LED filament packaging process

Abstract

The invention relates to the technical field of lamp filament packaging, in particular to an LED lamp filament packaging process which comprises the following steps: pre-activating the surface of a flexible substrate by adopting a supercritical carbon dioxide fluid assisted plasma processing technology, preparing a micro-nano array with a double-curvature bionic moth eye structure on the pre-activated substrate by adopting a femtosecond laser direct writing technology, and packaging the micro-nano array on the flexible substrate. A heterojunction thin film of indium gallium zinc oxide and graphene is grown on the surface of a micro-nano array through a pulse laser deposition technology, an LED chip array and the heterojunction thin film are in low-stress connection through a transient liquid phase diffusion welding technology, and the surface of an LED chip is coated with a perovskite quantum dot-liquid metal composite packaging layer. Phase-change material microcapsule heat dissipation structures are integrated at the two ends of the packaging body; the method has the beneficial effects that the supercritical carbon dioxide fluid assisted plasma treatment technology is adopted, the fluid viscosity is regulated and controlled by doping the perfluoropolyether surfactant, the nanoscale roughness of the surface of the substrate can be accurately controlled, meanwhile, the surface energy of the substrate can be increased to 65-80 mN / m, and a good foundation is provided for the subsequent process.

Description

Technical Field

[0001] This invention relates to the field of filament packaging, specifically to an LED filament packaging process. Background Technology

[0002] Traditional LED filament packaging technology has several shortcomings. In terms of substrate processing, conventional methods struggle to precisely control the surface energy and roughness of the substrate, affecting the quality of subsequent processes. Regarding light extraction structures, ordinary structured light extraction efficiency is limited and cannot meet the requirements for high-efficiency light emission.

[0003] In thin film growth technology, films prepared by traditional processes have unsatisfactory performance, such as low carrier mobility. In chip interconnect technology, traditional welding methods are prone to problems such as high stress and high interface void ratio, affecting connection reliability. In chip packaging layers, traditional packaging materials and structures are difficult to achieve comprehensive performance such as high luminous efficiency, wide color temperature adjustment range, and good heat dissipation. Flexible substrate materials have limited performance, and bending modulus and thermal conductivity need to be improved. In terms of heat dissipation structure, traditional heat dissipation methods are difficult to effectively reduce the peak heat flux density of the package. In addition, LED filaments prepared by traditional processes cannot reach ideal levels in terms of light decay, operating temperature, bending cycle tolerance, and electromagnetic shielding effectiveness. Summary of the Invention

[0004] The purpose of this invention is to provide an LED filament packaging process to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an LED filament packaging process, the method comprising the following steps: The surface of the flexible substrate is pre-activated using supercritical carbon dioxide fluid-assisted plasma treatment technology. The treatment pressure is 7.5-15MPa, the temperature is 35-50℃, and the treatment time is 15-45 seconds. After treatment, the surface energy of the substrate can be increased to 65-80mN / m. Micro-nano arrays with bi-curvature biomimetic moth-eye structures were fabricated on pre-activated substrates using femtosecond laser direct writing technology. The main period was 50-150 nm, the secondary period was 10-30 nm, and the structural depth gradient was 0.5-2 μm / 100 μm. Heterojunction films of indium gallium zinc oxide and graphene were grown on the surface of micro-nano arrays using pulsed laser deposition. The film thickness ranged from 30 to 100 nm, and the carrier mobility was ≥15 cm⁻¹. 2 / (V·s); The transient liquid phase diffusion welding technology is used to achieve low-stress connection between LED chip array and heterojunction thin film. The welding temperature is 120-140℃, the welding time is 0.5-2 seconds, and the interface void ratio is ≤0.1%.

[0006] Preferably, the supercritical carbon dioxide fluid is doped with a perfluoropolyether surfactant at a mass fraction of 0.1-0.5%. By adjusting the fluid viscosity to 1.2-3.5 mPa·s, the nanoscale roughness of the substrate surface can be precisely controlled, with a roughness Ra of 8-15 nm.

[0007] Preferably, the bi-curvature biomimetic moth eye structure is generated by a fractal algorithm, and its curvature radius is distributed in a logarithmic spiral along the radial direction. The angle between the structure sidewall and the substrate normal varies continuously from 5 to 85°, and the light extraction efficiency is improved to over 92%.

[0008] Preferably, in the IGZO / graphene heterojunction film, the graphene layer is grown on a copper foil by chemical vapor deposition and then transferred, with 1-3 layers. The interface between IGZO and graphene is formed into a nanoscale embedded structure by argon plasma bombardment, with an interface resistance ≤50Ω·μm. 2 .

