JPH0449770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a multi-functional element having both a varistor function and a capacitor function.

Conventional configurations and their problems Conventionally, as ceramics having voltage non-linear resistance characteristics, there are SiC varistors and varistors whose main component is zinc oxide. Such a varistor has a current I
-The voltage V characteristic is approximately expressed as I=(V/C)〓. Here, C is a constant specific to the varistor, and α is a voltage nonlinear index.
The Sic varistor utilizes a contact barrier between Sic particles, and α is about 2 to 7. In addition, zinc oxide varistors are made by adding Bi ₂ O ₃ to zinc oxide ZnO,
It is an element obtained by adding a trace amount of metal oxide such as CoO, MnO ₂ , Sb ₂ O ₃ and firing.
It is an element whose voltage nonlinearity index α is as high as 50.
Since such elements have excellent performance in absorbing high voltages, they are used for the purpose of stabilizing electronic equipment and protecting against abnormal voltages (surges). However, such conventional varistors have a small dielectric constant and a large dielectric loss angle tan δ of 5 to 10%, so they can only be used for varistor applications.

On the other hand, as capacitors, dielectric ceramics whose main components are barium titanate BaTiO ₃ and strontium titanate SrTiO ₃ , which have large dielectric constants, are widely used as small, large-capacity capacitors in electronic circuits. However, there is a drawback that if a current of 1 mA or more flows through the element, it will be destroyed and lose its function as a capacitor.

Recently, electronic equipment has come to require extremely high precision control, and not only industrial equipment but also consumer equipment has come to require extremely high precision due to the application of microcomputers. Furthermore, since logic circuits constituting microcomputers and the like operate using pulse signals, they inevitably have the disadvantage of being susceptible to noise. Therefore, if electronic computers, banking machines, traffic control equipment, etc. malfunction or are destroyed due to noise or surges, it becomes a social problem. Noise filters have conventionally been used as a measure against such problems. Noise is an interfering voltage other than the intended signal voltage when operating electronic equipment, and can be divided into those generated artificially and those generated by natural phenomena. This kind of noise was removed using a circuit that combined a coil and a capacitor. However, among the artificially generated noises, especially those caused by the opening and closing of circuit breakers on power transmission lines,
Noises caused by natural phenomena, especially those caused by lightning surges, have a low fundamental frequency of about 5 to 20 KHz, and it has not been possible to remove these noises using only the conventional combination of coils and capacitors. In view of these problems, noise filters that use a voltage nonlinear resistor (varistor) between lines or between lines and ground have recently been frequently used. Such a noise filter can remove a very wide range of noise, and is therefore effective in preventing malfunctions of microcomputer-controlled equipment. however,
This noise filter had the disadvantage that it required a large number of parts within the set, resulting in high costs, and was contrary to the technological trend toward miniaturization.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a method for manufacturing a multi-functional element that can inexpensively produce a multi-functional element having both a varistor function and a capacitor function.

Composition of the Invention In order to achieve this object, the manufacturing method of the present invention provides a manufacturing method in which a sintered body of dielectric porcelain is placed on the opposing surfaces of an insulating substrate in which continuous electrodes are formed on opposing surfaces and one end surface. The powder obtained by finely pulverizing the powder and the powder containing zinc oxide as the main component and several metal oxides are sprayed on both sides by plasma spraying to form a dielectric material and a voltage nonlinear resistor. Furthermore, after forming an insulator on the electrode on one end surface of the insulating substrate, continuous electrodes are formed on the respective surfaces of the dielectric, the voltage nonlinear resistor, and the insulator. Since the element thus obtained has the combined function of a varistor and a capacitor, it can be used as a single element in a conventional circuit in which a varistor and a capacitor are connected in parallel.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an equivalent circuit diagram of a multifunctional device obtained by the method of the present invention. FIG. 2 is also a cross-sectional view of the multifunctional device. 1 is a flat insulating substrate, 2
is a silver electrode, 3 is a dielectric, 4 is a voltage nonlinear resistor,
5 is an insulator, and 6 is an electrode.

First, SrO, SnO ₂ and ZnO ₂ are added to BaTiO ₃ powder.
0.01 to 1.0 mol% was added and thoroughly mixed. This was formed into a diameter of 25 mm and a thickness of 5 mm, and fired at a temperature of 1200 to 1300°C for 1 to 3 hours.The sintered body was then finely ground to produce a fine powder of dielectric material 3. Average particle size is approximately 20μm
It is.

