Patent Publication Number: US-2009230418-A1

Title: Light emitting diode package and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 2008-0022859 filed on Mar. 12, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to light emitting diode packages and a method of manufacturing the same, and more particularly, to a light emitting diode package and a method of manufacturing the same in which a light emitting diode chip is separated from phosphors, and a phosphor area is variable in shape to improve thermal balance and luminous efficiency. 
     2. Description of the Related Art 
     White light emitting diodes (hereinafter, simply referred to as an “LED”) are semiconductor device packages that display white by fabricating light sources using compound semiconductor materials, such as GaAs, AlGaAs, GaN, InGaN, and AlGaInP. 
     In general, factors used to determine characteristics of the LED package may include color, luminance, and a range of luminous intensity. The characteristics of the LED package are primarily determined by compound semiconductor materials of an LED used in the LED package. Secondarily, the characteristics of the LED package are affected by a package structure for mounting an LED chip. In order to obtain high luminance and luminance distribution according to the user&#39;s needs, the above-described primary factor according to the material development is limited. Therefore, the package structure has attracted much attention. 
     As information and communication devices have been reduced in size, thickness, and weight, components of the information and communication devices, for example, resistors, condensers, and noise filters, have been significantly reduced in size. The components are directly mounted onto the surface of a printed circuit board (PCB), and any devices so made are called surface mount devices (SMDs). 
     LED packages that are used as display devices have been correspondingly developed into SMD LED packages. This SMD LED package can replace the existing lighting lamp and is used as a character indicator, an image indicator, or a lighting indicator, which displays various colors. 
     As such, as the LED package is used in a wide range of applications, the required amount of luminance of lamps used daily or emergency signal lamps is increasing steadily. Recently, a high-power white LED package has come into widespread use. 
       FIG. 1  is an exemplary view illustrating a white LED package according to the related art. 
     As shown in  FIG. 1 , in an LED package according to the related art, a reflection hole is formed in a PCB  20  so that an LED  21  is mounted in the reflection hole, a reflective coating layer  20 - 1  formed of Ag is formed in the reflection hole, and then the reflective coating layer  20 - 1  is connected to package electrodes  22  and  23  to apply power to the LED  21 . 
     When the reflective coating layer  20 - 1  is formed in the PCB  20 , the LED  21  is located at a lower part of the reflection hole, and a P electrode and an N electrode of the LED  21  are electrically connected to the reflective coating layer  20 - 1 . 
     When the LED  21  is mounted in the reflection hole, a cathode electrode  22  and an anode electrode  23  are formed at both sides of the reflective coating layer  20 - 1  by a solder bonding method. Then, a phosphor molding unit  24  that includes a red phosphor, a green phosphor, and a blue phosphor is injected into the reflection hole of the PCB  20  mounted with the LED  21  so as to inhibit oxidization of a wire  21 - 2  and convert light generated from the LED  21  into white light. 
     The LED package then converts light generated from the LED  21  into white light in the phosphor molding unit  24 , and emits the white light to the outside by a mold lens  25 . 
     However, according to the related art, in the white LED package, heat generated from the LED  21  is directly transferred to the phosphor molding unit  24  to cause thermal deformation of the phosphors in the phosphor molding unit  21 . As a result, light conversion efficiency with which light generated from the LED  21  is converted into light having a different wavelength is reduced. 
     Further, since it is impossible to change the distance between the LED  21  and the phosphor molding unit  24  to obtain a desired distance, it is difficult to improve luminous efficiency of the LED package. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a light emitting diode package and a method of manufacturing the same in which a light emitting diode chip is separated from phosphors, and a phosphor area is variable in shape. 
     According to an aspect of the present invention, there is provided a light emitting diode package including: a package body; at least one LED chip mounted in an area of the package body and emitting excitation light; and a lens unit separated from the LED chip by a distance and mounted on an upper surface of the package body, wherein the lens unit may include a phosphor area located at one side of a lower part thereof, absorbing the excitation light of the LED chip, and generating wavelength-converted light. 
     The light emitting diode package may further include a reflective pattern formed of a metallic material, located on the upper surface of the package body, and connected to edges of the lens unit. 
     The package body may be a printed circuit board. 
     The package body may include a via for making an electrical connection of the LED chip to the outside. 
     The phosphor area may have a thickness increasing towards the center from edges or a uniform thickness at a lower surface of the lens unit. 
     The phosphor area may have a radial shape and be provided at one side of a lower part of the lens unit. 
     The phosphor area may include: a first phosphor area including a first phosphor and located at one side of the lower part of the lens unit; and a second phosphor area including a second phosphor and overlapping the first phosphor area. 
     According to another aspect of the present invention, there is provided a method of manufacturing a light emitting diode package, the method including: providing a lens unit formed of a transparent lens material; forming a recessed part at one portion of a plane of the lens unit and forming a phosphor area by filling and curing liquid resin including a phosphor; and mounting the lens unit on an upper surface of the package body so that the phosphor area of the lens unit is separated from at least one LED chip mounted in an area of the package body. 
     The recessed part may be formed by dry etching or wet etching one portion of a plane of the lens unit. 
