JP3775369B2 - Laser module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser chip carrier on which a laser chip is mounted in a laser module.
[0002]
[Prior art]
A laser module is generally used as a light source for optical communication. The laser module converts an external electrical signal into an optical signal and outputs the optical signal. The laser module contains a semiconductor laser chip. The laser module receives a drive current signal from the outside. This drive current signal is injected into the laser chip, whereby the laser chip emits light. The light emitted from the laser chip has a power corresponding to the drive current signal. If the drive current signal is modulated, the laser module outputs an optical signal modulated in the same manner as the drive current signal (see Patent Documents 1 and 2).
[0003]
FIG. 7 is a schematic perspective view showing a laser chip arranged in a conventional laser module. The laser chip 10 is mounted on the upper surface of the chip carrier 12. Conductor patterns 12 b and 12 b are provided on the upper surface of the chip carrier 12. The bottom surface of the laser chip 10 is in contact with the conductor pattern 12b. The electrode provided on the bottom surface of the laser chip 10 is electrically connected to the conductor pattern 12b. On the other hand, the electrode provided on the upper surface of the laser chip 10 is wire-bonded to the conductor pattern 12b via the wire 14.
[0004]
In the laser module, the wiring member 20 is disposed so as to face the chip carrier 12. Conductor patterns 22 a and 22 b are provided on the upper surface of the wiring member 20. These conductor patterns are electrically connected to two signal input pins (not shown) extending to the outside of the laser module. The laser module receives drive current signals via these signal input pins. The conductor pattern 22a is wire-bonded to the conductor pattern 12b by a wire 24a. Similarly, the conductor pattern 22b is wire-bonded to the conductor pattern 12b by a wire 24b.
[0005]
[Patent Document 1]
JP 2000-240874 A [Patent Document 2]
Japanese Patent Laid-Open No. 2000-91695
[Problems to be solved by the invention]
As shown in FIG. 7, a step corresponding to the thickness of the laser chip 10 is generated between the upper surface of the laser chip 10 and the upper surface of the chip carrier 12. Due to this step, the bonding wire 14 connecting the electrode on the upper surface of the laser chip 10 and the conductor pattern 12b becomes relatively long. When the bonding wire 14 is long, the inductance of the drive current path of the laser chip 10 increases. For this reason, the drive current signal input to the laser module is likely to deteriorate, and the output optical signal is likely to deteriorate accordingly. The deterioration of the drive current signal is particularly remarkable when the drive current signal is a high frequency signal.
[0007]
Accordingly, an object of the present invention is to shorten the bonding wire connected to the laser chip.
[0008]
[Means for Solving the Problems]
The chip carrier of the present invention has a laser chip mounted on the upper surface thereof. A lower electrode for injecting a drive current is provided on the lower surface of the laser chip. A conductor pattern is provided on the upper surface of the chip carrier. The lower electrode of the laser chip is electrically connected to this conductor pattern. An upper electrode for injecting a drive current is provided on the upper surface of the laser chip. This chip carrier has a conductive member extending from the vicinity of the upper electrode of the laser chip to the vicinity of the upper surface of the chip carrier. This conductive member has an inclined portion inclined with respect to the upper surface of the chip carrier. The upper electrode of the laser chip is wire bonded to this conductive member.
[0009]
The laser module of the present invention includes (a) the above chip carrier, (b) a wiring member facing the chip carrier and having first and second conductor patterns on its upper surface, and (c) the chip carrier and A housing that houses the wiring member, and (d) first and second signal input pins that are electrically connected to the first and second conductor patterns and extend outward from the housing, respectively. The first conductor pattern of the wiring member is wire bonded to the conductor pattern on the chip carrier. The second conductor pattern of the wiring member is wire bonded to the conductive member of the chip carrier. In this laser module, an electric circuit may be provided between the conductor pattern of the wiring member and the signal input pin. This electric circuit is, for example, an amplifier circuit for a driving current signal of a laser chip.
[0010]
A part of the conductive member is located near the upper electrode of the laser chip. This portion and the upper electrode can be wire-bonded using a short wire. The conductive member also includes a portion located near the top surface of the chip carrier. This portion and the second conductor pattern of the wiring member can be wire-bonded using a short wire.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. For the convenience of illustration, the dimensional ratios in the drawings do not necessarily match those described.
