This article, after briefly introducing the trend of EMI filters towards miniaturization and chip-based designs, focuses on the application of new materials and technologies in EMI filters and miniaturized chip-based magnetic components.
The miniaturization and lightweighting of electronic devices has driven the continuous development of EMI filters towards miniaturization and surface mount technology. Multilayer surface mount EMI devices are a new type of surface mount component (SMD) that has emerged in recent years with the development of high-density surface mount technology (SMT). Due to their great potential for miniaturization, they have become a hot topic in research and development in recent years. These EMI components include surface mount bead-type EMI/RFI suppressors, surface mount inductors, surface mount combined (LC type, etc.) filters, and surface mount chokes. In terms of size, the United States has established relevant standards, such as the 1008 (1.0mm × 0.8mm), 0805, 0603, and 2012 models. Because these EMI devices have special requirements for the ferrite materials used, requiring not only low sintering temperature and high resistivity, but also no reaction with the inner conductor, a great deal of effort and resources have been invested in researching ways to reduce the sintering temperature of these materials and improve their electromagnetic properties in recent years, resulting in many valuable achievements.
As the size of surface-mount EMI devices continues to shrink, achieving large inductance or impedance values in small-sized filters will be a key area of future research. Furthermore, to meet the demands of miniaturized IC circuits and precision PCB circuits for EMI suppression, research on thin-film combined filters is also increasing. Tektronix and Tohoku University have developed thin-film π-type and thin-film LC EMI filters, operating in the 1–1000 MHz frequency range with a maximum insertion loss of 25 dB. Because these EMI devices are manufactured entirely using thin-film technology, they hold promise for achieving higher integration levels.
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