M. R. Kalantary

The production of compositionally modulated alloys by simulated high speed electrodeposition from a single solution

Simulation of high speed electrodeposition, using a rotating cylinder electrode, has been carried out in order to obtain an operating window for applied current density and cathode electrode movement as a means of agitation. The electrolyte used was based on an acid sulphate, zinc-nickel alloy. Electroplating was carried out at room temperature in the range of current density from 0.5–130 A dm−2 and at cathode speeds of 0–1500 rpm on 99.5% purity iron tube. By assessing the deposit characteristics in terms of appearance, composition, crystal structure and corrosion resistance and correlating these results, it is possible to predict the conditions for production of compositionally modulated alloys from the simple zinc-nickel non-complexing electrolyte system.

A model for the mechanism of nickel fluoride cold sealing of anodized aluminium

The sealing of porous anodic oxide films on aluminium by the use of nickel fluoride solutions at ambient temperatures has been proposed as an alternative to hydrothermal sealing methods, on energy grounds. The process of cold sealing shows some promise and a mechanism is proposed as to how it may operate. As fluoride ions enter the pores, a place exchange mechanism occurs causing a shift in the local pH which is sufficient to cause nickel ions to precipitate. The nickel hydroxide blocks the pore mouths, effectively sealing the film. A slow step then occurs whereby water from the atmosphere diffuses into the film, effectively hydrating the film and causing general pore blocking. This slow step explains the ageing effect seen with such films. Eventually a film is produced which is effectively sealed.

Unipolar and bipolar pulsed current electrodeposition for PCB production

This paper is concerned with the study of square-wave unipolar pulse and bipolar pulse reverse electroplating and, particularly, the determination of pulse parameters to optimise through-hole plating rates and uniformity in the production of printed circuit boards (PCBs). The Wagner number, derived from cathode polarization behaviour in electroplating solutions, with and without plating additives, and under pulse plating conditions, was used to rationalize the data obtained. Fundamental predictions were found to compare favourably with results obtained from practical plating tests.

Physical properties of pulsed current copper electrodeposits

Square-wave unipolar pulse electroplating and bipolar pulse reverse electroplating of copper using an acid copper electrolyte of the type used for printed circuit board production has been studied. The effects of pulse-plated coatings on cathode efficiency and on the coatings properties, such as surface roughness, microhardness, stress-strain characteristics and elongation, are reported. The results show that microhardness, tensile strength and elongation are directly affected by the pulse technique used.

Optimization of the nickel fluoride cold sealing process

SUMMARYThis paper investigates the effect of varying sealing parameters, in order to optimize the conditions used to achieve a good seal quality for nickel fluoride cold sealed anodized aluminium. The effect of time, temperature and solution pH on seal quality was studied by British/ISO standards tests such as phosphoric acid/chromic acid, dye absorption and admittance. The quantity of nickel absorbed in the pores of anodic films as a function of solution parameters was measured by Atomic Absorption Spectroscopy (AAS), in order to find out the relationship between seal quality tests and nickel absorption.Although all the sealing parameters were found to have an effect on sealing quality and quantity of nickel absorbed in the pores, the major effect resulted from temperature which was found to be critical. The best results were found to be at a temperature of ≤ 25°C for a 20μm film. The quantity of nickel absorbed in the pores as shown by AAS, tends to correlate with the results of the seal quality tests.T...

Effect of post treatment on nickel fluoride cold sealed finishes

SUMMARYThe performance of accelerated aged (post-treatment) nickel fluoride cold sealed finishes is compared with those of room temperature aged and conventional hydrothermal sealed finishes. It was found that accelerated ageing at temperatures of 60 and 80°C for 5–30 minutes in deionized water will improve the results of sealing quality tests of cold sealed anodized finishes, however it does not satisfy all the sealing quality tests applied to conventional hydrothermal sealed films. The results of acid dissolution and dye spot tests are acceptable for post-treated cold sealed films, and in general even better results than conventional hydrothermal sealing can be obtained with various metal salts used as post-treatment. Nevertheless, the admittance test was found to be difficult to satisfy and further ageing of 1–14 days was necessary to pass it. Such a problem was overcome by dual sealing, in which the cold sealed film was treated for a very short time (0.5min/μm) in boiling deionized water, resulting in...

The role of surfactants in a cold sealing solution for anodic films on aluminium

Although the key in present cold sealing solution formulation practice is the presence of nickel fluoride, its performance can be optimized through the use of other parameters. In particular the effect of surfactants has been studied as a means of providing better penetration into the pores of the nickel salts before incipient precipitation occurs. Non-ionic and anionic surfactants appear to be best, but the effect depends upon the type and concentration of surfactant used