Research Papers

Analysis of ZnO Thin Film as Thermal Interface Material for High Power Light Emitting Diode Application

[+] Author and Article Information
S. Shanmugan

Nano Optoelectronics Research Laboratory,
School of Physics,
Universiti Sains Malaysia (USM),
Minden, Pulau Penang 11800, Malaysia
e-mail: shagan77in@yahoo.co.in

O. Zeng Yin, P. Anithambigai, D. Mutharasu

Nano Optoelectronics Research Laboratory,
School of Physics,
Universiti Sains Malaysia (USM),
Minden, Pulau Penang 11800, Malaysia

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received September 27, 2013; final manuscript received November 13, 2015; published online March 10, 2016. Assoc. Editor: Mark D. Poliks.

J. Electron. Packag 138(1), 011001 (Mar 10, 2016) (6 pages) Paper No: EP-13-1112; doi: 10.1115/1.4032029 History: Received September 27, 2013; Revised November 13, 2015

All solid-state lighting products produce heat which should be removed by use of a heat sink. Since the two mating surfaces of light emitting diode (LED) package and heat sink are not flat, a thermal interface material (TIM) must be applied between them to fill the gaps resulting from their surface roughness and lack of coplanarity. The application of a traditional TIM may squeeze out when pressure is applied to join the surfaces and hence a short circuit may result. To avoid such a problem, a thin solid film based TIM has been suggested. In this study, a zinc oxide (ZnO) thin film was coated on Cu substrates and used as the TIM. The ZnO thin film coated substrates were used as heat sink purposes in this study. The prepared heat sink was tested with 3 W green LED and the observed results were compared with the results of same LED measured at bare and commercial thermal paste coated Cu substrates boundary conditions. The influence of interface material thickness on total thermal resistance (Rth-tot), rise in junction temperature (TJ), and optical properties of LED was analyzed. A noticeable reduction in Rth-tot (5.92 K/W) as well as TJ (ΔTJ = 11.83 °C) was observed for 800 nm ZnO thin film coated Cu substrates boundary conditions when compared with bare and thermal paste coated Cu substrates tested at 700 mA. Change in TJ influenced the thermal resistance of ZnO interface material. Improved lux level and decreased correlated color temperature (CCT) were also observed with ZnO coated Cu substrates.

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Grahic Jump Location
Fig. 1

Cumulative structure function of 3 W LED for various boundary conditions measured at (a) 100 mA, (b) 350 mA, and (c) 700 mA

Grahic Jump Location
Fig. 2

Variation of junction temperature rise with respect to boundary conditions measured at (a) 100 mA, (b) 350 mA, and (c) 700 mA

Grahic Jump Location
Fig. 3

Surface morphology of (a) bare, (b) 400 nm, and (c) 800 nm ZnO thin film coated on the Cu substrates

Grahic Jump Location
Fig. 4

Change in CCT of 3 W LED for various boundary conditions measured at (a) 100 mA, (b) 350 mA, and (c) 700 mA

Grahic Jump Location
Fig. 5

Variation of Lux of 3 W LED for various boundary conditions observed at (a) 100 mA, (b) 350 mA, and (c) 700 mA



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