Influence of Deposition Parameters on Mechanical Stress and Magnetic Properties in Thick, Electroplated Co-Fe Flux Guides

Abstract

A notable advantage of electroplated binary Co-Fe alloys in MEMS applications like sensors and actuators is the high saturation flux density BS, which may reach values of 2.4 T in a composition range of 50 – 70 wt% Fe. In contrast, there are certain disadvantages limiting the use of these alloys, e. g. high film stress, high corrosion sensitivity and high magnetostriction. The mechanical and magnetic properties of Co-Fe films influence each other strongly. They are determined by the films’ microstructure, given by film texture, grain size and morphology, structural defects and impurities. In this study, the effect of process conditions like current density, pulse duration, duty cycle, pH-value of the plating bath and application of a constant magnetic field parallel to the electrode surface on film stress, microstructure and magnetic properties are examined.

Recent Developments of Magnetoresistive Sensors for Industrial Applications

“…The sensor described here is based on GMR spin valves due to their high sensitivity and linearity. Soft magnetic flux guides are used to attenuate and redirect the (external) magnetic flux in the air gap [ 76 , 77 , 78 , 79 , 80 , 81 , 82 ].…”

“…As the quality of the flux guides was crucial for the functionality of the sensor, investigations concerning the optimization of the electroplating process for the CoFe alloy were carried out. The goals were to increase the saturation flux density, B s , and to decrease the coercivity, H c , and the film stress [ 77 , 78 , 79 , 82 ].…”