Patent Publication Number: US-2015085527-A1

Title: Light source module, fabrication method therefor, and backlight unit including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2013-0114736, filed on Sep. 26, 2013, and Korean Patent Application No. 10-2014-0123053, filed on Sep. 16, 2014, which are hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light source module, a fabrication method therefor, and a backlight unit including the same, and more particularly, to a light source module having excellent luminous efficiency, a method of fabricating the same, and a slim backlight unit including the same. 
     2. Description of the Background 
     In general, backlight units are widely used to provide light to display devices, such as liquid crystal display (LCD) devices, or surface lighting devices. 
     Backlight units provided to LCD devices are mainly divided into a direct type and an edge type depending upon a position of light emitting devices. 
     Direct type backlight units have been mainly developed together with large screen LCDs of 20 inches or more and are characterized in that a plurality of light sources disposed under a diffusion plate directly emits light toward a front surface of an LCD panel. Such direct type backlight units are mainly used for large screen LCD devices requiring high luminance owing to higher luminous efficiency than the edge type backlight units. 
     Edge type backlight units are employed for relatively small-sized LCD devices such as monitors of laptop computers and desktop computers, and have excellent light uniformity, long lifespan, and an advantage for slimness in LCD devices. 
       FIG. 1  is a sectional view of a typical light emitting diode (LED) package and a backlight unit including the same. Referring to  FIG. 1 , an LED package  10  is mounted on a side surface of a backlight unit in the related art. In this case, on account of the height corresponding to the width of the LED package, there is a limitation in slimness of the backlight unit. 
     When the LED package has a decreased width to overcome such a limitation, current spreading deteriorates efficiency of the LED package. As such, despite a limitation in achieving slimness of the backlight units due to the LED package as described above, users demand slimmer backlight units. Therefore, there is a need for edge type backlight units including a novel LED package. 
     SUMMARY OF THE INVENTION 
     The present invention is aimed at providing a slim backlight unit of an edge type implemented by mounting a light emitting diode (LED) chip alongside a light guide plate. 
     In addition, the present invention is aimed at providing a light source module, a fabrication method therefor, and a backlight unit including the same, in which a light exit pathway is directed toward a light guide plate, by forming a wavelength conversion layer on a side surface of an LED chip facing toward the light guide plate, followed by forming a reflector on a region of the LED chip excluding the side surface thereof, thereby enhancing luminous efficiency of the LED chip when the LED chip is mounted alongside the light guide plate. 
     Further, the present invention is aimed at providing a light source module, a fabrication method therefor, and a backlight unit including the same, in which an underfill including a reflective material is formed between an LED chip and a substrate to prevent light generated from the LED chip from being emitted through other faces excluding a designated light exit face and concentrate the light on the light exit face, thereby enhancing luminous efficiency. 
     Furthermore, the present invention is aimed at providing a light source module, a fabrication method therefor, and a backlight unit including the same, in which an underfill is formed such that a reflective material is not coated onto a light exit face, thereby removing obstacles from a light exit pathway and decreasing a distance between an LED chip and a light guide plate to improve luminous efficiency. 
     In accordance with one aspect of the present invention, a light source module includes: a light emitting diode (LED) chip electrically connected to a substrate through a lower surface thereof and including a light exit face formed on one side surface thereof such that light of the LED chip is emitted therethrough; a wavelength conversion layer formed on the LED chip and enclosing at least the light exit face of the LED chip; and a reflector formed on a region of the LED chip excluding the light exit face. 
     The light source module may further include an underfill interposed between the substrate and the LED chip and including a reflective material. 
     The reflective material may include one material selected from the group consisting of TiO 2 , SiO 2 , ZrO 2 , PbCO 3 , PbO, Al 2 O 3 , ZnO, Sb 2 O 3 , and combinations thereof. 
     The underfill may include a fluorescent material. 
     The LED chip may be mounted on the substrate by flip-chip bonding or surface mount technology (SMT). 
