JP2003338427A - Manufacturing method of layered ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To configure a small-sized layered ceramic capacitor having a high breakdown voltage which is robust for the stress caused by warping. <P>SOLUTION: A ceramic sintered element 2 comprises a laminated element obtained by laminating alternately a plurality of inner electrodes 4a, 4b and ceramic layers 3, and small dielectric constant material 6. The inner electrodes 4a, 4b are so formed that the inner electrodes 4a are derived to a first end surface 21 of the ceramic sintered element 2 and the inner electrodes 4b are derived to its second end surface 22. Each small dielectric constant material 6 is formed in a predetermined shape on top and rear surfaces 23, 24 of the ceramic sintered element 2 and on two surfaces parallel with the section shown in Fig. 1. External electrodes 5a, 5b are formed on the first end surface 21 and the second end surface 22 of the ceramic sintered element 2 and above the four foregoing surfaces in contact with the surface 21 or the surface 22 respectively. Hereupon, each of the external electrodes 5a, 5b is so formed as to extend its end portions to the surfaces of each small dielectric constant material 6. <P>COPYRIGHT: (C)2004,JPO

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, and more particularly to a method for manufacturing a monolithic ceramic capacitor for medium and high voltages which requires high breakdown voltage.

[0002]

2. Description of the Related Art In recent years, with the demand for miniaturization of electronic devices and the like, surface mounting of electronic components has been advanced. Therefore, miniaturization is also required for electronic components used in electronic devices. In particular, a monolithic ceramic capacitor is required to have a higher capacity even though it is small.

Further, in switching power supply circuits and the like, capacitors for medium- and high-voltages with high withstand voltage are used. However, such capacitors for medium- and high-voltage not only have high withstand voltage, but as described above, Miniaturization is required.

The structure of a conventional monolithic ceramic capacitor will be described with reference to FIG. FIG. 3 is a side sectional view of a monolithic ceramic capacitor, wherein 1 is a monolithic ceramic capacitor, 2 is a ceramic sintered body, 3 is a ceramic layer having a high dielectric constant, 4a and 4b are internal electrodes, 5a and 5b are internal electrodes 4a, and 4b is an external electrode that is electrically connected to each of 4b, 21 is a first end surface of the ceramic sintered body 2, 22 is a second end surface of the ceramic sintered body 2, 23 is an upper surface of the ceramic sintered body 2,
Reference numeral 4 denotes the lower surface of the ceramic sintered body 2.

As shown in FIG. 3, the ceramic sintered body 2
Are formed by alternately stacking a plurality of internal electrodes 4a and 4b and high-dielectric-constant ceramic layers 3 and firing, and the internal electrodes 4a and 4b are extended to the first end face 21 and the second end face 22, respectively. Is formed. Further, external electrodes 5a and 5b are respectively provided from the first end surface 21 and the second end surface 22 of the ceramic sintered body 2 to the upper surface 23, the lower surface 24 and the other four side surfaces which are in contact with these end surfaces.

In such a monolithic ceramic capacitor 1, for example, as shown at point A in FIG. 3, the end of the external electrode 5b and the end of the internal electrode 4a are close to each other. Therefore, when a voltage higher than a predetermined voltage value is applied to the monolithic ceramic capacitor 1, a strong electric field is generated between the end of the external electrode 5b and the end of the internal electrode 4a. Further, since the ceramic layer has a high dielectric constant, when the electric field becomes stronger, the electric field is distributed to the outside of the ceramic sintered body 2. An electric field generated between areas other than the internal electrodes, particularly an electric field outside the ceramic sintered body 2, mainly triggers electric discharge, and when electric discharge is generated by this electric field, the element is dielectrically broken down. Similarly, discharge may occur at point B as well. In particular, due to the recent miniaturization, the ceramic layer forming the ceramic sintered body has become thin, and therefore the structure has a structure in which discharge may occur at a relatively low voltage.

As a structure for solving such a problem, there is a structure in which the ceramic layers between the inner electrodes of the uppermost layer and the lowermost layer and the upper surface and the lower surface perpendicular to the stacking direction of the ceramic sintered bodies are thickened. However, with such a structure, the height of the ceramic sintered body becomes high, which is against the miniaturization of the element.

