Patent ID: 6014209
Filing Date: 2000-01-11
Classification: G01N

Abstract:
Apparatus for optically inspecting the top layer of a multi-layered electronic part comprising also intermediate and bottom layers, the top layer including a pattern of conductors-to-be-inspected disposed upon an intermediate layer of transparent or translucent insulation having irregularly spaced and shaped bumps, and with some of the conductors angularly covering only portions thereof, said apparatus having, in combination, an incident light source of predetermined wavelength to which the intermediate insulation layer and not the conductors and other layers responds by fluorescing at a different wavelength; an optical path for directing the incident light vertically upon the top layer to cause reflection of the incident light back vertically to an inspection camera for imaging the top layer therein; means for filtering out the vertically reflected light of said predetermined wavelength to prevent its receipt by the camera; a collimating lens in front of the camera for collimating fluorescent light of said different wavelength emitted from the intermediate layer in all directions with at least some fluorescent rays being collimated from directions other than vertically, resulting from fluorescent emissions along such other directions from the intermediate layer including a fluorescence contribution from uncovered portions of said irregularly spaced and shaped bumps; means for selectively creating an image in the camera, only from the collimated returned fluorescing light rays while filtering all other incident light reflections to the camera from layers above and below the bumpy intermediate layer, thereby to present the non-fluorescing pattern of conductors on the top layer as contrasting dark images in a background of the fluorescing intermediate layer image, and with reflections from below the intermediate layer effectively disappearing.