JP2005129584A - Semiconductor laser device, packaging method and packaging equipment of semiconductor laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging method of a semiconductor laser element of high reliability which can function accurately by reducing or canceling remaining thermal stress which is generated in the semiconductor laser element when it is mounted on the surface of a substrate such as a submount. <P>SOLUTION: When a bonding material (solder) solidifies from a melting state, the semiconductor laser element 2 is subjected to forced cooling by e.g. a forced cooling fan 1. When the semiconductor laser element 2 whose line thermal expansion is larger than that of the substrate 3 is generally mounted on the surface of the substrate 3, the thermal stress which is generated in the semiconductor laser element 2 and going to remain is reduced or canceled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser device in which a semiconductor laser element is mounted on a substrate, a method for mounting such a semiconductor laser element, and a semiconductor laser element mounting apparatus.

  Conventionally, a semiconductor laser element chip such as an LD (Laser Diode; hereinafter abbreviated as LD) is mounted on a surface of a substrate such as a submount via a heat-meltable bonding material such as solder. In the process, the LD is placed together with the solder at a predetermined position on the submount, and the LD is placed on the sample table of the alloy furnace and heated together to perform bonding and mounting by solder. The surface of the submount and the surface involved in the mounting of the LD chip centering on the solder are heated by heating the submount with a heating means such as a heater stage.

  In general, a substrate such as a submount and an LD chip have different thermal conductivity and linear thermal expansion coefficient. For this reason, after the mounting process as described above, a thermal stress that cannot be ignored may remain between the mounted chip and the submount.

In order to reduce or eliminate such residual thermal stress, for example, a substrate such as a submount is made of a material having the same thermal expansion coefficient as that of the LD chip, or has a high thermal conductivity. This has been proposed (Patent Document 1).
JP 11-330324 A

  However, in the conventional technique as described above, for example, a gas introduced as a working atmosphere such as FO gas does not contribute to temperature control or the like. Generally, the linear thermal expansion profile is lower than that of the submount. Since the chip is larger, the thermal expansion at the time of solidification of the solder becomes larger at the LD, and the recovery of the thermal expansion is governed by the submount after the solidification of the solder. As a result, the LD chip and the submount at the time of solidification of the solder The difference in thermal expansion of the semiconductor layer remains as stress (residual thermal stress) in the LD after the completion of the mounting process (after solder solidification).

  In particular, solder such as Sn (tin) is often used as a bonding material. However, in the case of mounting using such solder, the stress remaining in the LD becomes large, and as a result, the output of the completed LD There is a problem that the reliability is deteriorated, such as a characteristic defect or a mounting defect. Further, due to such a large stress remaining in the LD, there is a problem that abnormal polarization outside the setting is generated in the LD, resulting in a severe defect as the LD.

  In addition, in the case of an LD having a plurality of light emitting points (light emitting sources) such as so-called multi-beam LDs, an abnormality in polarization due to the stress remaining in the LD as described above is generally caused by each light emitting point at the chip. Since it is arranged symmetrically with the central portion as an axis, it becomes more prominent than in the case of a single light source LD. Or, in the case of a semiconductor laser element having an optical system including a birefringent lens, the condensing distance of the output laser light becomes different for each of a plurality of light emitting sources (becomes inconsistent). There is a problem.

  Moreover, in the conventionally proposed technology as described above, the substrate such as the submount and the LD chip must be made of the same material with the same thermal expansion coefficient. As a practical solution, there were many inconveniences.

  The present invention has been made in view of such problems, and its purpose is to reduce residual thermal stress generated in a semiconductor laser device when a semiconductor laser device such as an LD is mounted on the surface of a substrate such as a submount. It is an object of the present invention to provide a semiconductor laser device which can be reduced or eliminated, and which can function reliably and accurately, a mounting method of such a semiconductor laser device, and a semiconductor laser device mounting apparatus.

  The semiconductor laser device of the present invention is a semiconductor laser device in which a semiconductor laser element having a material having an expansion coefficient different from that of the substrate is mounted on the surface of the substrate by fusion bonding of the bonding material. When solidifying, the semiconductor laser element is forcibly cooled.

  The mounting method of the semiconductor laser device according to the present invention is such that when the semiconductor laser device having a material having an expansion coefficient different from that of the substrate is mounted on the surface of the substrate by fusion bonding of the bonding material, the bonding material is solidified from the molten state. The semiconductor laser element is forcibly cooled.

  The semiconductor laser device mounting apparatus according to the present invention is a semiconductor laser device mounting apparatus for mounting a semiconductor laser device having a material having an expansion coefficient different from that of the substrate on the surface of the substrate by fusion bonding of the bonding material. A forced cooling means for forcibly cooling the semiconductor laser element when solidifying from the state is provided.

