Abstract
The silver diffusion and chemical reaction between Fe-Si-Cr alloy and Ag during multilayer metal power inductor preparation are investigated using scanning electron microscopy, field emission transmission electron microscopy and multipurpose X-Ray thin-film diffractometer. The experimental results show that a large amount of inner electrode, Ag, volatilize and diffuse under air atmosphere during co-firing, resulting in the reaction between Ag and thermally grown oxide layer, Cr2O3, forming flaky AgCrO2. The p-type semiconductor, AgCrO2 will cause the insulation degradation of the co-fired Fe-Si-Cr alloy multilayer chip inductors, hence reducing the power conversion efficiency due to the increase in eddy current loss.
Highlights
Wireless communications and portable mobile devices require higher performance and lower power consumption design due to the rapid development of social media platforms
The presence of an Ag and Cr-rich phase on the surface suggests that Ag diffuses outwardly from the inner electrode and reacts with Cr2O3, the thermally grown oxide (TGO) of Fe-Si-Cr particles, form the flaky secondary phase
The flaky phase on the surface of sample SL observed in Fig. 1 can be identified as AgCrO2 phase based on XRD, energy-dispersive spectrometer (EDS), and X-ray photoelectron spectra (XPS) analyses
Summary
Wireless communications and portable mobile devices require higher performance and lower power consumption design due to the rapid development of social media platforms. Fe-Si-Cr alloy has higher saturation magnetization and lower high-frequency magnetic loss, which exhibit better DC superposition characteristics, and play a key role in power chip inductors, making operation at higher rated currents possible.[1] At present, Fe-Si-Cr alloy inductor molding technology has been widely used. Since the multilayer Fe-Si-Cr alloy chip power inductor thickness is much thinner than the molding power chokes, it is in line with the thin-type smart phone trend and thereby will become the mainstream power chip inductors.[2] A chromium-rich layer is formed onto the Fe-Si-Cr alloy powder surface after annealing at high temperature because Cr is more oxidized than Fe and Si and tends to diffuse to the surface along the grain boundaries to react with oxygen ions.[3]
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