Gradient vacuum segmented glue filling and curing method for LED wall washer

Abstract

This invention discloses a gradient vacuum segmented potting and curing method for LED wall washer lights, comprising: pretreatment and tooling positioning, using biodegradable adhesive-resistant cotton to pre-seal non-sealed areas, pre-vacuuming and preheating; low-pressure slow potting of the bottom thermally conductive adhesive, combined with vibration degassing in a vacuum environment, filling to 70% of the cavity height; semi-curing and shaping, so that the bottom adhesive reaches a Shore A20~30 semi-cured state; surface weather-resistant adhesive replenishment, secondary degassing under slight negative pressure; three-stage gradient temperature rise curing (55℃~85℃ step temperature rise) combined with step cooling to eliminate thermal stress; post-treatment and testing. This invention solves the technical problems of residual air bubbles, contradictory adhesive layer performance, shrinkage cracking, and adhesive seepage contamination in the potting of long strip LED wall washer lights, achieving a waterproof rating of IP68 or higher, a thermal conductivity ≥2.0W / (m·K), significantly improving the yield rate, and is suitable for the encapsulation and processing of various long strip outdoor LED wall washer lights.

Description

Technical Field

[0001] This invention relates to the field of LED lighting packaging technology, specifically to a gradient vacuum segmented potting and curing method for LED wall washer lights, which is particularly suitable for the waterproof and thermally conductive packaging of long strip-shaped outdoor LED wall washer lights. Background Technology

[0002] As a core lighting fixture for outdoor landscape lighting, LED wall washer lights are constantly exposed to humid, high and low temperatures, and rain conditions. Their potting and encapsulation process directly determines the fixture's waterproof rating, thermal conductivity, and lifespan. Existing patents related to potting in wall washer lights primarily focus on structural improvements, such as creating a ring-shaped potting structure by adding a potting groove to the top of the aluminum extrusion profile (e.g., CN209445245U), or installing an anti-seepage component between the bottom wall of the mounting cavity and the circuit board (e.g., CN214038165U). However, these structural improvements fail to solve the technical challenges of the potting process itself.

[0003] Currently, traditional wall washer light potting processes mostly employ a one-time, full-filling under normal pressure and a single adhesive solution for overall curing, which has the following technical drawbacks: (1) The long and narrow cavity of the lamp body has a large flow resistance of glue when potting at normal pressure. Air bubbles are easily trapped in the gap between the lamp beads and the PCB board and at both ends of the lamp body, resulting in waterproof failure and thermal conduction failure. (2) A single adhesive cannot meet the requirements of thermal conduction buffering and surface weather protection. Soft thermal conductive adhesive is easy to deform and has poor surface scratch resistance. Hard sealant has high shrinkage stress, which can easily lead to the desoldering of lamp beads and cracking of glass cover. (3) Traditional one-time curing process has a high shrinkage rate of adhesive, which is prone to shrinkage pits and cracking of adhesive layer. In addition, during the dispensing process, the adhesive is easy to seep into non-sealed areas such as screw holes and heat dissipation fins. (4) The existing process environment is poorly adapted, the glue quality fluctuates greatly under different ambient temperatures, and the yield rate is low.

[0004] The search revealed that a systematic dispensing process combining "segmented dispensing + gradient vacuum control + semi-curing and shaping + three-stage gradient curing" is not publicly available in the prior art. Summary of the Invention

[0005] This invention aims to solve the technical problems in the existing LED wall washer light potting process, such as residual bubbles, single adhesive properties, shrinkage cracking, adhesive seepage pollution, and poor environmental adaptability. It provides a potting and curing method that can achieve bubble-free, high thermal conductivity, high weather resistance, low stress, and anti-seepage integrated processing.

[0006] The technical solution adopted in this invention is as follows: A gradient vacuum segmented potting and curing method for LED wall washer lights includes the following steps: Step S1, Pre-processing and tooling positioning: The LED wall washer light housing, PCB board, and glass cover are pre-assembled and framed, retaining the end caps for pre-reserved glue injection ports and stepped vents. The assembled light body is placed horizontally on a constant temperature vibration fixture, with the fixture clamping both ends of the light body to ensure a horizontal error of ≤0.5mm. The non-sealed areas inside the light housing (screw holes, heat dissipation channels, and vent valve mounting positions) are pre-sealed with biodegradable adhesive-resistant cotton, with the sealing thickness flush with the inner wall of the light housing. Then, the fixture and the light body are placed together into a vacuum potting chamber, the chamber is closed and sealed, and the chamber is pre-vacuumed, maintaining a vacuum level of -0.06MPa to -0.07MPa. The fixture and the light body are preheated to 35℃ to 40℃ and kept at that temperature for 10 to 15 minutes to eliminate moisture and residual air inside the light body.

