Core lamination technology for micromachined power inductive components

A manufacturable core lamination technology applicable to various magnetic alloys which have high magnetic saturation and high permeability was proposed and developed for high frequency (MHz regime) and high power density power applications. To assess the performance of the developed lamination technology for practical use, microinductors and an ultra-compact DC-DC converter module were fabricated as test vehicles and demonstrations. The lamination technology developed is sacrificial etching lamination which performs alternate plating of a magnetic material and a sacrificial material, and selective etching of the sacrificial material. Copper was employed as a sacrificial plating material in this work since it shows good etching selectivity against most of nickel, iron, and cobalt based alloys. This technology was designed to build highly laminated cores with the simple manufacturable lamination process without being constrained by the thickness of the lamination film. Since low temperature photolithography and electroplating is used, large numbers of cores or magnetic devices can be fabricated in batch-process, and the core can be directly fabricated on top of prefabricated integrated circuitry. The inductors fabricated with the copper sacrificial etching lamination demonstrated significantly effective performance at the low MHz frequency region. An ultra-compact DC-DC boost converter module was designed and fabricated utilizing a laminated inductor developed. The boost converter operating at 2.2 MHz showed the efficiency higher than 70% for the load condition of 0.5∼2 W when converting from 7 to 12V. The overall profile of the converter was less than 1mm and the inductor profile was only 700 mum.