Abstract:
An LED package structure and a method of fabricating the same. The LED package structure includes: a package unit including a submount with a cavity, and a light emitting chip disposed in the cavity; a first light-pervious element disposed in the cavity; a multi-layered dam structure concentrically disposed on the first light-pervious element or around a rim of the cavity; a first light-pervious packaging material filled in the dam structure; and a second light-pervious element that combines with the dam structure. Accordingly, the multi-layered dam structure provides an advantage of eliminating gaps and overcomes the problem resulting from the uneven thickness of the first light-pervious packaging material used in the prior technique, thereby ensuring high illumination efficiency and enhanced airtightness.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to package structures and methods of fabricating the same, and, more particularly, to an LED package structure and a method of fabricating the same. 
         [0003]    2. Description of Related Art 
         [0004]    Silicon material has been applied in the modern package of light emitting diode (LED) for phosphor protection, and the silicon material has advantageous features of high light-pervious efficiency and high heat-resistance, thereby being frequently used for covering phosphor to isolate heat generated by the LED, but incapable of efficiently isolating vapor, consequently the phosphor will lose efficacy due to contacting with the vapor. 
         [0005]    Please refer to  FIG. 1 , which is a sectional view diagram of an LED package structure according to US Patent Application Publication No. 2010/0163898. A substrate  11  with a circuit pattern  110  thereon is covered with a reflection layer  12 , and a portion of the circuit pattern  110  is exposed therefrom. A light emitting chip  13  is mounted on the reflection layer  12 , and is electrically connected to the exposed circuit pattern  110  via conductive element  14 , e.g. conductive wire. A reflector  15  with a light reflecting opening  150  is disposed on the reflection layer  12 , and the light emitting chip  13  is disposed in the light reflecting opening  150 . The light reflecting opening  150  is filled with a packaging material  16  and phosphor layer  17 . In order to enhance airtightness, a single ring of sealing glue (not shown) is coated on the rim of the light reflecting opening  150  of the reflector  15 , and then the reflector  15  is covered with an optical microstructure film  18  to seal the light reflecting opening  150 . However, both the packaging material  16  and the phosphor layer  17  are in a liquid form, and, in order to ensure the optical microstructure film  18  to seal up the light reflecting opening  150  of the reflector  15  tightly for preventing the packaging material  16  and the phosphor layer  17  from being spilt out, the phosphor layer  17  does not fill up the light reflecting opening  150 , thereby causing a gap  19  to appear between the optical microstructure film  18  and the phosphor layer  17  after the optical microstructure film  18  sealing up the light reflecting opening  150 , and further causing the thickness of the packaging material  16  or the phosphor layer  17  to become uneven, consequently the light emitting chip  13  cannot maintain high illumination efficiency and quality. 
         [0006]    Hence, how to solve the problem occurred in the prior technique is a highly urgent technique issue in the industry. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the drawbacks of the prior art mentioned above, it is therefore an objective of this invention to provide an LED package structure, comprising: a package unit having a submount with a cavity, and a light emitting chip disposed in the cavity; a first light-pervious element disposed in the cavity; a dam structure disposed on the first light-pervious element, and having an inner dam, an outer dam, a first containing space formed in the inner dam, and a second containing space formed between the inner dam and outer dam; a first light-pervious packaging material filled in the first containing space; and a second light-pervious element combined with the dam structure. 
         [0008]    The present invention further provides a method of fabricating an LED package structure, the method comprising: providing a package unit, the package unit having a submount with a cavity, and a light emitting chip disposed in the cavity; disposing a first light-pervious element in the cavity; disposing a dam structure on the first light-pervious element, the dam structure having an inner dam, an outer dam, a first containing space formed in the inner dam, and a second containing space formed between the inner dam and the outer dam; filling in the first containing space with a first light-pervious packaging material, the first light-pervious packaging material being larger in volume than the first containing space; and combining a second light-pervious element with the dam structure, thereby squeezing a portion of the first light-pervious packaging material into the second containing space. 
         [0009]    In an embodiment of the present invention, wherein the inner dam of the dam structure is disposed on the first light-pervious element, and the outer dam is disposed on a rim of the cavity. 
