JPH08213867A - Composite noise filter - Google Patents

Abstract

PURPOSE: To obtain a cut-off effect stable in terms of the structure by conducting high density mount of a complicated and subminiature circuit in the composite noise filter. CONSTITUTION: A conductor 2 is provided in a ferrite core 1. The ferrite core 1 and the conductor 2 are formed integrally and configured closely through sintering. A chip capacitor 3 is mounted to a recessed part or a throughhole of the ferrite core 1 and extended in parallel with the conductor 2. An electrode is formed to the end of the ferrite core 1 according to an equivalent circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite type noise filter in which an inductor and a capacitor are combined.

[0002]

2. Description of the Related Art As a means for absorbing electromagnetic interference noise in electronic equipment, there is a method of incorporating a composite noise filter formed by a combination of capacitors connected from the middle of two or more inductors to the ground side on a circuit board. Has been formed by inserting a ferrite bead core into the terminals on both ends of the capacitor, or by mounting the ferrite bead core and the capacitor on the lead terminal electrode.

However, in this case, the ferrite core must be inserted into the lead terminal, and in recent years when surface mounting is required, miniaturization is extremely difficult.

Therefore, various chip-type structures capable of surface mounting have been tried. For example, two through holes are provided at both ends of a U-shaped ferrite molded body, and a conductor formed by plating in the through holes, or Insert the conductor and fix the conductor with an adhesive, etc., and insert the chip capacitor into the center of the U-shaped ferrite molded body. At one end of this molded body, the chip capacitor and the two conductors are For example, a bonded electrode and an electrode individually formed on the other end (actual opening 1-110513, actual opening 1-1)
33815), as another example, an eyeglass-type one is known, in which grooves are formed at both ends and the center of the ferrite core, and conductors are formed by plating on the grooves at both ends, and the upper surface of the ferrite core is formed. Similarly, a ferrite core having three grooves is butted and fixed by abutting, and then a chip capacitor is loaded into the obtained central hole (Shokai 63-173914).

[0005]

With the above structure, a small composite noise filter has become possible in the current state of high-density mounting, but there are various problems in practical use. For example, when using a U-shaped ferrite molded body, a through hole is drilled in the ferrite molded body, a conductor is inserted into this through hole, the capacitor is fixed with an adhesive, then the capacitor is inserted in the center, and then the capacitor is inserted. Since the electrode and the conductor are connected, the work is complicated, and at the same time, there is concern about the connection reliability. Further, in the eyeglass type, since the ferrite cores of the same shape are butted, there is a problem in the blocking effect at the butted surfaces. That is, it is difficult to obtain a complete magnetic circuit around the inductor, and the blocking effect deteriorates.

Further, in a composite type noise filter in which a capacitor and an inductor are combined, there is a frequency band peculiar to the capacitor, and the frequency band of the inductor is also affected by it. In this case, in the through hole of the ferrite core, The frequency band of the inductor slightly changes depending on the position of the conductor. Therefore, it is desirable that the position of the conductor in the through hole be at a constant position as much as possible so that variation does not occur among products in response to a request for high attenuation in a specific frequency range according to the capacitor. Since the conventional one fixes the conductor with an adhesive, it is difficult to avoid position variation, and the frequency characteristic shifts, making it difficult to obtain a noise filter that has a stable blocking effect with little variation between products in a composite filter. It will be.

Further, the structure in which the inner surface of the through hole is plated to form a conductor cannot be thickened by the conductive layer on the inner surface of the hole, so that there is a problem that it is not suitable for a large current power supply element.

[0008]

DISCLOSURE OF THE INVENTION The present invention is a composite noise filter of a capacitor and an inductor which solves the above problems, and has a structure in which a chip capacitor and a conductor are extended in parallel from end face to end face on a ferrite core. At the same time, the ferrite core and the conductor are integrally molded, and the structure is brought into close contact by sintering, thereby providing a chip-shaped composite noise filter having stable performance.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a composite noise filter according to an embodiment of the present invention, FIG. 2 is a sectional view of the same, and FIG. 3 is an equivalent circuit thereof. 1 and 2, reference numeral 1 is a ferrite core having a through hole in the center, and 2 is a conductor, which is integrally molded with the ferrite core 1 and fixed by sintering. A rectangular chip capacitor 3 is loaded in the through hole of the ferrite core 1, one end of the ferrite core 1 is an electrode 4 to which the chip capacitor 3 and the conductor 2 are joined according to an equivalent circuit, and the other end is an electrode 4 individually. Are formed.

In this structure, since the portion where the chip capacitor 3 is loaded is a through hole, the overall strength of the ferrite core 1 is improved, and at the same time, the chip capacitor 3 can be securely fixed and protected. Further, it is characterized in that the effect of blocking the chip capacitor 3 from the outside is improved. Further, it has an excellent feature that a complete magnetic circuit is formed in the inductor itself.

The ferrite core 1 may be made of any material, for example, manganese-zinc type, nickel-copper-zinc type, nickel-zinc type, or copper-zinc type, manganese-type.
Examples include nickel-based ferrites. Here, it is particularly preferable that the amount of copper or copper compound in the ferrite is small, and 5 mol% or less of the total ferrite amount is preferable. That is, when the content is 5 mol% or more, copper or a copper compound diffuses in the conductor fixed by sintering, which increases the resistance value of the conductor, which is not preferable.

As the conductor 2 in the ferrite core 1, the material thereof is silver, silver-palladium, palladium, platinum,
Examples include copper. Especially when platinum is used, the effect of the present invention becomes remarkable. Further, as the shape of the conductor, a linear conductor is typically mentioned, but it is arbitrary such as a sawtooth shape, a rectangular shape, and a spring shape, and can be variously selected according to the type of noise to be cut off.

