Patent Publication Number: US-2022232700-A1

Title: Lighting device and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of the U.S. patent application Ser. No. 16/583,270, filed Sep. 26, 2019, which claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2018-182315, filed Sep. 27, 2018, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present disclosure relates to a lighting device and a method of manufacturing the lighting device. 
     Description of the Related Art 
     See, for example, Japanese Unexamined Patent Application Publication No. 2013-102201. 
     SUMMARY OF THE INVENTION 
     A lighting device includes a light emitting element, a light guide member, and a substrate. The light emitting element has element electrodes. A light guide member is to receive incoming light from the light emitting element and to emit light spreading along a plane. A substrate includes a base substrate having a film shape. Conductors are formed on parts of a first surface of the base substrate. An adhesive member is formed on a second surface of the base substrate. Through-holes penetrate the substrate in a thickness direction of the substrate. The substrate is provided on the light emitting element via the adhesive member of the substrate such that a surface of the light emitting element is exposed through each of the through-holes to define a bottomed hole. Each of the element electrodes is connected to each of the conductors via a filler filling the bottomed hole. The filler has a lower surface than a surface carrying the conductors of the substrate in a cross-sectional view. 
     A method of manufacturing a lighting device includes preparing a light emitting element having element electrodes and preparing a light guide member to receive incoming light from the light emitting element and to emit light spreading along a plane. The method further includes preparing a substrate including a base substrate having a film shape, conductors being formed on parts of a first surface of the base substrate, an adhesive member being formed on a second surface of the base substrate, and through-holes penetrating the substrate in a thickness direction of the substrate and adhering the light guide member to the substrate. The method further includes forming an intermediate structure having a bottomed hole formed in a location of each of the through-holes as a result of adhering an adhesive surface of the adhesive member of the substrate to a surface of the light emitting element having the element electrodes formed thereon, and connecting each of the element electrodes to each of the conductors via a filler on the intermediate structure, the filler being formed by injecting an electrically conductive paste into the bottomed hole and curing the electrically conductive paste, wherein the filler has a lower surface than a surface carrying the conductors of the substrate in a cross-sectional view. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of embodiments of the invention and many of the attendant advantages thereof will be readily obtained by reference to the following detailed description when considered in connection with the accompanying drawings. 
         FIG. 1  is a schematic plan view diagrammatically illustrating a lighting device according to a first embodiment; 
         FIG. 2  is a cross-sectional view of the lighting device of  FIG. 1  that is taken along line II-II; 
         FIG. 3  is a schematic explanatory perspective view of a part where a filler is injected in the lighting device according to the first embodiment; 
         FIG. 4  is a flowchart illustrating steps making up a method of manufacturing the lighting device according to the first embodiment; 
         FIG. 5  is a schematic plan view diagrammatically illustrating a light-emitting element assembly prepared by the method of manufacturing the lighting device according to the first embodiment; 
         FIG. 6  is a cross-sectional view of the light-emitting element assembly of  FIG. 5  that is taken along line VI-VI; 
         FIG. 7  is a schematic plan view diagrammatically illustrating a plane light-emitter on which wiring lines are formed by the method of manufacturing the lighting device according to the first embodiment; 
         FIG. 8  is a cross-sectional view of the plane light-emitter of  FIG. 7  that is taken along line VIII-VIII; 
         FIG. 9  is a schematic plan view diagrammatically illustrating a substrate on which through-holes are formed by the method of manufacturing the lighting device according to the first embodiment; 
         FIG. 10  is a cross-sectional view of the substrate of  FIG. 9  that is taken along line X-X; 
         FIG. 11  is a schematic plan view diagrammatically illustrating an intermediate structure formed by an adhering step of the method of manufacturing the lighting device according to the first embodiment; 
         FIG. 12  is a cross-sectional view of the intermediate structure of  FIG. 11  that is taken along line XII-XII; 
         FIG. 13A  is a schematic enlarged view of a terminal illustrated in  FIG. 7 ; 
         FIG. 13B  is a schematic enlarged view of a bottomed hole illustrated in  FIG. 11 ; 
         FIG. 14  is a cross-sectional view diagrammatically illustrating a modification of the lighting device according to the first embodiment; 
         FIG. 15  is a schematic plan view diagrammatically illustrating a plane light-emitter on which the wiring lines are formed by a method of manufacturing a lighting device according to a second embodiment; 
         FIG. 16  is a cross-sectional view of the plane light-emitter of  FIG. 15  that is taken along line XVI-XVI; 
         FIG. 17  is a cross-sectional view diagrammatically illustrating a substrate on which a through-hole is formed by the method of manufacturing the lighting device according to the second embodiment; 
         FIG. 18  is a cross-sectional view diagrammatically illustrating an intermediate structure formed by the adhering step of the method of manufacturing the lighting device according to the second embodiment; and 
         FIG. 19  is a cross-sectional view diagrammatically illustrating a lighting device manufactured by the method of manufacturing the lighting device according to the second embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of a lighting device according to the present invention will now be described with reference to the drawings. 
