A processing technology for inhibiting leakage current rise of aluminum electrolytic capacitor

Abstract

The application provides a treatment process for inhibiting leakage current rise of an aluminum electrolytic capacitor, and belongs to the technical field of capacitor manufacturing. The process aims to solve the problem that bubbles generated during aging hinder the repair of the dielectric layer, resulting in easy rise of leakage current in the prior art. The technical solution provided by the application comprises: performing first aging treatment on the aluminum electrolytic capacitor; then, storing the capacitor in a high-temperature environment at 65 DEG C to 135 DEG C without applying an external voltage; finally, performing second aging treatment on the capacitor after high-temperature and non-electric storage treatment. The application effectively eliminates the bubbles hindering the repair by introducing a high-temperature and non-electric storage step between the two aging processes, so that the second aging can deeply repair the dielectric layer, and finally form a more complete and dense dielectric oxide film, thereby significantly inhibiting the rise of leakage current and improving the long-term reliability of the capacitor.

Description

Technical Field

[0002] This invention relates to the field of capacitor manufacturing technology, and more specifically, to a process for suppressing leakage current rebound in aluminum electrolytic capacitors. Background Technology

[0003] The aging process commonly used in the industry typically involves applying the rated voltage to the capacitor continuously at high temperatures (such as 85℃~105℃) for a period of time to repair the dielectric layer. However, this traditional single-cycle continuous aging process presents a long-neglected but extremely critical technical challenge.

[0004] During the aging process, the electrolyte inside the capacitor inevitably undergoes electrochemical or thermal decomposition, producing hydrogen, oxygen, and other gaseous byproducts. These gases accumulate on the surface of the dielectric oxide layer, inside the etched holes of the aluminum foil, and between the winding layers, forming a layer of tiny bubbles. Since bubbles are insulators, this bubble layer physically isolates the electrolyte from the microscopic defects in the dielectric oxide layer to be repaired, forming a layer that... Figure 3 (a) shows the “bubble-covered - electrolyte-isolated” state. In this state, the electrolyte required for the repair reaction cannot reach the defect site, causing the electrochemical reaction to be interrupted in this area, and the defect cannot be effectively repaired.

[0005] More seriously, due to the lack of an effective bubble removal mechanism in traditional processes, these bubbles may remain inside the capacitor for a long time even after the aging process is complete. This puts the capacitor in a state of "pseudo-aging"—from the perspective of external electrical parameters, the leakage current decreases in the early stages of aging, seemingly indicating that aging is complete; however, in reality, the internal dielectric layer has not been fully repaired and densified. During subsequent storage or actual use, once temperature changes, mechanical vibrations, or electric fields cause the bubbles to move, break, or merge, the unrepaired defects previously covered by the bubbles will be re-exposed to the electric field, causing the leakage current to rise sharply, thus triggering premature product failure.

[0006] Currently, there is no mature solution in the industry that can effectively address this "pseudo-aging" phenomenon. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the defects in the prior art where bubbles generated during the aging process hinder the effective repair of the dielectric layer, resulting in incomplete repair of the capacitor dielectric layer, easy rebound of leakage current, and poor long-term reliability. The present invention provides a process for suppressing leakage current rebound in aluminum electrolytic capacitors that can effectively remove bubbles generated during the aging process, fully repair the dielectric layer, and thus significantly suppress leakage current rebound.

[0008] To solve the above-mentioned technical problems, the present invention provides a process for suppressing leakage current rebound in aluminum electrolytic capacitors, specifically adopting the following technical solution.

[0009] A process for suppressing leakage current rebound in aluminum electrolytic capacitors includes the following steps performed sequentially: The aluminum electrolytic capacitor undergoes its first aging treatment. The capacitor that has undergone the first aging treatment is placed in a high-temperature environment of 65°C to 135°C for static storage without applying any external voltage, resulting in a capacitor after high-temperature non-electric storage treatment; and The capacitors that have undergone the high-temperature non-electric storage treatment are subjected to a second aging treatment.

[0010] Furthermore, the duration of the step of static storage in a high-temperature environment is 12 to 48 hours, preferably 24 hours.

