JPH0661017A - Semiconductor porcelain composition and method for producing the same - Google Patents

Abstract

(57) Abstract: [configuration] crystal grains _{Sr 1-xy Ca x Ba y} Ti z Nb w Cu u O 3 ( wherein, x, y, z, respectively w and u, 0.001 ≦ x
≤ 0.250, 0.001 ≤ y ≤ 0.250, 0.99
00 <z <1.3000, 0.0001 ≦ w ≦ 0.01
00, a value in the range of 0.0001 ≦ u ≦ 0.0100,
And a composition represented by z + w> 1.0000), and further containing an alkali metal in the vicinity of the crystal grain boundary layer. [Effect] Provided are a semiconductor porcelain composition satisfying the five requirements of a large voltage non-linearity coefficient α, a low varistor voltage, a large insulation resistance, a large relative dielectric constant and a small dielectric loss required for a capacitive varistor, and a method for producing the same. However, the capacitive varistor manufactured from the composition can be used in an electric circuit mounted on electric and electronic devices corresponding to high frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor porcelain composition and a method for producing the same, more specifically, a capacitor used to protect electronic components and electric circuits from noise, pulses, static electricity, etc. generated in electronic devices and the like. Relates to a semiconductor porcelain composition for forming a conductive varistor and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the spread of information processing devices such as computers and OA devices, malfunctions of semiconductor parts such as ICs and transistors due to noise generated by these digital devices have become a problem. Further, since semiconductor parts have a drawback that they are easily destroyed by high voltage such as surge, pulse, static electricity, etc., electronic parts varistor elements are incorporated to protect each part.

A varistor is a functional element whose resistance value changes non-linearly according to the applied voltage, and its voltage-current characteristic is

[0004]

[Equation 1]

It is represented by Here, I is a current value flowing through the element, K is a varistor intrinsic coefficient, V is a voltage value applied across the varistor element, and α is a coefficient indicating non-linearity (voltage non-linear coefficient).

The evaluation of the varistor is represented by the voltage non-linear coefficient α, and the larger the voltage non-linear coefficient α, the greater the varistor effect. The voltage nonlinear coefficient α of the SiC varistor is 3 to 7, and the voltage nonlinear coefficient α of the ZnO varistor is 50 to 100. However, SiC, ZnO
Since the conventional varistor such as a system has a low electrostatic capacity, it has hardly been able to absorb noise having a high frequency component.
On the other hand, the capacitance of the ceramic capacitor is as high as 10 to 20 times that of the ZnO-based varistor, and is therefore used for absorbing and removing the noise and the like. On the contrary, it had a defect that it was weak against high voltage and was destroyed by surges. Therefore, a ZnO-based varistor and a capacitor are combined to form a parallel circuit, and the capacitor absorbs high-frequency noise while the varistor absorbs and removes a high voltage, which is contrary to the miniaturization of electronic devices. It was extremely disadvantageous in terms of mounting. Therefore, a capacitive varistor has been developed and put into practical use as a multi-functional element having one element having both functions of a capacitor characteristic and a varistor characteristic.
For the capacitive varistor, SrTiO ₃ system (JP-A-56-36) is used.
No. 103), Sr _1-x Ba _x TiO ₃ system (Japanese Patent Laid-Open No. Sho 5).
9-95203) and the like. These capacitive varistors have Sr as a main component, Nb, Y, W, Ta, Dy, etc., which are semiconducting agents as sub-components, Cu, Co, Mn, Ni, V, etc., as a voltage nonlinear coefficient improving agent, A sintering aid is added in combination with Si, Al, B, etc., is fired in a reducing atmosphere to obtain a porcelain sintered body, and then an insulating layer is formed at a crystal grain boundary of the porcelain sintered body. For this purpose, Na compounds and B ₂ O ₃ , Sb ₂ O ₃ , Bi ₂ O ₃ and Ti are used as diffusion substances.
O ₂ , MoO ₃ WO _{3 and the} like are used (Japanese Patent Laid-Open Publication No. 61-61160).
No. 131501). In addition, the semiconductor ceramic capacitor has a composition in which Nb or Mn is added to Sr _1-x Ca _x TiO ₃ and Bi, Cu, and Na are diffused in the crystal grain boundaries.