     The drawings that will be referred to in the following description schematically illustrate the present invention. Members shown in the drawings may be depicted exaggeratedly in their scales, intervals, positional relationships, and the like, and some of those members may be omitted from the drawings. In some cases, members depicted in plan views and those depicted in cross-sectional views may not match in their scales and intervals. In the following description, in principle, the same names and reference marks represent the same members or members substantially the same in configuration. Detailed description of such members will be omitted when necessary. In defining the positional relationship of lighting devices according to embodiments of the present invention, “upper side,” “lower side,” “left,” and “right” may be replaced with each other depending on situations. In this specification, “upper side,” “lower side,” and the like indicate the relative positions of constituent elements in drawings, which are referred to for better description, and, unless otherwise specified, do not indicate the absolute positions of the same. 
     First Embodiment 
       FIG. 1  is a schematic plan view diagrammatically illustrating a lighting device according to a first embodiment.  FIG. 2  is a cross-sectional view of the lighting device of  FIG. 1  that is taken along line II-II.  FIG. 3  is a schematic explanatory perspective view of a part where a filler is injected in the lighting device according to the first embodiment.  FIG. 1  illustrates a substrate surface opposite to a light emitting surface of a lighting device  10 . 
     Configuration of Lighting Device 
     The lighting device  10  includes a plane light-emitter  20  and a substrate  30  having through-holes. 
     The plane light-emitter  20  has a plurality of light emitting elements  25  and a support  24  that supports the light emitting elements  25 . The support  24  has an upper surface carrying one or more wiring lines  22 , and a lower surface serving as a light emitting surface. The wiring lines  22  electrically connect element electrodes  23 N and  23 P of the plurality of light emitting elements  25 . 
     The substrate  30  has a film-like base substrate  31 , conductors  32 , and an adhesive member  33 . The conductors  32  are formed on a part of an upper surface of the base substrate  31 . The adhesive member  33  is formed on a lower surface of the base substrate  31 . The substrate  30  has through-holes  35  penetrating the substrate  30  in its thickness direction. 
     The lighting device  10  is constructed by adhering an adhesive surface of the adhesive member  33  of the substrate  30  to a surface of the plane light-emitter  20  on which the wiring lines  22  are formed. As a result, the lighting device  10  has spaces  43  formed between the substrate  30  and the plane light-emitter  20  in such a way as to communicate with bottomed holes  41  formed in the location of the through-holes  35 . Bottomed holes  41  are filled with an electrically conductive paste, which cures to form a filler  50 . This filler  50  connects the wiring line(s)  22  to the conductors  32 . Each space  43  is located outside an opening  42  of the bottomed hole  41  in a plan view (see  FIGS. 2 and 3 ). In  FIG. 3 , the substrate  30  is broken to expose a part of the plane light-emitter  20 , where the vicinity of a terminal  21  connected to the wiring line  22  is diagrammatically illustrated. 
     Constituent elements of the lighting device  10  will be described in detail in order. 
     The wiring line  22  is patterned into a given shape on an upper surface of the light emitting element  25  and the upper surface of the support  24 . The wiring line  22  is a wiring line through which external power is supplied to the light emitting element  25 . As the wiring line  22 , an ordinary wiring line incorporated in a package substrate of a light-emitting device can be used. A metal material can be used as a material making up such a wiring line. For example, a simple substance metal, such as Ag, Al, Ni, Rh, Au, Cu, Ti, Pt, Pd, Mo, Cr, and W, or an alloy containing any one of these metals can be used preferably as the material of the wiring line. More preferably, a simple substance metal with high light reflectance, such as Ag, Al, Pt, and Rh, or alloy containing any one of these metals can be used. The wiring line  22  can be obtained also by printing and curing the electrically conductive paste. 
     The wiring line  22  is electrically connected to the terminals  21 . In a plan view, each terminal  21  is configured to have recess portions, i.e., a first recess portion  28   a , a second recess portion  28   b , and a third recess portion  28   c . Of these recess portions, the second recess portion  28   b  and the third recess portion  28   c  have the space  43  extending to a location outside the opening  42  of the bottomed hole  41  in a plan view. 
     The first recess portion  28   a  is formed into a circular shape between the second recess portion  28   b  and the third recess portion  28   c  in a plan view. The second recess portion  28   b  and the third recess portion  28   c  are formed into, for example, semi-circular shapes along the circumference of the first recess portion  28   a  in a plan view (see  FIGS. 3 and 13A ). When the opening  42  of the bottomed hole  41  is 500 μm to 600 μm in diameter, the second recess portion  28   b  and the third recess portion  28   c  are each 200 μm to 300 μm in width. The second recess portion  28   b  and the third recess portion  28   c , which have the space  43 , can be, for example, rectangular in a plan view. One or a plurality of such recess portions having the space  43  are provided. 
     The first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c  are, for example, each 5 μm to 30 μm in depth. Respective bottom surfaces of the first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c  are formed of a part of the upper surface of the support  24 . The height from the upper surface of the support  24  to an upper surface of a lead of the terminal  21  is, for example, 0.1 μm to 30 μm. The wiring line  22  is connected to an external power supply via the terminal  21 , the filler  50 , and the conductor  32 . 
