A mass transfer method

Abstract

The present application relates to a kind of mass transfer method, the mass transfer method includes the following steps: (1) the epitaxial wafer containing at least two LED chips is bonded with first substrate, forms bonding pair, the surface of the first substrate is sequentially provided with laser release layer and temporary adhesive layer from inside to outside;(2) the bonding pair is irradiated under laser, the epitaxial wafer is stripped, and LED chip is transferred to the first substrate;(3) LED chip is bonded with the second substrate provided with laser-induced release layer;(4) laser is transmitted through first substrate, decomposes laser release layer, and after stripping first substrate, glue is removed, and temporary adhesive layer and part of laser-induced release layer are removed;(5) laser irradiation remaining part of laser-induced release layer, corresponding position LED chip falls to substrate, and the turnover of LED chip is completed.The mass transfer method of the present application has good transfer precision, high efficiency, high yield and low process cost.

Description

Technical Field

[0001] This invention relates to the field of LED chip transfer technology, and more particularly to a mass transfer method. Background Technology

[0002] Micro-LEDs are miniature light-emitting diodes, each capable of independent emission. They can be applied to smart wearables, mobile phones, wall TVs, automotive displays, and AR / VR products. Compared to LCD and OLED display technologies, Micro-LEDs offer advantages such as high resolution, low power consumption, high brightness, high color saturation, fast response time, and long lifespan, making them a recognized next-generation display technology. However, unlike LEDs, which are approximately 3mm in size, Micro-LEDs are typically less than 50μm. This means that a larger number of Micro-LEDs are needed to construct a backlight or display, making it increasingly difficult for existing materials and processes to meet the processing requirements of Micro-LEDs.

[0003] Currently, the manufacturing process of Micro LED mainly involves four key technical challenges: chip epitaxy, mass transfer, metal eutectic bonding, and colorization. In Micro LED processing, the technology of rapidly and accurately transferring Micro-LED chips grown on an epitaxial substrate onto a driving circuit substrate and establishing a good electrical connection between them is called mass transfer technology. The number of Micro-LED chips to be transferred is enormous; therefore, the efficiency, yield, and cost of mass transfer determine the economic value of the product. Conventional LEDs use vacuum suction for transfer, but because vacuum tubes have a physical limit of approximately 80μm, they are not suitable for the mass transfer of Micro-LEDs. Therefore, mass transfer technology is a key technical constraint on the development of Micro-LEDs.

[0004] CN111095516A discloses a mass transfer device and a mass transfer method. The disclosed mass transfer device has multiple channels, with a first opening on the first surface of each channel and a second opening on the second surface of each channel. The distance between the channels gradually increases from the first surface to the second surface. The mass transfer method provided by this invention uses laser irradiation to cause Micro-LEDs on a first substrate to fall and enter the channels of the mass transfer device through the first openings. They then fall from the second openings of the channels into the Micro-LED mounting positions on the second substrate, thus transferring Micro-LEDs from the first substrate to the second substrate. The spacing on the second substrate is greater than that on the first substrate. The mass transfer process is simple and low-cost.

[0005] CN112992721A discloses a mass transfer method and apparatus for micro-light-emitting diodes (LEDs). The disclosed mass transfer method for micro-light-emitting diodes includes: providing multiple micro-light-emitting diodes, each micro-light-emitting diode including an epitaxial layer and a first electrode and a first magnetic pole connected to the epitaxial layer, with the first magnetic pole and the first electrode having a gap distance; providing multiple backplate assemblies, each backplate assembly including a backplate and a second electrode and a second magnetic pole connected to the backplate, with the second electrode and the first electrode corresponding in position, and the second magnetic pole and the first magnetic pole corresponding in position, and the second magnetic pole and the first magnetic pole having opposite magnetic properties; the multiple backplate assemblies are disposed on a second substrate; peeling the multiple micro-light-emitting diodes from the first substrate and transferring them into a solution; and connecting the multiple micro-light-emitting diodes in the solution to the multiple backplate assemblies one-to-one using an inkjet assembly, wherein the first magnetic pole and the second magnetic pole are magnetically attracted, and the first electrode and the second electrode are connected.

[0006] Existing mass transfer methods mainly include flexible stamping, electrostatic adsorption transfer, electromagnetic transfer, fluid self-assembly, and laser-induced transfer. While all these methods have certain advantages, they also have shortcomings in practical applications. For example, flexible stamping is prone to variability, has a large material CET (Chip Equivalent Tolerance), and suffers from insufficient transfer accuracy; electrostatic adsorption transfer is susceptible to damage to LED chips due to the applied voltage; electromagnetic transfer requires external ferromagnetic materials and magnetic layers, resulting in complex processes and high costs; and fluid self-assembly suffers from low reliability and efficiency. Laser-induced transfer offers high efficiency, low cost, and a simple process, and can achieve patterned transfer of chips, but its current transfer yield is only around 90%, severely limiting its application in mass transfer.

