Patent Publication Number: US-10790258-B2

Title: Electronic device and mounting structure of the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic device and a mounting structure of the same. 
     2. Description of Related Art 
     Conventionally, various semiconductor devices are known. For example, a semiconductor device disclosed in JP-A-2013-239740 is provided with a semiconductor chip, a die pad, a plurality of leads, and a sealing resin. The semiconductor chip is disposed on the die pad. The sealing resin covers the semiconductor chip, the die pad, and the plurality of leads. This semiconductor device is mounted to a circuit board via solder. 
     When the above conventional semiconductor device is in use, the constituent elements in the semiconductor device expand or contract with heat. Repeating such expansion/contraction gives rise to the possibility of cracks occurring in the solder joining the leads or in the sealing resin. 
     Another conventional semiconductor device has an insulating joining part interposed between the semiconductor chip and the die pad. When manufacturing such a product, the semiconductor chip inclines unreasonably relative to the die pad, giving rise to the possibility of an electrical connection unintentionally being established between the semiconductor chip and the die pad. 
     SUMMARY OF THE INVENTION 
     The present invention has been proposed under the foregoing circumstances, and has an object to provide an electronic device that is able to prevent cracks from occurring in a solder layer. 
     Also, the present invention has an object to provide an electronic device that, even if a crack does occur in the sealing resin, is able to prevent the crack from being exposed to the outside of the sealing resin. 
     Also, the present invention has an object to provide an electronic device that is able to prevent an electronic element from becoming electrically connected to a main electrode. 
     An electronic device that is provided according to a first aspect of the present invention includes an electronic element, a plurality of first sub-electrodes arrayed in a first direction, a plurality of second sub-electrodes arrayed in a second direction that is orthogonal to the first direction, a dummy electrode, and a sealing resin covering the electronic element, the plurality of first sub-electrodes, the plurality of second sub-electrodes and the dummy electrode. The sealing resin has a resin back surface from which the plurality of first sub-electrodes, the plurality of second sub-electrodes and the dummy electrode are exposed. The plurality of second sub-electrodes are located further in the first direction than any of the plurality of first sub-electrodes. The plurality of first sub-electrodes are located further in the second direction than any of the plurality of second sub-electrodes. The dummy electrode is located further in the first direction than any of the plurality of first sub-electrodes, and is located further in the second direction than any of the plurality of second sub-electrodes. 
     Preferably, the dummy electrode is insulated from all of the plurality of first sub-electrodes and the plurality of second sub-electrodes. 
     Preferably, the sealing resin has a resin lateral surface that stands erect from the resin back surface, and the dummy electrode, the plurality of first sub-electrodes and the plurality of second sub-electrodes are all exposed from the resin lateral surface. 
     Preferably, the dummy electrode is exposed from the resin lateral surface and has a dummy electrode first outer surface facing in the second direction, and the dummy electrode first outer surface is flush with a region, of the resin lateral surface, facing in the second direction. 
     Preferably, the dummy electrode is exposed from the resin lateral surface and has a dummy electrode second outer surface facing in the first direction, and the dummy electrode second outer surface is flush with a region, of the resin lateral surface, facing in the first direction. 
     Preferably, a linear mark is respectively formed on the dummy electrode first outer surface, the dummy electrode second outer surface, and the resin lateral surface. 
     Preferably, the dummy electrode has an erect sloping surface, the erect sloping surface stands erect from the dummy electrode back surface and slopes relative to the dummy electrode first outer surface and the dummy electrode second outer surface, the erect sloping surface faces outside the sealing resin as seen in a thickness direction of the electronic element, and the sealing resin has a resin corner part covering the erect sloping surface. 
     Preferably, the resin corner part constitutes part of the resin back surface, the resin corner part has a first lateral surface that is flush with the dummy electrode first outer surface and a second lateral surface that is flush with the dummy electrode second outer surface, and the first lateral surface and the second lateral surface constitute part of the resin lateral surface. 
     Preferably, the resin corner part has a corner edge extending in the thickness direction of the electronic element, and the first lateral surface and the second lateral surface are connected to each other via the corner edge and are orthogonal to each other. 
     Preferably, the dummy electrode has a dummy electrode back surface exposed from the sealing resin. 
     Preferably, the dummy electrode back surface is flat. 
     Preferably, the dummy electrode has a dummy electrode lateral surface that stands erect from the dummy electrode back surface, the dummy electrode lateral surface is covered by the sealing resin, and the dummy electrode lateral surface is located on the electronic element side of the dummy electrode. 
     Preferably, the dummy electrode lateral surface has an upper portion and a lower portion, and the upper portion of the dummy electrode lateral surface and the lower portion of the dummy electrode lateral surface each have a recessed shape that is recessed toward the center of the dummy electrode. 
     Preferably, the value of surface roughness of the dummy electrode lateral surface is greater than the value of surface roughness on the dummy electrode back surface. 
     Preferably, the surface area per unit area of the dummy electrode lateral surface is 1.5 to 2.5 times the surface area per unit area of the dummy electrode back surface. 
     Preferably, the dummy electrode has a dummy electrode front surface facing in the opposite direction to the dummy electrode back surface, and the dummy electrode front surface is entirely covered by the sealing resin. 
     Preferably, a dummy electrode recessed part that is recessed from the dummy electrode back surface is formed in the dummy electrode. 
     Preferably, the depth of the dummy electrode recessed part is ⅓ to ⅔ of a size of the dummy electrode in the thickness direction of the electronic element. 
     Preferably, the area of an opening of the dummy electrode recessed part in the dummy electrode back surface is ⅓ to ¾ of the area of the dummy electrode back surface. 
     Preferably, the outline of the opening of the dummy electrode recessed part has a shape that fits inside the outer edge of the dummy electrode back surface. 
     Preferably, the dummy electrode recessed part is open in the first direction and the second direction. 
     Preferably, the inner surface of the dummy electrode recessed part has a tip region that is connected to the dummy electrode back surface, and the tip region of the inner surface of the dummy electrode recessed part slopes in the thickness direction of the electronic element, such that the area of a cross-section along a plane that is orthogonal to the thickness direction of the electronic element gradually increases as the distance from the dummy electrode back surface increases. 
     Preferably, the dummy electrode, the plurality of first sub-electrodes and the plurality of second sub-electrodes are all made of the same material. 
     Preferably, the dummy electrode, the plurality of first sub-electrodes and the plurality of second sub-electrodes are all made of Cu. 
     Preferably, the electronic device is further provided with a back surface plating layer, and the back surface plating layer has a region formed on the dummy electrode back surface. 
     Preferably, the back surface plating layer is formed on the inner surface of the dummy electrode recessed part. 
     Preferably, the back surface plating layer is made of Sn. 
     Preferably, the electronic device is further provided with a front surface plating layer, and the front surface plating layer has a region formed on the dummy electrode front surface. 
     Preferably, the front surface plating layer is made of Ag. 
     Preferably, the plurality of first sub-electrodes are each exposed from the resin lateral surface and have a first sub-electrode outer surface facing in the second direction, and the first sub-electrode outer surface is flush with a region, of the resin lateral surface, facing in the second direction. 
     Preferably, a linear mark is formed on the first sub-electrode outer surface. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode back surface that is exposed from the sealing resin. 
     Preferably, the first sub-electrode back surface is flat. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode lateral surface that stands erect from the first sub-electrode back surface, the first sub-electrode lateral surface is covered by the sealing resin, and the first sub-electrode lateral surface connects an end part of the first sub-electrode outer surface in the first direction to an end part of the first sub-electrode outer surface on the opposite side to the first direction. 
     Preferably, the first sub-electrode lateral surface has a sub-upper portion and a sub-lower portion, and the sub-upper portion of the first sub-electrode lateral surface and the sub-lower portion of the first sub-electrode lateral surface each have a recessed shape that is recessed toward the center of the first sub-electrode. 
     Preferably, the value of surface roughness of the first sub-electrode lateral surface is greater than the value of surface roughness of the first sub-electrode back surface. 
     Preferably, the surface area per unit area of the first sub-electrode lateral surface is 1.5 to 2.5 times the surface area per unit area of the first sub-electrode back surface. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode front surface facing in the opposite direction to the first sub-electrode back surface, and the first sub-electrode front surface is covered by the sealing resin. 
     Preferably, a first sub-electrode recessed part that is recessed from the first sub-electrode back surface is formed in each of the plurality of first sub-electrodes. 
     Preferably, the outline of the opening of the first sub-electrode recessed part has a shape that fits inside the outer edge of the plurality of first sub-electrode back surfaces. 
     Preferably, the inner surface of the first sub-electrode recessed part has a tip region that is connected to the first sub-electrode back surface, and the tip region of the inner surface of the first sub-electrode recessed part slopes in the thickness direction of the electronic element, such that the area of a cross-section along a plane that is orthogonal to the thickness direction of the electronic element gradually increases as the distance from the first sub-electrode back surface increases. 
     Preferably, the electronic device is further provided with a back surface plating layer, and the back surface plating layer has a region formed on the first sub-electrode back surface. 
     Preferably, the back surface plating layer is formed on the inner surface of the first sub-electrode recessed part. 
     Preferably, the electronic device is further provided with a front surface plating layer, and the front surface plating layer has a region formed on the first sub-electrode front surface. 
     Preferably, the electronic device is further provided with a main electrode on which the electronic element is disposed. 
     Preferably, the electronic device is further provided with an extended part extending outside the main electrode from the main electrode, as seen in the thickness direction, the extended part is coupled to the main electrode and the dummy electrode, and the thickness of the extended part is less than the main electrode and the dummy electrode. 
     Preferably, when the extended part is viewed from the main electrode, the extended part is entirely surrounded by the sealing resin. 
     Preferably, the extended part extends toward the dummy electrode from the main electrode, in a direction intersecting both the first direction and the second direction. 
     Preferably, the dummy electrode has a dummy electrode main back surface and a dummy electrode sub-back surface that are exposed from the sealing resin, and, on the resin back surface, the dummy electrode main back surface and the dummy electrode sub-back surface are exposed in a state of being spaced from each other. 
     Preferably, the dummy electrode main back surface and the dummy electrode sub-back surface are flat. 
     Preferably, the dummy electrode has a dummy electrode front surface facing in the opposite direction to the dummy electrode main back surface and the dummy electrode sub-back surface, and the dummy electrode front surface is entirely covered by the sealing resin. 
     Preferably, the sealing resin has a resin lateral surface that stands erect from the resin back surface, and the dummy electrode is exposed from the resin lateral surface. 
     Preferably, the dummy electrode has a dummy electrode first outer surface facing in the second direction, a dummy electrode second outer surface facing in the first direction and an erect sloping surface that stands erect from the dummy electrode main back surface, the dummy electrode first outer surface and the dummy electrode second outer surface are both exposed from the resin lateral surface, the erect sloping surface slopes relative to the dummy electrode first outer surface and the dummy electrode second outer surface, and faces outside the sealing resin, as seen in the thickness direction of the electronic element, and the sealing resin has a resin corner part covering the erect sloping surface. 
     Preferably, the electronic device is further provided with a back surface plating layer, and the back surface plating layer has a region formed on the dummy electrode main back surface and the dummy electrode sub-back surface. 
     Preferably, the dummy electrode sub-back surface includes a dummy electrode first sub-back surface that is located in the first direction and a dummy electrode second sub-back surface that is located in the second direction. 
     Preferably, the electronic device is further provided with an independent dummy electrode that has an independent dummy electrode back surface exposed from the resin back surface and is not connected to the dummy electrode, and the independent dummy electrode is insulated from all of the plurality of first sub-electrodes, the plurality of second sub-electrodes and the dummy electrode. 
     Preferably, the independent dummy electrode back surface is flat. 
     Preferably, the independent dummy electrode has an independent dummy electrode front surface facing in the opposite direction to the independent dummy electrode back surface, and the independent dummy electrode front surface is entirely covered by the sealing resin. 
     Preferably, an independent dummy electrode recessed part that is recessed from the independent dummy electrode back surface is formed in the independent dummy electrode. 
     Preferably, the outline of the opening of the independent dummy electrode recessed part has a shape that fits inside the outer edge of the dummy electrode back surface. 
     Preferably, the inner surface of the independent dummy electrode recessed part has a tip region that is connected to the independent dummy electrode back surface, and the tip region of the inner surface slopes in the thickness direction of the electronic element, such that the area of a cross-section along a plane that is orthogonal to the thickness direction of the electronic element gradually increases as the distance from the independent dummy electrode back surface increases. 
     Preferably, the back surface plating layer has a region formed on the independent dummy electrode back surface. 
     Preferably, the back surface plating layer is formed on the inner surface of the independent dummy electrode recessed part. 
