JP4350382B2 - Semiconductor laser device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of a semiconductor laser device that has high heat dissipation, little stress applied to a semiconductor laser chip, and capable of stable bonding, and a manufacturing method thereof.
[0002]
[Prior art]
Generally, in a semiconductor laser device, heat is generated in a semiconductor laser chip (LD chip) by laser oscillation. In order to remove this heat, a semiconductor laser device in which a semiconductor laser chip is attached to a heat radiation stem made of metal has been proposed (see, for example, Patent Document 1). A semiconductor laser device in which a submount is interposed between the semiconductor laser chip and the stem has also been proposed in order to relieve the thermal stress caused by the difference in linear expansion coefficient between the semiconductor laser chip and the stem. (For example, refer to Patent Document 2). Note that the semiconductor laser chip usually has a junction down (J / D) structure in order to ensure heat dissipation.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-218244 ([0010] to [0012], FIG. 1)
[Patent Document 2]
JP 2000-68583 A ([0008], FIG. 1)
[0004]
[Problems to be solved by the invention]
Incidentally, in recent years, a semiconductor laser device (package) having higher heat dissipation has been demanded in accordance with a demand for higher output of the semiconductor laser device or a demand for a smaller package. Therefore, there is an increasing need to switch the metal material forming the stem to a material (for example, Cu) having a higher thermal conductivity than a conventionally used Fe-based material. However, since a material having high thermal conductivity generally has a large coefficient of linear expansion, there is a concern that the semiconductor laser chip may be damaged by the thermal stress generated by the difference in coefficient of linear expansion between the semiconductor laser chip and the stem. The
[0005]
This thermal stress depends on the difference in linear expansion coefficient as described above, and increases as the melting point (freezing point) of the solder material as the bonding material increases (in proportion). For this reason, if a metal material having high thermal conductivity is used as the stem material and an Au-based solder material having a high melting point (for example, the melting point of AuSn solder material is 283 ° C.), the thermal stress is very high. There is a problem of becoming larger.
[0006]
Therefore, in order to solve such a problem, it is conceivable to use a solder material having a low melting point as the bonding material. However, in this case, since there are very few Au-based solder materials having a melting point lower than that of the AuSn solder material, a solder material other than the Au-based solder has to be used in practice, but a solder material other than the Au-based solder material was used. In this case, a hard and brittle intermetallic compound is generated by the Au plating of the stem and the solder material at the time of joining. For this reason, there exists a problem that the stable joining cannot be obtained.
[0007]
Further, a countermeasure such as using a resin as a bonding material is also conceivable. However, in this case, when a semiconductor laser chip having a junction down structure is bonded (die-bonded) to the submount with resin (die bonding), the size of the semiconductor laser chip is very small (minimum), and the semiconductor laser rises due to the resin rising to the side surface. Since there is a problem that the chip is short-circuited, it is necessary to control the amount of resin applied finely or finely, but such control is very difficult.
[0008]
The present invention has been made to solve the above-described conventional problems, and has a high heat dissipation property, a stress applied to the semiconductor laser chip is reduced, and a semiconductor laser device capable of stable bonding, and the semiconductor laser. An object of the present invention is to provide a device manufacturing method.
[0009]
[Means for Solving the Problems]
A semiconductor laser device according to the present invention made to solve the above problems is a semiconductor laser device in which a semiconductor laser chip and a stem are arranged via a submount, and the semiconductor laser chip is made of a low melting point solder material. While the submount is joined to the submount, the submount is made of a thermosetting resin that cures at a temperature approximately equal to the melting point of the low melting point solder material or a thermoplastic resin that melts at a temperature approximately equal to the melting point of the low melting point solder material. It is characterized by being joined. The method for manufacturing the semiconductor laser device according to the present invention includes a step of bonding the semiconductor laser chip to the submount with a low melting point solder material, and a step of bonding the stem to the submount with a thermosetting resin or a thermoplastic resin. Simultaneously cooling the assembly to be joined to the melting point of the low melting point solder material and the curing temperature of the thermosetting resin or the melting temperature of the thermoplastic resin, and then cooling the assembly. It is a feature.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.
Embodiment 1 FIG.
The first embodiment relates to the structure of the semiconductor laser device.
FIG. 1 is an elevation view showing a configuration of a semiconductor laser device according to the present invention. As shown in FIG. 1, the semiconductor laser device S includes a laser diode chip 1 (hereinafter referred to as “LD chip 1”), a submount 2, and a high heat conduction stem 3 (or may be a normal Fe stem). And. Here, the LD chip 1 and the high heat conduction stem 3 are arranged so that the submount 2 is sandwiched between them. The semiconductor laser device S is used for optical storage, optical communication, and the like, for example.
