JPS62101014A - Ceramic 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 chip-type ceramic capacitors used for assembling circuits of various electronic devices. There are various types of ceramic capacitors, such as ceramic capacitors, cylindrical capacitors, columnar capacitors, and cylindrical capacitors, among which cylindrical ceramic capacitors generally have a structure as shown in FIG.

That is, a cap 3.3 whose inner surface has been previously plated with solder is fitted onto both ends of a cylindrical ceramic body 1 having electrodes 2, 2 formed on its surface and inner surface, and this is heated in a heating furnace. By remelting (reflowing) the solder, the electrode 2.2 and the caps 3, 3 are ensured to be in contact with each other, and at the same time, the caps 3, 3 are reliably attached to the ceramic body l.
The outer surfaces of the caps 3, 3 are also plated with solder to improve solderability to printed circuit boards and the like. In such a cylindrical ceramic capacitor, a silver electrode is generally employed as the electrode 2.2, but such a silver electrode 2.2 may undergo migration in the presence of moisture, causing a short circuit between the electrodes 2.2. Therefore, in order to prevent this migration, the exposed parts of the electrodes 2, 2 on the surface of the ceramic body are usually plated with solder or copper, and then coated with thermosetting exterior resin such as epoxy resin as shown in the figure. A coating 4 is formed.

However, in the ceramic capacitor as described above, in the process of heating and reflowing the solder plated on the inner surface of the cap 3, and in the process of heating and hardening the thermosetting exterior resin ff4. , heat shock is applied to the ceramic body 1, which may lead to deterioration of the characteristics of the ceramic capacitor.In addition to the solder paste flow process and the heating hardening process of the coating 4, the above-mentioned migration prevention process There is also the problem that the total number of processes increases because various processes are required, such as the plating process for the electrodes 2 and 2.These problems are not only for cylindrical ceramic capacitors, but also for cylindrical ceramic Although this problem also occurs in the case of capacitors, the following problem particularly occurs in the case of cylindrical ceramic capacitors.

That is, if it is cylindrical, the air inside the cylindrical ceramic body 1 expands during heating and curing of the above-mentioned exterior resin, breaks through the exterior resin coating 4 that has not yet been sufficiently hardened, and flows to the outside. Since the air may escape, fine ventilation holes may be formed in the coating 4, resulting in poor sealing.Therefore, moist air entering from the outside through these ventilation holes tends to cause migration of the electrodes 2, 2. There are problems like this.

In order to solve the above-mentioned problem, the ceramic capacitor of the present invention covers the end of a ceramic body having an electrode on its surface with a metal cap, and connects the metal cap and the electrode to a common The gist is that it is coated with a plating film.

In the ceramic capacitor with the above configuration, the electrode and the cap are coated with a common plating film, so the cap and electrode can be connected reliably with electricity without having to reflow the solder on the inner surface of the metal cap as in the conventional case. The cap can be brought into direct contact with the ceramic body, and the cap can be reliably fixed to the ceramic body. In addition, the common plating film described above does not require special solder plating on the electrodes to prevent electrode migration, nor does it require solder plating on the outer surface of the metal cap to improve solderability. serve as a substitute for them. Therefore, it is possible to omit the plating process on the inner and outer surfaces of the metal cap, the reflow process, the plating process on the electrodes to prevent migration, etc., which greatly improves manufacturing efficiency. The problem of heat shielding caused by the glue flow process is solved, and there is less risk of property deterioration.

Furthermore, even in the case of cylindrical ceramic capacitors, the above-mentioned common plating film prevents the air enclosed in the ceramic body from being released to the outside, so air vents are formed when the exterior resin coating is heated and cured. gone,
Therefore, the electrode is prevented from migrating due to moist outside air entering through the ventilation hole and short-circuiting with the other electrode.

] J1 Embodiments of the present invention will now be described with reference to FIGS. 1 and 2.

FIG. 1 illustrates a cylindrical ceramic capacitor using a cylindrical ceramic body 1. As shown in FIG. In this ceramic capacitor, electrodes 2.2 are formed at both ends of the ceramic body 1, and metal caps 3.3 covering these electrodes 2.2 are placed on both ends of the ceramic body 1. There is. Further, the electrode 2 and the metal cap 3 described above are covered with a common plating film 5, and a resin coating 4 is applied around them.

In such ceramic capacitors, common plating II! J5 ensures reliable contact between the electrode 2 and the metal cap 3, and also securely holds the cap 3 against the ceramic body 1. Therefore, when manufacturing the ceramic capacitor shown in FIG.
As in the past, after covering the ceramic body with a cap with solder plating on the inside, the cap can be securely attached to the ceramic body using reflow to ensure contact between the cap and the electrode. There is no need to hold it. Further, migration of the electrode 2 formed on the outer surface of the ceramic body 1 is also prevented by the common plating film 5 described above. As a result, the ceramic capacitor shown in FIG. 1 suffers much less heat shock during the manufacturing process than conventional capacitors, and characteristic deterioration is prevented accordingly. Further, since the common plating film 5 is formed so as to cover the entire outer surface of the metal cap 3.3, there is no need to separately apply solder plating to the cap 3 in advance as in the conventional case.

FIG. 2 illustrates a cylindrical ceramic capacitor using a cylindrical ceramic body l. When the cylindrical ceramic body 1 is used, as described above, when the outer resin to be cured 4 is heated and cured, the air sealed inside the ceramic body 1 expands, causing the problem that the outer resin is not yet fully cured. In some cases, it may break through the external resin coating 4 and escape to the outside, so the moist outside air that enters through the minute ventilation holes formed at that time causes migration to the electrodes 2 formed on the inner surface of the ceramic body 1. Although there is a concern that this may occur, there is no problem at all because the common plating film 5 covering the electrode 2 and the cap 3 reliably prevents release of the sealed air. Other matters are the same as those described in FIG.

Note that the plating film 5 can be easily formed by electrolytic plating or electroless plating of a metal such as solder, tin, or copper on the electrode 2 and the cap 3.

As mentioned above, in the ceramic capacitor of the present invention, the electrode and the cap placed on the end of the ceramic body are coated with a common plating film, so that electrical contact between the two is maintained by the plating film. This ensures that the cap is firmly fixed to the ceramic body. Therefore, not only can the above-mentioned flow process be omitted from the manufacturing process, but also the plating process to prevent electrode migration, which was indispensable in the past, and the cap to improve soldering properties with printed circuit boards. Since the formation of plating on the surface can also be omitted, manufacturing efficiency is greatly improved, and there is no possibility of deterioration of characteristics due to heat shock during reflow. In addition, even in the case of cylindrical ceramic capacitors, when the outer resin coating is heated and hardened, the common plating film acts as a sealing hole and prevents the expansion of the enclosed air from being released, so vent holes are formed in the coating. Therefore, migration of the electrodes due to the intrusion of moist outside air is also prevented. Furthermore, since the plating film of the ceramic capacitor of the present invention is visible from the outside, it is possible to judge by looking at the plating film how well the cap is held against the ceramic body and whether the electrical contact between the electrode and the cap is good or bad. There is also.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing a ceramic capacitor using a cylindrical ceramic body according to an embodiment of the present invention, and Fig. 2 is a sectional view showing a ceramic capacitor using the same cylindrical ceramic body. FIG. 3 is a cross-sectional view showing a conventional ceramic capacitor. ■... Ceramic body, 2... Electrode, 3... Metal cap, 5... Plating film.

Claims (1)

[Claims] (1) A ceramic capacitor characterized in that a metal cap is placed over the end of a ceramic body having an electrode on its surface, and the metal cap and the electrode are coated with a common plating film.