Abstract:
Provided is a method of manufacturing a light emitting diode (LED) package, the method including the steps of: preparing a package substrate having an LED chip mounted thereon; preparing a mold which has a convex portion, a plane portion extending outward from the convex portion, and a projecting portion formed on the lower surface of the plane portion, the projecting portion having a sharp end; engaging the mold with the package substrate such that the projecting portion is contacted with the surface of the package substrate; and filling transparent resin into the convex portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2007-0135476 filed with the Korea Intellectual Property Office on Dec. 21, 2007, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mold for forming a molding member and a method of manufacturing a light emitting diode (LED) package using the same. 
     2. Description of the Related Art 
     LEDs are semiconductor elements which convert electric energy into light energy, and are composed of compound semiconductor which emits light with a specific wavelength depending on energy bandgap. Further, LEDs are used in various fields such as optical communication and display. 
     LEDs are provided in a package type depending on the use purpose and requested shape thereof. In general, an LED package is manufactured by the following method. First, an LED chip is mounted on a substrate having an electrode pattern formed thereon or a lead frame, and a terminal of the LED chip is electrically connected to the electrode pattern (or lead). Then, a molding member is formed on the LED chip by using epoxy, silicon, or a combination thereof, and a convex lens is attached to the molding member. Then, the LED package is completed. 
     The lens is formed to increase light emission efficiency within a constant orientation angle. Depending on the shape of the lens, the propagating path of light can be differently set. 
       FIGS. 1A to 1D  are process diagrams briefly showing a conventional method of manufacturing an LED package. First, as shown in  FIG. 1A , a package substrate  13  having an LED chip  11  mounted thereon is prepared, and a molding member  16  surrounding the LED chip  11  is formed. 
     The package substrate  13  has a lead frame  15  inserted therein, and the LED chip  11  is mounted on the lead frame  15 , exposed through a groove formed on the top surface of the package substrate  13 , through an adhesive. 
     Further, an electrode pattern (not shown) of the LED chip  11  is connected to the lead frame  15  through a wiring process, and transparent resin is injected into the groove and is then solidified to form the molding member  16 . 
     As described above, the LED chip  11  is mounted on the package substrate  13 , and the molding member  16  is formed on the LED chip  16 . Then, as shown in  FIG. 1B , an adhesive for attaching a lens is coated on the surface of the molding member  16 . 
     Continuously, as shown in  FIG. 1C , a lens  19  which is previously manufactured by casting or the like is bonded on the adhesive  17 , and the adhesive  17  is then cured by a curing process. Accordingly, as shown in  FIG. 1D , the lens  19  is fixed on the molding member  16 . 
     In the conventional method, since the lens is formed on the molding member by the process of attaching the lens, a coupling force between the lens and the package substrate is so weak that they can be easily separated from each other. Further, the lens is separately formed. Therefore, the manufacturing process becomes complicated. 
     SUMMARY OF THE INVENTION 
     An advantage of the present invention is that it provides a method of manufacturing an LED package, in which a molding member with a convex lens shape is formed on a package substrate by injecting resin into a mold such that the manufacturing process can be simplified. In the method, the contact surface between the package substrate and the mold is minimized to thereby prevent resin from leaking and bubbles from being generated. 
     Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     According to an aspect of the invention, a method of manufacturing a light emitting diode (LED) package comprises the steps of: preparing a package substrate having an LED chip mounted thereon; preparing a mold which has a convex portion, a plane portion extending outward from the convex portion, and a projecting portion formed on the lower surface of the plane portion, the projecting portion having a sharp end; engaging the mold with the package substrate such that the projecting portion is contacted with the surface of the package substrate; and filling transparent resin into the convex portion. 
     In the preparing of the package substrate, a transparent-resin inlet or air discharge port passing through the package substrate may be formed. In preparing of the mold, a transparent-resin inlet or air discharge port passing through the convex portion may be formed. 
     Alternately, a transparent-resin inlet and an air discharge port passing through the package substrate may be formed, or a transparent-resin inlet and an air discharge port passing through the convex portion may be formed. 
     According to another aspect of the invention, a method of manufacturing an LED package comprises the steps of: preparing a package substrate having an LED chip mounted thereon; forming a projecting portion which projects from the surface of the package substrate and has an outer surface inclined toward the inside; preparing a mold which has a convex portion and a plane portion extending outward from the convex portion; engaging the mold with the package substrate such that the mold is contacted with the outer surface of the projecting portion; and filling transparent resin into the convex portion. 
     In the preparing of the package substrate, a transparent-resin inlet or air discharge port passing through the package substrate may be formed. In the preparing of the mold, a transparent-resin inlet or air discharge port passing through the convex portion may be formed. 
