Abstract:
The bottom metal contacts of a surface mount LED are extended wider than the glue covering the LED. The extensions provide more area for soldering to a motherboard.

Description:
[0001]    This is a copending patent application of U.S. Ser. No. 09/595,907 now pending and allowed. The invention relates to light emitting diodes (LED), particularly to surface mount LED package. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    (1) Filed of the Invention  
           [0003]    (2) Brief Description of the Related Art  
           [0004]    Prior art surface mount LED packages, as shown in FIGS. 1,2 and disclosed in Taiwan Patent Application No. 089109999 and co-pending U.S. patent application Ser. No. 09/596,907, have only single-side bottom metal exposed for making contact to a motherboard. The metal contact plates  11 ,  12  are covered with glue  15  on top as shown in FIG. 2. The metal plates  11 , 12  have recesses  14  along the vertical edges as shown in the top view FIG. 1, and also have recesses  17  along the horizontal bottom surfaces of the metal contact plates  11 ,  12  as shown in FIG. 2. These recesses are for sealing glue to lodge and the hold the structure together. The LED  10  is mounted on the first metal contact plate  11 . The top electrode of the LED  10  is wire-bonded to the second metal contact plate  12  by wire  13 .  
           [0005]    As shown in the cross-sectional view FIG. 2 along the section A-A′ in FIG. 1, the glue  15  fills up the recesses  17  at the bottom surface of the package and the recess  14  along the vertical sides of the package to solidify the structure. This structure only exposes the bottom surfaces of metal contact plates  11 ,  12  not occupied by the recesses for soldering purpose. This limited area for soldering reduces the reliability of the contact.  
         SUMMARY OF THE INVENTION  
         [0006]    An object of this invention is to improve the reliability of soldering of a surface mount LED package to a motherboard. Another object of this invention is to increase the soldering area of a surface mount LED package to a motherboard.  
           [0007]    These objects are achieved by adding extensions to the metal contacts beyond the borders of the glue covering the LED. The extension provides more areas for the contact to be soldered to a motherboard. 
       
    
    
     BRIEF DESCRIPTION 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 cross-sectional view of FIG. 1.  
         [0010]    [0010]FIG. 3 shows the wing-shaped contacts of the present invention.  
         [0011]    [0011]FIG. 4 shows the covering of the solder over the contact extensions.  
         [0012]    [0012]FIG. 5 shows the glue covering the bottom surfaces of the contacts.  
         [0013]    [0013]FIG. 6 shows the glue covering up to the bottom surfaces of the contacts.  
         [0014]    [0014]FIG. 7 shows the bottom contacts with rectangular recesses.  
         [0015]    [0015]FIG. 8 shows the bottom contacts with polygonal recesses.  
         [0016]    [0016]FIG. 9 shows the glue covering below the bottom surfaces of the contacts.  
         [0017]    [0017]FIG. 10 shows through holes in the contact metals for the glue to flow through and solidify.  
         [0018]    [0018]FIG. 11 shows roughened surfaces of the contact metals for increasing the gluing area.  
         [0019]    [0019]FIG. 12 shows a cup shape metal for focusing the light from the LED.  
         [0020]    [0020]FIG. 13 shows a package for mounting a LED with two top electrodes.  
         [0021]    [0021]FIG. 14 shows a package for mounting a LED with two bottom electrodes. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    [0022]FIG. 3 shows the basic structure of the present invention. A LED  20  with a bottom electrode is mounted on a contact metal plate  21  serving as first terminal. The top electrode of the LED  20  is wire-bonded to a second contact metal plate  22 . The contact metal plates,  21 ,  22  have recesses  27 . The LED  20  and a portion of the top surface of the metal content are covered and sealed with glue  25 , leaving extensions B of the metal plate  21 ,  22  uncovered. During sealing, the glue also fills the recesses  27  to solidify the sealed structure. The extensions B extend outside the sealed area, and allow more soldering area  26  for making contacts to a motherboard as shown in FIG. 4. Thus, the solderability of the contacts to a motherboard is improved.  
         [0023]    [0023]FIG. 5 shows a second embodiment of the invention. The structure is similar to FIG. 4 except that the glue  25  seals below the bottom surfaces of the metal plates  21 ,  22  by a depth C. Thus the structure is more fully sealed by the glue  25 . The extensions beyond the sealed area remains available to be soldered to a motherboard.  
         [0024]    [0024]FIG. 6 shows a third embodiment of the invention. The structure is similar to FIG. 3 except that the top surfaces of the metal contact plates  211 ,  221  are flat. The bottom recesses  271  of such a structure can be fabricated by chemical or machine etching.  
         [0025]    [0025]FIG. 7 shows a fourth embodiment of the present invention. The structure is similar to FIG. 6, except that the recess  37  at the bottom of the metal plates  31 ,  32  is rectangular in shape. The rectangular recess  371  holds more glue  35  to further solidify the structure.  
         [0026]    [0026]FIG. 8 shows a fifth embodiment of the present invention. The structure is similar to FIG. 6, except that the recess  371  at the bottom of the metal plates  311 ,  321  is of polygonal shape. The polygonal recess  371  holds more glue  35  to further solidify the structure  
         [0027]    [0027]FIG. 9 shows a sixth embodiment of the present invention.. The structure is similar to FIG. 8, except that the glued area below the recesses  371  at the bottom of the metal plates  311 , 321  is made wider than the width of the glued area  35  on top of the over the LED  20 . The extra widths D outside the recess  371  area increase the distance between the soldering spots on a motherboard, thus avoiding the likelihood of. short-circuiting between solders.  
         [0028]    [0028]FIG. 10 shows a seventh embodiment of the invention. The structure is similar to FIG. 3, except that two through holes  381  are inserted from the top surfaces of the metal plates  321 ,  311  to the bottom recess  27  (not shown). The through holes allow glue  25  to flow into the through holes  381 , thus further solidifying the structure.  
         [0029]    [0029]FIG. 11 shows an eighth embodiment of the invention. The structure is similar to FIG. 10 , except that the top surfaces  382  of the metal plates  311 ,  321  are roughened. The roughened surfaces increase the grip of the glue to the structure to further solidify the structure.  
         [0030]    [0030]FIG. 12 shows a ninth embodiment of the invention. The structure is similar to FIG. 3, except that the glue  35  on top of the metal plates  21 ,  22  forms a cup  39  to expose the LED  20 . The cup surface help focus the light emitted from the LED  20 .  
         [0031]    [0031]FIG. 13 shows a tenth embodiment of the present invention. The structure is similar to FIG. 8, except that the LED  201  has two top electrodes. The LED  201  straddles over the metal plates  31 ,  32  and is wire-bonded to these plates respectively by wires  131  and  132 .  
         [0032]    [0032]FIG. 14 shows an eleventh embodiment of the invention. The structure is similar to FIG. 8, except that the LED  202  has two bottom electrodes. The LED straddles over and are bonded to the metal plates  31 ,  32 .  
         [0033]    While the preferred embodiments of the invention have 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.