Semiconductor laser device and method for manufacturing semiconductor laser device
The semiconductor laser device addresses the challenge of heat transfer efficiency by using individually placed insulating members and a spanning solder layer to maintain heat dissipation efficiency despite small array pitches, ensuring effective heat transfer to the heat sink.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HAMAMATSU PHOTONICS KK
- Filing Date
- 2025-09-01
- Publication Date
- 2026-05-15
AI Technical Summary
The miniaturization of semiconductor laser bars has made it difficult to match the array pitch of each semiconductor laser bar unit with the conductor pattern on the insulating substrate, leading to decreased heat transfer efficiency in the heat dissipation path from the submount to the heat sink.
A semiconductor laser device with a laminated structure where insulating members are individually provided on each submount, joined to a heat sink via a first solder layer that spans across the submounts, allowing for precise alignment-free assembly and ensuring sufficient heat transfer efficiency even with small array pitches.
The solution ensures high heat transfer efficiency in the heat dissipation path from the submount to the heat sink, even with small array pitches, by eliminating the need for precise alignment and minimizing interference between insulating members.
Smart Images
Figure JP2025030756_15052026_PF_FP_ABST
Abstract
Description
Semiconductor Laser Device and Method for Manufacturing Semiconductor Laser Device
[0001] The present disclosure relates to a semiconductor laser device and a method for manufacturing a semiconductor laser device.
[0002] As a conventional semiconductor laser device, for example, there is a semiconductor laser device described in Patent Document 1. The semiconductor laser device described in Patent Document 1 includes a semiconductor laser bar unit in which a semiconductor laser bar is mounted on a submount. This semiconductor laser device includes a stacked structure in which a plurality of semiconductor laser bar units are stacked, and a heat sink having a heat conductive insulating substrate on one side surface. A conductor pattern is formed on the surface of the insulating substrate, and the submounts of each semiconductor laser bar unit constituting the stacked structure are joined to the conductor pattern by solder layers.
[0003] Japanese Unexamined Patent Application Publication No. 2017-28044
[0004] In recent years, with the demand for high integration of semiconductor laser bars, semiconductor laser bars have been on the path of miniaturization. As the size of the semiconductor laser bar is miniaturized, it has become difficult to match the array pitch of each semiconductor laser bar unit constituting the stacked structure and the conductor pattern on the surface of the insulating substrate. If a deviation occurs between the submount of each semiconductor laser bar unit and the conductor pattern on the surface of the insulating substrate, it is considered that the heat transfer efficiency in the heat dissipation path from the submount to the heat sink will decrease.
[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a semiconductor laser device and a method for manufacturing a semiconductor laser device that can sufficiently ensure the heat transfer efficiency in the heat dissipation path from the submount to the heat sink even when the array pitch of the semiconductor laser bar units is small.
[0006] The gist of the present disclosure is as follows.
[0007] [1] A semiconductor laser device comprising a heat sink having a mounting surface on one side, and a laminated structure formed by stacking a plurality of semiconductor laser bar units, each of which has a semiconductor laser bar mounted on a submount, wherein the laminated structure is fixed to the heat sink by joining each of the submounts to the mounting surface via an insulating member and a first solder layer, with each of the semiconductor laser bars spaced apart from the mounting surface, the insulating member is provided individually on each of the submounts, and the first solder layer extends across the mounting surface so as to span each of the submounts.
[0008] In this semiconductor laser device, insulating members are individually provided on each submount in advance, and the laminated structure can be mounted on the heat sink by joining each insulating member of the submount collectively with a first solder layer extending to the mounting surface of the heat sink. In this semiconductor laser device, there is no need to match the array pitch of each semiconductor laser bar unit constituting the laminated structure with the insulating members, and precise alignment between each insulating member and the first solder layer is also unnecessary. Therefore, even when the array pitch of the semiconductor laser bar units is small, sufficient heat transfer efficiency can be ensured in the heat dissipation path from the submount to the heat sink.
[0009] [2] The semiconductor laser apparatus according to [1], wherein in each of the semiconductor laser bar units, the end of the submount on the heat sink side protrudes toward the heat sink side more than the end face of the semiconductor laser bar on the heat sink side. In this case, a heat dissipation path from the submount to the heat sink via an insulating member and a first solder layer can be suitably formed.
[0010] [3] In each of the semiconductor laser bar units, the length of the heat sink-side end of the submount protruding from the heat sink-side end face of the semiconductor laser bar is greater than the thickness of the insulating member provided on the submount, as described in [2]. In this case, the proportion occupied by the submount in the heat dissipation path from the submount to the heat sink can be sufficiently secured. Therefore, the heat transfer efficiency in the heat dissipation path can be sufficiently increased.
