Effects of accelerator in a copper plating bath on interfacial microstructure and mechanical properties of SAC305/Cu solder joints

An accelerator, 3-(2-benzthiazolylthio)-1-propanesulfonsäure (ZPS), was used and formulated with a suppressor (polyethylene glycol, PEG) and chloride ions (Cl−) in electroplated Cu plating solution containing electrolytes (Cu sulfate and sulfuric acid) to prepare the Cu films. The preferred orientation of Cu film transformed from (200) to (220) with the addition of ZPS in plating solution containing (PEG and Cl−). The addition of ZPS in basic plating solution promoted the growth of Cu grains and increased the surface roughness of Cu film. The root mean square roughness of Cu film increased from 206.9 to 230.8 nm with increasing ZPS concentration. The impurity elements of electroplated Cu film were O, C, Cl, and S elements. With the further increase in ZPS, the number of void within Cu3Sn layer obviously reduced, improving the stability of the electroplated Cu solder joints subjected to thermal aging.