JPH0131287B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylindrical capacitor suitable for use in various filters such as a π-type filter.

Conventionally, various circuits that combine inductance and capacitance have been used as low-pass filters for high-frequency noise removal, or so-called EMI filters.Among these, the circuit shown in Figure 1 is called a π-type filter and is widely used. There is.

FIG. 2 is a longitudinal sectional view of a conventional π-type filter.

This filter 1 includes a capacitor C. This capacitor C includes a cylindrical dielectric 2, two internal electrodes 3a and 3b drawn out to opposing end faces 2a and 2b of the dielectric 2, and internal electrodes 3a and 3a drawn out to both end faces 2a and 2b. , 3b, and a center electrode 4 forming a capacitor corresponding to these internal electrodes 3a, 3b. The filter 1 is manufactured as follows. That is, as shown in FIG. 3, after winding the green sheet 5 on which internal electrodes 3a and 3b are printed, it is fired at, for example, 1200 to 1400°C, and further, for example, Ag ,
After applying and drying a conductive paint mainly composed of Ag-Pd or the like, baking is performed at, for example, 800 to 950°C. After press-fitting the outer terminal 6 into the capacitor C made in this way, the stopper 8 is attached to the through conductor 7.
a. Insert the ferrite bead 9, capacitor C, and stopper 8b in this order, and caulk the through conductor 7 to fix these parts. Furthermore, after that, it is immersed in molten solder liquid. In this way, the π-type filter 1 is produced.

By the way, the conventional cylindrical capacitor C applied to the π-type filter 1 as described above has the following drawbacks. That is, (A) only one dielectric layer can be used to form the center electrode 4, and a large capacity cannot be obtained. (B) Furthermore, since the central electrode 4 is applied using a brush, spatula, spray, etc., the dimensional accuracy is poor and the capacitance varies widely. In addition, in order to increase the capacitance, the width of the center electrode 4 must also be increased.
The gap width l between the end face electrodes 5a and 5b becomes smaller. Therefore, there is a high possibility that shoots, migration, etc. will occur due to the conductive paint protruding into the gap portion. (C) Also, when assembling the filter or attaching it to the electronic component mounting plate, so-called Ag cracking occurs where the external electrode diffuses into the solder, which has disadvantages such as poor appearance and a decrease in capacity. It was hot.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a cylindrical capacitor with laminated electrodes, small size, large capacity, and high insertion loss. The present invention
For this purpose, electrodes that mutually form a capacitor are wound in layers and embedded inside the dielectric, the outer edge of one electrode is extended to the end face of the dielectric and brought out to the outside, and the other electrode is The electrodes are drawn out through grooves cut radially inward from the circumferential surface of the dielectric.

Hereinafter, the present invention will be explained in detail based on the embodiments shown in FIGS. 4 to 7.

FIG. 4 is a longitudinal sectional view of a cylindrical capacitor according to the present invention. This cylindrical capacitor 11 includes a dielectric 12 made of ceramic. This dielectric 1
2, there are left and right electrodes 13a, 13b, and a center electrode 14 opposing these and forming a capacitor.
is wrapped and embedded. Left and right electrodes 13a, 1
3b is drawn out to the outside of the dielectric 12 by having its inner edges facing each other while maintaining a predetermined interval, and by extending these edges to both end surfaces 15a and 15b of the dielectric 12. It will be done. End surface electrodes 16a, which communicate with the left and right electrodes 13a, 13b, are provided on both end surfaces 15a, 15b of the dielectric 12, respectively.
16b is applied. Furthermore, in the dielectric 12,
A kerf 17 is formed from the center of the outer circumferential surface radially inward to the innermost layer central electrode 14 over the entire circumference. By filling the kerf 17 with a conductive member 18, each central electrode 14 is drawn out to the outer peripheral surface of the dielectric 12. A narrow annular outer electrode 20 that is electrically connected to the conductive member 18 is formed on the outer peripheral surface of the dielectric 12 . Therefore, this outer peripheral electrode 2
0 and the end face electrodes 16a, 16b are quite far apart.

The cylindrical capacitor 11 configured as described above is manufactured as follows. That is, first, dielectric 1
A belt-shaped green sheet 21 is prepared.
As shown in FIG. 5, on the surface of this green sheet 21, four central electrodes 14 and three pairs of left and right electrodes 13a, 13b are arranged alternately in the direction from the winding start end 21a to the winding end end 21b. Place them side by side. A predetermined interval is left in the left-right direction between the inner edges of the left and right electrodes 13a and 13b, and the outer edge of the left electrode 13a is attached to the left edge 21c of the green sheet 21, and the right edge of the right electrode 13b is attached to the green sheet 21. right edge 2
1d respectively. Furthermore, these electrodes 1
A winding end cover portion 21e in which these electrodes 13a, 13b, 14 are not formed is provided closer to the winding end 21b than 3a, 13b, 14. The length of these electrodes 13a, 13b, 14 in the winding direction
The lengths l ₁ and l ₂ are set so that the green sheet 21 can be wound approximately once in the finished state. Further, the length l ₃ of the winding end cover portion 21e is the length l 3 of the green sheet 21
Make the length so that it can be wound more than one turn when finished. The left and right electrodes 13a, 13b and the center electrode 14 are formed by applying conductive paint made of Ag--Pd, Pt--Pd, etc., which has excellent high temperature stability, by a technique such as silk printing, and drying it. After winding the green sheet 21 in the direction of the arrow with the winding start portion 21a inside, cut grooves 17 are cut radially inward in the center of the circumferential surface until reaching the center electrode 14 of the innermost layer. The dielectric body 12 is fired at 1400°C to obtain the dielectric body 12 in which the center electrode 14 and left and right electrodes 13a and 13b are embedded. Thereafter, this cut groove 17 is filled with a conductive member 18, and both end surfaces 1 of the dielectric 12 are filled with a conductive member 18.
3a, 13b and the center of the outer circumferential surface covering the conductive member 18 and after drying the conductive paint, for example.
The end electrodes 16a, 1 are baked at 800 to 950°C.
6b and the outer peripheral electrode 20 are formed. Thereby, a cylindrical capacitor 11 is obtained. In this example,
Although the grooves 17 were formed before firing, they can of course be formed after firing.

