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waterproof technical analysis of outdoor LED lamps

Apr 18, 2019

Waterproof Technical analysis of outdoor LED lamps


Outdoor lighting fixtures need to withstand the test of snow and ice, wind and lightning, and the cost is high. Because it is difficult to be repaired on the outer wall, it must meet the requirements of long-term stable work. The LED is a delicate semiconductor component. If it is wet, the chip will absorb moisture and damage the LED, PcB and other components. Therefore, the LED is suitable for drying and low temperature. To ensure long-term stable operation of LEDs under harsh outdoor conditions, the waterproof structure design of lamps is extremely critical.

 

At present, the waterproof technology of lamps is mainly divided into two directions: structural waterproofing and material waterproofing. The so-called structural waterproofing is that after the combination of various structural components of the product, it has been waterproof. The material is waterproof, so that when the product is designed, the position of the potting glue to seal the electrical components is left, and the glue material is used for waterproofing during assembly. The two waterproof designs are available for different product routes, each with its own advantages.

 

Factors affecting the waterproof performance of lamps

 

1, ultraviolet light

 

Ultraviolet rays have a destructive effect on the wire insulation, the outer protective coating, the plastic parts, the potting glue, the sealing ring rubber strip and the adhesive exposed to the outside of the lamp.

 

After the wire insulation layer is aged and cracked, water vapor will penetrate into the interior of the lamp through the gap of the wire core. After the coating of the lamp housing is aged, the coating on the edge of the casing is cracked or peeled off, and a gap may occur. After the plastic case ages, it will deform and crack. The aging of the electronic potting gel causes cracking. The sealing rubber strip is aging and deformed, and a gap will occur. The adhesive between the structural members is aged, and a gap is also formed after the adhesion is lowered. These are all damage to the waterproof ability of the luminaire by ultraviolet light.

 

2, high and low temperature

 

The outdoor temperature varies greatly every day. In summer, the surface temperature of the lamps can rise to 50-60 °C, and the temperature drops to 10-20 qC in the evening. The temperature in winter and snow can drop to below zero, and the temperature difference changes more throughout the year. Outdoor lighting in the high temperature environment in summer, the material accelerates aging deformation. When the temperature drops below zero, the plastic parts become brittle, under the pressure of ice and snow or cracking.

 

3, thermal expansion and contraction

 

Thermal expansion and contraction of the lamp housing: The temperature changes cause the thermal expansion and contraction of the lamp. Different materials (such as glass and aluminum profiles) have different linear expansion coefficients, and the two materials will be displaced at the joint. The process of thermal expansion and contraction is repeated continuously, and the relative displacement is repeated continuously, which greatly damages the airtightness of the lamp.

 

Internal air thermal expansion and contraction: The condensation of water droplets on the buried lamp glass can often be observed on the square floor, and how does the water droplets penetrate into the lamp filled with potting glue? This is the result of respiration during thermal expansion and contraction.

 

4, the structure of waterproof

 

Luminaires based on structural waterproof design need to be tightly matched with silicone sealing ring. The outer casing structure is more precise and complicated. It is usually suitable for large-sized lamps, such as strip floodlights, square and circular floodlights, etc. Lighting.

 

5, the material waterproof

 

The waterproof design of the material is insulated and waterproofed by filling potting glue, and the joint between the closed structural parts is bonded by the sealing glue, so that the electrical components are completely airtight and the waterproof effect of the outdoor lighting is achieved.

 

6, potting glue

 

With the development of waterproof material technology, various types and brands of special potting glues have appeared continuously, for example, modified epoxy resin, modified polyurethane resin, modified organic silica gel, and the like. Different chemical formulas, the physical and chemical properties of potting rubber, such as elasticity, molecular structure stability, adhesion, anti-uV, heat resistance, low temperature resistance, water repellency and insulation properties, are different.

 

Conclusion

 

Regardless of structural waterproofing or material waterproofing, for the long-term stable operation and low failure rate of outdoor lighting, a single waterproof design is difficult to achieve extremely high reliability, and the potential hidden danger of water seepage still exists.

Therefore, the design of high-end outdoor LED lamps is recommended to use waterproof technology to combine the advantages of structural waterproofing and material waterproofing technology to enhance the long-term stability of the LED circuit. If the material is waterproof, it can be added to the respirator to eliminate negative pressure. The structural waterproof design can also be considered to increase potting, double waterproof protection, improve the stability of outdoor lighting for long-term use, and reduce the rate of moisture failure.