Binding substrate, display device and preparation method

Abstract

The invention discloses a binding substrate, a display device and a preparation method. The binding base plate comprises a base plate substrate; the substrate comprises a substrate substrate, a plurality of binding pads, the binding pads are located on one side of the substrate substrate and arranged in an array mode, each binding pad is provided with a first opening, the side, provided with the binding pads, of the substrate substrate is provided with a circuit structure, and the circuit structure is electrically connected with the binding pads.

Description

Technical Field

[0001] The present application relates to the field of display technology, and specifically, to a binding substrate, a display device and a method for manufacturing the same. Background Art

[0002] Micro LED (micro light emitting diode) has the characteristics of not requiring a backlight and being able to self-luminate. Compared with LCD (liquid crystal display) and OLED (organic light emitting diode) products, it has the advantages of simple structure, long service life, high brightness, low power consumption, ultra-high resolution, etc., and therefore has good application prospects.

[0003] Micro LEDs need to be bonded to the Bonding Pad on the driver backplane through bonding technology to light up. Common bonding technologies include direct bonding, surface activated bonding, eutectic bonding, and laser-assisted bonding. Among them, eutectic bonding has the characteristics of low bonding (or annealing) temperature, low bonding pressure, simple process, high process compatibility (no need for ultra-high vacuum and extremely low surface roughness), and will be more suitable for completing 3D interconnection.

[0004] However, current display devices and methods for making the same still need to be improved. Summary of the invention

[0005] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0006] In one aspect of the present application, the present application provides a binding substrate. The binding substrate comprises: a base substrate; a plurality of binding pads, the plurality of binding pads are located on one side of the base substrate and arranged in an array, the binding pads have a first opening, and the base substrate has a circuit structure on one side where the binding pads are arranged, and the circuit structure is electrically connected to the binding pads.

[0007] Further, the bonding pad includes at least one first bonding metal layer, and the first opening is located on the first bonding metal layer.

[0008] Furthermore, the binding substrate satisfies at least one of the following conditions: the thickness of the first bonding metal layer is 2 μm to 6 μm; the depth of the first opening is 1-5 μm; the material forming the first bonding metal layer includes at least one of Cu, Au, Al, Ag and Ni.

[0009] Furthermore, the binding substrate further includes a eutectic alloy precursor layer, the eutectic alloy precursor layer at least covers a partial area of ​​the first opening, and the melting point of the material forming the eutectic alloy precursor layer is lower than the melting point of the material forming the first bonding metal layer.

[0010] Furthermore, the material forming the eutectic alloy precursor layer includes at least one of Sn and In.

[0011] Furthermore, the binding substrate satisfies at least one of the following conditions: in a direction perpendicular to the plane of the substrate, the thickness of the eutectic alloy precursor layer within the first opening is not greater than the depth of the first opening; the thickness of the eutectic alloy precursor layer is 1-2 μm; and the eutectic alloy precursor layer has a second opening on the side away from the first opening.

[0012] In another aspect of the present application, the present application proposes a display device. The display device includes: the aforementioned binding substrate; a plurality of micro LED chips, wherein the micro LED chips include micro LEDs and bonding terminals, the bonding terminals are electrically connected to the micro LEDs, the other end of the bonding terminals is connected to the binding pads of the binding substrate, the binding pads and the bonding terminals are connected via a eutectic alloy layer, and the orthographic projection of the bonding terminals on the binding substrate and the orthographic projection of the first opening of the binding substrate on the binding substrate have an overlapping area.

[0013] Furthermore, an end surface of the bonding terminal facing the binding substrate is located in the first opening.

[0014] Further, at least a portion of the eutectic alloy layer is formed by eutectic bonding of a eutectic alloy precursor layer, the bonding terminal and the binding pad.

[0015] Further, the material forming the eutectic alloy layer includes at least one of Cu-Sn, Cu-In, Au-Sn, Au-In, Al-Sn, Al-In, Ag-Sn, Ag-In, Ni-Sn and Ni-In.

