A method for increasing the specific capacity of a corrosion foil

Abstract

The present application relates to a method for improving the specific capacity of etching foil. The method comprises the following steps: placing the etching foil in an ammonia atmosphere, and then annealing; the annealing temperature is 320-540 DEG C, and the time is 2-10 hours. After the etching foil is placed in the ammonia atmosphere and annealed at a high temperature, the specific capacity of the etching foil can be obviously improved, and the bending strength of the etching foil is not reduced.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolytic capacitor manufacturing technology, and more specifically, to a method for improving the specific capacitance of etched foil. Background Technology

[0002] Capacitors are one of the three major passive electronic components and are an essential basic electronic component in electronic circuits, accounting for approximately 40% of all electronic components used. Classified by material, capacitors can be divided into ceramic capacitors, aluminum electrolytic capacitors, tantalum electrolytic capacitors, and film capacitors. Aluminum electrolytic capacitors account for 32.4% of the global capacitor market. In today's rapidly developing electronics industry, the demand for aluminum electrolytic capacitors is also rising. These are general-purpose electrolytic capacitors made of aluminum, known for their good electrical performance, wide applicability, and high reliability, used in circuits for tuning, filtering, coupling, bypassing, energy conversion, and time delay. However, the specific capacitance performance of existing conventional aluminum electrolytic capacitors is no longer sufficient for practical needs, making the development and supply of aluminum electrolytic capacitors with high specific capacitance performance particularly urgent.

[0003] In the electronic aluminum foil-etched foil-formed foil-capacitor industry chain, etched foil is a crucial raw material for capacitor production. It is typically made from electronic aluminum foil, where nanoscale pores are formed on the foil surface through an etching process. The specific capacitance of the etched foil directly determines the size, performance, and quality of the final capacitor. Traditional etched foil processing usually includes steps such as alkaline washing, acid washing, pore formation, pore enlargement, pure water rinsing, and drying. To obtain etched foil with a high specific capacitance, the concentration of the pore-forming solution, the pore-forming temperature, and the pore-forming electrolysis method are typically adjusted to increase the depth of the pores, thereby improving the specific capacitance of the etched foil.

[0004] For example, a Chinese patent entitled "A Pretreatment Method for Improving the Specific Capacitance of Medium-Voltage Corroded Foil and the Medium-Voltage Corroded Foil Prepared Thereby" uses a specific AC pretreatment to improve the uniformity and number of pores, thereby increasing the specific capacity of the subsequently obtained corroded foil. Another Chinese patent entitled "A Hole-Expanding Corrosion Method and Application for Low-Voltage Hard-State Corroded Foil" uses multiple electrochemical corrosion processes with different parameters to obtain corroded foil with a deeper corrosion layer and larger pore size, thereby increasing the capacity of aluminum electrolytic capacitors. A Chinese patent entitled "A Production Process for High-Specific-Capacitance Medium- and High-Voltage Electrode Foil" uses a specific multi-stage corrosion expansion treatment to solve the problems of parallel pores and shallow pores, thus improving the specific capacity of the electrode foil. However, the processing techniques for improving specific capacity are currently quite complex and often reduce the bending strength of the corroded foil.

[0005] Therefore, it is necessary to develop a technology that is simple to process, can improve the specific volume of the etched foil, and does not sacrifice the bending strength of the etched foil. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of existing methods for increasing the specific volume of etched foil, which sacrifice the flexural strength of the etched foil and involve complex processes. This invention provides a method for increasing the specific volume of etched foil. This method involves placing the etched foil in an ammonia atmosphere and subjecting it to high-temperature annealing, which significantly increases the specific volume of the etched foil without reducing its flexural strength. Specifically, the specific volume of the etched foil treated by this invention increases by 23.8% to 33.3%.

[0007] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0008] A method for increasing the specific volume of etched foil includes the following steps: placing the etched foil in an ammonia atmosphere and then annealing it; the annealing temperature is 320-540°C and the time is 2-10 hours.

