Abstract:
A lead frame for an LED package includes a substrate and a bonding electrode, a first connecting electrode, and a second connecting electrode embedded in the substrate. A top surface of the bonding electrode includes a first bonding surface and a second bonding surface spaced from the first bonding surface. A top surface of the first connecting electrode includes separated first and second connecting surfaces. Top surfaces of the bonding electrode, the first connecting electrode, and the second connecting electrode are exposed, and support and electrically connect with light emitting chips. LED packages can be mounted on the lead frame and electrically connect with each other. The conductive layout of the lead frame further permits installation of a zener diode which can be connected to the LED packages in series or in parallel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a divisional application of patent application Ser. No. 14/876,980, filed on Oct. 7, 2015, entitled “LEAD FRAME AND LIGHT EMITTING DIODE PACKAGE HAVING THE SAME”, assigned to the same assignee, which is based on and claims priority to Chinese Patent Application No. 201210551102.3 filed on Dec. 18, 2012, the contents of which are incorporated by reference herein. 
     
    
     FIELD 
       [0002]    The disclosure generally relates to a lead frame and a light emitting diode package having the lead frame, wherein heat dissipation from the light emitting diode package is improved and electrical wiring is versatile. 
       BACKGROUND 
       [0003]    A typical light emitting diode package includes a substrate, a first electrode and a second electrode arranged on the substrate, and a plurality of light emitting chips mounted on the substrate and electrically connecting to the first and second electrodes. 
         [0004]    In a typical light emitting diode (LED) package, only two electrodes are provided to supply electricity to the light emitting chips, such that the plurality of light emitting chips can only be connected in parallel with a power source. Furthermore, the typical LED package has a limited heat dissipation area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
           [0006]      FIG. 1  is a top planar view of a lead frame in accordance with an exemplary embodiment of the present disclosure. 
           [0007]      FIG. 2  is a bottom plan view of the lead frame of  FIG. 1 . 
           [0008]      FIG. 3  is a cross-sectional view of the lead frame of  FIG. 1  with a reflecting cup on the lead frame of  FIG. 1 , taken along a line of the lead frame of  FIG. 1 . 
           [0009]      FIG. 4  is a cross-sectional view of the lead frame of  FIG. 1  with a reflecting cup on the lead frame of  FIG. 1 , taken along a line IV-IV of the lead frame of  FIG. 1 . 
           [0010]      FIG. 5  is a top planar view of a light emitting diode package having two light emitting chips electrically connecting with each other in series on the lead frame of  FIG. 1 . 
           [0011]      FIG. 6  is an equivalent circuit diagram of the light emitting diode package of  FIG. 5 . 
           [0012]      FIG. 7  is a top planar view of a light emitting diode package having two light emitting chips electrically connecting with each other in parallel on the lead frame of FIG.  1 . 
           [0013]      FIG. 8  is an equivalent circuit diagram of the light emitting diode package of  FIG. 7 . 
           [0014]      FIG. 9  is a cross-sectional view of a light emitting diode package having a reflector and two light emitting chips connecting with each other in series on the lead frame of  FIG. 1 . 
           [0015]      FIG. 10  is a top view of a light emitting diode package having two light emitting chips connecting with each other in series and a zener diode connecting in parallel with one of the two light emitting chips on the lead frame of  FIG. 1 . 
           [0016]      FIG. 11  is a top view of a light emitting diode package having two light emitting chips connecting with each other in series and a zener diode connecting in parallel with the two serially-connected light emitting chips on the lead frame of  FIG. 1 . 
           [0017]      FIG. 12  is a top view of a light emitting diode package having two light emitting chips and a zener diode connecting in parallel with each other on a lead frame of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0018]    It will be appreciated that for simplicity and clarity of illustration, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. The description is not to be considered as limiting the scope of the embodiments described herein. 
         [0019]    The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series, and the like. 
         [0020]    Referring to  FIGS. 1-2 , a lead frame  100  in accordance with an exemplary embodiment of the present disclosure is provided. The lead frame  100  includes a substrate  10 , a bonding electrode  20 , a first connecting electrode  21 , and a second connecting electrode  22 . The bonding electrode  20 , the first connecting electrode  21 , and the second connecting electrode  22  are spaced apart from each other. 
         [0021]    The substrate  10  includes a flat top surface  101  and a flat bottom surface  102 . The flat bottom surface  102  is facing away from and parallel to the top surface  101 . 
         [0022]    The bonding electrode  20 , the first connecting electrode  21 , and the second connecting electrode  22  are embedded in the substrate  10 , and each have the same coplanar as the substrate  10 . That is, top surfaces of the bonding electrode  20 , the first connecting electrode  21 , and the second connecting electrodes  22  are exposed but coplanar with the top surface  101  of the substrate  10 . The bottom surfaces of the bonding electrode  20 , the first connecting electrode  21 , and the second connecting electrode  22  are exposed from but coplanar with the bottom surface  102  of the substrate  10 . 
