Copper Inner Electrode X7R MLCs Based on Zinc Borate Fluxed Barium Titanate

摘要

To demonstrate feasibility as copper cofired dielectrics, BaTiO_3 has been formulated into X7R dielectrics. This requires the development of a formulation that permits sintering at temperatures below ～1000 and in reducing atmospheres below pO_2 ～10~(-7) atms. ZnO-B_2O_3 based flux chemistries were explored with additional dopants including Li_2O or SrO to modify the densification and the temperature coefficient of capacitance (TCC) of BaTiO_3 dielectrics. X7R characteristics with relative dielectric permittivities ～2750 and tanδ ～0.01 at 1kHz were obtained at room temperature in multilayer capacitors fabricated in 3.2 mm x 1.6 mm size. Dielectric aging was evaluated at room temperature and found to be 1.1～2.2% pre decade, comparable to conventional MLCs. Further voltage saturation behavior was also investigated.