Mini LED display screen lamp panel and preparation method thereof

Abstract

The invention relates to the technical field of LED display screens, and discloses a Mini LED display screen lamp panel and a preparation method thereof.The preparation method comprises the steps that (1) a Mini LED chip is fixed to a substrate through die bonding solder paste, and an initial product is obtained; (2) carrying out AOI test on the initial product to obtain a detection result which comprises bad points with different defect types; (3) maintaining the initial product; and (4) baking is carried out, so that the die bonding solder paste is fully cured, and the qualified Mini LED display screen lamp panel is obtained. The solid crystal solder paste is prepared from the following raw materials in parts by weight: 100 parts of tin-based alloy powder, 8-15 parts of filler, 1-6 parts of a film-forming agent, 1-6 parts of an active agent, 0.1-2.5 parts of a thixotropic agent, 5-15 parts of a solvent and 0-5 parts of an auxiliary agent, the filler is epoxy resin and carbon nanotubes. By implementing the method and the device, the bad point repair efficiency and the yield of the Mini LED display screen lamp panel are improved, and the bonding effect of the Mini LED chip on the substrate is good.

Description

Technical Field

[0001] This invention relates to the technical field of LED displays, and more particularly to a Mini LED display panel and its manufacturing method. Background Technology

[0002] In the production process of Mini LED display lamp boards, the lamp surface manufacturing process typically includes the following steps: die bonding, AOI testing, reflow oven baking, and rework. Currently, the main process flow is as follows: after die bonding, AOI testing is performed, followed by filtering, baking, and solder melting of the lamp board. Finally, the coordinates of defective points identified by the AOI test are repaired. This process ensures the quality and performance of the Mini LED display lamp boards. However, the current process has the following problems: each defective point needs to be individually heated to disassemble the component. This process requires high-precision equipment and strict operation to avoid damage to surrounding components. After disassembling the component, a pusher is needed to treat the surface of the solder pads to scrape off residual solder paste. However, the flatness of the solder pads after disassembly is not ideal, affecting subsequent replacement and rework. After replacing the component, each rework point needs to be individually heated and soldered. This process is time-consuming and requires high-precision operation, increasing production costs and time. Therefore, the entire Mini LED display lamp board production process is cumbersome and time-consuming, and has high requirements for technology and equipment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a Mini LED display lamp board. The preparation process is simple and significantly improves the efficiency and yield of repairing defects on the Mini LED display lamp board.

[0004] Accordingly, the present invention also provides a Mini LED display panel, wherein the Mini LED chip and the substrate have high bonding strength, thereby extending the service life of the Mini LED display panel.

[0005] To address the aforementioned technical problems, the first aspect of this invention provides a method for preparing a Mini LED display panel, characterized by comprising:

[0006] (1) The Mini LED chip is fixed on the substrate using die bonding solder paste to obtain the initial product;

[0007] (2) Perform AOI testing on the initial product to obtain test results, the test results including defective points with different defect types;

[0008] (3) Repair the initial product;

[0009] (4) Bake to fully cure the die-bonding solder paste and obtain a qualified Mini LED display board;

[0010] The raw materials for preparing the die-bonding solder paste, by weight, include:

[0011] The mixture contains 100 parts of tin-based alloy powder, 8-15 parts of filler, 1-6 parts of film-forming agent, 1-6 parts of activator, 0.1-2.5 parts of thixotropic agent, 5-15 parts of solvent, and 0-5 parts of additives.

[0012] The filler is epoxy resin and carbon nanotubes.

[0013] As an improvement to the above solution, AOI testing is performed on the initial product, including:

[0014] Image information is obtained by acquiring images of the initial product;

[0015] The image information is processed and analyzed to obtain abnormal regions;

[0016] Defect analysis was performed on the abnormal area to obtain different defect types;

[0017] The defect type is output to obtain the detection result.

[0018] As an improvement to the above solution, the defect types include:

[0019] The first type of defect used to detect whether patch components are missing or have opposite polarity;

[0020] A second type of defect used to detect coordinate deviations in patch components;

[0021] The third type of defect is used to detect whether the arrangement of Mini LED beads is consistent;

[0022] The fourth type of defect used to detect whether Mini LEDs have surface contamination or scratches;

[0023] The fifth type of defect is used to detect whether Mini LEDs have abnormal brightness or color.

