JPH0389613A - Noise filter - Google Patents

Abstract

PURPOSE:To provide a noise filter with the noise absorbing capacity as a capacitive varistor, having reduced electrostatic capacitance, and the noise absorbing capacity as an inductance element, by arranging a magnetic material layer so that it overlaps at least a part of a line electrode which intersects a common electrode with a semiconductor porcelain layer between them. CONSTITUTION:A ferrite paste is applied by the screen printing method to form ferrite paste layers 10a to 10c so that parts, which are placed on the upper face of a semiconductor porcelain 7, of conductive paste layers 9a to 9c for each line electrode are partially covered with this ferrite paste. Thereafter, ferrite paste layers 10a to 10c are baked at 1000 deg.C for 30 minutes by the baking treatment to form the magnetic material layer. Thus, a three-terminal noise filter unit is constituted where an inductance L is combined besides a varistor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise filter constructed using semiconductor porcelain having varistor characteristics, and particularly to a noise filter having a structure in which a varistor is combined with an inductance.

[Conventional technology]

Varistors are generally known as elements that absorb transient noise. However, when using a varistor as a noise filter, attention is focused only on its voltage-current characteristics, and the actual situation is that the capacitance characteristics of the varistor are not effectively utilized.

In the case of ceramic varistors, most of them obtain varistor characteristics through grain boundary barriers, but at voltages below the breakdown voltage at the grain boundaries, they function as capacitors. Therefore, by actively utilizing this capacitor characteristic, it is also possible to absorb noise.

However, the capacitance of ceramic varistors is too large to be used as a noise filter for signal lines, so in reality, ceramic varistors are only used as noise absorbing elements for power supplies or noise filters for low frequency signal lines. It has not been done.

Diodes such as Zener diodes have conventionally been used as noise absorbing elements for signal lines. However, although diodes have high voltage suppression ability,
Since the absorption capacity for surges and the like is small, and the voltage suppression capacity is high, the energy may not be consumed and noise may be generated through the ground wiring or the like. Furthermore, the most commonly used capacitor-inductor composite device cannot absorb transient high-voltage noise.

[Technical Problems to be Solved by the Invention] In order to solve the above-mentioned problems, it is conceivable to use a capacitor-varistor multifunctional element that effectively utilizes the capacitance of the varistor. Furthermore, in order to further enhance the noise absorption effect, it is necessary to consider combining inductor components.

When an inductance is inserted as a series component of the varistor, the steep current flowing through the varistor element can be suppressed by the inductance, and the generation of secondary noise can be prevented. However, on the other hand, it is also expected that the absorption performance of the rising portion of the transient noise will deteriorate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a noise filter in which an inductance is combined with a varistor so as to take advantage of the advantages of inductance as described above, and which can be used for signal lines.

[Means for solving technical problems]

The present invention is a noise filter constructed using semiconductor ceramic having varistor characteristics. In order to extend from the first part to the second part of the side surface of this semiconductor porcelain,
At least one common electrode is formed in or on the semiconductor porcelain. Then, at least one line electrode separated from the common electrode via the semiconductor ceramic layer in the thickness direction of the semiconductor ceramic is arranged from a third part to a fourth part of the side surface of the semiconductor ceramic so as to intersect with the common electrode. It is formed to extend toward the section. The line electrode is formed inside the semiconductor ceramic or on the surface of the semiconductor ceramic.

Further, a magnetic layer is provided so as to overlap at least a portion of at least one of the line electrodes.

[Effect]

Since a magnetic layer is provided to overlap at least a portion of at least one line electrode made of semiconductor porcelain having varistor characteristics, it has noise absorption performance as an inductance in addition to noise absorption performance as a varistor. is given.

Furthermore, since the common electrode and line electrode are arranged to intersect with each other through the semiconductor ceramic layer, the noise absorption performance as a capacitor is achieved by utilizing the dielectric properties of the semiconductor ceramic which has varistor characteristics. is also given.

Therefore, since it has the characteristics of both an LC filter and a varistor, it is possible to absorb a wide variety of noises.

[Explanation of Examples]

Hereinafter, the structure of the noise filter of this embodiment will be clarified by explaining the method for manufacturing the noise filter of the first embodiment of the present invention.

As raw materials, ZnO, BitO, C with a purity of 99% or more
oo, Mn0z and 5bzOs, respectively, 98 mol%, 0.5 mol%, 0.5 mol%, 0.5 mol%, 0.
The mixture was weighed at a ratio of 5 mol % and mixed with pure water in a ball mill for 24 hours to obtain a mixture. Next, the obtained mixture was filtered and dried, and calcined at a temperature of 800° C. for 2 hours to obtain a calcined product.

Furthermore, the obtained calcined product was ground again and dispersed in a solvent together with a sulfuric binder to obtain a slurry.

The obtained slurry was cut into 50μm by doctor blade method.
The bottom was shaped into a raw sheet with a uniform thickness. This raw sheet,
A rectangular shape of a predetermined size was punched out to obtain a plurality of green sheets 1 to 5 shown in FIG.