[0009] Preferably, the process further includes coating the LED chip surface with a perovskite quantum dot-liquid metal composite encapsulation layer, wherein the liquid metal is a gallium indium tin alloy with a melting point adjusted to 10-25°C, and the volume ratio of quantum dots to liquid metal is 1:3-1:8. The composite layer forms an ordered array through microfluidic shear-induced self-assembly.

[0010] Preferably, the perovskite quantum dots have a CsPbBr3 / CsPbI3 core-shell structure, the shell thickness is controlled to 2-5nm through in-situ ion exchange reaction, the quantum dot emission wavelength is dynamically adjustable from 550-700nm through electric field modulation, and the color temperature adjustment range is 2000-10000K.

[0011] Preferably, the flexible substrate is a composite material of polyetheretherketone and carbon nanotubes, with a CNT mass fraction of 0.5-2%, the substrate bending modulus is adjusted to 2-8 GPa by magnetic field-assisted orientation, and the thermal conductivity is increased to 5-15 W / (m·K).

[0012] Preferably, the encapsulation also includes a phase change material microcapsule heat dissipation structure integrated at both ends of the encapsulation body. The phase change material is a paraffin / expanded graphite composite material with a phase change temperature of 40-60℃ and a microcapsule particle size of 10-50μm, which reduces the peak heat flux density of the encapsulation body by more than 60%.

[0013] Preferably, in transient liquid phase diffusion welding, the solder is a composite material of tin-silver-copper lead-free alloy and nano-silver particles, with a nano-silver mass fraction of 5-15%. During the welding process, a pulsed magnetic field of 0.1-1T and 10-100Hz is applied to promote the flow of liquid metal and achieve void-free welding.

[0014] Preferably, at a luminous efficacy of 200 lm / W, the light decay is ≤3% after 10,000 hours, the operating temperature is ≤60℃, and it can withstand ≥10,000 bending cycles with a curvature radius of 1mm without failure. It also has electromagnetic shielding effectiveness with attenuation of ≥20dB in the 30MHz-1.5GHz frequency band.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The LED filament packaging process proposed in this invention employs supercritical carbon dioxide fluid-assisted plasma treatment technology and dops with perfluoropolyether surfactants to regulate fluid viscosity, which can precisely control the nanoscale roughness of the substrate surface (Ra is 8-15nm), while increasing the substrate surface energy to 65-80mN / m, providing a good foundation for subsequent processes.

[0016] A biomimetic moth-eye structure micro-nano array with double curvature was fabricated using femtosecond laser direct writing technology. This structure was generated by a fractal algorithm, with the radius of curvature distributed in a logarithmic spiral along the radial direction. The angle between the sidewall of the structure and the normal of the substrate varies continuously from 5 to 85°, which improves the light extraction efficiency to over 92% and effectively enhances the luminescence efficiency.

[0017] Heterojunction films of indium gallium zinc oxide and graphene were grown using pulsed laser deposition. The film thickness was 30-100 nm, and the carrier mobility was ≥15 cm⁻¹. 2 / (V·s), and the interface between IGZO and graphene is formed by argon plasma bombardment to create a nanoscale embedded structure with an interface resistance ≤50Ω·μm. 2 This improves the performance of thin films.

[0018] The transient liquid phase diffusion welding technology is adopted, using a composite solder of tin-silver-copper lead-free alloy and nano-silver particles, and applying a pulsed magnetic field during the welding process to achieve low-stress connection between LED chip array and heterojunction thin film. The welding temperature is 120-140℃, the welding time is 0.5-2 seconds, and the interface void ratio is ≤0.1%, which improves the connection reliability. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: This invention provides a technical solution: a high-efficiency, dynamically adjustable color temperature LED filament package, the steps of which are as follows: 1. Substrate pretreatment Material selection: A flexible composite substrate of polyetheretherketone (PEEK) and carbon nanotubes (CNT) (CNT mass fraction 1.2%) with a thickness of 100 μm is used.

[0022] Surface activation: A perfluoropolyether surfactant (mass fraction 0.3%) was introduced into a supercritical carbon dioxide device, with a pressure of 10 MPa, a temperature of 40 °C, and a treatment time of 30 seconds. After treatment, the surface energy of the substrate increased to 72 mN / m (tested by a contact angle measuring instrument), and the roughness Ra=12 nm (AFM detection).

