High-voltage and ultrahigh-voltage tantalum capacitor cathode preparation method

Abstract

The invention discloses a preparation method of a high-voltage and ultrahigh-voltage tantalum capacitor cathode. The preparation method comprises the following steps of performing a pre-compensation forming process on a tantalum block; soaking in the solution A after high-temperature drying, then carrying out a high-temperature thermal decomposition process, and cooling after completion of the thermal decomposition process; carrying out an intermediate repair forming procedure, and then carrying out high-temperature drying; dipping in a solution B, then carrying out a high-temperature thermal decomposition process, and cooling after completion; carrying out an intermediate repair forming process, then dipping in the solution C, and then drying; carrying out high-temperature air decomposition, and then cooling; dipping in a solution D, then carrying out a high-temperature thermal decomposition process, and cooling after completing the thermal decomposition process; and then carrying out a final repair forming process, drying at a high temperature, and dipping a cathode auxiliary material to complete the preparation of the capacitor cathode. By obtaining the manganese dioxide layer, the influence of various stresses on the dielectric oxide film is reduced in multiple high-temperature thermal decomposition processes, the risk of leakage current increase or breakdown caused by degradation of weak parts or defects of the dielectric oxide film is reduced, and the qualified rate and reliability of the capacitor are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of capacitors, and in particular relates to a method for preparing a cathode of a high-voltage and ultra-high-voltage tantalum capacitor. Background Art

[0002] In the field of electronic component manufacturing technology, high-voltage and ultra-high-voltage solid electrolyte tantalum capacitors are an important electronic component, widely used in various high-voltage electronic circuits, and play the role of energy storage and filtering. High-voltage and ultra-high-voltage tantalum capacitors are affected by raw materials and dielectric oxide film generation processes. The dielectric oxide film has more or less weak parts or defects in the generation process. There are physical reactions and chemical reactions in the cathode manufacturing process. During multiple thermal decomposition processes, the dielectric oxide film is affected by various stresses of physical reactions and chemical reactions. The weak parts or defects of the dielectric oxide film are constantly deteriorating, causing the leakage current to increase during the formation of the intermediate patch after thermal decomposition, and the tantalum core is directly broken down in severe cases. In the cathode manufacturing process of high-voltage and ultra-high voltage products, the leakage current increases and breaks down during the formation of the patch. In severe cases, the product batch is scrapped, which seriously affects the qualified rate, quality consistency and stability of capacitor products. In order to improve the qualified rate, quality stability and reliability of capacitor products, the cathode manufacturing process of high-voltage and ultra-high voltage tantalum capacitors is technically overcome.

[0003] The patent document with announcement number CN117012553A discloses a tantalum capacitor cathode and a preparation method thereof, the preparation method comprising: preparing 5 to 7 groups of tantalum capacitors with a specific gravity of 1.0 g / cm 3 ~2.0g / cm 3 The specific gravity of each group of manganese nitrate solutions is different, and the specific gravity is 1.0g / cm 3 ~1.4g / cm 3 The manganese nitrate solution is added with catalyst and dispersant, with a specific gravity of 1.5g / cm 3 ~2.0g / cm 3 A catalyst is added to the manganese nitrate solution; a manganese dioxide strengthening treatment solution containing two kinds of manganese dioxide powder with different particle sizes is prepared; the anode core blocks after anodization are immersed and thermally decomposed in each group of manganese nitrate solutions for 1 to 4 times, immersed and thermally decomposed in the manganese dioxide strengthening treatment solution for 1 to 3 times, and then immersed and thermally decomposed in manganese nitrate solutions with different specific gravities to obtain; the inventive method improves the manganese dioxide filling rate and capacity achievement rate of the capacitor, reduces the porosity of the anode core blocks, improves the density of the cathode layer, and enhances the ability of the capacitor to resist wet heat stress.

[0004] The patent document with the announcement number CN106057469A discloses a method for preparing the cathode of a medium- and high-voltage solid electrolyte tantalum capacitor. The commonly available ammonium hydrogen phosphate is used as an additive to the manganese nitrate solution and as a catalyst in the thermal decomposition process of manganese nitrate. The prepared cathode manganese dioxide layer is continuous and dense, and can be in close contact with the oxidizing medium film. The electric field intensity generated under high voltage load is evenly distributed.

