Multi layer ceramic capacitor

Details Multi layer ceramic capacitor Multi layer ceramic capacitor

2000-03-14

2001-12-18

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrostatic capacitors

Fixed capacitor

C361S305000, C361S311000, C361S321400, C361S306300

Reexamination Certificate

active

06331929

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-layer ceramic capacitor having, for example, a laminated body of internal electrode patterns and ceramic layers, at end portions of which are provided external electrodes so as to connect with the internal electrodes, and in particular to a multi-layer ceramic capacitor in which de-lamination (i.e., separation between the layers) hardly occurs inside the laminated body.
2. Description of Related Art
In a multi-layer ceramic capacitor, a large number of layers are stacked or laminated, each having an internal electrode and made of dielectric material, wherein the internal electrodes face each other through the ceramic layers within this laminated body, and the above-mentioned internal electrodes extend out to the end surfaces of this laminated body. On the end portions including the end surfaces of the laminated body, to which those internal electrodes extend out, are formed external electrodes, and those external electrodes are connected to the above-mentioned internal electrodes which face each other through the ceramic layers within the laminated body.
The above-mentioned laminated body
3
of the multi-layer ceramic capacitor has a layer construction as shown in
FIG. 3
, for example. Namely, ceramic layers
7
,
7
. . . , each having an internal electrode
5
or
6
and made of a dielectric material, are laminated in the order shown in
FIG. 3
, and further, on both sides thereof, are stacked or laminated the ceramic layers
7
,
7
. . . in a plurality thereof, on which no electrode
5
or
6
is formed. At the end portions of the laminated body
3
having such a layer structure therein, the internal electrodes
5
and
6
are exposed, and as shown in
FIG. 1
, the above-mentioned external electrodes
2
and
2
are formed at the end portions of this laminated body
3
.
Such a multi-layer ceramic capacitor, ordinarily, is not manufactured one by one, in a unit of one part, but actually is obtained by a manufacturing method which will be described below. Namely, first of all, minute ceramic powder and organic binder are mixed to prepare a slurry, which is spread thinly on a carrier film made from a polyethylene terephthalate film, etc., by means of a doctor blade method. Then, it is dried and formed into a ceramic green sheet. Next, this ceramic green sheet is cut out into a desired size by a cutting head, while being mounted on the supporting sheet, and is printed with a conductive paste on one side surface thereof by a screen printing method, and is dried. With this, the ceramic green sheets
1
a
and
1
b
are obtained, on each of which plural sets of internal electrode patterns
2
a
and
2
b
are aligned or arranged in the vertical and horizontal directions, as shown in FIG.
6
.
Next, plural pieces of the ceramic green sheets
1
a
and
1
b
, each having the above-mentioned internal electrode patterns
2
a
and
2
b
thereon, are stacked or laminated, and further stacked are several pieces of the ceramic green sheets
1
,
1
. . . having no internal electrode
2
a
or
2
b
, at the top and the bottom surfaces thereof. They are compressed and form the laminated body. Here, the above ceramic green sheets
1
a
and
1
b
are stacked on one another, on which the internal electrode patterns
2
a
and
2
b
are shifted by half a length in a longitudinal direction thereof. After that, this laminated body is cut into a desired size, thereby to manufacture laminated raw chips, and those raw chips are baked. In this manner are obtained the laminated bodies shown in
FIGS. 1 and 3
.
Next, this baked laminated body
3
has a conductive paste applied to both ends thereof and is baked, and on the surface of the baked conductive film is provided a treated plating, thereby completing the multi-layer ceramic capacitor formed with external electrodes at both ends thereof, as shown in FIG.
1
.
Within the laminated body
3
of the ceramic layers
7
in the multi-layer ceramic capacitor mentioned above, stickiness or adhesiveness between the layers of the internal electrode
5
or
6
and the ceramic layer
7
is worse than the adhesiveness between the ceramic layers
7
themselves. Therefore, when baking the laminated body
3
, stresses occur inside the laminated body due to the differences in shrinkage rates and shrinking behaviors and so on, of the internal electrodes
5
and
6
and the ceramic layers
7
. Then, in particular on both end portions of the laminated body
3
, where the internal electrodes
5
and
6
are led out, there easily occurs a so-called de-lamination, i.e., the ceramic layers
7
peel off one another. Also, fine cracks easily occur inside the laminated body
3
.
In particular, in recent years, for obtaining a larger electrostatic capacity but having a small size, the internal electrode
5
or
6
and the ceramic layer
7
have a tendency to be thin in the film thickness thereof. Therefore, with the stress due to the differences in the shrinkage rates and the shrinking behaviors of the internal electrodes
5
and
6
and the ceramic layers
7
when being baked, the laminated body
3
is under a situation that cracks and de-lamination occur more easily therein.
SUMMARY OF THE INVENTION
An object, according to the present invention, for solving the problem in the conventional art mentioned above, is to provide a multi-layer ceramic capacitor, wherein the stress, caused in the laminated body when baking the laminated body due to the differences in the shrinkage rate and the shrinking behavior of the internal electrodes and the ceramic layers
7
, is released or mitigated, thereby hardly causing cracking and/or de-lamination inside the laminated body when baking.
According to the present invention, for achieving the above-mentioned object, the internal electrodes
5
and
6
facing each other through the ceramic layers
7
are formed so that conductor particles
8
are connected one by one, along the boundary surface between the ceramic layers
7
. With this, the stresses between the internal electrodes
5
and
6
and the ceramic layers
7
are released or mitigated, thereby preventing the laminated body
3
from cracks and de-laminations occurring therein when the laminated body
3
is baked.
Namely, according to the present invention, there is provided a multi-layer ceramic capacitor, comprising:
a laminated body
3
in which ceramic layers
7
and internal electrodes
5
and
6
are laminated on one another; and
external electrodes
2
and
2
provided at end portions of the laminated body
3
, in which the internal electrodes
5
and
6
opposing each other reach to either one of at least a pair of edges of the ceramic layers
7
, thereby leading out the internal electrodes
5
and
6
which oppose each other to either one of the end surfaces of the laminated body
3
, and connecting the internal electrodes
5
and
6
led out to the end surfaces of the laminated body
3
to the external electrodes
2
and
2
, respectively, whereby the internal electrodes
5
and
6
facing each other through the ceramic layers
7
within the laminated body
3
through the ceramic layers
7
are formed with conductor particles
8
, lying between the ceramic layers
7
one by one, along a boundary surface to the ceramic layers
7
, successively.
In the above, within the internal electrodes
5
and
6
are provided spaces
9
where no conductor particle exists, and the number of conductor particles
8
lying along the boundary surface to the ceramic layers
7
, between an adjacent space
9
, is equal to or less than 20. In every space
9
in the internal electrodes
5
and
6
, there lie a number of ceramic particles (10) equal to or more than ten. The spaces of the internal electrodes
5
and
6
occupy 25% to 75% of the area of the internal electrodes
5
and
6
.
With this multi-layer ceramic capacitor, the internal electrodes
5
and
6
, facing each other through the ceramic layers
7
within the laminated body
3
, are formed to lie or connect with one by one along the boundary

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