Fatih Alatas

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.

Contactless Functionality Inspection of Flat-Panel-Display Pixels and Thin-Film Transistors by Capacitive Coupling

A fast and thorough detection of structural and functional defects of flat-panel displays, large-area image detectors, and printed electronics requires a contactless and flexible inspection technique. Moreover, to accelerate the development of new products and to increase yields, efficient device characterization including the analysis of single component functionality and testing under operating conditions is essential. In this contribution, a contactless inspection method solely based on capacitive coupling is used to analyze pixel and thin-film transistor (TFT) functionality of active-matrix liquid crystal and electrophoretic display backplanes. Employing a capacitively coupled sensor, the measurement of the evolution of the pixel electrode voltage during TFT operation (switching) yields display flicker and TFT parameters, such as TFT on- and off-currents, TFT threshold, and intrinsic capacitance. To confirm the measurement results, the pixel voltage was also measured with an active voltage probe brought into contact with the pixel electrodes under test.