Patent Publication Number: US-2023156904-A1

Title: Substrate for mounting electronic element, electronic device, and electronic module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 17/040,890 filed on Sep. 23, 2020, which is a National Phase entry according to 35 U.S.C. 371 of International Application No. PCT/JP2019/013685 filed on Mar. 28, 2019, which claims priority to Japanese Patent Application Nos. 2018-062279 filed on Mar. 28, 2018, and 2018-101617 filed on May 28, 2018, the contents of which are entirely incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a substrate for mounting electronic element, an electronic device, and an electronic module. 
     BACKGROUND OF THE INVENTION 
     A substrate for mounting electronic element of the related art includes an insulating substrate including a first surface, a second surface, and side surfaces, an electronic element mounting portion and a wiring layer which are disposed on the first surface of the insulating substrate. After mounting electronic element on the electronic element mounting portion, the substrate for mounting electronic element is mounted in a package for mounting electronic element to obtain an electronic device (see Japanese Unexamined Patent Publication JP-A 2013-175508). 
     SUMMARY OF THE INVENTION 
     A substrate for mounting electronic element according to the disclosure includes a first substrate including a first surface and a second surface opposite to the first surface, a second substrate including a third surface and a fourth surface opposite to the third surface, and a plurality of heat dissipation bodies each including a fifth surfaces and a sixth surface opposite to the fifth surface, the first substrate including at least one mounting portion for at least one electronic element at the first surface, and the at least one mounting portion being a rectangular shape, the second substrate being made of metal, having a quadrangular shape, the plurality of heat dissipation bodies being made of a carbon material, and the fifth surface being connected to at least the second surface at location overlapped with the at least one mounting portion in a transparent plan view, heat conduction of the plurality of heat dissipation bodies in a direction perpendicular to a longitudinal direction of the at least one mounting portion and perpendicular to a direction along opposite sides of the second substrate being larger than heat conduction of the plurality of heat dissipation bodies in the longitudinal direction of the at least one mounting portion and in the direction along opposite sides of the second substrate in a transparent plan view of the substrate for mounting electronic element. 
     An electronic device of the disclosure includes the substrate for mounting electronic element described above, at least one electronic element mounted on the at least one mounting portion of the substrate for mounting electronic element, and a wiring substrate or a package for housing an electronic element on which the substrate for mounting electronic element is to be mounted. 
     An electronic module of the disclosure includes the electronic device described above and a module substrate to which the electronic device is to be connected. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1 A  is a top view illustrating a substrate for mounting electronic element according to a first embodiment, and  FIG.  1 B  is a bottom view of  FIG.  1 A ; 
         FIG.  2    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of the substrate for mounting electronic element illustrated in  FIGS.  1 A and  1 B ; 
         FIG.  3 A  is a vertical cross-sectional view of the substrate for mounting electronic element taken along the line A-A of  FIG.  1 A , and  FIG.  3 B  is a vertical cross-sectional view of the substrate for mounting electronic element taken along the line B-B of  FIG.  1 A ; 
         FIG.  4 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element illustrated in  FIG.  1 A , and  FIG.  4 B  is a vertical cross-sectional view of a structure including a wiring substrate or a package for housing electronic element and a module substrate, taken along the line B-B of  FIG.  4 A ; 
         FIG.  5    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of a substrate for mounting electronic element according toa second embodiment; 
         FIG.  6 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element according to the second embodiment, and  FIG.  6 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  6 A ; 
         FIG.  7    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of another example of the substrate for mounting electronic element according to the second embodiment; 
         FIG.  8 A  is a top view illustrating a state in which an electronic element is mounted on another example of the substrate for mounting electronic element according to the second embodiment, and  FIG.  8 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  8 A ; 
         FIG.  9    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of a substrate for mounting electronic element according to a third embodiment; 
         FIG.  10 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element according to the third embodiment, and  FIG.  10 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  10 A ; 
         FIG.  11    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of a substrate for mounting electronic element according to a fourth embodiment; 
         FIG.  12 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element according to the fourth embodiment, and  FIG.  12 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  12 A ; 
         FIG.  13    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of a substrate for mounting electronic element according to a fifth embodiment; 
         FIG.  14 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element according to the fifth embodiment, and  FIG.  14 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  14 A ; 
         FIG.  15 A  is a top view illustrating another example of the substrate for mounting electronic element according to the fifth embodiment, and  FIG.  15 B  is a bottom view of  FIG.  15 A ; 
         FIG.  16 A  is a top view illustrating a substrate for mounting electronic element according to a sixth embodiment, and  FIG.  16 B  is a bottom view of  FIG.  16 A ; 
         FIG.  17    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of the substrate for mounting electronic element illustrated in  FIGS.  16 A and  16 B ; 
         FIG.  18 A  is a vertical cross-sectional view taken along the line A-A of the substrate for mounting electronic element illustrated in  FIG.  16 A , and  FIG.  18 B  is a vertical cross-sectional view of the substrate for mounting electronic element taken along the line B-B of  FIG.  16 A ; 
         FIG.  19 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element illustrated in  FIG.  16 A , and  FIG.  19 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  19 A ; 
         FIG.  20 A  is a top view illustrating another example of the substrate for mounting electronic element according to the sixth embodiment, and  FIG.  20 B  is a bottom view of  FIG.  20 A ; 
         FIG.  21    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of a substrate for mounting electronic element according to a seventh embodiment; 
         FIG.  22 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element according to the seventh embodiment, and  FIG.  22 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  22 A ; 
         FIG.  23    is an exploded perspective view of a first substrate, a second substrate, and a heat dissipation body of a for mounting electronic element substrate according to an eighth embodiment; and 
         FIG.  24 A  is a top view illustrating a state in which an electronic element is mounted on the substrate for mounting electronic element according to the eighth embodiment, and  FIG.  24 B  is a vertical cross-sectional view taken along the line B-B of  FIG.  24 A . 
     
    
    
     DETAILED DESCRIPTION 
     Several exemplary embodiments of the disclosure will be described with reference to the accompanying drawings. 
     First Embodiment 
     A substrate for mounting electronic element  1  according to a first embodiment includes a first substrate  11 , a second substrate  12 , and heat dissipation bodies  13  as in the example shown in  FIGS.  1 A to  4 B . The electronic device includes the substrate for mounting electronic element  1 , an electronic element  2  mounted on a mounting portion  11   a  of the substrate for mounting electronic element  1 , and a wiring substrate  4  on which the substrate for mounting electronic element  1  is to be mounted. The electronic device is connected to a connection pad  6   a  located on a module substrate  6  which constitutes the electronic module, for example, by using a bonding material  7 . 
     The substrate for mounting electronic element  1  according to the embodiment includes the first substrate  11  including a first surface  111  and a second surface  112  opposite to the first surface  111 , the second substrate  12  including a third surface  121  and a fourth surface  122  opposite to the third surface  121 , and the plurality of heat dissipation bodies  13  each including a fifth surface  131  and a sixth surface  132  opposite to the fifth surface  131 . The first substrate  11  includes at least one mounting portion  11   a  for at least one electronic element  2  at the first surface  111 , and the at least one mounting portion  11   a  is a rectangular shape, the second substrate  12  is made of metal, and has a quadrangular shape, the plurality of heat dissipation bodies  13  is made of a carbon material, and the fifth surface  131  is connected to at least the second surface  112  at location overlapped with the at least one mounting portion  11   a  in a transparent plan view. The heat conduction of the plurality of heat dissipation bodies  13  in a direction perpendicular to a longitudinal direction of the at least one mounting portion  11   a  and perpendicular to a direction along opposite sides of the second substrate  12  is larger than the heat conduction of the plurality of heat dissipation bodies  13  in the longitudinal direction of the at least one mounting portion  11   a  and in the direction along the opposite sides of the second substrate  12  in a transparent plan view. The first substrate  11  includes a metal layer  14  on a surface thereof. In  FIGS.  4 A and  4 B , the electronic element  2  is mounted on an xy plane in a virtual xyz space. In  FIGS.  1 A to  4 B , an upward direction means a positive direction of a virtual z axis. The distinction between upper and lower sides in the following description is for convenience and does not limit the upper and lower sides when the substrate for mounting electronic element  1  or the like is actually used. 
     In the example illustrated in  FIGS.  1 A and  1 B , in the substrate for mounting electronic element  1 , the three heat dissipation bodies  13  are located in series in through holes  12   a  of the second substrate  12 , and the four metal layers  14  are located on the first surface  111  of the first substrate  11 . 
     The plurality of heat dissipation bodies  13  are shaded in the examples illustrated in  FIGS.  1 B and  2   . The metal layers  14  are shaded in the examples illustrated in  FIGS.  1 A,  3 B,  4 A and  4 B . In the example illustrated in  FIGS.  1 A,  1 B and  4 A , a region overlapping with the outer surfaces of the plurality of heat dissipation bodies  13  of the first substrate  11  in a transparent plan view is shown by a broken line. In the example illustrated in  FIG.  2   , in the first substrate  11 , the outer surface of the first substrate  11  which is invisible in a perspective view is shown by a broken line. In the example illustrated in  FIG.  2   , in the second substrate  12 , the outer surface of the second substrate  12  and the inner surface of the through hole  12   a,  which are invisible in a perspective view, are shown by broken lines. The mounting portion  11   a  of the electronic element  2  is arranged so as to overlap with the heat dissipation bodie  13  if seen in a transparent plan view. 
