Effects of High-g Impact on Physical, Electrical, and Optical Characteristics of Light-Emitting Diodes.

Previously, one of the tools available in automotive or aircraft accident analysis was the examination of the indicator bulbs. Currently, indicator bulbs have been largely replaced by light-emitting diodes (LEDs). Here a series of studies was carried out on impact effects on LEDs to determine whether their properties change after impact, and whether it is related to its working status (lit or unlit). The LEDs were measured before mechanical shock with a series of tests, including current-voltage, current-light, bandwidth, subject to impact ranging from 450 g to 2000 g, and then retested. The tests showed consistent slight but statistically significant increases in forward voltages at a given current after impact, which could be used to estimate the impact. Some LEDS were imaged before and after impact with thermal and X-ray imaging, but no mechanical changes were seen. It was not possible to determine the LED's working status from these test results.