JPH08186053A - Production of ceramic electronic device - Google Patents

Abstract

PURPOSE: To obtain a method for producing a ceramic electronic device with high efficiency in which residual carbon in a ceramic element can be decreased quickly after degreasing without having any adverse effect on the sintering of the ceramic element in the sintering process. CONSTITUTION: After ending the degreasing process, sintering is carried out until a predetermine temperature is reached while supplying moisture, independently from the moisture for sustaining a wet reducing atmosphere, at a rate of 3 mole per minute or above for one mole of residual carbon in a ceramic element at the end of the degreasing process. Firing is then carried out according to a predetermined temperature profile while supplying only the moisture for sustaining the wet reducing atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electronic component, and more specifically, it heats a ceramic element to decompose the binder and the like contained in the ceramic element to remove the degreasing step, and then wet the ceramic element. The present invention relates to a method for manufacturing a ceramic electronic component including a firing step of heat-treating and sintering in a reducing atmosphere.

[0002]

2. Description of the Related Art For example, as one of the methods for firing a ceramic element such as a monolithic ceramic capacitor element in which internal electrodes are formed by using a base metal material, wetting by adding hydrogen or water to an atmosphere containing nitrogen as a main component. There is a method of firing in a reducing atmosphere. In this method, the wet reducing atmosphere is controlled by detecting and managing the oxygen partial pressure in the atmosphere.

[0003]

However, the method of controlling only the oxygen partial pressure has the following problems.

When removing the residual carbon in the ceramic element after degreasing, in addition to the reaction such as C + O → CO (1) C + O ₂ → CO ₂ (2) CO + 1 / 2O ₂ → CO ₂ (3), A so-called water gas reaction such as C + H ₂ O → CO + H ₂ (4) C + 2H ₂ O → CO ₂ + 2H ₂ (5) occurs. But the formula
The water-gas reaction such as (4) and (5) is a direct reaction between residual carbon and water (water vapor). Therefore, depending on the method of detecting and controlling the oxygen partial pressure, It is impossible to detect and control such water-gas reaction, and to remove the residual carbon in the degreasing process,
The reality is that it is difficult to remove efficiently without adversely affecting the sintering of the ceramic element.

Further, an oxygen sensor of a type inserted in a firing furnace is usually 800 ° C. where residual carbon is mainly removed.
At the temperatures below, there is a problem that it is not easy to accurately detect the oxygen partial pressure because the reliability of the sensor output value is poor and the accuracy is low.

Further, when firing is performed in a conventional wet reducing atmosphere, there is a problem that the production rate is low because the rate of the water gas reaction is slow and the firing requires a long time.

The present invention solves the above-mentioned problems, and quickly reduces the residual carbon in the ceramic element after degreasing in the firing step without adversely affecting the sintering of the ceramic element. And a ceramic electronic component manufacturing method with high production efficiency.

[0008]

In order to achieve the above object, the inventor has conducted various experiments and studies, and while supplying water at a predetermined ratio, in addition to water for maintaining a wet reducing atmosphere. When it was found that the residual carbon in the ceramic element after degreasing rapidly decreased when firing was performed, the present invention was completed through further experiments and studies.

That is, the method for producing a ceramic electronic component of the present invention comprises a degreasing step of decomposing and removing an organic substance such as a binder contained in the ceramic element by heat-treating the ceramic element under predetermined conditions, and the degreasing step. After the completion, in a firing step of heat-treating and sintering the ceramic element in a wet reducing atmosphere, in addition to moisture for maintaining the wet reducing atmosphere, 1 mol of residual carbon in the ceramic element at the end of the degreasing step is added. On the other hand, firing is performed while supplying water at a rate of 3 mol or more per minute until reaching a predetermined temperature, and then firing with a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere. It is characterized by including a process.

Further, the moisture concentration in the atmosphere at the time of firing while supplying water at a rate of 3 mol or more per minute with respect to 1 mol of residual carbon in the ceramic element at the end of the degreasing step is from 10 to 10. It is characterized by being 25 vol%.

