Design and evaluation of polymer-carbon nanotube composites for reliable, low resistance, static and dynamic thermal interface materials

The development of new thermal interface materials (TIMs) represents a key challenge in the increasingly demanding electronics cooling sector. This work explores the potential of novel polymer-carbon nanotube (CNT) composites for static and dynamic TIM applications. Several polymers are evaluated experimentally for use in concert with a vertically aligned CNT forest to achieve improvements over the state of the art in terms of mechanics, reliability and thermal resistance. The vertically aligned CNT forest is grown on a metal foil substrate, delivering a form factor that is highly amenable to pick and place application of the TIM at production scale. A variety of application or infiltration techniques are evaluated for combining the candidate polymers with the CNT forest in a robust, repeatable, and thermally conducive manner. A modified ASTM-5470 stepped bar apparatus is used to compare the performance of the polymer CNT composites with a wide variety of leading commercially available thermal interface materials under loadings up to 690 kPa. Thermal resistances as low as 0.1 cm2-K/W were achieved with a polymer-CNT composite-aligning well with the thermal demands of spreader to heat sink interface applications. Next, a dynamic thermal tester is developed and used to evaluate the performance, durability, and fungibility of polymer-CNT composites for dynamic applications such as chip testing. The dynamic tester is designed to closely mimic the conditions present in automated burn-in systems used in commercial chip testing. The polymer CNT-composites delivered an over 3X increase in product lifetime when compared to state of the art materials subjected to this cyclic thermo-mechanical testing.