[0016] Furthermore, the display device has the first opening and the second opening, the depth of the first opening is h1, the depth of the second opening is h2, the bottom width of the first opening or the second opening is A, the opening width of the first opening or the second opening is B, and B>A; the thickness of the bonding terminal is greater than h1 and greater than h2; the width of the end of the bonding terminal on the side where the bonding terminal and the binding pad are connected is a, and the cross-sectional width of the bonding terminal at the height of h1 or h2 in the direction from the binding pad to the micro LED is b, and B>b, A>a.

[0017] Further, the display device satisfies at least one of the following conditions: h is 1 μm to 5 μm; A is 1 μm to 2 μm; B is 2 μm to 5 μm; a is 1 μm to 2 μm; and b is 2 μm to 5 μm.

[0018] In another aspect of the present application, the present application proposes a method for preparing a display device. The method includes: providing a binding substrate and a micro LED chip, wherein the binding substrate or the LED chip has a eutectic alloy precursor layer, and the binding substrate and the micro LED chip are as described above; aligning the micro LED toward the binding substrate so that the bonding terminals on the LED chip and the bonding pads on the binding substrate correspond one to one; and performing eutectic bonding on the micro LED chip and the binding substrate to form a eutectic alloy layer between the bonding terminals and the bonding pads.

[0019] Furthermore, the eutectic bonding process is performed at a temperature of 100° C. to 300° C., a pressure of 1 MPa to 10 MPa, and a time of 10 min to 2 h.

[0020] Furthermore, the eutectic alloy precursor layer is formed on the surface of the bonding terminal or the binding pad by chemical plating.

[0021] In general, the binding substrate, display device and preparation method proposed in the present application, by providing a binding pad containing a first opening (groove structure) on the binding substrate, the bonding terminal of the micro LED is provided in the first opening, and eutectic bonding is performed after alignment. The above technical solution has at least one of the following advantages: increasing the bonding area of ​​the micro LED and the binding substrate, significantly reducing the bonding resistance, and increasing the bonding strength; reducing the risk of relative sliding between the micro LED and the binding substrate during the eutectic bonding process, and improving the bonding accuracy; avoiding the problem of the middle layer metal being squeezed out of the bonding area and overflowing during the eutectic bonding process, and reducing the risk of short circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a conventional eutectic bonding structure in the prior art is shown;

[0023] Figure 2 A partial structural schematic diagram of a display device according to an embodiment of the present invention is shown;

[0024] Figure 3 A partial structural schematic diagram of a display device according to another embodiment of the present invention is shown;

[0025] Figures 4 to 16 A partial structural schematic diagram of a display device according to another embodiment of the present invention is shown;

[0026] Fig.17 A schematic diagram of a conventional eutectic bonding structure in the prior art is shown;

[0027] Fig.18 A flow chart of a method for manufacturing a display device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0028] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the art or the product specification are used.

[0029] In one aspect of the present invention, the present invention provides a binding substrate. Figure 5 , the binding substrate includes a base substrate 100, and a plurality of binding pads. The plurality of binding pads are located on one side of the base substrate and arranged in an array, and the binding pad has a first opening 10. The base substrate has a circuit structure on one side where the binding pad is arranged, and the circuit structure is electrically connected to the binding pad. When the binding substrate is used for a micro-LED light-emitting array, it has at least one of the following advantages: it increases the bonding area between the micro-LED and the binding substrate, significantly reduces the bonding resistance, and increases the bonding strength; it reduces the risk of relative sliding between the micro-LED and the binding substrate during eutectic bonding, and improves the bonding accuracy; it avoids the problem of the intermediate layer metal being squeezed out of the bonding area and overflowing during the eutectic bonding process, and reduces the risk of short circuit.

[0030] In the present application, the specific type of the binding substrate is not particularly limited, for example, it can be a substrate with a certain circuit structure that can bind other electronic components (such as a micro LD chip), and specifically, it can be a driving backplane with a driving circuit.

