Abstract:
The present invention related to a method of manufacturing an LED, including the steps of: first, forming a tape coppery metal strip; then, continuously pressing circuits on the tape coppery metal strip so as to form a carrier having circuit patterns of electric contacts on which the diode dies can be placed; next, electroplating a plurality of metal layers on the surface of the carrier; then, performing continuous injection molding on the carrier so as to form a protector having a designated shape; and curing and fixing the diode die on the carrier to connect to the terminal contact of the carrier via metal wire. A conductive or non-conductive adhesive is dropped onto the bonding position between the metal wire and the terminal of the carrier, and a soft paste is Anther applied to cover the diode die, the metal wire and the terminal.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a method of manufacturing an LED (Light Emitting Diode) and, more particularly, a method of manufacturing an LED on a tape coppery metal strip. 
   BACKGROUND TO THE INVENTION 
   The choices of packaging methods, materials and packaging equipments for LED&#39;s mainly depend on the factors such as functions, electrical/photoelectric properties, precision, unit price, etc. of LED chips. The LED industry has been developed for several decades, and has gone through the developments of lead LED, chip SMD LED, power LED, high power LED, etc. 
   When manufacturing a single LED carrier with ceramic materials used as the carrier, it is hard to form circuits on the surface of the carrier; namely, it is hard to form circuit patterns on the carrier. Therefore, there have disadvantages of difficulty in manufacture, poor precision and high cost. If a metal material (such as copper) is used as the carrier, a mask should be made in advance; then, after the procedure of exposure, the unwanted areas are etched by etching so as to form circuit patterns on the carrier. Such a manufacturing method is time-consuming because of the drift of the precision of each mask due to the variability in position thereon. Generally speaking, when a large current passes through a diode die, it is possible that the die may be loosen and even detached or cracked due to the thermal stress effect of the diode die. Therefore, it is indeed an important issue to avoid or reduce the thermal stress. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to provide a method of manufacturing an LED, capable of improving the precision so as to facilitate the manufacture of an LED and effectively reduce the cost, as well as avoiding the diode die from being loosen or cracked due to the thermal stress effect thereof. 
   The method of manufacturing an LED according to the present invention comprises the steps of: forming a tape coppery metal strip; continuously pressing circuits on the tape coppery metal strip so as to form a carrier having circuit patterns of electric contacts on which the diode dies can be placed; next, electroplating a plurality of metal layers on the surface of the carrier; then, continuously injecting chemical materials having a high glass transition point such as polyphthalamide (PPA) to be molded on the carrier so as to form a protector having a designated shape; and fixing the diode die in the interior of the protector, and welding metal wires to connect the die pads and the terminal contacts of the carrier. Meanwhile, a conductive or non-conductive adhesive is dropped onto the bonding position between the metal wires and the terminals of the carrier, and a soft paste is further applied to cover the diode dies, the metal wires and the terminals. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described by referring to the accompanying drawings in which: 
       FIG. 1  is a diagram showing the tape coppery metal strip of the present invention; 
       FIG. 2  is an enlarged fragmentary diagram of the tape coppery metal strip shown in  FIG. 1 ; 
       FIG. 3  is an enlarged fragmentary diagram of the circuit pattern on the carrier  24  shown in  FIG. 2 ; 
       FIG. 4  is a sectional diagram of the carrier shown in  FIG. 2 ; 
       FIG. 5A  is a plan view of the carrier on which a protector is formed according to the present invention; 
       FIG. 5B  is a side view of  FIG. 5A ; 
       FIG. 5C  is another side view of  FIG. 5A ; 
       FIG. 6A  and  FIG. 6B  are diagrams showing the protector of the present invention; 
       FIG. 7A  is a diagram showing the adhesive is applied on the carrier according to the present invention; 
       FIG. 7B  is a diagram showing the diode die is adhered to the adhesive according to the present invention; 
       FIG. 7C  is a diagram showing the diode die is baked to be cured and fixed on the carrier according to the present invention; 
       FIG. 8A  is a sectional view showing the curing and fixing of the diode die by eutectic mounting according to the present invention; 
       FIG. 8B  is a sectional view showing the curing and fixing of the diode die by flip-chip mounting according to the present invention; 
       FIG. 8C  is a sectional view showing the curing and fixing of the diode die by pick-up mounting according to the present invention; 
       FIG. 9A  is a diagram showing the bonding of the diode die of the present invention; 
       FIG. 9B  is a sectional diagram of  FIG. 9A ; 
       FIG. 10A  is a diagram showing the adhesive is dropped on the bonding positions between the metal wires and the terminals according to the present invention; 
       FIG. 10B  is a sectional diagram of  FIG. 10A ; 
       FIG. 11A  is a diagram showing a soft paste is applied to cover the diode dies, the metal wires and the terminals according to the present invention; 
       FIG. 11B  is a sectional diagram of  FIG. 11A ; 
       FIG. 12  is a diagram showing the oven for baking the adhesive and the soft paste of the present invention; 
       FIG. 13A  is a diagram showing the resin is injected into the protector according to the present invention; 
       FIG. 13B  is another diagram showing the resin is injected into the protector according to the present invention; and 
       FIG. 14A-FIG .  14 C are diagrams showing the ball on stick ball bonding according to the present invention. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  is a diagram showing the tape coppery metal strip of the present invention. As shown in  FIG. 1 , a tape coppery metal strip  20  is wound on a roller  22 . Unlike the single strip used in the conventional art in which after the process for a single strip is finished, the finished single strip must be removed from the working table and replaced with a new single strip, the tape coppery metal strip  20  of the present invention can be continuously processed, such as continuous pressing, fixing dies, bonding, dropping soft paste, etc., on the working table until the end of the tape coppery metal strip is reached. Thus, using the tape coppery metal strip of the present invention can increase the yield, improve the efficiency and reduce the labor cost. 
