Abstract:
There is provided a method of manufacturing a light emitting diode chip, the method including: providing a light emitting diode chip; forming a phosphor layer on a top of the light emitting diode chip; and forming phosphors of a lattice structure on the phosphor layer by an inkjet process using an ink containing phosphor powder. There is also provided A method of manufacturing a light emitting diode package, the method including: forming a phosphor layer with a predetermined thickness; forming phosphors of a lattice structure on the phosphor layer by an ink jet process using an ink containing phosphor powder; and disposing the phosphor layer having the phosphors of the lattice structure formed thereon on a top of the light emitting diode chip.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 2007-24368 filed on Mar. 13, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of manufacturing a light emitting diode (LED) package, more particularly, which allows phosphors of a lattice structure to be formed on a phosphor layer disposed on a light emitting surface of an LED chip of the LED package using an ink jet process, thereby increasing light emitting efficiency of the LED package and simplifying a manufacturing method thereof. 
         [0004]    2. Description of the Related Art 
         [0005]    A light emitting diode (LED) utilizes a phenomenon in which with a forward voltage applied to electrodes, electrons of a conduction band emit light equivalent to an energy required when transiting to recombine with holes of a valence band. The LED has various advantages over a conventional bulb to be extensively applied to electric and electronic products. That is, the LED is smaller-sized and lighter-weight, less heat-radiating, long in useful life and high in response rate. 
         [0006]    Recently, studies have been under way to increase light emitting efficiency of an LED device. One method is to form a structure or a pattern having a predetermined period on a surface of a phosphor in order to enhance light emitting efficiency of the LED device. 
         [0007]    That is, to form the phosphor in the LED device, mainly phosphor powder is formed into a slurry or paste to be applied on a flat surface. Here, an irradiated excited light source and light generated by subsequent excitation of the phosphor may be scattered or lost due to the phosphor powder, thereby degrading light emitting efficiency and brightness. 
         [0008]    To overcome this problem, there have been efforts to increase light emitting efficiency by forming a lattice structure on the phosphor. 
         [0009]      FIG. 1  is a cross-sectional view illustrating a conventional LED package disclosed in Korean Patent Publication No. 2006-0055934. 
         [0010]    Referring to  FIG. 1 , the LED package includes an LED  11 , a housing  14  for housing the LED chip therein and an amplifying plate  12  sealing the LED chip. 
         [0011]    Reflective plates  14   a  are formed inside the housing  14  to reflect light from the LED chip  11 , and the LED chip  11  is bonded to the housing by wires  18 . Also, microstructures  13  are formed on one surface of the amplifying plate  12 . The microstructures scatter light emitted from the LED chip to be amplified and emitted. Here, the pitch of the microstructures, depth of furrows and shapes may be varied to ensure light to be maximally refracted through the amplifying plate and thus to be maximally radiated forward. 
         [0012]    To form the lattice structure, for example, a photo-sensitive polymer is applied on the phosphor body and then an UV is irradiated to cure a predetermined lattice structure. Then a remaining area other than the lattice structure is etched to form a three-dimensional lattice structure. Alternatively, a photolithography may be employed to form the thin film-shaped phosphor of the lattice structure. 
         [0013]    However, when it comes to etching, it is hard to form a periodically uniform lattice structure due to problems associated with light control and resolution. Also, when the thin film-shaped phosphor is formed via photolithography, light generated inside the phosphor is trapped due to total reflection, thereby deteriorating light emitting efficiency. 
       SUMMARY OF THE INVENTION 
       [0014]    An aspect of the present invention provides a method of forming a lattice structure on a phosphor layer by an ink jet process, thereby simplifying a manufacturing process and ensuring a periodically uniform and precise lattice structure. 
         [0015]    An aspect of the present invention also provides a method of forming a lattice structure directly on a phosphor layer sheet to improve mass-producibiltiy. 
         [0016]    According to an aspect of the present invention, there is provided a method of manufacturing a light emitting diode chip, the method including: providing a light emitting diode chip; forming a phosphor layer on a top of the light emitting diode chip; and forming phosphors of a lattice structure on the phosphor layer by an inkjet process using an ink containing phosphor powder. 
         [0017]    The phosphor layer may be attached on the top of the light emitting diode chip, wherein the method may further include: mounting the light emitting diode chip having the phosphor layer attached on the top thereof in a housing; and molding an inner portion of the package housing with a transparent resin. 
         [0018]    The providing a light emitting diode chip may include: mounting the light emitting diode chip in the package housing; and molding an inner portion of the package housing with a transparent resin, wherein the phosphor layer is formed on a top of the transparent resin. 