[0011] Furthermore, the first aging treatment and the second aging treatment each independently include a pre-aging step at room temperature, a main aging step at high temperature, and a stable aging step at room temperature, performed sequentially, wherein: The room temperature pre-aging step includes: applying 50% to 80% of the rated voltage to the capacitor at a room temperature of 20°C to 30°C for 10 to 60 minutes. The high-temperature main aging step includes: applying a rated voltage to the capacitor at a high temperature of 85°C to 105°C for 30 to 180 minutes; and The room temperature stabilization aging step includes applying a rated voltage to the capacitor at a room temperature of 20°C to 30°C for 10 to 60 minutes.

[0012] Preferably, the temperature of the high-temperature main aging step is 95°C or 105°C.

[0013] Furthermore, the temperature of the high-temperature non-electric storage treatment is selected differently based on the diameter of the capacitor, wherein: When the diameter of the capacitor is greater than or equal to 16 mm, the temperature of the high-temperature environment is 65°C to 85°C. When the diameter of the capacitor is less than 16 mm, the temperature of the high-temperature environment is greater than 85°C to 135°C.

[0014] Preferably, the diameter of the capacitor is greater than or equal to 16 mm, and the temperature of the high-temperature environment is 70℃±2℃.

[0015] Preferably, the temperature of the high-temperature environment is 130℃±2℃.

[0016] Furthermore, both the first aging treatment and the second aging treatment consist of only a high-temperature main aging step performed at 85°C to 105°C, without including a room-temperature pre-aging step and a room-temperature stable aging step.

[0017] Furthermore, prior to the high-temperature non-electric storage treatment, a pre-venting treatment of the capacitor is included: placing the capacitor in a vacuum environment and maintaining it for 1 to 10 minutes to help expel the free gas inside the capacitor.

[0018] Furthermore, the high-temperature non-electric storage process is carried out in an inert gas protective atmosphere to prevent the capacitor from oxidizing at high temperatures.

[0019] Furthermore, the high-temperature non-electric storage treatment employs a gradient temperature increase procedure: The temperature is increased from room temperature to the target temperature in stages at a heating rate of 0.5℃ / min to 3℃ / min. At least one heat preservation platform is set up during the heating process, and the duration of each heat preservation platform is 1 to 6 hours.

[0020] Furthermore, after the high-temperature non-electric storage treatment is completed, the capacitor is slowly cooled to room temperature at a cooling rate of 0.5℃ / min to 2℃ / min.

[0021] Furthermore, the electrolyte used in the aluminum electrolytic capacitor contains ethylene glycol as the main solvent and adds ammonium dihydrogen phosphate as a repair promoter, wherein the mass percentage of ammonium dihydrogen phosphate is 0.5% to 2.0%.

[0022] The technical solution provided by this invention has the following advantages compared with the prior art: 1. Fundamentally solve the problem of "pseudo-aging" This invention innovatively introduces a high-temperature, non-electric storage step between two aging processes. Utilizing thermal motion and a settling process, it effectively promotes the dissipation or detachment of air bubbles adhering to the dielectric layer surface. This allows the electrolyte to rewet the entire dielectric layer surface—including microscopic defect areas previously uncovered due to air bubble obstruction—thus creating the necessary conditions for subsequent deep repair. Through a three-step synergistic mechanism of "preliminary repair → obstacle removal → deep repair," the "pseudo-aging" phenomenon in traditional processes is fundamentally eliminated.

[0023] 2. The integrity and density of the dielectric oxide film are significantly improved. Because the bubble barrier is effectively eliminated, the subsequent second aging treatment can deeply and effectively repair the microscopic defects that could not be completely repaired in the first aging process. Experimental data show that after treatment using the process of this invention, the density of the dielectric oxide film (indicated by porosity observed by SEM) is reduced from 3% to 5% in the traditional process to below 0.5%, and the uniformity of oxide film thickness is improved from 85% to 90% to over 98%.

[0024] 3. Leakage current rebound is significantly suppressed, and long-term reliability is greatly improved. Because the dielectric layer is more thoroughly repaired and densified, the leakage current level of the capacitor is effectively suppressed during long-term storage or use. After 500 hours of high-temperature no-load storage, the leakage current recovery rate of the capacitor treated with the process of this invention is less than 5%, while the leakage current recovery rate of the traditional single-age process is generally higher than 50%. At the same time, the durability life at rated voltage at 105℃ is extended from about 1000 hours with the traditional process to more than 2000 hours, and the batch consistency (leakage current standard deviation) of the product is improved by about 75%.

