Glue pouring process for outdoor small-spacing module

Abstract

The invention discloses an outdoor small-spacing module glue pouring technology. The technology comprises the steps that S1, dehumidification baking and surface cleaning are conducted on a module; s2, mixing the component A glue solution and the component B glue solution according to an accurate proportion, fully stirring and mixing, and then carrying out vacuum defoaming; s3, the module is placed in a jig to be horizontally fixed, and the jig and the module are integrally preheated to 40-50 DEG C; s4, the defoamed glue solution is transferred into a double-liquid glue pouring machine with a static mixing head, and a glue nozzle is controlled to move at a constant speed along a preset path in a micro-negative pressure environment to pour the glue solution on the surface of the module; s5, after glue filling is completed, standing and leveling are conducted on the module, and then non-contact heating and defoaming are conducted on the surface of glue; s6, the leveled module is subjected to primary curing and main curing; and S7, naturally cooling the module after curing, and performing appearance inspection and waterproof performance test on the potting surface. According to the invention, the quality problems of non-uniform color, inaccurate glue amount and the like of small-spacing module glue pouring can be effectively solved, and the packaging reliability of the module is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of LED display module manufacturing technology, and in particular to a potting process for outdoor small-pitch modules. Background Technology

[0002] Small-pitch LED display modules (typically referring to those with a pixel pitch of P2.0 or less) are gradually moving from indoor to outdoor applications due to their high resolution and seamless splicing advantages. However, the harsh outdoor environment presents challenges such as high humidity, large temperature differences, strong ultraviolet radiation, and rain erosion. Furthermore, the high density and tiny gaps between LED chips in small-pitch LED modules place extremely high demands on the potting process.

[0003] However, existing potting processes are mostly designed for large-pitch or ordinary LED modules. When applied directly to small-pitch modules, the following prominent technical problems arise: 1. The adhesive may precipitate or have uneven color due to storage, leading to inconsistent color on the module surface after curing, resulting in color difference patches and severely affecting the display effect; 2. With extremely high pixel density, air bubbles in the tiny gaps between LED beads are difficult to expel, forming visible defects after curing and affecting display consistency; 3. If the potting process is not properly controlled, adhesive stress or high temperature may damage the delicate surface-mount LED beads and driver ICs; 4. The amount of adhesive, the thickness of the adhesive layer, and its uniformity are difficult to control precisely. Insufficient adhesive or a thin adhesive layer will result in inadequate protection, while excessive or thick adhesive will easily cause overflow.

[0004] Therefore, there is an urgent need for a dedicated potting encapsulation method for outdoor small-pitch LED display modules to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an outdoor small-pitch module potting process with uniform adhesive layer color and precise quantitative control to ensure yield.

[0006] To solve the above technical problems, the present invention can be implemented using the following technical solutions: An outdoor small-pitch module potting process includes the following steps: S1. Dehumidify, bake, and clean the module, and mask the non-bonded areas of the module. S2. Mix component A and component B adhesive in a precise ratio and stir thoroughly before vacuum degassing. S3. Place the cleaned module into the fixture and fix it horizontally, and preheat the fixture and the module as a whole to 40℃-50℃; S4. Transfer the degassed adhesive to a two-component dispensing machine with a static mixing head, and pour the adhesive onto the module surface by controlling the nozzle to move at a uniform speed along the preset path under a slight negative pressure environment. S5. After the glue injection is completed, move the module together with the fixture to the dust-proof platform and let it stand still for leveling. Then, perform non-contact heating on the surface of the colloid to eliminate bubbles. S6. Perform preliminary curing and main curing on the leveled module. S7. After the curing is completed, naturally cool the module to room temperature, demold and remove the mask, and conduct appearance inspection and waterproof performance test on the glue injection surface.

[0007] In one embodiment, the step S1 includes the following steps: S11. Place the module in a constant-temperature oven and bake it at 60°C - 80°C for 2 - 4 hours. S12. Use high-purity anhydrous ethanol or a special cleaner, in cooperation with a dust-free cloth, cotton swab or ion air gun, to clean the surface of the module. S13. On the areas that need to be protected on the back and sides of the module, stick special high-temperature masking paper or silicone mask film.

[0008] In one embodiment, in the step S2, the component A glue liquid is the epoxy resin main agent, and the component B glue liquid is the curing agent. Before mixing the component A glue liquid and the component B glue liquid, first use a pneumatic-driven glue mixer to stir the component A glue liquid until the color of the component A glue liquid is evenly stirred.

