Control method for anodic oxidation constant-voltage treatment of tantalum capacitor

Abstract

The invention belongs to the technical field of tantalum capacitor manufacturing, and particularly relates to a control method for anodic oxidation constant-voltage treatment of a tantalum capacitor, which comprises the following steps of: calculating an end current of constant-voltage treatment of each product by adopting a residual current control method according to rated voltage, rated capacitance, a residual current coefficient and an anode parallel number; the residual current coefficient is divided into a high-voltage tantalum capacitor residual current coefficient and a low-voltage tantalum capacitor residual current coefficient; the residual current coefficient of the high-voltage tantalum capacitor is 0.1-0.3 [mu] A / [mu] F.V; the residual current coefficient of the low-voltage tantalum capacitor is 0.08-0.2 [mu] A / [mu] F.V; the residual current method is adopted to control the constant voltage stage in the anodic oxidation process of the tantalum capacitor, the quality of each batch of products is accurately controlled under the condition that the number of anodes, the weight of tantalum powder, the initial voltage drop and the like are different, the residual current value is set in advance, and manual sampling operation is effectively avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of tantalum capacitor manufacturing, and particularly relates to a control method for constant voltage treatment of tantalum capacitor anodic oxidation. Background Art

[0002] The existing control method for the constant voltage stage of tantalum capacitor anodic oxidation is to control the constant voltage time. The weight of the anode body powder in batches will cause different boost currents, and the difference in the number of anode bodies will lead to different initial voltage drops. If the same constant voltage time is used as the judgment criterion for the end of the constant voltage stage, the difference in DC leakage current and capacitance between batch products will be large. To control the influence caused by different numbers of anodes and powder weight errors, manual sampling inspection is required, and it is determined whether to end the constant voltage according to the data of the sampling inspection, which increases the manual operation cost. Therefore, in the case of different numbers of anodes and powder weight errors, how to achieve precise control of the constant voltage stage of each batch of products is crucial, which can effectively reduce the difference in DC leakage current and capacitance of batch products after anodic oxidation and eliminate the manual sampling inspection step.

[0003] The patent with the patent application number CN201711319318.6 discloses a method for reducing the leakage current value of non-solid electrolyte tantalum capacitors, which successively performs natural infiltration and current application in batches. The first applied current is 5-15% of the total boost current, and the second applied current is applied at a rate of 10-20% of the total boost current for 5-30 minutes; the current is applied in batches until the rated voltage and then the current is reduced, and the current is reduced to 50-80% of the total boost current, and the voltage value is continued to increase or even increase. This method can effectively reduce the leakage current value after the formation of non-solid electrolyte tantalum capacitors and improve the product reliability. However, this method has complex operations and cannot eliminate the differences between batch products.

[0004] The patent with the application number CN202011381517.1 discloses a method for reducing the leakage current after the formation of non-solid electrolyte tantalum capacitors, which includes the following steps: (1) sequentially performing natural infiltration, applying current in batches, boosting voltage and controlling temperature, and raising temperature and controlling pressure on the sintered anode tantalum block; the natural infiltration is: placing the anode tantalum block formed by sintering tantalum powder in the forming solution at 15 - 35°C for infiltration for 30 - 120 min. The applying current in batches is: first applying 5% - 15% of the boosting current value, with a boosting time of 30 - 120 min; then applying the remaining boosting current value. The boosting voltage and controlling temperature treatment is: boosting the anode tantalum block after the applying current in batches treatment to (T1 + 273°C) / (T2 + 273°C) times the forming voltage and keeping it constant for 1.5 - 2 h, and controlling the temperature of the forming solution at the temperature T1 during natural infiltration; the raising temperature and controlling pressure treatment is: after the boosting voltage and controlling temperature treatment, raising the temperature of the forming solution to T2, and raising the voltage to the forming voltage with a current of 10% - 50% of the boosting current value; the raising temperature and controlling pressure treatment is: after the boosting voltage and controlling temperature treatment, raising the temperature of the forming solution to 65 - 90°C, and raising the voltage to the forming voltage with a current of 10% - 50% of the boosting current value. However, this method still cannot eliminate the differences between batches of products. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention proposes a control method for constant voltage treatment of tantalum capacitor anodic oxidation.

[0006] Specifically, it is realized through the following technical solutions:

[0007] A control method for constant voltage treatment of tantalum capacitor anodic oxidation, which calculates the end current of constant voltage treatment for each batch of products by using the residual current control method according to the rated voltage, rated capacitance, residual current coefficient, and the number of anodes in parallel; the residual current coefficient is divided into the residual current coefficient of high-voltage tantalum capacitors and the residual current coefficient of low-voltage tantalum capacitors; the residual current coefficient of high-voltage tantalum capacitors is 0.1 - 0.3 μA / μF·V; the residual current coefficient of low-voltage tantalum capacitors is 0.08 - 0.2 μA / μF·V.

