Anisotropic nanolaminated CoNiFe cores integrated into microinductors for high-frequency dc–dc power conversion. (8th October 2015)

• Record Type: Journal Article
• Authors: Kim, Jooncheol; Kim, Minsoo; Kim, Jung-Kwun; Herrault, Florian; Allen, Mark G
• Is Part Of: Journal of physics. Volume 48:Number 46(2015)
• Publication Date: 2015-10-08
• Subjects: laminated soft magnetic alloy -- anisotropic CoNiFe -- suppressed eddy current losses -- microinductor; Physics -- Periodicals; 530
• DOI: 10.1088/0022-3727/48/46/462001
• Languages: English
• ISSNs: 0022-3727

Abstract

Abstract: This paper presents a rectangular, anisotropic nanolaminated CoNiFe core that possesses a magnetically hard axis in the long geometric axis direction. Previously, we have developed nanolaminated cores comprising tens to hundreds of layers of 300–1000 nm thick metallic alloys (i.e. Ni80 Fe20 or Co44 Ni37 Fe19 ) based on sequential electrodeposition, demonstrating suppressed eddy-current losses at MHz frequencies. In this work, magnetic anisotropy was induced to the nanolaminated CoNiFe cores by applying an external magnetic field (50–100 mT) during CoNiFe film electrodeposition. The fabricated cores comprised tens to hundreds of layers of 500–1000 nm thick CoNiFe laminations that have the hard-axis magnetic property. Packaged in a 22-turn solenoid test inductor, the anisotropic core showed 10% increased effective permeability and 25% reduced core power losses at MHz operation frequency, compared to an isotropic core of the identical geometry. Operating the anisotropic nanolaminated CoNiFe core in a step-down dc–dc converter (15 V input to 5 V output) demonstrated 81% converter efficiency at a switching frequency of 1.1 MHz and output power of 6.5 W. A solenoid microinductor with microfabricated windings integrated with the anisotropic nanolaminated CoNiFe core was fabricated, demonstrating a constant inductance of 600 nH up to 10 MHz and peak quality factor exceeding 20 at 4 MHz. The performance of the microinductor with the anisotropic nanolaminated CoNiFe core is compared with other previously reported microinductors.