     Alternately, a transparent-resin inlet and an air discharge port passing through the package substrate may be formed, or a transparent-resin inlet and an air discharge port passing through the convex portion may be formed. 
     According to a further aspect of the invention, a mold for forming a molding member on a package substrate having an LED chip mounted thereon comprises a convex portion; a plane portion that extends from the convex portion to form a plane surface; and a projecting portion that projects from the lower surface of the plane portion and of which the end is sharpened. 
     The convex portion may have a through-hole passing through the convex portion. In this case, the convex portion may have first and second through holes. 
     The projecting portion may have first and second surfaces, of which at least one is formed of an inclined surface. In this case, the first surface forms the outer surface of the projecting portion, and the second surface forms the inner surface of the projecting portion, the second surface extending vertically from the plane portion. Alternately, the first surface forms the outer surface of the projecting portion, and the second surface forms the inner surface of the projecting portion, the first surface extending vertically from the plane portion. 
     The first and second surfaces may be formed of inclined surfaces of which the ends meet each other. 
     According to a still further aspect of the invention, a method of manufacturing an LED package comprises the steps of: preparing a package substrate having an LED chip mounted thereon; preparing a mold which has a convex portion and a plane portion; engaging the mold with the package substrate; and filling transparent resin into the convex portion such that a hemispheric molding member is formed on the LED chip. Any one of the mold and the package substrate has a projecting portion with a sharp end. 
     The preparing of the package substrate may include the step of: forming a projecting portion which projects from the surface of the package substrate and has an outer inclined surface to be contacted with the mold. 
     The preparing of the mold may include the step of: forming a projecting portion which projects from the lower surface of the plane portion and has first and second surfaces of which the ends meet each other. 
     Any one of the first and second surfaces may be formed of an inclined surface. The first surface forms the outer surface of the projecting portion, and the second surface forms the inner surface of the projecting portion, the second surface extending vertically from the plane portion. Alternately, the first surface forms the outer surface of the projecting portion, and the second surface forms the inner surface of the projecting portion, the first surface extending vertically from the plane portion. 
     The first and second surfaces may be formed of inclined surfaces of which the ends meet each other. 
     The method may further include the step of separating the mold from the molding member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIGS. 1A to 1D  are process diagrams briefly showing a conventional method of manufacturing an LED package; 
         FIGS. 2A to 2C  are process diagrams for explaining a method of manufacturing a package according to an embodiment of the invention; 
         FIG. 3  is a diagram showing an example of an LED package substrate according to the invention; 
         FIGS. 4A and 4B  are diagrams of a mold for forming a molding member according to an embodiment of the invention; and 
         FIG. 5  is a cross-sectional view of a mold for forming a molding member according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     Hereinafter, a mold for forming a molding member of an LED package and a method of manufacturing a package using the same according to the present invention will be described in detail with reference to the accompanying drawings. 
       FIGS. 2A to 2C  are process diagrams for explaining a method of manufacturing a package according to an embodiment of the invention.  FIGS. 4A and 4B  are diagrams of a mold for forming a molding member according to an embodiment of the invention. 
     As shown in  FIG. 2A , a cup-shaped LED package substrate  120  is prepared, which has a groove  145  formed therein and at least one lead frame  110  provided on the bottom surface of the groove  145 . The inner side wall of the groove  145  may be formed with a reflecting surface which is inclined upward. 
     In  FIG. 2A , it is exemplified that the LED package substrate  120  is composed of a lower substrate  120   a  having the lead frame  110  and an upper substrate  120   b  having the groove  145 . Without being limited thereto, however, the LED package substrate may be another package substrate with a cup structure for chip mounting. 
     Subsequently, an LED chip  130  is mounted on the bottom surface of the groove  145 , and a terminal (not shown) of the LED chip  130  is electrically connected to the lead frame  110  through a wire  127 . In this case, the terminal may be connected by a flip-chip method. 
     The LED chip  130  may include a submount substrate and an LED chip mounted on the top surface of the submount substrate. Further, the LED chip  130  may be fixed to the top surface of the lead frame  110  through an adhesive such as Ag resin or eutectic solder. 
     The LED chip  130  includes at least one or more LEDs which generate blue, red, green, and ultraviolet (UV) wavelengths. For example, the LED chip  130  may be composed of only a blue LED or blue and red LEDs. 
     However, the present invention is not limited to such examples. The LED chip  130  may be composed of another single LED or other LEDs, if they generate blue, red, green, and UV wavelengths. 
     Next, transparent liquid resin mixed with phosphor materials is filled in the groove  145  of the package structure having the LED chip  130  mounted thereon, and is then cured to form a phosphor layer  140 . 