Further, after the degreasing process is completed, at least 800 ° C. is reached while supplying water at a rate of 3 mol or more per minute with respect to 1 mol of residual carbon in the ceramic element at the end of the degreasing process. It is characterized in that firing is performed, and thereafter, firing is performed with a predetermined temperature profile while supplying only moisture for maintaining a wet reducing atmosphere.

[0012]

In the firing step after completion of the degreasing step, in addition to the water content for maintaining the wet reducing atmosphere, at least 3 moles per minute of carbon remaining in the ceramic element at the end of the degreasing step is used. By supplying water in a ratio and performing firing until a predetermined temperature is reached, the above-mentioned formula is obtained without adversely affecting the sintering of the ceramic element.
Water gas reaction of (4) and (5) C + H ₂ O → CO + H ₂ (4) C + 2H ₂ O → CO ₂ + 2H ₂ (5) Promptly progress to efficiently reduce the carbon remaining in the ceramic element. In addition to the above, it is possible to reliably perform the sintering of the ceramic element by performing the firing in a predetermined temperature profile while supplying only the moisture for maintaining the wet reducing atmosphere, as a whole. Thus, the efficiency of firing can be improved.

Further, the moisture concentration in the atmosphere at the time of firing while supplying water at a rate of 3 mol or more per minute with respect to 1 mol of residual carbon in the ceramic element at the end of the degreasing step is 10 to 10. By setting it as 25 vol%, it becomes possible to efficiently reduce the carbon remaining in the ceramic element while maintaining a predetermined wet reducing atmosphere, and the present invention can be more effectively realized.

Furthermore, after the degreasing process is completed, the residual carbon content in the ceramic element at the end of the degreasing process is 1 mol, and
When baking is performed while supplying water at a rate of 3 mol or more per minute until it reaches at least 800 ° C, and then baking is performed with a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere. In the above formula
The water-gas reaction of (4) and (5) can be made to progress rapidly, and the carbon remaining in the ceramic element can be reduced more reliably and efficiently, and the moisture for maintaining the subsequent wet reducing atmosphere can be reduced. In the step of firing while supplying only the ceramic element, it becomes possible to surely perform the sintering of the ceramic element, and the present invention can be further effectively realized.

[0015]

EXAMPLES Examples of the present invention will be shown below to explain the features thereof in more detail. In this embodiment, a case of manufacturing a monolithic ceramic capacitor will be described as an example.

Stirring and mixing a dielectric material containing BaTiO ₃ as a main component (ceramic raw material powder), PVB (polyvinyl butyral) as a binder, a toluene / ethanol mixed solvent, and various additives with a ball mill. To prepare a slurry.

The thickness of this slurry after firing is 1
After being formed into a sheet having a thickness of 2 μm and dried, a nickel electrode (paste) was applied by pattern printing.

Then, 80 to 90 layers of this sheet are laminated, and dummy sheets not coated with nickel electrodes are laminated on the upper and lower sides thereof, and after pressure bonding and cutting, the dimension after firing is 2.6 mm. (Width) x 2.0 mm (length)
Individual ceramic elements (green chips) of × 1.25 mm (thickness) were obtained.

Then, the ceramic element is
Heat treatment was performed at 240 ° C. to decompose and remove (degrease) organic substances such as a binder in the ceramic element. The residual carbon in the ceramic element after this degreasing step was about 1.0% by weight.

100 g of this ceramic element (content of carbon = 1 g) was heated in a small batch furnace at a heating rate of 100 ° C. /
After raising the temperature to 800 ° C. at h, the temperature is raised from 800 ° C. to 1250 ° C. at a heating rate of 200 ° C./h, and then 125 ° C.
After holding at 0 ° C. for 2 hours to sinter the ceramic element, it was naturally cooled.

In this firing step, nitrogen gas, hydrogen gas and water vapor are supplied at a predetermined ratio to maintain a basic wet reducing atmosphere, and further 800
Up to ℃, apart from water (specifically 3.6 g / min) for maintaining a wet reducing atmosphere, 3 mol / min (specifically, 1 mol / mol residual carbon in the ceramic element) The temperature was raised while supplying water at a rate of 4.5 g / min. The water vapor concentration in the atmosphere at this time is about 10
It was vol%.

