JPH0729709A - Voltage-dependent nonlinear resistor - Google Patents

Abstract

PURPOSE:To provide a voltage-dependent nonlinear resistor which is so lessened in varistor voltage as to cope with a computer built-in equipment which operates on a low voltage, decreased in leakage current, and enhanced in electrical properties such as surge resistance and breakdown strength. CONSTITUTION:A voltage-dependent nonlinear resistor is formed of material composed of zinc oxide as a main component and elements such as bismuth, manganese, cobalt, and praseodymium or their chemical compounds as auxiliary components. 0.10 to 3.00mol% of bismuth, 0.10 to 3.00mol% of manganese, 0.10 to 3.00mol% of cobalt, and 0.005 to 1.00mol% of praseodymium in terms of their oxides, Bi2O3, Mn3O4, CoO, and Pr6O11 are added to zinc oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistor element (hereinafter referred to as a varistor) whose resistance value changes non-linearly according to an applied voltage. The present invention relates to a composition which can be applied to a device built in a computer, can reduce leakage current, and can improve electrical characteristics such as surge resistance and electrostatic resistance.

[0002]

2. Description of the Related Art In recent years, in the field of various electronic devices such as communication devices, miniaturization and rapid integration of electronic parts are accompanied, and accordingly, varistor used as a noise absorbing element is also small There is a strong demand for higher voltage and lower voltage. Further, in an electronic device equipped with a microcomputer, since the digital control process is performed, there is a possibility that the semiconductor device may be destroyed or malfunction due to EMI noise. There are many power supply parts and signal wiring parts in the path of this noise entering the electronic device.
The role of the noise filter used in the input / output portion of the signal wiring portion is emphasized. In order to solve the above-mentioned problem of EMI noise, it is necessary that noise is not emitted from the electronic device and does not enter the device. As an element for protecting electronic devices from such noise, a varistor containing zinc oxide as a main component has been proposed in the past (for example, Japanese Patent Laid-Open No. Sho 5).
No. 4-163395).

By the way, with a varistor containing zinc oxide as a main component, it is difficult to set the varistor voltage (V _1mA ) per 1 mm of the element thickness to 100 V or less. Can not. Here, the varistor voltage is controlled by the number of crystal grain boundaries existing between the electrodes of the element, and becomes lower as the number of crystal grain boundaries is smaller. Therefore, to obtain a low-voltage varistor element,
A method of reducing the thickness of the device to reduce the distance between the electrodes or growing crystal grains to reduce the number of crystal grain boundaries existing between the electrodes is adopted.

[0004]

However, in the above-mentioned conventional varistor, there is a problem in manufacturing because the strength decreases as the element thickness decreases, and the energy tolerance decreases as the volume of the element decreases. Furthermore, if the element is made thinner, the influence of the diffusion electrode material during firing will increase,
As a result, there is a problem that the resistance of the element decreases and the leakage current increases.

Further, when growing crystal grains in the conventional varistor described above, the variation in grain size tends to be large in the present firing technique, and therefore electrical characteristics such as varistor voltage, capacitance, and nonlinear coefficient are increased. There is a problem that variations occur. Further, current concentration is likely to occur in a portion where the crystal grains are large, so that there is a problem that surge resistance and electrostatic resistance are reduced.

The present invention has been made in view of the above conventional circumstances, and can be applied to computer equipment of low voltage drive by reducing the varistor voltage, leakage current can be reduced, and electrical resistance such as surge resistance and electrostatic resistance can be reduced. It is an object of the present invention to provide a voltage non-linear resistor whose characteristics can be improved.

[0007]

Means for Solving the Problems In order to achieve the above-mentioned object, the inventors of the present invention have studied various sub-components added to the main component zinc oxide. The present invention has been accomplished by finding that deterioration of electrical characteristics due to variations in thickness and crystal grains can be improved.

