Light emitting element repair method and display panel including repaired light emitting element

Abstract

A light-emitting element repair method according to an embodiment includes the following steps: removing a defective light-emitting element from a plurality of light-emitting elements transferred on a circuit board; manufacturing a repair light-emitting element on the board; forming a bonding material layer on the repair light-emitting element; and bonding the repair light-emitting element to the location where the defective light-emitting element was removed using the bonding material layer.

Description

Technical Field

[0001] The embodiments relate to a method for repairing light-emitting elements, a display panel including a light-emitting element repaired by the method, and a display device including the same. More particularly, they relate to a method for repairing micro-LEDs. Background Technology

[0002] Light-emitting diodes (LEDs), as inorganic light sources, are used in a variety of fields such as display devices, vehicle lighting, and general lighting. LEDs have advantages such as long lifespan, low power consumption, and fast response speed, and are therefore rapidly replacing existing light sources.

[0003] In addition, existing light-emitting diodes (LEDs) are mainly used as backlights in display devices. However, LED display devices that utilize smaller LEDs, i.e., those that use micro LEDs to directly realize images, are currently being developed.

[0004] Display devices typically utilize a mixture of blue, green, and red to achieve a variety of colors. To realize diverse images, display devices include multiple pixels, each pixel equipped with blue, green, and red sub-pixels, and the color of a specific pixel is determined by the color of these sub-pixels. The image is realized through the combination of these pixels.

[0005] LEDs can emit a variety of colors of light depending on their materials. Display devices can be provided by arranging individual micro LEDs that emit blue, green, and red light on a two-dimensional plane, or by arranging micro LEDs in a stacked structure of blue, green, and red LEDs on a two-dimensional plane.

[0006] Even in the case of smaller displays, millions or more microLEDs are typically required for a single display device. Due to the small size of microLEDs and the large number required, it is virtually impossible to mass-produce microLED display devices using existing die bonding technology that individually mounts LED chips. Therefore, technologies for transferring large numbers of microLEDs onto circuit boards and other substrates are currently being developed.

[0007] In addition, some of the microLEDs in the mass transfer may exhibit poor bonding or poor light emission characteristics, and these defective microLEDs need to be repaired. Repairing microLEDs usually involves replacing the defective ones with good ones. However, due to the small size of microLEDs, they cannot be picked up and mounted individually, making microLED repair quite difficult. Utility Model Content

[0008] The technical problem that this embodiment aims to solve is to provide a new technology capable of repairing light-emitting elements for displays, especially micro LEDs.

[0009] A display panel according to one embodiment includes: a circuit board having a first pad; a plurality of light-emitting elements disposed on the circuit board and having a second pad; and a metal bonding layer bonding the first pad and the second pad, wherein the plurality of light-emitting elements includes at least one repair light-emitting element, and the metal bonding layer bonding the second pad bonding the first pad and the repair light-emitting element is different in thickness and composition from the metal bonding layer bonding the second pad bonding the first pad to another light-emitting element.

[0010] A method for repairing a light-emitting element according to one embodiment includes the following steps: removing a defective light-emitting element from a plurality of light-emitting elements transferred on a circuit board; manufacturing a repair light-emitting element on the board; forming a bonding material layer on the repair light-emitting element; and bonding the repair light-emitting element to the location where the defective light-emitting element was removed using the bonding material layer.

[0011] A display panel according to one embodiment includes: a circuit board having a first pad; a plurality of first light-emitting elements disposed on the circuit board; a first metal bonding layer bonding the first light-emitting elements to the first pad; a first lower barrier layer disposed between the first metal bonding layer and the first pad; and a lower metal layer disposed between the first lower barrier layer and the first metal bonding layer, wherein the first metal bonding layer is an alloy layer, and the lower metal layer is a metal layer with a composition different from that of the first metal bonding layer.

[0012] A display device according to one embodiment includes the display panel. Attached Figure Description

[0013] Figure 1 This is a schematic perspective view illustrating the display device according to an embodiment.

[0014] Figure 2 This is a schematic plan view illustrating a display panel according to one embodiment.

[0015] Figure 3 In order to illustrate the display panel according to one embodiment, along Figure 2 The schematic partial cross-sectional view is obtained by cutting line AA′.

[0016] Figure 4a , Figure 4b , Figure 4c and Figure 4d A schematic cross-sectional view illustrating the micro-LED repair process according to an embodiment.

[0017] Figure 5a , Figure 5b , Figure 5c , Figure 5d and Figure 5e This is a schematic cross-sectional view illustrating a method for repairing a micro LED according to an embodiment.

[0018] Figure 6a , Figure 6b , Figure 6c , Figure 6d and Figure 6e This is a schematic cross-sectional view used to illustrate a micro-LED repair process according to yet another embodiment.

[0019] Figure 7 This is a schematic cross-sectional view used to illustrate a micro-LED repair process according to yet another embodiment.

[0020] Figure 8 This is a schematic plan view illustrating a display panel according to yet another embodiment.

[0021] Figure 9a , Figure 9b , Figure 9c , Figure 9d and Figure 9e This is a schematic cross-sectional view used to illustrate a micro-LED repair process according to yet another embodiment. Detailed Implementation

[0022] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. To fully convey the concept of this invention to those skilled in the art, the following embodiments are provided as examples. Therefore, this invention is not limited to the embodiments described below, and may be embodied in other forms. Furthermore, in the drawings, the width, length, thickness, etc., of the constituent elements may be exaggerated for convenience. Also, when described as one constituent element being "above" or "on top of" another constituent element, this includes not only cases where each part is "directly" located "above" or "on top of" another part, but also cases where another constituent element is sandwiched between each constituent element and another constituent element. Throughout the specification, the same reference numerals denote the same constituent elements.

