JP3250400B2 - Manufacturing method of ceramic electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electronic component, and more particularly, to a method of heat-treating a ceramic element to wet a ceramic element after a degreasing step of decomposing and removing a binder and the like contained in the ceramic element. The present invention relates to a method for manufacturing a ceramic electronic component including a firing step of performing heat treatment and sintering in a reducing atmosphere.

[0002]

2. Description of the Related Art For example, as one method of firing a ceramic element such as a multilayer ceramic capacitor element in which internal electrodes are formed using a base metal material, a wet method in which hydrogen or water is added to an atmosphere mainly containing nitrogen is used. There is a method of performing 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 for managing only the oxygen partial pressure has the following problems.

[0004] When removing the residual carbon in the ceramic element after degreasing, besides the reaction of 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 expression
Since the water gas reaction such as (4) and (5) is a direct reaction between residual carbon and water (steam), depending on the method of detecting and controlling the oxygen partial pressure, the equations (4) and (5) Such a water gas reaction cannot be detected and controlled, and residual carbon in the degreasing process is
In reality, it is difficult to efficiently remove ceramic elements without adversely affecting sintering or the like.

[0005] Further, an oxygen sensor of a type inserted into a firing furnace usually has a temperature of 800 ° C. at which residual carbon is mainly removed.
At the following temperatures, 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 carried out in a conventional wet reducing atmosphere, there is a problem that the rate of the water gas reaction is low and the firing requires a long time, resulting in low production efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to quickly reduce the residual carbon in a degreased ceramic element without adversely affecting sintering of the ceramic element in a firing step. It is an object of the present invention to provide a method of manufacturing a ceramic electronic component which is possible and has high production efficiency.

[0008]

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

That is, in the method for manufacturing a ceramic electronic component of the present invention, a degreasing step of heat-treating a ceramic element under predetermined conditions to decompose and remove an organic substance such as a binder contained in the ceramic element; After the completion, a firing step of heat-treating and sintering the ceramic element in a humid reducing atmosphere. In addition to water for maintaining the humid reducing atmosphere, the residual carbon in the ceramic element at the end of the degreasing step is reduced to 1 mol. On the other hand, baking is performed until a predetermined temperature is reached while supplying water at a rate of 3 mol or more per minute, and then baking is performed with a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere. And a process.

In addition, when the baking is performed while supplying water at a rate of 3 moles or more per minute with respect to 1 mole of the residual carbon in the ceramic element at the end of the degreasing step, the atmosphere has a water concentration of 10 to 10 moles. It is characterized by being 25 vol%.

Further, after completion of the degreasing step, water is supplied at a rate of at least 3 moles per minute to 1 mole of the residual carbon in the ceramic element at the end of the degreasing step until the temperature reaches at least 800 ° C. The calcination is performed, and thereafter, the calcination is performed with a predetermined temperature profile while supplying only moisture for maintaining a wet reducing atmosphere.

[0012]

In the firing step after the completion of the degreasing step, apart from the moisture for maintaining the moist reducing atmosphere, 3 mols or more per minute per 1 mol of the residual carbon in the ceramic element at the end of the degreasing step. By performing sintering until a predetermined temperature is reached while supplying moisture at a ratio, the above-described formula can be obtained without adversely affecting the sintering of the ceramic element.
(4) The water gas reaction of (5) C + H ₂ O → CO + H ₂ (4) C + 2H ₂ O → CO ₂ + 2H ₂ (5) Promptly proceed to efficiently reduce the carbon remaining in the ceramic element. Then, by performing sintering at a predetermined temperature profile while supplying only moisture for maintaining a wet reducing atmosphere, the sintering of the ceramic element can be reliably performed, and as a whole, As a result, the efficiency of firing can be improved.

Further, when the baking is performed while supplying water at a rate of 3 moles or more per minute with respect to 1 mole of the residual carbon in the ceramic element at the end of the degreasing step, the moisture concentration in the atmosphere is 10 to 10 moles. By setting the volume to 25 vol%, it is possible to efficiently reduce the carbon remaining in the ceramic element while maintaining a predetermined wet reducing atmosphere, and the present invention can be made more effective.

