Method for forming medium-high voltage sheet type solid electrolyte tantalum capacitor

Abstract

The invention discloses a method for forming a middle-high voltage sheet type solid electrolyte tantalum capacitor, and belongs to the technical field of tantalum capacitor manufacturing. The chip-type solid electrolyte tantalum capacitor is prepared by adopting a graded boosting method, and a Ta2O5 dielectric oxide film with stable quality and good consistency can be formed by using forming liquid formulas with different conductivities and graded boosting current density, so that the leakage current of the chip-type tantalum capacitor is effectively reduced. And secondly, by optimizing the formula of the forming liquid and forming the boost current density, the problems of large quality parameter fluctuation and poor consistency of the dielectric film in the prior art can be effectively solved, so that the performance stability and reliability of the chip-type high-tantalum capacitor are improved. Finally, the preparation method disclosed by the invention is simple in process, low in cost and easy to implement on an existing production line, and has a good industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of tantalum capacitor manufacturing, and in particular relates to a method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor. Background Art

[0002] Tantalum chip capacitors (Tantalum chip capacitors) are widely used in aviation, aerospace, and other fields due to their small size, high capacity, stability, and reliability, and hold broad application prospects. The quality of the Ta2O5 dielectric film in tantalum chip capacitors directly affects their leakage current. During the dielectric film formation process, the formulation and boost current density are key process factors affecting the film's quality.

[0003] Currently, the formation process generally uses a single formation liquid formula and a constant current density for boosted formation. However, this method makes it difficult to effectively control the growth rate and uniformity of the dielectric film, resulting in large leakage current and poor electrical parameter performance. Therefore, a new formation process is urgently needed to optimize the quality of the dielectric film and thus improve the performance of tantalum capacitors. Although some solutions have been proposed in the prior art, some problems and shortcomings still exist. Patent CN112530707A discloses a method for reducing the leakage current of non-solid electrolyte tantalum capacitors after formation. This patent effectively reduces the leakage current value of non-solid electrolyte tantalum capacitors after formation by changing the infiltration method and time of the anode tantalum block, the current addition process, and controlling the solution temperature. However, this patent still faces the problem of further optimizing the natural infiltration process, the current addition process, and the solution temperature control process to ensure sufficient infiltration of the anode tantalum block, further reduce the leakage current value, and improve product quality. Summary of the Invention

[0004] In order to solve the above problems, the present invention aims to provide a method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solution: a method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor, comprising the following steps:

[0006] Step 1: Pressing tantalum metal powder into tantalum blocks of a certain size, and sintering the tantalum blocks in a vacuum environment;

[0007] Step 2: Use the anodic oxidation method to form a Ta2O5 dielectric oxide film on the sintered tantalum block in a graded pressure-reduced manner, using a conductivity of (3.5±0.3)×10 3 μS / cm phosphate glycol solution, boosted to 1 / 2 forming voltage at a current density of 15 mA / g, and the forming temperature was 65°C;

[0008] Step 3: After increasing the voltage to 1 / 2 of the forming voltage, use a conductivity of (3.5±0.3)×10 3 μS / cm phosphoric acid aqueous solution, and continue to increase the voltage to the formation voltage at a current density of 25 mA / g, and the temperature of the phosphoric acid aqueous solution is 65°C;

[0009] Step 4: Determine whether the forming voltage is reached, if so, proceed to step 5, if not, return to step 3;

[0010] Step 5: Maintain constant pressure for 2 hours to form a stable Ta2O5 dielectric film.

[0011] The step 2 includes:

[0012] Step 201: Prepare a solution with a conductivity of (3.5±0.3)×10 at 65°C. 3 μS / cm phosphoric acid glycol solution;

[0013] Step 202: Immerse the tantalum block in a phosphate glycol solution;

[0014] Step 203: boosting the voltage of the sintered tantalum block at a current density of 15 mA / g until the voltage is boosted to 1 / 2 of the forming voltage.

[0015] The step 3 includes:

[0016] Step 301: Prepare a solution with a conductivity of (3.5±0.3)×10 at 65°C. 3 μS / cm phosphoric acid aqueous solution;

[0017] Step 302: Immerse the tantalum block, which has been boosted to 1 / 2 of the forming voltage, in a phosphoric acid aqueous solution;

[0018] Step 303: Continue to increase the voltage of the tantalum block at a current density of 25 mA / g until the voltage reaches the forming voltage.

[0019] The step 5 includes:

[0020] Step 501: forming a stable Ta2O5 dielectric film by maintaining a constant voltage for 2 hours;

[0021] Step 502: spraying the formed tantalum block with deionized water for 5 minutes, and then boiling the tantalum block in deionized water at 85° C. for 1 hour;

[0022] Step 503: After the tantalum block is boiled, washed, and dried, it is placed in a 10% by volume phosphoric acid solution and its electrical performance is tested using a leakage current tester. The test voltage is 70% of the final voltage, and the charging time is 1 minute. The leakage current of the tantalum block is checked to indicate the quality of the Ta2O5 dielectric film. The smaller the leakage current, the better the quality of the Ta2O5 dielectric film.

