JPS5910047B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing aluminum or tantalum solid electrolytic capacitors, and more particularly to a reconstitution process for solid electrolytic capacitors.

Conventionally, the reconstitution process for solid electrolytic capacitors that use aluminum, tantalum, etc. as anode elements uses a boric acid-citric acid-based reconstitution solution to increase the voltage to a specified voltage, and then maintains this voltage for a specified period of time. By doing so, the anodic oxide film is reformed and the damage to the anodic oxide film is repaired.

However, even with this, the repair of the film was not complete, and there were drawbacks of large leakage current and low breakdown voltage.An object of the present invention is to eliminate the above-mentioned drawbacks.

The above-mentioned object of the present invention is to produce a solid electrolytic capacitor for exterior packaging by subjecting an anode body element such as aluminum to chemical conversion and manganese dioxide firing, repeating the re-forming and manganese dioxide firing, and then performing graphite baking and silver paint baking. A solid electrolytic capacitor characterized in that, in the reconstitution step of the method, the voltage is increased at a constant rate to a predetermined voltage, the voltage is once returned to zero, and the voltage is increased again to the predetermined voltage, and then the predetermined voltage is held for a predetermined time. This can be achieved by the manufacturing method.

In the reconversion step, when the voltage is increased to a predetermined voltage, the dielectric film such as the aluminum oxide film formed in the reconversion step is damaged due to scintillation.

For this reason, it is necessary to return the voltage to zero and start forming again from a lower forming voltage. The process of repairing the oxide film with K is repeated, and then a predetermined voltage is maintained.

FIG. 1 shows the voltage increase in one reconversion step.

First, the voltage is increased at a constant rate for a time t.

After seconds, the voltage has reached the predetermined maximum voltage.

Immediately after reaching the voltage, the voltage is brought to zero, and then the voltage is increased again at a constant rate to a predetermined maximum voltage, which is repeated three times, and then this predetermined voltage is maintained as it is for a predetermined period of time.

In FIG. 1, the reformation voltage is increased at a constant rate.

Note that the predetermined maximum voltage can be the same value in each repeated boost.

As shown in FIGS. 2 and 3, the more times the boosting is repeated in each reformation process, the more the leakage current of the aluminum solid capacitor can be reduced and the breakdown voltage can be lowered.

It is usually desirable to repeat the pressure increase four times.

Example: An etched aluminum element (2 x 3 x 6) was used as an anode, and a chemical solution of boric acid, citric acid, and monohydrate was used for the chemical conversion process, and a constant Na current of 9.6 mA was applied to raise the voltage to 138 V. After increasing the voltage, this voltage was maintained for 2 hours to form an aluminum oxide film.

Thereafter, this element was immersed in a manganese nitrate solution and thermally decomposed to sinter the manganese dioxide layer.

For the reconversion step, a boric acid-<monoethylene glycol citric acid chemical solution was used, and the pressure increase rate was 9v/min.
After increasing the voltage to a voltage of 7.-9 ov, the voltage was immediately returned to zero, and the voltage was repeatedly increased to 90 V at a rate of 9 V/'min, and then this voltage was held for 20 minutes.

The number of pressurization repetitions was 2, 3 or 4 depending on the lot.

After this re-formation, manganese dioxide calcination is performed in the same manner as after the above-mentioned chemical formation step.

After repeating a series of four re-formed manganese monooxide firings while lowering the maximum voltage each time, the graphite layer was baked by immersing it in a graphite powder suspension, and further re-forming was performed once at a voltage of 50 V. .

Next, silver paste was baked onto this element, and finally it was packaged.

Figure 2 shows the results of measuring the leakage current 30 seconds after applying a rated voltage of 25 V'aj to a 1 μF, 25 V aluminum solid electrolytic capacitor. The leakage current A of the capacitor is 4 times, and the vertical axis is the percentage of the cumulative number of capacitors in which a current less than the leakage current leaked to the number of test lots.

FIG. 3 shows the results of measuring the breakdown voltage of this product, where the horizontal axis is the number of repetitions of boosting in each re-formation process, and the vertical axis is the breakdown voltage V.

It can be seen that as the number of repetitions of boosting in each reformation process increases, the leakage current decreases and the breakdown voltage increases.

Comparative Example An aluminum solid electrolytic capacitor was manufactured by the conventional method in the same manner as in the example except that in each reconstitution step, the voltage was increased to the predetermined maximum voltage and then held at this voltage for 20 minutes. did.

The results of measuring the leakage current and breakdown voltage of this product are also shown in Figures 2 and 3.

[Brief explanation of the drawing]

Figure 1 is a graph of re-forming voltage per hour showing the repetition of boosting in each re-forming process, and Figure 2 is a graph of product capacitor leakage Kl with the number of repetitions of boosting in each re-forming process as a parameter. FIG. 3 is a graph of breakdown voltage of a manufactured capacitor per number of boost repetitions in each reformation process. 1...Number of boosting: 1 time (conventional method), 2...
・Number of boost repetitions: 2 times, 3...Number of boost repetitions: 3 times, 4...Number of pressure rise repetitions: 4 times.

Claims (1)

[Claims] 1. In the re-forming step of the solid electrolytic capacitor manufacturing method, which includes the step of chemically forming the anode element to form a dielectric film, firing manganese dioxide, and re-forming, the voltage is increased once to a predetermined voltage at a constant rate. 1. A method for manufacturing a solid electrolytic capacitor, which comprises repeatedly returning the voltage to zero and increasing the voltage at a constant rate to a predetermined voltage again, and then maintaining the predetermined voltage for a predetermined time.