Reliability and Lifetime Assessment of Optical Materials in LED-Based Products

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Lumen depreciation is one of the major failure modes in light-emitting diode (LED) systems. It originates from the degradation of the different components within the system, including the chip, the driver, and the optical materials (i.e., phosphorous layer). The kinetics of degradation in real-life applications is relatively slow, and in most cases, it takes several years to see an obvious deterioration of optical properties. A highly accelerated stress testing (HAST) setup and a methodology to extrapolate the results to real applications are therefore needed to test the reliability of LED package and lens materials. Employing HAST concept in LED industry is inevitable due to the necessity of assessing the reliability of new products in a short period of time. This chapter aims at briefly explaining the degradation mechanism of optical components in LED package and how they contribute to the lumen depreciation of the LED package. The concept of HAST and the way the reliability of LED packages can be assessed will also be explained.
Original languageEnglish
Title of host publicationSolid State Lighting Reliability Part 2
Subtitle of host publicationComponents to Systems
EditorsWillem Dirk van Driel, Xuejun Fan, Guo Qi Zhang
Place of PublicationCham
Number of pages25
ISBN (Electronic)978-3-319-58175-0
ISBN (Print)978-3-319-58174-3
Publication statusPublished - 2018

Publication series

NameSolid State Lighting Technology and Application Series
ISSN (Print)2196-4203
ISSN (Electronic)2196-4211

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project
Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.


  • Encapsulants
  • Yellowing
  • Blue light exposure
  • Oxidation
  • Stress testing


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