An 86% Efficiency, 20MHz, 3D-Integrated Buck Converter with Magnetic Core Inductor Embedded in Interposer Fabricated by Epoxy/Magnetic-Filler Composite Build-Up Sheet

This paper presents a three-dimensional (3D) -integrated buck converter implemented on an interposer with an embedded magnetic core inductor. The converter realizes small footprint, low fabrication cost, high efficiency, and fast load transient response by using the proposed build-up lamination process. In the proposed interposer build-up lamination process, epoxy/magnetic-filler composite sheet is used to form a fully closed magnetic circuit spiral inductor inside the build-up layer without using any expensive magnetic thin film deposition process. Furthermore, a control chip suitable for high switching frequency operation is proposed and designed by a 0.35μm standard CMOS process. With these proposed technologies, the proposed 3D-integrated buck converter shows maximum efficiency of 87.0/86.0% at 16/20MHz switching frequency with a voltage conversion of 5V to 3.3V. The load transient response is less than 2.6μs at the load step between 80mA and 460mA.