Patent Publication Number: US-2018040780-A1

Title: Light-emitting device and method for producing the same

Description:
TECHNICAL FIELD 
     The present invention relates to a light-emitting device including a plurality of light-emitting diodes (LEDs) mounted to a metal substrate, and to a method for producing the light-emitting device. 
     BACKGROUND ART 
     Recently, illumination devices using light-emitting diodes (LEDs) as light sources have become widely used. With the widespread use, there is an increasing need for illumination devices having improved light extraction efficiency and improved ability to be mass-produced and which are less expensive, in addition to having reduced sizes and thicknesses. To reduce the sizes and thicknesses of illumination devices and to increase their light extraction efficiency by improving the heat dissipation properties, the so-called flip-chip mounting is being employed for an increasing number of light-emitting devices. With the flip-chip mounting, LEDs are directly bonded to a lead frame, which is a type of metal substrate. 
     However, in the case of light-emitting devices for which flip-chip mounting to a lead frame is employed, the lead frame includes a plurality of spaced coupling leads for LEDs, and thus, height differences between the coupling leads, bending, and warping, for example, are problems with flip-chip mounting. As a technique for solving the problems, a technique disclosed in Patent Document 1 is known. The technique is to insert an electrically insulating reinforcing plate adjacent to inner ends of the plurality of coupling leads in a lead frame to correct warping. 
     However, the technique of placing a reinforcing member adjacent to the backside of the lead frame poses problems. The problems include increased cost due to higher number of components, increased production time due to additional steps, and a decreased production yield due to decreased resin flowability in the subsequent resin molding. 
     One conventional technique for solving the above-described problems of Patent Document 1 is the so-called dicing before grinding technique using a metal substrate as proposed in Patent Document 2. Hereinafter, the light-emitting device of Patent Document 2, which is produced by a dicing before grinding technique, will be described with reference to  FIG. 22 .  FIG. 22  is partially simplified without deviating from the gist of the invention of Patent Document 2. 
       FIGS. 22A to 22E  illustrate production steps for a light-emitting device  100  using a dicing before grinding technique. Step A is a groove forming step. In this step, electrode separation grooves  103  are formed in the surface of a metal substrate  102  to a predetermined depth. Step B is a resin pouring step. In this step, an insulative resin  104  is poured into the electrode separation grooves  103 . 
     Step C is an LED mounting step. In this step, LEDs  101  are flip-chip mounted to the surface of the metal substrate  102 . Each of the LEDs  101  is positioned at the surface of the metal substrate  102  so as to lie over the electrode separation groove  103 , to be coupled to the metal substrate  102  via bumps  105   a ,  105   b.    
     Step D includes a reflective frame forming step and an encapsulation resin pouring step. In these steps, first, a reflective frame  106  is provided around each of the LEDs  101 , which are mounted to the surface of the metal substrate  102 , and subsequently, a light-transmissive encapsulation resin  107  is poured inside the reflective frame  106 . The light-transmissive encapsulation resin  107  may be a transparent resin or a phosphor-containing transparent resin. Light emitted from the LEDs  101  can be wavelength-converted by the phosphor-containing light-transmissive encapsulation resin  107 . 
     Step E includes a grinding step and a cutting and separation step. In the grinding step, the metal substrate  102  is ground from the backside to the position of the dicing line T, which is indicated by the dashed line in Step D, so as to expose the electrode separation grooves  103  and the insulative resin  104 . As a result of exposing the electrode separation grooves  103 , the metal substrate  102  is divided into left and right portions with the electrode separation grooves  103  being the boundaries. Thus, pairs of electrode portions  102   a ,  102   b , to which the LEDs  101  are coupled, are formed. In the cutting and separation step, the reflective frame  106  is cut along the cutting line D, indicated by the dashed line, into portions each of which includes an individual LED  101 . In this manner, individual light-emitting devices  100  are completed. 
     RELATED ART DOCUMENTS 
     Patent Documents 
     [Patent document 1] Japanese Unexamined Patent Application Publication No. 2013-157357 (see FIG. 2). 
     [Patent document 2] Japanese Unexamined Patent Application Publication No. 2004-119981 (see FIG. 3). 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     The dicing before grinding technique disclosed in Patent Document 2 is a technique for mass-producing single-piece light-emitting devices  100  by the cutting and separation step. In each of the mass-produced light-emitting devices  100 , the two electrode portions  102   a ,  102   b  of the metal substrate  102  are separated from each other as a result of grinding and are bonded to each other only by the bonding force of the insulative resin  104 , which is poured into the electrode separation groove  103 . Thus, the bond strength is low, and there is a possibility that the light-emitting devices  100  may become broken while being handled as a light-emitting device. In addition, the reflective frame  106  is merely adhered to the surface of the metal substrate  102  and thus does not increase the bond strength between the electrode portions  102   a ,  102   b.    
     An object of the present invention is to provide a light-emitting device that is mass-produced using a dicing before grinding technique. The light-emitting device includes electrode portions in a metal substrate, and the bond between the electrode portions, after being separated from one another by grinding, is strong. In particular, for large light-emitting devices in which a plurality of LEDs are coupled together in series to a metal substrate, a strong bond between the electrode portions in the metal substrate is achieved. 
     Means of Solving the Problems 
     In order to achieve the above object, a light-emitting device according to one aspect of the present invention includes a metal substrate, insulative portions, a plurality of LEDs, a support frame, and an encapsulation resin. The metal substrate includes electrode portions. The insulative portions are disposed in the metal substrate. The insulative portions each separate corresponding ones of the electrode portions from each other so that one of the electrode portions serves as an anode and an other of the electrode portions serves as a cathode. The insulative portions each include an electrode separation groove in the metal substrate and an insulative resin formed within the electrode separation groove. The plurality of LEDs are positioned at a surface of the metal substrate. Each of the LEDs lies over a corresponding one of the insulative portions and are electrically coupled to corresponding ones of the electrode portions. The support frame is disposed so as to surround an outer perimeter of the metal substrate. The support frame includes an inner wall portion and an outer wall portion. The inner wall portion is formed within a recessed groove along the outer perimeter of the metal substrate. The outer wall portion covers an outer perimeter surface of the metal substrate. The encapsulation resin is formed within the support frame to encapsulate at least partially the LEDs. 
