ELECTRODEPOSITON OF GOLD AND CO-DEPOSITS FROM A CN-FREE BATH: THE ROLE OF METAL SUBSTRATE (Abstract/Poster in atti di convegno)

Type
Label
  • ELECTRODEPOSITON OF GOLD AND CO-DEPOSITS FROM A CN-FREE BATH: THE ROLE OF METAL SUBSTRATE (Abstract/Poster in atti di convegno) (literal)
Anno
  • 2005-01-01T00:00:00+01:00 (literal)
Alternative label
  • L. Marcucci, L. Doubova, M. Fabrizio, S. Barison, M. Battagliarin, E. Miorin, C. Pagura, S. Daolio (2005)
    ELECTRODEPOSITON OF GOLD AND CO-DEPOSITS FROM A CN-FREE BATH: THE ROLE OF METAL SUBSTRATE
    in Meeting on Syntheses and Methodologies in Inorganic Chemistry SAMIC 2005 - Trends in Nanoscience, Bressanone (BZ), Italy, 4-7 December 2005
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • L. Marcucci, L. Doubova, M. Fabrizio, S. Barison, M. Battagliarin, E. Miorin, C. Pagura, S. Daolio (literal)
Note
  • Abstract (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • CNR-IENI (literal)
Titolo
  • ELECTRODEPOSITON OF GOLD AND CO-DEPOSITS FROM A CN-FREE BATH: THE ROLE OF METAL SUBSTRATE (literal)
Abstract
  • Gold coatings are extensively employed in different industrial branches (jewellery, microelectronics, etc.). During last decade the properties of CN-free bath which are able to substitute the present standard commercial bath containing cyanide electrolytes in various amounts have been intensively investigated. In this perspective, gold deposition of high quality and suitable properties from CN-free bath has been studied in our laboratory [1,2]. The interdiffusion and subsequent spread of some base metal to the surface as well as the cleaning and preparation processes preceding the gold plating could influence the quality of gold deposits [3]. In this work the interest has been focused on the role of metal substrates and the effect of various experimental conditions on film growth. Films composition and electrochemical behaviour were investigated, with particular emphasis to the relationship between metal substrate dissolution and films characteristics. Pure gold, copper and Ni-coated copper were employed as different substrates. Gold coatings were obtained by galvanic deposition at constant current of 2 mA cm-2 from a home-made gold sulphite bath containing ethylenediaminetetraacetic acid (EDTA). Thicknesses in the range 5÷10 ?m were obtained depending on deposition time. The weight/volume ratios, measured for all deposits and reported in Fig.1, gave an estimated value of the density of the electrodeposits, around 18.9 g cm-3. The gold deposits were characterized by means of cyclic voltammetry and electrochemical impedance spectroscopy in the sulphuric-acid electrolyte solution. Thickness and roughness were measured by mechanical profiler. Chemical composition and distribution were analyzed by secondary ion mass spectrometry (SIMS) that gave useful information on the surface and near-surface regions of coatings and substrates. Crystalline structure was studied by X-ray diffractometry (XRD). Morphology modification was studied by means of Scanning electron microscopy (SEM). Quantitative analysis on bath composition and degradation was carried out by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The electrochemical studies show that the copper diffused through the deposits, bringing to copper dissolution. This phenomenon was confirmed by the XRD and SIMS analyses that revealed the presence of the base metal inside the gold deposits. The ICP-MS measurements ascertained the copper presence in the solution after electrochemical tests on copper samples covered by thick gold deposits. On the contrary, the insertion of a nickel-plated barrier in the case of Au/Ni/Cu samples between base copper metal and gold deposits prevented the copper dissolution. Moreover, the Ni dissolution was not evidenced. Besides pure gold deposits, an investigation on gold-ceramic powder co-deposits has been carried out. As reported in previous investigation [4-6], the properties of gold co-deposits are defined both by the nature and size of the dispersed particles. By the addition of very low amount of sub-micrometric SiC powder to the bath, noticeable morphological and microstructural modifications in the gold coatings have been observed. The SEM micrograph reported in Fig.2 shows, as an example, the surface morphology of a SiC-Au coating. Studying the metal substrate influence, an inhibition effect induced by the SiC particles on copper diffusion inside the gold co-deposits was detected. Further investigation on the inhibition effect of copper diffusion and on crystallization phenomena are in progress by electrochemical measurements using rotating electrodes, together with the investigation of other co-deposits. (literal)
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