JP2002353007A - Voltage-dependent nonlinear resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite perovskite-based varistor which has superior electrical characteristics and a relatively low varistor voltage and the function of which is not damaged, even if the varistor is subjected to high-temperature soldering. SOLUTION: This composite perovskite-based varistor is composed of a composite perovskite semiconductor porcelain, containing at least one component selected from among a first component composed of oxides of Sr, Ba, Ca, and Ti, a second component composed of at least one oxide selected from among the oxides of R (Y and lantanoids), and a third component composed of at least one oxide selected from among the oxides of M (Nb and Ta), a fourth component consisting of Si oxide, and a fifth component consisting of Co oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage-dependent nonlinear resistor (varistor), and more particularly to (Sr, Ba, C
a) A varistor provided with a composite perovskite-based porcelain having a composition of TiO ₃ .

[0002]

2. Description of the Related Art A varistor is a resistance element whose resistance changes nonlinearly in response to a change in applied voltage.
A resistance element whose resistance value sharply decreases when a voltage higher than a certain voltage value is applied.

There are various types of porcelains mainly composed of varistors, but (Sr, Ba, C
a) The composite perovskite-based porcelain having the composition of TiO ₃ has both functions of non-linearity of resistance and capacitance, so that it can absorb a surge voltage generated in an electronic device and can reduce noise. It is very suitable for removing. For example, it is applied to a ring varistor for a DC micromotor.

A varistor provided with this composite perovskite-based porcelain can control the temperature dependence of the varistor voltage by selecting the A-site ratio, that is, the molar ratio of Sr, Ba and Ca. That is, in order to prevent the varistor voltage (voltage at which the resistance value sharply decreases) from dropping as the temperature rises during operation and prevent an excessive current from flowing through the varistor or cause thermal runaway, the temperature dependency is reduced to around zero. Can be adjusted. Japanese Patent Publication No. 8-28287 (Japanese Unexamined Patent Publication No.
No. 46702), JP-A-3-45559 and JP-A-294497 (JP-A-3-23757).
Discloses a varistor in which the temperature dependence of the varistor voltage is adjusted as described above.

[0005]

In recent years, when mounting electronic devices such as varistors, the speed of soldering work has been improved, and high-temperature soldering and lead-free soldering have been used. The temperature is increasing. For this reason, the varistor is subjected to severe soldering conditions, and a thermal crack due to a local thermal shock is easily generated. Further, an Ag (silver) electrode is generally used as an electrode of the varistor, but at a high temperature of soldering, an Ag component of this electrode elutes into the solder, and at least a part of the electrode is lost. As a result, the function as a varistor may be impaired.

In order to obtain a varistor resistant to such thermal shock, Japanese Patent Application Laid-Open No. 63-276201 discloses a varistor.
In the publication, a ring varistor made of TiO ₂ ceramics is described, but no specific data is described. Moreover, such a TiO ₂ -based varistor porcelain cannot be adopted because it is considerably inferior to the composite perovskite-based varistor porcelain in terms of electric characteristics relating to capacitance and varistor voltage controllability.

In order to obtain a varistor resistant to thermal shock, the applicant of the present invention has prepared a first component comprising oxides of Sr, Ba, Ca and Ti and at least one oxide selected from oxides of R (Y and lanthanoids). A second component consisting of
At least one selected from oxides of (Nb and Ta)
The composition of the composite perovskite-based semiconductor porcelain containing at least one of the third component composed of a seed and the fourth component composed of an oxide of Si is 0.10 ≦ a / (a + b +
c) ≦ 0.40, 0.30 ≦ b / (a + b + c) ≦ 0.
50, 0.20 <c / (a + b + c) ≦ 0.50, 0.
84 ≦ (a + b + c + e) / (d + f) ≦ 1.16,
1.0 ≦ (e + f) /d×100≦10.0, g / d ×
100 ≦ 0.6 (where a represents Sr of the first component as SrO
, B is the number of moles of Ba in the first component converted to BaO, c is the number of moles of Ca in the first component converted to CaO, and d is the mole of Ti in the first component converted to TiO _2. The number and e represent R of the second component as YO _3/2 , CeO ₂ , PrO
_{11/6, TbO 7/4, RO 3/} 2 moles converted respectively (other lanthanides), f is the third component M
Is the number of moles converted to NbO _5/2 and TaO _5/2 , respectively, and g is the number of moles converted to Si of the fourth component to SiO ₂ ), and a varistor substantially free of Mg is proposed first. (Japanese Patent Application 2000-347896).

However, in the varistor previously proposed by the present applicant, under the manufacturing conditions taking heat resistance into consideration,
It was very difficult to obtain a relatively low varistor voltage of 3-15V.

Accordingly, an object of the present invention is to provide a composite perovskite-based varistor which has excellent electrical characteristics and whose function is not impaired even when high-temperature soldering is performed.

Another object of the present invention is to provide a composite perovskite-based varistor having a relatively low varistor voltage.

