Testing method for integrated circuit packaging boards using a laser in vacuum.

摘要

For testing the integrity of conducting lines on or in a substrate , the following steps are executed: (I) Selected pads (P21) are irradiated by a focused laser beam so that they are positively charged due to photoemission of electrons. The charges propagate through existing conductors so that all selected pads (P21) and all pads connected to them (P22) assume a specific voltage. (II) The whole surface is irradiated by a flooding laser beam. Photoemission of electrons will now occur from those pads which were not charged previously (P11, P12). (III) The photoelectrons emitted in step II are detected by a channel plate arrangement and a position-sensitive detector thus revealing the spatial distribution of uncharged pads. This method is performed in vacuum and allows completely contactless testing of circuitry to detect line interruptions as well as shortcuts between separate lines. It is suited for surface lines, buried lines, and in particular also for via connections.