         [0023]    Referring to  FIG. 2 , the bonding electrode  20  includes a first connecting portion  2041 , a second connecting portion  2042 , and a main connecting portion  205  connecting the first and second connecting portions  2041 ,  2042 . 
         [0024]    The first and second connecting portions  2041 ,  2042  are parallel to each other. The main connecting portion  205  is located between the first and second connecting portions  2041 ,  2042 . Opposite ends of the main connecting portion  205  connect with inner ends of the first and second connecting portions  2041 ,  2042  respectively. 
         [0025]    A width of the first connecting portion  2041  equals a width of the second connecting portion  2042 . The width of the first connecting portion  2041  is larger than a width of the main connecting portion  205 . A recess  300  is defined among the first connecting portion  2041 , the second connecting portion  2042 , and the main connecting portion  205 . 
         [0026]    In at least one embodiment, the first and second connecting portions  2041 ,  2042  are integrally formed with the main connecting portion  205 . 
         [0027]    The first connecting electrode  21  is located in the recess  300  and is surrounded by the first connecting portion  2041 , the second connecting portion  2042 , and the main connecting portion  205 . The first connecting electrode  21  is spaced apart from the first connecting portion  2041 , the second connecting portion  2042 , and the main connecting portion  205 . 
         [0028]    In at least one embodiment, the second connecting electrode  22  is located at a right side of the bonding electrode  20  along a longitudinal direction of the substrate  10  or located on an end of the substrate  10 . The second connecting electrode  22  is spaced apart from the bonding electrode  20 . The bottom surface of the bonding electrode  20  occupies more than eighty percent of the entire area of the surface lead frame  100 . The bonding electrode  20 , the first connecting electrode  21 , and the second connecting electrode  22  are made of metal or metallic materials with good thermal conductivity. 
         [0029]    Referring to  FIG. 4 , a top end of the main connecting portion  205  of the bonding electrode  20  along with a width direction of the bonding electrode  20  defines a cavity  203 . The cavity  203  is recessed along a direction from a top surface of the bonding electrode  20  towards a bottom surface of the main connecting portion  205 . The cavity  203  does not penetrate through the entire thickness of bonding electrode  20 . A depth of the cavity  203  preferably equals one half of the thickness of the bonding electrode  20  in the exemplary embodiment. 
         [0030]    In at least one embodiment, a first bonding surface  201  and a second bonding surface  202  are defined by the cavity  203  in the top surface of the bonding electrode  20 . 
         [0031]    Referring to  FIG. 3-4 , a top end of the first connecting electrode  21  along a transverse direction of the substrate  10  defines a through groove  2213 . The groove  213  is recessed along a direction from the top surface of the first connecting electrode  21  towards the bottom surface of the first connecting electrode  21 . The groove  213  does not penetrate through the full thickness of the first connecting electrode  21 . A depth of the groove  213  can equal the depth of the cavity  203  in the bonding electrode  20 . A width of the groove  213  equals that of the cavity  203  in the bonding electrode  20 . In at least one embodiment, the cavity  203  is longitudinally aligned with the groove  213  along the substrate  10 . 
         [0032]    The presence of the groove  213  divides the top surface of the first connecting electrode  21  into a first connecting surface  211  and a second connecting surface  212 , each being located at opposite sides of the groove  213 . 
         [0033]    A reflector  30  is located on the top surface  101  of the substrate  10 . The reflector  30  covers an outer periphery of the bonding electrode  20 , an outer periphery of the first connecting electrode  21 , and an outer periphery of the second connecting electrode  22 . 
         [0034]    The reflector  30  is made of polymeric materials, such as Epoxy Molding Compound (EMC) or Silicone Molding Compound (SMC). 
         [0035]    In at least one embodiment, the reflector  30  includes a first receiving portion  301  and a second receiving portion  303  separated from the first receiving portion  301  by a dam  31 . The dam  31  is located at a central portion of the reflector  30 . The dam  31  extends transversely along the substrate  10 , and is over the cavity  203  and the groove  213  as shown in  FIGS. 3 and 4 . A part of the substrate  10  fills in the cavity  203  and the groove  213 . 
         [0036]    A width of the dam  31  gradually decreases from a bottom end on the substrate  10  towards a top end far away from the substrate  10 . The width of the bottom end of the dam  31  is larger than the width of the cavity  203 , but is less than the width of the first connecting electrode  21  longitudinally along the substrate  10  as shown in  FIG. 4 . 
         [0037]    The first bonding surface  201  of the bonding electrode  20  and the first connecting surface  211  of the first connecting electrode  21  are exposed at the bottom of the first receiving portion  301  of the reflector  30  as shown in  FIG. 3 . The second bonding surface  202  of the bonding electrode  20 , the second connecting surface  212  of the first connecting electrode  21 , and the top surface of the second connecting electrode  22  are exposed at the bottom of the second receiving portion  303  of the reflector  30 . In this embodiment, a height of the dam  31  is less than a height of the surrounding portion  305  of the reflector  30 . 
