Process for improving anodic oxidation consistency of anode foil for aluminum electrolytic capacitor

Abstract

The invention discloses a process for improving anodic oxidation consistency of an anode foil for an aluminum electrolytic capacitor, and relates to the technical field of capacitor manufacturing, and the process comprises the steps of multi-stage washing, etching, feeding, multi-stage formation, intermediate treatment, first post-treatment, roasting, second post-treatment, stability treatment, drying, rolling, inspection and packaging. Wherein the multi-stage formation adopts three-stage oxidation of low-temperature and low-current, medium-temperature and medium-current and low-temperature and high-current, so that an oxidation film forms a base layer, a growth layer and a high-density protection layer which are uniformly overlapped layer by layer, and the consistency and compactness of the oxidation film are synergistically improved through dynamic water washing, air drying and temperature field and fluid field regulation and control technologies; the oxide film is repaired through first post-treatment, the pore size of the oxide film is reduced, and the compactness of the oxide film is improved; and high-temperature roasting is combined, and a second post-treatment step is carried out, so that the oxidation film forms an aluminum oxide crystal structure which is stable, high in hardness and compact in structure, and the water resistance and reliability of the finished anode foil are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor manufacturing, and particularly relates to a process for improving the anodic oxidation uniformity of anodes for aluminum electrolytic capacitors. Background Art

[0002] Due to their high specific capacitance, excellent voltage resistance characteristics, and cost advantages, aluminum electrolytic capacitors have been widely used in fields such as consumer electronics, power management, automotive electronics, and industrial control. Among them, the anode foil, as a core component, directly affects the performance, reliability, and lifespan of the capacitor.

[0003] In the production process of aluminum electrolytic capacitors, the anode foil usually undergoes anodic oxidation treatment to form an oxide film with high dielectric strength on its surface. The quality of this oxide film (including thickness uniformity, compactness, etc.) plays a crucial role in the leakage current, voltage resistance characteristics, and stability of the capacitor. However, in actual mass production, after the anode foil is processed by the existing traditional anodic oxidation process, it is difficult to effectively control the uniformity of the surface oxide film thickness of the obtained anode foil, resulting in a large fluctuation in the uniformity of the anode foil oxide film thickness, leading to significant fluctuations in the electrical performance of the capacitor, and problems such as a reduction in the yield of aluminum electrolytic capacitors and poor capacitance stability.

[0004] Traditional anodic oxidation processes mainly improve the performance of the anode foil by adjusting the electrolyte formulation or controlling the current density. For example, a specific forming process is adopted, including steps such as pretreatment, primary forming, and phosphoric acid treatment, to form a uniform oxide film on the aluminum foil surface. However, these methods are difficult to ensure the uniformity of the oxide film thickness on a continuous production line, and the continuous production stability is low, resulting in large fluctuations in the capacitor performance and making it difficult to meet large-scale mass production requirements.

[0005] To solve the above problems, researchers have tried various improvement measures. For example, a sintering process is adopted, where an aluminum powder slurry is coated on the aluminum foil substrate and subjected to high-temperature sintering to form an anode foil with a three-dimensional porous structure, and then an anodic oxidation process is carried out. This method improves the specific capacitance and mechanical properties of the anode foil to a certain extent, but in large-scale industrial production, the combination of the sintering process and the anodic oxidation process has limitations such as complex processes and high costs, resulting in the loss of the cost advantage of aluminum electrolytic capacitors due to their wide application, which is contradictory to actual production.

[0006] With the growing market demand for high-performance and long-life capacitors, the development of an efficient, stable, and low-cost anodic oxidation process has become an urgent need in the industry. Therefore, researching a process that can improve the anodic oxidation uniformity of anodes for aluminum electrolytic capacitors has important practical significance and broad application prospects.

[0007] In summary, it is found that the prior art has at least the following technical problems:

[0008] The existing anodizing film-forming process has technical problems such as low thickness uniformity and low continuous production stability in large-scale production of anodized films of anode foil. Summary of the invention

[0009] The purpose of the present invention is to provide a process for improving the consistency of anodizing of anode foil for aluminum electrolytic capacitors, so as to solve the technical problems of low thickness uniformity and low continuous production stability of anodized films of anode foil in mass production in the existing anodizing film forming process.

[0010] The various technical effects that can be produced by the preferred technical solutions among the various technical solutions provided by the present invention are described in detail below.

[0011] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0012] The present invention provides a process for improving the anodizing consistency of anodizing foil for aluminum electrolytic capacitors, comprising the following steps: S1, multi-stage water washing: using high-purity aluminum foil, washing with an acidic or alkaline solution, neutralizing and washing with a neutralizer, washing with deionized water with multiple stages of heating, and finally drying with low-temperature drying air to form a clean aluminum foil;

[0013] S2, etching: chemically etching the clean aluminum foil to form a low-pressure etching foil;

[0014] S3, power feeding: the low-voltage corrosion foil is energized via a conductive roller, and a conductive liquid is sprayed with high-pressure atomization at a dynamic contact point between the conductive roller and the low-voltage corrosion foil;

[0015] S4, multi-stage formation: firstly, the first stage is formed at low temperature and low current, then the second stage is formed at medium temperature and medium current, and finally the third stage is formed at low temperature and high current; through the three-stage formation, a multi-layer oxide film is generated on the surface of the low-pressure corrosion foil to form a primary anode foil; dynamic water washing and air drying are required between the three stages;

[0016] During the detection, the temperature distribution and flow of the electrolyte in the electrolytic cell are measured by setting a temperature sensor and a fluid flow direction sensor, and the temperature field and fluid field of the electrolyte are analyzed; by setting an air pump gas unit and a propeller convection unit, the electrolyte is stirred and driven to flow, so that the components of the electrolyte are evenly mixed, the temperature in the temperature field of the electrolytic cell is uniform, and the flow rate in the fluid field is uniform;

[0017] S5, intermediate treatment: chemically treating the primary anode foil with a phosphoric acid solution to generate a water-resistant composite oxide film, thereby forming an intermediate treated anode foil;

[0018] S6. First post-treatment: Anodize the medium-treated anode foil at a medium temperature and high current to repair the composite oxide film on the surface of the medium-treated anode foil, increase the density of the composite oxide film, and form the first anode foil.