[0023] Compared with the existing technology, this technical solution mainly solves the following problems:

[0024] 1) By using different conductivity liquid formulations and graded boost current density, a Ta2O5 dielectric film with stable quality and good consistency can be formed, thereby effectively improving the electrical parameter performance of chip tantalum capacitors;

[0025] 2) Using a step-by-step pressure-boosting method, a low-conductivity ethylene glycol phosphoric acid solution is used in the initial stage of forming the Ta2O5 dielectric film, which helps control the uniform growth of the film and avoid local defects in the Ta2O5 dielectric film. In the subsequent stages, a higher-conductivity phosphoric acid aqueous solution is used to accelerate the film growth rate and improve production efficiency.

[0026] 3) By optimizing the formulation of the forming solution and the formation of the boost current density, it is possible to effectively overcome the problems of large fluctuations and poor consistency in the quality parameters of the dielectric film in the existing technology, thereby improving the performance stability of the chip tantalum capacitor;

[0027] 4) The preparation method is simple in process, low in cost, and can be easily implemented on existing production lines, thus having good prospects for industrial application. DETAILED DESCRIPTION

[0028] The present invention is further described below with reference to specific embodiments. However, it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various modifications, substitutions and changes made according to common technical knowledge and customary means in the field are included in the scope of the present invention.

[0029] The present invention aims to provide a method for forming medium- and high-voltage chip-type solid electrolyte tantalum capacitors, which can effectively improve the quality of the Ta2O5 dielectric film of chip-type tantalum capacitors. The method comprises the following steps:

[0030] Example 1:

[0031] Step 1: Pressing tantalum metal powder into tantalum blocks of a certain size, and sintering the tantalum blocks in a vacuum environment;

[0032] Step 2: Using the step-by-step pressure-boosting method, the conductivity is 3.2×10 3 μS / cm phosphate glycol solution, and the current density was increased to 1 / 2 the forming voltage at 15 mA / g;

[0033] Step 201: Prepare a solution with a conductivity of 3.2×10 at 65°C. 3 μS / cm phosphoric acid glycol solution;

[0034] Step 202: Immerse the tantalum block in the ethylene glycol phosphoric acid solution;

[0035] Step 203: Boost the voltage of the tantalum block at a current density of 15 mA / g until the voltage is boosted to 1 / 2 of the forming voltage.

[0036] Step 3: After increasing the voltage to 1 / 2 of the forming voltage, use a conductivity of 3.8×10 3 μS / cm phosphoric acid aqueous solution, and continue to increase the voltage at a current density of 25 mA / g to the formation voltage;

[0037] Step 301: Prepare a solution with a conductivity of 3.8×10 at 65°C. 3 μS / cm phosphoric acid aqueous solution;

[0038] Step 302: Immerse the tantalum block, which has been boosted to 1 / 2 of the forming voltage, in the phosphoric acid aqueous solution;

[0039] Step 303: Continue to increase the voltage of the tantalum block at a current density of 25 mA / g until the voltage reaches the forming voltage.

[0040] Step 5: Maintain constant pressure at the forming voltage for 2 hours to form a stable Ta2O5 dielectric film;

[0041] Step 501: forming a stable Ta2O5 dielectric film by maintaining a constant voltage for 2 hours;

[0042] Step 502: spraying the formed tantalum block with deionized water for 5 minutes, and then boiling the tantalum block in deionized water at 85° C. for 1 hour;

[0043] Comparative Example 1:

[0044] A method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor is to form a Ta2O5 dielectric film on the surface of a tantalum porous body. The difference between the forming method and the embodiment 1 is that a dielectric film with a conductivity of 2.9×10 3 μS / cm2 ethylene glycol phosphate solution was used and the voltage was increased to the forming voltage at a current density of 15 mA / g.

[0045] Step 503: After the tantalum block is boiled, washed, and dried, it is placed in a 10% by volume phosphoric acid solution and subjected to an electrical performance test using a leakage current tester. The test voltage is 70% of the final voltage, and the charging time is 1 minute. The leakage current of the tantalum block is tested to indicate the quality of the Ta2O5 dielectric film. The smaller the leakage current, the better the quality of the Ta2O5 dielectric film. The average leakage current is shown in Table 1:

[0046] Table 1 Test results

[0047]

[0048] Example 2:

[0049] Another specific embodiment of the present invention is as follows:

[0050] Step 2: Use the step-by-step pressure-boosting method, using a conductivity of 3.5×10 3 μS / cm ethylene glycol phosphoric acid solution, and the voltage was increased to 1 / 2 the forming voltage at a current density of 15 mA / g;

[0051] Step 201: Prepare a solution with a conductivity of 3.5×10 at 65°C. 3 μS / cm ethylene glycol phosphoric acid solution;

[0052] Step 202: Immerse the tantalum block in the ethylene glycol phosphoric acid solution;

[0053] Step 203: Boost the voltage of the tantalum block at a current density of 15 mA / g until the voltage is boosted to 1 / 2 of the forming voltage.

