JPH0653047A - Noise filter - Google Patents

Abstract

PURPOSE:To enable the compact and integrated surface package to be made feasible with high precision capable of absorbing high-frequency noise having L and C (inductance and capacitance) as distribution constants. CONSTITUTION:The noise filter is composed of a laminated body comprising dielectric sheets 10 and 20 in square shape while the dielectric sheet 10 is provided with zigzag conductors 11 and 12 connected to a pair of sides insulated from another pair of sides as well as an inner conductor 15 arranged between both conductors 11 and 12 electrically connected to these conductors 11 and 12 but likewise insulated from another pair of sides. The other dielectric sheet 20 is provided with a grounding conductor 25 insulated from the sides corresponding to the pair of sides connected to the zigzag conductors 11, 12 but connected to the other pair of sides. The zigzag conductors 11, 12 are composed to be the inductance component to high-frequency noise so that capacitances may be formed respectively between the zigzag conductors 11, 12 as well as inner conductor 15 and the grounding conductor 25 through the intermediary of the dielectric sheet 20. Furthermore, a pair of signal electrodes 51, 52 connecting to the zigzag conductors 11, 12 as well as a grounding electrode connecting to the grounding conductor 25 are to be formed on the side of the laminated body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise filter suitable for absorbing high frequency noise in a signal line.
More specifically, it relates to a noise filter that combines a distributed constant type circuit and a capacitor section.

[0002]

2. Description of the Related Art In digital equipment such as a computer, there is a problem that if high-frequency noise is mixed in, malfunctions are likely to occur, and that unnecessary electromagnetic waves that may damage other electronic equipment are emitted from the wiring. Therefore, a noise filter that removes high frequency noise is used in the signal line. An LC filter is used as the noise filter. The electronic components of this LC filter are provided for each signal line, and an LC filter in which a capacitor element and an inductor element are combined is used.

As an LC filter in which a capacitor element and an inductor element are combined, a three-terminal type capacitor 5 as shown in FIG. 6 is used. This three-terminal type capacitor 5 has electrodes 1 on both sides of a disk-shaped dielectric 6.
(The opposite side is not shown) is formed so that a capacitance is formed between both electrodes. The electrode 1 is electrically connected to a U-shaped lead wire 2 and further connected to an external electrode via a ferrite bead 4. Further, a lead wire 3 for grounding is connected to an electrode (not shown). An equivalent circuit of the three-terminal type capacitor 5 is shown in FIG. Other than this, there is an LC filter made by combining a chip component such as a chip capacitor and an inductor element.

[0004]

In a conventional LC filter such as a three-terminal type capacitor, lead wires and ferrite beads protrude from the dielectric, so that it is difficult to mount it on a substrate at high density, resulting in a small device. Cannot be transformed. Therefore, there has been a demand for the development of an LC filter that is compatible with the surface mounting technique and does not require a large component space. Further, the conventional LC filter made by combining the capacitor element and the inductor element has a problem that high-frequency noise cannot be removed due to resonance due to the residual inductance on the ground side of the capacitor element as the signal frequency becomes faster. It was

An object of the present invention is to provide a noise filter which can remove high frequency noise and does not require a wide space for components when it is surface-mounted on a substrate.

[0006]

The structure of the present invention for achieving the above object will be described with reference to FIGS. 1 and 3, the ceramic sheet portion is shown in an enlarged manner in the thickness direction for ease of explanation. The noise filter of the present invention includes a laminated body 40 in which a rectangular first dielectric sheet 10 and a second dielectric sheet 20 having the same shape and size as the sheet 10 are laminated and integrated. The first dielectric sheet 10 is formed in a meandering shape having intervals 13 and 14 electrically connected to a pair of sides and electrically insulated from a pair of sides different from the pair of sides. And second meandering conductors 11, 12 and first and second meandering conductors 11, 12
An inner conductor 15 disposed between the first and second meandering conductors and electrically connected to each of the first and second meandering conductors and electrically insulated from another pair of sides. Prepare In addition, the second dielectric sheet 2
0 is the first and second meandering conductors 1 of the first dielectric sheet 10.
A ground having a pair of sides 23 and 24 electrically insulated from a pair of sides corresponding to a pair of sides to which 1 and 12 are electrically connected, and electrically connected to another pair of sides. The conductor 25 is provided on the sheet surface. Further, the first and second meandering conductors 11 and 12 of the first dielectric sheet 10 are configured so as to be an inductance component with respect to high frequency noise, and the first meandering conductor 1 is interposed via the second dielectric sheet 20.
1, the second meandering conductor 12, the inner conductor 15 and the ground conductor 2
5 and 5 respectively to form a capacitance. Further, first and second signal electrodes 51 and 52 respectively connected to the first and second meandering conductors 11 and 12 exposed on the side surface of the stacked body 40 are formed on this side surface, and on the other side surface of the stacked body 40. Grounding electrodes 53 and 54 respectively connected to the exposed ground conductor 25 are formed on the side surfaces. The equivalent circuit of the noise filter of the present invention can be represented as shown in FIG.

