JPH09208300A - Voltage nonlinear resistor porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the unevenness in varistor voltage among rough bodies in the same production lot and improve energy resistance by incorporating zinc oxide, specified subsidiary components and Ag. SOLUTION: Zinc oxide is wet-mixed with 0.1-5mol% oxide of a rare earth element, 0.01-1mol% oxide of an alkaline earth metal, 0.0001-0.6mol% oxide of a trivalent metal and 0.1-5mol% cobalt oxide as subsidiary components and 0.005-0.5mol% Ag and the resultant wet mixture is dried to form a powdery mixture. This mixture is mixed with a bonding resin, granulated and compacted to obtain a compact. The binder is removed from the compact by calcining at 700-1,000 and then the compact is fired at 1,100-1,450 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistor porcelain composition having a sufficient energy resistance even at a high varistor voltage.

[0002]

2. Description of the Related Art In recent years, with the rapid development of semiconductor technology, electric equipment and power equipment such as personal computers and communication devices using semiconductor elements such as microprocessors and semiconductor circuits are becoming smaller and higher in performance. It is making rapid progress.

On the other hand, however, with such progress, the withstand voltage, surge resistance, and noise resistance of these devices and parts cannot be said to be sufficient. Therefore, it is extremely important to protect these devices and parts from abnormal surges and noises or to stabilize the circuit voltage.

In order to solve these problems, it is required to develop a voltage non-linear resistor porcelain composition having extremely large voltage non-linearity, large energy withstanding capability, surge withstanding capability and long life.

Conventionally, SrTi has been used for these purposes.
Voltage non-linear resistor ceramics or varistors containing O ₃ , ZnO or the like as a main component are used. In particular, a varistor containing ZnO as a main component has characteristics such as a low limiting voltage and a large voltage non-linearity coefficient. It is used for protection. In particular, Japanese Examined Japanese Patent Publication Sho 56-257
As disclosed in Japanese Patent Laid-Open No. 64, No. 64, the main component is ZnO, and the subcomponents are rare earth element oxides, alkaline earth element oxides, and trivalent elements (B, Al, Ga, In, Y, C).
It is generally known that a varistor composed of one or more oxides of r, Fe, Sb, and) and cobalt oxide has an extremely small voltage non-linearity coefficient and excellent surge absorption characteristics. Here, the oxide of an element that becomes trivalent can take several valences, but particularly an oxide of an element that becomes chemically stable is a trivalent oxide,
Specifically, it is the one shown above.

[0006]

However, with the miniaturization of the equipment, when miniaturizing these varistor, there arises a problem that the energy withstand voltage also decreases. This is because the energy withstand voltage is proportional to the volume.
The same applies to the O-type varistor. Further, the ZnO varistor can obtain an arbitrary varistor voltage by selecting the firing conditions such as the firing temperature and the firing atmosphere. However, in the conventional composition and manufacturing method, it is difficult to uniformly burn the varistor element body, so that the varistor voltage greatly varies depending on the position in one element body and the element bodies in the same production lot. Variations in the varistor voltage depending on the position within one element body tend to lower the energy breakdown voltage. In addition, variations in the varistor voltage between the element bodies in the same manufacturing lot cause a decrease in yield during manufacturing.

Therefore, according to the present invention, the energy withstand voltage is sufficiently high even if the element is miniaturized, and since each element body can be uniformly fired, it is possible to arrange the elements within one element body or between element bodies in the same manufacturing lot. The present invention provides a voltage non-linear resistor porcelain composition having a small varistor voltage variation.

[0008]

The present inventor has conducted extensive studies to achieve the above object, and as a result, by adding Ag to a conventional voltage non-linear resistor ceramic composition,
It has been found that the energy tolerance becomes large, and the present invention has been completed based on this finding.

Specifically, it is achieved by the following constitutions (1) to (3).

(1) A voltage non-linear resistor having zinc oxide as a main component, one or more rare earth element oxides, alkaline earth element oxides, and trivalent element oxides, and a subcomponent of cobalt oxide. A voltage non-linear resistor porcelain composition, characterized in that Ag is contained in the porcelain composition.

By adding Ag, the energy resistance becomes large, and even if the varistor voltage becomes large, it is possible to suppress a sharp decrease in the energy resistance.

