Patent Publication Number: US-2023163250-A1

Title: Light emitting device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. Pat. Application No. 17/162,913, filed on Jan. 29, 2021, which is a continuation application of U.S. Pat. Application No. 16/428,959, filed on May 31, 2019, now U.S. Pat. No. 10,930,820. This application claims priority to Japanese Patent Application No. 2018-107569, filed on Jun. 5, 2018. The entire disclosures of U.S. Pat. Application Nos. 17/162,913 and 16/428,959, and Japanese Patent Application No. 2018-107569 are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
       1 . Technical Field 
     The present disclosure relates to a light emitting device. 
       2 . Description of Related Art 
     A light emitting element package including a base part, which includes a frame and an upward-facing surface, and a light emitting element such as a LED element or a semiconductor laser element on the upward-facing surface of the base part has been known. In addition, various materials can be employed for a base member serving as a package body, and examples of the materials include ceramics. JP 2014-68013 A describes a light emitting element package in which a light emitting element is disposed on a surface of a package body formed by a ceramic layer. 
     SUMMARY 
     On the other hand, because a light emitting element such as a semiconductor laser element generates heat, heat dissipation is required to be considered when manufacturing a light emitting element package. The light emitting element package described in JP 2014-68013 A has a structure in which a light emitting element is disposed on a ceramic, and has room for improvement with regards to heat dissipation. 
     A light emitting device according to certain embodiments of the present disclosure includes a first semiconductor laser element, a light reflecting member, a base member, and a wire. The first semiconductor laser element is configured to emit light. The light reflecting member is configured to reflect the light emitted from the first semiconductor laser element. The base member includes a bottom part having an arrangement surface, and a frame part bonded to the bottom part and forming a frame surrounding the arrangement surface. The frame part has an upper surface, a lower surface, a step portion inside of the frame, a bonding surface bonded to the bottom part, a first inner surface extending below the bonding surface, a second inner surface extending above the bonding surface, a first planar surface defining a planar surface of the step portion on an upper surface side, and a first electrode layer and a second electrode layer electrically connected to each other. The second electrode layer is disposed on the first planar surface of the frame part. The wire is bonded to the second electrode layer and electrically connected to the first semiconductor laser element. A width of the bonding surface on a first planar surface side is greater than a width of the bonding surface on an opposite side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic perspective view of a light emitting device according to a first embodiment. 
         FIG.  2    is a schematic top view for illustrating an internal structure of the light emitting device according to the first embodiment. 
         FIG.  3    is a schematic cross-sectional view of the light emitting device taken along a line III-III in  FIG.  1   . 
         FIG.  4 A  is a schematic perspective view for illustrating a method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  4 B  is a schematic cross-sectional view taken along a line BI-BI in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  4 C  is a sectional view taken along a line BII-BII in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  4 D  is a schematic perspective view of a bottom part of the light emitting device according to the first embodiment. 
         FIG.  4 E  is a schematic top view of a frame part of the light emitting device according to the first embodiment. 
         FIG.  4 F  is a schematic bottom view of the frame part of the light emitting device according to the first embodiment. 
         FIG.  5 A  is a schematic perspective view for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  5 B  is a schematic cross-sectional view taken along a line BI-BI in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  5 C  is a schematic cross-sectional view taken along a line BII-BII in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  6 A  is a schematic perspective view for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  6 B  is a schematic cross-sectional view taken along line BI-BI in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  6 C  is a schematic cross-sectional view taken along line BII-BII in  FIG.   4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  7 A  is a schematic perspective view for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  7 B  is a schematic cross-sectional view taken along line BI-BI in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  7 C  is a schematic cross-sectional view taken along line BII-BII in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  8 A  is a schematic perspective view for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  8 B  is a sectional view on line BI-BI in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  8 C  is a schematic cross-sectional view taken along line BII-BII in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  9 A  is a schematic perspective view for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  9 B  is a schematic cross-sectional view taken along line BI-BI in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  9 C  is a schematic cross-sectional view taken along line BII-BII in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  9 D  is a schematic top view of a substrate of the light emitting device according to the first embodiment. 
         FIG.  10 A  is a schematic view for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  10 B  is a schematic cross-sectional view taken along line BI-BI in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  10 C  is a schematic cross-sectional view taken along line BII-BII in  FIG.  4 A  for illustrating the method of manufacturing the light emitting device according to the first embodiment. 
         FIG.  11    is a schematic cross-sectional view of a light emitting device according to a second embodiment. 
         FIG.  12 A  is a schematic perspective view of a bottom part of the light emitting device according to the second embodiment. 
         FIG.  12 B  is a schematic perspective view of the bottom part of the light emitting device according to the second embodiment. 
         FIG.  13    is a schematic top view of a substrate of the light emitting device according to the second embodiment. 
         FIG.  14    is a schematic cross-sectional view of a light emitting device according to a first modified example. 
         FIG.  15    is a schematic cross-sectional view of a light emitting device according to a second modified example. 
         FIG.  16    is a schematic cross-schematic perspective view of a bottom part of the light emitting device according to the second modified example. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Certain embodiments of the present invention will be described below with reference to the drawings. The embodiments shown below are intended to embody the technical idea of the present invention, and are not intended to limit the scope of the present invention. Further, in the descriptions below, the same names and reference numerals denote the same or similar members, and detailed descriptions thereof are omitted as appropriate. The sizes, positional relationships and the like of members shown in the drawings may be exaggerated for clarity of description. 
