Heat Conduction in High Thermal Conductivity Networked Composite Films for Thermal Interface Materials

摘要

Fast and efficient exchange of thermal energy plays a vital role in the thermal management of electronic and optoelectronic devices. A critical component for thermal management is a thermal interface material (TIM) that is used to minimize the contact thermal resistance between surfaces and to provide a low resistance pathway to spread and remove heat. Ideal TIMs must pass several key requirements: 1) high thermal conductivity κ and low thermal contact resistance with the mating surfaces; 2) easy to apply with controlled thickness; 3) low temperature processing; 4) able to accommodate thermally induced mechanical stresses during on-off cycling of the device. Particle-based composites have reasonable slurry viscosities, however their thermal conductivity are usually very low (<10 Wm~(-1)K~(-1)), even when high k nanofillers are employed, due to the thermal interface resistance between nanoparticles and the polymer matrix or the absence of high κ pathways. We recently demonstrated high k in bulk nanocomposites of silver nanoparticles dispersed in epoxy and cured at low temperature (150°C). A nanocomposite with 30 vol. % 20nm particles exhibited k ~30 WiTf ~(-1)K~(-13). The mechanism responsible for enhancing κ was found to be the self-construction, through in-situ sintering, of high aspect ratio metallic networks inside the nanocomposite. Therefore these materials are named high thermal conductivity networked (HTCNet) composites. The objective of this work is to explore the thermal conductance of films of HTCNet composites for possible applications as Networked TIMs (Net-TlMs) and to understand if the high thermal conductivity observed in bulk samples can be extended to confined systems.