[0023] 2. Fabrication of micro / nano structures Femtosecond laser direct writing: Using a femtosecond laser with a wavelength of 800nm ​​and a pulse width of 50fs, a double curvature moth-eye structure template is generated through a fractal algorithm; the laser power is 200mW and the scanning speed is 100mm / s, forming an array on the substrate with a main period of 100nm, a secondary period of 20nm, and a depth gradient of 1.5μm / 100μm; the angle between the sidewall of the structure and the normal of the substrate varies continuously within the range of 15-75° (SEM observation).

[0024] 3. Heterojunction film growth IGZO / graphene preparation: First, two layers of graphene were grown on copper foil by CVD, then transferred to a substrate and IGZO thin film was grown by pulsed laser deposition (PLD); PLD parameters: laser energy density 2 J / cm². 2 Frequency 5Hz, oxygen pressure 1×10 -3 Pa, film thickness 80 nm; argon plasma bombardment (100 W power, 60 s time) forms a nanoscale mosaic structure with an interface resistance of 35 Ω·μm. 2 (Four-probe test).

[0025] 4. Chip soldering and packaging Transient liquid phase welding: The solder is a composite of SAC305 lead-free alloy (Sn96.5Ag3Cu0.5) and 10wt% nano-silver particles; a pulsed magnetic field (0.5T, 50Hz) is applied during welding, the temperature is 130℃, the time is 1 second, and the void ratio is 0.05% (X-ray detection); Dynamic color temperature encapsulation layer: a composite layer of CsPbBr3 / CsPbI3 core-shell quantum dots (shell thickness 3nm) and liquid metal GaInSn (volume ratio 1:5) is coated; self-assembly is induced by microfluidic shear (flow rate 10mm / s) to form an ordered array with a period of 500nm; when a 50V / mm electric field is applied, the emission wavelength is continuously adjusted from 520nm (green light) to 650nm (red light), and the color temperature range is 2700-6500K.

[0026] 5. Performance Testing Luminous efficacy: 205 lm / W (integrating sphere test); Reliability: 2.8% light decay after 10,000 hours (LM-80 standard); Flexibility: Resistance change rate ≤1% after 10,000 bends (curvature radius 1mm); Electromagnetic shielding: Attenuation ≥22dB in the 30MHz-1.5GHz frequency band (vector network analyzer test).

[0027] Example 2: Ultra-low thermal resistance, high-reliability LED filament packaging, the steps are as follows: 1. Substrate optimization Material selection: Polyimide (PI) and boron nitride (BN) nanosheet composite substrate (BN mass fraction 0.8%) with a thickness of 80 μm was used; Thermal expansion matching: CTE was adjusted to 6ppm / ℃ (matching the LED chip) by adding nano-SiO2 (particle size 20nm). Surface treatment: After supercritical CO2 treatment (pressure 12MPa, temperature 45℃, time 25 seconds), the surface energy is 75mN / m.

[0028] 2. Microstructure fabrication Femtosecond laser two-photon polymerization: Using photoresist IP-Dip, a three-dimensional fractal structure is directly written through the two-photon absorption effect; structural parameters: principal period 80nm, secondary period 15nm, depth 1.2μm, sidewall roughness Ra≤8nm (TEM observation); the structure surface is coated with 50nm thick Al2O3 (ALD process) to enhance light reflection.

[0029] 3. Preparation of conductive thin films AZO / Ag nanowire composite film: First, an AZO film (thickness 60 nm) was prepared by spin coating; then Ag nanowires (diameter 30 nm, length 20 μm, concentration 0.1 mg / mL) were sprayed to form a mesh transparent electrode; the composite film has a transmittance of 96.5% (UV-Vis test) and a haze of <2%.

[0030] 4. Chip integration and heat dissipation Low-temperature welding: SnBiAg lead-free solder (melting point 138℃) is used in combination with 5wt% core-shell Cu@Ni nanoparticles; welding temperature 145℃, time 1.5 seconds, interfacial shear strength 45MPa (tested by universal testing machine); phase change heat dissipation structure: paraffin / expanded graphite microcapsules (particle size 30μm, phase change temperature 50℃) are embedded at both ends of the package; the microcapsules are arranged into a honeycomb structure by 3D printing, and the peak heat flux density is reduced by 65% ​​(tested by infrared thermal imager).

