Carrier film and method of making same

Abstract

The present disclosure provides a kind of bearing adhesive film and its preparation method, belong to the field of optoelectronic manufacturing technology.The bearing adhesive film includes adhesive material layer, the surface of the adhesive material layer is modified surface, the viscosity of the surface layer area of the adhesive material layer close to the modified surface is higher than the viscosity of the internal area of the adhesive material layer away from the modified surface.The present disclosure can improve the problem that PDMS glue is difficult to meet the contradictory demand of high viscosity and high elasticity simultaneously.

Description

Technical Field

[0001] This disclosure relates to the field of optoelectronic manufacturing technology, and in particular to a carrier adhesive film and its preparation method. Background Technology

[0002] In the mass transfer of Micro LEDs, the carrier film (e.g., PDMS) is a core component ensuring the integrity and accuracy of chip transfer. Typically, the carrier film needs to have high viscosity to ensure that the chip, after laser dissociation, is quickly adsorbed and fixed on the surface of the carrier film as it falls from the wafer, preventing chip slippage and displacement. Simultaneously, the carrier film must also have high elasticity to cushion the impact energy of the falling chip, preventing chip chipping, cracking, electrode damage, and other problems caused by impact, thus ensuring chip integrity and improving transfer yield.

[0003] In related technologies, increasing the surface viscosity of PDMS adhesives often requires modification or adjustment of curing conditions. However, modification increases raw material costs and process complexity, while adjusting curing conditions sacrifices the elasticity of the adhesive. Therefore, PDMS adhesives cannot simultaneously meet the contradictory requirements of high viscosity and high elasticity. Summary of the Invention

[0004] This disclosure provides a carrier adhesive film and its preparation method, which can improve the problem that PDMS adhesive cannot simultaneously meet the contradictory requirements of high viscosity and high elasticity. The technical solution is as follows: This disclosure provides a carrier adhesive film, which includes an adhesive layer. One surface of the adhesive layer is a modified surface, and the viscosity of the surface region of the adhesive layer near the modified surface is higher than the viscosity of the inner region of the adhesive layer away from the modified surface.

[0005] In another implementation of the present disclosure, the ratio of the thickness of the surface region of the adhesive layer near the modified surface to the thickness of the adhesive layer is less than or equal to 1:5.

[0006] In another implementation of the present disclosure, the viscosity of the surface region of the adhesive layer near the modified surface is greater than or equal to 11000 mPa·s, and the elastic modulus of the inner region of the adhesive layer away from the modified surface is 1 MPa to 1.6 MPa.

[0007] In another implementation of the present disclosure, the adhesive layer includes a PDMS layer, and the mass ratio of the main agent to the curing agent in the adhesive layer is greater than or equal to 10:1.

[0008] This disclosure provides a method for preparing a carrier adhesive film, the method comprising: forming an adhesive layer on a substrate; and modifying the surface of the adhesive layer away from the substrate to form a modified surface, wherein the viscosity of the surface region of the adhesive layer near the modified surface is higher than the viscosity of the inner region of the adhesive layer away from the modified surface.

[0009] In another implementation of the present disclosure, modifying the surface of the adhesive layer away from the substrate to form a modified surface includes: subjecting the surface of the adhesive layer to plasma bombardment treatment to form the modified surface.

[0010] In another implementation of this disclosure, plasma bombardment treatment of the surface of the adhesive layer includes: placing the adhesive layer in a chamber, controlling the vacuum degree of the chamber to be 0.1 Pa to 10 Pa, introducing a mixture of oxygen and argon into the chamber, with the volume ratio of oxygen to argon being 1:3 to 1:5; adjusting the plasma generation power to 50 W to 150 W, controlling the distance between the surface of the adhesive layer and the plasma discharge region to be 5 mm to 15 mm, and performing plasma bombardment treatment on the surface of the adhesive layer for 30 s to 120 s to complete the surface activation modification of the adhesive layer.

[0011] In another implementation of the present disclosure, plasma bombardment treatment of the surface of the adhesive layer includes: plasma bombardment treatment of the surface of the adhesive layer, such that the plasma bombardment acts on the adhesive layer to a depth of 0.1 μm to 1 μm.

[0012] In another implementation of the present disclosure, modifying the surface of the adhesive layer away from the substrate to form a modified surface includes: etching the surface of the adhesive layer with a chemical etchant to break the molecular chains on the surface of the adhesive layer, thereby forming a modified surface on the surface of the adhesive layer.