[0007] Therefore, it is crucial to provide a high-yield laser-induced technology solution to address the problem of mass transfer. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a mass transfer method that ensures high transfer accuracy, high efficiency, high yield, low process cost, and enables laser sorting and release of different chips.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a mass transfer method, which includes the following steps:

[0011] (1) An epitaxial wafer containing at least two (5, 10, 15, 20, 50, etc.) LED chips is bonded to a first substrate to form a bonding pair. A laser release layer and a temporary adhesive layer are sequentially disposed on the surface of the first substrate from the inside to the outside.

[0012] (2) Irradiate the bonding pair under laser light, peel off the epitaxial wafer, and transfer the LED chip onto the first substrate;

[0013] (3) Bond the LED chip from step (2) to the second substrate having the laser-induced release layer, wherein the LED chip is in contact with the laser-induced release layer;

[0014] (4) Pass the laser through the first substrate to decompose the laser release layer, peel off the first substrate and remove the adhesive, remove the temporary adhesive layer and part of the laser-induced release layer, so that the LED chips are distributed independently.

[0015] (5) The remaining part of the laser-induced release layer is irradiated by laser, and the corresponding LED chip falls to the substrate, completing the flipping of the LED chip.

[0016] In this invention, the mass transfer method does not require complex equipment, and can easily and conveniently realize the mass transfer of LED chips. It has good transfer accuracy, high efficiency, high yield and low process cost. Among them, steps (1)-(2) belong to the laser (LLO) stripping stage of LED chips. In this process, the stripped chips are transferred intact and in situ to the first substrate. Steps (3)-(5) belong to the LED chip flipping stage. In this process, the laser-induced sorting of chips is realized through simple operation to complete the flipping of the corresponding chips.

[0017] Preferably, in step (1), the bonding method includes thermo-press bonding.

[0018] Preferably, the temperature of the hot-press bonding is 120-180℃, such as 130℃, 140℃, 150℃, 160℃, 170℃, etc.

[0019] Preferably, the hot-press bonding time is 5-10 minutes, such as 6 minutes, 7 minutes, 8 minutes, 9 minutes, etc.

[0020] Preferably, the pressure of the hot-press bonding is 1-5kN, such as 1.5kN, 2kN, 2.5kN, 3kN, 3.5kN, 4kN, 4.5kN, etc.

[0021] Preferably, the vacuum degree of the thermocompression bonding is ≤0.1 mTorr, for example 0.09 mTorr, 0.07 mTorr, 0.05 mTorr, 0.03 mTorr, etc.

[0022] Preferably, in the bonding pair, the LED chip is in contact with the temporary adhesive layer.

[0023] Preferably, the LED chip includes a Micro-LED chip.

[0024] Preferably, the thickness of the laser emission layer is 100-1000nm, such as 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, etc., and more preferably 100-500nm.

[0025] In this invention, the thickness of the laser release layer is 100-1000nm. If the thickness is too high, it will easily cause the adhesive to delaminate, and on the other hand, it will also result in too much residual adhesive after debonding, which will require a longer time for subsequent Plasma adhesive removal or result in incomplete adhesive removal. If the thickness is too thin, it will lead to insufficient laser absorption, and the transmitted laser may damage the LED chip.

[0026] Preferably, the laser-emitting layer is made of UV-responsive polyimide (PI), which has strong UV absorption properties.

[0027] Preferably, the material of the laser emission layer includes WLP LB210 and / or WLPLB220.

[0028] The reason for preferring the laser-emitting materials described above in this invention is that these materials exhibit excellent UV laser absorption and response at 150 mJ / cm². 2 Automatic separation can be achieved under laser energy, and residual adhesive can be easily removed by Plasma.

[0029] Preferably, the thickness of the temporary adhesive layer is 1-20 μm, such as 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 6 μm, 18 μm, etc., and more preferably 1-10 μm.

[0030] Preferably, the temporary adhesive layer is made of an olefin polymer.

[0031] Preferably, the material of the temporary adhesive layer includes WLP TB 1238 WLPTB4130 or Any one or at least two combinations of WLP TB130, wherein typical but non-limiting combinations include: WLP TB1238 and The combination of WLP TB4130, WLPTB4130 and The combination of WLP TB130, WLP TB1238, WLP TB4130 and Combinations such as WLP TB130, etc.

[0032] The reason why the above-mentioned temporary adhesive materials are preferred in this invention is that they have excellent chemical resistance and excellent adhesion to both laser-responsive materials and LEDs.

[0033] Preferably, the method for preparing the laser-emitting layer includes the following steps:

[0034] A laser-emitting material is coated onto a first substrate and cured to obtain the laser-emitting layer.

[0035] Preferably, the coating method includes spin coating.