[0019] S7. Calcination treatment: Perform high-temperature treatment on the first anode foil to convert the crystals of the composite oxide film into α-Al2O3 type, improve the density of the composite oxide film, and form the calcined anode foil.

[0020] S8. Second post-treatment: Chemically treat the calcined anode foil with a phosphoric acid solution to regenerate a water-resistant composite oxide film and form the second anode foil.

[0021] S9. Stability treatment: Neutralize and wash the second anode foil with a neutralizing agent, and wash it with warm deionized water in multiple stages to form the final-treated anode foil.

[0022] S10. Drying: Dry the final-treated anode foil to form the finished anode foil.

[0023] S11. Rewinding;

[0024] S12. Inspection and packaging.

[0025] In one of the embodiments, the multi-stage water washing step of S1 includes:

[0026] S1.1. Deionized water heating and cleaning: Immerse the high-purity aluminum foil in deionized water at a temperature of 50 - 60°C, apply ultrasonic vibration, and continuously clean for 3 - 5 minutes.

[0027] S1.2. Acidic or alkaline solution cleaning: Use a sulfuric acid solution with a mass fraction of 5 - 10% or a sodium hydroxide solution with a mass fraction of 5 - 8% to clean the high-purity aluminum foil at room temperature for 5 - 8 minutes.

[0028] S1.3. Neutralizing agent washing: Use a sodium bicarbonate solution or ammonia water solution with a mass fraction of 3 - 5% to wash the high-purity aluminum foil at room temperature for at least 3 minutes.

[0029] S1.4. Ethanol washing: Use an ethanol solution with a volume fraction of 70 - 80% to soak the high-purity aluminum foil at room temperature for 2 - 3 minutes.

[0030] S1.5. Low-temperature and dry air drying: In a clean environment, use dry air at a temperature of 25 - 35°C and a wind speed of 3 - 5 m / s to dry the high-purity aluminum foil until there is no water trace on the surface, forming a clean aluminum foil.

[0031] In one embodiment, in step S3, a conductive liquid is sprayed between the conductive roller and the low-voltage etched foil to reduce the contact impedance between the low-voltage etched foil and the conductive roller and improve the power reception uniformity of the low-voltage etched foil.

[0032] In one embodiment, a silver coating is plated on the conductive roller, and the silver coating contacts the low-voltage etched foil to reduce the contact impedance between the conductive roller and the low-voltage etched foil.

[0033] In one embodiment, the multi-stage forming step of S4 includes:

[0034] S4.1, the first-stage forming: at a forming temperature of 10 - 15 °C and a current density of 5 - 10 mA / cm 2 , using a maleic acid solution with a mass fraction of 5 - 10% as the forming solution, boosting the voltage to 50% of the target voltage, and maintaining a constant voltage for 10 - 15 minutes;

[0035] S4.2, the first dynamic water wash: rinsing the low-voltage etched foil that has completed step S4.1 with deionized water at a water temperature of 40 - 50 °C for 1 - 2 minutes;

[0036] S4.3, the second-stage forming: at a forming temperature of 60 - 70 °C and a current density of 10 - 20 mA / cm 2 , using a boric acid solution with a mass fraction of 10 - 15% as the forming solution, boosting the voltage to 80% of the target voltage, and maintaining a constant voltage for 20 - 25 minutes;

[0037] S4.4, the second dynamic water wash: rinsing the low-voltage etched foil that has completed step S4.3 with deionized water at a water temperature of 40 - 50 °C for 1 - 2 minutes;

[0038] S4.5, the third-stage forming: at a forming temperature of 25 - 30 °C and a current density of 20 - 30 mA / cm 2 , using an ammonium dihydrogen phosphate solution with a mass fraction of 5 - 10% as the forming solution, boosting the voltage to 100% of the target voltage, and maintaining a constant voltage for 5 - 10 minutes;

[0039] S4.6, the third dynamic water wash: rinsing the primary anode foil that has completed step S4.5 with deionized water at a water temperature of 40 - 50 °C for 1 - 2 minutes;

[0040] S4.7, dynamic air drying: in a clean environment, using dry air at a temperature of 25 - 35 °C to air dry the primary anode foil that has completed step S4.6 until there is no water trace on the surface.

[0041] In one embodiment, S5, intermediate treatment: Immerse the primary anode foil in a phosphoric acid solution with a mass fraction of 1-3%, and treat it at room temperature for 1-3 minutes to generate a water-resistant composite oxide film, forming the intermediate-treated anode foil;

[0042] After the intermediate treatment step of S5, it needs to be washed with water;

[0043] S5.1, washing: Use deionized water to wash the intermediate-treated anode foil at a water temperature of 40-50°C with a flow rate of 5-8 L / min for 3-5 minutes.

[0044] In one embodiment, S6, first post-treatment: At a formation temperature of 70-80°C and a current density of 15-25 mA / cm 2 Under the condition of using a boric acid solution with a mass fraction of 10-15% as the formation solution, perform anodic oxidation on the intermediate-treated anode foil, reduce the voltage to 60% of the target voltage, and keep the voltage constant for 30-40 minutes to form the first anode foil;

[0045] After the first post-treatment step of S6, it needs to be washed with water;

[0046] S6.1, washing: Use deionized water to wash the first anode foil at a water temperature of 40-50°C with a flow rate of 5-8 L / min for 3-5 minutes.

[0047] In one embodiment, the roasting treatment step of S7 includes:

[0048] S7.1, pre-roasting: Place the first anode foil in a nitrogen atmosphere, and increase the temperature to 300-350°C at a heating rate of 1-5°C / min, and keep the temperature for 30-1 hour;

[0049] S7.2, normal roasting: In the first stage, place the first anode foil in an argon atmosphere, and increase the temperature to 450-500°C at a heating rate of 5-10°C / min, and keep the temperature for 20-30 minutes;

[0050] In the second stage, increase the temperature of the first anode foil to 550-600°C at a heating rate of 2-5°C / min, and keep the temperature for 10-20 minutes;

[0051] S7.3, cooling: In the furnace, reduce the temperature of the first anode foil to 200-250°C at a cooling rate of 10-15°C / min, and then place it in the air atmosphere outside the furnace to cool naturally to room temperature, releasing the residual stress of the first anode foil treated in step S7.2 to form the roasted anode foil.