     Furthermore, in order to achieve the above object, a method according to one aspect of the present invention for producing a light-emitting device is performed as follows. Insulative portions are formed by forming electrode separation grooves of a predetermined depth in a metal substrate and pouring an insulative resin into the electrode separation grooves. The metal substrate includes electrode portions. LED mounting is performed by positioning a plurality of LEDs at a surface of the metal substrate in such a manner that each of the LEDs lies over a corresponding one of the insulative portions and electrically coupling each of the LEDs to an anode of a corresponding one of the electrode portions and to a cathode of a corresponding one of the electrode portions. The electrode portions are separated from one another by the insulative portions. A support frame surrounding an outer perimeter of the metal substrate is formed. The support frame includes an inner wall portion formed within a recessed groove and an outer wall portion covering an outer perimeter surface of the metal substrate. The recessed groove is formed along the outer perimeter of the metal substrate. The metal substrate is ground from a backside of the metal substrate to an extent that the insulative portions are exposed. 
     Effects of the Invention 
     In the light-emitting device according to one aspect of the present invention, the inner wall portion of the support frame is formed within the recessed groove in the metal substrate and the outer wall portion of the support frame covers the outer perimeter surface of the metal substrate. This configuration reinforces the bond between the electrode portions in the metal substrate, which are separated from one another by the insulative portions, and as a result, the metal substrate is unified as a whole to form a rigid substrate. 
     Furthermore, in the method according to one aspect of the present invention for producing a light-emitting device, a support frame is provided so as to surround the outer perimeter of the metal substrate to which LEDs are mounted, and this support frame reinforces the bond between the electrode portions in the metal substrate. This configuration facilitates mass production of large light-emitting devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a light-emitting device according to a first embodiment of the present invention. 
         FIG. 2  is a top view of the light-emitting device illustrated in  FIG. 1 . 
         FIG. 3  is a bottom view of the light-emitting device illustrated in  FIG. 1 . 
         FIGS. 4A to 4D  illustrate a process of a method for producing the light-emitting device illustrated in  FIG. 1 , with the first half of the process being illustrated. 
         FIGS. 5E to 5G  illustrate the process of the method for producing the light-emitting device illustrated in  FIG. 1 , with the second half of the process being illustrated. 
         FIG. 6  is a sectional view of a light-emitting device according to a second embodiment of the present invention. 
         FIG. 7  is a top view of the light-emitting device illustrated in  FIG. 6 . 
         FIGS. 8A and 8B  illustrate a process of a method for producing the light-emitting device illustrated in  FIG. 6 . 
         FIG. 9  is a sectional view of a light-emitting device according to a third embodiment of the present invention. 
         FIG. 10  is a top view of the light-emitting device illustrated in  FIG. 9 . 
         FIGS. 11A to 11D  illustrate a process of a method for producing the light-emitting device illustrated in  FIG. 9 , with the first half of the process being illustrated. 
         FIGS. 12E to 12G  illustrate the process of the method for producing the light-emitting device illustrated in  FIG. 9 , with the second half of the process being illustrated. 
         FIG. 13  is a sectional view of a light-emitting device according to a fourth embodiment of the present invention. 
         FIG. 14  is a top view of the light-emitting device illustrated in  FIG. 13 . 
         FIGS. 15A and 15B  illustrate a process of a method for producing the light-emitting device illustrated in  FIG. 13 . 
         FIG. 16  is a sectional view of a light-emitting device according to a fifth embodiment of the present invention. 
         FIG. 17  is a top view of the light-emitting device illustrated in  FIG. 16 . 
         FIG. 18  is a sectional view of a light-emitting device according to a sixth embodiment of the present invention. 
         FIG. 19  is a top view of an illumination device including light-emitting devices according to the second embodiment of the present invention. 
         FIG. 20  illustrates a circuit configuration of the illumination device illustrated in  FIG. 19 . 
         FIG. 21  illustrates a circuit configuration of an illumination device including light-emitting devices according to another embodiment of the present invention. 
         FIGS. 22A to 22E  illustrate a process of a method for producing a conventional light-emitting device. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. Throughout the embodiments, similar or corresponding elements are assigned the same reference numerals, and redundant descriptions will be omitted. 
     First Embodiment 
       FIGS. 1 to 3  illustrate a light-emitting device according to a first embodiment of the present invention. A light-emitting device  10  according to this embodiment includes a metal substrate  2 , a pair of insulative portions  3 , three electrode portions  2   a ,  2   b ,  2   c , two LEDs  1   a ,  1   b , a support frame  4 , and a light-transmissive encapsulation resin  5 . The metal substrate  2  is rectangular. The insulative portions  3  divide the metal substrate  2  into electrically isolated portions. The electrode portions  2   a ,  2   b ,  2   c  are formed by dividing the metal substrate  2  by the insulative portions  3 . The LEDs  1   a ,  1   b  are positioned at the surface of the metal substrate  2 . Each of the LEDs  1   a ,  1   b  lies over a corresponding one of the insulative portions  3  to be electrically coupled to corresponding ones of the electrode portions  2   a ,  2   b ,  2   c . The support frame  4  is disposed so as to surround the outer perimeter of the metal substrate  2 . The light-transmissive encapsulation resin  5  is formed within the support frame  4 . 