     Preferably, the independent dummy electrode includes a first independent dummy electrode that is disposed in the first direction and is located between the plurality of first sub-electrodes and the dummy electrode, and a second independent dummy electrode that is disposed in the second direction and is located between the plurality of second sub-electrodes and the dummy electrode. 
     Preferably, the first independent dummy electrode and the second independent dummy electrode are both exposed from the resin lateral surface. 
     Preferably, the shape of the first independent dummy electrode and the shape of the first sub-electrodes are respectively the same as the shape of the second independent dummy electrode and the shape of the second sub-electrodes. 
     Preferably, the main electrode has a main electrode front surface on which the electronic element is disposed and a main electrode back surface facing in the opposite direction to the main electrode front surface, and the main electrode back surface is exposed from the sealing resin. 
     Preferably, the main electrode back surface is flat. 
     Preferably, the electronic device is further provided with a plurality of wires, the plurality of wires are each bonded to the electronic element, and the plurality of wires are each bonded to any of the plurality of first sub-electrodes or any of the plurality of second sub-electrodes. 
     Preferably, the electronic device is further provided with a joining layer interposed between the electronic element and the main electrode. 
     Preferably, the joining layer is made of a conductive material. 
     Preferably, the joining layer is made of Ag. 
     Preferably, the electronic device is further provided with an additional dummy electrode, and the additional dummy electrode is disposed on the opposite side to the dummy electrode with the plurality of first sub-electrodes sandwiched therebetween. 
     An electronic device that is provided according to a second aspect of the present invention includes an electronic element, a main electrode on which the electronic element is disposed, and a sealing resin covering the electronic element and the main electrode. The main electrode has a main electrode front surface on which the electronic element is disposed and a main electrode back surface facing in the opposite direction to the main electrode front surface. The main electrode back surface is exposed from the sealing resin, and the main electrode back surface has a region that protrudes outside of the main electrode front surface, as seen in the thickness direction of the electronic element. 
     Preferably, the main electrode back surface protrudes outside of the main electrode front surface, as seen in the thickness direction of the electronic element, around the entire periphery of the main electrode. 
     Preferably, the main electrode has a main electrode lateral surface connecting the main electrode front surface to the main electrode back surface, and the main electrode lateral surface has a recessed portion that is recessed toward the center of the main electrode. 
     Preferably, an end part on the main electrode back surface side of the recessed portion is located outside of the main electrode front surface, as seen in the thickness direction of the electronic element. 
     Preferably, the recessed portion has a region that is located more on the center side of the main electrode than is an end of the main electrode front surface, as seen in the thickness direction. 
     Preferably, the recessed portion is formed around the entire periphery of the main electrode. 
     Preferably, the value of surface roughness of the main electrode lateral surface is greater than the value of surface roughness of the main electrode back surface. 
     Preferably, the surface area per unit area of the main electrode lateral surface is 1.5 to 2.5 times the surface area per unit area of the main electrode back surface. 
     Preferably, the main electrode lateral surface includes a main upper portion and a main lower portion, and the main upper portion is located more on the main electrode front surface side than the main lower portion in the thickness direction. 
     Preferably, a crack extending in the thickness direction is formed in the sealing resin, the main electrode lateral surface is located more on the main electrode back surface side than an end of the crack on the main electrode back surface side, and the end of the crack on the main electrode back surface side contacts the main electrode lateral surface. 
     Preferably, the crack extends starting from the end of the main electrode front surface. 
     Preferably, the main upper portion has a recessed shape that is recessed toward the center of the main electrode. 
     Preferably, an end part on the main electrode back surface side of the main upper portion is located outside of the main electrode front surface, as seen in the thickness direction of the electronic element. 
     Preferably, the main lower portion slopes in the thickness direction, so as to form an acute angle with the main electrode back surface. 
     Preferably, a size of the main lower portion in the thickness direction is less than a size of the main upper portion in the thickness direction. 
     Preferably, the main electrode lateral surface includes a main intermediate portion, and the main intermediate portion is located between the main upper portion and the main lower portion, in the thickness direction, and the main intermediate portion has a recessed shape that is recessed toward the center of the main electrode. 
     Preferably, an end part on the main electrode back surface side of the main intermediate portion is located outside of the main electrode front surface, as seen in the thickness direction of the electronic element. 
     Preferably, the main upper portion slopes in the thickness direction, so as to form an acute angle with the main electrode front surface, and the main lower portion slopes in the thickness direction, so as to form an acute angle with the main electrode back surface. 
     Preferably, the main electrode back surface is flat. 
     Preferably, the area of the electronic element as seen in the thickness direction occupies 80 percent or more of the area of the main electrode surface. 
     Preferably, the electronic element is further provided with an extended part extending outside the main electrode from the main electrode, and the thickness of the extended part is less than the main electrode, as seen in the thickness direction. 
     Preferably, the extended part is entirely surrounded by the sealing resin, when the extended part is viewed from the main electrode. 
     Preferably, the electronic device is further provided with a back surface plating layer, and the back surface plating layer has a region formed on the main electrode back surface. 
     Preferably, the back surface plating layer is made of Sn. 
     Preferably, the electronic device is further provided with a front surface plating layer, and the front surface plating layer has a region formed on the main electrode front surface. 
     Preferably, the front surface plating layer is made of Ag. 
     Preferably, the electronic device is further provided with a plurality of first sub-electrode arrayed in the first direction and a plurality of second sub-electrodes arrayed in a second direction that is orthogonal to the first direction. 
     Preferably, the sealing resin has a resin lateral surface, the plurality of first sub-electrodes each have a first sub-electrode outer surface that is exposed from the resin lateral surface and faces in the second direction, and the first sub-electrode outer surface is flush with a region, of the resin lateral surface, facing in the second direction. 
     Preferably, a linear mark is formed on the first sub-electrode outer surface. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode back surface that is exposed from the sealing resin. 
     Preferably, the first sub-electrode back surface is flat. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode lateral surface that stands erect from the first sub-electrode back surface, the first sub-electrode lateral surface is covered by the sealing resin, and the first sub-electrode lateral surface connects an end part of the first sub-electrode outer surface in the first direction to an end part of the first sub-electrode outer surface on the opposite side to the first direction. 
     Preferably, the first sub-electrode lateral surface has a sub-upper portion and a sub-lower portion, and the sub-upper portion of the first sub-electrode lateral surface and the sub-lower portion of the first sub-electrode lateral surface each have a recessed shape that is recessed toward the center of the first sub-electrode. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode front surface facing in the opposite direction to the first sub-electrode back surface, and the first sub-electrode front surface is covered by the sealing resin. 
     Preferably, the electronic device is further provided with a plurality of wires, the plurality of wires are each bonded to the electronic element, and the plurality of wires are each bonded to any of the plurality of first sub-electrodes or any of the plurality of second sub-electrodes. 
     Preferably, the electronic device is further provided with a joining layer interposed between the electronic element and the main electrode. 
     Preferably, the joining layer is made of a conductive material. 
     Preferably, the joining layer is made of Ag. 
     Preferably, the joining layer has a region that protrudes outside of the electronic element, as seen in the thickness direction. 
     An electronic device that is provided according to a third aspect of the present invention includes an electronic element, a main electrode on which the electronic element is disposed, an insulating joining part interposed between the electronic device and the main electrode, a plurality of insulating spacers mixed in the joining part, and a sealing resin covering the electronic element and the main electrode. 
     Preferably, the plurality of spacers each directly contact the electronic element. 
     Preferably, the plurality of spacers each directly contact the main electrode. 
     Preferably, the electronic device is further provided with a front surface plating layer, the front surface plating layer has a region formed on the main electrode, and the plurality of spacers each directly contact the front surface plating layer. 
     Preferably, the plurality of spacers all have a spherical shape. 
     Preferably, the diameter of each of the plurality of spacers is 5 to 15 μm. 
     Preferably, the plurality of spacers are made of a divinylbenzene polymer. 
     Preferably, the plurality of spacers are dispersed, as seen in the thickness direction of the electronic element. 
     Preferably, the plurality of spacers number ten or more. 
     Preferably, the electronic device is further provided with a plurality of insulating fillers that are mixed in the joining part. 
     Preferably, the volume of each of the plurality of fillers is less than the volume of each of the plurality of spacers. 
     Preferably, the plurality of fillers all have a spherical shape. 
     Preferably, the diameter of each of the plurality of fillers is 1 to 3 μm. 
     Preferably, the plurality of fillers are made of SiO 2 , an organic material, or a mixed material of an organic material and a non-organic material. 
     Preferably, the plurality of fillers are dispersed, as seen in the thickness direction of the electronic element. 
     Preferably, the plurality of fillers number ten or more. 
     Preferably, a portion of the plurality of fillers are exposed from the joining part and contact the sealing resin. 
     Preferably, the main electrode has a main electrode front surface on which the electronic element is disposed and a main electrode back surface facing in the opposite direction to the main electrode front surface, and the main electrode back surface is exposed from the sealing resin. 
     Preferably, the electronic device is further provided with a second electronic element, where the electronic element is taken as a first electronic element, and the second electronic element is disposed on the main electrode. 
     Preferably, the electronic device is further provided with a joining layer interposed between the second electronic element and the main electrode. 
     Preferably, the joining layer is made of a conductive material. 
     Preferably, the joining layer is made of Ag. 
     Preferably, the electronic device further includes a plurality of first sub-electrodes arrayed in a first direction and a plurality of second sub-electrodes arrayed in a second direction that is orthogonal to the first direction. 
     Preferably, the sealing resin has a resin lateral surface, the plurality of first sub-electrodes are each exposed from the resin lateral surface and have a first sub-electrode outer surface facing in the second direction, and the first sub-electrode outer surface is flush with a region, of the resin lateral surface, facing in the second direction. 
     Preferably, a linear mark is formed on the first sub-electrode outer surface. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode back surface that is exposed from the sealing resin. 
     Preferably, the first sub-electrode back surface is flat. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode lateral surface that stands erect from the first sub-electrode back surface, the first sub-electrode lateral surface is covered by the sealing resin, and the first sub-electrode lateral surface connects an end part of the first sub-electrode outer surface in the first direction to an end part of the first sub-electrode outer surface on the opposite side to the first direction. 
     Preferably, the first sub-electrode lateral surface has a sub-upper portion and a sub-lower portion, and the sub-upper portion of the first sub-electrode lateral surface and the sub-lower portion of the first sub-electrode lateral surface each have a recessed shape that is recessed toward the center of the first sub-electrode. 
     Preferably, the plurality of first sub-electrodes each have a first sub-electrode front surface facing in the opposite direction to the first sub-electrode back surface, and the first sub-electrode front surface is covered by the sealing resin. 
     Preferably, the electronic device is further provided with a plurality of wires, any of the plurality of wires is bonded to the first electronic element or the second electronic element, and any of the plurality of wires is bonded to any of the plurality of first sub-electrodes or any of the plurality of second sub-electrodes. 
     A mounting structure provided according to a fourth aspect of the present invention includes the electronic device provided according to any of the first aspect to the third aspect of the present invention, a circuit board, and a solder layer interposed between the circuit board and the plurality of first sub-electrodes and between the circuit board and the plurality of second sub-electrodes. 
     Other features and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of an electronic device of a first embodiment. 
         FIG. 2  is a bottom view of the electronic device shown in  FIG. 1 . 
         FIG. 3  is a right side view of the electronic device shown in  FIG. 1 . 
         FIG. 4  is a rear view of the electronic device shown in  FIG. 1 . 
         FIG. 5  is a partial cross-sectional view along a line V-V in  FIG. 2 . 
         FIG. 6  is a partial cross-sectional view along a line VI-VI in  FIG. 2 . 
         FIG. 7  is a partial cross-sectional view along a line VII-VII in  FIG. 2 . 
         FIG. 8  is a plan view that omits a sealing resin from  FIG. 1 . 
         FIG. 9  is a plan view that omits a plurality of wires and an electronic element from  FIG. 8 . 
         FIG. 10  is a partial cross-sectional view along a line X-X in  FIG. 7 . 
         FIG. 11  is an enlarged partial view of an upper right area in  FIG. 8 . 
         FIG. 12  is an enlarged partial view of an upper left area in  FIG. 2 . 
         FIG. 13  is a partial cross-sectional view along a line XIII-XIII in  FIG. 11 . 
         FIG. 14  is a partial cross-sectional view along a line XIV-XIV in  FIG. 11 . 
         FIG. 15  is a partial cross-sectional view along a line XV-XV in  FIG. 11 . 
         FIG. 16  is a partial cross-sectional view along a line XVI-XVI in  FIG. 11 . 
         FIG. 17  is a partial cross-sectional view along a line XVII-XVII in  FIG. 11 . 
         FIG. 18  is a partial cross-sectional view along a line XVIII-XVIII in  FIG. 11 . 
         FIG. 19  is an enlarged view of a right side area in  FIG. 3  (linear marks are shown in exaggerated form). 
         FIG. 20  is an enlarged view of a left side area in  FIG. 4  (linear marks are shown in exaggerated form). 
