JPH0443608A - Manufacture of voltage-dependent nonlinear resistor ceramic composition and varistor - 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 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.

α 1 =(V/C) 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.

Recently, products containing 5rTi03 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 Although the dielectric constant of the above-mentioned 5rTiO-based device, which functions as both a varistor and a capacitor, is about 10 times higher than that of a ZnO-based varistor, its α and surge resistance are small, making it difficult to use as a varistor. This had the disadvantage that when the voltage was lowered, the characteristics deteriorated.

Therefore, it is an object of the present invention 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 producing the varistor.

Means for Solving the Problems In order to solve the above problems, in the present invention, (Sr+-
Jgx) aTios (0,001≦χ≦0.300.
0.950≦a<1.000) (hereinafter referred to as the first component) is 90°000 to 99.998 molχ, Nbt05
．． TatOs+ WOs, DytOs, Y! 03+
LazO+CeO,,Sagos,Pr,O,,,N
At least one kind (hereinafter referred to as the second component) of d2O, o, ooi to 5.000 molχ, AltOi
, 5bzOx, BaO, BeO, PbO, BtOs, C
r1OsFezO,, CdO, K10. CaO, Co,
Ot, CuO, Cu, O, Li to, LiFMg
O, Mn0z, Mo0=, tia, 0. NaF,
Nip, RhtOx, Sea, Ag, 05i
Oz, SiC, SrO, Tl tCh, Th0z,
TiO2, V2O5, Bizo*, Zn0Zr
At least one or more of O□, 5nOz (hereinafter the third
100 parts by weight of the main component containing 0.001-5.000 molχ of MgTi (h 60.
000-32.500molχ, 5i(h 40.
000 to 67.5solχ
We attempted to solve the problem by obtaining a voltage-dependent nonlinear resistor ceramic composition consisting of 0.001 to 10.000 parts by weight of an additive (hereinafter referred to as the fourth component) fired at 1300'C. It is something to do.

In addition, a composition consisting of the above main ingredients and additives was added to 1100
It is an object of the present invention to provide a method for manufacturing a varistor fired at a temperature of 1,200°C or higher in a reducing atmosphere, and a method for manufacturing a varistor fired at a temperature of 900 to 1,300°C in an oxidizing atmosphere. It is something to do.

Effect In the above invention, the first component is the main component, and 5r
By substituting a part of Sr in Ti03 with M, the high resistance layer formed at the grain boundary becomes strong against the number of resistors. In addition, by making the stoichiometric ratio of A sites such as Sr and Mg and the stoichiometric ratio of B sites such as Ti excessive,
It is possible to lower the internal resistance of the grains and increase the dielectric constant of the dielectric material formed at the grain boundaries.Furthermore, the second component is a metal oxide that mainly promotes semiconducting of the first component. In addition, 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 contributes to improving the dielectric constant, α, and surge resistance. 12
Since it is relatively low at 30 to 1250"C, it becomes a liquid phase when fired at a temperature around the melting point, which promotes the reaction of other components and the growth of particles. Therefore, the third component is likely to segregate at grain boundaries. This makes it easier for grain boundaries to become highly resistive, improving varistor and capacitor functions.Also, grain growth is promoted, which lowers varistor voltage, and grain size uniformity improves, resulting in stable characteristics. In particular, surge resistance is improved.

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

First, MgTiOs, sio! were weighed with various composition ratios as shown in Table 1 below, and milled using a ball mill etc.
Mix for 48r. Next, after drying, it is baked 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 form the fourth component. The components, the third component, and the fourth component are weighed so as to have the composition ratio shown in Table 1 below, mixed with 24Rr using a ball mill, etc., dried, and an organic binder such as polyvinyl alcohol is added at 10wtχ to produce the product. After graining, 10φXI' with a press pressure of 1 (t/ej)
(m) and baked at 1100"C for 12 hours to remove the binder. Next, the temperature and time are varied as shown in Table 1 (first baking), followed by reduction. The product is fired in an oxidizing atmosphere, for example, N, :H, -9:1 gas, at various temperatures and times (second firing), and then fired in an oxidizing atmosphere at various temperatures and times (second firing). 3
firing).

(Margin below) A conductive paste such as 8g 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 in this way, and 3
The electrode 2.3 is baked with Win to form the electrode 2.3, a lead wire (not shown) is attached with 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.

In Table 2, the dielectric constant is calculated from the capacitance at IKHz, and α is α-1/log (V+o-a/VIIIA) (where Vl, A, V, ., A is 1 This is the voltage applied to both ends of the element when an i current is applied to A, 10-.). Further, the surge resistance is evaluated based on the maximum pulse current value when the rate of change of V, A after applying the pulse IT current is within ±10%.

(Left below) In the present invention, (Sri-MMgx)dl of the first component
The reason for specifying the range of χ for Os is that if X is smaller than 0.001, there will be no effect, and if Since Mg precipitates as a single phase, the structure becomes non-uniform,
This is because V becomes too high and the characteristics deteriorate.

In addition, the range of a was specified because if it is smaller than 0.950, crystals of Ti alone will precipitate and the structure will become non-uniform, resulting in deterioration of properties, and if it exceeds 1.000, it will be formed at grain boundaries. This is because the dielectric constant of the dielectric becomes smaller. Furthermore, the second component has no effect at less than 0.001 molχ; O
If it exceeds OOmolχ, 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. And the third component is 0.001wol
No effect is shown below χ, 5, OOO+molχ
If it exceeds this amount, it will segregate at grain boundaries and form a second phase, resulting in deterioration of properties. Moreover, the fourth component is MgTio
It is a substance with the lowest melting point in the phase diagram of the two-component system of z and Stow, and the melting point becomes high outside this range.

