Use of Titanates to Achieve a Temperature-Stable Low-Temperature Cofired Ceramic Dielectric for Wireless Applications

A low-loss and near-zero temperature coefficient of resonant frequency ( T _f) low-temperature cofired ceramic (LTCC) host dielectric was developed for portable consumer wireless device applications. The low T _f was realized by compensating the Al₂O₃-filled-glass dielectric with admixtures of TiO₂ (negative temperature coefficient of dielectric constant ( T _ɛ)) in the starting formulation. XRD data indicated a portion of the TiO₂ in the starting formulation dissolved into the glass, and extensive formation of crystalline titanium compounds was observed via a nucleation and growth mechanism. The dissolution of TiO₂ in the glass and subsequent formation of titanium compounds was believed to result in the relatively small amount of TiO₂ required to achieve a near-zero T _f in the final sintered structure.