JPH0812809B2 - Method of manufacturing voltage non-linear resistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a voltage nonlinear resistor containing zinc oxide as a main component.

(Prior Art) A voltage non-linear resistor is generally called a varistor, which is usually an insulator and has a property of acting as a conductor when an excessive voltage is applied, and has a voltage stabilizing element, a surge absorber,
Widely used for arresters, etc.

A zinc oxide varistor recently developed as such a non-linear resistor has, for example, zinc oxide as a main component, and a predetermined amount of bismuth oxide, cobalt oxide, manganese oxide,
Additives such as antimony oxide, chromium oxide, and nickel oxide are added and mixed, and the mixture is pressure-molded and then fired,
Manufactured through the steps of attaching electrodes to the obtained sintered body,
Its non-linear characteristic was extremely excellent.

(Problems to be Solved by the Invention) However, in such a conventional method of manufacturing a non-linear resistor, the crystal system and particle size of the raw material in mass production of the resistor are not specified, and the raw material in various states is not specified. Was used.

For example, nickel oxide has a cubic crystal system and an average particle size of
Those having a particle size of 0.4 to 2.2 μm and manganese dioxide having an orthorhombic crystal system and an average particle size of 1 to 25 μm were used.

Therefore, in the conventional method for manufacturing a non-linear resistor, when the non-linear resistor is industrially mass-produced, a non-linear characteristic is deteriorated or a variation in the characteristic occurs. Especially, variation and surge of the characteristic in a minute current region occur. There is a problem that the variation rate of the minute current region after withstanding is large, and the quality such as the charging life characteristic and the minute current characteristic is not stable.

An object of the present invention is a voltage nonlinear resistor capable of reducing the variation in the voltage and current characteristics in the minute current region where the resistance current is 1 mA or less and reducing the deterioration in the minute current region after the surge resistance. Is to obtain a manufacturing method of.

(Means for Solving the Problem) In order to achieve this object, the method for producing a voltage non-linear resistor of the present invention comprises zinc oxide as a main component, to which an additive containing at least nickel oxide is added and mixed, In the method for manufacturing a voltage nonlinear resistor in which this mixture is molded and fired, the crystal system of the nickel oxide before mixing is made into a hexagonal crystal,
The feature is that the average particle size is 1.2 μm or less.

Further, the method for producing a voltage non-linear resistor according to the present invention comprises zinc oxide as a main component, an additive containing at least manganese dioxide is added to and mixed with the zinc oxide, and the mixture is molded and then fired. In the production method, the crystal system of manganese dioxide before mixing is tetragonal and the average particle size is 12 μm or less.

Further, the method for producing a voltage non-linear resistor of the present invention is a voltage non-linear resistor in which zinc oxide is a main component, an additive containing at least nickel oxide and manganese dioxide is added and mixed, and the mixture is molded and then fired. In the method for manufacturing the resistor, the crystal system of nickel oxide before mixing is hexagonal,
The average particle size is 1.2 μm or less, and the crystal system of manganese dioxide before mixing is tetragonal, and the average particle size is 12 μm.
It is characterized in that it is set to m or less.

(Operation) In the method for producing a voltage non-linear resistor of the present invention, by specifying the crystal system and the average particle size of the nickel oxide raw material, V _1mA which is the voltage across both ends when a direct current of 1 mA is applied and the non-linear index α Variations within lots and between lots are reduced, quality in mass production is stable, and variations in the rate of change of V _1mA before and after the application of surge voltage can be reduced.

Further, in the present invention, the variation of the V _1mA change rate can be improved by specifying the crystal system and the average particle size of the manganese dioxide raw material, but in this case, the variation of V _1mA and α can be particularly reduced.

(Example) Next, the Example of the manufacturing method of the voltage nonlinear resistor of this invention is described.

First, a zinc oxide raw material adjusted to a predetermined particle size and Bi ₂ O ₃ , Co ₃ O ₄ , MnO ₂ , Sb ₂ O ₃ , Cr ₂ O ₃ , SiO ₂ , N adjusted to a predetermined particle size.
A predetermined amount of an additive such as iO is mixed. At this time, in the first embodiment of the present invention, the crystal system of NiO before mixing is hexagonal and the average particle size is 1.2 μm or less. In the second embodiment of the present invention, the crystal of MnO ₂ before mixing is made. The system is tetragonal and the average grain size is 12 μm or less. In the third embodiment of the present invention, the NiO crystal system before mixing is hexagonal and the average grain size is
In addition to 1.2 μm or less, the crystal system of manganese dioxide before mixing is tetragonal, and the average particle size is 12 μm or less.

