Factors Affecting the Waterproof Performance of Lamps
Outdoor lighting fixtures have long withstood the test of ice, snow, scorching sun, wind, rain, and lightning, and the cost is relatively high, and it is difficult to disassemble and repair on the external wall, and needs to meet the requirements of long-term stable work. The LED is a delicate and noble semiconductor component. If it gets wet, the chip will absorb moisture and damage the LED, PcB and other components. LED is suitable for working in dry and lower temperature. To ensure that the LED can work stably for a long time under harsh outdoor conditions, the design of the waterproof structure of the lamp is extremely critical.
The current waterproof technology of lamps and lanterns is mainly divided into two directions: structural waterproofing and material waterproofing. The so-called structural waterproofing means that after the components of each structure of the product are combined, they already have the waterproof function. When the material is waterproof, it is necessary to set aside potting glue to seal the position of the electrical components during product design, and use glue material to achieve waterproofing during assembly. The two waterproof designs are suitable for different product lines, and each has its own advantages.
1. Ultraviolet rays
Ultraviolet rays have a destructive effect on the wire insulation layer, shell protective coating, plastic parts, potting glue, sealing rubber strips, and adhesives exposed outside the lamp.
After the wire insulation layer is aged and cracked, water vapor will penetrate into the lamp through the gaps in the wire core. After the aging of the lamp shell coating, the coating on the edge of the shell cracks or peels off, and there will be some gaps. After the plastic shell is aged, it will deform and crack. The aging of the electronic potting gel will cause cracking. The sealing rubber strip is aging and deformed, and there will be gaps. The adhesive between the structural parts is aging, and there will be gaps after reducing the adhesion. These are the damage of ultraviolet rays to the waterproof ability of lamps.
2. High and low temperature
The outdoor temperature changes greatly every day. In summer, the surface temperature of the lamps can rise to 50～60℃ during the day and drop to 10～20 qC at night. In winter, the temperature can drop to below zero on icy and snowy days, and the temperature difference varies more throughout the year. Outdoor lamps and lanterns in the summer high temperature environment, the material accelerates aging and deformation. When the temperature drops below zero, the plastic parts become brittle, or crack under the pressure of ice and snow.
3. Thermal expansion and contraction
Thermal expansion and contraction of the lamp shell: The change of temperature causes the lamp to expand and contract. Different materials (such as glass and aluminum) have different linear expansion coefficients, and the two materials will shift at the joint. The process of thermal expansion and contraction is repeated cyclically, and the relative displacement will be repeated continuously, which greatly damages the air tightness of the lamp.
The internal air expands with heat and shrinks with cold: The water droplets on the glass of the buried lamp can often be observed on the ground of the square, but how do the water droplets penetrate into the lamps filled with potting glue? This is the result of breathing when heat expands and cold contracts. When the temperature rises, under the action of huge negative pressure, the moist air penetrates into the interior of the lamp body through tiny gaps in the material of the lamp body, and encounters a lower temperature lamp shell, condenses into water droplets and gathers. After the temperature is lowered, under the action of positive pressure, air is discharged from the lamp body, but the water droplets are still attached to the lamp. The breathing process of temperature changes is repeated every day, and more and more water accumulates inside the lamps. The physical changes of thermal expansion and contraction make the design of waterproof and air tightness of outdoor LED lamps a complicated system engineering.