Abstract:
A light emitting apparatus includes a light emitting diode including a body with a light emitting diode chip packaged therein and a plurality of lead electrodes contacted with one side of the body and a board including a plurality of electrode pads connected to lower surfaces of the lead electrodes of the light emitting diode. The lower surfaces of the lead electrodes of the light emitting diode correspond to top surfaces of electrode pads of the board with same shapes. The lower surfaces of the lead electrodes of the light emitting diode are disposed within a region of top surfaces of the electrode pads of the board, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of pending U.S. application Ser. No. 12/365,483, which claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2008-0011761 (filed on Feb. 5, 2008), which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    A light emitting diode (LED) constitutes a light emitting source by using a compound semiconductor material, such as a GaAs-based compound semiconductor material, an AlGaAs-based compound semiconductor material, a GaN-based compound semiconductor material, an InGaN-based compound semiconductor material or an InGaAlP-based compound semiconductor material. 
         [0003]    The LED is packaged and used as a light emitting device for emitting light having various colors. Such an LED is used as a light source in various fields, such as a lightening indicator for displaying colors, a character indicator, and an image indicator. 
       SUMMARY 
       [0004]    Embodiments provide a light emitting apparatus comprising an improved tilt between a light emitting device and a board, and a light unit having the same. 
         [0005]    Embodiments provide a light emitting apparatus, in which a lead electrode of a light emitting device has the same shape as a pad of a board, and a light unit having the same. 
         [0006]    Embodiments provide a light emitting apparatus, in which a plurality of light emitting devices are mounted on a flexible board with a stiffener thereunder, and a light unit having the same. 
         [0007]    An embodiment provides a light emitting apparatus comprising: a light emitting device comprises a light emitting element and a plurality of external leads; and a plurality of electrode pads under the light emitting device. 
         [0008]    An embodiment provides a light emitting apparatus comprising: a plurality of light emitting devices comprising a light emitting element and a plurality of external leads; and a flexible board comprising a plurality of electrode pads thereon electrically connected to the external leads, and a stiffener thereunder. 
         [0009]    An embodiment provides a light unit comprising: a plurality of light emitting devices comprising a light emitting element and a plurality of external leads; a board comprising a plurality of electrode pads electrically connected to the plurality of light emitting devices; and a light guide plate on one side of the light emitting device. 
         [0010]    The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side sectional view of a light emitting apparatus according to a first embodiment. 
           [0012]      FIG. 2  is a projection plan view of a light emitting device on a board in  FIG. 1 . 
           [0013]      FIG. 3  is a side sectional view of the light emitting device in  FIG. 1 . 
           [0014]      FIG. 4  is a front view of the light emitting device in  FIG. 1 . 
           [0015]      FIG. 5  is a bottom view of the light emitting device in  FIG. 1 . 
           [0016]      FIG. 6  is a plan view of the board in  FIG. 1 . 
           [0017]      FIG. 7  is a detailed side sectional view of the board in  FIG. 1 . 
           [0018]      FIG. 8  is a perspective view of a light unit according to a second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0019]    Hereinafter, a light emitting apparatus and a light unit having the same according to embodiments will be described in detailed with reference to the accompanying drawings. 
         [0020]      FIG. 1  is a side sectional view of a light emitting apparatus according to a first embodiment, and  FIG. 2  is a projection plan view of a light emitting device on a board in  FIG. 1 . 
         [0021]    Referring to  FIGS. 1 and 2 , the light emitting apparatus  160  comprises a light emitting device  100  and a board  140 . 
         [0022]    The light emitting device  100  comprises a light emitting diode (LED) chip  120  and a plurality of lead terminals  132  and  133 . The light emitting device  100  emits a color light, such as a red color, a green color and a blue color, or emits a white color. 
         [0023]    At least one LED chip  120  may be arranged in each light emitting device. For example, the light emitting device may selectively comprise color LED chips, such as a red LED chip, a blue LED chip, a green LED chip, and a yellow green LED chip. 
         [0024]    First ends of the lead terminals  132  and  133  are electrically connected to the LED chip  120 , and external leads  134  and  135  being second ends of the lead terminals  132  and  133  are disposed under the light emitting device  100 . 
         [0025]    The board  140  comprises a flexible PCB (printed circuit board), and a plurality of electrode pads  114  and  145  are disposed over the board  140 . The electrode pads  144  and  145  may be formed in the same shape as the external leads  134  and  135  of the light emitting device  100 , and may be larger in size than the external leads  134  and  135  of the light emitting device  100 . For example, both of the external leads  134  and  135  and the electrode pads  144  and  145  may be formed in a circular shape, a polygonal shape, or a shape bent at a predetermined angle. The electrode pads  144  and  145  may be 1-1.5 times larger in size than the external leads  134  and  135 . 
