Abstract:
The invention relates to an LED package having a metal reflective layer for focusing and emitting light through a side of the package, and a manufacturing method of the same. The LED package includes a substrate with an electrode formed thereon, a light emitting diode chip disposed on the substrate, and an encapsulant covering the LED chip and the substrate to protect the LED chip. The LED package also includes a metal reflective layer surrounding side surfaces of the encapsulant to form a light transmitting surface on a top surface of the encapsulant. The invention minimizes light loss, improves luminance, can be mass-produced as a PCB type, and adopts EMC transfer molding to minimize irregular color distribution, thereby improving optical quality.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims the benefit of Korean Patent Application No. 2005-53163 filed on Jun. 20, 2005, 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 Light Emitting Diode (LED) package having a metal reflective layer for focusing and emitting light through one side of the package, and a method of manufacturing the same. More particularly, the invention relates to an LED package with a metal reflective layer minimized in light loss and improved in luminance, which can be mass-manufactured as a PCB type in a small size unaffected by the size of an LED chip, and is improved in productivity. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, amobile phone or PDA adopts a light emitting diode (LED) package in various sizes for a backlight. 
         [0006]    As the backlights are becoming slimmer, the LED packages adopted therein are also becoming slimmer these days. 
         [0007]    The LED package  300  shown in  FIG. 1  is described in U.S. Patent No. 2003-0094622, in which a reflective layer  312  is formed of a lead frame for an LED chip  310  mounted in the package  300 , and the package is sealed with a sealing plate  314  that covers the LED chip  310  and the reflective layer  312 . 
         [0008]    In this conventional LED package  300 , the reflective layer  312  is made of an Ag-plated layer to focus and emit light from the LED chip  310  through one side of the package. 
         [0009]    However, in such a conventional structure, the LED chip  310  is formed in a recess  322  of the substrate, and a separate sealing plate  314  covers the recess  322 , and thus limiting automated manufacturing and mass-production. 
         [0010]      FIGS. 2(   a ) and  2 ( b ) illustrate a different structure of LED package  400  of the prior art. An LED chip  412  is mounted on a substrate  410 , and a molded part  414  with a cavity therein is adhered on the substrate  410 . Then, a resin solution with phosphor and epoxy mixed therein is injected into the space  414   a  to be cured, and the complete structure is diced. However, as an additional process is required to adhere the molded part  414  on the substrate  410 , the manufacturing process is not efficient in terms of productivity. 
         [0011]    In addition, as shown in  FIG. 3 , in the conventional LED package  400 , the resin solution with the phosphor and epoxy mixed therein is injected into the space  414   a  in the molded part  414  and cured for about 1 hour to form an encapsulant  416 . In such a curing process, the phosphor in the epoxy  418   a  of the encapsulant  416  tends to precipitate, causing irregular color distribution. Therefore, such a conventional LED package  400  yields low-uniformity and rather mediocre color development. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention has been made to solve the foregoing problems of the prior art and therefore an object of certain embodiments of the present invention is to provide an LED package having a metal reflective layer, which does not require a molded part, and thus can have a minimal thickness, and a method of manufacturing the same. 
         [0013]    Another object of certain embodiments of the invention is to provide an LED package having a metal reflective layer, which can be mass-produced without being affected by the LED chip size, and can be easily manufactured in a small size, and a method of manufacturing the same. 
         [0014]    Further another object of certain embodiments of the invention is to provide an LED package having a metal reflective layer, which adopts Epoxy Molding Compound (EMC) transfer molding to minimize irregular color distribution and enhance uniform color development, and a method of manufacturing the same. 
         [0015]    Yet another object of certain embodiments of the invention is to provide an LED package minimized in light loss and improved in luminance, which can be mass-produced and is improved in productivity, and a method of manufacturing the same. 
         [0016]    According to an aspect of the invention for realizing the object, there is provided a light emitting diode package for emitting light from a light emitting diode chip in one direction, including: a substrate with an electrode formed thereon; a light emitting diode chip disposed on the substrate; an encapsulant covering the LED chip and the substrate to protect the LED chip; and a metal reflective layer surrounding side surfaces of the encapsulant to form a light transmitting surface on a top surface of the encapsulant. 
