What are the technical requirements for LED potting?

LED encapsulant is a type of auxiliary material for LED potting, featuring high transmittance, high refractive index, and good fluidity. It can protect LED chips, enhance light extraction efficiency, relieve stress, has low viscosity, is easy to defoam, suitable for encapsulation and molding, improving the durability and reliability of LEDs. Currently, the common requirements for LED encapsulants include flame retardancy, color, hardness, waterproofing, quick-drying, adhesion, thermal conductivity, etc. How to select the right LED encapsulant? Common types of LED encapsulants Currently, the commonly used encapsulants include epoxy resin and silicone thermal conductive encapsulants. Silicone, with its high transmittance, high refractive index, good thermal stability, low stress, and low moisture absorption, is significantly superior to epoxy resin. It is widely used in high-power LED packaging but at a higher cost. Research has shown that increasing the refractive index of silicone can effectively reduce the loss of photons caused by physical barriers in the refractive index and enhance external quantum efficiency. However, the performance of silicone is greatly affected by environmental temperature. As the temperature rises, the thermal stress within silicone increases, leading to a decrease in its refractive index, thereby affecting the LED light efficacy and intensity distribution.

Requirements for selecting suitable LED encapsulant Flame retardancy of LED encapsulant Addition molding is better than condensation molding. The flame retardant level of condensation molding is UL 94V-1, and addition molding can reach UL 94V-0. Color of LED encapsulant Silicone rubber sealants can all serve the purpose of encapsulation, but transparent ones are suitable for products with light sources, such as LED modules and LED soft light strips, because transparent ones can effectively transmit light, while black ones cannot. In terms of usage, for example, some parts of bare IC chips may be sensitive to light, so black electronic encapsulation adhesive can solve this problem. For example, some cameras require flash connectors that need to receive external light and must use transparent packaging.

The hardness of LED encapsulant The hardness of condensation-type transparent encapsulants for electronic components is around 20, while that of black/white/gray is around 30. The hardness of addition-type transparent encapsulants for electronic components ranges from 0 to 35, and that of black/white/gray ranges from 0 to 70. The higher the hardness, the greater the specific gravity. When mixed at a hardness of 20-30, the density is around 1.02, and when the hardness exceeds 70, the specific gravity will reach around 1.6. Waterproofing Good adhesion leads to better waterproofing performance, with condensation-type adhesives achieving the IPX7 waterproof rating. Quick-drying property Addition-type encapsulants for electronic components can be heat-cured, with a usage temperature range of -50 to 250°C. Adhesive properties The adhesive properties of the condensation type are generally better than those of the addition type, and they can adhere to materials such as PVC plastic, ceramic metal, and ABS plastic. Thermal conductivity Compared to other encapsulants, addition-type electronic component encapsulants are distinguished by their thermal conductivity and flame retardancy. Thermal conductivity The thermal conductivity of LED encapsulant is around 0.17-0.37, while that of black/white/gray is around 0.6-0.8.