     The LED chip may include a first semiconductor layer doped with a first conductivity-type impurity; an active layer formed under the first semiconductor layer; a second semiconductor layer doped with a second conductivity-type impurity and formed under the active layer; a first electrode electrically connected to the first semiconductor layer; a second electrode electrically connected to the second semiconductor layer; a first electrode pad electrically connected to the first electrode; and a second electrode pad electrically connected to the second electrode, wherein the LED chip may be electrically connected to the substrate through the first and second electrode pads. 
     In accordance with another aspect of the present invention, a backlight unit includes: a light guide plate; and a light source module placed on at least one side of the light guide plate and emitting light, wherein the light source module includes: a light emitting diode (LED) chip electrically connected to a substrate through a lower surface thereof and including a light exit face formed on one side surface thereof such that light of the LED chip is emitted therethrough; a wavelength conversion layer formed on the LED chip and enclosing at least the light exit face of the LED chip; and a reflector formed on a region of the LED chip excluding the light exit face. 
     The light source module may further include an underfill interposed between the substrate and the LED chip and including a reflective material. 
     The underfill may include a fluorescent material. 
     The LED chip may be mounted on the substrate by flip-chip bonding or surface mount technology (SMT). 
     In accordance with a further aspect of the present invention, a method of fabricating a light source module includes: fabricating a light emitting diode (LED) chip including a light exit face formed on one side surface thereof such that light of the LED chip is emitted therethrough; forming a wavelength conversion layer on the LED chip to enclose at least the light exit face of the LED chip; and forming a reflector on a region of the LED chip excluding the light exit face. 
     Forming the reflector may include: forming the reflector on an upper surface and a side surface of the LED chip; and exposing the wavelength conversion layer by removing the reflector from a region corresponding to the light exit face when the reflector is formed on the light exit face. 
     Exposing the wavelength conversion layer may include removing the reflector from the region corresponding to the light exit face by fly cutting. 
     The method may further include forming an underfill including a reflective material between the substrate and the LED chip after forming the reflector. 
     Forming the underfill may include forming a dam placed on the substrate to adjoin the light exit face of the LED chip; injecting the underfill into a region between the substrate and the LED chip; and removing the dam after forming the underfill. 
     The method may further include electrically connecting the LED chip to a substrate, wherein the LED chip may be mounted on the substrate by flip-chip bonding or surface mount technology (SMT). 
     Fabricating the LED chip may include: forming a first semiconductor layer doped with a first conductivity-type impurity; forming an active layer under the first semiconductor layer; forming a second semiconductor layer doped with a second conductivity-type impurity under the active layer; forming a first electrode electrically connected to the first semiconductor layer; forming a second electrode electrically connected to the second semiconductor layer; forming a first pad electrically connected to the first electrode; and forming a second pad electrically connected to the second electrode. 
     According to embodiments of the invention, an LED chip is mounted alongside a light guide plate, thereby providing a slim backlight unit of an edge type. 
     In addition, according to the embodiments of the invention, a light exit pathway is directed toward a light guide plate by forming a wavelength conversion layer on a side surface of an LED chip facing toward the light guide plate, followed by forming a reflector on a region of the LED chip excluding the side surface thereof, thereby enhancing luminous efficiency of the LED chip when the LED chip is mounted alongside the light guide plate. 
     Further, according to the embodiments of the invention, an underfill including a reflective material is formed between the LED chip and the substrate to prevent light generated from the LED chip from being emitted through other faces thereof excluding a designated light exit face and concentrating the light on the light exit face, thereby enhancing luminous efficiency. 