         [0019]    The phosphors of the lattice structure may be arranged in a plurality of dots. The phosphors of the lattice structure may have a refractivity greater than a refractivity of the phosphor layer. 
         [0020]    According to another aspect of the present invention, there is provided a method of manufacturing a light emitting diode package, the method including: forming a phosphor layer with a predetermined thickness; forming phosphors of a lattice structure on the phosphor layer by an ink jet process using an ink containing phosphor powder; and disposing the phosphor layer having the phosphors of the lattice structure formed thereon on a top of the light emitting diode chip. 
         [0021]    The disposing the phosphor layer may include: attaching the phosphor layer having the phosphors of the lattice structure formed thereon on the top of the light emitting diode chip; mounting the light emitting diode chip having the phosphor layer attached thereon in a package housing; and molding an inner portion of the package housing with a transparent resin. 
         [0022]    The disposing the phosphor layer may include: mounting the light emitting diode chip in the package housing; molding an inner portion of the package housing with a transparent resin; and attaching the phosphor layer having the phosphors of the lattice structure formed thereon on a top of the transparent resin. 
         [0023]    The phosphors of the lattice structure may be formed on a sheet of the phosphor layer, wherein the method may further include: cutting the sheet of the phosphor layer having the phosphors of the lattice structure into unit chips before the disposing the phosphor layer having the phosphors of the lattice structure formed thereon. 
         [0024]    The phosphors of the lattice structure may be arranged in a plurality of dots. The phosphors of the lattice structure may have a refractivity greater than a refractivity of the phosphor layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0025]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0026]      FIG. 1  is a cross-sectional view illustrating a conventional light emitting diode package; 
           [0027]      FIGS. 2A to 2E  are a flow chart illustrating a method of manufacturing a light emitting diode package according to an exemplary embodiment of the invention; 
           [0028]      FIGS. 3A to 3D  are a flow chart illustrating a method of manufacturing a light emitting diode package according to another exemplary embodiment of the invention; 
           [0029]      FIG. 4A  is a cross-sectional view and  FIG. 4B  is a perspective view illustrating a method of forming a phosphor of a lattice structure on a phosphor layer by an ink jet process, respectively according to an exemplary embodiment of the invention; 
           [0030]      FIGS. 5A to 5C  are a flow chart illustrating a method of forming a phosphor layer having a phosphor of a lattice structure thereon according to another embodiment of the invention; 
           [0031]      FIGS. 6A to 6C  are a flow chart illustrating a method of manufacturing an LED package according to an exemplary embodiment of the invention, which adopts a phosphor layer having a phosphor of a lattice structure formed thereon by the method shown in  FIG. 5 ; and 
           [0032]      FIGS. 7A to 7C  are a flow chart illustrating a method of manufacturing an LED package according to another exemplary embodiment of the invention, which adopts a phosphor layer having a phosphor of a lattice structure formed thereon by the method shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]    Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0034]      FIG. 2  is a flow chart illustrating a method of manufacturing a light emitting diode (LED) package according to an exemplary embodiment of the invention. 
         [0035]    As shown in  FIG. 2A , first, an LED chip  21  is provided. 
         [0036]    The present embodiment employs an LED chip cut into unit chips at a wafer level. 
         [0037]    As shown in  FIG. 2B , a phosphor layer  22  is formed on the LED chip  21 . 
         [0038]    The phosphor layer  22  may be formed by applying a paste having dispersible phosphor powder of nano particles mixed in a transparent polymer resin on the LED chip  21  and curing the paste. The transparent polymer resin may utilize a curable resin or an acrylic resin. Particularly, the transparent polymer may adopt an epoxy polymer resin or a silicon polymer resin. 
         [0039]    As shown in  FIG. 2C , phosphors  23  of a lattice structure are formed on the phosphor layer  22 . 
         [0040]    In the present embodiment, the lattice-structured phosphors  23  are formed by an ink jet process. The lattice-structured phosphors define protrusions on the phosphor layer  22 , thereby forming microstructures on the phosphor layer  22 . 
         [0041]    In the present embodiment, a plurality of dots  23  protruded from the phosphor layer  22  define the lattice structure. 
         [0042]    With the lattice-structured phosphors  23  formed, light generated inside the phosphor layer  22  can be extracted forward through the lattice-structured phosphors  23  by bragg scattering. This light extraction mechanism resulting from the bragg scattering induced by the lattice structure is governed by a height or period of the lattice structure. 
