JPH04361513A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To obtain a laminated ceramic capacitor at low cost by preventing the injection fault and the loss of electrostatic capacitance of inner electrode material. CONSTITUTION:The title capacitor is formed by providing an outer electrode 12 on both edge faces of a ceramic main body 10 and by forming a plurality of inner electrodes which are conductive to the outer electrode 12 by injecting inner electrode material into the internal space of the ceramic main body 10. The ceramic powder 15 contained in the compositional material of the inner electrode 11 is formed by ceramic particles coated with conductive metal. As the ceramic powder 15 does not react or calcimined with the ceramic main body 10 at the time of calcination, the internal space is not narrowed. As the surface layer of the grains of ceramic powder has conductivity, no chipping is generated on the inner electrode.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor in which internal electrodes are formed by injecting internal electrode material into the internal space of a ceramic body.

0002

2. Description of the Related Art The above-mentioned multilayer ceramic capacitor generally has a structure as shown in FIGS. 9 and 10. This capacitor includes a hexahedral ceramic main body 20, a plurality of internal electrodes 21 that partition the ceramic main body 20 into a plurality of ceramic layers, and a pair of side end faces and side end faces of the ceramic main body 20 that are electrically connected to the internal electrodes 21. It has an external electrode 22 provided on a portion of four surfaces around the periphery.

The outline of manufacturing a capacitor having such a structure is as follows. First, a green sheet is prepared from a mixture of a ceramic dielectric such as BaTiO3, a binder, and a solvent, and cut into a predetermined size. Next, a paste ink as an internal electrode material consisting of a heat-dispersible substance, ceramic powder, palladium powder, binder, and solvent is prepared and applied onto the cut sheet by screen printing or the like. After this is laminated and pressed to integrate, the binder is removed and fired. By firing, the heat scattering substance in the internal electrode material is scattered, and a ceramic main body having a space at the position of the internal electrode is produced. This internal space communicates with one of both end faces of the ceramic main body, and ceramic powder in the internal electrode material is scattered in the internal space. Moreover, the height of the internal space is related to the particle size of the ceramic powder. and,
After forming an external electrode on the side end surface of the ceramic body and its vicinity, lead or a lead alloy is injected into the internal space from the external electrode side that communicates with the internal space by reducing or pressurizing the ceramic body. At the same time as forming the electrodes, the internal and external electrodes are connected, and the ceramic body is divided into multiple ceramic layers to provide a capacitor function.

0004

[Problems to be Solved by the Invention] However, according to the above manufacturing method, the volume of the laminated sheet body decreases by about 20% due to the heat shrinkage of the ceramic due to firing, and the internal space formed by the scattering of the heat-dispersible material decreases. This makes it difficult to inject internal electrode material. Furthermore, during firing, the ceramic powder in the internal electrode material reacts or sinters with the ceramic dielectric of the sheet material, which also causes shrinkage of the sheet body, narrowing the internal space and causing failure in the injection of the internal electrode material. .

Furthermore, as shown in FIGS. 10 and 11, the ceramic powder 25 in the internal electrode material is scattered on the internal electrode 21 to form so-called ceramic pillars, but the ceramic powder 25 is made of pure nonmetallic material. Since it is an inorganic material, defects occur in the internal electrodes 21 for obtaining capacitance, and the area of the internal electrodes 21 decreases accordingly, resulting in loss of capacitance. In order to reduce defects, the particle size of the ceramic powder 25 contained in the internal electrode material may be reduced, but this will conversely narrow the internal space, which will hinder the injection work of the internal electrode material.

On the other hand, the internal electrode material uses an expensive noble metal such as palladium, and since a large amount of this is used as a component of the internal electrode material, the manufacturing cost becomes high. Therefore, an object of the present invention is to provide a multilayer ceramic capacitor that prevents injection failure of internal electrode materials and loss of capacitance, and reduces costs.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the multilayer ceramic capacitor of the present invention is such that the ceramic powder used for the conventional internal electrode material is made by coating ceramic particles with a conductive metal. It is characterized by certain things. In the capacitor of the present invention, since the ceramic powder is used as the internal electrode material, the ceramic powder is difficult to react with or sinter with the ceramic dielectric during firing, and a sufficiently large internal space can be secured. In addition, due to the conductive metal film on the surface of the ceramic powder particles scattered in the internal space, the ceramic powder that forms the ceramic pillar in the internal space does not cause damage to the internal electrodes and maintains the dielectric constant of the ceramic dielectric material sufficiently. It can be used for

Although the conductive metal that coats the ceramic particles is not specified, metals such as palladium and platinum are suitable in order to fully exhibit the above-mentioned effects. Even if these metals are expensive, they only need to be formed into an extremely thin film, so the amount used is small and the cost does not increase. Ceramic particles are made of known materials, such as barium titanate (Ba
It is sufficient to use TiO3). In addition, the particle size of the ceramic powder having a conductive metal film is 1 to 10 μm.
It is desirable to have a diameter of about m.

[0009]

EXAMPLES The multilayer ceramic capacitor of the present invention will be explained below based on examples. 1 and 2 show an example, and this capacitor has a hexahedral ceramic body 1
0, a plurality of internal electrodes 11 that partition the ceramic body 10 into ceramic layers, and an external electrode 12 electrically connected to the internal electrodes 11. As is clear from these figures, the structure of the capacitor itself is the same as the conventional one shown in FIGS. 9 and 10, but the constituent material of the internal electrode 11, especially the ceramic powder contained in the constituent material, makes the ceramic particles conductive. The difference is that it is coated with metal.

