Formation method of small chip wide electrode foil for high-density chip capacitor

Abstract

This invention relates to the field of electrode foil manufacturing technology, and particularly to a method for forming small-width electrode foil for high-density surface-mount capacitors. The method includes the following steps: S1, surface pretreatment: The aluminum foil is immersed in a diluted pretreatment solution at 60-70°C, followed by ultrasonic treatment; after washing, it is treated with pure water at 90-95°C for 12-15 minutes, and then air-dried to complete the surface pretreatment; S2, primary formation; S3, secondary formation; S4, tertiary formation. This invention provides a method for forming small-width electrode foil for high-density surface-mount capacitors to solve the problems in related technologies where high specific capacitance and low leakage current cannot be simultaneously achieved, and where bending performance is poor.

Description

Technical Field

[0001] This application relates to the field of electrode foil manufacturing technology, and in particular to a method for forming a small wide electrode foil for high-density chip capacitors. Background Technology

[0002] Electrode foil is a crucial basic material that determines the performance of aluminum electrolytic capacitors. With the rapid development of electronic components towards miniaturization, high density, surface mounting, and integration, high-density surface-mount aluminum electrolytic capacitors have been widely used in consumer electronics, new energy, industrial control, and communications. The electrode foil requires etching, hydration, and multi-stage formation processes to generate a dense, uniform, and low-defect alumina dielectric film on the porous surface of the etched aluminum foil. This formation process directly determines the electrode foil's specific capacitance, leakage current, mechanical strength, and bending performance.

[0003] Currently, the mainstream formation processes for small-sized wide electrode foils in the industry are mainly divided into two categories: organic acid formation system and inorganic acid-boric acid composite formation system. Among them, pure organic acid formation has the advantages of high capacity conversion rate and good basic bending strength, but for small-sized wide electrode foils of 5mm and below, there are problems such as stress concentration at the cutting edge and obvious edge accumulation effect of formation current, which easily leads to foil breakage and poor film uniformity. Although inorganic acid composite boric acid formation has excellent product life, ripple resistance and charge-discharge performance, and high substrate strength, it has the disadvantages of low capacity conversion rate, high production cost, and small-sized wide foils are prone to crystal brittleness and insufficient bending resistance. Summary of the Invention

[0004] This application provides a method for forming small wide electrode foils for high-density surface mount capacitors, in order to solve the problems of high specific capacitance and low leakage current, as well as poor bending performance, that exist in the formation process of small wide electrode foils in related technologies.

[0005] A method for forming small, wide electrode foils for high-density surface mount capacitors includes the following steps: S1. Surface pretreatment: The aluminum foil is placed in a pretreatment solution diluted at 60~70℃, immersed, and then ultrasonically treated; after washing, it is treated with pure water at 90~95℃ for 12~15 minutes, and then air-dried to complete the surface pretreatment. The pretreatment solution includes a pretreatment solution and deionized water in a mass ratio of 1:(9~10). S2, Primary Formation: S201. Preparation of primary electrolyte: Add a primary modifier to a 1~1.5 mol / L ammonium azelate solution and adjust the pH to 5.0~5.5 to obtain the primary electrolyte. The amount of the primary modifier added is 5~8% of the mass of the ammonium azelate solution. S202. The surface-pretreated aluminum foil is used as the anode and the lead plate is used as the cathode. The aluminum foil is placed in the primary electrolyte and pulsed DC formation is carried out simultaneously. After step-by-step voltage increase, the aluminum foil is taken out, cleaned and drained to obtain the primary formation electrode foil. S3, Secondary Formation: S301. Preparation of secondary electrolyte: Add primary modifier to borate composite solution and adjust pH to 6.0~6.5 to obtain secondary electrolyte. The amount of primary modifier added is 4~6% of the mass of borate composite solution. S302. The primary formed electrode foil is placed in the secondary electrolyte, and bidirectional pulsed formation is performed. After step-by-step voltage increase, it is taken out and cleaned, and then immersed in the secondary modifier for 10-15 minutes. After draining, the secondary formed electrode foil is obtained. S4, Level 3 Transformation: S401. Preparation of tertiary electrolyte: After mixing the carboxylate solution with the borate composite solution, add the secondary modifier and adjust the pH to 5.5~6.0 to obtain the tertiary electrolyte; S402. The secondary-formed electrode foil is placed in the tertiary electrolyte and formed by DC superimposed pulse formation. After being taken out and cleaned, it is heat-treated at 300~350℃ and kept at the temperature for 20~25min. After cooling to room temperature, it is immersed in the secondary modifier for 8~10min and dried to obtain a small wide electrode foil for high-density chip capacitors. The pretreatment solution preparation method includes: adding nano-titanium dioxide and polyglycolic acid to deionized water at 50~60℃, dispersing at high speed, cooling to 30~35℃, adding sophorolipid, sonicating, and allowing to stand to degas, to obtain the pretreatment solution; The preparation method of the primary modifier includes: slowly adding titanium tetrachloride dropwise into deionized water at 0~5℃ and stirring, then adding lithium fluoride and sodium hypophosphite, and adjusting the pH to 4.0~4.5 after stirring to obtain the modifier. The mass ratio of titanium tetrachloride, lithium fluoride, sodium hypophosphite and deionized water is (1~2):1:(3~5):50. The preparation method of the secondary modifier includes: adding lipoic acid and tannic acid to deionized water at 65~70℃, stirring and then cooling to 35~40℃, adding carbon nitride, and ultrasonic treatment to obtain the secondary modifier. The mass ratio of lipoic acid, tannic acid, carbon nitride and deionized water is (6~8):3:1:200.