The cylindrical capacitor 11 made in this way is
It is incorporated into a π-type filter in the same manner as the capacitor 1 shown in FIG.

FIG. 6 is a developed perspective view of another green sheet used for manufacturing the cylindrical capacitor 11.

In this example, two green sheets 31a, 31
A green sheet 31b is prepared with left and right electrodes 13a and 13b on one green sheet 31a, and a center electrode 14 is formed on the other green sheet 13b. The lengths of these electrodes 13a, 13b, 14 may be the same or different, but when these green sheets 31a, 31b are wound in layers, these electrodes 13a, 13b are wound in multiple layers. The length must be such that it can be laminated in layers. The inner edges of the left and right electrodes 13a, 13b are arranged at a predetermined interval from each other in the left-right direction, the outer edge of the left electrode 13a is the left edge 13c of the green sheet 31a, and the outer edge of the right electrode 13b is the green sheet 31a. and the right edge 31d of the right side edge 31d. Central electrode 14
The left and right edges of the green sheet 31b are located inside the left and right edges 31e and 31f of the green sheet 31b.
Each electrode 13 of both green sheets 31a, 31b
On the winding end side of a, 13b, and 14, a winding end portion 31g in which no electrode is formed is provided over a length of one or more turns in the winding end state. Then, the other green sheet 31b is overlapped and wound on the surface of one green sheet 31a, and fired. Other manufacturing methods are similar to those shown in the previous embodiment. The cylindrical capacitor made in this manner has essentially the same effects as those of the above embodiment.

FIG. 7 shows the results of applying the cylindrical capacitor 11 to a filter and comparing the filter characteristics with those of a conventional filter. As is clear from the figure, the filter to which this example is applied exhibits better filter characteristics than the conventional product.

As described above, according to the present invention, a cylindrical dielectric is provided, and electrodes forming a capacitor are alternately wound and embedded in layers inside the dielectric, and one electrode is connected to the inner edge of the dielectric. The electrodes face each other at a predetermined distance, and their outer edges extend to the end face of the dielectric body and are drawn out to the outside. By forming a deep kerf and filling this kerf with a conductive material that conducts with the other electrode, the other electrode is drawn out, so even though it is made to the same dimensions as conventional products, Inside, electrodes constituting a capacitor are formed in multiple layers.
Therefore, the cylindrical capacitor can have a large capacity. Furthermore, since the electrodes can be pattern-printed, their dimensions and shapes can be set accurately, and variations in capacitance are almost eliminated. Therefore, variations in characteristics between products are reduced and quality is improved.
Furthermore, since the outer peripheral electrode is not used to obtain capacitance, it can be made much narrower than the central electrode, which is conventionally formed outside. Therefore, the gap width between the outer peripheral electrode and the end face electrodes formed at both ends of the dielectric becomes large, and shorts and migration hardly occur. Moreover, since the electrodes that form the capacitor are all embedded in the dielectric material, it has excellent practical effects such as no Ag cracking and no capacitance change even if it is immersed in solder liquid during filter assembly. is demonstrated.

[Brief explanation of drawings]

Figure 1 is an equivalent circuit of a π-type filter, Figure 2 is a vertical cross-sectional view of a π-type filter using a conventional cylindrical capacitor, and Figure 3 is a green sheet used when manufacturing a conventional cylindrical capacitor. An exploded perspective view of
4 to 6 show examples of the present invention, FIG. 4 is a longitudinal sectional view of a cylindrical filter, and FIG. 5 is an exploded perspective view of a green sheet used for manufacturing the cylindrical filter shown in FIG. 4. 6 is a developed perspective view of another green sheet applied to an embodiment of the present invention, and FIG. 7 is a characteristic diagram of a filter constructed from a cylindrical capacitor of the present invention. 11... Capacitor, 12... Dielectric, 13
a, 13b, 14... electrode, 15a, 15b...
End face, 17... kerf, 18... conductive member.

Claims (1)

[Claims] 1 Equipped with a cylindrical dielectric body, inside this dielectric body, electrodes forming a capacitor are alternately wound and embedded in a layered manner, and one electrode has inner edges facing each other with a predetermined interval maintained, and , the outer edge thereof is extended to the end face of the dielectric body and drawn out to the outside, and a kerf is formed in the dielectric body from the outer circumferential face to the other electrode in the radial direction. A cylindrical capacitor in which the other electrode is drawn out by filling the cut groove with a conductive member that conducts with the other electrode.