[0031] For ease of understanding, the following first briefly explains why the binding substrate can achieve the above beneficial effects:

[0032] As mentioned above, the current binding substrate mostly uses eutectic bonding when bonding micro-LED chips. Eutectic bonding is divided into solid-solid bonding and solid-liquid bonding. The solid-solid bonding method is to form a bond through diffusion between metals under high pressure at a temperature lower than the melting point of the bonding metal. Since this method has high requirements for surface roughness and surface structure, slow diffusion, and long bonding time, it is less used. Solid-liquid bonding is also called isothermal solidification or instantaneous liquid phase bonding (Solid-Liquid-Inter-Diffusion Bonding, SLID). SLID is a bonding technology based on the formation of intermetallic compounds. Its bonding mechanism is to deposit a high melting point metal (MH) and a low melting point solder (ML) in the chip bonding area. By heating the chip to be bonded to above the melting point of the solder, the molten solder and the high melting point metal undergo solid-liquid interdiffusion, reacting to form an intermetallic compound, and finally ML is transformed into a high melting point thermodynamically stable intermetallic compound. The melting point of the intermetallic compound solder joint generated by this method is greater than the melting point of the solder, and can withstand the subsequent stacking process when the bonded solder joint does not melt and maintains good structural stability. Therefore, SLID can achieve the goal of low-temperature bonding and high-temperature service. However, in the related art, reference Figure 1 Since there is liquid phase bonding in the solid-liquid bonding process and the substrate needs to be pressurized during the bonding process, it is easy to cause the liquid phase material to overflow and be squeezed out of the bonding area. In particular, when the binding substrate is used to bind micro LED chips for display devices, since the micro LED chips are mostly arranged in an array and the distance between adjacent micro LED chips is short, the spacing between multiple binding pads is also short, and the molten metal contacts the pads or terminals of adjacent LED chips, causing a short circuit. In the binding substrate proposed in the present application, by providing a first opening on the surface of the binding pad, the depth of the opening can be used to accommodate the liquid phase material during the solid-liquid bonding process to prevent the conductive material from overflowing due to extrusion. At the same time, since there are multiple binding pads arranged in an array on the substrate, the first opening can also play a role in limiting the structure of the binding terminal of the micro LED, thereby preventing the substrate or substrate from shifting due to the bonding pressurization process.

[0033] According to some examples of the present application, the specific structure of the binding pad is not particularly limited, and those skilled in the art can select it according to actual conditions. For example, the binding pad may be a single-layer structure or a multi-layer structure. In some examples, the binding pad may have a first bonding metal layer 210, and the first opening 10 is located on the first bonding metal layer 210. In some examples, the binding pad includes at least one first bonding metal layer 210. When the binding pad has multiple first bonding metal layers 210, the first opening 10 is located on the first bonding metal layer 210 at the top (away from the side of the substrate substrate) of the binding pad. The first bonding metal layer 210 is used to achieve electrical connection with components such as micro LED chips through solid-liquid bonding. For example, the thickness of the first bonding metal layer 210 can be 2-6μm. For example, it can be 2μm, 3μm, 4μm, 5μm, 6μm or any value therebetween. The first bonding metal layer 210 with a thickness in the above range has a better bonding effect. Since the first bonding metal layer 210 is used to connect with micro LED chips, etc. through eutectic bonding, at least a portion of the metal in the first bonding metal layer 210 will react during the eutectic bonding process. Therefore, a first bonding metal layer with an appropriate thickness can avoid the first bonding metal layer from reacting completely during the bonding process due to the thickness being too thin. When the thickness is too thick, the overall thickness of the binding substrate will be increased, but the bonding effect of the binding pad will not be further improved. When the binding pad is formed by a single layer of the first bonding metal layer 210, the thickness of the first bonding metal layer is the thickness of the binding pad; when the binding pad is composed of a multi-layer structure, the thickness of the binding pad is greater than the thickness of the first bonding metal layer. At this time, the specific thickness of the binding pad is not particularly limited, and those skilled in the art can select it according to actual conditions. For example, the thickness of the binding pad can be several microns greater than the thickness of the first bonding metal layer 210, such as 1-5μm greater.

[0034] It should be noted here that, since the first bonding metal layer has a first opening, the first bonding metal layer 210 may have different thicknesses at different positions. The first opening 10 may be located in the center of the first bonding metal layer. The depth of the first opening 10 is not particularly limited, and may be, for example, 1-5 μm. The first opening of the above depth may be formed by a relatively simple method (such as etching), and the depth is moderate, which can play a sufficient role in limiting the liquid metal, and will not cause alignment difficulties due to excessive depth, or damage the bonding terminals of the micro-LED due to excessive stress. The material for forming the first bonding metal layer is not particularly limited, and those skilled in the art may select it according to their needs, for example, it may include at least one of Cu, Au, Al, Ag and Ni. The first bonding metal layer may select a metal with a higher melting point, and the first bonding metal layer 210 is used to form a eutectic bond with the eutectic alloy precursor layer. For example, the material of the first bonding metal layer can be selected from Cu (melting point 1083° C.), Au (melting point 1064° C.), Al (melting point 660° C.), Ag (melting point 961° C.), Ni (melting point 1453° C.), and the like.

