Comprehensive properties study of low-temperature imidized polyimide with curing accelerators

Over the last few years, low-temperature curing polyimide (PI) has turned out to be a significant target for the advanced electronic package. Although the curing accelerators have been confirmed to be capable of significantly decreasing the curing temperature, their effects on properties have not been comprehensively examined. In this study, polyamide acid is synthesized by pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA), and the process of low-temperature imidization is investigated by introducing six accelerators, i.e., quinoline (QL), isoquinoline (IQL), 2-methyl quinoline (2-QL), 4-methyl quinoline (4-QL), 8-methyl quinoline (8-QL), as well as 5,6,7,8-tetrahydroquinoline (THQL). As revealed from the results, the polyimide films formed using 4-QL and QL have exhibited prominent mechanical, thermal, and electrical properties. For the PI-4-QL, the tensile strength is 151.87 MPa, elongation-at-break reaches 161.36%, and the weight loss of 5% is observed at 533 °C; for the PI-QL, the tensile strength is 134.82 MPa, elongation-at-break reaches 145.16%, and the weight loss of 5% reaches 545 °C. As indicated from the results, the boiling point, acidity and molecular structure of the low-temperature curing accelerators show significant effects. Lower acidity and steric hindrance between the accelerator and amide bond facilitate the low-temperature imidization of polyamide acid. Furthermore, the as-prepared low-temperature cured PIs of 4-QL and QL would exhibit wide applications in advanced packaging industry.