Transit Time Dependent Condition Monitoring of PCBs During Testing for Diagnostics in Electronics Industry

In this paper, a novel planar microwave sensor for nondestructive measurement of strain during testing of printed circuit board (PCBs) is proposed. Planar microstrip patch bridged on both sides with squared split ring resonator is used to measure strain. Measurement of stress of isotropic dielectricmaterials in their linear elastic region that are uses as PCB substrates is also done using the proposed method. The designed microwave probe works at a frequency of 2.45 GHz. The feasibility of the use of time-domain reflectometry method to monitor strain in materials is presented here. The proposed sensor exhibits a sensitivity of about 333 ps for every 1% change in strain. Finite integration technique and real-time measurements have been done to corroborate the relation derived between the transmit time and the strain experienced by the material. The correlation between the simulated and measured strain is about 99.3%. The proposed sensor can be used for faster and accurate testing of PCB substrates without requiring complex calibrations.