Micro/Millimeter-Wave Dielectric Indialite/Cordierite Glass-Ceramics Applied as LTCC and Direct Casting Substrates

Indialite/cordierite glass-ceramics demonstrate excellent microwave dielectric properties such as a low dielectric constant of 4.7 and an extremely high quality factor Qf of more than 200 × 10³ GHz when crystallized at 1300°C/20 h, which are essential criteria for application to 5G/6G mobile communication systems. The glass-ceramics applied to dielectric resonators, low-temperature co-fired ceramic (LTCC) substrates, and direct casting glass substrates are reviewed in this paper. The glass-ceramics are fabricated by the crystallization of glass with cordierite composition melted at 1550°C. The dielectric resonators are composed of crystallized glass pellets made from glass rods cast in a graphite mold. The LTCC substrates are made from indialite glass-ceramic powder crystallized at a low temperature of 1000°C/1 h, and the direct casting glass-ceramic substrates are composed of crystallized glass plates cast on a graphite plate. All these materials exhibit excellent microwave dielectric properties.