Development of BaTiO_3 Based X7R Wafers for Single-Layer Capacitors

摘要

Research on the development and characterization of X7R BaTiO_3 dielectric wafers for high frequency single-layer capacitors has been carried out. Commercial BaTiO_3 powders were processed and optimized in dielectric constant (ε_r), dissipation factor (DF) and temperature coefficient of capacitance (TCC). The results indicate a strong effect of sintering temperature on dielectric properties as well as on mechanical properties of the BaTiO_3. It has been shown that the highest dielectric constant is achieved at high sintering temperatures ( > 1400℃) and lowest TCC at lower sintering temperatures ( < 1300℃). By optimizing fabrication process e.g. dry pressing, cold isostatic pressing, sintering, and machining such as grinding and lapping, BaTiO_3 wafers of dielectric constant from 3400 to 3600, with a diameter approximately 50mm and thickness 150μm, have been manufactured successfully. The fabricated thin wafers exhibit the X7R capacitor characteristics of the dissipation factor ( < 3%) and temperature coefficient of capacitance ( < +- 15%) in the temperature range of-55℃ to 125℃.