JPS5919444B2 - Manufacturing method of voltage nonlinear resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a voltage nonlinear resistor with good limiting voltage ratio and temperature characteristics.

Zn made by adding Bi, Co, Mn and other oxides to ZnO
It is well known that O sintered bodies exhibit remarkable non-ohmic properties, and are widely used as varistors for absorbing abnormal voltage surges in electric circuits and stabilizing circuit voltages.

However, varistors with better characteristics, such as smaller limiting voltage ratios at large currents (e.g., the ratio of the voltage VIOA at IOA to the varistor voltage ■, mA), are important factors in surge absorption characteristics. , 15
Products with excellent temperature characteristics that can withstand use at temperatures between 0 and 200°C.
There is an increasing demand in the market for varistor voltages per lam thickness (■1mA/dragon) that are extremely low and for products that can absorb higher energy surges.

It has a significantly superior limiting voltage ratio for the purpose of protecting silicon-controlled flow restrictors SCR, and can be installed near car batteries and used in a temperature range of 150 to 200 degrees Celsius.
One example is one that can be used in low-voltage circuits in automobiles.

Conventionally, Zn has been used as a low voltage varistor for 30 to 50V.
Bi2O3, Co203, Mn02, TiO
2, etc., Bi2O3 and CO□03 to ZnO
, MnO2, BeO, etc., and these can grow ZnO crystal particles to a considerable extent, making it possible to increase the varistor voltage (vtmv4) to 40V or more.

However, these devices had very poor temperature characteristics, and also had poor limiting voltage ratio and surge resistance characteristics.

When 5b203, which has a remarkable effect on improving temperature characteristics and surge resistance characteristics, is added to these systems, Z
Grain growth of nO crystal grains is suppressed, and VtmA/7W7W
increases more than twice as much as when 5b203 was not added.

Therefore, it has been difficult to improve the temperature characteristics and surge resistance without increasing the varistor voltage.

Furthermore, although BeO is not desirable from a safety and health standpoint, as another attempt, we made ZnO fine particles obtained by crushing a ZnO sintered body in advance, sprinkled with additives, and molded them.
A method of firing the varistor to obtain an element with a low varistor voltage was also considered.

However, with this method, even if the ZnO molded body is simply fired at high temperature for a long time, it is not possible to easily obtain a low voltage element.

In this method, the ZnO particles coated with additives are crystalline particles that have been fired at high temperatures and have undergone sufficient sintering. The element did not grow very much, therefore hardly contracted, had extremely large pores, and had a moisture resistance problem.

Since the contact between the ZnO particles is close to a point contact state, the current density at the contact point increases during surge absorption, and the limiting voltage ratio at large currents, which is an important factor in surge absorption properties, increases.

Further, when a high-energy surge that causes heat generation is applied, there is a problem in that the heat generation at the contact point and accompanying melting result in a significant deterioration of characteristics.

On the other hand, ZnO contains Bi, Sb, Co, Mn, and Cr.
ZnO varistors containing sb and oxides such as Ni and Ni are excellent in almost all characteristics as a varistor, such as good temperature characteristics and excellent limiting voltage ratio characteristics.

However, a varistor with this composition has V 1 mA/m?
The problem was that it was not possible to make products with a small H.

The present invention solves the above problems, and in a composition system containing sb, the varistor voltage is as low as 30 to 50V, there are few pores, the limiting voltage ratio (v1oA/■1mA) is small, and the temperature characteristics are excellent. In addition, a new manufacturing method has been realized for voltage nonlinear resistors for overvoltage absorption that can withstand high-energy surges.

Its characteristics include, for example, Zo. Bi, Sb
In a formulation in which an oxide such as Co or Mn or Co and Mn is always added, and the sintered body itself exhibits remarkable non-ohmic properties when mixed, molded, and fired, a portion of the ZnO raw material is Ba.

At least one of the alkaline earth or alkali metal components such as Sr, Ca, Na, etc. is converted into an oxide of 0.
Bi2O3,5i containing 1 to 5 mol%, replaced with ZnO particles (the ZnO particles) obtained by decomposing a sintered body mainly composed of ZnO with water, and not solidly dissolved in the spinel phase.
Additive components other than components such as 02 and a part of the ZnO raw material are replaced with powder of a spinel phase compound prepared by mixing, molding, firing, and powdering using them, and then mixing, molding, and firing. It is in.

The details will be explained below with reference to examples and comparative examples.

