Coherent light generators – Particular temperature control
Reexamination Certificate
2002-02-08
2003-06-03
Ip, Paul (Department: 2828)
Coherent light generators
Particular temperature control
C372S036000
Reexamination Certificate
active
06574254
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of Invention
This invention relates to laser diode package, in particular to the heat sink of a laser diode package.
(2) Brief Description of Related Art
In the prior art of a laser diode, the substrate is an insulator, incapable of effectively sinking the heat generated in the laser diode.
FIGS. 1-3
show such a prior art laser diode package.
FIG. 1
shows the top view of a surface mount package. The substrate is the insulated substrate
10
of a printed circuit board. Metal plates
11
,
12
,
13
serve as leads. A metal pedestal
111
is place on the metal plate
11
for mounting a laser diode. Semicircular recesses
14
are cut into the metal plates,
11
,
12
,
13
for inserting clamping screws onto the substrate
10
.
FIG. 2
shows a laser diode
15
mounted on the pedestal
111
. The laser diode
15
emits light rays B and F left and right respectively of the laser diode
15
along the section line AA′ as shown in
FIG. 3. A
photo diode
16
is mounted on the metal plate
11
for monitoring the light rays B. The light ray F is emitted from the package. The metal plate
11
serves as the lead for the bottom electrode of the laser diode
15
. The top electrode of the laser diode
15
is wire bonded by wire
17
to the metal plate
12
, serving as another lead for the laser diode
15
. The top electrode of the photodiode
16
is wire-bonded by wire
18
to the metal plate
13
.
A glue
19
is used to seal the laser diode
15
and the photo diode
16
. The glue
19
covers up to the edge of the laser diode
15
, leaving an open end to emit the light without attenuation. The metal plates
11
,
12
,
13
may each have plated through channels as shown in
FIG. 3
, or plated through holes (not shown) or folded plate (not shown) for easy surface mounting to a circuit board.
Such a prior art package has poor heat sinking capability, because the printed circuit substrate is a poor heat conductor. When is laser diode is energized, the heat cannot be removed effectively and may cause the laser diode to be overheated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a laser diode package, capable of heat sinking effectively the heat generated in the laser diode. Another object of the invention is to provide a laser diode package having provisions to monitor the heat generated in the laser diode. Still another object of the invention is to provide means to automatically adjust the power generated by the laser diode.
These objects are achieved in this invention by using thick metal plates serving both as leads and substrate for the laser diode. The thick metal plates serve as good heat sinks. One of the thick plates has a step. A monitoring photo diode is mounted in the lower platform of the step. A glue is used to seal the laser diode and the photo diode and to aggregate the metal plates, the laser diode and the photo diode together as a unitary structure.
REFERENCES:
patent: 6300674 (2001-10-01), Wang
patent: 2002/0034834 (2002-03-01), Verdiell
patent: 2002/0037142 (2002-03-01), Rossi
Al-Nazer Leith
Harvatek Corp.
Ip Paul
Lin Patent Agent H. C.
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