JP2001168447A - Laser diode optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient high-output laser diode optical module, which can efficiently radiate heat generated, when a high-out laser emits light to the outside without allowing the heat to stay in a package, and in addition, will not impair optical coupling. SOLUTION: In this laser diode optical module 1, constituted by housing a laser diode 3 in the package 2, a Peltier element 12 fitted with a cooling plate 13 made of a electrical insulating material and a mounting plate 14 mode of another electrical insulating material is fixed to the external surface of the bottom plate 11 of the package 2, to which optical module parts are fixed. It is preferable to have the Peltier element 12 coated with a moisture-proofing film in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode optical module used for optical communication.

[0002]

2. Description of the Related Art The demand for optical communication as communication means has been steadily increasing with the expansion of communication demand, and a laser diode optical module is one of the main components used for this optical communication. The laser diode optical module is mainly used as an amplification excitation light source of a fiber amplifier which is a kind of optical amplifier. In order to multiplex optical signals or extend the non-repeated distance of light, it is necessary to increase the output of fiber amplifiers, and in fiber amplifiers, it is necessary to increase the output of laser diodes that affect the amplification degree. Have been.

[0003] In order to increase the output of a laser diode, it is necessary to lower the temperature of the laser diode, which rises during laser emission. FIGS. 5A and 5B show an example of a conventional laser diode optical module. In the laser diode optical module 101, a material having a high thermal conductivity for promoting heat radiation from the laser diode 103, for example, a submount 104 made of diamond, and a Cu-W alloy having a high thermal conductivity in the package 102 (Hereinafter, referred to as “Cu-W”) and an L-carrier 108.

A Peltier for cooling them
The element 112 is composed of the L-carrier 108 and the bottom plate 111 (C
u-W), a cooling plate 113 made of an electrical insulator
(Al _TwoO_Three) And heat sink 114 (Al_TwoO_ThreeMounted via
Have been. The bottom plate 111 has mounting holes 11 for mounting.
5 are provided.

[0005] The amount of heat radiated from the Peltier element 112 includes heat (about 1 W) from the laser diode 103 and
This is operating heat (approximately 3 W) generated by the operation of the Peltier element 112, and it is important to reduce the thermal resistance of the heat radiation system to improve the heat radiation from the laser diode 103. Therefore, as a conventional technique, the bottom plate 1 of the package 102 is used.
For example, a method of using Cu-W having a high thermal conductivity for 11 and making the thickness of the portion of the bottom plate 111 on which the heat radiating plate 114 is placed thinner than the surroundings to make it concave is adopted.

[0006]

In the structure shown in FIGS. 5 (a) and 5 (b), the L-carrier 108 (Cu-W as a conductor) and the cooling plate 113 (Al ₂ O _{3 as} an electrical insulator) are used. It is necessary to join between the bottom plate 111 (Cu-W of the conductor) and the radiator plate 114 (Al ₂ O ₃ of the electric insulator) with solder such as Pb or Sn. In current processes, there are oxides and minute voids at the junction. Therefore, the thermal resistance of one solder bonding layer is 0.4 ° C./W, and the thermal resistance of two solder bonding layers is 0.8 ° C./W.
And hinders the heat transfer.

Further, since the heat sink 114 having a high temperature is provided inside the package 102, the heat is
It stays inside and hinders heat dissipation.

The present invention provides a high-output laser diode optical module that efficiently radiates heat generated by high-power laser emission to the outside and does not impair optical coupling.

[0009]

SUMMARY OF THE INVENTION In an optical module having a laser diode provided in a package, a cooling plate of an electrical insulator and an electrical insulator are attached to an outer surface of a bottom plate of the package to which the optical module components are fixed. Fix the Peltier device with the plate. That is, the conventional Peltier device is
Although the Peltier device is housed in a sealed package, the Peltier device is mounted outside the package. still,
The mounting plate serves both to mount the laser diode optical module to a printed circuit board or the like and to radiate the operating heat of the Peltier device.

If the thickness of the optical module component mounting portion of the bottom plate is made thinner than the periphery and is depressed, the heat generated by the laser diode can be easily transmitted to the outside, and the Peltier for the laser diode can be easily assembled when assembling the optical module. This is preferable because the displacement of the element in the planar direction can be reduced and efficient heat radiation is possible. Further, it is more preferable that the bottom plate, the cooling plate and the mounting plate are made of AlN having a large thermal conductivity because heat is easily transferred to the outside.