〔Example〕

0.5 mol% Ba to 99.5 mol% Zn
After adding CO3 and mixing thoroughly, press molding and
It was baked for 1 to 10 hours at a humidity in the range of 0 to 1400°C.

The obtained sintered body contains Zn with a particle size of approximately 2 to 200 μm.
It has a structure in which O crystal particles are surrounded by a barium oxide layer several hundreds of times thick, and the ZnO particles that are fired at a higher temperature and for a longer time have a larger particle size.

The sintered bodies were boiled in pure water to dissolve the Ba component at the grain boundaries in the water, thereby breaking the sintered bodies and taking out the ZnO crystal particles in the sintered bodies as they were.

The obtained ZnO crystal particles have a radius of approximately 2 to 200μ.
Next, the ZnO shown in column 1 of Table 1 contains at least Bi,
Sb, and Co or Mn 1 or Co and Mn
In a formulation containing an oxide of , a spinel phase compound was prepared.

Table 1, column (2) shows the composition of the spinel phase compound formed in the formulation in column 1.

These fired samples were pulverized to produce powder samples of spinel phase compounds.

Next, in the formulation shown in column I of Table 1, one of the total ZnO raw materials was added without changing the composition of the entire system.
Replace the amount corresponding to 0 mol % with ZnO particles (core ZnO particles) having a size of 2 μm or more and less than 30 μm within the range of 2 to 200 μm taken out by the above method, and add other than B i203 and S b 203 Things and Zn
A part of O was replaced with a spinel phase compound powder sample having the composition shown in column (■) of Table 1, mixed and molded, and then heated at 1300°C.
, baked for 3 hours.

The sintered body thus obtained has a diameter of approximately 141nrI.
An ohmic electrode was provided on this and various characteristics as a surge absorbing element were measured.

The results are shown in the method column of Table 2-1, 2, 3, and 4.

In this method, in the composition corresponding to 1-3 in column 1 of Table 1, the amount of core ZnO particles is kept constant at 10 mol%, and the characteristics when the particle size of the core ZnO particles is changed are as follows.
Shown in the table.

In addition, in this method, in the composition corresponding to 1-3 in column 1 of Table 1, the varistor voltage (Vl mA/urn) and the limiting voltage ratio (VIOA/
The figure shows how the current (1 mA) changes.

As is clear from the figure, the core ZnO particles are 1 to 40 mol%.
The varistor (■1mA/mIIL) is 30V or more and 50V or less within the range of
A) is approximately 1.6 or less.

When it becomes less than 1 mol%, the varistor voltage (■1
mA/mm2) becomes very high and exceeds 40 mol%, not only does the control voltage ratio (1oA/1mA) become very large, but also the varistor voltage (VlmA) increases.

[Comparative example]

The characteristic values for a formulation having the same composition as in the example and consisting of raw material oxides are shown in the column C of Table 2.

In addition, the characteristic values in the case where the proportion of the ZnO raw material corresponding to 10 mol% of the total blended composition is replaced with core ZnO particles in the formulation shown in column 1 of Table 1, which has the same composition as the example, are shown in Table 2. It is shown in the column b.

Next, using the formulation 1 in Table 1 column
Unlike method a, in which the composition of the spinel phase compound is changed by replacing O particles with additives depending on the formulation, the composition of the spinel phase is kept constant, and the total amount of 5b203 in each formulation in column Adjust the amount of the compound added and add it so that it is included in the spinel phase, and further add other additive components that are insufficient just by adding the spinel phase compound, so that the entire lamp has the same composition as in column ■. The characteristic values in this case are shown in the d-method column of Table 2.

In this case, the spinel phase compound is Zn0
6.98 mol, 5b01.17 mol, Co 2030.
44 mol, Mn 023 0.44 mol, Ni 00.89 mol 1. Cr203
0. A composition having a composition of 9 moles of O was used.

Further, Table 4 shows the characteristics of the device according to the present invention and the conventional product.

In Tables 2, 3, and 4, surge breakdown energy is the energy applied to an element when it is destroyed by a surge, expressed with respect to unit varistor voltage. A Joule element means that if 1rnA is set to 16V, it will be destroyed by a surge energy of 16 Joules.

In addition, the humidity charge rate is 1
Voltage VtO generated across the element when 0 μA is applied
It is the value obtained by dividing □A (150°C) by the voltage □1mA (RT) generated across the device when 1mA flows at room temperature.

This value is a guide to the quality of both the humidity and voltage nonlinearity characteristics of the varistor, and the larger the value, the better these characteristics. suitable for absorption.