     Each light emitting element  25  has a semiconductor layer formed on a light-transmissive element substrate, such as sapphire. The semiconductor layer is composed of an n-side semiconductor layer, an active region, and a p-side semiconductor layer that are stacked in increasing order from the element substrate side. As the light emitting element  25  capable of emitting UV-rays and visible light ranging from blue light to green light, for example, a GaN-based element or a InGaN-based element, which is exemplified by a nitride semiconductor In X Al Y Ga 1-X-Y N (0≤X≤1, 0≤Y≤1, X+Y≤1), can be used. The light emitting element  25  can dispense with the element substrate. The light emitting element  25  is, for example, rectangular in a plan view. It can be, however, circular, elliptical, triangular, or polygonal, such as hexagonal. It is preferable that the light emitting element  25  have negative and positive element electrodes  23 N and  23 P disposed on the same surface. 
     The plurality of light emitting elements  25  are, for example, electrically connected in series and in parallel to each other. The plane light-emitter  20  carries, for example, sixteen light emitting elements  25  arranged into a four by four matrix. These sixteen light emitting elements  25  are, for example, configured into a 4-parallel/4-series circuit and are electrically connected to each other. The plurality of light emitting elements  25  can be put in wiring arrangement in which each light emitting element  25  is driven independently. An interval between light emitting elements  25  adjacent to each other is, for example, about 3 mm to 10 mm. 
     The support  24  is a member that supports the light emitting elements  25  and other elements. The support  24  covers an upper surface of a light guide member  27  and side surfaces of the light emitting elements  25  and side surfaces of light-transmissive members  26 . It is preferable that the support  24  be made of a material with high light reflectance. It is preferable that the light reflectance of the support  24  for light with an emission peak wavelength from the light emitting element  25  be 70% or higher, more preferably, be 80% or higher, and, further preferably, be 90% or higher. For example, a resin material containing a light reflective substance can be used as the support  24 . Such light reflective substances include titanium oxide, silicon oxide, zirconium oxide, potassium titanate, aluminum oxide, aluminum nitride, boron nitride, zinc oxide, calcium carbonate, barium sulfate, and mullite. It is preferable that the resin material have a resin-based base material made mainly of a thermosetting resin, such as epoxy resin, silicone resin, silicone modified resin, and phenol resin. To improve its light reflectance, the support  24  can be designed to have dotted shapes or a shape similar to a Fresnel lens. 
     The plane light-emitter  20  further has the light-transmissive members  26 , the light guide member  27 , and bonding members  29 . 
     Each light-transmissive member  26  is disposed in such a way as to cover a lower surface of the light emitting element  25 , the lower surface serving as a light-extracting surface. The light-transmissive member  26  is a light-transmissive member containing a fluorescent material. Examples of the fluorescent material making up the light-transmissive member  26  include a yttrium-aluminum-oxide-based fluorescent material (YAG-based fluorescent material), Tb 2.95 Ce 0.05 Al 5 O 12 , Y 2.90 Ce 0.05 Tb 0.05 Al 5 O 12 , Y 2.94 Ce 0.05 Pr 0.01 Al 5 O 12 , and Y 2.90 Ce 0.05 Pr 0.05 Al 5 O 12 . A package in which the light emitting elements  25 , the support  24 , and the light-transmissive members  26  are integrated together can be used. 
     A light-transmissive resin material, glass, or the like can be used as a material making up the light-transmissive member  26 . For example, a thermosetting resin, such as silicone resin, silicone modified resin, epoxy resin, and phenol resin, can be used as the above material. A thermoplastic resin, such as polycarbonate resin, acrylic resin, methyl pentene resin, and polynorbornene resin, can also be used as the above material. A silicone resin having superior light resistance and heat resistance is particularly preferable as such a material. It is preferable that, for light from a light-emitting diode, the light-transmissive member  26  show light transmissivity of 70% or higher, and more preferably, light transmissivity of 80% or higher. 
     The light guide member  27  is a light-transmissive member which receives incoming light from a light source and emits light spreading along a plane. The light guide member  27  has a lower surface, which is a first main surface, and an upper surface opposite to the first surface, the upper surface being a second main surface. The first main surface of the light guide member  27  serves as a light emitting surface. The light guide member  27  can be given a plane shape of, for example, a substantially rectangular shape or substantially circular shape. The light guide member  27  has a plurality of fourth recess portions  27   a  formed on its upper surface serving as the second main surface, the fourth recess portions  27   a  being recess portions in which the light-transmissive members  26  are placed respectively. The light-transmissive member  26  is placed in each fourth recess portion  27   a , where the light emitting element  25  is bonded to an upper surface of the light-transmissive member  26 . The first main surface of the light guide member  27  can be formed into a flat surface or can be provided with irregularities, lens shapes, or the like. On the first main surface of the light guide member  27 , a conical or pyramidal recess portion can be formed on a part corresponding to a location right above the light emitting element  25  so that light coming out of the light emitting element  25  is scattered sidewise right above the light emitting element  25 . In another case, a convex, such as a hemispherical lens and Fresnel lens, can be formed on the part corresponding to the location right above the light emitting element  25  so that light coining out of the light emitting element  25  is condensed right above the light emitting element  25 . 