[0036] Preferably, the curing temperature is 100-300℃, such as 120℃, 140℃, 160℃, 180℃, 200℃, 220℃, 240℃, 260℃, 280℃, etc., and the curing time is 5-10min, such as 6min, 7min, 8min, 9min, etc.

[0037] Preferably, the method for preparing the temporary adhesive layer includes the following steps:

[0038] A temporary adhesive material is coated onto the laser release layer and cured to obtain the temporary adhesive layer.

[0039] Preferably, the coating method includes spin coating.

[0040] Preferably, the curing temperature is 100-200℃, such as 120℃, 140℃, 160℃, 180℃, etc., and the curing time is 5-15min, such as 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, etc.

[0041] Preferably, in step (2), the wavelength of the laser is 200-400nm, such as 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, etc., and more preferably 266nm.

[0042] Preferably, after stripping the epitaxial wafer, the LED chip is further cleaned and dried.

[0043] Preferably, the cleaning solvent includes concentrated hydrochloric acid, wherein the mass percentage of hydrogen chloride in the concentrated hydrochloric acid is 20% or more, such as 25%, 30%, 35%, etc.

[0044] Preferably, the cleaning time is 10-60 seconds, such as 20 seconds, 30 seconds, 40 seconds, 50 seconds, etc.

[0045] Preferably, the drying temperature is 50-70°C, such as 55°C, 60°C, 65°C, etc.

[0046] Preferably, in step (3), the bonding temperature is 20-30℃, such as 22℃, 24℃, 26℃, 28℃, etc.

[0047] Preferably, the bonding pressure is 1-3 kN, such as 1.5 kN, 2 kN, 2.5 kN, etc.

[0048] Preferably, the bonding time is 5-30 min, such as 10 min, 15 min, 20 min, 25 min, etc.

[0049] Preferably, the vacuum degree of the bonding is ≤0.1 mTorr, for example 0.09 mTorr, 0.07 mTorr, 0.05 mTorr, 0.03 mTorr, etc.

[0050] Preferably, in step (3), the thickness of the laser-induced release layer is 1-5 μm, such as 2 μm, 3 μm, 4 μm, etc., and more preferably 2-3 μm.

[0051] In this invention, the thickness of the laser-induced release layer is 1-5 μm. The reason for controlling the thickness within this range is that if the thickness is too high, the laser-induced material will not be completely decomposed after laser irradiation, resulting in residual adhesive; if the thickness is too thin, due to wafer warpage and substrate TTV, the thickness of the laser-induced release layer will affect the bonding quality and cause bonding bubble problems.

[0052] Preferably, the laser-induced release layer is made of a triazine polymer.

[0053] Preferably, the material of the laser-induced release layer includes WLP LAP810 and / or WLP LAP811, further optimized WLP LAP810.

[0054] In this invention, the material of the laser-induced release layer is preferably... WLP LAP810 is preferred because it not only exhibits excellent absorption properties at 308nm and 355nm, but also rapidly generates gas under laser irradiation, inducing the chip to separate from the adhesive layer. Furthermore, the laser-induced release layer has excellent laser resolution, enabling laser-induced release of a single chip.

[0055] Preferably, in step (4), the wavelength of the laser is 300-400nm, such as 308nm, 320nm, 340nm, 360nm, 380nm, etc., and more preferably 355nm.

[0056] Preferably, the energy of the laser is 100-300 mJ / cm². 2 For example, 120mj / cm 2 140mj / cm 2 160mj / cm 2 180mj / cm 2 200mj / cm 2 220mj / cm 2 240mj / cm 2 260mj / cm 2 280mj / cm 2 wait.

[0057] In this invention, the energy of the laser is 100-300 mJ / cm². 2 The reason for controlling the energy within this range is that excessive laser energy can easily damage the chip; while insufficient energy will prevent automatic separation and result in a large amount of residual adhesive, making adhesive removal more difficult.

[0058] Preferably, in step (4), the method of removing adhesive includes plasma adhesive removal.

[0059] Preferably, the adhesive removal includes the following steps:

[0060] First, the adhesive is removed in an oxygen atmosphere, and then a second removal is performed in an oxygen and argon atmosphere.

[0061] Preferably, in the first degumming process, the oxygen flow rate is 40-60 mL / min, such as 45 mL / min, 50 mL / min, 55 mL / min, etc., more preferably 50 mL / min, the power is 1-3 kW, such as 1.5 kW, 2 kW, 2.5 kW, etc., and the time is 3-8 min, such as 4 min, 5 min, 6 min, 7 min, etc., more preferably 5 min.

[0062] Preferably, in the second degumming process, the oxygen flow rate is 40-60 mL / min, such as 45 mL / min, 50 mL / min, 55 mL / min, etc., more preferably 50 mL / min; the argon flow rate is 100-200 mL / min, such as 120 mL / min, 140 mL / min, 160 mL / min, 180 mL / min, etc., more preferably 150 mL / min; the power is 1-3 kW, such as 1.5 kW, 2 kW, 2.5 kW, etc.; and the time is 5-20 min, such as 10 min, 15 min, etc.