[0023] A display panel according to one embodiment includes: a circuit board having a first pad; a plurality of light-emitting elements disposed on the circuit board and having a second pad; and a metal bonding layer bonding the first pad and the second pad, wherein the plurality of light-emitting elements includes at least one repair light-emitting element, and wherein the metal bonding layer bonding the first pad and the repair light-emitting element to the second pad is different from the metal bonding layer bonding the second pad and the first pad to another light-emitting element in terms of thickness or composition.

[0024] In one embodiment, the upper surface of the repair light-emitting element may be positioned higher than the upper surface of the other light-emitting element.

[0025] The metal bonding layer may include AuSn, CuSn, or In.

[0026] In one embodiment, each of the light-emitting elements can emit light of one of the colors: blue, green, and red.

[0027] In another embodiment, each of the light-emitting elements may be configured to emit all light, including blue, green and red light.

[0028] A method for repairing a light-emitting element according to one embodiment includes the following steps: removing a defective light-emitting element from a plurality of light-emitting elements transferred on a circuit board; manufacturing a repair light-emitting element on the board; forming a bonding material layer on the repair light-emitting element; and bonding the repair light-emitting element to the location where the defective light-emitting element was removed using the bonding material layer.

[0029] By forming a bonding material layer on the repair light-emitting element, the repair light-emitting element can be easily bonded to the circuit board.

[0030] The bonding material layer may include In. Because In has a relatively low melting temperature, it is possible to bond the repair light-emitting element without affecting other light-emitting elements.

[0031] The steps of transferring multiple light-emitting elements onto a circuit board may include the following steps: forming a bonding material layer on a first pad on the circuit board; arranging the multiple light-emitting elements on the bonding material layer; and forming a metal bonding layer by heating the bonding material layer.

[0032] Furthermore, when removing the defective light-emitting element, the metal layer is also removed, and the first pad may remain. The repair light-emitting element can be bonded to the remaining first pad.

[0033] In one embodiment, a plurality of repair light-emitting elements can be fabricated together on the substrate, and bonding material layers can be formed on the plurality of repair light-emitting elements respectively. A portion of the plurality of repair light-emitting elements is transferred to a temporary substrate, and the repair light-emitting elements transferred to the temporary substrate are transferred to a carrier substrate. The repair light-emitting elements on the carrier substrate are bonded together at the location where the defective light-emitting element has been removed using the bonding material layers.

[0034] Furthermore, the repair light-emitting element transferred onto the temporary substrate can be arranged corresponding to the position where the defective light-emitting element was removed.

[0035] Furthermore, the carrier substrate may include an adhesive tape, and the light-emitting element for repair may be transferred onto the adhesive tape.

[0036] In another embodiment, a single repair light-emitting element may be provided on the substrate, which may be attached to the location on the circuit board where the faulty light-emitting element has been removed.

[0037] Furthermore, multiple faulty light-emitting elements on the circuit board can be repaired using multiple substrates with individual repair light-emitting elements arranged on them.

[0038] In addition, the defective light-emitting element repair method may further include the following step before the step of forming a bonding material layer on the first pad: forming a barrier metal layer on the first pad.

[0039] Furthermore, the barrier metal layer can also be removed when removing the metal bonding layer.

[0040] In one embodiment, the barrier metal layer may include a lower barrier metal layer and an upper barrier metal layer. Furthermore, when removing the metal bonding layer, the upper barrier metal layer is also removed, and the lower barrier metal layer may remain.

[0041] A display panel according to one embodiment includes: a circuit substrate having a first pad; a plurality of first light-emitting elements disposed on the circuit substrate; a first metal bonding layer bonding the first light-emitting elements to the first pad; a lower barrier layer disposed between the first metal bonding layer and the first pad; and a lower metal layer disposed between the lower barrier layer and the first metal bonding layer, wherein the first metal bonding layer is an alloy layer, and the lower metal layer is a metal layer with a composition different from that of the first metal bonding layer.

[0042] The lower metal layer is included so that when the second light-emitting element is used to replace the first light-emitting element for repair, the lower metal layer can be mixed with the bonding material layer to form a bonding layer, thereby improving the adhesion of the second light-emitting element.

[0043] The first metal bonding layer may include Au and In, and the lower metal layer may include Au.

[0044] Furthermore, the lower metal layer can contact the lower barrier layer.

[0045] The display panel may include an upper barrier layer disposed between the first metal bonding layer and the lower metal layer. Furthermore, the upper barrier layer may contact both the first metal bonding layer and the lower metal layer.

[0046] The first light-emitting element may include: a second pad; and a third barrier layer disposed on the second pad, wherein the first metal bonding layer may be disposed between the lower metal layer and the third barrier layer.

[0047] The display panel may further include: at least one second light-emitting element disposed on the circuit board; and a second metal bonding layer for bonding the second light-emitting element to the first pad, wherein the second metal bonding layer may include the metal elements of the lower metal layer.

[0048] Furthermore, the display panel may also include a lower barrier layer disposed between the second metal bonding layer and the first pad, and the lower barrier layer may contact the first pad and the second metal bonding layer.

