Preparation method of LED display module

Abstract

The invention relates to the technical field of LED display module preparation, in particular to a preparation method of an LED display module, which comprises the following steps: carrying out substrate pretreatment and anti-corrosion coating deposition; printing a high-thermal-conductivity silver adhesive and mounting the high-thermal-conductivity silver adhesive on the driving chip Carrying out flip-chip bonding and reflow soldering on the LED chip; performing nano-scale sealant vacuum filling and sealing; performing dynamic voltage driving circuit integration; embedding the micro-channel heat dissipation structure; and carrying out multispectral calibration and aging test. According to the invention, the titanium nitride coating and the bi-component modified silica gel are used for cooperative protection, the TiN coating is used for blocking water and oxygen permeation, and a flip-chip bonding process is combined to eliminate the oxidation risk of a lead, so that the light transmittance of the module is still greater than or equal to 95% in an environment of 85 DEG C / 85% RH, and the adaptability to a severe environment is remarkably improved; the driving efficiency of the module can reach 92% under the brightness of 1000 nits by combining heat dissipation of the micro-channel, meanwhile, the module supports wide-temperature work from-40 DEG C to 125 DEG C, and the problems of energy consumption and thermal runaway in a high-brightness scene are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of LED display module preparation, and specifically to a method for preparing an LED display module. Background Art

[0002] An LED display module is an independent display unit composed of LED chips, a driving circuit, a substrate, and a packaging structure. It realizes image or text display through arrayed LED chips. Multiple modules can be spliced to form a large-sized display screen, which is widely used in outdoor advertising, stage backgrounds, traffic signs, etc. Its core structure includes a substrate for carrying LEDs, a driving circuit for controlling brightness, a packaging layer for protecting the chips, and a heat dissipation component.

[0003] Generally, traditional LED display modules have significant defects in environmental tolerance. Their packaging materials mostly use epoxy resin, which is prone to colloid yellowing when exposed to ultraviolet light or high humidity environments for a long time, resulting in a significant decrease in light transmittance and accelerating the oxidation of solder joints. Especially in outdoor or industrial environments, the service life is severely shortened. At the same time, traditional driving circuits rely on low-frequency switching devices, with low power conversion efficiency. A large amount of heat is generated during high-brightness operation and the energy consumption remains high. This not only increases the burden on the heat dissipation system but also causes light decay problems due to excessive temperature rise, limiting the brightness and stability of the display module.

[0004] Based on this, the present invention provides a method for preparing an LED display module to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing an LED display module. The prepared high-strength metal connector material not only has good mechanical properties but also has excellent corrosion resistance, effectively ensuring its quality and quality.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] The present invention proposes a method for preparing an LED display module, including the following steps:

[0008] S1. Perform substrate pretreatment and deposition of an anti-corrosion coating;

[0009] S2. Print high-thermal-conductivity silver glue and mount the driving chips;

[0010] S3. Perform flip-chip bonding and reflow soldering of the LED chips;

[0011] S4. Implement vacuum encapsulation with nanoscale sealant;

[0012] S5. Integrate a dynamic voltage driving circuit;

[0013] S6. Embed the microchannel heat dissipation structure. Precision mill a microchannel with a width of 0.3 mm and a depth of 1 mm on the back of the aluminum substrate, embed a copper heat pipe with a thermal conductivity of 400 W / (m·K), connect to an external liquid cooling system with a flow rate of 0.5 L / min and a water temperature of 25 ± 1°C, and the module thermal resistance ≤ 0.5 °C / W;

[0014] S7. Conduct multi-spectral calibration and aging tests.

[0015] Preferably, the implementation steps of step S1 are as follows:

[0016] S1.1. Deposit a 10-μm-thick titanium nitride coating on the surface of the aluminum-based PCB through a vacuum sputtering process, with a sputtering power of 5 kW, an argon flow rate of 50 sccm, a deposition temperature of 200°C, and a vacuum degree ≤ 1×10 -3 Pa;

[0017] S1.2. Subsequently, use a plasma cleaning process to activate the surface of the substrate. The cleaning power is 300 W, the oxygen flow rate is 20 L / min, and it lasts for 5 min to remove organic residues.

[0018] Preferably, the implementation steps of step S2 are as follows:

[0019] S2.1. Print a conductive adhesive with a silver content of 85% in the pad area of the substrate through a fully automatic screen printing machine, with a squeegee pressure of 0.5 MPa, a printing speed of 50 mm / s, and an adhesive layer thickness of 80 ± 5 μm;

[0020] S2.2. When mounting the GaN drive chip, use a vacuum chip mounting process with a mounting accuracy of ±15 μm and a nozzle vacuum degree of -85 kPa.

