JPS6032342B2 - Ceramic materials for reduction and reoxidation type semiconductor capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on the mother Ti03, BaZ3, Bi203, Ti0
The present invention relates to a ceramic material for a reduction and reoxidation type semiconductor capacitor, which contains Ni compound No. 2 as a main component and a trace amount of a Ni compound.

Semiconductor ceramic capacitors are generally given various names depending on the starting materials and manufacturing methods.

That is, the Iso TiO3 system and its solid melt system are mainly used as starting materials, and some semiconductor ceramic capacitors containing SrTiO3 as a main component have also been put into practical use.
The manufacturing method based on these starting materials takes full advantage of the characteristics of each type of porcelain, and includes a grain boundary type that utilizes the grain boundaries of the porcelain, a weir layer type that utilizes the porcelain surface, and a reduced type (also known as a reoxidation type). There are a wide variety of manufacturing methods depending on the purpose and application. Reduction-reoxidation type semiconductor porcelain capacitors are usually obtained by heat-treating dielectric porcelain in a reducing atmosphere, applying silver paste for electrodes to semiconductor porcelain, and then heat-treating it. A thin dielectric layer is formed between the silver electrodes.

This thin dielectric layer contributes to the capacitance and insulation resistance of the capacitor, and is also highly dependent on the dielectric constant of the dielectric ceramic. In reduction and reoxidation type semiconductor ceramic capacitors, when the capacitance per unit area is increased, the dielectric layer becomes thinner and the insulation resistance inevitably decreases.On the other hand, when trying to increase the insulation resistance, the conductor layer becomes thicker and the unit area becomes thinner. It has the property that the capacity per area decreases. Further, the temperature characteristic of the capacitance of this dielectric layer appears as the temperature characteristic of the capacitance of the reduction-reoxidation type semiconductor ceramic capacitor, and is extremely similar to the temperature characteristic curve of the dielectric ceramic before reduction. In other words, it is presumed that this thin conductor layer was formed when the surface of the semiconductor porcelain obtained by reduction was oxidized again during the heat treatment during electrode formation. It is something that will be done. In addition, in order to form a thin and homogeneous conductor layer on the semiconductor porcelain surface, the dielectric porcelain surface must be homogeneous,
Furthermore, it is necessary that the particles consist of several peaks or less. In order to obtain a reduction-reoxidation type semiconductor ceramic capacitor with small capacitance change with temperature, high insulation resistance, and large capacity, it is necessary to have a large dielectric constant and a small change in dielectric constant with temperature. In addition, the porcelain surface is a dielectric porcelain consisting of homogeneous small particles of a few 1 or less, and the porcelain surface layer can be easily formed into a dielectric layer at the heat treatment temperature used when forming a silver electrode on the surface of the reduced porcelain. A porcelain material that meets the requirements must be obtained.

Conventionally, many reduction and reoxidation type ceramic materials for semiconductor capacitors have been disclosed in patent publications and literature, and have been put into practical use. is as low as 3000-5000.

In addition, the cue l'-point in the temperature characteristics of the capacitance of the reduction-reoxidation type semiconductor ceramic and the temperature characteristic of the capacitance of the dielectric ceramic is 30 ~
Conventional reduction-reoxidation semiconductor capacitors with large capacitance and high insulation resistance had an extremely large rate of change in capacitance with respect to temperature. The present invention was made in response to the demand for smaller parts and higher quality due to the recent miniaturization and quality stabilization of electronic devices.It eliminates the conventional drawbacks and maintains a capacitance change rate with temperature within ±30%. In order to obtain a reduction and reoxidation type semiconductor capacitor that is small and has high insulation resistance, the dielectric porcelain has a surface homogeneous layer, a homogeneous grain size of less than a few feet, and a dielectric constant of 60.
It provides porcelain materials with high grades ranging from 0.00 to 8000.

That is, the present invention provides (1-m-n)(x mother Ti03
3) Ten mBi203 ten nTi02 (however, x
= 0.99 to 0.80, y 0.01 to 0.20, m 0.01 to 3.0 mol%, n = 0.1 to 8.0 mol%)
The Ni compound is converted to Ni0 and is 0.032 to 2.37.
This applies to a porcelain material containing 6 mol%. Conventionally, Mn compounds have been mainly used as additives to ceramic materials for reduction-reoxidation type semiconductor ceramic capacitors. For example, in the compositions of sample numbers 2 to 7 in Table 1, Ni○ was replaced with Mn0 and an appropriate amount was added. In order to keep the temperature characteristics of the capacitor within ±30%, the permittivity of the ceramic material must be only about 500, and the insulation resistance of the capacitor must be reduced to 1.
In order to make it more than 00 MO', the limit is an areal capacity of 0.3 F/ground.

