JPH09246085A - Manufacture of multilayered ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To omit a preparing work of baking and prevent adhesion of impurities to the surface of a green chip, by covering the outermost layer surface of a laminated body constituted of ceramic dielectric layers and inner electrode layers with a sheet layer composed of zirconia powder, and cutting, separating and collectively baking the laminated body. SOLUTION: A sheet layer 4 of 7-30μm is formed by using zirconia fine powder stabilized with calcia and binder. A ceramic invalid layer 3 which is previously prepared is stacked on the zirconia layer 4. Necessary number of sheets of ceramic dielectric layers 1 on which inner electrode layers 2 are printed are stacked, and further the invalid layers 3 are stacked. The sheet layer 4 composed of zirconia power is stacked and pressed on the uppermost layer of a laminated body, and a laminated body wherein the upper and the lower layers are covered with the sheet layers 4 composed of zirconia powder is formed. After that, the laminated body is cut into segments having specified sizes and forms, separated and baked.

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 monolithic ceramic capacitor.

[0002]

2. Description of the Related Art In a conventional method of manufacturing a monolithic ceramic capacitor, a plurality of ceramic dielectric layers and internal electrode layers are alternately laminated and pressure-bonded to obtain a laminated body. After that, it is cut into a predetermined shape and separated to obtain a green chip. Next, after this green chip was soaked in zirconia powder, the zirconia powder was further packed in an alumina-based sheath laid on the bottom surface and baked.

[0003]

In the above conventional manufacturing method, it is necessary to prepare the zirconia powder to prevent the green chips from adhering to the zirconia powder in advance before the firing and the filling in the sheath. Impurities such as sheath components that react with the green chip during the sintering process are likely to adhere to the surface of the chip, causing defects in appearance and characteristics.

It is an object of the present invention to provide a method for manufacturing a monolithic ceramic capacitor which can omit the preparation work for firing and can prevent the adhesion of impurities to the surface of the green chip.

[0005]

To achieve this object, the present invention covers the outermost layer surface of a laminate of a ceramic dielectric layer and an internal electrode layer with a sheet layer made of zirconia powder,
The intended purpose is achieved by integrally firing after cutting and separating.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method according to claim 1 of the present invention is a laminated body in which a plurality of ceramic dielectric layers and internal electrode layers are alternately laminated, and at least one outermost layer surface of the laminated body is formed. The sheet is covered with a sheet layer made of zirconia powder, and the laminated body is cut and integrally fired. This eliminates the need for preparatory work for adapting the green chip to the zirconia powder, and prevents impurities such as sheath components from adhering to the surface of the green chip.

According to the second aspect of the present invention, the thickness of the sheet layer made of zirconia powder covering the outermost layer surface is set to 7
˜30 μm. This is the lower limit of the thickness necessary to prevent the firing adhesion between green chips and the reaction with impurities, and the upper limit that does not affect the external dimensions and shape of the chip element when removing the outermost zirconia layer after firing. It has been set.

According to the above means, since the laminate is covered with zirconia, which has a low reactivity with impurities, the reaction with impurities in the sintering process can be prevented, and the appearance and characteristics will not be deteriorated. Further, since the chips are not attached to each other and the firing sheath is not attached at the time of firing, the firing sheath filling preparation work is unnecessary.

Embodiments of the present invention will be described below. (Embodiment 1) FIG. 1 is a perspective view of a green chip of the present embodiment, FIG. 2 is a perspective view of a laminated body, and FIG. 3 is a perspective view of a laminated ceramic capacitor. 1 and 2, 1 is a ceramic dielectric layer, 2 is an internal electrode layer, 3 is an ineffective layer, and 4 is a sheet layer made of zirconia powder.
In FIG. 3, reference numeral 5 denotes an external electrode.

First, calcia-stabilized zirconia fine powder was mixed with polyvinyl butyral as a binder.
A 5 μm sheet layer 4 is created. Next, on the zirconia layer 4, a ceramic ineffective layer 3 containing barium titanate as a main component, which has been prepared in advance, is laminated. Next, the required number of ceramic dielectric layers 1 containing barium titanate as a main component, to which the internal electrode layers 2 are applied, are laminated, and then the ineffective layer 3 is further laminated. The sheet layer 4 made of the zirconia powder is laminated and pressed on the uppermost layer of the laminated body to form a laminated body in which upper and lower layers are covered with the sheet layer 4 made of zirconia powder. After that, a green chip that is cut into a predetermined shape and separated is obtained.

