Patent Publication Number: US-10777720-B2

Title: Light emitting module and light emitting module manufacturing method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 15/465,899 filed Mar. 22, 2017 which is a continuation of prior International Application No. PCT/JP2015/004816 filed on Sep. 18 2015, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-196387 filed on Sep. 26, 2014, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the present disclosure relate to a light emitting module, and a light emitting module manufacturing method. 
     BACKGROUND 
     Light emitting modules including light emitting elements like a Light Emitting Diode (LED) are broadly applied to indoor, outdoor, stationary, and movable display devices, indication lamps, various switches, signaling devices, and optical devices like a commonly used lighting device. Among such light emitting modules that include LEDs, a light transmissive emitting module that has multiple LEDs disposed between two light transmissive substrates is known as a suitable device for display devices and indication lamps that display various letter strings, geometric figures, and patterns. 
     By applying flexible substrates formed of a light transmissive resin as the light transmissive substrates, a constraint for an attaching surface for the light emitting module as the display device and the indication lamp is eased, and thus the convenience and availability of the light transmissive emitting module are improved. 
     A light transmissive emitting module employs a structure that has multiple LED chips disposed between a pair of light transmissive insulation substrates each including a conductive circuitry layer. Each of the multiple LED chips includes a pair of electrodes, and the electrodes are electrically connected to the conductive circuitry layer formed on the light transmissive insulation substrate. A flexible light transmissive resin is filled in between the pair of light transmissive insulation substrates. The LED chip is held by the light transmissive resin with the electrodes being in contact with the corresponding pieces of the conductive circuitry layer. 
     In the above light emitting module, an improvement for the connection reliability between the electrode of the LED chip and the conductive circuitry layer is desired. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exemplary cross-sectional view illustrating a general structure of a light emitting module in accordance with an embodiment; 
         FIG. 2  is a perspective view of a light emitting element; 
         FIG. 3  is a cross-sectional view illustrating an enlarged portion of the light emitting module; 
         FIG. 4  is a diagram illustrating an example connection between a conductor pattern and the light emitting element; 
         FIG. 5  is an exemplary diagram illustrating a bump prior to a rounding process; 
         FIG. 6A  is a diagram for explaining the rounding process by using a jig; 
         FIG. 6B  is a diagram for explaining the rounding process by using the jig; 
         FIG. 6C  is a diagram for explaining the rounding process by using the jig; 
         FIG. 7A  is a diagram for explaining the rounding process by using a jig and a resin sheet; 
         FIG. 7B  is a diagram for explaining the rounding process by using the jig and the resin sheet; 
         FIG. 7C  is a diagram for explaining the rounding process by using the jig and the resin sheet; 
         FIG. 8A  is a diagram for explaining the rounding process by using a jig and a resin sheet; 
         FIG. 8B  is a diagram for explaining the rounding process by using the jig and the resin sheet; 
         FIG. 9A  is a diagram for explaining a light emitting module manufacturing method in accordance with the embodiment; 
         FIG. 9B  is a diagram for explaining the light emitting module manufacturing method in accordance with the embodiment; 
         FIG. 9C  is a diagram for explaining the light emitting module manufacturing method in accordance with the embodiment; 
         FIG. 9D  is a diagram for explaining the light emitting module manufacturing method in accordance with the embodiment; 
         FIG. 10A  is a diagram for explaining a light emitting module manufacturing method in accordance with a modified example; 
         FIG. 10B  is a diagram for explaining a light emitting module manufacturing method in accordance with the modified example; 
         FIG. 10C  is a diagram for explaining a light emitting module manufacturing method in accordance with the modified example; 
         FIG. 10D  is a diagram for explaining a light emitting module manufacturing method in accordance with the modified example; 
         FIG. 11  is a diagram illustrating a dynamic viscosity of the resin sheet prior to a thermal curing process; 
         FIG. 12A  is a diagram for explaining a light emitting module manufacturing method in accordance with a modified example; 
         FIG. 12B  is a diagram for explaining a light emitting module manufacturing method in accordance with the modified example; 
         FIG. 12C  is a diagram for explaining a light emitting module manufacturing method in accordance with the modified example; 
         FIG. 12D  is a diagram for explaining a light emitting module manufacturing method in accordance with the modified example; 
         FIG. 13  is a diagram illustrating a dynamic viscosity of the resin sheet prior to the thermal curing process; and 
         FIG. 14  is a diagram illustrating an elastic modulus of the resin sheet after the thermal curing process. 
     
    
    
     DETAILED DESCRIPTION 
     A light emitting module according to an embodiment includes a first light transmissive insulator, a conductive circuitry layer formed on a surface of the first light transmissive insulator, a second light transmissive insulator disposed so as to face the conductive circuitry layer, a light emitting element disposed between the first light transmissive insulator and the second light transmissive insulator, and connected to the conductive circuitry layer, and a third light transmissive insulator which is disposed between the first light transmissive insulator and the second light transmissive insulator, and is thermosetting. 
     A light emitting module in accordance with a first embodiment of the present disclosure will be explained below with reference to the figures.  FIG. 1  is an exemplary cross-sectional view illustrating a general structure of a light emitting module  1  in accordance with this embodiment. 
     As illustrated in  FIG. 1 , the light emitting module  1  includes a pair of light transmissive films  4 ,  6 , a resin layer  13  formed between the light transmissive films  4 ,  6 , and multiple light emitting elements  22  disposed within the resin layer  13 . 
     The light transmissive films  4 ,  6  are each a rectangular film that has a planar lateral direction as a lengthwise direction. The light transmissive films  4 ,  6  each have a thickness of 50 to 300 μm, and have a light transmissive property for visible light. It is preferable that the total light transmittance of the light transmissive films  4 ,  6  should be equal to or greater than 90%, and more preferably, equal to or greater than 95%. The total light transmittance means a total light transmittance measured in compliance with JIS K7375: 2008. In addition, both the light transmissive films  4 ,  6  are flexible, and have abending elastic modulus that is substantially 0 to 320 kgf/mm 2  (excluding zero). The bending elastic modulus means a value measured through a scheme in compliance with, for example, ISO 178 (JIS K7171: 2008). 
     When the thickness of the light transmissive films  4 ,  6  exceeds 300 μm, the flexibility of the light transmissive films  4 ,  6 , decreases, and the total light transmittance thereof decreases. In addition, when the thicknesses of the light transmissive films  4 ,  6  becomes lower than 5 μm, a large deformation of the light transmissive films  4 ,  6  is expected when the light transmissive films  4 ,  6  are integrated with the light emitting elements  22 . Hence, it is preferable that the light transmissive films  4 ,  6  should have a thickness of 50 to 300 μm. 
     Example materials of the light transmissive films  4 ,  6  are polyethylene-terephthalate (PET), polyethylene-naphthalate (PEN), polycarbonate (PC), polyethylene-succinate (PES), a cyclic-olefin resin (e.g., ARTON (product name) available from JSR Corporation), and an acrylic resin. 
     In the pair of light transmissive films  4 ,  6 , a lower surface of the light transmissive film  4  is formed with multiple pieces of a conductor pattern  5  that has a thickness of substantially 0.05 to 2 μm. 
     For the conductor pattern  5 , a light transmissive conductive material, such as an Indium Tin Oxide (ITO), Fluorine-doped Tin Oxide (FTO), zinc oxide, or Indium Zinc Oxide (IZO), is applied. The conductor pattern  5  can be formed by, for example, patterning like laser processing or etching performed on a thin film formed on the light transmissive film  4  by sputtering or electron beam vapor deposition. 
     The conductor pattern  5  can be also formed on the light transmissive film  4  by screen printing of a mixture material of particles of a light transmissive conductive material having an average particle diameter of 10 to 300 nm with a light transmissive resin binder. In addition, the conductor pattern  5  can be formed by forming a thin film formed of the above mixture material on the light transmissive film  4 , and by patterning this thin film by laser processing or photo-lithography. 
