U.S. patent application number 15/094201 was filed with the patent office on 2016-08-04 for conductive polymer composition with a dual crosslinker system for capacitors.
This patent application is currently assigned to Kemet Electronics Corporation. The applicant listed for this patent is Kemet Electronics Corporation. Invention is credited to Antony P. Chacko, Yaru Shi, Edgar White.
Application Number | 20160225532 15/094201 |
Document ID | / |
Family ID | 52390342 |
Filed Date | 2016-08-04 |
United States Patent
Application |
20160225532 |
Kind Code |
A1 |
Shi; Yaru ; et al. |
August 4, 2016 |
Conductive Polymer Composition with a Dual Crosslinker System for
Capacitors
Abstract
A capacitor with improved electronic properties is described.
The capacitor has an anode, a dielectric on said anode and a
cathode on the dielectric. The cathode has a conductive polymer
defined as --(CR.sup.1R.sup.2CR.sup.3R.sup.4--).sub.x-- wherein at
least one of R.sup.1, R.sup.2, R.sup.3 or R.sup.4 comprises a group
selected from thiophene, pyrrole or aniline with the proviso that
none of R.sup.1, R.sup.2, R.sup.3 or R.sup.4 contain --SOOH or
COOH; a organofunctional silane; and an organic compound with at
least two functional groups selected from the group consisting of
carboxylic acid and epoxy.
Inventors: |
Shi; Yaru; (Simpsonville,
SC) ; Chacko; Antony P.; (Simpsonville, SC) ;
White; Edgar; (Simpsonville, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kemet Electronics Corporation |
Simpsonville |
SC |
US |
|
|
Assignee: |
Kemet Electronics
Corporation
|
Family ID: |
52390342 |
Appl. No.: |
15/094201 |
Filed: |
April 8, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14339200 |
Jul 23, 2014 |
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15094201 |
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61857878 |
Jul 24, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 2261/3223 20130101;
C09D 165/00 20130101; C09D 165/00 20130101; H01G 9/0036 20130101;
H01G 9/028 20130101; C08G 2261/794 20130101; H01G 9/0425 20130101;
H01G 9/15 20130101; C08G 2261/135 20130101; C08G 2261/76 20130101;
C08G 2261/1424 20130101; H01B 1/127 20130101; C08G 2261/51
20130101; C08L 25/18 20130101; C08K 5/5435 20130101 |
International
Class: |
H01G 9/042 20060101
H01G009/042; H01G 9/00 20060101 H01G009/00; H01B 1/12 20060101
H01B001/12; H01G 9/15 20060101 H01G009/15 |
Claims
1-32. (canceled)
33. A conductive polymer dispersion comprising a solvent, a
conductive polymer, an organic silane and an organic compound with
two or more functional groups selected from the group consisting of
epoxy and carboxylic acid.
34. The conductive polymer dispersion of claim 33 wherein said
conductive polymer is defined as
--(CR.sup.1R.sup.2CR.sup.3R.sup.4--).sub.x-- wherein at least one
of R.sup.1, R.sup.2, R.sup.3 or R.sup.4 comprises a group selected
from thiophene, pyrrole or aniline with the proviso that none of
R.sup.1, R.sup.2, R.sup.3 or R.sup.4 contain --SOOH or COOH.
35. The conductive polymer dispersion of claim 34 wherein said
conductive polymer is poly(3,4-ethylenedioxythiophene).
36. The conductive polymer dispersion of claim 33 comprising
0.0005-0.1 grams of said organofunctional silane per gram of said
conductive polymer dispersion.
37. The conductive polymer dispersion of claim 33 comprising
0.001-0.1 grams of said organic compound per gram of said
conductive polymer dispersion.
38. The conductive polymer dispersion of claim 33 further
comprising a dopant.
39. The conductive polymer dispersion of claim 38 wherein said
dopant comprises a polyanion.
40. The conductive polymer dispersion of claim 39 wherein said
polyanion is polystyrene sulfonic acid.
41. The conductive polymer dispersion of claim 38 wherein said
dopant is present in an amount of 0.05-0.3 grams per gram of said
conductive polymer.
42. The conductive polymer dispersion of claim 33 wherein said
organic silane is a glycidyl silane defined by the formula:
##STR00007## wherein R.sub.1 is an alkyl of 1 to 14; and each
R.sub.2 is independently an alkyl of 1 to 6 carbons.
43. The conductive polymer dispersion of claim 42 wherein R.sub.1
is selected from the group consisting of methyl, ethyl and
propyl.
44. The conductive polymer dispersion of claim 42 wherein said
glycidyl silane is: ##STR00008##
45. The conductive polymer dispersion of claim 33 wherein said
organofunctional silane is defined by the formula:
XR.sub.1Si(R.sub.3).sub.3-n(R.sub.2).sub.n wherein X is an organic
functional group selected from amino, epoxy, anhydride, hydroxy,
mercapto, sulfonate, carboxylate, phosphonate, halogen, vinyl,
methacryloxy, ester and alkyl; R.sub.1 is an aryl or
(CH.sub.2).sub.m wherein m can be 0 to 14; R.sub.2 is individually
a hydrolysable functional group; R.sub.3 is individually an alkyl
functional group of 1-6 carbons; and n is 1 to 3.
46. The conductive polymer dispersion of claim 45 wherein said
hydrolysable functional group is selected from the group selected
from alkoxy, acyloxy, halogen and amine.
47. The conductive polymer dispersion of claim 33 wherein said
organofunctional silane is defined by the formula:
Y(Si(R.sub.3).sub.3-n(R.sub.2)O.sub.2 wherein Y is any organic
moiety that contains reactive or nonreactive functional groups such
as alkyl, aryl, sulfide or melamine; R.sub.2 is individually a
hydrolysable functional group; R.sub.3 is individually an alkyl
functional group of 1-6 carbons; and n is 1 to 3.
48. The conductive polymer dispersion of claim 33 wherein said
organofunctional silane is selected from the group consisting of:
3-glycidoxypropyltrimethoxysilane, 3-aminopropytriethoxysilane,
aminopropylsilanetriol, (triethoxysilyl)propylsuccinic anhydride,
3-mercaptoprpyltrimethoxysilane, vinyltrimethoxysilane,
3-metacryloxypropyltrimethoxysilane, 3-trihydroxysilyl-1-propane
sulfonic acid and octyltriethyoxysilane.
49. The conductive polymer dispersion of claim 33 wherein said
epoxy crosslinking compound comprises at least two epoxy
groups.
50. The conductive polymer dispersion of claim 49 wherein said
epoxy crosslinking compound is defined by the formula: ##STR00009##
wherein the X is an alkyl or substituted alkyl of 0-14 carbons, an
aryl or substituted aryl, an ethylene ether or substituted ethylene
ether, polyethylene ether or substituted polyethylene ether with
2-20 ethylene ether groups or combinations thereof.
51. The conductive polymer dispersion of claim 50 wherein said
substitute is an epoxy group.
