Research Papers

Effect of Packaging Architecture on the Optical and Thermal Performances of High-Power Light Emitting Diodes

[+] Author and Article Information
Thong Kok Law

Department of Avionics Systems,
Nanyang Polytechnic,
180 Ang Mo Kio Avenue 8,
569830, Singapore
e-mail: LAW_Thong_Kok@nyp.edu.sg

Fannon Lim

School of Engineering,
University of Glasgow,
Glasgow G12 8LT, UK
e-mail: Fannon.Lim@glasgow.ac.uk

Yun Li

Department of Systems Power and Energy,
University of Glasgow,
Glasgow G12 8LT, UK
e-mail: Yun.Li@glasgow.ac.uk

XuePeng Puan

School of Engineering,
University of Glasgow,
Glasgow G12 8LT, UK
e-mail: 2110141P@student.gla.ac.uk

G. K. E. Sng

School of Engineering,
University of Glasgow,
Glasgow G12 8LT, UK
e-mail: 2110199S@student.gla.ac.uk

J. W. Ronnie Teo

Department of Joining Technology,
Singapore Institute of Manufacturing
2 Fusionopolis Way,
138634, Singapore
e-mail: jwtew@simtech.a-star.edu.sg

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received September 24, 2016; final manuscript received February 13, 2017; published online June 14, 2017. Assoc. Editor: Xiaobing Luo.

J. Electron. Packag 139(3), 031003 (Jun 14, 2017) (5 pages) Paper No: EP-16-1108; doi: 10.1115/1.4036066 History: Received September 24, 2016; Revised February 13, 2017

The phosphor and die bonding configuration affect the optical efficiency and thermal performance in phosphor-coated white light emitting diodes (LEDs). In this paper, light emission studies reveal that the chromaticity shift and light extraction losses depend on the uniformity of phosphor particles deposited over the LED surface. A nonuniform and sparse phosphor layer affects the correlated color temperature (CCT) and the spectral Y–B ratio due to the disproportionate contribution of light emission between the LED device and the phosphor layer. Furthermore, the Y–B ratio was observed to reduce with temperature due to higher Stoke's energy and light extraction losses in the phosphor layer. As a result, the Y–B ratio exhibits an inverse relationship with the package's thermal resistance as a function of temperature. On the other hand, the thermal performance of a LED package is dependent on the die-bonding configurations (conventional and flip-chip). Due to the improved heat dissipation capabilities in flip-chip bonding, the temperature rise and thermal resistance of the package were observed to reduce with temperature. By alleviating the heat accumulation in the package, more stable colorimetric properties such as CCT and Y–B ratio can be achieved.

Copyright © 2017 by ASME
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Fig. 1

Integrated LED measurement system consists of an integrating hemi-sphere, a Peltier-based temperature controller, a source measure unit, and a transient thermal tester

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Fig. 2

Radiant efficiency of various LED packages at different (a) current densities and (b) operating temperatures

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Fig. 3

Typical light emission (inset) and cross-sectional SEM images for each pcLED packages: (a) P1W, (b) S1W, and (c) S03W. Direct blue light emission can be observed through the phosphor layer (yellow–orange emission).

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Fig. 4

Y–B ratio of different white pcLED packages as a function of operating temperatures. Inset: Typical spectral power distribution of white pcLED package.

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Fig. 5

LED junction temperature rise of blue and white LED packages at various operating temperatures

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Fig. 6

Thermal resistance of (a) 1 W and S1W and (b) 0.3 W LED packages at different operating temperatures




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