JPH04337688A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To reduce a parasitic inductance of a wiring and to simultaneously obtain cooling capacity in a semiconductor laser having a Peltier element for high speed response operation. CONSTITUTION:An insulating board 5 is placed on a metal base 4 mounted on a Peltier element, and a semiconductor laser 1 is coupled to a signal input line 10 by a bonding wire 7 via a strip line 6. Both characteristics in which an S21 parameter is 4GHz and a cooling capacity is 45 deg.C, are simultaneously performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device having a built-in Peltier element and having wide-band response performance.

0002

2. Description of the Related Art Regarding semiconductor laser devices incorporating a Peltier element, there are two basic characteristics that may be in a trade-off relationship, as will be explained in detail later. First, the response band characteristics and cooling capacity of each mechanism will be summarized, and conventional technologies will be discussed.

[0003] In the first response band characteristic, the band of the semiconductor laser chip is of course considered, but in the gigabit compatible area, the band of the package must be taken into account. In particular, the parasitic impedance of the signal line is the main cause of loss of bandwidth and must be reduced as much as possible.

5(a), (b) ((a) is a plan view, ((a) is a plan view, (
b) is a sectional view), the configuration of this type of semiconductor laser device will be roughly described. Semiconductor laser 1 is heat sink 2
It is mounted on the chip carrier on the metal base 4 or on the metal base protrusion 3 via the metal base 4 . metal base 4
A lens 18 is included in the metal base tip 4.
In a, there is an optical fiber 2 whose tip is protected by a ferrule 20.
1 is fixed by YAG welding with a slide ring 19. The output light from the semiconductor laser 1 is coupled to the optical fiber 21 by this series of structures. A photodiode 16 for monitoring rear output light is also mounted on the metal base 4. The metal base 4 is attached to the inside of the metal case 23 via the Peltier element 22, and the ferrule 20
and metal case 23 are connected and sealed with solder 24. Chip thermistor 17 is mounted adjacent to semiconductor laser 1 on a chip carrier or metal base protrusion 3 .

[0005] For applications of digital transmission exceeding 2 Gb/s, a so-called butterfly-type metal case 23 is used as shown in FIG.
In addition, a distributed feedback semiconductor laser is often used as the semiconductor laser 1, and an optical isolator 25 is often inserted between the lens 18 and the ferrule 20. This butterfly-type metal case 23 can be provided with a multilayer wiring shelf portion 8 on the inner wall side of the lead terminal, and the present invention relates to the connection wiring between this shelf portion and the semiconductor laser 1 on the metal base 4. .

The conventional example shown in FIGS. 3 and 4 will be explained. These figures show the shape of the connection from the semiconductor laser 1 to the metal case lead terminal wiring shelf 8.

FIG. 4 shows an example of direct wiring by wire bonding. In this case, the inductance of the bonding wire 7 itself is weak between the semiconductor laser 1 and the signal input line 10, and the grounding of the bonding wire 7 between the case grounding electrode 9 and the metal base 4 is weak, so that high frequency signals are not affected. , the metal base 4 is a metal case (Fig. 5
23), it becomes a floating state via the Peltier element (22 in FIG. 5). For this reason, a dip appears in the frequency response characteristic as shown by the broken line in FIG. 6, and waveform distortion occurs in high-speed digital modulation.

On the other hand, in the ribbon lead connection shown in FIG. 3, the above-mentioned weak grounding is eliminated and the frequency response characteristics are improved.

Now, let's turn to the second major characteristic, which is the cooling capacity. In this type of semiconductor laser device with a built-in Peltier element, the semiconductor laser is normally kept at 25°C, so a cooling capacity of 40°C is required for the worst case temperature of 65°C. The reason for the inhibition of this cooling ability is the heat dissipation from the Peltier element (22 in Figure 5) itself.
This means that it flows back through the wiring or ferrule above the ferrule.

0010

[Problems to be Solved by the Invention] That is, in the conventional example shown in FIG. 3, the connection using the ribbon lead 14 increases heat dissipation circulation, so the required cooling capacity of 45°C cannot be achieved, and the cooling capacity is limited to about 40°C. was there. On the other hand, in the conventional example shown in FIG. 4, which was connected by bonding wires, a cooling capacity of 45° C. was achieved, but as mentioned above, the response band was limited and it could not support digital transmission exceeding 2 Gb/s.

As described above, the conventional technology has a problem in that there is a trade-off relationship between response band characteristics and cooling capacity, and it is not possible to improve them at the same time.

0012

[Means for Solving the Problems] A semiconductor laser device of the present invention is a semiconductor laser device in which a semiconductor laser is mounted on a Peltier element in a metal case, and in which wiring between a signal input lead terminal of the metal case and the semiconductor laser is provided. is via a strip line on the surface of the insulating substrate mounted on the Peltier element, and the strip line and the lead terminal are wired by wire bonding. A ground electrode pattern is fixedly mounted on the Peltier element, and a ground electrode pattern is provided as a pattern on the insulating substrate that extends to the vicinity of the strip line of the signal line.
The ground electrode pattern and the metal substrate are connected by solder through the through hole of the insulating substrate, and the ground electrode pattern and the ground lead terminal of the metal package are connected by wire bonding.