     The material of the conductor pattern  5  is not limited to the light transmissive conductive material, and particles of a non-light transmissive conductive material, such as gold, silver, or copper, may be applied to the light transmissive film  4  in a meshed shape. For example, a photo-sensitive compound of a non-light transmissive conductive material like halogenated silver may be applied to the light transmissive film  4  to form a thin film, and exposure and development may be performed on this thin film to form the conductor pattern  5  in a meshed shape. In addition, a slurry containing the particles of a non-light transmissive conductive material may be applied by screen printing, etc., in a meshed shape to form the conductor pattern  5 . 
     It is preferable that the conductor pattern  5  should have a light transmissive property that sets the total light transmittance (e.g., JIS K7105) of the entire light emitting module  1  to be equal to or greater than 1%. When the total light transmittance of the entire light emitting module  1  is less than 1%, a light emitting dot is not recognized as a bright point. The light transmissive property of the conductor pattern  5  itself varies depending on a structure of the conductor pattern  5 , but it is preferable that the total light transmittance should be within the range between 10 and 85%. 
     The resin layer  13  is an insulator formed between the light transmissive film  4  and the light transmissive film  6 . The resin layer  13  is formed of a thermosetting resin, and has a light transmissive property for visible light. The resin layer  13  is formed of a resin with characteristics that satisfy predetermined conditions, such as the lowest melt viscosity prior to curing, a temperature at the lowest melt viscosity prior to curing, a melt viscosity change rate until reaching the temperature at the lowest melt viscosity prior to curing, a Vicat softening temperature after curing, a tensile storage elastic modulus after curing, and a glass transition temperature after curing. 
     The resin layer  13  in accordance with this embodiment is formed of an epoxy-based resin that is the thermosetting resin. It is desirable that the thermosetting resin which forms the resin layer  13  should have a lowest melt viscosity VC 1  prior to curing. a lowest melt viscosity VC 1  is within a range between 10 and 10000 Pa·s at the temperature within a range between 80 and 160° C. In addition, it is desirable that a melt viscosity change rate VR until reaching a temperature T 1  (maximum softening temperature) at the lowest melt viscosity VC 1  prior to curing should be equal to or lower than 1/1000 (equal to or lower than 1 over 1000). It is desirable that the resin layer  13  should have a Vicat softening temperature T 2  after reaching the lowest melt viscosity by heating, i.e., after cured which is within a range between 80 and 160° C., and have a tensile storage elastic modulus EM which is within a range between 0.01 and 1000 GPa at a temperature within a range between 0 and 100° C. In addition, it is desirable that the resin layer  13  should have a glass transition temperature T 3  of 100 to 160° C. 
     Example preferable physical values of the thermosetting resin are as follows: 
     Lowest melt viscosity VC 1 : 10 to 10000 Pa·s; 
     Temperature T 1  (maximum softening temperature) at lowest melt viscosity VC 1 : 80 to 160° C.; 
     Melt viscosity change rate VR until reaching temperature T 1 : equal to or lower than 1/1000; 
     Vicat softening temperature T 2 : 80 to 160° C.; 
     Tensile storage elastic modulus EM: 0.01 to 1000 GPa at temperature within a range between 0 and 100° C.; and 
     Glass transition temperature T 3 : 100 to 160° C. 
     Note that the melt viscosity measurement was made to obtain a value by changing the temperature of a measurement sample from 50 to 180° C. in accordance with the scheme described in JIS K7233. The Vicat softening temperature was a value obtained under a condition with a test load of 10 N, and a temperature rise speed of 50° C./hour in accordance with A50 described in JIS K7206 (ISO 306: 2004). The glass transition temperature and the melt temperature were obtained by differential scanning calorimetric measurement in accordance with a scheme in compliance with JIS K7121 (ISO 3146). The tensile storage elastic modulus is a value obtained in accordance with a scheme in compliance with JIS K7244-1 (ISO 6721). More specifically, this is a value obtained by performing sampling on a measurement sample that had an constant temperature rise from −100° C. to 200° C. at 1° C. by 1° C. per a minute at a frequency of 10 Hz using a dynamic viscosity automatic measurement apparatus. 
     The resin layer  13  is filled around electrodes  28 ,  29  without a void. As illustrated in  FIG. 1 , the area of each electrode  28 ,  29  provided on the upper surface of the light emitting element  22  is smaller than the area of the upper surface (e.g., light emitting surface) of the light emitting element  22 . In addition, the electrodes  28 ,  29  protrude from the upper surface of the light emitting element  22  toward the conductor pattern  5 . In this case, a microscopic empty space is formed between the upper surface of the light emitting element  22  and the conductor pattern  5 . It is preferable that the resin layer  13  should be also filled in this microscopic empty space. 
     A thickness T 2  of the resin layer  13  is smaller than a height T 1  of the light emitting element  22  so as to enable the conductor pattern  5  to be excellently in contact with the electrodes  28 ,  29 . The light transmissive film  4  intimately in contact with the resin layer  13  is formed in a curved shape that has a portion where the light emitting element  4  is disposed protruding outwardly, and a portion between the light emitting elements  22  concaved. The curved light transmissive film  4  in this manner pushes the conductor pattern  5  against the electrodes  28 ,  29 . Hence, the electrical connection between the conductor pattern  5  and the electrodes  28 ,  29 , and the reliability thereof are improved. 
     Note that it is preferable that the resin layer  13  should be formed of a material that contains a main component which is a thermosetting resin, but may contain other resin components as needed. Example known thermosetting resins are an epoxy-based resin, an acrylic-based resin, a styrene-based resin, an ester-based resin, an urethane-based resin, a melamine resin, a phenol resin, an unsaturated polyester resin, and a diallyl phthalate resin. Among those resins, the epoxy-based resin is suitable as a material for the resin layer  13  since it has excellent light transmissive property, electrical insulation characteristic, flexibility, and further fluidity when softened, adhesiveness after cured, and anti-weatherability. The resin layer  13  may be formed of resins other than the epoxy-based resin. 
       FIG. 2  is a perspective view illustrating the light emitting element  22 . The light emitting element  22  is a square LED chip that has a side of 0.3 to 3 mm. As illustrated in  FIG. 2 , the light emitting element  22  is an LED chip that includes a base substrate  23 , an N-type semiconductor layer  24 , an active layer  25 , and a P-type semiconductor layer  16 . The rated voltage for the light emitting element  22  is substantially 2.5 V. 
     The base substrate  23  is a sapphire substrate or a semiconductor substrate. By applying the base substrate  23  that has an optical transmissive property, light is emitted from both upper and lower surfaces of the light emitting element  22 . The N-type semiconductor layer  23  that is formed in the same shape as the base substrate  23  is formed on the upper surface of the base substrate  23 . The N-type semiconductor layer  24  is formed of, for example, n-GaN. 
     Laid over on the upper surface of the N-type semiconductor layer  24  are an active layer  25  and a P-type semiconductor layer  26  in this sequence. The active layer  25  is formed of, for example, InGaN. In addition, the P-type semiconductor layer is formed of, for example, p-GaN. Note that the light emitting element  22  may employ a Double-Hetero (DH) structure, or a Multi-Quantum Well (MQW) structure. 
     Cut portions are respectively formed at corner portions of the active layer  25  and the P-type semiconductor layer  26  laid over on the N-type semiconductor layer  24 , and a surface of the N-type semiconductor layer  24  is exposed from such cut portions. The exposed portion of the N-type semiconductor layer  24  from the active layer  25  and the P-type semiconductor layer  26  is formed with an electrode  29  (electrode pad) that is electrically connected with the N-type semiconductor layer  24 . In addition, the corner portion of the P-type semiconductor layer  26  is formed with the electrode  28  (electrode pad) that is electrically connected to the P-type semiconductor layer  26 . 
     The electrodes  28 ,  29  are each formed of copper (Cu) or gold (Au), and are each a pad electrode having a conductive bump  30  formed on the upper surface. The bump  30  is a metal bump formed of a metal, such as gold (Au) or a gold alloy. The bump  30  may be a solder bump instead of a metal bump. 
