Table 8. Summary of The failure modes and failure mechanisms involved with these single, double and triple stresses on the LEDs.

External stress(es) applied	Failure sites	Failure modes	Failure mechanisms	References
Electrical stress	Chip Level	Lumen degradation, increase in reverse leakage current, increase in parasitic series resistance and short circuit.	Defects in LED chip, electromigration of the metal atoms in the electrical contact to the surface of the LED die, instability in Mg diffusion in p- GaN layer and dislocation generation and movement at chip level	26,27,28,29,30,31,32,33,34,35,36
	Package level	Lumen degradation	Carbonization of encapsulation and phosphor thermal quenching	3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43
Thermal stress	Package level	Lumen degradation, Detachment of encapsulant from molding part	Browning of the white reflector molding part of device	44
	Chip level	Lumen degradation	Degradation of the phosphors conversion efficiency	20, 44, 45
Electrical stress and thermal stress	Chip level	Lumen depreciation	Crack in the LED chip	30, 31
	Package level	Lumen degradation	Encapsulant yellowing, lens cracking or solder joint fatigue	46, 47, 48, 49, 50
Thermal stress and moisture stress	Chip level	Lumen degradation, Forward voltage change, permanent destruction of LED i.e. no light	Wire ball bond fatigue	7
	Package level	Reduction of the overall light output,	LED chip-die attach delamination, moisture entrapment in encapsulant, and lens cracking	4, 5, 6, 7, 8, 51, 52
Thermal, electrical and moisture stresses (MET test proposed in this work)	Chip level	Rapid Lumen depreciation, forward voltage drop	LED chip/die attach delamination, defects in LED chip	Proposed mechanism in this paper
	Package level	Rapid Lumen degradation	Browning of the white silicone reflector molding part of device, encapsulant detachment from molding part	Proposed mechanism in this paper