Electrochemical Behavior Research Of Copper Anode In Copper Electroplating Process

Metallic copper has been widely empolyed as the anode material in varieties of copper electroplating processes. The thorough study on the electrochemical behavior of copper anode in copper electroplating will have great significance for the selection of copper anode materials and the prevention of anodic passivation. The elemental composition and crystalline structure of pure copper, common phosphor copper and microcrystalline phosphor copper were firstly studied in this thesis, then linear sweep voltammetry, chronoamperometry and chronopotentiometry were employed to study the electrochemical behavior of these three kinds of copper anodes in acidic sulfate copper electroplating system, pyrophosphate copper electroplating system and HEDP cyanide-free alkaline copper electroplating system, respectively. Finally, the surface morphology and elemental composition of the corroded copper anodes were identified by SEM and EDS.The content of phosphorus in pure copper anode is less than 0.0010%, while that in common phosphor copper anode and microcrystalline phosphor copper anode is 0.0484% and 0.0422%, respectively. Phosphorus distributes quite uniformly in pure copper anode and microcrystalline phosphor copper anode, whereas, in common phosphor copper anode, the distribution of phosphorus is not so uniform as in pure copper anode and microcrystalline phosphor copper anode. Besides, pure copper anode, common phosphor copper anode and microcrystalline phosphor copper anode have obvious preferred orientation in(220),(200),(111) lattice plane respectively.In acidic sulfate copper electroplating system, the critical passivation potential of pure copper anode, common phosphor copper anode and microcrystalline phosphor copper anode were confirmed as 0.400 V, 0.442 V, 0.455 V respectively, the critical passivation current density were 22.406 A/dm2, 24.406 A/dm2, 26.701 A/dm2 respectively, the passivation current density were 4.341 A/dm2, 5.047 A/dm2, 5.665 A/dm2 respectively. The minimum apparent activation energy, the most difficult to occur passivation when potentiostatic oxidation and the widest discharge window when galvanostatic oxidation of microcrystalline phosphor copper anode indicate that it is the most suitable anode material in acidic sulfate copper electroplating system. The product layer which is loose porous and easy to fall off was observed on the surface of the corroded copper anodes. O, Cl, S, Cu and other elements were confirmed in the corrosion product layer.In pyrophosphate copper electroplating system, both pure copper anode and common phosphor copper anode appeared passivation around 0.2V and 0.8V, while microcrystalline phosphor copper anode appeared passivation only around 0.8V. The electrochemical dissolution of copper anodes was characterized by mixed control. Pure copper anode is the most difficult to occur passivation while microcrystalline phosphor copper anode is the easiest during potentiostatic and galvanostatic oxidation. Dense porous oxide film or phihole structure formed on the surface of the corroded copper anodes and the corrosion product mainly contained C, O, Cu, besides, it may also contain P and K.In HEDP cyanide-free alkaline copper electroplating system, the results of anodic polarization indicated that passivation phenomenon wasn’t observed before oxygen evolution on pure copper anode, while common phosphor copper anode and microcrystalline phosphor copper anode appeared slight passivation at 0.4V. Reaction current of pure copper anode was the largest under the same oxidation potential. Bead-like particulate substance formed on the surface of the corroded pure copper anode while it was large dispersed crystal particles on the surface of both corroded common phosphor copper anode and microcrystalline phosphor copper anode. C and Cu were confirmed in the corrosion product layer of all the three kinds of copper anodes, O was detected in the corrosion product layer of common phosphor copper, while O, P, S and K elements were detected in the corrosion product layer of microcrystalline phosphor copper.