Here, each component will be specifically described. The voltage nonlinear resistor porcelain composition according to the present invention is as follows:
It consists of zinc oxide as the main component and the following five components as subcomponents. The rare earth element oxide (first auxiliary component) is L
a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, D
It is composed of at least one oxide selected from y, Ho, Er, Tm, Yb and Lu. Alkaline earth element oxides (second subcomponent) are Mg, Ca, Ba and Sr.
Of these, it is composed of at least one oxide. Oxides of trivalent elements (third subcomponent) are B, Y, S
It is composed of at least one oxide of b, Cr, Mo, W, Al, Ga and In. Further, cobalt oxide (fourth subcomponent) and Ag (fifth subcomponent) need not be particularly described.

(2) Ag of 0.005 mol% to 0.5
The voltage non-linear resistor porcelain composition according to (1), which is characterized by containing mol%.

When the Ag content is in the above range, the energy resistance is particularly increased, which is preferable.

(3) The alkaline earth oxide is Sr oxide, and the content thereof is 0.005mo in terms of SrO.
The voltage non-linear resistor porcelain composition according to claim 2, characterized in that the content is 1% to 5 mol%.

When the content of the Sr oxide is within the above range, the non-linearity coefficient becomes particularly large, which is preferable.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The voltage non-linear resistor porcelain composition according to the present invention will be described in detail. As described above, the main components are zinc oxide and the first to fourth subcomponents. It is a composition in which Ag is contained as a fifth subcomponent in the existing voltage non-linear resistance ceramic composition.

(Composition) By containing Ag, it is possible to perform uniform firing and reduce variations in varistor voltage. Further, by including Ag, it is possible to suppress the deterioration of the energy withstand amount even if the firing temperature is changed and the varistor voltage is increased.

This is because if there is a variation in the varistor voltage depending on the location in one element, the current concentrates on the low voltage portion, and the energy withstand capability of the entire element decreases. The varistor voltage depends on the number of grain boundaries, but the presence of Ag promotes uniform grain growth and makes the grain size almost uniform, which reduces variations in varistor voltage within a single element body and increases energy resistance. It is thought that it has become.
Further, it is possible to perform even firing between the bodies in the same lot.

The content of Ag is 0.005 to 0.5 mo.
It is preferably 1%. This is because if it is less than 0.005 mol%, the effect of increasing the energy resistance is not remarkable, and if it exceeds 0.5 mol%, the nonlinear coefficient decreases.

Among the above-mentioned second subcomponents, that is, the oxides of alkaline earth elements, preferably Sr oxide is an essential component. This is because Sr oxide has a nonlinear coefficient α due to its addition.
The effect of increasing the value is larger than that of the second sub ingredient which may be added, and the decrease of the non-linear coefficient α value when Ag is added (A
The addition of g is effective in increasing the energy resistance, but the nonlinear coefficient decreases depending on the amount. ) Is effective in compensating for. Here, when Sr oxide is used as an essential component, its content is preferably 0.005 to 5 mol% in terms of SrO. 0.0
If it is less than 05 mol%, the effect of increasing the non-linearity coefficient due to the inclusion of the Sr oxide does not appear.
If it exceeds mol%, the load life in high temperature and high humidity tends to be short, and the surge life tends to be shortened.

Furthermore, it is preferable that the third subcomponent, that is, the oxide of an element which becomes trivalent, be further divided into two components and added. That is, the elements constituting the oxide are B, Y,
At least one of Sb, Cr, Mo and W and at least one of Al, Ga and In are contained. This is because the former is present at the grain boundary and serves as an insulating layer, and the latter is present within the grain, which contributes to the improvement of the characteristics of voltage non-linearity by lowering the grain resistance.

The content of each of the above subcomponents except Ag is Sr.
It may be the same as the conventional one except that an oxide is essential.

That is, the content of the above-mentioned first subcomponent (rare earth element oxide) is not more than 0 in terms of R ₂ O ₃ (R is a rare earth element).
It is preferably 1 mol% to 5 mol%. 0.1
This is because if it is less than mol%, the non-linearity tends to decrease, and if it exceeds 5 mol%, the surge life tends to decrease.

The content of the second subcomponent (alkaline earth element oxide) is preferably 0.01 to 1 mol% in terms of MO (M is an alkaline earth element). 0.01
This is because if it is less than mol%, the non-linearity decreases, and if it exceeds 1 mol%, the load life in high temperature and high humidity becomes short. Here, the case where Sr oxide is used as an essential component is as described above. Further, it is generally known that alkaline earth elements and alkaline elements have the same effect as a sub-component of a zinc oxide varistor, and the second sub-component is not only an alkaline earth oxide but also K, Alkali oxides composed of the elements Rb and Cs may be used.

