A method for mass transfer of micro-light-emitting diodes and a display device

Abstract

This invention provides a mass transfer method for micro-light-emitting diodes (LEDs) and a display device. The mass transfer method includes: providing a substrate with multiple micro-LEDs bonded to it, and a display substrate with multiple pads; aligning the side of the substrate with the bonded micro-LEDs above the side of the display substrate with the pads; and while applying pressure to the substrate, irradiating it with a laser from above, causing the micro-LEDs at the irradiated locations to peel off to the display substrate. This method helps avoid cold solder joints and improves display performance.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a mass transfer method and display device for micro light-emitting diodes. Background Technology

[0002] Micro LED chips have advantages such as small size, high resolution, high brightness, high luminous efficiency, and low power consumption, and have become a research focus in the display field.

[0003] Among them, how to transfer a large number of micro LED chips onto the display substrate has become a major challenge for mass transfer technology. Summary of the Invention

[0004] This invention provides a mass transfer method and display device for micro light-emitting diodes, which can avoid the problem of poor soldering and improve the display effect.

[0005] In a first aspect, embodiments of the present invention provide a mass transfer method for micro-light-emitting diodes, comprising:

[0006] A carrier substrate with multiple micro light-emitting diodes bonded to it is provided, and a display substrate with multiple pads is provided;

[0007] The side of the intermediate substrate to which the plurality of micro light-emitting diodes are bonded is placed above the side of the display substrate to which the plurality of pads are formed for alignment.

[0008] During the process of applying pressure to the intermediate substrate, the intermediate substrate is irradiated with a laser from above, causing the micro light-emitting diodes at the irradiated locations to be stripped to the display substrate.

[0009] In one possible implementation, the provision of a carrier substrate to which a plurality of micro light-emitting diodes are bonded includes:

[0010] Obtain the coordinate positions of each of the pads on the display substrate;

[0011] The intermediate substrate is bonded with double-sided adhesive;

[0012] The plurality of micro-light-emitting diodes are placed on the side of the double-sided adhesive away from the intermediate substrate according to the coordinate positions, so that the intermediate substrate adheres the plurality of micro-light-emitting diodes.

[0013] In one possible implementation, the double-sided adhesive includes a first adhesive layer and a second adhesive layer that are sequentially separated from the intermediate substrate. The second adhesive layer is used to bond the plurality of micro light-emitting diodes. During the process of irradiating the intermediate substrate with a laser from above, the second adhesive layer loses its adhesiveness, causing the micro light-emitting diodes at the irradiated positions to be peeled off from the intermediate substrate to the display substrate.

[0014] In one possible implementation, the laser is an infrared laser.

[0015] In one possible implementation, the double-sided adhesive also includes a substrate layer located between the first adhesive layer and the second adhesive layer.

[0016] In one possible implementation, after peeling the micro-light-emitting diode from the intermediate substrate to the display substrate, the method further includes:

[0017] Peel the double-sided adhesive off the intermediate substrate.

[0018] In one possible implementation, after peeling the micro-light-emitting diode from the intermediate substrate to the display substrate, the method further includes:

[0019] At least one of the first adhesive layer and the second adhesive layer is left on the display substrate and reused as an optical film layer of the display substrate. In one possible implementation, after irradiating the intermediate substrate with a laser from above the intermediate substrate, the method further includes:

[0020] After a first preset time interval, the laser irradiation of the intermediate substrate is stopped;

[0021] After a second preset time period, the pressure applied to the intermediate substrate is removed.

[0022] In one possible implementation, after placing the plurality of micro-light-emitting diodes according to the coordinate positions on the side of the double-sided adhesive away from the intermediate substrate, the method further includes:

[0023] The side of the intermediate substrate to which the plurality of micro-light-emitting diodes are bonded is placed in a container containing flux, so that the flux remains on the bonding electrodes of each micro-light-emitting diode. Secondly, embodiments of the present invention also provide an intermediate substrate, comprising:

[0024] The substrate and double-sided adhesive adhered to the surface of the substrate, the double-sided adhesive comprising a first adhesive layer and a second adhesive layer, the second adhesive layer being used to bond multiple micro light-emitting diodes, the second adhesive layer having variable adhesion.

[0025] In one possible implementation, the double-sided adhesive also includes a substrate layer located between the first adhesive layer and the second adhesive layer.

[0026] In one possible implementation, the intermediate substrate is reused as a protective cover for the display substrate.

[0027] Thirdly, embodiments of the present invention also provide a display device, comprising:

[0028] The display substrate includes the plurality of microlight-emitting diodes fixed using the mass transfer method described in any of the above descriptions.

[0029] In one possible implementation, a first adhesive layer and a second adhesive layer are sequentially adjacent to the display substrate, and each of the micro light-emitting diodes is partially covered by the second adhesive layer.

