KR100349304B1 - The additives for low-temperature sintering and low-voltage driven varistor - Google Patents

Abstract

The present invention discloses an additive to be mixed in an SrTiO ₃ -based low voltage driven varistor having both a capacitor function and a varistor function.

The additive of the present invention is a CuO-SiO ₂ -AO ₂ -BO ₂ -C ₂ O ₃ -based composition, and consists of a ratio of 80 to 90: 10 to 20: 0 to 5: 0 to 10: 0 to 5 mol. The additive of the present invention is added to the SrTiO ₃ varistor 0.05 to 5.5 wt% to prepare a low-temperature sintering and low voltage drive type SrTiO ₃ varistor.

The additive according to the present invention can lower the sintering temperature by about 100 ~ 150 ℃, can shorten the heat treatment process can reduce the cost of manufacturing, it is useful in the manufacture of low voltage driven low voltage driven varistor Can be used.

Description

Low Temperature Sintering and Low Voltage Driven Additives in Varistor Devices {THE ADDITIVES FOR LOW-TEMPERATURE SINTERING AND LOW-VOLTAGE DRIVEN VARISTOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a manufacturing technology of a multifunctional semiconducting ceramic component device having a capacitor function and a varistor (Varistor) function, which can be manufactured by low temperature sintering technology as well as at low voltage. It relates to a low temperature sintering and low voltage drive type additive of a SrTiO ₃ based varistor that can be driven.

At present, the electronic device is in a trend of light and thin. As miniaturization and portability of electronic components are required, the driving voltage of internal circuits of current electronic products is also lowered. Therefore, it is necessary to lower the driving voltage of the varistor element located in the internal circuit. Therefore, the trend of varistors in the future is the development of devices that are small, low-voltage driving type, and can function as a complex function to block abnormal current and absorb noise.

Since the ordinary SrTiO ₃ device has a high dielectric constant, it can be used as a dielectric material, and can be manufactured as a varistor device capable of performing a complex function by giving it semiconductivity.

The varistor characteristic shown here has a characteristic of I = (V / C) ^α instead of the current-voltage characteristic taking an ohmic characteristic of V = I · R.

Where I: current V: applied voltage C: constant α: nonlinear coefficient [α = log (I / V)]

α represents the nonlinear degree of the current-voltage characteristic. That is, the degree of non-ohmic (non-ohmic) represents the α value of 1 means that it takes an ohmic form. However, in more or less cases, the current-voltage characteristic is non-ohmic. In summary, the greater the value of α, the greater the non-ohmic degree of the current-voltage characteristic. In other words, the larger the value of α, the better the varistor characteristic is. The nonlinear nature of these varistors keeps the resistance of the SrTiO ₃ specimen up to a certain voltage so that no current flows. However, when a voltage above a certain voltage (varistor voltage) is applied, the resistance is drastically lowered, and the current flows rapidly, and even when an abnormal voltage is applied, the excessive abnormal voltage is suppressed to stabilize the voltage, thereby protecting the device inside the electronic circuit. . In addition, the dielectric property of SrTiO ₃ itself serves as a capacitor to absorb abnormal current or noise introduced from the outside.

As described above, a method of simultaneously displaying both functions and lowering the varistor voltage to a low voltage is being applied to a miniaturized and portable electronic product.

1 shows a bulk SrTiO ₃ low voltage driven varistor process according to the prior art.

The performance of the semiconducting SrTiO ₃ -based device thus manufactured depends on the grains in the device and the characteristics of the grain boundaries.

In order to provide the semiconductivity of the grains, the powder obtained by adding a pentavalent additive in the mixing of the raw material powder of SrCO ₃ and TiO ₂ is calcined to impart semiconductivity. After molding the powder, the semiconductive ceramic specimen is manufactured by sintering at a high temperature of 1450 ° C. or higher in a reducing atmosphere of reducing gas in order to give semiconductivity again. The oxide-mixed compositions are applied to the surface of the specimen thus prepared and heat-treated at a temperature range of 900 to 1200 ° C. to thermally diffuse the oxide-mixed compositions into grain boundaries to form grain boundaries as an insulating layer. In this case, the insulating layer of the grain boundary formed by thermal diffusion causes a structure like a BL (Boundary Layer) capacitor, and serves as a capacitor having a high capacitance. In addition, the grain boundary acts as a resistance layer that interrupts the flow of electric current, and thus acts as a varistor. Accordingly, one of the above-mentioned electronic devices can manufacture a low voltage driving type varistor capable of acting as a capacitor that absorbs noise and a varistor capable of suppressing an abnormal voltage.

