Preparation of high-dielectric-constant Ag@Al2O3/polyimide composite films for embedded capacitor applications

In recent years, novel materials for embedded capacitor applications are in great demand. This paper reported the preparation of a novel high dielectric constant Ag@Al₂O₃/polyimide composite film for embedded capacitor applications. Firstly, nano-sized Ag particle was synthesized through a redox reaction between silver nitrate and N, N-dimethylformamide and the obtained Ag nanoparticles were treated with aluminum isopropoxide (AIP) to form an Al₂O₃ thin layer on its surface (Ag@Al₂O₃). Then these Ag@Al₂O₃ nano-particles were doped in polyimide by in-situ polymerization to prepare the Ag@Al₂O₃/polyimide composite films. Results indicated that a typical core-shell structure was obtained and the sizes of Ag@Al₂O₃ particles were all in nanometer level. Experimental results for Ag@Al₂O₃/PI composite films showed that the Ag@Al₂O₃ nano particles were well dispersed in the PI matrix. After Ag@Al₂O₃ particles´ addition, a slight decrease in mechanical properties of composite films was found. Moreover, the dielectric constant (k) increased gradually with Ag@Al₂O₃ content before reaching the percolation threshold. In contrast, the value of loss tand remained at a low level (<;0.02) before reaching the threshold.