[0006] Preferably, in S202, the pulsed DC formation conditions are: pulse voltage 20~40V, duty cycle 50%, and frequency 100Hz; The step-up voltage conditions are as follows: initial voltage 20V, hold for 12~15min; then increase to 40V at a rate of 5V every 5min, hold for 20~25min.

[0007] Preferably, in the borate composite solution of S301, the concentration of ammonium borate is 0.5~0.6 mol / L and the concentration of sodium hexametaphosphate is 0.06~0.08 mol / L.

[0008] Preferably, in step S301, the preparation of the secondary electrolyte further includes the addition of a pretreatment solution, wherein the amount of the pretreatment solution added is 3-5% of the mass of the borate composite solution.

[0009] Preferably, in S302, the bidirectional pulse formation conditions are: forward pulse voltage 40~60V, duty cycle 40%, frequency 150Hz; reverse pulse voltage 8~12V, duty cycle 20%, frequency 150Hz. The step-up voltage conditions are as follows: initial voltage 40V, hold for 15~20min; then increase to 60V at a rate of 10V every 10min, hold for 25~30min.

[0010] Preferably, in S401, the volume ratio of the carboxylate solution to the borate composite solution is 1:1.

[0011] Preferably, in S401, the carboxylate solution is selected from ammonium 2,5-furandicarboxylate solution, and the concentration of the ammonium 2,5-furandicarboxylate solution is 0.8 mol / L.

[0012] Preferably, in step S401, the amount of secondary modifier added is 6-8% of the total mass of the carboxylate solution and the borate composite solution.

[0013] Preferably, in S402, the DC superimposed pulse formation conditions are: DC voltage 60~70V, superimposed pulse voltage 5V, duty cycle 30%, frequency 200Hz, and held for 40~50 minutes.

[0014] Preferably, in the pretreatment solution, the mass ratio of sophorolipid, nano-titanium dioxide, polyglycolic acid and deionized water is 1:(1~2):1:20.

[0015] The beneficial effects of the technical solution provided in this application include: This application provides a method for forming small-width electrode foils for high-density surface-mount capacitors. A pretreatment solution is used to impregnate and modify the surface of the small-width etched aluminum foil. Sophorolipids, as a biosurfactant, can be uniformly adsorbed on the cut edges of the aluminum foil, weakening the edge current accumulation effect. Nano-titanium dioxide fills the microcracks and lattice defects in the edge cuts. Polyglycolic acid imparts flexibility and toughness to the oxide film. After hydration treatment, uniform Al(OH)3 is generated on the surface of the aluminum foil. At the same time, the pretreatment solution is added to the secondary electrolyte to further strengthen the edge film structure and improve the bending resistance of the electrode foil.

