JP4235487B2 - Voltage nonlinear resistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage non-linear resistance body mainly composed of zinc oxide suitable for an overvoltage protection element.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Laid-Open No. 1-25205
[Patent Document 2]
Japanese Patent Laid-Open No. 9-326305
A voltage non-linear resistance body containing zinc oxide (ZnO) as a main component is characterized by a low limiting voltage and a large voltage non-linear coefficient. Therefore, it is widely used as a varistor for the purpose of overvoltage protection of equipment including a semiconductor element having a small overcurrent withstand capability. The voltage nonlinear resistor includes ZnO as a main component and a subcomponent for improving characteristics. For example, in Patent Document 1, as a subcomponent, ZnO as a main component is disclosed.
0.08 ~ 5.0at% of total amount of at least one rare earth element
Co 0.1 ～ 10.0at%
0.01-5.0at% of at least one of Mg and Ca
0.01-1.0at% in total of at least one of K, Cs, Rb
Cr 0.01 ~ 1.0at%
B 0.0005-0.1at%
At least one of Al, GA and In in a total amount of 0.0001 to 0.05 at%
And a composition to which B (boron) is further added. In addition, at% shows atomic%.
[0003]
In Patent Document 2, as a subcomponent with respect to ZnO as a main component.
0.08 ~ 5.0at% of total amount of at least one rare earth element
Co 0.1 ～ 10.0at%
Ca 0.1 ~ 0.5at%
0.01-1.0at% of at least one of K, Cs, Rb
Cr 0.1 ~ 0.6at%
At least one of Al, Ga, and In is 0.0004 to 0.03 at% in total
Is disclosed.
[0004]
[Problems to be solved by the invention]
By the way, when manufacturing a voltage non-linear resistor containing K and B as in Patent Documents 1 and 2, K and B are added as these oxides, or are added to the oxides during the firing process. Is added as a compound. However, since the melting points of the oxides of K and B are low, K and B are likely to be scattered during firing. For this reason, it has been difficult to mass-produce voltage nonlinear resistors having the same characteristics with high yield.
[0005]
Accordingly, an object of the present invention is to provide a voltage non-linear resistor capable of obtaining the required surge withstand capability and electric charging life characteristics even though it does not contain an additive component that easily scatters.
[0006]
[Means for Solving the Problems]
In order to solve the above problems and achieve the above object, the present invention provides:
It consists of a main component composed of zinc oxide (ZnO) and a subcomponent added to this main component,
0.05-3.0 atomic% Pr (praseodymium),
0.1-5.0 atomic% Co (cobalt),
0.01-0.5 atomic% Mo (molybdenum) and V (vanadium)And bothWhen,
0.001 to 0.02 atomic% Al (aluminum),
0.001 to 0.5 atomic% Si (silicon),
One or both of 0.01-0.5 atomic% Mg (magnesium) and Ca (calcium)
And it does not contain Na (sodium), K (potassium), Rb (rubidium) ”and Cs (cerium).
[0007]
[Action and effect of the invention]
In the present invention, Pr, one or both of Ca and Mg,Mo When V With bothAre used together. These contribute to the improvement of surge withstand capability and electrical charging life characteristics, and can provide a highly reliable non-linear resistor. Pr, Co, Mo and V used in the present inventionAnd bothHowever, the mechanism by which the subcomponent consisting of one or both of Al, Si, Mg and Ca contributes to the improvement of surge withstand capability and the service life characteristics is not accurately known. However, Pr, Co,Mo When V And both, Si, Mg / Ca sintered body segregation at the triple point is recognized. Therefore, these elements are considered to be elements that do not easily enter the grains. If these elements are present in the vicinity of the grain boundary, migration of interstitial Zn ions is suppressed, and it is considered that the surge withstand capability and the life performance are improved.
In addition, the voltage non-linear resistor according to the present invention is not added with an auxiliary component such as B and K, which is unlikely to be scattered. Can be improved.
[0008]
Embodiment
In order to produce samples as voltage non-linear resistors or varistors of Examples and Comparative Examples according to the present invention, ZnO powder as a main component was prepared, and Pr, Co, Mo, V, Pr to obtain Al, Si, Ca, Mg₆O₁₁, Co_ThreeO_Four, MoO_Three, V₂O_Three, Al₂O_Three, SiO₂, CaCO_Three, MgO was prepared. Next, Pr₆O₁₁, Co_ThreeO_Four, MoO_Three, V₂O_Three, Al₂O_Three, SiO₂, CaCO_Three, MgO are weighed to a ratio that can obtain the subcomponents (Pr, Co, Mo, V, Al, Si, Ca, Mg) shown in atomic%, that is, at% in Table 1, and this is used as a main component in ZnO. In addition, an organic binder, an organic solvent and an organic plasticizer were further added and mixed for 24 hours by a ball mill to prepare a slurry.
