Abstract:
An LED package having a dual structure for lateral emission of light includes an LED chip, a lower structure, a lower lens and an upper lens. The lower structure includes a pair of electric connection parts, a package body, and a transparent encapsulant filled in the recess of the package body to seal the LED chip. The upper-hemispheric lower lens is fixed to an upper part of the lower structure with a bottom part thereof attached to an upper surface of the transparent encapsulant. The funnel-shaped upper lens is fixed to an upper end of the lower lens, and includes an axially symmetrical reflecting surface for laterally reflecting light from the lower lens, and an emitting surface for laterally emitting light reflected from the reflecting surface. The upper lens and the lower lens are separately molded and combined together to easily manufacture and efficiently install the LED package.

Description:
CLAIM OF PRIORITY 
     This application claims the benefit of Korean Patent Application No. 2005-65505 filed on Jul. 19, 2005, 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 a light emitting diode package having a lens structure for lateral emission of light, and more particularly, to a light emitting diode package which is easily manufactured by separately molding an upper lens and a lower lens and binding them together, and is efficiently installed. 
     2. Description of the Related Art 
     With recent developments in electronic devices industry, Liquid Crystal Displays (LCDs) are drawing attention as the next-generation display apparatus. An LCD does not generate light on its own, and thus typically requires a backlight module for generating light at the back of an LCD panel. 
       FIG. 1  is a sectional view illustrating an example of a conventional side-emitting Light Emitting Diode (hereinafter, referred to as LED) used in an LCD backlight module, disclosed in U.S. Pat. No. 6,679,621. 
     Referring to  FIG. 1 , the LED lens  10  disclosed in the above document includes an upper part having a reflecting surface I and a refracting surface H, and a lower part having a refracting surface  12 . In three dimensions, the LED lens  10  is shaped symmetrically about an axis A. 
     In this LED lens, light emitted from a focus F is reflected on the reflecting surface I and then exits through the refracting surface H to the outside, or light exits directly through the refracting surface  12 . As a result, light is hardly emitted upward but emitted laterally about the axis A. 
     However, the above conventional LED  10  has following problems. 
     First, it is difficult to mold the LED lens  10 . That is, it is difficult to precisely form a connection part L connecting the refracting surface H and the lower refracting surface  12 , and an inner vertex P where the reflecting surfaces I converge. Also, there may be lines formed on or in the proximity of the connection part L of the lens  10 . 
     Further, an additional process is required to prevent air bubbles while filling in a space S housing an LED chip denoted by the focus F with resin. 
     This process is explained with reference to  FIGS. 1  and  2 . First, the LED lens  10  is placed upside down and transparent resin  24  is poured to fill in the space S of the LED lens  10 . In the meantime, the LED chip  22  is mounted on a substrate  20 , and the coupled structure is attached to the upside-down LED lens  10  such that the LED chip  22  is positioned inside the space S of the LED lens  10 . The final structure is overturned again into the original position, which is shown in  FIG. 2 . 
     However, in this case, the air bubbles produced in the resin  24  in the space S cannot escape, which may degrade optical characteristics of the LED package. In addition, the LED chip  22  is immersed in the resin  24  in the space S, which results in the overflowing resin that is difficult to handle. 
     Moreover, the LED lens  10  has a complex structure and thus needs to be molded with resin having excellent moldability such as polycarbonate (PC) or polyethylene (PE). However, these kinds of resin are deformed typically at about 150° C., which restricts the process of mounting the package of  FIG. 2  on the backlight module. That is, the package should be mounted on the backlight module without any exposure of heat to the lens  10 , which complicates the manufacturing conditions. 
       FIG. 3  illustrates another conventional example with a lens structure improved from that in  FIGS. 1 and 2 . An LED lens  50  of  FIG. 3  has a different configuration of a refracting surface H from that in  FIG. 1  in order to increase light emission efficiency. The rest of the configuration except the refracting surface H is substantially identical with that in  FIGS. 1 and 2 . Also, a pair of leads  64  is added to supply power to the LED chip. 