Since the package is mounted on a Peltier element having a small projected area and has an unstable surface and requires vibration resistance, it is preferable to perform the following. That is, a Peltier element with a cooling plate and a heat sink is fixed at the center of the lower surface of the bottom plate of the package to which the optical module is fixed, and mounting holes are similarly formed at both ends of the lower surface of the bottom plate in the longitudinal direction. Fix the mounting plate. This mounting plate is Al ₂
It is preferable to use a material having a low thermal conductivity, such as O ₃ or a resin, because heat from the mounting surface of the laser diode optical module is not transmitted to the bottom plate through the mounting plate.

The dimension of the mounting plate from the lower surface of the bottom plate to the mounting surface is equal to or smaller than the sum of the cooling plate, the Peltier element, and the heat sink. This is because when the mounting plate of the laser diode optical module is fastened to the mounting surface with screws, the mounting plate is elastically deformed, and the lower surface of the heat radiating plate always adheres to the mounting surface. As a result, the operating heat of the Peltier element is efficiently transferred to the mating component.

Since the Peltier device is exposed not to the inside of the sealed package but to the external environment, it is preferable to apply a moisture-proof coating to the Peltier device so that the performance of the Peltier device does not deteriorate due to moisture absorption and condensation. desirable.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention will be described with reference to FIGS. 1 (a) and 1 (b). Laser diode optical module 1 of the present invention
Is composed of a package 2 for housing the optical module components therein, a cooling plate 13 for cooling heat generated by the laser diode 3, and a Peltier element 12 with a mounting plate 14. The Peltier element 12 is fixed to the outer surface of the bottom plate 11 of the package 2. still,
The optical module components are composed of a laser diode 3, a photodiode 4, a collimating lens 9, and mounts and carriers for supporting them, and are main components for optical communication connected to an external optical fiber (not shown). It is.

When the Peltier device 12 is exposed to an external environment, its performance deteriorates due to moisture absorption, dew condensation, and the like. Therefore, in a conventional laser diode optical module, the Peltier device 12 is housed in a sealed package 2. I was In the present invention, the Peltier device 12 is provided with a moisture-proof coating as a measure against moisture absorption and dew condensation, and the Peltier device 12 is mounted outside the package 2.

(Embodiment 1) Referring to FIG.
This will be described in (b). A 0.5 mm thick Fe—Ni—Co alloy (for example, Kovar) is used for the side plate 10 of the package 2, and a 0.5 mm thick Cu is used for the bottom plate 11.
-W was used. The dimensions of the package 2 are 21 mm in length,
The width is 13 mm and the height is 5 mm.

The side plate 10 is made of Fe-N having a thickness of 0.5 mm.
Ni (1 μm) / A is made by cutting from a plate material of i-Co alloy to increase the adhesive strength with the brazing material when brazing.
u (1 μm) plating was applied. Al ₂ O ₃ and Fe-
The electrode portion 17 formed of a Ni—Co alloy lead was fixed to the side plate 10 with a silver brazing (800 ° C.).

Next, 0.5 mm thick Cu
-W, which is made by cutting from the plate material, and is made of Ni in order to increase the adhesive strength with the brazing material when brazing similarly to the side plate 10.
(1 μm) / Au (1 μm) plating was performed. Then, the four side plates 10 and one bottom plate 11 were inserted into a carbon mold to form a temporary assembly, and fixed in a hydrogen gas furnace to the shape shown in FIG. The heating condition in the furnace was 450 ° C. × 30 min. It is. Further, the collimating lens 9 is provided with gold solder of AuSn.
(350 ° C. × 30 min.).

Subsequently, the optical module parts were assembled. After bonding the laser diode 3 on the submount 5 (diamond) with AuSn (300 ° C. × 2 min.), This is mounted on the subcarrier 6 in the same manner as AuSn (300 ° C. × 2 mi).
n. ). Further, the photodiode 4 was bonded to the mount 7 and the subcarrier 6 and the mount 7 were bonded to the L-carrier 8 with AuSn (300 ° C. × 2 min.). Then, after mounting this L-carrier 8 at a predetermined position on the bottom plate 11 with AuSn (300 ° C. × 2 min.), The lid 16 was fixed by seam welding.