     The package body may include a reflective pattern formed of a metallic material, located on the upper surface of the package body, and connected to edges of the lens unit. 
     The package body may be a printed circuit board. 
     The package body may include a via for making an electrical connection of the LED chip to the outside. 
     In the mounting the lens unit on an upper surface of the package body, the lens unit may be mounted on the upper surface of the package body through paste applied to the edges of a lower surface thereof. 
     In the forming a phosphor area, the phosphor area may have a thickness increasing towards the center from edges or a uniform thickness at the lower surface of the lens unit. 
     In the forming a phosphor area, the phosphor area may be located at a lower part of the lens unit and have a radial shape to diffuse wavelength-converted light. 
     In the forming a phosphor area, the phosphor area may include: a first phosphor area including a first phosphor and located at one side of the lower part of the lens unit; and a second phosphor area including a second phosphor and overlapping the first phosphor area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is an exemplary view illustrating an LED package according to the related art; 
         FIG. 2  is a cross-sectional view illustrating a light emitting diode package according to an exemplary embodiment of the invention; 
         FIGS. 3A to 3C  are cross-sectional views illustrating a process of manufacturing the light emitting diode package according to the embodiment of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view illustrating a light emitting diode package according to another embodiment of the invention; 
         FIG. 5  is a cross-sectional view illustrating a light emitting diode package according to still another embodiment of the invention; and 
         FIG. 6  is a cross-sectional view illustrating a light emitting diode package according to yet another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the description of the invention, if it is determined that a detailed description of commonly-used technologies or structures related to a light emitting diode package of the invention may unnecessarily obscure the subject matter of the invention, the detailed description will be omitted. 
       FIG. 2  is a cross-sectional view illustrating a light emitting diode (LED) package according to an exemplary embodiment of the invention.  FIGS. 3A to 3C  are cross-sectional views illustrating a process of manufacturing the LED package according to the exemplary embodiment of the invention. 
     As shown in  FIG. 2 , an LED package  100  according to this embodiment includes a package body  110 , such as a printed circuit board, at least one LED chip  120 , and a lens unit  130 . The LED chip  120  is mounted in the area of the package body  110 , and emits excitation light. The lens unit  130  includes a hemispheric lens area  131  and a phosphor area  133 . The hemispheric lens area  131  is separated from the LED chip  120 , and mounted on an upper surface of the package body  110 . The phosphor area  133  is located at a portion of a lower surface of the lens area  131 , and absorbs the excitation light of the LED chip  120  to generate wavelength-converted light. Here, a reflective layer (not shown) is provided along a bottom surface of the area of the package body  110  in which the at least one LED chip  120  is mounted. The reflective layer reflects excitation light and wavelength-converted light to emit the excitation light and the wavelength-converted light to the outside. 
     Further, in order to make an electrical connection of the LED chip  120  to the outside, a via  111  may be provided under the area of the package body  110  in which the at least one chip  120  is selectively mounted. 
     The lens unit  130  is placed on the upper surface of the package body  110  and separated by the distance D from the LED chip  120  corresponding to the lens unit  130 . Here, the lens unit  130  includes the hemispheric lens area  131  and the phosphor area  133 . Examples of phosphors of the phosphor area  133  may include i) rare-earth oxide, sulfide, and nitride phosphors or ii) semiconductor nitride, sulfide, oxide, and phosphide phosphors. 
     Here, the phosphors of the phosphor area  133  may be formed into a predetermined shape on the lower surface of the lens unit  130 . For example, as shown in  FIG. 2 , the phosphors have a thickness increasing towards the center from both edges. Light with high intensity incident from the center of the LED chip  120  and light incident from the edges of the LED chip  120  respond to the phosphor area  133 , thereby emitting uniform wavelength-converted light. Alternatively, the phosphor area  133  may correspond to the LED chip  120 , be located at the lower surface of the lens unit  130 , and overlap the area of the package body  110 . 
     As described above, in the LED package  100  according to this embodiment, the lens unit  130  is mounted while being separated by the distance D from the LED chip  120  corresponding to the lens unit  130 . Since heat generated from the LED chip  120  is not directly transferred to the phosphor area  133 , the phosphors of the phosphor area  133  are not thermally deformed, thereby improving luminous efficiency and reliability of the LED package  100 . 
     Further, the lens unit  130  may be mounted on the package body  110  by changing the distance D between the LED chip  120  and the phosphor area  133 . The lens unit  130  may be replaced with another lens unit having a phosphor area with a different shape from that of the phosphor area  133 . 
     Hereinafter, a method of manufacturing the LED package  100  according to the exemplary embodiment of the invention will be described with reference to  FIGS. 3A to 3C . 
     As shown in  FIG. 3A , in order to manufacture the LED package  100  according to the embodiment of the invention, a recessed part  132  is formed in the center of a plane of the hemispheric lens area  131  that is formed of a transparent lens material. 
     In order to form the recessed part  132  in the center of the plane of the lens area  131 , a photo resist pattern (not shown) is formed on the plane of the lens area  131 , and then etched. Dry etching or wet etching may be selectively performed according to the shape of the recessed part  132 . The recessed part  132  may be formed by using a method of injecting a molten lens material into a mold having a shape corresponding to the shape of the lens area  131  and the groove part  132 , and hardening the injected lens material. 