     The insulative portions  3  include a pair of electrode separation grooves  3   a  and an insulative resin  3   b . The electrode separation grooves  3   a  are disposed in the metal substrate  2  and the insulative resin  3   b  fills the electrode separation grooves  3   a . The electrode separation grooves  3   a  are disposed to extend through the metal substrate  2  to the backside thereof, and as illustrated in  FIG. 3 , are disposed along the entire width of the metal substrate  2 . In the metal substrate  2 , the electrical flow is interrupted by the pair of insulative portions  3 , and as a result, the three electrode portions  2   a ,  2   b ,  2   c , separated from one another by the insulative portions  3 , are formed in the metal substrate  2 . 
     The two LEDs  1   a ,  1   b  are each positioned at the surface of the metal substrate  2  so as to lie over the insulative portion  3  to be electrically coupled to corresponding ones of the three electrode portions  2   a ,  2   b ,  2   c , which are separated from one another by the insulative portions  3 . In this case, as illustrated in  FIG. 1 , the two LEDs  1   a ,  1   b  are mounted in the same polarity direction to corresponding ones of the electrode portions  2   a ,  2   b ,  2   c , and are coupled together in series to the electrode portions  2   a ,  2   b ,  2   c . Specifically, for the LED  1   a , the electrode portion  2   a  is one electrode serving as an anode and the electrode portion  2   b  is the other electrode serving as a cathode, whereas for the LED  1   b , the electrode portion  2   b  is one electrode serving as an anode and the electrode portion  2   c  is the other electrode serving as a cathode. The LEDs  1   a ,  1   b  are coupled to the corresponding ones of the electrode portions  2   a ,  2   b ,  2   c  via bumps (not illustrated). Furthermore, external electrodes  6   a ,  6   b  are disposed at the respective ends of the backside of the metal substrate  2 . Between the external electrodes  6   a ,  6   b , current flows through the LEDs  1   a ,  1   b  via the electrode portions  2   a ,  2   b ,  2   c.    
     The support frame  4  includes an inner perimeter surface  4   a , which surrounds the outer perimeter of the metal substrate  2  and is inclined toward the bottom. In a lower region of the support frame  4 , an inner wall portion  4   b  and an outer wall portion  4   c  are disposed along the entire perimeter of the support frame  4 . The inner wall portion  4   b  is formed within a recessed groove  7 , which is disposed along the outer perimeter of the metal substrate  2 . The outer wall portion  4   c  covers an outer perimeter surface  8  of the metal substrate  2  in close contact with the outer perimeter surface  8 . Desirably, the support frame  4  is made of a highly reflective resin so that the support frame  4  can be highly reflective to the light emitted from the LEDs  1   a ,  1   b . However, by coating at least the inner perimeter surface  4   a  with a highly reflective coating material, the support frame  4  can be made to be comparably highly reflective. 
     The light-transmissive encapsulation resin  5  is formed within the support frame  4  and encapsulates the LEDs  1   a ,  1   b . The light-transmissive encapsulation resin  5  is poured to a level near the upper end of the support frame  4  and covers the topsides of the LEDs  1   a ,  1   b . The topsides are light-emitting surfaces. The light-transmissive encapsulation resin  5  is a phosphor-containing transparent resin. For example, by using an yttrium-aluminum-garnet (YAG) phosphor-containing transparent resin as the light-transmissive encapsulation resin, white light-emitting devices can be configured using a blue LED. 
     In the light-emitting device  10  configured as described above, the inner wall portion  4   b  of the support frame  4  is formed within the recessed groove  7  in the metal substrate  2  and the outer wall portion  4   c  of the support frame  4  covers the outer perimeter surface  8  of the metal substrate  2 . This configuration reinforces the bond between the three electrode portions  2   a ,  2   b ,  2   c  in the metal substrate  2 , which are separated from one another by the insulative portions  3 , and as a result, the metal substrate  2  is unified as a whole to form a rigid substrate. The resin for forming the support frame  4  may be the same as or different from the insulative resin  3   b  for forming the insulative portions  3  in the metal substrate  2 . The support frame  4  includes the inner wall portion  4   b  and the outer wall portion  4   c.    
     Next, a method for producing the light-emitting device configured as described above will be described with reference to  FIGS. 4 and 5 .  FIGS. 4A to 4D  illustrate Steps A to D, the first half of the production process for the light-emitting device  10 . Step A in  FIG. 4  is a groove forming step. In this step, a pair of electrode separation grooves  3   a  are formed in the surface of the metal substrate  2  to a predetermined depth. The electrode separation grooves  3   a  are disposed along the entire width of the metal substrate  2  and are parallel to each another. Further, the recessed groove  7  is formed along the outer perimeter of the metal substrate  2  over the entire perimeter. The recessed groove  7  is formed to be shallower than the electrode separation grooves  3   a . The metal substrate  2 , prior to the grinding step, has a thickness greater than the thickness of the metal substrate  2  of the light-emitting device  10  illustrated in  FIG. 1 . The grinding step will be described later. 
     Step B is a resin pouring step. In this step, the insulative resin  3   b  is poured into the electrode separation grooves  3   a , and a resin is poured into a support frame forming mold (not illustrated), which is placed at the metal substrate  2 , to form the support frame  4  to a predetermined shape. The inner wall portion  4   b  is formed by the resin in the recessed groove  7 , and the outer wall portion  4   c  is formed so as to cover the outer perimeter surface  8  of the metal substrate  2 . The outer wall portion  4   c  is in close contact with the outer perimeter surface  8  of the metal substrate  2 . Examples of the insulative resin  3   b  and the resin for forming the support frame  4  include epoxy resins, silicone resins, and liquid crystal polymers. The insulative resin  3   b  is to be poured into the electrode separation grooves  3   a.    
