JPH06201954A - Optical bench - Google Patents

Abstract

PURPOSE:To eliminate thermal effect exerted on other optical parts at the time of soldering, and to solder plural optical parts with high accuracy and with high reliability by one kind of solder. CONSTITUTION:On an optical bench 11 for soldering and fixing optical parts such as an LD 52 and a monitor 53, etc., a fixed pad 12 is provided at every optical parts. The fixed pad 12 has a solder layer 13 for brazing the optical parts on the surface, and consists of a laminated structure in which a heater 14 which is heated by electric conduction and melts the solder layer 13 is embedded inside. The heater 14 embedded in the fixed pad 12 is isolated electrically, and can be heated separately, respectively. In such a way, partial heating of a fixed pad unit is executed, and thermal effect exerted on other optical parts is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical bench for mounting an optical component such as a semiconductor laser, and more particularly to an optical bench improved by introducing partial heating.

[0002]

2. Description of the Related Art As the application of optical communication spreads from trunk lines to subscriber systems, development of inexpensive and highly reliable optical transceiver modules is required. This optical transmission / reception module is one in which a semiconductor laser for transmission (LD for transmission), a semiconductor light receiving element for reception (PD for reception), a lens, an optical waveguide for multiplexing / demultiplexing, etc. are integrally incorporated. In order to integrally assemble these optical components such as LD, PD, and lens, a method of aligning and fixing with high accuracy, low loss, high productivity, and high reliability is required.

Many methods have been conventionally proposed as this type of centering and fixing method, but the method of fixing using solder is the most reliable and general method. This is the optical waveguide 51, the LD 52, and the LD output monitor P as shown in FIG.
In mounting the optical transceiver module including the D53, the lens 54, the PD 55, the optical fiber 56, etc., the LD 52 is first soldered and fixed to the optical bench 57 serving as a substrate. Next, the LD 52 is caused to emit light to align the monitor PD 53, and is fixed by soldering at a position where the output of the monitor PD 53 is maximized.

At this time, a grip adjusting device as shown in FIG. 6 is used to grip the optical component and change or adjust its position. These two arms 61, 61 that are moved by a fine movement mechanism of several axes are attached to a base 62.
An optical component such as the monitor PD 53 is gripped between the first and the first 61 to adjust the positioning.

The optical bench 57 to which the LD 52 is fixed is placed on the heater 63, and heating is performed after the alignment of the monitor PD 53 is completed, and the solder is melted to fix the monitor PD 53. At this time, the solder of the LD 52 previously fixed by heating should not move by being melted. Therefore, the solder used for fixing the monitor PD 53 has a lower melting point than the solder used for fixing the LD 52, and the soldering temperature needs to be lower than the melting point of the LD fixing solder.

Thereafter, the same operation is repeated until the lens 5
4, PD55 is fixed in order, and finally the optical fiber 5
The fixed optical waveguide 51 of 6 is aligned and fixed on the fixed base 59. Incidentally, 59 is an optical waveguide fixing substrate, and 60 is a fiber block.

[0007]

However, the above-mentioned prior art has the following drawbacks.

(1) Since the whole of the optical bench 57 is heated by the heater 63, the parts other than the part where the optical parts are fixed are also heated. Therefore, the number of kinds of optical parts to be fixed is different. Requires different solder.

(2) Considering the heat resistance of the optical components such as LD and PD to be fixed and the heat resistance after mounting, the melting point of the solder must be set within the range of about 100 to 350 ° C. However, since it is necessary to provide a temperature difference in each fixing step within this range, only 4 to 6 steps of soldering can be performed, and thus the number of parts that can be fixed is also limited.

(3) Since it is necessary to select a solder based on the melting point, solder that easily creeps or solder that has poor wettability must be used, which causes a deterioration in reliability.

(4) Since it is necessary to heat the entire optical bench, the heating area is large, and therefore the heater capacity must be increased. As a result, heat is transmitted to the gripping means such as the arm that grips the optical component and expands.
The position of the optical component after cooling deviates from the desired position.

(5) Further, it takes a long time to heat up and cool the entire optical bench, which deteriorates the productivity and makes the products such as the optical system module expensive.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a new optical bench capable of fixing a large number of optical components with one type of brazing material with high accuracy, high reliability and high productivity. Especially.

