JP3240048B2 - Manufacturing method of multilayer ceramic capacitor - 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 for manufacturing a multilayer ceramic capacitor. More specifically, the present invention relates to a method for manufacturing a multilayer ceramic capacitor in which post-heat treatment is performed under specific conditions after heating and firing.

[0002]

2. Description of the Related Art A conventional method for manufacturing a multilayer ceramic capacitor is as follows. First, a slurry composed of a dielectric powder, a binder, a plasticizer and an organic solvent is used to form a layer having a thickness of several tens μm on an organic film by a doctor blade method. A ceramic dielectric green sheet is formed. Next, an internal electrode is printed on the ceramic dielectric green sheet, and a plurality of sheets obtained by removing the organic film are stacked, and then a laminated molded body is manufactured by pressure bonding. Further, the laminated molded body is cut into chips, degreased, and after sintering, external electrodes are formed. Conventionally, Pd or a noble metal containing Pd as a main component has been used as an internal electrode. However, in order to meet the demand for cost reduction from the market, the internal electrode is replaced with relatively inexpensive Ni or a metal containing Ni as a main component. Ni internal electrode laminated ceramic capacitors have been developed.

By the way, this Ni internal electrode laminated ceramic
In the manufacture of ceramic capacitors, especially firing and external electrode firing
The heat treatment represented by the composition prevents oxidation of the Ni internal electrode.
Atmosphere with a low oxygen partial pressure that does not oxidize Ni
You have to do it in an atmosphere. But on the other hand the ceramic
Relatively high, such as firing of dielectrics and firing of external electrodes
Performing heat treatment at low temperature under low oxygen partial pressure induces ceramics
The conductor layer is reduced, resulting in poor life characteristics of the finished product.
Cause transformation. Therefore, make the dielectric material resistant to reduction.
(See, for example, Japanese Patent Application Laid-Open No. 55-37).
568, JP-A-61-256968,
No. 60-109104). But dielectric material
Only by increasing the resistance to reduction by optimizing the composition of the material
There is naturally a limit, so the fired device must be
Heat treatment under high temperature and partial pressure of oxygen for higher reliability
Attempts have been made. For example, JP-A-5-283
No. 278 and JP-A-6-45182 disclose “9
00 ° C to 1100 ° C, 10 ^-Four-10^-7atm oxygen partial pressure
Heat treatment under the pressure is proposed to adjust the oxygen partial pressure.
Is, for example, a wetter with water temperature adjusted to about 0 to 75 ° C.
N humidified using_TwoGas "is used. reliability
This heat treatment, which is performed for the purpose of enhancing
Heat treatment ". The firing of the external electrode is also described above.
For the same reason as_Two/ H_TwoFiring in an O-based atmosphere
Examples have been reported.

[0004]

However, considering the industrial realization of the re-oxidation heat treatment using the humidified N ₂ gas, which is performed for the purpose of improving the reliability, the complexity of handling steam and the accompanying complexity are considered. There is a problem in that securing the reliability of the product becomes unstable due to an increase in the price of the production apparatus, an increase in the production cost, and a narrow adjustment range of the amount of water vapor.

The present invention has been made in view of the above circumstances, and in particular, in a reoxidation heat treatment performed to improve the reliability, the reoxidation heat treatment which is industrially highly productive while ensuring the reliability of the final product. It is an object of the present invention to provide a method for manufacturing a multilayer ceramic capacitor which realizes the above.

[0006]

To SUMMARY OF THE INVENTION To achieve the above object, a manufacturing method of a multilayer ceramic capacitor of the present invention comprises a laminate of the internal electrodes and the ceramic made of a metal mainly composed of N i or Ni a method of manufacturing a multilayer ceramic capacitor, the laminate, after firing, by oxygen and heat-treated in an atmosphere supplied by the decomposition of the carbonic acid gas containing carbon dioxide, by the firing
The reduced ceramic is reoxidized. With such a configuration, reoxidation heat treatment with high industrial productivity can be realized while ensuring the reliability of the final product.

In the manufacturing method of the present invention, the laminate is preferably heat-treated at a temperature of 600 ° C. to 1100 ° C., and more preferably at a temperature of 700 ° C. to 1000 ° C. This is because reoxidation is performed efficiently and sufficiently.

