Patent Publication Number: US-2009236623-A1

Title: Light emitting diode device

Description:
BACKGROUND 
     1. Field of Invention 
     The present invention relates to a light emitting diode device, and more particularly to a light emitting diode device with evenly radiated light color. 
     2. Description of Related Art 
     Blue light emitting diode (LED) chips are coated with phosphor paste such that the blue light is mixed with the illuminated light from the phosphor paste to generate a fluorescent cool-white light which is visible to the human eye. 
     With regard to conventional lens package technology for an LED, the phosphor paste fills the reflector cup in which the blue light emitting diode chip is mounted. However, the reflector cup shape is mostly designed for the reflecting light without considering the radiated color after light reflection. 
     Hence, the phosphor paste is unevenly spread on the blue LED chip and results in various light colors illuminating from the respective area with different epoxy thickness. Generally speaking, the illuminated light color is close to blue because the thin covered epoxy has shorter blue light transmission path and less probability for the blue light being received and radiated by the phosphor paste. In contrast, the illuminated light color is close to yellow when the covered epoxy is thick. As a result, the light is radiated with uneven colors. 
     Another conventional lens package technology including the combination of the pattern and the electrophoretic deposition (EPD) method is also applied to fill the blue LED chip with phosphor paste. Through this technology, the thickness of the phosphor paste can be controlled within a predetermined range precisely, and within a 10-percentage variation range. 
     With respect to the luminous energy for a conventional LED chip, the front luminous energy is larger than the flank luminous energy such that the phosphor paste at the front of the chip needs to be spread thicker than the phosphor past on the sides of the chip to provide a uniform white light appearance. Nevertheless, the spread thickness is limited within 10-percentage variation range, and the radiated light with uneven colors problem cannot be solved with this technology. 
     Moreover, the method of applying the pattern technology to package the phosphor paste is preferably suitable for a flip chip type light emitting diode, but not acceptable to a wire bonding type light emitting diode because the pattern will damage the wires soldered on the chip. In addition, the electrophoretic deposition (EPD) technology needs extra facilities and advanced processes that increase production cost. 
     As a result, providing a light emitting diode device with even radiated light color and simplified fabrication processes to satisfy the needs of various lamps becomes the aim of the present invention. 
     SUMMARY 
     It is therefore an aspect to provide a light emitting diode device with evenly radiated light color. 
     In accordance with an embodiment of the present invention, the light emitting diode device includes an LED chip, a reflector cup, a substrate, and a phosphor paste wherein the reflector cup is set on the substrate. The reflector cup includes a wall defining a room in which the LED chip is mounted and filled with phosphor paste to cover the LED chip. The phosphor paste includes paste and phosphorus being held in the paste whereby the LED chip emits fluorescent light through the phosphorus. 
     The height between the wall and the LED chip have a first predetermined proportion, and the distances between the corresponding inner edges and the LED chip also have a second predetermined proportion wherein the first predetermined proportion is larger than the second predetermined proportion. 
     As a result, the light emitting diode device of the present invention has the following effects: 
     1. Because the first predetermined proportion is larger than the second predetermined proportion, the phosphor paste at the front of the LED chip is thicker than the phosphor paste on the sides of the LED chip to provide a uniform radiated light color. 
     2. Compared with the conventional technology that can only be applied to the flip chip type light emitting diode, or that needs extra facilities and advanced process, the wall and the reflector cup of the light emitting diode device in accordance with the present invention can be formed by extrusion or injection molding process to reduce the production cost. 
     3. The wall includes the same contour with enlarged proportion as the LED chip as viewed from their tops such that the phosphor paste can be evenly spread on the LED chip through the restriction of the wall after injecting the phosphor paste into the room defined by the wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, 
         FIG. 1  is a top view of a light emitting diode device of a first embodiment in accordance with the present invention; 
         FIG. 2  is a sectional view of the light emitting diode device of the first embodiment in accordance with  FIG. 1 ; and 
         FIG. 3  is a sectional view of the light emitting diode device of a second embodiment in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the figures, in which like reference numerals are carried forward. 