     First Embodiment 
       FIG.  1    is a schematic view of a light emitting device  1  according to a first embodiment,  FIG.  2    is a top view for illustrating an internal structure of a base member of the light emitting device, and  FIG.  3    is a sectional view taken along on line III-III in  FIG.  1   . In  FIG.  2   , for showing the internal structure, a cover  120 , an adhesion portion  130  and a lens member  140  are indicated by a broken line, and portions which are seen when viewed through the cover  120 , the adhesion portion  130  and the lens member  140  are indicated with a solid line. In addition, for avoiding complication of the drawings, a wire  180  as shown in  FIG.  3    is omitted in  FIG.  2   . 
     In the light emitting device  1 , light radiated from a plurality of semiconductor laser elements  170  is reflected by a light reflecting surface of light reflecting members  150 , and is emitted outside through the lens member  140 . As shown in  FIG.  2   , three sub-mounts  160 , on each of which at least one of the semiconductor laser elements  170  is disposed, are arranged, and the light reflecting members  150  are disposed each corresponding to at least one of the semiconductor laser elements  170 . Each of the plurality of semiconductor laser elements  170  radiate light to a corresponding one of light reflecting members  150 , and the corresponding light reflecting member  150  reflects light from the corresponding semiconductor laser element  170  toward the lens member  140 . The light emitting device  1  includes a package configured to emit light, and a mounting substrate on which the package is mounted. Alternatively, a light emitting device without the mounting substrate may be considered as the light emitting device  1 . 
     The light emitting device  1  includes a substrate  100  as the mounting substrate, and also includes a base member  110 , the cover  120 , the adhesion portion  130 , the lens member  140 , the light reflecting members  150 , the sub-mounts  160 , the semiconductor laser elements  170 , and the wires  180 , which are constituent elements included in the package. In addition, in a sealed space formed by bonding the base member  110  to the cover  120 , the light reflecting members  150  and the sub-mounts  160  on each of which at least one of the semiconductor laser elements  170  is disposed are arranged. Further, the wires  180  for electrically connecting semiconductor laser elements  170  disposed on the base member  110  are provided. In addition, as shown in  FIG.  3   , the base member  110  includes a frame part  111  and a bottom part  118 . 
     The substrate  100  is bonded to the frame part  111  and/or the bottom part  118 . In addition, the frame part  111  is bonded to the cover  120  at a side opposite to a bonding surface bonded with the substrate  100 . The cover  120  is bonded to the lens member  140  with an adhesive agent disposed therebetween. The adhesion portion  130  is formed by solidification of the adhesive agent. A gap is created between the cover  120  and the lens member  140  by forming the adhesion portion  130 . Hereinafter, the light emitting device  1  will be described along with description of operations in manufacturing of the light emitting device  1 . 
       FIGS.  4 A to  10 A  are schematic views for illustrating operations until the light emitting device  1  is obtained. In addition,  FIGS.  4 B to  10 B or  4 C to  10 C  show schematic cross-sectional views in the steps so as to correspond to  FIGS.  4 A to  10 A , respectively.  FIGS.  4 B to  10 B  are schematic cross-sectional views corresponding to line BI-BI shown in  FIG.  4 A .  FIGS.  4 C to  10 C  are schematic cross-sectional views corresponding to line BII to BII shown in  FIG.  4 A . Dotted lines S 1  and S 2  are not constituent elements of a light emitting element  2 , but auxiliary lines for indicating correspondence in directions of the light emitting device  2  in the respective drawings. In addition, an auxiliary line in each cross-sectional view indicates a front side of the cross-sectional view, such that the auxiliary line in each cross-sectional view corresponds to a corresponding one of the auxiliary lines in the schematic view in a corresponding one of  FIGS.  4 A,  5 A,  6 A,  7 A,  8 A,  9 A, and  10 A . For example, the cross-sectional view of the base member  110  in  FIG.  5 B  with a line S 1  is taken along a line corresponding to a line BI-BI in  FIG.  4 A , where the front face in  FIG.  5 B  is at the S 1  line side of the base member  110  in  FIG.  5 A . 
     As shown in  FIGS.  4 A and  4 D , the frame part  111  and the bottom part  118  which form the base member  110  are provided. A metal such as Cu or Al can be used for the bottom part  118 , and a ceramic such as alumina (Al 2 O 3 ) or AlN can be used for the frame part  111 . Any appropriate material may be used for the bottom part  118 , but at least, the bottom part  118  has a heat dissipation higher than that of the frame part  111 , and the bottom part  118  has a thermal conductivity higher than that of the frame part  111 . 
     The bottom part  118  includes a bonding surface bonded to the substrate  100 , and an arrangement surface on which the light reflecting member  150 , the sub-mount  160  and the semiconductor laser element  170  are disposed. Each of the bonding surface and the arrangement surface has a rectangular shape. In addition, the thickness from the bonding surface to the arrangement surface is substantially uniform. In the present disclosure, a rectangular shape with modified corners such as rounded corners and/or slanted corners is also referred to as “a rectangular shape”. Similarly, a polygonal shape with rounded corners or the like is also referred to as a “polygonal shape”. In addition, when a corner of a rectangular shape or a polygonal shape is modified, the modified corner portion is considered to be included in a corresponding side of the rectangular shape or the polygonal shape. A surface bonded to the substrate  100  is considered as a bottom surface. The bonding surface of the bottom part  118  can be regarded as the bottom surface. The bottom surface and the arrangement surface may alternatively have any appropriate shapes other than the shapes described above. 
