Study on copper electroplating additives for blind via filling

A copper plating process for blind via filling was introduced.The bath composition and process conditions are as follows:CuSO4 ·5H2 O 200 g/L,H2 SO4 75 g/L,Cl 55 mg/L,inhibitor(polyethylene–propylene glycol monobutyl ether) 30 mL/L,leveling agent(a nitrogen-containing heterocyclic compound) 3 mL/L,accelerator(sodium N,N-dimethyl-dithiocarbamylpropylsulfonate) 2 mL/L,temperature 23 °C,current density 1.4 A/dm2,cathode motion 16 times/min,and air agitation.The influences of inhibitor,accelerator,and leveling agent on blind via filling effectiveness of FR-4 substrate were studied.The results showed that the dosages of inhibitor and accelerator have great effect on blind via filling,while the leveling agent has slight effect on it.The blind via filling quality is excellent with a filling ratio higher than 95% when the said three additives are added with a suitable amount to plating bath.The ductility and reliability of the copper coating obtained can meet the application requirements of printed circuit boards.