52. The conductive polymer dispersion of claim 50 wherein alkyl or
substituted alkyl has 0-6 carbons.
53. The conductive polymer dispersion of claim 50 wherein said
epoxy crosslinking is selected from the group consisting of:
ethylene glycol diglycidyl ether, propylene glycol diglycidyl
ether, 1,4-butanediol diglycidyl ether, pentylene glycol diglycidyl
ether, hexylene glycol diglycidyl ether, cyclohexane dimethanol
diglycidyl ether, resorcinol glycidyl ether, glycerol diglycidyl
ether, glycerol polyglycidyl ethers, diglycerol polyglycidyl
ethers, trimethylolpropane polyglycidyl ethers, sorbitol diglycidyl
ether (Sorbitol-DGE), sorbitol polyglycidyl ethers, polyethylene
glycol diglycidyl ether, polypropylene glycol diglycidyl ether,
polytetramethylene glycol diglycidyl ether, di(2,3-epoxypropyl)
ether, 1,3-butadiene diepoxide, 1,5-hexadiene diepoxide,
1,2,7,8-diepoxyoctane, 1,2,5,6-Diepoxycyclooctane, 4-vinyl
cyclohexene diepoxide, bisphenol A diglycidyl ether and an
maleimide-epoxy compound.
54. The conductive polymer dispersion of claim 33 wherein said
epoxy crosslinking compound is a glycidyl ether.
55. The conductive polymer dispersion of claim 54 wherein said
glycidyl ether is defined by the formula: ##STR00010## wherein
R.sub.3 is an alkyl or substituted alkyl of 1-14 carbons or an
ethylene ether.
56. The conductive polymer dispersion of claim 55 wherein said
R.sub.3 is an alkyl or substituted alkyl of 2-6 carbons.
57. The conductive polymer dispersion of claim 55 wherein said
R.sub.3 is a polyethylene ether.
58. The conductive polymer dispersion of claim 57 wherein said
polyethylene ether has 1-220 ethylene ether groups.
59. The conductive polymer dispersion of claim 54 wherein said
R.sub.3 is an alkyl substituted with a group selected from hydroxy,
##STR00011## and --(CH.sub.2OH).sub.xCH.sub.2OH wherein X is 1 to
14.
60. The conductive polymer dispersion of claim 54 wherein said
glycidyl ether is selected from the group consisting of:
##STR00012##
61. The conductive polymer dispersion of claim 33 further wherein
comprises an carboxylic acid.
62. The conductive polymer dispersion of claim 61 wherein said
carboxylic acid is an aromatic acid.
63. The conductive polymer dispersion of claim 62 further wherein
said aromatic acid is selected from the group consisting of
phthalic acid and benzoic acid.
64. The conductive polymer dispersion of claim 33 wherein said
organic compound is a carboxylic crosslinking compound with two or
more carboxylic acid groups.
65. The conductive polymer dispersion of claim 64 wherein said
carboxylic crosslinking compound is aromatic acid with carboxylic
groups.
66. The conductive polymer dispersion of claim 65 wherein said
carboxylic crosslinking compound is selected from the group
consisting of: oxalic acid, malonic acid, succinic acid, glutaric
acid, adipic acid, pimelic acid, suberic acid, azelaic acid,
sebacic acid, dodecanedioic acid, phthalic acids, maleic acid,
muconic acid, citric acid, trimesic acid and polyacrylic acid.
67-104. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims priority to pending U.S.
Provisional Patent Application No. 61/857,878 filed Jul. 24,
2013.
BACKGROUND
[0002] The present invention is related to an improved
polymerization method for preparing solid electrolytic capacitors.
More specifically, the present invention is related to an improved
method of forming a solid electrolyte capacitor and an improved
capacitor formed thereby. Even more specifically, the present
invention is related to a capacitor comprising improved
crosslinking within the conductive polymeric cathode layer thereby
improving adhesion as evidenced by improved ESR and ESR
stability.
[0003] Electroconductive polymers are widely used in capacitors,
solar cells and LED displays. The electroconductive polymers
include polypyrrole, polythiophene and polyaniline. Among them, the
most commercially successful conductive polymer is
poly(3,4-ethylenedioxy thiophene) (PEDOT). One way to apply PEDOT
is by forming the PEDOT polymer via in-situ chemical or
electrochemical polymerization. The other way is to use it as a
PEDOT dispersion preferably with a polyanion, which has much better
solubility than PEDOT itself. More particularly, PEDOT-polystyrene
sulfonic acid (PEDOT-PSSA) dispersion has gained a lot of attention
due to its high conductivity and good film forming property.
[0004] Today, almost all electronic components are mounted to the
surface of circuit boards by means of infra-red (IR) or convection
heating of both the board and the components to temperatures
sufficient to reflow the solder paste applied between copper pads
on the circuit board and the solderable terminations of the surface
mount technology (SMT) components. A consequence of surface-mount
technology is that each SMT component on the circuit board is
exposed to soldering temperatures that commonly dwell above
180.degree. C. for close to a minute, typically exceeding
230.degree. C., and often peaking above 250.degree. C. If the
materials used in the construction of capacitors are vulnerable to
such high temperatures, it is not unusual to see significant
positive shifts in ESR leading to negative shifts in circuit
performance. SMT reflow soldering is a significant driving force
behind the need for capacitors having temperature-stable ESR.
[0005] Equivalent Series Resistance (ESR) stability of the
capacitors requires that the interface between the cathode layer,
cathodic conductive layers, conductive adhesive, and leadframe have
good mechanical integrity during thermo mechanical stresses. Solid
electrolytic capacitors are subject to various thermomechanical
stresses during assembly, molding, board mount reflow, etc. During
board mount the capacitors are often subjected to temperatures
above 250.degree. C. These elevated temperatures create stresses in
the interfaces due to coefficient of thermal expansion (CTE)
mismatches between adjacent layers. The resultant stress causes
mechanical weakening at the interfaces. In some cases this
mechanical weakening causes delamination. Any physical separation
of the interfaces causes increases in electrical resistance between
the layers and thus an increased ESR in the finished capacitor.
[0006] PEDOT-PSSA polymer film often does not have enough
mechanical strength or sufficient adhesion to the underlying
surface. In capacitors, poor film quality and adhesion results in
poor ESR or poor ESR stability under processing conditions.
Polymeric binders can be added to enhance the mechanical properties
of the PEDT-PSSA film and adhesion to the anode. In U.S. Pat. No.
6,987,663, which is incorporated herein by reference, the
conductive polymer coating included at least one polymeric organic
binder. In U.S. Pat. No. 7,990,684, which is incorporated herein by
reference, the conductive polymer coating contains a Novolak
polymer resin and a sulfonated polyester as binders.
[0007] The polymer binder may be formed "in situ" during the drying
step as described in U.S. Published Patent Application
2012/0256117, which is incorporated herein by reference, wherein
described is a polymer dispersion of PEDOT-PSSA comprising a
polyhydric alcohol and an organic substance having two or more
functional groups which can be polycondensed with the polyhyric
alcohol to form a polymer binder "in situ".