Therefore, the present invention is a voltage non-linear resistor characterized in that each element of bismuth, manganese, cobalt or praseodymium or a compound thereof is added to zinc oxide as a main component as a sub ingredient.

Here, when the above-mentioned subcomponents are added, each element is its oxide Bi ₂ O ₃ , Mn ₃ O ₄ , and Co.
Converted to O and Pr ₆ O ₁₁ , 0.10 to 3.00 mol%,
0.10〜3.00mol%, 0.10〜3.00mol%, 0.005〜1.00m
It is desirable to add in the range of ol%. This is because the effect of improving the electrical characteristics can be remarkably obtained. That is,
By adding the above-mentioned Pr ₆ O ₁₁ in a predetermined amount, it is possible to improve the non-linear coefficient and the electrostatic resistance, and by adding the above Mn ₃ O ₄ and CoO, the non-linear coefficient, the insulation resistance and the surge withstand can be improved. Can be achieved. Further, the above Bi ₂ O ₃
The varistor voltage can be reduced by adding a predetermined amount of.

In order to manufacture the above voltage non-linear resistor, zinc oxide is mixed with the above-mentioned various subcomponents, and the mixture is molded into a predetermined shape, and the molded body is fired at a high temperature to obtain a sintered body. After that, the electrodes can be formed on both main surfaces of the sintered body, which is substantially the same as the conventional method.

[0011]

According to the voltage non-linear resistor of the present invention, since bismuth, manganese, cobalt, and praseodymium are added to zinc oxide as subcomponents, the varistor voltage can be reduced without reducing the thickness of the element. It is possible to avoid a decrease in mechanical strength and a decrease in energy resistance. In addition, current concentration due to variations in crystal particles is less likely to occur, surge withstand characteristics can be improved, and electronic devices driven by low voltage can be protected from EMI noise.

[0012]

EXAMPLES Examples of the present invention will be described below. This example describes a characteristic test conducted to manufacture the voltage non-linear resistor of the present invention and confirm the effect thereof.

First, a method of manufacturing the voltage nonlinear resistor of this embodiment will be described. Prepare ZnO which is the main component,
Bi ₂ O ₃ , Mn ₃ O ₄ , CoO, and Pr ₆ O
_After adding a predetermined amount of ₁₁ and mixing them well,
Calcination is performed at a temperature of 700-900 ℃ for several hours.

Next, the above calcined powder is sufficiently crushed by a ball mill and then pressed into a disk shape having a diameter of 6 mm and a thickness of 0.6 mm. Next, this molded body is heated in the atmosphere at 1250 to
A sintered body is obtained by heating and firing at a temperature of 1400 ° C for 3 hours. The thus-obtained sintered body was ground to a thickness of 0.5 mm, and then both main surfaces thereof had a diameter of 3 mm.
mm of Ag paste is applied and then baked to form electrodes. As a result, the voltage nonlinear resistor of this example is manufactured.

[0015]

[Table 1]

Table 1 shows the results of a characteristic test conducted to confirm the effect of the voltage non-linear resistor obtained by the above manufacturing method. This test is based on the above-mentioned Bi ₂ O ₃ , Mn.
The addition amount of ₃ O ₄ , CoO, and Pr ₆ O ₁₁ is 0.00-
5.00mol%, 0.00 ~ 5.00mol%, 0.00 ~ 5.00mol%, 0.0
A large number of samples were prepared by changing the range of 00 to 5.000 mol% (see Sample No. 1 to No. 27). Sample No. 1 in the table
To 9 is Pr ₆ O ₁₁ weight Sample No. 10 to 15 are the amount of CoO,
Sample Nos. 16 to 21 are Mn ₃ O ₄ amount, Sample Nos. 22 to 2
7 shows the amount of Bi ₂ O ₃ varied within the above range.