In the present invention, since the Peltier element 12 is mounted outside the hermetic package 2, the performance of the Peltier element 12 is slightly deteriorated due to moisture absorption, dew condensation, and the like.
As a countermeasure for this, a moisture-proof coat (a parylene resin is coated by a chemical vapor deposition method) called Technicoat (trade name) is applied to the Peltier element 12 in advance.

On the lower surface of the bottom plate 11 (where the cooling plate 13 is joined), Pb-64Sn
Pre-heated and crimped. And the cooling plate 1
3 (Al ₂ O ₃ ) and the Peltier element 12 with the mounting plate 14 (Al ₂ O ₃ ) are placed in a hydrogen furnace (190 ° C. × 30 mi).
n. ) To heat and join. The mounting plate 14 is provided with a mounting hole 15.

In the first embodiment, as described above, the bottom plate 1
The material of No. 1 was Cu-W, the material of the cooling plate 13 and the mounting plate 14 for cooling and radiating heat above and below the Peltier element 12 was Al ₂ O _3, and materials having a proven track record in the prior art were selected.

By employing the structure shown in FIG. 1, the solder bonding layer becomes only one layer between the bottom plate 11 and the cooling plate 13, and the solder bonding layer of the laser diode optical module according to the prior art is two layers. Less. That is, it is a great merit that the thermal resistance of 0.4 ° C./W for one solder bonding layer can be omitted. In addition, since the Peltier element 12 is arranged outside the package 2, it is preferable in that the operating heat does not stay inside the package 2 and the laser diode 3 is cooled.

(Embodiment 2) In Embodiment 2, as shown in FIG. 2, the optical module component mounting portion of the bottom plate 11 (Cu-W) having a thickness of 0.5 mm is thinned by cutting to a thickness of 0.3 mm. Then, an optical module component was mounted on the portion having a thickness of 0.3 mm. This aims at efficiently transferring the heat from the L-carrier 8 to the outside. Except for the shape change in which a part of the bottom plate 11 is thinned, the material of each material, the package dimensions, and the like are exactly the same as those in the first embodiment.

Embodiment 3 The structure and dimensions of Embodiment 3 are as follows.
(The thickness at which the optical module parts are mounted on the bottom plate 11 is 0.3
All of them are the same as the embodiment 2 of FIG. The different point is that the materials of the bottom plate 11, the cooling plate 13, and the mounting plate 14 are changed. That is, compared to the second embodiment,
The material of the bottom plate 11 is changed from Cu-W to AlN,
And the material of the mounting plate 14 are Al ₂ O ₃ (thermal conductivity 17 W / (m ·
K)) to high thermal conductivity AlN (thermal conductivity 170W /
(mK)). This is intended to efficiently transfer the operating heat of the Peltier element 12 to an attachment partner (not shown). The thermal conductivity of Cu-W and AlN is similar.

The side plate 10 is made of a 0.5 mm thick Fe--Ni
-Co, the bottom plate 11 is made of 0.5 mm thick AlN, and is plated with Ni (1 μm) / Au (1 μm) to increase the adhesive strength with the brazing material when brazing each.
No. 0 was assembled with gold brazing, and the side plate 10 and bottom plate 11 were joined with silver brazing. Assembly of optical module parts, Peltier element with cooling plate 13 and mounting plate 14
Examples 1 and 2 such as a method of soldering with Pb-64Sn
Is the same as

Although AlN is preferable from the viewpoint of heat conduction, the results have been poor in the past, and the linear expansion coefficient of AlN
(Linear expansion coefficient 4.5 × 10 ⁻⁶ / K) refers to Al ₂ O ₃ (linear expansion coefficient 6.7 × 10 ⁻⁶ / K) or Cu—W (linear expansion coefficient 6.5 × 10 ⁶ / K).
⁻⁶ / K), it was confirmed by the following test whether or not a problem with the temperature rise / fall occurred, but no problem was found. Incidentally, since the proven materials were used in Examples 1 and 2, the results of the confirmation test did not have any problem as expected.

The confirmation test is called a power cycle test, and the test is performed under an environment of a predetermined temperature cycle while applying an alternating current to the Peltier device 12 of the laser diode optical module 1. The evaluation is made based on the rate of change of the AC resistance value of the Peltier element before and after giving the temperature history. The method, conditions and judgment are as follows: Peltier element 1 of laser diode optical module 1
An AC current of 1.2 A is passed through the sample _{No. 2} and the AC resistance value R1 at the beginning of the test is measured. The history of the temperature cycle shown in FIG. 4 is given to the laser diode optical module 1 for 100 cycles. The alternating current resistance value R ₂ after 100 cycles the temperature history of the measuring. If the rate of change of the AC resistance value R ₂ / R ₁ = 1.1 or less, it is judged as acceptable.

