How should we choose LED lenses? Why do lens beads turn yellow?

LED lens It has a wide range of applications in everyday life and can be used in many settings; even when deployed outdoors, it delivers excellent performance. As a result, many businesses purchase it for routine use. There’s also some valuable knowledge to consider when selecting LED lenses—let’s explore it together.

I. Check the product’s light transmittance.

LED lenses are primarily used for lighting, so they must deliver excellent light transmission. If their light transmission is poor, the illumination will be insufficient, rendering the purchase of an LED lens largely pointless. Therefore, when selecting an LED lens, start by evaluating its light-transmission performance and prioritize models with superior results when making your decision and placing your order.

Second, consider the service life of the LED lens.

Equipment will inevitably degrade over time, but under normal conditions its service life remains quite long. The same holds true for LED focusing lenses. If you purchase a high‑quality LED lens, it will continue to perform well for an extended period even as it ages. By contrast, lower‑quality products may not offer a long service life.

Third, consider the product’s price customization.

LED lens There is no standardized pricing for custom LED lens products; prices vary depending on specifications and materials. For customers with specific budget constraints who wish to purchase LED lenses, it’s advisable to research pricing beforehand and then work with manufacturers to tailor the product to your needs, prioritizing options that offer the best value for money.

According to LED lens manufacturers, one common issue with LED lenses is their tendency to turn black. The coating on LED leads is silver-plated. Since sulfur-containing gases can react with the silver coating of the light source through the porous silicone or gaps in the lead frame, the plastic used to manufacture these lead frames typically features a highly porous structure.

One reason: the coating on the LED lens‑type LED beads has undergone sulfidation and discolored.

After a LED light source undergoes sulfidation, the functional areas of the lamp turn black, the luminous flux gradually declines, and the color temperature shifts noticeably. The electrical conductivity of silver sulfide increases with rising temperature, making leakage currents more likely during operation. Even more seriously, the silver layer can be completely corroded, exposing the underlying copper layer.

It exhibits a strong affinity for silver, sulfur, oxygen, and chlorine. Silver readily adsorbs water molecules from the air, forming a thin water film on its surface. Oxygen, sulfur, and chlorine in the air penetrate this water film, yielding insoluble silver oxide, silver sulfide, and silver chloride, which corrode the silver surface and lead to discoloration.

Compared with a smooth silver-plated layer, a rough silver-plated surface is more prone to water condensation, allowing corrosive media to penetrate and leading to discoloration.

After silver plating, the surface cannot be thoroughly cleaned; the residual plating solution contains silver ions, which will rapidly discolor upon exposure to humid air.

Reason number two: LED lens The adhesive on the bead‑sticking sheet has discolored.

LED chips are bonded to the leadframe using adhesive (except in eutectic bonding). As lens manufacturers well know, the LED chip is the primary heat source, and all heat must be dissipated from this location. Because the light emitted by the LED chip is not blue—having a shorter wavelength and higher energy—the molecular chains of the die‑attach adhesive remain in a high‑energy state over extended periods. The die‑attach adhesive serves as the thermal interface between the chip and the package, and this very factor can cause it to discolor.

Epoxy resin readily carbonizes at high temperatures, and prolonged exposure to blue light can cause its molecular bonds to break, resulting in yellowing. The halogenation, sulfidation, and oxidation of silver within the adhesive lead to a reduction in the thermal conductivity and bonding strength of the die-attach adhesive.

Reason 3: The packaging adhesive has aged and discolored.

Since LED chips must be protected with transparent adhesive, it’s important to prioritize factors such as high refractive index and high light transmittance when selecting the adhesive. Common choices include silicone adhesives or epoxy adhesives. However, these adhesives can undergo molecular bond degradation when exposed to light over extended periods.