JPH10270289A - Chip-type lc varistor and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized chip-type LC varistor of high reliability at low cost which has both the characteristic of an LC filter for restraining high frequency noise and characteristic of a varistor for absorbing a surge of static electricity or the like. SOLUTION: A first capacitance obtaining electrode 2 is formed on one main surface A of a varistor porcelain single plate 1. A second capacitance obtaining electrode 4 is formed on the other main surface B. An insulating layer 3, obtained by heat-treating glass paste containing ferrite magnetic powder is formed, covering the first electrode 2. I/O electrodes 5 which are electrically connected with the first electrode 2 are formed in both end portions of the varistor porcelain single plate 1 in the longitudinal direction. An electrode 6 for grounding which is electrically connected with the second electrode 4 is formed on at least the one side surface of the varistor porcelain single plate 1. The device normally acts as an LC filter and functions as a varistor, when a surge infiltrates the filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a chip-type LC varistor having an inductor component and a capacitor component using a ceramic varistor, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, electronic devices have been used in various fields of society, and most of them use digital signals containing many noise components. Therefore, when using these electronic devices, it is necessary to take measures for preventing noise interference. For noise suppression, EMI
(Electro Magnetic Interference) countermeasures (to avoid generating noise) and immunity (Immunity) countermeasures (to prevent equipment from malfunctioning even if there is noise). EMC (Electro Magnetic Compat
) is being actively researched.

In the study of such EMC, an inductor or an LC filter is generally used to suppress high-frequency noise, and a varistor is used to absorb a surge such as static electricity. In electronic devices such as word processors and personal computers, whose demand has been rapidly increasing recently, in addition to high frequency noise mainly caused by harmonics of digital signals,
When inputting data with an input device such as a keyboard, static electricity generated by the human body may cause malfunctions or damage to circuits such as ICs and LSIs of electronic devices, and it is necessary to use both elements of the LC filter and the varistor. It is highly desired to develop a composite element having the characteristics of these elements.

[0004] In addition, as electronic devices have been reduced in size, such noise suppression devices have also been required to be reduced in size, and the composite device meets the demand for downsizing. In order to meet the demand for miniaturization, a laminated composite device has been proposed in Japanese Patent Application Laid-Open No. Hei 4-257110. This composite element is formed by laminating and integrating a laminated chip inductor formed by laminating ferrite sheets on which strip-shaped conductor lines are formed and a laminated chip capacitor formed by laminating varistor sheets formed with counter electrodes. Is formed.

[0005]

Problems to be Solved by the Invention
The composite device proposed in Japanese Patent Application Publication No. 0-205400 integrates an LC filter and a varistor, which conventionally had to be mounted separately, into one.
Since it is composed of three parts, it contributes to the miniaturization of electronic equipment. However, this composite element is manufactured by laminating a magnetic material and a varistor material and then integrally firing them. At the time of firing, the components of the respective materials are mutually diffused. Therefore, even if each element made of a magnetic material alone or a varistor material alone has excellent characteristics, the characteristics are deteriorated by forming a composite element. In addition, when two kinds of materials are laminated and fired, it is necessary to match the shrinkage ratios of the two kinds of materials, and the management in the manufacturing process is performed when manufacturing a single element using each single material. In comparison, difficult condition selection is required. Due to the above-mentioned lamination of different materials and the co-firing of different materials, the composite element proposed in JP-A-4-257110 is
It is difficult to ensure stable characteristics and reliability,
There is a problem that the yield is poor, the manufacturing cost is high, and it is not possible to supply inexpensive products.

The present invention has been made in view of the above circumstances, and can solve the problems of the composite device proposed in Japanese Patent Application Laid-Open No. 4-257110, can be surface-mounted, and can provide an LC filter and a varistor. It is an object of the present invention to provide a small, highly reliable and inexpensive chip-type LC varistor which has both functions of a single component, is inexpensive to manufacture, and has a method of manufacturing the same.

[0007]

A chip-type LC varistor according to claim 1 is a chip-type LC varistor having an inductor component and a capacitor component, wherein a rectangular parallelepiped ceramic varistor and a first main surface of the ceramic varistor are provided. A first capacitance acquisition electrode provided on a first capacitance acquisition electrode, a second capacitance acquisition electrode provided on a second principal surface opposite to the first principal surface, and a part or a part of the first capacitance acquisition electrode. And an insulating layer containing a magnetic powder formed in a manner to cover the whole.

