Mechanical properties of Sn electrodeposited in supercritical CO2 emulsions using micro-compression test

Display Omitted SnO2 is observed in the Sn film plated by conventional method (CONV).Sn film plated with supercritical CO2 emulsion (EP-SCE) is consisted of pure Sn.Grain size of the Sn film by CONV is smaller than that of the EP-SCE film.Grain size of the EP-SCE film can be as large as 60µm.Yield strength of the CONV pillar is higher than that of the EP-SCE pillar. This paper reports mechanical properties of Sn films electrodeposited by the conventional method (CONV) and supercritical CO2 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 60µm, which was much larger than the CONV film. Moreover, presence of SnO2 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.