Abstract
The promotion effect of tin on direct copper electroplating process via sulfide was investigated. It is found the direct plating rate on Tin-Palladium sol colloid activated nonconductive substrate can be accelerated about 4-10 times by Na2S, but it only accelerated about 1.5 times for polymer protected palladium colloid activated nonconductive substrate. The increased promotion effect via Na2S of Tin-palladium colloid is due to one of the followings: (1) the higher concentration; (2) the uniform particle size and distribution; (3) an interaction between the Sn and Pd in the colloid. Comparison between polymer protected palladium colloid and Tin-Palladium colloid exclude the possibility of other factors but the interaction between Sn and Pd in the colloid.