Mechanical properties of Sn electrodeposited in supercritical CO sub(2) emulsions using micro-compression test

This paper reports mechanical properties of Sn films electrodeposited by the conventional method (CONV) and supercritical CO sub(2) emulsions (EP-SCE). Sn is often used in electric devices as solders and load bearing components. Defects formed in the Sn structures could be fatal and can cause malfunction or shorten life time of the devices. Therefore, it is necessary to investigate the mechanical properties to understand the reliability and life time. The Sn films were prepared in an electrolyte of the acid Sn solution. Sn pillars for mechanical properties measurement were fabricated by focused ion beam and evaluated by a micro-compression test. Yield strength of the CONV pillar was higher than that of the EP-SCE pillar. Grain size of the EP-SCE film was about 60 [mu]m, which was much larger than the CONV film. Moreover, presence of SnO sub(2) in the CONV film by was confirmed by X-ray photoelectron spectroscopy. Therefore, the high purity of Sn and the large crystal size are believed to be the main causes for the lower strength of the EP-SCE pillar when compared to the CONV pillar.