         [0017]    According to another aspect of the invention for realizing the object, there is provided a method of manufacturing a light emitting diode package for emitting light from a light emitting diode chip in one direction, including steps of: providing a substrate with an electrode formed thereon; disposing a light emitting diode chip on the substrate; forming an encapsulant on the light emitting diode chip and the substrate; cutting the encapsulant; and forming a reflective layer on the encapsulant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The above and other objects, 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: 
           [0019]      FIG. 1  is a sectional view illustrating an LED package according to the prior art; 
           [0020]      FIG. 2  illustrates another LED package according to the prior art, in which (a) is an explanatory view illustrating cutting a molded part, and (b) is a longitudinal sectional view; 
           [0021]      FIG. 3  illustrates a work process with epoxy resin constituting an encapsulant of the LED package according to the prior art; 
           [0022]      FIG. 4  is a configuration view illustrating an LED package having a metal reflective layer according to the present invention, in which (a) is a perspective view of the exterior, and (b) is a sectional view illustrating the LED package having a light transmitting surface on an upper part thereof; 
           [0023]      FIG. 5  is a view illustrating the step-by-step process of manufacturing the LED package having a metal reflective layer according to the present invention; 
           [0024]      FIG. 6  is a view illustrating the step-by-step process of manufacturing a variation of the LED package having a metal reflective layer; and 
           [0025]      FIG. 7  is a view illustrating EMC transfer molding to form an encapsulant in the manufacturing process of the LED package according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0027]    As shown in  FIG. 4 , an LED package  1  having a metal reflective layer according to the present invention is for emitting light from an LED chip  5  in one direction of an encapsulant  10 . 
         [0028]    Light is emitted through a light transmitting surface  17  which is preferably in front and in parallel with a plane where the LED chip  5  is disposed. 
         [0029]    The LED package  1  having a metal reflective layer according to the present invention has a substrate with electrodes  15   a  and  15   b  formed thereon. The substrate  15  may preferably be a Printed Circuit Board (PCB) or a ceramic substrate having pattern electrodes  15   a  and vertical electrodes  15   b  such as vias. 
         [0030]    In addition, an LED chip  5  is electrically connected to the electrode  15   a  and mounted on the substrate  15 . The LED chip  5  may be a horizontal type with all of its electric terminals formed only on an upper surface thereof, or a vertical type with the electric terminal formed on upper and lower surfaces thereof. 
         [0031]    In addition, an encapsulant  10  is formed on the LED chip  5  and the substrate  15  to cover them. The encapsulant  10  is made by curing epoxy resin, and preferably is formed via Epoxy Molding Compound (EMC) transfer molding using epoxy molding compound with phosphor mixed therein in order to minimize irregular color distribution. 
         [0032]    According to the present invention, when the encapsulant  10  is disposed on the LED chip  5  and the substrate  15  in a desired form, a reflective layer  20  is formed on the encapsulant  10  with a light transmitting surface  17  on one surface, i.e., an upper surface of the encapsulant  10  as shown in  FIG. 4(   b ). 
         [0033]    The reflective layer  20  is made of metal selected from a group consisting of Al, Au, Ag, Ni, W, Ti and Pt. The reflective layer  20  is formed on side surfaces of the encapsulant  10  via electroless plating or electroplating, or surrounding the entire surfaces of the encapsulant  10  via vacuum deposition, with an upper surface of the encapsulant polished to form the light transmitting surface  17 . 
         [0034]    Therefore, the reflective layer  20  surrounds the entire side surfaces, except the portion of the light transmitting surface  17 , of the encapsulant  10  without any spots missed. 
         [0035]    A manufacturing process  100  of an LED package having a metal reflective layer according to the present invention will now be explained hereinafter. 
         [0036]    As shown in  FIG. 5 , the manufacturing process  100  of the LED package having a metal reflective layer according to the present invention starts with a step  102  of providing a substrate  15  with electrodes  15   a  and  15   b  formed thereon. 
         [0037]    In addition, the substrate  10  is provided with pattern electrodes  15   a  and vertical electrodes  15   b  such as vias for supplying power to the LED chips and electrodes  15   c  for plating a reflective layer later. 
         [0038]    The substrate  15  can be a PCB or a ceramic substrate with vertical electrodes  15   b  such as vias formed thereon, and each of the pattern electrodes  15   a  connected to the LED chip  5  is electrically connected to each of the vertical electrode  15   b  such as a via. 
         [0039]    In the next step  104 , the LED chip  5  is mounted on the substrate  15 . 
         [0040]    In this step  104 , a plurality of LED chips  5  are simultaneously mounted on predetermined locations on one substrate  15 , and each of the LED chips  5  is electrically connected to each of the pattern electrodes  15   a  on the substrate  15  via wires. 
         [0041]    In the next step  106 , an encapsulant  10  is formed on the LED chip  5  and the substrate  15 . 
         [0042]    In this step  106 , the encapsulant  10  is formed via EMC transfer molding using an epoxy molding compound with phosphor mixed therein in order to minimize irregular color distribution after it is cured. 
