Porous Al2O3 thick films fabricated by aerosol deposition and low loss Al2O3–Cyanate ester hybrid films by resin infiltration

Al2O3-cyanate ester hybrid thick films were fabricated, for 3-D integrated substrates, by resin infiltration into Al2O3 porous thick films fabricated by aerosol deposition (AD) at room temperature. The surface roughness and packing density of the fabricated porous Al2O3 thick films was controlled by carrier gas flow and, as a result, uniform porous Al2O3 thick films were fabricated on glass and Cu substrates at room temperature by AD. There was no peak shift or peak broadening of XRD patterns in the porous Al2O3 thick films compared to dense Al2O3 thick films made with submicron-starting powders. Al2O3-cyanate ester hybrid thick films were fabricated by resin infiltration into the porous Al2O3 thick films, and heated to 280 C for 5 h to cure the cyanate ester. The polymerisation of cyanate ester monomers was confirmed FTIR by after curing. The microstructures of Al2O3-cyanate ester hybrid thick films were observed by SEM after focused ion-beam milling. The relative permittivity and loss tangent of Al2O3-cyanate ester hybrid thick films were 6.7 at 1 MHz and 0.001, respectively. The Al2O3 content in the hybrid thick films was calculated using Hashin-Shtrikman bound theory with 3-D electrostatic simulations, and the calculated content was 72 vol% near a face-centred cubic structure.