As is clear from the comparison of methods d and C in Table 2, method d has the effect of greatly reducing the varistor voltage of 1 mA/mm with the core ZnO particles for any composition containing ZnO as the main component. shows.

This is considered to be because the added core ZnO particles absorb the fine particles of Zoo and grow even larger, so that a sintered body with good sinterability is formed.

Generally, in zinc oxide varistors made by adding Bi2O3 and other additives to ZnO, the inclusion of 5b203 improves the temperature characteristics and surge resistance characteristics, but the s
Since the solid phase reaction involving the b-acid component is related to the phenomenon of suppressing the growth of ZnO grains, it is difficult to reduce the voltage.

However, when core ZnO particles are added, Zn due to the sb acid component
Since the grain growth rate of the core ZnO particles is greater than the grain growth suppressing effect of nO, it is possible to achieve a lower voltage and to create an element with much better temperature characteristics than a system that does not contain the sb acid component. I can do it.

On the other hand, as shown in the d method column of Table 2, sb
If a substance whose main component is a spinel phase containing an acid component is prepared in advance and added in place of 5b203,
Since the solid solution spinel phase compound containing Sb is stable against B1□03, the solid phase reaction involving the sb acid component, which is related to the grain growth suppressing effect of ZnO, can be almost avoided during the heating process, and the The grain growth rate of the core ZnO particles increases accordingly.

Therefore, compared to when adding 5b203, the grain growth rate is higher, and the sinterability is significantly increased, such as fewer pores, and the varistor voltage (■ 1 mA/mm) reduction in the limiting voltage ratio (Vl OA / 1 mA), improved surge characteristics, and improved temperature characteristics.

In addition to this, the yield of the product was significantly improved.

In this way, by using the d method, which is an improvement on the b method, it is possible to manufacture an element with characteristics that can be put to practical use.

In this case, by including and adding the sb acid component to the spinel phase compound, the solid phase reaction involving Sb formation can be controlled and the grain growth inhibiting effect of ZnO can be suppressed.

However, in this method, although the 5b203 component is not the only component, other additive components that exhibit the effect of suppressing the grain growth of ZnO are added, so that the effect of suppressing the growth of ZnO grains by these components also works.

Therefore, if the effect of inhibiting the growth of ZnO grains due to these components can be suppressed, the pressure can be lowered even further, and the particle size distribution of ZnO particles in the sintered body becomes uniform, thereby further improving the properties.

In the present invention, by solving this problem, the characteristics are greatly improved.

That is, as shown in the example, Bi and S are added to ZnO.
When oxides such as b and Co or Mn or Co and Mn are added, mixed, molded, and fired, part of the Zn, 0JJj material is replaced with core ZnO particles in a formulation in which the sintered body itself exhibits remarkable non-ohmic properties. , B 120
When additives other than 3 and SiO□ and a portion of ZnO are replaced with spinel phase compound powder formed from them, mixed, molded, and fired, as shown in the method a column of Table 2 1 to 4, it is possible to obtain a powder with low pressure. It is possible to fabricate a device that can be made into a material with a high temperature and has excellent other properties.

This improves the sinterability, such as the uniformity of the microstructure of the sintered body and the reduction of porosity, which was achieved in the d method, by controlling the effect of suppressing the growth of ZnO particles by the additive components of 5b203. This is because it has become possible to further improve the characteristics by reducing the voltage (■1mAZ dragon), limiting voltage ratio (■1oA/v1mA), improving surge characteristics, and improving humidity characteristics at 5 degrees Celsius.

In addition to this, the yield of the product was significantly improved.

Table 3 shows the firing conditions of 130% in method a of the present invention.
The temperature is kept constant at 0°C for 3 hours, and the core Z to be replaced corresponds to 10 mol% of the total composition of the ZnO raw material.
The figure shows changes in characteristics of nO particles when the particle size range is changed.

By setting the particle size of the core ZnO particles to 2 μm or more and less than 30 μm, the varistor voltage (V
+ mA/mvt) is 30V to 50V,
Varistors with excellent limiting voltage ratio and humidity characteristics can be manufactured.

When the core ZnO particle is 30 pm or more, V1mA/m
m becomes less than 30V.

Regarding non-ohmic properties, in this method, components such as Co and Mn that contribute to improving non-ohmic properties diffuse from the spinel phase into other coexisting phases at high temperatures.
, c, and b.

