Electrodeposition of Copper as a Route for Tantalum Drawing

Abstract

Electrodeposition of thin copper layers on tantalum rods was applied for tantalum wire drawing. The influence of surface finishing, cathodic current density, and acid sulphate bath composition on the adhesion of the deposits was studied. The copper coatings were more adherent when obtained on a sandblasted surface. Chemical and electrochemical surface treatments did not affect significantly the adhesion. The statistical Taguchi method was employed for studying the influence of electrolysis parameters on adhesion, using the L₉ orthogonal array with three factors at three levels each. The analysis of results showed a great influence of current density on adhesion, whereas the other factors, CuSO₄ and H₂SO₄ concentrations, presented low and no significant effect, respectively. Tantalum rods electroplated by copper under the best conditions (sandblasted surface, 30 mA cm^–2 cathodic current density, 150 g L^–1 CuSO₄, and 30 g L^–1 H₂SO₄) were drawn. The superficial finishing of the tantalum wires was better than those obtained by the traditional route (insertion of tantalum rod into a copper tube and drawing).