Modelling the capacitive coupling of sensors applied to the contactless inspection of planar electronics

A model aimed to describe the capacitance between probe electrodes and the conductive parts of planar electronic devices is presented. The probe electrodes are the constitutive part of a sensor chip used in an inspection system which is exclusively based on capacitive coupling and employed for the inspection of devices such as flat panel displays and printed electronic circuits. Finite element (FE) simulations of the sensor signal are used to determine the model parameters and to verify the obtained results. The capacitive coupling for arbitrary configurations of parallel arranged conductor tracks and various distances between the tracks and the sensor chip is reproduced by the model. Absolute values of the capacitance with deviations below 5% can be obtained.