     The thickness of the light emitting element  22  excluding the bump is substantially 100 μm, and the height of the bump  30  is substantially 60 μm. 
     The light emitting elements  22  are disposed at an equal pitch so as to have a distance d between the adjacent light emitting elements  22 . The distance d is equal to or shorter than 1500 μm. The number of light emitting elements  22  in the light emitting module  1  can be designed as appropriate in accordance with the specification of the light emitting module  1 , such as an external dimension, and the light emitting surface area. 
       FIG. 3  is a cross-sectional view illustrating a part of the light emitting module  1  in an enlarged-manner. As illustrated in  FIG. 3 , the electrodes  28 ,  29  of the light emitting element  22  are electrically connected to the conductor pattern  5  via the respective bumps  30 . 
     The bump  30  is formed of gold, an AuSn alloy, silver, copper, nickel, an alloy with a metal other than the foregoing metals, a mixture material, an eutectic material, an amorphous material, etc. The bump  30  may be formed of a solder, an eutectic solder, a mixture material of metal particles with a resin, an anisotropic conductive film, etc. The bump  30  may be formed as a wire bump using, for example, a wire bonder. In addition, the bump  30  can be also formed by performing electrolytic plating or non-electrolytic plating on the electrode  28 ,  29 . The bump  30  can be also formed by inkjet printing of an ink containing metal particles on the electrode  28 ,  29  and by calcination. Still further, a paste containing metal particles may be printed or applied to the electrode  28 ,  29  to form the bump  30 , or the bump  30  may be formed on the electrode  28 ,  29  by technologies, such as ball mounting, pellet mounting, and vapor deposition sputtering. 
     It is preferable that a melting-point temperature of the bump  30  should be equal to or higher than 180° C., and more preferably, equal to or higher than 200° C. A practical upper limit of the temperature is equal to or lower than 1100° C. When the melting-point temperature of the bump  30  is lower than 180° C., in a vacuum thermal pressing process in the manufacturing process of the light emitting module  1 , the bump  30  is largely deformed, and thus the sufficient thickness is not ensured. In addition, the bump  30  may spread out from the electrode  28 ,  29 . In this case, the spreading portions of the bump  30  out from the electrode  28 ,  29  disrupts traveling light from the light emitting element  22 . 
     The melting-point temperature of the bump  30  is measurable using, for example, a DSC-60 differential scanning calorimeter available from SHIMADZU Corporation. As for the melting-point temperature measurement, for example, a sample of substantially 10 mg is subjected to a temperature rise 5° C. by 5° C. per a minute. When a solidus temperature and a liquidus temperature differ from each other, a value of the solidus temperature may be considered as the melting-point temperature of the bump  30 . 
     A dynamic hardness DHV of the bump  30  is equal to or larger than 3 and equal to or smaller than 150, and preferably, equal to or larger than 5 and equal to or smaller than 100, and more preferably, equal to or larger than 5 and equal to or smaller than 50. When the dynamic hardness DHV of the bump  30  is less than 3, in a vacuum thermal pressing process in the manufacturing process of the light emitting module, the bump  30  is largely deformed, and thus the sufficient thickness is not ensured. In addition, the bump  30  may spread out from the electrode  28 ,  29 . In this case, the spreading portions of the bumps  30  from the electrode  28 ,  29  disrupt traveling light from the light emitting element  22 . Conversely, when the dynamic hardness DHV of the bump  30  exceeds 150, in a vacuum thermal pressing process in the manufacturing process of the light emitting module, the bump  30  deforms the light transmissive film  4 . In this, this results in a poor visual inspection result of the light emitting module  1 , and a poor connection between the light emitting element  22  and the conductor pattern  5 . 
     The dynamic hardness DHV of the bump  30  is obtained by, for example, a test using a SHIMADZU dynamic ultrafine hardness gauge DUH-W201S provided by SHIMADZU Corporation. In such a test, under an environment at which the temperature is 20° C., a diamond square pyramid indenter (Vickers indenter) with an angle between opposite surfaces that is 136 degrees is pushed in the bump  30  at a load speed of 0.0948 mN/sec. Next, a test force (P/mN) when the push-in depth (D/μm) of the Vickers indenter reaches 0.5 μm is substituted in the following formula.
 
DHV=3.8584 P/D2=15.4336 P
 
     It is preferable that the height of the bump  30  should be equal to or larger than 5 μm and equal to or smaller than 80 μm, and more preferably, equal to or larger than 10 μm and equal to or smaller than 60 μm. When the height of the bump  30  is less than 5 μm, a short-circuit prevention effect between the conductor pattern  5  and the P-type semiconductor layer  26  of the light emitting element  22  or between the conductor pattern  5  and the N-type semiconductor layer  24  becomes insufficient. Conversely, when the height exceeds 80 μm, in a vacuum thermal pressing process in the manufacturing process of the light emitting module, the bump  30  may deform the light transmissive film  4 . In this case, this results in a poor visual inspection result of the light emitting module  1 , and a poor connection between the light emitting element  22  and the conductor pattern  5 . 
     In addition, it is preferable that a contact area between the electrode  28 ,  29  of the light emitting element  22  and the bump  30  should be equal to or larger than 100 μm 2  and equal to or smaller than 15,000 μm 2 , and more preferably, equal to or larger than 400 μm 2  and equal to or smaller than 8,000 μm 2 . Each dimension is a measured value under a stable environment in which a room temperature and the temperature of the measurement sample are 20° C.±2° C. 
       FIG. 4  illustrates an example connection between the conductor pattern  5  and the light emitting element  22 . The electrodes  28 ,  29  of the light emitting element  22  are connected to the respective adjoining pieces of the conductor pattern  5 . 
     The pair of light transmissive films  4 ,  6 , the resin layer  13 , and the multiple light emitting elements  22  are integrated by vacuum thermal pressing. Hence, at least a part of the bump  30  is electrically connected to the electrode  28 ,  29  of the light emitting element  22  in an un-melted condition. Accordingly, a contact angle between the upper surface of the electrode  28 ,  29  and the bump  30  becomes, for example, equal to or smaller than 135 degrees. 
     The light emitting element  22  emits light by an applied DC voltage via the electrodes  28 ,  29 . When, for example, the light emitting module  1  has two strings each including seven light emitting elements  22 , the conductor pattern  5  of the light emitting module  1  forms a 7-series and 2-parallel circuit. The light emitting elements  22  connected in series have the current that has the same magnitude across the whole light emitting elements  22 . 
     The light emitting element  22  of the light emitting module  1  employing the above structure has the bumps  30 . Hence, even if the flexible light emitting module  1  in which the light emitting elements  22  are embedded is bent in such a way that the side at which the electrodes  28 ,  29  are formed is convexed, the bump  30  ensures the sufficient height, and thus a short-circuit between the conductor pattern  5  and the light emitting element  22  is preventable. 
     &lt;Manufacturing Method&gt; 
     Next, an explanation will be given of a manufacturing method of the light emitting module  1  in accordance with this embodiment. 
     First, the light emitting element  22  formed with the electrode  28  and the electrode  29  (anode electrode and cathode electrode or cathode electrode and anode electrode) is prepared. 
     Next, the bumps  30  are formed on the respective electrodes  28 ,  29  of the light emitting element  22 . Hence, the light emitting element  22  formed with the respective bumps  30  on the electrodes  28 ,  29  as illustrated in  FIG. 2  is finished. As for the formation scheme of the bump  30 , a scheme of forming a gold or gold-alloy bump from an Au wire or an Au-alloy wire using a wire bump processing apparatus is applicable. It is preferable that the applied wire has a diameter of equal to or greater than 15 μM and equal to or smaller than 75 μm. 
     In accordance with this embodiment, a wire bonding apparatus is applied. By performing discharge at the tip of the wire, the wire tip is melted to form a ball, and the ball and the electrode  28 ,  29  are connected by ultrasound. Next, with the ball being connected to the electrode  28 ,  29 , the ball is cut from the wire. Hence, as illustrated in  FIG. 5 , the bump  30  that has a protrusion left at the upper end is formed on the upper surface of the electrode  28 ,  29 . 
