Abstract:
The invention relates to an LED package for facilitating color mixing using a diffuser and a manufacturing method of the same. The LED package includes a substrate with an electrode formed thereon, and an LED chip mounted on the substrate. The LED package also includes an encapsulant applied around the light emitting diode chip, containing a diffuser. The LED package further includes a lens part disposed on the light emitting diode chip and the encapsulant to radiate light in a wide angle. The LED package allows light from the light emitting diode chip to be emitted out of the package without distortion. The invention allows light to exit through the encapsulant containing the diffuser and the lens part, achieving uniform diffusion and emission of light from the LED chip, thereby increasing a radiating angle and obtaining a uniform light source.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims the benefit of Korean Patent Application No. 2005-67859 filed on Jul. 26, 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 incorporating a diffuser to facilitate color mixing and to a manufacturing method of the same. More particularly, the invention relates to an LED package in which a diffuser is applied to an encapsulant disposed in an upper part of an LED chip to achieve color mixing, enabling uniform emission without distortion of light from the LED chip in a wide radiating angle, thereby facilitating color mixing while reducing a thickness and enhancing a degree of freedom of a lens part, and to a manufacturing method of the same.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, various sizes of LED packages are used for backlight units of mobile phones or Personal Digital Assistants (PDAs).  
         [0006]     Such conventional LED packages are increasingly reduced in its thickness as the backlight units are becoming slimmer.  
         [0007]     For such backlight units, the LED packages are popular as light sources therefor, and thus various structures or shapes of LED package are currently examined and developed.  
         [0008]     The LED packages used for LCD Televisions or monitors are structurally categorized into an edge lighting type, a top emitter, and a side emitter. The most important factor among these LED packages is to achieve good color mixing to make a white light source.  
         [0009]     Such an example of a conventional LED package is illustrated in  FIG. 1 .  
         [0010]     The conventional LED package  200 , disclosed in U.S. Patent No. 2005-0057144, includes a substrate  205  with electrode patterns  207   a  and  207   b  formed thereon, and an LED chip  210  mounted on the electrode pattern  207   b  and electrically connected to the electrode patterns  207   a  and  207   b  by wires  211 .  
         [0011]     The conventional LED package  200  has a reflecting frame  212  disposed on the substrate  205  for housing the LED chip  210 , and a reflecting layer  214  formed on an inner side of the reflecting frame  212 . The reflecting layer  214  serving as a reflecting surface is made of Al and/or Ag having high reflectivity deposited or painted thereon.  
         [0012]     In addition, a wavelength-converting material part  220  is formed in an inner space of the reflecting frame  212  where the LED chip  210  is mounted. The wavelength-converting material part  220  comprises transparent resin containing a phosphor  222   a  and a diffuser  222   b,  and encapsulates the LED chip  210 .  
         [0013]     In the above-described LED package  200 , when emission takes place from the LED chip  210  and light is emitted, the light is directed to the wavelength-converting material part  220  by the reflecting layer  214 . The light then collides with the phosphor  222   a  contained in the wavelength-converting part  220  to excite the phosphor  222   a,  and is scattered by a plurality of diffusers  222   b  contained in the wavelength-converting material part  220 . As a result, light having a longer wavelength than the light that was incident onto the phosphor  222   a  exits the package due to the interaction between the phosphor  222   a  and the diffuser  222   b.    
         [0014]     Although the conventional technology is useful for elongating the wavelength of light emitted from the LED chip  210  and emitting white light, it does not necessarily allow uniform light emission. The conventional technology allows color mixing to generate white light, but emits white light only forward without a variety in radiating angles. Further, as it realizes white light using the phosphor  222   a,  it has mediocre color reproducibility.  
         [0015]     Another conventional LED package  250  is illustrated in  FIG. 2 .  
         [0016]     As disclosed in Japanese Patent Application Publication No. 2001-60724, the LED package  250  includes an LED chip  260  positioned in a lamp housing  255  having a hollow part, electrodes  262   a  and  262   b  drawn out from the LED chip  260 , and an encapsulant  270  filled in the lamp housing  255  for fixing the LED chip  260  and the electrodes  262   a  and  262   b.    
         [0017]     In such a conventional LED package  250 , the lamp housing  255  having a hollow part is disposed such that its emitting surface is positioned in a lower part., Then, the encapsulant  270  composed of transparent thermosetting resin with glass beads  272  having a high refractive ratio mixed therein at a suitable ratio is injected into the hollow part of the lamp housing  255  from the back of the LED chip  260 .  
