Abstract:
An LED package includes a substrate, an LED die, and an encapsulating layer. The LED die is arranged on the substrate. The encapsulating layer covers the LED die and at least a part of the substrate. The encapsulating layer includes a light dispersing element. A light scattering intensity of the light dispersing element is proportional to the light intensity of light generated by the LED die and illuminated at the encapsulating layer. A luminance at a center of the LED package is substantially identical to that at a circumference of the LED package.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure generally relates to LED technology, and particularly to an LED package. 
         [0003]    2. Description of the Related Art 
         [0004]    Light emitting diodes (LEDs) have been promoted as a widely used light source by many advantages, such as high luminosity, low operational voltages, low power consumption, compatibility with integrated circuits, easy driving, long-term reliability, and environmental friendliness. LEDs are commonly applied in a plurality of lighting applications. 
         [0005]    However, LED packages must overcome certain light illumination uniformity challenges. LED is a point light source and the center of the commonly used LED package has higher light intensity than the circumference. The non-uniformity of light illumination of the LED package will cause bad effects on the usage of LED. 
         [0006]    What is needed, therefore, is an LED package, which can increase light illumination uniformity, and ameliorate the described limitations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the LED package. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
           [0008]      FIG. 1  is a schematic cross section of an LED package in accordance with a first embodiment. 
           [0009]      FIG. 2  is a schematic plot of distribution curve of luminous intensity of the LED package of  FIG. 1 . 
           [0010]      FIG. 3  is a view similar to  FIG. 1  showing the LED package of  FIG. 1  having a modified substrate. 
           [0011]      FIG. 4  is a schematic cross section of an LED package in accordance with a second embodiment. 
           [0012]      FIG. 5  is a schematic cross section of an LED package in accordance with a third embodiment. 
           [0013]      FIG. 6  is a schematic top view of the atomization level of the outer surface of the LED package of  FIG. 5 . 
           [0014]      FIG. 7  is a schematic cross section of an LED package in accordance with a fourth embodiment. 
           [0015]      FIG. 8  is a schematic cross section of an LED package in accordance with a fifth embodiment. 
           [0016]      FIG. 9  is a schematic cross section of an LED package in accordance with a sixth embodiment. 
           [0017]      FIG. 10  is a schematic cross section of an LED package in accordance with a seventh embodiment. 
           [0018]      FIG. 11  is a schematic cross section of an LED package in accordance with an eighth embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Embodiments of an LED package as disclosed are described in detail here with reference to the drawings. 
         [0020]    Referring to  FIG. 1 , an LED package  50  in accordance with a first embodiment includes a substrate  51 , an LED die  52  arranged on the substrate  51 , an encapsulating layer  53  covering the LED die  52 , and a light dispersing element inside the encapsulating layer  53 . The encapsulating layer  53  includes a luminescent material  55 . The density of the light dispersing element is proportional to the intensity of light illuminated on the encapsulating layer  53 . 
         [0021]    The substrate  51  is Al 2 O 3 , silicon, SiC, ceramic, polymer, or insulant quartz. The substrate  51  includes a circuit electrically connecting with the LED die  52 . The circuit includes a first electrode  510  and a second electrode  512 . The LED die  52  is arranged on the first electrode  510  and electrically connecting with the first electrode  510  and the second electrode  512  through wires  514 . The LED die  52  can also be arranged by manner of flip-chip (not shown). The first electrode  510  and the second electrode  512  of the circuit extend from the upper surface to the bottom surface of the substrate  51  to make the LED package  50  a surface mounted device (SMD). 
         [0022]    The LED die  52  can be a compound semiconductor of group III-V elements or group II-VI elements. Light emitted from the LED die  24  can be visible, invisible, or a mixture of visible and invisible. 
