Patent Publication Number: US-2012043576-A1

Title: Led package structure

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a light emitting diode (LED) package structure. 
     2. Description of Related Art 
     Presently, LEDs are preferred for use in non-emissive display devices than CCFLs (cold cathode fluorescent lamp) due to their high brightness, long lifespan, and wide color range. Especially, high-brightness, high-power LEDs are preferred for use over the past year. 
     However, high-brightness, high-power LEDs, while generating large amounts of light, also generate large amounts of heat which can cause thermal degradation of the characteristics of the LEDs and reduce the overall lifespan of the LEDs. A typical LED package structure includes an LED die adhered on a silicon substrate. The silicon substrate generally has good processability but a relatively poor heat conductivity. The LED package structure uses the silicon substrate to transfer the heat. Unfortunately, the silicon substrate is not efficient enough to solve the thermal degradation problem of the LED. 
     What is needed, therefore, is an LED package structure which can overcome the limitations described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an LED package structure according to a first embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view of an LED package structure according to a second embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view of an LED package structure according to a third embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view of an LED package structure according to a fourth embodiment of the present disclosure. 
         FIG. 5  is a cross-sectional view of an LED package structure according to a fifth embodiment of the present disclosure. 
         FIG. 6  is a cross-sectional view of an LED package structure according to a sixth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the disclosure will now be described in detail with reference to the accompanying drawings. 
     Referring to  FIG. 1 , an LED package structure  10  in accordance with a first embodiment of the disclosure is illustrated. The LED package structure  10  includes a substrate  11 , an LED die  12 , two electrodes  13 , and two metal wires  14  electrically connecting the LED die  12  with the electrodes  13 . 
     The substrate  11  is a part of a wafer before the LED package structure  10  is made. The LED package structure  10  is packaged before the wafer is cut into pieces wherein the substrate  11  is obtained from one of the pieces. The wafer and accordingly the substrate  11  are made of silicon. The substrate  11  has a first surface  112  and a second surface  114  opposite to the first surface  112 . The substrate  11  defines a concave groove  123  in the first surface  112  for receiving the LED die  12  therein. The substrate  11  defines a central opening  116  and two lateral through holes  118  by E-beam or other energy beam. The through holes  118  and the central opening  116  are spaced from each other. The central opening  116  and the through holes  118  are defined through the first surface  112  and the second surface  114 . A heat conductive pillar  16  is formed in the central opening  116  and two electrically conductive pillars  18  are formed in the through holes  118  by Physical Vapor Deposition (PVD) or other physical deposition method. 
     The LED die  12  is arranged in the concave groove  123  to thermally connect a top of the heat conductive pillar  16 . The LED die  12  is made of Group III-V semiconductor compound or Group II-VI semiconductor compound. In this embodiment, the LED die  12  is a horizontal type LED. A eutectic layer  121  is formed between the LED die  12  and the heat conductive pillar  16 . The eutectic layer  121  is formed by two metal layers (not shown) respectively connecting the heat conductive pillar  16  with bottom of the LED die  12  and joined together by eutectic bonding. The eutectic layer  121  contains at least one selected from Au, Sn, In, Al, Ag, Bi, Be or an alloy thereof. 
     Each of the electrodes  13  is mounted on the substrate  11  and electrically connects with the corresponding electrically conductive pillar  18 . In this embodiment, tops of the electrically conductive pillars  18  are exposed to the concave groove  123 , and the electrodes  13  are disposed at a bottom of the concave groove  123 . A heat conductive plate  17  is attached to the second surface  114  of the substrate  11  and arranged under the heat conductive pillar  16 . The heat conductive plate  17  and the heat conductive pillar  16  can be made of copper. The heat conductive pillar  16  connects the LED die  12  with the heat conductive plate  17  to conduct heat from the LED die  12  to the heat conductive plate  17 . Two contact pads  19  are attached to the second surface  114  of the substrate  11  and electrically connect with the electrically conductive pillars  18 , respectively. In this embodiment, the contact pads  19  and the heat conductive plate  17  are spaced from each other. 
