Using the previously obtained stress distributions in an Al line after relaxation by plastic deformation, another possible relaxation process by diffusion was analyzed. Even after this relaxation occurs, some stresses still remain in the Al line. If these remaining stresses are large enough, they can be responsible for the growth of voids causing line failure. Using a theory for diffusional growth of grain‐boundary voids, the time to failure of the Al line was estimated analytically. The previous and present papers together constitute a full analysis of the so‐called ‘‘stress migration’’ phenomenon.