JPH0443603A - How to manufacture baristas - Google Patents

Abstract

PURPOSE:To improve characteristics of permittivity, varistor voltage, surge yield strength, etc. by preparing ceramic composition by using the respective specified quantities of component wherein a part of Sr of SrTiO3 is substituted by Mg, component composed of two kinds of different metal oxide, and component wherein MgTiO3 and SiO2 are mixed and baked. CONSTITUTION:Main component is constituted by containing the following; 90.000-99.998 mol% of Sr1-xMgxTiO3 (0.001<=x<=0.300) 0.001-5.000 mol% of at least one or more kinds out of Nb2O5, Ta2O5, WO3, etc. and 0.001-5.000 mol% of at least one ore more kinds out of Al2O3, Sb2O3, BaO, etc. Admixture is made by baking, at 1200 deg.C or higher, mixture composed of 60.000-32.500 mol% of MgTiO3 and 40.000-67.5 mol% of SiO2. Ceramic composition is prepared by using 100 wt.% of the main component and 0.001-10.000 wt.% of the admix ture. Thereby varistor voltage is lowered; stability of characteristics is increased because the uniformity of grain diameter is improved; especially surge yield strength is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to capacitor characteristics and 71' risk characteristics for protecting equipment semiconductors and circuits from abnormal high voltages, noise, static electricity, etc. generated in electrical and electronic equipment. The present invention relates to a method for manufacturing a voltage-dependent nonlinear resistor ceramic composition and a varistor.

BACKGROUND ART Conventionally, SiC varistors with voltage-dependent nonlinear resistance characteristics have been used to absorb abnormally high voltages, remove noise, eliminate sparks, and counter static electricity in various electrical and electronic devices.
When a ZnO-based varistor or the like is used, the voltage-current characteristics of such a varistor can be expressed approximately as shown in the following equation.

α 1 = (V/C) Here, ■ is the voltage, C is a constant specific to the varistor, and α is the 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.

Recently, a product containing 5rTi03 as the main component and having both varistor and capacitor properties has been developed, and it is used as IC and L in electronic devices such as combinators.
It is used to protect semiconductor devices such as SI.

Problems to be Solved by the Invention The element having the functions of both a varistor and a capacitor whose main component is 5rTi (h) as described in Problem 1-8 has an mN ratio about 10 times higher than that of a ZnO-based varistor, but it has problems with α and surge. It has the disadvantage that its withstand capacity is small, and its characteristics tend to deteriorate when the varistor voltage is lowered.

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

! l! ! Means for Solving the Problems In order to solve the above problems, in the present invention, Sr1-x
MgllTi03 (0.001≦x≦0.300)
(hereinafter referred to as the first component) is 90.000-99.998
Mol! ,NbtOs+ TaxesWO3,Oy! 0
3. hos, LatOs+Ce(h, 5at(hrPr
601++Nd2O3, x at least one type (hereinafter referred to as the second component) of 0.001 to 5.000s+
olχ, Alt03,5bJ=, BaO, Be0p b
o, BJ3, Cr2O3,:l, FeJx
, Cd01K 2O3, lCab, C0tOi
+ Cu0Cu2O3,,l,i,O,LiF,MgO
,MnO,,Mo0=,NarO,NaF,Ni0Rh
2O3,i, 5eOz, Ag2O3,,5iOz
, SiC, SrO, Tl z(h, Th0z,
Tiozν, O3, Bi, Os, ZnO, Zr0i,
100 fj parts of a t component containing 0.001 to 5.000 molχ of at least one type (hereinafter referred to as the third component) of 5 nOz;
~32.500IlolX, 5iOz 40.00
A mixture consisting of 0 to 67.5 mol χ
Additive obtained by firing at 00℃ (hereinafter referred to as the fourth component)
Voltage-dependent nonlinear resistor M consisting of 0.001 to 10.000 parts by weight! The aim is to solve this problem by obtaining an i-cell composition.

In addition, a composition consisting of the above main ingredients and additives was added to 1100
We provide a method for producing a varistor fired at a temperature of 1200°C or higher, and a method for producing a varistor fired at a temperature of 1200°C or higher in a reducing atmosphere and then at 900 to 1300°C in an oxidizing atmosphere. This is what I am trying to do.

