Patent Publication Number: US-2011062474-A1

Title: Light-emitting diode device and fabrication method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light-emitting diode device and a fabrication method thereof, and more particularly to a light-emitting diode device fabricated using an injection molding technique or a transfer molding technique and the fabrication method thereof. 
     2. Description of the Related Art 
     A typical light-emitting diode (LED) device includes a lead frame, an LED die, a transparent layer, a reflecting cup, and a lens. The frame includes a mounting pad, on which the LED die is placed. A portion of the lead frame is formed within the reflecting cup having an opening, over which the lens is attached. The transparent layer is disposed in the lens, is covering the LED die. 
     The above-mentioned lens is pre-molded, and then is manually aligned with and fastened over the opening. U.S. Pat. No. 7,456,499, U.S. Pat. No. 6,274,924, and U.S. Pat. No. 7,458,703 all disclose analogous LED devices including pre-molded lenses. However, manual assembly of the lens may increase manufacturing time and cost, and precise manual assembly operations are not easily maintained, resulting in low production yields. 
     Further, the reflecting cup, the transparent layer, and the lens are formed in different fabricating steps and using different molds. As such, the fabricating procedure of the typical LED devices is complex. A complex fabricating procedure is not easily managed, and may cause low yield and high production cost. 
     In view of the above-mentioned issues, a new LED device having no such issues is required. 
     SUMMARY OF THE INVENTION 
     To avoid the above-mentioned issues, the present invention provides a light-emitting diode device formed using an injection molding technique or a transfer molding technique and a fabrication method thereof. 
     One embodiment of the present invention provides a light-emitting diode device, which includes a frame, a light-emitting diode die, a fluorescent layer, a reflector, and a lens. The light-emitting diode die is disposed on the frame. The fluorescent layer is molded to cover the light-emitting diode die. The reflector is molded on the frame, surrounding the light-emitting diode die, wherein the reflector is configured to direct light in a predetermined direction. The lens is molded within the reflector, covering the fluorescent layer. 
     The present invention discloses a fabrication method of a light-emitting is diode device, which comprises the steps of: providing a frame; disposing a light-emitting diode die on the frame; molding a fluorescent layer covering the light-emitting diode; molding a reflector disposed on the frame, surrounding the light-emitting diode die, and configured to direct light in a predetermined direction; and molding a lens, covering the fluorescent layer, in the reflector. 
     To better understand the above-described objectives, characteristics and advantages of the present invention, embodiments, with reference to the drawings, are provided for detailed explanations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described according to the appended drawings in which: 
         FIG. 1  is a stereoscopic view illustrating a light-emitting diode device according to one embodiment of the present invention; 
         FIG. 2  is a top view of the light-emitting diode device of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view along line A-A of  FIG. 1 ; 
         FIG. 4  is an upward view showing a frame according to one embodiment of the present invention; 
         FIG. 5  is a cross-sectional view showing a light-emitting diode device according to an alternative embodiment of the present invention; 
         FIG. 6  is a cross-sectional view showing a light-emitting diode device according to an alternative embodiment of the present invention; 
         FIG. 7  is a cross-sectional view showing a light-emitting diode device according to an alternative embodiment of the present invention; and 
         FIG. 8  is a flow chart showing the fabrication method of a light-emitting diode device according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a stereoscopic view illustrating a light-emitting diode device  1  according to one embodiment of the present invention;  FIG. 2  is a top view of the light-emitting diode device  1  of  FIG. 1 ; and  FIG. 3  is a cross-sectional view along line A-A of  FIG. 1 . Referring to  FIGS. 1 to 3 , in one embodiment of the present invention, a light-emitting diode device  1  comprises a frame  11 , a light-emitting diode (LED) die  12 , a fluorescent layer  13 , a reflector  14 , and a lens  15 . The LED die  12  is disposed on the frame  11  so as to obtain support. The fluorescent layer  13  is molded over the LED die  12 , covering the LED die  12 . The reflector  14  is molded on the frame  11  and surrounds the LED die  12 . The reflector  14  has an opening  141 , wherein light radiated from the LED die  12  passes through the opening  141  to the exterior of the light-emitting diode device  1 . The lens  15  is molded within the reflector  14  and covers the fluorescent layer  13 . 