     Furthermore, according to the embodiments of the invention, the underfill is formed such that a reflective material is not coated onto the light exit face, thereby removing obstacles from a light exit pathway and decreasing a distance between an LED chip and a light guide plate to improve luminous efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present invention will become apparent from the detailed description of the following embodiments in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a sectional view of a light emitting diode package and a backlight unit including the same in the related art; 
         FIGS. 2 to 5  are sectional views of light source modules according to embodiments of the present invention; 
         FIG. 6(   a ) is a plan view of a LED chip shown in  FIGS. 2 to 5 ; 
         FIG. 6(   b ) is a sectional view of the LED chip taken along line I-I′ shown in  FIG. 6(   a ); 
         FIG. 7  is an exploded perspective view of a display device including a backlight unit according to one embodiment of the present invention; 
         FIG. 8  is a sectional view of the display device taken along line II-II′ shown in  FIG. 7 ; and 
         FIGS. 9 to 11  show a fabrication process for a light source module according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of examples so as to fully convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the embodiments disclosed herein and may also be implemented in different forms. In addition, shapes of elements may be exaggerated in the drawings. Throughout the specification, like reference numerals denote like elements having the same or similar functions. Modifications of elements falling within the spirit and scope of the present invention do not include restrictive meanings, are provided for clearly representing the spirit of the present invention, and can be restricted only by the appended claims. 
     Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings such that those skilled in the art to which the present invention pertains can readily carry out the present invention. 
       FIGS. 2 to 5  are sectional views of light source modules according to exemplary embodiments of the invention. Referring to  FIGS. 2 to 5 , a light source module  100  according to one exemplary embodiment of the invention includes a light emitting diode (LED) chip  110 , a wavelength conversion layer  120 , and a reflector  130 . 
     The LED chip  110  includes a growth substrate  111  and a semiconductor stack  113 . The LED chip  110  may be electrically connected to a substrate  140  by direct flip-chip bonding or surface mount technology (SMT). Electrode pads  37   a,    37   b  exposed on a lower surface of the LED chip  110  are electrically connected to substrate pads  141   a,    141   b  through bumps  150   a,    150   b,  respectively. Since the light source module  100  does not use wires, a molding component is not required to protect the wires, and portions of the wavelength conversion layer  120  need not be removed in order to expose bonding pads. Accordingly, the flip-chip type LED chip  110  exhibits less color deviation and luminance unevenness than LED chips using bonding wires. This also makes it possible to simplify a module fabrication process. 
     The wavelength conversion layer  120  covers the LED chip  110 . The LED chip  110  includes a side surface through which light is emitted, that is, a light exit face EA. The wavelength conversion layer  120  may enclose at least the light exit face EA and may also enclose an upper surface and side surfaces of the LED chip  110 . That is, the wavelength conversion layer may be formed only on the light exit face EA, or on the light exit face EA, the upper surface, and some of the side surfaces of the LED chip  110 . Alternatively, the wavelength conversion layer may also be formed on the upper surface and all of the side surfaces of the LED chip  110  including the light exit face EA. In addition, the wavelength conversion layer  120  may be formed of a fluorescent material capable of converting a wavelength of light emitted from the LED chip  110 . The wavelength conversion layer  120  may be coated to a predetermined thickness onto the LED chip  110 , to cover the upper and side surfaces of the LED chip  110 . When the wavelength conversion layer  120  covers the upper and side surfaces of the LED chip, a thickness of a region covering the upper surface may be the same as, or different from, that of a region covering the side surfaces. In addition, a region covering the light exit face EA may have a different thickness than that of a region covering the upper and side surfaces excluding the light exit face EA. 
     The reflector  130  is formed on a region of the LED chip  110  excluding the light exit face EA. At this time, the reflector  130  may be formed directly on the LED chip  110 , or on another element interposed therebetween. That is, the reflector  130  may be formed directly on the LED chip  110  as shown in  FIG. 2 , or on the wavelength conversion layer  120  formed on the LED chip  110 , as shown in  FIGS. 3 and 4 , according to various embodiments. 
     The reflector  130  serves to reflect light toward the light exit face EA. That is, the reflector formed on the region of the LED chip  110  excluding the light exit face EA serves to guide light toward the light exit face EA, so as to emit the light therethrough. 