[0016] During primary formation, ammonium azelate and a primary modifier are used as the primary electrolyte. A positive pulse promotes oxide film growth within the pores. Ti 4+ Doping replaces part of the Al in the alumina lattice 3+ The process involves several steps: First, lithium fluoride and sodium hypophosphite are used to refine the oxide film grains and promote film formation, thereby increasing the dielectric constant and specific capacitance of the oxide film. Second, a borate composite solution and a primary modifier are used as the secondary electrolyte. The borate composite solution includes ammonium borate and sodium hexametaphosphate, which promotes oxide film crystallization and increases strength. Simultaneously, sodium hexametaphosphate forms a dense phosphate protective film at the edges, suppressing edge current concentration. Third, a mixture of ammonium 2,5-furandicarboxylate solution and the borate composite solution, along with the secondary modifier, is used as the tertiary electrolyte. Nano-carbon nitride possesses excellent thermal stability and conductivity, which can buffer the difference in thermal expansion coefficients between the aluminum substrate and the oxide film. Combined with heat treatment, this improves the crystallinity of the film layer, achieving a significant reduction in leakage current under high specific capacitance conditions. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the formation method of a small, wide electrode foil for a high-density surface-mount capacitor provided in this application; Figure 2 In the formation method of the small wide electrode foil for the high-density chip capacitor provided in this application, the flowchart of step S2: primary formation is as follows: Figure 3 In the formation method of the small wide electrode foil for the high-density chip capacitor provided in this application, the flowchart of step S3: secondary formation is as follows: Figure 4 The flowchart of step S4: three-stage formation in the formation method of the small wide electrode foil for the high-density chip capacitor provided in this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] See Figures 1-4 As shown, this application provides a method for forming a small wide electrode foil for a high-density surface-mount capacitor.

[0021] The aluminum foil used in the following examples is etched foil with a width of 4 mm; sulfuric acid or ammonia is actually used to adjust the pH.

[0022] Unless otherwise specified, the amount of liquid used in operations such as immersion should be sufficient to cover the aluminum foil.

[0023] In the following examples and comparative examples, the average molecular weight of sophorolipid used was 690; the average molecular weight of polyglycolic acid was 10,000, and the specification was 800 mesh; the nano titanium dioxide was anatase type with a particle size of 20-25 nm; and the carbon nitride was nanosheet powder with a particle size of 40-45 nm.

[0024] Example 1 The method for forming small-width electrode foils for high-density surface-mount capacitors provided in this embodiment includes the following steps: S1. Surface pretreatment: The aluminum foil is placed in a pretreatment solution diluted at 70°C and soaked for 20 minutes, followed by ultrasonic treatment at 150W for 5 minutes. After washing, it is treated with pure water at 95°C for 12 minutes and then air-dried at a wind speed of 0.5 m / s to complete the surface pretreatment. The pretreatment solution is a mixture of pretreatment solution and deionized water at a mass ratio of 1:9. S2, Primary Formation: S201. Preparation of primary electrolyte: Add 6% of primary modifier to a 1 mol / L ammonium azelate solution and adjust the pH to 5.5 to obtain the primary electrolyte. The 6% refers to the amount of primary modifier added being 6% of the mass of the ammonium azelate solution. S202. Use the pre-treated aluminum foil as the anode and the lead plate as the cathode, and keep the distance between the plates 15cm. Place the plates in the primary electrolyte, turn on the pulse power supply, and use pulsed DC formation. During the pulse cycle, the pulse voltage is 20~40V, the duty cycle is 50%, and the frequency is 100Hz. A stepped voltage increase operation is performed simultaneously to avoid oxide film defects caused by sudden voltage rise and to ensure film uniformity and stability: the initial power supply output voltage is set to 20V and held for 15 minutes to allow the aluminum foil surface to initially form an oxide film. Then, the voltage is increased by 5V every 5 minutes. After the voltage reaches 40V, it is held for 25 minutes to ensure that the oxide film grows fully. After removal, it is washed with deionized water and drained at room temperature (25°C) to obtain a primary formation electrode foil. S3, Secondary Formation: S301. Preparation of secondary electrolyte: Add 3% pretreatment solution and 5% primary modifier to the borate composite solution, adjust the pH to 6.0 to obtain the secondary electrolyte. 3% refers to the amount of pretreatment solution added being 3% of the mass of the borate composite solution, and 5% refers to the amount of primary modifier added being 5% of the mass of the borate composite solution. In the borate composite solution, the concentration of ammonium borate is 0.5 mol / L and the concentration of sodium hexametaphosphate is 0.06 mol / L.