[0049] The display panel may further include: an upper barrier layer disposed between the first metal bonding layer and the lower metal layer, wherein the upper barrier layer may contact the first metal bonding layer.

[0050] The second metal bonding layer may be thicker than the first metal bonding layer.

[0051] Furthermore, the upper surface of the second light-emitting element is positioned higher than the upper surface of the first light-emitting element.

[0052] In one embodiment, each of the first light-emitting element and the second light-emitting element emits light of one color: blue, green, or red.

[0053] In another embodiment, each of the light-emitting elements is configured to emit all of the following: blue light, green light, and red light.

[0054] A display device according to one embodiment includes the display panel.

[0055] The embodiments will now be described in detail with reference to the accompanying drawings.

[0056] Figure 1 This is a schematic perspective view illustrating the display device according to an embodiment.

[0057] The light-emitting element is not particularly limited, but it can be used in VR display devices such as smartwatches 1000a and VR headsets 1000b, or AR display devices such as augmented reality glasses 1000c.

[0058] A display panel for displaying images is installed inside the display device. Figure 2 This is a schematic plan view illustrating a display panel 1000 according to one embodiment. Figure 3 It is along Figure 2The schematic partial cross-sectional view is obtained by cutting line AA′.

[0059] Reference Figure 2 and Figure 3 The display panel 1000 includes a circuit board 110 and light-emitting elements 100 and 100a. Here, the light-emitting elements 100 and 100a can be smaller-sized LEDs, collectively referred to as micro LEDs. For example, the light-emitting element 100 can have a size of less than 500μm × 500μm, and further, it can have a size of less than 100μm × 100μm. However, this invention does not limit the size of the light-emitting element 100 to a specific size.

[0060] The circuit board 110 may include circuitry for passive or active matrix driving. In one embodiment, the circuit board 110 may internally include wiring and resistors. In another embodiment, the circuit board 110 may include wiring, transistors, and capacitors. The circuit board 110 may also have pads on its upper surface for allowing electrical connections to the internally disposed circuitry.

[0061] Multiple light-emitting elements 100 and 100a are neatly arranged on the circuit board 110. Light-emitting element 100 refers to a high-performance light-emitting element mounted on the circuit board 110 via mass transfer, and light-emitting element 100a refers to a repaired light-emitting element. The structure of light-emitting element 100a may be the same as that of light-emitting element 100, but is not necessarily limited to this. The spacing between light-emitting elements 100 and 100a may be wider than the width of the light-emitting elements.

[0062] In one embodiment, the light-emitting elements 100 and 100a can be sub-pixels that emit light of a specific color, and these sub-pixels can constitute a pixel. For example, blue LEDs, green LEDs, and red LEDs can be adjacent to each other to constitute a pixel. However, the present invention is not limited to this; the light-emitting elements 100 and 100a can also have a stacked structure that emits light of various colors respectively. For example, each light-emitting element 100 and 100a has a stacked structure in which blue LEDs, green LEDs, and red LEDs overlap each other; therefore, one light-emitting element can also constitute a pixel.

[0063] The light-emitting element 100 may have a pad 105, which can be bonded to a corresponding pad 115 on the circuit board 110 via a bonding layer 120. For example, the bonding layer 120 may include a bonding material such as AuSn, CuSn, or In.

[0064] Additionally, the light-emitting element 100a may have a pad 105a, which can be bonded to a corresponding pad 115a on the circuit board 110 via a bonding layer 120a. The pad 105a can be formed using the same material as the pad 105 and have the same layer structure, but is not limited thereto; it can be formed using different materials and may have different layer structures. Similarly, the pad 115a can be formed using the same material as the pad 115 and have the same layer structure, but is not limited thereto. For example, the pad 115a may be a variation of the material and structure of the pad 115. This will be explained in detail below.

[0065] In one embodiment, the upper surface of the light-emitting element 100a may be positioned higher than the upper surface of the light-emitting element 100. Specifically, the bonding layer 120a may be thicker than the bonding layer 120, or the pad 105a may be thicker than the pad 105. Furthermore, the composition of the bonding layer 120a may differ from that of the bonding layer 120. For example, the Ni content of the bonding layer 120 may be higher than that of the bonding layer 120a. Furthermore, the Au content of the bonding layer 120 may be higher than that of the bonding layer 120a. And, the In content of the bonding layer 120a may be higher than that of the bonding layer 120.

[0066] The display panel 1000 may include at least one light-emitting element 100a. In particular, the light-emitting element 100a may be distinguished from the light-emitting element 100 by means of the structure or composition of the bonding layer 120a, or the height of the upper surface of the light-emitting element 100a.

[0067] Figure 4a , Figure 4b , Figure 4c and Figure 4d A schematic cross-sectional view illustrating the micro-LED repair process according to an embodiment.

[0068] Reference Figure 4a The circuit board 110 has pads 115. Pads 115 are connected to the circuitry within the circuit board 110 and provide contact points for connecting the light-emitting elements 100 to the circuitry. On the circuit board 110, pads 115 are arranged in each area where a light-emitting element 100 will be mounted for mounting multiple light-emitting elements 100. Pads 115 can be formed using a metal layer including Au. For example, pads 115 can have a Cu / Ni / Au multilayer structure.