     As a material making up the light guide member  27 , a thermoplastic resin material, such as acryl, polycarbonate, cyclic polyolefin, polyethylene terephthalate, and polyester, a thermosetting resin material, such as epoxy and silicone, or an optically transparent material, such as glass, can be used. The thermoplastic resin material is particularly preferable because it can be manufactured efficiently by injection molding. Among thermoplastic resin materials, polycarbonate is preferred most because of its high transparency and inexpensiveness. The light guide member  27  can be formed, for example, by injecting molding or transfer molding. The light guide member  27  can be of a monolayer structure or of a laminated structure composed of a plurality of light-transmissive layers. 
     Each bonding member  29  is a member that fixes the light-extracting surface of the light emitting element  25  to the light-transmissive member  26 . It is preferable that the bonding member  29  be a member that guides light from the light emitting element  25  to the light-transmissive member  26 . Examples of the base material of the bonding member  29  include a silicone resin, an epoxy resin, a phenol resin, a polycarbonate resin, an acrylic resin, and a modified resin created by modifying any one of these resins. Using the epoxy resin as the material of the bonding member  29  is preferable because it improves the hardness of the plane light-emitter  20  to make it harder than a case of using the silicone resin. The silicone resin and modified silicone resin are preferable because of their superior heat resistance and light resistance. The bonding member  29  can contain the same fluorescent material as the fluorescent material making up the light-transmissive member  26 . 
     The base substrate  31  has a plurality of the through-holes  35  (two through-holes  35  in  FIG. 1 ) which are filled with the filler  50 . The base substrate  31  is the body of the substrate  30 , and is made of an insulating material having flexibility. For example, polyimide is used preferably as a material making up the base substrate  31 . A reinforced plastic molding compound (e.g., glass epoxy, prepreg, or the like) made by impregnating a fibered reinforcing material, such as glass cloth and carbon fiber, with a resin is also used preferably as the material of the base substrate  31 . Further, a resin film made of polyethylene terephthalate (PET), polyethylene naphthalate, polyether imide, polyphenylene sulfide, liquid crystal polymer, or the like can also be used. The base substrate  31  is, for example, about 10 μm to 40 μm in thickness. 
     The conductors  32  are, for example, electrically conductive foils formed on the base substrate  31 . The conductors  32  are formed into given wiring patterns in a plan view and are electrically connected to the plurality of light emitting elements  25  to form an electric circuit. A plurality of the conductors  32  (two conductors  32  in  FIG. 1 ) are formed such that through-holes to be filled with the filler  50  communicate with the through-holes  35  of the base substrate  31 . It is preferable that a material making up each conductor  32  have high heat conductivity. Such an electrically conductive material as copper is an example of the above material. The conductor  32  can be formed by performing plating or applying or printing an electrically conductive paste. The conductor  32  is thinner than the base substrate  31 , having a thickness of, for example, about 5 μm to 25 μm. Other materials that can be adopted as materials making up the conductor  32  include aluminum foil, aluminum alloy foil, and stainless steel foil. 
     The adhesive member  33  sticks the base substrate  31  to the plane light-emitter  20 . The adhesive member  33  can be a double-faced adhesive tape, a hot-melt type adhesive sheet, or an adhesive liquid or an adhesive sheet made of a thermosetting resin or thermoplastic resin. In this embodiment, for example, the adhesive member  33  is provided as an acrylic double-faced adhesive tape. When the adhesive member  33  is a double-faced adhesive tape, through-holes communicating with the through-holes  35  of the base substrate  31  and with the through-holes of the conductors  32  are formed on the double-faced adhesive tape. The adhesive member  33  is equal in both length and width to the base substrate  31 . The adhesive member  33  is thicker than the base substrate  31 , having a thickness of, for example, about 50 μm. When the double-faced adhesive tape is a strip-like double-faced adhesive tape, a plurality of the adhesive members  33  can be arranged in the direction of their width at given intervals and stuck the base substrate  31  to the plane light-emitter  20 . 
     The substrate  30  is, for example, about 20 μm to 100 μm in thickness. The through-holes  35  formed on the substrate  30  are, for example, each 500 μm to 600 μm in diameter. 
     The lighting device  10  is constructed by adhering the substrate  30  to the upper surface of the plane light-emitter  20  such that the terminals  21  of the plane light-emitter  20  are counter to the through-holes  35  of the substrate  30 . When the substrate  30  and the plane light-emitter  20  are adhered together, the bottomed holes  41  are formed in the location of the through-holes  35 . The second recess portion  28   b  and the third recess portion  28   c  of the terminals  21  communicate with the bottomed hole  41  and extend to a location outside the opening  42  of the bottomed hole  41  in a plan view. 