     The substrate  140  includes the substrate pads  141   a,    141   b  electrically connected to the LED chip  110 . The bumps  150   a,    150   b  are placed on the substrate pads  141   a,    141   b,  respectively. Although not particularly limited, the substrate  140  may be, for example, a metal printed circuit board (PCB), which is advantageous for heat dissipation. The substrate  140  may be a bar-type substrate having major and minor axes. 
     An underfill  200  is interposed between the LED chip  110  and the substrate  140 . The underfill  200  serves to reflect light generated from the LED chip  110 , thereby enhancing luminous efficiency. In addition, the underfill  200  serves to prevent moisture infiltration between the LED chip  110  and the substrate  140 . The underfill  200  includes a reflective material. For example, the underfill  200  may include a resin and a reflective material within the resin. The reflective material may include a material selected from TiO 2 , SiO 2 , ZrO 2 , PbCO 3 , PbO, Al 2 O 3 , ZnO, Sb 2 O 3 , and combinations thereof. The underfill  200  is formed up to a region aligned with one surface of the LED chip  110  defined as the light exit face EA. Although not particularly limited, the underfill  200  may be formed by dispensing. The underfill  200  may further include a fluorescent material (not shown). The underfill  200  may have predetermined adhesive strength. 
     As such, the light source module  100  can concentrate light on a side surface thereof (light exit face EA) using the reflector  130  and the underfill  200 , while minimizing light loss, thereby maximizing luminous efficiency. 
     In addition, the LED chip  110  is electrically connected to the substrate  140  by direct flip-chip bonding or SMT, whereby the light source module  100  can achieve high efficiency and compactness, as compared with the typical light source module of a package type using wires. Further, the light source module  100  can be made slimmer than a typical package type light source module mounted on a side surface of a light guide plate. 
     The structure of the LED chip  110  will be described in more detail with reference to  FIGS. 6(   a ) and  6 ( b ).  FIG. 6(   a ) is a plan view of the LED chip shown in  FIG. 5 , and  FIG. 6(   b ) is a sectional view of the LED chip taken along line I-I′ shown in  FIG. 6(   a ). Referring to  FIGS. 6(   a ) and  6 ( b ), a light emitting diode (LED) chip according to the invention may include a growth substrate  111  and a semiconductor stack  113 . 
     The semiconductor stack  113  includes a first semiconductor layer  23  formed on the growth substrate  111  and doped with a first conductivity-type impurity, and mesas M separated from each other on the first semiconductor layer  23 . Each of the mesas M includes an active layer  25  and a second semiconductor layer  27  doped with a second conductivity-type impurity. The active layer  25  is interposed between the first and second semiconductor layers  23 ,  27 . Reflective electrodes  30  are placed on the mesas M, respectively. 
     The mesas M may have an elongated shape and extend parallel to each other in one direction as shown in the drawings. Such a shape makes it simple to form the same shape of mesas M on chip regions of the growth substrate  111 . 
     Although the reflective electrodes  30  may be formed on the respective mesas M after the mesas M are formed, the present invention is not limited thereto. Alternatively, the reflective electrodes  30  may be formed in advance on the second semiconductor layer  27 , before the mesas M are formed and after growth of the second semiconductor layer  27 . The reflective electrodes  30  cover substantially all upper surfaces of the mesas M and have substantially the same shape as that of a plane of the mesas M. 
     The reflective electrodes  30  include a reflective layer  28  and may further include a barrier layer  29 . The barrier layer  29  may cover an upper surface and side surfaces of the reflective layer  28 . For example, the barrier layer  29  may be formed to cover the upper surface and the side surfaces of the reflective layer  28  by forming a pattern of the reflective layer  28 , followed by forming the barrier layer  29  on the pattern. By way of example, the reflective layer  28  may be formed by depositing Ag, Ag alloys, Ni/Ag, NiZn/Ag, or TiO/Ag, followed by patterning. The barrier layer  29  may be formed of Ni, Cr, Ti, Pt, Rd, Ru, W, Mo, TiW, or a composite layer thereof, and prevents diffusion or contamination of metallic materials in the reflective layer. 
