U.S. patent application number 12/665963 was filed with the patent office on 2010-07-22 for solid electrolytic capacitor.
This patent application is currently assigned to SANYO ELECTRIC CO., LTD.. Invention is credited to Kohei Goto, Kazuhiro Kato, Yuji Miyachi.
Application Number | 20100182736 12/665963 |
Document ID | / |
Family ID | 40225914 |
Filed Date | 2010-07-22 |
United States Patent
Application |
20100182736 |
Kind Code |
A1 |
Miyachi; Yuji ; et
al. |
July 22, 2010 |
SOLID ELECTROLYTIC CAPACITOR
Abstract
Provided is a solid electrolytic capacitor excellent in
reliability, particularly in ESR property. In a solid electrolytic
capacitor having a solid electrolyte layer, the solid electrolyte
layer has a conductive polymer layer formed by a chemical
polymerization method or an electrolytic polymerization method,
using a polymerization liquid containing at least a monomer and a
dopant-introducing agent. The dopant-introducing agent contains a
dopant-introducing agent containing at least alkylammonium ions as
a cationic component. The dopant-introducing agent in the
polymerization liquid may further contain a dopant-introducing
agent containing at least metal ions as a cationic component.
Inventors: |
Miyachi; Yuji; (Daito-shi,
JP) ; Goto; Kohei; (Daito-shi, JP) ; Kato;
Kazuhiro; (Daito-shi, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
SANYO ELECTRIC CO., LTD.
Moriguchi-shi, Osaka
JP
|
Family ID: |
40225914 |
Appl. No.: |
12/665963 |
Filed: |
April 24, 2008 |
PCT Filed: |
April 24, 2008 |
PCT NO: |
PCT/JP2008/057989 |
371 Date: |
December 22, 2009 |
Current U.S.
Class: |
361/525 |
Current CPC
Class: |
H01G 9/15 20130101; Y02E
60/13 20130101; H01G 9/028 20130101; H01G 9/0036 20130101; H01G
11/48 20130101 |
Class at
Publication: |
361/525 |
International
Class: |
H01G 9/025 20060101
H01G009/025; H01G 9/15 20060101 H01G009/15 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 2007 |
JP |
2007-173619 |
Jul 2, 2007 |
JP |
2007-173624 |
Claims
1. A solid electrolytic capacitor having a solid electrolyte layer,
wherein said solid electrolyte layer has a conductive polymer layer
formed by a chemical polymerization method and/or an electrolytic
polymerization method, using a polymerization liquid containing at
least a monomer and a dopant-introducing agent, and said
polymerization liquid contains the dopant-introducing agent
containing at least alkylammonium ions as a cationic component.
2. The solid electrolytic capacitor according to claim 1, wherein
said alkylammonium ions are primary ammonium ions.
3. The solid electrolytic capacitor according to claim 1, wherein
an alkyl group of said alkylammonium ion has a carbon number of 1
to 4.
4. The solid electrolytic capacitor according to claim 1, wherein
an anionic component of the dopant-introducing agent containing at
least the alkylammonium ions as said cationic component is aromatic
sulfonic acid ions.
5. The solid electrolytic capacitor according to claim 4, wherein
said aromatic sulfonic acid ions are tetralin sulfonic acid
ions.
6. The solid electrolytic capacitor according to claim 1, wherein
said polymerization liquid further contains a dopant-introducing
agent containing metal ions as a cationic component.
7. The solid electrolytic capacitor according to claim 6, wherein
an anionic component of the dopant-introducing agent containing at
least the metal ions as said cationic component is naphthalene
sulfonic acid ions or anions of a derivative thereof.
8. The solid electrolytic capacitor according to claim 1, wherein
said monomer is pyrrole or a derivative thereof.
Description
TECHNICAL FIELD
[0001] The present invention relates to a solid electrolytic
capacitor using a conductive polymer as a solid electrolyte
layer.
BACKGROUND ART
[0002] Recently, as electronic equipment is reduced in size and
weight, high-frequency capacitors with a lower impedance in a high
frequency region, a smaller size, and a larger capacity have been
required.
[0003] Although mica capacitors, film capacitors, ceramic
capacitors, and the like are used as high-frequency capacitors,
these capacitors are not suitable for large capacity
applications.
[0004] On the other hand, examples of capacitors suitable for large
capacity applications include aluminum electrolytic capacitors,
tantalum electrolytic capacitors, and the like. However, although
the aluminum electrolytic capacitor can achieve a large capacity
with low cost, it has problems such as temporal change due to
evaporation of an electrolytic solution as it uses the electrolytic
solution, high impedance in a high frequency region, and the
like.
