Sandwich Architecture Disentangles Thermal Transport and Interfacial Adhesion Tradeoff in Polytetrafluoroethylene Composite Copper Clad Laminates

Efficient thermal management and reliable interfacial adhesion remain challenging for high‐power, high‐frequency copper‐clad laminates (CCLs) due to the intrinsic trade‐off between thermal conductivity and bonding strength in conventional polymer composites. Here, a functional‐gradient sandwich architecture polytetrafluoroethylene (PTFE) based CCL is developed to decouple heat transport and interfacial bonding. The laminate consists of a central thermal conductive (TC) layer and two adhesive layers. The proposed architecture introduces synergistic functional regions with tailored filler networks. Large spherical boron nitride (SBN) particles construct interconnected three‐dimensional thermal pathways in TC layer, whereas hybrid small sized hexagonal boron nitride (hBN) and silicon nitride (Si 3 N 4 ) fillers are incorporated into the adhesive layers to enhance mechanical interlocking with copper foils and preserve certain thermal transport capability. Meanwhile, the low‐polarity PTFE matrix and electrically insulating ceramic fillers with optimized compositions maintain the intrinsic dielectric stability. In addition, a thickness‐dependent thermal transport model is established to correlate effective thermal conductivity with the relative layer thickness. The optimized sandwich CCLs achieve high thermal conductivity (3.96 W/m K), strong peel strength (1.5 N/mm), and ultralow dielectric loss (<0.0005), providing a general structural strategy to overcome the intrinsic trade‐off between thermal transport, interfacial adhesion and dielectric reliability in polymer‐based electronic substrates.