In Tables 1 and 2, the leftmost No. represents the sample number. In Table 1, each subcomponent is shown in atomic% (at%). Table 1 does not show ZnO as a main component, but each sample contains ZnO as the balance. Accordingly, the total atomic% of the main component and each subcomponent is 100%. Sample numbers marked with * are comparative examples outside the scope of the present invention.
[0009]
Table 1
No. Pr Co Mo V Al Si Ca Mg
1 * 0.02 2.0 0.2 0.2 0.005 0.2 0.2 0.2
2 0.05 2.0 0.2 0.2 0.005 0.2 0.2 0.2
Three 0.5 2.0 0.2 0.2 0.005 0.2 0.2 0.2
Four 3.0 2.0 0.2 0.2 0.005 0.2 0.2 0.2
Five* 5.0 2.0 0.2 0.2 0.005 0.2 0.2 0.2
6 * 0.5 0.05 0.2 0.2 0.005 0.2 0.2 0.1
7 0.5 0.1 0.2 0.2 0.005 0.2 0.2 0.1
8 0.5 5.0 0.2 0.2 0.005 0.2 0.2 0.1
9 * 0.5 7.0 0.2 0.2 0.005 0.2 0.2 0.1
Ten* 0.5 2.0 0.005 0 0.005 0.2 0.1 0.2
11 0.5 2.0 0.01 0 0.005 0.2 0.1 0.2
12 0.5 2.0 0.5 0 0.005 0.2 0.1 0.2
13* 0.5 2.0 0.7 0 0.005 0.2 0.1 0.2
14* 0.5 2.0 0 0.005 0.005 0.2 0.1 0.2
15 0.5 2.0 0 0.01 0.005 0.2 0.1 0.2
16 0.5 2.0 0 0.5 0.005 0.2 0.1 0.2
17 * 0.5 2.0 0 0.7 0.005 0.2 0.1 0.2
18 0.5 2.0 0.025 0.025 0.005 0.2 0.1 0.2
19 0.5 2.0 0.1 0.1 0.005 0.2 0.1 0.2
20 0.5 2.0 0.2 0.2 0.005 0.2 0.1 0.2
twenty one* 0.5 2.0 0.2 0.2 0.0005 0.2 0.3 0.05
twenty two 0.5 2.0 0.2 0.2 0.001 0.2 0.3 0.05
twenty three 0.5 2.0 0.2 0.2 0.02 0.2 0.3 0.05
twenty four* 0.5 2.0 0.2 0.2 0.03 0.2 0.3 0.05
twenty five* 0.5 2.0 0.2 0.2 0.005 0.0005 0.2 0.2
26 0.5 2.0 0.2 0.2 0.005 0.001 0.2 0.2
27 0.5 2.0 0.2 0.2 0.005 0.5 0.2 0.2
28 * 0.5 2.0 0.2 0.2 0.005 0.7 0.2 0.2
29 * 0.5 2.0 0.2 0.2 0.005 0.2 0.005 0
30 0.5 2.0 0.2 0.2 0.005 0.2 0.01 0
31 0.5 2.0 0.2 0.2 0.005 0.2 0.5 0
32 * 0.5 2.0 0.2 0.2 0.005 0.2 0.7 0
33 * 0.5 2.0 0.2 0.2 0.005 0.2 0 0.005
34 0.5 2.0 0.2 0.2 0.005 0.2 0 0.01
35 0.5 2.0 0.2 0.2 0.005 0.2 0 0.5
36 * 0.5 2.0 0.2 0.2 0.005 0.2 0 0.7
37 0.5 2.0 0.2 0.2 0.005 0.2 0.025 0.025
38 0.5 2.0 0.2 0.2 0.005 0.2 0.1 0.1
39 0.5 2.0 0.2 0.2 0.005 0.2 0.2 0.2
[0010]
Next, a ceramic green sheet, that is, a porcelain green sheet having a thickness of 30 μm was prepared by a doctor blade method using the slurry of each sample. Next, each ceramic green sheet was cut into a desired size to obtain a plurality of green sheets. A conductive paste made of, for example, palladium paste for obtaining the first internal electrode 2a of FIG. 1 is applied to one of the plurality of green sheets by screen printing, and the second internal electrode is applied to one of the other green sheets. A conductive paste made of, for example, palladium paste for obtaining 2b was applied by screen printing.