[0013] In another implementation of the present disclosure, modifying the surface of the adhesive layer away from the substrate to form a modified surface includes: forming a photosensitizer layer on the surface of the adhesive layer away from the substrate; exposing the photosensitizer layer to cause a crosslinking reaction in the interface region where the adhesive layer and the photosensitizer layer are in contact, thereby forming a modified surface on the surface of the adhesive layer; and removing the photosensitizer layer.

[0014] The beneficial effects of the technical solutions provided in this disclosure include at least the following: The carrier adhesive film provided in this embodiment optimizes performance by creating a modified surface on the adhesive layer, resulting in a higher viscosity in the surface region near the modified surface compared to the internal region. The modified surface layer exhibits a change in molecular structure and a significant increase in surface viscosity, enabling rapid adsorption of the core particles falling after laser dissociation, effectively preventing slippage or displacement and ensuring precise positioning. Meanwhile, the unmodified internal region of the adhesive layer retains its high elasticity after complete curing, effectively buffering the impact kinetic energy of the falling core particles and reducing the core particle damage rate by more than 80%. This fundamentally solves the technical bottleneck of the inability to simultaneously achieve both viscosity and elasticity, while also avoiding the risk of delamination and detachment.

[0015] Meanwhile, compared to the two-stage spin coating and curing process, the present invention can achieve complete curing after a single spin coating and then modify the surface. This not only reduces one spin coating and curing operation, shortening the process steps, reducing operational complexity and production time, but also eliminates the need to add any modifiers. Viscosity can be increased simply through surface modification, thereby reducing raw material costs and lowering the cost of large-scale mass production. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a carrier adhesive film provided in an embodiment of this disclosure; Figure 2 This is a flowchart of a method for preparing a carrier adhesive film according to an embodiment of this disclosure.

[0018] The markings in the diagram are explained as follows: 10. Adhesive layer; 11. Surface area; 20. Modified surface. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0020] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” “top,” and “bottom,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0021] Figure 1 This is a schematic diagram of a carrier adhesive film provided in an embodiment of this disclosure. Figure 1 As shown, the carrier adhesive film includes an adhesive layer 10, one surface of which is a modified surface 20. The viscosity of the surface region 11 of the adhesive layer 10 near the modified surface 20 is higher than the viscosity of the inner region of the adhesive layer 10 away from the modified surface 20.

[0022] The carrier adhesive film provided in this embodiment optimizes performance by providing a modified surface 20 on the surface of the adhesive layer 10, making the viscosity of the surface region 11 of the adhesive layer 10 near the modified surface 20 higher than that of the internal region. The modified surface molecular structure changes, and the surface viscosity is significantly increased, enabling rapid adsorption of the core particles falling after laser dissociation, effectively preventing them from sliding or shifting and ensuring accurate positioning. Meanwhile, the internal region of the unmodified adhesive layer 10 retains the high elasticity after complete curing, effectively buffering the impact kinetic energy of the falling core particles and reducing the core particle damage rate by more than 80%. This fundamentally solves the technical bottleneck of the inability to simultaneously achieve both viscosity and elasticity, while avoiding the risk of delamination and detachment.

[0023] Meanwhile, compared to the two-stage spin coating and curing process, the present invention can achieve complete curing after a single spin coating and then modify the surface. This not only reduces one spin coating and curing operation, shortening the process steps, reducing operational complexity and production time, but also eliminates the need to add any modifiers. Viscosity can be increased simply through surface modification, thereby reducing raw material costs and lowering the cost of large-scale mass production.

[0024] Optionally, the ratio of the thickness of the surface region 11 of the adhesive layer 10 near the modified surface 20 to the thickness of the adhesive layer 10 is less than or equal to 1:5.

[0025] For example, the thickness of the surface region 11 of the adhesive layer 10 near the modified surface 20 is 0.1 μm to 1 μm, and the thickness of the adhesive layer 10 is 5 μm to 20 μm.

