JPS58171812A - Electrolytic condenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic capacitor, and more particularly to a sealed structure for an aluminum electrolytic capacitor.

Conventionally, aluminum electrolytic capacitors have been constructed as shown in FIG. In other words, by roughening a metal foil such as aluminum that has a valve effect, the surface area is expanded, and then a dielectric film is formed on this surface by anodizing to form an anode body, and a cathode foil facing this is formed. The capacitor element 1 is formed by winding it together with a separator and impregnating it with a driving electrolyte (hereinafter referred to as paste). It is housed in a metal case 4 with the open end sealed.

Unlike other capacitors, this type of aluminum electrolytic capacitor uses a paste composed of ethylene glycol, boric acid, adipic acid, etc., so the paste evaporates through the sealing rubber 3 for use against Japan, and static electricity builds up. The capacitance decreased and the tan δ increased, and as shown in FIG. 2, the final phenomenon of the life was a disconnection state.

In order to minimize such phenomena and extend the service life, sealing members and sealing methods for aluminum electrolytic capacitors have been studied.

In particular, as shown in FIG. 3, improvements have been made to the sealing member and sealing method. That is, a sealing member 6 made of a non-rubber-like elastic material such as polytetrafluoroethylene is used and sealed by a press-fitting method to form an aluminum electrolytic capacitor.

A feature of this aluminum electrolytic capacitor is that unlike rubber materials, the diffusion coefficient of the paste is close to 0, so evaporation of the paste is extremely small and the life span is significantly extended. In addition, as shown in Figure 4 a and b, the external lead machine
Due to the hardness of the sealing member, the internal stress does not propagate to the internal capacitor element 1. Incidentally, FIG. 4a shows the characteristics of the rubber seal, and FIG. 4 shows the characteristics of the rubber seal.

However, this type of aluminum electrolytic capacitor has the following problems.

In other words, the sealing material for this type of aluminum electrolytic capacitor is sealed by a press-fitting method using a resin material such as tetrafluoroethylene, and the expansion coefficients of the metal case and this type of resin material are shown in Table 1. As shown in FIG. A phenomenon occurred in which leakage occurred from the gap at the contact interface with the member 6.

Table 1 Furthermore, the portion 6 of the external lead wire 2 in Fig. 6 that is housed within the sealing member δ is also a contact portion between a resin material and metal.
The paste also leaks to the outside due to the difference in thermal expansion coefficient in this area, and if the paste is present in this area, the leakage current will increase because this area has almost no dielectric film. Cause. If paste leakage occurs when this aluminum electrolytic capacitor is attached to a printed wiring board together with other circuit electronic components, short circuits may occur on the board, and circuit characteristics may deteriorate due to increased leakage current. .

The present invention was made in view of the current situation, and
By using a completely new sealing member, the above-mentioned drawbacks of the prior art are eliminated.

The technical content of the present invention is characterized in that it uses a sealing member formed by bonding a non-rubber-like elastic body and a rubber-like elastic body. Hereinafter, the structure and operation of the present invention will be explained in detail.

The present invention analyzes the paste leakage phenomenon that occurs through temperature cycle tests, etc. of aluminum electrolytic capacitors that use synthetic resin for the sealing member and is sealed with a bottomed cylindrical metal case, and improves the material and structure of the sealing part. In order to solve this problem, a rubber-like elastic body 7 having strong resistance to passage of organic solvents used in pastes such as ethylene glycol, ethylene glycol methyl ether, N, N dimethyl formamide, etc. is used as shown in Fig. 6. A sealing member 9 made by stacking and bonding a non-rubber-like elastic body (or synthetic resin) 8 on the inside of a cylindrical metal case 4 with a bottom and adhering it to the outside is used to seal the case by press-fitting. It is something.

The sealing member 9 according to the present invention has an outer diameter larger than the inner diameter of the metal case 4. This dimensionally large
When an aluminum electrolytic capacitor formed by press-fitting and sealing the sealing member 9 by a pressing method is subjected to a test such as a temperature cycle, paste leakage does not occur because the rubber-like elastic body 7 shrinks slightly due to temperature. Moreover, the sealing member 9 according to the present invention
The structure has a non-rubber-like elastic body 8 on the outside, and the lead wire 2 of the external drawer is fixed, so the lead wire 2
Mechanical stress generated when the capacitor element 1 is mounted on a printed circuit board is not propagated to the internal capacitor element 1, and an increase in leakage current does not occur. Furthermore, it is possible to prevent defects caused by detergents that tend to occur with conventional rubber seals, and corrosion defects caused by penetration of chlorinated organic solvents used for flux cleaning during soldering on printed circuit boards through the seal rubber. An electrolytic capacitor can be realized.

In addition to the above-mentioned combinations of the non-rubber-like elastic body and the rubber-like elastic body, a combination using a non-rubber-like elastic body on the inside and a rubber-like elastic body on the outside can be considered. This combination causes some problems in fixing the lead wires.