         [0043]    As in the present embodiment, the ink jet process, when employed to form the lattice structure, allows control of an amount and size of droplets ejected according to characteristics of a head used. Accordingly, a height, width and period of the lattice structure can be adjusted freely. Moreover, the ink jet process precludes a need for a conventional exposure process requiring a mask, but enables the lattice structure to be formed by directly printing a phosphor-containing ink. This simplifies a process significantly and increases economic efficiency due to a minimal amount of phosphors used. 
         [0044]    The ink used in the ink jet process may be formed by mixing dispersible phosphor powder of nano particles, a solvent and curable polymer. The ink may have a proper viscosity to be ejected by a nozzle and the lattice-structured phosphors can be adjusted in height depending on the viscosity. 
         [0045]    In addition, the lattice-structured phosphors  23  may be made of a material having a refractivity identical to or higher than the underlying phosphor layer  22  to eliminate total reflection effects. 
         [0046]    Referring to  FIG. 2D , the LED chip  21  having the phosphor layer  22  attached thereon is mounted in a package housing  24 . 
         [0047]    A metal terminal (not shown) is disposed in the package housing  24  to have the LED chip  21  mounted thereon. The metal terminal and the LED chip  21  may be electrically connected together by wire bonding and flip chip bonding. 
         [0048]    In  FIG. 2D , a connection between the LED chip and the package housing is not illustrated specifically. But LED chip mounted in the package housing means the LED chip electrically connected to the terminal in the package housing. 
         [0049]    Inside the package housing  24 , reflective plates  24   a  are formed in the shape of a circular truncated cone to reflect light generated from the LED chip forward. The reflective plates  24   a  may be formed by thinly coating Al, Ag, Cr, Ni or Ti on a surface of a thermo-setting polymer resin or a metal plate. 
         [0050]    Referring to  FIG. 2E , an inner portion of the package housing  24  is molded with a transparent resin  25 . 
         [0051]    The transparent resin  25  protects the LED chip mounted in the housing  24  from external environment. Also, the resin  25  may be phosphor-containing. The transparent resin may utilize a transparent polymer resin and particularly an epoxy resin or a silicon resin. 
         [0052]      FIGS. 3A to 3D  are a flow chart illustrating a method of manufacturing an LED package according to another embodiment of the invention. 
         [0053]    Referring to  FIG. 3A , an LED chip  31  is mounted in a package housing  34 . 
         [0054]    The LED chip  31  mounted in the package housing  34  means the LED chip  31  electrically connected to a terminal of the package housing  34  by wire bonding or flip chip bonding. 
         [0055]    Referring to  FIG. 3B , an inner portion of the housing package  34  is molded with a transparent resin  35 . 
         [0056]    The transparent resin  35  may utilize a transparent polymer resin, and particularly, an epoxy resin or a silicon resin. 
         [0057]    As shown in  FIG. 3C , a phosphor layer is formed on the transparent resin  35 . 
         [0058]    The phosphor layer  32  may be formed by applying a phosphor paste having phosphor powder and an epoxy resin mixed therein on a transparent resin and curing the phosphor paste. 
         [0059]    Referring to  FIG. 3D , phosphors  33  are formed on the phosphor layer  32  by an ink jet process. 
         [0060]    Here, the procedure of forming the phosphors of a lattice structure  33  can be performed in the same manner as the procedure shown in  FIG. 2C . 
         [0061]      FIG. 4A  is a cross-sectional view and  FIG. 4B  is a perspective view illustrating a method of manufacturing phosphors of a lattice structure on a phosphor layer by an ink jet process as shown in the embodiments of  FIGS. 2 and 3 . 
         [0062]    Referring to  FIGS. 4A and 4B , phosphors  43  of a lattice structure are formed using an ink jet nozzle  47  on a phosphor layer  42  of a chip size formed on an LED chip or a transparent resin. 
         [0063]    In the present embodiment, the ink jet nozzle  47  is made to eject droplet discontinuously to allow a plurality of protruded dots to be arranged in a lattice structure. However, the configuration and characteristics of the nozzle may be varied. That is, the droplets may be ejected continuously from the nozzle to form the continuously protruded dots of phosphors having a lattice structure. 
         [0064]    The ink for use in the ink jet process may utilize phosphor powder, a solvent and a polymer resin. The ink may have a viscosity varied by adjusting a ratio of the polymer resin to the solvent, which are mixed together. With the viscosity of the ink varied, the phosphors of the lattice structure can be adjusted in height and area. Also, the size and height of the dots defining the lattice-structured phosphors can be adjusted basically by varying a nozzle size of a head, a driving voltage and a driving waveform, thereby producing the lattice-structure phosphors of a desired size and shape. 
