Preparation method and system of anode of tantalum capacitor with low ESR

Abstract

The invention belongs to the technical field of tantalum anodes, and particularly relates to a preparation method and system of a low-ESR tantalum capacitor anode.The method comprises the steps that during energizing, high-frequency pressure waves are applied to energizing liquid at intervals so that the energizing liquid can evenly permeate into the tantalum anode, the uniformity of the concentration of the energizing liquid inside and outside the tantalum anode can be improved, current distribution can be more uniform, and the ESR performance of the tantalum capacitor can be improved; the growth rate of the oxide film is consistent, the ESR is reduced, the temperature of the energizing liquid is 70-90 DEG C, high-frequency pressure waves are carried out once every 10-30 min, and the high-frequency pressure waves are kept for 1-5 min each time until the energizing process is finished; in the manganese leaching process, low-frequency pressure waves are applied to manganese leaching liquid at intervals, so that the diffusion rate of manganous nitrate ions is increased, the manganous nitrate ions permeate into pores of the tantalum anode more quickly, a MnO2 layer is evenly deposited in a wider area, the problem that the MnO2 layer is too thin or hollow due to poor permeability is solved, ESR is reduced, the temperature of the manganese leaching liquid is 35-45 DEG C, and the service life of the manganese leaching liquid is prolonged. The low-frequency pressure waves are applied once every 2-4 minutes, and each time is kept for 20-40 seconds until the manganese leaching process is finished.

Description

Technical Field

[0001] The present invention belongs to the technical field of tantalum anodes, and particularly relates to a preparation method and system for an anode of a low-ESR tantalum capacitor. Background Art

[0002] A tantalum capacitor is a high-performance electrolytic capacitor with tantalum metal as the core material, which has the characteristics of small volume, large capacitance, high reliability, etc., and is widely used in electronic devices. Its preparation method includes pressing tantalum powder into shape, high-temperature sintering, energization (anodic oxidation), manganese impregnation (coating), graphite and silver layer coating, lead wire welding and encapsulation, etc.

[0003] However, when energizing some high-energy tantalum anodes or high-specific-capacitance tantalum anodes with larger volumes, uneven penetration may occur, resulting in inconsistent solution concentrations, uneven current distribution, inconsistent oxidation film growth rates, and oxygen bubbles generated by the oxygen evolution reaction adhering to the surface and inside of the tantalum anode, hindering the uniform deposition of Ta2O5, making the thickness of the oxidation film uneven, and leading to an increase in leakage current and ESR. In the manganese impregnation process, due to the poor permeability of the manganese nitrate solution, it is easy to cause the MnO2 layer inside the porous tantalum anode to be too thin or have voids, unable to completely cover the surface of the Ta2O5 dielectric layer, also resulting in an increase in ESR. Moreover, multiple manganese impregnations will make the MnO2 layer on the surface of the tantalum anode too thick, and it is prone to cracking or peeling under stress during thermal decomposition, further leading to an increase in ESR.

[0004] In the prior art, in order to improve the impregnation effect of the solution, methods such as vacuum impregnation devices and step-by-step boosting energization are adopted. However, these methods have problems such as complex equipment, high cost, long time consumption, etc., and cannot completely solve the problem of incomplete solution impregnation. Summary of the Invention

[0005] In view of this, the present invention provides a preparation method and system for an anode of a low-ESR tantalum capacitor to solve the technical problem that the ESR of the tantalum anode prepared by energization and manganese impregnation in the prior art is relatively large.

[0006] To achieve the above object, the present application adopts the following scheme: A preparation method for an anode of a low-ESR tantalum capacitor, during the energization process, a high-frequency pressure wave is intermittently applied to the energization solution to enable the energization solution to uniformly penetrate into the tantalum anode, improve the uniformity of the energization solution concentration inside and outside the tantalum anode, make the current distribution more uniform, the oxidation film growth rate consistent, and reduce the ESR. Among them, the temperature of the energization solution is 70°C - 90°C, the high-frequency pressure wave is applied once every 10 min - 30 min, and each time it is maintained for 1 min - 5 min until the energization process ends; During the manganese immersion process, a low-frequency pressure wave is intermittently applied to the manganese immersion solution to increase the diffusion rate of manganese nitrate ions, so that the manganese nitrate ions can penetrate into the pores of the tantalum anode faster, enabling the MnO2 layer to be evenly deposited in a wider area, avoiding the problems of too thin or hollow MnO2 layer caused by poor permeability, and reducing the ESR. Among them, the temperature of the manganese immersion solution is 35°C - 45°C, the low-frequency pressure wave is applied every 2 min - 4 min, and each time it is maintained for 20 s - 40 s until the end of the manganese immersion process.

[0007] Preferably, the forming process specifically includes the following steps: S11. The forming solution is a phosphoric acid solution or a mixed solution of phosphoric acid and ethylene glycol. Immerse the tantalum anode in the mixed solution and apply a DC voltage to generate a Ta2O5 dielectric layer. S12. Heat the temperature of the mixed solution to 70°C - 90°C. S13. When starting to form the tantalum anode, apply a high-frequency pressure wave of 20 KHz - 100 KHz to the mixed solution intermittently, turn it on every 10 min - 30 min, and each time it is turned on for 1 min - 5 min.