     The first substrate  11  is comprised of a single layer or a plurality of insulating layers and includes the first surface  111  (an upper surface in  FIGS.  1 A to  4 B ) and the second surface  112  (a lower surface in  FIGS.  1 A to  4 B . The first substrate  11  is comprised of a single insulating layer in the example illustrated in  FIGS.  1 A to  4 B . The first substrate  11  has a rectangular plate-like shape including two sets of opposite sides (4 sides) with respect to each of the first surface  111  and the second surface  112  in a plan view. In the examples illustrated in  FIGS.  1 A to  4 B , the first substrate  11  has a rectangular shape which is long in a direction of arrangement (arrangement of the plurality of mounting portions  11   a ) of the plurality of electronic elements  2  in a plan view. The first substrate  11  functions as a support for supporting the plurality of electronic elements  2  and the plurality of electronic elements  2  are adhered and fixed on the plurality of mounting portions  11   a  located on the first surface  111  of the first substrate  11  via bonding members. The first surface  111  includes the at least one mounting portion  11   a  for the at least one electronic element  2  which is a longitudinal region, and in the example illustrated in  FIGS.  1 A to  4 B , the plurality of mounting portions  11   a  are provided. 
     As the first substrate  11 , for example, ceramics such as an aluminum oxide sintered body (alumina ceramics), an aluminum nitride sintered body, a mullite sintered body, or a glass ceramic sintered body can be used. If the first substrate  11  is made of, for example, an aluminum nitride sintered body, a raw material powder such as aluminum nitride (AlN), erbium oxide (Er 2 O 3 ), and yttrium oxide (Y 2 O 3 ) is mixed with an appropriate organic binder and solvent or the like to prepare a slurry. A ceramic green sheet is produced by forming this slurry into a sheet shape by employing a well-known doctor blade method, calendar roll method, or otherwise. If necessary, a plurality of ceramic green sheets are laminated and the ceramic green sheets are fired at a high temperature (about 1800° C.) to manufacture the first substrate  11  including a single layer or a plurality of insulating layers. 
     The second substrate  12  includes the third surface  121  (an upper surface in  FIGS.  1 A to  3 B ) and the fourth surface  122  (a lower surface in  FIGS.  1 A to  3 B ). The third surface  121  and the fourth surface  122  are located opposite to each other. The second substrate  12  has a quadrangular plate-like shape including two sets of opposing sides (4 sides) with respect to each of the third surface  121  and the fourth surface  122  in a plan view. 
     For the second substrate  12 , for example, a metal material such as copper (Cu), copper-tungsten (Cu—W), and copper-molybdenum (Cu—Mo) can be used. The second substrate  12  includes the through hole  12   a  which passes from the third surface  121  to the fourth surface  122 . The through holes  12   a  are areas where the plurality of heat dissipation bodies  13  are located. 
     The plurality of heat dissipation bodies  13  each include the fifth surface  131  (an upper surface in  FIGS.  1 A to  3 B ) and the sixth surface  132  (a lower surface in  FIGS.  1 A to  3 B ). The fifth surface  131  and the sixth surface  132  are located opposite to each other. The plurality of heat dissipation bodies  13  have a quadrangular plate-like shape including two sets of opposing sides (4 sides) with respect to each of the fifth surface  131  and the sixth surface  132  in a plan view. 
     The plurality of heat dissipation bodies  13  are made of, for example, a carbon material and are formed as a structure in which graphenes in which six-membered rings are covalently connected are stacked. This structure is constituted by a material in which each surface is joined by Van der Waals forces. 
     The plurality of heat dissipation bodies  13  are located in the through holes  12   a  of the second substrate  12  as in the example illustrated in  FIGS.  1 A to  4 B . The fifth surfaces  131  of the plurality of heat dissipation bodies  13  are located on the third surface side  121  of the second substrate  12 , and the sixth surfaces  132  of the plurality of heat dissipation bodies  13  are located on the fourth surface  122  side. 
     As the first substrate  11 , an aluminum nitride sintered body having excellent thermal conductivity is preferably used. As the second substrate  12 , a substrate made of Cu having an excellent thermal conductivity is preferably used. In the second substrate  12  and the plurality of heat dissipation bodies  13 , the inner surface of the through hole  12   a  of the second substrate  12  and the outer surfaces of the plurality of heat dissipation bodies  13  are bonded by, for example, a bonding material made of an active brazing material such as TiCuAg alloy or TiSnAgCu alloy. The bonding material is arranged between the second substrate  12  and the plurality of heat dissipation bodies  13  in a thickness of about 10 μm. 
     In the first substrate  11  and the second substrate  12 , the second surface  112  of the first substrate  11  and the third surface  121  of the second substrate  12  are bonded by, for example, a bonding material made of an active brazing material such as TiCuAg alloy or TiSnAgCu. Further, in the first substrate  11  and the plurality of heat dissipation bodies  13 , the second surface  112  of the first substrate  11  and the fifth surface  131  of the plurality of heat dissipation bodies  13  are bonded by, for example, a bonding material made of an active brazing material such as TiCuAg alloy or TiSnAgCu. The bonding material with a thickness of about 10 μm is arranged between the first substrate  11  and the second substrate  12  and between the first substrate  11  and the plurality of heat dissipation bodies  13 . 
     The first substrate  11 , the second substrate  12 , and the plurality of heat dissipation bodies  13  may be simultaneously joined. For example, the plurality of heat dissipation bodies  13  may be located in the through holes  12   a  of the second substrate  12  and the first substrate  11  may be joined to the second substrate  12  and the plurality of heat dissipation bodies  13 . In this case, for example, by joining while applying pressure from the first surface  111  side of the first substrate  11  and the fourth surface  122  side of the second substrate  12 , the first substrate  11 , the second substrate  12 , and the plurality of heat dissipation bodies  13  are well joined and the substrate for mounting electronic element  1  having excellent reliability can be obtained. 
     The first substrate  11  has a quadrangular shape in a plan view as in the example illustrated in  FIGS.  1 A to  4 B . The second substrate  12  has a quadrangular shape in a plan view as in the example illustrated in  FIGS.  1 A to  4 B . The plurality of heat dissipation bodies  13  have a quadrangular shape in a plan view as in the example illustrated in  FIGS.  1 A to  4 B . A quadrangular composite substrate is formed by bonding the first substrate  11  and the second substrate  12  together, and by bonding the first substrate  11  and the plurality of heat dissipation bodies  13  together. The quadrangular shape means a quadrangle such as a square and a rectangle. In the example illustrated in  FIGS.  1 A to  3 B , in a plan view, the first substrate  11  and the second substrate  12  have a rectangular shape and the plurality of heat dissipation bodies  13  have a square shape. Therefore, the first substrate  11 , the second substrate  12 , and the plurality of heat dissipation bodies  13  form a rectangular composite substrate. 
     A substrate thickness T 1  of the first substrate  11  is, for example, about 50 μm to 500 μm, and a substrate thickness T 2  of the second substrate  12  is, for example, about 100 μm to 2000 μm. A substrate thickness T 3  of the plurality of heat dissipation bodies  13  is, for example, about 100 μm to 2000 μm. The substrate thickness T 2  of the second substrate  12  and the substrate thickness T 3  of the plurality of heat dissipation bodies  13  are provided with the same thickness within a range of about 5% (0.95T 2 ≤T 3 ≤1.05T 2 ). If the first substrate  11  and the second substrate  12  are T 2 &gt;T 1  and the first substrate  11  and the plurality of heat dissipation bodies  13  are T 3 &gt;T 1 , the heat of the first substrate  11  can be favorably radiated to the plurality of heat dissipation bodies  13 . 
     As in the example illustrated in  FIG.  2   , a thermal conductivity κα of the first substrate  11  is substantially constant in the x direction and the y direction in a planar direction, and the thermal conductivity in the z direction, which is the thickness direction, of the first substrate  11  is the same as the thermal conductivity in the x direction and the y direction in the planar direction (καx≈καy≈καz). For example, if an aluminum nitride sintered body is used as the first substrate  11 , the first substrate  11  is a substrate having a thermal conductivity κα of about 100 to 200 W/m·K. 
     A thermal conductivity κβ of the second substrate  12  is substantially constant in the x direction and the y direction in the planar direction, as in the example illustrated in  FIG.  2   , and the thermal conductivity in the z direction, which is the thickness direction, of the first substrate  11  is also the same as the thermal conductivity in the z direction and the y direction in the planar direction (κβx≈κβy≈κβz). For example, if copper is used as the second substrate  12 , the second substrate  12  is a substrate having a thermal conductivity κβ of about 400 W/m·K. 
     A thermal conductivity λ of the plurality of heat dissipation bodies  13  has different magnitudes in the x and y directions in the planar direction. The relationship between the thermal conductivity λx, λy, and λz in each direction of the plurality of heat dissipation bodies  13  illustrated in  FIG.  2    satisfies “thermal conductivity λx thermal conductivity λz&gt;&gt;thermal conductivity λy”. The thermal conductivities λ of the plurality of heat dissipation bodies  13  in the x direction in the planar direction is the same as the thermal conductivities λ of the plurality of heat dissipation bodies  13  in the z direction which is the thickness direction, and the thermal conductivities λ of the plurality of heat dissipation bodies  13  in the y direction in the planar direction are different from each other. For example, the thermal conductivities λx and thermal conductivities λz of the plurality of heat dissipation bodies  13  are about 1000 W/m·K and the thermal conductivities λy of the plurality of heat dissipation bodies  13  are about 4 W/m·K. 
     The thermal conductivity of the substrate for mounting electronic element  1  according to the embodiment can be measured by an analysis method such as a laser flash method. Also, if measuring the thermal conductivity of the plurality of heat dissipation bodies  13 , the bonding material which joins the first substrate  11  and the plurality of heat dissipation bodies  13  and the bonding material which joins the second substrate  12  and the plurality of heat dissipation bodies  13  are removed, and the measurement can be carried out on the plurality of heat dissipation bodies  13  by an analysis method such as laser flash method. 