[0025] 4. Refined process control for products of different specifications This invention sets different temperature ranges for high-temperature, non-electric storage based on the different diameters of capacitors (reflecting the mechanical strength of the casing), effectively avoiding the physical damage problem of "bulging bottom" caused by the thermal expansion of internal gas in large-diameter capacitors. It takes into account both product performance and production yield, reflecting a deep consideration of engineering practice.

[0026] 5. Highly flexible in process, adaptable to diverse production needs. This invention is applicable to both sophisticated processes that include complete three-stage aging and simplified processes that only include high-temperature main aging. It can achieve the core effect of suppressing leakage current rebound under different production conditions, and has good industrial applicability and economy. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0028] Figure 1 A schematic flowchart of a process for suppressing leakage current rebound in aluminum electrolytic capacitors provided in an embodiment of the present invention; Figure 2 This is a schematic diagram comparing the effects of the process of this invention with that of the traditional process; Figure 3 This is a schematic diagram of the microscopic mechanism of the process of the present invention, wherein... Figure 3 (a) shows the state where microscopic defects are covered by bubbles. Figure 3(b) shows the state of the defects after high-temperature, electricity-free storage, where bubbles have disappeared and the electrolyte has rewetted the defects. Figure 3 (c) shows the state after the second aging when the defects were completely repaired.

[0029] The meanings of the markings in the diagram are as follows: 1—Anode aluminum foil; 2—Dielectric oxide layer; 3—Microscopic defects; 4—Electrolyte; 5—Bubble; S10—First aging treatment; S11—Pre-aging at room temperature; S12—Main aging at high temperature; S13—Stable aging at room temperature; S20—High-temperature non-electric storage treatment; S30—Second aging treatment; S31—Room temperature pre-aging; S32—High temperature main aging; S33—Room temperature stable aging; 210—Traditional process; 212—Problem of “pseudo-aging”; 220—Process of this invention; 224—Bubble elimination effect; 225—Deep repair effect. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. The embodiments described below are only some preferred embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0032] I. Explanation of Nouns and Terms To facilitate understanding of the technical solution of this invention, the key terms and concepts involved in this application are explained below: (1) Pseudo-aging: This refers to a state in which, during the aging process of aluminum electrolytic capacitors, gases generated by the decomposition or volatilization of the electrolyte accumulate on the surface of the dielectric oxide layer, forming a bubble layer. This bubble layer physically hinders the electrolyte from wetting the micro-defects to be repaired, resulting in an interruption or incomplete oxide film repair reaction. Although the leakage current of capacitors in the "pseudo-aging" state decreases in the early stage of aging, the dielectric layer is not truly and completely repaired, and the leakage current will significantly increase during subsequent storage or use.

[0033] (2) High-temperature non-electric storage treatment: This refers to a heat treatment process in which the capacitor is placed in a preset high-temperature environment, but no external working voltage or aging voltage is applied to the capacitor during the entire treatment. The core function of this step is to use thermal energy to drive bubble desorption, rather than to repair the dielectric layer through an electric field.

[0034] (3) High-temperature main aging step: refers to the core processing stage in the capacitor aging process in which voltage is applied at a higher temperature to accelerate the repair reaction of the dielectric oxide film.

[0035] (4) Bulging phenomenon: This refers to the phenomenon in which the bottom of a large-diameter aluminum electrolytic capacitor bulges outward due to irreversible deformation caused by the pressure generated by the thermal expansion of the internal gas during high-temperature processing, exceeding the mechanical strength limit of the bottom of the aluminum shell. Bulging will damage the sealing structure of the capacitor and lead to product scrap.

[0036] II. Core Process Principles Please see Figures 1 to 3 This invention provides a process for suppressing leakage current rebound in aluminum electrolytic capacitors, aiming to fundamentally solve the problem of "pseudo-aging" caused by air bubbles generated during the aging process in the background art.

[0037] Traditional process 210 typically involves only a single aging process. While this process can repair some defects in the dielectric layer, the bubbles 5 generated simultaneously hinder the contact between the electrolyte 4 and the microscopic defects 3, resulting in incomplete repair and creating a potential risk of subsequent leakage current resurgence. The core concept of this invention lies in introducing a separate process stage of "high-temperature, non-electric storage" between the first and second aging stages. By utilizing thermal energy rather than an electric field, the bubble barrier generated in the first aging stage is directionally eliminated, allowing the second aging stage to achieve deep repair under ideal conditions of full contact between the electrolyte and the dielectric layer.

