Abstract:
A light-emitting device includes first and second lead frames spaced apart from each other, the first and second lead frames each comprising a top surface, an opposing bottom surface, and sidewalls arranged between the top surface and the bottom surface thereof, at least one of the first and second lead frames comprise three inset sidewalls that at least partially define a fixing space, the fixing space undercutting at least one of the first lead frame and second lead frame, a light-emitting diode chip arranged on the first surface of the first or second lead frame, a resin part disposed in the fixing space to support the first and second lead frames, and the first and second lead frames exposed to the outside through bottom surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/633,856, filed on Feb. 27, 2015, now issued as U.S. Pat. No. 9,203,006, which is a continuation of U.S. patent application Ser. No. 14/480,042, filed on Sep. 8, 2014, now issued as U.S. Pat. No. 9,147,821, which is a continuation of U.S. patent application Ser. No. 13/921,556, filed on Jun. 19, 2013, now issued as U.S. Pat. No. 8,829,552, which is a continuation of U.S. patent application Ser. No. 13/105,549, filed on May 11, 2011, now issued as U.S. Pat. No. 8,558,270, which is a continuation of U.S. patent application Ser. No. 12/339,665, filed on Dec. 19, 2008, now issued as U.S. Pat. No. 7,964,943, and claims priority from and the benefit of Korean Patent Application No. 10-2008-0114624, filed on Nov. 18, 2008, which are all hereby incorporated by reference for all purposes as if fully set forth herein. 
    
    
     BACKGROUND 
     The present disclosure relates to a light emitting device, and more particularly, to a light emitting device that is configured to enhance adhesive force between a lead frame and a molding unit by forming a fixing space through the lead frame and integrally forming the molding unit on the top surface of the lead frame and in the fixing space. 
     Generally, a light emitting device uses a variety of light emitting chips. For example, a light emitting diode (LED) uses an element that generates minority carriers (electrons or holes) injected using a p-n junction of a semiconductor and emits light by recombination of the carriers. The LED consumes less electricity and has several to tens times more service life than the incandescent light bulb or a fluorescent lamp. That is, the LED is excellent in terms of the power consumption and endurance. 
     Since the LEDs can efficiently emit the light using a low voltage, they have been used for home appliances, electronic display boards, display devices, and a variety of automated machines. Recently, as the devices are getting smaller and slimmer, the LEDs have been made in a surface mount device type so that they can be directly mounted on a printed circuit board. Particularly, a light emitting device that is designed such that a separate insulation substrate is not used but a lead frame is used instead of the insulation substrate and a molding unit is directly formed on the lead frame has been recently proposed. 
     However, there are limitations due to a structure of the molding unit formed only on a top surface of the lead frame in that a phenomenon where a boundary surface between the lead frame and the molding unit is widened as the molding unit is easily separated from the lead frame by external causes such as increase of ambient temperature during a reflow process occurs. 
     Accordingly, the light emitting diode and wires enclosed by the molding unit may be damaged by being exposed to air or moisture. In addition, a bending portion may be cut by the separation of the molding unit. 
     SUMMARY 
     The present disclosure provides a light emitting device that is designed to physically improve adhesive force between a lead frame and a molding unit by forming a fixing space through the lead frame and integrally forming the molding unit on a top surface of the lead frame and in the fixing space during a molding unit forming process. 
     In accordance with an exemplary embodiment, a light emitting device including: a plurality of lead frame units spaced apart from each other, each of the lead frame units being provided with at least one fixing space perforating a body thereof in a vertical direction; a light emitting diode chip mounted on one of the lead frame units; and a molding unit that is integrally formed on top surfaces of the lead frame units and in the fixing spaces to protect the light emitting diode chip. 
     The fixing spaces may include outer fixing holes that are formed at all or some of a region where the lead frame units face each other and opposite side edge regions of the lead frame units. 
     The fixing spaces may include at least one inner fixing hole formed in an inner region of the lead frame units. 
     Stepped portions may be formed on sidewalls of the fixing spaces spaces so that a lower portion area of the fixing space is greater than an upper portion area of the fixing space. 