     Referring to  FIG. 2 , the frame  11  may comprise a die support  111 , a first electrode  112 , and a second electrode  113 . The LED die  12  is disposed on the die support  111  so as to be supported. In addition, the die support  111  can be of high thermal conductivity; thus heat from the LED die  12  can be dissipated by the die support  111  so as to improve the heat dissipation efficiency of the LED die  12 , to lower the operating temperature of the LED die  12 , and to increase the lifespan of the LED die  12 . The first electrode  112  and the second electrode  113  are separately disposed on two opposite sides of the die support  111  and are configured to allow the LED die  12  to electrically connect to an external power source. 
     Specifically, referring to  FIG. 4 , the die support  111  may include a reduced section  1111  formed around the middle of the die support  111 . The LED die  12  is disposed on the reduced section  1111 . The width of the reduced section  1111  may be adapted to match the size of the LED die  12 . Each of the first electrode  112  and the second electrode  113  may include a protruding section  1121  or  1131  protruding adjacent to the corresponding edges of the reduced section  1111 . The matched design of the reduced section  1111  and the two protruding sections  1121  and  1131  may reduce the distances between the LED die  12  and the first and second electrodes  112  and  113 . 
     In addition, in one embodiment of the present invention, each protruding section  1121  or  1131  can protrude from a corresponding connecting section  1122  or  1132 , which can have a shallow circular segment shape and are disposed within the reflector  14 . The die support  111  and the connecting sections  1122  and  1132  are configured to occupy the most area delineated by the reflector  14  so that the light-emitting diode device  1  may have high heat dissipation efficiency. Each of the first and second electrodes  112  and  113  may separately include an externally extended section  1123  or  1133  extending externally from a side of the corresponding connecting sections  1122  or  1132  opposite to the protruding section  1121  or  1131 , wherein the externally extended sections  1123  and  1133  are disposed outside the reflector  14 . In addition, the frame  11  may further comprise a dielectric portion  114  disposed between the first and second electrodes  112  and  113  and the die support  111 . The dielectric portion  114  is provided to electrically insulate the first and second electrodes  112  and  113  from the die support  111 . As such, the light-emitting diode device  1  has a thermally and electrically separated structure. 
     In one embodiment of the present invention, the LED die  12  can be wired to the protruding sections  1121  and  1131  using wires  16  for electrical connection. 
     In one embodiment of the present invention, the material of the first and second electrodes  112  and  113  and die support  111  can be copper. The LED die  12  can be a laser diode, III-V group compound semiconductor light-emitting diode, or II-VI group compound semiconductor light-emitting diode. 
     The inner surface of the reflector  14  facing the LED die  12  is an inclined surface  142  defining an accommodation space  143  having a cross section, parallel to the frame  11 , which gradually increases from a location adjacent to the frame  11  to a location adjacent to the opening  141 . In one embodiment of the present invention, the reflector  14  has a cup-like shape. The diameters of the cross sections of the accommodation space  143  increase along a direction from the frame  11  to the opening  141 . Light from the LED die  12  is reflected by the inclined surface  142 , passing through the opening  141  toward the outside of the light-emitting diode device  1 . 
     The reflector  14  can be directly molded on the frame  11 . In other words, the reflector  14  can be directly formed on the frame  11  using an injection molding technique or a transfer molding technique. The reflector  14  is not independently formed and then attached to the frame  11 . Because the frame  11  is made of metal, the frame  11  has high strength property, so the frame  11  can withstand the pressure used in an injection molding process or a transfer molding process. Therefore, the reflector  14  of the light-emitting diode device  1  can be directly molded on the frame  11 . In one embodiment of the present invention, the reflector  14  can include silicone resin and white particles, wherein the white particle can be silicon dioxide. 
     Referring to  FIG. 3 , the fluorescent layer  13  configured to cover the LED die  12  may include fluorescent powder uniformly dispersed within the fluorescent layer  13 . The fluorescent powder can be excited by a portion of light emitted from the LED die  12 , generating complimentary light, and the complementary light can mixed with another portion of light to allow the light-emitting diode device  1  to generate white light. In one embodiment of the present invention, the fluorescent layer  13  may comprise a transparent polymer, wherein the polymer can be epoxy resin, silicone resin or a hybrid thereof. The fluorescent layer  13  can be directly molded on the frame  11 . Namely, the fluorescent layer  13  can be directly formed on the frame  11  using an injection molding technique or a transfer molding technique. 
     Referring to  FIG. 3 , the lens  15  can be directly molded within the reflector  14 , covering the whole fluorescent layer  13 . Further, the lens  15  can also be directly formed on the frame  11 , in the accommodation space  143  of the reflector  14  using an injection molding technique or a transfer molding technique. In one embodiment of the present invention, the material of the lens  15  can be transparent silicone resin. 