     Step C is an LED mounting step. In this step, the LEDs  1   a ,  1   b  are positioned at the surface of the metal substrate  2  in such a manner that the LEDs  1   a ,  1   b  lie over the respective insulative portions  3 . The metal substrate  2  is divided by the insulative portions  3 . The two LEDs  1   a ,  1   b  are flip-chip mounted via bumps (not illustrated) to the corresponding ones of the three electrode portions  2   a ,  2   b ,  2   c  of the metal substrate  2 , which are separated from one another by the insulative portions  3 . The two LEDs  1   a ,  1   b  are mounted in the same polarity direction to the corresponding ones of the electrode portions  2   a ,  2   b ,  2   c , and are coupled to each other in series. The LEDs may be mounted by wire bonding depending on the structure. 
     Step D is an encapsulation resin pouring step. In this step, the light-transmissive encapsulation resin  5  is poured inside the support frame  4  to encapsulate the LEDs  1   a ,  1   b . The light-transmissive encapsulation resin  5  is a phosphor-containing transparent resin. By using a YAG phosphor-containing transparent resin, white light can be produced using a blue LED via wavelength conversion. 
       FIGS. 5E to 5G  illustrate Steps E to G, the second half of the production process for the light-emitting device  10 . Steps E and F in  FIG. 5  are illustrations of the grinding step. In Step E, a pre-grinding state is illustrated, and in Step F, a post-grinding state is illustrated. In this step, the backside of the metal substrate  2  is ground to a depth at which the electrode portions  2   a ,  2   b ,  2   c  are separated from one another. Specifically, the backside is ground to a grinding line T, which is indicated by the dashed line. Thus, the electrode separation grooves  3   a  and the insulative resin  3   b  of the insulative portions  3  are exposed, and as a result, the electrode portions  2   a ,  2   b ,  2   c  are separated from one another. The grinding of the backside of the metal substrate  2  is applied within a region not contacting the bottom of the recessed groove  7  for the support frame  4 . The recessed groove  7  is shallower than the electrode separation grooves  3   a . Thus, the inner wall portion  4   b  of the support frame  4  remains present within the recessed groove  7 . Also, the backside of the outer wall portion  4   c  of the support frame  4  is located above the grinding line T. With this configuration, the outer wall portion  4   c  is protected from damage from the grinding of the backside of the metal substrate  2 . Also, in the grinding step, in order to protect, for example, the LEDs  1   a ,  1   b , which are mounted to the surface of the metal substrate  2 , the support frame  4 , and the light-transmissive encapsulation resin  5  from damage, it is desirable that a grinding protection tape (not illustrated) be laminated to the top surface of the support frame  4 , and that the workpiece, with the grinding protection tape on, be set on a grinder. 
     Step G is an external electrode forming step. In this step, a pair of external electrodes  6   a ,  6   b  are provided at the respective ends of the backside of the metal substrate  2  so that electrical current can flow through the LEDs  1   a ,  1   b  via the electrode portions  2   a ,  2   b ,  2   c  of the metal substrate  2 . With this step, the light-emitting device  10  illustrated in  FIG. 1  is completed. 
     In the production method according to the above embodiment, pouring of the insulative resin  3   b  into the electrode separation grooves  3   a  in the metal substrate  2  and forming of the support frame  4  are performed in the same step. As a result, the production process is simplified. 
     Next, operations of the light-emitting device  10  will be described with reference to  FIG. 1 . As described above, the LED  1   a  is mounted to the metal substrate  2  with the electrode portion  2   a  serving as an anode and the electrode portion  2   b  serving as a cathode, and the LED  1   b  is mounted to the metal substrate  2  with the electrode portion  2   b  serving as an anode and the electrode portion  2   c  serving as a cathode. Thus, the two LEDs  1   a ,  1   b  are coupled together in series to the three electrode portions  2   a ,  2   b ,  2   c  of the metal substrate  2 , which are separated from one another by the insulative portions  3 . When a driving voltage is applied externally, via the external electrodes  6   a ,  6   b , across the electrode portions  2   a ,  2   c  at the respective ends, the two LEDs  1   a ,  1   b  are actuated to light up. 
     Second Embodiment 
       FIGS. 6 to 8  illustrate a light-emitting device according to a second embodiment of the present invention. Compared with the light-emitting device  10  of the first embodiment, in which the two LEDs  1   a ,  1   b  are coupled together in series, a light-emitting device  20  according to this embodiment is a large light-emitting device in which six LEDs  1   a ,  1   b ,  1   c ,  1   d ,  1   e ,  1   f  are coupled together in series. However, except for this feature, the light-emitting device  20  is similar to the light-emitting device  10  in general configuration and production method. Thus, similar or corresponding elements to those of the light-emitting device  10  of the first embodiment are assigned the same reference numerals, and redundant descriptions will be omitted. 
     As illustrated in  FIGS. 6 and 7 , the light-emitting device  20  includes a metal substrate  22 , six insulative portions  3 , a support frame  4 , seven electrode portions  2   a ,  2   b ,  2   c ,  2   d ,  2   e ,  2   f ,  2   g , six LEDs  1   a  to  1   f , a light-transmissive encapsulation resin  5 , and external electrodes  6   a ,  6   b . The metal substrate  22  is rectangular and large. The insulative portions  3  are spaced along the longitudinal direction of the metal substrate  22  at a predetermined interval. The support frame  4  is provided so as to surround the entire outer perimeter of the metal substrate  22 . The electrode portions  2   a ,  2   b ,  2   c ,  2   d ,  2   e ,  2   f ,  2   g  are portions of the metal substrate  22 , which are separated from one another by the six insulative portions  3 . The LEDs  1   a  to  1   f  are flip-chip mounted by being positioned at the surface of the metal substrate  22  and being electrically coupled to corresponding ones of the electrode portions  2   a  to  2   g . The LEDs  1   a  to  1   f  lie over the respective insulative portions  3 . The light-transmissive encapsulation resin  5  is poured inside the support frame  4  to encapsulate the LEDs  1   a  to  1   f . The external electrodes  6   a ,  6   b  are disposed at the backside of the metal substrate  22  at the respective ends in the longitudinal direction. As with the first embodiment, the inner wall portion  4   b  and the outer wall surface  4   c  are disposed in a lower region of the support frame  4 . The inner wall portion  4   b  is formed within the recessed groove  7 , which is disposed along the outer perimeter of the metal substrate  22 . The outer wall surface  4   c  covers the outer perimeter surface  8  of the metal substrate  22 . 