     &lt;Rounding Process&gt; 
     The microscopic protrusion left at the upper end of the bump  30  may be left as it is, but a rounding process may be performed on the bump  30  when desired by depressing the upper surface of the bump  30 . 
     As an example, as illustrated in  FIG. 5 , the protrusion formed when cut from the wire is left at the upper portion of the bump  30 . This protrusion is called a tail. When the diameter of a surface in contact with the electrode  28 ,  29  is A, and the height of the bump  30  is B, it is desirable that the shape of the bump  30  should satisfy a condition that is B/A=0.2 to 0.7. Hence, when the shape of the bump  30  is out of this numerical value range, the rounding process is performed. 
       FIGS. 6A to 6C  are each a diagram for explaining the rounding process using a press plate  500 . After the bump  30  is formed, the light emitting element  22  is disposed on a bump bonding apparatus (unillustrated). Next, as illustrated in  FIG. 6A , with the lower surface of the press plate  500  provided at the bump bonding apparatus being in parallel with the electrodes  28 ,  29 , the press plate  500  is positioned on the space above the bump  30 . 
     Subsequently, the press plate  500  is moved down, and as illustrated in  FIG. 6B , the press plate  500  is depressed against the upper portion of the bump  30 . At this time, the press plate  500  is moved down until the height of the bump becomes the desired height B. The tail of the bump  30  is crushed by the press plate  500 . Hence, as illustrated in  FIG. 6C , a sequential surface that has no protrusion at the upper portion of the bump  30  is formed. This sequential surface becomes flat at the upper end portion of the bump  30 . 
     The rounding process may be performed by pressing the bump  30  via a resin sheet. In this case, a resin sheet  501  formed of, for example, PET, a fluorine resin, TPX, or olefin is attached to the lower surface of the press plate  500 . Next, as illustrated in  FIG. 7A , with the lower surface of the press plate  500  on which the resin sheet  501  is disposed being in parallel with the electrodes  28 ,  29 , the press plate  500  is positioned above the bump  30 . 
     Next, the press plate  500  is moved down, and as illustrated in  FIG. 7B , the resin sheet  501  is pushed against the upper portion of the bump  30 . In this case, the press plate  500  is moved down so as to accomplish the bump height that is the desirable height B. The tail of the bump  30  is crushed by the resin sheet  501 . Hence, as illustrated in  FIG. 7C , a sequential surface that has no protrusion at the upper portion of the bump  30  is formed. The sequential surface formed on the bump  30  by the rounding process using the resin sheet  501  becomes a convex curved surface upwardly at the upper end of the bump  30 . 
     In accordance with the rounding process using the resin sheet  501 , for example, as illustrated in  FIG. 8A , the press plate  500  to which the resin sheet  501  is attached is disposed above the light emitting element  22 , while a press plate  502  to which a resin sheet  503  is attached is disposed below the light emitting element  22 . Those resin sheets  501 ,  503  have a larger thickness than a value obtained by adding the thickness of the light emitting element  22  and the height B of the bump  30 . 
     Next, the press plate  500  is moved down, while the press plate  502  is moved up, thereby holding the light emitting element  22  therebetween to press the light emitting element  22 . Hence, as illustrated in  FIG. 8B , the light emitting element  22  becomes a condition embedded in the resin sheets  501 ,  503 . At this time, the bump  30  of the light emitting element  22  is subjected to the rounding process, and thus the tail is crushed. The displacement amount of the press plates  500 ,  502  at the time of pressing is determined in accordance with the target height of the bump  30 . 
     Next, the pressing to the light emitting element  22  is finished, and the resin sheets  501 ,  503  are removed from the light emitting element  22 . Hence, the light emitting element  22  that has the bump  30  formed with the sequential surface that is a sequential curved surface is obtained. The light emitting element  22  may be disposed on the press plate  502  without the resin sheet  503 , and the press work may be directly performed on this light emitting element  22 . 
     As explained above, the bump  30  is formed on the upper surface of the light emitting element  22 . The present disclosure is not limited to this scheme, and in addition to the formation of a wire bump using a wire bonder, for example, the bump  30  can be formed by electrolytic plating or non-electrolytic plating on the electrode  28 ,  29 . In addition, the bump  30  can be formed by ink-jet printing of an ink containing metal particles on the electrode  28 ,  29 , and by calcination. Still further, a paste containing metal particles may be printed or applied to the electrode  28 ,  29  to form the bump  30 , and the bump  30  may be also formed on the electrode  28 ,  29  by technologies, such as ball mounting, pellet mounting, and vapor deposition sputtering. In addition, a material, such as a metal like gold, silver, copper, or nickel, an alloy like a tin-gold alloy, an eutectic material, an amorphous material, and solder is applicable for the bump  30 . 
     After the bump  30  is formed on the light emitting element  22 , the light transmissive film  4  having the conductor pattern  5  formed on the upper surface is prepared. Next, as illustrated in  FIG. 9A , the resin sheet  130  with a light transmissive property is disposed on the upper surface of the light transmissive film  4 . The resin sheet  130  may be tentatively tacked to the light transmissive film  4  by an adhesive. 
     The resin sheet  130  mainly contains a resin that is thermosetting and has a light transmissive property for visible light. An example resin sheet  130  is a sheet formed of, for example, an epoxy-based resin. This resin sheet  130  is shaped in the substantially same shape as that of the light transmissive film  4 . 
     It is preferable that the resin sheet  130  should have the lowest melt viscosity prior to curing which is within a range between 10 and 10000 Pa·s, and a temperature Mp within a range between 80 and 160° C. when the viscosity of the resin sheet  130  becomes the lowest melt viscosity. It is preferable that, when the resin sheet  130  is subjected to temperature rise from the room temperature to the temperature Mp, the melt viscosity change rate of the resin sheet  130  should be equal to or smaller than 1/1000. It is preferable that the Vicat softening temperature of the resin sheet  130  after reaching the lowest melt viscosity by heating and cured should be within a range between 80 and 160° C. It is preferable that the tensile storage elastic modulus of the resin sheet  130  should be within a range between 0.01 to 1000 GPa at a temperature within a range between 0 to 100° C. It is preferable that the glass transition temperature of the resin sheet  130  should be 100 to 160° C. 
     It is appropriate if the resin sheet  130  has a thickness capable of sufficiently filling the space between the light transmissive films  4 ,  6  caused by disposing the light emitting element  22  therebetween. When the thickness (T) of the resin sheet  130  is made thinner than the height (H) of the light emitting element  22 , the thickness of the resin sheet  130  may be determined based on the difference (H−T). 
     Next, as illustrated in  FIG. 9B , the light emitting element  22  is disposed on the upper surface of the resin sheet  130 . The light emitting element  22  is disposed in such a way that the surface on which the electrodes  28 ,  29  are formed faces the light transmissive film  4 . In addition, the light emitting element  22  is positioned in such a way that the electrodes  28 ,  29  are located above the corresponding pieces of the conductor pattern  5 . 
     Subsequently, as illustrated in  FIG. 9C , the light transmissive film  6  is disposed above the light emitting element  22 . 
     Next, a laminated body that includes the light transmissive films  4 ,  6 , the resin sheet  130 , and the light emitting elements  22  is pressurized while being heated under a vacuum condition. 
     The heating and pressing process (vacuum thermal compression bonding process) under the vacuum atmosphere may be performed at two steps. 
     In the first step, the resin sheet  130  is pressurized and heated until reaching a temperature T 1  (° C.). When the temperature at which the viscosity of the resin sheet  130  becomes the lowest melt viscosity is Mp (° C.), the temperature T 1  is a temperature that satisfies the following conditional expression (1). It is preferable that the temperature T 1  should satisfy a conditional expression (2).