         [0065]    As described above, the ink jet process, when used in forming the lattice-structured phosphors allows the microstructures to be more easily adjusted in shape and spacing than conventional etching or photolithography. Also, the ink jet process enables direct printing on the phosphors, thereby simplifying an overall process. 
         [0066]      FIGS. 5A to 5C  are a flow chart illustrating a method of forming a phosphor layer having phosphors of a lattice structure formed thereon according to another exemplary embodiment of the invention. 
         [0067]    Referring to  FIG. 5A , a phosphor layer sheet  52  is formed. 
         [0068]    The phosphor layer sheet  52  is formed to a predetermined thickness by curing a transparent resin having phosphor powder mixed therein. 
         [0069]    As shown in  FIG. 5B , phosphors  53  are formed on the phosphor sheet  52  by an ink jet process. 
         [0070]    According to the present embodiment, the ink jet nozzle  57  is moved in a direction indicated with arrows along the phosphor sheet  52 . In the present embodiment, the dot-shaped phosphors of a lattice structure are formed but the lattice-structure phosphors can be formed without interruption by adjusting characteristics of the ink jet nozzle  57 . 
         [0071]    Referring to  FIG. 5C , the phosphor sheet  52  having the lattice-structured phosphors  53  thereon is cut into unit chips  52   a,    52   b,  and  52   c.    
         [0072]    As in the present embodiment, the phosphors of the lattice structure are formed at a time on the phosphor layer sheet, and then cut into unit chips of a desired size. This facilitates an overall process over a case where the ink jet process is performed on respective unit LED chips or an LED package. 
         [0073]      FIGS. 6A to 6C  are a flow chart illustrating a method of manufacturing an LED package according to an exemplary embodiment of the invention, which adopts a phosphor layer having phosphors of a lattice structure formed thereon by the method shown in  FIG. 5 . 
         [0074]    Referring to  FIG. 6A , a phosphor layer  66  having phosphors of a lattice structure formed thereon is bonded to an LED chip  61 . 
         [0075]    Here, the phosphor layer  66  having the lattice-structured phosphors formed thereon is the unit chip phosphor layer manufactured by the method shown in  FIGS. 5A to 5C . In the present embodiment, unlike the embodiment of  FIG. 2 , the phosphor layer  66  having the lattice-structured phosphors formed thereon is integrally fabricated on a sheet and cut into unit chips to be bonded onto the LED chip. This accordingly simplifies a manufacturing process. 
         [0076]    Referring to  FIG. 6B , the LED chip  61  where the phosphor layer  66  having the lattice-structured phosphors are attached is mounted in a package housing  64 . Referring to  FIG. 6C , an inner portion of the package housing  64  is molded with a transparent resin. 
         [0077]      FIGS. 6B and 6C  of the present embodiment are performed in an identical process to  FIGS. 2D and 2E . 
         [0078]      FIGS. 7A to 7C  are a flow chart illustrating a method of manufacturing an LED package according to another embodiment of the invention. 
         [0079]    Referring to  FIG. 7A , an LED chip  71  is mounted in a package housing  74  and referring to  FIG. 7B , an inner portion of the package housing  74  is molded with a transparent resin  75 . 
         [0080]    In the present embodiment,  FIGS. 7A and 7B  of the present embodiment are performed in an identical process to  FIGS. 3A and 3B . 
         [0081]    As shown in  FIG. 7C , a phosphor layer  76  having phosphors of a lattice structure formed thereon is bonded to the transparent resin  75 . 
         [0082]    Here, the phosphor layer  76  having the lattice-structured phosphors formed thereon is a unit chip phosphor layer fabricated by processes of  FIGS. 5A to 5C . In the present embodiment, unlike  FIG. 3 , the phosphor layer  76  having the lattice-structured phosphors formed thereon is integrally fabricated and then bonded onto the LED chip, thereby simplifying a manufacturing process. 
         [0083]    As described above, the present invention is not limited to the aforementioned embodiments and drawings attached. That is, a type of a phosphor-containing ink used in the ink jet process and shape of the lattice-structured phosphors may be varied. 
         [0084]    As set forth above, according to exemplary embodiments of the invention, an ink jet method is employed to form lattice-structured phosphors on a phosphor layer. This realizes a periodically uniform and more precise lattice structure and simplifies a process of manufacturing the lattice-structured phosphors. 
         [0085]    While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.