Sulfur-Rich Ageing Mechanism of Silicone Encapsulant Used in LED Packaging

An Experimental and Molecular Dynamic Simulation Study

Journal article (2022)

Authors

Wei Chen Changzhou Institute of Technology Research for Solid State Lighting, Fudan University
Ye Chen Changzhou Institute of Technology Research for Solid State Lighting, Hohai University
Yixing Cao Fudan University
Z. Cui Electronic Components, Technology and Materials - EEMCS
Xuejun Fan Lamar University
Kouchi Zhang Electronic Components, Technology and Materials - EEMCS
J. Fan Fudan University, Changzhou Institute of Technology Research for Solid State Lighting, Electronic Components, Technology and Materials - EEMCS
Research Group
Electronic Components, Technology and Materials (EEMCS) (TU Delft)
Copyright: © 2022 Wei Chen, Ye Chen, Yixing Cao, Z. Cui, Xuejun Fan, Kouchi Zhang, J. Fan
DOI
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https://doi.org/10.3389/fmats.2022.819294
Molecular dynamics Humidity Degradation mechanism LED packaging Silicone encapsulant Sulfur-rich
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Published Date

2022

Language

English

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Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Microelectronics

Research Group

Electronic Components, Technology and Materials

Abstract

In a light-emitting diode (LED) package, silicone encapsulant serves as a chip protector and enables the light to transmit, since it exhibits the advantages of high light transmittance, high refractive index, and high thermal stability. However, its reliability is still challenged under harsh operation conditions. In this study, the optical and mechanical properties of silicone encapsulant, including appearance, light transmittance, Young’s modulus, and tensile strength, were experimentally monitored during the sulfur-rich ageing process. Meanwhile, the Fourier transform infrared (FTIR) spectroscopy and molecular dynamics (MD) simulation were used to reveal its degradation mechanism. The results show that 1) in the sulfur (S8)-rich ageing process, the severe vulcanization reaction occurred in silicone encapsulant assisted only by high temperature and high moisture, with the existence of H2S as the reaction product of S8 and H2O vapor. 2) Vulcanization characterized by the formation of the sulfhydryl (-SH) group lowered both optical and mechanical properties of silicone encapsulant. 3) The hydrolysis reaction featured by the formation of the hydroxyl (-OH) group decreased the mechanical performances of silicone encapsulant but brought slight harm to its optical performances.