Near-Theoretical Thermal Conductivity Silver Nanoflakes as Reinforcements in Gap-Filling Adhesives.

The rapid development of highly integrated microelectronic devices causes urgent demands for advanced thermally conductive adhesives (TCAs) to solve the interfacial heat transfer issue. Due to their natural two-dimensional structure and isotropic thermal conductivity, metal nanoflakes are promising fillers blended with polymer to develop high-performance TCAs. However, achieving corresponding TCAs with thermal conductivity over 10 W m K at filler content below 30 vol% remains challenging so far. This longstanding bottleneck is mainly attributed to the fact that most current metal nanoflakes are prepared by "bottom-up" processes (e. g., solution-based chemical synthesis) and inevitably contain lattice defects or impurities, resulting in lower intrinsic thermal conductivities, only 20 - 65% of the theoretical value. Here, a "top-down" strategy by splitting highly purified Ag foil with nanoscale thickness was adopted to prepare two-dimensional Ag nanoflakes with an intrinsic thermal conductivity of 398.2 W m K , reaching 93% of the theoretical value. After directly blending with epoxy, the resultant Ag/epoxy exhibited a thermal conductivity of 15.1 W m K at low filler content of 18.6 vol%. Additionally, in practical microelectronic cooling performance evaluations, the interfacial heat-transfer efficiency of our Ag/epoxy achieved ≈ 1.4 times that of the state-of-the-art commercial TCA. This article is protected by copyright. All rights reserved.