A 200 °C curable soft magnetic composite with high permeability and low core loss for power applications at >1 MHz

Abstract

Low-temperature curable soft magnetic composites (SMCs) could be a good choice for high-frequency power applications because of their low eddy current loss and low processing temperature. However, most low-temperature curable SMCs have a shortcoming of low relative permeability, i.e., typically less than 30, due to their low packing density. To improve the relative permeability of such the low-temperature curable SMCs and ensure the applicability in power conversion with acceptable low core loss density, we proposed 200 ℃ curable SMCs cores with permalloy flakes and spherical powders with an acrylic polymer coating, i.e., TMPTA. The relative permeability, core loss density, hysteresis loops, and inductance versus DC bias of the cores were measured. The highest relative permeability of the SMCs cores increased to 38.7 as well as the maximum Bs of 1.140 T with acceptable low core loss density in the case of 15wt% permalloy flakes. It was found that the flakes could not only increase the packing density, but also provided more ‘conductive’ paths for magnetic flux. The reliability and the efficiency tests of the SMCs core with 15wt% permalloy flakes proved the feasibility of its applicability for high-frequency power converters.