Abstract:
A light-emitting diode (LED) is provided. An LED die includes a first semiconductor layer, a light-emitting layer, a second semiconductor layer, a first electrode and a second electrode. At least a part of the first semiconductor is exposed from the light emitting layer and the second semiconductor layer. The first electrode and the second electrode is disposed on top of the exposed first semiconductor layer and the second semiconductor layer respectively. At least two metal pads are disposed on top of the first electrode and the second electrode of the LED die respectively. Each of the metal pads has a side surface. A fluorescent layer is disposed on a surface of the LED die. The fluorescent layer directly contacts with the side surfaces of the metal pads and fills a gap between the metal pads.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional application of and claims the priority benefit of a prior application Ser. No. 12/552,368, filed on Sep. 2, 2009, now allowed. The prior application Ser. No. 12/552,368 claims the priority benefit of Taiwan application serial no. 097137793, filed on Oct. 1, 2008. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a light-emitting diode (LED). 
       BACKGROUND OF THE INVENTION 
       [0003]    A light-emitting diode (LED) is a light-emitting device manufactured by semiconductor materials with two electrodes. The light-emitting principle of the LED is that by applying a voltage between the electrodes and supplying an extremely small current, excess energy can be released in the form of light via the recombination process of electrons and holes. The LED is different from an incandescent bulb in that the former is luminescent with advantages of low power consumption, elongated lifetime, no warm-up time, and fast response. In addition, because the LED is small, vibration tolerable, and suitable for mass production, it is easy to be manufactured in an extremely tiny or a matrix form in accordance with application requirements. Currently, the LED is widely applied to indicator and display apparatuses of information, communication, and consumer electronic products, and has become a dispensable and important device in daily lives. 
         [0004]    Presently, most LEDs are coated with fluorescent powders in the packages during the packaging process. Thereby, the stress problem will occur in the packages. The invention provides an LED in a single light-mixing chip, which can be packaged directly, and hence reducing effectively the stress problem as described above. 
       SUMMARY 
       [0005]    An embodiment of the invention is to provide a light-emitting diode (LED), in which metal pads can be exposed for the convenience of subsequent wiring and packaging processes. 
         [0006]    An embodiment of the invention is to provide a light-emitting diode (LED), in which a single light-mixing chip can be provided for direct packaging and reducing the stress problem in the packaged LED. 
         [0007]    An embodiment of the invention provides a light-emitting diode (LED) including an LED die, at least two metal pads, and a fluorescent layer. The LED die includes a first semiconductor layer, a light-emitting layer, a second semiconductor layer, a first electrode and a second electrode. The light-emitting layer is disposed on the first semiconductor layer. The second semiconductor layer is disposed on the light-emitting layer. At least a part of the first semiconductor is exposed from the light emitting layer and the second semiconductor layer. The first electrode and the second electrode are disposed on top of the exposed first semiconductor layer and the second semiconductor layer respectively. The at least two metal pads are disposed on top of the first electrode and the second electrode of the LED die respectively, wherein each of the metal pads has a side surface. The fluorescent layer is disposed on a surface of the LED die. The fluorescent layer directly contacts with the side surfaces of the metal pads and fills a gap between the metal pads. The top surface of the fluorescent layer is flat in a cross-section view. The thickness of the fluorescent layer is greater than 30 μm. All side surfaces of the fluorescent layer are respectively aligned with all outer side surfaces of the LED die. 
         [0008]    An embodiment of the invention provides a light-emitting diode (LED) including an LED die, at least two metal pads, and a fluorescent layer. The LED die includes a first semiconductor layer, a light-emitting layer, a second semiconductor layer, a first electrode and a second electrode. The light-emitting layer is disposed on the first semiconductor layer. The second semiconductor layer is disposed on the light-emitting layer. At least a part of the first semiconductor is exposed from the light emitting layer and the second semiconductor layer. The first electrode and the second electrode are disposed on top of the exposed first semiconductor layer and the second semiconductor layer respectively. The at least two metal pads are disposed on top of the first electrode and the second electrode of the LED die respectively, wherein each of the metal pads has a side surface. The fluorescent layer is disposed on a surface of the LED die. The fluorescent layer directly contacts with the side surfaces of the metal pads and fills a gap between the metal pads. The top surface of the fluorescent layer is parallel to the top surface of the light-emitting layer in a cross-section view. The thickness of the fluorescent layer is greater than 30 μm. All side surfaces of the fluorescent layer are respectively aligned with all outer side surfaces of the LED die. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows a structural schematic diagram according to a preferred embodiment of the invention; 
           [0010]      FIG. 2  shows a flowchart according to a preferred embodiment of the invention; 
           [0011]      FIG. 3  shows a flowchart for forming an LED die according to a preferred embodiment of the invention; 
           [0012]      FIG. 4A  shows a structural schematic diagram according to another preferred embodiment of the invention; 
           [0013]      FIG. 4B  shows a structural schematic diagram according to another preferred embodiment of the invention; 
           [0014]      FIG. 5  shows a structural schematic diagram according to another preferred embodiment of the invention; 
           [0015]      FIG. 6  shows a flowchart according to a preferred embodiment of the invention; 
           [0016]      FIG. 7  shows a structural schematic diagram according to another preferred embodiment of the invention; and 
           [0017]      FIG. 8  shows a flowchart according to a preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In order to make the structure and characteristics as well as the effectiveness of the invention to be further understood and recognized, the detailed description of the invention is provided as follows along with preferred embodiments and accompanying figures. 
