Investigation of the dielectric permittivity of anodic aluminum oxide substrates for multi-chip modules

The present article describes the investigations, performed in order to determine some dielectric characteristics of anodic aluminum oxide (AAO), obtained by electrochemical anodization process. The AAO layer is grown directly on aluminum substrates, considered as suitable carriers for multi-chip modules (MCM). Test samples for measurements of the dielectric permittivity and loss tangent were elaborated by anodization in 5% oxalic acid electrolyte. The chosen measurement technique is based on the ring resonator method. The values, obtained for the S21 parameter of a two-port ring resonator, were used to determine the permittivity of the board substrate.