On the other hand, the addition of Ni compounds to the ceramic material according to the present invention has a remarkable effect on improving the characteristics of small-sized, large-capacity reduction-reoxidation type semiconductor ceramic capacitors, and
．． With the addition of 0.15% by weight of Nj compound, the insulation resistance of several MO's and the unit area capacity of 0.42 wF/ were reduced to 0.01% by weight.
By adding 12% by weight of Ni compound, the unit area capacity became 0.
It is almost the same as 41F/, but the insulation resistance is about 15M.
A porcelain material dramatically improved from that of Q/ was obtained. Hereinafter, the present invention will be described in detail with reference to examples.

The sample was prepared as follows.

That is, &Ti03 is produced by mixing mother C03 and Ti02 in an equimolar ratio, calcining the mixture at 1150° C. for 2 hours, and pulverizing the reactant. Similarly, the equimolar ratio of European C0
3 and Zr02 are mixed, the mixture is suspended at 1200q0 for 2 hours, and the reaction product is pulverized to obtain BaZr03. String Ti03, Europe Z3, Ti02, Bi02, and Ni compounds are each weighed to give the desired composition, and wet mixed in a pot mill for about 1 minute. After mixing, dehydrate and dry, add about 20% of organic binder such as polyvinyl alcohol.
．． Add 5% by weight, size the particles, and mold them into a willow shape with a diameter of 16 ribs and a thickness of 0.6 cm under a pressure of 1000 k9/square. Next, the formed disc is fired for 2 hours at 1300q0. The thus obtained ceramic body is heat treated at a temperature of 100,000 ℃ for 2 hours in a reducing atmosphere containing 10% hydrogen and 90% nitrogen to obtain semiconductor porcelain. A silver paste for electrodes was applied to this semiconductor ceramic and heat treated in an oxidizing atmosphere at 650 to 800 qo for 30 minutes to produce a reduction and reoxidation type semiconductor capacitor. Table 1 shows the characteristics of the capacitor manufactured by the above method.

Table 1 Note that when measuring the sample, the capacitance and dielectric positive temperature are determined by the frequency lk
The insulation resistance was measured after applying a voltage of 15 VDC for 19 seconds at Hz and a voltage of 0.1 Vrms.

Also, the temperature characteristics of the capacity are -3 based on the capacity of 2500.
This is the rate of change in capacity at 0,000 and 185 qo. Sample numbers 2-7, 9-1315-1922 in Table 1
~28 are related to the present invention, and sample numbers 1, 8, 1
4, 20, 21, and 29 are outside the scope of the present invention for comparison.

As is clear from Table 1 and the figures, the ceramic material according to the present invention has very excellent characteristics as a reduction-reoxidation type semiconductor capacitor.

For example, sample number 5 in Table 1 has an areal capacitance of 0.41 rF/ground, and an insulation resistance of approximately 150 MQ', and the temperature characteristics of the capacitance are also within ±20%, which is a dramatic characteristic for a conventional semiconductor capacitor. Improvements have been made. That is, it is characterized by excellent characteristics such as high insulation resistance while maintaining a very large capacitance per unit area, and a capacitance change rate with respect to temperature of 4. This is due to the extremely high dielectric constant of dielectric ceramic. Therefore, even if the thickness of the thin dielectric is set to be the same or thicker than that of a conventional reduction-reoxidation semiconductor capacitor, the capacitance per unit area can be increased because of its high dielectric constant. Furthermore, as shown in the drawing, the temperature characteristics of the capacitance of the dielectric ceramic A and the reduction-reoxidation semiconductor capacitor B are very similar.
The Curie points also differ within 100C. This shows that the thin exposed layer of the conventional reduction-reoxidation type semiconductor capacitor is very similar to the dielectric porcelain before reduction, and the surface of the reduced semiconductor porcelain is oxidized again. This shows that the government has returned to its agenda. The reason for the limited composition range in the present invention is as follows. {1} Good capacitance and insulation resistance characteristics can be obtained even with BaTi03 alone, but since the Curie point is at a high temperature, it is difficult to obtain a flat capacitance temperature characteristic.

