An improved analytical method for reducing edge built up and estimation of thickness in selective plating using variable perimeter-to-area ratio window test mask

In this paper, we attempt to present a new approach and analytical relation between perimeter-to-area ratio (P/A) and the plated thickness using Variable Area Window (VAW) test mask for improved thickness estimation. Although, the approach is illustrated using selective plating of gold films by varying two dimensional patterned windows on metallised silicon surface as an example, yet the method can be applied to other cases also. The method includes selective electroplating of gold in rectangular and circular windows wherein P/A of patterned shapes (squares, rectangles and circles) has been varied from 0.001 cm-1 to 0.4 cm-1 i.e. a factor of 400, a range normally used for practical modern MEMS devices. Experiments show that in general the thickness increases with increasing P/A because of current crowding. However, in contrast to using current density for control of this current crowding as reported in literature, we report that by careful design of mask pattern and improved material parameters, one can control and even achieve a slope reversal in the plot of thickness vs. P/A. The increase in thickness as measured by slope of linear fit is about 3 µm/(P/A in µm-1) for sharp edges compared to about 0.8 µm/(P/A in µm-1) for curved edges within the experimental errors. The general applicability of these relations to practical cases is confirmed by analysing the previously reported trends of data from the literature on Ni films using similar patterned shapes.


    

SF EXPO China 2015 - An Industry Pageant Worthwhile to Attend!

SF EXPO China 2015

SF EXPO China 2015 is short for The 11th Guangzhou (China) International Surface Finishing, Electroplating and Coating Exhibition, held by China Electroplating Association, China Surface Engineering Association Painting of Branch and Wise Exhibition (Guangdong) Co., Ltd. It will take place from 11-13 May 2015 at Guangzhou Poly World Trade Center (China). As the most professional and rapidly developing surface finishing exhibition, SF EXPO China has become a significant surface industry event in China and the first and only UFI approved surface exhibition in the world. SF EXPO has attracted a lot of leading international surface suppliers.

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Allium sativum (Garlic) as green corrosion inhibitor for low carbon steel in HCl solutions

Fig.9c: SEM micrograph of low carbon steel surface after 24 h of immersion in 1 M HCl + 300 ppm of allium sativum at 25°C

The use of allium sativum (garlic) as a green inhibitor for the corrosion of low carbon steel in 1M HCl has been studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM) techniques and weight loss measurements. Allium sativum has been proved to be good inhibitor. This reduction in the corrosion rate was due to the formation of an external layer formed by S-containing film present in the extract which was adsorbed physically on the metal surface. Allium sativum acted as a mixed type of inhibitor. The inhibition efficiency increases with increasing the inhibitor concentration, but decreases with raising the temperature. The adsorption of allium sativum on the metal surface follows Temkin’s adsorption isotherm. From EFM the causality factors are very close to theoretical values which indicate that the measured data are of good quality. Nyquist plots show a single capacitive loop in uninhibited and inhibited solutions.


    

Electrochemical Investigations for the Corrosion Control of Aluminum using an Eco friendly Natural Inhibitor

Fig. 2: Potentiodynamic polarization plots for the corrosion of aluminum containing different concentrations of CLE in H2SO4 (pH=3) at 30 oC

The inhibitive effect of Curry leaves extract (CLE) on the corrosion behavior of aluminum in sulfuric acid (pH = 3) was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in the temperature range of 30 °C to 50 °C. The study was done by varying the concentrations of inhibitor from 0.05 g L−1 to 0.4 g L−1. The surface morphology was studied using scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). Inhibition efficiency was found to increase with increase in inhibitor concentration and decrease with increase in temperature. CLE acted as an anodic type inhibitor at lower concentrations of inhibitor and behaved as a mixed type at higher concentrations of inhibitor and underwent both physisorption and chemisorption on the surface of the metal and followed the Langmuir adsorption isotherm.


    

Effect of 0.5wt% Cu Content on the Electrochemical Corrosion of Heat Treated Al-6Si-0.5Mg Alloy in Simulated Seawater

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Al-Si hypoeutectic alloys produced by casting are mostly used in the automotive industry, especially for engine blocks. They have the advantage of low weight associated with low coefficient of thermal expansion and excellent mechanical properties. The corrosion resistance of these alloys in coastal area, particularly in seawater environment is not well known. In this investigation, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation have been used to evaluate the corrosion resistance of Cu free and 0.5wt% Cu content Al-6Si-0.5Mg alloy in simulated seawater environment. The 0.5wt% Cu addition to the Al-6Si-0.5Mg alloy showed that Cu decreased susceptibility to electrochemical corrosion compared to the Cu free Al-6Si-0.5Mg alloy. The magnitude of open circuit potential (OCP), corrosion potential (Ecorr) and pitting corrosion potential (Epit) of Al-6Si-0.5Mg alloy in simulated seawater were shifted to the more noble direction due to 0.5wt% Cu addition and thermal modification.