JPH04337687A - Semiconductor laser module - Google Patents

Abstract

PURPOSE:To improve the optical coupling reliability of a semiconductor laser module by reducing the kinds of solder at the time of assembling the module and realizing use of only solder in which a creep scarcely occurs. CONSTITUTION:A heat sink 2 on which a semiconductor laser chip 1 is fusion- bonded, is fusion-bonded to a position 41 protruding from a surface of a metal plate 4 on which a microlens 7 is mounted and a carrier 80 placing a photodiode 8 is fusion-bonded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a semiconductor laser module.

0002

2. Description of the Related Art Semiconductor lasers have been put into practical use as light sources for optical fiber communications for some time. In particular, distributed feedback semiconductor lasers that oscillate in a single-axis mode are used as light sources for trunk optical fiber communications.
dback laser diode (DFB laser) has been put into practical use in recent years, and
It is used for transmission in the 1 to 2 Gbps range in the band, and research and development is being conducted on devices that operate at even higher speeds of several Gbps to 10 Gbps.

[0003] Since the characteristics and reliability of semiconductor lasers are greatly affected by temperature rise due to self-heating, semiconductor lasers for communications are used by being fused to a heat sink, and especially in the case of DFB lasers used in the Gbps region. is usually modularized by being mounted on a Peltier element for temperature control.

FIG. 3 shows a conceptual diagram of the internal structure of a conventional semiconductor laser module. Semiconductor laser 1 is heat sink 2
The heat sink 2 is fused to the carrier 3 using a solder 102. The semiconductor laser 1 is mounted on this carrier 3 and after being selected and screened, is assembled into a module. Ceramics such as aluminum oxide is used for the upper surface of the Peltier element 9, and the carrier 3 on which the semiconductor laser is mounted, the microlens 7, the optical fiber terminal part 6, etc.
It is necessary to build a strong structure that ensures order stability. On the other hand, it is also necessary to lower the thermal resistance in order to dissipate heat from the semiconductor laser, so in consideration of both, a carrier 3 equipped with a semiconductor laser and a photodiode 8 for monitoring are installed as shown in the figure. Career 80
is mounted on a metal substrate 4 on which a microlens 7 is mounted.

[0005]

The semiconductor laser module having the structure shown in FIG. 3 has the following problems. semiconductor laser 1 and heat sink 2,
Since the heat sink 2 and the carrier 3 and the carrier 3 and the substrate 4 are fused in order, it is necessary to lower the melting point of the solder in sequence. However, in general, the lower the melting point of the solder, the more likely it is to cause the so-called creep phenomenon, so in order to ensure the required stability on the μm order between the semiconductor laser and the end of the microlens or single mode fiber, the type of solder that can be used is had the disadvantage of being extremely limited. For example, in FIG. 3, if a general Au:Sn 20% eutectic (melting point 280°C) is used for the solder 101 that fuses the semiconductor laser to the heat sink, the solder 102 that fuses the heat sink is made of Au:Sn.
Even if n90% eutectic (melting point 217°C) is used, the solder 103 that fuses the carrier is at most Pb:S.
There is no choice but to use n62% eutectic (melting point 183°C). Pb:Sn for fixing optical components in semiconductor laser modules
It has recently been reported that when 62% eutectic is used, optical coupling may deteriorate under certain usage conditions due to solder creep, making it impossible to ensure the required reliability.

[0006]

[Means for Solving the Problems] The semiconductor laser module of the present invention has a heat sink to which a semiconductor laser is fused.
It is characterized by being directly attached to the substrate fixed to the Peltier element. Furthermore, the semiconductor laser module described above is characterized in that the portion of the substrate where the heat sink is fused protrudes from the surface of the substrate where the carrier on which the photodiode is mounted is fused.

[0007]

[Example] Next, an example of the present invention will be described. FIG. 1 is a conceptual diagram of the internal structure of a semiconductor laser module according to an embodiment of the present invention. A heat sink 2 to which a semiconductor laser 1 is fused is fused to a portion 41 of a metal substrate 4 to which a microlens 7 is attached, protruding from the surface to which a carrier 80 carrying a photodiode 8 is fused. As the solder used, the solder 101 that fuses the semiconductor laser to the heat sink is a general Au:Sn 20% eutectic,
Solder 1 for fusing the heat sink to the protrusion 41 of the substrate 4
02 can be made of only a hard material that does not easily cause creep, such as 90% Au:Sn eutectic. Note that the attachment of the substrate 4 to the Peltier element 9 and the attachment of the microlens 7 and the optical fiber 6 to the substrate 4 are the same as in the conventional case.

FIG. 2 is a conceptual diagram of the internal structure of a semiconductor laser module according to another embodiment of the present invention. In this embodiment, the protruding portion of the substrate is not integrally formed with the substrate 4, but a separate block 42 is made of a high melting point wax material 10 such as AgCu.
It has a structure in which it is attached using 4. The rest is the same as the previous example. Since the optical fiber terminal 6 covered with a metal sleeve is laser welded, the material of the substrate body 4 is generally made of iron, but if the structure of this embodiment is adopted, the heat sink can be fused. block 42
The advantage is that the heat dissipation effect can be improved by using CuW or the like, which has a coefficient of linear expansion that is not much different from that of the substrate and has good thermal conductivity.

[0009]

[Effect of the invention] The heat sink on which the semiconductor laser is mounted,
Since the structure is directly fused to the metal substrate for fixing optical components without using a carrier, the type of solder used when assembling the semiconductor laser module is reduced, and only solder that does not easily cause creep can be used. This has the effect of improving optical coupling reliability.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of the internal structure of a semiconductor laser module that is an embodiment of the present invention.

FIG. 2 is a schematic diagram of a second embodiment.

FIG. 3 is a conceptual diagram of the internal structure of a conventional semiconductor laser module.

[Explanation of symbols]

1 Semiconductor laser 2 Heat sink 4 Board 6 Optical fiber 7 Micro lens 8 Photodiode 9 Peltier element

Claims (2)

[Claims] Claim 1: In a semiconductor laser module in which an optical fiber, a microlens for condensing laser light, a semiconductor laser, and a monitoring photodiode are arranged and fixed with their optical axes aligned with each other, the semiconductor laser is fused. A semiconductor laser module characterized in that a heat sink is directly attached to a substrate fixed to a Peltier element. 2. The semiconductor laser module according to claim 1, wherein a portion of the substrate to which the heat sink is fused protrudes from a surface of the substrate to which the carrier on which the photodiode is mounted is fused. Semiconductor laser module.