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 2D 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−1 K−1 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 is adopted to prepare 2D Ag nanoflakes with an intrinsic thermal conductivity of 398.2 W m−1 K−1, reaching 93% of the theoretical value. After directly blending with epoxy, the resultant Ag/epoxy exhibits a thermal conductivity of 15.1 W m−1 K−1 at low filler content of 18.6 vol%. Additionally, in practical microelectronic cooling performance evaluations, the interfacial heat‐transfer efficiency of the Ag/epoxy achieves ≈1.4 times that of the state‐of‐the‐art commercial TCA. 2D Ag nanoflakes with intrinsic thermal conductivity (398.2 W m−1 K−1) close to theoretical value are prepared using the “top‐down” method. After directly blending with epoxy (18.6 vol%) without any complex surface modification, hybridization, and structural design, the interfacial heat‐transfer efficiency of the obtained gap‐filling adhesive is ≈1.4 times that of the state‐of‐the‐art counterpart.