[0005] The tantalum solid electrolytic capacitor is a capacitor
with less capacity degradation, as it uses solid manganese dioxide
as an electrolyte. However, since a coating film of manganese
dioxide has poor self-repairing ability, there are disadvantages
such as the risk of catching fire when a dielectric coating film is
damaged while electric power is being supplied.
[0006] Consequently, to solve the problems described above, it has
been proposed recently to use a conductive polymer that is
excellent in electric conductivity and easily forms a solid
electrolyte, as a solid electrolyte. With this technique, it has
become possible to obtain a solid electrolytic capacitor that can
be manufactured with less cost, ensures capacitance, and has no
damage in a dielectric coating film and less leakage current, when
compared with the solid electrolytic capacitor described above.
[0007] Herein, the conductive polymer refers to a polymer obtained
by polymerizing pyrrole, thiophene, furan, aniline, and the
like.
[0008] Such a solid electrolytic capacitor has also been required
to have a reduced ESR (Equivalent Series Resistance), a reduced LC
(Leakage Current), and the like to improve reliability.
[0009] To solve the problems as described above, methods of forming
a conductive polymer as a solid electrolyte layer, using an
electrolytic polymerization liquid prepared by mixing a plurality
of dopant-introducing agents having different properties, have been
proposed (for example, Patent Document 1).
Patent Document 1: Japanese Patent Laying-Open No. 2005-116777
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0010] However, reliability cannot be improved sufficiently even
with the methods described above, and in particular it has been
required to further reduce the ESR.
Means for Solving the Problems
[0011] To solve the problems described above, a first aspect of the
present invention is characterized in that, in a solid electrolytic
capacitor having a solid electrolyte layer, the solid electrolyte
layer has a conductive polymer layer formed by a chemical
polymerization method and/or an electrolytic polymerization method,
using a polymerization liquid containing at least a monomer and a
dopant-introducing agent, and that the polymerization liquid
contains the dopant-introducing agent containing at least
alkylammonium ions as a cationic component. The alkylammonium ions
are preferably primary ammonium ions, and an alkyl group preferably
has a carbon number of 1 to 4. Further, it is preferable that an
anionic component of the dopant-introducing agent containing at
least the alkylammonium ions as the cationic component is aromatic
sulfonic acid ions, in particular tetralin sulfonic acid ions.
[0012] Further, another aspect of the present invention is
characterized in that, in the polymerization liquid, the
dopant-introducing agent further contains a dopant-introducing
agent containing metal ions as a cationic component. An anionic
component of the dopant-introducing agent is preferably naphthalene
sulfonic acid ions or anions of a derivative thereof.
EFFECTS OF THE INVENTION
[0013] With a configuration of the present invention, a solid
electrolytic capacitor excellent in reliability, particularly in
ESR property, can be provided.
BEST MODES FOR CARRYING OUT THE INVENTION
[0014] Best modes for carrying out the present invention will be
described below.
Embodiment 1
[0015] FIG. 1 is a front sectional view of a solid electrolytic
capacitor of the present invention. A capacitor element 8 is formed
by sequentially forming a dielectric coating film layer 2, a solid
electrolyte layer 3, a conductive carbon layer 4, and a silver
paste layer 5 on a peripheral surface of an anode body 1 provided
with an anode lead 10.
[0016] Specifically, capacitor element 8 is formed by forming
dielectric coating film layer 2 using an acid such as phosphoric
acid, adipic acid, or the like, on the peripheral surface of anode
body 1 made of a valve metal provided with anode lead 10 made of a
valve metal, and forming solid electrolyte layer 3 on a peripheral
surface of dielectric coating film layer 2. Preferably, anode lead
10 and anode body 1 are made of the same valve metal.
[0017] Herein, solid electrolyte layer 3 includes a conductive
polymer layer formed using a dopant-introducing agent containing
alkylammonium ions as a cationic component. The conductive polymer
layer is formed, for example, by using a heterocyclic compound such
as thiophene or pyrrole and/or a derivative thereof, or aniline
and/or a derivative thereof, as a monomer, and forming the
conductive polymer layer by a chemical polymerization method using
a polymerization liquid containing the monomer, an oxidant, and a
dopant-introducing agent, or by an electrolytic polymerization
method using a polymerization liquid containing the monomer and a
dopant-introducing agent. Preferably, pyrrole or a derivative
thereof is used as the monomer. Various additives may be added to
the polymerization liquid.