     FIG. 2  is an enlarged fragmentary diagram of the tape coppery metal strip shown in  FIG. 1 . As shown in  FIG. 2 , by way of continuous pressing, the tape coppery metal strip  20  shown in  FIG. 1  is formed as a carrier  24  having circuit patterns of electric contacts, on which diode dies (not shown) can be placed. The tape carrier  24  can have various sizes. Meanwhile, the circuit pattern on the carrier  24 , as shown in  FIG. 3  which is an enlarged fragmentary diagram of the circuit pattern on the carrier  24  shown in  FIG. 2 , can be designed to a desired circuit pattern according to the needs. 
     FIG. 4  is a sectional diagram of the carrier shown in  FIG. 2 . In order to increase the conductivity of the carrier  24 , reduce the surface impedance thereof, enhance the lighting intensity and improve the capability of the soldering tin, a plurality of metal layers can be electroplated on the surface of the carrier  24 . As shown in  FIG. 4 , nickel  26 , silver  28  and tin  30  are individually electroplated on the surface of the coppery carrier  24  (gold can also be used), so that the above-mentioned functions can be achieved. 
     FIG. 5A  is a plan view of the carrier on which a protector is formed according to the present invention,  FIG. 5B  is a side view of  FIG. 5A , and  FIG. 5C  is another side view of FIG.  5 A. As shown in these drawings, a protector  32  having a designated shape can be formed on the tape carrier  24  by way of continuous injection molding. As shown in  FIG. 6A  and  FIG. 6B , which are diagrams showing the protector of the present invention, the height of the protector  32  formed on the carrier  24  is set to B; the diode die  34  is placed on the carrier  24 , and the height from the bottom of the protector  32  to the top of the diode die  34  is set to A. The height B is higher than the height A. Thus, the diode die  34  and the carrier  24  can be integrally formed in the interior of the protector  32 , so that the protector  32  can protect the diode die  34  to avoid from extruding damage, and various photodiodes with different functions can be placed on the designated areas. Further, the protector  32  is made of a heat-resistant chemical material of polyphthalamide (PPA) having a high glass transition point (Tg); this material can be used in the present invention so that the protector  32  can be manufactured easily by way of the injection molding of plastics, and the manufacturing method thereof has the advantages of high precision and low cost. 
     FIG. 7A  is a diagram showing the adhesive is applied on the carrier according to the present invention,  FIG. 7B  is a diagram showing the diode die is adhered to the adhesive according to the present invention, and  FIG. 7C  is a diagram showing the diode die is baked to be cured and fixed on the carrier according to the present invention. As shown in these drawings, first, a conductive or non-conductive adhesive  36  is applied on the designated position of the carrier  24  where the diode die  34  will be placed; after being placed on said position, the diode die  34  is adhered by the adhesive  36 , and then entirely put into the oven  38  to cure the adhesive  36  by the baking of the oven  38  which may be a hot air type oven, an infrared oven or a reflow oven. Further, the method of curing and fixing the diode die  34  on the carrier  24  includes eutectic method, flip chip method or pick up method.  FIG. 8A  to  FIG. 8C  are sectional views showing the curing and fixing of the diode die according to the present invention, of which  FIG. 8A  shows the eutectic method of curing and fixing the diode die,  FIG. 8B  shows the flip chip method of curing and fixing the diode die, and  FIG. 8C  shows the pick up method of curing and fixing the diode die. 