[0008] The atmosphere may contain carbon dioxide gas enough to supply an amount of oxygen necessary for re-oxidation. Specifically, as described above, the atmosphere contains 3% by volume or more. Preferably contains 10% by volume or more of carbon dioxide gas. This is for further improving the reliability of the final product.
Preferably, the atmosphere is a mixed gas of carbon dioxide gas and non-oxidizing gas. As the non-oxidizing gas, a gas that does not contain oxygen atoms and cannot supply oxygen even when thermally decomposed can be used. Specifically, an inert gas such as argon or a nitrogen gas can be suitably used. Nitrogen gas is particularly preferred as the non-oxidizing gas.

It is preferable that the laminate is heat-treated in the atmosphere in a temperature decreasing step after firing.
This is because productivity is further improved by performing re-oxidation heat treatment using heating during firing.

Further, the laminate is fired, and a paste containing a metal as a main component is applied to the laminate as an external electrode,
Thereafter, it is preferable to perform a heat treatment in the atmosphere and sinter the paste. This is because the productivity is further improved by simultaneously firing and reoxidizing the external electrode.

[0011] Further, in the temperature decreasing process after firing the laminate, heat treatment is performed in the atmosphere, a paste containing a metal as a main component is applied to the laminate as an external electrode, and then heat treatment is performed again in the atmosphere. Preferably, the paste is fired together. This is because the reliability of the final product can be further improved by performing the reoxidation heat treatment not only at the time of firing the laminated body but also at the time of firing the external electrodes.

As described above, according to the present invention, it is possible to reduce the cost of the manufacturing apparatus itself and the manufacturing running cost due to the complexity of using steam industrially, as compared with the case where steam is used. At the same time, the carbon dioxide concentration can be increased up to 100% by volume without being restricted by the reasons of the apparatus, so that even when a large amount of heat treatment is performed, high reliability can be stably secured.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have studied in detail the problems in carrying out a reoxidation heat treatment using steam (by humidification) on an industrial scale, and have obtained the following conclusions. The problem is that the industrial use of steam for high-temperature heat treatment is complicated compared to using other industrial gases generally called dry gas, and the absolute amount of steam that can be adjusted accordingly. Is small, and the adjustment range of the amount of water vapor is extremely narrow. For example, in the above-mentioned patent publication, the temperature adjustment of the wetter is set to 0-7.
This indicates that the temperature is set to 5 ° C., in other words, the dew point of the atmosphere gas used for the heat treatment is set to 0 to 75 ° C.

[0014] The dew point means that dew condensation easily occurs when the temperature of the atmosphere gas is lower than the dew point temperature. Therefore, in the apparatus for performing the heat treatment, at least all the parts through which the atmosphere gas flows are adjusted. This means that the temperature needs to be maintained above the desired dew point. In other words, in order to prevent this dew condensation, it is necessary to constantly heat all parts such as pipes through which the humidified atmosphere gas flows, by using a heater or the like in order to maintain the temperature above the dew point of the atmosphere gas. Due to this, members used in the apparatus are required to have higher heat resistance than general. Further, in order to prevent the humidified atmospheric gas from escaping into a relatively low temperature portion in the apparatus, and to prevent dew condensation there, a higher airtightness than a general industrial heat treatment furnace is required. These greatly increase the price of the manufacturing apparatus itself and also require more power than necessary from the viewpoint of running cost, resulting in an increase in manufacturing cost.

Another problem is that the amount of absolute water vapor that can be adjusted is extremely small. The re-oxidation heat treatment using water vapor in the prior art utilizes the oxygen dissociated from the water on the left side in the chemical formula (Formula 1) shown below, in other words, using the water vapor as an oxygen supply source to re-oxidize the dielectric. Is to try.

[0016]

Embedded image

However, when humidification is performed using a wetter or the like whose water temperature is adjusted to about 0 to 75 ° C. as shown in the above prior art, the humidified atmosphere is theoretically considered due to the vapor pressure of water. The amount of water vapor in the gas is 0.6-38
Calculated as% by volume. In addition, since it is industrially difficult to handle an atmosphere gas having a high dew point as described above, humidification up to a dew point of 50 ° C., which is commonly found in a humidification function in a heat treatment furnace of about 1000 ° C. which is commercially available, was considered. In some cases, the adjustment range of the amount of water vapor in the atmospheric gas is restricted to a narrower range of 0.6 to 12.2% by volume. When an attempt is made to perform re-oxidation heat treatment using such an atmosphere gas having a small absolute amount of water vapor, especially in a large amount in an industrial sense, in other words, as many elements as possible are loaded in a heat treatment apparatus and re-oxidation heat treatment is performed at once. In the case of trying, the effect of the case where steam was not sufficiently spread in the apparatus due to the low concentration of steam in the atmospheric gas, or the case where steam was consumed for re-oxidation because the absolute amount itself was small, was large, and was expected at first. There is a problem that the re-oxidation heat treatment cannot be achieved and the reliability of the product cannot be sufficiently secured.

