Use of interconnect resistance as a reliability tool

Methods are described which have successfully measured the electrical resistance change induced by strain and fatigue in leaded electrical interconnections. The dependance of electrical resistance on elastic strain, plastic deformation, and cyclic fatigue is examined. A type of spectroscopy for fatigue testing which measures the amplitude of the resistance change at harmonics of the fatigue cycling frequency is described. The spectroscopic method is shown to have the advantage of greater sensitivity, and of providing more information than conventional methods. An analytical frame work is developed, and recently published data for gull-wing leads and lap shear solder joints are examined using it. The cause for the limiting resistance fluctuations in these measurements is investigated. It is argued that after calibration, the method can be used to measure strain level, shorten fatigue tests, and reliably detect interconnect failures