Light-emitting device

Abstract

Provided is a light-emitting device comprising: a semiconductor laser element including gallium nitride; a housing having a recess where the semiconductor laser element is located; a lid closing the opening of the recess of the housing; and a first bonding material which bonds the lid to the housing. A member forming the bottom surface of the recess is a heat conduction body. The space in the recess contains oxygen. The first bonding material melts at 300°C or lower in an atmosphere containing oxygen. The light-emitting device may further include: a heat dissipation body bonded to a lower surface of the housing; and a second bonding material which bonds the heat dissipation body to the housing. The second bonding material may melt at a lower temperature than the first bonding material.

Description

Light-emitting device

[0001] The present disclosure relates to a light emitting device.

[0002] There is a light-emitting device in which a laser light source is sealed inside a package and the light emitted from the laser light source is stably emitted. In International Publication No. 2020 / 175303, the light emitted from the light source in a direction along the bottom surface of the package is reflected upward by a mirror. In this case, it is known that the deterioration of gallium nitride (GaN)-based laser diodes can be suppressed by including oxygen inside the package.

[0003] One aspect of the present disclosure is a light-emitting device comprising: [1] a semiconductor laser element containing gallium nitride, a housing having a recess in which the semiconductor laser element is located, a lid sealing the open surface of the recess of the housing, and a first bonding material bonding the lid to the housing, wherein a member forming the bottom surface of the recess is a heat conductor, the recess contains oxygen, and the first bonding material melts at 300°C or less in an oxygen-containing atmosphere. [2] The light-emitting device of [1], comprising: a heat sink bonded to a bottom surface of the housing, and a second bonding material bonding the heat sink to the housing, wherein the second bonding material melts at a temperature lower than that of the first bonding material. [3] The light-emitting device of [1], comprising: a heat sink bonded to a bottom surface of the housing, and a second bonding material bonding the heat sink to the housing, wherein the second bonding material melts at 300°C or less but higher than that of the first bonding material. [4] The light-emitting device of [2] or [3], wherein the heat sink includes a metal-core printed wiring board. [5] The light-emitting device of [2] or [3], wherein the first bonding material and the second bonding material are either tin-silver-nickel solder, tin-silver-copper solder, tin-zinc solder, or tin-bismuth solder. [6] The light-emitting device of any of [1] to [5], wherein the heat conductor has wiring electrically connecting to the semiconductor laser element. [7] The light-emitting device of any of [1] to [6], wherein the semiconductor laser element is bonded to the recess with a conductive resin bonding material containing silver, copper, or gold. [8] The light-emitting device of [2] or [3], wherein the semiconductor laser element is bonded to the recess with a third bonding material, and the melting temperature of the third bonding material is higher than the melting temperatures of the first bonding material and the second bonding material. [9] The light-emitting device of [8], wherein the first bonding material, the second bonding material, and the third bonding material have at least some of their components different from each other.

[0004] Fig. 1 is an overall perspective view showing the structure of a light emitting device of a first embodiment; Fig. 2 is a cross-sectional view showing the structure of a light emitting device of a first embodiment; Fig. 3 is a cross-sectional view showing a first modified example of the light emitting device of a first embodiment; Fig. 4 is a cross-sectional view showing a second modified example of the light emitting device of a second embodiment;

[0005] 1A and 1B are diagrams showing the structure of a light emitting device 1 according to a first embodiment. Fig. 1A is an overall perspective view, and Fig. 1B is a cross-sectional view taken along line AA in Fig. 1A.

[0006] The light emitting device 1 includes a package 10 , a lid 30 , a substrate 50 , a light emitting element 21 , and a reflector 22 .

[0007] The package 10 is a housing that has a recess 10H near the center of the surface on the +Z side opposite the substrate 50 in the Z direction perpendicular to the top surface of the substrate 50, which is the bonding surface of the package 10, and accommodates the light emitting element 21 and the reflector 22 in the recess 10H. The longitudinal direction of the package 10 is defined as the X-axis direction, and the Y-axis is defined as being perpendicular to the X-axis and Z-axis.