[0069] Additionally, a barrier layer 121 is provided on the pad 115, and a bonding material layer 123 is provided on the barrier layer 121. The barrier layer 121 prevents the bonding material layer 123 from diffusing into the pad 115, thereby preventing damage to the pad 115. The barrier layer 121 can be a metal layer mixed with the bonding material layer 123, or it can be a metal layer used to block the diffusion of the bonding material layer 123. For example, the barrier layer 121 may include at least one metal selected from Ni, Cr, Ti, Ta, Mo, and W. As an example, the barrier layer 121 may also have a Cr / Ni or Ti / Ni multilayer structure.

[0070] The bonding material layer 123 may include AuSn, CuSn, or In. Typically, the bonding material layer 123 is provided on the pad 115 for collective transfer utilizing micro-LED technology.

[0071] In addition, although not shown, a metal layer such as an Au layer mixed with the bonding material layer 123 may be sandwiched between the barrier layer 121 and the bonding material layer 123.

[0072] Additionally, the light-emitting element 100 has a pad 105. The pad 105 corresponds to the pad 115 on the circuit board 110. As shown, the pad 105 can be a raised pad protruding from the light-emitting element 100, but it does not necessarily need to have a raised shape. Multiple light-emitting elements 100 will move to the positions of their corresponding pads 115 on the circuit board 110.

[0073] Reference Figure 4b The light-emitting elements 100 are neatly arranged on the pads 105. Figure 4a After the bonding material layer 123 is applied, the bonding layer 120 is formed by heating it at the bonding temperature. The barrier layer 121 and the bonding material layer 123 may also be mixed with each other, and at least a portion of the pad 105 may be mixed with the bonding material layer 123. With the bonding layer 120, the light-emitting element 100 can be stably attached to the circuit board 110.

[0074] Reference Figure 4c , as reference Figure 4b After the light-emitting element 100 is bonded to the circuit board 110, a defect in the light-emitting element 100 may be detected. For example, the defect in the light-emitting element 100 may occur due to incorrect bonding or due to poor performance of the light-emitting element 100.

[0075] In this case, the defective light-emitting element 100 is removed from the circuit board 110. After the light-emitting element 100 is removed, the remaining bonding layer 120 is also removed, and the barrier layer 121 can also be completely removed. The bonding layer 120 and the barrier layer 121 can be removed using a laser. Accordingly, after removing the light-emitting element 100 from the circuit board 110, a pad 115 may remain. The pad 115a can be the same as the pad 115 attached before the light-emitting element 100, but it can also be a variation of the pad 115. For example, the pad 115a may also include the metallic material of the bonding material layer 123.

[0076] Additionally, a repair light-emitting element 100a is provided on the pad 115a. The repair light-emitting element 100a is used to replace the defective light-emitting element 100 and can have the performance required by the light-emitting element 100. Furthermore, the light-emitting element 100a can have the same structure as the general structure of the light-emitting element 100, but is not necessarily limited to this.

[0077] In addition, the light-emitting element 100a may have a pad 105a. The pad 105a may be the same as the pad 105 described above in terms of material and layer structure, but is not necessarily limited to this.

[0078] Additionally, a bonding material layer 123a is provided on the pad 105a. The bonding material layer 123a may include a bonding material such as AuSn, CuSn, or In. In one embodiment, the bonding material layer 123a has a melting point equal to or lower than the melting point of the bonding material layer 123 described above.

[0079] Reference Figure 4d After the bonding material layers 123a are neatly arranged on the corresponding pads 115a, the bonding layer 120a is formed by heating them at the bonding temperature. The light-emitting element 100a is bonded to the circuit board 110 via the bonding layer 120a. The bonding layer 120a can be constructed using the same components as the bonding layer 120, but it can also be constructed using other components.

[0080] In this embodiment, a bonding material layer 123a is provided on the pad 105a of the repair light-emitting element 100a to mount the repair light-emitting element 100a onto the circuit board 110. In the case of micro LEDs, due to the small size of the light-emitting element 100, it is very difficult to form the bonding material layer 123a on the pad 115a of the circuit board 110. In contrast, since the bonding material layer 123a is provided on the pad 105a of the light-emitting element 100a, it is easy to form the bonding material layer 123a. Therefore, the repair light-emitting element 100a can be easily mounted in the area where the defective light-emitting element 100a has been removed.

[0081] The following will describe in detail the micro-LED repair method according to the embodiments.

[0082] Figure 5a , Figure 5b , Figure 5c , Figure 5d and Figure 5e This is a schematic cross-sectional view illustrating a method for repairing a micro LED according to an embodiment.

[0083] First, refer to Figure 5a Repair light-emitting elements 100a can be arranged on substrate 21. Substrate 21 can be a growth substrate for growing epitaxial layers. For example, substrate 21 can be a sapphire substrate, silicon substrate, GaAs substrate, etc.

[0084] The light-emitting element 100a can be fabricated using an epitaxial layer grown on the substrate 21, and may include a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer. Furthermore, the light-emitting element 100a may have a structure of multiple LED stacks.

[0085] Each of the light-emitting elements 100a has a pad 105a, and a bonding material layer 123a is provided on the pad 105a. For example, the bonding material layer 123a can also be provided by individually distributing the bonding material layer 123a on the pad 105a, or the bonding material layer 123a can be formed on the pad 105a in one step by immersing the pad 105a in molten bonding material.

[0086] Reference Figure 5b The light-emitting element 100a for repair is transferred onto a temporary substrate 210. The temporary substrate 210 can be a strip. After the light-emitting elements 100 are collectively transferred onto the circuit board 110, defective light-emitting elements 100 are detected by inspecting the light-emitting elements 100. The repair light-emitting element 100a is transferred onto the temporary substrate 210 in a manner corresponding to the position of such defective light-emitting element 100. The repair light-emitting element 100a can be separated from the substrate 210 using selective laser ablation technology.