     The thermal conductivity λx of the plurality of heat dissipation bodies  13  in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a  and perpendicular to the direction along the opposite sides of the second substrate  12  is larger than the thermal conductivity λy of the plurality of heat dissipation bodies  13  in the longitudinal direction of the at least one mounting portion  11   a  and in the direction along the opposite sides of the second substrate  12 . Also, the plurality of heat dissipation bodies  13  are arranged such that the thermal conductivity λz in the thickness direction of the plurality of heat dissipation bodies  13  is larger than the thermal conductivity λy in the longitudinal direction of the at least one mounting portion  11   a  and the direction along the opposite sides of the second substrate  12  (thermal conductivities λx and λz&gt;&gt;thermal conductivity λy). 
     Further, the plurality of heat dissipation bodies  13  are arranged such that the thermal conductivity λy in the direction in which the plurality of heat dissipation bodies  13  are aligned, that is, in the direction between the at least one mounting portion  11   a  for the adjacent electronic elements  2 , is smaller than the thermal conductivity λx in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned and the thermal conductivity λz in the thickness direction of the plurality of heat dissipation bodies  13  (thermal conductivities λx and λz&gt;&gt;thermal conductivity λz). 
     The metal layer  14  is located on the first surface  111  of the first substrate  11  around the plurality of heat dissipation bodies  13  in a plan view (a transparent plan view). Further, the metal layer  14  and the heat dissipation bodie  13  are alternately located in the longitudinal direction of the first substrate  11  in a plan view (a transparent plan view). The metal layer  14  is used, for example, as a connecting portion between an electrode of the electronic element  2  and a connecting member  3  such as a bonding wire. The metal layer  14  is a member for electrically connecting the electronic element  2  and the wiring conductor of the wiring substrate  4 . 
     The metal layer  14  includes a thin film layer and a plating layer. The thin film layer has, for example, an adhesion metal layer and a barrier layer. The adhesion metal layer constituting the thin film layer is formed on the first surface  111  of the first substrate  11 . The adhesion metal layer is made of, for example, tantalum nitride, nickel-chrome, nickel-chrome-silicon, tungsten-silicon, molybdenum-silicon, tungsten, molybdenum, titanium, chromium, or the like, and is deposited on the first surface  111  of the first substrate  11  by adopting a thin film forming technique such as a vapor deposition method, an ion plating method, or a sputtering method. For example, if forming using a vacuum deposition method, the first substrate  11  is installed in a film forming chamber of a vacuum evaporation system and a metal piece to be an adhesion metal layer is arranged at the evaporation source in the film forming chamber, and then, while the film forming chamber is in a vacuum state (pressure of 10 −2  Pa or less), the metal piece placed in the vapor deposition source is heated for vapor deposition, and by depositing the molecules of the vapor-deposited metal piece on the first substrate  11 , a thin film metal layer to be an adhesion metal layer is formed. Then, a resist pattern is formed on the first substrate  11  on which the thin film metal layer is formed by using a photolithography method, and then the excess thin film metal layer is removed by etching to form the adhesion metal layer. The barrier layer is deposited on the upper surface of the adhesion metal layer, and the barrier layer has good adhesiveness and wettability with the adhesion metal layer and the plating layer and has a function of firmly joining the adhesion metal layer and the plating layer and preventing mutual diffusion between the adhesion metal layer and the plating layer. The barrier layer is made of, for example, nickel-chromium, platinum, palladium, nickel, cobalt or the like, and is deposited on the surface of the adhesion metal layer by a thin film forming technique such as a vapor deposition method, an ion plating method, or a sputtering method. 
     The thickness of the adhesion metal layer is preferably about 0.01 μm to 0.5 μm. If the thickness of the adhesion metal layer is less than 0.01 μm, it tends to be difficult to firmly adhere the adhesion metal layer onto the first substrate  11 . If thickness of the adhesion metal layer exceeds 0.5 μm, peeling of the adhesion metal layer is likely to occur due to internal stress during film formation of the adhesion metal layer. In addition, the thickness of the barrier layer is preferably about 0.05 μm to 1 μm. If the thickness of the barrier layer is less than 0.05 μm, defects such as pinholes tend to occur, and thus it is difficult to function as a barrier layer. If the thickness of the barrier layer exceeds 1 μm, peeling of the barrier layer is likely to occur due to internal stress during film formation. 
     The plating layer is deposited on the surface of the thin film layer by electrolytic plating or electroless plating. The plating layer is made of a metal having excellent corrosion resistance and connectivity with the connecting member, such as nickel, copper, gold, or silver, and for example, a nickel plating layer having a thickness of about 0.5 μm to 5 μm and a gold plating layer having a thickness of about 0.1 μm to 3 μm are sequentially deposited. As a result, corrosion of the metal layer  14  can be effectively suppressed and the metal layer  14  and the wiring conductor formed on the wiring substrate  4  can be firmly bonded. 
     Further, a metal layer such as copper (Cu) or gold (Au) may be arranged on the barrier layer so that the plating layer can be formed well. Such a metal layer is formed by a method similar to that of a thin film layer. 
     If forming the metal layer  14  on the first surface  111  of the first substrate  11  and forming the plating layer on the metal layer  14 , if a protective film made of resin, ceramics, metals, or the like is provided on the exposed sixth surfaces  132  of the plurality of heat dissipation bodies  13  in advance, the plurality of heat dissipation bodies  13  made of carbon material are not exposed if manufacturing the substrate for mounting electronic element  1 . Therefore, it is possible to reduce deterioration caused by chemicals or the like. 
     The electronic element  2  is mounted on the mounting portion  11   a  located on the first surface  111  side of the substrate for mounting electronic element  1  and the substrate for mounting electronic element  1  is mounted on the wiring substrate  4  or a package for housing electronic element  5 , in such a manner that an electronic device can be manufactured. The electronic element  2  mounted on the substrate for mounting electronic element  1  is, for example, a light emitting element such as a Laser Diode (LD) or a Light Emitting Diode (LED) or a light receiving element such as a Photo Diode (PD). For example, after the electronic element  2  is fixed on the mounting portion  11   a  by a bonding material such as Au—Sn, the electrode of the electronic element  2  and the metal layer  14  are electrically connected via the connecting member  3  such as a bonding wire, in such a manner that the electronic element  2  is mounted on the substrate for mounting electronic element  1 . For example, as similar to the first substrate  11 , the wiring substrate  4  or the package for housing electronic element  5  on which the substrate for mounting electronic element  1  is to be mounted can use an insulating substrate such as ceramics and includes a wiring conductor on the surface thereof. Then, the metal layer  14  of the substrate for mounting electronic element  1  and the wiring substrate  4  or the wiring conductor of the package for housing electronic element  5  are electrically connected. 
     In accordance with the electronic device according to the embodiment, the substrate for mounting electronic element  1  including the above configuration, the electronic element  2  mounted on the mounting portion  11   a  of the substrate for mounting electronic element  1 , and the wiring substrate  4  or the package for housing the electronic element  5  on which the substrate for mounting electronic element  1  is to be mounted are provided. 
     The electronic device according to the embodiment is connected to the wiring conductor and the connection pad  6   a  of the module substrate  6  via the bonding material  7  such as solder to form an electronic module. 
     According to the embodiment, the substrate for mounting electronic element includes the first substrate  11  including the first surface  111  and the second surface  112  opposite to the first surface  111 , the second substrate  12  including the third surface  121  and the fourth surface  122  opposite to the third surface  121 , and the plurality of heat dissipation bodies  13  each including the fifth surface  131  and the sixth surface  132  opposite to the fifth surface  131 , the first substrate  11  including at least one mounting portion  11   a  for at least one electronic element  2  at the first surface  111 , and the at least one mounting portion  11   a  being a rectangular shape, the second substrate  12  being made of metal, having a quadrangular shape, the plurality of heat dissipation bodies  13  being made of a carbon material, and the fifth surface  131  being connected to at least the second surface  112  at location overlapped with the at least one mounting portion  11   a  in a transparent plan view, the heat conduction of the plurality of heat dissipation bodies  13  in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a  and perpendicular the direction along the opposite side of the second substrate  12  is larger than the heat conduction of the plurality of heat dissipation bodies  13  in the longitudinal direction of the at least one mounting portion  11   a  and in the direction along the opposite side to the second substrate  12  in a transparent plan view of the substrate for mounting electronic element  1 . With the above configuration, for example, if the electronic device is operated, the heat generated from the electronic element  2  becomes large and evenly transmitted to the opposite sides of the second substrate  12  and heat dissipation of the substrate for mounting electronic element  1  becomes good. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     In addition, the plurality of heat dissipation bodies  13  are aligned inside the second substrate  12  and, in the transparent plan view, the plurality of heat dissipation bodies  13  have a greater heat conduction in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned than in the direction in which the plurality of heat dissipation bodies  13  are aligned. Due to the above configuration, heat transfer is suppressed in the direction in which the plurality of heat dissipation bodies  13  of the first substrate  11  and the second substrate  12  are aligned, and it is possible to increase the heat transfer in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  on the first substrate  11  and the second substrate  12  are aligned. Therefore, it is possible to restrain heat from staying in the substrate for mounting electronic element  1  and to improve the heat dissipation of the substrate for mounting electronic element  1 . As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, if the heat conduction of the second substrate  12  is larger than the heat conduction of the first substrate  11  and smaller than the heat conduction of the plurality of heat dissipation bodies  13  in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned (the x direction in  FIGS.  1 A to  4 B ), if the heat generated in the electronic element  2  or the metal layer  14  is transferred toward the second substrate  12  via the first substrate  11 , heat is favorably transferred in the second substrate  12  and heat dissipation is facilitated, and if heat is diffused and transferred in the thickness direction of the plurality of heat dissipation bodies  13  to the adjacent heat dissipation bodies  13  via the second substrate  12 , heat can be satisfactorily transferred in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned at the boundary between the second substrate  12  and the heat dissipation body  13 . Therefore, if the electronic element  2  is operated, the heat dissipation of the substrate for mounting electronic element  1  becomes good, and thus the distortion of the substrate for mounting electronic element  1  can be suppressed and the electronic element  2  can be operated for a long time. Also, since heat can be satisfactorily transferred in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a  at the boundary between the second substrate  12  and the heat dissipation body  13 , if the electronic element  2  is operated, the heat dissipation of the substrate for mounting electronic element  1  becomes good. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed and the electronic element  2  can be operated for a long time. 
