An aluminum electrolytic capacitor and a method of manufacturing the same

Abstract

The application discloses an aluminum electrolytic capacitor and a manufacturing method thereof, comprising an aluminum shell, a core package placed in the aluminum shell, and a terminal cover plate assembly for packaging the core package in the aluminum shell; wherein the core package comprises electrolytic paper, an anode aluminum foil and a cathode foil; wherein the surface of the anode aluminum foil is formed with a microstructure with multiple topologies through laser etching topology expansion and chemical corrosion expansion; and the microstructure is at least one of a rectangular matrix, a strip-shaped groove matrix, a hole array and a slit array. The application solves the technical problems of the prior art, such as difficult accurate control and online automatic monitoring of process parameters, insufficient product control stability, and large dielectric loss factor and high heat generation caused by the nanoscale aperture formed by traditional acid corrosion being easily blocked by a thick oxide film in high-voltage applications.

Description

Technical Field

[0001] This invention belongs to the field of electronic device technology, and in particular relates to an aluminum electrolytic capacitor and its manufacturing method. Background Technology

[0002] In existing technologies, the positive electrode foil used in aluminum electrolytic capacitors is generally produced by surface etching with sulfuric acid, hydrochloric acid, and nitric acid, combined with electrolytic etching to expand the surface area, and then electrochemically generating an aluminum oxide film with permanent dielectric properties. The electrochemical etching process requires a large amount of sulfuric acid, hydrochloric acid, and nitric acid, and the etching process is relatively complex and inefficient. The corrosion porosity is basically free corrosion between metal phases, and the number and area of ​​porosity are easily affected by the passivation film, which gradually weakens the etching process. Furthermore, the quality control parameters are greatly affected by temperature, equipment speed fluctuations, current, and the ratio of acid radicals in the bath solution. The monitoring methods are not yet automated and can not be controlled online in real time. Finally, the technical indicators are determined by weighing and measuring the weight loss ratio. Currently, the industry can achieve 140µm thick aluminum foil with a chemical weight loss ratio of 25%-20%, of which the residual core thickness is still 30-40µm. However, the aluminum foil is brittle when mechanically bent after formation, making it impossible to produce small-width wafers. Its general application scenarios are limited. At present, this type of traditional technology is only limited to low-end voltage technology requirements, generally 250VF-700VF aluminum foil. When this type of 800VF-1200VF foil is used to manufacture ultra-high voltage finished capacitors, the product exhibits a particularly large DF value (usually 15-25%), and the heat generation does not meet the requirements for low thermal resistance.

[0003] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0004] The purpose of this invention is to provide an aluminum electrolytic capacitor and a method for manufacturing the same, so as to solve at least one of the problems in the background art described above.

[0005] To achieve the above objectives, the technical solution of this invention is implemented as follows: An aluminum electrolytic capacitor includes: an aluminum shell, a core package placed inside the aluminum shell, and a terminal cover assembly for encapsulating the core package inside the aluminum shell; wherein the core package includes electrolytic paper, an anode aluminum foil, and a cathode foil; wherein the surface of the anode aluminum foil is formed with a multi-topological microstructure by laser etching and chemical etching; the microstructure is at least one of a rectangular matrix, a strip slot matrix, a hole array, and a slit array.

[0006] In some embodiments, the anode aluminum foil includes two opposing sides, wherein each side is formed with the aforementioned multi-topological microstructure by laser etching and chemical etching.

[0007] In some embodiments, the microstructure is obtained by simultaneously combining roll-to-roll online etching of aluminum foil with acid etching.

[0008] 4. The aluminum electrolytic capacitor as described in claim 3, wherein the ratio of the acid solution is sulfuric acid: hydrochloric acid = 3:1-2:1.

[0009] In some embodiments, the specific volume of the anode aluminum foil is 0.05-0.2 μF / cm², and the number of pores on the surface of the aluminum foil is 20 / 100 μm. 2 .

[0010] Another technical solution of this invention is: A method for manufacturing an aluminum electrolytic capacitor includes the following steps: Step 1: Laser etching is performed on the high-purity aluminum foil to form a microstructure with a topological expansion on the surface of the high-purity aluminum foil, and the high-purity aluminum foil after laser etching is post-processed. Step 2: The aluminum foil after laser etching is chemically etched to form an aluminum foil with a more porous and effective pure interface, and then acid radicals are removed by alkaline washing and water washing. Step 3: Perform conventional electrochemical formation process on the aluminum foil to grow an oxide film interface layer, and obtain the aluminum foil for the anode of the aluminum electrolytic capacitor; Step 4: The aluminum foil anode of the aluminum electrolytic capacitor obtained in Step 3 is wound with electrolytic paper and cathode foil to obtain an aluminum electrolytic capacitor core package. The core package is then encapsulated in an aluminum shell and a capacitor cover plate to obtain an aluminum electrolytic capacitor.

[0011] In some embodiments, in step one, a microstructure with multiple topologies that meet the design requirements is etched by laser ablation of a high-purity aluminum foil with a thickness of 60μm-200μm; wherein the microstructure is one or more of a rectangular matrix or a strip-shaped slot matrix, a dense array of holes, or a slit array.

