Preparation of fluorinated polyimides with low dielectric constants and low dielectric losses by combining ester groups and triphenyl pyridine structures

Abstract

As 5G communication develops rapidly, the traditional interlayer insulating dielectric material polyimide (PI) can no longer meet the requirements of large-scale integrated circuits, high-velocity, high-frequency communication, and other microelectronic applications, and urgently needs modification. In this paper, we superimpose the modification effects of bulk triphenyl pyridine structure and ester group structure and combine the bulk and low polarizability groups to successfully prepare a new type of PI with a low dielectric constant (D_k) and low dielectric loss (D_f) at high frequency. The research focuses on the structure–property correlation of PIs, especially the effect of fluorine content on the dielectric properties. Firstly, three bulk diamine monomers (BPAB, PBAB3F, PBAB6F) containing a triphenyl pyridine structure were designed and synthesized, which were then polymerized with the 2,2-propenylidene-4,1-phenylene-1,3-dihydro-1,3-dioxo-5-isobenzofuran carboxylic acid ester (BTPDA) to obtain three new PIs with different fluorine contents (PI-EH, PI-ECF₃, PI-E2CF₃, respectively). Testing results show that the dielectric properties and moisture absorption of the PIs are improved with increased fluorine content. The new PIs showed excellent properties, such as low dielectric constants (D_k = 2.84–2.74 @ 10 GHz and D_f = 0.00373–0.00338 @ 10 GHz), low water absorption (0.94–0.73%), and high hydrophobicity (contact angle = 77–97°), with PI-E2CF₃ having the best overall performance. The present study was carried out to provide a reference for preparing high-frequency, low dielectric constant, and low-loss interlayer dielectric materials.