     Further, if the heat conduction of the second substrate  12  is larger than the heat conduction of the plurality of heat dissipation bodies  13  in the direction in which the plurality of heat dissipation bodies  13  are aligned (they direction in  FIGS.  1 A to  4 B ) and is smaller than the heat conduction of the plurality of heat dissipation bodies  13  in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned (the x direction in  FIGS.  1 A to  4 B ), even if heat is transferred to the adjacent heat dissipation body  13  via the second substrate  12 , it is difficult to transfer heat in the direction in which the plurality of heat dissipation bodies  13  are aligned at the boundary between the second substrate  12  and the heat dissipation body  13  (the y direction in  FIGS.  1 A to  4 B ) and it is easy to transfer heat in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned (the x direction in  FIGS.  1 A to  4 B ). Therefore, the heat transferred from the second substrate  12  can be restrained from being transferred toward the electronic element  2 , and the heat of the second substrate  12  can be satisfactorily transferred in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned. Thus, if the electronic element  2  is operated, the heat dissipation of the substrate for mounting electronic element  1  becomes good, the distortion of the substrate for mounting electronic element  1  can be suppressed, and thus the electronic element  2  can be operated for a long time. In addition, the heat transferred from the second substrate  12  can be satisfactorily transferred in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a,  and even if the electronic element  2  is continuously operated for a long period of time, the heat dissipation of the substrate for mounting electronic element  1  will be good. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed and the electronic element  2  can be continuously operated for a long period of time. 
     Especially if an optical element such as LD or LED is mounted as the electronic element  2 , by suppressing the distortion of the substrate for mounting electronic element  1 , it is possible to make the substrate for mounting electronic element  1  for an optical device capable of accurately emitting light. 
     The substrate for mounting electronic element  1  according to the embodiment can be suitably used in a thin and high-power electronic device and the reliability of the substrate for mounting electronic element  1  can be improved. For example, if an optical element such as an LD or LED is mounted as the electronic element  2 , it can be preferably used as a substrate for mounting electronic element  1  for an optical device that is thin and has excellent directivity. 
     If the plurality of heat dissipation bodies  13  are larger than (larger than the electronic element  2 ) the mounting portion  11   a  in a transparent plan view as in the example illustrated in  FIGS.  1 A to  4 B , the heat of the electronic element  2  is satisfactorily transferred to the heat dissipation body  13 , which is located so as to overlap with the electronic element  2  in a transparent plan view, and heat is easily satisfactorily transferred in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned, and further heat transfer is suppressed in the direction in which the plurality of heat dissipation bodies  13  adjacent to the electronic element  2  are aligned. Therefore, the distortion of the substrate for mounting electronic element  1  can be suppressed. Further, heat transfer in the longitudinal direction of the at least one mounting portion  11   a  is suppressed via the heat dissipation body  13 , and thus it is possible to restrain heat from staying in the substrate for mounting electronic element  1  and suppress distortion of the substrate for mounting electronic element  1 . 
     If the metal layer  14  does not overlap with the heat dissipation body  13  in a transparent plan view as in the example illustrated in  FIGS.  1 A to  4 B , that is, is arranged outside the outer edge of the heat dissipation body  13 , the heat of the electronic element  2  is more easily transferred toward the heat dissipation body  13  than the metal layer  14 , and the heat of the electronic element  2  is hard to be transferred to the position facing the electronic element  2  via the metal layer  14 . As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed well. 
     Further, in a plan view (a transparent plan view), the metal layers  14  are located so as to interpose the heat dissipation body  13  in the direction in which the plurality of heat dissipation bodies  13  are aligned, the heat transmitted to the metal layer  14  becomes more easily dissipated in the metal layer  14 , and the heat transfer in the direction in which the heat dissipation bodies  13  adjacent to the electronic element  2  are aligned via the metal layer  14  is suppressed. Therefore, the heat of the electronic element  2  is satisfactorily transferred to the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned via the heat dissipation body  13 , and thus the distortion of the substrate for mounting electronic element  1  can be suppressed more effectively. 
     Further, if the metal layer  14  and the heat dissipation body  13  are alternately located in the direction in which the plurality of heat dissipation bodies  13  are aligned in a plan view (a transparent plan view), the heat transferred to the metal layer  14  is effectively dissipated in the metal layer  14  and the heat transfer in the direction in which the heat dissipation bodies  13  adjacent to the electronic element  2  are aligned via the metal layer  14  is suppressed. Therefore, the heat of the electronic element  2  is satisfactorily transferred via the heat dissipation body  13  in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed better. 
     In a longitudinal cross-sectional view in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned, as shown in the example illustrated in  FIG.  2   , if the plurality of heat dissipation bodies  13  have greater heat conduction in the thickness direction (the z direction in  FIGS.  1 A to  4 B ) than in the direction perpendicular to the thickness direction (the y direction in  FIGS.  1 A to  4 B ), heat transfer in the direction in which the plurality of heat dissipation bodies  13  are aligned can be suppressed and heat transfer in the thickness direction of the plurality of heat dissipation bodies  13  can be increased. Therefore, it is possible to restrain heat from staying in the substrate for mounting electronic element  1  and to improve the heat dissipation of the substrate for mounting electronic element  1 . As a result, distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Since the heat conduction in the direction (the x direction in  FIGS.  1 A to  4 B ) perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned and in the thickness direction (the z direction in  FIGS.  1 A to  4 B ) of the plurality of heat dissipation bodies  13  is greater than the thermal conductivity in the direction in which the plurality of heat dissipation bodies  13  are aligned (they direction in  FIGS.  1 A to  4 B ), it is possible to suppress heat transfer in the direction in which the plurality of heat dissipation bodies  13  are aligned and to improve heat dissipation of the substrate for mounting electronic element  1 . As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, as in the example illustrated in  FIGS.  1 A to  4 B , in a plan view, the plurality of heat dissipation bodies  13  are located in series in the longitudinal direction of the first substrate  11 , each heat dissipation body  13  suppresses heat transfer in the longitudinal direction of the first substrate  11 , and thus the heat of the electronic element  2  can be satisfactorily transferred via the heat dissipation body  13  in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned. 
     In accordance with the electronic device according to the embodiment, by including the substrate for mounting electronic element  1  including the above configuration, the electronic element  2  mounted on the mounting portion  11   a  of the substrate for mounting electronic element  1 , and the wiring substrate  4  on which the substrate for mounting electronic element  1  is to be mounted or the package for housing the electronic element  5 , the electronic device having excellent long-term reliability can be provided. 
     In accordance with the electronic module according to the embodiment, by having the electronic device including the above configuration and the module substrate  6  to which the electronic device is to be connected, it is possible to provide excellent long-term reliability. 
     Second Embodiment 
     Next, a substrate for mounting electronic element according to a second embodiment will be described with reference to  FIGS.  5  to  6 B . 
     In the substrate for mounting electronic element  1  according to the second embodiment, a difference from the substrate for mounting electronic element  1  of the above-described embodiment is that a third substrate  16  is located on the fourth surface  122  of the second substrate  12  and the sixth surfaces  132  of the plurality of heat dissipation bodies  13 . That is, the heat dissipation body  13  located in the through hole  12   a  of the second substrate  12  is covered with the first substrate  11  and the third substrate  16  and the second substrate  12  so as not to be exposed. 
     In the example illustrated in  FIGS.  5  to  6 B , in the substrate for mounting electronic element  1 , three heat dissipation bodies  13  are located in series within the through holes  12   a  of the second substrate  12 , and four metal layers  14  are located on the first surface  111  of the first substrate  11 . 
     The plurality of heat dissipation bodies  13  are shaded in the example illustrated in  FIG.  5   . The metal layer  14  and a mounting layer  15  are shaded in the example illustrated in  FIGS.  6 A and  6 B . In the example illustrated in  FIG.  6 A , a region overlapping with the outer surface of the heat dissipation body  13  of the first substrate  11  in a transparent plan view is shown by a broken line. In the example illustrated in  FIG.  2   , in the first substrate  11  and the third substrate  16 , the outer surface of the first substrate  11  which is invisible in a perspective view is indicated by a broken line. In the example illustrated in  FIG.  5   , in the second substrate  12 , the outer surface of the second substrate  12  and the inner surface of the through hole  12   a  which are invisible in a perspective view are shown by broken lines. The mounting portion  11   a  of the electronic element  2  is arranged so as to overlap the heat dissipation body  13  if seen in a transparent plan view. 