[0035] According to the examples of the present application, the shape of the first opening 10 and the shape of the bonding pad are not particularly limited. At least a portion of the cross-sectional shape of the first opening 10 is a straight line or an inwardly concave arc. In some examples, the shape of the first opening can be consistent with the shape of the bonding pad, especially the shape of the first bonding metal layer. For example, referring to Figures 6 to 9 The first opening and / or the first bonding metal layer may have a square, circle, triangle, pentagon or other shapes. For example, the orthographic projection of the first opening 10 on the base substrate 100 may be a triangle, rectangle, rhombus, polygon with more than four sides, circle or ellipse. Thus, the bonding area is further increased, the bonding strength is increased, the bonding accuracy is improved, and the problem of the intermediate layer metal (liquid during bonding) being squeezed out of the bonding area and overflowing is avoided.

[0036] Further, refer to Fig.10 , the binding substrate may further include a eutectic alloy precursor layer 400. The eutectic alloy precursor layer 400 may be formed of a material having a melting point lower than the melting point of the material forming the first bonding metal layer, for example, it may be at least one of In and Sn. During the bonding process with the micro LED chip, the eutectic alloy precursor layer may act as a "solder", undergo solid-liquid diffusion, and form an intermetallic compound. The eutectic alloy precursor layer 400 may cover at least a portion of the first opening. For example, the eutectic alloy precursor layer 400 may only cover the bottom surface of the first opening, or part / all of the side walls of the opening. In other examples, in order to reduce the difficulty of preparation, refer to Fig.10, the eutectic alloy precursor layer 400 can cover the entire area of ​​the first opening 20 and the surface of the first bonding metal layer away from the substrate 100. Since the first opening has a certain depth, during bonding, the portion of the surface of the first bonding metal layer away from the substrate 100 where the first opening is not provided will not be subjected to pressure even during bonding, so the eutectic alloy precursor layer 400 at this position will not migrate to the adjacent bonding pad due to extrusion.

[0037] The eutectic alloy precursor layer may be at least partially located in the first opening, and the thickness of the eutectic alloy precursor layer located in the first opening in a direction perpendicular to the plane where the substrate is located is not greater than the depth of the first opening. That is, in the recess where the first opening is located, the eutectic alloy precursor layer does not protrude from the first opening in a direction perpendicular to the substrate. Thus, it is possible to avoid overfilling the first opening due to the excessive thickness of the eutectic alloy precursor layer or unreasonable position setting, thereby reducing the ability of the first opening to define the bonding terminal of the micro-LED.

[0038] Specifically, the thickness of the eutectic alloy precursor layer may be 1-2 μm. For example, it may be 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or any value therebetween. In some examples, the eutectic alloy precursor layer may have a second opening on a side away from the first opening.

[0039] In another aspect of the present application, the present application provides a display device. Fig.13 The display device includes the aforementioned binding substrate and a plurality of micro LED chips 600. The micro LED chip 600 includes a micro LED and a bonding terminal 700, one end of the bonding terminal 700 is electrically connected to the micro LED, and the other end is connected to the binding pad 210 of the binding substrate, and the binding pad 210 and the bonding terminal 700 are connected through a eutectic alloy layer 410. There is an overlapping area between the orthographic projection of the bonding terminal on the binding substrate and the orthographic projection of the first opening of the binding substrate on the binding substrate. The display device has at least one of the advantages of high production yield and reliable connection between the micro LED chip 600 and the binding substrate.

[0040] In some examples, the end surface of the bonding terminal facing the binding substrate is located in the first opening. Therefore, the bonding terminal can be limited by the first opening to prevent the binding substrate or the micro LED chip from shifting during the binding process.