To with respect to providing a multi-functional semiconductive ceramic element using the SrTiO ₃ in Japanese Patent Application 07,342,164 number given like Kanda Osamu (Kanda Osamu) at least in order to form a grain boundary insulating layer (resist layer) Co, Cu, Mn By applying an oxide material containing at least one of and at least one of B, Bi, and Na, a grain boundary was formed as an insulating layer to improve performance.

In addition, Japanese Patent Application No. 04009752 assigned to Ito Masahiro et al. Proposed a device that adds a small amount of additive NaNbO ₃ or NaTaO ₃ to serve as a capacitor as well as a low voltage drive type varistor.

However, the low voltage-driven SrTiO ₃ based semiconducting ceramic parts according to the prior art are manufactured with SrTiO ₃ based high sintering temperature of more than 1450 ℃, and this high sintering temperature is not only a process problem but also high production cost and Na ion. It is an additive that moves according to voltage application and has a problem in practical application.

In addition, the low-voltage driving type SrTiO ₃ -based semiconducting ceramic material according to the prior art is not satisfactory in its chemical composition, manufacturing sintering temperature and the like.

In addition, the low-voltage-driven SrTiO _3- based semiconductor ceramic parts according to the prior art are coated with oxide mixed compositions on the surface of the sintered specimen to produce a low-voltage-driven varistor capable of two functions, a capacitor and a varistor. There is a problem in that the process of heat treatment again in the temperature range of 900 ~ 1200 ℃ has to be added.

The present invention for overcoming the limitations and problems of the prior art is a low temperature sintering additive of SrTiO ₃ low voltage driven varistor that can not only solve the process problems by lowering the high sintering temperature of more than 1450 ℃ but also lower the production cost The purpose is to provide.

In addition, the present invention is a SrTiO _3- based low voltage driven varistor that can function as a capacitor and varistor without the process of heat-treating again in the temperature range of 900 ~ 1200 ℃ after applying the oxide mixed composition on the surface of the sintered specimen Another purpose is to provide additives.

Another object of the present invention is to provide a low voltage driving additive of a bulk SrTiO ₃ based low voltage driven varistor, which is operated under a significantly lower voltage than the related arts.

In order to achieve the above object, the present invention provides an additive mixed in an SrTiO ₃ -based low voltage driven varistor, wherein the additive is a low temperature sintered and low voltage driven CuO-SiO ₂ -AO ₂ -BO ₂ -C ₂ O ₃ based composition. 80 to 90: 10 to 20: 0 to 5: 0 to 10: 0 to 5 mol is mixed in a ratio, characterized in that 0.05 to 5.5 wt% is added to the SrTiO _3- based low voltage drive varistor.

In particular, the additive according to the present invention comprises at least one composition selected from the group consisting of AO ₂ , BO ₂ and C ₂ O ₃ with CuO-SiO ₂ composition as an essential component.

Here, A and B are Ba, Ce, Ge, Hf, Mn, Mo, Nb, Pb, Pt, Re, Ru, Se, Si, Sn, Fe, Th, Ti, U is one of U, V, W and Zr, and C is Al, As, Au, B, Bi, Dy, Er, Eu, Fe, Ga, Gd, La, Mn, Nd, Rh, Sb, Sc, Sm, Tb, Tl, Tm, V, Y, Yb, Cr, In, Lu.

Such an additive according to the present invention can form an insulating layer (resistance layer) at the SrTiO ₃ grain boundary, which is a perovskite oxide dielectric, to simultaneously perform a capacitor function and a varistor function. In particular, a high sintering temperature of 1450 ° C. or higher is 100-150. It can be lowered by about ℃, reducing the cost of manufacturing.

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the invention described below with reference to the accompanying drawings by those skilled in the art.

1 is a process block diagram illustrating a bulk SrTiO ₃ based varistor process according to the prior art;

2 is a process block diagram showing a method of manufacturing a SrTiO ₃ based varistor to which low temperature sintering and a low voltage driven additive are added according to a preferred embodiment of the present invention;

Figure 3 is a perspective view showing an example of the varistor to which the low-temperature sintering and low-voltage driving additive is added according to the present invention.

<Description of the symbols for the main parts of the drawings>

1: lead wire

2: all poles

3: Semiconducting Ceramic Specimen

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

FIG. 2 is a process block diagram showing a method of manufacturing SrTiO ₃ based varistor using low temperature sintering and low voltage driving additive according to a preferred embodiment of the present invention.

In order to manufacture a composite functional semiconducting ceramic device using SrTiO ₃ , the semiconductivity of the SrTiO ₃ grains and the role of the insulating layer (resistance layer) of the grain boundaries are important, so that grains impart semiconductivity and an insulating layer (resistance layer) ) Needs to be formed.