         [0010]    In an embodiment of the present invention, the package unit further comprises: leads disposed in the cavity and extending to a region outside of the submount; conductive elements electrically connected to the light emitting chip and the leads; and a second light-pervious packaging material filled in the cavity to encapsulate the leads, the light emitting chip, and the conductive elements. 
         [0011]    In another embodiment of the present invention, the package unit further comprises: conductive pillars disposed in the cavity; conductive elements connected to the light emitting chip and the conductive pillars; and a second light-pervious packaging material filled in the cavity and encapsulating the conductive pillars, the light emitting chip, and the conductive elements. 
         [0012]    In yet another embodiment of the present invention, the dam structure is formed by means of printing, dispensing, or covering a dry film and patterning the thy film. In an embodiment of the present invention, the inner dam and the outer dam are concentrically disposed on the first light-pervious element or on a rim of the cavity; the first transmission element is made of a silicon material; the dam structure is made of dry film, UV glue, B-stage epoxy resin, or glass frit; the second light-pervious element is made of silicon material; the second light-pervious element comprises a lens disposed thereon, or a lens contour; and the first light-pervious packaging material and second light-pervious packaging material are separately made of silica gel or epoxy resin, and the first light-pervious packaging material or the second light-pervious packaging material further comprise a fluorescent material. 
         [0013]    In view of the above, in the LED package structure of the present invention and the method of fabricating the same, the first light-pervious element is first disposed in the cavity of the package unit, and then the multi-layered dam structure is concentrically disposed on the first light-pervious element and/or a rim of the cavity; subsequently, an excess amount of the first light-pervious packaging material is filled in the first containing space of the dam structure, and then surplus of the first light-pervious packaging material is squeezed into the second containing space of the dam structure while the second light-pervious element combines with the dam structure, thereby filling up the first containing space with the first light-pervious packaging material for eliminating gap, and further avoiding uneven thickness of the first light-pervious packaging material due to gap as in the prior technique, consequently maintaining high illumination efficiency, also enabling the second light-pervious element to tightly integrate with the dam structure and providing enhanced airtightness. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]    The invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein: 
           [0015]      FIG. 1  is a sectional view diagram showing an LED of US Patent Application Publication Number 2010/0163898; 
           [0016]      FIGS. 2A through 2E  are sectional view diagrams depicting an LED package structure and a method of fabricating the same of a first embodiment according to the present invention, wherein FIG.  2 A′ is another embodiment of  2 A, FIG.  2 E′ is another embodiment of  FIG. 2E , and FIG.  2 E″ shows a second light transmitting element with a lens contour; 
           [0017]      FIGS. 3A through 3C  are sectional view diagrams of an LED package structure and a method of fabricating the same of a second embodiment according to the present invention, wherein FIG.  3 C′ is another embodiment of  3 C; and 
           [0018]    FIGS.  4 A through  4 C′ are sectional view diagrams depicting an LED package structure and a method of fabricating the same of a third embodiment according to the present invention, wherein FIG.  4 C′ is another embodiment of  FIG. 4C . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0019]    The following illustrative embodiments are provided to illustrate the disclosure of the present invention; those in the art can apparently understand these and other advantages and effects after reading the disclosure of this specification. The present invention can also be performed or applied by other different embodiments. The details of the specification may be on the basis of different points and applications, and numerous modifications and variations can be devised without departing from the spirit of the present invention. 
       First Embodiment 
       [0020]    Please refer to FIGS.  2 A through  2 E″, which illustrate a method of fabricating an LED package structure of the first embodiment according to the present invention. 
         [0021]    As shown in FIGS.  2 A and  2 A′, first, a package unit  20  is provided that comprises a submount  21  with a cavity  210 , leads  22  disposed in the cavity  210  and extending to a region outside of the submount  21 , a light emitting chip (or light emitting chips)  23  mounted on a bottom of the cavity  210 , conductive elements  231  that are electrically connected to the light emitting chip  23  and the leads  22 , and a second light-pervious packaging material  24  that is filled in the cavity  210  to encapsulate the leads  22 , the light emitting chip  23 , and the conductive elements  231 . In an embodiment of the present invention, the conductive elements  231  are bonding wires, and the light emitting chips  23  may also be electrically connected to the leads  22  by means of flip chip via bumps. Alternatively, as the package unit  20 ′ shown in FIG.  2 A′, the leads  22  may be replaced with conductive pillars  22 ′ disposed in the cavity  210 , wherein the second light-pervious packaging material  24  also encapsulates the conductive pillars  22 ′, the light emitting chip  23 , and the conductive elements  231 . The package unit  20  shown  FIG. 2A  is described as follows. 