[0024] As an improvement to the above scheme, in step (4), the baking temperature is 200℃-250℃, the heating rate is 1℃ / s-3℃ / s, the baking time is 1min-6min, and the baking atmosphere is an inert gas.

[0025] As an improvement to the above scheme, the carbon nanotubes are aminosilane-grafted carbon nanotubes, and the weight ratio of epoxy resin to aminosilane-grafted carbon nanotubes is (3-7):1.

[0026] As an improvement to the above solution, the epoxy resin has an epoxy value of 0.55eq / 100-0.62eq / 100 and a viscosity of 2000cps-5000cps at 25°C.

[0027] The epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and alicyclic epoxy resin;

[0028] The carbon nanotubes without aminosilane grafts have an aspect ratio of 300-600 and an average particle size of 20nm-40nm.

[0029] As an improvement to the above scheme, the method for preparing the aminosilane-grafted carbon nanotubes includes: treating the carbon nanotubes with an acid solution and then reacting them with aminosilane in an alkaline environment; wherein the weight ratio of the carbon nanotubes to the aminosilane is (0.8-2):1.

[0030] The aminosilane is one or more of γ-aminopropyltriethoxysilane, 4-amino-3,3-dimethylbutyltrimethoxysilane, (4-amino-3,3-dimethylbutyl)(methyl)dimethoxysilane, and (2-aminoisopropyl)triethoxysilane.

[0031] As an improvement to the above scheme, in step (4), the baking temperature is 130℃-180℃ and the time is 60min-120min.

[0032] As an improvement to the above scheme, the tin-based alloy powder comprises the following components by mass percentage: Ag 0.5%–1%, Cu 0.2%–0.6%, Ni 0.05%–0.08%, Bi 0.005%–0.02%, Sb 0.005%–0.02%, with the balance being Sn;

[0033] The tin-based alloy powder has a D50 of 8 μm to 12 μm and a specific surface area of ​​1 m². 2 / cm 3 ~1.5m 2 / cm 3 .

[0034] As an improvement to the above solution, the film-forming agent is one or more of hydrogenated rosin resin, polymerized rosin, disproportionated rosin resin, acid-modified rosin, acrylic resin, and phenolic resin.

[0035] The active agent is a lactic acid-glycolic acid copolymer and phthalic acid;

[0036] The thixotropic agent is one or more of the following: dehydrated castor oil fatty acids, ricinoleic acid, polymerized dehydrated castor oil, hydrogenated castor oil, modified hydrogenated castor oil, and ethylene bis-stearamide.

[0037] The solvent is one or more of the following: dipropylene glycol methyl ether, hexanediol, tetrahydrofurfuryl alcohol, butyl acetate, benzyl alcohol, nitromethane, glycerol, propylene glycol, ethylene glycol, ethanol, methanol, diethylene glycol dibutyl ether, and diethylene glycol monomethyl ether.

[0038] A second aspect of the present invention also provides a Mini LED display panel, which is prepared by the above-described preparation method.

[0039] Implementing this invention has the following beneficial effects:

[0040] In this application, by first repairing defects in the initial Mini LED display board product obtained after preliminary fixing, and then uniformly baking and curing the die-bonding solder paste on the entire board, the Mini LED chips can be firmly bonded to the substrate, forming a qualified Mini LED display board with good performance. This avoids the operation of heating and desoldering when repairing defects on the board, and also eliminates the need to use push pins to remove the original die-bonding solder paste on the pads, thus maintaining the integrity of the original pads. Moreover, after rework, there is no need to solder the repaired points separately, avoiding secondary heating of the Mini LED display board, greatly improving the repair efficiency of defects, and helping to improve the yield of Mini LED display boards.

[0041] Furthermore, the raw materials for preparing the die-bonding solder paste in this application, by weight, include: 100 parts of tin-based alloy powder, 8-15 parts of filler, 1-6 parts of film-forming agent, 1-6 parts of activator, 0.1-2.5 parts of thixotropic agent, 5-15 parts of solvent, and 0-5 parts of additives; wherein, the filler is epoxy resin and carbon nanotubes, which gives the die-bonding solder paste good initial adhesion and good fluidity before curing, facilitating the repair, adjustment, and disassembly of Mini LED chips, and after curing, it has high bonding strength, heat resistance, and thermal conductivity, effectively extending the service life of the Mini LED display board. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described in further detail below.