[0030] In one possible implementation, the first adhesive layer and the second adhesive layer are doped with transparent diffusing particles, and the first adhesive layer and the second adhesive layer are reused as optical film layers of the display substrate.

[0031] The beneficial effects of this invention are as follows:

[0032] This invention provides a mass transfer method and display device for micro-light-emitting diodes (LEDs). The mass transfer method first provides a substrate with multiple micro-LEDs bonded to it, and a display substrate with multiple solder pads. Then, the side of the substrate with the bonded micro-LEDs is placed above the side of the display substrate with the solder pads for alignment. Next, while applying pressure to the substrate, a laser is used to irradiate the substrate from above, causing the micro-LEDs at the irradiated locations to peel off to the display substrate. Because the substrate with the bonded micro-LEDs has relatively high flatness, the misalignment of the micro-LEDs peeled off to the display substrate is avoided. Furthermore, by irradiating the substrate with a laser from above while applying pressure, both the flatness of the substrate and the stability of the soldering are ensured. This avoids the problem of poor soldering between the micro-LEDs and the solder pads of the display substrate, improving the display effect. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of one of the die bonding processes used in related technologies;

[0034] Figure 2 To adopt Figure 1 The diagram shown illustrates one type of printing misalignment defect in the die bonding process.

[0035] Figure 3 A flowchart of one method of a mass transfer method for a micro light-emitting diode provided in an embodiment of the present invention;

[0036] Figure 4 for Figure 3 A flowchart illustrating one method of step S101;

[0037] Figure 5 This is a flowchart of one method in a mass transfer method for a micro light-emitting diode provided in an embodiment of the present invention;

[0038] Figure 6 This is a process flow diagram corresponding to one of the mass transfer methods for micro light-emitting diodes provided in an embodiment of the present invention;

[0039] Figure 7 A schematic diagram of one structure of a mid-mount substrate provided in an embodiment of the present invention;

[0040] Figure 8 This is a schematic diagram of one possible structure of double-sided adhesive in a mid-mount substrate provided by an embodiment of the present invention;

[0041] Figure 9 This is a schematic diagram of one structure of a display device provided in an embodiment of the present invention;

[0042] Figure 10 For along Figure 9 A schematic diagram of one type of cross-sectional structure in the direction shown in MM;

[0043] Figure 11 For along Figure 9 A schematic diagram of one type of cross-sectional structure in the direction shown in MM. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Furthermore, the embodiments and features in the embodiments of the present invention can be combined with each other without conflict. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms "comprising" or "including," or similar terms as used in this invention, mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0046] It should be noted that the dimensions and shapes of the figures in the accompanying drawings do not reflect actual proportions and are intended only to illustrate the content of the invention. Furthermore, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0047] In related technologies, the following are commonly used: Figure 1 The die bonding process is shown. Combined with... Figure 1 As shown, the die bonding process mainly includes four steps, from S01 to S04. S01: Surface treatment of the pads; this can involve cleaning the substrate; or applying anti-oxidation treatments such as electroless gold plating or OSP to the pad surface. S02: Solder application; solder paste can be printed onto the corresponding pad positions using a printer; however, due to substrate expansion and contraction, batch variations, and the expansion and contraction of the stencil, the solder paste may exhibit issues such as… Figure 2 The printing offset shown is poor. in, Figure 2 In the diagram, 01 represents the substrate, 02 represents the solder pad, 03 represents the solder paste, 04 represents the stencil, 05 represents the scraper, 06 represents the chip, 07 represents the reflow oven, and 08 represents the camera.

[0048] S03: Die Bonding; Traditional die bonding is divided into swing arm type and pin-type. Both place the chip on the pads of the substrate, relying on the adhesiveness of the solder paste to keep the chip on the substrate. S04: Reflow Soldering; This mainly involves placing the substrate with the chip bonded to it in a reflow oven. Through hot air reflow soldering, the solder paste and the chip bonding electrodes (pads) are subjected to high temperatures to form an alloy layer, which fixes the chip to the substrate. However, due to the fluidity of the solder paste during the high-temperature process, the chip may shift or tilt, affecting the brightness consistency of the module and even causing large-viewing-angle color shift. For example, in area a, the tilt angle of the red sub-pixel (R) is 0.377°, the tilt angle of the green sub-pixel (G) is 0.883°, and the tilt angle of the blue sub-pixel (B) is 0.029°. For example, in region b, the tilt angle of R is 9.817°, the tilt angle of G is 7.3°, and the tilt angle of B is 1.727°. The tilt angle of region b is too large compared to region a, causing obvious uneven brightness and a pitted appearance. Moreover, during the soldering process, because the chip is floating above the pads, the probability of cold solder joints forming between the solder and the metal pads increases, and the chip tilt leads to a large viewing angle difference.

