Low‐Dielectric SiO₂/Polyimide Prepreg Composite With Enhanced Interfacial, Thermal, and High‐Frequency Properties

A low‐dielectric prepreg composite was developed for high‐frequency electronic packaging by combining a thermally stable, modified polyimide (PI) matrix with silane‐functionalized SiO 2 fillers. A radical crosslinking network was constructed using dicumyl peroxide (DCP) as the initiator and triallyl cyanurate (TAC) as the multifunctional crosslinker, enabling covalent interfacial bonding and three‐dimensional network formation. FT‐IR and DSC analyses confirmed the disappearance of maleimide and allyl double bonds and the formation of SiOSi bonds, indicating complete curing and interfacial reactions. Thermomechanical analysis showed that the SiO 2 ‐filled composite exhibited a 30%–35% reduction in thermal expansion coefficient compared to the unfilled sample. A 90° peel test revealed over 30% enhancement in interfacial adhesion due to silane‐induced chemical bonding. Dielectric measurements at 10 GHz demonstrated a significantly improved dielectric constant (2.1) and dissipation factor (0.0022) relative to the control. S‐parameter analysis further confirmed reduced signal loss and enhanced signal integrity, with return loss below −35 dB and insertion loss near −2.0 dB. These results validate the effectiveness of the proposed PI/SiO 2 composite as a multifunctional material platform for next‐generation high‐speed I/O and RF packaging applications.