[0005] The above patent discloses that by adding different proportions of catalysts to manganese nitrate solutions of various specific gravities, the thermal decomposition temperature can be lowered and the influence of thermal stress on the dielectric oxide film on the surface of the tantalum block can be reduced. However, it does not solve the technical problem of repairing the dielectric oxide film after decomposition. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a cathode of a high-voltage and ultra-high-voltage tantalum capacitor.

[0007] The present invention is achieved through the following technical solutions.

[0008] The present invention provides a method for preparing a cathode of a high-voltage or ultra-high-voltage tantalum capacitor, comprising the following steps:

[0009] S1: Pre-forming process of tantalum block;

[0010] S2: After high-temperature drying, the solution A is immersed, and then a high-temperature thermal decomposition process is performed, and then cooling is completed. This step is repeated multiple times;

[0011] S3: Performing an intermediate forming process, followed by high temperature drying;

[0012] S4: impregnating solution B, then performing a high temperature thermal decomposition process, cooling after completion, and repeating this step multiple times;

[0013] S5: performing an intermediate patch forming process, then dipping in solution C, and then drying;

[0014] S6: performing high temperature air decomposition and then cooling;

[0015] S7: impregnating solution D, and then performing a high temperature thermal decomposition process, cooling after completion, and repeating this step multiple times;

[0016] S8: Perform the final filling forming process, impregnate the cathode auxiliary material after high-temperature drying, and complete the capacitor cathode preparation.

[0017] Preferably, the solution A is a manganese nitrate solution, comprising a step solution with a specific gravity below 1.6, and the proportion of catalyst added to each solution increases by 0.1-1% as the specific gravity increases;

[0018] The solution B is a manganese nitrate solution, comprising various step solutions with specific gravity ranging from 1.7 to 1.9, and the catalyst ratio added to each solution is 1.5-4%;

[0019] The solution C is a manganese nitrate solution, which is prepared from manganese dioxide powder, silicon dioxide, and manganese nitrate solution. The silicon dioxide accounts for 1-10% of the mass of the manganese dioxide powder. 1000-3000 ml of manganese nitrate solution is added per kilogram of manganese dioxide powder. Its specific gravity in the cathode of the tantalum capacitor is 2.0-3.5;

[0020] The solution D is a manganese nitrate solution, with a specific gravity of 1.3-1.8 in each step solution, and the catalyst is added in a ratio of 1.5-4%;

[0021] The catalyst includes one or more of ammonium nitrate, urea, peracetic acid, nickel nitrate, and ammonium perchlorate.

[0022] Preferably, the immersion temperature in steps S2, S4, S5 and S7 is 25-45°C and the immersion time is 3-20min;

[0023] Before the high temperature thermal decomposition process, a dehydration treatment can be adopted, and the dehydration temperature is 45-90° C. and the dehydration time is 3-15 minutes.

[0024] Preferably, the temperature in the high temperature thermal decomposition process in steps S2, S4, S7 and the high temperature air decomposition process in step S6 is 185-230°C; the time is 3-20 minutes; and the oxygen content during decomposition is 5-20%.

[0025] Preferably, the cooling in steps S2, S4, S6 and S7 includes air cooling or static cooling to below 30°C.

[0026] Preferably, in the reparation forming process in steps S1, S3, S5 and S6, a reparation forming liquid is used which is a mixture of one or more liquids selected from pure deionized water, ethanol, ethylene glycol and n-butanol and one or more selected from glacial acetic acid, acetic acid and citric acid.

[0027] Preferably, the conductivity of the forming solution in the forming process in steps S1, S3, S5 and S6 is 1-5 μs / cm, the boost current is 5-30 μA / mg, the constant voltage time is 10-50 min, and the constant voltage time is calculated after the forming voltage is reached; the forming voltage in step S1 is 0.7-0.9 U 形 The voltage for forming the complement in steps S3 and S5 is 1.3-1.6U 额 The voltage for forming the complement in step S8 is 1.2-1.5U 额 .

[0028] Preferably, the high temperature drying in steps S2, S3 and S8 is carried out in a high temperature oven or a high temperature thermal decomposition furnace. When a high temperature oven is used, the temperature is 110-150°C and the drying time is 10-20 minutes. When a high temperature thermal decomposition furnace is used, the temperature is 185-230°C, the decomposition time is 3-15 minutes, and the oxygen content in the furnace is 5-20%.

