Hierarchical Nested Surface Channels for Reduced Particle Stacking and Low-Resistance Thermal Interfaces

This paper reports on the improvement of thermal interfaces through the control of particle stacking during bondline formation. Particle stacking occurs in highly filled materials due to pressure gradients developing during squeeze flow over a rectangular surface, resulting in non-uniform interface properties and thick bondlines with a large thermal resistance. Nested surface channel designs are presented to create a uniform pressure drop as interface material flows across a rectangular surface. Reductions in thermal resistance of 2-3times compared with that of flat surfaces are demonstrated with similar reductions in bondline thickness and assembly pressure. We obtained thermal resistances as low as 2 Kmm²/W for thin bondlines (< 5 mum). Comparative power-cycling results also demonstrate improved reliability against paste pump-out with nested channel interfaces.