[0008] Preferably, the manganese immersion process specifically includes the following steps: S21. Wash and dry the tantalum anode obtained after forming with deionized water. S22. The manganese immersion solution is a manganese nitrate solution. Immerse the tantalum anode in the manganese nitrate solution and thermally decompose it to generate a MnO2 layer. S23. Maintain the temperature of the manganese nitrate solution at 35°C - 45°C. S24. When starting to immerse the tantalum anode in manganese, apply a low-frequency pressure wave of 10 KHz - 40 KHz to the manganese nitrate solution, apply it every 2 min - 4 min, and each time the application time is 20 s - 40 s.

[0009] Preferably, the manganese immersion process includes 2 to 4 manganese immersion steps, and as the number of manganese immersion times increases, both the frequency and the application time of the low-frequency pressure wave decrease in sequence.

[0010] Preferably, when the manganese immersion process includes 3 manganese immersion steps, in the first manganese immersion, the concentration of the manganese nitrate solution is 20%, the frequency of the low-frequency pressure wave is 35 KHz, it is applied every 2 min, and each time it is 30 s.

[0011] Preferably, when the manganese immersion process includes 3 manganese immersion steps, in the second manganese immersion, the concentration of the manganese nitrate solution is 30%, the frequency of the low-frequency pressure wave is 25 KHz, it is applied every 2 min, and each time it is 25 s.

[0012] Preferably, when the manganese immersion process includes three manganese immersion steps, during the third manganese immersion, the concentration of the manganese nitrate solution is 30%, the frequency of the low-frequency pressure wave is 15 KHz, it is applied once every 2 minutes, and each time is 20 s.

[0013] A preparation system for an anode of a low-ESR tantalum capacitor includes an energizing device and a manganese immersion device. A penetration defoaming component is provided on the energizing device, and the penetration defoaming component can generate a high-frequency pressure wave of 20 KHz - 100 KHz. An air-raid shelter component is provided on the manganese immersion device, and the air-raid shelter component can generate a low-frequency pressure wave of 10 KHz - 40 KHz.

[0014] Preferably, the energizing device specifically includes a first metal sheet, a circulating water pump, an energizing tank, an overflow plate, and an energizing DC power supply. The energizing tank is used to hold the energizing solution. The first metal sheet is arranged on the mouth of the energizing tank through an insulating gasket. A plurality of first tantalum wires are arranged at intervals on the lower surface of the first metal sheet. The tantalum anode to be energized is arranged on the first tantalum wires. The positive pole of the energizing DC power supply is connected to the first metal sheet, and the negative pole is connected to the energizing tank. The overflow plate is vertically arranged in the energizing tank, and a liquid replenishing chamber is formed between the overflow plate and one side surface of the energizing tank. And the height of the overflow plate is higher than the height of the tantalum anode, which is used to ensure the liquid level of the energizing solution so that the solution just submerges the upper part of the tantalum anode, and the overflowed solution flows to the liquid replenishing chamber. The circulating water pump is connected to the liquid replenishing chamber and the energizing tank, and is used to pump the solution in the liquid replenishing chamber back into the energizing tank to realize solution circulation. A first heater is arranged at the lower part of the energizing tank, and the penetration defoaming component is arranged on the outer wall of the energizing tank.

[0015] Preferably, the manganese immersion device specifically includes a second metal sheet and a conical manganese immersion tank. The conical manganese immersion tank is used to hold the manganese immersion solution. The second metal sheet is arranged on the mouth of the conical manganese immersion tank. A plurality of second tantalum wires are arranged at intervals on the lower surface of the second metal sheet. The tantalum anode to be manganese-immersed is arranged on the second tantalum wires. A discharge port is arranged at the conical part of the conical manganese immersion tank. A second heater is arranged at the lower part of the conical manganese immersion tank, and the air-raid shelter component is arranged on the outer wall of the conical manganese immersion tank.

[0016] In the above method and system for preparing the anode of a low-ESR tantalum capacitor, during energization, the 20KHz - 100KHz high-frequency pressure wave generated by the penetration and defoaming component 7 triggers the generation, expansion, and violent rupture of tiny bubbles in the energizing solution. The jets generated by the bubble rupture will impact the surface and the interior pores of the tantalum anode 1, effectively avoiding gas retention. At the same time, it improves the permeability of phosphate ions in the solution, makes the current density distribution more uniform, the growth rate of the oxide film more consistent. And when using the high-frequency pressure wave intermittently, the solution can be stirred and degassed more frequently, which is beneficial to maintaining the uniformity and stability of the solution, reducing the situation of uneven oxide film thickness, and lowering the leakage current and ESR. When performing manganese impregnation using the manganese impregnation device provided by the present invention, the 10KHz - 40KHz low-frequency pressure wave generated by the air-raid shelter component 15, the microjets and shock waves generated by the cavitation effect can increase the turbulence degree of the solution, reduce the concentration gradient in the solution, and improve the diffusion rate of manganese nitrate ions, so that the manganese nitrate ions can penetrate into the pores of the tantalum anode 1 faster, and the MnO2 layer after thermal decomposition is uniformly deposited in a wider area, avoiding the problems of too thin MnO2 layer or voids caused by poor permeability, thereby reducing the ESR and improving the performance of the tantalum capacitor.