[0038] like Figure 3 As shown, its microscopic mechanism can be summarized into three stages: Phase 1 – First Aging and Bubble Formation Figure 3 (a) Under the conditions of applied voltage and heat, the electrolyte 4 undergoes an electrochemical repair reaction at the microscopic defects 3 in the dielectric oxide layer 2 on the surface of the anode aluminum foil 1, generating new alumina to fill the defects. However, the byproduct gas generated by the reaction accumulates near the defects to form bubbles 5, physically isolating the microscopic defects 3 from the electrolyte 4, and the repair reaction is forced to stop in this area.

[0039] Second stage – High-temperature, electricity-free storage to eliminate air bubbles [ Figure 3(b) : Under conditions where no voltage is applied, the capacitor is placed in a high-temperature environment of 65°C to 135°C. Without the constraint of an electric field and with the thermal energy provided by the high temperature, the adhesion of bubbles 5 to the surface of the dielectric oxide layer 2 weakens, causing them to gradually detach, dissolve in the electrolyte 4, or migrate to other areas. After the bubble barrier is removed, the electrolyte 4 can completely re-wet the micro-defects 3.

[0040] Phase Three – Second Deep Repair of Aging [ Figure 3 (c) : Under the condition that the bubbles have been removed and the electrolyte has fully wetted all micro-defects, the voltage and temperature are applied again, and the electrochemical reaction can proceed efficiently and without hindrance. All defects are completely repaired, forming a complete, uniform and dense dielectric oxide layer 2.

[0041] III. Examples The present invention will now be described in more detail through specific embodiments. Example 1

[0042] This embodiment provides a process for suppressing leakage current rebound in aluminum electrolytic capacitors, the process of which is as follows: Figure 1 As shown.

[0043] The objects to be processed are a batch of aluminum electrolytic capacitors with a diameter of 10mm, a rated voltage of 50V, and a capacitance of 100μF.

[0044] Step S10: First aging treatment. An aging voltage is applied to the capacitor to perform electrochemical repair. In this embodiment, the first aging treatment adopts a three-stage process: Room temperature pre-aging S11: At room temperature of 25°C, apply 60% of the rated voltage (i.e., 0V) to the capacitor for 20 minutes; High-temperature main aging S12: Heat to 95℃, apply 50V rated voltage, and continue for 60 minutes; Stable aging of S13 at room temperature: Reduce the temperature to 25°C and continue to apply 50V for 20 minutes.

[0045] Step S20: High-temperature non-electric storage treatment. Remove the capacitors that have completed the first aging process from the aging equipment and place them in a constant temperature oven preheated to 100°C. Do not apply any voltage and let them stand for 24 hours.

[0046] Step S30: Second aging treatment. After the capacitors have been stored at high temperature, they are taken out and allowed to cool naturally to room temperature. Then, the same three-stage process as the first aging treatment is performed (25℃ pre-aging for 20 min → 95℃ main aging for 60 min → 25℃ stable aging for 20 min).

[0047] After processing in this embodiment, the initial leakage current of the capacitor is ≤0.003CV (far superior to the industry standard of 0.01CV). After 500 hours of storage at 85°C without load, the leakage current recovery rate is only 3.2%, while the leakage current recovery rate of the same specification capacitor using the traditional single aging process (main aging at 95°C for 60 minutes) is as high as 58% under the same conditions. This embodiment fully demonstrates the effectiveness of the basic solution of the present invention. Example 2

[0048] This embodiment addresses the engineering problem of "bulging" in large-diameter capacitors (≥16mm) during high-temperature processing by providing an optimized process solution.

[0049] The objects to be processed are a batch of aluminum electrolytic capacitors with a diameter of 35mm, a rated voltage of 63V, and a capacitance of 1000μF.

[0050] Both step S10 (first aging treatment) and step S30 (second aging treatment) adopt the same three-stage process as in Example 1 (room temperature pre-aging → 95℃ high temperature main aging for 60 min → room temperature stable aging). The key difference lies in the temperature setting of step S20 (high temperature non-electric storage).