That is, as shown in an enlarged view of the internal electrode 11 in FIG.
Ceramic powder 15 as ceramic pillars is scattered in the electrode 11, and the thickness of the electrode 11 is related to the particle size of the powder 15. As is clear from FIG. 3, the ceramic powder 15 consists of ceramic particles 15a and a conductive metal film 15b covering the ceramic particles 15a, and since the surface layer of the powder 15 has conductivity, No partial defects occur, and the area of the internal electrodes 11 does not decrease. Therefore, the capacitance does not decrease and the dielectric constant of the ceramic main body 10 can be fully utilized.

Next, manufacturing of the capacitor having the above structure will be briefly described with reference to FIGS. 4 to 8. First, a green sheet is prepared from a mixture of a ceramic dielectric such as BaTiO3, a binder, and a solvent in the same manner as in the conventional method, and cut into a predetermined size. The internal electrode materials used in this example include 30 wt% carbon, 5 to 40 wt% ceramic powder having a film of the conductive metal, and 5 ethyl cellulose.
A paste ink consisting of ~10 wt% and pine oil (remaining amount) wt% is prepared. As can be understood from these ink components, inexpensive nonmetallic materials are used for the internal electrode materials.

This ink is applied onto the cut sheet 30 by screen printing or the like to form an internal electrode film 31 (see FIG. 4). After combining an appropriate number of these and laminating and pressurizing them to integrate them, a laminated sheet body as shown in FIG. 5 was obtained.
Perform binder removal firing. During firing, carbon, which is a heat-dissipating substance in the internal electrode material, scatters, producing a ceramic main body 30 having an internal space at the position of the internal electrode. A cross section of the ceramic main body 30 shown in FIG. 5 taken along line BB is shown in FIG. As can be seen from FIG. 6, the internal space 32
Ceramic powder 33 serving as ceramic pillars is scattered in the space, and the height of the internal space 32 is related to the particle size of the ceramic powder 33. Further, the internal space 32 communicates with one of both end surfaces of the ceramic main body 30.

[0013] Thereafter, Ag or Ag is applied to the pair of side end surfaces and a portion of the four surfaces surrounding the side end surfaces of the ceramic body 30.
An external electrode 34 made of /Pd is formed (see FIG. 7). Then, by injecting lead or a lead alloy into the internal space 32 from the external electrode 34 side by reducing or applying pressure, a plurality of internal electrodes 35 are formed within the ceramic body 30 and at the same time, the internal electrodes 35 and external electrodes 34 are connected. Ceramic body 3
0 is divided into multiple ceramic layers to provide a capacitor function (see Figure 8).

[0014]

[Effects of the invention] The multilayer ceramic capacitor of the present invention has
As explained above, since the ceramic powder in the internal electrode material is ceramic particles coated with conductive metal,
It has the following effects. (1) Since the surface layer of the ceramic powder particles is a film of conductive metal, the ceramic powder hardly reacts or sinters with the ceramic dielectric during firing, and the internal space hardly becomes narrow. Therefore, it is easy to inject the internal electrode material into the internal space. (2) Since the surface layer of the ceramic powder particles is a conductive metal film, the ceramic powder scattered in the internal electrodes is also substantially conductive, and no damage to the internal electrodes occurs. Therefore, the capacitance increases by 10 to 20% compared to the conventional case. (3) By (2), the capacitor can be made smaller if the capacitance is the same as the conventional capacitance, and the capacitance can be increased if the capacitance is the same size. (4) Since inexpensive nonmetallic materials can be used as internal electrode materials, manufacturing costs are reduced.

[Brief explanation of drawings]

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

FIG. 2 is a cross-sectional view of the capacitor in FIG. 1 taken along line AA.

FIG. 3 is an enlarged view of internal electrodes in the capacitor shown in FIG. 2;

4 is a perspective view showing a green sheet and a green sheet on which an internal electrode film is formed in the process of manufacturing a capacitor as shown in FIGS. 1 and 2. FIG.

5 is a perspective view of a ceramic body obtained by integrating an appropriate number of green sheets shown in FIG. 4; FIG.

6 is a cross-sectional view of the ceramic body of FIG. 5 along line B-B; FIG.

7 is a perspective view showing a state in which external electrodes are formed on the ceramic main body of FIG. 5. FIG.

8 is a sectional view showing a state when internal electrode material is injected into the internal space of the ceramic main body of FIG. 7. FIG.

FIG. 9 is a perspective view of a conventional capacitor.

10 is a cross-sectional view of the capacitor in FIG. 9 taken along line CC; FIG.

11 is an enlarged view of internal electrodes in the capacitor shown in FIG. 10. FIG.

[Explanation of symbols]

10 Ceramic body 11 Internal electrode 12 External electrode 15 Ceramic powder 15a Ceramic particles 15b Conductive metal film

Claims (1)

[Claims] Claim 1: A multilayer ceramic capacitor in which an external electrode is provided on a ceramic main body, and a plurality of internal electrodes that are electrically connected to the external electrode are formed by injecting an internal electrode material into an internal space formed within the ceramic main body. , a multilayer ceramic capacitor characterized in that the ceramic powder in the internal electrode material is ceramic particles coated with a conductive metal.