[0009] Through extensive research, the inventors of this invention discovered that placing the etched foil in an ammonia atmosphere and annealing it at a specific temperature significantly increases its specific volume without sacrificing its flexural strength. The reason is that, in the method of this invention, annealing at 320–540°C for a specific time (2–10 hours) allows ammonia to decompose hydrogen and nitrogen atoms. The hydrogen atoms do not react with aluminum but further generate hydrogen gas, while the nitrogen atoms uniformly adhere to the surface of the etched foil and fully react with aluminum at 320–540°C to form an aluminum nitride film. This results in the surface of the etched foil being primarily covered by the aluminum nitride film. After the treatment using this method, the etched foil undergoes further formation treatment, and the surface of the aluminum foil after formation treatment is still covered by a relatively complete aluminum nitride film. If the etched foil is not treated using the method of this invention, it will primarily form aluminum oxide on its surface during subsequent formation treatments. Theoretically, the dielectric constant of single-phase pure alumina is 39.992, while that of single-phase pure aluminum nitride is 60.619, indicating that aluminum nitride has a higher dielectric constant. According to the capacitance calculation formula: C = εA / d (where C represents the capacitance, ε represents the dielectric constant, A represents the area of ​​the capacitor plates, and d represents the distance between the plates), an increase in the dielectric constant can proportionally increase the specific capacitance. Since the surface of the etched foil treated by the method of this invention is mainly covered by an aluminum nitride film, the specific capacitance of the etched foil is significantly improved.

[0010] If an ammonia atmosphere is not created, the specific volume of the etched foil after treatment will show almost no improvement. Similarly, if a nitrogen atmosphere or a nitrogen-free inert atmosphere (such as argon) is used instead of an ammonia atmosphere, the specific volume of the etched foil will also show almost no improvement. If the annealing time is too short, the improvement in specific volume will be insignificant. This may be because although aluminum nitride forms during annealing, the short annealing time prevents the formation of a complete aluminum nitride film. If the annealing temperature is too low, the specific volume of the etched foil after treatment will also show almost no improvement.

[0011] The method for increasing the specific volume of etched foil according to the present invention involves placing the etched foil in an ammonia atmosphere and annealing it at a high temperature. This significantly increases the specific volume of the etched foil without reducing its flexural strength. Specifically, the specific volume of the etched foil treated by the method of the present invention increases by 23.8% to 33.3%.

[0012] Typically, before treatment using the method described above to increase the specific volume of the etched foil (i.e., before placing the etched foil in an ammonia atmosphere), the specific volume of the etched foil is 90.2–92.3 μF / cm³. 2 .

[0013] Preferably, the purity of the ammonia gas reaches 99.999% or higher.

[0014] Preferably, the annealing temperature is increased at a heating rate of 3 to 10°C.

[0015] Preferably, the annealing temperature is 450–540°C.

[0016] More preferably, the annealing temperature is 500–540°C.

[0017] Annealing within this temperature range results in a more significant increase in the specific volume of the etched foil.

[0018] More preferably, the annealing temperature is 500–520°C.

[0019] Preferably, the annealing time is 5 to 10 hours.

[0020] At the specified annealing time, the increase in specific volume of the etched foil is more pronounced.

[0021] More preferably, the annealing time is 8 to 10 hours.

[0022] Typically, after annealing, the temperature is reduced to room temperature at a rate of 5–8 °C / min.

[0023] Typically, the ambient temperature is 20–30°C.

[0024] Preferably, the specific process of placing the etched foil in an ammonia atmosphere is as follows: placing the etched foil in a sealed space, drawing a vacuum, and then filling it with ammonia.

[0025] Typically, the pressure of the vacuum is ≤8×10⁻⁶. -1 Pa.

[0026] Preferably, the method for increasing the specific volume of the etched foil is carried out in a vacuum annealing furnace.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The method for improving the specific volume of etched foil according to the present invention involves placing the etched foil in an ammonia atmosphere and subjecting it to high-temperature annealing treatment. This significantly increases the specific volume of the etched foil without reducing its flexural strength. Specifically, the specific volume of the etched foil treated by the method of the present invention increases by 23.8% to 33.3%. Detailed Implementation

[0029] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0030] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this invention are commercially available.

[0031] Example 1

[0032] This embodiment provides a method for improving the specific capacity of etched foil, which includes the following steps:

[0033] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace, and the vacuum pressure was ≤8×10⁻⁶. -1 Pa, then fill with 99.999% pure ammonia gas, so that the etched foil is placed in an ammonia atmosphere; then heat the vacuum annealing furnace to 450℃ at a heating rate of 10℃ / min and hold for 2 hours to complete the annealing; finally, cool the vacuum annealing furnace to room temperature at a cooling rate of 5℃ / min, thus completing the increase of the specific volume of the etched foil.

