Abstract:
Provided is an LED package including a printed circuit board (PCB); a conductive structure that is formed on the PCB and is composed of any one selected from a silicon structure and an aluminum structure; and an LED chip that is mounted on the PCB and is electrically connected to the PCB through the conductive structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2007-0083886 filed with the Korea Intellectual Property Office on Aug. 21, 2007, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light emitting diode (LED) package, and more specifically, to a chip-on-board (COB) LED package which can reduce a manufacturing cost. 
     2. Description of the Related Art 
     LED is a semiconductor element which converts electric energy into light energy and is composed of a compound semiconductor which emits a specific wavelength of light depending on an energy bandgap. LED is used in optical communication, display (mobile display, computer monitor), backlight unit (BLU) for LCD and so on. 
     When LED is used for a mobile display and a computer monitor, a light source is positioned on one surface of a screen, and light is uniformly distributed through a light guide plate. Therefore, the number of LED chips to be used is small. 
     On the other hand, when LED is used as a backlight source for large-sized TVs, a light source should be disposed under the screen. Therefore, the number of LED chips to be used increases, compared with when the light source is positioned on one surface of the screen. In general, several hundreds to several thousands of LED chips are used. In this case, a COB method is used, in which several hundreds to several thousands of LED packages are mounted on a substrate, or LED chips are directly mounted on a printed circuit board (PCB). 
       FIG. 1  is a cross-sectional view of a conventional LED package serving as a backlight source, in which LED chips are directly mounted on a PCB. 
     As shown in  FIG. 1 , the conventional LED package  10  includes a PCB  11  and a plurality of LED chips  13  mounted on the PCB  11 . 
     On the PCB  11 , a plurality of electrode pads  12  are formed so as to be electrically connected to the LED chips  13  through wires  15 . The electrode pad  12  is formed of Au (gold) or Ag (silver). 
     On the LED chip  13 , a molding compound  17  is formed so as to protect the LED chip  13  and the wire  15 . 
     The conventional LED package  10  constructed in such a manner generates light by using an electrical signal supplied through the PCB  11 . 
     In the conventional LED package  10 , however, the electrode pads  12  formed on the PCB  11  are formed of a metallic material such as Au or Ag, and the number of LED chips  13  mounted on the PCB  11  reaches several hundreds to several thousands. Therefore, the number of electrode pads  12  which are to be formed in accordance with the number of LED chips  13  inevitably increases, thereby increasing the manufacturing cost. 
     Further, since the heat generated from the LED chips is not effectively radiated, the brightness of the LED chips decreases, and thus the lifespan thereof decreases. 
     SUMMARY OF THE INVENTION 
     An advantage of the present invention is that it provides an LED package in which conductive structures formed of silicon are mounted on a PCB, instead of electrode pads formed of Au or Ag, which makes it possible to reduce the manufacturing cost. 
     Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     According to an aspect of the invention, an LED package comprises a printed circuit board (PCB); a conductive structure that is formed on the PCB and is composed of any one selected from a silicon structure and an aluminum structure; and an LED chip that is mounted on the PCB and is electrically connected to the PCB through the conductive structure. 
     The conductive structure may have a thickness of several hundred μm. 
     The LED chip may be connected to the conductive structure through wire bonding. 
     The LED package further comprises a conductive adhesive layer for mounting the LED chip on the surface of the conductive structure. 
     The LED package further comprises a molding compound that packages the conductive structure and the LED chip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a cross-sectional view of a conventional LED package serving as a backlight source, in which LED chips are directly mounted on a PCB; and 
         FIG. 2  is a cross-sectional view of an LED package according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     Hereinafter, an LED package and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 2  is a cross-sectional view of an LED package according to an embodiment of the invention. 
     As shown in  FIG. 2 , the LED package  100  according to the embodiment of the invention includes a PCB  110 , an LED chip  130  mounted on the PCB  110 , and a plurality of conductive structures  120  and  120   a  which electrically connect the PCB  110  to the LED chips  130 . 
     The PCB  110  is a metal PCB in which a flexible PCB formed of polyimide is attached to the top surface of a heat radiating body formed of metal with high heat conductivity through an adhesive so as to enhance heat radiation performance. The LED chip  130  is directly mounted on the top surface of the flexible PCB and is connected to the conductive structures  120  formed on the top surface of the flexible PCB through a wire  150  so as to receive a current. 
     Alternatively, the PCB  110  may be a PCB formed of resin, on which an electrode circuit for electrically connecting the LED chip  130  is formed. The PCB formed of resin may have a heat radiating body attached to the bottom surface thereof. 
     Although not shown, the LED chip  130  includes a light emission structure, in which an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are sequentially laminated, and n- and p-electrodes which supply electrons and holes to the n-type semiconductor layer and the p-type semiconductor layer, respectively. 
     To prevent the damage of the LED chip caused by electrostatic discharge (ESD) occurring during the process, the LED chip  130  may further include an ESD prevention circuit such as a Zener diode. 
     The conductive structures  120  are formed on the PCB  110  so as to be connected to the electrode circuit within the PCB  110 , and are electrically connected to the terminals (the n- and p-electrodes) of the LED chip  130 , respectively, through the wire  150 . 
     The conductive structures  120  and  120   a  are formed of a silicon or aluminum structure and has a thickness of several hundred μm. 
     The conductive structure  120   a  attached to the bottom surface of the LED chip  130  is electrically connected to the ESD prevention circuit (Zener diode) formed in the LED chip  130  so as to serve as a ground terminal. 
     The LED chip  130  may be fixed to the top surface of the conductive structure  120   a  through a conductive adhesive such as Ag epoxy or eutectic solder. 
     On the LED chip  130 , a molding compound  170  is formed so as to package the LED chip  130  and the wire  150 . The molding compound  170  is formed of solid transparent resin such as silicon resin, epoxy resin, or synthetic resin. 
     In the LED package constructed in such a manner, since the silicon structure or aluminum structure is used as the electrode pattern for electrically connecting the terminals of the LED chip to the PCB, it is possible to reduce a material cost, compared with in the related art. 
     In the related art, a metallic material such as Au or Ag is plated on a PCB so as to form an electrode pattern, and the electrode pattern is electrically connected to terminals of an LED chip through a wire. However, since the number of LED chips which are to be mounted on the PCB so as to be used as a light source of a backlight reaches several hundreds to several thousands, the number of electrode pads which are to be formed in accordance with the number of LED chips inevitably increases. Therefore, the manufacturing cost increases. In the present invention, however, since the silicon or aluminum structure which is cheaper than Au or Ag is used as the electrode pad of the PCB, it is possible to reduce the manufacturing cost, compared with in the related art. 
     Further, the LED package according to the invention exhibits more excellent heat radiation performance than the conventional LED package. 
     That is, the electrode pad of the PCB used in the conventional LED package is formed by plating the terminals of the PCB with a metallic material such as Au or Ag, and the thickness of the electrode pad is no more than several tens A. On the other hand, the conductive structure, which is used in the present invention and is formed of silicon or aluminum, has a thickness of several hundreds μm. Therefore, it is possible to more effectively radiate heat generated from the LED chip than in the related art. 
     In the LED package according to the invention, as the conductive structure composed of silicon or aluminum is formed as an electrode pad on the PCB, a material cost for forming the electrode pad can be reduced, and the heat radiation effect can be further enhanced. All LED packages in which a silicon or aluminum structure is formed as an electrode pad of a PCB are included in the present invention, regardless of the type of the PCB and LED chips. 
     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.