Effects of Carbon Loading on the Performance of Functionalized Carbon Nanotube Polymer Heat Sink for High Power Light-Emitting Diode in Switching Applications

Abstract

The functionalized carbon nanotube has been shown to be a viable filler material to increase the thermal conductivity of elastomer heat sinks. However, the effect of the amount of fillers used, that is, the carbon loading in elastomers is still unknown. This study focuses on varying the carbon loading percentage, in 0.2 wt% increment (0.2, 0.4, etc.), to quantify the performance improvements of the elastomer heat sinks. The carbon nanotubes were functionalized with short-chain silane functional groups to allow the blend to be more miscible. This process also allows the formation of a heat spreading network of carbon nanotubes utilizing the phonon transfer mechanism well known for this type of fillers. The performance indicators are the heat spreading signatures evolution in 30 min of infrared thermal imaging and the extent of the cumulative structure function of the heat sinks when high power LEDs are mounted directly on the plastic heat sinks as a heat source. The results show an interesting change in the heat transfer mechanism for heat sink with higher carbon loading as compared to those with lower carbon loading. The boundary for such change in heat transfer occurs at 0.6 wt% of carbon nanotube. Finally, the results are compared to an aluminum heat sink of similar size and we find that the heat dissipation for the heat sink with higher carbon loading performs better than the aluminum heat sink. This indicates that functionalized carbon nanotubes loaded heat sink has the potential of replacing aluminum heat sinks especially in the weight sensitive application with a 25% reduction in weight.