Therefore, in the method for manufacturing a multilayer ceramic capacitor according to the present invention, the reoxidation heat treatment for ensuring the reliability of the product is performed in an atmosphere containing at least 3% by volume or more of carbon dioxide gas in a temperature range of 600 ° C. to 1100 ° C. Went under.

According to the present invention, the re-oxidation heat treatment is performed by utilizing oxygen dissociated from carbon dioxide gas, in other words, using carbon dioxide gas as an oxygen supply source, as shown in the following chemical formula (2). It performs oxidation.

[0020]

Embedded image

In the reoxidation heat treatment according to the present invention, since the carbon dioxide gas, which is a gas at normal temperature and normal pressure, is used, when the steam is used, the handling is complicated. There is no special increase in the price of the product or the production cost. Further, since there is no problem such as dew condensation, the amount of carbon dioxide as an oxygen supply source can be freely changed between 0 and 100% by volume while taking into account the amount of heat treatment performed once and the reliability of the finished product. Furthermore, the re-oxidation heat treatment according to the present invention can be performed simultaneously and continuously with the firing step and the external electrode firing step, so that the production running cost does not increase.

As the dielectric powder as a raw material of the ceramic used in the present invention, various dielectric powders used in the production of ceramic electronic parts are used. For example, barium titanate, titanium oxide, barium oxide, Oxides such as zirconium, carbonates such as barium carbonate and calcium carbonate, nitrides such as silicon nitride, silicon nitride and aluminum nitride, carbides such as silicon carbide and titanium carbide, and mixtures thereof, and further improved properties thereof Such as a mixture to which a compound such as manganese or calcium is added to have resistance to reduction, and, also, are not limited to, various types of dielectric powders conventionally used when manufacturing ceramic electronic components, and the like. It is appropriately selected and used depending on the type and use of the intended ceramic electronic component. A glass frit may be added to these dielectric powders.

The organic binder used for molding these is not particularly limited,
For example, butyral resin, acrylic resin, styrene resin, etc., as a plasticizer, for example, dibutyl phthalate, benzyl butyl phthalate, polyethylene glycol, etc., as a dispersant, for example, a higher fatty acid such as oleic acid, and as a solvent, for example, toluene, Butyl acetate,
Various resins, plasticizers, dispersants, and solvents conventionally used in the process of manufacturing such ceramic electronic components, such as trichloroethane, can be used as appropriate. The amount of the organic binder used is not particularly limited because it varies depending on the type and use of the intended ceramic electronic component, the type of the raw material dielectric powder to be used, and the like.
For example, it is about 2 to 20% by weight based on the whole weight.

Usually, the aforementioned dielectric powder, organic binder,
Using a plasticizer that can be used as necessary, and an organic solvent that can dissolve the organic binder, mix to form a slurry, for example, forming a ceramic dielectric thin layer on an organic film by a doctor blade method as described above to form a green layer. Make a sheet. This is dried, an internal electrode is printed on the ceramic dielectric sheet, and a plurality of sheets obtained by removing the organic film are stacked, and then a laminated molded body is manufactured by pressure bonding. Furthermore, this laminated molded body is cut into chips,
Obtain a ceramic molded body.

The molding method described above is a method often used in the production of multilayer ceramic capacitors. However, the method is not limited to this method at all, and depends on the type and use of the intended ceramic electronic component. Various molding methods conventionally applied can be adopted. As the internal electrode, a method of printing and forming in a predetermined shape by a printing method is most often used, but is not limited thereto. For forming electrodes by printing, usually Ni
Alternatively, the most general method is printing by a screen printing method using a paste containing Ni as a main component. It is to be noted that a metal containing Ni as a main component is used as an internal electrode if Ni1 is used as long as conductivity as an intended electrode is obtained.
It means that other inorganic substances and the like may be appropriately blended instead of 00% by weight.