[0018] The alkylammonium ions as the cationic component of the
dopant-introducing agent refer to alkylammonium ions in which at
least one of hydrogen groups of an ammonium ion is substituted with
an alkyl group. Preferably, the alkyl group has a carbon number of
1 to 4. If the alkyl group has a carbon number of 5 or more, the
effect of reducing the ESR may not be obtained. The alkyl group
used herein also includes an alkyl group in which a portion or all
of hydrogen groups of the alkyl group are substituted with other
functional groups, and may be, for example, an alkoxy alkyl group,
a hydroxy alkyl group, or the like.
[0019] An anionic component of the dopant-introducing agent is not
particularly limited, and can be arbitrarily selected from
well-known ones. As the anionic component, aromatic sulfonic acid
ions, in particular tetralin sulfonic acid ions, are preferable.
The aromatic sulfonic acid ions and the tetralin sulfonic acid ions
also include those in which a portion of hydrogen groups attached
to an aromatic ring or a tetralin ring is substituted with a
functional group such as an alkyl group.
[0020] On a peripheral surface of solid electrolyte layer 3 formed
as described above, conductive carbon layer 4 and silver paste
layer 5 are sequentially formed using a well-known method, and thus
capacitor element 8 is produced.
[0021] Anode lead 10 of capacitor element 8 is connected with an
anode lead frame 20, and silver paste layer 5 is connected with a
cathode lead frame 21. Molding is performed to coat capacitor
element 8 with an outer packaging resin 7, except for portions of
anode lead frame 20 and cathode lead frame 21. The portions of
anode lead frame 20 and cathode lead frame 21 exposed from outer
packaging resin 7 are bent to follow outer packaging resin 7, and
thus the solid electrolytic capacitor of the present invention is
produced.
Embodiment 2
[0022] A solid electrolytic capacitor of Embodiment 2 of the
present invention will be described below. The solid electrolytic
capacitor of Embodiment 2 of the present invention also has the
structure shown in FIG. 1, as in the solid electrolytic capacitor
of Embodiment 1. Solid electrolyte layer 3 of Embodiment 2 also
includes a conductive polymer layer, as in Embodiment 1. A method
of forming the conductive polymer layer is identical to the method
in Embodiment 1.
[0023] A dopant-introducing agent used in forming the conductive
polymer layer of Embodiment 2 is made of a plurality of materials,
and contains at least a dopant-introducing agent containing
alkylammonium ions as a cationic component and a dopant-introducing
agent containing metal ions as a cationic component. Herein, the
alkylammonium ions refer to those in which at least one of hydrogen
groups of an ammonium ion is substituted with an alkyl group. The
alkyl group also includes an alkyl group in which a portion or all
of hydrogen groups thereof are substituted with other functional
groups.
[0024] An anionic component of the dopant-introducing agent
containing the alkylammonium ions as the cationic component is
preferably aromatic sulfonic acid ions, in particular, tetralin
sulfonic acid ions. The tetralin sulfonic acid ions according to
the present invention also include those in which a portion of
hydrogen groups attached to a tetralin ring is substituted with
another functional group. When tetralin sulfonic acid alkylamine is
used as a dopant-introducing agent, a solid electrolytic capacitor
formed using it exhibits excellent ESR property.
[0025] Further, an anionic component of the dopant-introducing
agent containing the metal ions as the cationic component is
preferably naphthalene sulfonic acid ions. When naphthalene
sulfonic acid metal salt is taken into the conductive polymer layer
as a dopant-introducing agent, the conductive polymer layer
exhibits excellent heat resistance. Therefore, a solid electrolytic
capacitor having less change in ESR before and after reflow and
excellent heat resistance can be provided. Herein, the naphthalene
sulfonic acid ions of the present invention also include those in
which a portion of hydrogen groups attached to a naphthalene ring
is substituted with another functional group.
[0026] A mole ratio of the dopant-introducing agent containing the
metal ions as the cationic component to the dopant-introducing
agent containing the alkylammonium ions as the cationic component
is preferably 1/3 or less. If the dopant containing the metal ions
as the cationic component is increased more than this ratio, the
effect of reducing the ESR in the solid electrolytic capacitor is
deteriorated. More preferably, the mole ratio of the
dopant-introducing agent containing the metal ions as the cationic
component to the dopant-introducing agent containing the
alkylammonium ions as the cationic component is 1 to 4. A solid
electrolytic capacitor produced using this ratio is excellent in
ESR property.
