JP2002246207A - Voltage nonlinear resistor and porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in which it is hard to manufacture varistors that are excellent in loading service life characteristics and kept high in uniformity. SOLUTION: This varistor is formed of ZnO as a main component, and Pr, Co, Cr, Al or Ga or In, Si, and (Ca+Sr) are added as auxiliary components to the main component, where Si and (Ca+Sr) amount to 0.001 to 0.5 atom % and 0.01 to 0.5 atom %, respectively, and the ratio Ca/Sr is set at 0 to 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistor and a resistor ceramic composition containing zinc oxide (Zn0) as a main component and suitable as a resistor for an overvoltage protection element.

[0002]

2. Description of the Related Art A voltage non-linear resistor mainly composed of Zn0 has characteristics such as a low limiting voltage and a large voltage ratio linear coefficient. It is widely used as a varistor for the purpose of overvoltage protection of electronic devices configured.

Various non-linear components are added to a voltage non-linear resistor mainly composed of Zn0 to improve characteristics. Japanese Patent Publication No. 1-25205 discloses that Zn0 is a main component, and at least one kind of rare earth element as a subcomponent is 0.08 to 5.0 atomic% in total, and 0.1 to 10.0 atomic% of Co. %, At least one of Mg and Ca is 0.01 to 5.0 atomic%, at least one of K, Cs and Rb is 0.01 to 1.0 atomic% in total, and Cr is 0.01 to 1.0 atomic%. 0 at%, B at 0.0005 to 0.1 at%, and at least one of Al, GA, and In at a total amount of 0.0001 to 0.05 at% to improve long wave tail surge resistance. Is disclosed.

Japanese Patent Application Laid-Open No. 9-326305 discloses that Zn0 is used as a main component, and at least one rare earth element is added as a subcomponent in a total amount of 0.08 to 5.0 atomic% and Co is added in a content of 0.1 to 0.1 atomic%. 0.1 to 0.5 at%, 0.1 to 0.5 at% of Ca, 0.01 to 1.0 at% of at least one of K, Cs, and Rb, 0.1 to 0.6 at% of Cr %, At least one of Al, Ga, and In in a total amount of 0.0
It is disclosed that B (boron) is further added in an amount of 0.0005 to 0.1 atomic% to 004 to 0.03 atomic% in addition to the above-mentioned components and the above components to increase the allowable power.

[0005]

The secondary components disclosed in the above two publications include K (potassium) and B
(Boron). K and B are supplied in the form of these oxides or compounds that can become oxides during the firing process during the manufacture of the voltage non-linear resistor. But K
Since the oxides of B and B have a low melting point and are liable to be scattered during the firing step, the variability of the characteristics is inevitably increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a voltage non-linear resistor which can be manufactured while suppressing variations in electrical characteristics, has a small change in leakage current and a small asymmetrical deterioration in the service life characteristics, and a voltage non-linear resistor. It is to provide a porcelain composition.

[0007]

In order to solve the above-mentioned problems and to achieve the above-mentioned object, the present invention comprises ZnO (zinc oxide) as a main component and Pr (praseodymium) as a sub-component at 0.05%. 3.00 atomic%, Co (cobalt) 0.1-5.0 atomic%, Cr (chromium) 0.01-
0.50 atomic%, at least one of Al (aluminum), Ga (gallium) and In (indium) is 0.001 to 0.020 atomic%, and Si (silicon) is 0.0
01 to 0.500 atomic%, and Ca + Sr (however, C
a / Sr of 0 to 50) is added in an amount of 0.01 to 0.50 atomic%.

[0008] The composition for obtaining the resistor is ZnO
(Zinc oxide) as a main component, and Pr as a subcomponent.
The compound is converted to Pr (praseodymium) of 0.05 to
3.00 atomic%, Co compound is converted to Co (cobalt), 0.1 to 5.0 atomic%, Cr compound is converted to Cr (chromium), 0.01 to 0.50 atomic%, Al compound And at least one of Ga compound and In compound is A
0.001 to 0.020 atomic% in terms of l (aluminum), Ga (gallium) and In (indium), and 0.001 in terms of Si compound in terms of Si (silicon).
It is desirable that the amount is 0.01 to 0.50 atomic% in terms of Ca + Sr (where Ca / Sr is 0 to 50) and the Ca compound + Sr compound is added in an amount of 0.01 to 0.50 atomic%.