[0011]

According to the present invention, Sr,
A first component comprising an oxide of Ba, Ca and Ti;
(Y and lanthanoid) oxides
A second component consisting of at least one and an acid of M (Nb and Ta)
Of a third component comprising at least one member selected from the group consisting of
A fourth component comprising at least one component and an oxide of Si;
And a fifth component comprising a Co oxide
The composition of the perovskite semiconductor ceramic is 0.30 ≦ a /
(A + b + c) ≦ 0.40, 0.30 ≦ b / (a + b +
c) ≦ 0.40, 0.25 ≦ c / (a + b + c) ≦ 0.
35, 0.84 ≦ (a + b + c + e) / (d + f) ≦
1.01, 1.0 ≦ (e + f) / d × 100 ≦ 10.
0, g / d × 100 ≦ 0.6, 0.01 ≦ h / d × 10
0 ≦ 1.50 (where a is Sr of the first component to SrO
The converted mole number, b, is obtained by converting Ba of the first component to BaO.
The number of moles, c, is the mole of Ca of the first component converted to CaO.
The number d is the first component Ti₂Number of moles converted to
e represents R of the second component as YO_3/2, CeO₂, PrO
_11/6, TbO_7/4, RO_3/2(Other Lanta
And f is M of the third component.
To NbO_5/2, TaO_5/2Moles converted to
The number and g represent the fourth component Si as SiO₂Number of moles converted to
h represents Co of the fifth component as CoO_4/3In moles converted to
A varistor is provided.

[0012] By adding _{CoO 4/3,} which reduces the varistor voltage _{E 10.} However, if the addition amount is too large, sintering becomes excessive and thermal cracks are likely to occur, so the addition amount has an upper limit. By adding such an appropriate amount of CoO _4/3 to the above-described composition, a varistor having a large base strength after re-oxidation and a low frequency of occurrence of thermal cracks in a thermal shock test using a soldering iron can be used. A relatively low varistor voltage of ~ 15V can be obtained.

By reducing the amount of SiO ₂ used as a sintering aid as much as possible, the thermal shock resistance of the varistor is enhanced, and the occurrence of thermal cracks due to local thermal shock due to severe soldering conditions is suppressed. In addition, the decrease in sinterability caused by the decrease in the amount of SiO ₂ is caused by the total A / B represented by (a + b + c + e) / (d + f) (including other elements that can enter the lattice of the A-site component due to the ionic radius. (The ratio of the total number of moles of the A-site component to the total number of moles of the B-site component including other elements that can enter the lattice of the B-site component). Furthermore, by appropriately selecting these, the A site molar ratio, and the amount and type of the semiconducting agent in a well-balanced manner, the electrical characteristics of the varistor can be improved.

In the present invention, not only simple A / B, which is the ratio of the number of moles of the A-site component due to Sr, Ba and Ca alone to the number of moles of the B-site component due to Ti alone, but also includes additives. A parameter of total A / B, which is the molar ratio of the perovskite constituent ions, is introduced. That is, it is considered that what contributes to the sinterability is not the simple A / B but the total A / B. In particular, among the additives, the semiconducting agent is an important solid-solution ion, and in the case of the present invention in which the amount of addition is large, if a simple A / B is used, the error increases, and the total A / B
By using B, accurate control is possible only, and a varistor without characteristic variations can be provided.

As described above, in the above-described composition range of the present invention, in the varistor having a large base strength after re-oxidation and a low frequency of occurrence of cracks (thermal cracks) in a thermal shock test using a soldering iron, the varistor is 3 to 3 times. A varistor voltage as low as 15 V can be obtained.

The composition of the first component and at least one of the second and third components is 0.96 ≦ (a + b +
It is preferable that c + e) / (d + f) ≦ 1.01. Further, the composition of at least one of the second component and the third component is 1.0 ≦ (e + f) /d×100≦4.0.
Is also preferable. Further, the composition of the fourth component is g
It is also preferable that /d×100≦0.3. Furthermore, the composition of the fifth component is 0.01 ≦ h / d × 100 ≦
It is also preferably 1.00.

The porcelain is composed of Li, Na, Mn, Ni, Cu,
It further contains a sixth component consisting of at least one selected from oxides of Zn, Sc, Fe, Ga, In, Mo and W, and 0 <i / d × 100 ≦ 0.1 (provided that
i is the sixth component Li, Na, Mn, Ni, Cu, Zn,
Sc, Fe, Ga, In, Mo, and W are LiO _1/2 , N
aO _1/2 , MnO, NiO, CuO, ZnO, ScO
_3/2 , FeO _3/2 , GaO _3/2 , InO _3/2 ,
MoO ₃ , WO ₃ ).

[0018] By adding the sixth component may be adjusted electrical characteristics such as varistor voltage E ₁₀ and the non-linear coefficient alpha. For example, Mn has the effect of increasing the nonlinear coefficient α. Various components other than those listed here can be used. If the addition amount is too large, the varistor voltage E ₁₀ becomes 15 V
That's all.

It is preferable that an electrode is formed on the surface of the porcelain, and that the electrode be made of Cu or a material containing Cu as a main component. In the latter case, the electrode is more preferably made of Cu containing Cu alloy or glass frit.