[0087] Reference Figure 5c The light-emitting element 100a, which has been transferred to the temporary substrate 210, is then transferred to the carrier substrate 310. The carrier substrate 310 may have an adhesive tape 315 on its surface. The adhesive tape 315 may also be formed using a material that is easily deformable.

[0088] The temporary substrate 210 can be removed from the light-emitting element 100a, so the bonding material layer 123a can be disposed on the opposite side of the carrier substrate 310.

[0089] Reference Figure 5dThe circuit board 110 and the carrier substrate 310, which remove defective light-emitting elements 100, move closer to each other, thereby arranging the light-emitting elements 100a at corresponding positions on the circuit board 110. (Refer to...) Figure 4c Note that after the defective light-emitting element 100 is removed, the bonding layer 120 can also be removed, and pad 115a may remain. The barrier layer 121 formed on pad 115 can also be completely removed.

[0090] Additionally, the adhesive tape 315 on the carrier substrate 310 can be separated from the upper surface of the light-emitting element 100 mounted on the circuit board 110. However, the present invention is not limited to this, and the adhesive tape 315 can also contact the light-emitting element 100. Subsequently, by heating the bonding material layer 123a, the light-emitting element 100a is bonded to the circuit board 110.

[0091] Reference Figure 5e A display panel with a repaired light-emitting element 100a is provided by separating the carrier substrate 310 from the light-emitting element 100a. The upper surface of the light-emitting element 100a may be substantially the same as or slightly higher than the upper surface of the light-emitting element 100.

[0092] According to this embodiment, a faulty light-emitting element 100 disposed on the circuit board 110 can be replaced with a repair light-emitting element 100a through a single repair process.

[0093] Figure 6a , Figure 6b , Figure 6c , Figure 6d and Figure 6e This is a schematic cross-sectional view used to illustrate a micro-LED repair process according to yet another embodiment.

[0094] First, refer to Figure 6a The light-emitting element 100a for repair is formed on the substrate 21a. In this embodiment, a single light-emitting element 100a is provided on the substrate 21a. Multiple substrates 21a having a single light-emitting element 100a can be provided. The substrate 21a can be a growth substrate for manufacturing the light-emitting element 100a. The substrate 21a has a width wider than the width of the light-emitting element 100a, therefore, the substrate 21a is easier to process than the light-emitting element 100a.

[0095] As described above, the light-emitting element 100a has a pad 105a on which a bonding material layer 123a is provided.

[0096] Reference Figure 6bThe light-emitting element 100a is arranged and bonded on the circuit board 110 at the location where the defective light-emitting element 100 is removed. Although the light-emitting element 100a is difficult to process due to its small size, it can be easily processed by using a substrate 21a that is larger than the light-emitting element 100a.

[0097] As described above, the defective light-emitting element 100 and bonding layer 120 on the circuit board 110 are removed, leaving a pad 115a. A bonding material layer 123a disposed on the repair light-emitting element 100a is bonded to the pad 105a to form a bonding layer 120a, and the light-emitting element 100a is bonded to the circuit board 110 through the bonding layer 120a.

[0098] Reference Figure 6c Substrate 21a is removed from light-emitting element 100a. For example, substrate 21a can be removed from light-emitting element 100a using laser ablation, chemical etching, SLO, etc.

[0099] Reference Figure 6d and Figure 6e Subsequently, at another location where the defective light-emitting element 100 has been removed, a repair light-emitting element 100a is bonded using a substrate 21a, and the substrate 21a is removed from the light-emitting element 100a. By repeatedly performing the process of bonding the light-emitting element 100a at the location where the defective light-emitting element 100 has been removed using multiple substrates 21a having the repair light-emitting element 100a, all defective light-emitting elements 100 on the circuit board 110 can be repaired.

[0100] In this embodiment, the upper surface of the repair light-emitting element 100a mounted on the circuit board 110 can be higher than the upper surface of the light-emitting element 100. This prevents the light-emitting element 100 on the circuit board 110 from being damaged by the substrate 21a. However, this invention is not necessarily limited to this; the upper surfaces of the light-emitting elements 100 and 100a can also be at the same height.

[0101] Figure 7 This is a schematic cross-sectional view used to illustrate a micro-LED repair process according to yet another embodiment.

[0102] Reference Figure 7 In the above embodiment, although it was described with a single barrier layer 121 sandwiched between the pad 115 on the circuit board 110 and the bonding material layer 123, the difference in this embodiment is that multiple barrier layers 121a and 121b are arranged.

[0103] That is, as shown in the figure, a lower barrier layer 121a, an intermediate layer 122, and an upper barrier layer 121b can be sandwiched between the pad 115 and the bonding material layer 123. Here, the lower barrier layer 121a and the upper barrier layer 121b can include Ni, Cr, Ti, Ta, Mo, or W. As an example, the upper barrier layer 121b can include Ni, which is easily mixed with the bonding material layer 123, and the lower barrier layer 121a can include Cr, Ti, Ta, Mo, or W, which blocks the bonding material layer 123. Additionally, the intermediate layer 122 can be a metal layer separating the lower barrier layer 121a and the upper barrier layer 121b, for example, it can be an Au layer. In particular, the intermediate layer 122 can be a metal layer that is easily mixed with the bonding material layer 123.