[0008] Another problem associated with PEDOT-Polyanion, especially
PEDOT-PSSA conductive polymer film is the hydroscopic property of
the polyanions. Polyanions readily absorb water during the
capacitor processing steps (for example, dipping coating cycles) or
moisture from the environment, and resulted in swelling of the
conductive polymer film. The swollen conductive film is typically
subjected to drying steps later on. The swelling/shrinking cycles
often cause the conductive polymer film to delaminate from the
substrate. In capacitor application, it is manifested as
deteriorated performance such as positive ESR shift.
[0009] EP 0844284, which is incorporated herein by reference,
describes a conductive polymer self-doped by --SOOH and/or --COOH
functional groups wherein the self-doping groups are on the
conductive polymer structure. An advantage of using self-doped
conductive polymer over external doped polymer as in the case of
PEDT-polyanion dispersion, is the elimination of polyanions which
are detrimental to moisture resistance. Still, these self-doped
polymer films have poor water or solvent resisting properties. The
conductive polymer film's water resistance property can be improved
by reacting the self doping groups --SOOH or --COOH with a
crosslinking compound having 2 or more functional groups such as a
hydroxyl, a silanol, a thiol, an amino or an epoxy group.
[0010] For more hydroscopic externally doped PEDOT-PSSA, U.S.
Published Patent Application 2010/0091432, which is incorporated
herein by reference, described the use of organic substance with a
mono epoxy group in PEDOT-PSSA to improve its water resistance. In
comparison, an epoxy compound having multiple epoxy groups in the
conductive polymer composition resulted in inferior water
resistance property and higher ESR.
[0011] In spite of the ongoing efforts there is still a significant
problem associated with coating stability in electrolytic
capacitors utilizing conductive polymer cathodes. Further advances
in the art are provided herein.
SUMMARY
[0012] It is an object of the invention to provide an improved
capacitor.
[0013] A particular feature of the invention is a capacitor with
lower ESR and improved ESR stability, particularly, after
heating.
[0014] These and other advantages, as will be realized, are
provided in a capacitor. The capacitor has an anode, a dielectric
on said anode and a cathode on the dielectric. The cathode has a
conductive polymer defined as
--(CR.sup.1R.sup.2CR.sup.3R.sup.4--).sub.x-- wherein at least one
of R.sup.1, R.sup.2, R.sup.3 or R.sup.4 comprises a group selected
from thiophene, pyrrole or aniline with the proviso that none of
R.sup.1, R.sup.2, R.sup.3 or R.sup.4 contain --SOOH or COOH; a
organofunctional silane; and an organic compound with at least two
functional groups selected from the group consisting of carboxylic
acid and epoxy.
[0015] Yet another embodiment is provided in a conductive polymer
dispersion comprising a solvent, a conductive polymer, an
organofunctional silane and an organic compound with two or more
functional groups selected from the group consisting of epoxy and
carboxylic acid.
[0016] Yet another embodiment is provided in a method for preparing
a capacitor comprising:
forming an anode; forming a dielectric on the anode; and forming a
cathode on the dielectric comprising: forming a conductive layer
comprising: a conductive polymer defined as
--(CR.sup.1R.sup.2CR.sup.3R.sup.4--).sub.x-- wherein at least one
of R.sup.1, R.sup.2, R.sup.3 or R.sup.4 comprises a group selected
from thiophene, pyrrole or aniline with the proviso that none of
R.sup.1, R.sup.2, R.sup.3 or R.sup.4 contain --SOOH or COOH; an
organofunctional silane; and an organic compound with two or more
functional groups selected from the group consisting of epoxy and
carboxylic acid.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a schematic cross-sectional view of an embodiment
of the invention.
[0018] FIG. 2 is a schematic partial cross-sectional view of an
embodiment of the invention.
[0019] FIG. 3 is a flow chart representation of an embodiment of
the invention.
DESCRIPTION
[0020] The present invention is directed to a dual crosslinker
system including the combination of two crosslinking agents, an
organofunctional silane and an organic compound with at least two
functional groups selected from the group consisting of epoxy and
carboxylic acid which provides a surprising synergy when compared
with single crosslinker systems. In addition, by using this dual
crosslinker system, polymeric organic binders can be avoided in
some embodiments, while still achieving lower ESR and improved ESR
stability.
[0021] The invention will be described with reference to the
various figures forming an integral non-limiting component of the
disclosure. Throughout the disclosure similar elements will be
numbered accordingly.
[0022] An embodiment of the invention is illustrated in
cross-sectional schematic side view in FIG. 1. In FIG. 1, a
capacitor, generally represented at 10, comprises an anode, 12,
with an anode lead wire, 14, extending therefrom or attached
thereto. The anode lead wire is preferably in electrical contact
with an anode lead, 16. A dielectric, 18, is formed on the anode
and preferably the dielectric encases at least a portion, and
preferably the entire, anode. A cathode, 20, is on the dielectric
and encases a portion of the dielectric with the proviso that the
cathode and anode are not in direct electrical contact. A cathode
lead, 22, is in electrical contact with the cathode. In many
embodiments it is preferred to encase the capacitor in a
non-conductive resin, 24, with at least a portion of the anode lead
and cathode lead exposed for attachment to a circuit board as would
be readily understood by one of skill in the art. The cathode may
comprise multiple sub-layers. The present invention is directed to
improvements in the cathode layer, 20, and more particularly to the
formation of the cathode layer.
[0023] An embodiment of the invention is illustrated in partial
cross-sectional schematic view in FIG. 2. In FIG. 2, the cathode,
20, comprises multiple interlayers, 201-204, which are illustrated
schematically, wherein the cathode is formed on the dielectric, 18.
While not limited thereto the cathode interlayers are preferably
selected from layers of conductive polymer, carbon containing
layers and metal containing layers most preferably in sequential
order. In a particularly preferred embodiment a first interlayer,
201, is at least one conductive polymer layer formed either by
in-situ polymerization or by repeated dipping in a slurry of
conductive polymer with at least partial drying between dips. It is
well understood that soldering a lead frame, or external
termination, to a polymeric cathode is difficult. It has therefore
become standard in the art to provide conductive interlayers which
allow for solder adhesion. A second interlayer, 202, which is
preferably at least one carbon interlayer, is typically applied to
the conductive polymer interlayer, 201. The carbon interlayer, or
series of carbon interlayers, provides adhesion to the conductive
polymer interlayer and provides a layer upon which a third
interlayer, which is preferably at least one metal containing
interlayer, 203, will adequately adhere. Particularly preferred
metal containing layers comprise silver, copper or nickel. The
metal interlayer allows external terminations, such as a cathode
lead to be attached to the cathodic side of the capacitor such as
by solder or an adhesive interlayer, 204.
