Metal working – Barrier layer or semiconductor device making – Barrier layer device making
Reexamination Certificate
2001-01-25
2002-12-10
Niebling, John F. (Department: 2812)
Metal working
Barrier layer or semiconductor device making
Barrier layer device making
Reexamination Certificate
active
06491733
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates an apparatus for manufacturing a solid electrolytic capacitor particularly of a kind having a solid electrolytic layer made of an electroconductive polymer.
2. Description of the Related Art
In recent years, rapid progress has been made in high-speed digital signal processing and multimedia appliances have come to have a high-speed feature along with a compact size. The need has incidentally increased to use downsized and flattened power supplies for high-frequency driving and, therefore, stabilization and noise reduction have now come to be an important factor. Under these circumstances, a solid electrolytic capacitor, an important circuit component part, is desired to have a low ESR (equivalence series resistance) so that it can adapt to a rapid change in voltage, and also to have a compact size and a large capacity so that it can be surface mounted.
A solid electrolytic capacitor of a kind having a solid electrolytic layer made of an electroconductive polymer can meet the requirement. Hereinafter, the solid electrolytic capacitor will be discussed.
FIG. 12A
illustrates a sectional representation of the standard solid electrolytic capacitor
60
. The solid electrolytic capacitor
60
includes a capacitor element
45
embedded in a covering resin
49
with respective portions of anode and cathode terminals
46
and
47
exposed to the outside thereof.
The capacitor element
45
is made up of a porous anode element
40
, a dielectric oxide film
42
formed on a surface of the anode element
40
, a solid electrolytic layer
43
formed over the dielectric oxide film
42
and a cathode layer
44
formed over the solid electrolytic layer
43
.
FIG. 12B
is a fragmentary enlarged diagram showing the anode element
40
. The porous anode element
40
has a plurality of micropores
62
on its surface as shown in FIG.
12
B.
The porous anode element
40
is obtained by pressing a powder of a valve action metal, for example, tantalum to a desired shape and then sintering it, and the anode element
40
has embedded therein an anode lead line
41
in the form of a tantalum wire with a portion of the anode lead line exposed to the outside. The anode lead line
41
is connected with the anode terminal
46
. The dielectric oxide film
42
is obtained by anodizing the surface of the anode element
40
. The solid electrolytic layer
43
is made of an electroconductive polymer such as polypyrrole. The anode terminal
46
is connected with the anode lead line
41
by welding and the cathode terminal
47
is connected with the cathode layer
44
by the use of an electroconductive bonding agent
48
. The exposed portions of the anode and cathode terminals
46
and
47
are bent inwardly so that the capacitor
60
can be surface-mountable as a capacitor chip on a planar support surface.
A method of manufacturing the solid electrolytic capacitor
60
will be discussed with reference to a flowchart of
FIG. 13
showing the sequence of making the solid electrolytic capacitor
60
according to the prior art.
As shown therein the tantalum metal powder with the anode lead line
41
embedded therein is pressed to a desired shape and is then sintered to provide the porous anode element
40
(Shaping and Sintering Step).
Subsequently, using a phosphoric acid, the anode element
40
is anodized to form the dielectric oxide film
42
on an outer surface of the anode element
40
(Anodizing Step).
After the anode element
40
has been impregnated with a pyrrole monomer solution, the anode element
40
is dipped into a solution with an oxidizing agent, or after the anode element
40
has been dipped into the solution with the oxidizing agent, the anode element
40
is impregnated with a pyrrole monomer solution and the solid electrolytic layer
43
is formed over the dielectric oxide film
42
by means of a chemical oxidation polymerization(Polymerization Step).
Thereafter, carbon is coated, a silver paint is coated and drying is performed to complete formation of the cathode layer
44
, thereby completing the capacitor element
45
(Cathode Forming Step).
Then, the anode lead line
41
extending from the capacitor element
45
is welded to the anode terminal
46
of a lead frame and the cathode layer
44
is connected with the cathode terminal
47
by the use of an electroconductive bonding agent
48
(Fabrication Step). The capacitor element
45
is thereafter resin-molded in an epoxy covering resin
49
with respective portions of the anode and cathode terminals
46
and
47
exposed to the outside of the covering resin
49
(Resin-encasing Step). In general, by the sequence discussed above, a batch of capacitors
60
are manufactured at a time with the anode and cathode terminals
46
and
47
of one capacitor
60
continuous with those of the next adjacent capacitor
60
. Accordingly, as a final step, the capacitors
60
connected together are separated into the individual capacitors
60
which are subsequently tested to provide the individual solid electrolytic capacitors
60
(Finishing Step).
FIG. 14
shows a schematic layout of a portion of the capacitor manufacturing apparatus where polymerization is carried out, and
FIG. 15
is a fragmentary enlarged perspective view of the polymerization part of FIG.
14
. As shown in
FIG. 14
, the polymerization part includes one first array of baths
50
and
50
A, four second arrays of baths
50
and
50
A, and two third arrays of baths
50
and
50
A, and these first, second, and third arrays are arranged in parallel. These arrays include a plurality of polymerization baths
50
, and baths
50
A for cleansing, drying, and so on. The first array is a polymerization (A) process line for forming the solid electrolytic layer
43
made of polypyrrole on an outer surface
63
(
FIG. 12B
) of the anode element
40
(that is, the surface except for the micropores
62
of the anode element
40
) by means of a chemical oxidation polymerization. The second lines are polymerization (B) process lines for forming the solid electrolytic layer
43
made of polypyrrole within the micropores of the anode element
40
by means of a chemical oxidation polymerization. The third lines are polymerization (C) process lines for forming the solid electrolytic layer
43
made of an electroconductive polymer such as polythiophene, which is different from polypyrrole, by means of a chemical oxidation polymerization.
Each of the first, second, and third lines includes a plurality of polymerization baths
50
as shown in FIG.
14
. As shown in
FIGS. 14 and 15
, the polymerization baths
50
are arranged in line and connected, and a conveyance between the baths was performed manually by an attendant worker
61
.
It is difficult to form the solid electrolytic layer
43
within the micropores
62
as well as on the outer surface
63
of the anode element
40
, and the solid electrolytic layer
43
having a desired thickness cannot be formed by one polymerization step. Accordingly, since each of the processes is required to be repeated several ten times, a considerably complex process such as 3 repetitions of the polymerization process A and
14
repetitions of the polymerization process B for each of the 4 lines, has been required.
FIGS. 16A and 16B
are a plan view and a sectional view, respectively, of the polymerization bath
50
which is used for a chemical oxidation polymerization in the polymerization process. In
FIG. 16A
, the polymerization bath
50
has an open-topped cavity
64
, a supply passage
51
for supplying the cavity
64
with a polymerization solution
54
from a tank (not shown) of the polymerization solution
54
, the supply passage
51
being defined at a center of the bottom surface of the cavity
64
and communicated with the cavity
64
, weir boards
52
A and
52
B which are placed in the cavity
64
, and waste liquid tubes
53
A and
53
B for draining an overflow of the polymerization solution
54
over the weir boards
52
A and
52
B.
Hereinafter, an operation of the polymerization ba
Shiragami Masaki
Terada Mitsuo
Ueno Motonobu
Matsushita Electric - Industrial Co., Ltd.
Niebling John F.
Stevenson André C
Wenderoth , Lind & Ponack, L.L.P.
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