     The frame part  111  has a first electrode layer  112  at the bottom surface, which is a surface bonded to the substrate  100 . The first electrode layer  112  includes, for example, a metal layer, and is bonded to a metal film  103  of the substrate  100 . Electric power is supplied to the semiconductor laser element  170  through the metal film  103 . In addition, the frame part  111  has a step portion inside the frame. The step portion included in the frame part  111  extends inward of the frame part  111 , and a planar surface of the step portion at the bottom surface  118  side is a bonding surface  113  bonded to the bottom part  118 . Thus, the planar surface intersecting the inner surface  116  form a step portion with the inner surface  116  on an inner side of the frame formed by the frame part  111 . In the present specification, of two opposite planar surfaces, a planar surface closer to the substrate  100  is referred to as a “lower surface”, and a planar surface opposite to the lower surface is referred to as an “upper surface”, for the sake of convenience. Alternatively, a planar surface closer to the lens member  140  is referred to as an “upper surface”, and the surface opposite to the upper surface is referred to as a “lower surface”. In  FIG.  4 A , the frame part  111  is arranged such that the upper surface faces downward and the lower surface faces upward. 
       FIG.  4 E  is a top view of the frame part  111 , and  FIG.  4 F  is a bottom view of the frame part  111 . The frame part  111  includes the bonding surface  113  at a planar surface of the step portion  111  that is seen in a bottom view (that is, the lower surface of the step portion  111 ). A second electrode layer  114  to be electrically connected to a semiconductor laser element  170  is disposed at the planar surface of the step portion that is seen in a top view (that is, the lower surface of the step portion  111 ). The planar surface intersects at least a part of the inner surface  117 , and is different from the bonding surface  113 . The second electrode layer  114  is electrically connected to the first electrode layer  112  through, for example, a via hole. The second electrode layer  114  includes, for example, a metal layer, and is arranged on a ceramic layer, and therefore is not exposed to the lower surface of the step portion. Further, in the bottom view, the step portion is disposed along all of the four sides of the frame part  111 , but in the top view, the step portion is disposed along only three sides of the four sides of the frame part  111 , and is not disposed along the other one side of the four sides except for end portions overlapping two sides at both ends. That is, the region having the step portion in the top view does not correspond to the region having the step portion in the bottom view. For bonding of the bonding surface  113  of the step portion to the bottom part  118 , the step portion is disposed along the entire periphery of the frame part  111  in the bottom view. On the other hand, the planar surface of the step portion that is seen in the top view has a region sufficient for disposing the second electrode layer, and is not necessarily disposed along the entire periphery. 
     In addition, the bonding surface  113  has a width along a side opposite to a side not provided with the second electrode layer  114  larger than a width of the bonding surface  113  along each of other sides of the bonding surface  113 . On the other hand, a surface of the frame part  111  bonded to the substrate  100  is designed such that a width along a side not provided with the second electrode layer  114  and a width along a side opposite thereto is the same . In other words, the shortest distance between a pair of opposite lateral surfaces of the frame part  111  meeting the surface of the frame part  111  bonded with the substrate  100  and the shortest distance between another pair of opposite lateral surfaces of the frame part  111  intersecting the surface of the frame part  111  bonded with the substrate  100  are the same at corresponding positions of each pair of opposite sides. The term “the same” as used herein refers to that a difference between two or more values to be compared is within a design tolerance. With such a structure, a force applied to the base member  110  at the time of bonding the frame to the substrate  100  by soldering can be balanced. The term “corresponding positions of each pair of opposite sides” as used herein refers to, with two sides opposite to and parallel to each other, a certain position in one of the two sides and a position in the other of the two sides with the shortest distance therebetween. 
     Next, as shown in  FIG.  5 A , the bonding surface  113  of the frame part  111  is bonded to the bottom part  118 . For the bonding, for example, a silver brazing material containing Ag as a main component and containing Cu can be used, and other metal brazing materials can also be used. As shown in  FIG.  4 A , silver brazing material is applied to the bonding surface of the frame part  111  while the bottom surface of the frame part  111  faces upward, and the bottom part  118  is placed inside the frame of the frame part  111  with the silver brazing material melted by heating. The silver brazing material is then cooled to bond the frame part  111  to the bottom part  118 , so that the base member  110  is formed. The silver brazing material is applied to a bonding region between the frame part  111  and the bottom part  118 , with the bonding region plated with Ni. 
     Thus, as shown in  FIGS.  5 B and  5 C , the bonding surface of the bottom part  118  bonded to the frame part  111  has a size smaller than a size of a frame formed by an inner surface  115  (first inner surface) intersecting the bottom surface of the frame part  111 , and is located inward of the frame formed by the inner surface  115 . In other words, the inner surface  115  intersects the bonding surface  113  around a periphery of the bottom part  118  in a plan view, and an area within an intersection line between the inner surface  115  and the bonding surface  113  in the plan view having a size larger than a size of the arrangement surface of the bottom part  118 . Further, the shapes of the inner surface  115  of the frame part  111  and a lateral surface  119  of the bottom part  118  are designed so that the arrangement surface of the bottom part  118  is bonded to the bonding surface  113  at the step portion of the frame part  111 . The light emitting device  1  according to the first embodiment is designed so that the height from the bottom surface of the frame part  111  to the bonding surface  113  is the same as the height of the bottom part  118 , and the periphery of the bottom part  118  is located inward of the frame formed by the inner surface  115  intersecting the bonding surface  113 . 