[0024] An embodiment of the invention is illustrated in flow chart
form in FIG. 3. In FIG. 3, the method of forming a solid
electrolytic capacitor of the instant invention is illustrated. In
FIG. 3, an anode is provided at 32. A dielectric is formed on the
surface of the anode at 34 with a particularly preferred dielectric
being the oxide of the anode. A cathode layer is formed at 36
wherein the cathode comprises multiple interlayers. Interlayers may
include at least one conducting polymer layer wherein the
intrinsically conducting polymer is either formed in-situ or the
layer is formed by coating with a slurry comprising intrinsically
conducting polymer. The interlayers also preferably comprise at
least one carbon containing layer and at least one metal containing
layer. Anode and cathode leads are attached to the anode and
cathode respectively at 38 and the capacitor is optionally, but
preferably, encased at 40 and tested.
[0025] The conductive polymer layer may be formed in a single step
wherein a slurry is applied comprising at least the conductive
polymer and optionally the crosslinkers, and any adjuvants such as
binder, dopant, organic acid and the like. Alternatively, the
conductive polymer layer may be formed in multiple steps wherein
components of the layer are applied separately. In one embodiment a
conductive polymer layer is coated after coating one or both
crosslinkers. In another embodiment the conductive polymer is
applied in concert with a first crosslinker followed by application
of the second crosslinker. Separating the components and applying
them sequentially instead of in concert is beneficial in some
embodiments since the mixture of conductive polymer and
crosslinkers may react prematurely thereby decreasing the pot-life
of the slurry. In a particularly preferred embodiment the
conductive polymer and glycidyl silane are in one slurry with the
second crosslinker, such as glycidyl ether, applied separately and
preferably after application of slurry containing the conductive
polymer.
[0026] The anode is a conductor preferably selected from a metal or
a conductive metal oxide. More preferably the anode comprises a
mixture, alloy or conductive oxide of a valve metal preferably
selected from Al, W, Ta, Nb, Ti, Zr and Hf. Most preferably the
anode comprises at least one material selected from the group
consisting of Al, Ta, Nb and NbO. An anode consisting essentially
of Ta is most preferred. Conductive polymeric materials may be
employed as an anode material. Particularly preferred conductive
polymers include polypyrrole, polyaniline and polythiophene.
[0027] The cathode is a conductor preferably comprising a
conductive polymeric material. Particularly preferred conductive
polymers include intrinsically conductive polymers most preferably
selected from polypyrrole, polyaniline and polythiophene. Metals
can be employed as a cathode material with valve metals being less
preferred. The cathode may include multiple interlayers wherein
adhesion layers are employed to improve adhesion between the
conductor and the termination. Particularly preferred adhesion
interlayers include carbon, silver, copper, or another conductive
material in a binder. The cathode is preferably formed by dipping,
coating or spraying either a slurry of conductive polymer or a
conductive polymer precursor which is polymerized by an oxidant as
known in the art. Carbon and metal containing layers are typically
formed by dipping into a carbon containing liquid or by coating.
The carbon containing layers and metal containing layers can be
formed by electroplating and this is a preferred method, in one
embodiment, particularly for the metal containing layer.
[0028] The dielectric is a non-conductive layer which is not
particularly limited herein. The dielectric may be a metal oxide or
a ceramic material. A particularly preferred dielectric is the
oxide of a metal anode due to the simplicity of formation and ease
of use. The dielectric is preferably formed by dipping the anode
into an anodizing solution with electrochemical conversion.
Alternatively, a dielectric precursor can be applied by spraying or
printing followed by sintering to form the layer. When the
dielectric is an oxide of the anode material dipping is a preferred
method whereas when the dielectric is a different material, such as
a ceramic, a spraying or coating technique is preferred.
[0029] The anode lead wire is chosen to have low resistivity and to
be compatible with the anode material. The anode lead wire may be
the same as the anode material or a conductive oxide thereof.
Particularly preferred anode lead wires include Ta, Nb and NbO. The
shape of the anode lead wire is not particularly limiting.
Preferred shapes include round, oval, rectangular and combinations
thereof. The shape of the anode lead wire is preferably chosen for
optimum electrical properties.
[0030] The conductive polymer has a backbone defined as
--(CR.sup.1R.sup.2--CR.sup.3R.sup.4--).sub.x--wherein at least one
of R.sup.1, R.sup.2, R.sup.3 or R.sup.4 comprises a group selected
from thiophene, pyrrole or aniline which may be substituted wherein
subscript x is at least 2 to no more than 1000. None of R.sup.1,
R.sup.2, R.sup.3 or R.sup.4 contain --SOOH or COOH. Hydrogen and
lower alkyls of less than five carbons are particularly suitable.
Thiophenes are particularly preferred with
poly(3,4-ethylenedioxythiophene) being most preferred.
[0031] The conductive polymer layer comprises two crosslinkers
which function synergistically to provide an improved capacitor
with lower ESR. The first crosslinker is an organofunctional silane
and the second is an organic compound with at least two functional
groups selected from epoxy and carboxylic acid. Organofunctional
silane, more particularly, glycidyl silane crosslinkers have been
taught in the art, however, it is widely known that excessive
amounts of silane crosslinker makes dried conductive polymer film
rigid and fragile, consequently ESR and ESR stability suffer with
increased concentration of silane. Therefore, the artisan has been
limited to the amount of crosslinking to be achieved since the
concentration of silane in the conductive polymer must be limited
to minimize ESR. Organofunctional silane has never reached the
theoretical potential as a crosslinker in capacitors.
[0032] Organic compounds with one epoxy group have been taught in
the art to enhance water resistance, as described in U.S. Published
Patent Application 2010/0091432. However, if more than one epoxy
group is utilized the water resistance is not improved as much. The
teaching from prior art is that crosslinking compounds with more
than one functional crosslinking group become sterically bulky
after the crosslinking reaction, which prevents them from spreading
into the conductive polymer homogeneously and therefore they fail
to improve the water resistance effectively. Organic compounds with
more than one epoxy group have therefore been considered unsuitable
for use in electronic capacitors since the polymeric cathode layer
tends to delaminate due to excessive water absorption thereby
rendering the capacitor useless.
[0033] It is surprising that the combination of organofunctional
silane and organic compound with more than one crosslinking group,
especially more than one epoxy group, react synergistically
providing a much lower ESR at a given level of organofunctional
silane without an increase in water absorption as would be
expected, particularly for the epoxy crosslinking compound with
more than one epoxy group. This unexpected synergism allows for the
use of a higher concentration of organofunctional silane and epoxy
crosslinking compound combined, and therefore more crosslinking
sites, than previously considered possible. The increase in
crosslinking increases the structural integrity of the conductive
polymer layer as evidenced by lower ESR.
[0034] It is even more surprising that the combination of
organofunctional silane and organic compound with more than one
carboxylic group also shows a synergistic function and provides a
much lower ESR at a given level of organofunctional silane.
