KR20110072333A - ZnO-BASED VARISTOR COMPOSITION - Google Patents

Abstract

PURPOSE: A ZnO system varistor composite is provided to offer a better physical characteristic required in a varistor like a nonlinear coefficient, a clamping voltage ratio, and a surge absorption resolution. CONSTITUTION: The ZnO system varistor composite does not include Bi2O3, Sb2O3 and Pr6O11. The ZnO system varistor composite includes Ca, Mg, Co, Cr and La. The ZnO system varistor composite includes other metal atom within a range of 0.01-30 at % of the total included metal atom.

Description

VANO-based varistor composition

The present invention relates to a varistor composition, and more particularly, to a ZnO-based varistor composition comprising zinc oxide (ZnO) as a main component.

ZnO-based varistors formed of ZnO-Bi-based or ZnO-Pr-based materials of the varistors have better voltage nonlinearity and better surge current resistance than SiC-based varistors and SrTiO _3- based varistors. Due to its excellent ability to protect electronic devices from current, it is widely used as a material for surge protection devices.

However, the ZnO-Bi-based varistor is composed of Bi ₂ O ₃ , Sb ₂ O ₃ , Mn, Co, Ni, Cr, glass frit, Al, K, etc. The Bi ₂ O ₃ component is ESD (Electro -Static Discharge) Because of low resistance, ZnO-Bi-based varistors including the same have disadvantages of poor ESD characteristics. In addition, since the Sb ₂ O ₃ component is classified as a carcinogen and the concentration is regulated, the ZnO-Bi-based varistor including the same has a disadvantage in that it is not free to manufacture. In addition, ZnO-Pr-based varistors have a good voltage nonlinearity, but have a drawback in that leakage current is greater than that of ZnO-Bi-based varistors. In addition, since a large amount of expensive components (Pd, etc.) are used, there is a disadvantage in that the manufacturing cost is high.

On the other hand, in recent years, high-density mounting is rapidly progressing due to the miniaturization and miniaturization of surface-mount devices (SMDs) and miniaturization of electronic components according to the trend of lighter and shorter and higher functionalization of electronic devices. Since the signal rates of circuits in SMD electronics range from hundreds of MHz to several GHz, the capacitance of varistors must be considerably lowered to prevent signal delays at these high signal rates, and, if necessary, lowered to less than 1 pF.

Since ZnO-type varistors have high dielectric constants of up to several hundreds, in order to have a small capacitance, the electrode area must be considerably reduced. However, reducing the electrode area to have a small capacitance results in a reduction in surge resistance, which also leads to a problem that the varistor manufacturing process is quite difficult. Accordingly, there is a need for a ZnO type varistor composition having a low dielectric constant.

The present invention is to solve the above problems of the prior art, Bi ₂ O ₃ which negatively affects the electrostatic discharge (ESD) characteristics of the varistor, Sb ₂ O _{3 as an} environmental regulatory component and high temperature sintering are required It is composed of new components that replace the Pr-based components, which cause an increase in manufacturing cost, and have excellent overall physical properties required for the varistors, and in particular, varistors capable of ensuring a low clamping voltage with a small capacitance It is an object to provide a varistor composition for use in the preparation of the compound.

ZnO-based varistor composition comprising a ZnO-based varistor composition, which does not contain Bi ₂ O ₃ , Sb ₂ O ₃ and Pr ₆ O ₁₁ and contains Ca, Mg, Co, Cr, and La. To provide.

The ZnO-based varistor composition, based on the total metal atoms contained in the composition, Zn 35 ~ 97 at%, Ca 0.2 ~ 30 at%, Mg 1 ~ 30 at%, Co 0.2 ~ 5 at%, Cr 0.05 ~ 3 at % And La 0.05 to 3 at%.

The present invention also provides

Preparing a calcined powder by mixing, pulverizing and calcining ZnO with components not including Bi ₂ O ₃ , Sb ₂ O _3, and Pr ₆ O ₁₁ and including Ca, Mg, Co, Cr, and La;

Inserting a binder into the calcined powder, shaping and sintering; And

It provides a method for producing a ZnO-based varistor comprising the step of applying an electrode to the sintered body and package treatment.

The present invention also provides

It provides a ZnO-based varistor made of the varistor composition described above.