     As with the first embodiment, the six LEDs  1   a  to  1   f  are flip-chip mounted in the same polarity direction to the surface of the metal substrate  22 , and are coupled together in series to the electrode portions  2   a  to  2   g , which are separated from one another by the insulative portions  3 . The electrode portions  2   a ,  2   g , to which the two outermost LEDs,  1   a ,  1   f , are respectively coupled, are coupled to the external electrodes  6   a ,  6   b , respectively. 
     Next, a method for producing the light-emitting device configured as described above will be described with reference to  FIG. 8 .  FIGS. 8A and 8B  illustrate production steps for the light-emitting device  20 . Step A corresponds to the production steps A to E for the light-emitting device  10  of the first embodiment, and Step B corresponds to the production step G for the light-emitting device  10 . The production process in Steps A and B in  FIG. 8  is similar to that for the light-emitting device  10  in the first embodiment except for the number of the insulative portions in the metal substrate, the number of the electrode portions separated from one another by the insulative portions, and the number of the LEDs positioned at the metal substrate so as to lie over the respective insulative portions and flip-chip mounted to corresponding ones of the electrode portions. Thus, similar or corresponding elements are assigned the same reference numerals, and redundant descriptions will be omitted. 
     Next, operations of the light-emitting device  20  will be described with reference to  FIG. 6 . When a driving voltage is applied externally across the external electrodes  6   a ,  6   b , the series-coupled six LEDs  1   a  to  1   f  are actuated to light up. The external electrodes  6   a ,  6   b  are directly coupled respectively to the electrode portions  2   a ,  2   g  at the respective ends of the metal substrate  22 . That is, the number of series-coupled LEDs is increased, and as a result, the light-emitting device  20  has a high luminance. 
     Third Embodiment 
       FIGS. 9 to 12  illustrate a light-emitting device according to a third embodiment of the present invention. A light-emitting device  30  according to this embodiment is different from the above-described light-emitting device of the first embodiment in that the light-emitting device  30  includes a shield wall  33  between the two LEDs  1   a ,  1   b , which are mounted to the metal substrate  32 . Except for this feature, the light-emitting device  30  is similar to the light-emitting device of the first embodiment in general configuration and production method. Thus, similar or corresponding elements to those of the light-emitting device  10  of the first embodiment are assigned the same reference numerals, and redundant descriptions will be omitted. 
     As illustrated in  FIGS. 9 and 10 , the light-emitting device  30  includes the shield wall  33 . The shield wall  33  is located at an approximately middle position between the pair of insulative portions  3 , which are disposed in the metal substrate  32 . The shield wall  33  is approximately parallel to the insulative portions  3 . The shield wall  33  is, in cross section, trapezoidal and symmetrical with respect to the vertical axis. The shield wall  33  includes reflective surfaces  33   a ,  33   b  on the respective opposite sides. The reflective surfaces  33   a ,  33   b  are inclined at an inclination angle approximately equal to the inclination angle of the inner perimeter surface  4   a  of the support frame  4 . The height of the shield wall  33  is approximately equal to the height of the support frame  4 . The light-transmissive encapsulation resin  5  fills the space up to the height of the top surface of the shield wall  33 . A leg portion  33   c  is disposed in a lower region of the shield wall  33  and extends downwardly. The leg portion  33   c  is formed within a recessed groove  34 , which is disposed in the surface of the metal substrate  32 . The depth of the recessed groove  34  is approximately equal to the depth of the recessed groove  7  in the metal substrate  32 . Within the recessed groove  7 , the inner wall portion  4   b  of the support frame  4  is formed. Thus, the metal substrate  32  is continuous under the leg portion  33   c . Thus, the three electrode portions  2   a ,  2   b ,  2   c , which are separated from one another by the insulative portions  3 , are formed in the metal substrate  32 . 
     The shield wall  33  serves as a shield for preventing light emitted from the two LEDs  1   a ,  1   b , mounted to the metal substrate  32 , from affecting each other. The shield wall  33  also serves as a reflector for reflecting light emitted from the LEDs  1   a ,  1   b  and causing the light to propagate upwardly. Thus, it is desirable to use a highly reflective resin as a shield wall-forming resin for forming the shield wall  33  or to apply a highly reflective coating material to the reflective surfaces  33   a ,  33   b  of the shield wall  33 . Furthermore, in this embodiment, the reflective surfaces  33   a ,  33   b  of the shield wall  33  are linearly inclined to reflect light emitted from the LEDs  1   a ,  1   b . Alternatively, the reflective surfaces  33   a ,  33   b  may be curvedly inclined to produce a similar reflection effect. In this embodiment, the shield wall  33  is provided between the two LEDs  1   a ,  1   b , so that light emitted from the side surfaces of the LEDs  1   a ,  1   b  can be reflected. Because of this configuration, the light-emitting device  30  has improved light emission intensity compared with the light-emitting device  10  of the first embodiment. 
     Next, a method for producing the light-emitting device  30  configured as described above will be described with reference to  FIGS. 11 and 12 .  FIGS. 11A to 11D  illustrate Steps A to D, the first half of the production process for the light-emitting device  30 .  FIGS. 12E to 12G  illustrate Steps E to G, the second half of the production process for the light-emitting device  30 . Step A in  FIG. 11  is a groove forming step. In this step, as with the first embodiment, the pair of electrode separation grooves  3   a  are formed in the surface of the metal substrate  32  with a predetermined distance in between and the recessed groove  7  is formed along the outer perimeter of the metal substrate  32 . In addition, the recessed groove  34  is formed in an approximately middle position between the pair of electrode separation grooves  3   a . The recessed groove  34  is parallel to the electrode separation grooves  3   a  and disposed along the entire width of the metal substrate  32 . The recessed groove  7  and the recessed groove  34  have an approximately equal depth and are shallower than the electrode separation grooves  3   a.    