The degreasing to remove the organic binder by heat decomposition is as follows:
The type and amount of the binder used, the type of the dielectric powder, the type and size of the target ceramic electronic component, the size, the processing amount, the size of the heating device, and the like are not particularly limited. In a mixed gas atmosphere of gas or nitrogen gas and hydrogen gas, heat treatment can be performed at a maximum temperature of 300 to 800 ° C. for 1 to several tens of hours, and at a temperature increase rate of 5 to 400 ° C./hour until reaching the maximum temperature. preferable. In particular, it is more preferable to perform the heat treatment under a nitrogen gas atmosphere at a maximum temperature of 400 to 700 ° C. for 2 to 10 hours, and at a temperature increase rate of 10 to 100 ° C./hour until reaching the maximum temperature.

The sintering also varies depending on the conditions as described above, and is not particularly limited.
1 hour to several tens of hours at 400 ° C, 50 to the maximum temperature
It is preferable to perform the heat treatment at a heating rate of 400 ° C./hour. In particular, in an atmosphere having an oxygen partial pressure of 1 × 10 ⁻⁷ atm or less, heat treatment can be performed at a maximum temperature of 1200 to 1400 ° C. for 1 to 5 hours, and at a heating rate of 100 to 300 ° C./hour until reaching the maximum temperature. More preferred.

The subsequent reoxidation heat treatment for the purpose of ensuring reliability in the present invention is performed in a temperature range of 600 ° C. to 1100 ° C. in an atmosphere containing at least 3% by volume or more of carbon dioxide as an oxygen supply source. Is preferred. At a low temperature, the reoxidation reaction is slow. On the other hand, at an excessively high temperature, the Ni metal used as the internal electrode is oxidized excessively, and there is a risk that the capacity is reduced. In the temperature range of not less than 1000 ° C., it is more preferable to perform heat treatment using such a specific atmosphere gas.

The specific atmospheric gas used in the present invention only needs to contain a sufficient amount of carbon dioxide gas for reoxidation, and a portion other than the carbon dioxide gas is a non-oxidizing gas such as an inert gas which does not contribute to a chemical reaction. Any non-oxidizing gas may be used.
General and inexpensive nitrogen gas is suitable. Although not particularly limited, the content of carbon dioxide gas is preferably from 10 to 90% by volume, and more preferably from 15 to 90% by volume.

The sintered body obtained as described above is subjected to a polishing treatment such as barrel polishing or sand blasting to expose the internal electrodes, and a metal paste containing, for example, a metal such as Cu as a main component is applied. An external electrode is formed by performing a heat treatment in accordance with the above, and the external electrode is further subjected to Ni plating or solder plating to obtain a final product. Although not particularly limited, it is preferable to use a thick-film technique that is generally used for manufacturing many electronic components for forming the external electrodes.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to the drawings. First, a method for manufacturing a laminated body after sintering used as a common sample in Examples and Comparative Examples will be described. Barium titanate (BaT) is used as a dielectric material.
A composition in which 0.5 wt% of manganese dioxide (MnO ₂ ) was added as an additive to 99.5 wt% of iO ₃ ) was used. Here, BaTiO ₃ was synthesized by wet mixing barium carbonate (BaCO ₃ ) and titanium dioxide (TiO ₂ ) as reagents in a ball mill, followed by drying and calcining at 1200 ° C. for 2 hours in air. Further, the calcined BaTiO ₃ was wet-pulverized by a ball mill, and adjusted so that the average particle diameter thereof by observation with a scanning electron microscope (SEM) was 0.8 μm.
On the other hand, MnO ₂ was prepared by wet-pulverizing MnO ₂ as a reagent in a ball mill in the same manner to adjust the average particle diameter by SEM observation to 1 μm.

The thus prepared BaTiO ₃ and M
130 parts by weight of nO ₂ mixed to have the above composition, 23 parts by weight of polyvinyl butyral resin as an organic binder, and 5 parts of dibutyl phthalate as a plasticizer.
Parts by weight, 154 parts by weight of butyl acetate as a solvent are mixed,
A dielectric slurry was prepared. This dielectric slurry was dried on a polyethylene terephthalate (PET) film by a doctor blade method to a sheet thickness of 40 μm.
It was molded so that

Next, a commercially available Ni paste (manufactured by Sumitomo Metal Mining Co., Ltd.) was formed on the dried dielectric sheet by a screen printing method in a desired pattern so that the film thickness after drying was 4 μm. . Further, the dielectric sheet on which the Ni paste was formed by printing was peeled off from the PET film, and 21 sheets were laminated and pressed (that is, 20 effective layers) so that the internal electrode patterns faced each other, and integrated. This is 2mm ×
An unsintered laminate was obtained by cutting into 4 mm chips.

