This investigation elucidates stress evolution in situ in tin strips under electromigration using synchrotron radiation x-ray. Minute variations in stress are determined precisely using intense x-rays. Back stresses gradient with the values of 5.5 and 16.5 MPa/cm, which are induced by the current densities of 1 x 10(3) and 5 x 10(3) A/cm(2), respectively, are measured directly. The effective diffusivities that include both grain and lattice diffusion at various current densities are determined. The Joule heating is observed, ranging from 5 to 15 degrees C, according to various current densities passed through the stripes. Results of this study suggest that the protective oxide layer on the surfaces significantly influences the kinetics of stress evolution.