JPS5982702A - Voltage nonlinear resistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage nonlinear resistor, and more particularly to a voltage nonlinear resistor containing zinc oxide (ZnO) as a main component and used as an overvoltage protection element.

Conventionally, for the purpose of overvoltage protection of electronic and electrical equipment,
Silicon carbide (8iC), selenium (8e), silicon (81), or ZnO-based varistors are used. Among them, ZnO-based varistors generally have a low limiting voltage and are non-linear in voltage. It has characteristics such as a large exponent.Therefore, it is suitable for protecting against overvoltage in equipment made of devices with low overcurrent resistance such as semiconductor devices, so it can be used instead of varistors made of 8iC. Hiro (K has become used).

The main component is ZnO, and the subcomponents include rare earth elements, cobalt (Co), potassium (K), and rubidium (Rh).
It is known that a voltage nonlinear resistor manufactured by adding at least one of cesium (C3) and chromium (Cr) in the form of an element or a compound and firing it has excellent voltage nonlinearity. There is.

However, this voltage nonlinear resistor has drawbacks such as a slightly low long-tailed surge resistance and a low electrostatic life performance, which poses problems in miniaturizing the device. We have investigated the mechanism of element destruction due to long wave tail surges, and have achieved further prevention of destruction. At the same time, we have developed a voltage nonlinear resistor that is small, has high long wave tail resistance, and has excellent voltage applied life characteristics. The purpose is to provide the body.

Here, the present inventor has proposed that in a conventional voltage nonlinear resistor containing ZnO as a main component and adding at least one of rare earth elements, Co, K*Cs, and Rlb and KCr as subcomponents, We have discovered that when a surge of large IF current with a long wave tail is applied, current concentration occurs due to t-field concentration at the outer periphery of the electrode provided on the element surface, and such current flow causes destruction of the element. . In addition, it is recognized that there is a local inhomogeneous part inside the resistor (7), and when the DC V is not flowing, the I to this inhomogeneous part is
A rating of 1 was given indicating that F current concentration occurs, resulting in characteristic deterioration.

Research has been conducted to solve these problems, and additional sub-components include boron (B), aluminum (At),
By adding at least one of gallium (Ga) and indium (In), the outer periphery of the element has a slightly higher resistance than the inside, and this prevents current concentration at the outer periphery of the electrode and reduces long wave tail surges. We have discovered a fact that makes it possible to improve tolerance. - The present invention was completed based on the discovery that the non-uniformity within the resistor was simultaneously eliminated, and a voltage-free antibody with a significantly improved lifespan of energization could be obtained.

According to the present invention, ZnO is the main component, and rare earth elements, Co, K, R, b,
A conventional voltage nonlinear resistor containing a small amount of Cs (both one type and Cr), and further contains B, Al, and O as subcomponents.
a.

Provided is a voltage nonlinear resistor characterized by adding at least one type of In.

The voltage nonlinear resistor according to the present invention is generally manufactured by firing and sintering a mixture of ZnO and an additive metal or compound at high temperature in an oxygen-containing atmosphere.

Usually, additive components are added in the form of metal oxides, but compounds that can become oxides during the firing process, such as carbonates, hydroxides, fluorides, and their solutions, can also be used, or they can also be added as single elements. It can also be used in the form of oxides during the firing process.

According to a particularly preferred method, the voltage nonlinear resistor of the present invention is prepared by thoroughly mixing ZnO powder with powder of an additive metal or compound, and calcining the mixture in air at 500 to 1000°C for several hours before firing. It is manufactured by thoroughly crushing the calcined material, molding it into a predetermined shape, and then firing it in air at a temperature of about 1100° to 1400° C. for several hours. If the firing temperature is lower than 1100°C, the sintering will be insufficient and the properties will be unstable.

Moreover, at temperatures higher than 1400° C., it becomes difficult to obtain a homogeneous sintered body, voltage nonlinearity decreases, and there are difficulties in reproducibility such as control of characteristics, making it difficult to obtain a work of art that can be put to practical use.

Examples are now presented to further illustrate the invention.

Example ZnO powder K Pr5O+l+ CO3O4+ K2C
O3+ Cr+Oa + B2O3.

AlI2O3 powder was added in an amount corresponding to the predetermined atomic ratio listed in Table 81 of Rikuki, and after thorough mixing, 500 to 1
It was calcined at 000°C for several hours. Next, the calcined product was sufficiently crushed, a binder was added thereto, it was pressure-molded into a disc shape with a diameter of 17 lines, and it was fired in air at 1100"C to 1400C for 1 hour to obtain a sintered body. The thickness of the sintered body obtained by
They polished a dragon sample and baked electrodes on both sides to create an element, and measured its electrical properties 5).

