Al2O3-polyimide composite thick films for integrated substrates were successfully fabricated at room temperature by an aerosol deposition method (ADM). When using as-received a-Al2O3 as a starting powder, the Al2O3-polyimide composite thick films exhibited a high dielectric loss and high frequency dependence. The relative permittivity and tan δ of the Al2O3-polyimide composite thick films using as-received Al2O3 powder were 6.7 and 0.026 at 1MHz, respectively. However, their dielectric loss was remarkably decreased from 0.026 to 0.007 at 1MHz after post-annealing at 100oC although their relative permittivity did not change. It was determined that the decreases of dielectric loss mainly depended on the state of the Al2O3. Based on these results, the heat treatment of the Al2O3 starting powder was carried out in order to fabricate Al2O3-polyimide composite films with a low dielectric loss at room temperature. As a result, their tan δ was also decreased from 0.026 to 0.007 without a long post-annealing. It was confirmed that the preparation of the ceramic Al2O3 starting powder was important for the roomtemperature fabrication of the aerosol deposited Al2O3-polyimide composite thick films with a low dielectric loss.

Keywords: Aerosol deposition method, Al2O3, polyimide, polymer composite, heat treatment, room temperature process, integrated substrates.