     After the mesas M are formed, an edge of the first semiconductor layer  23  may also be subjected to etching. As a result, an upper surface of the substrate  21  may be exposed. A side surface of the first semiconductor layer  23  may also be formed. 
     The LED chip according to the invention further includes a lower insulation layer  31  to cover the mesas M and the first semiconductor layer  23 . The lower insulation layer  31  has openings in specific regions thereof to allow electrical connection to the first and second semiconductor layers  23 ,  27 . For example, the lower insulation layer  31  may have openings that expose the first semiconductor layer  23  and openings that expose the reflective electrodes  30 . 
     The openings may be placed between the mesas M and near an edge of the substrate  21 , and may have an elongated shape extending along the mesas M. In addition, the openings may be restrictively placed on the mesas M to be biased to the same ends of the mesas. 
     The LED chip according to the invention further includes a current spreading layer  33  formed on the lower insulation layer  31 . The current spreading layer  33  covers the mesas M and the first semiconductor layer  23 . The current spreading layer  33  has openings placed above the respective mesas M, such that the reflective electrodes are exposed therethrough. The current spreading layer  33  may form ohmic contact with the first semiconductor layer  23  through the openings of the lower insulation layer  31 . The current spreading layer  33  is electrically insulated from the mesas M and the reflective electrodes  30 , by the lower insulation layer  31 . 
     The openings of the current spreading layer  33  have a larger area than those of the lower insulation layer  31 , so as to prevent the current spreading layer  33  from contacting the reflective electrodes  30 . 
     The current spreading layer  33  is formed over a substantially overall upper area of the substrate  31  except for the openings thereof. Accordingly, current can be easily dispersed through the current spreading layer  33 . The current spreading layer  33  may include a highly reflective metal layer, such as an Al layer, and the highly reflective metal layer may be formed on a bonding layer, such as a Ti, Cr, Ni layer or the like. In addition, a protective layer having a monolayer or composite layer structure of Ni, Cr, or Au may be formed on the highly reflective metal layer. The current spreading layer  33  may have a multilayer structure of, for example, Ti/Al/Ti/Ni/Au. 
     The LED chip further includes an upper insulation layer  35  formed on the current spreading layer  33 . The upper insulation layer  35  has openings that expose the current spreading layer  33  and openings that expose the reflective electrodes  30 . The upper insulation layer  35  may be formed using an oxide insulation layer, a nitride insulation layer, a mixed layer or an alternating stack of these insulation layers, or polymer such as polyimide, Teflon, Parylene, or the like. 
     First and second electrode pads  37   a,    37   b  are formed on the upper insulation layer  35 . The first electrode pad  37   a  is connected to the current spreading layer  33  through the openings of the upper insulation layer  35 , and the second electrode pad  37   b  is connected to the reflective electrodes  30  through the openings of the upper insulation layer  35 . The first and second electrode pads  37   a,    37   b  may be used as pads for connection of bumps for mounting the LED chip on a circuit board, or pads for SMT. 
     The first and second electrode pads  37   a,    37   b  may be formed simultaneously by the same process, for example, by photolithography and etching, or by lift-off technology. The first and second electrode pads  37   a,    37   b  may include a bonding layer formed of, for example, Ti, Cr, Ni, or the like, and a highly conductive metal layer formed of Ag, Au, and the like. The first and second electrode pads  37   a,    37   b  may be formed such that ends thereof are placed on the same plane, and the LED chip may be accordingly bonded to a conductive pattern, formed at the same height on the substrate, by flip-chip bonding. 
     The LED chip is completely fabricated by dividing the growth substrate  111  into individual LED chip units. The growth substrate  111  may also be removed from the LED chip before or after being divided into the individual LED chip units. 