[0049] After reflow soldering, step S05: Illumination Test; the substrate is illuminated and optically tested using a camera. Then, step S06: Rework; based on the test results, any poorly soldered areas are re-soldered and secured. Because the probability of cold solder joints is high, rework and resoldering are costly.

[0050] Therefore, embodiments of the present invention provide a mass transfer method and display device for micro light-emitting diodes to avoid cold solder joint problems and improve display effects.

[0051] like Figure 3 As shown, this embodiment of the invention provides a mass transfer method for micro light-emitting diodes, the method comprising:

[0052] S101: Provides a carrier substrate with multiple micro light-emitting diodes bonded to it, and a display substrate with multiple pads.

[0053] In the specific implementation process, firstly, a substrate 40 with multiple micro-light-emitting diodes 60 bonded to it is provided, and a display substrate 10 with multiple pads 20 is provided. The substrate 40 with multiple micro-light-emitting diodes 60 bonded to it can be prepared using mass transfer methods in related technologies. For example, the micro-light-emitting diodes 60 prepared on the blue film 50 can be bonded to the substrate 40 by needle-punching. Of course, the substrate 40 with multiple micro-light-emitting diodes 60 bonded to it can also be prepared according to the actual application needs, and is not limited here. The substrate 40 can be a glass substrate or a printed circuit board (PCB), and is not limited here. In addition, the substrate 40 can meet the following conditions: thickness greater than 1 mm, flatness ±5 μm, light transmittance greater than 90%, and heat resistance. In one exemplary embodiment, the substrate 40 can withstand heat conditions such as a heating temperature of 240°C and a heating time of 10 s. Furthermore, the specific number of micro-light-emitting diodes 60 bonded to the intermediate substrate 40 can be set according to actual application needs, and is not limited here. The specific number of multiple pads 20 formed on the display substrate 10 can also be set according to actual application needs, and is not limited here. Each micro-light-emitting diode 60 is bonded and coupled to the corresponding pad 20 on the display substrate 10, which can be achieved through bonding electrodes 601 provided on the micro-light-emitting diode 60 and the corresponding pad 20 on the display substrate 10.

[0054] It should be noted that the micro-LED 60 in this embodiment of the invention can be a submillimeter-sized light-emitting diode (Mini-LED) or a micro-sized light-emitting diode (Micro LED). Mini-LED refers to a light-emitting diode with a size between 80μm and 300μm. When Mini-LEDs are used as pixels in the display substrate 10 to form a self-emissive display, a higher pixel density can be achieved compared to small-pitch LED displays. When Mini-LEDs are used as a light source in a backlight module, an ultra-thin light source module can be created through a denser arrangement of light sources; combined with local dimming technology, the display screen including the Mini-LED backlight module will have better contrast and high dynamic range lighting rendering effects. Micro-LEDs with a size smaller than 80μm can be directly used as pixels in display substrates for near-eye, wearable, and handheld terminals.

[0055] S102: Align the side of the intermediate substrate where the plurality of micro light-emitting diodes are bonded to the display substrate above the side of the display substrate where the plurality of pads are formed.

[0056] In specific implementation, the side of the intermediate substrate 40 where multiple micro-light-emitting diodes 60 are bonded is placed above the side of the display substrate 10 where multiple pads 20 are provided for alignment, in order to improve the bonding accuracy between the micro-light-emitting diodes 60 and the pads 20. In one exemplary embodiment, the side of the intermediate substrate 40 where multiple micro-light-emitting diodes 60 are bonded is placed above the side of the display substrate 10 where multiple pads 20 are provided, at a predetermined distance. This predetermined distance can be set according to actual application needs and is not limited here.

[0057] S103: During the process of applying pressure to the intermediate substrate, the intermediate substrate is irradiated with a laser from above, causing the micro light-emitting diodes at the irradiated positions to be stripped to the display substrate.

[0058] In the specific implementation process, while applying pressure to the intermediate substrate 40, a laser is used to irradiate the intermediate substrate 40 from above. This ensures the flatness of the intermediate substrate 40, and the energy from the laser irradiation can peel the micro-LEDs 60 at the irradiated location to the display substrate 10. On one hand, welding under pressure facilitates a full bond between the micro-LEDs 60 and the pads 20, reducing the probability of poor soldering. On the other hand, the high flatness during welding avoids tilting and voids in the corresponding chips of the micro-LEDs to be welded.

[0059] In embodiments of the present invention, such as Figure 4 As shown, step S101 provides a carrier substrate to which multiple micro light-emitting diodes are bonded, including:

[0060] S201: Obtain the coordinate positions of each of the pads on the display substrate;

[0061] S202: Attach the intermediate substrate to the double-sided adhesive;

[0062] S203: Place the plurality of micro-light-emitting diodes on the side of the double-sided adhesive away from the intermediate substrate according to the coordinate positions, so that the intermediate substrate adheres the plurality of micro-light-emitting diodes.