Examples of the method for integrally molding the ferrite core 1 and the conductor 2 of the present invention include press molding, extrusion molding, injection molding, and casting molding. Ferrite having a through hole in the center while containing the conductor 2. Integrated with core 1,
After firing, the chip capacitor 3 is loaded and adhered in the through hole of the ferrite core 1 and electrodes are provided at both ends to form a composite noise filter.

FIG. 4 is another embodiment of the present invention, and is a perspective view of a composite noise filter in which four conductors 2 and one chip capacitor 3 are loaded in a ferrite core 11, and FIG. 5 is an equivalent circuit thereof. Is. Here, the number of through holes for loading the chip capacitors is one in FIGS. 1 and 4, but it may be two or more, and the number of conductors is arbitrary, and the filter characteristics can be changed by further increasing the number. At the same time, the noise filter of a more complicated circuit can be easily miniaturized. In the structure of FIG. 4, the positions of the four conductors 2 are completely arbitrary and can be appropriately determined so that the electrodes on both ends of the ferrite core 11 can be easily arranged.

Further, as shown in FIG. 6, the chip capacitor 3 may be loaded into the two through holes of the ferrite core 21, and the three conductors 2 closely fixed in the ferrite core 21 may be provided. FIG. 7 is an equivalent circuit thereof.

Although electrodes on both ends of the ferrite core are not shown in FIGS. 4 and 6, they are provided on one end of the chip capacitor, one end of the conductor and the end of the ferrite core according to the equivalent circuits of FIGS. 5 and 7. Connect to the electrodes. Here, the equivalent circuit of the composite type noise filter of FIG. 4 is shown in FIG. 5, but an equivalent circuit as shown in FIG. 3 can be obtained by changing the connection of the electrodes, and this is the same in other embodiments. is there. Therefore, other equivalent circuits are possible depending on the electrode connection method.

FIG. 8 shows another embodiment of the noise filter of the present invention, in which the conductor 2 is integrally molded with the ferrite core 31,
It is fixed by sintering. The rectangular chip capacitor 3 is loaded in the recess of the ferrite core 31, the electrode 4 to which the chip capacitor 3 and the conductor 2 are joined is formed at one end of the ferrite core 31, and the electrode 4 is individually formed at the other end. Has been done. The equivalent circuit is the same as in FIG.

FIG. 9 shows another embodiment of the present invention in which three conductors 2 are closely fixed in a ferrite core 41, and two chip capacitors 3 are loaded in two recesses of the ferrite core 41. The equivalent circuit is the same as in FIG.

FIG. 10 shows another embodiment of the present invention. Between the two ferrite cores 51 to which the conductor 2 is closely fixed,
A chip capacitor 13 is adhered and fixed in a sandwich shape. The equivalent circuit is the same as in FIG.

FIG. 11 shows another embodiment of the present invention, in which two chip capacitors 23 are sandwiched and fixed to the upper and lower surfaces of a ferrite core 61 to which two conductors 2 are closely fixed. FIG. 12 is an equivalent circuit thereof.

[0021]

The composite noise filter of the present invention has various characteristics as follows. 1) Since the ferrite core and the conductor are integrally molded, the work is facilitated and a highly reliable connection can be obtained. In addition, since a plurality of inductors and capacitors can be combined, more complicated circuits can be mounted at high density. 2) It can be sufficiently used as a device for a large-current power supply. 3) The fixing structure of the ferrite core and the conductor is stable in terms of productivity without variation, and the ferrite core and the conductor are in close contact with each other without a gap, so that the cutoff effect as the inductor is surely improved. It has a great feature that the high attenuation amount in a specific frequency range required according to the capacity of the capacitor has little variation among products.

[Brief description of drawings]

FIG. 1 is a perspective view showing a composite type noise filter according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of the composite noise filter shown in FIG.

3 is an equivalent circuit of the composite noise filter shown in FIG.

FIG. 4 is a perspective view showing a composite type noise filter according to another embodiment of the present invention.

5 is an equivalent circuit of the composite noise filter shown in FIG.

FIG. 6 is a perspective view showing a composite type noise filter according to another embodiment of the present invention.

FIG. 7 is an equivalent circuit of the composite noise filter shown in FIG.

FIG. 8 is a perspective view showing a composite type noise filter according to another embodiment of the present invention.

FIG. 9 is a perspective view showing a composite type noise filter according to another embodiment of the present invention.

FIG. 10 is a perspective view showing a composite type noise filter according to another embodiment of the present invention.

FIG. 11 is an equivalent circuit of the composite noise filter shown in FIG.

[Explanation of symbols]

 1 Ferrite Core 2 Conductor 3 Chip Capacitor 4 Electrode 11 Ferrite Core 13 Chip Capacitor 21 Ferrite Core 23 Chip Capacitor 31 Ferrite Core 41 Ferrite Core 51 Ferrite Core 61 Ferrite Core

[Procedure amendment]

[Submission date] January 16, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 12

[Correction method] Added

[Correction content]

FIG. 12 is a circuit diagram showing an equivalent circuit of the composite noise filter of FIG.

Claims (1)

[Claims] 1. A composite noise filter comprising a combination of a capacitor and an inductor in which a capacitor and a conductor are extended in parallel from a ferrite core to a ferrite core, and a conductor formed so as to penetrate the ferrite core is integrally molded with the ferrite core. And a structure in which the conductor is tightly fixed by sintering, and one end of the conductor, one end of the capacitor, and an electrode provided at the end of the ferrite core are connected according to an equivalent circuit.