Drainage-Induced Dry-Out of Thermal Greases

In this study, the mechanism of grease dry-out, a long-term failure mode of thermal greases, is investigated using optical microscopy and infrared (IR) thermography. Results show that the dry-out phenomenon is accelerated in aged greases and we suggest that this is due to inhomogeneities in the filler packing structure that develop over time due to segregation of the grease components, though they may also occur at time zero due to insufficient mixing during grease formulation. Theories describing fluid flow through porous media are used as a preliminary framework for understanding the grease dry-out process and its dependence on local variations in the grease microstructure and on matrix-filler compatibility.