[0020]

FIG. 1 is a plan view showing the structure of a ring varistor according to an embodiment of the present invention, and FIG.
It is a line sectional view.

In FIG. 1, reference numeral 10 denotes a varistor porcelain formed in a ring shape, and 11 denotes an electrode formed on one surface thereof. In this embodiment, five electrodes 11 are provided at equal angles. As shown in FIG. 1B, the varistor porcelain 10 includes an internal semiconductor portion 10a and an insulating layer 10b formed near the entire surface thereof.

The composition of the varistor porcelain 10 will be described below.

The varistor porcelain 10 comprises a first component of a composite perovskite comprising oxides of Sr, Ba, Ca and Ti, R (Y and lanthanoids (La, Ce, Pr, N
d, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb and Lu)) at least one of a second component comprising at least one selected from oxides and M (Nb and Ta) a third component comprising at least one selected from oxides; , A fourth component composed of an oxide of Si and a fifth component composed of an oxide of Co.
a is the number of moles of Sr of the first component converted to SrO, b is the number of moles of Ba of the first component converted to BaO, c is the number of moles of Ca of the first component converted to CaO, and d is the first component. Ti
Is the number of moles converted to TiO ₂ , and e represents R of the second component as YO
_3/2 , CeO ₂ , PrO _11/6 , _{TbO 7/4} , R
The number of moles converted to O _3/2 (other lanthanoids), and f represents M of the third component as NbO _5/2 , TaO
_The number of moles converted to _5/2 and g are Si of the fourth component.
Is the number of moles converted to SiO ₂ , and h is Co to CoO _4/3
The varistor porcelain has the following composition: 0.30 ≦ a / (a + b + c) ≦ 0.40;
0.30 ≦ b / (a + b + c) ≦ 0.40, 0.25 ≦
c / (a + b + c) ≦ 0.35, 0.84 ≦ (a + b +
c + e) / (d + f) ≦ 1.01, 1.0 ≦ (e + f)
/D×100≦10.0, g / d × 100 ≦ 0.6,
0.01 ≦ h / d × 100 ≦ 1.50 This composition is more preferably 0.96 ≦ (a + b + c + e) /
(D + f) ≦ 1.01, 1.0 ≦ (e + f) / d × 10
0 ≦ 4.0, g / d × 100 ≦ 0.3, 0.01 ≦ h /
d × 100 ≦ 1.00.

The first component is a main component of the varistor porcelain 10, and in the composite perovskite, is composed of an A-site component composed of Sr, Ba and Ca and a B-site component composed of Ti. The second component and the third component are metal oxides that contribute to semiconductor conversion, and the fourth component is added mainly for improving sinterability. Further, the fifth component is added to lower the varistor voltage.

The electrical properties of the varistor is mainly expressed in temperature characteristics and nonlinear coefficient of varistor voltage E ₁₀ alpha. Varistor voltage _{E 10} represents an applied voltage value when a current flows in 10mA varistor, the nonlinear coefficient alpha is expressed by general _{α = 1 / log (E 10} / E 1). However, E ₁ is the applied voltage value when a current flows in 1mA in the varistor.

The Sr, Ba and Ca mole ratios of the A site component are set so that Sr is 0.30 or more and 0.40 or less,
Is set to be 0.30 or more and 0.40 or less, and Ca is set to 0.25 or more and 0.35 or less.
Control of the varistor voltage E _10, it is possible to improve the electrical characteristics improve and resistance to thermal shock resistance of the varistor, such as E ₁₀ temperature characteristics and nonlinear coefficient alpha. That, Sr is too large becomes E ₁₀ temperature characteristic negative, becomes high varistor voltage E ₁₀ is too small. Also,
Ba is too large too much or nonlinear coefficient varistor voltage E ₁₀ becomes higher α decreases, becomes too small E ₁₀ temperature characteristic becomes negative. Furthermore, Ca is nonlinear coefficient α with respect to the varistor voltage E ₁₀ be too much or too less becomes small. In addition, Ca is too large, the varistor voltage E ₁₀ becomes difficult to control becomes extremely large, resulting in too little E ₁₀ temperature characteristic becomes negative.

More preferably, the mol% (calculated by the number of moles of metal ions) of the semiconducting agent (second and / or third component) with respect to the main component (TiO ₂ ) is 1.0 or more and 10.0 or less. By setting the value to be 1.0 or more and 4.0 or less, the thermal shock resistance of the varistor can be enhanced. That is, if the amount of the semiconducting agent is too large or too small, a thermal crack is easily generated.

The total A / B is 0.84 or more and 1.
By setting so as to be 01 or less, more preferably 0.96 or more and 1.01 or less,
As described later, the sinterability can be improved even when the amount of the fourth component (SiO ₂ ) is reduced. That is, if the total A / B is too large or too small, sintering is hindered, and the substrate becomes insulated by reoxidation. Also, if the total A / B is too large or too small, the strength is reduced and thermal cracks are easily generated. In a region where the amount of SiO ₂ is small and the amount of the semiconducting agent is large as described above, the upper limit of the total A / B is set to 1.0 in order to maintain the thermal crack resistance.
Control is set to 1 or less.

