A Multilayer Power Inductor Fabricated by Cofirable Ceramic/Ferrite Materials With LTCC Technology

Abstract

A cofired hetero-laminated low-temperature cofired ceramics (LTCC) power inductor device comprising cofirable NiCuZn ferrite body and Zn2SiO4 ceramic layers was designed, manufactured, and characterized. These produced LTCC power inductors were revealed to possess excellent characteristics including high inductance of $2.0~\mu \text{H}$ , small volume of 2 $\times1.2\times0.9$ mm3 (0805 packaging standard), low resistance of $0.20~\Omega $ , large current handling capability of 430 mA, low cost, and wide operating temperature range via a combination of characterization tools. Unlike the previously reported ceramic/ferrite hetero-laminates fabrication method, the process introduced in this paper involves no extra buffer layer or mechanical pressing sinter. Instead, a conventionally standard LTCC process was used for manufacturing these power inductors. To select the NiCuZn ferrite body with simultaneous high inductance and current handling capability for targeted power inductor design, the saturation magnetization and intrinsic coercivity of a variety of NiCuZn ferrite body prepared under different compositions, additives, and sintering conditions were carefully measured via vibrating sample magnetometer and under swept superpositioned dc magnetic field. Then, the power inductors with uniform sizes were mass produced using the selected NiCuZn body and Zn2SiO4 ceramic layers. The microstructure, magnetic element interdiffusion, interior circuit position, and inductance were detailed examined utilizing scanning electron microscopy, energy-dispersive X-ray spectroscopy, industrial computerized tomography scan, and RF impedance/material analyzer.