An invention that solves these problems is disclosed in Japanese Patent Laid-Open No.
It is disclosed in Japanese Patent Publication No. 1-233363.

In the monolithic ceramic capacitor disclosed in this publication, a plurality of high dielectric constant ceramic layers and internal electrodes are alternately laminated, and low dielectric constant ceramic layers are laminated on the upper surface and the lower surface of the laminated body. At the same time, it is fired to form a ceramic sintered body, and external electrodes are formed on the surface of the ceramic sintered body. With such a structure, the electric field generated between the terminal portion of the external electrode and the internal electrode is suppressed and the breakdown voltage is increased without making the outer shape relatively large.

[0010]

However, the above-mentioned laminated ceramic capacitor has the following problems to be solved. The high-dielectric-constant ceramic layer and the low-dielectric-constant ceramic layer do not completely match even if they have similar shrinkage characteristics because the ceramic materials forming them differ. Therefore, even if they are laminated and fired, delamination may occur due to the difference in shrinkage characteristics, resulting in a low product yield.

Further, after mounting the monolithic ceramic capacitor having such a structure on the board, the board may be bent, etc.
A stress perpendicular to the lamination direction of the ceramic sintered body may be applied. In this case, stress is applied to the entire interface between the low-dielectric constant layer and the high-dielectric constant layer, which are relatively weakly coupled, and thus delamination is likely to occur.

An object of the present invention is to provide a small-sized monolithic ceramic capacitor which has a high breakdown voltage, is strong against external force, and a manufacturing method thereof.

[0013]

According to the present invention, there is provided a step of laminating a plurality of internal electrodes and a ceramic layer to form a laminated body, and a ceramic slurry having a low dielectric constant lower than that of the ceramic layer. A step of adhering to the first and second end surfaces of the laminated body and both ends of a surface perpendicular to the laminating direction between the first and second end surfaces and then drying to form a low dielectric constant material; Removing the low dielectric constant material formed on the first and second end faces of the internal electrode to expose the internal electrodes; firing the laminate together with the low dielectric constant material to obtain a ceramic sintered body; And forming an external electrode on the first and second end faces of the united body and the low dielectric constant body.

Further, according to the present invention, a step of laminating a plurality of internal electrodes and a ceramic layer to form a laminated body, and a low-dielectric-constant ceramic slurry having a relative dielectric constant lower than that of the ceramic layer are provided. The step of adhering to both ends of the second end surface and the surface perpendicular to the stacking direction between the first and second end surfaces and then drying to form a low dielectric constant material; and firing the stack together with the low dielectric constant material. To obtain the ceramic sintered body, the step of removing the low dielectric constant material formed on the first and second end faces of the ceramic sintered body to expose the internal electrodes, and the first step of the ceramic sintered body. And a step of forming an external electrode on the second end face and the low dielectric constant material.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Regarding the structure and manufacturing method of a laminated ceramic capacitor according to an embodiment of the present invention,
This will be described with reference to FIGS. 1 and 2. FIG. 1 is a side sectional view of a monolithic ceramic capacitor. In FIG. 1, 1
Is a monolithic ceramic capacitor, 2 is a ceramic sintered body,
3 is a high dielectric constant ceramic layer, 4a and 4b are internal electrodes,
Reference numerals 5a and 5b are external electrodes that are electrically connected to the internal electrodes 4a and 4b, 6 is a low dielectric constant material having a relative dielectric constant lower than that of the ceramic layer 3, 21 is a first end surface of the ceramic sintered body 2, and 22 is a ceramic sintered The second end surface of the united body 2, 23 is the upper surface of the ceramic sintered body 2, and 24 is the lower surface of the ceramic sintered body 2.

As shown in FIG. 1, the ceramic sintered body 2
Is formed of a laminated body formed by alternately laminating a plurality of internal electrodes 4a and 4b and a ceramic layer 3, and a low dielectric constant body 6. The internal electrode 4a is formed so as to extend to the first end surface 21 of the ceramic sintered body 2, and the internal electrode 4b is formed so as to extend to the second end surface 22 of the ceramic sintered body 2.