In the first, second, and third embodiments, the package 2 is supported by the Peltier element 12 having a smaller projected area than the package 2, and has a slightly unstable structure. Therefore, when vibration or some external force is applied to the package 2, the bottom plate 1
1. The strength of each joint between the cooling plate 13, the Peltier element 12, and the mounting plate 14 is concerned. Example 4 corresponds to this
It is.

(Embodiment 4) Embodiment 4 is shown in FIGS. 3 (a) and 3 (b).
The structure shown in FIG. The package 2 is all the same as the third embodiment.
-Co alloy, the bottom plate 11 is made of AlN, and the optical module mounting portion is thinner than the surroundings). Preheat and crimp. Then, the cooling plate 13 (AlN) and the heat radiating plate 18 (Al
N) with the Peltier element 12 attached thereto, and placed in a hydrogen furnace (1).
90 ° C. × 30 min. ) To heat and join.

Next, a mounting plate 14 (provided with mounting holes 15) having a thickness of 0.5 mm and having an L-shaped cross section is made of Al ₂ O ₃ , and thermal conductivity is set at both ends of the lower surface of the package 2 in the longitudinal direction. 3 was bonded to the portion shown in FIG. 3 with an adhesive resin having a small thermal conductivity (thermal conductivity 0.5 W / (m · K)). Al with low thermal conductivity is attached to the mounting plate 14.
_The reason for using ₂ O ₃ (thermal conductivity 17 W / (m · K)) is to prevent heat from the mounting surface from being transferred to the bottom plate 11 through the mounting plate 14 and increasing the temperature inside the package 2. is there.
Incidentally, the temperature difference between the upper and lower sides of the Peltier element 12 is about 4
It is around 5 ° C. Although the mounting plate 14 is made of Al ₂ O ₃ , it is preferable that the mounting plate 14 be made of a resin having a low thermal conductivity for the above-described reason.

The dimension h ₁ from the bottom plate 11 to the mounting surface of the mounting plate 14 is set to be 0.2 mm smaller than the dimension h ₂ which is the sum of the cooling plate 13, the Peltier element 12 and the heat radiating plate 18. did. This is intended to ensure that when the laser diode module is mounted on the mounting surface, the lower surface of the heat radiating plate 18 always adheres to the mounting surface. A power cycle test was also performed on Example 4, but there was no problem.

Comparative Example 1 Comparative Example 1 is shown in FIGS. 5 (a) and 5 (b). A 0.5 mm-thick Fe-Ni-Co alloy was used for the side plate 110 of the package 102 as in Examples 1 and 2, and a 0.5 mm-thick Cu-W was used for the bottom plate 111. Package dimensions are 21mm long and 13m wide
m, height 8 mm.

A side plate 110 and a bottom plate 111 are manufactured in the same processing method as in the embodiment, and Ni (1 μm) / Au (1 μm) plating is performed to increase the bonding strength with the brazing material when brazing. Was assembled. The bottom plate 111 is the same as that of the second embodiment.
The optical module component mounting portion was thinned to 0.3 mm as in the cases of 3 and 4.

Next, the optical module parts are assembled in the same manner as in the embodiment, and the lower surface of the L-carrier 108 (Cu-W) and the cooling plate 113 (Al ₂ O ₃ ) of the Peltier element are connected to Pb-
64Sn solder and then Peltier device 11
The heat sink 114 (Al ₂ O ₃ ) of No. ₂ was joined to a predetermined position of the bottom plate 111 (Cu-W) with Pb-64Sn solder.
Again, having two solder bonding layers is disadvantageous in terms of thermal resistance. Table 1 shows dimensions, materials, and structures of Examples 1 to 4 and Comparative Example 1, and Table 2 shows physical properties of each material.

[0036]

[Table 1]

[0037]

[Table 2]

The outputs of the laser diode optical modules of Examples 1 to 4 and Comparative Example 1 were tested and evaluated. The test method is as follows: 2 V x 600 mA D
Apply C current. In the first embodiment, when the power is output without loss in the first embodiment, the power is 200 mW and the heat is 1000 mW. Therefore, the light output was measured, and what percentage of 200 mW was reduced was evaluated. During the test, a Peltier device having a sufficient capacity was used as a mounting partner for mounting the laser diode optical module, and the mounting bottom surface of the laser diode optical module was kept constant at 70 ° C. Table 3 shows the results.

