Abstract:
A method for manufacturing a light emitting diode (LED) assembly comprises the steps of: covering a light-reflection layer onto a substrate layer, covering a light-emitting layer onto the light-reflection layer, and forming a P type electrode and an N type electrode extended from the light-emitting layer, perforating through the light-reflection layer, and exposed from the substrate layer to form an LED chip structure; packaging the LED chip structure with a light-transmissible packaging material and keeping the P type electrode and the N type electrode exposed from the light-transmissible packaging material to form a molded LED chip cell; and electrically connecting the P type electrode and the N type electrode of the molded LED chip cell to a circuit board, so as to manufacture the LED assembly.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for manufacturing a light emitting diode (LED) assembly, and more particularly to the method for manufacturing the LED assembly with an molded LED chip cell directly mounted on a circuit board. 
       BACKGROUND OF THE INVENTION 
       [0002]    In daily life, for identifying objects and directions in dark environment, it is usually necessary to provide illumination for us via the utilization of a light emitting assembly. Among the light emitting assemblies, LED has become the most popular light emitting assembly gradually due to global energy saving trend and its advantages of long usage life and low power consumption. 
         [0003]    However, besides the usage of wide-field illumination, due to that the LED has the advantages of long usage life and low power consumption, LED is also usually applied to be assembled into the LED assembly to provide for the backlight of the electronic devices or for other utilization. Among numerous LED assemblies, the technology of chip-flipping is to directly mount a packaged LED structure to a carrier without wire-bonging, so that it is widely used by the most people skilled in the arts. 
         [0004]    Based on the background as mentioned, following up, a representative technology for manufacturing an LED assembly via manufacturing a chip-flipped type packaged LED structure in prior art is disclosed for more detail illustration. Please refer to the drawings from  FIG. 1A  to  FIG. 1E , which illustrate a series of steps for manufacturing the LED assembly in the prior art. As shown in  FIG. 1A , when manufacturing a chip-flipped type packaged LED structure  100  (shown in  FIG. 1E ), firstly, it is necessary to prepare a flipped-type LED structure  1 . At this step, it is necessary to prepare a substrate as a light-transmissible substrate layer  11 . 
         [0005]    Following up, it is necessary to form a buffer layer,  12  an N type electrode cladding sub-layer  13 , a multiple quantum well  14 , a P type electrode cladding sub-layer  15 , a light-transmissible conductive film  16  and a reflection layer  17 . 
         [0006]    The buffer layer  12  covers the light-transmissible substrate layer  11 ; the N type electrode cladding sub-layer  13  covers the buffer layer  12 ; the multiple quantum well  14  covers the N type electrode cladding sub-layer  13 ; the P type electrode cladding sub-layer  15  covers the multiple quantum well  14 ; the light-transmissible conductive film  16  covers the P type electrode cladding sub-layer  15 ; and the reflection layer  17  covers the light-transmissible conductive film  16 . Next, it is necessary to make a P type electrode  18  be extended from the light-transmissible conductive film  16 , and make an N type electrode  19  be extended from the N type electrode cladding sub-layer  13 . Moreover, it is able to plate gold (Au), tin (Sn) or gold-tin (Au—Sn) alloy (not shown) on the P type electrode  18  and the N type electrode  19 , so as to manufacture the flipped-type LED structure  1 . 
         [0007]    As shown in  FIG. 1B , next, it is necessary to prepare a carrier  2  comprising a carrier body  21 , a P type electrode layer  22  and an N type electrode layer  23 . The carrier body  21  has a top surface  211 , a bottom surface  212 , a first side  213  and a second side  214 . The P type electrode layer  22  and the N type electrode layer  23  are respectively arranged to wrap the first side  213  and the second side  214 . 
         [0008]    As shown in  FIG. 1C , after preparing the carrier  2 , it is necessary to respectively arrange two conductive members  3  and  3   a  on the P type electrode  22  and the N type electrode  23  of the carrier  2 . Preferably, the conductive members  3  and  3   a  can be soldering contacts on the carrier, and the soldering contacts can be made by plating gold or silver. 
