Patent Publication Number: US-2022231208-A1

Title: Composite lead frame and light-emitting diode package structure including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Utility Model Patent Application No. 110200689, filed on Jan. 20, 2021. 
     FIELD 
     The disclosure relates to a lead frame and a package structure, and more particularly to a composite lead frame having a reflector cup and a light-emitting diode package structure including the composite lead frame for packaging a diode chip. 
     BACKGROUND 
     A conventional lead frame package for high luminance light-emitting diode element is generally made by etching or stamping a metallic material, such as copper alloy or aluminum alloy, into a flat lead frame, after which a molding compound, such as an epoxy molding compound (EMC), is injection molded on a surface of the lead frame to form a packaging cup for reflecting light emitted from the light-emitting diode element. 
     Although the epoxy molding compound has good mechanical property and good metal bonding, it has poor weather resistance and poor light stability. As the use time increases, the originally white epoxy molding compound of the packaging cup used for reflecting the light will begin to age, to yellow and deteriorate, thereby gradually reducing reflectivity of light of the packaging cup and shortening the service life of the conventional lead frame package. 
     SUMMARY 
     Therefore, an object of the present disclosure is to provide a composite lead frame that can alleviate at least one of the drawbacks of the prior art. 
     According to one aspect of this disclosure, a composite lead frame for mounting a light-emitting diode chip thereon includes a chip mounting seat, a plurality of fillers, and a reflector cup. 
     The chip mounting seat includes at least two electrodes spaced apart from each other by a gap and configured to electrically connect with the light-emitting diode chip. Each electrode has a plate shape with an upper surface, a lower surface opposite to the upper surface, and at least one through hole extending from the upper surface to the lower surface. 
     The fillers are made of polymer materials and are filled in the gap and the at least one through hole. 
     The reflector cup is disposed on and cooperates with the upper surfaces of the electrodes to define a receiving space for receiving the light-emitting diode chip. The reflector cup is made of a material different from that of the filler, and is composed of a silicon-based polymer material and a white inorganic filling material. The reflector cup is simultaneously connected to the electrodes and the fillers filled in the gap and the at least one through hole. 
     Another object of the present disclosure is to provide a light-emitting diode package structure that can alleviate at least one of the drawbacks of the prior art. 
     According to another aspect of this disclosure, a light-emitting diode package structure includes the composite lead frame as described above, a light-emitting diode unit, and an encapsulant. The light-emitting diode unit includes a light-emitting diode chip mounted on the upper surface of one of the electrodes and electrically connected to the electrodes. The encapsulant is transparent, and is filled in the receiving space for encapsulating the light-emitting diode chip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a sectional view illustrating a light-emitting diode package structure in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a perspective view of a composite lead frame of the embodiment; and 
         FIG. 3  is a sectional view taken along line III-III of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 to 3 , a light-emitting diode package structure  200  in accordance with an embodiment of the present disclosure includes a composite lead frame  2 , a light-emitting diode unit  3 , and an encapsulant  4 . 
     The composite lead frame  2  includes a chip mounting seat  21 , a plurality of fillers  22 , and a reflector cup  23 . 
     The chip mounting seat  21  is made of a material selected from copper alloy or iron-nickel alloy, and includes two electrodes  211  that are spaced apart from each other by a gap  210  and that are configured to electrically connect with the light-emitting diode unit  3 . Each of the electrodes  211  has a plate shape with an upper surface  2111 , a lower surface  2112  opposite to the upper surface  2111 , and at least one through hole  212  extending from the upper surface  2111  to the lower surface  2112 . 
     In this embodiment, each electrode  211  is formed as a square copper plate by stamping or etching, and has a plurality of the through holes  212  (only two are shown in  FIGS. 1 and 3 ) extending from the upper surface  2111  to the lower surface  2112  of a corresponding one of the electrodes  211 . However, the shape of each of the electrode  211  and the through hole  212  and the number of the through hole  212  in each electrode  211  are not limited to what is disclosed herein, and may be varied according to the requirements, as long as the electrodes  211  are electrically independent of each other and have the through holes  212 . 