[0012]
(First embodiment)
The configuration of the semiconductor laser module 1 according to the first embodiment will be described with reference to FIGS. FIG. 1 is a partially broken perspective view showing the configuration of the laser module 1. FIG. 2 is a partially cutaway side view of the laser module 1. FIG. 3 is a perspective view showing the configuration of the chip carrier 12 built in the laser module 1. 1 and 2, the upper wall of the housing 8 of the laser module 1 is not shown.
[0013]
The laser module 1 is a butterfly type module. A chip carrier 12 is accommodated in the housing 8 of the laser module 1. The chip carrier 12 is insulative or semi-insulating. The chip carrier 12 has a rectangular parallelepiped shape. The top surface of the chip carrier 12 is substantially parallel to the bottom surface of the housing 8. The chip carrier 12 is mounted on the mounting member 16. The mounting member 16 is fixed on the Peltier element 18. The Peltier element 18 is fixed to the bottom surface of the housing 8.
[0014]
A semiconductor laser chip 10 and a metal block 30 are mounted on the upper surface 12 a of the chip carrier 12. The laser chip 10 has two electrodes for injecting a drive current, that is, an upper electrode and a lower electrode (not shown). The upper electrode is provided on the upper surface of the laser chip 10, and the lower electrode is provided on the bottom surface of the laser chip 10. On the upper surface of the chip carrier 12, a conductor pattern 12b is also provided. The laser chip 10 is installed on the conductor pattern 12b. The lower electrode of the laser chip 10 is electrically connected to the conductor pattern 12b. The conductor pattern 12 b extends from the laser chip 10 to one edge of the chip carrier 12.
[0015]
Two wiring members 20 and 21 are further accommodated in the housing 8. These wiring members 20 and 21 are respectively attached to two opposite side walls of the housing 8. The wiring members 20 and 21 are disposed on both sides of the chip carrier 12. The height of each upper surface of the wiring members 20, 21 is substantially equal to the height of the upper surface 12 a of the chip carrier 12. The wiring members 20 and 21 are each made of ceramic which is an insulator. A plurality of conductor patterns 22 are respectively provided on the upper surfaces of the wiring members 20 and 21. A signal input pin 26 is connected to each conductor pattern 22. These signal input pins 26 extend outward from the side wall of the housing 8.
[0016]
One wiring member 20 is wire-bonded to the chip carrier 12. Specifically, the conductor pattern 12b on the chip carrier 12 and the conductor pattern 22a on the wiring member 20 are wire-bonded by a wire 24a. Further, the metal block 30 on the chip carrier 12 and the conductor pattern 22b on the wiring member 20 are wire-bonded by wires 24b.
[0017]
A lens 40 is also accommodated in the housing 8. The lens 40 is disposed so as to face the light emitting surface of the laser chip 10. The lens 40 condenses the laser light emitted from the laser chip 10. A ferrule 42 is attached to the front wall of the housing 8. The ferrule 42 contains an optical fiber (not shown). This optical fiber is optically connected to the laser chip 10 via the lens 40. Laser light from the laser chip 10 is collected by the lens 40 and sent to the optical fiber in the ferrule 42. Laser light is output to the outside of the laser module 1 through this optical fiber.
[0018]
The feature of this embodiment is that a metal block 30 is installed on the chip carrier 12. The metal block 30 has a right triangular prism shape. The metal block 30 is installed with its slope 30a facing upward. The inclined surface 30a is inclined at a certain angle with respect to the upper surface 12a of the chip carrier 12. The inclined surface 30 a extends from the vicinity of the upper surface of the laser chip 10 to the vicinity of the upper surface 12 a of the chip carrier 12. The metal block 30 has two side surfaces 30b and 30c orthogonal to each other. The side surface 30 b is in contact with the upper surface 12 a of the chip carrier 12. The side surface 30 c faces the laser chip 10. The edge where the inclined surface 30 a and the side surface 30 b intersect is aligned with the edge of the chip carrier 12. The height of the metal block 30 along the direction perpendicular to the upper surface 12 a is substantially the same as the height of the laser chip 10.