[0043] To address the above problems, the first aspect of this invention provides a method for manufacturing a Mini LED display panel, comprising:

[0044] (1) The Mini LED chip is fixed on the substrate using die bonding solder paste to obtain the initial product;

[0045] (2) Perform AOI testing on the initial product to obtain test results, the test results including defective points with different defect types;

[0046] (3) Repair the initial product;

[0047] (4) Bake to fully solidify the die bonding solder paste and obtain a qualified Mini LED display board.

[0048] By repairing defects in the initial Mini LED display board obtained after preliminary fixing, and then uniformly baking and curing the die-bonding solder paste on the entire board, the Mini LED chips can be firmly bonded to the substrate, forming a qualified Mini LED display board with good performance. This avoids the need for heating and desoldering operations when repairing defects on the board, and also eliminates the need to use push pins to remove the original die-bonding solder paste from the pads, thus maintaining the integrity of the original pads. Furthermore, there is no need to separately solder the repaired points after rework, avoiding secondary heating of the Mini LED display board, greatly improving the efficiency of defect repair and contributing to a higher yield of Mini LED display boards.

[0049] Each step will be explained in detail below:

[0050] Regarding (1), the Mini LED chip is fixed on the substrate using die-bonding solder paste to obtain the initial product;

[0051] Specifically, the process involves setting pads on the substrate, then printing die-bonding solder paste at the pad locations as solder joints, and finally transferring the Mini LED chip to the corresponding solder joints for fixation, thus securing the Mini LED chip on the substrate.

[0052] Understandably, before repairing defects in the initial Mini LED display board obtained after preliminary fixing, AOI (Automated Optical Inspection) testing is required to identify the defects. Therefore, it is necessary to ensure that the Mini LED chip has good initial adhesion to the substrate before the die-bonding solder paste has cured, ensuring the accuracy of the AOI test results and good operability so that the chip can be easily disassembled and refixed during rework.

[0053] Preferably, the raw materials for preparing the die-bonding solder paste, by weight, include: 100 parts of tin-based alloy powder, 8-15 parts of filler, 1-6 parts of film-forming agent, 1-6 parts of activator, 0.1-2.5 parts of thixotropic agent, 5-15 parts of solvent, and 0-5 parts of additives, wherein the filler is epoxy resin and carbon nanotubes. In this application, the addition of filler to the solder paste system formed by tin-based alloy powder allows the epoxy resin and carbon nanotubes to interact with other components in the system. On the one hand, this improves the initial adhesion of the Mini LED chip to the substrate, ensuring the accuracy of AOI inspection results, and also improves the bonding strength of the Mini LED chip after curing on the substrate, ensuring that the Mini LED chip is not easily detached from the substrate by external forces during use, resulting in a Mini LED display panel with high bonding strength. On the other hand, it also improves the heat resistance, conductivity, and mechanical strength of the Mini LED chip on the substrate, effectively improving the yield of the Mini LED display panel.

[0054] Furthermore, the surface tension of epoxy resin is lower than that of metal, promoting the spread of other components in the system on the substrate surface to form a physical adsorption layer. Simultaneously, it can synergize with thixotropic agents to form a three-dimensional network structure encapsulating the tin-based alloy powder. This achieves temporary fixation of the component through van der Waals forces, ensuring the Mini LED chip is firmly bonded to the substrate even before the die-bonding solder paste cures. This facilitates AOI testing and yields highly accurate test results. Preferably, the epoxy resin has an epoxy value of 0.55eq / 100-0.62eq / 100 and a viscosity of 2000cps-5000cps at 25°C. When used in conjunction with film-forming agents and other components, it can achieve initial fixation and final firm bonding of the Mini LED chip, while also giving the system good flowability, allowing for easy chip disassembly and refixation during rework. Exemplarily, the epoxy resin is bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, alicyclic epoxy resin, etc.