[0029] Preferably, the step S5 is dried twice, the first drying temperature is 45-60° C., and the drying time is 20-40 min; the second drying temperature is 130-160° C., and the drying time is 30-50 min.

[0030] Preferably, in step S8, the cathode auxiliary material includes graphite and silver paste.

[0031] The beneficial effects of the present invention are:

[0032] The preparation method of the present invention reduces the thermal decomposition temperature of the furnace body in the cathode preparation by adding catalysts in different proportions to various manganese nitrate solutions with different specific gravities. Under the action of the catalyst, the manganese dioxide layer obtained by low-temperature thermal decomposition can achieve the same or better effect as the manganese dioxide layer obtained by high-temperature thermal decomposition, thereby ensuring the quality of the manganese dioxide layer and reducing the influence of various stresses on the dielectric oxide film during multiple high-temperature thermal decomposition processes, reducing the risk of increased leakage current or breakdown caused by degradation of its weak parts or defects, and improving the product qualification rate and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a process flow chart of the present invention; DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0035] Embodiment 1:

[0036] like Figure 1 As shown, a method for preparing a cathode of a high-voltage and ultra-high-voltage tantalum capacitor comprises the following steps:

[0037] S1: Pre-forming the tantalum block, wherein a dielectric oxide film is electrochemically formed on the surface and inside of the tantalum block, and the process of forming the dielectric oxide film is an existing technology;

[0038] S2: After high-temperature drying, the capacitor is immersed in solution A, and then subjected to a high-temperature thermal decomposition process, followed by cooling. This step is repeated multiple times according to the capacitor model;

[0039] S3: Performing an intermediate forming process, followed by high temperature drying;

[0040] S4: Dipping in solution B, then performing a high-temperature thermal decomposition process, followed by cooling. This step is repeated multiple times depending on the capacitor model;

[0041] S5: performing an intermediate patch forming process, then immersing in solution C, which is a strengthening solution, and then drying;

[0042] S6: performing high temperature air decomposition and then cooling;

[0043] S7: dipping in solution D, then performing a high temperature thermal decomposition process, followed by cooling, and this step is repeated multiple times depending on the capacitor model;

[0044] S8: Perform the final filling forming process, impregnate the cathode auxiliary material after high-temperature drying, and complete the capacitor cathode preparation.

[0045] The solution A is a manganese nitrate solution, comprising step solutions with a specific gravity of 1.3, and the proportion of catalyst added to each solution increases by 0.1% as the specific gravity increases;

[0046] The solution B is a manganese nitrate solution, comprising various step solutions with a specific gravity of 1.7, and the catalyst ratio added to each solution is 1.5%;

[0047] The solution C is a manganese nitrate solution, which is prepared from manganese dioxide powder, silicon dioxide, and manganese nitrate solution. The silicon dioxide accounts for 1% of the mass of the manganese dioxide powder. 1000 ml of manganese nitrate solution is added for every kilogram of manganese dioxide powder. Its specific gravity in the cathode of the tantalum capacitor is 2.0.

[0048] The solution D is a manganese nitrate solution, with a specific gravity of 1.3 and a step solution, and the catalyst is added in a proportion of 1.5%;

[0049] The catalyst includes ammonium nitrate, urea and peracetic acid.

[0050] In the steps S2, S4, S5 and S7, the immersion temperature is 25° C. and the immersion time is 3 min;

[0051] Before the high-temperature thermal decomposition process, a dehydration method can be used for treatment, the dehydration temperature is 45° C., the dehydration time is 3 minutes, and after the dehydration is completed, the material is placed in a coating furnace for thermal decomposition.

[0052] The temperature in the high temperature thermal decomposition process in steps S2, S4, and S7 and the high temperature air decomposition process in step S6 is 185°C; the time is 3 minutes; and the oxygen content during decomposition is 5%.

[0053] In the steps S2, S4, S6 and S7, the cooling is performed by standing and cooling at room temperature to below 30°C.

[0054] In the replenishment formation process in steps S1, S3, S5 and S6, a replenishment formation liquid prepared by mixing pure deionized water with glacial acetic acid and acetic acid is used to meet the conductivity control requirements of the formation liquid.