[0039]

[Table 3] note. Output% = light output ÷ 200 mW × 100

In the second embodiment, the bottom plate 11 (Cu
Although the mounting position of the optical module component of -W) was merely reduced from 0.5 mm to 0.3 mm, the optical output was improved by 0.5% as compared with the first embodiment. In the third embodiment, the material of the bottom plate 11 is changed from Cu-W to Al
Instead of N, the material of the cooling plate 13 and the mounting plate 14 was changed from Al ₂ O ₃ to AlN having a large thermal conductivity, but the light output was improved by 2.0% compared to the second embodiment.

The fourth embodiment is basically similar to the third embodiment. The difference is that the third embodiment has a structure in which the mounting plate, which is one component, performs both mounting and heat dissipation of the Peltier element (FIG. 2). On the other hand, the fourth embodiment is different from the first embodiment in that the mounting and the heat radiation of the Peltier element are divided into two parts, a mounting plate and a heat radiating plate for the purpose of earthquake resistance (FIG. 3). As a result, the light output of the fourth embodiment becomes the third embodiment.
2.5% lower than

Comparative Example 1 according to the prior art has a structure in which the Peltier device of Example 2 is disposed inside a package, and is made of a material used for a bottom plate, plates above and below the Peltier device for cooling and radiating heat, and the like. Is the same as in the second embodiment. That is, the optical output of Comparative Example 1 in which the Peltier element is disposed inside the package is 4.0% lower than that of Example 2. Also,
Compared to Example 3 having the highest light output according to the present invention, Comparative Example 1 resulted in 6% lower.

[0043]

The Peltier device that cools a high-power laser diode generates operating heat. Conventionally, this Peltier device is housed in a package together with an optical module. For this reason, operating heat is not preferable in terms of cooling the temperature of the laser diode from the viewpoint of heat transfer efficiency to the inside of the package and the heat transfer efficiency to the outside.

By mounting this Peltier element outside the package, the operating heat of the Peltier element does not stay inside the package, the efficiency of heat transfer to the outside is improved, and the optical coupling is not impaired. A good laser diode optical module.

[Brief description of the drawings]

FIG. 1 is an external view and a sectional view of a laser diode optical module according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a laser diode optical module according to second and third embodiments of the present invention.

FIG. 3 is an external view and a sectional view of a laser diode optical module according to a fourth embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between time and temperature in a power cycle test.

FIG. 5 is an external view and a sectional view of a laser diode optical module according to an embodiment of the prior art.

[Explanation of symbols]

 1. 1. Laser diode optical module Package 3. Laser diode 4. Photodiode 5. Submount 6. Subcarrier 7. Mount 8. L-carrier 9. Collimating lens 10. Side plate 11. Bottom plate 12. Peltier device 13. Cooling plate 14. Mounting plate 15. Mounting hole 16. Lid 17. Electrode section 18. Heat sink

Claims (6)

[Claims] 1. An optical module comprising a laser diode provided in a package, wherein a cooling plate of an electrical insulator and a mounting plate of an electrical insulator are provided on an outer surface of a bottom plate of the package to which an optical module component is fixed. A laser diode optical module, wherein the Peltier element is fixed. 2. The laser diode optical module according to claim 1, wherein the thickness of the mounting portion of the bottom plate on which the optical module component is mounted is made thinner than the surroundings and is depressed. 3. The apparatus according to claim 1, wherein the bottom plate, the cooling plate, and the mounting plate are A
3. The laser diode optical module according to claim 1, comprising 1N. 4. An optical module comprising a laser diode provided in a package, wherein a cooling plate of an electrical insulator and a heat radiating plate of an electrical insulator are provided on an outer surface of a bottom plate of the package to which the optical module components are fixed. Peltier element is fixed, and a mounting plate is fixed to both ends of the outer surface of the bottom plate. Further, the dimension h ₁ from the outer surface of the bottom plate to the mounting surface of the mounting plate is the cooling plate and the Peltier device. laser diode optical module, wherein the dimension of the sum of the heat radiating plate h ₂ equal to or smaller and. 5. The laser diode optical module according to claim 4, wherein said mounting plate is made of Al ₂ O ₃ or resin. 6. The laser diode optical module according to claim 1, wherein a moisture-proof coating is applied to the Peltier device.