         [0026]    The plurality of light emitting devices  100  are arranged on the board  140  in a predetermined direction, and the external leads  134  and  135  of the light emitting device  100  are electrically connected to the electrode pads  144  and  145  on the board  140 . The external leads  134  and  135  of the light emitting device  100  are bonded to the electrode pads  144  and  145  on the board  140  by solders through a surface mount technology (SMT) process. In this case, the external leads  134  and  135  of the light emitting device  100  may be bonded within regions of the electrode pads  144  and  145 . Accordingly, since the light emitting device  100  is arranged in parallel to the electrode pads  144  and  145  of the board  140 , the tilt problem of the light emitting device  100  can be solved. 
         [0027]    A tilt value of the light emitting device  100  may be within ±0.2 mm with respect to the top surface of the board  140 . 
         [0028]      FIG. 3  is a side sectional view of the light emitting device in  FIG. 2 ,  FIG. 4  is a front view of the light emitting device in  FIG. 2 , and  FIG. 5  is a bottom view of the light emitting device in  FIG. 2 . 
         [0029]    Referring to  FIGS. 3 and 4 , the light emitting device  100  may be implemented with a side view type package or a top view type package, and may be variously applied as a light source of an LCD device in a portable phone, a portable computer, etc., and a light emitting device of a lighting field. For convenience of explanation, the side view type package will be described as an example. 
         [0030]    The light emitting device  100  comprises an LED chip  120 , a package body  110  with an opening  113 , and a plurality of lead terminals  132  and  133 . 
         [0031]    The package body  110  may be formed of at least one of printed circuit board (PCB), silicon, silicon carbide (SiC), aluminum nitride (AlN), poly phthalamide (PPA), and liquid crystal polymer, but the package body  110  is not limited thereto. 
         [0032]    Furthermore, the package body  110  may be injection molded with injection material, or may be formed using an etching process, or may be formed of a PCB, but the package body  110  is not limited thereto. The injection material can form the package body in a desired shape by using press, for example, Cu/Ni/Ag alloy, and a material of structure of such an injection material may be changed. 
         [0033]    The opening  113  may be formed on one side of the package body  110 . The opening  113  serves to perform a reflection cup function and may be formed with a predetermined depth and in a predetermined shape. A circumference surface of the opening  113  may be formed vertically or slopingly, but it is not limited thereto. Furthermore, according to the current embodiment, the opening  113  may not be formed in the package body  110 . 
         [0034]    The plurality of lead terminals  132  and  133  are disposed in the package body  110  and may be implemented lead frames. 
         [0035]    First ends  130  and  131  of the lead terminals  132  and  133  may be exposed to the opening  113  by passing through both sides of the package body  110 . The external leads  134  and  135  being second ends of the lead terminals  132  and  133  are disposed under the package body  110 . Accordingly, the external leads  134  and  135  of the lead terminals  132  and  133  may be disposed under the package body  110  through a forming process. 
         [0036]    The first ends  130  and  131  of the lead terminals  132  and  133  are electrically connected to the LED chip  120  within the opening  113 . The LED chip  120  and the first ends  130  and  131  of the lead terminals  132  and  133  may be connected together by wires or may be connected together by die bonding or flip boding, but it is not limited thereto. The LED chip  120  comprises a nitride semiconductor light emitting device. 
         [0037]    The package body  110  may comprise semiconductor devices such as a light receiving device or a protecting device, but it is not limited thereto. The protecting device may be implemented with a Zener diode. The Zener diode protects the LED chip from electrostatic discharge (ESD). 
         [0038]    A resin (not shown) is formed in the opening  113 . The resin protects the LED chip  120  by using silicon or transparent resin such as epoxy. At least one kind of phosphor may be added to the resin, but it is not limited thereto. The surface of the resin may be formed in a flat shape, a concave shape, or a convex shape, but it is not limited thereto. 
         [0039]    Referring to  FIGS. 4 and 5 , the external leads  134  and  135  of the lead terminals  132  and  133  may be formed such that they are received in grooves  119  formed on both bottom sides of the package body  110 . The external leads  134  and  135  are formed with a flat plate with a predetermined shape and it can improve adhesiveness of the solders in the SMT process. 