[0034] Example 2

[0035] This embodiment provides a method for improving the specific capacity of etched foil, which includes the following steps:

[0036] The etched foil (specific volume 90.2 μF / cm³) 2The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1 Pa, then fill with 99.999% pure ammonia gas, so that the etched foil is placed in an ammonia atmosphere; then heat the vacuum annealing furnace to 500℃ at a heating rate of 10℃ / min and hold for 8 hours to complete the annealing; finally, cool the vacuum annealing furnace to room temperature at a cooling rate of 5℃ / min, thus completing the increase of the specific volume of the etched foil.

[0037] Example 3

[0038] This embodiment provides a method for improving the specific capacity of etched foil, which includes the following steps:

[0039] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1 Pa, then fill with 99.999% pure ammonia gas, so that the etched foil is placed in an ammonia atmosphere; then heat the vacuum annealing furnace to 520℃ at a heating rate of 10℃ / min and hold for 8 hours to complete the second annealing; finally, cool the vacuum annealing furnace to room temperature at a cooling rate of 5℃ / min, thus completing the increase of the specific volume of the etched foil.

[0040] Example 4

[0041] This embodiment provides a method for improving the specific capacity of etched foil, which includes the following steps:

[0042] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1 Pa, then fill with 99.999% pure ammonia gas, so that the etched foil is placed in an ammonia atmosphere; then heat the vacuum annealing furnace to 540℃ at a heating rate of 3℃ / min and hold for 8 hours, and finally cool the vacuum annealing furnace to room temperature at a cooling rate of 5℃ / min, thus completing the increase of the specific volume of the etched foil.

[0043] Comparative Example 1

[0044] This comparative example provides a method for processing the specific volume of etched foil, which includes the following steps:

[0045] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1Pa; then heat the vacuum annealing furnace to 450℃ at a heating rate of 10℃ / min and hold for 2 hours to complete the vacuum annealing; finally, cool the vacuum annealing furnace to room temperature at a cooling rate of 5℃ / min to complete the processing of this comparative method.

[0046] Comparative Example 2

[0047] This comparative example provides a method for processing the specific volume of etched foil, which includes the following steps:

[0048] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1 Pa, then fill with nitrogen gas of 99.99% purity, so that the etched foil is placed in a nitrogen atmosphere; then heat the vacuum annealing furnace to 450°C at a heating rate of 10°C / min and hold for 2 hours to complete the annealing; finally, cool the vacuum annealing furnace to room temperature at a cooling rate of 5°C / min to complete the processing of this comparative method.

[0049] Comparative Example 3

[0050] This comparative example provides a method for processing the specific volume of etched foil, which includes the following steps:

[0051] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1 Pa, then fill with 99.99% pure argon gas, so that the etched foil is placed in an argon atmosphere; then heat the vacuum annealing furnace to 450°C at a heating rate of 10°C / min and hold for 2 hours to complete the second annealing; finally, cool the vacuum annealing furnace to room temperature at a cooling rate of 5°C / min to complete the processing of this comparative method.

[0052] Comparative Example 4

[0053] This comparative example provides a method for improving the specific volume of etched foil, which includes the following steps:

[0054] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1 Pa, then fill with ammonia gas of 99.999% purity, so that the etched foil is placed in an ammonia atmosphere; then heat the vacuum annealing furnace to 450°C at a heating rate of 10°C / min and hold for 1 hour, and finally cool the vacuum annealing furnace to room temperature at a cooling rate of 5°C / min, thus completing the processing of this comparative method.

[0055] Comparative Example 5

[0056] This comparative example provides a method for improving the specific volume of etched foil, which includes the following steps:

[0057] The etched foil (specific volume 90.2 μF / cm³) 2 The Lidong Technology Ls92 was placed in a vacuum annealing furnace and evacuated to a vacuum level of ≤8×10. -1 Pa, then fill with ammonia gas with a purity of 99.999% to place the etched foil in an ammonia atmosphere; then heat the vacuum annealing furnace to 270°C at a heating rate of 10°C / min and hold for 2 hours; finally, cool the vacuum annealing furnace to room temperature at a cooling rate of 5°C / min to complete the process of this comparative method.

[0058] Performance testing

[0059] The specific volume and flexural strength of the etched foils after treatment in each embodiment and comparative example were tested. The specific test methods or procedures are as follows:

[0060] Specific capacitance: Tested according to the method of electrode foil for aluminum electrolytic capacitors in the group standard T / CECA22-2017 of the China Electronic Components Industry Association. The test conditions are as follows: capacitance tester: measurement accuracy ±2%, test frequency: 120±5Hz. Z Measurement voltage: 21V; Measurement tank: 500ml glass cup; Thermometer: 100℃ range, ±1℃ accuracy; Pure water: 1000ml; Ammonium adipate: 150g (capacitor grade); Resistivity: 6.5Ω·cm / 70±2℃; pH: 6.7.