[0009]

The invention of each claim has the following effects. (1) K (potassium) and B (boron) that are easily scattered
, The variation in the characteristics of the voltage nonlinear resistor during mass production can be suppressed. (2) Not containing K and B, but containing Si and M (Ca, S
r) is included in a predetermined range to prevent the deterioration of various electrical properties,
In addition, it is possible to achieve the suppression of the leakage current change and the suppression of the asymmetrical deterioration in the charging life characteristic. Although it is not clear why the subcomponent according to the present invention improves the application life characteristics, it is recognized that the subcomponent according to the present invention is segregated at the triple point of the sintered body, and is an element hard to enter the crystal grains. This is probably due to something. It is considered that the presence of the subcomponent element near the grain boundary suppresses the migration of interstitial Zn ions. Since the above migration is considered to be related to characteristic deterioration,
According to the present invention, characteristic deterioration is reduced.

[0010]

Embodiments and Examples Next, embodiments and examples of the present invention and comparative examples will be described with reference to Tables 1 to 5 and FIG. In each table, the composition ratio of the sub-component shown in atomic%, the ratio of Ca and Sr, and various characteristics are shown. In addition,
In the column of ΔV 1 _μA , + indicates the characteristic in the positive direction, and-indicates the characteristic in the negative direction.

In order to obtain a voltage non-linear resistor according to the present invention and a comparative example, zinc oxide Zn0 powder as a main component,
Pr (praseodymium), Co (cobalt), Cr (chromium), Al (aluminium) or Ga as a subcomponent
(Gallium) or In (indium), Si (silicon),
Each compound of Ca (calcium) and Sr (strontium) was prepared. Each of the sub-component compounds is praseodymium oxide Pr ₆ O ₁₁ , cobalt oxide Co ₃ O _4, and chromium oxide C
r ₂ O ₃ , aluminum oxide Al ₂ O ₃ or gallium oxide Ga ₂ O ₃ or indium oxide In ₂ O ₃ and silicon oxide Si
O ₂ , calcium carbonate CaCO _3, and strontium carbonate SrCO ₃ were used. That is, the Zn0 as the main component to obtain a non-linear resistor according to the present invention, from 0.05 to 3.00 atomic% Pr ₆ O ₁₁ as a secondary component in terms of Pr, the Co ₃ O ₄ Co 0.1 to 5.0 atomic% in terms of
Cr ₂ O ₃ is converted to Cr to 0.01 to 0.50 atomic%,
Al ₂ O ₃ or a Ga ₂ O ₃ or In ₂ O ₃ in terms of Al or Ga, or an In 0.001 to 0.020 atomic%, SiO
₂ converted to Si, 0.001 to 0.500 atomic%, C
aCO ₃ + SrCO ₃ is converted to Ca + Sr from 0.01 to
Numerous porcelain compositions, i.e., porcelain materials, to which 0.50 at% was added were prepared as shown in Tables 1 to 4. Tables 1 to 5
The porcelain material of the comparative example shown in FIG. Table 1
The atomic% (in terms of percentage of metal element or Si) of the subcomponents in Table 5 is 100 with the number of Zn atoms being 100.
Is shown as a ratio of the number of atoms of Pr, Co, Cr, Al or Ga or In, Ca, Sr to the number of atoms of. For example, the composition of the metal element and Si of Sample No. 2 can be represented by the following chemical formula, that is, the composition formula. Zn ₁₀₀ Pr _0.02
Co _2.0 Cr _0.2 Al _0.005 Si _0.2 Ca _0.2 Sr _0.2
Although Zn0 is not shown in the sample of Table 5, Zn is 10
0 atomic%. Sample numbers marked with * in Tables 1 to 5 indicate comparative examples.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

[Table 4]

[0016]

[Table 5]