[0008] The package 10 has a frame 11 that surrounds the side surfaces of the recess 10H, and a bottom plate 12 that closes the lower end, which is the end on the -Z side, of the frame 11 and forms the bottom surface of the recess 10H. The light emitting element 21 and the reflector 22 are located on the bottom plate 12. The light emitting element 21 is bonded to the bottom plate 12 by a bonding member 73, which is an example of a third bonding material of the present disclosure.

[0009] The bottom plate 12 is a heat conductor having a higher thermal conductivity than the frame 11 in at least one direction. The bottom plate 12 may have a higher thermal conductivity than the frame 11 in, for example, the Z direction from one surface of the package 10 to the other. The thermal conductivity of the bottom plate 12 may be, for example, 90 W / m·K or more, 120 W / m·K or more, 200 W / m·K or more, or 300 W / m·K or more. The bottom plate 12 may be made of a material having a high thermal conductivity, such as a metal or ceramic. The metal may be, for example, copper, aluminum, or an alloy containing at least one of these. The ceramic may include a single-crystalline inorganic material in addition to a polycrystalline inorganic material. In one embodiment, the thermal conductivity of the bottom plate 12 may be higher than the thermal conductivity of the frame 11 in any direction.

[0010] The frame 11 may be made of ceramic, such as alumina, aluminum nitride, silicon nitride, zirconia, or resin. Wiring 111 is located within the frame 11. The wiring 111 may include a via conductor or the like. One end of this wiring 111 is located within the recess 10H of the frame 11 and is connected to an electrode. Electrical connection between this electrode and the light-emitting element 21 allows a drive signal to be sent to the light-emitting element 21. The connection between the electrode and the light-emitting element 21 may be, for example, a bonding wire 81.

[0011] The light-emitting element 21 is a laser diode (LD). The LD may be a semiconductor laser element (GaN-based LD) having a crystal containing gallium nitride (GaN), and may emit, for example, blue light. Here, the light-emitting element 21 may be located on the inner surface of the recess 10H, for example, on the inner bottom surface, or may be an edge-emitting type that emits light in the +X direction along the bottom surface.

[0012] The reflector 22 is a bounce-up mirror that reflects the light emitted from the light-emitting element 21 and changes the direction of the light upward along the Z-axis. Note that a plurality of light-emitting elements 21 and reflectors 22 may be positioned within the recess 10H. Also, a common reflector 22 may be used for a plurality of light-emitting elements 21.

[0013] The lid 30 is located above the package 10, i.e., on the +Z side. The lid 30 is bonded to the upper surface of the package 10 by a bonding member 71, sealing the open surface of the recess 10H. The bonding member 71 is an example of a first bonding material in the present disclosure. The gas inside the sealed recess 10H contains oxygen. The base may be at normal pressure. The lid 30 has a light-transmitting portion. The lid 30 is, for example, an airtight, light-transmitting member, and may be, for example, borosilicate glass or sapphire glass. The surface of the lid 30 may be anti-reflectively coated (AR coated). Light emitted from the light-emitting element 21, which is oriented in the +Z direction by the reflector 22, passes through the lid 30 and is emitted to the outside of the light-emitting device 1.

[0014] The package 10 may be a surface-mount type. The surface-mount type package 10 has its bottom surface, which is the -Z side, bonded to a substrate 50. The substrate 50 may be a metal-core printed circuit board (MCPCB). The substrate 50 is bonded to the bottom end surface of the frame 11 with a bonding member 72. The bonding member 72 is an example of the second bonding material of the present disclosure. The bonding member 72 is a conductive bonding member that electrically connects the wiring 111 in the frame 11 and the wiring 51 on the substrate 50. The base 52 of the substrate 50 is a heat sink with high thermal conductivity. The base 52 is bonded to the bottom plate 12 and quickly dissipates heat generated by the light-emitting element 21 to the outside via the bottom plate 12. The base 52 may be ceramic or metal. If the base 52 is metal, the base 52 is insulated from the wiring 51. The base 52 and the bottom plate 12 may be made of the same material. A plurality of packages 10 each including a light emitting element 21 and a reflector 22 may be bonded onto the substrate 50 .

