Available at: http://digitalcommons.calpoly.edu/theses/359
Date of Award
MS in Industrial Engineering
Industrial and Manufacturing Engineering
Light-emitting diodes (LEDs) have recently become exceedingly popular in general lighting. As their popularity grows, the demand of more complex and more powerful systems grows as well. While optical characteristics are a crucial component of any lighting product, the main selling point of an LED is their long life and reliability. Unfortunately, the lifetime and reliability of a LED are heavily dependent on the junction temperature of the LED.
Thermal management for LEDs has become an important field study for LEDs. Unfortunately, as the LEDs grow smaller and more integrated, it becomes impossible at times to directly measure their junction temperature. When this occurs, the use of the forward-voltage to junction-temperature coefficient, or K-factor, can be used to aid in measuring the junction temperature. Often the K-factor value is quoted as a constant, even while the rest of the LED degrades.
This thesis explores the use of the K-factor and attempts to determine if there is a significant change in the K-factor due to degradation. To test this, a custom data acquisition system was built. Two test groups were thermally aged and periodically recalibrated to detect any changes in the K-factor. At the end of the 3000-hour test, one board had failed due to degradation, while the second board did show a statistically significant change in the K-factor; which was slightly more than 10%.