       FIG. 5  is a cross-sectional view showing a light-emitting diode device  2  according to an alternative embodiment of the present invention. In another embodiment of the present invention, the light-emitting diode device  2  may comprise a frame  21 , an LED die  22 , a fluorescent layer  13 , a reflector  14 , and a lens  15 . The frame  21  may include two electrodes  211 . The LED die  22  is disposed on the frame  21 , flip-chip bonded to the two electrodes  211  by bumps  18 . The fluorescent layer  13  is molded over the LED die  22 , covering the LED die  22 . The reflector  14  is molded on the frame  21 , surrounding the LED die  22 . The reflector  14  has an opening, through which light is emitted from the LED die. The lens  15  is molded within the reflector  14 , covering the fluorescent layer  13 . 
       FIG. 6  is a cross-sectional view showing a light-emitting diode device  3  according to an alternative embodiment of the present invention. In another embodiment of the present invention, the light-emitting diode device  3  comprises a frame  11 , an LED die  12 , a fluorescent layer  13 , a reflector  34 , and a lens  35 . The LED die  12  is disposed on the frame  11  to obtain support. The fluorescent layer  13  is molded over the LED die  12 , covering the LED die  12 . The reflector  34  is molded on the frame  11 , surrounding the LED die  12 . The reflector  11  has an opening, through which light is emitted from the LED die. The reflector  34  includes a stepped surface  341 , formed inside the reflector  34 . The lens  35  is molded within the reflector  34 , covering the fluorescent layer  13 , wherein the lens  35  can cover a portion of the stepped surface  341 . 
       FIG. 7  is a cross-sectional view showing a light-emitting diode device  4  according to an alternative embodiment of the present invention. In another embodiment of the present invention, the light-emitting diode device  4  comprises a frame  21 , an LED die  22 , a fluorescent layer  13 , a reflector  34 , and a lens  35 . The frame  21  comprises two electrodes  211 . The LED die  22  is disposed on the frame  21 , flip-chip bonded to the two electrodes  211  by bumps  18 . The fluorescent layer  13  is molded over the LED die  22 , covering the LED die  22 . The reflector  14  is molded on the frame  21 , surrounding the LED die  22 . The reflector  14  has an opening, through which light is emitted from the LED die. The reflector  34  includes a stepped surface  341 , formed inside the reflector  34 . The lens  35  is molded within the reflector  34 , covering the fluorescent layer  13 , wherein the lens  35  can cover a portion of the stepped surface  341 . 
     The present invention provides a fabrication method of a light-emitting diode device. In Step S 81 , a frame is initially provided. In Step S 82 , an LED die is disposed on the frame. In one embodiment, the frame includes a die support and two electrodes, wherein the LED die is disposed on the die support, electrically connecting to the two electrodes using wires. In another embodiment, the frame includes two electrodes, and the LED die is flip-chip bonded to the two electrodes. In one embodiment of the present invention, the electrode comprises a gold coated copper electrode or a silver coated copper electrode, and the die support comprises a gold coated copper die support or a silver coated copper die support. In Step S 83 , the fluorescent layer is molded on the LED die, wherein the fluorescent layer can be formed using an injection molding technique or a transfer molding technique. In Step S 84 , a reflector is molded on the frame, surrounding the LED die. The reflector is configured to direct light in a predetermined direction. The reflector can be formed using an injection molding technique or a transfer molding technique. In Step S 85 , a lens is molded within the reflector, covering the fluorescent layer. The lens can be formed using an injection molding technique or a transfer molding technique. 
     In summary, a light-emitting diode device comprises a frame, an LED is die, a fluorescent layer, a reflector, and a lens. The LED die is disposed on the frame, which is mainly constituted of metal so as to improve the heat dissipation of the LED die. Because the frame is mainly constituted of metal, the fluorescent layer, the reflector, and the lens can be molded directly on the frame using an injection molding technique or a transfer molding technique. As such, the assembly alignment procedure and some assembly steps used for assembling typical light-emitting diode devices are not needed. 
     Clearly, following the description of the above embodiments, the present invention may have many modifications and variations. Therefore, the scope of the present invention shall be considered with the scopes of the dependent claims. In addition to the above detailed description, the present invention can be broadly embodied in other embodiments. The above-described embodiments of the present invention are intended to be illustrative only, and should not become a limitation of the scope of the present invention. Numerous alternative embodiments may be devised by persons skilled in the art without departing from the scope of the following claims.