Abstract: In order to test conductors on substrates for current constricting defects, such as cracks, narrow conductors, line breaks and intermittent opens, a test signal combining two alternating current signals at different frequencies and direct current offset signal is applied to the conductor. Upon encountering a defect, intermodulation signals are generated and detected. The phase of the detected signal and the phase of a reference signal are compared. The difference between the phase of the two signals is indicative of the presence of a defect in the conductor. The invention has particular application for testing thin conductors.

Abstract: The tester and method for nondestructively detecting nonlinearity faults in conductors includes the application of a composite AC and DC drive signal to the device under test in such manner that nonlinearities in the device under test produce fault signals including second harmonics, due to local changes of resistance caused by ohmic heating. Electronic filters are used to select out and amplify the second harmonic only, eliminating the direct current and fundamental frequency components of the initial test pulse, plus third and subsequent harmonics. The filtered second harmonic signals from the device under test are then phase-compared to a phase-shifted second harmonic signal produced by a frequency doubler from the test signal generator oscillator to cancel out the second harmonic signals from the good conductor; the remaining phase anomaly signals control a threshold detector remaining to provide fault indication.