Abstract:
A package having a light-emitting element includes a substrate having a light-emitting element disposed thereon, an insulating layer formed on the substrate and having an opening for exposing the light-emitting element, a florescent layer formed in the opening of the insulating layer for encapsulating the light-emitting element, and a transparent material formed on the florescent layer and the insulating layer. As such, a specific space can be defined by the insulating layer for exposing the light-emitting element and forming the fluorescent layer, thereby overcoming the problem of non-uniform coating of phosphor powder as encountered in prior techniques.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims under 35 U.S.C. §119(a) the benefit of Taiwanese Application No. 100112424, filed Apr. 11, 2011, the entire contents of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to semiconductor packages, and more particularly, to a package having a light-emitting element and a fabrication method thereof. 
     2. Description of Related Art 
     Along with the development of semiconductor technologies, various semiconductor packages have appeared. Fabrication of a light-emitting diode (LED) package involves frame design (including light extraction and heat dissipation), chip selection and arrangement, chip bonding, gold wire formation, phosphor coating, silicone lens disposing and so on. These fabrication processes greatly affect the characteristics of the LED package such as thermal performance (thermal resistance), luminous flux, light-emitting efficiency, correlated color temperature (CCT), color rendering index (CRI), light color uniformity, lifetime and so on. 
     Generally, the phosphor coating process plays a key role in achieving high light color uniformity and high luminous flux. Referring to  FIG. 1A , a fluorescent layer  14  is conventionally formed by uniformly distributing a phosphor powder in an encapsulant through dispensing. However, under long-term use, particles  140  of the fluorescent layer  14  can be non-uniformly distributed due to deposition. As such, light from the LED chip  11  takes different paths and portions of the fluorescent powder distant from the LED chip  11  reflect light, thus resulting in non-uniform light color distribution and making it difficult to meet user demands. 
     Accordingly, other coating techniques are developed, such as a conformal coating method of  FIG. 1B , a thin film attaching method of  FIG. 1C  or a spray coating method of  FIG. 1D . 
     However, in  FIG. 1B , an electrophoresis process needs to be performed for coating the fluorescent layer  14  on the LED chip  11 . Such an electrophoresis process requires specific devices, thus resulting in a high fabrication cost. 
     Further, in  FIG. 1C , a thin film  14 ′ of phosphor powder is attached to a transparent material  15  around the LED chip  11  so as to be positioned distant from the LED chip  11  that dissipates a large amount of heat. However, as the transparent material  15  has a low refractive index (a resin material has a refractive index of 1.54 and the phosphor powder has a refractive index of 1.8), it results in a low light-emitting efficiency of the LED chip  11 . 
     Furthermore, the spray-coating method of  FIG. 1D  can only be applicable to a COB (chip on board) type LED package instead of an LED package with the substrate thereof having a recess. If a spray coating process is performed to a substrate  10  having a recess  100 , particles  140  (phosphor powder) of the fluorescent layer  14  can be sprayed onto a reflective layer  16  on inclined surfaces of the recess  100 , thus reducing the reflective area of the reflective layer  16  and accordingly decreasing the light-emitting efficiency of the LED chip  11 . 
     Therefore, there is a need to provide a fabrication method of a package having a light-emitting element so as to overcome the above-described drawbacks. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a fabrication method of a package having a light-emitting element, which comprises the steps of: providing a substrate having at least a light-emitting element disposed thereon; forming an insulating layer on the substrate, wherein the insulating layer has an opening for exposing the light-emitting element; forming a fluorescent layer in the opening of the insulating layer for encapsulating the light-emitting element; and forming a transparent material on the fluorescent layer and the insulating layer. 
     In another embodiment of the fabrication method of the present invention, the substrate has a recess for the light-emitting element to be disposed therein. The insulating layer can be formed on the substrate and in the recess and have an opening for exposing the light-emitting element and portions of the recess. 
     The formation of the insulating layer can comprise: forming a resist layer on the substrate, in the recess and on the light-emitting element, wherein the resist layer has open areas for exposing portions of the substrate and the recess; forming the insulating layer on the portions of the substrate and the recess exposed from the open areas; and removing the resist layer for exposing the light-emitting element and portions of the recess. 