[0041] According to some examples of the present invention, at least a portion of the eutectic alloy layer is formed by eutectic bonding of a eutectic alloy precursor layer, a bonding terminal, and a binding pad. The eutectic alloy precursor layer may be the eutectic alloy precursor layer in the aforementioned binding substrate. The specific structure and materials of the eutectic alloy precursor layer and the binding pad have been described in detail above and will not be repeated here.

[0042] Similar to the binding pad, the specific structure and composition of the bonding terminal are not particularly limited, and those skilled in the art can choose according to actual conditions. For example, the side of the bonding terminal used to form the eutectic alloy layer may further have a second bonding metal layer. The second bonding metal layer is formed of a material having a higher melting point than the eutectic alloy precursor layer, and can undergo eutectic bonding with the eutectic alloy precursor layer material. The material of the second bonding metal layer can be selected from at least one of Cu, Au, Al, Ag and Ni, and the material of the second bonding metal layer and the material of the first bonding metal layer can be the same or different.

[0043] According to an embodiment of the present invention, the material forming the eutectic alloy layer may include one eutectic alloy precursor layer or two layers. Specifically, before eutectic bonding is performed, refer to Fig.11 , multiple micro LED chips are fixed on the LED chip substrate 500, and both the side of the LED chip substrate 500 and the side of the binding substrate may have a eutectic alloy precursor layer. Alternatively, a eutectic alloy precursor layer 400 is provided on one side of the LED chip substrate 500 or the side of the binding substrate, and the eutectic alloy layer is formed by a eutectic alloy precursor layer, a first bonding metal layer and a second bonding metal layer. The material forming the eutectic alloy layer is not particularly limited, and for example, may include at least one of Cu-Sn, Cu-In, Au-Sn, Au-In, Al-Sn, Al-In, Ag-Sn, Ag-In, Ni-Sn and Ni-In.

[0044] According to some embodiments of the present invention, the bonding terminal may be at least partially located in the first opening. Thus, the depression of the first opening can limit the liquid phase material, prevent it from being squeezed out of the bonding area and overflowing, reduce the risk of short circuit, and prevent the substrate from moving relative to each other during bonding, resulting in inaccurate alignment. At the same time, the bonding area between the bonding terminal and the bonding pad of the bonding substrate is increased, and the bonding resistance is reduced.

[0045] In some examples, the binding pad has a first opening, and the eutectic alloy precursor layer has a second opening. The depth of the first opening is h1, and the depth of the second opening is h2, and h1 and h2 may be equal or unequal. When the thickness of the eutectic alloy precursor layer is thin, the thickness of the eutectic alloy precursor layer may be ignored, and h1 may be considered equal to h2.

[0046] In some examples, reference Fig.12 In order to obtain a better eutectic bonding effect, each structural component can meet at least one of the following conditions:

[0047] The bottom width of the first opening or the second opening (the opening in contact with the eutectic alloy precursor layer) is A, and the opening width of the first opening or the second opening is B, where B>A. In other words, the opening may have an inclined sidewall. This helps reduce the difficulty of alignment. Fig.12 In the figure, the thickness of the eutectic alloy precursor layer can be ignored, and h1 can be regarded as equal to h2 (h in the figure). The overall height of the bonding terminal is greater than h when the self-bonding pad points to the direction of the micro-LED. The cross-sectional width of the bonding terminal at the height h is b. The width of the end of the bonding terminal and the bonding pad on the side where they meet is a, and the structures of the components satisfy B>b, A>a.

[0048] In some examples, the sizes of the above components are not particularly limited. For example, h can be 1 μm to 5 μm, A can be 1 μm to 2 μm, B can be 2 μm to 5 μm, a can be 1 μm to 2 μm, and b can be 2 μm to 5 μm. When the sizes of the above components meet the above ranges, sufficient alignment margins can be reserved to meet the alignment accuracy requirements.

[0049] According to an embodiment of the present invention, h is 1 μm to 5 μm. For example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value therebetween. According to an embodiment of the present invention, A is 1 μm to 2 μm. For example, it can be 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or any value therebetween. According to an embodiment of the present invention, B is 2 μm to 5 μm. For example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value therebetween. According to an embodiment of the present invention, a is 1 μm to 2 μm. For example, it can be 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or any value therebetween. According to an embodiment of the present invention, b is 2 μm to 5 μm. For example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or any value therebetween. As a result, the alignment accuracy between the micro LED and the binding substrate is improved, and the risk of relative sliding between the micro LED and the binding substrate during the eutectic bonding process is reduced.

