Abstract:
A blue LED or ultra-violet (UV) LED chip is packaged with a cover of fluorescent material. When the LED emits blue or UV light, the light is converted into colorless or white light radiating from the package. The package is furnished with bottom contacts for surface mounting.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    (1) Field of the Invention  
           [0002]    This invention relates to light emitting diodes (LED), particularly to the LED package.  
           [0003]    (2) Brief Description of Related Art  
           [0004]    In the prior art, colorless or white light can be produced by using a blue LED chip or a ultra-violet LED chip emitting through a fluorescent material. A typical prior structure package is shown in FIG. 1. A LED chip  10  is mounted on a metallic plate  11 . The top electrode of the chip  10  is wire-bonded by wire  13  to a second metal plate serving as a lead  12  for surface mounting. The bottom electrode of the LED chip  10  is in contact with the metal plate  11 , which serves as another lead for surface mounting. The chip  10  is covered with a fluorescent glue  16  as shown in FIG. 2. The glue penetrates through two via holes  14  in the metal plates  11  and  12  to strengthen the adhesion of the glue  16  to the metal plates  11  and  12  and to fix their relative positions. When the blue or UV light is emitted from the LED, the light from the package appears as colorless.  
           [0005]    The prior art shown in FIGS. 1 and 2 consumes a great deal of fluorescent glue material and hence expense for packaging the LED. The thick glue also attenuates the light emitted from the LED.  
         SUMMARY OF THE INVENTION  
         [0006]    An object of this invention is to reduce the cost of producing colorless light. Another object of this invention is to reduce the amount of fluorescent glue used for a blue light emitting diode to produce a colorless light. Still another object of this invention is to reduce the attenuation of the light emitted from the LED due to the glue.  
           [0007]    These objects are achieved by using a thin cover with fluorescent material. 
       
    
    
     BRIEF DESCIPRTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 shows the top view of a prior art LED package.  
         [0009]    [0009]FIG. 2 shows the side view of FIG. 1.  
         [0010]    [0010]FIG. 3 shows the first embodiment of the present invention with a wrap-around fluorescent cover.  
         [0011]    [0011]FIG. 4 shows the second embodiment of the present invention with flat fluorescent cover.  
         [0012]    [0012]FIG. 5 shows a third embodiment of the present invention with air space between the LED and the fluorescent cover.  
         [0013]    [0013]FIG. 6 shows a fourth embodiment of the present invention with zigzag leads.  
         [0014]    [0014]FIG. 7 shows a fifth embodiment of the present invention with folded leads.  
         [0015]    [0015]FIG. 8 shows a sixth embodiment of the present invention with air space between the LED and the fluorescent cover.  
         [0016]    [0016]FIG. 9 shows a seventh embodiment of the present invention with an opaque side-wall.  
         [0017]    [0017]FIG. 10 shows an eighth embodiment of the present invention with glue covering the total length of the leads.  
         [0018]    [0018]FIG. 11 shows a ninth embodiment of the present invention with air space between the LED and the fluorescent cover extending to cover the length of the bottom leads.  
         [0019]    [0019]FIG. 12 shows the tenth embodiment of the present invention similar to FIG. 11 but with zigzag leads.  
         [0020]    [0020]FIG. 13 shows an eleventh embodiment of the present invention similar to FIG. 7 with the width of the fluorescent cover extending to cover the length of the metal leads.  
         [0021]    [0021]FIG. 14 shows a twelfth embodiment of the present invention similar to FIG. 8 but with the width of the fluorescent cover covering the length of the metal leads.  
         [0022]    [0022]FIG. 15 shows the thirteenth embodiment of the present invention similar to FIG. 9 but with the width of the fluorescent covering the length of the metal leads. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    [0023]FIG. 3 shows the first embodiment of the present invention. A blue or ultra-violet LED  10  chip is mounted on a metal plate  11  serving as the contact lead for the bottom electrode of the LED  10  of a surface mount package. The top electrode of the LED  10  is wire-bonded by wire  13  to a second metal plate  12  serving as the second contact lead of the LED  10  for the surface mount package. The LED is imbedded in glue  261  which feeds through two via holes or edge recess  14  for holding the structure in place and which spreads along the bottoms of the leads  11  and  12  to fix the relative positions of the leads  11  and  12 . A cover  262  composed of fluorescent material is used to cover the glue  261 . When a light is emitted from the blue LED chip, the fluorescent cover converts the blue light into colorless light.  
