Abstract:
The present invention provides a package of LED chips. The package comprises a transparent plate having a front surface and a rear surface, a plurality of LED chips disposed on the front surface, two opposite front surface reflective walls disposed on the front surface and located at two opposite outsides of the plurality of LED chips, a front surface phosphor gel filling between the two opposite front surface reflective walls, two opposite rear surface reflective walls disposed on the rear surface and a rear surface phosphor gel filling between the two opposite rear surface reflective walls. The present invention realizes the light of the package of LED chips can be extracted from both the front side and the rear side to enhance the light extraction efficiency.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Taiwanese Application Serial Number 102130864, filed Aug. 28, 2013 which is herein incorporated by reference. 
       BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a package of Light Emitting Diode (LED) chips. More particularly, the present invention relates to a package of a plurality of LED chips of which light can be extracted from both a front side and a rear sideof the package. 
         [0004]    2. Description of Related Art 
         [0005]    A conventional structure of a package of LED chips is that the LED chips are covered by phosphor gel and the extracted light is white light. The package can be disposed on circuit boards and be applied to various products, such as lamps or backlight modules of the televisions. 
         [0006]    The conventional package of LED chips uses interior sides of the housing of the package as reflective surfaces to reflect the light that comes from the LED chips. The reflected light is used to excite more phosphors that are located close to the outside edges of the phosphor gels. The reflective surfaces also reflect the excited light coming from h phosphors, thus increasing the light extraction efficiency. 
         [0007]    The package of LED chips includes the package of a single chip, and the package of chips connected to form a circuit. The difference of the product characteristics between the package of chips and the package of a single chip is that lamps made up of the former require simpler structures and manufacturing processes. There is no need for soldering a lot of packages of a single chip individually onto the circuit boards. 
         [0008]      FIG. 1  is a diagram illustrating a conventional package of a single chip wherein the package has a reflective wall. The package  100  includes a housing  110 . A top part of the housing  110  is served as a reflective wall  111  and an interior side of the housing  110  is served as a reflective surface  112 . The reflective surface  112  is generally white. In addition, the package  100  has an LED chip  113  and a phosphor gel  114 . The reflective surface  112  can reflect the light that comes from the LED chip  113  toward the lateral sides to excite more phosphors (not shown) which are located close to outside edges of the phosphor gel  114 . The reflective surface  112  also reflects the excited light coming from the phosphors, thus increasing the light extraction efficiency. 
         [0009]      FIG. 2  is a diagram illustrating a cross-sectional view of the conventional package  100  of a single LED chip in  FIG. 1 , wherein the package  100  has the reflective wall  111 .  FIG. 2  is used to expound the function of the reflective surface  112  of the reflective wall  111 . As shown in  FIG. 2 , the reflective surface  112  reflects the reference lights A, B, C, D, and D′, C′, B′, A′ that are from the LED chip  113  toward the lateral sides to excite more phosphors  115  which are located dose to outside edges of the phosphor gel  114 . The reflective surface  112  also reflects the excited light coming from the phosphors  115 . 
         [0010]      FIG. 3  is a diagram illustrating another conventional package  300  of LED chips, wherein the package  300  has a reflective wall  311 . The package  300  includes a substrate  310 , the reflective wall  311  disposed on the top of the substrate  310 , and an interior side of the substrate  310  is served as a reflective surface  312 . Generally, the reflective surface  312  is white. In addition, the package  300  has LED chips  313  and a phosphor gel  314 . The reflective surface  312  can reflect the light that is from the LED chips  313  toward the lateral sides to excite more phosphors (not shown) which are located close to outside edges of the phosphor gel  314 . The reflective surface  312  also reflects the light coming from the phosphors, thus increasing the light extraction efficiency. The function of the reflective wall  311  is the same as the descriptions of  FIG. 2 . 
         [0011]    Furthermore, the aforementioned packages usually have a reflective surface at a die bonding platform which is used for fixing the chip(s) to reflect the light extracted from the rear surfaces of the LED chips to enhance the light extraction efficiency, such as the die bonding platform  116  in  FIG. 1  and in  FIG. 3 . Hence, light of the conventional packages of the LED chips can merely be extracted from the front sides of the packages and enhance the light extraction efficiency of the front sides of the packages. The light is unable to be extracted from the front sides as well as the rear sides of the packages simultaneously and it is unable to enhance the light extraction efficiency of the rear sides of the packages. 
       SUMMARY 
       [0012]    The present invention provides a package of LED chips. The package includes LED chips fixed on a single surface (a front surface) of a transparent plate and reflective walls and phosphor gels disposed on both the front surface and the e surface of the transparent plate. Therefore, the light extracted from both the front side and the rear side of the package of LED chips to enhance the light extraction efficiency of both the front side and the rear side. 