     Step B is a resin pouring step. In this step, as with the first embodiment, the insulative resin  3   b  is poured into the electrode separation grooves  3   a , and a resin is poured inside the mold frame of a support frame forming mold to form the support frame  4  to a predetermined shape. The support frame forming mold is placed at the metal substrate  32 . Simultaneously with the placement of the support frame forming mold, a mold for forming the shield wall  33  is placed to form the shield wall  33 . In the process, the resin in the recessed groove  34  forms the leg portion  33   c  of the shield wall  33 . Examples of the insulative resin  3   b , the resin for forming the support frame  4 , and the resin for forming the shield wall  33  include epoxy resins, silicone resins, and liquid crystal polymers. The insulative resin  3   b  is to be poured into the electrode separation grooves  3   a.    
     Step C is an LED mounting step. In this step, the two LEDs  1   a ,  1   b  are positioned at the surface of the metal substrate  32 , which is partitioned into left and right sections by the shield wall  33 , in such a manner that the LEDs  1   a ,  1   b  lie over the respective insulative portions  3 . The two LEDs are flip-chip mounted via bumps (not illustrated) to the corresponding ones of the three electrode portions  2   a ,  2   b ,  2   c  of the metal substrate  32 , which are separated from one another by the insulative portions  3 . The two LEDs  1   a ,  1   b  are mounted in the same polarity direction to the corresponding ones of the electrode portions  2   a ,  2   b ,  2   c , and are coupled to each other in series. 
     Step D is an encapsulation resin pouring step. In this step, the light-transmissive encapsulation resin  5  is poured inside the support frame  4  to encapsulate the LEDs  1   a ,  1   b . The light-transmissive encapsulation resin  5  is supplied to the height of the top surfaces of the support frame  4  and the shield wall  33 . By using a YAG phosphor-containing transparent resin as the light-transmissive encapsulation resin  5 , white light can be produced by wavelength-converting the light emitted from a blue LED. 
       FIGS. 12E and 12F  are illustrations of a grinding step for the metal substrate  32 . In Step E, a pre-grinding state is illustrated, and in Step F, a post-grinding state is illustrated. In this grinding step, the backside of the metal substrate  32  is ground to a depth at which the electrode portions  2   a ,  2   b ,  2   c  are separated from one another. Specifically, the backside is ground to a grinding line T, which is indicated by the dashed line. Thus, the electrode separation grooves  3   a  and the insulative resin  3   b  of the insulative portions  3  are exposed, and as a result, the electrode portions  2   a ,  2   b ,  2   c  are separated from one another. The grinding of the backside is applied within a region not contacting the bottoms of the recessed groove  7  for the support frame  4  and the recessed groove  34  for the shield wall  33 . The recessed groove  7  and the recessed groove  34  are shallower than the electrode separation grooves  3   a . Thus, the inner wall portion  4   b  of the support frame  4  remains present within the recessed groove  7 , and the leg portion  33   c  of the shield wall  33  remains present within the recessed groove  34 . As a result, the portion of the metal substrate  32  under the leg portion  33   c  remains present, and thus the LED  1   a  and the LED  1   b  are electrically coupled to each other with the electrode portion  2   b  remaining undivided. Also, as with the first embodiment, the backside of the outer wall portion  4   c  of the support frame  4  is located above the grinding line T. With this configuration, the outer wall portion  4   c  is protected from damage from the grinding of the backside of the metal substrate  32 . Also, in the grinding step, in order to protect, for example, the LEDs  1   a ,  1   b , which are mounted to the surface of the metal substrate  32 , the support frame  4 , the shield wall  33 , and the light-transmissive encapsulation resin  5  from damage, it is desirable that a grinding protection tape (not illustrated) be laminated to the top surfaces of the support frame  4  and the shield wall  33 , and that the workpiece, with the grinding protection tape on, be set on a grinder. 
     Step G is an external electrode forming step. In this step, a pair of external electrodes  6   a ,  6   b  are provided at the respective ends of the backside of the metal substrate  32  so that electrical current can flow through the LEDs  1   a ,  1   b  via the electrode portions  2   a ,  2   b ,  2   c  of the metal substrate  32 . With this step, the light-emitting device  30  illustrated in  FIG. 9  is completed. 
     In the production method according to the above embodiment, pouring of the insulative resin  3   b  into the electrode separation grooves  3   a  in the metal substrate  32 , forming of the support frame  4 , and forming of the shield wall  33  are performed in the same step. As a result, the production process is simplified. 
     In the light-emitting device  30 , which is produced by the production process described above, the backside of the metal substrate  32  is ground in the grinding step to an extent that the insulative portions  3  are exposed, but the inner wall portion  4   b  and the outer wall portion  4   c  of the support frame  4  surrounds the outer perimeter of the metal substrate  32  for reinforcement. As a result, the metal substrate  32  is unified as a whole to form a rigid substrate. 
     Next, operations of the light-emitting device  30  will be described with reference to  FIG. 9 . In this embodiment, the two LEDs  1   a ,  1   b  are shielded from each other by the shield wall  33 , but the metal substrate  32  is continuous under the shield wall  33  as described above. Thus, as with the first embodiment, the LED  1   a  is mounted to the metal substrate  32  with the electrode portion  2   a  serving as an anode and the electrode portion  2   b  serving as a cathode, and the LED  1   b  is mounted to the metal substrate  32  with the electrode portion  2   b  serving as an anode and the electrode portion  2   c  serving as a cathode. Thus, the two LEDs  1   a ,  1   b  are coupled together in series to the three electrode portions  2   a ,  2   b ,  2   c  of the metal substrate  32 , which are separated from one another by the insulative portions  3 . When a driving voltage is applied externally, via the external electrodes  6   a ,  6   b , across the electrode portions  2   a ,  2   c  at the respective ends, the two LEDs  1   a ,  1   b  are actuated to light up. 
