JPH10199752A - Multilayer ceramic electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a distortion in thermal contraction ratio owing to a difference of thermal expansion coefficient between ceramics and an external electrode and prevent a generation of cracks by a method wherein the external electrodes are formed only at both end surfaces to which an internal electrode of a lamination is exposed. SOLUTION: Internal electrodes 6 are alternately provided so as to expose to an end surface of a ceramic layer 5. A lamination 7 is constituted by this plurality of ceramic layers 5 and internal electrodes 6. External electrodes 8 are provided only on both end surfaces to which the internal electrodes 6 of this lamination 7 are alternately exposed, whereby a distortion due to a difference of thermal contraction ratio is removed in a manufacturing process. Thereby, multilayer ceramic electronic parts which can be sufficiently endured if a heat cycle is applied thereto are manufactured without generating cracks in a ceramic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic electronic component such as a multilayer ceramic capacitor and a multilayer varistor used in various electronic devices.

[0002]

2. Description of the Related Art Generally, in the field of electronic parts, there is a strong demand for lighter, thinner, smaller, and higher performance, and as a countermeasure, generally, those having a laminated structure are often used.

A multilayer ceramic electronic component represented by a conventional multilayer ceramic capacitor has been configured as shown in FIGS. That is, the internal electrodes 2 are provided so as to be alternately exposed between the plurality of ceramic layers 1 on the opposite end faces. The external electrode 3 is formed.

With such a configuration, the manufacturing method is such that a plurality of internal electrodes 2 are formed by printing an electrode paste on a ceramic raw sheet alternately so as to reach opposite edges, and at least the uppermost layer is formed. A ceramic green sheet having no electrodes formed thereon is pressed and molded into a predetermined size to form an electronic component body. External electrodes 3 are applied to both ends of the electronic component body, and then fired. To form a multilayer ceramic electronic component.

[0005]

In the conventional structure and manufacturing method described above, when cooling from the maximum temperature during firing, the difference in the contraction rate due to the difference in the thermal expansion coefficient between the external electrode 3 and the ceramic layer 1 is increased. And cracks 4 occur in the ceramic layer 1 as shown in FIG. 7, resulting in a variation in electrical characteristics. This crack 4 occurs because the external electrodes 3 are formed on the four surfaces adjacent to both end surfaces of the electronic component body, and the strain due to the difference in shrinkage described above is concentrated on the end of the external electrode 3. , On the line connecting the ends of the external electrodes 3.

That is, when the external electrodes 3 are formed not only on the end faces but also on the four faces adjacent to the end faces, the stress due to the difference in thermal contraction acts three-dimensionally and is formed on the four faces adjacent to the end faces. The end of the external electrode 3 is the external electrode 3 on the end face.
It is considered that the stress is concentrated on the end portions of the four surfaces of the external electrode 3 and the cracks 4 occur in the ceramic layer 1.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer ceramic electronic component which eliminates the above-mentioned drawbacks of the prior art and does not generate cracks during manufacturing.

[0008]

In order to solve the above-mentioned problems, a laminated ceramic electronic component according to the present invention has a structure in which internal electrodes of a laminated body having internal electrodes alternately exposed on an end face between ceramic layers are provided. The external electrodes are formed only on the both end faces that are exposed.

With the above configuration, it is possible to prevent cracks from being generated in the ceramic layer due to distortion due to thermal contraction caused by a difference in thermal expansion coefficient between the ceramic and the external electrode.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to the first aspect of the present invention is directed to a laminated body having internal electrodes alternately exposed on the end faces between ceramic layers. An electrode is formed, and it is possible to prevent the occurrence of cracks due to a difference in the heat shrinkage rate during the manufacturing process.

According to a second aspect of the present invention, the reinforcing electrode is provided so as to cover the external electrode and to extend over the other four surfaces adjacent to the end face of the laminate, and to peel off the external electrode from the laminate. Can be prevented.

Hereinafter, a specific example of an embodiment of the multilayer ceramic electronic component of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway perspective view of a multilayer ceramic electronic component as an example of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG.
FIG. 4 is an exploded perspective view showing the same manufacturing process, FIG. 4 is a process diagram showing the same manufacturing method, and FIG. 5 is a sectional view of a main part showing another example.

First, in FIGS. 1 and 2, 5 is a ceramic layer, 6 is an internal electrode provided so as to be alternately exposed on the end face of the ceramic layer 5, and 7 is a plurality of ceramic layers 5 and the internal electrode. The laminated body constituted by 6 and 8 are external electrodes provided only on both end faces of the laminated body 7 which are alternately exposed.

