Breaking the Thermal Conductivity–Adhesion–Viscosity Trade‐off in Thermally Conductive Adhesive via Hyperbranched Networks and Multi‐Scale Fillers

Abstract Thermally conductive adhesives are essential for thermal management in high‐power optoelectronic systems, where they provide both efficient heat dissipation and strong mechanical bonding. However, achieving high thermal conductivity alongside strong adhesion and low viscosity remains a fundamental challenge due to conflicting material requirements. Herein, a molecularly engineered thermally conductive adhesive is reported that uniquely and simultaneously overcomes these trade‐offs by integrating amino‐ and phenylboronic acid‐functionalized hyperbranched polysiloxane into a polydimethylsiloxane matrix filled with multi‐scale aluminum fillers. A coupled dynamic‐covalent network originating from the hyperbranched polysiloxane enhances both bulk and interfacial dissipation through reversible boronic‐ester exchange, while the multi‐scale aluminum architecture increases maximum packing and connectivity yet suppresses viscosity growth, enabling ultra‐high filler loading without sacrificing bonding. The resulting thermally conductive adhesive achieves a thermal conductivity of 6.21 W m −1 K −1 , an adhesion strength of 5.13 MPa, and a low viscosity of 253.0 Pa s. Device‐level validation confirms its excellent dispensability, ability to lower operational temperature and relieve thermomechanical stress, thereby establishing a distinct design paradigm that links molecular structure, filler architecture, and thermo‐mechanical reliability in one coherent framework.