[0012] In some embodiments, the rectangular matrix or strip groove matrix, the diffused holes, and the slit array of the microstructure are composed of equal-height sides intersecting on different planes and the plane itself.

[0013] In some embodiments, in step two, the aluminum foil after laser etching is subjected to chemical etching treatment. The chemical etching treatment uses a mixture of sulfuric acid and hydrochloric acid as the etching solution, wherein the ratio of sulfuric acid to hydrochloric acid is 3:1-2:1.

[0014] In some embodiments, in step one, the laser etching process parameters are set as follows: spot diameter is 20 μm, line spacing in the warp and weft directions is 20 μm, etching depth is 60 μm, etching line diameter is 3 μm, area of ​​the retained boss is 80 μm², and laser power is 300 W.

[0015] The beneficial effects of the technical solution of this invention are: Compared with existing technologies, the aluminum electrolytic capacitor and its manufacturing method of this invention solve the technical problems of traditional chemical corrosion processes, such as difficulty in accurately controlling process parameters and online automated monitoring, insufficient quality control stability, and the tendency of nanoscale pores formed by traditional acid corrosion to be blocked by thick oxide films in high-voltage applications, resulting in a large dielectric loss factor and high heat generation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a three-dimensional schematic diagram of the aluminum foil anode of an aluminum electrolytic capacitor according to an embodiment of the present invention; Figure 2 This is an enlarged schematic diagram of the aluminum foil anode of an aluminum electrolytic capacitor according to an embodiment of the present invention; Figure 3 This is a three-dimensional schematic diagram of the aluminum foil anode of an aluminum electrolytic capacitor according to another embodiment of the present invention; Figure 4 This is a three-dimensional schematic diagram of the aluminum foil anode of an aluminum electrolytic capacitor according to another embodiment of the present invention; Figure 5 yes Figure 4 An enlarged schematic diagram of the aluminum foil anode of an aluminum electrolytic capacitor in an embodiment; Figure 6 yes Figure 3 A magnified view of part A in the diagram; Figure 7 yes Figure 6 A magnified view of a portion of the image; Figure 8 This is a three-dimensional schematic diagram of an aluminum electrolytic capacitor according to an embodiment of the present invention; Figure 9 yes Figure 8 A three-dimensional schematic diagram of the core package of an aluminum electrolytic capacitor in the embodiment; Figure 10 yes Figure 9 A three-dimensional schematic diagram of the aluminum foil anode of an aluminum electrolytic capacitor, as shown in the example. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects of the embodiments of the present invention clearer and more understandable, and to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0019] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be for both fixing and circuit connection purposes.

[0020] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, unless otherwise expressly specified and limited, "a plurality of" means two or more. Terms such as "installed," "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two components or an interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] According to Figures 1-7As shown, an aluminum foil 100 for an aluminum electrolytic capacitor anode, as an embodiment of the present invention, includes two opposing surfaces, wherein each surface is formed with a multi-topological microstructure 101 by laser etching and chemical etching. The thickness of the aluminum foil 100 is 60-200 μm, and the microstructure 101 is at least one of a rectangular matrix, a strip groove matrix, a hole array, and a slit array.

[0023] In some embodiments, the microstructure 101 is obtained by simultaneously performing online etching of 100 rolls of aluminum foil and acid etching; wherein the ratio of the acid is sulfuric acid: hydrochloric acid = 3:1-2:1.

[0024] In some embodiments, the microstructure 101 includes holes 102 formed by laser etching, the diameter of which is 500 nanometers to 5 micrometers; the holes are formed by symmetrical sides of different planes intersecting with the planes to form a topologically expanded structure. This arrangement effectively avoids the problem of high-pressure oxide films clogging the small holes, increasing the actual area of ​​the microstructure.

[0025] In some embodiments, the etching line diameter of the microstructure 101 is 0.5-10 μm, and the area of ​​the retained boss is 25-300 μm².

[0026] In some embodiments, an aluminum oxide film with permanent dielectric properties is generated on the surface of the laser-etched aluminum foil by electrochemical formation treatment.

[0027] In some embodiments, the specific capacitance of the anode aluminum foil is 0.05-0.2 μF / cm², which is determined by a formation voltage of 1200-2000 VF and a withstand voltage of 1200-2000 VF.

[0028] In some embodiments, the number of pores on the surface of the aluminum foil 100 is 20 / 100μm. 2 .

[0029] This aluminum electrolytic capacitor's anode aluminum foil eliminates the need to add aluminum powder particles to the anode foil surface, significantly reducing the weight of the anode foil. While increasing the anode foil area, it also increases the anode foil's flexibility, making it easier to wind.

