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Correction published on 8 June 2016, see Micromachines 2016, 7(6), 100.

Open AccessArticle
Micromachines 2016, 7(4), 60; doi:10.3390/mi7040060

Polymer Magnetic Composite Core Based Microcoils and Microtransformers for Very High Frequency Power Applications

1
Laboratory for Microactuators, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany
2
Voxalytic GmbH, Rosengarten 3, 76228 Karlsruhe, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Stephanus Büttgenbach
Received: 15 January 2016 / Revised: 24 March 2016 / Accepted: 28 March 2016 / Published: 5 April 2016
(This article belongs to the Special Issue Magnetic MEMS)
View Full-Text   |   Download PDF [9177 KB, uploaded 8 June 2016]   |  

Abstract

We present a rapid prototyping and a cost effective fabrication process on batch fabricated wafer-level micro inductive components with polymer magnetic composite (PMC) cores. The new PMC cores provide a possibility to bridge the gap between the non-magnetic and magnetic core inductive devices in terms of both the operating frequency and electrical performance. An optimized fabrication process of molding, casting, and demolding which uses teflon for the molding tool is presented. High permeability NiFeZn powder was mixed with Araldite epoxy to form high resistive PMC cores. Cylindrical PMC cores having a footprint of 0.79 mm 2 were fabricated with varying percentage of the magnetic powder on FR4 substrates. The core influence on the electrical performance of the inductive elements is discussed. Inductor chips having a solenoidal coil as well as transformer chips with primary and secondary coils wound around each other have been fabricated and evaluated. A core with 65% powder equipped with a solenoid made out of 25 µm thick insulated Au wire having 30 turns, yielded a constant inductance value of 2 µH up to the frequency of 50 MHz and a peak quality factor of 13. A 1:1 transformer with similar PMC core and solenoidal coils having 10 turns yielded a maximum efficiency of 84% and a coupling factor of 96%. In order to protect the solenoids and to increase the mechanical robustness and handling of the chips, a novel process was developed to encapsulate the components with an epoxy based magnetic composite. The effect on the electrical performance through the magnetic composite encapsulation is reported as well. View Full-Text
Keywords: microtransformer; polymer magnetic composite (PMC); microcoil; MEMS; wirebonding; very high frequency (VHF); passive components; power conversion; micro-machining microtransformer; polymer magnetic composite (PMC); microcoil; MEMS; wirebonding; very high frequency (VHF); passive components; power conversion; micro-machining
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Mariappan, S.G.; Moazenzadeh, A.; Wallrabe, U. Polymer Magnetic Composite Core Based Microcoils and Microtransformers for Very High Frequency Power Applications. Micromachines 2016, 7, 60.

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