     Inclined surfaces may be formed at the sidewalls of the fixing spaces so that a lower portion area of the fixing space is greater than an upper portion area of the fixing space. 
     The light emitting device may further include a reflector formed on top surfaces of the lead frame units and surrounding the light emitting diode chip. 
     The molding unit may include a phosphor to alter a wavelength of light emitted from the light emitting diode chip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments can be understood in more detail from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a light emitting device according to an exemplary embodiment; 
         FIG. 2  is a bottom perspective view of the light emitting device of  FIG. 1 ; 
         FIG. 3 a    is a bottom view of a lead frame depicted in  FIGS. 1 and 2 ; 
         FIG. 3 b    is a bottom view of the light emitting device of  FIGS. 1 and 2 . 
         FIG. 4  is a perspective view of a light emitting device according to another exemplary embodiment; 
         FIG. 5  is a bottom perspective view of the light emitting device of  FIG. 4 ; 
         FIG. 6 a    is a bottom view of a lead frame depicted in  FIGS. 4 and 5 ; 
         FIG. 6 b    is a bottom view of the light emitting device of  FIGS. 4 and 5 ; and 
         FIGS. 7 to 9  are cross-sectional views illustrating modified examples of the light emitting devices of the exemplary embodiments of  FIGS. 1 through 6   b.    
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of a light emitting device according to an exemplary embodiment,  FIG. 2  is a bottom perspective view of the light emitting device of  FIG. 1 ,  FIG. 3 a    is a bottom view of a lead frame depicted in  FIGS. 1 and 2 , and  FIG. 3 b    is a bottom view of the light emitting device of  FIGS. 1 and 2 . 
     As shown in  FIGS. 1 to 3   b , a light emitting device according to an exemplary embodiment includes a plurality of lead frame units  10 , a light emitting diode chip  130  mounted on one of the lead frame units  10 , and a molding unit  140  that is formed on a top surface of the lead frame units  10  to protect the light emitting diode chip  130 . 
     The lead frame units  10  are for mounting the light emitting diode chip  130  or connected to the light emitting diode chip  130  to apply external power to the light emitting diode chip  130 . In this exemplary embodiment, a separate supporting unit such as a separate insulation substrate for supporting the lead frame units  10  is not provided, but the lead frame unit  10  formed of metal functions as the substrate. For example, the lead frame units  10  include first and second lead frames  110  and  120  that are spaced apart from each other at a predetermined interval. At this point, the first and second lead frames  110  and  120  may not be formed in a plate shape but in a convex shape. 
     The first and second lead frames  110  and  120  are provided with fixing spaces formed through bodies of the first and second lead frames  110  and  120  in a vertical direction. 
     When the molding unit  140  is formed on top surfaces of the first and second lead frames  110  and  120 , molding resin for the molding unit  140  is filled in the fixing spaces  20  such that the molding resin applied on the top surfaces of the first and second lead frames  110  and  120  and the molding resin filled in the fixing spaces  20  can be monolithic. That is, the fixing spaces  20  function to allow the molding unit  140  to be securely adhered to the top surfaces of the lead frame units  10 . 
     As shown in  FIGS. 1 through 3   b,  the fixing spaces include outer fixing holes  111  and  121  that are formed at a region where the first and second lead frames  110  and  120  face each other and a region surrounding opposite side edges of the respective first and second lead frames  110  and  120 . At this point, the outer fixing holes  111  and  121  may be some or all of the above described regions. In this exemplary embodiment, the fixing holes  111  and  121  are formed to be connected to each other at the facing region where the first and second lead frames  110  and  120  face each other and the regions adjacent to the facing regions. 
     At this point, stepped portions  113  and  123  may be formed on sidewalls of the outer fixing holes  111  and  121  such that an area of a lower portion of each of the outer fixing holes  111  and  121  is greater than an upper portion of each of the outer fixing holes  111  and  121 . Therefore, the molding unit  140  formed on the top surfaces of the first and second lead frames  110  and  120  extends to the outer fixing holes  111  and  121  and is hooked on the stepped portions  113  and  123 . Therefore, the separation of the molding unit  140  from the first and second lead frames  110  and  120  can be physically prevented. A method for making the lower portion of the molding unit  140  formed in the outer fixing holes  111  and  121  have a greater area than the upper portion of the molding portion  140  is not limited to the above. That is, the method may be variously modified and the modified examples will be described later. 