The varistor composition of the present invention has excellent physical properties required for varistors such as nonlinear coefficient, clamping voltage ratio, and surge absorption capacity, and in particular, provides excellent ESD characteristics because it does not contain Bi ₂ O ₃ . In addition, since it does not include the environmental regulation component Sb ₂ O ₃ provides excellent work safety, and does not include the Pr-based components that require high-temperature sintering to increase the manufacturing cost can reduce the manufacturing cost of the varistor. In particular, since the varistor composition of the present invention can have a low capacitance while having a small capacitance, it is possible to manufacture a varistor that does not cause a signal delay even in an electronic product having a signal speed of several hundred MHz to several GHz.

ZnO-based varistor composition comprising a ZnO-based varistor composition, which does not contain Bi ₂ O ₃ , Sb ₂ O ₃ and Pr ₆ O ₁₁ , but contains Ca, Mg, Co, Cr, and La. It is about.

ZnO-based varistor composition of the present invention, based on the total metal atoms contained in the composition Zn 35 ~ 97 at%, Ca 0.2 ~ 30 at%, Mg 1 ~ 30 at%, Co 0.2 ~ 5 at%, Cr 0.05 ~ It is preferable to include 3 at% and La 0.05 to 3 at%, more preferably, Zn 45 to 97 at%, Ca 0.2 to 30 at%, Mg 1 to 30 based on the total metal atoms included in the composition It is preferable to include at%, Co 0.2-2.5 at%, Cr 0.05-1 at% and La 0.05-0.4 at%.

When Ca is included in the above content range, a composition having excellent overall physical properties required for the varistor can be obtained, and in particular, a composition having excellent nonlinearity can be obtained. It is also possible to obtain a composition having a low capacitance while having a small capacitance. In the case where Ca exceeds 30 at%, the content of Zn is relatively reduced, so that the composition is not sintered well, the sintering density is lowered, and the overall physical properties of the varistor may be lowered.

When Mg is included in the above content range, a composition having excellent overall physical properties required for the varistor can be obtained, and in particular, a composition having a low capacitance and a low clamping voltage can be obtained. . When the Mg exceeds 30 at%, the content of Zn is relatively reduced, so that the composition is not sintered well, so that the sintered density is lowered and the physical properties of the varistor may be lowered.

When Co is included in the above content range, a composition having excellent nonlinearity is obtained. In particular, more preferable nonlinearity is obtained when Co is added at 0.2 to 2.5 at%.

In addition, in the case where Cr is included in the above content range, an excellent composition in terms of resistivity is obtained. In the above, when Cr exceeds the upper limit, a problem arises in that the nonlinearity is lowered. Furthermore, more preferable specific resistance is obtained when Cr is added at 0.05-1.0 at%.

In addition, when La is included in the above content range, a composition excellent in resistivity is obtained. In the above, when La exceeds the upper limit, a problem arises in that the nonlinearity is lowered. Furthermore, more preferable specific resistance is obtained when La is added at 0.05 to 0.4 at%.

ZnO-based varistor composition of the present invention may further comprise Al 0.005 ~ 0.2 at% based on the total atomic weight of the composition.

In addition, the ZnO-based varistor composition of the present invention may further include other metal atoms in the range of 0.01 to 30 at% based on the total metal atoms included in the composition in addition to the above components. Examples of the other metal atoms include Mn, Zr, Li, Na, K, and Ga.

Zn is added as ZnO to the ZnO-based varistor composition of the present invention; Ca may be added in one or two or more mixed forms selected from the group consisting of CaCO ₃ , CaO, and the like; Mg may be added in one or two or more mixed forms selected from MgO and MgCO ₃ ; Co may be added in one or two or more mixed forms selected from the group consisting of Co ₃ O ₄ , CoO, and the like; Cr may be added selected from the group consisting of Cr ₂ O ₃ and the like; La may be added selected from the group consisting of La ₂ O ₃ and the like.

In addition,

Preparing a calcined powder by mixing, pulverizing and calcining ZnO with components not including Bi ₂ O ₃ , Sb ₂ O _3, and Pr ₆ O ₁₁ and including Ca, Mg, Co, Cr, and La;

Inserting a binder into the calcined powder, shaping and sintering; And

It relates to a method for producing a ZnO-based varistor comprising the step of applying an electrode and the package treatment to the sintered body.

The manufacturing method may be carried out by employing a method known in the art, except for using a novel composition.