[0063] Preferably, in step (5), the wavelength of the laser is 300-400nm, such as 308nm, 320nm, 355nm, 365nm, etc., and more preferably 355nm.

[0064] Preferably, the energy of the laser is 80-200 mJ / cm². 2 For example, 80mj / cm 2 100mj / cm 2 120mj / cm 2 140mj / cm 2 160mj / cm 2 180mj / cm 2 wait.

[0065] In this invention, the energy of the laser is 80-200 mJ / cm². 2 The reason for controlling the energy within this range is that if the energy is too high, the LAP811 will generate gas rapidly, causing the chip to deviate or bend when it is released onto the carrier board. High-energy lasers may even shatter the chip. If the energy is too low, the chip transfer will fail. Even if the transfer is successful, the LAP cannot be completely decomposed by the laser, resulting in residual adhesive.

[0066] Preferably, the substrate includes a TFT substrate.

[0067] Preferably, the materials of the first substrate and the second substrate include glass or sapphire.

[0068] As a preferred technical solution, the preparation method includes the following steps:

[0069] (1) Spin-coat a laser emitting material onto a first substrate and cure it at 100-300℃ for 5-10 min to obtain a laser emitting layer with a thickness of 100-1000 nm;

[0070] A temporary adhesive material is spin-coated onto the laser release layer and cured at 100-200℃ for 5-15 minutes to obtain a temporary adhesive layer with a thickness of 1-20μm.

[0071] An epitaxial wafer containing at least two LED chips is brought into contact with a temporary adhesive layer on a first substrate, and hot-pressed for 5-10 minutes under conditions of 120-180℃, 1-5kN pressure and ≤0.1mTorr vacuum to form a bonding pair.

[0072] (2) Irradiate the bonding pair under a laser with a wavelength of 200-400nm, peel off the epitaxial wafer, clean the LED chip with concentrated hydrochloric acid for 10-60s, and dry it at 50-70℃ to transfer the LED chip onto the first substrate.

[0073] (3) Spin-coating laser-induced release material onto the second substrate and curing it to obtain a laser-induced release layer with a thickness of 1-5 μm;

[0074] The LED chip in step (2) is brought into contact with the laser-induced release layer on the second substrate and bonded for 5-30 minutes under the conditions of temperature 20-30℃, pressure 1-3kN and vacuum degree ≤0.1mTorr;

[0075] (4) Wavelengths of 300-400 nm and energies of 100-300 mJ / cm 2 The laser passes through the first substrate, decomposes the laser release layer, peels off the first substrate, removes the adhesive, removes the temporary adhesive layer and part of the laser-induced release layer, so that the LED chips are distributed independently.

[0076] The specific method for removing the adhesive is as follows: under the conditions of an oxygen flow rate of 40-60 mL / min and a power of 1-3 kW, plasma treatment is carried out for 3-8 min to complete the first adhesive removal; then under the conditions of an oxygen flow rate of 40-60 mL / min, an argon flow rate of 100-200 mL / min and a power of 1-3 kW, plasma treatment is carried out for 5-20 min to complete the second adhesive removal.

[0077] (5) Using wavelengths of 300-500 nm and energies of 80-200 mJ / cm 2 The laser irradiates the remaining laser-induced release layer, and the corresponding LED chip falls onto the TFT substrate, completing the LED chip flipping.

[0078] Compared with the prior art, the present invention has the following beneficial effects:

[0079] (1) The mass transfer method described in this invention ensures high transfer accuracy, high efficiency, high yield, low process cost, and can realize laser sorting and release of different chips.

[0080] (2) In the application of Micro-LED, the mass transfer method described in this invention has a transfer accuracy within ±2.1μm and a product yield of over 60.3%. Attached Figure Description

[0081] Figure 1 This is a schematic diagram of the epitaxial wafer containing an LED chip described in step (1) of Example 1;

[0082] Figure 2 This is a schematic diagram of the bonding pair described in step (1) of Example 1;

[0083] Figure 3 This is a schematic diagram of the intermediate transition of the LED chip to the first substrate in step (2) of Embodiment 1;

[0084] Figure 4 This is a schematic diagram of the structure after the LED chip is transferred to the first substrate in step (2) of Embodiment 1;

[0085] Figure 5 This is a schematic diagram of the structure of the bonded component described in step (3) of Example 1;

[0086] Figure 6 This is a schematic diagram of step (4) of Example 1, which involves decomposing the laser-emitting layer.