[0025] S302. Place the primary formation electrode foil in the secondary electrolyte and perform bidirectional pulse formation. During the pulse cycle, the forward pulse voltage is 50V, the duty cycle is 40%, and the frequency is 150Hz; the reverse pulse voltage is 10V, the duty cycle is 20%, and the frequency is 150Hz. Simultaneously perform stepped voltage boosting: initially set the power supply output voltage to 40V and maintain it for 15 minutes to allow an oxide film to initially form on the aluminum foil surface. Then, increase the voltage by 10V every 10 minutes until the voltage reaches 60V and maintain it for 25 minutes. After removal, it is washed with deionized water, then immersed in a secondary modifier for 10 minutes, and drained to obtain a secondary formed electrode foil; S4, Level 3 Transformation: S401. Preparation of tertiary electrolyte: Mix 0.8 mol / L ammonium 2,5-furandicarboxylate solution with borate composite solution in S301 at a volume ratio of 1:1, add 6% secondary modifier, and adjust pH to 5.5 to obtain tertiary electrolyte; S402. Place the secondary formation electrode foil in the tertiary electrolyte and perform DC superimposed pulse formation: DC voltage 60V, superimposed pulse positive voltage 5V, duty cycle 30%, frequency 200Hz, and hold for 40min.

[0026] After removal and cleaning, the electrode foil is heat-treated at 320℃ for 20 minutes, cooled to room temperature, immersed in a secondary modifier for 8 minutes, and dried to obtain a small wide electrode foil for high-density surface-mount capacitors. In this embodiment, the pretreatment solution used in S1 is prepared by the following method: At 55℃, 5g of nano-titanium dioxide and 5g of polyglycolic acid were added to 100g of deionized water. After high-speed dispersion, the mixture was cooled to 35℃, and 5g of sophorolipid was added. The mixture was ultrasonicated at 150W for 5 minutes and then allowed to stand to remove bubbles, thus obtaining the pretreated solution.

[0027] The preparation method of the primary modifier used in S201 is as follows: At 5°C, 2g of titanium tetrachloride was slowly added dropwise to 100g of deionized water and stirred. Then, 2g of lithium fluoride and 8g of sodium hypophosphite were added, and the pH was adjusted to 4.5 after stirring to obtain the modifier. The preparation method of the secondary modifier used in S301 is as follows: At 65°C, 3.5g of lipoic acid and 1.5g of tannic acid were added to 100g of deionized water. After stirring, the mixture was cooled to 35°C, and 0.5g of carbon nitride was added. After ultrasonic treatment at 150W, a secondary modifier was obtained.

[0028] Example 2 The difference from Example 1 is that in this example, no pretreatment solution is added to the secondary electrolyte in step S301.

