Influence of chloride anions and polyethylene glycol on the morphology of electrodeposited copper layers

An optimisation of copper electrodeposition on a 200 μm stainless steel wire substrate, for the production of X-ray metallic capillary optics, is presented. The formation of a parabolic wire mandrel by electrodeposition of a copper layer is a useful, fast and relatively cheap method to manufacture mandrels for metallic X-ray capillary optics. Traditionally, a mandrel is formed mechanically or by chemical treatment. In this paper we show that a controlled withdrawal of a stainless steel wire from the electroforming bath during copper electrodeposition results in precise formation of a mandrel with planned parabolic shapes. We found that by carefully adjusting the concentrations of additives, such as accelerator (chloride anions), inhibitor (polyethylene glycol), brightener (bis(3-sulfopropyl) disulfide) and leveller (dodecyltrimethylammonium chloride), in the electrolytic acid copper sulphate bath a smooth surface on the copper layer was obtained. The tuning of accelerator and inhibitor concentrations was carried out at fixed concentrations of the brightener and leveller and at fixed cathode current density. The results showed that the mean surface roughness of a mandrel was comparable to that of the stainless steel substrate and the surface waviness of the electrodeposited layer was about two times larger than that of the substrate.

► Copper electrodeposition in the presence of additives. ► Effects of chloride anions and polyethylene glycol in electroplating bath on morphology of copper deposit. ► Competition between various additives – Cl, PEG, SPS and DTAC. ► Optimisation of surface roughness and waviness by tuning of chloride anions and polyethylene glycol concentrations.