[0009] In one embodiment, in the step S2, after the component A glue liquid and the component B glue liquid are mixed at a weight ratio of 10:1, place them in a vacuum degassing device and degas at a vacuum degree of -0.095 MPa to -0.1 MPa for 3 - 8 minutes until there are no visible bubbles in the glue liquid.

[0010] In one embodiment, in the step S4, the pouring speed is 5 - 15 mm / s, the height of the glue nozzle from the surface of the module is 1 mm - 3 mm, and the pouring path is a "return" shape or a "Z" shape spiral progressive path.

[0011] In one embodiment, in the step S5, the standing leveling time is 10 - 20 minutes. For non-contact heating to eliminate bubbles, use an infrared light source with a wavelength greater than 800 nm or a hot air gun, with a heating temperature of 60°C - 80°C and an action time of 30 - 60 seconds.

[0012] In one embodiment, the step S6 includes the following steps: S61. Place the leveled module in a curing furnace and let it stand still in an environment of 45°C ± 5°C for 1 - 1.5 hours for preliminary curing. S62. Raise the temperature at a rate of 1 - 2°C / min to 80°C ± 5°C and maintain this temperature for 2.5 - 4 hours to complete the main curing.

[0013] In one embodiment, the actual amount of glue can be monitored by weighing the difference in weight of the module before and after glue pouring, so that the amount of glue poured into a single module is within the range of (65±3)g. After pouring, the glue completely covers the LED lamp base with a coverage thickness of more than 1mm, and ensures that the glue does not contact the light-emitting surface of the LED lamp bead or the back of the module.

[0014] In one embodiment, the module weighs 557g before glue application and 621g after glue application, and the weight difference is monitored at least once per hour.

[0015] In one embodiment, the two-component dispensing machine and nozzle must meet lead-free requirements. Beneficial effects

[0016] 1. By first stirring the A component adhesive until the color is uniform, the sedimentation and color stratification of the A component adhesive are effectively broken, ensuring the color uniformity of the cured adhesive layer from the source, thereby eliminating color difference in the module.

[0017] 2. By setting precise mixing ratios, module dispensing volume, and adhesive layer thickness standards, and combining this with timed weighing and verification during the dispensing process, high precision and consistency control of dispensing volume can be achieved.

[0018] 3. By adopting dehumidification treatment and vacuum degassing process, internal corrosion, electrochemical migration and optical defects caused by moisture and air bubbles are fundamentally eliminated, thereby enabling the module to reach and maintain the IP68 protection level.

[0019] 4. The low-speed micro-negative pressure potting process combined with infrared secondary defoaming can effectively fill the micron-level gaps and eliminate tiny air bubbles between pixels, making the potting process in this invention applicable to small-pitch modules below P2.0.

[0020] 5. By using a stepped preliminary curing and main curing process, the shrinkage stress of the adhesive can be reduced, thereby protecting precision SMT components and ensuring product yield and long-term reliability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall process of the glue-filling process for the outdoor small-pitch module of the present invention; Figure 2 This is a schematic diagram of step S1 of the potting process for outdoor small-pitch modules of the present invention; Figure 3 This is a schematic diagram of step S6 in the potting process of the outdoor small-pitch module of the present invention. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] It should be noted that when an element is said to be "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is said to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. Conversely, when an element is said to be "directly on" another element, there is no intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] Please see Figures 1 to 3 An outdoor small-pitch module potting process includes the following steps: S1. Dehumidify, bake, and clean the module, and mask the non-bonded areas of the module. S2. Mix component A and component B adhesive in a precise ratio and stir thoroughly before vacuum degassing. S3. Place the cleaned module into the fixture and fix it horizontally, and preheat the fixture and the module as a whole to 40℃-50℃; S4. Transfer the degassed adhesive to a two-component dispensing machine with a static mixing head, and pour the adhesive onto the module surface by controlling the nozzle to move at a uniform speed along the preset path under a slight negative pressure environment. S5. After the glue is poured, move the module and fixture to a dustproof water platform and let it stand and level. Then, use non-contact heating to defoam the surface of the glue. S6. Perform preliminary curing and main curing on the leveled modules; S7. After curing, allow the module to cool naturally to room temperature, demold and remove the mask, and inspect the appearance and waterproof performance of the filling surface.

