Thermomechanical stress due to tensile and compressive strain is a critical aspect in packaging technology. Residual thermomechanical stress due to large difference in coefficients of thermal expansion between materials generates reliability problems not only at the bonded interfaces but also for the lifetime of the active regions of high power semiconductors. Raman spectroscopy is a non-destructive method to investigate the residual stress in semiconductors. Blue LEDs based on gallium nitride bonded to a silicon carrier by a gold layer were soldered with eutectic gold-tin solder on a copper substrate. The bond line thickness was varied by application of a bond force between 0 and 21 N and the thickness of the copper substrate was chosen between 1 and 0.2 mm. The Raman shift of the E2 H phonon mode in the GaN layer was measured between -50° and 180°C. The temperature and assembly depending Raman shifts were analysed using literature data to access the residual thermomechanical stress. The stress was mapped through the surface to measure its homogeneity. Finite analysis simulation were performed for further analysis

Thermomechanical Stress in GaN LED Soldered on Copper Substrate Evaluated by Raman Measurements and Computer Modelling

Signorini Raffaella;Pedron Danilo;Conti Fosca
;
2018

Abstract

Thermomechanical stress due to tensile and compressive strain is a critical aspect in packaging technology. Residual thermomechanical stress due to large difference in coefficients of thermal expansion between materials generates reliability problems not only at the bonded interfaces but also for the lifetime of the active regions of high power semiconductors. Raman spectroscopy is a non-destructive method to investigate the residual stress in semiconductors. Blue LEDs based on gallium nitride bonded to a silicon carrier by a gold layer were soldered with eutectic gold-tin solder on a copper substrate. The bond line thickness was varied by application of a bond force between 0 and 21 N and the thickness of the copper substrate was chosen between 1 and 0.2 mm. The Raman shift of the E2 H phonon mode in the GaN layer was measured between -50° and 180°C. The temperature and assembly depending Raman shifts were analysed using literature data to access the residual thermomechanical stress. The stress was mapped through the surface to measure its homogeneity. Finite analysis simulation were performed for further analysis
2018
IEEE/THERMINIC-2018
978-1-5386-6759-0
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3285850
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