Further, after the completion of the degreasing step, the amount of carbon remaining in the ceramic element at the end of the degreasing step is 1 mol, and
In the case where baking is performed at a temperature of at least 800 ° C. while supplying water at a rate of 3 mol or more per minute, and then baking is performed with a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere. Has the above formula
The water gas reaction of (4) and (5) proceeds promptly, and the carbon remaining in the ceramic element can be more reliably and efficiently reduced. In the step of baking while supplying only, it is possible to reliably perform sintering of the ceramic element, and the present invention can be further made effective.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, and features thereof will be described in more detail. In this embodiment, a case where a multilayer ceramic capacitor is manufactured will be described as an example.

A dielectric material (ceramic raw material powder) mainly composed of BaTiO ₃ , PVB (polyvinyl butyral) as a binder, a mixed solvent of toluene / ethanol, and various additives are stirred and mixed using a ball mill. To prepare a slurry.

The slurry after firing has a thickness of 1
After forming into a sheet having a thickness of 2 μm and drying, a nickel electrode (paste) was applied by pattern printing.

Then, while 80 to 90 layers of this sheet are laminated, a dummy sheet on which nickel electrodes are not applied is laminated on the upper and lower surfaces of the sheet, pressed, cut, and fired to have a dimension of 2.6 mm. (Width) x 2.0mm (length)
× 1.25 mm (thickness) of each ceramic element (green chip) was obtained.

Then, this ceramic element is placed in air,
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 the degreasing step was about 1.0% by weight.

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

In this firing step, a basic wet reducing atmosphere is maintained by supplying nitrogen gas, hydrogen gas and water vapor at a predetermined ratio.
Until the temperature reaches 0 ° C., apart from water (specifically, 3.6 g / min) for maintaining a moist reducing atmosphere, 3 moles per minute (specifically, 1 mole of residual carbon in the ceramic element) The temperature was raised while supplying water at a rate of 4.5 g / min. At this time, the concentration of water vapor in the atmosphere is about 10
vol%.

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

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

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 was performed under the conditions of the above-described example and comparative example. And FIG. 2 (comparative example).

FIG. 2 shows that in the case of the comparative example in which the sintering was performed by supplying only water for maintaining the moist reducing atmosphere, 8
When the temperature reaches 00 ° C., the CO and CO ₂ concentrations in the atmosphere are still high, indicating that the residual carbon has not been sufficiently removed.

On the other hand, sintering was carried out while supplying water at a rate of 3 moles per minute to 1 mole of residual carbon in the ceramic element, separately from water for maintaining the wet reducing atmosphere. In the case of the embodiment, as shown in FIG. 1, when the temperature reached 800 ° C., almost no CO and CO ₂ were recognized in the atmosphere (both CO and CO ₂ were 10 p).
pm or less), it can be seen that the residual carbon has been sufficiently removed.

Further, with respect to the multilayer ceramic capacitor obtained by forming the terminal electrodes on the fired ceramic element (multilayer ceramic capacitor element), the variation in capacitance, the presence or absence of capacitance reduction / capacity formation, the 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 multilayer ceramic capacitor according to the example has a good result that the variation in capacitance is small, the insulating property is high, and the equivalent series resistance is small as compared with the comparative example. In addition, no decrease in capacity or no capacity formation was observed.

As described above, by firing under the conditions shown in the above-described embodiment, a decrease in capacity and a lack of capacity due to cut-off of the internal electrode do not occur, and the equivalent series resistance is low and the high insulation resistance is low. It becomes possible to obtain the object to be fired.

In the above embodiment, apart from the water for maintaining the moist reducing atmosphere, the water was removed at a rate of 3 moles per minute with respect to 1 mole of the residual carbon in the ceramic element at the end of the degreasing step. The case where baking was performed until the temperature reached 800 ° C. while supplying water was described. However, the ratio of water supplied separately from the water for maintaining the moist reducing atmosphere was determined by determining the amount of residual carbon in the ceramic element at the end of the degreasing step by 1 It is possible to variously change the condition of 3 moles or more per minute with respect to the mole within the range. However, the supply ratio of water is usually preferably in the range of 3 mol 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 to be 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 within the range. This is because, if the water vapor concentration deviates from the above range, in some cases, the progress rate of the water gas reaction decreases,
This is because the sintering of the ceramic element is adversely affected.

