JPH0130287B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming external electrodes of a multilayer feedthrough capacitor formed by stacking dielectric sheets provided with electrodes.

Conventionally, in this type of multilayer feedthrough capacitor, in order to form external electrodes, dielectric sheets 2, 2, . A capacitor unit 4 is prepared in which the electrodes 1, 1, . . . are alternately led out on the inner peripheral wall and outer peripheral wall of the laminated body of dielectric sheets, respectively, which are laminated in a columnar shape having through holes 3, and first,
As shown in FIG. 1b, a paste made by kneading silver (Ag) powder with organic varnish is applied or printed concentrically on one end surface of the capacitor unit 4 and dried to form electrode films 5 and 6. do. Below, the first
As shown in Figure c, Figure 1 d and Figure 1 e, the electrode films 7, 8, 9 and 10 are
The capacitor unit 4 is formed with the same method as above and then fired to form an external electrode 11 consisting of the electrode films 6, 8, and 9 and an external electrode 12 consisting of the electrode films 5, 7, and 10. was.

When the external electrodes 11 and 12 are formed as described above, it is necessary to repeat the process of applying and drying the paste four times, which increases the number of man-hours. This increases the cost of multilayer feedthrough capacitors, while also causing problems such as migration and diffusion into the solder (solder bleed phenomenon).

The present invention has been made to solve the above problems, and its purpose is to form a two-layer electrode film on a capacitor unit of a multilayer feedthrough capacitor by electroless plating and electrolytic plating, and to form a two-layer electrode film by electrolytic plating with paint. By etching away the electroless plating film where no film was formed and separating it into two external electrodes, silver paste can be applied and baked using electroless plating and electrolytic plating techniques such as nickel and copper. The objective is to form the external electrodes of a multilayer feedthrough capacitor without using the above method.

Hereinafter, a method of forming an external electrode using the capacitor unit 4 of FIG. 1a will be explained with reference to FIGS. 2a to 2e.

As shown in FIG. 2a, the capacitor unit 4 is immersed in an electroless plating solution of nickel (Ni), copper (Cu), or an alloy thereof to coat its entire outer surface.
Electroless plating layer 21 with a thickness of 0.5 μm to 1.5 μm
form.

Thereafter, paint 22 is applied or printed on the electroless plating layer 21 so as to surround the through hole 3 on both end surfaces of the capacitor unit 4, as shown in FIG. 2b.

The paint 22 is an acid-resistant and water-resistant insulating material made of, for example, epoxy resin or modified vinyl resin.

As mentioned above, the capacitor unit 4 coated or printed with the paint 22 is made of nickel (Ni),
It is immersed in an electrolyte of copper (Cu), gold (Au) or silver (Ag) to a thickness of 0.3μ as shown in Figure 2c.
An electrolytic plating layer 23 having a thickness of m or more is formed.

Next, the capacitor unit 4 on which the electroless plating layer 21, the paint 22, and the electrolytic plating layer 23 have been formed is immersed in a solvent such as trichlorethylene or perchloroethylene, which is a material from which the paint 22 can be easily removed. , as shown in FIG. 2d, the paint 22 is removed.

The capacitor unit 4 from which the paint 22 has been removed in the above step is then immersed in an aqueous solution of ferric chloride or the like, and at least the electroless plating layer 21' not covered by the electrolytic plating layer 23 is etched away. be done. That is, the electroless plating layer 21
Due to the difference in chemical etching or film thickness depending on the type of metal and the electrolytic plating layer 23, as shown in FIG. is removed, and two external electrodes 24 and 25 are formed on the capacitor unit 4, separated by the area where the paint 22 is applied.

Of the external electrodes 24 and 25, the external electrode 24 on the side of the through hole 3 is electrically connected to a through terminal (not shown).

In the multilayer feedthrough capacitor in which the external electrodes 24 and 25 are formed as described above, there is no need to use silver (Ag), so migration of the external electrodes and solder cracking do not occur.

By the way, when a voltage of 100 volts DC was applied to the above multilayer feedthrough capacitor that was not coated with an exterior material in an atmosphere with a humidity of 95% to 98%, it was found that the multilayer capacitors were laminated using the methods shown in Figures 1a to 1e. In the type feedthrough capacitor,
A short-circuit failure occurred after 250 hours, and all samples had short-circuit failures after 2000 hours.
In the multilayer feedthrough capacitor produced by the method shown in FIG.

It goes without saying that in the above embodiment, the capacitor unit 4 is not limited to that shown in FIG. 1a. Furthermore, the materials of the paint, solvent, and electrodes are also completely arbitrary.

As is clear from the above detailed description, the present invention uses electroless plating and electrolytic plating to form external electrodes of multilayer feedthrough capacitors without applying silver paste and baking. By doing so, a large number of products can be processed simultaneously by electroless plating and electrolytic plating, and mass production of multilayer feedthrough capacitors becomes extremely easy.

In addition, since silver (Ag) is not used in the electrode material,
There is no migration phenomenon or diffusion of electrodes into the solder, and problems such as dielectric breakdown or loss of external electrodes can be completely prevented.

[Brief explanation of drawings]

1a, 1b, 1c, 1d, and 1e are explanatory diagrams of a method for forming an external electrode of a conventional multilayer feedthrough capacitor, and FIG. 2a and FIG. FIG. 2b, FIG. 2c, FIG. 2d and FIG. 2e are explanatory diagrams of a method of forming an external electrode of a multilayer feedthrough capacitor according to the present invention, respectively. 1... Electrode, 2... Dielectric sheet, 3... Through hole, 4... Capacitor unit, 21... Electroless plating film, 22... Paint, 23... Electrolytic plating film, 24, 25... External electrode.

Claims (1)

[Claims] 1. A capacitor unit in which dielectric sheets equipped with electrodes are laminated to form a columnar shape having a through hole in the axial center, and the electrodes are alternately led out on the inner peripheral wall and outer peripheral wall of this columnar laminate, respectively. In the external electrode forming method, an electroless plating layer is applied to the entire outer surface of the capacitor unit, and then a water-resistant and acid-resistant paint is applied to both end faces of the capacitor unit so as to surround the through hole. ,
Next, after applying an electrolytic plating layer to the entire surface, the paint is removed, and then the electroless plating layer formed under the paint is removed by etching, and the electroless plating layer formed on the inner circumferential wall of the through hole of the capacitor unit is removed. A method for forming an external electrode of a multilayer feedthrough capacitor, characterized in that a feedthrough terminal is made conductive through a plating layer.