Encapsulated carbon nanotube array as a thermal interface material compatible with standard electronics packaging
Ruixiang Bai, Yangbing Wei, Jiyuan Xu, Xiaobo Li, Menglin Li, Ziwen Zou, Xinyan Huang, Chengyu Liu, Yiwei Sun, Menglong Hao
Abstract
Vertically aligned carbon nanotubes arrays (VACNTs) are a promising candidate for the thermal interface material (TIM) of next-generation electronic devices due to their attractive thermal and mechanical properties. However, the environment required for synthesizing VACNTs is harsh and severely incompatible with standard device packaging processes. VACNTs’ extremely low in-plane thermal conductivity also limits its performance for cooling hot spots. Here, using a transfer-and-encapsulate strategy, a two-step soldering method is developed to cap both ends of the VACNTs with copper microfoils, forming a standalone Cu-VACNTs-Cu sandwich TIM and avoiding the need to directly grow VACNTs on chip die. This new TIM is fully compatible with standard packaging, with excellent flexibility and high thermal conductivities in both in-plane and through-plane directions. The mechanical compliance behavior and mechanism, which are critical for TIM applications, are investigated in depth using in situ nanoindentation. The thermal performance is further verified in an actual light emitting diode (LED) cooling experiment, demonstrating low thermal resistance, good reliability, and achieving a 17 °C temperature reduction compared with state-of-the-art commercial TIMs. This study provides a viable solution to VACNTs’ longstanding problem in device integration and free-end contact resistance, bringing it much closer to application and solving the critical thermal bottleneck in next-generation electronics.