Abstract:
Surface mount diodes are mass produced by first cutting a metal plate to form a plurality of vertical slits within metal plate. Parallel lines are cut midway between the slits to form wings for the slits. The wings are folded to form the bottoms for surface mounting. Glue is applied over the metal plate to form focusing cups.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    (1) Field of Invention  
           [0002]    This patent application is copending with U.S. patent application Ser. No. 09/731,223. This invention relates to optical semiconductor device package, particularly to packages with focusing cups. The semiconductor device may be a light emitting device such as diode, a laser diode, . . . etc. The semiconductor diode may also be a light absorbing device such an image sensor, photo diode... etc.  
           [0003]    (2) Brief Description of Related Art  
           [0004]    FIGS.  1 - 5  show a prior art technique of fabricating a diode package with a focusing cup. A metal plate is punched with holes  15  to yield a matrix of frames  13 . Each frame has two metal plates  11 ,  12 . The first metal plate  11  has two horizontal ends, the inner end  111  and outer end  112 . The second metal plate  12  has horizontal ends, the inner end  121  and outer end  122 .  
           [0005]    In the next step, the metal plates  11 ,  12  are partially covered with an insulating material such as glue to form a cup  10  and bottom support  14  as shown in the top view FIG. 2. The cup is lined with reflecting coating to focus the light emitted from the diode.  
           [0006]    Each semi-finished unit has the outer ends of the metal plates  112  and  122  extending outside the cup  10  as tabs. The section view along the section line A-A′ is shown in FIG. 4. The inner end  121  is mounted with the optical diode, which is wire bonded to the inner end  111 .  
           [0007]    The outer end  112  of metal plate  11  and the outer end  122  of metal plate  12  are then folded as shown in FIG. 5 to form the bottom contacts of the surface mount package.  
           [0008]    Such a structure requires a thick support  14  to withstand the bending moment of the outer end  112  of metal plate  11  and outer end  122  of metal plate  12  as described in a copending U.S. patent application Ser. No. 09/731,223, which disclosed a method of using a pre-formed folded frame to reduce the thickness of the package.  
         SUMMARY OF THE INVENTION  
         [0009]    An object of this invention is to provide a method of mass production of the folded frame structure disclosed in copending U.S. patent application Ser. No. 09/731,223. Another object of this invention is to reduce the cost of fabricating an optical diode package with a focusing cup.  
           [0010]    These objects are obtained by preforming the folded bottom contacts of surface mount optical diodes on a metallic substrate before the substrate is diced into individual packages. The metallic substrate is cut with vertical parallel slits inside the horizontal edges of the substrate. Lines parallel to the slits are cut between the slits to form two wings for each slit. The two wings are folded to form the bottom contacts for the surface-mount package. Glues are poured into a mold over and under the metal substrate to form focusing cups and bottom support  14 . The metal substrate and the glue are then diced to form individual packages. The diodes are mounted inside the cups and connected to the divided metal leads at the bottoms of the cups. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 shows the prior art frame for mass producing the optical diode packages with the focusing cups.  
         [0012]    [0012]FIG. 2 shows the mounting of the cups on the frame in FIG. 1  
         [0013]    [0013]FIG. 3 shows the individual unit.  
         [0014]    [0014]FIG. 4 shows the cross-section view of the diode with a focusing cup.  
         [0015]    [0015]FIG. 5 shows the folding of the bottom contacts for surface mounting.  
         [0016]    [0016]FIG. 6 shows the basic structure of the metallic substrate of the present invention.  
         [0017]    [0017]FIG. 7 shows the mounting of the focusing cups over the metallic substrate.  
         [0018]    [0018]FIG. 8 shows the 3-dimensional view of the structure shown in FIG. 7.  
         [0019]    [0019]FIG. 9 shows the individual unit after dicing.  
         [0020]    [0020]FIG. 10 shows the cross-sectional view of FIG. 9.  
         [0021]    [0021]FIG. 11 shows a second embodiment of the present invention.  
         [0022]    [0022]FIG. 12 shows a third embodiment of the present invention.  
         [0023]    [0023]FIG. 13 shows a 3-dimensional view of FIG. 12.  
         [0024]    [0024]FIG. 14 shows the bottom view of FIG. 12.  
         [0025]    [0025]FIG. 15 shows a fourth embodiment of the present invention with the three dimensional view of a multiple lead package.  
