Lifetime enhancement of high-power light-emitting diodes using thermal paths in ceramic package

By inserting the Ag thermal paths located under the GaN-based light-emitting diode (LED) chip in a low-temperature co-fired ceramic package, junction-to-atmosphere thermal resistance could be reduced from 53 to 13 K/W. Temperature-stress accelerated life tests were carried out to check the effect of thermal improvement on reliability and to estimate lifetime as a function of junction temperature. After a 4000-hour test, the lifetimes of the degraded LED packages were estimated. The mean time to failure (MTTF) was below 20 000 hours at 35 C atmosphere temperature for the conventional LEDs. On the other hand, the estimated MTTF was over 50 000 at the same atmosphere temperature for the improved LEDs.