         [0038]    Alternatively, the reflector  30  can be formed with the substrate  10  as a single piece. The reflector  30  is made as a layer of a polymer material, wherein the reflector  30  and the substrate  10  are made of the same material. 
         [0039]    Referring to  FIGS. 5-6 , a first light emitting chip  41  is mounted on the first bonding surface  201  and a second light emitting chip  42  is mounted on the second bonding surface  202 . The first light emitting chip  41  electrically connects with the first bonding surface  201  and the first connecting surface  211  of the first connecting electrode  21  by two wires  40 . The second light emitting chip  42  also electrically connects with the second connecting surface  212  of the first connecting electrode  21  and the second connecting electrode  22  by two wires  40 . The first bonding surface  201  and the second bonding surface  202  being connected by the bottom end of the bonding electrode  20 , the first connecting surface  211  and the second connecting surface  212  are thus connected by the bottom end of the first connecting electrode  21 . The first light emitting chip  41  and the second light emitting chip  42  electrically connect with each other in series, as shown in  FIG. 6 . 
         [0040]    Referring to  FIGS. 7-8 , the first light emitting chip  41  is mounted on the first bonding surface  201  and the second light emitting chip  42  is mounted on the second bonding surface  202 . The first light emitting chip  41  electrically connects with the first bonding surface  201  and the first connecting surface  211  of the first connecting electrode  21  by two wires  40 . The second light emitting chip  42  electrically connects with the second connecting surface  212  and the second bonding surface  202  by two wires  40 . The second bonding surface  202  electrically connects with the second connecting electrode  22  by a single wire  40 . 
         [0041]    The first light emitting chip  41  and the second light emitting chip  42  electrically connect with each other in parallel, as shown in  FIG. 8 . 
         [0042]    In the above configuration, the first light emitting chip  41  and the second light emitting chip  42  can be electrically connected with each other on the lead frame  100  either in series or in parallel, and the electrical wiring between the first light emitting chip  41  and the second light emitting chip  42  is rendered versatile. 
         [0043]    Referring to  FIG. 9 , an encapsulation layer  50  is formed to cover the first light emitting chip  41 , the second light emitting chip  42 , and the dam  31  in the reflector  30 . The encapsulation layer  50  is made of transparent materials, such as epoxy resin or silicone. The encapsulation layer  50  can be doped with phosphor powders. In at least one embodiment, light emitted from the first light emitting chip  41  and light emitted from the second light emitting chip  42  can mix to form white light. 
         [0044]    According to the present disclosure, the bonding electrode  20  being made of metallic materials ensures good thermal conductivity. The bottom surface of the bonding electrode  20  occupies more than eighty percent of the entire area of the bottom surface of the lead frame  100 , and heat generated from the first light emitting chip  41  and the second light emitting chip  42  is rapidly conducted to the bottom surface of the lead frame  100  for dissipation. The heat dissipating efficiency of the light emitting package is high. 
         [0045]    The reflector  30  and the substrate  10  are made of reflecting materials, such as EMC or SMC. The reflecting efficiency of the reflector  30  is thus increased to promote light extraction efficiency of the light emitting package. 
         [0046]    Referring to  FIG. 10 , when the first and second light emitting chips  41 ,  42  electrically connect with each other in series, a zener diode  60  electrically connects with the bonding electrode  20  and the first connecting electrode  21 . The zener diode  60  electrically connects with the first light emitting chip  41  in parallel, reducing the risk of electrostatic discharge and damage to the first light emitting chip  41 . In at least one embodiment, the zener diode  60  is mounted on the top surface of the first bonding surface  201 . The zener diode  60  is electrically connects with the first bonding surface  201  by a wire  40 , to directly connect with the first connecting surface  211  of the first connecting electrode  21 . 
         [0047]    Alternatively, in this disclosure, the zener diode  60  can be mounted on the second connecting surface  212  or on the top surface of the substrate  10 . 
         [0048]    Referring to  FIG. 11 , the zener diode  60  can be mounted on the second connecting electrode  22  to directly connect by a wire  40  with the bonding electrode  20  and the second connecting electrode  22 . This arrangement allows the zener  60  to electrically connect with the serially-connected first and second light emitting chips  41 ,  42  in parallel. Thereby, electrostatic discharge and damage to the first and second light emitting chips  41 ,  42  is avoided. 
         [0049]    Referring to  FIG. 12 , when the first and second light emitting chips  41 ,  42  electrically connect with each other to the lead frame  100  in parallel, the zener diode  60  can electrically connect with the bonding electrode  20  and with the first connecting electrode  21  by two wires  40 . This arrangement will connect the first light emitting chip  41 , the second light emitting chip  41 , and the zener diode  60  in parallel on the lead frame  100 . In at least one embodiment, the zener diode  60  is mounted on the first connecting surface  211  of the first connecting electrode  21 . 
         [0050]    The embodiments shown and described above are only examples. Many details are often found in the art such as the other features of the lead frame and light emitting diode package having the same. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes can be made in the detail, including in matters of shape, size, and arrangement of the parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above can be modified within the scope of the claims.