3D Micro-Transformers Fabricated Inside Ferrite-Dielectric LTCC Substrate

Abstract

Presented findings referee to continuance of research of ceramic passive components (inductors and transformers). Paper presents design, fabrication and characterization results of three 3D micro-transformers fabricated inside combined ferrite-dielectric LTCC (Low Temperature Co-fired Ceramics)stack. Basic designed geometry consists of centrally connected three turn square overlapping windings (primary and secondary)placed on different tape layers of the formed LTCC stack. Transformers windings are placed on outer dielectric tapes and number of ferrite tapes in between is varied. Characterization is performed in lower RF range and results of transformer windings inductance and Q-factor are presented. It is shown that inductance and Q-factor values of primary winding do not vary much with increase of thickness of ferrite layer. However, increase of the same characteristics value of secondary winding is noticeable as number of in-between tapes increases (44% inductance and 25% Q-factor value of the secondary winding).