Research on Obtaining and Characterizing Ni - W Electroplating Alloys for Micro-Electro Mechanics

Abstract

The present research aimed to electrodeposit and characterize Ni-W alloys for different technological parameters, being an example of “induced co-deposition”, in which a certain metal (for example: Mo, W) can be co-deposited as an alloy, but it cannot be measured in its pure state. The investigated characteristics were the efficiency current, the average thickness, and the structural properties of the obtained deposits. The current efficiency decreases with an increased applied current density, and the tungsten content remains constant at around 11% for different current densities (10 mA·cm−2 and 16 mA·cm−2, respectively). An increase in the temperature of the electrolyte leads to the inclusion of more tungsten. The deposit tungsten content and the current efficiency are directly related to pH. The deposit hardness directly relates to the alloy composition, deposit morphology, and coating thickness. The higher hardness, approximatively 100 HV were measured and the optimal brightness were observed for the alloys obtained at increased current density (i = 16 mA·cm−2, T = 50°C, pH = 8), or to a basic pH (i = 10 mA·cm−2, T = 50°C, pH = 9.23). The scanning electron microscopy (SEM) technique was used to analyze the surface morphology, and energy dispersive spectroscopy (EDS) analysis was carried out to determine the composition of the alloys. The metallic surface brightness (%) was evaluated using the miniature spectrometer, based on the reflection property of the electrodeposited metallic layer, scanning the all-wavelength range between 200-1100 nm.