A review on discoloration and high accelerated testing of optical materials in LED based-products

M. Yazdan Mehr, M.R. Toroghinejad, F. Karimzadeh, W.D. van Driel, G.Q. Zhang

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)
6 Downloads (Pure)


Reduction of intensity of light output is one of the most common degradation modes in light-emitting diode (LED) systems. It starts from the failure of the various components in the system, including the chip, the driver, and optical components (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. Highly Accelerated Stress Testing (HAST) set-up and a methodology to extrapolate the results to real time applications are therefore needed to test the reliability of LED packages and lens materials. Using 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 paper aims at briefly clarifying the degradation mechanisms of optical components in LED packages and explaining how they contribute to the depreciation of light output of the LED systems. The concept of HAST and the way the reliability of LED packages can be evaluated will also be discussed.

Original languageEnglish
Pages (from-to)136-142
Number of pages7
JournalMicroelectronics Reliability
Publication statusPublished - 2018

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care 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.


  • Encapsulant
  • LED
  • Lens/encapsulant
  • Lumen depreciation
  • Reliability


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