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

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.