     Further, a gap is generated between the inner surface  115  and the lateral surface  119 . As described above, the frame part  111  can be formed of a ceramic, and the degree of sintering in manufacturing may not be constant. Thus, shapes and/or size of manufactured frame parts  111  may be varied. In manufacturing of the light emitting device  1 , with consideration of design tolerance, the shapes of the frame part  111  and the bottom part  118  are designed so as to generate a gap of 0.1 mm between the frame part  111  and the bottom part  118 . The shapes of the frame part  111  and the bottom part  118  may be designed such that a gap of 0.1 mm or more or a gap of 0.1 mm or less is present. The size of the gap is preferably in a range of 0.1 mm to 0.5 mm. Accordingly, the bottom part  118  can be properly bonded to the bonding surface of the frame part  111 , and the heat dissipation property of the bottom part  118  can be improved, so that the base member  110  excellent in heat dissipation property can be formed. 
     The size of the planar surface of the bottom part  118 , which is bonded to the bonding surface  113 , is larger than the size of a frame formed by the step portion. More specifically, the size of the planar surface of the bottom part  118 , which is bonded to the bonding surface  113  of the frame part  111 , is larger than the size of the frame formed by an inner surface  116  (second inner surface) intersecting an inner end of the bonding surface  113 , and the frame formed by the inner surface  116  is covered with the bottom part  118 . In other words, the inner surface  116  intersects the bonding surface  113  over the arrangement surface, and an area within an intersection line between the inner surface  116  and the bonding surface  113  in the plan view having a size smaller than the size of the arrangement surface. 
     In addition, the relationship between the frame formed by the inner surface  115  intersecting an inner end of the bottom surface of the frame part  111  and the frame formed by an inner surface  117  (second inner surface) intersecting an inner end of the upper surface of the frame part  111  is such that the width of the frame formed by the inner surface  115  is larger than the width of the frame formed by the inner surface  117  when seen in the S 1  direction, and the widths of both frames are the same as each other when seen in the S 2  direction. In the S 1  direction, there is a side along which the step portion for the second electrode layer is not formed in top view, and the width of the frame at the lower surface side is larger than the width of the frame at the upper surface side for forming the bonding surface at the side corresponding to the side along which the step portion is not formed. In the S 2  direction, both sides are provided with the step portion for the second electrode layer, and therefore the bonding surface can be formed using a region corresponding to the step portion, so that the width of the frame at the lower surface side may not be larger than the width of the frame at the upper surface side. 
     Both sides of the frame part  111  when viewed in the S 2  direction are provided with the first electrode layer on the bottom surface of the frame part  111 . Both sides of the frame part  111  when viewed in the S 1  direction are not provided with the first electrode layer on the bottom surface of the frame part  111 . 
     In view of a heat dissipation performance, it is preferable that the bottom part  118  have a large size. Meanwhile, when the width of the bottom surface of the frame part  111  is reduced, at the time of performing soldering, solder may be brought into contact with or connected to both the first electrode layer and the bottom part  118 . While the inner surfaces  115  and  117  are not required to have the same size as each other when viewed in the S 2  direction, the inner surface  115  is located at a predetermined distance from the first electrode layer. The position of the inner end of the bottom surface of the frame part  111  is determined with a spacing of 0.3 mm or more from the first electrode layer having a width of 0.5 mm. The first electrode layer  112  is electrically connected to the second electrode layer  114  through a conductive portion provided inside the frame part  111 . 
     An additional explanation will be given about determination of the structures of the frame part  111  and the bottom part  118 . In view of a heat dissipation performance, a material having a good heat dissipation is desired to be used for the bottom part  118  so that heat is diffused from a position at which the semiconductor laser element  170 , which is a main heat source, is arranged, so that a metal such as Cu is more preferably used for the bottom part  118  than a ceramic. In addition, the bottom part  118  is preferably large at a certain degree, and it is preferable that a portion exposed as an arrangement surface is made of metal. Further, for bonding the bottom surface  118  to the substrate  100 , and effectively dissipating heat to the substrate  100  through the bonded portion, it is preferable that a material having poor heat dissipation is not disposed between the arrangement surface and the bonding surface bonded with the substrate  100 . 
     In addition, in view of strength, and shape stability at the time of using the light emitting device  1 , it is preferable that the outer frame of the base member is made of ceramic. Further, in order to provide a metal layer for electrically connecting the semiconductor laser element, it is necessary to form a step portion at a part of the ceramic frame. Accordingly, the base member  110  in the light emitting device  1  is required to include at least: a frame that surrounds the periphery; a bottom part on which a semiconductor laser is disposed; and a step portion for providing a metal layer. 
     The step portion in a top view is not required to be provided over the entire inner periphery of the frame part  111 , and a region to be provided with the step can be appropriately adjusted according to the number of semiconductor laser elements  170  arranged in the light emitting device  1 , or a combination in arrangement of a plurality of semiconductor laser elements  170 . For example, the step portion is provided along one side or two sides of the frame part  111 , or it may be necessary to provide the step portion over the entire periphery. The “combination in arrangement of a plurality of semiconductor laser elements  170 ” refers to, for example, a case where semiconductor laser elements having the same color and the same performance are disposed, or a case where semiconductor laser elements having different colors are disposed. 
     With consideration of these, a metal is used for the bottom part  118  while the frame part  111  is formed of a ceramic, so that interface between the frame part and the bottom part is formed for improving the heat dissipation . Further, a gap is provided with consideration of a design tolerance associated with a ceramic. Thus, it is possible to provide the base member  110  having good heat dissipation compared to a case where the arrangement surface of the base member  110  on which the semiconductor laser element  170  is disposed is formed of a ceramic. 
