Fabrication and Characterisation of Carbon Nanotube Array Thermal Interface Materials

Licentiatavhandling, 2018

The performance of electronic devices has long been limited by thermal dissipation which will result in device failure if not handled properly. The next generation of integrated circuit (IC) devices will feature new packaging technologies like heterogeneous integration as well as 3D stacking which entails additional emphasis on the thermal management solutions employed. Therefore, new materials are in demand to meet the increased thermal dissipation requirements to allow continued scaling in terms of cost per performance and increased device reliability.


The largest bottleneck in thermal dissipation originates from thermal interfaces between different surfaces. For this purpose thermal interface materials (TIMs) are used to conform and bridge the interface and thereby alleviate the thermal dissipation restrictions in the interface. However, commercially available TIMs are either of metallic or polymeric nature which implies a compromise between thermal performance and reliability. Carbon nanotube (CNT) arrays have been suggested as a future potential material in order to achieve a TIM with superior thermal and mechanical properties that would ensure simultaneous high thermal performance and reliability. However, proper bonding solutions are still to be developed in order to apply CNT array TIMs in thermal dissipation applications and to ensure a successful market realisation.

 
This thesis first outlines the field by presenting a thorough literature review of organic functionalization methods for CNT array TIMs. Three different approaches are identified: polymer embedding, polymer bonding and self-assembly based functionalization. The thesis then presents two experimental studies on CNT array TIMs. The first focuses on the development and characterisation of a CNT array TIM using a novel self-assembly based bonding method by employing epoxy chemistry for covalent anchoring. The second part focuses on a reliability study of a CNT array TIM assembled using a polymer bonding method, which is an aspect that previously has been overlooked. The results from the reliability study gave indications that the
mechanical bonding between the CNT array and the growth substrate was susceptible for rapid degradation and further research is required in this field to address this challenge.