[0007]

[Function] First dielectric sheet 10 and second dielectric sheet 20
The first and second meandering conductors 11 and 12 between and function as inductors when a high frequency signal flows. This is because the first and second meandering conductors 11 and 12 meander and thus have a long conductor distance. The first dielectric sheet 11, the second meandering conductor 12, the inner conductor 15 and the second dielectric sheet 2 on the first dielectric sheet 10 via the second dielectric sheet 20.
Since a capacitance is formed between the ground conductor 25 and the ground conductor 25 above 0, a potential difference occurs between the ground conductor 25 and the meandering conductors 11 and 12 and the ground conductor 25 which are in the energized state, functioning as a capacitor and absorbing high frequency noise. To be done.

[0008]

EXAMPLES Examples of the present invention will be described below. The invention is not limited to this embodiment. The noise filter of the embodiment will be described with reference to FIGS. First, the thickness is about 3
Three 0 μm dielectric green sheets were prepared. This dielectric green sheet is formed by coating the upper surface of a polyester base sheet with, for example, a barium titanate-based dielectric slurry having JIS-R characteristics by a doctor blade method and then drying. One each was used as the first ceramic green sheet, the second ceramic green sheet, and the third ceramic green sheet.

Then, a conductive paste containing Pd as a main component was screen-printed on each surface of the first ceramic green sheet and the second ceramic green sheet in different patterns, and dried at 80 ° C. for 4 minutes. That is, as shown in FIG. 2, the first ceramic green sheet 10 is provided with spaces 13 and 14 electrically connected to a pair of sides and electrically insulated from a pair of sides different from the pair of sides. The meandering first and second meandering conductors 11, 1 having
2 and the first and second meandering conductors 11 and 12 are electrically connected to the first and second meandering conductors and electrically insulated from the other pair of sides. , 14 are printed on.
In addition, the second ceramic green sheet 20 is electrically insulated from a pair of sides corresponding to a pair of sides to which the first and second meandering conductors 11 and 12 of the first dielectric sheet 10 are electrically connected. A grounding conductor 25 is formed by printing, which has a gap 23, 24 and is electrically connected to another pair of sides.

Two sheets of the screen-printed first and second ceramic green sheets 10 and 20 are laminated in this order, and a third ceramic green sheet 30 on which no conductive paste is printed is superposed on the uppermost layer. I matched it. Each of these green sheets becomes the dielectric sheet of the present invention. The laminated body 40 shown in FIG. 3 was thermocompression-bonded and integrated, and then sintered at 1300 ° C. for about 1 hour to obtain a sintered body. As shown in FIG. 3, the sintered body is barrel-polished to form a first meandering conductor 11 and a second meandering conductor 12 on the peripheral side surfaces of the sintered body.
(Not shown in FIG. 3) and the ground conductor 25 were exposed.

Next, as shown in FIG. 4, a conductive paste containing Ag as a main component is applied to the exposed portions of the meandering conductors 11 and 12 and the ground conductor 25 on the peripheral side surface of the sintered body,
By baking, the signal electrodes 51 and 52 and the ground electrodes 53 and 54 were formed, respectively. This electrically connects the first meandering conductor 11 to the first signal electrode 51, the second meandering conductor 12 to the second signal electrode 52, and the grounding conductor 23 to the first and second grounding electrodes 53 and 54, respectively. A noise filter connected to was obtained.

In order to investigate the characteristics of this noise filter, this noise filter was mounted on a separately prepared conductor wiring board by using solder. The signal electrodes 51 and 52 are soldered to the signal line. Also, the grounding electrodes 53, 5
4 is grounded via an external line.

In this state, a high frequency signal was input from one end of the signal line and the output signal was measured at the other end to obtain the insertion loss. As a result, it was found that the insertion loss sharply increased as the frequency increased, and this noise filter had good filter characteristics.