  In the semiconductor laser device or the semiconductor laser device mounting method or the semiconductor laser device mounting apparatus of the present invention, a semiconductor whose thermal expansion is generally larger than that of the substrate by forcibly cooling the semiconductor laser device when the bonding material solidifies from a molten state. Residual thermal stress generated in the semiconductor laser element when the laser element is mounted on the surface of the substrate is reduced or eliminated.

  More specifically, the semiconductor laser element is forcibly cooled when the bonding material is solidified from a molten state, so that the thermal expansion of the semiconductor laser element and the thermal expansion of the substrate when the bonding material is solidified are aligned.

  Alternatively, by forcibly cooling the semiconductor laser element when the bonding material solidifies from the molten state, the thermal stress remaining between the semiconductor laser element and the substrate when the bonding material is solidified is subjected to the forced cooling. It is lower than the residual thermal stress in the case where there is not.

  Alternatively, when the semiconductor laser element is forcibly cooled when the bonding material solidifies from the molten state, the material mechanical strain on the surface of the substrate of the semiconductor laser element when the bonding material is solidified is subjected to the forced cooling. The distortion is lower than that in the case where there is no such distortion.

  According to the semiconductor laser device or the semiconductor laser element mounting method or the semiconductor laser element mounting device of the present invention, the semiconductor laser element is forcibly cooled when the bonding material solidifies from the molten state, so that the thermal expansion is generally higher than that of the substrate. Residual thermal stress generated in the semiconductor laser element when a large semiconductor laser element is mounted on the surface of the substrate is reduced or eliminated, so that the reliability of the completed semiconductor laser device can be increased. Can function correctly.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a semiconductor laser device mounting apparatus according to an embodiment of the present invention. The semiconductor laser device mounting method or semiconductor laser device according to the embodiment of the present invention is embodied by the operation or action of the semiconductor laser device mounting apparatus, and will be described below together. .

  This semiconductor laser element mounting apparatus is given as an example of the simplest structure. In the semiconductor laser device mounting apparatus shown in FIG. 1, a forced cooling fan 1 is provided as a forced cooling means, and a chip such as solder (not shown in FIG. 1) is solidified when solidified from a molten state. The semiconductor laser element 2 is forcibly air-cooled by blowing cold air (air) 100 from above on the semiconductor laser element 2, and the degree of thermal expansion is larger than that of the substrate 3 such as a submount. The residual thermal stress generated in 2 is reduced or eliminated to the extent that there is no practical problem.

  In this semiconductor laser device mounting apparatus, the semiconductor laser device 2 is placed together with solder at a predetermined position on the substrate 3, and the semiconductor laser device 2 is placed on the sample table 8 in the alloy furnace 5 and heated at once. The surface of the substrate 3 and the surface involved in the mounting in the semiconductor laser element 2 are heated by the heater stage 4 with the solder at this time as a center.

  The semiconductor laser element 2 and the substrate 3 are joined by heating and melting the solder in this manner. After the heating, the semiconductor laser element 2 is forced by the forced cooling fan 1 according to the present embodiment. To be cooled. That is, the semiconductor laser element 2 is forcibly cooled by the forced cooling fan 1 until the solder is sufficiently cooled and solidified, and the magnitude of the thermal expansion of the semiconductor laser element 2 is the magnitude of the thermal expansion of the substrate 3. Will be aligned. As a result, when the solder is sufficiently cooled and solidified, no residual thermal stress remains in the semiconductor laser element 2, or such residual thermal stress is reduced or eliminated to a level that is practically negligible. .

  FIG. 2 shows an example of the structure of the semiconductor laser device mounting apparatus in the case where a solid refrigerant such as ice is used as the forced cooling means.

  The semiconductor laser device mounting apparatus shown in FIG. 2 has a structure in which a ceramic plate 7 is disposed immediately above the semiconductor laser device 2 and an ice cup 6 is placed thereon. The semiconductor laser device mounting apparatus of FIG. 2 using a solid refrigerant such as ice bag 6 can be mounted at a higher temperature compared to the air cooling system as shown in FIG. It is also effective when a material having a higher thermal expansion coefficient is mounted.

  FIG. 3 shows an example of indirect forced cooling by the gaseous refrigerant 9. That is, for example, FO gas 10 such as nitrogen gas is introduced as a working atmosphere of the mounting process, and forced cooling means 21 using a gas refrigerant 9 such as air or nitrogen as a refrigerant is arranged on the upper part to cool the FO gas 10. Then, the semiconductor laser device 2 is cooled by the cooled FO gas 10.

