Comparison of online and offline tests in LED accelerated reliability tests under temperature stress

Hong-Liang Ke; Lei Jing; Qun Gao; Yao Wang; Jian Hao; Qiang Sun; Zhi-Jun Xu

doi:10.1364/AO.54.009906

Applied Optics
Vol. 54,
Issue 33,
pp. 9906-9910
(2015)
•https://doi.org/10.1364/AO.54.009906

Comparison of online and offline tests in LED accelerated reliability tests under temperature stress

Hong-Liang Ke, Lei Jing, Qun Gao, Yao Wang, Jian Hao, Qiang Sun, and Zhi-Jun Xu

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Hong-Liang Ke, Lei Jing, Qun Gao, Yao Wang, Jian Hao, Qiang Sun, and Zhi-Jun Xu, "Comparison of online and offline tests in LED accelerated reliability tests under temperature stress," Appl. Opt. 54, 9906-9910 (2015)

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Abstract

Accelerated aging tests are the main method used in the evaluation of LED reliability, and can be performed in either online or offline modes. The goal of this study is to provide the difference between the two test modes. In the experiments, the sample is attached to different heat sinks to acquire the optical parameters under different junction temperatures of LEDs. By measuring the junction temperature in the aging process ( $T_{j 1}$ ), and the junction temperature in the testing process ( $T_{j 2}$ ), we achieve consistency with an online test of $T_{j 1}$ and $T_{j 2}$ and a difference with an offline test of $T_{j 1}$ and $T_{j 2}$ . Experimental results show that the degradation rate of the luminous flux rises as $T_{j 2}$ increases, which yields a difference of projected life $L_{70 %}$ of 8% to 13%. For color shifts over 5000 h of aging, the online test shows a larger variation of the distance from the Planckian locus, about 40% to 50% more than the normal test at an ambient temperature of 25°C.

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	$T_{a}$ (°C)	Heat Sink	$T_{j}$ (°C)
Aging	80	Ceramic	118.2–120.3
Online	25	Air	119.5–121.5
Offline 1	25	Ceramic	72.1–73.2
Offline 2	25	Aluminum	59.2–60.3

	$T_{j 2} = 120 ° C$			$T_{j 2} = 72 ° C$			$T_{j 2} = 60 ° C$
	$α$	RMSE	$L_{70 %}$ (h)	$α$	RMSE	$L_{70 %}$	$α$	RMSE	$L_{70 %}$
Sample 1	$2.58 E - 5$	$3.25 E - 2$	13820	$2.43 E - 5$	$6.32 E - 2$	14680	$2.39 E - 5$	$7.23 E - 2$	14920
Sample 2	$2.88 E - 5$	$2.25 E - 2$	12380	$2.78 E - 5$	$7.12 E - 2$	12830	$2.62 E - 5$	$7.31 E - 2$	13610
Sample 3	$2.97 E - 5$	$3.86 E - 2$	12010	$2.74 E - 5$	$8.59 E - 2$	13020	$2.72 E - 5$	$8.53 E - 2$	13110
Sample 4	$3.33 E - 5$	$3.65 E - 2$	10710	$3.02 E - 5$	$6.52 E - 2$	11810	$2.95 E - 5$	$8.56 E - 2$	12090
Sample 5	$4.19 E - 5$	$3.96 E - 2$	8510	$4.03 E - 5$	$5.95 E - 2$	8850	$4.01 E - 5$	$4.21 E - 2$	8890

	Duv (0–5000 h)
	120°C	72°C	120°C–72°C
Sample 1	0.0065	0.0043	0.0022
Sample 2	0.0072	0.0048	0.0024
Sample 3	0.0068	0.0045	0.0023
Sample 4	0.0071	0.0051	0.0020
Sample 5	0.0075	0.0052	0.0023

	$T_{a}$ (°C)	Heat Sink	$T_{j}$ (°C)
Aging	80	Ceramic	118.2–120.3
Online	25	Air	119.5–121.5
Offline 1	25	Ceramic	72.1–73.2
Offline 2	25	Aluminum	59.2–60.3

	$T_{j 2} = 120 ° C$			$T_{j 2} = 72 ° C$			$T_{j 2} = 60 ° C$
	$α$	RMSE	$L_{70 %}$ (h)	$α$	RMSE	$L_{70 %}$	$α$	RMSE	$L_{70 %}$
Sample 1	$2.58 E - 5$	$3.25 E - 2$	13820	$2.43 E - 5$	$6.32 E - 2$	14680	$2.39 E - 5$	$7.23 E - 2$	14920
Sample 2	$2.88 E - 5$	$2.25 E - 2$	12380	$2.78 E - 5$	$7.12 E - 2$	12830	$2.62 E - 5$	$7.31 E - 2$	13610
Sample 3	$2.97 E - 5$	$3.86 E - 2$	12010	$2.74 E - 5$	$8.59 E - 2$	13020	$2.72 E - 5$	$8.53 E - 2$	13110
Sample 4	$3.33 E - 5$	$3.65 E - 2$	10710	$3.02 E - 5$	$6.52 E - 2$	11810	$2.95 E - 5$	$8.56 E - 2$	12090
Sample 5	$4.19 E - 5$	$3.96 E - 2$	8510	$4.03 E - 5$	$5.95 E - 2$	8850	$4.01 E - 5$	$4.21 E - 2$	8890

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Applied Optics