     The filler  50  is a member formed by injecting an electrically conductive paste into the bottomed hole  41  and curing the electrically conductive paste there. The filler  50  electrically connects the wiring line  22  of the plane light-emitter  20  to the conductor  32  of the substrate  30 . The electrically conductive paste is made by dispersing a resin with an electrically conductive material in the form of nanoparticles or globular or scale-like grains with a grain diameter of several tens of μm or less. Using the electrically conductive paste made of a metal material with high heat conductivity, such as Ag and Cu, improves the heat dissipation of the lighting device  10 . 
     Method of Manufacturing Lighting Device 
     A method of manufacturing the lighting device  10  will then be described with reference to  FIGS. 4 to 13B .  FIG. 4  is a schematic flowchart illustrating steps making up a method of manufacturing the lighting device according to the first embodiment.  FIG. 5  is a schematic plan view diagrammatically illustrating a light-emitting element assembly prepared by the method of manufacturing the lighting device according to the first embodiment.  FIG. 6  is a cross-sectional view of the light-emitting element assembly of  FIG. 5  that is taken along line VI-VI.  FIG. 7  is a schematic plan view diagrammatically illustrating the plane light-emitter on which the wiring lines are formed by the method of manufacturing the lighting device according to the first embodiment.  FIG. 8  is a cross-sectional view of the plane light-emitter of  FIG. 7  that is taken along line VIII-VIII.  FIG. 9  is a schematic plan view diagrammatically illustrating the substrate on which the through-holes are formed by the method of manufacturing the lighting device according to the first embodiment.  FIG. 10  is a cross-sectional view of the substrate of  FIG. 9  that is taken along line X-X.  FIG. 11  is a schematic plan view diagrammatically illustrating an intermediate structure formed by an adhering step of the method of manufacturing the lighting device according to the first embodiment.  FIG. 12  is a cross-sectional view of the intermediate structure of  FIG. 11  that is taken along line XII-XII.  FIG. 13A  is a schematic enlarged view of the terminal illustrated in  FIG. 7 .  FIG. 13B  is a schematic enlarged view of the bottomed hole illustrated in  FIG. 11 . The method of manufacturing the lighting device  10  includes a plane light-emitter preparing step S 1 , a substrate preparing step S 2 , an adhering step S 3 , and an electrically conductive paste injecting step S 4 , which are carried out in the order of steps S 1 , S 2 , S 3 , and S 4 . Each of these steps will hereinafter be described. 
     The plane light-emitter preparing step S 1  is a step of preparing the plane light-emitter  20  including the plurality of light emitting elements  25 , and the support  24  having a first surface that carries the wiring lines  22  electrically connecting the element electrodes  23 N and  23 P of the plurality of light emitting elements  25  and the other surface that serves as the light emitting surface. The plane light-emitter  20  is manufactured by, for example, preparing a light-emitting element assembly  9  illustrated in  FIGS. 5 and 6  and forming the wiring lines  22  on an electrode surface of the light-emitting element assembly  9 . The light-emitting element assembly  9  has sixteen light emitting elements  25  arranged into a four by four matrix, the support  24  supporting the light emitting elements  25 , the light-transmissive members  26 , the light guide member  27 , and the bonding members  29 . The light-emitting element assembly  9  is different from the plane light-emitter  20  in that the light-emitting element assembly  9  has no wiring line  22 . The light-emitting element assembly  9  manufactured in advance can be used. 
     To manufacture the light emitting element  25 , for example, a sapphire substrate is used as a light-transmissive substrate, on which a semiconductor layer made of a nitride semiconductor including an active region of an InGaN-based substance is formed by metal organic chemical vapor deposition (MOCVD). On the semiconductor layer, for example, the positive and negative element electrodes  23 P and  23 N made of an Au/Ti alloy are formed. Through this process, a chip of the light emitting element  25  is manufactured. 
     To manufacture the light-emitting element assembly  9 , the light guide member  27  having the plurality of fourth recess portions  27   a  is prepared first. The upper surface, i.e., second main surface of the light guide member  27  made of, for example, polycarbonate carries sixteen fourth recess portions  27   a  arranged into the four by four matrix. According to this embodiment, four light emitting elements  25  are connected in series to form a row, and four rows of these light emitting elements  25  are connected in parallel. However, depending on intended configuration, they can be arranged such that two light emitting elements  25  are connected in series to form a row and eight rows of these light emitting elements  25  are connected in parallel. In another case, every light emitting element  25  can be connected to another one independently. 
     Subsequently, a resin layer containing a fluorescent material is filled into the fourth recess portions  27   a  of the light guide member  27  by, for example, screen printing, potting, or the like. The resin layer is cured in the fourth recess portions  27   a  to form the light-transmissive members  26 . A sheet of the light-transmissive member  26  can be prepared, in which case pieces of the light-transmissive member  26  each cut out from the sheet into a proper size are placed in the fourth recess portions  27   a  of the light guide member  27 , respectively. 
     Subsequently, each light-transmissive member  26  has its upper surface coated with the material of the bonding member, such as a liquid silicone resin, and the chip of the light emitting element  25  is bonded to the material of the bonding member from above. As a result, the bonding member  29  is disposed on the upper surface of the light-transmissive member  26  and on the side surfaces of the light emitting element  25 , thus fixing the light emitting element  25  to the upper surface of the light-transmissive member  26 . 