[0015] Next, the bonding member 70 will be described. GaN-based LDs are known to deteriorate, particularly in the latter half of the 300°C range. Therefore, the various components of the light-emitting device 1, including the light-emitting element 21, must be bonded at temperatures in the lower 300°C range or lower. In particular, the bonding members 71 and 72 should melt at 300°C or lower. It has also been known that the progression of deterioration of GaN-based LDs can be reduced by operating them in an oxygen-containing atmosphere. Therefore, the bonding member 71 used during sealing, in this case, during bonding of the lid 30, must be capable of bonding in an oxygen-containing atmosphere while satisfying the above temperature conditions.

[0016] In the light-emitting device 1 of this embodiment, the package 10, the light-emitting element 21, and the reflector 22 are bonded together as a primary assembly, followed by the lid 30, which is then sealed. Furthermore, the package 10 is bonded to the substrate 50 as a secondary assembly. Therefore, as described above, the light-emitting element 21 and the reflector 22 can be bonded at approximately 300°C, regardless of the presence or absence of oxygen during bonding. That is, the melting temperature of the bonding member 73 may be higher than that of the bonding members 71 and 72. For this bonding, a typical gold-tin (Au-Sn) solder containing 80% Au and 20% Sn and having a melting temperature of 280-300°C may be used. Alternatively, a sintering paste, which is a fluid conductive resin bonding material, may be used for this bonding. The sintering paste has fluidity, with particles of a conductive metal such as silver, copper, or gold dispersed in a base material such as a resin and / or solvent. The sintering paste hardens and bonds when heated to 200-250°C, and does not remelt even when reheated above that temperature. Therefore, in this case, the heating temperature of the sintering paste when bonding the light emitting element 21 and the reflector 22 may be lower than the melting temperature of the bonding members 71 and 72 .

[0017] The order in which the lid 30 and the substrate 50 are joined to the package 10 is not particularly limited. Examples of joining materials that can seal the lid 30 in the presence of oxygen include tin-silver-copper (Sn-Ag-Cu) solder (Sn-Ag-Cu solder), tin-silver-nickel (Sn-Ag-Ni) solder, tin-zinc (Sn-Zn) solder, and tin-bismuth (Sn-Bi) solder. The melting temperatures of SAC solder and tin-silver-nickel solder are approximately 230°C. The melting temperature of tin-zinc solder is approximately 220°C. The melting temperature of tin-bismuth solder is approximately 160°C. The magnitude relationship between the melting temperatures of the joining members 71 and 72 depends on which is used for joining first. When the lid body 30 is joined before being joined to the substrate 50, SAC solder, tin-silver-nickel solder, or tin-zinc solder is used as the joining member 71 for joining the lid body 30, and tin-bismuth solder, which has a lower melting temperature than the joining member 71, is used as the joining member 72 for joining the substrate 50. When the lid body 30 is joined after being joined to the substrate 50, tin-bismuth solder is used as the joining member 71 for joining the lid body 30, and SAC solder, tin-silver-nickel solder, or tin-zinc solder, which has a higher melting temperature than the joining member 71, is used as the joining member 72 for joining the substrate 50. As described above, the joining of the lid body 30 is performed in the presence of oxygen.

[0018] In this way, in the light-emitting device 1, during secondary mounting using the bonding member 72 and sealing of the recess 10H using the bonding member 71, the bonding member to be bonded later has a lower melting temperature than the bonding member to be bonded earlier. This prevents the previously bonded bonding members from remelting. The previously bonded bonding members include the bonding members for the light-emitting element 21 and the reflector 22. Furthermore, any of the bonding members described above can be bonded in the presence of oxygen. Therefore, the gas in the sealed recess 10H contains oxygen.