The unsintered laminate was sequentially heat-treated according to the heat treatment process flowchart shown in FIG.

First, as a degreasing step, FIG.
The heat treatment was performed under the following conditions in accordance with the temperature-time schedule diagram of the degreasing step shown in FIG. (Degreasing conditions) Heating rate: 50 ° C./hour Maximum temperature: 400 ° C. Maximum temperature holding time: 4 hours Cooling temperature: 100 ° C./hour Atmospheric gas: Nitrogen gas Next, the firing step is shown in FIG. 1 (C). The heat treatment was performed under the following conditions according to the temperature-time schedule diagram of the firing step. (Firing) Heating temperature: 200 ° C / hour Maximum temperature: 1300 ° C Maximum temperature holding time: 2 hours Cooling temperature: 200 ° C / hour Atmospheric oxygen partial pressure: 1 × 10 ^-11 to 1 × 10 ^-9 atm The laminated body obtained after sintering was heat-treated under the following conditions as a re-oxidation heat treatment.

That is, a container made of zirconia having a volume of 300 cc was prepared, and after firing, the laminated body was made 10,000
Each piece was loaded, and heat treatment was performed for 2 hours under the reoxidation heat treatment conditions shown in (Table 1) using an atmosphere heat treatment furnace having an inner volume of about 5 liters. During the heat treatment, the total amount of the atmospheric gas supplied to the furnace was adjusted to 2 liters per minute under the standard condition.

Finally, a polishing treatment by barrel polishing is performed on each of the 100 elements in the sample subjected to the re-oxidation heat treatment under each of the working conditions to expose the internal electrodes.
u paste (Namics) was applied to the end face. A sample coated with a Cu paste on the end face is heated at 800 ° C. in a nitrogen atmosphere.
After heat treatment for 1 hour, the external electrode portion was subjected to Ni plating and solder plating to obtain a multilayer ceramic capacitor as a final product. For multilayer ceramic capacitors obtained by different re-oxidation heat treatment conditions,
A reliability test was performed by applying a voltage of 32 V in a thermostat at 85 ° C. for 1000 hours. After this reliability test, the probability that the element was short-circuited was calculated. The results are shown in Table 1.

In Comparative Example 1, which was carried out for comparison, the same laminated body after sintering was placed in a container made of zirconia having a volume of 300 cc in the same manner as in the example according to the present invention.
In this comparative example 1, only the atmosphere gas condition was changed to nitrogen gas only, and 2 liters per minute were supplied at a standard condition, and 900 ° C. was used. For 2 hours.
Further, each of the 100 devices was subjected to barrel polishing to expose the internal electrodes, and external electrodes were formed using the same materials and conditions as in the above example.

In Comparative Examples 2 and 3 performed for comparison with the conventional method, the laminated body after sintering and 300 cc
It is the same as using an atmosphere heat treatment furnace with an internal volume of about 5 liters in a container made of zirconia having a volume of about 5 liters, but the dew point is 30 ° C. by using a wetter only in the atmosphere gas condition. Nitrogen gas humidified as described above and nitrogen gas humidified so as to have a dew point of 50 ° C., and supplied at a standard rate of 2 liters per minute,
Heat treatment was performed at 900 ° C. for 2 hours. After that, the same processing and evaluation as in the example and comparative example 1 were performed.

[0040]

[Table 1]

Here, in the experiment of Comparative Example 1, heat treatment was performed in an atmosphere gas containing neither water vapor nor carbon dioxide.
All of the samples were short-circuited after the reliability test. Comparative Examples 2 and 3 are experimental examples of reoxidation heat treatment using humidified nitrogen gas, which is a conventional technique, and the water vapor concentration was calculated from the water vapor pressure at each dew point.
According to the results of Examples 1 to 24 according to the present invention (Table 1), the short-circuit defect rate after the reliability test was reduced as compared with Comparative Example 1 in which heat treatment was performed only with nitrogen gas containing no carbon dioxide gas. You can see that it is. In particular, in each of Examples 7 to 24 in which the concentration of carbon dioxide was set to 3% by volume or more, the short-circuit failure rate was remarkably reduced, and a re-oxidation heat treatment was performed using a humidified nitrogen gas, which is a conventional technique. It can be seen that the effect is high even when compared with the results of Comparative Example 2 and Comparative Example 3. In Comparative Examples 2 and 3, the relatively high short-circuit failure rate after the reliability test is considered to be due to the difficulty and instability of humidification of the atmosphere gas using the wetter.