     The third substrate  16  includes a seventh surface  161  (an upper surface in  FIGS.  5  to  6 B ) facing the fourth surface  122  of the second substrate  12  and the sixth surfaces  132  of the plurality of heat dissipation bodies  13  and an eighth surface  162  (a lower surface in  FIGS.  5  to  6 B ) opposite to the seventh surface  161 . The third substrate  16  has a rectangular plate-like shape including two sets of opposing sides (4 sides) with respect to each of the seventh surface  161  and the eighth surface  162  in a plan view. 
     Since the third substrate  16  includes the seventh surface  161  facing the fourth surface  122  of the second substrate  12  and the sixth surfaces  132  of the plurality of heat dissipation bodies  13  and the eighth surface  162  opposite to the seventh surface  161 , the distortion of the substrate for mounting electronic element  1  due to the difference in thermal expansion between the first substrate  11  and the second substrate  12  and the plurality of heat dissipation bodies  13  is suppressed and the displacement of the electronic element  2  or the distortion of the substrate for mounting electronic element  1  is suppressed. As a result, the electronic element  2  can be operated for a long time. 
     The third substrate  16  can be manufactured by using the same material and method as those of the first substrate  11  described above. As in the example illustrated in  FIGS.  6 A and  6 B , as similar to the first substrate  11 , the thermal conductivity λy of the third substrate  16  is substantially constant in the x and y directions in the planar direction, and the thermal conductivity in the z direction, which is the thickness direction, of the third substrate  16  is also the same as the thermal conductivity in the x and y directions in the planar direction (λγx≈λγy≈λγz). For example, if an aluminum nitride sintered body is used as the third substrate  16 , a substrate having a thermal conductivity λy of about 100 to 200 W/m·K is used as the third substrate  16 . 
     In the substrate for mounting electronic element  1  according to the second embodiment, the second surface  112  of the first substrate  11 , the third surface  121  of the second substrate  12 , and the fifth surfaces  131  of the plurality of heat dissipation bodies  13  are joined by a bonding material such as an active brazing material made of TiCuAg alloy, TiSnAgCu alloy, or the like. Also, the seventh surface  161  of the third substrate  16 , the fourth surface  122  of the second substrate  12 , and the sixth surfaces  132  of the plurality of heat dissipation bodies  13  are joined by a bonding material such as an active brazing material made of TiCuAg alloy, TiSnAgCu alloy, or the like. 
     Also in the substrate for mounting electronic element  1  according to the second embodiment, as similar to the first embodiment, the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16  are quadrangular in a plan view. A quadrangular composite substrate is formed by bonding the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16 . In the example shown in  FIGS.  5  to  6 B , the first substrate  11 , the second substrate  12 , and the third substrate  16  have a rectangular shape and a rectangular composite substrate is formed. 
     The first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrates  16  may be joined at the same time. For example, the heat dissipation body  13  may be located in the through hole  12   a  of the second substrate  12  and the first substrate  11  and the third substrate  16  may be joined to the second substrate  12  and the plurality of heat dissipation bodies  13  to form the same. In this case, for example, by joining while applying pressure from the first surface  111  side of the first substrate  11  and the eighth surface  162  side of the third substrate  16 , the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16  are well bonded to each other, and thus the substrate for mounting electronic element  1  having excellent reliability can be obtained. Also, by bonding the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16  at the same time, it is possible to suppress the exposure of the plurality of heat dissipation bodies  13  during manufacturing, and thus the deterioration due to the outside air can be suppressed. 
     Since the second substrate  12  and the plurality of heat dissipation bodies  13  are located between the first substrate  11  and the third substrate  16 , the distortion of the substrate for mounting electronic element  1  due to the difference in thermal expansion between the first substrate  11  and the second substrate  12  and the plurality of heat dissipation bodies  13  is suppressed. Therefore, by suppressing the displacement of the electronic element  2  or the distortion of the substrate for mounting electronic element  1 , favorable light emission can be facilitated. 
     In particular, if the third substrate  16  uses a substrate of the same material as the first substrate  11 , that is, if using an aluminum nitride sintered body with 150 W/m·K for example, as the first substrate  11 , if the aluminum nitride sintered body with 150 W/m·K is used as the third substrate  16 , the distortion of the substrate for mounting electronic element  1  is more effectively suppressed. As a result, the light can be easily emitted favorably. 
     The substrate thickness T 1  of the first substrate  11  is, for example, about 50 μm to 500 μm and the substrate thickness T 2  of the second substrate  12  is, for example, about 100 μm to 2000 μm. The substrate thickness T 3  of the plurality of heat dissipation bodies  13  is, for example, about 100 μm to 2000 μm. 
     The substrate thickness of the third substrate  16  is, for example, about 50 μm to 500 μm, as similar to the substrate thickness T 1  of the first substrate  11 . If the substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  are located at the same thickness within a range of about 10% (0.90T 1 ≤T 4 ≤1.10T 1 ), by suppressing the distortion of the substrate for mounting electronic element  1  more effectively, it is possible to easily satisfactorily emit light. For example, if the substrate thickness of the first substrate  11  is 100 μm, the substrate thickness of the third substrate  16  may be 100 μm (90 μm to 110 μm). 
     The substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  may be smaller than the substrate thickness T 3  of the plurality of heat dissipation bodies  13  (T 3 &gt;T 1 , T 3 &gt;T 4 ). 
     Further, as illustrated in the examples of  FIGS.  5  to  6 B , the mounting layer  15  may be located in the mounting portion  11   a  of the first substrate  11 . The mounting layer  15  is used as a mounting area for the electronic element  2 . Joining the substrate for mounting electronic element  1  and the electronic element  2  or the heat dissipation of the electronic element  2  to the substrate for mounting electronic element  1  can be made favorable. The mounting layer  15  may be smaller than the plurality of heat dissipation bodies  13  in a transparent plan view. The mounting layer  15  can be manufactured by a method similar to that of the metal layer  14  described above. 
     In addition, the third substrate  16  may include a bonding layer located on the eighth surface  162  side. The bonding layer located on the third substrate  16  can be used for bonding the substrate for mounting electronic element  1  and the conductor layer located on the wiring substrate  4  or the package for housing electronic element  5 , for example. The bonding layer can be manufactured by a method similar to that of the metal layer  14  described above. In addition, the bonding layer is located on substantially the entire lower surface of the third substrate  16  so as to cover the plurality of heat dissipation bodies  13  in a transparent plan view, and thus the heat dissipation from the substrate for mounting electronic element  1  to the wiring substrate  4  or the package for housing electronic element  5  can be made favorable. 
     The mounting layer  15  and the bonding layer include a plating layer on the surface thereof, similar to the metal layer  14 . 
     Further, as in the example illustrated in  FIGS.  7  to  8 B , the plurality of heat dissipation bodies  13  may have a circular shape, a polygonal shape, or the like in a plan view. 
     The substrate for mounting electronic element  1  according to the second embodiment can be manufactured by using the same manufacturing method as that of the substrate for mounting electronic element  1  according to the above embodiment. 
     Third Embodiment 
     Next, an electronic device according to a third embodiment will be described with reference to  FIGS.  9  to  10 B . 
     In the substrate for mounting electronic element  1  according to the third embodiment, a difference from the substrates for mounting electronic element  1  according to the above-described embodiments is that the heat dissipation body  13  is longer in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned than in the direction in which the plurality of heat dissipation bodies  13  are aligned. 
     In the example illustrated in  FIGS.  9  to  10 B , in the substrate for mounting electronic element  1 , the three heat dissipation bodies  13  are located in series within the through holes  12   a  of the second substrate  12 , and the four metal layers  14  are located on the first surface  111  of the first substrate  11 . 
     The plurality of heat dissipation bodies  13  are shaded in the example illustrated in  FIG.  9   . The metal layer  14  and the mounting layer  15  are shaded in the example illustrated in  FIGS.  10 A and  10 B . In the example illustrated in  FIG.  10 A , a region overlapping with the outer surfaces of the plurality of heat dissipation bodies  13  of the first substrate  11  in a transparent plan view is shown by a broken line. In the example illustrated in  FIG.  9   , in the first substrate  11  and the third substrate  16 , the outer surface of the first substrate  11  which is invisible in a perspective view is illustrated by a broken line. In the example illustrated in  FIG.  9   , in the second substrate  12 , the outer surface of the second substrate  12  and the inner surface of the through hole  12   a  which are invisible in a perspective view are illustrated by broken lines. The mounting portion  11   a  of the electronic element  2  is arranged so as to overlap the heat dissipation body  13  if seen in a transparent plan view. 
     In the substrate for mounting electronic element  1  according to the third embodiment, if the heat dissipation body  13  is long in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned, the heat transfer in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned can be further increased. Therefore, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, if the plurality of heat dissipation bodies  13 , as in the example illustrated in  FIGS.  9  to  10 B , extend in the side surface of the substrate for mounting electronic element  1  in a direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned, the heat transfer between the electronic elements  2  is suppressed, and thus the heat dissipation of the substrate for mounting electronic element  1  is improved. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, a member having a high heat conduction may be brought into contact with the exposed side surfaces of the plurality of heat dissipation bodies  13  to enhance the heat dissipation property. 
     In the substrate for mounting electronic element  1  according to the third embodiment, the substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  are, for example, about 50 μm to 500 μm, and the substrate thickness T 2  of the second substrate  12  and the substrate thickness T 3  of the plurality of heat dissipation bodies  13  are, for example, about 100 μm to 2000 μm. 
     Further, also in the substrate for mounting electronic element  1  according to the third embodiment, similar to the substrate for mounting electronic element  1  according to the second embodiment, the mounting layer  15  may be smaller than the heat dissipation body  13  and may be located inside the heat dissipation body  13  in a transparent plan view. 