[0011] [4] The semiconductor laser apparatus according to any one of [1] to [3], wherein the shapes of the insulating members provided individually on each of the submounts are identical to each other. In this case, the uniformity of the shapes of the insulating members equalizes the distortion of each insulating member during thermal expansion due to heat dissipation, thereby suppressing the effect of stress on the laminated structure and the heat sink.
[0012] [5] The semiconductor laser apparatus according to any one of [1] to [4], wherein each of the insulating members is provided on the entire end face of each of the submounts on the heat sink side. In this case, the insulating members can be prevented from becoming a bottleneck, and sufficient heat transfer efficiency can be ensured in the heat dissipation path from the submount to the heat sink.
[0013] [6] The semiconductor laser apparatus according to any one of [1] to [5], wherein the width of each of the insulating members in the stacking direction of the plurality of semiconductor laser bar units is equal to the width of the end face on the heat sink side of each of the submounts in the stacking direction. In this case, it is possible to suppress the insulating members from becoming a bottleneck and to ensure sufficient heat transfer efficiency in the heat dissipation path from the submount to the heat sink. Furthermore, even when the array pitch of the semiconductor laser bar units is small, it is possible to suppress interference between the insulating members of adjacent semiconductor laser bar units.
[0014] [7] The semiconductor laser apparatus according to any one of [1] to [6], wherein the width of each of the insulating members in the stacking direction of the plurality of semiconductor laser bar units is wider than the width of each of the end faces on the heat sink side of the submount in the stacking direction. In this case, insulating members can be easily provided on the submount even if the width of the submount in the stacking direction is small.
[0015] [8] A semiconductor laser apparatus according to any one of [1] to [7], wherein in each of the semiconductor laser bar units, a second solder layer is provided so as to cover the entire surface of the submount, and the semiconductor laser bar and the insulating member are fixed to the submount via the second solder layer. This improves the workability when joining the semiconductor laser bar and the insulating member to the submount. Furthermore, because the second solder layer is provided on the entire surface of the submount, it is possible to suppress the excess portion of the second solder layer from wrapping around to the emission end face of the semiconductor laser bar when joining the semiconductor laser bar to the submount.
[0016] [9] The semiconductor laser apparatus according to [8], wherein the melting point of the first solder layer is lower than the melting point of the second solder layer. In this case, when the laminated structure is joined to the heat sink by the first solder layer, it is possible to suppress the melting of the second solder layer used for joining the submount to the semiconductor laser bar and the submount to the insulating member.
[0017]
[10] The semiconductor laser apparatus according to [8], wherein the melting point of the first solder layer and the melting point of the second solder layer are equal. In this case, when the first solder layer is used for joining, the already joined second solder layer may remelt, but by adjusting the joining temperature and heating time based on this, the joining of both can be suitably carried out.
[0018]
[11] A method for manufacturing a semiconductor laser device, comprising: a forming step of stacking a plurality of semiconductor laser bar units, each having a semiconductor laser bar mounted on a submount, to form a stacked structure; and a fixing step of preparing a heat sink having a mounting surface on one side, and fixing the stacked structure to the heat sink by joining each of the submounts to the mounting surface via an insulating member and a first solder layer, wherein in the forming step, the insulating member is individually provided on each of the submounts, and in the fixing step, the insulating member individually provided on each of the submounts is joined to the mounting surface via the first solder layer, with the first solder layer extending over each of the submounts to the mounting surface of the heat sink.
[0019] In this semiconductor laser device manufacturing method, insulating members are individually provided on each submount in advance, and the laminated structure is mounted on the heat sink by joining each insulating member of the submount collectively with a first solder layer extending to the mounting surface of the heat sink. In this semiconductor laser device manufacturing method, it is not necessary to match the array pitch of each semiconductor laser bar unit constituting the laminated structure with the insulating members, and precise alignment between each insulating member and the first solder layer is also unnecessary. Therefore, even when the array pitch of the semiconductor laser bar units is small, sufficient heat transfer efficiency can be ensured in the heat dissipation path from the submount to the heat sink.
[0020] According to this disclosure, even when the array pitch of the semiconductor laser bar unit is small, sufficient heat transfer efficiency can be ensured in the heat dissipation path from the submount to the heat sink.
[0021] Figure 1 is a schematic cross-sectional view showing the configuration of a semiconductor laser device according to one embodiment of the present disclosure. Figure 2 is a schematic side view showing the configuration of electrodes. Figure 3 is an enlarged cross-sectional view of the main part of the semiconductor laser device shown in Figure 1. Figures (a) to (c) are schematic cross-sectional views showing the manufacturing process of the semiconductor laser device shown in Figure 1. Figures (a) and (b) are schematic cross-sectional views showing modified examples of the bonding of insulating members to the semiconductor laser bar unit.