[0013]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 5, which has been briefly described above, shows the wiring method according to the first embodiment of the present invention, and FIG. 1 shows the wiring portion extracted.

The semiconductor laser 1 and heat sink 2 are exactly the same as those of the conventional device. Strip line 6 on metal base 4
The semiconductor laser is connected to one end of a strip line 6 at an interval of about 0.5 mm by wire bonding. The other end is aligned with the end of the metal base 4, and the lead terminal wiring shelf part 8 of the metal case is
They are arranged to face the pattern of the signal input line 10 above, and the heights are also made to be the same so that the length of the wiring between them is the shortest. The maximum distance between the metal base 4 and the shelf 8 is about 0.3 mm. In this case, since there is a step between the case ground electrode 9 and the surface of the metal base 4 by the thickness of the insulating substrate 5, the wire bonding between the two becomes slightly longer.

As for the characteristics of the semiconductor laser device manufactured by this method, the frequency response characteristic has been improved to a dip depth of about 5 bB while maintaining a cooling capacity of 45° C. similar to that of the conventional example shown in FIG.

FIG. 2 shows a second embodiment of the invention. Here, the insulating substrate 5 is enlarged and the wiring pattern on the surface is formed using strip lines 6 and sheet resistors.
0Ω matching resistor 11, bias semiconductor laser 1
A characteristic feature is that a resistor 12 and a resistor 13 are arranged for applying voltage to the strip line 6, and a ground pattern is also arranged near the strip line 6 at the same time. This ground pattern is in contact with the metal base 4 through the through hole 15 with solder. In this example, there is no bonding step difference on the ground side, and as with the signal input line, ground wiring can be done with the shortest pattern, and by surrounding the strip line 6 with the ground pattern, the floating property can be improved. That is, in this example, FIG.
It was possible to obtain good frequency characteristics in which no dip was observed at a cutoff frequency of 4 GHz, which is shown by the solid line, and at the same time, the cooling capacity was also able to be maintained at 45° C. as in the first embodiment. Further, a pattern for mounting a chip inductor and a chip capacitor on the tip of the bias resistor 12 was provided on the insulating substrate 5, thereby successfully blocking the negative influence from the bias line on the frequency characteristics.

[0017]

[Effects of the Invention] As explained above, the semiconductor laser device according to the present invention has an insulating substrate mounted on a metal base on a Peltier element, and uses strip lines on the surface of the insulating substrate.
By avoiding the use of thin and long bonding wires for signal input lines, or by surrounding the strip line with a ground pattern, you can improve the frequency characteristics. At the same time, the wiring between the wiring shelf on the inner wall of the case and the metal base By using a short bonding wire, there is an effect that the cooling capacity is not impaired.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a wiring system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a wiring system according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a conventional wiring system.

FIG. 4 is a diagram showing another conventional wiring system.

FIG. 5 is a plan view (a) and a longitudinal cross-sectional view (b) showing the structure of a semiconductor laser device according to a first embodiment of the present invention.

6 is a diagram illustrating the frequency response customization of a semiconductor laser device according to a second embodiment of the present invention in comparison with the conventional example of FIG. 4; FIG.

[Explanation of symbols]

1 Semiconductor laser 2 Heat sink 3 Chip carrier or metal base protrusion 4
Metal base 5 Insulating substrate 6 Strip line 7 Bonding wire 8 Metal case lead terminal wiring shelf 9 Case ground electrode 10 Signal input line 11 Matching resistor 12 Bias resistor 13 Bias resistor 14 Ribbon lead 15 Through hole 16 Monitor photodiode 17 Chip thermistor 18 Lens 19 Slide ring 20 Ferrule 21 Optical fiber 22 Peltier element 23 Metal case 24 Solder 25 Optical isolator

Claims (2)

[Claims] 1. In a semiconductor laser device in which a semiconductor laser is mounted on a Peltier element in a metal case, wiring between a lead terminal of the metal case and the semiconductor laser is connected to an insulator mounted on the Peltier element. 1. A semiconductor laser device, wherein wiring is provided through a strip line on a surface of a substrate, and the strip line and the lead terminal at an end of the insulating substrate are wired by wire bonding. 2. The semiconductor laser device according to claim 1, wherein the semiconductor laser and the insulating substrate are fixed on one metal substrate and mounted on the Peltier element, and the strip is formed on the surface of the insulating substrate. A ground electrode pattern is provided that extends close to the line, and solder is applied between the metal substrate and the ground electrode pattern through a through hole in the insulating substrate, and wire bonding is applied between the ground electrode pattern and the ground lead terminal of the metal case. A semiconductor laser device characterized in that the semiconductor laser device is connected to each other by.