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 VlmA becomes smaller, VlmA becomes higher and becomes weaker against surges. The reason why the firing temperature of the fourth component is specified as 1 or higher is that the temperature at which the fourth component with a low melting point is synthesized is 1.
This is because the temperature is 200°C or higher. In addition, the temperature of the first firing was specified because the melting point of the fourth component was 1230 to 4250.
°C, therefore, if fired at a temperature of 1100°C or higher, the fourth component will be in a state close to a liquid phase and sintering will be accelerated; if it is lower than 1100°C, the liquid phase sintering effect of the fourth component This is because there is no Furthermore, the temperature of the second firing is specified because if it is less 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 reason why the temperature for the third firing was specified was that if it was less than 900'C, the resistance of the grain boundaries would not increase sufficiently, and VIIIA would become too low, deteriorating the varistor characteristics. This is because if the capacitance is increased too much, the capacitance becomes too small and the capacitance 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 practical example, regarding the combination of additives, the first component is (Sri-Jgx)aTiOs (0,
001≦X≦0.300.0.950≦a <1.00
0), Nb, O,, TatOs, WOs as the second component
, DytOi+YxOs, LatOs, Ce0z, AlzOi+ PbO, Cr2O2, Cd as the third component
O, KJ, Cot's, Cu0Cute, gate nO1
, MoO3, NiO, AgtO, SiC, Tlt03.
ZnO, ZrO2゜ MgTiOx, S as the fourth component
Although only tow is shown, other combinations include 5az03. Pr1O+++N'zO
x, as the third component Sb, O, , [1aOBeO,BJ
s, FezO! , CaO, LizO, LiF, MgO,
NatO, NaFRhzO), Se0g, 5iOz, S
rO, T11J, Ti0z, VzOs, BlzOiSn
o! It was confirmed that similar effects could be obtained by combining compositions using 7.

Also, for the second component and the fourth component, 2
It was also confirmed that there is no problem even if more than one type is used in combination within a predetermined range.

Even if the fourth component is fired at a temperature of 1100°C or higher, the fourth component becomes a liquid phase, which promotes the reaction of other components and the growth of particles, making it easier for the third component to segregate at the grain boundaries. This has the effect of making it easier for the resistance to increase, and improving the varistor function and capacitor function.

According to the present invention, due to the liquid phase sintering effect of the fourth component, the varistor voltage is low due to the large particle size, the dielectric constant and α are large, and the variation in particle size is reduced. Since the current is small, the surge current flows uniformly through the element, and
Since Mg effectively increases the resistance of the grain boundaries, it is possible to obtain the effect of increasing surge resistance.

[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. l... Sintered body, 2.3... Electrode. Name of agent: Patent attorney Shigetaka Awano (1 person)
Component, 2nd component, 3rd component, 4th composition diagram\3

Claims (3)

[Claims] (1) (Sr_1_-_xMg_x)_aTiO_3(
0.001≦x≦0.300, 0.950≦a<1.0
00) to 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_
0.001 to 5.000 mol of at least one of 2O_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, C
uO, Cu_2O, Li_2O, LiF, MgO, Mn
O_2, MoO_3, Na_2O, NaF, NiO, R
h_2O_3, SeO_2, Ag_2O, SiO_2,
SiC, SrO, Tl_2O_3, ThO_2, TiO
_2, V_2O_5, Bi_2O_3, ZnO, ZrO
_2, at least one type of SnO_2 0.0
100 parts by weight of the main component containing 01 to 5.000 mol% and MgTiO_3 60.000 to 32.500
mol%, SiO_2 40.000-67.5 mol
% and 0.001 to 10.000 parts by weight of an additive obtained by firing a mixture consisting of (2) (Sr_1_-_xMg_x)_aTiO_3(
0.001≦x≦0.300, 0.950≦a<1.0
00) to 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_
0.001 to 5.000 mol of at least one of 2O_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, C
uO, Cu_2O, Li_2O, LiF, MgO, Mn
O_2, MoO_3, Na_2O, NaF, NiO, R
h_2O_3, SeO_2, Ag_2O, SiO_2,
SiC, SrO, Tl_2O_3, ThO_2, TiO
_2, V_2O_5, Bi_2O_3, ZnO, Zr_
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%, and 60.000 to 32.500 m of MgTiO_3
ol%, SiO_2 40.000-67.5 mol%
A composition consisting of 0.001 to 10.000 parts by weight of an additive obtained by baking a mixture consisting of
A method for manufacturing a varistor, characterized in that the varistor is fired at a temperature of 1100°C or higher. (3) (Sr_1_-_xMg_x)_aTiO_3(
0.001≦x≦0.300, 0.950≦a<1.0
00) to 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_
0.001 to 5.000 mol of at least one of 2O_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, C
uO, Cu_2O, Li_2O, LiF, MgO, Mn
O_2, MoO_2, Na_2O, NaF, NiO, R
h_2O_3, SeO_2, Ag_2O, SiO_2,
SiC, SrO, Tl_2O_3, ThO_2, V_2
O_5, Bi_2O_3, ZnO, ZrO_2, SnO
At least one type of _2 from 0.001 to 5.0
100 parts by weight of the main component containing 00 mol% and Mg
TiO_3 60.000-32.500mol%, S
Additive 0.001 obtained by firing a mixture consisting of iO_2 40.000 to 67.5 mol% at 1200°C or higher
~10.000 parts by weight was heated at 1100°C.
A method for manufacturing a varistor, which comprises firing in the above manner, followed by firing at 1200°C or higher in a reducing atmosphere, and then firing at 900 to 1300°C in an oxidizing atmosphere.