[0063] In the specific implementation process, steps S201 to S203 are implemented as follows:

[0064] First, the coordinate positions of each pad 20 on the display substrate 10 are obtained. In one exemplary embodiment, the coordinate positions of each pad 20 on the display substrate 10 can be scanned using a die bonding device and recorded. Then, the intermediate substrate 40 is bonded to the double-sided adhesive 30. The double-sided adhesive 30 can be bonded to one side surface of the intermediate substrate 40. Then, according to the coordinate positions of each pad 20, multiple micro-light-emitting diodes 60 are placed on the side of the double-sided adhesive 30 facing away from the intermediate substrate 40. In this way, multiple micro-light-emitting diodes 60 are bonded to the side of the double-sided adhesive 30 facing away from the intermediate substrate 40. Provided that the intermediate substrate 40 and the double-sided adhesive 30 have good flatness, the problem of tilting of the micro-light-emitting diodes 60 is avoided. Moreover, the process of bonding the micro-light-emitting diodes 60 to the intermediate substrate 40 is based on the pre-obtained coordinate positions of each pad 20, ensuring the bonding accuracy of the micro-light-emitting diodes 60.

[0065] In this embodiment of the invention, after step S203: placing the plurality of micro-light-emitting diodes on the side of the double-sided adhesive away from the intermediate substrate according to the coordinate positions, the method further includes:

[0066] The side of the intermediate substrate to which the plurality of micro light-emitting diodes are bonded is placed in a container containing flux, so that the flux remains on the bonding electrodes of each micro light-emitting diode.

[0067] In the specific implementation process, after placing multiple micro-LEDs 60 on the side of the double-sided adhesive 30 away from the intermediate substrate 40 according to the coordinate positions of the pads 20, the side of the intermediate substrate 40 with the multiple micro-LEDs 60 bonded together can be placed in a container containing flux 70 by dipping in flux 70. This ensures that flux 70 remains on the bonding electrodes 601 of each micro-LED 60. The flux 70 is non-conductive and volatilizes during heating, leaving a small residue, which improves the efficiency of the bonding electrodes 601 of the micro-LEDs 60 bonding with the pads 20 to form a metal compound, thus improving die bonding efficiency. Furthermore, this embodiment of the invention uses the process of dipping in flux 70 instead of the solder paste printing process in related technologies, avoiding problems such as solder paste misalignment and micro-LED 60 offset or tilting.

[0068] In the specific implementation process, in addition to the process of dipping flux 70, flux 70 can also be sprayed or applied to leave flux 70 on the bonding electrodes 601 of each micro light-emitting diode 60.

[0069] In this embodiment of the invention, the double-sided adhesive 30 includes a first adhesive layer 301 and a second adhesive layer 302 that are sequentially separated from the intermediate substrate 40. The second adhesive layer 302 is used to bond the plurality of micro light-emitting diodes 60. During the process of irradiating the intermediate substrate 40 with a laser from above, the second adhesive layer 302 loses its adhesiveness, causing the micro light-emitting diodes 60 at the irradiated position to be peeled off from the intermediate substrate 40 to the display substrate 10.

[0070] In specific implementation, the double-sided adhesive 30 includes a first adhesive layer 301 and a second adhesive layer 302 sequentially facing away from the intermediate substrate 40, and its adhesiveness is variable. The second adhesive layer 302 is used to bond multiple micro-light-emitting diodes (LEDs) 60. In one exemplary embodiment, the initial adhesive force of the second adhesive layer 302 can be 1N / 25mm to 5N / 25mm. After irradiation at 240°C for 10 seconds, the adhesive force of the second adhesive layer 302 decreases. Thus, the double-sided adhesive 30 ensures the adhesion performance of the intermediate substrate 40 to the micro-light-emitting diodes 60. Furthermore, during laser irradiation of the intermediate substrate 40 from above, the second adhesive layer 302 loses its adhesiveness due to the heat-induced adhesion reduction characteristics and the photoinitiator adhesion reduction characteristics. This allows the micro-light-emitting diodes 60 at the laser-irradiated location to be peeled from the intermediate substrate 40 to the display substrate 10, thereby improving the transfer efficiency of the micro-light-emitting diodes.

[0071] In this embodiment of the invention, the laser is an infrared laser with relatively high irradiation energy, ensuring the adhesion reduction efficiency of the second adhesive layer during the irradiation of the intermediate substrate 40. In one exemplary embodiment, a single infrared laser 80 can be used to irradiate each micro-light-emitting diode 60 individually. In another exemplary embodiment, multiple infrared lasers 80 can be used to irradiate the micro-light-emitting diodes 60 in different areas. Of course, the micro-light-emitting diodes 60 can be irradiated according to actual application needs, and this is not limited here.

