Abstract
Tensile tests were carried out for electro-deposited copper foils. The thickness of the foils was 8μm and 20μm. The effect of the thickness on the deformation behavior and the tensile strength was investigated. The tensile strength of the thicker foil was slightly lower than that of the thinner foil. On the other hand, the elongation of the thicker foil is larger. In-situ X-ray stress measurement was conducted to estimate the deformation damage of the foils under tensile loading. In the elastic region, the stress measured by the X-ray was identical to the applied stress. However, when the plastic deformation occurred, the discrepancy between them became large due to the intergranular strain. The discrepancy of the thicker foil was larger than the thinner one. Then the fatigue tests were carried out. The fatigue strength of the thinner foils was higher. The thickness effect for the fatigue strength was larger than that for the tensile strength. The full width of half maximum, FWHM, was a function of both the applied stress and the number of stress cycles. Change of the value of FWHM with stress cycles corresponded to that of the maximum applied strain. The fatigue damage could be evaluated on the basis of the value of FWHM.
