Ni-Cu-Zn ferrites with high Curie temperature for multilayer inductors with increased operating temperatures

We studied the sintering behavior and magnetic properties of Ni(0.60-y)Cu(y)Zn(0.42)Fe(1.98)O(3.99)ferrites. The shrinkage is shifted toward lower temperature with increasing Cu content y. The addition of Bi(2)O(3)sintering aid induces enhanced shrinkage atT mu = 135-250 depending on the composition, sintering temperature and concentration of sintering additive. Ferrites withy = 0.20 show a high Curie temperature ofT(c )= 307 degrees C. Multilayer inductors were fabricated and cofired at 900 degrees C using ferrite tapes without and with 0.75 wt% Bi2O3. The compatibility of ferrite tapes with different metal pastes (Ag, AgPd, and Au) was evaluated. Ferrite tapes were also integrated between layers of low-kdielectric CT708 tapes and successfully cofired at 900 degrees C. Preliminary tests indicate that the multilayer inductors can be operated up to temperatures of 250 degrees C. This demonstrates that high-TcNi-Cu-Zn ferrites are promising magnetic materials for inductive components for high operating temperatures.

Automated summary

The sintering behavior and magnetic properties of Ni-Cu-Zn ferrites were studied, revealing that shrinkage shifts to lower temperature with increasing Cu content. The addition of Bi(2)O(3) sintering aid enhances the sintering shrinkage. The fabricated ferrites exhibit good performance at high temperatures.