Ferrite–Polymer–Composite Materials for Inductive Electronic Components

Based on the established inductor design rules, an innovative transformer was realized in a low-cost process using a novel ferrite-polymer composite material on conventional epoxy board. The low processing temperature (100°C), however, permits application also on other thermally sensitive substrates like semiconductor wafers. The transmitted power and efficiency of the transformer were 90W and 93%, respectively, as compared to 97% when sintered bulk ferrite cores are used.. The ratio of polymer and ferrite powder in the ferrite-polymer compound was chosen according to the Maxwell-Garnett mixing rule. With optimized particle size, ferrite content and microstructure, a permeability of up to μ = 30 is achieved. The achieved results are compared with theoretical predictions. The lower permeability of the ferrite-polymer composite in comparison to bulk ferrite material increases the lower limit of the frequency window of operation for this device.