[0022] Hereinafter, with reference to the drawings, preferred embodiments of a semiconductor laser apparatus and a method for manufacturing a semiconductor laser apparatus relating to one aspect of this disclosure will be described in detail.
[0023] Figure 1 is a schematic side view showing the configuration of a semiconductor laser device according to one embodiment of the present disclosure. In Figure 1, for the convenience of explaining the overall configuration of the semiconductor laser device, the second solder layer 22, metal layer 24, and metal layers 25 (25A, 25B), which will be described later, are omitted. As shown in Figure 1, the semiconductor laser device 1 is configured to include a heat sink 2, a laminated structure 3 formed by stacking a plurality of semiconductor laser bar units 4, and a pair of electrodes 5, 5. The semiconductor laser bar unit 4 is composed of a semiconductor laser bar 11 and a submount 12.
[0024] The semiconductor laser device 1 has a rear cooling structure in which cooling is performed on the opposite side of the direction of laser light oscillation. With this cooling structure, the heat generated in the semiconductor laser bar 11 during laser oscillation is dissipated to the heat sink 2 via a submount 12 or the like. In this embodiment, the heat sink 2 is formed in the shape of a thick plate from a material with excellent heat conductivity. Copper, CuW (copper tungsten), copper diamond composite material, etc. can be used as the material for forming the heat sink 2. The surface layer on the mounting surface M side of the heat sink 2 may be formed from copper, CuW, or copper diamond composite material, and the other parts may be formed from Kovar, 42 alloy (an alloy of iron with 42% nickel) which has a coefficient of thermal expansion similar to that of copper, CuW, or copper diamond composite material. One surface of the heat sink 2 is a flat surface and is the mounting surface M on which the laminated structure 3 is mounted. A channel for a cooling medium such as water may be formed inside the heat sink 2.
[0025] The semiconductor laser bar unit 4 consists of one semiconductor laser bar 11 and one submount 12. The semiconductor laser bar 11 and the submount 12 are electrically and thermally connected to each other. The semiconductor laser bar 11 is, for example, plate-shaped. The leading edge of the semiconductor laser bar 11 is an emission end surface 11a having multiple emission points. In the example shown in Figure 1, the multiple emission points on the emission end surface 11a are arranged at predetermined intervals in the depth direction of the paper.
[0026] The semiconductor laser bar 11 has a substrate made of, for example, a compound semiconductor. On the substrate, an active layer is located at positions corresponding to a plurality of emission points, and cladding layers are located on both sides of the active layer. Examples of substrate materials include gallium arsenide (GaAs), gallium nitride (GaN), aluminum gallium arsenide (AlGaAs), gallium phosphide (GaP), aluminum gallium nitride (AlGaN), and indium phosphide (InP). In this embodiment, the main component of the substrate is gallium arsenide (GaAs), the active layer further contains indium (In), and the cladding layer further contains aluminum (Al).
[0027] The submount 12 is formed in a plate shape from a material having thermal and electrical conductivity. Examples of materials for forming the submount 12 include copper tungsten (CuW), aluminum nitride (AlN), silicon carbide (SiC), tungsten (W), copper molybdenum (MoCu) composite material, and copper diamond composite material. In this embodiment, the submount 12 is formed from copper tungsten (CuW). The surface of the submount 12 may have two plating layers formed on it, for example, nickel (Ni) and gold (Au).
[0028] In the laminated structure 3, multiple semiconductor laser bar units 4 are stacked such that submounts 12 and semiconductor laser bars 11 are arranged alternately. An additional submount 12 is stacked on one end of the stacked semiconductor laser bar unit 4 of the laminated structure 3. The laminated structure 3 is positioned relative to the mounting surface M of the heat sink 2 such that the stacking direction X of the semiconductor laser bar units 4 coincides with the in-plane direction of the mounting surface M of the heat sink 2.
[0029] As an example, the width of the semiconductor laser bar 11 in the stacking direction X is approximately 100 μm to 150 μm. Also, the width of the submount 12 in the stacking direction X is approximately 100 μm to 500 μm. The array pitch P of the semiconductor laser bar 11 in the stacked structure 3 is the distance between adjacent semiconductor laser bar 11 in the stacking direction X, and is approximately 100 μm to 500 μm depending on the thickness of the submount 12 in the stacking direction X.
