Analysis of the structure of printed circuit boards by means of the eddy current technique

This paper proposes an innovative application of the eddy current testing ( EC) technique for printed circuit boards (PCB) inspection. For this purpose , a unique probe has been designed and fabricated. The probe is composed of a meander-exciting coil and a solenoid pick-np coil. The probe can detect various defects on the conductors; of PCBs, such as cracks, partial decline s and chipped defects. The construction of the probe, the principles of det ection and samples from scanning are presented A strong relationship betwee n the amplitude and the phase of the output signal had been observed. This relationship allows a new approach to the analysis of signals obtained comb ining the amplitude and the phase for a new filtering method. Data from the phase characteristic can be used to set thresholds in the amplitude's filt ering process. Thereby: signals coming from soldering points and defects ca n be separated Experimental data have confirmed efficiency of this inspecti on process. Application of the EC technique may be extended to the inspecti on of multi-layer PCBs in the future.