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

Abstract

The application provides a flexible packaging process for an AM glass-based small-pitch display screen, which comprises the following steps: substrate pretreatment: after ultrasonic cleaning for 5 min under the condition of 45-55 DEG C by using a mixed solution of deionized water and isopropyl alcohol with a volume ratio of 3:1, rinsing for 2 min by using deionized water and drying treatment, and then activating the surface of the substrate by using plasma; LED chip mass transfer: aligning and transferring the LED chip to the predetermined position of the activated substrate, and fixing the LED chip to the substrate; high-thermal-conductivity packaging glue coating: performing plasma cleaning and 120 DEG C baking and dehumidification on the substrate fixed with the chip, then directionally coating high-thermal-conductivity glue; high-thermal-conductivity glue curing: after pre-curing the substrate coated with the high-thermal-conductivity glue, performing step-by-step curing; optical film lamination: performing quantum dot film lamination and anti-reflection layer spraying on the surface of the cured substrate. The application adopts the high-thermal-conductivity glue of polyurethane modified epoxy resin+AlN / BN / carbon fiber composite filler, effectively improves the thermal conduction effect, and prolongs the service life of the LED.

Description

TECHNICAL FIELD

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

[0002] With the rapid development of Mini / Micro-LED display technology, the application demand of small-pitch display screen (Pitch≤0.5mm) in high-end commercial display, virtual reality (VR), vehicle-mounted display and other fields has increased rapidly. Compared with traditional PCB substrates, active matrix (AM) glass substrates have become an ideal carrier for high-resolution Micro-LED displays due to their high flatness, low coefficient of thermal expansion (CTE) and excellent signal transmission capability. However, the brittleness and low thermal conductivity of the glass substrate have put higher requirements on the packaging process, and traditional epoxy resin packaging or silicone potting cannot meet the needs of high thermal conductivity, ultra-thin and flexible packaging. SUMMARY

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

[0004] To achieve the above purpose, the present application is implemented by the following technical scheme: a flexible packaging process for an AM glass-based small-pitch display screen, comprising the following steps:

[0005] S1: substrate pretreatment: after ultrasonic cleaning for 5min at 45-55℃ using a mixed solution of deionized water and isopropyl alcohol with a volume ratio of 3:1, rinsing for 2min with deionized water and drying treatment, the substrate surface is activated by plasma;

[0006] S2: LED chip mass transfer: aligning and transferring the LED chip to the predetermined position of the activated substrate and fixing it to the substrate;

[0007] S3: high-thermal-conductivity packaging glue coating: plasma cleaning and 120℃ baking and dehumidifying are performed on the substrate with fixed chips, and then high-thermal-conductivity glue is directionally coated;

[0008] S4: high-thermal-conductivity glue curing: after pre-curing the substrate coated with high-thermal-conductivity glue, step curing is performed;

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

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

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

[0012] The encapsulation glue layer has the following properties:

[0013] Thermal conductivity in 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 grid method).

[0017] As a further preferred, the high thermal conductive glue applies electric field or magnetic field during coating process to make the boron nitride sheet filler orientally arranged;

[0018] When electric field induction is adopted, direct current or alternating current electric field of 0.5-2kV / mm is applied, and the action time is 5-15 minutes;

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

[0020] As a further preferred, the high thermal conductive glue has a coating thickness less than 100μm.

[0021] As a further preferred, the process of pre-curing and then step curing includes:

[0022] UV pre-curing: 365nm UV light is adopted, light intensity 50±5mW / cm 2 Irradiation for 5±0.5 seconds to make the surface form a preliminary crosslinked layer;

[0023] Step heat curing:

[0024] First stage: 80±2℃ for 10±1min to make the internal uncured resin low-viscosity flow;

[0025] Second stage: temperature rise to 120±2℃ at 2℃ / min, keep for 15±1min to promote the orientation arrangement of the thermal conductive filler;

[0026] Third stage: temperature rise to 150±2℃ at 1℃ / min, keep for 20±1min to complete the deep curing;

[0027] Cooling: decrease to 80℃ at 0.5℃ / min, then cool to room temperature naturally.