[0055] It is easy to understand that the addition of epoxy resin reduces the thermal conductivity of the solder paste system, thereby affecting the heat dissipation performance of Mini LEDs. Therefore, this application incorporates carbon nanotubes into the system to improve the thermal conductivity of the die-bonding solder paste and enhance heat dissipation, ensuring that the heat generated by the chip during rework and baking can be effectively conducted to the substrate, preventing chip overheating. In this application, the carbon nanotubes are aminosilane-grafted carbon nanotubes. Besides improving the thermal conductivity of the die-bonding solder paste, they also improve the interfacial bonding strength with components such as epoxy resin and tin-based alloy powder, thereby increasing the adhesive strength, tensile strength, shear strength, and temperature stability of the die-bonding solder paste. This prevents agglomerates formed by carbon nanotubes from hindering the uniform distribution of alloy powder, which would lead to increased solder joint porosity. Simultaneously, it promotes the uniform dispersion of carbon nanotubes, providing good electrical conductivity for the die-bonding solder paste to ensure the electrical connection between the chip and the substrate, improving the luminous efficiency and brightness of the LED display panel.

[0056] Further, the preparation method of the aminosilane-grafted carbon nanotubes includes: treating the carbon nanotubes with an acid solution, and then reacting them with aminosilane in an alkaline environment; wherein the weight ratio of the carbon nanotubes to the aminosilane is (0.8-2):1. In some specific and preferred embodiments, the preparation method of the aminosilane-grafted carbon nanotubes includes: placing the carbon nanotubes in an acid solution and sonicating them at 50℃-65℃ for 2h-4h; subsequently, reacting them with aminosilane at a pH of 9-11 and maintaining the temperature at 60℃-80℃ for 4h-6h. It can be understood that the preparation method of the silane-grafted carbon nanotubes also includes: washing and removing impurities from the product and vacuum drying it; the washing can be done with ethanol or deionized water, and the vacuum drying can be carried out at 50℃-65℃. Optionally, the acid solution can be a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of (2.5-3.5):1, and the aminosilane can be γ-aminopropyltriethoxysilane, 4-amino-3,3-dimethylbutyltrimethoxysilane, (4-amino-3,3-dimethylbutyl)(methyl)dimethoxysilane, (2-aminoisopropyl)triethoxysilane, etc.

[0057] Furthermore, the carbon nanotubes without aminosilane grafting have an aspect ratio of 300-600 and an average particle size of 20nm-40nm. The weight ratio of epoxy resin to aminosilane-grafted carbon nanotubes is (3-7):1. The interaction between the epoxy resin with a specific viscosity and the aminosilane-grafted carbon nanotubes can further control the flowability and conductivity of the die-bonding solder paste, giving it high initial tack before curing. Moreover, the amino groups can promote the curing of epoxy resin, forming a dense three-dimensional network structure, improving the bonding strength, temperature resistance, and thermal conductivity after curing, and effectively extending the service life of the Mini LED display panel.

[0058] Preferably, the tin-based alloy powder comprises the following components by mass percentage: Ag 0.5%–1%, Cu 0.2%–0.6%, Ni 0.05%–0.08%, Bi 0.005%–0.02%, Sb 0.005%–0.02%, with the balance being Sn. Compared to existing tin-based alloy powders, the tin-based alloy powder of the present invention uses a Sn-Ag-Cu alloy as the main component. Through the adjustment of various trace elements, the grain size is refined, and the strength, hardness, and heat resistance of the alloy are improved, thereby enhancing the stability and ductility of the solder paste and meeting the packaging requirements of Mini LED chips.

[0059] Furthermore, the tin-based alloy powder has a D50 of 8 μm to 12 μm and a specific surface area of ​​1 m². 2 / cm 3 ~1.5m 2 / cm 3 .

[0060] Optionally, the film-forming agent is one or more of hydrogenated rosin resin, polymerized rosin, disproportionated rosin resin, acid-modified rosin, acrylic resin, and phenolic resin.

[0061] Optionally, the activator is a lactic acid-glycolic acid copolymer and phthalic acid. The difference in melting temperature allows the film-forming agent, thixotropic agent and other effective components to play their roles at different temperatures. When the temperature rises to the point where the tin-based alloy powder melts, both the lactic acid-glycolic acid copolymer and phthalic acid can decompose without residue. Moreover, it can accelerate the reaction rate of the ring-opening reaction of the epoxy resin and increase the degree of crosslinking of the filler in the system.

[0062] Furthermore, the mass ratio of the lactic acid-glycolic acid copolymer to phthalic acid is 1:(0.5-0.8). If the mass ratio of the lactic acid-glycolic acid copolymer is too large, the activity of the activator will be low; if the mass ratio of phthalic acid is too large, it will cause corrosion to the circuit board.