[0026] Specifically, in this embodiment, before potting the LED module, the LED module to be potted is first checked for defects such as deformation, damage, missing or improperly inserted LED beads. If all the checks are satisfactory, the LED module is placed in a constant temperature oven and baked at 60℃-80℃ for 2-4 hours. This step thoroughly removes moisture from the PCB, LED beads, and packaging materials, effectively preventing 'bubbles' or 'fog inside the LED beads' after potting, ensuring the quality of the product after potting. After the LED module is dehumidified, high-purity anhydrous ethanol or a special cleaning agent, along with a lint-free cloth, cotton swabs, or an ion gun, is used to clean the surface of the module, removing solder slag, dust, fingerprints, and oil stains, ensuring the cleanliness of the module's potting surface. At the same time, special high-temperature masking tape or silicone masking film is applied to the back of the module (terminals and interfaces) and the sides where protection is needed to prevent the adhesive from contaminating non-potting areas such as sockets and waterproof connectors.

[0027] Subsequently, a two-component epoxy resin potting compound was selected. Component A is the main epoxy resin agent, which is black in color, while component B is the curing agent, specifically an amine or anhydride curing agent. Because component A may precipitate or exhibit uneven coloring during storage, direct use would result in inconsistent color on the cured module surface, causing color patches and severely affecting the display effect. Therefore, component A needs to be stirred using a pneumatically driven mixer until its color is uniform and no whitening is observed before being mixed with component B. By first stirring component A until its color is uniform, the sedimentation and color stratification of component A are effectively broken down, addressing the issue from the source. To ensure the uniformity of the cured adhesive layer's color and eliminate color differences in the modules, the A and B components are weighed at a 10:1 weight ratio and thoroughly mixed in a low-speed mixer to avoid introducing too much air during high-speed mixing. After the A and B components are well mixed, the mixture is immediately placed in a vacuum degassing machine and degassed for 3-8 minutes at a vacuum of -0.095MPa to -0.1MPa until the adhesive is clear and free of bubbles. By first dehumidifying and then vacuum degassing, internal corrosion, electrochemical migration, and optical defects in the LED module caused by moisture and bubbles can be prevented, thus enabling the LED module to achieve and maintain an IP68 protection rating.

[0028] Once the module and adhesive are prepared, place the module into a dedicated fixture for horizontal fixation. Then, preheat the fixture and the module as a whole to 40℃-50℃. Preheating reduces the viscosity of the adhesive, allowing it to flow more easily and penetrate into tiny gaps after pouring.

[0029] The vacuum-degassed adhesive is then transferred to a two-component dispensing machine with a static mixing head. Simultaneously, a fixture containing the module is installed on the two-component dispensing machine, and the machine's program (coordinates, air pressure, dispensing volume, etc.) is set. The machine is then started, and the nozzle is driven to pour the adhesive along a spiral path in a "U" or "Z" shape. The dispensing speed of the nozzle is 5-15 mm / s, and the nozzle is 1-3 mm above the module surface, allowing the adhesive to naturally cover the entire module surface by its own leveling properties. By controlling the pouring speed at 5-15 mm / s, turbulence can be avoided, air bubble entrainment can be prevented, and sufficient wetting and penetration can be ensured, as well as precise control of the amount and shape of the adhesive. If the speed is too fast (e.g., >20 mm / s), the adhesive will cause turbulence and splashing on the module surface, which can easily entrain air into the adhesive and form tiny air bubbles that are difficult to eliminate. Low-speed flow is laminar flow, which allows the adhesive to move forward and spread smoothly and sequentially. The low speed also gives the adhesive sufficient time to fully penetrate every micro-bubble through its surface tension and capillary action. By observing the corners, we can achieve seamless encapsulation and ensure a complete seal. This also ensures that the cross-sectional shape and amount of adhesive deposited along the path are uniform, avoiding localized areas that are too thick or too thin. Controlling the height between the nozzle and the module surface to 1mm-3mm minimizes the impact of adhesive drop. If the nozzle is too high (e.g., >5mm), the dripping adhesive will impact the already spread adhesive surface, easily trapping air and forming bubbles. This may also disturb delicate and unfixed surface-mount components, ultimately ensuring the quality of the potting.

[0030] After the adhesive is poured, the module and fixture can be moved to a dustproof water platform for static leveling. The static leveling time is 10-20 minutes. Then, the surface of the adhesive is defoamed by non-contact heating. This non-contact heating defoaming uses an infrared light source with a wavelength greater than 800nm ​​or a hot air gun, with a heating temperature of 60℃-80℃ and an action time of 30-60 seconds. By allowing the adhesive to stand, the surface tension of the adhesive allows it to flow and level completely automatically. If the standing and leveling time is less than 10 minutes, the leveling process is not fully completed. If the standing and leveling time is longer than 20 minutes, the adhesive may begin to gel initially, affecting the efficiency of subsequent operations and increasing the risk of dust contamination. In addition, since small air bubbles may appear during the dispensing process, an infrared light source with a wavelength greater than 800nm ​​or a hot air gun can be used to non-contactly scan and heat the adhesive surface at a distance of 10cm-15cm. The heating temperature is precisely controlled within the range of 60℃-80℃ to prevent overheating of the adhesive. Heating reduces the surface tension of the adhesive, causing the micro-bubbles to break and disappear, thus ensuring the yield rate of the product. The use of low-speed micro-negative pressure dispensing combined with infrared secondary defoaming process can effectively fill the micron-level gaps and eliminate micro-bubbles between pixels, making the dispensing process of this invention applicable to small-pitch modules below P2.0, thereby improving the adaptability of the dispensing process to high-density pixels.

