Flexible packaging process of AM glass-based small-spacing display screen

Abstract

The invention provides a flexible packaging process of an AM glass-based small-spacing display screen, which comprises the following steps: substrate pretreatment: carrying out ultrasonic cleaning for 5 minutes by using a mixed solution of deionized water and isopropyl alcohol in a volume ratio of 3: 1 at 45-55 DEG C, washing for 2 minutes by using deionized water, drying, and activating the surface of the substrate by using plasma; transferring a large amount of LED chips: aligning the LED chips, transferring the LED chips to a preset position of the activated substrate, and fixing the LED chips on the substrate; coating high-thermal-conductivity packaging glue: carrying out plasma cleaning and 120 DEG C baking dehumidification on the substrate on which the chip is fixed, and then directionally coating the high-thermal-conductivity glue; curing the high-thermal-conductivity glue, namely pre-curing the substrate coated with the high-thermal-conductivity glue and then carrying out stepped curing; and optical film lamination: performing quantum dot film lamination and anti-reflection layer spraying on the surface of the cured substrate. The heat-conducting glue with polyurethane modified epoxy resin and AlN / BN / carbon fiber composite filler is adopted, so that the heat-conducting effect is effectively improved, and the service life of an LED is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of environmentally friendly latex paint, in particular to a flexible packaging process for an AM glass-based small-pitch display screen. Background Art

[0002] With the rapid development of Mini / Micro-LED display technology, demand for fine-pitch displays (pitch ≤ 0.5mm) has surged in applications such as high-end commercial displays, virtual reality (VR), and automotive displays. Compared to traditional PCB substrates, active-matrix (AM) glass substrates are ideal for high-resolution Micro-LED displays due to their high flatness, low coefficient of thermal expansion (CTE), and excellent signal transmission capabilities. However, the brittleness and low thermal conductivity of glass substrates place higher demands on the packaging process. Traditional epoxy resin encapsulation or silicone potting cannot meet the requirements for high thermal conductivity, ultra-thinness, and flexibility. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention provides a flexible packaging process for an AM glass-based fine-pitch display screen to solve the problems raised in the above background technology.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions: A flexible packaging process for AM glass-based fine-pitch display screens, comprising the following steps:

[0005] S1: Substrate pretreatment: Use a mixed solution of deionized water and isopropyl alcohol with a volume ratio of 3:1 to ultrasonically clean the substrate at 45-55°C for 5 minutes, rinse with deionized water for 2 minutes, and dry the substrate. Then, activate the substrate surface with plasma.

[0006] S2: Mass transfer of LED chips: Aligning and transferring the LED chips to predetermined positions on the activated substrate and fixing them on the substrate;

[0007] S3: High thermal conductivity packaging adhesive coating: The substrate with the chip fixed is plasma cleaned and baked at 120°C for dehumidification, and then high thermal conductivity adhesive is coated in a directional manner;

[0008] S4: Curing of high thermal conductivity adhesive: pre-curing the substrate coated with high thermal conductivity adhesive and then performing step curing;

[0009] S5: Optical film bonding: quantum dot film bonding and anti-reflection layer spraying are performed on the surface of the cured substrate.

[0010] As a further preference, the plasma is specifically a mixed gas of oxygen and nitrogen, and the ratio of the oxygen to nitrogen is 70%:30%.

[0011] As a further preferred embodiment, the high thermal conductive adhesive is made of the following components: 25-35wt% of polyurethane modified epoxy resin, 20-30wt% of aluminum nitride, 10-15wt% of boron nitride nanosheets, 3-5wt% of carbon fiber fragments, 0.2wt% of defoaming agent and 0.5wt% of photoinitiator;

[0012] The encapsulation layer has the following properties:

[0013] Thermal conductivity in the vertical direction ≥1.5W / (m·K) (ASTM D5470 test);

[0014] Breakdown voltage>15kV / mm (IEC 60243 standard);

[0015] Thermal expansion coefficient <30ppm / ℃ (TMA method, -40~150℃);

[0016] Adhesion>8MPa (GB / T 9286 cross-cut method).

[0017] As a further preferred embodiment, the high thermal conductivity colloid applies an electric field or a magnetic field during the coating process to align the boron nitride flake fillers;

[0018] When electric field induction is used, a DC or AC electric field of 0.5-2 kV / mm is applied for 5-15 minutes;

[0019] When magnetic field induction is used, a vertical magnetic field of 1-5 T is applied, and the boron nitride filler is coated with Fe3O4.