     In  FIG.  6 A , the light reflecting member  150 , and the sub-mount  160  on which the semiconductor laser element  170  is arranged are bonded to the arrangement surface of the formed base member  110 . The position at which the light reflecting member  150  and the sub-mount  160  are disposed is determined according to a position based on the frame part  111  rather than a position based on the bottom part  118 . That is, the light reflecting member  150  and the sub-mount  160  are disposed according to, rather than a distance or a coordinate from a specific position on the bottom part  118 , a distance or a coordinate from a predetermined position on the frame part  111 . 
     A gap is generated between the frame part  111  and the bottom part  118  as described above, so that the bottom part  118  is movable in a frame formed by the frame part  111  before the bottom part  118  is fixed with the frame part  111 . Therefore, the bottom part  118  may move at the time of performing bonding by brazing. For example, in the light emitting device  1 , the shape of the frame of the frame part  111  is similar to the shape of the bonding surface of the bottom part  118 , but as a result of performing bonding, the center points of the frame part  111  and the bottom part  118  may not correspond to each other, or the distance between the frame part  111  and the bottom part  118  may not be uniform. Therefore, it is preferable to adjust the arrangement position so that the position with respect to the frame part  111  is uniform for easily performing alignment between manufactured light emitting devices  1  even when the bottom part  118  is misaligned. The smaller the gap between the frame part  111  and the bottom part  118 , the smaller the misalignment due to shifting. 
     The light reflecting member  150  has a light reflecting surface at one or more surfaces. The light reflecting member  150  is irradiated with light radiated from the semiconductor laser element  170 , and therefore in the light reflecting member  150 , it is desirable that a material resistant to heat be used as a main material, and a material having a high reflectivity be used for the light reflecting surface. Glass such as quartz or BK 7  (borosilicate glass), a metal such as aluminum, Si or the like can be employed as a main material of the light reflecting member  150 , and a metal, a dielectric multilayer film or the like can be employed for the light reflecting surface. If necessary, in the light emitting device  1 , the light reflecting member  150  may have a plurality of light emitting surfaces, or a light reflecting member may be disposed in addition to the light reflecting member  150 . Further, a respective one of light reflecting members  150  is provided for a respective one of semiconductor laser elements  170 , but one light reflecting member  150  may be arranged for three semiconductor laser elements  170 , or one light reflecting member  150  may be provided for a plurality of semiconductor laser elements. 
     For the sub-mount  160 , aluminum nitride, or silicon carbide can be used. The sub-mount  160  is provided with a metal film, and the semiconductor laser element  170  is fixed to the sub-mount  160  via an electrically conductive layer of Au-Sn or the like. 
     The semiconductor laser element  170  is bonded to the sub-mount  160  at the bottom surface thereof, and radiates light from a lateral surface closer to the light reflecting member  150 . Laser light radiated from the semiconductor laser element  170  has an elliptical far-field pattern (hereinafter, referred to as “FFP”) having a length in a layering direction of a plurality of semiconductor layers including an active layer is larger than a length thereof in a direction perpendicular to the layering direction, on a surface parallel to a light emitting end surface. 
     The “FFP” as used herein refers to a light intensity distribution of radiated light measured on a surface apart from the light emitting end surface of the semiconductor laser element to a certain degree and parallel to the light emitting end surface. The shape of the FFP is specified as a shape given by a main part of light. Here, the main part of light from the laser element refers to a part of laser light with an intensity range of a peak intensity value to any appropriate lower intensity value such as 1/e 2 . 
     The light emitting device  1  includes one or more semiconductor laser elements  170 , and in  FIGS.  6 A to  6 C , three semiconductor laser elements  170  are disposed. The number of the disposed semiconductor laser elements  170  is not limited to 3, and may be 1 or more. Light emitted from these semiconductor laser elements  170  may have the same color, or different colors. For example, the three semiconductor laser elements  170  of the light emitting device  1  may include a first semiconductor laser element which emits red light; a second semiconductor laser element which emits green light; a third semiconductor laser element which emits blue light. 
     The peak emission wavelength of red light is in a range of, for example,  605  nm to 750 nm. Examples of the semiconductor laser element which emits red light include those containing a semiconductor of InAlGaP type, GaInP type, GaAs type or AlGaAs type. The peak emission wavelength of green light is in a range of, for example, 495 nm to 570 nm. Examples of the semiconductor laser element which emits green light include semiconductor laser elements containing a nitride semiconductor. The peak emission wavelength of blue light is in a range of, for example, 420 nm to 494 nm. Examples of the semiconductor laser element which emits blue light include semiconductor laser elements containing a nitride semiconductor. Examples of the nitride semiconductor include GaN, InGaN and AlGaN. 
     In  FIG.  7 A , with wires bonded to the second electrode layer  114  in the frame part  111  and the semiconductor laser element  170 , the second electrode layer  114  is electrically connect to the semiconductor laser element  170 . For example, using a wire bonding device, one end of an Au wire is bonded to the semiconductor laser element  170 , and the other end is bonded to the second electrode layer  114 . When a protective element such as a Zener diode is arranged on the sub-mount  160 , the protective element is also electrically connected by the wire  180 . 
     As shown in  FIGS.  6 A and  6 B , the step portion for providing the second electrode layer  114  is provided along three sides in top view, and is not provided along one side except for portions overlapping other sides. 
     The light reflecting member  150  is disposed between the one side along which the step portion is not formed and the semiconductor laser element  170  or the sub-mount  160 , and the side along which the step portion is not formed is located at a side opposite to the semiconductor laser element  170  with the light reflecting member  150  disposed therebetween. Light radiated from the semiconductor laser element  170  is reflected by the light reflecting member  150  to travel upward. As can be understood from  FIGS.  7 A and  7 B , if the side along which the step portion is not formed is provided with a step portion, and the second electrode layer  114  on the side is electrically connected to the semiconductor laser element  170  by the wire, the wire is present in a light traveling direction, and thus blocks the light. In view of this, a step portion for the second electrode layer  114  is not provided on a side at the light reflecting member  150  side, and thus the second electrode layer  114  can be appropriately disposed to allow reduction in the size of the light emitting device  1 . 
