A NEW HYBRID TECHNOLOGY FOR PLANAR MICROTRANSFORMER FABRICATION

We have developed a new printed circuit board ( PCB) technology adapte d for the fabrication of ultra-flat microtransformers. The two outer l ayers of the PCB stack comprise the electrical windings of the inducti ve devices, while the inner layer is made of a micro-patterned amorpho us magnetic ribbon with extremely high relative magnetic permeability (mu(r) approximate to 100000). Two basic configurations were considere d; one being based on a toroidal magnetic core and the other on a rect angular (E-shaped) magnetic core. The electrical properties of the mic rotransformers have been studied as a function of frequency. Inductanc es were found to be as much as 30 mu H at 1 kHz, a relatively high val ue compared to microtransformers of similar size. Despite a relatively high leakage flux, voltage transformation efficiencies were measured between 89% and 98%. The high performance of these devices is primaril y due to the use of the high permeability magnetic core. The character istics of these devices are discussed in light of geometrical consider ations and finite element calculations. (C) 1998 Elsevier Science S.A. All rights reserved.