[0052] In one of the embodiments, S8, second post-treatment: immersing the baked anode foil in a phosphoric acid solution with a mass fraction of 1-3% at room temperature for 1-3 minutes to form the second anode foil.

[0053] In one embodiment, the stability processing step of S9 includes:

[0054] S9.1, neutralization treatment: immerse the second anode foil in a 5% by mass sodium hydroxide solution at room temperature, the solution temperature is 25-30° C., and treat for 3 minutes;

[0055] S9.2, deionized water cleaning: use deionized water at a temperature of 50° C. and a flow rate of 8 L / min to rinse the second anode foil after step S9.1 for 5 minutes to form the final treated anode foil.

[0056] The beneficial effects of the present invention are as follows:

[0057] The process for improving the anodic oxidation consistency of anode foil for aluminum electrolytic capacitors provided by the present invention proposes optimization measures to address the problems of poor uniformity of oxide film thickness and low continuous production stability in mass production of existing anodizing film-forming processes, thereby achieving a significant improvement in the quality of the oxide film of the anode foil.

[0058] First, through the multi-stage water washing step S1, impurities on the surface of the high-purity aluminum foil are effectively removed to improve the uniformity of subsequent anodization. Secondly, in the feeding step S3, high-pressure atomization is used to spray the conductive liquid to make the contact between the low-voltage corrosion foil and the conductive roller more stable, reducing the deviation of the oxide film thickness caused by uneven current distribution.

[0059] In the multi-stage formation step S4, a three-stage oxidation process of low temperature and low current, medium temperature and medium current, and low temperature and high current is adopted, combined with dynamic water washing and low temperature air drying, so that a multi-layered oxide layer is formed. The oxide layer formed by each oxidation formation step is superimposed layer by layer, and the uniformity of the oxide film at each location of the primary anode foil is controlled; and each oxidation step needs to be cleaned to avoid the formation liquid of the upward stage from remaining in the pores of the oxide film, to prevent the oxidation formation of the next stage from being affected, which is conducive to improving the uniformity of the next oxide layer generation, thereby improving the uniformity of the overall oxide film and effectively improving the structure of the oxide film. After the final dynamic water washing, the oxide film stress of the primary anode foil is gradually reduced by cooling and air drying, thereby improving the density and stability of the oxide film.

[0060] At the same time, temperature sensors and fluid flow direction sensors are set to monitor the temperature field and fluid field in the electrolytic cell, and the air pump aeration unit and propeller convection unit are used to promote the uniform distribution of the electrolyte, thereby ensuring the uniformity of the oxide film generated on the anode foil under a large-scale production environment and making the generation of the oxide film more uniform.

[0061] Subsequent intermediate treatment step S5, first post-treatment step S6, calcination treatment step S7, and second post-treatment step S8, through chemical treatment with phosphoric acid solution, secondary anodic oxidation, and high-temperature calcination, transform the composite oxide film from amorphous (non-crystalline) Al2O3, hydrated alumina film, and porous Al2O3 into γ'-Al2O3 gradually during the pre-calcination stage of the calcination treatment, then into γ-Al2O3 type in the first stage of normal calcination, and finally generate the α-Al2O3 type crystal with the tightest crystal structure in the second stage of normal calcination. During the cooling treatment, the residual stress of the first anode foil and the oxide film is gradually reduced; thereby significantly improving the water resistance, denseness, and stability of the oxide film, and further enhancing the reliability of the capacitor.

[0062] After the final stability treatment step S9 and drying step S10, the residual treatment liquid and substances of the second anode foil after the second post-treatment step S8 are further removed, and the stability of the oxide film is improved; the acidic residues on the surface of the oxide film of the second anode foil are reduced, the stability of the solid electrolyte in the capacitor is less affected, the performance of the capacitor is stabilized, and the excellent corrosion resistance and consistency of the anode foil during long-term use are ensured.

[0063] The process of the present invention not only optimizes the uniformity of the oxide film thickness, reduces the performance fluctuations of the capacitor, but also improves the stability and consistency of the production process, increases the product qualification rate of the aluminum electrolytic capacitor, and has important practical value for the large-scale industrial production of aluminum electrolytic capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0065] Figure 1 is one of the process flowcharts of the present invention;

[0066] Figure 2 is the second process flowchart of the present invention;

[0067] Figure 3 is the SEM image of the cross-sectional microstructure of the oxide film of the first anode foil after step S6 of the present invention;

[0068] Figure 4 is the SEM image of the surface microstructure of the oxide film of the second anode foil after step S8 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0069] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0070] A process for improving the anodic oxidation consistency of anodes for aluminum electrolytic capacitors is provided in the specific embodiments. The process includes steps of multi-stage water washing, etching, feeding electricity, multi-stage forming, intermediate treatment, first post-treatment, roasting, second post-treatment, stability treatment, drying, winding, inspection and packaging; among them, the multi-stage forming adopts three-stage oxidation of low temperature and low current - medium temperature and medium current - low temperature and high current, so that the oxide film forms a base layer, a growth layer and a high-density protective layer, and the layers are evenly stacked to improve the specific capacitance of the anode foil; and through dynamic water washing, air drying and temperature field and fluid field control technologies, the consistency and compactness of the oxide film are synergistically improved; and the oxide film is repaired through the first post-treatment to reduce the pore size of the oxide film and increase the compactness of the oxide film; combined with high-temperature roasting and through the second post-treatment step, the oxide film forms a stable, high-hardness and tightly-structured alumina crystal structure, enhancing the water resistance and reliability of the finished anode foil; effectively solving the technical problems that in the existing anodic oxidation film-forming process, under mass production, the anodic oxidation film of the anode foil has low thickness uniformity and low continuous production stability.