[0104] Furthermore, a metal layer, such as an Au layer, that is easily mixed with the bonding material layer 123 can be further arranged on the upper barrier layer 121b.

[0105] When bonding the light-emitting element 100, the pad 105 of the light-emitting element 100 is disposed on the bonding material layer 123 to form a bonding layer 120. Subsequently, when removing a defective light-emitting element 100, the bonding layer 120 is also removed, at which time the upper barrier layer 121b is also removed. However, unlike the above embodiment, in this embodiment, the lower barrier layer 121a may remain, thus preventing damage to the pad 115 by means of the lower barrier layer 121a.

[0106] Furthermore, according to this embodiment, when the lower barrier layer 121a and the upper barrier layer 121b are formed as different metal layers, the composition of the bonding layer formed when bonding the light-emitting element 100 and the bonding layer formed when bonding the repair light-emitting element 100a can be different from each other.

[0107] Furthermore, metal bonding is typically formed by mixing metallic materials. However, a barrier layer may not be suitable for alloy formation, and the alloy formation temperature may be too high. Additionally, since the already formed alloy layer remains stable, it is difficult to use this alloy layer for metal bonding. The following describes a display panel suitable for bonding and repairing light-emitting elements, and a bonding method for the repaired light-emitting elements.

[0108] Figure 8 This is a schematic partial cross-sectional view used to illustrate a display panel according to yet another embodiment. Here, Figure 8 Corresponding to along Figure 2 The section is obtained by the intercepting line AA′.

[0109] Here, as described above, the light-emitting elements 100 and 100a are smaller-sized LEDs collectively referred to as micro LEDs, for example, they may have a size of less than 500μm × 500μm, and further, less than 100μm × 100μm. However, the present invention does not limit the size of the light-emitting elements 100 and 100a to a specific size.

[0110] The circuit board 110 may include circuitry for passive or active matrix driving. In one embodiment, the circuit board 110 may internally include wiring and resistors. In another embodiment, the circuit board 110 may include wiring, transistors, and capacitors. The circuit board 110 may also have pads on its upper surface for allowing electrical connections to the internally disposed circuitry.

[0111] Multiple light-emitting elements 100, 100a are neatly arranged on the circuit board 110. Light-emitting element 100 refers to a high-performance light-emitting element mounted on the circuit board 110 by mass transfer, and light-emitting element 100a refers to a repair light-emitting element replacing a defective light-emitting element 100. The structure of light-emitting element 100a may be the same as that of light-emitting element 100a, but is not necessarily limited thereto. In one embodiment, the spacing between light-emitting elements 100, 100a may be wider than the width of a single light-emitting element 100.

[0112] In one embodiment, the light-emitting elements 100 and 100a can be sub-pixels that emit light of a specific color, and these sub-pixels can constitute a pixel. For example, blue LEDs, green LEDs, and red LEDs can be adjacent to each other to constitute a pixel. However, the present invention is not limited to this; the light-emitting elements 100 and 100a can also have a stacked structure that emits light of various colors respectively. For example, each light-emitting element 100 and 100a has a stacked structure so that blue LEDs, green LEDs, and red LEDs overlap each other; therefore, one light-emitting element can also constitute a pixel. In one embodiment, a green LED can be arranged between a blue LED and a red LED. In another embodiment, a blue LED can be arranged between a green LED and a red LED. In this case, the brightness of the blue LED can be relatively reduced, and the brightness of the green LED can be further increased, so the mixing ratio of red, green, and blue can be easily adjusted.

[0113] The light-emitting element 100 may have a pad 105, which can be bonded to a corresponding pad 115 on the circuit board 110 via a bonding layer 220. For example, the bonding layer 120 may include a bonding material such as Sn or In. In particular, the bonding layer 220 may be an alloy layer including Au and In.

[0114] In one embodiment, the barrier layer 107 may be disposed between the bonding layer 220 and the pad 105. In another embodiment, the material of the barrier layer 107 may be mixed with and dispersed within the bonding layer 220.

[0115] Additionally, a lower barrier layer 121a is disposed between the pad 115 and the bonding layer 220. The lower barrier layer 121a may contact the pad 115. The lower barrier layer 121a may include Ni, Cr, Ti, Ta, Mo, or W.

[0116] A lower metal layer 221a may be disposed between the lower barrier layer 121a and the bonding layer 220. The lower metal layer 221a is spaced apart from the bonding layer 220, and therefore remains in a state where it is not mixed with the bonding layer 220. The lower metal layer 221a is a metal layer mixed with a bonding material layer such as Sn or In; for example, it may be formed using Au. The lower metal layer 221a may contact the lower barrier layer 121a.

[0117] An upper barrier layer 121b may be disposed between the lower metal layer 221a and the bonding layer 220. The upper barrier layer 121b may include Ni, Cr, Ti, Ta, Mo, or W. The upper barrier layer 121b may be a metal layer of the same material as the lower barrier layer 121b, but is not limited thereto. In this embodiment, the upper barrier layer 121b may include Ni, Cr, Ti, Ta, Mo, or W suitable for blocking the bonding layer 220. The upper barrier layer 121b blocks the bonding layer 220, thus preventing the lower metal layer 221a from mixing with the bonding layer 220. The upper barrier layer 121b may be in contact with the lower metal layer 221a.

[0118] Additionally, the light-emitting element 100a may have a pad 105a, which can be bonded to the corresponding pad 115a on the circuit board 110 via the bonding layer 220a. The pad 105a may be formed using the same material as the pad 105 and have the same layer structure, but it is not limited to this; it may be formed using different materials and may have different layer structures.

