JPH03109261A - Production of porcelain composition for nonlinear resistor having voltage dependency and varistor - Google Patents

Abstract

PURPOSE:To provide the porcelain compsn. ensuring low varistor voltage and high surge resistance by adding an additive contg. SrTiO3 and SiO2 to a base having a specified compsn. based on Sr-Ba-Ti-O type oxide. CONSTITUTION:A base contg. 90-99.998mol% multiple oxide represented by the formula, 5-0.001mol% one or more among Nb2O5, Ta2O5, WO3, Dy2O3, Y2O3, La2O3, CeO2, Sm2O3, Pr6O11 and Nd2O3 and 6-0.001mol% one or more among Al2O3, Sb2O3, BaO, BeO, PbO, B2O3, Cr2O3, Fe2O3, CdO, K2O, CaO, Co2O3, CuO, Cu2O, Li2O, LiF, MgO, MnO2, MoO3, etc., is prepd. An additive obtd. by calcining a mixture of 60-32.5mol% SrTiO3 with 40-67.5mol% SiO2 at >=1,200 deg.C is added to the base by 0.001-10 pts.wt. per 100 pts.wt. of the base to produce a porcelain compsn. for a nonlinear resistor having voltage dependency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a voltage having capacitor characteristics and varistor characteristics to protect semiconductors and circuits of equipment from abnormal high voltage, noise, static electricity, etc. generated in electrical equipment and electronic equipment. The present invention relates to a dependent nonlinear resistor ceramic composition and a method for manufacturing a varistor.

Conventional technology Conventionally, SiC varistors and Z
nO type varistors are used. The voltage-current characteristics of such a varistor can be approximately expressed as in the following equation.

I=(V/C) α Here, ■ is a current, ■ is a voltage, C is a constant specific to the varistor, and α is a voltage-current nonlinear index.

The α of SiC varistors is about 2 to 7, and the α of some ZnO-based varistors is as high as 50. Such varistors have excellent performance in absorbing relatively high voltages, but due to their low dielectric constant and small inherent capacitance, they have little ability to absorb relatively low voltages below the varistor voltage. It has no effect, and the dielectric loss tan δ is as large as 5 to 10%.

On the other hand, semiconductor capacitors with an apparent dielectric constant of about 5×10' and a tan δ of about 1% are used to remove these low voltage noises. However, when a voltage or current exceeding a certain limit is applied to such a semiconductor capacitor due to a surge or the like, the capacitance decreases or breaks down, and the capacitor no longer functions as a capacitor.

Therefore, recently, a product that has SrTiO3 as its main component and has both varistor and capacitor properties has been developed, and it
It is used to protect semiconductor devices such as SI.

Problems to be Solved by the Invention The above-mentioned element that has SrTiO3 as a main component and functions as both a varistor and a capacitor has a dielectric constant about 10 times higher than that of a ZnO-based varistor, but its α and surge resistance are small, making it difficult to use as a varistor. The drawback was that the characteristics tend to deteriorate when the voltage is lowered.

Therefore, an object of the present invention is to provide a voltage-dependent nonlinear resistor ceramic composition that has a large dielectric constant, a low varistor voltage, a large α, and a large surge withstand capacity, and a method for manufacturing the varistor.

Means for Solving the Problems In order to solve the above problems, in the present invention, S r 1
- x Ba x T 103 (1) Sr1-xBa
xTiO3 (0.001≦x≦0.300) (hereinafter referred to as the first component) from 90.000 to 99.998 mol
%, Nb2O5, Ta205°wo3. D)'203
．． Y2O3, La20:+, CeO, Sm2O3, P
r,,O,.

0.001 to 5.000 mol% of at least one type of Nb2O3 (hereinafter referred to as the second component), Al2O
3,5b203゜Bad, Bed, pbo, B2
O3, Cr2O3, Fe2O3, ccto.

K2O, CaO, Co2O3, Cub, Cu2O,
t, 12o, LiF, MgO.

MnO2, MoO3, Ha2e, NaF, Nip,
Rh2O3, 5ea2゜Ag2O, SiO2, Si
C, SrO, Tl□03. 'rho2. Tie...
.

