Abstract:
An exemplary light emitting diode (LED) includes an LED chip and a transparent sealant covering the LED chip. The sealant contains transparent filling particles and phosphor particles, wherein the filling particles are adjacent each other. Intervals are defined between the filling particles, and the phosphor particles are located in the intervals.

Description:
FIELD OF THE INVENTION 
     Cross-Reference to Related Application 
     This application is related to, and claims the benefit of, a foreign priority application filed in Taiwan as Ser. No. 096141373 on Nov. 2, 2007. The related application is incorporated herein by reference. 
     The present disclosure relates to sealed light emitting diodes (LEDs). 
     GENERAL BACKGROUND 
     LEDs are well-known solid state devices that can generate light having a peak wavelength in a specific region of the visible spectrum. LEDs are widely used as illuminators, indicators and displays due to their fast response time, high color saturation, and long life. 
     Referring to  FIG. 7 , a related art LED  10  includes a substrate  11 , an LED chip  12 , two conducting wires  13 , a first electrode  14 , a second electrode  15 , a first connecting pin  16 , a second connecting pin  17 , and a transparent sealant  18 . 
     The substrate  11  includes an upper surface  111  and a lower surface  112 . The first electrode  14 , the second electrode  15 , and the LED chip  12  are symmetrically formed on the upper surface  111  of the substrate  11 , wherein the first electrode  14  and the second electrode  15  are respectively located at two opposite sides of the LED chip  12 . 
     One of the two conducting wires  13  interconnects the LED chip  12  and the first electrode  14 , and the other conducting wire  13  interconnects the LED chip  12  and the second electrode  15 . The first connecting pin  16  passes through the substrate  11 . One end of the first connecting pin  16  is connected to the first electrode  14 , and the other end of the first connecting pin  16  protrudes out from the lower surface  112  of the substrate  11 . The second connecting pin  17  also passes through the substrate  11 . One end of the second connecting pin  17  is connected to the second electrode  15 , and the other end of the second connecting pin  17  protrudes out from the lower surface  112  of the substrate  11 . 
     The sealant  18  is formed on the upper surface  111  of the substrate  11  and covers the first electrode  14 , the second electrode  15 , and the LED chip  12 . The sealant  18  includes a plurality of phosphor particles  181  therein. The LED chip  12  is a blue LED chip which emits blue light. The phosphor particles  181  may be yttrium aluminum garnet (YAG). 
     When an operation voltage is provided between the first connecting pin  16  and the second connecting pin  17 , the operation voltage across the LED chip  12  makes the LED chip  12  emit blue light. Some of the blue light illuminates the phosphor particles  181  thereby causing the phosphor particles  181  to emit yellow light. The blue light mixed with the yellow light forms white light. 
     In manufacture of the LED  10 , the sealant  18  is initially in a non-solid state prior to being heated and solidified. During this time, the LED  10  may be placed somewhere such as at a workstation for a relatively long time. As a result, the phosphor particles  181  in the sealant  18  are liable to slowly drift down to positions adjacent to the upper surface  111  of the substrate  11  due to the effects of gravity. When this happens, a distribution of the phosphor particles  181  is uneven along vertical directions. In operation of the LED  10 , the uneven distribution of the phosphor particles  181  results in uneven transmission of the blue light through the sealant  18 , and the chroma of the white light formed by the mixed blue light and yellow light varies with different viewing angles. 
     It is desired to provide a new LED which can overcome the described limitations. 
     SUMMARY 
     An exemplary LED includes an LED chip and a transparent sealant covering the LED chip. The sealant contains a plurality of transparent filling particles and a plurality of phosphor particles. The filling particles are adjacent each other. A plurality of intervals are defined between the filling particles, and the phosphor particles are located in the intervals. 
     Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a cross-section of an LED of a first embodiment of the present invention. 
         FIG. 2  is a cross-section of an LED of a second embodiment of the present invention. 
         FIG. 3  is a cross-section of an LED of a third embodiment of the present invention. 
         FIG. 4  is a cross-section of an LED of a fourth embodiment of the present invention. 
         FIG. 5  is a cross-section of an LED of a fifth embodiment of the present invention. 
         FIG. 6  is a cross-section of an LED of a sixth embodiment of the present invention. 
         FIG. 7  is a cross-section of a related art LED. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings to describe various embodiments in detail. 
     Referring to  FIG. 1 , an LED  20  of a first embodiment includes a substrate  21 , an LED chip  22 , two conducting wires  23 , a first electrode  24 , a second electrode  25 , a first connecting pin  26 , a second connecting pin  27 , and a transparent sealant  28 . 
     The substrate  21  includes an upper surface  211  and a lower surface  212 . The first electrode  24 , the second electrode  25 , and the LED chip  22  are symmetrically formed on the upper surface  211  of the substrate  21 , wherein the first electrode  24  and the second electrode  25  are respectively located at two opposite sides of the LED chip  22 . The substrate  21  is typically a square plate. 
     One of the two conducting wires  23  interconnects the LED chip  22  and the first electrode  24 . The other conducting wire  23  interconnects the LED chip  22  and the second electrode  25 . The first connecting pin  26  passes through the substrate  21 . One end of the first connecting pin  26  is connected to the first electrode  24 , and the other end of the first connecting pin  26  protrudes out from the lower surface  212  of the substrate  21 . The second connecting pin  27  also passes through the substrate  21 . One end of the second connecting pin  27  is connected to the second electrode  25 , and the other end of the second connecting pin  27  protrudes out from the lower surface  212  of the substrate  21 . 