[0119] In one embodiment, the upper surface of the light-emitting element 100a may be located higher than the upper surface of the light-emitting element 100. Specifically, the bonding layer 220a may be thicker than the bonding layer 220, or the pad 105a may be thicker than the pad 105. Furthermore, the composition of the bonding layer 220a may be similar to that of the bonding layer 220. In particular, the bonding layer 220a includes the metallic composition of the lower metal layer 221a. For example, the bonding layer 220a may be an alloy layer of Au and In. However, the content of each component in the bonding layer 220a may differ from the content of each component in the bonding layer 220.

[0120] Additionally, a barrier layer 107a may be disposed between the pad 105a and the bonding layer 220a. The barrier layer 107a may be a metal layer of the same material as the barrier layer 107, but is not limited thereto. Furthermore, the metal material of the barrier layer 107a may be mixed with the bonding layer 220a and dispersed within the bonding layer 220a.

[0121] In one embodiment, a lower barrier layer 121a may remain between the pad 115 and the bonding layer 220a. In particular, the lower barrier layer 121a may include Ni, Cr, Ti, Ta, Mo, or W. In another embodiment, the lower barrier layer 121a may be mixed with and dispersed within the bonding layer 220a. For example, if the lower barrier layer 121a is formed using Ni, Ni may be dispersed within the bonding layer 220a.

[0122] According to this embodiment, there is a difference in that the lower metal layer 221a remains on the underside of the light-emitting element 100, while the lower metal layer 221a does not remain on the underside of the light-emitting element 100a. Therefore, when the light-emitting element 100 is removed due to poor bonding, the lower metal layer 221a can be used for bonding the repair light-emitting element 100a.

[0123] Figure 9a , Figure 9b , Figure 9c , Figure 9d and Figure 9e This is a schematic cross-sectional view used to illustrate a micro-LED repair process according to yet another embodiment.

[0124] Reference Figure 9a The circuit board 110 has pads 115. Pads 115 are connected to circuitry within the circuit board 110 and provide contact points for connecting the light-emitting elements 100 to the circuitry. On the circuit board 110, for mounting multiple light-emitting elements 100, pads 115 are arranged in each area where the light-emitting elements 100 will be mounted. Pads 115 can be formed using a metal layer including Au. For example, pads 115 can have a Cu / Ni / Au multilayer structure.

[0125] Additionally, a lower barrier layer 121a, a lower metal layer 221a, an upper barrier layer 121b, an upper metal layer 221b, and a bonding material layer 223 are provided on the pad 115. The lower barrier layer 121a is disposed between the pad 115 and the lower metal layer 221a.

[0126] The lower metal layer 221a is separated from the upper metal layer 221b by the upper barrier layer 121a. The lower metal layer 221a can be formed using the same metal layer as the upper metal layer 221b, for example, it can be formed using an Au layer, but it is not limited to this. The upper metal layer 221b can be formed using a metal layer that is mixed with the bonding material layer 223 during the bonding process to form an alloy.

[0127] The bonding material layer 223 can be formed by forming an alloy during the bonding process. For example, the bonding material layer 223 can be formed using an In layer. Typically, the bonding material layer 223 is provided on the pad 115 for mass transfer using micro-LED technology.

[0128] The upper barrier layer 121b prevents the metallic components of the bonding material layer 223 from diffusing to the lower metal layer 221a. For example, the upper barrier layer 121b may include at least one metal selected from Ni, Cr, Ti, Ta, Mo, and W. As an example, the barrier layer 121 may also have a multilayer structure of Cr / Ni or Ti / Ni.

[0129] Additionally, the light-emitting element 100 has a pad 105. The pad 105 corresponds to the pad 115 on the circuit board 110. As shown, the pad 105 can be a raised pad protruding from the light-emitting element 100, but it does not necessarily need to have a raised shape. Multiple light-emitting elements 100 will move to the positions of the corresponding pads 115 on the circuit board 110.

[0130] A barrier layer 107 and a metal layer 109 may be provided on the pad 105. The metal layer 109 may be formed using a metallic substance that is mixed with the bonding material layer 223 to form an alloy. The barrier layer 107 protects the pad 105 during the alloying of the bonding material layer 223 and the metal layer 109. For example, the barrier layer 107 may include at least one metal selected from Ni, Cr, Ti, Ta, Mo, and W.

[0131] Reference Figure 9b The metal layer 109 of the light-emitting element 100 is neatly arranged in Figure 9a After the bonding material layer 223 is applied, the bonding layer 220 is formed by heating it at the bonding temperature. The upper metal layer 221b, the bonding material layer 223, and the metal layer 109 can be mixed and alloyed to form the bonding layer 220. Therefore, the bonding layer 220 can include the metal composition of the bonding material layer 223, the metal composition of the upper metal layer 221b, and the metal composition of the metal layer 109. In order to form a good bonding layer 220, the thickness of the bonding material layer 223 and the thicknesses of the upper metal layer 221b and the metal layer 109 can be controlled in an appropriate ratio.

[0132] According to this embodiment, a bonding layer 220 is formed between the upper barrier layer 121b and the barrier layer 107. The light-emitting element 100 can be stably attached to the circuit board 110 via the bonding layer 120. The upper barrier layer 121b prevents alloying of the lower metal layer 221a by blocking the diffusion of metallic material from the bonding layer 220 to the lower metal layer 221a. However, at least a portion of the upper barrier layer 121b can be mixed and dispersed within the bonding layer 220.

