Electroplated Films Research Articles

An Evaluation of the Wear Resistance of Electroplated Nickel Coatings Composited with 2,2,6,6-Tetramethylpiperidine 1-oxyl-Oxidized Cellulose Nanofibers.

In this study, the wear resistance of nickel (Ni)-cellulose nanofiber (CNF) composite electroplated films on steel plates (JIS SPCC, cold-rolled steel) was evaluated, including their surface and microstructural properties. In the CNF sample, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized CNF was used. As a result of the ball-on-disk abrasion test, in which steel (SUJ2) balls were used as the counterpart material, the plated film obtained with the addition of 1 g/L of CNF to the plating solution showed the highest wear resistance in this study. Compared to the conventional Ni-plated film without CNF, the abrasion loss volume on the plated side was reduced by approximately 79%, and that on the ball side was reduced remarkably by 94%. A microstructural analysis of the abrasion scars showed areas where co-deposited CNFs were stretched in the direction of abrasion, suggesting that the wear reduction effect was caused by sliding between the individual CNFs within the aggregates. Moreover, the hardness of the plated film increased when the Ni crystallite size became finer. It was confirmed that the co-deposition of fine CNFs is effective in improving hardness, whereas the co-deposition of a certain degree of aggregated CNFs is effective in exhibiting the wear reduction effect.

Investigation of Effects of Electroplating Conditions on TEMPO-Oxidized Cellulose Nanofiber Composited Nickel Electroplated Films

The effects of plating conditions on nickel (Ni) electroplated films composited with 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized CNFs (CNFs) were investigated. Plating experiments were performed by varying the amount of CNFs added to the Watt's bath, the current density, and the stirring speed. The plated film obtained at 3 g/L, 2.5 A/cm2, and 300 rpm of them respectively, reached an average 483 HV of the surface hardness, which was the highest in this study. The surface hardness of the conventional Ni film without CNFs plated under the same conditions was an average of 239 HV, and the hardness improvement effect was more than twice as high. The hardness improvement effect due to dispersion enhancement tended to increase as more CNFs were more finely and densely composited into the Ni film, although different trends were observed when the current density was varied.

In situ tensile testing of tin (Sn) whiskers in a focused ion beam (FIB)/scanning electron microscope (SEM)

Tin and tin-alloyed electroplated films are known to be susceptible to whisker growth under a range of conditions, many of which result in the generation of compressive stresses in the film. Compressive stress is considered to be one of the primary causes for whisker nucleation and growth. While extensive investigations have been performed on whisker growth, there have been few studies on the mechanical properties of tin whiskers themselves. We report on the tensile behavior of tin whiskers that were obtained by indentation and furnace aging of electroplated tin films on copper disks. Tensile tests of the whiskers were conducted in situ in a dual beam focused ion beam (FIB)-scanning electron microscope (SEM) system using a micro electro-mechanical systems (MEMS) based tensile testing stage. The strength of the whiskers was found to decrease with an increase in gage length and aged whiskers were found to be weaker than their indented counterparts. The observed gage length effect can be attributed to the probability of finding more defects as the whisker length increases. The effect of processing on the observed strength variation was investigated by analyzing the oxygen content in the whiskers via energy dispersive spectroscopy and the microstructure through transmission electron microscopy (TEM). The deformation mechanisms of whiskers were also inferred using post-mortem TEM. It was observed that the whiskers grown by indentation were dislocation free both before and after deformation. In contrast, whiskers grown by aging showed notable dislocation content (arranged in low energy configurations) even before deformation.

Measurement of Adhesion Strength of Al Electroplating Film on AZ31, AZ61, and AZ91 Substrates

Introduction Mg alloys recently have a great attention and are expected to be substitute materials for iron and aluminum in the fields of automobile and aerospace etc, due to the lightweight and high specific strength. The alloys are also used in the electronic devices since they have a high electrical conductivity and electromagnetic shielding properties. However these alloys have poor corrosion resistance because dense oxide film is not formed on the surface naturally. Therefore chemical conversion or anodization is required as a surface treatment of Mg alloys. However these treated surfaces show insulation properties, therefore the usage of the alloys for the electronics parts is limited.Electroplating of Al on Mg substrate has some merits for corrosion protection. Because dense passive film is formed on the surface, and if galvanic corrosion occurs, the corrosion rate may progress slowly due to close standard electrode potential in both metals. Therefore development of direct electroplating technique is expected from industry.In the previous studies, relatively good Al electroplating film was formed on AZ121 (12 mass%Al, 1 mass%Zn) alloy and relatively poor adhesion films were formed on AZ31 (3 mass%Al, 1 mass%Zn) and AZ91 (9 mass%Al, 1 mass%Zn). However few papers reported about relationship between adhesion strength and substrate composition of Mg alloys.In this study, we aim application of direct Al electroplating for AZ31, AZ61, and, AZ91 alloys. As the first step of the study, relationships between adhesion strength of Al electroplating film and composition of substrate of Mg alloy or grain size of AZ31 alloy were investigated. Experimental The electrolyte was prepared by mixing of AlCl3and 1-ethyl-3-methylimidazolium chloride (EMIC) with a molar ratio of 2 : 1. Substrates of AZ31, AZ61, and AZ91 alloys were used to investigate dependency of Al concentration in substrate. AZ31 of average grain size with 12.3, 22.8, 39.5, 88.6, and 111 µm were used to investigate dependency of grain size. A pure Al plate was used as a counter electrode. These substrates were polished and ultrasonically washed by acetone, then polished again in the glove box before the electroplating. A pure Al wire was used as a reference electrode. Electroplating experiment was carried out in the glove box with a pure argon gas by current pulse electrolysis under the condition of frequency of 4 Hz, duty ratio of 80 %, current density of 1.7 mA cm-2, electric quantity of 15 C cm-2, and temperature of 283 K. The surface morphologies and cross-sectional view of electroplated films were observed by scanning electron microscopy (SEM). The adhesion strength of Al film for Mg alloys substrates were measured by PosiTest Pull-off Adhesion Tester. Results and discussion In the specimens of Al electroplating, silver white surface were formed on the every substrate of Mg alloys. The electroplated film had no space between Al electroplating film and AZ91 substrate, however there were small spaces in AZ31 and AZ61. The adhesion strength of Al electroplating films for AZ31, AZ61, and AZ91 were 1.0, 1.1, and 1.3 MPa respectively. Increase of Al concentration in Mg alloys, the adhesion strength increased. Mg alloys are consisted by Mg-rich α-phase and Al-higher content γ-phase (Mg17Al12). Then Al electrodeposits easily on γ-phase compare with α-phase, and it may be considered that adhesion strength of electrodeposits for γ-phase is stronger than α-phase. When Al concentration in Mg alloys increases, area of γ-phase Mg on the surface also increases. It results that the adhesion strength also increases with increasing Al concentration. In the electroplating for several grain sizes of AZ31, adhesion strength of 12.3, 22.8, 39.5, 88.6, and 111 µm were 0.83, 0.91, 0.88, 1.02, and 1.03 MPa, respectively. It may be considered that the adhesion of the Al electrodeposits on grain boundary is not strong compare with the grains. The surface formed by lager grain size has low grain boundary. Therefore electroplating film on lager grain size containing low grain boundary may show stronger adhesion strength.

