Patent Publication Number: US-2010110686-A1

Title: Led light module

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to an LED light module, and particularly, to an LED light module of white light resulting from a mixture of asymmetric lights. 
     2. Description of the Prior Art 
     LED has advantages of high brightness, mercury-free, long life expectancy, and less energy consumption so that LED is considered as one of the light sources in the next generation. LED may be used as the major light source in cell phones, automotive lightings, and outdoor large displays. In addition, LED has characteristics of high saturation and good color reproduction and has potential for replacing CCFL in the back light module. 
       FIG. 1  and  FIG. 2  are schematic diagrams illustrating a conventional bullet-shaped LED package  10 .  FIG. 1  shows the bullet-shaped LED package  10  in a cross-sectional view, and  FIG. 2  shows a top view diagram of the bullet-shaped LED package  10 . The bullet-shaped LED package  10  has a lead frame  12 , a resin molding  14 , and an LED die  16 . The lead frame  12  includes a base  121  and two leads  122 . The LED die  16  is disposed on the base  121  and electrically connected to the leads  122  through a respective wire  18  for power supply that allows the LED die  16  for radiation. The LED die  16 , the base  121 , and the front end of the lead  122  are encapsulated by the resin molding  14 . As shown in  FIG. 1 , the front of the resin molding  14  is a sphere surface  141 , and the LED die  16  is disposed at the radius of curvature of the sphere surface  141 . The lights generated by the LED die  16  are refracted and at the sphere surface  141 , and the refracted lights are scattered symmetrically. Additionally, the refracted lights follow the Lambert&#39;s cosine law and have a Lambertain light distribution property. 
     Please refer to  FIG. 3 .  FIG. 3  is a schematic diagram illustrating another conventional back light module  20 . The back light module  20  provides white lights by means of mixing lights from a red LED package  22 , a green LED package  24 , and a blue LED package  26 , in which the lights from the red LED package  22 , the green LED package  24 , and the blue LED package  26  have a Lambertain light distribution property. However, the overlapped region of the lights from the red LED package  22 , the green LED package  24 , and the blue LED package  26  is limited by the position of the LED packages and the symmetrical distribution of the lights generated by the red LED package  22 , the green LED package  24 , and the blue LED package  26 . It is difficult to overlap the red lights, the blue lights, and the green lights from the respective LED package for providing well mixed white lights. 
     In order to provide well mixed white lights, a conventional surface mount device (SMD) type LED package  30  is shown in  FIG. 4 . The SMD type LED package  30  packages a plurality of LED dies, such as two red LED dies  32 ,  36 , a blue LED die  34 , and a green LED die  38  in a reflective cup  40 . The LED dies are electrically connected to a plurality of wires  42  for power supply. Lights generated by the LED dies  32 ,  34 ,  36 , and  38  are reflected at the surface of the reflective cup  40  and mixed to result in white lights having Lambertain light distribution property. However, the SMD type LED package  30  have to package several LED dies in the same reflective cup  40  that increases complexity of manufacturing process and production cost. If one of the packaged LED die breaks down, the defective LED die decreases reliability and the yield of the back light module having the SMD type LED package  30 . Besides, it is difficult to replace the defective LED die. Therefore, the SMD type LED package  30  is not an ideal light source for back light module. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary objective of the present invention is to solve the problems of uneven mixing light, high production cost, and laborious product maintenance. 
     According to the present invention, an LED light module capable of providing well mixed lights. The LED light module includes a substrate and a plurality of shifted-disposed LED packages disposed on the substrate, in which the shifted-disposed LED packages are arranged as a polygon. Each of the shifted-disposed LED packages has a base, an LED die disposed aside from a center of the base in a predetermined distance. 
     The LED light module of the present invention uses the shifted-disposed LED packages as its light source. Lights generated by the shifted-disposed LED packages are distributed asymmetrically and are refracted in a particular direction. Accordingly, lights of different colors are overlapped in a predetermined region and resulted in well mixed white light. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  and  FIG. 2  are schematic diagrams illustrating a conventional bullet-shaped LED package. 