         FIG. 21  is a right side view of a mounting structure including the electronic device of the first embodiment. 
         FIG. 22  is a partial cross-sectional view of the mounting structure (corresponds to  FIG. 14 ). 
         FIG. 23  is a partial cross-sectional view of the mounting structure (corresponds to  FIG. 15 ). 
         FIG. 24  is a partial cross-sectional view of the mounting structure (corresponds to  FIG. 16 ). 
         FIG. 25  is a partial cross-sectional view of the mounting structure (corresponds to  FIG. 17 ). 
         FIG. 26  is a partial cross-sectional view of the mounting structure (corresponds to  FIG. 18 ). 
         FIG. 27  is a cross-sectional view of an electronic device according to a first modification of the first embodiment. 
         FIG. 28  is a bottom view of an electronic device according to a second modification of the first embodiment. 
         FIG. 29  is a plan view of an electronic device of a second embodiment. 
         FIG. 30  is a partial cross-sectional view along a line XXX-XXX in  FIG. 29 . 
         FIG. 31  is an enlarged partial view of a right side area in  FIG. 30 . 
         FIG. 32  is a right side view of a mounting structure including the electronic device of the second embodiment. 
         FIG. 33  is a cross-sectional view of an electronic device according to a first modification of the second embodiment. 
         FIG. 34  is a bottom view of an electronic device of a third embodiment. 
         FIG. 35  is a right side view of the electronic device shown in  FIG. 34 . 
         FIG. 36  is a rear view of the electronic device shown in  FIG. 34 . 
         FIG. 37  is a partial cross-sectional view along a line XXXVII-XXXVII in  FIG. 34 . 
         FIG. 38  is an enlarged partial view of an upper left area in  FIG. 34 . 
         FIG. 39  is a partial enlarged plan view of the electronic device shown in  FIG. 34  that corresponds to the opposite side of  FIG. 38  (sealing resin is omitted). 
         FIG. 40  is a partial cross-sectional view along a line XL-XL in  FIG. 39 . 
         FIG. 41  is a partial cross-sectional view along a line XLI-XLI in  FIG. 39 . 
         FIG. 42  is a right side view of a mounting structure including the electronic device of the third embodiment. 
         FIG. 43  is a partial cross-sectional view of the mounting structure (corresponds to  FIG. 40 ). 
         FIG. 44  is a bottom view of an electronic device according to a first modification of the third embodiment. 
         FIG. 45  is an enlarged partial view of an upper left area in  FIG. 44 . 
         FIG. 46  is a partial enlarged plan view of the electronic device shown in  FIG. 44  that corresponds to the opposite side of  FIG. 45  (sealing resin is omitted). 
         FIG. 47  is a partial cross-sectional view along a line XLVII-XLVII in  FIG. 46 . 
         FIG. 48  is a partial cross-sectional view of a mounting structure including the electronic device according to the first modification of the third embodiment (corresponds to  FIG. 47 ). 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. 
     First, a first embodiment will be described with reference to  FIGS. 1 to 26 . 
       FIG. 1  is a plan view of an electronic device A 10  of the first embodiment.  FIG. 2  is a bottom view of the electronic device A 10 .  FIG. 3  is a right side view of the electronic device A 10 .  FIG. 4  is a rear view of the electronic device A 10 .  FIG. 5  is a partial cross-sectional view along a line V-V in  FIG. 2 .  FIG. 6  is a partial cross-sectional view along a line VI-VI in  FIG. 2 .  FIG. 7  is a partial cross-sectional view along a line VII-VII in  FIG. 2 . 
     The electronic device A 10  shown in these figures is constituted as a surface-mountable electronic device. In the present embodiment, the electronic device A 10  is a QFN (quad flat non-leaded package) type semiconductor device, and is produced by molded array packaging (MAP), for example. 
     The electronic device A 10  is provided with an electronic element  1 , a main electrode  2 , a plurality of first sub-electrodes  3 , a plurality of second sub-electrodes  4 , a dummy electrode  5 , a front surface plating layer  61 , a back surface plating layer  62 , a joining layer  71 , a plurality of wires  79 , and a sealing resin  8 . 
       FIG. 8  is a plan view that omits the sealing resin  8  from  FIG. 1 .  FIG. 9  is a plan view that omits the electronic element  1  and the plurality of wires  79  from  FIG. 8 .  FIG. 10  is a partial cross-sectional view along a line X-X in  FIG. 7 .  FIG. 11  is an enlarged partial view of an upper right area in  FIG. 8 .  FIG. 12  is an enlarged partial view of an upper left area in  FIG. 2 . 
     In the present embodiment, the electronic element  1  shown in  FIGS. 5 to 8  is a semiconductor element. The electronic element  1  takes on a rectangular shape as seen in a thickness direction Z of the electronic element  1  (as seen in plan view). The size of the electronic element  1  in a first direction X is 4 to 8 mm, for example. The size of the electronic element  1  in a second direction Y is 4 to 8 mm, for example. In the present embodiment, the size of the electronic element  1  in the first direction X and the size of the electronic element  1  in the second direction Y are both 5.1 mm. 
       FIG. 13  is a partial cross-sectional view along a line XIII-XIII in  FIG. 11 . 
     The main electrode  2  shown in  FIG. 2 ,  FIGS. 5 to 8  and  FIG. 13  is made of a conductive material. The main electrode  2  is formed by patterning such as etching or the like being performed on a metal plate that is made of Cu, for example. The electronic element  1  is disposed on the main electrode  2 . 
     As shown in  FIG. 13 , the main electrode  2  has a main electrode front surface  21 , a main electrode back surface  22 , and a main electrode lateral surface  23 . 
     The main electrode front surface  21  faces in one thickness direction Z. The main electrode front surface  21  is flat and has a rectangular shape. The electronic element  1  is disposed on the main electrode front surface  21 . In the present embodiment, the size of the main electrode surface  21  in the first direction X and the size of the main electrode surface  21  in the second direction Y are both 5.4 mm. Preferably, the area of the electronic element  1  as seen in the thickness direction Z occupies 80 percent or more of the area of the main electrode surface  21 . 
     The main electrode back surface  22  faces in the other thickness direction Z. The main electrode back surface  22  faces in the opposite direction to the main electrode front surface  21 . The main electrode back surface  22  is flat and has a rectangular shape. The main electrode back surface  22  is exposed from the sealing resin  8  (i.e., is not covered by the sealing resin  8 ). The main electrode back surface  22  has a region that protrudes outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 . In the present embodiment, the main electrode back surface  22  protrudes outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 , around the entire periphery of the main electrode  2 . Thus, the area of the main electrode back surface  22  is greater than the area of the main electrode surface  21 . 
     The main electrode lateral surface  23  connects the main electrode front surface  21  to the main electrode back surface  22 . The main electrode lateral surface  23  is covered by the sealing resin  8 . In the present embodiment, the main electrode lateral surface  23  has undergone rough surface machining. The value of surface roughness of the main electrode lateral surface  23  is greater than the value of surface roughness of the main electrode back surface  22 . The surface area per unit area (rectangular area defined by unit length×unit length; the same applied below) of the main electrode lateral surface  23  is, for example, 1.5 to 2.5 times the surface area per unit area of the main electrode back surface  22 . The rough surface machining of the present embodiment need not be performed on the main electrode lateral surface  23 . 
     The main electrode lateral surface  23  has a recessed portion  231  that is recessed toward the center (or inwardly) of the main electrode  2 . An end part  231 A on the main electrode back surface  22  side of the recessed portion  231  is located outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 . The recessed portion  231  has a region  231 B that is located more on the center side of the main electrode  2  than is the end of the main electrode surface  21 , as seen in the thickness direction Z. The recessed portion  231  is formed around the entire periphery of the main electrode  2 . In the present embodiment, the recessed portion  231  is formed in the main electrode  2  because the main electrode  2  is formed by etching a lead frame. 
     The main electrode lateral surface  23  includes a main upper portion  23 A and a main lower portion  23 B. 
     The main upper portion  23 A is located more on the main electrode front surface  21  side than the main lower portion  23 B in the thickness direction Z. In the present embodiment, the main upper portion  23 A has a recessed shape that is recessed toward the center of the main electrode  2 . That is, in the electronic device A 10 , the main upper portion  23 A constitutes the recessed portion  231 . An end part  23 AA on the main electrode back surface  22  side of the main upper portion  23 A is located outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 . In the present embodiment, the end part  23 AA on the main electrode back surface  22  side of the main upper portion  23 A is entirely located outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 . 
     The main lower portion  23 B slopes in the thickness direction Z, so as to form an acute angle with the main electrode back surface  22 . The size of the main lower portion  23 B in the thickness direction Z is less than the size of the main upper portion  23 A in the thickness direction Z. One conceivable reason of this is that the mask for etching that covers the main electrode back surface  22  has a comparatively small opening, and thus the amount of etching solution that flows toward the main electrode front surface  21  side from the main electrode back surface  22  side is less than the amount of etching solution that flows toward the main electrode back surface side from the main electrode front surface  21  side. The main lower portion  23 B is entirely located outside of the main electrode surface  21 , as seen in the thickness direction Z. 
       FIG. 14  is a partial cross-sectional view along a line XIV-XIV in  FIG. 11 . 
     The plurality of first sub-electrodes  3  shown in  FIGS. 2, 3, 5, 8, 9, 11, 12 and 14  are arrayed in the first direction X. The plurality of first sub-electrodes  3  are located further in the second direction Y than any of the plurality of second sub-electrodes  4 . The plurality of first sub-electrodes  3  are made of a conductive material. The plurality of first sub-electrodes  3  are formed by patterning such as etching or the like being performed on a metal plate made of Cu, for example. 
     As shown in  FIG. 14 , the plurality of first sub-electrodes  3  each have a first sub-electrode front surface  31 , a first sub-electrode back surface  32 , a first sub-electrode lateral surface  33 , and a first sub-electrode outer surface  35 . 
     The first sub-electrode front surface  31  faces in one thickness direction Z. The first sub-electrode front surface  31  is flat. The first sub-electrode front surface  31  is covered by the sealing resin  8 . 
     The first sub-electrode back surface  32  faces in the other thickness direction Z. The first sub-electrode back surface  32  faces in the opposite direction to the first sub-electrode front surface  31 . The first sub-electrode back surface  32  is flat. The first sub-electrode back surface  32  is exposed from the sealing resin  8 . 
     The first sub-electrode outer surface  35  faces in the second direction Y. In the present embodiment, the first sub-electrode outer surface  35  is exposed from the sealing resin  8 . 
     The first sub-electrode lateral surface  33  connects the first sub-electrode front surface  31  to the first sub-electrode back surface  32 . The first sub-electrode lateral surface  33  stands erect from (or intersects) the first sub-electrode back surface  32 . The first sub-electrode lateral surface  33  is covered by the sealing resin  8 . As shown in  FIGS. 11 and 12 , the first sub-electrode lateral surface  33  connects an end part  35 A of the first sub-electrode outer surface  35  in the first direction X to an end part  35 B of the first sub-electrode outer surface  35  on the opposite side to the first direction X. In the present embodiment, the first sub-electrode lateral surface  33  has undergone rough surface machining. The value of surface roughness of the first sub-electrode lateral surface  33  is greater than the value of surface roughness of the first sub-electrode back surface  32 . The surface area per unit area of the first sub-electrode lateral surface  33  is, for example, 1.5 to 2.5 times the surface area per unit area of the first sub-electrode back surface  32 . The rough surface machining of the present embodiment need not be performed on the first sub-electrode lateral surface  33 . 
     The first sub-electrode lateral surface  33  includes a first sub-upper portion  33 A and a first sub-lower portion  33 B. 
     The first sub-upper portion  33 A is located more on the first sub-electrode front surface  31  side than the first sub-lower portion  33 B in the thickness direction Z. In the present embodiment, the first sub-upper portion  33 A has a recessed shape that is recessed toward the center of the first sub-electrode  3 . The first sub-lower portion  33 B has a recessed shape that is recessed toward the center of the first sub-electrode  3 . The first sub-upper portion  33 A and the first sub-lower portion  33 B have a recessed shape because the first sub-electrode  3  is formed by etching a lead frame. 
     A first sub-electrode recessed part  38  is formed in each of the plurality of first sub-electrodes  3 . The first sub-electrode recessed part  38  is recessed from the first sub-electrode back surface  32 . The depth of the first sub-electrode recessed part  38  is, for example, ⅓ to ⅔ of the size of the first sub-electrode  3  in the thickness direction Z of the electronic element  1 . The area of the opening of the first sub-electrode recessed part  38  in the first sub-electrode back surface  32  is, for example, ⅓ to ¾ of the area of the first sub-electrode back surface  32 . The outline of the opening of the first sub-electrode recessed part  38  has a shape that fits inside the outer edge of the first sub-electrode back surface  32 . In the present embodiment, the outline of the opening of the first sub-electrode recessed part  38  has a rectangular shape. The outline of the opening of the first sub-electrode recessed part  38  may have a different shape from the present embodiment, such as a circular shape or a polygonal shape. 
     The inner surface  381  of the first sub-electrode recessed part  38  has a tip region  381 A that is connected to the first sub-electrode back surface  32 . The tip region  381 A of the inner surface  381  of the first sub-electrode recessed part  38  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the first sub-electrode back surface  32  increases. The first sub-electrode recessed part  38  thereby has a shape in which the opening narrows. This is because the first sub-electrode recessed part  38  is formed by etching using an etching solution. The same applies to a second sub-electrode recessed part  48 , a dummy electrode recessed part  58  and an independent dummy electrode recessed part  548  that will be discussed later. 
       FIG. 15  is a partial cross-sectional view along a line XV-XV in  FIG. 11 . 
     The plurality of second sub-electrodes  4  shown in  FIGS. 2, 4, 6, 8, 9, 11, 12 and 15  are disposed in the second direction Y. The plurality of second sub-electrodes  4  are located further in the first direction X than any of the plurality of first sub-electrodes  3 . The plurality of second sub-electrodes  4  are made of a conductive material. The plurality of second sub-electrodes  4  are formed by patterning such as etching or the like being performed on a metal plate made of Cu, for example. 
     As shown in  FIG. 15 , the plurality of second sub-electrodes  4  each have a second sub-electrode front surface  41 , a second sub-electrode back surface  42 , a second sub-electrode lateral surface  43  and a second sub-electrode outer surface  45 . 