[0028] As a further preferred, the process of quantum dot film lamination includes:

[0029] Substrate pretreatment: plasma cleaning of the substrate, followed by isopropanol and deionized water ultrasonic cleaning;

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

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

[0032] Quantum dot film alignment lamination: precise alignment with CCD vision alignment system, and secondary roll pressing;

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

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

[0035] Substrate pretreatment: oxygen plasma treatment to improve surface energy to ≥38mN / m, and N2 gas blowing to remove dust;

[0036] Nanosol preparation: preparation of SiO2 nanoparticle-containing sol with particle size 10-20nm and solid content 5wt% of ethanol:deionized water 7:3;

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

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

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

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

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

[0042] 3. UV pre-curing and gradient heating are used to prevent filler sedimentation and reduce thermal stress, thereby further improving the heat dissipation and service life of the display screen. Attached Figure Description

[0043] Figure 1 This is a flow chart of the flexible packaging process for the AM glass-based small-pitch display screen of the present invention. Detailed Implementation

[0044] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0045] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0046] This invention provides a flexible packaging process for AM glass-based small-pitch displays, comprising the following steps:

[0047] S1: Substrate pretreatment: After ultrasonic cleaning for 5 min at 45-55℃ using a mixed solution of deionized water and isopropanol with a volume ratio of 3:1, the substrate is rinsed with deionized water for 2 min and dried. Then, the substrate surface is activated by plasma.

[0048] Specifically, plasma is a mixture of oxygen and nitrogen gas, with an oxygen to nitrogen ratio of 70%:30%.

[0049] It should be noted that the substrate treated with plasma must be processed into the next step within 4 hours.

[0050] In the embodiment, the substrate is activated and then subjected to AOI and laser repair. The process is as follows: using a high-resolution (1 μm precision) optical scanner to detect the surface of the substrate, the detection content is metal trace fracture, open circuit (connection with line width less than 10 μm) and foreign matter pollution, and the repair method is laser repair.

[0051] The step of laser repair is a prior art method, and will not be described in detail.

[0052] S2: LED chip mass transfer: aligning and transferring the LED chip to the predetermined position of the activated substrate, and fixing it to the substrate.

[0053] Specifically, the LED chip mass transfer adopts the method of elastic stamp transfer. Specifically, a growth substrate with a plurality of LED chips is provided; the LED chips are separated from the growth substrate by a laser lift-off 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 by negative pressure adsorption; the LED chips are accurately aligned and transferred to the predetermined position of the target substrate; the LED chips are fixed to the target substrate by hot pressing or UV curing; finally, optical detection and selective laser repair are performed to realize high-precision and high-efficiency LED chip batch transfer.

[0054] S3: High thermal conductivity encapsulation glue coating: the substrate with the fixed chip is subjected to plasma cleaning and 120°C baking and dehumidification, and then high thermal conductivity glue is directionally coated;

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

[0056] The high thermal conductivity glue is prepared by planetary stirring and ultrasonic dispersion.

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

[0058] The vertical direction thermal conductivity coefficient is ≥1.5 W / (m·K) (ASTM D5470 test);

[0059] The breakdown voltage is >15 kV / mm (IEC 60243 standard);

[0060] The thermal expansion coefficient is <30 ppm / ℃ (TMA method, -40-150℃);

[0061] Adhesion > 8 MPa (GB / T 9286 crosshatch method).

[0062] In this embodiment, the high-thermal-conductivity glue applies an electric field or a magnetic field during the coating process to orient the boron nitride flake filler;

[0063] When electric field induction is used, a direct current or alternating current electric field of 0.5-2 kV / mm is applied, and the action time is 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 subjected to Fe3O4 coating treatment;

[0065] The oriented arrangement causes the boron nitride flake filler to be oriented and arranged along a predetermined direction, thereby significantly improving the thermal conductivity of the encapsulation glue in the thickness direction.

[0066] It should be noted that the high-thermal-conductivity glue has a coating thickness of less than 100 μm.

[0067] Specifically, the boron nitride nanosheet (10-15 wt%) is oriented and arranged (vertical direction thermal conductivity ≥ 1.5 W / (m·K)) by electric field / magnetic field induction, and the synergistic effect of aluminum nitride (20-30 wt%) and carbon fiber fragments (3-5 wt%) forms a three-dimensional high-efficiency thermal conduction path, effectively solving the problem of local heat accumulation of small-pitch LEDs. The polyurethane-modified epoxy resin matrix gives the glue layer high adhesion (> 8 MPa) and low thermal expansion coefficient (< 30 ppm / ℃), matches the thermal deformation of the glass substrate and the LED chip, and at the same time has a breakdown voltage > 15 kV / mm, ensuring insulation reliability in a high-voltage environment.