         FIG. 3  is a schematic diagram illustrating another conventional back light module. 
         FIG. 4  is a schematic diagram illustrating a conventional surface mount device (SMD) type LED package. 
         FIG. 5  through  FIG. 9  are schematic diagrams illustrating an LED light module according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part of this application. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     Please refer to  FIG. 5  through  FIG. 9 .  FIG. 5  through  FIG. 9  are schematic diagrams illustrating an LED light module  50  according to a preferred embodiment of the present invention. As shown in  FIG. 5 , the LED light module  50  has a substrate  52  and a plurality of shifted-disposed LED packages disposed on the substrate  52 . For example, the shifted-disposed LED packages of the present preferred embodiment include a red shifted-disposed LED package  54 , a green shifted-disposed LED package  56 , and a blue shifted-disposed LED package  58 . Red lights from the red shifted-disposed LED package  54 , green lights from the green shifted-disposed LED package  56 , and the blue lights from blue shifted-disposed LED package  58  are overlapped and resulted in well mixed white lights, and accordingly, the LED light module  50  is capable of providing well mixed white lights. The substrate  52  may be a single-layered or a multi-layered circuit board for electrical connection of the shifted-disposed LED packages or electrical connection among the shifted-disposed LED packages, other devices on the substrate, and devices for power supply. Furthermore, a reflective layer (not shown) is preferably disposed on the substrate  52  for improving light emitting efficiency of the LED light module  50 . 
     Please refer to  FIG. 5  in company with  FIG. 6  and  FIG. 7 .  FIG. 6  shows the structure of the green shifted-disposed LED package  56  as an example to illustrate the structures of the shifted-disposed LED packages of the present invention.  FIG. 7  shows a polar coordinate representation of the angular distribution of light intensity of shifted-disposed LED packages of the present invention. As shown in  FIG. 6 , the green shifted-disposed LED package  56  has a base  561 , a green LED die  562 G, and a lens  563 . The base  561  includes a center  564 . Any line passing through the center  564  divides the base  561  into two equal parts. The preferable base  561  is a plane and has a reflective layer (not shown) disposed thereon. The green LED die  562 G is disposed on a top surface  565  of the base  561 , and is electrically connected to the base  561 , the substrate  52 , and other circuits through wires (not shown) or other electrical connections. The green LED die  562  may be a flip-chip disposed on the base  561 . The green shifted-disposed LED package  56  is packaged by a packaging material, such as epoxy, organic resin, transparent ceramic material, transparent glass material, transparent insulating material, or combinations thereof, to encapsulate the green LED die  562 G and the base  561  for protection and to form a lens  563  of a cambered surface disposed on the light exiting surface of the green LED die  562 G. The cambered surface of the lens  563  may have an arc surface of a sphere or a spheroid. Lights from the green LED die  562 G are refracted and dispersed at the surface of the lens  563 . 
     As shown in  FIG. 6 , the green LED die  562 G of the present invention is not disposed on the center  564  of the base  561  and is not overlapped with the center  564  of the base. The green LED die  562  is shifted from the center  564  to a position aside from the center  564  in a predetermined distance. For example, the preferable predetermined distance between the center of the green LED die  562 G and the center  564  of the base  561  is equal to the width (W) of the green LED die  562 G. The green LED die  562 G is not disposed on the center  564  of the base  561  or at the radius of curvature of the lens  56 . The green LED die  562 G is disposed aside from the center  564  of the base  561 . Therefore, the green shifted-disposed LED package  56  is defined as a shifted-disposed LED package. Lights generated by the green LED die  562 G are refracted at the lens  563  and are tilted to a predetermined direction. As shown in  FIG. 6 , the green LED die  562 G is positioned at the right side of the center  564 . Lights generated by the green LED die  562 G pass through the lens  563  and tilt to the left side of the center  564  opposite to the position of the green LED die  562 G. And accordingly, lights generated by the shifted-disposed LED package are asymmetrically dispersed and have a non-Lambertain light distribution property. 