[0030] In each of the semiconductor laser bar units 4 constituting the laminated structure 3, the end face 12a of the submount 12 opposite to the heat sink 2 is flush with the output end face 11a of the semiconductor laser bar 11, including the second solder layer 22 described later (see Figure 3). Also, in each of the semiconductor laser bar units 4 constituting the laminated structure 3, the end face 12b of the submount 12 on the heat sink 2 side protrudes toward the heat sink 2 side more than the end face 11b of the semiconductor laser bar 11 on the heat sink 2 side. The laminated structure 3 is fixed to the heat sink 2 by joining each of the submounts 12 to the mounting surface M, with each of the semiconductor laser bars 11 spaced apart from the mounting surface M.
[0031] The pair of electrodes 5 are components that apply a driving voltage from a power source (not shown) to each semiconductor laser bar 11 contained in the laminated structure 3. In this embodiment, each of the pair of electrodes 5 is formed in the form of a thin film and is electrically connected to a submount 12 located at one end of the laminated structure 3 and to a submount 12 located at the other end of the laminated structure 3, respectively. As the material for forming the electrodes 5, copper (Cu) or the like can be used, considering the ease of thin film processing.
[0032] When joining the electrode 5 and the submount 12, the difference in thermal expansion coefficients between the constituent materials of the electrode 5 and the submount 12 is taken into consideration, and as shown in Figure 2, a notch 5a is provided at the joining portion of the electrode 5 to the submount 12. In the example in Figure 2, the notch 5a is provided in a rectangular shape from the tip side of the electrode 5 (the side of the emission end face 11a of the semiconductor laser bar 11) to the base side (the side of the mounting surface M). Also in the example in Figure 2, multiple notches 5a are provided at predetermined intervals in the direction of the arrangement of multiple emission points on the emission end face 11a. Due to these notches 5a, the tip portion of the electrode 5 is comb-shaped.
[0033] Next, we will explain in more detail the connection configuration between the laminated structure 3 and the heat sink 2 described above.
[0034] Figure 3 is an enlarged cross-sectional view of the main part of the semiconductor laser device shown in Figure 1. When joining the laminated structure 3 and the heat sink 2, as shown in Figure 3, a first solder layer 21, a second solder layer 22, and an insulating member 23 are provided. The first solder layer 21 is a layer that joins the submount 12 to the heat sink 2 via the insulating member 23. When joining the laminated structure 3 to the heat sink 2, the first solder layer 21 extends across the mounting surface M so as to span each of the submounts 12. Examples of methods for forming the first solder layer 21 include vapor deposition or sheet attachment.
[0035] In this embodiment, the first solder layer 21 is provided over substantially the entire surface of the heat sink 2, excluding the edges of the mounting surface M, so as to correspond to the entire arrangement area of the laminated structure 3 when viewed from the direction normal to the mounting surface M. As a result, all submounts 12 from one end to the other in the stacking direction X of the laminated structure 3 are joined to the heat sink 2 collectively by a single first solder layer 21 on the mounting surface M.
[0036] The melting point of the first solder layer 21 is lower than that of the second solder layer 22 used for joining the semiconductor laser bar 11 and the submount 12. In other words, the constituent material of the first solder layer 21 is selected from a material with a lower melting point than that of the constituent material of the second solder layer 22. Examples of constituent materials for the first solder layer 21 include indium (In)-based solder and SnAgCu-based solder. The melting point of SnAgCu-based solder is approximately 217°C to 220°C, and the melting point of indium (In)-based solder is approximately 156°C. In this embodiment, the first solder layer 21 is formed from indium (In)-based solder from the viewpoint of being lead-free.
[0037] The second solder layer 22 is a layer that joins the semiconductor laser bar 11 to the submount 12 and is a layer that joins the insulating member 23 to the submount 12. The second solder layer 22 is provided on the surface of the submount 12. The method for forming the second solder layer 22 is the same as for the first solder layer 21, for example, by vapor deposition or sheet attachment. In this embodiment, the second solder layer 22 is provided so as to cover the entire surface of the submount 12.
[0038] Examples of materials that can be used to construct the second solder layer 22 include gold-tin (AuSn) solder. The melting point of gold-tin (AuSn) solder is approximately 280°C. The thickness of the second solder layer 22 may be less than the thickness of the first solder layer 21. For example, if the thickness of the first solder layer 21 is 20 μm, the thickness of the second solder layer 22 may be about 5 μm. This allows the semiconductor laser bar units 4 to be densely stacked in the laminated structure 3.
