Balancing of plating solution in CuCN electroplating process

This study investigates the characteristics of CuCN electroplating as an undercoating to determine the optimum plating solution balance, temperature, and so on. To evaluate its feasibility as an undercoating, the Hull-cell pattern and surface characteristics are observed during CuCN electroplating. If the CuCN concentration is too high, powder “deposit” pattern appeared in the area due to the decreased free NaCN concentration, and “no plating” pattern appeared in the area of low-current. If the NaCN concentration is too high, “no plating” pattern appeared. Therefore, the optimal concentration balance between CuCN and NaCN was confirmed as 5:7. The plating thickness and its deviation according to plating solution concentration, plating solution temperature, and surface roughness increased. In particular, the plating thickness increased with increasing plating solution temperature in the same plating solution concentration range, but the plating thickness deviation decreased. Also, surface roughness was increased with increasing plating solution concentration at the same plating temperature, but the plating thickness deviation decreased. Therefore, in this study, the optimal temperature of CuCN electroplating was set to 323 K, and the optimal concentrations of CuCN and NaCN were set to 50 and 70 g/L, respectively.