     Once the recessed part  132  is formed at the center of the plane of the lens area  131 , as shown in  FIG. 3B , liquid resin containing phosphors is injected into the recessed part  132  and then cured to form the phosphor area  133 . 
     Specifically, examples of the phosphors contained in the liquid resin to form the phosphor area  133  may include i) rare-earth oxide, sulfide, and nitride phosphors or ii) semiconductor nitride, sulfide, oxide, and phosphide phosphors. The phosphors may be filled and cured in the recessed part  132  by a method such as screen printing. 
     Then, as shown in  FIG. 3C , the lens unit  130  including the phosphor area  133  is mounted on the upper surface of the area of the package body  110  mounted with at least one LED chip  120 . 
     At this time, the lens unit  130  may be mounted on the upper surface of the package body  110  by using paste applied to the edges, and the area in the package body  110  mounted with the LED chip  120  may be formed to adjust the distance D between the phosphor area  133  and the LED chip  120 . The phosphor area  133  may be formed at the inside of the lens unit  130  in order to increase the distance D between the phosphor area  133  and the LED chip  120 . 
     The problem that it is impossible to change the distance between the LED  21  and the phosphor molding unit  24  to obtain a desired distance can be easily solved since the phosphor area  133  is directly formed and mounted in the lens unit  130  in the LED package  100  according to this embodiment. Furthermore, since it is possible to easily remove the lens unit  130 , the lens unit  130  can be exchanged into a lens unit having a phosphor area with a different shape from that of the phosphor area  133  to meet the user&#39;s needs. 
     As described above, the lens unit  130  is easily removed and exchanged into a lens unit having a phosphor area with a different shape from that of the phosphor area  133 . As shown in  FIG. 4 , in an LED package  200  according to another exemplary embodiment of the invention, instead of the lens unit  130 , a lens unit  230  having a phosphor area  233  with a uniform thickness at a bottom surface thereof may be mounted on an upper surface of a package body  210 . 
     As shown in  FIG. 5 , in an LED package  300  according to still another exemplary embodiment of the invention, a phosphor area  333  having a radial shape is formed at a lower part of the lens unit  330 , and converts a wavelength of light generated from an LED chip  320  to diffuse light to the outside through a lens area  331 . Luminous efficiency of the LED package  300  can be improved by diffusing the wavelength-converted light by using the phosphor area  333  having the radial shape. 
     Optionally, the LED package  300  according to this embodiment may include a reflective pattern  340 . The reflective pattern  340  is provided at the upper surface of a package body  310  and serves as a mounting frame formed of a metallic material for the lens unit  330 . The reflective pattern  340  facilitates mounting the lens unit  330  to thereby improve the luminous efficiency of the LED package  300 . 
     As shown in  FIG. 6 , an LED package  400  according to yet another embodiment of the invention includes a phosphor area having a first phosphor area  433 - 1  and a second phosphor area  433 - 2  that are located at a lower part of a lens unit  430  and overlap each other. The phosphor area converts a wavelength of light generated from the LED chip  420  and emits the wavelength-converted light to the outside through a lens area  431 . The first phosphor area  433 - 1  and the second phosphor area  433 - 2  constitute the phosphor area. In particular, for white light emission, a phosphor for converted red light may be included in the first phosphor area  433 - 1 , and phosphors for converted blue light and converted green light may be included in the second phosphor area  433 - 2 . 
     Here, in order to form the first phosphor area  433 - 1  and the second phosphor area  433 - 2 , that is, first dry etching is performed on the lens area  431  to form a first recessed part for the first phosphor area  433 - 1 , and second wet etching is performed on the first phosphor area  433 - 1  filled and cured in the first recessed part to form a second recessed part for the second phosphor area  433 - 2 . After the second etching is completed, the second phosphor area  433 - 2  may be formed. 
     Like the LED package  300  according to still another embodiment of the invention, the LED package  400  according to this embodiment of the invention includes a reflective pattern  440  that is located on the upper surface of a package body  410  and serves as a mounting frame formed of a metallic material for the lens unit  430 . The reflective pattern  440  facilitates mounting the lens unit  430  and improves the luminous efficiency of the LED package  400 . 
     As described above, the lens unit having the phosphor area variable in shape is separated from the LED chip by the predetermined distance, the lens unit can be mounted or demounted, and the thickness and shape of the phosphor area are variously controlled, such that thermal deformation of the phosphors can be prevented, and the luminous efficiency of the LED package can be improved. 
     As set forth above, according to the exemplary embodiments of the invention, since the lens unit corresponding to the LED chip is separated from the LED chip by the predetermined D, heat generated from the LED chip is not directly transferred to the phosphor area, thereby preventing thermal deformation of the phosphors and improving luminous efficiency and reliability of the LED package. 
     Further, according to the embodiments of the invention, an LED package is provided in which a lens unit can be mounted on a package body by controlling a distance D between the LED chip and the phosphor area, and the lens unit can be replaced with a lens unit having a phosphor area variable in shape. 
     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.