[0019]
The bonding wire 14 is connected between the upper electrode of the laser chip 10 and the inclined surface 30 a of the metal block 30. The bonding wire 24 b is connected between the conductor pattern 22 b of the wiring member 20 and the slope 30 a of the metal block 30. As a result, the conductor pattern 22b and the upper electrode of the laser chip 10 are electrically connected. On the other hand, the lower electrode of the laser chip 10 is electrically connected to the conductor pattern 12b of the chip carrier 12, and the conductor pattern 12b is wire-bonded to the conductor pattern 22a of the wiring member 20. As a result, the lower electrode of the laser chip 10 is electrically connected to the conductor pattern 22a. In this manner, a current path including the conductor pattern 22a, the wire 24a, the conductor pattern 12b, the laser chip 10, the wire 14, the metal block 30, the wire 24b, and the conductor pattern 22b is formed. Due to the skin effect, most of the current flows through the surface layer portion of the metal block 30 including the slope 30a.
[0020]
Signal input pins 26a and 26b are connected to the conductor patterns 22a and 22b, respectively. During the operation of the laser module 1, an external drive circuit is connected to the signal input pins 26a and 26b. The external drive circuit generates a drive current for the laser chip 10 and passes it from one of the signal input pins 26a and 26b to the other. This drive current flows through the current path and is injected into the laser chip 10. Thereby, the laser chip 10 emits laser light.
[0021]
Below, the advantage of this embodiment is demonstrated. As is apparent from a comparison between FIG. 3 and FIG. 7, in the chip carrier 12 of this embodiment, the bonding wire 14 connected to the laser chip 10 is shorter than that of the prior art. This is because the step between the upper surface of the laser chip 10 and the upper surface 12 a of the chip carrier 12 is filled with the metal block 30. The slope 30 a of the metal block 30 is inclined from the height of the upper electrode of the laser chip 10 to the height of the conductor pattern 22 b of the wiring member 20. Therefore, the wires 14 and 24b can be connected between two points having approximately the same height. For this reason, the wire 14 and the wire 24b can be shortened. As a result, the inductance of the drive current path can be suppressed and deterioration of the output optical signal can be prevented.
[0022]
Further, the connection between the wire 14 and the wire 24b via the conductive slope 30a produces another advantage. Below, this advantage is demonstrated, comparing FIG. 3 with FIG. Here, FIG. 4 is a perspective view showing the chip carrier 12 on which the metal block 50 having a shape different from that of the metal block 30 of the present embodiment is mounted.
[0023]
The metal block 50 shown in FIG. 4 has a rectangular parallelepiped shape. In addition to the conductor pattern 12b, a conductor pattern 12c is provided on the upper surface 12a of the chip carrier 12. The metal block 50 is installed on the conductor pattern 12c and is electrically connected to the conductor pattern 12c. An upper surface 50 a of the metal block 50 is wire-bonded to the upper electrode of the laser chip 10 with a wire 14. The conductor pattern 12c is wire-bonded to the conductor pattern 22b of the wiring member 20 with a wire 24b. The metal block 50 has substantially the same height as the laser chip 10. For this reason, the length of the wire 14 may be short.
[0024]
However, when the metal block 50 of FIG. 4 is used, the following problems occur. In the metal block 50, most of the drive current signal of the laser chip 10 flows through the surface layer portion including the upper surface 50a and the side surface 50b due to the skin effect. Since the upper surface 50a and the side surface 50b, and the side surface 50b and the conductor pattern 12c are orthogonal to each other, the path of the drive current signal also has a right angle bend. When a drive current signal is caused to flow along such a path having a sharp bend, the drive current signal is likely to deteriorate, and the output optical signal is likely to deteriorate accordingly. This deterioration is particularly noticeable in high frequency signals. That is, the sharp bending of the drive current path mainly degrades the high frequency performance of the laser module. Further, in the example of FIG. 4, there is a steep current path narrowing between the metal block 50 and the conductor pattern 12c. Such narrowing of the current path also degrades high frequency performance.