[0031] After the adhesive has leveled, the module undergoes preliminary and primary curing. Specifically, during the preliminary curing process, the leveled module is placed in a curing oven and left to stand at 45℃±5℃ for 1-1.5 hours for initial curing. At this temperature, the cross-linking reaction starts slowly, and the adhesive gradually and uniformly transitions from a liquid to a gel state. This allows time for any remaining trace gases to escape. Preliminary curing allows the adhesive to initially gel and set, preventing stress from being directly generated by high temperatures. After preliminary curing, the curing oven is then heated by 1-2℃. The temperature is raised to 80℃±5℃ at a rate of / min, and the module is maintained at this temperature for 2.5-4 hours to complete the main curing of the module. Main curing at this temperature allows the molecular chains to obtain sufficient kinetic energy, accelerates the cross-linking reaction, and ensures that the adhesive network structure is complete and dense. This guarantees the long-term weather resistance, water resistance, and mechanical protection performance of the LED module. Furthermore, the stepped primary curing and main curing process reduces the shrinkage stress of the adhesive, thereby protecting the precision SMT components and ensuring the product yield and long-term reliability.

[0032] After the module undergoes initial and main curing, the cured module is allowed to cool naturally to room temperature before demolding and removal of the mask. Simultaneously, the potting surface is inspected for appearance, and optical consistency and waterproof performance are tested after power-on. After the LED module cools to room temperature, the high-temperature masking tape or silicone masking film on the back (terminals and interfaces) and sides of the module is removed. The module is then placed under specialized lighting for multi-angle inspection of the glue surface's uniformity, flatness, and any defects. Samples of the module are then subjected to IP67 or IP68 level waterproof and dustproof tests to verify the potting sealant effect. After potting the first LED module, the operator performs a self-inspection, which is then jointly verified by quality control personnel and equipment technicians. A confirmation slip for the first piece is recorded. This process allows for the identification of systemic and global setting errors, such as incorrect glue mixing ratios, potting path coordinate offsets, and improper air pressure settings, facilitating timely correction.

[0033] In addition, during the potting process of the LED module, the actual potting amount can be monitored by weighing the difference in weight of the module before and after potting, so as to ensure high precision and consistency control of the potting amount. Specifically, before step S1, the LED module is weighed. In this embodiment, the weight of the module before weighing is 557g. After the module is potted, i.e. after step S7, it is weighed again. In this embodiment, the weight of the module after potting is 621g. Therefore, the potting amount of a single module can be controlled within the range of (65±3)g. At the same time, after the pouring is completed, it is checked whether the glue completely covers the LED lamp feet and the coverage thickness is greater than 1mm, and it is ensured that the glue does not contact the light-emitting surface of the LED lamp beads and the back of the module.

[0034] Furthermore, the monitoring frequency for the weight difference of the LED modules is at least once per hour. Since the curing quality of component A and component B adhesives strictly depends on a 10:1 weight ratio, during continuous production, the metering system of the dual-component dispensing machine may experience slight proportional drift due to mechanical wear, adhesive temperature changes, etc., causing the actual dispensing amount to deviate from the preset range of (65±3)g. This deviation is gradual and subtle; if not intervened in time, it will cause batch-wide curing defects after a certain period. Therefore, weighing the modules once per hour ensures the good curing yield of subsequent batches. Ultimately, by setting precise mixing ratios, module dispensing amounts, and adhesive layer thickness standards, combined with timed weighing verification during the dispensing process, high-precision and consistent control of the dispensing amount can be achieved.