 
 Mp− 50° C.≤ T 1&lt; Mp   (1)
 
 Mp− 30° C.≤ T 1&lt; Mp   (2)
 
     In addition, Mp−10° C.≤T 1 &lt;Mp may be set. 
     In the second step, the resin sheet  130  is pressurized while being heated until reaching a temperature T 2  (° C.). The temperature T 2  is a temperature that satisfies the following conditional expression (3). It is preferable that the temperature T 2  should satisfy a conditional expression (4).
 
 Mp≤T 2&lt; Mp+ 50° C.  (3)
 
 Mp+ 10° C.≤ T 2&lt; Mp+ 30° C.  (4)
 
     By adopting such a heating condition, the laminated body can be pressurized with the resin sheet  130  being softened as appropriate. In addition, the resin layer  13  can be formed by filling the softened resin sheet  130  in between the light transmissive film  4  and the light transmissive film  6  while connecting the electrodes  28 ,  29  of the light emitting element  22  disposed on the conductor pattern  5  via the resin sheet  130  to the predetermined pieces of the conductor pattern  5 . 
     When the temperature T 1  in the first step is less than a lower limit value that is Mp−50° C. indicated in the conditional expression (1), the softening of the resin sheet  130  becomes insufficient. Consequently, the intimate contact of the resin sheet  130  with the light emitting element  22  decreases, which may result in an insufficient connection between the corresponding pieces of the conductor pattern  5  and the electrodes  28 ,  29  of the light emitting element  22 . 
     Conversely, when the temperature T 1  in the first step is equal to or greater than an upper limit value that is Mp in the conditional expression (1), the resin sheet  130  is hardened. Consequently, the intimate contact of the resin sheet  130  with the light emitting element  22  decreases, which may result in an insufficient connection between the corresponding pieces of the conductor pattern  5  and the electrodes  28 ,  29  of the light emitting element  22 . 
     When the temperature T 2  in the second step is less than a lower limit value that is Mp indicated in the conditional expression (3), the curing of the resin sheet  130  becomes insufficient. Consequently, the intimate contact of the resin sheet  130  with the light emitting element  22  may decrease. 
     Conversely, when the temperature T 2  in the second step is equal to or higher than an upper limit value that is Mp+50° C. indicated in the conditional expression (3), the light transmissive films  4 ,  6  are softened, which may result in a deformation of the entire laminated body. 
     &lt;Thermal Compression Bonding Process&gt; 
     It is preferable that the thermal compression bonding process for the laminated body under the vacuum atmosphere should be carried out as follow. The above laminated body is pre-pressurized so as to cause each component to be intimately in contact with each other. Next, a work space where the pre-pressurized laminated body is disposed is vacuumed until the vacuum degree of 5 kPa is accomplished, and the laminated body is pressurized while being heated to the above temperature. By performing thermal compression bonding on the pre-pressurized laminated body under the vacuum atmosphere as explained above, as illustrated in  FIG. 9D , the softened resin sheet  130  can be filled in the space between the light transmissive film  4  and the light transmissive film  6  without a void. 
     It is preferable that the vacuum atmosphere at the time of thermal compression bonding should be equal to or lower than 5 kPa. The pre-pressurizing process to pre-pressurize the laminated body may be omitted, but in this case, a positional displacement of the laminated body, etc., is likely to occur. Hence, it is preferable to perform pre-pressurization. 
     When the thermal compression bonding on the laminated body is performed under an ambient atmosphere or in a low vacuum condition, air bubbles are likely to be left within the light emitting module  1  having undergone the thermal compression bonding, in particular, around the light emitting element  22 . Air trapped in the left air bubbles within the light emitting module  1  is pressurized. This may cause an expansion of the light emitting module  1  after the thermal compression bonding, and a peeling between the light emitting element  22  and the light transmissive films  4 ,  6 . In addition, when air bubbles and an expansion are present in the light emitting module  1 , in particular, near the light emitting element  22 , light will be scattered non-uniformly, resulting in a poor visual inspection result of the light emitting module  1 . 
     As explained above, with the resin sheet  130  being present between the conductor pattern  5  and the electrodes  28 ,  29  of the light emitting element  22 , by performing the thermal compression bonding process, the resin layer  13  can be formed around the light emitting element  22  while electrically connecting the electrodes  28 ,  29  with the corresponding pieces of the conductor pattern  5 . In addition, a part of the resin layer  13  can be filled excellently in the space between the upper surface of the light emitting element  22  and the conductor pattern  5 . 
     By performing the above thermal compression bonding on the laminated body, the finished light emitting module  1  illustrated in  FIG. 1  is obtained. In accordance with the manufacturing method in this embodiment, the light emitting module  1  that has improved electrical connection between the corresponding pieces of the conductor pattern  5  and the electrodes  28 ,  29  of the light emitting element  22 , and reliability thereof is manufactured with an excellent reproducibility. Although the processes in  FIGS. 9A to 9D  advance with the light emitting element  22  being directed downwardly, the processes may advance with the light emitting element  22  being directed upwardly. 
     In accordance with this embodiment, the explanation has been given of an example case in which the resin layer  13  is formed using the single resin sheet  130 , but the resin layer  13  may be formed using multiple (e.g., two) resin sheets. 
     More specifically, as illustrated in  FIG. 10A , a thermosetting resin sheet  131  is disposed on the upper surface of the light transmissive film  4  so as to cover the conductor pattern  5 . This resin sheet  131  is formed of the same material as that of the resin sheet  130 . In addition, the thickness of the resin sheet  131  is substantially equivalent to a total of the height of the bump  30  on the light emitting element  22  and the height of the electrode  28 ,  29 . 
     Next, as illustrated in  FIG. 10B , the multiple light emitting elements  22  are disposed on the upper surface of the resin sheet  131 . The light emitting element  22  is disposed in such a way that the electrodes  28 ,  29  face the resin sheet  131 . 
     Next, as illustrated in  FIG. 10C , a thermosetting resin sheet  132  and the light transmissive film  6  are disposed on the light emitting element  22 . This resin sheet  132  is also formed of the same material as that of the resin sheet  130 . 
     Subsequently, as illustrated in  FIG. 10D , the laminated body that includes the light transmissive films  4 ,  6 , the resin sheets  131 ,  132 , and the light emitting elements  22  is pressurized while being heated under a vacuum atmosphere. The light emitting module  1  can be manufactured through the above steps. In accordance with this light emitting module  1 , the resin layer  13  is formed by a first resin layer formed of the resin sheet  131 , and a second resin layer formed of the resin sheet  132 . 
     In this case, the light transmissive film  6  may be utilized as a tentative base body, the entire laminated body may be pressurized to electrically connect the electrodes  28 ,  29  of the light emitting element  22  with the corresponding pieces of the conductor pattern  5 , and the light transmissive film  6  and the resin sheet  132  may be peeled. Next, a resin sheet and an eventual light transmissive film which have the same thicknesses as those of the peeled ones may be pasted to manufacture the light emitting module  1 . 
     More specifically, the light transmissive film  6  and the resin sheet  132  are removed from the laminated body that includes the integrated light transmissive films  4 ,  6 , resin sheets  131 ,  132 , and light emitting elements  22 . Next, the replacements of the removed light transmissive film  6  and resin sheet  132  may be pasted on the surface of the resin sheet  131 . 
     An example resin sheet also applicable to form the resin layer  13  is a thermoplastic resin. An example thermoplastic resin is thermoplastic elastomer. Elastomer is an elastic material that is a polymer material. Example known elastomers are acrylic-based elastomer, olefin-based elastomer, styrene-based elastomer, ester-based elastomer, and urethane-based elastomer. 
     It is preferable that the above thermoplastic resin should have a Vicat softening temperature within a range between 80 to 160° C., and the tensile storage elastic modulus within a range between 0.01 to 10 GPa at a temperature of 0 to 100° C. It is preferable that the thermoplastic resin should not be melted at the Vicat softening temperature, and have the tensile storage elastic modulus which is equal to or greater than 0.1 MPa at the Vicat softening temperature. It is preferable that the thermoplastic resin should have a melting-point temperature which is equal to or higher than 180° C., or a melting-point temperature higher than the Vicat softening temperature by equal to or higher than 40° C. It is preferable that the thermoplastic resin should have a glass transition temperature which is equal to or lower than −20° C. when applied to form the resin layer  13 . 