     At this time, the transparent resin may be input into the groove  145  through a dispensing process or the like and is formed of any one of epoxy, silicon, strained silicon, urethane resin, oxetane resin, acrylic resin, polycarbonate, and polyimide. 
     The phosphor layer  140 , which is formed by mixing resin with phosphor materials, includes phosphor materials which convert a wavelength into any one of yellow, red, and green. The phosphor materials can be determined depending on the light emission wavelength of the LED chip  130 . 
     That is, phosphor materials which can convert light emitted from the LED chip  130  to implement white light are used. For example, when the LED chip  130  is composed of a blue LED, yellow phosphor materials are used as the phosphor materials. 
     In the invention, however, the phosphor layer  140  is not an essential component, but may be omitted. 
     As described above, after the package substrate  120  having the LED chip  130  mounted thereon is prepared, a first through-hole  150   a  passing through the package substrate  120  and the lead frame  110  is formed. 
     The first through-hole  150   a  may be used as a transparent resin inlet or air discharge port. As shown in  FIG. 3 , two through-holes  150  may be formed. That is, the first and second through-holes  150   a  and  150   b  may be formed so as to be used as a transparent resin inlet and an air discharge port, respectively. 
     Continuously, as shown in  FIG. 2B , a mold  160  for forming a molding member is engaged with the surface of the package substrate  120  having the first through-hole  150   a  provided therein, and the transparent resin  151  is injected into a space between the package substrate  120  and the mold  160 . The transparent resin  151  may be injected by an injector such as a dispenser or the like and is formed of any one of epoxy, silicon, strained silicon, urethane resin, oxetane resin, acrylic resin, polycarbonate, and polyimide. 
     The mold  160  includes a convex portion  161 , a plane portion  163  extending outward from the convex portion  161 , and a projecting portion  165  formed on the lower surface of the plane portion  164 . The projecting portion  165  has an inclined surface. 
     The convex portion  161  defines a space between the package substrate  120  and the mold  160 . That is, the space is formed by the convex portion  161  of the mold  160 . 
     Meanwhile, a second through-hole  150   b  is formed in the convex portion  161  of the mold  160 . The second through-hole  150   b  may be used as a transparent resin inlet or air discharge port. 
     That is, as the transparent resin is injected into the convex portion  161  through the first through-hole  150   a  of the package substrate  120 , the air within the convex portion  161  is discharged to the outside through the second through-hole  150   b  provided in the convex portion  161 . 
     On the contrary, the transparent resin may be injected through the second through-hole  150   b , and the air may be discharged through the first through-hole  150   a.    
     Meanwhile, as shown in  FIG. 3 , when the first and second through-holes  150   a  and  150   b  are formed in the package substrate  120 , the transparent resin is injected through the first through-hole  150   a , and the air is discharged through the second through-hole  150   b . Therefore, the mold  160  does not need to have a through-hole formed therein. 
     Alternately, when both of the first and second through-holes  150   a  and  150   b  are formed in the convex portion  161  of the mold  160 , the package substrate  120  may not have a through-hole. 
     When the injecting of the transparent resin  151  through the first or second through-hole  150   a  or  150   b  is completed in such a manner that the transparent resin  151  is completely filled in the convex portion  161 , the package structure is moved to a high-temperature chamber to cure the transparent resin. 
     In such a process that the transparent resin is injected and cured, the transparent resin  151  filled in the convex portion  161  may leak to the outside such that bubbles are generated in the convex portion  161 . 
     To solve this problem, the package substrate  120  and the mold  160  are engaged in such a manner that they come in line contact with each other. 
     For example, as shown in  FIG. 2B , the projecting portion  165  having an inclined surface is provided on the plane portion  163  of the mold  160  contacted with the package substrate  120 . In this case, the end of the projecting portion  165  is sharpened in such a manner that the contact surface between the package substrate  120  and the mold  160  is minimized. 
     As shown in  FIGS. 4A and 4B , the projecting portion  165  is formed to project from the plane portion  163  and has first and second surfaces  165   a  and  165   b . At least one of the first and second surfaces  165   a  and  165   b  is formed of an inclined surface such that the end of the projecting portion  165  has a sharp end. 
     That is, both of the first and second surfaces  165   a  and  165   b  are formed of inclined surfaces, or one of the first and second surfaces  165   a  and  165   b  is formed of an inclined surface. In this case, since the ends of the first and second surfaces  165   a  and  165   b  meet each other, the end of the projecting portion  165  has a sharp shape. 