Carboxylic groups are not considered reactive toward --SOOH or
--COON groups under normal capacitor processing conditions as
described in "Mixed sulfonic-carboxylic anhydrides. I. Synthesis
and thermal stability. New syntheses of sulfonic anhydrides", by
Yehuda Mazur, Michael H. Karger, J. Org. Chem., 1971, 36 (4), pp
528-531. The ESR improvement may be attributed to reactions between
the organofuncational silane and the carboxylic crosslinking
compound, and other components of the conductive polymer
dispersion. Herein, although we discuss dual crosslinker systems of
organosilane and epoxy crosslinking compound or dual crosslinker
systems of organosilane and carboxylic crosslinking system, a
multi-crosslinker system than contains 3, or 4, or even more
crosslinkers is envisioned.
[0035] The organofunctional silane concentration may range from
about 0.05 wt % to about 10 wt % of the conductive polymer
dispersion at a percent solids of about 0.2 to 10 wt %. More
preferably, the organofunctional silane concentration may range
from about 0.1 wt % to about 5 wt % of the conductive polymer and
even more preferably about 0.1 wt % to about 2 wt %.
[0036] Organofunctional silane is defined by the formula:
XR.sub.1Si(R.sub.3).sub.3-n(R.sub.2).sub.n
wherein X is an organic functional group such as amino, epoxy,
anhydride, hydroxy, mercapto, sulfonate, carboxylate, phosphonate,
halogen, vinyl, methacryloxy, ester, alkyl, etc; R.sub.1 is an aryl
or alkyl (CH.sub.2), wherein m can be 0 to 14; R.sub.2 is
individually a hydrolysable functional group such as alkoxy,
acyloxy, halogen, amine or their hydrolyzed product; R.sub.3 is
individually an alkyl functional group of 1-6 carbons; n is 1 to
3.
[0037] The organofunctional silane can also be dipodal, define by
the formula:
Y(Si(R.sub.3).sub.3-n(R.sub.2).sub.n).sub.2
wherein Y is any organic moiety that contains reactive or
nonreactive functional groups, such as alkyl, aryl, sulfide or
melamine; R.sub.3, R.sub.2 and n are defined above. The
organofunctional silane can also be multi-functional or polymeric
silanes, such as silane modified polybutadiene, or silanbe modified
polyamine, etc.
[0038] Examples of organofunctional silane include
3-glycidoxypropyltrimethoxysilane, 3-am inopropytriethoxysilane, am
inopropylsilanetriol, (triethoxysilyl)propylsuccinic anhydride,
3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane,
3-methacryloxypropyltrimethoxysilane, 3-trihydroxysilyl-1-propane
sulfonic acid, octyltriethyoxysilane, bis(triethoxysilyl)octane,
etc. The examples are used to illustrate the invention and should
not be regarded as conclusive.
[0039] A particularly preferred organofunctional silane is glycidyl
silane defined by the formula:
##STR00001##
wherein R.sub.1 is an alkyl of 1 to 14 carbons and more preferably
selected from methyl ethyl and propyl; and each R.sub.2 is
independently an alkyl or substituted alkyl of 1 to 6 carbons.
[0040] A particularly preferred glycidyl silane is
3-glycidoxypropyltrimethoxysilane defined by the formula:
##STR00002##
which is referred to herein as "Silane A" for convenience.
[0041] The second crosslinker, which is an organic compound with at
least two functional groups selected from epoxy and carboxylic
acid, has a concentration preferred range from about 0.1 wt % to
about 10 wt % of the conductive polymer dispersion at a percents
solids of about 0.2 to about 10 wt %. More preferably, the glycidyl
ether concentration may range from about 0.2 wt % to about 5 wt %
of the conductive polymer and even more preferably about 0.2 wt %
to about 2 wt %.
[0042] The second crosslinker with at least two epoxy groups is
referred to herein as an epoxy crosslinking compound and is defined
by the formula:
##STR00003##
wherein the X is an alkyl or substituted alkyl of 0-14 carbons,
preferably 0-6 carbons; an aryl or substituted aryl, an ethylene
ether or substituted ethylene ether, polyethylene ether or
substituted polyethylene ether with 2-20 ethylene ether groups or
combinations thereof. A particularly preferred substitute is an
epoxy group.
[0043] Examples of epoxy crosslinking compounds having more than
one epoxy groups include ethylene glycol diglycidyl ether (EGDGE),
propylene glycol diglycidyl ether (PGDGE), 1,4-butanediol
diglycidyl ether (BDDGE), pentylene glycol diglycidyl ether,
hexylene glycol diglycidyl ether, cyclohexane dimethanol diglycidyl
ether, resorcinol glycidyl ether, glycerol diglycidyl ether (GDGE),
glycerol polyglycidyl ethers, diglycerol polyglycidyl ethers,
trimethylolpropane polyglycidyl ethers, sorbitol diglycidyl ether
(Sorbitol-DGE), sorbitol polyglycidyl ethers, polyethylene glycol
diglycidyl ether (PEGDGE),polypropylene glycol diglycidyl ether,
polytetramethylene glycol diglycidyl ether, di(2,3-epoxypropyl)
ether, 1,3-butadiene diepoxide, 1,5-hexadiene diepoxide,
1,2,7,8-diepoxyoctane, 1,2,5,6-diepoxycyclooctane, 4-vinyl
cyclohexene diepoxide, bisphenol A diglycidyl ether,
maleimide-epoxy compounds, etc.
[0044] A preferred epoxy crosslinking compound is glycidyl ether,
defined by the formula:
##STR00004##
wherein R.sub.3 is an alkyl or substituted alkyl of 1-14 carbons,
preferably 2-6 carbons; an ethylene ether or polyethylene ether
with 2-20 ethylene ether groups; a alkyl substituted with a group
selected from hydroxy, or
##STR00005##
or --(CH.sub.2OH).sub.xCH.sub.2OH wherein X is 1 to 14.
[0045] Particularly preferred glycidyl ethers are represented
by:
##STR00006##
[0046] The organic compound with at least two carboxylic functional
groups is referred to herein as a carboxylic crosslinking
compound.
[0047] Examples of carboxylic crosslinking compounds include but
are not limited by, oxalic acid, malonic acid, succinic acid,
glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic
acid, sebacic acid, dodecanedioic acid, phthalic acids, maleic
acid, muconic acid, citric acid, trimesic acid, polyacrylic acid,
etc. Particularly preferred organic acids are aromatic acid such as
phthalic acid, and particularly ortho-phthalic acid, which
decreases ESR. The reaction of the crosslinkable functionality and
the crosslinkers occurs at elevated temperature which occurs during
the normal processing steps of capacitor manufacture.