         [0009]    As shown in  1 D, when the conductive members  3  and  3   a  are the soldering contacts made by plating gold or silver, it is necessary to flip the flipped-type LED structure  1  to execute an eutectic process under an eutectic temperature, so as to make the gold and silver element particles of the conductive elements  3  and  3   a  permeate into the gold, tin or gold-tin alloy plated on the P type electrode  18  and N type electrode  19 . Through the eutectic process, it is able to make the P type electrode  18  and N type electrode  19  of the flipped-type LED structure  1  be electrically connected to the P type electrode layer  22  and N type electrode layer  23  of the carrier  2  respectively via the conductive elements  3  and  3   a . In practice, the conductive members  3  and  3   a  also can be gold (Au), tin (Sn) or gold-tin (Au—Sn) alloy deposited on the carrier  2 , and it is also able to form soldering contacts made by plating gold or silver on the P type electrode  18  and the N type electrode  19 , so as to execute the eutectic process as mentioned. Except for above method, when the conductive members  3  and  3   a  are tin balls or tin paste, through a reflow soldering process, the P type electrode  18  and N type electrode  19  also can be electrically connected to the P type electrode layer  22  and N type electrode layer  23  respectively via the conductive elements  3  and  3   a.    
         [0010]    As shown in  FIG. 1E , after electrically connecting the P type electrode  18  and N type electrode  19  to the P type electrode layer  22  and N type electrode layer  23  respectively, it is necessary to execute a packaging process of packaging the flipped-type LED structure  1 , the conductive members  3  and  3   a  by a light-transmissible packaging material  4 , so as to manufacture the flipped-type packaged LED structure  100  after the light-transmissible packaging material  4  is cured. Finally, it is necessary to mount the flipped-type packaged LED structure  100  onto a circuit board (not shown) by soldering, and then an LED assembly (not shown) is manufactured. 
         [0011]    Any person skilled in ordinary art can easily make out that in the prior art as disclosed, it is necessary to electrically connect the P type electrode  18  and N type electrode  19  of the flipped-type LED structure  1  to the P type electrode layer  22  and N type electrode layer  23  firstly, and then fill the light-transmissible packaging material  4  to the flipped-type LED structure  1 , the conductive members  3  and  3   a ; therefore, it is very inconvenient that it is necessary to execute both the eutectic process and the packaging process to manufacture the flipped-type packaged LED structure  100 , and then to mount the flipped-type packaged LED structure  100  on the circuit by soldering. 
         [0012]    Nevertheless, due to that it is necessary to apply a filling pressure to a die when filling the light-transmissible packaging material  4  therein, it would bring the problem that the light-transmissible packaging material  4  overflows to the carrier  2 ; moreover, the defective rate of electrical connection between the conductive members  3 ,  3   a  and the carrier  2  would be increased due to that the conductive members  3  and  3   a  would be pressed when suffering the filling pressure. 
         [0013]    Based on the background, the inventor of the present invention is of the opinion that it is necessary to provide a new method for manufacturing a LED assembly, so as to improve the problems as mentioned above. 
       SUMMARY OF THE INVENTION 
       [0014]    Due to that the method for manufacturing the flipped-type packaged LED structure as provided in the prior art exists the problems of that it brings the inconvenience of executing a series of complex processes including both the eutectic process and the packaging process, causes the light-transmissible packaging material overflowing to the carrier, and increases the defective rate of electrical connection between the conductive members and the carrier. Thus, the primary objective of the present invention is to provide a method for manufacturing a LED assembly, by which a packaging process of manufacturing a molded LED chip cell is executed to make a P type electrode and an N type electrode exposed thereof, so as to replace the flipped-type packaged LED structure to directly mounted on a circuit board. Though the method, the problems as mentioned can be effectively solved. 