         [0040]    Referring to  FIG. 5 , the external leads  134  and  135  may be formed in a circular shape, an elliptical shape, a polygonal shape, or a shape in which some portions of the external leads  134  and  135  are cut or bent at a predetermined angle. As an example, the external leads  134  and  135  may be formed in a shape in which their inner sides  134 A and  135 A extend in a rear surface direction of the package body  110  with respect to the forming direction, for example, a           shape. 
         [0041]      FIG. 6  is a plan view of the board in  FIG. 1 . 
         [0042]    Referring to  FIG. 6 , a plurality of electrode pads  144  and  145  are disposed on the board  140 . The electrode pads  144  and  145  may be formed in the same shape as the external leads ( 134  and  135  in  FIG. 5 ). The electrode pads  144  and  145  may be formed in a circular shape, an elliptical shape, a polygonal shape, or a shape bent at a predetermined angle. As an example, the electrode pads  144  and  145  may be formed in a shape in which their inner sides  144 A and  145 A protrude from a rectangular shape, for example, a           shape. 
         [0043]    Referring to  FIGS. 5 and 6 , the side lengths D 5 , D 6 , D 7  and D 8  of the electrode pads  144  and  145  may be equal to or greater than the side lengths D 1 , D 2 , D 3  and D 4  of the external leads  134  and  135 . Herein, the side lengths D 5 , D 6 , D 7  and D 8  of the electrode pads  144  and  145  are 1-1.5 times longer than the side lengths D 1 , D 2 , D 3  and D 4  of the external leads  134  and  135 . The opposite sides D 1  and D 5 , D 2  and D 6 , D 3  and D 7 , D 4  and D 8  are formed to correspond to each other in the same shapes. 
         [0044]    Furthermore, the plurality of electrode pads  144  and  145  have a shape symmetrical to one another, and the inner regions may be larger than the outer regions. Moreover, the plurality of external leads  134  and  135  may be formed with sizes of the corresponding regions at the corresponding positions of the electrode pads  144  and  145 . 
         [0045]    The electrode pads  144  and  145  may be larger in size than the external leads  134  and  135 . For example, the electrode pads  144  and  145  may be 1-1.5 times larger in size than the external leads  134  and  135 . 
         [0046]    Since the entire regions of the external leads  134  and  135  of the light emitting device  100  are contacted within the electrode pads  144  and  145  of the board  140 , it is possible to prevent the inclination of the center of gravity applied to both sides of the light emitting device  100 . 
         [0047]    Furthermore, the electrode pads  144  and  145  of the board  140  can solve the tilt problem of the dispensed solder thereon, and can also solve the heat dissipation problem through the uniform contact with the external leads  134  and  135 . 
         [0048]      FIG. 7  is a detailed side sectional view of the board in  FIG. 1 . 
         [0049]    Referring to  FIG. 7 , the board  140  is a double side flexible circuit board and comprises a base film  141 , first and second copper foil layers  142  and  143 , first and second adhesive layers  145  and  146 , first and second coverlay layers  147  and  148 , an insulating ink layer  149 , a stiffener  150 , and a solder resist  153 . 
         [0050]    The base film  141  may comprise a polyimide film, and the first and second copper foil layers  142  and  143  are attached to both sides of the base film  141  by using a base adhesive. 
         [0051]    Predetermined circuit patterns may be formed in the first copper foil layer  142  and/or the second copper foil layer  143  and may be connected together through interface such as vias, via holes, or through-holes. 
         [0052]    A plating layer (not shown) may be formed on/under the first and second copper foil layers  142  and  143 . A gold plating layer (not shown) may be formed in an opened region  152  of the first copper foil layer  142  by an electroless plating process in order to protect the circuit patterns and prevent their oxidation. A copper plating layer may be formed in regions other than the opened region. 
         [0053]    The opened region  152  of the first copper foil layer  142  serves as the electrode pads  144  and  145 . The first coverlay layer  147  is attached to the top of the first coil layer  152 A by using the first adhesive layer  145 , and the insulating ink layer  149  is formed on the first coverlay layer  147 . 
         [0054]    The insulating ink layer  149  is coated using a permanent ink (photo solder resist ink (PSR)) which is a permanent compound having durability in physical and chemical environments. Accordingly, the insulating ink layer  149  can protect the circuits and prevent the solder overlapping phenomenon between the circuits during the mounting of parts. 
         [0055]    The second coverlay layer  148  is attached to the bottom of the second copper foil layer  143  by using the second adhesive layer  146 , and the stiffener  150  is attached to the bottom of the second coverlay layer  148 . 
