The Internal Stress in Ni, NiFe , CoFe , and CoNi Layers Measured by the Bent Strip Method

A chloride plating bath, containing boric acid and saccharin has been optimized to obtain homogeneous Co-Ni deposits over normalSi/SiO2/normalTi/normalNi substrate. The goal is to explore the synergy of these layers in microsystems applications. Anomalous codeposition occurs and both electrochemical and structural results indicate that obtained Co-Ni layers correspond to solid solutions of face-centered cubic (fcc) structure, whose composition may be varied as a function of the electrodeposition parameters. Results of the electrochemical and magnetic characterization carried out are presented, showing the trends of a soft magnetic material, i.e., high saturation magnetization (1.2 T) and low coercivity. Smooth surfaces and a steady deposition rate were observed in the Co-Ni deposits on silicon-based unpatterned substrates. In order to check the versatility and the compatibility of this Co-Ni electrodeposition with the standard microsystems fabrication technology, two processes, surface- and bulk-technology based, have been carried out. Due to the high selectivity and homogeneity of the Co-Ni layer, it has been possible to pattern the deposits with a definition down to 10 μm, as well as to fabricate 3D structures. Methods to liberate the Co-Ni films from the silicon-based substrate have been developed; as a result, low-stressed freestanding structures are presented. © 2002 The Electrochemical Society. All rights reserved.

Section: Resultsmentioning

confidence: 99%

Development and Characterization of Co-Ni Alloys for Microsystems Applications

Duch

Estéve

Gómez

et al. 2002

“…Tensile stress is very common in electrodeposits [18][19][20][21] and cannot be due to the thermal expansion mismatch between the deposit and the substrate, because the electrodeposition is carried out at low temperatures. In some cases it is suggested that this intrinsic stress arises from the nonequilibrium growth during the electrodeposition or to the inclusion of additives or reaction products thereof in the deposit.…”

Section: Resultsmentioning

confidence: 99%

Residual Stress and Other Structural Characteristics of Electroplated ZnNi Alloys

García

Sarret

Müller

et al. 2002

Zinc-nickel alloys obtained from a new alkaline electrolyte were characterized by analyzing their composition, morphology, structural parameters, and residual stress. The influence of various deposition parameters, such as current density, plating temperature, or deposit thickness, on these coating characteristics was analyzed. The results indicated that the alloys maintained their characteristics in a wide range of deposition conditions: they were uniform in appearance, consisted of almost pure ␥ phase, and had a tensile stress lower than that measured for other Zn-Ni alloys of similar composition obtained from other electrolytes.In response to the demand of the automotive industry for better corrosion protection, various processes have been developed to obtain zinc-X alloys (X ϭ Ni, Co, Fe). Of these, zinc-nickel alloys with 10-14% Ni provide the best salt spray corrosion resistance, as well as the best performance for the cyclic heat/corrosion tests. These Zn-Ni alloys are commonly obtained from weakly acidic electrolytes 1-8 and more recently from alkaline baths. 9-13 These alkaline processes tend to have current efficiencies lower than the acid ones, but in contrast, they exhibit a very good metal distribution over the normal current density range and they are much less corrosive.At the LCTEM of the University of Barcelona a new alkaline electrolyte has been developed to obtain Zn-Ni alloy coatings with 12-16% Ni at the current densities used in the automotive industry. The coatings are obtained with a relatively high current efficiency and this bath is now being commercialized by MacDermid, Inc., as MACZINI. The prime objective of the present study is to characterize the zinc-nickel alloys obtained with this new electrolyte by analyzing their morphology and structural parameters. Residual stress is also determined since it affects some of the most important properties of electrodeposits. The stress values obtained for these alloys are compared with those of other Zn-Ni alloys of similar composition but obtained from acid baths. Since most of the electrocoating characteristics are structure dependent and structure, in turn, is determined by the plating conditions, the second objective is to attempt to establish the relationship between electrodeposition parameters, structural properties, and functionality. Table I summarizes the bath components and the plating conditions used in this study. Zinc-nickel coatings were deposited galvanostatically on commercial steel sheets with this electrolyte. Three steels obtained from different suppliers were used; two of them were similar nonpolished sheets while the third was the polished and zincplated panel used in Hull cell experiments. Before deposition, the 8 ϫ 10 cm steel cathodes were degreased using a standard procedure. The galvanized sheets were previously treated with diluted HCl to dissolve the thin zinc layer. The deposits were obtained in a 12 L cell equipped with an external tank for electrolyte recirculation. The plating temperature was kept constant at 20...

“…In single-beam laser deflectometry, a laser beam is reflected from the substrate and curvature changes are obtained by monitoring the position of the reflected spot. [1][2][3][4][5][6][7][8][9]14,15 Since stress resolution scales with the square of the substrate thickness, sputtered metallic layers on thin inert wafers are frequently used as samples to maximize resolution. 16, 17 Floro and Chason developed an improved version of this technique that relies on monitoring the deflection of an array of equally spaced laser beams reflected from the substrate to measure all components of in-plane substrate curvature with high resolution and robustness.…”

mentioning

confidence: 99%

In Situ Stress Measurement During Aluminum Anodizing Using Phase-Shifting Curvature Interferometry

Çapraz

Hebert

Shrotriya

2013

Stress measurements yield insight into technologically relevant deformation and failure mechanisms in electrodeposition, battery reactions, corrosion and anodic oxidation. Aluminum anodizing experiments were performed to demonstrate the effectiveness of phase-shifting curvature interferometry as a new technique for high-resolution in situ stress measurement. This method uses interferometry to monitor surface curvature changes, from which stress evolution is inferred. Phase-shifting of the reflected beams enhanced measurement sensitivity, and the separation of the optical path from the electrochemical cell in the present system provided increased stability. Curvature changes as small as 10−3 km−1 were detected, at least comparable to the resolution of state-of-the-art multiple beam deflectometry. It was demonstrated that small curvature change rates of 10−3 km−1s−1 could be reliably measured, indicating that the technique can be applied to bulk samples. The dependence of the stress change during anodizing on current density (tensile at low current density, but increasingly compressive at higher current densities) was quantitatively consistent with earlier multiple-beam deflectometry measurements. The close similarity between the results of these different high-resolution measurements helps to resolve conflicting reports of anodizing-induced stress changes found in the literature.