[0007] Step S2: Low-pressure slow-filling and initial vacuum degassing of the bottom thermal conductive adhesive: A high thermal conductivity flexible potting solution is prepared at the bottom layer. This solution uses an organosilicon thermally conductive adhesive with a composite filler of alumina and boron nitride, exhibiting a thermal conductivity ≥2.0 W / (m·K) and a viscosity controlled at 800~1000 mPa·s. Low-pressure potting is performed from the bottom of the lamp body through the injection port, with an injection pressure of 0.1~0.15 MPa and an injection speed controlled at 5~8 mL / min. The adhesive slowly rises along the guide ribs on the side wall of the lamp body, filling 70% of the lamp body cavity and completely encapsulating the PCB board and electronic components. After potting, a vacuum of -0.06 MPa to -0.07 MPa is maintained. A constant-temperature vibration fixture is activated, with a vibration frequency of 20~30 Hz and an amplitude of 0.2~0.3 mm. Vibration degassing is performed for 15~20 minutes until no bubbles overflow from the adhesive surface. Vibration is then stopped, and the solution is allowed to stand under vacuum for 5~10 minutes to allow the adhesive to naturally level.

[0008] Step S3, Semi-curing and pretreatment: Close the vacuum chamber, slowly introduce dry air to restore normal pressure, and start the tooling heating module for low-temperature pre-curing. The curing temperature is 45℃~50℃, and the curing time is 30~40 minutes, so that the bottom thermally conductive adhesive reaches a semi-cured state with a Shore A hardness of 20~30. After semi-curing, remove the biodegradable adhesive-resistant cotton in the non-sealed area, clean the inside of the lamp body to remove adhesive residue, and at the same time raise the tooling temperature gradient to 55℃~60℃ and keep it at that temperature for 10~15 minutes to prepare for surface adhesive pouring.

[0009] Step S4, Surface weather-resistant adhesive filling and secondary venting: Prepare a high-weather-resistant hardened adhesive for the surface layer, using UV-resistant and anti-aging epoxy resin with a Shore D hardness of 70-80 and a viscosity controlled at 1200-1500 mPa·s. Apply the adhesive from the same injection port at a pressure of 0.15-0.2 MPa and a speed of 3-5 mL / min until the adhesive is flush with the lamp body end face. During the application process, maintain a slight negative pressure at a vacuum level of -0.03 MPa to -0.04 MPa to help expel air bubbles from the surface adhesive and prevent air entrapment. After application, turn off the negative pressure and allow the surface to stand for 8-10 minutes to allow the adhesive to flow naturally and form a smooth sealing surface.

[0010] Step S5, Three-stage gradient curing and stress relief: A three-stage gradient temperature curing process is used to avoid stress caused by rapid shrinkage of the adhesive layer. First stage (low temperature setting stage): temperature 55℃~60℃, curing time 50-60min, to allow the surface adhesive to initially solidify and prevent the adhesive from flowing and deforming. The second stage (medium-temperature curing stage): temperature 70℃~75℃, curing time 80-90min, to complete the cross-linking reaction between the bottom layer and the surface layer, and improve the overall strength of the adhesive layer. The third stage (high-temperature post-curing stage): temperature 80℃~85℃, curing time 30-40min, to enhance the weather resistance and thermal conductivity stability of the adhesive layer; After curing, a stepped cooling process is performed, reducing the temperature by 10°C every 10 minutes until room temperature is reached. This eliminates thermal stress between the adhesive layer and the lamp body and glass mask, preventing the adhesive layer from cracking and the mask from deforming.