     Further, also in the substrate for mounting electronic element  1  according to the third embodiment, if the substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  are located at the same thickness within a range of about 10% (0.90T 1 ≤T 4 ≤1.10T 1 ), by suppressing the distortion of the substrate for mounting electronic element  1  more effectively, it is possible to easily satisfactorily emit light. For example, if the substrate thickness T 1  of the first substrate  11  is 100 μm, the substrate thickness T 4  of the third substrate  16  may be 100 μm (90 μm to 110 μm). 
     The substrate for mounting electronic element  1  according to the third embodiment can be manufactured by the same method as the substrates for mounting electronic element  1  according to the above-described embodiments. 
     Fourth Embodiment 
     Next, an electronic device according to a fourth embodiment will be described with reference to  FIGS.  11  to  12 B . 
     In the substrate for mounting electronic element  1  according to the fourth embodiment, a difference from the substrates for mounting electronic element  1  according to the above-described embodiments is that the sizes of the plurality of heat dissipation bodies  13  are different in a transparent plan view. 
     In the example illustrated in  FIGS.  11  to  12 B , in the substrate for mounting electronic element  1 , the three heat dissipation bodies  13  are located in series in the through holes  12   a  of the second substrate  12 , and the four metal layers  14  are located on the first surface  111  of the first substrate  11 . 
     The plurality of heat dissipation bodies  13  are shaded in the example illustrated in  FIG.  11   . The metal layer  14  and the mounting layer  15  are shaded in the example illustrated in  FIGS.  12 A and  12 B . In the example illustrated in  FIG.  12 A (a), a region overlapping the outer surfaces of the plurality of heat dissipation bodies  13  of the first substrate  11  in a transparent plan view is shown by a broken line. In the example illustrated in  FIG.  11   , in the first substrate  11  and the third substrate  16 , the outer surface of the first substrate  11  which is invisible in a perspective view are shown by a broken line. In the example illustrated in  FIG.  11   , in the second substrate  12 , the outer surface of the second substrate  12  and the inner surface of the through hole  12   a  which are invisible in a perspective view are shown by broken lines. The mounting portion  11   a  of the electronic element  2  is arranged so as to overlap the heat dissipation body  13  if seen in a transparent plan view. 
     In the plurality of heat dissipation bodies  13 , as seen in a transparent plan view, as in the example illustrated in  FIGS.  11  to  12 B , if the size of the heat dissipation body  13  arranged near the central portion of the substrate for mounting electronic element  1  is larger than the size of the heat dissipation body  13  arranged near the outer peripheral portion of the substrate for mounting electronic element  1 , heat transfer in the direction perpendicular to the longitudinal direction of the first substrate  11  in the vicinity of the central portion can be increased. Therefore, it is possible to suppress heat from staying in the first substrate  11  and heat dissipation of the substrate for mounting electronic element  1  is improved. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     The substrate for mounting electronic element  1  according to the fourth embodiment can be preferably used in an electronic device in which the plurality of mounted electronic elements  2  have different sizes. Further, as in the example illustrated in  FIGS.  12 A and  12 B , the sizes of the mounting layer  15  may be different in a plan view. 
     The substrate for mounting electronic element  1  according to the fourth embodiment can be manufactured by using the same manufacturing method as those of the substrates for mounting electronic element  1  according to the above-described embodiments. 
     Fifth Embodiment 
     Next, an electronic device according to a fifth embodiment will be described with reference to  FIGS.  13  to  14 B . 
     In the substrate for mounting electronic element  1  according to the fifth embodiment, a difference from the substrates for mounting electronic element  1  according to the above-described embodiments is that the plurality of heat dissipation bodies  13  are arranged in a direction in which the plurality of heat dissipation bodies  13  are aligned and in a direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned. 
     In the example illustrated in  FIGS.  13  to  14 B , the substrate for mounting electronic element  1  includes the twelve heat dissipation bodies  13  located in the through holes  12   a  of the second substrate  12 , and the two metal layers  14  are located on the first surfaces  111  of the first substrate  11 . 
     The plurality of heat dissipation bodies  13  are shaded in the example illustrated in  FIG.  13   . The metal layer  14  and the mounting layer  15  are shaded in the example illustrated in  FIGS.  14 A and  14 B . In the example illustrated in  FIGS.  14 A and  14 B , a region overlapping with the outer surfaces of the plurality of heat dissipation bodies  13  of the first substrate  11  in a transparent plan view is shown by a broken line. In the example illustrated in  FIG.  13   , in the first substrate  11  and the third substrate  16 , the outer surface of the first substrate  11  which is invisible in a perspective view is shown by a broken line. In the example illustrated in  FIG.  13   , in the second substrate  12 , the outer surface of the second substrate  12  and the inner surface of the through hole  12   a  which are invisible in a perspective view are shown by broken lines. The mounting portion  11   a  of the electronic element  2  is arranged so as to overlap the heat dissipation body  13  if seen in a transparent plan view. 
     If an interval L 1  between the adjacent heat dissipation bodies  13  in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned (the x direction in  FIGS.  14 A and  14 B ) is larger than an interval L 2  between the heat dissipation bodies  13  adjacent to each other in the direction in which the plurality of heat dissipation bodies  13  are aligned (the y direction in  FIGS.  14 A and  14 B ) (L 1 &gt;L 2 ), it is possible to reduce heat transfer in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned. Therefore, heat dissipation of the substrate for mounting electronic element  1  is improved, and thus the distortion of the substrate for mounting electronic element  1  can be suppressed. In particular, the interval L 1  between the adjacent heat dissipation bodies  13  in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned may be at least twice the interval L 2  between the adjacent heat dissipation bodies  13  in the direction in which the plurality of heat dissipation bodies  13  may be aligned (L 1 &gt;2L 2 ). 
     Also, as in the example illustrated in  FIGS.  15 A and  15 B , with the arrangement in the direction in which the plurality of heat dissipation bodies  13  are aligned (the y direction in  FIGS.  15 A and  15 B ) and the arrangement in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned (the x direction in  FIGS.  15 A and  15 B ), if the heat dissipation bodies  13  are arranged so as to be displaced in the direction in which the plurality of heat dissipation bodies  13  are aligned, the distance between the electronic elements  2  adjacent to each other in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned is increased and the heat dissipation of the substrate for mounting electronic element  1  is improved. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     In the example illustrated in  FIGS.  13  to  15 B , the heat dissipation body  13  is arranged in three rows in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned. However, two or four or more rows may be arranged in the direction perpendicular to the direction in which the plurality of heat dissipation bodies  13  are aligned. 
     Sixth Embodiment 
     Next, an electronic device according to a sixth embodiment will be described with reference to  FIGS.  16 A to  19 B . 
     In the substrate for mounting electronic element  1  according to the sixth embodiment, a difference from the substrates for mounting electronic element  1  according to the above-described embodiments is that the plurality of heat dissipation bodies  13  are located in a matrix inside the second substrate  12 . In addition, the first surface  111  includes the at least one mounting portion  11   a  for the electronic element  2  which is a longitudinal region, and the one mounting portion  11   a  is provided in the examples illustrated in  FIGS.  16 A to  20 B . The one mounting portion  11   a  has a rectangular shape in which one end in the longitudinal direction is located at the outer edge of the first surface  111 . 
     In the examples illustrated in  FIGS.  16 A to  19 B , the substrate for mounting electronic element  1  includes the twelve heat dissipation bodies  13  in a transparent plan view. With respect to the arrangement of the twelve heat dissipation bodies  13 , four heat dissipation bodies are arranged side by side in terms of the longitudinal direction (the y direction in  FIGS.  16 A to  19 B ) of the mounting portion  11   a,  and three heat dissipation bodies are arranged side by side in terms of the direction perpendicular to the longitudinal direction (the x direction in  FIGS.  16 A to  19 B ) of the mounting portion  11   a.    
     The through hole  12   a  of the second substrate  12  has a polygonal shape such as a rectangular shape or a circular shape in a plan view. The through hole  12   a  has a quadrangular shape in a plan view in the example illustrated in  FIGS.  16 A to  19 B . The second substrate  12  includes the plurality of through holes  12   a  arranged side by side in a matrix in a plan view. In the example illustrated in  FIGS.  16 A to  19 B , the four through holes  12   a  are arranged in the longitudinal direction (y direction in  FIGS.  16 A to  19 B ) and the three through holes  12   a  are arranged in the direction (x direction in  FIGS.  16 A to  19 B ) perpendicular to the longitudinal direction, and thus the second substrate  12  has the twelve through holes  12   a  in a plan view in the example illustrated in  FIGS.  16 A to  19 B . Each of the twelve through holes  12   a  has the heat dissipation body  13   a  located therein. In addition, in the examples illustrated in  FIGS.  16 A to  19 B , the second substrate  12  includes a plurality of lattice portions located in a matrix in a plan view. 
     The fifth surfaces  131  of the plurality of heat dissipation bodies  13  are located on the third surface  121  side of the second substrate  12 , and the sixth surfaces  132  of the plurality of heat dissipation bodies  13  are located on the fourth surface  122  side. Some of the plurality of heat dissipation bodies  13  are located so as to overlap the mounting portion  11   a  in a transparent plan view, as in the example illustrated in  FIGS.  16 A to  19 B . 
     In the example illustrated in  FIGS.  16 A to  19 B , in the substrate for mounting electronic element  1 , in a transparent plan view, four heat dissipation bodies are arranged side by side in the longitudinal direction, and three heat dissipation bodies are arranged side by side in the direction perpendicular to the longitudinal direction, and thus a total of the twelve heat dissipation bodies  13  are located in the through holes  12   a  of the second substrate  12 . 
