Performance limits of ultra-thin printed circuit board inductors

Printed circuit board integrated inductors allow a significant size reduction of small and medium sized power converters and offer a cost effective way to new applications that need thin, bendable and reliable inductors. Components thin as printed circuit boards are already demonstrated, but even thinner and smaller components are desired. This publication explores the limits for a size reduction. As the most important parameter for power applications, the limitation by losses, expressed by the quality factor as a figure of merit, is investigated more in detail. The calculation is reduced to few key parameters, which are used for a parametric analysis. It is compared to a detailed calculation of example inductors, which takes real geometries into account, and to measurement results of realized samples. As a main result, considering geometrical parameters, the inductivity value of an integrated inductor is limited by its diameter and its track pitch. The quality factor, however, is in first order dependent only on the component thickness and decreases for thinner components. The results show that the simplified analysis is a useful tool to support a decision in the trade off between electrical performance and building height of a printed circuit board integrated inductor.