In addition,

It provides a ZnO-based varistor made of the varistor composition of the above; It provides an electrical device comprising the ZnO-based varistor.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited by the following examples. The following examples can be appropriately modified and changed by those skilled in the art within the scope of the present invention.

Examples 1 to 17 Preparation of Laminated Varistors

POWDER ZnO CaCO ₃ MgO Co ₃ O ₄ Cr ₂ O ₃ La ₂ O ₃ Al ₂ O ₃ Zn at% Ca at% Mg at% Co at% Cr at% La at% Al at% Example 1 87.6 10 One One 0.2 0.2 - Example 2 85.6 10 3 One 0.2 0.2 - Example 3 83.6 10 5 One 0.2 0.2 - Example 4 81.1 10 7.5 One 0.2 0.2 - Example 5 78.6 10 10 One 0.2 0.2 - Example 6 68.6 10 20 One 0.2 0.2 - Example 7 58.6 10 30 One 0.2 0.2 - Example 8 66.6 2 30 One 0.2 0.2 - Example 9 58.6 30 10 One 0.2 0.2 - Example 10 38.6 30 30 One 0.2 0.2 - Example 11 66.59 2 30 One 0.2 0.2 0.01 Example 12 58.59 10 30 One 0.2 0.2 0.01 Example 13 38.59 30 30 One 0.2 0.2 0.01 Example 14 38.58 30 30 One 0.2 0.2 0.02 Example 15 38.57 30 30 One 0.2 0.2 0.03 Example 16 38.55 30 30 One 0.2 0.2 0.05 Example 17 38.50 30 30 One 0.2 0.2 0.10

The ingredients in Table 1 were weighed at a predetermined composition ratio, and charged into a ball mill containing partially stabilized zirconia (PSZ) together with ion-exchanged water three times the weight of the weighed material, mixed and ground. Thereafter, dehydration and drying were performed to prepare granulated powder. The granulated powder thus obtained was calcined at a temperature of 700 ° C. for 2 hours in the air, and sufficiently ground to prepare a calcined powder.

Subsequently, BM2 (manufactured by SEKISUI) and BM-SZ (manufactured by SEKISUI) as an organic binder, dioctyl phthalate (DOP) as an organic plasticizer, toluene and ethanol as an organic solvent were added to the calcined powder, and wet-pulverized to form a ceramic sheet. A slurry was prepared.

Next, using the doctor blade method, the slurry was formed into a sheet shape having a thickness of about 33 μm on a PET film (polyethylene telephthalate), and then cut into predetermined dimensions to form a plurality of ceramic sheets.

Next, the Pd paste was screen printed on the surface of the ceramic sheet, stretched from one end surface of each ceramic sheet, and an electrode pattern was formed in a rectangle so that the other end was located on the ceramic sheet. And the ceramic sheet in which the electrode pattern was formed was laminated | stacked in this way, these laminated ceramic sheets were sandwiched and crimped | bonded by the ceramic sheet (protective layer) in which the electrode pattern was not formed, and the laminated body was formed.

The obtained laminate was cut into 1.6 mm long and 0.8 mm wide, accommodated in Zr Saggar, subjected to binder removal at 400 ° C. in air, and then calcined at 1200 ° C. in air for 3 hours to produce a ceramic sintered body. It was. Then, Ag paste was prepared, Ag paste was applied to both ends of the ceramic sintered body, and then baked at a temperature of 800 ° C. to form an external electrode to fabricate a laminated varistor.

Test Example: Measurement of Physical Properties of Varistor Devices

The relative density, varistor voltage (V1mA), leakage current (IL), nonlinearity index (α), dielectric constant (ε), and ZnO of the varistor chip manufactured in Examples 1 to 17 described above. Specific resistance (ρ) was measured by a conventional method and is shown in Table 2 below.