[0026] In the above implementation method, only the surface region 11, which accounts for only 5% to 20% of the thickness, needs to be modified to obtain a sufficiently high surface viscosity. This allows for the rapid adsorption of Micro LED chips falling after laser dissociation, preventing them from sliding or shifting on the adhesive film surface and ensuring the accuracy of transfer positioning. Meanwhile, the unmodified internal region, which accounts for 80% to 95%, retains its original high elasticity after complete curing. This effectively buffers the impact kinetic energy during chip falling, reducing the incidence of chip chip chipping, cracking, and electrode damage by more than 80%, thus significantly improving the transfer yield while ensuring chip integrity.

[0027] Secondly, this thin-layer modification design significantly reduces process complexity and production costs. Compared to the traditional process that requires two spin coats and staged curing, the embodiments disclosed herein employ a single spin coat and complete overall curing before surface modification, reducing one spin coat and curing operation. This significantly shortens the process steps, reducing operational complexity and production time, and also avoiding the risk of delamination and peeling between different adhesive layers due to performance differences during the two spin coat processes.

[0028] Optionally, the viscosity of the surface region 11 of the adhesive layer 10 near the modified surface 20 is greater than or equal to 11000 mPa·s, and the elastic modulus of the inner region of the adhesive layer 10 away from the modified surface 20 is 1 MPa to 1.6 MPa.

[0029] In this embodiment, the high viscosity design of the surface region 11 of the adhesive layer 10 (≥11000 mPa·s) fully meets the adsorption and fixation requirements of Micro LED chips after laser dissociation. The high viscosity surface can quickly generate sufficient van der Waals forces to adsorb the chips, preventing them from sliding or shifting on the adhesive film surface, ensuring transfer positioning accuracy, and adapting to the micron-level alignment requirements of mass transfer.

[0030] The elastic modulus of the internal region is between 1 MPa and 1.6 MPa. This modulus range provides sufficient deformation capacity to absorb the impact kinetic energy of the falling core through its own compression deformation, reducing the incidence of problems such as core chipping, cracking, and electrode damage. At the same time, it will not cause the entire film to collapse due to excessive elasticity, thus avoiding the core from sinking too deep into the adhesive layer and affecting the subsequent pickup and transfer efficiency.

[0031] Optionally, the adhesive layer 10 includes a PDMS layer, and the mass ratio of the main agent to the curing agent in the adhesive layer 10 is greater than or equal to 10:1.

[0032] When the ratio of main agent to curing agent exceeds 10:1, the internal crosslinking density of PDMS is moderate, and the elastic modulus can be stably controlled within a buffer zone of 1 MPa to 1.6 MPa. This allows for sufficient absorption of the impact kinetic energy when Micro LED chips fall, reducing the incidence of problems such as chip chip breakage, cracking, and electrode damage. If the proportion of curing agent is higher, the material will become too hard and brittle, losing its buffering capacity and increasing the risk of process brittleness.

[0033] Figure 2 This is a flowchart illustrating a method for preparing a carrier adhesive film according to an embodiment of this disclosure. Figure 2 As shown, the preparation method includes: Step S11: Form an adhesive layer 10 on the substrate.

[0034] Step S12: Modify the surface of the adhesive layer 10 away from the substrate to form a modified surface 20.

[0035] The viscosity of the surface region 11 of the adhesive layer 10 near the modified surface 20 is higher than the viscosity of the inner region of the adhesive layer 10 away from the modified surface 20.

[0036] The method for preparing the carrier adhesive film provided in this embodiment modifies the surface of the adhesive layer 10 to form a modified surface 20, making the viscosity of the surface region 11 of the adhesive layer 10 near the modified surface 20 higher than that of the internal region, thereby optimizing performance. The surface molecular structure changes after modification, and the surface viscosity is significantly increased, which can quickly adsorb the core particles falling after laser dissociation, effectively preventing them from sliding or shifting and ensuring accurate positioning; while the internal region of the unmodified adhesive layer 10 still maintains the high elasticity after complete curing, which can effectively buffer the impact kinetic energy when the core particles fall, reducing the core particle damage rate by more than 80%, fundamentally solving the technical bottleneck of not being able to balance viscosity and elasticity, and avoiding the risk of delamination and peeling.

[0037] Meanwhile, compared to the two-stage spin coating and curing process, the present invention can achieve complete curing after a single spin coating and then modify the surface. This not only reduces one spin coating and curing operation, shortening the process steps, reducing operational complexity and production time, but also eliminates the need to add any modifiers. Viscosity can be increased simply through surface modification, thereby reducing raw material costs and lowering the cost of large-scale mass production.

