Materials/processing approaches to phase stabilization of thermally conductive pastes

Previously reported thermally conductive pastes based on simple dispersions of boron nitride particles in mineral oil were observed to undergo phase separation when stressed thermal-mechanically. Such stressing of thermal pastes was carried out to simulate the mechanical shearing action imposed on such pastes as a result of the anticipated differential motion of contacted heat-transfer surfaces and the paste during transient heating/cooling in various cooling assemblies. In the present work, the tendency of thermally conductive pastes to phase-separate during such simulated functional use was eliminated and given attributes of reworkability and corrosion inhibition by a combination of several approaches. These included: (1) the use of surface modification agents such as coupling agents and/or polymers on boron nitride particles: (2) milling conditions employed; and (3) the selection of novel oily and oxidation-resistant vehicle material systems to interact with the modified particle surfaces while preventing corrosion of contacted metallic surfaces