     As such, the LED chip, according to the present invention, which is directly bonded to the substrate by flip-chip bonding, has advantages of achieving high efficiency and compactness, as compared with the typical light emitting device of a package type. 
       FIG. 7  is an exploded perspective view of a display device including a backlight unit according to one embodiment of the present invention, and  FIG. 8  is a sectional view of the display device taken along line II-II′ shown in  FIG. 7 . 
     Referring to  FIGS. 7 and 8 , the display device includes a display panel DP for displaying images, a backlight unit BLU disposed at the rear side of the display panel DP and emitting light, a frame  240  supporting the display panel DP and receiving the backlight unit BLU, and a top cover  280  surrounding the display panel DP. 
     The display panel DP includes a color filter substrate FS and a thin film transistor (TFT) substrate SS assembled to each other to face each other while maintaining a uniform cell gap. The display panel DP may further include a liquid crystal layer between the color filter substrate FS and the thin film transistor substrate SS, depending upon a type thereof. 
     Although not shown in detail, the thin film transistor substrate SS includes gate lines and data lines, which cross each other to define pixels therebetween, and a thin film transistor placed in each crossing region therebetween and connected to a pixel electrode mounted in each of the pixels, in one-to-one correspondence. The color filter substrate FS includes R, G and B color filters corresponding to the respective pixels, a black matrix disposed along the periphery of the substrate and shielding the gate lines, data lines and thin film transistors, and a common electrode covering all of these components. Here, the common electrode may be formed on the thin film transistor substrate SS. 
     The backlight unit BLU supplies light to the display panel DP, and includes a lower cover  270  partially open at an upper side thereof, a light source module  100  disposed on one side within the lower cover  270 , and a light guide plate  250  disposed parallel to the light source module  100  to convert point light into surface light. In the related art, the light source module  100  is usually disposed on an inner side surface of the lower cover  270 . In this case, due to the width of the light source module  100 , there is a limitation in reducing the height of the backlight unit or the display panel including the backlight unit. According to the present invention, the light source module  100  is placed on the bottom surface within the lower cover  270 , thereby making the backlight unit or the display panel including the backlight unit slimmer than in the related art. The light source module  100 , placed on the bottom surface within the lower cover  270 , can be illustrated as being disposed parallel to the light guide plate  250 , according to descriptions thereof. 
     In addition, the backlight unit BLU according to the invention further includes optical sheets  230  placed on the light guide plate  250  to diffuse and collect light, and a reflective sheet  260  placed below the light guide plate  250  to reflect light, which travels towards the lower portion of the light guide plate  250 , toward the display panel DP. 
     Herein, detailed descriptions of the light source module  100  will not omitted. Refer to  FIG. 5  for details thereof. 
     The light source module  100  is fabricated by directly mounting LED chips on a substrate by flip-chip bonding or SMT, followed by forming underfills including reflective fillers between the substrate and the LED chips. Accordingly, the light source module  100  is advantageous for slimness of the backlight unit and capable of maximizing luminous efficiency by concentrating light on a side thereof using the reflector and the underfills while minimizing light loss. 
       FIGS. 9 to 11  show a fabrication process for a light source module according to an exemplary embodiment of the present invention. Referring to  FIGS. 9 to 11 , the fabrication process for the light source module includes fabricating an LED chip. In this operation, an LED chip  110  is first fabricated. 
     The LED chip  110  may be fabricated by forming a semiconductor stack  113  on a growth substrate  111 . The LED  110  may be formed on a lower portion thereof with electrode pads  37   a,    37   b.  Features of the light source module are the same as those of the light source module shown in  FIGS. 2 to 5 . Accordingly, like features are denoted by like reference numerals and will be briefly described in relation to the fabrication process without providing detailed descriptions thereof. 
