JPH0529107A - Voltage nonlinear resistor - Google Patents

Abstract

PURPOSE:To provide a voltage nonlinear resistor of zinc oxide where the voltage nonlinear coefficient is great, and the leak current is small, and the change of the varistor voltage due to large current pulse application is small. CONSTITUTION:Using zinc oxide (ZnO) as a main ingredient, bismuth oxide (Bi2O3), cobalt oxide (CoO), manganese oxide (MnO), antimony oxide (Sb2O3), and lead 2inc borosilicate glass frit are mixed as subingredients, and further zirconium oxide (ZrO2) is added and mixed by 0.05-5.9mol% to form a sintered substance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistor used in surge absorbing elements, voltage stabilizing elements, lightning arresters and the like, the resistance value of which varies with applied voltage.

[0002]

2. Description of the Related Art Voltage non-linear resistors (hereinafter referred to as varistor) are widely used in surge absorbing elements, voltage stabilizing elements, lightning arresters and the like. Conventionally, for these applications, SiC
Varistors have been used. However, these varistors have drawbacks such as a small voltage nonlinear coefficient. As a solution to these drawbacks, a zinc oxide varistor containing zinc oxide (ZnO) as a main component has been developed. The zinc oxide varistor has a large voltage non-linearity coefficient α,
It has excellent surge resistance and is widely used (Japanese Patent Publication No. 56-6127). The zinc oxide varistor has zinc oxide (ZnO) as a main component, and bismuth oxide (Bi ₂ O ₃ ), cobalt oxide (CoO), manganese oxide (MnO), antimony oxide (Sb ₂ O ₃ ) and the like are mixed as additives. However, there is a varistor fired at 1000 to 1350 ° C.

[0003]

In the zinc oxide varistor, the voltage non-linearity coefficient (α) and the varistor voltage (V _1mA ) are practically important factors in showing the electrical characteristics. α indicates how the voltage of the electric circuit in which the varistor is inserted is controlled, and the larger α is, the better the rise is. V _1mA is a value that is determined by the circuit voltage that is actually used, and is adjusted to a value specified in advance by the product. Also,
Not only α and V _1mA, but also the value of leakage current (IR) is an important factor. When using a varistor for overvoltage protection, a smaller leakage current (IR) is desired. By the way, in an electric circuit of a communication device, a varistor is generally used in a state in which a constant voltage load is applied, and is used as a so-called surge absorbing element that absorbs a large current pulse caused by opening and closing a switch. However, the conventional varistor containing ZnO as a main component has a drawback that the rising voltage (V _1mA ) decreases when a constant voltage load is applied for a long time, and the leakage current increases accordingly. Was there. Even when a high-current pulse is applied, it has the same drawbacks, and the excellent voltage nonlinearity of the varistor containing ZnO as a main component cannot be maintained.

Further, in the ZnO varistor, in order to increase the voltage non-linearity coefficient α, it was indispensable to add bismuth oxide (Bi ₂ O ₃ ) as one of the auxiliary components. Most of this varistor is bismuth oxide (Bi
A high resistance grain boundary layer containing ₂ O ₃ ) as a main component surrounds ZnO crystal grains that have been made into a semiconductor, and has a structure in which there are numerous rows and columns. Certainly obtained by adding Bi ₂ O _3, the voltage nonlinearity is large α is good, also the rising voltage V _{1 mA,} to obtain those practically appropriate value, Bi ₂ O ₃
Compared with the one without addition, it shows remarkably excellent characteristics and is of great practical value. However, this Bi ₂ O ₃
Has a low melting point and crystal transformation occurs at a relatively low temperature, and easily vaporizes at a high temperature. Such instability of Bi ₂ O ₃ with respect to temperature means that V _1mA decreases and leakage current (IR) increases due to characteristic deterioration when a large current pulse is applied, that is, when a large surge current is applied. There was a problem in improving the reliability of the varistor element.
An object of the present invention is to provide a voltage non-linear resistor in which such conventional drawbacks are eliminated.

[0005]

The present invention is directed to zinc oxide (Z
nO) as a main component and bismuth oxide (B
i ₂ O ₃ ), cobalt oxide (CoO), manganese oxide (M
nO), antimony oxide (Sb ₂ O ₃ ) and zinc borosilicate glass are each 0.1 to 10 mol%, 0.05 to
10 mol%, 0.05-6.0 mol%, 0.05-6.
Zirconium oxide (ZrO ₂ ) is added in an amount of 0.05 to 0.05% by weight to a raw material blended with 0 to 0.05% by weight.
A voltage non-linear resistor comprising a sintered body obtained by adding and blending 5.0 mol%.

[0006]

According to the present invention, the voltage nonlinear coefficient α is large,
A leak current is small, a change in V _{1 mA} is small in response to a voltage load and application of a large current pulse, and a voltage nonlinear resistor having very stable characteristics can be obtained. Moreover, the reliability of voltage load and large current pulse is improved, and it can be expected to be used in a wide range of applications such as communication equipment as a ZnO varistor that is excellent as an overvoltage protection element and a surge absorption element that absorbs a large current pulse generated when a switch is opened and closed. Is. Such excellent properties can be obtained because the grain boundary layer contains bismuth, zirconium, zinc borosilicate glass, and other subcomponents of ZnO.
It is characterized in that it is present around the crystal grains, and this structure makes the characteristics as a varistor excellent.