     The light emitting diode chip  130  is for emitting light by receiving the external power. The light emitting diode chip  130  may be selected among chips that emit light from an infrared band to a ultraviolet band. The light emitting diode chip  130  is mounted on the first lead frame  110  and electrically connected to the second lead frame  120  by a wire  150 . The wire  150  may be formed of gold (Au) or aluminum (Al) through and connected to the second lead frame  120  through, for example, a wire connecting process. 
     The molding unit  140  is for protecting the light emitting diode chip  130  and the wire  150  by enclosing the same. A method of forming the molding unit  140  and a shape of the molding unit  140  can be variously realized. For example, the molding unit  140  may be formed through a transfer molding method where a mold having a cavity having a polygonal or hemispherical cavity and molding resin is filled in the cavity. In this exemplary embodiment, the molding unit  140  is formed through a transfer molding method using a mold having a cavity that is designed to apply the molding resin on a portion of the top surfaces of the first and second lead frames  110  and  120  and fill the molding resin in the fixing holes  111  and  121 . Therefore, the molding unit  140  is integrally formed a portion of the top surfaces of the first and second lead frames  110  and  120 , which includes a first region at which the light emitting diode chip  130  and the wire  150  are formed, a second region around the first region, and a third region defining the fixing space  20 . 
     The molding unit  140  may be formed of transparent silicon resin or epoxy resin that has a relatively high rigidity. However, the present invention is not limited to this. That is, other kinds of resin that is transparent to transmit light may be used in accordance with the use of the light emitting device. Further, a variety of phosphors (not shown) may be mixed with the molding unit  140  to realize a variety of colors by changing a wavelength of the light emitted from the light emitting diode chip  130 . 
       FIG. 4  is a perspective view of a light emitting device according to another exemplary embodiment,  FIG. 5  is a bottom perspective view of the light emitting device of  FIG. 4 ,  FIG. 6 a    is a bottom view of a lead frame depicted in  FIGS. 4 and 5 , and  FIG. 6 b    is a bottom view of the light emitting device of  FIGS. 4 and 5 . 
     The light emitting device of this exemplary embodiment is almost identical to that of the foregoing embodiment of  FIGS. 1 through 3   b  except that the fixing spaces  20  are modified. In the following description for this exemplary embodiment, parts identical to those of the foregoing exemplary embodiment will not be described. 
     Referring to  FIGS. 4 through 6   b,  according to this exemplary embodiment, the fixing space  20  further includes one or more inner fixing holes  115  and  125  formed through the bodies of the first and second lead frames  110  and  120  in the vertical direction. Sizes, shapes, and number of the inner fixing holes  115  and  125  are not specifically limited. Any things will be possible as far as the portions of the molding unit  140 , which are filled and formed in the inner fixing holes  115  and  125  are monolithic with the portion of the molding unit  140 , which is formed on the top surfaces of the first and second lead frames  110  and  120 . In this exemplary embodiment, the inner fixing holes  115  and  125  are formed in a variety of shapes such as a circular shape, an oval shape, and a rectangular shape. At this point, like the stepped portions  113  and  123  formed in the sidewalls of the outer fixing holes  111  and  121  in the foregoing exemplary embodiment, stepped portions  117  and  127  are formed on inner sidewalls of the inner fixing holes  115  and  125  such that an lower area is greater than an upper area. Accordingly, the molding unit  140  is hooked on the stepped portions  113 ,  117 ,  123 , and  127  and thus the separation of the molding unit  140  from the first and second lead frames  110  and  120  can be prevented. are formed on inner walls 
     Although the fixing spaces  20  include all of the outer fixing holes  111  and  121  and the inner fixing holes  115  and  125  as in this exemplary embodiment, it may be possible the fixing spaces  20  include only the inner fixing holes  115  and  125 . 
