The U.S. Department of Energy's CALiPER program has released Report 20.3, which is part of a series of investigations on LED PAR38 lamps. Report 20.3 focuses on an evaluation of robustness. Three samples each of 40 of the Series 20 PAR38 lamps (including LED and benchmark conventional lamps) underwent multi-stress testing, whereby samples were subjected to increasing levels of simultaneous thermal, humidity, electrical, and vibrational stress. The results don't explicitly predict expected lifetime or reliability, but they can be compared with one another, as well as with benchmark conventional products, to assess the relative robustness of the product designs.

On average, the 32 LED lamp models tested were substantially more robust than the conventional benchmark lamps. As with other performance attributes, however, there was great variability in the robustness and design maturity (or difference in time to stress-induced failure, which is related to failure mechanism characteristics) of the LED lamps. Several LED lamp samples failed within the first one or two levels of the 10-level stress plan, while all three samples of some lamp models completed all 10 levels.

One potential area of improvement is design maturity, given that more than 25% of the lamp models demonstrated a difference in failure level for the three samples that was greater than or equal to the maximum for the benchmarks. At the same time, the fact that nearly 75% of the lamp models exhibited better design maturity than the benchmarks is noteworthy, given the relative stage of development for the technology.

For a closer look at the findings, download the full report from the DOE SSL website.