[0071] The first embodiment of the process for improving the anodic oxidation consistency of anodes for aluminum electrolytic capacitors is as Figure 1 shown, and includes the following steps: S1. Multi-stage water washing: Using high-purity aluminum foil, washing with an acidic or alkaline solution, neutralizing with a neutralizing agent, multi-stage warm water washing with deionized water, and finally air drying with low-temperature drying to form a clean aluminum foil;

[0072] S2. Etching: Chemically etching the clean aluminum foil to form a low-voltage etched foil;

[0073] S3. Feeding electricity: Passing electricity through the low-voltage etched foil by a conductive roller, and spraying a conductive liquid in a high-pressure atomized manner at the dynamic contact point between the conductive roller and the low-voltage etched foil;

[0074] S4. Multi-stage forming: First, perform the first-stage forming with low temperature and low current, then perform the second-stage forming with medium temperature and medium current, and finally perform the third-stage forming with low temperature and high current; through the three-stage forming, a multi-layer oxide film is generated on the surface of the low-voltage etched foil to form a primary anode foil; dynamic water washing and air drying are required between the three-stage forming;

[0075] During this period, by setting a temperature sensor and a fluid flow direction sensor, the temperature distribution and electrolyte flow in the electrolytic cell are measured, and the temperature field and fluid field of the electrolyte are analyzed; by setting an air pump gas-emitting unit and a propeller convection unit, the electrolyte flow is stirred and driven, so that the components of the electrolyte are evenly mixed, the temperature at each part of the temperature field in the electrolytic cell is uniform, and the flow velocity at each part of the fluid field is uniform;

[0076] S5, Intermediate Treatment: Chemically treat the primary anode foil with a phosphoric acid solution to generate a water-resistant composite oxide film, forming an intermediate-treated anode foil;

[0077] S6, First Post-treatment: Perform anodic oxidation on the intermediate-treated anode foil at medium temperature and high current to repair the composite oxide film on the surface of the intermediate-treated anode foil, increase the density of the composite oxide film, and form a first anode foil;

[0078] S7, Calcination Treatment: Perform high-temperature treatment on the first anode foil to convert the crystals of the composite oxide film into the α-Al2O3 type, improve the density of the composite oxide film, and form a calcined anode foil;

[0079] S8, Second Post-treatment: Chemically treat the calcined anode foil with a phosphoric acid solution to regenerate a water-resistant composite oxide film, forming a second anode foil;

[0080] S9, Stability Treatment: Neutralize and wash the second anode foil with a neutralizing agent, and wash it with warm deionized water in multiple stages to form a final-treated anode foil;

[0081] S10, Drying: Dry the final-treated anode foil to form a finished anode foil;

[0082] S11, Rewinding;

[0083] S12, Inspection and Packaging.

[0084] During application, in step S1, the high-purity aluminum foil used is a high-purity aluminum foil with an aluminum content of up to 99.999%, and the total impurity content is ≤10 ppm, which is suitable for high-voltage or high-reliability capacitors.

[0085] The low-voltage etched foil formed in step S2 has a specific capacitance of 0.8 - 1.2 μF / cm 2 .

[0086] In step S3, a conductive liquid is sprayed between the conductive roller and the low-voltage etched foil to reduce the contact impedance between the low-voltage etched foil and the conductive roller and improve the evenness of power reception of the low-voltage etched foil.

[0087] To improve the conductive effect and reduce the impedance, further, a silver coating is plated on the conductive roller, and the silver coating contacts the low-voltage etched foil to reduce the contact impedance between the conductive roller and the low-voltage etched foil.

[0088] During application, by spraying the conductive liquid and the silver coating, the contact impedance between the low-voltage etched foil and the conductive roller is reduced. Without having to increase the voltage, the current can be increased to a large extent, avoiding burning out the low-voltage etched foil due to excessive voltage during the formation process. At the same time, it can improve the evenness of heat shrinkage of the electrode foil during the anodic oxidation process, realizing the formation of a high-consistency and high-dielectric-constant oxide film and the toughness of the electrode foil.

[0089] Through the multi-stage formation in step S4 and the first post-treatment in S6, a multi-layer oxide layer is formed in step S4, which includes a hard, highly adhesive base layer with large pores, a growth layer with extremely small pores and extremely high density, and a high-density protective layer with medium pores, relatively hard texture and high density. Finally, the re-anodization in step S6 is treated with a densification formation to achieve multi-layer composite and density of the oxide layer, forming a uniform and dense oxide film, thereby improving the uniformity of the oxide layer of the anode foil, improving the consistency of the anode foil at various locations, and increasing the specific capacitance value.

[0090] Through the multi-stage water washing step S1, impurities on the surface of the high-purity aluminum foil are effectively removed, improving the uniformity of subsequent anodization. Secondly, in the feeding step S3, high-pressure atomization is used to spray the conductive liquid to make the contact between the low-voltage corrosion foil and the conductive roller more stable, reducing the deviation of the oxide film thickness caused by uneven current distribution.

[0091] In the multi-stage formation step S4, a three-stage oxidation process of low temperature and low current, medium temperature and medium current, and low temperature and high current is adopted, combined with dynamic water washing and low temperature air drying, so that a multi-layered oxide layer is formed. The oxide layer formed by each oxidation formation step is superimposed layer by layer, and the uniformity of the oxide film at each location of the primary anode foil is controlled; and each oxidation step needs to be cleaned to avoid the formation liquid of the upward stage from remaining in the pores of the oxide film, to prevent the oxidation formation of the next stage from being affected, which is conducive to improving the uniformity of the next oxide layer generation, thereby improving the uniformity of the overall oxide film and effectively improving the structure of the oxide film. After the final dynamic water washing, the oxide film stress of the primary anode foil is gradually reduced by cooling and air drying, thereby improving the density and stability of the oxide film.

[0092] At the same time, temperature sensors and fluid flow direction sensors are set to monitor the temperature field and fluid field in the electrolytic cell, and the air pump aeration unit and propeller convection unit are used to promote the uniform distribution of the electrolyte, thereby ensuring the uniformity of the oxide film generated on the anode foil under a large-scale production environment and making the generation of the oxide film more uniform.

[0093] The subsequent intermediate treatment step S5, the first post-treatment step S6, the roasting treatment step S7, and the second post-treatment step S8, through phosphoric acid solution chemical treatment, secondary anodization and high-temperature roasting, make the oxide film gradually transform from amorphous (non-crystalline) Al2O3, hydrated aluminum oxide film and porous Al2O3 into γ'-Al2O3 in the pre-burning stage of the roasting treatment, and then transform it into γ-Al2O3 type in the first stage of normal firing, and finally generate α-Al2O3 type crystals with the tightest crystal structure in the second stage of normal firing, and gradually reduce the residual stress of the first anode foil and the oxide film during the annealing treatment; thereby significantly improving the water resistance, density and stability of the oxide film, and thus improving the reliability of the capacitor.

