ELECTRICAL-RESISTANCE AS AN INDICATOR OF FATIGUE

The dependence of the electrical resistance on strain and fatigue was analyzed for the case of electrical interconnections subjected to a sinusoidal strain. Measurements of the resistance change at the drive frequency, and twice the drive frequency provided greater sensitivity than static resistance measurements. Equations were developed to model the electrical resistance to second order in the strain. The resistance change gives a direct measure of the interconnect strain. The amplitude of the resistance change at twice the drive frequency was found to increase rapidly with fatigue. The ratio of the resistance change at twice the drive frequency to the change at the drive frequency was approximately 20% at low cycle fatigue failure. The ratio was suggested as a fatigue indicator for reliability analyses or for accelerated testing.