         [0013]    The present invention provides a package of LED chips. The package includes a transparent plate, LED chips, two opposite front surface reflective walls, a front surface phosphor gel, two opposite rear surface reflective walls, and a rear surface phosphor gel. The transparent plate has a front surface and an opposite rear surface opposite to the front surface. The LED chips are disposed on the front surface of the transparent plate. The two opposite front surface reflective walls are d posed on the front surface of the transparent plate and on two opposite outsides of the LED chips. The front surface phosphor gel fills a space between the two opposite front surface reflective walls. The two opposite rear surface reflective walls are disposed on the rear surface of the transparent plate. The rear surface phosphor gel fills a space between the two opposite rear surface reflective walls. 
         [0014]    In this way, on the front surface of the transparent plate, vertical lights from the front surfaces of the LED chips would emit upward to excite the phosphors which are located close to a central area of the front surface phosphor gel. The lateral lights would be reflected by the front surface reflective walls on the front surface of the transparent plate to excite more phosphors which are located close to outside edges of the front surface phosphor gel. Besides, the front surface reflective walls also reflect the excited light coming from the phosphors to enhance the light extraction efficiency at the front side of the package of LED chips. 
         [0015]    Moreover, on the ear surface of the transparent plate, vertical lights from the rear surfaces of the LED chips would emit downward to excite the phosphors which are located close to a central area of the rear surface phosphor gel. The lateral lights would be reflected by the rear surface reflective walls on the rear surface of the transparent plate to excite more phosphors which are located close to outside edges of the rear sur/”face phosphor gel. Besides, the rear surface reflective walls also reflect the excited light coming from the phosphors, thereby enhancing the light extraction efficiency at the rear side of the package of LED chips. Thus, the light of the package can be extracted from both the front side and the rear side of the package, while both the light extraction efficiency of the front side and the rear side is promoted. 
         [0016]    In addition, besides the aforementioned front surface phosphor gel or the rear surface phosphor gel including the yellow phosphors, the front surface phosphor gel and/or the rear urface phosphor gel are allowed to be mixed with a few red phosphors to enhance color rendering index (CRI). 
         [0017]    It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
           [0019]      FIG. 1  is a diagram illustrating a conventional package of a single hip wherein the package has a reflective wall; 
           [0020]      FIG. 2  is a diagram illustrating a cross-sectional view of a conventional package of a single LED chip in  FIG. 1 , wherein the package has a reflective wall; 
           [0021]      FIG. 3  is a diagram illustrating another conventional package of LED chips, wherein the package has a reflective wall; 
           [0022]      FIG. 4  is a diagram illustrating a package of LED chips according to an exemplary embodiment of the present invention; and 
           [0023]      FIG. 5  is a diagram illustrating a cross-sectional view of a package of LED chips in  FIG. 4  according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
         [0025]    Please refer to  FIG. 4  and  FIG. 5 . According to an exemplary embodiment of the present invention, a package of LED chips  400  includes a transparent plate  410 , LED chips  420 , two opposite front surface reflective walls  430 , a front surface phosphor gel  440 , phosphors  441  of the front surface phosphor gel  440 , two opposite e surface reflective walls  450 , a rear surface phosphor gel  460 , and phosphors  461  of the rear surface phosphor gel  460 . The package of LED chips  400  can generate white light and so on. 
         [0026]    The transparent plate  410  can be a translucent board that is clear or slightly blurry, and can be made of a material such as glass, polymer, resin, or aluminum oxide. The transparent plate  410  has a front surface  411  and a rear surface  412  opposite to the front surface  411 . 
         [0027]    The LED chips  420  are fixed on the front surface  411  of the transparent plate  410 . The LED chips  420  can generate blue light or ultraviolet light. The jumper wires  421  that can be the golden wires, the alloy wires, the copper wires or the aluminum wires are used to connect the positive electrodes and the negative electrodes of the adjacent LED chips  420  to form a series circuit, a parallel circuit, a circuit that the LED chips  420  are connected in series to form series connections and then the series connections are connected in parallel, or a circuit that the LED chips  420  are connected in parallel to form parallel connections and then the parallel connections are connected in series. After that, a positive electrode of the LED chip  420  on a front end of the circuit and a negative electrode of the LED chip  420  on a rear end of the circuit are respectively connected to two end plates  413  fixed on the transparent plate  410 . The end plates  413  can be connected to a power source (not shown) to provide the required power for enabling the LED chips  420 . In an embodiment, the LED chips  420  are disposed on the end plates  413  by flip chip technology (not shown) to improve the heat dissipation efficiency of the LED chips  420  to increase the package of LED chips  400  reliability. In another embodiment, the wavelength of the light from the LED chips  420  is between 370 nm and 530 nm and the light can excite green phosphors, yellow phosphors or red phosphors to generate lights having different colors to modulate and acquire the required color temperature, such as the warm white light or the cool white light. In another embodiment, the wavelength of the light from the LED chips  420  is between 600 nm and 630 nm and the light can excite blue phosphors to modulate and acquire the required color temperature, such as the warm white light or the cool white light. 
