Laminated capacitor, printed circuit board, decoupling...

Details Laminated capacitor, printed circuit board, decoupling... Laminated capacitor, printed circuit board, decoupling...

2003-11-13

2004-09-21

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrostatic capacitors

Fixed capacitor

C361S306300, C361S321100, C361S321500, C361S311000, C361S313000

Reexamination Certificate

active

06795294

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to laminated capacitors, printed circuit boards, decoupling circuits, and high-frequency circuits, and more particularly, to laminated capacitors advantageously applicable to high-frequency circuits, and to printed circuit boards, decoupling circuits, and high-frequency circuits all including the laminated capacitors.
2. Description of the Related Art
A conventional laminated capacitor related to the present invention is, for example, described in Japanese Unexamined Patent Application Publication No. 11-144996 (patent reference
1
).
FIG. 7
is a plan view showing the appearance of a laminated capacitor
1
described in patent reference
1
.
The laminated capacitor
1
is provided with a rectangular parallelepiped capacitor body
2
. The capacitor body
2
has two rectangular main surfaces
3
and
4
opposing each other, and two side surfaces
5
and
6
opposing each other and extending in a longer-side direction of the main surfaces
3
and
4
, and two end surfaces
7
and
8
opposing each other and extending in a shorter-side direction of the main surfaces
3
and
4
, the side surfaces and the end surfaces connected to the main surfaces
3
and
4
.
The capacitor body
2
is provided with a plurality of dielectric layers
9
extending in the direction of the main surfaces
3
and
4
, and is also provided inside thereof with at least a pair of the first and the second internal electrodes, not shown in the figure, facing each other across a specific dielectric layer
9
in order to define a capacitor unit. The first and the second internal electrodes respectively have the first and the second lead electrodes extending onto the side surfaces
5
and
6
and the end surfaces
7
and
8
of the capacitor body
2
.
On the side surfaces
5
and
6
and the end surfaces
7
and
8
of the capacitor body
2
, the first external terminal electrodes
10
electrically connected to the first internal electrode through the first lead electrodes, and the second external terminal electrodes
11
electrically connected to the second internal electrode through the second lead electrodes are provided. To distinguish more easily the first external terminal electrodes
10
from the second external terminal electrodes
11
, the first external terminal electrodes
10
are shown in white, and the second external terminal electrodes
11
are shown in black in the figure.
Two first external terminal electrodes
10
are provided on each of the side surfaces
5
and
6
, and one first external terminal electrode
10
is provided on each of the end surfaces
7
and
8
. Two second external terminal electrodes
11
are disposed on each of the side surfaces
5
and
6
so as to be disposed alternately with the first external terminal electrodes
10
, and one second external terminal electrode
11
is disposed on each of the end surfaces
7
and
8
so as to be disposed alternately with the first external terminal electrode
10
.
In the laminated capacitor
1
shown in
FIG. 7
, since the first external terminal electrodes
10
and the second external terminal electrodes
11
are adjacent to each other over the side surfaces
5
and
6
and the end surfaces
7
and
8
, all the first external terminal electrodes
10
and all the second external terminal electrodes
11
are disposed alternately through the two side surfaces
5
and
6
and the two end surfaces
7
and
8
.
FIG. 7
also shows typical paths and directions of current flowing through the laminated capacitor
1
by arrows. As indicated by the arrows, the current flows from the first external terminal electrodes
10
to the second external terminal electrodes
11
at the state or the point of time of the figure.
When the current flows in that way, magnetic flux having a direction determined by the direction of the current is generally induced, and therefore, a self-inductance is generated. In this case, in close vicinity of external terminal electrodes
10
and
11
, the current flows away from the first external terminal electrodes
10
toward the second external terminal electrodes
11
. So the directions of the current are opposite between adjacent external terminal electrodes
10
and
11
, and therefore the magnetic flux is effectively canceled. As a result, the equivalent series inductance (ESL) of the laminated capacitor
1
is reduced, and therefore, the laminated capacitor
1
can be advantageously applied to high-frequency circuits.
As shown in
FIG. 7
, an end surface pitch Pe which defines the interval between adjacent first and second external terminal electrodes
10
and
11
disposed on the end surfaces
7
and
8
is made equal to a side surface pitch Ps defining the interval between adjacent first and second external terminal electrodes
10
and
11
disposed on the side surfaces
5
and
6
in the conventional laminated capacitor
1
.
The effect of magnetic-flux cancellation, described above, between adjacent first and second external terminal electrodes
10
and
11
depends on the magnitudes of the pitches Pe and Ps. The smaller the pitches Pe and Ps are, the larger the effect of magnetic-flux cancellation is. Therefore, when the end surface pitch Pe is equal to the side surface pitch Ps as in the laminated capacitor
1
shown in
FIG. 7
, the effect of magnetic-flux cancellation between adjacent first and second external terminal electrodes
10
and
11
disposed on the end surfaces
7
and
8
is substantially equal to the effect of magnetic-flux cancellation between adjacent first and second external terminal electrodes
10
and
11
disposed on the side surfaces
5
and
6
.
Under this condition, since the number of the first and the second external terminal electrodes
10
and
11
disposed on the end surfaces
7
and
8
is smaller than the number of the first and the second external terminal electrodes
10
and
11
disposed on the side surfaces
5
and
6
in the laminated capacitor
1
shown in
FIG. 7
, the effect of magnetic-flux cancellation works at fewer locations on the end surfaces
7
and
8
. The effect of magnetic-flux cancellation on the end surfaces
7
and
8
is consequently expected to be inferior to that on the side surfaces
5
and
6
. Therefore, if the effect of magnetic-flux cancellation on the end surfaces
7
and
8
is made stronger, the ESL of the laminated capacitor
1
can be further reduced.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a laminated capacitor having a greatly reduced ESL.
In addition, preferred embodiments of the present invention provide a printed circuit board, a decoupling circuit, and a high-frequency circuit all including such a novel laminated capacitor.
A laminated capacitor according to a preferred embodiment of the present invention includes a substantially rectangular capacitor body having two opposite main surfaces, and two opposite side surfaces connected to the main surfaces and extending in a longer-side direction of the main surfaces, and two opposite end surfaces connecting the main surfaces and extending in a shorter-side direction of the main surfaces.
The capacitor body includes a plurality of dielectric layers extending in the direction of the main surfaces, and at least a pair of the first and the second internal electrodes facing each other across a specific dielectric layer to define a capacitor unit. The first and the second internal electrodes respectively include the first and the second lead electrodes extending onto the side surfaces and the end surfaces of the capacitor body.
The first external terminal electrodes electrically connected to the first internal electrode through the first lead electrodes and the second external terminal electrodes electrically connected to the second internal electrode through the second lead electrodes are disposed on the side surfaces and the end surfaces of the capacitor body.
At least two first external terminal electrodes are disposed on

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