Patent Publication Number: US-2022238503-A1

Title: Display module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a bypass continuation of International Application No. PCT/KR2021/014142, filed on Oct. 13, 2021, which is based on and claims priority to Korean Patent Application No. 10-2020-0134891, filed on Oct. 19, 2020, in the Korean Intellectual Property Office, and Korean Patent Application No. 10-2021-0040332, filed on Mar. 29, 2021, in the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     1. Field 
     The disclosure relates to a display module manufactured through a fluidic self-assembly method. 
     2. Description of Related Art 
     The disclosure relates to a fluidic self-assembly method of transferring a light-emitting device in fluid to a mounting position on a substrate. The fluidic self-assembly method allows an ultra-small self-light-emitting device, such as a micro LED or a nano wire, to be transferred to a large area substrate. 
     The substrate used in the fluidic self-assembly method may be provided with multiple mounting grooves to which light-emitting devices are inserted. A pair of substrate electrode pads may be provided in the bottom of the mounting groves, and an anode electrode and a cathode electrode of the light-emitting device may be connected thereto. 
     Faulty light-emitting devices that have been transferred to the substrate may be identified during an inspection process, and may be removed from the mounting grooves and substituted with normal light-emitting devices. However, if the pair of substrate electrode pads disposed at the bottom of the mounting grooves are damaged when the faulty light-emitting devices are separated from the mounting grooves, it may be difficult to mount the replacement light-emitting devices. 
     SUMMARY 
     One or more embodiments may address at least the above-mentioned problems and/or disadvantages and may provide at least the advantages described below. Accordingly, in accordance with an aspect of the disclosure, a display module in which faulty micro-LEDs have been transferred by a fluidic self-assembly may be repaired. 
     According to embodiments of the disclosure, a display module includes: a substrate; a plurality of inorganic light-emitting diodes provided in a plurality of mounting grooves formed in the substrate, the plurality of inorganic light-emitting diodes comprising an inorganic light-emitting diode that has a first chip electrode and a second chip electrode; a first substrate electrode pad and a second substrate electrode pad provided at a bottom surface of a mounting groove from among the plurality of mounting grooves, the first substrate electrode pad being electrically coupled to the first chip electrode and the second substrate electrode pad being electrically coupled to the second chip electrode; and a third substrate electrode pad and a fourth substrate electrode pad provided around the mounting groove. 
     At least one of the third substrate electrode pad and the fourth substrate electrode pad extends along a side wall of the mounting groove. 
     The third substrate electrode pad and the fourth substrate electrode pad may be symmetrically provided with respect to a center of the mounting groove. 
     The third substrate electrode pad and the fourth substrate electrode pad may be asymmetrically provided with respect to a center of the mounting groove. 
     The substrate may include an insulting layer provided on the third substrate electrode pad and the fourth substrate electrode pad. 
     The third substrate electrode pad may be electrically coupled to the first chip electrode by a first conductor, and the fourth substrate electrode pad may be electrically coupled to the second chip electrode of the inorganic light-emitting diode by a second conductor. 
     A post may be provided on a light-emitting surface of the inorganic light-emitting diode, and the post may include a magnetic layer. 
     The magnetic layer may be formed of Germanium (Ge). 
     The post may be offset from a center of the light-emitting surface. 
     The post may be provided at a position corresponding to one of the first chip electrode and the second chip electrode. 
     The plurality of mounting grooves include another mounting groove adjacent to the mounting groove. 
     A fifth substrate electrode pad and a sixth substrate electrode pad may be provided at a bottom surface of the another mounting groove. 
     The first substrate electrode pad may be electrically coupled to the fifth substrate electrode pad, and the second substrate electrode pad may be electrically coupled to the sixth substrate electrode pad. 