         [0023]    The encapsulating layer  53  is a transparent hemispherical shell with uniform thickness covering the LED die  52 . Understandably, a number of the LED die  52  can be more than one and the encapsulating layer  53  can cover a plurality of LED dies. The encapsulating layer  53  defines a space  54  with the substrate  51 , and the LED die  52  is arranged inside the space  54 . The encapsulating layer  53  can be transparent material, such as silicone, epoxy, quartz, or glass. 
         [0024]    The light dispersing element is a plurality of light scattering particles  56  spreading in the encapsulating layer  53 . The density of the light scattering particles  56  is proportional to the intensity of light illuminated on the encapsulating layer  53  from the LED die  52 . In this embodiment, the intensity of light illuminated on the encapsulating layer  53  from the LED die  52  is higher at the top (center) and lower at the bottom (periphery) of the encapsulating layer  53 . So that the density of the light scattering particles  56  is higher at the top (center) and lower at the bottom (periphery) of the encapsulating layer  53 . The light scattering particles  56  can be TiO 2 , plastic, polymethylmethacrylate (PMMA), fused silica, Al 2 O 3 , MgO, or other transparent oxide. The shape of the light scattering particles  56  are not limited and can be spherical, rod, or any other shape. In this embodiment, the light scattering particles  56  are spherical. 
         [0025]    The density of the luminescent material  55  is proportional to the intensity of light illuminated on the encapsulating layer  53  from the LED die  52 . In this embodiment, the density of the luminescent material  55  is higher at the top (center) of the encapsulating layer  53  and lower at the bottom (periphery) of the encapsulating layer  53 . Other optical element can also be filled between the LED die  52  and the encapsulating layer  53 . The luminescent material  55  can be garnet compound, silicate, sulfide, phosphate, nitride, oxynitride, or SiAlON. 
         [0026]    The LED package  50  includes an optical axis I.  FIG. 2  is a schematic plot of distribution curve of luminous intensity of the LED package of  FIG. 1 . Referring to  FIG. 2 , the x-axis is the angle away from the optical axis I, and the y-axis is the intensity of light illuminated. The light intensity is basically the same near the optical axis I which means that the light illuminated by the LED package  50  has a higher uniformity. 
         [0027]    The substrate  51  of the LED package  50  in accordance with the first embodiment can be of other structure as shown in  FIG. 3 . The substrate  51   a  includes a circuit electrically connecting to an LED die  52   a.  The circuit includes a first electrode  510   a  and a second electrode  512   a.  A heat dissipating lump  511   a  is arranged in the middle of the substrate  51   a.  The LED die  52   a  is arranged on the heat dissipating lump  511   a  and electrically connects with the first electrode  510   a  and the second electrode  512   a  through wires  514   a.  The first electrode  510   a  and the second electrode  512   a  of the circuit extend from the upper surface to the bottom surface of the substrate  51   a  to make the LED package  50   a  a surface mounted device (SMD). 
         [0028]    Referring to  FIG. 4 , an LED package in accordance with a second embodiment includes an encapsulating layer  53   b  directly covering the LED die  52   b  by molding. The luminescent material  55   b  and the light scattering particles  56   b  are arranged inside the encapsulating layer  53   b.    