     The metal layer  14  located on the first surface  111  of the first substrate  11  is used as the mounting portion  11   a  of the electronic element  2  or a connecting portion of the connecting member  3  such as a bonding wire, and the metal layer  14  is a member for electrically connecting the electronic element  2  and the wiring conductor of the wiring substrate  4 . 
     In a longitudinal cross-sectional view of the at least one mounting portion  11   a  in the longitudinal direction, if the heat conduction of the plurality of heat dissipation bodies  13  in the thickness direction (the z direction in  FIGS.  16 A to  19 B ) is greater than the heat conduction of the plurality of heat dissipation bodies  13  in the direction perpendicular to the thickness direction (the y direction in  FIGS.  16 A to  19 B ), the heat transfer to the longitudinal direction of the at least one mounting portion  11   a  is suppressed, and thus the heat is less likely to stay in the at least one mounting portion  11   a.  Therefore, it becomes easy to radiate heat to the fourth surface  122  side of the second substrate  12  and the sixth surface  132  side of the plurality of heat dissipation bodies  13 . As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Also, in the plurality of heat dissipation bodies  13 , the heat conduction in the direction perpendicular to the longitudinal direction (the x direction in  FIGS.  16 A to  19 B ) of the at least one mounting portion  11   a  and the thickness direction (the z direction in  FIGS.  16 A to  19 B ) of the plurality of heat dissipation bodies  13  is greater than the heat conduction in the longitudinal direction (they direction in  FIGS.  16 A to  19 B ) of the at least one mounting portion  11   a.  Therefore, it is possible to suppress heat transfer in the longitudinal direction of at least one mounting portion  11   a  and improve the heat dissipation of the substrate for mounting electronic element  1 . As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, as seen in a transparent plan view, if the plurality of heat dissipation bodies  13  are located in a matrix inside the second substrate  12 , it is possible to suppress heat transfer in the longitudinal direction of the at least one mounting portion  11   a  and increase the heat transfer in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a.  Therefore, it is possible to restrain heat from staying in the substrate for mounting electronic element  1  and to improve the heat dissipation of the substrate for mounting electronic element  1  so that the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     In addition, in the plurality of heat dissipation bodies  13 , the third surface  121  and the side surfaces are well retained, and thus good heat transfer can be achieved between the first substrate  11  and the plurality of heat dissipation bodies  13  and between the second substrate  12  and the plurality of heat dissipation bodies  13 . Therefore, heat dissipation of the substrate for mounting electronic element  1  is improved. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, if the heat conduction of the second substrate  12  is higher than the heat conduction of the first substrate  11  and lower than the heat conduction in the direction perpendicular to the longitudinal direction (the x direction in  FIGS.  16 A to  19 B ) of the at least one mounting portion  11   a,  if the heat generated in the electronic element  2  or the metal layer  14  is transferred toward the second substrate  12  through the first substrate  11 , good heat transfer is carried out in the second substrate  12  and this facilitates heat dissipation, and if heat is diffused in the thickness direction of the plurality of heat dissipation bodies  13  to the adjacent heat dissipation bodies  13  via the second substrate  12 , heat can be satisfactorily transferred in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a  at the boundary between the second substrate  12  and the heat dissipation body  13 . Therefore, even if the electronic element  2  is continuously operated for a long period of time, the heat dissipation of the substrate for mounting electronic element  1  is carried out satisfactorily. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed and the electronic element  2  can be continuously operated for a long period of time. 
     Further, if the heat conduction of the second substrate  12  is higher than the heat conduction of the plurality of heat dissipation bodies  13  in the longitudinal direction of the at least one mounting portion  11   a  and is smaller than the heat conduction of the plurality of heat dissipation bodies  13  in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a,  even if heat is transferred to the adjacent heat dissipation body  13  via the second substrate  12 , it is difficult to transfer heat in the longitudinal direction of the at least one mounting portion  11   a  at the boundary between the second substrate  12  and the heat dissipation body  13  and it is easy to transfer heat in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a.  Therefore, it is possible to restrain the heat transferred from the second substrate  12  from being transferred toward the electronic element  2 , and the heat of the second substrate  12  can be satisfactorily transferred to the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a.  Thus, even if the electronic element  2  is continuously operated for a long period of time, the heat dissipation of the substrate for mounting electronic element  1  is carried out satisfactorily. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed and the electronic element  2  can be continuously operated for a long period of time. 
     Also, as in the example illustrated in  FIGS.  20 A and  20 B , if, with the arrangement in the longitudinal direction (y direction in  FIGS.  20 A and  20 B ) of the at least one mounting portion  11   a  and the arrangement in the direction (x direction in  FIGS.  20 A and  20 B ) perpendicular to the longitudinal direction of the at least one mounting portion  11   a,  the heat dissipation body  13  is arranged to be displaced in the longitudinal direction of the at least one mounting portion  11   a,  in any region of the mounting portions  11   a,  the heat dissipation body  13  is located in a direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a.  Therefore, by eliminating the region where the heat dissipation body  13  is not located in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a,  in each region, the heat dissipation of the substrate for mounting electronic element  1  becomes good, and thus the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     The substrate for mounting electronic element  1  according to the sixth embodiment can be manufactured by using the same manufacturing method as those of the substrates for mounting electronic element  1  according to the above embodiments. 
     Seventh Embodiment 
     Next, a substrate for mounting electronic element according to a seventh embodiment will be described with reference to  FIGS.  21  to  22 B . 
     In the substrate for mounting electronic element  1  according to the seventh embodiment, a difference from the substrate for mounting electronic element  1  according to the sixth embodiment described above is that the third substrate  16  is located on the fourth surface  122  of the second substrate  12  and the sixth surfaces  132  of the plurality of heat dissipation bodies  13 . That is, the heat dissipation body  13  located in the through hole  12   a  of the second substrate  12  is covered with the first substrate  11 , the third substrate  16 , and the second substrate  12  so as not to be exposed. 
     In the example illustrated in  FIGS.  21  to  22 B , the substrate for mounting electronic element  1  includes the twelve heat dissipation bodies  13  in a transparent plan view. With respect to the arrangement of the twelve heat dissipation bodies  13 , four heat dissipation bodies are arranged side by side in terms of the longitudinal direction (the y direction in  FIGS.  21  to  22 B ), and three heat dissipation bodies are arranged side by side in terms of the direction perpendicular to the longitudinal direction (the x direction in  FIGS.  21  to  22 B ). 
     The plurality of heat dissipation bodies  13  are shaded in the example illustrated in  FIG.  21   . The metal layer  14  is shaded in the example illustrated in  FIGS.  22 A and  22 B . In the example illustrated in  FIGS.  22 A and  22 B , in the second substrate  12 , the outer surface of the second substrate  12  and the inner surface of the through hole  12   a  which are invisible in a perspective view are shown by broken lines. Further, the mounting portion  11   a  of the electronic element  2  is arranged so as to overlap with some of the plurality of heat dissipation bodies  13  in a transparent plan view. 
     The third substrate  16  includes a seventh surface  161  (an upper surface in  FIGS.  21  to  22 B ) facing the fourth surface  122  of the second substrate  12  and the sixth surfaces  132  of the plurality of heat dissipation bodies  13  and an eighth surface  162  (a lower surface in  FIGS.  21  to  22 B ) opposite to the seventh surface  161 . Therefore, the distortion of the substrate for mounting electronic element  1  due to the difference in thermal expansion between the first substrate  11  and the second substrate  12  and the plurality of heat dissipation bodies  13  is suppressed, and thus the electronic element  2  can be operated for a long period of time while suppressing the displacement of the electronic element  2  or the distortion of the substrate for mounting electronic element  1 . The third substrate  16  has a rectangular plate-like shape including two sets of opposing sides (four sides) with respect to each of the seventh surface  161  and the eighth surface  162  in a plan view. 
     The third substrate  16  can be manufactured by using the same material and method as those of the first substrate  11  described above. As in the example illustrated in  FIG.  21   , as in the case of the first substrate  11 , the thermal conductivity κγ of the third substrate  16  is substantially constant in the x direction and the y direction in the planar direction, and the thermal conductivity in the z direction which is the thickness direction of the third substrate  16  is also the same as the thermal conductivity in the x direction and the y direction in the planar direction (κγx≈κγy≈κγz). For example, if an aluminum nitride sintered body is used as the third substrate  16 , as the third substrate  16 , a substrate having a thermal conductivity κγ of about 100 to 200 W/m·K is used. 
     In the substrate for mounting electronic element  1  according to the seventh embodiment, the second surface  112  of the first substrate  11 , the third surface  121  of the second substrate  12 , and the fifth surfaces  131  of the plurality of heat dissipation bodies  13  are joined by a bonding material such as an active brazing material made of TiCuAg alloy, TiSnAgCu alloy, or the like. The seventh surface  161  of the third substrate  16 , the fourth surface  122  of the second substrate  12 , and the sixth surfaces  132  of the plurality of heat dissipation bodies  13  are joined by a bonding material such as an active brazing material made of TiCuAg alloy, TiSnAgCu alloy, or the like. 
     Also in the substrate for mounting electronic element  1  according to the seventh embodiment, similar to the above-described embodiments, the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16  have a quadrangular shape in a plan view. A quadrangular composite substrate is formed by bonding the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16  to each other. In the example illustrated in  FIGS.  21  to  22 B  the first substrate  11 , the second substrate  12 , and the third substrate  16  have a rectangular shape, and thus a rectangular composite substrate is formed. 