[0008] When the residual current coefficient is higher than the above range, the anodic oxidation inside the anode tantalum block is not complete, and there is a situation where the thickness of some oxide films inside the anode tantalum block is lower than that outside the anode tantalum block. When the residual current coefficient is lower than the above range, the constant voltage time is too long, which will promote the growth of the crystal oxide film. Too high or too low residual current coefficient is not conducive to the DC leakage current performance.

[0009] The calculation formula of the residual current control method is: the end current in the constant stage = residual current coefficient × rated voltage × rated capacitance × number of anodes in parallel.

[0010] The rated voltage of the high-voltage tantalum capacitor ≥ 63V.

[0011] The rated voltage of the low-voltage tantalum capacitor is < 63V.

[0012] The second object of the present invention is to provide: an application of a control method for constant voltage treatment of tantalum capacitor anodic oxidation in constant current boost and constant voltage current reduction anodic oxidation, pulsed anodic oxidation, and constant rate anodic oxidation.

[0013] Beneficial effects:

[0014] The present invention uses the residual current method to control the constant voltage stage in the anodic oxidation process of tantalum capacitors, achieving precise control of the quality of each batch of products in the case of differences in the number of anodes, tantalum powder weight, and initial voltage drop, and setting the residual current value in advance, effectively avoiding manual sampling operations.

[0015] The residual current method of the present invention can be applied to constant current boost and constant voltage current reduction anodic oxidation, pulsed anodic oxidation, and constant rate anodic oxidation, and is suitable for the constant voltage stage control of various anodic oxidation methods. Specific embodiments

[0016] The following further details the specific embodiments of the present invention, but the present invention is not limited to these embodiments, and any improvement or substitution based on the basic spirit of this embodiment still falls within the scope protected by the claims of the present invention.

[0017] The methods, test conditions, and instrument equipment for measuring the DC leakage current and capacitance of the examples and comparative examples in the present invention are as follows:

[0018] DC leakage current test method, test conditions, and instrument equipment: Tonghui Electronics TH2686C type current tester, and the test voltage and charging time are shown in Table 1.

[0019] Capacitance test method, test conditions, and instrument equipment: Tonghui Electronics TH2615E type capacitance meter, and the test frequency is 100Hz ± 5Hz.

[0020] Example 1

[0021] A control method for constant voltage treatment of tantalum capacitor anodic oxidation, the steps are as follows:

[0022] (1) Prepare 10 tantalum capacitor anode sintered blocks. According to the rated voltage of 125V, the rated capacitance of 1000 μF, and the residual current coefficient of 0.2 μA / μF·V, using the calculation formula of the residual current control method, the end current of the constant voltage treatment of this batch of products is obtained as 0.25A;

[0023] (2) Immerse the tantalum capacitor anode sintered block in a forming solution containing 75 wt% ethylene glycol - deionized water - phosphoric acid at 75°C. Set the boost current to 3.6 A and start constant - current boosting. When the voltage is boosted to 200 V, start constant - voltage current - reduction. When the current drops to 0.25 A, the constant - voltage treatment ends;

[0024] (3) After the constant - voltage treatment ends, take out the anodized anode, rinse it with deionized water at 90°C for 150 min, then dry it at 120°C for 30 min and conduct DC leakage current and capacitance tests.

[0025] Example 2

[0026] A control method for constant - voltage treatment of tantalum capacitor anodization, the steps are as follows:

[0027] (1) Prepare 40 tantalum capacitor anode sintered blocks. According to the rated voltage of 125 V, rated capacitance of 1000 μF, and residual current coefficient of 0.2 μA / μF·V, using the calculation formula of the residual - current control method, the end - current of the constant - voltage treatment for this batch of products is obtained as 1 A;

[0028] (2) Immerse the tantalum capacitor anode sintered block in a forming solution containing 75 wt% ethylene glycol - deionized water - phosphoric acid at 75°C. Set the boost current to 14.6 A and start constant - current boosting. When the voltage is boosted to 200 V, start constant - voltage current - reduction. When the current drops to 1 A, the constant - voltage treatment ends;

[0029] (3) After the constant - voltage treatment ends, take out the anodized anode, rinse it with deionized water at 90°C for 150 min, then dry it at 120°C for 30 min and conduct DC leakage current and capacitance tests.

[0030] Example 3

[0031] A control method for constant - voltage treatment of tantalum capacitor anodization, the steps are as follows:

[0032] (1) Prepare 100 tantalum capacitor anode sintered blocks. According to the rated voltage of 10 V, rated capacitance of 1000 μF, and residual current coefficient of 0.15 μA / μF·V, using the calculation formula of the residual - current control method, the end - current of the constant - voltage treatment for this batch of products is obtained as 0.15 A;

[0033] (2) Immerse the tantalum capacitor anode sintered block in a forming solution containing nitric acid - deionized water at 75°C. Set the boost current to 0.82 A and start constant - current boosting. When the voltage is boosted to 25 V, start constant - voltage current - reduction. When the current drops to 0.15 A, the constant - voltage treatment ends;

[0034] (3) After the constant voltage treatment is completed, take out the anodized anode, rinse it with deionized water at 90°C for 150 minutes, and then dry it at 120°C for 30 minutes before performing DC leakage current and capacitance tests.