     According to embodiments of the disclosure, a display module includes: a substrate; a thin-film transistor (TFT) layer provided on the substrate, a plurality of mounting grooves being provided in the TFT layer; a plurality of inorganic light-emitting diodes provided in the plurality of mounting grooves, the plurality of inorganic light-emitting diodes comprising an inorganic light-emitting diode that has a first chip electrode and a second chip electrode; a first substrate electrode pad and a second substrate electrode pad provided at a bottom surface of a mounting groove from among the plurality of mounting grooves, the first substrate electrode pad being electrically coupled to the first chip electrode and the second substrate electrode pad being electrically coupled to the second chip electrode; and a third substrate electrode pad and a fourth substrate electrode pad provided on a side wall of the mounting groove. The first substrate electrode pad and the third substrate electrode pad may are electrically coupled to a first electrode wiring provided on the TFT layer, and the second substrate electrode pad and the fourth substrate electrode pad are electrically coupled to a second electrode wiring provided on the TFT layer. 
     The display module may further include an insulating layer covering the third substrate electrode pad and the fourth substrate electrode pad. 
     Another mounting groove from among the plurality of mounting grooves may be adjacent the mounting groove, and a fifth substrate electrode pad and a sixth substrate electrode pad may be provided at a bottom surface of the another mounting groove. 
     The first substrate electrode pad may be electrically coupled to the fifth substrate electrode pad, and the second substrate electrode pad may be electrically coupled to the sixth substrate electrode pad. 
     According to embodiments of the disclosure, a display module includes: a substrate; a first substrate electrode pad and a second substrate electrode pad provided in a first groove of the substrate; an inorganic light-emitting diode provided in the first groove and electrically connected to the first substrate electrode pad and the second substrate electrode pad; a third substrate electrode pad provided on the substrate and electrically connected to the first substrate electrode pad; and a fourth substrate electrode pad provided on the substrate and electrically connected to the second substrate electrode pad. 
     The third substrate electrode pad may be provided on an upper surface of the substrate and extend along a side wall of the first groove. 
     The third substrate electrode pad may be provided on an upper surface of the substrate, and may extend along a side wall of the first groove and a side wall of a second groove adjacent the first groove. 
     The display module may further include an insulating layer provided in the first groove between the inorganic light-emitting diode and the third substrate electrode pad. 
     The display module may further include a gate electrode wiring provided in the second groove adjacent the first groove. 
     The display module may further include a common electrode wiring provided in a third groove adjacent the first groove. 
     The third substrate electrode pad and the fourth substrate electrode pad may be provided in a fourth groove adjacent the second groove. 
     The display module may further include an insulator filling the fourth groove and covering the third substrate electrode pad and the fourth substrate electrode pad. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will be more apparent by describing certain embodiments, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view illustrating a display module according to an embodiment; 
         FIG. 2  is an enlarged view illustrating a pixel area of the display module shown in  FIG. 1  according to an embodiment; 
         FIG. 3  is a cross-sectional view taken along line A-A shown in  FIG. 2  according to an embodiment; 
         FIG. 4  is a view illustrating a faulty light-emitting device being separated from a mounting groove of a substrate according to an embodiment; 
         FIG. 5  is a view illustrating an insulating layer that has been removed from a portion of a third and fourth substrate electrode pads positioned at a side wall of a mounting groove of a substrate according to an embodiment; 
         FIG. 6  is a view illustrating an example of inserting a light-emitting device for repair into a mounting groove according to an embodiment; 
         FIG. 7  is a view illustrating an auxiliary mounting groove adjacent to a mounting groove of a substrate according to an embodiment; 
         FIG. 8  is a view illustrating a pair of electrode pads formed at a mounting groove of a substrate according to an embodiment; 
         FIG. 9  is a perspective view illustrating a light-emitting device according to an embodiment; 
         FIG. 10  is a cross-sectional view illustrating the light-emitting device shown in  FIG. 9  in a mounting groove of a substrate according to an embodiment; and 
         FIG. 11  is a cross-sectional view along line B-B shown in  FIG. 10  according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the disclosure will be described herein in greater detail with reference to the accompanying drawings. The embodiments described herein may be variously modified. Specific embodiments may be illustrated in the drawings and described in detail in the description. However, the specific embodiments described in the accompanied drawings are merely to assist in the understanding of the various embodiments. Accordingly, the various embodiments are not for limiting the scope of the disclosure to a specific embodiment, and should be interpreted to include all modifications, equivalents and/or alternatives of the embodiments. 