V2O5, Bi2O3, ZnO, Zr0z, SnO2
Main component 1 containing 0.001 to 5.000 mol% of at least one of the following (hereinafter referred to as the third component)
00 parts by weight and SrTiO360, 000-32.50
0mol%, 5i0240.000-67.5mol
% (hereinafter referred to as the fourth component)> 0.001 to 10.
The purpose is to solve this problem by obtaining a voltage-dependent nonlinear resistor ceramic composition comprising 1,000 parts by weight.

In addition, a composition consisting of the above main ingredients and additives was added to 1100
An object of the present invention is to provide a method for manufacturing a varistor fired at a temperature of 1200°C or higher, and further a method for manufacturing a varistor fired at a temperature of 1200°C or higher in a reducing atmosphere and then at a temperature of 900 to 1300°C in an oxidizing atmosphere. In the above invention, the first component is the main component, and by replacing a portion of Sr in SrTiO3 with Ca, the high resistance layer formed at the grain boundaries becomes strong against surges.

Further, the second component is mainly a metal oxide that promotes the semiconductor formation of the first component. Further, the third component contributes to improving the dielectric constant, α, and surge resistance, and the fourth component is effective in reducing the varistor voltage and improving the dielectric constant. In particular, since the fourth component has a relatively low melting point of 1230 to 1250° C., when fired at a temperature around the melting point, it turns into a liquid phase, which promotes the reactions of the other components and the growth of particles.

Therefore, the third component is likely to segregate in the grain boundary portion, making the grain boundary more likely to have a high resistance, thereby improving the varistor function and capacitor function. In addition, since grain growth is promoted, the varistor voltage is lowered, and the uniformity of the grain size is improved, resulting in improved stability of characteristics, and in particular, improved surge resistance.

Example The present invention will be specifically explained below with reference to Examples.

First, SrTiO3.5i02 was weighed at various composition ratios as shown in Table 1 below, and was weighed using a ball mill etc.
Mix for hours. Next, after drying, the mixture is fired at various temperatures as shown in Table 1 below, and then ground again for 24 hours using a ball mill, etc., and then dried to obtain a fourth component. Then,
First component, second component, third component.

The fourth component was weighed to have the composition ratio shown in Table 1 below, mixed for 30 hours using a ball mill, etc., and then dried.
10wt of organic binder such as polyvinyl alcohol
% and granulated, it is formed into a disk shape of 10φXi' (in) with a press pressure of 1 (t/cd), and is baked at 1100° C. for 4 hours to remove the binder. Next, firing is performed at various temperatures and times as shown in Table 1 (first firing), and then in a reducing atmosphere, for example, N2:H2=9:
Firing in the gas of 1 at various temperatures and times (second firing)
do. After that, firing is performed in an oxidizing atmosphere at various temperatures and times (third firing).

(Margin below) A conductive paste such as Ag is applied by screen printing or the like, leaving the outer periphery on the side plane of the sintered body 1 shown in FIGS. 1 and 2 obtained as above. , 570
℃ and 5 ml to form electrodes 2 and 3. Next, lead wires (not shown) are attached using solder or the like, and a resin (not shown) such as epoxy is applied. The characteristics of the device thus obtained are shown in Table 2 below.

In Table 2, the dielectric constant is calculated from the capacitance at IKHz, and α is (Z = 1/log (VIOIIIA / VII
IIA) (However, VIIIAIVIOIIIA is the voltage applied across the device when a current of 1 mA or 10 mA is applied.). In addition, the surge resistance is determined by the rate of change of V1m^ after applying a pulsed current of ±10
The evaluation is based on the maximum pulse current value within %.