[0030] As another embodiment of the present invention, a method for manufacturing aluminum foil anodes for aluminum electrolytic capacitors is provided, comprising the following steps: S10. Laser etching is performed on the high-purity aluminum foil to form a microstructure with a topological expansion on the surface of the high-purity aluminum foil, and the high-purity aluminum foil after laser etching is post-processed. Specifically, by laser ablation of high-purity aluminum foil with a thickness of 60μm-200μm, a microstructure with multiple topologies conforming to the design requirements is etched out; wherein, the microstructure is one or more of the following: a rectangular matrix or a strip groove matrix, a perforated array of holes, or a slit array; the rectangular matrix or strip groove matrix, the perforated array of holes, or the slit array of the microstructure is composed of equal-height sides intersecting on different planes and the plane itself.

[0031] The post-processing of the high-purity aluminum foil after laser etching includes: cleaning the high-purity aluminum foil after laser etching to remove residual ablation material on the surface of the aluminum foil, thereby achieving weight reduction and material reduction of the aluminum foil.

[0032] In some embodiments, by adjusting the process parameters of the picosecond or femtosecond laser machine, the spot diameter is determined to be approximately 50 μm to 5 μm, and ablation subtraction is performed in the latitude and longitude directions. The row spacing is between 50 μm and 5 μm, the depth is 0.5 to 10 times the row spacing, and the line diameter etched by step scanning is approximately 0.5 μm to 10 μm. After laser etching in the latitude and longitude directions, the area of ​​the remaining protrusion is 300 μm. 2 -25μm 2 The power of the laser matrix should be selected between 10W and 1000W.

[0033] In this embodiment of the invention, high-purity aluminum foil is directly laser-etched to expand its surface. Compared with adding aluminum powder particles to the surface of the aluminum foil for sintering, this invention does not increase the weight of the aluminum foil, and the resulting aluminum foil is thinner, more tough, and less prone to breakage during winding.

[0034] In some embodiments, a 140 μm thick high-purity aluminum foil is used for surface etching using a picosecond laser. The laser etching process parameters are set as follows: spot diameter 20 μm, scan spacing in the longitudinal and latitudinal directions 20 μm, etching depth 60 μm, etching line diameter 3 μm, retained protrusion area 80 μm², and laser power 300 W. The laser scans and etches the aluminum foil surface according to a preset rectangular matrix path. During the etching process, the laser beam ablates a crisscrossing groove structure on the aluminum foil surface, forming a regular microscopic matrix. After etching, the aluminum foil surface exhibits a uniformly distributed array of rectangular protrusions, with the grooves formed by laser etching between the protrusions.

[0035] In some embodiments, the surface morphology of the laser-etched aluminum foil is observed using a scanning electron microscope (SEM) after laser etching for correction. SEM observation reveals a regularly arranged rectangular protrusion structure with smooth surfaces, clear edges, and uniform groove depth. The microstructure formed by laser etching significantly increases the surface area of ​​the aluminum foil, providing a sufficient interface for subsequent oxide film growth.

[0036] S20. The aluminum foil after laser etching is chemically etched to form an aluminum foil with a more porous and effective pure interface, and acid radicals are removed by alkaline washing and water washing. Specifically, the aluminum foil after laser etching is subjected to chemical etching treatment. The chemical etching treatment uses a mixture of sulfuric acid and hydrochloric acid as the etching solution, wherein the ratio of sulfuric acid to hydrochloric acid is 3:1-2:1.

[0037] In this embodiment of the invention, the area of ​​the aluminum foil is greatly increased and its electrochemical performance is improved by combining laser etching for topological expansion in step one with electrochemical etching for expansion (acid etching + electro-etching) in step two. Furthermore, by directly performing laser etching on the aluminum foil surface, this invention allows for precise control of the number of pores per unit area on the aluminum foil surface, thereby producing a high-precision anode foil.

[0038] S30. Perform conventional electrochemical formation process on aluminum foil to grow an oxide film interface layer, and obtain aluminum foil for aluminum electrolytic capacitor anode.

[0039] In step S30, by electrochemically forming the etched surface and finally applying a voltage of 800VF-2000F, a capacitor with a specific capacitance of 0.05UF / CM2-0.2UF / CM2 is obtained. The specific capacitance is determined by electrochemically energizing the substrate with a final voltage of 1200VF-2000VF in the subsequent formation tank to obtain the aforementioned specific capacitance technical parameters. Through process tracking of the capacitors made from this foil, the parameters are found to be one unit lower than those of traditional foils. The charge and discharge characteristics are close to those of BOPP (polypropylene) high-voltage film capacitors, and the ripple current tolerance is directly close to 10 times that of aluminum electrolytic capacitors made from traditional anode foils. Furthermore, by producing a 100UF 800V ultra-high voltage capacitor, its ripple current tolerance reaches 10Arms / 100khz, and its lifespan is close to that of an ideal capacitor.

[0040] In some embodiments, the electrochemical formation treatment is carried out in a formation tank built into a high-vapor pressure autoclave-high-boiling-point apparatus, using boric acid solution as the formation liquid, and applying a voltage of 590-700 VF. Formation under high vapor pressure further improves the quality of the oxide film.

[0041] In some embodiments, the laser-etched aluminum foil is subjected to electrochemical formation treatment, with an applied voltage of 1200-2000 VF. The electrochemical formation process generates an aluminum oxide film with permanent dielectric properties on the surface of the aluminum foil.