[0025]
On the other hand, in the chip carrier 12 of this embodiment, the metal block 30 has a slope 30a, and a drive current flows along this slope 30a. For this reason, there is no sharp bend in the current path. Therefore, it is possible to prevent deterioration of the high frequency performance.
[0026]
Yet another advantage will be described. The chip carrier 12 of this embodiment is easy to manufacture. The metal block 30 is a metal part having a simple structure. For this reason, it can be manufactured inexpensively and easily. The metal block 30 can be mounted by the same method as the laser chip 10 in the process of mounting the laser chip 10 on the chip carrier 12. There is no need to prepare special equipment for mounting the metal block 30.
[0027]
(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a perspective view showing the configuration of the chip carrier 12 of this embodiment. In the second embodiment, a metal block 31 having a shape different from that of the metal block 30 of the first embodiment is mounted on the chip carrier 12. Other configurations are the same as those of the first embodiment.
[0028]
As shown in FIG. 5, the metal block 31 has a polygonal column shape. Similar to the metal block 30, the metal block 31 has a conductive slope 31a. The inclined surface 31a is inclined at a constant angle with respect to the upper surface 12a of the chip carrier 12. The inclined surface 31 a extends from the vicinity of the upper surface of the laser chip 10 to the vicinity of the upper surface 12 a of the chip carrier 12. The metal block 31 is installed on the upper surface 12a of the chip carrier 12 with the inclined surface 31a facing upward.
[0029]
The difference from the first embodiment is that horizontal surfaces 31 d and 31 e are provided on both sides of the slope 31 a of the metal block 31. The horizontal surfaces 31 d and 31 e are substantially parallel to the upper surface 12 a of the chip carrier 12. The horizontal surface 31 d has a height close to the upper surface of the laser chip 10. The horizontal surface 31 e has a height close to the conductor pattern 22 b of the wiring member 20. The slope 31a is sandwiched between horizontal surfaces 31d and 31e. The horizontal surface 31 d is wire-bonded to the upper electrode of the laser chip 10 by the wire 14. The horizontal surface 31e is wire-bonded to the conductor pattern 22b of the wiring member 20 by a wire 24b. The drive current of the laser chip 10 flows along the slope 31a and the horizontal surfaces 31d and 31e.
[0030]
Below, the advantage of this embodiment is demonstrated. The chip carrier of this embodiment has the same effect as the chip carrier of the first embodiment. That is, since the metal block 31 fills the step between the upper surface of the laser chip 10 and the upper surface 12a of the chip carrier 12, the bonding wire 14 can be shortened. Thereby, degradation of the output optical signal can be suppressed. In addition, since there is no sharp bend in the current path, deterioration of the high frequency performance can be suppressed. Since the metal block 31 is a metal part having a simple structure, the chip carrier of this embodiment is easy to manufacture.
[0031]
The chip carrier of this embodiment has yet another advantage. That is, in this embodiment, the chip carrier 12 can be easily wire bonded to the laser chip 10 and the wiring member 20. This is because the bonding wires 14 and 24b are joined to the horizontal surfaces 31d and 31e, respectively. Bonding wires are easier to connect between horizontal surfaces than between slopes and horizontal surfaces. If the bonding operation becomes easier, the productivity of the chip carrier and the laser module will increase accordingly.
[0032]
(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a perspective view showing the configuration of the chip carrier 12 of this embodiment. In the third embodiment, a block 32 having a structure different from that of the metal blocks 30 and 31 is mounted on the chip carrier 12. Other configurations are the same as those of the first embodiment.
[0033]
The block 32 has a triangular prism shape like the metal block 30 of the first embodiment. However, the block 32 is not entirely made of metal. The block 32 includes a triangular prism-shaped ceramic base 32a and a conductor pattern 32b that covers the entire slope of the base 32a. The upper surface of the conductor pattern 32b is inclined at a constant angle with respect to the upper surface 12a of the chip carrier 12. The block 32 is installed on the upper surface 12a of the chip carrier 12 with the conductor pattern 32b facing upward. The height of the block 32 along the direction perpendicular to the upper surface 12 a is substantially the same as the height of the laser chip 10.