(Left below) In the present invention, 1, the first component Sr+-xBaxTlo
The reason for specifying the range of +X is that if X is smaller than 01001, there will be no effect, and if it exceeds 0.300, lattice defects will be less likely to occur, so semiconductor formation will not be promoted, and Ba will be present at the grain boundaries. This is because since it precipitates as a single phase, the structure becomes non-uniform, VIIllA becomes too high, and the properties deteriorate. Furthermore, if the second component is less than 0.001 mol%, it does not show any effect, and if it exceeds 5.000 mol%, it segregates at the grain boundaries, suppresses the increase in grain boundary resistance, and forms a second phase at the grain boundaries. This is because the characteristics deteriorate. Moreover, the third component is 0. 5. No effect is shown when OO is less than 1 mol%.
This is because if it exceeds 0.000 mol %, it segregates at grain boundaries and forms a second phase, resulting in deterioration of properties.

This is because the fourth component is a substance with the lowest melting point in the phase diagram of the two-component system of SrTiO3 and 5i02, and the melting point becomes high outside this range. Further, if the amount of the fourth component added is less than 0.001 parts by weight, no effect will be shown.
This is because if it exceeds 10,000 parts by weight, the resistance of the grain boundaries increases, but the width of the grain boundaries increases, so the capacitance decreases and V + mA increases, making it weak against surges. Furthermore, the firing temperature of the fourth component was specified because the temperature at which the fourth component having a low melting point is synthesized is 1200°C. The temperature for the first firing was specified because the melting point of the fourth component was 1230 to 1250°C.
This is because when fired at a temperature of 1100°C or higher, the fourth component enters a state close to a liquid phase and accelerates firing.
This is because there is no liquid phase sintering effect due to the fourth component at temperatures below .degree. In addition, the temperature for the second firing was set at 1200°C.
This is because if it is less than that, the sintered body after the first firing will not be sufficiently reduced, and both the varistor characteristics and the capacitor characteristics will deteriorate.

Furthermore, the temperature of the third firing was specified because the resistance of grain boundaries cannot be sufficiently increased below 900°C.
This is because ＾ becomes too low and the varistor characteristics deteriorate.
This is because if the temperature exceeds 1300° C., the capacitance becomes too small and the capacitor characteristics deteriorate. Furthermore, it was confirmed that the same effect can be obtained whether the atmosphere for the first firing is an oxidizing atmosphere or a reducing atmosphere.

In addition, in this example, regarding the combination of additives, SrBaTiO(1)Sr1-xB was used as the first component.
axTiO3 (0.001≦x≦0.300), second
Nb as a component: 05. Ta205. YO3゜DY
203. Y2O3, La2O3, CeO,,, Sm20
111. PraONd203, Al2O as the third component
:+, PbO, B:03. Cr2O3°Fe201.
CdO, 20. CO2O3, CuO, Cu2O, Li
2O, MgOMnO2, MOO3, Nip, SeO2,
Ag2o, SiC, Tl2O:lBi2O:+,
Zr0z, SrTiO3 as the fourth component. Sin...
Although only 5b20+ was shown as the third component,
Bad.

Bed, Cab, LiF, Na: 0. NaF,
Rh20+, Sin. , SrO, The2. T
It was confirmed that a similar effect could be obtained with a composition combination using iO2, V2O5, ZnO, and 5n02. Furthermore, it was also confirmed that two or more types of the second component and the fourth component may be used in combination within a predetermined range.

Note that the first component, second component, third component, and fourth component are 11
Just by firing at 00℃ or higher, the fourth component becomes a liquid phase,
In order to promote the reaction of other components and the growth of particles, the third component is more likely to segregate at the grain boundaries, making it easier for the grain boundaries to become highly resistive, improving varistor and capacitor functions. effective.

Effects of the Invention As shown above, according to the present invention, the particle size is large due to the liquid phase sintering effect of the fourth component, so the varistor voltage is low, the dielectric constants ε and α are large, and the variation in particle size is small. Therefore, surge current flows uniformly through the element, and B
Since grain boundaries are effectively made to have a high resistance by a, the effect of increasing surge resistance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a top view showing an element according to the invention, and FIG. 2 is a sectional view showing the element according to the invention. 1... Sintered body, 2, 3... Electrode.

