Abstract:
A method of packaging light emitting diodes includes providing a wafer having a plurality of LEDs thereon, forming at least a sealant surrounding the LEDs, providing a glass substrate to cover the LEDs, the sealant, and the wafer, providing a UV hardening process to harden the sealant, forming a polarization film on the glass substrate, and dicing the wafer.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a method of packaging light emitting diodes (LEDs), and more particularly, to a method of packaging LEDs that generate polarizing lights. 
         [0003]    2. Description of the Prior Art 
         [0004]    Since the LED has the advantages of a long lifetime, a small size, a high resistance to earthquakes, and a low consumption of electric power, the LED is widely applied as a pilot lamp or a light source for various household appliances and instruments. Additionally, the LED has been developed toward producing colorful lights and high brightness in recent years, so that the LED is further applied in large-sized display signboards and traffic lights, and may substitute for tungsten lamps and mercury lamps to become a stream of illumination light sources with low power consumption and low contamination in the future. 
         [0005]    The traditional method of packaging semiconductor devices including LEDs comprises a lead type packaging method and a chip type packaging method. The lead type LED elements usually serve as pilot devices of various circuits or electronic instruments.  FIG. 1  is a schematic diagram of a lead type LED element  10  according to the prior art. The lead type LED element  10  comprises a LED  12 , a cup shape carrier  14 , a leading wire  16 , and a side leading wire  18 . According to a packaging process, the LED  12  is set to the hollow of the cup shape carrier  14 , and the cup shape carrier  14  is then filled up with a seal material  22  that can fix the LED  12  on the cup shape carrier  14 . Next, an N type electrode and a P type electrode (not shown) of the LED  12  are connected to the leading wire  16  and the side leading wire  18  through wires, respectively. Finally, a protecting unit  20  is used to cover the LED  12  and a portion of the leading wire  16  and the side leading wire  18 . 
         [0006]    Please refer to  FIG. 2 .  FIG. 2  is a schematic diagram of the chip type LED element  30  according to the prior art. The prior art chip type LED element  30  comprises a base seat  32  having two electrodes  40 ,  42 , and a LED  34  having an N type electrode  36  and a P type electrode  38  corresponding with the electrodes  40  and  42  respectively. In the process of fabricating the chip type LED element  30 , the LED  34  is glued on the base seat  32  with a silver glue (not shown). Then, a wire bonding process is performed to connect the N type electrode  36  and the P type electrode  38  of the LED  34  to the electrodes  40 ,  42  of the base seat  32  through two conductive wires  44 ,  46  individually. After the wire bonding process, a sealing process is performed by setting the whole LED element  30  in a mold (not shown), filling up the mold with epoxy resin or other similar materials, and taking the LED element  30  out of the mold after it hardens. Finally, the LEDs  34 , the base seat  32 , and all the electrodes and wires are covered in a plastic mold  48  that is composed of epoxy resin. 
         [0007]    Generally, LEDs are applied in LCD displays, projectors, and pilot lamps. The light sources of those appliances have to be polarized lights. Therefore, when a conventional LED is used to serve as a light source of the appliance, a polarization film has to be formed on the LED, or a polarization layer has to be formed on the surface of the LED after it is packaged for satisfying the standards of the light sources for those appliances. 
       SUMMARY OF INVENTION 
       [0008]    It is therefore an objective of the claimed invention to provide a method of packaging LEDs utilizing methods of packaging a liquid crystal on silicon (LCOS) displays or a contact image sensor (CIS) that can package the polarization layer together with LED elements to solve the above-mentioned problem, making another polarization film on LED appliances of the prior art. 
         [0009]    According to the claimed invention, the method of packaging light emitting diodes (LEDs) comprises providing a wafer having a plurality of LEDs thereon and forming at least a sealant surrounding the LEDs on the wafer. Then a glass substrate is provided for covering the LEDs, the sealant, and the wafer, and the sealant is exposed under an ultraviolet (UV) light to perform an ultraviolet curing process for hardening the sealant. Then, a polarization layer is formed on the glass substrate. Finally, the glass substrate and the wafer are diced to separate the LEDs and finish the process of packaging LEDs. 
         [0010]    The present invention utilizes methods of packaging LCOS or CIS to form LEDs on the semiconductor wafer directly and cover the LEDs by a glass substrate to form protection. Therefore the present invention does not need to utilize epoxy resin material to form the protection on the surface of the LEDs, and also does not need a cup shape carrier to separate each LED according to the method of packaging LEDs according to the prior art. Furthermore, according to the present invention, a polarization layer is formed on the surface of the glass substrate before packaging LEDs. As a result, the LED element serving as a light source in each appliance does not require another polarization board to be made after packaging. This effectively simplifies the process of fabricating LEDs for use as a light source in the appliances. 
         [0011]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a schematic diagram of a lead type LED element according to the prior art. 
           [0013]      FIG. 2  is a schematic diagram of a chip type LED element according to the prior art. 