[0061] Bending strength: Tested according to the method for electrode foil of aluminum electrolytic capacitors in the group standard T / CECA22-2017 of the China Electronic Components Industry Association. The test tensile speed was 10±1 mm / min, and the tensile force at break was measured in N / cm. Simultaneously, untreated etched foil (specific capacitance 90.2 μF / cm) was also tested. 2 The bending strength of the Lidong Technology Ls92 was tested and the result was 90 N / cm.

[0062] The test results of specific volume and flexural strength of the etched foils after treatment in each embodiment and comparative example are shown in Table 1 below.

[0063] Table 1. Test results of specific volume and bending strength of the etched foils after treatment in each embodiment and comparative example.

[0064]

[0065]

[0066] As shown in Table 1, the specific volume of the etched foil treated by the method of the present invention for improving the specific volume of the etched foil was significantly increased, with an increase of 23.8% to 33.3%, and the bending strength did not decrease significantly. Among them, compared with Example 1, Examples 2, 3 and 4 underwent annealing treatment at higher temperatures for longer periods, resulting in a more significant increase in the specific volume of the etched foil; furthermore, compared with Example 2, the annealing temperatures of Examples 3 and 4 were further increased, and the specific volume of the etched foil was also further increased.

[0067] Comparative Example 1's etched foil was annealed at a specific temperature, but without an ammonia atmosphere; the specific volume of the annealed foil showed almost no improvement. Comparative Example 2's etched foil was annealed in a nitrogen atmosphere at a specific temperature; the specific volume of the annealed foil also showed almost no improvement. Comparative Example 3's etched foil was annealed in an argon atmosphere at a specific temperature; the specific volume of the annealed foil also showed almost no improvement. Comparative Example 4's etched foil was annealed in an ammonia atmosphere for a shorter time, resulting in a minimal increase in specific volume. Comparative Example 5's etched foil was also annealed in an ammonia atmosphere, but at a lower temperature; the specific volume showed almost no improvement.

[0068] As can be seen from the above, the method of improving the specific volume of the etched foil of the present invention, which involves placing the etched foil in an ammonia atmosphere and annealing it at a suitable high temperature and time, can significantly improve the specific volume of the etched foil without reducing its bending strength.

[0069] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For example, the method of the present invention can be combined with existing etching foil production processes, specifically, ammonia gas is introduced in the final drying step of the etching foil, and annealing is performed at the temperature of the present invention for a specific time; it can also be combined with the etching foil-forming foil process, specifically, an ammonia atmosphere is created in the high-temperature treatment process (adjusted within the temperature range of the present invention) during the etching foil forming process, all of which fall within the protection scope of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for improving the specific volume of etched foil, characterized in that, The process includes the following steps: placing the etched foil in an ammonia atmosphere and then annealing it; the annealing temperature is 320-540°C and the time is 2-10 hours.

2. The method for improving the specific volume of etched foil according to claim 1, characterized in that, Before being treated using the method described above, the specific volume of the etched foil was 90.2–92.3 μF / cm³. 2 .

3. The method for improving the specific volume of etched foil according to claim 1, characterized in that, The purity of the ammonia gas is 99.99% or higher.

4. The method for improving the specific volume of etched foil according to claim 1, characterized in that, The temperature is increased to the annealing temperature at a heating rate of 3 to 10°C.

5. The method for improving the specific volume of etched foil according to claim 1, characterized in that, The annealing temperature is 450–540°C.

6. The method for improving the specific volume of etched foil according to claim 1, characterized in that, The annealing temperature is 500–540°C.

7. The method for improving the specific volume of etched foil according to claim 1, characterized in that, The annealing time is 5 to 10 hours.

8. The method for improving the specific volume of etched foil according to claim 1, characterized in that, After annealing, cool to room temperature at a rate of 5–8 °C / min.

9. The method for improving the specific volume of etched foil according to claim 1, characterized in that, The specific process of placing the etched foil in an ammonia atmosphere is as follows: place the etched foil in a sealed space, evacuate the vacuum, and then fill it with ammonia.

10. The method for improving the specific volume of etched foil according to claim 1, characterized in that, The method is carried out in a vacuum annealing furnace.

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