[0034]
The conductor pattern 32 b is wire-bonded to the upper electrode of the laser chip 10 by the wire 14. The conductor pattern 32b is wire-bonded to the conductor pattern 22b of the wiring member 20 with a wire 24b. For this reason, the drive current of the laser chip 10 flows through the conductor pattern 32b.
[0035]
The chip carrier of this embodiment has the same effect as the chip carrier of the first embodiment. That is, since the block 32 fills the step between the upper surface of the laser chip 10 and the upper surface 12a of the chip carrier 12, the length of the bonding wire 14 can be shortened. Thereby, degradation of the output optical signal can be suppressed. In addition, since there is no sharp bend in the current path, deterioration of the high frequency performance can be suppressed.
[0036]
This embodiment has yet another advantage. Since the block 32 has a configuration in which the conductor pattern 32b is provided on the surface of the ceramic base 32a, there is room for a contrivance in the conductor pattern 32b, and the application range is wide. For example, impedance matching can be achieved by providing a resistance in the conductor pattern 32b.
[0037]
The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the gist thereof.
[0038]
In the above embodiment, the conductor pattern 22 of the wiring members 20 and 21 and the signal input pin 26 are directly connected. However, the conductor pattern 22 and the signal input pin 26 may be electrically connected via an electric circuit. This electric circuit may be, for example, a circuit that amplifies the drive current signal of the laser chip 10.
[0039]
【The invention's effect】
The chip carrier of the present invention has a conductive member extending from the vicinity of the upper electrode of the laser chip to the vicinity of the upper surface of the chip carrier. Therefore, the drive current path can be formed by wire bonding the upper electrode and the conductive member with a short wire. Therefore, the laser module provided with the chip carrier of the present invention can output an optical signal with little deterioration and is excellent in high-frequency performance.
[Brief description of the drawings]
FIG. 1 is a partially broken perspective view showing a configuration of a laser module according to a first embodiment.
FIG. 2 is a partially cutaway side view showing the configuration of the laser module of the first embodiment.
FIG. 3 is a perspective view showing the configuration of the chip carrier of the first embodiment.
FIG. 4 is a perspective view showing a configuration of a chip carrier of a comparative example.
FIG. 5 is a perspective view showing a configuration of a chip carrier of a second embodiment.
FIG. 6 is a perspective view illustrating a configuration of a chip carrier according to a third embodiment.
FIG. 7 is a perspective view showing a configuration of a conventional chip carrier.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laser module, 8 ... Housing | casing, 10 ... Laser chip, 12 ... Chip carrier, 12b and 12c ... Conductor pattern, 14, 24a and 24b ... Bonding wire, 16 ... Mounting member, 18 ... Peltier device as temperature control means , 20 and 21 ... wiring member 20 ... conductor pattern, 26 ... signal input pin, 30 to 32 and 50 ... wiring block, 32b ... inclined conductor pattern, 40 ... lens, 42 ... ferrule.

Claims (2)

A laser chip having an upper electrode and a lower electrode for injecting a drive current;
  A wiring member having first and second conductor patterns on its upper surface;
  A third conductor pattern wire-bonded to the first conductor pattern is provided on the upper surface, the laser chip is mounted so that the lower electrode is in contact with the third conductor pattern, and juxtaposed with the wiring member Chip carrier,
  A housing for housing the laser chip, the wiring member, and the chip carrier;
  First and second signal input pins electrically connected to the first and second conductor patterns of the wiring member, respectively, and extending to the outside of the housing;
A laser module comprising:
  A conductive member having an inclined surface extending from near the upper electrode of the laser chip to near the upper surface of the chip carrier is further provided on the chip carrier,
  The conductive member includes a portion having a height substantially equal to the upper electrode of the laser chip, and this portion and the upper electrode of the laser chip are wire-bonded,
  The laser module, wherein a portion of the conductive member located in the vicinity of the wiring member is wire-bonded to a second conductor pattern on the wiring member. The conductive member has both end portions extending substantially parallel to the upper surface of the chip carrier with the inclined surface interposed therebetween,
  One of the both ends is wire bonded to the upper electrode of the laser chip,
2. The laser module according to claim 1, wherein the other of the both end portions is wire-bonded to the second conductor pattern on the wiring member.

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