     In the above-described fabrication methods, the light-emitting element can be a light-emitting diode (LED). The insulating layer can be made of one of the group consisting of silicone gel, silicone resin and epoxy resin. The transparent material can be made of one of the group consisting of silicone gel, silicone resin and epoxy resin. The fluorescent layer can be made of phosphor powder or phosphor powder mixed with a polymer glue material. 
     According to the present invention, the insulating layer is patterned to form an opening therein such that the light-emitting element can be exposed from the opening and a fluorescent layer can further be formed in the opening for encapsulating the light-emitting element, thereby overcoming non-uniform coating of phosphor powder as encountered in the prior art and maintaining a preferred light-emitting efficiency. 
     Further, through the patterning process of the insulating layer, the fluorescent layer can be easily formed with a reduced fabrication cost. Furthermore, the thickness of the fluorescent layer is easy to control so as to provide a preferred light-emitting efficiency and maintain uniform distribution of light color due to uniform thickness of the fluorescent layer. 
     The fabrication methods of the present invention can be applied to various kinds of substrates. 
     In addition, the present invention provides a package having a light-emitting element, which comprises: a substrate; at least a light-emitting element disposed on the substrate; an insulating layer formed on the substrate and having an opening for exposing the light-emitting element; a fluorescent layer formed in the opening of the insulating layer for encapsulating the light-emitting element; and a transparent material formed on the fluorescent layer and the insulating layer. 
     In another embodiment of the package of the present invention, the substrate has a recess so as for the light-emitting element to be disposed therein. The insulating layer is formed on the substrate and in the recess and has an opening for exposing the light-emitting element. 
     In the above-described packages, the light-emitting element can be a light-emitting diode (LED). The insulating layer can be made of one of the group consisting of silicone gel, silicone resin and epoxy resin. The transparent material can be made of one of the group consisting of silicone gel, silicone resin and epoxy resin. The fluorescent layer can be made of phosphor powder or phosphor powder mixed with a polymer glue material. 
     Therefore, by defining a specific space in the insulating layer for exposing the light-emitting element and encapsulating the light-emitting element with a fluorescent layer, the present invention overcomes non-uniform coating of phosphor powder as encountered in the prior art and eliminates the need of expensive devices for controlling the thickness of the fluorescent layer. Furthermore, through the insulating layer, the present invention can easily control the thickness of the fluorescent layer so as to provide a preferred light-emitting efficiency and maintain uniform distribution of light color due to uniform thickness of the fluorescent layer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A to 1D  are schematic cross-sectional views showing different embodiments of conventional LED packages; 
         FIGS. 2A to 2F  are schematic cross-sectional views showing a fabrication method of a package having a light-emitting element according to the present invention; and 
         FIGS. 3A to 3F  are schematic cross-sectional views showing a fabrication method of a package having a light-emitting element according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparent to those in the art after reading this specification. 
     It should be noted that all the drawings are not intended to limit the present invention. Various modification and variations can be made without departing from the spirit of the present invention. Further, terms such as “one”, “above”, etc. are merely for illustrative purpose and should not be construed to limit the scope of the present invention. 
       FIGS. 2A to 2F  show a fabrication method of a package having light-emitting elements according to the present invention. 
     Referring to  FIG. 2A , a substrate  10  is provided, which has a plurality of light-emitting elements such as LED chips  21  disposed thereon and electrically connected to the substrate  20  (not shown). 
     Referring to  FIG. 2B , a resist layer  22  is formed on the substrate  20  and the LED chips  21  and a plurality of open areas  220  are formed in the resist layer  22  by patterning so as to expose portions of the substrate  20 . The resist layer  22  can be a photoresist layer or a dry film. 
     Referring to  FIG. 2C , an insulating layer  23  is formed on the portions of the substrate  20  exposed through the open areas  220 . In the present embodiment, the insulating layer  24  is made of one of the group consisting of silicone gel, silicone resin and epoxy resin, but is not limited thereto. 
     Referring to  FIG. 2D , the resist layer  22  is removed so as to form openings in the insulating layer  23  for exposing the LED chips  21  and portions of the substrate  20  previously covered by the resist layer  22 . 
     Referring to  FIG. 2E , a fluorescent layer  24  is formed in the openings of the insulating layer  23  on the exposed LED chips  21  and the exposed portions of the substrate  20  through a dispensing process or a spray coating process to thereby encapsulate the LED chips  21 . The fluorescent layer  24  is made of a light conversion material, such as a phosphor powder or a phosphor powder mixed with a polymer glue material. 
