Abstract:
A dimmable light-emitted diode (LED) packaging structure is described. The dimmable LED packaging structure employs a plurality of first fluorescent layers respectively positioned on some of a plurality of first types of LED chips to solve the problems of color temperature and light mixing uniformity. Further, a second fluorescent layer overlays the first fluorescent layers and a potion of the first types of LED chips to simplify the manufacturing step of dimmable LED packaging structure.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a light-emitted diode (hereinafter LED), and more particularly to a dimmable LED. 
       BACKGROUND OF THE INVENTION 
       [0002]      FIG. 1  is a conventional LED packaging structure. The LED packaging structure is configured to be a chip-on-board (COB) packaging structure and includes a substrate  100 , a plurality of LED chips  102  disposed on the substrate  100 , and the phosphor glue  104  filled within the sidewall  103  for overlaying the LED chips  102 , wherein the phosphor glue  104  composed of phosphor powder includes the fluorescent glue with warm white and cold white characteristics. 
         [0003]    As shown in  FIG. 1 , the LED packaging structure is made of a light-mixed manner by the phosphor powder with two different concentrations, i.e. phosphor glue with warm white characteristic  104   a  and phosphor glue with cold white characteristic  104   b,  to perform a glue-dispensing process. After the process of chip attachment and wire bonding are complete, the phosphor glue  104  in different proportions arrangements is packaged in the different warm white and cold white regions respectively for dispensing the glue to meet the different requirements of color temperatures. Although the color temperature of the LED packaging structure can be changed, it is necessary to enclose the phosphor glue  104  by using a light cover to form a light-mixed chamber (not shown) above the substrate  100 . In this manner, it is required to construct a larger space for the light-mixed condition, which results in uneven light-mixed status of the LED chips  102  in the different warm white and cold white regions respectively. Moreover, it is demanded to perform disadvantageously two processes of glue dispensation of the warm white characteristic  104   a  and phosphor glue with cold white characteristic  104   b  in the different warm white and cold white regions, which are complicated manufacturing steps. 
         [0004]    Consequently, there is a need to develop a novel LED packaging structure to solve the problems of color temperature irregular change, uneven light-mixed situation and manufacturing complicated steps in the aforementioned descriptions. 
       SUMMARY OF THE INVENTION 
       [0005]    One objective of the present invention is to provide a dimmable light-emitted diode (LED) packaging structure by employing a plurality of first fluorescent layers disposed on one portion of the first types of LED chips correspondingly to solve the problems of color temperature irregular change and uneven mixing-light. 
         [0006]    Another objective of the present invention is to provide a dimmable LED packaging structure by employing a second fluorescent layer for overlaying the first fluorescent layers and the other portion of the first types of LED chips to solve the problem of complicated manufacturing steps. 
         [0007]    According to the above objectives, the present invention sets forth a dimmable LED packaging structure. The dimmable LED comprises a substrate; an annual sidewall disposed on the substrate; a plurality of first types of LED chips disposed on the substrate within the annual sidewall, wherein each of the first types of LED chips emits a light ray; a plurality of first fluorescent layers disposed on one portion of the first types of LED chips correspondingly; and a second fluorescent layer filled within the annual sidewall for overlaying the first fluorescent layers and the other portion of the first types of LED chips, wherein when the one portion of the first types of LED chips emit the light rays through the first fluorescent layers and the second fluorescent layer and when the other portion of the first types of LED chips emit the light rays through the second fluorescent layer, the light rays on a surface of the first fluorescent layers are mixed with a surface of the other portion of the first types of LED chips for dimming the LED. 
         [0008]    In one embodiment, the dimmable LED further comprises a plurality of second types of LED chips disposed on the substrate within the annual sidewall and staggered with the first types of LED chips. Each of the first types of LED chips is a blue LED chip and each of the second types of LED chips is a red LED chip. A ratio of an amount of the blue LED chips and an amount of the red LED chips is between one-to-one (1:1) and three-to-one (3:1). When each of the first types of LED chips is an LED chip with a vertical structure, an area of each of the first fluorescent layers is either less than or equal to an area of the LED chip with the vertical structure. Further, when each of the first types of LED chips is an LED chip with a horizontal structure, an area of each of the first fluorescent layers is either greater than or equal to an area of the LED chip with the horizontal structure. 