     Subsequently, the light guide member  27  is overlaid with the material of the support by, for example, transfer molding such that the material of the support covers the light emitting element  25 . A part of the material of the support is then ground to expose the element electrodes  23 N and  23 P of the light emitting element  25 , thereby forming the support  24 . The support  24  covers the side surfaces of the light emitting element  25 , of the light-transmissive member  26 , and of the bonding member  29 . Through the above procedure, the light-emitting element assembly  9  can be manufactured. 
     To form the wiring lines  22  on the electrode surface of the light-emitting element assembly  9 , for example, known methods, such as sputtering, vapor deposition, atomic layer deposition (ALD), and plating, can be used. As a wiring material, metal layers, such as Cu, Ni, and Au layers or Ni, Ru, and Au layers that are stacked in increasing order, are formed substantially on the whole surface of the element electrodes  23 N and  23 P of the light emitting elements  25  and that of the support  24 , by sputtering or the like. Subsequently, the wiring material is patterned by, for example, thick film printing or laser ablation, to form the wiring lines  22 . Through this process, as illustrated in  FIGS. 7 and 8 , the terminal  21  on a P-side (left side in  FIG. 7 ) and the terminal  21  on an N-side (right side in  FIG. 7 ) are formed as well. In a plan view, the terminals  21  are each larger in width than the wiring line and are larger in plane shape than the light emitting element  25 . Each terminal  21  is formed such that it has the first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c . The plane light-emitter  20  is manufactured in this manner. 
     In this embodiment, the plane light-emitter  20  has 2 terminals  21  for sixteen light emitting elements  25 . However, when the maximum number of terminals  21  are arranged, 2 terminals  21  can be provided for each light emitting element  25 . The terminals  21  are disposed in the locations counter to the through-holes  35  of the substrate  30  (which will be described later on) such that the number of the terminals  21  is equal to the number of the through-holes  35 . 
     As illustrated in  FIGS. 9 and 10 , the substrate preparing step S 2  is a step of preparing the substrate having the film-like base substrate  31 , the conductors  32  formed on a part of a first surface of the base substrate  31 , the adhesive member  33  formed on the other surface of the base substrate  31 , and the through-holes  35  penetrating the substrate in its thickness direction. The adhesive member  33  is, for example, a double-faced adhesive tape. The adhesive member  33  has one adhesive surface stuck to the base substrate  31 , and the other adhesive surface covered with a peelable film  34 . 
     Alternately, the substrate preparing step S 2  can have a step of preparing a wiring substrate having the base substrate  31  on which the conductors  32  are formed, a step of adhering one adhesive surface of the adhesive member  33  to the base substrate  31 , and a step of forming the through-holes  35 . 
     The through-holes  35  are formed in the locations counter respectively to the terminals  21  of the plane light-emitter  20  such that the number of the through-holes  35  is equal to that of the terminals  21 . The through-holes  35  are formed by drilling and can be formed also by, for example, punching or laser emission. Each through-hole  35  is, for example, circular in plane shape. The through-hole  35  is, for example, about 500 μm to 600 μm in diameter. The substrate  30  is, for example, 100 μm in thickness. When punching or laser emission is adopted to form the through-hole  35 , the shape of the through-hole  35  is not limited to a circular shape but can be an ellipse, a polygonal shape, such as rectangle, a dumbbell shape, or a star shape. 
     The adhering step S 3  is a step of adhering the adhesive surface of the adhesive member  33  of the substrate  30  to the surface of the plane light-emitter  20  on which the wiring lines  22  are formed. At this step, the peelable film  34  is peeled off the substrate  30  to expose the adhesive surface of the adhesive member  33 , and the adhesive surface of the adhesive member  33  is pressure-bonded to the surface of the plane light-emitter  20  on which the wiring lines  22  are formed. At this time, the substrate  30  and the plane light-emitter  20  are aligned to set the terminals  21  of the plane light-emitter  20  counter to the through-holes  35  of the substrate  30 , and then are bonded together. 
     By this adhering step, an intermediate structure  40  illustrated in  FIGS. 11 and 12  is formed. The intermediate structure  40  has the substrate  30  and the plane light-emitter  20 . The intermediate structure  40  has the spaces  43  formed between the substrate  30  and the plane light-emitter  20 , the spaces  43  communicating with the bottomed holes  41  formed in the location of the through-holes  35 . As illustrated in  FIGS. 13A and 13B , each space  43  of the intermediate structure  40  is located outside the opening  42  of the bottomed hole  41  in a plan view. The second recess portion  28   b  and the third recess portion  28   c  of the terminal  21  communicate with the bottomed hole  41  and extend to a location outside the opening  42  of the bottomed hole  41  in a plan view. 