[0017] In addition, when using the high-frequency pressure wave intermittently during energization, a good energization effect can be achieved without the need for a step-by-step boosting energization process, avoiding the problem of long time-consuming for multi-stage energization and improving the efficiency. When using the low-frequency pressure wave intermittently during manganese impregnation, the number of manganese impregnation times can be reduced, thus avoiding problems such as too thick MnO2 layer, cracking or shedding during thermal decomposition caused by multiple manganese impregnations, and improving the quality and performance of the product. Brief Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the energization device in the present invention.

[0019] Figure 2 It is a schematic structural diagram of the manganese impregnation device in the present invention.

[0020] In the figure, tantalum anode 1, tantalum wire 2, first metal sheet 3, insulating gasket 4, liquid supply tank 5, circulation water pump 6, penetration and defoaming component 7, first heater 8, energization tank 9, overflow plate 10, second metal sheet 13, manganese impregnation tank 14, air-raid shelter component 15, discharge port 16, second heater 17, energization DC power supply 18. Detailed Embodiments

[0021] To facilitate the understanding of the present application, the present application will be described more comprehensively below in conjunction with the accompanying drawings. And the preferred embodiments of the present application are given. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0023] This application provides a method for preparing an anode of a low-ESR tantalum capacitor, comprising the following steps: During the forming process, a high-frequency pressure wave is intermittently applied to the forming solution to enable the forming solution to uniformly penetrate into the tantalum anode, improve the uniformity of the forming solution concentration inside and outside the tantalum anode, make the current distribution more uniform, the growth rate of the oxide film consistent, and reduce the ESR. Wherein, the temperature of the forming solution is 70°C - 90°C, the high-frequency pressure wave is applied every 10 min - 30 min, and each time it is maintained for 1 min - 5 min until the forming process ends; During the manganese impregnation process, a low-frequency pressure wave is intermittently applied to the manganese impregnation solution to increase the diffusion rate of manganese nitrate ions, so that the manganese nitrate ions can penetrate into the pores of the tantalum anode faster, and the MnO2 layer is uniformly deposited in a wider area, avoiding the problems of too thin MnO2 layer or voids caused by poor permeability, and reducing the ESR. Wherein, the temperature of the manganese impregnation solution is 35°C - 45°C, the low-frequency pressure wave is applied every 2 min - 4 min, and each time it is maintained for 20 s - 40 s until the manganese impregnation process ends. The high-frequency pressure wave and the low-frequency pressure wave can be generated by a shock wave generator, a pulsed pneumatic generator, a cavitating jet generator, etc. In this embodiment, an ultrasonic generator is preferably used.

[0024] During preparation, first, the tantalum anode 1 is subjected to high-temperature vacuum sintering to obtain the tantalum anode 1 of the required specification. Then, it is formed using a forming device. During forming, the forming solution used is generally a phosphoric acid solution or a mixed solution of phosphoric acid and ethylene glycol. The tantalum anode 1 is immersed in the forming solution, and the forming solution is heated. At the same time, a high-frequency pressure wave is applied to the forming solution, which is turned on every 10 min - 30 min, and the opening time each time is maintained for 1 min - 5 min until the forming process ends; after the forming process of the tantalum anode 1 is completed and subjected to pre-treatment such as cleaning, a manganese nitrate solution required for the manganese impregnation process is prepared and placed in a manganese impregnation device. The tantalum anode 1 is immersed in the manganese nitrate solution, and the heating device required for the manganese impregnation process is turned on, etc., to control the relevant parameters of the manganese impregnation process (temperature 35°C - 45°C). At the same time, a low-frequency pressure wave is applied to the manganese nitrate solution, which is turned on every 2 min - 4 min, and the opening time each time is maintained for 20 s - 40 s until the manganese impregnation process ends.

[0025] During energization, the 20KHz - 100KHz high-frequency pressure waves generated by the penetration and degassing component 7 trigger the generation, expansion, and violent rupture of tiny bubbles in the energizing solution. The jets generated by the bubble rupture will impact the surface and the interior of the pores of the tantalum anode 1, effectively avoiding gas retention. At the same time, it improves the permeability of phosphate ions in the solution, making the current density distribution more uniform, the growth rate of the oxide film more consistent. When using high-frequency pressure waves intermittently, the solution can be stirred and degassed more frequently, which is conducive to maintaining the uniformity and stability of the solution, reducing the unevenness of the oxide film thickness, and reducing leakage current and ESR. When using the manganese dipping device provided by the present invention for manganese dipping, the 10KHz - 40KHz low-frequency pressure waves generated by the air-raid shelter component 15, the microjets and shock waves generated by the cavitation effect can increase the turbulence degree of the solution, reduce the concentration gradient in the solution, and improve the diffusion rate of manganese nitrate ions, so that the manganese nitrate ions can penetrate into the pores of the tantalum anode 1 faster, and the MnO2 layer after thermal decomposition is evenly deposited in a wider area, avoiding the problems of too thin or hollow MnO2 layer caused by poor permeability, thereby reducing ESR and improving the performance of tantalum capacitors.

