抄録
Effects of addition agents in chemical copper plating solution were mainly investigated by total current-potential curves.
Decrease of deposition rate resulted from the addition of a small amount of thiourea was proved to be caused by its poisoning action on anodic reaction of formaldehyde. At the same time, remarkable improvement was observed in the stability of the solution.
It was found that inhibiting action of hexamine was due to the suppression of cathode reaction, in contrast with the addition of thiourea.
EDTA promoted the plating reaction, and it was considered to be due to the excitation of local reaction caused by the co-existence of formaldehyde and copper-EDTA complex ion.
In conclusion, a chemical copper plating bath is recommended for practical use, having the following composition and operating conditions.
Copper sulfate 0.04M
Rochelle salt 0.1M
Caustic soda to pH 12.5
Pam-formaldehyde 0.3-0.5M
Thiourea 0.05-0.2mg/l
Temperature 20-25°C
Agitation Agitation in the air-saturated state
