Method and system for localization of open defects in electronic devices with a dc squid based rf magnetometer

Abstract

Non-destructive localization of open defects in electronic devices is performed with a DC SQUID based RF magnetometer capable of sensing coherent magnetic fields up to 200 MHz and higher. RF magnetic fields (or RF current) images are correlated to conductive paths layout of the electronic device, and the open defect is pinpointed at a location of RF current disappearance on the current image. The bandwidth limitations associated with transmission line delays between SQUID circuit and readout electronic, as well as with near-field coupling between different parts of the measurement scheme, are overcome by superimposing the RF flux emanating from device under study on the modulation flux to produce at the SQUID output a binary phase modulated RF voltage, which is processed to lock the static flux, and to control modulation regime by producing an AC bias for the RF flux. RF readout electronics is based on a double lock-in through sequential demodulation of the RF component of the output SQUID voltage at the modulation flux frequency ωand the RF flux frequency ω.