     Fourth Embodiment 
       FIGS. 13 to 15  illustrate a light-emitting device according to a fourth embodiment of the present invention. Compared with the light-emitting device  30  of the third embodiment, in which the two LEDs  1   a ,  1   b  are coupled together in series, a light-emitting device  40  according to this embodiment is a large light-emitting device in which four LEDs  1   a ,  1   b ,  1   c ,  1   d  are coupled together in series. However, except for this feature, the light-emitting device  40  is similar to the light-emitting device  30  in general configuration and production method. Thus, similar or corresponding elements to those of the light-emitting device  30  of the third embodiment are assigned the same reference numerals, and redundant descriptions will be omitted. 
     As illustrated in  FIGS. 13 and 14 , the light-emitting device  40  includes a metal substrate  42 , four insulative portions  3 , a support frame  4 , five electrode portions  2   a ,  2   b ,  2   c ,  2   d ,  2   e , four LEDs  1   a ,  1   b ,  1   c ,  1   d , three shield walls  33 , a light-transmissive encapsulation resin  5 , and external electrodes  6   a ,  6   b . The metal substrate  42  is rectangular and large. The insulative portions  3  are spaced along the longitudinal direction of the metal substrate  42  at a predetermined interval. The support frame  4  is formed so as to surround the entire outer perimeter of the metal substrate  42 . The electrode portions  2   a ,  2   b ,  2   c ,  2   d ,  2   e  are separated from one another by the four insulative portions  3 . The LEDs  1   a ,  1   b ,  1   c ,  1   d  are flip-chip mounted to the surface of the metal substrate  42  to be electrically coupled to corresponding ones of the electrode portions  2   a  to  2   e . The LEDs  1   a ,  1   b ,  1   c ,  1   d  lie over the respective insulative portions  3 . The shield walls  33  are disposed on the surface of the metal substrate  42  to shield the four LEDs  1   a  to  1   d , each from adjacent one(s) of the four LEDs. The light-transmissive encapsulation resin  5  is disposed inside the support frame  4  to encapsulate the LEDs  1   a  to  1   d . The external electrodes  6   a ,  6   b  are disposed at the backside of the metal substrate  42  at the respective ends in the longitudinal direction. 
     As with the third embodiment, the four LEDs  1   a  to  1   d  are flip-chip mounted in the same polarity direction to the surface of the metal substrate  42 , and are coupled together in series to the electrode portions  2   a  to  2   e  of the metal substrate  42 , which are separated from one another by the insulative portions  3 . The electrode portions  2   a ,  2   e , to which the two outermost LEDs,  1   a ,  1   d , are respectively coupled, are coupled to the external electrodes  6   a ,  6   b , respectively. 
       FIGS. 15A and 15B  illustrate a production process for the light-emitting device  40  according to the fourth embodiment. Steps A and B correspond to the steps for the light-emitting device  30  of the third embodiment. Step A corresponds to the steps from the groove forming step through the grinding step, which are illustrated in  FIGS. 11 and 12 . Step B corresponds to the external electrode forming step illustrated therein. The production process in  FIG. 15 , including Steps A and B, is similar to the production process for the light-emitting device  30  of the third embodiment except for the number of the insulative portions  3  in the metal substrate  42 , the number of the electrode portions  2   a  to  2   e  of the metal member  42 , which are separated from one another by the insulative portions  3 , the number of the LEDs  1   a  to  1   d , positioned at the surface of the metal substrate  42  so as to lie over the respective insulative portions  3  and flip-chip mounted to corresponding ones of the electrode portions  2   a  to  2   e , and the number of the shield walls  33 , which shield the LEDs, each from adjacent one(s) of the LEDs. Thus, similar or corresponding elements are assigned the same reference numerals, and redundant descriptions will be omitted. 
     Operations of the LED light-emitting device  40  will be described with reference to  FIG. 13 . When a driving voltage is applied across the electrode portions  2   a ,  2   e  at the respective ends via the external electrodes  6   a ,  6   b , the four series-coupled LEDs  1   a  to  1   d  are actuated to light up. Light emitted from the LEDs  1   a  to  1   d  can be reflected by the inner perimeter surface  4   a  of the support frame  4 , which surrounds the LEDs  1   a  to  d , and by the reflective surfaces  33   a ,  33   b  of the shield walls  33 , and therefore light propagating upward will increase in intensity. Thus, the light-emitting device  40  has a high luminance. 
     Fifth Embodiment 
       FIGS. 16 and 17  illustrate a light-emitting device according to a fifth embodiment of the present invention. The light-emitting device  50  of this embodiment includes a support frame  54  and shield walls  53 , which are different in shape from those of the light-emitting device  40  of the fourth embodiment. The support frame  54  surrounds the outer perimeter of the metal substrate  42 , and the shield walls  53  shield the four LEDs  1   a  to  1   d , each from adjacent one(s) of the four LEDs. That is, in the fourth embodiment, the inner perimeter surface  4   a  of the support frame  4  and the reflective surfaces  33   a ,  33   b  of the shield walls  33  are both inclined surfaces, whereas, in this embodiment, an inner perimeter surface  54   a  of the support frame  54  and reflective surfaces  53   a ,  53   b  of the shield walls  53  on the respective opposite sides are vertical surfaces. As a result, the light emitted from the LEDs  1   a  to  1   d  will not diffuse upward but will propagate directly upward, and thus the emitted light can easily reach remote locations. As a result, the light-emitting device is suitable as, for example, a light-emitting device such as a camera flashlight. An inner wall portion  54   b  and an outer wall portion  54   c  are disposed in a lower region of the support frame  54 . The inner wall portion  54   b  is formed within the recessed groove  7 , which is formed along the outer perimeter of the metal substrate  42 . The outer wall portion  54   c  covers the outer perimeter surface  8  of the metal substrate  42 . A leg portion  53   c  is disposed in a lower region of the shield wall  53 . The leg portion  53   c  is formed within a recessed groove  34 , which is disposed in the metal substrate  42 . Except for this feature, this embodiment is similar to the fourth embodiment in general configuration and production method. Thus, similar or corresponding elements to those of the light-emitting device  40  of the fourth embodiment are assigned the same reference numerals, and redundant descriptions will be omitted. 