[0011]
Although not shown in detail, the LD chip 1 is a semiconductor laser chip having a junction down structure, and its active layer (not shown) is formed in a portion near the submount in the LD chip 1. As a result, the release or movement of heat generated in the LD chip 1 due to the laser oscillation to the high heat conduction stem 3 is promoted. In this LD chip 1, when a voltage is applied between a p-electrode (not shown) and an n-electrode (not shown) and a current exceeding a threshold value flows, laser oscillation occurs near the active layer. A laser beam is generated, and this laser beam is emitted to the outside through an optical waveguide (not shown) formed in the vicinity of the active layer.
[0012]
The submount 2 is formed of silicon carbide (SiC), aluminum nitride (AlN), or the like, and relieves thermal stress caused by a difference in linear expansion coefficient between the LD chip 1 and the high thermal conduction stem 3. The high thermal conduction stem 3 is formed of a metal having high thermal conductivity such as copper (Cu), and the surface thereof is plated with gold. Then, the high heat conduction stem 3 receives heat generated in the LD chip 1 by laser oscillation and releases it to the outside. That is, the high heat conduction stem 3 cools the LD chip 1.
[0013]
In this semiconductor laser device S, the LD chip 1 is bonded to the LD chip side surface of the submount 2 by a low melting point solder material 4. Here, since the low melting point solder material 4 is not in contact with the gold-plated high thermal conduction stem 3, it is not necessary to use an Au-based solder material, and a stable joint can be obtained even if a low melting point solder material is used. (For example, InPb solder).
[0014]
On the other hand, the high heat conduction stem 3 is joined to the high heat conduction stem side surface of the submount 2 by a joining resin 5. The bonding resin 5 may be any resin as long as it can bond the submount 2 made of silicon carbide, aluminum nitride or the like and the high heat conduction stem 3 made of copper or the like and plated with gold. A curable epoxy resin or the like can be used. The bonding resin 5 preferably has a high thermal conductivity. However, since the heat generated in the LD active layer spreads in the submount, even if a resin having a thermal conductivity lower than that of the solder material is used, the heat dissipation is achieved. There is no significant effect on sex.
[0015]
In the semiconductor laser device S according to the first embodiment, the LD chip 1 and the submount 2 are bonded at low temperature using a low melting point solder material 4 as a bonding material (die bonding is performed). In such joining with solder material, the supply amount of solder material can be controlled finely or finely by solder vapor deposition or solder plating, etc., so that the rise of solder due to excessive supply of joining material causes LD chip short circuit. The stable joining can be obtained. When the LD chip 1 and the submount 2 are bonded with resin, it is extremely difficult to control the supply amount to be minute or minute.
[0016]
Further, in the semiconductor laser device S according to the first embodiment, the high thermal conductivity stem 3 and the submount 2 are bonded at a low temperature (die bonding) using the bonding resin 5 as a bonding material. Thus, since resin is used as the bonding material, a hard and brittle intermetallic compound is not generated between the high heat conduction stem 3 and the submount, and stable bonding can be obtained. When the high heat conduction stem 3 and the submount 2 are joined with a low melting point solder material that is not Au-based, an intermetallic compound having a hard and brittle property is generated, and it is difficult to obtain a stable joint.
[0017]
As described above, in the semiconductor laser device S according to the first embodiment, the LD chip 1 and the submount 2 are bonded at a low temperature, and the high thermal conduction stem 3 and the submount 2 are also bonded at a low temperature. For this reason, in the joining process, the temperature of the LD chip 1, the submount 2 or the high heat conduction stem 3 does not increase so much. For this reason, although a metal material such as copper having a high thermal conductivity but a high linear expansion coefficient is used as the material of the high thermal conductivity stem 3, the thermal stress applied to the LD chip 1 in the joining process. Is reduced. As a result, it is possible to obtain a semiconductor laser device S with high heat dissipation and low stress. Since bonding at a low temperature is possible, the same effect can be obtained by making the submount highly conductive.
[0018]
Embodiment 2. FIG.
The second embodiment of the present invention will be described below. The second embodiment relates to a method for manufacturing the semiconductor laser device S according to the first embodiment.
According to the manufacturing method of the semiconductor laser device S according to the second embodiment, the process of joining the LD chip 1 to the submount 2 with the low melting point solder material 4 and the high heat conduction stem 3 in the single joining process and the joining resin 5 and the process of joining to the submount 2 are performed simultaneously.
[0019]
In the method of manufacturing the semiconductor laser device S, the low melting point solder material 4 and the bonding resin 5 are such that the melting point (freezing point) of the low melting point solder material 4 and the curing temperature (curing temperature) of the bonding resin 5 are substantially equal. Select. Then, a thin layer of the low melting point solder material 4 is formed on the LD chip 1 (or the surface of the submount 2 on the LD chip side) by solder vapor deposition or solder plating, while the high heat conduction stem 3 (or the high heat conduction stem of the submount 2). The thermosetting bonding resin 5 is thinly applied to the side surface.