     The electrically conductive paste injecting step S 4  is a step of injecting the electrically conductive paste into the bottomed holes  41  of the intermediate structure  40 . At this step, the wiring lines  22  are electrically connected to the conductors  32  via the filler  50  that is the electrically conductive paste having been injected into the bottomed holes  41  and cured there (see  FIGS. 1 and 2 ). When the electrically conductive paste is injected into each bottomed hole  41  by a method properly selected from, for example, the screen printing method, a method using a dispenser, and an ink jetting method, the electrically conductive paste comes in contact with the terminal  21  making up the bottom surface of the bottomed hole  41 . At this time, the electrically conductive paste coming in contact with the upper surface of the lead of the terminal  21  spreads further by a capillary phenomenon to enter the first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c . As a result, the electrically conductive paste is filled smoothly into the bottomed hole  41  to reach respective bottom surfaces and inner peripheral surfaces of the first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c . A part of the second recess portion  28   b  and the third recess portion  28   c  forms the space  43 . Because the bottomed hole  41  communicates with the space  43  formed between the plane light-emitter  20  and the substrate  30 , the electrically conductive paste is filled into the space  43  by the capillary phenomenon. In a plan view, the space  43  extend to a location outside the opening  42  of the bottomed hole  41 . This structure allows the electrically conductive paste to proceed deeper to an inner part of the bottomed hole  41  beyond a space beneath the opening  42 . As a result, the electrically conductive paste spreads smoothly to the bottom surface of the bottomed hole  41 . 
     The electrically conductive paste can catch air when it is injected into the bottomed hole  41 . In such a case, in the space beneath the opening  42 , the space  43  can serve as an air pocket into which air escapes as the electrically conductive paste comes in contact with the terminal  21 . 
     Afterward, the electrically conductive paste filled into the bottomed hole  41  is cured by heat to form the filler  50 , which electrically connects the wiring line  22  of the plane light-emitter  20  to the conductor  32  of the substrate  30 . By the above steps, a final structure of the lighting device  10  illustrated in  FIGS. 1-2  can be manufactured. This manufacturing method increases a contact area between the electrically conductive paste and the lead of the terminal  21 . 
     According to the method of manufacturing the lighting device of the embodiment, when the electrically conductive paste is injected into the bottomed hole  41 , a contact area between the electrically conductive paste and the wiring line of the plane light-emitter  20  increases due to the presence of the space  43 , resulting in an increased degree of adhesion between the electrically conductive paste and the wiring line. Hence, the lighting device with improved connection reliability can be manufactured. 
     In the lighting device of the first embodiment, a recess portion can be formed on the filler, as illustrated in  FIG. 14 .  FIG. 14  is a cross-sectional view diagrammatically illustrating a modification of the lighting device manufactured by the method of manufacturing the lighting device according to the first embodiment. A lighting device  10 B is different from the lighting device  10  in that the cross-sectional shape of a filler  50 B of the lighting device  10 B is different from that of the filler  50  of the lighting device  10 . Following the curing of the electrically conductive paste, the center of an upper surface of the filler SOB can sink in, depending on a material making up the electrically conductive paste filling the bottomed hole  41 , to become lower than the upper surface of the substrate  30 . Even in such a case, because of the presence of the first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c , the lighting device with improved connection reliability can be manufactured. 
     Level differences can be formed by the following methods to form the first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c . For example, on the upper surface of the support  24 , the upper surface serving as the bottom surfaces of the first recess portion  28   a , the second recess portion  28   b , and the third recess portion  28   c , a recess portion of about 30 μm in depth can be formed in advance. In this case, these recess portions are made deeper. In this case, the thickness of the wiring line  22  can be reduced to, for example, about 500 angstroms (0.05 μm), and therefore the overall thickness of the plane light-emitter can be reduced as well. In another case, for example, when the wiring line  22  is formed, the thickness of the part of terminal  21  that is other than the bottom surfaces of the first, second, and third recess portions  28   a ,  28   b , and  28   c  can be made larger by about 30 μm than the thickness of the part of terminal  21  that make up the bottom surfaces so that the bottom surfaces of the first, second, and third recess portions are flush with the upper surface of the wiring line  22 . 
     Second Embodiment 
     A lighting device according to a second embodiment will now be described.  FIG. 15  is a schematic plan view diagrammatically illustrating the plane light-emitter on which the wiring lines are formed by a method of manufacturing a lighting device according to a second embodiment.  FIG. 16  is a cross-sectional view of the plane light-emitter of  FIG. 15  that is taken along line XVI-XVI.  FIG. 17  is a cross-sectional view diagrammatically illustrating the substrate on which the through-holes are formed by the method of manufacturing the lighting device according to the second embodiment.  FIG. 18  is a cross-sectional view diagrammatically illustrating an intermediate structure formed by the adhering step of the method of manufacturing the lighting device according to the second embodiment.  FIG. 19  is a cross-sectional view diagrammatically illustrating a lighting device manufactured by the method of manufacturing the lighting device according to the second embodiment. 
     In the following description, the same constituent elements as described in the first embodiment will be denoted by the same reference marks and will be omitted in further description. 