Table 4 shows typical characteristics of conventional low voltage varistors manufactured by adding oxides of Bi, Co, Mn and Ti to ZnO and characteristic values of the varistor according to the present invention. .

It is shown that the voltage nonlinear resistor according to the present invention is significantly superior in all characteristics.

In the Examples and Comparative Examples shown in Tables 2, 3, and 4, core ZnO particles prepared by adding B a C03 to ZnO are used. In addition, Sr and Ca are added to ZnO.

It can also be produced by using water to decompose a sintered body to which alkaline earth or alkali metal components such as Na, Li, or Cs are added, and the same effect can be obtained by using these core ZnO particles. be able to.

In addition, although pure core ZnO particles are used in these examples, they do not necessarily have to be pure, and as long as they are components that can be mixed with ZnO without impairing the varistor effect, they can be concentrically formed in the ZnO crystal in advance. You can leave it.

B12O3゜5b203. to ZnO. Co2032Mn0
In the zinc oxide varistor to which □, NIo, cr2o3, etc. are added, Co, Mn, Ni components, etc. are dissolved in the ZnO crystal phase.

These components that can be solid-dissolved in ZnO are added to ZnO together with Ba component.
Even if it is added to nO and fired, a sintered body similar to that obtained when only Ba component is added is obtained, and by decomposing this with water, Co and Mn are added to ZnO.

Core ZnO particles containing Ni in solid solution can be taken out.

This core ZnO particle The pure core Z used in the examples and comparative examples
Even if it is used in place of nO particles, there is essentially no difference in the properties, and in fact, there is a tendency for the properties to become better.

In the production of core ZnO particles, a method of boiling in pure water was used in the examples.

The purpose of this is to increase the rate of fermentation and decomposition of the grain boundary layer into water and promote the decomposition of the sintered body, and boiling itself is not an essential condition for removing the core ZnO particles.

In addition, in the above examples and comparative examples, oxides such as Bi, Sb and Co or Mn or Co and Mn are added to ZnO as the basic composition, and Cr, N
Although oxides such as i, Si, etc. are added, Cr, Ni,
It goes without saying that the same effect can be obtained by containing components other than oxides such as Si that are effective in improving voltage nonlinearity characteristics and other varistor characteristics.

As explained above, the present invention is characterized by the phenomenon that when core ZnO particles are added to a mixture of ZnO and at least Bi2O3 and fired, the core ZnO particles grow significantly, and
In a formulation in which at least B12O3 and 5b203 are added to O, and oxides such as Co2M"n, Ni-\)C[, etc. are added, sb acid has a remarkable effect on improving temperature characteristics and surge resistance characteristics. When added as a component in the spinel phase compound, the effect of suppressing grain growth of ZnO by the sb acid component is suppressed, and all additives other than the sb component that are solid-dissolved in the spinel phase are included in the spinel phase. This method takes advantage of the fact that when these additives are added, the effect of inhibiting ZnO grain growth by those additives is suppressed.

The present invention provides an element for absorbing high-energy surges in low-voltage circuits, which can be used not only at room temperature but also at
It has become possible to manufacture voltage nonlinear resistors with high yield as elements that can be used even in the high temperature range of 00°C.

Moreover, using the technology according to the present invention, Bi, Sb and ZnO can be added to ZnO.
In a formulation that always contains oxides such as Co or Mn or CO and Mn, the amount and particle size of the core ZnO particles to replace a part of the ZnO raw material, the particle size of the sb acid component spinel phase compound, the firing conditions of the element, etc. By changing the varistor voltage, voltage nonlinear resistors with various varistor voltages and excellent humidity characteristics, limiting voltage ratio characteristics, etc. can be easily obtained.

[Brief explanation of the drawing]

The figure shows the replacement amount of core ZnO particles with respect to the ZnO raw material, varistor voltage (VomA), and limiting voltage ratio (V10A/v1
mA).

Claims (1)

[Claims] I In a formulation that contains ZnO as the main component and contains at least additional components of Bi, Sb, and Co or Mn, and the sintered body itself exhibits non-ohmic properties when fired, it accounts for 1 to 40 mol% of the total composition of the ZnO raw material. The corresponding amount is 2
``replaced with ZnO particles having a particle size of µm or more and less than 30 µm, and use them to mix, mold, calcinate, and then pulverize the component that solidly dissolves in the spinel phase and a part of the ZnO raw material. A method for manufacturing a voltage nonlinear resistor, which comprises replacing the powder with a powder sample of a spinel phase compound prepared by mixing, molding, and firing.