         [0028]    The two opposite front surface reflective walls  430  are disposed on the front surface  411  of the transparent plate  410 , as shown in  FIG. 5 . The front surface reflective walls  430  can be disposed on the front surface  411  of the transparent plate  410  and located on the two opposite outsides of the LED chips  420  by a dispenser using silicone liquid. After the curing of the silicone liquid, the two opposite front surface reflective walls  430  would naturally have cross sections of an inverted V shape or an inverted U shape due to the surface tension and the wettability to the transparent plate  410 , as shown in  FIG. 5 ; thereby capable of being used as the reflective surface  431 . It is not necessary to precisely restrict the distances between one of the two opposite front surface reflective walls  430  and one of the LED chips  420  at the central area because the reflective surfaces  431  always have the reflective effect at any areas as long as the lateral lights from the front surface of the LED chips  420  can reach the reflective surfaces  431  of the front surface reflective walls  430 . The reference light travel path is as shown as A, B, C, D, and D′, C′, B′, A′ in  FIG. 5 . Moreover, a viscosity of the silicone liquid is around 3500 cps (Centipoises). The material of forming the front surface reflective walls  430  is silicone, epoxy, glass or acrylic. 
         [0029]    The material of the front surface phosphor gel  440  can be a transparent silicone including phosphors  441 . The front surface phosphor gel  440  fills a space between the two opposite front surface reflective walls  430  when the front surface phosphor gel  440  is liquid state and submerges the LED chips  420 , and is shaped after the curing. The front surface phosphor gel  440  filling the space between the two opposite front surface reflective walls  430  also has a cross section of V shape or a U shape. The phosphors  441  of the front surface phosphor gel  440  are green phosphors, yellow phosphors, red phosphors, or blue phosphors. 
         [0030]    Furthermore, as shown in  FIG. 5 , the two opposite rear surface reflective wails  450  are disposed on the rear surface  412  of the transparent plate  410 . Similar to the process for making the front reflective walls  430 , the rear surface reflective walls  450  can be dispensed on the rear surface  412  of the transparent plate  410  by a dispenser using the silicone liquid and located at the positions corresponding to the front surface reflective walls  430  vertically. After the curing of the silicone liquid, the two opposite rear surface reflective walls  450  would naturally have cross sections of a V shape or a U shape due to the surface tension and the wettability to the transparent plate  410 , as shown in  FIG. 5 ; thereby capable of being used as the reflective surface  451 . It is not necessary to precisely restrict the distance between one of the two opposite rear surface reflective walls  450  and one of the LED chips  420  on the front surface because the reflective surfaces  451  always have the reflective effect at any areas as long as the lateral lights from the rear surface of the LED chips  420  reaches the reflective surfaces  451  of the rear surface reflective walls  450 . The reference light travel path is as shown as E, F, G, H and H′, G′, F′, E′ in  FIG. 5 . Moreover, a viscosity of the silicone liquid is around 3500 cps (Centipoises). The material of forming the rear surface reflective walls  450  is silicone, epoxy, glass or acrylic. 
         [0031]    The material of the rear surface phosphor gel  460  can be a transparent silicone including phosphors  461 . The rear urface phosphor gel  460  also fills a space between the two opposite rear surface reflective walls  450  when the rear surface phosphor gel  460  is liquid state and submerges a portion of the rear surface  412  of the transparent plate  410  located between the two opposite rear surface reflective walls  450 , and is shaped after the curing. The rear surface phosphor gel  460  filling the space between the two opposite rear surface reflective walls  450  also has a cross section of a V shape or a U shape. The phosphors  461  of the rear surface phosphor gel  460  are green phosphors, yellow phosphors, red phosphors, or blue phosphors. 
         [0032]    In addition, in order to make the color temperature of the light extracted from the front surface phosphor gel  440  correspond with that of the rear surface phosphor gel  460 , the ratio of the phosphors  441  within the front surface phosphor gel  440  and the ratio of the phosphors  461  within the rear surface phosphor gel  460  can be adjusted. 
         [0033]    Besides the front surface phosphor gel  440  or the rear surface phosphor gel  460  including the yellow phosphors, the front surface phosphor gel  440  and/or the rear surface phosphor gel  460  are allowed to be mixed with a few little red phosphors to enhance a color rendering index (CRI). 
         [0034]    Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
         [0035]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.