The content of the third subcomponent (oxide of an element becomes trivalent) is a M _'2 O ₃ in terms of 0.0001 to 0.6
It is preferably mol%. When further divided into two components, the content of at least one oxide of B, Y, Sb, Cr, Mo and W is 0.01 in terms of M ′ ₂ O _3.
It is preferably ˜0.5 mol%. 0.01mo
If it is less than 1%, the surge life is reduced, and 0.5 mol%
This is because if the value exceeds 1.0, sintering is hindered and a varistor voltage of 180 V or less per 1 mm cannot be obtained. Further, the content of at least one oxide of Al, Ga and In is 0.0001 to 0.1 m in terms of M ′ ₂ O _3.
ol% is preferred. This is because if it is less than 0.0001 mol%, the limiting voltage increases, and if it exceeds 0.1 mol%, the leakage current increases.

The content of the fourth subcomponent (cobalt oxide) is preferably 0.1 to 5 mol% in terms of CoO. If it is less than 0.1 mol%, the non-linearity tends to decrease, and if it exceeds 5 mol%, the surge life tends to be shortened, which is not preferable.

The voltage non-linear resistance ceramics, which is a sintered body obtained by firing the voltage non-linear resistance ceramic composition having the above composition, has grains of 1 to 100 μm and Z
It is considered that nO, CoO, and an oxide composed of at least one of Al, Ga, and In exist mainly in grains, and Ag and other components exist in grain boundaries.

(Manufacturing Method) The voltage non-linear resistor porcelain composition according to the present invention is easily manufactured by a known ceramic technique. The manufacturing method will be described below. The starting materials weighed in the composition of the present invention are mixed in a wet ball mill until uniform. The raw material may be any of oxides, carbonates, oxalates, nitrates and the like as long as it becomes an oxide in the firing process. After the mixture is dried, a binder resin such as polyvinyl alcohol (PVA) is mixed and granulated to form a predetermined shape. Here, the mixture may be calcined at 700 ° C to 1000 ° C. When calcining, the mixture is dried, then calcined at a predetermined temperature, and the calcined product is pulverized by a wet ball mill. The molded body is 1150 ° C to 1 after debinding.
Bake in the range of 450 ° C. The firing atmosphere may be either an oxidizing atmosphere such as air or a non-oxidizing atmosphere such as nitrogen or argon, and the varistor voltage can be set arbitrarily by selecting the firing temperature, the firing atmosphere and the like.

Further, the sintered body is provided with electrodes according to a standard method to form a voltage non-linear resistance element. The applied electrode is A
The characteristics of g, Cu, Al, Zn, In, Sn, etc. are almost the same regardless of which metal is used. As a method of applying, any method such as paste baking, vapor deposition, electrolytic plating, etc. may be used. At this time, a coat such as glass may be applied. Further, as its application, it can be used for all voltage non-linear resistance elements for household electric appliances, industrial equipment, etc., and particularly for large-sized elements for industrial equipment such as high voltage. desirable.

[0031]

EXAMPLES Specific examples of the present invention will be described below.

Sample ZrO ₂ balls were charged with pure water and a dispersant in a monopot and the composition was as shown in Table 1 after firing.
ZnO as a main component and various additives (oxides) as subcomponents were weighed and put in, and mixed for 16 hours. Here, in Table 1, only the composition of the auxiliary component as an additive is described. The remaining amount is mainly ZnO. Then transfer the mixture to an evaporation dish,
After drying in a dryer at 130 ° C for 16 hours, crushing this with a mortar and pestle, adding PVA as a binder resin
The mixture was granulated with a 350 sieve, transferred to an evaporation dish, and dried in a drier at 80 ° C. for 30 minutes. This has a diameter of 11.3 mm,
Press-molded into a disc with a thickness of 3.0 mm (molding density 3.0-
4.0 g / cm ³ ) and holding at 500 to 800 ° C. for 2 hours to remove the resin, and then 1 in air or nitrogen atmosphere.
A sintered body was obtained by holding at 150 to 1350 ° C. for several hours and firing. Specifically, firing was performed at 1310 ° C. to obtain a varistor voltage of 150 V, and firing was performed at 1270 ° C. to obtain a varistor voltage of 180 V. The firing atmosphere at that time was in the air up to 600 to 800 ° C., and the atmosphere up to the above holding temperature was a nitrogen atmosphere. Table 1
Sample Nos. 1 and 2 have a varistor voltage of about 150 V per mm, and Sample Nos. 3 to 3 from Tables 1 to 2
No. 19 was burned to 180V. Further, Ag paste was printed on the surface, and this was baked at 500 ° C. to 700 ° C. to form electrodes, and voltage non-linear resistance elements were prepared.