[0020] As a further preference, the coating thickness of the high thermal conductive adhesive is less than 100 μm.

[0021] As a further preferred embodiment, the process of pre-curing followed by step curing includes:

[0022] UV pre-curing: using 365nm UV light, light intensity 50±5mW / cm 2 Irradiate for 5±0.5 seconds to form a preliminary cross-linking layer on the surface;

[0023] Step heat curing:

[0024] Stage 1: Maintain at 80±2℃ for 10±1min to allow the uncured resin inside to flow at low viscosity;

[0025] The second stage: heating to 120±2℃ at 2℃ / min and maintaining for 15±1min to promote the orientation of thermal conductive fillers;

[0026] The third stage: heating to 150±2℃ at 1℃ / min, maintaining for 20±1min to complete deep curing;

[0027] Cooling: Cool down to 80°C at 0.5°C / min, then cool naturally to room temperature.

[0028] As a further preference, the process of laminating the quantum dot film includes:

[0029] Substrate pretreatment: The substrate is plasma cleaned and then ultrasonically cleaned with isopropyl alcohol and deionized water;

[0030] OCA optical adhesive coating: Use UV curable optical transparent adhesive with a thickness of 25μm for roller lamination, with a lamination pressure of 0.3-0.5MPa and a speed of 0.5m / min;

[0031] Vacuum degassing: degassing at -90kPa, 60℃ for 10min;

[0032] Quantum dot film alignment and lamination: CCD visual alignment system is used for precise alignment and secondary roller pressing is applied;

[0033] UV curing: 365nm UV LED irradiation, curing dose 1000mJ / cm 2 .

[0034] As a further preference, the anti-reflection layer spraying process is:

[0035] Substrate pretreatment: Oxygen plasma treatment is used to increase the surface energy to ≥38mN / m, and N2 gas is used to blow and remove dust;

[0036] Preparation of nanosol: Prepare a sol containing SiO2 nanoparticles with a particle size of 10-20 nm and a solid content of 5 wt% in a ratio of 7:3 ethanol to deionized water;

[0037] Ultrasonic atomization spraying: using 20kHz ultrasonic atomization spraying system, spraying distance 10cm, air pressure 0.2MPa, speed 50mm / s, spraying 2 layers;

[0038] Step curing: first hot air curing at 80℃ for 5 minutes, then annealing at 150℃ for 10 minutes.

[0039] The present invention provides a flexible packaging process for an AM glass-based fine-pitch display screen, which has the following beneficial effects:

[0040] 1. The present invention adopts a thermal conductive adhesive of polyurethane modified epoxy resin + AlN / BN / carbon fiber composite filler, which effectively improves the thermal conductivity and increases the service life of the LED.

[0041] 2. By inducing the vertical orientation of BN nanosheets, a vertical heat conduction path is formed, effectively reducing the thermal resistance of the LED junction temperature.

[0042] 3. UV pre-curing and gradient heating are used to avoid filler sedimentation, reduce thermal stress, and further improve the heat dissipation effect and service life of the display. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The figure is a flow chart of the flexible packaging process of the AM glass-based fine-pitch display screen of the present invention. DETAILED DESCRIPTION

[0044] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0045] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0046] In one aspect, the present invention provides a flexible packaging process for an AM glass-based fine-pitch display screen, comprising the following steps:

[0047] S1: Substrate pretreatment: Use a mixed solution of deionized water and isopropyl alcohol with a volume ratio of 3:1 to ultrasonically clean the substrate at 45-55°C for 5 minutes, rinse with deionized water for 2 minutes, and dry the substrate. Then, activate the substrate surface with plasma.

[0048] The plasma is specifically a mixed gas of oxygen and nitrogen, with the ratio of oxygen to nitrogen being 70%:30%.

[0049] It should be noted that the substrate after plasma treatment needs to proceed to the next process within 4 hours.

[0050] In this embodiment, after the substrate is activated, AOI and laser repair are required. The specific process is to use a high-resolution (1μm accuracy) optical scanner to detect the surface of the substrate. The detection content is metal trace breakage, open circuit (connection with a line width of less than 10μm) and foreign matter contamination. The repair method is laser repair.

[0051] Among them, the laser repair step is an existing technical means and will not be described in detail here.