[0072] In this embodiment of the invention, the double-sided adhesive 30 further includes a substrate layer located between the first adhesive layer 301 and the second adhesive layer 302. The substrate layer can be PI or PET, and is not limited thereto. The substrate layer not only increases the rigidity of the double-sided adhesive 30, facilitating its attachment to the intermediate substrate 40, but also reduces manufacturing defects such as wrinkles and bubbles, making it easier to remove and effectively avoiding breakage problems caused by removing the adhesive layer separately.

[0073] In an embodiment of the present invention, after peeling the micro light-emitting diode from the intermediate substrate to the display substrate, the method further includes:

[0074] Peel the double-sided adhesive off the intermediate substrate.

[0075] In a specific implementation, after the micro-LED 60 is peeled from the intermediate substrate 40 to the display substrate 10, the double-sided adhesive 30 can be peeled off from the intermediate substrate 40. Since the second adhesive layer 302 loses its adhesiveness during laser irradiation, the micro-LED 60 can be quickly peeled from the intermediate substrate 40 to the display substrate 10. Subsequently, the double-sided adhesive 30 can be directly removed from the intermediate substrate 40. In one exemplary embodiment, heating, ultraviolet (UV) irradiation, or solvent dissolution can be used to reduce the adhesion of the first adhesive layer 301, thereby improving the reusability of the intermediate substrate 40 and reducing manufacturing costs.

[0076] In an embodiment of the present invention, after peeling the micro light-emitting diode from the intermediate substrate to the display substrate, the method further includes:

[0077] At least one of the first adhesive layer and the second adhesive layer is left on the display substrate and reused as an optical film layer of the display substrate.

[0078] In a specific implementation, after the micro-light-emitting diode 60 is peeled from the intermediate substrate 40 to the display substrate 10, at least one of the first adhesive layer 301 and the second adhesive layer 302 can remain on the display substrate 10 and be reused as an optical film layer of the display substrate 10. In one exemplary embodiment, the second adhesive layer 302 remains on the display substrate 10; since the second adhesive layer 302 loses its adhesiveness and has fluidity during laser irradiation, the second adhesive layer 302 flows and coats the micro-light-emitting diode 60 during heating and welding, and combines with the display substrate 10, ensuring the hermeticity of the encapsulation and improving the performance of the display substrate 10; in addition, the first adhesive layer 301 can be removed from the display substrate 10 through a de-adhesion treatment, so that after the micro-light-emitting diode 60 is peeled from the intermediate substrate 40 to the display substrate 10, only the second adhesive layer 302 can remain on the display substrate 10. Furthermore, the second adhesive layer 302 may be doped with transparent diffusion particles, and the second adhesive layer 302 can be reused as an optical film layer of the display substrate 10. In this way, while ensuring welding efficiency, the manufacturing cost of the display substrate 10 is reduced.

[0079] In one exemplary embodiment, the first adhesive layer 301 remains on the display substrate 10. During laser irradiation, the second adhesive layer 302 evaporates upon heating, while the first adhesive layer 301 becomes fluid upon heating. Simultaneously with heating and welding, the first adhesive layer 301 flows and coats the micro-light-emitting diode 60, bonding with the display substrate 10, ensuring hermetic sealing and improving the performance of the display substrate 10. It should be noted that when the double-sided adhesive 30 also includes a substrate layer located between the first adhesive layer 301 and the second adhesive layer 302, the substrate layer can be removed after the second adhesive layer 302 evaporates upon heating, thus ensuring that the first adhesive layer 301 flows and coats the micro-light-emitting diode 60, similarly ensuring hermetic sealing. Furthermore, the first adhesive layer 301 can be doped with transparent diffusing particles, allowing it to be reused as an optical film layer of the display substrate 10. This reduces the manufacturing cost of the display substrate 10 while maintaining welding efficiency.

[0080] In one exemplary embodiment, the first adhesive layer 301 and the second adhesive layer 302 remain on the display substrate 10. During laser irradiation, the second adhesive layer 302 exhibits fluidity. Simultaneously with heating and welding, the second adhesive layer 302 flows and coats the micro-light-emitting diode 60, bonding with the display substrate 10 to ensure hermetic sealing and improve the performance of the display substrate 10. Furthermore, the first adhesive layer 301 can be cured, increasing its hardness and ensuring the flatness of the display substrate 10. Both the first adhesive layer 301 and the second adhesive layer 302 can be doped with transparent diffusing particles, allowing them to be reused as optical film layers of the display substrate 10. This reduces the manufacturing cost of the display substrate 10 while maintaining welding efficiency.