[0039] The insulating member 23 is a heat-conducting and electrically insulating member interposed between the laminated structure 3 and the heat sink 2. Examples of constituent materials for the insulating member 23 include aluminum nitride (AlN), silicon carbide (SiC), and diamond. In this embodiment, the insulating member 23 is formed of aluminum nitride (AlN). The insulating member 23 is provided individually on each of the submounts 12. The shape of the insulating member 23 provided individually on each of the submounts 12 is identical to that of the other.
[0040] The insulating member 23 is in the form of a sheet having the same planar shape as the end face 12c of the submount 12 on the heat sink 2 side. Specifically, the width W1 of each insulating member 23 (width in the stacking direction X of the semiconductor laser bar unit 4) is equal to the width W2 of each end face 12c of the submount 12 on the heat sink 2 side in the said stacking direction X. Here, the width W2 of the end face 12c is the width including the second solder layer 22. Also, the length L1 of each semiconductor laser bar 11 emission point of the insulating member 23 in the alignment direction is equal to the length L2 of each end face 12c of the submount 12 on the heat sink 2 side in the said alignment direction (see Figure 2).
[0041] Each insulating member 23 is provided on the entire end face 12c of the submount 12 on the heat sink 2 side, so as not to protrude from the submount 12 in the stacking direction X. In other words, the insulating member 23 is provided at the tip of the submount 12 that protrudes beyond the end face 11b on the heat sink side of the semiconductor laser bar 11, in the form of a leg that extends the submount 12. In this state, in each of the semiconductor laser bar units 4, the protrusion length S of the end 12b of the submount 12 on the heat sink 2 side from the end face 11b on the heat sink 2 side of the semiconductor laser bar 11 (length including the second solder layer 22) is greater than the thickness T of the insulating member 23 provided on the submount 12.
[0042] The ratio of the protruding length S of the submount 12 to the thickness T of the insulating member 23 is not particularly limited, but for example, it is 1.2:1 to 5:1. By satisfying such a ratio range, most of the heat dissipation path from the semiconductor laser bar 11 to the heat sink 2 can be constituted by the submount 12 having better heat conductivity. Also, the shortage of the thickness of the insulating member 23 can be suppressed, and the electrical insulation between the submount 12 and the heat sink 2 can be sufficiently maintained. Note that the magnitude relationship between the protruding length S of the submount 12 and the thickness T of the insulating member 23 does not necessarily have to be such that the protruding length S is larger than the thickness T as described above. The protruding length S may be smaller than the thickness T, or the protruding length S and the thickness T may be equal.
[0043] On both surfaces in the thickness direction of the insulating member 23, metal layers 24 may be formed by vapor deposition or the like from the viewpoint of improving the bonding strength with the first solder layer 21 and the second solder layer 22. The metal layer 24 has, for example, a three-layer structure of titanium (Ti) / platinum (Pt) / gold (Au). The thickness of the metal layer 24 is, for example, about 1 μm. Thereby, while suppressing the cost, both improvement of the bonding strength and improvement of the heat conductivity can be achieved.
[0044] On both surfaces in the stacking direction X of the semiconductor laser bar 11, metal layers 25 may be formed by vapor deposition or the like from the viewpoint of improving the bonding strength with the second solder layer 22. The metal layers 25 on both surfaces of the semiconductor laser bar 11 may have the same configuration as each other, or may have different configurations from each other. When the metal layers 25 on both surfaces of the semiconductor laser bar 11 have different configurations from each other, for example, a metal layer 25A having a three-layer structure of titanium (Ti) / platinum (Pt) / gold (Au) is formed on the surface on the submount 12 side (the surface on the p-type semiconductor layer side), and a metal layer 25B having a five-layer structure of gold germanium (AuGe) / nickel (Ni) / titanium (Ti) / Pt (platinum) / Au (gold) is formed on the surface on the side opposite to the submount 12 (the surface on the n-type semiconductor layer side). The metal layer 25B may have a five-layer structure of Au (gold) / gold germanium (AuGe) / Au (gold) / titanium (Ti) / Pt (platinum) / Au (gold).
[0045] In the semiconductor laser device 1 having the above-described configuration, a driving voltage is applied to the stacked structure 3 via the pair of electrodes 5, so that a driving current is supplied to each semiconductor laser bar 11 included in the stacked structure 3, and laser light oscillates from a plurality of emission points on the emission end face 11a. Heat generated in the semiconductor laser bar 11 during laser oscillation is radiated from the adjacent submount 12 to the heat sink 2 via the insulating member 23.
[0046] Next, a method for manufacturing the semiconductor laser device 1 described above will be explained.