[0029] Example 3 The method for forming small-width electrode foils for high-density surface-mount capacitors provided in this embodiment includes the following steps: S1. Surface pretreatment: The aluminum foil is placed in a pretreatment solution diluted at 60°C and soaked for 30 minutes, followed by ultrasonic treatment at 150W for 5 minutes. After washing, it is treated with pure water at 90°C for 15 minutes and then air-dried at a wind speed of 0.5 m / s to complete the surface pretreatment. The pretreatment solution is a mixture of pretreatment solution and deionized water at a mass ratio of 1:10. S2, Primary Formation: S201. Preparation of primary electrolyte: Add 5% of primary modifier to a 1.5 mol / L ammonium azelate solution and adjust the pH to 5.0 to obtain the primary electrolyte. The 5% refers to the amount of primary modifier added being 5% of the mass of the ammonium azelate solution. S202. Use the pre-treated aluminum foil as the anode and the lead plate as the cathode, and keep the distance between the plates 15cm. Place the plates in the primary electrolyte, turn on the pulse power supply, and use pulsed DC formation. During the pulse cycle, the pulse voltage is 20~40V, the duty cycle is 50%, and the frequency is 100Hz. Simultaneously perform stepped voltage increase operation: initially set the power supply output voltage to 20V and maintain it for 12 minutes to allow the aluminum foil surface to initially form an oxide film. Then, increase the voltage by 5V every 5 minutes. After the voltage reaches 40V, maintain it for 20 minutes to ensure that the oxide film grows fully. After removal, it is washed with deionized water and drained at room temperature (25°C) to obtain a primary formation electrode foil. S3, Secondary Formation: S301. Preparation of secondary electrolyte: Add 5% pretreatment solution and 4% primary modifier to the borate composite solution, adjust the pH to 6.5 to obtain the secondary electrolyte. 5% refers to the amount of pretreatment solution added being 5% of the mass of the borate composite solution, and 4% refers to the amount of primary modifier added being 4% of the mass of the borate composite solution. In the borate composite solution, the concentration of ammonium borate is 0.6 mol / L and the concentration of sodium hexametaphosphate is 0.06 mol / L.

[0030] S302. Place the primary formation electrode foil in the secondary electrolyte and perform bidirectional pulse formation. During the pulse cycle, the forward pulse voltage is 40~60V, the duty cycle is 40%, and the frequency is 150Hz; the reverse pulse voltage is 8V, the duty cycle is 20%, and the frequency is 150Hz. Simultaneously perform stepped voltage boosting: initially set the power supply output voltage to 40V and maintain it for 20 minutes to allow an oxide film to initially form on the aluminum foil surface. Then, increase the voltage by 10V every 10 minutes until the voltage reaches 60V and maintain it for 30 minutes. After removal, it is washed with deionized water, then immersed in a secondary modifier for 15 minutes, and drained to obtain a secondary formed electrode foil; S4, Level 3 Transformation: S401. Preparation of tertiary electrolyte: Mix 0.8 mol / L ammonium 2,5-furandicarboxylate solution with the borate composite solution in S301 at a volume ratio of 1:1, add 7% secondary modifier, and adjust the pH to 6.0 to obtain tertiary electrolyte; S402. Place the secondary formation electrode foil in the tertiary electrolyte and perform DC superimposed pulse formation: DC voltage 70V, superimposed pulse positive voltage 5V, duty cycle 30%, frequency 200Hz, and hold for 40min.

[0031] After removal and cleaning, the electrode foil is heat-treated at 300℃ for 25 minutes, cooled to room temperature, and then immersed in a secondary modifier for 10 minutes. After drying, a small wide electrode foil for high-density surface-mount capacitors is obtained. In this embodiment, the pretreatment solution used in S1 is prepared by the following method: At 50℃, 7.5g of nano titanium dioxide and 5g of polyglycolic acid were added to 100g of deionized water. After high-speed dispersion, the mixture was cooled to 30℃, 5g of sophorolipid was added, and the mixture was sonicated at 150W for 5 minutes and then allowed to stand to remove bubbles to obtain the pretreated solution.

[0032] The preparation method of the primary modifier used in S201 is as follows: At 5°C, 4g of titanium tetrachloride was slowly added dropwise to 100g of deionized water and stirred. Then, 2g of lithium fluoride and 6g of sodium hypophosphite were added, and the pH was adjusted to 4.0 after stirring to obtain the modifier. The preparation method of the secondary modifier used in S301 is as follows: At 70°C, 3g of lipoic acid and 1.5g of tannic acid were added to 100g of deionized water. After stirring, the mixture was cooled to 40°C, and 0.5g of carbon nitride was added. After ultrasonic treatment at 150W, a secondary modifier was obtained.