           [0014]      FIG. 3  to  FIG. 6  are schematic diagrams of a method of packaging LEDs according to the present invention. 
           [0015]      FIG. 7  is a schematic diagram of another embodiment of a method of packaging LEDs according to the present invention. 
           [0016]      FIG. 8  is a flow chart of a method of packaging LEDs according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Please refer to  FIG. 3  to  FIG. 6 , which are schematic diagrams of a method of packaging LEDs according to the present invention. As shown in  FIG. 3 , a plurality of LEDs  52  and corresponding wires are formed on a surface of the substrate  50  that is a semiconductor wafer, a glass substrate, or a quartz substrate. And referring to  FIG. 4 , a plurality of sealants  54 , having individual seal pattern, are formed on the surface of the substrate  50  to surround the LEDs  52 , respectively. Then, a transparent substrate  56 , a glass substrate or a quartz substrate used for packaging LCOS is laminated on the substrate  50  and covers the LEDs  52  and the sealant  54  to perform a lamination process. The sealant  54  is then exposed under an ultraviolet (UV) light for hardening the sealant  54 , so that the transparent substrate  56  is fixed on the substrate  50 . 
         [0018]    Please refer to  FIG. 5 , a polarization layer  58  is formed on the surface of a transparent substrate  56  by a deposition method, or a polarization film is glued on the transparent substrate  56  to form the polarization layer  58 . As shown in  FIG. 6 , the substrate  50 , the transparent substrate  56 , and the polarization layer  58  are cut together along the seal patterns of the sealants surrounding each of the LEDs  52  to separate each LED  52  so as to form a plurality of LED dies and finish the process of packaging the LEDs. 
         [0019]    In the present embodiment, the LEDs  52  are discretely set on the surface of the substrate  50 . And each of the sealants  54  surrounds each of the LEDs  52 , so a diced LED die  60  only comprises a single LED  52 . And the diced LED die  60  can be directly set in various circuits or electronic instruments such as pilot lamps, just like the conventional lead type LEDs. 
         [0020]    Please refer to  FIG. 7 .  FIG. 7  is a schematic diagram of another embodiment according to the present invention. In the present embodiment, a diced LED element  70  comprises a quartz substrate  72 , a glass substrate  74  opposite to the quartz substrate  72 , a plurality of LEDs  76  and corresponding wires positioned on the surface of the quartz substrate  72 , and a sealant  78  surrounding the LEDs  76 , which fix the glass substrate  74  on the quartz substrate  72 . The LED element  70  further comprises a polarization layer  80  set on the surface of the glass substrate  74 . It should be noted that the LED element  70  comprises a plurality of LEDs  76  that are arranged in an array. Therefore, the LED element  70  can be directly applied to an appliance, such as a LCD, that needs a planar light source. On the other hand, the quartz substrate  72  has a characteristic of being pervious to light, so that the present invention comprises forming a polarization layer  82  on the surface of the quartz substrate  72  before cutting the glass substrate  74  and the quartz substrate  72 , and cutting the polarization layer  82  together with the quartz substrate  72 . As a result, the LEDs device  72  can be applied to an appliance which needs a double-sided light source. 
         [0021]    Taken together, please refer to  FIG. 8 .  FIG. 8  is flow chart of the method of packaging LEDs according to the present invention. The present invention comprises the following steps: 
         [0022]    Step  102 : Provide a wafer and form a plurality of LEDs and corresponding wires on the surface of the wafer. 
         [0023]    Step  104 : Form at least a sealant on the wafer surface, the sealant having a seal pattern surrounding the LEDs. 
         [0024]    Step  106 : Perform a lamination process to make a transparent substrate cover the wafer, the LEDs, and the sealant. 
         [0025]    Step  108 : Expose the sealant under an ultraviolet (UV) light to harden the sealant and fix the transparent substrate on the wafer. 
         [0026]    Step  110 : Form a polarization layer on the transparent substrate. 
         [0027]    Step  112 : Dice the wafer along the seal pattern of the sealant that surrounds each of the LEDs so as to form a plurality of LED dies. 
         [0028]    In contrast to the prior art, the present invention utilizes packaging technology of LCOS or CIS to perform the method of packaging LEDs. The present invention utilizes a glass to cover the LEDs, and to set a space for setting the LEDs with a wafer and sealant that does not need to form the base seats or plastic molds of the prior art surrounding the LEDs. So the LED packaging technology of the present invention represents breakthrough advancement. In addition, according to the present invention, a polarization layer is optically formed on the surface of the transparent substrate, and the polarization layer is cut together with LEDs to make the LEDs device produce polarized lights after packaging. This LED meets the demands of polarizing light sources of general appliances. As a result, the packaged LED elements can be directly set on each appliance according to the present invention and further simplify assembly and the manufacturing process, along with lowering the manufacturing cost of each appliance. 
         [0029]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.