Characterization and analysis adhesion of copper coating electrodeposited on flexibile substrates

Abstract

In this study, electrodeposition of nano-crystalline copper coatings (ED-Cu) from the sulphate bath on different substrate by the regime of direct current (DC) has been investigated. Composite systems of copper thin coatings (5-20 µm) on metal foil of copper, brass and stainless steel were fabricated. Electrodeposition was performed at constant current density (50 mA•cm-2) in the open type electrochemical cell with application magnetic stirrer (100 rpm) in order to mixing electrolyte. Adhesion of coatings on different substrates was investigated by Vickers microindentation hardness testing in order to determinate relation between microhardness of the coatings and adhesion strength of the coatings to the substrates. The observed adhesion parameter is called the critical reduction depth. In order to evaluate the results of adhesion obtained by Vickers method, bidirectional bending test technique was performed to assess the adhesion behaviour of ED-Cu coatings to the substrates. Bidirectional bending test machine was specially designed for this study. The mechanism performs bending of the sample under controlled and automated conditions. The critical cycle number (start of detachment of the coating from the foil) is observed. Then, the values of adhesion parameters obtained by applying two different measurement methods were compared. A comparative investigation showed that the ED-Cu coatings produced on brass substrate had much better adhesion then the same coating on steel, but weaker adhesion than Cu on Cu foil. It has also been confirmed that with increasing thickness of the copper coatings, adhesion decreases.