The electrical characteristics are as follows: 1 mA of 1
Voltage between electrodes VImA when current flows, 1mA to 10m
The nonlinear index α at A and the long wave tail-to-edge current withstand capacity are 2 m, L:, the furnace wave V of 100 A, and the current is 2 m.
The change in 1 mA before and after applying 0 times was determined. In addition, as a charging life characteristic, the change in inter-electrode voltage vl-A was determined when a DC current of 20 mA was applied for 5 minutes and a 1 μAW current was applied before and after. The non-linear index α is obtained by approximating the change in the element current (2) with respect to the voltage V using the following equation.

■=(V/c)" Here, C is the voltage per unit thickness of the needle element with a current density of l mA/d.The electrical characteristics of the needle when the composition of the voltage nonlinear resistor is varied The measurement results are listed in Table 1.The blend composition shown in Table 1 is expressed by the atomic ratio calculated from the ratio of the number of atoms of the added element to the sum VC of the number of atoms of each component metal element in the raw material ( 6) Table 1 Table 1 (Continued) Sample/I61 shown in Table 1 contains Pr, C6, and K in ZnO.

It corresponds to the conventional sintered body manufactured by adding only Cr, and its long wave tail surge current characteristics are -793 and the energized life characteristics are -
23,1, and the nonlinear index α is 34. The purpose of the present invention is to achieve good long-wave tail surge current withstand capability, i.e., the rate of change for 72m people is closer to 0% than -79.3, and to improve the charging life characteristics, i.e., the rate of change in lμA is -79.3. 0% from Section 23.5
According to Table 1, samples close to
3, A116~419, 422~/%24,
,%27~Shoulder 3t.

/1633-435. Among them, sample 431 has a low nonlinear index a and is not suitable for practical use. Therefore, Pr is O, O
S ~ 5.0 atoms, Co 0.1 to 10 atoms, K 0
．． 01 to 1.0 atomic percent, Cr is 0.01 to 1.0 atomic percent, B is 5 x 10 to 1 x 10 atomic percent, M is 1 x 10 to 5
It is necessary to add within the range of ×10 atoms. Above 1st
As is clear from the table, P r + Co as a subcomponent
System K containing jK + Cr.

By adding B and 1, the long wave tail surge current withstand capacity and charging life characteristics are significantly improved. This is ZnO
Ni Pr, Co, Ni, Cr, BoAI! This can only be achieved when the two coexist.

(9) When these subcomponents are added alone, the voltage nonlinearity is extremely poor, and only haboohmic and linear characteristics are obtained, making it impossible to put it to practical use.

Although Table 1 only exemplifies PrK as a rare earth element, Table 2 also shows the effect of adding B and M on rare earth elements other than Pr or rare earth elements of class 23 or higher. It can be seen that even with rare earth elements other than Pr, the long-wave tail surge current withstand capacity and the charged life can be significantly improved without losing the excellent nonlinearity.

Table 2 (lO) Table 2 (Continued) Table 3 shows the characteristics of the nonlinear resistor produced by adding R, b, and Cs instead of K. Table wc4 shows the characteristics of the nonlinear resistor when K, Rb, and Cs are added together.

In all cases of Table 3 and Table 4, B and AI! The effect of adding K is that the long-wave tail surge current withstand capacity and the charging life are significantly increased without losing the excellent nonlinearity as in the case of K alone [points attached to F4]. In this case as well, the rare earth element has a ratio of 0.08 to 5.0 atoms,
Co has 0.1 to 10.0 atoms, K, Cs, ]1.
b is at least one type in total amount of 001 to 1.0 atoms 9b
, Cr is 001 to 1.0 atoms, B is 5 x 10 to 1 x I
O atom chi AI! must be added in an amount of 0.0001 to 0.05 atoms. In these cases, rare earth elements and Co are added to ZnO.

This is achieved only by the coexistence of at least one of K, Cm, and Rh, C, B, and A/, and when these subcomponents are added alone, voltage nonlinearity is extremely poor. However, only certain characteristics can be obtained, and it cannot be put to practical use.

AI again! When gallium or indium was used instead, the same effects as shown in Tables 1 to 4 were obtained.

As mentioned above, ZnO is the main component, rare earth elements, C
o%, at least one of Cm and -Rh, and Cr.

B and AI! , Ga, and In, the voltage nonlinear resistor of the present invention is added as a subcomponent.
While maintaining good non-linearity, the long-wave tail surge current resistance (1) and the life expectancy have been significantly improved, so it can be used extremely effectively as a varistor.

(15) 9-

Claims (1)

[Claims] The main component is zinc oxide, and as subcomponents at least one rare earth element (0.08 to 5.0 atomic percent in total), 0.1 to 10.0 atomic percent of Co/Q, potassium, rubidium. and at least one type of cesium in a total amount of 0
．． 01 to 1.0 atoms, 0.01 to 1.0 atoms of chromium, 5 x 10 to 1 x 10 atoms of boron, and a total amount of at least one of aluminum, gallium, and indium of 1 x lθ to 5 x 10 A patented T-stone voltage non-linear resistor made by adding a certain amount of atoms and firing it.