Reaction mechanism investigation of low Df epoxy-active ester film composites for 10 GHz high-frequency communications

Abstract

The role of electronic-grade thin film composite materials in packaging circuits (integrated circuits) and printed circuit boards is critical. Developing epoxy-based thin film composite materials with low dielectric loss (Df) is a significant challenge, especially for that used in high frequency communication (eg. 10 GHz). Active esters, as excellent curing agents, do not form strongly polar hydroxyl groups upon reacting with epoxy resins, which offers significant advantages for low Df thin film composites. In this study, a low Df and high thermal resistance thin film composites was prepared by selecting epoxy resins with biphenyl structures and active esters with dicyclopentadiene groups. The introduction of rigid groups reduces the motility of the molecular chains, and its electron conjugation effect weakens the impact of an external electric field on the molecular dipole moment. The essence of low Df is explained by DFT calculations, in which the quenching effect of active esters on oxygen anions reduces the polarity of the molecular. Meanwhile, ensuring sufficient reaction at a sufficiently high temperature can reduce the number of residual free molecule fragments and ensure the integrity of the cross-link network. This work provides a new direction for the design of the next generation of high-performance low Df composites by deeply explaining the nature of active esters in reducing dielectric loss.