[0020]
Next, after assembling the LD chip 1, the submount 2 and the high heat conduction stem 3 in a predetermined form, the assembly is heated to a temperature slightly higher than the melting point of the low melting point solder material 4 or the curing temperature of the bonding resin 5. Heat to As a result, the low melting point solder material 4 is melted and adhered to the LD chip 1 and the submount 2, and the bonding resin 5 is cured to bond the high heat conduction stem 3 and the submount 2. Thereafter, the assembly is cooled to room temperature. As a result, the low melting point solder material 4 is solidified to join the LD chip 1 and the submount 2 together. If the curing time is insufficient, batch processing is performed in a high-temperature bath or reflow.
[0021]
According to the manufacturing method of the semiconductor laser device S according to the second embodiment, the LD chip 1, the submount 2, and the high heat conduction stem 3 can be bonded at a relatively low temperature (for example, about 150 ° C. to 250 ° C.). These are not very hot. For this reason, although a metal material such as copper having a high thermal conductivity and a high linear expansion coefficient is used as the material of the high thermal conduction stem 3, the thermal stress applied to the LD chip 1 in the joining process is high. Reduced. Therefore, it is possible to obtain a semiconductor laser device S with high heat dissipation and low stress. In addition, since the LD chip 1, the submount 2 and the high heat conduction stem 3 can be bonded in a single bonding process, the manufacturing process of the semiconductor laser device S is simplified and required for manufacturing the semiconductor laser device S. Time and cost can be reduced.
[0022]
In the semiconductor laser device S or the manufacturing method thereof, a thermosetting resin such as an epoxy resin is used as the bonding resin 5, but a thermoplastic resin may be used. In this case, the assembly composed of the LD chip 1, the submount 2 and the high heat conduction stem 3 is heated to a temperature slightly higher than the melting point of the low melting point solder material 4 or the melting temperature of the bonding resin 5, and then cooled to room temperature. That's fine.
[0023]
【The invention's effect】
According to the present invention, it is possible to provide a semiconductor laser device with high heat dissipation, reduced stress applied to the semiconductor laser chip, and capable of stable bonding, and a method for manufacturing the semiconductor laser device.
[Brief description of the drawings]
FIG. 1 is a schematic elevation view of a semiconductor laser device according to the present invention.
[Explanation of symbols]
S semiconductor laser device, 1 LD chip (laser diode chip), 2 submount, 3 high thermal conduction stem, 4 low melting point solder material, 5 bonding resin.

Claims (4)

A semiconductor laser device in which a semiconductor laser chip and a stem are arranged via a submount,
While the semiconductor laser chip is bonded to the submount by a low melting point solder material,
A semiconductor laser device, wherein the stem is joined to the submount by a thermosetting resin that cures at a temperature substantially equal to the melting point of the low melting point solder material . A semiconductor laser device in which a semiconductor laser chip and a stem are arranged via a submount,
While the semiconductor laser chip is bonded to the submount by a low melting point solder material,
A semiconductor laser device, characterized in that the stem is joined to the submount by a thermoplastic resin that melts at a temperature substantially equal to the melting point of the low melting point solder material. The semiconductor laser chip and the stem are arranged via the submount, and the semiconductor laser chip is joined to the submount by the low melting point solder material, while the stem is cured at a temperature substantially equal to the melting point of the low melting point solder material. A method of manufacturing a semiconductor laser device bonded to a submount by a curable resin,
The step of joining the semiconductor laser chip to the submount with a low melting point solder material and the step of joining the stem to the submount with a thermosetting resin are performed on the assembly to be joined with the melting point and thermosetting property of the low melting point solder material. A method of manufacturing a semiconductor laser device, wherein the semiconductor laser device is simultaneously heated by being heated to a temperature higher than a curing temperature of the resin and then cooled . The semiconductor laser chip and the stem are arranged via the submount, and the semiconductor laser chip is joined to the submount by the low melting point solder material, while the stem is melted at a temperature substantially equal to the melting point of the low melting point solder material. A method of manufacturing a semiconductor laser device joined to a submount by a plastic resin,
The step of bonding the semiconductor laser chip to the submount with a low melting point solder material and the step of bonding the stem to the submount with a thermoplastic resin are carried out by attaching the assembly to be bonded to the melting point of the low melting point solder material and the thermoplastic resin. A method of manufacturing a semiconductor laser device, which is performed by simultaneously heating to a temperature higher than the melting temperature and then cooling.

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