     As used herein, the terms “1st” or “first” and “2nd” or “second” may use corresponding components regardless of importance or order and are used to distinguish a component from another without limiting the components. Further, expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. 
     It is to be understood that the terms such as “comprise” or “include” are used herein to designate a presence of a characteristic, number, step, operation, element, component, or a combination thereof, and not to preclude a presence or a possibility of adding one or more of other characteristics, numbers, steps, operations, elements, components or a combination thereof. When a certain element is indicated as being “coupled with/to” or “connected to” another element, it may be understood as the certain element being directly coupled with/to another element or as being coupled through other element. On the other hand, when a certain element is indicated as “directly coupled with/to” or “directly connected to” another element, it may be understood as the other element not being present between the certain element and another element. 
     In the disclosure, the expression “same” may not only mean fully matching, but also include a difference to a degree taking into consideration a processing error range. 
     In addition thereto, in describing the disclosure, in case it is determined that the detailed description of related known technologies may unnecessarily confuse the gist of the disclosure, the detailed description thereof will be abridged or omitted. 
     In the disclosure, a display module may be a flat panel display panel that includes micro LEDs, which are light-emitting diodes of less than or equal to 100 μm. The display module that includes the micro LEDs may provide a better contrast, response time, and energy efficiency than a liquid crystal display (LCD) panel which requires a backlight. A micro LED may be formed of inorganic material and may be brighter, have better light-emitting efficiency, and longer lifespan than an organic light emitting diode (OLED). The micro LED may be a semiconductor chip capable of emitting light on its own when power is provided, and may exhibit a fast response rate, a low power, and high brightness. Specifically, the micro LED exhibits higher efficiency in converting electricity to photons compared to LCDs or OLEDs. That is, the micro LED exhibits a higher “brightness per watt” compared to LCD or OLED displays. Accordingly, the micro LED may be configured to exhibit the same brightness with about half of the energy compared to larger LEDs (width, height, and depth exceeding 100 μm, respectively) or OLEDs. In addition to the above, the micro LEDs may realize a high resolution, superior color, contrast and brightness, represent a wide range of colors accurately, and realize a clear screen even in the outdoors. Further, the micro LEDs formed of inorganic material are resistant against a burn in phenomenon and have low heat generation, thereby providing a long lifespan. 
     The micro LED may be a vertical-type micro LED of which a pair of electrodes (an anode electrode and a cathode electrode) are respectively disposed at a light-emitting surface and an opposite surface of the light-emitting surface. The micro LED may also be a flip-type micro LED of which the pair of electrodes are disposed at an opposite surface of the light-emitting surface. 
     The micro LED may include a post having a magnetic layer to facilitate insertion of the micro LED into the mounting groove by a magnetic field applied when performing the fluidic self-assembly. The post may protrude from the light-emitting surface of the micro LED by a predetermined length. The magnetic layer included in the post may include diamagnetic materials (Diamagnetism; e.g., Ge) or materials having magnetic-field characteristics (e.g., Cr, Mn, Fe, Co, Ni, Cu). 
     A substrate may include multiple pixel areas arranged in matrix form at a front surface. Multiple sub pixels disposed at one pixel area may form one pixel. For example, one of the pixel areas may include three sub pixels. The three sub pixels may be formed of micro LEDs capable of expressing red (R), green (G) and blue (B) colors, respectively. 
     The substrate may be configured such that a TFT layer on which a thin film transistor (TFT) circuit is formed is disposed at the front surface, and a circuit configured to provide power to the TFT circuit and electrically couple with a separate control substrate may be disposed at a rear surface. 
     The substrate may be formed with multiple mounting grooves to which multiple micro LEDs are mounted. At the bottom of the respective mounting grooves, a pair of substrate electrode pads may be disposed, and at a side wall and surrounding part of the respective mounting grooves, the pair of substrate electrode pads for the repair of the faulty micro LED may be formed. 