[0055] The above-mentioned formation is to use a tantalum block whose dielectric oxide film has been formed in the formation process or a tantalum block whose film has been thermally decomposed for a certain number of times, and use a film formation liquid to perform constant current boosting and constant voltage current reduction at a certain current density. The formation voltage in each stage is different. The conductivity of the formation liquid in the formation process in the steps S1, S3, S5, and S6 is 1μs / cm, the boost current is 5μA / mg, the constant voltage time is 10min, and the constant voltage time is calculated after the formation voltage is increased; the formation voltage in the step S1 is 0.7U 形 The voltage for forming the complement in steps S3 and S5 is 1.3U 额 The voltage for forming the complement in step S8 is 1.2U 额 .

[0056] The high temperature drying in steps S2, S3 and S8 is carried out after the formation by using a high temperature oven or a high temperature thermal decomposition furnace. When a high temperature oven is used, the temperature is 110°C and the drying time is 10 minutes; when a high temperature thermal decomposition furnace is used, the temperature is 185°C, the decomposition time is 3 minutes, and the oxygen content in the furnace is 5%.

[0057] In step S5, drying is performed twice, the first drying temperature is 45° C., and the drying time is 20 min; the second drying temperature is 130° C., and the drying time is 30 min.

[0058] In step S8, the cathode auxiliary materials are graphite and silver paste.

[0059] Embodiment 2:

[0060] like Figure 1 As shown, a method for preparing a cathode of a high-voltage and ultra-high-voltage tantalum capacitor comprises the following steps:

[0061] S1: Pre-forming the tantalum block, wherein a dielectric oxide film is electrochemically formed on the surface and inside of the tantalum block, and the process of forming the dielectric oxide film is an existing technology;

[0062] S2: After high-temperature drying, the capacitor is immersed in solution A, and then subjected to a high-temperature thermal decomposition process, followed by cooling. This step is repeated multiple times according to the capacitor model;

[0063] S3: Performing an intermediate forming process, followed by high temperature drying;

[0064] S4: Dipping in solution B, then performing a high-temperature thermal decomposition process, followed by cooling. This step is repeated multiple times depending on the capacitor model;

[0065] S5: performing an intermediate patch forming process, then immersing in solution C, which is a strengthening solution, and then drying;

[0066] S6: performing high temperature air decomposition and then cooling;

[0067] S7: dipping in solution D, then performing a high temperature thermal decomposition process, followed by cooling, and this step is repeated multiple times depending on the capacitor model;

[0068] S8: Perform the final filling forming process, impregnate the cathode auxiliary material after high-temperature drying, and complete the capacitor cathode preparation.

[0069] The solution A is a manganese nitrate solution, comprising a step solution with a specific gravity of 1.5, and the proportion of catalyst added to each solution increases by 1% as the specific gravity increases;

[0070] The solution B is a manganese nitrate solution, comprising various step solutions with a specific gravity of 1.9, and the catalyst ratio added to each solution is 4%;

[0071] The solution C is a manganese nitrate solution, which is prepared by manganese dioxide powder, silicon dioxide, and manganese nitrate solution. The silicon dioxide accounts for 10% of the mass of the manganese dioxide powder. 3000 ml of manganese nitrate solution is added for every kilogram of manganese dioxide powder. Its specific gravity in the cathode of the tantalum capacitor is 3.5;

[0072] The solution D is a manganese nitrate solution, a step solution with a specific gravity of 1.8, and a catalyst added in a ratio of 4%;

[0073] The catalyst includes peracetic acid, nickel nitrate and ammonium perchlorate.

[0074] In the steps S2, S4, S5 and S7, the immersion temperature is 45° C. and the immersion time is 20 min;

[0075] Before the high-temperature thermal decomposition process, a dehydration treatment can be adopted, the dehydration temperature is 90° C., the dehydration time is 15 minutes, and after the dehydration is completed, the product is placed in a coating furnace for thermal decomposition.

[0076] The temperature in the high temperature thermal decomposition process in steps S2, S4, S7 and the high temperature air decomposition process in step S6 is 230°C; the time is 20 minutes; and the oxygen content during decomposition is 20%.

[0077] The cooling in steps S2, S4, S6 and S7 is air cooling to below 30°C.

[0078] In the replenishment formation process in steps S1, S3, S5 and S6, a replenishment formation liquid mixed with ethanol, acetic acid and citric acid is used to meet the conductivity control requirements of the formation liquid.