[0033] Example 4 The method for forming small-width electrode foils for high-density surface-mount capacitors provided in this embodiment includes the following steps: S1. Surface pretreatment: The aluminum foil is placed in a pretreatment solution diluted at 70°C and soaked for 20 minutes, followed by ultrasonic treatment at 150W for 5 minutes. After washing, it is treated with pure water at 95°C for 12 minutes and then air-dried at a wind speed of 0.5 m / s to complete the surface pretreatment. The pretreatment solution is a mixture of pretreatment solution and deionized water at a mass ratio of 1:9. S2, Primary Formation: S201. Preparation of primary electrolyte: Add 8% of primary modifier to a 1 mol / L ammonium azelate solution and adjust the pH to 5.5 to obtain the primary electrolyte. The 8% refers to the amount of primary modifier added being 8% of the mass of the ammonium azelate solution. S202. Use the pre-treated aluminum foil as the anode and the lead plate as the cathode, and keep the distance between the plates 15cm. Place the plates in the primary electrolyte, turn on the pulse power supply, and use pulsed DC formation. During the pulse cycle, the pulse voltage is 20~40V, the duty cycle is 50%, and the frequency is 100Hz. A stepped voltage increase operation is performed simultaneously to avoid oxide film defects caused by sudden voltage rise and to ensure film uniformity and stability: the initial power supply output voltage is set to 20V and held for 12 minutes to allow the aluminum foil surface to initially form an oxide film. Then, the voltage is increased by 5V every 5 minutes. After the voltage reaches 40V, it is held for 20 minutes to ensure that the oxide film grows fully. After removal, it is washed with deionized water and drained at room temperature (25°C) to obtain a primary formation electrode foil. S3, Secondary Formation: S301. Preparation of secondary electrolyte: Add 6% of primary modifier to the borate composite solution and adjust the pH to 6.0 to obtain the secondary electrolyte. The 6% refers to the amount of primary modifier added being 6% of the mass of the borate composite solution. In the borate composite solution, the concentration of ammonium borate is 0.5 mol / L and the concentration of sodium hexametaphosphate is 0.08 mol / L.

[0034] S302. Place the primary formation electrode foil in the secondary electrolyte and perform bidirectional pulse formation. During the pulse cycle, the forward pulse voltage is 50V, the duty cycle is 40%, and the frequency is 150Hz; the reverse pulse voltage is 12V, the duty cycle is 20%, and the frequency is 150Hz. Simultaneously perform stepped voltage boosting: initially set the power supply output voltage to 40V and maintain it for 15 minutes to allow an oxide film to initially form on the aluminum foil surface. Then, increase the voltage by 10V every 10 minutes until the voltage reaches 60V and maintain it for 25 minutes. After removal, it is washed with deionized water, then immersed in a secondary modifier for 10 minutes, and drained to obtain a secondary formed electrode foil; S4, Level 3 Transformation: S401. Preparation of tertiary electrolyte: Mix 0.8 mol / L ammonium 2,5-furandicarboxylate solution with borate composite solution in S301 at a volume ratio of 1:1, add 8% secondary modifier, and adjust pH to 5.5 to obtain tertiary electrolyte; S402. Place the secondary formation electrode foil in the tertiary electrolyte and perform DC superimposed pulse formation: DC voltage 60V, superimposed pulse positive voltage 5V, duty cycle 30%, frequency 200Hz, and maintain for 50min.

[0035] After removal and cleaning, the electrode foil is heat-treated at 350℃ for 20 minutes, cooled to room temperature, immersed in a secondary modifier for 8 minutes, and dried to obtain a small wide electrode foil for high-density surface-mount capacitors. In this embodiment, the pretreatment solution used in S1 is prepared by the following method: At 60℃, 10g of nano titanium dioxide and 5g of polyglycolic acid were added to 100g of deionized water. After high-speed dispersion, the mixture was cooled to 35℃, and 5g of sophorolipid was added. The mixture was ultrasonicated at 150W for 5 minutes and then allowed to stand to remove bubbles, thus obtaining the pretreated solution.

[0036] The preparation method of the primary modifier used in S201 is as follows: At 0℃, 4g of titanium tetrachloride was slowly added dropwise to 100g of deionized water and stirred. Then, 2g of lithium fluoride and 10g of sodium hypophosphite were added, and the pH was adjusted to 4.5 after stirring to obtain the modifier. The preparation method of the secondary modifier used in S301 is as follows: At 65°C, 4g of lipoic acid and 1.5g of tannic acid were added to 100g of deionized water. After stirring, the mixture was cooled to 35°C, and 0.5g of carbon nitride was added. After ultrasonic treatment at 150W, a secondary modifier was obtained.