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

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

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

[0071] UV pre-curing can quickly shape the surface of the high-thermal-conductivity glue (FTIR detection C=C double bond conversion rate ≥ 30%), prevent filler settlement in the subsequent heat curing stage, and form a "shell-liquid core" structure to avoid loss of fluidity in the initial heat curing stage.

[0072] Step curing:

[0073] First stage: 80±2℃ for 10±1 min to make the internal uncured resin flow at low viscosity (viscosity reduced to 300±50 cP);

[0074] Second stage: increase temperature to 120±2℃ at 2℃ / min, keep for 15±1min, promote the orientation arrangement of the thermal conductive filler (Al2O3 / BN);

[0075] Third stage: increase temperature to 150±2℃ at 1℃ / min, keep for 20±1min, complete the deep curing (curing degree≥98%);

[0076] Cooling: decrease temperature to 80℃ at 0.5℃ / min, then cool to room temperature naturally.

[0077] Among them, the 80℃ stage: reduce the viscosity of the resin (Brookfield RV test: from 5000cP→300cP), which is beneficial to the bubble discharge (porosity<0.3%).

[0078] 120℃ stage: through slow heating (2℃ / min) to make the BN sheet filler orient along the heat flow direction; the resin gels (the viscosity rises to 10 4 cP), locking the position of the filler.

[0079] 150℃ stage: complete curing (DMA test Tg≥130℃), form a three-dimensional thermal conductive network (thermal resistance<0.3K·cm 2 / W); eliminate the interface stress caused by the difference in CTE (micro-infrared detection residual stress reduction of 60%).

[0080] Gradient cooling (0.5℃ / min): avoid the adhesion of the filler-resin interface caused by sudden cooling (SEM shows that the interface porosity is<0.1%); maintain the integrity of the thermal conductive path (after high-temperature aging for 1000h, the thermal conductivity attenuation is<5%).

[0081] The highest curing temperature is controlled at 150℃, which avoids the damage of high temperature to the glass substrate or quantum dot material, and is suitable for the low-temperature process requirements of flexible substrate.

[0082] S5: optical film lamination: quantum dot film lamination and anti-reflection layer spraying on the surface of the cured substrate.

[0083] Among them, the process of quantum dot film lamination includes:

[0084] Substrate pretreatment: plasma cleaning (Ar / O2 mixed gas, 100W, 30s) is performed on the substrate, followed by isopropanol and deionized water ultrasonic cleaning (40kHz, 5min);

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

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

[0087] Quantum dot film alignment: precise alignment was performed by using a CCD vision alignment system (accuracy ±10 μm), and secondary roller pressing (0.2 MPa, 60℃ preheating) was applied;

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

[0089] The anti-reflection layer spraying process was as follows:

[0090] Substrate pretreatment: oxygen plasma treatment (50 W, 2 min) was used to improve the surface energy to ≥38 mN / m, and N2gas was used for blowing to remove dust;

[0091] Nanosol preparation: an ethanol: deionized water sol of 7:3 containing SiO2nanoparticles with a particle size of 10-20 nm and a solid content of 5 wt% was prepared;

[0092] Ultrasonic atomization spraying: a 20 kHz ultrasonic atomization spraying system was used, the spraying distance was 10 cm, the air pressure was 0.2 MPa, the walking speed was 50 mm / s, and 2 layers were sprayed (with an interval of 30 s for solvent evaporation);

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

[0094] The results of the anti-reflection coating detection performance need to reach: SiO2coating thickness 100±5 nm, refractive index 1.46, visible light reflectance <0.5% (550 nm wavelength), and no scratches after 500g load steel wool rubbing test for 100 times.

[0095] Specifically, uniform ultrathin molding of the high-thermal-conductivity glue is realized by ultrasonic atomization spraying and directional coating technology, which meets the micron-level gap filling requirements of small-pitch display screens (Pitch≤0.5 mm).

