Effects of Silver Ions on High-Speed Electroless Copper

Formaldehyde is one of the mostly used reductants in electroless copper. Silver ions were introduced into the plating bath to improve the plating rates and the film ductility. The linear scan voltammetry was used to study the influence of silver ions on the reduction behavior of copper, which indicates that the silver ions were co-reduced with copper. The incorporation of silver increased copper deposition rate. The plating rate increased from 17 mu m h(-1) in the silver-free solution to 29 mu m h(-1) as 25 mg L-1 Ag2SO4 was added. Folding tests were performed to illustrate the effect of silver on film ductility. The addition of silver ions in the plating baths improved the folding endurance of copper layers. The stability of the plating bath containing 20 mg L-1 Ag2SO4 was investigated using UV/Vis absorption spectroscopy. The bath was stable for at least 2 weeks.