     The substrate may further include an auxiliary mounting groove for mounting the micro LED for repair when the faulty micro LED is to be used without removing it from the mounting groove. The auxiliary mounting groove may be disposed with the pair of substrate electrode pads at the bottom. The auxiliary mounting groove may be filled with an insulating material up to a height corresponding to the front surface of the substrate. The micro LED for repair may be mounted in the auxiliary mounting groove after removing the insulating material. 
     The mounting groove and the auxiliary mounting groove of the substrate may each be formed of a shape corresponding to a shape of the micro LED (e.g., a cube, a cuboid, a circle, an oval, etc.). 
     Multiple side surface wirings may be formed in an edge area of the substrate, and be spaced apart from each other at a certain distance. The multiple side surface wirings may be configured such that one end part is electrically coupled with multiple first connection pads formed at the edge area included in the front surface of the substrate, and the other end part is electrically coupled with multiple second connection pads formed at the edge area included in the rear surface of the substrate. The multiple first connection pads may be coupled with the TFT circuit provided at the TFT layer through wiring, and the multiple second connection pads may be coupled with a driving circuit disposed at the rear surface of the substrate through wiring. 
     The display module may be configured to realize, based on forming multiple side surface wirings, a bezel-less display module by minimizing a dummy area at the front surface of the substrate and maximizing an active area, and a mounting density of micro LEDs with respect to the display module may be increased. Accordingly, the bezel-less display module may provide a large format display device by coupling multiple display modules together. In this case, the respective display modules may be formed to maintain a pitch between the respective pixels of adjacent display modules by minimizing the dummy area of the adjacent display modules to be the same as a pitch between the respective pixels in a single display module. Accordingly, a seam appearing at a coupling part between the respective display modules may be prevented. 
     The side surface wirings may be formed in plurality with a certain distance therebetween at respective edge areas corresponding to two sides of the substrate that face each other from among the edge areas corresponding to four surfaces of the substrate. However, embodiments are not limited thereto, and the side surface wirings may be formed in plurality with a certain distance therebetween at the edge areas corresponding to two sides of the substrate that are adjacent to each other. In addition, the side surface wirings may be formed in plurality with a certain distance therebetween only at a single edge area corresponding to one side from among the edge areas or may be formed in plurality with a certain distance therebetween at the edge areas corresponding to the three sides. 
     The display module may be installed and applied to a wearable device, a portable device, a handheld device, an electronic product requiring various displays or electrical fields as a single unit, and may be applied to a display device such as a monitor for a personal computer (PC), a high resolution television (TV), a signage (or, digital signage), an electronic display and the like through a plurality of assembly arrangements as a matrix-type. 
       FIG. 1  is a perspective view illustrating the display module according to an embodiment,  FIG. 2  is an enlarged view illustrating the pixel area of the display module shown in  FIG. 1 , and  FIG. 3  is a cross-sectional view taken along line A-A shown in  FIG. 2 . 
     Referring to  FIG. 1  and  FIG. 3 , the display module  1  according to an embodiment may include a substrate  10 , and multiple light-emitting devices  100  mounted to the substrate  10 . 
     The TFT layer  30 , which includes the TFT circuit, may be disposed at the front surface of the substrate  10 . A driver integrated circuit (IC) for controlling the TFT circuit may be disposed at the rear surface of the substrate  10 . 
     The front surface of the substrate  10  may include an active area which corresponds to an image area, and a dummy area which does not emit light. The active area may be divided into multiple pixel areas  31  to which multiple pixels are disposed, respectively. The dummy area may be included in the edge area of the substrate  10 . 
     The TFT circuit and the driver IC may be electrically coupled through multiple VIA wirings formed in multiple VIA holes formed through the substrate  10 , or electrically coupled through multiple side surface wirings formed along the edge area of the substrate  10 . For example, the substrate  10  may be a glass substrate or a synthetic resin substrate. In case the substrate  10  is a synthetic resin substrate, the TFT circuit and the driver IC may be electrically coupled through VIA wirings. In addition, it is difficult to form the VIA hole through a glass substrate compared to the synthetic resin substrate. Therefore, in case the substrate  10  is a glass substrate, the TFT circuit and the driver IC may be electrically coupled through side surface wirings. 