[0011] Step S6, Post-processing and Inspection: After curing, remove the lamp body, cut off excess glue from the injection port and vent, and sand it smooth. Perform waterproof and thermal conductivity tests on the lamp. The waterproof rating should reach IP68 or above, and the thermal conductivity deviation should be ≤5%. Discard unqualified products to complete the entire glue injection and curing process.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) By using a gradient vacuum injection method of low-pressure slow injection at the bottom layer + vacuum vibration degassing + surface micro negative pressure injection, combined with biodegradable adhesive-resistant cotton pre-sealing, the residual air bubbles in the long strip cavity are effectively eliminated, the waterproof rating reaches IP68 or above, and the adhesive is prevented from seeping into non-sealed areas. (2) The functional layered design of the bottom layer of high thermal conductivity flexible adhesive and the top layer of high weather resistance hard adhesive is adopted. The bottom layer adhesive ensures thermal conductivity and buffer performance (thermal conductivity ≥2.0W / (m·K)), and the top layer adhesive ensures weather resistance and surface hardness (Shore D70~80), which overcomes the technical contradiction that a single adhesive liquid cannot take into account both thermal conductivity and weather resistance. (3) The first stress relief process of “semi-curing and shaping + three-stage gradient heating and curing + step cooling” is created. Semi-curing and shaping ensures the interfacial bonding strength between the bottom layer adhesive and the top layer adhesive. Three-stage curing controls the shrinkage rate. Step cooling eliminates thermal stress and effectively avoids shrinkage pits, cracks and mask deformation. (4) The process parameters are precise and controllable, and the environmental adaptability is strong, which can significantly improve the yield of glue dispensing and reduce production costs. Attached Figure Description

[0013] Figure 1 This is a process flow diagram of the gradient vacuum segmented potting and curing method for the LED wall washer light of the present invention. Detailed Implementation Example 1

[0014] Take a 1200mm long LED wall washer light body and perform potting and curing processes, referring to... Figure 1 The curing method includes the following steps: Step S1: Place the lamp body horizontally on the constant temperature vibration fixture with a levelness error of 0.3mm. Use biodegradable adhesive cotton to seal the screw holes and heat dissipation channels. After placing it in the vacuum chamber, pre-evacuate to -0.065MPa, preheat to 38℃, and keep warm for 10min.

[0015] Step S2: Prepare the silicone thermally conductive adhesive (alumina + boron nitride filler, thermal conductivity 2.2 W / (m·K), viscosity 900 mPa·s), pour it into the cavity to 70% height at a pressure of 0.12 MPa and a speed of 6 mL / min, maintain a vacuum of -0.065 MPa, degas it by vibration at a frequency of 25 Hz and an amplitude of 0.25 mm for 18 min, and let it stand for 5 min.

[0016] Step S3: Restore normal pressure, pre-cur at 48℃ for 35 minutes until the adhesive layer hardness reaches Shore A25, remove the adhesive-resistant cotton and clean it, then heat to 58℃ and hold for 10 minutes.

[0017] Step S4: Prepare epoxy resin potting compound (Shore D75, viscosity 1350mPa·s), fill it with 0.18MPa pressure and 4mL / min until the end face is flush, maintain vacuum of -0.035MPa to degas, and let it stand for 10min.

[0018] Step S5: Three-stage curing: 58℃ / 60min→72℃ / 90min→82℃ / 40min, with a step-down temperature of 10℃ every 10min to room temperature.

[0019] Step S6: Post-treatment and testing: Waterproof rating IP68, thermal conductivity 2.1W / (m·K), no bubbles, no cracks, no glue seepage.

[0020] The LED wall washer light prepared in this embodiment underwent 500 high and low temperature cycle tests (-40℃~85℃) and a 72-hour water immersion test. The light fixture functioned normally, with no water ingress or adhesive layer cracking. The yield rate reached 98.5%, which is significantly higher than the approximately 85% of the traditional process. Example 2

[0021] An LED wall washer light body with a length of 1800mm was subjected to potting and curing processes using essentially the same process parameters as in Example 1. The differences were that the potting speed was adjusted to 5mL / min (bottom layer) and 3mL / min (top layer), the vibration degassing time was extended to 20min, and the three-stage curing times were adjusted to 60min, 90min, and 40min respectively, remaining unchanged. Test results showed that the waterproof rating reached IP68, the adhesive layer was free of bubbles and cracks, and the yield rate reached 97.8%, proving that the method of this invention has good adaptability to wall washer lights of different lengths. Comparative Example

[0022] The process employs a traditional one-time, atmospheric pressure full-filling method, with a single silicone adhesive undergoing integral curing without vacuum degassing, segmented filling, or segmented curing. Test results show: visibly visible residual air bubbles within the adhesive layer; a waterproof rating of only IP65; low surface hardness (Shore A30) and poor scratch resistance; and the appearance of shrinkage pits and localized cracking after curing, resulting in a yield rate of approximately 82%.

