Compound additives and stress study of EDTA-2Na chemical copper plating system in printed circuit boards

In the processing technology of printed circuit boards, the common electroless copper plating technology of ethylenediaminetetraacetic acid disodium (EDTA-2Na) has the problems of large surface stress, uneven crystal particles, and large surface roughness of the copper plating layer. To remedy the above shortcomings and meet the current requirements for copper interconnects in printed circuit boards (PCBs), the present study has investigated a chemical copper plating system that combines a high deposition rate with low stress. An electroless copper plating was then performed on a polyacrylonitrile-butadiene-styrene (ABS) plastic resin plate with 2,6-diaminopyridine (2,6-DAP), 2,2-bipyridine, sodium hydroxyethyl sulfonate (SHES) and NiSO₄·6H₂O as supplementary additives. By using scanning electron microscopy (SEM), electrochemical, atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses, it has been shown that the average surface roughness Ra became reduced from 202 nm to 76.1 nm when using additives in the chemical copper plating process. Also, the internal stresses of the deposited copper layer on the (220) and (311) planes of a crystalline copper layer decreased from − 70.48 and − 53.03 to − 27.31 and − 27.16 MPa, respectively. The composite additive improved the quality of the copper layer of the EDTA-2Na-based chemical copper plating system, increasing the practical range of industrial applications and facilitating the subsequent application of higher-precision processing.