[0047] The manufacturing method of the semiconductor laser device 1 according to the present embodiment includes a forming step S01 and a fixing step S02. The forming step S01 is a step of forming a stacked structure 3 by stacking a plurality of semiconductor laser bar units 4 in which the semiconductor laser bars 11 are mounted on the submounts 12. In the forming step S01, as shown in FIG. 4(a), a semiconductor laser bar 11 on which a metal layer 25A and a metal layer 25B are previously formed, a submount 12 on which a second solder layer 22 is previously formed on the entire surface, and an insulating member 23 on which metal layers are previously formed on both surfaces in the thickness direction are prepared.
[0048] Next, with the metal layer 25A facing the submount 12 side, the semiconductor laser bar 11 and the submount 12 are joined with the second solder layer 22 to form a semiconductor laser bar unit 4. When forming the semiconductor laser bar unit 4, it is preferable to position the semiconductor laser bar 11 and the submount 12 using a predetermined positioning jig (not shown) so that the emission end face 11a of the semiconductor laser bar 11 and the end face 12a of the submount 12 are flush.
[0049] Furthermore, an insulating member 23 is joined to the tip of the submount 12 that protrudes beyond the heat sink side end face 11b of the semiconductor laser bar 11 with a second solder layer 22. This provides an insulating member 23 to each of the submounts 12 individually. When joining the insulating members 23, it is preferable to use a predetermined positioning jig (not shown) to position the insulating member 23 relative to the end face 12c of the submount 12. The joining of the semiconductor laser bar 11 to the submount 12 and the joining of the insulating member 23 to the submount 12 may be performed either first or simultaneously.
[0050] After forming the required number of semiconductor laser bar units 4 with insulating members 23, as shown in Figure 4(b), a submount 12 of another semiconductor laser bar unit 4 is joined to the semiconductor laser bar 11 of one semiconductor laser bar unit 4 with a second solder layer 22 to form a laminated structure 3. When forming the laminated structure 3, it is preferable to position the semiconductor laser bar units 4 using a predetermined positioning jig (not shown) so that the emission end face 11a of the semiconductor laser bar 11 and the end face 12a of the submount 12 are flush.
[0051] The fixing step S02 is the step of fixing the laminated structure 3 to the heat sink 2. In fixing step S02, as shown in Figure 4(c), a heat sink 2 having a mounting surface M on one side is prepared. A first solder layer 21 is pre-extended on the mounting surface of the heat sink 2 so as to extend over each of the submounts 12 included in the laminated structure 3.
[0052] Next, the laminated structure 3 is set on the mounting surface M side of the heat sink 2. Then, with each of the semiconductor laser bars 11 separated from the mounting surface M, each of the submounts 12 is joined to the mounting surface M via the insulating member 23 and the first solder layer 21. As described above, the first solder layer 21 extends across each of the submounts 12 included in the laminated structure 3 on the mounting surface of the heat sink 2. Therefore, by joining the insulating members 23 individually provided on each of the submounts 12 to the mounting surface M all at once via the first solder layer 21, the laminated structure 3 can be fixed to the heat sink 2 without individually positioning the insulating members 23 individually provided on each of the submounts 12 relative to the first solder layer 21.
[0053] For joining the components using the first solder layer 21 and the second solder layer 22, a reflow oven can be used, for example. By heating the second solder layer 22 to a temperature above its melting point using a reflow oven, the semiconductor laser bar 11 and insulating member 23 can be joined to the submount 12, and the semiconductor laser bar units 4 can be joined to each other. Also, by heating the first solder layer 21 to a temperature above its melting point using a reflow oven, the laminated structure 3 and the heat sink 2 can be joined. In the above process, when the first solder layer 21 is heated, the second solder layer 22 is also reheated, but because the melting point of the first solder layer 21 is lower than that of the second solder layer 22, it is possible to reheat the second solder layer 22 without melting it.
[0054] Finally, by joining electrodes 5 to a submount 12 located at one end of the stacked structure 3 and another submount 12 located at the other end of the stacked structure 3 with a second solder layer 22, the semiconductor laser apparatus 1 shown in Figures 1 to 3 is obtained.
[0055] As explained above, in the semiconductor laser device 1, insulating members 23 are individually provided on each of the submounts 12 in advance, and the laminated structure 3 can be mounted on the heat sink 2 by joining each insulating member 23 of the submounts 12 together with a first solder layer 21 that extends to the mounting surface M of the heat sink 2. In the semiconductor laser device 1, there is no need to match the arrangement pitch of each semiconductor laser bar unit 4 constituting the laminated structure 3 with the insulating member 23, and precise alignment between each insulating member 23 and the first solder layer 21 is also unnecessary. Therefore, even when the arrangement pitch of the semiconductor laser bar units 4 is small, sufficient heat transfer efficiency can be ensured in the heat dissipation path from the submount 12 to the heat sink 2.