[0027] On a peripheral surface of solid electrolyte layer 3
produced using the materials described above, conductive carbon
layer 4 and silver paste layer 5 are formed by a conventionally
well-known method, and thus capacitor element 8 is produced.
[0028] Anode lead 10 of capacitor element 8 produced as described
above is connected with anode lead frame 20, and silver paste layer
5 is connected with cathode lead frame 21. Then, capacitor element
8 is coated with outer packaging resin 7, with portions of anode
and cathode lead frames 20 and 21 being exposed. Anode and cathode
lead frames 20 and 21 exposed from outer packaging resin 7 are bent
to follow outer packaging resin 7, and thus the solid electrolytic
capacitor is completed.
EXAMPLES
[0029] Embodiment 1 of the present invention was studied as
described below.
Example 1
[0030] On a peripheral surface of an anode body made of a valve
metal provided with an anode lead, a dielectric coating film layer
was formed by a conventionally well-known method. Subsequently, a
solid electrolyte layer was formed. Specifically, a conductive
pre-coat layer was formed on a surface of the dielectric coating
film layer by a conventionally well-known method, and then
electrolytic polymerization was performed using the conductive
pre-coat layer as an anode, using a polymerization liquid
containing pyrrole (0.2 mol/l) as a monomer and tetralin sulfonic
acid methylamine (0.1 mol/l) as a dopant-introducing agent, to form
a conductive polymer layer.
[0031] Thereafter, a conductive carbon layer and a silver paste
layer were formed on a peripheral surface of the solid electrolyte
layer by a conventionally well-known method, and thus a capacitor
element was produced.
[0032] After producing the capacitor element, the anode lead was
connected with an anode lead frame by resistance welding or the
like, and the silver paste layer was connected with a cathode lead
frame, with a conductive paste or the like being interposed
therebetween. The capacitor element was coated with an outer
packaging resin such that portions of the anode lead frame and the
cathode lead frame were exposed. The exposed anode and cathode lead
frames were bent to follow the outer packaging resin, and thereby a
solid electrolytic capacitor was completed.
Example 2
[0033] A solid electrolytic capacitor was produced as in Example 1
except for using tetralin sulfonic acid ethylamine (0.1 mol/l) as a
dopant-introducing agent.
Example 3
[0034] A solid electrolytic capacitor was produced as in Example 1
except for using tetralin sulfonic acid ethoxypropylamine (0.1
mol/l) as a dopant-introducing agent.
Example 4
[0035] A solid electrolytic capacitor was produced as in Example 1
except for using tetralin sulfonic acid butylamine (0.1 mol/l) as a
dopant-introducing agent.
Example 5
[0036] A solid electrolytic capacitor was produced as in Example 1
except for using tetralin sulfonic acid diisopropylamine (0.1
mol/l) as a dopant-introducing agent.
Example 6
[0037] A solid electrolytic capacitor was produced as in Example 1
except for using tetralin sulfonic acid dipropylamine (0.1 mol/l)
as a dopant-introducing agent.
Example 7
[0038] A solid electrolytic capacitor was produced as in Example 1
except for using tetralin sulfonic acid triethylamine (0.1 mol/l)
as a dopant-introducing agent.
Comparative Example 1
[0039] A solid electrolytic capacitor was produced as in Example 1
except for using tetralin sulfonic acid sodium (0.1 mol/l) as a
dopant-introducing agent.
[0040] ESRs of the solid electrolytic capacitors of Examples 1 to 7
and Comparative Example 1 described above were measured. Table 1
shows the results.
TABLE-US-00001 TABLE 1 ESR [m.OMEGA.] Example 1 9.6 Example 2 9.7
Example 3 10.7 Example 4 11.2 Example 5 9.6 Example 6 10.4 Example
7 10.7 Comparative 11.7 Example 1
[0041] As can be seen from Table 1, in the solid electrolytic
capacitors in which a cationic component of the dopant-introducing
agent is alkylammonium ions (Examples 1 to 7), the ESRs are
suppressed low, when compared with that of the solid electrolytic
capacitor in which a cationic component of the dopant-introducing
agent is metal ions (Comparative Example 1). It can also be seen
that a lower amino group with a shorter chain length has a greater
effect of reducing the ESR. Further, it is found as a result of
comparing Examples 1 to 4 that, among primary amines, a primary
amine having an alkyl group with a smaller carbon number (i.e.,
shorter chain length) has a greater effect of reducing the ESR.
