JP2964689B2 - 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 used for various electronic devices.

[0002]

2. Description of the Related Art In recent years, demand for multilayer ceramic capacitors has been increasing with the miniaturization and higher frequency of electronic devices.

FIG. 2 shows a process of manufacturing a conventional general multilayer ceramic capacitor. Hereinafter, a general manufacturing method will be described with reference to FIG. First, a green sheet is prepared by a doctor blade method or the like using a slurry composed of a dielectric powder such as barium titanate, an organic binder, a plasticizer and an organic solvent. Next, an internal electrode is formed on this sheet by a screen printing method or the like using a conductive paste mainly containing a noble metal such as palladium.

Next, the green sheets on which the internal electrodes are formed are arranged so that the internal electrodes are alternately opposed to each other with the dielectric layer interposed therebetween, and are sequentially laminated, and the lamination is repeated up to a desired number. The molded body thus obtained is cut into a chip having a desired size, and the organic binder component is degreased.
Bake at 400 ° C. Next, a conductive paste such as silver, silver-palladium or the like is applied so that the internal electrodes appearing at both ends of the thus obtained sintered body are electrically connected, and the external electrodes are formed by baking. Manufactures multilayer ceramic capacitors.

[0005]

However, in the above-described structure, as the number of stacked compacts increases, the compacts are first cracked by the internal pressure of carbon dioxide or the like generated by the decomposition of organic components in the degreasing step. Or, in the subsequent firing step, due to thermal stress generated due to the difference in thermal expansion coefficient between the ceramic dielectric layer and the internal electrode, structural defects such as delamination occur inside the sintered element, etc. This has been a major issue in the production of multilayer ceramic capacitors, for example, the non-defective product ratio has deteriorated and the cost has increased.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a method for manufacturing a multilayer ceramic capacitor capable of almost completely suppressing the occurrence of structural defects such as cracks and delaminations.

[0007]

In order to achieve the above object, a method of manufacturing a multilayer ceramic capacitor according to the present invention comprises:
Ceramic dielectric layer based on barium titanate
Heat treatment in vacuum of compacts with alternately laminated electrodes
A first step, and then a second step of degreasing the molded body,
Next, a third step of holding the molded body in a humidity atmosphere
And a fourth step of firing the formed body to obtain a sintered body
And then at the exposed ends of the internal electrodes of this sintered body
A fifth step of forming an external electrode.

[0008]

According to this method, in the first step, the boiling point of the volatile substances such as the residual solvent and the plasticizer contained in the molded body is reduced by heat-treating the molded body in a vacuum in the first step .
Therefore, it can be easily removed from the molded body. Ma
This time was, for gas volatilized escapes from the interior to the exterior moldings, fine voids are formed throughout the molded body. Then, in the next second step, the combustion gas of the organic binder component is easily discharged out of the compact through the holes.
Become a Rukoto, it is carried out degreasing without generation of internal stress
And suppresses the occurrence of structural defects in the compact in the second step
can do.

[0009] Barium titanate, which is the main component of the dielectric layer, contains unreacted barium particles . The surface layer of these particles easily reacts with water vapor in the air to form barium hydroxide. Therefore, the compact in such a state is the second
In step, the molded body as shown in the following chemical formula (1)
And the barium hydroxide surface reacts with ester contained in the organic binder, fine particles of barium oxide to produce
Become.

Ba (OH) 2 + RCOOR ′ → BaO + RCOOH + R′OH (1) The fine particles of barium oxide thus generated form a dielectric layer.
Order to bind together the raw material particles to form, in the fourth step
In this case, the deformation resistance of the molded body against a thermal reaction caused by the oxidative expansion of the internal electrode is increased, which causes a structural defect . For this purpose, in the third step, the compact is maintained in a constant humidity atmosphere, so that the barium oxide fine particles generated in the second step are reacted with water vapor as shown in the following chemical formula (2) to again react with the water vapor. By returning to barium hydroxide, bonding between the raw material particles can be reduced .
Therefore, in the fourth step, the deformation resistance of the compact is reduced.
This makes it possible to almost completely suppress the occurrence of structural defects during the firing process.

BaO + H ₂ O → Ba (OH) ₂
(2) As described above, the present invention exerts the effect of suppressing the occurrence of structural defects in vacuum in the next degreasing step and in the humid atmosphere in the next firing step.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a manufacturing process of a multilayer ceramic capacitor according to an embodiment of the present invention.
First, 100 parts by weight of barium titanate powder, 30 parts by weight of polyvinyl butyral resin, 150 parts by weight of butyl acetate,
Dioctyl phthalate (4 parts by weight)
The mixture was kneaded for 0 hour to prepare a dielectric layer slurry, and a dielectric layer was formed on the base film by a reverse roll method using the slurry to produce a green sheet.

Next, the green sheet produced above is peeled off from the base film, and is sequentially laminated on a pallet prepared in advance by using a pressure press, so that the lowermost support layer which does not contribute to the electric capacity has a desired thickness. Formed. Thereafter, using a commercially available internal electrode paste containing 100% palladium as a conductor, a step of forming internal electrodes in a pattern so as to alternately reach different ends on a green sheet by a screen printing method; The steps of laminating the peeled green sheets were sequentially repeated, and after laminating 70 layers, a support layer having the same thickness as the lowermost layer was formed on the uppermost layer to produce a laminated molded body. . Further, the molded body thus obtained was cut into chips having desired dimensions.