[0050] In another aspect of the present invention, the present invention provides a method for preparing a display device. The display device prepared by the preparation method may be the display device described above, and thus, may have all the features and advantages of the display device described above, which will not be described in detail here. The preparation method of the display device is described in detail according to a specific embodiment of the present invention:

[0051] refer to Fig.18 , the method comprising:

[0052] S100: Provides binding substrate and micro LED chips.

[0053] According to an embodiment of the present invention, referring to Figure 11-17 The binding substrate includes a base substrate 100 and a binding pad disposed on the binding substrate 100. The following description is made by taking an example that the binding pad has a first bonding metal layer 210 and the first opening 10 is formed on the first bonding metal layer 210.

[0054] The micro LED chip includes an LED chip substrate 500 , and micro LEDs 600 and bonding terminals 700 disposed in an array on the substrate 500 .

[0055] The binding substrate and micro LED chip provided in this step may be the binding substrate and micro LED chip described above, and thus have the same features and advantages as described above, which will not be repeated here.

[0056] According to an embodiment of the present invention, referring to Figures 2 to 9 , the binding substrate can be formed by the following steps:

[0057] The bonding pad can be formed based on the first bonding metal layer. A first bonding metal precursor layer 200 can be provided on the substrate 100, and the first bonding metal precursor layer 200 can be formed by a sputtering or electroplating process. Then, a photoresist is provided on the first bonding metal precursor layer 200 and patterned to form a photoresist pattern layer 300. The first bonding metal precursor layer 200 is etched based on the photoresist pattern layer 300 to form a first bonding metal layer 210, and after removing the photoresist pattern layer 300, a bonding metal layer 210 can be obtained.

[0058] According to an embodiment of the present invention, the patterning process includes: exposing the photoresist precursor layer through a half-tone mask, and obtaining the photoresist pattern layer 300 after development; or, obtaining the photoresist pattern layer 300 through an imprint process. According to an embodiment of the present invention, at least a part of the cross-sectional shape of the photoresist pattern layer 300 is a straight line or an inwardly concave arc. According to an embodiment of the present invention, the shape of the orthographic projection of the photoresist pattern layer 300 on the substrate substrate 100 will affect the shape of the first bonding metal layer 210 obtained subsequently, so similarly, the shape of the orthographic projection of the photoresist pattern layer 300 on the substrate substrate 100 can also be a triangle, a rectangle, a rhombus, a polygon with more than four sides, a circle or an ellipse. Thus, after the first bonding metal precursor layer 200 is etched based on the photoresist pattern layer 300, the desired first bonding metal layer 210 can be obtained.

[0059] S200: setting a eutectic alloy precursor layer.

[0060] According to an embodiment of the present invention, a eutectic alloy precursor layer is provided in this step. The eutectic alloy precursor layer may be provided on one side of the first bonding metal layer and / or the second bonding metal layer. The melting point of the material of the eutectic alloy precursor layer 400 is respectively less than the melting point of the first bonding metal layer 210 and the melting point of the second bonding metal layer.

[0061] The eutectic alloy precursor layer 400 may be formed by methods including but not limited to sputtering deposition, chemical plating, etc., and the thickness of the eutectic alloy precursor layer 400 is 1 μm to 2 μm. For example, it may be 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or any value therebetween. In some examples, the eutectic alloy precursor layer 400 may be formed by chemical plating. Thus, it is possible to avoid the formed eutectic alloy precursor layer 400 from overfilling the first opening, resulting in insufficient depth of the first opening.

[0062] For example, refer to Figure 11-Figure 14 A eutectic alloy precursor layer 400 may be formed on the first opening 10 , the eutectic alloy precursor layer 400 extends outside the first opening 10 , and the eutectic alloy precursor layer 400 defines a second opening for accommodating at least a portion of the bonding terminal 700 in a subsequent bonding operation.

[0063] Alternatively, refer to Figure 15-16 , the eutectic alloy precursor layer 400 may be disposed on a side of the bonding terminal 700 away from the LED chip substrate 500 .

[0064] S300: Perform alignment processing.

