An Automatic Measurement Method of PCB Stub Based on Rotational Computed Laminography Imaging

Back drilling technique is useful for high-speed printed circuit board (PCB) design. Currently, the stub length is measured by the destructive method that involves cutting the PCB and obtaining the results by optical imaging of the cut surface. X-ray computed laminography (CL) is an applicable technique for high-resolution imaging of plate-like object, which greatly contributes to stub nondestructive measurement. However, the interslice aliasing artifacts in the reconstructed images resulting from incomplete projection data make it difficult to position the trace layer and drilling tip. For better application to engineering, we propose to segment reconstructed slices (cross sections) of the PCB by self-training network and automatically locate key positions to measure stub length. Experiments on both simulated data and real data are carried out to verify the accuracy of the segmentation and measurement results for the proposed method. The proposed method can not only achieve nondestructive automatic rapid measurement but obtain similar results to the state-of-the-art destructive method, which brings great value to via stub measurement in practical engineering applications.