JPH0824083B2 - Noise filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a noise filter using a semiconductor porcelain material exhibiting voltage non-linearity, and particularly to a noise filter using a composite material containing semiconductor porcelain powder. Regarding filters.

[Conventional technology]

2. Description of the Related Art Microcomputers have been installed in various electric and electronic devices for industrial and consumer use, or have been connected to microcomputers by communication lines. In such a microcomputer-equipped device or a device connected to the microcomputer, various noise absorbing elements are used in order to prevent malfunction of the microcomputer and destruction of the device due to noise.

Conventionally commonly used noise absorbing elements include capacitors, inductances and varistors. The capacitor and the inductance are suitable for absorbing high frequency noise, and the varistor is suitable for absorbing transient noise.

Since each of the noise absorbing elements as described above has its own characteristic, these noise absorbing elements are used in combination in accordance with the frequency band for absorbing various noises and the absorption level.

On the other hand, when it is necessary to absorb noise in the high frequency signal line like the signal line of the microcomputer-equipped device as described above, the noise absorbing element is required to have a small capacitance. Further, in recent years, the signal voltage has become relatively low, about 3 to 5 V, corresponding to the decreasing tendency of the driving voltage of ICs and LSIs.

[Technical problem to be solved by the invention]

Conventionally, a varistor as a noise absorbing element could not be used for high speed signal lines. This is (a)
The voltage used in high-speed signal tines is as low as 3 to 5V, and the varistor voltage is 5 to ensure IC protection.
It is required to be 8V or less, but it was not possible to stably manufacture such low varistor voltage elements, and (b) to reduce the varistor voltage, varistor characteristics sandwiched between electrodes It is necessary to make the layer thin, but when the thickness of the characteristic layer becomes thin, the capacitance becomes large.

On the other hand, a structure in which a noise absorbing element is incorporated in a connector of a device is widely used. A through-cylindrical shape made of ceramics is often used as the noise absorbing element incorporated in the connector. However, since it is made of ceramics, it is fragile, and chips or cracks tend to occur when it is incorporated into a connector.

Therefore, an object of the present invention is to provide a noise filter that has a low varistor voltage that can be used as a noise absorbing element for high-speed signal lines, has a sufficiently low electrostatic capacitance, and is unlikely to cause chips or cracks during handling. It is in.

[Means for solving technical problems]

The noise filter of the present invention is configured by using a plate-shaped molded body formed by molding a mixed material containing a semiconductor ceramic powder exhibiting voltage non-linearity and a synthetic resin. At least one common electrode is formed in the formed body or a main surface of the formed body, and a first external electrode is formed on a side surface of the formed body so as to be electrically connected to the common electrode. . Also, so that the common electrode and the molded body layer are overlapped with each other,
At least one line electrode is arranged so as to intersect with the common electrode, and a second external electrode is formed on the side surface of the molded body so as to be electrically connected to the line electrode.

As the semiconductor porcelain powder exhibiting voltage non-linearity in the present invention, various semiconductor porcelain powders mainly composed of semiconductor porcelain powder such as ZnO, SrTiO ₃ or SiC and conventionally used as varistor materials are used.

The synthetic resin mixed with the semiconductor porcelain powder,
Various thermosetting resins such as epoxy resin, fluorine-based resin or rubber-based resin such as silicon resin, or a mixture of these resins with glass filler or carbon filler may be used. As a molded body formed by molding a mixed material of the above materials, for example, a product molded by various molding methods such as heat molding at a temperature of 150 ° C. or sheet molding can be used.

[Action]

By increasing the grain size of the semiconductor porcelain powder in the compact, the varistor voltage can be reduced without reducing the thickness of the compact layer between the common electrode and the line electrode.

Further, since the synthetic resin is included and the common electrode and the line electrode are crossed and the overlapping area is reduced, the capacitance is reduced.

Further, since the synthetic resin is mixed, impact resistance is enhanced.

[Explanation of Example]

 Examples of the present invention will be described below.

Preparation of semiconductor porcelain powder As semiconductor porcelain powder, the following three types of powder were prepared: ZnO-based powder, SrTiO ₃ -based powder, and SiC-based powder.

[ZnO-based powder]

ZnO, CoCO ₃ , MnCO ₃ , so as to contain ZnO 98.3 mol%, Co ₂ O ₃ 0.5 mol%, MnO 0.5 mol%, Sb ₂ O ₃ 0.2 mol% and Bi ₂ O ₃ 0.5 mol%. Sb ₂ O ₃ and Bi ₂ O ₃ were weighed and wet mixed by a ball mill. The slurry obtained by mixing was dried and passed through a 50 mesh sieve.

The sifted raw material powder was fired in air at a temperature of 1200 ° C. for 5 hours. Further, the calcined raw material was crushed by a ball mill, dried, and then classified so as to have a particle size in the range of 10 μm to 20 μm, to prepare a ZnO-based powder as a semiconductor ceramic powder.