     The second sub-electrode front surface  41  faces in one thickness direction Z. The second sub-electrode front surface  41  is flat. The second sub-electrode front surface  41  is covered by the sealing resin  8 . 
     The second sub-electrode back surface  42  faces in the other thickness direction Z. The second sub-electrode back surface  42  faces in the opposite direction to the second sub-electrode front surface  41 . The second sub-electrode back surface  42  is flat. The second sub-electrode back surface  42  is exposed from the sealing resin  8 . 
     The second sub-electrode outer surface  45  faces in the first direction X. In the present embodiment, the second sub-electrode outer surface  45  is exposed from the sealing resin  8 . 
     The second sub-electrode lateral surface  43  connects the second sub-electrode front surface  41  to the second sub-electrode back surface  42 . The second sub-electrode lateral surface  43  stands erect from the second sub-electrode back surface  42 . The second sub-electrode lateral surface  43  is covered by the sealing resin  8 . As shown in  FIGS. 11 and 12 , the second sub-electrode lateral surface  43  connects an end part  45 A of the second sub-electrode outer surface  45  in the second direction Y to an end part  45 B of the second sub-electrode outer surface  45  on the opposite side to the second direction Y. In the present embodiment, the second sub-electrode lateral surface  43  has undergone rough surface machining. The value of surface roughness of the second sub-electrode lateral surface  43  is greater than the value of surface roughness of the second sub-electrode back surface  42 . The surface area per unit area of the second sub-electrode lateral surface  43  is, for example, 1.5 to 2.5 times the surface area per unit area of the second sub-electrode back surface  42 . The rough surface machining of the present embodiment need not be performed on the second sub-electrode lateral surface  43 . 
     The second sub-electrode lateral surface  43  includes a second sub-upper portion  43 A and a second sub-lower portion  43 B. 
     The second sub-upper portion  43 A is located more on the second sub-electrode front surface  41  side than the second sub-lower portion  43 B in the thickness direction Z. In the present embodiment, the second sub-upper portion  43 A has a recessed shape that is recessed toward the center of the second sub-electrode  4 . The second sub-lower portion  43 B has a recessed shape that is recessed toward the center of the second sub-electrode  4 . The second sub-upper portion  43 A and the second sub-lower portion  43 B have a recessed shape because the second sub-electrodes  4  are formed by etching a lead frame. 
     A second sub-electrode recessed part  48  is formed in each of the plurality of second sub-electrodes  4 . The second sub-electrode recessed part  48  is recessed from the second sub-electrode back surface  42 . The depth of the second sub-electrode recessed part  48  is, for example, ⅓ to ⅔ of the size of the second sub-electrodes  4  in the thickness direction Z of the electronic element  1 . The area of the opening of the second sub-electrode recessed part  48  in the second sub-electrode back surface  42  is, for example, ⅓ to ¾ of the area of the second sub-electrode back surface  42 . The outline of the opening of the second sub-electrode recessed part  48  has a shape that fits inside the outer edge of the second sub-electrode back surface  42 . In the present embodiment, the outline of the opening of the second sub-electrode recessed part  48  has a rectangular shape. The outline of the opening of the second sub-electrode recessed part  48  may have a different shape from the present embodiment, such as a circular shape or a polygonal shape. 
     An inner surface  481  of the second sub-electrode recessed part  48  has a tip region  481 A connected to the second sub-electrode back surface  42 . The tip region  481 A of the inner surface  481  of the second sub-electrode recessed part  48  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the second sub-electrode back surface  42  increases. The second sub-electrode recessed part  48  thereby has a shape in which the opening narrows. 
       FIG. 16  is a partial cross-sectional view along a line XVI-XVI in  FIG. 11 .  FIG. 17  is a partial cross-sectional view along a line XVII-XVII in  FIG. 11 .  FIG. 18  is a partial cross-sectional view along a line XVIII-XVIII in  FIG. 11 . 
     The dummy electrode  5  shown in  FIGS. 2, 11, 12, 16, 17 and 18  is located further in the first direction X than any of the plurality of first sub-electrodes  3 , and is located further in the second direction Y than any of the plurality of second sub-electrodes  4 . The dummy electrode  5  is made of a conductive material. The dummy electrode  5  is formed by patterning such as etching or the like being performed on a metal plate made of Cu, for example. The dummy electrode  5 , the main electrode  2 , the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4  are formed from a single lead frame. Therefore, the dummy electrode  5 , the main electrode  2 , the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4  are all made of the same material. As mentioned previously, in the present embodiment, the dummy electrode  5 , the main electrode  2 , the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4  are all made of Cu. Also, the respective thicknesses (size in the thickness direction Z) of the dummy electrode  5 , the main electrode  2 , the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4  are the same as each other. The dummy electrode  5  is insulated from all of the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4 . 
     As shown in  FIGS. 16, 17 and 18 , the dummy electrode  5  has a dummy electrode front surface  51 , a dummy electrode back surface  52 , a dummy electrode lateral surface  53 , a dummy electrode first outer surface  551 , a dummy electrode second outer surface  552 , and an erect sloping surface  56 . 
     The dummy electrode front surface  51  faces in one thickness direction Z. The dummy electrode front surface is flat. The dummy electrode front surface  51  is entirely covered by the sealing resin  8 . 
     The dummy electrode back surface  52  faces in the other thickness direction Z. The dummy electrode back surface  52  faces in the opposite direction to the dummy electrode front surface  51 . The dummy electrode back surface  52  is flat. The dummy electrode back surface  52  is exposed from the sealing resin  8 . 
     The dummy electrode first outer surface  551  faces in the second direction Y. In the present embodiment, the dummy electrode first outer surface  551  is exposed from the sealing resin  8 . 
     The dummy electrode second outer surface  552  faces in the first direction X. In the present embodiment, the dummy electrode second outer surface  552  is exposed from the sealing resin  8 . 
     The erect sloping surface  56  stands erect from the dummy electrode back surface  52 , and slopes relative to the dummy electrode first outer surface  551  and the dummy electrode second outer surface  552 . The erect sloping surface  56  is connected to the dummy electrode first outer surface  551  and the dummy electrode second outer surface  552 . The erect sloping surface  56  faces outside the sealing resin  8 , as seen in the thickness direction Z of the electronic element  1 . 
     The dummy electrode lateral surface  53  connects the dummy electrode front surface  51  to the dummy electrode back surface  52 . The dummy electrode lateral surface  53  stands erect from the dummy electrode back surface  52 . The dummy electrode lateral surface  53  is covered by the sealing resin  8 . The dummy electrode lateral surface  53  is located on the electronic element  1  side in the dummy electrode  5 . In the present embodiment, the dummy electrode lateral surface  53  has undergone rough surface machining. The value of surface roughness of the dummy electrode lateral surface  53  is greater than the value of surface roughness of the dummy electrode back surface  52 . The surface area per unit area of the dummy electrode lateral surface  53  is, for example, 1.5 to 2.5 times the surface area per unit area of the dummy electrode back surface  52 . The rough surface machining of the present embodiment need not be performed on the dummy electrode lateral surface  53 . 
     The dummy electrode lateral surface  53  includes a dummy upper portion  53 A and a dummy lower portion  53 B. 
     The dummy upper portion  53 A is located more on the dummy electrode front surface  51  side than the dummy lower portion  53 B in the thickness direction Z. In the present embodiment, the dummy upper portion  53 A has a recessed shape that is recessed toward the center of the dummy electrode  5 . The dummy lower portion  53 B has a recessed shape that is recessed toward the center of the dummy electrode  5 . The dummy upper portion  53 A and the dummy lower portion  53 B have a recessed shape because the dummy electrode  5  is formed by etching a lead frame. 
     A dummy electrode recessed part  58  is formed in the dummy electrode  5 . The dummy electrode recessed part  58  is recessed from the dummy electrode back surface  52 . The depth of the dummy electrode recessed part  58  is, for example, ⅓ to ⅔ of the size of the dummy electrode  5  in the thickness direction Z of the electronic element  1 . The area of the opening of the dummy electrode recessed part  58  in the dummy electrode back surface  52  is, for example, ⅓ to ¾ of the area of the dummy electrode back surface  52 . The outline of the opening of the dummy electrode recessed part  58  has a shape that fits inside the outer edge of the dummy electrode back surface  52 . In the present embodiment, the outline of the opening of the dummy electrode recessed part  58  has a rectangular shape. The outline of the opening of the dummy electrode recessed part  58  may have a different shape from the present embodiment, such as a circular shape or a polygonal shape. 
     An inner surface  581  of the dummy electrode recessed part  58  has a tip region  581 A that is connected to the dummy electrode back surface  52 . The tip region  581 A of the inner surface  581  of the dummy electrode recessed part  58  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the dummy electrode back surface  52  increases. The dummy electrode recessed part  58  thereby has a shape in which the opening narrows. 
     The dummy electrode  5  mentioned previously is disposed in one of the four corners of the sealing resin  8 . As shown in  FIGS. 2 and 8 , in the present embodiment, three additional dummy electrodes  59  are disposed in addition to the dummy electrode  5 . The three additional dummy electrodes  59  are respectively disposed in the other corners of the sealing resin  8 . One of the three additional dummy electrodes  59  is disposed on the opposite side to the dummy electrode  5  with the plurality of first sub-electrodes  3  sandwiched therebetween. One of the three additional dummy electrodes  59  is disposed on the opposite side to the dummy electrode  5  with the plurality of second sub-electrodes  4  sandwiched therebetween. One of the three additional dummy electrodes  59  is disposed on the opposite side to the dummy electrode  5  with the main electrode  2  sandwiched therebetween. The additional dummy electrodes  59  have a similar configuration to the dummy electrode  5 , and thus description thereof will be omitted. 
     An extended part  29  shown in  FIGS. 7 to 10  extends outside the main electrode  2  from the main electrode  2 , as seen in the thickness direction Z. The extended part  29  is coupled to the main electrode  2  and the dummy electrode  5 . The thickness of the extended part  29  is less than the main electrode  2  and the dummy electrode  5 . When the extended part  29  is viewed from the main electrode  2 , the extended part  29  is entirely peripherally surrounded by the sealing resin  8 . In the present embodiment, the extended part  29  is not exposed from the sealing resin  8 . The extended part  29  extends toward the dummy electrode  5  from the main electrode  2  in a direction intersecting both the first direction X and the second direction Y. In manufacturing of the electronic device A 10 , the extended part  29  functions to support the main electrode  2  before the sealing resin  8  is formed. 
     The front surface plating layer  61  shown in  FIGS. 13 to 18  has a region formed on the main electrode front surface  21 , a region formed on the first sub-electrode front surface  31 , a region formed on the second sub-electrode front surface  41 , and a region formed on the dummy electrode front surface  51 . The first sub-electrode front surface  31 , the second sub-electrode front surface  41  and the dummy electrode front surface  51  are covered by the sealing resin  8  via the front surface plating layer  61 . The front surface plating layer  61  consists of Ag, for example. The electronic device A 10  does not, however, need to be provided with the front surface plating layer  61 . Note that illustration of the front surface plating layer  61  is omitted in figures other than  FIGS. 13 to 18 . 
     The back surface plating layer  62  shown in  FIGS. 13 to 18  has a region formed on the main electrode back surface  22 , a region formed on the first sub-electrode back surface  32 , a region formed on the second sub-electrode back surface  42 , and a region formed on the dummy electrode back surface  52 . The back surface plating layer  62  is made of Sn, for example. Furthermore, in the present embodiment, the back surface plating layer  62  is formed on the inner surface  381  of the first sub-electrode recessed part  38 , the inner surface  481  of the second sub-electrode recessed part  48 , and the inner surface  581  of the dummy electrode recessed part  58 . The back surface plating layer  62  is formed in order to facilitate adhering a solder layer  802  discussed later. Note that illustration of the back surface plating layer  62  is omitted in figures other than  FIGS. 13 to 18 . 
     The joining layer  71  shown in  FIGS. 5 to 7  and  FIG. 13  is interposed between the electronic element  1  and the main electrode  2 . The joining layer  71  is for joining the electronic element  1  to the main electrode  2 . The joining layer  71  directly contacts the electronic element  1  and the front surface plating layer  61 . The joining layer  71  contacts an area, of the main electrode surface  21 , on which the front surface plating layer  61  is formed. In the present embodiment, the joining layer  71  is made of a conductive material. The material constituting the joining layer  71  is Ag, for example. The joining layer  71  has a region that protrudes outside of the electronic element  1 , as seen in the thickness direction Z. 
     The plurality of wires  79  shown in  FIG. 8  are each bonded to the electronic element  1 . The plurality of wires  79  are each bonded to any of the plurality of first sub-electrodes  3  or any of the plurality of second sub-electrodes  4 . In the present embodiment, the plurality of wires  79  are each bonded to any of the plurality of first sub-electrodes  3  or any of the plurality of second sub-electrodes  4  via the front surface plating layer  61 . Note that the plurality of wires  79  are not bonded to the dummy electrode  5 . 
     The sealing resin  8  consists of an insulating resin, and specifically consists of a black epoxy resin, for example. The sealing resin  8  covers the electronic element  1 , the main electrode  2 , the plurality of first sub-electrodes  3 , the plurality of second sub-electrodes  4 , the dummy electrode  5 , the front surface plating layer  61 , the joining layer  71 , and the plurality of wires  79 . 
     The sealing resin  8  has a resin front surface  81 , a resin back surface  82 , and a resin lateral surface  85 . The resin front surface  81  faces in one thickness direction Z. The resin front surface  81  is flat. 
     The resin back surface  82  faces in the other thickness direction Z. The resin back surface  82  is flat. The main electrode  2 , the plurality of first sub-electrodes  3 , the plurality of second sub-electrodes  4  and the dummy electrode  5  are respectively exposed from the resin back surface  82 . 
     The resin lateral surface  85  stands erect from the resin back surface  82 . The dummy electrode  5 , the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4  are all exposed from the resin lateral surface  85 . 