Example
(Psalm thickness) Characteristics of Powder Composition Physical property measurement result ZnO CaCO ₃ MgO Al ₂ O ₃ Relative density (%) Vn
(V / ㎛) IL
(μA / cm ² ) α ε ρ Zn at% Ca at% Mg at% Al at% 1 MHz (Ωcm) Example 1 87.6 10 One - 98.8 0.580 - 81 547 0.8 Example 2 85.6 10 3 - 96.9 0.594 - 31 468 1.1 Example 3 83.6 10 5 - 95.5 0.693 - 84 392 1.1 Example 4 81.1 10 7.5 - 92.9 0.836 - 157 329 1.2 Example 5 78.6 10 10 - 90.9 - - 46 269 1.4 Example 6 68.6 10 20 - 92.0 - - - 132 1.7 Example 7 58.6 10 30 - 93.0 - - - 82 2.1 Example 8 66.6 2 30 - 92.0 - - - 79 1.9 Example 9 58.6 30 10 - 94.0 2.19 0.8 45 25 2.1 Example 10 38.6 30 30 - 94.7 2.06 3 56 35 2.2 Example 11 66.59 2 30 0.01 95.0 1.38 0.2 79 127 1.9 Example 12 58.59 10 30 0.01 95.3 1.40 0.3 62 89 1.9 Example 13 38.59 30 30 0.01 97.0 2.35 0.08 162 35 2.2 Example 14 38.58 30 30 0.02 95.4 1.87 0.5 88 42 4.0 Example 15 38.57 30 30 0.03 94.5 1.73 3 59 45 4.2 Example 16 38.55 30 30 0.05 95.4 1.77 89 15 44 3.4 Example 17 38.50 30 30 0.10 96.1 1.22 313 9 52 4.3

As confirmed in Table 1, the varistor made of the varistor composition of the present invention was found to have a high density, a high varistor voltage, a small leakage current, and a specific resistance. In particular, it was confirmed that the varistor having excellent nonlinearity (see FIG. 1) and having a very low dielectric constant according to the composition and having a small capacitance without being constrained by the area of the electrode.

In the present invention, a method of measuring the specific resistance of the ZnO particles may be measured as a method of estimating the degree of improving the high current characteristic and the clamping voltage characteristic of the varistor. 2 and 4 show the measurement of lZl in the range of 1 MHz to 3 GHz using an RF impedance / Material Analyzer (Agilent E4991A). In the graph, the lowest value of IZI represents the resistance of the ZnO particles, and the lower the value, the better the characteristics. As shown in Figures 2 and 4, the specific resistance of the ZnO particles in the present invention exhibited excellent overall characteristics.

1 shows I-V curves of ZnO-based varistors prepared in Examples 1, 3 to 5, and 7 of the present invention.

2 is IZI (Ω) -Freq. Of the ZnO-based varistors prepared in Examples 1 to 7 of the present invention. The graph is shown.

FIG. 3 shows I-V curves of ZnO-based varistors prepared in Examples 10 and 13 to 17 of the present invention.

4 is IZI (Ω) -Freq. Of ZnO-based varistors prepared in Examples 10 and 13 to 17 of the present invention. The graph is shown.

Claims (7)

A ZnO-based varistor composition, which does not contain Bi ₂ O ₃ , Sb ₂ O _3, and Pr ₆ O _11, and contains Ca, Mg, Co, Cr, and La. The method according to claim 1, Zn 35 ~ 97 at%, Ca 0.2 ~ 30 at%, Mg 1 ~ 30 at%, Co 0.2 ~ 5 at%, Cr 0.05 ~ 3 at% and based on the total metal atoms included in the composition ZnO-based varistor composition comprising La 0.05 ~ 3 at%. The ZnO-based varistor composition according to claim 2, further comprising Al 0.005-0.2 at% based on the total atomic weight of the composition. The ZnO-based varistor composition according to claim 3, wherein other metal atoms are further added in an amount of 0.01 to 30 at% based on the total atomic weight of the composition in addition to the component. The method of claim 2, wherein Zn is added as ZnO for preparing the composition; Ca is added in the form of 1 type, or 2 or more types selected from CaCO ₃ and CaO; Mg is added in one form or a mixture of two or more kinds selected from MgO and MgCO ₃ ; Cr is added as Cr ₂ O ₃ ; La is ZnO-based varistor composition, characterized in that the addition of La ₂ O ₃ . Preparing a calcined powder by mixing, pulverizing and calcining ZnO with components not including Bi ₂ O ₃ , Sb ₂ O _3, and Pr ₆ O ₁₁ and including Ca, Mg, Co, Cr, and La; Inserting a binder into the calcined powder, shaping and sintering; And A method of manufacturing a ZnO-based varistor, comprising the step of applying an electrode to the sintered body and package processing. ZnO-based varistor made of the varistor composition of claim 1.

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