The chip type LC varistor according to claim 2 is
The semiconductor device according to claim 1, further comprising an insulating layer formed so as to cover part or all of the second capacitance acquisition electrode.

According to a third aspect of the present invention, there is provided a chip-type LC varistor.
3. The input / output electrode provided at both ends of the ceramic varistor and electrically connected to the first capacitance obtaining electrode according to claim 1, and the first and second electrodes except both ends of the ceramic varistor. 4. A ground electrode provided on a surface substantially perpendicular to the second main surface and electrically connected to the second capacitance acquisition electrode is further provided.

A chip type LC varistor according to claim 4 is
The ceramic varistor according to any one of claims 1 to 3, wherein the ceramic varistor is a semiconductor porcelain single plate containing strontium titanate as a main component.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a chip-type LC varistor having an inductor component and a capacitor component, wherein the first main surface of the rectangular parallelepiped ceramic varistor is provided. Forming a capacitance acquisition electrode; forming a second capacitance acquisition electrode on a second main surface of the ceramic varistor facing the first main surface; and forming the first capacitance acquisition electrode Forming an insulating layer containing a magnetic substance powder in a mode that covers a part or all of the insulating layer.

In the chip-type LC varistor of the present invention, a capacitance obtaining electrode is formed on the surface of the ceramic varistor, and an insulating layer containing a magnetic powder is formed so as to cover a part or all of the capacitance obtaining electrode. ing. Therefore, the chip-type LC varistor of the present invention has an equivalent circuit as shown in FIG. Conventionally, the insulating layer is formed in order to enhance the reliability of the component. However, not only is the insulating layer mixed with a magnetic powder to improve the reliability, but also the inductor component (L component) is added to the element. You can have. Further, since the ceramic varistor is used as the element body, it normally operates as an LC filter, but functions as a varistor when a surge enters.

According to the present invention, a composite element having both characteristics of an LC filter and a varistor can be manufactured by forming an insulating layer containing a capacitance obtaining electrode and a magnetic substance powder on a ceramic varistor. Unlike the case where the materials are laminated and fired, the material characteristics do not deteriorate. Further, unlike the case where two kinds of materials are used, it is not necessary to consider the matching of the shrinkage ratio, so that the management in the manufacturing process is simplified and the manufacturing cost can be reduced. As described above, according to the present invention, a small, inexpensive and highly reliable chip type is used without using a technique of bonding and co-firing of different materials, which is costly and it is difficult to secure sufficient reliability. An LC varistor can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments.

(First Embodiment) FIG. 1A is a perspective view of a chip type LC varistor (first embodiment) of the present invention, and FIG. 1B is a side view thereof. In the figure, reference numeral 1 denotes a varistor porcelain single plate as a body of a chip type LC varistor. The varistor porcelain veneer 1 is 3.2 m long
m, a width of 1.6 mm, a thickness of about 0.8 mm, and a first main surface A which is an upper surface in FIGS. 1 (a) and 1 (b).
And a second main surface B which is parallel to and opposite to the main surface A.
The varistor porcelain veneer 1 is obtained by firing a ceramic material containing strontium titanate (SrTiO ₃ ) as a main component.

On the main surface A of the varistor porcelain veneer 1, a first capacitance acquisition electrode 2 having a thickness of 5 to 10 μm is provided at a central portion (width 0.4 to 0.8 mm) in the width direction over the entire region in the longitudinal direction.
Are formed. The first capacitance acquisition electrode 2 is made of silver (A
g) The paste is heat-treated. Also, both ends of the varistor porcelain veneer 1 in the longitudinal direction are placed on the first capacitance acquisition electrode 2 and the main surface A of the varistor porcelain veneer 1 on which the first capacitance acquisition electrode 2 is not formed. An insulating layer 3 having a thickness of 30 to 40 μm is formed over the entire region except for
The insulating layer 3 covers most of the area of the first capacitance acquisition electrode 2. The insulating layer 3 is obtained by heat-treating a glass paste containing 5 to 50% by weight of ferrite magnetic powder. On the main surface B of the varistor porcelain veneer 1, a second capacitance acquisition electrode 4 of the same material as the first capacitance acquisition electrode 2 having a thickness of 5 ~ 10μ
m.