     However, as the package of  FIG. 3  has the identical basic configuration with that in  FIGS. 1 and 2 , it is not free from the aforementioned problems regarding its structure and manufacturing processes. Further, the lens  50  has to be made of the same material as the LED lens  10  of  FIGS. 1 and 2 , which restricts the temperature conditions allowed in the manufacturing processes. 
     SUMMARY OF THE INVENTION 
     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 dual lens structure which is easily manufactured by separately molding and then binding an upper lens and a lower lens that are configured to laterally emit substantially all of the light from an LED chip, and is efficiently installed. 
     According to an aspect of the invention for realizing the object, there is provided a light emitting diode (LED) package having a dual lens structure including: an LED chip; a lower structure including a pair of electric connection parts for supplying power to the LED chip, a package body holding the electric connection parts and having a recess for upwardly guiding light from the LED chip, and a transparent encapsulant filled in the recess of the package body to seal the LED chip; a hemispheric lower lens fixed to an upper surface of the lower structure with a bottom part thereof attached to an upper surface of the transparent encapsulant; and a funnel-shaped upper lens fixed to an upper end of the lower lens, including an axially symmetrical reflecting surface for laterally reflecting light from the lower lens, and an emitting surface for laterally emitting light reflected from the reflecting surface. 
     Preferably, the lower lens has a planar undersurface for surface-to-surface contact with the upper surface of the lower structure. 
     The LED package according to the present invention may further include a transparent adhesive layer between the lower structure and the lower lens. 
     Preferably, the lower lens may have a groove formed on an upper end around an axis thereof, and the upper lens may have a projection which is formed on a lower end thereof and inserted into the groove of the lower lens, thereby being combined with the lower lens. At this time, the LED package may further include an adhesive layer between the groove of the lower lens and the projection of the upper lens. In addition, the upper lens may further include a plurality of second projections formed around the projection, and the lower lens may further include a plurality of second grooves formed around the groove for receiving the second projections. 
     Preferably, the lower lens has a plurality of projections on a periphery of an undersurface thereof, and the lower structure has a plurality of grooves formed around the recess for receiving the projections. 
     Preferably, each of the lower lens and the upper lens is made of one selected from a group consisting of epoxy molding compound, silicone, and epoxy resin. 
     The LED package according to the present invention may further include a heat conducting part for supporting the LED chip within the package body. The heat conducting part has a recess formed on a position directly below the recess of the package body for upwardly reflecting light generated from the LED chip. At this time, the heat conducting part may be integral with one of the electric connection parts. In addition, the heat conducting part may be composed of a plurality of metal plates, and the recess of the heat conducting part may be a hole formed in an uppermost one of the metal plates. Moreover, a portion of the heat conducting part and a portion of the package body around the LED chip may be cut out to form a slit-shaped path extending to the electric connection part, and the LED chip may be connected to the electric connection part by a wire through the slit-shaped path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a sectional view illustrating a conventional LED lens; 
         FIG. 2  is a sectional view illustrating a conventional LED package including the LED lens shown in  FIG. 1 ; 
         FIG. 3  is a side view illustrating another conventional LED package; 
         FIG. 4  is a perspective view illustrating an LED package according to the present invention; 
         FIG. 5  is an exploded view illustrating the LED package shown in  FIG. 4 ; 
         FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 4 ; 
         FIG. 7  is an exploded view illustrating the LED package shown in  FIG. 6 ; 
         FIG. 8  is a sectional view illustrating an LED package according to another embodiment of the present invention; 
         FIG. 9  is a sectional view illustrating a stepwise manufacturing method of the LED package according to the present invention; 
         FIG. 10  is a sectional view illustrating a stepwise manufacturing method of the LED package according to another embodiment of the present invention; 
         FIG. 11  is a perspective view illustrating the LED package in  FIG. 10(   a ) with transparent resin removed; 
         FIG. 12  is a sectional view illustrating a stepwise manufacturing method of an LED package according to yet another embodiment of the present invention; and 
         FIG. 13  is a sectional view illustrating a step of the manufacturing method of the LED package according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
       FIG. 4  is a perspective view illustrating an LED package having a dual lens structure according to the present invention,  FIG. 5  is an exploded view of the LED package shown in  FIG. 4 ,  FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 4 , and  FIG. 7  is an exploded view of the LED package shown in  FIG. 6 . 
