Laminated ceramic electronic component

Details Laminated ceramic electronic component Laminated ceramic electronic component

2000-06-14

2001-09-18

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrostatic capacitors

Fixed capacitor

C361S321200, C361S321300, C361S306300, C361S311000, C428S192000, C428S209000

Reexamination Certificate

active

06292353

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laminated ceramic electronic component such as a laminated capacitor and laminated varistor and, more specifically, to a laminated ceramic electronic component in which the electrode structure is improved.
2. Description of the Related Art
FIG. 3
is a vertical cross section showing one example of a conventional laminated capacitor.
The laminated capacitor
51
comprises a ceramic sintered body
52
constructed of a dielectric ceramic. A plurality of inner electrodes
53
to
56
are disposed in the laminated capacitor
51
so as to be stacked one on top of the other along the direction of thickness via respective ceramic layers. The inner electrodes
53
and
55
extend to one end face
52
a
of the ceramic sintered body
52
, while the inner electrodes
54
and
56
extend to the opposite end face
52
b
. Outer electrodes
57
and
58
are formed so as to cover the end faces
52
a
and
52
b
, respectively.
The outer electrodes
57
and
58
of the laminated capacitor
51
include electrode cover members
57
a
and
58
a
which cover the upper face
52
c
and lower face
52
d
in order to be mounted on the surface of a printed circuit board.
The length of the electrode cover members
57
a
,
58
a
as measured along the direction between the end faces
52
a
and
52
b
, is as short as possible to achieve miniaturization of the laminated capacitor
51
. As a result, the distance e between the inner side edge of the electrode cover members
57
a
,
58
a
and the outermost side edge of the electrodes
57
,
58
are made to be relatively small in the conventional laminated capacitor
51
. In the outer electrode
58
, for example, the distance e is 1 to 1.5 times as long as Lg (the distance between the tips
53
a
and
55
a
of the inner electrodes
53
and
55
, respectively, and the outer most side edge of the outer electrode
58
). A similar relationship exists on left hand side of the capacitor.
When the laminated capacitor
51
is packaged on the printed circuit board by soldering, a heat pulse is applied to the laminated capacitor
51
. In response to this heat pulse, the outer electrodes
57
and
58
and the inner electrodes
53
to
56
in the laminated capacitor
51
are more likely to contract than the ceramic material. This contraction stress tends to concentrate at the inner side edges of the cover members
57
a
and
58
a
of the outer electrodes
57
and
58
, for example at the location indicated by arrow B in FIG.
3
. Also, the heat pulse stress is readily concentrated at the tip portions of the inner electrodes
53
to
56
located within the ceramic sintered body
52
. Accordingly, cracks are sometimes generated between the site indicated by the arrow B and the tip
53
a
of the inner electrodes
53
.
When the printed circuit board suffers a temperature variation or is bent after the laminated ceramic capacitor has been mounted on the printed circuit, cracks as described above are liable to occur by a stress ascribed to bending or heat impact applied to the ceramic sintered body
52
.
The distances e and Lg tend to be shorter as the laminated capacitor is miniaturized. Consequently, these cracks tend to be generated more frequently since the site indicated by the arrow B comes closer to the tip
53
a
of the inner electrode
53
.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a reliable laminated ceramic electronic component wherein the generation of cracks is reduced when a heat pulse is applied to the ceramic electronic component when it is mounted on the printed circuit board or when the circuit board is bent.
To this end, the present invention provides a laminated ceramic electronic component comprising: a ceramic sintered body having a first and second edge faces in opposed relation with each other; a plurality of inner electrodes, which is disposed so as to be stacked along the direction of thickness via a ceramic layer in the ceramic sintered body, pulled out of the first or second edge face; and a first and second outer electrodes formed so as to cover the first and second edge faces of the ceramic sintered body in opposed relation with each other, wherein the first and second outer electrodes comprise electrode cover members not only covering the first and second edge faces of the ceramic sintered body but also extending to the upper and lower faces, and to both side faces of the ceramic sintered body, and wherein the distance e between the outermost side edge of the outer electrode and the inner side edge of the electrode cover member of the outer electrode, and the distance Lg between the outermost side edge of the outer electrode and the tip of the inner electrode electrically connected to the opposed outer electrode, satisfy the following relation:
1.5×
Lg≦e≦
3.5
×Lg
Preferably, the distance e and the distance Lg is determined so as to satisfy the relation of 2.0×Lg≦e≦3.5×Lg.
While the laminated ceramic electronic component according to the present invention can be applied for various objects such as laminated capacitors, laminated varistors and laminated thermistors, the ceramic sintered body may be constructed using dielectric ceramics that is formed into a laminated capacitor in a specified aspect of the present invention.


REFERENCES:
patent: 5512353 (1996-04-01), Yokotani et al.
patent: 5659456 (1997-08-01), Sano et al.
patent: 5712758 (1998-01-01), Amano et al.
patent: 5801111 (1998-09-01), Wada et al.
patent: 5812363 (1998-09-01), Kuroda et al.
patent: 5933318 (1999-08-01), Tomono et al.
patent: 5985414 (1999-11-01), Fukuda et al.

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