Effect of patterned surfaces on thermal impedance reduction

Abstract

COMSOL was used to simulate how these structures will enhance the heat transfer from the heat source and predict heat transfer enhancement. Proof of concept experiment was performed using patterned surfaces and Polydimethylsiloxane (PDMS). It was shown that effective thermal conductivity of PDMS can be enhanced by at least 6-fold and ITR can be reduced by 10 times using surface patterning.

This work develops a new scheme to increase heat transfer from the light emitting diodes (LED) to heat sink and reduce thermal interface impedances. LEDs packaging has three different main streams: lighting, electrical driver and thermal management. While other streams are growing really fast, thermal management is in its early stages. Like any other packages, LEDs thermal management is a combination of external cooling systems, heat spreaders, and thermal interfaces and among them the latter one has received less attention due to its complexity and difficulties. It has been estimated that up to 30% of input power will dissipate to heat at the interfaces and increase LED junction temperature. Higher junction temperature consequently will decrease both luminous efficiency and life time of the LED. This work introduces a new method to decrease interface thermal resistance using engineered surfaces. These surfaces will be patterned with micron size copper pillars and the effect of diameter (D), height (h) and pitch (P) of these pillars as well as their shape will be addressed.