Field-structured magnetic platelets as a route to improved thermal interface materials

Abstract

The development of high-performance thermal interface materials (TIMs) is crucial to enabling future generations of microelectronics because the TIM is usually the limiting thermal resistance in the heat removal path. Typical TIMs achieve modest thermal conductivities by including large volume fractions of randomly-dispersed, highly-conductive, spherical particles in a polymer resin. This paper explores field-structured magnetic platelet composites as a new approach to more effective TIMs. The motivation for this approach is rooted in shape functional theory, which shows that when the particle material has a significantly higher thermal conductivity than that of the polymer, the particle shape and orientation are the factors that limit conductivity enhancement. Oriented platelets are highly effective for heat transfer and if these are magnetic, then magnetic fields can be used to both orient and agglomerate these into structures that efficiently direct heat flow. In this paper we show that such field-structured composites have a thermal conductivity anisotropy of ∼3, and at the highest particle loading of 16 vol.% we have achieved a 23-fold conductivity enhancement, which is 3-times larger than that achieved in unstructured platelet composites and 8-times greater than unstructured spherical particle composites.