     When the LED package structure  10  works, heat generated from the LED die  12  can be rapidly conducted to the heat conductive plate  17  through the heat conductive pillar  16  whereby the heat dissipating efficiency of the LED package structure  10  is increased. Thus, the heat is more quickly and efficiently transported away from the LED die  12  and a lifespan of the LED package structure  10  is increased. 
     Referring to  FIG. 2 , an LED package structure  20  in accordance with a second embodiment includes a substrate  21 , an LED die  22 , two electrodes  23  electrically connecting with the LED die  22 , and two electrically conductive pillars  28  respectively connecting to the electrodes  23 . The substrate  21  has a first surface  212  and a second surface  214  opposite to the first surface  212 . A concave groove  223  is defined in the first surface  212  for receiving the LED die  22  therein. The difference of the LED package structure  20  from the LED package structure  10  of the first embodiment is that the electrically conductive pillars  28  are arranged apart from the concave groove  223 . Each of the electrodes  23  has a bottom part mounted on the first surface  212  defining a bottom of the concave groove  223 , a top part mounted to the first surface  212  to electrically connect to the electrically conductive pillar  28 , and a middle part extending over an inclined portion of the top first surface  212  defining an inclined circumferential periphery of the concave groove  223 . 
     Referring to  FIG. 3 , an LED package structure  30  in accordance with a third embodiment includes a substrate  31  and an LED die  32 . A first electrically conductive pillar  381 , a second electrically conductive pillar  382 , and a heat conductive pillar  36  are formed in the substrate  31 . A heat conductive plate  37  and a contact pad  39  are attached to a bottom of the substrate  31 . The difference of the LED package  30  from the LED package structure  10  of the first embodiment is that the LED die  32  is a vertical type LED. The LED die  32  has a top electrode (not labeled) connecting an electrode  33  by a metal wire  34 , and a bottom electrode (not labeled) directly connecting the first electrically conductive pillar  381 . The second electrically conductive pillar  382  electrically connects the electrode  33  with the contact pad  39 . The heat conductive plate  37  electrically connects the first electrically conductive pillar  381 . 
     Referring to  FIG. 4 , an LED package structure  40  in accordance with a fourth embodiment includes a substrate  41  and an LED die  42 . The substrate  41  has a first surface  412  and a second surface  414  opposite to the first surface  412 . A concave groove  423  is defined in the first surface  412  of the substrate  41  for receiving the LED die  42  therein. A first electrically conductive pillar  481 , a second electrically conductive pillar  482 , and a heat conductive pillar  46  are formed in the substrate  41 . The difference of the LED package structure  40  from the LED package structure  30  of the third embodiment is that the second electrically conductive pillar  482  is arranged apart from the concave groove  423 . An electrode  43  is similar to the electrode  23  of the second embodiment. The electrode  43  extends from a bottom of the concave groove  423  to a top end of the second electrically conductive pillar  482 . 
     Referring to  FIG. 5 , an LED package structure  50  in accordance with a fifth embodiment includes a substrate  51  and an LED die  52 . A first electrically conductive pillar  581 , a second electrically conductive pillar  582 , and a heat conductive pillar  56  are formed in the substrate  51 . An electrode  53  is mounted on the substrate  51  and electrically connected with the second electrically conductive pillar  582 . The difference of the LED package structure  50  from the LED package structure  40  of the fourth embodiment is that the LED die  52  is a flip chip bonded to the first electrically conductive pillar  581  and the electrode  53 . 
     Referring to  FIG. 6 , an LED package structure  60  in accordance with a sixth embodiment includes a substrate  61  and an LED die  62 . The difference of the LED package structure  60  from the LED package structure  10  of the first embodiment is that the LED package structure  60  includes a plurality of heat conductive pillars  66  arranged in the substrate  61  and under the LED die  62  to thermally connect to the LED die  62 . 
     It is to be understood, however, that even though numerous characteristics and advantages of certain embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.