Next, an organic binder, an organic solvent and an organic plasticizer were added to the porcelain material of each sample, and the mixture was subjected to a ball mill.
Mix for hours to make a slurry. Next, a ceramic green sheet having a thickness of 30 μm was formed by a doctor blade method using each slurry, and a conductive paste composed of a palladium paste was screen-printed on the sheet to form a conductor layer for an internal electrode. Next, two green sheets are overlapped so that a pair of internal electrodes can be obtained, and a stacked body in which dummy green sheets are further stacked vertically is formed.
After these were heated and pressed, they were cut into a predetermined chip shape to obtain a green chip. After debinding the green chip at 300 ° C. for 3 hours, the green chip was fired at 1200 ° C. for 2 hours to obtain a sintered body. FIG. 1 shows a sintered body represented by first, second and third layers 1, 2, 3 and first and second internal electrodes 4 and 5, and first and second external terminal electrodes 6. , 7 are varistors (voltage non-linear resistor elements). The first layer 1 made of a voltage non-linear resistor disposed between the first and second internal electrodes 4 and 5 is non-linear when a voltage is applied to the first and second internal electrodes 4 and 5. Sexual resistance. In this example, the second and third layers 2 and 3 are also voltage non-linear resistors, but part or all of them may be made of porcelain having no voltage non-linearity.
Layers 2 and 3 can be omitted. The first and second external terminal electrodes 6 and 7 are formed by applying an electrode paste mainly composed of Ag to the end face of each sintered body and baking the paste at 800 ° C. The first and second external terminal electrodes 6 and 7 are electrically connected to the first and second internal electrodes 4 and 5, respectively.

The sintered body according to the present invention contains Pr, Co, Cr, Al at a ratio specified in the claims to Zn0.
Or, it is a porcelain resistor containing Ga or In, Si, Ca + Sr or Sr. Each element of the subcomponent is contained in the sintered body after firing in the form of an oxide.

The characteristics of each sample are as follows. The varistor voltage V _1mA per 1 mm thickness (V / m) when 1 mA flows between the external electrodes 6 and 7 of the varistor of each sample configured as shown in FIG.
m) and the varistor voltage V _{10 mA} (V / mm) per 1 mm thickness when 10 mA was passed, and the nonlinear coefficient α was determined by the following equation. α = log (10/1) / log ( _V10mA / _V1mA )

In order to measure the _charging life characteristics, a dc constant voltage _equivalent to 90% of _{VlmA was} applied to the varistor of each sample in dry air at 85 ° C. for 500 hours.
_Rate of change of electrode voltage V _lμA when μA current is applied ΔV
_lμA was determined. It should be noted that ΔV in both the case where the current flows in the forward direction (+ direction) and the case where the current flows in the reverse direction (− direction).
_lμA was determined.

As is clear from Tables 1 to 5, the varistors having the composition according to the present invention have a non-linear coefficient α of 20 or more, a varistor voltage V _{1 mA} of 400 (V / mm) or more, and a service life characteristic, that is, a leakage current. The rate of change ΔV 1 _μA has a target characteristic within + 10% to ₋₁₀ %. Further, according to the present invention, the difference due to the polarity of the leakage current change rate ΔV 1 _μA is reduced. That is, asymmetric deterioration is reduced. Further, variations in characteristics between varistors during mass production are reduced.

As is clear from Sample Nos. 2 to 4, Pr
Is within the range of 0.05 to 3.0 atomic%, the above-mentioned target characteristics can be obtained. However, when Pr becomes 0.02 atomic% and 4.0 atomic% as shown in sample numbers 1 and 5, α And ΔV
_{1 μA} deviates from the target characteristic. Therefore, the preferred amount of Pr is 0.05 to 3.0 atomic%.

As is clear from Sample Nos. 7 and 8, Co
Is 0.1 and 5.0 atomic%, the target characteristics can be obtained. However, as shown in Sample Nos. 6 and 9, Co is 0.1 atomic%.
At 05 and 6.0 atomic%, α and ΔV 1 _μA deviate from the target characteristics. Therefore, the preferred amount of Co is 0.1 to
5.0 atomic%.

As is apparent from Sample Nos. 11 and 12, the target characteristics can be obtained when Cr is 0.01 and 0.5 atomic%. In the case of 005 and 0.6, not all items can be included in the target characteristics. Therefore, the preferred amount of Cr is 0.01 to 0.5 atomic%.

