Solid electrolytic capacitor

Details Solid electrolytic capacitor Solid electrolytic capacitor

2003-06-06

2004-09-14

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrolytic systems or devices

Solid electrolytic capacitor

C361S508000, C361S509000, C361S512000, C361S525000, C361S528000, C029S025030

Reexamination Certificate

active

06791822

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a solid electrolytic capacitor for use in an electronic circuit in an electronic device.
BACKGROUND OF THE INVENTION
As electronic devices handles higher frequencies according to development of digital technology, a high-frequency capacitor having a small size, a large capacitance, a small internal impedance at high frequencies is demanded. To have the internal impedance reduced, a solid electrolytic capacitor are focused to have a small equivalent serial resistance (ESR) as well as a small equivalent serial inductance (ESL) at high frequencies.
FIG. 11
illustrates a conventional solid electrolytic capacitor
301
. A porous valve metal film
201
is formed by etching a valve metal film made of valve metal, such as aluminum. A dielectric layer
202
is formed on the porous valve metal film
201
. An insulating isolator layer
209
for separating between a lead portion of the porous valve metal film
201
and a solid electrolyte layer
206
is formed on the dielectric layer
202
. The solid electrolyte layer
206
is provided on the dielectric layer
202
. A carbon layer
207
is provided on the solid electrolyte layer
206
, and a silver paste layer
208
is formed on the carbon layer
207
, thus providing a capacitor element. The carbon layer
207
and the silver paste layer
208
functions as a collector. A desired number of such capacitor elements are stacked with silver paste. The silver paste layer
208
of each capacitor element is joined to a negative electrode lead frame
211
with the silver paste while the lead portion of the porous valve metal film
201
is joined to a positive electrode lead frame
212
by welding or the like. The stacked capacitor elements are then encapsulated by molding in a resin package
210
.
FIG. 12
illustrates another conventional solid electrolytic capacitor
302
. A dielectric layer
223
is formed on a porous valve metal body
222
. One end of a valve metal lead
221
made of tantalum or niobium is embedded in the body
222
. An insulating isolator layer
227
is provided between the valve metal lead
221
and the dielectric layer
223
. A solid electrolyte layer
224
made of electrically conductive polymer is formed on the dielectric layer
223
. A collector consisting of a carbon layer
225
and a silver paste layer
226
is formed on the solid electrolyte layer
224
. The silver paste layer
226
is joined to a negative electrode lead frame
229
by the silver paste while the valve metal lead
221
is joined to a positive electrode lead frame
230
by welding. The stacked capacitors are then encapsulated by molding in a resin package.
The conventional solid electrolytic capacitor
301
with the positive electrode made of aluminum has an ESR smaller than that of the conventional solid electrolytic capacitor
302
with the positive electrode made of tantalum, but has a capacitance smaller than that of the capacitor
302
. The conventional solid electrolytic capacitor
302
with the positive electrode made of tantalum has a large capacitance but has a large ESR.
SUMMARY OF THE INVENTION
A first capacitor element includes a porous valve metal film, a first dielectric layer provided on the porous valve metal film, a first solid electrolyte layer provided on the first dielectric layer, and a first collector layer provided on the first solid electrolyte layer.
A second capacitor element includes a valve metal film, a porous valve metal body provided on the valve metal film, a second dielectric layer provided on the porous valve metal body, a second solid electrolyte layer provided on the second dielectric layer, and a second collector layer provided on the second solid electrolyte layer.
A solid electrolytic capacitor includes a stacked-assembly including the first capacitor element and the second capacitor element stacked, a package for encapsulating the stacked-assembly, a first external electrode connected to the porous valve metal film and the valve metal film, and a second external electrode connected to the first and second collector layers. At least a portion of the first external electrode is provided on a first side of the package. At least a portion of the second external electrode is provided on a second side of the package.
The capacitor has a small size and a large capacitance while having a small equivalent serial resistance and a small equivalent serial inductance.


REFERENCES:
patent: 5153820 (1992-10-01), MacFarlane et al.
patent: 5227960 (1993-07-01), Kunishi et al.
patent: 5587872 (1996-12-01), Lian et al.
patent: 6459565 (2002-10-01), Lessner et al.
patent: 6678149 (2004-01-01), Matsumoto et al.
patent: 6680841 (2004-01-01), Tadanobu et al.

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