The low dielectric material 6 is formed on the upper surface 23, the lower surface 24, and the side surfaces perpendicular to the stacking direction of the ceramic sintered body 2 with a predetermined thickness, and from the first end surface 21 and the second end surface 22 to the stack body. Is formed by a predetermined length in the center direction.

The external electrode 5a is formed from the first end surface 21 of the ceramic sintered body 2 to the four surfaces in contact with this surface, and is electrically connected to the internal electrode 4a. Similarly, the external electrode 5b is formed from the second end surface 22 of the ceramic sintered body 2 to the four surfaces in contact with this surface, and is electrically connected to the internal electrode 4b. Further, the external electrodes 5a and 5b are formed so that their ends are on the surface of the low dielectric constant material 6.

With such a structure, since the high dielectric constant ceramic layer 3 and the low dielectric constant body 6 are provided between the end of the external electrode 5b and the end of the uppermost internal electrode 4a, both end portions are formed. The distance between them becomes longer. Further, since the length of the low dielectric constant material 6 in the upper surface direction is longer than the length of the outer electrode 5b in the upper surface direction, it is possible to suppress the amount of the electric field generated between both ends leaking to the outside of the laminated ceramic capacitor. As a result, the voltage (withstand voltage) at which discharge occurs between both electrodes can be increased.

Further, by using a low dielectric constant material, it is possible to achieve a higher breakdown voltage with a thinner thickness than when using a ceramic layer used for a laminated body.

Further, even if the substrate is subjected to stress due to strain or the like in the mounted state, the low dielectric constant body is formed only in the vicinity of the end portions of the four faces of the laminated body, so that the ceramic layer and the low dielectric constant body are formed. The stress applied to the interface is reduced. This allows
Generation of interfacial peeling between layers can be suppressed, and a high-strength multilayer ceramic capacitor can be formed.

Next, a method of manufacturing the monolithic ceramic capacitor will be described with reference to FIG. FIG. 2 is a side sectional view showing the structure of the monolithic ceramic capacitor along the manufacturing process. In FIG. 2, 1 is a monolithic ceramic capacitor, 2 is a ceramic sintered body, 3 is a ceramic layer, 4
a and 4b are internal electrodes, 5a and 5b are internal electrodes 4, respectively.
External electrodes conducting to a and 4b, 6 a low dielectric constant material having a lower relative dielectric constant than the ceramic layer 3, 21 a first end face of the laminated body 20 and the ceramic sintered body 2, 22 a laminated body 20 and a ceramic sintered body. The second end surface of the united body 2, 23 is the upper surface of the laminated body 20 and the ceramic sintered body 2, and 24 is the lower surface of the laminated body 20 and the ceramic sintered body 2.

Reference numeral 20 is a laminated body composed of internal electrode patterns and high dielectric constant ceramic green sheets, and 30.
Is a ceramic green sheet formed from a ceramic slurry, 40a and 40b are internal electrode patterns formed from a conductive paste, and 60 is a low dielectric constant material before sintering, which is formed from a ceramic slurry having a low dielectric constant.

First, as a pre-stage of lamination, BaTiO ₃
Rare earth oxide and alkaline earth oxide powders are mixed with the powder as a main component, and a binder containing vinyl acetate as a main component, a dispersant, a plasticizer, and water as a solvent are added to prepare a ceramic slurry. This ceramic slurry is applied to a predetermined thickness and dried to form a ceramic green sheet 30, and a conductive paste mainly containing Ni is printed on the surface of the predetermined ceramic green sheet 30 to form the internal electrode pattern 40a. , 40b are formed.

Next, as shown in FIGS. 2 (a) and 2 (b), first, a ceramic green sheet 30 having no internal electrode is placed, and the internal electrode 4a, 4b is placed on the surface thereof.
The ceramic green sheets 30 respectively formed with are laminated alternately. Further, the ceramic green sheets 30 on which the internal electrodes are not formed are laminated on the upper surface and pressed to form the laminated body 20.

In FIG. 2, the ceramic green sheet 30 in which the internal electrodes are not formed is one layer, but a plurality of layers may be laminated. Similarly, the ceramic green sheets 30 on which the internal electrodes 4a and 4b are formed are not three layers, but are laminated in a predetermined number so that a desired capacitance can be obtained.

