LAUSR

An accelerator, 3-(2-benzothiazolylthio)-1-propanesulfonsäure (ZPS), and a suppressor, polyethylene glycol (PEG), were employed and formulated with chloride ions (Cl − ) in plating solution containing electrolytes (CuSO 4 and H 2 SO 4 ) to prepare Cu film, respectively. Microstructural characterization using transmission electron microscopy and electron backscatter diffraction revealed that the addition of PEG could inhibit the formation of twins and the ZPS had a significant promoting effect. The results of X-ray diffraction indicated the preferred crystallographic orientation (200) of entire electroplated Cu films was changed with the addition of PEG in basic plating solution. The function of ZPS altered the preferred crystallographic orientation from (200) to (111). The roughness of electroplated Cu film was analyzed by scanning electron microscopy and atomic force microscopy. The Cu grain size increased and the Cu surface became rough (RMS: 238.4 nm) under the function of ZPS. The impurity examination based on X-ray photoelectron spectroscopy and electron microprobe analysis indicated that the addition of PEG and ZPS resulted in high-level impurity incorporation, inducing the formation of massive voids within Cu 3 Sn layer and causing the microstructural instability of the SAC305/Cu solder joints during aging.