[0063] Optionally, the thixotropic agent is one or more of the following: dehydrated castor oil fatty acids, ricinoleic acid, polymerized dehydrated castor oil, hydrogenated castor oil, modified hydrogenated castor oil, and ethylene bis-stearamide.

[0064] Optionally, the solvent is one or more selected from dipropylene glycol methyl ether, hexanediol, tetrahydrofurfuryl alcohol, butyl acetate, benzyl alcohol, nitromethane, glycerol, propylene glycol, ethylene glycol, ethanol, methanol, diethylene glycol dibutyl ether, and diethylene glycol monomethyl ether.

[0065] Optionally, the additives may be defoamers, antioxidants, viscosity modifiers, corrosion inhibitors, etc. Examples of defoamers include mineral oil, polyoxyethylene glycerol ether, polyoxypropyl glycerol ether, polyoxypropyl polyoxyethyl glycerol ether, methylsiloxane oil, dimethyl silicone oil, etc.; examples of antioxidants include triphenyl phosphate, triphenyl phosphite, butylated hydroxyanisole, butylated hydroxytoluene; examples of viscosity modifiers include polyacrylates, cellulose derivatives, low molecular weight alcohols, low molecular weight ethers, etc.; examples of corrosion inhibitors include benzotriazole, ethylene bis-stearamide, quaternary ammonium compounds, etc.

[0066] In some specific embodiments, the method for preparing the die-bonding solder paste includes:

[0067] A. Mix the solvent, film-forming agent and thixotropic agent, heat to 170℃~190℃ and stir evenly, then cool to 60℃~80℃, add the activator and auxiliary agent in sequence, stir to dissolve, and cool to room temperature to obtain the first mixture;

[0068] B. Mix the first mixture and the filler evenly, then add the tin-based alloy powder and mix evenly to obtain the final product.

[0069] Regarding (2), perform AOI testing on the initial product to obtain test results, the test results including defective points with different defect types;

[0070] In this step, AOI equipment is used to perform AOI testing on the fixed Mini LED chips. The AOI equipment can accurately identify defective points and record their coordinates for subsequent rework, avoiding sending defective boards to the subsequent assembly stage, thereby reducing repair costs or avoiding scrapping unrepairable products.

[0071] The AOI testing items mainly include: positional offset, missing parts, incorrect parts, and reversed polarity. Specifically, the AOI testing of the initial product includes:

[0072] (21) Image acquisition is performed on the initial product to obtain image information;

[0073] In this step, high-resolution cameras, multispectral sensors, linear / area array scanners, and other equipment can be used to photograph the initial product from multiple angles under standardized lighting conditions, and the image information can be obtained through a display screen.

[0074] In some embodiments, a high-resolution camera can be used to take pictures and use its front light to detect the appearance of the initial product, chip position, polarity markings, etc.; a multispectral light source can also be used to enhance the defect contrast and detect defects such as electrode oxidation and electrode surface contamination; a linear / area array scanner can also be used for continuous large-area screening and dynamically capture solder paste flow to detect defects such as surface contamination or scratches, and display specific test images, such as solid color, grayscale gradient, checkerboard, etc.

[0075] (22) Perform image processing and analysis on the image information to obtain abnormal regions;

[0076] In this step, abnormal areas can be marked by comparing with a preset "gold template" (i.e., a standard image), and feature extraction includes positional deviation, missing parts, incorrect parts, and polarity reversal. Specifically, the "gold module" can be used to determine the positional deviation of the LED chip, and brightness / color analysis can be used to quantify the brightness and color coordinates of each pixel, thereby determining whether it exceeds the tolerance range.

[0077] (23) Perform defect analysis on the abnormal area to obtain different defect types;

[0078] In this step, based on a preset defect threshold, unqualified areas are marked. For example, if the brightness difference is >10% or the color difference E is >3, the product can be marked as unqualified (NG). This step mainly inspects the bonding quality of the Mini LED chips in the initial product, and does not require inspection of the welding quality. If defects are found after AOI testing, rework can be carried out in a timely manner to ensure that the LED display board is qualified before baking and curing.

