Photometric and colorimetric assessment of LED chip scale packages by using a step-stress accelerated degradation test (SSADT) method

Photometric and colorimetric assessment of LED chip scale packages by using a step-stress accelerated degradation test (SSADT) method

Qian, Cheng (Beihang University; Changzhou Institute of Technology Research for Solid State Lighting)
Fan, Jiajie (Hohai University; Changzhou Institute of Technology Research for Solid State Lighting)
Fang, Jiayi (Hohai University; Changzhou University)
Yu, Chaohua (Hohai University; Changzhou Institute of Technology Research for Solid State Lighting)
Ren, Y. (Beihang University)
Fan, Xuejun (Lamar University)
Zhang, Kouchi (TU Delft Electronic Components, Technology and Materials)

2017

By solving the problem of very long test time on reliability qualification for Light-emitting Diode (LED) products, the accelerated degradation test with a thermal overstress at a proper range is regarded as a promising and effective approach. For a comprehensive survey of the application of step-stress accelerated degradation test (SSADT) in LEDs, the thermal, photometric, and colorimetric properties of two types of LED chip scale packages (CSPs), i.e., 4000 °K and 5000 °K samples each of which was driven by two different levels of currents (i.e., 120 mA and 350 mA, respectively), were investigated under an increasing temperature from 55 °C to 150 °C and a systemic study of driving current effect on the SSADT results were also reported in this paper. During SSADT, junction temperatures of the test samples have a positive relationship with their driving currents. However, the temperature-voltage curve, which represents the thermal resistance property of the test samples, does not show significant variance as long as the driving current is no more than the sample's rated current. But when the test sample is tested under an overdrive current, its temperature-voltage curve is observed as obviously shifted to the left when compared to that before SSADT. Similar overdrive current affected the degradation scenario is also found in the attenuation of Spectral Power Distributions (SPDs) of the test samples. As used in the reliability qualification, SSADT provides explicit scenes on color shift and correlated color temperature (CCT) depreciation of the test samples, but not on lumen maintenance depreciation. It is also proved that the varying rates of the color shift and CCT depreciation failures can be effectively accelerated with an increase of the driving current, for instance, from 120 mA to 350 mA. For these reasons, SSADT is considered as a suitable accelerated test method for qualifying these two failure modes of LED CSPs.

Accelerated aging
Chip scale package
Light-emitting diode
Reliability qualification
Step stress test

http://resolver.tudelft.nl/uuid:70bdeffb-22dd-4b9f-bf7c-4a8a24ed902c

https://doi.org/10.3390/ma10101181

1996-1944

Materials, 10 (10)

Institutional Repository

journal article

© 2017 Cheng Qian, Jiajie Fan, Jiayi Fang, Chaohua Yu, Y. Ren, Xuejun Fan, Kouchi Zhang