     A pixel driving method of the display module  1  according to an embodiment may be an active matrix (AM) driving method or a passive matrix (PM) driving method. The display module  1  may include a pattern of wiring which electrically connects the respective micro LEDs according to the AM driving method or the PM driving method. 
     Referring to  FIG. 2 , the respective pixel areas  31  may be disposed with micro LEDs  100 ,  120  and  140  which act as multiple sub pixels. The micro LED  100  may be configured to emit a red light, the micro LED  120  may be configured to emit a green light, and the micro LED  140  may be configured to emit a blue light which are disposed to one pixel area form one pixel. Although it has been described as three sub pixels forming one pixel, embodiments are not limited thereto, and, for example, two sub pixels emitting different colors may form one pixel, or four sub pixels emitting different colors may form one pixel. 
     The display module  1  may be configured such that multiple micro LEDs are mounted by the fluidic self-assembly method. To this end, multiple mounting grooves  41  to which multiple micro LEDs may be inserted are provided on the TFT layer  30  of the substrate  10 . 
     Referring to  FIG. 2  and  FIG. 3 , at least two or more multiple mounting grooves  41  may be formed with respect to the one pixel area. For example, the number of mounting grooves  41  provided in one pixel area may correspond to the number of micro LEDs disposed to one pixel area. As in  FIG. 2 , three mounting grooves may be provided so that three micro LEDs  100 ,  120  and  140  may be mounted to one pixel area  31 . 
     The mounting groove  41  may be formed through an insulating layer  40  formed on the TFT layer  30 . The insulating layer  40  may be formed of an organic material or an inorganic material. A protective film  43  may be provided on the insulating layer  40 . 
     The mounting groove  41  may be formed at a predetermined depth. The micro LED  100  inserted into the mounting groove  41  may be configured such that a post  115  of the micro LED  100  protrudes outside of the mounting groove  41 . For example, the post  115  may vertically extend past an upper surface of the insulating layer  40 . 
     The mounting groove  41  may be configured such that a first substrate electrode pad  51  and a second substrate electrode pad  52  are disposed at the bottom thereof. In this case, the bottom of the mounting groove  41  may be a top surface of the TFT layer  30 . 
     The first substrate electrode pad  51  may be connected with a first chip electrode  111  of the micro LED  100 . A solder ball or a solder past may be applied on the first substrate electrode pad  51  so that an electric connection and a physical connection may be formed. Accordingly, the first substrate electrode pad  51  may be configured such that the first chip electrode  111  of the micro LED  100  is electrically and physically coupled to the first chip electrode  111  through the solder ball or the solder paste. 
     The second substrate electrode pad  52  may be connected with a second chip electrode  112  of the micro LED  100 . The second substrate electrode pad  52  may be electrically and physically coupled with the second chip electrode  112  of the micro LED  100  in the same connection method as the first substrate electrode pad  51 . 
     The first substrate electrode pad  51  may be, for example, electrically coupled to a gate electrode wiring  53  provided on the TFT layer  30 . In this case, the second substrate electrode pad  52  may be electrically coupled to a common electrode wiring  54  provided on the TFT layer  30 . 
     A third substrate electrode pad  60  and a fourth substrate electrode pad  70  corresponding to respective mounting grooves  41  may be formed on the substrate  10  so that the micro LEDs for repair may be electrically coupled. The third substrate electrode pad  60  and the fourth substrate electrode pad  70  may be substrate electrode pads for repair. 
     The third substrate electrode pad  60  may be formed on the insulating layer  40 . The third substrate electrode pad  60  may be configured such that a first part  61  is electrically coupled with the gate electrode wiring  53 , a second part  62  is disposed at a surrounding part of the mounting groove  41 , and a third part  63  extends from the second part  62  to the side wall of the mounting groove  41 . 
     The second part  62  and the third part  63  of the third substrate electrode pad  60  may be used selectively according to the type or form of the micro LED for repair. For example, the second part  62  or the third part  63  of the third substrate electrode pad  60  may be used taking into consideration the position of the first chip electrode of the micro LED for repair. 
