Abstract:
A method of fabricating an optical device is disclosed. The method comprises the step of forming an optical stack of laminated lenses and a phosphor film therebetween. The method further comprises the step of attaching the optical stack to an LED die. In addition, an optical device fabricated by the above method is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an optical device, and in particular relates to an optical device in which the LED die is not directly connected to the phosphor material. 
         [0003]    2. Description of the Related Art 
         [0004]    In conventional skills, several methods for packing an optical device such as a high power chip are as following. 
         [0005]    Referring to  FIG. 1   a , a conventional optical device includes a reflector cup  10 , an LED die  12  on the reflector cup  10 , a phosphor powered layer  14  of different thicknesses covering at least the LED die  12 , epoxy  10  for attaching the LED die  12  to the reflector cup  10 , and glue  16  for packing the optical device. 
         [0006]    Referring to  FIG. 1   b , a conventional optical device includes a reflector cup  100 , a submount die  102  on the reflector cup  100 , an LED die  104  on the submount die  102 , a phosphor powered layer  106  of an uniform thickness covering at least the LED die  104 , epoxy  110  for attaching the LED die  104  to the reflector cup  100 , and glue  108  for packing the optical device. 
         [0007]    However, no matter how the profile of the phosphor powered layer is formed, light output efficiency degrades because the phosphor powered layer directly contacts the LED die. This severely affects performance of the optical device. 
         [0008]    Accordingly, an optical device capable of enhancing light output efficiency and fabrication methods thereof is desirable. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    In one embodiment, a method of fabricating an optical device is disclosed. The method comprises the step of forming an optical stack of laminated lenses and a phosphor film therebetween. The method further comprises the step of attaching the optical stack to an LED die. 
         [0010]    In another embodiment, an optical device is also disclosed. The optical device comprises an LED die on a base, an adhesive material covering the LED die, an optical stack of laminated lenses and a phosphor film therebetween. The optical stack is over the LED die and is attached thereto by means of the adhesive material. 
         [0011]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0013]      FIGS. 1A and 1B  are cross sections of a conventional optical device; and 
           [0014]      FIG. 2A˜2G  are cross sections of one embodiment for a method of fabricating an optical device. 
           [0015]      FIG. 3  is a schematic view showing the demolding process. 
           [0016]      FIG. 4  is a schematic view showing an optical stack array including a plurality of isolated optical stacks. 
           [0017]      FIG. 5  is a schematic view showing an optical device subject to a reliability test. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
         [0019]      FIG. 2A˜2G  are cross sections of one embodiment for a method of fabricating an optical device. 
         [0020]    As shown in  FIG. 2A , a mold  200  is provided. The mold  200 , for example, is made up of a metal material, a plastic material or a ceramic material. At the same time, another mold, such as the mold  210  shown in  FIG. 2F , can be prepared in the step. 
         [0021]    As shown in  FIG. 2B , an optical material is dispensed to the molds  200  and  210  in sequence, thus forming lenses  202  and  212  therein, respectively. The lenses  202  or  212  consist of a lens array, and the lenses  202  and  212  use transparent polymer materials. The step of dispensing an optical material to each mold to form lenses therein employs a mesh print process. It is noted that only the mold  200  possessing lenses  202  therein is shown here for purpose of simplicity. 
         [0022]    As shown in  FIG. 2C , the mold  200  possessing lenses  202  therein is then disposed on a tooling  204 . The tooling  204  may be made up of metal. 
         [0023]    As shown in  FIG. 2D , a phosphor film  206  is formed on a substrate  208 , and the processing continues to let the phosphor film  206  face the lens array of the mold  200  when attaching the substrate  208  thereto. As a result, the phosphor film  206  attaches to the lens array of the mold  200 . Attachment of the phosphor film  206  to the lens array of the mold  200  can be carried out using any suitable adhesive materials. 
         [0024]    Thereafter, as shown in  FIG. 2E , the substrate  208  is removed from the phosphor film  206 . Removal of the substrate  208  from the phosphor film  206  can use any suitable methods. The substrate  208  is made up of transparent materials. In other embodiments, the substrate  208  is not removed. 
         [0025]    As shown in  FIG. 2F , the mold  210  with the lenses  212  facing downward which can be prepared in previous steps is attached to the phosphor film  206  in a manner that each of the lenses  212  is opposite to each of the lenses  202 . Attachment of the mold  210  with the lenses  212  to the phosphor film  206  can be carried out using any suitable adhesive materials. 
         [0026]    As shown in  FIG. 2G , the processing continues to perform a demolding step so that the mold  210  is removed from the lenses  212  and the phosphor film  206 . 
         [0027]    Referring to  FIG. 3 , it depicts demolding step in which the molds  210  and  200  are peeled off, thus, a structure  2000  including a lot of connected optical stacks consisting of an upper lens  212 , a lower lens  202  and a phosphor film  206  therebetween is obtained. 
         [0028]    As shown in  FIG. 4 , various isolated optical stacks  2000   a  are obtained after a cutting step. Each optical stack can be utilized for packing of an optical device. 
         [0029]    As shown in  FIG. 5 , an optical stack consisting of an upper lens  212 , a lower lens  202  and a phosphor film  206  therebetween is attached to a base  500  with an LED die  502  thereon by means of an adhesive material  504  such as glue. In doing so, the phosphor film  206  dose not contact the LED die  502  so that emission efficiency of the LED die  502  won&#39;t degrade. 
         [0030]    Although the surfaces of the laminated lenses  202  and  212  not connected to the phosphor film  206  are shaped in convex, they can be shaped in concave or have other desirable shapes in other embodiments. 
         [0031]    While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.