Soft magnetic materials for power inductors: State of art and future development

Soft magnetic materials play important roles in both power generation and conversion devices. One of their important applications is power inductor, which acts as an energy transfer station, transferring the direct current energy and blocking the high-frequency alternating current. With the rapid development of circuit topologies and power semiconductors, the power inductors with higher inductance performance, smaller size and higher energy efficiency are required. Based on the world-wide progress, this review gives a comprehensive and critical description on the fundamentals and development of the soft magnetic materials for the power inductors. The relationship between the properties of soft magnetic materials and the inductance performance of device is discussed in detail. The industry status of the power inductors based on both soft ferrites and soft magnetic composites (SMCs) is analyzed. The material selection, fabrication process and microstructure-properties relationships for ferrites and SMC materials are summarized. In particular, this review emphatically compares the difference between the conventional magnetic cores and the multilayer/molding inductors in processing and material selection. The challenges and opportunities of the soft magnetic materials are also highlighted for future development.