     The fourth substrate electrode pad  70  may be formed on the insulating layer  40  as with the third substrate electrode pad  60 . In this case, the fourth substrate electrode pad  70  may be disposed symmetrically with the third substrate electrode pad  60  based on a center of the mounting groove  41 . 
     The fourth substrate electrode pad  70  may be configured such that a first part  71  is electrically coupled with the common electrode wiring  54 , a second part  72  is disposed at the surrounding part of the mounting groove  41 , and a third part  73  extends from the second part  72  to the side wall of the mounting groove  41 . 
     The fourth substrate electrode pad  70  may be configured such that the second part  72  and the third part  73  are used selectively according to the type or form of the micro LED for repair as with the third substrate electrode pad  60 . For example, the second part  72  or the third part  73  of the fourth substrate electrode pad  70  may be used taking into consideration the position of the second chip electrode of the micro LED for repair. 
     The third and fourth substrate electrode pads  60  and  70  may be covered by an insulating layer  80  so as to prevent undesired electrical coupling with another electronic device or the like when not in use. 
     When using the third and fourth substrate electrode pads  60  and  70  to connect the micro LED for repair to the substrate  10 , a part of the insulating layer  80  may be removed to expose a part of the third and fourth substrate electrode pads  60  and  70 . 
     The micro LED  100  may be a flip-type micro LED in which a p-type semiconductor layer  101 , an active layer  102 , and an n-type semiconductor layer  103  are sequentially stacked, and the first and second chip electrodes  111  and  112  are disposed at an opposite surface  105  of the light-emitting surface  104 . However, the micro LED  100  is not limited to the flip-type micro LED and may be a vertical-type micro LED. 
     The micro LED  100  may include a post  115  having a magnetic layer  116  to facilitate insertion of the micro LED into the mounting groove  41  by a magnetic field applied to the substrate  10  when performing the fluidic self-assembly. 
     The post  115  may protrude by a predetermined length from the light-emitting surface  104  of the micro LED  100 . The magnetic layer included in the post  115  may include diamagnetic materials (Diamagnetism; e.g., Ge) or materials having magnetic-field characteristics (e.g., Cr, Mn, Fe, Co, Ni, Cu). 
     The post  115  may be positioned on the light-emitting surface  104 , and disposed biased to one side of the light-emitting surface  104  as in  FIG. 3 . Accordingly, as the orientation is arranged so that the first chip electrode  111  corresponds to the first substrate electrode pad  51  and the second chip electrode  112  corresponds to the second substrate electrode pad  52  by the magnetic field when performing the fluidic self-assembly, the micro LED  100  may be inserted into the mounting groove  41 . In addition, the micro LED  100  may be configured such that the light-emitting surface  104  is prevented from being inserted to the mounting groove  41  in an orientation facing the bottom of the mounting groove  41  by the post  115 . 
     The post  115  may be removed from the micro LED  100  through a separate process that is performed after the micro LED  100  is mounted to the mounting groove  41 . 
     A thermocompression process may be carried out after the multiple micro LEDs have been transferred to the substrate  10 . In this case, a metal bond state may be formed where the first and second chip electrodes  111  and  112  are respectively fused with the first and second substrate electrode pads  51  and  52  by the heat applied thereto. 
     A process of substituting (i.e., replacing) a faulty micro LED with a micro LED for repair will be described below. 
       FIG. 4  is a view illustrating a faulty light-emitting device being separated from a mounting groove of a substrate,  FIG. 5  is a view illustrating an insulating layer that has been removed from a part of an additional electrode pad positioned at a side surface of the mounting groove of the substrate, and  FIG. 6  is a view illustrating an example of having inserted the light-emitting device for repair in the mounting groove. 
     After transferring the multiple micro LEDs to the substrate  10  through the fluidic self-assembly method, it may be determined whether or not the micro LED  100  is faulty. 
     For example, an Electroluminescence (EL) test may be performed while sending electricity to the substrate  10  to check for faulty micro LEDs. In this regard, a faulty micro LED will not emit light. 
