JPH03211704A - How to manufacture baristas - 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 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 voltages, 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.

1 = (V/C) α Here, I 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 4 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 the semiconductor capacitor is destroyed, and the capacitor no longer functions as a capacitor.

Recently, products containing 5rTiOa as the main component and having both varistor and capacitor properties have been developed, and ICs and L
It is used to protect semiconductor devices such as SI.

Problems to be Solved by the Invention The above-mentioned 5rTiOa-based element that 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. It has the disadvantage 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 value, 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 x
-x B azTios(0, OO1≦x≦0.300
') (hereinafter referred to as the first component) from 90.000 to 99.9
98mo1%, Nb20s, Taxoa, W
Os, D>' 20B.

Y2O3, L a20s, Ce 02. Sm201P
re○1. .

At least one type of N d x Os (hereinafter referred to as the second component) is contained in an amount of 0.001 to 5. OOOmo 1%,
AI! zoa, 5bxOa, Bad, Bed, Pb0゜8201+, Cr20B, Fe20s, CdO, 2
0゜Cab, Co20s, Cub, Cu2O, Li2
0゜L i F, MgO, MnO2, MOOn, N
a20.

NaF, Nip, RhzOs, 5e02. AIIJzO
.

S i 02. S i C, S r O, Tj'20
s, ThO2゜TiO2, V2O5, Bi2O5, Z
At least one of nO, ZrO2°S n 02 (hereinafter referred to as the third component) is 0.001 to 5. OOO
100 parts by weight of the main component containing 1% Mo and Ca
Ti0s60.000-5.000mol%, Si
A voltage-independent non-voltage-dependent mixture consisting of 0.001 to 10.000 parts by weight of an additive (hereinafter referred to as the fourth component) obtained by baking a mixture consisting of 1% O□40.000 to 67.5 mo at 1200 to 1300°C The aim is to solve the problem by obtaining a linear resistor ceramic composition.

Effect In the above invention, the first component is the main component, and S
By substituting a portion of Sr in r T t Os with Ba, the high resistance layer formed at the grain boundaries becomes strong against surges. The second component is mainly a metal oxide that promotes semiconducting of the first component. Further, the third component contributes to improving the dielectric constant, α, and surge resistance, and the fourth component contributes to a decrease in varistor voltage.

This is effective in 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 be segregated in the grain boundary portion, and the resistance of the grain boundary is likely to be increased, thereby improving the varistor function and the capacitor function.

Further, 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 described below with reference to Examples.

Weighed CaT ios and S io2 at various composition ratios as shown in Table 1 below, and heated them in a ball mill for 20 hours.
r Mix. Next, after drying, it is fired at various temperatures as shown in Table 1 below, and then heated again using a ball mill etc.
After pulverizing for 0 hours, it is dried to obtain the fourth component. Next, the first component and the second component.

'Weigh the M3 component and the 4th component so that they have the composition ratio shown in Table 1 below, mix them in a ball mill for 24 hours, dry them, add 1Qwt% of an organic binder such as polyvinyl alcohol, and granulate them. After that, 1 (t/al
It was molded into a disc shape of 10φXi' (,) using a press pressure of >, and was fired at 1000° C. for 10 hours to remove the binder. Next, as shown in Table 1, firing is performed at various temperatures and times (first firing), and then a reducing atmosphere such as N2:H
Baking is performed in a gas ratio of 2=9:1 at various temperatures and times (second baking). After that, firing is performed in an oxidizing atmosphere at various temperatures and times (third firing).

The thus obtained sintered body 1 shown in FIGS. 1 and 2 was coated with a conductive paste such as A[lr by screen printing or the like, leaving the outer periphery on both planes, and heated at 600°C for 5 m.
The electrode 2.3 is formed by firing at 1n. Next, the lead wires are attached using solder or the like, and a resin such as epoxy is applied. The characteristics of the device thus obtained are shown in Table 2 below.

The dielectric constant is calculated from the capacitance at IKHz, and α is a = 1/L o g(V]o*^/V+m^) (However, ■1mjA+ VIOIIA is 1mA, lQmA
This is the voltage applied across the device when a current of . )
It was evaluated by Further, the surge resistance is evaluated based on the maximum pulse current value when the rate of change in VlmA after applying the pulse current is within ±10%.