         [0009]    An area of each of the first fluorescent layers is 0.8 time to 2 times an area of the first types of LED chips. Each of the first fluorescent layers is a phosphor sheet with warm white characteristic. A bottom surface of each of the first fluorescent layers further comprises a laminating layer for adhering the first fluorescent layers to the one portion of the first types of LED chips correspondingly. The second fluorescent layer is phosphor glue with cold white characteristic. 
         [0010]    According to the above-mentioned descriptions, the dimmable LED packaging structure employs a plurality of first fluorescent layers disposed on one portion of the first types of LED chips correspondingly to solve the problems of color temperature irregular change and uneven mixing-light, and employs a second fluorescent layer for overlaying the first fluorescent layers and the other portion of the first types of LED chips to solve the problem of complicated manufacturing steps. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a conventional LED packaging structure; 
           [0013]      FIG. 2  is a schematic top view of LED packaging structure according to one embodiment of the present invention; 
           [0014]      FIG. 3  is a cross-sectional view of the LED packaging structure along the line A-A′ in  FIG. 2  according to one embodiment of the present invention; 
           [0015]      FIG. 4  is a schematic view of the wiring arrangement of the LED packaging structure according to one embodiment of the present invention; and 
           [0016]      FIG. 5  is a schematic view of the wiring arrangement of the LED packaging structure according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The dimmable LED packaging structure in the present invention employs the annual sidewall to form a chip attachment region compose of an area with cold white characteristic and an area with warm white characteristic wherein the area with cold white characteristic includes blue LED chips without phosphor sheets with warm white characteristic and the area with warm white characteristic includes blue LED chips with phosphor sheets with warm white characteristic. In other words, the phosphor sheets with warm white characteristic are attached to a portion of blue LED chips so that the area with cold white characteristic is staggered with the area with warm white characteristic for adjusting the color temperature of the dimmable LED packaging structure and for mixing uniformly the light rays between the area with cold white characteristic and the area with warm white characteristic. 
         [0018]    Please refer to  FIG. 2  and  FIG. 3 .  FIG. 2  is a schematic top view of LED packaging structure according to one embodiment of the present invention.  FIG. 3  is a cross-sectional view of the LED packaging structure along the line A-A′ in  FIG. 2  according to one embodiment of the present invention. As shown in  FIG. 2  and  FIG. 3 , the dimmable LED packaging structure includes a substrate  200 , an annual sidewall  202 , a plurality of first types of LED chips  204 , a plurality of first fluorescent layers  206 , a second fluorescent layer  208  and a laminating layer  212 . 
         [0019]    In one case, the substrate  200  may be ceramic substrate with electrical insulation and is composed of ceramic material selected from one group consisting of aluminium oxide, aluminium nitride, zirconium oxide and calcium fluoride. The annual sidewall  202  disposed on the substrate  200  surrounds the first types of LED chips  204  so that the second fluorescent layer  208  overlays the first fluorescent layers  206  and the other portion of the first types of LED chips  204 . The first types of LED chips  204  disposed on the substrate  200  within the annual sidewall  202 , wherein each of the first types of LED chips  204  emits a light ray. In one embodiment, each of the first types of LED chips  204  is a blue LED chip. 
         [0020]    As shown in  FIG. 2  and  FIG. 3 , a plurality of first fluorescent layers  206  are disposed on one portion of the first types of LED chips  204  correspondingly. That is, the first fluorescent layers  206  are stacked on the top surface of the one portion of the first types of LED chips  204  so that the one portion of the first types of LED chips  204  sequentially are disposed on the first fluorescent layers  206  and the second fluorescent layer  208 . In one embodiment, the bottom surface of each of the first fluorescent layers  206  further includes a laminating layer  212  for adhering the first fluorescent layers  206  to the surfaces of the one portion of the first types of LED chips  204  correspondingly. In one embodiment, the laminating layer  212  may be selected from the group consisting of silver glue, tin glue, speculum metal, and Au—Sn alloy and laminating layer  212  facilitates the thermal conductivity of the dimmable LED packaging structure. 
