JPH038766A - Production of voltage-dependent nonlinear resistor porcelain composition and 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 CaTiO3 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% CaTiO3 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. Dependency Nonlinear Resistor Ceramic Composition ゎ and u/lJ7,70□Building 1ka+:m I! a t 6 too. 7 Amo・Members Conventional technology Conventionally, SiC varistors, which have voltage-dependent nonlinear resistance characteristics, 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 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 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 the semiconductor capacitor is destroyed, and the capacitor no longer functions as a capacitor.

Therefore, recently, a product that has 5rTiCh as its main component and has both varistor and capacitor characteristics has been developed, and it has been developed as an IC, L
It is used to protect semiconductor devices such as SI.

Problems to be Solved by the Invention The above-mentioned 5rTi03-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, it is an object of the present invention to provide a voltage-dependent nonlinear resistor ceramic composition with a large dielectric constant (low varistor voltage), a large α, and a large surge withstand capacity, and a method for manufacturing a varistor. It is.

Means for Solving the Problems In order to solve the above problems, in the present invention, 5raTi
○3 (0.950≦a≦1.000) (hereinafter referred to as the first component) is 90.000 to 99.998 mo 1
%, Nb2O5, Ta205. WO3, Dy2O3゜Y
2O3, La2O3, CeO2, Sm2O3, Pre
o+Nd2O3 (both one or more types (hereinafter referred to as the second type))
0.001 to 5.000 mo 1%.

A　I2O3, Sb2O3, BaO, Bed, PbO.

B2O3, Cr2O3, Fe2O3, CdO, 20°CdO, Co2O3, CaO, Cu2O, Li20°LiF, MgO, MnO2, MoO3, Na2O.

NaF, Nip, Rh2O3, SeO2, Ag2O.

S iCh, S i C, S ro, T I2O3, T
hO2゜T i 02 , V2O5, B 12O3,
A small amount of ZnO, Z ro2゜5n02 (both one or more types (hereinafter referred to as the third component) is 0.001 to 5.00
100 parts by weight of the main component containing 1% Mo and CaT
iO360.000~32.500mo 1%, Si○
A voltage-dependent nonlinear resistor ceramic composition consisting of an additive (hereinafter referred to as the fourth component) o, which is obtained by firing a mixture consisting of 240.000 to 67.500 mol% at 1200°C, and 1 to 10.000 parts by weight of OO. It is an attempt to solve the problem by obtaining things.

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 manufacturing 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, CaTiO3 and Si02 were weighed at various composition ratios as shown in Table 1 below, and 2
08 r Mix. 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 so as to have the composition ratio shown in Table 1 below, mixed in a ball mill, etc. (24), and then dried to form a polyvinyl After adding 10 wt% of organic binder such as alcohol and granulating, 10φX with a press pressure of 1 (t/cwt)
It (mm) was formed into a disc shape and heated at 1000℃ for 10 hours.
Fire to remove binder. Next, as shown in Table 1, 2-hour firing (first firing) is performed at various temperatures, followed by 4-hour firing (1st firing) at various temperatures in a reducing atmosphere, for example, a gas with N2:H2 = 9:1. 2nd firing). Furthermore, after that, 4) (r firing (
3rd firing).

A conductive paste such as Ag was 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 in this way.
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.

Note that the apparent permittivity is calculated from the capacitance at IKHz, and α is α=1/Log (V+omA/V+mA) (however,
VlmA and V+omA are voltages applied across the element when currents of 1 mA and 10 mA are applied. ) was evaluated.

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) In addition, the range of a for the first component 5raTi○3 was specified because a is thicker than 1.000 (if this is the case, lattice defects will be less likely to occur and semiconductor formation will not be promoted; If Vl mA is too high (too much, the characteristics will deteriorate, or less than 0.950)
This is because Ti becomes too excessive and TiO2 crystals are formed, the structure becomes non-uniform and the properties deteriorate. Furthermore, if the second component is less than 1 mol% of O, OO, it does not show any effect; If 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 O, OO
If it is less than 1 mol%, no effect is shown; 5. OOOmo 1
If it exceeds %, it segregates at grain boundaries and forms a second phase, resulting in deterioration of properties. Moreover, the fourth component is CaTiO3
In the phase diagram of the two-component system of and 5i02, CaT i○36
0.000-32.500mo 1%, Sio240
．． 000 to 67.500 mo 1% is a substance with the lowest melting point, and outside that range the melting point is high. Also, the amount of the fourth component added is 0.00 to 67.500 mo.
If it is less than 0.001 parts by weight, no effect will be shown, and if it exceeds 10.000 parts by weight, the grain boundary resistance will be high (but the width of the grain boundaries will be thick), so the capacitance will be small and V + mA will be high (
It is weak against surges.Also, the fourth
The firing temperature of the components was specified because the temperature at which the fourth component with a low melting point is synthesized is 1200° C. or higher. The temperature of the first firing was specified because the melting point of the fourth component is 1230 to 1250°C, so if fired at a temperature of 1100°C or higher, the fourth component would be in a state close to a liquid phase and sintering would be difficult. This is because the fourth component has no liquid phase sintering effect below 1100°C. 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 for the third firing was specified because if it is less than 900°C, the resistance of the grain boundaries will not increase sufficiently, resulting in VlmA becoming too low and the varistor characteristics will deteriorate.If it exceeds 1300°C, it will become static. This is because 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, as the second component, in addition to the components listed in the above examples, Sm2O3, Prs 0, etc. 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, PbO, B203, C
aO, Li20°L iF, Na2O, NaF, Rh
2O3, SeO2, Ag2O, SiO2, SiC, Sr
O.

TI203, ThO2, TiO2, and ZnO can be used, and like the second component, two or more types may be combined and used in the amount 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 dielectric constants ε and α are large (and because the variation in particle size is small, the surge current is distributed uniformly to the element. The effect of increasing current and 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, 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%, CaTiO_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
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%, CaTiO_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, 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%, CaTiO_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
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.