceeding 100% when the capacitance of Comparative Example 1 without phosphorus-containing film generation treatment is 100%. The value is shown.

  On the other hand, all of Comparative Examples 1 to 11 that deviated from the conditions of the present invention had a capacitance value of less than 100%. Comparative Example 1 does not perform the phosphorus-containing film generation process, and is used as a reference j for comparing capacitances. Since Comparative Example 2 has a low Pb content, an unetched portion was generated during etching, and Comparative Example 3 had a high Pb content, resulting in surface dissolution during etching, both of which were inferior in capacitance. .

  In Comparative Example 4, since the phosphoric acid concentration is low in the phosphorous-containing film treatment, the dissolution loss is small and the uneven oxide film is not sufficiently removed, and the P / O value is small and the amount of the phosphorous-containing film produced is small. , Capacitance is inferior. In Comparative Example 5, since the phosphoric acid concentration was high, the produced phosphorus-containing film was non-uniform and the number of coarse defects in the film increased, resulting in inferior capacitance.

  In Comparative Example 6, the liquid temperature in the phosphorus-containing film generation treatment was low, and as a result, the loss on dissolution (ΔW) was small. Therefore, the uneven oxide film was not sufficiently removed, and the P / O value was small and phosphorus was low. The production amount of the contained film is also reduced and the capacitance is inferior. In Comparative Example 7, the liquid temperature in the phosphorus-containing film generation treatment was high, and as a result, the dissolution weight loss increased. Therefore, the generated phosphorus-containing film became non-uniform, resulting in an increase in coarse defects in the film and poor capacitance.

  Comparative Example 8 has a short treatment time in the phosphorus-containing film generation treatment, resulting in a decrease in dissolution loss, and Comparative Example 9 has a long treatment time in the phosphorus-containing film production treatment, resulting in an increase in dissolution loss. Similarly, the capacitance was inferior.

  In Comparative Example 10, since the final annealing temperature is low, the surface concentration of Pb is small, the number of pits generated is reduced, and the capacitance is lowered. In Comparative Example 11, since the final annealing temperature is high, the flaking of the foil surface becomes strong, and the oxide film is destroyed when peeled, resulting in a decrease in capacitance.

Claims (3)

Pb: an aluminum foil containing 0.1 to 2.0 ppm, and the ratio P / O of the phosphorus detection intensity and the oxygen detection intensity on the aluminum foil surface measured by fluorescent X-ray emission spectrometry after the final annealing is 1 An aluminum foil for electrolytic capacitor electrodes, characterized in that it is .5 to 3.0. Pb after foil rolling: An aluminum foil containing 0.1 to 2.0 ppm is brought into contact with a phosphoric acid solution having a concentration of 1 to 5%, and the surface of the aluminum foil has a dissolution loss ΔW of 0.03 to 0.30 g / After the treatment to m ² , the ratio of phosphorus detection intensity and oxygen detection intensity on the aluminum foil surface measured by fluorescent X-ray emission spectroscopic analysis was annealed at a temperature of 510 to 570 ° C. in an inert gas atmosphere P / The manufacturing method of the aluminum foil for electrolytic capacitor electrodes characterized by making O into 1.5-3.0. The method for producing an aluminum foil for an electrolytic capacitor electrode according to claim 2, wherein the aluminum foil for electrolytic capacitor electrodes is brought into contact with a phosphoric acid solution having a concentration of 1 to 5% and a temperature of 20 to 80 ° C for 1 to 30 seconds.