Accurate modeling of stresses and strains and prediction of stresses leading to stress‐assisted diffusive voiding in interconnection metallizations requires measurement of the stress/strain state of the lines during thermal cycling. X‐rays are a proven method for measuring strains and calculating stresses in lines and yield precise results when properly interpreted. We highlight two x‐ray geometries we have used to successfully determine the strain and stress state of unpassivated and passivated aluminum alloy lines. There is good agreement between the two techniques. Additionally, we have measured strain relaxation in the lines. We correlate the relaxation in passivated Al alloy lines with direct observation of stress‐induced voiding performed using a scanning transmission electron microscope.