Surface mount package for long lead devices

Details Surface mount package for long lead devices Surface mount package for long lead devices

2001-09-10

2002-07-23

Gaffin, Jeffrey (Department: 2841)

Electricity: conductors and insulators

Conduits, cables or conductors

Preformed panel circuit arrangement

C174S258000, C174S261000, C174S262000, C174S266000, C361S760000, C361S719000, C361S774000, C361S803000, C257S698000

Reexamination Certificate

active

06423906

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to package for electronic devices, in particular to a surface mount package.
(2) Background of the Invention
Many kinds of electronic devices such as capacitors, resistors have long leads. With the advent of printed circuits, it is desirable to use surface mount packages for the devices for easy connection to the printed circuit board.
FIG. 1A
shows top view of a conventional package for a typical long lead device. A substrate
20
has two via holes
24
through which the leads of a device (not shown) can extend.
FIG. 1B
shows the side view of section A—A′ of FIG.
1
A. The substrate
20
has two grooves
22
outside the via holes
24
. When the leads of a device is inserted through the via holes, the leads are bent outward against the grooves
22
and recessed in the grooves
22
as shown in FIG.
1
C.
FIG. 1D
shows the side view of the package with a device
10
inserted through the package. The two leads
12
of the device
10
are inserted through the substrate
20
and bent outward. Because of the recessed grooves
22
, the bottom ends of the bent leads
12
are flush with the bottom of the substrate
20
. Thus the bottom surface of the package is flat for surface mounting to a printed circuit board.
However the rounded ends of the leads do not provide a big contact area for soldering to the printed circuit board, the soldering reliability. Although the ends of the leads
12
may be crimped flat to increase the contact area, the increase in soldering area is limited.
SUMMARY OF THE INVENTION
An object of this invention is provide a package for surface mounting of long-lead electronic devices. Another object of this invention is to provide a big-area bonding pad for improving the soldering reliability of a surface mount package.
These objects are achieved by using plated through via holes in the substrate of the surface-mount package. The leads of the device are inserted into the plated through via holes. The bottom of the plated through metal is enlarged as a pad to provide a large reliable surface mounting surface. Upon heating the leads are soldered to the walls of the plated through holes. Alternatively, the leads of leads can be folded before inserting into the plated through holes.


REFERENCES:
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patent: 4303798 (1981-12-01), Paunovic
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patent: 5180440 (1993-01-01), Siegel et al.
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patent: 5699613 (1997-12-01), Chong et al.
patent: 5726862 (1998-03-01), Huynh et al.
patent: 5953214 (1999-09-01), Dranchak et al.
patent: 6071756 (2000-06-01), Sines et al.

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