Effect of Combinatory Additive for Copper Electroplating of Printed Circuit Boards in Acidic Bath on Properties of Plating Bath and Coating

Electroplated Cu coating was prepared by introducing a combinatory additive FX-203 into an acidic plating bath.The effect of the combinatory additive on the quality of coating and property of plating bath was investigated based on Hull cell test and electrochemical test as well as scanning electron microscopic and X-ray diffraction analysis.Results indicate that the bright area and throwing power of the bath increase initially and decrease later with increasing concentration of the additive.The optimized plating bath consisted of 75g/L CuSO4·5H2O,180g/L H2SO4,16mg/L toughened polystyrene TPS,0.6mg/L methanol(M),60mg/L polyethylene glycol(PEG)and 60 mg/L Cl-,while the optimized temperature and plating duration were 20～40℃ and 15 min.Resultant Cu coating was smooth and bright with a bright area of 1.7～9.2 cm and current density of 0.11～12.48 A/dm2,consisting of evenly distributed fine grains.The plating bath had a throwing power of96.1%,deep-plating ability of over 5 and current efficiency under1～4A/dm2 of about 100%.Meanwhile,the combinatory additive was able to cause negative shift of cathodic peak potential by 80 mV and decrease the peak current density from 43 mA/cm2 to 30mA/cm2.As-plated Cu coating consisted of face centered cubic Cu and preferentially oriented along the (111) crystal face.The adhesion force of the coating was in accordance with Chinese standard GB 5270-85,and it had good corrosion resistance as well.In general,FX-203 additive is superior to similar commercial additives and is suitable for industrial Cu electroplating in acidic hath.