[0051] Considering that the 35mm diameter capacitor aluminum shell has a large bottom area and relatively weak mechanical strength to resist internal pressure, if a storage temperature above 100℃ is used, the pressure generated by the thermal expansion of residual gas and electrolyte vapor inside may exceed the aluminum shell's tolerance limit, causing the bottom to bulge and deform, resulting in product scrap. Therefore, in this embodiment, the high-temperature non-electric storage temperature is set at 70℃, and the storage time remains 24 hours.

[0052] A temperature of 70°C is sufficient to promote the desorption of bubbles from the dielectric layer surface (especially with a sufficient treatment time of up to 24 hours), while the resulting internal pressure is far below the bulging threshold of the aluminum casing for this specification of capacitor. Testing showed that the capacitors treated in this embodiment had no bulging defects, achieving a product qualification rate of 99.2%, and the leakage current recovery rate was only 4.5% after 500 hours of high-temperature storage, significantly better than traditional processes. This embodiment verifies the scientific validity and practicality of setting a lower storage temperature for large-diameter capacitors. Example 3

[0053] This embodiment aims to achieve the best possible repair results and is suitable for small capacitors (diameter <16mm) with extremely high reliability requirements.

[0054] The objects to be processed are a batch of aluminum electrolytic capacitors with a diameter of 10mm, a rated voltage of 50V, and a capacitance of 100μF.

[0055] Step S10, the first aging process, adopts a three-stage process, in which the temperature of the high-temperature main aging S12 is set at 105°C (higher than 95°C in Example 1) and lasts for 120 minutes to obtain a stronger repair drive.

[0056] The temperature for the high-temperature, non-electric storage treatment in step S20 is set at 130°C for 24 hours. The high temperature of 130°C provides a strong thermal driving force, enabling the bubbles generated during the first aging process to detach from the surface of the medium layer extremely quickly and completely.

[0057] Step S30, the second aging treatment, is exactly the same as the first aging treatment (main aging at 105℃ for 120 min).

[0058] The capacitor treated in this embodiment has an initial leakage current value ≤0.001CV. After 1000 hours of storage at 85℃ without load, the leakage current recovery rate is only 1.8%. After 2000 hours of durability testing at 105℃ and rated voltage, the capacitance change rate is less than ±8%, the increase in the loss tangent is minimal, and all electrical parameters remain highly stable. This embodiment demonstrates that, within the thermal stress range that the capacitor body can withstand, appropriately increasing the high-temperature storage temperature without electricity and the main aging temperature can further improve the repair effect and long-term reliability. Example 4

[0059] This embodiment provides a process solution that includes pre-venting pretreatment, which is particularly suitable for capacitor products with large diameter or ultra-high reliability requirements.

[0060] The specific steps are as follows: Step S01: Pre-venting treatment. The aluminum electrolytic capacitors that have completed core assembly, are impregnated with electrolyte, but have not yet aged are placed in a vacuum drying oven. The oven temperature is controlled at 70℃, and the vacuum level is maintained at -0.09MPa for 5 minutes. This vacuum environment effectively extracts the free gas remaining between the aluminum foil winding layers inside the capacitor, reducing the initial content of bubbles during subsequent aging.

[0061] Step S10: First aging treatment. A three-stage process is adopted (25℃ pre-aging for 20 min → 95℃ main aging for 60 min → 25℃ stable aging for 20 min).

[0062] Step S20: High-temperature non-electric storage treatment. For capacitors with a diameter ≥ 16 mm, the set temperature is 70 °C; for capacitors with a diameter < 16 mm, the set temperature is 130 °C. The storage time is 24 hours for both.

[0063] Step S30: Second aging treatment. Same as the first aging treatment.

[0064] Comparative tests showed that the "vacuum pre-venting + high-temperature non-electric storage" combination solution reduced the total amount of residual gas inside the capacitor by approximately 30% to 40% compared to the solution using high-temperature non-electric storage alone. The density of the dielectric oxide film after the second aging process was further improved, and the leakage current level was reduced by approximately 15% to 20%. This combination solution is particularly suitable for applications with extremely stringent requirements for leakage parameters (such as medical electronics and aerospace). Example 5

[0065] To further optimize the effect of high-temperature non-electric storage and avoid thermal shock to the internal structure of the capacitor caused by a sudden increase in temperature, this embodiment provides a high-temperature non-electric storage scheme with gradient temperature rise.