[0026] In addition, when using high-frequency pressure waves intermittently during energization, a good energization effect can be achieved without going through the process of step-by-step voltage boosting for energization, avoiding the problem of long time consumption in multi-stage energization and improving efficiency; when using low-frequency pressure waves intermittently during manganese dipping, the number of manganese dipping times can be reduced, thus avoiding problems such as too thick MnO2 layer, cracking or falling off during thermal decomposition caused by multiple manganese dips, and improving the quality and performance of the product.

[0027] Specifically, the energization process specifically includes the following steps: S11. The energizing solution is a phosphoric acid solution or a mixed solution of phosphoric acid and ethylene glycol. Immerse the tantalum anode in the mixed solution and apply a DC voltage to generate a Ta2O5 dielectric layer. S12. Heat the temperature of the mixed solution to 70°C - 90°C. S13. When starting to energize the tantalum anode, intermittently apply high-frequency pressure waves of 20KHz - 100KHz to the mixed solution, turn on once every 10min - 30min, and each time the opening time is 1min - 5min.

[0028] During preparation, specifically, the tantalum anode 1 obtained through preliminary treatment (such as high-temperature vacuum sintering after pre-forming tantalum powder and tantalum wire 2) is carefully immersed in the mixed solution, ensuring that the tantalum anode 1 is completely covered by the solution. After the tantalum anode 1 is immersed in the mixed solution, a DC power supply is connected, and a DC voltage is applied to the tantalum anode 1. Under the action of the electric field, phosphate ions in the solution will migrate to the surface of the tantalum anode 1 and react with the tantalum anode 1, gradually generating a Ta2O5 dielectric layer on the surface and inside the pores of the tantalum anode 1; the solution temperature in the container containing the tantalum anode 1 and the mixed solution is heated to 70°C - 90°C using a heating device (such as a heater, etc.) to improve the fluidity of the solution, reduce the surface tension of the solution, and help the solution better penetrate into the porous structure of the tantalum anode 1. After starting to energize the tantalum anode 1, a high-frequency pressure wave of 20KHz - 100KHz is applied, once every 10min - 30min, and each application time lasts for 1min - 5min. When the high-frequency pressure wave propagates in the mixed solution, it can impact the surface and inside the pores of the tantalum anode 1, expel the trapped gas, and ensure the uniform growth of the Ta2O5 dielectric layer. By improving the solution permeability and avoiding gas retention, the phosphate ions in the solution can react more uniformly with the tantalum anode 1, so that the Ta2O5 dielectric layer is uniformly deposited on the surface and inside the pores of the tantalum anode 1, avoiding defects such as voids and cracks.

[0029] Due to the improvement of solution permeability and the solution of the gas retention problem, the thickness of the Ta2O5 dielectric layer is more uniform and the density is higher, reducing the defects in the dielectric layer, thereby improving the quality of the Ta2O5 dielectric layer. And the uniform and dense Ta2O5 dielectric layer can reduce the electron transport resistance in the dielectric layer, lower the equivalent series resistance (ESR) of the tantalum capacitor, and improve the performance of the tantalum capacitor.

[0030] Specifically, the manganese immersion process specifically includes the following steps: S21. Wash the tantalum anode obtained after energization with deionized water and dry it; S22. The manganese immersion solution is a manganese nitrate solution. Immerse the tantalum anode in the manganese nitrate solution to thermally decompose and form a MnO2 layer; S23. Maintain the temperature of the manganese nitrate solution at 35°C - 45°C; S24. When starting to immerse the tantalum anode in manganese, apply a low-frequency pressure wave of 10KHz - 40KHz to the manganese nitrate solution, turn it on once every 2min - 4min, and each on-time is 20s - 40s.

[0031] During operation, the tantalum anode 1 obtained through the energization process is placed in deionized water for boiling and washing. During the boiling and washing process, a certain temperature and time are maintained (specifically, it can be set according to the actual situation, with the temperature being 90°C - 100°C and the boiling and washing time being 15 min - 30 min) to remove the residual energization solution and other impurities on the surface of the tantalum anode 1. After the boiling and washing is completed, the tantalum anode 1 is taken out and placed in a drying device for drying (the drying temperature is 110°C - 120°C and the drying time is 20 min - 40 min) to remove the surface moisture and ensure that the tantalum anode 1 is dry. Prepare a manganese nitrate solution as the solution for the manganese impregnation process. Carefully immerse the dried tantalum anode 1 into the manganese nitrate solution to ensure that the tantalum anode 1 is completely covered by the solution. Use a heating device or a constant temperature water bath, etc., to maintain the temperature of the solution in the container containing the tantalum anode 1 and the manganese nitrate solution at 35°C - 45°C. When starting to impregnate the tantalum anode 1 with manganese, apply a low-frequency pressure wave of 10 KHz - 40 KHz to the solution, apply it once every 2 min - 4 min, and each application time lasts for 20 s - 40 s. During the manganese impregnation process, the manganese ions in the manganese nitrate solution will gradually adsorb on the surface of the tantalum anode 1 and then undergo a thermal decomposition reaction at a certain temperature to form a MnO2 layer.