The fourth component (S) with respect to the main component (TiO ₂ )
By setting the molar percentage of iO ₂ ) to be 0.6 or less, more preferably 0.3 or less, the thermal shock resistance of the varistor can be greatly increased. That is, SiO ₂ is added as a sintering aid, and if it is contained, it can be stably fired even if its composition fluctuates. However, if its amount increases, thermal cracks are likely to occur.

The fifth component (C) with respect to the main component (TiO ₂ )
oO _4/3 ) is more preferably 0.01 or more and 1.0 or less, and more preferably 0.01 or more and 1.0 or less.
0 by setting to become less, it is possible to reduce the varistor voltage E ₁₀ without causing thermal cracking. That is, when include CoO _4/3 varistor voltage E ₁₀ becomes small and the addition amount is too large, because the thermal cracking become excessive sintering tends to occur.

By not substantially containing Mg, the thermal shock resistance of the varistor can be improved.
That is, if Mg is contained in the porcelain, thermal cracks are likely to occur. "Substantially not contained" indicates that the content is generally less than 0.001 mol%.

The varistor porcelain 10 is composed of Li, Na, Mn,
A sixth material made of at least one selected from oxides of Ni, Cu, Zn, Sc, Fe, Ga, In, Mo and W.
A component (additional additive) may be further contained. The content is Li, Na, Mn, Ni, Cu, Zn, S
c, Fe, Ga, In, Mo and W are converted to LiO _1/2 , Na
O _1/2 , MnO, NiO, CuO, ZnO, ScO
_3/2 , FeO _3/2 , GaO _3/2 , InO _3/2 ,
If the number of moles is calculated as MoO ₃ or WO ₃ , 0
It is preferable that <i / d × 100 ≦ 0.1. This allows adjusting the electrical characteristics such as varistor voltage E ₁₀ and the non-linear coefficient alpha. For example, Mn is capable of increasing the nonlinear coefficient alpha, the amount is too large, the varistor voltage E ₁₀ becomes high as more than 15V.

The varistor porcelain 10 may contain other elements, for example, P, S, K, Al, Zr, and the like as unavoidable impurities in addition to such additives. Such elements usually exist as oxides.

As described above, the varistor porcelain 10 is a polycrystal composed of a perovskite crystal. Each of the components is partially dissolved in the crystal grains to enter the perovskite-type crystal, and partially exists as an oxide or a composite oxide at the crystal grain boundaries. For example, Ba, Ca, Sr,
Ti, Nb, Ta, Y, lanthanoids, etc. are present abundantly in crystal grains, and Mo, W, Mn, Si, etc. are abundantly present at crystal grain boundaries.

The average crystal grain size of the varistor porcelain 10 is usually about 0.5 to 10 μm, especially about 1 to 6 μm.

The electrode 11 is formed of Cu or a material containing Cu as a main component. If the electrode is formed of Ag, the high temperature of soldering causes the Ag component of this electrode to elute into the solder, and at least a part of the electrode is lost. The electrode 11 is hardly corroded even at a high temperature and can withstand a high-temperature soldering operation.

Materials containing Cu as a main component include Cr, Z
Cu alloy such as r, Ag, Ti, Be, Zn, Sn, Ni, Al or Si, or Li, Na, K, Sr, B
a, Mn, Cu, Cu containing Zn, B, Si, Al, Bi, or glass frit by oxide such as Pb.

FIG. 2 is a characteristic diagram showing the ratio of the remaining electrode area to the solder temperature when Cu and Ag are used as the electrode materials, respectively.

After a flux is applied to a ring varistor as a sample and preheated, the ring varistor is immersed in a solder bath of eutectic solder at each temperature for 5 seconds.

As is apparent from FIG.
At 0 ° C., the erosion progresses in the Ag electrode and the residual electrode area is about 55.5%, whereas the Cu electrode does not erode at all and the residual electrode area is 100%.

Next, a method of manufacturing the varistor porcelain 10 will be briefly described.

The varistor porcelain 10 mixes raw material powders,
It is obtained by treating in the order of calcination, pulverization, molding, binder removal, reduction firing, and reoxidation.

As the raw material powder, a powder of a compound of each of the constituent elements of the porcelain is usually used. As the raw material powder, an oxide or a compound which becomes an oxide by firing, for example, a carbonate, a hydroxide, or the like can be used. For example, taking Ba as an example, its raw materials are BaCO ₃ , BaS
iO ₃ , BaO, BaCl ₂ , Ba (OH) ₂ , Ba
(NO ₃ ) ₂ , alkoxide (eg, (CH ₃ O) ₂ B
At least one barium compound such as a) can be used. The average particle size of the raw material powder is usually 0.2 to 5 μm.
m.

First, the raw material powder is weighed so that the final composition becomes the above-mentioned composition, and is usually wet-mixed. Then
After the dehydration treatment, it is dried and calcined at about 1800 to 1250 ° C. for about 2 to 4 hours. Next, after pulverizing the calcined product, an organic binder is added, and water, a pH adjuster, a humectant and the like are further added and mixed. Next, after the mixture is molded and subjected to binder removal treatment, the mixture is reduced to 1250 to 140 in a reducing atmosphere.
It is baked at about 0 ° C. for about 2 to 4 hours to obtain a semiconductor porcelain.