     When the resin layer  13  is formed by the thermosetting resin sheet and the thermoplastic resin sheet, first, the light emitting elements  22  are held between the thermosetting resin sheet and the thermoplastic resin sheet. Next, the thermosetting resin sheet, the thermoplastic resin sheet, and the light emitting elements  22  are held between the light transmissive films  4 ,  6 , and the laminated body as illustrated in  FIG. 10D  is formed. Subsequently, this laminated body is pressurized and heated. This accomplishes an electrical connection of the conductor pattern  5  with the light emitting element  22 , thermal curing of the thermosetting resin sheet, and filling of the thermoplastic resin sheet in the space between the upper surface of the light emitting element  22  and the light transmissive film  4 . 
     The electrical connection of the conductor pattern  5  with the light emitting element  22 , the thermal curing of the thermosetting resin, and the filling of the thermoplastic resin may be carried out at individual pressurization and heating processes. In this case, either one of the electrical connection of the conductor pattern  5  with the light emitting element  22  or the thermal curing of the thermosetting resin sheet may be simultaneously performed with the heating process for filling the thermoplastic resin in the concavity and convexity. 
     Alternatively, after the electrical connection of the conductor pattern  5  with the light emitting element  22  by the thermosetting resin and the thermal curing of the thermosetting resin are performed at the respective appropriate temperatures by the pressurization and heating process, the thermoplastic resin may be stacked. Next, this thermoplastic resin may be pressurized and heated to fill the thermoplastic resin in the concavity and convexity that are formed between the thermosetting resin and the light emitting element  22 . 
     When the pressurization and heating process (vacuum thermal compression bonding process) under a vacuum atmosphere is to be performed on the thermoplastic resin, first, with the thermoplastic resin being heated so as to be a temperature T within a range that is, for example, Mp−10 (° C.)≤T≤Mp+30 (° C.) where Mp is the Vicat softening temperature of the thermoplastic resin, the laminated body may be pressurized. In addition, the temperature T may be within a range that is Mp−10 (° C.)≤T≤Mp+10 (° C.). Either the electrical connection of the conductor pattern  5  with the light emitting element  22  by the thermosetting resin or the thermal curing of the thermosetting resin may be performed simultaneously with the heating on the thermosetting resin, or may be performed individually as explained above. 
     This embodiment also covers the following aspects. 
     1) [when Thermosetting Resin Sheet is Single Layer] 
     In this case, the start material includes the light transmissive film  4 , the conductor pattern  5 , the resin sheet  130  formed of the thermosetting resin, the light emitting elements  22 , and the light transmissive film  6 . The light emitting module is formed through the following processes. The laminated body that includes the light transmissive film  4 , the conductor pattern  5 , the resin sheet  130 , and the light emitting elements  22  is subjected to a first pressurization and heating process to embed the light emitting elements  22  in the resin sheet  130 , and to connect the light emitting elements  22  with the conductor pattern  5 . Next, this laminated body is subjected to a second pressurization and heating process to perform thermal curing on the resin sheet  130 . 
     2) [when Thermosetting Resin Sheet is Two Layers] 
     In this case, the start material includes the light transmissive film  4 , the conductor pattern  5 , the resin sheet  131  formed of the thermosetting resin, and the light emitting elements  22 . The light emitting module is formed through the following processes. The laminated body that includes the light transmissive film  4 , the conductor pattern  5 , the resin sheet  131 , and the light emitting elements  22  is subjected to a first pressurization and heating process to electrically connect the light emitting element  22  with the conductor pattern  5  by the bump  30  that passes completely through the resin sheet  131 . Next, the laminated body is subjected to a second pressurization and heating process to perform thermal curing on the resin sheet  131 . Subsequently, the resin sheet  132  formed of the thermosetting resin and the light transmissive film  6  are laminated in sequence on the laminated body. Next, the laminated body is subjected to a third pressurization and heating process to fill the resin sheet  132  formed of the thermosetting resin into the concavity and convexity of the base surface. Subsequently, the laminated body is subjected to a fourth pressurization and heating process to cure the resin sheet  132 . 
     3) [when Thermosetting Resin Sheet and Thermoplastic Resin Sheet are Applied (Laminated Film)] 
     The start material includes the light transmissive film  4 , the conductor pattern  5 , the resin sheet  131  formed of the thermosetting resin, and the light emitting elements  22 . The light emitting module is formed through the following processes. The laminated body that includes the light transmissive film  4 , the conductor pattern  5 , the resin sheet  131 , and the light emitting elements  22  is subjected to a first pressurization and heating process to electrically connect the light emitting element  22  with the conductor pattern  5  by the bump  30  that passes completely through the resin sheet  131 . Next, the laminated body is subjected to a second pressurization and heating process to perform thermal curing on the resin sheet  131 . Subsequently, the resin sheet  132  formed of a thermoplastic resin and the light transmissive film  6  are laminated in sequence on the laminated body. Next, the laminated body is subjected to a third pressurization and heating process to fill the resin sheet  132  formed of the thermoplastic resin into the concavity and convexity of the base surface. 
     In addition, the following structure is also employable if desirable. 
     For example, the start material includes the light transmissive film  4 , the conductor pattern  5 , the resin sheet  131  formed of the thermoplastic resin, and the light emitting modules  22 . The light emitting module is formed through the following processes. The laminated body that includes the light transmissive film  4 , the conductor pattern  5 , the thermoplastic resin sheet  131 , and the light emitting elements  22  is subjected to a first pressurization and heating process to electrically connect the light emitting element  22  with the conductor pattern  5  by the bump  30  that passes completely through the thermoplastic resin sheet  131 . Next, the resin sheet  132  formed of the thermosetting resin, and the light transmissive film  6  are laminated in sequence on the laminated body. Subsequently, the laminated body is subjected to a second pressurization and heating process to fill the resin sheet  132  formed of the thermosetting resin into the concavity and convexity of the base surface. When desired, the laminated body is subjected to a third pressurization and heating process to thermally cure the resin sheet  132  formed of the thermosetting resin. 
     Note that in the above embodiment, as illustrated in  FIG. 2 , the applied light emitting element  22  has the two electrodes on the one surface. However, a light emitting element (double-sided-electrode light emitting element) that has the respective electrodes on the upper surface and the lower surface is also applicable. In addition, the light emitting module  1  may include both the light emitting element  22  that has the two electrodes on the one surface, and the double-sided-electrode light emitting element. When the double-sided-electrode light emitting element is applied, the conductor circuitry layers are provided at both the light transmissive films  4 ,  6 . In accordance with the double-sided-electrode light emitting element, the bump is provided at the light-emitting-surface side of the light emitting element. 
     In the above embodiment, as illustrated in  FIG. 2 , the explanation has been given of an example case in which the electrodes  28 ,  29  (pad electrodes) of the light emitting element  22  that has the two electrodes on the one surface have different thicknesses. The present disclosure is not limited to this example case, and for example, the surface heights of the bumps  30  can be aligned by having the electrodes  28 ,  29  that have the same thickness, and by changing the diameter of the bump  30  between both the electrodes. 
     When the electrodes  28 ,  29  have the same thickness, and the respective bumps  30  have the same diameter, the top of the bump  30  on the electrode  29  is lower than the top of the bump  30  on the electrode  28 . In this case, when the light emitting element  22  is pushed in until the lower bump  30  reaches the conductor pattern  5  by the compression at the time of pressurization and heating, a connection between the bump  30  and the conductor pattern  5  is obtained. This process can be performed in both the case in which the connection between the bump  30  and the conductor pattern  5  is to be obtained using the thermosetting resin sheet and the case in which the connection between the bump  30  and the conductor pattern  5  is to be obtained using the thermoplastic resin. 