[0056] In this embodiment, in each of the semiconductor laser bar units 4, the end portion 12b of the submount 12 on the heat sink 2 side protrudes toward the heat sink 2 side more than the end face 11b of the semiconductor laser bar 11 on the heat sink 2 side. With this configuration, a heat dissipation path from the submount 12 to the heat sink 2 via the insulating member 23 and the first solder layer 21 can be suitably formed.
[0057] In this embodiment, in each of the semiconductor laser bar units 4, the protrusion length S of the end portion 12b of the submount 12 on the heat sink 2 side from the end face 11b of the semiconductor laser bar 11 on the heat sink 2 side is greater than the thickness T of the insulating member 23 provided on the submount 12. With this configuration, a sufficient proportion of the heat dissipation path from the submount 12 to the heat sink 2 can be ensured. Therefore, the heat transfer efficiency in the heat dissipation path can be sufficiently increased.
[0058] In this embodiment, the insulating members 23 individually provided on each of the submounts 12 have the same shape. In this case, because the shapes of the insulating members 23 are the same, the distortion when each insulating member 23 undergoes thermal expansion due to heat dissipation is made uniform, and the influence of stress on the laminated structure 3 and the heat sink 2 can be suppressed.
[0059] In this embodiment, each insulating member 23 is provided on the entire end face 12c of each submount 12 on the heat sink 2 side. Furthermore, in this embodiment, the width W1 of each insulating member 23 in the stacking direction X of the multiple semiconductor laser bar units 4 is equal to the width W2 of each end face 12c of the submount on the heat sink 2 side in the same stacking direction X. With this configuration, it is possible to suppress the insulating member 23 from becoming a bottleneck and to ensure sufficient heat transfer efficiency in the heat dissipation path from the submount 12 to the heat sink 2. Even when the array pitch P of the semiconductor laser bar units 4 is small, it is possible to suppress interference between the insulating members 23 of adjacent semiconductor laser bar units 4.
[0060] In this embodiment, a second solder layer 22 is provided on each of the semiconductor laser bar units 4 so as to cover the entire surface of the submount 12. The semiconductor laser bar 11 and the insulating member 23 are fixed to the submount 12 via the second solder layer 22. This improves the workability when joining the semiconductor laser bar 11 and the insulating member 23 to the submount 12. Furthermore, because the second solder layer 22 is provided on the entire surface of the submount 12, it is possible to suppress the excess portion of the second solder layer 22 from wrapping around to the emission end face 11a of the semiconductor laser bar 11 when joining the semiconductor laser bar 11 to the submount 12.
[0061] In this embodiment, the melting point of the first solder layer 21 is lower than that of the second solder layer 22. This prevents the second solder layer 22, which is used for joining the submount 12 to the semiconductor laser bar 11 and the submount 12 to the insulating member 23, from melting when the laminated structure 3 is joined to the heat sink 2 by the first solder layer 21.
[0062] This disclosure is not limited to the embodiments described above. For example, as shown in Figures 5(a) and 5(b), the width W1 of each insulating member 23 in the stacking direction X of the multiple semiconductor laser bar units 4 may be wider than the width W2 of the end face 12c on the heat sink 2 side of each submount 12 in the stacking direction X. With these configurations, even if the width of the submount 12 (width W2 of the end face 12c) in the stacking direction X is small, the insulating member 23 can be easily provided on the submount 12.
[0063] In the example shown in Figure 5(a), the width W1 of the insulating member 23 in the stacking direction X is wider than the width W2 of the end face 12c of the submount 12 in the stacking direction X, and the width center of the insulating member 23 in the stacking direction X coincides with the width center of the end face 12c of the submount 12 in the stacking direction X. In this case, the strain caused by thermal expansion of each insulating member 23 due to heat dissipation is transmitted equally to the submount 12 from left to right, thereby suppressing irregular strain in the submount 12.
[0064] In the example shown in Figure 5(b), the width W1 of the insulating member 23 in the stacking direction X is wider than the width W2 of the end face 12c of the submount 12 in the stacking direction X, and the end faces of the insulating member 23 and the submount 12 in the stacking direction X are flush with each other. In this case, positioning when joining the insulating member 23 to the end face 12c of the submount 12 becomes easier, and complexity in the manufacturing process of the semiconductor laser device 1 can be avoided.
[0065] Furthermore, in the above embodiment, the melting point of the first solder layer 21 is lower than the melting point of the second solder layer 22, but the melting points of the first solder layer 21 and the second solder layer 22 may be equal. In this case, the already joined second solder layer 22 may remelt when joining with the first solder layer 21, but by adjusting the joining temperature and heating time based on this, the joining of both can be suitably carried out.