A predetermined amount of an aqueous polyvinyl alcohol solution or the like is added to these raw material powders, preferably mixed by a disper mill, and then preferably granulated by a spray dryer to obtain a granulated product. After granulation, it is molded into a predetermined shape under a molding pressure of 800 to 1000 kg / cm ² . The temperature rise and fall rate of the molded body is 50
Preliminary calcination is performed at a temperature of ~ 70 ° C / hr at 800-1000 ° C and a holding time of 1-5 hours.

Before calcination, the molded body should be heated / cooled at a rate of 10-100 ° C / hr.
It is preferable to keep the binder at 400 to 600 ° C. for 1 to 10 hours to scatter and remove the binder.

Next, a high resistance layer is formed on the side surface of the calcined calcined body. For this, a mixture paste for side surface high resistance layer, which is obtained by adding ethyl cellulose, butyl carbitol, n-butyl acetate or the like as an organic binder to a predetermined amount of Bi ₂ O ₃ , Sb ₂ O ₃ , SiO ₂ or the like, is added to 60 to 300 μm. Apply to the side of the calcined body to the thickness of. Next, this is main-baked under the conditions of a temperature raising / lowering rate of 40 to 60 ° C / hr, 1000 to 1300 ° C, preferably 1100 to 1250 ° C for 3 to 7 hours. A glass paste prepared by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder is applied on the above-mentioned insulating coating layer to a thickness of 100 to 300 µm, and the temperature rising / falling rate is 100 ~ in air. 200 ° C / hr, 400-6
It is preferable to form the glass layer by heat-treating at a temperature of 00 ° C. for 0.5 to 2 hours.

After that, both end surfaces of the obtained voltage nonlinear resistor are
Polish with water or oil using a # 400-2000 equivalent abrasive such as ₂ O ₃ or diamond. Next, after cleaning the polished surface, electrodes are provided, for example, by spraying, on the polished both end surfaces by, for example, aluminum or the like to obtain a voltage non-linear resistor.

Next, a comparative experiment example of the voltage nonlinear resistor manufactured by the manufacturing method of the present invention and the voltage nonlinear resistor manufactured by the manufacturing method outside the scope of the invention will be described.

Experimental Example 1 In Experimental Example 1, the crystal system of the additive was Bi, which was monoclinic.
₂ O ₃ , cubic Sb ₂ O ₃ , cubic Co ₃ O ₄ , hexagonal C
As r ₂ O ₃ , amorphous SiO ₂ , orthorhombic MnO ₂ , and NiO, the cubic system of the comparative example and the hexagonal system of the present invention were used, and the crystal grain size was changed. Is 0.3, 0.7, 1.2, 1.5 μm, 5 types not specified are prepared, diameter 47 mm, height 22.5 mm, V
Manufacture a resistor of _1mA = 200V / mm,
The current characteristics were investigated. The results are shown in Table 1.

From the results of Table 1, in the manufacturing method of the first embodiment, NiO
By making the crystal system of the raw material hexagonal, the standard deviation within the lot and between lots of V _1mA and the nonlinear index α becomes smaller than that of the cubic system of the comparative example, and especially the V _1mA before and after the surge application. It can be seen that the standard deviation of the rate of change becomes small.

In the comparison of crystal grain sizes, the standard deviations of V _1mA and the nonlinear index α are not very different at 0.3, 0.7, and 1.2 μm, but it is found that the values become remarkably high when not specified.

The standard deviation of the rate of change of V _1mA after the application of surge is 0.
The values are relatively small in the case of 3,0.7 and 1.2 μm, but they are about twice the value in the case of 1.5 μm, and even more about that value when not specified. Recognize.

Experimental Example 2 In Experimental Example 2, in the additive, the crystal system was monoclinic Bi.
₂ O ₃ , cubic Sb ₂ O ₃ , cubic Co ₃ O ₄ , hexagonal C
Using r ₂ O ₃ , amorphous SiO ₂ , cubic NiO, and MnO ₂ of the orthorhombic system of the comparative example and the tetragonal system of the present invention, and the grain size , 3,7,12,15μm, 5 types not specified, diameter 47mm, height 22.5mm, V _1mA = 200V
A / mm resistor was manufactured, and the voltage and current characteristics in the minute current region were investigated.