[0038] Step S11 may include the following steps: The first step is to determine the materials of the adhesive layer 10 and the substrate.

[0039] For example, PDMS adhesive is selected, and the mass ratio of the main agent to the curing agent of PDMS adhesive is controlled to be 10:1.

[0040] The initial temperature of the PDMS adhesive is 25℃, and the initial viscosity is 1000-2000 cSt. This viscosity range is suitable for the centrifugal spreading requirements of the spin coating process. It will not cause excessive splashing of the adhesive or excessively thin film thickness during spin coating due to too low viscosity, nor will it cause uneven spreading of the adhesive or pinhole defects due to too high viscosity.

[0041] For example, an ultra-smooth glass or silicon substrate is selected with a surface roughness Ra≤0.2nm to ensure that there are no microscopic protrusions at the contact surface between the adhesive layer and the substrate, thus avoiding uneven adhesive film thickness; the total thickness variation (TTV) is ≤10μm to ensure the overall flatness of the substrate and prevent excessive film thickness deviation between the edge and the center due to substrate warping during the homogenization process.

[0042] The second step is substrate pretreatment.

[0043] First, a three-step cleaning method using acetone, isopropanol, and deionized water, combined with ultrasonic vibration, is employed to remove surface particles, grease, and organic residues, ultimately achieving a Class 1 cleanliness level (i.e., no visible contaminants on the surface and a particle density ≤ 1 particle / cm³). 2 This prevents impurities from becoming the source of adhesive layer delamination and bubble formation, ensuring the uniformity of the adhesive film.

[0044] Then, an amino or epoxy silane coupling agent is selected to form a monolayer on the substrate surface by dip coating or spin coating. The functional groups at both ends of the agent can form chemical bonds with the hydroxyl groups on the substrate surface and the siloxane chains of PDMS, respectively, which greatly improves the interfacial adhesion between the substrate and PDMS and avoids the problem of edge lifting and overall peeling due to the stress of the adhesive layer in subsequent processes.

[0045] The third step is to apply the adhesive evenly in a single pass and allow it to fully cure.

[0046] First, the mixed and degassed PDMS adhesive solution is dropped onto the center of the substrate, and a spin coater with dual-stage speed control is used. First, the spin coater rotates at a low speed of 500 rpm to 800 rpm for 5 to 10 seconds to pre-spread the adhesive solution, avoiding splashing caused by high-speed rotation. Then, the speed is increased to 1000 rpm to 1800 rpm for 20 to 40 seconds. Utilizing the dynamic balance between centrifugal force and adhesive viscosity, a uniform adhesive film with a thickness of 5 μm to 20 μm is formed, with a film thickness uniformity of ±3%. This process eliminates the need for layering adhesives of different viscosities, reducing the steps of spin coater and pre-curing, shortening the process, and avoiding interlayer interface defects and delamination risks that may occur with layered structures.

[0047] Then, the substrate after homogenization is placed in a constant temperature curing oven and cured at 120°C to 160°C for 25 to 50 minutes. This temperature range is higher than the complete curing threshold of PDMS, which can ensure that the PDMS crosslinking reaction is fully carried out.

[0048] After curing, PDMS exhibits a uniform and highly elastic state, with an elastic modulus stable between 1.0 MPa and 1.6 MPa. This modulus range can effectively buffer the impact kinetic energy when Micro LED chips fall, reducing the damage rate of chip chip chipping, cracking, etc. At this time, the overall viscosity is 6000 mPa·s to 9000 mPa·s, which is lower than the 11000 mPa·s requirement after surface modification. However, this lays the foundation for subsequent modification of only the surface 0.1 μm to 1 μm area to increase the surface viscosity to ≥11000 mPa·s, without the need to adjust the curing conditions to increase the overall viscosity.

[0049] In this embodiment of the disclosure, step S12 may include various implementation methods.

[0050] In one implementation, step S12 includes: subjecting the surface of the adhesive layer 10 to plasma bombardment treatment to form a modified surface 20.

[0051] Optionally, plasma bombardment treatment of the surface of the adhesive layer 10 includes: The first step is to place the adhesive layer 10 in the chamber, control the vacuum degree of the chamber to be 0.1 Pa to 10 Pa, and introduce a mixture of oxygen and argon into the chamber, with the volume ratio of oxygen to argon being 1:3 to 1:5.

