JPH0729708A - 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 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 at least an element or its chemical compound selected from bismuth, manganese, cobalt, praseodymium, or lanthanum as an auxiliary component. Or, 010 to 3.00mol% of bismuth, 0.10 to 3.00mol% of manganese, 0.10 to 3.00mol% of cobalt, 0.005 to 0.50mol% of praseodymium, and 0.01 to 0.50mol% of lanthanum in terms of their oxides, Bi2O3, Mn3O4, CoO, Pr6O11, and Le2O3 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 computer built-in device, 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 have been accompanied, and along with this, miniaturization of varistor used as a noise absorbing element has also progressed. There is a strong demand for higher voltage and lower voltage. For example, in an electronic device equipped with a microcomputer, since the digital control process is performed, the semiconductor device may be damaged or malfunction due to EMI noise. There are many power supply parts and signal wiring parts in the path of intrusion of this noise into the electronic device. Therefore, the role of the noise filter used in the input / output parts of the power supply part and the signal wiring part is emphasized.

To solve the 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 that protects electronic devices from such noise, a varistor containing zinc oxide as a main component has been conventionally proposed (for example, Japanese Patent Laid-Open No. 54-1633).
95). 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, so that it cannot be applied to a low-voltage driven computer-equipped device. 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, conventionally, in order to obtain a low-voltage varistor element, the thickness of the element is reduced to reduce the distance between electrodes, or the number of crystal grain boundaries existing between electrodes is reduced by growing crystal grains. Has been 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 crystal grains are grown in the conventional varistor described above, the variation in grain size tends to be large in the current sintering technology, and therefore electrical characteristics such as varistor voltage, capacitance, and voltage non-linearity coefficient. There is a problem in that there is variation. 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 body amount 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 characterized in that at least one element of bismuth, manganese, cobalt, praseodymium, or lanthanum or a compound thereof is added to zinc oxide as a main component as a sub-component, and a voltage non-linear resistance. It is the body.

Here, when the above-mentioned subcomponents are added, each element is its oxide Bi ₂ O ₃ , Mn ₃ O ₄ , and Co.
O, respectively in terms of _{Pr 6 O 11, Le 2 O} 3 0.10~
3.00mol%, 0.10〜3.00mol%, 0.10〜3.00mol%, 0.
It is desirable to add it in the range of 005 to 0.50 mol% and 0.01 to 0.50 mol%. This is because the effect of improving the electrical characteristics can be remarkably obtained. That is, the above-mentioned Pr ₆ O ₁₁ , Le ₂
By adding a predetermined amount of O ₃ , it is possible to improve the non-linear coefficient and the electrostatic withstand capability, and the above Mn ₃ O ₄ ,
The addition of CoO can improve the nonlinear coefficient, insulation resistance, and surge resistance. Further, the varistor voltage can be reduced by adding a predetermined amount of Bi ₂ O ₃ mentioned above.

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 nonlinear resistor of the present invention, since bismuth, manganese, cobalt, praseodymium and lanthanum are added to zinc oxide as sub-components, the varistor voltage can be reduced without reducing the thickness of the device. From
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 in turn, low-voltage driven electronic devices 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, manufacture of the voltage non-linear resistor of this embodiment
The method will be described. Prepare ZnO which is the main component,
Bi to this₂O₃, Mn₃O_Four, CoO, Pr ₆O₁₁,
And Le₂O₃Add a specified amount of
After mixing, calcination is carried out at a temperature of 700 to 900 ° C for several hours.
U

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 amount of addition of ₃ O ₄ , CoO, Pr ₆ O ₁₁ , and Le ₂ O ₃ is 0.00 to 5.00 mol%, 0.00 to 5.00 mol%, 0.00 to 5.
A large number of samples were prepared by changing the range of 00 mol%, 0.000 to 0.100 mol%, 0.000 to 1.000 mol% (Sample No. 1
See No. 30). In the table, sample Nos. 1 to 6 are Le ₂ O
₃ amount, sample Nos. 7 to 12 are Pr ₆ O ₁₁ amount, sample No. 13
~ 18 is the amount of CoO, sample Nos. 19-24 are Mn ₃ O
_The amount of Bi ₂ O ₃ was changed within the above range for each of the _four amounts and sample Nos. 25 to 30.