[0048] The construction and manufacture of solid electrolyte
capacitors is well documented. In the construction of a solid
electrolytic capacitor a valve metal preferably serves as the
anode. The anode body can be either a porous pellet, formed by
pressing and sintering a high purity powder, or a foil which is
etched to provide an increased anode surface area. An oxide of the
valve metal is electrolytically formed to cover up to all of the
surfaces of the anode and to serve as the dielectric of the
capacitor. The solid cathode electrolyte is typically chosen from a
very limited class of materials, to include manganese dioxide or
electrically conductive organic materials including intrinsically
conductive polymers, such as polyaniline, polypyrol, polythiophene
and their derivatives. The solid cathode electrolyte is applied so
that it covers all dielectric surfaces and is in direct intimate
contact with the dielectric. In addition to the solid electrolyte,
the cathodic layer of a solid electrolyte capacitor typically
consists of several layers which are external to the anode body. In
the case of surface mount constructions these layers typically
include: a carbon layer; a cathode conductive layer which may be a
layer containing a highly conductive metal, typically silver, bound
in a polymer or resin matrix; and a conductive adhesive layer such
as silver filled adhesive. The layers including the solid cathode
electrolyte, conductive adhesive and layers there between are
referred to collectively herein as the cathode which typically
includes multiple interlayers designed to allow adhesion on one
face to the dielectric and on the other face to the cathode lead. A
highly conductive metal lead frame is often used as a cathode lead
for negative termination. The various layers connect the solid
electrolyte to the outside circuit and also serve to protect the
dielectric from thermo-mechanical damage that may occur during
subsequent processing, board mounting, or customer use.
[0049] In the case of conductive polymer cathodes the conductive
polymer is typically applied by either chemical oxidation
polymerization, electrochemical oxidation polymerization or by
dipping, spraying, or printing of pre-polymerized dispersions.
[0050] In one embodiment the conductive polymer layer is added as a
slurry wherein the slurry is applied to a surface by dipping or
coating. The slurry comprises a solvent, preferably water, the
conductive polymer, preferably poly(3,4-ethylenedioxythiophene), a
organofunctional silane and a second crosslinker which is an
organic compound with at least two functional groups selected from
epoxy and carboxylic acid. The solvent is preferably polar
solvents, such as water, alcohols or acetonitrile, and a mixture of
water with polar solvent, with water being the most preferred
solvent. The solvent is in sufficient ratio to achieve a viscosity
suitable for achieving an adequate coating with additional solvent
being undesirable as the solvent is typically removed after
application. The organofunctional silane is preferably present in
an amount of 0.0005-0.1000 grams per gram of conductive polymer
dispersion. More preferably the organofunctional silane is
preferably present in an amount of 0.001-0.050 grams per gram of
conductive polymer dispersion. The second crosslinker is preferably
present in an amount of 0.001-0.100 grams per gram of conductive
polymer. More preferably the epoxy crosslinking compound or the
carboxylic crosslinking compound is preferably present in an amount
of 0.002-0.050 grams per gram of conductive polymer.
[0051] Apart from the conductive polymer, solvent, organofunctional
silane and the second crosslinker, the slurry may further comprise
other additives such as conductivity enhancing additives,
surface-active substances, coverage enhancing additives and
optionally a polymer binder.
[0052] Organic acids, and particularly aromatic organic acids are
beneficial in some embodiments of the slurry and in the capacitor
formed by the slurry. Examples of organic acids can include, formic
acid, acetic acid, propanoic acid, oxalic acid, malonic acid,
succinic acid, glutaric acid, adipic acid, pimelic acid, suberic
acid, azelaic acid, sebacic acid, dodecanedioic acid, benzoic acid,
phthalic acids, maleic acid, muconic acid, etc. Particularly
preferred organic acids are phthalic acid, and particularly
ortho-phthalic acid, and benzoic acid both of which further
decrease ESR and improve coverage. The slurry preferably comprises
0-0.10 grams of organic acid per gram of conductive polymer
dispersion.
[0053] The slurry may contain surface active additives such as
acetylenic diols, alkyl carboxylates, alkyl sulfate, alkyl
sulfonate, fluoroalkyl surfactant or any other surface active
substances.
[0054] The slurry may contain conductive enhancing additives such
as dimethylsulfoxide (DMSO), dimethylformamide (DMF),
dimethylacetamide (DMAc), ethylene glycol, propylene glycol,
etc.
[0055] The conductive polymer layer preferably comprises a dopant,
and more preferably a polyanion dopant. The polyanion dopant can be
present in an amount of up to 90 wt % even though not all polyanion
functions as a dopant. It is preferable to have a dopant
concentration from about 5 wt % to about 30 wt %, more preferably
12 wt % to about 25 wt % and most preferably about 21 wt %. Any
suitable dopant may be used such as 5-sulfosalicylic acid,
dodecylbenzenesulfonate, p-toluenesulfonate or chloride. A
particularly exemplary dopant is p-toluenesulfonate. A particularly
preferred polyanion dopant is polystyrene sulfonic acid.
[0056] The carbon layer serves as a chemical barrier between the
solid electrolyte and the silver layer. Critical properties of the
layer include adhesion to the underlying layer, wetting of the
underlying layer, uniform coverage, penetration into the underlying
layer, bulk conductivity, interfacial resistance, compatibility
with the silver layer, buildup, and mechanical properties.
[0057] The cathodic conductive layer, which is preferably a silver
layer, serves to conduct current from the lead frame to the cathode
and around the cathode to the sides not directly connected to the
lead frame. The critical characteristics of this layer are high
conductivity, adhesive strength to the carbon layer, wetting of the
carbon layer, and acceptable mechanical properties.
[0058] Throughout the description stated ranges, such as 0-6 or
0.1-0.6 refer to all intermediate ranges with the same number of
significant figures as the highest significant figure listed.
EXAMPLES
Preparation of PEDOT-PSSA and Conductive Polymer Dipsersion
[0059] A 4 L plastic jar, provided with a cooling jacket, was
initially charged with 125 g of PSSA, 2531 g of DI water, 28.5 g of
1% iron(III) sulphate, and 21.5 g of sodium peroxodisulphate. The
contents were mixed using a rotor--stator mixing system with
perforated stator screen with a round hole diameter of 1.6 mm.
Subsequently, 11.25 g of 3,4-ethylenedioxythiophene (PEDOT) was
added dropwise. The reaction mixture was sheared continuously with
a shear speed of 8000 RPM with the rotor-stator mixing system for
an additional 23 hours. The dispersion was treated with cationic
and anionic exchange resin and filtered to get PEDOT-PSSA base
slurry.
[0060] Conductive polymer dispersion was prepared by mixing
PEDOT-PSSA base slurry with other additives and crosslinkers.