[0079] The above-mentioned formation is to use a tantalum block whose dielectric oxide film is formed in the formation process or a tantalum block whose film is thermally decomposed a certain number of times, and use a film formation liquid to perform constant current boosting and constant voltage current reduction at a certain current density. The formation voltage in each stage is different. The conductivity of the formation liquid in the formation process in the steps S1, S3, S5, and S6 is 5μs / cm, the boost current is 30μA / mg, the constant voltage time is 50min, and the constant voltage time is calculated after the formation voltage is increased; the formation voltage in the step S1 is 0.9U 形 The voltage for forming the complement in steps S3 and S5 is 1.6U 额 The voltage for forming the complement in step S8 is 1.5U 额 .

[0080] The high temperature drying in steps S2, S3 and S8 is carried out after the formation by using a high temperature oven or a high temperature thermal decomposition furnace. When using a high temperature oven, the temperature is 150°C and the drying time is 20 minutes; when using a high temperature thermal decomposition furnace, the temperature is 230°C, the decomposition time is 15 minutes, and the oxygen content in the furnace is 20%.

[0081] In step S5, drying is performed twice, the first drying temperature is 60° C., and the drying time is 40 min; the second drying temperature is 160° C., and the drying time is -50 min.

[0082] In step S8, the cathode auxiliary materials are graphite and silver paste.

[0083] Embodiment 3:

[0084] like Figure 1 As shown, a method for preparing a cathode of a high-voltage and ultra-high-voltage tantalum capacitor comprises the following steps:

[0085] S1: Pre-forming the tantalum block, wherein a dielectric oxide film is electrochemically formed on the surface and inside of the tantalum block, and the process of forming the dielectric oxide film is an existing technology;

[0086] S2: After high-temperature drying, the capacitor is immersed in solution A, and then subjected to a high-temperature thermal decomposition process, followed by cooling. This step is repeated multiple times according to the capacitor model;

[0087] S3: Performing an intermediate forming process, followed by high temperature drying;

[0088] S4: Dipping in solution B, then performing a high-temperature thermal decomposition process, followed by cooling. This step is repeated multiple times depending on the capacitor model;

[0089] S5: performing an intermediate patch forming process, then immersing in solution C, which is a strengthening solution, and then drying;

[0090] S6: performing high temperature air decomposition and then cooling;

[0091] S7: dipping in solution D, then performing a high temperature thermal decomposition process, followed by cooling, and this step is repeated multiple times depending on the capacitor model;

[0092] S8: Perform the final filling forming process, impregnate the cathode auxiliary material after high-temperature drying, and complete the capacitor cathode preparation.

[0093] The solution A is a manganese nitrate solution, comprising a step solution with a specific gravity of 1.4, and the proportion of catalyst added to each solution increases by 0.6% as the specific gravity increases;

[0094] The solution B is a manganese nitrate solution, comprising various step solutions with a specific gravity of 1.8, and the catalyst ratio added to each solution is 2.6%;

[0095] The solution C is a manganese nitrate solution, which is prepared from manganese dioxide powder, silicon dioxide, and manganese nitrate solution. The silicon dioxide accounts for 6% of the mass of the manganese dioxide powder. 2000 ml of manganese nitrate solution is added for every kilogram of manganese dioxide powder. Its specific gravity in the cathode of the tantalum capacitor is 2.9.

[0096] The solution D is a manganese nitrate solution, with a specific gravity of 1.5 and a step solution, and the catalyst is added in a proportion of 3.1%;

[0097] The catalyst includes ammonium nitrate and ammonium perchlorate.

[0098] In the steps S2, S4, S5 and S7, the immersion temperature is 34° C. and the immersion time is 12 min;

[0099] Before the high-temperature thermal decomposition process, a dehydration method can be used for treatment, the dehydration temperature is 67° C., the dehydration time is 10 minutes, and after the dehydration is completed, the material is placed in a coating furnace for thermal decomposition.

[0100] The temperature in the high temperature thermal decomposition process in steps S2, S4, and S7 and the high temperature air decomposition process in step S6 is 199°C; the time is 14 minutes; and the oxygen content during decomposition is 14%.

[0101] The cooling in steps S2, S4, S6 and S7 is air cooling to below 30°C.

[0102] In the replenishment formation process in steps S1, S3, S5 and S6, a replenishment formation liquid mixed with ethylene glycol, n-butanol, glacial acetic acid and citric acid is used to meet the conductivity control requirements of the formation liquid.

