JPS5867018A - Electrolytic capacitor - 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 electrolytic capacitors, and more particularly to improvements in chip-type electrolytic capacitors formed with a synthetic resin exterior.

With the miniaturization of electronic components, such as the use of ICs in electronic circuits, when electrolytic capacitor elements are extremely small and are wound with several layers of electrode foil to a diameter of less than 5 mm, the exterior of the element should be replaced with an aluminum case, etc. A method has been adopted in which the element itself is molded with synthetic resin. However, because electrolytic capacitor elements have a polar structure and are impregnated with electrolyte, unlike other electronic components, the exterior must have sufficient airtightness to maintain constant electrical characteristics such as capacitance. is required. In other words, since an electrolytic capacitor element generates hydrogen gas by electrolyzing the electrolyte when current is passed through it, it not only prevents the evaporation of the electrolyte and the inhalation of impurities, but also can withstand the increase in internal pressure caused by the generated gas. It is necessary to maintain sufficient airtightness.

Therefore, when an electrolytic capacitor element is packaged with a synthetic resin, the adhesion between the terminals drawn out from the electrolytic capacitor element, that is, the metal plate, and the synthetic resin is an important factor in maintaining the airtightness of the package. In particular, when the metal plates for terminals become smaller due to miniaturization of electrolytic capacitor elements, it is necessary to maintain airtightness between the two even more strongly. In general, thermoplastic synthetic resins have lower adhesion to metals than thermosetting synthetic resins, and there is a high risk that an exterior made of thermoplastic synthetic resin alone will have poor airtightness. In addition, in the case of thermosetting synthetic resin, the molding temperature is as high as 150 to 180°C, and when an electrolytic capacitor element impregnated with an electrolytic solution is molded, the electrolytic solution evaporates during heat treatment, so the impregnation of the electrolytic solution is difficult. must be done after molding. However, when an element is molded only with thermosetting synthetic resin, when the molding pressure acts on the element, the element is compressed and solidified, so even if it is impregnated with electrolyte after molding, the electrolyte will not be sufficiently impregnated. This causes problems such as a decrease in capacitance and an increase in tan δ, or if the chemical oxide film is damaged due to compression, this causes an increase in leakage current. Further, when an injection hole is formed for impregnation with an electrolytic solution, sealing the injection hole with a thermosetting resin is extremely troublesome and may cause airtight leakage.

An object of the present invention is to form a thermosetting synthetic resin layer on an exterior body made of thermoplastic synthetic resin to compensate for the drawback of thermoplastic synthetic resin having low adhesion to metal.

In this invention, an electrolytic capacitor element is enclosed in a storage space formed inside an exterior body molded from thermoplastic synthetic resin, and a terminal connected to an electrode foil of the electrolytic capacitor element and drawn out from the exterior body. It is characterized in that the outer surface of the exterior body as well as the surface near the exterior body is coated with a thermosetting synthetic resin layer.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

1 and 2 show an embodiment of the electrolytic capacitor of the present invention, FIG. 1 is a perspective view showing its external shape, and FIG. 2 is a cross section taken along the line ■-■ in FIG. 1. . In the figure, the exterior body 2 that encloses the electrolytic capacitor element is a bottomed rectangular cylindrical exterior body piece 2A molded from thermoplastic synthetic resin such as polypropylene, noryl, nylon, PBT, PPS, etc.
2B joined together, and a cylindrical wound electrolytic capacitor element 6 is sealed inside a storage space 4 formed in this exterior body 2. This electrolytic capacitor element 7r
Terminal 8.1 connected to the electrode foil on the anode side or cathode side of 6
0 are drawn out from the end faces of the electrolytic capacitor element 6 in opposite directions, and are further drawn out to the outside of the sheath 2 through the longitudinal end face of the sheath 2, that is, the joint between the sheath pieces 2A and 2B. There is.

In this embodiment, the terminal 8.1o consists of an inner lead 12 that is directly connected to the electrode foil and an outer lead 14 that allows an external connection, the inner lead 12 being of the same kind of metal as the electrode foil and the outer The leads 14 are made of metal that can be soldered, for example, and are both formed in a band shape. Each lead 12, 14 is fixed in the embedded part of the exterior body 2 by means such as crimping or welding. The outer surface of the exterior body 2, except for a part thereof, is coated with a thermosetting synthetic resin layer 16 of epoxy, phenol, etc. together with the surface portion near the exterior body of the terminal 8.10 pulled out from the exterior body 2. ing. The terminals 8 and 10 are bent onto the upper surface of the synthetic resin layer 16 formed on the side surface of the exterior body 2 and are used as face bonding terminals for direct attachment to a printed circuit board or the like.