[0133] The barrier layer 107 can protect the pad 105 by preventing the metallic material of the bonding layer 220 from diffusing into the pad 105. However, at least a portion of the barrier layer 107 can be mixed and dispersed within the bonding layer 220.

[0134] Reference Figure 9c , as reference Figure 9b After the light-emitting element 100 is bonded to the circuit board 110, a defect in the light-emitting element 100 can be detected. For example, the defect in the light-emitting element 100 can occur due to incorrect bonding or due to poor performance of the light-emitting element 100.

[0135] In this case, the defective light-emitting element 100 is removed from the circuit board 110. After removing the light-emitting element 100, the remaining bonding layer 220 is also removed, and the barrier layer 121b can also be completely removed. For example, the bonding layer 220 and the barrier layer 121b can be removed using a laser. Accordingly, after removing the light-emitting element 100 from the circuit board 110, a lower metal layer 221a remains on the upper part of the pad 115.

[0136] Reference Figure 9d A repair light-emitting element 100a is provided on pad 115. The repair light-emitting element 100a is used to replace the defective light-emitting element 100 and can have the performance required by the light-emitting element 100. Furthermore, the light-emitting element 100a can have the same structure as the general structure of the light-emitting element 100, but is not limited thereto.

[0137] In addition, the light-emitting element 100a may have a pad 105a. The pad 105a may be the same as the pad 105 described above in terms of material and layer structure, but is not necessarily limited to this.

[0138] Additionally, a barrier layer 107a, a metal layer 109a, and a bonding material layer 223a are provided on the pad 105a. The barrier layer 107a is provided to protect the pad 105a, and the metal layer 109a is provided to form a bonding layer together with the bonding material layer 223a.

[0139] The bonding material layer 223a may include a bonding material such as Sn or In. In one embodiment, the bonding material layer 223a may have a melting point equal to or lower than the melting point of the bonding material layer 223 described above.

[0140] Reference Figure 9e After the bonding material layers 223a are neatly arranged on the corresponding pads 115, the bonding layer 220a is formed by heating it at a bonding temperature. The light-emitting element 100a is bonded to the circuit board 110 via the bonding layer 220a. The bonding layer 220a can be formed by mixing the metal layer 109a, the lower metal layer 221a, and the bonding material layers 223a. Furthermore, at least a portion of the metallic material of the lower barrier layer 121a or the barrier layer 107a can be mixed into the bonding layer 220a. The bonding layer 220a can be constructed using the same components as the bonding layer 220, or it can be constructed using other components.

[0141] Furthermore, since the method of bonding and repairing the light-emitting element 100a is the same as the one mentioned above... Figures 5a to 5e Or refer to Figures 6a to 6e The methods of explanation are similar, therefore, to avoid repetition, detailed explanations are omitted.

[0142] According to this embodiment, a lower metal layer 221a and an upper metal layer 221b are provided on the pad 115, and the lower metal layer 221a can be used for bonding the repair light-emitting element 100a, thereby improving the bonding force of the repair light-emitting element 100a.

[0143] The above description describes various embodiments, but the present invention is not limited to these embodiments. Furthermore, matters or elements described with respect to one embodiment may be applied to another embodiment without departing from the technical concept of the present invention.

Claims

1. A display panel, characterized in that, include: The circuit board has a first pad; Multiple first light-emitting elements are arranged on the circuit board; A first metal bonding layer bonds the first light-emitting element to the first pad; A first lower barrier layer is disposed between the first metal bonding layer and the first pad; A lower metal layer is disposed between the first lower barrier layer and the first metal bonding layer; and An upper barrier layer is disposed between the first metal bonding layer and the lower metal layer. The first metal bonding layer is an alloy layer, and the lower metal layer is a metal layer with a different composition from the first metal bonding layer. The lower metal layer is in contact with the first lower barrier layer.

2. The display panel according to claim 1, characterized in that, The first metal bonding layer comprises Au and In. The lower metal layer includes Au.

3. The display panel according to claim 1, characterized in that, The upper barrier layer contacts the first metal bonding layer and the lower metal layer.

4. The display panel according to claim 1, characterized in that, The first light-emitting element includes: The second pad; and A third barrier layer is disposed on the second pad. The first metal bonding layer is disposed between the lower metal layer and the third barrier layer.

5. The display panel according to claim 1, characterized in that, Also includes: At least one second light-emitting element is disposed on the circuit board; as well as A second metal bonding layer bonds the second light-emitting element to the first pad. The second metal bonding layer includes the metal elements of the lower metal layer.

6. The display panel according to claim 5, characterized in that, Also includes: A second lower barrier layer is disposed between the second metal bonding layer and the first pad, and the second lower barrier layer contacts the first pad and the second metal bonding layer.

7. The display panel according to claim 6, characterized in that, The upper barrier layer contacts the first metal bonding layer.

8. The display panel according to claim 5, characterized in that, The second metal bonding layer is thicker than the first metal bonding layer.

9. The display panel according to claim 5, characterized in that, The upper surface of the second light-emitting element is positioned higher than the upper surface of the first light-emitting element.

10. The display panel according to claim 5, characterized in that, Each of the first and second light-emitting elements emits light of one color: blue, green, or red.

11. The display panel according to claim 5, characterized in that, Each of the first light-emitting element and the second light-emitting element is configured to emit all kinds of light, including blue light, green light and red light.

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