         [0018]     Then, after the glass beads  272  precipitate in the encapsulant  270  made of transparent thermosetting resin, the encapsulant  270  is heated and cured to complete the LED package  250 .  
         [0019]     In such a conventional LED package  250 , the glass beads  272  in the encapsulant  270  of transparent thermosetting resin function as a diffuser and scatter light to some degree. However, the light is directed only forward in a not-so-wide radiating angle due to the hollow part of the lamp housing  255 , and it is difficult to reduce the thickness of the LED package  250  due to the structural characteristics of the electrodes  262   a  and  262   b  and the lamp housing  255 .  
         [0020]     In addition, the conventional LED package  250  is complicated to manufacture, thus not suitable for mass production.  
         [0021]      FIG. 3  illustrates yet another conventional LED package  300 . The conventional LED package  300  includes a base substrate  305  with electrodes  310   a  and  310   b  formed thereon, an LED chip  312  mounted on and connected to the electrodes  310   a  and  310   b,  and a molded frame  315  having a groove, thus being fixed around the LED chip  312 .  
         [0022]     Then, a molding member  317  containing a diffuser  317   a  is filled in the groove of the molded frame  315 . This conventional LED package  300  achieves high luminance and contrast ratio using the diffuser  317   a  contained in the molding member  317  made of transparent resin, thereby enabling a high contrast display in a large angle of visibility in high precision.  
         [0023]     However, the conventional LED package  300  also emits light only forward from the molded frame  315 , and does not achieve excellent light emission.  
         [0024]     When applied to the backlight units to produce white light using red, green, and blue lights, each of the above described LED packages  200 ,  250  and  300  is required in a plural number to uniformly illuminate a large area and mix colors, increasing the number of components.  
         [0025]     Therefore, the conventional LED packages  200 ,  250  and  300  result in increased manufacturing costs of the LCD products due to the increased number of components.  
       SUMMARY OF THE INVENTION  
       [0026]     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 using a diffuser which achieves uniform emission of light generated from an LED chip to make a uniform light source, and a manufacturing method of the same.  
         [0027]     Another object of certain embodiments of the invention is to provide an LED package using a diffuser which emits light generated from an LED chip in a wide radiating angle without distortion of light, thereby increasing a degree of freedom and reducing a thickness of a lens part, and a manufacturing method of the same.  
         [0028]     Further another object of certain embodiments of the invention is to provide an LED package using a diffuser which constitutes a Liquid Crystal Display (LCD) backlight unit in a fewer number, thereby decreasing the number of LED package components and reducing the manufacturing costs of the LCD backlight unit, and a manufacturing method of the same.  
         [0029]     According to an aspect of the invention for realizing the object, there is provided a light emitting diode package including: a substrate with an electrode formed thereon; a light emitting diode chip mounted on the substrate; an encapsulant applied around the light emitting diode chip, the encapsulant containing a diffuser; and a lens part disposed on the light emitting diode chip and the encapsulant to radiate light in a wide angle, whereby light from the light emitting diode chip is emitted out of the package without distortion.  
         [0030]     Preferably, the substrate has a step formed on an upper surface thereof, the step surrounding a portion of the substrate where the light emitting diode chip is mounted.  
         [0031]     Preferably, the substrate has a reflective layer formed on a side surface of a recessed portion formed on an upper surface thereof, the reflective layer surrounding the light emitting diode chip mounted on the substrate.  
         [0032]     Preferably, the lens part is made of a material mixed with a phosphor.  
         [0033]     Preferably, the lens part is made of a material mixed with a diffuser.  
         [0034]     Preferably, the lens part is made of a material mixed with a phosphor and a diffuser.  
         [0035]     According to another aspect of the invention for realizing the object, there is provided a manufacturing method of a light emitting diode package including steps of: providing a substrate with an electrode formed thereon; mounting a light emitting diode chip on the substrate; applying an encapsulant containing a diffuser to cover the light emitting diode chip; and attaching a lens part on the encapsulant, whereby light from the light emitting diode chip is emitted out of the package without distortion.  
         [0036]     In addition, the diffuser comprises an opal based material.  