         [0022]    As shown in  FIG. 2B , a first light-pervious element  25  of a silicon material is embedded in the cavity  210 , and the silicon material may be glass. 
         [0023]    As shown in  FIG. 2C , a dam structure  26  is formed around a rim of the first light-pervious element  25  by means of printing, and the dam structure  26  comprises an inner dam  261 , an outer dam  262  concentrically disposed with the inner dam  261 , a first containing space  26   a  formed in the inner dam  261 , and a second containing space  26   b  formed between the inner dam  261  and the outer dam  262 . In an embodiment of the present invention, the first containing space  26   a  has a flat area larger than or equal to a light illumination area of the light emitting chips  23 , and the dam structure  26  is made of UV glue, B-stage epoxy resin, or glass fit. In addition to the printing means, the dam structure  26  may be formed by means of dispensing or covering a dry film and patterning the dry film. 
         [0024]    As shown in  FIG. 2D , the first containing space  26   a  is filled up with a first light-pervious packaging material  27 . In an embodiment of the present invention, the first light-pervious packaging material  27  is larger in volume than the first containing space  26   a . Hence, the first light-pervious packaging material  27  is taller than a top rim of the dam structure  26  due to substance surface tension. 
         [0025]    Please refer to FIGS.  2 E and  2 E′, a second light-pervious element  28  made of, e.g., silicon material (can be glass) is combined with the dam structure  26 , and a portion of the first light-pervious packaging material  27  is squeezed into the second containing space  26   b , thereby enabling the first light-pervious packaging material  27  to fill up the first containing space  26   a  and avoiding uneven thickness of the first light-pervious packaging material  27 , as shown in  FIG. 2E . As shown in FIG.  2 E′, a lens contour  280   a  is further included on a surface of the second light-pervious element  28  that opposes to another surface of the second light-pervious element  28  that is in contact with the first light-pervious packaging material  27 . 
         [0026]    In an embodiment of the present invention, the first light-pervious packaging material  27  and the second light-pervious packaging material  24  are made of silica gel or epoxy resin, the first light-pervious packaging material  27  or the second light-pervious packaging material  24  may further comprise a fluorescent material. 
       Second Embodiment 
       [0027]    Please refer to  FIGS. 3A through 3C , which illustrate a method of fabricating an LED package structure of the second embodiment according to the present invention. The second embodiment differs from the first embodiment in the means of fabricating the dam structure. 
         [0028]    As shown in  FIG. 3A , a structure the same as that shown in FIG.  2 A′ is provided. Then, a first light-pervious element  25  is provided to seal the cavity  210 , and a dam structure  26  is disposed around a rim of the cavity  210 . 
         [0029]    As shown in  FIG. 3B , a first containing space  26   a  is filled with a first light-pervious packaging material  27 , and the first light-pervious packaging material  27  is larger in volume than the first containing space  26   a.    
         [0030]    Please refer to FIGS.  3 C and  3 C′. A second light-pervious element  28  is combined with the dam structure  26 , and the surplus of the first light-pervious packaging material  27  is squeezed into the second containing space  26   b , as shown in  FIG. 3C . The second light-pervious element  28  may further comprise a lens  280 , as shown in FIG.  3 C′. Similarly, the second light-pervious element  28  may further comprise a lens contour (not shown) on a surface opposing to another surface that is in contact with the first light-pervious packaging material  27 . 
       Third Embodiment 
       [0031]    Please refer to FIGS.  4 A through  4 C′, which illustrate a method of fabricating an LED package structure of the third embodiment according to the present invention. The third embodiment differs from the first and second embodiment in the means of fabricating the dam structure. 