In particular, when the width of the lead wire is widened, since there is a rubber-like elastic body on the outside, the mechanical stress due to the spread is transmitted to the inside, which is undesirable because it causes dust.

Hereinafter, it will be explained in detail using specific examples.

FIG. 6 shows an aluminum electrolytic capacitor according to an embodiment of the present invention, in which the sealing member 9 is made of ethylene propylene terpolymer (EPT) for the rubber-like elastic body 7, and the non-rubber-like elastic body 8 is made of Flanated polyethylene was used.

Here, in this way, the rubber-like elastic body 7 and the non-rubber-like elastic body 8
If they are overlapped, a gap will be created in the overlapping part due to the suppression method 7 in the manufacture of aluminum electrolytic capacitors (lackiness, variations in the dimensions of the sealing member 9, etc.), and the paste will enter this area and cause the above-mentioned problem. In this way, it comes into contact with a portion of the lead wire 2 of the external drawer receptacle that is housed in the sealing member 9 and has almost no dielectric oxide film formed thereon, causing an increase in leakage current.

Therefore, in the present invention, the rubber-like elastic body 7 and the non-rubber-like elastic body 8 are laminated together. When pasting polytetrafluoroethylene, the area must be treated with metallic sodium (either corona discharge treatment or styrene graphite treatment), and an adhesive that does not contain halogen-based adhesives, which can cause corrosion of aluminum electrolytic capacitors, is used. A method of bonding rubber materials together, or a method of placing uncured rubber on the surface of polytetrafluoroethylene treated as described above, heating and pressurizing it to 120"C to 150C to vulcanize it, and simultaneously bonding it. Two types of sealing members were made using each of the 50V and 1μF.
A group of aluminum electrolytic capacitors completed by press-fitting a sealing material made only of polytetrafluoride, and a seal made by bonding vulcanized EPT to polyethylenetetrafluoride using a non-halogen adhesive. A product group (B) completed by press-fitting unvulcanized rubber with a sealing material bonded to polytetrafluoroethylene after heating and pressurizing unvulcanized rubber (B) Heat resistance test.

Stability tests at low and high temperatures were conducted. The results are shown in Table 2.

Table 2 As is clear from Table 2, the properties of the sealing member made by laminating a rubbery elastic material and a non-rubberlike elastic material are significantly improved compared to those made only of a non-rubberlike elastic material. In addition, the sealing member obtained by bonding both of them had almost the same characteristics regardless of the bonding method.

Moreover, as shown in FIG. 7, the high-temperature load characteristics of an aluminum electrolytic capacitor using a conventional sealing member made only of polytetrafluoroethylene are almost the same as those using the bonded sealing member of the present invention. It has characteristics.

As described above, according to the electrolytic capacitor of the present invention, by using a sealing member in which a rubber-like elastic body and a non-rubber-like elastic body are bonded together, the performance of the electrolytic capacitor can be improved, and This makes it possible to achieve longer life.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional aluminum electrolytic capacitor, Figure 2 is a diagram showing the life characteristics of a conventional aluminum electrolytic capacitor, and Figure 3 is a cross-sectional view of an aluminum electrolytic capacitor using a non-rubber-like elastic material as a sealing member. Figures 4a and 4b are diagrams showing the state of mechanical stress on an aluminum electrolytic capacitor due to various sealing members, Figure 6 is an explanatory diagram for explaining paste evaporation, and Figure 6 is an embodiment of the present invention. FIG. 7, which is a sectional view of an aluminum electrolytic capacitor according to an example, is a comparison diagram showing the characteristics of a capacitor using a sealing member made of a non-rubber-like elastic body and a capacitor using a bonded sealing member. 1... Capacitor element, 2... Lead wire, 4... e0 metal case, 7... Rubber-like elastic body, 8... Non-rubber-like Elastic body, 9...
Sealing member. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 ■ Pull r II (). y) - 349 Figure 4 (Otsu) 0) Figure 5
6th fl 7th bat ^ nTF+ (Kikiri-

Claims (3)

[Claims] (1) A capacitor element in which electrode foil is wound together with a separator and impregnated with an electrolytic solution is housed in a metal case, and the open end of the metal case is sealed; 1. An electrolytic capacitor characterized in that the capacitor is sealed by press-fitting a sealing member having an outer diameter larger than that of the non-rubber-like elastic body and a rubber-like elastic body bonded together. (2) The electrolytic capacitor according to claim 1, wherein the non-rubber-like elastic body is press-fitted so that it is disposed on the outside and the rubber-like elastic body is disposed on the capacitor element side. (3) The electrolytic capacitor according to claim 2, wherein the non-rubber-like elastic body and the rubber-like elastic body are bonded together using a non-halogen adhesive.