JPS60105202A - 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 constructed from sintered oxides of zinc, niobium, and manganese.

Conventionally, silicon carbide (
SiC varistors, which are formed by molding and sintering SiC varistors whose main component is 5ite) with the addition of a ceramic binder, are widely used in practice. Further, in order to improve the characteristics of this SiC varistor, methods such as adding various substances to the ceramic binder9 and changing the firing atmosphere have been tried. However, Si
The characteristic of C varistor is that it utilizes the voltage dependence of contact resistance based on particle contact between SiG particles.
Considering the size of SiC particles, there is a limit to how thin the varistor element can be made to be, and SiG itself is an extremely hard material and requires high firing temperatures, making it difficult to freely control its properties. However, there was a limit to the improvement of the characteristics.

The voltage-current jII characteristic of a general K varistor is expressed by the following relational expression.

α! =Cv In the formula, the symbol represents current, V represents voltage, and G and α are constants. In particular, α is an index called a nonlinear coefficient, and the larger α is, the better the nonlinear characteristics are. C is a constant determined by the material, etc., but in practice it is a constant current, for example 1 m
It is expressed as the voltage (referred to as varistor voltage) V+ between the varistor element terminals when a current flows through the varistor element.

In the SiC varistor that has been put into practical use for a long time, α is 3.
6. In addition, in order to lower the varistor voltage V, it has been done to reduce the thickness of the element or to add a conductive substance such as carbon to the ceramic binder and sinter it. . However, with these methods, the mechanical strength of the sintered body is weak9, and when a conductive substance is added, the nonlinear coefficient α becomes even smaller, which causes problems in terms of properties as a varistor.

On the other hand, bidirectional voltage regulator diodes can be manufactured with a relatively low Zener voltage and have a large nonlinear coefficient α, so when used in low voltage circuits such as electronic devices using semiconductor components. However, since the surge resistance is approximately proportional to the volume of the element, it is difficult to absorb excessive surge energy. My father, a recently developed varistor is a sintered lead oxide varistor, which uses zinc oxide (ZnO) as a product and oxides of several substances such as bismuth, manganese, cobalt, and antimony as subcomponents. There is a body. However, although this zinc oxide varistor has the advantage of having a very large nonlinear coefficient α, it also contains substances such as bismuth that evaporate extremely easily at the high temperatures required for firing, so this may evaporate during the firing process. This has the drawback that it is difficult to mass-produce varistors with good and uniform characteristics at a high yield because it causes variations in varistor characteristics or the sintered bodies fuse together. In addition, since zinc oxide varistors generally have a relatively high varistor voltage (100V or more), it is necessary to reduce the thickness of the element in order to lower the varistor voltage, but as mentioned above, reducing the thickness of the element reduces the surge resistance. There is a problem in that the voltage decreases, making it difficult to respond to the recent trend toward lower voltages in electronic devices, devices, and the like.

The present invention was made by focusing on the above-mentioned drawbacks of conventional varistors, and while taking advantage of the essential advantage of zinc oxide varistors, which have a large nonlinear coefficient α, the present invention contains materials with drawbacks such as bismuth. It is an object of the present invention to provide a varistor that has excellent electrical characteristics without causing problems and can be mass-produced with high yield and reproducibility.

That is, the present invention uses zinc oxide (ZnO) as a main component, and niobium is added to the zinc oxide (ZnO), which is converted into niobium pentoxide (Nb, O,).
05-10 mob%, manganese to manganese dioxide (M
This is a voltage non-linear resistor made of a sintered fc sintered body containing 0.1 to 10 rnot% in terms of nO2).

The method for manufacturing the sintered body constituting the present invention will be described below based on Examples.

First, add niobium oxide to zinc oxide (ZnO) at a concentration of 0.05 to IDmot% in terms of dioff pentoxide (Nb205).
, manganese oxide to manganese dioxide (Mn02) K
ZnO is added in a range of 0.1 to 10 moz% by
The sum of +Nb2O, +Mn0v is 100 mot%
Accurately weigh the raw material oxide so that Next, these mixtures are sufficiently wet-pulverized and mixed using a pulverizing mixer such as a ball mill, followed by dehydration and drying. Add this dry mixture to approx.
After calcining at 00 to 950℃, polyvinyl alcohol (
A granulated powder is prepared by adding an organic binder such as Pvm). The raw materials used at this time include hydroxide, sulfide,
Compounds other than oxides can be used as long as they are converted into oxides by heating, such as carbides and carbonates.