     In the above embodiment, as illustrated in, for example,  FIG. 9C or 10C , the explanation has been given of an example case in which, by integrally pressurizing the laminated body that includes the light transmissive films  4 ,  6 , the resin sheets  130 ,  131 ,  132 , and the light emitting elements  22 , the electrical connection between the bump  30  of the light emitting element  22  and the conductor pattern  5  of the light transmissive film  4  is obtained. Various modifications can be made to the manufacturing process of the light emitting module  1 . 
       FIG. 11  illustrates a dynamic viscosity (η*) of the resin sheet prior to thermal curing. The viscoelastic curved line of the thermosetting resin sheet prior to the thermal curing is indicated as L, and the temperature of the thermosetting resin sheet at the lowest melt viscosity, i.e., the maximum softening temperature (cured temperature) is indicated as Mp. 
     The maximum softening temperature Mp can take the value that is 80 to 160° C. or 80 to 150° C. The upper limit is defined by, for example, the maximum softening temperature of a PET film which is 180° C. A more preferable range of the maximum softening temperature Mp is within a range between 100 to 130° C. This is because the resin characteristics (the lowest melt viscosity, intimate contact, etc.) can be easily controlled. In  FIG. 11 , T 1  indicates the pressurization and heating temperature when an LED chip that has two electrodes on the one surface is mounted on a light transmissive film formed with a conductor pattern via a thermosetting resin sheet and is thermally pressed. T 2  indicates the thermal curing process temperature when the temperature is increased after the light emitting element  22  is electrically connected to the conductor pattern, and thermal curing is performed on the thermosetting resin. 
     In  FIG. 11 , each point A to E indicates the following condition. 
     [Point A]: the upper limit point enabling a disposition of an LED (tentative tacking viscosity or tentative tacking upper limit viscosity). This is the upper limit point at which the disposed light emitting element (LED) is prevented from being detached or from being displaced displaced since the viscosity of the resin is too high (i.e., the resin is too hard) and the tacking is not excellent after the LED is disposed (mounted) at a prescribed position (the position of the connection pad of the conductor pattern), and when the process transitions to the subsequent process. That is, this is a chip mounting upper limit viscosity. 
     [Point C]: the upper limit point enabling the LED to be embedded (packaging viscosity or packaging upper limit viscosity). This is the upper limit point at which the resin is sufficiently filled around the LED in the vacuum thermal compression bonding process to embed the LED. That is, the filling control upper limit viscosity. 
     [Point D]: the lower limit value enabling a flow control (fluidization preventive viscosity or fluidization preventive lower limit viscosity). In a vacuum thermal compression bonding process of embedding an LED, when the viscosity of the resin is low, pressure produces a flow when the temperature is increased to the curing temperature, the fluidized resin displaces the position of the light emitting element (LED), and in an extremely case, a liquefaction of the resin occurs, and the necessary resin is flown out from the film external contour end (in this case, the necessary resin thickness for the device structure cannot be ensured). That is, this is the lower limit viscosity for a flow control. 
     [Point E]: the upper limit point enabling an electrical connection with the LED (pressurization connection upper limit viscosity). This is an upper limit viscosity enabling the bump of the LED to reach the conductor pattern and to obtain a connection between the LED and the conductor pattern at the time of thermal pressing. In general, this is a thermal press connection upper limit viscosity. 
     [Point B]: the lower limit viscosity that covers the above restrictions at A, C, D, and E. That is, the same viscosity as that of the point D. 
     In  FIG. 11 , the points A and B are located at a room temperature Tr, i.e., at a normal temperature (25° C.), while the points C and D are located at the maximum softening temperature Mp. In addition, the point E is located at a thermal press temperature T 1  enabling the bump of the LED to pass completely through the resin and to obtain a connection with the conductor pattern. 
     In  FIG. 11 , based on the knowledges by the inventor of the present disclosure, the points C and D define a gate over the process. That is, when the laminated body is subjected to thermal curing at the temperature T 2  after being subjected to thermal pressing at the temperature T 1 , various cases, such as a case in which no pressurization is performed at the maximum softening temperature Mp, a case in which the pressurization is continuously performed, and a case in which the pressurization is performed while the pressurization level is decreased, are available. Hence, as for the process designing, it is necessary that the resin is not fluidized at the point D under the pressurization. 
     In addition, when the temperature transitions from T 1  to T 2 , it is necessary that the resin is soft to some level at the maximum softening temperature Mp. Hence, it is necessary that the viscoelastic characteristic of the resin should be within a range between C to D at the maximum softening temperature. 
     Still further, it is necessary that the viscoelastic characteristic of the resin should be within the range between A and B at the room temperature Tr, and should be equal to or lower than E at the thermal press temperature T 1 . That is, in view of the process designing, it is preferable that the viscoelastic characteristic curved line of the resin should be within a region defined by interconnecting A, B, C, and D or A, B, C, D, and E by straight lines (i.e., A-B-D-C-A or A-B-D-C-E-A). Note that the thermal pressing for obtaining an electrical connection with the LED may be performed at the viscosity that is equal to or lower than E and equal to or higher than B, D at the temperature T 1  in principle. 
     As for actual values, the dynamic viscosity at each point is as follow. 
     A: 1,000,000 poise (V1) 
     C: 10,000 poise (V2) 
     D: 500 poise (V3) 
     E: 50,000 poise (V4) 
     B: 500 poise 
     In addition, based on the above conditions, the region between C and D becomes 500 to 10,000 poise, but 2,000 to 5,000 poise is more preferable for the region between C and D which facilitates a flow control, and which enables an LED to be embedded at low pressure. 
     When the sealing viscosity is not requisite, the gate at the maximum softening temperature of the thermosetting resin becomes A to F because of the point F over the maximum softening temperature Mp which has the same viscosity as that of the point E. Hence, the region is defined by ABFD or ABEFD. 
       FIGS. 12A to 12D  illustrates an example manufacturing method of the light emitting module  1  applied for measurement. However, the following measurement is common to the above various embodiments, such that the LED is held between the two thermosetting resin sheets and thermally pressed, the LED is embedded in a thick thermosetting resin sheet, and an electrical connection with the LED is obtained by the thermosetting resin sheet that is thinner than the LED, and the remaining is embedded by the thermoplastic resin sheet. An explanation will be below given of an example manufacturing process as illustrated in  FIGS. 12A to 12D . 
     First, as illustrated in  FIG. 12A , the light emitting element  22  is disposed on the upper surface of the resin sheet  131  (thermosetting resin sheet) which is stacked on the light transmissive film  4 , and which has a thickness of substantially 60 μm. Next, prior to disposing the light transmissive film on the light emitting element  22 , initially, the light emitting element  22  is subjected to vacuum thermal compression bonding (thermal pressing) to the conductor pattern  5  at the vacuum degree of, for example, 5 kPa. Hence, as illustrated in  FIG. 12B , the bump  30  of the light emitting element  22  passes completely through the resin sheet  131 , and reaches the conductor pattern  5 . Accordingly, the bump  30  is electrically connected to the corresponding piece of the conductor pattern  5 . 
     When, for example, the lowest melt viscosity of the resin sheet is 3000 poise, and the temperature Mp at which the resin sheet is cured is 130° C., in the above thermal compression bonding, the resin sheet is heated to substantially 100° C., and the pressure of 0.2 MPa is applied to the light emitting element  22  (LED). 
     Next, as illustrated in  FIG. 12C , disposed on the light emitting element  22  are the resin sheet  132  which is thermosetting, and which has a thickness of substantially 60 μm, and the light transmissive film  6 . Subsequently, as illustrated in  FIG. 12D , the laminated body that includes the light transmissive films  4 ,  6 , the resin sheets  131 ,  132 , and the light emitting elements  22  is pressurized while being heated under the vacuum atmosphere. 
