Effects of solder paste on thermal and optical performance of high-power ThinGaN white LED
Soldering & Surface Mount Technology
ISSN: 0954-0911
Article publication date: 14 May 2018
Issue publication date: 24 May 2018
Abstract
Purpose
Thermal management of high-power (HP) light-emitting diodes (LEDs) is an essential issue. Junction temperature (TJ) and thermal resistance (Rth) are critical parameters in evaluating LEDs thermal management and reliability. The purpose of this paper is to study thermal and optical characteristics of ThinGaN (UX:3) white LED mounted on SinkPAD by three types of solder paste (SP): No-Clean SAC305 (SP1), Water-Washable SAC305 (SP2) and No-Clean Sn42/Bi57.6/Ag0.4 (SP3).
Design/methodology/approach
Thermal transient tester (T3Ster) machine is used to determine TJ and total thermal resistance (Rth–JA). In addition, the LED’s optical properties are measured via thermal and radiometric characterization of power LEDs (TeraLED) system. The LED is mounted on SinkPAD using SP1, SP2 and SP3 by stencil printing to control a thickness of SP and reflow soldering oven to minimize the number of voids. The LED with SP1, SP2 and SP3 is tested at various input currents and ambient temperatures.
Findings
The results indicate that at high input current, which equals to 1,200 mA, Rth–JA and TJ, respectively, are reduced by 30 and 17 per cent between SP1 and SP2. At same current value, Rth–JA and TJ are minimized by 42 and 25 per cent between SP1 and SP3, respectively. In addition, at an ambient temperature of 85°C, Rth–JA and TJ are decreased by 34 and 7 per cent between SP1 and SP2, respectively. Similarly, the reduction in Rth–JA and TJ between SP1 and SP3 is 44 and 10 per cent, respectively. Luminous flux, luminous efficacy and color shift of the LED with the three types of SPs are compared and discussed. It is found that the SP1 improves the chromatic properties of the LED by increasing the overall light efficiency and decreasing the color shift.
Originality/value
Thermal and optical performance of ThinGaN LEDs mounted on SinkPAD via three types of SPs is compared. This investigation can assist the research on thermal management of HP ThinGaN-based LEDs.
Keywords
Acknowledgements
The authors would like to acknowledge Institute of Postgraduate Studies (IPS) of Universiti Sains Malaysia (USM) for the financial support through USM Fellowship. Also, the authors acknowledge with gratitude the support by Chan Kin Leong and Hung Choon Keat from QAV Technologies for X-ray analysis and M.K. Dheepan for CAD drawing support.
Citation
Raypah, M.E., Devarajan, M. and Sulaiman, F. (2018), "Effects of solder paste on thermal and optical performance of high-power ThinGaN white LED", Soldering & Surface Mount Technology, Vol. 30 No. 3, pp. 182-193. https://doi.org/10.1108/SSMT-11-2017-0040
Publisher
:Emerald Publishing Limited
Copyright © 2018, Emerald Publishing Limited