         [0019]      FIG. 1  shows a structural schematic diagram according to a preferred embodiment of the invention. As shown in the figure, the present embodiment provides a light-emitting diode (LED)  1 , which comprises an LED die  10 , one or more metal pads  12 , and a fluorescent layer  16 . The LED die  10  includes two electrodes  107 . The number of the metal pads  12  according to the present embodiment is two. The two metal pads  12  are set on the two electrodes  107 , respectively. The fluorescent layer  16  is set on the LED die  10 . In addition, the fluorescent layer  16  does not cover the two metal pads  12  completely. Instead, the metal pads  12  are exposed for the convenience of subsequent wiring and packaging processes. The fluorescent layer  16  converts partial or all of light with a first wavelength produced by the LED die  10  to light with at least a second wavelength for producing light mixing. The LED  1  provided according to the present embodiment is a light-mixing chip, which can be packaged directly without the need of coating fluorescent powders on the package. The thickness of the fluorescent layer  16  is greater than 30 μm. The materials of the fluorescent layer  16  include fluorescent powders and an organic polymer material. The fluorescent powders are chosen from the group comprising red fluorescent powders, green fluorescent powders, blue fluorescent powders, and the combination of the fluorescent powders described above. 
         [0020]    The LED die  10  described above further comprises a first semiconductor layer  101 , a light-emitting layer  103 , and a second semiconductor layer  105 . The light-emitting layer  103  is set on the first semiconductor layer  101 ; the second semiconductor layer  105  is set on the light-emitting layer  103 ; the metal pads  12  are set on the electrodes  107 . When the first semiconductor layer  101  is P-type, the second semiconductor layer  105  is N-type. Alternatively, when the first semiconductor layer  101  is N-type, the second semiconductor layer  105  is P-type. 
         [0021]      FIG. 2  shows a flowchart according to a preferred embodiment of the invention. As shown in the figure, in contrast to  FIG. 1 , which shows an LED  1 , the present figure shows a method for manufacturing the LED  1 . To manufacture the LED  1 , the step S 10  is first executed for forming an LED die  10 , which includes two electrodes  107 . Referring together to  FIG. 3 , the method for forming the LED die  10  comprises the step S 101  forming a first semiconductor layer  101 ; the step S 103  forming a light-emitting layer  103  on the first semiconductor layer  101 ; and finally the step S 105  forming a second semiconductor layer  105  on the light-emitting layer  103 . 
         [0022]    After the step S 10  is completed, the step S 12  is executed for forming one or more metal pads  12  on the two electrodes  107  of the LED die  10 . Next, the step S 14  is executed for forming a fluorescent layer  16  on the LED die  10 . The fluorescent layer  16  does not cover the metal pads  12  completely. Instead, the metal pads  12  are left exposed for the convenience of subsequent wiring and packaging processes. 
         [0023]    For forming the fluorescent layer  16  on the LED die  10 , glue dispensing, spraying, or pouring methods are applied. For avoiding the fluorescent layer  16  from covering the metal pads  12  completely during the forming process of the fluorescent layer  16 , prior to forming the fluorescent layer  16  on the LED die  10  using the glue dispensing, spraying, or pouring methods, a mask is used on the metal pads  12 . The mask can mask the metal pads  12  and expose the location to form the fluorescent layer  16 . Besides, the mask is manufactured by lithography or by screen-printing using organic polymer materials such as photoresist. The LED die is divided a plurality of chips. The glue ratio in the glue dispensing, spraying, or pouring methods is controlled according to the photoelectric properties of each the chip. 
         [0024]      FIGS. 4A and 4B  show structural schematic diagrams according to other preferred embodiments of the invention. As shown in the figures, according to the present embodiments, two LED structures are provided. The difference between the present embodiments and the one described above is that, according to the present embodiments, the shape of the fluorescent layer  16  can be changed by etching. The shapes of the fluorescent layer  16  can be trapezoidal or upside-down trapezoidal. 