[0007]

The conventional SrTiO ₃ -based capacitive varistor as described above is a multi-functional element having both functions of varistor characteristics and capacitor characteristics, and is characterized by being small in size. It is suitable for protecting small electronic devices that incorporate ICs and LSIs. However, semiconductor components in recent years may be destroyed by relatively low-voltage pulses, static electricity, etc., which were not destroyed by conventional semiconductor components at the same time when the operating voltage became low. As a capacitive varistor for protecting a circuit, one having a larger voltage non-linearity coefficient α, a lower varistor voltage and a larger insulation resistance, and a capacitor having a large relative dielectric constant and a small dielectric loss is desired.

Up to now, in order to obtain a large relative dielectric constant and a low varistor voltage characteristic, either the wall thickness of the element body or the crystal grain size is increased. . However, the method of reducing the thickness of the element body has a limit because the strength is lowered, the insulation resistance is lowered, and the element is easily electrically broken. Further, in the method of increasing the crystal grain size, since abnormal grains grow during firing and a uniform crystal grain size cannot be obtained, the voltage non-linearity coefficient α decreases, and there is a problem that the element is easily broken electrically. there were.

The present invention has been made in view of the above problems, and it is a large voltage non-linearity required for a capacitive varistor used for high frequency electronic / electronic equipment etc. equipped with a semiconductor component operating at a low voltage. 5 with coefficient α, low varistor voltage, large insulation resistance, large relative permittivity and small dielectric loss
An object of the present invention is to provide a semiconductor porcelain composition for a capacitive varistor that satisfies one of the two conditions and a method for producing the same.

[0010]

As a result of earnest research to solve the above problems, a semiconductor ceramic having a perovskite type crystal structure represented by ABO ₃ has a non-stoichiometric composition ratio ([A] / [B ] It was found that the voltage non-linearity coefficient α, varistor voltage, insulation resistance, relative permittivity and dielectric loss change due to a slight variation in the ratio. In order to achieve the above-mentioned object, the present invention is an invention made based on the above-mentioned findings, and in order to solve the problem, the semiconductor porcelain composition according to the present invention has an Sr _1-xy Ca _x Ba _y Ti _z Nb _w Cu _u O ₃
(In the formula, x, y, z, w, and u are each 0.001
≤ x ≤ 0.250, 0.001 ≤ y ≤ 0.250, 0.
9900 <z <1.3000, 0.0001 ≦ w ≦ 0.
0100, a value in the range of 0.0001 ≦ u ≦ 0.0100 and a value in the range of z + w> 1.0000), and an alkali metal is further included near the grain boundary layer. It is characterized by that.

Further, in the above-mentioned method for producing a semiconductor porcelain composition, the total amount of SrCO ₃ , CaCO ₃ and BaCO ₃ is 10%.
With respect to 0.00 mol, TiO ₂ is from 99.00 to 130.
00 mol, Nb ₂ O ₅ in an amount in the range of 0.01 to 1.01 mol, and the total of TiO ₂ and Nb ₂ O ₅ is 100 m.
ol and 0.01 mol to 1.00 m of CuO
It is characterized in that the mixture is mixed at a ratio of the amount of ol to carry out semiconducting firing, and a metal oxide containing an alkali metal is applied to the sintered body after firing and grain boundary insulating firing is performed.

[0012]

In the semiconductor porcelain composition, the inside of the crystal grains is made into a semiconductor in the step of semiconducting firing in a reducing atmosphere, and the crystal grains are grown. Thermal diffusion and formation of crystal grain boundaries are simultaneously performed to form a grain boundary layer.

Generally, in a semiconductor ceramic obtained by firing in a reducing atmosphere, abnormal grain growth is likely to occur and a mixed grain structure is likely to occur, so that the number of crystal grain boundaries in the direction of current flow tends to vary depending on the location. Variations in the thickness and composition distribution of the Therefore, by combining a main component porcelain material and a metal oxide for grain boundary insulation, five conditions of a large voltage nonlinear coefficient α, a low varistor voltage, a large insulation resistance, a large relative permittivity and a small dielectric loss are set. A semiconductor porcelain composition for a capacitive varistor that satisfies the above requirements has been realized.