Sample Nos. 15, 16, 32, 33, 34,
As is clear from 37, 38 and 39, Al or Ga or I
When n is 0.001 to 0.02 atomic%, target characteristics can be obtained, but sample numbers 14, 17, 31, 35, 3
As is clear from FIGS. 6 and 40, when these are 0.0005 and 0.003 atomic%, not all items can be set as target characteristics. Therefore, the preferred amount of Al, Ga or In is 0.001 to 0.02 atomic%.

As is clear from sample numbers 19 and 20,
When Si is 0.001 and 0.5 at%, the target characteristics are obtained. However, as shown in Sample Nos. 18 and 21, when Si becomes 0.0005 and 0.6 at%, all the items are set to the target characteristics. Can not fit. Therefore, the preferable amount of Si is 0.001 to 0.5 atomic%.

Sample numbers 23, 24, 25, 26, 27,
As is clear from FIG.
5 atomic% and the ratio Ca / Sr of Ca and Sr is 5
When the value is 0 or less, the target characteristics can be obtained. However, as shown in Sample Nos. 22, 29 and 30, if the above conditions are not satisfied, all items cannot be included in the target characteristics. Therefore, the preferred amount of Ca + Sr is 0.001 to 0.5 atomic%.

Although not shown in the above table, sample No. 1
0.005 atomic% of Al instead of 0.02 atomic% of Al
A varistor identical to that of Sample No. 16 was prepared, and the characteristics were measured. The same characteristics as those of Reference No. 16 were obtained. Further, a varistor in which the sum of Al, Ga, and In or the sum of two arbitrarily selected from them was contained in the range of 0.001 to 0.02 atomic% was produced, and these characteristics were measured. The target characteristics were obtained. Further, when a number of varistors having the same composition were made and the variation in the characteristics was determined, the variation according to the present invention was smaller than that outside the scope of the present invention.

[0029]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The auxiliary component can be supplied as a compound different from the oxide or carbonate of each element or the element alone. (2) The structure of the varistor can be different from that of FIG. For example, an electrode may be provided on one main surface and the other main surface of a plate-shaped voltage non-linear resistor to form a varistor.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a varistor according to an embodiment of the present invention.

[Explanation of symbols]

 1 voltage non-linear resistor layer 4,5 internal electrode 6,7 external terminal electrode

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akihisa Matsuda 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd. F-term (reference) 4G030 AA08 AA09 AA11 AA22 AA28 AA32 AA34 AA36 AA37 BA04 5E034 CA08 CB01 DA10 DC01 DE07 EA09 5G303 AA10 AB14 BA12 CA01 CB01 CB06 CB09 CB10 CB26 CB30 CB32 CB38 CB42

Claims (2)

[Claims] 1. ZnO (zinc oxide) as a main component and Pr (praseodymium) as an auxiliary component in an amount of 0.05 to
3.00 atomic%, Co (cobalt) 0.1 to 5.0 atomic%, Cr (chromium) 0.01 to 0.50 atomic%, A
at least one of l (aluminum), Ga (gallium) and In (indium) is 0.001 to 0.02
0 atomic%, 0.001 to 0.500 atomic% of Si (silicon), and Ca + Sr (Ca / Sr is 0 to 50)
Is added in an amount of 0.01 to 0.50 atomic%. 2. A Zn compound (ZnO) as a main component, and a Pr compound as a sub-component thereof in an amount of 0.05 to 3.00 atomic% in terms of Pr (praseodymium).
(Cobalt) in terms of 0.1 to 5.0 atom%, Cr compound in terms of Cr (chromium) 0.01 to 0.50 atom%, of Al compound, Ga compound and In compound. At least one kind is converted into Al (aluminum), Ga (gallium), and In (indium), respectively, and 0.0
01 to 0.020 atomic%, 0.001 to 0.500 atomic% of Si compound in terms of Si (silicon), and Ca + Sr compound of Ca + Sr (where Ca / Sr is 0
To 50), wherein the composition is added in an amount of from 0.01 to 0.50 atomic%.