[0081] In this embodiment of the invention, the intermediate substrate 40 is reused as a protective cover for the display substrate 10.

[0082] In practical implementation, the intermediate substrate 40 can be reused as a protective cover for the display substrate 10, improving the protection performance of the display substrate 10 while transferring the micro-light-emitting diode 60. Furthermore, a coating with specific functions can be applied to the protective cover to enhance the performance of the display substrate 10. This coating can be one or more of an anti-glare (AG) protective film, an anti-fingerprint (AF) film, and an anti-ultraviolet (UV) protective film, and is not limited here. Of course, other films can be applied according to actual application needs, and can be implemented with reference to relevant technologies, which will not be detailed here.

[0083] It should be noted that the pressure applied to the intermediate substrate 40 can be a uniform and equal force applied to the intermediate substrate 40, thereby avoiding warping of the intermediate substrate 40 and ensuring its flatness. During the laser irradiation process of the intermediate substrate 40, pressure needs to be continuously applied to the intermediate substrate 40 to ensure that the bonding electrodes 601 of the micro-light-emitting diode 60 and the pads 20 are not tilted or have voids when soldering them. When the display substrate 10 is used in a display device, it ensures brightness uniformity and avoids color shift and pitting. Moreover, applying pressure to the intermediate substrate 40 while using laser irradiation for soldering is beneficial for the formation of metal oxides between the bonding electrodes 601 and the pads 20 of the micro-light-emitting diode 60, reducing the probability of cold solder joints.

[0084] In embodiments of the present invention, such as Figure 5 As shown, in step S103, after irradiating the intermediate substrate with a laser from above, the method further includes:

[0085] S301: After a first preset time interval, stop irradiating the intermediate substrate with laser;

[0086] S302: After a second preset time, remove the pressure applied to the intermediate substrate.

[0087] In the specific implementation process, steps S301 to S302 are implemented as follows:

[0088] First, during the application of pressure to the intermediate substrate 40, after irradiating the intermediate substrate 40 with a laser from above, the laser irradiation is stopped after a first preset time interval. This ensures that the degree of laser irradiation on each micro-LED 60 is approximately the same, guaranteeing the uniformity of the soldering of each micro-LED 60. The first preset time interval can be set by those skilled in the art according to actual application needs, and is not limited here. After a second preset time interval, the pressure applied to the intermediate substrate 40 is removed, ensuring sufficient soldering of each micro-LED 60 to the pad 20. The second preset time interval can be set by those skilled in the art according to actual application needs, and is not limited here.

[0089] The following example uses a double-sided adhesive 30 comprising a first adhesive layer 301 and a second adhesive layer 302 sequentially separated from the intermediate substrate 40, and three micro-light-emitting diodes 60. Figure 6 The process flow diagram shown illustrates the mass transfer method of the micro light-emitting diode 60 provided in this embodiment of the invention.

[0090] First, the coordinate positions of each pad 20 on the display substrate 10 are obtained; in one exemplary embodiment, the coordinate positions of each pad 20 on the display substrate 10 can be obtained by a die bonding device. Then, the first adhesive layer 301 of the double-sided adhesive 30 is bonded to the intermediate substrate 40; then, according to the coordinate positions of each pad 20 on the display substrate 10, the micro-light-emitting diodes 60 arranged on the blue film 50 are bonded to the side of the second adhesive layer 302 away from the intermediate substrate 40 by needle punching; then, the side of the intermediate substrate 40 with multiple micro-light-emitting diodes 60 bonded is placed in a container containing flux 70, i.e., immersed in flux 70, so that flux 70 remains on the bonding electrodes 601 of each micro-light-emitting diode 60; then, the side of the intermediate substrate 40 with multiple micro-light-emitting diodes 60 bonded after being immersed in flux 70 is placed above the side of the display substrate 10 with multiple pads 20 for alignment; then, pressure is applied to the intermediate substrate 40, the pressure direction being as follows. Figure 6 In the direction indicated by the middle arrow Y, and while applying pressure to the intermediate substrate 40, a laser is used to irradiate the intermediate substrate 40 from above. For example, an infrared laser 80 is used, with an irradiation temperature of 240°C and an irradiation duration of 8 seconds. During laser irradiation, the bonding electrodes 601 of the micro-LEDs 60 form an alloy with the pads 20, thereby completing die bonding. Moreover, during laser irradiation, the second adhesive layer 302 loses its adhesiveness, allowing for easy separation of the intermediate substrate 40 from the multiple micro-LEDs 60. Furthermore, the double-sided adhesive 30 can be removed from the intermediate substrate 40, improving the reusability of the intermediate substrate 40 and saving manufacturing costs.