[0066] The capacitors that have undergone the first aging treatment are placed in a programmable temperature control chamber, and the following heating-holding program is executed: First heating stage: Increase the temperature from room temperature to 80℃ at a rate of 2℃ / min, and hold for 2 hours; Second heating stage: Increase from 80℃ to 105℃ at a rate of 1℃ / min, and hold for 4 hours; The third heating stage: the temperature is increased from 105℃ to 130℃ at a rate of 0.5℃ / min, and held for 18 hours; The material was allowed to cool naturally to room temperature, completing the high-temperature, non-electric storage process.

[0067] The advantages of this gradient heating scheme are: (1) The gradual heating allows the thermal stress generated by the different thermal expansion coefficients of the various materials (aluminum foil, electrolytic paper, and rubber seals) inside the capacitor to be fully released, preventing damage to the sealing structure; (2) Different temperature stages allow bubbles of different sizes and adhesion to be desorbed in sequence—larger and weaker bubbles are desorbed at low temperatures, and small and stubborn bubbles are desorbed at high temperatures, achieving the classification and thorough removal of bubbles; (3) During the heating process, the viscosity of the electrolyte decreases with the increase of temperature, and the fluidity is enhanced, which is more conducive to wetting the micro-defects deep in the etched holes.

[0068] Comparative tests showed that, compared with the direct constant temperature of 130℃, the gradient heating scheme (total duration 24 hours) improved the batch consistency (standard deviation) of capacitor leakage current by about 25%, reduced the deformation rate of capacitor shell by about 40% after high-temperature storage, and increased the product qualification rate from 92% to 98.5%. Example 6

[0069] For applications requiring ultra-high reliability (such as aerospace, deep-sea exploration, etc.), this embodiment provides a processing technology that includes multiple "aging-storage" cycles.

[0070] The specific process is as follows: Perform the first aging treatment (three-stage, main aging at 95℃ for 60 minutes); Perform the first high-temperature, non-electric storage treatment (100℃, 24h); Perform a second aging process (three-stage, main aging at 95℃ for 60 minutes). Perform a second high-temperature, non-electric storage treatment (100℃, 12h, time shortened); Perform the third aging process (three-stage, 95℃ main aging for 60 minutes).

[0071] The medium layer is repaired layer by layer through two cycles (three aging cycles + two intermediate storage cycles). Each repair goes beyond the previous bubble removal to further repair more microscopic defects.

[0072] Experimental data shows that after three aging cycles, the uniformity of the dielectric oxide film thickness of the capacitor is improved to over 98.5% (compared to approximately 85%–90% for traditional single aging). After 2000 hours of durability testing at 105℃ and rated voltage, the leakage current recovery rate is only 1.2%, far below the industry standard requirements. Example 7

[0073] The inventors of this invention further discovered that the effectiveness of high-temperature, non-electric storage treatment is closely related to the viscosity characteristics of the electrolyte. When the electrolyte viscosity is low, bubbles are more likely to detach from the surface of the dielectric layer and dissolve in the electrolyte at high temperatures.

[0074] Based on this, this embodiment provides an electrolyte optimization scheme that is compatible with the process of the present invention: the electrolyte contains ethylene glycol as the main solvent and adds ammonium dihydrogen phosphate (NH4H2PO4) as a repair promoter, wherein the mass percentage of ammonium dihydrogen phosphate is 0.5% to 2.0%.

[0075] This phosphate additive acts as a surfactant during high-temperature, non-electrostatic storage, further reducing the interfacial tension between the electrolyte and air bubbles, and accelerating bubble desorption and dissolution. Simultaneously, ammonium dihydrogen phosphate participates in the electrochemical reaction during the second aging process, promoting the formation of a denser phosphate composite oxide film and further enhancing the insulation performance of the dielectric layer.

[0076] Experiments have verified that, after 24 hours of storage at 130°C without electricity, the residual bubble rate on the surface of the dielectric layer of the aluminum electrolytic capacitor using this compatible electrolyte decreased from approximately 5.8% to below 0.3%, and the leakage current recovery rate decreased from 4.7% to 1.1%, achieving a significant synergistic effect. Example 8

[0077] Further research by the inventors revealed that the cooling method after high-temperature, non-electric storage treatment also has a significant impact on the performance of the final product. If the capacitor is rapidly cooled from a high temperature (e.g., 130°C) by direct exposure to room temperature air, thermal stress will be generated inside the capacitor due to the difference in material shrinkage rate, which may lead to microcracks in the dielectric oxide film and introduce new defects.