[0065] According to an embodiment of the present invention, during the alignment process, reference is made to Figures 11 to 13 , Fig.15 At least a portion of the bonding terminal 700 is disposed in the first opening 10, and a eutectic alloy precursor layer 400 is disposed between the first bonding metal layer 210 and the bonding terminal 700. Thus, by disposing the first opening 10, the bonding terminal 700 is disposed in the first opening 10, and when eutectic bonding is performed after alignment, the bonding area, bonding strength, and bonding accuracy can be increased, and the bonding material can be prevented from being squeezed out of the bonding area and overflowing.

[0066] It should be noted that the parameters of the first opening 10 or the second opening 20 (such as depth, bottom width, opening width, cross-sectional shape, orthographic projection shape, etc.), specification parameters of the bonding terminal 700, alignment accuracy, etc. have been described in detail above and will not be repeated here.

[0067] S400: Eutectic bonding process

[0068] According to an embodiment of the present invention, a eutectic bonding process is performed in this step to form a eutectic alloy layer to achieve electrical connection between the LED chip and the binding substrate.

[0069] According to an embodiment of the present invention, referring to Fig.14 , Fig.16 , the melting point of the eutectic bonding precursor layer material is relatively low, therefore, by depositing a high melting point metal (such as the first bonding metal layer, the second bonding metal layer) and a low melting point solder (eutectic bonding precursor layer material) in the bonding area, the bonding part is heated to above the melting point of the solder, so that the molten solder and the high melting point metal undergo solid-liquid interdiffusion, react to form an intermetallic compound, and finally the low melting point solder is transformed into a high melting point thermodynamically stable intermetallic compound to achieve solid-liquid eutectic bonding. The melting point of the intermetallic compound solder joint formed by eutectic bonding is greater than the melting point of the solder joint, and can withstand the subsequent stacking process when bonding again, and the bonded solder joint does not melt, and maintains good structural stability, achieving the goal of low temperature bonding and high temperature service.

[0070] According to an embodiment of the present invention, the conditions of the eutectic bonding process are not particularly limited, for example, the temperature is 100°C to 300°C, the pressure is 1MPa to 10MPa, and the time is 10min to 2h. According to an embodiment of the present invention, the temperature of the eutectic bonding process is 100°C, 150°C, 200°C, 250°C, 300°C or any value therebetween, the pressure is 1MPa, 2MPa, 4MPa, 5MPa, 6MPa, 8MPa, 10MPa or any value therebetween, and the time is 10min, 30min, 1h, 1.5h, 2h or any value therebetween.

[0071] In general, the preparation method sets a first opening 10 (groove structure) on the binding substrate, sets the bonding terminal 700 of the micro LED in the first opening 10, and performs eutectic bonding after alignment. Therefore, the preparation method has at least one of the following advantages: increasing the bonding area between the micro LED and the binding pad of the binding substrate, significantly reducing the bonding resistance, and increasing the bonding strength; reducing the risk of relative sliding between the micro LED and the binding substrate during eutectic bonding, and improving the bonding accuracy; avoiding the problem of the middle layer metal being squeezed out of the bonding area and overflowing during the eutectic bonding process, thereby reducing the risk of short circuit.

[0072] It should be noted that the specific types, structures, materials, specifications (such as thickness, etc.), and preparation methods of the above-mentioned binding substrates and micro LED chips are not particularly limited, and those skilled in the art can choose according to actual needs, which will not be repeated here. For example, the substrate substrate 100 in the binding substrate may also include a driving unit and a wiring structure, and the driving unit includes a TFT (Thin Film Transistor).

[0073] According to the embodiments of the present application, there are no special requirements for the specific type of the display device, and technical personnel in this field can flexibly select it according to actual needs. For example, the display device can be a mobile phone, a television, a notebook, an iPad, a game console, a kindle, a car display device, and all other devices and apparatuses with a display function.

[0074] Those skilled in the art will understand that, in addition to the organic electroluminescent device described above, the display device also includes the necessary structures or components of a conventional display panel. Taking a mobile phone as an example, it also includes an encapsulation layer, a glass cover, an audio module, a camera module, a touch module and other structures.