         [0026]    [0026]FIG. 16 shows a fifth embodiment of the present invention with multiple lead package.  
         [0027]    [0027]FIG. 17 shows a sixth embodiment of the present invention with zig-zag leads.  
         [0028]    [0028]FIG. 18 shows a bottom view of FIG. 17. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    [0029]FIG. 6 shows a common metal substrate for mass producing surface mount optical diodes with focusing cups, The common metallic substrate is cut with vertical slits  25  and cut along the dotted lines  26 . The wings  211  and  221  created by the cuts  26  are folded downward along the horizontal edges of the dotted circle as bottom contacts  212  and  222 , respectively, of a surface mount package. While FIG. 6 shows the slits  25  are shown as a number of single long slits, the individual slits may be sectionalized the strengthen the structure.  
         [0030]    [0030]FIG. 7 shows that the metal frame is then covered with insulating material  20  ( usually glue) except in the circular cups to expose the inner terminals  211  and  221 .  
         [0031]    [0031]FIG. 8 shows the three dimensional view of FIG. 7 with cups surrounded by insulating walls  20 . Note that the folded ends of the wings contact at the bottom of the walls  20 . The chips are then mounted and wire-bonded in the cups. The structure is then sawed along the dot-dash horizontal and vertical lines.  
         [0032]    [0032]FIG. 9 shows individual unit after the sawing step shown in FIG. 8 (chips, wire-bonding and glue within the cup are not shown in FIG. 9).  
         [0033]    [0033]FIG. 10 shows the cross-section view of FIG. 9 along the dot-dash section line A-A′. A semiconductor die is mounted on the inner end  221  of metal wing  22  and is wire bonded to the inner end  211  of a metal wing  21 .  
         [0034]    [0034]FIG. 11 shows another embodiment of the present invention which is similar to FIG. 10 except that the vertical folded part the metal wing is exposed and not covered by the insulating material forming the cups. Exposing the vertical fold has the advantage that during subsequent soldering of the bottom contact to a motherboard, the solder can climb up the vertical wall to insure better soldering.  
         [0035]    [0035]FIG. 12 shows a third embodiment of the present invention. The metal leads  31  and  32  are folded outward to form bottom contacts  351 ,  352  for surface mounting to a motherboard. The metal leads  31 ,  32  are covered with insulating material  20  except in the cup area. An optical diode chip is mounted on the upper end  321  of the folded metal wing or lead  32  and is wire bonded to the upper end  311  of the metal wing or lead  31 .  
         [0036]    [0036]FIG. 13 shows a 3-dimensiona view of FIG. 12.  
         [0037]    [0037]FIG. 14 shows the bottom view of FIG. 13 showing the bottom contacts  351 ,  352  of the metal leads  312 ,  322  respectively. The two contacts  351  and  352  are separated by an insulator  24 .  
         [0038]    [0038]FIG. 15 shows a fourth embodiment of the present invention for a semiconductor chip with four electrodes. The four electrode semiconductor device (not shown) is mounted inside the focusing cup. Four preformed bent metal frames are used for contacts  41 ,  42 ,  43 ,  44 . The shape of each metal leads is similar to that in FIG. 12 with an outwardly bent flange as bottom contact. A glue  20  is cast over the metal frames to form a focusing cup and to seal the entire structure except the bottom of the cup. The bottom of the cup is exposed for connecting the metal plates to the four electrodes of the semiconductor device.  
         [0039]    [0039]FIG. 16 shows a fifth embodiment of the present invention. The structure is also for a four-electrode semiconductor device, similar to FIG. 15. However, the bonding pads of the semiconductor device are not symmetrically located. Therefore the shapes of the metal frames are not of the same shape to mate with the bonding pads of the semiconductor device. While the metal leads  51 ,  53  are similar in shape as metal leads  41 ,  43  in FIG. 15, the metal leads  52 ,  54  are different from metal leads  42 ,  44 . Metal leads  53  has a zigzag shape and metal lead has an L-shape. The shapes not limited to these shapes, so long as the top surface of the metal leads can mate with the electrodes.  
         [0040]    [0040]FIG. 17 shows a sixth embodiment of the present invention. The structure is similar to FIG. 13, except that the width of the metal leads is flush with the width of the glue  20  covering the leads  31  and  32 . FIG. 18 shows the bottom view of FIG. 17.  
         [0041]    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.