JPH038767A - Voltage-dependent nonlinear resistor ceramic composition and method for producing varistor - Google Patents

Abstract

PURPOSE:To improve dielectric constant and extent of surge resistance by constructing a composition from composition composed of a principal component, such as SrTiO3, Nb2O5 or Al2O3, and an additive prepared by calcining a mixture of MgTiO3 with SiO2. CONSTITUTION:The subject composition is formed from 100 pts.wt. principal component composed of 90-99.998mol% first component of SraTiO3 (a is 0.95-1), 0.001-5mol% second component and 0.001-5mol% third component and 0.001-10 pts.wt. additive. The above-mentioned second component is composed of one or more of Nb2O5, Ta2O5, WO3, Dy2O3, etc. The aforementioned third component is composed of one or more of Al2O3, Sb2O3, BaO, BeO, PbO, etc. Furthermore, the above-mentioned additive is obtained by calcining a mixture composed of 60-32.5mol% MgTiO3 and 40-67.5mol% SiO2 at >=1200 deg.C temperature.

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, ■ 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 vanostars 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 are not suitable for absorbing relatively low voltages below the varistor voltage. It shows almost 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 is destroyed and the capacitor no longer functions as a capacitor.

Therefore, recently, a product that has 5rTi○3 as its main component and has both varistor and capacitor properties has been developed, and it is used in IC, L, and other electronic devices such as computers.
It is used to protect semiconductor devices such as SI.

Problems to be Solved by the Invention The above-mentioned 5rTi03-based element, which functions as both a varistor and a capacitor, has a dielectric constant about 10 times higher than that of a ZnO-based varistor, but has a small α and surge resistance (, This has the disadvantage that when the varistor voltage is lowered, the characteristics tend to deteriorate.

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

Means for Solving the Problems In order to solve the above problems, in the present invention, S r a
T i 03 (0.950≦a≦1.000) (
(hereinafter referred to as the first component) is 90. OOO~99.998m
o 1%, Nb2O5, Ta205. WO3, Dy2O
3゜Y2O3, La2O3, ceO2, Sm2O3, P
Of r601Nd203, at least 1ill or more (hereinafter referred to as the second component) is 0.001 to 5. OOOmo
1%.

A1203, Sb2O3, BaO, Bed, PbO.

B2O3, Cr2O3, Fe2O3, CaO, 20°CaO, CO2O3, CuO, Cu2O, L 120L
i F, MgO, MnO2, MOO3, Na2O.

NaF, NiO, Rh2O3, 5eOz, 'Ag2O.

S i 02. S i C, S ro, T I2O3,
ThO3, TiO2, V2O5T B 12O3, Zn
At least one of O, Z ro3, and SnO2 (hereinafter referred to as the third component) in an amount of 0.001 to 5. OOOmo
100 parts by weight of the main component containing 1% MgTi (
h60, OOO~32.500mo 1%, SiO24
A voltage-dependent nonlinear resistor consisting of 0.001 to 10.000 parts by weight of an additive (hereinafter referred to as the fourth component) obtained by firing a mixture consisting of 1% of 0.000 to 67.500 mo at 1200°C or higher. The aim is to solve the problem by obtaining a porcelain composition.

Further, a method for producing a varistor comprising firing the above composition at 1100°C or higher, or firing the above composition at 1100°C or higher and then firing at 1200°C or higher in a reducing atmosphere,
The present invention proposes a method for producing a varistor in which the varistor is then fired at 900 to 1300°C in an oxidizing atmosphere.

Effect In the above invention, the first component is the main component, and the second component is the main component.
The components are mainly metal oxides that promote semiconducting of the first component. Also, the third component is the dielectric constant.

α contributes to improving the 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. Furthermore, 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.