     In  FIG.  8 A , the frame part  111  of the base member  110  and the cover  120  are bonded together to hermetically seal a space in which the semiconductor laser elements  170  is arranged. For example, on the lower surface of the cover  120 , a region bonded to the base member  110  is provided with a metal film, and the base member  110  is bonded and fixed to the cover  120  via AuSn or the like disposed therebetween. The semiconductor laser elements  170  are disposed in the closed space, so that collection of organic substances and the like on the light emitting end surface of the semiconductor laser element  170  can be reduced. 
     For the cover  120 , for example, glass provided with a metal film or sapphire provided with a metal film can be used, and in particular, it is preferable to use sapphire provided with a metal film. While spread of light causes increase in size of a lens portion to transmit the light, using sapphire for the lens portion of the lens member  140  allows for reducing degree of spread of light because sapphire has a relatively high refractive index, so that the size of the lens portion of the lens member  140  can be reduced. Further, sapphire has relatively high strength, and is therefore hardly broken, so that hermetic reliability of a closed space can be secured. 
     In  FIG.  9 A , the base member  110  is mounted on the substrate  100 . The substrate  100  is bonded to the bottom surface of the frame part  111  and the bottom part  118  of the base member  110 . The bonding can be performed by soldering. As shown in  FIGS.  9 B and  9 C , the substrate  100  includes a heat dissipation portion  101 , an insulating portion  102  and the metal film  103 . The heat dissipation portion  101  is formed of, for example, a metal such as Cu, the insulating portion  102  is formed of an insulating material, and the metal film  103  is formed of a metal such as Cu similarly to the heat dissipation portion  101 . 
     The heat dissipation portion  101  is bonded to the bottom part  118  of the base member  110 , and the metal film  103  or the insulating portion  102  is bonded to the frame part  111 . Thus, the substrate  100  is designed such that the metal film  103  and the heat dissipation portion  101  are provided on the same plane. More specifically, the heat dissipation portion  101  has a protruded structure protruded toward the base member  110  in a cross-sectional view or a side view, and is formed so as to be exposed in a region bonded to the bottom part  118  of the base member  110 . On the other hand, in a region where the substrate  100  is bonded to the frame part  111 , the heat dissipation portion  101  does not protrude, and the heat dissipation portion  101  is not exposed by the insulating portion  102  disposed on the heat dissipation portion  101 . In a bonding region of the substrate  100  that corresponds to a side of the frame part  111  provided with the first electrode layer  112 , the metal film  103  is disposed on the insulating portion  102 . Further, a predetermined spacing is provided between the heat dissipation portion  101  and the metal film  103  so that the heat dissipation portion  101  and the metal film  103  are not in contact with each other and electrically connected to each other. A part of the region provided with a predetermined spacing overlaps a part of the gap between the frame part  111  and the bottom part  118 . 
       FIG.  9 D  is a top view of a bonding surface of the substrate  100  which is bonded to the base member  110 . As shown in  FIG.  9 D , at the bonding surface of the substrate  100 , the substrate  100  includes the insulating portion  102 , the metal film  103 , and an exposed portion  106  (a protruding section having an exposed surface) in which the heat dissipation portion  101  is disposed. Further, the metal film  103  includes metal regions  104  and an insulating region  105 . The exposed portion  106  is bonded to the bottom part  118 , and the metal regions  104  is bonded to the bottom surface of the frame part  111 . 
     The shape of the exposed portion  106  represents a region where the heat dissipation portion  101  protrudes. In addition, the shape of the exposed portion  106  corresponds to the shape of the bottom surface of the bottom part  118 , and is designed to have a size slightly larger than a size of the bottom surface of the bottom part  118 . If the size of the exposed portion  106  is equal to the size of the bottom surface of the bottom part  118 , solder cannot expand outward of the bonding surface when soldering, so that the solder may have an excessive thickness between the substrate  100  and the base member  110 . Further, in a top view, each metal region  104  includes two portions located at both sides of the insulating region  105 , Of the two portions of each metal region  104 , a portion located closer to the center of the substrate  100  is bonded to the frame part  111 . By the bonding, each of the metal region  104  is electrically connected to a corresponding first electrode layer  112 . 
     With the metal films  103  and the exposed portion  106  of the heat dissipation portion  101  that are located at the same height, as described above, it is possible to reduce lifting of the frame part  111  or the bottom part  118  from the substrate  100  when bonding of the substrate  100  to the base member  110 . If the degree of the lifting is increased, bonding strength may be reduced, or a non-bonded region may be partially formed, and therefore the possibility that detachment of the package from a mounting substrate occurs may be increased. Further, with the entirety of bottom surface of the bottom part  118  bonded to the exposed portion  106  of the heat dissipation portion  101 , heat can be efficiently dissipated to the substrate  100 . 
