2001 Volume 69 Issue 5 Pages 329-334
The purpose of this investigation was to study Sn-Cu alloy electroplating for Pb-free solder from acid sulfate baths (2 M H2SO4 + 0.2 M SnSO4 + 0.008 M CuSO4) containing N,N-bis (polyoxyethylene) octadecylarnine(POOA) by means of various electrochemical methods, scanning electron microscopic observation, X-ray diffractometry, etc. POOA was adsorbed on the electrode in the range of potentials from 0 to −1.2 V, and POOA adsorbed on the electrode exhibited strong inhibitory effect on the electrochemical reduction of Cu(II) ion. Needle-like or dendritic electrodeposits were obtained from acid sulfate bath in the absence of organic additives. On the other hand, block-like or granular crystals were observed on the whole surface by adding POOA. Sn-Cu alloy electrodeposits containing 2.8∼6.0 at%Cu were obtained from acid sulfate baths containing 1 mM POOA under galvanostatic conditions (0.5∼7.0 A dm−2). Cu contents in electrodeposits decreased with increasing the current density, and increased with increasing the concentration of CuSO4. Sn-Cu alloy electrodeposits consist of β-Sn phase and η(Cu6Sn5) phase, and its solidus temperature is 227°C.