         [0021]    Specifically, the first fluorescent layers  206  are coated on the one portion of the first types of LED chips  204  to serve as the fluorescent function of warm white characteristic (e.g. red color temperature) for converting the original light of the one portion of the first types of LED chips  204  into the light rays  214  with predetermined color temperature. For example, the ultraviolet ray is converted into the visible light with blue color and the visible light with blue color emits the first fluorescent layers  206  with warm color temperature to generate the light with warm white characteristic. In one preferred embodiment, each of the first fluorescent layers  206  is a phosphor sheet with warm white characteristic which are stacked on the one portion of the first types of LED chips  204  wherein the phosphor sheet with warm white characteristic is a red phosphor sheet. 
         [0022]    In  FIG. 2  and  FIG. 3 , the second fluorescent layer  208  is filled within the annual sidewall  202  for overlaying the first fluorescent layers  206  and the other portion of the first types of LED chips  204  and the second fluorescent layer  208  is filled to the spacer between the first types of LED chips  204  to serve as the fluorescent function of cold white characteristic (e.g. blue color temperature). For example, the second fluorescent layer  208  is the phosphor glue with clod white characteristic. Further, in one embodiment, the present invention fills the phosphor glue with clod white characteristic in the same concentration to the annual sidewall  202  for simplifying the manufacturing process of the dimmable LED packaging structure. 
         [0023]    As shown in  FIG. 3 , when the one portion of the first types of LED chips  204  emit the light rays  214  through the first fluorescent layers  206  and the second fluorescent layer  208  and when the other portion of the first types of LED chips  204  emit the light rays  214  through the second fluorescent layer  208 , the light rays  214  on a surface of the first fluorescent layers  206  are mixed with a surface of the other portion of the first types of LED chips  204  for dimming the LED. 
         [0024]    Specifically, the first fluorescent layers  206  are disposed on the one portion of the first types of LED chips  204  respectively so that the first fluorescent layers  206  convert the light rays of the one portion of the first types of LED chips  204  into the light with warm white characteristic. The first fluorescent layers  206  are not disposed on the other portion of the first types of LED chips  204  so that the other portion of the first types of LED chips  204  directly forms the light rays with cold white characteristic. Since the two light rays with different color temperature are adjacent each other and the one portion of the first types of LED chips  204  having the first fluorescent layers  206  are adjoined to the other portion of the first types of LED chips  204  without the first fluorescent layer  206 , the color temperature of the dimmable LED packaging structure can be adjusted to mix uniformly the light ray. 
         [0025]    Moreover, in  FIG. 2  and  FIG. 3 , the second fluorescent layer  208  is covered on the one portion of the first types of LED chips  204  having first fluorescent layers  206  thereon and the other portion of the first types of LED chips  204  without first fluorescent layers  206  thereon. Thus, the one portion of the first types of LED chips  204  having first fluorescent layers  206  thereon are staggered with the other portion of the first types of LED chips  204  without first fluorescent layers  206 , and the second fluorescent layer  208  is covered with the first fluorescent layers  206  so that the light rays with warm color and cold color are mixed uniformly near the light emission region  207 . In other words, the first types of LED chips  204  near the light emission region  207  are capable of adjusting the color temperature and mixing the light rays uniformly. For example, the one portion of the first types of LED chips  204  having first fluorescent layers  206  thereon and the other portion of the first types of LED chips  204  without first fluorescent layers  206  near the annual sidewall  202  can mix the light rays adequately such that the dimmable LED packaging structure can be adjusted to mix evenly the light ray. 