[0052] S2: Mass transfer of LED chips: Align and transfer the LED chips to the predetermined position of the activated substrate and fix them on the substrate.

[0053] Specifically, the mass transfer of LED chips adopts the elastic stamp transfer method. Specifically, a growth substrate with multiple LED chips is provided; the LED chips are separated from the growth substrate through a laser peeling process; the separated LED chips are self-assembled to a temporary carrier; an elastic stamp with a micropore array is used to pick up the LED chips through negative pressure adsorption; the LED chips are precisely aligned and transferred to the predetermined position of the target substrate; the LED chips are fixed to the target substrate through hot pressing or UV curing; and finally, optical inspection and selective laser repair are performed to achieve high-precision and high-efficiency batch transfer of LED chips.

[0054] S3: High thermal conductivity packaging adhesive coating: The substrate with the chip fixed is plasma cleaned and baked at 120°C for dehumidification, and then high thermal conductivity adhesive is coated in a directional manner;

[0055] In this embodiment, the high thermal conductive adhesive is made of the following components: 25-35wt% of polyurethane modified epoxy resin, 20-30wt% of aluminum nitride, 10-15wt% of boron nitride nanosheets, 3-5wt% of carbon fiber fragments, 0.2wt% of defoaming agent and 0.5wt% of photoinitiator, wherein the aluminum nitride has a particle size of 3μm and is treated with a titanate coupling agent, the boron nitride nanosheets have a thickness of 100nm, and the surface of the carbon fiber fragments is treated with insulation.

[0056] The high thermal conductivity colloid was prepared by planetary stirring and ultrasonic dispersion.

[0057] The encapsulation adhesive layer prepared by the method has the following properties:

[0058] Thermal conductivity in the vertical direction ≥1.5W / (m·K) (ASTM D5470 test);

[0059] Breakdown voltage>15kV / mm (IEC 60243 standard);

[0060] Thermal expansion coefficient <30ppm / ℃ (TMA method, -40~150℃);

[0061] Adhesion>8MPa (GB / T 9286 cross-cut method).

[0062] In this embodiment, an electric field or a magnetic field is applied to the high thermal conductivity colloid during the coating process to orient the boron nitride flake fillers;

[0063] When electric field induction is used, a DC or AC electric field of 0.5-2 kV / mm is applied for 5-15 minutes;

[0064] When magnetic field induction is used, a vertical magnetic field of 1-5 T is applied, and the boron nitride filler is coated with Fe3O4;

[0065] The directional arrangement enables the boron nitride flake fillers to be oriented in a predetermined direction, thereby significantly improving the thermal conductivity of the encapsulation adhesive in the thickness direction.

[0066] It should be noted that the coating thickness of the high thermal conductive adhesive is less than 100 μm.

[0067] Specifically, electric / magnetic field-induced directional alignment of boron nitride nanosheets (10-15wt%) (vertical thermal conductivity ≥1.5W / (m·K)), combined with the synergistic effect of aluminum nitride (20-30wt%) and carbon fiber fragments (3-5wt%), creates a three-dimensional, highly efficient thermal conductivity path, effectively addressing the localized heat accumulation problem in fine-pitch LEDs. A polyurethane-modified epoxy resin matrix imparts high adhesion (>8MPa) and a low thermal expansion coefficient (<30ppm / °C) to the adhesive layer, matching the thermal deformation of the glass substrate and LED chip. Furthermore, a breakdown voltage of >15kV / mm ensures insulation reliability in high-voltage environments.

[0068] S4: Curing of high thermal conductivity adhesive, pre-curing the substrate coated with high thermal conductivity adhesive and then performing step curing;

[0069] In this embodiment, the process of performing step curing after pre-curing includes:

[0070] UV pre-curing: using 365nm UV light (light intensity 50±5mW / cm 2 ) irradiate for 5±0.5 seconds to form a preliminary cross-linked layer on the surface (curing depth 10-20 μm);

[0071] UV pre-curing can quickly shape the surface of the high thermal conductive adhesive (FTIR detection C=C double bond conversion rate ≥30%), preventing filler sedimentation in the subsequent heat curing stage; and forming a "shell-liquid core" structure to avoid loss of fluidity in the early stage of heat curing.