[0087] Figure 7 This is a structural diagram of the component after step (4) of Example 1 is completed;

[0088] Figure 8 This is a schematic diagram of the LED chip falling onto the TFT substrate in step (5) of Example 1;

[0089] Among them, 1-LED chip; 2-epitaxy wafer; 3-temporary adhesive layer; 4-laser release layer; 5-first substrate; 6-laser induced release layer; 7-second substrate; 8-TFT substrate. Detailed Implementation

[0090] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0091] Example 1

[0092] This embodiment provides a mass transfer method, the flowchart of which is as follows: Figure 1-8 As shown, the mass transfer method includes the following steps:

[0093] (1) Laser emission material LB210 was spin-coated on the first substrate 5 (sapphire) and cured at 200°C for 5 min to obtain a laser emission layer 4 with a thickness of 300 nm.

[0094] Temporary adhesive material TB1238 was spin-coated onto the laser release layer and cured at 150°C for 5 min to obtain a temporary adhesive layer 3 with a thickness of 3 μm.

[0095] The epitaxial wafer 2 containing LED chip 1 (see structural diagram) Figure 1 (As shown) It contacts the temporary adhesive layer on the first substrate and is hot-pressed for 8 minutes under the conditions of temperature 150℃, pressure 3kN and vacuum degree ≤0.1mTorr to form a bond pair (structural schematic diagram as shown). Figure 2 (as shown);

[0096] (2) Irradiate the bonding pair with a laser of wavelength 248nm, as shown by the arrow. Peel off the epitaxial wafer (made of sapphire), then clean the LED chip with concentrated hydrochloric acid for 20s and dry it at 60°C, so that the LED chip is transferred onto the first substrate. The process is illustrated in the diagram below. Figure 3 As shown in the diagram, the structural schematic is as follows: Figure 4 As shown;

[0097] (3) Laser-induced release material LAP811 was spin-coated onto the second substrate 7 (sapphire) and cured to obtain a laser-induced release layer 6 with a thickness of 3 μm;

[0098] The LED chip from step (2) is brought into contact with the laser-induced release layer on the second substrate and bonded for 20 minutes under conditions of 100°C, 1 kN pressure, and ≤0.1 mTorr vacuum. The structural schematic diagram of the bonded component is shown below. Figure 5 As shown;

[0099] (4) A wavelength of 355 nm and an energy of 150 mJ / cm 2 The laser beam passes through the first substrate and decomposes the laser emission layer, as shown in the schematic diagram. Figure 6 As shown in the diagram, the direction of laser transmission is indicated by the arrow. After peeling off the first substrate, the adhesive is removed, and the temporary bonding layer and part of the laser-induced release layer are removed, allowing the LED chips to be distributed independently. A schematic diagram is shown below. Figure 7 As shown;

[0100] The specific method for removing the adhesive is as follows: under the conditions of an oxygen flow rate of 50 mL / min and a power of 2 kW, plasma treatment is carried out for 8 min to complete the first adhesive removal; then under the conditions of an oxygen flow rate of 50 mL / min, an argon flow rate of 150 mL / min and a power of 2 kW, plasma treatment is carried out for 15 min to complete the second adhesive removal.

[0101] (5) A wavelength of 355nm and an energy of 120mJ / cm were used. 2 The laser irradiates the remaining laser-induced release layer, causing the corresponding LED chip to fall onto the TFT substrate 8, as shown in the schematic diagram. Figure 8 As shown, the LED chip is flipped to achieve laser-induced sorting of Micro-LEDs.

[0102] Example 2

[0103] This embodiment provides a mass transfer method, which includes the following steps:

[0104] (1) A laser emitting material LB220 was spin-coated onto the first substrate glass and cured at 100°C for 10 min to obtain a laser emitting layer with a thickness of 1000 nm.

[0105] Temporary adhesive material TB4130 was spin-coated onto the laser release layer and cured at 100°C for 15 min to obtain a temporary adhesive layer with a thickness of 20 μm.

[0106] The epitaxial wafer containing the LED chip is brought into contact with a temporary adhesive layer on the first substrate, and hot-pressed for 10 minutes under the conditions of temperature 120℃, pressure 1kN and vacuum degree ≤0.1mTorr to form a bonding pair.

[0107] (2) Irradiate the bonding pair under a laser with a wavelength of 248nm, peel off the epitaxial wafer, clean the LED chip with concentrated hydrochloric acid for 10s, and dry it at 50°C to transfer the LED chip onto the first substrate.

[0108] (3) Laser-induced release material LAP810 was spin-coated onto the second substrate glass and cured to obtain a laser-induced release layer with a thickness of 5 μm;

[0109] The LED chip in step (2) is brought into contact with the laser-induced release layer on the second substrate and bonded for 10 min under the conditions of 60°C, 1kN pressure and ≤0.1mTorr vacuum.

[0110] (4) A wavelength of 308 nm and an energy of 200 mJ / cm 2 The laser passes through the first substrate, decomposes the laser release layer, peels off the first substrate, removes the adhesive, removes the temporary adhesive layer and part of the laser-induced release layer, so that the LED chips are distributed independently.

