Zn thin film on Al metal as thermal substrates for LED application: thermal and optical performance
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Zn thin film on Al metal as thermal substrates for LED application: thermal and optical performance Subramani Shanmugan1 · Devarajan Mutharasu2 Received: 23 July 2019 / Accepted: 6 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Zn thin film at various thickness was deposited on Al substrates and used as thermal interface materials and tested their performance on affecting the thermal and optical properties of the LED at various driving currents. The total thermal resistance (Rth-tot) of the LED showed the influence of various thickness and annealing temperatures and observed low value for 300 nm and 400 nm at ~ 150 °C. High difference in Rth-tot (∆Rth-tot − 3.78 K/W) was recorded with 300 nm Zn thin film annealed at 150 °C compared with bare Al substrates measured at 700 mA. Higher annealing temperature does not show much improvement on reducing the Rth-tot of the LED. Among the all Zn film studied, 300 nm thickness and annealed at 150 °C showed better performance on reducing the rise in junction temperatures (TJ) and the observed difference in TJ value was 8.07 °C compared with that of bare Al substrate measured at 700 mA. The optical output of LED was also supported the observed results and achieved improved light output for the same boundary conditions. High value in lux values was observed for the LED with 300 nm thickness and annealed at 150 °C and 350 °C for all driving currents. The roughness of Zn thin film increased with thickness and annealing temperature increased upto 500 nm and 350 °C respectively. The highest and lowest surface roughness of 112 nm and 21 nm were recorded for 500 nm and 800 nm thick Zn from 150 °C annealed samples respectively and supported the observation made by both thermal and optical analysis of the given LED. Overall, we may consider Zn thin film as solid thin film interface material for LED packaging application. Keywords LED · Zn thin film · Thermal transient analysis · Optical performance · Surface analysis
* Subramani Shanmugan [email protected] 1
Nano Optoelectronics Research Laboratory, School of Physics, UniversitiSains Malaysia (USM), 11800 Minden, Pulau Pinang, Malaysia
2
Western Digital, Persiaran Cassia Selatan 1, MK.13, Batu Kawan, Seberang Perai Selatan 14100, Pulau Pinang, Malaysia
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S. Shanmugan, D. Mutharasu
1 Introduction As LEDs are integrated into more applications, enclosures become miniaturized and hence increased power densities. Thermal interface materials (TIMs) effectively conduct the heat are required and much attention has been given to the development of such materials with high thermal conductivity for alleviating the heat dissipation problem (Mirmira et al. 2001). TIMs can roughly be classified as coatings (Li et al. 2000), (Marotta et al. 1999), (Muzychka et al. 1999), thermal fluids (Das and Sadhal 1998), thermal grease (Lu et al. 1998), and resilient thermal conductors (Zhao and Phelan 1999). Silver filled composites enhances joint conduct
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