[0021] Preferably, the implementation steps of step S3 are as follows:

[0022] S3.1. Bond the flip-chip structure MiniLED chip to the gold-plated copper pillar bumps through an eutectic soldering process, with a soldering pressure of 10 N, a temperature of 280°C, and using AuSn alloy solder;

[0023] S3.2. The substrate enters a nitrogen-protected reflow soldering furnace, with a peak temperature of 250°C, a heating rate of 2°C / s, and an oxygen content in the furnace < 50 ppm.

[0024] Preferably, the implementation steps of step S4 are as follows:

[0025] S4.1. Coat the surface of the LED array with a two-component modified silica gel. The vacuum degassing process has a vacuum degree of 0.1 Pa, an injection pressure of 0.3 MPa, and an adhesive layer thickness of 200 μm;

[0026] S4.2. The curing is carried out in two stages: the first stage is pre-curing at 60°C for 30 minutes, and the second stage is final curing at 150°C for 2 hours to form a light transmittance ≥ 95% and IP68 waterproof encapsulation layer.

[0027] Preferably, the implementation steps of step S5 are as follows:

[0028] S5.2. Integrate a digitally adjustable DC-DC converter on the back of the substrate, with an efficiency of 98% and an output current of 10A;

[0029] S5.3. Process vertical interconnection holes through a laser drilling process, with a laser wavelength of 1030nm, a power of 50W, a wiring impedance ≤ 5mΩ, a power supply ripple ≤ 20mV, and an operating temperature range of -40 to 125°C.

[0030] Preferably, the implementation steps of step S7 are as follows:

[0031] S7.1. Place the LED display module under a multi-spectral analysis system, and adjust the LED brightness and color coordinates through an adaptive algorithm, with a chromaticity tolerance Δu'v' ≤ 0.002;

[0032] S7.2. The aging test is carried out in an 85°C / 85%RH environmental chamber for 240h to screen out defective modules with a light decay > 5% or a color shift > 3%.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] Through the collaborative protection of the titanium nitride coating and the two-component modified silica gel, the TiN coating blocks the penetration of water and oxygen, and the silica gel encapsulation layer resists ultraviolet aging. Combining with the flip-chip bonding process eliminates the risk of lead oxidation, enabling the module to still maintain a light transmittance ≥ 95% in an 85°C / 85%RH environment, significantly improving the adaptability to harsh environments. At the same time, the present invention also adopts a GaN driving chip and a dynamic voltage regulating DC-DC converter to reduce the conduction loss, and combines with microchannel heat dissipation to quickly dissipate heat, enabling the module to achieve a driving efficiency of 92% at a brightness of 1000nits, reducing the power consumption by 12%, and at the same time supporting wide-temperature operation from -40 to 125°C, solving the problems of energy consumption and thermal runaway in high-brightness scenarios. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0036] Embodiment, the present invention proposes a preparation method for an LED display module, including the following steps:

[0037] S1. Perform substrate pretreatment and deposition of anti-corrosion coating;

[0038] S2. Print high thermal conductivity silver paste and mount the driving chip;

[0039] S3. Perform flip-chip soldering and reflow soldering of LED chips;

[0040] S4. Implement vacuum potting with nano-level sealant;

[0041] S5. Integrate the dynamic voltage driving circuit;

[0042] S6. Embed the microchannel heat dissipation structure. Precision mill a microchannel with a width of 0.3 mm and a depth of 1 mm on the back of the aluminum substrate, embed a copper heat pipe with a thermal conductivity of 400 W / (m·K), connect to an external liquid cooling system with a flow rate of 0.5 L / min and a water temperature of 25 ± 1°C, and the module thermal resistance ≤ 0.5°C / W;

[0043] S7. Perform multi-spectral calibration and aging test.

[0044] Among them, it should also be noted that the implementation steps of step S1 are as follows:

[0045] S1.1. Deposit a 10-μm-thick titanium nitride coating on the surface of the aluminum-based PCB by vacuum sputtering process, with a sputtering power of 5 kW, an argon flow rate of 50 sccm, a deposition temperature of 200°C, and a vacuum degree ≤ 1×10 -3 Pa;

[0046] S1.2. Subsequently, use the plasma cleaning process to activate the substrate surface, with a cleaning power of 300 W, an oxygen flow rate of 20 L / min, and continue for 5 min to remove organic residues.