         [0029]    Referring to  FIG. 5 , an LED package  40  in accordance with a third embodiment includes a substrate  41 , an LED die  42  arranged on the substrate  41 , an encapsulating layer  43  covering the LED die  42 , and a luminescent material  45  inside the encapsulating layer  43 . The difference from the first embodiment is that there is no light scattering particles in the encapsulating layer  43  and the outer surface of the encapsulating layer  43  includes an atomization layer  46  as light dispersing element by atomization treatment. The degree of atomization is proportional to the light intensity illuminated on the encapsulating layer  43  from the LED die  42 . In this embodiment, the degree of atomization is higher at the center and lower at the periphery. (as shown in  FIG. 6 ) 
         [0030]    Referring to  FIG. 7 , an LED package  70  in accordance with a fourth embodiment includes a substrate  71 , an LED die  72  arranged on the substrate  71 , an encapsulating layer  73  covering the LED die  72 , and a luminescent material  75  inside the encapsulating layer  73 . The difference from the first embodiment is that there is no light scattering particles in the encapsulating layer  73  and the outer surface of the encapsulating layer  73  includes a sandblasted layer  76  as light dispersing element by sandblasting. The sand blasting layer  76  is formed by high speed impact of copper ore sand, quartz sand, emery sand, iron sand, or sea sand to the outer surface of the encapsulating layer  73 . The sand blasting layer  76  includes a plurality of micro-recesses (not labeled) therein. The density of the micro-recesses of the sandblasted layer  76  is proportional to the light intensity illuminated on the encapsulating layer  73  from the LED die  72 . In this embodiment, the density of micro-recesses of the sandblasted layer  76  is higher at the center and lower at the periphery. 
         [0031]    Referring to  FIG. 8 , an LED package  20  in accordance with a fifth embodiment includes a substrate  21 , an LED die  22  arranged on the substrate  21 , and an encapsulating layer  23  covering the LED die  22 . There is a space  24  defined between the substrate  21  and the encapsulating layer  23 . The difference from the first embodiment is that a layer of luminescent material  25  is arranged on the inner surface of the encapsulating layer  23 , and there is no luminescent material in the encapsulating layer  23 . The layer of luminescent material  25  is spaced from the LED die  22  with a certain distance to prevent the layer of luminescent material  25  from high temperature. A plurality of light scattering particles  26  is arranged inside the encapsulating layer  23 . The density of the plurality of light scattering particles  26  is proportional to the light intensity illuminated on the encapsulating layer  23  from the LED die  22 . In this embodiment, the intensity of light illuminated on the encapsulating layer  23  from the Led die  22 , and, correspondingly, densities of the light scattering particles  26  are higher at the center and lower at the bottom. The light scattering particles  26  can be TiO 2 , plastic, polymethylmethacrylate (PMMA), fused silica, Al 2 O 3 , MgO, or other transparent oxide. The shape of the light scattering particles  26  is not limited and can be spherical, longitudinal, or other shape. In this embodiment, the light scattering particles  26  are spherical. 
         [0032]      FIG. 9  shows an LED package  60  in accordance with a sixth embodiment including a layer of luminescent material  65  arranged on the inner surface of the encapsulating layer  63 . The difference from the fifth embodiment is that an atomization layer  66  is arranged on the outer surface of the encapsulating layer  63  without any light scattering particles inside the encapsulating layer  63 . 
         [0033]      FIG. 10  shows an LED package  80  in accordance with a seventh embodiment including a layer of luminescent material  85  arranged on the inner surface of an encapsulating layer  83 . The difference from the sixth embodiment is that a sandblasted layer  86  is arranged on the outer surface of the encapsulating layer  83  to replace the atomization layer  66  of the sixth embodiment. 
         [0034]      FIG. 11  shows an LED package  30  in accordance with an eighth embodiment including an LED die  32 , an encapsulating layer  33 , and a plurality of light scattering particles  36  inside the encapsulating layer  33 . This embodiment is similar to the fifth embodiment of  FIG. 8  except that a layer of luminescent material  35  is arranged on the outer surface of the encapsulating layer  33 . The density of the luminescent material in the layer of luminescent material  35  is proportional to the light intensity illuminated on the encapsulating layer  33  from the LED die  32 . The densities of the light scattering particles  36  are proportional to the light intensity illuminated on the encapsulating layer  33  from the LED die  32 . The layer of luminescent material  35  can be arranged on the inner surface, the outer surface, or both the two surfaces of the encapsulating layer  33  to increase the uniformity of light emitted out from the LED die  32 . The outer surface of the layer of luminescent material  35  can include an atomization layer or a sandblasted layer or both. 
         [0035]    It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structures and functions of the embodiment(s), the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.