FIG. 3 shows the electrolytic capacitor element 6 and its terminal structure. The internal lead 12 is bent to face the center of the element 6, and the external lead 1 is placed on the upper or lower surface of the internal lead 12.
4 and weld them together.

Incidentally, uneven portions 17 are formed on both sides of the tip of the external lead 14 in order to improve adhesion to the synthetic resin of the exterior body 2.

The exterior body 2 that exteriorizes the electrolytic capacitor element 6
consists of two exterior body pieces 2A and 2B each having a storage space 4 formed therein, as shown in FIG.
A small-diameter protrusion 18 is formed at the center of the outer surface of A, and an injection hole 20 for injecting electrolyte into the storage space 4 is bored in this protrusion 1'''8.
is placed in the center of the storage space 4 of the facing exterior body pieces 2A, 2B, and with the terminal 8.10 pulled out to the outside of the exterior body pieces 2A, 2B, heat welding or ultrasonic welding is performed while applying pressure. When the exterior body pieces 2A and 2B are joined, the electrolytic capacitor element 6 is sealed inside the exterior body 2 as shown in FIG. Then, as shown in FIG. 6, a thermosetting synthetic resin layer 16 is formed on the outer surface of the exterior body 2 and the surface portions of the terminals 8 and 10 pulled out from the exterior body 2, excluding the injection holes 20, and then the injection holes are Electrolytic solution 22 is injected from 20 to impregnate the electrolytic capacitor element 6. After impregnation with this electrolyte, Fig. 7 (A)
A trapezoidal plug 24 made of thermoplastic synthetic resin is inserted into the injection hole 20 as shown in FIG.
The injection hole 20 is closed as shown in B).

With the above configuration, the outer surface of the exterior body 2 molded from thermoplastic synthetic resin and the surface near the exterior body 2 of the terminal 8.10 pulled out from the exterior body 2 are coated with the thermosetting synthetic resin layer 16. Therefore, the exterior body pieces 2A, 2 of the exterior body 2
The formation of the synthetic resin layer 16 maintains a high degree of airtightness at the joint part B and the lead-out part of the terminal 8.10, so evaporation of the electrolyte and absorption of impurities can be prevented, and the electrical characteristics can be maintained for a long time. It can be maintained constant over time. Note that the injection hole 20 formed in the exterior body 2 can be reliably closed by thermal treatment, and sufficient airtightness can be ensured.

Furthermore, a storage space 4 larger than the electrolytic capacitor element 6 is formed inside the two exterior body pieces 2B, and the thermosetting synthetic resin layer 16 is formed after the exterior body pieces 2, A, and 2B are joined. As a result, the exterior body pieces 2A, 2B are formed on the exterior body 2.
The molding pressure during bonding or formation of the synthetic resin layer 16 is blocked by the exterior body 2 and does not act on the electrolytic capacitor element 6, so that solidification of the electrolytic capacitor element 6 and damage to the chemical oxide film can be prevented. In other words, by preventing solidification, the electrolytic capacitor element 6 can be sufficiently impregnated with the electrolyte, thereby preventing inconveniences such as a decrease in capacitance and an increase in tan δ, and preventing damage to the chemical oxide film to prevent leakage. Current can be suppressed. As a result, an electrolytic capacitor with excellent electrical characteristics can be obtained.

As explained above, according to the present invention, a thermosetting synthetic resin layer is formed on the surface of the exterior body made of thermoplastic synthetic resin and on the surface near the exterior body of the terminal pulled out from the exterior body, resulting in excellent airtightness. This results in an exterior body that maintains constant electrical characteristics.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the electrolytic capacitor of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a perspective view showing an electrolytic capacitor element and its terminal structure. Fig. 4 is an explanatory diagram showing the packaging method, Fig. 5 is a perspective view of the element packaged with the packaging body, Fig. 6 is a sectional view showing the electrolytic capacitor before being impregnated with electrolyte, and Figs. 7 (A) and (B). ) is an explanatory diagram showing a method of closing an injection hole. 2... Exterior body, 2A, 2B... Exterior body piece, 4...
Storage space, 6... Electrolytic capacitor element, 8, lO...
- Terminal, 16... thermosetting synthetic resin layer. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) An exterior body molded from thermoplastic synthetic resin, an electrolytic capacitor element sealed in a storage space formed inside the exterior body, and an electrolytic capacitor element connected to the electrode foil of the electrolytic capacitor element and 1. An electrolytic capacitor comprising a thermosetting synthetic resin layer formed on the outer surface of the G2 exterior body as well as the surface near the exterior body of a terminal pulled out from the exterior body. (2) The electrolytic capacitor according to claim 1, wherein the exterior body is constructed by joining together exterior body pieces in the shape of a square cylinder with a bottom in which the storage space is formed.