[0103] The above-mentioned formation is to use a tantalum block whose dielectric oxide film has been formed in the formation process or a tantalum block whose film has been thermally decomposed for a certain number of times, and use a film formation liquid to perform constant current boosting and constant voltage current reduction at a certain current density. The formation voltage in each stage is different. The conductivity of the formation liquid in the formation process in the steps S1, S3, S5, and S6 is 3μs / cm, the boost current is 21μA / mg, the constant voltage time is 35min, and the constant voltage time is calculated after the formation voltage is increased; the formation voltage in the step S1 is 0.8U 形 The voltage for forming the complement in steps S3 and S5 is 1.4U 额 The voltage for the complementary formation in step S8 is 1.4U 额 .

[0104] The high temperature drying in steps S2, S3 and S8 is carried out after the formation of the patch by using a high temperature oven or a high temperature thermal decomposition furnace. When a high temperature oven is used, the temperature is 110-150°C and the drying time is 16 minutes. When a high temperature thermal decomposition furnace is used, the temperature is 204°C, the decomposition time is 9 minutes, and the oxygen content in the furnace is 13%.

[0105] In step S5, drying is performed twice, the first drying temperature is 50° C., and the drying time is 30 min; the second drying temperature is 150° C., and the drying time is 40 min.

[0106] In step S8, the cathode auxiliary materials are graphite and silver paste.

[0107] The main equipment required for the capacitor cathode preparation method of the present invention includes a high-temperature thermal decomposition furnace, an immersion tank, a forming tank, a forming power supply, a multimeter, a conductivity tester, a specific gravity meter, etc.

[0108] The high-temperature thermal decomposition furnace sets the thermal decomposition temperature of the solution at each stage according to the process requirements (controlled by the oxygen content); after the impregnation tank is cleaned, the manganese nitrate solution is placed in it and heated and circulated according to the required temperature of various solutions; after the forming tank is cleaned, the solution is prepared according to the process; after the forming power is turned on, the forming voltage and boost current are set according to the process requirements; the multimeter is used to detect the power output voltage and the voltage of the product during the forming process; the conductivity tester is used to detect the conductivity of the forming solution; the hydrometer is used to test the specific gravity of various manganese nitrate solutions.

[0109] Comparative Example 1:

[0110] 100V 10μF-V capacitor prepared by conventional process.

[0111] Comparative Example 2:

[0112] 160V 10μF-V capacitor prepared by conventional process.

[0113] By using the capacitor cathodes prepared in Examples 1 and 3, 10 pieces were randomly selected together with the cathode samples used in Comparative Examples 1 and 2 for electrical performance testing, and their electrical performance parameters are shown in Tables 1 and 2; by using the capacitor cathodes prepared in Examples 1 and 3, 100V 10μF-V capacitors and 60V 10μF-V capacitors were prepared, and 100 capacitors were randomly selected together with the capacitors of Comparative Examples 1 and 2, and after completing the process of bonding, molding, end treatment, rib cutting, aging, aging, high and low temperature screening, measurement, shaping, etc. according to conventional processes, the qualified rate of finished products was statistically calculated, as shown in Tables 3 and 4.

[0114] Table 1 Comparison of 100V10μF-V cathode electrical performance parameters

[0115]

[0116] Table 2 Comparison of qualified rate of 100V10μF-V finished products

[0117]

[0118]

[0119] Table 3 Comparison of 160V10μF-V cathode electrical performance parameters

[0120]

[0121] Table 4 Comparison of qualified rate of 160V10μF-V finished products

[0122] Group Finished product qualification rate (%) Comparative Example 1 53 Example 1 67 Example 2 60 Example 3 71

[0123] It can be seen from Tables 1-4 that the electrical performance parameters of the capacitor cathode material prepared by the process method of the present invention are significantly improved, which can improve the consistency and stability of the capacitor electrical performance parameters, and improve the qualification rate and reliability of the capacitor prepared therefrom.

Claims

1. A method for preparing a cathode of a high voltage or ultra-high voltage tantalum capacitor, characterized in that: The following steps are involved: S1: Performing a pre-complementation forming process on the tantalum block; S2: After high-temperature drying, the solution A is immersed, and then a high-temperature thermal decomposition process is performed, and then cooling is completed. This step is repeated multiple times; S3: Performing an intermediate forming process, followed by high temperature drying; S4: impregnating solution B, then performing a high temperature thermal decomposition process, cooling after completion, and repeating this step multiple times; S5: performing an intermediate patch forming process, then dipping in solution C, and then drying; S6: performing high temperature air decomposition and then cooling; S7: impregnating solution D, and then performing a high temperature thermal decomposition process, cooling after completion, and repeating this step multiple times; S8: Perform the final filling forming process, impregnate the cathode auxiliary material after high-temperature drying, and complete the capacitor cathode preparation.