The green chips were packed in the following three types of alumina-based sheaths and baked at a temperature of 1300 ° C. (1) Sprinkle zirconia powder on the bottom surface, (2) coat the surface with zirconia, (3) unprocessed.

After firing, each chip element is polished with a barrel polishing machine to remove the upper and lower sheet layers 4 and to polish the end surfaces to expose the internal electrodes 3. The external electrode 5 is applied and baked on the end face, and the external electrode 5
The monolithic ceramic capacitor was completed by performing a plating process on the top. The appearance (pinhole) inspection results of the finished product thus obtained and the finished product obtained by the conventional method are shown in (Table 1).
Table 2 shows the electrical characteristics (short) selection results.

[0013]

[Table 1]

[0014]

[Table 2]

As is clear from (Table 1), the product of the present invention has a remarkably low occurrence rate of appearance defects as compared with the conventional product, and further, a good effect can be obtained regardless of the firing sheath filling condition. In addition, from Table 2 as well, the product of the present invention had a lower occurrence rate of defective electrical characteristics than the conventional product, and in particular, there was no occurrence of a short circuit defect which is considered to be caused by a defective appearance.

(Embodiment 2) Next, in Embodiment 2, only the thickness of the sheet 4 made of zirconia powder used on the upper and lower surfaces of the laminate is changed, and the other conditions are exactly the same as those of Embodiment 1. Created.

The thickness of the zirconia layer 4 was as follows. (1) 3 μm, (2) 7 μm, (3) 25 μm,
(4) 30 μm, (5) 35 μm.

Tables 1 and 2 show the inspection results of the appearance and electrical characteristics of the monolithic ceramic capacitors produced under the above conditions.

As is clear from (Table 1) and (Table 2), those using the sheet layer 4 having a thickness in the range of 7 to 30 μm have the same appearance and electrical characteristics as those of the first embodiment. It can be seen that is very low and good results are obtained. However, in the case of the sheet layer 4 having a thickness of 3 μm, the zirconia sheet is too thin to be peeled from the carrier film for molding,
The good sheet layer 4 was not obtained and the lamination was stopped. On the other hand, when the sheet layer 4 having a thickness of 35 μm is used, when the sintered portion of the sheet layer 4 is removed using a barrel polishing machine or the like, since the thickness of the sheet layer 4 is large, the polishing time becomes long and the sintered portion is removed. If completely removed, the inner part of the sintered body is also greatly polished, and the internal electrodes are exposed from the side surface of the sintered body, which may adversely affect the electrical characteristics.
Since the external dimensions became defective, the evaluation was stopped at that point.

In this embodiment, zirconia stabilized with calcia was used, but yttria stabilized material may be used. Furthermore, the sheet layer 4 for covering the laminate does not have to have the same thickness in the upper and lower layers, and may have a thickness such that it can be peeled from the zirconia sheet carrier film, and may be any combination as long as it does not exceed 30 μm.

[0021]

As described above, according to the method for manufacturing a monolithic ceramic capacitor according to the present invention, since the green chip is fired in a state of being covered with a sheet layer made of zirconia powder having low reactivity with impurities, the impurities are removed. Even if it adheres,
It is possible to obtain a monolithic ceramic capacitor of excellent quality without causing defects in appearance and electrical characteristics, and it is possible to omit the preparatory work for accommodating zirconia powder for the purpose of preventing adhesion of chip elements to each other during firing.

[Brief description of drawings]

FIG. 1 is a perspective view of a green chip according to an embodiment of the present invention.

FIG. 2 is a perspective view of a laminate according to an embodiment of the present invention.

FIG. 3 is a perspective view of a multilayer ceramic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic dielectric layer 2 Internal electrode layer 3 Invalid layer 4 Sheet layer 5 External electrode

Claims (2)

[Claims] 1. A laminate in which a plurality of ceramic dielectric layers and internal electrode layers are alternately laminated, at least one outermost layer surface is covered with a sheet layer made of zirconia powder, and then the laminate having the sheet layer is cut. And a method for manufacturing a monolithic ceramic capacitor, which is characterized by integrally firing. 2. The method for producing a monolithic ceramic capacitor according to claim 1, wherein the thickness of the sheet layer made of zirconia powder is 7 to 30 μm.