     The first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrates  16  may be joined at the same time. For example, the heat dissipation body  13  may be located in the through hole  12   a  of the second substrate  12 , and the first substrate  11  and the third substrate  16  may be joined to the second substrate  12  and the plurality of heat dissipation bodies  13  to form the same. In this case, for example, by bonding while applying pressure from the first surface  111  side of the first substrate  11  and the eighth surface  162  side of the third substrate  16 , the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16  are well joined to each other, and thus the substrate for mounting electronic element  1  having excellent reliability can be obtained. Also, by bonding the first substrate  11 , the second substrate  12 , the plurality of heat dissipation bodies  13 , and the third substrate  16  at the same time, it is possible to suppress the exposure of the plurality of heat dissipation bodies  13  during manufacturing and suppress the deterioration due to the outside air. 
     Since the second substrate  12  and the plurality of heat dissipation bodies  13  are located between the first substrate  11  and the third substrate  16 , the distortion of the substrate for mounting electronic element  1  due to the difference in thermal expansion between the first substrate  11 , the second substrate  12  and the plurality of heat dissipation bodies  13  is suppressed. Therefore, by suppressing the displacement of the electronic element  2  or the distortion of the substrate for mounting electronic element  1 , the light can be easily emitted favorably. 
     In particular, if the third substrate  16  uses a substrate of the same material as the first substrate  11 , that is, for example, if using an aluminum nitride sintered body with 150 W/m·K as the first substrate  11 , if an aluminum nitride sintered body with 150 W/m·K is used as the third substrate  16 , the distortion of the substrate for mounting electronic element  1  is more effectively suppressed. As a result, favorable light emission can be facilitated. 
     The substrate thickness T 1  of the first substrate  11  is, for example, about 50 μm to  500  μm, and the substrate thickness T 2  of the second substrate  12  is, for example, about 100 μm to 2000 μm. The substrate thickness T 3  of the plurality of heat dissipation bodies  13  is, for example, about 100 μm to 2000 μm. 
     Further, the substrate thickness T 4  of the third substrate  16  is, for example, about 50 μm to 500 μm, as similar to the substrate thickness T 1  of the first substrate  11 . If the substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  are located at the same thickness within a range of about 10% (0.90T 1 ≤T 4 ≤1.10T 1 ), by suppressing the distortion of the substrate for mounting electronic element  1  more effectively, it is possible to easily satisfactorily emit light. For example, if the substrate thickness T 1  of the first substrate  11  is 100 μm, the substrate thickness T 4  of the third substrate  16  may be 100 μm (90 μm to 110 μm). 
     The substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  may be smaller than the substrate thickness T 3  of the plurality of heat dissipation bodies  13  (T 3 &gt;T 1 , T 3 &gt;T 4 ). 
     In addition, the third substrate  16  may include a bonding layer located on the eighth surface  162  side. The bonding layer located on the third substrate  16  can be used for joining the substrate for mounting electronic element  1  and the conductor layer located on the wiring substrate  4  or the package for housing electronic element  5 , for example. The bonding layer can be manufactured by a method similar to that of the metal layer  14  described above. In addition, by placing the bonding layer on substantially the entire lower surface of the third substrate  16  so as to cover the plurality of heat dissipation bodies  13  in a transparent plan view, the heat dissipation from the substrate for mounting electronic element  1  to the wiring substrate  4  or the package for housing electronic element  5  can be improved. 
     Similar to the metal layer  14 , the bonding layer includes a plating layer on the surface thereof. 
     The substrate for mounting electronic element  1  according to the seventh embodiment can be manufactured by using the same manufacturing method as those of the substrates for mounting electronic element  1  according to the above embodiments. 
     Eighth Embodiment 
     Next, an electronic device according to an eighth embodiment will be described with reference to  FIGS.  23  to  24 B . 
     In the substrate for mounting electronic element  1  according to the eighth embodiment, a difference from the substrates for mounting electronic element  1  according to the sixth and seventh embodiments described above is that a plurality of heat dissipation bodies  13  which are long in the longitudinal direction (the y direction in  FIGS.  23  to  24 B ) are arranged in the direction perpendicular to the longitudinal direction (the x direction in  FIGS.  23  to  24 B ). 
     The plurality of heat dissipation bodies  13  are shaded in the example illustrated in  FIG.  23   . The metal layer  14  is shaded in the example illustrated in  FIGS.  24 A and  24 B . In the example illustrated in  FIG.  23   , in the second substrate  12 , the outer surface of the second substrate  12  and the inner surface of the through hole  12   a,  which are invisible in a perspective view, are shown by broken lines. The mounting portion  11   a  of the electronic element  2  is arranged so as to overlap with some of the plurality of heat dissipation bodies  13  in a transparent plan view. 
     In the examples shown in  FIGS.  23  to  24 B , the substrate for mounting electronic element  1  includes the three heat dissipation bodies  13  in a transparent plan view. With respect to the arrangement of the three heat dissipation bodies  13 , one heat dissipation body is arranged in terms of the longitudinal direction (the y direction in  FIGS.  23  to  24 B ), and three heat dissipation bodies are arranged side by side in terms of the direction perpendicular to the longitudinal direction (the x direction in  FIGS.  23  to  24 B ). 
     In the substrate for mounting electronic element  1  according to the eighth embodiment, the mounting portion  11   a  of the electronic element  2  is located in a region overlapping with one heat dissipation body  13  in a transparent plan view. In this case, the thermal conductivity λy of the plurality of heat dissipation bodies  13  in the longitudinal direction (the y direction in  FIGS.  23  to  24 B ) of the plurality of mounting portions  11   a  is smaller than the thermal conductivity λx in the direction perpendicular to the longitudinal direction of the mounting portion  11   a.  (λx&gt;&gt;λy). 
     Further, in the substrate for mounting electronic element  1  according to the eighth embodiment, if the plurality of heat dissipation bodies  13  are long in the direction crossing the longitudinal direction of the at least one mounting portion  11   a,  the heat transfer in the direction perpendicular to the longitudinal direction of the mounting portion  11   a  can be further increased. As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, if the plurality of heat dissipation bodies  13  extend in the longitudinal direction of the at least one mounting portion  11   a  to the side surface of the substrate for mounting electronic element  1  as in the example illustrated in  FIGS.  23  to  24 B , the heat dissipation of the substrate for mounting electronic element  1  becomes favorable over the length direction (y direction in  FIGS.  23  to  24 B ) of the mounting portion  11   a . As a result, the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     In addition, if a plurality of heat dissipation bodies extend to the side surface of the substrate for mounting electronic element  1  in the direction perpendicular to the longitudinal direction of the at least one mounting portion  11   a,  the heat dissipation of the substrate for mounting electronic element  1  becomes favorable, and thus the distortion of the substrate for mounting electronic element  1  can be suppressed. 
     Further, a member having excellent heat conduction may be brought into contact with the exposed side surfaces of the plurality of heat dissipation bodies  13  to enhance heat dissipation. 
     In the substrate for mounting electronic element  1  according to the eighth embodiment, the substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  are, for example, about 50 μm to 500 μm, and the substrate thickness T 2  of the second substrate  12  and the substrate thickness T 3  of the plurality of heat dissipation bodies  13  are, for example, about 100 μm to 2000 μm. 
     Further, also in the substrate for mounting electronic element  1  according to the eighth embodiment, if the substrate thickness T 1  of the first substrate  11  and the substrate thickness T 4  of the third substrate  16  are located at the same thickness within a range of about 10% (0.90T 1 ≤T 4 ≤1.10T 1 ), by suppressing the distortion of the substrate for mounting electronic element  1  more effectively, it is possible to easily satisfactorily emit light. For example, if the substrate thickness T 1  of the first substrate  11  is 100 μm, the substrate thickness T 4  of the third substrate  16  may be 100 μm (90 μm to 110 μm). 
     The substrate for mounting electronic element  1  according to the eighth embodiment can be manufactured by the same method as those of the substrates for mounting electronic element  1  according to the above embodiments. 
     The disclosure is not limited to the examples of the embodiments described above and various modifications can be made. For example, the metal layer  14  located on the first surface  111  of the first substrate  11  is formed by the thin film method in the above example, but it may be a metal layer using a well-known co-firing method or post-firing method of the related art. If such a metal layer  14  is used, the metal layer  14  is preliminarily located on the first surface  111  of the first substrate  11  before joining the first substrate  11  and the plurality of heat dissipation bodies  13 . The method described in the above embodiments may be used in order to improve the flatness of the first substrate  11 . 
     Further, the substrate for mounting electronic element  1  may include a chamfer, a notch, or the like at a corner or a side of the substrate for mounting electronic element  1  in a plan view. 
     In the substrates for mounting electronic element  1  according to the first embodiment to the eighth embodiment, the first substrate  11  or the third substrate  16  is formed of a single insulating layer. However, the number of insulating layers may be different. For example, in the substrate for mounting electronic element  1  according to the first embodiment, the first substrate  11  may be formed of two or more insulating layers. 
     In the substrates for mounting electronic element  1  according to the first embodiment to the fifth embodiment, the three heat dissipation bodies  13  are accommodated in the three through holes  12   a  of the second substrate  12 . However, it may be a substrate for mounting electronic element  1  in which four or more through holes  12   a  and heat dissipation bodies  13  are arranged in a direction in which the plurality of heat dissipation bodies  13  are aligned. 
     Further, the substrates for mounting electronic element  1  according to the first embodiment to the eighth embodiment may be combined. For example, in the substrate for mounting electronic element  1  according to the first embodiment, the substrates for mounting electronic element  1  according to the third to fifth embodiments, and the like, as similar to the substrate for mounting electronic element  1  according to the second embodiment, the plurality of heat dissipation bodies  13  may be circular in a plan view.