[0042] In some embodiments, the aluminum foil is subjected to electrochemical formation treatment by placing it in a boric acid solution and applying a voltage of 1500 VF. During the formation process, an aluminum oxide film is gradually formed on the surface of the aluminum foil. After formation, the specific capacitance of the anode foil is measured to be 0.12 μF / cm², and the withstand voltage is 1500 VF.

[0043] In this embodiment of the invention, laser etching technology is used to replace the traditional chemical etching process for expanding the surface area of ​​aluminum foil. By precisely controlling the laser process parameters, a regular microstructure is formed on the aluminum foil surface, achieving a digitally controllable expansion effect. This solves the problem that the number and area of ​​pores in the traditional chemical etching process are easily weakened by the passivation film. The expansion efficiency is not affected by various factors such as temperature, current, and acid ratio, resulting in strong process controllability and significantly improved quality control stability. It also avoids the environmental pollution caused by the large-scale use of strong acids such as sulfuric acid, hydrochloric acid, and nitric acid. Furthermore, the diameter of the pores formed by laser etching can be controlled from 500 nanometers to 5 micrometers. This breakthrough overcomes the limitations of traditional acid etching, which restricts pore sizes from 10 nanometers to 3 nanometers. It allows the oxide film thickness to grow to the required maximum without clogging capillary capacitor pores. It solves the problem of thicker oxide films on anode foils prepared using traditional processes clogging micropores in high-voltage applications, leading to higher dielectric loss factors and higher heat generation. This enables aluminum electrolytic capacitors to overcome the technical bottleneck of 750WV withstand voltage, achieving ultra-high voltage applications of 750VDC-850VDC. In high-voltage applications of 800VF-2000VF, the dielectric loss factor is significantly lower than that of traditional processes, and the charge / discharge characteristics are close to those of BOPP high-voltage film capacitors, with a lifespan approaching that of ideal capacitors.

[0044] As another embodiment of the present invention, the method for manufacturing aluminum foil anodes of aluminum electrolytic capacitors includes the following steps: Step S200: The high-purity aluminum foil roll is simultaneously etched online and acid-etched, wherein the ratio of acid is sulfuric acid: hydrochloric acid = 3:1-2:1.

[0045] Specifically, a laser-induced die-cutting process is used on high-purity aluminum foil before acid etching to create pre-drilled holes in a matrix of laser-etched dots. This helps to achieve a larger longitudinal tangential area for the holes during subsequent acid etching. The size of the increased capacitance area is closely related to the depth and uniformity of the laser etching, as well as the thickness of the aluminum foil. Furthermore, the laser etching die-cutting process optimizes the previous limitation of 10⁻³ nanometers in the maximum diameter of holes created by acid etching. The diameter and depth of the laser-burned holes can be digitally controlled to over 500 nanometers, meaning that the oxide film thickness can be electrochemically grown to the required maximum. The formation of a thick aluminum oxide dielectric film can overcome the voltage bottleneck of ultra-high voltage electrolytic capacitors, effectively solving the problem of small hole diameters in the acid etching process clogging the capillary capacitor holes. This oxide film-type aluminum electrolytic capacitor will be able to break through the technical bottleneck of 750WV withstand voltage; this technology currently achieves 750VDC-850VDC technical specifications.

[0046] Laser etching of 75μm-200μm anode aluminum foil determined the spot diameter to be approximately 100μm-5μm, the scan spacing in the longitudinal and latitudinal directions to be 50μm-5μm, the depth to be 0.5-12 times the scan spacing, and the etching line diameter on the aluminum foil surface to be approximately 0.25μm-25μm. After laser longitudinal and transverse etching, the area of ​​the remaining boss is 300μm. 2 -25μm 2， The laser power should be selected between 10W and 1000W.

[0047] By simultaneously combining roll-to-roll online etching with acid etching, both sides of high-purity aluminum foil can be etched at the same time, which can greatly improve efficiency. Furthermore, because the process steps are combined, the number of processes is reduced, and the quality of the etched aluminum foil is greatly improved.

[0048] In this embodiment of the invention, the combined process of laser etching and chemical etching synergistically enhances the surface expansion effect. Laser pre-drilling increases the longitudinal tangential area of ​​the drilled hole surface in subsequent acid etching, resulting in a comprehensive weight loss of 25%-40%, which is superior to the 20%-25% weight loss ratio of traditional single chemical etching process. The prepared anode foil has a ripple current tolerance capability 10 times that of traditional aluminum electrolytic capacitors, and its ripple current tolerance capability reaches 10 Arms at a frequency of 100kHz, significantly improving the ability of aluminum electrolytic capacitors to develop towards high voltage and high performance.

[0049] Step 201: Electrochemical acid etching is performed on the aluminum foil obtained in step 200 to obtain aluminum foil for the anode of aluminum electrolytic capacitor.