     FIG. 9A  is a diagram showing the bonding of the diode die of the present invention, and  FIG. 9B  is a sectional diagram of  FIG. 9A . The cured and fixed diode die  34  should be subjected to the process of electrical connection; namely, a pad of the diode die  34  is electrically connected to a terminal  42  of the carrier by using metal wires  40  such as gold wires, aluminum wires or copper wires. The method for electrical connection includes the bonding methods such as ultrasonic bonding, ultrasonic thermo bonding, ball on stick ball bonding, etc., so that the metal wires  40  are electrically connected to the pad of the diode die  34  and the terminal  42  of the carrier, respectively. Further, the ball on stick ball bonding is shown in  FIG. 14A  to  FIG. 14C . One end of the metal wire  40  assumes a ball shape and is pressed to connect with the pad  35  of the diode die  34 . The other end of the metal wire  40  assumes a line shape and is pressed to connect with the terminal  42  so that the other end of the metal wire  40  is to assume the fishtail shape, and then a ball  41 , the shape of which is like the ball-shaped end of the metal wire  40 , is pressed onto the bonding position between the metal wire  40  and the terminal  42 ; namely, the fishtail-shaped end of the metal wire  40  is pressed to connect with the terminal  42 . Thus, the connection effect between the metal wire  40  and the terminal  42  is enhanced so as to avoid the loosing, even detachment, of the metal wire  40  from the terminal  42 . 
     FIG. 10A  is a diagram showing the adhesive is dropped on the bonding positions between the metal wires and the terminals according to the present invention, and  FIG. 10B  is a sectional diagram of  FIG. 10A . As shown in these drawings, a conductive or non-conductive adhesive  46  is dropped on the bonding positions between the metal wires  40  and the terminals  42  of the carrier  24  so as to enhance the strength of the connecting point between the metal wire  40  and the terminal  42  and increase the adhesive strength. 
     FIG. 11A  is a diagram showing a soft paste is applied to cover the diode dies, the metal wires and the terminals according to the present invention, and  FIG. 11B  is a sectional diagram of  FIG. 11A . As shown in these drawings, after the processes of bonding the diode dies  34  and the metal wires  40  and dropping the adhesive  46  thereon are finished, a soft paste  48  is further applied to cover the diode dies  34 , the metal wires  40  and the terminals  42 . The soft paste  48  is capable of absorbing the thermal stress of the diode dies  34  generated due to being electrified and of resisting the internal stress of the protector  32  to protect the diode dies  34 , and thus the yield rate of LED can be increased. Moreover, a soft paste  48  incorporating chemical powders having a diffusive property or a light wavelength transformation function can be used. 
   After the above-mentioned processes of applying the adhesive  46  and the soft paste  48  are finished, as shown in  FIG. 12  which is a diagram of the oven for baking the adhesive and the soft paste according to the present invention, the LED which has gone through the above-mentioned processes is put into an oven  50  which may be a hot air type oven, an infrared oven or a reflow oven to cure the adhesive  46  and the soft paste  48  by the baking process. 
   After the above-mentioned process of baking and curing the adhesive  46  and the soft paste  48  is finished, as shown in  FIG. 13A  which is a diagram showing the resin is injected into the protector according to the present invention, a protective resin  52  that is pervious to light is injected into the cave  56  of the protector  32  and onto the soft paste  48 , the shape of which assumes a tangent plane with the top of the protector  32 . The resin pervious to light can also assume other shapes; as shown in  FIG. 13B  which is another diagram showing the resin is injected into the protector according to the present invention, the resin  54  is injected into the cave  56  of the protector  32  and assumes a hemisphere on the top of the protector  32 ; alternatively, the injected resin can have a designed surface that has a prism effect (not shown). The purpose of injecting the protective resin pervious to light into the cave of the protector as mentioned above enables the LED having a better lighting efficiency and an excellent optical derivative property. 
   Although the manufacturing method of the present invention is explained by referring to a single LED in the above drawings for easy understanding, yet in an actual process, the LED is manufactured through a carrier formed by the tape coppery metal strip. 
   The method of manufacturing an LED of the present invention, capable of continuously carrying out the processes of pressing dies, injection molding and baking by using a tape coppery metal strip, can improve the precision, facilitate the manufacturing of an LED and effectively reduce the cost; meanwhile, the use of adhesives, soft pastes and resins can avoid the diode die from being loosen, detached or cracked due to the thermal stress effect thereof. 
   With the detailed description of the above-mentioned embodiment, it is desired to clearly describe the features and spirits of the present invention and should not be considered as a limitation on the scope of the present invention by the above-mentioned preferred embodiment; on the contrary, the purpose thereof is desired to cover various modifications and equivalent alterations under the scope of the appended claims of the present invention.