JPH0444410B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an electrolytic capacitor with an improved sealing body, and its purpose is to significantly improve reliability. Conventional technology Generally, as shown in Figure 3, electrolytic capacitors are made by forming a dielectric film on the surface of a metal foil with valve action, such as aluminum or tantalum, through anodic oxidation treatment to form an anode foil, and a cathode facing the anode foil. A capacitor element 1 is constructed by winding a pallet such as electrolytic paper between the foil and impregnating it with a driving electrolyte (hereinafter referred to as electrolyte), and an internal lead 5 drawn out from the capacitor element 1. and inserting the solderable external lead wire 4 connected to the internal 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 body 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, isobutylene/isoprene rubber has been frequently used as a sealing material with low gas permeability. Problems to be Solved by the Invention The above-mentioned isobutylene/isoprene rubber has lower gas permeability than any other rubber, and is not suitable for electrolytes using highly volatile organic vehicles such as dimethylformamide (hereinafter referred to as DMF). On the other hand, it is essential to maintain airtightness at high temperatures. However, when used for a long period of time at a high temperature of about 150°C, the hardness decreases. Furthermore, when immersed in highly polar solvents such as DMF at high temperatures, they tend to swell, soften, and partially dissolve. Means for Solving the Problems The present invention solves the above-mentioned problems, and includes a hexafluoroethylene propylene resin on the surface of the capacitor element in the opening of the case housing the capacitor element.
This electrolytic capacitor is characterized in that it is sealed by fitting a sealing body formed integrally with isobutylene/isoprene rubber on the outer surface. Function: Hexafluoroethylene propylene resin is placed on the case opening and the surface facing the capacitor element, which prevents the isobutylene/isoprene rubber from being attacked by the solvent in the electrolyte and also increases the hardness of the rubber at high temperatures. Reinforce the drop. Examples Examples of the present invention will be described below. Table 1 shows the hydrogen gas permeability of hexafluoroethylene propylene resin and isobutylene/isoprene rubber, and Table 2 shows the hydrogen gas permeability of the hexafluoride ethylene propylene resin and isobutylene/isoprene 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 hexafluoride resin is excellent for electrolytes using DMF as a solvent, but it has high gas permeability and lacks airtightness as an elastic sealant. Isobutylene/isoprene rubber has good airtightness, but is not suitable for areas that come into contact with electrolytes containing DMF as a solvent, and furthermore, the hardness decreases significantly when left at high temperatures. Focusing on the above points, when using a highly volatile electrolyte containing DMF, the inner surface of the side in contact with the electrolyte, that is, the capacitor element 1 side, as shown in FIGS. 1 and 2, By using an elastic sealing body 6 that is integrally molded so that the hexafluoroethylene propylene resin 6b is present and the isobutylene/isoprene rubber 6a is present on the outside to maintain airtightness, the permeation of the electrolyte is prevented. We were able to obtain a highly reliable electrolytic capacitor that prevented this and maintained airtightness. Even when a relatively stable solvent containing ethylene glycol is used, a more reliable electrolytic capacitor can be obtained by the two-layer sealing body 6 made of isobutylene/isoprene rubber 6a and hexafluoroethylene propylene resin 6b. Needless to say, it is possible. Next, the rating is 10V, 220μF, and the case size is 10mmφ
20mmL, rated 50V, 10μF, case size 8mmφ
125 of a product using two-layer rubber consisting of conventional isobutylene/isoprene rubber and the hexafluoroethylene propylene resin and isobutylene/isoprene rubber of the present invention as an elastic sealing body for an electrolytic capacitor with ×16 mmL lead wires in the same direction. 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, Figures 4 and 5.

[Table] The electrolyte used in this test is a solvent mixed with DMF. The test was conducted on 20 pieces of each type. As is clear from the test results, the electrolytic capacitor using the two-layer sealing body of the present invention is a high-performance, long-life, highly reliable capacitor that can guarantee high temperatures. Note that the same effect can be obtained from this two-layer rubber by laminating silicone rubber or other materials to form a multilayer structure, or by using it as a rubber material for bonding with a resin base such as phenol. Effects of the Invention Since the electrolytic capacitor of the present invention is configured as described above, the sealing body is not dissolved or swollen by the solvent in the electrolyte, and the hardness of the sealing rubber is less reduced at high temperatures. Therefore, an electrolytic capacitor using this sealing body has a long life and high reliability, which can guarantee high temperatures, and has extremely high industrial value.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of an electrolytic capacitor according to the present invention, FIG. 2 is a perspective view of an embodiment of an elastic sealing body of a capacitor according to the present invention, and FIG. 3 is a sectional view of a conventional electrolytic capacitor. Figure 4 is rated at 10V, 220μF
For the electrolytic capacitor, A is the electrostatic dissolution amount-time characteristic diagram, B is the tanδ-time characteristic diagram, and Figure 5 is the rated 50V.
For a 10μF electrolytic capacitor, A is the electrostatic dissolution amount vs. time characteristic diagram, B is the tanδ vs. time characteristic diagram. 1: Capacitor element, 2: Case, 3, 6: Elastic sealing body, 6a: Isobutylene/isoprene rubber, 6b: Hexafluoroethylene propylene resin.

Claims (1)

[Claims] 1. The opening of the case housing the capacitor element is sealed by fitting a sealing body integrally constructed with hexafluoroethylene propylene resin on the surface facing the capacitor element and isobutylene/isoprene rubber on the outer surface. An electrolytic capacitor featuring: