JP2001217498A - Semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To firmly braze a semiconductor laser chip to a laser stem and improve a wettability of a brazing material for brazing the laser stem to a heat sink in a semiconductor laser which is made by brazing the semiconductor laser chip to the laser stem with In and then brazing the laser stem to the heat sink. SOLUTION: The semiconductor laser is made by brazing the semiconductor laser chip 16 to the laser stem 15 with In and then brazing the laser stem 15 to the heat sink 14. At least a part of the laser stem 15 which is in contact with the heat sink 14 is surface-treated with a metal thin film 20. A part of the laser stem 15 in contact with the semiconductor laser chip 16 is not formed with a metal thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly to a semiconductor laser in which a structure of a mounting portion of a semiconductor laser chip is improved.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. H10-190130
As shown in the publication, a semiconductor laser having a structure in which a semiconductor laser chip is bonded on a heat sink (heat spreader) is known. In addition to fixing the semiconductor laser chip directly on the heat sink in this way, there is also known a structure in which a semiconductor laser is bonded to a laser stem and the laser stem is fixed on the heat sink.

[0003] In order to join a semiconductor laser chip to a metal member such as a heat sink or a laser stem as described above, a brazing method using solder, In, or the like is often used. When performing this brazing, the method disclosed in
As shown in -190130, in order to improve the wetting property of the brazing material, the surface to be brazed is widely treated with a metal thin film. In particular, when a semiconductor laser chip is bonded to a laser stem, a gold thin film is often formed on the surface of the laser stem to which the semiconductor laser chip is bonded.

[0004]

However, as described above, the semiconductor laser chip of the laser stem is joined to a semiconductor laser in which the semiconductor laser chip is brazed to the laser stem by In, especially a high-power type semiconductor laser. If there is a gold thin film on the surface,
Gold and In partially alloy with each other, causing a problem that In is not uniformly melted. If this is the case, uniform brazing becomes impossible, which causes problems such as an increase in thermal resistance of this portion and a decrease in mechanical strength.

Therefore, a metal thin film other than gold, for example, Ni
Attempts have been made to solve the above-mentioned problems by forming a thin film of Pt or Pt.

However, it has been found that such a problem causes another problem due to the thin film of Ni, Pt, or the like formed at the portion of the laser stem joined to the heat sink. That is, in order to maintain the performance of the semiconductor laser, it is necessary to join the laser stem and the heat sink at a low temperature of less than 150 ° C., which is the melting point of In for brazing the laser stem and the semiconductor laser chip. At this time, if a thin film of Ni, Pt, or the like is formed on the portion of the laser stem that is joined to the heat sink, the wetting property of the brazing material will deteriorate and brazing will not be good, and the desired joining strength will not be obtained. That is, there arises such a problem that the heat dissipation cannot be achieved.

In order to solve this problem, it has been considered to clean the bonding surface with a flux. However, in such a case, the number of steps involved in the flux cleaning is increased, and contamination of the semiconductor laser by the flux residue becomes a problem. .

[0008] The present invention has been made in view of the above circumstances, and a semiconductor laser chip is provided with In
In a semiconductor laser in which the laser stem is brazed to a heat sink, the semiconductor laser chip is successfully brazed to the laser stem, while the solder material that joins the laser stem to the heat sink is welded. It is an object of the present invention to provide a semiconductor laser whose performance can be improved without requiring flux cleaning or the like.

[0009]

As described above, the semiconductor laser according to the present invention is a semiconductor laser in which a semiconductor laser chip is brazed to a laser stem by In and the laser stem is brazed to a heat sink. At least a part of a portion of the stem in contact with the heat radiating plate is surface-treated with a gold thin film, and a gold thin film is not formed on a portion of the laser stem in contact with the semiconductor laser chip.

The surface of the laser stem in contact with the semiconductor laser chip is desirably treated with at least one of Ni and Pt thin films.

Preferably, the laser stem is made of copper or copper / tungsten. And this laser stem, with respect to the heat sink, the melting point of In 15
It is desirable to braze with low-temperature solder having a melting point lower than 0 ° C.

In the semiconductor laser of the present invention,
The heat sink is fixed in the semiconductor laser package via the Peltier element, and the junction of the laser stem, the heat sink, the Peltier element and the semiconductor laser package has a melting point of 15 ° C.
It is desirable to braze with low-temperature solder of less than 0 ° C.

In the semiconductor laser of the present invention,
It is desirable that the heat sink is fixed in the semiconductor laser package via the Peltier element, and that a gold thin film is formed on at least a part of the Peltier element joined to the heat sink and at least a part of the part joined to the semiconductor laser package.

[0014]

According to the semiconductor laser of the present invention, since the gold thin film is not formed in the portion of the laser stem in contact with the semiconductor laser chip, the above-mentioned problem caused by the presence of the gold thin film in this portion, that is, The problem that uniform brazing becomes impossible and the thermal resistance of this part becomes high and the mechanical strength becomes low can be solved.

On the other hand, in the semiconductor laser of the present invention, since at least a part of the portion of the laser stem that is in contact with the heat sink is surface-treated with a thin gold film, the portion is not subjected to flux cleaning. Also, the wetting property of the brazing material is improved, so that the brazing can be performed well. Therefore, the joining strength of the brazed portion is increased, and the heat dissipation is also improved. If the flux cleaning need not be performed as described above, the number of steps involved in the flux cleaning can be increased, and the contamination of the semiconductor laser due to the flux residue can be avoided.

When the laser stem is soldered to the heat sink with a low-temperature solder having a melting point lower than 150 ° C. of In, the brazing portion between the semiconductor laser chip and the laser stem by In is: It is possible to prevent adverse effects from high temperatures.

Further, a heat sink is fixed in the semiconductor laser package via a Peltier device, and a laser stem,
In the same manner as described above, when the joint between the heat sink, the Peltier element, and the semiconductor laser package is brazed with low-temperature solder having a melting point of less than 150 ° C., a high temperature is applied to the brazing portion between the semiconductor laser chip and the laser stem by In. Can be prevented from being adversely affected.

Further, in the semiconductor laser of the present invention, the radiator plate is fixed in the semiconductor laser package via the Peltier device, and at least a part of the Peltier device bonded to the radiator plate and a portion bonded to the semiconductor laser package In the case where a gold thin film is formed, the thermal conductivity of the gold thin film is high, so that the thermal contact resistance is reduced and the cooling efficiency is improved.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a side view of a semiconductor laser according to a first embodiment of the present invention, and FIG. 2 shows an exploded view of a main part thereof.

As shown, the semiconductor laser includes a package 12 comprising a package base 10 and a package cap 11, a Peltier device 13 fixed on the package base 10, and a heat spreader (radiation) on the Peltier device 13. It has a laser stem 15 fixed via a plate 14 and a semiconductor laser chip 16 attached to the laser stem 15.

A window glass 17 is attached to a window formed in the package cap 11, and a laser beam 18 emitted from a semiconductor laser chip 16 is applied to the window glass 17.
And is emitted out of the package 12.

Referring to FIG. 2, the above-mentioned configuration will be described in more detail together with the manufacturing method. Laser stem 15
Is made of Cu and its surface is plated with Ni. The lower surface 15 b of the laser stem 15, that is, the surface in contact with the heat spreader 14 is, for example, Au
Although the surface treatment is performed by the (gold) thin film 20, the surface treatment by the Au thin film is not performed on the surface 15a to which the semiconductor laser chip 16 is bonded.

On the other hand, the upper surface and the lower surface of the Peltier element 13, that is, the surface to be joined to the heat spreader 14 and the surface to be joined to the package base 10 are surface-treated by Au plating 21 (the lower surface is not shown). You.

On the joint surface 15a of the laser stem 15,
The semiconductor laser chip 16 is brazed by In.
After that, this laser stem 15 and heat spreader 14,
Heat spreader 14, Peltier device 13, Peltier device
13 and the package base 10 are soldered with a low temperature solder having a melting point lower than 150 ° C.
Brazed by 2, 23, 24 respectively.

As described above, in the semiconductor laser of this embodiment, the semiconductor laser chip of the laser stem 15
Since the Au thin film is not formed in the portion in contact with 16, a problem caused by the existence of the Au film in this portion, that is, uniform brazing becomes impossible, and the thermal resistance of this portion increases. The problem that the mechanical strength is reduced can be solved.

On the other hand, in this semiconductor laser, the portion of the laser stem 15 in contact with the heat spreader 14 is surface-treated with the Au thin film 20, so that this portion can be brazed without flux cleaning. Is improved, and brazing can be performed satisfactorily. Therefore, the joining strength of the brazed portion is increased, and the heat dissipation is also improved. If the flux cleaning need not be performed as described above, the number of steps involved in the flux cleaning can be increased, and the contamination of the semiconductor laser due to the flux residue can be avoided.

Then, the laser stem 15 and the heat spreader 14, the heat spreader 14 and the Peltier device 13, the Peltier device 13 and the package base 10 are connected to the melting point 15 of In.
Since each is brazed by low-temperature solders 22, 23, and 24 having a melting point lower than 0 ° C., a brazing portion between the semiconductor laser chip 16 and the laser stem 15 by In,
It is possible to prevent adverse effects from high temperatures.

Since the upper surface and the lower surface of the Peltier element 13 are each surface-treated by Au plating 21 having high thermal conductivity, the Peltier element 13 is compared with the case where a metal thin film such as Ni is formed on these surfaces. Peltier device 13 and package base 10 between device 13 and heat spreader 14
And the thermal contact resistance between them is lower, and the cooling efficiency is improved.

The joining of the laser stem 15 and the heat spreader 14 is preferably carried out by brazing in consideration of conductivity and heat dissipation. For joining, an adhesive may be applied in consideration of workability.

FIG. 3 shows a side view of the semiconductor laser according to the second embodiment of the present invention. In FIG. 3, elements that are the same as the elements in FIG. 1 are given the same reference numerals, and overlapping descriptions thereof will be omitted (hereinafter the same). As shown, in this embodiment, the heat spreader 14 and the upper surface of the Peltier element 13 are adhered by the adhesive 30, and the lower surface of the Peltier element 13 and the package base 10 are adhered by the adhesive 31. As the adhesives 30, 31, for example, EPOXY TE
An epoxy-based adhesive “# 310” manufactured by CHNOLOGY or the like can be suitably used.

If a thermosetting silicone adhesive such as “DA6523” manufactured by Dow Corning Toray Silicone Co., Ltd. is used as the adhesives 30 and 31, the pot life is long and the adhesives are applied. The light emission position of the semiconductor laser chip can be easily adjusted later. The adhesive curing conditions when using the adhesive `` DA6523 '' are 80
° C, 45 hours.

When the adhesive is used, the thermal contact resistance between the joining members tends to be higher than when the brazing is applied.
If Au plating is applied to the upper surface and the lower surface respectively, the effect of reducing the thermal contact resistance and increasing the cooling efficiency can be obtained. Conventionally, the upper surface and the lower surface of the Peltier element are generally plated with Ni, respectively. However, since Au has higher thermal conductivity than Ni, Au is used to reduce the thermal contact resistance.
Applying plating is more effective.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a side view of a semiconductor laser according to a third embodiment of the present invention.
The semiconductor laser according to the third embodiment basically differs from the semiconductor laser according to the second embodiment in FIG. 3 in that the laser stem 15 and the heat spreader 14 are brazed and Sn- The difference is that In solder 40 is used.

Hereinafter, the structure of the semiconductor laser will be described in more detail together with a method of manufacturing the same. In this embodiment, the laser stem 15 is made of Cu whose surface is plated with Ni, and has a size of 7 × 5.2 × 3 mm. A part (1 × 3 mm) of the surface 15 a (7 × 3 mm) of the laser stem 15 to which the semiconductor laser chip 16 is bonded is N
An i / Pt / In thin film is deposited, and the lower surface of the laser stem 15, that is, the surface in contact with the heat spreader 14
An Au thin film is deposited on a part (6 × 4.2 mm) of 15b (7 × 5.2 mm).

Then, the Ni / Pt of the laser stem 15 is formed.
/ In thin film deposited on the semiconductor laser chip
16 is heated to about 200 ° C. for bonding.

Next, on the lower surface 15b of the laser stem 15 to which the semiconductor laser chip 16 has been bonded, the Au thin film is deposited on the lower surface 15b, and the pellet-shaped Sn-In solder 40 (t) is formed.
0.1 × 6.5 × 4 mm), and heated to 130 ° C. in an atmosphere of 3% of hydrogen and 97% of nitrogen to melt the Sn-In solder 40 and scrub the Sn-In solder 40 with a sharp metal rod.
Wet uniformly on the Au thin film deposition surface.