     Referring to  FIG. 2F , a transparent material  25  is formed on the fluorescent layer  24  and the insulating layer  23  so as to form an LED package  2 . Therein, the transparent material  25  can be one of the group consisting of silicone gel, silicone resin and epoxy resin, and have a refractive index between 1.2 and 2.5. Generally, the transparent material  25  is also referred to as a lens. 
     The LED package  2  has a substrate  20  with LED chips  21  disposed thereon, an insulating layer  23  formed on the substrate  20  and having openings for exposing the LED chips  21 , respectively, a fluorescent layer  24  formed in the openings of the insulating layer  23  for encapsulating the LED chips  21 , and a transparent material  25  formed on the fluorescent layer  24  and the insulating layer  23 . 
     Through a general patterning process (such as exposure and development of a photoresist layer) and a phosphor powder coating process, the LED chips  21  are exposed through the openings of the insulating layer  23  and encapsulated by the fluorescent layer  24 , thereby reducing the fabrication cost and overcoming the conventional drawback of non-uniform coating of phosphor powder. 
       FIGS. 3A to 3F  show another fabrication method of a package having light-emitting elements according to the present invention. The present embodiment is similar to the above-described embodiment. An only difference therebetween is the substrate structure. 
     Referring to  FIG. 3A , a substrate  20 ′ having a plurality of recesses  200  is provided. Each of the recesses  200  has a bottom surface  200   a , and two side inclined surfaces  200   b  having a reflective layer  26  disposed thereon. A plurality of LED chips  21  are disposed on the bottom surfaces  200   a  of the recesses  200 , respectively, and electrically connected to the substrate  20 ′ (not shown). 
     Referring to  FIG. 3B , a resist layer  22  is formed on the substrate  20 ′, in the recesses  200  and on the LED chips  21 , and a plurality of open areas  220  are formed in the resist layer  22  to expose portions of the substrate  20 ′ and the surfaces of the recesses  200 , for example, the reflective layer  26  of the recesses  200 . 
     Referring to  FIG. 3C , an insulating layer  23  is formed on the portions of the substrate  20  and the surfaces of the recesses  200  exposed from the open areas  220  (that is, the exposed reflective layer  26 ). 
     Referring to  FIG. 3D , the resist layer  22  is removed so as to form openings in the insulating layer  23  for exposing the LED chips  21  and portions of the recesses  200  previously covered by the resist layer  22 , i.e. the bottom surfaces  200   a  of the recesses  200 . 
     Referring to  FIG. 3E , a fluorescent layer  24  is formed in the openings of the insulating layer  23  on the exposed LED chips  21  and the bottom surfaces  200   a  of the recesses  200  through a dispensing process or a spray coating process to thereby encapsulate the LED chips  21 . 
     During the spray coating process of the fluorescent layer, since the inclined surfaces  200   b  of the recesses  200  are covered by the insulating layer  23 , particles of the fluorescent layer  24  cannot be sprayed onto the inclined surfaces  200   b , thereby avoiding reduction of the reflective area of the reflective layer  26  and improving the light-emitting efficiency of the LED chips  21 . 
     Referring to  FIG. 3F , a transparent material  25  is formed on the fluorescent layer  24  and the insulating layer  23  so as to form another LED package  2 ′. 
     The LED package  2 ′ has a substrate  20 ′ having a plurality of recesses  200  each having an LED chip  21  disposed therein, an insulating layer  23  formed on the substrate  20  and in the recesses  200  and having openings for exposing the LED chips  21 , respectively, a fluorescent layer  24  formed in the openings of the insulating layer  23  for encapsulating the LED chips  21 , and a transparent material  25  formed on the fluorescent layer  24  and the insulating layer  23 . 
     Therefore, by using several general processes in combination, the present invention avoids the use of expensive devices required in the prior art, thereby effectively reducing the fabrication cost. 
     Further, through a patterning process, the present invention can easily control the thickness of the fluorescent layer so as to provide a preferred light-emitting efficiency and maintain uniform distribution of light color due to uniform thickness of the fluorescent layer. 
     The above-described descriptions of the detailed embodiments are only to illustrate the preferred implementation according to the present invention, and it is not to limit the scope of the present invention. Accordingly, all modifications and variations completed by those with ordinary skill in the art should fall within the scope of present invention defined by the appended claims.