         [0056]    The first coverlay layer  147  and the second coverlay layer  148  may be formed of polyimide. The stiffener  150  may be implemented with a polyimide film, and it reinforces the stiffness of the board  140  and prevents the bending thereof. The stiffener  150  prevents the tilt caused by the light emitting device ( 100  in  FIG. 1 ) mounted by an SMT process. 
         [0057]    On the top of the board  140 , a portion of the first copper foil layer  142  is opened to expose the electrode pads  144  and  145 . A solder resist  153  may be coated in an entire or partial surrounding of the opened region of the first copper foil layer  142 . Herein, after the light emitting device  100  is mounted on the electrode pads  144  and  145 , the solder resist  153  prevents the contamination of the mounted region and reduces the tilt of the mounted light emitting device. The thickness or height of such a solder resist  153  may be changed. 
         [0058]    Although the board  140  has been described with reference to the single-side exposed structure of the electrode pads  144  and  145 , it can also be implemented with a double-side exposed structure. Furthermore, the board  140  may be changed within the technical scope of the embodiments. 
         [0059]      FIG. 8  is a perspective view of a display device according to a second embodiment. 
         [0060]    Referring to  FIG. 8 , the display device  170  comprises a light emitting apparatus  160 , a light guide plate  173 , a reflection plate  171 , an optical sheet  175 , and a display panel  177 . The light emitting apparatus  160 , the light guide plate  173 , the reflection plate  171 , and the optical sheet  175  may be defined as a light unit. 
         [0061]    The light emitting apparatus  160  comprises a plurality of light emitting devices  100  on a board  140  and is disposed in one side of the light guide plate  173 . The light emitting apparatus  160  may be disposed on either or both sides of the light guide plate  173 , but it is not limited thereto. 
         [0062]    The light emitting apparatus  160  comprises the light emitting devices  100  and the board  140  and emits color lights, such as a red color, a green color and a blue color, or emits a white color. 
         [0063]    The board  140  may be implemented with a flexible board, and electrode pads  144  and  145  have the same shapes as the lead terminals ( 134  and  135  in  FIG. 1 ) with the larger sizes. 
         [0064]    Therefore, the light emitting devices  100  mounted on the board  140  is not almost tilted. Furthermore, the stiffener ( 150  in  FIG. 7 ) of the board  140  supports the board  140  in order not to be tilted in any one direction when boding the light emitting device  100 . Thus, it is possible to prevent the tilt problem of the light emitting device  100  and improve the electrical reliability of the light emitting device  100 . 
         [0065]    The light guide plate  173  serves as a light guide panel (LGP). The light guide plate  173  may comprise reflection patterns on the rear surface thereof, but it is not limited thereto. The light guide plate  173  guides light incident from the light emitting apparatus  160 , and reflects the guided light toward the panel direction. In this case, the surface light is irradiated onto the light guide plate  173 . 
         [0066]    The tilt problem of the light emitting devices  100  in the light emitting apparatus  160  can be solved. In this case, it is possible to prevent the light leakage phenomenon that some of the light emitted from the light emitting device  100  leaks out. Furthermore, it is possible to solve the problem that a portion of the light guide plate  173  becomes dark. 
         [0067]    The reflection plate  171  may be disposed on the rear surface of the light guide plate  173 , or may be disposed on the rear surface of the light guide plate  173  and a side where no light is incident. 
         [0068]    The reflection plate  171  reflects light leaking downward through the light guide plate  173  toward the direction of the panel. 
         [0069]    At least one optical sheet  175  may be disposed on the light guide plate  173  and may comprise a diffusion sheet, a prism sheet, and a brightness enhancement sheet. The diffusion sheet is disposed on the light guide plate  173  to diffuse the incident light. The prism sheet may comprise a horizontal prism sheet and/or a vertical prism sheet, and a brightness enhancement sheet. The prism sheet condenses the light diffused by the diffusion sheet toward a light emission region. 
         [0070]    The display panel  177  is disposed on the optical sheet  175  to display information according to the light irradiated from the light unit. A polarizer may be attached to the display panel  177 , but it is not limited thereto. 
         [0071]    In the description of the embodiments, it will be understood that when a layer (or film), region, pattern or component is referred to as being ‘on’ or ‘under’ another layer (or film), region, or patterns, the terminology of ‘on’ and ‘under’ comprises both the meanings of ‘directly’ and ‘indirectly’. 
         [0072]    Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is comprised in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
         [0073]    Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.