[0111] The specific method for removing the adhesive is as follows: under the conditions of an oxygen flow rate of 40 mL / min and a power of 3 kW, plasma treatment is performed for 3 min to complete the first adhesive removal; then under the conditions of an oxygen flow rate of 60 mL / min, an argon flow rate of 200 mL / min and a power of 1 kW, plasma treatment is performed for 10 min to complete the second adhesive removal.

[0112] (5) Using a wavelength of 355nm and an energy of 200mJ / cm 2 The laser irradiates the remaining laser-induced release layer, and the corresponding LED chip falls onto the TFT substrate, completing the LED chip flipping.

[0113] Example 3

[0114] This embodiment provides a mass transfer method, which includes the following steps:

[0115] (1) A laser emitting material LB210 was spin-coated on a first sapphire substrate and cured at 300°C for 5 min to obtain a laser emitting layer with a thickness of 100 nm.

[0116] Temporary adhesive material TB130 was spin-coated onto the laser release layer and cured at 200℃ for 5 min to obtain a temporary adhesive layer with a thickness of 12 μm.

[0117] The epitaxial wafer containing the LED chip is brought into contact with a temporary adhesive layer on the first substrate, and hot-pressed for 5 minutes under the conditions of temperature 180℃, pressure 5kN and vacuum degree ≤0.1mTorr to form a bonding pair.

[0118] (2) Irradiate the bonding pair under a laser with a wavelength of 248nm, peel off the epitaxial wafer, clean the LED chip with concentrated hydrochloric acid for 60s, and dry it at 70°C to transfer the LED chip onto the first substrate.

[0119] (3) Laser-induced release material LAP811 was spin-coated onto the second substrate glass and cured to obtain a laser-induced release layer with a thickness of 2 μm;

[0120] The LED chip in step (2) is brought into contact with the laser-induced release layer on the second substrate and bonded for 30 min under the conditions of temperature 30℃, pressure 3kN and vacuum degree ≤0.1mTorr;

[0121] (4) A wavelength of 308 nm and an energy of 100 mJ / cm 2 The laser passes through the first substrate, decomposes the laser release layer, peels off the first substrate, removes the adhesive, removes the temporary adhesive layer and part of the laser-induced release layer, and separates the LED chip.

[0122] The specific method for removing the adhesive is as follows: under the conditions of an oxygen flow rate of 60 mL / min and a power of 1 kW, plasma treatment is carried out for 8 min to complete the first adhesive removal; then under the conditions of an oxygen flow rate of 40 mL / min, an argon flow rate of 100 mL / min and a power of 3 kW, plasma treatment is carried out for 20 min to complete the second adhesive removal.

[0123] (5) A wavelength of 355nm and an energy of 80mJ / cm² were used. 2 The laser irradiates the remaining laser-induced release layer, and the corresponding LED chip falls onto the TFT substrate, completing the LED chip flipping.

[0124] Example 4

[0125] The difference between this embodiment and Embodiment 1 is that the thickness of the laser emission layer is 80nm, while the rest is the same as in Embodiment 1.

[0126] Example 5

[0127] The difference between this embodiment and Embodiment 1 is that the laser-induced release material is replaced by LAP810 instead of LAP811; otherwise, they are the same as in Embodiment 1.

[0128] Examples 6-7

[0129] The difference between Examples 6 and 7 and Example 1 is that the thickness of the laser-induced release layer is 0.5 μm (Example 6) and 5.5 μm (Example 7), respectively, while the rest is the same as Example 1.

[0130] Comparative Example 1

[0131] This comparative example provides a mass transfer method, which includes the following steps:

[0132] (1) Spin-coating UV-reducing adhesive onto a first sapphire substrate;

[0133] (2) The epitaxial wafer containing the LED chip is brought into contact with the UV anti-adhesion adhesive on the first substrate, and bonded for 5 minutes under the conditions of room temperature, pressure of 3kN and vacuum degree ≤0.1mTorr to form a bonding pair;

[0134] (3) Irradiate the bonding pair under a laser with a wavelength of 248nm, peel off the epitaxial wafer, clean the LED chip with concentrated hydrochloric acid for 60s, and dry it at 70°C to transfer the LED chip onto the first substrate.

[0135] (4) Spin-coat the laser-induced release material onto the second substrate glass and bond the LED chip from step (2) to the laser-induced release layer on the second substrate.

[0136] (5) Using 365nm at 300mw / cm 2 After the UV lamp irradiates the UV-reducing adhesive layer and the first substrate is peeled off, the LED chip transfer is achieved.

[0137] (6) A wavelength of 355nm and an energy of 80mJ / cm² were used. 2 The laser irradiates the remaining laser-induced release layer, and the corresponding LED chip falls onto the TFT substrate, completing the LED chip flipping.