     As shown in an expanded portion of  FIG. 2B , when it is assumed that the first surface  165   a  is set to an outer surface and the second surface  165   b  is set to an inner surface, the first surface  165   a  may be formed of an inclined surface, and the second surface  165   b  may be formed to extend vertically from the plane portion  163 . Alternately, the second surface  165   b  may be formed of an inclined surface, and the first surface  165   a  may be formed to extend vertically from the plane portion  163 . 
     As described above, the projecting portion  165  projecting from the plane portion  163  is contacted with the package substrate  120 . In this case, since the end of the projecting portion  165  is sharpened, the projecting portion  165  comes in line contact with the package substrate  120 . 
     In such a case, when the mold  160  comes in line contact with the package substrate  120 , it is possible to enhance the airtightness of the convex portion  161  during a clamping process for engaging the mold  160  and the package substrate  120 . 
     That is, since pressure applied to the mold  160  during the clamping process is all concentrated on the end of the projecting portion  165 , it is possible to secure sufficient airtightness such that the transparent resin does not leak, even though low pressure is applied. 
     Meanwhile, high pressure may be applied to secure the airtightness within the convex portion  161 . However, when high pressure is applied, the lead frame may be deformed. 
     Therefore, proper pressure is applied to secure the airtightness within the convex portion  161  without the deformation of the lead frame  110 , thereby preventing the transparent resin from leaking. 
     Continuously, when the curing process of the transparent resin  151  is completed, a molding member  152  with a lens shape is formed by separating the mold  160  from the molding member  152 , as shown in  FIG. 2C . 
     When the molding member is formed through the above-described process, a separate lens does not need to be prepared, and a process for attaching a lens to the package substrate does not need to be performed. Therefore, the manufacturing process is simplified. 
     Further, when the molding member is formed, the projecting portion with a sharp end is formed on the surface of the package substrate contacted with the mold such that the contact surface between the package substrate and the mold is minimized. Then, since pressure is concentrated on the end of the projecting portion, it is possible to secure the airtightness of the convex portion without the deformation of the lead frame. 
     Therefore, since the transparent resin is prevented from leaking such that bubbles are not generated, it is possible to further enhance light efficiency. 
     In this embodiment, in order to the contact surface between the package substrate and the mold during the clamping process, the projecting portion with a sharp end is formed on the lower surface of the plane portion contacted with the package substrate. However, instead of the projecting portion formed on the plane portion, a projecting portion with a sharp end may be formed on the surface of the package substrate. 
     That is, a projecting portion with a sharp end is provided on the surface of the package substrate, which is to be contacted with the mold, such that part of the projecting portion is included in the convex portion. Then, the inclined surface of the projecting portion comes in line contact with the mold. 
       FIG. 5  is a cross-sectional view of a mold for forming a molding member according to another embodiment of the invention, showing a state where a projecting portion is formed on the surface of the package substrate such that the package substrate comes in line contact with the mold. 
     As shown in  FIG. 5 , the package substrate  120  according to this embodiment includes a projecting portion  175  formed on the surface thereof, the projecting portion  175  having first and second surfaces  175   a  and  175   b  of which the ends meet each other. 
     At least one of the first and second surfaces  175   a  and  175   b  is formed of an inclined surface, and the end of the projecting portion  175  has a sharp shape. 
     That is, both of the first and second surfaces  175   a  and  175   b  are formed of inclined surfaces, or only one of the first and second surfaces  175   a  and  175   b  is formed of an inclined surface. In this case, since the ends of the first and second surfaces  175   a  and  175   b  meet each other, the end of the projecting portion  175  has a sharp shape. At this time, the outer surface of the projecting portion  175 , that is, the first surface  175   a  should be formed of an inclined surface, in order for line contact with the mold  160 . In particular, the first surface  175   a  should be inclined toward the side where the LED chip is mounted. 
     When the clamping process is performed, part of the projecting portion  175  projecting from the surface of the package substrate  120  is included in the convex portion  161  of the mold  160 , and the first surface  175   a  comes in line contact with the mold  160 . 
     As described above, the mold having the dome-shaped or hemispheric convex portion is prepared and then engaged with the package substrate such that a space is formed in the convex portion. Then, transparent resin is injected into the space and is cured in such a manner that a dome-shaped or hemispheric molding member is formed on the surface of the package substrate. 
     In this embodiment, the process of attaching a lens to a molding member may be omitted. Therefore, the manufacturing process can be simplified. 
     Further, since the projecting portion with a sharp end is provided, the contact surface between the mold and the package substrate is minimized when the mold and the package substrate are engaged with each other. Then, the transparent resin is prevented from leaking, so that bubbles are not generated, which makes it possible to enhance light efficiency. 
     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.