[0011]
Next, two green sheets coated with conductive paste are stacked, and dummy green sheets are stacked on top and bottom of these, and these are heated and pressed to be cut into a predetermined chip shape. Got.
[0012]
Next, the green chip was debindered at 300 ° C. for 3 hours, and then fired at 1250 ° C. for 2 hours to obtain a sintered body 1 having the structure shown in FIG. In the sintered body 1 in FIG. 1, first and second internal electrodes 2a and 2b are arranged above and below a ceramic layer 1a as a voltage nonlinear resistor, and a ceramic layer is disposed below the second internal electrode 2b. 1b is disposed, and the ceramic layer 1c is disposed on the upper side of the first internal electrode 2a.
[0013]
Next, an electrode paste containing Ag as a main component is applied to both end faces of the sintered body 1 and baked at 800 ° C. to form the first and second external terminal electrodes 3 and 4 to complete the multilayer varistor. It was. The first external electrode 3 is connected to the first internal electrode 2a, and the second external electrode 4 is connected to the second internal electrode 2b.
[0014]
The non-linear coefficient α, surge resistance (A), and electrical charging life characteristics of the laminated varistor of each sample were measured as follows.
The non-linear coefficient α is a varistor voltage V per 1 mm of the ceramic layer 1a when 1 mA is applied to each sample varistor formed as shown in FIG._1mA[V / mm] and varistor voltage V per mm of the ceramic layer 1a when 10 mA is applied_10mA[V / mm] was calculated and used to calculate according to the following equation.
α = log (10/1) / log (V_10mA/ V_1mA)
[0015]
Surge resistance is applied to the varistor of Fig. 1 by applying an impact current of 8/10 µsec twice at 5 minute intervals, and the varistor voltage V_1mAThe limit current value (A) at which the change does not change by ± 10% was measured.
[0016]
The service life characteristic is the rate of change of varistor voltage in the positive direction 1mA before and after energization + △ V_1mA(%) And change rate of varistor voltage in negative direction 1mA-△ V_1mA(%) And determined. In addition, varistor voltage change rate at the time of positive direction current + △ V_1mA(%) Is 1mA varistor voltage V_1mABetween the electrodes 2a and 2b when a positive current of 1 μA was applied to the varistor before and after applying a DC constant voltage equivalent to 90% of the varistor to the varistor placed in 85 ° C dry air for 500 hours. Obtain the voltage and calculate the voltage between the electrodes before energization as V_1mAAnd interelectrode voltage V after energization_1mAFrom ′, the following equation was obtained.
+ △ V_1mA= {(V_1mA-V_1mA') / V_1mA} × 100 (%)
Rate of change of varistor voltage at negative current -V_1mA(%) Is the varistor voltage change rate at the time of positive current + △ V, except that the direction of 1mA current is changed to the negative direction._1mAIt calculated | required by the method similar to (%).
[0017]
Table 2 shows 1 mA varistor voltage V of sample Nos. 1 to 39._1mA(V / mm), non-linear coefficient α, surge resistance (A), rate of change in varistor voltage at positive current indicating the life characteristics of charging_1mA(%) And rate of change of varistor voltage during negative current -V_1mA(%).