[0052] Specifically, this may include: fixing the substrate horizontally on the sample stage inside the plasma chamber, and adjusting the vertical distance between the surface of the adhesive layer 10 and the plasma discharge region to 5 mm to 15 mm.

[0053] The vertical distance between the surface of the adhesive layer 10 and the plasma discharge area is within the above-mentioned range, which ensures that the plasma active particles can fully reach the adhesive surface, while avoiding excessive local energy and microcracks caused by excessive etching of the adhesive surface due to the distance being too close.

[0054] Next, after closing the chamber door, start the vacuum system to control the vacuum level in the chamber within a low-pressure range of 0.1 Pa to 10 Pa.

[0055] A low-pressure environment reduces the probability of collisions between gas molecules and plasma particles, increases the mean free path of active particles, and ensures that the plasma can act uniformly on the entire surface of the adhesive material.

[0056] Subsequently, a mixture of oxygen and argon is introduced into the chamber, with the volume ratio of the two controlled to be 1:3 to 1:5. Oxygen, as a reactive gas, has high-energy ions that can break the CH bonds on the PDMS surface through chemical reactions, introducing oxygen-containing functional groups. Argon, as an inert gas, has ions that can remove organic contaminants from the surface and increase surface roughness through physical bombardment, while avoiding excessive oxidation of the PDMS surface by a single oxygen plasma, which could lead to cracking.

[0057] The total flow rate of the mixed gas is controlled between 20 sccm and 40 sccm, and the pressure in the chamber is kept stable between 0.3 Torr and 1 Torr.

[0058] The second step involves adjusting the plasma generation power to 50W to 150W, controlling the distance between the surface of the adhesive layer 10 and the plasma discharge region to 5mm to 15mm, and subjecting the surface of the adhesive layer 10 to plasma bombardment treatment for 30s to 120s to complete the surface activation modification of the adhesive layer 10.

[0059] Optionally, plasma bombardment treatment of the surface of the adhesive layer 10 includes: plasma bombardment treatment of the surface of the adhesive layer 10, such that the plasma bombardment acts on the adhesive layer 10 to a depth of 0.1 μm to 1 μm.

[0060] Specifically, this may include: starting the plasma generator and adjusting the discharge power to the range of 50W to 150W. The particle energy corresponding to this power range is 0eV to 20eV, which is just higher than the molecular bond energy of PDMS. This can break the surface molecular chains but will not destroy the internal cross-linked structure.

[0061] For example, the bombardment treatment time is controlled between 30s and 120s. If the time is too short, the surface functional groups will not be introduced sufficiently and the viscosity will be limited. If the time is too long, the PDMS surface will be over-etched and low molecular weight molecules will migrate to the surface, which will reduce the modification effect and even cause the adhesive layer to crack.

[0062] During the bombardment process, high-energy ions only act on the surface region 11 of the adhesive layer 10, which is 0.1 μm to 1 μm deep. This depth is only 2% to 20% of the total thickness of the adhesive (5 μm to 20 μm), ensuring that the unbombarded internal region (accounting for 80% to 98%) completely retains the original cross-linked structure after full curing, and the elastic modulus remains unchanged. After the bombardment is completed, the plasma power supply is turned off, and the substrate is removed after the chamber cools to room temperature.

[0063] In this embodiment of the disclosure, three sets of process parameters can be selected based on the different core particle size and laser dissociation kinetic energy.

[0064] The first group is suitable for small-sized core particles (<50μm), using 50W power and 30s processing time. The surface viscosity can reach 11000mPa·s, and the bottom elastic modulus is maintained at 1.0MPa, taking into account both adsorption force and buffering capacity.

[0065] The second group is suitable for standard-sized core particles (50μm to 100μm), using 100W power and 60s processing time, increasing the surface viscosity to 14000mPa·s and the bottom elastic modulus to 1.3MPa.

[0066] The third group is suitable for large-size, high-energy core particles (>100μm), using 150W power and 120s processing time, with a surface viscosity of 16000mPa·s and a bottom elastic modulus of 1.6MPa, which can withstand higher impact kinetic energy and significantly reduce core particle damage rate.

[0067] In another implementation, step S12 includes: etching the surface of the adhesive layer 10 with a chemical etchant to break the molecular chains on the surface of the adhesive layer 10, thereby forming a modified surface 20 on the surface of the adhesive layer 10.