Furthermore, on the green sheet 2, a conductive paste mainly composed of an alloy of silver and palladium is printed by a screen printing method so as to extend from one edge 2a of the green sheet 2 to the other edge ji2b. A conductive paste layer 6 for electrodes was formed. This common electrode conductive paste layer 6 is baked by firing to be described later to complete the common electrode.

The raw sheets 1 to 5 in Fig. 2 are stacked as shown in the figure, crimped in the thickness direction, cut into a predetermined size, and then
It was baked at a temperature of 00'C for 2 hours.

The fired semiconductor porcelain 7 thus obtained is shown in FIG.

In the semiconductor ceramic 7, the common electrode conductive paste layer described above is baked during firing to form the common electrode 6 in the form of an internal electrode. That is, from the first side surface 7a as the first portion of the semiconductor ceramic 7 to the second side surface 7a as the second portion.
The common electrode 6 is extended to reach the side surface 7b.

Next, as shown in FIG. 4, the first side surface of the semiconductor ceramic 7? A pair of conductive paste layers 8a for terminal electrodes covering a and 7b
, 8b, and line electrode conductive pastes Ji9a to 9C are formed. These terminal electrode conductive paste layers 8a, 8
b and the line electrode conductive paste layers 9a to 9C are formed by applying a conductive paste mainly composed of a silver-palladium alloy to the surface of the semiconductor ceramic 7 by screen printing.

As is clear from Figure 4, the conductive paste for line electrodes j! 9a to 9c are the third portions of the semiconductor ceramic 7 in this embodiment.
It is formed on the upper surface of the semiconductor ceramic 7 so as to connect the side surface 7c and the fourth side surface 7d.

The conductive paste layers 8a and 8b for terminal electrodes and the conductive paste layers 9a to 9c for line electrodes are baked by a baking process to be described later, and are completed as terminal electrodes and line electrodes.

Next, as shown in FIG. 1(a), NiZn ferrite calcined powder is applied so as to cover a part of the upper surface of the semiconductor 1ff17 of each line electrode conductive paste N9a to 9c. A ferrite paste made into a paste by adding an aX binder and a solvent is applied by screen printing to form ferrite paste layers 10a to 1.
Form 0c. After that, at a temperature of 1000°C for 30
Depending on the process, the minute baking is performed on the ferrite paste layer 10a-
10C is baked to form the magnetic layer, and at the same time, the above-described terminal electrode conductive paste layer 8a is formed.

8b and line electrode conductive paste layers 9a to 9C are baked to form terminal electrodes and line electrodes.

Furthermore, as shown in FIG. 5, in order to seal the top surface of the semiconductor porcelain 7, glass paste 11 is applied so as to cover most of the area of the top surface of the semiconductor porcelain 7 that is sandwiched between the terminal electrodes 8a and 8b. The noise filter 12 of this example was obtained by printing and baking at a temperature of 300°C.

In the noise filter 12 configured as described above,
By using both ends of each line electrode 9a to 9C as input/output terminals and connecting the terminal electrodes 8a and 8b connected to the common electrode 6 to ground potential, the noise filter unit shown in FIG. In other words, it can be seen that each noise filter unit constitutes a three-terminal noise filter unit in which an inductance L is combined in addition to a varistor.

In addition, in the above embodiment, as shown in FIG. 1(a),
A magnetic layer 1 is formed on each line so as to cover part of the poles 9a to 9C.
However, as shown in FIG. 6(a), the magnetic layer 10 may be formed to cover most of each line electrode i9a to 9c. In this case, Since each of the line electrodes 9a to 9C is covered with a magnetic layer 10 on both sides of the part where it intersects with the common electrode 6, the equivalent circuit of each noise filter unit is shown in FIG. 6(b).
) as shown.

The glass paste 11 shown in FIG. 5 was baked on the top surface of the noise filter shown in FIG. 6(a) to produce a noise filter of the second example. The noise filter of this second embodiment and the noise filter 1 of the first embodiment described above.
2 characteristics were measured.

The results are shown in Table 1.

(Hereinafter, blank spaces) Table 1 In Table 1, α represents the voltage nonlinear coefficient, and the value represents the rate of change in the varistor voltage when an 8×20μ triangular current wave with a wavefront value of 30A is applied.

In addition, using a commercially available noise simulator, 50 ns, 2
The output waveform when a rectangular voltage pulse of KV is applied is the seventh
In FIG. 7, solid lines P and Q indicate the first and second lines, respectively. The characteristics of the noise filter of the second embodiment are shown,
The broken line R shows the characteristics of a commercially available ZnO disc varistor having a varistor voltage of 22V.

As is clear from FIG. 7, the first. It can be seen that the noise filter of the second example has a great effect in suppressing noise in the rising portion, and exhibits superior noise absorption performance compared to the conventional disk type varistor.

8 to 10 are perspective views for explaining a third embodiment of the present invention.