Although the first and second ceramic green sheets are laminated one by one in the embodiment, the number of laminated first and second ceramic green sheets of the present invention is not limited to this. . By appropriately increasing the number of layers, the capacitance formed by the inner conductor and the ground conductor and the inductance formed by the meandering conductor can be changed to change the insertion loss. For example, the total number of layers of the first ceramic green sheet and the second ceramic green sheet may be odd, or a plurality of the same sheets may be continuously laminated to adjust the inductance and the capacitance or to adjust the allowable current amount. May be. Further, by changing the shape such as the width or the curvature of each of the meandering conductors of the meandering conductor, the inductance can be changed and the insertion loss can be changed. Also, by changing the area of the electrode surface of the internal conductor, the allowable current value can be changed without damaging the noise filter or the like. Further, although the example in which the uppermost third dielectric sheet is one is shown, a plurality of sheets may be laminated. When another protective means is provided on the second dielectric sheet,
The third dielectric sheet need not be laminated. Further, the two electrodes 53 and 54 are separately provided as grounding electrodes on the side surface of the laminated body, but either one may be provided.

[0015]

As described above, according to the present invention, the inner conductor is arranged between the meandering conductor of the first dielectric sheet and the ground conductor of the second dielectric sheet used for signal transmission. By doing so, the inductance component and the capacitance component are uniformly distributed around the meandering conductor, and the capacitance and the inductance can be distributedly distributed as a whole. Further, the first and second meandering conductors having an inductance component are arranged with the inner conductor interposed therebetween,
Since a capacitance is formed between the inner conductor and the ground conductor, a noise filter is obtained which is a composite of a distributed constant type circuit having an inductance component before and after the distributed constant type capacitance component of the central portion and a capacitor portion as a whole. . Furthermore, because the residual inductance on the ground side can be reduced, self-resonance can be suppressed. Compared to the conventional noise filter consisting of L and C, it has excellent high-frequency noise absorption performance, enabling compact and integrated surface mounting. Noise filter can be obtained.

[Brief description of drawings]

1 is a noise filter of an embodiment of the present invention AA of FIG.
FIG.

FIG. 2 is a perspective view of the laminated body before being laminated.

FIG. 3 is a perspective view of a sintered body obtained by firing the laminated body.

FIG. 4 is a perspective view of a noise filter manufactured by providing external electrodes around the sintered body.

FIG. 5 is an equivalent circuit diagram of the noise filter of the present invention.

FIG. 6 is a configuration diagram of a conventional LC filter.

FIG. 7 is an equivalent circuit diagram thereof.

[Explanation of symbols]

10 First Dielectric Sheet (First Ceramic Green Sheet) 11 First Meandering Conductor 12 Second Meandering Conductor 13, 14 Electrically Insulated Space 15 Inner Conductor 20 Second Dielectric Sheet (Second Ceramic Green Sheet) 23 , 24 electrically insulated spacing 25 ground conductor 30 third dielectric sheet (third ceramic green sheet) 40 laminated body 51 first signal electrode 52 second signal electrode 53 first ground electrode 54 second ground Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Masuda 2270 Yokose, Yokose-cho, Chichibu-gun, Saitama Sanryo Materials Co., Ltd. Ceramics Laboratory

Claims (2)

[Claims] 1. A laminated body (40) in which a rectangular first dielectric sheet (10) and a second dielectric sheet (20) having the same shape and size as the sheet (10) are laminated and integrated. The first dielectric sheet (10) includes a space (13, 14) electrically connected to a pair of sides and electrically insulated from a pair of sides different from the pair of sides. The first and second meandering conductors (11, 12) which are formed in a meandering shape and are arranged between the first and second meandering conductors (11, 12).
Intervals (13, 12) electrically connected to the meandering conductors (11, 12) and electrically insulated from the other pair of sides, respectively.
An inner conductor (15) having an inner conductor (15) on the surface of the sheet, and the second dielectric sheet (20) is the first dielectric sheet (1).
The first and second meandering conductors (11, 12) of (0) have a space (23, 24) electrically insulated from a pair of sides corresponding to a pair of sides electrically connected to each other, and separate A ground conductor (25) electrically connected to the pair of sides of the first dielectric sheet (10), and the first and second meandering conductors (11,
12) is configured to serve as an inductance component with respect to high frequency noise, and includes the first meandering conductor (1) through the second dielectric sheet (20).
1), the second meandering conductor (12), and the internal conductor (15) and the grounding conductor (25) are respectively configured to form a capacitance, and are exposed on the side surface of the laminate (40). The first and second signal electrodes (51, 52) respectively connected to the first and second meandering conductors (11, 12) are formed on this side surface, and are exposed on another side surface of the laminate (40). Grounding conductor (25)
A noise filter characterized in that grounding electrodes (53, 54) respectively connected to are formed on this side surface. 2. The noise filter according to claim 1, wherein the third dielectric sheet (30) having no conductor formed on the sheet surface is laminated on the uppermost layer of the laminate (40) to be integrated.