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MMM 2022

November 07, 2022

Minneapolis, United States

Magnetic properties of Fe Ni films deposited on a non

In recent years, the driving frequency of electric equipment has increased, and we need to reduce eddy current loss to apply typical metallic soft magnetic materials into high-frequency driving equipment. As a practical method to reduce the loss is a reduction in the thickness, we recently reported a fabrication process of Fe-Ni thin films (< 10 μm) using an electroless plating method 1. Although many reports for electroless deposited Fe-Ni films, as well as ours, employed conductive substrates 2-3, the conductive substrates are not suitable since eddy current also flows in the substrates. We, therefore, focused on the polyimide (PI) used as a non-conductive substrate and investigated a fabrication process of Fe-Ni films using the PI substrate.
Since the PI does not have catalytic activity for the deposition of Fe-Ni films, we investigated a chemical metallization process of PI 4. First, we immersed the PI sheet in a KOH solution and then in an AgNO3 one. By these immersions, the PI sheet obtains catalytic activity. The details of our electroless plating process are described in Ref. 1.
To obtain suitable conditions for the metallization of the PI surface, we investigated the effect of immersion time in KOH and AgNO3 on the film thickness. Figure 1 shows the thickness as a function of the immersion time in each solution. The thickness slightly increased with increasing the immersion time in AgNO3, and we observed the correlation between thickness and the immersion time in KOH, implying that the immersion time in KOH is more important than that for AgNO3.
Figure 2 shows the coercivity of the films as a function of thickness. We changed the thickness by adjusting the DMAB concentration or the deposition time. In our experimental conditions, the coercivity increased with increasing the thickness due to an increase in the roughness, and the value of coercivity was almost the same as previously reported ones (Hc =30-96 A/m) using conductive substrates 1-3.5. We, therefore, concluded that the Fe-Ni films with low coercivity could be obtained by the optical metallization of the PI surface.
1 T. Yanai et al., AIP Advances, Vol.10 ,#015047 (2020)
2 R. Anthony et al., Applied Surface Science, Vol.357 , pp.385-390 (2015)
3 M. Takai et al., IEICTE Trans. Electron., Vol.E78-C , pp. 1530-1535 (1995)
4 G. Stéphane et al., Applied surface science, Vol.307, pp.716-723 (2014)
5 T. Yokoshima et al., Journal of Electroanalytical Chemistry, Vol.491 , pp.197-202 (2000)

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Yuka Yamaguchi and 5 other authors

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