Metal working – Barrier layer or semiconductor device making – Barrier layer device making
Reexamination Certificate
1998-12-08
2001-04-10
Booth, Richard (Department: 2812)
Metal working
Barrier layer or semiconductor device making
Barrier layer device making
C361S513000, C361S519000, C361S523000, C361S529000
Reexamination Certificate
active
06214060
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a capacitor element for a solid electrolytic capacitor utilizing valve metal such as tantalum or aluminum. The present invention also relates to a process of making such a capacitor element.
2. Description of the Related Art
A conventional capacitor element used for a solid electrolytic capacitor may have the following arrangements.
Referring to
FIG. 14
of the accompanying drawings, the illustrated conventional capacitor element includes a porous capacitor chip
2
and an anode wire
3
projecting from a top face
2
a
of the chip
2
. The capacitor chip
2
is prepared by compacting powder of valve metal (such as tantalum) into a porous mass and then sintering the porous mass. The anode wire
3
may also be made of tantalum. For providing a capacitor function, the capacitor element is subjected to the following process steps.
First, as shown in
FIG. 15
, the porous sintered capacitor chip
2
and part of the anode wire
3
are immersed in an aqueous solution B of e.g. phosphoric acid in a container A. In this state, the immersed chip
2
and anode wire
3
are subjected to anodic oxidation (electrolytic oxidation) by applying a direct current. As a result, a dielectric coating
4
of e.g. tantalum pentoxide is formed on the surfaces of the tantalum particles and on the immersed root portion of the anode wire
3
, as shown in FIG.
15
.
Then, as shown in
FIG. 16
, the dielectrically coated chip
2
is immersed in an aqueous solution D of e.g. manganese nitrate in another container C to such an extent that the top surface
2
a
of the chip
2
is not submerged under the surface of the manganese nitrate solution, the chip
2
being thereafter taken out of the solution for baking. This step is repeated plural times to form a layer
5
of solid electrolyte (e.g. manganese dioxide) on the dielectric coating
4
.
Finally, as shown in
FIG. 17
, a metallic cathode terminal layer
6
(made of nickel for example) is formed on the solid electrolyte layer
5
with an intervening layer of e.g. graphite being interposed between the cathode terminal layer
6
and the electrolyte layer
5
.
According to the conventional process described above, in order to electrically insulate the cathode terminal layer
6
from the anode wire
3
with the use of the dielectric layer
4
, it is necessary to prevent the electrolytic layer
5
and the cathode terminal layer
6
from being formed on the top surface
2
a
of the chip
2
. For that purpose, as shown in
FIG. 16
, the top surface
2
a
of the chip
2
should be kept above the surface of the aqueous solution while the other portions of the chip
2
are immersed in the solution. However, preparation of arrangements for performing such a positional adjustment can often be troublesome. Besides, even with those arrangements, the resulting cathode terminal layer
6
may often be formed on the top surface
2
a
as well, unfavorably coming into contact with the anode wire
3
.
Reference is now made to
FIG. 18
which shows a conventional solid electrolytic capacitor using the capacitor element described above. As illustrated, the conventional solid electrolytic capacitor is provided with an anode plate
7
welded to the free end of the anode wire
3
over a distance S. The same capacitor is also provided with a resin package
8
for enclosing the chip
2
, the anode wire
3
and the anode plate
7
. The bottom surface of the cathode terminal layer
6
(in
FIG. 18
, the upright surface parallel to the top surface
2
a
) is electrically connected to a cathode plate
9
.
Another type of conventional solid electrolytic capacitor is shown in FIG.
19
. The illustrated capacitor includes an anode lead terminal
10
welded to the anode wire
3
, and a cathode lead terminal
11
connected to the cathode terminal layer
6
. The chip
2
, the anode wire
3
and part of the respective lead terminals
10
,
11
are enclosed by a resin package
12
.
For manufacturing the conventional capacitor shown in
FIG. 18
or
FIG. 19
, the anode plate
7
(
FIG. 18
) or the anode lead terminal
10
(
FIG. 19
) will be connected to the anode wire
3
by welding for example. According to this method, however, the heat generated for performing the welding may cause damage to the dielectric layer
4
, the solid electrolytic layer
5
and the cathode terminal layer
6
. For avoiding this problem, the anode wire
3
is rendered to have a rather great length L. However, such an arrangement unfavorably increases the entire length of the resulting solid electrolytic capacitor. In addition, the conventional anode wire
3
needs an additional length S for attachment of the anode plate
7
(or lead terminal
10
), which further increases the entire length of the capacitor. Supposing that the sizes of the package
12
(
FIG. 19
) are fixed to predetermined values, as the length of the anode wire
3
increases, the volume of the capacitor chip
2
should be reduced. As a result, the impedance characteristics of the resulting solid electrolytic capacitor will unfavorably be deteriorated.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention is to provide a process for making a capacitor element which eliminates or reduces the above-described problems.
Another object of the present invention is to provide a capacitor element which eliminates or reduces the above-described problems.
A further object of the present invention is to provide a solid electrolytic capacitor utilizing such a capacitor element.
According to a first aspect of the present invention, there is provided a process for making a capacitor element for a solid electrolytic capacitor, the process comprising steps of:
compacting valve metal powder into a porous chip so that an anode wire projects from the porous chip via an end surface;
fixing an anode plate to the anode wire;
applying a synthetic resin material on the anode wire between the anode plate and said end surface of the porous chip; and
forming a dielectric layer, a solid electrolytic layer and a cathode terminal layer on the porous chip.
According to the above process, a synthetic resin material is applied on the anode wire before plural layers are formed on the porous chip. Thus, in manufacture, the anode wire and the end surface of the porous chip are prevented from being unduly covered with the plural layers.
According to a preferred embodiment, the valve metal powder comprises tantalum powder.
The anode plate may be fixed to the anode wire by welding using a laser beam.
According to the preferred embodiment, the anode plate is fixed to the anode wire in a manner such that the anode wire extends perpendicularly from the anode plate.
With such an arrangement, the overall length of the product capacitor element can be short.
Specifically, the synthetic resin material may be applied on the anode wire so that the resin material covers only the anode wire and said end surface of the porous chip.
According to a second aspect of the present invention, there is provided a capacitor element for a solid electrolytic capacitor comprising:
a porous chip made of valve metal powder;
an anode wire projecting from the porous chip via an end surface of the porous chip;
an anode plate fixed to the anode wire;
a synthetic resin material applied on the anode wire between the anode plate and said end surface of the porous chip; and
a dielectric layer, a solid electrolytic layer and a cathode terminal layer formed on the porous chip.
Preferably, the synthetic resin material covers the anode wire and said end surface of the porous chip but not the layers formed on the porous chip.
According to a third aspect of the present invention, there is provided a solid electrolytic capacitor comprising:
a porous chip made of valve metal powder;
an anode wire projecting from the porous chip via an end surface of the porous chip;
an anode plate fixed to the anode wire;
a first resin material applied on the anode wire between the anode plate and said end surface of the porous chip;
a d
Booth Richard
Merchant & Gould P.C.
Nguyen Ha Tran
Rohm & Co., Ltd.
LandOfFree
Process of making a capacitor element for a solid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process of making a capacitor element for a solid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process of making a capacitor element for a solid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2532455