         [0015]    Means of the present invention for solving the problems as mentioned above is to provide a method for manufacturing a light emitting diode (LED) assembly, and the method comprises the steps of: covering a light-reflection layer onto a substrate layer, covering a light-emitting layer onto the light-reflection layer, and forming a P type electrode and an N type electrode extended from the light-emitting layer, perforating through the light-reflection layer, and exposed from the substrate layer to form an LED chip structure; packaging the LED chip structure with a light-transmissible packaging material and keeping the P type electrode and the N type electrode exposed from the light-transmissible packaging material to form a molded LED chip cell; and electrically connecting the P type electrode and the N type electrode of the molded LED chip cell to a circuit board, so as to manufacture the LED assembly. 
         [0016]    In the preferred embodiment of the present invention, the LED chip structure comprises a substrate layer, a reflection layer, a light-transmissible conductive sub-layer, a P type electrode cladding sub-layer, a light-transmissible multiple quantum well and an N type electrode cladding sub-layer. The reflection layer covers the substrate layer, the light-transmissible conductive sub-layer covers the reflection layer, the P type electrode cladding sub-layer covers the light-transmissible conductive sub-layer, the light-transmissible multiple quantum well covers the P type electrode cladding sub-layer, and the N type electrode cladding sub-layer covers the light-transmissible multiple quantum well. The light-transmissible conductive sub-layer, the P type electrode cladding sub-layer, the light-transmissible multiple quantum well and the N type electrode cladding sub-layer can be viewed as the light-emitting layer. 
         [0017]    Comparing with the conventional method for manufacturing the LED assembly via manufacturing a chip-flipped type packaged LED structure in prior art, in the present invention, a packaging process of manufacturing a molded LED chip cell is executed to make a P type electrode and an N type electrode exposed thereof, so that the molded LED chip cell can be applied to replace the flipped-type packaged LED structure to directly mounted on a circuit board to manufacture the LED assembly. Obviously, through the method as provided in the present invention, it is more convenient to manufacture the LED assembly. 
         [0018]    In the method for manufacturing the LED assembly as disclosed in the present invention, it is unnecessary to use the carrier; therefore, there is no problem of that the light-transmissible packaging material overflows to the carrier in the whole manufacturing steps. Furthermore, there would be less electrical connection defection of the molded LED chip cell caused by filling the light-transmissible packaging material to the LED chip structure to form the molded LED chip cell. By the way, it is able to make the overall dimension of molded LED chip cell approaching to the overall dimension of the LED chip structure, i.e., it is able to make the overall dimension of the molded LED chip cell be much less than the overall dimension of the flipped type packaged LED structure as provided in the prior art, so as to increase the space utilization rate of that the molded LED chip cells are arranged on the circuit board. 
         [0019]    To make a summary, through the method as provided in the present invention, it not only can make the manufacturing of the LED assembly become more convenient, but also can upgrade the quality of the manufacturing the LED assembly. By the way, through the method as provided in the present invention, it also can effectively increase the space utilization rate of that the molded LED chip cells are arranged on the circuit board. 
         [0020]    The devices, characteristics, and the preferred embodiment of this invention are described with relative figures as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The structure and the technical means adopted by the present invention to achieve the above and other objectives can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein 
           [0022]      FIG. 1A  to  FIG. 1E  illustrate a series of steps for manufacturing the LED assembly in the prior art; 
           [0023]      FIG. 2A  illustrates the step of manufacturing an LED chip structure in the preferred embodiment of the present invention; 
           [0024]      FIG. 2B , which illustrates the step of packaging the LED chip structure to manufacture the molded LED chip cell in accordance with the preferred embodiment of the present invention; 
           [0025]      FIG. 2C  illustrates the step of preparing a circuit board in accordance with the preferred embodiment of the present invention; and 
           [0026]      FIG. 2D  illustrates the step of mounting the molded LED chip cell on the circuit board by a soldering process in accordance with the preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    The method for manufacturing LED assembly as provided in accordance with the present invention can be widely applied to manufacture many kinds of LED assemblies, and the combined applications of the present invention are too numerous to be enumerated and described, so that only one preferred embodiment is disclosed as follows for representation. 