[0035] Example 4

[0036] A control method for the constant voltage treatment of tantalum capacitor anodization is as follows:

[0037] (1) Prepare 400 tantalum capacitor anode sintered blocks. According to the rated voltage of 10V, the rated capacitance of 1000 μF, and the residual current coefficient of 0.15 μA / μF·V, using the calculation formula of the residual current control method, the end current of the constant voltage treatment for this batch of products is obtained as 0.6A.

[0038] (2) Immerse the tantalum capacitor anode sintered blocks in a solution formed by nitric acid - deionized water at 75°C, set the boosting current to 3.2A, start constant current boosting, when the voltage is boosted to 25V, start constant voltage and current reduction, and when the current drops to 0.6A, the constant voltage treatment ends.

[0039] (3) After the constant voltage treatment is completed, take out the anodized anode, rinse it with deionized water at 90°C for 150 minutes, and then dry it at 120°C for 30 minutes before performing DC leakage current and capacitance tests.

[0040] Comparative Example 1

[0041] A control method for the constant voltage treatment of tantalum capacitor anodization is as follows:

[0042] (1) Prepare 10 tantalum capacitor anode sintered blocks with a rated voltage of 125V and a rated capacitance of 1000 μF; immerse the tantalum capacitor anode sintered blocks in a solution formed by 75wt% ethylene glycol - deionized water - phosphoric acid at 75°C, set the boosting current to 3.6A, start constant current boosting, when the voltage is boosted to 200V, start constant voltage and current reduction, and when the constant voltage time reaches 8h, the constant voltage treatment ends.

[0043] (2) After the constant voltage treatment is completed, take out the anodized anode, rinse it with deionized water at 90°C for 150 minutes, and then dry it at 120°C for 30 minutes before performing DC leakage current and capacitance tests.

[0044] Comparative Example 2

[0045] A control method for the constant voltage treatment of tantalum capacitor anodization, which is different from Comparative Example 1 in that the number of sintered blocks is 40 and the boosting current is 14.6A.

[0046] Comparative Example 3

[0047] A control method for constant voltage treatment of tantalum capacitor anodic oxidation is as follows:

[0048] (1) Prepare 100 anode sintered blocks of tantalum capacitors with a rated voltage of 10V and a rated capacitance of 1000 μF; Immerse the anode sintered blocks of tantalum capacitors in a solution formed by nitric acid and deionized water at 75°C, set the boost current to 0.82A, start constant current boosting, when the voltage is boosted to 25V, start constant voltage and current reduction, and when the constant voltage time reaches 3h, the constant voltage treatment ends;

[0049] (2) After the constant voltage treatment ends, take out the anodes after anodic oxidation, rinse them with deionized water at 90°C for 150 min, and then dry them at 120°C for 30 min, and then perform DC leakage current and capacitance tests.

[0050] Comparative Example 4

[0051] A control method for constant voltage treatment of tantalum capacitor anodic oxidation, which is different from Comparative Example 3 in that the number of sintered blocks is 400 and the boost current is 3.2A.

[0052] The DC leakage current and capacitance test results of the examples and comparative examples are shown in Table 1.

[0053] Table 1

[0054]

[0055] As can be seen from Examples 1-4 in Table 1, when using residual current control for constant voltage treatment, the difference between the DC leakage current and capacitance of the obtained anodes is small. From Comparative Examples 1-4, it can be seen that within the same constant voltage time, as the number of anodes increases, both the DC leakage current and capacitance gradually increase, and the electrical performance differences between batches of products are relatively large. In addition, the DC leakage current of the anodes obtained by the residual current method is smaller.

Claims

1. A control method for constant voltage treatment of anodic oxidation of tantalum capacitors, characterized in that: The ending current of the constant voltage treatment for each batch of products is calculated by the residual current control method according to the rated voltage, rated capacitance, residual current coefficient and the number of anodes connected in parallel; the residual current coefficient is divided into the residual current coefficient of high-voltage tantalum capacitors and the residual current coefficient of low-voltage tantalum capacitors; the residual current coefficient of the high-voltage tantalum capacitors is 0.1 to 0.3 μA / μF·V; the residual current coefficient of the low-voltage tantalum capacitors is 0.08 to 0.2 μA / μF·V.

2. A control method for constant voltage treatment of anodic oxidation of tantalum capacitors as claimed in claim 1, characterized in that: The calculation formula of the residual current control method is: the end current of the constant stage = residual current coefficient × rated voltage × rated capacitance × number of anodes connected in parallel.

3. A control method for constant voltage treatment of anodic oxidation of tantalum capacitors as claimed in claim 1, characterized in that: The rated voltage of the high-voltage tantalum capacitor is ≥63V.

4. A control method for constant voltage treatment of anodic oxidation of tantalum capacitors as claimed in claim 1, characterized in that: The rated voltage of the low-voltage tantalum capacitor is less than 63V.

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