[0079] Furthermore, the defect types include: a first defect type for detecting whether the patch element has missing parts and / or reverse polarity; a second defect type for detecting whether the patch element has coordinate deviation; a third defect type for detecting whether the Mini LED beads are arranged consistently; a fourth defect type for detecting whether the Mini LED has surface contamination or scratches; and a fifth defect type for detecting whether the Mini LED has abnormal brightness or color.

[0080] (24) Output the defect type to obtain the detection result.

[0081] In this step, a test report is generated based on the recorded inspection data. The test items include defect location, type, and images, and are associated with information such as production batch, time, and operator. Further, qualified products proceed to the next process, while unqualified products are automatically marked with defect locations and removed by a sorting mechanism to the rework area for repair.

[0082] Regarding (3), repairing the initial product;

[0083] In this step, due to the good viscosity and fluidity of the die-bonding solder paste, the Mini LED chip can be easily disassembled and re-fixed during the repair process without damaging the Mini LED chip or impairing its performance.

[0084] Regarding (4), baking is performed to fully solidify the die-bonding solder paste and obtain a qualified Mini LED display board;

[0085] In this step, the baking temperature is 200℃-250℃, the heating rate is 1℃ / s-3℃ / s, the baking time is 1min-6min, and the baking atmosphere is an inert gas. For example, the temperature can be increased to 217℃ at a heating rate of 2℃ / s, and then reflow soldered at 217℃ for 5min under a nitrogen atmosphere. This allows the epoxy resin and other components in the system to fully cure, thereby triggering the melting and recrystallization of the tin-based alloy, forming a stable metal bonding layer, and promoting the curing of the die-bonding solder paste. Specifically, qualified Mini LED display panels that meet the performance standards can be placed in a thermal cycling baking oven and kept at a constant temperature until the die-bonding solder paste has cured, after which they can be removed from the oven.

[0086] Understandably, step (4) in this application also includes electrical testing of the obtained Mini LED display panel in order to obtain a qualified Mini LED display panel.

[0087] The present invention will be further described below with reference to specific embodiments:

[0088] Example 1

[0089] This embodiment provides a method for preparing a Mini LED display screen light panel, including:

[0090] (1) The Mini LED chip is fixed on the substrate using die bonding solder paste to obtain the initial product;

[0091] (2) Perform AOI testing on the initial product to obtain test results, the test results including defects with different defect types; specifically:

[0092] (21) Image acquisition is performed on the initial product to obtain image information;

[0093] (22) Perform image processing and analysis on the image information to obtain abnormal regions;

[0094] (23) Perform defect analysis on the abnormal area to obtain different defect types;

[0095] (24) Output the defect type to obtain the detection result;

[0096] (3) Repair the defects in the initial product according to the different defect types of the defects;

[0097] (4) Keep the temperature in a 130℃ hot cycle baking oven for 120 minutes to allow the die bonding solder paste to fully solidify and obtain a qualified Mini LED display board.

[0098] The raw materials for preparing the die-bonding solder paste, by weight, include: 100 parts of tin-based alloy powder, 8 parts of filler, 2 parts of phenolic resin, 2 parts of activator, 0.2 parts of hydrogenated castor oil, and 7 parts of solvent.

[0099] The tin-based alloy powder is SAC305 alloy powder; the tin-based alloy powder has a D50 of 10 μm and a specific surface area of ​​1.2 m². 2 / cm 3 ;

[0100] The filler is a mixture of bisphenol F epoxy resin and carbon nanotubes in a weight ratio of 3:1. The bisphenol F epoxy resin has an epoxy value of 0.55eq / 100-0.62eq / 100 and a viscosity of 2000cps-500cps at 25°C (Nan Ya Plastics, Taiwan, NPEF-170). The carbon nanotubes have an aspect ratio of 400 and an average particle size of 20nm.

[0101] The active agent is a lactic acid-glycolic acid copolymer and phthalic acid in a mass ratio of 1:0.6; the solvent is dipropylene glycol methyl ether and hexanediol in a volume ratio of 1:1.

[0102] Accordingly, this embodiment also provides a Mini LED display panel prepared by the above method.

[0103] Example 2

[0104] This embodiment provides a method for preparing a Mini LED display lamp board, which is basically the same as that in Embodiment 1, except that:

[0105] The raw materials for preparing the die-bonding solder paste, by weight, include: 100 parts of tin-based alloy powder, 15 parts of filler, 6 parts of phenolic resin, 6 parts of activator, 2.5 parts of hydrogenated castor oil, and 15 parts of solvent.