Next, an organic binder containing CaZrO ₃ as a main component and vinyl acetate as a main component, a dispersant, a plasticizer, and water as a solvent are added to prepare a ceramic slurry having a low dielectric constant. The laminated body 20 is added to the ceramic slurry.
The first end face 21 and the second end face 22 of each of the above are soaked to a predetermined depth with each faced down, and dried to place the low dielectric constant material 60 at a predetermined position as shown in FIG.
A laminated body 20 coated with is formed.

Next, the first and second end faces 2 of the laminated body 20.
The low dielectric constant body 60 formed on the surfaces 1 and 22 is scraped off by a method such as polishing or sandblasting to form the internal electrode pattern 40.
By exposing and burning a and 40b, a ceramic sintered body 2 as shown in FIG. 2D is formed. Here, the firing condition is about 4 in an oxygen-nitrogen mixed atmosphere.
After degreasing at 00 ° C., baking was performed at about 1300 ° C. in a hydrogen-nitrogen mixed atmosphere.

The first and second end faces 21 and 22 of the ceramic sintered body 2 are dipped in a metal electrode paste containing Ag or Cu as a main component and applied. This is sintered, and Ni plating and Sn plating or Ni plating and solder plating are further applied to the outer surface thereof to form external electrodes 5a and 5b as shown in FIG. 2 (e).

Using the above manufacturing method, a laminated ceramic capacitor was prepared and the withstand voltage and strain strength were measured. The monolithic ceramic capacitor used for this measurement has a ceramic sintered body with external dimensions of 3.2 mm × 1.6 mm ×
1.0 mm, the thickness of the ceramic layer is 0.1 mm,
The low dielectric constant material is formed to have a thickness of 0.15 mm.

For comparison, a conventional monolithic ceramic capacitor having the structure shown in FIG. 3 was also formed with the same dimensions.

Here, in the withstand voltage measurement test, the DC voltage applied between the external electrodes is increased to measure the discharge start voltage, and in the strain strength measurement test, the laminated ceramic capacitor is mounted on the substrate. The substrate was bent in a direction perpendicular to the main surface, and the amount of bending that caused cracks in the laminated ceramic capacitor was measured. The results are shown in Table 1.

[0033]

[Table 1]

As shown in Table 1, the product of the present invention has excellent withstand voltage and strain strength as compared with the conventional product.

In the above embodiment, the low dielectric constant material formed on the end face is removed before firing, but the invention is not limited to this, and it may be removed after firing, for example.
In this case, the internal electrodes may be exposed by removing by a polishing method such as polishing or sandblasting as in the case of removal before firing. Since the step of removing the low dielectric constant is for exposing the internal electrode and enabling connection with the external electrode, it is not necessary to remove the low dielectric constant of the entire end face. There is no problem even if there is some remaining rate.

Further, in addition to the polishing for removing the low dielectric constant in the above embodiment, polishing for corner chamfering may be performed to prevent chipping or cracking. The polishing for chamfering the corners may be performed in any process before firing, after firing, before formation of the low dielectric constant, and after formation, and if possible, at the same time during polishing for removing the low dielectric constant. You may make it chamfer a corner.

As described above, the ceramic sintered body is formed of the ceramic layer and the low dielectric constant material, and the low dielectric constant material is formed at both ends of the surface perpendicular to the stacking direction between the end surfaces from which the internal electrodes are drawn out. By arranging the tips of the external electrodes on the low dielectric constant material, it is possible to form a high breakdown voltage monolithic ceramic capacitor that is strong against stress caused by stress due to difference in contraction rate due to firing and strain.

[0038]

According to the present invention, a plurality of internal electrodes and a ceramic layer are laminated to form a laminated body, and a ceramic slurry having a low dielectric constant lower than that of the ceramic layer is drawn out from the internal electrode. The first and second end surfaces and the first and second end surfaces are adhered to both ends of the surface perpendicular to the stacking direction and then dried to form a low dielectric constant material. The low dielectric constant material formed on the second end face is removed to expose the internal electrodes, and the laminated body is fired together with the low dielectric constant material to obtain a ceramic sintered body. External electrodes are formed on the end face of No. 2 and the low dielectric constant material. Also,
Instead of removing the low dielectric constant material on the first and second end faces before firing, the low dielectric constant material on the first and second end faces is removed after firing.