In the present invention, in order to increase the semiconductorization of the SrTiO ₃ -based crystal grains, Nb ⁵⁺ is mixed and calcined. At the same time CuO-SiO ₂ -AO ₂ -BO ₂ not only to increase the role of the insulating layer (resistance layer) of the grain boundary but also to reduce the sintering temperature and to shorten the special heat treatment process for forming the insulating layer at the grain boundary in the general process. C ₂ O ₃ -based composition (80 ~ 90: 10 ~ 20: 0 ~ 5: 0 ~ 10: 0 ~ 5 mol ratio) was added as an additive. Thereafter, the mixture is sintered at a temperature below the normal sintering temperature in a reducing atmosphere of a mixed gas composed of 95% nitrogen-5% hydrogen. In the present invention, Zr or Ti was used as the A or B metal element, and Al was used as the C metal element.

As a result, it is possible to manufacture a multifunctional SrTiO ₃ semiconducting ceramic component device which operates as a protection device at a low voltage in the form of a bulk and has good capacitance. It can be produced by lowering.

In addition, since the important variables of the prepared specimens are the semiconductivity of the grains and the insulating layer (resistance layer) of the grain boundaries, the microstructure of the sintered specimens was confirmed to confirm these variables. The microstructure of the specimen was observed by scanning electron microscopy (SEM) and optical microscope (OM) after the thermal etching (Thermal etching) after grinding the specimen. The elements present in the grain boundary were measured by WDS (EDS), a scanning electron microscope analyzer. As a result of the measurement, those present in the grain boundary were confirmed to be CuO-SiO ₂ -AO ₂ -BO ₂ -C ₂ O ₃ -based compounds prepared in the present invention.

Hereinafter, a specific manufacturing method of the present invention will be described with reference to FIG. 2.

Strontium carbonate (SrCO ₃ ) and titanium oxide (TiO ₂ ) are mixed in a mol ratio of 1: 1, and 0.07 mol% of Nb ₂ O ₅ is added as a dopant to impart n-type semiconductivity. Mix through ball milling, one of the solid phase methods. This mixture is calcined to obtain a SrTiO ₃ compound which is a semiconductive perovskite oxide.

Its crystallinity is confirmed by XRD.

At the same time, the resist is formed at the grain boundaries of the SrTiO ₃ system obtained through the above-mentioned method, and the additives capable of lowering the high sintering temperature, which is a problem in manufacturing the SrTiO ₃ system, are mixed and dried.

Additive is a mixture of CuO-SiO ₂ -ZrO ₂ -TiO ₂ -Al ₂ O ₃ system (80 ~ 90: 10 ~ 20: 0 ~ 5: 0 ~ 10: 0 ~ 5 mol ratio), 0.05 ~ 5.5 wt% added And remix via wet ball milling, one of the solid phase methods. According to the present invention, Zr or Ti may be replaced by a metal element having two or four outermost electrons. The same effect can be obtained even if Al is replaced with a metal element having three outermost electrons.

That is, A and B are Ba, Ce, Ge, Hf, Mn, Mo, Nb, Pb, Pt, Re, Ru, Se, Si, Sn, Fe, Th, Ti, U, which are +2 or + 4-valent metal elements. , V, W, Zr, and C is a + trivalent metal element Al, As, Au, B, Bi, Dy, Er, Eu, Fe, Ga, Gd, La, Mn, Nd, Rh , Sb, Sc, Sm, Tb, Tl, Tm, V, Y, Yb, Cr, In, Lu may be any one.

In addition, when the A metal element and the B metal element are the same, the additive according to the present invention may be represented as a mixture of CuO—SiO ₂ —AO ₂ (BO ₂ ) —C ₂ O ₃ .

It is dried and then shaped and sintered for 2 hours at each temperature ranging from 1200 to 1400 ° C. in a reducing atmosphere of gas mixed with nitrogen-hydrogen (95% -5% ratio). The cooling step was a furnace cooling step. The specimens thus obtained not only have semiconductivity but also have a high apparent dielectric constant. In addition, a semiconducting ceramic SrTiO ₃ -based specimen having good nonlinear resistance even at low voltage is obtained. In addition, by using SrTiO ₃ can be produced by lowering the high sintering temperature was limited to 100 ~ 150 ℃ when manufacturing an electronic component device.

In addition, the present invention can replace the separate heat treatment process performed to form an insulating layer (resistance layer) at the grain boundary with an additive, which can be omitted.

Table 1 shows the composition ratio of the specimen prepared according to the present invention, Table 2 shows the data (data) obtained by evaluating the electrical properties of each specimen.

