Thin Flexible Thermal Ground Planes: Fabrication and Scaling Characterization

Thermal ground planes (TGPs) are passive thermal management devices that utilize the latent heat associated with phase change to achieve high effective thermal conductance, similar to heat pipes. In this paper, we develop flexible TGPs with an ultra-thin thickness of 0.5 mm using copper-cladded polyimide as the encasing material, woven copper mesh as a wick, and electroplated copper pillars to support a vapor core. The lowest thermal resistance of one TGP is characterized to be only 1/3 that of an equivalently sized copper heat spreader. The effects of size scaling of evaporator and condenser, and overall TGP sizes on the thermal resistances of TGPs are experimentally characterized. A simple series thermal resistance model, which accounts for vapor core thermal resistance, is developed to predict the measured results. This experimentally validated model can be used for the design of TGPs with varying sizes of evaporator and condenser, and overall size.