     Referring to  FIGS. 4 to 7 , the LED package  100  having a dual lens structure according to the present invention includes a lower structure  110 , a lower lens  160  and an upper lens  180 . 
     The lower structure  110  includes a heat conducting part  112 , a lead  120 , a package body  130  holding parts of the heat conducting part  112  and the lead  120 , and a transparent encapsulant  140 . 
     The package body  130  is generally made of resin that is opaque or has high reflectivity. The package body  130  has a recess  132  surrounded by a stepped lower lens seating part  134 , in a central portion of an upper part  130   a  thereof. 
     The heat conducting part  112  is made of metal or preferably a metal plate and has a recess  114  formed on an upper surface thereof for housing an LED chip  102  therein. The heat conducting part  112  is electrically connected to the LED chip  102  by a wire  104  to function as an internal electric connection part. A part of the heat conducting part  112  is extended out of the package body  130  to form a lead  116 . In addition, the recess  114  functions as a reflecting mirror for upwardly reflecting light from the LED chip  102 . 
     The lead  120  has an electric connection part  118  electrically connected to the LED chip  102  by a wire  104 , and is insulated from the heat conducting part  112  by a part of the package body  130 . 
     The transparent encapsulant  140  is filled in the recess  114  of the heat conducting part  112  and in the recess  132  of the package body  130 . 
     The transparent encapsulant  140  is made of highly transparent resin that can transmit light generated from the LED chip  102  with minimum loss. Preferably, it can be made of elastic resin. Elastic resin refers to gel-type resin such as silicone, which exhibits minimal change by single-wavelength light, such as yellowing, while having high refractivity, thus demonstrating excellent optical characteristics. Further, unlike epoxy, it maintains gel or elastomer state even after being cured, and thus can stably protect the chip  102  from thermal stress, vibrations and external impacts. 
     In addition, the transparent encapsulant  140  is filled in the recesses  114  and  132  in a liquid state and cured, thus advantageously eliminating air bubbles therein during the curing process. That is, in the conventional LED package in  FIG. 2 , the resin  24  is cured with the lower part of the lens  10  and the substrate  20  combined together so that the air bubbles produced in the resin  24  may not escape. However, the transparent encapsulant  140  in the present invention is exposed to ambient air while being cured in the manufacturing process, allowing air bubbles to easily escape to the outside. 
     Here, an ultraviolet ray absorbent for absorbing ultraviolet rays generated from the LED chip  102  or phosphors for converting monochromatic light into white light can be mixed into the resin that constitutes the transparent encapsulant  140 . 
     The lower lens  160  is bonded to the upper surface of the transparent encapsulant  140  by a transparent adhesive layer  150 . The lower lens  160  is transparent and shaped like an upper hemisphere which is symmetrical about an axis A. The lower lens  160  has a flange  162  formed along a lower periphery, and has a recess  164  that is extended downward in the axial direction of the axis A in an upper end thereof. 
     The upper lens  180  is transparent and shaped like a funnel which is symmetrical about the axis A. The upper lens  180  has a projection  182  formed on a lower end thereof. The projection  182  is fixedly inserted into the groove  164  of the lower lens  160  by a transparent adhesive layer  170  therebetween. The projection  182  extends upward to a side surface  184  and a light emitting surface  186 . A reflecting surface  188  is formed on inner surfaces of the upper lens  180  to internally reflect light, or to preferably satisfy total internal reflection conditions. 
     The lower lens  160  and the upper lens  180  are combined together to have a substantially hourglass-shaped section. Therefore, a portion of light generated from the LED chip  102  is reflected at sides of the lower lens  160  to the outside. Another portion of light passes through the lower lens  160 , internally reflected by the reflecting surface  188  of the upper lens  180 , and emitted to the outside through the emitting surface  186 . Therefore, light generated from the LED chip  102  is hardly emitted upward but mainly emitted laterally. 
