JPS584448B2 - Method for manufacturing reduction and reoxidation type semiconductor ceramic capacitor body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a reduction and reoxidation type conductive ceramic capacitor body that can provide a capacitor with well-balanced characteristics.

Semiconductor ceramic capacitors are already known in which a BaTi03-based semiconductor composition is sintered to become a semiconductor, the surface is coated with silver paint, and a dielectric layer is provided on the semiconductor ceramic surface by heat treatment.

However, in this type of device, if you increase the capacitance, the insulation resistance or breakdown voltage will decrease, and conversely, if you try to improve the insulation resistance or breakdown voltage, the capacitance will decrease or the electrostatic If an attempt was made to increase both the capacitance and breakdown voltage, there was a drawback that the rate of change in capacitance due to temperature would increase.

In addition, it is generally difficult to select the electrodes for this type of device, and the characteristics of the capacitor are affected by the type and condition of the electrodes, and the dielectric layer and weir layer may be destroyed if soldering is performed over the electrodes. However, it also had drawbacks such as being useless as a capacitor.

BaT allows for free selection of flat electrodes.
Boundary layer type semiconductor ceramic capacitors in which Cu, Bi, Mn, etc. are diffused are known, but the insulation resistance changes greatly depending on temperature and applied voltage, and the capacitance changes due to temperature. The problem was that the ratio was high.

This invention eliminates the above-mentioned drawbacks, and has a high dielectric constant, low dielectric loss, high insulation resistance, high breakdown voltage, and low capacitance change rate depending on temperature, and low insulation resistance due to temperature and applied voltage. A method for producing a reduction and reoxidation type semiconductor ceramic capacitor body that has a small change in temperature, does not change its characteristics even when soldering is performed on the electrodes, and provides a stable semiconductor ceramic capacitor with excellent moisture resistance. This is what we provide.

To carry out the method of this invention, first, BaCO3, SrC
O3 and TiO2 are mixed and calcined in an oxidizing atmosphere at a temperature of 1000 to 1200C for about 2 hours to form (Ba, Sr)T.
iOA-made with additives Bi203, Zr0
2 and mix, then 1300~ in an oxidizing atmosphere.
It is fired at a temperature of 1400° C., and then heated with a trowel at a temperature of about 1100° C. in a reducing atmosphere containing hydrogen or carbon monoxide.

A semiconductor ceramic capacitor is obtained by heating at a temperature of 900 to 1050 C in an oxidizing atmosphere and then providing electrodes.

Hereinafter, the present invention will be described in detail with reference to examples.

Blend and mix BaCO3sSrCO3, Tt02, 9
Calcined for 2 hours at a temperature range of 50 to 1200℃ (Ba,
Sr) Make Tie3 and add B1203, which is an additive.
*ZrO2 was added in the proportions shown in Table 1, and approximately 3.5 weight cents of vinyl resin was added as a binder for sizing.

Next, this was made into a diameter of 12 mm and a wall thickness of 0.0 mm using a hydraulic press.
It was molded into a 6 mm disk, placed on top of alumina boxes, and fired in air at a temperature of about 1350C for 2 hours.

Subsequently, heat treatment was performed at a temperature of 900 to 1250°C for 2 hours in a reducing atmosphere consisting of 15% hydrogen and 85% nitrogen by volume, followed by heat treatment in air for 30 minutes at 850°C to 1100°C, followed by cooling. A semiconductor porcelain body with a dull color tone was obtained.

Silver paint was applied to the obtained semiconductor ceramic body, dried, and a silver electrode was baked in the air at about 800° C. for 5 minutes to obtain each sample of a semiconductor ceramic capacitor.

FIG. 1 shows a semiconductor porcelain capacitor obtained by the method of the present invention, in which 1 is a semiconductor porcelain, 2 is a dielectric layer, and 3 and 4 are silver electrodes.

Next, for each sample, capacitance, dielectric loss, insulation resistance, breakdown voltage, C. When the R product and the rate of change in capacity with temperature were measured, the measurement results shown in Table 2 were obtained.

Capacitance: The electrode area provided on both sides of the sample was 1 cm2, the temperature was 25°C, the frequency was IKHz, and the voltage was 0.3Vr. m. It is the capacitance value per area when measured in s.

Dielectric loss: This is a value measured in accordance with the capacitance measurement conditions.

Insulation resistance: At a temperature of 25°C, a DC voltage of 25°C is applied to the sample.
This is the value obtained 25 seconds after V was applied.

Breakdown voltage: indicates the lower limit of the voltage at which the current increases rapidly when the DC voltage applied to the sample is increased at a temperature of 25°C.

C. R product: indicates the product of capacitance and insulation resistance.

Capacity temperature: Rate of change based on capacity at 25℃
Measured the capacitance temperature characteristics between -30C and +85C,
This shows the upper and lower limits of the rate of change in capacity.

The sample numbers in Tables 1 and 2 match, and the * marks in the table are outside the scope of this invention, and the others are within the scope.

As is clear from Table 2, the products within the scope of the present invention are excellent in each property, and moreover, the properties are well balanced with each other.

Figure 2 shows the capacitance-temperature characteristics measured for sample No. 1 and I1. Sample No. 11 (within the scope of the invention) has a flatter capacitance-temperature characteristic compared to sample No. 1 (outside the scope of the invention). It can be seen that it can be used in a wide temperature range.

Next, in order to examine the moisture resistance, the sample was boiled for 2 hours, thoroughly dried, and the insulation resistance was measured.

Table 3 shows the measurement results, and the reason why only the insulation resistance was measured for each sample is because changes in insulation resistance directly affect other characteristics, and it can be used as a guide for investigating various changes in characteristics. Therefore, it is clear that the material according to the present invention has excellent moisture resistance.