         [0028]    Please refer to the drawings from  FIG. 2A  to  FIG. 2D , which illustrate a series of steps for manufacturing the LED assembly in accordance with the preferred embodiment of the present invention. The most important concept, which is disclosed in the preferred embodiment of the present invention, is to manufacture a molded LED chip cell  200  (shown in  FIG. 2B ) firstly, and then to manufacture a LED assembly  300  (shown in  FIG. 2D ). As shown in  FIG. 2A , which illustrates the step of manufacturing an LED chip structure in the preferred embodiment of the present invention. When manufacturing the molded LED chip cell  200 , it is necessary to manufacture an LED chip structure  5 . At this moment, it is necessary to prepare a substrate as a substrate layer  51 . 
         [0029]    Next, following up it is necessary to form the a reflection layer  52 , a light-transmissible conductive sub-layer  53 , a P type electrode cladding sub-layer  54 , a light-transmissible multiple quantum well  55  and an N type electrode cladding sub-layer  56 . The reflection layer  52  covers the substrate layer  51 , the light-transmissible conductive sub-layer  53  covers the reflection layer  52 , the P type electrode cladding sub-layer  54  covers the light-transmissible conductive sub-layer  53 , the light-transmissible multiple quantum well  55  covers the P type electrode cladding sub-layer  54 , and the N type electrode cladding sub-layer  56  covers the light-transmissible multiple quantum well  55 . The light-transmissible conductive sub-layer  53 , the P type electrode cladding sub-layer  54 , the light-transmissible multiple quantum well  55  and the N type electrode cladding sub-layer  56  can be viewed as a light-emitting layer  50 . 
         [0030]    The substrate layer  51  can be a substrate composed of at least one material of silicon carbide (SiC), aluminum oxide (Al 2 O 3 ), gallium arsenide (GaAs), silicon (Si), sapphire, copper (Cu), copper-tungsten (Cu—W) alloy and gallium phosphide (GaP). The reflection layer  52  is composed of at least one compound of titanium dioxide and silicon dioxide (TiO 2 /SiO 2 ), aluminum oxide and silicon dioxide (Al 2 O 3 /SiO 2 ), and Silicon Nitride and silicon dioxide (Si 3 N 4 /SiO 2 ). The light-transmissible conductive sub-layer  53  is formed by an annealing process for a Nickel-Gold (Ni—Au) metal film under the annealing temperature of 500° C. to 550° C. 
         [0031]    Next, it is necessary to bore, via etching or drilling, a P type electrode extension recess (not shown) and an N type electrode extension recess from the substrate layer  51  toward the light-emitting layer  50 , wherein the P type electrode extension recess is bored to contact with the P type electrode cladding sub-layer  54 , and the N type electrode extension recess is bored to contact with the N type electrode cladding sub-layer  56  and isolated by an isolation film  57 . Then, it is necessary to make a P type electrode  58  be extended from the P type electrode cladding sub-layer  54 , perforating the light-transmissible conductive sub-layer  53 , the reflection layer  52  and the substrate layer  51  via the P type electrode extension recess, and exposed from the substrate layer  51 . Meanwhile, it is necessary to make an N type electrode  59  be extended from the N type electrode cladding sub-layer  56 , perforating the light-transmissible multiple quantum well  55 , the P type electrode cladding sub-layer  54 , the light-transmissible conductive sub-layer  53 , the reflection layer  52  and the substrate layer  51  via the P type electrode extension recess, and exposed from the substrate layer  51 . Thus, through the isolation film  57 , the N type electrode  59  can keep electrical isolation with respect to the light-transmissible multiple quantum well  55 , the P type electrode cladding sub-layer  54 , the light-transmissible conductive sub-layer  53 , the reflection layer  52  and the substrate layer  51 . Up to now, the manufacturing of the LED chip structure  5  is finished. 
