Innovative Construction of High‐Performance Polyimide Composites: Ultra‐Integration of Low Thermal Expansion, Super Flexibility, and Exceptional Thermal Conductivity

ABSTRACT To address warping and heat issues in miniaturized electronics, polyimide (PI) films require enhanced dimensional stability and thermal conductivity. Traditional inorganic fillers often compromise other properties, while multi‐filler systems face interfacial challenges. Here, a novel multifunctional negative thermal expansion (NTE) inorganic nanoparticle Hf 2 (WO 4 )(PO 4 ) 2 (HWP) with high thermal conductivity is successfully prepared. Surface modification of HWP particles has been conducted using silane coupling agents with six various functional groups. The coefficient of thermal expansion (CTE) results show that the KH‐550 modified HWP has the best interfacial compatibility after adding to the PI matrix. When the addition amount reaches 60 vt%, the CTE drops to 20.4 ppm/K, which is close to that of copper. Benefiting from the good comprehensive performance of 550‐mHWP, 550/PI‐25 film exhibits a low CTE of 27.8 ppm/K, excellent flexibility, a thermal conductivity of 0.896 W/m·K, while hardly damaging its dielectric properties. The 550‐mHWP/PI composite film successfully addresses the long‐standing challenge in microelectronic systems where achieving simultaneous control over low thermal expansion coefficient, exceptional flexibility, superior thermal conductivity, and reduced dielectric properties has been problematic. This breakthrough material system presents a viable pathway for advancing intelligent microelectronics development.