     In the meantime, since the lower lens  160  and the upper lens  180  are separately molded and bonded together by the adhesive layer  170 , they can be manufactured in a simple form compared with the conventional lenses in  FIGS. 1 to 3 . Thus, they can be manufactured using at least one selected from a group consisting of epoxy molding compound (EMC), silicone and epoxy resin besides polycarbonate and polyethylene. Once cured, these materials are not deformed even at a temperature of 150° C. or higher, and thus the lower and upper lenses  160  and  180  have greater process flexibility in terms of temperature and heat conditions compared with the conventional lenses. As a result, the LED package  100  can be manufactured at a relatively high temperature of at least 150° C. In particular, when mounting the LED package  100  to the backlight module, the leads  116  and  120  can be connected to wires of the substrate through various processes involving high temperature such as welding and soldering. 
     Meanwhile, the adhesive layers  150  and  170  can be substituted by other means or omitted. For example, before the transparent encapsulant  140  is completely cured, a transparent adhesive or epoxy can be applied on an undersurface of the lower lens  160 , and the lower lens  160  can be placed on the upper surface of the transparent encapsulant  140 , thereby solidly adhering the lower lens  160  to the transparent encapsulant  140  without forming any interfacial adhesive layers. 
     In addition, the projection  182  of the upper lens  180  can be formed to tightly fit into a groove  164  of the lower lens  160  or formed a bit larger than the groove  164  so that the projection  182  can be press-fitted into the groove  164 , thereby binding the lower lens  160  with the upper lens  180 . Needless to say, a small amount of adhesive can be poured into the groove  164  where the projection  182  can be inserted, thereby enhancing the effect of pressed-fitting. 
     Another binding structure of the lower and upper lenses will now be explained with reference to  FIG. 8 . 
     Referring to  FIG. 8 , the lower lens  160 - 1  has projections  163  on an undersurface thereof. These projections  163  are inserted into grooves (not shown) formed on the seating part  134  (see  FIGS. 6 and 7 ) of the package body, thereby binding the lower lens  160 - 1  with the package body. Needless to say, an adhesive can be poured into the grooves of the seating part and the projections  163  can be inserted thereinto, thereby enhancing the effect of binding by insertion. 
     In addition, projections  183  are formed also on a lower surface of the upper lens  183 , and corresponding grooves are formed on an upper end of the lower lens  160  so that the projections  183  are inserted into the grooves to bind the upper lens  180  with the lower lens  160 . Needless to say, an adhesive can be poured into the grooves of the lower lens  160  and the projection  183  can be inserted thereinto, thereby enhancing the effect of binding by insertion. 
     In the meantime, the heat conducting part  112  may not function as an electric connection part. For example, rather than connecting the lead  116  with the heat conducting part  112 , another lead  120  having an electric connection part  118  can be formed to supply power to the LED chip  102 . 
     In addition, instead of forming a recess  114  on the heat conducting part  112 , the height of an upper part  130   a  of the package body  130  can be increased, thereby ensuring a sufficient thickness of the transparent encapsulant  140  covering the LED chip  102  and the wires  104 . Alternatively, the wires  104  can be formed low as shown in  FIGS. 10 and 11 , explained later, so that the wires  104  can be sealed without the recess  114  nor having to increase the height of the upper part  130   a  of the package body  130 . 
     Now, a manufacturing method of the LED package  100  having a dual lens structure according to the present invention will be explained with reference to  FIG. 9 . 
     First, as shown in  FIG. 9(   a ), a heat conducting part  112  formed integrally with a lead  116 , having a recess  114  on a central portion of an upper surface thereof, and a lead  120  having an electric connection part  118  are prepared. Then, a package body  130  is formed to hold the heat conducting part  112  and the electric connection part  118 , and has a recess  132  formed in a position above the heat conducting part  112  and the electric connection part  118 . Next, an LED chip  102  is mounted on the recess  114  of the heat conducting part  112 , and connected to the heat conducting part  112  and the electric connection part  118  by wires  104 . 