[0031] 5. Packaging and Testing Quantum dot encapsulation layer: A composite layer of CdSe / ZnS quantum dots (6nm particle size) and silicone (refractive index 1.7) with a thickness of 20μm is coated; a gradient coating process is adopted: the bottom layer has a quantum dot mass fraction of 3%, the top layer has 1%, and the transition layer is achieved by electrospinning (PVDF nanofibers); performance data: luminous efficacy 198lm / W, color rendering index Ra=95; operating temperature 58℃ (ambient temperature 25℃, current 200mA); luminous flux retention rate of 99.2% after 10,000 bends (curvature radius 1.5mm); no corrosion after salt spray test (5% NaCl, 48 hours), insulation resistance >100MΩ.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An LED filament packaging process, characterized in that: The method includes the following steps: The surface of the flexible substrate is pre-activated using supercritical carbon dioxide fluid-assisted plasma treatment technology. The treatment pressure is 7.5-15MPa, the temperature is 35-50℃, and the treatment time is 15-45 seconds. After treatment, the surface energy of the substrate can be increased to 65-80mN / m. Micro-nano arrays with bi-curvature biomimetic moth-eye structures were fabricated on pre-activated substrates using femtosecond laser direct writing technology. The main period was 50-150 nm, the secondary period was 10-30 nm, and the structural depth gradient was 0.5-2 μm / 100 μm. Heterojunction films of indium gallium zinc oxide and graphene were grown on the surface of micro-nano arrays using pulsed laser deposition. The film thickness ranged from 30 to 100 nm, and the carrier mobility was ≥15 cm⁻¹. 2 / (V·s); The transient liquid phase diffusion welding technology is used to achieve low-stress connection between LED chip array and heterojunction thin film. The welding temperature is 120-140℃, the welding time is 0.5-2 seconds, and the interface void ratio is ≤0.1%.

2. The LED filament packaging process according to claim 1, characterized in that: By doping supercritical carbon dioxide fluid with perfluoropolyether surfactants at a mass fraction of 0.1-0.5%, and adjusting the fluid viscosity to 1.2-3.5 mPa·s, precise control of the nanoscale roughness of the substrate surface can be achieved, with a roughness Ra of 8-15 nm.

3. The LED filament packaging process according to claim 1, characterized in that: The hyperbolic moth-eye structure is generated using a fractal algorithm. Its radius of curvature is distributed in a logarithmic spiral along the radial direction. The angle between the sidewall of the structure and the normal of the substrate varies continuously from 5 to 85°, and the light extraction efficiency is improved to over 92%.

4. The LED filament packaging process according to claim 1, characterized in that: In the IGZO / graphene heterojunction film, the graphene layer is grown on a copper foil via chemical vapor deposition and then transferred, with 1-3 layers. The interface between IGZO and graphene is formed into a nanoscale interlocking structure by argon plasma bombardment, with an interface resistance ≤50Ω·μm. 2 .

5. The LED filament packaging process according to claim 1, characterized in that: It also includes coating the surface of LED chips with a perovskite quantum dot-liquid metal composite encapsulation layer, where the liquid metal is a gallium indium tin alloy with a melting point adjusted to 10-25℃, and the volume ratio of quantum dots to liquid metal is 1:3-1:

8. The composite layer forms an ordered array through microfluidic shear-induced self-assembly.

6. The LED filament packaging process according to claim 1, characterized in that: The perovskite quantum dots have a CsPbBr3 / CsPbI3 core-shell structure. The shell thickness is controlled to 2-5 nm through in-situ ion exchange reaction. The emission wavelength of the quantum dots can be dynamically adjusted from 550-700 nm by electric field modulation, and the color temperature can be adjusted from 2000-10000 K.

7. The LED filament packaging process according to claim 1, characterized in that: The flexible substrate is a composite material of polyetheretherketone and carbon nanotubes, with a CNT mass fraction of 0.5-2%. The substrate bending modulus is adjusted to 2-8 GPa through magnetic field-assisted orientation, and the thermal conductivity is increased to 5-15 W / (m·K).

8. The LED filament packaging process according to claim 1, characterized in that: It also includes a phase change material microcapsule heat dissipation structure integrated at both ends of the package. The phase change material is a paraffin / expanded graphite composite material with a phase change temperature of 40-60℃ and a microcapsule particle size of 10-50μm. The peak heat flux density of the package is reduced by more than 60%.

9. The LED filament packaging process according to claim 1, characterized in that: In transient liquid phase diffusion welding, the solder is a composite material of tin-silver-copper lead-free alloy and nano-silver particles, with a nano-silver mass fraction of 5-15%. During the welding process, a pulsed magnetic field of 0.1-1T and 10-100Hz is applied to promote the flow of liquid metal and achieve void-free welding.

10. The LED filament packaging process according to claim 1, characterized in that: With a luminous efficacy of 200 lm / W, the light decay is ≤3% after 10,000 hours, the operating temperature is ≤60℃, and it can withstand ≥10,000 bending cycles with a curvature radius of 1mm without failure. It also has electromagnetic shielding effectiveness: attenuation ≥20dB in the 30MHz-1.5GHz frequency band.

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