[0068] Specifically, this may include: First, wiping the surface of the adhesive layer 10 with isopropanol and rinsing with deionized water to remove surface dust, mold release agents and other contaminants, so as to avoid uneven local modification caused by contaminants during the etching process and ensure the consistency of surface viscosity after etching.

[0069] Then, the pretreated PDMS adhesive is immersed in a prepared fluoride etchant solution (such as a mixture of hydrofluoric acid and ammonium fluoride).

[0070] For example, the etching temperature is maintained at 25°C to 40°C, without the need for additional heating equipment.

[0071] For example, the etching time is controlled between 10s and 30s. If the time is too short, the surface molecular chains will not be broken enough, and the viscosity will be limited. If the time is too long, the etching depth will exceed 1μm, which will destroy the overall structure of the adhesive layer and reduce the proportion of the internal high elastic area.

[0072] During the etching process, fluoride ions directionally break the Si-O-Si molecular chains on the PDMS surface, removing low molecular weight components from the surface layer. At the same time, they increase the surface roughness and the density of active functional groups, raising the surface viscosity to ≥11000 mPa·s. This allows for the rapid adsorption of Micro LED chips that fall after laser dissociation. Meanwhile, the bottom of the unetched adhesive layer does not come into contact with the etchant and retains its original high elasticity after complete curing. The elastic modulus remains stable in the range of 1.0 MPa to 1.6 MPa, effectively buffering the kinetic energy of chip collisions.

[0073] After etching, the substrate is removed and subjected to three steps: rinsing with deionized water, ultrasonic cleaning with isopropanol, and drying with nitrogen to remove residual fluoride etchant from the surface. Therefore, it usually requires 2 to 3 cycles of cleaning to ensure that there is no etchant residue on the surface. After cleaning, the core transfer process must be carried out within 1 hour to avoid the PDMS surface hydrophobicity recovery leading to a decrease in viscosity.

[0074] In another implementation, step S12 includes the following steps: The first step is to form a photosensitive layer on the surface of the adhesive layer 10 that is away from the substrate.

[0075] Specifically, this may include: applying a UV photosensitive agent layer of uniform thickness to the surface of the fully cured PDMS adhesive layer 10 using a spin coating or dip coating process.

[0076] For example, the photosensitizer should be an acrylate or epoxy UV resin system that is compatible with PDMS and has high photoreactivity, to ensure that the photosensitizer can uniformly wet the PDMS surface and form a continuous film without pinholes or bubbles.

[0077] After coating, place the substrate in an oven at 80°C to 120°C for 5 to 30 minutes to allow the photosensitive layer to dry initially and stabilize its viscosity, thus preventing uneven thickness caused by the flow of the photosensitive layer during subsequent exposure. The thickness of the dried photosensitive layer should be controlled within the range of 0.05 mm to 0.10 mm.

[0078] The second step is to expose the photosensitive layer to cause a cross-linking reaction at the interface between the adhesive layer 10 and the photosensitive layer, so as to form a modified surface 20 on the surface of the adhesive layer 10.

[0079] Specifically, this may include: placing the dried substrate into an exposure machine, controlling the vacuum level to >0.08MPa to ensure close contact between the photosensitive layer and the PDMS surface, reducing uneven modification caused by light scattering. Exposure is performed using a 365nm ultraviolet light source, with the exposure energy controlled at 100mJ / cm². 2 Up to 300mJ / cm 2 The exposure time is 2 to 10 seconds. This wavelength is the absorption peak of the UV photosensitive agent, with energy below 100 mJ / cm². 2 At this time, the cross-linking reaction of the photosensitizer is insufficient, and it cannot form enough chemical bonds with the PDMS surface molecules, resulting in limited improvement in surface viscosity; the energy is higher than 300 mJ / cm 2 This may lead to excessive aging of the PDMS surface and the appearance of microcracks.

[0080] During the exposure process, the photosensitizer absorbs ultraviolet light energy and undergoes a photopolymerization reaction. The active groups form a cross-linked network with the siloxane molecules on the surface of PDMS, which changes the molecular structure of the interface region (depth 0.1μm to 1μm) where PDMS and photosensitizer are in contact. The surface viscosity can be increased to more than 20,000 mPa·s, which is much higher than the upper limit of 16,000 mPa·s for plasma modification. This enables the rapid adsorption of large-size, high-kinetic-energy Micro LED chips, preventing them from sliding or shifting and ensuring transfer and positioning accuracy.