Next, a method of manufacturing the multilayer ceramic electronic component having the above-described structure will be described. First, SrTiO ₃
(98.0 mol%) as the main component, and Nb ₂ O
₅ (1.0 mol%) and MnO (1.0 mol%) are mixed with each other to form a ceramic material of 600 to 1200 in air.
C. and calcined so that the average particle size becomes 0.5 μm or less, and the pulverized fine powder was used as a starting material.

The starting material of the fine powder is dispersed in a solvent together with an organic binder such as butyral resin in a solvent to form a slurry, and the slurry is cut into a predetermined size into a raw sheet having a thickness of about 20 μm by a doctor blade method. did.

Next, as shown in FIG. 3, an internal electrode paste 10 made of Pd was pattern-printed on a raw sheet 9 by screen printing according to a predetermined size. A plurality of the raw sheets 9 on which the internal electrode paste 10 was printed in this way were laminated, and those on which the internal electrode paste was not printed were laminated on the uppermost and lowermost raw sheets 9a. Further, the raw sheet 9 on which the internal electrode paste 10 is printed is laminated so that the side on which the internal electrode paste 10 is formed up to the edge alternately comes to the opposite edge, and finally pressurized while heating. Crimped.

Next, degreasing at 600 to 1250 ° C. in air,
After the calcination, an external electrode paste made of Ag-Pd is applied on four surfaces adjacent to both end surfaces on which the internal electrodes 6 are exposed so as not to flow around, and then coated in a reducing atmosphere at 1200 to 13%.
It was baked at 50 ° C. After this firing, 900-12 in air
It was reoxidized at 50 ° C. to obtain a multilayer ceramic electronic component shown in FIGS.

If there is a concern that the external electrode 8 will peel off,
A reinforcing electrode paste made of Ag is applied so as to cover the external electrodes 8 so as to be formed also on a part of the four adjacent surfaces, and baked in air at 850 ° C. for 15 minutes to form the reinforcing electrode 1.
1 was formed.

FIG. 4 shows this manufacturing method, and FIG. 5 shows its structure. Further, as a specific example, a ceramic with a varistor function, in which 30 effective layers having internal electrodes formed thereon and having dimensions of 3.2 mm in width, 1.6 mm in depth and 0.5 mm in thickness, and ineffective layers arranged on upper and lower end surfaces, is laminated. The capacitors were used as capacitors, and their capacities, variations in capacities, and cracking rates are shown in Table 1. However, the respective conditions such as firing at this time are as follows: degreasing and calcination in the powder stage in air at 1200 ° C. for 2 hours, and firing in a reducing atmosphere of N ₂ : H ₂ = 99: 1 is 13 hours.
The reoxidation was performed at 1100 ° C. for 1 hour at 00 ° C. for 2 hours.

The capacitance C is a value at a measured voltage of 1.0 V and a frequency of 1.0 kHz. The cracking rate is determined by embedding a measured varistor function-equipped ceramic capacitor in a resin and performing polishing such as buffing. And obtained by microscopic observation.

[0022]

[Table 1]

As can be seen from Table 1, the multilayer ceramic electronic component according to the present invention has less cracks than the prior art, and the variation in capacitance is significantly reduced.

In this embodiment, an SrTiO ₃ -based material is used as the ceramic material, but other dielectric materials such as BaTiO ₃ and semiconductor ceramics such as ZnO and thermistors are also effective. .

Although Pd was used for the internal electrode paste 10 and Pd-Ag was used for the external electrode paste, Pt, Pd-Ag and the base metals Ni and Cu were used for the internal electrodes, and Pt, Pd, and Ni were used for the external electrodes. , Cu, or a paste of a mixture thereof may be used.

[0026]

As described above, according to the present invention, it is possible to obtain a laminated ceramic electronic component which can sufficiently withstand a heat cycle without causing cracks in the ceramic layer.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a laminated ceramic electronic component according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the main part.

FIG. 3 is an exploded perspective view during the manufacturing process.

FIG. 4 is a manufacturing process diagram of the same.

FIG. 5 is a sectional view of a main part according to another embodiment.

FIG. 6 is a partially cutaway perspective view of a conventional multilayer ceramic electronic component.

FIG. 7 is a cross-sectional view of the main part.

[Explanation of symbols]

 Reference Signs List 5 ceramic layer 6 internal electrode 7 laminate 8 external electrode 11 reinforcing electrode

Continued on the front page (72) Inventor Kaori Okamoto 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Kimio Kobayashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A multilayer ceramic electronic component in which external electrodes are formed only on both exposed end faces of an internal electrode of a laminate having internal electrodes alternately exposed on end faces between ceramic layers. 2. The multilayer ceramic electronic component according to claim 1, wherein external electrodes provided on both end surfaces of the multilayer body are covered, and reinforcing electrodes are provided so as to extend over the other four surfaces adjacent to the end surface of the multilayer body. .