[0091] Based on the same inventive concept, such as Figure 7 As shown, this embodiment of the invention also provides a carrier substrate 40, which includes:

[0092] The substrate 400 and the double-sided adhesive 30 attached to the surface of the substrate 400, the double-sided adhesive 30 including a first adhesive layer 301 and a second adhesive layer 302 that are sequentially opposite to the substrate, the second adhesive layer 302 being used to bond a plurality of micro light-emitting diodes 60, and the adhesiveness of the second adhesive layer 302 being variable.

[0093] In practice, the adhesive properties of the second adhesive layer 302 are variable; in particular, the second adhesive layer 302 has the characteristic of losing its adhesiveness after laser irradiation. Thus, after multiple micro-LEDs 60 are bonded to the intermediate substrate 40 via the second adhesive layer 302, laser irradiation of the intermediate substrate 40 can peel the multiple micro-LEDs 60 off the intermediate substrate 40, thereby improving the transfer efficiency of the micro-LEDs 60 from the intermediate substrate 40.

[0094] In embodiments of the present invention, such as Figure 8As shown, the double-sided adhesive 30 also includes a substrate layer 90 located between the first adhesive layer 301 and the second adhesive layer 302. The substrate layer can be PI or PET, and is not limited thereto. The substrate layer not only increases the rigidity of the double-sided adhesive 30, making it easier to attach to the intermediate substrate 40, but also reduces manufacturing defects such as wrinkles and bubbles, making it easier to remove and effectively avoiding breakage problems caused by peeling off the adhesive layer separately.

[0095] In this embodiment of the invention, the intermediate substrate 40 is reused as a protective cover for the display substrate 10. This improves the performance of the intermediate substrate 40.

[0096] Based on the same inventive concept, such as Figure 9 As shown, this embodiment of the invention also provides a display device, which includes:

[0097] Display substrate 10, the display substrate 10 including the plurality of micro light-emitting diodes 60 fixed by the mass transfer method as described in any of the preceding claims.

[0098] In embodiments of the present invention, such as Figure 10 The following is along Figure 9 The schematic diagram of one cross-sectional structure in the direction shown in the middle MM shows that the display device also includes a first adhesive layer 301 and a second adhesive layer 302 that are sequentially close to the display substrate 10, and each of the micro light-emitting diodes 60 is partially covered by the second adhesive layer 302.

[0099] In practical implementation, the display device also includes a first adhesive layer 301 and a second adhesive layer 302 sequentially adjacent to the display substrate 10. Each micro-light-emitting diode 60 is partially covered by the second adhesive layer 302, thereby ensuring the structural stability of the micro-light-emitting diode 60 while maintaining the hermeticity of the encapsulation and improving the performance of the display device. Furthermore, the second adhesive layer 302 has variable adhesion; during laser irradiation, the second adhesive layer 302 loses its adhesion, ensuring the coating performance of the second adhesive layer 302 on each micro-light-emitting diode 60.

[0100] In one exemplary embodiment, the first adhesive layer 301 and the second adhesive layer 302 are doped with transparent diffusing particles, and the first adhesive layer 301 and the second adhesive layer 302 are reused as optical film layers of the display substrate 10. This ensures the light extraction efficiency of the display device.

[0101] In one exemplary embodiment, such as Figure 11 The following is along Figure 9The schematic diagram shows one cross-sectional structure along the MM direction. The display device includes a second adhesive layer 302, and each micro-light-emitting diode 60 is partially covered by the second adhesive layer 302, thereby ensuring the hermeticity of the display device's packaging. Furthermore, the adhesive layer 302 has variable adhesion; during laser irradiation, the second adhesive layer 302 loses its adhesion, ensuring the second adhesive layer 302's coverage of each micro-light-emitting diode 60.

[0102] The principle of the display device provided in this embodiment of the invention is similar to that of the aforementioned mass transfer method. Therefore, the implementation of this display device can refer to the implementation of the display substrate 10 in the aforementioned mass transfer method, and the repeated parts will not be described again.

[0103] In specific implementation, the display device provided in the embodiments of the present invention can be any product or component with display function, such as a mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, or navigator. Other essential components of this display device are understood by those skilled in the art and will not be described in detail here, nor should they be construed as limiting the present invention.

[0104] This invention provides a mass transfer method and display device for micro-light-emitting diodes (LEDs) 60. The mass transfer method first provides a carrier substrate 40 with multiple micro-light-emitting diodes 60 bonded to it, and a display substrate 10 with multiple pads 20. Then, the side of the carrier substrate 40 with the bonded micro-light-emitting diodes 60 is placed above the side of the display substrate 10 with the pads 20 for alignment. Then, while applying pressure to the carrier substrate 40, a laser is used to irradiate the carrier substrate 40 from above, causing the micro-light-emitting diodes 60 at the irradiated locations to peel off to the display substrate 10. Because the carrier substrate 40 with the bonded micro-light-emitting diodes 60 has relatively high flatness, the misalignment of the multiple micro-light-emitting diodes 60 peeled off to the display substrate 10 is avoided. Furthermore, because the carrier substrate 40 is irradiated with a laser from above while applying pressure, both the flatness of the carrier substrate 40 and the stability of the soldering are ensured. This avoids the problem of poor soldering between the micro light-emitting diode 60 and the pad 20 of the display substrate 10, thus improving the display effect.