The maximum temperature of the firing process (1250 ° C.)
The oxygen partial pressure in the above was set to 10 ⁻¹² to 10 ⁻¹¹ MPa.

For comparison, all the firing steps (8
Firing was performed by supplying only water (specifically, 3.6 g / min) for maintaining the wet reducing atmosphere within the range up to reaching 00 ° C.

FIG. 1 (Example) shows the relationship between the firing temperature and the CO and CO ₂ concentrations in the atmosphere until the firing temperature reaches 800 ° C. when firing is performed under the conditions of the above-mentioned Examples and Comparative Examples. And it shows in FIG. 2 (comparative example).

From FIG. 2, in the case of the comparative example in which only the water for maintaining the wet reducing atmosphere was supplied for firing, 8
It can be seen that the concentration of CO and CO ₂ in the atmosphere was still high when the temperature reached 00 ° C., and the residual carbon was not sufficiently removed.

On the other hand, in addition to water for maintaining a wet reducing atmosphere, firing was performed while supplying water at a rate of 3 moles per minute with respect to 1 mole of residual carbon in the ceramic element. In the case of the example, as shown in FIG. 1, when the temperature reached 800 ° C., almost no CO or CO ₂ was found in the atmosphere (both CO and CO ₂ were 10 p
It can be seen that residual carbon is sufficiently removed.

Further, regarding a laminated ceramic capacitor obtained by forming a terminal electrode on a ceramic element after firing (multilayer ceramic capacitor element), there is a variation in capacitance, the presence or absence of capacitance reduction / non-formation, and insulation resistance ( Various characteristics such as logIR) and equivalent series resistance were measured. Table 1 shows the results.

[0028]

[Table 1]

As shown in Table 1, the monolithic ceramic capacitors according to the examples have good results that the variation in capacitance is small, the insulating properties are high, and the equivalent series resistance is small as compared with that of the comparative example. It was obtained, and neither the capacity decrease nor the capacity non-formation was observed.

As described above, by performing the firing under the conditions as shown in the above-mentioned embodiment, the capacity reduction and the capacity non-formation due to the breakage of the internal electrode does not occur, the equivalent series resistance is low, and the high insulation resistance is high. It becomes possible to obtain the object to be fired.

In the above embodiment, in addition to the water content for maintaining the wet reducing atmosphere, the water content is 3 mol / min for 1 mol of carbon residue in the ceramic element at the end of the degreasing process. While the case where the firing was performed until the temperature reached 800 ° C. while supplying the water, the ratio of the water supplied separately from the water for maintaining the wet reducing atmosphere is 1% of the residual carbon amount in the ceramic element at the end of the degreasing step. It is possible to change variously in the range of 3 mol or more per minute with respect to the mol. However, the water supply rate is usually preferably in the range of 3 to 15 mol per minute with respect to 1 mol of residual carbon in the ceramic element at the end of the degreasing step.

However, since the amount of water supplied separately from the water for maintaining the wet reducing atmosphere is also related to the water vapor concentration in the atmosphere, the water vapor concentration in the atmosphere is usually 10 to 25 vol%. It is desirable to keep the range. This is because when the water vapor concentration deviates from the above range, the progress rate of the water gas reaction becomes low in some cases,
This is because it has an adverse effect on the sintering of the ceramic element.

Further, in the above-mentioned embodiment, in addition to the water content for maintaining the wet reducing atmosphere, the water content is 3 mol / min for 1 mol of the residual carbon amount in the ceramic element at the end of the degreasing step. In the above description, the firing was carried out until the temperature reached 800 ° C. while supplying the water. In addition to the water for maintaining the wet reducing atmosphere, the water was fed at a predetermined ratio of the present invention to a temperature of around 1000 ° C. In some cases, it may be possible to further reliably remove residual carbon and perform good firing by firing while supplying only water for maintaining a wet reducing atmosphere.