Next, add Bi ₂ O ₃ to the ZnO powder for the total amount.
0.5 mol% _, 0.5 mol% _Co2O3 , 0.5% _MnO2 ,
Sb ₂ O ₃ was added at a ratio of 1.0 mol % and Cr ₂ O ₃ was added at a ratio of 0.5 mol % and mixed thoroughly. This is 25mm in diameter and 5mm thick.
After sintering at 1250° C. for 2 hours, the sintered couple was pulverized to produce a fine powder of the voltage nonlinear resistor 4. The average particle size is approximately 20 μm.

Next, an alumina substrate 1 was prepared, and a silver electrode paste was applied so that the opposing surfaces and one end surface were electrically connected, and baked at 800° C. to form a continuous silver electrode 2.

Next, fine powder of the dielectric material 3 is sprayed by plasma spraying on one side of the opposing surfaces on which the silver electrodes 2 are formed to form the dielectric material 3, and the other surface is similarly plasma sprayed. Therefore, fine powder of the voltage non-linear resistor 4 was thermally sprayed to form the voltage non-linear resistor 4.
This was subjected to 2H heat treatment at a temperature of 700°C to 800°C.

Next, a glass paste made of SiO ₂ -PbO-B ₂ O or the like is applied onto the silver electrode 2 formed on one end surface of the alumina substrate 1 and baked at 600 to 800°C to form an insulator 5 made of glass. did. In addition to forming the insulator 5 from glass, the alumina substrate 1
After heating to 150°C, insulating resin powder such as epoxy was coated on the silver electrode 2 formed on one end face and cured at 150°C to form an insulator 5. Thereafter, when the insulator 5 was glass, a silver electrode paste was applied to the surfaces of the dielectric 3 and the voltage nonlinear resistor 4, and baked at 800° C. to form the electrode 6. Further, when the insulator 5 was made of resin, the electrode 6 was formed by electrolytic spraying of aluminum or the like. Note that this electrode 6 is formed continuously over both surfaces of the dielectric 3 and the voltage nonlinear resistor 4 with an insulator 5 in between.

The plasma spraying method is a method in which an oxide is melted at a high temperature by an electric arc, and at the same time is blown away by a high-pressure inert gas to adhere to the object to form a film. The thermal spraying conditions in this example were to melt the powder with an electric arc of 60 to 80Kw,
The spraying distance was 10 cm, and Ar was used as the inert gas.

The shape of the multi-functional device obtained in this way according to the above example is 10 mm x 10 mm, and the alumina substrate 1
The thickness of the dielectric material 3 and the voltage nonlinear resistor 4 were 100 μ to 1 mm. And the performance is capacitance 3~10nF, tanδ1.5~2%, varistor voltage 40
~200V, α was 20~40, and surge resistance was 500~1000A. These properties can be varied by varying the plasma spray time. Further, the thermal spraying time in the above example is 30 seconds to 2 minutes.

Although BaTiO ₃ ceramic was used as the dielectric material, any ceramic capacitor material that can be used to form a dielectric material by plasma spraying is effective in view of the effects of the present invention.

Further, although an alumina substrate is used as the insulating substrate, any substrate having excellent heat resistance and on which electrodes can be formed is effective.

Effects of the Invention As described above in detail, the present invention can be achieved by forming a dielectric material and a voltage nonlinear resistor by plasma spraying on opposing surfaces of an insulating substrate on which electrodes are formed. It is possible to provide an element that has both the functions of a capacitor and a varistor, and its practical value is great as a noise countermeasure component for electronic equipment.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an equivalent circuit of a multi-functional device obtained by the method of the present invention, and FIG. 2 is a cross-sectional view of the multi-functional device also obtained by an embodiment of the method of the present invention. 1... Insulating substrate (alumina substrate), 2... Silver electrode, 3... Dielectric, 4... Voltage nonlinear resistor, 5
...Insulator, 6...Electrode.

Claims (1)

[Claims] 1. Continuous electrodes are formed on opposing surfaces and one end surface of an insulating substrate with excellent heat resistance, and powder obtained by pulverizing a sintered body of dielectric porcelain is placed on one electrode on the opposing surfaces. A dielectric material is formed by thermal spraying using a plasma spraying method, and powder containing zinc oxide as a main component and several kinds of metal oxides is similarly formed on the other electrode on the opposing surfaces to provide voltage resistance. After forming a linear resistor and further forming an insulator on an electrode on one end surface of the insulating substrate, continuous electrodes are formed on the respective surfaces of the dielectric, the voltage nonlinear resistor, and the insulator. A method for manufacturing a multifunctional device.