[0106] In step (4), the die bonding solder paste is kept at a constant temperature in a 180°C hot cycle baking oven for 65 minutes to fully cure, thus obtaining a qualified Mini LED display board.

[0107] Example 3

[0108] This embodiment provides a method for preparing a Mini LED display lamp board, which is basically the same as that in Embodiment 1, except that:

[0109] The raw materials for preparing the die-bonding solder paste, by weight, include: 100 parts of tin-based alloy powder, 12 parts of filler, 4 parts of phenolic resin, 4 parts of activator, 1.5 parts of hydrogenated castor oil, and 11 parts of solvent.

[0110] In step (4), the die bonding solder paste is kept at a constant temperature in a 150°C hot cycling oven for 90 minutes to fully cure, thus obtaining a qualified Mini LED display board.

[0111] Example 4

[0112] This embodiment provides a method for preparing a Mini LED display lamp board, which is basically the same as that in Embodiment 3, except that:

[0113] The tin-based alloy powder comprises the following components by mass percentage: Ag 0.8%, Cu 0.4%, Ni 0.06%, Bi 0.008%, Sb 0.006%, with the balance being Sn.

[0114] Example 5

[0115] This embodiment provides a method for preparing a Mini LED display lamp board, which is basically the same as that in Embodiment 4, except that:

[0116] The filler is an epoxy resin and a carbon nanotube grafted with aminosilane in a weight ratio of 3:1. The preparation method of the carbon nanotube grafted with aminosilane includes: placing the carbon nanotube in an acid solution and sonicating it at 60°C for 3 hours; then, under the condition of pH 10 and maintaining the temperature at 70°C, reacting it with aminosilane for 5 hours to obtain the filler. The aminosilane is γ-aminopropyltriethoxysilane, and the weight ratio of the carbon nanotube to the aminosilane is 1.2:1.

[0117] Example 6

[0118] This embodiment provides a method for preparing a Mini LED display lamp board, which is basically the same as that in Embodiment 5, except that:

[0119] The filler is bisphenol F type epoxy resin and carbon nanotubes in a weight ratio of 7:1;

[0120] The weight ratio of the carbon nanotubes to the aminosilane is 2:1.

[0121] Example 7

[0122] This embodiment provides a method for preparing a Mini LED display lamp board, which is basically the same as that in Embodiment 5, except that:

[0123] The filler is bisphenol F type epoxy resin and carbon nanotubes in a weight ratio of 5:1.

[0124] The weight ratio of the carbon nanotubes to the aminosilane is 0.8:1.

[0125] Example 8

[0126] This embodiment provides a method for preparing a Mini LED display lamp board, which is basically the same as that in Embodiment 4, except that:

[0127] The filler is bisphenol F type epoxy resin, aminosilane and carbon nanotubes in a weight ratio of 6.6:1:1.2.

[0128] Performance testing

[0129] 1. Thrust: The Mini LED display lamp board obtained after step (4) in Examples 1-8 was subjected to thrust test. The test results are shown in Table 1.

[0130] 2. Yield: The yield of the Mini LED display lamp boards obtained in Examples 1-8 was tested.

[0131] Table 1 Performance test results of Mini LED chip adhesion on substrate

[0132] Display panel thrust / N Yield / % Example 1 12.5 97.5 Example 2 12.6 97.2 Example 3 12.8 97.3 Example 4 13.0 97.9 Example 5 14.3 98.8 Example 6 13.9 98.5 Example 7 13.8 98.6 Example 8 13.4 98.1

[0133] The results above show that by repairing the defects in the initial product of the Mini LED display lamp board after preliminary fixing, and then uniformly baking and curing the die-bonding solder paste on the entire lamp board, and optimizing the raw materials for the die-bonding solder paste preparation by adding epoxy resin and carbon nanotubes, especially when the carbon nanotubes are modified with aminosilane, the efficiency of defect repair is greatly improved, the bonding strength of the die-bonding solder paste after curing is also improved, and the yield of the Mini LED display lamp board is effectively improved.