[0054] Step 3: After increasing the voltage to 1 / 2 of the forming voltage, use a conductivity of 3.5×10 3 μS / cm phosphoric acid aqueous solution, and continue to increase the voltage at a current density of 25 mA / g to the formation voltage;

[0055] Step 301: Prepare a solution with a conductivity of 3.5×10 at 65°C. 3 μS / cm phosphoric acid aqueous solution;

[0056] Step 302: Immerse the tantalum block, which has been boosted to 1 / 2 of the forming voltage, in the phosphoric acid aqueous solution;

[0057] Step 303: Continue to increase the voltage of the tantalum block at a current density of 25 mA / g until the voltage reaches the forming voltage.

[0058] Step 5: Maintain constant pressure at the forming voltage for 2 hours to form a stable Ta2O5 dielectric film;

[0059] Step 501: maintaining a constant voltage for 2 hours to form a stable Ta2O5 dielectric film;

[0060] Step 502: spraying the formed tantalum block with deionized water for 5 minutes, and then boiling the tantalum block in deionized water at 85° C. for 1 hour;

[0061] Comparative Example 2

[0062] A method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor is to form a Ta2O5 dielectric film on the surface of a tantalum porous body. The difference between the forming method and the second embodiment is that a dielectric film with a conductivity of 2.9×10 3 μS / cm2 ethylene glycol phosphate solution was used and the voltage was increased to the forming voltage at a current density of 15 mA / g.

[0063] Step 503: After the tantalum block is boiled, washed, and dried, it is placed in a 10% by volume phosphoric acid solution and tested for electrical properties using a leakage current tester. The test voltage is 70% of the final voltage, and the charging time is 1 minute. The leakage current of the tantalum block is tested to indicate the quality of the Ta2O5 dielectric film. The smaller the leakage current, the better the quality of the Ta2O5 dielectric film. The average leakage current is shown in Table 2:

[0064] Table 2 Test results

[0065]

[0066] Example 3:

[0067] Step 2: Using the step-by-step boosting method, the conductivity is 3.8×10 3 μS / cm ethylene glycol phosphoric acid solution, and the voltage was increased to 1 / 2 the forming voltage at a current density of 15 mA / g;

[0068] Step 201: Prepare a solution with a conductivity of 3.8×10 at 65°C. 3 μS / cm ethylene glycol phosphoric acid solution;

[0069] Step 202: Immerse the tantalum block in the ethylene glycol phosphoric acid solution;

[0070] Step 203: Boost the voltage of the tantalum block at a current density of 15 mA / g until the voltage is boosted to 1 / 2 of the forming voltage.

[0071] Step 3: After increasing the voltage to 1 / 2 of the forming voltage, use a conductivity of 3.2×10 3 μS / cm phosphoric acid aqueous solution, and continue to increase the voltage at a current density of 15 mA / g to the formation voltage;

[0072] Step 301: Prepare a solution with a conductivity of 3.2×10 at 65°C. 3 μS / cm phosphoric acid aqueous solution;

[0073] Step 302: Immerse the tantalum block, which has been boosted to 1 / 2 of the forming voltage, in the phosphoric acid aqueous solution;

[0074] Step 303: Continue to increase the voltage of the tantalum block at a current density of 25 mA / g until the voltage reaches the forming voltage.

[0075] Step 5: Maintain constant pressure at the forming voltage for 2 hours to form a stable Ta2O5 dielectric film;

[0076] Step 501: forming a stable Ta2O5 dielectric film by maintaining a constant voltage for 2 hours;

[0077] Step 502: spraying the formed tantalum block with deionized water for 5 minutes, and then boiling the tantalum block in deionized water at 85° C. for 1 hour;

[0078] Comparative Example 3:

[0079] A method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor is to form a Ta2O5 dielectric film on the surface of a tantalum porous body. The difference between the formation method and the third embodiment is that a tantalum capacitor with a conductivity of 2.9×10 3 μS / cm2 ethylene glycol phosphate solution was used and the voltage was increased to the forming voltage at a current density of 15 mA / g.