Effect In the above invention, the first component is the main component, and 5
Part of Sr in rTiOs? By substituting Ig, 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, the fourth component has a relatively low melting point of 1230 to 1250"C, so when fired at a temperature around the melting point, it turns into a liquid phase, promoting the reaction of the other components and grain growth. Therefore, the grain boundary area The third component becomes more likely to segregate, making grain boundaries more likely to have high resistance, improving varistor and capacitor functions.Also, grain growth is promoted, which lowers varistor voltage and improves grain size uniformity. This improves the stability of the characteristics, especially the surge resistance.

Example The present invention will be explained in a mimetic manner by giving examples below.

First, MgTiO3,5iOz was weighed at various composition ratios as shown in Table 1 below, and then milled using a ball mill or the like at 24
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,
The first component, second component, third component, and fourth component are
The composition ratio shown in the table was weighed, mixed for 24 hours using a ball mill, etc., dried, and granulated by adding lQwt@ of an organic binder such as polyvinyl alcohol, followed by pressing pressure of I (t/d). It was molded into a disk shape of 10φ Then, it is fired (second firing) in a reducing atmosphere, for example, a gas of N, :Hz=9:1, at various temperatures and times.Furthermore, after that,
Firing is performed in an oxidizing atmosphere at various temperatures and times (third firing).

(Hereinafter, blank space) A conductive paste such as Ag is applied by screen printing or the like, leaving the outer periphery on both planes of the sintered body 1 shown in FIGS. 1 and 2 obtained as described above. 630
℃, 3m1n to form ti2.3,
A lead wire (not shown) is 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 addition, in Table 2, the dielectric constant is calculated from the capacitance at 11 Hz, and α is a −1/log(V + ama/V IIIA)
(However, VI IIA, V + ohm is 1!m
A, is the voltage applied across the element when a current of 10IIA is applied. ) was evaluated. In addition, the surge withstand capacity is ±10% change rate of V after applying pulsed t current.
The evaluation is based on the maximum pulsed electric slag value when the value is within the range.

(Hereinafter, blank space) In the present invention, Sr I-xM mouth T of the first component is 0.
The reason for specifying the range of X is that 2O3, Y2O3, La2O3, Ce
O2, Sm2O3, Pr6O11, Nd2O. If it exceeds 300, lattice defects are less likely to occur, so semiconductor formation is not promoted, and grain boundaries occur. This is because 1g precipitates as a single phase, resulting in a non-uniform structure, resulting in an excessively high V l+IA and deterioration of properties. Furthermore, if the second component is O, OO1
If it is less than mol.chi., it will not show any effect, and if it exceeds 5.000 mol.chi., it will segregate at the grain boundaries, suppress the increase in grain boundary resistance, and form a second phase at the grain boundaries, resulting in deterioration of properties. Further, the third component exhibits no effect when it is less than 0.001 molχ, and when it exceeds 5.000 molχ, it segregates at grain boundaries and forms a second phase, resulting in deterioration of properties. The fourth component is a substance with the lowest melting point in the phase diagram of the binary system of MgTiOs, Si, and Oz, and has a high melting point outside of this range. Also,
The amount of the fourth component added is 2O3, Y2O3, La2O3, C
eO2, Sm2O3, Pr6O11, Nd2O. 001
If it is less than 31 parts by weight, no effect will be shown, and if it exceeds 10,000 parts by weight, the grain boundary resistance will increase, but the width of the grain boundaries will become thicker, so the capacitance will decrease and (1). A is high
This makes it vulnerable to surges.

Furthermore, the firing temperature of the fourth component was specified in 9 because the temperature at which the fourth component with a low melting point is synthesized is 1200°C. The temperature for the first firing was determined to be 110"C because the melting point of the fourth component is 1230-1250"C.
This is because if the fourth component is fired at a temperature of 0° C. or higher, the fourth component will be in a state close to a liquid phase and sintering will be promoted, and if it is less than 1100″c, the fourth component will not have a liquid phase sintering effect. Further, the temperature of the second firing is specified because if it is lower than 1200°C, 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 if it is less than 900°C, the resistance of the grain boundaries will not increase sufficiently, and the VImA will become too low and the varistor characteristics will deteriorate.
This is because if the temperature exceeds 00° 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, the first component is Sr+-JgxTi03 (0.001≦x
≦0.300), Nbz05+Ta2O as the second component
3, sJO3, Dy1OsYtOs, LatOi, Ce
0z, a+, o,, pb as the third component.