         [0043]    As shown in  FIG. 7 , in the process of EMC transfer molding  200  adopted for forming the encapsulant  10 , the substrates  15  and the LED chips  5  are inserted into a mold  210  maintained at about 150° C. to 190° C., and a solid mixture  220  of transparent EMC and phosphor maintained at about 80° C. to 90° C. is injected into the mold  210 . Then, the mixture  220  of the transparent EMC and the phosphor is compressed at 500 to 1000 psi so that the mixture of the transparent EMC and the phosphor changes in its phase from solid to liquid inside the mold  210 . This liquid mixture  220  of the transparent EMC and the phosphor flows over the substrate  15  and the LED chip  5  to form the encapsulant  10 . After 5 to 7 minutes without applying heat and compression, it is cured in a short time from liquid phase to solid phase. 
         [0044]    After the curing is completed, the substrate  15  and the LED chip  5  with the encapsulant  10  formed thereon is separated from the mold  210  to complete the encapsulant  10 . 
         [0045]    In the encapsulant  10  formed via the above described EMC transfer molding, the phosphor  222   b  does not precipitate in the transparent EMC  222   a , which minimizes irregular color distribution and enhances uniformity of color development. 
         [0046]    After the encapsulant  10  is completed, the encapsulant  10  is cut in the next step  108 . 
         [0047]    In this step  108 , in order to form a desired shape of encapsulant  10  for the LED chips  5 , only the encapsulant  10  is diced or etched. In this step  108 , the encapsulant  10  is formed such that the lower periphery thereof exposes the electrode  15   c  for plating. 
         [0048]    Then, a reflective layer  20  is formed on the encapsulant  10  in the next step  110 . The reflective layer  20  is formed as a plated layer  22  on the encapsulant  10  by electroless plating or electro-plating highly reflective metal selected from a group consisting of, for example, Al, Au, Ag, Ni, W, Ti and Pt. At this point, the plated layer  22  is formed integrally with the encapsulant  10  to completely surround the side surfaces of the encapsulant  10 , thereby preventing leakage of light. 
         [0049]    With the reflective layer  20  formed as just described, the light transmitting surface  17  is formed on an upper surface of the encapsulant  10 . 
         [0050]    In the next step  112 , the plated layer  22  and the substrate  15  are cut horizontally and vertically into individual LED packages to obtain a plurality of LED packages  1 . 
         [0051]    In this step  112 , each of the LED packages  1  has the light transmitting surface  17  formed on an upper surface of the encapsulant  10 , and the metal reflective layer  20  surrounds the side surfaces of the encapsulant  10  so that light from the LED chip is leaked only through the light transmitting surface  17 . 
         [0052]    Alternatively, as shown in  FIG. 6 , in the step  110  of forming the reflective layer  20  on the encapsulant  10 , a sputtered layer  22 ′ is formed via vacuum sputtering using highly reflective metal selected from a group consisting of, for example, Al, Au, Ag, Ni, W, Ti and Pt to surround the outer surfaces of the encapsulant  10 . In this case, the sputtered layer  22 ′ is formed integrally with the encapsulant  10  to completely surround the outer surfaces of the encapsulant  10  so as not to allow any leakage of light. 
         [0053]    In the next step  110 ′, an upper surface of the sputtered layer  22 ′ is polished to be removed, thus forming the light transmitting surface  17  on an upper surface of the encapsulant  10 . 
         [0054]    Thus is completed a structure with the light transmitting surfaces  17  formed on upper surfaces of the encapsulant  10 . 
         [0055]    In the next step  112 , the substrate  15  is cut horizontally and vertically into individual LED packages to obtain a plurality of LED packages  1 . 
         [0056]    Through the above steps, each LED package  1  is completed with the light transmitting surface  17  formed on an upper surface of the encapsulant  10  and the metal reflective layer  20  surrounding the side surfaces of the encapsulant, thereby allowing leakage of light from the LED chip  5  only through the light transmitting surface  17 . 
         [0057]    According to the present invention as set forth above, a reflective layer and an encapsulant are integrated to minimize the thickness of the LED package, thereby easily applicable to various types of slimmer backlights. 
         [0058]    In addition, the present invention does not need a molded part in addition to an encapsulant, allowing a thin, small-sized structure, and adopts highly reflective metal for a reflective layer surrounding the surfaces of the encapsulant, except the portion of the light transmitting surface, to minimize leakage of light. 
         [0059]    In addition, in the present invention, the entire process including mounting the LED chip, molding and dicing is conducted on a PCB, enabling mass-production with significantly improved productivity. 
         [0060]    Furthermore, the present invention adopts EMC transfer molding using an epoxy molding compound with phosphor mixed therein so that the phosphor does not precipitate after the encapsulant is cured, thereby minimizing irregular color distribution and significantly improving optical quality. 
         [0061]    Certain exemplary embodiments of the invention have been explained and shown in the drawings as presently preferred. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. While the present invention has been shown and described in connection with the preferred 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.