However, by barrel-testing the mother TiO3 with BaZrO3, the Curie point can be moved to the lower side by 6 to 8°C per 31 mol% of the armature Z. Therefore, when BaZr03 is replaced with 20 mol% BaTi03, the Curie point becomes 0.
The temperature will be around ℃ or below, but the capacitance and insulation resistance will be the first.
As shown in the table, there are no inconveniences. However, due to the temperature characteristics of the capacitance, the rate of change on the high temperature side becomes large, which is not preferable. Therefore, in order to keep the temperature characteristic of the capacitance within ±20%, it is optimal to replace 3 of the base Z with Iso Tj03 by about 10%. In the present invention, the substitution amount of 3 in Europe for BaTi03 is 20 mol%.
is the limit. Moreover, if BaZr03 is less than 1 mol%, the Curie point is high and the temperature characteristic of capacity exceeds ±20%, which is not preferable. ■ Ni compound converted to Ni0 is 0.03
This is because if it is less than 2 mol %, the insulation resistance is low relative to the capacity, and the effects of large capacity and high insulation resistance, which are the characteristics of the present invention, are difficult to recognize. It is clear from Table 1 that the optimum amount of Ni0 to be added is about 0.380 to 0.475 mol%. Dielectric porcelain with addition of 0.380 to 0.475 mol% is yellow, but with addition of 0.951 to 1.268 mol%, it is yellow-green; When the amount exceeds 5 mol%, the color becomes light green, and 2.
At 376 mol%, the color turns dark green and some abnormal growth is observed, and when 3.169 mol% is added, the porcelain particles completely grow abnormally, so it is not acceptable, and the limit is 2.376 mol% based on the porcelain particle size.

Further, when 3.169 mol % is added, a resistivity of several hundred kilograms is exhibited, which is not good because it becomes a semiconductor before being reduced. Note that the Ni compounds include Ni2Q, NiC03, NjS04, N
i(N03) etc., converted to Ni0 is 0.0
It may be used in the addition range of 32 to 2.376 mol%, and Ni
It is not limited to 0. ■ Addition of B1203 is 0.
If it is less than 0.01 mol %, part of the dielectric porcelain will become semiconducting during firing, and the particles will grow, making it impossible to obtain a homogeneous dielectric porcelain with the desired grain size.

Approximately 1.0 mol% of Bi203 is the maximum liquid amount, and if it exceeds 3.0 mol%, the amount of evaporation of Bi203 will increase during firing of Yukatai porcelain, causing non-uniform distribution of the porcelain composition and causing warpage. . Furthermore, the porcelain after reduction is brittle, and in extreme cases may be damaged when taken out from the reduction furnace.
Bj02 not only contributes to flattening the temperature characteristics of the capacitance of dielectric ceramics, but also has the effect of shifting the Curie point, and when the amount of Bi203 added increases to 2.5 mol%, The Curie point moves to the lower temperature side,
At 2.5 to 3.0 mol %, the Curie point stops moving, and when it exceeds 3.0 mol %, it has the effect of starting to move to a higher temperature side from that point. {4' Also, the addition of Ti02 is not limited to the idea of titanium richness compared to BaTi03, but the addition of Ti02 lowers the firing temperature of Yukata porcelain, and has the effect of having a large effect on flattening the temperature characteristics of the capacitance. There is.

Also, in reduction, the addition of Ti02 has remarkable effects such as lowering the specific resistance and reducing temperature, and the optimum addition amount is about 2.5 mol%. However, even if the amount of Ti02 added is less than 0.1 mol %, it is effective in lowering the specific resistance and reduction temperature during reduction, but the temperature characteristics of the capacity cannot be flattened. Moreover, when it exceeds 8.0 mol%, the temperature characteristics of the capacitance become extremely flat, but the yield rate of the dielectric ceramic decreases proportionally, and giant abnormally grown particles appear on the porcelain surface, causing the particle size to decrease. This is undesirable as it becomes non-uniform and causes a decrease in insulation resistance. As described above, the reduction and reoxidation semiconductor capacitor made of a ceramic material characterized by adding a Ni compound to the composition of side Ti03, mother Z3, Bi203, and Ti02 according to the present invention has high insulation resistance, It has the excellent characteristics of a small capacitance change rate with respect to temperature and a large capacity, and it seems to be sufficient to meet the demands of the times for miniaturization and high stability of electronic components.
It has great industrial value.

[Brief explanation of drawings]

The figure is a characteristic diagram showing the capacitance change with respect to temperature of sample number 5 in Table 1, and is a comparison between dielectric ceramic A and reduction-reoxidation type semiconductor capacitor B.

Claims (1)

[Claims] 1 (1-m-n)(xBaTiO_3+yBaZrO
_3) +mBi_2O_3+nTiO_2 composition
A ceramic material for a reduction and reoxidation type semiconductor capacitor, characterized in that it contains an i-compound in an amount of 0.032 to 2.376 mol% in terms of NiO. However, x=0.99~0.8 y=0.01~0.2 (x+y=1) m=0.0001~0.03 n=0.001~0.08