[0050] Specifically, after laser etching of 140MM-200MM anode aluminum foil using the process parameters in step 20, the material undergoes deep processing. Under the condition of a sulfuric acid: hydrochloric acid ratio of 3:1-2:1, the temperature is controlled between 70-90℃, and the overvoltage is 6-11V for 100-180 seconds. The overall weight loss under high-speed laser etching and chemical acid etching reaches more than 25%, while the maximum overall weight loss under low speed reaches 30-40%.

[0051] In step 201, further, electrochemical formation is performed using a 2-20 MPa high-vapor, high-boiling-point device with a built-in formation tank. The specific volume obtained by electrochemical formation with pure boric acid is 1.3 UF / CM. 2 ~0.85UF / CM 2 The voltage is 700VF-590VF. The specific capacitance is determined by electrochemically energizing the aluminum foil of the aluminum electrolytic capacitor with a final voltage of 590VF-700VF in the subsequent formation cell, to obtain the specific capacitance technical parameters.

[0052] In one embodiment, a high-purity aluminum foil with a thickness of 180 μm was used. First, a femtosecond laser was employed for pre-isolating a dot matrix pattern of holes. The laser scanned the aluminum foil surface in a dot-matrix mode, forming a regularly arranged array of holes. The laser etching process parameters were set as follows: spot diameter 15 μm, hole spacing 15 μm, etching depth 30 μm, hole diameter 1 μm, and laser power 200 W. After laser pre-isolating, the aluminum foil was placed in a mixture of sulfuric acid and hydrochloric acid for chemical etching. The etching solution ratio was 2.5:1 (sulfuric acid to hydrochloric acid by volume), the etching temperature was controlled at 80°C, an overvoltage of 8V was applied, and the etching time was 140 seconds.

[0053] During the chemical etching process, the acid penetrates into the aluminum foil along the laser-pre-drilled holes, forming tunnel-like corrosion pores around the holes. The laser pre-drilling increases the longitudinal tangential area of ​​the acid-etched pore surface, making the etching process more uniform and efficient. After etching, the overall weight loss of the aluminum foil was measured to be 32%, significantly higher than the 20% to 25% weight loss of traditional single chemical etching processes. The aluminum foil treated with the composite process was then subjected to alkaline washing and water washing to remove residual acid radicals. Subsequently, it underwent electrochemical formation treatment in a high-pressure autoclave-high-boiling-point device. The formation tank pressure was set to 10 MPa, pure boric acid solution was used as the formation solution, and a voltage of 650 VF was applied for formation. After formation, the specific volume of the anode foil was measured to be 1.05 μF / cm², and the withstand voltage was 650 VF. Transmission electron microscopy was used to observe the cross-sectional morphology of the aluminum foil after the composite process. It was observed that the diameter of the holes formed by the laser pre-drilling was approximately 1.5 μm, and nanoscale tunnel pores formed by chemical etching were distributed around the holes. The pore size of laser-pre-generated holes is much larger than the 10-nanometer to 3-nanometer pore size formed by traditional acid etching, providing ample space for oxide film growth and effectively avoiding the problem of high-pressure oxide film clogging capillaries.

[0054] The prepared anode foil was used to assemble aluminum electrolytic capacitors, and their performance in medium- and high-voltage applications was tested. When a 10 Arms ripple current was applied at a frequency of 100 kHz, the capacitor exhibited excellent ripple current tolerance, which was 10 times that of conventional aluminum electrolytic capacitors. The capacitor operated continuously at its rated voltage with a dielectric loss factor of less than 5% and significantly lower heat generation than capacitors prepared using conventional processes.

[0055] By employing a combined process of laser pre-hole generation and chemical etching, the surface area expansion effect of aluminum foil is synergistically improved. Laser pre-hole generation provides a larger reaction interface for subsequent chemical etching, making the etching process more uniform and efficient, and significantly improving the overall weight loss ratio. Simultaneously, the larger pore size formed by laser pre-hole generation overcomes the limitations of traditional acid etching pore size, solving the problem of high-pressure oxide film clogging capillary pores, enabling the anode foil to be used in the fabrication of higher-voltage capacitors. Furthermore, compared to adding aluminum powder particles to the aluminum foil surface for sintering, this invention does not increase the weight of the aluminum foil, and the resulting aluminum foil is thinner, more resilient, and less prone to breakage during winding.

[0056] Reference Figures 8-10 As shown, as another embodiment of the present invention, an aluminum electrolytic capacitor 200 is also provided, including an aluminum shell 201, a core package 202 placed inside the aluminum shell 201, and a terminal cover assembly 203 for encapsulating the core package inside the aluminum shell; wherein, the core package 202 includes electrolytic paper 204, an anode aluminum foil 100, and a cathode foil 205; wherein, the surface of the anode aluminum foil 100 is formed with a multi-topological microstructure 101 by laser etching and chemical etching; the microstructure 101 is at least one of a rectangular matrix, a strip slot matrix, a hole array, and a slit array.