[0078] Based on this, this embodiment provides a controlled cooling scheme: after the high-temperature non-electric storage treatment is completed, the capacitor is slowly cooled to room temperature at a rate of 0.5℃ / min to 2℃ / min, preferably at a cooling rate of 1℃ / min. This slow cooling process can be performed in a programmable thermostat or by transferring the capacitor to a gradient cooling furnace.

[0079] After adopting the controlled slow cooling scheme, the thermal stress cracking phenomenon of the capacitor dielectric oxide film was effectively suppressed, the microcrack density observed under scanning electron microscopy was reduced by about 70%, and the initial leakage current value after the second aging was further reduced by about 10% to 15%, thus further ensuring the long-term reliability of the product. Example 9

[0080] This embodiment aims to verify the universality and robustness of the core concept of the present invention. Even if the complex three-stage aging process is simplified by omitting the room temperature pre-aging and room temperature stable aging steps and retaining only the high temperature main aging, the core step introduced by the present invention—high temperature non-electric storage treatment—can still play a key role and bring about significant performance improvement.

[0081] Specifically, both the first and second aging treatments consisted of a single high-temperature main aging step at 95°C for 60 minutes, excluding pre-aging and stabilization aging. The intermediate high-temperature, non-electric storage treatment was conducted at 100°C for 24 hours.

[0082] Experimental results show that, compared with the traditional process of performing only one 95°C high-temperature aging process, the capacitor using the simplified "aging-storage-aging" structure of this embodiment has a leakage current recovery rate of 6.8% after 500 hours of high-temperature storage, while the traditional process has a rate of 55%. This indicates that the key to solving the "pseudo-aging" problem lies in inserting a de-energized high-temperature resting process between the two voltage-applied aging processes, rather than in the complexity of the aging process itself. The existence of this embodiment can effectively prevent others from circumventing the protection scope of this invention by simplifying the aging process.

[0083] IV. Summary of Results Data To more intuitively demonstrate the technical effects of the present invention, the key performance indicators of the above embodiments and conventional processes are summarized in Table 1.

[0084] Table 1 Comparison of performance of each embodiment with traditional process

[0085] The following conclusions can be drawn from the data in Table 1: (1) In all embodiments using the process of the present invention, the leakage current recovery rate is significantly lower than that of the traditional process (≤6.8% vs. ≥50%), indicating that the present invention has a universal effect in suppressing leakage current recovery; (2) The leakage current recovery rate of each preferred embodiment (Examples 1 to 8) is controlled below 5%, which is excellent; (3) The porosity of the dielectric oxide film decreased from 3% to 5% in the traditional process to 0.2% to 1.2%, proving that the density of the dielectric layer was substantially improved; (4) Except for the embodiment where the pursuit of extreme performance leads to a slight decrease in the yield rate, the product yield rate of most solutions is higher than that of traditional processes, indicating that the present invention improves performance without sacrificing production yield.

[0086] The process for suppressing leakage current rebound in aluminum electrolytic capacitors provided by this invention has broad industrial application prospects and significant economic value.

[0087] In the field of automotive electronics, aluminum electrolytic capacitors used in key modules such as engine control units (ECUs), anti-lock braking systems (ABS), and airbag controllers need to operate stably for extended periods within a wide temperature range of -40°C to 125°C. The capacitors produced by the process of this invention, due to their extremely low leakage current recovery rate, ensure that these safety-related systems will not fail due to capacitor failure throughout the entire lifespan of the vehicle, greatly improving driving safety.

[0088] In the fields of industrial control and server power supplies, equipment typically requires 24 / 7 uninterrupted operation, and the reliability of the power supply directly affects the stability of the entire system. The high-reliability capacitors produced by this invention effectively prevent overheating and premature failure caused by increased leakage current, ensuring the continuous and stable operation of critical infrastructure such as data centers, communication base stations, and large-scale automated production lines.

[0089] In the field of medical devices, such as life support systems and precision diagnostic instruments, the failure of any component can have catastrophic consequences. The capacitor provided by this invention has extremely high stability and predictability, meeting the highest reliability standards required by medical devices.

