Reliability Problems of Optoactive Materials in LED Packaging

(18:36 + Q&A) Prof. Gabor Harsanyi, Budapest University of Technology and Economics
From the 2024 IEEE Symposium on Reliability for Electronics and Photonics Packaging
Summary: LEDs (Light-Emitting Diodes) are widely used not only in decorative illumination but also in everyday lighting in buildings, public areas, and automotive fields. These application areas often mean harsh environments, for example, regarding the humidity content of the surrounding air: besides outdoor and automotive illumination, even the household use cases (kitchen, bathroom, cellar) may represent extreme temperature and humidity variations (often reaching relative humidity levels close to 100%) for these devices; thus, their reliability behavior in such circumstances should be better understood. Moisture and temperature ageing tests with appropriate environmental parameter settings were performed as accelerated lifetime tests to investigate not only the effect of temperature but also that of humidity on the ageing and reliability of LED packages containing RGB (red green blue) chips and phosphor-converted white (pcW) LEDs. The ageing was followed by through monitoring optical/electrical/spectral parameter changes and also with material analysis. Moisture material interaction models were proposed and set up.
Lighting appliances often fail because of breakdown of the conditioning electronics. This is, however, not always true: the LED devices themselves can also fail in many cases. The packaging mold material over the chip(s) is filled into the small pool of the plastic package frame containing the lead frame. This is ether transparent (in the case of RGB LEDs) or is filled with light-converting phosphor material (e.g. yellow phosphor is combined with blue chips to get white light output). Such LEDs generally have very large resistance value or even open circuit failure. Since LED devices are usually connected in series, the overall lighting module fails.
LEDs can also fail due to their slow ageing process: degradation of the brightness (luminous output) can be experienced (e.g. a loss of 30%). Our results demonstrate that temperature-humidity-accelerated ageing processes are more severe than expected from previous assumptions (such as a 10000-hour life). RGB and pcW LEDs showed strongly different ageing behavior. The weakest result was experienced with the cool white (pcW) LED types. The possible reason of this behavior will also be discussed.
Bio: Prof. Gábor Harsányi graduated in electrical engineering from the Budapest University of Technology and Economics in 1981 and received doctorate (dr. univ.) in Electronics Technology from the same university in 1984. Thereafter, he moved to the Microelectronics Company (MEV, Hungary) where he developed his expertise in hybrid integrated circuits and sensorics. In 1992, he received his Ph.D. from the Hungarian Academy of Sciences. Since 1984, he has been a member of the research and teaching staff of the Department of Electronics Technology, Budapest University of Technology and Economics in various positions, and became the head of department in 2003 and is professor emeritus since 2024. His main research topics are: reliability physics of high density electronic interconnection systems, sensors in biomedical applications. Hi published two books: “Polymer Films in Sensor Applications”, and “Sensors in Biomedical Applications”, which became part of the basic literature in sensorics. Dr. Harsanyi conducted a large number of scientific and industrial research and development projects, published more than 300 papers and has more than 2000 citations. He was a regular tutor of short courses organized by IMAPS, IEEE and Europractice. He was also member of the Technical Program Committee of IMAPS-Europe for several years and received the IMAPS Fellowship Award in 1998. He is Senior Member of IEEE Electronics packaging Society. 

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