N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine (
THPED) and ethyl-diamine-tetra acetic acid (
EDTA·2Na) dual-
chelating-agent system was introduced to decrease the costs and increase the stability of the bath and quality of the plating for
electroless copper plating.Thus a systematical investigation was carried out with respect to the technology and plating performance based on the THPED-EDTA·2Na dual-chelating agent system.The
optimized plating technology was determined,while the morphologies of the resulting platings were observed using a scanning electron microscope.Results indicated that the
plating rate firstly increased and then decreased with increasing concentration of EDTA·2Na,while it firstly decreased and then increased with increasing concentration of THPED.Moreover,the
plating rate firstly increased and then decreased with increasing concentration of CuSO-4· 5H-2O and HCHO,while it increased with increasing the pH value and temperature of the plating bath.Besides,the additives including 2-MBT,2,2-dipyridyl and K-4Fe(CN)-6·3H-2O had great effects on the plating rate and surface qualities of the copper coating,so did the additive polyethyleneglycol-1000(PEG-1000),although it had little effect on the plating rate.The optimized bath for the electroless copper plating was suggested to be composed of 10.0 g/L THPED,8.7 g/L EDTA·2Na,16.0 mL/L HCHO,12.0 g/L CuSO-4 5·H-2O,40.0 mg/L K-4Fe(CN)-6·3H-2O,10.0 mg/L 2,2′-dipyridyl,1.0 g/L PEG-1000,0.5 mg/L 2-MBT; and the optimized plating parameters were suggested to be pH value 13.2 and bath temperature 50 ℃.The plating bath showed good stability at the optimized plating conditions and the plating rate in a duration of 30 min was as high as 4.05 μm/h.The resulting copper coating was smooth and bright,showing good surface quality.