Chip type solid electrolytic capacitor and its manufacturing...

Details Chip type solid electrolytic capacitor and its manufacturing... Chip type solid electrolytic capacitor and its manufacturing...

1999-06-16

2001-05-22

Reichard, Dean A. (Department: 2831)

Electricity: electrical systems and devices

Electrolytic systems or devices

Solid electrolytic capacitor

C361S523000, C361S301300, C361S528000

Reexamination Certificate

active

06236561

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a chip type solid electrolytic capacitor used for surface mount technology in a variety of electronic equipment and a manufacturing method thereof.
BACKGROUND OF THE INVENTION
In recent years, use of chip type electronic components has been rapidly increasing as electronic equipment requires reduction in size and weight and the surface mount technology progresses forward. This applies to capacitors, also, and a reduction in size and an increase in per unit capacity are required for chip type solid electrolytic capacitors.
A description of a conventional chip type solid electrolytic capacitor is made in the following:
FIG. 9
shows a prior art chip type solid electrolytic capacitor. Reference symbol
21
is a capacitor element in FIG.
9
. The capacitor element
21
is prepared, according to a widely known method, by forming an oxide layer
23
, an electrolyte layer
24
and a carbon layer
25
in succession on the surface of a porous anode body
22
formed by powder molding and sintering of a valve metal with an anode lead wire
27
buried inside thereof. And, one end of the anode lead wire
27
is exposed. Then a cathode layer
26
composed of a silver paint is formed over the carbon layer
25
.
The anode lead wire
27
extending out of the capacitor element
21
is cut with the necessary portion thereof left and then the cathode layer
26
of the capacitor element
21
is connected with and fixed to a cathode lead frame
28
a
formed on a belt like metal frame
28
by means of a conductive adhesive
31
.
By resistance welding, the anode lead wire
27
is joined with and fixed to an anode lead frame
28
b
formed on the same frame
28
.
Next, the capacitor element
21
fixed to the foregoing frame
28
is encapsulated with an electrically insulating resin by a transfer molding method to form a resin package
32
. The cathode lead frame
28
a
and anode lead frame
28
b
of the frame
28
are cut to a predetermined length to serve as a terminal. And, a capacitor element
21
is cut off from the frame
28
.
Then, both lead frames
28
a
and
28
b
are bent along the periphery of the resin package
32
to make a cathode terminal
28
d
and an anode terminal
28
e
, respectively, thus completing a chip type solid electrolytic capacitor.
However, with the foregoing prior art chip type solid electrolytic capacitor, the cathode lead frame
28
a
of the frame
28
has a gutter-like guide
29
formed by bending both edges upward for aligning the position of the capacitor element
21
and is bent at a shoulder
30
downward by one step in a step-wise manner to provide a place for connection beneath the cathode layer
26
of the capacitor element
21
. The connection is performed by means of the conductive adhesive
31
. Furthermore, since the cathode lead frame
28
a
and anode lead frame
28
b
of the frame
28
are respectively bent to form the cathode terminal
28
d
and anode terminal
28
e
after the capacitor element
21
has been encapsulated with an electrically insulating resin, the volume of the capacitor element
21
cannot be increased if the capacitor element
21
is to be contained in the predetermined volume of the resin package
32
, thus presenting a problem to be solved.
In other words, a section provided on the end part of the cathode lead frame
28
a
for the connection with the cathode layer
26
by the shoulder
30
, where the cathode lead frame
28
a
is bent downward by one step in a step-wise manner, a part of the cathode terminal
28
bent along the periphery of the resin package
32
and a part of the anode terminal
28
e
together prevent the capacitor element
21
from being increased in volume.
Further, when the anode lead wire
27
is joined with the anode lead frame
28
b
by resistance welding, the junction between the anode lead frame
28
b
and the anode lead wire
27
tends to become long due to a flattening process applied to the place of the anode lead frame
28
b
where the anode lead wire
27
is joined, thereby causing a problem of hindering the volume of the capacitor element
21
from being increased.
The present invention deals with these problems involved with prior art chip type solid electrolytic capacitors and serves the purpose of providing a chip type solid electrolytic capacitor, whereby large capacity in the smallest possible size is realized, and disclosing its manufacturing method.
SUMMARY OF THE INVENTION
A chip type electrolytic capacitor of the present invention has:
a capacitor element with an anode lead wire built in while the anode lead wire is exposed at one end;
an anode lead frame with a first end connected to the anode lead wire extending from the capacitor element and a second end acting as an external connection terminal;
a cathode lead frame with a first end connected to a cathode layer of the capacitor element and a second end made to serve as an external connection terminal; and
an electrically insulating resin package encapsulating the capacitor element, and comprising a structure which exposes part of the external connection terminal of the anode lead frame and the cathode lead frame, such that each frame is almost flush with the outer surface of the resin package.
A manufacturing method of a chip type solid electrolytic capacitor according to the present invention comprising:
preparing a resin molding die wherein a parting line coincides with an outer surface of a resin package that encapsulates a capacitor element, with which an anode lead frame and a cathode lead frame are exposed such that each frame is made almost flush with the outer surface of the resin package; and
encapsulating the capacitor element with an electrically insulating resin by using the resin molding die.
The present invention makes it possible to provide a chip type solid electrolytic capacitor having a large capacity in the smallest possible size.


REFERENCES:
patent: 3588628 (1971-06-01), Peck
patent: 4017773 (1977-04-01), cheseldine.
patent: 4166286 (1979-08-01), Boissonnault.
patent: 4539623 (1985-09-01), Irikura et al.
patent: 4581479 (1986-04-01), Moore et al.
patent: 5424907 (1995-06-01), Kojima et al.
patent: 5905301 (1999-05-01), Ichikawa et al.
patent: 10092697 (1998-04-01), None
patent: 2 123 610 (1984-02-01), None

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