Note that Nb, Ta, Y, lanthanoid, M
For each raw material powder such as o, W, Mn, Si, etc., the oxide thereof may be added at the time of mixing after calcination. Co may be mixed with other raw materials at once before calcining, or CoO _4/3 may be added after calcining.

The semiconductor porcelain obtained in this manner is, for example, 800 to 1 mm in an oxidizing atmosphere such as air so that an appropriate varistor voltage according to the purpose can be obtained.
Heat treatment (reoxidation treatment) is performed at a temperature of about 000 ° C. By this heat treatment, the insulating layer 10b is formed on the surface layer. Varistor characteristics are exhibited by the presence of the insulating layer. If the insulating layer is thick, the nonlinear coefficient α and the varistor voltage increase, and if the insulating layer is thin, the nonlinear coefficient α and the varistor voltage decrease, so that the insulating layer has an appropriate thickness according to the characteristics required for the product. Heat treatment conditions may be appropriately selected.

After the re-oxidation treatment, an electrode is formed on one surface of the varistor porcelain with Cu or a material containing Cu as a main component, to obtain a varistor.

[0048]

Hereinafter, the present invention will be described in more detail with reference to specific examples.

[0049]Example 1  In Example 1, the mol% and the type of the
A / B, SiO₂% Of CoO and CoO_4/3Mole of
% And other parameters such as
This is a comparison using samples with different ratios.

First, as raw materials SrCO ₃ , BaC
_{O 3, CaCO 3, TiO 2} , NbO 5/2, Si
O ₂ and CoO _4/3 were converted and weighed so as to have the compositions shown in Table 1, mixed, mixed using a wet media mill for 10 to 20 hours, dehydrated and dried.

The obtained mixture was subjected to 11 using a tunnel furnace.
After calcining at 50 ° C., the mixture was coarsely pulverized, mixed again by a wet media mill for 10 to 20 hours, then dehydrated and dried. Next, the mixture was mixed with 1.0 to 1.5% by weight of polyvinyl alcohol as an organic binder, granulated, and molded at a molding pressure of 2 t / cm ² to have an outer diameter of 12 mm.
A molded body having an inner diameter of 9 mm and a thickness of 1.0 mm was produced.

After demolding the molded body in an air atmosphere at about 1000 ° C., N ₂ (95% by volume) + H ₂
In a (5% by volume) reducing atmosphere, baking was performed at about 1300 ° C. for 4 hours to obtain a semiconductor porcelain. Next, the semiconductor porcelain was reoxidized in air at 900 ° C. for 4 hours to obtain a varistor porcelain.

Next, as shown in FIG. 1, a Cu paste is applied to one surface of the varistor porcelain 10 and baked at 750 ° C. in a neutral atmosphere to form a five-pole Cu electrode 11 as shown in FIG. This was used as a varistor sample for measurement.

[0054] Then, the measures of _{E 1} and _{E 10} at 20 ° C. for each sample, using the _{E 1} and _{E 10} was measured, alpha = 1 / _log nonlinear coefficient alpha from _(E 10 / _{E 1)} I asked. Furthermore, it was determined also the temperature characteristic of the varistor voltage E ₁₀ (temperature coefficient). Furthermore, each sample was subjected to a thermal crack test.

[0055] Determination of _{E 1} and _{E 10} was measured using the measurement circuit shown in FIG. In this measurement circuit, the ammeter 30
Are connected in series between a varistor 31 and a DC constant current source 32, and a voltmeter 33 is connected in parallel to the varistor 31. E ₁ and E ₁₀ are 1 mA each for the varistor 31.
And the voltage between both terminals of the varistor 31 when a current of 10 mA flows was measured using an ammeter 30 and a voltmeter 33.

The temperature characteristic (temperature coefficient) ΔE _10T of the varistor voltage E ₁₀ is ΔE _10T = ｛E for each sample.
_{10 (85) -E 10 (20} )} / {E 10 (20) ×
(85-20)｝ × 100 [% / ° C.] E ₁₀ (20) and E ₁₀ (85) are each 2
A varistor voltage _{E 10} at 0 ℃ and temperature of 85 ° C.. These were measured using a thermostat.

The thermal crack test was performed by bringing a soldering iron having a preset temperature into contact with the electrode surface of the sample left at room temperature for 3 seconds while supplying eutectic solder. As the temperature of the soldering iron, three temperatures of 360 ° C, 400 ° C and 450 ° C were used. The number of samples was 100, and the presence or absence of cracks was visually determined using alcohol. Table 1 shows the results.

[0058]

[Table 1]

[0059] The molar ratio of the A site component, the electrical characteristics of the varistor, especially a significant effect on the temperature characteristic of the varistor voltage E _10. E ₁₀ temperature characteristics, -0.05 + 0.0
It is desirable to be in the range of 5% / ° C. Therefore, samples 15 to 18 are not in the preferable range.

