Abstract
The states on surface and cross-section of electroplated bright tin deposit and the effects of annealing on its crystal structure were observed with microscope, electron microscope, and X-ray diffractometer. The results were compared with those of other non-bright tin deposits.
The results obtained were as follows:
1. Bright tin deposit consisted of microcrystals with higher orientation. Grain size of the crystals seemed to be 0.5-0.8μ. The states on its cross-section were observed to be fibre structure combined with band structure.
Electrodeposited tin always consisted of β-Sn of tetragonal system, and α-Sn of cubic system was not observed even when it was deposited at 5°C.
2. The change of surface state by annealing at 150-200°C for 30min. was observed with microscope. It was partly changed to amorphous state when observed with X-ray. However, no change of surface state and crystal structure by annealing was seen in non-bright deposits. Transition point of 161°C between β-Sn and γ-Sn was not analyzed by the above methods.
3. The remarkable change by annealing would be caused by internal stress. It is assumed that stress and grain size after annealing were larger, by which recrystallization was promoted. On the other hand, very little effects of annealing were given on non-bright deposits owing to their rough structure and small stress.
