LEDs burn out before becoming a hazard

17 Jun 2002

Although European safety standards treat LEDs for consumerproducts the same as lasers the sources burn out before exceeding themaximum permitted exposure for a Class 1 source, two Germansemiconductor companies told ILSC 99.

LEDs have an optical performance between coherent point sources andbroadband incoherent lamps. Joerg Angerstein of Vishay Semiconductor ofHeilbronn and Werner Horak of Siemens in Munich told delegates that theytested the LEDs to destruction without exceeding safety limits butwarned that new types of LEDs may not behave in the same way.

High temperatures reduce their efficiency of mass-produced LEDs andshift the wavelength to higher values. When the companies tested visibleand infrared LEDs with abnormally high currents, the optical outputsexceeded Class 1 limits and tailed off without exceeding the maximumpermitted exposure. The chips then shorted or burned out.