JPS60107802A - Voltage nonlinear resistance element - 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 [Field of the Invention] The present invention relates to a voltage non-linear resistor, and more particularly to a voltage non-linear resistor containing zinc oxide (ZnO) as a main component and used as an overvoltage protection element.

[Prior art and its problems]

Conventionally, varistors containing silicon carbide (SiC), selenium (be)t silicon (Si), or ZnO as a main component have been used for the purpose of overvoltage protection of electronic devices and electric value devices. Among them, varistors whose main component is ZnO generally have a low limiting voltage and a large voltage nonlinearity index. For this reason, it is suitable for protecting against overvoltage in equipment made of devices with low overcurrent resistance such as semiconductor elements, so varistors made of SJC have been widely used for nine generations.

In addition, ZnO is the main component, and rare earth elements, cobalt (Co), magnesium (Mg), calcium (
at least one of potassium (K), potassium (K),
A voltage nonlinear resistor manufactured by adding at least 1'4gi of rubidium (Rb) and cesium (Cs) and chromium (CCr)' in the form of an element or compound and firing it has excellent voltage nonlinearity. It is known that there are However, this voltage nonlinear resistor has drawbacks such as a somewhat low long-wave tail surge resistance and a low energized life performance, which poses problems in miniaturizing the device.

[Purpose of the invention]

The present invention has investigated the destruction mechanism of elements due to long wave tail surges, and has achieved further prevention of destruction, and at the same time has improved the energized life characteristics. The purpose is to provide an excellent voltage nonlinear resistor.

[Key points of the invention]

Here, the present inventor has proposed that the main component is ZnO, and the subcomponents are at least one of rare earth a7c=, C01Mg, Ca, and at least one of K, Cs, and Rb.
(In the voltage nonlinear resistor of IE button technology, when a large surge of υ1t with a long wave tail is applied, current concentration due to electric field concentration occurs at the outer periphery of the electrode provided on the element surface. We have discovered that the concentration of current that is generated and exerts force causes the destruction of the element.

It was also confirmed that there were local inhomogeneities inside the resistor, and it was found that current concentration in these inhomogeneities occurred during reverse DC current, resulting in 71d2 deterioration.

As we proceeded with our research to solve these problems, we found that borosilicate glass and aluminum (A
By adding a small amount (or one kind) of I), 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. discovered that it is possible to improve the long-wave tail surge withstand capability.On the other hand, the inhomogeneity inside the resistor also disappears, resulting in a voltage nonlinear resistor with a significantly improved energized life. , completed the invention.

Therefore, according to the present invention, a conventional voltage nonlinear resistor containing ZnO as a main component and containing a rare earth element, at least one of CO, Mg, and Ca, at least one of K, Ilb, and Cs, and Cr as a subcomponent. In addition, borosilicate glass oxide 6, Al, and Ga are further added as subcomponents.

Provided is a voltage nonlinear resistor characterized in that at least one type of In is added.

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 in a high τ product in an oxygen-containing atmosphere.

Usually, the additive component is gold, which is added in the form of tetraoxide, but compounds that can become oxides during the firing process, such as carbonates, hydroxides, fluorides, and their solutions, can also be used. It is used in the form of a single element (it can also be converted into an oxide 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 open 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.

Further, 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 product for practical use.

[Embodiments of the invention]

Examples are now presented to further illustrate the invention.

Example ZnO powder contains Pr6O11, co304e Mgo,
K2co3. Cr2O3゜A1203 powder was added in an amount corresponding to the predetermined atomic percent listed in Table 2 below, and borosilicate glass A having the composition shown in Table 1 was added in a predetermined weight percent and thoroughly mixed. Calcining was performed at 500 to 1000°C for several hours.

Next, the calcined product was thoroughly crushed, a binder was added, and it was pressure-molded into a disc shape with a diameter of 17 wR, and the shape was 1100'U~1.
A sintered body was obtained by firing at 400° C. for 1 hour in open air. The sintered body thus obtained was polished into a sample with a thickness of 2 terms, electrodes were baked on both sides of the sample, an element was made, and its +li gas characteristics were evaluated.

The electrical characteristics are as follows:
The voltage between the electrodes when a current of V+ mA, l mA is applied
~] Non-linear index α at OmA As a long wave tail surge current withstand capacity, a rectangular forming current of 100A in 2 m direction was applied once and the change in VlmA before and after was measured. In addition, as the life characteristics of the applied voltage, we measured the change in the electrode 1g1 voltage v1μA when a DC current of 20 mA was applied for 5 minutes and a current of 1μA was passed before and after.

