Pulse Electrodeposition of High Moment-High Resistivity Cofex (X=P, O) Alloys and Multilayers for Inductor Application

Abstract

Growing application of magnetic thin films and inductor chips for analog circuits in mobile phones, MEMS and defense sector technologies rise the need for development of new allows with low energy losses to serve as core material during electromagnetic induction process. Electrodeposition is a cost effective approach to achieve this. The new alloys and their electrodeposition/synthesis process foresee an immediate and direct implementation in future product designs and development and can be easily integrated in an existing manufacturing schemes. The presented work leverages earlier results related to electrochemical synthesis of ferromagnetic alloys. In particular, the work on electrodeposition process for high magnetic moment alloys such as CoNiFe and CoFe i,ii,iii, studies of additive incorporation phenomenon in magnetic alloysi v,v,vi and studies of oxide/hydroxide incorporation in magnetic alloys through the interfacial precipitation process vii,viii,ix. Results will be presented describing synthesis process and bath chemistry for highly resistive CoFeX alloys (X=O and/or P) using electrodeposition process with simultaneous Fe(OH)3 precipitation/incorporation and/or (PO3)3- and (H2PO2)- reduction. Fe-oxide/hydroxide and P inclusions in CoFe matrix serve as resistivity controlling phase in the bulk alloy and as a highly resistive barrier layer in the CoFeX/X laminated structures. The main result is design of a a cost-effective electrodeposition process and solution chemistry yielding the CoFeX alloys in composition range where the maximum possible magnetic moment and permeability is expected (Ms ≈ 2.4 T, μ > 1000). The overall content of the “X” component is designed to yield resistivity above 100 μΩcm. These alloys are tested for high frequency applications and their Snoek limit is identified. The correlation between the CoFeX alloys and CoFeX/X laminates properties and their metallurgical structure is discussed.i) S.R. Brankovic, N. Vasiljevic, and N. Dimitrov. “Applications to magnetic recording and microelectronic technologies.” Modern Electroplating (2010): 573-615.ii) S.R. Brankovic, N. Vasiljevic, T. J. Klemmer, and E. C. Johns. Journal of the Electrochemical Society 152, (2005): C196-C202.iii) S.R. Brankovic, X.M. Yang, T. J. Klemmer, and M. Seigler. IEEE Transactions on Magnetics 42, (2006): 132-139.iv) S.R. Brankovic, R. Haislmaier, and N. Vasiljevic. Electrochemical and Solid-State Letters 10, (2007): D67-D71.v) J. George, J. Rantschler, S. Bae, D. Litvinov, and S.R. Brankovic, Journal of the Electrochemical Society 155, (2008): D589-D594.vi) S.R. Brankovic, Electrochimica Acta 84 (2012): 139-144.vii) S.R. Brankovic, S. Bae, and D. Litvinov, Electrochimica Acta 53, (2008): 5934-5940.viii) J. George, S. Elhalawaty, A. J. Mardinly, R. W. Carpenter, D. Litvinov, and S.R. Brankovic, Electrochimica Acta 110 (2013): 411-417ix) S. Elhalawaty, R. W. Carpenter, J. George, and S. R. Brankovic. Journal of the Electrochemical Society 158, (2011): D641-D646.2011): D641-D646.