Input / output electrodes 5 are formed at both ends of the varistor porcelain veneer 1 in the longitudinal direction.
It is electrically connected to the first capacitance acquisition electrode 2. A grounding electrode 6 is formed on at least one side surface of the varistor porcelain veneer 1 at the center in the longitudinal direction, and the grounding electrode 6 is electrically connected to the second capacitance obtaining electrode 4. Connected.

The chip type L of the present invention having such a configuration
In the C varistor, a first capacitance acquisition electrode 2 and a second capacitance acquisition electrode 4 are formed on both main surfaces A and B of the varistor porcelain veneer 1, and most of the first capacitance acquisition electrode 2 is formed. To cover
By forming the insulating layer 3 containing ferrite magnetic powder,
A chip-type LC varistor having an equivalent circuit as shown in FIG. 2 is obtained, which is a composite element for noise countermeasures that can absorb high-frequency noise and surge such as static electricity. Further, since the configuration is such that the thin-film capacitance acquiring electrode, the insulating layer, and the like are formed on the varistor porcelain single plate 1 having the dimensions described above, a sufficient miniaturization can be realized.

Next, a method of manufacturing such a chip type LC varistor of the present invention will be described. First, the varistor porcelain veneer 1 is manufactured in the following procedure. A raw material for semiconductor porcelain containing strontium titanate as a main component is press-formed or sheet-formed to obtain a single-plate shaped body. After debinding the single-plate shaped body in the air, the compact is placed in a reducing atmosphere.
Sintering is performed at 00 to 1500 ° C. to obtain a semiconductor porcelain veneer.
A diffusing agent containing, for example, sodium carbonate (Na ₂ CO ₃ ) as a main component is applied to one surface of the obtained semiconductor porcelain veneer, and a heat treatment is performed at 900 to 1100 ° C. in the atmosphere for grain boundary insulation. The varistor porcelain single plate 1 of the grain boundary insulation type is obtained.

Next, the silver paste is applied to both main surfaces A and B of the varistor porcelain veneer 1 manufactured as described above, and the main surface A covers the central portion in the width direction of the varistor porcelain veneer 1 in the entire longitudinal direction. In the embodiment, on the main surface B, the coating is applied to the central portion in the longitudinal direction of the varistor porcelain veneer 1 in the entire width direction and then heat-treated at 600 to 800 ° C. in the air to obtain the first capacity. Electrode 2 and the second capacitance acquisition electrode 4 are formed.
FIG. 3 is a perspective view showing a state after the first capacitance acquisition electrode 2 and the second capacitance acquisition electrode 4 are formed. FIG. FIG. 3B shows a state in which the acquisition electrode 2 is formed, and FIG. 3B shows a state in which the second capacitance acquisition electrode 4 is formed on the main surface B.

Next, ferrite magnetic powder is applied on the main surface A of the varistor porcelain veneer 1 so as to cover most of the area of the first capacitance acquisition electrode 2 over the entire area except for both ends in the longitudinal direction. Apply a glass paste containing ~ 50% by weight,
Heat treatment is performed at 600 to 800 ° C. in the air to form an insulating layer 3.
To form FIG. 4 is a top view showing a state after the insulating layer 3 is formed.

Finally, input / output electrodes 5 are formed on both ends of the varistor porcelain veneer 1 in the longitudinal direction in such a manner as to be electrically connected to the first capacitance acquisition electrodes 2. A grounding electrode 6 is formed at a central portion in the longitudinal direction of at least one side surface of the first electrode 1 so as to be electrically connected to the second capacitance acquiring electrode 4, and heat treatment is performed in the air at 600 to 800 mm.
C. to produce a chip-type LC varistor having the configuration shown in FIG.

(Second Embodiment) FIG. 5 is a side view of a chip type LC varistor (second embodiment) of the present invention. In the second embodiment, in addition to the configuration of the above-described first embodiment, an insulating layer is formed on the main surface B of the varistor porcelain single plate 1. That is, the second capacitance obtaining electrode 4 and the second
On the main surface B of the varistor porcelain veneer 1 on which the capacitance acquisition electrodes 4 are not formed, a glass paste containing no ferrite magnetic powder is applied over the entire area except for both ends in the width direction of the varistor porcelain veneer 1. An insulating layer 7 formed by heat treatment is formed. The other configuration is the same as that of the first embodiment described above, and the same portions are denoted by the same reference numerals and description thereof will be omitted.