[0072] Step heat curing:

[0073] Stage 1: Maintain at 80±2℃ for 10±1min to allow the uncured resin inside to flow at low viscosity (viscosity drops to 300±50cP);

[0074] The second stage: heating to 120±2℃ at 2℃ / min and maintaining for 15±1min to promote the orientation of thermal conductive filler (Al2O3 / BN);

[0075] The third stage: heat up to 150±2℃ at 1℃ / min, maintain for 20±1min, and complete deep curing (curing degree ≥98%);

[0076] Cooling: Cool down to 80°C at 0.5°C / min, then cool naturally to room temperature.

[0077] Among them, at the 80°C stage: the resin viscosity is reduced (Brookfield RV test: from 5000 cP to 300 cP), which is conducive to the discharge of bubbles (porosity <0.3%).

[0078] 120℃ stage: slowly increase the temperature (2℃ / min) to orient the BN flake filler along the heat flow direction; the resin gels (viscosity rises to 10 4 cP), lock the packing position.

[0079] 150℃ stage: fully cured (DMA test Tg≥130℃), forming a three-dimensional thermal conductive network (thermal resistance <0.3K·cm 2 / W); eliminate the interfacial stress caused by CTE difference (microscopic infrared detection of residual stress reduced by 60%).

[0080] Gradient cooling (0.5°C / min): Avoid debonding of the filler-resin interface due to sudden cooling (SEM shows interface porosity <0.1%); maintain the integrity of the thermal conductivity path (thermal conductivity attenuation <5% after 1000h of high-temperature aging).

[0081] The maximum curing temperature is controlled at 150°C to avoid high temperature damage to the glass substrate or quantum dot material, and is suitable for the low-temperature process requirements of flexible substrates.

[0082] S5: Optical film bonding: quantum dot film bonding and anti-reflection layer spraying are performed on the surface of the cured substrate.

[0083] The process of quantum dot film lamination includes:

[0084] Substrate pretreatment: The substrate was plasma cleaned (Ar / O2 mixed gas, 100W, 30s), followed by ultrasonic cleaning with isopropyl alcohol and deionized water (40kHz, 5min);

[0085] OCA optical adhesive coating: Use UV-curable optically transparent adhesive (transmittance ≥ 92%, haze < 0.5%) with a thickness of 25 μm (± 2 μm) for roller lamination, with a lamination pressure of 0.3-0.5 MPa and a speed of 0.5 m / min;

[0086] Vacuum degassing: degassing at -90kPa, 60℃ for 10min;

[0087] Quantum dot film alignment and lamination: CCD visual alignment system (accuracy ±10μm) is used for precise alignment, and secondary roller pressure is applied (0.2MPa, 60℃ preheating);

[0088] UV curing: 365nm UV LED irradiation, curing dose 1000mJ / cm 2 .

[0089] The anti-reflective layer spraying process is:

[0090] Substrate pretreatment: Oxygen plasma treatment (50W, 2min) was used to increase the surface energy to ≥38mN / m, and N2 gas was used to blow away dust;

[0091] Preparation of nanosol: Prepare a sol containing SiO2 nanoparticles with a particle size of 10-20 nm and a solid content of 5 wt% in a ratio of 7:3 ethanol to deionized water;

[0092] Ultrasonic atomization spraying: using 20kHz ultrasonic atomization spraying system, spraying distance 10cm, air pressure 0.2MPa, speed 50mm / s, spraying 2 layers (solvent volatilization interval 30s);

[0093] Step curing: first hot air curing at 80℃ for 5 minutes, then annealing at 150℃ for 10 minutes;

[0094] The anti-reflective coating performance test results must meet the following requirements: SiO2 coating thickness 100±5nm, refractive index 1.46, visible light reflectivity <0.5% (550nm wavelength), and pass the 500g load steel wool friction test 100 times without scratches.

[0095] Specifically, ultrasonic atomization spraying and directional coating technology are used to achieve uniform ultra-thin molding of high thermal conductivity adhesive, meeting the micron-level gap filling requirements of small-pitch display screens (Pitch≤0.5mm).

[0096] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A flexible packaging process for AM glass-based small-pitch display screens, characterized in that: The following steps are involved: S1: Substrate pretreatment: Use a mixed solution of deionized water and isopropyl alcohol with a volume ratio of 3:1 to ultrasonically clean the substrate at 45-55°C for 5 minutes, rinse with deionized water for 2 minutes, and dry the substrate. Then, activate the substrate surface with plasma. S2: Mass transfer of LED chips: Aligning and transferring the LED chips to predetermined positions on the activated substrate and fixing them on the substrate; S3: High thermal conductivity packaging adhesive coating: The substrate with the chip fixed is plasma cleaned and baked at 120°C for dehumidification, and then high thermal conductivity adhesive is coated in a directional manner; S4: Curing of high thermal conductivity adhesive, pre-curing the substrate coated with high thermal conductivity adhesive and then performing step curing; S5: Optical film bonding: quantum dot film bonding and anti-reflection layer spraying are performed on the surface of the cured substrate.