Strain rate effects on the mechanical behavior of nanocrystalline Au films

The effect of fabrication, film thickness, and strain rate on the mechanical behavior of Au films with 100 nm (evaporated gold) and 200 nm (electroplated gold) average grain sizes was investigated. Uniaxial tension was imposed at 10 − 3 –10 − 6 s − 1 strain rates on evaporated 0.5 μm and 0.65 μm thick Au specimens, and at 10 − 2 –10 − 5 s − 1 on electroplated 2.8 μm thick Au specimens. Strain rates between 10 − 3 and 10 − 5 s − 1 had a marked impact on the ultimate strain of evaporated films and less significant effect on their yield and saturation stress. The ductility increased with decreasing strain rate and it varied between 2–4.5% for 500–650 nm thick films and 3.4–10.6% for 2.8 μm thick films. When compared at the same strain rate, the thick electroplated films were more ductile than the thin evaporated films, but their yield and saturation stresses were lower, possibly due to their larger grain size. Qualitatively, the stress–strain behavior was consistent at all rates except at the slowest that resulted in significantly different trends. A marked decrease of the maximum strength, effective Young's modulus, and yield strength occurred at 10 − 6 s − 1 for thin, and at 10 − 5 s − 1 for thick films, while for 500 nm thin films multiple stress localizations per stress–strain curve were recorded. Because of temperature, applied stress, and grain size considerations this behavior was attributed to dislocation creep taking place at a strain rate comparable to the applied strain rate.

Channeling effects during focused-ion-beam micromachining of copper

The rapid introduction of copper metallization for semiconductor devices has prompted increased research into focused-ion-beam micromachining of copper. Studies with the aim of increasing the material removal rate of Cu by focused-ion-beam micromachining have been complicated by variable micromachining behavior apparently resulting from differing Cu film morphologies produced by the various Cu deposition procedures. This work examined the micromachining behavior of thin copper films produced by physical-vapor deposition (PVD) and electroplating, as well as single-crystal copper samples. PVD copper films were found to be preferentially textured along 〈111〉, with a columnar grain structure. Channeling effects within this type of grain structure provide a geometric enhancement of the material removal rate of 30% when the sample normal is tilted 12° from the incident ion beam, regardless of sample rotation. Single-crystal (111) copper was found to exhibit similar material removal rate enhancement (averaged over 360° rotation) when tilted 12°, verifying that the etching enhancement observed in the PVD films is directly related to their 〈111〉 texture. Compared to the PVD film, electroplated (EP) copper thin films contained a significantly more random grain orientation. Consequently, the EP films did not exhibit any appreciable variation in material removal rate beyond the expected cosine dependence when tilted with respect to the incident Ga+ beam normal. Micromachining of the electroplated films, which have larger randomly oriented grains, results in grain decoration due to preferential etching producing severe micromachining-induced topography.

Laser surface alloying of zinc-nickel doubly electroplated films on steel

A new method has been developed in which zinc-nickel doubly-coated films were electroplated onto steel substrates and then irradiated, using a high powered YAG laser with kaleidoscope for surface modification to alloy the zinc-nickel films.

RELATION OF COERCIVE FORCE TO STRUCTURAL PROPERTIES OF ELECTROPLATED FILMS

Coercive forces (He) of Fe–Ni films were observed to depend on thickness, Fe/Ni ratio, and preferred crystal orientation in accordance with predictions based on the Behringer–Smith model. Annealing induces marked crystal growth and orientation of [111] axis normal to the plane in the Ni-rich films (> 80% Ni), but only moderate growth in the Fe-rich (< 80% Ni) films. He for Ni-rich films increases markedly while He for iron-rich films decreases slightly due to annealing. Variations of the anisotropy field, Hk, due to applied stress, indicate that reduction of He for the Fe-rich films results from moderate crystal growth while the increase of He for the Ni-rich films is due to the preferred orientation.