[0057] The anode aluminum foil 100 includes two opposing sides, wherein each side is formed with the multi-topological microstructure 101 by laser etching and chemical etching. In this process, laser etching technology is used to precisely and controllably process the microstructure of the aluminum foil surface, forming crisscrossing equal-height side surfaces and planes that together constitute the actual area after topological expansion. This replaces the random porosity process in traditional chemical etching, achieving a digitally controllable expansion effect. The microstructure is either a rectangular matrix or a strip-shaped groove matrix. These two structural forms provide a regular and uniform expansion effect, which is beneficial for the uniform growth of the oxide film during subsequent electrochemical formation.

[0058] In some embodiments, the laser etching process employs a dot-matrix laser etching method to pre-create holes, resulting in hole diameters ranging from 500 nanometers to 5 micrometers. The diameter of the laser-ablated holes can be controlled to be above 500 nanometers, breaking through the limitations of traditional acid etching with hole diameters in the 10-nanometer to 3-nanometer range, and solving the problem of high-pressure oxide film clogging capillary pores. The holes are formed by symmetrical sides intersecting different planes, creating a topologically expanded structure. This design effectively avoids the problem of high-pressure oxide film clogging small pores, increasing the actual area of ​​the microstructure. Furthermore, the aluminum foil of this aluminum electrolytic capacitor does not require the addition of aluminum powder particles to the anode foil surface, significantly reducing the weight of the anode foil. While increasing the anode foil area, it also increases the flexibility of the anode foil, facilitating winding.

[0059] In some embodiments, an aluminum oxide film with permanent dielectric properties is generated on the surface of the laser-etched aluminum foil by electrochemical formation treatment.

[0060] In some embodiments, the microstructure is obtained by simultaneously performing online etching of aluminum foil roll to roll and acid etching; wherein the ratio of acid is sulfuric acid: hydrochloric acid = 3:1-2:1.

[0061] In some embodiments, the electrochemical formation process is carried out in a formation tank built into a high-pressure steam autoclave-high-boiling-point device, using boric acid solution as the formation liquid, and applying a voltage of 590-700VF.

[0062] In some embodiments, the thickness of the high-purity aluminum foil is 140-200 μm. This thickness range is suitable for combined laser etching and chemical etching processes.

[0063] Furthermore, the specific capacitance of the anode foil is 0.05-0.2 μF / cm², which is determined by the formation voltage of 1200-2000 VF and the withstand voltage is 1200-2000 VF.

[0064] In some embodiments, the microstructure includes holes formed by laser etching, the diameter of which is 500 nanometers to 5 micrometers.

[0065] In some embodiments, the etching line diameter of the microstructure is 0.5-10 μm, and the area of ​​the retained boss is 25-300 μm².

[0066] In some embodiments, the number of pores on the surface of the aluminum foil is 20 / 100μm. 2 .

[0067] Reference Figures 1-3 , Figure 5 As shown, in some embodiments, a spacer is formed between the two sides of the anode aluminum foil, and the holes are formed on both sides respectively. (Refer to...) Figure 6 , Figure 7 As shown, in some implementations, the holes are irregularly shaped with crisscrossing patterns.

[0068] As another embodiment of the present invention, a method for manufacturing an aluminum electrolytic capacitor is provided, comprising the following steps: Step 1: Laser etching is performed on the high-purity aluminum foil to form a microstructure with a topological expansion on the surface of the high-purity aluminum foil, and the high-purity aluminum foil after laser etching is post-processed. Specifically, by laser ablation of high-purity aluminum foil with a thickness of 60μm-200μm, a microstructure with multiple topologies conforming to the design requirements is etched out; wherein, the microstructure is one or more of the following: a rectangular matrix or a strip groove matrix, a perforated array of holes, or a slit array; the rectangular matrix or strip groove matrix, the perforated array of holes, or the slit array of the microstructure is composed of equal-height sides intersecting on different planes and the plane itself.

[0069] The post-processing of the high-purity aluminum foil after laser etching includes: cleaning the high-purity aluminum foil after laser etching to remove residual ablation material on the surface of the aluminum foil, thereby achieving weight reduction and material reduction of the aluminum foil.

[0070] In some embodiments, by adjusting the process parameters of the picosecond or femtosecond laser machine, the spot diameter is determined to be approximately 50 μm to 5 μm, and ablation subtraction is performed in the latitude and longitude directions. The row spacing is between 50 μm and 5 μm, the depth is 0.5 to 10 times the row spacing, and the line diameter etched by step scanning is approximately 0.5 μm to 10 μm. After laser etching in the latitude and longitude directions, the area of ​​the remaining protrusion is 300 μm. 2 -25μm 2 The power of the laser matrix should be selected between 10W and 1000W.

[0071] In this embodiment of the invention, high-purity aluminum foil is directly laser-etched to expand its surface. Compared with adding aluminum powder particles to the surface of the aluminum foil for sintering, this invention does not increase the weight of the aluminum foil, and the resulting aluminum foil is thinner, more tough, and less prone to breakage during winding.

