Patent Publication Number: US-2010127291-A1

Title: Light emitting diode

Description:
BACKGROUND  
     1. Technical Field 
     The disclosure relates to light emitting diodes (LEDs), and more specifically to a light emitting diode (LED) having an improved encapsulation. 
     2. Description of Related Art 
     Presently, LEDs are preferred for use in non-emissive display devices than CCFLs (cold cathode fluorescent lamp) due to their high brightness, long lifespan, and wide color range. 
     A typical LED includes a base, an LED chip disposed on the base and an encapsulation encapsulating the LED chip. The encapsulation forms a flat light emitting surface on an outer surface thereof. The flat light emitting surface causes a total internal reflection of the light emitted from the LED chip, to thereby block the light from exiting through the light emitting surface. Therefore a light extraction efficiency of the LED is relatively low. 
     Therefore, an LED is desired to overcome the above described shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The FIGURE is a cross-sectional view of an LED according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT 
     Referring to the FIGURE, a light emitting diode (LED)  10  includes an electrically insulating base  2 , a first conductive member  6 , a second conductive member  7 , an LED chip  20 , a first encapsulation unit  30  and a second encapsulation unit  36 . The first and second conductive members  6 ,  7  are both electrically and thermally conductive. 
     The base  2  includes an upper surface  211  and a bottom surface  221  opposite to the upper surface  211 . A receiving recess  23  is depressed from the upper surface  211  of the base  2 . An opening  235  is thus defined through the upper surface  211  of the base  2  and communicates with the receiving recess  23 . The receiving recess  23  is cup-shaped and converges downwardly along an axial direction of the LED  10 . The receiving recess  23  has a depth less than a height of the base  2 . Accordingly, the base  2  forms a mounting surface  232  at a bottom side of the receiving recess  23 . The base  2  further forms a reflecting surface  231  surrounding the receiving recess  23  and between the opening  235  and the mounting surface  232 . The reflecting surface  231  is tapered from the opening  235  towards the mounting surface  232 . A layer of material with high light reflectivity, such as mercury, can be coated on the reflecting surface  231  of the base  2 . 
     The LED chip  20  is received in the receiving recess  23  and mounted on the mounting surface  232  of the base  2 . The LED chip  20  has a first electrode  21  and a second electrode  22  respectively formed on an upper surface and a bottom surface of the LED chip  20 . 
     The first conductive member  6  is in electrical connection with the first electrode  21  of the LED chip  20  via a gold wire  4 . The first conductive member  6  includes a first inner electrode  28 , a first conductive pole  24  and a first outer electrode  26 . The second conductive member  7  is directly connected to the second electrode  22  of the LED chip  20 . The second conductive member  7  includes a second inner electrode  29  located under the LED chip  20  and is in electrical connection with the second electrode  22  of the LED chip  20 , a second conductive pole  25  and a second outer electrode  27 . The first inner electrode  28  and the second inner electrode  29  are formed on the mounting surface  232 , and spaced from each other. 
     The first outer electrode  26  and the second outer electrode  27  are formed on the bottom surface  221  of the base  2 , and spaced from each other. The first conductive pole  24  and the second conductive pole  25  extend through the base  2  from the mounting surface  232  to the bottom surface  221 . The first conductive pole  24  and the second conductive pole  25  can be formed by filling electrically and thermally conductive material into through-holes pre-defined in the base  2 . The first inner electrode  28  and the first outer electrode  26  are respectively located on two ends of the first conductive pole  24  and are electrically connected by the first conductive pole  24 . The second inner electrode  29  and the second outer electrode  27  are respectively located on two ends of the second conductive pole  25  and are electrically connected by the second conductive pole  25 . 
     A first encapsulation material is filled in the receiving recess  23  of the base  2  and forms the first encapsulation unit  30  which encapsulates the LED chip  20  on the base  2 . The first encapsulation material includes light penetrable material, such as glass, epoxy, or resin. The first encapsulation unit  30  includes a light emitting surface  31  on a top thereof. The light emitting surface  31  defines a plurality of recesses  32  concaved downward, whereby a plurality of first protrusions  321  are formed between the recesses  32 . The recesses  32  and the first protrusions  321  are alternately arranged. 
     The second encapsulation unit  36  is formed from a second encapsulation material. The second encapsulation material includes light penetrable material, such as glass, epoxy, or resin. The second encapsulation unit  36  includes a plurality of filling portions  34  and a plurality of second protrusions  33 . The filling portions  34  correspond to the recesses  32  of the first encapsulation unit  30 , respectively. Each of the filling portions  34  fills in a corresponding recess  32 . The second protrusions  33  correspond to the first protrusions  321  of the first encapsulation unit  30 , respectively. Each of the second protrusions  33  is located on a corresponding first protrusion  321 . The second protrusions  33  include a wavelength conversion material  35  dispersed in the second encapsulation material. The wavelength conversion material  35 , for example, is phosphor powder. 
     The first encapsulation material and the second encapsulation material further include particles, such as nano-particles or molecule particles, for adjusting a light refractive index thereof. The nano-particles are made of a material selected from one of titanium dioxide, tantalum dioxide and silicon dioxide. The molecule particles are made of phenol. The first encapsulation material has more particles than the second encapsulation material, whereby the first encapsulation material has a greater light refractive index than the second encapsulation material. The second encapsulation material has a greater light refractive index than air. 
     Since the light emitting surface  31  is uneven, when light emitted from the LED chip  20  reaches the light emitting surface  31 , the reflection of the light back to the inside of the LED  10  at the light emitting surface  31  can be decreased or even avoided. This facilitates extraction of the light to the outside of the LED  10  and the light extraction efficiency of the LED  10  can be improved. 
     It will be obvious that, within the scope of the invention, many variations are possible to those skilled in the art. The scope of protection of the invention is not limited to the example given herein.