Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-11-02
2004-06-15
Martin, David (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S748000, C361S760000, C174S250000, C257S678000
Reexamination Certificate
active
06751101
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic component and a method of producing the same, and more particularly to a ceramic electronic component having improved external terminal electrodes and a method of producing the same.
2. Description of the Related Art
FIG. 15
is a perspective view showing a conventional ceramic electronic component
1
.
The ceramic electronic component
1
defines a capacitor, an inductor, a resonator, a circuit substrate, or other suitable electronic components. The ceramic electronic component
1
includes a member
2
having a laminated or single-layer structure.
The ceramic electronic component member
2
has a rectangular parallelepiped shape which includes first and second main surfaces
3
and
4
disposed opposite to each other and four side surfaces
5
,
6
,
7
, and
8
connecting the first and second main surfaces
3
and
4
. A plurality of external terminal electrodes
9
is provided on at least one side surface of the ceramic electronic component member
2
, for example, on the side surfaces
5
and
7
. These external terminal electrodes
9
are provided on the inner walls
10
of concavities having a semicircular cross-section provided on the side surfaces
5
and
7
.
The ceramic electronic component
1
is produced as follows.
First, a ceramic green molded product
11
as shown in
FIG. 16
is produced. When the ceramic electronic component member
2
has a laminated structure, a plurality of ceramic green sheets are laminated to produce the ceramic molded product
11
. A plurality of the ceramic electronic components
1
are produced from the ceramic green molded product
11
.
Next, a plurality of through-holes
12
are formed in the ceramic green molded product
11
as shown in FIG.
16
. The positions of the through-holes
12
correspond to positions where the external terminal electrodes
9
are to be formed.
Moreover, as shown in
FIG. 16
, cutting grooves
15
are formed on one main surface
13
or on both main surfaces
13
and
14
of the ceramic green molded product
11
.
FIG. 18
clearly shows that the cutting groove
15
is formed on both of the main surfaces
13
and
14
. When a plurality of the ceramic electronic components
1
are produced in a later process, the cutting grooves
15
facilitate breaking along the boundary lines between the plurality of the ceramic electronic components. For example, the cutting grooves
15
are formed to have a depth that is equal to about one third to one sixth of the thickness of the ceramic green molded product
11
.
Then, the ceramic green molded product
11
is fired, whereby a ceramic sintered product
16
can be obtained.
FIG. 17
is a cross-sectional view of a portion of the ceramic sintered product
16
.
Subsequently, electrically conductive paste
17
is applied on the inner walls of the through-holes
12
, and thereby, the terminal conductors
18
to be formed into the external terminal electrodes
9
are formed on the inner walls of the through-holes
12
, respectively, as shown in FIG.
17
. To form each terminal conductor
18
, for example, screen printing is performed. That is, the ceramic sintered product
16
is placed on a stand
21
having holes
20
to which a vacuum is applied as shown by arrows
19
, with the holes
20
and the through-holes
12
being aligned. The electrically conductive paste
17
is applied onto the inner walls of the through-holes
12
by moving a squeegee
23
over a screen
22
.
In the above-described screen printing process, the electrically conductive paste
17
is applied to the main surface
13
of the ceramic sintered product
16
in a desired pattern, if necessary, whereby conductor films for wiring are formed.
Succeedingly, the terminal conductors
18
and the conductor wiring films formed with the conductive paste
17
are fired.
If the ceramic green molded product
11
has a laminated structure, the process illustrated in
FIG. 17
is carried out for the ceramic green molded product
11
in the green state. In some cases, the conductive paste
17
forming the terminal conductors
18
and the other wiring conductors are fired together with the ceramic green molded product
11
.
Next, the surfaces of the terminal conductors
18
are plated with nickel/gold, nickel/tin, nickel/solder, or other suitable conductive material.
Next, components are mounted on the main surface
13
of the ceramic sintered product
16
.
The cutting grooves
15
may be formed after the process illustrated
FIG. 17
, which is carried out before firing, after the plating process, or after the components are mounted.
The ceramic sintered product
16
having the terminal conductors
18
disposed on the inner walls of the through-hole
12
are formed as described above.
FIG. 18
shows a portion of the ceramic sintered product
16
.
Then, the ceramic sintered product
16
is broken along the cutting grooves
15
, and the plurality of the ceramic electronic components
1
are separated.
FIG. 19
is a partially enlarged perspective view of a portion of the separated ceramic electronic component
1
.
FIG. 19
shows a concavity
10
formed by splitting the through-hole
12
and the external terminal electrode
9
formed by splitting the terminal conductor
18
.
When the ceramic sintered product
16
is broken as described above, the terminal conductors
18
are split when tensile stress is applied. Therefore, the splitting forms split surfaces
24
which are exposed on the external terminal electrode
9
.
The above-described ceramic electronic component
1
and the method of producing the same have the following problems.
The split surfaces
24
formed on the external terminal electrodes
9
oxidize because they are not plated with the plating film. Thus, the soldering properties of the split surfaces
24
are deteriorated. As a result, satisfactory soldering to the external terminal electrodes
9
is not possible.
Moreover, when the ceramic sintered product
16
are broken along the cutting grooves
15
, the through-holes
12
are split in such a manner that the terminal conductors
18
on the inner walls of the through-holes
12
are torn off. Thus, the terminal conductors
18
often do not accurately split into halves along the cutting groove
15
. In some cases, severe defects are caused. That is, one of the halves is chipped which causes electrical disconnection. Moreover, a fatal deficiency may be caused. That is, the terminal conductors
18
may be partially chipped together with a portion of the ceramic sintered product
16
.
To solve the above-described problems, the thickness of each terminal conductor
18
and that of the plating film formed thereon is decreased. However, the decrease of the thickness causes a defect, such as disconnection.
If the external terminal electrodes
9
are formed after the ceramic sintered product
16
is broken along the cutting grooves
15
, the above-described problems are solved. However, in this case, the production efficiency is deteriorated.
Moreover, to solve the above-described problem of chipping of the external terminal electrodes
9
caused when the ceramic sintered product
16
is broken along the cutting grooves
15
, the terminal conductors
18
must be hollow, as clearly shown in FIG.
17
. Therefore, the diameter of the through-hole
12
cannot be significantly reduced. As a result, the size of the ceramic electronic component
1
cannot be significantly reduced.
As shown in
FIG. 17
, the terminal conductors
18
are formed to be hollow as described above while the peripheries of the holes
21
of the stand
20
are not smeared with the conductive paste
17
. Accordingly, the conductive paste
17
must be screen-printed while a vacuum is applied to the holes
20
each having a diameter larger than the through-holes
12
. Thus, portions
25
extending onto the main surfaces
13
and
14
are formed for each of the external terminal electrodes
9
. However, the presence of the extended portions
25
prevents substantial reduction of the interval at whi
Keating & Bennett LLP
Levi Dameon E.
Murata Manufacturing Co. Ltd.
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