     In  FIG.  10 A , the lens member  140  is fixed to the cover  120  using an adhesive agent. By the adhering, the adhesion portion  130  is formed between the cover  120  and the lens member  140 , and the light emitting device  1  shown in  FIGS.  1  to  3    is obtained. The adhesion portion  130  is not formed on the entire region of the upper surface of the cover  120  or the entire region of the lower surface of the lens member  140 , and is provided at such a position where the adhesion portion  130  does not interrupt a path of light emitted from the semiconductor laser element  170 . More specifically, in the light emitting device  1 , a main part of light emitted by the semiconductor laser element  170  is incident on and emitted from a region of the lens member  140  which has a lens shape. Therefore, it is desirable to use the adhesive agent such that the adhesion portion  130  is not formed on the lower surface of the lens member  140  which corresponds to the region having a lens shape, and the adhesion portion  130  is formed in an outer peripheral region of the lens member  140 . It is preferable that an ultraviolet ray-curable resin is used for an adhesive agent that forms the adhesion portion  130 . An ultraviolet ray-curable resin can be cured in a relatively short time without heating the resin, so that the lens member  140  is easily fixed at a desired position. 
     As shown in  FIGS.  10 B and  10 C , the lens member  140  has a lens shape in which a plurality of lens portions is connected. Further, the lens member  140  is designed such that one lens portion corresponds to one semiconductor laser element, and such that lens portions transmit main parts of light radiated from different semiconductor laser elements. For the lens member  140 , for example, glass such as BK 7  or B 270  can be used. 
     The light emitting device  1  according to the first embodiment is manufactured in the manner described above. The steps for manufacturing the light emitting device  1  is not limited to the steps described above with reference to  FIGS.  4 A to  10 A . 
     Second Embodiment 
       FIG.  11    is a sectional view of a light emitting device  2  according to a second embodiment. The schematic view of the appearance of the light emitting device  2  is not different from that in  FIG.  1   , and the internal structure of the light emitting device  2  in top view is not different from that in  FIG.  2   . The light emitting device  2  according to the second embodiment is different from the light emitting device  1  according to the first embodiment in the structure of a bottom part of a base member. In particular, in the second embodiment, the bonding surface of the bottom part, which is bonded to a substrate, is different from that in the first embodiment. Thus, with an insulating portion and an exposed portion on the bonding surface of the substrate that have shapes adapted to the bonding surface of the bottom part, structures, materials and the like as described in the first embodiment can be employed for other configurations. 
     As described in the step related to  FIG.  5 A  for the light emitting device  1  of the first embodiment, it is desirable to dispose the bottom part  118  such that the distance between the frame part  111  and the bottom part  118  is entirely uniform at the time of bonding the frame part  111  to the bottom part  118 . However, misalignment may occur in the process of bonding. If the degree of misalignment is great, a part of the bottom part  118  is brought into contact with the frame part  111 . Further, if the spacing between the bottom part  118  and the frame part  111  is narrower than a designed spacing, and accordingly the distance between the first electrode layer  112  and the bottom part  118  at this part is reduced, then electrical connection may be established between the first electrode layer  112  and the bottom part  118  at the time of bonding the frame part  111  and the bottom part  118  to the substrate  100  by soldering, which may lead to defectiveness of a light emitting device. 
     Thus, in the light emitting device  2  according to the second embodiment, a depressed portion  214  is formed on at least the outer edge of a bonding surface  215  of a bottom part  213  bonded with a substrate  200 . With this structure, the spacing between a frame part  211  and a bottom part  213  along a plane corresponding to the bottom surface, which is the bonding surface  215  bonded with the substrate  200 , of a base member  210  is greater than the spacing between the frame part  211  and the bottom part  213  along a plane corresponding to a bonding surface  212  bonded with the frame part  211 . 
       FIGS.  12 A and  12 B  show an example of the bottom part  213  having the depressed portion  214 . In one example, a protruded shape of the bottom part  213  forms a depression of the depressed portion  214 . A protruding region having a protruded shape forms the bonding surface  215  bonded with the substrate  200 , and the bonding surface  215  may have a shape obtained by scaling down a shape similar to the shape of an outer frame portion of the bottom part  213  as shown in  FIG.  12 A , or a circular shape as shown in  FIG.  12 B .  FIG.  13    is a schematic view showing a bonding surface of the substrate  200  when the protruding region has a circular shape. As shown in  FIG.  13   , an exposed portion  201  has a circular shape in corresponding to the bonding surface  215  of the base member  210 . 
     The depressed portion  214  has a spacing and height that sufficiently allows for preventing occurrence of the above-described defect in a step of soldering the base member to the substrate  200 . For example, the light emitting device  1  of the first embodiment is designed such that a spacing of about 0.1 mm is provided in the light emitting device  1 , and the depression may be designed so as to have a width of about 0.1 mm as long as a spacing of at least about 0.1 mm may be provided. Thus, even if the frame part  211  is in contact with a lateral surface of the bottom part  213  at the bonding surface  212  side bonded with the frame part  211 , it is possible to maintain a spacing of about 0.1 mm between the frame part  211  and the bottom part  213  on the bonding surface bonded with the substrate  200 . Further, for example, the light emitting device  1  of the first embodiment is designed such that the distance between the lateral surface  119  of the bottom part  118  and the first electrode layer  112  is 0.3 mm or more. When the width of the depression is designed, the width of the depression may be similarly selected with consideration of the design of the frame part so that a distance of approximately 0.3 mm from the first electrode layer  112  is maintained. The spacing of 0.3 mm is one example in design of the light emitting device  1 , and a predetermined spacing to be provided may be appropriately selected according to the shape and materials of the light emitting device. 