Claims (1)

[Claims] (1) Sr_1_−_xBa_xTiO_3 (0.00
1≦x≦0.300) from 90.000 to 99.998m
ol%, Nb_2O_5, Ta_2O_5, YO_3,
Dy_2O_3, Y_2O_3, La_2O_3, Ce
O_2, Sm_2O_3, Pr_6O_1_1, Nd_
At least one type of 2O_3 from 0.001 to 5
．． 000mol%, Al_2O_3, Sb_2O_3,
BaO, BeO, PbO, B_2O_3, Cr_2O_
3, Fe_2O_3, CdO, K_2O, CaO, Co
_2O_3, CuO, Cu_2O, Li_2O, LiF
, MgO, MnO_2, MoO_3, Na_2O, Na
F, NiO, Rh_2O_3, SeO_2, Ag_2O
, SiO_2, SiC, SrO, Tl_2O_3, Th
O_2, TiO_2, V_2O_5, Bi_2O_3,
100 parts by weight of the main component containing 0.001 to 5.000 mol% of at least one of ZnO, ZrO_2, and SnO_2, and SrTiO_360.000 to
32.500mol%, SiO_240.000~67
．． 1. A voltage-dependent nonlinear resistor ceramic composition comprising 0.001 to 10.000 parts by weight of an additive obtained by firing a mixture of 5 mol % at 1200° C. or higher. (1) Sr_1_-_xBa_xTiO_3(0.00
1≦x≦0.300) from 90.000 to 99.998m
ol%, Nb_2O_5, Ta_2O_5, YO_3,
Dy_2O_3, Y_2O_3, La_2O_3, Ce
O_2, Sm_2O_3, Pr_6O_1_1, Nd_
At least one type of 2O_3 from 0.001 to 5
．． 000mol%, Al_2O_3, Sb_2O_3,
BaO, BeO, PbO, B_2O_3, Cr_2O_
3, Fe_2O_3, CdO, K_2O, CaO, Co
_2O_3, CuO, Cu_2O, Li_2O, LiF
, MgO, MnO_2, MoO_3, Na_2O, Na
F, NiO, Rh_2O_3, SeO_2, Ag_2O
, SiO_2, SiC, SrO, Tl_2O_3, Th
O_2, TiO_2, V_2O_5, Bi_2O_3,
100 parts by weight of the main component containing 0.001 to 5.000 mol% of at least one of ZnO, ZrO_2, and SnO_2, and SrTiO_360.000 to
32.500mol%, SiO_240.000~67
．． A method for manufacturing a varistor, characterized in that a composition comprising 0.001 to 10.000 parts by weight of an additive obtained by firing a mixture of 5 mol % at 1200°C or higher is fired at 1100°C or higher. (3) Sr_1_-_xBa_xTiO_3(0.00
1≦x≦0.300) from 90.000 to 99.998m
ol%, Nb_2O_5, Ta_2O_5, YO_3,
Dy_2O_3, Y_2O_3, La_2O_3, Ce
O_2, Sm_2O_3, Pr_6O_1_1, Nd_
At least one type of 2O_3 from 0.001 to 5
．． 000mol%, Al_2O_3, Sb_O_3, B
aO, BeO, PbO, B_2O_3, Cr_2O_3
, Fe_2O_3, CdO, K_O, CaO, CO_2
O_3, CuO, Cu_2O, Li_2O, LiF, M
gO, MnO_2, MOO_3, Na_2O, NaF,
NiO, Rh_2O_3, SeO_2, Ag_2O, S
iO_2, SiC, SrO, T1_2O_3, ThO_
2, TiO_2, Y_2O_5, Bi_2O_3, Zn
100 parts by weight of the main component containing 0.001 to 5.000 mol% of at least one of O, ZrO_2, and SnO_2, and SrTiO_360.000 to 32
．． 500mol%, SiO_240.000~67.5
A composition consisting of 0.001 to 10.000 parts by weight of an additive obtained by firing a mixture consisting of mol% at 1200°C or higher is fired at 1100°C or higher, and then fired at 1200°C or higher in a reducing atmosphere. , then 90°C in an oxidizing atmosphere.
A method for manufacturing a varistor, characterized in that the varistor is fired at a temperature of 0 to 1300°C.