[0072] In some embodiments, a 140 μm thick high-purity aluminum foil is used for surface etching using a picosecond laser. The laser etching process parameters are set as follows: spot diameter 20 μm, scan spacing in the longitudinal and latitudinal directions 20 μm, etching depth 60 μm, etching line diameter 3 μm, retained protrusion area 80 μm², and laser power 300 W. The laser scans and etches the aluminum foil surface according to a preset rectangular matrix path. During the etching process, the laser beam ablates a crisscrossing groove structure on the aluminum foil surface, forming a regular microscopic matrix. After etching, the aluminum foil surface exhibits a uniformly distributed array of rectangular protrusions, with the grooves formed by laser etching between the protrusions.

[0073] In some embodiments, the surface morphology of the laser-etched aluminum foil is observed using a scanning electron microscope (SEM) after laser etching for correction. SEM observation reveals a regularly arranged rectangular protrusion structure with smooth surfaces, clear edges, and uniform groove depth. The microstructure formed by laser etching significantly increases the surface area of ​​the aluminum foil, providing a sufficient interface for subsequent oxide film growth.

[0074] Step 2: The aluminum foil after laser etching is chemically etched to form an aluminum foil with a more porous and effective pure interface, and then acid radicals are removed by alkaline washing and water washing. Specifically, the aluminum foil after laser etching is subjected to chemical etching treatment. The chemical etching treatment uses a mixture of sulfuric acid and hydrochloric acid as the etching solution, wherein the ratio of sulfuric acid to hydrochloric acid is 3:1-2:1.

[0075] In this embodiment of the invention, the area of ​​the aluminum foil is greatly increased and its electrochemical performance is improved by combining laser etching for topological expansion in step one with electrochemical etching for expansion (acid etching + electro-etching) in step two. Furthermore, by directly performing laser etching on the aluminum foil surface, this invention allows for precise control of the number of pores per unit area on the aluminum foil surface, thereby producing a high-precision anode foil.

[0076] Step 3: Perform conventional electrochemical formation process on the aluminum foil to grow an oxide film interface layer, and obtain the aluminum foil for the anode of the aluminum electrolytic capacitor; In step three, electrochemical formation is performed on the etched surface, and a voltage of 800VF-2000F is applied to obtain a capacitor with a specific capacitance of 0.05UF / CM2-0.2UF / CM2. The specific capacitance is determined by electrochemical activation at a final voltage of 1200VF-2000VF in the subsequent formation tank to obtain the aforementioned specific capacitance technical parameters. Through process tracking of capacitors made from this foil, the parameters are found to be one unit lower than those of traditional foils. The charge and discharge characteristics are close to those of BOPP (polypropylene) high-voltage film capacitors, and the ripple current withstand capability is directly close to 10 times that of aluminum electrolytic capacitors made from traditional anode foils. Furthermore, by producing a 100UF 800V ultra-high voltage capacitor, its ripple current withstand capability reaches 10Arms / 100khz, and its lifespan is close to that of an ideal capacitor.

[0077] In some embodiments, the electrochemical formation treatment is carried out in a formation tank built into a high-vapor pressure autoclave-high-boiling-point apparatus, using boric acid solution as the formation liquid, and applying a voltage of 590-700 VF. Formation under high vapor pressure further improves the quality of the oxide film.

[0078] In some embodiments, the laser-etched aluminum foil is subjected to electrochemical formation treatment, with an applied voltage of 1200-2000 VF. The electrochemical formation process generates an aluminum oxide film with permanent dielectric properties on the surface of the aluminum foil.

[0079] In some embodiments, the aluminum foil is subjected to electrochemical formation treatment by placing it in a boric acid solution and applying a voltage of 1500 VF. During the formation process, an aluminum oxide film is gradually formed on the surface of the aluminum foil. After formation, the specific capacitance of the anode foil is measured to be 0.12 μF / cm², and the withstand voltage is 1500 VF.

[0080] Step 4: The aluminum foil anode of the aluminum electrolytic capacitor obtained in Step 3 is wound with electrolytic paper and cathode foil to obtain an aluminum electrolytic capacitor core package. The core package is then encapsulated in an aluminum shell and a capacitor cover plate to obtain an aluminum electrolytic capacitor.

[0081] In this embodiment of the invention, laser etching technology is used to replace the traditional chemical etching process for expanding the surface area of ​​aluminum foil. By precisely controlling the laser process parameters, a regular microstructure is formed on the aluminum foil surface, achieving a digitally controllable expansion effect. This solves the problem that the number and area of ​​pores in the traditional chemical etching process are easily weakened by the passivation film. The expansion efficiency is not affected by various factors such as temperature, current, and acid ratio, resulting in strong process controllability and significantly improved quality control stability. It also avoids the environmental pollution caused by the large-scale use of strong acids such as sulfuric acid, hydrochloric acid, and nitric acid. Furthermore, the diameter of the pores formed by laser etching can be controlled from 500 nanometers to 5 micrometers. This breakthrough overcomes the limitations of traditional acid etching, which restricts pore sizes from 10 nanometers to 3 nanometers. It allows the oxide film thickness to grow to the required maximum without clogging capillary capacitor pores. It solves the problem of thicker oxide films on anode foils prepared using traditional processes clogging micropores in high-voltage applications, leading to higher dielectric loss factors and higher heat generation. This enables aluminum electrolytic capacitors to overcome the technical bottleneck of 750WV withstand voltage, achieving ultra-high voltage applications of 750VDC-850VDC. In high-voltage applications of 800VF-2000VF, the dielectric loss factor is significantly lower than that of traditional processes, and the charge / discharge characteristics are close to those of BOPP high-voltage film capacitors, with a lifespan approaching that of ideal capacitors.