Although the reason for this is not known, conceivably it is
because, when an alkyl group has a longer chain length, a molecule
becomes bulky, stable and highly dispersed micelles cannot be
formed, and effective doping cannot be performed, and thereby the
effect of reducing the ESR is less likely to be obtained.
[0042] Next, Embodiment 2 of the present invention was studied as
described below.
Example 8
[0043] On a peripheral surface of an anode body provided with an
anode lead, a dielectric oxide coating film layer was formed by a
conventionally well-known method. Subsequently, a conductive
pre-coat layer was formed by a chemical polymerization method, and
then a capacitor element having the formed conductive pre-coat
layer was immersed in an electrolytic polymerization liquid
containing at least pyrrole (0.2 mol/l) as a monomer, tetralin
sulfonic acid methylamine as a dopant-introducing agent containing
alkylammonium ions as a cationic component, and alkylnaphthalene
sulfonic acid sodium as a dopant-introducing agent containing metal
ions as a cationic component, with concentrations of the
dopant-introducing agents being adjusted such that a mole ratio of
tetralin sulfonic acid methylamine to alkylnaphthalene sulfonic
acid sodium was set to 4 to 1, and a total of 0.1 mol/l of the
dopant-introducing agents was contained. Subsequently, electrolytic
polymerization was performed using the conductive pre-coat layer as
an anode, to form a conductive polymer layer. Thereafter, a solid
electrolytic capacitor was produced as in Example 1.
Example 9
[0044] A solid electrolytic capacitor was produced as in Example 8
except for using tetralin sulfonic acid ethylamine instead of
tetralin sulfonic acid methylamine.
Example 10
[0045] A solid electrolytic capacitor was produced as in Example 8
except for using tetralin sulfonic acid ethoxypropylamine instead
of tetralin sulfonic acid methylamine.
Example 11
[0046] A solid electrolytic capacitor was produced as in Example 10
except for adjusting such that a mole ratio of tetralin sulfonic
acid ethoxypropylamine to alkylnaphthalene sulfonic acid sodium was
set to 2 to 1, and a total of 0.1 mol/l of the dopant-introducing
agents was contained.
Comparative Example 2
[0047] A solid electrolytic capacitor was produced as in Example 8
except for using tetralin sulfonic acid sodium instead of tetralin
sulfonic acid methylamine.
Comparative Example 3
[0048] A solid electrolytic capacitor was produced as in Example 11
except for using tetralin sulfonic acid sodium instead of tetralin
sulfonic acid ethoxypropylamine.
[0049] ESRs of the solid electrolytic capacitors of Examples 8 to
11 and Comparative Examples 2 and 3 described above were measured.
Table 2 shows the results.
TABLE-US-00002 TABLE 2 ESR [m.OMEGA.] Example 8 11.4 Example 9 11.3
Example 10 11.1 Example 11 10.6 Example 12 11.0 Comparative 11.8
Example 2 Comparative 11.7 Example 3
[0050] As can be seen from Table 2, in the solid electrolytic
capacitors in Examples 8 to 11 in which alkylammonium ions are
contained as a cationic component of the dopant-introducing agent,
the ESRs are suppressed low, when compared with those of
Comparative Examples 2 and 3 in which only a dopant-introducing
agent containing metal ions as a cationic component is used.
[0051] Further, it is found as a result of comparing Examples 10
and 11 that the ESR can be suppressed lower when a ratio of mixing
the dopant-introducing agents is adjusted such that a mole ratio of
the dopant-introducing agent containing the alkylammonium ions as
the cationic component to the dopant-introducing agent containing
the metal ions as the cationic component is set to 4 to 1, which is
a desired ratio of mixing the dopant-introducing agents.
[0052] The examples described above are merely provided to describe
the present invention, and should not be interpreted as restricting
the invention described in the scope of claims. The present
invention can be freely modified within the scope of claims and
within the scope having equivalent meaning.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 is a front sectional view of a solid electrolytic
capacitor of the present invention.
DESCRIPTION OF THE REFERENCE SIGNS
[0054] 1 anode body [0055] 2 dielectric coating film layer [0056] 3
solid electrolyte layer [0057] 4 conductive carbon layer [0058] 5
silver paste layer [0059] 7 outer packaging resin [0060] 8
capacitor element [0061] 10 anode lead [0062] 20 anode lead frame
[0063] 21 cathode lead frame
* * * * *