JP2000077211A - Producing method of laminated ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a producing method of a laminated ceramic electronic component with has few defects and is superior in lifetime characteristics. SOLUTION: Ceramic materials are formed in to a sheet, and inner electrode materials are printed on the sheet. By laminating and sintering a plural of sheets, a ceramic element assembly 12 and inner electrodes 14 are formed. Outer electrodes 16, 18 are formed so that they can be connected at right angles to inner electrodes 14 in the planes which are arranged facing each other in the ceramic element assembly 12. As a result, this laminated ceramic electronic component 10 is manufactured. Before sintering the assembly, carbon is added at least to either of the ceramic material or the inner electrode material.

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 electronic component, and more particularly to a method for manufacturing a multilayer ceramic electronic component such as a multilayer varistor.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of equipment and the speeding up of circuits, chipping and high frequency of elements have been progressing, and many small multilayer ceramic chip parts have been used. Furthermore, many components that have been large in the past are often stacked for miniaturization and chip formation. Also,
In recent years, product liability and manufacturer liability have been strengthened in accordance with the Product Liability Act, and there has been a demand for better characteristics in terms of product safety, especially life characteristics.

[0003] Such a multilayer ceramic electronic component is
It has a structure as shown in FIG. The multilayer ceramic electronic component 10 includes a ceramic body 12. A plurality of internal electrodes 14 are formed in the ceramic body 12. Adjacent ones of the internal electrodes 14 are ceramic body 1
2 are drawn out on opposite sides. The external electrode 1 is provided on the side of the ceramic body 12 from which the internal electrode 14 is drawn.
6, 18 are formed. Therefore, the adjacent internal electrodes 14 are connected to the external electrodes 16 and 18, respectively.

[0004] Such a multilayer ceramic electronic component 10
As shown in FIG. 2, the ceramic raw material is formed into a film by, for example, sheet molding or the like, and a green sheet 20 is formed. On the green sheet 20, an internal electrode material 22 is printed. At this time, the internal electrode material 22 is printed so as to be drawn to one end of the green sheet 20. A plurality of such green sheets 20 are laminated, and green sheets 20 on which no internal electrode material is printed are laminated above and below. By firing the thus obtained laminate, the green sheet 20 becomes the ceramic body 12 and the internal electrode material 22 becomes the internal electrode 14. Furthermore, the internal electrode 1
The external electrodes 1 are provided on the side surfaces of the ceramic body 12 where
By forming 6 and 18, the multilayer ceramic electronic component 10 is formed. Note that a material to be an external electrode may be applied to the laminate before firing, and the external electrode may be formed at the same time as firing the laminate.

[0005] Such a multilayer ceramic electronic component 10
Then, the ceramic body 12 functions as a characteristic portion. For example, in the case of a multilayer varistor, when a voltage higher than a predetermined voltage is applied between the external electrodes 16 and 18, the ceramic body 1
2, the resistance value decreases sharply, and a current flows. Such a laminated varistor is used, for example, in a circuit including an IC, and is used to protect the IC from being applied with an excessive voltage.

[0006]

However, when a multilayer ceramic electronic component is manufactured, static electricity is generated and charged in the sheet due to friction between a raw material formed in a film shape and processing equipment. The sheet charged in this way attracts and adheres to the surrounding dust and metal powder and the like, resulting in the incorporation of foreign matter, leading to generation of voids and deterioration of characteristics. The voids cause diffusion of the internal electrodes and the like, which may lead to deterioration of the life characteristics.

In the case of a laminated varistor, in addition to the problems of such foreign matter and voids, there is a problem that the release of a binder or the like added to the sheet and the diffusion of oxygen to the grain boundaries must be improved. If the release of the binder and the like and the diffusion of oxygen to the grain boundaries are not performed effectively, the varistor voltage and large non-linearity cannot be obtained, and the life characteristics will be deteriorated and the surge resistance will be reduced.

[0008] Therefore, a main object of the present invention is to provide a method of manufacturing a multilayer ceramic electronic component capable of obtaining a multilayer ceramic electronic component having few defects and having excellent life characteristics.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a laminated ceramic electronic component, which comprises a step of laminating a ceramic material and an internal electrode material by sheet molding or printing and then firing. A method for manufacturing a multilayer ceramic electronic component, characterized by adding carbon to at least one of a ceramic material and an internal electrode material. In this method for manufacturing a multilayer ceramic electronic component, the amount of carbon added is preferably 0.1 to 5% by weight based on the ceramic material.
The amount of carbon added was 0.1% with respect to the internal electrode material.
It is preferably from 10 to 10% by weight. As this multilayer ceramic electronic component, for example, a multilayer varistor can be manufactured. In this case, Zn is used as the ceramic material.
A varistor material containing O as a main component can be used.

[0010] Since carbon has conductivity, the sheet formed from the raw material has conductivity, and even if there is friction with processing equipment or the like, static electricity is not easily generated. Therefore, it is possible to prevent dust or metal powder from adhering to the sheet, and to suppress generation of defects such as voids. This effect also has the effect of improving the life characteristics. Further, since the green sheet is not charged, the handling becomes very easy, which can contribute to an improvement in the yield rate in manufacturing. In addition, the carbon is burned by firing the laminated body and becomes CO ₂ or CO, and does not remain in the fired element. Even if carbon remains in the element, the amount is as small as about 10 to 30 ppm and does not affect the characteristics.

