JPH0154851B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrolytic capacitor with an improved sealing body, and its purpose is to significantly improve reliability. Generally, as shown in Figure 1, electrolytic capacitors are made by forming a dielectric film on the surface of a valve metal foil such as aluminum or tantalum through anodizing treatment to form an anode body, and an opposing cathode foil. It is wound with a separator such as electrolytic paper in between and impregnated with a driving electrolytic solution (hereinafter referred to as electrolytic solution) to form a capacitor element 1, and an internal lead 5 drawn out from the capacitor element 1 and the inside of this Insert the solderable external lead wire 4 connected to the lead 5 into the insertion hole of the elastic sealing body 3,
This is housed in a metal case 2, and the opening of the case 2 is sealed tightly. In the electrolytic capacitor configured as described above, since an electrolytic solution is used, when the temperature rises, the electrolytic solution passes through the elastic sealing member 3 and escapes to the outside, so it cannot be used in a high-temperature atmosphere for a long period of time. When this happens, the electrolyte evaporates to dryness, causing the capacitor to no longer function as a capacitor, and the loss value of the capacitor to increase. For this reason, ethylene propylene rubber is also frequently used as a sealing material with excellent heat resistance, and ethylene propylene rubber can withstand long-term use at high temperatures of around 150°C, with relatively little change in hardness. However, gas permeability is on the same level as natural rubber, and it is difficult to handle electrolytes using highly volatile organic solvents such as dimethylformamide (hereinafter referred to as DMF).
The drawback was that airtightness could not be maintained at high temperatures. Therefore, the inventors of the present invention have studied various rubber materials and have found that reliability can be significantly improved by using a sealing body made of integrally molded ethylene propylene rubber and urethane rubber. That is, in the present invention, the opening of a case housing a capacitor element is sealed by fitting a sealing body integrally formed with ethylene propylene rubber on the inner surface on the side of the capacitor element and urethane rubber on the outer surface. An electrolytic capacitor with the following characteristics. The present invention will be explained below based on specific examples. Table 1 shows the hydrogen gas permeability of urethane rubber and ethylene propylene rubber, and Table 2 shows the hydrogen gas permeability of urethane rubber and ethylene propylene rubber at 125°C.
A comparison with the initial value of hardness measured after leaving the product in the room for 1000 hours and returning it to room temperature is shown.

【table】

[Table] Table 3 shows the changes in rubber when immersed in DMF at 125°C for 500 hours.

[Table] From these test results, ethylene propylene rubber is excellent for electrolytes using DMF as a solvent, but
It has high gas permeability and lacks airtightness as an elastic sealant. Although urethane rubber has good airtightness, it is not suitable for areas that come into contact with electrolytes containing DMF as a solvent, and when using highly volatile electrolytes containing DMF, the As shown in Fig. 3, ethylene propylene rubber 6b is present on the inner surface of the side in contact with the electrolyte, that is, the capacitor element 1 side, and urethane rubber 6a is present on the outside to maintain airtightness. By using the elastic sealing body 6, it was possible to prevent the permeation of the electrolytic solution and maintain airtightness, thereby obtaining a highly reliable electrolytic capacitor. Even when a relatively stable solvent containing ethylene glycol or the like is used, a more reliable electrolytic capacitor can be obtained by using the two-layer sealing body 6 made of ethylene propylene rubber 6a and urethane rubber 6b. Not even. Next, the rating is 10V, 220μF, case size 10mm〓×
20mm ^L , rated 50V, 10μF, case size 8mm〓×
16 ^L of electrolytic capacitors with lead wires in the same direction as shown in Figure 1, which uses a two-layer rubber consisting of conventional ethylene propylene rubber and the urethane rubber and ethylene propylene rubber of the present invention as an elastic sealing body at 125°C. A life test was conducted in which the rated voltage was applied for 2000 hours in an atmosphere of The results are shown in Table 4. Figure 4 shows the rating in the above life test.
10V, 220μF capacitance, tan δ-time characteristic diagram. Figure 5 is a rated 50V, 10 μF capacitance, tan δ-time characteristic diagram in the same life test.

[Table] The electrolyte used in this test is a solvent mixed with DMF. The test was conducted for 20 pieces each. As is clear from the test results, the electrolytic capacitor using the double-layer rubber of the present invention has high performance, is capable of guaranteeing high temperatures, and has a long life and high reliability. Note that the same effect can be obtained by using this two-layer rubber as a multilayer material by laminating silicone rubber or other materials, or as a rubber material for bonding with a resin base material such as phenol. As described above, the present invention greatly contributes to improving the reliability of electrolytic capacitors and has extremely great industrial value.

[Brief explanation of drawings]

Figure 1 is a sectional view of a conventional electrolytic capacitor, Figure 2 is a cross-sectional view of a conventional electrolytic capacitor.
The figure is a sectional view of an embodiment of the electrolytic capacitor of the present invention, Figure 3 is a perspective view of an embodiment of the elastic sealing body of the capacitor according to the present invention, and Figure 4 is a rated 10V,
220 μF capacitance, tan δ - time characteristic diagram. Figure 5 is a rated 50 V, 10 μF capacitance, tan δ - time characteristic diagram. 1: capacitor element, 2: case, 3, 6: elastic sealing body, 6a: urethane rubber, 6b: ethylene propylene rubber.

Claims (1)

[Claims] 1. The opening of the case housing the capacitor element is sealed by fitting a sealing body integrally formed with ethylene propylene rubber on the inner surface on the capacitor element side and urethane rubber on the outer surface. Electrolytic capacitor.