Tantalum chip capacitor with cut-grooved lead frame

Details Tantalum chip capacitor with cut-grooved lead frame Tantalum chip capacitor with cut-grooved lead frame

2002-02-19

2003-01-28

Dinkins, Anthony (Department: 2831)

Electricity: electrical systems and devices

Electrolytic systems or devices

Liquid electrolytic capacitor

C361S529000

Reexamination Certificate

active

06512668

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to tantalum chip capacitors with lead frames and, more particularly, to a tantalum chip capacitor with a cut-grooved anode lead frame designed to allow a tantalum element set in a small-sized resin mold package of the capacitor to have a desired size, thus restricting an increase in impedance of the tantalum chip capacitor regardless of a reduction in the size of the package according to the recent trend of smallness of the tantalum chip capacitors.
2. Description of the Prior Art
As well known to those skilled in the art, tantalum chip capacitors have been widely used in a variety of applied circuits operated, with low rated voltages, in addition to a variety of industrial electronic equipments. Particularly, such tantalum chip capacitors have been preferably used in circuits, the operational performances of which are determined by their frequency characteristics. In the prior art, portable communication equipments typically use such tantalum chip capacitors for accomplishing a noise reduction.
As shown in
FIGS. 1 and 2
, a conventional tantalum chip capacitor
100
includes a tantalum element
102
, which is set in a resin mold package
112
at a predetermined position. A anode lead wire
108
integrally extends from the tantalum element
102
, while the inside end of the anode lead frame
104
is welded to the anode lead wire
108
into a single body and extends to the outside of the package
112
. The tantalum chip capacitor
100
also has a cathode lead frame
114
, wherein its inside end is attached to the tantalum element
102
and its outside end extends to the outside of the package
112
. The inside end of the anode lead frame
104
has a straight edge as shown in
FIG. 3
, so it may be called hereinafter “a straight lead frame”. The anode lead wire
108
is welded to the straight lead frame
104
through a spot welding process using an electrode welding rod
110
as shown in
FIG. 4
after partially overlapping the lead wire
108
on the lead frame
104
.
In order to spot-weld the straight lead frame
104
to the anode lead wire
108
, it is necessary to make the upper and lower parts of the end of the anode lead wire
108
into flat surfaces. This process is called “bending process” and the boundary between the flat surfaces and un-pressed part is called “bending line”. Each of the flat surfaces starts at a bending line and is terminated at the end of the lead wire
108
, and acts as a contact surface for the welding. The bending line is formed on the anode lead wire
108
by applying pressure to the lead wire
108
before the spot welding process. When the lead frame
104
is welded to the anode lead wire
108
, the straight edge of the lead frame
104
is laid on the upper flat surface of the anode lead wire
108
along a welding line, thus defining a welded area starting at the welding line and terminated at the outside end of the lead wire
108
. In such a case, the welding line is spaced apart from the bending line by a distance “L” as shown in
FIGS. 3 and 4
. After the lead frame
104
is welded to the lead wire
108
into a single body, an epoxy molding process is performed to form the package
112
enclosing the tantalum element
102
, the anode lead wire
108
, the anode lead frame
104
, and the cathode lead frame
114
.
In accordance with the recent trend of compactness and smallness of electronic equipments, it has been necessary to reduce the size of such tantalum chip capacitors. However, in the prior art, such a small-sized tantalum chip capacitor is problematic in that it reduces the size of the tantalum element
102
due to the straight lead frame
104
inevitably occupying substantial space inside the small-sized package
112
. When the size of the tantalum element
102
is reduced as described above, the capacitance of the tantalum chip capacitor is reduced. Such a reduction in the capacitance results in an undesirable increase in impedance of the tantalum chip capacitor.
In conventional small-sized tantalum chip capacitors having the straight anode lead frames, it is almost impossible to reduce the size of the straight lead frame. That is, when the straight anode lead frame is reduced in its size in an effort to prevent a reduction in the size of the tantalum element, the package cannot firmly hold the anode lead frame and allows the lead frame to be easily removed from the capacitor. Therefore, the straight anode lead frame must maintain a sufficient size, so the lead frame undesirably occupies substantial space inside the package when the capacitor size is reduced to accomplish the recent trend of smallness of the tantalum chip capacitor.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a tantalum chip capacitor which has a cut-grooved anode lead frame welded to the anode lead wire of a tantalum element at a welded area moved outward from a position of the conventional welded area, thus resulting in the enlargement of the tantalum element size.
Another object of the present invention is to provide a tantalum chip capacitor, which restricts an increase in its impedance regardless of a reduction in the size of its package according to the recent trend of smallness of tantalum chip capacitors, and which thus has improved performance.
In order to accomplish the above objects, the present invention provides a tantalum chip capacitor, comprising: a tantalum element, produced using tantalum oxide as a dielectric substance; an anode lead wire extending outward from a side surface of the tantalum element, and having flat surfaces on the upper and lower surfaces of the end portion thereof; a cathode lead frame the inside end of which is attached to the tantalum element and the outside end of which forms a mounting terminal for surface-mounting the tantalum chip capacitor on a circuit board; an anode lead frame having a cut groove at the center of the inside end thereof, the inside end being welded to the lead wire at the overlapped part of the upper flat surface of the lead wire and the inside end having the cut groove, the outside end forming a mounting terminal for surface-mounting the tantalum chip capacitor on the circuit board; and a mold package enclosing the tantalum element, the lead wire, a part of the cathode lead frame attached to the tantalum element, and a part of the anode lead frame welded to the lead wire.
In the tantalum chip capacitor of this invention, the cut groove may have a V-shaped profile or an arc-shaped profile. In addition, the cut groove has a depth set to 4%~50% of a reference length which is the length of the part of the anode lead frame enclosed in the package.


REFERENCES:
patent: 6343005 (2002-01-01), Tadanobu et al.
patent: 8-195330 (1996-07-01), None
patent: 8-316104 (1996-11-01), None
Japanese Patent Abstract Publication No. 02-087612, Publication Date Mar. 28, 1990.

Affiliated with

Also associated with

Rating

Tantalum chip capacitor with cut-grooved lead frame does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Tantalum chip capacitor with cut-grooved lead frame, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tantalum chip capacitor with cut-grooved lead frame will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3028153