The limitation of each component as in the claims is that
The value of _{Sr 1-xy Ca x Ba y} Ti z Nb w Cu u O 3 of x, 0.001 ≦
The dielectric loss becomes large outside the range of x ≦ 0.250.
On the other hand, when the value of y is less than 0.001, the insulation resistance becomes small, and when the value of y exceeds 0.250, the voltage nonlinear coefficient α becomes small. When the value of z is 0.9900 or less, the relative dielectric constant is small, and when the value of z is 1.3000 or more, the insulation resistance and the voltage non-linearity coefficient are small. The value of w is 0.000
If it is less than 1, the varistor voltage is high and the dielectric loss is large, and if the value of w exceeds 0.0101, the insulation resistance is small. When the value of u is less than 0.0001, the insulation resistance becomes small, and when the value of u exceeds 0.0200, the dielectric loss becomes large. In addition, the value of z + w is limited to z + w
When the value of is less than 1.0000, the dielectric loss is large and the voltage nonlinearity coefficient is small. Further, the alkali metal diffuses in the grains to form a high resistance diffusion layer, which contributes to the improvement of the voltage nonlinear coefficient α.

[0015]

EXAMPLES Examples of the semiconductor ceramic composition and the method for producing the same according to the present invention will be described below.

First, SrCO ₃ , CaCO ₃ , BaCO _3, TiO ₂ , Nb ₂ O ₅ and CuO are mixed at the ratios shown in Table 1 as raw materials for ceramics synthesis. Further, one or two kinds selected from SiO ₂ or Al ₂ O ₃ is added in an appropriate amount. For the compounding, each raw material is accurately weighed and mixed with an appropriate amount of boulders, a dispersant, and pure water in a pot mill for 24 hours. The mixed slurry-like raw materials are dehydrated and dried and crushed. The crushed powder is transferred into a firing crucible made of, for example, zirconia, and calcination synthesis is performed at 1100 ° C. X that the prescribed solid solution has been synthesized
It was confirmed by line analysis and composition analysis.

Next, the calcined synthetic powder is crushed and sized to a uniform powder of about 1.0 μm. An organic binder or the like is added to this powder, which is pressure-molded into a disk shape having a diameter of 10 mm and a thickness of 500 μm, and degreased at 1000 ° C. The degreased body is filled in, for example, a firing crucible made of alumina, and is semiconducting and firing in a reducing atmosphere to obtain a semiconducting sintered body. The semiconducting firing is performed in a temperature range of 1380 to 1550 ° C. in a mixed gas atmosphere of 1 to 15% hydrogen and 85 to 99% nitrogen, and
Bake for 8.0 hours. Next, after thoroughly washing the obtained sintered body, a metal oxide paste for insulating the grain boundaries is applied to the surface and dried. Here, the metal oxide paste is Li
_A composition containing ₂ CO ₃ in the form of a kneading paste is used, and the coating amount is about 20 to 100 mg per 1 g of the sintered body. The sintered body to which the metal oxide paste is applied is 0.5 to 4.0 in the temperature range of 950 to 1300 ° C. in the atmosphere.
After firing for a time, the grain boundaries of the sintered body are insulated to obtain a semiconductor ceramic composition.

Further, in order to examine the characteristics of the semiconductor porcelain composition, silver paste is applied to both surfaces thereof and baked at a temperature of 800 ° C. to form electrodes to complete the device.

The evaluation of the completed semiconductor porcelain composition was performed as follows.

The electrical characteristics are the apparent relative permittivity ε _app ,
The dielectric loss DF (%) was evaluated with an impedance analyzer, and the insulation resistance IR (Ω) was evaluated with a DC constant voltage power supply.
Apparent relative permittivity ε _app is AC1kHz, applied voltage 1V
It is a value calculated from the capacitance value measured in step 1 and the dimensions of the element. The dielectric loss DF (%) is a value measured at AC 1 kHz and applied voltage 1V. The insulation resistance IR (Ω) is a value calculated by applying a DC voltage of 25 V between the electrodes on both sides of the semiconductor porcelain composition, measuring the current flowing for 1 minute, and calculating the value. The voltage non-linearity coefficient α and the varistor voltage V _1mA were calculated from the current-voltage curve obtained by measuring the current when a voltage was applied every 5 V for 1 second from ₁ V to 100 V.