First, MgT i○3. SiC2 was weighed at various composition ratios as shown in Table 1 below, and 2
Mix for 0 hours. Next, after drying, the mixture is fired at various temperatures as shown in Table 1 below, ground again at 208 r with a ball mill, etc., and dried to obtain the fourth component. Next, the first component, second component, third component, and fourth component were weighed to have the composition ratio shown in Table 1 below, mixed in a ball mill for 248 r, dried, and mixed with polyvinyl alcohol, etc. After adding 10 wt% of organic binder and granulating it, 1oφXIt was added with a press pressure of 1 (t/c/).
(mm) and baked at 1000° C. for 10 hours to remove the binder. Next, as shown in Table 1, the temperature was varied and fired for 3 hours (first firing), and then the temperature was varied for 4 hours in a reducing atmosphere, for example, N2:) (2=9:1 gas). Firing (second firing).After that, firing for 4 hours at various temperatures in an oxidizing atmosphere (third firing).
firing).

The thus obtained sintered body 1 shown in FIGS. 1 and 2 was coated with a conductive paste such as M by screen printing, leaving the outer periphery on both planes, and heated at 600°C for 5 m.
The electrodes 2 and 3 are 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.

Note that the apparent permittivity is calculated from the capacitance at IKHz, and α is α=1/Log (V+ornA/V+mA) (however, VlmA and VHmA are the values of the element when a current of 1mA and 10mA is applied. It is the voltage applied across both ends.).

In addition, the surge withstand capacity is Vl after applying a pulsed current.
The evaluation is based on the maximum pulse current value when the rate of change in mA is within ±10%.

(Margin below) Also, the reason why the range of 5raTi03 of the first component was specified is that when a is larger than 1.000, lattice defects are less likely to occur, so semiconductor formation is not promoted, and VlmA becomes too high. When the characteristics deteriorate and become smaller than 0.95, Ti
This is because TiO2 crystals are formed when TiO2 becomes too excessive, resulting in a non-uniform structure and deterioration of properties. Furthermore, the second component has no effect when O,OO is less than 1 mol%, and 5.0
If it exceeds 00 mol %, 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. Furthermore, if the third component is less than 0.001 mol%, it will not be effective, and if it exceeds 5,000 mol%, it will segregate at grain boundaries and form a second phase, resulting in deterioration of properties.

In addition, the fourth component is MgTiO360.000-32.500 in the phase diagram of the two-component system of MgTiCh and 5i02.
mol%, SiCh 40.000-67, 50
Those within the range of 0 m o '1% are the substances with the lowest melting points, and those outside this range have higher melting points. Furthermore, if the amount of the fourth component added is less than 0.001 parts by weight, no effect will be shown, and if it exceeds 10.000 parts by weight, the resistance of the grain boundaries will increase, but the width of the grain boundaries will become thicker, so the capacitance will increase. As V+ mA becomes smaller, V+ mA becomes higher (and weaker against surge). Also, the firing temperature of the fourth component was specified so that the temperature at which the fourth component with a low melting point was synthesized was 1200°C. This is because the temperature of the first firing was specified because the melting point of the fourth component was between 1200 and 1200.
Since the temperature is 50°C, firing at a temperature of 1,100°C or higher causes the fourth component to enter a state close to a liquid phase, promoting sintering, while below 1,100°C, the liquid phase sintering effect of the fourth component decreases. This is because there is no. 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 VlmA will become too low (too much), and the varistor characteristics will deteriorate; if it exceeds 1300°C, This is because the capacitance becomes too small and the capacitor characteristics deteriorate.
It was confirmed that the same effect can be obtained whether the firing atmosphere is an oxidizing atmosphere or a reducing atmosphere.

In addition, as the second component, in addition to the components listed in the above examples, Sm2O3 and Prso++ may be used, and two or more types may be combined and used in an amount within the above range. . Further, as the third component, in addition to the components mentioned in the above examples, Bad, Bed, PbO,
B203, CaOCu20. L i20. L iF,
MgO, Na2O.

NaF, Rh2O3, 5e02. Ag2O.