[0019] Even if the solder has the same components, different component ratios can result in different melting temperatures. However, such solder may begin to melt partially even at temperatures lower than the melting temperature. As a result, if secondary mounting and sealing are performed using solder with the same components but different component ratios, the previously fixed solder may partially melt or harden and loosen during subsequent soldering, resulting in misalignment. Therefore, it is preferable that the combination of joining members 71 and 72 has at least some of the components different from each other. Furthermore, even when combining solders with different components, it is more preferable that the difference in melting temperature be large.

[0020] Furthermore, even if there is a temperature difference, if the temperature difference is small, for example, between SAC solder and tin-zinc solder, even solder with a high melting temperature may become soft. Therefore, for the solder used for sealing and secondary mounting, a combination with a large difference in melting temperature may be preferentially selected.

[0021] 2A and 2B are cross-sectional views showing modified examples of the light-emitting device 1 of this embodiment. The cross section is taken along the cross-sectional line AA in FIG. 1A. In the modified example 1 shown in FIG. 2A, the light-emitting device 1a may have a window 31 on the side surface on the +X side. The window 31 is optically transparent and allows the emitted light of the light-emitting element 21 to be emitted directly to the outside of the light-emitting device 1a. This means that the light-emitting device 1a does not have a reflector. Furthermore, the lid 30a may not be optically transparent. In this case, the lid 30a may be made of a metal such as copper, aluminum, or an alloy thereof. Alternatively, the lid 30a may be made of ceramic.

[0022] In Modification 2 shown in FIG. 2B , light-emitting device 1b may have a protrusion 121 extending from bottom plate 12a in the +Z direction. Light-emitting element 21 may be located on a side surface of protrusion 121, for example, on the +X side. Accordingly, the light emission direction faces the +Z direction. As a result, light emitted from light-emitting element 21 passes through lid 30 as is and is emitted to the outside of light-emitting device 1b. Therefore, light-emitting device 1b does not have a reflector.

[0023] Also, when the light-emitting element 21 is a vertical-cavity surface-emitting laser element (VCSEL), the light-emitting element 21 emits light directly through the +Z side cover 30 without using a reflector and toward the outside and above the light-emitting device 1b.

[0024] Second Embodiment Next, a light emitting device 1c according to a second embodiment will be described. Fig. 3 is a cross-sectional view of the light emitting device 1c according to the second embodiment. The cross section is taken along the line AA in Fig. 1A.

[0025] In the second embodiment, the light emitting device 1c may be integrated with the bottom plate 12c of the package 10c by connecting the portion corresponding to the substrate. The bottom plate 12c has a protrusion 121 that fits into the lower end of the frame 11. The light emitting element 21 and the reflector 22 are bonded to the upper surface, which is the +Z side of the protrusion 121, via a bonding member 71. In other words, the light emitting device 1c does not need to have a separate substrate such as an MCPCB. If the frame 11 and the bottom plate 12c are bonded in advance before mounting or sealing, or are integrally formed, bonding can be performed at high temperatures without considering deterioration of the light emitting element 21 or the like. In other words, for example, gold-tin solder or frit glass may be used for bonding.

[0026] In addition, if the bottom plate 12c on which the light-emitting element 21 and the reflector 22 are mounted is joined after the lid body 30 to seal the recess 10H, a joining material having a lower melting temperature in the presence of oxygen than the joining material used to join the lid body 30 may be used.

[0027] The light emitting element 21 and an electrode (not shown) exposed on the inner wall surface of the frame body 11 may be connected by a bonding wire 81. Wiring 111 inside the frame body 11 connects this electrode to a connection electrode 15 located on the outer surface of the frame body 11. Therefore, the bottom plate 12c does not need to have wiring inside.

[0028] During mounting, the light emitting element 21 and the reflector 22 are first bonded with a bonding member 73 as a primary mounting, and then the lid 30 is sealed by bonding with a bonding member 71. The gas in the recess 10H contains oxygen. The bonding member 73 may be gold-tin solder or a sintering paste that is hardened by heating.

[0029] Similarly to the above, when gold-tin solder is used as the joining member 73, the joining member 71 has a melting temperature of 300° C. or less, which is lower than that of the gold-tin solder. Furthermore, as described above, the joining member 71 can be joined in the presence of oxygen. Therefore, the joining member 71 may be SAC solder, gold-zinc solder, gold-bismuth solder, or the like.

