Area of contact and thermal transport across transfer-printed metal-dielectric interfaces

Recent experiments suggest that the interfacial thermal conductance of transfer printed metal-dielectric interfaces is ∼45 MW/m²K at 300 K, approaching that of interfaces formed using physical vapor deposition. We investigate this anomalous result using a combination of theoretical deformation mechanics and nanoscale thermal transport. Our analysis shows that plastic deformation and capillary forces lead to significantly large fractional areal coverage of ∼0.25. The conductance predicted from theory is on the same order of magnitude (∼18 MW/m²K) as the experimental data and partially explains the temperature trend. There remains a quantitative discrepancy between data and theory that is not explained through deformation of the asperities alone. We suggest that capillary bridges formed in the small asperities contribute significantly to heat conduction. A preliminary analysis shows this to be plausible based on available data. This work shows that metallic interconnects formed using transfer printing are not at a disadvantage compared to ones formed using vapor deposition, in terms of heat flow characteristics.