[0047] Among them, it should also be noted that the implementation steps of step S2 are as follows:

[0048] S2.1. Print conductive paste with 85% silver content in the pad area of the substrate through a fully automatic screen printer, with a squeegee pressure of 0.5 MPa, a printing speed of 50 mm / s, and a glue layer thickness of 80 ± 5 μm;

[0049] S2.2. When mounting the GaN driving chip, use the vacuum mounting process, with a mounting accuracy of ±15 μm and a nozzle vacuum degree of -85 kPa.

[0050] Among them, it should also be noted that the implementation steps of step S3 are as follows:

[0051] S3.1. Bond the flip-chip structure MiniLED chip to the gold-plated copper pillar bumps by the eutectic soldering process, with a soldering pressure of 10 N, a temperature of 280°C, and use AuSn alloy solder;

[0052] S3.2. The substrate enters a nitrogen - protected reflow soldering furnace with a peak temperature of 250°C, a heating rate of 2°C / s, and an oxygen content in the furnace of <50 ppm.

[0053] Among them, it should also be noted that the implementation steps of step S4 are as follows:

[0054] S4.1. Coating a two - component modified silica gel on the surface of the LED array, with a vacuum degree of 0.1 Pa, an injection pressure of 0.3 MPa, and a glue layer thickness of 200 μm in the vacuum potting process;

[0055] S4.2. Curing is carried out in two stages: the first stage is pre - curing at 60°C for 30 min, and the second stage is final - curing at 150°C for 2 h to form a light - transmissivity ≥ 95% and IP68 waterproof encapsulation layer.

[0056] Among them, it should also be noted that the implementation steps of step S5 are as follows:

[0057] S5.2. Integrating a digital - adjustable DC - DC converter on the back of the substrate, with an efficiency of 98% and an output current of 10 A;

[0058] S5.3. Processing vertical interconnection holes through a laser drilling process, with a laser wavelength of 1030 nm, a power of 50 W, a wiring impedance ≤ 5 mΩ, a power supply ripple ≤ 20 mV, and an operating temperature range of - 40 to 125°C.

[0059] Among them, it should also be noted that the implementation steps of step S7 are as follows:

[0060] S7.1. Place the LED display module under a multi - spectral analysis system, and adjust the LED brightness and chromaticity coordinates through an adaptive algorithm, with a chromaticity tolerance Δu'v' ≤ 0.002;

[0061] S7.2. The aging test is carried out in an 85°C / 85% RH environmental chamber for 240 h to screen out defective modules with a light decay > 5% or a color deviation > 3%.

[0062] Example 1, in this example, the following steps are included:

[0063] S1. Perform substrate pretreatment and anti - corrosion coating deposition. Specifically, it includes the following steps:

[0064] S1.1. Deposit a 10 - μm - thick titanium nitride coating on the surface of the aluminum - based PCB through a vacuum sputtering process, with a sputtering power of 5 kW, an argon flow rate of 50 sccm, a deposition temperature of 200°C, and a vacuum degree ≤ 1×10 -3 Pa;

[0065] S1.2. Subsequently, use a plasma cleaning process to activate the surface of the substrate, with a cleaning power of 300 W, an oxygen flow rate of 20 L / min, and continue for 5 min to remove organic residues;

[0066] S2. Print the high - thermal - conductivity silver paste and mount the drive chip. Specifically, it includes the following steps:

[0067] S2.1. Use a fully automatic screen printer to print a conductive paste with 85% silver content on the substrate pad area. The squeegee pressure is 0.5 MPa, the printing speed is 50 mm / s, and the adhesive layer thickness is 80 ± 5 μm;

[0068] S2.2. When mounting the GaN drive chip, use a vacuum chip - mounting process with a mounting accuracy of ±15 μm and a nozzle vacuum of - 85 kPa;

[0069] S3. Perform flip - chip soldering and reflow soldering of the LED chip. Specifically, it includes the following steps:

[0070] S3.1. Bond the flip - chip structure MiniLED chip to the gold - plated copper pillar bumps through an eutectic soldering process. The soldering pressure is 10 N, the temperature is 280 °C, and use AuSn alloy solder;

[0071] S3.2. The substrate enters a nitrogen - protected reflow soldering furnace. The peak temperature is 250 °C, the heating rate is 2 °C / s, and the oxygen content in the furnace is <50 ppm;

[0072] S4. Implement vacuum potting with a nanoscale sealant. Specifically, it includes the following steps:

[0073] S4.1. Coat the surface of the LED array with a two - component modified silica gel. The vacuum degree of the vacuum potting process is 0.1 Pa, the injection pressure is 0.3 MPa, and the adhesive layer thickness is 200 μm;

[0074] S4.2. Curing is carried out in two stages: the first stage is pre - curing at 60 °C for 30 min, and the second stage is final - curing at 150 °C for 2 h to form a light - transmittance ≥95% and IP68 waterproof encapsulation layer;

