Micromachined thick-film copper power inductors and transformers for integrated power converters

Abstract

This work presents surface-micromachined, air-core, power inductors and transformers for next-generation, integrated, high-frequency switching power converters operating in the 50– 500 MHz frequency range. The high-performance devices are realized by a multilayer, copper electroforming process that enables low resistance, three-dimensional, free-standing structures for high mutual inductance coupling and low parasitic capacitance. Three fabricated inductor designs are presented with areas 1– 4 mm2, inductance densities > 100 nH/mm2, and quality factors up to 21. Three transformer designs are also presented, all with areas 2.25 mm2 and primary inductances of 47 nH but with variable secondary inductances to yield voltage gains from 1:1 up to 1:3.5.