[0060] Even E ₁₀ temperature characteristics good, those varistor voltage E ₁₀ is high is deviated from the spirit of the present invention. Samples 8, 10 and 19 are considerably high varistor voltage _{E 10} for Ca is too large, it can not be adopted. The varistor voltage _{E 10,} and it is desired at 15V or less, therefore, the sample 9, 11 and 18 are not preferred ranges.

Further, since the nonlinear coefficient α is desired to be 3.0 or more, the samples 12 to 17 are not in the desired range.

[0062] _{Therefore, E 10} temperature characteristic is -0.05 +
In the range of 0.05 [% / ° C.] and the varistor voltage E ₁₀
Is not more than 15 V, and the non-linear coefficient α is not less than 3.0, the samples 1 to 7 can be said to be preferable ranges of the present invention. This corresponds to the A site molar ratio defined in claim 1.
Within this range, cracks did not occur in the thermal crack tests at soldering iron temperatures of 360 ° C, 400 ° C and 450 ° C.

In particular, sample 4 has varistor voltages E ₁₀ , E
₍₁₀₎ The balance between the temperature characteristics and the nonlinear coefficient α is the best, and the molar ratio of the A-site component around this is the most preferable range of the present invention.

[0064]Example 2  In Example 2, the ratio by the sample in which the amount of the semiconducting agent was changed was
It is a comparison.

The other parameters such as the A-site molar ratio, the type of the semiconducting agent, the total A / B, the mol% of SiO _{2 and} the mol% of CoO _4/3 are _kept constant, and the mol% of the semiconducting agent is shown in Table 2. Specimens were prepared in the same manner as in Example 1 except that those shown in Table 1 were used, and the same measurements were performed on these samples as in Example 1. Table 2 shows the results.

[0066]

[Table 2]

The amount of the semiconducting agent affects the thermal crack resistance of the varistor porcelain. Samples 20 and 25
Since the amount of the semiconducting agent is too small and too large, thermal cracks occur in a test at a soldering iron temperature of 360 ° C., which is not preferable. Therefore, when the soldering iron temperature is 36
Samples 4 and 21 to 24 in which thermal cracks do not occur in the test at 0 ° C. are within the preferred range of the present invention. This corresponds to the mol% of the semiconducting agent specified in claim 1.

Further, the sample 24 has a soldering iron temperature of 400
Since thermal cracks occur in the tests at 400 ° C. and 450 ° C., Samples 4 and 21 to 23 in which no cracks occur in the thermal crack tests at 400 ° C. and 450 ° C. fall within the more preferable range of the present invention. This corresponds to the mol% of the semiconducting agent specified in claim 3. Sample 4
Is the most preferred range of the present invention.

[0069]Example 3  Example 3 is based on a sample in which the type of the semiconducting agent is changed.
It is a comparison.

The other parameters such as the A site molar ratio, the mol% of the semiconducting agent, the total A / B, the mol% of SiO _{2 and} the mol% of CoO _4/3 are _kept constant, and the type of the semiconducting agent is shown in Table 3. Specimens were prepared in the same manner as in Example 1 except that those shown in Table 1 were used, and the same measurements were performed on these samples as in Example 1. Table 3 shows the results.

[0071]

[Table 3]

In any of Samples 4 and 26 to 42, no thermal cracks were generated in the test where the soldering iron temperature was 360 ° C. and the test where the soldering iron temperature was 400 ° C.
_{O 5/2, TaO 5/2,} YO 3/2, LaO 3/2,
CeO ₂ , PrO _11/6 , NdO _3/2 , SmO
_{3/2, EuO 3/2, GdO 3/2,} TbO 7/4,
DyO _3/2 , HoO _3/2 , ErO _3/2 , TmO
_3/2 , YbO _3/2 , LuO _3/2 or NbO _5/2
The use of + YO _3/2 (equimolar number) is a preferred range of the present invention. This corresponds to the type of semiconducting agent specified in claim 1.

[0073]Example 4  In Example 4, the ratio by the sample in which the total A / B was changed was
It is a comparison.

The other parameters such as the A site molar ratio, the mol% and type of the semiconducting agent, the SiO ₂ mol% and the CoO _4/3 mol% are _kept constant, and the total A / B is shown in Table 4. Samples were prepared in the same manner as in Example 1 except that the measurement was performed, and the same measurement as in Example 1 was performed on these samples. Table 4 shows the results.

[0075]

[Table 4]

The value of the total A / B affects the sinterability of the porcelain. Samples 43 and 49 do not operate as varistors because the total A / B is too small and too large, respectively, so that dense porcelain cannot be sintered, and the whole is insulated by reoxidation. further,
Thermal cracks also occur when the soldering iron temperature is 360 ° C.

As can be seen from Table 4, in a region where the amount of SiO ₂ is small and the amount of the semiconducting agent is large,
To maintain thermal crack resistance, total A /
In particular, it is essential to control the upper limit of B. When the total A / B exceeds 1.16, thermal cracks occur at 360 ° C., and when the total A / B exceeds 1.01, thermal cracks occur at 400 ° C. and 450 ° C.