[0090] In aerospace, defense, and other fields, electronic equipment needs to operate in harsh environments such as vibration, shock, and extreme temperatures. This invention improves the intrinsic quality and stress resistance of capacitors by deeply repairing defects in the dielectric layer, thus meeting the stringent selection requirements for components in these high-end applications.

[0091] Furthermore, the process of this invention does not require the addition of expensive special equipment; it can be achieved using only conventional constant temperature ovens and aging power supplies. The cost of modifying existing production lines is low, the implementation is easy, and it has good economic efficiency and feasibility for promotion.

[0092] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and all such simple modifications fall within the protection scope of the present invention.

[0093] For example, although the high-temperature non-electric storage time is set to 24 hours in the preferred embodiment, in actual production, it can be flexibly adjusted within the range of 12 hours to 48 hours according to factors such as capacitor specifications, electrolyte formula, and equipment conditions, and the core effect of the present invention can be achieved in all cases.

[0094] For example, the specific temperature values ​​mentioned in this invention (such as 65℃, 70℃, 85℃, 95℃, 100℃, 105℃, 130℃, 135℃, etc.) are all allowed to have a normal process fluctuation of ±2℃, which does not affect the implementation of the technical solution of this invention and the realization of the effect.

[0095] For example, the specific time values ​​listed in this invention (such as 10 minutes, 20 minutes, 30 minutes, 60 minutes, 120 minutes, 24 hours, etc.) are all allowed to have a conventional process deviation of ±10%, which will not affect the realization of the core effect of this invention.

Claims

1. A process for suppressing leakage current rebound in aluminum electrolytic capacitors, characterized in that, This includes the following steps performed sequentially: The aluminum electrolytic capacitor undergoes its first aging treatment. The capacitor that has undergone the first aging treatment is placed in a high-temperature environment of 65°C to 135°C for static storage without applying any external voltage to obtain a capacitor after high-temperature non-electric storage treatment; and the capacitor after high-temperature non-electric storage treatment is subjected to a second aging treatment.

2. The processing technology according to claim 1, characterized in that, The first aging treatment and the second aging treatment each independently include the following sub-steps: Room temperature pre-aging step: At room temperature of 20°C to 30°C, apply 50% to 80% of the rated voltage to the capacitor for 10 to 60 minutes. High-temperature main aging step: Applying the rated voltage to the capacitor at a high temperature of 85°C to 105°C for 30 to 180 minutes; and Room temperature stabilization aging step: Apply the rated voltage to the capacitor at a room temperature of 20°C to 30°C for 10 to 60 minutes.

3. The processing technology according to claim 2, characterized in that, The temperature of the high-temperature main aging step is 95°C or 105°C.

4. The processing technology according to claim 1, characterized in that, The duration of the static storage is 12 to 48 hours.

5. The processing technology according to claim 1, characterized in that, The temperature of the high-temperature environment is selected according to the diameter of the capacitor, wherein: When the diameter of the capacitor is greater than or equal to 16 mm, the temperature of the high-temperature environment is 65°C to 85°C. When the diameter of the capacitor is less than 16 mm, the temperature of the high-temperature environment is greater than 85°C to 135°C.

6. The processing technology according to claim 1, characterized in that, Before the static storage, the process includes a pre-venting step for the capacitor: placing the capacitor in a vacuum environment for 1 to 10 minutes to remove free gas from inside the capacitor.

7. The processing technology according to claim 1, characterized in that, The static storage is carried out using a gradient heating program: the temperature is increased from room temperature to the target temperature in stages at a heating rate of 0.5℃ / min to 3℃ / min, and at least one heat preservation platform is set up during the heating process, with each heat preservation platform lasting for 1 to 6 hours.

8. The processing technology according to claim 1, characterized in that, After the static storage is completed, the capacitor is cooled to room temperature at a cooling rate of 0.5°C / min to 2°C / min.

9. The processing technology according to claim 1, characterized in that, The electrolyte of the aluminum electrolytic capacitor contains ammonium dihydrogen phosphate, and the mass percentage of ammonium dihydrogen phosphate is 0.5% to 2.0%.

10. The processing method according to claim 1, characterized in that, The first aging treatment and the second aging treatment each include only one high-temperature main aging step, without the room temperature pre-aging step and the room temperature stable aging step. The high-temperature main aging step is carried out at 85°C to 105°C.

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