Basic knowledge of waterproof LED outdoor lamps

Outdoor lighting has been subjected to the test of ice, snow, scorching sun, wind, rain and thunder for a long time, and the cost is relatively high. However, it is difficult to dismantle and repair when used on the outer wall, and it needs to meet the requirements of long-term stable work. The LED is very fragile semiconductor components. If it gets wet, the chip will absorb moisture and damage the LED, PCB and other components. LEDs are suitable for working in dry and cooler temperatures. To ensure long-term stable operation of LEDs under harsh outdoor conditions, the waterproof structure design of lamps is extremely critical.

The current waterproof technology of lamps is mainly divided into two directions: structural waterproofing and material waterproofing. The structural waterproofing means that after the components of each structure of the product are combined, the waterproof function is already available. The waterproofing of materials means that when designing the product, the location of the potting glue to seal the electrical components should be reserved, and the glue material should be used to achieve waterproofing during assembly. The two waterproof designs are suitable for different product routes and have their own advantages.

Factors affecting the waterproof performance of lamps

1. Ultraviolet rays

Ultraviolet rays have a damaging effect on the wire insulation layer, protective coating of the casing, plastic parts, potting glue, sealing rubber strips, and adhesives exposed to the outside of the lamp.

After the insulation layer of the wire is aged and cracked, the water vapor will penetrate the interior of the lamp through the gap of the wire core. After the shell coating of the lamp is aged, the coating on the edge of the shell is cracked or peeled off, and there will be some gaps. After the plastic casing is aged, it will deform and crack. The aging of the electronic potting compound can cause cracking. When the sealing rubber strip is aging and deformed, gaps will appear. The adhesive between the structural parts is aging, and gaps can also appear after reducing the adhesion. These are the damage of ultraviolet rays to the waterproof ability of lamps.

2. High and low temperature

Outdoor temperature varies greatly every day. In summer, the surface temperature of lamps and lanterns can rise to 50-60 °C during the day, and drop to 10-20 °C at night. In winter, the temperature in ice and snow days can drop to below zero, and the temperature difference throughout the year changes even more. In the high temperature environment of summer, the material of outdoor lamps will accelerate aging and deformation. When the temperature drops below freezing, plastic parts become brittle, or crack under the pressure of ice and snow.

3. Thermal expansion and contraction

The thermal expansion and contraction of the lamp housing: the change of temperature causes the thermal expansion and contraction of the lamp. The linear expansion coefficients of different materials (such as glass and aluminum profiles) are different, and the two materials will shift at the joint. The process of thermal expansion and contraction is repeated in cycles, and the relative displacement is repeated continuously, which greatly damages the air tightness of the lamps.

The internal air expands and contracts with heat: condensation of water droplets on the glass of buried lamps can often be observed on the ground of the square, and how do the water droplets penetrate the lamps filled with potting glue? This is the result of breathing as heat expands and cools contract. As soon as the temperature rises, under the action of huge negative pressure, the humid air penetrates the interior of the lamp body through the tiny gaps in the material of the lamp body, and then encounters the lower temperature lamp shell, where it condenses into water droplets and gathers. After the temperature is lowered, under the action of positive pressure, the air is discharged from the lamp body, but the water droplets are still attached to the lamp body. The breathing process of temperature changes is repeated every day, and more and more water accumulate inside the lamps. The physical changes of thermal expansion and contraction make the design of waterproof and air tightness of outdoor LED lamps a complex system engineering.