Miniaturization of Planar Packaged Inductor Using NiZn and Low Cost Screen Printing Technique

Abstract

Given the recent interest in power delivery design for the Internet of Things (IoT), current work aims to design a packaged power delivery solution for IoT. The power inductor takes up a large amount of the area in such an implementation. Planar power inductors are preferred for fabrication simplicity and cost. However, air core inductors do not have sufficient area efficiency for IoT solutions, necessitating the integration of a magnetic core on a planar inductor. This research demonstrates a low cost method of miniaturizing planar inductors using stencil printing technique with a magnetic composite for embedded power inductors for IoT edge device applications. Planar spiral inductors of varying dimensions and inductances are designed using a full wave EM solver. Inductors are then fabricated on FR4 using standard printed wiring board process. NiZn is a low loss magnetic material and is mixed with an epoxy and solvent to facilitate stencil printing. Stencil printing is a low cost fabrication method with great utility to electronic packaging. A single layer of NiZn is screen printed as squares directly on the fabricated spiral inductors. Measurements are performed using a vector network analyzer at frequencies between 10 and 50 MHz. The measured inductance of the inductors ranges from 37 nH-340 nH without NiZn to 42 nH-452 nH with a single NiZn layer at the operating frequencies. In addition, the Q factor is actually improved at the frequency of operation, as the inductance gained from the magnetic layer is more significant than the loss incurred. This increase in inductance leads to great potential for decrease of size of packaged inductors.