     The above description of the shifted-disposed LED packages uses the green shifted-disposed LED package  56  as an example. Both of the red shifted-disposed LED package  54  and blue shifted-disposed LED package  58  have similar structures as the green shifted-disposed LED package  56 . For the sake of describing the present invention in an easier way, the center  564  of the base  561  of the present preferred embodiment is overlapped with the radius of curvature of the lens  563 . The area of the base  561  is equal to the area of the cross-section passing through the radius of curvature of the lens  56 . However, the present invention is not limited to the above-mentioned preferred embodiment. The center of the base may be vertically positioned at a point on or above the radius of curvature of the lens. The center of the base may be positioned at a point on the left side or on the right side of the radius of curvature of the lens. The size of the base may be larger than or smaller than the cross-section of the lens  56 . Please refer to  FIG. 8 . A thin film  62  of good reflective property or a refractive index smaller than the lens  563  may be formed on a portion of the surface of the lens  563 . Lights against the center  564  striking at the thin film  62  are reflected that are gathered in the overlapped region for mixing lights to increase light extraction efficiency of the LED die  562 G. 
     Please refer to  FIG. 5  in company with  FIG. 9 .  FIG. 9  is a schematic diagram showing the LED light module  50  along the Z-axis in  FIG. 5 . As shown in  FIG. 5 , the red shifted-disposed LED package  54 , green shifted-disposed LED package  56  and blue shifted-disposed LED package  58  are arranged as a triangle, and the distance between any two of the shifted-disposed LED packages is of equal length. The shifted-disposed LED packages may not be limited to be arranged as an equilateral triangle. The position of the shifted-disposed LED packages may be determined depending on the illumination region of the tilted lights generated by the shifted-disposed LED packages. The centers  544 ,  564 ,  584  of the respective shifted-disposed LED packages are positioned at vertices of the triangle and the sides of the triangle define an area of the triangle  60 . It should be noted that the red LED die  542 R of the red shifted-disposed LED package  54 , the green LED die  562 G of the green shifted-disposed LED package  56 , and the blue LED die  582 B of the blue shifted-disposed LED package  58  are positioned out of the area of the triangle  60 . In addition, the red LED die  542 R, the green LED die  562 G, and the blue LED die  582 B are disposed in the projection area of the respective lens  543 ,  563 ,  583 . (In other words, the red LED die  542 R, the green LED die  562 G, and the blue LED die  582 B may be disposed in the shadowed area of  FIG. 5 .) Please refer to  FIG. 9 . Since lights generated by the shifted-disposed LED packages of the present invention are asymmetrically dispersed, these lights are tilted against to the direction of the respective LED die shifted from the center of the respective base. Therefore, lights generated by the red shifted-disposed LED package  54 , the green shifted-disposed LED package  56 , and the blue shifted-disposed LED package  58  are gathered in the overlapped region above the area of the triangle  60 , and the overlapped lights are mixed into white light of uniformity. 
     As described above, the present invention uses shifted-disposed LED packages as its light source, and the LED dies disposed therein are disposed out of the area of the triangle defined by the centers of the bases. The LED dies and the respective centers of the base are disposed in a predetermined length. Lights generated by the shifted-disposed LED package are asymmetrically dispersed, and are tilted to a predetermined direction opposite to the direction which the LED dies shifted from the center of the base. The position of the shifted-disposed LED packages improves the usability of the red light, the green light and the blue light generated by the shifted-disposed LED packages, in which the red light, the green light, and the blue light are gathered in the overlapped region in a maximal level and mixed into white lights of uniformity. The above-mentioned preferred embodiment provides white lights by means of overlapping red light, green light, and blue light. Other combinations of color lights are allowable. For example, combination of yellow light and blue light, combination of magenta light and green light, or combination of cyan light and red light are allowable for the present invention. Furthermore, the position and the number of the shifted-disposed LED packages may be modified depending on the color of the light sources. The shifted-disposed LED packages may be arranged as a rectangular, a pentagon, a hexagon, or a polygon as required. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.