[0081] The third step is to remove the photosensitizer layer.

[0082] After exposure, the substrate is immersed in alkaline developer for 10 to 15 seconds. Uncrosslinked photosensitizers are dissolved and removed by the developer, leaving only the modified layer that has undergone crosslinking reaction with the PDMS surface. The substrate surface is then rinsed with deionized water to remove residual developer and photosensitizer fragments, ensuring that no photosensitizer remains.

[0083] The above is not intended to limit this disclosure in any way. Although this disclosure has been disclosed above through embodiments, it is not intended to limit this disclosure. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this disclosure. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this disclosure without departing from the content of the technical solution of this disclosure shall still fall within the scope of the technical solution of this disclosure.

Claims

1. A carrier adhesive film, characterized in that, The carrier adhesive film includes an adhesive layer (10), one surface of which is a modified surface (20). The viscosity of the surface region (11) of the adhesive layer (10) near the modified surface (20) is higher than the viscosity of the inner region of the adhesive layer (10) away from the modified surface (20).

2. The carrier adhesive film according to claim 1, characterized in that, The ratio of the thickness of the surface region (11) of the adhesive layer (10) near the modified surface (20) to the thickness of the adhesive layer (10) is less than or equal to 1:

5.

3. The carrier adhesive film according to claim 1, characterized in that, The viscosity of the surface region (11) of the adhesive layer (10) near the modified surface (20) is greater than or equal to 11000 mPa·s, and the elastic modulus of the inner region of the adhesive layer (10) away from the modified surface (20) is 1 MPa to 1.6 MPa.

4. The carrier adhesive film according to any one of claims 1 to 3, characterized in that, The adhesive layer (10) includes a PDMS layer, and the mass ratio of the main agent to the curing agent in the adhesive layer (10) is greater than or equal to 10:

1.

5. A method for preparing a carrier adhesive film, characterized in that, The preparation method includes: A layer of adhesive material (10) is formed on the substrate. The surface of the adhesive layer (10) away from the substrate is modified to form a modified surface (20), and the viscosity of the surface region (11) of the adhesive layer (10) near the modified surface (20) is higher than the viscosity of the inner region of the adhesive layer (10) away from the modified surface (20).

6. The preparation method according to claim 5, characterized in that, Modifying the surface of the adhesive layer (10) away from the substrate to form a modified surface (20) includes: The surface of the adhesive layer (10) is subjected to plasma bombardment treatment to form the modified surface (20).

7. The preparation method according to claim 6, characterized in that, Plasma bombardment treatment of the surface of the adhesive layer (10) includes: Place the adhesive layer (10) in the chamber, control the vacuum degree of the chamber to be 0.1 Pa to 10 Pa, and introduce a mixture of oxygen and argon into the chamber. The volume ratio of oxygen to argon is 1:3 to 1:

5. Adjust the plasma generation power to 50W to 150W, control the distance between the surface of the adhesive layer (10) and the plasma discharge area to 5mm to 15mm, and perform plasma bombardment treatment on the surface of the adhesive layer (10) for 30s to 120s to complete the surface activation modification of the adhesive layer (10).

8. The preparation method according to claim 6, characterized in that, Plasma bombardment treatment of the surface of the adhesive layer (10) includes: The surface of the adhesive layer (10) is subjected to plasma bombardment treatment, so that the depth of plasma bombardment on the adhesive layer (10) is 0.1 μm to 1 μm.

9. The preparation method according to claim 5, characterized in that, Modifying the surface of the adhesive layer (10) away from the substrate to form a modified surface (20) includes: The surface of the adhesive layer (10) is etched using a chemical etchant to break the molecular chains on the surface of the adhesive layer (10) and form a modified surface (20) on the surface of the adhesive layer (10).

10. The preparation method according to claim 5, characterized in that, Modifying the surface of the adhesive layer (10) away from the substrate to form a modified surface (20) includes: A photosensitive layer is formed on the surface of the adhesive layer (10) away from the substrate; The photosensitive layer is exposed to cause a cross-linking reaction at the interface between the adhesive layer (10) and the photosensitive layer, so as to form a modified surface (20) on the surface of the adhesive layer (10). Remove the photosensitizer layer.

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