[0096] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flexible packaging process for AM glass-based small-pitch displays, characterized in that, Includes the following steps: S1: Substrate pretreatment: After ultrasonic cleaning for 5 min at 45-55℃ using a mixed solution of deionized water and isopropanol with a volume ratio of 3:1, the substrate is rinsed with deionized water for 2 min and dried. Then, the substrate surface is activated by plasma. S2: Mass transfer of LED chips: Aligning and transferring LED chips to predetermined positions on the activated substrate, and fixing them onto the substrate; S3: High thermal conductivity encapsulant coating: The substrate with the chip fixed is subjected to plasma cleaning and 120°C baking for dehumidification, and then high thermal conductivity adhesive is applied in a directional manner. S4: High thermal conductivity adhesive curing, the substrate coated with high thermal conductivity adhesive is pre-cured and then stepped curing is performed. S5: Optical film lamination: Quantum dot film lamination and anti-reflective layer spraying are performed on the surface of the cured substrate; The high thermal conductivity adhesive is made of the following components: 25-35 wt% polyurethane modified epoxy resin, 20-30 wt% aluminum nitride, 10-15 wt% boron nitride nanosheets, 3-5 wt% carbon fiber fragments, 0.2 wt% defoamer, and 0.5 wt% photoinitiator; During the coating process, an electric or magnetic field is applied to the high thermal conductivity adhesive to cause the boron nitride sheet filler to be oriented. The process of pre-curing followed by step curing includes: UV pre-curing: Using 365nm UV light with a light intensity of 50±5 mW / cm², irradiate for 5±0.5 seconds to form a preliminary cross-linking layer on the surface; Stepped thermosetting: First stage: Maintain at 80±2℃ for 10±1min to allow the uncured resin inside to flow at low viscosity; Second stage: Increase the temperature to 120±2℃ at 2℃ / min and hold for 15±1min to promote the orientation and alignment of the thermally conductive filler; Third stage: Increase the temperature to 150±2℃ at 1℃ / min, hold for 20±1min, and complete the deep curing; Cooling: Reduce the temperature to 80°C at a rate of 0.5°C / min, then allow it to cool naturally to room temperature.

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

3. The flexible packaging process for an AM glass-based small-pitch display screen according to claim 1, characterized in that: The high thermal conductivity adhesive has the following properties: The vertical thermal conductivity is ≥1.5 W / (m·K), which is obtained by ASTM D5470 testing. The breakdown voltage is >15 kV / mm, and the breakdown voltage is obtained by testing according to the IEC 60243 standard; The coefficient of thermal expansion is <30 ppm / ℃, which is obtained by TMA method at -40~150℃; The adhesion is >8 MPa, and the adhesion is obtained by cross-cut test according to GB / T 9286.

4. The flexible packaging process for an AM glass-based small-pitch display screen according to claim 1, characterized in that: When using electric field induction, apply a DC or AC electric field of 0.5-2kV / mm for 5-15 minutes. When magnetic field induction is used, a vertical magnetic field of 1-5T is applied, and the boron nitride packing is subjected to... Coating treatment.

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

6. The flexible packaging process for an AM glass-based small-pitch display screen according to claim 1, characterized in that: The quantum dot film bonding process includes: Substrate pretreatment: The substrate is subjected to plasma cleaning, followed by ultrasonic cleaning with isopropanol and deionized water. OCA optical adhesive coating: A 25μm thick UV-curable optical transparent adhesive is used for roller pressing and bonding, with a bonding pressure of 0.3-0.5MPa and a speed of 0.5m / min; Vacuum degassing: Degassing for 10 minutes under conditions of -90 kPa and 60℃; Quantum dot film alignment and bonding: A CCD vision alignment system is used for precise alignment, followed by secondary rolling pressure. UV curing: 365nm UV LED irradiation, curing dose 1000mJ / cm².

7. The flexible packaging process for an AM glass-based small-pitch display screen according to claim 1, characterized in that: The anti-reflective layer spraying process is as follows: Substrate pretreatment: Oxygen plasma treatment was used to increase the surface energy to ≥38mN / m, and then... Air blowing to remove dust; Preparation of nanosols: formulation of nanosols containing Nanoparticles, with a particle size of 10-20 nm, and a sol with a solid content of 5 wt% ethanol:deionized water in a ratio of 7:3; Ultrasonic atomization spraying: A 20kHz ultrasonic atomization spraying system is used, with a spraying distance of 10cm, an air pressure of 0.2MPa, a travel speed of 50mm / s, and 2 layers are sprayed. Step curing: First, cure with hot air at 80℃ for 5 minutes, then anneal at 150℃ for 10 minutes.

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