[0035] Finally, to prevent cross-contamination and ensure the environmental compliance of the end products, the two-component dispensing machine and nozzle in this embodiment must meet lead-free requirements. By using 316L stainless steel or specific types of PEEK (polyetheretherketone) engineering plastics for the nozzle and parts in contact with the adhesive, it can be ensured that the lead-free adhesive does not contain heavy metals restricted by the RoHS directive, thereby guaranteeing that the produced products meet environmental compliance requirements.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of this invention. Those skilled in the art can readily implement this invention based on the accompanying drawings and the above description; however, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the invention's technical solution, utilizing the disclosed technical content, are equivalent embodiments of this invention; furthermore, any equivalent changes, alterations, or variations made to the above embodiments based on the essential technology of this invention still fall within the protection scope of this invention's technical solution.

Claims

1. A potting process for outdoor small-pitch modules, characterized in that, It includes the following steps: S1. Dehumidify and bake the module and clean its surface, and mask the non-glue-injected area of the module; S2. Mix the component A glue liquid and the component B glue liquid in an exact proportion, fully stir and mix them, and then perform vacuum degassing; S3. Place the cleaned module in a fixture and fix it horizontally, and preheat the fixture and the module as a whole to 40°C - 50°C; S4. Transfer the degassed glue liquid to a two-component glue injection machine with a static mixing head, and control the glue nozzle to move uniformly along a preset path under a slightly negative pressure environment to pour the glue liquid onto the surface of the module; S5. After the glue injection is completed, move the module together with the fixture to a dust-proof platform and let it stand still for leveling, and then perform non-contact heating to eliminate bubbles on the surface of the colloid; S6. Perform preliminary curing and main curing on the module that has completed leveling; S7. After the curing is completed, naturally cool the module to room temperature, demold and remove the mask, and perform appearance inspection and waterproof performance test on the glue-injected surface.

2. The potting process for outdoor small-pitch modules according to claim 1, characterized in that: The step S1 includes the following steps: S11. Place the module in a constant temperature oven and bake it at 60°C - 80°C for 2 - 4 hours; S12. Use high-purity anhydrous ethanol or a special cleaning agent, in cooperation with a dust-free cloth, cotton swab or ion air gun, to clean the surface of the module; S13. Stick special high-temperature masking paper or silicone masking film on the areas that need to be protected on the back and side of the module.

3. The potting process for outdoor small-pitch modules according to claim 1, characterized in that: In the step S2, the component A glue liquid is an epoxy resin main agent, the component B glue liquid is a curing agent, and before mixing the component A glue liquid and the component B glue liquid, first use a pneumatic-driven glue mixer to stir the component A glue liquid until the color of the component A glue liquid is evenly stirred.

4. The potting process for outdoor small-pitch modules according to claim 3, characterized in that: In the step S2, after the component A glue liquid and the component B glue liquid are mixed in a weight ratio of 10:1, place them in a vacuum degassing device and degas for 3 - 8 minutes under a vacuum degree of -0.095 MPa to -0.1 MPa until there are no visible bubbles in the glue liquid.

5. The potting process for outdoor small-pitch modules according to claim 1, characterized in that: In the step S4, the pouring speed is 5 - 15 mm / s, the height of the glue nozzle from the surface of the module is 1 mm - 3 mm, and the pouring path is a "return" shape or a "Z" shape spiral progressive path.

6. The potting process for outdoor small-pitch modules according to claim 1, characterized in that: In the step S5, the standing still and leveling time is 10 - 20 minutes, and the non-contact heating to eliminate bubbles uses an infrared light source with a wavelength greater than 800 nm or a hot air gun, its heating temperature is 60°C - 80°C, and the action time is 30 - 60 seconds.

7. The potting process for outdoor small-pitch modules according to claim 1, characterized in that: The step S6 includes the following steps: S61. Place the leveled module in a curing furnace and stand still for 1 - 1.5 hours in an environment of 45°C ± 5°C for preliminary curing; S62. Raise the temperature to 80°C ± 5°C at a rate of 1 - 2°C / min and maintain it at this temperature for 2.5 - 4 hours to complete the main curing.

8. The potting process for outdoor small-pitch modules according to claim 1, characterized in that: Weigh the weight difference of the module before and after glue injection to monitor the actual glue injection amount, so that the glue injection amount of a single module is within the range of (65 ± 3) g. After the pouring is completed, the glue liquid completely covers the LED lamp pins and the covering thickness is greater than 1 mm, and ensure that the glue liquid does not contact the light-emitting surface of the LED lamp beads and the back of the module.

9. The potting process for outdoor small-pitch modules according to claim 8, characterized in that: The weight of the module before glue injection is 557 g, the weight after glue injection is 621 g, and the monitoring frequency of the weight difference is at least once per hour.

10. The potting process for outdoor small-pitch modules according to claim 1, characterized in that: The two-component dispensing machine and nozzle must meet lead-free requirements.

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