Design and synthesis of intrinsic black polyimide with full visible-light absorption and low coefficient of thermal expansion for black flexible copper clad laminates

With the rapid growth of microelectronics and optoelectronics, the demand for black polyimides (BPIs) with exceptional comprehensive performance has increased dramatically. 3,6-diaryl-2,5-dihydropyrrolo [3,4-c]pyrrole-1,4-dione (TDPP) is a well-known organic dye that has strong visible absorption. In this study, a novel diamine (DPPTPDA) containing TDPP-based chromophore was successfully synthesized, and an intrinsic BPI (DPPTPPI) was then obtained by the polymerization of DPPTPDA with pyromellitic dianhydride (PMDA). With the introduction of TDPP-based chromophores, the light absorption of DPPTPPI is significantly red-shifted and broadened, exhibiting complete absorption in the visible range. To explore the underlying electron nature of DPPTPPI, density functional theory calculations are carried out. The result shows that the outstanding light absorption of DPPTPPI is mostly owing to the electron transitions of HOMO→LUMO+1 that occur in the TDPP-based chromophores units. Meanwhile, DPPTPPI exhibits a low coefficient of thermal expansion and excellent electrical performances. The flexible copper clad laminate based on DPPTPPI films show high solder heat resistance and peel strength. The study provides theoretical implications for the molecular design of high-performance intrinsic BPI materials targeting practical microelectronic applications.