[0075] S5. Integrate the dynamic voltage drive circuit. Specifically, it includes the following steps:

[0076] S5.2. Integrate a digital - adjustable DC - DC converter on the back of the substrate with an efficiency of 98% and an output current of 10 A;

[0077] S5.3. Process vertical interconnection holes through a laser drilling process. The laser wavelength is 1030 nm, the power is 50 W, the wiring impedance ≤5 mΩ, the power supply ripple ≤20 mV, and the operating temperature range is - 40 to 125 °C;

[0078] S6. Embed the micro - channel heat - dissipation structure. Precision mill a micro - channel with a width of 0.3 mm and a depth of 1 mm on the back of the aluminum substrate, embed a copper heat pipe with a thermal conductivity of 400 W / (m·K), connect to an external liquid - cooling system with a flow rate of 0.5 L / min and a water temperature of 25 ± 1 °C, and the module thermal resistance ≤0.5 °C / W;

[0079] Example 2. In this example, the sputtering power in step S1.1 is 3 kW, and the others are the same as in Example 1;

[0080] Example 3. In this example, the Ag content in the silver paste in step S2.1 is 70%, and the others are the same as in Example 1;

[0081] Example 4. In this example, the peak temperature in step S3.2 is 230 °C, and the others are the same as in Example 1;

[0082] Example 5. In this example, the thickness of the glue layer in step S4.1 is 150 μm, and the width of the microchannel in step S6 is 0.5 mm, and the others are the same as in Example 1;

[0083] The data in Examples 1 to 5 are shown in Table 1:

[0084] Table 1 Process data parameter table of Examples 1 to 5

[0085]

[0086] Perform the following performance tests on the LED display modules prepared by each process in Examples 1 to 5 according to the following experimental process, Table 2:

[0087] Table 2 Performance test standards

[0088]

[0089]

[0090] The comparison of the performance data of the examples is shown in Table 3;

[0091] Table 3 Comparative table of performance data of Examples 1 to 5

[0092] Experimental group Salt spray resistance of coating (h) Thermal resistance (℃ / W) Light transmittance (%) <![CDATA[Weld shear force (N / mm 2 )]]> Drive efficiency (%) Example 1 1020 0.48 95.3 15.2 92 Example 2 680 0.50 95.1 15.0 90 Example 3 1000 0.65 94.8 14.8 89 Example 4 1015 0.49 95.0 10.1 91 Example 5 1018 0.82 91.5 15.1 90

[0093] Comparative Example 1. In this comparative example, the plating material is replaced, and Al2O3 is used to replace TiN in step S1.1, and the others are the same as in Example 1;

[0094] Comparative Example 2. In this comparative example, the drive chip is replaced, and an Si-based drive chip is used to replace GaN in step S2.2, and the others are the same as in Example 1;

[0095] Comparative Example 3. In this comparative example, the solder alloy is replaced, and Sn63Pb37 is used to replace AuSn in step S3.1, and the others are the same as in Example 1;

[0096] Comparative Example 4. In this comparative example, epoxy resin is used to replace the modified silica gel in step S4.1, and the others are the same as in Example 1;

[0097] Comparative Example 5. In this comparative example, in step S6, the microchannel was cancelled, and the rest was the same as in Example 1;

[0098] The performance data comparison of the comparative examples is shown in Table 4;

[0099] Table 4 Comparison table of performance data of Comparative Examples 1 to 5

[0100] Experimental group Salt spray resistance of coating (h) Thermal resistance (℃ / W) Light transmittance (%) <![CDATA[Weld shear force (N / mm 2 )]]> Drive efficiency (%) Comparative example 1 400 0.50 94.8 14.9 91 Comparative example 2 1015 0.49 95.1 15.0 78 Comparative example 3 1008 0.48 95.0 5.3 90 Comparative example 4 995 0.47 89.2 14.8 89 Comparative example 5 1022 2.1 95.2 15.1 91

[0101] Data analysis and conclusion:

[0102] According to the data of each group in Tables 1 to 3, it can be seen that in Example 1 of the present invention compared with Example 2, the coating thickness is increased, the salt spray resistance time is extended by 50%, the thermal conductivity is increased by 40%, the thermal resistance is reduced by 23%, the solder joint shear force is increased by 50%, cold welding defects are avoided, the light transmittance meets the standard, and ultraviolet aging cracking is avoided. At the same time, the thermal resistance is reduced by 40%, ensuring high brightness stability.