[0032] Due to the appropriate solution temperature and the action of the low-frequency pressure wave, the thickness of the MnO2 layer is more uniform and the density is higher, reducing the defects in the dielectric layer, thereby improving the quality of the MnO2 layer. The uniform and dense MnO2 layer can reduce the electron transport resistance in the electrolyte, lower the equivalent series resistance (ESR) of the tantalum capacitor, and improve the performance of the tantalum capacitor.

[0033] Preferably, the manganese impregnation process includes 2 to 4 manganese impregnation steps, and as the number of manganese impregnation times increases, both the frequency and the application time of the low-frequency pressure wave decrease in sequence.

[0034] The tantalum anode 1 has a porous structure. Multiple manganese impregnations can make the manganese nitrate solution gradually penetrate into the deeper pores of the tantalum anode 1, enabling the MnO2 layer to grow uniformly inside and on the surface of the tantalum anode 1, filling more pores, and increasing the density of the MnO2 layer; during each manganese impregnation process, a new MnO2 layer can grow on the surface of the MnO2 layer formed in the previous time, repairing possible minor defects such as voids and cracks in the previous time, thereby improving the overall quality of the MnO2 layer.

[0035] In the initial stage of manganese impregnation, by adopting a relatively high frequency of low-frequency pressure wave and a relatively long application time, a strong cavitation effect and mechanical stirring effect can be generated. The strong stirring can quickly break the surface tension of the solution, enable the manganese nitrate solution to quickly penetrate into the pores of the tantalum anode 1, and at the same time discharge the gas in the pores, creating good conditions for the uniform deposition of MnO2. As the number of manganese impregnation times increases, the low-frequency pressure wave and the application time are appropriately reduced. At this time, the main function of the low-frequency pressure wave is to optimize the growth process of the MnO2 layer, make the MnO2 crystals grow more uniformly on the existing basis, and reduce the agglomeration and uneven growth of the grains.

[0036] Preferably, when the manganese impregnation process includes three manganese impregnation steps, in the first manganese impregnation, the concentration of the manganese nitrate solution is 20%, the frequency of the low-frequency pressure wave is 35 KHz, it is applied once every 2 minutes, and each time is 30 s. In the second manganese impregnation, the concentration of the manganese nitrate solution is 30%, the frequency of the low-frequency pressure wave is 25 KHz, it is applied once every 2 minutes, and each time is 25 s. In the third manganese impregnation, the concentration of the manganese nitrate solution is 30%, the frequency of the low-frequency pressure wave is 15 KHz, it is applied once every 2 minutes, and each time is 20 s.

[0037] Furthermore, please refer to Figure 1 and Figure 2 , the present application also provides a preparation system for the anode of a low-ESR tantalum capacitor, including an energizing device and a manganese impregnation device. A penetration and defoaming component 7 is arranged on the energizing device, and the penetration and defoaming component can generate a high-frequency pressure wave of 20 KHz - 100 KHz. An air-raid shelter component 15 is arranged on the manganese impregnation device, and the air-raid shelter component can generate a low-frequency pressure wave of 10 KHz - 40 KHz. The defoaming component 7 and the air-raid shelter component 15 can be a shock wave generator, a pulse pneumatic generator, a cavitation jet generator, etc. In this embodiment, preferably an ultrasonic generator.

[0038] Specifically, the energizing device specifically includes a first metal sheet 3, a circulating water pump 6, an energizing tank 9, an overflow plate 10, and an energizing DC power supply 18. The energizing tank 9 is used to contain an energizing solution. The first metal sheet 3 is disposed on the mouth of the energizing tank 9 through an insulating gasket 4. A plurality of first tantalum wires 2 are spacedly arranged on the lower surface of the first metal sheet 3. The tantalum anode 1 to be energized is disposed on the first tantalum wires 2. The positive pole of the energizing DC power supply 18 is connected to the first metal sheet 3, and the negative pole is connected to the energizing tank 9. The overflow plate 10 is vertically disposed in the energizing tank 9, forming a liquid replenishing chamber 5 between it and one side surface of the energizing tank 9. Moreover, the height of the overflow plate 10 is higher than the height of the tantalum anode 1, which is used to ensure the liquid level of the energizing solution so that the solution just submerges the upper part of the tantalum anode 1. The overflowed solution flows to the liquid replenishing chamber 5. The circulating water pump 6 is connected to the liquid replenishing chamber 5 and the energizing tank 9, and is used to pump the solution in the liquid replenishing chamber 5 back into the energizing tank 9 to realize solution circulation. A first heater 8 is disposed at the lower part of the energizing tank 9, and a permeation defoaming assembly 7 is disposed on the outer wall of the energizing tank 9.