Further, in the examples using the same carbon dioxide concentration (Examples 7 to 12 in which the carbon dioxide concentration was 3% by volume, Examples 13 to 18 in which the carbon dioxide concentration was 15% by volume, and 50% by volume in the carbon dioxide concentration) In comparison with Examples 19 to 24), it was found that the effect when the heat treatment temperature was 700 to 1000 ° C. was particularly high. Furthermore, in Examples 14 to 17 and Examples 20 to 23 in which the short-circuit failure rate became 0%, since carbon dioxide gas was used as the atmospheric gas, there was no problem such as dew condensation. It can be said that it is a result of easily and stably realizing that the carbon dioxide gas concentration of (i) is relatively high (15% by volume and 50% by volume).

The atmosphere heat treatment furnace used in the embodiment is industrially very common, but in the embodiment of the present invention, carbon dioxide gas was used as an oxygen supply source for re-oxidation, so that the condensation heat treatment was carried out. There is no danger. Therefore, it goes without saying that there is no increase in the price of the manufacturing apparatus itself and no improvement in the manufacturing running cost due to the prevention of dew condensation.

As another embodiment, as shown in the flow chart of the heat treatment step shown in FIG. 2A and the temperature-time schedule diagram of the firing + reoxidation step shown in FIG. The calcination step and the reoxidation step are performed by holding and firing, and performing a heat treatment in an atmosphere containing (preferably 3% by volume or more) carbon dioxide in a temperature range of 600 ° C. to 1100 ° C. during the subsequent temperature cooling process. Can be performed collectively and continuously, and the manufacturing running cost can be further reduced. In the method in which the firing step and the re-oxidation step are performed simultaneously and continuously, the re-oxidation heat treatment is performed at 600 ° C.
It is clear that the same effect as in the above-described embodiment can be expected by performing the heat treatment in a temperature range of 0 ° C. or lower in an atmosphere containing carbon dioxide gas. Further, the temperature of the heat treatment is more preferably set to 700 ° C. or more and 1000 ° C. or less, and the atmosphere gas for the heat treatment is preferably a mixed gas of carbon dioxide gas and nitrogen gas.

Also, as shown in the flow chart of the heat treatment step shown in FIG. 3A and the temperature-time schedule of the re-oxidation + external electrode baking step shown in FIG. It is possible to further reduce the manufacturing running cost by performing the steps and collectively and continuously. That is, specifically, as an example, Examples 1 to
At 24, the Cu paste applied as the external electrode was heat-treated in a nitrogen atmosphere. By performing the heat treatment in an atmosphere containing carbon dioxide gas, the reoxidation step and the external electrode baking step can be performed collectively and continuously. In the method in which the re-oxidation step and the external electrode baking step are performed simultaneously and continuously, the re-oxidation heat treatment includes a carbon dioxide gas in a temperature range of 600 ° C. or more and 1100 ° C. or less, as in the above-described embodiment. It is apparent that the same effect as in the above-described embodiment can be expected by performing the heat treatment in the atmosphere. Further, the temperature of the heat treatment is more preferably set to 700 ° C. or more and 1000 ° C. or less, and the atmosphere gas for the heat treatment is preferably a mixed gas of carbon dioxide gas and nitrogen gas. Further, by performing the external electrode firing step in a mixed gas of carbon dioxide gas and nitrogen gas, reduction of the reoxidized ceramic dielectric can be suppressed.

Further, as shown in the flow chart of the heat treatment step shown in FIG. 4, the firing step and the re-oxidation step are performed collectively and continuously, and then the re-oxidation step and the external electrode firing step are collectively and continuously performed. Needless to say, a method of performing the above may be adopted. This is effective in ensuring the reliability of the final product after such multiple re-oxidation heat treatments.