The nonlinear index α is obtained by approximating the change in the element current I with respect to the voltage V by the following equation.

I = (V/C)'' where C is the voltage per unit thickness of the element when the current density is i 1171/4''. Table 2 shows the measurement results of electrical characteristics when the composition of the voltage nonlinear resistor was varied. The compositions shown in Table 2 are expressed in atomic % calculated from the ratio of the number of atoms of the added potassium element to the total number of atoms of each component metal element in the raw materials. In addition, the amount of Pr, Co, and Mg in the samples shown in Table 2 is shown in Table 1, Table 2, Table 2 (continued)
*K.

This corresponds to the conventional sintered body manufactured by adding only Cr, and its long wave tail surge current characteristics are -7.54%, the energized life characteristics are -20.1%, and the nonlinearity index is 41. The object of the present invention is to have good long wave tail surge current withstand capability, i.e. -75,4
%, closer to 0%, improved charging life characteristics, immediate F-)
-20. Samples closer to 0% than 1% are m3~ from Table 1.
Part 6. Na9~12.1m15~N117. m2
0~HI122, -24~Ta26, m29
~ten 32, N133~*35. Among these, samples m 32 and m 35 have a low nonlinear index α and are not suitable for practical use. Therefore, Pr is 0808 to 5.0 at%, CO is 0.1 to 10 at%, and Mg is 0.01 to 5.0 at%.
0 at%, K is 0.01 to 1.0 at%, Cr is 0.0
1 to 1.0 at%, AI is l×10 to 5×10 at%
It is necessary to add within this range.

As is clear from Table 2, Pr is a subcomponent.

Yarns containing Co, Mg, and K contain borosilicate glass and A
By adding I, the long wave tail surge current withstand capacity and the charging life characteristics are significantly improved. In addition, ZnO NiP r
, CO, Mg + K + borosilicate glass, AI
This can only be achieved when the two coexist. If these subcomponents are added alone, voltage nonlinearity will be extremely poor and only baohmic characteristics will be obtained, making it impossible to put them to practical use.

In addition, borosilicate glasses having compositions other than A shown in Table 1 also showed improved long-wave tail surge resistance and charging life characteristics as in the case of A. This is shown in Table 3.

In Tables 2 and 3, only Pr is exemplified as a rare earth element, but rare earth elements other than Pr or two or more types of rare earth elements may also be used for borosilicate glass and A.
It was found that the addition of I significantly improved the long-wave tail surge current withstand capacity and charge life characteristics without losing the excellent nonlinearity as in the case of Pr alone1. It is shown in Table 4.

Also, Caj! instead of MgO! Similar effects can be obtained when ig and Ca coexist, when Rb, Cs and these elements coexist instead of K, or when Ga and In are used instead of At. These are shown in Tables 5 to 7.

Note that the amount of borosilicate glass added is from 5 X 10-'ffi amount% to lXl0-2 as shown in the examples.
It is desirable that the amount is in the range of % by weight, and if it is added in excess of this range, the non-linear index will decrease, so it is not practical.Table 4, Table 5, Table 5, Table 7. As mentioned above, zinc oxide is the main component, and at least one rare earth element is added to this in a total amount of 0.
08 to 5.0 at%, cobalt at 0.1 to 10.0 at%, and 0.0 at % of magnesium and calcium. O1~1
．． By further adding borosilicate glass to a composition consisting of 0 at%, 0.01 to 1.0 at% of chromium, and a small amount of one of aluminum, gallium, and indium (both in total amount of 1xlO to 5x10 at%). , a voltage nonlinear resistance element with long wave tail surge resistance and a long life when applied with electricity can be obtained.

Claims (1)

[Claims] 1) Zinc oxide as a main component, and at least one rare earth element as a subcomponent in a total amount of 0.08 to 5.0 atomic %.
, 0.1 to 10.0 atom % of cobalt, and 0.1 to 10.0 atom % of at least one of magnesium and calcium. O1~5.0
atomic%, at least one of potassium, cesium, and rubidium in a total amount of 0.01 to 1.0 atomic%, and chromium in a total amount of 0.01 to 1.0 atomic%.
．． 1 to 1.0 atoms of O, at least one of aluminum, gallium, and indium in a total amount of 1xlO to 5x10
1. A voltage nonlinear resistance element, characterized in that it is made by further adding borosilicate glass to a composition containing the additives in an atomic percent range, and firing the mixture. 2) A voltage nonlinear resistance element according to claim 1, characterized in that borosilicate glass is added in an amount of 5 x lθ to 11 x lO atomic % in terms of boron.