     The fabrication of the LED chip includes forming a first semiconductor layer doped with a first conductivity-type impurity, forming an active layer under the first semiconductor layer, and forming a second semiconductor layer doped with a second conductivity-type impurity under the active layer. Thereafter, a first electrode is formed to be electrically connected to the first semiconductor layer, a second electrode is formed to be electrically connected to the second semiconductor, and first and second pads are formed to be electrically connected to the first and second electrodes, respectively. 
     Next, in an operation of forming a wavelength conversion layer, a wavelength conversion layer  120  is formed to enclose at least a light exit face of the LED chip. Then, in an operation of forming a reflector  130 , the reflector  130  is formed on a region of the LED chip excluding the light exit face. 
     The reflector  130  may be formed directly on the LED chip, or on another element such as the wavelength conversion layer  120  formed on the LED chip according to various embodiments. When the reflector is formed on the light exit face, the wavelength conversion layer is exposed by removing the reflector from a region corresponding to the light exit face. 
     The exposed wavelength conversion layer  120  corresponds to the light exit face EA of the LED chip  110 . Although not particularly limited, fly cutting may be used to remove the reflector  130 . 
     The fabrication process for the light source module according to the embodiment of the invention further includes electrically connecting the LED chip to a substrate. In this operation, the electrode pads  37   a,    37   b  of the LED chip  110  are connected to substrate pads  141   a,    141   b  of a substrate  140 , respectively. At this time, the LED chip  110  may be directly electrically connected to the substrate  140  by flip-chip bonding or surface mount technology (SMT). Here, bumps  150   a,    150   b  are interposed between the substrate pads  141   a,    141   b  and the electrode pads  37   a,    37   b,  respectively. 
     According to the embodiment of the invention, the operations of forming the wavelength conversion layer and the reflector and the operation of electrically connecting the LED chip to the substrate may be performed in a different order. That is, the LED chip may be electrically connected to the substrate before or after the wavelength conversion layer and the reflector are formed on the LED chip. 
     The fabrication process for the light source module further includes forming an underfill  200  between the substrate  140  and the LED chip  110 . Specifically, a dam  170  is formed on a surface corresponding to the light exit face EA of the LED chip  110 . The dam  170  contacts the light exit face EA of the LED chip  110 . The dam  170  is placed to adjoin the substrate  140 . The dam  170  may be formed on the substrate  140  by a frame structure including photoresist or adhesives. The underfill is injected into a region between the substrate and the LED chip after the dam  170  is formed. In this case, the dam  170  serves to restrict a region in which the underfill  200  will be formed. Particularly, the dam  170  prevents the underfill  200  from extending to the light exit face EA. The dam  170  may be removed by etching or other physical methods after the underfill  200  is formed. 
     The underfill  200  serves to reflect light generated from the LED chip  110 , thereby enhancing luminous efficiency, and to prevent infiltration of moisture. The underfill  200  includes a reflective material. For example, the underfill  200  may include a resin and a reflective material within the resin, and the reflective material may include one material selected from the group consisting of TiO 2 , SiO 2 , ZrO 2 , PbCO 3 , PbO, Al 2 O 3 , ZnO, Sb 2 O 3 , and combinations thereof. The dam  170  allows the underfill  200  to be formed up to a region aligned with the light exit face EA. Although not particularly limited, the underfill  200  may be formed by dispensing. The underfill  200  may further include a fluorescent material (not shown). The underfill  200  may have predetermined adhesive strength. 
     As described above, the light source module according to the embodiment of the invention can concentrate light on a side thereof using the reflector  130  and the underfill  200  while minimizing light loss, thereby maximizing luminous efficiency. 
     In addition, the light source module according to the invention, in which the LED chip  110  is electrically connected to the substrate  140  by direct flip-chip bonding or SMT, can achieve high efficiency and compactness, as compared with the typical light source module of a package type using wires. 
     While various embodiments of the present invention have been described, the present invention is not limited to a particular embodiment. In addition, the elements illustrated in the specific embodiment may be used for other embodiments in the same or similar way, without departing from the spirit and the scope of the present invention.