Capacitor Manufacturing Example 1
[0061] A series of tantalum anodes (33 microfarads, 25V) were
prepared. The tantalum was anodized to form a dielectric on the
tantalum anode. The anode thus formed was dipped into a solution of
iron (III) toluenesulfonate oxidant for 1 minute and sequentially
dipped into ethyldioxythiophene monomer for 1 minute. The anodes
were washed to remove excess monomer and by-products of the
reactions after the completion of 60 minutes polymerization, which
formed a thin layer of conductive polymer (PEDOT) on the dielectric
of the anodes. This process was repeated until a sufficient
thickness was achieved. The conductive polymer dispersion was
applied to form an external polymer layer. After drying,
alternating layers of decanediamine toluenesulfonate and conductive
polymer dispersion was applied and repeated 4-5 more times. The
anodes with conductive polymer layer were washed and dried,
followed by sequential coating of a graphite layer and a silver
layer to produce a solid electrolytic capacitor. Parts were
assembled, packaged and surface mounted. ESR was measured before
and after surface mount.
Capacitor Manufacturing Example 2
[0062] A series of tantalum anodes (330 microfarads, 6V) were
prepared. The tantalum was anodized to form a dielectric on the
tantalum anode. The anode thus formed was dipped into a solution of
iron (III) toluenesulfonate oxidant for 1 minute and sequentially
dipped into ethyldioxythiophene monomer for 1 minute. The anodes
were washed to remove excess monomer and by-products of the
reactions after the completion of 60 minutes polymerization, which
formed a thin layer of conductive polymer (PEDOT) on the dielectric
of the anodes. This process was repeated until a sufficient
thickness was achieved. Conductive polymer dispersion was applied
to form an external polymer layer. After drying, this process was
repeated 2 more times, followed by sequential coating of a graphite
layer and a silver layer to produce a solid electrolytic capacitor.
Parts were assembled, packaged and surface mounted. ESR was
measured before and after surface mount.
Comparative Example 1
[0063] To 120 g of the PEDOT-PSSA conductive polymer was added 4.8
g of DMSO and 0.48 g of 3-glycidoxypropyltrimethoxysilane (Silane
A). The conductive polymer dispersion was mixed in a container by
rolling overnight. The solid capacitor was produced following the
process in Capacitor Manufacturing Example 1.
Comparative Example 2
[0064] Same as Comparative Example 1, except that 0.96 g of Silane
A was used to prepare the conductive polymer dispersion.
Comparative Example 3
[0065] Same as Comparative Example 1, except that 1.44 g of Silane
A was used to prepare the conductive polymer dispersion.
Inventive Example 1
[0066] To 120 g of the PEDOT-PSSA conductive polymer was added 4.8
g of DMSO, 0.48 g of Silane A and 0.96 g of EGDGE. The conductive
polymer dispersion was mixed in a container by rolling overnight.
The solid capacitor was produced following the process in Capacitor
Manufacturing Example 1.
[0067] To 120 g of the PEDOT-PSSA conductive polymer was added 4.8
g of DMSO, 0.96 g of Silane A and 0.48 g of EGDGE. The conductive
polymer dispersion was mixed in a container by rolling overnight.
The solid capacitor was produced following the process in Capacitor
Manufacturing Example 1.
[0068] To compare the dual crosslinker system with single
crosslinker system using glycidyl silane crosslinker a series of
comparative polymer slurries were prepared with various amounts of
3-glycidoxypropyltrimethoxysilane (Comparative Example 1-3) as
presented in Table 1. A tantalum capacitor was formed using the
polymer slurry to form the polymeric cathode layer. Anode and
cathode terminations were formed in identical manner using
conventional technologies. As noted therein, ESR increased with
increasing crosslinker which is contrary to the desire in the art.
Inventive samples were prepared using various amounts of silane
crosslinker with various amounts of EDDGE crosslinker as presented
in Table 1. The ESR was measured with the results reproduced in
Table 1. The results clearly illustrate the synergistic effect of
improved ESR resulting from the inventive dual crosslinker
system.
TABLE-US-00001 TABLE 1 Examples Crosslinkers ESR (m.OMEGA.) Comp. 1
Silane A 0.4% 39.77 Comp. 2 Silane A 0.8% 44.49 Comp. 3 Silane A
1.2% 46.91 Inv. 1 Silane A 0.4%, 30.93 EGDGE 0.8% Inv. 2 Silane A
0.8%, 36.83 EGDGE 0.4%
Comparative Example 4
[0069] To 80 g of the PEDOT-PSSA conductive polymer was added 3.2 g
of DMSO, 0.32 g of Silane A and 2.56 g of a commercial polyester
binder (44% aqueous dispersion). The conductive polymer dispersion
was mixed in a container by rolling overnight. The solid capacitor
was produced following the process in Capacitor Manufacturing
Example 1.
Comparative Example 5
[0070] A commercial PEDOT-PSSA conductive polymer dispersion
Clevios.TM. K from Heraeus of Leverkusen/Germany (KV2) was used to
produce the solid capacitor following the process in Capacitor
Manufacturing Example 1.
Inventive Example 3
[0071] To 80 g of the PEDOT-PSSA conductive polymer was added 3.2 g
of DMSO, 0.32 g of Silane A and 0.64 g of PEGDGE. The conductive
polymer dispersion was mixed in a container by rolling overnight.
The solid capacitor was produced following the process in Capacitor
Manufacturing Example 1.
Inventive Example 4
[0072] Same as Comparative Example 4, except that BDDGE instead of
PEGDGE was used to prepare the conductive polymer dispersion.
Inventive Example 5
[0073] Same as Comparative Example 4, except that GDGE instead of
PEGDGE was used to prepare the conductive polymer dispersion.
Inventive Example 6
[0074] Same as Comparative Example 4, except that Sorbitol-DGE
instead of PEGDGE was used to prepare the conductive polymer
dispersion.
[0075] A series of diglycidyl ether crosslinker slurry were
prepared in Example 3-6 with the components and their levels
presented in Table 2. Capacitors were formed using the slurry as in
Capacitor Manufacturing Example 1 and the ESR was measured before
and after conventional mounting using conventional surface mount
technology (SMT) with a reflow temperature of 260.degree. C.
Comparative Example 4 was identically prepared utilizing Silane A
and a commercial polyester binder. Comparative example 5 used a
commercial polymer slurry KV2. All inventive examples showed
similarly lower ESR values compared with the two comparative
examples under the experimental condition. After SMT mounting, all
inventive examples showed no detrimental ESR shift and are much
more stable than the comparative examples.
TABLE-US-00002 TABLE 2 Pre Post Mount Mount SMT ESR Examples
Crosslinkers ESR (m.OMEGA.) (m.OMEGA.) Inv. 3 Silane A 0.4%, 34.99
32.30 PEGDGE 0.8% Inv. 4 Silane A 0.4%, 33.31 30.36 BDDGE 0.8% Inv.
5 Silane A 0.4%, 32.82 30.21 GDGE 0.8% Inv. 6 Silane A 0.4%, 31.88
29.21 Sorbitol-DGE 0.8% Comp. 4 Silane A 0.4% 48.83 58.86
Commercial polyester binder 1.4% Comp. 5 Commercial conductive
polymer 32.25 56.54 dispersion (KV2)
Comparative Example 6
[0076] To 200 g of the PEDOT-PSSA conductive polymer was added 8 g
of DMSO and 0.8 g of Silane A. The conductive polymer dispersion
was mixed in a container by rolling overnight. The solid capacitor
was produced following the process in Capacitor Manufacturing
Example 1.