Further, since carbon is released as a gas at the time of firing, fine pores are formed in portions where carbon was present. The pore formed in this way is
It promotes the release of the combustion gas of the binder and the moisture contained in the sheet and the introduction of the external atmosphere into the element.
Therefore, an unnecessary atmosphere in the element is released to the outside, and an external necessary atmosphere is introduced into the inside, thereby promoting uniform sintering of the particles. Addition of carbon to the internal electrode material does not have much effect of preventing the generation of static electricity, but can provide an effect of promoting the exchange of atmosphere through the internal electrode.

In today's multilayer ceramic electronic components, it is common to make the element film thickness thin and multilayer, but in this case, the sheet density is increased, and as a result, the effect of atmosphere exchange is lost. Have been done. In particular, in a multilayer varistor containing ZnO as a main component, oxygen is required at the grain boundaries for sintering and the development of characteristics. Deterioration of life characteristics easily occurs. However, by adding carbon to the ceramic material and the internal electrode material, the exchange of atmosphere is promoted, and a multilayer varistor having good characteristics can be obtained.

If the amount of carbon exceeds 5% by weight with respect to the ceramic material, the combustion of carbon may be incomplete during firing, or the residual pores in which carbon has been burned may not be sufficiently eliminated by sintering. If the amount of carbon is less than 0.1% by weight based on the ceramic material, charging is likely to occur as in the case where carbon is not added. for that reason,
The amount of carbon added is 0.1% with respect to the ceramic material.
It is preferably in the range of ５5% by weight. For the same reason, the amount of carbon added is
It is preferably in the range of 0.5 to 10% by weight.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, a method of manufacturing a multilayer varistor will be described as an example of a multilayer ceramic electronic component having a structure as shown in FIG. First, Al, Bi, Co, Mn, Sb, Y, Si, B
And the like are mixed and crushed. Then, after dehydration and drying, granulation is performed, and the obtained powder is calcined. The calcined material is roughly pulverized, and mixed and pulverized again with a ball mill or the like to form a slurry. The slurry is dewatered and dried to produce a powder, and a binder, a dispersant and carbon are added to the powder to form a sheet. The sheet is punched into a predetermined size to form a green sheet. As shown in FIG. 2, an internal electrode material obtained by adding carbon to a green sheet is printed, and a plurality of green sheets are laminated in a predetermined order and direction to obtain a laminate. The thus obtained laminate is heated in a furnace to decompose and release a resin component such as a binder, and then fired, and the electrodes are baked on the exposed portions of the internal electrodes, as shown in FIG. A laminated varistor of the structure is formed.

In such a laminated type varistor, the sheet is made conductive by adding carbon to the varistor material and the internal electrode material, and is hardly charged by friction with processing equipment. Therefore, the surrounding dust and metal powder are hardly adsorbed, and the generation of voids and deterioration of characteristics can be prevented. In addition, during firing, carbon becomes CO ₂ or C
O is released as a gas such as O, and fine pores are formed in the portion where carbon was present. By such pores, unnecessary gases such as combustion gas such as a binder and moisture are released, and an external necessary atmosphere is introduced. In particular, in the case of a multilayer varistor, oxygen is required at the grain boundaries for sintering and the development of characteristics, but oxygen contained in the external atmosphere can be introduced because fine pores are formed. And good characteristics can be obtained.

[0017]

[Embodiment] For ZnO100, Al is Al_TwoO_ThreeConvert to
100 ppm, Bi is Bi _TwoO_ThreeConverted to 1.
0 mol%, Co is Co_TwoO_Three0.5 mol converted to
%, Mn is 0.5 mol% in terms of MnO, Sb is S
bO_3/20.5 mol% when converted to Y_TwoO_ThreeConvert to
1.0 mol%, Si is SiO_TwoConverted to 0.
2 mol%, B is B_TwoO_ThreeConverted to 0.2 mol%
And mix and crush with a ball mill for 60 hours.
Was. After that, dewater, dry and granulate with a 60 # sieve.
Powder was obtained. This powder is calcined at 750 ° C. for 2 hours.
After coarsely pulverizing the calcined product, re-use it with a ball mill.
A slurry was obtained by mixing and pulverizing. This slurry is dewatered,
Drying gave a powder.

A solvent, a binder, a dispersant and carbon were added to the powder in an amount of 0 to 10% by weight to form a 50 μm thick sheet. This sheet was punched into a predetermined size to obtain a green sheet. An internal electrode material was printed on a part of the green sheet by a screen printing method in a shape as shown in FIG. As an internal electrode material, Ag / Pd (0% by weight, 5% by weight, 10% by weight, and 20% by weight) (A
g: Pd = 9: 1) A paste was used. Further, these green sheets and sheets on which the internal electrode material was printed were laminated in a predetermined order and direction to obtain a laminate. After the resin thus obtained was decomposed and released at 600 ° C., the laminate thus obtained was fired at 850 to 900 ° C. for 3 hours to obtain a sintered body. An Ag electrode material was applied to the exposed portion of the internal electrode of the sintered body, and baked at 800 ° C. to form an external electrode to obtain a sample.

