Patent Publication Number: US-RE42179-E

Title: Light emitting diode package with coaxial leads

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to light emitting device, particularly to the package of light emitting device (LED) or laser diode (LD). 
     2. Brief Description of Related Art 
       FIG. 1  shows a prior art package for a LED. A LED  10  chip is mounted in a recess at the top of lead  11  of the LED package, which is in contact with the bottom electrode of the LED  10 . The top electrode of the LED  10  is wire bonded to a second lead  12  of the package with a metal wire  14 . The top portions of the leads  11 ,  12  are imbedded in protective glue  13 . 
     When such a package is mounted on a planar display board, the board usually has printed wiring on the underside. The LED leads can only reach the printed wiring through plated through holes. When a customer changes the display panel pattern, a new printed wiring board must be furnished. Therefore, such a LED package lacks design flexibility for a display. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a LED package design flexibility in mounting on a display panel. Another object of this invention is to provide a LED package which can easily be removed and inserted into a mother board. Still another object of this invention is to save space between the LED leads. 
     These objects are achieved by providing the LEDs with coaxial leads. The coaxial leads are separated from each other by an insulating sleeve. For a LED with a bottom electrode, the LED can be mounted on top of the inner lead, or mounted on the side of the a protruded inner leads to change the direction of light emission. For a LED with two bottom electrodes, the two bottom electrodes can straddle over the planar tops of the two coaxial leads, or straddles over the two coaxial leads along their telescopic sides. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art LED package. 
         FIG. 2  shows a first embodiment of the present invention for a LED package with two coaxial leads. 
         FIG. 3  shows a second embodiment of the present invention with coaxial leads and side-mount LED. 
         FIG. 4  shows a third embodiment of the present invention with coaxial leads for LED with two bottom electrodes. 
         FIG. 5  shows a fourth embodiment of the present invention with coaxial leads for side-mount LED with two bottom electrodes. 
     
    
    
     DETAILED DESCRIPTION THE INVENTION 
       FIG. 2  shows the basic structure of the LED package based on the present invention. The package has two concentric leads: an inner leads  21  and outer lead  22 . The two concentric leads  21 ,  22  are separated by an insulating sleeve  23 . Both the top surfaces of the two leads  21  and  22  are made planar. The LED chip  20  with a bottom electrode and a top electrode is mounted on top of the inner lead  21 . The top electrode of the LED  20  is wire bonded to the outer lead  22  through a wire  24 . 
     The dotted lines show how the LED package of the present invention is inserted into a display panel board. The bottom layer  271  of this dotted structure is a soft conducting layer, which supplies the first power source. The top layer  272  of this dotted structure is a soft conducting layer, which supplies the second power source. In between the bottom soft layer  271  and top soft layer  272  is a soft insulating layer  273 . When the LED package is inserted into the display panel board, the inner lead  21  makes contact with the bottom layer  271  and the outer lead  22  makes contact with top layer  272 . Thus, the LED  20  is energized. The soft conducting layer refers to conducting sponge, conducting rubber or metallic mesh. The soft insulating layer refers to glue, sponge, etc. The leads  21 ,  22  are selected from metal which can withstand repeated insertions. 
       FIG. 3  shows a second embodiment of the present invention. The structure is similar to that in  FIG. 2 , except that the LED  20  is mounted on the side of a protruded inner lead  21 . In this structure, the light emitted from the LED  20  is orthogonal to that emitted from that in FIG.  2 . Other reference numerals refer to the corresponding parts in FIG.  2 . 
       FIG. 4  shows a third embodiment of the present invention. This structure is applicable to a LED  202  with two bottom electrodes with solder  281 ,  282 . Both the top surfaces of the two leads  21  and  22  are made planar. These two electrodes straddle over the top of the inner leads  21  and the top of the outer lead  22  to make contacts. Other parts with the same reference numerals as that shown in  FIG. 2  perform the same corresponding functions. 
       FIG. 5  shows a fourth embodiment of the present invention. This application is applicable to a LED  202  with two bottom electrodes with solder  281 ,  282 , but light emission orthogonal to that in FIG.  4 . The coaxial leads has a telescopic inner lead  21  protruding over the inner lead  22 . The LED  202  has soldered electrodes  281 ,  282  straddling over the inner coaxial lead  21  and the outer coaxial lead  22 . Because the insulating layer  23  plus the outer lead  22  is made very thin with a thickness d, the soldered leads  281 ,  282  of the LED  202  are aligned along the vertical surfaces of the coaxial leads. Other parts with the same reference numerals as that in  FIG. 2  perform the same corresponding functions. 
     While the preferred embodiments has been described, it will be apparent to those skilled in the art that various modification may be made in the embodiments without departing from the spirit of the present invention. Such modifications are all within the scope of the present invention.