Mounting structure for semiconductor laser module

Details Mounting structure for semiconductor laser module Mounting structure for semiconductor laser module

2002-04-02

2004-04-13

Ip, Paul (Department: 2828)

Coherent light generators

Particular temperature control

Heat sink

C372S034000

Reexamination Certificate

active

06721341

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a semiconductor laser module which is suitable for the use in particularly high temperature environments, and a Thermo-module (TEC: Thermo Electric Cooler) used in the semiconductor laser module.
BACKGROUND OF THE INVENTION
Recently, a great number of semiconductor lasers have been used as a light source for signals and a pumping light source for an optical fiber amplifier in optical transmissions. Where the semiconductor laser is used as signal light source and a pumping light source in optical transmissions, it is frequently used as a semiconductor laser module. The semiconductor laser module is a device in which a laser beam from a semiconductor laser is optically coupled to an optical fiber.
FIG. 6
shows one example of structures of such a semiconductor laser module. A semiconductor laser module
40
illustrated in
FIG. 6
is such that in a package
11
, Thermo-module
42
is fixed on the bottom
11
a
of a package. A substrate
16
, on which a semiconductor laser element
13
, a thermistor
14
and a lens
15
are fixed, is fixed on the Thermo-module
42
. Also, an optical fiber
17
is fixed in a throughhole
11
c
secured at a sidewall
11
b
of the package
11
. In
FIG. 6
,
50
indicates a heat sink.
The semiconductor laser module
40
has a function by which a laser beam emitted from the semiconductor laser element
13
is condensed by using the lens
15
and is made incident into the end face of the optical fiber
17
. Subsequently, the laser beam is propagated in the optical fiber
17
and is provided for a specified usage.
In the semiconductor laser module
40
, an electric current is fed to drive the semiconductor laser element
13
, whereby the temperature of the semiconductor laser element
13
is increased by the generation of heat. The temperature rise will become a cause from which changes in the oscillation wavelength and optical output of the semiconductor laser element
13
results.
Therefore, a thermistor
14
is fixed in the vicinity of the semiconductor laser element
13
, which measures the temperature of the semiconductor laser element
13
. Using a value measured by the thermistor
14
, the electric current fed into a Thermo-module
42
is controlled, whereby the temperature of the semiconductor laser element
13
is kept at a required value by the current control, and the characteristics of the semiconductor laser element
13
are stabilized.
The Thermo-module
42
used in the semiconductor laser module
40
has, generally as shown in
FIG. 7A
, P type thermoelectric converting elements
18
being a P type semiconductor and N type thermoelectric converting elements
19
being an N type semiconductor
19
. The P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are disposed alternatively in a row, and are arranged between two insulation layers
12
a
and
12
b
, for example, consisting of ceramic. The P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are electrically connected to each other in series. By application of a direct current voltage to the P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
, heat is conveyed to or absorbed on the surfaces of the insulation layers
12
a
and
12
b
, whereby an object is heated or cooled.
FIG. 7A
shows a cross section of the Thermo-module
42
. The Thermo-module
42
is such that P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are placed between two ceramic-made insulation substrates
12
a
and
12
b
made of alumina or aluminum nitride. These thermoelectric effect elements
18
and
19
are electrically connected to each other by electrodes
12
formed on the surface of the insulation substrates
12
a
and
12
b.
FIG. 7B
is a perspective view of a Thermo-module
42
illustrated with the insulation substrates
12
a
and
12
b
omitted. The Thermo-module
42
is formed so that a number of thermoelectric converting elements
18
and
19
are two dimensionally uniformly disposed on the insulation substrates
12
a
and
12
b.
FIG. 7C
shows an electric connection of the respective thermoelectric effect elements
18
and
19
, wherein the P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are alternatively connected in series.
The number of thermoelectric elements
18
and
19
to be connected changes in compliance with application. Such that, for example, the number of pairs of the p type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
being from
20
through
40
may be used in a semiconductor laser module.
Such a Thermo-module
42
may be produced as shown below. First, an ingot is produced of material powder mainly consisting of bismuth (Bi) and tellurium (Te) by a single crystallizing method or a hot-pressing method. And, the ingot is cut like chips to produce the P type thermoelectric converting elements
18
and N-type thermoelectric converting elements
19
. (For example, this is a publicly known technology disclosed by Japanese Laid-Open Patent Publication Nos. 202343 of 1989 and 106478 of 1989).
Next, as shown in
FIG. 8A
, a plurality of electrodes
12
c
are installed on the insulation substrate
12
a
, and at the same time soldering paste
12
e
is coated on the respective electrodes
12
c
. Next, as shown in
FIG. 8B
, the chip-like P type thermoelectric converting elements
18
are placed one by one on the respective electrodes
12
c
. Thereafter, as shown in
FIG. 8C
, the above chip-like N type thermoelectric converting elements
19
are placed one by one on the respective electrodes
12
c
, whereby the P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are disposed alternatively.
And, as in
FIG. 8A
above, a plurality of electrodes
12
c
are installed in the insulation substrate
12
b
, and at the same time, soldering paste
12
e
is coated on the respective electrodes
12
c
. And, as shown in
FIG. 8D
, the insulation substrate
12
b
having the electrodes
12
c
provided are arranged on the insulation substrate
12
a
on which the P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are placed. The arrangement is carried out so that the electrodes
12
c
secured on the insulation substrates
12
b
are bridged on the electrodes
12
c
secured on the insulation substrates
12
a
. That is, adjacent electrodes
12
c
on the upper insulation substrate
12
b
are, respectively, put on the P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
on the electrodes
12
c
of the lower insulation substrates
12
a.
In this state, soldering paste
12
e
is reflown in a soldering reflow furnace (not illustrated). By reflow, the P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are bonded between two insulation substrates
12
a
and
12
b
, and at the same time, the P type thermoelectric converting elements
18
are electrically connected to the N type thermoelectric converting elements
19
in series via electrodes
12
c
. And, a Thermo-module
42
shown in
FIG. 8E
can be produced by the above production process.
The reason why heating and cooling actions can be produced by feeding an electric current to a Thermo-module are described below. That is, as described above, the P type thermoelectric converting elements
18
and N type thermoelectric converting elements
19
are placed between two insulation substrates
12
a
and
12
b
, and are electrically connected to each other in series. Therefore, as shown in
FIG. 7A
, by application of a direct current voltage from outside the Thermo-module
42
, an electric current flows from the insulation substrate
12
a
toward the insulation substrate
12
b
in the P type thermoelectric converting elements
18
, and flows from
12
b
toward
12

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