The prepared samples were evaluated by the following procedures and methods. A current of 1 mA and 10 mA is applied to both ends of the sample, and the output voltages V1 mA and V10 mA at both ends are measured to obtain a varistor voltage (V1 mA) and a nonlinear coefficient α.
Was measured. For α, α = 1 / log (V10m
A / V1 mA). Next, the surge withstand capability was measured. The surge withstand capability was such that a current wave of 8 × 20 μsec was applied twice at one minute intervals, left for 5 minutes, and then the varistor voltage was measured to check the change in the varistor voltage. In the surge withstand capability measurement, the crest value of the current wave was increased stepwise from 100 A to 50 A, and the current at which the varistor voltage changed by 5% or more was examined. The life was evaluated at a temperature of 85 ° C. and a humidity of 8
A DC load of 90% of the varistor voltage was applied in a 5% constant temperature bath. After 500 hours, the varistor voltage was taken out of the constant temperature bath and the change in the varistor voltage was examined. Further, the cross section of the sample is polished,
The occurrence of voids of μm or more was investigated. Table 1 shows the results of these measurements. In Table 1, sample number 1
Sample No. 7 and Sample No. 3 and Sample No. 13 were evaluated twice with the same specifications to see reproducibility.

[0020]

[Table 1]

As can be seen from Table 1, by adding carbon to the ceramic sheet, the life characteristics and the surge resistance can be improved. Further, there is an effect of improving the nonlinear coefficient α. Although the data could not be displayed, the handling of the sheet to which carbon was added was very easy. The addition of carbon to the electrode material has less effect as described above than the addition of carbon to the ceramic material, but has an effect on the life characteristics.

However, if too much carbon is added, the number of voids is increased, and the life characteristics and the surge resistance are reduced. This is because the increase in the amount of carbon resulted in incomplete combustion of carbon and the residual pores in which carbon was burned could not be sufficiently eliminated by sintering. Therefore, in the surge withstand capability, the flow of current was suppressed, and in the life evaluation, the permeation of humidity occurred to deteriorate the life characteristics. For these reasons, the amount of carbon added to the ceramic sheet is preferably set to 5% by weight or less. Further, the addition amount of carbon to the internal electrode material is preferably 10% by weight or less for the same reason as the addition to the ceramic sheet.

Although the lower limit of the amount of carbon added to the ceramic sheet is not specifically shown in the data, it is 0.1% by weight.
If it is less than the above, charging tends to occur as in the case of no additive, and handling becomes difficult. Therefore, the addition amount of carbon is preferably 0.1% by weight or more. The particle size of carbon is considered to be related to the particle size of the ceramic material and the sintered particles, and the most effective particle size of carbon should be selected depending on the material. In this embodiment, the sheet method is used, but a printing method or another method may be basically used. Further, it is apparent that the method for manufacturing a multilayer ceramic electronic component of the present invention can be applied not only to a multilayer varistor but also to a case of manufacturing another multilayer ceramic electronic component such as a multilayer capacitor.

[0024]

According to the method for manufacturing a multilayer ceramic electronic component of the present invention, by adding carbon to a ceramic material or an internal electrode material, conductivity can be imparted, charging can be prevented, and dust and dust can be prevented. Adhesion of metal powder and the like can be prevented. Therefore, the generation of voids can be suppressed, and the characteristics of the multilayer ceramic electronic component can be improved. Also, by burning carbon during firing,
Fine pores are formed in the part where carbon was present,
Unnecessary gas and the like are released through the pores, and an external necessary atmosphere is introduced. As a result, the sintered state of the ceramic becomes good, and a multilayer ceramic electronic component having excellent characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one example of a multilayer ceramic electronic component to which a manufacturing method of the present invention is applied;

FIG. 2 is a plan view showing a green sheet on which an internal electrode material is printed to produce the multilayer ceramic electronic component shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 laminated ceramic electronic component 12 ceramic body 14 internal electrode 16 external electrode 18 external electrode 20 green sheet 22 internal electrode material

 ──────────────────────────────────────────────────の Continued on front page (72) Inventor Kazuhiro Kaneko 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Inside Murata Manufacturing Co., Ltd. (72) Inventor Kenjiro Hatano 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto No. F-term in Murata Manufacturing Co., Ltd. (reference) 5E034 CA07 CA08 CB01 CC02 CC17 DA02 DC01

Claims (4)

[Claims] 1. A method for manufacturing a laminated ceramic electronic component, comprising a step of laminating a ceramic material and an internal electrode material by sheet molding or printing and then firing the ceramic material, wherein the ceramic material and the internal electrode material are pre-fired. Wherein carbon is added to at least one of the above. 2. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein the amount of the carbon added is 0.1 to 5% by weight based on the ceramic material. 3. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein the amount of the carbon added is 0.1 to 10% by weight based on the internal electrode material. 4. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein the ceramic material is a varistor material containing ZnO as a main component.