5i02, SiC, SrO, T1203'I'110
2. TiO2 can be used, and like the second component, two or more types can be used in combination in the amount added within the above-mentioned range. Furthermore, although only some of the combinations of these additives are shown in the above examples, it was confirmed that similar effects can be obtained with other combinations.

Effects of the Invention As shown above, according to the present invention, the varistor voltage is low because the particle size is large (and the surge current flows uniformly through the element because the permittivity ε and α are large and the variation in particle size is small). Therefore, the effect of increasing 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. 1... Sintered body, 2, 3... Electrode.

Claims (1)

[Claims] (1) Sr_aTiO_3 (0.950≦a≦1.00
0) from 90.000 to 99.998 mol%, Nb_2
O_5, Ta2O_5, WO_3, Dy_2O_3, Y
_2O_3, La_2O_3, CeO_2, Sm_2O
0.001 to 5.000 mol% of at least one of _3, Pr_6O_1_1, Nd_2O_3,
Al_2O_3, Sb_2O_3, BaO, BeO, P
bO, 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, NaF, NiO, Rh_
2O_3, SeO_2, Ag_2O, SiO_2, Si
C, SrO, Tl_2O_3, ThO_2, TiO_2
, V_2O_5, Bi_2O_3, ZnO, ZrO_2
．． 0.001 of at least one type of SnO_2
100 parts by weight of the main component containing ~5.000 mol%, MgTiO_3 60.000-32.500 mol%, SiO_240
．． A mixture consisting of 000 to 67.500 mol%
Additives baked at 00°C or higher 0.001 to 10.0
00 parts by weight of a voltage-dependent nonlinear resistor ceramic composition. (2) Sr_aTiO_3 (0.950≦a≦1.00
0) from 90.000 to 99.998 mol%, Nb_2
O_5, Ta_2O_5, WO_3, Dy_2O_3,
Y_2O_3, La_2O_3, CeO_2, Sm_2
0.001 to 5.000 mol% of at least one of O_3, Pr_6O_1_1, Nd_2O_3
, 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, Cu
O, Cu_2O, Li_2O, LiF, MgO, MnO
_2, MoO_3, Na_2O, NaF, NiO, Rh
_2O_3, SeO_2, Ag_2O, SiO_2, S
iC, SrO, Tl_2O_3, ThO_2, TiO_
2, V_2O_5, Bi_2O_3, ZnO, ZrO_
2.0.00 of at least one type of SnO_2
100 parts by weight of the main component containing 1 to 5.000 mol%, MgTiO_3 60.000 to 32.500 mol%, SiO_240
．． A mixture consisting of 000 to 67.500 mol%
Additives baked at 00°C or higher 0.001 to 10.0
A method for manufacturing a varistor, characterized in that a composition comprising 0.00 parts by weight is fired at 1100°C or higher. (3) Sr_aTiO_3 (0.950≦a≦1.00
0) from 90.000 to 99.998 mol%, Nb_2
O_5, Ta_2O_5, WO_3, Dy_2O_3,
Y_2O_3, La_2O_3, CeO_2, Sm_2
0.001 to 5.000 mol% of at least one of O_3, Pr_6O_1_1, Nd_2O_3
, 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, Cu
O, Cu_2O, Li2O, LiF, MgO, MnO_
2, MoO_3, Na_2O, NaF, NiO, Rh_
2O_3, SeO_2, Ag_2O, SiO_2, Si
C, SrO, Tl_2O_3, ThO_2, TiO_2
, V_2O_5, Bi_2O_3, ZnO, ZrO_2
, at least one type of SnO_2 at 0.001
100 parts by weight of the main component containing ~5.000 mol%, MgTiO_3 60.000-32.500 mol%, SiO_240
．． A mixture consisting of 000 to 67.500 mol%
Additives baked at 00°C or higher 0.001 to 10.0
00 parts by weight is fired at 1100°C or higher, then fired at 1200°C or higher in a reducing atmosphere, and then fired at 900 to 1300°C in an oxidizing atmosphere. Method.