[0030] Such strong bonding and sealing, which reduces the progression of deterioration of the light emitting element 21, allows oxygen-containing gas to be trapped within the recess 10H.

[0031] As described above, the light-emitting device 1 of this embodiment includes a light-emitting element 21, which is a semiconductor laser element containing gallium nitride; a package 10 having a recess 10H in which the light-emitting element 21 is located; a lid 30 that seals the upper surface of the package 10 on the +Z side, which is the open surface of the recess 10H; and a bonding member 71 that bonds the lid 30 to the package 10. The bottom plates 12, 12a that form the bottom surface of the recess 10H are heat conductors. Oxygen is contained within the recess 10H. The bonding member 71 melts at 300°C or less in an oxygen-containing atmosphere. Thus, when sealing the recess 10H, the bonding member 71 is used, which can melt and bond within a temperature range that does not adversely affect the light-emitting element 21 even in an oxygen-containing atmosphere. This allows the light-emitting device 1 to appropriately seal the oxygen-containing gas within the recess 10H. Therefore, the light-emitting device 1 enables the GaN-based light-emitting element 21 (LD) to operate stably and with a longer life.

[0032] The light emitting device 1 may also include a substrate 50 bonded to the underside of the package 10, and a bonding member 72 bonding the substrate 50 and the package 10 together. The bonding member 72 may melt at a lower temperature than the bonding member 71. When the package 10 is mounted on the substrate 50 as a second mounting after sealing the recess 10H, the melting temperature of the bonding member 72 is lower than the melting temperature of the bonding member 71. This allows the light emitting device 1 to stably operate the light emitting element 21 that is precisely fixed and sealed together with oxygen.

[0033] Alternatively, the bonding member 72 may melt at a temperature equal to or lower than 300° C. but higher than the temperature of the bonding member 71. The recess 10H of the package 10 may be sealed after it is mounted on the substrate 50. In this case, the light emitting device 1 can also stably operate the light emitting element 21 that is fixed with high precision and sealed together with oxygen.

[0034] The substrate 50 may also include an MCPCB, which allows the light emitting element 21 to be easily mounted and allows heat generated as the light emitting element 21 operates to be quickly released.

[0035] The bonding members 71 and 72 may be any of tin-silver-nickel solder, tin-silver-copper solder, tin-zinc solder, and tin-bismuth solder. These have various melting temperatures of 300°C or less in an oxygen-containing atmosphere. Therefore, bonding using these bonding members 71 and 72 allows oxygen-containing gas to be sealed in the recess 10H without adversely affecting the light-emitting element 21.

[0036] Furthermore, the frame 11 may have wiring 111 on the inside or surface thereof for electrically connecting the light emitting elements 21 to the outside. This allows the light emitting device 1 to stably supply necessary signals to the light emitting elements 21.

[0037] The light-emitting element 21 may be bonded to the bottom plate 12, 12a using a sintering paste containing silver, copper, or gold. The sintering paste has a thermosetting temperature in the low 200°C range and does not remelt even when reheated after hardening. Therefore, even when used for bonding prior to other solder bonding, it can bond objects with high precision and strength.

[0038] Alternatively, the light-emitting element 21 may be joined to the bottom plate 12 using a joining member 73 such as gold-tin solder. The melting temperature of the joining member 73 is higher than that of the joining members 71 and 72. Since the joining of the light-emitting element 21 in the primary mounting step is naturally performed before sealing, the melting temperature of the joining member 73 is set higher than that of the joining members 71 and 72 used in sealing and secondary mounting. Furthermore, oxygen is not required. Therefore, in this case, joining can be performed using gold-tin solder, which has a higher melting temperature in the range of 300°C or less in an oxygen-free environment. The melting temperature of gold-tin solder is approximately 280-300°C. This ensures a difference in melting temperature between the gold-tin solder and the solder used for sealing. This further reduces the risk of misalignment of the light-emitting element 21 during sealing and secondary mounting.