Pressure molding is performed at a pressure of 15 WKm to form a disc with a diameter of 15 WKm and a thickness of about 11.5 W. This molded body is 1000~1400
The sintered body is heated in air at ℃ for 1 to 4 hours.

Next, a metal film of silver, copper, Niracle, aluminum or the like is formed on both sides of this sintered body to serve as a metal layer.

This metal film is usually formed by applying and baking silver paint, or by methods such as vapor deposition, sputtering, and plating.

The metal oxide varistor of the present invention is manufactured as described above, but since the sintered body of this varistor itself has non-linear characteristics, the varistor voltage and non-linear characteristics can be adjusted by changing the raw material composition and firing conditions. It is possible to control the linearity coefficient over a wide range. Table 1 shows that Zn
The values of the varistor voltage v1 and the nonlinear coefficient α of varistors manufactured with various blending ratios of O1Nb, O, and MnO□ are shown.

Table 1 Also, Figure 1 shows the results in Table 1, with the MnO blending ratio constant at 1.0 m04% and Nl: +20. Figure 2 is a graph plotting the varistor voltage v1 and the nonlinear coefficient α when the mixture ratio of is varied. Figure 2 shows the graph when the mixture ratio of Nb2O is constant at 1.0 m04% and the mixture ratio of MnO2 is varied. It is a graph plotting the varistor voltage V and the value of the nonlinear coefficient α when In addition, the varistor voltage vl is the voltage across the varistor when a current of 1 m is passed through the varistor, and the nonlinear coefficient α is calculated from the measured current of 1 mA and the varistor voltage when 10 ff is passed through the varistor. It is a value.

As is clear from Figure 1, the blending ratio of Nb and O is 0.0.
When it is less than 5 mot% and exceeds 1 o m04%, the varistor voltage v1 becomes low, but the nonlinear coefficient α also becomes small accordingly, and especially when it exceeds 10111 Ot coefficient, it tends to decrease rapidly. The electrical characteristics are comparable to those of the 5iC varistor. Also, the second
As is clear from the figure, the blending ratio of MnO□ is 0.1 m
It has been found that the same results as above can be obtained when the content is less than 0.01% and greater than 10.04%.

Therefore, for a varistor having electrical characteristics with a low varistor voltage v1 and a large nonlinear coefficient α, the amount of niobium compound added to ZnO is 0.05 to 10 m04 in terms of Nb and O. It can be seen that the amount of manganese compound is within the range of 0.1 to 10 m1t in terms of MnO. Looking at Table 1, it can be seen that the samples excluding the compounding ratio of Y1 are suitable for the material composition of the varistor of the present invention, and the varistor has a low varistor voltage V and excellent electrical characteristics with a large nonlinear coefficient α. is obtained.

As explained above, the metal oxide varistor of the present invention has characteristics such as a lower varistor voltage and a larger nonlinear coefficient than conventional varistors, and also does not contain components such as bismuth oxide that easily evaporates during firing. Since there is almost no change in composition due to firing, it has the advantage that varistors that are uniform and have excellent characteristics can be mass-produced with good reproducibility and yield. In addition, since the varistor of the present invention is made of a ceramic body, it has a higher discharge withstand capacity than conventional low-voltage silicon varistors, and therefore effectively absorbs surges of external energy such as lightning and protects electronic components in electronic devices. It also has the ability to protect.

[Brief explanation of the drawing]

FIG. 1 shows a varistor with a material composition of ZnO, Nb2O, and MnO2, in which MnO7 is added to 1. Om04%
Figure 2 is a graph showing the values of the varistor voltage v1 and the nonlinear coefficient α when the blending ratio of Nb and O is changed, assuming that the mixture ratio of Nb and O is constant.
2O, 1. It is a graph showing the varistor voltage V of the varistor and the value of the nonlinear coefficient α when the blending ratio of MnO is changed while Om0 is constant at 4%.

Claims (1)

[Claims] Zinc oxide (ZnO) is the main component, and niobium is converted into niobium pentoxide (Nb20.).
A voltage nonlinear resistor made of a sintered body containing 0.1 to 1 omoz% of manganese in terms of manganese dioxide (MnO2).