     Refer to  FIG. 1 .  FIG. 1  illustrates a top view of a light emitting diode device of a first embodiment in accordance with the present invention. The light emitting diode device  100  includes a LED chip  110 , a reflector cup  120 , a substrate  130 , and a phosphor paste  140  wherein the reflector cup  120  is set on the substrate  130 . The reflector cup  120  includes a wall  121  defining a room in which the LED chip  110  is mounted. 
     The wall  121  and the LED chip  110  have the same contour as viewed from their tops wherein the contour of the wall  121  is an enlarged proportion to the contour of the LED chip  110 . In this configuration, the gap between the LED chip  110  and the wall  121  can be filled with the phosphor paste  140  when the phosphor paste  140  is injected into the room defined by the wall  121  to cover the LED chip  110 . 
     In one of the embodiments, the LED chip  110  includes a top plane in the form of a first rectangle composed of a first length and a first width, and the wall  121  includes an inner edge in the form of a second rectangle composed of a second length and a second width. The corresponding first length and the second length define a first distance there between, and the corresponding first width and the second width define a second distance there between wherein the first distance is identical to the second distance. 
     In another of the embodiments, the LED chip  110  includes a top plane in the form of a first square, and the wall  121  includes an inner edge in the form of a second square wherein the perimeter of the second square is a proportional extension of that of the first square. 
     Refer to  FIG. 2 .  FIG. 2  illustrates a sectional view of the light emitting diode device of the first embodiment in accordance with  FIG. 1 . 
     The reflector cup  120  is made of metal, plastic, glass or other transparent materials. The wall  121  includes a first space  1211  defined by the corresponding inner edges of the wall  121 , and a second space  1212  defined by the top and the bottom of the wall  121 . The LED chip  110  includes a third space  1101  defined by the opposite outer edges of the LED chip  110 , and a fourth space  1102  defined by the top and the bottom of the LED chip  110 . The first space  1211  is 1.15 to 2 multiple of the third space  1101 , and the second space  1212  is 2 to 5 multiple of the fourth space  1102 . 
     In addition, the second space  1212  and the fourth space  1102  has a first ratio in the range between 2 to 5, and the first space  1211  and the third space  1101  has a second ratio in the range between 1.15 to 2. 
     The phosphor paste  140  includes paste and phosphorus being held in the paste whereby the LED chip  110  emits the fluorescent light (such as yellow, red or green light) through the phosphorus. Partial light beams emitted from the LED chip  110  are reflected by the inner side of the wall  121  because the inner side of the wall  121  is parallel to the flank of the LED chip  110 . Consequently, the reflected light beam is fully absorbed by the phosphorus to generate the light color complementary to original color of the LED chip  110 . 
     Refer to  FIG. 3 .  FIG. 3  illustrates a sectional view of the light emitting diode device of a second embodiment in accordance with the present invention. 
     In the second embodiment, the light emitting diode device  200  includes an LED chip  210 , a reflector cup  220 , a substrate  230 , and a phosphor paste  240  wherein the configuration of the above members is identical to that of the first embodiment, so there is no more description herein. 
     In addition, the spaces  2211 ,  2212 ,  2101 , and  2102  are also identical to the first space  1211 , the second space  1212 , the third space  1101 , and the fourth space  1102 , and the ratios between the space  2212  and the space  2102 , and between the space  2211  and the space  2101  are respectively identical to the first ratio and the second ratio illustrated in the first embodiment. 
     The difference between the first embodiment and the second embodiment is that the inner side of the wall  221  in the second embodiment is a bevel thereby forming an angle  2213  between the dotted line perpendicular to the top of the LED chip  210  and the bevel. The angle  2213  has a range between 0 degrees and 10 degrees. Consequently, partial light beam emitted from the LED chip  210  is reflected by the inner side of the wall  221  in the form of bevel to be fully absorbed by the phosphorus of the phosphor paste  240  to generate the light color complementary to original color of the LED chip  210 . 
     Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.