2. The flexible packaging process for an AM glass-based fine-pitch display screen according to claim 1, characterized in that: The plasma is specifically a mixed gas of oxygen and nitrogen, and the ratio of the oxygen to nitrogen is 70%:30%.

3. The flexible packaging process for an AM glass-based fine-pitch display screen according to claim 1, characterized in that: The high thermal conductive adhesive is made of the following components: 25-35wt% of polyurethane modified epoxy resin, 20-30wt% of aluminum nitride, 10-15wt% of boron nitride nanosheets, 3-5wt% of carbon fiber fragments, 0.2wt% of defoaming agent and 0.5wt% of photoinitiator; The encapsulation layer has the following properties: Thermal conductivity in the vertical direction ≥1.5W / (m·K) (ASTM D5470 test); Breakdown voltage>15kV / mm (IEC 60243 standard); Thermal expansion coefficient <30ppm / ℃ (TMA method, -40~150℃); Adhesion>8MPa (GB / T 9286 cross-cut method).

4. The flexible packaging process for an AM glass-based fine-pitch display screen according to claim 1, characterized in that: The high thermal conductivity colloid applies an electric field or a magnetic field during the coating process to align the boron nitride flake fillers; When electric field induction is used, a DC or AC electric field of 0.5-2 kV / mm is applied for 5-15 minutes; When magnetic field induction is used, a vertical magnetic field of 1-5 T is applied, and the boron nitride filler is coated with Fe3O4.

5. The flexible packaging process for an AM glass-based fine-pitch display screen according to claim 3, characterized in that: The coating thickness of the high thermal conductive adhesive is less than 100 μm.

6. The flexible packaging process for an AM glass-based fine-pitch display screen according to claim 1, characterized in that: The process of pre-curing followed by step curing includes: UV pre-curing: using 365nm UV light, light intensity 50±5mW / cm 2 Irradiate for 5±0.5 seconds to form a preliminary cross-linking layer on the surface; Step heat curing: Stage 1: Maintain at 80±2℃ for 10±1min to allow the uncured resin inside to flow at low viscosity; The second stage: heating to 120±2℃ at 2℃ / min and maintaining for 15±1min to promote the orientation of thermal conductive fillers; The third stage: heating to 150±2℃ at 1℃ / min, maintaining for 20±1min to complete deep curing; Cooling: Cool down to 80°C at 0.5°C / min, then cool naturally to room temperature.

7. The flexible packaging process for an AM glass-based fine-pitch display screen according to claim 1, characterized in that: The process of laminating the quantum dot film includes: Substrate pretreatment: The substrate is plasma cleaned and then ultrasonically cleaned with isopropyl alcohol and deionized water; OCA optical adhesive coating: Use UV curable optical transparent adhesive with a thickness of 25μm for roller lamination, with a lamination pressure of 0.3-0.5MPa and a speed of 0.5m / min; Vacuum degassing: degassing at -90kPa, 60℃ for 10min; Quantum dot film alignment and lamination: CCD visual alignment system is used for precise alignment and secondary roller pressing is applied; UV curing: 365nm UV LED irradiation, curing dose 1000mJ / cm 2 .

8. The flexible packaging process for an AM glass-based fine-pitch display screen according to claim 1, characterized in that: The anti-reflection layer spraying process is: Substrate pretreatment: Oxygen plasma treatment is used to increase the surface energy to ≥38mN / m, and N2 gas is used to blow and remove dust; Preparation of nanosol: Prepare a sol containing SiO2 nanoparticles with a particle size of 10-20 nm and a solid content of 5 wt% in a ratio of 7:3 ethanol to deionized water; Ultrasonic atomization spraying: using 20kHz ultrasonic atomization spraying system, spraying distance 10cm, air pressure 0.2MPa, speed 50mm / s, spraying 2 layers; Step curing: first hot air curing at 80℃ for 5 minutes, then annealing at 150℃ for 10 minutes.

Images