Next, using the molded article obtained above,
First, a test was performed to confirm the effect of holding in a vacuum. That is, the above-mentioned molded body was placed in a commercially available vacuum drying furnace at a vacuum degree of 0.1 Torr, 0.5 Torr, 1.0 Torr,
1.5 Torr, holding temperature 100 ° C, 150 ° C, 200
By changing the temperature and the holding time to 30 minutes (0.5 hours), 1 hour, and 3 hours, respectively, a total of 36 kinds of samples were manufactured for each condition. The sample thus held under various conditions in a vacuum was held in an electric furnace in the air at 350 ° C. for 5 hours for degreasing the organic binder, and then baked at 1300 ° C. for 2 hours. The appearance and the inside were observed, and the incidence of structural defects such as delamination was examined. In addition, the above-mentioned molded body which was not held in vacuum was fired at the same time, and used as a standard sample for comparison. The above firing results are collectively shown in the following (Table 1) as the non-defective rate for 1000 samples.

[0015]

[Table 1]

As is clear from Table 1, when the compact was not held in vacuum, many structural defects were generated, whereas in the sample held in vacuum according to the present invention, Vacuum degree 1.0 Torr or less, holding temperature 150
It can be seen that an excellent effect on the occurrence of structural defects of the sintered body can be obtained under the conditions of not less than ° C and the holding time not less than 1 hour. However, since a good product rate of 100% has not yet been obtained in (Table 1), it can be seen that the problem was not completely solved only by holding in a vacuum according to the present invention.

Then, a test was conducted in which the above molded article held in vacuum was held in a constant humidity atmosphere. First, a vacuum degree of 1.0 Torr and a holding temperature of 150
The organic binder was degreased by using a molded body that had been treated at a temperature of 1 ° C. and a holding time of 1 hour, and was kept at 350 ° C. for 5 hours in an electric furnace in the air. Using a commercially available environmental tester, the degreased molded body thus obtained was adjusted to a relative humidity of 30%.
%, 40%, 50%, and 60%, and the holding temperature is 25 ° C. and 55%.
C., 75.degree. C., 95.degree. C., 105.degree. C., and the holding time was changed to 30 minutes (0.5 hours), 1 hour, and 3 hours, respectively. Each was produced. The sample thus held under various conditions in a humidity atmosphere was fired in an electric furnace at 1300 ° C. for 2 hours, and the appearance and the inside of the obtained device were observed, and the occurrence rate of structural defects such as delamination was observed. Examined. The above firing results are collectively shown in the following (Table 2) as the non-defective rate for 1000 samples. Note that, as standard data for comparison when not held in a humidity atmosphere, data under the conditions of the vacuum degree of 1.0 Torr, the holding temperature of 150 ° C., and the holding time of 1 hour in (Table 1) were transcribed.

[0018]

[Table 2]

As is clear from Table 2, in the sample held in a vacuum according to the present invention, the molded body was degreased and then kept in a constant humidity atmosphere, that is, a relative humidity of 40% or more.
It can be seen that by performing the treatment at a holding temperature of 25 ° C. to 95 ° C. for a holding time of 1 hour or more, an extremely excellent effect on the occurrence of structural defects in the sintered body can be obtained. That is, by maintaining the sample held in vacuum in a constant humidity atmosphere after degreasing, a 100% non-defective rate is obtained for the first time as shown in (Table 2). It is possible to suppress it almost completely.

In the above embodiment, the case where palladium is used as the internal electrode has been described. However, the present invention can be applied to a case where palladium as a main component such as palladium-silver is used. It is.

[0021]

As described above , according to the present invention, the occurrence of structural defects in a sintered body can be almost completely suppressed, and the occurrence of defective products can be almost eliminated. It brings epoch-making effects such as a significant cost reduction in the production of

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process of a multilayer ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a view showing a manufacturing process of a conventional multilayer ceramic capacitor.

Continuing on the front page (72) Tatsuro Kikuchi, Inventor 1006 Kadoma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Masakazu Tanahashi 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yasutaka Horibe 1006 Kadoma Kadoma, Kadoma City, Osaka Pref. Person 1006 Kadoma Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-59-208816 (JP, A) JP-A-2-154409 (JP, A) JP-A 62-282427 ( JP, A) JP-A-59-92512 (JP, A) Patent 2876811 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01G 4/12

Claims (3)

(57) [Claims] 1. A ceramic containing barium titanate as a main component.
A molded body obtained by alternately stacking dielectric layers and internal electrodes
A first step of heat treatment in a vacuum, and then degreasing the compact
And then placing the molded body in a humidity atmosphere
A third step of holding, and then firing and sintering the compact
A fourth step of obtaining a body, and then of said internal electrodes of said sintered body
A fifth step of forming external electrodes on the exposed both ends.
Method of manufacturing a multilayer ceramic capacitors. 2. The first step is to maintain the degree of vacuum at 1 Torr or less.
The method for manufacturing a multilayer ceramic capacitor according to claim 1, wherein the holding temperature is 150 ° C or more and the holding time is 1 hour or more . 3. The third step is to maintain a relative humidity of 40% or more.
The method is carried out at a temperature of 25 to 95 ° C and a holding time of 1 hour or more.
Alternatively, the method for manufacturing a multilayer ceramic capacitor according to claim 2 .