Evaluation Method The electrical characteristics, energy resistance, and varistor voltage variation in one element were measured for these samples.

(Electrical characteristics) As for the electric characteristics, the varistor voltage per 1 mm (V _1mA / m) according to Kesley 237 is used.
m) and the non-linear coefficient α at 0.1 mA to 1 mA and 1 mA to 10 mA. The nonlinear coefficient α is represented by the following equation.

Α _0.1 = log ₁₀ (1 / 0.1) / log
₁₀ (V _1mA / V _0.1mA ) α ₁ = log ₁₀ (10/1) / log ₁₀ (V _10mA /
V _1mA ) Here, V _0.1mA , V _1mA , and V _10mA are respectively 0.
The varistor voltage at 1 mA, 1 mA, and 10 mA is shown.

(Energy tolerance) Energy tolerance is 2
A square wave of × 10 ^-3 sec is used to generate energy at intervals of approximately 5 minutes.
The varistor voltage (V _1mA ) at _1mA is measured by applying every 0J to 20J, and V is compared with that before the energy is applied.
How much _1mA changed, that is, the change rate (ΔV
_1mA / V _1mA ) was obtained, and the maximum applied energy at which the value was within 10% was defined as the energy withstand capability.

(Varistor voltage variation in the element body) The variation in the varistor voltage in the element body is about 150 mm of electrode blocks of 0.5 mm side are formed on one surface of the disk-shaped element body, Each was measured and calculated. This is because the electrode formed on the entire surface of the element body is 0.5 mm.
The electrodes were grouped by dicing so as to form a grid with intervals, thereby forming electrode blocks of 0.5 mm sides. 1 for each formed electrode block
Electrode voltage (V _1mA ) when a current of mA / cm ² is applied
Was measured. Next, for one element, the standard deviation of V _1mA and the expected value of all the measured blocks were calculated, the coefficient of variation (CV value) was obtained, and this value was used as a scale of variation.

C. V. Value = standard deviation / expected value As mentioned above, if there is variation in the varistor voltage depending on the location in one element, current concentrates on the low voltage part,
The energy tolerance of the device as a whole is reduced. Therefore,
C. V. The smaller the value, the more uniformly baked.

Evaluation Results Table 1 shows the results for each evaluation item for the samples in which the Ag content was changed and the varistor voltage was changed.

From sample Nos. 1 and 3 and 2 and 7, A
It can be seen that the inclusion of g does not cause a decrease in the energy withstand amount with an increase in the varistor voltage and also increases the energy withstand amount. In addition, those containing no Ag and those containing little Ag (Sample No. 4) are V
C. showing a variation of _{1 mA} V. You can see that the value is large. Furthermore, the content of Ag is 0.005-0.5 mol
% Has a large energy tolerance, and the nonlinear coefficient α is also 3
It is 0 or more and is preferable.

[0041]

[Table 1]

Table 2 shows the results for each evaluation item for the samples having different Sr oxide contents.

Non-linear coefficient α depending on the content of Sr oxide
Is larger. However, when the content of Sr oxide is 7.0 mol%, the energy resistance is as small as 60, so it is understood that the content has an upper limit. Therefore, the content of Sr oxide is 0.01 in terms of SrO.
~ 5.0mol% has a large energy resistance,
The nonlinear coefficient α is also preferably 30 or more.

[0044]

[Table 2]

[0045]

The voltage non-linear resistance ceramic composition according to the present invention has a sufficiently high energy withstand voltage even when the element is miniaturized. In addition, variations in varistor voltage between each body in one body and in the same manufacturing lot are small, and the manufacturing yield is improved.

Claims (3)

[Claims] 1. A voltage non-linearity having zinc oxide as a main component, one or more oxides of rare earth element oxides, alkaline earth element oxides, and oxides of trivalent elements, and subcomponents of cobalt oxide. A resistor porcelain composition containing Ag, which is characterized by containing Ag. 2. The content of Ag is 0.005 mol% to 0.
It is 5 mol%, The voltage nonlinear resistor porcelain composition of Claim 1 characterized by the above-mentioned. 3. The alkaline earth oxide is Sr oxide, and the content thereof is 0.005 mol% in terms of SrO.
The voltage non-linear resistance ceramic composition according to claim 2, wherein the content is 5 mol%.