Thus, the low dielectric constant material can be easily arranged between the ceramic layer and the tip of the external electrode. Also, unlike the conventional one in which a low dielectric constant material is formed by layers, since it is formed by adhering a ceramic slurry, it is possible to reduce the thickness of the low dielectric constant material. Withstand voltage can be improved with almost no change in dimensions. Furthermore, since the low dielectric constant material is partially formed at both end portions of the surface perpendicular to the stacking direction between the first and second end surfaces, as in the conventional case,
Different from the case where it is formed on the entire surface perpendicular to the stacking direction between the first and second end surfaces, it is possible to suppress peeling due to the difference in shrinkage ratio between the ceramic layer and the low dielectric constant material during firing. Therefore, it is possible to improve the strain strength when the monolithic ceramic capacitor is mounted on the substrate.

[Brief description of drawings]

FIG. 1 is a side sectional view of a monolithic ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a side cross-sectional view showing the structure of a monolithic ceramic capacitor along the manufacturing process of the monolithic ceramic capacitor.

FIG. 3 is a side sectional view of a conventional monolithic ceramic capacitor.

[Explanation of symbols]

1-multilayer ceramic capacitor 2-ceramic sintered body 3-High dielectric constant ceramic layer 4a, 4b-internal electrodes 5a, 5b-external electrodes 6-Low dielectric constant ceramic body 20-laminate 21-First end face of ceramic sintered body 2 and laminate 20 22-Second end face of ceramic sintered body 2 and laminate 20 23-Top surfaces of the ceramic sintered body 2 and the laminated body 20 24-Lower surfaces of the ceramic sintered body 2 and the laminated body 20 30-ceramic green sheet 40a, 40b-Patterns for internal electrodes 60-Ceramic body with low dielectric constant before sintering

Claims (2)

[Claims] 1. A ceramic sintered body and a ceramic sintered body are disposed so as to overlap each other in the thickness direction through a ceramic layer in the ceramic sintered body, and are alternately drawn out to first and second end surfaces of the ceramic sintered body. Multiple internal electrodes,
A method of manufacturing a monolithic ceramic capacitor comprising external electrodes formed on the first and second end faces, the method comprising: laminating the plurality of internal electrodes and a ceramic layer to form a laminated body; A low-dielectric-constant ceramic slurry having a relative dielectric constant lower than that of the layer is attached to both ends of the first and second end faces and a face perpendicular to the laminating direction between the first and second end faces, and then dried. Forming a low dielectric constant material, and removing the low dielectric constant material formed on the first and second end surfaces of the laminated body to expose the internal electrodes; and And a step of forming a ceramic sintered body by firing with an index body, and a step of forming external electrodes on the first and second end faces of the ceramic sintered body and the low dielectric constant body. Manufacturing method of multilayer ceramic capacitor. 2. A ceramic sintered body and a ceramic sintered body are disposed so as to overlap each other in the thickness direction through a ceramic layer in the ceramic sintered body, and are alternately drawn out to the first and second end faces of the ceramic sintered body. Multiple internal electrodes,
A method of manufacturing a monolithic ceramic capacitor comprising external electrodes formed on the first and second end faces, the method comprising: laminating the plurality of internal electrodes and a ceramic layer to form a laminated body; A low-dielectric-constant ceramic slurry having a relative dielectric constant lower than that of the layer is attached to both ends of the first and second end faces and a face perpendicular to the laminating direction between the first and second end faces, and then dried. To form a low dielectric constant material, a step of firing the laminate together with the low dielectric constant material to obtain a ceramic sintered body, and a step of forming the ceramic sintered body on the first and second end surfaces. A step of removing the low dielectric constant material to expose the internal electrodes; and a step of forming external electrodes on the first and second end surfaces of the ceramic sintered body and the low dielectric constant material. To manufacture a monolithic ceramic capacitor .