Patent Publication Number: US-2012025214-A1

Title: Led packaging structure and packaging method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority of Chinese Patent Application CN201010243390.7 filed Jul. 30, 2010, the entire contents of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention belongs to the field of manufacturing a photoelectric device, and relates to an LED packaging structure and manufacturing method thereof. 
     BACKGROUND OF THE INVENTION 
     The light emitting diode (LED) source has several advantages of high efficiency, long life and no harmful substances such as Hg and the likes. With the rapid development of LED technology, the LED&#39;s properties, such as brightness, lifetime and the likes, have been greatly improved, such that it has found an increasing application in a variety of areas ranging from outdoor lighting such as street lamps to indoor lighting such as decorative lights, in which the LED is used or replaced as a light source. 
     In the LED packaging structure, in order to enhance the brightness of the LED and achieve a better effect of reliability, silicone, epoxy resin or the likes is usually used to form a lens of hemispherical or other shapes in the LED surface, to enhance the light extracting rate of the LED. Currently, the lens in the LED surface is formed primarily by two packaging processes. One is to form the lens in the LED surface by a mold, and the other is to firstly form the lens by injection molding, and then to adhere the Tens on the LED surface by coating or applying colloid. 
     As an example, a power LED with a lens molded by injecting colloid at the bottom, and manufacturing method thereof are disclosed in China patent application of publication number CN101162750, including the steps of: arranging plastic injection and vent holes on a substrate; installing an LED chip to the substrate and completing electrical connections; then pressing a mold for lens molding on the substrate; injecting an encapsulant colloid from the plastic injection holes at the bottom of the substrate; after completion of the colloid injection, curing the colloid and removing the mold; and completing the molding of the package lens of the LED chip. However, this manufacturing method needs to use the mold for lens molding, and the production process is relatively complex. If an automatic machine is used for molding, the investment in the machine will be very high, but productivity is low; if a simple jig is used for molding, it is difficult to control the quality of the lens and LED packaging process. 
     As another example, a packaging method for a high power white LED is disclosed in China patent application of publication number CN10101404317, including the steps of: step 1 of providing two sheets of electrodes and a base for installing the two sheet of electrodes; step 2 of fixing an LED chip within the above base and baking it; step 3 of bonding wires to connect positive and negative poles of the LED chip to said two sheet of electrodes respectively; step 4 of covering said base with a lens and adhering the lens to the base; and step 5 of baking the above components to achieve a fixed shape. However, this packaging method of adhering the injection molding lens to the surface of the LED chip will produce an interface between the lens and the packaging materials, which will cause a certain loss in the light extracting rate; and the interface between different materials will also cause the issues such as light attenuation etc., due to the problems such as thermal mismatch etc., in the process of long-term use; at the same time, there are also problems with this packaging method in the process of production, for example it is difficult to control the packaging quality and achieve automatic production. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide an LED packaging structure with low cost, controllable quality and direct shaping without mold, in order to overcome the shortcomings and deficiencies of prior art. 
     Meanwhile, the present invention also provides a packaging method for said LED packaging structure. 
     AN LED packaging structure includes a substrate, an LED chip, one or more convex walls and a colloid lens shaped by the restriction of the convex walls. Said convex walls are arranged on the substrate, at least one LED chip is arranged on the substrate within an area surrounded by the convex walls, and the colloid lens enclosing the LED chip is arranged within the area surrounded by the convex walls. The colloid lens is formed with desired colloid shape by placing a liquid colloid within the area confined by the convex walls and utilizing surface tension of the liquid, and is cured. 
     AN LED packaging method includes the steps of: 
     S1: forming a convex wall on a substrate; 
     S2: fixing at least one LED chip onto the substrate within a confined area formed by the convex wall; 
     S3: dispensing a colloid above the confined area formed by the convex wall, and forming a colloid lens to isolate the LED chip from environment. 
     Compared to prior art, the LED packaging structure of the present invention is simple and reasonable, and is easy to produce and improve yield. 
     Compared to prior art, the LED packaging method of the present invention can directly conducts dispensing process above the LED chip, and simultaneously uses a structure of the convex walls to prevent the encapsulant colloid fluid from extending outwardly thereby to form the encapsulant colloid lens of regular shape, with the process simple and the quality controllable. At the same time, it is suitable for wafer level packaging with high packaging efficiency and low production costs. 
     In order to more clearly understand the present invention, the implementations of the invention will be set forth in conjunction with the drawings hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         FIG. 1  is a cross section schematic view of first embodiment of the LED packaging structure of the present invention. 
         FIG. 2  is a top view of the LED packaging structure shown in  FIG. 1 . 
         FIGS. 3   a ,  3   b  and  3   c  are cross section schematic views of the packaging structure in various steps in the packaging flow of first embodiment of the LED packaging structure of the present invention. 
         FIG. 4  is a top view of f the LED packaging structure of the present invention on a wafer. 
         FIG. 5  is a cross section schematic view of second embodiment of the LED packaging structure of the present invention. 
         FIG. 6  is a top view of the LED packaging structure shown in  FIG. 5 . 
         FIG. 7  is a cross section schematic view of third embodiment of the LED packaging structure of the present invention. 
