Abstract: A method and system for the electrical and electro-optical inspection and testing of unpopulated electronic printed circuit boards, ceramic substrates and other like items which have conductive pathways formed thereon, vias, through-connectors and other interconnected conducting surfaces. The item under test is placed within a sealable gastight chamber filled with an ionizable gaseous atmosphere, such as argon, at low pressure. An electro-luminescent gas plasma discharge is produced within the chamber between a grid placed either over or below the item under test by application of a positive polarity potential to the grid and selective application of a constant current negative potential to particular test points on the item to be tested via a computer controlled movable probe.

Abstract: An automatic, electro-optical testing apparatus which employs electro-luminescence for the testing of items such as printed circuit boards, ceramic substrates and the like for electrical continuity. A unipotential array of conductor wires lying in substantially the same plane is supported within a sealable test chamber over an item under test to develop a desired electric field between exposed conductive surfaces of the item under test and the unipotential array of parallel conductors. Electro-luminescence is produced in a gaseous atmosphere within the sealable test chamber around test points contacted by a movable probe and around all conductive parts on the item under test and having electrical continuity with the test point contacted by the movable probe. The invention thus comprised eliminates the source of undesired background noise illumination while maintaining all of the transparent parallel conductor grid wires of a unipotential array at the same electric potential.