     The region, of the resin lateral surface  85 , facing in the second direction Y is flush with the first sub-electrode outer surface  35  and the dummy electrode first outer surface  551 . The region, of the resin lateral surface  85 , facing in the second direction Y, the first sub-electrode outer surface  35  and the dummy electrode first outer surface  551  are surfaces cut by a dicing blade (illustration omitted). Thus, as shown in  FIG. 19 , linear marks are formed on the region, of the resin lateral surface  85 , facing in the second direction Y, the first sub-electrode outer surface  35 , and the dummy electrode first outer surface  551 . The linear marks are formed when dicing is performed with the dicing blade. Specifically, linear marks  859  are formed on the resin lateral surface  85 , linear marks  359  are formed on the first sub-electrode outer surface  35 , and linear marks  559  are formed on the dummy electrode first outer surface  551 . 
     The region, of the resin lateral surface  85 , facing in the first direction X is flush with the second sub-electrode outer surface  45  and the dummy electrode second outer surface  552 . The region, of the resin lateral surface  85 , facing in the first direction X, the second sub-electrode outer surface  45  and the dummy electrode second outer surface  552  are surfaces cut by the dicing blade. Thus, as shown in  FIG. 20 , linear marks are formed on the region, of the resin lateral surface  85 , facing in the first direction X, the second sub-electrode outer surface  45 , and the dummy electrode second outer surface  552 . Specifically, linear marks  859  are formed on the resin lateral surface  85 , linear marks  459  are formed on the second sub-electrode outer surface  45 , and linear marks  559  are formed on the dummy electrode second outer surface  552 . 
     As shown in  FIGS. 11, 12 and 18 , the sealing resin  8  has a resin corner part  86  covering the erect sloping surface  56 . The resin corner part  86  constitutes part of resin back surface  82 . The resin corner part  86  has a first lateral surface  861  that is flush with the dummy electrode first outer surface  551  and a second lateral surface  862  that is flush with the dummy electrode second outer surface  552 . The first lateral surface  861  and the second lateral surface  862  constitute part of the resin lateral surface  85 . The resin corner part  86  has a corner edge  865  extending in the thickness direction Z of the electronic element  1 . The first lateral surface  861  and the second lateral surface  862  are connected to each other via the corner edge  865  and are orthogonal to each other. 
     As shown in  FIG. 13 , a crack  89  may form in the sealing resin  8 . In the present embodiment, the crack  89  extends in the thickness direction Z starting from the end of the main electrode surface  21 . The main electrode lateral surface  23  is located more on the main electrode back surface  22  side than the end of the crack  89  on the main electrode back surface  22  side. Also, the end of the crack  89  on the main electrode back surface  22  side contacts the main electrode lateral surface  23 . Thus, the crack  89  is not exposed to the outside of the sealing resin  8 . That is, the crack  89  is entirely located inside the sealing resin  8 . 
       FIG. 21  is a right side view of a mounting structure B 1  that includes the electronic device of the first embodiment.  FIGS. 22 to 26  are partial cross-sectional views of the mounting structure B 1 .  FIGS. 22 to 26  respectively correspond to  FIGS. 14 to 18 . 
     The mounting structure B 1  is provided with the electronic device A 10 , a circuit board  801 , and a solder layer  802 . The solder layer  802  is interposed between the circuit board  801  and the plurality of first sub-electrodes  3 , between the circuit board  801  and the plurality of second sub-electrodes  4 , and between the circuit board  801  and the dummy electrode  5 . In the present embodiment, the first sub-electrode recessed part  38 , the second sub-electrode recessed part  48  and the dummy electrode recessed part  58  are filled with the solder layer  802 . The solder layer  802  also contacts the back surface plating layer  62 . 
     Next, the operation and effects of the present embodiment will be described. 
     In the present embodiment, the electronic device A 10  is provided with the dummy electrode  5 . The dummy electrode  5  is located further in the first direction X than any of the plurality of first sub-electrodes  3 , and is located further in the second direction Y than any of the plurality of second sub-electrodes  4 . According to such a configuration, the dummy electrode  5  is joined to the circuit board  801  via the solder layer  802 . Distribution of thermal stress generated in the solder layer  802  that is interposed between the electronic device A 10  and the circuit board  801  is thereby attained, making it possible to reduce thermal stress generated in the solder layer  802  that is interposed between each of the first sub-electrodes  3  and the circuit board  801  and between each of the second sub-electrodes  4  and the circuit board  801 . Accordingly, cracks occurring in the solder layer  802  that is interposed between each of the first sub-electrodes  3  and the circuit board  801  and between each of the second sub-electrodes  4  and the circuit board  801  can be prevented. 
     In the present embodiment, the dummy electrode  5  is insulated from all of the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4 . 
     According to such a configuration, even if a crack occurs in the solder layer  802  that is interposed between the dummy electrode  5  and the circuit board  801 , the electrical connection between each of the first sub-electrodes  3  and the circuit board  801  and the electrical connection between each of the second sub-electrodes  4  and the circuit board  801  are secured. Thus, according to the present embodiment, malfunctioning of the electronic device A 10  can be prevented from occurring. 
     In the present embodiment, the dummy electrode  5  has the erect sloping surface  56 . The erect sloping surface  56  stands erect from the dummy electrode back surface  52 , and slopes relative to the dummy electrode first outer surface  551  and the dummy electrode second outer surface  552 . The erect sloping surface  56  faces outside the sealing resin  8 , as seen in the thickness direction Z of the electronic element  1 . The sealing resin  8  has the resin corner part  86  covering the erect sloping surface  56 . In such a configuration, the dummy electrode  5  does not constitute the corner of the electronic device A 10 . Metal burrs can thereby be prevented from being generated on the corner of the electronic device A 10  when the sealing resin  8  and the like are diced by the dicing blade. 
     In the present embodiment, the dummy electrode recessed part  58  that is recessed from the dummy electrode back surface  52  is formed in the dummy electrode  5 . According to such a configuration, the dummy electrode  5  can be prevented from exfoliating from the solder layer  802 , by filling the dummy electrode recessed part  58  with the solder layer  802 . 
     In the present embodiment, the inner surface  581  of the dummy electrode recessed part  58  has the tip region  581 A that is connected to the dummy electrode back surface  52 . The tip region  581 A of the inner surface  581  of the dummy electrode recessed part  58  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the dummy electrode back surface  52  increases. According to such a configuration, the solder layer  802  is unlikely to come out of the dummy electrode recessed part  58 . Therefore, the dummy electrode  5  can be more effectively prevented from exfoliating from the solder layer  802 . 
     In the present embodiment, the first sub-electrode recessed part  38  that is recessed from the first sub-electrode back surface  32  is formed in the first sub-electrodes  3 . According to such a configuration, the first sub-electrode  3  can be prevented from exfoliating from the solder layer  802 , by filling the first sub-electrode recessed part  38  with the solder layer  802 . 
     In the present embodiment, the inner surface  381  of the first sub-electrode recessed part  38  has the tip region  381 A that is connected to the first sub-electrode back surface  32 . The tip region  381 A of the inner surface  381  of the first sub-electrode recessed part  38  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the first sub-electrode back surface  32  increases. According to such a configuration, the solder layer  802  is unlikely to come out of the first sub-electrode recessed part  38 . Therefore, the first sub-electrodes  3  can be more effectively prevented from exfoliating from the solder layer  802 . 
     In the present embodiment, the second sub-electrode recessed part  48  that is recessed from the second sub-electrode back surface  42  is formed in the second sub-electrodes  4 . According to such a configuration, the second sub-electrodes  4  can be prevented from exfoliating from the solder layer  802 , by filling the second sub-electrode recessed part  48  with the solder layer  802 . 
     In the present embodiment, the inner surface  481  of the second sub-electrode recessed part  48  has the tip region  481 A that is connected to the second sub-electrode back surface  42 . The tip region  481 A of the inner surface  481  of the second sub-electrode recessed part  48  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the second sub-electrode back surface  42  increases. According to such a configuration, the solder layer  802  is unlikely to come out of the second sub-electrode recessed part  48 . Therefore, the second sub-electrodes  4  can be more effectively prevented from exfoliating from the solder layer  802 . 
     When the electronic device A 10  is in use, the electronic element  1 , the main electrode  2 , the joining layer  71 , and the sealing resin  8  thermally expand and contract repeatedly. The crack  89  could thereby possibly be generated in the sealing resin  8 . The inventors found that the crack  89  often occurred starting from somewhere on the main electrode  2 . In the present embodiment, the main electrode back surface  22  has a region that protrudes outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 . According to such a configuration, in the case where the crack  89  is generated starting from somewhere on the main electrode  2  and spreads toward the resin back surface  82 , the crack  89  is prevented from spreading by the main electrode lateral surface  23 . The crack  89  can thereby be prevented from being exposed to the outside of the sealing resin  8 . As a result, deterioration in the appearance of the electronic device A 10  can be prevented, and moisture outside the sealing resin  8  can be prevented from reaching the main electrode  2  through the crack  89 . 
     The inventors found that the crack  89  was, in particular, often generated starting from the boundary between the main electrode lateral surface  23  and the main electrode surface  21  (i.e., end part of the main electrode surface  21 ). In the present embodiment, the end part on the main electrode back surface  22  side of the recessed portion  231  of the main electrode lateral surface  23  is located outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 . According to such a configuration, even if the crack  89  is generated and spreads toward the resin back surface  82  side, the crack  89  is prevented from spreading by the inner surface of the recessed portion  231 . The crack  89  can thereby be prevented from being exposed to the outside of the sealing resin  8 . As a result, deterioration in the appearance of the electronic device A 10  can be prevented, and moisture outside the sealing resin  8  can prevent from reaching the main electrode  2  through the crack  89 . 
     In the present embodiment, the area of the electronic element  1  as seen in the thickness direction Z occupies 80 percent or more of the area of the main electrode surface  21 . The crack  89  thus tends to be generated in the case where the area of the electronic element  1  as seen in the thickness direction Z is comparatively large relative to the main electrode front surface  21 . Therefore, a configuration that can prevent the crack  89  from being exposed to the outside of the sealing resin  8  is particularly preferred for the configuration of the present embodiment in which the area of the electronic element  1  as seen in the thickness direction Z is comparatively large relative to the main electrode front surface  21 . 
     A first modification of the first embodiment will be described with reference to  FIG. 27 . 
       FIG. 27  is a cross-sectional view of the electronic device A 11  according to the first modification of the first embodiment. 
     Note that, in the following description, the same reference signs are given to configuration that is the same as or similar to that discussed previously, and description thereof will be omitted as appropriate. 
     An electronic device A 11  of the present modification differs from the foregoing electronic device A 10  in that the main electrode lateral surface  23  has a main upper portion  23 E, a main lower portion  23 F, and a main intermediate portion  23 G. 
     The main upper portion  23 E is located more on the main electrode front surface  21  side than the main lower portion  23 F in the thickness direction Z. 
     The main upper portion  23 E slopes in the thickness direction Z, so as to form an acute angle with the main electrode front surface  21 . The main lower portion  23 F slopes in the thickness direction Z, so as to form an acute angle with the main electrode back surface  22 . The main lower portion  23 F is entirely located outside of the main electrode surface  21 , as seen in the thickness direction Z. 
     The main intermediate portion  23 G is located between the main upper portion  23 E and the main lower portion  23 F in the thickness direction Z. The main intermediate portion  23 G has a recessed shape that is recessed toward the center of the main electrode  2 . That is, in the present modification, the main intermediate portion  23 G constitutes the recessed portion  231 . An end part  23 GA on the main electrode back surface  22  side of the main intermediate portion  23 G is located outside of the main electrode surface  21 , as seen in the thickness direction Z of the electronic element  1 . To form the main intermediate portion  23 G, an etching solution can, for example, be injected to the main electrode  2  in a direction that slopes relative to the main electrode front surface  21 , when forming the main electrode  2 . 
     Operation and effects similar to the operation and effects discussed in relation to the electronic device A 10  are also achieved by such a configuration. 
     A second modification of the first embodiment will be described with reference to  FIG. 28 . 
       FIG. 28  is a bottom view of an electronic device A 12  according to the second modification of the first embodiment. 
     The electronic device A 12  of the present modification differs from the foregoing electronic device A 10  in the shape of the dummy electrode recessed part  58  of the dummy electrode  5 . 
     The dummy electrode recessed part  58  is also formed in the dummy electrode  5  in the present modification. The dummy electrode recessed part  58  is recessed from the dummy electrode back surface  52 . The depth of the dummy electrode recessed part  58  is, for example, ⅓ to ⅔ of the size of the dummy electrode  5  in the thickness direction Z of the electronic element  1 . The area of the opening of the dummy electrode recessed part  58  in the dummy electrode back surface  52  is, for example, ⅓ to ¾ of the area of the dummy electrode back surface  52 . In the present modification, the dummy electrode recessed part  58  is open in the first direction X and the second direction Y. Thus, the dummy electrode recessed part  58  takes on an L shape, as seen in the thickness direction Z of the dummy electrode recessed part  58 . Description other than about the dummy electrode recessed part  58  will be omitted in the present modification, because the description of the electronic device A 10  can be applied. 
     Operation and effects similar to the operation and effects discussed in relation to the electronic device A 10  are also achieved by such a configuration. 
     A second embodiment will be described with reference to  FIGS. 29 to 31 . 
       FIG. 29  is a plan view of the electronic device A 20  of the second embodiment.  FIG. 30  is a partial cross-sectional view along a line XXX-XXX in  FIG. 29 .  FIG. 31  is an enlarged partial view of a right side area in  FIG. 30 . 