[0075] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0076] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of this specification. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0077] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A binding substrate, characterized in that: include: Base plate substrate; a plurality of binding pads, the plurality of binding pads are located on one side of the base substrate and arranged in an array, the binding pads having a first opening, A side of the base substrate where the binding pad is disposed has a circuit structure, and the circuit structure is electrically connected to the binding pad.

2. The binding substrate according to claim 1, characterized in that: The bonding pad includes at least one first bonding metal layer, and the first opening is located on the first bonding metal layer.

3. The binding substrate according to claim 2, characterized in that: The binding substrate satisfies at least one of the following conditions: The thickness of the first bonding metal layer is 2 μm to 6 μm; The depth of the first opening is 1-5 μm; The material forming the first bonding metal layer includes at least one of Cu, Au, Al, Ag and Ni.

4. The binding substrate according to claim 1, characterized in that: further comprising a eutectic alloy precursor layer, the eutectic alloy precursor layer at least covering a portion of the first opening, the melting point of a material forming the eutectic alloy precursor layer being lower than the melting point of a material forming the first bonding metal layer, The material forming the eutectic alloy precursor layer includes at least one of Sn and In.

5. The binding substrate according to claim 4, characterized in that: Satisfy at least one of the following conditions: In a direction perpendicular to the plane of the substrate, the thickness of the eutectic alloy precursor layer in the first opening is not greater than the depth of the first opening; The thickness of the eutectic alloy precursor layer is 1-2 μm; The eutectic alloy precursor layer has a second opening on a side away from the first opening.

6. A display device, characterized in that: include: The binding substrate according to any one of claims 1 to 5; A plurality of micro LED chips, each of which comprises a micro LED and a bonding terminal, wherein the bonding terminal is electrically connected to the micro LED, and the other end of the bonding terminal is connected to a bonding pad of the bonding substrate, The binding pad and the bonding terminal are connected via a eutectic alloy layer. An orthographic projection of the bonding terminal on the binding substrate and an orthographic projection of the first opening of the binding substrate on the binding substrate have an overlapping area.

7. The display device according to claim 6, characterized in that: An end surface of the bonding terminal facing the binding substrate is located in the first opening.

8. The display device according to claim 6, characterized in that: At least a portion of the eutectic alloy layer is formed by eutectic bonding of a eutectic alloy precursor layer, a second bonding metal layer of the bonding terminal, and a first bonding metal layer of the bonding pad.

9. The display device according to claim 6, characterized in that: The material forming the eutectic alloy layer includes at least one of Cu-Sn, Cu-In, Au-Sn, Au-In, Al-Sn, Al-In, Ag-Sn, Ag-In, Ni-Sn and Ni-In.

10. The display device according to claim 9, characterized in that: The display device has the first opening and the second opening, the depth of the first opening is h1, the depth of the second opening is h2, the bottom width of the first opening or the second opening is A, the opening width of the first opening or the second opening is B, and B>A; The thickness of the bonding terminal is greater than h1 and greater than h2; The width of the end of the bonding terminal and the binding pad on one side is a, and the cross-sectional width of the bonding terminal at a height of h1 or h2 in the direction from the binding pad to the micro LED is b, and B>b, A>a.

11. The display device according to claim 10, characterized in that: Satisfy at least one of the following conditions: h is 1 μm to 5 μm; A is 1 μm to 2 μm; B is 2 μm to 5 μm; a is 1 μm to 2 μm; b is 2μm~5μm.

12. A method for preparing a display device, characterized in that: include: A binding substrate and a micro LED chip are provided, wherein the binding substrate or the LED chip has a eutectic alloy precursor layer, the binding substrate is as described in any one of claims 1 to 5, and the micro LED chip is as described in any one of claims 6 to 11; Aligning the micro LED toward the binding substrate so that the bonding terminals on the LED chip correspond to the binding pads on the binding substrate one by one; The micro LED chip and the binding substrate are subjected to a eutectic bonding process to form a eutectic alloy layer between the bonding terminal and the binding pad.

13. The preparation method according to claim 12, characterized in that: The temperature of the eutectic bonding process is 100° C. to 300° C., the pressure is 1 MPa to 10 MPa, and the time is 10 min to 2 h.

14. The preparation method according to claim 12, characterized in that: The eutectic alloy precursor layer is formed on the surface of the bonding terminal or the binding pad by chemical plating.

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