[0037] Comparative Example 1 The difference between this comparative example and Example 1 is that, in this comparative example, no primary modifier is added during the preparation of the primary electrolyte in step S201, and the borate composite solution is used as the secondary electrolyte in step S301. That is, no primary modifier and pretreatment solution are added during the preparation of the secondary electrolyte.

[0038] Comparative Example 2 The difference between this comparative example and Example 1 is that, in this comparative example, no secondary modifier is added in step S401, and no impregnation with the secondary modifier is performed in step S402.

[0039] Comparative Example 3 The difference between this comparative example and Example 1 is that in this comparative example, step S1 does not involve immersion in the pretreatment solution, and step S301 does not involve adding the pretreatment solution.

[0040] For the high-density chip capacitor small wide electrode foil (hereinafter referred to as "small wide electrode foil") prepared by the formation method provided in the examples and comparative examples, the capacitance, leakage current and bending times were tested in accordance with SJ / T 11140-2022 "Electrode Foil for Aluminum Electrolytic Capacitors". The performance test results are shown in Table 1.

[0041] Table 1 Performance test results of small-width electrode foils in the examples and comparative examples In Table 1, specific capacitance = electrostatic capacitance / electrode foil area.

[0042] The primary modifiers added to the secondary electrolyte include titanium tetrachloride and Ti. 4+ Doping with sodium hypophosphite effectively improves the dielectric constant of Al2O3. Sodium hypophosphite promotes film formation at the bottom of pores, reduces defects, and increases specific capacitance. In the secondary modifier added during tertiary formation, thioctic acid and tannic acid form a chelate film, improving the film's density and reducing leakage current. Comparative Example 1 lacks Ti... 4+ Doping significantly reduced the specific volume, while insufficient film formation at the bottom of the pores led to an increase in leakage current. Comparative Example 2, lacking a secondary modifier, had a higher specific volume, but its leakage current was significantly higher than that of Example 1. Comparative Example 3, lacking a pretreatment solution, had more residual impurities on the electrode foil surface, more defects in the oxide film layer, and a decline in related performance.

[0043] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for forming a small wide electrode foil for a high-density surface-mount capacitor, characterized in that, It includes the following steps: S1. Surface pretreatment: The aluminum foil is immersed in a pretreatment solution diluted at 60~70℃ and then ultrasonically treated. After washing, the surface is treated with pure water at 90-95℃ for 12-15 minutes, and then air-dried to complete the surface pretreatment. The pretreatment diluent consists of a pretreatment solution and deionized water in a mass ratio of 1:(9-10). S2, Primary Formation: S201. Preparation of primary electrolyte: Add a primary modifier to a 1~1.5 mol / L ammonium azelate solution and adjust the pH to 5.0~5.5 to obtain the primary electrolyte. The amount of the primary modifier added is 5~8% of the mass of the ammonium azelate solution. S202. The surface-pretreated aluminum foil is used as the anode and the lead plate is used as the cathode. The aluminum foil is placed in the primary electrolyte and pulsed DC formation is carried out simultaneously. After step-by-step voltage increase, the aluminum foil is taken out, cleaned and drained to obtain the primary formation electrode foil. S3, Secondary Formation: S301. Preparation of secondary electrolyte: Add primary modifier to borate composite solution and adjust pH to 6.0~6.5 to obtain secondary electrolyte. The amount of primary modifier added is 4~6% of the mass of borate composite solution. S302. The primary formed electrode foil is placed in the secondary electrolyte, and bidirectional pulsed formation is performed. After step-by-step voltage increase, it is taken out and cleaned, and then immersed in the secondary modifier for 10-15 minutes. After draining, the secondary formed electrode foil is obtained. S4, Level 3 Transformation: S401. Preparation of tertiary electrolyte: After mixing the carboxylate solution with the borate composite solution, add the secondary modifier and adjust the pH to 5.5~6.0 to obtain the tertiary electrolyte; S402. The secondary-formed electrode foil is placed in the tertiary electrolyte and formed by DC superimposed pulse formation. After being taken out and cleaned, it is heat-treated at 300~350℃ and kept at the temperature for 20~25min. After cooling to room temperature, it is immersed in the secondary modifier for 8~10min and dried to obtain a small wide electrode foil for high-density chip capacitors. The pretreatment solution preparation method includes: adding nano-titanium dioxide and polyglycolic acid to deionized water at 50~60℃, dispersing at high speed, cooling to 30~35℃, adding sophorolipid, sonicating, and allowing to stand to degas, to obtain the pretreatment solution; The preparation method of the primary modifier includes: slowly adding titanium tetrachloride dropwise into deionized water at 0~5℃ and stirring, then adding lithium fluoride and sodium hypophosphite, and adjusting the pH to 4.0~4.5 after stirring to obtain the modifier. The mass ratio of titanium tetrachloride, lithium fluoride, sodium hypophosphite and deionized water is (1~2):1:(3~5):