[0014]

The optical bench of the present invention is an optical bench for positioning and brazing fixing optical components such as LDs, PDs and lenses, and brazing optical components on the optical bench. A fixed pad having a brazing material for heating and a heater that melts the brazing material by generating heat when energized is provided independently for each optical component, and the heater is independently made to generate heat.

In this case, the fixed pad provided on the optical bench is a heater layer formed by closely sandwiching a metal heating element between insulating layers in order from the substrate toward the surface, and a heater layer and a solder layer are closely attached. It is preferable to have a laminated structure including a buffer layer for soldering and a solder layer for soldering the optical component.

More specifically, the optical bench is S
The fixed pad provided on the Si substrate is composed of an SiO ₂ insulating layer, a Ti
Buffer layer, Pt heating element layer, SiO ₂ insulating layer, Ti buffer layer, Pt oxidation preventing layer, Au soldering layer, Pb-Sn
It is preferable to have a laminated structure having a solder layer.

The fixing of the optical component is not limited to one surface of the optical bench, and therefore, the fixing pad may be provided on both surfaces. An optical bench for positioning and brazing and fixing optical components such as LDs, PDs, and lenses is applied to a light source module, an optical transmission / reception module, etc. in which these optical components are integrally incorporated.

Although solder can be given as a typical brazing material, various other brazing materials conventionally used may be used. The heater may have a laminated structure in which a heating circuit formed by etching a metal film is sandwiched between insulating films. The size of the fixing pad is an appropriate size necessary for fixing the optical component. This is because if it is too large, the thermal effect on other pads cannot be ignored, and the optical bench cannot be downsized, and if it is too small, it becomes difficult to fix optical components. In any case, the size of each fixing pad is a very small area compared to the optical component fixing surface of the optical bench.

Further, the fixing pad does not necessarily have to be prepared for all the optical components that require brazing. For example, in the first optical component to be brazed, which serves as a positioning reference, the other optical components are not yet fixed, so that the other optical components are not affected and the conventional brazing method is used. Just use it,
No fixed pad is required. Further, in order to heat the heater independently for each fixed pad, the wiring for energizing each heater is a separate circuit.

[0020]

[Operation] One optical component is positioned on the corresponding fixed pad. After positioning, the heater forming a part of the fixed pad is energized to generate heat. Then, only the pad portion that fixes the optical component is heated,
The heating also melts the brazing material forming the surface of the fixed pad to fuse one optical component to the fixed pad. When the energization is stopped and the brazing material is cooled, the one optical component is brazed and fixed on the fixing pad.

Similarly, the heaters are caused to generate heat independently for each fixed pad to braze and fix other optical components on the fixed pad. At this time, since the heater independently generates heat for each fixed pad, the heat is prevented from being transmitted to other fixed pads. Therefore, the brazing material of the optical component already fixed on the fixing pad will not be melted and the positioned position will not be displaced. Also,
Since the heating for brazing is partial heating instead of total heating, and the thermal influence on other parts is reduced, only one brazing material is required regardless of the number of optical components brazed to the optical bench.

[0022]

Embodiments of the optical bench of the present invention will be described below with reference to the drawings. Here, an application example of the present invention to an optical transmission / reception module will be described, but the basic configuration of the optical transmission / reception module is the same as FIG. 5 described in the conventional example.

The optical bench 11 according to this embodiment has a structure as shown in FIG. In order to position and braze and fix optical components such as LDs, PDs, and lenses, the optical bench 11 is composed of a silicon single crystal substrate having a thermal expansion coefficient close to that of the optical components. A fixing pad 12 for brazing and fixing an optical component such as an LD on the optical bench 11 is separately provided at a position where the optical component is mounted and fixed.

The fixing pad 12 is a solder layer 13 provided on the surface for brazing an optical component such as an LD.
And a heater 14 embedded under the solder layer 13 in order to generate heat by energization to melt the solder. The heater 14 of each fixed pad 12 has two current-carrying wires 15 extending from each fixed pad, and these are electrically connected to the electrode pads 16 provided at the end of the optical bench 11, and the heaters 14 are electrically connected. Each of the fixed pads 12 is made to generate heat independently. It should be noted that one of the conducting wires 15 of each fixed pad 12 may be common.
In particular, if the back surface of the optical bench 11 is used as a common electrode, the number of conductive wirings 15 and electrode pads 16 can be reduced by half.