[0134] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a Mini LED display screen light panel, characterized in that, include: (1) The Mini LED chip is fixed on the substrate using die bonding solder paste to obtain the initial product; (2) Perform AOI testing on the initial product to obtain test results, the test results including defective points with different defect types; (3) Repair the initial product; (4) Bake to fully cure the die-bonding solder paste and obtain a qualified Mini LED display board; The raw materials for preparing the die-bonding solder paste, by weight, include: The mixture contains 100 parts of tin-based alloy powder, 8-15 parts of filler, 1-6 parts of film-forming agent, 1-6 parts of activator, 0.1-2.5 parts of thixotropic agent, 5-15 parts of solvent, and 0-5 parts of additives. The filler is epoxy resin and carbon nanotubes.

2. The method for preparing the Mini LED display lamp board as described in claim 1, characterized in that, AOI testing of the initial product includes: Image information is obtained by acquiring images of the initial product; The image information is processed and analyzed to obtain abnormal regions; Defect analysis was performed on the abnormal area to obtain different defect types; The defect type is output to obtain the detection result.

3. The method for preparing the Mini LED display lamp board as described in claim 2, characterized in that, The defect types include: The first type of defect used to detect whether patch components are missing or have opposite polarity; A second type of defect used to detect coordinate deviations in patch components; The third type of defect is used to detect whether the arrangement of Mini LED beads is consistent; The fourth type of defect used to detect whether Mini LEDs have surface contamination or scratches; The fifth type of defect is used to detect whether Mini LEDs have abnormal brightness or color.

4. The method for preparing the Mini LED display lamp board as described in claim 1, characterized in that, In step (4), the baking temperature is 200℃-250℃, the heating rate is 1℃ / s-3℃ / s, the baking time is 1min-6min, and the baking atmosphere is an inert gas.

5. The method for preparing the Mini LED display lamp board as described in claim 1, characterized in that, The carbon nanotubes are grafted aminosilane carbon nanotubes, and the weight ratio of epoxy resin to grafted aminosilane carbon nanotubes is (3-7):

1.

6. The method for preparing the Mini LED display lamp board as described in claim 4, characterized in that, The epoxy resin has an epoxy value of 0.55eq / 100-0.62eq / 100 and a viscosity of 2000cps-5000cps at 25°C. The epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and alicyclic epoxy resin; The carbon nanotubes without aminosilane grafts have an aspect ratio of 300-600 and an average particle size of 20nm-40nm.

7. The method for preparing the Mini LED display lamp board as described in claim 5, characterized in that, The method for preparing the aminosilane-grafted carbon nanotubes includes: treating the carbon nanotubes with an acid solution and then reacting them with aminosilane in an alkaline environment; wherein the weight ratio of the carbon nanotubes to the aminosilane is (0.8-2):

1. The aminosilane is one or more of γ-aminopropyltriethoxysilane, 4-amino-3,3-dimethylbutyltrimethoxysilane, (4-amino-3,3-dimethylbutyl)(methyl)dimethoxysilane, and (2-aminoisopropyl)triethoxysilane.

8. The method for preparing the Mini LED display lamp board as described in claim 1, characterized in that, The tin-based alloy powder comprises the following components by mass percentage: Ag 0.5%–1%, Cu 0.2%–0.6%, Ni 0.05%–0.08%, Bi 0.005%–0.02%, Sb 0.005%–0.02%, with the balance being Sn; The tin-based alloy powder has a D50 of 8 μm to 12 μm and a specific surface area of ​​1 m². 2 / cm 3 ~1.5m 2 / cm 3 .

9. The method for preparing the Mini LED display lamp board as described in claim 1, characterized in that, The film-forming agent is one or more of hydrogenated rosin resin, polymerized rosin, disproportionated rosin resin, acid-modified rosin, acrylic resin, and phenolic resin; The active agent is a lactic acid-glycolic acid copolymer and phthalic acid; The thixotropic agent is one or more of the following: dehydrated castor oil fatty acids, ricinoleic acid, polymerized dehydrated castor oil, hydrogenated castor oil, modified hydrogenated castor oil, and ethylene bis-stearamide. The solvent is one or more of the following: dipropylene glycol methyl ether, hexanediol, tetrahydrofurfuryl alcohol, butyl acetate, benzyl alcohol, nitromethane, glycerol, propylene glycol, ethylene glycol, ethanol, methanol, diethylene glycol dibutyl ether, and diethylene glycol monomethyl ether.

10. A Mini LED display panel, characterized in that, The Mini LED display panel is prepared by the preparation method described in any one of claims 1-9.