Contactless Inspection of Flat-Panel Displays and Detector Panels by Capacitive Coupling

As the variety and application areas of planar electronic devices such as flat-panel displays (FPDs) and detector panels increase, flexible inspection methods are becoming more and more important. In this paper, a contactless inspection technique exploiting the capacitive coupling between probe electrodes and the conductive parts of the devices is presented. Measuring principle and setup, as well as sensor chip design, are illustrated and discussed in detail. To evaluate the performance of the system, inspection results of FPD backplanes and X-ray detector panels are compared with the optical images of the inspected areas. Various typical panel defects and defect conglomerations are resolved and can be unambiguously distinguished. Moreover, a precise classification of the detected defects is obtained. Finally, the detectability of device defects beyond the shown examples and the application to thin-film-transistor parameter extraction is discussed.