In the second embodiment, as in the first embodiment, an equivalent circuit as shown in FIG. 2 is formed, which has both characteristics of an LC filter and a varistor, and has a high frequency noise. And surges such as static electricity can be absorbed together.
Further, since the insulating layer 7 is formed on the main surface B of the varistor porcelain veneer 1, unnecessary conduction with other conductors of the second capacitance acquiring electrode 4 and the grounding electrode 6 can be prevented. There is no restriction on the arrangement of the chip type LC varistors, and the degree of freedom of arrangement is improved.

The manufacturing conditions including the chip size of the varistor porcelain veneer 1 are the same as those of the first embodiment, and the second varistor porcelain veneer 1 has an insulating layer 7 containing no magnetic powder on the main surface B side. The chip type LC varistor according to the embodiment has the following characteristics, and sufficient characteristics of both the LC filter and the varistor are achieved. Inductor L = 65.3nH Capacitor C = 2215pF Varistor voltage V _ImA = 21.3V Specific linear coefficient α = 9.5

In the above-described example, the case where strontium titanate is used as a main component of the semiconductor ceramic material of the varistor ceramic single plate 1 has been described.
Zinc oxide (ZnO), barium titanate (BaTi
Of course, various materials exhibiting varistor characteristics such as O ₃ ) may be used as a main component.

[0027]

As described above, in the chip-type LC varistor of the present invention, since the first and second capacitance obtaining electrodes and the insulating layer containing the magnetic powder are formed on the ceramic varistor, the high frequency operation is achieved. A composite element for noise suppression having both characteristics of an LC filter for suppressing noise and a varistor for absorbing surges such as static electricity is obtained. In addition, it is possible to provide a chip-type LC varistor having a low manufacturing cost, a high yield, a small size, an inexpensive reliability and a low cost without requiring a difficult step of bonding different materials and co-firing as in the conventional composite element. The present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a perspective view and a side view of a chip-type LC varistor (first embodiment) of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the chip-type LC varistor of the present invention.

FIG. 3 is a perspective view showing an intermediate state in a manufacturing process of the chip-type LC varistor of the present invention.

FIG. 4 is a top view showing an intermediate state in a manufacturing process of the chip-type LC varistor of the present invention.

FIG. 5 is a side view of a chip-type LC varistor (second embodiment) of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 varistor porcelain single plate 2 first capacitance obtaining electrode 3 insulating layer containing ferrite magnetic powder 4 second capacitance obtaining electrode 5 input / output electrode 6 grounding electrode 7 insulating layer containing no ferrite magnetic powder A, B main surface

Claims (5)

[Claims] 1. A chip-type LC varistor having an inductor component and a capacitor component, comprising: a rectangular parallelepiped ceramic varistor; a first capacitance acquisition electrode provided on a first main surface of the ceramic varistor; And a second capacitance obtaining electrode provided on a second main surface opposite to the main surface of the first electrode, and an insulating material including a magnetic powder formed so as to cover part or all of the first capacitance obtaining electrode. A chip-type LC varistor, comprising: 2. The chip-type LC varistor according to claim 1, further comprising an insulating layer formed so as to cover a part or the whole of the second capacitance obtaining electrode. 3. An input / output electrode provided at both ends of the ceramic varistor and electrically connected to the first capacitance obtaining electrode, and the first and second electrodes excluding both ends of the ceramic varistor. 2. A ground electrode provided on a surface substantially perpendicular to the main surface of the first electrode and electrically connected to the second capacitance obtaining electrode.
Or the chip-type LC varistor according to 2. 4. The chip type L according to claim 1, wherein said ceramic varistor is a semiconductor porcelain single plate containing strontium titanate as a main component.
C varistor. 5. A method for manufacturing a chip-type LC varistor having an inductor component and a capacitor component, wherein a step of forming a first capacitance acquisition electrode on a first main surface of a rectangular parallelepiped ceramic varistor; Forming a second capacitance obtaining electrode on a second main surface of the ceramic varistor opposite to the first main surface; and covering a part or all of the first capacitance obtaining electrode. Forming an insulating layer containing body powder.