     Referring to  FIG. 4 , when removing the faulty micro LED  100  from the mounting groove  41 , the first and second substrate electrode pads  51  and  52  may be forcibly separated from the first and second chip electrodes  111  and  112  of the faulty micro LED  100 . In this regard, a surface  51   a  of the first substrate electrode pad  51  and a surface  52   a  of the second substrate electrode pad  52  to which the first and second chip electrodes  111  and  112  were previously bonded may be damaged as in  FIG. 4 . Accordingly, it may not be possible to reuse the first and second substrate electrode pads  51  and  52  of the mounting groove  41 . 
     A pre-process for mounting a micro LED  100   a  for repair of a fair quality may be carried out once the faulty micro LED  100  has been removed. 
     Referring to  FIG. 5 , the third parts  63  and  73  of the third and fourth substrate electrode pads  60  and  70  may be exposed. To this end, a part of the insulating layer  80  covering the third parts  63  and  73  of the third and fourth substrate electrode pads  60  and  70  may be removed. 
     Referring to  FIG. 6 , the micro LED  100   a  for repair may have a predetermined length, and the first and second chip electrodes  111   a  and  112   a  may be disposed at both ends. 
     Before inserting the micro LED  100   a  for repair in the mounting groove  41 , solder pastes  113   a  and  114   a  may be applied to the third parts  63  and  73  of the third and fourth substrate electrode pads  60  and  70  with the insulating layer  80  removed. 
     The micro LED  100   a  for repair may be inserted in the mounting groove  41  and may be configured such that the first and second chip electrodes  111   a  and  111   b  are electrically coupled to the third and fourth substrate electrode pads  60  and  70 , respectively, through the solder pastes  113   a  and  114   a.    
     As described above, by providing the third and fourth substrate electrode pads  60  and  70  at the side wall and surrounding part of the mounting groove  41 , the micro LED  100   a  for repair may be easily mounted to the substrate  10 . 
     According to the position of the first and second chip electrodes  111   a  and  111   b  of the micro LED for repair, the second parts  62  and  72  or the third parts  63  and  73  of the third and fourth substrate electrode pads  60  and  70  may be selectively used. For example, based on the first chip electrode  111   a  being positioned at the side part of the micro LED and the second chip electrode  111   b  being positioned at the light-emitting surface of the micro LED, a part of the insulating layer  80  covering the third part  63  of the third substrate electrode pad  60  and the second part  72  of the fourth substrate electrode pad  70  may be used. 
       FIG. 7  is a view illustrating an auxiliary mounting groove formed in the insulating layer adjacent to the mounting groove. 
     The display module  1  applied to a large format display such as a TV may be configured such that an area of the respective pixel areas is sufficiently larger than an area of multiple sub pixels. For example, the area of one pixel area may be greater by at least three folds or more than the area of the multiple sub pixels. For example, the area of a pixel that includes three sub pixels may have an area that is three times larger than an area of the three sub pixels. 
     In this case, additional mounting grooves  42  corresponding to the respective mounting grooves  41  may be further provided on the substrate  10 . The additional mounting groove  42  may be disposed spaced apart from the mounting groove  41 . The additional mounting groove  42  may be formed in the insulating layer  40 . 
     The additional mounting groove  42  may be configured such that a fifth substrate electrode pad  56  and a sixth substrate electrode pad  57  are disposed at the bottom of the additional mounting groove  42 . In this case, the fifth substrate electrode pad  56  may be electrically coupled to the gate electrode wiring  53 , and the sixth substrate electrode pad  57  may be electrically coupled to the common electrode wiring  54 . 
     The additional mounting groove  42  may be filled with an insulator  47 . The insulator  47  may be formed to have a top end that roughly corresponds to a top end of the insulating layer  80 . By filling the additional mounting groove  42  with the insulator  47 , the micro LED may be inserted into the mounting groove  41  and not inserted to the additional mounting groove  42 , when proceeding with the initial fluidic self-assembly. 
     The third and fourth substrate electrode pads  60  and  70  may have a symmetrical pattern based on the center of the mounting groove  41 . However, embodiments are not limited thereto, and the third and fourth substrate electrode pads  60  and  70  may have an asymmetrical pattern based on the center of the mounting groove  41 . 