         FIG. 8  is a top view of the LED packaging structure shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiment 1 
     Now refer to  FIGS. 1 and 2 , wherein  FIG. 1  is a cross section schematic view of first embodiment of the LED packaging structure of the present invention, and  FIG. 2  is a top view of the LED packaging structure shown in  FIG. 1 . The LED packaging structure includes a substrate  10 , an LED chip  20 , a convex wall  30  and a colloid lens  40 . The convex wall  30  is arranged on the substrate  10  to form a confined area, and at least one LED chip  20  is arranged within the confined area of the convex wall  30  and fixed onto the substrate  10 . The colloid lens  40  is arranged on the surface of said LED chip  20  and encloses the LED chip  20 . 
     In particular, said substrate  10  can be silicon wafer, ceramic plate, printed circuit board (PCB), metal-based printed circuit board (MCPCB) or glass sheet. 
     Said convex wall  30  has a width of 10 um˜5000 um and a height of 5 um˜5000 um. Said convex wall  30  can be an arc ring, a polygon ring, a ring surrounded by a combination of arc and polygon, or an intermittent type of enclosed structure. The material of said convex wall is silicone, epoxy resin, metal, oxide, nitride, polyimide, photoresist permanently usable after being cured, or a mixture thereof. 
     The material of said colloid lens is epoxy resin, silicone, modified material of epoxy or silicone, or a mixture of the above and phosphor. 
     Refer to  FIGS. 3   a ,  3   b  and  3   c , which are cross section schematic views of the packaging structure in various steps in the packaging flow of the LED packaging structure of the present invention. The LED packaging structure of the present invention can be formed by the following steps: 
     S1: a convex wall  20  is formed on the substrate  10 . The convex wall  30  can be formed by a process of lithography shaping, or by a process of first performing a convex wall  30  and then adhering the convex wall  30  onto the substrate  10 . 
     S2:at least one LED chip  20  is fixed to the substrate  10  and located within the confined area formed by the convex wall  30 . 
     S3: a colloid lens  40  is formed on the substrate  10 . In particular, dispensing process is conducted above the confined area formed by the convex wall  30 , and a colloid drops onto the substrate  10  within the confined area to enclose the LED chip  20 . At the same tune, as the colloid is liquid, the convex wall  30  limits outward expansion of the colloid at this time; and due to the surface tension of the colloid, a sphere-like colloid lens  40  is formed on the LED chip  20  after the colloid is cured. In this packaging step, a variety of colloid lenses  40  with sphere-like surface and different sizes can be formed according to the colloid characteristic and by controlling the dispensing amount, thereby to achieve various light emitting effect. 
     Refer to  FIG. 4 , which is a top view of f the LED packaging structure of the present invention on a wafer. In the packaging process of the present invention, multiple LED package structures can be formed simultaneously on a wafer, which can have a size of 2 inches to 12 inches. The LED packaging structure also can be formed on the ceramic substrate, the metal-based PCB substrate. The ceramic substrate or metal-based PCB substrate has an unlimited size. On the same wafer or the same piece of substrate, with the same process, the size of the LED packaging structure can be adjusted according to design requirements, and then the singulation process is conducted thereby to improve production efficiency. 
     Embodiment 2 
     Refer to  FIGS. 5 and 6 , wherein  FIG. 5  is a cross section schematic view of second embodiment of the LED packaging structure of the present invention, and  FIG. 6  is a top view of the LED packaging structure shown in  FIG. 5 . The LED packaging structure of the second embodiment is roughly the same as the LED packaging structure of the first embodiment except that: an inner convex wall  32  and an outer convex wall  34  are arranged on the substrate  10 , and the radius of the outer convex wall  34  is greater than that of the inner convex wall  32 . One LED chip  20  is arranged within the confined area of the inner convex wall  32  and fixed onto the substrate  10 . The inner convex wall  32  is used to coat a phosphor layer  50  formed by phosphor and silicone, while the outer convex wall  34  is used for shaping package of the colloid lens  40 . Both the phosphor layer  50  and colloid lens  40  make use of the principle that a liquid is naturally shaped by the surface tension with the edges restricted by the convex walls. The number of the convex wall rings can not be limited, and depends on the needs of the process. The principle remains that the droplets are naturally shaped under the effect of surface tension in case annular convex walls are restricted. 
     Embodiment 3 
     Refer to  FIGS. 7 and 8 , wherein  FIG. 7  is a cross section schematic view of third embodiment of the LED packaging structure of the present invention, and  FIG. 8  is a top view of the LED packaging structure shown in  FIG. 7 . The LED packaging structure of the third embodiment is roughly the same as the LED packaging structure of the second embodiment except that multiple LED chips  20  are arranged within the confined area of the inner convex wall  32  and fixed onto the substrate  10 . Said multiple LED chips  20  can have the same size or different sizes. The multiple LED chips  20  can have various types, i.e. a multi-chip module composed of chipsets emitting different light. 
     Compared to prior art, the present invention directly conducts dispensing process on the LED chip to form an encapsulant colloid lens, and simultaneously uses a structure of the convex walls to prevent the encapsulant colloid fluid from extending outwardly thereby to form the encapsulant colloid lens of regular shape, with the process simple and the quality controllable. At the same time, it is suitable for wafer level packaging with high packaging efficiency and low production costs. 
     The present invention is not limited to the above implementations. If changes and variations of the invention are not departed from the spirit and scope of the invention, and these changes and variations fall within the scope of the claims of the invention and equivalent technology, then the present invention is also intended to encompass these changes and variations.