[0021]

[Table 1]

[0022]

[2 in Table 1]

[0023]

[3 in Table 1]

[0024]

[4 in Table 1]

[0025]

[5 in Table 1]

[0026]

[6 in Table 1]

The data on the electrical characteristics in Table 1 show the average value of 100 randomly taken semiconductor porcelain compositions from the same lot. As is clear from Table 1,
According to the semiconductor porcelain composition and the method for producing the same according to the present invention, the apparent relative permittivity ε _app is 1.0 × 10 ⁴ or more,
Moreover, the insulation resistance IR is 3.0 × 10 ⁶ Ω or more,
Since the value of the dielectric loss DF is also 1.5% or less, it was confirmed that the function as a capacitor was satisfied.

The varistor characteristic has a voltage nonlinear coefficient α
Is 10 or more, and the varistor voltage V _1mA Is 100V or more
The lower withstand voltage was DC 200 V or higher. Example
Then as a metal oxide, Li₂CO₃Kneading composition containing
I used a metal oxide paste in the shape of a tongue
A compound containing a metal (K, Na, Rb, etc.) or
Any metal oxide containing a mixture may be used.

[0029]

As described above in detail, in the semiconductor ceramic composition according to the present invention, the inside of the crystal grains is Sr _1-xy Ca _x Ba _y Ti _z N
b _w Cu _u O ₃ (where x, y, z, w and u are respectively
0.001 ≤ x ≤ 0.250, 0.001 ≤ y ≤ 0.2
50, 0.9900 <z <1.3000, 0.0001
≦ w ≦ 0.0101, 0.0001 ≦ u ≦ 0.0100
Value in the range of z + w> 1.0000)
Since it has a composition shown by and further contains an alkali metal in the vicinity of the grain boundary layer, a large voltage nonlinear coefficient α,
A semiconductor porcelain composition for a capacitive varistor satisfying the five conditions of low varistor voltage, high insulation resistance, high relative permittivity and low dielectric loss can be obtained.

Further, in the above-mentioned method for producing a semiconductor porcelain composition, the total amount of SrCO ₃ , CaCO ₃ and BaCO ₃ is 1
With respect to 00.00 mol, TiO ₂ is 99.00 to 13
0.00 mol, 0.01 mol to 1.01 m of Nb ₂ O ₅
and an amount within the range of ol, in which the total amount of TiO ₂ and Nb ₂ O ₅ exceeds 100 mol, and CuO is 0.01 mol to
The mixture is mixed at a ratio of 1.00 mol to perform semiconductor firing, and the sintered body after firing is coated with a metal oxide containing an alkali metal and subjected to grain boundary insulation firing, which impairs the conventional process. Without this, it is possible to manufacture a semiconductor porcelain composition having both excellent capacitor characteristics and varistor characteristics.

Therefore, the present invention provides a semiconductor porcelain composition and a semiconductor porcelain composition which satisfy the five requirements of a large voltage non-linearity coefficient α, a low varistor voltage, a large insulation resistance, a large relative dielectric constant and a small dielectric loss required for a capacitive varistor. A capacitive varistor, which provides the manufacturing method and is made from the composition,
It can be used for electric circuits that are mounted on electric and electronic devices that support high frequencies.

Claims (2)

[Claims] 1. The crystal grains are Sr _1-xy Ca _x Ba _y Ti _z Nb _w Cu _u O ₃
(In the formula, x, y, z, w, and u are each 0.001
≤ x ≤ 0.250, 0.001 ≤ y ≤ 0.250, 0.
9900 <z <1.3000, 0.0001 ≦ w ≦ 0.
0101, 0.0001 ≦ u ≦ 0.0100, and z + w> 1.0000), and further contains an alkali metal near the crystal grain boundary layer. A semiconductor porcelain composition characterized by being present. 2. The total amount of SrCO ₃ , CaCO ₃ and BaCO ₃ is 1
With respect to 00.00 mol, TiO ₂ is 99.00 to 13
0.00 mol, Nb ₂ O ₅ in an amount within the range of 0.01 to 1.01 mol, and the total of TiO ₂ and Nb ₂ O ₅ is 10
If the amount exceeds 0 mol and CuO is 0.01 mol to 1.0
2. The mixture is mixed in an amount ratio of 0 mol to perform semiconducting firing, the metal oxide containing an alkali metal is applied to the fired sintered body, and the grain boundary insulating firing is performed.
A method for producing the semiconductor porcelain composition described.