         [0025]      FIG. 5  shows a structural schematic diagram according to another preferred embodiment of the invention. As shown in the figure, the present embodiment provides an LED  1  comprising an LED die  10 , one or more metal pads  12 , a dielectric layer  18 , and a fluorescent layer  16 . The LED die  10  includes two electrodes  107 . The metal pads are set on the electrodes  107  of the LED die  10 . The dielectric layer  18  is set on the LED die  10 , and is located on the periphery of the metal pads  12 . The fluorescent layer  16  is set on the dielectric layer  18 , and is located on the periphery of the metal pads  12 . The fluorescent layer  16  converts partial or all of light with a first wavelength produced by the LED die  10  to light with at least a second wavelength for producing light mixing. In addition, the fluorescent layer  16  does not cover the metal pads  12  completely. Instead, the metal pads  12  are exposed for the convenience of subsequent wiring and packaging processes. The LED  1  provided according to the present embodiment is a light-mixing chip, which can be packaged directly without the need of coating fluorescent powders on the package. Besides, the thickness of the fluorescent layer  16  is greater than 30 μm. The LED die  10  further includes a first semiconductor layer  101 , a light-emitting layer  103 , and a second semiconductor layer  105 . 
         [0026]      FIG. 6  shows a flowchart according to a preferred embodiment of the invention. As shown in the figure, in contrast to  FIG. 5 , which shows an LED  1 , the present figure shows a method for manufacturing the LED  1 . To manufacture the LED  1 , the step S 10  is first executed for forming an LED die  10 . Then the step S 12  is executed for forming one or more metal pads  12  on the electrodes  107  of the LED die  10 . Next, the step S 13  is executed for forming a dielectric layer  18  on the LED die  10 . Finally, the step S 14  is executed for forming a fluorescent layer  16  on the dielectric layer  18 . The fluorescent layer  16  does not cover the metal pads  12  completely. Instead, the metal pads  12  are left exposed for the convenience of subsequent wiring and packaging processes. 
         [0027]    For forming the fluorescent layer  16  on the LED die  10 , glue dispensing, spraying, or pouring methods are applied. For avoiding the fluorescent layer  16  from covering the metal pads  12  completely during the forming process of the fluorescent layer  16 , prior to forming the fluorescent layer  16  on the LED die  10  using the glue dispensing, spraying, or pouring methods, a mask is used on the metal pads  12 . The mask can mask the metal pads  12  and expose the location to form the fluorescent layer  16 . Besides, the mask is manufactured by lithography or by screen-printing using organic polymer materials such as photoresist. 
         [0028]      FIG. 7  shows a structural schematic diagram according to another preferred embodiment of the invention. As shown in the figure, for packaging the LED  1  provided in  FIG. 1 , the LED  1  is set on a carrier  2 . Then, the metal pads  12  are connected by wiring. Finally, use packaging glue  3  to cover the carrier  2  and the LED  1 . The material of the packaging glue  3  is organic polymer, and fluorescent powders can be further contained therein. The organic polymer material of the packaging glue  3  differs from the organic polymer material of the fluorescent layer described in  FIG. 1 . In addition, the packaging glue  3  and fluorescent layer  16  are not processed simultaneously. The baking time of the two is also different, which can reduce the stress problem effectively produced in the package of the LED  1 . Moreover, the packaging structure according to present embodiment can be applied to the embodiment of  FIG. 5 . 
         [0029]      FIG. 8  shows a flowchart according to a preferred embodiment of the invention. As shown in the figure, for packaging the LED  1  provided in  FIG. 1 , the step S 16  is first executed for setting a carrier  2  to the LED  1  and opposite to the fluorescent layer  16 . Then the step S 18  is executed for connecting the metal pads  12  by wiring. Finally, the step S 19  is executed for coving the carrier  2  and the LED  1  by packaging glue  3 . The packaging method provided according to the present embodiment can be applied to the LED 1  provided in  FIG. 5 , and will not be described in detail. 
         [0030]    It is known from above that the invention provides an LED and a method for manufacturing the same. The characteristics of the invention include that the metals pads are left exposed for the convenience of subsequent wiring and packaging processes. In addition, the LED provided by the invention is a single light-mixing chip, which can be packaged directly without the need of coating fluorescent powders on the packaging glue. Because the fluorescent layer and the packaging glue are not processed simultaneously and are of different materials, the stress problem in the packaged LED can be reduced effectively. 
         [0031]    Accordingly, the invention conforms to the legal requirements owing to its novelty, nonobviousness, and utility. However, the foregoing description is only embodiments of the invention, not used to limit the scope and range of the invention. Those equivalent changes or modifications made according to the shape, structure, feature, or spirit described in the claims of the invention are included in the appended claims of the invention.