 The results are shown in Table 2.

From the results of Table 2, in the manufacturing method of the second embodiment, Mn
Since the crystal system of the O ₂ raw material is a tetragonal system, the standard deviation of the V _1mA change rate is smaller than that of the orthorhombic system of the comparative example, and particularly the standard deviation of V _1mA and α is small. I understand.

In comparing the crystal grain sizes, the standard deviation of V _1mA and the nonlinear index α is a relatively small value in the case of 3,7,12 μm, but is a value about twice that in the case of 15 μm. Therefore, it can be seen that the value will be about twice that if not specified.

Also, the standard deviation of the rate of change of V _1mA after applying a surge is 3,
In the case of 7,12 μm, the value is relatively small, but 15 μm,
Also, it can be seen that the values are remarkably high when not specified.

Experimental Example 3 In Experimental Example 3, in the additive, the crystal system was monoclinic Bi.
₂ O ₃ , cubic Sb ₂ O ₃ , cubic Co ₃ O ₄ , hexagonal C
As the crystal system of r ₂ O ₃ , amorphous SiO ₂ and NiO, the cubic system of the comparative example, the hexagonal system of the present invention, and the MnO ₂
Using the orthorhombic system of Comparative Example and the tetragonal system of the present invention, the crystal grain size of NiO is 0.3, 0.7,
1.2, 1.5 μm, 5 types not specified, the grain size of MnO ₂ is
3,7,12,15μm, 5 types not specified, diameter 47mm,
A resistor with a height of 22.5 mm and V _1mA = 200 V / mm was manufactured, and the voltage and current characteristics in the minute current region were investigated. The results are shown in Table 3.

From the results of Table 3, in the manufacturing method of the third embodiment, Ni
By changing the crystal system of the O raw material to the hexagonal system and the crystal system of the MnO ₂ raw material to the tetragonal system, the change of V _1mA , the nonlinear index α, and the V _1mA after the surge application from the comparative example It can be seen that the variation in the rate can be further reduced.

In the comparison of the crystal grain sizes, the same tendency as in the above-mentioned first and second examples was shown, and the crystal grain size of NiO was
When the crystal grain size of MnO ₂ is 1.2 μm or less, and when the crystal grain size of MnO ₂ is 12 μm or less, the standard deviation values are relatively small for V _1mA , nonlinear index α, and V _1mA change rate after surge application, and there are few variations in characteristics. It was confirmed.

(Effects of the Invention) As described in detail above, the method for producing a voltage non-linear resistor of the present invention is characterized by specifying the crystal system and the average particle size of the nickel oxide raw material or the manganese dioxide raw material, and Direct current by specifying the system and average particle size
V _1mA is a voltage across that which causes 1 mA, nonlinear index alpha,
Further, it is possible to reduce the variation in the rate of change of V _1mA after application of a surge, stabilize the quality in mass production, and provide a voltage non-linear resistor having high safety and durability.

It was also confirmed that other characteristics such as the life span, the withstand voltage of lightning surge discharge, the withstand voltage of switching surge discharge, and the limiting voltage were improved.

Claims (3)

[Claims] 1. A method for producing a voltage non-linear resistor, which comprises zinc oxide as a main component, an additive containing at least nickel oxide is added to and mixed with the mixture, and the mixture is molded and fired. Hexagonal crystal system,
A method of manufacturing a voltage non-linear resistor characterized in that the average particle size is 1.2 μm or less. 2. A method for producing a voltage non-linear resistor, which comprises zinc oxide as a main component, and an additive containing at least manganese dioxide, which is added and mixed, and which is molded and fired. Is a tetragonal crystal system and the average grain size is 12 μm or less. 3. A method for producing a voltage non-linear resistor, which comprises zinc oxide as a main component, and an additive containing at least nickel oxide and manganese dioxide, which is added and mixed, and the mixture is molded and fired, before the mixing. The nickel oxide crystal system having a hexagonal crystal structure and an average particle size of 1.2 μm or less, and the manganese dioxide crystal system before mixing having a tetragonal crystal system having an average particle size of 12 μm or less are used. Manufacturing method of non-linear resistor.