     An electronic device A 20  is provided with a first electronic element  1 A, a second electronic element  1 B, a main electrode  2 , a plurality of first sub-electrodes  3 , a plurality of second sub-electrodes  4 , a dummy electrode  5 , a front surface plating layer  61 , a back surface plating layer  62 , a joining layer  71 , a joining part  72 , a plurality of spacers  74 , a plurality of fillers  75 , a plurality of wires  79 , and a sealing resin  8 . 
     The electronic device A 20  differs from the foregoing electronic device A 10  with regard to the first electronic element  1 A, the second electronic element  1 B, the joining layer  71 , the joining part  72 , the plurality of spacers  74 , the plurality of fillers  75 , and the plurality of wires  79 . Therefore, description of the other constituent elements including the main electrode  2 , the plurality of first sub-electrodes  3 , the plurality of second sub-electrodes  4 , the dummy electrode  5 , the front surface plating layer  61 , the back surface plating layer  62  and the sealing resin  8  will be omitted in the present embodiment, because the description of the electronic device A 10  can be applied. 
     In the present embodiment, the first electronic element  1 A and the second electronic element  1 B are semiconductor elements. The first electronic element  1 A and the second electronic element  1 B take on a rectangular shape, as seen in the thickness direction Z of the first electronic element  1 A and the second electronic element  1 B. The first electronic element  1 A and the second electronic element  1 B are disposed on the main electrode  2 . Specifically, the first electronic element  1 A and the second electronic element  1 B are disposed on the main electrode front surface  21 . 
     The joining layer  71  is interposed between the second electronic element  1 B and the main electrode  2 . The joining layer  71  is for joining the second electronic element  1 B to the main electrode  2 . The joining layer  71  directly contacts the second electronic element  1 B and the front surface plating layer  61 . The joining layer  71  contacts an area, of the main electrode surface  21 , exposed from the front surface plating layer  61 . In the present embodiment, the joining layer  71  is made of a conductive material. The joining layer  71  derives from a silver paste. The material constituting the joining layer  71  is Ag, for example. The joining layer  71  has a region that protrudes outside of the second electronic element  1 B, as seen in the thickness direction Z. 
     The joining part  72  is interposed between the first electronic element  1 A and the main electrode  2 . The joining part  72  is for joining the first electronic element  1 A to the main electrode  2 . The joining part  72  directly contacts the first electronic element  1 A and the front surface plating layer  61 . The joining part  72  contacts an area, of the main electrode surface  21 , exposed from the front surface plating layer  61 . In the present embodiment, the joining part  72  consists of an insulating material. The joining part  72  has a region that protrudes outside of the first electronic element  1 A, as seen in the thickness direction Z. 
     The plurality of spacers  74  have insulating properties and are mixed in the joining part  72 . The plurality of spacers  74  each directly contact the first electronic element  1 A. In the present embodiment, the plurality of spacers  74  each directly contact the front surface plating layer  61 . The plurality of spacers  74  all have a spherical shape. The diameter of each of the plurality of spacers  74  is, for example, 5 to 15 μm. The material constituting the plurality of spacers  74  is a divinylbenzene polymer. The plurality of spacers  74  are dispersed, as seen in the thickness direction Z of the electronic element  1 . The plurality of spacers  74  number ten or more, for example. 
     The plurality of fillers  75  have insulating properties and are mixed in the joining part  72 . The volume of each of the plurality of fillers  75  is less than the volume of each of the plurality of spacers  74 . The plurality of fillers  75  all have a spherical shape. The diameter of each of the plurality of fillers  75  is 1 to 3 μm. The material constituting the plurality of fillers  75  is, for example, SiO 2 , an organic material, or a mixed material of an organic material and a non-organic material. The plurality of fillers  75  are dispersed, as seen in the thickness direction Z of the first electronic element  1 A. The plurality of fillers  75  number ten or more, for example. As shown in  FIG. 31 , a portion of the plurality of fillers  75  are exposed from the joining part  72  and contact the sealing resin  8 . 
     The plurality of wires  79  are each bonded to the first electronic element  1 A or the second electronic element  1 B. 
     Any of the plurality of wires  79  is bonded to any of the plurality of first sub-electrodes  3  or any of the plurality of second sub-electrodes  4 . In the present embodiment, the plurality of wires  79  are each bonded to any of the plurality of first sub-electrodes  3  or any of the plurality of second sub-electrodes  4  via the front surface plating layer  61 . Any of the plurality of wires  79  is bonded to the first electronic element  1 A and the second electronic element  1 B. The plurality of wires  79  are not bonded to the dummy electrode  5 . 
       FIG. 32  is a right side view of a mounting structure B 2  including the electronic device of the second embodiment. 
     The mounting structure B 2  is provided with the electronic device A 20 , a circuit board  801 , and a solder layer  802 . The solder layer  802  is interposed between the circuit board  801  and the plurality of first sub-electrodes  3 , between the circuit board  801  and the plurality of second sub-electrodes  4 , and between the circuit board  801  and the dummy electrode  5 . In the present embodiment, the first sub-electrode recessed part  38 , the second sub-electrode recessed part  48  and the dummy electrode recessed part  58  are filled with the solder layer  802 . The solder layer  802  also contacts the back surface plating layer  62 . 
     According to the present embodiment, the following operation and effects are achieved, in addition to the operation and effects described in the first embodiment. 
     In the present embodiment, the plurality of insulating spacers  74  are mixed in the joining part  72 . According to such a configuration, the plurality of spacers  74  define the distance by which the first electronic element  1 A is separated from the main electrode  2 . Accordingly, the first electronic element  1 A can be prevented from contacting the main electrode  2 , by the first electronic element  1 A sloping relative to the main electrode  2 . A fault involving the first electronic element  1 A becoming electrically connected to the main electrode  2  can thereby be prevented. 
     In the present embodiment, a portion of the plurality of fillers  75  are exposed from the joining part  72  and contact the sealing resin  8 . According to such a configuration, an uneven surface can be formed by the surface of the joining part  72  and the plurality of fillers  75 . The uneven surface readily adheres to the sealing resin  8 . Accordingly, even if the sealing resin  8  and the joining part  72  thermally expand and contract repeatedly when the electronic device A 20  is in use, cracks are unlikely to occur in the sealing resin  8 . Also, according to a configuration in which fillers  75  are exposed from the joining part  72 , the joining part  72  is unlikely to expand outwardly. Therefore, the second electronic element  1 B can be disposed in closer proximity to the first electronic element  1 A. Accordingly, miniaturization of the electronic device A 20  as seen in plan view (as seen in the thickness direction Z) can be attained. 
     The configuration of the present embodiment may be combined with the configuration of each modification of the first embodiment. 
     A first modification of the second embodiment will be described with reference to  FIG. 33 . 
       FIG. 33  is a cross-sectional view of the electronic device A 21  according to the first modification of the second embodiment. 
     An electronic device A 21  of the present modification differs from the foregoing electronic device A 20  in that the front surface plating layer  61  is not provided. In the present modification, the plurality of spacers  74  each directly contact the main electrode front surface  21 . 
     Operation and effects similar to the operation and effects discussed in relation to the electronic device A 20  are also achieved by such a configuration. 
     The configuration of the present modification may be combined with the configuration of each modification of the first embodiment. 
     A third embodiment will be described with reference to  FIGS. 38 to 43 . 
       FIG. 34  is a bottom view of an electronic device A 30  of the third embodiment.  FIG. 35  is a right side view of the electronic device A 30 .  FIG. 36  is a rear view of the electronic device A 30 .  FIG. 37  is a partial cross-sectional view along a line XXXVII-XXXVII in  FIG. 34 .  FIG. 38  is an enlarged partial view of an upper left area in  FIG. 34 .  FIG. 39  is a partial enlarged plan view of the electronic device A 30  that corresponds to the opposite side of  FIG. 38 .  FIG. 40  is a partial cross-sectional view along a line XL-XL in  FIG. 39 .  FIG. 41  is a partial cross-sectional view along a line XLI-XLI in  FIG. 39 . Note that  FIG. 39  omits the sealing resin  8 , and the resin lateral surface  85  and the resin corner part  86  are respectively illustrated by virtual lines (two-dot chain lines). 
     The electronic device A 30  is provided with an electronic element  1 , a main electrode  2 , a plurality of first sub-electrodes  3 , a plurality of second sub-electrodes  4 , a dummy electrode  5 , a front surface plating layer  61 , a back surface plating layer  62 , a joining layer  71 , a plurality of wires  79 , and a sealing resin  8 . 
     The electronic device A 30  of the present embodiment differs from the foregoing electronic device A 10  and electronic device A 20  in the shape of the dummy electrode  5 . Therefore, in the present embodiment, matters concerning the dummy electrode  5  will be described, and description of other matters will be omitted in the present embodiment because the description of the electronic device A 10  can be applied. 
     Dummy electrodes  5  including three additional dummy electrodes  59  are respectively disposed at the four corners of the sealing resin  8 . The dummy electrodes  5  each have a dummy electrode front surface  51 , a dummy electrode main back surface  521 , a dummy electrode sub-back surface  522 , a dummy electrode lateral surface  53 , a dummy electrode first outer surface  551 , a dummy electrode second outer surface  552 , and an erect sloping surface  56 . In the present embodiment, the dummy electrodes  5  are insulated from all of the plurality of first sub-electrodes  3  and the plurality of second sub-electrodes  4 . 
     As shown in  FIGS. 34 and 38 , the dummy electrode main back surface  521  and the dummy electrode sub-back surface  522  are both exposed from a resin back surface  82  of the sealing resin  8 . In the present embodiment, the dummy electrode sub-back surface  522  includes a dummy electrode first sub-back surface  522 A that is located in the first direction X and a dummy electrode second sub-back surface  522 B that is located in the second direction Y. The dummy electrode first sub-back surface  522 A has a band-like shape extending in the second direction Y. The dummy electrode second sub-back surface  522 B has a band-like shape extending in the first direction X. Also, in the present embodiment, the dummy electrode main back surface  521  and the dummy electrode sub-back surface  522  are exposed in a state of being spaced from each other on the resin back surface  82 . More specifically, as shown in  FIG. 38 , the dummy electrode main back surface  521  and the dummy electrode first sub-back surface  522 A are exposed from the resin back surface  82  in a state of being spaced from each other in the first direction X. The dummy electrode main back surface  521  and the dummy electrode second sub-back surface  522 B are exposed from the resin back surface  82  in a state of being spaced from each other in the second direction Y. As shown in  FIGS. 40 and 41 , the dummy electrode main back surface  521 , the dummy electrode first sub-back surface  522 A and the dummy electrode second sub-back surface  522 B are all flat. 
     As shown in  FIG. 37 , the dummy electrode  5  is coupled to an end part of an extended part  29  that extends outside the main electrode  2  from the main electrode  2 . The dummy electrode main back surface  521  and the dummy electrode sub-back surface  522  are, similarly to the extended part  29 , formed by a portion remaining as a result of partially etching only a lower half cross-section in the thickness direction Z of a lead frame. Here, as shown in  FIGS. 40 and 41 , a cavity part of the dummy electrode  5  that is located between the dummy electrode main back surface  521  and the dummy electrode sub-back surface  522  in the first direction X or the second direction Y is filled with the sealing resin  8 . 
     The dummy electrode front surface  51  faces in the opposite direction to the dummy electrode main back surface  521  and the dummy electrode sub-back surface  522 . As shown in  FIG. 39 , the shape of the dummy electrode front surface  51  is substantially the same as the dummy electrode front surface  51  of the electronic device A 10 . Also, as shown in  FIGS. 40 and 41 , the dummy electrode front surface  51  is flat. The dummy electrode front surface  51  is entirely covered by the sealing resin  8 . 
     As shown in  FIGS. 35, 38 and 39 , the dummy electrode first outer surface  551  faces in the second direction Y. The dummy electrode first outer surface  551  connects the dummy electrode front surface  51  to the dummy electrode main back surface  521 , and the dummy electrode front surface  51  to the dummy electrode first sub-back surface  522 A. The dummy electrode first outer surface  551  is exposed from the resin lateral surface  85  of the sealing resin  8 . 
     As shown in  FIGS. 36, 38 and 39 , the dummy electrode second outer surface  552  faces in the first direction X. The dummy electrode second outer surface  552  connects the dummy electrode front surface  51  to the dummy electrode main back surface  521 , and the dummy electrode front surface  51  to the dummy electrode second sub-back surface  522 B. The dummy electrode second outer surface  552  is exposed from the resin lateral surface  85  of the sealing resin  8 . 
     As shown in  FIGS. 37 and 38 , the erect sloping surface  56  stands erect from the dummy electrode main back surface  521 , and slopes relative to the dummy electrode first outer surface  551  and the dummy electrode second outer surface  552 . The erect sloping surface  56  is connected to the dummy electrode first outer surface  551  and the dummy electrode second outer surface  552 . The erect sloping surface  56  faces outside the sealing resin  8 , as seen in the thickness direction Z of the electronic element  1 . A resin corner part  86  of the sealing resin  8  that covers the erect sloping surface  56  is formed on the outside thereof. The shape of the resin corner part  86  is substantially the same as the resin corner part  86  of the electronic device A 10 . 
     As shown in  FIGS. 40 and 41 , the dummy electrode lateral surface  53  connects the dummy electrode front surface  51  to the dummy electrode first sub-back surface  522 A or the dummy electrode front surface  51  to the dummy electrode second sub-back surface  522 B. The dummy electrode lateral surface  53  is entirely covered by the sealing resin  8 . The dummy electrode lateral surface  53  includes the dummy upper portion  53 A and the dummy lower portion  53 B. The dummy upper portion  53 A and the dummy lower portion  53 B are similar to the dummy upper portion  53 A and the dummy lower portion  53 B of the electronic device A 10 , and thus description thereof will be omitted here. 
     As shown in  FIGS. 40 and 41 , the back surface plating layer  62  has a region formed on the dummy electrode main back surface  521  and the dummy electrode sub-back surface  522 . The back surface plating layer  62  is made of Sn, for example. Here, the back surface plating layer  62  also has a region formed on the inner surface of the cavity part of the dummy electrode  5  that is located between the dummy electrode main back surface  521  and the dummy electrode sub-back surface  522  in the first direction X or the second direction Y. Note that illustration of the back surface plating layer  62  is omitted in figures other than  FIGS. 40 and 41 . 
