Metal working – Barrier layer or semiconductor device making – Barrier layer device making
Reexamination Certificate
2001-01-10
2003-01-21
Nguyen, Ha Tran (Department: 2812)
Metal working
Barrier layer or semiconductor device making
Barrier layer device making
C029S730000, C029S742000
Reexamination Certificate
active
06508846
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process and an apparatus for fabricating solid electrolytic capacitors.
BACKGROUND OF THE INVENTION
JP-B No. 51489/1987, JP-B No. 51491/1987, JP-B No. 66373/1992, U.S. Pat. No. 4,580,855, etc. disclose solid electrolytic capacitors which comprise a capacitor element including a member of valve-action metal and impregnated with a TCNQ complex salt as an electrolyte, the metal member having a chemical conversion coating. By “TCNQ” is meant 7,7,8,8-tetracyanoquinodimethane.
FIG. 8
shows one type of solid electrolytic capacitor which is already known and has a bottomed tubular aluminum case
9
housing a capacitor element
1
, filled with an epoxy resin
91
and having its opening sealed off. As shown in
FIG. 9
, the capacitor element
1
comprises an anode foil
11
which is an etched aluminum foil provided with a chemical conversion coating, and a cathode foil
12
opposed to and superposed on the anode foil
11
with a separator
13
interposed therebetween. The capacitor element is prepared by rolling up the assembly of the foils and the separator, and impregnating the resulting roll with a solid electrolyte such as a TCNQ complex salt. A pair of lead tab terminals
14
,
14
are joined to the anode foil
11
and the cathode foil
12
, with lead wires
15
,
15
extending from the respective terminals.
The solid electrolytic capacitor described is fabricated by filling a suitable amount of powder of TCNQ salt into a case
9
first, heating the case at 250 to 350° C. to melt the salt into a liquid, immersing the roll into the molten salt to impregnate the roll with the salt, thereafter rapidly cooling the roll as placed in the case to solidify the salt and finally filling an epoxy resin
91
into the case
9
.
Further attention has been directed to solid electrolytic capacitors which are compact, have a great capacity and are small in equivalent series resistance (ESR) and in which an electrically conductive polymer, such as polypyrrole, polythiophene, polyfuran or polyaniline, is used as an electrolyte. Like the structure shown in
FIG. 9
, the solid electrolytic capacitor of this type is prepared by rolling up an anode foil
11
provided with a chemical conversion coating and a cathode foil
12
opposed thereto, with a separator
13
interposed between the foils, to obtain a rolled-up element, forming an electrically conductive polymer layer in the rolled-up element to obtain a capacitor element
1
, fitting a sealing rubber packing
90
to the capacitor element
1
at one end thereof having projecting lead tab terminals
14
,
14
, and thereafter placing the element
1
into an aluminum case
9
as shown in
FIGS. 6
, (
a
), (
b
) and (
c
). The case
9
is then constricted at an opening end portion thereof to hold the packing
90
by the end portion in pressing contact with its periphery to seal off the case
9
.
With the conventional process for fabricating the solid electrolytic capacitor wherein the electrolyte is an electrically conductive polymer, a chemical conversion coating, electrically conductive polymer layer, graphite layer and silver paint layer are successively formed on the surface of a sintered anode member or an anode foil of a valve-action metal, such as aluminum or tantalum, and a cathode lead wire is joined to the coated anode member or foil with an electrically conductive adhesive or the like. However, this process of fabrication is considerably more cumbersome than the usual process of fabricating electrolytic capacitors which comprises rolling up an anode foil provided with a chemical conversion coating and a cathode foil opposed thereto, with a paper separator interposed between the foils, and impregnating the resulting rolled-up element (hereinafter referred to as “capacitor element”) with an electrolyte.
On the other hand, the above-mentioned conductive polymer layer is formed, for example, by electrolytic polymerization or vapor phase polymerization, whereas it is not easy to form the conductive polymer layer in the capacitor element of the rolled-up type by electrolytic polymerization or vapor phase polymerization. Although it appears feasible to form a chemical conversion coating and a conductive polymer layer on an anode foil first and to subsequently roll up the foil along with a cathode foil opposed to the anode foil, difficulty is encountered in rolling up the foils without causing damage to the chemical conversion coating or conductive polymer layer.
The conductive polymer layer can be formed alternatively by chemical polymerization in a liquid phase, whereas this process is conventionally low in work efficiency since it is necessary to repeat five to ten times the procedure of dipping the capacitor element in a chemical polymerization mixture, prepared by diluting with an organic solvent the monomer to be made into the conductive monomer by oxidation polymerization and adding an oxidizer to the solution, and drying the dipped element.
Accordingly, the present applicants developed a process for fabricating a solid electrolytic capacitor comprising a capacitor element including an anode member provided with a chemical conversion coating and an electrically conductive polymer serving as a cathode electrolyte and impregnating the capacitor element, the process having the steps of dissolving an oxidizer in a monomer to be made into the conductive polymer by oxidation polymerization to obtain a mixture and dipping the capacitor element in the mixture (JP-B No. 50558/1998). This process eliminated the need for the repetitions of dipping the capacitor element in the chemical polymerization mixture and the subsequent heat treatment, making it possible to obtain compact solid electrolytic capacitors of large capacity and low ESR by a simple procedure.
FIG. 7
shows the layout of production equipment for practicing the process proposed by the applicants for fabricating the solid electrolytic capacitor. With this equipment, a mixing station
5
and an impregnating station
6
are interconnected by a container conveyor
4
, and an element conveyor
3
is disposed along the container conveyor
4
. Containers
2
each having a plurality of solution cavities
20
are fed to the mixing station
5
, and the monomer to be made into the conductive polymer by oxidation polymerization and an oxidizer (dopant) are placed into the cavities
20
of each container
2
to mix the two solutions together and to thereby initiate the oxidation polymerization of the monomer. The container
2
containing the mixture is thereafter transported toward the impregnating station
6
by the container conveyor
4
.
On the other hand, a group
10
of capacitor elements connected to one another is transported by the element conveyor
3
toward the impregnating station
6
, at which the capacitor elements are dipped in the mixture in the respective cavities
20
of the container
2
.
Consequently, the capacitor elements are impregnated with the mixture of monomer and oxidizer, respectively. The capacitor elements are thereafter allowed to stand in air having a temperature of about 30° C. to about 50° C. and a humidity of at least 60% for about 30 minutes for the progress of polymerization reaction and further heat-treated in an oven having a temperature of about 160° C. for about 5 minutes for drying, whereby a polymer layer is formed over the chemical conversion coating on the anode member.
However, the solid electrolytic capacitors fabricated by the conventional process shown in
FIG. 7
have the problem that the electrical characteristics, such as ESR, vary from capacitor to capacitor, failing to provide the desired performance as the case may be.
SUMMARY OF THE INVENTION
Accordingly, the present applicants have conducted intensive research to overcome the above problem and consequently found that the mixture of monomer and oxidizer placed in the cavities of the container are not in the form of a uniform mixture at the impregnating station, and that the unevenness of the mixture exerts an influence on the properties of
Fuchigami Hidemi
Honda Nobuhiro
Yamada Kazuaki
Armstrong Westerman & Hattori, LLP
Nguyen Ha Tran
Sanyo Electric Co,. Ltd.
LandOfFree
Process and apparatus for fabricating solid electrolytic... 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 and apparatus for fabricating solid electrolytic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and apparatus for fabricating solid electrolytic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3025672