The reason why the composition range is limited in this invention is as follows.

That is, replacing Ba in BaT+03 with Sr is
This is because the dielectric loss increases if the base composition is only BaT103, and the reason why the substitution amount is set to 5 to 35 atoms is as follows.
This is because when the number of atoms is less than 5, the dielectric loss increases, and when it exceeds 35, abnormal particles are deposited on the surface and the capacitance becomes small.

Furthermore, when only Bi203 is added to (Ba,Sr)Ti03, sintering is difficult, probably because Bi203 evaporates, and when only ZrO2 is added, it becomes difficult to reduce5, so Bi203 and ZrO2 coexist. They were made to have a correlation with each other.

Furthermore, the reason why Bi203 is 1 to 4% by weight of (Ba,Sr)Ti03 is that less than 1% by weight is difficult to reduce, and the entire porcelain is easily reoxidized at the reoxidation temperature, which reduces the capacitance. , 4 weight la, the capacitance becomes small and the dielectric loss becomes large.

Sarakomata Zr02 (Ba, Sr) Tie3 1.6
~5.0 weight in advance and (X-1) ~ (X+3) weight was set as 1.6 weight and (x-i) less than 1.6 weight and (x-i) weight, it would be difficult to sinter, This is also because the capacitance becomes smaller.

Also, if it exceeds 5.0% by weight and (X+3) weight,
This is because abnormal particles are deposited on the surface and the breakdown voltage and capacitance are reduced.

Next, in the process of compounding and mixing raw materials to make porcelain in this invention, first calcination is performed to make (Ba, Sr)Ti03, and the calcination temperature ranges from 1000 to 1200°C. preferable.

This was obtained by calcining at less than 1000°C (Ba, Sr
) When Tie3 is used, a large peak appears in the capacitance-temperature characteristic, probably because (Ba, Sr)Tio3, Bi203, and TrO2 form a solid solution, and the rate of change in capacitance due to temperature becomes large.

Also, (Ba, Sr) Tie calcined at over 1200℃
This is because if No. 3 is used, it is partially sintered, so it is impossible to crush, mix, finely grind, or evenly mix the additives.

The mixed powder may be fired at a temperature of 1300 to 1400C.

This is because firing becomes difficult at temperatures below 1300°C, and
This is because porcelain fired at temperatures exceeding 00°C bond together, making industrial production impossible.

In addition, in the reduction process after firing, the temperature is 950 to 1200℃.
It is sufficient to process within the temperature range.

When the temperature is lower than 950° C., the capacitance becomes small and the dielectric loss becomes large.

Moreover, when the temperature exceeds 1200° C., the breakdown voltage decreases.

In the step of re-oxidizing the raw material, it is preferable to perform the treatment at 900 to 1050°C.

If the temperature is lower than 900°C, the breakdown voltage will be low and the moisture resistance will be poor.

Furthermore, if the temperature exceeds 1000°C, the entire ceramic will be reoxidized, making it impossible to obtain a semiconductor ceramic capacitor with a high dielectric constant.

In general, after reduction and reoxidation type semiconductor ceramic capacitors have been subjected to reduction treatment, they are heated again in an oxidizing atmosphere to provide electrodes and to form a dielectric layer by reoxidizing the ceramic.

However, according to the method of this invention, since a very stable dielectric layer is formed on the semiconductor porcelain before applying the electrodes, the characteristics are not influenced by the application of the electrodes, and are different from those of ordinary semiconductors. In addition to baking silver in the same way as porcelain capacitors, electrodes can be formed by vapor deposition or any other method.

Therefore, it has a great practical advantage in that there is no risk of deterioration of the characteristics even if processes such as soldering are performed on the electrodes.

Furthermore, the semiconductor ceramic capacitor obtained by the method of this invention has excellent moisture resistance.

This is because the grain size of porcelain is very dense, about 1μ, so a uniform dielectric layer is formed under the electrode without any gaps.
It is also believed that the ability to choose from a wide range of electrode types makes it possible to provide corrosion-resistant electrodes.

Furthermore, this is because the surface dielectric layer is formed not only on the electrodes but on almost the entire surface of the porcelain, which prevents discharge from occurring on the porcelain surface, which contributes to its moisture resistance. It is thought that this is the case.

As described above, the present invention provides a semiconductor ceramic capacitor with well-balanced characteristics, that is, a high dielectric constant, low dielectric loss, high insulation resistance, high breakdown voltage, and high capacitance change rate due to temperature change. In addition, changes in insulation resistance due to applied voltage are small, and even if soldering is performed on the electrodes, the characteristics do not change, making it possible to obtain a stable semiconductor ceramic capacitor with excellent moisture resistance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor ceramic capacitor obtained according to the present invention, and FIG. 2 is a capacitance-temperature characteristic diagram of the semiconductor ceramic capacitor. 1... Semiconductor ceramic, 2... Dielectric layer,
3, 4... Silver electrode.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a reduction and reoxidation type semiconductor ceramic capacitor body comprising the following steps. (1) Using calcined (Ba,Sr)Ti03 as a base material in which Ba in BaTi03 is replaced with 5-35 atoms of Sr, additives Bi203 and Zr02 are added at x and y weights, respectively. The process of adding and mixing the composition range shown below. x(=Bt203)-1 to 4 weight, y(=ZrO2)-1.6 to 5 weight, and (x-1
) to (x+3) (2) Calcining the mixture in an oxidizing atmosphere. (3) A step of heat treatment in a reducing atmosphere. (4) A step of heat treatment in an oxidizing atmosphere.