[0138] Performance testing

[0139] The following statistics were performed on the Micro-LEDs processed by the mass transfer method described in Examples 1-7 and Comparative Example 1:

[0140] The test results are summarized in Table 1.

[0141] Table 1

[0142] Transfer accuracy (μm) Product yield (%) Example 1 0.95 98.3 Example 2 1.5 96.2 Example 3 1.2 97.6 Example 4 1.2 81.3 Example 5 0.8 95.4 Example 6 1.2 60.3 Example 7 2.1 96.5 Comparative Example 1 ＞2 30～40％

[0143] Analysis of the data in Table 1 shows that the mass transfer method described in this invention achieves a transfer accuracy within 2.1 μm and a product yield of over 60.3% in Micro-LED applications. The mass transfer method described in this invention ensures high transfer accuracy, high efficiency, high yield, and low process cost.

[0144] Analysis of Comparative Example 1 and Example 1 shows that the performance of Comparative Example 1 is not as good as that of Example 1, proving that the mass transfer method described in this invention is superior to the methods of the prior art.

[0145] Analysis of Example 4 and Example 1 shows that the performance of Example 4 is not as good as that of Example 1, which proves that the thickness of the laser release layer is too thin. Some chip surfaces have traces of laser ablation, resulting in poor yield of transferred chips. Controlling the thickness within the range of 300-1000nm can prevent laser energy from passing through the laser release material.

[0146] Analysis of Example 5 and Example 1 shows that the performance of Example 5 is inferior to that of Example 1, proving that the material of the laser-induced release layer is preferred. The WLP LAP810 is more conducive to mass transfer processes.

[0147] Analysis of Examples 6-7 and Example 1 shows that the performance of Examples 6-7 is not as good as that of Example 1, proving that the thickness of the laser-induced release layer has a great influence on the transfer yield. If the thickness is too thin, bubbles will be generated after bonding and poor bonding will occur in some areas; if the thickness is too thick, chip misalignment will be easily caused. Therefore, a thickness of 1-5 μm is more conducive to the mass transfer process.

[0148] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A mass transfer method, characterized in that, The mass transfer method includes the following steps: (1) An epitaxial wafer containing at least two LED chips is bonded to a first substrate to form a bonding pair. A laser emission layer and a temporary adhesive layer are sequentially disposed on the surface of the first substrate from the inside to the outside. (2) Irradiate the bonding pair under laser light, peel off the epitaxial wafer, and transfer the LED chip onto the first substrate; (3) Bond the LED chip from step (2) to the second substrate having the laser-induced release layer, wherein the LED chip is in contact with the laser-induced release layer; (4) Pass the laser through the first substrate to decompose the laser release layer, peel off the first substrate and remove the adhesive, remove the temporary adhesive layer and part of the laser-induced release layer, so that the LED chips are distributed independently. (5) The remaining part of the laser-induced release layer is irradiated by laser, and the corresponding LED chip falls to the substrate, completing the flipping of the LED chip; The thickness of the laser emission layer is 100-1000 nm; In step (3), the thickness of the laser-induced release layer is 1-5 μm; The laser-induced release layer is made of triazine polymer.

2. The mass transfer method according to claim 1, characterized in that, In step (1), the bonding method includes hot-press bonding.

3. The mass transfer method according to claim 2, characterized in that, The temperature for hot-press bonding is 120-180℃.

4. The mass transfer method according to claim 2, characterized in that, The hot-press bonding time is 5-10 minutes.

5. The mass transfer method according to claim 2, characterized in that, The pressure for hot-press bonding is 1-5 kN.

6. The mass transfer method according to claim 2, characterized in that, The vacuum degree of the thermo-pressed bonding is ≤0.1 mTorr.

7. The mass transfer method according to claim 1, characterized in that, In the bonding pair, the LED chip is in contact with the temporary adhesive layer.

8. The mass transfer method according to claim 1, characterized in that, The LED chip includes a Micro-LED chip.

9. The mass transfer method according to claim 1, characterized in that, The laser-emitting layer is made of UV-responsive polyimide.

10. The mass transfer method according to claim 1, characterized in that, The thickness of the temporary adhesive layer is 1-20 μm.

11. The mass transfer method according to claim 1, characterized in that, The temporary adhesive layer is made of olefin polymers.

12. The mass transfer method according to claim 1, characterized in that, The method for preparing the laser emission layer includes the following steps: A laser-emitting material is coated onto a first substrate and cured to obtain the laser-emitting layer.

13. The mass transfer method according to claim 12, characterized in that, The coating method includes spin coating.

14. The mass transfer method according to claim 12, characterized in that, The curing temperature is 100-300℃, and the curing time is 5-10 min.

15. The mass transfer method according to claim 1, characterized in that, The method for preparing the temporary adhesive layer includes the following steps: A temporary adhesive material is coated onto the laser release layer and cured to obtain the temporary adhesive layer.