  By adopting such a configuration, the gas refrigerant 9 can be circulated independently from the FO gas 10 in the working atmosphere, so that stable cooling is continuously performed and the gas refrigerant 9 is lost. And can be performed at low cost.

  FIG. 4 shows an example of indirect forced cooling with the liquid refrigerant 11. That is, the FO gas 10 is introduced as a working atmosphere of the mounting process, and the forced cooling means 22 using the liquid refrigerant 11 such as cooling water or liquid nitrogen as a refrigerant is arranged on the upper part to cool the FO gas 10 and cool it. The semiconductor laser element 2 is cooled by the FO gas 10.

  By adopting such a configuration, the liquid refrigerant 11 can be circulated independently from the FO gas 10 in the working atmosphere, so that the semiconductor laser element 2 is not wetted and is more stable than the case of the air refrigerant. Liquid cooling can be continuously performed at low cost without losing the liquid refrigerant 11.

  FIG. 5 shows an example of indirect forced cooling by the Peltier module 12. That is, for example, a FO gas 10 such as nitrogen gas is introduced as a working atmosphere of the mounting process, and a Peltier module 12 that performs forced cooling by a so-called Peltier effect is arranged as a forced cooling means on the upper part to cool the FO gas 10. The semiconductor laser device 2 is cooled by the cooled FO gas 10.

  By adopting such a configuration, it is possible to control the cooling state (temperature state) of the semiconductor laser element 2 while the bonding material such as solder is solidified with higher accuracy.

  Next, the operation of the semiconductor laser device mounting apparatus, the semiconductor laser device mounting method, or the semiconductor laser device according to the present embodiment will be described.

  FIG. 6 shows the time course of temperature and linear expansion profile for each of the substrate (submount) and the semiconductor laser element (GaAs-LD) in the semiconductor laser element mounting apparatus or mounting method according to the present embodiment. Is schematically represented. In FIG. 6, the LD temperature 601 and the heater stage temperature 602 are indicated by solid lines, and the submount linear thermal expansion 603 and LD linear thermal expansion 604 are indicated by dotted lines.

  The thermal stress remaining in the semiconductor laser element 2 after the solder is completely solidified is governed by the linear thermal expansion coefficient of the substrate 3. For this reason, in order to reduce or eliminate the thermal stress remaining in the semiconductor laser element 2, when the solder is completely solidified, the linear expansion 604 of the semiconductor laser element 2 (LD) and the line of the substrate 3 (submount) The size of the expansion 603 must be the same.

  Therefore, by concentrating and forcibly cooling only the semiconductor laser element 2 until the melted solder is solidified, the difference in thermal expansion between the two is reduced. By aligning the linear expansion 604 of the semiconductor laser element 2 and the linear expansion 603 of the substrate 3 to the same size, the thermal stress remaining in the semiconductor laser element 2 can be reduced or eliminated. As a result, the reliability of the completed semiconductor laser device can be increased, and the semiconductor laser device can function accurately.

  In order to confirm the effect of the semiconductor laser device mounting apparatus or the mounting method according to the present embodiment, the mounting process using the ice cup 6 as shown in FIG. The polarization of the semiconductor laser device thus obtained was examined, and the residual state of thermal stress was evaluated based on the result.

  As a result, as schematically shown in FIG. 7 (single light source type) and FIG. 8 (multiple light source type), the semiconductor laser element 2 mounted on the surface of the substrate 3 via the solder 13 is It was confirmed that the distortion was eliminated to almost 0 (zero). In addition, in the case of the multiple light source type of FIG. 8, it was confirmed that no inconvenient bias or distortion (error) occurred in the output laser optical axes of the two light emitting sources 14a and 14b. Further, as shown in FIG. 9, it was confirmed that no significant polarization or the like due to the residual thermal stress after mounting occurred.

Comparative example

  Here, as a comparative example, a conventional general mounting apparatus and a mounting process using the same will be described. FIG. 10 shows an example of a conventional semiconductor laser device mounting apparatus.

  The semiconductor laser elements 2 placed at predetermined positions on the substrate 3 are placed on the sample stage 8 of the alloy furnace 5 and heated together in the alloy furnace 5 to perform soldering. In such a conventional mounting apparatus, generally, the substrate 3 is heated by the heater stage 4 to melt the solder. And it was trying to cool naturally about solidification of solder. The FO gas 10 is also used to fill the atmosphere, and contributes substantially to cooling and the like.

