The Coffin-Mansion relation refers to expansion mismatches, and is applied in reliability considerations. The expansion mismatch is caused not only by a difference of expansion coefficients between the materials (i.e. component and board), but also by differences in temperatures. Changes in temperature will have an effect on the product life of the component. Through investigating the fatigue process, Coffin and Manson attempted to determine the number of cycles at which the failure criteria was reached. They stressed components to a level, at which plastic deformation was reached.