In these embodiments, nitrogen gas is used as the atmospheric gas other than carbon dioxide gas. However, an inert gas such as argon gas or helium, which is apparently not affecting the redox of the internal electrode metal and dielectric. Gas may be used.

The main component of the metal paste used as the external electrode is not limited to Cu, and a metal paste mainly containing another metal may be used as long as it is generally used for manufacturing a Ni internal electrode multilayer ceramic capacitor. I do not care.

It should be noted that the temperature shown in FIG.
In the time schedule diagram, the temperatures at the start of heating and at the end of cooling are illustrated near 0 ° C. for convenience, but as is clear from the gist of the present invention, these temperatures are not particularly limited. Obviously, for example, the temperature may be about room temperature.

[0050]

As described above, according to the present invention,
A method of manufacturing a multilayer ceramic capacitor comprising a laminate of the internal electrodes and the ceramic made of a metal mainly composed of Ni or Ni, a pre-Symbol laminate after firing, a heat treatment in an atmosphere containing carbon dioxide the oxygen supplied by the decomposition of the carbon dioxide Te, instead by the firing
By re-oxidizing the prepared ceramics, it is possible to realize re-oxidation treatment with high industrial productivity while ensuring the reliability of the final product.

[Brief description of the drawings]

FIG. 1A is a flowchart of a processing step for explaining an example of a processing step of the present invention, FIG. 1B is a view showing an example of a temperature-time schedule of a degreasing step, and FIG. It is a figure which shows the example of a time schedule diagram.

FIG. 2 (A) is a flowchart of a processing step for explaining another example of the processing step of the present invention, and FIG. 2 (B) is a view showing an example of a temperature-time schedule of a firing + reoxidation step.

FIG. 3 (A) is a process flowchart for explaining another example of the process of the present invention, and FIG. 3 (B) is a diagram showing an example of a temperature-time schedule of a reoxidation + external electrode firing process.

FIG. 4 is a heat treatment process flowchart for explaining another example of the treatment process of the present invention.

Continuation of the front page (56) References JP-A-5-335177 (JP, A) JP-A-4-212405 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 4 / 00-4/42

Claims (10)

(57) [Claims] 1. A method for manufacturing a multilayer ceramic capacitor including a laminate of ceramics and an internal electrode made of Ni or a metal containing Ni as a main component, wherein said laminate is fired and then an atmosphere containing carbon dioxide gas is fired. Heat treatment under the oxygen supplied by the decomposition of the carbon dioxide gas ,
A method for manufacturing a multilayer ceramic capacitor, comprising reoxidizing the ceramic reduced by the firing . 2. The method according to claim 1, wherein the laminate is at a temperature of 1200.degree.
2. The laminated ceramics according to claim 1, wherein the ceramics is fired at a temperature of not more than ℃.
Method of manufacturing capacitor. 3. The method according to claim 1, wherein the laminate is at a temperature of 600 ° C. or more and 1100 ° C.
The method for producing a multilayer ceramic capacitor according to claim 1, wherein the heat treatment is performed below. 4. The method according to claim 1, wherein the laminated body is at least 700 ° C.
The method for manufacturing a multilayer ceramic capacitor according to claim 3, wherein the heat treatment is performed below. 5. The method for manufacturing a multilayer ceramic capacitor according to claim 1, wherein said atmosphere contains 3 % by volume or more of carbon dioxide gas. 6. The method for manufacturing a multilayer ceramic capacitor according to claim 1, wherein the atmosphere is a mixed gas of a carbon dioxide gas and a non-oxidizing gas. 7. The method according to claim 6, wherein the non-oxidizing gas includes a nitrogen gas. 8. The method for manufacturing a multilayer ceramic according to claim 1, wherein the multilayer body is heat-treated in the atmosphere in a temperature decreasing step after firing. 9. The laminate according to claim 1, wherein the laminate is baked, a paste containing a metal as a main component is applied to the laminate as an external electrode, and then heat treatment is performed in the atmosphere and the paste is baked. A method for manufacturing the multilayer ceramic capacitor according to any one of the above. 10. A heat treatment under the atmosphere in a temperature decreasing process after firing the laminate, applying a paste containing a metal as a main component to the laminate as an external electrode, and then performing a heat treatment again under the atmosphere. The method for manufacturing a multilayer ceramic capacitor according to claim 1, wherein the paste is fired together with the paste.