Vertically aligned carbon nanotube based thermal interface materials for low contact pressure and low ambient pressure applications

摘要

High performance thermal interface materials (TIMs) are an essential tool for maintaining modern electronics within their temperature allowances. Especially challenging are sensitive electronics that cannot tolerate high contact pressures in the system packaging. Pressure applied to the TIM is often relied upon to minimize the bond line thickness, maintain alignment, and maximize contact area. In this work, vertically aligned carbon nanotube (CNT) forests on metal substrates are investigated as a potential solution for low contact pressure applications. Carbon nanotube based TIMs have high thermal conductance at very low contact pressure and do not degrade when mechanically deformed, which offers the potential for a superior alternative to the current TIM solutions. Also, CNT array interfaces are dry and chemically stable from cryogenic to elevated temperatures, simplifying installation and preventing thermal pump-out. At a contact pressure of only 10 kPa, a prototype CNT TIM delivered a conductance of 1,400 W/m2K (resistance of 7 cm2-K/W), significantly outperforming comparable commercial TIMs. Next, to evaluate performance for applications requiring large TIM thicknesses and mechanical compliance, three individual CNT arrays were stacked vertically and bonded using a thin polymer layer. The stacked CNT TIM based gap pads had cross plane thickness of up to 900 μm. When stacked, the CNT TIMs still provided excellent thermal performance, with conductances approaching 900 W/m2K. Finally, the CNT TIMs were tested under vacuum conditions to evaluate their potential performance in aerospace applications.