         [0032]    As shown in  FIG. 2B , which illustrates the step of packaging the LED chip structure to manufacture the molded LED chip cell in accordance with the preferred embodiment of the present invention. After manufacturing the LED chip structure  5 , a packaging process can be executed. When executing the packaging process, a light-transmissible packaging material  6 , such as light-transmissible packaging gel or rubber, is applied to package the LED chip structure  5  to keep the P type electrode  58  and the N type electrode  59  being exposed of the light-transmissible packaging material  6 , after the light-transmissible packaging material  6  is cured, the manufacturing of the molded LED chip cell  200  is finished. 
         [0033]    As shown in  FIG. 2C , which illustrates the step of preparing a circuit board in accordance with the preferred embodiment of the present invention. Before manufacturing the LED assembly  300  (shown in  FIG. 2D ), it is necessary to prepare a circuit board  7  comprising a substrate layer  71 , a first circuit arrangement layer  72  and a second circuit arrangement layer  73 . The first circuit arrangement layer  72  and the second circuit arrangement layer  73  are deposited on two surfaces, opposite to each other, of the substrate layer  71 , and at least one of the first circuit arrangement layer  72  and the second circuit arrangement layer  73  is arranged with a LED driving/control circuit (not shown). In the preferred embodiment, the LED driving/control circuit is arranged on the first circuit arrangement layer  72 . Preferably, the circuit board  7  can be a printed circuit board, such as an FR4 (an abbreviation for Flame Retardant 4) copper clad laminate, or any other circuit board arranged with the LED driving/control circuit. 
         [0034]    As shown in  FIG. 2D , which illustrates the step of mounting the molded LED chip cell on the circuit board by a soldering process in accordance with the preferred embodiment of the present invention. After preparing the circuit board  7 , it is able to mount the molded LED chip cell thereon to make the P type electrode  58  and the N type electrode  59  be electrically connected to the LED driving/control circuit arranged on the first circuit arrangement layer  72  respectively. After finishing the soldering process, the manufacturing of the LED assembly is finished. More preferably, when executing the soldering process, a melted or partial-melted soldering ball or soldering paste made of tin can be applied to attach to the P type electrode  58  and the N type electrode  59 , or be applied to attach to the soldering pin, contact or pad of the LED driving/control circuit arranged on the first circuit arrangement layer  72 , and then a reflow soldering and low-temperature solidification process can be executed. 
         [0035]    After reading the technology as disclosed above, it is believable that any person skilled in ordinary art can reasonably make out that in the method for manufacturing the LED assembly  300  in accordance with the present invention, the packaging process of manufacturing the molded LED chip cell  200  is executed to make the P type electrode  58  and the N type electrode exposed thereof, so that the molded LED chip cell  200  can be applied to replace the flipped-type packaged LED structure to directly mounted on a circuit board to manufacture the LED assembly. Obviously, through the method as provided in the present invention, it is more convenient to manufacture the LED assembly. 
         [0036]    In the method for manufacturing the LED assembly  300  as disclosed in the present invention, it is unnecessary to use the carrier  2  as disclosed in the prior art; therefore, there is no problem of that the light-transmissible packaging material  6  overflows to the carrier  2  in the whole manufacturing steps. Furthermore, there would be less electrical connection defection of the molded LED chip cell  200  caused by filling the light-transmissible packaging material  6  to the LED chip structure to form the molded LED chip cell  200 . By the way, it is able to make the overall dimension of molded LED chip cell  200  approaching to the overall dimension of the LED chip structure  5 , i.e., it is able to make the overall dimension of the molded LED chip cell  200  be much less than the overall dimension of the flipped type packaged LED structure  100  as provided in the prior art, so that more molded LED chip cell(s)  200  can be mounted to the circuit board to increase the space utilization rate of that the molded LED chip cell(s)  200  are arranged on the circuit board  7 . 
         [0037]    To make a summary, through the method as provided in the present invention, it not only can make the manufacturing of the LED assembly  300  become more convenient, but also can upgrade the quality of the manufacturing the LED assembly  300 . By the way, through the method as provided in the present invention, it also can effectively increase the space utilization rate of that the molded LED chip cells  200  are arranged on the circuit board  7 . 
         [0038]    Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.