50. The preparation method of the secondary modifier includes: adding lipoic acid and tannic acid to deionized water at 65~70℃, stirring and then cooling to 35~40℃, adding carbon nitride, and ultrasonic treatment to obtain the secondary modifier. The mass ratio of lipoic acid, tannic acid, carbon nitride and deionized water is (6~8):3:1:

200.

2. The method for forming small wide electrode foils for high-density surface-mount capacitors as described in claim 1, characterized in that: In S202, the pulsed DC formation conditions are: pulse voltage 20~40V, duty cycle 50%, frequency 100Hz; The step-up voltage conditions are as follows: initial voltage 20V, hold for 12~15min; then increase to 40V at a rate of 5V every 5min, hold for 20~25min.

3. The method for forming small wide electrode foils for high-density surface-mount capacitors as described in claim 1, characterized in that: In the borate composite solution of S301, the concentration of ammonium borate is 0.5~0.6 mol / L and the concentration of sodium hexametaphosphate is 0.06~0.08 mol / L.

4. The method for forming a small wide electrode foil for a high-density surface-mount capacitor as described in claim 1, characterized in that: In step S301, the preparation of the secondary electrolyte also includes the addition of a pretreatment solution, wherein the amount of the pretreatment solution added is 3-5% of the mass of the borate composite solution.

5. The method for forming a small wide electrode foil for a high-density surface-mount capacitor as described in claim 1, characterized in that: In S302, the bidirectional pulse formation conditions are: forward pulse voltage 40~60V, duty cycle 40%, frequency 150Hz; reverse pulse voltage 8~12V, duty cycle 20%, frequency 150Hz. The step-up voltage conditions are as follows: initial voltage 40V, hold for 15~20min; then increase to 60V at a rate of 10V every 10min, hold for 25~30min.

6. The method for forming a small wide electrode foil for a high-density surface-mount capacitor as described in claim 1, characterized in that: In S401, the volume ratio of the carboxylate solution to the borate composite solution is 1:

1.

7. The method for forming a small wide electrode foil for a high-density surface-mount capacitor as described in claim 1, characterized in that: In S401, the carboxylate solution is selected from ammonium 2,5-furandicarboxylate solution, and the concentration of the ammonium 2,5-furandicarboxylate solution is 0.8 mol / L.

8. The method for forming a small wide electrode foil for a high-density surface-mount capacitor as described in claim 1, characterized in that: In S401, the amount of secondary modifier added is 6-8% of the total mass of the carboxylate solution and the borate composite solution.

9. The method for forming a small wide electrode foil for a high-density surface-mount capacitor as described in claim 1, characterized in that: In S402, the DC superimposed pulse formation conditions are: DC voltage 60~70V, superimposed pulse voltage 5V, duty cycle 30%, frequency 200Hz, and held for 40~50 minutes.

10. The method for forming a small wide electrode foil for a high-density surface-mount capacitor as described in claim 1, characterized in that: In the pretreatment solution, the mass ratio of sophorolipid, nano-titanium dioxide, polyglycolic acid and deionized water is 1:(1~2):1:20.

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