[0094] After the final stability treatment step S9 and the drying step S10, the residual treatment liquid and substances of the second anode foil after the second post-treatment step S8 are further removed to improve the stability of the oxide film; the acidic residues on the surface of the oxide film of the second anode foil are reduced, the stability of the solid electrolyte in the capacitor is reduced, the performance of the capacitor is stabilized, and excellent corrosion resistance and consistency are ensured during the long-term use of the anode foil.

[0095] Therefore, through the process for improving the anodization consistency of the anode foil for aluminum electrolytic capacitors of the present invention, optimization measures are proposed for the problems of poor thickness uniformity of the oxide film and low stability in continuous production existing in the existing anodization film-forming process, and a significant improvement in the quality of the oxide film of the anode foil is achieved.

[0096] The process of the present invention not only optimizes the thickness uniformity of the oxide film, increases the specific capacitance, reduces the performance fluctuation of the capacitor, but also improves the stability and consistency of the production process, improves the product qualification rate of the aluminum electrolytic capacitor, and has important practical value for the large-scale industrial production of the aluminum electrolytic capacitor.

[0097] As an optional implementation mode

[0098] Regarding the specific cleaning steps of the multi-stage water washing in the above S1 step, in this embodiment Figure 2 As shown, S1.1, deionized water heating and cleaning: S1.1, immerse the high-purity aluminum foil in deionized water at a temperature of 50-60 °C, and apply ultrasonic vibration for continuous cleaning for 3-5 minutes; promote the removal of easily detachable impurities on the surface of the aluminum foil, so as to remove the easily detachable impurities on the high-purity aluminum foil;

[0099] S1.2, acidic or alkaline solution cleaning: Use sulfuric acid with a mass fraction of 5-10% or sodium hydroxide solution with a mass fraction of 5-8%, and clean the high-purity aluminum foil at room temperature for 5-8 minutes; by using an acidic or alkaline solution to wash the high-purity aluminum foil treated in step S1.1, the strongly adherent grease, impurities, and oxides can be removed, and the grease, impurities, and oxide layer attached to the surface of the high-purity aluminum and infiltrated into the shallow layer of the surface can be removed;

[0100] S1.3, neutralizing agent washing: Use sodium bicarbonate solution or ammonia water solution with a mass fraction of 3-5%, and wash the high-purity aluminum foil at room temperature for at least 3 minutes; by using sodium bicarbonate solution or ammonia water solution to wash the high-purity aluminum foil treated in step S1.2, the attached acidic or alkaline solution can be removed, and the residual acidic or alkaline substances can be neutralized;

[0101] S1.4, Ethanol washing: Use an ethanol solution with a volume fraction of 70 - 80%, and soak the high-purity aluminum foil at room temperature for 2 - 3 minutes. By washing the high-purity aluminum foil treated in step S1.3 with the ethanol solution, the neutralizing agent can be washed away, and the residual substances of the neutralizing agent can be removed.

[0102] S1.5, Low-temperature and dry air drying: In a clean environment, use dry air with a temperature of 25 - 35°C and a wind speed of 3 - 5 m / s to dry the high-purity aluminum foil until there is no water trace on the surface, forming a clean aluminum foil.

[0103] During application, the high-purity aluminum foil will adsorb grease, oxides, or form Al2O3 during rolling or storage, and it needs to be thoroughly removed by acid-base cleaning to avoid insufficient purity of the aluminum foil caused by the introduction of impurities and prevent oxide film defects caused by residual impurities.

[0104] In step S1.5, when drying, the dry air used is dry air with a relative humidity of 10 - 20%RH.

[0105] After drying experiment comparison:

[0106]

[0107] Among them, preferably, dry air with a relative humidity of 20%RH is used, and the drying time is set to at least 6 minutes to control the surface water content of the high-purity aluminum foil within an appropriate range and avoid the situation of generating static electricity.

[0108] Regarding the specific chemical conversion steps of the multi-stage chemical conversion in the above S4 step, this embodiment is as follows Figure 2 As shown, S4.1, First-stage chemical conversion: Under the conditions of a chemical conversion temperature of 10 - 15°C and a current density of 5 - 10 mA / cm2, use a maleic acid solution with a mass fraction of 5 - 10% as the chemical conversion solution, boost the voltage to 50% of the target voltage, and keep the voltage constant for 10 - 15 minutes. Low-temperature chemical conversion forms a hard and strongly adherent basic oxide layer with larger voids as the first layer of the oxide film.

[0109] S4.2, First dynamic water washing: Use deionized water to rinse the low-voltage etched foil completed in step S4.1 at a water temperature of 40 - 50°C for 1 - 2 minutes. Through the first dynamic water washing, the residues of the chemical conversion solution on the surface of the low-voltage etched foil and the oxidation substances that are not firmly combined with the metallic aluminum of the low-voltage etched foil can be removed.

[0110] S4.3, Second-stage formation: Under the conditions of a formation temperature of 60 - 70 °C and a current density of 10 - 20 mA / cm2, a boric acid solution with a mass fraction of 10 - 15% is used as the formation solution, the voltage is increased to 80% of the target voltage, and the constant voltage is maintained for 20 - 25 minutes; Medium-temperature and medium-current formation forms a growth oxide layer with extremely small pores and extremely high density. Due to the high density but relatively low hardness of the growth oxide layer, it adheres to the base oxide layer, which is the first layer of the oxide film, and can intertwine with the large pores of the base oxide layer, making the growth oxide layer and the base oxide layer have a tight structure, reducing the amount and rate of oxide shedding on the growth oxide layer in subsequent formation steps.

[0111] S4.4, Second dynamic water wash: Use deionized water to rinse the low-voltage etched foil that has completed step S4.3 at a water temperature of 40 - 50 °C for 1 - 2 minutes; Through the second dynamic water wash, the formation solution residues and oxidation substances that are not stably combined with the base oxide layer on the surface of the low-voltage etched foil after being treated in step S4.3 can be removed.