  FIG. 11 shows the time course of temperature and linear expansion profile for each of the substrate (submount) 3 and the semiconductor laser element (LD) 2 in such a conventional semiconductor laser element mounting apparatus or mounting method therefor. This is shown schematically. In FIG. 11, the heater stage temperature 701 is indicated by a solid line, and the linear thermal expansion 702 of the submount and the linear thermal expansion 703 of the LD are indicated by dotted lines.

  Since the linear thermal expansion coefficient of the LD is larger than that of the submount, the magnitude of the linear thermal expansion before the solder is solidified (in the molten state of the solder) is larger in the LD.

  When the solder is solidified, since the submount has a sufficiently larger volume than the LD, recovery of thermal expansion is governed by the submount. For this reason, even if the solder is naturally cooled from the molten state and solidified, the LD and the submount are also naturally cooled during that time, so the difference in thermal expansion between the LD and the submount does not decrease, and as a result The difference in linear thermal expansion between the LD and the submount remains in the LD (semiconductor laser element 2) as material mechanical stress (thermal stress).

  In particular, in the case of a multi-beam LD, the LD chip is distorted over an angle Δθ as shown in FIG. 12 due to the residual thermal stress as described above, and the optical axis of the laser output is distorted. As a result, in the case of the semiconductor laser device having the optical system 130 including the birefringent lens 131 as shown in FIG. 13 as an example, the condensing distances of the laser beams of the two semiconductor laser elements 2a and 2b are mutually different. It will be different.

  As described above, in the semiconductor laser device, the semiconductor laser device mounting method, and the semiconductor laser device mounting apparatus according to the present embodiment, the heat remaining in the semiconductor laser device 2 with a size that cannot be ignored by the conventional technology. The mechanical stress can be reduced or eliminated to a negligible level, thereby further improving the reliability of the completed semiconductor laser device and realizing an accurate and desirable laser output function.

  The present invention is applicable to a semiconductor laser device in which a semiconductor laser element is mounted on a substrate, a method for mounting such a semiconductor laser element, and a semiconductor laser element mounting apparatus. The semiconductor laser device provided in the chip can be suitably used for mounting on a substrate without causing optical axis distortion or the like.

1 is a diagram showing a schematic configuration of a semiconductor laser device mounting apparatus according to an embodiment of the present invention. It is a figure showing the example at the time of using a solid refrigerant | coolant as a forced cooling means. It is a figure showing an example of the structure which cools a semiconductor laser element with a gaseous refrigerant. It is a figure showing the example which uses a liquid refrigerant as a refrigerant. It is a figure showing an example in the case of indirect forced cooling by a Peltier module. It is the figure which represented typically about the time course of the temperature about each of a board | substrate and a semiconductor laser element, and a linear expansion profile. It is the figure which represented typically the mounting state without distortion of single light source type LD. It is the figure which represented typically the mounting state without distortion of multiple light source type LD. It is a figure showing an example of the generation | occurrence | production state of the polarized light resulting from the residual thermal stress after mounting. It is a figure showing an example of the conventional semiconductor laser element mounting apparatus as a comparative example. It is a figure showing the time course of the temperature and linear expansion profile about each of a board | substrate and a semiconductor laser element in the conventional mounting method. The figure showing an example in which the multi-beam LD mounted by the conventional semiconductor laser device mounting apparatus is distorted due to the residual thermal stress after mounting and the optical axis of the output laser is also distorted. It is. As a result of the multi-beam LD mounted by the conventional semiconductor laser device mounting apparatus being distorted due to the residual thermal stress after mounting, the converging distances of the laser beams output from the two semiconductor laser devices of the multi-beam LD are mutually different. It is a figure showing an example of the state from which it became different.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Forced cooling fan, 2 ... Semiconductor laser element, 3 ... Board | substrate, 4 ... Heater stage, 5 ... Alloy furnace, 6 ... Ice cup, 7 ... Ceramic plate, 8 ... Sample stand, 9 ... Gas refrigerant, 10 ... FO gas, 11 ... liquid refrigerant, 12 ... Peltier module, 13 ... solder

Claims (20)