Psalm No. Amount of Nb ₂ O ₅ (mol%) Additive (CuO-SiO _{2 type} ) (wt%) Sintering Temperature One 0.7 3 1200 ℃ 2 0.7 5 1200 ℃ 3 0.7 3 1250 ℃ 4 0.7 5 1250 ℃ 5 0.7 3 1300 ℃ 6 0.7 5 1300 ℃ 7 0.7 3 1350 ℃ 8 0.7 5 1350 ℃ 9 0.7 3 1400 ℃ 10 0.7 5 1400 ℃ 11 0.7 3 1450 ℃ 12 0.7 5 1450 ℃

Psalm No. ε (× 10 ⁴ ) V _1mA α Relative Sintered Density (B.D.) One 2.1 1.64 - 72.02 2 2.0 1.73 - 73.04 3 3.1 3.56 8.5 90.42 4 3.1 3.32 9.6 89.74 5 3.4 3.95 10.3 92.31 6 3.7 3.46 12.7 92.11 7 4.0 4.31 11.1 94.02 8 4.4 3.84 13.6 93.68 9 4.1 4.60 10.3 95.07 10 4.2 4.02 12.1 94.19 11 4.2 4.48 9.2 95.08 12 4.3 3.73 10.7 94.89

Note) α = 1 / log (V _{10 mA} / V _{1 mA} )

BD = W _(dry) / [ W _(catcher) -W _(suspension) ]

Where B.D. Bulk Density

V _10mA : Voltage when current is 10mA

V _1mA : Voltage when current is 1mA

W: Weight

As can be seen from Table 1 and Table 2, the additive driving voltage of the specimen can realize a significantly lower driving voltage than the low-voltage SrTiO _3- based device according to the prior art.

Therefore, by using the process of the present invention, not only the capacitance is high, but also SrTiO ₃ varistors can be manufactured that can be driven under the low voltage required for miniaturization and portability of electronic products.

In addition, the manufacturing problems to be manufactured at a high temperature of more than 1450 ℃ which is a constraint when manufacturing an electronic device using the SrTiO ₃ system composition to be manufactured at a temperature of 100 ~ 150 ℃ lower (about 1300 ~ 1350 ℃ range) than 1450 ℃ This solves the limitations of manufacturing SrTiO ₃ electronic components.

3 is a schematic perspective view showing an example of a low voltage driven varistor according to the present invention.

That is, the SrTiO ₃ based semiconducting ceramic specimen 3 is manufactured in bulk by the manufacturing method according to the present invention, and electrodes 2 are formed at both ends of the specimen 3, and at one end of the electrode 2 It shows a structure in which the lead wire (1) for electrically connecting with the electrical device is connected.

As mentioned above, it should be understood that those skilled in the art can make modifications and changes to the present invention without changing the gist of the present invention as it merely illustrates one preferred embodiment of the present invention.

Therefore, the additive of the present invention can form an insulating layer (resistance layer) at the SrTiO ₃ grain boundary, which is a perovskite oxide dielectric, to simultaneously perform a capacitor function and a varistor function, and in particular, lower the sintering temperature by about 100 to 150 ° C. In addition to reducing the manufacturing cost, it is possible to provide a low voltage driven varistor that can be driven under low pressure, which can be useful for miniaturized and portable electronic products.

Claims (7)

In the additive mixed in the SrTiO ₃ low voltage drive varistor, The additive is a low-temperature sintering and low-voltage driven component CuO and SiO ₂ is made of a mixture of 80 to 90: 10 to 20 mol ratio, The additive is a low temperature sintering and low-voltage driving type additives of SrTiO ₃ based varistor characterized in that the addition of 3 ~ 5 wt% on the SrTiO ₃ based low-voltage driving type varistor. delete The method of claim 1, The additive is a low-temperature sintering and low voltage driven additive of SrTiO ₃ -based varistor comprising at least one composition selected from the group consisting of AO ₂ , BO ₂ and C ₂ O ₃ in addition to the CuO and SiO ₂ components. The method of claim 3, wherein A is a low-temperature sintering and low-voltage driving additive of SrTiO _3- based varistor, characterized in that +2 or +4 metal element. The method of claim 3, wherein B is a low-temperature sintering and low-voltage driving additive of SrTiO _3- based varistor, characterized in that +2 or +4 is a metal element. The method of claim 3, wherein Wherein, C is a low-temperature sintering and low voltage drive type additive of SrTiO ₃ varistor, characterized in that the + _trivalent metal element. The method of claim 3, wherein The CuO-SiO ₂ -AO ₂ -BO ₂ -C ₂ O ₃ -based composition of the SrTiO _3- based varistor, characterized in that consisting of 80 to 90: 10 to 20: 0 to 5: 0 to 10: 0 to 5 mol ratio Low temperature sintering and low voltage driven additives.