Comparison of effect of epoxy and silicone adhesive on the lifetime of plastic LED package

To compare the reliability of plastic LED packages based on different types of bonding adhesive, we designed two plastic LED package models using epoxy or silicone as bonding adhesive with normal refractive index (NRI) silicone, or high refractive index (HRI) silicone, as encapsulant. In addition, thermal acceleration tests were performed for 1,000 hours under three different temperatures, and optical characteristics were measured every 250 hours. Exponential decay of luminous flux of the plastic LED package was assumed and extrapolation was used to analyze the time-to-failure (TTF) of the plastic LED packages. From TTF data, statistical analysis was performed and reliability parameters such as acceleration factor (AF) and B-10 lifetime at 40A degrees C were estimated according to types of bonding adhesive and silicone encapsulant in plastic LED packages, with 90% confidence.