[0039] Specifically, the manganese immersion device specifically includes a second metal sheet 13 and a conical manganese immersion tank 14. The conical manganese immersion tank 14 is used to contain a manganese immersion solution. The second metal sheet 13 is disposed on the mouth of the conical manganese immersion tank 14. A plurality of second tantalum wires 2 are spacedly arranged on the lower surface of the second metal sheet 13. The tantalum anode 1 to be manganese immersed is disposed on the second tantalum wires 2. A discharge port 16 is disposed at the conical part of the conical manganese immersion tank 14. A second heater 17 is disposed at the lower part of the conical manganese immersion tank 14, and an air-raid shelter assembly 15 is disposed on the outer wall of the conical manganese immersion tank 14.

[0040] The tantalum anode 1 after pre-burying and forming tantalum powder and tantalum wire 2 is subjected to high-temperature vacuum sintering. A plurality of sintered tantalum anodes 1 are evenly spot-welded on the first metal sheet 3. The first metal sheet 3 is placed on the energizing tank 9 and insulated by the insulating gasket 4. A phosphoric acid solution or a mixed solution of phosphoric acid and ethylene glycol with a concentration of 0.01%-0.5% is contained in the energizing tank 9. The overflow plate 10 in the energizing tank 9 can ensure the liquid level of the energizing solution, so that the solution just covers the upper part of the tantalum anode 1. The overflowed solution flows to the liquid replenishing tank 5, and the circulating water pump 6 pumps the solution in the liquid replenishing tank 5 back into the energizing tank 9 to make the solution circulate. Then, start the second heater 17 to heat the temperature of the solution in the energizing tank 9 to 70°C - 90°C. Connect the positive electrode of the energizing DC power supply 18 to the metal sheet, and connect the negative electrode of the energizing DC power supply 18 to the energizing tank 9 to ensure its power-on. When starting to energize the tantalum anode 1, the permeation and defoaming assembly 7 is turned on once every 10 min - 30 min, and the opening time each time is 1 min - 5 min to generate high-frequency pressure waves. The tantalum anode 1 obtained through the energizing process is cleaned and dried to remove the residual energizing solution and other impurities on the surface of the tantalum anode 1. Add a manganese nitrate solution to the manganese dipping tank 14. Evenly spot-weld the tantalum anode 1 on the second metal sheet 13. Place the second metal sheet 13 on the manganese dipping tank 14 to immerse the dried tantalum anode 1 into the manganese nitrate solution, ensuring that the tantalum anode 1 is completely covered by the solution. Turn on the second heater 17 to maintain the temperature of the solution in the manganese dipping tank 14 at 35°C - 45°C. When starting to dip the tantalum anode 1 in manganese, start the air-raid shelter assembly 15 to generate low-frequency pressure waves, which is turned on once every 2 min - 4 min, and the opening time each time lasts for 20 s - 40 s. During the manganese dipping process, the manganese ions in the manganese nitrate solution will gradually adsorb on the surface of the tantalum anode 1 and then undergo a thermal decomposition reaction at a certain temperature to form a MnO2 layer.

[0041] When energizing using the energizing device provided by the present invention, the high-frequency pressure wave of 20KHz - 100KHz generated by the penetration defoaming component 7 triggers the generation, expansion, and violent rupture of tiny bubbles in the energizing liquid. The jet generated by the bubble rupture impacts the surface and the interior pores of the tantalum anode 1, effectively avoiding gas retention. At the same time, it improves the permeability of phosphate ions in the solution, making the current density distribution more uniform, the growth rate of the oxide film more consistent. When using high-frequency pressure waves at intervals, the solution can be stirred and degassed more frequently, which is beneficial to maintaining the uniformity and stability of the solution, reducing the unevenness of the oxide film thickness, and reducing leakage current and ESR. When performing manganese immersion using the manganese immersion device provided by the present invention, the low-frequency pressure wave of 10KHz - 40KHz generated by the air-raid shelter component 15, the micro-jet and shock wave generated by the cavitation effect can increase the turbulence degree of the solution, reduce the concentration gradient in the solution, and improve the diffusion rate of manganese nitrate ions, so that the manganese nitrate ions can penetrate into the pores of the tantalum anode 1 faster, enabling the MnO2 layer after thermal decomposition to be uniformly deposited in a wider area, avoiding problems such as too thin or voids in the MnO2 layer caused by poor permeability, thereby reducing ESR and improving the performance of the tantalum capacitor.

[0042] In addition, when using the energizing device provided by the present invention, a good energizing effect can be achieved without going through a staged boost energization process, avoiding the problem of long time-consuming for multi-stage energization and improving efficiency. When using the manganese immersion device provided by the present invention, the number of manganese immersion times can be reduced, thus avoiding problems such as too thick MnO2 layer, cracking or peeling during thermal decomposition caused by multiple manganese immersions, and improving the quality and performance of the product.

[0043] The following are specific experimental examples to further illustrate the technical solutions and technical effects of the present invention. It should be noted that the following experimental examples are only for further explaining the present invention and do not limit the technical solutions of the present invention. Embodiment

[0044] Tantalum powder with a specific capacitance of 70000 μF·V / g is formed into a number of tantalum blanks with a weight of 160 mg, a diameter of Ø3 mm, and a pressing density of 5.0 g / cm 3 ³. The tantalum blanks are sintered in a vacuum high-temperature sintering furnace at 1340 °C for 25 minutes to obtain the sintered tantalum anode 1. A number of tantalum anodes 1 are evenly spot-welded on the first metal sheet 3 and placed in the energizing tank 9 as shown in Figure 1 . 0.1% concentration phosphoric acid is used as the energizing liquid, the heating temperature is 80 °C, the energizing voltage is 30 V, the current density is 80 mg / g, and the constant voltage time is 2 h. The frequency of the high-frequency pressure wave is 50KHz, applied once every 15 minutes, and each application time is 2 minutes until the energization ends. The tantalum anode 1 obtained after energization is placed in a deionized water tank and boiled and washed for 30 minutes, and then dried in a drying oven at 100 °C for 20 minutes.