     An example of the third and fourth substrate electrode pads being disposed asymmetrically based on the center of the mounting groove will be described below-. 
       FIG. 8  is a view illustrating another example of a pair of electrode pads formed at the mounting groove of the substrate,  FIG. 9  is a perspective view illustrating a light-emitting device that may be inserted into the mounting groove of the substrate shown in  FIG. 8 ,  FIG. 10  is a cross-sectional view illustrating an example of the light-emitting device shown in  FIG. 9  having been inserted to the mounting groove of the substrate, and  FIG. 11  is a cross-sectional view along line B-B shown in  FIG. 10 . 
     Referring to  FIG. 8 , a mounting groove  141  formed on the substrate may be formed roughly in a circular-shape. 
     The mounting groove  141  may be configured such that a first substrate electrode pad  151  and a second substrate electrode pad  152  are disposed at the bottom thereof. In this case, the bottom of the mounting groove  141  may be a top surface of the TFT layer. 
     The surrounding part of the mounting groove  141  may be disposed with a third substrate electrode pad  162  and a fourth substrate electrode pad  172 . In this case, the third and fourth substrate electrode pads  162  and  172  may be disposed to form a rough right angle. The third substrate electrode pad  162  may be electrically coupled with the gate electrode wiring of the TFT layer, and the fourth substrate electrode pad  172  may be electrically coupled with the common electrode wiring of the TFT layer. 
     Referring to  FIG. 9 , a micro LED  200  for repair which may be inserted into the mounting groove  141  may be formed roughly in a circular-shape. The micro LED  200  for repair may be configured such that a first chip electrode  211  and a second chip electrode  212  are disposed on the light-emitting surface. For example, the first chip electrode  211  may be disposed at a center of the light-emitting surface, and the second chip electrode  212  may be disposed spaced apart from the first chip electrode  211  to surround a part of an outer circumference of the first chip electrode  211 . 
     The micro LED  200  for repair may be configured so that a p-type semiconductor layer  201 , an active layer  202 , and an n-type semiconductor layer  203  are sequentially stacked. The first chip electrode  211  may be coupled to the n-type semiconductor layer  203 , and the second chip electrode may be coupled with the p-type semiconductor layer  201 . Insulator  214  may electrically isolate the first and second chip electrodes  211  and  212  from each other. 
     The micro LED  200  for repair may be configured such that a post  215  has a smaller diameter than the diameter of the first chip electrode  212 , and may be disposed on the first chip electrode  212 . The post  215  may include a magnetic layer  216  formed of diamagnetic materials (Diamagnetism; e.g., Ge) or materials having magnetic-field characteristics (e.g., Cr, Mn, Fe, Co, Ni, Cu). 
     Referring to  FIG. 10  and  FIG. 11 , when a first substrate electrode pad and a second substrate electrode pad  151   a  and  152   a  formed at the bottom of the mounting groove  141  are damaged in the process of removing the faulty micro LED mounted to the mounting groove  141 , the third and fourth substrate electrode pads  162  and  172  disposed at the surrounding part of the mounting groove  141  may be used to mount the micro LED  200  for repair in the mounting groove  141 . For example, the mounting groove  141  may be formed in an insulating layer  140  that is provided on a TFT layer  130  which is provided on substrate  110 . Protective film  143  may be provided on the insulating layer  140 . 
     The micro LED  200  for repair may be inserted in the mounting groove  141  such that the first chip electrode  211  is electrically coupled with the third substrate electrode pad  162  through a first coupling wiring  166 , and the second chip electrode  212  is electrically coupled with the fourth substrate electrode pad  172  through a second coupling wiring  176 . The first and second coupling wirings  166  and  176  may be configured to form a right angle. 
     The third and fourth substrate electrode pads  162  and  172  may be covered by an insulating layer. The insulating layer may be removed when the micro LED  200  for repair is to be placed. 
     Embodiments have been described respectively and individually, but each embodiment may not necessarily be implemented on its own, and the configuration and operations of each embodiment may be implemented in combination with at least one other embodiment. 
     While embodiments have been particularly shown and described, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.