[0082] This aluminum electrolytic capacitor's anode aluminum foil eliminates the need to add aluminum powder particles to the anode foil surface, significantly reducing the weight of the anode foil. While increasing the anode foil area, it also increases the anode foil's flexibility, making it easier to wind.

[0083] It is understood that the above description is a further detailed explanation of the invention in conjunction with specific / preferred embodiments, and it should not be considered that the specific implementation of the invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the inventive concept, and all such substitutions or modifications should be considered within the scope of protection of this patent. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the invention.

[0084] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of different embodiments or examples, without contradiction. Although embodiments of the invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope defined by the appended claims.

[0085] Furthermore, the scope of this invention is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, means, methods, and steps described in the specification. Those skilled in the art will readily understand that existing or later-developed disclosures, processes, machines, manufactures, compositions of matter, means, methods, or steps that perform substantially the same function as the corresponding embodiments described herein or obtain substantially the same results as the embodiments described herein can be utilized. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, means, methods, or steps within their scope.

Claims

1. An aluminum electrolytic capacitor, characterized in that: The invention includes an aluminum shell, a core package placed inside the aluminum shell, and a terminal cover assembly for encapsulating the core package inside the aluminum shell; wherein the core package includes electrolytic paper, an anode aluminum foil, and a cathode foil; wherein the surface of the anode aluminum foil is formed with a multi-topological microstructure by laser etching and chemical etching; the microstructure is at least one of a rectangular matrix, a strip slot matrix, a hole array, and a slit array.

2. The aluminum electrolytic capacitor as described in claim 1, characterized in that: The anode aluminum foil includes two opposing sides, wherein each side is formed with the aforementioned multi-topological microstructure by laser etching and chemical etching.

3. The aluminum electrolytic capacitor as described in claim 2, characterized in that: The microstructure is obtained by simultaneously combining roll-to-roll online etching with acid etching.

4. The aluminum electrolytic capacitor as described in claim 3, characterized in that: The ratio of the acid solution is sulfuric acid: hydrochloric acid = 3:1-2:

1.

5. The aluminum electrolytic capacitor as described in claim 1, characterized in that: The specific volume of the anode aluminum foil is 0.05-0.2 μF / cm², and the number of pores on the surface of the aluminum foil is 20 / 100 μm. 2 .

6. A method for manufacturing an aluminum electrolytic capacitor, characterized in that, Includes the following steps: Step 1: Laser etching is performed on the high-purity aluminum foil to form a microstructure with a topological expansion on the surface of the high-purity aluminum foil, and the high-purity aluminum foil after laser etching is post-processed. Step 2: The aluminum foil after laser etching is chemically etched to form an aluminum foil with a more porous and effective pure interface, and then acid radicals are removed by alkaline washing and water washing. Step 3: Perform conventional electrochemical formation process on the aluminum foil to grow an oxide film interface layer, and obtain the aluminum foil for the anode of the aluminum electrolytic capacitor; Step 4: The aluminum foil anode of the aluminum electrolytic capacitor obtained in Step 3 is wound with electrolytic paper and cathode foil to obtain an aluminum electrolytic capacitor core package. The core package is then encapsulated in an aluminum shell and a capacitor cover plate to obtain an aluminum electrolytic capacitor.

7. The method for manufacturing an aluminum electrolytic capacitor as described in claim 6, characterized in that: In step one, a high-purity aluminum foil with a thickness of 60μm-200μm is laser-ablated to etch a microstructure with multiple topologies that meet the design requirements; wherein, the microstructure is one or more of the following: a rectangular matrix or a strip-shaped slot matrix, a dense array of holes, or a slit array.

8. The method for manufacturing an aluminum electrolytic capacitor as described in claim 7, characterized in that: The rectangular matrix or strip slot matrix, the numerous holes, and the slit array of the microstructure are composed of equal-height sides intersecting on different planes and the plane itself.

9. The method for manufacturing an aluminum electrolytic capacitor as described in claim 7, characterized in that: In step two, the aluminum foil after laser etching is subjected to chemical etching treatment. The chemical etching treatment uses a mixture of sulfuric acid and hydrochloric acid as the etching solution, wherein the ratio of sulfuric acid to hydrochloric acid is 3:1-2:

1.

10. The method for manufacturing an aluminum electrolytic capacitor as described in claim 6, characterized in that: In step one, the laser etching process parameters are set as follows: spot diameter is 20μm, line spacing in the warp and weft directions is 20μm, etching depth is 60μm, etching line diameter is 3μm, area of ​​the retained boss is 80μm², and laser power is 300W.

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