Comparative Example 7
[0077] To 200 g of the PEDOT-PSSA conductive polymer was added 8 g
of DMSO and 0.8 g of Silane A. The conductive polymer dispersion
was mixed in a container by rolling overnight. The solid capacitor
was produced following the process in Capacitor Manufacturing
Example 2.
Inventive Example 7
[0078] To 200 g of the PEDOT-PSSA conductive polymer was added 8 g
of DMSO, 0.8 g of Silane A and 2 g of o-phthalic acid (PA). The
conductive polymer dispersion was mixed in a container by rolling
overnight. The solid capacitor was produced following the process
in Capacitor Manufacturing Example 1.
Inventive Example 8
[0079] To 200 g of the PEDOT-PSSA conductive polymer was added 8 g
of DMSO, 0.8 g of Silane A and 2 g of o-phthalic acid (PA). The
conductive polymer dispersion was mixed in a container by roller
overnight. The solid capacitor was produced following the process
in Capacitor Manufacturing Example 2.
[0080] The dual crosslinker system using glycidyl silane
crosslinker and phthalic acid crosslinker showed improved ESR and
ESR stability relative to the comparative examples using only the
silane crosslinker.
TABLE-US-00003 TABLE 3 NB# Crosslinkers ESR (m.OMEGA.) Comp. 6
Silane A 0.4% 38.3 Inv. 7 Silane A 0.4%, PA 1% 31.8 Comp. 7 Silane
A 0.4% 54.6 Inv. 8 Silane A 0.4%, PA 1% 28.8
Inventive Example 9
[0081] To 80 g of the PEDOT-PSSA conductive polymer was added 3.2 g
of DMSO, 0.32 g of Silane A and 0.56 g of EGDGE. The conductive
polymer dispersion was mixed in a container by rolling overnight.
The solid capacitor was produced following the process in Capacitor
Manufacturing Example 1.
Inventive Example 10
[0082] Same as Comparative Example 9, except that 0.64 g of GDGE
instead of EGDGE was used to prepare the conductive polymer
dispersion.
Inventive Example 11
[0083] Same as Comparative Example 9, except that 0.72 g of
Sorbitol-DGE instead of EGDGE was used to prepare the conductive
polymer dispersion.
Inventive Example 12
[0084] To 80 g of the PEDOT-PSSA conductive polymer was added 3.2 g
of DMSO, 0.32 g of Silane A, 0.56 g of PA and 0.56 g of EGDGE. The
conductive polymer dispersion was mixed in a container by rolling
overnight. The solid capacitor was produced following the process
in Capacitor Manufacturing Example 1.
Inventive Example 13
[0085] To 80 g of the PEDOT-PSSA conductive polymer was added 3.2 g
of DMSO, 0.32 g of Silane A, 0.64 g of GDGE and 0.48 g of PA. The
conductive polymer dispersion was mixed in a container by rolling
overnight. The solid capacitor was produced following the process
in Capacitor Manufacturing Example 1.
Inventive Example 14
[0086] To 80 g of the PEDOT-PSSA conductive polymer was added 3.2 g
of DMSO, 0.32 g of Silane A, 0.40 g of PA and 0.72 g of
Sorbitol-DGE. The conductive polymer dispersion was mixed in a
container by rolling overnight. The solid capacitor was produced
following the process in Capacitor Manufacturing Example 1.
[0087] Conductive polymer slurries were prepared as above with, in
some instances, the additional incorporation of ortho-phthalic
acid. The addition of ortho-phthalic acid had two benefits: further
ESR reduction and improved anode edge and corner coverage. The edge
and corner coverage was rated by visual observation and 99% means
that all corners and edges are covered.
TABLE-US-00004 TABLE 4 Post 4.sup.th 5.sup.th Pre Mount Slurry
Slurry Mount SMT Cycle Cycle ESR ESR Cover Cover Examples
Crosslinkers (m.OMEGA.) (m.OMEGA.) age % age % Inv. 9 Silane A 0.4%
34.13 34.03 95% 96% EGDGE 0.7% Inv. 10 Silane A 0.4% 34.15 34.98
97% 98% GDGE 0.8% Inv. 11 Silane A 0.4% 30.87 30.03 97% 99%
Sorbitol-DGE 0.9% Inv. 12 Silane A 0.4% 32.41 29.83 96% 98% EGDGE
0.7% PA 0.7% Inv. 13 Silane A 0.4%, 34.59 31.94 98% 99% GDGE 0.8%,
PA 0.6% Inv. 14 silane 0.4%, 31.75 30.50 98% 99% Sorbitol-DGE 0.9%,
PA 0.5%
Comparative Example 8
[0088] Same as Comparative Example 5.
Inventive Example 15
[0089] To 600 g of the PEDOT-PSSA conductive polymer was added 24 g
of DMSO and 2.4 g of Silane A. The conductive polymer dispersion
was mixed in a container by rolling overnight. The solid capacitor
was produced following the process in Capacitor Manufacturing
Example 1, except that after the conductive polymer layer was
applied, the anode was soaked in 2.5% of EGDGE ethanol solution for
5 minute and dried to form a crosslinker coating. The rest of the
anode manufacturing process remained the same.
Inventive Example 16
[0090] Same as Inventive Example 15, except that 2.5% of
Sorbitol-DGE ethanol solution was used instead of EGDGE ethanol
solution.
[0091] The dual crosslinker can also be applied separately in two
steps. The 1.sup.st crosslinker Silane A was included in the
conductive polymer dispersion, the 2.sup.nd crosslinker (glycidyl
ether) was applied as a separate coating afterwards. This process
again showed better ESR than the commercial conductive polymer
dispersion KV2 applied in one step coating.
TABLE-US-00005 TABLE 5 Pre Post Mount Mount SMT ESR Examples
Crosslinker Coating ESR (m.OMEGA.) (m.OMEGA.) Inv. 15 2.5% EGDGE
ethanol solution 31.58 27.62 Inv. 16 2.5% Sorbitol-DGE ethanol
29.23 30.57 solution Comp. 8 Commercial conductive polymer 36.61
44.41 dispersion (KV2)
[0092] The dual crosslinker system demonstrated good ESR and ESR
stability when compared with single crosslinker system or polymeric
binders, even in the situation when one of the crosslinker can't
readily crosslink the conductive polymer PEDOT-PSSA itself. The
surprisingly good electrical performance can only be attributed to
the synergy of the two different types of crosslinkers, either by
crosslinking reactions between them, or with other components in
the conductive polymer dispersion.
[0093] The invention has been described with particular reference
to preferred embodiments without limit thereto. One of skilled in
the art would realize additional embodiments and improvements which
are not specifically enumerated but which are within the scope of
the invention as specifically set forth in the claims appended
hereto.
* * * * *