[0039] Furthermore, the bonding members 71-73 used for primary mounting, secondary mounting, and sealing may have at least some of their components different from each other. Even bonding members with the same components can have different melting temperatures by varying their component ratios. However, bonding members with such different component ratios may partially melt even at temperatures below their melting temperature. As a result, misalignment of the previously bonded components may occur. Therefore, by using bonding members with different components, the light-emitting device 1 can be mounted and sealed more firmly and accurately.

[0040] The above-described embodiment is merely an example, and various modifications are possible. For example, in the above embodiment, the bottom plates 12 and 12c are separated from the electrical path as heat conductors, but this is not limiting. For example, the heat conductors may also serve as ground surfaces.

[0041] Furthermore, the shape of the recess 10H is not limited to the above-described shape, and may be other shapes.

[0042] Furthermore, the GaN-based laser diode serving as the light-emitting element 21 may be a laser diode that emits light other than blue light. Furthermore, a plurality of GaN-based laser diodes may emit light of different wavelengths.

[0043] Furthermore, when a plurality of light-emitting elements are mounted on the substrate 50, each housed in a separate package 10, some of the light-emitting elements may not be GaN-based laser diodes. In this case, bonding in an oxygen-containing environment does not need to be considered when sealing a package housing elements other than a GaN-based laser diode.

[0044] In the above description, the wiring 111 includes a via conductor, but this is not limiting. The wiring 111 may also include a castellation, a side electrode, or the like.

[0045] In addition, the specific details of the configuration, structure, positional relationship, materials, etc. shown in the above embodiment can be appropriately changed without departing from the spirit of the present disclosure. The scope of the present invention includes the scope of the invention described in the claims and its equivalents.

[0046] The present disclosure can be used in a light-emitting device.

[0047] REFERENCE SIGNS LIST 1, 1a to 1c Light emitting device 10, 10c Package 10H Recess 11 Frame 111 Wiring 12, 12a, 12c Bottom plate 121 Protrusion 15 Connection electrode 21 Light emitting element 22 Reflector 30, 30a Lid 31 Window 50 Substrate 51 Wiring 52 Base 70 to 73 Bonding member 81 Bonding wire

Claims

1. A light emitting device comprising: a semiconductor laser element containing gallium nitride; a housing having a recess in which the semiconductor laser element is located; a lid sealing an open face of the recess of the housing; and a first bonding material bonding the lid to the housing, wherein a member forming a bottom surface of the recess is a heat transfer material; oxygen is contained within the recess; and the first bonding material melts at 300°C or less in an oxygen-containing atmosphere.

2. The light emitting device according to claim 1, comprising: a heat sink joined to the underside of the housing; and a second bonding material joining the heat sink and the housing, wherein the second bonding material melts at a lower temperature than the first bonding material.

3. The light emitting device according to claim 1, comprising: a heat sink joined to the underside of the housing; and a second bonding material joining the heat sink and the housing, wherein the second bonding material melts at a temperature of 300°C or lower and higher than the temperature of the first bonding material.

4. The light emitting device according to claim 2 or 3, wherein said heat sink comprises a metal core printed wiring board.

5. The light emitting device according to claim 2 or 3, wherein the first bonding material and the second bonding material are any one of tin-silver-nickel solder, tin-silver-copper solder, tin-zinc solder, and tin-bismuth solder.

6. The light emitting device according to any one of claims 1 to 5, wherein the housing has wiring that electrically connects to the semiconductor laser element.

7. The light emitting device according to any one of claims 1 to 6, wherein the semiconductor laser element is bonded to the recess with a conductive resin bonding material containing silver, copper or gold.

8. A light emitting device as described in claim 2 or 3, wherein the semiconductor laser element is bonded to the recess by a third bonding material, and the melting temperature of the third bonding material is higher than the melting temperatures of the first bonding material and the second bonding material.

9. The light emitting device according to claim 8, wherein the first bonding material, the second bonding material, and the third bonding material are at least partially different from each other in components.

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