       FIG. 42  is a right side view of a mounting structure B 3  including the electronic device of the third embodiment.  FIG. 43  is a partial cross-sectional view of the mounting structure B 3 .  FIG. 43  corresponds to  FIG. 40 . 
     The mounting structure B 3  is provided with the electronic device A 30 , a circuit board  801 , and a solder layer  802 . The solder layer  802  is interposed between the circuit board  801  and the plurality of first sub-electrodes  3 , between the circuit board  801  and the plurality of second sub-electrodes  4 , and between the circuit board  801  and the dummy electrode  5 . In the present embodiment, the solder layer  802  is interposed between the dummy electrode main back surface  521  and the circuit board  801  and between the dummy electrode sub-back surface  522  and the circuit board  801 . Here, as shown in  FIG. 43 , the solder layer  802  does not adhere to the resin back surface  82  of the sealing resin  8  that is located between the dummy electrode main back surface  521  and the dummy electrode second sub-back surface  522 B in the second direction Y. Similarly, the solder layer  802  does not adhere to the resin back surface  82  that is located between the dummy electrode main back surface  521  and the dummy electrode second sub-back surface  522 B in the first direction X (illustration omitted). Note that the first sub-electrode recessed part  38  and the second sub-electrode recessed part  48  are also respectively filled with the solder layer  802  in the present embodiment, similarly to the electronic device A 10 . The solder layer  802  also contacts the back surface plating layer  62 . 
     According to the present embodiment, the following operation and effects are achieved, in addition to the operation and effects described in the first embodiment. 
     In the present embodiment, the dummy electrode main back surface  521  and the dummy electrode sub-back surface  522  are exposed in a state of being spaced from each other on the resin back surface  82  of the sealing resin  8 . Here, the inventors revealed that thermal stress generated in the solder layer  802  due to the temperature cycle when the electronic device A 30  is in use is mostly concentrated in the solder layer  802  that is interposed between the dummy electrodes  5  that are located at the four corners of the sealing resin  8  and the circuit board  801 . In the present embodiment, the dummy electrode main back surface  521  is located at the outermost edge of the four corners. The dummy electrode first sub-back surface  522 A is located in the first direction X and the dummy electrode second sub-back surface  522 B is located in the second direction Y, adjacent to the dummy electrode main back surface  521 . According to such a configuration, thermal stress generated in the solder layer  802  that is interposed between the dummy electrode first sub-back surface  522 A and the circuit board  801  or the dummy electrode second sub-back surface  522 B and the circuit board  801  is reduced to less than thermal stress generated in the solder layer  802  that is interposed between the dummy electrode back surface  52  of the electronic device A 10  and the circuit board  801 . Therefore, even if a crack occurs in the solder layer  802  that is interposed between the dummy electrode main back surface  521  and the circuit board  801 , the crack can be prevented from spreading by the solder layer  802  that is interposed between the dummy electrode first sub-back surface  522 A and the circuit board  801  or the dummy electrode second sub-back surface  522 B and the circuit board  801 . Accordingly, cracks can be more effectively prevented from occurring in the solder layer  802  that is interposed between each of the first sub-electrodes  3  and the circuit board  801  or each of the second sub-electrodes  4  and the circuit board  801 . 
     The configuration of the present embodiment may be combined with the configuration of each modification of the first embodiment or the second embodiment. 
     A first modification of the third embodiment will be described with reference to  FIGS. 44 to 48 . 
       FIG. 44  is a bottom view of an electronic device A 31  according to the first modification of the third embodiment.  FIG. 45  is an enlarged partial view of an upper left area in  FIG. 44 .  FIG. 46  is a partial enlarged plan view of the electronic device A 31  that corresponds to the opposite side of  FIG. 45 .  FIG. 47  is a partial cross-sectional view along a line XLVII-XLVII in  FIG. 46 . Note that  FIG. 46  omits the sealing resin  8 , and the resin lateral surface  85  and the resin corner part  86  are respectively illustrated with virtual lines (two-dot chain lines). 
     The electronic device A 31  of the present modification differs from the foregoing electronic device A 30  in that an independent dummy electrode  54  is further provided. 
     The independent dummy electrode  54  shown in  FIGS. 44, 45 and 46  is not coupled to the dummy electrode  5 . Also, the independent dummy electrode  54  is insulated from all of the plurality of first sub-electrodes  3 , the plurality of second sub-electrodes  4  and the dummy electrodes  5  including the additional dummy electrodes  59 . In the present modification, the independent dummy electrode  54  includes a first independent dummy electrode  549 A that is disposed in the first direction X and is located between the plurality of first sub-electrodes  3  and the dummy electrode  5 , and a second independent dummy electrode  549 B that is disposed in the second direction Y and is located between the plurality of second sub-electrodes  4  and the dummy electrode  5 . The independent dummy electrode  54  is made of a conductive material. The independent dummy electrode  54  is formed by patterning such as etching or the like being performed on a metal plate made of Cu, for example. 
     As shown in  FIG. 44 , only in the present modification do the three additional dummy electrodes  59  other than dummy electrode  5  that is disposed in one of the four corners of the sealing resin  8  indicate assemblies that are constituted by the dummy electrode  5 , the first independent dummy electrode  549 A, and the second independent dummy electrode  549 B. 
     In the present modification, the shape of the first independent dummy electrode  549 A and the first sub-electrodes  3  are respectively the same as the shape of the second independent dummy electrode  549 B and the second sub-electrodes  4 . Note that the independent dummy electrode  54  can also take any shape other than the shape in the present modification. As shown in  FIG. 47 , the independent dummy electrode  54  has an independent dummy electrode front surface  541 , an independent dummy electrode back surface  542 , an independent dummy electrode lateral surface  543 , and an independent dummy electrode outer surface  545 . 
     The independent dummy electrode front surface  541  faces in one thickness direction Z. In the present modification, the independent dummy electrode front surface  541  is a portion corresponding to a first sub-electrode front surface  31  of the first sub-electrode  3  or a second sub-electrode front surface  41  of the second sub-electrodes  4 . The independent dummy electrode front surface  541  is flat. The independent dummy electrode front surface  541  is entirely covered by the sealing resin  8 . 
     The independent dummy electrode back surface  542  faces in the other thickness direction Z. In the present modification, the independent dummy electrode back surface  542  is a portion corresponding to a first sub-electrode back surface  32  of the first sub-electrode  3  or a second sub-electrode back surface  42  of the second sub-electrodes  4 . The independent dummy electrode back surface  542  faces in the opposite direction to the independent dummy electrode front surface  541 . The independent dummy electrode back surface  542  is flat. The independent dummy electrode back surface  542  is exposed from the resin back surface  82  of the sealing resin  8 . 
     The independent dummy electrode outer surface  545  faces in the first direction X or the second direction Y. In the present modification, the independent dummy electrode outer surface  545  is a portion corresponding to a first sub-electrode outer surface  35  of the first sub-electrodes  3  or a second sub-electrode outer surface  45  of the second sub-electrodes  4 . Also, in the present modification, the independent dummy electrode outer surface  545  is exposed from the resin lateral surface  85  of the sealing resin  8 . Accordingly, the first independent dummy electrode  549 A and the second independent dummy electrode  549 B are both exposed from the resin lateral surface  85 . 
     The independent dummy electrode lateral surface  543  connects the independent dummy electrode front surface  541  to the independent dummy electrode back surface  542 . In the present modification, the independent dummy electrode lateral surface  543  is a portion corresponding to a first sub-electrode lateral surface  33  of the first sub-electrodes  3  or a second sub-electrode lateral surface  43  of the second sub-electrodes  4 . The independent dummy electrode lateral surface  543  stands erect from the independent dummy electrode back surface  542 . The second sub-electrode lateral surface  43  is covered by the sealing resin  8 . As shown in  FIGS. 45 and 46 , the dummy electrode lateral surface  53  connects an end part  545 A of the independent dummy electrode outer surface  545  to an end part  545 B of the independent dummy electrode outer surface  545 . The independent dummy electrode lateral surface  543  includes an independent dummy upper portion  543 A and an independent dummy lower portion  543 B. The independent dummy upper portion  543 A and the independent dummy lower portion  543 B are similar to the first sub-upper portion  33 A and the first sub-lower portion  33 B of the first sub-electrodes  3  or the second sub-upper portion  43 A and the second sub-lower portion  43 B of the second sub-electrodes  4 , and thus description thereof will be omitted here. 
     An independent dummy electrode recessed part  548  is formed in each of the independent dummy electrode  54 . In the present modification, the independent dummy electrode recessed part  548  is a portion corresponding to the first sub-electrode recessed part  38  of the first sub-electrodes or the second sub-electrode recessed part  48  of the second sub-electrodes  4 . The independent dummy electrode recessed part  548  is recessed from the independent dummy electrode back surface  542 . The outline of the opening of the independent dummy electrode recessed part  548  has a shape that fits inside the outer edge of the independent dummy electrode back surface  542 . In the present modification, the outline of the opening of the independent dummy electrode recessed part  548  has a rectangular shape. The outline of the opening of the independent dummy electrode recessed part  548  may have a different shape from the present modification, such as a circular shape or a polygonal shape. 
     An inner surface  548 A of the independent dummy electrode recessed part  548  has a tip region  548 B that is connected to the independent dummy electrode back surface  542 . The tip region  548 B of the inner surface  548 A of the independent dummy electrode recessed part  548  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the independent dummy electrode back surface  542  increases. The independent dummy electrode recessed part  548  thereby has a shape in which the opening narrows. 
     As shown in  FIG. 47 , the back surface plating layer  62  has a region formed on the independent dummy electrode back surface  542 . The back surface plating layer  62  is made of Sn, for example. In the present modification, the back surface plating layer  62  is further formed on the inner surface  548 A of the independent dummy electrode recessed part  548 . Note that illustration of the back surface plating layer  62  is omitted in figures other than  FIG. 47 . 
     As shown in  FIG. 46 , in the present modification, the plurality of wires  79  are not bonded to either the first independent dummy electrode  549 A or the second independent dummy electrode  549 B. 
       FIG. 48  is a partial cross-sectional view of a mounting structure B 31  including the electronic device according to the first modification of the third embodiment.  FIG. 48  corresponds to  FIG. 47 . 
     The mounting structure B 31  is provided with the electronic device A 31 , a circuit board  801 , and a solder layer  802 . The solder layer  802  is interposed between the circuit board  801  and the plurality of first sub-electrodes  3 , between the circuit board  801  and the plurality of second sub-electrodes  4 , between the circuit board  801  and the dummy electrode  5 , and between the circuit board  801  and the independent dummy electrode  54 . In the present modification, the first sub-electrode recessed part  38 , the second sub-electrode recessed part  48  and the independent dummy electrode recessed part  548  are filled with the solder layer  802 . The solder layer  802  also contacts the back surface plating layer  62 . 
     According to the present modification, the following operation and effects are achieved, in addition to the operation and effects described in the third embodiment. 
     In the present modification, the independent dummy electrode  54  that is not coupled to the dummy electrode  5  is further provided. The independent dummy electrode  54  is disposed between the dummy electrode  5  and the plurality of first sub-electrodes  3  or the dummy electrode and the plurality of second sub-electrodes  4 , in the four corners of the sealing resin  8  of the electronic device A 31 . Therefore, the plurality of first sub-electrode  3  are arrayed in a state of being sandwiched on both sides by the first independent dummy electrodes  549 A in the first direction X. Similarly, the plurality of second sub-electrodes  4  are disposed in a state of being sandwiched on both sides by the second independent dummy electrodes  549 B in the second direction Y. According to such a configuration, thermal stress generated in the solder layer  802  that is interposed between each of the first sub-electrodes  3  and the circuit board  801  and each of the second sub-electrodes  4  and the circuit board  801  can be further reduced by the independent dummy electrodes  54 . Accordingly, the effect of preventing cracks in the solder layer  802  that is interposed between the first sub-electrodes  3  and the circuit board  801  and in the solder layer  802  that is interposed between the second sub-electrodes  4  and the circuit board  801  can be further enhanced compared with the electronic device A 30 . 
     In the present modification, the independent dummy electrode recessed part  548  that is recessed from the independent dummy electrode back surface  542  is formed in the independent dummy electrode  54 . According to such a configuration, the independent dummy electrode  54  can be prevented from exfoliating from the solder layer  802  by filling the independent dummy electrode recessed part  548  with the solder layer  802 . 
     In the present modification, the inner surface  548 A of the independent dummy electrode recessed part  548  has the tip region  548 B that is connected to the independent dummy electrode back surface  542 . The tip region  548 B of the inner surface  548 A of the independent dummy electrode recessed part  548  slopes in the thickness direction Z of the electronic element  1 , such that the area of a cross-section along a plane that is orthogonal to the thickness direction Z of the electronic element  1  gradually increases as the distance from the independent dummy electrode back surface  542  increases. According to such a configuration, the solder layer  802  is unlikely to come out from the independent dummy electrode recessed part  548 . Thus, the independent dummy electrode  54  can be more effectively prevented from exfoliating from the solder layer  802 . 
     The configuration of the present modification may be combined with the configuration of each modification of the first embodiment or the second embodiment. 
     The present invention is not limited to the foregoing embodiments. Various design modifications can be made to the specific configurations of the respective parts of the present invention. The configuration of the foregoing embodiments and modifications can be combined with each other. 
     Configurations of the present invention and variations thereof are enumerated below as Appendixes. 
     APPENDIXES 
     1A. An electronic device including: 
     