         [0032]    As shown in  FIG. 4A , a structure the same as that shown in FIG.  2 A′ is provided. Then, a first light-pervious element  25  is provided to seal the cavity  210 . Subsequently, an inner dam  261  is disposed on the first light-pervious element  25 , and the outer dam  262  is disposed on a rim of the cavity  210 . In an embodiment of the present invention, a first containing space  26   a  is formed in the inner dam  261 , and a second containing space  26   b  is formed between the inner dam  261  and the outer dam  262 . 
         [0033]    As shown in  FIG. 4B , the first containing space  26   a  is filled with a first light-pervious packaging material  27 , and the first light-pervious packaging material  27  is larger in volume than the first containing space  26   a.    
         [0034]    As shown in FIGS.  4 C and  4 C′, a second light-pervious element  28  is combined with the dam structure  26 , and the surplus of the first light-pervious packaging material  27  is squeezed into the second containing space  26   b , as shown in  FIG. 4C . A lens  280  may be further disposed on the second light-pervious element  28 , as shown in FIG.  4 C′. Similarly, the second light-pervious element  28  may further comprise a lens contour (not shown) on another surface opposing to the surface that is in contact with the first light-pervious packaging material  27 . 
         [0035]    According to the method, the present invention further provide an LED package structure, comprising: a package unit  20 ,  20 ′, a first light-pervious element  25 , a dam structure  26 , a first light-pervious packaging material  27 , and a second light-pervious element  28 . 
         [0036]    The package unit  20  comprises a submount  21  with a cavity  210 , leads  22  disposed in the cavity  210  and extending to a region outside of the submount  21 , a light emitting chip (or light emitting chips)  23  mounted in the cavity  210 , conductive elements  231  electrically connected to the light emitting chips  23  and the leads  22 , and a second light-pervious material  24  filled in the cavity  210 . In an embodiment of the present invention, the leads  22  functioning as an electrical connecting path may be replaced with conductive pillars  22 ′ disposed in the cavity  210 , wherein the second light-pervious packaging material also encapsulates the leads  22  (or conductive pillars  22 ′), the light emitting chip  23 , and the conductive elements  231 . 
         [0037]    The first light-pervious element  25  is made of a silicon material and disposed to seal the cavity  210 . 
         [0038]    The dam structure  26 , which comprises an inner dam  261  and an outer dam  262 , is disposed concentrically on the first light-pervious element  25  or on a rim of the cavity  210 . In an embodiment of the present invention, the inner dam  261  is disposed on the first light-pervious element  25 , while the outer dam  262  is disposed on a rim of the cavity  210 . A first containing space  26   a  may be disposed in the inner dam  261 , and a second containing space  26   b  may be formed between the inner dam  261  and the outer dam  262 . The dam structure  26  may be made of dry film, UV glue, B-stage epoxy resin, or glass frit. 
         [0039]    The first containing space  26   a  is completely filled by the first light-pervious packaging material  27 , and the second containing space  26   b  is filled with a portion of the first light-pervious packaging material  27 . 
         [0040]    The second light-pervious element  28  is made of silicon material, and combines with the dam structure  26 . The LED package structure may further comprise a lens  280  disposed on the second light-pervious element  28 . 
         [0041]    In view of the above, according to the LED package structure and the method of fabricating the same according to the present invention, the first light-pervious element is disposed to seal the cavity of the package unit; the dam structure comprising the inner dam and the outer dam is concentrically disposed on the first light-pervious element and/or a rim of the cavity; and the first containing space of the dam structure is filled with excess amount of first light-pervious packaging material, thereby allowing the surplus of the first light-pervious packaging material to be squeezed into the second containing space of the dam structure while combining the second light-pervious element with the dam structure. Consequently, the first containing space is filled with the first light-pervious packaging material without leaving a gap, thereby avoiding the problem of uneven thickness of the first light-pervious packaging material caused by existing gap as happened in prior technique, consequently maintaining high illumination efficiency. 
         [0042]    Furthermore, the multi-layered dam structure having the inner dam and the outer dam, providing a better means for tightly integrating the second light-pervious element with the dam structure. 
         [0043]    The invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.