[0007]

EXAMPLES The present invention will be described in detail below with reference to examples. As a starting material for obtaining the varistor of the present invention, a purity of 9
9.9% or more of zinc oxide (ZnO), bismuth oxide (B
i ₂ O ₃ ), cobalt oxide (CoO), manganese carbonate (M
Powders of nCO ₃ ), antimony oxide (Sb ₂ O ₃ ), zirconium oxide (ZrO ₂ ) and zinc borosilicate glass frit were used. A predetermined amount of each of these powders was weighed and mixed with pure water in a ball mill for 70 hours. Next, the mixed liquid was filtered and dried to obtain a mixed powder, which was crushed for 10 minutes by a Likai machine, and heat-treated at a temperature of 500 ° C. for 2 hours. A small amount of binder (PVA2.
5% aqueous solution) and mixed with a liquor machine, and then a sized powder is produced using a sieve, and the diameter is 12 mm,
It was press-molded into a cylinder having a height of 15 mm. Firing 1100
It was carried out at a temperature of ~ 1300 ° C for 1.5 hours. The obtained sintered body was cut to a thickness of 1 mm, polished, and a silver electrode having a diameter of 8 mm was baked. The characteristics such as α, V _1mA , and leakage current were calculated by measuring the voltage-current characteristics with a DC power supply. The varistor voltage was a voltage per 1 mm in thickness when a current of 1 mA was applied. The leakage current (IR) value was evaluated as the value at a voltage of 80% of V _{1 mA} . High current pulse characteristic is 30
The rate of change was calculated by measuring V _1mA after applying a pulse of 00A (current waveform 8 × 20 μsec) once, and the characteristic was evaluated. The constant voltage load characteristic was measured by measuring V _1mA after applying a direct current voltage of 80% of the varistor voltage for 1000 hours in a constant temperature bath at a temperature of 80 ° C. to calculate the change rate, and the characteristic evaluation was performed with this. Table 1 shows the composition ratio of the zinc borosilicate glass used. Tables 2 to 11 show the composition ratio of the starting materials and the characteristics of the obtained sintered body.

[0008]

[Table 1]

[0009]

[Table 2]

[0010]

[Table 3]

[0011]

[Table 4]

[0012]

[Table 5]

[0013]

[Table 6]

[0014]

[Table 7]

[0015]

[Table 8]

[0016]

[Table 9]

[0017]

[Table 10]

[0018]

[Table 11]

FIG. 2 shows No. 1 in Table 4. The results of measuring a wide range of current-voltage characteristics using 24 samples are shown. It is clear that it shows excellent characteristics over a wide current range, especially in a low current range, showing how small the leakage current is. 1 is shown in Table 4.
19-No. The values of α and V _1mA obtained from the 27 samples are Z
7 is a graph showing the relationship with the amount of rO ₂ added.
As is clear from this figure, by adding ZrO ₂ , α increases and V _1mA also tends to increase. Figure 3
Is the No. of Table 4. 19-No. The obtained value of the leakage current (IR) with 27 samples is a graph showing the relationship between the addition amount of ZrO _2. As is clear from this figure, Z
The addition of rO ₂ reduces the wetting current,
It becomes a minimum value at 1.0 mol%. 4 is shown in Table 4. 1
9-No. 27 is a graph showing a voltage change of V _{1 mA} after applying a DC voltage load and applying a large current pulse, in relation to the amount of ZrO ₂ added, according to Sample No. 27. ZrO ₂
It is apparent that when V is added, the voltage change of V _{1 mA} is extremely small with respect to both the DC voltage application and the large current pulse application.

[0020]

As described above, the voltage non-linear resistor according to the present invention has a large voltage non-linear coefficient α, a small leakage current, and V when a voltage load or a large current pulse is applied.
The change of _1mA is small and very stable characteristics can be obtained. The voltage non-linear resistor of the present invention having such characteristics is expected to have a wide range of applications such as communication devices as a ZnO varistor excellent in an overvoltage protection element, a surge absorption element that absorbs a large current pulse generated when a switch is opened and closed, and the like. It is possible.

[Brief description of drawings]

[Fig. 1] Voltage non-linearity coefficient α, varistor voltage V _1mA , and Z
It is a figure showing the relation with the amount of addition of rO ₂ .

FIG. 2 is a voltage-current characteristic diagram in an example of the present invention.

FIG. 3 is a diagram showing the relationship between leakage current (IR) and the amount of ZrO ₂ added.

FIG. 4 is a diagram showing the relationship between the voltage change of V _1mA and the addition amount of ZrO ₂ after applying a DC voltage load and a large current pulse.

Claims (1)

Claims: 1. A main component is zinc oxide (ZnO), and auxiliary components include bismuth oxide (Bi ₂ O ₃ ), cobalt oxide (CoO), manganese oxide (MnO), and antimony oxide (Sb). ₂ O ₃ ) and zinc borosilicate glass are respectively 0.1-10 mol%, 0.05-10 mol%, 0.05
~ 6.0 mol%, 0.05-6.0 mol% and 0.0
Non-linear voltage resistance comprising a sintered body obtained by adding and blending 0.05 to 5.0 mol% of zirconium oxide (ZrO ₂ ) to a raw material containing 5 to 10.0% by weight. body.