In the above embodiment, the case of firing a ceramic element using BaTiO ₃ -based ceramic has been described as an example, but the case of firing a ceramic element using another type of ceramic (that is, other types of ceramics). When manufacturing ceramic electronic parts using different types of ceramics)
The present invention can also be applied to, and in that case, the same effect can be obtained.

In the above embodiments, the case of manufacturing a monolithic ceramic capacitor has been described as an example, but the present invention is not limited to the method of manufacturing a monolithic ceramic capacitor, and a ceramic filter, a ceramic multi-layer substrate or the like may be used. It can be applied when manufacturing various ceramic electronic components.

The present invention is not limited to the above-mentioned embodiments in other points as well, and relates to the specific structure of the ceramic element, the pattern of the internal electrodes, the temperature conditions of the degreasing step, the temperature profile of the firing step, and the like. Various applications and modifications can be made within the scope of the invention.

[0037]

As described above, according to the method for manufacturing a ceramic electronic component of the present invention, in the firing step after the degreasing step is completed, in addition to the moisture for maintaining the wet reducing atmosphere, the degreasing step is completed. While supplying water at a rate of 3 mol or more per minute with respect to 1 mol of residual carbon in the ceramic element, firing is performed until a predetermined temperature is reached, and then only water for maintaining a wet reducing atmosphere is supplied. Since firing is performed with a predetermined temperature profile, it is possible to efficiently reduce the carbon remaining in the ceramic element without adversely affecting the sintering of the ceramic element, and The element can be reliably sintered, and the firing efficiency can be significantly improved as a whole.

Further, the moisture concentration in the atmosphere during firing is 10 to 10 moles of residual carbon in the ceramic element at the end of the degreasing step while supplying moisture at a rate of 3 moles or more per minute. By setting it as 25 vol%, it becomes possible to efficiently reduce the carbon remaining in the ceramic element while maintaining a predetermined wet reducing atmosphere, and the present invention can be more effectively realized.

Further, after the degreasing process is completed, the residual carbon content in the ceramic element at the end of the degreasing process is 1 mol,
By firing at a temperature of at least 800 ° C. while supplying water at a rate of 3 mol or more per minute, and then firing at a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere, a ceramic is obtained. It is possible to reduce the carbon remaining in the element more reliably and efficiently, and to ensure the sintering of the ceramic element in the subsequent step of firing while supplying only the water for maintaining the wet reducing atmosphere. Therefore, the present invention can be further effectively realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a firing temperature and CO and CO ₂ concentrations in an atmosphere in a firing step of a method for manufacturing a ceramic electronic component according to an example of the present invention.

FIG. 2 is a diagram showing the relationship between the firing temperature and the CO and CO ₂ concentrations in the atmosphere in the firing process of the comparative example.

Claims (3)

[Claims] 1. A degreasing step of decomposing and removing an organic substance such as a binder contained in the ceramic element by heat-treating the ceramic element under predetermined conditions, and after the degreasing step is completed, the ceramic element is placed in a wet reducing atmosphere. In the firing step of heat-treating and sintering, in addition to the water content for maintaining the wet reducing atmosphere, 1 mol of carbon remains in the ceramic element at the end of the degreasing step.
A baking step of supplying water at a rate of 3 mol or more per minute and performing baking until a predetermined temperature is reached, and then performing baking at a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere. A method of manufacturing a ceramic electronic component, comprising: 2. The moisture concentration in the atmosphere when firing is performed while supplying moisture at a rate of 3 mol or more per minute with respect to 1 mol of residual carbon in the ceramic element at the end of the degreasing step. It is 25 vol%, The manufacturing method of the ceramic electronic component of Claim 1 characterized by the above-mentioned. 3. After the completion of the degreasing step, the amount of residual carbon in the ceramic element at the end of the degreasing step is 1 mol with respect to 1 mole.
It is characterized in that it is baked at a temperature of at least 800 ° C. while supplying water at a rate of 3 mol or more per minute, and then is baked at a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere. A method of manufacturing a ceramic electronic component according to claim 1.