In the present embodiment, the substrate forming the optical bench 11 has a thickness of 1 mm, a width of 15 mm and a length of 15 mm.
The Si substrate was used, and the fixing pads 12 were provided at four places on the Si substrate according to the number of optical components. As described above, the heaters 14 embedded in the respective fixed pads 12 are electrically independent and can be heated independently.

The sectional structure of the fixing pad in this embodiment is as shown in FIG. An SiO ₂ insulating layer 32 is provided as an insulating film on a Si substrate 31, and a Ti buffer layer 33, a Pt heating element layer 34 serving as a heating element, a SiO ₂ insulating layer 35 for insulation, and a Ti buffer layer 36 are provided on the SiO ₂ insulating layer 32. , Pt oxidation preventive layer 37, Au layer for soldering, soldering layer 38,
And the Pb-Sn eutectic solder layer 39 is laminated in order toward the surface.

The heater layer 41 has a basic structure in which a Pt heating element layer 34 is laminated between the SiO ₂ layers 32 and 35 serving as insulating layers, and in the embodiment, a Ti buffer layer 33 is interposed. The upper and lower Ti layers 33, 36 are provided between the SiO ₂ layer and the Pt layer because they have good adhesion to SiO ₂ and can form a strong connection with Pt. Further, the upper Pt layer 37 plays a role of preventing the Ti layer 36 from being oxidized in a high temperature state during soldering.

The heater 14 is the heater layer 41 to which the current-carrying wiring 15 and the electrode pad 16 are added, and the buffer layer 42 is a Ti buffer layer 36 that adheres the heater layer 41 and the solder layer 39 on the surface. , Pt oxidation preventive layer 37 and Au soldering layer 38.

In this embodiment, the lower SiO ₂ layer 32 is Si
It is obtained by thermal oxidation of a single crystal, and other metal layers are obtained by vacuum evaporation. The upper SiO ₂ layer 35 is manufactured by the CVD method used in the semiconductor manufacturing process.

In the present embodiment, the Pt layer 43 serving as a heating element has a fine pattern having a width of several μm and is used as the fixed pad 12.
Was drawn over the entire area, the unnecessary portion was removed by etching to form a heat generating circuit, and the resistance value thereof was adjusted to obtain a desired heat generation amount. This patterning and removal of unnecessary portions of the other metal layers were performed using a semiconductor process. In addition, the drawing over the entire pad is
This is because the front surface of the fixed pad has a uniform heat generation distribution.

FIG. 4 shows the energization temperature characteristics of the optical bench manufactured in this example. The central portion of the fixed pad was heated to 300 ° C. by applying a voltage of 2.6V. The temperature was 150 ° C or lower at a position 3 mm away from the end of the fixed pad. From this, it is clear that each fixed pad can be heated and soldered in fixed pad units without raising the temperature of the portion other than the fixed pad.

On the optical bench manufactured as described above, optical components are mounted by a grip adjusting device as shown in FIG. The LD 52 is fixed by soldering in advance. The soldering and fixing are performed in the same manner as in the monitor PD 53 described below. The optical bench 11 according to the present embodiment is placed on the heat insulating plate 18, and L
D52 is caused to emit light, and the monitor PD 53 is aligned at a position where the output of the monitor PD 53 is maximum. This alignment is
It is performed by gripping between the two arms 61, 61 attached to the base 62. After aligning the monitor PD 53, the electrode rod 1 brought into contact with the selected electrode pad 16
The electrode pad 16 was energized from 7 to heat only the desired fixed pad to melt the solder layer on the surface of the fixed pad, and the monitor PD 53 was fixed by soldering.

In this example, the solder was Pb-Sn eutectic (melting point 183 ° C.) and the soldering temperature was 230 ° C. 230 ° C was reached in about 2 minutes from the start of energization, and 1
After leaving for 1 minute and ending the energization, the solder solidified after 1 minute. At this time, since the thermal expansion of the gripping means for gripping the monitor PD 53 is so small that it can be ignored, the positional accuracy of the monitor PD 53 after cooling was extremely good.

Optical components other than the monitor PD are also mounted in the same manner. The other steps are the same as those in the conventional technique.

The optical transceiver module mounted in this example was subjected to a heat cycle test of 2,000 ° C. to 70 ° C. 1 cycle / 30 minutes for 2000 cycles.
The average optical output drop is 0.2 dB and maximum is 0.5 dB with 0
It was proved to have high reliability.