     Thereafter, as shown in  FIG. 9(   b ), transparent resin is filled in the recesses  114  and  132  and cured to form a transparent encapsulant  140 , thereby obtaining a lower structure  110 . This lower structure  110  is identical with the one explained hereinabove with reference to  FIGS. 4 to 7 . 
     Next, as shown in  FIG. 9(   c ), an adhesive layer  150  is applied on an upper surface of the transparent encapsulant  140  to attach a lower lens  160  on the transparent encapsulant  140 . Then, as shown in  FIG. 9(   d ), an adhesive layer  170  is applied to bond an upper lens  180  on the lower lens  160 , thereby completing an LED package  100  according to the present invention. The LED package  100  has the same configuration explained hereinabove with reference to  FIGS. 4 to 7 . 
     As described above, the lower structure  110 , the lower lens  160  and the upper lens  180  are individually formed, and combined together in their order to complete the LED package. This allows simplifying the shapes of the lower and upper lenses  160  and  180 , and easier manufacturing process of the LED package  100 . 
     In the meantime, before conducting the step of  FIG. 9(   c ), electric/optical tests can be conducted on the structure of  FIG. 9(   b ). Thereby, defects can be detected in the middle process to avoid any unnecessary follow-up procedures. 
     Now, an LED package having a dual lens structure and a manufacturing method of the same according to another embodiment of the present invention will be explained with reference to  FIGS. 10 and 11 . 
     The LED package  100 - 1  according to this embodiment has the identical configuration with the aforedescribed LED package  100  except a lower structure  110 - 1 . Therefore, the same reference numerals are used for the corresponding components. 
     First, referring to  FIGS. 10(   a ) and  11 , a heat conducting part  112  formed integrally with a lead  116 , having a recess  114  on a center of an upper surface, and a lead  120  having an electric connection part  118  are prepared. At this time, the heat conducting part  112  has a slit-shaped path  115  extending to the electric connection part  118 . A package body  130  is formed to hold the heat conducting part  112  and the electric connection part  118 . The package body  130  has a recess  132  formed above the heat conducting part  112  and the electric connection part  118 , and has a slit-shaped path  131  connected to the slit-shaped path  115  of the heat conducting part  112 . Next, an LED chip  102  is mounted on a recess  114  of the heat conducting part  112  and connected to the heat conducting part  112  and the electric connection part  118  by wires  104 . At this time, a wire  104  is connected to an upper surface of the heat conducting part  112  inside the recess  114 , and the other wire  104  is connected to the heat conducting part  112  through the paths  115  and  131 . 
     Thereafter, transparent resin is filled in the recess  114  and the paths  115  and  131  and cured to form a first transparent encapsulant  140 , thereby obtaining a lower structure  110 - 1 . At this time, an ultra-violet ray absorbent for absorbing the ultra-violet rays generated from the LED chip  102  or phosphors for converting monochromatic light into white light may be mixed into the resin constituting the first transparent encapsulant  140 . 
     Then, as shown in  FIG. 10(   b ), transparent resin is filled in the recess  132  of the package body  130  and cured to form a second encapsulant  142 . 
     The first and second transparent encapsulants  140  and  142  are made of resin having high transparency, which can transmit light generated from the LED chip  102  with minimum loss, and preferably, made of elastic resin. The elastic resin refers to silicone or gel-type resin, which exhibits minimal change by single wavelength light, such as yellowing, while having high refractivity, thus demonstrating excellent optical characteristics. In addition, unlike epoxy, it maintains gel or elastomer state after it is cured, thus it can protect the chip  102  more stably from thermal stress, vibrations, and external impacts. 
     Next, as shown in  FIG. 10(   c ), an adhesive layer  150  is applied on an upper surface of the second transparent encapsulant  142  to attach a lower lens  160  thereon. Then, as shown in  FIG. 10(   d ), an adhesive layer  170  is applied to bond the upper lens  180  on the lower lens  160 , thereby completing the LED package  100 - 1 . 
     As described hereinabove, the LED package  100 - 1  has substantially the identical structure with the LED package  100  explained with reference to  FIGS. 4 to 7 , except a lower structure  110 - 1 . 