The insulation resistance value I when a voltage of 50% of the varistor voltage of each of the above sample Nos. 1 to 30 was applied for 30 seconds
R, varistor voltage (V _1mA ), and _1mA to 10mA for each sample
The non-linear coefficient (α _1-10mA ) when the current flows and the electrostatic capacity were measured, as well as the surge resistance and electrostatic resistance. 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, each sample No. 1, No. 7, No. 8 in which the amounts of Pr ₆ O ₁₁ and Le ₂ O ₃ were 0, 0.001 mol%
In the case of No. 6, the electrostatic resistance and the nonlinear coefficient are slightly low, and in the case of Sample No. 6 in which the amount of Le ₂ O ₃ is 1.0, the varistor voltage is slightly higher. On the other hand, the above Pr ₆
The amount of O ₁₁ is 0.005 to 0.100 mol% and the amount of Le ₂ O _{3 is} 0.01 to 0.
In the case of Sample Nos. 2 to 5 and 9 to 12, the nonlinear coefficient is improved to 24.5 to 35.2 and the electrostatic withstand capacity is improved to 20 to 30 Kv, which results in the above Pr ₆ O ₁₁ and Le ₂ O ₃ It can be seen that the nonlinear coefficient and electrostatic withstand capability can be improved by adding a prescribed amount of.

The amount of Mn ₃ O ₄ and CoO is 0 mol.
In the case of each sample No. 13 and No. 19 which was made into%, the insulation resistance value and the non-linear coefficient were a little low.
In the case of Sample Nos. 18 and 24 where 0 was set, the varistor voltage was relatively high. On the other hand, the above addition amount is 0.01
~ 3.00 mol% of each sample No. 14-17, 20-23
, The resistance value is 20.3 to 90.3 MΩ, and the nonlinear coefficient is 22.9.
~ 36.6, surge withstand and electrostatic withstand are as high as 200A and 30Kv, respectively. From this fact, the above Mn ₃ O ₄ and CoO
By adding a predetermined amount of resistance, resistance value, nonlinear coefficient,
It can be seen that the surge withstand and electrostatic withstand characteristics can be improved.

Further, sample No. 25 in which the amount of Bi ₂ O ₃ was 0 mol% and sample No. 25 in which the amount of addition was 5.0 mol% were used.
In the case of 30, both have relatively high varistor voltages of 59 V or higher. On the other hand, the Bi ₂ O ₃ content is 0.01 to 3.
The varistor voltage of each sample 26 to 29, which was set to 00 mol%,
It is as small as 28.2 to 43.2V, and 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
O₁₁, Le₂O₃Each sample No. 1 by adding
Varistor voltage, surge withstand, static
Characteristics such as electrical withstand capability can be improved, and eventually low voltage drive
Compatible with electronic devices equipped with computers. in
Also when the addition amount of each of the above subcomponents is within the above range,
The reliability of quality can be improved by further improving each electrical characteristic.
Can be improved.

[0022]

As described above, according to the voltage nonlinear resistor of the present invention, at least one element of bismuth, manganese, cobalt, praseodymium, and lanthanum or a compound thereof is added to zinc oxide as a main component as a subcomponent. Since it is added, it is possible to reduce the varistor voltage to support low voltage drive built-in computer equipment, to reduce the leakage current, and to improve the 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 at least one element selected from bismuth, manganese, cobalt, praseodymium, or lanthanum or a compound thereof is added. 2. The method according to claim 1, wherein the elements of bismuth, manganese, cobalt, praseodymium, and lanthanum are oxides of Bi ₂ O ₃ , Mn ₃ O ₄ , CoO, and Pr.
Converted to ₆ O ₁₁ and Le ₂ O ₃ , 0.10 to 3.00 mol respectively
%, 0.10 to 3.00 mol%, 0.10 to 3.00 mol%, 0.005 to 0.
A voltage non-linear resistor characterized by being added in an amount of 50 mol%, 0.01 to 0.50 mol%.