[0018]
Table 2
No. V_1mA    α Surge resistance + ΔV_{1 μ A}  -ΔV_{1 μ A}
( V / mm ) ( A) (%) (% )
1 * 300 Five 6 -35.0 -50.0
2 478 15 20 -5.0 -6.8
Three 550 20 twenty five -2.1 -2.4
Four 650 twenty three 30 -4.3 -5.4
Five* 715 9 6 -25.0 -40.0
6 * 305 6 8 -25.0 -38.0
7 482 16 30 -2.5 -2.8
8 555 20 twenty five -5.1 -6.8
9 * 604 9 8 -20.0 -30.0
Ten* 350 9 8 -30.0 -43.0
11 475 twenty five 28 -3.1 -3.3
12 553 20 32 -5.0 -5.8
13* 380 8 8 -23.0 -35.0
14* 350 9 8 -35.0 -48.0
15 470 twenty three twenty five -5.6 -6.3
16 560 twenty one 28 -7.0 -8.3
17 * 400 7 Ten -25.0 -35.0
18 483 twenty five 28 -3.0 -3.3
19 530 27 twenty five -3.5 -3.7
20 540 twenty three twenty five -4.9 -5.3
twenty one* 390 9 7 -21.0 -30.0
twenty two 480 twenty five twenty five -2.5 -3.0
twenty three 490 twenty four 28 -5.6 -6.6
twenty four* 430 Ten 9 -32.0 -40.0
twenty five* 350 8 8 -27.0 -39.0
26 450 twenty three twenty five -3.0 -3.5
27 580 twenty five 28 -4.3 -4.9
28 * 308 Ten Five -29.0 -40.0
29 * 310 8 8 -32.0 -43.0
30 458 twenty four twenty five -3.5 -4.0
31 565 26 twenty five -5.6 -7.0
32 * 320 9 8 -30.0 -44.0
33 * 380 6 8 -30.0 -40.0
34 470 twenty one twenty three -3.9 -4.2
35 580 twenty five twenty five -6.0 -6.5
36 * 350 6 Ten -28.0 -38.0
37 480 twenty three 28 -5.3 -5.6
38 520 twenty five twenty five -3.9 -4.3
39 560 twenty five twenty five -6.0 -6.3
[0019]
In this embodiment, the value of the nonlinear coefficient α is 10 or more, the surge resistance is 10 A or more, the varistor voltage change rate + ΔV_1mAAnd-△ V_1mAA product having an absolute value of 10 or less was regarded as a non-defective product.
As is clear from Sample Nos. 2 to 4 in Tables 1 and 2, a varistor having a Pr of 0.05 to 3.0 at% is a good product.
As is clear from Sample Nos. 7 and 8, a varistor with a Co of 0.1 to 5.0 at% is a good product.
Further, as is clear from Sample Nos. 11 and 12, a varistor having Mo of 0.01 to 0.5 at% is a good product.
As is clear from Sample Nos. 15 and 16, a varistor having a V of 0.01 to 0.5 at% is a good product.
As is clear from Sample Nos. 11, 12, 15, 16, 18, 19, and 20, good products can be obtained by adding either or both of Mo and V within a range of 0.01 to 0.5 at%. can get.
Further, as is clear from Sample Nos. 22 and 23, a varistor having an Al of 0.001 to 0.02 at% is a good product.
Further, as apparent from Sample Nos. 26 and 27, the varistors having Si of 0.001 to 0.5 at% are non-defective products.
Further, as is clear from sample Nos. 30 and 31, a varistor having a Ca of 0.01 to 0.5 at% is a good product.
Further, as is apparent from Sample Nos. 34 and 35, a varistor having an Mg of 0.01 to 0.5 at% is a good product.
As is clear from Sample Nos. 30, 31, 34, 35, 37, 38, and 39, good products can be obtained by adding either or both of Ca and Mg within the range of 0.01 to 0.5 at%. can get.
[0020]
When many varistors having the same sample number belonging to the scope of the present invention were prepared and the variation in the characteristics of Table 2 in the same sample was examined, the variation was smaller than that of a varistor containing K or B as a conventional subcomponent. That is, since the subcomponent according to the present invention does not contain K and B which are likely to be scattered during firing, there is less characteristic variation during mass production, and the yield is increased.
In addition, according to the present embodiment, it is possible to provide a varistor that has a large surge withstand and a small change in leakage current in the electric charging life characteristic and a small asymmetric deterioration without degrading various electrical characteristics of the varistor. .
[0021]
[Modification]
The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible.
(1) The main component is calcined in advance, a mixture of a plurality of subcomponents is also calcined in advance, and the calcined subcomponent can be added to the calcined main component.
(2) Instead of adding Pr, Co, Mo, V, Al, Si, Ca, Mg as subcomponents with these oxides or carbonates, add them as subcomponent elements or other compounds. Can do.
(3) The firing temperature can be changed within a sinterable range.
(4) The multilayer ceramic varistor can be configured to have a plurality of first and second internal electrodes 2a, 2b.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a varistor according to an embodiment of the present invention.
[Explanation of symbols]
1 Sintered body
1a, 1b, 1c ceramic layer
2a, 2b first and second internal electrodes
3,4 First and second external terminal electrodes

Claims (1)

It consists of a main component consisting of zinc oxide and a subcomponent added to this main component,
0.05-3.0 atomic% Pr,
0.1-5.0 atomic% Co,
Both 0.01-0.5 atomic percent Mo and V ;
0.001 to 0.02 atomic% Al,
0.001 to 0.5 atomic% Si,
A voltage non-linear resistance element characterized by being composed of either one or both of 0.01 to 0.5 atomic% of Mg and Ca and not containing Na, K, Rb and Cs.

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