       FIGS. 7 to 9  are cross-sectional views illustrating modified examples of the light emitting device of the foregoing exemplary embodiments. 
     The modified examples of  FIGS. 7 to 9  are almost similar to the foregoing embodiments of  FIGS. 1 through 6   a  except that a reflector  160  is further provided, the lead frame unit  10  is modified, and the fixing spaces  20  are modified. In the following description for the modified example, parts identical to those of the foregoing embodiments will not be described. 
     In the modified example of  FIG. 7 , a reflector  160  for collecting or scattering the light emitted from the light emitting diode chip  130  is formed on an edge of the top surfaces of the lead frame units  10 . At this point, a reflecting surface is formed on an inner surface of the reflector  160  to direct the light emitted from the light emitting diode chip  130  in a desired direction. Alternatively, the reflector  160  may be formed of a transparent material to scatter the light generated from the light emitting diode chip  130  in a desired direction. 
     The reflector  160  may be formed through the previously described transfer molding method. In addition, as the reflector  160  is formed, the molding unit  140  may be formed through not only the transfer molding method but also a dotting method. 
     In the modified example of  FIG. 8 , unlike the foregoing embodiments, the lead frame units  10  include three lead frames spaced apart from each other. For example, the lead frame units  10  may further include a third lead frame  170  disposed between the first and second lead frames  110  and  120  and the light emitting diode chip  130  is mounted on the third lead frame  170 . At this point, a contacting surface between the light emitting diode chip  130  and the third lead frame  170  may be insulated. In addition, the light emitting diode chip  130  is electrically connected to the first and second lead frames  110  and  120  by respective wires  150   a  and  150   b.    
     At this point, the outer fixing holes  111  and  121  and the inner fixing holes  115  and  125  are formed through the first and second lead frames  110  and  120  and the stepped portions  113 ,  117 ,  123 , and  127  are formed on the sidewalls of the outer and inner fixing holes  111 ,  121 ,  115 , and  125 . Likewise, outer and inner fixing holes  171  and  175  are formed through the third lead frame  170  and stepped portions  137  and  177  are formed on sidewalls of the outer and inner fixing holes  171  and  175 . Accordingly, the adhesive force between the molding unit  140  and the lead frame units  10  can be improved. Further, the reflector  160  may be formed on the first and second lead frames  110  and  120 . 
     In the modified example of  FIG. 9 , a shape of the fixing spaces is varied. That is, instead of forming the stepped portions  113 ,  117 ,  123 , and  127  on the sidewalls of the outer and inner fixing holes  111 ,  121 ,  115 , and  125  so that the lower area can be greater than the upper area, the inner sidewalls of the outer and inner fixing holes  111 ,  121 ,  115 , and  125  are provided with inclined surfaces  118 ,  119 ,  128 , and  129  such that the areas of the outer and inner fixing holes  111 ,  121 ,  115 , and  125  gradually increase downward. Although the inclined surfaces are formed on all of the inner sidewalls of the fixing spaces  20 , the present invention is not limited to this configuration. That is, the inclined surfaces may be formed only on some of the inner walls. Accordingly, the separation of the molding unit  140  can be prevented by portions of the molding unit  140  that are filled and formed in the outer and inner fixing holes  111 ,  121 ,  115 , and  125 . 
     According to the exemplary embodiments, a phenomenon where a boundary surface between the lead frame and the molding unit is widened can be prevented by improving an adhering performance of the molding unit to the lead frame by forming the fixing space through the body of the lead frame in the vertical direction and integrally forming the molding unit on a top surface of the lead frame and in the fixing space of the lead frame. 
     Furthermore, as the upper area of the fixing space is less than the lower area of the fixing space, the separation of a portion of the molding unit, which is formed on the top surface of the lead frame, from the lead frame can be physically prevented by a portion of the molding unit, which is formed on the fixing space. 
     Although the light emitting device has been described with reference to the specific embodiments, it is not limited thereto. Therefore, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the present invention defined by the appended claims.