Further, in the above embodiment, apart from the water for maintaining the moist reducing atmosphere, the water is retained at a rate of 3 moles per minute with respect to 1 mole of the residual carbon in the ceramic element at the end of the degreasing step. Although the case where the baking was performed until the temperature reached 800 ° C. while supplying the water was described, separately from the water for maintaining the moist reducing atmosphere, the baking was performed to around 1000 ° C. while supplying the water at a predetermined ratio according to the present invention. After that, by performing calcination while supplying only moisture for maintaining a wet reducing atmosphere, residual carbon may be removed more reliably, and good calcination may be performed in some cases.

Further, in the above embodiment, the case where the ceramic element using the BaTiO ₃ ceramic is fired has been described as an example. However, the case where the ceramic element using another type of ceramic is fired (that is, other types of ceramic elements) is fired. When manufacturing ceramic electronic components using various types of ceramics)
The present invention can be applied to any of them, and in that case, the same effect can be obtained.

Further, in the above embodiment, the case of manufacturing a multilayer ceramic capacitor has been described as an example. However, the present invention is not limited to the method of manufacturing a multilayer ceramic capacitor. It can be applied to the case of manufacturing various ceramic electronic components.

The present invention is not limited to the above embodiment in other respects, but 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, in the method for manufacturing a ceramic electronic component of the present invention, in the firing step after the completion of the degreasing step, apart from the moisture for maintaining the wet reducing atmosphere, After sintering until a predetermined temperature 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, while supplying only water for maintaining a wet reducing atmosphere, Since firing is performed at a predetermined temperature profile, it is possible to efficiently reduce carbon remaining in the ceramic element without adversely affecting the sintering of the ceramic element, The sintering of the element can be surely performed, and as a whole, the efficiency of firing can be greatly improved.

When the baking is performed while supplying water at a rate of 3 moles or more per minute with respect to 1 mole of the residual carbon in the ceramic element at the end of the degreasing step, the atmosphere has a water concentration of 10 to 10 moles. By setting the volume to 25 vol%, it is possible to efficiently reduce the carbon remaining in the ceramic element while maintaining a predetermined wet reducing atmosphere, and the present invention can be made more effective.

Further, 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,
By sintering at a temperature of at least 800 ° C. while supplying water at a rate of 3 mol or more per minute, and then sintering with a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere, ceramic The carbon remaining in the element can be reduced more reliably and efficiently, and the sintering of the ceramic element is ensured in the subsequent firing step while supplying only water for maintaining a wet reducing atmosphere. And the present invention can be made more effective.

[Brief description of the drawings]

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

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

Claims (3)

(57) [Claims] A degreasing step of heat-treating the ceramic element under predetermined conditions to decompose and remove an organic substance such as a binder contained in the ceramic element; and after the degreasing step, the ceramic element is placed in a moist reducing atmosphere. A sintering step of performing heat treatment and sintering, in addition to water for maintaining a moist reducing atmosphere, one mole of carbon remaining in the ceramic element at the end of the degreasing step;
Baking until a predetermined temperature is reached while supplying moisture at a rate of 3 moles or more per minute, and baking with a predetermined temperature profile while supplying only moisture for maintaining a wet reducing atmosphere. A method for manufacturing a ceramic electronic component, comprising: 2. The method according to claim 1, wherein the baking is performed while supplying water at a rate of 3 moles or more per minute with respect to 1 mole of the residual carbon in the ceramic element at the end of the degreasing step. 2. The method for producing a ceramic electronic component according to claim 1, wherein the content is 25 vol%. 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.
Baking is performed until water reaches at least 800 ° C. while supplying water at a rate of 3 mols or more per minute, and then baking is performed with a predetermined temperature profile while supplying only water for maintaining a wet reducing atmosphere. A method for manufacturing a ceramic electronic component according to claim 1.