According to the present embodiment, since the solder that is melted by heating is only the solder of the fixed pad, the solder such as the LD52 that has been previously fixed does not melt, and therefore the LD52 is melted by the solder. Etc. will not move. The solder used for fixing the monitor PD 53 may have the same melting point as the solder used for fixing the LD 52 and the like, and the soldering temperature need not be lower than the melting point of the LD fixing solder and the like.

As described above, only the desired fixing pad is heated and the other parts are not heated. Therefore, only one type of solder is required regardless of the number of optical parts to be fixed, and a temperature difference is given to each fixed part. There is no need to limit the number of optical components that can be fixed.

Further, since it is not necessary to select a solder depending on the melting point, it is not necessary to use a solder that easily creeps or a solder that has poor wettability, and it is excellent in reliability. Moreover, it is not necessary to heat the entire optical bench, and the heating area is reduced. Is small, the heater capacity can be small. As a result, expansion of the gripping means such as an arm that grips the optical component can be avoided, and the position of the optical component after cooling does not deviate from the desired position. Further, since it is only necessary to raise and cool only a small heating area, it is possible to raise and cool the heating time in a short time and to improve the productivity.

In particular, by applying it to a mounting technique of a waveguide type optical component such as an optical transceiver module, it is possible to reduce the number of processes, reduce the cost due to the reduction of components, and reduce the size.
It is possible to fully meet the demand for optical communication that spreads to subscriber systems.

The present invention is not limited to the composition, the shape of parts, the material, etc. of the cross section of the fixed pad described in this embodiment. For example, I used a silicon substrate for the optical bench,
Other materials such as glass may be used. Further, in FIG. 1, the optical bench 11 is placed on the heat insulating plate 18 and heating is performed only by the heater of the fixed pad portion. However, for example, the heat insulating plate 18 is replaced with a heater, and residual heat below the melting temperature of the solder is used. You may make it implement.

[0041]

The present invention has the following effects.

(1) Since only the fixing pad for fixing the optical components can be effectively heated, a large number of optical components can be brazed with one type of solder.

(2) Since only one type of brazing material is required, a brazing material having high reliability such as brazing property and creep property can be selected and used, and high reliability can be obtained.

(3) Since the heating area is the fixed pad and is smaller than the optical bench, the thermal expansion of the gripping means such as the arm for gripping the optical component to change and adjust its position can be ignored, Therefore, the positional accuracy of the optical component after cooling becomes extremely good.

(4) Since the heating area is very small,
Cooling can be done in a short time, productivity can be improved, and cost reduction can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a method of mounting an optical component using an optical bench of the present invention.

FIG. 2 is a perspective view showing an embodiment of an optical bench of the present invention.

FIG. 3 is a sectional view showing an embodiment of a fixed pad structure of an optical bench according to the present invention.

FIG. 4 is a temperature characteristic diagram with respect to a conduction voltage of a heater of the optical bench of the present embodiment.

FIG. 5 is a perspective view showing an example of an internal structure of a conventional optical transceiver module.

FIG. 6 is a perspective view showing a method of mounting an optical component using a conventional optical bench.

[Explanation of symbols]

 11 Optical Bench 12 Fixed Pad 13 Solder Layer 14 Heater 15 Conductive Wiring 16 Electrode Pad 17 Electrode Bar 18 Insulation Plate 52 LD (Semiconductor Laser) 53 Monitor PD (Semiconductor Photo Detector for Monitor)

Claims (3)

[Claims] 1. An optical bench for positioning and brazing optical components such as a semiconductor laser, a semiconductor light receiving element, and a lens, wherein a brazing material for brazing the optical components on the optical bench, and an electric current. An optical bench, characterized in that a fixed pad having a heater for generating heat to melt the brazing material is provided independently for each optical component, and the heater is independently heated for each fixed pad. 2. The optical bench according to claim 1, wherein the fixed pad provided on the optical bench is formed by closely sandwiching a metal heating element between insulating layers in order from the substrate toward the surface. An optical bench having a laminated structure including a buffer layer for closely adhering a heater layer and a solder layer, and a solder layer for soldering optical components. 3. The optical bench according to claim 1, wherein the optical bench is composed of a Si substrate, and the fixed pads provided on the Si substrate are a SiO ₂ insulating layer and a Ti buffer in order from the substrate to the surface. Layer, Pt
An optical bench having a laminated structure including a heating element layer, a SiO ₂ insulating layer, a Ti buffer layer, a Pt oxidation preventing layer, an Au soldering layer, and a Pb—Sn solder layer.