Although the sample 48 had a soldering iron temperature of 360 ° C. and no thermal cracks, the varistor voltage E ₁₀
Has greatly exceeded 15V. Therefore, sample 4
And 44 to 47 are preferred ranges of the present invention. This corresponds to the total A / B range defined in claim 1.

[0079] Furthermore, Sample 4 and 45 to 47 do not thermal cracking occurs even in test soldering iron temperature of 400 ° C. and 450 ° C., and also the varistor voltage _{E 10} 15
V or less, which is a more preferable range of the present invention.
This corresponds to the total A / B range defined in claim 3. This corresponds to the total A / B range defined in claim 2. Note that the vicinity of the total A / B where the B site component is slightly rich as in the sample 4 is the most preferable range of the present invention.

[0080]Example 5  This Example 5 is based on SiO 2₂By changing the mole% of the sample
It is a comparison.

A site molar ratio, mol% of semiconducting agent and
Type, total A / B and CoO _4/3Mole% of
Keep other parameters constant,₂Table 5 shows the mole% of
The same as in Example 1 except that
In the same manner as in Example 1.
Various measurements were performed. Table 5 shows the results.

[0082]

[Table 5]

SiO ₂ is added as a sintering aid, and if it is contained, it can be stably fired even if its composition fluctuates. However, if its amount increases, thermal cracks are likely to occur.

Samples 54 and 55 are not preferable because thermal cracks are generated even in a test in which the soldering iron temperature is 360 ° C. because the amount of SiO ₂ is too large. Therefore, the samples 4 and 50 to 53 in which the thermal crack does not occur even in the test in which the soldering iron temperature is 360 ° C. and the test in which the soldering iron temperature is 400 ° C. are the preferred ranges of the present invention. This corresponds to the mol% of SiO ₂ defined in claim 1. The sample 50 is made of Si
This is the case where the added amount of O ₂ is 0, but actually, the SiO ₂ content of the sample 50 is not 0 because each raw material contains SiO ₂ as an impurity.

Further, the sample 53 has a soldering iron temperature of 450.
Thermal cracks occur in the test at
Even if the test is performed at a temperature of 450 ° C
Samples 4 and 50 to 52 in which no cracks are generated
It will be a good range. This corresponds to the SiO 2 defined in claim 4.
₂Corresponds to the mole% of In addition, the SiO 2 around the sample 4 ₂
Is the most preferred range of the present invention.Example 6  This Example 6 uses CoO_4/3Sample with different mole% of
This is a comparison.

A site molar ratio, mol% of semiconducting agent and
Type, total A / B and SiO ₂Mol% of other
With the parameters constant,_4/3Table 6 shows the mole% of
The same as in Example 1 except that
In the same manner as in Example 1.
Various measurements were performed. Table 6 shows the results.

[0087]

[Table 6]

[0088] By adding _{CoO 4/3,} the varistor voltage _{E 10} becomes small. However, when this addition amount is too large, sintering becomes excessive and thermal cracks are easily generated.

Sample 56 is shown as a comparative example without CoO _4/3 . The sample 56 is varistor voltage _{E 10} is gone beyond 15V. Sample 62 is
The soldering iron temperature is 360 ° C due to too much CoO _4/3
The test described above is not preferable because thermal cracks occur. Therefore, a test with a soldering iron temperature of 360 ° C.
Samples 4 and 57 to 61 in which thermal cracks do not occur even in the test at ° C. are the preferred ranges of the present invention. This corresponds to the molar percentage of CoO _4/3 specified in claim 1.

The sample 61 has a soldering iron temperature of 450.
Since a thermal crack occurs in the test at a temperature of 450 ° C., the samples 4 and 57 to 60 in which the thermal crack does not occur even in a test at a soldering iron temperature of 450 ° C. are in the more preferable range of the present invention. This corresponds to the CoO defined in claim 5.
_This corresponds to _4/3 mol%. In addition, Co around the sample 4
O _4/3 mol% is the most preferred range of the present invention.

[0091]Example 7  Example 7 is a sample in which the type and amount of the additive were changed.
It is a comparison by.

A site molar ratio, mol% and type of semiconducting agent, total A / B, SiO ₂ mol%, and CoO
Samples were prepared in the same manner as in Example 1 except that other parameters such as _4/3 mol% were kept constant and the types and amounts of the additional additives were as shown in Table 7. The same measurement as in Example 1 was performed. Table 7 shows the results.

[0093]

[Table 7]

[0094] adding additives has the effect of adjusting the electrical characteristics such as α varistor voltage E ₁₀ and non-linear coefficient. Mn increases the nonlinear coefficient α. Although not shown in Table 7, other Li, Na, Ni, Cu, Zn, Sc, F
A similar effect is observed for e, Ga and In.

[0095] Sample 66, because the amount is too large, the varistor voltage _{E 10} exceeds the 15V. Therefore, the samples 63 to 65 in which the mol% with respect to the main component is 0.10 or less are a preferable range of the present invention. This is included in the type and mol% of the additive additive specified in claim 6.