[0080] Step 503: After the tantalum block is boiled, washed, and dried, it is placed in a 10% by volume phosphoric acid solution and tested for electrical properties using a leakage current tester. The test voltage is 70% of the final voltage, and the charging time is 1 minute. The leakage current of the tantalum block is tested to indicate the quality of the Ta2O5 dielectric film. The smaller the leakage current, the better the quality of the Ta2O5 dielectric film. The average leakage current is shown in Table 3:

[0081] Table 3 Test results

[0082]

[0083] Due to the advanced nature of this technical solution, it can be widely used in application fields such as electronic component manufacturing and tantalum capacitor manufacturing. First, this technical solution adopts a graded boosting method to prepare chip solid electrolyte tantalum capacitors. By using forming solution formulas with different conductivity and graded boosting current density, it can form a Ta2O5 dielectric oxide film with stable quality and good consistency, thereby effectively reducing the leakage current of the chip tantalum capacitor. Secondly, by optimizing the forming solution formula and the forming boosting current density, the use of ethylene glycol phosphoric acid solution with low conductivity in the initial stage of forming the Ta2O5 dielectric film is conducive to controlling the uniform growth of the film layer and avoiding local defects in the Ta2O5 dielectric film; the use of phosphoric acid aqueous solution with higher conductivity in the subsequent stage can accelerate the film growth rate and improve production efficiency; it can effectively overcome the problems of large fluctuations and poor consistency of dielectric film quality parameters in the existing technology, thereby improving the performance stability and reliability of chip high tantalum capacitors. Finally, the preparation method of the present invention is simple in process, low in cost, easy to implement on existing production lines, and has good prospects for industrial application. Therefore, this technical solution has broad market application prospects and demand.

[0084] The above describes in detail the method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor provided by the present invention. Specific examples are used herein to illustrate the structure and operating principles of the present invention. The description of the above embodiments is intended only to facilitate understanding of the method and core concepts of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications fall within the scope of protection of the claims.

Claims

1. A method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor, characterized by: The film growth is controlled by a step-by-step pressure increase method, which includes the following steps: Step 1: Pressing tantalum metal powder into tantalum blocks of a certain size, and sintering the tantalum blocks in a vacuum environment; Step 2: Use the anodic oxidation method to increase the voltage of the sintered tantalum block to 1 / 2 of the forming voltage for the first time, and the forming solution formula is selected with a conductivity of (3.5±0.3)×10 3 μS / cm phosphate glycol solution, with a boost current density of 15 mA / g; Step 3: The tantalum block in step 2 is boosted to form a voltage for the second time, and the conductivity of the forming solution is selected to be (3.5±0.3)×10 3 μS / cm phosphoric acid aqueous solution, boost current density of 25mA / g; Step 4: Determine whether the forming voltage is reached, if so, proceed to step 5, if not, return to step 3; Step 5: Form a stable Ta2O5 dielectric film under constant pressure.

2. The method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor according to claim 1, wherein: The step 2 is specifically as follows: Step 201: Prepare a solution with a conductivity of (3.5±0.3)×10 at 65°C. 3 μS / cm phosphoric acid glycol solution; Step 202: Immerse the tantalum block in a phosphate glycol solution; Step 203: The sintered tantalum block is voltage-increased at a current density of 15 mA / g until the voltage reaches 1 / 2 of the forming voltage, and the forming temperature is 65° C.

3. The method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor according to claim 1, wherein: The step 3 is specifically as follows: Step 301: Prepare a solution with a conductivity of (3.5±0.3)×10 at 65°C. 3 μS / cm phosphoric acid aqueous solution; Step 302: immersing the tantalum block, which has been boosted to 1 / 2 of the forming voltage, in a phosphoric acid aqueous solution; Step 303: Continue to increase the voltage of the tantalum block at a current density of 25 mA / g until the voltage reaches the forming voltage.

4. The method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor according to claim 1, wherein: The step 5 is specifically as follows: Step 501: maintaining a constant voltage for 2 hours to form a stable Ta2O5 dielectric film; Step 502: Boil and wash the formed tantalum block; Step 503: After the tantalum block is boiled, cleaned, and dried, the tantalum block is subjected to electrical testing.

5. The method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor according to claim 4, wherein: The step 501 specifically includes spraying the formed tantalum block with deionized water for 5 minutes, and then boiling the tantalum block in deionized water at 85° C. for 1 hour.

6. The method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor according to claim 1, wherein: Specifically, step 503 includes placing the tantalum block in a 10% by volume phosphoric acid solution, and performing an electrical performance test using a leakage current tester. The test voltage is 70% of the final formed voltage, and the charging time is 1 minute.

7. The method for forming a medium- and high-voltage chip-type solid electrolyte tantalum capacitor according to claim 1, wherein: The specific operation of determining the formed voltage in step 4 is to adjust the multimeter to the DC voltage range, connect the red test lead to the anode of the formed tank, and connect the black test lead to the cathode of the formed tank to measure the formed voltage.

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