JPH0732086B2 - Electrode material for voltage nonlinear resistors - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrode material used for a voltage non-linear resistor.

2. Description of the Related Art Voltage nonlinear resistors (hereinafter referred to as varistor) are widely used for surge absorbers, voltage stabilizers, lightning arresters, and the like. Conventionally, silicon carbide varistor and silicon varistor have been provided for these applications. However, these varistors have drawbacks that the voltage non-linearity coefficient α is small, their characteristics cannot be adjusted arbitrarily, or their shapes are large, and their applications were naturally limited.

In order to improve these drawbacks, a varistor of an oxide sintered body was developed, which was mainly composed of zinc oxide (ZnO), to which a small amount of several kinds of metal oxides were added, and which was mixed, molded and fired. It was Although the varistor has an excellent voltage non-linearity coefficient, its application is about to be expanded, but it is still insufficient in the electric circuit of a highly developed communication device.

Generally, the voltage non-linearity of a varistor is evaluated by the values of the voltage non-linearity coefficients α and Vi shown by the following equation.

I / i = (V / Vi) α where I is the current flowing through the varistor, V is the applied voltage, and Vi is the voltage at a constant current i amperes and is usually called the rising voltage.

Α and Vi are practically important constants for showing the electrical characteristics of the varistor. That is, α indicates how the voltage of the electric circuit in which the varistor is inserted is controlled,
The larger the value of α, the better the rise of the voltage. The value of α is preferably large except for special applications, and a value of “30” or more is desirable. Vi is determined by how much voltage is used, and is adjusted to a value specified in advance by each product.

Problems to be Solved by the Invention By the way, considering the usage conditions in the electric circuit of communication equipment, the increase in leakage current with respect to surge current is small and the limiting voltage ratio characteristic (generally, the voltage between terminals of a varistor when 1 mA flows). A varistor excellent in the voltage non-linearity in the large current region by the ratio of the terminal voltage of the same varistor when a current of V _1mA and another value flows) is required.

However, as a glass frit component in the electrode material
Bi ₂ O ₃ 40 to 90% by weight, B ₂ O ₃ 10 to 30% by weight, SiO ₂ 5
When the conventional electrode material using bismuth borosilicate glass containing ~ 25 wt% is used for the ZnO varistor, the characteristics of varistor voltage in surge current withstanding are large and the limiting voltage ratio is not satisfactory. Is.

An object of the present invention is to improve the characteristics of the varistor voltage and the improvement of the limiting voltage ratio in the surge current withstanding capability of ZnO type varistor.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention, as a glass component of the electrode material of the voltage nonlinear resistor containing ZnO as a main component,
Boron in the form of B ₂ O ₃ is 10 to 30% by weight, and silicon is in the form of SiO ₂ 5
Lead borosilicate zinc bismuth glass containing ~ 25% by weight, 50-75% by weight of lead in the form of PbO, 5 to 35% by weight of zinc in the form of ZnO and 5 to 30% by weight of bismuth in the form of Bi ₂ O _3. Is used as a glass frit.

Action According to the above configuration, lead borosilicate zinc bismuth glass is Zn
By using it as the glass component of the electrode material of the O-based varistor, the characteristic deterioration of the varistor voltage and the improvement of the limiting voltage ratio in the surge current withstanding of the ZnO-based varistor can be achieved.

Example Hereinafter, an example of the present invention will be described in comparison with a conventional example.

First, 96 mol% ZnO, 0.6 mol% Bi ₂ O ₃ , 0.5 mol% CoO, 0.9 mol% MnO ₂ , 0.9 mol% Sb ₂ O ₃ and 0.6 mol% NiO.
0.5% by mol of Cr ₂ O ₃ was weighed and mixed by a ball mill. After drying the mixed slurry thus obtained, 700 ~ 950
It was calcined at ℃ (this calcination may be omitted), a binder (5% PVA aqueous solution) was added, and pressure-molded into a disk shape. After that, it was fired at 1100-1300 ℃, and the obtained sintered body (diameter 7m
m) was polished to a thickness of 10 mm, and then a silver electrode having a diameter of 5 mm was baked.

For the silver electrode used here, a predetermined amount (5% by weight ratio) of lead borosilicate zinc bismuth glass powder (Table 1 below shows the composition ratio of the lead zinc borosilicate bismuth glass used) was weighed,
It is made into a paste by kneading it with a vehicle (30% by weight) of Ag cellulose (65% by weight) in which butyl carbitol is dissolved in ethyl cellulose. Table 2 below shows the composition ratio of the conventional bismuth borosilicate glass.

Table 3 below shows the electrical characteristics of the thus obtained sintered body.

This Table 3 is calculated from the result of measuring the voltage-current characteristics from 1 μA to 10 A. The non-linear index is 0.1 mA α1 mA between the current of 0.1 mA and 1 mA, and the varistor voltage V per unit thickness of the element.
_1mA / mm ,, ratio of V _10A to V _1mA at current value 10A V _10A / V _1mA
(Limit voltage ratio) and surge current withstand voltage characteristic _{VmA 1mA}
Change rate ΔV / V _1mA (%).

For surge current withstand characteristics, the impact current (600A in this case) with a standard current waveform of 8 × 20μsec specified is applied twice at 5 minute intervals, and the rate of change of varistor voltage V _1mA is calculated. went.

As shown in Table 3, in comparison with the sample No. 1 containing bismuth borosilicate glass, the varistor using the samples No. 2 to 7 of the present invention has a very good surge current withstanding characteristic and a limited voltage characteristic. It has been improved and satisfies the characteristics required for a varistor used for an electric circuit of a communication device.

The effective composition range of the glass component is such that boron is 10 to 30% by weight in the form of B ₂ O ₃ , silicon is 5 to 25% by weight in the form of SiO ₂ , and lead is 50 to 75% by weight in the form of PbO. % Lead, bismuth lead borosilicate glass containing 5 to 35% by weight of zinc in the form of ZnO and 5 to 30% by weight of bismuth in the form of Bi ₂ O ₃ .

Outside of these composition ranges, 0.1mA α1mA is less than 30,
Either V _10A / V _1mA is 1.45 or more and the characteristic deterioration of varistor voltage due to surge current withstanding becomes large, which makes it unsuitable as a varistor for electric circuits of communication equipment.

Effects of the Invention As described above, when the electrode material of the present invention is printed and baked to form a ZnO-based varistor, excellent voltage non-linear characteristics are exhibited from a small current region to a large current region, and the electrical properties of communication equipment are high. It is possible to obtain a varistor having an extremely excellent surge current withstanding characteristic suitable for a circuit.

Claims (1)

[Claims] 1. Boron in the form of B ₂ O ₃ is contained in the form of B ₂ O _{3 in} an amount of 10 to 30 as a glass component of an electrode material of a voltage nonlinear resistor containing ZnO as a main component.
% By weight, 5 to 25% by weight of silicon in the form of SiO ₂ , 50 to 75% by weight of lead in the form of PbO, 5 to 35% by weight of zinc in the form of ZnO, 5 of bismuth in the form of Bi ₂ O _3. An electrode material for a voltage non-linear resistor using lead borosilicate bismuth borosilicate glass as a glass frit containing up to 30% by weight.