(Left below) Also, the first component S r + - xB axT t Os
The reason for specifying the range of
precipitates as a single phase, resulting in a non-uniform structure and ■
1. This is because A becomes too high and the characteristics deteriorate. Furthermore, if the second component is less than ○, ○01 mo1%, it does not show any effect, and 5. When OOOmo exceeds 1%, it segregates at the grain boundaries, suppresses the increase in resistance of the grain boundaries, and forms a second phase at the grain boundaries, resulting in deterioration of properties. Also, the third component is 0.00
If it is less than 1 mo 1%, it will not show any effect; 5. OOOmo1
If it exceeds %, it segregates at grain boundaries and forms a second phase, resulting in deterioration of properties. And the fourth component is CaT
It is a substance with the lowest melting point in the phase diagram of the binary system of iOs and SiO2, and its melting point increases outside this range. Further, the amount of the fourth component added is 0.001
If it is less than 10,000 parts by weight, it will not be effective, and if it exceeds 10,000 parts by weight, the grain boundary resistance will increase, but the convergence of the grain boundaries will become thicker, so the capacitance will become smaller and vl and A will become higher, which will prevent surges. It becomes weaker. 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. or higher. Also, the first
The firing temperature was determined based on the fact that the melting point of the fourth component was 1230.
~1250°C, so if fired at a temperature of 1200°C or higher, the fourth component will be in a state close to a liquid phase and sintering will be accelerated; below 1200°C, the fourth component has no liquid phase sintering effect. It's for a reason. 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. 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 V1+aA will become too low, deteriorating the varistor characteristics, and if it exceeds 1300°C, This is because the capacitance becomes too small and the capacitor characteristics deteriorate. Also,
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. Furthermore, in this example, regarding the combination of additives, 5r was added as the first component.
1-xBa engineering Ti0s (0,001≦x≦0.300)
, N b206. as the second component. T as+06. W
O2, DV203゜Y2O3, L a20s+CCO2
, Nd20a, Alx0B, PbO, C as the third component
r2O5, CdO.

K2O, CO20s, Cub, CuzO, MgO.

MnO2, Mo5s, N t O, A gx○, SiC
.

T 12011. Z r 0.2, C as the fourth component
aTiOs.

Although only Sm20R+ P reo7.5i02 is shown, Sm20R+ P reo7. and as the third component S b2o,, B a○, B e O, B201
1゜Fe2es, Cab, Li2O, LiF, Na2O
.

NaF, Rh20s, SeO2, S i02. Sr○.

T h O2, T i 02. V2O6, Biz○
,,ZnO.

It was confirmed that similar effects can be obtained by combining compositions using SnO2. Also, the first component.

It has been confirmed that simply performing the first firing of the second, third, and fourth components is effective in lowering the varistor voltage and increasing the dielectric constant ε.

Effects of the Invention As described above, according to the present invention, the varistor voltage is low because the particle size is large, the dielectric constants ε and a are large, and the variation in particle size is small, so that surge current flows uniformly through the element. Since the grain boundaries are effectively made highly resistive by Ba, the effect of increasing the 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 (3)

[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, 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, 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 a main component containing 0.001 to 5.000 mol% of at least one of ZnO, ZrO_2, and SnO_2, and CaTiO_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. (2) Sr_1_-_xBa_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, 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 a main component containing 0.001 to 5.000 mol% of at least one of ZnO, ZrO_2, and SnO_2, and CaTiO_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, WO_3,
Dy_2O_3, Y_2O_3, La_2O_3, Ce
O_2, Sm_2O_3, Pr_8O_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 a main component containing 0.001 to 5.000 mol% of at least one of ZnO, ZrO_2, and SnO_2, and CaTiO_360.000 to
32.500mol%, SiO_240.000~67
．． A composition consisting of 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, and then fired at 1200°C or higher in a reducing atmosphere. and then firing at 900 to 1300°C in an oxidizing atmosphere.