In this embodiment, as shown in FIG. 8, on the upper surface of the semiconductor ceramic 7, parallel to the internal common electrode 6, but on both sides of the area where the common electrode 6 is provided so as not to overlap with the common electrode 6. The first magnetic layers 13a and 13b are formed on the top. Then, as shown in FIG. 9, the first magnetic body N15a
, 13b, each line electrode 9a to 13b is formed by applying a conductive paste mainly composed of Ag-Pd alloy.
9C is prominent.

Furthermore, as shown in FIG. 10, the line electrodes 9a to
9C, second magnetic layers I4a and 14b are formed above the line electrodes 9a to 9C in the region where the first magnetic layers 13a and 13b are provided, and each line electrode 9a to 9C are the first. Second magnetic layer 1
3a, 13b, 14a, and 14b.

The characteristics of the noise filter of the third example having the structure shown in FIG. 10 were measured using a commercially available simulator. For comparison, 1. from the structure of FIG. A noise filter from which the second magnetic layer was removed was prepared as a comparative example. The measurement time is 50 μsec.

This was done by applying a 2KV rectangular voltage pulse.

The output waveform is shown in FIG.

In FIG. 11, the solid line S shows the characteristics of the third embodiment, and the broken line T shows the characteristics of the comparative example.As is clear from the comparison of the characteristics, the structure of the example is effective in suppressing noise in the rising part. It can be seen that the noise absorption effect is higher than when the inductance component is not connected.

In the above embodiment, only the common electrode 6 in the form of an internal electrode was fired together with the semiconductor ceramic composition, but the conductive paste that constitutes the other electrodes and the ferrite paste that constitutes the magnetic layer may be fired at the same time. However, if all are fired at the same time, it is necessary to consider the shrinkage rate and other factors when choosing materials such as ferrite paste.

Furthermore, in each of the embodiments described above, each line electrode was formed on the upper surface of the semiconductor porcelain 7, and only the upper part of the semiconductor porcelain sandwiched between the internal common electrode 6 was used as a characteristic part. By forming line electrodes on the lower surface side, it is possible to configure more noise filter units.

Further, although the common electrode 6 is configured in the form of an internal electrode, the same effects as in each of the above embodiments can be obtained even if the common electrode 6 is formed on the lower surface of the semiconductor ceramic 7.

Further, each of the line electrodes 9a to 9c may also be configured in the form of an internal electrode within the semiconductor ceramic 7 instead of on the outer surface such as the upper surface or the lower surface of the semiconductor ceramic 7.

However, in that case, it is necessary to provide a magnetic layer within the semiconductor ceramic 7 so as to be in contact with the internal line electrode.

〔Effect of the invention〕

As described above, in the present invention, in a noise filter configured using semiconductor ceramic having varistor characteristics, the noise filter overlaps at least a portion of the line electrode provided to intersect with the common electrode via the semiconductor layer. Because the magnetic layer is arranged in this way, it has both the noise absorption performance of a capacitive varistor with low capacitance and the noise absorption performance of an inductance element, that is, it adds varistor function to the conventional LC type noise filter. A noise filter corresponding to this structure is realized. Therefore, it is possible to obtain a high-performance noise filter that has a wide range of noise absorption performance against various noises, is compact, and can be used in signal lines and the like.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are perspective views and equivalent circuit diagrams showing the main parts of the first embodiment of the present invention, and FIG. 2 is a raw sheet and common electrode used in manufacturing the first embodiment. 3 is a perspective view showing the semiconductor porcelain, FIG. 4 is a perspective view showing the state in which line electrodes and terminal electrodes are formed, and FIG. FIG. 6(a) is a perspective view of the noise filter of the second embodiment of the present invention, FIG. 6(b) is its equivalent circuit diagram, and FIG. 7 is the first embodiment.
．． A diagram showing the characteristics of the second embodiment and the conventional example, FIG. 8 is a perspective view for explaining the first magnetic layer in the third embodiment of the present invention, and FIG. 9 is a diagram showing the characteristics of the first magnetic layer. FIG. 10 is a perspective view of a third embodiment of the present invention, and FIG. 11 is a diagram showing characteristics of the third embodiment and a comparative example. . In the figure, 6 is a common electrode, 7 is semiconductor porcelain, 7a, 7
b is the first. The first as the second part. Second side, 7c
, 7d is the third. Third as the fourth part. The fourth aspect,
9a to 9c are line electrodes, 10.10a, 10b, 13
a, 13b, 14a. 14b indicates a magnetic layer.

Claims (1)

[Scope of Claims] Semiconductor porcelain having varistor characteristics; and at least one wire formed within or on the surface of the semiconductor porcelain so as to extend from a first portion toward a second portion of a side surface of the semiconductor porcelain. a common electrode extending from a third portion toward a fourth portion of the side surface of the semiconductor ceramic so as to intersect the common electrode across the semiconductor ceramic layer in the thickness direction of the semiconductor ceramic; A noise filter comprising: at least one line electrode formed within or on the surface of the semiconductor ceramic; and a magnetic layer provided to overlap at least a portion of the at least one line electrode. .