[0023] The comparison shows that the method of the present invention is significantly superior to the traditional process in terms of waterproof rating, adhesive layer performance, and yield.

Claims

1. A gradient vacuum segmented potting and curing method for LED wall washer lights, characterized in that, Includes the following steps: Step S1, Pre-processing and tooling positioning: The LED wall washer light housing, PCB board, and glass cover are pre-assembled and framed, with the end cap reserved for glue injection port and stepped venting port. The assembled light body is then placed horizontally on a constant temperature vibration fixture. Biodegradable adhesive-resistant cotton is used to pre-seal the non-sealed areas inside the lamp housing. Then, the tooling and lamp body are placed into the vacuum potting cavity, the cavity is pre-vacuumed, and the vacuum degree is maintained at -0.06MPa~-0.07MPa. The tooling and lamp body are preheated to 35℃~40℃ and kept at that temperature for 10~15 minutes. Step S2: Low-pressure slow-filling and initial vacuum degassing of the bottom thermal conductive adhesive: A highly thermally conductive flexible potting liquid is prepared at the bottom layer and injected at low pressure from the bottom of the lamp body through the injection port. The injection pressure is 0.1~0.15MPa and the injection speed is controlled at 5~8mL / min, filling the lamp body cavity to 70% of its height. After the injection is completed, maintain a vacuum of -0.06MPa to -0.07MPa, start the constant temperature vibration fixture, vibrate and degas for 15 to 20 minutes, then stop the vibration and keep it in a vacuum state for 5 to 10 minutes. Step S3, Semi-curing and pretreatment: Close the vacuum chamber, restore normal pressure, and start the tooling heating module for low-temperature pre-curing. The curing temperature is 45℃~50℃ and the curing time is 30~40 minutes, so that the bottom thermally conductive adhesive reaches a semi-cured state and the adhesive layer hardness is Shore A20~30. After semi-curing, remove the biodegradable adhesive cotton, clean the inside of the lamp body, and at the same time raise the temperature gradient of the tooling to 55℃~60℃ and keep it warm for 10~15 minutes. Step S4, Surface weather-resistant adhesive filling and secondary venting: Prepare a surface high weather-resistant hard glue solution, and inject the glue from the same injection port. The injection pressure is 0.15~0.2MPa, and the injection speed is 3~5mL / min until the glue solution is flush with the end face of the lamp body. During the glue injection process, turn on the micro negative pressure and maintain the vacuum degree at -0.03MPa~-0.04MPa. After applying the adhesive, turn off the negative pressure and let it stand for 8-10 minutes; Step S5, Three-stage gradient curing and stress relief: A three-stage gradient temperature curing process is adopted: First stage: Temperature 55℃~60℃, curing time 50-60min; Second stage: Temperature 70℃~75℃, curing time 80-90min; Third stage: Temperature 80℃~85℃, curing time 30-40min; After curing, perform a step-down cooling process, reducing the temperature by 10°C every 10 minutes until room temperature is reached; Step S6, Post-processing and Inspection: After curing, remove excess adhesive from the injection port and vent, and conduct waterproof and thermal conductivity tests.

2. The method according to claim 1, characterized in that, The horizontality error of the lamp body in step S1 is ≤0.5mm.

3. The method according to claim 1, characterized in that, The sealing thickness of the biodegradable adhesive cotton mentioned in step S1 is flush with the inner wall of the lamp housing.

4. The method according to claim 1, characterized in that, The bottom layer of high thermal conductivity flexible potting liquid mentioned in step S2 is an organosilicon thermally conductive adhesive with a composite filler of alumina and boron nitride, with a thermal conductivity ≥2.0W / (m·K) and a viscosity controlled at 800~1000mPa·s.

5. The method according to claim 1, characterized in that, The vibration frequency of the constant temperature vibration fixture mentioned in step S2 is 20~30Hz and the amplitude is 0.2~0.3mm.

6. The method according to claim 1, characterized in that, The surface high weather-resistant hard potting liquid mentioned in step S4 is a UV-resistant and anti-aging epoxy resin potting liquid with a surface hardness of Shore D 70~80 and a viscosity controlled at 1200~1500mPa·s.

7. The method according to claim 1, characterized in that, The three-stage gradient curing described in step S5 is carried out in a vacuum potting cavity.

8. The method according to claim 1, characterized in that, The waterproof rating of the waterproof test in step S6 reaches IP68 or above, and the thermal conductivity deviation is ≤5%.

Images