So that [SrTiO ₃ system powder] _{Sr 0.80 Ca 0.20 Y 0.005 Ti 1.0} O 3, SrCO 3, Ca
CO ₃ , Y ₂ O ₃ and TiO ₂ were weighed and wet mixed with a ball mill. The resulting mixed slurry was dried and passed through a 50 mesh screen. The sifted raw material powder in air,
Baking was performed at a temperature of 1200 ° C. for 2 hours, and further, baking was performed at a temperature of 1400 ° C. for 3 hours in an N ₂ + H ₂ atmosphere. The calcined raw material is crushed with a ball mill and dried, and then the particle size is 10 μm to 20 μm.
SrTiO ₃ -based powder was prepared by classifying so as to have a particle size of μm.

[SiC powder]

Commercially available SiC powder (passed through 100 mesh) was pulverized with a jet mill and classified to prepare 10 to 20 μm SiC-based powder.

Preparation of noise filter To 95% by weight of the above-mentioned three types of semiconductor porcelain powder, 5% by weight of epoxy resin and 20% by weight of ethyl alcohol were added to form a slurry, and a sheet with a thickness of 100 μm was formed by the doctor blade method. Prepared and dried.

After drying, a plurality of sheets are prepared, and the line electrodes 1a to 1d, the common electrode 2 and the line electrodes 3a to 3 shown in the perspective view in FIG.
d was formed by sputtering Ni on one main surface of the sheets 4 to 6. In addition, each line electrode 1a ~ 1d, 3a
In order to clarify the positional relationship between ~ 3d and the common electrode, FIGS. 2 (a) to (c) show plan views of the sheets 4 to 6, respectively.

Next, the sheets 7 and 8 are laminated on the upper and lower surfaces of the sheets 4 to 6, and a pressure of 5 ton / cm ² is applied in the thickness direction, at 150 ° C.
Molded by heating at the temperature of 15 minutes. The obtained molded body 9 is shown in a perspective view in FIG. Further, as shown in FIG. 4, external electrodes 11a to 11h, 12a to 12h and 13a, 13b were formed on the molded body 9. These external electrodes were formed by applying Ag conductive paste and heat-treating at a temperature of 150 ° C. for 1 hour.

As a comparative example, a noise filter having the same size and the same electrode structure as the noise filter of the example was produced by using a ZnO-based semiconductor ceramic instead of the molded body of the example. Used in this comparative example
ZnO-based semiconductor porcelain contains Bi, Mn, Co and Sb in addition to ZnO.
Etc. have been added.

Characteristics of Examples and Comparative Examples The characteristics of the noise filters of the three types of examples produced as described above and the noise filter of the comparative example are shown in the following first example.
Shown in the table.

In Table 1, V _1mA indicates the varistor voltage when a current of _1mA is applied, and V _P indicates the maximum output voltage when a rectangular voltage wave of 2kV, 50n seconds is applied. In addition, the drop test was performed by freely dropping each noise filter from a height of 2 m onto a concrete floor to check for any abnormality.

As is clear from Table 1, in any of the examples using the semiconductor porcelain powder of any one of ZnO-based powder, SrTiO ₃ -based powder and SiO-based powder, the varistor voltage and static voltage were higher than those of the noise filter of the comparative example. It can be seen that the capacitance can be reduced. Further, in the examples, since the molded body in which the resin is mixed is used, the bending strength is considerably higher than that of the noise filter of the comparative example, and it is understood that no abnormality occurs in the drop test.

〔The invention's effect〕

According to the present invention, since the synthetic resin is mixed in the molded body and the line electrode and the common electrode are arranged so as to intersect with each other, the electrostatic capacitance and the varistor voltage can be effectively reduced. it can. Therefore, since a noise filter consisting of a varistor can be used for a noise filter element for a signal line, which has been considered difficult to use a varistor in the past, it is possible to effectively absorb transient noise in the signal line. Is possible.

Furthermore, in the present invention, since a molded body made of a mixed material containing a semiconductor porcelain powder and a synthetic resin is used, impact resistance is also enhanced, and accidents such as chipping and cracks during handling of the noise filter are effectively performed. Can be prevented.

[Brief description of drawings]

FIG. 1 is an exploded perspective view for explaining a sheet prepared in an embodiment of the present invention and an electrode shape formed on a main surface of the sheet, and FIGS. 2A to 2C are line electrodes and common electrodes. 3 is a perspective view showing a molded body, and FIG. 4 is a perspective view showing a state in which internal electrodes are applied to the molded body. In the figure, 1a to 1d, 3a to 3d are line electrodes, 2 is a common electrode, 9 is a molded body, and 11a to 11h, 12a to 12h, 13a and 13b are external electrodes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Yukawa 2-26-10 Tenjin Tenjin, Nagaokakyo-shi, Kyoto Stock Company Murata Manufacturing Co., Ltd. (72) Inventor Yukio Sakabe 2-26-10 Tenjin, Nagaokakyo, Kyoto Stock Company Murata Manufacturing Co., Ltd. (56) Reference Japanese Patent Laid-Open No. 53-44899 (JP, A) Actual Development 61-203503 (JP, U)

Claims (1)

[Claims] 1. A plate-shaped molded body formed by molding a mixed material containing a semiconductor porcelain powder showing voltage non-linearity and a synthetic resin, and at least one common body formed in the molded body or on the main surface of the molded body. An electrode, a first external electrode electrically connected to the common electrode, and formed on a side surface of the molded body, and intersecting the common electrode so as to overlap with the common electrode via a molded body layer. And a second external electrode that is electrically connected to the line electrode and is formed on a side surface of the molded body. filter.