Outdoor lighting fixtures need to withstand the test of ice and snow, 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 waterproof material is the position of the sealed electrical component when the product is designed. The glue material is used for waterproofing during assembly.
Factors affecting the waterproof performance of lamps
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. Electron potting colloids can crack when aged. 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 adhesive force is lowered. These are all damage to the waterproof ability of the luminaire.
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 ℃ 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.
Thermal expansion and contraction of the lamp housing: The change of temperature causes the thermal expansion and contraction of the lamp. The coefficient of linear expansion of different materials is different, 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 air tightness of the lamp.
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.
However, the structure of the waterproof design of the luminaire has higher requirements for machining, and the dimensions of each component must be precisely matched. Only waterproof materials can be guaranteed with suitable materials and construction.
The long-term stability of the waterproof structure of the luminaire is closely related to its design, performance of the selected lamp material, processing accuracy, and assembly technology.
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 achieve the waterproof function of the outdoor lighting.
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 so on.