[0045] First manganese immersion: Pour 20% manganese nitrate solution with a density of about 1.22 g / cm³ into the manganese immersion tank 14, and heat it to 40°C. Place the dried tantalum anode 1 on the fixed clamp in the manganese immersion tank 14 so that the manganese nitrate solution just covers the upper part of the tantalum anode 1. The total manganese immersion time is 20 minutes. The frequency of the low-frequency pressure wave is 35 KHz, applied once every 2 minutes, 30 s each time. After the manganese immersion is completed, place the tantalum anode 1 in the film furnace for thermal decomposition to deposit the MnO₂ layer, with the temperature set at 220°C and the film time of 20 min. 3 ,And heat it to 40°C. Place the dried tantalum anode 1 on the fixed clamp in the manganese immersion tank 14 so that the manganese nitrate solution just covers the upper part of the tantalum anode 1. The total manganese immersion time is 20 minutes. The frequency of the low-frequency pressure wave is 35 KHz, applied once every 2 minutes, 30 s each time. After the manganese immersion is completed, place the tantalum anode 1 in the film furnace for thermal decomposition to deposit the MnO₂ layer, with the temperature set at 220°C and the film time of 20 min.

[0046] Second manganese immersion: Pour 30% manganese nitrate solution with a density of about 1.34 g / cm³ into the manganese immersion tank 14 3 ,And heat it to 40°C. Place the tantalum anode 1 after the first manganese immersion on the fixed clamp in the manganese immersion tank 14 so that the manganese nitrate solution just covers the upper part of the tantalum anode 1. The total manganese immersion time is 20 minutes. The frequency of the low-frequency pressure wave is 25 KHz, applied once every 2 minutes, 25 s each time. After the manganese immersion is completed, place the tantalum anode 1 in the film furnace for thermal decomposition to deposit the MnO₂ layer, with the temperature set at 220°C and the film time of 20 min.

[0047] Third manganese immersion: Pour 30% manganese nitrate solution with a density of about 1.34 g / cm³ into the manganese immersion tank 14 3 ,And heat it to 40°C. Place the tantalum anode 1 after the second manganese immersion on the fixed clamp in the manganese immersion tank 14 so that the manganese nitrate solution just covers the upper part of the tantalum anode 1. The total manganese immersion time is 15 minutes. The frequency of the low-frequency pressure wave is 15 KHz, applied once every 2 minutes, 20 s each time. After the manganese immersion is completed, place the tantalum anode 1 in the film furnace for thermal decomposition to deposit the MnO₂ layer, with the temperature set at 220°C and the film time of 20 min.

[0048] Detect the equivalent series resistance of the tantalum capacitor anode prepared, and count the number of energization times, manganese immersion times and total duration used this time. The results are shown in Table 1.

[0049] Comparative example The difference between this comparative example and the above examples is that: use the traditional energization and manganese immersion process methods, that is, without using high-frequency and low-frequency pressure waves. Detect the equivalent series resistance of the tantalum capacitor anode prepared, and count the number of energization times, manganese immersion times and total duration used this time. The results are shown in Table 1.

[0050] Table 1 Comparison table of data in examples and comparative examples

[0051] It can be seen from the data in Table 1 that the number of energizing times and the number of manganese dipping times in the examples are both reduced by 2 times compared with the comparative examples, thereby reducing the energizing duration and the manganese dipping duration. Using the method provided by the present invention, the total energizing duration and the manganese dipping duration in the entire process flow are reduced by 95 minutes, improving the work efficiency.

[0052] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A method for preparing an anode of a low ESR tantalum capacitor, characterized in that, During the energizing process, a high-frequency pressure wave is applied to the energizing solution intermittently to enable the energizing solution to uniformly penetrate into the tantalum anode, improve the uniformity of the energizing solution concentration inside and outside the tantalum anode, make the current distribution more uniform, ensure the consistent growth rate of the oxide film, and reduce the ESR. Among them, the temperature of the energizing solution is 70°C - 90°C, the high-frequency pressure wave is applied every 10 min - 30 min, and each application lasts for 1 min - 5 min until the energizing process ends; During the manganese impregnation process, a low-frequency pressure wave is applied to the manganese impregnation solution intermittently to increase the diffusion rate of manganese nitrate ions, enable the manganese nitrate ions to penetrate into the pores of the tantalum anode faster, and make the MnO2 layer uniformly deposited in a wider area, avoiding the problems of too thin or voids in the MnO2 layer caused by poor permeability, and reducing the ESR. Among them, the temperature of the manganese impregnation solution is 35°C - 45°C, the low-frequency pressure wave is applied every 2 min - 4 min, and each application lasts for 20 s - 40 s until the manganese impregnation process ends.