[0112] S4.5, Third-stage formation: Under the conditions of a formation temperature of 25 - 30 °C and a current density of 20 - 30 mA / cm2, an ammonium dihydrogen phosphate solution with a mass fraction of 5 - 10% is used as the formation solution, the voltage is increased to 100% of the target voltage, and the constant voltage is maintained for 5 - 10 minutes. Low-temperature and high-current formation forms a high-density protective layer with medium pores, relatively hard texture, high density, and strong adhesion, which can protect the oxides of the growth oxide layer and form an oxide film with a stable structure, uniform texture, and high consistency.

[0113] S4.6, Third dynamic water wash: Use deionized water to rinse the primary anode foil that has completed step S4.5 at a water temperature of 40 - 50 °C for 1 - 2 minutes; Through the third dynamic water wash, the formation solution residues and oxidation substances that are not stably combined with the growth oxide layer on the surface of the low-voltage etched foil after being treated in step S4.4 can be removed.

[0114] S4.7, Dynamic air drying: In a clean environment, use dry air with a temperature of 25 - 35 °C to air-dry the primary anode foil that has completed step S4.6 until there is no water trace on the surface.

[0115] In the above formation steps of S4.1, S4.3, and S4.5, the target voltage = the rated voltage of the capacitor × the safety margin coefficient; in steps S4 and S6, the safety margin coefficient is set to 1.3 - 1.5.

[0116] During application, through three-stage formation of low-temperature and low-current - medium-temperature and medium-current - low-temperature and high-current, combined with dynamic water wash between each stage of formation, uniform gradient growth of the oxide film is achieved, thus realizing high-quality growth of the oxide film in the main formation stage.

[0117] Regarding the specific processing steps of the intermediate treatment in the above-mentioned step S5, this embodiment is as follows Figure 2 As shown, S5. Intermediate treatment: Immerse the primary anode foil in a phosphoric acid solution with a mass fraction of 1-3%, and treat it at room temperature for 1-3 minutes to generate a water-resistant composite oxide film, forming an intermediate-treated anode foil;

[0118] After the intermediate treatment step of S5, it needs to be washed with water;

[0119] S5.1. Washing: Use deionized water to wash the intermediate-treated anode foil at a water temperature of 40-50°C with a flow rate of 5-8 L / min for 3-5 minutes; After washing in step S5.1, the residual substances of the phosphoric acid solution in the intermediate treatment can be removed, reducing the probability of defects in the oxide film in the subsequent first post-treatment.

[0120] Regarding the specific formation steps of the first post-treatment in the above-mentioned step S6, this embodiment is as follows Figure 2 As shown, S6. First post-treatment: Under the conditions of a formation temperature of 70-80°C and a current density of 15-25 mA / cm 2 , use a boric acid solution with a mass fraction of 10-15% as the formation solution to perform anodic oxidation on the intermediate-treated anode foil, reduce the voltage to 60% of the target voltage, and keep the voltage constant for 30-40 minutes to form the first anode foil;

[0121] After the first post-treatment step of S6, it needs to be washed with water;

[0122] S6.1. Washing: Use deionized water to wash the first anode foil at a water temperature of 40-50°C with a flow rate of 5-8 L / min for 3-5 minutes.

[0123] When in application, as Figure 3 shown, after the first post-treatment in step S6, the composite oxide film treated in S5 can be repaired, the amount of oxides in the oxide film can be increased, the density of the oxide film can be improved, the specific capacitance of the anode foil can be further improved, and at the same time, the bonding degree of the oxide layer in the oxide film is high and the structural stability is good.

[0124] Regarding the specific processing steps of the roasting treatment in the above-mentioned step S7, this embodiment is as follows Figure 2 As shown, S7.1. Pre-roasting: Place the first anode foil in a nitrogen atmosphere, and increase the temperature to 300-350°C at a heating rate of 1-5°C / min, and keep the temperature for 30-1 hour;

[0125] S7.2. Main roasting: In the first stage, place the first anode foil in an argon atmosphere, and increase the temperature to 450-500°C at a heating rate of 5-10°C / min, and keep the temperature for 20-30 minutes;

[0126] In the second stage, the temperature of the first anode foil is raised to 550 - 600 °C at a heating rate of 2 - 5 °C / min and held for 10 - 20 minutes.

[0127] S7.3, annealing: In the furnace, the temperature of the first anode foil is lowered to 200 - 250 °C at a cooling rate of 10 - 15 °C / min, and then it is placed in the air atmosphere outside the furnace and naturally cooled to room temperature to release the stress of the first anode foil treated in step S7.2, forming a calcined anode foil.

[0128] During application, through the calcination treatment step S7, the crystals of the composite oxide film treated in step S6 are gradually transformed from amorphous (non-crystalline) Al2O3, hydrated alumina film and porous Al2O3 into γ'-Al2O3 in the pre-calcination stage of the calcination treatment, then into γ-Al2O3 type in the first stage of normal calcination, and finally into the most closely packed α-Al2O3 type crystals in the second stage of normal calcination. The residual stress of the first anode foil and the oxide film is gradually reduced during the annealing treatment; thus, the water resistance, compactness and stability of the oxide film are significantly improved, and further the reliability of the capacitor is enhanced.

[0129] Regarding the specific treatment steps of the second post-treatment in the above step S8, this embodiment is as Figure 2 shown, S8, second post-treatment: At room temperature, the calcined anode foil is immersed in a phosphoric acid solution with a mass fraction of 1 - 3%, and treated for 1 - 3 minutes to form a second anode foil.

[0130] During application, after the calcination treatment in step S7, the unstable crystals of the oxide film are transformed into stable crystals, and then further treated with a phosphoric acid solution to generate a water-resistant composite oxide film on the surface of the oxide film with high stability, high uniformity and high consistency in combination with the oxide film, as Figure 4 shown; the amount of aluminum phosphate generated can hinder the migration of oxygen-containing substances (such as water) into it, so that porous aluminum hydroxide cannot be formed, thereby improving the water resistance of the oxide film. Finally, the anode foil obtains a composite oxide film with high reliability, and at the same time, the specific capacitance and production efficiency of the anode foil can also be improved.