         [0024]    [0024]FIG. 4 shows a second embodiment of the present invention. The structure is similar to FIG. 3 except a flat fluorescent plate  263  is used to serve as the cover instead of the wrap-over cover  262  in FIG. 3. Other corresponding parts serve the same function as that in FIG. 3.  
         [0025]    [0025]FIG. 5 shows a third embodiment of the present invention. Instead of the glue  261  used in FIG. 3, the space between the chip  10  and the fluorescent cover is back-filled with air  266 . Glue  17  is used only to fill the through holes  14  in metal plates  11  and  12  and to spread along the bottom surfaces of the metal plates to hold the structure in place. The absence of glue between the chip  10  and the cover  262  reduce the attenuation of the emitted light from the LED  10 .  
         [0026]    [0026]FIG. 6 shows a fourth embodiment of the present invention. The structure is similar to that in FIG. 5 except that the metal leads  11  and  12  have a zigzag shape. The zigzag leads increases the adhesion area between the glue  17  and the leads  11 ,  12 , thereby increasing the rigidity.  
         [0027]    [0027]FIG. 7 shows a fifth embodiment of the present invention. The structure is similar to that in FIG. 3 except that the leads  11 ,  12  in FIG. 3 are replaced with folded leads  21 ,  22  around an insulating substrate  27 . The folded leads form flat bottom contacts more suitable for surface mounting.  
         [0028]    [0028]FIG. 8 shows a sixth embodiment of the present invention. The structure is similar to that in FIG. 7 except that the space  266  between the LED  10  and the fluorescent cover  262  is filled with air, which has less attenuation to the light emitted from the LED  10 .  
         [0029]    [0029]FIG. 9 shows a seventh embodiment of the present invention. The structure is similar to that in FIG. 4 except that an opaque side-wall  28  is erected around the glue  261 . The opaque side-wall  28  prevents the emitted light from the LED  10  to irradiate sidewise, thereby concentrating the light toward the fluorescent cover  263 .  
         [0030]    [0030]FIG. 10 shows an eighth embodiment of the present invention. The structure is similar to that in FIG. 4 except that the width of the glue  261  and the fluorescent cover  263  is extended to be of the same length as the leads  11  and  12 . The glue  261  makes the leads  11  and  12  more rigid for easy surface mounting to a circuit board.  
         [0031]    [0031]FIG. 11 shows a ninth embodiment of the present invention. The structure is similar to that in FIG. 5 except that the width of the fluorescent cover  262  is extended to be of the same length as the leads  11  and  12 . The fluorescent cover  262  adds to the rigidity of the leads  11  and  12  for easy surface mounting to a circuit board.  
         [0032]    [0032]FIG. 12 shows a tenth embodiment of the present invention. The structure is similar to that in FIG. 11 except that the leads  11  and  12  are zigzag. The zigzag bend increases the area imbedded in the glue  17 , thereby strengthening the leads  11  and  12 .  
         [0033]    [0033]FIG. 13 shows an eleventh embodiment of the present invention. The structure is similar to that in FIG. 7 except that the width of the fluorescent cover  262  is extended to be equal to the length of the folded leads  21  and  22  around the insulating substrate  27 . The lengthened fluorescent cover  262 , together with the glue  261  makes the folded more rigid.  
         [0034]    [0034]FIG. 14 shows a twelfth embodiment of the present invention. The structure is similar to that in FIG. 8 except that the fluorescent cover  262  is extended to a width equal to the length of the leads  21  and  22 . The extended fluorescent cover  262  makes the leads  21  and  22  more rigid.  
         [0035]    [0035]FIG. 15 shows that thirteenth embodiment of the present invention. The structure is similar to that in FIG. 9 except that the fluorescent  263 , the glue  261  and the side-wall  28  are extended to a width equal to the length of the leads  11  and  12 . The extended glue  261  and the side-wall  28  makes the leads  11 ,  12  more rigid.  
         [0036]    While the preferred embodiment of the invention has been described, it will be apparent to those skilled in the art that various modifications may be made in the embodiments without departing from the spirit of the present invention. Such modifications are all within the scope of this invention.