         
         
           
             an electronic element; 
             a main electrode on which the electronic element is disposed; and 
             a sealing resin covering the electronic element and the main electrode, 
             wherein the main electrode has a main electrode front surface on which the electronic element is disposed and a main electrode back surface facing in an opposite direction to the main electrode front surface, 
             the main electrode back surface is exposed from the sealing resin, and 
             the main electrode back surface has a region that protrudes outside of the main electrode front surface, as seen in a thickness direction of the electronic element.
 
2A. The electronic device according to Appendix 1A, wherein the main electrode back surface protrudes outside of the main electrode front surface, around an entire periphery of the main electrode, as seen in the thickness direction of the electronic element.
 
3A. The electronic device according to Appendix 1A or 2A, wherein the main electrode has a main electrode lateral surface connecting the main electrode front surface to the main electrode back surface, and the main electrode lateral surface has a recessed portion that is recessed toward a center of the main electrode.
 
4A. The electronic device according to Appendix 3A, wherein an end part on the main electrode back surface side of the recessed portion is located outside of the main electrode front surface, as seen in the thickness direction of the electronic element.
 
5A. The electronic device according to Appendix 3A or 4A, wherein the recessed portion has a region that is located more on a center side of the main electrode than is an end of the main electrode front surface, as seen in the thickness direction.
 
6A. The electronic device according to any of Appendixes 3A to 5A, wherein the recessed portion is formed around the entire periphery of the main electrode.
 
7A. The electronic device according to Appendix 3A, wherein a value of surface roughness of the main electrode lateral surface is greater than a value of surface roughness of the main electrode back surface.
 
8A. The electronic device according to Appendix 7A, wherein a surface area per unit area of the main electrode lateral surface is 1.5 to 2.5 times a surface area per unit area of the main electrode back surface.
 
9A. The electronic device according to any of Appendixes 3A to 8A, wherein the main electrode lateral surface includes a main upper portion and a main lower portion, and the main upper portion is located more on the main electrode front surface side than the main lower portion in the thickness direction.
 
10A. The electronic device according to any of Appendixes 3A to 9A, wherein a crack extending in the thickness direction is formed in the sealing resin, the main electrode lateral surface is located more on the main electrode back surface side than an end of the crack on the main electrode back surface side, and the end of the crack on the main electrode back surface side contacts the main electrode lateral surface.
 
11A. The electronic device according to Appendix 10A, wherein the crack extends starting from an end of the main electrode front surface.
 
12A. The electronic device according to Appendix 9A, wherein the main upper portion has a recessed shape that is recessed toward the center of the main electrode.
 
13A. The electronic device according to Appendix 12A, wherein an end part on the main electrode back surface side of the main upper portion is located outside of the main electrode front surface, as seen in the thickness direction of the electronic element.
 
14A. The electronic device according to Appendix 12A or 13A, wherein the main lower portion slopes in the thickness direction, so as to form an acute angle with the main electrode back surface.
 
15A. The electronic device according to any of Appendixes 12A to 14A, wherein a size of the main lower portion in the thickness direction is less than a size of the main upper portion in the thickness direction.
 
16A. The electronic device according to Appendix 9A, wherein the main electrode lateral surface includes a main intermediate portion, the main intermediate portion is located between the main upper portion and the main lower portion in the thickness direction, and the main intermediate portion has a recessed shape that is recessed toward the center of the main electrode.
 
17A. The electronic device according to Appendix 16A, wherein an end part on the main electrode back surface side of the main intermediate portion is located outside of the main electrode front surface, as seen in the thickness direction of the electronic element.
 
18A. The electronic device according to Appendix 16A or 17A, wherein the main upper portion slopes in the thickness direction, so as to form an acute angle with the main electrode front surface, and the main lower portion slopes in the thickness direction, so as to form an acute angle with the main electrode back surface.
 
19A. The electronic device according to any of Appendixes 1A to 18A, wherein the main electrode back surface is flat.
 
20A. The electronic device according to any of Appendixes 1A to 19A, wherein an area of the electronic element as seen in the thickness direction occupies 80 percent or more of an area of the main electrode surface.
 
21A. The electronic device according to any of Appendixes 1A to 20A, further including an extended part extending outside the main electrode from the main electrode, as seen in the thickness direction, and a thickness of the extended part is less than the main electrode.
 
22A. The electronic device according to Appendix 21A, wherein, when the extended part is viewed from the main electrode, the extended part is entirely peripherally surrounded by the sealing resin.
 
23A. The electronic device according to any of Appendixes 1A to 22A, further including a back surface plating layer, wherein the back surface plating layer has a region formed on the main electrode back surface.
 
24A. The electronic device according to Appendix 23A, wherein the back surface plating layer is made of Sn.
 
25A. The electronic device according to any of Appendixes 1A to 24A, further including a front surface plating layer, wherein the front surface plating layer has a region formed on the main electrode front surface.
 
26A. The electronic device according to Appendix 25A, wherein the front surface plating layer is made of Ag.
 
27A. The electronic device according to Appendix 1A, further including a plurality of first sub-electrodes arrayed in a first direction and a plurality of second sub-electrodes arrayed in a second direction that is orthogonal to the first direction.
 
28A. The electronic device according to Appendix 27A, wherein the sealing resin has a resin lateral surface, the plurality of first sub-electrodes are each exposed from the resin lateral surface and have a first sub-electrode outer surface facing in the second direction, and the first sub-electrode outer surface is flush with a region, of the resin lateral surface, facing in the second direction.
 
29A. The electronic device according to Appendix 28A, wherein a linear mark is formed on the first sub-electrode outer surface.
 
30A. The electronic device according to Appendix 28A, wherein the plurality of first sub-electrodes each have a first sub-electrode back surface that is exposed from the sealing resin.
 
31A. The electronic device according to Appendix 30A, wherein the first sub-electrode back surface is flat.
 
32A. The electronic device according to Appendix 30A or 31A, wherein the plurality of first sub-electrodes each have a first sub-electrode lateral surface that stands erect from the first sub-electrode back surface, the first sub-electrode lateral surface is covered by the sealing resin, and the first sub-electrode lateral surface connects an end part of the first sub-electrode outer surface in the first direction to an end part of the first sub-electrode outer surface on an opposite side to the first direction.
 
33A. The electronic device according to Appendix 32A, wherein the first sub-electrode lateral surface has a sub-upper portion and a sub-lower portion, and the sub-upper portion of the first sub-electrode lateral surface and the sub-lower portion of the first sub-electrode lateral surface each have a recessed shape that is recessed toward the center of the first sub-electrode.
 
34A. The electronic device according to any of Appendixes 30A to 33A, wherein the plurality of first sub-electrodes each have a first sub-electrode front surface facing in an opposite direction to the first sub-electrode back surface, and the first sub-electrode front surface is covered by the sealing resin.
 
35A. The electronic device according to Appendix 27A, further including a plurality of wires, wherein the plurality of wires are each bonded to the electronic element, and the plurality of wires are each bonded to any of the plurality of first sub-electrodes or any of the plurality of second sub-electrodes.
 
36A. The electronic device according to any of Appendixes 1A to 35A, further including a joining layer interposed between the electronic element and the main electrode.
 
37A. The electronic device according to Appendix 36A, wherein the joining layer is made of a conductive material.
 
38A. The electronic device according to Appendix 37A, wherein the joining layer is made of Ag.
 
39A. The electronic device according to any of Appendixes 36A to 38A, wherein the joining layer has a region that protrudes outside of the electronic element, as seen in the thickness direction.
 
40A. A mounting structure of an electronic device, including the electronic device according to Appendix 27A, a circuit board, and a solder layer interposed between the circuit board and the plurality of first sub-electrodes and between the circuit board and the plurality of second sub-electrodes.
 
1B. An electronic device comprising:
 
             an electronic element; 
             a main electrode on which the electronic element is disposed; 
             an insulating joining part interposed between the electronic element and the main electrode; 
             a plurality of insulating spacers mixed in the joining part; and 
             a sealing resin covering the electronic element and the main electrode.
 
2B. The electronic device according to Appendix 1B, wherein the plurality of spacers each directly contact the electronic element.
 
3B. The electronic device according to Appendix 1B or 2B, wherein the plurality of spacers each directly contact the main electrode.
 
4B. The electronic device according to Appendix 1B or 2B, further including a front surface plating layer, wherein the front surface plating layer has a region formed on the main electrode, and the plurality of spacers each directly contact the front surface plating layer.
 
5B. The electronic device according to any of Appendixes 1B to 4B, wherein the plurality of spacers all have a spherical shape.
 
6B. The electronic device according to Appendix 5B, wherein a diameter of each of the plurality of spacers is 5 to 15 μm.
 
7B. The electronic device according to any of Appendixes 1B to 6B, wherein the plurality of spacers are made of a divinylbenzene polymer.
 
8B. The electronic device according to any of Appendixes 1B to 7B, wherein the plurality of spacers are dispersed, as seen in the thickness direction of the electronic element.
 
9B. The electronic device according to any of Appendixes 1B to 8B, wherein the plurality of spacers number ten or more.
 
10B. The electronic device according to any of Appendixes 1B to 9B, further including a plurality of insulating fillers mixed in the joining part.
 
11B. The electronic device according to Appendix 10B, wherein a volume of each of the plurality of fillers is less than a volume of each of the plurality of spacers.
 
12B. The electronic device according to Appendix 11B, wherein the plurality of fillers all have a spherical shape.
 
13B. The electronic device according to Appendix 12B, wherein a diameter of each of the plurality of fillers is 1 to 3 μm.
 
14B. The electronic device according to any of Appendixes 10B to 13B, wherein the plurality of fillers are made of SiO 2 , an organic material, or a mixed material of an organic material and a non-organic material.
 
15B. The electronic device according to any of Appendixes 10B to 14B, wherein the plurality of fillers are dispersed, as seen in the thickness direction of the electronic element.
 
16B. The electronic device according to any of Appendixes 10B to 15B, wherein the plurality of fillers number ten or more.
 
17B. The electronic device according to any of Appendixes 10B to 16B, wherein a portion of the plurality of fillers are exposed from the joining part and contact the sealing resin.
 
18B. The electronic device according to Appendix 1B, wherein the main electrode has a main electrode front surface on which the electronic element is disposed and a main electrode back surface facing in an opposite direction to the main electrode front surface, and the main electrode back surface is exposed from the sealing resin.
 
19B. The electronic device according to any of Appendixs 1B to 18B, further including a second electronic element, where the electronic element is taken as a first electronic element, wherein the second electronic element is disposed on the main electrode.
 
20B. The electronic device according to Appendix 19B, further including a joining layer interposed between the second electronic element and the main electrode.
 
21B. The electronic device according to Appendix 20B, wherein the joining layer is made of a conductive material.
 
22B. The electronic device according to Appendix 21B, wherein the joining layer is made of Ag.
 
23B. The electronic device according to any of Appendixes 19B to 22B, further including a plurality of first sub-electrodes arrayed in a first direction and a plurality of second sub-electrodes arrayed in a second direction that is orthogonal to the first direction.
 
24B. The electronic device according to Appendix 23B, wherein the sealing resin has a resin lateral surface, the plurality of first sub-electrodes are each exposed from the resin lateral surface and have a first sub-electrode outer surface facing in the second direction, and the first sub-electrode outer surface is flush with a region, of the resin lateral surface, facing in the second direction.
 
25B. The electronic device according to Appendix 24B, wherein a linear mark is formed on the first sub-electrode outer surface.
 
26B. The electronic device according to Appendix 24B, wherein the plurality of first sub-electrodes each have a first sub-electrode back surface that is exposed from the sealing resin.
 
27B. The electronic device according to Appendix 26B, wherein the first sub-electrode back surface is flat.
 
28B. The electronic device according to Appendix 26B or 27B, wherein the plurality of first sub-electrodes each have a first sub-electrode lateral surface that stands erect from the first sub-electrode back surface, the first sub-electrode lateral surface is covered by the sealing resin, and the first sub-electrode lateral surface connects an end part of the first sub-electrode outer surface in the first direction to an end part of the first sub-electrode outer surface on an opposite side to the first direction.
 
29B. The electronic device according to Appendix 28B, wherein the first sub-electrode lateral surface has a sub-upper portion and a sub-lower portion, and the sub-upper portion of the first sub-electrode lateral surface and the sub-lower portion of the first sub-electrode lateral surface each have a recessed shape that is recessed toward the center of the first sub-electrode.
 
30B. The electronic device according to any of Appendixes 26B to 29B, wherein the plurality of first sub-electrodes each have a first sub-electrode front surface facing in an opposite direction to the first sub-electrode back surface, and the first sub-electrode front surface is covered by the sealing resin.
 
31B. The electronic device according to Appendix 23B, further includes a plurality of wires, any of the plurality of wires is bonded to the first electronic element or the second electronic element, and any of the plurality of wires is bonded to any of the plurality of first sub-electrodes or any of the plurality of second sub-electrodes.
 
32B. A mounting structure of an electronic device including the electronic device according to Appendix 23B, a circuit board, and a solder layer interposed between the circuit board and the plurality of first sub-electrodes and between the circuit board and the plurality of second sub-electrodes.