Abstract
Three types of free-standing copper thin films were produced by electrodeposition using sulfate solution: CC films made under constant current, CC-B films with brightener and CC-TU films with thiourea. The effect of grain size on the tensile and fatigue properties was studied. The grain size of CC, CC-B, CC-TU thin films measured by TEM was 420, 241, and 28.7nm. Those films did not have any strong texture. With decreasing grain size, the fatigue limit as well as the tensile strength got higher, following the Hall-Petch relation. On the other hand, the threshold stress intensity for crack propagation increased linearly with the square root of the grain size. At high stress intensity facters, striation were observed on the fracture surface of CC and CC-B films, while only fine granular feature was observed for CC-TU.
