Polymer bonded soft magnetics for EMI filter applications

Abstract:
In this study, polymer bonded soft magnetic materials (PBSMM) were investigated for the application as a magnetic core and electromagnetic shielding material in inductive devices for EMI filter applications. The nature of the switch mode power converters makes them a potential source of EMI noise. EMI filters are generally necessary to ensure electromagnetic compatibility of converters to the other electronic equipment. Conventional discrete EMI filters usually comprise passive components with different volume and form factors. The manufacturing of conventional inductive components requires different processing and packaging technologies, of which many include cost intensive processing steps. Due to the parasitics of the discrete components and their interconnections the effective filter frequency range is limited. As a result discrete EMI filters are usually not integrable into an arbitrary formed volume and show relative high production costs. This study aims on solving this issue by the integration of inductive EMI filter components using polymer bonded soft magnetics. PBSMMs were produced using thermoplastic polyamide 6 matrix materials. The filler materials were chosen from the wide range of different soft magnetics. The magnetic properties were characterized using injection molded ring core test specimens and a computer controlled hysteresis recorder as well as an impedance analyzer. Inductive devices with PBSMM as magnetic core have great potentials in automotive applications that have to meet a high geometric flexibility and demanding electromagnetic compatibility requirements.