         [0037]     Further, the opal based material is one selected from a group consisting of barium titanate, titanium dioxide, aluminum oxide, silicon dioxide and combinations thereof. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0038]     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:  
         [0039]      FIG. 1  is a sectional view illustrating a conventional LED package;  
         [0040]      FIG. 2  is a sectional view illustrating another conventional LED package;  
         [0041]      FIG. 3  is a sectional view illustrating yet another conventional LED package;  
         [0042]      FIG. 4  is a sectional view illustrating an LED package using a diffuser according to the present invention;  
         [0043]      FIG. 5  is an exploded view illustrating the LED package according to the present invention;  
         [0044]      FIG. 6  is an exploded view illustrating a cavity of the LED package using a diffuser according to the present invention;  
         [0045]      FIG. 7  is a perspective view illustrating the LED package using a diffuser with an encapsulant applied on the substrate of the LED package using a diffuser according to the present invention;  
         [0046]      FIG. 8  is a view illustrating traces of light scattered, reflected and diffused out of the LED package using a diffuser according to the present invention; and  
         [0047]      FIG. 9 ( a ) and ( b ) are views illustrating the LED packages, using a diffuser of the invention disposed in an array to be used for an LCD backlight. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0048]     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0049]     As shown in  FIG. 4 , an LED package  1  using a diffuser according to the present invention has a substrate  10  with electrodes  5   a  and  5   b  formed thereon. The substrate  10  preferably has a planar structure molded with molding material, and has each of the electrodes  5   a  and  5   b  formed thereon to provide power to an LED chip  20  described later.  
         [0050]     The LED chip  20  is mounted on an upper part of the substrate  10  and electrically connected to the electrodes  5   a  and  5   b  by wire bonding, etc. The invention is applicable to either a horizontal type of LED chip  20  with all electric terminals formed on an upper surface thereof, or a vertical type of LED chip  20  with electric terminals formed on both upper and lower surfaces thereof.  
         [0051]     In addition, a step  25  is formed on an upper surface of the substrate  10  to surround the portion where the LED chip  20  is mounted.  
         [0052]     Such a step  25  is formed in an annular form on an upper surface of the substrate  10 , and as described later, an encapsulant  30  is applied in an appropriate amount in a recessed portion formed by the step  25  and thus prevented from spreading over the substrate  10 .  
         [0053]     In addition, the encapsulant  30  is applied to cover the LED chip  20  and the substrate  10 . As shown in detail in  FIG. 7 , the encapsulant  30 , which is applied on the substrate  10  to surround the LED chip  20 , contains a diffuser  32  therein. The encapsulant  30  serves to maintain a uniform light source generated from the LED chip  20 , and has a diffuser  32  added thereto in order to enable diffusion of light.  
         [0054]     Therefore, the encapsulant  30  adjusts the degree of scattering, transmittance and refraction of light with the diffuser  32  contained therein, thereby assisting uniform emission of light.  
         [0055]     The encapsulant  30  is made of resin such as silicone or epoxy, and the diffuser  32  is made of an opal based material, i.e., one selected from a group consisting of, barium titanate, titanium dioxide, aluminum oxide, silicon dioxide and combinations thereof. The diffuser  32  is added to the encapsulant  30  in the amount of 25 weight % or less of the total weight of the encapsulant  30 .  
         [0056]     In addition, the LED package  1  has a lens part  40  disposed above the LED chip  20  and the encapsulant  30  to emit light in a wide radiating angle. The lens part  40  is formed by curing epoxy resin and the like, and preferably is made of transparent epoxy. Preferably, the lens part  40  may be made of a material with a phosphor  42  mixed therein.  
         [0057]     Moreover, preferably, the lens part  40  may be made of a material with a diffuser  32  mixed therein instead of a phosphor  42 , or both a phosphor  42  and a diffuser  32  mixed therein.  
         [0058]     As shown in  FIG. 6 , the LED package  1  of the invention may preferably comprise a so-called cavity structure in which the LED chip  20  is mounted in a recessed portion on the substrate  10 , and thus surrounded by a reflecting layer  50  formed on a side surface of the recessed portion.  
         [0059]     The reflecting layer  50  may be formed by plating or depositing metal selected from a group consisting of Al, Au, Ag, Ni, W, Ti and Pt, or by applying a paint of high reflectivity.  
         [0060]     A manufacturing method of the LED package  1  using a diffuser according to the present invention will now be explained in detail.  
         [0061]     The manufacturing method of the LED package using a diffuser starts with a step of providing the substrate  10  with the electrodes  5   a  and  5   b  formed thereon.  
