Method and apparatus for non-contact opens/shorts testing of electrical

Abstract

A circuit is tested for unwanted shorts and opens by positioning the circuit between a pair of electrodes in a chamber filled with an inert gas with the circuit conductors facing one of the electrodes. The circuit is charged by applying a selected voltage to the electrodes to produce an electric field extending generally perpendicular to the circuit, the voltage polarity being such that the one electrode carries the negative electrical charge. The circuit is then subjected to a pulsed laser beam brought to a focus between the one electrode and a selected spot on a conductor of the circuit so as to ionize the chamber gas at the beam focus to form a plasma so that an electric charge is imparted to that spot and to other circuit conductor portions having electrical continuity with that spot. The circuit is then discharged by reversing the polarity of the applied voltage and increasing the voltage magnitude substantially to the breakdown voltage of the chamber gas so as to form a glowing discharge plasma in the chamber gas opposite the charged portions of the circuit conductors. The circuit is observed to determine which portions of its conductors are glowing and therefore have electrical continuity with the selected conductor spot and which portions are not.