     The sealant  28  is formed on the upper surface  211  of the substrate  21  and covers the first electrode  24 , the second electrode  25 , and the LED chip  22 . The sealant  28  includes a plurality of transparent filling particles  280  and a plurality of phosphor particles  281 . The filling particles  280  and the phosphor particles  281  are randomly oriented and positioned, but are substantially evenly distributed in the sealant  28 . The filling particles  280  occupy a large amount of space within the sealant  28 , and adjacent filling particles  280  contact each other. Typically, the filling particles  280  occupy a total amount of space that is larger than a total amount of space occupied by the actual sealant  28  itself. A plurality of spaces (not labeled) are defined between the filling particles  280  for receiving the phosphor particles  281 . In other words, the phosphor particles  281  are located in intervals between the filling particles  280 . Typically, at least some of the phosphor particles  281  contact adjacent filling particles  280 . 
     The LED chip  22  is a blue LED chip which emits blue light. The phosphor particles  281  may be YAG The filling particles  280  may be hollow transparent balls or solid transparent balls that are made of transparent resin such as polymethyl methacrylate (PMMA). The filling particles  280  may be spherical or elliptical. A diameter of each filling particle  280  is typically 3˜15 times that of each phosphor particle  281 . A volume of each filling particle  280  is typically 27˜3375 times that of each phosphor particle  281 . 
     In summary, the sealant  28  includes the plurality of filling particles  280  therein and the phosphor particles  281  located in the intervals between the filling particles  280 . Accordingly, when the sealant  28  is in a non-solid state during manufacture of the LED  20 , the phosphor particles  281  in the sealant  28  are held in position and are not liable to drift down due to the effects of gravity. That is, the filling particles  280  partly or even completely block migration of the phosphor particles  281  to other intervals further down in the sealant  28 . Thus in the duly manufactured LED  20 , a distribution of the phosphor particles  281  is substantially even. The substantially even distribution of the phosphor particles  281  enables the blue light to transmit substantially evenly through the sealant  28 , and enables the chroma of white light formed by mixed blue light and yellow light to be uniform. 
     Moreover, the filling particles  280  function as scattering elements for evenly diffusing the blue light and the yellow light so as to form even, pure white light. 
     Referring to  FIG. 2 , a cross-section of a second embodiment of an LED is shown. The LED  30  is different from the LED  20  of the first embodiment in that the substrate  21  of the LED  20  is replaced by a box  31 . A first electrode  34 , an LED chip  32 , two wires  33 , a second electrode  35 , and a sealant  38  are received in the box  31 . The box  31  includes a bottom plate  311  and a plurality of side walls  31 . 2  extending from the bottom plate  311 . An obtuse angle is formed between each side wall  312  and the bottom plate  311 . The first electrode  34 , the LED chip  32 , and the second electrode  35  are disposed on the bottom plate  311 . Two connecting pins  36 ,  37  pass through the bottom plate  311  to protrude out from the bottom plate  311 , and top ends of the connecting pins  36 ,  37  respectively connect to the first electrode  34  and the second electrode  35 . The side walls  312  can reflect light back to a center of the LED  30  according to the obtuse angle between each side wall  312  and the bottom plate  311 . Thus a luminance of the LED  30  at the center thereof can be increased. 
     Referring to  FIG. 3 , a cross-section of a third embodiment of an LED is shown. The LED  40  is different from the LED  30  of the second embodiment in that a right angle is formed between each of side walls  412  and a bottom plate  411 . This can further increase a luminance of the LED  40  at a predetermined viewing angle. 
     Referring to  FIG. 4 , a cross-section of a fourth embodiment of an LED is shown. The LED  50  is different from the previously described embodiments in that an LED chip  52  is formed on a first electrode  54 , with a bottom surface of the LED chip  52  connected to the first electrode  54  via silver adhesive. First and second connecting pins  56 ,  57  are formed on surfaces of a substrate  51 , and are respectively located at two opposite sides of the substrate  51 . Cross-sections of the first and second connecting pins  56 ,  57  are U-shaped. The first electrode  54  sandwiched between the LED chip  52  and the substrate  51  is connected to the first connecting pin  56 . The second electrode  55  formed on the substrate  51  is connected to the second connecting pin  57 . The second electrode  55  is connected to a top surface of the LED chip  52  via a connecting wire (not labeled). A sealant (not labeled) is generally partially hemispherical or dome-shaped. 
     Referring to  FIG. 5 , a cross-section of a fifth embodiment of an LED is shown. The LED  60  differs from the previously described embodiments in that a first electrode  64  includes a bowl-shaped terminal. An LED chip  62  is located on a bottom surface of the bowl-shaped terminal, thereby connecting to the first electrode  64 . The sealant  68  covers the bowl-shaped terminal and the LED chip  62 . The LED  60  further includes a transparent shell  69  for receiving part of the first electrode  64 , part of a second electrode  65 , the LED chip  62 , a connecting wire  63 , and the sealant  68 . A space between the sealant  68  and the shell  69  is typically an air gap. 
     Referring to  FIG. 6 , a cross-section of a sixth embodiment of an LED is shown. The LED  70  differs from the previously described embodiments in that filling particles  780  are tetrahedrons. The filling particles  780  and phosphor particles  781  are randomly oriented and positioned, but are substantially evenly distributed in a sealant (not labeled). Adjacent filling particles  780  contact each other, and the phosphor particles  781  are located in intervals between the filling particles  780 . 
     In an alternative embodiment, the LED chip  22  is an ultraviolet LED chip and the phosphor particles  281  are red, blue and green phosphor particles. The filling particles  280  may be made of glass. In another alternative embodiment, a reflecting layer is formed on the internal surface of the box  31  to improve light utilization efficiency. In a further alternative embodiment, the filling particles  780  may have shapes selected from the group consisting of cubic, cuboid, cuboidal, and octahedral. 
     It is to be further understood that even though numerous characteristics and advantages of the present disclosure have been set out in the foregoing description, together with details of the structures and functions of embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.