Batch-type millimeter-size transformers for miniaturized power applications

We have developed a novel batch-type technology for making three-dimensiona l (3-D) millimeter-sized transformers for ultrasmall low-power (0.1 to 1 Wa tt) applications. The technology uses the 3-D micropatterning of ferrite wa fers by powder blasting to form the magnetic cores of the inductive devices , and combines these cores with electrical windings made by flex-foil print ed circuit board technology. Microfabrication and assembly of the parts can be done in a batch process on a wafer/foil level, opening the way to furth er size reduction of the components. We have measured the inductive and res istive properties of our devices as a function of frequency and device geom etry. The results clearly show the high potential of our technology for pow er applications in which small-size is important.