     The method of manufacturing the lighting device according to the second embodiment is the same as the method described above, and therefore description of the method will be omitted unless needed to describe the differences between the second embodiment and the first embodiment. At the plane light-emitter preparing step S 1 , a plane light-emitter  20 C illustrated in  FIG. 15  is prepared. The plane light-emitter  20 C is different from the plane light-emitter  20  illustrated in  FIG. 7  in that the shape of terminals  21 C connected to the wiring lines  22  are different from the shape of the terminals of the plane light-emitter  20 . Each terminal  21 C has no recess portion and is formed into a flat shape substantially uniform in thickness. The plane light-emitter  20 C can be manufactured by forming the wiring lines  22 , which are arranged into a pattern illustrated in  FIG. 15 , on the electrode surface of the light-emitting element assembly  9  illustrated in  FIG. 5 . 
     At the substrate preparing step S 2 , a substrate  30 C illustrated in  FIG. 17  is prepared. The substrate  30 C is different from the substrate  30  illustrated in  FIG. 10  in that the sectional shape of a through-hole  35 C is different from that of the through-hole of the substrate  30 . The through-hole  35 C is formed as a through-hole punched in the substrate  30 C to penetrate it from the surface carrying the conductor  32  to the adhesive surface. As a result, the through-hole  35 C formed on the substrate  30 C is larger in width at the adhesive surface than at the surface carrying the conductor  32 . Specifically, the through-hole  35 C has an opening formed on the side where the adhesive member  33  is located and an opening formed on the side where the conductor  32  is located, and the former opening is wider than the latter one. In the through-hole  35 C, an inner peripheral surface  36  near the opening formed on the adhesive member  33  side is a tapered surface that widens as it approaches the opening formed on the adhesive member  33  side. 
     At the adhering step S 3 , the peelable film  34  is peeled off the substrate  30 C to expose the adhesive surface of the adhesive member  33 , and the adhesive surface of the adhesive member  33  is pressure-bonded to the surface of the plane light-emitter  20 C on which the wiring lines  22  are formed. At this time, the substrate  30 C and the plane light-emitter  20 C are aligned to set the terminals  21  of the plane light-emitter  20 C counter to the through-holes  35 C of the substrate  30 C, and then are bonded together. By this adhering step, an intermediate structure  40 C illustrated in  FIG. 18  is formed. The intermediate structure  40 C has the substrate  30 C and the plane light-emitter  20 C. The intermediate structure  40 C has spaces  43 C formed between the substrate  30 C and the plane light-emitter  20 C, the spaces  43 C communicating with bottomed holes  41 C formed in the location of the through-holes  35 C. Each space  43 C is located outside the opening  42  of the bottomed hole  41 C in a plan view. The space  43 C is formed between the inner peripheral surface  36  of the through-hole  35 C of the substrate  30 C and the surface of the plane light-emitter  20 C on which the wiring lines  22  are formed. 
     At the electrically conductive paste injecting step S 4 , the wiring lines  22  are electrically connected to the conductors  32  via the filler  50  that is the electrically conductive paste having been injected into bottomed holes  41 C of the intermediate structure  40 C and cured there (see  FIG. 19 ). When the electrically conductive paste is injected into each bottomed hole  41 C by, for example, screen printing, the electrically conductive paste comes in contact with the terminal  21 C making up the bottom surface of the bottomed hole  41 C. Because the bottomed hole  41 C communicates with the space  43 C formed between the inner peripheral surface  36  of the through-hole  35 C of the substrate  30 C and the surface of the plane light-emitter  20 C on which the wiring lines  22  are formed, the electrically conductive paste spreads to fill the space  43 C. In a plan view, the space  43 C extend to a location outside the opening  42  of the bottomed hole  41 C. This structure allows the electrically conductive paste to proceed deeper to an inner part of the bottomed hole  41 C beyond a space beneath the opening  42 . The electrically conductive paste is, therefore, filled smoothly into the bottomed hole  41 C. The electrically conductive paste can catch air when it is injected into the bottomed hole  41 C. In such a case, in the space beneath the opening  42 , the space  43  can serve as a path through which air escapes as the electrically conductive paste comes in contact with the terminal  21 C. 
     Afterward, the electrically conductive paste filling the bottomed hole  41 C is cured by heat to form the filler  50 , which electrically connects the wiring line  22  of the plane light-emitter  20 C to the conductor  32  of the substrate  30 C. By the above steps, the lighting device  10 C illustrated in  FIG. 19  is manufactured. By this manufacturing method, a contact area between the electrically conductive paste and the lead of the terminal  21 C increases in the lighting device  10 C. 
     The lighting device  10 C can be manufactured in such a way that in the intermediate structure  40 C, the plane light-emitter  20 C is replaced with the plane light-emitter  20  of  FIG. 8 , which is adhered to the substrate  30 C, and then the electrically conductive paste is injected. 
     The lighting device according to the present invention has been described specifically in DESCRIPTION OF THE EMBODIMENTS. The substance of the present invention, however, is not limited to the above description but must be interpreted broadly based on what is claimed. Obviously, various modifications and variations of the invention that are achieved based on the above description are also included in the scope of the present invention.