         [0026]    Please continuously refer to  FIG. 2  and  FIG. 3 . In one embodiment, when each of the first types of LED chips  204  is an LED chip with a vertical structure, an area A 2  of each of the first fluorescent layers  206  is either less than or equal to an area A 1  of the LED chip with the vertical structure wherein the two electrodes of the LED chip with the vertical structure are disposed in the two sides of the LED extension layer. The LED chip with the vertical structure is an opaque layer served as a lining layer and thus, the LED chip with the vertical structure is in opaque status such that the light is emitted from the surface of the chip and the light is blocked from the lateral side. Therefore, the area A 2  of each of the first fluorescent layers  206  is either less than or equal to an area A 1  of the LED chip with the vertical structure. In one preferred embodiment, the area A 2  of each of the first fluorescent layers is 0.8 time to 1 time an area of the first types of LED chips with the vertical structure. In this case of  FIG. 2  and  FIG. 3 , the area A 1  is equal to the area A 2 . 
         [0027]    In another embodiment, when each of the first types of LED chips  204  is an LED chip with a horizontal structure, an area A 2  of each of the first fluorescent layers is either greater than or equal to an area A 1  of the LED chip with the horizontal structure wherein the two electrodes of the LED chip with the horizontal structure are disposed in the same side of the LED chip. The LED chip with the horizontal structure is a transparent substrate served as a lining layer and thus, the LED chip with the horizontal structure is in transparent status such that the light is emitted from the lateral side. Therefore, when the area A 2  of each of the first fluorescent layers  206  is either greater than or equal to an area A 1  of the LED chip with the vertical structure, more light with warm white characteristic are generated. In one preferred embodiment, the area A 1  of the first types of LED chips with the horizontal structure is 1 time to 2 times an area of each of the first fluorescent layers. In this case of  FIG. 2  and  FIG. 3 , the area A 1  is equal to the area A 2 . 
         [0028]    Thus, the dimmable LED packaging structure is applicable to the LED chips with the vertical structure and/or the horizontal structure wherein an area A 2  of each of the first fluorescent layers is 0.8 time to 2 times, but not limited to lower time or higher times, an area A 1  of the first types of LED chips. 
         [0029]      FIG. 4  is a schematic view of the wiring arrangement of the dimmable LED packaging structure according to one embodiment of the present invention. The first types of LED chips  204  sequentially includes N-type semiconductor layer, semiconductor emitting layer, P-type semiconductor layer wherein the N-type semiconductor layer may be N-type GaN layer, semiconductor emitting layer may be semiconductor with GaN or indium gallium nitride, and the P-type semiconductor layer may be P-type GaN layer. The N-type GaN layer and P-type GaN layer are electrically connected to the positive electrode and negative electrode respectively of the external power source by wiring  400  so that the first types of LED chips  204  turn on and thus electron-hole pairs of the semiconductor layer make the composite actions by the forward biasing voltage and the semiconductor emitting layer emits the light ray. 
         [0030]    The dimmable LED packaging structure further includes encapsulating glue (not shown), e.g. silicon resin or epoxy, having higher transparent property and electrical insulation for covering the annual sidewall  202  and the second fluorescent layer  208  and for enclosing the dimmable LED packaging structure. 
         [0031]      FIG. 5  is a schematic view of the wiring arrangement of the LED packaging structure according to another embodiment of the present invention. A plurality of second types of LED chips  210  are disposed on the substrate  200  within the annual sidewall  202  and staggered with the first types of LED chips  204 . In one embodiment, the second types of LED chips  210  in the chip attachment region within the annual sidewall  202  are red LED chips to improve the color rendering index (CRI) of the dimmable LED packaging structure. In other words, the amount of the red LED chip and distribution status can be controller to adjust the CRI to reduce the light attenuation effect of the red LED chip. In one preferred embodiment, a ratio of an amount of the blue LED chips and an amount of the red LED chips is between one-to-one and three-to-one, but not limited, and between arbitrary values of the ratio. 
         [0032]    According to the above-mentioned descriptions, the dimmable LED packaging structure employs a plurality of first fluorescent layers disposed on one portion of the first types of LED chips correspondingly to solve the problems of color temperature irregular change and uneven mixing-light, and employs a second fluorescent layer for overlaying the first fluorescent layers and the other portion of the first types of LED chips to solve the problem of complicated manufacturing steps. 
         [0033]    As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative rather than limiting of the present invention. It is intended that they cover various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.