Similarly, the surface of the heat spreader 14 to which the laser stem 15 is to be bonded is provided with a pellet-shaped Sn-I
The n-solder 40 (t0.1 × 10 × 7 mm) is placed and heated to 230 ° C. in an atmosphere of 3% of hydrogen and 97% of nitrogen.
Is melted, and the Sn-In solder 40 is scrubbed with a sharp metal rod to uniformly wet a portion in contact with the laser stem 15.

Then, the laser stem 15 with the Sn-In solder 40 and the heat spreader 14 are overlapped, and the two are joined while heating to 130 ° C. in an atmosphere of 3% hydrogen and 97% nitrogen. By the above series of operations, the laser stem 15 was formed using the Sn-In solder 40 without flux cleaning and at a relatively low temperature of 130 ° C.
And the heat spreader 14 can be joined sufficiently firmly. Specifically, it is possible to secure a shear strength of 20 kg or more.

The heat spreader 14 and the Peltier element 13, for example, the package base 10 made of Au-plated KOVAR material and the Peltier element 13 are joined using the Sn-In solder 40 in the same manner as described above. However, in this embodiment, these parts are adhered by the adhesives 30 and 31 in the same manner as in the second embodiment in consideration of the workability of the scrubbing of the solder and the time load.

In this embodiment, a temperature detecting thermistor 32 is attached to the laser stem 15 for adjusting the temperature of the semiconductor laser. The thermistor 32 has a diameter of 1 mm and a depth of 4.2 mm opened in the laser stem 15.
And is fixed by the adhesive 33. As the adhesive 33, an adhesive having high thermal conductivity, for example, a room-temperature-curable silicone adhesive "TSE3946" manufactured by Toshiba Silicone Co., Ltd. is suitable. When this silicone adhesive “TSE3946” is applied, the adhesive curing conditions in the present embodiment are as follows. Room temperature, one week.

Finally, the Peltier device 13, thermistor 32 and the semiconductor laser chip 16 are connected to the package terminals by wire bonding using low-temperature solder (Sn-In solder, Sn-Pb-In solder, etc.), and the window glass 17 is attached. The packaged cap 11 is hermetically sealed with dry gas and joined to the package base 10 by seam welding to complete the semiconductor laser of the present embodiment.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a main part of the semiconductor laser of FIG. 1;

FIG. 3 is a partially cutaway side view showing a semiconductor laser according to a second embodiment of the present invention.

FIG. 4 is a partially cutaway side view showing a semiconductor laser according to a third embodiment of the present invention.

[Explanation of symbols]

 10 Package Base 11 Package Cap 12 Package 13 Peltier Device 14 Heat Spreader 15 Laser Stem 15a Bonding Surface of Laser Stem to Semiconductor Laser Chip 15b Lower Surface of Laser Stem 16 Semiconductor Laser Chip 17 Window Glass 18 Laser Beam 20 Au Thin Film 21 Au Plating 22, 23 , 24 Low temperature solder 31, 32, 33 Adhesive 40 Sn-In solder

Claims (6)

[Claims] 1. A semiconductor laser in which a semiconductor laser chip is brazed to a laser stem by In and the laser stem is brazed to a heat sink, at least a part of a portion of the laser stem in contact with the heat sink is gold. A semiconductor laser, which is surface-treated with a thin film, wherein a gold thin film is not formed on a portion of the laser stem in contact with the semiconductor laser chip. 2. The semiconductor laser according to claim 1, wherein a portion of said laser stem in contact with said semiconductor laser chip is surface-treated with at least one of Ni and Pt thin films. 3. The laser stem according to claim 1, wherein the laser stem is made of copper or copper / tungsten.
The semiconductor laser as described. 4. The semiconductor laser according to claim 1, wherein said laser stem is brazed to said heat sink with low-temperature solder having a melting point of less than 150 ° C. 5. The heat sink is fixed in a semiconductor laser package via a Peltier device, and a joint between the laser stem, the heat sink, the Peltier device and the semiconductor laser package is soldered with a low-temperature solder having a melting point of less than 150 ° C. 2. The method according to claim 1, wherein
The semiconductor laser according to any one of claims 1 to 4. 6. The heat sink is fixed in a semiconductor laser package via a Peltier element, and a gold thin film is formed on at least a part of the Peltier element joined to the heat sink and a part joined to the semiconductor laser package. The semiconductor laser according to claim 1, wherein the semiconductor laser is formed.