Highly Thermally Conductive and Low Dielectric Loss Flexible Printed Circuit Board with Anisotropically Arranged BN Filler and Its Application in the Field of Flexible Electronics

ABSTRACT The field of flexible electronics has flourished in recent years. Among its key elements, the flexible printed circuit (FPC) stands out as a fundamental building block, forming a circuit system. However, as power density continues to increase, issues related to heat dissipation and electromagnetic interference become increasingly prominent. Together, these factors pose growing challenges to the reliability of FPCs. In this paper, we introduce a method for preparing a flexible printed circuit using hexagonal boron nitride (h‐BN) and polyurethane (PU). The resulting h‐BN/PU‐based flexible printed circuit (hBP‐FPC) achieves high thermal conductivity, low dielectric loss, and robust bending resistance. The BN filler endows hBP‐FPC with significant thermal conductivity anisotropy. The in‐plane thermal conductivity of the prepared hBP‐FPC material reaches 4.1 W (m K) ⁻¹ , and the cross‐plane thermal conductivity is 1.4 W (m K) ⁻¹ . A significant temperature reduction (7.1–19.2°C) is achieved in the hBP‐FPC compared to commercial FPC over the power density range of 0.125–0.375 W/cm ² . This study provides a promising strategy for developing high‐performance substrates for next‐generation high‐power‐density flexible electronics.