     Sixth Embodiment 
       FIG. 18  illustrates a light-emitting device according to a sixth embodiment of the present invention. In the light-emitting device  60  according to this embodiment, the light-transmissive encapsulation resin  5 , which is formed within the support frame  4 , does not encapsulate the entireties of the LEDs  1   a ,  1   b  but encapsulates only the lateral sides and bottomsides of the LEDs  1   a ,  1   b  so as to expose the topsides. The topsides are light-emitting surfaces of the LEDs  1   a ,  1   b . Except for this feature, the light-emitting device  60  is similar in general configuration to the light-emitting device  30  of the third embodiment. The light-emitting device  30  is illustrated in  FIG. 9 . Thus, similar or corresponding elements to those of the light-emitting device  30  are assigned the same reference numerals, and redundant descriptions will be omitted. 
     With the light-emitting device  60  according to this embodiment, light emitted from the topsides of the LEDs  1   a ,  1   b  is not wavelength-converted by a phosphor, and therefore the light-emitting device  60  is suitable for use as a single-color light-emitting device. Furthermore, because of the absence of a phosphor over the topsides of the LEDs  1   a ,  1   b , there is no conversion loss that may otherwise occur from wavelength conversion, and this results in the effect of increasing the light output. 
       FIGS. 19 and 20  illustrate an illumination device including a plurality of the light-emitting devices  20  according to the second embodiment. The light-emitting device  20  is illustrated in  FIG. 6 . 
     The illumination device  200  illustrated in  FIG. 19  includes a circuit board  202 , two electrode traces  202   a ,  202   b , and four light-emitting devices  20 . The electrode traces  202   a ,  202   b  are disposed on the circuit board  202  to extend parallel to each other. The light-emitting devices  20  are arranged on the electrode traces  202   a ,  202   b . The four light-emitting devices  20  are coupled together in parallel to the electrode traces  202   a ,  202   b . At one ends of the two electrode traces  202   a    202   b , external coupling electrodes  206   a ,  206   b  are respectively disposed. When a driving voltage is applied across the external coupling electrodes  206   a ,  206   b , the four light-emitting devices  20  light up. Thus, the illumination device  200  has a luminance corresponding to combined luminances of the four light-emitting devices. 
       FIG. 20  illustrates a circuit configuration of the illumination device  200 . The four light-emitting devices  20  are coupled together in parallel to the two electrode traces  202   a ,  202   b , which are respectively coupled to the two external coupling electrodes  206   a ,  206   b . That is, in this illumination device  200 , the four light-emitting devices  20  are coupled together in parallel between the external coupling electrodes  206   a ,  206   b . In each of the light-emitting devices  20 , the six LEDs  1   a  to  1   f , in the same polarity direction, are coupled together in series. When a driving voltage is applied across the external coupling electrodes  206   a ,  206   b , the 24 LEDs, which constitute the four light-emitting devices  20 , light up. Thus, high luminance illumination is achieved 
     The illumination device  200  can be made simply by mounting a plurality of the light-emitting devices  20  of the present invention on the circuit board  202 . The circuit board  202  has a simple electrode structure, which includes the two electrode traces  202   a ,  202   b  and the external coupling electrodes  206   a ,  206   b . In addition, by varying the number of the light-emitting devices  20  to be mounted, illumination devices of various luminances can be made. The light-emitting devices to be mounted to the circuit board  202  are not limited to the light-emitting devices  20  of the second embodiment, and any of the light-emitting devices of the other embodiments described above may be employed. Furthermore, as illustrated in  FIG. 21 , a light-emitting device  70  may be formed using a single large metal substrate. The light-emitting device  70  includes four light-emitting strings  71 , arranged side by side, and in each of the light-emitting strings  71 , six LEDs are coupled together in series. The light-emitting device  70  may be mounted to the circuit board  202  described above to form an illumination device  300 , which is similar to the above-described illumination device. The four light-emitting strings  71 , arranged side by side, are each insulated from adjacent one(s) of the four light-emitting strings  71 . 
     As described above, light-emitting devices according to the present invention are applicable to any of a variety of illumination devices, and are suitable as a light source for general illumination purposes, a light source for a liquid crystal display backlight, and a light source for a camera flashlight, for example. 
     DESCRIPTION OF THE REFERENCE NUMERAL 
     
         
           1   a  to  1   f  LED 
           2 ,  22 ,  32 ,  42  metal substrate 
           2   a  to  2   g  electrode portion 
           3  insulative portion 
           3   a  electrode separation groove 
           3   b  insulative resin 
           4 ,  54  support frame 
           4   a ,  54   a  inner perimeter surface 
           4   b ,  54   b  inner wall portion 
           4   c ,  54   c  outer wall portion 
           5  light-transmissive encapsulation resin 
           6   a ,  6   b  external electrode 
           7  recessed groove 
           8  outer perimeter surface 
           10 ,  20 ,  30 ,  40 ,  50 ,  60 ,  70  light-emitting device 
           33 ,  53  shield wall 
           33   a ,  33   b ,  53   a ,  53   b  reflective surface 
           33   c ,  53   c  leg portion 
           34  recessed groove 
           71  light-emitting string 
           200 ,  300  illumination device 
           202  circuit board 
           202   a ,  202   b  electrode trace 
           206   a ,  206   b  external coupling electrode