[0103] In summary, in Example 1 of the present invention, the coating and the drive cooperate. The TiN coating and the GaN drive achieve high environmental tolerance and low energy consumption. The combination of 85% Ag paste + 0.3 mm microchannel enables the thermal resistance ≤ 0.5 °C / W, supports the junction temperature ≤ 85 °C at 1000 nits brightness, achieving thermal management balance. At the same time, the 250 °C reflow soldering process is compatible with the segmented curing silicone process, avoiding thermal expansion mismatch of materials.

[0104] In Comparative Examples 1 to 5, the non-optimal solutions of the coating material, drive chip, solder, sealant, and heat dissipation structure lead to a significant decrease in performance. Therefore, the parameters of Example 1 of the present invention are the best examples.

[0105] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0106] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing an LED display module, characterized in that, Including the following steps: S1. Conduct substrate pretreatment and deposition of anti-corrosion coating; S2. Print high thermal conductivity silver paste and mount drive chips; S3. Conduct flip-chip soldering and reflow soldering of LED chips; S4. Implement vacuum potting of nano-level sealant; S5. Conduct integration of dynamic voltage drive circuit; S6. Embed a microchannel heat dissipation structure, precisely mill a microchannel with a width of 0.3 mm and a depth of 1 mm on the back of the aluminum substrate, embed a copper heat pipe with a thermal conductivity of 400 W / (m·K), connect to an external liquid cooling system with a flow rate of 0.5 L / min and a water temperature of 25 ± 1°C, and the module thermal resistance ≤ 0.5°C / W; S7. Conduct multi-spectral calibration and aging test.

2. The manufacturing method of an LED display module according to claim 1, wherein, The implementation steps of step S1 are as follows: S1.1 Deposit a 10-μm-thick titanium nitride coating on the surface of the aluminum-based PCB through a vacuum sputtering process, with a sputtering power of 5 kW, an argon flow rate of 50 sccm, a deposition temperature of 200 °C, and a vacuum degree ≤ 1×10 -3 Pa; S1.

2. Subsequently, use the plasma cleaning process to activate the substrate surface, with a cleaning power of 300 W, an oxygen flow rate of 20 L / min, and a duration of 5 min to remove organic residues.

3. The manufacturing method of an LED display module according to claim 2, characterized in that The implementation steps of step S2 are as follows: S2.

1. Print conductive paste with 85% silver content on the substrate pad area through a fully automatic screen printing machine, with a squeegee pressure of 0.5 MPa, a printing speed of 50 mm / s, and a paste layer thickness of 80 ± 5 μm; S2.

2. When mounting the GaN drive chip, use the vacuum mounting process, with a mounting accuracy of ±15 μm and a nozzle vacuum of -85 kPa.

4. The manufacturing method of an LED display module according to claim 3, characterized in that, The implementation steps of step S3 are as follows: S3.

1. Bond the flip-chip structure MiniLED chip to the gold-plated copper column bumps through the eutectic soldering process, with a soldering pressure of 10 N, a temperature of 280°C, and use AuSn alloy solder; S3.

2. The substrate enters a nitrogen-protected reflow soldering furnace, with a peak temperature of 250°C, a heating rate of 2°C / s, and the oxygen content in the furnace < 50 ppm.

5. The manufacturing method of an LED display module according to claim 4, characterized in that, The implementation steps of step S4 are as follows: S4.

1. Coating a two-component modified silica gel on the surface of the LED array, with a vacuum potting process vacuum of 0.1 Pa, a filling pressure of 0.3 MPa, and a paste layer thickness of 200 μm; S4.

2. Curing is divided into two stages: the first stage is pre-curing at 60°C for 30 min, and the second stage is final-curing at 150°C for 2 h to form a waterproof encapsulation layer with a light transmittance ≥ 95% and IP68 protection.

6. The manufacturing method of an LED display module according to claim 5, characterized in that, The implementation steps of step S5 are as follows: S5.

2. Integrate a digital adjustable DC-DC converter on the back of the substrate, with an efficiency of 98% and an output current of 10 A; S5.

3. Process vertical interconnection holes through the laser drilling process, with a laser wavelength of 1030 nm, a power of 50 W, a wiring impedance ≤ 5 mΩ, a power supply ripple ≤ 20 mV, and an operating temperature range of -40 to 125°C.

7. The manufacturing method of an LED display module according to claim 6, characterized in that, The implementation steps of step S7 are as follows: S7.

1. Place the LED display module under a multi-spectral analysis system, and adjust the LED brightness and color coordinates through an adaptive algorithm, with a chromaticity tolerance Δu'v' ≤ 0.002; S7.

2. The aging test lasts for 240 h in an 85°C / 85% RH environmental chamber to screen defective modules with a light decay > 5% or a color deviation > 3%.

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