The embodiments and examples described above all illustrate the present invention by way of example and not by way of limitation, and the present invention can be embodied in other various modifications and alterations. . Therefore, the scope of the present invention is defined only by the appended claims and their equivalents.

[0097]

According to the present invention, as described [Effect Invention above in detail, by adding CoO _4/3, which reduces the varistor voltage E _10. However, if the addition amount is too large, sintering becomes excessive and thermal cracks are likely to occur, so the addition amount has an upper limit. Furthermore, by appropriately selecting these, the A site molar ratio, and the amount and type of the semiconducting agent in a well-balanced manner, the electrical characteristics of the varistor can be improved. That is, such an appropriate amount of Co
By adding O _4/3 to the above-described composition, a relatively low varistor of 3 to 15 V is used for a varistor having a large base strength after re-oxidation and a low frequency of occurrence of thermal cracks in a thermal shock test using a soldering iron. Voltage can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing a structure of a ring varistor according to an embodiment of the present invention, and a sectional view taken along line AA of FIG.

FIG. 2 is a characteristic diagram showing a ratio of a remaining electrode area to a solder temperature when Cu and Ag are used as electrode materials, respectively.

3 is a circuit diagram showing a measuring circuit of _{E 1} and _{E 10.}

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Varistor porcelain 10a Semiconductor part 10b Insulating layer 11 Electrode 30 Ammeter 31 Varistor 32 DC constant current source 33 Voltmeter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Matsuoka Dai 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Minoru Ogasawara 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Co., Ltd. F-term (reference) 5E034 CA08 CC01

Claims (9)

[Claims] 1. From oxides of Sr, Ba, Ca and Ti
The first component and an oxide of R (Y and lanthanoid)
A second component comprising at least one selected from the group consisting of:
At least one selected from oxides of (Nb and Ta)
At least one component of the third component consisting of a seed and Si
A fourth component composed of an oxide and a fifth component composed of an oxide of Co
Of composite perovskite-based semiconductor porcelain containing
0.30 ≦ a / (a + b + c) ≦ 0.40, 0.
30 ≦ b / (a + b + c) ≦ 0.40, 0.25 ≦ c /
(A + b + c) ≦ 0.35, 0.84 ≦ (a + b + c +
e) / (d + f) ≦ 1.01, 1.0 ≦ (e + f) / d
× 100 ≦ 10.0, g / d × 100 ≦ 0.6, 0.0
1 ≦ h / d × 100 ≦ 1.50 (where a is the first component
Is the number of moles of Sr converted to SrO, and b is Ba of the first component.
Is the number of moles converted to BaO, and c is Ca
The number of moles converted to O, and d is the first component Ti₂To
The converted number of moles, e represents R of the second component as YO_3/2, Ce
O₂, PrO _11/6, TbO_7/4, RO_3/2(That
Is the number of moles converted to other lanthanoids) and f is
M of the third component is NbO_5/2, TaO_5/2To each
The converted mole number and g are obtained by converting Si of the fourth component to SiO.₂Convert to
The number of moles, h, is obtained by converting Co of the fifth component to CoO_4/3Convert to
Voltage dependence characterized by the following:
Non-linear resistor. 2. The composition of the first component and at least one of the second component and the third component has a composition of 0.9.
2. The voltage-dependent nonlinear resistor according to claim 1, wherein 6 ≦ (a + b + c + e) / (d + f) ≦ 1.01. 3. 3. The composition of at least one of the second component and the third component is 1.0 ≦ (e + f) / d × 1.
3. The voltage-dependent nonlinear resistor according to claim 1, wherein 00 ≦ 4.0. 4. The composition of the fourth component is g / d × 100.
The voltage-dependent nonlinear resistor according to any one of claims 1 to 3, wherein ≤ 0.3. 5. The composition of the fifth component is 0.01 ≦ h /
2. The structure according to claim 1, wherein d.times.100.ltoreq.1.00.
5. The voltage-dependent nonlinear resistor according to any one of items 1 to 4. 6. The method according to claim 1, wherein the porcelain is Li, Na, Mn, Ni,
Acids of Cu, Zn, Sc, Fe, Ga, In, Mo and W
A sixth component consisting of at least one selected from
It further contains 0 <i / d × 100 ≦ 0.1 (
Where i is the sixth component Li, Na, Mn, Ni, Cu,
Zn, Sc, Fe, Ga, In, Mo and W are converted to LiO
_1/2, NaO_1/2, MnO, NiO, CuO, Zn
O, ScO _3/2, FeO_3/2, GaO_3/2, In
O_3/2, MoO₃, WO₃Is the number of moles converted to
6. The method according to claim 1, wherein
2. The voltage-dependent nonlinear resistor according to 1. 7. The device according to claim 1, further comprising an electrode formed on a surface of the porcelain, wherein the electrode is made of Cu or a material containing Cu as a main component. Voltage-dependent non-linear resistor. 8. The voltage-dependent nonlinear resistor according to claim 7, wherein said electrode is made of a Cu alloy. 9. The voltage-dependent nonlinear resistor according to claim 7, wherein the electrode is made of Cu containing glass frit.