     Therefore, the depressed portion  214  preferably has a width similar to a width of a gap that would be secured when the bottom part  213  does not have the depressed portion  214  and misalignment of the bottom part  213  with respect to the frame part  211  does not occur. The depressed portion  214  may have a width equal to or greater than a width of the gap, or may have such a shape that a part of the depression portion has a width equal to or greater than a width of the gap, as in the bottom part  213  in which the protruding region has a circular shape as shown in  FIG.  12   . However, because an increase in width of the depression leads to a decrease in bonding area with the substrate  200 , it is desirable that the depressed portion  214  be prevented from having an excessively large width for attaining sufficient bonding, and the width of the depressed portion  214  is desirably 0.1 mm to 0.5 mm. For example, when a bonding surface has a circular shape as shown in  FIG.  12   , the depressed portion  214  may be designed such that the narrowest part of the depression has a width similar to that of a gap to be secured. 
     Further, the depressed portion  214  secures a height that allows a solder extended out from the bonding surface  215  of the bottom part  213  bonded with the substrate  200  to extend upward along a lateral surface meeting the bonding surface  215  bonded with the substrate  200 , and to be retained in the depression. The height of the depressed portion  214  desirable to be secured is varied according to a material and an amount of solder to be used. For example, the depressed portion  214  secures a height of about 0.2 mm in the light emitting device  2 . 
     When the bonding surface bonded with the substrate has a rectangular or square shape with four modified corners, as in the bottom part  118  described for the light emitting device  1  or the bottom part  213  shown as one example in  FIG.  12   , the exposed portion at the substrate side has a shape according to the shape of the bonding surface, and accordingly, self-alignment occurs at the time of bonding the bottom part to the substrate. 
     On the other hand, when the bonding surface  215  bonded with the substrate  200  has a circular shape as in the bottom part  213  shown in  FIG.  12 B  as one example, the exposed portion  201  at the substrate side having a circular shape according to the shape of the bonding surface allows the bonding surface of the bottom part  213  to be located inward of the outer periphery of the exposed portion  201 . Further, with the bonding surface  215  and the exposed portion  201  having such circular shapes, even in a state where the bonding surface  215  and the exposed portion  201  are bonded with each other via a solder, the substrate  200  and the bottom part  213  are movable along a rotating direction of the circular shape until the solder is solidified. With the bonding surface  215  bonded with the substrate  200  and having a circular shape, when misalignment occurs in arrangement of the frame part  211  and the bottom part  213 , the arrangement can be adjusted in a rotating direction, so that misalignment of the frame part  211  with respect to the substrate  200  can be corrected. 
     First Modified Example 
     A light emitting device  3  according to a first modified example has a structure different from that in the light emitting device  2  shown in the second embodiment, so as to obtain a light emitting device in which the spacing between a frame part and a bottom part along a plane corresponding to a bonding surface bonded with a substrate is greater than the spacing between the frame part and the bottom part along a plane corresponding to a bonding surface bonded with the frame part. 
       FIG.  14    is a cross-sectional view of the light emitting device  3  according to the first modified example. As shown in  FIG.  14   , in the light emitting device  3 , a depressed portion  312  is formed in a frame part  311 , so that the spacing between the frame part  311  and a bottom part  313  along a plane corresponding to a bonding surface bonded with a substrate  300  is greater than the spacing between the frame part  311  and the bottom part  313  along a plane corresponding to a bonding surface bonded with the frame part  311 . In other words, a size of the area within the intersection line between the inner surface of the frame part  311  and the bonding surface is smaller than a size of an area within an intersection line between the inner surface of the frame part  311  and the bottom surface of the frame part  311  in the plan view. The light emitting device  3  may be produced by a method including processing the shape of the frame part  311  as described above, and in the light emitting device  3 , the substrate  100  in the first embodiment can be employed as such unlike the light emitting device  2 . 
     Second Modified Example 
       FIG.  15    is a cross-sectional view of a light emitting device  4  according to a second modified example. In addition,  FIG.  16    is a schematic view of a bottom part according to the second modified example. As shown in  FIG.  15   , the light emitting device  4  includes a bottom part  412 , in which a bonding surface bonded with a substrate  400  has a size smaller than a size of a bonding surface bonded with a frame part  411  at a bottom part  412 , and a lateral surface  413  is inclined. With inclination of the lateral surface  413  as described above, the spacing between the frame part  411  and the bottom part  412  on the bonding surface bonded with the substrate  400  can be greater than the spacing between the frame part  411  and the bottom part  412  at the bonding surface bonded with the frame part  411 . Instead of inclination of the bottom part  412 , the frame part  411  may be provided with inclination as in the first modified example. 
     Certain embodiments and modified examples of the light emitting device according to the present invention has been described above, but the light emitting device for implementing the technical idea of the present invention is not limited to these embodiments and modified examples described above. For example, while a light emitting device in which three semiconductor laser elements are arranged has been described, one or more semiconductor laser elements may be arranged in the light emitting device. Also, the light emitting device may not include the light reflecting member  150  so that light radiated from a semiconductor laser element travels in a direction of the lens member  140 . 
     In addition, the light emitting device having configurations described in the present disclosure is not limited to the structures of the light emitting devices  1  to  4 . For example, the present invention can be applied even to a light emitting device having a constituent element which is not illustrated in descriptions of any of the light emitting devices  1  to  4 , and having difference in a structure from a structure in the light emitting device as described above cannot be a ground for failure to apply the present invention. 
     On the other hand, the present invention can be applied without necessity of sufficiently including all constituent elements of the light emitting device described in the embodiments and modified examples above. For example, when some constituent elements of the light emitting device disclosed in the first embodiment are not described in claims, the constituent elements which are not described in claims may have any appropriate structure, and the freedom of design thereof such as replacement, omission, modification of the shape, change of materials, and the like by a person skilled in the art is accepted, with which application of the invention is claimed. 
     The light emitting device described in certain embodiments can be used for projectors, on-vehicle headlights, illuminations, backlights of display devices, and the like.