2. A method for preparing a cathode of a high voltage or ultra-high voltage tantalum capacitor according to claim 1, characterized in that: The solution A is a manganese nitrate solution, comprising a step solution with a specific gravity below 1.6, and the proportion of catalyst added to each solution is 0.1-1% and increases with the specific gravity; The solution B is a manganese nitrate solution, comprising various step solutions with specific gravity ranging from 1.7 to 1.9, and the catalyst ratio added to each solution is 1.5-4%; The solution C is a manganese nitrate solution, which is prepared from manganese dioxide powder, silicon dioxide, and manganese nitrate solution. The silicon dioxide accounts for 1-10% of the mass of the manganese dioxide powder. 1000-3000 ml of manganese nitrate solution is added per kilogram of manganese dioxide powder. Its specific gravity in the cathode of the tantalum capacitor is 2.0-3.5; The solution D is a manganese nitrate solution, with a specific gravity of 1.3-1.8 in each step solution, and the catalyst is added in a ratio of 1.5-4%; The catalyst includes one or more of ammonium nitrate, urea, peracetic acid, nickel nitrate, and ammonium perchlorate.

3. A method for preparing a cathode of a high voltage and ultra-high voltage tantalum capacitor according to claim 1, characterized in that: In the steps S2, S4, S5 and S7, the immersion temperature is 25-45°C and the immersion time is 3-20min; Before the high temperature thermal decomposition process, a dehydration treatment can be adopted, and the dehydration temperature is 45-90° C. and the dehydration time is 3-15 minutes.

4. A method for preparing a cathode of a high voltage or ultra-high voltage tantalum capacitor according to claim 1, characterized in that: The temperature in the high temperature thermal decomposition process in steps S2, S4, S7 and the high temperature air decomposition process in step S6 is 185-230°C; the time is 3-20 minutes; and the oxygen content during decomposition is 5-20%.

5. A method for preparing a cathode of a high voltage or ultra-high voltage tantalum capacitor according to claim 1, characterized in that: The cooling in steps S2, S4, S6 and S7 includes air cooling or static cooling to below 30°C.

6. A method for preparing a cathode for a high voltage or ultra-high voltage tantalum capacitor according to claim 1, characterized in that: In the reparation forming process in steps S1, S3, S5 and S6, a reparation forming liquid is used which is a mixture of one or more liquids selected from pure deionized water, ethanol, ethylene glycol and n-butanol and one or more selected from glacial acetic acid, acetic acid and citric acid.

7. A method for preparing a cathode of a high voltage or ultra-high voltage tantalum capacitor according to claim 6, characterized in that: In the steps S1, S3, S5 and S6, the conductivity of the forming solution in the forming process is 1-5 μs / cm, the boost current is 5-30 μA / mg, the constant voltage time is 10-50 min, and the constant voltage time is calculated after the forming voltage is reached; the forming voltage in step S1 is 0.7-0.9U 形 The voltage for forming the complement in steps S3 and S5 is 1.3-1.6U 额 The voltage for forming the complement in step S8 is 1.2-1.5U 额 .

8. A method for preparing a cathode of a high voltage or ultra-high voltage tantalum capacitor according to claim 1, characterized in that: In the steps S2, S3 and S8, the high temperature drying is carried out in a high temperature oven or a high temperature thermal decomposition furnace. When a high temperature oven is used, the temperature is 110-150°C and the drying time is 10-20 minutes. When a high temperature thermal decomposition furnace is used, the temperature is 185-230°C, the decomposition time is 3-15 minutes, and the oxygen content in the furnace is 5-20%.

9. A method for preparing a cathode of a high voltage or ultra-high voltage tantalum capacitor according to claim 1, characterized in that: In step S5, drying is performed twice, the first drying temperature is 45-60° C., and the drying time is 20-40 min; the second drying temperature is 130-160° C., and the drying time is 30-50 min.

10. A method for preparing a cathode for a high voltage or ultra-high voltage tantalum capacitor according to claim 1, characterized in that: In step S8, the cathode auxiliary material includes graphite and silver paste.

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