     As described above, the lower structure  110 - 1 , the lower lens  160  and the upper lens  180  are individually formed and then combined together in their order to complete the LED package  100 - 1 . This allows simplifying the shapes of the lower and upper lenses  160  and  180  and easy manufacturing process of the LED package  100 - 1 . 
     In the meantime, before conducting the step of  FIG. 10(   c ), electric/optical tests may be conducted on the structure of  FIG. 10(   b ). This allows detecting defects in the middle process, thereby avoiding any unnecessary follow-up procedures. 
     Now, an LED package having a dual lens structure and a manufacturing method of the same according to yet another embodiment of the present invention will be explained with reference to  FIG. 12 . 
     The LED package  100 - 2  according to this embodiment has the substantially identical configuration with the LED package  100  described hereinabove except a lower structure  110 - 2 . Therefore, the same reference numerals are given to corresponding components. 
     Specifically, the heat conducting part  112  of the LED package  100  is one member, but a heat conducting part corresponding to the LED package  100 - 2  according to this embodiment may be composed of an upper metal plate  112   a  and a lower metal plate  112   b . The upper metal plate  112   a  has a recess  114  formed thereon for housing an LED chip  102  and is extended out of the package body  130  to form a lead  116 . The lower metal plate  112   b  is integrally combined with the upper metal plate  112   a  to draw out the heat generated from the LED chip  102  and transferred via the upper metal plate  112   a . The upper and lower metal plates  112   a  and  112   b  can be combined together by adhesion, welding (spot welding) to operate as one member. 
     The rest of the configuration of the LED package  100 - 2  except the above described points is identical with the LED package  100 , and the corresponding manufacturing method of the LED package  100 - 2  is also identical with the method shown in  FIG. 8 . 
     In the meantime, the heat conducting part having a plurality of metal plates  112   a  and  112   b  as described above can be adopted in the lower structure  110 - 1  shown in  FIGS. 10 and 11 . For example, the path  113  of  FIG. 11  can be formed on the portion of the metal plate  112   a  toward the electric connection part  118 , and also the path  131  of  FIG. 11  can be formed in the adjacent part of the package body  130 , extending to the path  113 . 
     The rest of the configuration of this embodiment is identical with the LED package  100  shown in  FIGS. 4 to 7 , and the rest of the manufacturing steps are identical with those in  FIG. 9 . 
     Now, mass-production of the LED package according to the present invention will be explained with reference to  FIG. 13 . A frame sheet  200  can be used to form a plurality of lower structures  110 , thereby simultaneously manufacturing a plurality of LED packages. 
     The frame sheet  200  has a plurality of heat conducting parts  112  and leads  116  and  120  formed therein and holes H formed in the periphery for fixing and guiding. The lead  116  is connected integrally with the heat conducting part  112 , and the other lead  120  is located in opposite side of the heat conducting part  112 . Using molds (not shown), resin is injection-molded onto these heat conducting parts  112  and the leads  120  to obtain a plurality of lower structures  110 . 
     At this time, the lower structure  110  can be any one of the structures described hereinabove, but is exemplified with the one shown in  FIGS. 4 to 7  for the sake of convenience. That is, the configuration of  FIG. 13  can be understood from that of  FIG. 9(   a ). 
     Next, the step of  FIG. 9(   b ) is conducted, and then, the leads  116  and  120  are cut out along the trimming line L T  to obtain each unit structure. A plurality of combined structures of lower structures  110  and transparent encapsulants  140  can be obtained through a single procedure. 
     Then, the steps of  FIGS. 9(   c ) and  9 ( d ) are conducted to obtain the LED package  100 . 
     Alternatively, after conducting the steps of  FIGS. 9(   b ) through  FIG. 9(   d ), the cutting procedure can be conducted to obtain a plurality of unit LED packages  100 . This allows obtaining a plurality of LED packages  100  in a single procedure, increasing efficiency. 
     As set forth above, the LED package having a dual lens structure according to the present invention is easily manufactured by separately molding and then binding an upper lens and a lower lens configured to laterally emit light from an LED chip, and is efficiently installed. 
     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.