Insulation resistance (I) when 50% of the varistor voltage of each sample No. 1-27 was applied for 30 seconds
R), varistor voltage (V _1mA ), and _1mA to 10 for each sample
The non-linear coefficient (α _{1-10 mA} ) when a current of mA flows and the electrostatic capacity were measured, and the surge withstand amount A and the electrostatic withstand amount Kv were measured. The above surge resistance is the current value at which the varistor element is not destroyed even when a triangular current wave of 8 × 20 μs is applied, and the electrostatic withstand capacity is the discharge voltage at which the element is not destroyed even when an electrostatic discharge pulse conforming to IEC 801-2 is applied. Indicates the maximum value.

In Table 1, the amounts of Pr ₆ O ₁₁ are 0 and 0.00.
In the case of each sample No. 1 and No. 2 with 1 mol%, the electrostatic withstand capacity and the nonlinear coefficient are slightly low, and Pr ₆ O ₁₁
In the case of Sample No. 9 in which the amount was 5.0 mol%, the nonlinear coefficient was high, but the varistor voltage was slightly high. On the other hand, each sample No. 3 in which the amount of Pr ₆ O ₁₁ is 0.005 to 1.0 mol%
In the case of ~ 8, the nonlinear coefficient is 26.9-37.2, and the electrostatic withstand capability is
It is improved to 30 Kv, and it can be seen that the nonlinear coefficient and the electrostatic withstand capability can be improved by adding a predetermined amount of Pr ₆ O ₁₁ .

The amount of CoO and Mn ₃ O ₄ is 0 mol.
%, Each sample No. 10 and No. 16 has low insulation resistance and non-linear coefficient.
%, The varistor voltage is high in the case of each sample No. 15 and 21. On the other hand, the above addition amount is 0.01 to 3.00
In the case of each sample No. 11 to 14 and 17 to 20 in mol%, the resistance value is 20.7 to 105 MΩ, the nonlinear coefficient is 22.9 to 38.5,
The surge withstand capability and electrostatic withstand capability are as high as 200A and 30Kv, respectively. Thus, it can be seen that the addition of the above-mentioned Mn ₃ O ₄ and CoO in a predetermined amount makes it possible to improve the characteristics of resistance, non-linear coefficient, surge resistance, and electrostatic resistance.

Further, sample No. 22 in which the amount of Bi ₂ O ₃ was 0 mol% and sample No. 22 in which the amount of addition was 5.0 mol% were used.
In the case of No. 27, the varistor voltage is high in both cases. On the other hand, in each of the samples 23 to 26 in which the Bi ₂ O ₃ amount was 0.01 to 3.00 mol%, the varistor voltage was 28.2 to 43.2V.
The varistor voltage can be lowered by adding a predetermined amount of Bi ₂ O ₃ .

As described above, according to this embodiment, as described above.
ZnO, Bi₂O₃, Mn₃O _Four, CoO, Pr₆
O₁₁By adding the specified amount of
Electricity such as pressure, nonlinear coefficient, surge resistance and electrostatic resistance
Computer that can improve its dynamic characteristics and is driven by low voltage
Compatible with electronic devices equipped with.

[0022]

As described above, according to the voltage non-linear resistor according to the present invention, each element of bismuth, manganese, cobalt and praseodymium or its compound is added as a sub-component to the zinc oxide as the main component. This has the effects of reducing the voltage and supporting low-voltage drive built-in computer equipment, reducing the leakage current, and improving electrical characteristics such as surge resistance and electrostatic resistance.

Claims (2)

[Claims] 1. A voltage non-linear resistor comprising zinc oxide as a main component, to which bismuth, manganese, cobalt, praseodymium elements or compounds thereof are added as accessory components. 2. The bismuth and man according to claim 1,
The oxides of the elements gun, cobalt, praseodymium
Bi₂O₃, Mn₃O_Four, CoO, Pr ₆O₁₁Converted to
0.10〜3.00mol%, 0.10〜3.00mol%,
0.10 to 3.00 mol%, 0.005 to 1.00 mol%
A voltage non-linear resistor characterized in that