JPH031819B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrolytic solution for driving an electrolytic capacitor, and by significantly lowering the specific resistance of the electrolytic solution, the tangent of the loss angle and high frequency characteristics of the electrolytic capacitor are improved. The present invention provides an electrolytic capacitor that has a long life and high reliability at high temperatures and can suppress changes in capacitance and increases in leakage current. [Prior Art and Problems] Conventionally, so-called ethylene glycol/boric acid ester-based electrolytes have been used as electrolytes for driving aluminum electrolytic capacitors, particularly for medium and high voltages. When this type of electrolyte is heated, the esterification reaction between ethylene glycol and boric acid progresses, and water is generated at this time.This water reacts with the aluminum foil that is the material of the capacitor element in the electrolytic capacitor. Electrolytic capacitors using this electrolyte could not be used for higher temperature purposes because it would dissolve and generate hydrogen gas, causing an increase in the internal pressure of the capacitor. In addition, in order to solve the above-mentioned problem, an electrolytic solution of the same type that promotes esterification and removes the produced water has been proposed, but although the reaction with water is suppressed, the viscosity of the electrolytic solution increases. The electrolytic capacitor using this electrolyte has a significantly increased resistivity, and the loss angle tangent and impedance at high frequencies have significantly increased, making it impossible to meet the demands for high characteristics. For these reasons, electrolytic capacitors for high temperatures do not use ethylene glycol/boric acid ester electrolytes, but rather organic acid electrolytes containing relatively large molecular weight organic acids or their salts as solutes. It is being considered. The solute of organic acid electrolyte for medium and high pressure is 1.6.
- Decanedicarboxylic acid (Japanese Patent Publication No. 13293/1983 ``Electrolytic solution for driving electrolytic capacitors'') is known,
Electrolytic capacitors that use an electrolyte containing 1.6-decanedicarboxylic acid have a low initial capacitance because the solute itself reacts with the aluminum foil that forms the capacitor element to form a complex, and it also has low initial capacitance during high-temperature load tests and high-temperature no-load tests. Tests showed an extreme decrease in capacitance and a significant increase in leakage current.
The demand for electrolytic capacitors with higher performance could not be met. [Improvements and Summary of the Invention] However, the present invention can eliminate the above-mentioned drawbacks. Specifically, the present invention can eliminate the above-mentioned drawbacks. By using it as an electrolyte, it prevents the formation of complexes between 1,6-decanedicarboxylic acid and aluminum foil, suppresses capacitance changes and increases in leakage current of electrolytic capacitors, and further lowers the specific resistance of the electrolyte, increasing the loss angle. By reducing the tangent of and impedance at high frequencies, we can provide electrolytic capacitors with higher performance and reliability. [Example] Next, the above-mentioned 1.6-decanedicarboxylic acid and 1.10
Examples of the electrolytic solution according to the present invention in which a mixture of -decanedicarboxylic acids or a mixture of their salts are dissolved in ethylene glycol are shown in Table 1 together with conventional examples. The electrolyte composition is wt%, and the specific resistance (Ω cm) is at a liquid temperature of 20°C. Also, the spark voltage is 85℃
belongs to.

【table】

【table】

【table】

[Table] Next, out of the electrolytes shown in Table 1, the temperature 105 Table 2 shows the results of a high-temperature load test at 1000 hours of rated voltage applied at ℃. Table 3 also shows the results of a high temperature no-load test (105°C, 1000 hours) on an electrolytic capacitor (rated 400V, 22μF). (Each value of the initial and post-test characteristics is the average value of each 20 electrolytic capacitors.)

【table】

[Table] [Effect of the invention] As can be seen from Tables 2 and 3, Conventional Example 2
In this case, the initial capacitance is approximately 10% lower than the rated value, and the rate of change is large even after testing. Further, as can be seen from Table 3, in Conventional Example 2, the leakage current is 30 times or more. The phenomenon shown in the conventional example shown in Tables 2 and 3 is due to the presence of the electrolyte in the driving electrolyte as described above.
1.6- Decanedicarboxylic acid reacts with the aluminum foil forming the capacitor element and significantly reduces its surface area, resulting in a decrease in capacitance, which is proportional to the surface area, and an increase in leakage current. Decanedicarboxylic acid reacts with the dielectric aluminum anodic oxide film to form an unstable aluminum complex film, which dissolves in the driving electrolyte at high temperatures, resulting in an increase in leakage current. On the other hand, the present invention prevents such a phenomenon by suppressing the complex formation of 1.6-decanedicarboxylic acid by using 1.10-decanedicarboxylic acid or its salt as a solute together with 1.6-decanedicarboxylic acid or its salt. be able to. Furthermore, by lowering the specific resistance, the tangent of the loss angle and the impedance at high frequencies can be kept low. Next, we will discuss the effect on product properties caused by suppressing complex formation by mixing 1.10-decanedicarboxylic acid or its salt, for example.
1.6-In an electrolyte containing 10wt% of decanedicarboxylic acid
Figure 1 shows, as an example, the change in the ratio of initial capacitance to the rated capacitance when 1.10-decanedicarboxylic acid is added.
Figure 2 shows the change in leakage current value in the high temperature no-load test after 1000 hours. The electrolytic capacitors used here all have a rating of 400V and 10μF, and each value is the average value of 20 capacitors. As can be seen from FIG. 1, when the concentration of 1.10-decanedicarboxylic acid added is low, the initial capacitance value is low. Addition of 0.5wt% has little effect, but 1wt%
The addition of is sufficient to produce the effect. Therefore, 1wt%
The above addition is preferable. As can be seen from FIG. 2, when the concentration of 1.10-decanedicarboxylic acid added is low, the leakage current value increases, and decreases in the order of addition of 0.5 wt% and 1 wt%. The effect is small when added at 0.5 wt%, but the effect becomes sufficiently clear when added at 1 wt%. Therefore, by using the driving electrolyte according to the present invention, it is possible to provide an electrolytic capacitor with higher performance and higher reliability. [Scope of practical application of the invention] In the components of the electrolytic solution according to the present invention, the amount of the mixed solute of 1.6-decanedicarboxylic acid and 1.10-decanedicarboxylic acid is preferably in the range of 8wt% to 30wt%, and 8wt% or less If it is, the specific resistance becomes large, and conversely, if it exceeds 30 wt%, the spark voltage of the electrolyte decreases, so that neither of them can be put to practical use.

[Brief explanation of the drawing]

Figure 1 shows the results for 1,6-decanedicarboxylic acid.
A characteristic diagram showing the relationship between the added concentration of 1.10-decanedicarboxylic acid and the ratio between the initial capacitance and the rated capacitance of an electrolytic capacitor. FIG. 3 is a characteristic diagram showing the relationship between leakage current of an electrolytic capacitor.

Claims (1)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor, characterized in that the main solute is a mixture of 1.6-decanedicarboxylic acid and 1.10-decanedicarboxylic acid or a mixture of their salts, and ethylene glycol is used as a solvent.