CrtOs, CdO,K,O,Co2O3,! ＋C
ub, Cu, O, Mn01. Mo01. NiON
loA, SiC, TltOs, ZnO, Zr0z, and only MgTiO3 and SiO□ are shown as the fourth component, but in addition, 511203. Prb
O+ I+ Nd2O3,s, 5btO as third component
,, Bad, Bed, 810. , Fet03.
Cab, Litu, LiF, MgONatO,
NaF, Rhz03.5eat, 5ift, Sr
O, Th0z, Tl0z, VtO5Bigot, S
It was confirmed that similar effects can be obtained by combining compositions using now. Furthermore, it was also acknowledged that two or more types of the second component and the third component may be used in combination within a predetermined range.

Note that the first component, second component, third component, and fourth component are
Just by firing, the fourth component turns into a liquid phase, which promotes the reaction of other components and the growth of grains, making it easier for the third component to segregate at the grain boundaries, making the grain boundaries more likely to have high resistance. This has the effect of improving the varistor function and capacitor function.

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

[Brief explanation of the drawing]

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. ]... Sintered body, 2.3... Electrode. Name of agent: Patent attorney Shigetaka Awano

Claims (3)

[Claims] (1) Sr_1_-_xMg_xTiO_3(0.00
1≦x≦0.300) from 90.000 to 99.998m
ol%, Nb_2O_5, Ta_2O_5, WO_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_3,
NaF, NiO, Rh_2O_3, SeO_2, Ag_
2O, SiO_2, SiC, SrO, Tl_2O_3,
ThO_2, TiO_2, V_2O_5, Bi_2O_
3. 100 parts by weight of a main component containing 0.001 to 5.000 mol% of at least one of ZnO, ZrO_2, and SnO_2, and MgTiO_360.00
0~32.500mol%, SiO_240.000~
A voltage-dependent nonlinear resistor ceramic composition comprising 0.001 to 10.000 parts by weight of an additive obtained by firing a mixture consisting of 67.5 mol % at 1200° C. or higher. (2) Sr_1-xMg_xTiO_3 (0.001≦
x≦0.300) from 90.000 to 99.998 mol
%, Nb_2O_5, Ta_2O_5, WO_3, Dy
_2O_3, Y_2O_3, La_2O_3, CeO_
2, Sm_2O_3, Pr_6O_1_1, Nd_2O
_0.001 to 5.0 of at least one type of 3
00mol%, Al_2O_3, Sb_2O_3, Ba
O, BeO, PbO, B_2O_3, Cr_2O_3,
Fe_2O_3, CdO, K_2O, 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, Tl_2O_3, ThO_
2, TiO_2, V_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 MgTiO_360.000 to 32
．． 500mol%, SiO_240.000~67.5
1. A method for producing a varistor, characterized in that a composition comprising 0.001 to 10.000 parts by weight of an additive is obtained by firing a mixture consisting of mol % at 1200°C or higher, and firing at 1100°C or higher. (3) Sr_1-xMg_xTiO_3 (0.001≦
x≦0.300) from 90.000 to 99.998 mol
%, Nb_2O_5, Ta_2O_5, WO_3, Dy
_2O_3, Y_2O_3, La_2O_3, CeO_
2, Sm_2O_3, Pr_6O_1_1, Nd_2O
_0.001 to 5.0 of at least one type of 3
00mol%, Al_2O_3, Sb_2O_3, Ba
O, BeO, PbO, B_2O_3, Cr_2O_3,
Fe_2O_3, CdO, K_2O, 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, Tl_2O_3, ThO_
2, TiO_2, V_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 MgTiO_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. and then 9 hours in an oxidizing atmosphere.
A method for manufacturing a varistor, characterized in that the varistor is fired at a temperature of 00 to 1300°C.