         [0062]     The electrodes  5   a  and  5   b  are formed on the substrate  10  to supply power to the LED chip  20 , and as described later, the step  25  is formed on an upper surface of the substrate  10 , surrounding the portion where the LED chip  20  is mounted.  
         [0063]     In addition, as shown in  FIG. 5 , the substrate  10  may comprise a structure, in which the LED chip  20  is positioned on a protruding portion of the substrate  10 , or as shown in  FIG. 6 , may comprise a cavity structure, in which the LED chip  20  is disposed within a recessed portion surrounded by the reflecting layer  50 .  
         [0064]     Next, the LED chip  20  is disposed on the substrate  10 . The LED chip  20  is mounted on the substrate  10 , and electrically connected to the electrodes  5   a  and  5   b  of the substrate  10  by wire bonding.  
         [0065]     Then, the encapsulant  30  is applied on the LED chip  20  and the substrate  10 .  
         [0066]     In this step, the encapsulant  30  is transparent epoxy resin containing a diffuser  32 . As shown in  FIG. 7 , the amount of the encapsulant  30  applied is determined beforehand such that the encapsulant  30  is filled inside the recessed portion formed by the step  25  of the substrate  10  and does not spread over the substrate  10  to drip due to surface tension of the encapsulant  30 .  
         [0067]     Next, the lens part  40  is attached on the encapsulant  30 . In this step, the lens part  40  is placed over the encapsulant  30 , and as shown in  FIG. 8 , the encapsulant  30  fills up a recess  44  formed on a bottom surface of the lens part  40  to attach the lens part  40  on the substrate  10 . Then, the encapsulant  30  is cured to integrally form the lens part  40  with the substrate  10 .  
         [0068]     In this step, the lens part  40  may be made of transparent material, which however may be prepared in advance to contain either a phosphor  42  or a diffuser  32  mixed therein, or both a phosphor  42  and a diffuser  32  mixed therein.  
         [0069]     As shown in  FIG. 9 , the LED package  1  using a diffuser according to the present invention may be arranged in a plural number in a row to be disposed as an array in an LCD backlight unit.  
         [0070]     In the LED package  1  using a diffuser with above described configuration, the lens part  40  is attached to the substrate  10  via the encapsulant  30  containing the diffuser  32 , which is applied on the substrate  10  where the LED chip  20  is mounted.  
         [0071]     In the LED package  1  using a diffuser according to the present invention, when light is generated from the LED chip  20 , the light is emitted through the encapsulant  30  and the lens part  40 , and thus emitted in a wide radiating angle. Specifically, light is diffused more broadly due to the diffuser  32  contained in the encapsulant  30  and/or the lens part  40 , achieving a wider radiating angle, thereby uniformly illuminating a large area with a fewer number of LED packages  1 .  
         [0072]     When the light is emitted from the LED chip  20  to pass through the encapsulant  30  and the lens part  40 , the light is diffused at the diffuser  32 , thereby reflected or scattered in more various directions, allowing uniform mixing of colors. This is suitable for a structure such as the LCD backlight unit, which requires uniform mixing of red, green and blue lights.  
         [0073]     In addition, the LED package  1  is a structure in which the light from the LED chip  20  is emitted out of the package without distortion by the assistance of only the diffuser  32 . Thus, the lens part  40  is free to be configured in various structures. That is, the lens part  40  can have various structures such as in a small height or asymmetrical shape depending on the structural characteristics of the LCD backlight unit, thereby increasing a degree of freedom of the lens part  40 .  
         [0074]     In addition, the lens part  40  can be made of a material mixed with a phosphor  42  in addition to the diffuser  32 , enabling more various color mixing, thereby attaining desired good quality white light.  
         [0075]     According to the present invention set forth above, the light generated from the LED chip passes through the encapsulant containing the diffuser and the lens part to exit the package, achieving uniform diffusion and emission without distortion of light, thereby obtaining a uniform light source with an enlarged radiating angle.  
         [0076]     In addition, as light generated from the LED chip is emitted in a wider angle by the diffuser, the lens part can be configured variously such as with a lower height, thereby reducing the thickness and increasing a degree of freedom of the lens part.  
         [0077]     Furthermore, the invention allows a wide radiating angle, enabling construction of the LCD backlight unit with a fewer number of LED packages and with a reduced number of LED package components, thereby reducing the manufacturing costs of the LCD backlight unit.  
         [0078]     While the present invention has been shown and described in connection with the preferred embodiments, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 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.