2. The preparation method of the anode of the low-ESR tantalum capacitor according to claim 1, characterized in that, The energizing process specifically includes the following steps: S11. The energizing solution is a phosphoric acid solution or a mixed solution of phosphoric acid and ethylene glycol. Immerse the tantalum anode in the mixed solution and apply a DC voltage to generate a Ta2O5 dielectric layer; S12. Heat the temperature of the mixed solution to 70°C - 90°C; S13. When starting to energize the tantalum anode, apply a high-frequency pressure wave of 20 KHz - 100 KHz to the mixed solution intermittently, turn it on every 10 min - 30 min, and each turn-on time is 1 min - 5 min.

3. The preparation method of the anode of the low-ESR tantalum capacitor according to claim 1, wherein The manganese impregnation process specifically includes the following steps: S21. Wash and dry the tantalum anode obtained by energizing with deionized water; S22. The manganese impregnation solution is a manganese nitrate solution. Immerse the tantalum anode in the manganese nitrate solution to thermally decompose and generate an MnO2 layer; S23. Maintain the temperature of the manganese nitrate solution at 35°C - 45°C; S24. When starting to impregnate the tantalum anode with manganese, apply a low-frequency pressure wave of 10 KHz - 40 KHz to the manganese nitrate solution, turn it on every 2 min - 4 min, and each turn-on time is 20 s - 40 s.

4. The preparation method of the anode of the low-ESR tantalum capacitor according to claim 3, characterized in that, The manganese impregnation process includes 2 to 4 impregnation steps. As the number of impregnation steps increases, the frequency and application time of the low-frequency pressure wave both decrease successively.

5. The preparation method of the anode of the low-ESR tantalum capacitor according to claim 4, characterized in that, When the manganese impregnation process includes 3 impregnation steps, in the first impregnation, the concentration of the manganese nitrate solution is 20%, the frequency of the low-frequency pressure wave is 35 KHz, it is applied every 2 min, and each application lasts for 30 s.

6. The preparation method of the anode of the low-ESR tantalum capacitor according to claim 5, wherein When the manganese impregnation process includes 3 impregnation steps, in the second impregnation, the concentration of the manganese nitrate solution is 30%, the frequency of the low-frequency pressure wave is 25 KHz, it is applied every 2 min, and each application lasts for 25 s.

7. The method for preparing the anode of the low-ESR tantalum capacitor according to claim 6, characterized in that, When the manganese impregnation process includes 3 impregnation steps, in the third impregnation, the concentration of the manganese nitrate solution is 30%, the frequency of the low-frequency pressure wave is 15 KHz, it is applied every 2 min, and each application lasts for 20 s.

8. A preparation system for an anode of a low-ESR tantalum capacitor, characterized in that, It includes an energizing device and a manganese dipping device. An osmotic defoaming component is provided on the energizing device, and the osmotic defoaming component can generate high-frequency pressure waves of 20KHz - 100KHz. An air-raid shelter component is provided on the manganese dipping device, and the air-raid shelter component can generate low-frequency pressure waves of 10KHz - 40KHz.

9. The preparation system of the low-ESR tantalum capacitor anode according to claim 8, characterized in that, The energizing device specifically includes a first metal sheet, a circulating water pump, an energizing tank, an overflow plate, and an energizing DC power supply. The energizing tank is used to hold the energizing solution. The first metal sheet is arranged on the mouth of the energizing tank through an insulating gasket. A number of first tantalum wires are arranged at intervals on the lower surface of the first metal sheet, and the tantalum anode to be energized is arranged on the first tantalum wires. The positive pole of the energizing DC power supply is connected to the first metal sheet, and the negative pole is connected to the energizing tank. The overflow plate is vertically arranged in the energizing tank, forming a liquid replenishing chamber between it and one side surface of the energizing tank, and the height of the overflow plate is higher than the height of the tantalum anode, which is used to ensure the liquid level of the energizing solution so that the solution just submerges the upper part of the tantalum anode, and the overflowed solution flows to the liquid replenishing chamber. The circulating water pump is connected to the liquid replenishing chamber and the energizing tank, and is used to pump the solution in the liquid replenishing chamber back into the energizing tank to achieve solution circulation. A first heater is arranged at the lower part of the energizing tank, and the osmotic defoaming component is arranged on the outer wall of the energizing tank.

10. The preparation system of the low-ESR tantalum capacitor anode according to claim 8, wherein, The manganese dipping device specifically includes a second metal sheet and a conical manganese dipping tank. The conical manganese dipping tank is used to hold the manganese dipping solution. The second metal sheet is arranged on the mouth of the conical manganese dipping tank. A number of second tantalum wires are arranged at intervals on the lower surface of the second metal sheet, and the tantalum anode to be dipped in manganese is arranged on the second tantalum wires. A discharge port is arranged at the conical part of the conical manganese dipping tank. A second heater is arranged at the lower part of the conical manganese dipping tank, and the air-raid shelter component is arranged on the outer wall of the conical manganese dipping tank.

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