16. The mass transfer method according to claim 15, characterized in that, The coating method includes spin coating.

17. The mass transfer method according to claim 15, characterized in that, The curing temperature is 100-200℃, and the curing time is 5-15 min.

18. The mass transfer method according to claim 1, characterized in that, In step (2), the wavelength of the laser is 200-400 nm.

19. The mass transfer method according to claim 1, characterized in that, After the epitaxial wafer is stripped, the LED chip is also cleaned and dried.

20. The mass transfer method according to claim 19, characterized in that, The cleaning solvent includes concentrated hydrochloric acid, wherein the mass percentage of hydrogen chloride in the concentrated hydrochloric acid is more than 20%.

21. The mass transfer method according to claim 19, characterized in that, The cleaning time is 10-60 seconds.

22. The mass transfer method according to claim 19, characterized in that, The drying temperature is 50-70℃.

23. The mass transfer method according to claim 1, characterized in that, In step (3), the bonding temperature is 20-30℃.

24. The mass transfer method according to claim 23, characterized in that, The bonding pressure is 1-3 kN.

25. The mass transfer method according to claim 23, characterized in that, The bonding time is 5-30 min.

26. The mass transfer method according to claim 23, characterized in that, The vacuum degree of the bonding is ≤0.1mTorr.

27. The mass transfer method according to claim 1, characterized in that, In step (4), the wavelength of the laser is 300-400 nm.

28. The mass transfer method according to claim 27, characterized in that, The energy of the laser is 100-300 mJ / cm². 2 .

29. The mass transfer method according to claim 1, characterized in that, In step (4), the adhesive removal method includes plasma adhesive removal.

30. The mass transfer method according to claim 29, characterized in that, The adhesive removal process includes the following steps: First, the adhesive is removed in an oxygen atmosphere, and then a second removal is performed in an oxygen and argon atmosphere.

31. The mass transfer method according to claim 30, characterized in that, In the first degumming process, the oxygen flow rate is 40-60 mL / min, the power is 1-3 kW, and the time is 3-8 min.

32. The mass transfer method according to claim 30, characterized in that, In the second degumming process, the oxygen flow rate is 40-60 mL / min, the argon flow rate is 100-200 mL / min, the power is 1-3 kW, and the time is 5-20 min.

33. The mass transfer method according to claim 1, characterized in that, In step (5), the wavelength of the laser is 300-400 nm.

34. The mass transfer method according to claim 33, characterized in that, The energy of the laser is 80-200 mJ / cm². 2 .

35. The mass transfer method according to claim 1, characterized in that, The substrate includes a TFT substrate.

36. The mass transfer method according to claim 1, characterized in that, The first and second substrates are made of materials including glass or sapphire.

37. The mass transfer method according to claim 1, characterized in that, The mass transfer method includes the following steps: (1) Spin-coating laser emitting material onto the first substrate and curing it at 100-300℃ for 5-10 min to obtain a laser emitting layer with a thickness of 100-1000 nm; A temporary adhesive material is spin-coated onto the laser release layer and cured at 100-200℃ for 5-15 min to obtain a temporary adhesive layer with a thickness of 1-20 μm. An epitaxial wafer containing at least two LED chips is brought into contact with a temporary adhesive layer on a first substrate, and hot-pressed for 5-10 minutes under conditions of 120-180℃, 1-5 kN, and ≤0.1 mTorr to form a bonding pair. (2) Irradiate the bonding pair under a laser with a wavelength of 200-400 nm, peel off the epitaxial wafer, clean the LED chip with concentrated hydrochloric acid for 10-60 s, and dry it at 50-70℃ to transfer the LED chip onto the first substrate; (3) Spin-coating laser-induced release material onto the second substrate and curing it to obtain a laser-induced release layer with a thickness of 1-5 μm; The LED chip in step (2) is brought into contact with the laser-induced release layer on the second substrate and bonded for 5-30 min under the conditions of temperature 20-30℃, pressure 1-3 kN and vacuum degree ≤0.1 mTorr; (4) Wavelengths of 300-400 nm and energies of 100-300 mJ / cm 2 The laser passes through the first substrate, decomposes the laser release layer, peels off the first substrate, removes the adhesive, removes the temporary adhesive layer and part of the laser-induced release layer, so that the LED chips are distributed independently. The specific method for removing the adhesive is as follows: under the conditions of an oxygen flow rate of 40-60 mL / min and a power of 1-3 kW, plasma treatment is performed for 3-8 min to complete the first adhesive removal; then under the conditions of an oxygen flow rate of 40-60 mL / min, an argon flow rate of 100-200 mL / min and a power of 1-3 kW, plasma treatment is performed for 5-20 min to complete the second adhesive removal. (5) Use wavelengths of 300-500 nm and energies of 80-200 mJ / cm 2 The laser irradiates the remaining laser-induced release layer, and the corresponding LED chip falls onto the TFT substrate, completing the LED chip flipping.

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