A semiconductor laser device in which a semiconductor laser element made of a material having an expansion coefficient different from that of the substrate is mounted on the surface of the substrate by fusion bonding of a bonding material,
A semiconductor laser device, wherein the semiconductor laser element is forcibly cooled when the bonding material solidifies from a molten state. 2. The semiconductor laser device according to claim 1, wherein a material of the semiconductor laser element has an expansion rate higher than an expansion rate due to heating at the time of fusion bonding of the bonding material. The semiconductor laser element is forcibly cooled when the bonding material is solidified from a molten state, so that the thermal expansion of the semiconductor laser element and the thermal expansion of the substrate are aligned in a state where the bonding material is solidified. The semiconductor laser device according to claim 1. By forcibly cooling the semiconductor laser element when the bonding material is solidified from a molten state, the forced cooling can be applied to the thermal stress remaining between the semiconductor laser element and the substrate when the bonding material is solidified. 2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is lower than the residual thermal stress when the step is not performed. By forcibly cooling the semiconductor laser element when the bonding material is solidified from a molten state, the mechanical cooling of the semiconductor laser element with respect to the surface of the substrate in the state in which the bonding material is solidified can be performed. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is lower than a distortion in a case where the step is not performed. The semiconductor laser device according to claim 1, wherein the semiconductor laser element has a plurality of light emitting sources in one element. By forcibly cooling the semiconductor laser element when the bonding material is solidified from a molten state, errors in output optical axes from a plurality of light emitting sources in the semiconductor laser element in a state where the bonding material is solidified, The semiconductor laser device according to claim 6, wherein the error is lower than an error when no forced cooling is performed. In mounting a semiconductor laser element of a material having a different expansion coefficient from that of the substrate on the surface of the substrate by fusion bonding of the bonding material,
A method for mounting a semiconductor laser device, comprising: forcibly cooling the semiconductor laser device when the bonding material is solidified from a molten state. 9. The method of mounting a semiconductor laser device according to claim 8, wherein a material of the semiconductor laser device has an expansion rate higher than an expansion rate due to heating at the time of fusion bonding of the bonding material. The semiconductor laser element is forcibly cooled when the bonding material solidifies from a molten state, and the thermal expansion of the semiconductor laser element and the thermal expansion of the substrate after the bonding material solidifies are aligned. The method for mounting a semiconductor laser device according to claim 8. The semiconductor laser element is forcibly cooled when the bonding material solidifies from a molten state, and the thermal stress remaining between the semiconductor laser element and the substrate after the bonding material is solidified is reduced by the forced cooling. 9. The method of mounting a semiconductor laser device according to claim 8, wherein the residual thermal stress is lower than that when not applied. The semiconductor laser element is forcibly cooled when the bonding material is solidified from a molten state, and the mechanical cooling of the surface of the substrate of the semiconductor laser element after the bonding material is solidified is subjected to the forced cooling. 9. The method of mounting a semiconductor laser device according to claim 8, wherein the distortion is lower than the distortion when not applied. 9. The semiconductor laser device mounting method according to claim 8, wherein the semiconductor laser device has a plurality of light emitting sources in one device. The semiconductor laser element is forcibly cooled when the bonding material solidifies from a molten state, and errors in output optical axes from a plurality of light sources in the semiconductor laser element after the bonding material is solidified are 9. The method of mounting a semiconductor laser device according to claim 8, wherein the error is lower than an error in a case where the cooling is not performed. A semiconductor laser device mounting apparatus for mounting a semiconductor laser device having a material having an expansion coefficient different from that of the substrate on the surface of the substrate by fusion bonding of a bonding material,
A semiconductor laser element mounting apparatus comprising: a forced cooling means for forcibly cooling the semiconductor laser element when the bonding material is solidified from a molten state. The forced cooling means forcibly cools the semiconductor laser element when the bonding material is solidified from a molten state, whereby the thermal expansion of the semiconductor laser element and the thermal expansion of the substrate after the bonding material is solidified. The semiconductor laser device mounting apparatus according to claim 15, wherein: The forced cooling means forcibly cools the semiconductor laser element when the bonding material is solidified from a molten state, so that the heat remaining between the semiconductor laser element and the substrate after the bonding material is solidified. The semiconductor laser device mounting apparatus according to claim 15, wherein the stress is made lower than a residual thermal stress when the forced cooling is not performed. The forced cooling means forcibly cools the semiconductor laser element when the bonding material is solidified from a molten state, so that the semiconductor laser element after the bonding material is solidified is mechanically applied to the surface of the substrate. The semiconductor laser device mounting apparatus according to claim 15, wherein the distortion is lower than the distortion when the forced cooling is not performed. The semiconductor laser element has a plurality of light emission sources in one element,
The forced cooling means forcibly cools the semiconductor laser element when the bonding material is solidified from a molten state, whereby output light from a plurality of light emitting sources in the semiconductor laser element after the bonding material is solidified The semiconductor laser device mounting apparatus according to claim 15, wherein an error of the axis is made lower than an error when the forced cooling is not performed. A heating means for melting at least the bonding material at the time of the fusion bonding and a forced cooling means for forcibly cooling the semiconductor laser element when the bonding material solidifies from a molten state function independently. The semiconductor laser device mounting apparatus according to claim 15, wherein the device is capable of being provided.

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