Mean-time-to-failure evaluations of encapsulation materials for LED package in accelerated thermal tests

The mean-time-to-failure (MTTF) evaluation of encapsulation materials of LED package in accelerated thermal tests is presented. The Weibull and Arrhenius theory was used to characterize the thermal degradations of encapsulation materials for LED package in a quantitative investigation. The shape parameter, scale parameter, MTTF and activation energy (Ea) could be obtained to potentially provide clear values for comparison and understanding. The results showed that the glass as encapsulation material of LED modules exhibited better thermal stability than the silicone encapsulation by about 7 times in lumen loss, 2 times in chromaticity shift, and 3 times in correlated color temperature at 150 °C. Furthermore, an order magnitude MTTF improvement at room temperature was achieved in the glass encapsulation case.

► We demonstrate glass-based encapsulating phosphor with good thermal stability.
► We have practiced that glass-based encapsulating phosphor poses good lifetime than silicone one.
► The glass phosphor is good in lumen degradation and less chromaticity shift under accelerated test.