     When, for example, the lowest melt viscosity of the resin sheet is 3000 poise, and the temperature Mp at which the resin sheet is cured is 130° C., in the above thermal compression bonding, the laminated body is heated to 140° C., and the pressure of 0.2 MPa is applied to the laminated body. 
     Through the above processes, the light emitting module  1  is manufactured. 
       FIG. 13  is a diagram illustrating initial states of the resin sheets  130  to  132  which are thermosetting, i.e., the dynamic viscosity prior to thermal curing. The horizontal axis of the graph in  FIG. 13  indicates a temperature (° C.), while the vertical axis indicates a dynamic viscosity (poise). Each curved line L 1  to L 5  indicates a viscoelastic characteristic of the resin sheet prior to thermal curing. The dynamic viscosity is obtainable by dynamic viscoelastic measurement. The dynamic viscoelastic measurement indicates the stress to the resin sheet when a constant cyclic sinusoidal wave strain is applied to the resin sheet. In general, the greater the dynamic viscosity is, the harder the material is, and the smaller the dynamic viscosity is, the softer the material is. 
     As illustrated in, for example,  FIG. 12A , it is preferable that the resin sheet should be soft to some level when the light emitting elements  22  are disposed thereon. More specifically, when, for example, using an apparatus like a mounter, the light emitting element  22  is disposed on the resin sheet, it is preferable that the resin sheet should be soft to a level that enables the bump  30  of the light emitting element  22  to be slightly embedded in the resin sheet. When the resin sheet is soft to some level, the light emitting element  22  disposed by the mounter is tentatively tacked on the resin sheet. Hence, when the light transmissive film  4  on which the light emitting element  22  is already disposed is moved, and when the light transmissive film  6  is stacked on the light transmissive film  4 , the light emitting element  22  is not displaced relative to the resin sheet, and thus the light emitting element  22  is precisely positioned. 
     In general, the mounting of the light emitting element  22  by the mounter is carried out at a room temperature, and thus when, for example, the resin sheet is 25° C., it is preferable that the dynamic viscosity of the resin sheet should be equal to or lower than 1.0 E×06 poise below the dashed line passing through the point A. 
     The thermal compression bonding on the laminated body that includes the light transmissive films, the resin sheets, the light emitting elements, etc., are carried out at a lower temperature than the temperature at which the resin sheet becomes the lowest melt viscosity, i.e., a lower temperature than the temperature Mp at which resin sheet starts curing. Next, the laminated body having undergone the thermal compression bonding is maintained in the pressurized condition until becoming the temperature Mp at which the resin sheet starts curing if desirable. Hence, when the dynamic viscosity is too small, the resin sheet may flow out from between the light transmissive films, and the position of the light emitting element  22  may be displaced together with the flowing resin. Accordingly, it is preferable that the dynamic viscosity of the resin sheet should be equal to or higher than 500 poise above the dashed line passing through the point D. That is, it is preferable that the minimum dynamic viscosity of the resin sheet should be equal to or greater than 500 poise. 
     When, for example, the light transmissive films  4 ,  6  are formed of PET that has a thickness of substantially 100 μm, it is preferable that the temperature Mp should be lower than the softening temperature of PET. Since the softening temperature of PET is substantially 180° C., the temperature Mp becomes, for example, 80 to 160° C. More preferably, the temperature Mp is 80 to 150° C., and roughly 100 to 130° C. Accordingly, when the temperature is 130° C., it is preferable that the dynamic viscosity should be equal to or higher than 500 poise. 
     While the thermal compression bonding is being performed on the laminated body that includes the light transmissive films, the resin sheets, and the light emitting elements, etc., as illustrated in, for example,  FIG. 9D ,  FIG. 10D , and  FIG. 12D , it is necessary to cause the resin sheet to go around the light emitting element  22  without a void. Hence, the resin sheet should be softened to some level at the temperature Mp. Accordingly, it is preferable that the dynamic viscosity of the resin sheet should be equal to or lower than 1.0 E×04 poise below the dashed line passing through the point C at the temperature Mp. Hence, it is preferable that the dynamic viscosity should be equal to or lower than 1.0 E×04 poise at the temperature 130° C. 
     In this embodiment, by performing thermal compression bonding on the laminated body, the bumps  30  of the light emitting element  22  pass completely through the resin sheet, and reach the conductor pattern of the light transmissive film. Hence, when the laminated body is subjected to thermal compression bonding, it is necessary that the resin sheet should be softened to some level. After the thermal compression bonding starts, and until the desired pressure is applied to the laminated body, the laminated body is heated to substantially 100 to 110° C. Hence, it is preferable that the dynamic viscosity of the resin sheet should be equal to or lower than 50000 poise below the dashed line passing through the point E at the temperature of substantially 110° C. 
     In view of the foregoing, it is preferable that the resin layer  13  of the light emitting module  1  should be formed using a resin sheet which has the dynamic viscoelastic characteristic which is indicated by a curved line within the region defined by straight lines interconnecting the points A, B, C, D, and E in  FIG. 13  that shows the transition of dynamic viscosity from substantially 25° C. to substantially 130° C. 
     For example, in the example case illustrated in  FIG. 13 , it is preferable to form the resin layer  13  of the light emitting module  1  using the resin sheet that has the dynamic viscoelastic characteristics indicated by curved lines L 3 , and L 4 . In addition, the resin sheet that has the dynamic viscoelastic characteristic indicated by a curved line L 2  is also applicable. This is because the resin sheet that has the dynamic viscoelastic characteristic indicated by the curved line L 2  satisfies the necessary dynamic viscosity condition upon formation of the resin layer at the points A to E. 
       FIG. 14  is a diagram illustrating the tensile storage elastic modulus when the above resin sheet  130 ,  131 , etc., is cured. As illustrated in  FIG. 14 , the resin sheet that has the dynamic viscoelastic characteristics indicated by L 2  and L 3  in  FIG. 13  shows a characteristic that has a constant and stable tensile elastic modulus from the temperature lower than the normal temperature to 100° C. after cured. In addition, when heated beyond the softening temperature, the viscosity once keenly decreases, but then becomes the stable characteristic that has the constant tensile storage elastic modulus. Hence, by using the above resin sheet  130 ,  131 , etc., the highly reliable light emitting module  1  can be provided. 
     The tensile storage elastic modulus of the resin sheet after thermally cured is within a range between 1 to 10 GPa at the temperature of −50 to 100° C., and a change in tensile storage elastic modulus is within a single digit (less than 10 times). 
     Example thermosetting resin sheets applicable are an epoxy-based resin, and further an acrylic-based resin, a styrene-based resin, an ester-based resin, an urethane-based resin, a melamine resin, a phenol resin, an unsaturated polyester resin, and a diallyl phthalate resin, and are replaceable with each other. 
     The measurement of the dynamic viscoelastic modulus in  FIG. 13  was carried out using a measurement sample which had a length of 20 mm, a width of 7 mm, and a thickness of 0.06 mm, and under the conditions which were a tensile mode, a temperature rise speed of 2.5° C./min, a measurement cycle of 2.5 s, a frequency of 1 Hz, and a temperature range between 60 to 180° C. As for the measurement of the tensile storage elastic modulus in  FIG. 14 , such a measurement was carried out using a test sample which had a length of 20 mm, a width of 7 mm, and a thickness of 0.06 mm, and under the conditions which were a tensile mode, a temperature rise speed of 2° C./min, a measurement cycle of 3 s, a frequency of 2 Hz, and a temperature range between −60 and 280° C. In addition, the tensile elastic modulus in  FIG. 14  is a value obtained through a scheme in compliance with the above JIS K7244-1 (ISO 6721). 
     Several embodiments of the present disclosure have been explained above, but those embodiments are merely presented as examples, and are not intended to limit the scope of the present disclosure. Those novel embodiments can be carried out in other various forms, and various omissions, replacements, and modifications can be made thereto without departing from the scope of the present disclosure. Those embodiments and modified forms thereof are within the scope and spirit of the present disclosure, and within the invention as recited in appended claims and the equivalent range thereto.