[0066] For example, the temperature during joining with the first solder layer 21 may be slightly lower than the temperature during joining with the second solder layer 22, and the heating time (melting time) during joining with the first solder layer 21 may be shorter than the heating time (melting time) during joining with the second solder layer 22. This allows for suitable joining with the first solder layer 21 while suppressing excessive expansion of the alloy layer due to the remelting of the already joined second solder layer 22. The formation of the alloy layer between the already joined second solder layer 22 and the member to be joined proceeds more slowly than the formation of the alloy layer between the first solder layer 21 and the member to be joined. Therefore, suitable joining with the first solder layer 21 (i.e., formation of an alloy layer of suitable thickness) is possible within a range in which the joining of the second solder layer 22 can be maintained in a good state.
[0067] Alternatively, the joining of the second solder layer 22 to the member to be joined may be limited to temporary fixing at a temperature below the melting point or for a short heating time, and the subsequent joining of the first solder layer 21 to the member to be joined may be carried out at a higher temperature or for a longer heating time than when joining the second solder layer 22 to the member to be joined, thereby performing the joining by the first solder layer 21 and the joining by the second solder layer 22 simultaneously.
[0068] 1...Semiconductor laser device, 2...Heat sink, 3...Laminated structure, 4...Semiconductor laser bar unit, 11...Semiconductor laser bar, 11b...End face, 12...Submount, 12b...End, 12c...End face, 21...First solder layer, 22...Second solder layer, 23...Insulating member, M...Mounting surface, S...Protrusion length of the end of the submount, T...Thickness of the insulating member, W1...Width of the insulating member, W2...Width of the end face of the submount, X...Lamination direction.
Claims
1. A semiconductor laser device comprising: a heat sink having a mounting surface on one side; and a laminated structure formed by stacking a plurality of semiconductor laser bar units, each of which has a semiconductor laser bar mounted on a submount, wherein the laminated structure is fixed to the heat sink by joining each of the submounts to the mounting surface via an insulating member and a first solder layer, with each of the semiconductor laser bars spaced apart from the mounting surface; the insulating member is provided individually on each of the submounts; and the first solder layer extends across the mounting surface so as to span each of the submounts.
2. The semiconductor laser apparatus according to claim 1, wherein in each of the semiconductor laser bar units, the end of the submount on the heat sink side protrudes toward the heat sink side more than the end face of the semiconductor laser bar on the heat sink side.
3. In each of the semiconductor laser bar units, the length of the heat sink-side end of the submount protruding from the heat sink-side end face of the semiconductor laser bar is greater than the thickness of the insulating member provided on the submount, as described in claim 2.
4. The semiconductor laser apparatus according to any one of claims 1 to 3, wherein the shapes of the insulating members provided individually on each of the submounts are identical to each other.
5. The semiconductor laser apparatus according to any one of claims 1 to 4, wherein each of the insulating members is provided on the entire end face of each of the submounts on the heat sink side.
6. The semiconductor laser apparatus according to any one of claims 1 to 5, wherein the width of each of the insulating members in the stacking direction of the plurality of semiconductor laser bar units is equal to the width of each end face on the heat sink side of the submount in the stacking direction.
7. The semiconductor laser apparatus according to any one of claims 1 to 6, wherein the width of each of the insulating members in the stacking direction of the plurality of semiconductor laser bar units is wider than the width of each end face on the heat sink side of the submount in the stacking direction.
8. The semiconductor laser apparatus according to any one of claims 1 to 7, wherein in each of the semiconductor laser bar units, a second solder layer is provided so as to cover the entire surface of the submount, and the semiconductor laser bar and the insulating member are fixed to the submount via the second solder layer.
9. The semiconductor laser apparatus according to claim 8, wherein the melting point of the first solder layer is lower than the melting point of the second solder layer.
10. The semiconductor laser apparatus according to claim 8, wherein the melting point of the first solder layer is equal to the melting point of the second solder layer.
11. A method for manufacturing a semiconductor laser device, comprising: a forming step of stacking a plurality of semiconductor laser bar units, each having a semiconductor laser bar mounted on a submount, to form a stacked structure; and a fixing step of preparing a heat sink having a mounting surface on one side, and fixing the stacked structure to the heat sink by joining each of the submounts to the mounting surface via an insulating member and a first solder layer, wherein in the forming step, the insulating member is individually provided on each of the submounts, and in the fixing step, the insulating member individually provided on each of the submounts is joined to the mounting surface via the first solder layer, with the first solder layer extending over each of the submounts to the mounting surface of the heat sink.