[0105] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0106] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A mass transfer method of micro light emitting diodes, characterized by, The method comprises the following steps: providing a middle carrier substrate to which a plurality of micro light emitting diodes are attached, and a display substrate provided with a plurality of pads; aligning the side of the middle carrier substrate to which the plurality of micro light emitting diodes are attached with the side of the display substrate provided with the plurality of pads; in the process of applying pressure to the middle carrier substrate, irradiating the middle carrier substrate from above with laser light to cause the micro light emitting diodes at the irradiated position to be detached from the middle carrier substrate and attached to the display substrate; the method of providing a middle carrier substrate to which a plurality of micro light emitting diodes are attached comprises the following steps: adhering the middle carrier substrate to double-sided adhesive tape; placing the plurality of micro light emitting diodes on the side of the double-sided adhesive tape away from the middle carrier substrate to cause the middle carrier substrate to attach the plurality of micro light emitting diodes; wherein the double-sided adhesive tape comprises a first adhesive layer and a second adhesive layer in sequence away from the middle carrier substrate, and the second adhesive layer is used to attach the plurality of micro light emitting diodes, and in the process of irradiating the middle carrier substrate from above with laser light, the second adhesive layer loses adhesion, causing the micro light emitting diodes at the irradiated position to be detached from the middle carrier substrate and attached to the display substrate; after the micro light emitting diodes are detached from the middle carrier substrate and attached to the display substrate, the method further comprises the following steps: leaving at least one of the first adhesive layer and the second adhesive layer on the display substrate and reusing it as an optical film layer of the display substrate.

2. The mass transfer method of claim 1, wherein, the method of providing a middle carrier substrate to which a plurality of micro light emitting diodes are attached further comprises the following steps: obtaining the coordinate positions of each of the pads on the display substrate; placing the plurality of micro light emitting diodes on the side of the double-sided adhesive tape away from the middle carrier substrate according to the coordinate positions to cause the middle carrier substrate to attach the plurality of micro light emitting diodes.

3. The mass transfer method of claim 1, wherein, The laser is an infrared laser.

4. The mass transfer method of claim 3, wherein, The double-sided adhesive tape further comprises a base material layer between the first adhesive layer and the second adhesive layer.

5. The mass transfer method of claim 4, wherein, after the micro light emitting diodes are detached from the middle carrier substrate and attached to the display substrate, the method further comprises the following steps: detaching the double-sided adhesive tape from the middle carrier substrate.

6. The mass transfer method according to any one of claims 1 to 5, wherein after irradiating the middle carrier substrate from above with laser light, the method further comprises the following steps: after a first preset time interval, stop irradiating the middle carrier substrate with laser light; after a second preset time interval, remove the pressure applied to the middle carrier substrate.

7. The mass transfer method according to any one of claims 1 to 5, wherein after placing the plurality of micro light emitting diodes on the side of the double-sided adhesive tape away from the middle carrier substrate according to the coordinate positions, the method further comprises the following steps: placing the side of the middle carrier substrate to which the plurality of micro light emitting diodes are attached in a container containing flux, so that the flux remains on the bonding electrodes of each of the micro light emitting diodes.

8. A mesoporous substrate, characterized in that, The method comprises the following steps: a substrate and double-sided adhesive tape attached to the surface of the substrate, the double-sided adhesive tape comprising a first adhesive layer and a second adhesive layer in sequence away from the substrate, the second adhesive layer being used to attach a plurality of micro light emitting diodes, and the second adhesive layer having variable adhesion; and the middle carrier substrate being reused as a protective cover plate of a display substrate.

9. The intermediate substrate of claim 8, wherein, The double-sided adhesive tape further comprises a base material layer between the first adhesive layer and the second adhesive layer.

10. A display device, characterized by comprising: The method comprises the following steps: A display substrate comprising the plurality of micro-LEDs fixed by the mass transfer method of any one of claims 1-7.

11. The display device of claim 10, wherein, Further comprising a first adhesive layer and a second adhesive layer sequentially adjacent to the display substrate, each of the micro-LEDs being partially covered by the second adhesive layer.

12. The display device of claim 11, wherein, The first adhesive layer and the second adhesive layer are doped with transparent diffusion particles, and the first adhesive layer and the second adhesive layer are multiplexed as an optical film layer of the display substrate.

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