On-Chip Sensor for Monitoring Crack Propagation in Solder Joints Using RF Signals: Electrical Modeling and Circuit Design

This letter presents an on-chip scale crack sensor for solder joints using radio frequency signals, essential for enhancing the reliability of electronic packages. The sensor design includes a Class F power amplifier and an envelope detector, based on an equivalent circuit model of cracked solder joints. Circuit simulations reveal that as a crack initiate, a resonant dip in the S-parameter pattern appears, with the resonant frequency decreasing as the crack propagates. Leveraging the resonant dip as a prognostic factor, the sensor can accurately characterize cracks in solder joints with easy-to-handle dc output. The sensor, which provides a maximum crack length sensitivity of 0.05 GHz/ $\upmu$ m, is highly sensitive and can be fabricated on-chip.