     The fillers  22  are filled in the through holes  212  of the electrodes  211  and the gap  210  between the electrodes  211 . The fillers  22  may be made of a thermosetting or thermoplastic polymer material, and may be transparent or opaque. The fillers  22  have good adhesion to the reflector cup  23 . To be specific, the fillers  22  may be made of epoxy resin or black resin, but is not limited thereto. 
     The reflector cup  23  is disposed on and cooperates with the upper surfaces  2111  of the electrodes  211  to define a receiving space  213  for receiving the light-emitting diode unit  3  and for exposing a portion of the upper surfaces  2111  of the electrodes  211 . 
     Specifically, the reflector cup  23  is white, and corresponds in position with the through holes  212  of the electrodes  211 . The reflector cup  23  has a top surface  231  distal from the upper surfaces  2111  of the electrodes  211 , and an inner peripheral surface  232  tapering downwardly from an inner periphery of the top surface  231  toward the upper surfaces  2111  of the electrodes  211 . The inner peripheral surface  232  has an angle of inclination greater than 90 degrees with respect to the upper surfaces  2111  of the electrodes  211 . Since the fillers  22  are filled in the gap  210  between the electrodes  211  and the through holes  212  in the electrodes  211 , the reflector cup  23  is not only connected to the upper surfaces  2111  of the electrodes  211 , but is also simultaneously connected to the fillers  22  filled in the gap  210  and the through holes  212 . Thus, adhesion between the reflector cup  23  and the electrodes  211  can be enhanced through the fillers  22 . In this embodiment, the through holes  212  are formed in the electrodes  211  at positions corresponding to that of the reflector cup  23 , and are not located in the receiving space  213 . 
     The reflector cup  23  is made of a material different from that of the filler  22 , and is composed of a silicon-based polymer material and a white inorganic filling material. The silicon-based polymer material includes silicone, but is not limited thereto. The white inorganic filling material is selected from one of barium sulfate and titanium dioxide, but is not limited thereto. 
     The light-emitting diode unit  3  includes a light-emitting diode chip  31  mounted on the upper surface  2111  of one of the electrodes  211 , and a plurality of guide wires  32  for electrically connecting the light-emitting diode chip  31  to the electrodes  211 . 
     The encapsulant  4  is transparent, and is filled in the receiving space  213  for encapsulating the light-emitting diode unit  31 . The encapsulant  4  is made of an encapsulating material with high light transmittance and including epoxy resin or silicone. Thus, the encapsulant  4  will not affect the light emitting efficiency of the light-emitting diode chip  31  while protecting the light-emitting diode unit  3 . 
     When the light-emitting diode chip  31  mounted on the chip mounting seat  21  emits light, the reflector cup  23  can reflect at least a portion of the angle of light emitted by the light-emitting diode chip  31  to change the direction of the light path, so that the light travels toward a light exit side, that is, an opening at one side of the reflector cup  23  opposite to the chip mounting seat  21 , to increase the light emitting efficiency of the light-emitting diode chip  31 . 
     The advantages of the light-emitting diode package structure  200  of this disclosure can be summarized as follows: 
     1. The chip mounting seat  21  is formed with the through holes  212  that are filled with the fillers  22 . Therefore, through the connection of the fillers  22  and the reflector cup  23 , adhesion between the reflector cup  23  and the chip mounting seat  21  can be enhanced. 
     2. Through the disposition and the material selection of the reflector cup  23 , the light resistance and stability of the reflector cup  23  can be increased to maintain its reflectivity. 
     3. The reflector cup  23  is composed of a silicon-based polymer material and a white inorganic filling material, so that, apart from improving its reflectivity of light, it is also prevented from being directly irradiated by the excitation light of the light-emitting diode chip  31 , which can cause photodegradation. Hence, the problem of yellowing and deterioration caused by poor weather resistance of the packaging cup of the conventional lead frame package that is made of epoxy molding compound can be resolved. 
     4. By using the fillers  22  to strengthen the connection between the reflector cup  23  and the chip mounting seat  21 , the reflector cup  23  cannot be easily removed from the chip mounting seat  21 . 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.