[0131] Regarding the specific treatment steps of the second post-treatment in the above step S9, this embodiment is as Figure 2 shown, S9.1, neutralization treatment: At room temperature, the second anode foil is immersed in a sodium hydroxide solution with a mass fraction of 5%, the solution temperature is 25 - 30 °C, and treated for 3 minutes; by using a low-concentration alkaline solution, the acidic substances remaining on the surface of the second anode foil after the treatment in step S8 are neutralized and washed away, and at the same time, the aluminum phosphate formed in step S8 can also be avoided from being damaged.

[0132] S9.2, Deionized water cleaning: Use deionized water to rinse the second anode foil after step S9.1 at a water temperature of 50°C with a flow rate of 8 L / min for 5 minutes to remove the residual alkaline neutralizing solution and form the final treated anode foil.

[0133] During application, after the final stability treatment step S9 and the drying step S10, the residual treatment liquid and substances on the second anode foil after the second post-treatment step S8 are further removed to improve the stability of the oxide film; the acidic residues on the surface of the oxide film of the second anode foil are reduced, the stability of the solid electrolyte in the capacitor is less affected, the performance of the capacitor is stabilized, and the anode foil has excellent corrosion resistance and consistency during long-term use.

[0134] The performance of the anode foil for aluminum electrolytic capacitors prepared by the process for improving the anodization consistency of the anode foil for aluminum electrolytic capacitors according to the present invention has a certain improvement compared with the anode foil of the ordinary forming process. The specific performance is shown in Table 1 below. An experiment was conducted on the anode foil with a thickness of 80 μm, and the experimental parameters are shown in the following table:

[0135] Forming voltage (V) Withstand voltage value (V) <![CDATA[Specific capacitance (μF / cm 2 )]]> 30 31.2 78.22 60 61.8 23.65 90 92.3 8.73

[0136] The second embodiment of the process for improving the anodization consistency of the anode foil for aluminum electrolytic capacitors. The difference between this embodiment and the first embodiment is that the conductive liquid in step S3 can be: a 50 - 100 g / L sodium sulfate solution or a 5 - 15 g / L phosphoric acid solution, and 0.1 - 0.5% polyethylene glycol (PEG - 400) is added as a wetting agent.

[0137] During spraying, the atomization pressure is 0.2 - 0.4 MPa, the flow rate is 5 - 8 ml / min, and to avoid volatilization, the temperature of the conductive liquid is 25 - 35°C.

[0138] During application, when a conductive roller with a silver coating is in contact with the low - voltage etched foil, the impedance between the conductive roller and the low - voltage etched foil can be reduced, the current intensity can be increased, and the formation of oxides can be promoted.

[0139] The third embodiment of the process for improving the consistency of anodizing of anode foil for aluminum electrolytic capacitors is different from the first embodiment in that a plurality of temperature sensors and fluid flow direction sensors are provided; wherein a temperature sensor is provided every 20 cm along the length of the electrolytic cell, and the accuracy of measuring temperature is ±0.5°C; a fluid flow direction sensor is provided every 30 cm along the length of the electrolytic cell, and is arranged at one third of the depth of the electrolyte from top to bottom in the vertical direction; a plurality of air pump gas generating units and propeller convection units are provided; wherein the air pump gas generating units are provided along the length of the electrolytic cell. One propeller convection unit is arranged every 1m in the length direction of the electrolytic cell, and nitrogen is emitted at a flow rate of 0.1-0.3L / min. The bubble diameter is controlled at 1-2mm and is evenly distributed; one propeller convection unit is respectively arranged at both ends of the length direction of the electrolytic cell, and the two propeller convection units are respectively located on different sides of the electrolytic cell, and the jet directions are opposite to each other. The two propeller convection units are arranged at a height of one-third of the bottom of the electrolytic cell, and the rotation speed is controlled at 100-200 revolutions per minute. The flow rate of the chemical solution is controlled at 0.2-0.5m / s, so that the electrolyte forms a circulation in the cell.

[0140] On the plane, the aluminum foil is located and passes between the two propeller convection units.

[0141] When performing the multi-stage formation of step S4, each electrolytic cell is provided with a temperature sensor, a fluid flow direction sensor, an air pump venting unit and a propeller convection unit to stir and drive the electrolyte to flow, so that the components of the electrolyte are evenly mixed, the temperature of the temperature field in the electrolytic cell is uniform, and the flow rate of the fluid field is uniform, thereby promoting the uniformity and consistency of the oxide film formation of the aluminum foil.

[0142] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A process for improving the consistency of anodizing of anode foil for aluminum electrolytic capacitors, characterized in that: The following steps are involved: S1. Multi-stage water washing: Use high-purity aluminum foil, wash it with acidic or alkaline solution, neutralize it with a neutralizer, wash it with deionized water with warm water for multiple stages, and finally dry it with low-temperature drying air to form a clean aluminum foil; S2, etching: chemically etching the clean aluminum foil to form a low-pressure etching foil; S3, power feeding: the low-voltage corrosion foil is energized via a conductive roller, and a conductive liquid is sprayed with high-pressure atomization at a dynamic contact point between the conductive roller and the low-voltage corrosion foil; S4, multi-stage formation: firstly, the first stage is formed at low temperature and low current, then the second stage is formed at medium temperature and medium current, and finally the third stage is formed at low temperature and high current; through the three-stage formation, a multi-layer oxide film is generated on the surface of the low-pressure corrosion foil to form a primary anode foil; dynamic water washing and air drying are required between the three stages; During the detection, the temperature distribution and flow of the electrolyte in the electrolytic cell are measured by setting a temperature sensor and a fluid flow direction sensor, and the temperature field and fluid field of the electrolyte are analyzed; by setting an air pump gas unit and a propeller convection unit, the electrolyte is stirred and driven to flow, so that the components of the electrolyte are evenly mixed, the temperature in the temperature field of the electrolytic cell is uniform, and the flow rate in the fluid field is uniform; S5, intermediate treatment: chemically treating the primary anode foil with a phosphoric acid solution to generate a water-resistant composite oxide film, thereby forming an intermediate treated anode foil; S6, first post-treatment: performing medium-temperature high-current anodic oxidation on the intermediate-treated anode foil to repair the composite oxide film on the surface of the intermediate-treated anode foil and increase the compactness of the composite oxide film to form a first anode foil; S7, calcination treatment: subjecting the first anode foil to high temperature treatment to convert the crystals of the composite oxide film into α-Al2O3 type, thereby increasing the density of the composite oxide film and forming a calcined anode foil; S8, second post-treatment: chemically treating the calcined anode foil with a phosphoric acid solution to generate a water-resistant composite oxide film again to form a second anode foil; S9, stability treatment: neutralizing and washing the second anode foil with a neutralizer, and washing with deionized water in multiple stages with warm water to form a final treated anode foil; S10, drying: drying the final treated anode foil to form a finished anode foil; S11, rolling; S12. Inspection and packaging.

2. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The multi-stage water washing steps of S1 include: S1.

1. Deionized water heating cleaning: immerse the high-purity aluminum foil in deionized water at a temperature of 50-60°C, apply ultrasonic vibration, and continue cleaning for 3-5 minutes; S1.2, acidic or alkaline solution cleaning: use 5-10% sulfuric acid or 5-8% sodium hydroxide solution at room temperature to clean the high-purity aluminum foil for 5-8 minutes; S1.3, neutralizing agent washing: using a 3-5% by mass sodium bicarbonate solution or an ammonia solution to wash the high-purity aluminum foil at room temperature for at least 3 minutes; S1.4, ethanol washing: using a 70-80% volume fraction ethanol solution, soaking the high-purity aluminum foil at room temperature for 2-3 minutes; S1.

5. Low-temperature, dry air drying: In a clean environment, use dry air at a temperature of 25-35° C. and a wind speed of 3-5 m / s to air-dry the high-purity aluminum foil until there is no water mark on the surface, thereby forming the clean aluminum foil.

3. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: In step S3, a conductive liquid is sprayed between the conductive roller and the low-voltage etching foil to reduce the contact impedance between the low-voltage etching foil and the conductive roller and improve the uniformity of the low-voltage etching foil receiving electricity.

4. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 3, characterized in that: A silver coating is plated on the conductive roller, and the silver coating is in contact with the low-voltage corrosion foil, so as to reduce the contact impedance between the conductive roller and the low-voltage corrosion foil.

5. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The multi-stage formation steps of S4 include: S4.1, the first stage of formation: at a formation temperature of 10-15°C and a current density of 5-10 mA / cm 2 Under the conditions, a maleic acid solution with a mass fraction of 5-10% is used as the forming solution, the voltage is increased to 50% of the target voltage, and the constant voltage is maintained for 10-15 minutes; S4.2, first dynamic water washing: using deionized water at a water temperature of 40-50° C. to wash the low-pressure corrosion foil after completing step S4.1, and the washing lasts for 1-2 minutes; S4.3, second stage formation: at a formation temperature of 60-70°C and a current density of 10-20 mA / cm 2 Under the conditions, a boric acid solution with a mass fraction of 10-15% is used as the forming solution, the voltage is increased to 80% of the target voltage, and the constant voltage is maintained for 20-25 minutes; S4.4, second dynamic water washing: using deionized water at a water temperature of 40-50° C. to rinse the low-pressure corrosion foil after completing step S4.3, and the rinsing lasts for 1-2 minutes; S4.5, the third stage of formation: at a formation temperature of 25-30°C and a current density of 20-30 mA / cm 2 Under the conditions, a 5-10% by mass ammonium dihydrogen phosphate solution is used as the chemical forming solution, the voltage is increased to 100% of the target voltage, and the constant voltage is maintained for 5-10 minutes; S4.6, third dynamic water washing: using deionized water at a water temperature of 40-50° C. to rinse the primary anode foil after completing step S4.5, the rinsing lasting 1-2 minutes; S4.

7. Dynamic air drying: In a clean environment, use dry air at a temperature of 25-35° C. to air dry the primary anode foil completed in step S4.6 until there is no water on the surface.

6. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: S5, intermediate treatment: immersing the primary anode foil in a phosphoric acid solution with a mass fraction of 1-3%, and treating at room temperature for 1-3 minutes to generate a water-resistant composite oxide film to form the intermediate treated anode foil; After the intermediate treatment step in S5, it needs to be washed with water; S5.

1. Water washing: use deionized water at a water temperature of 40-50° C. at a flow rate of 5-8 L / min to wash the treated anode foil. The washing lasts for 3-5 minutes.

7. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: S6, first post-treatment: at a formation temperature of 70-80°C and a current density of 15-25 mA / cm 2 Under the conditions of , using a boric acid solution with a mass fraction of 10-15% as a chemical forming solution, anodizing the anode foil treated in the middle, reducing the voltage to 60% of the target voltage, and maintaining the constant voltage for 30-40 minutes to form the first anode foil; After the first post-treatment step of S6, it needs to be washed with water; S6.

1. Water washing: use deionized water at a water temperature of 40-50° C. and a flow rate of 5-8 L / min to wash the first anode foil. The washing lasts for 3-5 minutes.

8. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The roasting step of S7 includes: S7.1, pre-burning: placing the first anode foil in a nitrogen atmosphere, heating the temperature to 300-350°C at a heating rate of 1-5°C / min, and keeping the temperature for 30-1 hour; S7.2, sintering: In the first stage, the first anode foil is placed in an argon atmosphere, and the temperature is increased to 450-500° C. at a heating rate of 5-10° C. / min, and kept at this temperature for 20-30 minutes; In the second stage, the temperature of the first anode foil is raised to 550-600° C. at a heating rate of 2-5° C. / min and kept at this temperature for 10-20 minutes; S7.3, cooling down: lowering the temperature of the first anode foil to 200-250°C at a cooling rate of 10-15°C / min in the furnace, and then naturally cooling the first anode foil to room temperature in the air atmosphere outside the furnace to release the residual stress of the first anode foil treated in step S7.2, thereby forming the baked anode foil.

9. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: S8. Second post-treatment: immersing the calcined anode foil in a phosphoric acid solution with a mass fraction of 1-3% at room temperature for 1-3 minutes to form the second anode foil.

10. The process for improving the anodizing consistency of anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The stability processing steps of S9 include: S9.1, neutralization treatment: immerse the second anode foil in a 5% by mass sodium hydroxide solution at room temperature, the solution temperature is 25-30° C., and treat for 3 minutes; S9.2, deionized water cleaning: use deionized water at a temperature of 50° C. and a flow rate of 8 L / min to rinse the second anode foil after step S9.1 for 5 minutes to form the final treated anode foil.

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