Low dielectric silsesquioxane-modified benzocyclobutene composites

Abstract

Benzocyclobutene (BCB) resin has been widely used as an advanced electronic packaging material due to its excellent low-dielectric (low-k) properties, good thermal stability, and high planarization. However, it is still urgent to further reduce its dielectric constant for high-frequency applications. Herein, a series of organoalkoxysilane (D4Sin)-functionalized thermosetting benzocyclobutene (BCB) resins were reported. Precursors with the large hindrance of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4Vi) ring as the core, as well as tunable vinyl and methoxyl substituents as pendant groups, have been successfully prepared by the efficient platinum-catalyzed hydrosilylation reaction. They can further undergo the pre-polymerization via hydrolytic condensation of methoxyl groups and post-thermal curing processes via thermal-induced ring-opening and Diel-Alder reactions between vinyl groups and bis (benzocyclobutenyl) divinyltetramethylsiloxane (DVS-BCB), respectively. The fully cured materials exhibited excellent dielectric properties with a dielectric constant (Dk) of 2.20 and a dissipation factor (Df) of 7.04 × 10−4, good thermal stability (the 5% weight loss temperature, Td5 ˃ 445 °C), strong hydrophobicity (water contact angle >100°) and good mechanical properties. Compared with traditional thermosetting BCB resins, this procedure combined BCB resins with silsesquioxanes including the ladder/cage-like or network topological structures. This work provided a simple and universal method to construct intrinsically porous materials of organoalkoxysilane-functionalized BCB resins, laying the foundation for the future fabrication of ultra-low dielectric electronic packaging materials with nanoscale pores.