Characterisation of Low-Temperature Co-Firable Green Tapes for Making Fused Silica Laminated Composites

Abstract

For achieving high-temperature resistance and a broadband of microwave transmission, ceramic metamaterials consisting of fused silica ceramic substrates and electrically conductive networks/ arrays are desirable. A new strategy of fabricating the fused silica metamaterials is to combine the low temperature co-fired ceramic (LTCC) technique with a method of ceramic joining via green tapes. The important part of the new strategy lies in the preparation of suitable green tapes that are co-firable with a conductive silver-based film/strip and have a strong affinity to the fused silica substrates. Therefore, in this paper, three green tape materials were prepared and intensively characterised using scanning electron microscopy, x-ray diffraction, dilatometry, dielectric measurement, etc. It was found that the tape materials were based on dielectric glasses and crystalline phases of major eulytite and minor cristobalite, leading to rather low levels of dielectric constant (<6) and loss tangent (in the order of 10-3). The three tape materials also had different levels of thermal expansion coefficients, co-firability with a conductive silver-based paste, and bondability to the fused silica substrates. These findings suggest that one can achieve desirable ceramic matematerials with well-controlled shapes and dimensions of the condutive networks/arrays after properly laminating the green tapes between the fused silica substrates.